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Sample records for absorption fluorescence excitation

  1. Evidence for excitation of fluorescence in RPE melanin by multiphoton absorption

    NASA Astrophysics Data System (ADS)

    Glickman, Randolph D.; Rockwell, Benjamin A.; Noojin, Gary D.; Stolarski, David J.; Denton, Michael L.

    2002-06-01

    Previously, we reported that ultrashort, near infrared (NIR) laser pulses caused more DNA breakage in cultured retinal pigment epithelial (RPE) cells than did CW, NIR laser radiation delivering a similar radiant exposure. We hypothesized that this difference was due to multiphoton absorption in an intracellular chromophore such as the RPE melanin. We investigated two-photon excitation of fluorescence in a suspension of isolated bovine RPE melanosomes exposed to a 1-KHz train of approximately 50- fsec laser pulses at 810 nm from a Ti:Sapphire laser, and compared this to the fluorescence excited by CW exposures at 406 nm from a Krypton ion laser. Fluorescence was measured with a PC-based spectrometer. The CW sources excited fluorescence with a peak at 525 nm. The fluorescence intensity depended on the irradiance of the sample, as well as the melanosome concentration. Peak fluorescence was obtained with a suspension of ~2 x 107 melanin granules/ml. The 810-nm, ultrashort pulses also excited fluorescence, but with a broader, lower-amplitude peak. The weaker fluorescence signal excited by the 810-nm ultrashort pulse laser for a given melanosome concentration, compared to 406-nm CW excitation, is possibly due to the smaller two- photon absorption cross-section. These results indicate the involvement of multiphoton absorption in DNA damage.

  2. Photoadaptation in marine phytoplankton: changes in spectral absorption and excitation of chlorophyll a fluorescence

    SciTech Connect

    Neori, A.; Holm-Hansen, O.; Mitchell, B.G.; Kiefer, D.A.

    1984-10-01

    The optical properties of marine phytoplankton were examined by measuring the absorption spectra and fluorescence excitation spectra of chlorophyll a for natural marine particles collected on glass fiber filters. Samples were collected at different depths from stations in temperate waters of the Southern California Bight and in polar waters of the Scotia and Ross Seas. At all stations, phytoplankton fluorescence excitation and absorption spectra changed systematically with depth and vertical stability of the water columns. In samples from deeper waters, both absorption and chlorophyll a fluorescence excitation spectra showed enhancement in the blue-to-green portion of the spectrum (470-560 nm) relative to that at 440 nm. Since similar changes in absorption and excitation were induced by incubating sea water samples at different light intensities, the changes in optical properties can be attributed to photoadaptation of the phytoplankton. The data indicate that in the natural populations studied, shade adaptation caused increases in the concentration of photosynthetic accessory pigments relative to chlorophyll a. These changes in cellular pigment composition were detectable within less than 1 day. Comparisons of absorption spectra with fluorescence excitation spectra indicate an apparent increase in the efficiency of sensitization of chlorophyll a fluorescence in the blue and green spectral regions for low light populations. 30 references, 6 figures.

  3. Excitation energy dependence of excited states dynamics in all- trans-carotenes determined by femtosecond absorption and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Kosumi, Daisuke; Yanagi, Kazuhiro; Nishio, Tomohiro; Hashimoto, Hideki; Yoshizawa, Masayuki

    2005-06-01

    Ultrafast relaxation kinetics in β-carotene and lycopene has been investigated by femtosecond absorption and fluorescence spectroscopies using tunable excitation pulses. The transient signals induced by the photoexcitation with larger excess energy have broader bands and longer lifetimes both in the 11Bu+and21Ag- excited states. The excess vibrational energy remains longer than several picoseconds and slows the relaxation kinetics in carotenoids.

  4. Fluorescence, Absorption, and Excitation Spectra of Polycyclic Aromatic Hydrocarbons as a Tool for Quantitative Analysis

    ERIC Educational Resources Information Center

    Rivera-Figueroa, A. M.; Ramazan, K. A.; Finlayson-Pitts, B. J.

    2004-01-01

    A quantitative and qualitative study of the interplay between absorption, fluorescence, and excitation spectra of pollutants called polycyclic aromatic hydrocarbons (PAHs) is conducted. The study of five PAH displays the correlation of the above-mentioned properties along with the associated molecular changes.

  5. Saturable absorption dynamics in the triplet system and triplet excitation induced singlet fluorescence of some organic molecules

    NASA Astrophysics Data System (ADS)

    Gratz, H.; Penzkofer, A.

    2001-01-01

    The triplet saturable absorption behaviour of the xanthene dyes eosin Y, erythrosin B, and rose bengal and of the fullerene molecule C 70 is studied. The molecules are excited to the S 1-state by intense picosecond pulses (wavelength λP=527 nm). They relax dominantly to the triplet system by intersystem crossing. The triplet-triplet saturable absorption is investigated with time-delayed intense picosecond pulses (wavelength λL=1054 nm) in the transparency region of the molecules in the singlet ground state. Higher excited-state triplet absorption cross-sections and higher excited-state triplet relaxation times are determined by numerical simulation of the experimental results. Time-resolved fluorescence measurements reveal higher excited-state triplet to singlet back-intersystem-crossing and multi-step triplet photoionization. Additionally the two-photon absorption cross-sections at λL=1054 nm are determined by measurement of the fundamental pulse two-photon induced fluorescence relative to the second-harmonic pulse single-photon induced fluorescence.

  6. Excited-state intramolecular proton transfer of 2-acetylindan-1,3-dione studied by ultrafast absorption and fluorescence spectroscopy

    PubMed Central

    Verma, Pramod Kumar; Steinbacher, Andreas; Schmiedel, Alexander; Nuernberger, Patrick; Brixner, Tobias

    2015-01-01

    We employ transient absorption from the deep-UV to the visible region and fluorescence upconversion to investigate the photoinduced excited-state intramolecular proton-transfer dynamics in a biologically relevant drug molecule, 2-acetylindan-1,3-dione. The molecule is a ß-diketone which in the electronic ground state exists as exocyclic enol with an intramolecular H-bond. Upon electronic excitation at 300 nm, the first excited state of the exocyclic enol is initially populated, followed by ultrafast proton transfer (≈160 fs) to form the vibrationally hot endocyclic enol. Subsequently, solvent-induced vibrational relaxation takes place (≈10 ps) followed by decay (≈390 ps) to the corresponding ground state. PMID:26798837

  7. Fluorescence excitation and ultraviolet absorption spectra and theoretical calculations for benzocyclobutane: Vibrations and structure of its excited S{sub 1}(π,π{sup *}) electronic state

    SciTech Connect

    Shin, Hee Won; Ocola, Esther J.; Laane, Jaan; Kim, Sunghwan

    2014-01-21

    The fluorescence excitation spectra of jet-cooled benzocyclobutane have been recorded and together with its ultraviolet absorption spectra have been used to assign the vibrational frequencies for this molecule in its S{sub 1}(π,π{sup *}) electronic excited state. Theoretical calculations at the CASSCF(6,6)/aug-cc-pVTZ level of theory were carried out to compute the structure of the molecule in its excited state. The calculated structure was compared to that of the molecule in its electronic ground state as well as to the structures of related molecules in their S{sub 0} and S{sub 1}(π,π{sup *}) electronic states. In each case the decreased π bonding in the electronic excited states results in longer carbon-carbon bonds in the benzene ring. The skeletal vibrational frequencies in the electronic excited state were readily assigned and these were compared to the ground state and to the frequencies of five similar molecules. The vibrational levels in both S{sub 0} and S{sub 1}(π,π{sup *}) states were remarkably harmonic in contrast to the other bicyclic molecules. The decreases in the frequencies of the out-of-plane skeletal modes reflect the increased floppiness of these bicyclic molecules in their S{sub 1}(π,π{sup *}) excited state.

  8. Solvent Effects on the Electronic Absorption and Fluorescence Spectra of HNP: Estimation of Ground and Excited State Dipole Moments.

    PubMed

    Desai, Vani R; Hunagund, Shirajahammad M; Basanagouda, Mahantesha; Kadadevarmath, Jagadish S; Sidarai, Ashok H

    2016-07-01

    We report the effect of solvents on absorption and fluorescence spectra of biologically active 3(2H)-pyridazinone namely 5-(2-hydroxy-naphthalen-1-yl)-2-phenyl-2H-pyridazin-3-one (HNP) in different solvents at room temperature. The ground and the excited state dipole moments of HNP molecule was estimated from Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations using the solvatochromic shift method. The ground state dipole moment (μ g ) was also estimated by Guggenheim and Higasi method using the dielectric constant and refractive index of solute at different concentrations, the μ g value obtained from these two methods are comparable to the μ g value obtained by the solvatochromic shift method. The excited state dipole moment (μ e ) is greater than the ground state dipole moment (μ g ), which indicates that the excited state is more polar than the ground state. Further, we have evaluated the change in dipole moment (Δμ) from the solvatochromic shift method and on the basis of molecular-microscopic solvent polarity parameter[Formula: see text], later on the values were compared. PMID:27220623

  9. Ultrafast Time-Resolved Emission and Absorption Spectra of meso-Pyridyl Porphyrins upon Soret Band Excitation Studied by Fluorescence Up-Conversion and Transient Absorption Spectroscopy.

    PubMed

    Venkatesh, Yeduru; Venkatesan, M; Ramakrishna, B; Bangal, Prakriti Ranjan

    2016-09-01

    thermally equilibrated Qx state by vibrational cooling/relaxations of excess energy within solvent. This relaxed Qx state decays to ground as well as triplet state by 7-8 ns time scale. The femtosecond transient absorption studies of TpyPs in three different excitations at S2 (400 nm), Qy (515 nm), and Qx (590 nm) along with extensive global and target model analysis of TA data exclusively generate the true spectra of each excited species/state with their respective lifetimes along with microscopic rate constants associated with each state. The following five exponential components with lifetime values of 65-70 fs, ∼0.3-0.5 ps, ∼20 ± 2 ps, ∼7 ± 1 ns, and 1-2 μs are observed which are associated with S2, Qy, hot Qx, thermally relaxed Qx, and lowest triplet (T1) states, respectively, when excited at S2, and four (Qy, hot Qx, thermally relaxed Qx, and lowest triplet (T1) states) and three (hot Qx, thermally relaxed Qx, and lowest triplet (T1) states) states are obtained when excited at 515 nm (Qy) and 590 nm (Qx), respectively, as expected. The TA results parallel the fluorescence up-conversion studies, and both the results not only compliment each other but also unveil the ultrafast internal conversion from S2 to Qy, S2 to Qx, and Qy to Qx for all three isomers in a similar fashion with nearly equal characteristic decay times. PMID:27494567

  10. Excitation/Detection Strategies for OH Planar Laser-Induced Fluorescence Measurements in the Presence of Interfering Fuel Signal and Absorption Effects

    NASA Technical Reports Server (NTRS)

    Heath, Christopher M.; Anderson, Robert C.; Hicks, Yolanda R.

    2011-01-01

    Planar laser-induced fluorescence (PLIF) excitation/detection methods have been applied to obtain spatial distributions of the hydroxyl [OH] reacting intermediary and hydrocarbon [HC] primary species in laminar and turbulent combustion reactions. In this report, broadband and narrowband excitation/filtering techniques are explored to identify an optimal experimental configuration yielding significant fluorescent signal with low absorption losses. The combustion environments analyzed include 1) a laminar non-premixed methane/air flame and 2) a turbulent, non-premixed Jet-A/air fueled flame within a lean flame tube combustor. Hydrocarbon-based fuel and OH were excited via the R1 (1), R1(10) and R2(7) transitions of the A(sup 2)Epsilon(+) X(sup 2)pi(1,0) band using a broadband Nd:YAG pumped optical parametric oscillator (OPO) and narrowband Nd:YAG/dye laser with ultraviolet frequency extension (UVX) package. Variables tested for influence on fluorescent signal and absorption characteristics were excitation line, laser energy, exciting linewidth, combustion reactants, and test flow conditions. Results are intended to guide the transition from a dye/UVX laser to an OPO system for performing advanced diagnostics of low-emission combustion concepts.

  11. Multiphoton excitation of fluorescent DNA base analogs

    NASA Astrophysics Data System (ADS)

    Katilius, Evaldas; Woodbury, Neal W.

    2006-07-01

    Multiphoton excitation was used to investigate properties of the fluorescent DNA base analogs, 2-aminopurine (2AP) and 6-methylisoxanthopterin (6MI). 2-aminopurine, a fluorescent analog of adenine, was excited by three-photon absorption. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2AP for DNA-protein interaction studies. However, high excitation power and long integration times needed to acquire high signal-to-noise fluorescence correlation curves render three-photon excitation FCS of 2AP not very useful for studying DNA base dynamics. The fluorescence properties of 6-methylisoxanthopterin, a guanine analog, were investigated using two-photon excitation. The two-photon absorption cross-section of 6MI was estimated to be about 2.5×10-50 cm4s (2.5 GM units) at 700 nm. The two-photon excitation spectrum was measured in the spectral region from 700 to 780 nm; in this region the shape of the two-photon excitation spectrum is very similar to the shape of single-photon excitation spectrum in the near-UV spectral region. Two-photon excitation of 6MI is suitable for fluorescence correlation measurements. Such measurements can be used to study DNA base dynamics and DNA-protein interactions over a broad range of time scales.

  12. Multiphoton excitation fluorescence correlation spectroscopy of fluorescent DNA base analogs

    NASA Astrophysics Data System (ADS)

    Katilius, Evaldas; Woodbury, Neal W.

    2004-06-01

    Two- and three-photon excitation was used to investigate the properties of two fluorescent DNA base analogs: 2-aminopurine and 6-methylisoxanthopterin. 2-aminopurine is a widely used fluorescent analog of the DNA base adenine. Three-photon excitation of 2-aminopurine is achievable by using intense femtosecond laser pulses in 850-950 nm spectral region. Interestingly, the three-photon excitation spectrum is blue-shifted relative to the three-times-wavelength single-photon excitation spectrum. The maximum of the absorbance band in the UV is at 305 nm, while the three-photon excitation spectrum has a maximum at around 880 nm. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2-aminopurine for DNA-protein interaction studies. However, due to relatively small three-photon absorption cross-section, a good signal-to-noise fluorescence correlation curves take very long time to obtain. Fluorescence properties of 6-methylisoxanthopterin, the fluorescent analog of guanine, were investigated using two-photon excitation. This molecule has the lowest energy absorption band centered around 350 nm, thus, two-photon excitation is attainable using 700 to 760 nm output of Ti-sapphire laser. The excitation spectrum of this molecule in the infrared well matches the doubled-wavelength single-photon excitation spectrum in the UV. The high fluorescence quantum yield of 6-methylisoxanthopterin allows efficient fluorescence correlation measurements and makes this molecule a very good candidate for using in in vitro DNA-protein interaction studies.

  13. Prediction of BOD, COD, and Total Nitrogen Concentrations in a Typical Urban River Using a Fluorescence Excitation-Emission Matrix with PARAFAC and UV Absorption Indices

    PubMed Central

    Hur, Jin; Cho, Jinwoo

    2012-01-01

    The development of a real-time monitoring tool for the estimation of water quality is essential for efficient management of river pollution in urban areas. The Gap River in Korea is a typical urban river, which is affected by the effluent of a wastewater treatment plant (WWTP) and various anthropogenic activities. In this study, fluorescence excitation-emission matrices (EEM) with parallel factor analysis (PARAFAC) and UV absorption values at 220 nm and 254 nm were applied to evaluate the estimation capabilities for biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total nitrogen (TN) concentrations of the river samples. Three components were successfully identified by the PARAFAC modeling from the fluorescence EEM data, in which each fluorophore group represents microbial humic-like (C1), terrestrial humic-like organic substances (C2), and protein-like organic substances (C3), and UV absorption indices (UV220 and UV254), and the score values of the three PARAFAC components were selected as the estimation parameters for the nitrogen and the organic pollution of the river samples. Among the selected indices, UV220, C3 and C1 exhibited the highest correlation coefficients with BOD, COD, and TN concentrations, respectively. Multiple regression analysis using UV220 and C3 demonstrated the enhancement of the prediction capability for TN. PMID:22368505

  14. Solvent effects on the absorption and fluorescence spectra of quinine sulphate: Estimation of ground and excited-state dipole moments

    NASA Astrophysics Data System (ADS)

    Joshi, Sunita; Pant, Debi D.

    2012-06-01

    Ground and excited state dipole moments of probe quinine sulphate (QS) was obtained using Solvatochromic shift method. Higher dipole moment is observed for excited state as compared to the ground state which is attributed to the higher polarity of excited state.

  15. Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Basavaraja, Jana; Suresh Kumar, H. M.; Inamdar, S. R.; Wari, M. N.

    2016-02-01

    The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of π → π* transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (μe). It is observed that dipole moment value of excited state (μe) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state.

  16. Absorption and fluorescence spectroscopy on a smartphone

    NASA Astrophysics Data System (ADS)

    Hossain, Md. Arafat; Canning, John; Cook, Kevin; Ast, Sandra; Rutledge, Peter J.; Jamalipour, Abbas

    2015-07-01

    A self-powered smartphone-based field-portable "dual" spectrometer has been developed for both absorption and fluorescence measurements. The smartphone's existing flash LED has sufficient optical irradiance to undertake absorption measurements within a 3D-printed case containing a low cost nano-imprinted polymer diffraction grating. A UV (λex ~ 370 nm) and VIS (λex ~ 450 nm) LED are wired into the circuit of the flash LED to provide an excitation source for fluorescence measurements. Using a customized app on the smartphone, measurements of absorption and fluorescence spectra are demonstrated using pH-sensitive and Zn2+-responsive probes. Detection over a 300 nm span with 0.42 nm/pixel spectral resolution is demonstrated. Despite the low cost and small size of the portable spectrometer, the results compare well with bench top instruments.

  17. Intramolecular charge transfer with the planarized 4-cyanofluorazene and its flexible counterpart 4-cyano-N-phenylpyrrole. Picosecond fluorescence decays and femtosecond excited-state absorption.

    PubMed

    Druzhinin, Sergey I; Kovalenko, Sergey A; Senyushkina, Tamara A; Demeter, Attila; Machinek, Reinhard; Noltemeyer, Mathias; Zachariasse, Klaas A

    2008-09-11

    The fluorescence spectrum of the rigidified 4-cyanofluorazene (FPP4C) in n-hexane consists of a dual emission from a locally excited (LE) and an intramolecular charge-transfer (ICT) state, with an ICT/LE fluorescence quantum yield ratio of Phi'(ICT)/Phi(LE) = 3.3 at 25 degrees C. With the flexible 4-cyano- N-phenylpyrrole (PP4C) in n-hexane, such an ICT reaction also takes place, with Phi'(ICT)/Phi(LE) = 1.5, indicating that for this reaction, a perpendicular twist of the pyrrole and benzonitrile moieties is not required. The ICT emission band of FPP4C and PP4C in n-hexane has vibrational structure, but a structureless band is observed in all other solvents more polar than the alkanes. The enthalpy difference Delta H of the LE --> ICT reaction in n-hexane, -11 kJ/mol for FPP4C and -7 kJ/mol for PP4C, is determined by analyzing the temperature dependence of Phi'(ICT)/Phi(LE). Using these data, the energy E(FC,ICT) of the Franck-Condon ground state populated by the ICT emission is calculated, 41 (FPP4C) and 40 kJ/mol (PP4C). These large values for E(FC,ICT) lead to the conclusion that with FPP4C and PP4C, direct ICT excitation, bypassing LE, does not take place. FPP4C has an ICT dipole moment of 15 D, similar to that of PP4C (16 D). Picosecond fluorescence decays allow the determination of the ICT lifetime, from which the radiative rate constant k'(f)(ICT) is derived, with comparable values for FPP4C and PP4C. This shows that an argument for a twisted ICT state of PP4C cannot come from k'(f)(ICT). After correction for the solvent refractive index and the energy of the emission maximum nu(max)(ICT), it appears that k'(f)(ICT) is solvent-polarity-independent. Femtosecond transient absorption with FPP4C and PP4C in n-hexane reveals that the ICT state is already nearly fully present at 100 fs after excitation, in rapid equilibrium with LE. In MeCN, the ICT state of FPP4C and PP4C is likewise largely developed at this delay time, and the reaction is limited by dielectric

  18. Laser Excited Fluorescence Studies Of Black Liquor

    NASA Astrophysics Data System (ADS)

    Horvath, J. J.; Semerjian, H. G.

    1986-10-01

    Laser excited fluorescence of black liquor was investigated as a possible monitoring technique for pulping processes. A nitrogen pumped dye laser was used to examine the fluorescence spectrum of black liquor solutions. Various excitation wavelengths were used between 290 and 403 nm. Black liquor fluorescence spectra were found to vary with both excitation wavelength and black liquor concentration. Laser excited fluorescence was found to be a sensitive technique for measurement of black liquor with good detection limits and linear response over a large dynamic range.

  19. Two-photon fluorescence excitation spectroscopy of biological molecules

    NASA Astrophysics Data System (ADS)

    Meshalkin, Yuri P.; Alfimov, E. E.; Groshev, D. E.; Makukha, V. K.

    1996-06-01

    The UV fluorescence spectra of aromatic amino-acids and some proteins at two photon excitation by second harmonic of Nd:YAG laser are received. Two-photon absorption cross sections of tryptophan, tyrosine, phenylalanine and proteins: bovine serum albumin, lysozyme, trypsin, (alpha) - chymotrypsinogen and pepsin at wavelength 532 nm were measured by means of the two-quantum standard method.

  20. Intravital Fluorescence Excitation in Whole-Animal Optical Imaging

    PubMed Central

    Bixler, Joel N.; Kong, Ying; Cirillo, Jeffrey D.; Maitland, Kristen C.

    2016-01-01

    Whole-animal fluorescence imaging with recombinant or fluorescently-tagged pathogens or cells enables real-time analysis of disease progression and treatment response in live animals. Tissue absorption limits penetration of fluorescence excitation light, particularly in the visible wavelength range, resulting in reduced sensitivity to deep targets. Here, we demonstrate the use of an optical fiber bundle to deliver light into the mouse lung to excite fluorescent bacteria, circumventing tissue absorption of excitation light in whole-animal imaging. We present the use of this technology to improve detection of recombinant reporter strains of tdTomato-expressing Mycobacterium bovis BCG (Bacillus Calmette Guerin) bacteria in the mouse lung. A microendoscope was integrated into a whole-animal fluorescence imager to enable intravital excitation in the mouse lung with whole-animal detection. Using this technique, the threshold of detection was measured as 103 colony forming units (CFU) during pulmonary infection. In comparison, the threshold of detection for whole-animal fluorescence imaging using standard epi-illumination was greater than 106 CFU. PMID:26901051

  1. Photosynthetic light-harvesting complexes: fluorescent and absorption spectroscopy under two-photon (1200-1500 nm) and one-photon (600-750 nm) excitation by laser femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Stepanenko, Il'ya A.; Kompanets, Viktor O.; Chekalin, Sergey V.; Makhneva, Zoya K.; Moskalenko, Andrey A.; Razjivin, Andrei P.

    2010-09-01

    The pathways of excitation energy transfer (EET) via pigments of the light-harvesting antenna are still in discussion. The bacteriochlorophyll fluorescence of peripheral light-harvesting complexes (LH2) from purple bacteria can be observed upon two-photon excitation (TPE) within 1200-1500 nm spectral range (a broad band near 1300 nm). Earlier the occurrence of this band was taken as an evidence for the participation of "dark" carotenoid S1 state in EET processes (see [Walla et al., Proc. Nat. Acad. Sci. U.S.A. 97, 10808-10813 (2000)] and references in it). However we showed that TPE spectrum of LH2 fluorescence within 1200-1500 nm is not associated with carotenoids [Stepanenko et al., J. Phys. Chem. B. 113(34), 11720-11723 (2009)]. Here we present TPE spectra of fluorescence for chromatophores and lightharvesting complexes LH2 and LH1 from wild-type cells and from carotenoid-depleted or carotenoidless mutant cells of several purple bacteria. The broad band within 1300-1400 nm was found for all preparations. Absorption pump-probe femtosecond spectroscopy applied to LH2 complex from Rb. sphaeroides revealed the similar spectral and kinetic patterns for TPE at 1350 nm and one-photon excitation at 675 nm. Analysis of pigment composition of this complex by high-pressure liquid chromatography showed that even under mild isolation conditions some bacteriochlorophyll molecules were oxidized to 3-acetyl-chlorophyll molecules having the long-wavelength absorption peak in the 650-700 nm range. It is proposed that these 3-acetyl-chlorophyll molecules are responsible for the broad band in TPE spectra within the 1200-1500 nm region.

  2. Photosynthetic light-harvesting complexes: fluorescent and absorption spectroscopy under two-photon (1200-1500 nm) and one-photon (600-750 nm) excitation by laser femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Stepanenko, Il'ya A.; Kompanets, Viktor O.; Chekalin, Sergey V.; Makhneva, Zoya K.; Moskalenko, Andrey A.; Razjivin, Andrei P.

    2011-02-01

    The pathways of excitation energy transfer (EET) via pigments of the light-harvesting antenna are still in discussion. The bacteriochlorophyll fluorescence of peripheral light-harvesting complexes (LH2) from purple bacteria can be observed upon two-photon excitation (TPE) within 1200-1500 nm spectral range (a broad band near 1300 nm). Earlier the occurrence of this band was taken as an evidence for the participation of "dark" carotenoid S1 state in EET processes (see [Walla et al., Proc. Nat. Acad. Sci. U.S.A. 97, 10808-10813 (2000)] and references in it). However we showed that TPE spectrum of LH2 fluorescence within 1200-1500 nm is not associated with carotenoids [Stepanenko et al., J. Phys. Chem. B. 113(34), 11720-11723 (2009)]. Here we present TPE spectra of fluorescence for chromatophores and lightharvesting complexes LH2 and LH1 from wild-type cells and from carotenoid-depleted or carotenoidless mutant cells of several purple bacteria. The broad band within 1300-1400 nm was found for all preparations. Absorption pump-probe femtosecond spectroscopy applied to LH2 complex from Rb. sphaeroides revealed the similar spectral and kinetic patterns for TPE at 1350 nm and one-photon excitation at 675 nm. Analysis of pigment composition of this complex by high-pressure liquid chromatography showed that even under mild isolation conditions some bacteriochlorophyll molecules were oxidized to 3-acetyl-chlorophyll molecules having the long-wavelength absorption peak in the 650-700 nm range. It is proposed that these 3-acetyl-chlorophyll molecules are responsible for the broad band in TPE spectra within the 1200-1500 nm region.

  3. Laser Excited Fluorescence For Forensic Diagnostics

    NASA Astrophysics Data System (ADS)

    McKinney, Robert E.

    1986-07-01

    The application of laser excited fluorescence to the detection and identification of latent fingerprints was first accomplished ten years ago. The development of the technology has progressed rapidly with the introduction of commercial equipment by several manufacturers. Systems based on Argon-ion, Copper-vapor, and frequency-doubled Nd:YAG lasers are compared. The theoretical basis of detection by fluorescence is discussed along with the more useful techniques of dye staining. Other applications of the laser excited fluorescence in forensic investigation include gunshot residue analysis, serology, collection of trace evidence, and document examination.

  4. Temperature dependence of the excited state absorption of alexandrite

    SciTech Connect

    Shand, M.L.; Jenssen, H.P.

    1983-03-01

    The temperature dependence from 28 to 290/sup 0/C of the excited-state absorption cross section sigma /SUB 2a/ (E) in the gain wavelength region of alexandrite has been determined from the temperature dependence of the single pass gain (SPG) and of the fluorescence. sigma /SUB 2a/ (E) and the emission cross section increase with temperature at approximately the same rate.

  5. Enhanced melanin fluorescence by stepwise three-photon excitation.

    PubMed

    Kerimo, Josef; Rajadhyaksha, Milind; DiMarzio, Charles A

    2011-01-01

    The fluorescence of eumelanin (from Sepia officinalis and black human hair) was activated and enhanced by almost three orders of magnitude by exposure to near-infrared radiation. No activation or enhanced emission was observed when the samples were heated up to 100°C. The near-infrared irradiation caused obvious changes to the eumelanin and could be seen by fluorescence and bright field imaging. The area of enhanced emission appeared to originate from a region with changes in the morphology of the eumelanin's granule and increased with exposure time. At least two different components with enhanced fluorescence were activated and could be distinguished by their excitation properties. One component could be excited efficiently with wavelengths in the visible region and exhibited linear absorption dependence with respect to the laser power level. The second component could be excited efficiently using near-infrared wavelengths by a nonlinear process and exhibited a third-order dependence on the excitation. The third-order dependence is explained by a step-wise excited-state absorption process since the same third-order dependence was present when either continuous wave or femtosecond pulsed laser, with similar average-power levels, was used. PMID:21668873

  6. Fluorescent excitation of interstellar H2

    NASA Technical Reports Server (NTRS)

    Black, John H.; Van Dishoeck, Ewine F.

    1987-01-01

    The infrared emission spectrum of H2 excited by ultraviolet absorption, followed by fluorescence, was investigated using comprehensive models of interstellar clouds for computing the spectrum and to assess the effects on the intensity to various cloud properties, such as density, size, temperature, and the intensity of the UV radiation field. It is shown that the absolute H2 IR line intensities depend primarily on the density of the cloud and the strength of the incident UV radiation, and to a much lesser exent on the temperature of the gas, the total thickness of the cloud, and the optical properties of the grains. A variety of recent observational results are discussed with reference to theoretical models. It is shown that the rich H2 emission spectrum of the reflection nebula NGC 2023 can be reproduced by a model with density of about 10,000/cu cm, temperature of about 80 K, and UV flux approximately 300 times that of the Galactic background starlight.

  7. Fluorescence lifetime excitation cytometry by kinetic dithering.

    PubMed

    Li, Wenyan; Vacca, Giacomo; Castillo, Maryann; Houston, Kevin D; Houston, Jessica P

    2014-07-01

    Flow cytometers are powerful high-throughput devices that capture spectroscopic information from individual particles or cells. These instruments provide a means of multi-parametric analyses for various cellular biomarkers or labeled organelles and cellular proteins. However, the spectral overlap of fluorophores limits the number of fluorophores that can be used simultaneously during experimentation. Time-resolved parameters enable the quantification of fluorescence decay kinetics, thus circumventing common issues associated with intensity-based measurements. This contribution introduces fluorescence lifetime excitation cytometry by kinetic dithering (FLECKD) as a method to capture multiple fluorescence lifetimes using a hybrid time-domain approach. The FLECKD approach excites fluorophores by delivering short pulses of light to cells or particles by rapid dithering and facilitates measurement of complex fluorescence decay kinetics by flow cytometry. Our simulations demonstrated a resolvable fluorescence lifetime value as low as 1.8 ns (±0.3 ns) with less than 20% absolute error. Using the FLECKD instrument, we measured the shortest average fluorescence lifetime value of 2.4 ns and found the system measurement error to be ±0.3 ns (SEM), from hundreds of monodisperse and chemically stable fluorescent microspheres. Additionally, we demonstrate the ability to detect two distinct excited state lifetimes from fluorophores in single cells using FLECKD. This approach presents a new ability to resolve multiple fluorescence lifetimes while retaining the fluidic throughput of a cytometry system. The ability to discriminate more than one average fluorescence lifetime expands the current capabilities of high-throughput and intensity-based cytometry assays as the need to tag one single cell with multiple fluorophores is now widespread. PMID:24668857

  8. Fluorescence lifetime excitation cytometry by kinetic dithering

    PubMed Central

    Li, Wenyan; Vacca, Giacomo; Castillo, Maryann; Houston, Kevin D; Houston, Jessica P

    2014-01-01

    Flow cytometers are powerful high-throughput devices that capture spectroscopic information from individual particles or cells. These instruments provide a means of multi-parametric analyses for various cellular biomarkers or labeled organelles and cellular proteins. However, the spectral overlap of fluorophores limits the number of fluorophores that can be used simultaneously during experimentation. Time-resolved parameters enable the quantification of fluorescence decay kinetics, thus circumventing common issues associated with intensity-based measurements. This contribution introduces fluorescence lifetime excitation cytometry by kinetic dithering (FLECKD) as a method to capture multiple fluorescence lifetimes using a hybrid time-domain approach. The FLECKD approach excites fluorophores by delivering short pulses of light to cells or particles by rapid dithering and facilitates measurement of complex fluorescence decay kinetics by flow cytometry. Our simulations demonstrated a resolvable fluorescence lifetime value as low as 1.8 ns (±0.3 ns) with less than 20% absolute error. Using the FLECKD instrument, we measured the shortest average fluorescence lifetime value of 2.4 ns and found the system measurement error to be ±0.3 ns (SEM), from hundreds of monodisperse and chemically stable fluorescent microspheres. Additionally, we demonstrate the ability to detect two distinct excited state lifetimes from fluorophores in single cells using FLECKD. This approach presents a new ability to resolve multiple fluorescence lifetimes while retaining the fluidic throughput of a cytometry system. The ability to discriminate more than one average fluorescence lifetime expands the current capabilities of high-throughput and intensity-based cytometry assays as the need to tag one single cell with multiple fluorophores is now widespread. PMID:24668857

  9. Spectroscopy of α,ω-dithienyl polyenes: evidence for two-photon absorption states from fluorescence studies

    NASA Astrophysics Data System (ADS)

    Natarajan, Lalgudi V.; Kirkpatrick, Sean M.; Sutherland, Richard L.; Sowards, Laura A.; Spangler, Charles W.; Fleitz, Paul A.; Cooper, Thomas M.

    1998-10-01

    The photophysics of a series (alpha) ,(omega) -dithienyl polyenes was studied. Both one photon excited fluorescence and fluorescence originating from two photon absorption states were investigated. There is strong evidence of two photon absorption from fluorescence studies in agreement with our earlier studies involving nonlinear absorption.

  10. Up-converted fluorescence from photosynthetic light-harvesting complexes linearly dependent on excitation intensity.

    PubMed

    Leiger, Kristjan; Freiberg, Arvi

    2016-01-01

    Weak up-converted fluorescence related to bacteriochlorophyll a was recorded from various detergent-isolated and membrane-embedded light-harvesting pigment-protein complexes as well as from the functional membranes of photosynthetic purple bacteria under continuous-wave infrared laser excitation at 1064 nm, far outside the optically allowed singlet absorption bands of the chromophore. The fluorescence increases linearly with the excitation power, distinguishing it from the previously observed two-photon excited fluorescence upon femtosecond pulse excitation. Possible mechanisms of this excitation are discussed. PMID:25764015

  11. Ultra-violet and resonant laser ablation coupled with microwave induced plasma atomic emission spectrometry and determination of tin in nickel based alloys by electrothermal atomizer atomic absorption and laser excited atomic fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Yang, Xiaodong

    Chapter 1 reviews laser ablation in analytical atomic spectrometry. Laser ablation is categorized into two functions: one is used as a sample introduction method, the other function is used as a microprobe analysis method. Both fundamental and applicational aspects are reviewed with the citations of related papers. This chapter also serves as an introduction to the work which is described in chapter 2 and chapter 3 as laser ablation is a relatively new research area for the research group. In chapter 2, instrumentation for excimer (308nm) laser ablation of samples was coupled with a microwave induced plasma (MLP), and evaluated for its potential as an approach to solid sampling for atomic emission spectrometry. Operating parameters were optimized, and the effects of laser repetition rate and number of laser shots on the emission signal were investigated. The UV excimer laser removed more material than would be expected of an infrared laser of similar energy. The chromium detection limit in the solid steel sample was estimated to be about 500 mug/g. In chapter 3, a wavelength tunable optical parametric oscillator (OPO) laser was used to ablate a steel sample into the same apparatus described in chapter 2. The emission signal for the elements was selectively enhanced when the ablation wavelength was tuned to be in resonance with any atomic transition of that element. This was the first report of the observation of resonant ablation by use of optical detection, as prior reports of resonant ablation have used mass spectrometric detectors. Chapter 4 reviews the publications in laser excited atomic fluorescence spectrometry in recent eight years. The focus of the review is on recent development on new instruments and applications of this technique. Chapter 5 studies the determination of tin in nickel-based alloys with laser excited atomic fluorescence in a graphite furnace. Zeeman electrothermal atomizer atomic absorption spectrometry and inductively coupled plasma mass

  12. Excitation-resolved fluorescence tomography with simplified spherical harmonics equations

    NASA Astrophysics Data System (ADS)

    Klose, Alexander D.; Pöschinger, Thomas

    2011-03-01

    Fluorescence tomography (FT) reconstructs the three-dimensional (3D) fluorescent reporter probe distribution inside biological tissue. These probes target molecules of biological function, e.g. cell surface receptors or enzymes, and emit fluorescence light upon illumination with an external light source. The fluorescence light is detected on the tissue surface and a source reconstruction algorithm based on the simplified spherical harmonics (SPN) equations calculates the unknown 3D probe distribution inside tissue. While current FT approaches require multiple external sources at a defined wavelength range, the proposed FT method uses only a white light source with tunable wavelength selection for fluorescence stimulation and further exploits the spectral dependence of tissue absorption for the purpose of 3D tomographic reconstruction. We will show the feasibility of the proposed hyperspectral excitation-resolved fluorescence tomography method with experimental data. In addition, we will demonstrate the performance and limitations of such a method under ideal and controlled conditions by means of a digital mouse model and synthetic measurement data. Moreover, we will address issues regarding the required amount of wavelength intervals for fluorescent source reconstruction. We will explore the impact of assumed spatially uniform and nonuniform optical parameter maps on the accuracy of the fluorescence source reconstruction. Last, we propose a spectral re-scaling method for overcoming the observed limitations in reconstructing accurate source distributions in optically non-uniform tissue when assuming only uniform optical property maps for the source reconstruction process.

  13. Two-photon-excited fluorescence spectroscopy of atomic fluorine at 170 nm

    NASA Technical Reports Server (NTRS)

    Herring, G. C.; Dyer, Mark J.; Jusinski, Leonard E.; Bischel, William K.

    1988-01-01

    Two-photon-excited fluorescence spectroscopy of atomic fluorine is reported. A doubled dye laser at 286-nm is Raman shifted in H2 to 170 nm (sixth anti-Stokes order) to excite ground-state 2P(0)J fluorine atoms to the 2D(0)J level. The fluorine atoms are detected by one of two methods: observing the fluorescence decay to the 2PJ level or observing F(+) production through the absorption of an additional photon by the excited atoms. Relative two-photon absorption cross sections to and the radiative lifetimes of the 2D(0)J states are measured.

  14. Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols

    SciTech Connect

    Lee, Hyun Ji; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.

    2013-05-10

    Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of SOA generated from two monoterpenes, limonene and a-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ~100 ppb ammonia vapor in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (~0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for excitation = 420+- 50 nm and emission = 475 +- 38 nm. The window of the strongest fluorescence shifted to excitation = 320 +- 25 nm and emission = 425 +- 38 nm for the a-pinene-derived SOA. Both regions overlap with the excitation-emission matrix (EEM) spectra of some of the fluorophores found in primary biological aerosols. Our study suggests that, despite the low quantum yield, the aged SOA particles should have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.

  15. Evanescent Excitation and Emission in Fluorescence Microscopy

    PubMed Central

    Axelrod, Daniel

    2013-01-01

    Evanescent light—light that does not propagate but instead decays in intensity over a subwavelength distance—appears in both excitation (as in total internal reflection) and emission (as in near-field imaging) forms in fluorescence microscopy. This review describes the physical connection between these two forms as a consequence of geometrical squeezing of wavefronts, and describes newly established or speculative applications and combinations of the two. In particular, each can be used in analogous ways to produce surface-selective images, to examine the thickness and refractive index of films (such as lipid multilayers or protein layers) on solid supports, and to measure the absolute distance of a fluorophore to a surface. In combination, the two forms can further increase selectivity and reduce background scattering in surface images. The polarization properties of each lead to more sensitive and accurate measures of fluorophore orientation and membrane micromorphology. The phase properties of the evanescent excitation lead to a method of creating a submicroscopic area of total internal reflection illumination or enhanced-resolution structured illumination. Analogously, the phase properties of evanescent emission lead to a method of producing a smaller point spread function, in a technique called virtual supercritical angle fluorescence. PMID:23561516

  16. High-intensity xenon pulse light source for fluorescence excitation

    NASA Astrophysics Data System (ADS)

    Miyamoto, Makoto; Ueno, Kazuo

    1997-05-01

    A newly developed 60W xenon flash lamp, L6604 and L6605, achieves the goals of longer operating life, higher output, and improved light stability. It operates at 2 Joules per flash input energy with approximately a 4 microsecond flash duration. The stability achieved is 2-3 percent peak-to-peak during a lifetime of 5 X 10e7 flashes, which is almost double that of conventional xenon flash lamps. This newly developed xenon flashlamp should serve as an excellent light source for analytical cytology and other fluorescence instruments. It can function as a high output, stable excitation light source for conventional fluorescence or delayed luminescence with a CCD. Besides providing powerful and stable illumination for absorption analysis of cells on slides, this lamp eliminates the optical artifacts associated with vibration of the stage which often limit throughput. This paper will describe in detail performance improvements obtained from this newly developed xenon flash lamp.

  17. Visible-wavelength two-photon excitation microscopy for fluorescent protein imaging.

    PubMed

    Yamanaka, Masahito; Saito, Kenta; Smith, Nicholas I; Arai, Yoshiyuki; Uegaki, Kumiko; Yonemaru, Yasuo; Mochizuki, Kentaro; Kawata, Satoshi; Nagai, Takeharu; Fujita, Katsumasa

    2015-10-01

    The simultaneous observation of multiple fluorescent proteins (FPs) by optical microscopy is revealing mechanisms by which proteins and organelles control a variety of cellular functions. Here we show the use of visible-light based two-photon excitation for simultaneously imaging multiple FPs. We demonstrated that multiple fluorescent targets can be concurrently excited by the absorption of two photons from the visible wavelength range and can be applied in multicolor fluorescence imaging. The technique also allows simultaneous single-photon excitation to offer simultaneous excitation of FPs across the entire range of visible wavelengths from a single excitation source. The calculation of point spread functions shows that the visible-wavelength two-photon excitation provides the fundamental improvement of spatial resolution compared to conventional confocal microscopy. PMID:26238663

  18. Visible-wavelength two-photon excitation microscopy for fluorescent protein imaging

    NASA Astrophysics Data System (ADS)

    Yamanaka, Masahito; Saito, Kenta; Smith, Nicholas I.; Arai, Yoshiyuki; Uegaki, Kumiko; Yonemaru, Yasuo; Mochizuki, Kentaro; Kawata, Satoshi; Nagai, Takeharu; Fujita, Katsumasa

    2015-10-01

    The simultaneous observation of multiple fluorescent proteins (FPs) by optical microscopy is revealing mechanisms by which proteins and organelles control a variety of cellular functions. Here we show the use of visible-light based two-photon excitation for simultaneously imaging multiple FPs. We demonstrated that multiple fluorescent targets can be concurrently excited by the absorption of two photons from the visible wavelength range and can be applied in multicolor fluorescence imaging. The technique also allows simultaneous single-photon excitation to offer simultaneous excitation of FPs across the entire range of visible wavelengths from a single excitation source. The calculation of point spread functions shows that the visible-wavelength two-photon excitation provides the fundamental improvement of spatial resolution compared to conventional confocal microscopy.

  19. Terbium chloride--aluminum chloride vapor system. I. Absorption and excitation spectra

    SciTech Connect

    Caird, J.A.; Carnall, W.T.; Hessler, J.P.; Williams, C.W.

    1981-01-15

    The absorption spectrum of the vapor complex formed at elevated temperatures between TbCl/sub 3/ and AlCl/sub 3/ has been measured in the region 20 000--50 000 cm/sup -1/. Oscillator strengths of f--f absorption bands below 37 000 cm/sup -1/ were determined. Strong absorption due to opposite parity 4f/sup 7/5d states was observed in the 37 000 to 50 000 cm/sup -1/ region with a peak molar absorptivity of approximately 500 l/mol cm. Significant additional absorption attributed to a molecular complex was also observed in this region. By measuring the excitation spectrum it was found that the molecular absorption does not appear to lead to fluorescence of the /sup 5/D/sub 4/ state. In contrast, absorption by the 4f/sup 7/5d states does result in strong /sup 5/D/sub 4/ fluorescence.

  20. Studies on external electric field effects on absorption and fluorescence spectra of NADH

    NASA Astrophysics Data System (ADS)

    Nakabayashi, Takakazu; Islam, Md. Serajul; Li, Liming; Yasuda, Masahide; Ohta, Nobuhiro

    2014-03-01

    Electric field effects on absorption and fluorescence spectra have been investigated for NADH that is a representative autofluorescent chromophore in cells. The change in electric dipole moment following absorption is significant in the electroabsorption spectrum, indicating charge transfer character in the excited state. The fluorescence intensity decreases in the presence of an electric field, which arises from the field-induced increase in the rate of the non-radiative process. The blue shift of the fluorescence spectrum and the increase in the fluorescence lifetime of NADH are measured in yeast cells, which is discussed in terms of a local electric field around NADH.

  1. Absorption and fluorescent spectral studies of imidazophenazine derivatives.

    PubMed

    Ryazanova, O A; Zozulya, V N; Voloshin, I M; Karachevtsev, V A; Makitruk, V L; Stepanian, S G

    2004-07-01

    Absorption and fluorescent spectra as well as fluorescence polarization degree of imidazo-[4,5-d]-phenazine (F1) and its two modified derivatives, 2-trifluoridemethylimidazo-[4,5-d]-phenazine (F2) and 1,2,3-triazole-[4,5-d]-phenazine (F3), were investigated in organic solvents of various polarities and hydrogen bonding abilities. Extinction coefficients of F2 and F3 are increased, their fluorescence Stokes shifts are reduced in comparison with those for unmodified imidazophenazine. For F3 a red shift of the longwave absorption band is observed by 15-20 nm. Modifications of imidazophenazine have led to a sufficient increase of fluorescence polarization degrees that enables to use F2 and F3 as promising fluorescent probes with polarization method application. The configuration, atomic charge distribution and dipole moments of the isolated dye molecules in the ground state were calculated by the DFT method. The computation has revealed that ground state dipole moments of F1, F2, and F3 differ slightly and are equal to 3.5, 3.2, and 3.7D, respectively. The changes in dipole moments upon the optical excitation for all derivatives estimated using Lippert equation were found to be Deltamu = 9 D. The energies of the electronic S1<--S0 transition in solvents of different proton donor abilities were determined, and energetic diagram illustrating the substituent effect was plotted. For nucleoside analogs of these compounds, covalently incorporated into a nucleotide chain, we have considered a possibility to use them as fluorescent reporters of hybridization of antisense oligonucleotides, as well as molecular anchors for its stabilization. PMID:15248979

  2. Theoretical investigations of absorption and fluorescence spectra of protonated pyrene.

    PubMed

    Chin, Chih-Hao; Lin, Sheng Hsien

    2016-05-25

    The equilibrium geometry and 75 vibrational normal-mode frequencies of the ground and first excited states of protonated pyrene isomers were calculated and characterized in the adiabatic representation by using the complete active space self-consistent field (CASSCF) method. Electronic absorption spectra of solid neon matrixes in the wavelength range 495-415 nm were determined by Maier et al. and they were analyzed using time-dependent density functional theory calculations (TDDFT). CASSCF calculations and absorption and emission spectra simulations by one-photon excitation equations were used to optimize the excited and ground state structures of protonated pyrene isomers. The absorption band was attributed to the S0 → S1 electronic transition in 1H-Py(+), and a band origin was used at 20580.96 cm(-1). The displaced harmonic oscillator approximation and Franck-Condon approximation were used to simulate the absorption spectrum of the (1) (1)A' ← X[combining tilde](1)A' transition of 1H-Py(+), and the main vibronic transitions were assigned for the first ππ* state. It shows that the vibronic structures were dominated by one of the eight active totally symmetric modes, with ν15 being the most crucial. This indicates that the electronic transition of the S1((1)A') state calculated in the adiabatic representation effectively includes a contribution from the adiabatic vibronic coupling through Franck-Condon factors perturbed by harmonic oscillators. The present method can adequately reproduce experimental absorption and fluorescence spectra of a gas phase. PMID:27181017

  3. Fluorescent and dynamic properties of optically excited dysprosium trifluoride

    NASA Astrophysics Data System (ADS)

    Xu, Li-Wen; Crosswhite, H. M.; Hessler, Jan P.

    1984-07-01

    Fluorescent, excitation, and absorption spectra of DyF3 are reported. The energies of the electronic states of the ground level are significantly shifted compared to those of the dilute system DyxLa1-xF3 and are consistent with recent specific heat measurements from 5 to 350 K. The fluorescent decay rate K of the (4F9/2)1 state follows the equation K(μs-1)=1.600+0.0307 T(K), where T(K) is the absolute temperature. At 0 K the quantum efficiency is approximately 4.5×10-4. The decay rate is determined by the donor-to-acceptor transfer rate, where an acceptor is a pair of coupled dysprosium ions which deactivate the (4F9/2)1 state. Cross relaxation of the form 4F9/2+6H15/2→6F3/2+6H5/2 is calculated to be the dominant dipole-dipole decay channel. Comparison of high-resolution absorption line shapes, measured above 4.2 K, and below the ferromagnetic transition 2.53 K shows a shift of the line centers, and a reduction, by a factor of 6 in the linewidths. These results are consistent with analogous measurements performed on the Ising antiferromagnet dysprosium aluminum garnet and reflect the short-range order of the system.

  4. Ultrafast excited-state dynamics and fluorescence deactivation of near-infrared fluorescent proteins engineered from bacteriophytochromes.

    PubMed

    Zhu, Jingyi; Shcherbakova, Daria M; Hontani, Yusaku; Verkhusha, Vladislav V; Kennis, John T M

    2015-01-01

    Near-infrared fluorescent proteins, iRFPs, are recently developed genetically encoded fluorescent probes for deep-tissue in vivo imaging. Their functions depend on the corresponding fluorescence efficiencies and electronic excited state properties. Here we report the electronic excited state deactivation dynamics of the most red-shifted iRFPs: iRFP702, iRFP713 and iRFP720. Complementary measurements by ultrafast broadband fluorescence and absorption spectroscopy show that single exponential decays of the excited state with 600~700 ps dominate in all three iRFPs, while photoinduced isomerization was completely inhibited. Significant kinetic isotope effects (KIE) were observed with a factor of ~1.8 in D2O, and are interpreted in terms of an excited-state proton transfer (ESPT) process that deactivates the excited state in competition with fluorescence and chromophore mobility. On this basis, new approaches for rational molecular engineering may be applied to iRFPs to improve their fluorescence. PMID:26246319

  5. Ultrafast excited-state dynamics and fluorescence deactivation of near-infrared fluorescent proteins engineered from bacteriophytochromes

    NASA Astrophysics Data System (ADS)

    Zhu, Jingyi; Shcherbakova, Daria M.; Hontani, Yusaku; Verkhusha, Vladislav V.; Kennis, John T. M.

    2015-08-01

    Near-infrared fluorescent proteins, iRFPs, are recently developed genetically encoded fluorescent probes for deep-tissue in vivo imaging. Their functions depend on the corresponding fluorescence efficiencies and electronic excited state properties. Here we report the electronic excited state deactivation dynamics of the most red-shifted iRFPs: iRFP702, iRFP713 and iRFP720. Complementary measurements by ultrafast broadband fluorescence and absorption spectroscopy show that single exponential decays of the excited state with 600 ~ 700 ps dominate in all three iRFPs, while photoinduced isomerization was completely inhibited. Significant kinetic isotope effects (KIE) were observed with a factor of ~1.8 in D2O, and are interpreted in terms of an excited-state proton transfer (ESPT) process that deactivates the excited state in competition with fluorescence and chromophore mobility. On this basis, new approaches for rational molecular engineering may be applied to iRFPs to improve their fluorescence.

  6. Optimal fluorescence waveband determination for detecting defect cherry tomatoes using fluorescence excitation-emission matrix

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A multi-spectral fluorescence imaging technique was used to detect defect cherry tomatoes. The fluorescence excitation and emission matrix was used to measure for defects, sound surface, and stem areas to determine the optimal fluorescence excitation and emission wavelengths for discrimination. Two-...

  7. Study on excitation and fluorescence spectrums of Japanese citruses to construct machine vision systems for acquiring fluorescent images

    NASA Astrophysics Data System (ADS)

    Momin, Md. Abdul; Kondo, Naoshi; Kuramoto, Makoto; Ogawa, Yuichi; Shigi, Tomoo

    2011-06-01

    Research was conducted to acquire knowledge of the ultraviolet and visible spectrums from 300 -800 nm of some common varieties of Japanese citrus, to investigate the best wave-lengths for fluorescence excitation and the resulting fluorescence wave-lengths and to provide a scientific background for the best quality fluorescent imaging technique for detecting surface defects of citrus. A Hitachi U-4000 PC-based microprocessor controlled spectrophotometer was used to measure the absorption spectrum and a Hitachi F-4500 spectrophotometer was used for the fluorescence and excitation spectrums. We analyzed the spectrums and the selected varieties of citrus were categorized into four groups of known fluorescence level, namely strong, medium, weak and no fluorescence.The level of fluorescence of each variety was also examined by using machine vision system. We found that around 340-380 nm LEDs or UV lamps are appropriate as lighting devices for acquiring the best quality fluorescent image of the citrus varieties to examine their fluorescence intensity. Therefore an image acquisition device was constructed with three different lighting panels with UV LED at peak 365 nm, Blacklight blue lamps (BLB) peak at 350 nm and UV-B lamps at peak 306 nm. The results from fluorescent images also revealed that the findings of the measured spectrums worked properly and can be used for practical applications such as for detecting rotten, injured or damaged parts of a wide variety of citrus.

  8. Multispectral excitation based multiple fluorescent targets resolving in fluorescence molecular tomography

    NASA Astrophysics Data System (ADS)

    Zhou, Yuan; Guang, Huizhi; Pu, Huangsheng; Zhang, Jiulou; Bai, Jing; Luo, Jianwen

    2016-04-01

    Fluorescence molecular tomography (FMT) can visualize biological activities at cellular and molecular levels in vivo, and has been extensively used in drug delivery and tumor detection research of small animals. The ill-posedness of the FMT inverse problem makes it difficult to reconstruct and resolve multiple adjacent fluorescent targets that have different functional features but are labeled with the same fluorochrome. An algorithm based on independent component analysis (ICA) for multispectral excited FMT is proposed to resolve multiple fluorescent targets in this study. Fluorescent targets are excited by multispectral excitation, and the three-dimensional distribution of fluorescent yields under the excitation spectrum is reconstructed by an iterative Tikhonov regularization algorithm. Subsequently, multiple fluorescent targets are resolved from mixed fluorescence signals by employing ICA. Simulations were performed and the results demonstrate that multiple adjacent fluorescent targets can be resolved if the number of excitation wavelengths is not smaller than that of fluorescent targets with different concentrations. The algorithm obtains both independent components that provide spatial information of different fluorescent targets and spectral courses that reflect variation trends of fluorescent yields along with the excitation spectrum. By using this method, it is possible to visualize the metabolism status of drugs in different structure organs, and quantitatively depict the variation trends of fluorescent yields of each functional organ under the excitation spectrum. This method may provide a pattern for tumor detection, drug delivery and treatment monitoring in vivo.

  9. Fluorescence and picosecond laser photolysis studies on the deactivation processes of excited hydrogen bonding systems

    NASA Astrophysics Data System (ADS)

    Ikeda, Noriaka; Okada, Tadashi; Mataga, Noboru

    1980-01-01

    The fluorescence quenching reaction of 2-naphthylamine and 1-pyrenol due to hydrogen bonding interaction with pyndine has been investigated Absorption spectra due to the state formed by charge transfer from excited naphthylamine to hydrogen bonded pyridine have been observed by means of picosecond laser photolysis.

  10. Quantitative absorption and fluorescence studies of NO between 1060 and 2000 A

    NASA Technical Reports Server (NTRS)

    Guest, J. A.; Lee, L. C.

    1981-01-01

    Synchrotron radiation in the 1060 to 2000 A region was used to measure the average absorption and fluorescence cross sections of NO and to determine approximate photodissociation quantum yields. Several vibrational levels of the D(2) sigma(+), E(2) sigma(+), and B(2) delta states have high fluorescence quantum yields. The C(2) and B(2) states do not fluoresce when the excitation energies are above the first dissociation limit, in accord with previous experiments. In general, the fluorescence yields decrease with increasing photon energy. The quantitative measurements are compared with spectroscopic observations and are found to be reasonably consistent.

  11. The two-photon excitation cross section of 6MAP, a fluorescent adenine analogue.

    PubMed

    Stanley, Robert J; Hou, Zhanjia; Yang, Aiping; Hawkins, Mary E

    2005-03-01

    6MAP is a fluorescent analogue of adenine that undergoes Watson-Crick base pairing and base stacking in double-stranded DNA. The one-photon absorption spectrum of 6MAP is characterized by a maximum around 330 nm with moderate quantum yield fluorescence centered at about 420 nm. To take advantage of this probe for confocal and single-molecule microscopy, it would be advantageous to be able to excite the analogue via two photons. We report the first determination of the two-photon excitation cross section and spectrum for 6MAP from 614 to 700 nm. The power dependence of the fluorescence indicates that emission results from the absorption of two photons. The one-photon and two-photon emission line shapes are identical within experimental error. A study of the concentration dependence of the fluorescence yield for one-photon excitation shows no measurable quenching up to about 5 microM. The maximum in the two-photon excitation spectrum gives a two-photon cross section, delta(TPE), of 3.4 +/- 0.1 Goeppert-Mayer (G.M.) at 659 nm, which correlates well with the one-photon absorption maximum. This compares quite favorably with cross sections of various naturally fluorescent biological molecules such as flavins and nicotiamide. In addition, we have also obtained the two-photon-induced fluorescence emission spectrum of quinine sulfate. It is approximately the same as that for one-photon excitation, suggesting that two-photon excitation of quinine sulfate may be used for calibration purposes. PMID:16851408

  12. Two-photon excited UV fluorescence for protein crystal detection

    PubMed Central

    Madden, Jeremy T.; DeWalt, Emma L.; Simpson, Garth J.

    2011-01-01

    Two-photon excited ultraviolet fluorescence (TPE-UVF) microscopy is explored for sensitive protein-crystal detection as a complement to second-order nonlinear optical imaging of chiral crystals (SONICC). Like conventional ultraviolet fluorescence (UVF), TPE-UVF generates image contrast based on the intrinsic fluorescence of aromatic residues, generally producing higher fluorescence emission within crystals than the mother liquor by nature of the higher local protein concentration. However, TPE-UVF has several advantages over conventional UVF, including (i) insensitivity to optical scattering, allowing imaging in turbid matrices, (ii) direct compatibility with conventional optical plates and windows by using visible light for excitation, (iii) elimination of potentially damaging out-of-plane UV excitation, (iv) improved signal to noise through background reduction from out-of-plane excitation and (v) relatively simple integration into instrumentation developed for SONICC. PMID:21931215

  13. Two-photon excited UV fluorescence for protein crystal detection

    SciTech Connect

    Madden, Jeremy T.; DeWalt, Emma L.; Simpson, Garth J.

    2011-10-01

    Complementary measurements using SONICC and TPE-UVF allow the sensitive and selective detection of protein crystals. Two-photon excited ultraviolet fluorescence (TPE-UVF) microscopy is explored for sensitive protein-crystal detection as a complement to second-order nonlinear optical imaging of chiral crystals (SONICC). Like conventional ultraviolet fluorescence (UVF), TPE-UVF generates image contrast based on the intrinsic fluorescence of aromatic residues, generally producing higher fluorescence emission within crystals than the mother liquor by nature of the higher local protein concentration. However, TPE-UVF has several advantages over conventional UVF, including (i) insensitivity to optical scattering, allowing imaging in turbid matrices, (ii) direct compatibility with conventional optical plates and windows by using visible light for excitation, (iii) elimination of potentially damaging out-of-plane UV excitation, (iv) improved signal to noise through background reduction from out-of-plane excitation and (v) relatively simple integration into instrumentation developed for SONICC.

  14. Two-photon excited fluorescence emission from hemoglobin

    NASA Astrophysics Data System (ADS)

    Sun, Qiqi; Zeng, Yan; Zhang, Wei; Zheng, Wei; Luo, Yi; Qu, Jianan Y.

    2015-03-01

    Hemoglobin, one of the most important proteins in blood, is responsible for oxygen transportation in almost all vertebrates. Recently, we discovered two-photon excited hemoglobin fluorescence and achieved label-free microvascular imaging based on the hemoglobin fluorescence. However, the mechanism of its fluorescence emission still remains unknown. In this work, we studied the two-photon excited fluorescence properties of the hemoglobin subunits, heme/hemin (iron (II)/(III) protoporphyrin IX) and globin. We first studied the properties of heme and the similar spectral and temporal characteristics of heme and hemoglobin fluorescence provide strong evidence that heme is the fluorophore in hemoglobin. Then we studied the fluorescence properties of hemin, globin and methemoglobin, and found that the hemin may have the main effect on the methemoglobin fluorescence and that globin has tryptophan fluorescence like other proteins. Finally, since heme is a centrosymmetric molecule, that the Soret band fluorescence of heme and hemoglobin was not observed in the single photon process in the previous study may be due to the parity selection rule. The discovery of heme two-photon excited fluorescence may open a new window for heme biology research, since heme as a cofactor of hemoprotein has many functions, including chemical catalysis, electron transfer and diatomic gases transportation.

  15. Widefield multiphoton excited fluorescence microscopy for animal study in vivo

    NASA Astrophysics Data System (ADS)

    Cheng, L.-C.; Chang, C.-Y.; Lin, C.-H.; Su, Y.-D.; Huang, T.-Y.; Chen, S.-J.

    2010-08-01

    Unlike conventional multiphoton excited microscopy according to pixel-by-pixel point scanning, a widefield multiphoton excited microscopy based on spatiotemporal focusing has been developed to construct three-dimensional (3D) multiphoton fluorescence images only with the need of an axial scanning. By implementing a 4.0 W 10 kHz femtosecond laser amplifier with an instant strong peak power and a fast TE-cooled EMCCD camera with an ultra-sensitive fluorescence detection, the multiphoton excited fluorescence images with the excitation area over 100 μm x 100 μm can be achieved at a frame rate up to 80 Hz. A mechanical shutter is utilized to control the exposure time of 1 ms, i.e. average ten laser pulses reach the fluorescent specimen, and hence an uniform enough multiphoton excited fluorescence image can be attained with less photobleaching. The Brownian motion of microbeads and 3D neuron cells of a rat cerebellum have been observed with a lateral spatial resolution of 0.24 μm and an axial resolution of 2.5 μm. Therefore, the developed widefield multiphoton microscopy can provide fast and high-resolution multiphoton excited fluorescence images for animal study in vivo.

  16. Optimal Fluorescence Waveband Determination for Detecting Defective Cherry Tomatoes Using a Fluorescence Excitation-Emission Matrix

    PubMed Central

    Baek, In-Suck; Kim, Moon S.; Lee, Hoosoo; Lee, Wang-Hee; Cho, Byoung-Kwan

    2014-01-01

    A multi-spectral fluorescence imaging technique was used to detect defective cherry tomatoes. The fluorescence excitation and emission matrix was used to measure for defects, sound surface and stem areas to determine the optimal fluorescence excitation and emission wavelengths for discrimination. Two-way ANOVA revealed the optimal excitation wavelength for detecting defect areas was 410 nm. Principal component analysis (PCA) was applied to the fluorescence emission spectra of all regions at 410 nm excitation to determine the emission wavelengths for defect detection. The major emission wavelengths were 688 nm and 506 nm for the detection. Fluorescence images combined with the determined emission wavebands demonstrated the feasibility of detecting defective cherry tomatoes with >98% accuracy. Multi-spectral fluorescence imaging has potential utility in non-destructive quality sorting of cherry tomatoes. PMID:25405507

  17. Fluorescence excitation spectra of all-trans-1,6-diphenylhexatriene conformers: Adiabatic conformer equilibration in the 21Ag state

    NASA Astrophysics Data System (ADS)

    Turek, Andrzej M.; Krishna, Tallapragada S. R.; Brela, Mateusz; Saltiel, Jack

    2016-03-01

    Fluorescence spectra of all-trans-1,6-diphenyl-1,3,5-hexatriene were measured in n-hexadecane at 99 °C by varying λexc in the 294-404 nm range. Resolution of this spectral matrix into s-trans,s-trans and s-cis,s-trans conformer fluorescence spectra yields the λexc dependence of fractional contributions which are converted to conformer specific fluorescence excitation spectra. Conformer absorption spectra obtained from the fluorescence excitation spectra are remarkably similar, but differ significantly from absorption spectra derived from a spectrothermal absorption spectral matrix measured in n-alkanes under isopolarizability conditions. The results reveal substantial conformer equilibration in the excited state. Theory is consistent with adiabatic conformer equilibration in the 21Ag state.

  18. Fluorescence excitation-emission matrix spectroscopy of vitiligo skin in vivo (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Zhao, Jianhua; Richer, Vincent; Al Jasser, Mohammed; Zandi, Soodabeh; Kollias, Nikiforos; Kalia, Sunil; Zeng, Haishan; Lui, Harvey

    2016-02-01

    Fluorescence signals depend on the intensity of the exciting light, the absorption properties of the constituent molecules, and the efficiency with which the absorbed photons are converted to fluorescence emission. The optical features and appearance of vitiligo have been explained primarily on the basis of reduced epidermal pigmentation, which results in abnormal white patches on the skin. The objective of this study is to explore the fluorescence properties of vitiligo and its adjacent normal skin using fluorescence excitation-emission matrix (EEM) spectroscopy. Thirty five (35) volunteers with vitiligo were acquired using a double-grating spectrofluorometer with excitation and emission wavelengths of 260-450 nm and 300-700 nm respectively. As expected, the most pronounced difference between the spectra obtained from vitiligo lesions compared to normally pigmented skin was that the overall fluorescence was much higher in vitiligo; these differences increased at shorter wavelengths, thus matching the characteristic spectral absorption of epidermal melanin. When comparing the fluorescence spectra from vitiligo to normal skin we detected three distinct spectral bands centered at 280nm, 310nm, and 335nm. The 280nm band may possibly be related to inflammation, whereas the 335 nm band may arise from collagen or keratin cross links. The source of the 310 nm band is uncertain; it is interesting to note its proximity to the 311 nm UV lamps used for vitiligo phototherapy. These differences are accounted for not only by changes in epidermal pigment content, but also by other optically active cutaneous biomolecules.

  19. Moving in on the Action: An Experimental Comparison of Fluorescence Excitation and Photodissociation Action Spectroscopy.

    PubMed

    Wellman, Sydney M J; Jockusch, Rebecca A

    2015-06-18

    Photodissociation action spectroscopy is often used as a proxy for measuring gas-phase absorption spectra of ions in a mass spectrometer. Although the potential discrepancy between linear optical and photodissociation spectra is generally acknowledged, direct experimental comparisons are lacking. In this work, we use a quadrupole ion trap that has been modified to enable both photodissociation and laser-induced fluorescence to assess how closely the visible photodissociation action spectrum of a fluorescent dye reflects its fluorescence excitation spectrum. Our results show the photodissociation action spectrum of gaseous rhodamine 110 is both substantially narrower and slightly red-shifted (∼120 cm(-1)) compared to its fluorescence excitation spectrum. Power dependence measurements reveal that the photodissociation of rhodamine 110 requires, on average, the absorption of three photons whereas fluorescence is a single-photon process. These differing power dependences are the key to interpreting the differences in the measured spectra. The experimental results provide much-needed quantification and insight into the differences between action spectra and linear optical spectra, and emphasize the utility of fluorescence excitation spectra to provide a more reliable benchmark for comparison with theory. PMID:26020810

  20. Characterization and measurement results of fluorescence in absorption optical filter glass

    NASA Astrophysics Data System (ADS)

    Reichel, S.; Biertümpfel, R.; Engel, A.

    2015-09-01

    Optical filter glasses (absorption filters) are for example used for spectroscopy. The filter glass absorbs the unwanted light and has a nearly angle independent spectral characteristic. The absorbed light can lead to (self-) fluorescence, i. e. the filter glass itself re-emits fluorescence light at a different wavelength - compared to the incident (excitation) light. This fluorescence light can disturb the measurement signal. In order to obtain an optimized optical design the fluorescence properties of the glasses must be known. By knowing fluorescence properties one can design a system with a good signal-to-noise ratio. We will present our measurement set-up for fluorescence measurements of optical filter glass. This set-up was used to obtain fluorescence measurement results for different optical filter glasses. For the first time we present results on the fluorescence level for different optical filter glasses. In addition the effect of excitation wavelength on the fluorescence level will be studied. Besides other factors, fluorescence depends on impurities of the raw material of the glass melt. Due to small fluctuations of the raw material used for the glass production the fluorescence of the same filter glass type can fluctuate from melt-to-melt. Thus, results from different melts will be shown for the same filter glass type.

  1. Visualization of molecular fluorescence point spread functions via remote excitation switching fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Su, Liang; Lu, Gang; Kenens, Bart; Rocha, Susana; Fron, Eduard; Yuan, Haifeng; Chen, Chang; van Dorpe, Pol; Roeffaers, Maarten B. J.; Mizuno, Hideaki; Hofkens, Johan; Hutchison, James A.; Uji-I, Hiroshi

    2015-02-01

    The enhancement of molecular absorption, emission and scattering processes by coupling to surface plasmon polaritons on metallic nanoparticles is a key issue in plasmonics for applications in (bio)chemical sensing, light harvesting and photocatalysis. Nevertheless, the point spread functions for single-molecule emission near metallic nanoparticles remain difficult to characterize due to fluorophore photodegradation, background emission and scattering from the plasmonic structure. Here we overcome this problem by exciting fluorophores remotely using plasmons propagating along metallic nanowires. The experiments reveal a complex array of single-molecule fluorescence point spread functions that depend not only on nanowire dimensions but also on the position and orientation of the molecular transition dipole. This work has consequences for both single-molecule regime-sensing and super-resolution imaging involving metallic nanoparticles and opens the possibilities for fast size sorting of metallic nanoparticles, and for predicting molecular orientation and binding position on metallic nanoparticles via far-field optical imaging.

  2. Time-resolved Hyperspectral Fluorescence Spectroscopy using Frequency Modulated Excitation

    SciTech Connect

    ,; Neill, M

    2012-07-01

    An intensity-modulated excitation light source is used together with a micro channel plate intensified CCD (ICCD) detector gated at a slightly different frequency to generate a beat frequency from a fluorescent sample. The addition of a spectrograph produces a hyperspectral time-resolved data product where the resulting beat frequency is detected with a low frame rate camera. Measuring the beat frequency of the spectrum as a function of time allows separation of the excited fluorescence from ambient constant light sources. The excitation and detector repetition rates are varied over a range of discrete frequencies, and the phase shift of the beat wave maps out the emission decay rate(s).

  3. Excited state dynamics of brightly fluorescent second generation epicocconone analogues.

    PubMed

    Chatterjee, Soumit; Karuso, Peter; Boulangé, Agathe; Franck, Xavier; Datta, Anindya

    2015-05-21

    The natural product epicocconone, owing to its unique fluorescence properties, has been developed into a range of products used in biotechnology, especially proteomics. However, its weak green fluorescence in its native state, while advantageous for proteomics applications, is a disadvantage in other applications that require two-color readouts. Here we report the photophysical characterization of two brightly fluorescent analogues of epicocconone. These analogues, with naphthyl or pyridyl groups replacing the heptatriene chain, resulted in bright fluorescence in both the native state and the long Stokes shifted enamine. Time-resolved fluorescence studies and DFT calculations were carried out to understand the excited state processes involved in fluorescence. Results showed the p-chloro group on the pyridyl is responsible for the high fluorescence of the native fluorophore. The application of one of these compounds for staining electrophoresis gels is exemplified. PMID:25902354

  4. Fluorescence yields from photodissociative excitation of HCOOH, HCOOCH3, and CH3COOH in the vacuum-ultraviolet region

    NASA Technical Reports Server (NTRS)

    Suto, Masako; Wang, Xiuyan; Lee, L. C.

    1988-01-01

    The photoexcitation processes of HCOOH, HCOOCH3, and CH3COOH were studied in the vacuum-ultraviolet region by using synchroton radiation and a pulsed discharge lamp as light sources. The absorption and fluorescence cross sections of these molecules were measured in the 106-250-nm region. Fluorescences were detected from photoexcitation of HCOOH and HCOOCH3, but not from CH3COOH. Fluorescence produced at 123.9 nm was dispersed and identified as the excited OH and HCOO radicals. Fluorescence quantum yields of HCOOH and HCOOCH3 increase with decreasing excitation wavelengths with maxima of 5 and 0.3 percent at 106 nm, respectively.

  5. High resolution fluorescent bio-imaging with electron beam excitation.

    PubMed

    Kawata, Yoshimasa; Nawa, Yasunori; Inami, Wataru

    2014-11-01

    We have developed electron beam excitation assisted (EXA) optical microscope[1-3], and demonstrated its resolution higher than 50 nm. In the microscope, a light source in a few nanometers size is excited by focused electron beam in a luminescent film. The microscope makes it possible to observe dynamic behavior of living biological specimens in various surroundings, such as air or liquids. Scan speed of the nanometric light source is faster than that in conventional near-field scanning optical microscopes. The microscope enables to observe optical constants such as absorption, refractive index, polarization, and their dynamic behavior on a nanometric scale. The microscope opens new microscopy applications in nano-technology and nano-science.Figure 1(a) shows schematic diagram of the proposed EXA microscope. An electron beam is focused on a luminescent film. A specimen is put on the luminescent film directly. The inset in Fig. 1(a) shows magnified image of the luminescent film and the specimen. Nanometric light source is excited in the luminescent film by the focused electron beam. The nanometric light source illuminates the specimen, and the scattered or transmitted radiation is detected with a photomultiplier tube (PMT). The light source is scanned by scanning of the focused electron beam in order to construct on image. Figure 1(b) shows a luminescence image of the cells acquired with the EXA microscope, and Fig. 1(c) shows a phase contrast microscope image. Cells were observed in culture solution without any treatments, such as fixation and drying. The shape of each cell was clearly recognized and some bright spots were observed in cells. We believe that the bright spots indicated with arrows were auto-fluorescence of intracellular granules and light- grey regions were auto-fluorescence of cell membranes. It is clearly demonstrated that the EXA microscope is useful tool for observation of living biological cells in physiological conditions.jmicro;63/suppl_1/i

  6. Spectral signatures of fluorescence and light absorption to identify crude oils found in the marine environment

    NASA Astrophysics Data System (ADS)

    Baszanowska, E.; Otremba, Z.

    2014-08-01

    To protect the natural marine ecosystem, it is necessary to continuously enhance knowledge of environmental contamination, including oil pollution. Therefore, to properly track the qualitative and quantitative changes in the natural components of seawater, a description of the essential spectral features describing petroleum products is necessary. This study characterises two optically-different types of crude oils (Petrobaltic and Romashkino) - substances belonging to multi-fluorophoric systems. To obtain the spectral features of crude oils, the excitation-emission spectroscopy technique was applied. The fluorescence and light absorption properties for various concentrations of oils at a stabilised temperature are described. Both excitation-emission spectra (EEMs) and absorption spectra of crude oils are discussed. Based on the EEM spectra, both excitation end emission peaks for the wavelengthindependent fluorescence maximum (Exmax/ Emmax) - characteristic points for each type of oil - were identified and compared with the literature data concerning typical marine chemical structures.

  7. Investigation of two-photon absorption properties in new A-D-A compounds emitting blue and yellow fluorescence

    NASA Astrophysics Data System (ADS)

    Jin, Fan; Cai, Zhi-Bin; Huang, Jiu-Qiang; Li, Sheng-Li; Tian, Yu-Peng

    2015-08-01

    Three new acceptor-donor-acceptor compounds (LBQ, DBQ, BYQ) were synthesized and characterized by infrared, hydrogen nuclear magnetic resonance, mass spectrometry and elemental analysis. Their photophysical properties were investigated including linear absorption, single-photon excited fluorescence, fluorescence quantum yield and two-photon absorption. These compounds in CH2Cl2 exhibit good fluorescence quantum yield which are 0.36, 0.26, and 0.25 and the largest two-photon absorption cross-section which are 48, 36, and 181 GM respectively. Under the excitation of Ti: sapphire laser with a pulse width of 140 fs, LBQ and DBQ emit blue two-photon excited fluorescence (TPEF), while BYQ emits bright yellow TPEF. BYQ has a good solubility in water and the σ can be as large as 130 GM, so it shows promising applications in many pharmaceutical and biological fields.

  8. Enhancement of resonant absorption through excitation of SPR

    NASA Astrophysics Data System (ADS)

    Giulietti, Danilo; Calcagno, L.; Curcio, Alessandro; Cutroneo, M.; Galletti, Mario; Skala, J.; Torrisi, L.; Zimbone, M.

    2016-09-01

    In this experiment the absorption of the laser radiation impinging on polymeric films with Au nanoparticles implanted in surface was studied. By varying the polarization and the incidence angle of the laser radiation on target, the role in the laser absorption of both excitation of surface plasmons and excitation of electronic plasma waves at critical density through resonant absorption was highlighted. In conditions of p-polarized laser irradiations at 1015 W /cm2 intensity, resonant absorption can be induced in films enhancing proton and ion acceleration. Plasma on-line diagnostics is based on SiC detectors. Measurements of kinetic energy of accelerated ions indicate a significant increment using p-polarized laser light with respect to no-polarized light irradiation.

  9. Investigation of two-photon absorption induced excited state absorption in a fluorenyl-based chromophore.

    PubMed

    Li, Changwei; Yang, Kun; Feng, Yan; Su, Xinyan; Yang, Junyi; Jin, Xiao; Shui, Min; Wang, Yuxiao; Zhang, Xueru; Song, Yinglin; Xu, Hongyao

    2009-12-01

    Two-photon absorption induced excited state absorption in the solution of a new fluorenyl-based chromophore is investigated by a time-resolved pump-probe technique using femtosecond pulses. With the help of an additional femtosecond open-aperture Z-scan technique, numerical simulations based on a three-energy level model are used to interpret the experimental results, and we determine the nonlinear optical parameters of this new chromophore uniquely. Large two-photon absorption cross section and excited state absorption cross section for singlet excited state are obtained, indicating a good candidate for optical limiting devices. Moreover, the influence of two-beam coupling induced energy transfer in neat N,N'-dimethylformamide solvent is also considered, although this effect is strongly restrained by the instantaneous two-photon absorption. PMID:19894682

  10. Failure of Energy Transfer between Identical Aromatic Molecules on Excitation at the Long Wave Edge of the Absorption Spectrum

    PubMed Central

    Weber, Gregorio; Shinitzky, Meir

    1970-01-01

    Electronic energy transfer among identical molecules has been followed by the depolarization of the fluorescence in concentrated solutions as well as in dimers, polymers, and micelle systems. In the many aromatic fluorophores examined, unlike a few nonaromatic ones, transfer is much decreased or altogether undetectable on excitation at the red edge of the absorption spectrum. The phenomenon is not due to the transfer taking place during a small fraction of the total fluorescence lifetime, nor is it explainable by a decrease in overlap of absorption and emission upon edge excitation. PMID:16591825

  11. Fluorescence from VUV excitation of formaldehyde

    NASA Technical Reports Server (NTRS)

    Suto, Masako; Wang, Xiuyan; Lee, L. C.

    1986-01-01

    The 105-180-nm photoabsorption and fluorescence cross sections of H2CO are determined experimentally using a synchrotron-radiation light source and the apparatus described by Lee (1980). The results are presented in tables and graphs and discussed. VUV emission with threshold wavelength 140.3 nm is detected and attributed to the A 1Pi - X 1Sigma(+) system of CO, and UV emission from the HCO (B-X) system is found below a 147.5-nm threshold, the H-HCO dissociation energy having an upper limit of 3.61 + or - 0.03 eV. At 116 nm, the maximum quantum yields of the VUV and UV fluorescences are about 1.6 and 0.23 percent, respectively.

  12. Transient absorption spectroscopy detection of sensitized delayed fluorescence in chiral benzophenone/naphthalene systems

    NASA Astrophysics Data System (ADS)

    Bonancía, Paula; Jiménez, M. Consuelo; Miranda, Miguel A.

    2011-10-01

    Transient absorption spectroscopy has proven to be a powerful tool to investigate the formation and decay of excited singlet states upon triplet-triplet annihilation, following T-T energy transfer from a selectively excited sensitizer. Thus, upon selective excitation of benzophenone (BZP) by laser flash photolysis (LFP) at λ = 355 nm in the presence of naphthalene (NPT), a negative band centered at 340 nm has been detected, with growth and decay in the microsecond timescale. It has been assigned to the P-type NPT delayed-fluorescence. In the case of chiral BZP/NPT systems, stereodifferentiation has been observed in the kinetics of the involved photophysical processes.

  13. Vibronic Structures in Absorption and Fluorescence Spectra of Firefly Oxyluciferin in Aqueous Solutions.

    PubMed

    Hiyama, Miyabi; Noguchi, Yoshifumi; Akiyama, Hidefumi; Yamada, Kenta; Koga, Nobuaki

    2015-01-01

    To elucidate the factors determining the spectral shapes and widths of the absorption and fluorescence spectra for keto and enol oxyluciferin and their conjugate bases in aqueous solutions, the intensities of vibronic transitions between their ground and first electronic excited states were calculated for the first time via estimation of the vibrational Franck-Condon factors. The major normal modes, overtones and combination tones in absorption and fluorescence spectra are similar for all species. The theoretical full widths at half maximum of absorption spectra are 0.4-0.7 eV and those for the fluorescence spectra are 0.4-0.5 eV, except for phenolate-keto that exhibits exceptionally sharp peak widths due to the dominance of the 0-0' or 0'-0 band. These spectral shapes and widths explain many relevant features of the experimentally observed spectra. PMID:25946599

  14. Far wing depolarization of light - Generalized absorption profiles. [in laser fluorescence spectroscopy of Sr vapor

    NASA Technical Reports Server (NTRS)

    Thomann, P.; Burnett, K.; Cooper, J.

    1981-01-01

    An absorption (and/or emission) event which takes place during a strong collision is called a 'correlated event'. It is discussed how correlated events affect the far red wing depolarization of fluorescence. Attention is given to an atomic vapor which is irradiated by linearly polarized light of a frequency on the red side of the resonance line. Two limiting cases are considered, corresponding to excitation in the impact region and in the quasi-static wing. In the quasi-static wing, absorption of a photon followed by fluorescence (rather than Rayleigh scattering), occurs mostly during a collision. Correlated events dominate the scattering process. Expressions derived for the polarization of the fluorescent light are applied to far red wing depolarization. It is found that the polarization of the fluorescent light does not go to zero in the far wing, but depends crucially on the detailed nature of the anisotropy in the long-range part of the interatomic potential.

  15. Mechanism of two-photon excited hemoglobin fluorescence emission

    NASA Astrophysics Data System (ADS)

    Sun, Qiqi; Zheng, Wei; Wang, Jiannong; Luo, Yi; Qu, Jianan Y.

    2015-10-01

    Hemoglobin, one of the most important proteins in the human body, is composed of "heme" groups (iron-containing rings) and "globins" (proteins). We investigate the two-photon excited fluorescence of hemoglobin and its subunit components (heme and globin). We measure the hemoglobin fluorescence lifetime by using a streak camera of ps resolution and confirm that its lifetime is in femtosecond scale. In the study of the fluorescence properties of heme and globin, the experimental results reveal that heme is the sole fluorophore of hemoglobin. Hemoglobin fluorescence can be effectively excited only via two-photon process, because heme has a centrosymmetric molecular structure and two-photon allowed transition is forbidden for single-photon process and vice versa due to the Laporte parity selection rule.

  16. Mechanism of two-photon excited hemoglobin fluorescence emission.

    PubMed

    Sun, Qiqi; Zheng, Wei; Wang, Jiannong; Luo, Yi; Qu, Jianan Y

    2015-10-01

    Hemoglobin, one of the most important proteins in the human body, is composed of “heme” groups (iron-containing rings) and “globins” (proteins). We investigate the two-photon excited fluorescence of hemoglobin and its subunit components (heme and globin). We measure the hemoglobin fluorescence lifetime by using a streak camera of ps resolution and confirm that its lifetime is in femtosecond scale. In the study of the fluorescence properties of heme and globin, the experimental results reveal that heme is the sole fluorophore of hemoglobin. Hemoglobin fluorescence can be effectively excited only via two-photon process, because heme has a centrosymmetric molecular structure and two-photon allowed transition is forbidden for single-photon process and vice versa due to the Laporte parity selection rule. PMID:26506468

  17. Development of laser excited atomic fluorescence and ionization methods

    SciTech Connect

    Winefordner, J.D.

    1991-01-01

    Progress report: May 1, 1988 to December 31, 1991. The research supported by DE-FG05-88ER13881 during the past (nearly) 3 years can be divided into the following four categories: (1) theoretical considerations of the ultimate detection powers of laser fluorescence and laser ionization methods; (2) experimental evaluation of laser excited atomic fluorescence; (3) fundamental studies of atomic and molecular parameters in flames and plasmas; (4) other studies.

  18. Fluorescence spectroscopy of excitation transfer in Photosystem 1

    SciTech Connect

    Mukerji, I.

    1990-12-01

    This thesis centers on the study of excitation transfer in a photosynthetic antenna array. The spectroscopic properties of two pigment-protein complexes were investigated. These complexes, isolated from higher plants, display an unusual temperature dependent fluorescence behavior. The author have chosen to study this fluorescence behavior with respect to energy transfer to the reaction center and in an isolated intact antenna preparation. A Photosystem 1 complex, PSI-200, was isolated from spinach. We have characterized this system by both steady state and time-resolved fluorescence spectroscopy. Fluorescence polarization measurements indicate that this emission arises from pigments which absorb in the long wavelength region of the spectrum and comprise a relatively small portion of the antenna population. Comparison of spectral characteristics were made with a PSI complex isolated from the thermophilic cyanobacterium, Synechococcus, sp. To address the role of Chl b in stimulating long wavelength fluorescence and the temperature dependence of the system, we have studied the energy transfer dynamics in an antenna complex, LHC-I isolated from PSI-200. Kinetic measurements indicate that initially absorbed excitation is rapidly redistributed to longer wavelength emitting pigments within 40 ps. The temperature dependence of F685 results from increased back transfer from long wavelength emitters to F685. We suggest that changes in excitation transfer between the various emitting species and a non-radiative fluorescence quenching mechanism account for the temperature dependence of the system. 144 refs., 50 figs., 3 tabs.

  19. Photon statistics of atomic fluorescence after {pi}-pulse excitation

    SciTech Connect

    Yoshimi, Kazuyoshi; Koshino, Kazuki

    2010-09-15

    The photon statistics of atomic fluorescence after {pi}-pulse excitation is investigated in a system in which the input and output ports are connected to an atom. Since spontaneous decay during input pulse excitation occurs, the output pulse generally contains a multiphoton component with a certain probability. We quantitatively evaluate the probability of the output pulse containing multiple photons and determine the conditions for ideal single-photon generation.

  20. Neuron absorption study and mid-IR optical excitations

    NASA Astrophysics Data System (ADS)

    Guo, Dingkai; Chen, Xing; Vadala, Shilpa; Leach, Jennie; Kostov, Yordan; Bewley, William W.; Kim, Chul-Soo; Kim, Mijin; Canedy, Chadwick L.; Merritt, Charles D.; Vurgaftman, Igor; Meyer, Jerry R.; Choa, Fow-Sen

    2012-02-01

    Neuronal optical excitation can provide non-contacting tools to explore brain circuitry and a durable stimulation interface for cardiac pacing and visual as well as auditory sensory neuronal stimulation. To obtain accurate absorption spectra, we scan the transmission of neurons in cell culture medium, and normalize it by subtracting out the absorption spectrum of the medium alone. The resulting spectra show that the main neuronal absorption peaks are in the 3000- 6000nm band, although there is a smaller peak near 1450nm. By coupling the output of a 3μm interband cascade laser (ICL) into a mid-IR fluorozirconate fiber, we can effectively deliver more than 1J/cm2 photon intensity to the excitation site for neuronal stimulation.

  1. Excitation dynamics in Phycoerythrin 545: modeling of steady-state spectra and transient absorption with modified Redfield theory.

    PubMed

    Novoderezhkin, Vladimir I; Doust, Alexander B; Curutchet, Carles; Scholes, Gregory D; van Grondelle, Rienk

    2010-07-21

    We model the spectra and excitation dynamics in the phycobiliprotein antenna complex PE545 isolated from the unicellular photosynthetic cryptophyte algae Rhodomonas CS24. The excitonic couplings between the eight bilins are calculated using the CIS/6-31G method. The site energies are extracted from a simultaneous fit of the absorption, circular dichroism, fluorescence, and excitation anisotropy spectra together with the transient absorption kinetics using the modified Redfield approach. Quantitative fit of the data enables us to assign the eight exciton components of the spectra and build up the energy transfer picture including pathways and timescales of energy relaxation, thus allowing a visualization of excitation dynamics within the complex. PMID:20643051

  2. A search for molecular hydrogen fluorescence near 100 km. [excitation by solar extreme UV radiation

    NASA Technical Reports Server (NTRS)

    Feldman, P. D.; Takacs, P. Z.

    1975-01-01

    The fluorescence of H2 in the Lyman band system, excited by solar extreme ultraviolet radiation, provides a means for the optical detection of H2 in the upper atmosphere. In particular, the Ly beta line of hydrogen is nearly degenerate with the (6,0) P1 transition, and absorption in this line produces fluorescence in the v-prime = 6 progression, principally at 1265, 1366, 1462 and 1608 A. Absorption by O2 rapidly attenuates the Ly beta from an overhead sun below 100 km and also significantly attenuates the fluorescent radiation. Far-ultraviolet dayglow spectra from 1130 to 1510 A obtained from an Aerobee rocket experiment on 11 December 1972 give an upper limit for any H2 emission which is a factor of 5 higher than expected according to recent hydrogen models.

  3. Double-excitation fluorescence spectral imaging: eliminating tissue auto-fluorescence from in vivo PPIX measurements

    NASA Astrophysics Data System (ADS)

    Torosean, Sason; Flynn, Brendan; Samkoe, Kimberley S.; Davis, Scott C.; Gunn, Jason; Axelsson, Johan; Pogue, Brian W.

    2012-02-01

    An ultrasound coupled handheld-probe-based optical fluorescence molecular tomography (FMT) system has been in development for the purpose of quantifying the production of Protoporphyrin IX (PPIX) in aminolevulinic acid treated (ALA), Basal Cell Carcinoma (BCC) in vivo. The design couples fiber-based spectral sampling of PPIX fluorescence emission with a high frequency ultrasound imaging system, allowing regionally localized fluorescence intensities to be quantified [1]. The optical data are obtained by sequential excitation of the tissue with a 633nm laser, at four source locations and five parallel detections at each of the five interspersed detection locations. This method of acquisition permits fluorescence detection for both superficial and deep locations in ultrasound field. The optical boundary data, tissue layers segmented from ultrasound image and diffusion theory are used to estimate the fluorescence in tissue layers. To improve the recovery of the fluorescence signal of PPIX, eliminating tissue autofluorescence is of great importance. Here the approach was to utilize measurements which straddled the steep Qband excitation peak of PPIX, via the integration of an additional laser source, exciting at 637 nm; a wavelength with a 2 fold lower PPIX excitation value than 633nm.The auto-fluorescence spectrum acquired from the 637 nm laser is then used to spectrally decouple the fluorescence data and produce an accurate fluorescence emission signal, because the two wavelengths have very similar auto-fluorescence but substantially different PPIX excitation levels. The accuracy of this method, using a single source detector pair setup, is verified through animal tumor model experiments, and the result is compared to different methods of fluorescence signal recovery.

  4. Fourier transform two-dimensional fluorescence excitation spectrometer by using tandem Fabry-Pérot interferometer

    NASA Astrophysics Data System (ADS)

    Anzai, Hiroshi; Joshi, Neeraj Kumar; Fuyuki, Masanori; Wada, Akihide

    2015-01-01

    A Fourier transform two-dimensional fluorescence excitation spectrometer (FT-2DFES) was developed based on the multiplex technique using a tandem Fabry-Pérot interferometer (tandem FPI). In addition to the advantage of the multiplex technique, the main advantage of the tandem FPI is applicable to the modulation of transition with a large absorption bandwidth (larger than 100 nm) and is thus applicable to the modulation of the excitation of molecules in the condensed phase. As a demonstration of the effectiveness of FT-2DFES, we succeeded in separately observing the fluorescence excitation peaks from a mixed methanol solution of laser dyes (coumarin 480, rhodamine 6G, DCM (4-dicyanomethylene-2-methyl-6-(p-(dimethylamino)styryl)-4H-pyran), and LDS750). Furthermore, the energy transfer from rhodamine 6G to LDS750 was observed.

  5. The excited-state chemistry of protochlorophyllide a: a time-resolved fluorescence study.

    PubMed

    Dietzek, Benjamin; Kiefer, Wolfgang; Yartsev, Arkady; Sundström, Villy; Schellenberg, Peter; Grigaravicius, Paulius; Hermann, Gudrun; Popp, Jürgen; Schmitt, Michael

    2006-08-11

    The excited-state processes of protochlorophyllide a, the precursor of chlorophyll a in chlorophyll biosynthesis, are studied using picosecond time-resolved fluorescence spectroscopy. Following excitation into the Soret band, two distinct fluorescence components, with emission maxima at 640 and 647 nm, are observed. The 640 nm emitting component appears within the time resolution of the experiment and then decays with a time constant of 27 ps. In contrast, the 647 nm emitting component is built up with a 3.5 ps rise time and undergoes a subsequent decay with a time constant of 3.5 ns. The 3.5 ps rise kinetics are attributed to relaxations in the electronically excited state preceding the nanosecond fluorescence, which is ascribed to emission out of the thermally equilibrated S(1) state. The 27 ps fluorescence, which appears within the experimental response of the streak camera, is suggested to originate from a second minimum on the excited-state potential-energy surface. The population of the secondary excited state is suggested to reflect a very fast motion out of the Franck-Condon region along a reaction coordinate different from the one connecting the Franck-Condon region with the S(1) potential-energy minimum. The 27 ps-component is an emissive intermediate on the reactive excited-state pathway, as its decay yields the intermediate photoproduct, which has been identified previously (J. Phys. Chem. B 2006, 110, 4399-4406). No emission of the photoproduct is observed. The results of the time-resolved fluorescence study allow a detailed spectral characterization of the emission of the excited states in protochlorophyllide a, and the refinement of the kinetic model deduced from ultrafast absorption measurements. PMID:16841352

  6. Integrated ultrasonic particle positioning and low excitation light fluorescence imaging

    SciTech Connect

    Bernassau, A. L.; Al-Rawhani, M.; Beeley, J.; Cumming, D. R. S.

    2013-12-09

    A compact hybrid system has been developed to position and detect fluorescent micro-particles by combining a Single Photon Avalanche Diode (SPAD) imager with an acoustic manipulator. The detector comprises a SPAD array, light-emitting diode (LED), lenses, and optical filters. The acoustic device is formed of multiple transducers surrounding an octagonal cavity. By stimulating pairs of transducers simultaneously, an acoustic landscape is created causing fluorescent micro-particles to agglomerate into lines. The fluorescent pattern is excited by a low power LED and detected by the SPAD imager. Our technique combines particle manipulation and visualization in a compact, low power, portable setup.

  7. Integrated ultrasonic particle positioning and low excitation light fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Bernassau, A. L.; Al-Rawhani, M.; Beeley, J.; Cumming, D. R. S.

    2013-12-01

    A compact hybrid system has been developed to position and detect fluorescent micro-particles by combining a Single Photon Avalanche Diode (SPAD) imager with an acoustic manipulator. The detector comprises a SPAD array, light-emitting diode (LED), lenses, and optical filters. The acoustic device is formed of multiple transducers surrounding an octagonal cavity. By stimulating pairs of transducers simultaneously, an acoustic landscape is created causing fluorescent micro-particles to agglomerate into lines. The fluorescent pattern is excited by a low power LED and detected by the SPAD imager. Our technique combines particle manipulation and visualization in a compact, low power, portable setup.

  8. Orthogonal spectra and cross sections: Application to optimization of multi-spectral absorption and fluorescence lidar

    SciTech Connect

    Shokair, I.R.

    1997-09-01

    This report addresses the problem of selection of lidar parameters, namely wavelengths for absorption lidar and excitation fluorescence pairs for fluorescence lidar, for optimal detection of species. Orthogonal spectra and cross sections are used as mathematical representations which provide a quantitative measure of species distinguishability in mixtures. Using these quantities, a simple expression for the absolute error in calculated species concentration is derived and optimization is accomplished by variation of lidar parameters to minimize this error. It is shown that the optimum number of wavelengths for detection of a species using absorption lidar (excitation fluorescence pairs for fluorescence lidar) is the same as the number of species in the mixture. Each species present in the mixture has its own set of optimum wavelengths. There is usually some overlap in these sets. The optimization method is applied to two examples, one using absorption and the other using fluorescence lidar, for analyzing mixtures of four organic compounds. The effect of atmospheric attenuation is included in the optimization process. Although the number of optimum wavelengths might be small, it is essential to do large numbers of measurements at these wavelengths in order to maximize canceling of statistical errors.

  9. Optimizing ultrafast illumination for multiphoton-excited fluorescence imaging.

    PubMed

    Stoltzfus, Caleb R; Rebane, Aleksander

    2016-05-01

    We study the optimal conditions for high throughput two-photon excited fluorescence (2PEF) and three-photon excited fluorescence (3PEF) imaging using femtosecond lasers. We derive relations that allow maximization of the rate of imaging depending on the average power, pulse repetition rate, and noise characteristics of the laser, as well as on the size and structure of the sample. We perform our analysis using ~100 MHz, ~1 MHz and 1 kHz pulse rates and using both a tightly-focused illumination beam with diffraction-limited image resolution, as well loosely focused illumination with a relatively low image resolution, where the latter utilizes separate illumination and fluorescence detection beam paths. Our theoretical estimates agree with the experiments, which makes our approach especially useful for optimizing high throughput imaging of large samples with a field-of-view up to 10x10 cm(2). PMID:27231620

  10. Optimizing ultrafast illumination for multiphoton-excited fluorescence imaging

    PubMed Central

    Stoltzfus, Caleb R.; Rebane, Aleksander

    2016-01-01

    We study the optimal conditions for high throughput two-photon excited fluorescence (2PEF) and three-photon excited fluorescence (3PEF) imaging using femtosecond lasers. We derive relations that allow maximization of the rate of imaging depending on the average power, pulse repetition rate, and noise characteristics of the laser, as well as on the size and structure of the sample. We perform our analysis using ~100 MHz, ~1 MHz and 1 kHz pulse rates and using both a tightly-focused illumination beam with diffraction-limited image resolution, as well loosely focused illumination with a relatively low image resolution, where the latter utilizes separate illumination and fluorescence detection beam paths. Our theoretical estimates agree with the experiments, which makes our approach especially useful for optimizing high throughput imaging of large samples with a field-of-view up to 10x10 cm2. PMID:27231620

  11. Development of a confocal laser scanning fluorescence microscope using two-photon excitation in combination with time-gated detection

    NASA Astrophysics Data System (ADS)

    Sytsma, Joost; Vroom, Jurrien; Gerritsen, Hans C.; Levine, Yehudi K.

    1995-03-01

    Fluorescent molecules having single-photon absorption in the blue and the UV can be excited with infra-red light via a process known as two-photon excitation. The combination of this technique with scanning techniques can be exploited for 3D microscopic imaging. The two- photon process is confined to a restricted volume in the sample determined by the laser focus, resulting in inherent confocality. Other advantages are reduced photo-bleaching of the samples and a larger penetration depth of the excitation light. The implementation of time-gated detection techniques allows fluorescent lifetime imaging. This drastically improves the selectivity and contrast of the images.

  12. Nanoparticle metrology in sol-gels using multiphoton excited fluorescence

    NASA Astrophysics Data System (ADS)

    Karolin, J.; Geddes, C. D.; Wynne, K.; Birch, D. J. S.

    2002-01-01

    We have developed a method of measuring the growth of nanoparticles during sol-gel glass formation based on labelling the particle with a fluorescent dye and determining the multiphoton excited decay of fluorescence anisotropy due to Brownian rotation. Multiphoton excitation is shown to give a higher dynamic range of measurement than one-photon excitation. We illustrate the sub-nanometre resolution and stability of our approach by detecting a 0.8-1.1 nm silica particle hydrodynamic mean radius increase in a tetramethylorthosilicate sol at pH 2.3 labelled with rhodamine 6G and observed over ≈4 weeks and also with a stable silica colloid of radius 6 nm, pH 8.9, labelled with a 6-methoxyquinoline-type dye.

  13. Anti-Stokes Fluorescent Probe with Incoherent Excitation

    PubMed Central

    Li, Yang; Zhou, Shifeng; Dong, Guoping; Peng, Mingying; Wondraczek, Lothar; Qiu, Jianrong

    2014-01-01

    Although inorganic anti-Stokes fluorescent probes have long been developed, the operational mode of today's most advanced examples still involves the harsh requirement of coherent laser excitation, which often yields unexpected light disturbance or even photon-induced deterioration during optical imaging. Here, we demonstrate an efficient anti-Stokes fluorescent probe with incoherent excitation. We show that the probe can be operated under light-emitting diode excitation and provides tunable anti-Stokes energy shift and decay kinetics, which allow for rapid and deep tissue imaging over a very large area with negligible photodestruction. Charging of the probe can be achieved by either X-rays or ultraviolet-visible light irradiation, which enables multiplexed detection and function integration with standard X-ray medical imaging devices. PMID:24518662

  14. Absorption Reconstruction Improves Biodistribution Assessment of Fluorescent Nanoprobes Using Hybrid Fluorescence-mediated Tomography

    PubMed Central

    Gremse, Felix; Theek, Benjamin; Kunjachan, Sijumon; Lederle, Wiltrud; Pardo, Alessa; Barth, Stefan; Lammers, Twan; Naumann, Uwe; Kiessling, Fabian

    2014-01-01

    Aim: Fluorescence-mediated tomography (FMT) holds potential for accelerating diagnostic and theranostic drug development. However, for proper quantitative fluorescence reconstruction, knowledge on optical scattering and absorption, which are highly heterogeneous in different (mouse) tissues, is required. We here describe methods to assess these parameters using co-registered micro Computed Tomography (µCT) data and nonlinear whole-animal absorption reconstruction, and evaluate their importance for assessment of the biodistribution and target site accumulation of fluorophore-labeled drug delivery systems. Methods: Besides phantoms with varying degrees of absorption, mice bearing A431 tumors were imaged 15 min and 48 h after i.v. injection of a fluorophore-labeled polymeric drug carrier (pHPMA-Dy750) using µCT-FMT. The outer shape of mice and a scattering map were derived using automated segmentation of the µCT data. Furthermore, a 3D absorption map was reconstructed from the trans-illumination data. We determined the absorption of five interactively segmented regions (heart, liver, kidney, muscle, tumor). Since blood is the main near-infrared absorber in vivo, the absorption was also estimated from the relative blood volume (rBV), determined by contrast-enhanced µCT. We compared the reconstructed absorption with the rBV-based values and analyzed the effect of using the absorption map on the fluorescence reconstruction. Results: Phantom experiments demonstrated that absorption reconstruction is possible and necessary for quantitative fluorescence reconstruction. In vivo, the reconstructed absorption showed high values in strongly blood-perfused organs such as the heart, liver and kidney. The absorption values correlated strongly with the rBV-based absorption values, confirming the accuracy of the absorption reconstruction. Usage of homogenous absorption instead of the reconstructed absorption map resulted in reduced values in the heart, liver and kidney, by

  15. Fluorescence upconversion properties of a class of improved pyridinium dyes induced by two-photon absorption

    NASA Astrophysics Data System (ADS)

    Xu, Guibao; Hu, Dawei; Zhao, Xian; Shao, Zongshu; Liu, Huijun; Tian, Yupeng

    2007-06-01

    We report the fluorescence upconversion properties of a class of improved pyridinium toluene- p-sulfonates having donor- π-acceptor (D- π-A) structure under two-photon excitation at 1064 nm. The experimental results show that both the two-photon excited (TPE) fluorescence lifetime and the two-photon pumped (TPP) energy upconversion efficiency were increased with the enhancement of electron-donating capability of the donor in the molecule. It is also indicated that an overlong alkyl group tends to result in a weakened molecular conjugation, leading to a decreased two-photon absorption (TPA) cross section. By choosing the donor, we can obtain a longest fluorescence lifetime of 837 ps, a highest energy upconversion efficiency of ˜6.1%, and a maximum TPA cross-section of 8.74×10 -48 cm 4 s/photon in these dyes.

  16. Photodissociation of vibrationally excited water in the first absorption band

    NASA Astrophysics Data System (ADS)

    Weide, Klaus; Hennig, Steffen; Schinke, Reinhard

    1989-12-01

    We investigate the photodissociation of highly excited vibrational states of water in the first absorption band. The calculation includes an ab initio potential energy surface for the Östate and an ab initio X˜→Ã transition dipole function. The bending angle is fixed at the equilibrium value within the ground electronic state. Most interesting is the high sensitivity of the final vibrational distribution of OH on the initially prepared vibrational state of H2 O. At wavelengths near the onset of the absorption spectrum the vibrational state distribution can be qualitatively understood as a Franck-Condon mapping of the initial H2 O wave function. At smaller wavelengths final state interaction in the excited state becomes stronger and the distributions become successively broader. Our calculations are in satisfactory accord with recent measurements of Vander Wal and Crim.

  17. Unmixing multiple adjacent fluorescent targets with multispectral excited fluorescence molecular tomography.

    PubMed

    Zhou, Yuan; Guang, Huizhi; Pu, Huangsheng; Zhang, Jiulou; Luo, Jianwen

    2016-06-20

    Fluorescence molecular tomography (FMT) can visualize biological activities at cellular and molecular levels in vivo, and has been extensively used in drug delivery and tumor detection research of small animals. The ill-posedness of the FMT inverse problem makes it difficult to reconstruct and unmix multiple adjacent fluorescent targets that have different functional features but are labeled with the same fluorochrome. A method based on independent component analysis for multispectral excited FMT was proposed in our previous study. It showed that double fluorescent targets with certain edge-to-edge distance (EED) could be unmixed by the method. In this study, the situation is promoted to unmix multiple adjacent fluorescent targets (i.e., more than two fluorescent targets and EED=0). Phantom experiments on the resolving ability of the proposed algorithm demonstrate that the algorithm performs well in unmixing multiple adjacent fluorescent targets in both lateral and axial directions. And also, we recovered the locational information of each independent fluorescent target and described the variable trends of the corresponding fluorescent targets under the excitation spectrum. This method is capable of unmixing multiple fluorescent targets with small EED but labeled with the same fluorochrome, and may be used in imaging of nonspecific probe targeting and metabolism of drugs. PMID:27409108

  18. Small fluorescence-activating and absorption-shifting tag for tunable protein imaging in vivo

    PubMed Central

    Plamont, Marie-Aude; Billon-Denis, Emmanuelle; Maurin, Sylvie; Gauron, Carole; Pimenta, Frederico M.; Specht, Christian G.; Shi, Jian; Quérard, Jérôme; Pan, Buyan; Rossignol, Julien; Moncoq, Karine; Morellet, Nelly; Volovitch, Michel; Lescop, Ewen; Chen, Yong; Triller, Antoine; Vriz, Sophie; Le Saux, Thomas; Jullien, Ludovic; Gautier, Arnaud

    2016-01-01

    This paper presents Yellow Fluorescence-Activating and absorption-Shifting Tag (Y-FAST), a small monomeric protein tag, half as large as the green fluorescent protein, enabling fluorescent labeling of proteins in a reversible and specific manner through the reversible binding and activation of a cell-permeant and nontoxic fluorogenic ligand (a so-called fluorogen). A unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, provides high labeling selectivity. Y-FAST was engineered from the 14-kDa photoactive yellow protein by directed evolution using yeast display and fluorescence-activated cell sorting. Y-FAST is as bright as common fluorescent proteins, exhibits good photostability, and allows the efficient labeling of proteins in various organelles and hosts. Upon fluorogen binding, fluorescence appears instantaneously, allowing monitoring of rapid processes in near real time. Y-FAST distinguishes itself from other tagging systems because the fluorogen binding is highly dynamic and fully reversible, which enables rapid labeling and unlabeling of proteins by addition and withdrawal of the fluorogen, opening new exciting prospects for the development of multiplexing imaging protocols based on sequential labeling. PMID:26711992

  19. Small fluorescence-activating and absorption-shifting tag for tunable protein imaging in vivo.

    PubMed

    Plamont, Marie-Aude; Billon-Denis, Emmanuelle; Maurin, Sylvie; Gauron, Carole; Pimenta, Frederico M; Specht, Christian G; Shi, Jian; Quérard, Jérôme; Pan, Buyan; Rossignol, Julien; Moncoq, Karine; Morellet, Nelly; Volovitch, Michel; Lescop, Ewen; Chen, Yong; Triller, Antoine; Vriz, Sophie; Le Saux, Thomas; Jullien, Ludovic; Gautier, Arnaud

    2016-01-19

    This paper presents Yellow Fluorescence-Activating and absorption-Shifting Tag (Y-FAST), a small monomeric protein tag, half as large as the green fluorescent protein, enabling fluorescent labeling of proteins in a reversible and specific manner through the reversible binding and activation of a cell-permeant and nontoxic fluorogenic ligand (a so-called fluorogen). A unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, provides high labeling selectivity. Y-FAST was engineered from the 14-kDa photoactive yellow protein by directed evolution using yeast display and fluorescence-activated cell sorting. Y-FAST is as bright as common fluorescent proteins, exhibits good photostability, and allows the efficient labeling of proteins in various organelles and hosts. Upon fluorogen binding, fluorescence appears instantaneously, allowing monitoring of rapid processes in near real time. Y-FAST distinguishes itself from other tagging systems because the fluorogen binding is highly dynamic and fully reversible, which enables rapid labeling and unlabeling of proteins by addition and withdrawal of the fluorogen, opening new exciting prospects for the development of multiplexing imaging protocols based on sequential labeling. PMID:26711992

  20. Two-color two-photon excited fluorescence of indole: Determination of wavelength-dependent molecular parameters

    NASA Astrophysics Data System (ADS)

    Herbrich, Sebastian; Al-Hadhuri, Tawfik; Gericke, Karl-Heinz; Shternin, Peter S.; Smolin, Andrey G.; Vasyutinskii, Oleg S.

    2015-01-01

    We present a detailed study of two-color two-photon excited fluorescence in indole dissolved in propylene glycol. Femtosecond excitation pulses at effective wavelengths from 268 to 293.33 nm were used to populate the two lowest indole excited states 1La and 1Lb and polarized fluorescence was then detected. All seven molecular parameters and the two-photon polarization ratio Ω containing information on two-photon absorption dynamics, molecular lifetime τf, and rotation correlation time τrot have been determined from experiment and analyzed as a function of the excitation wavelength. The analysis of the experimental data has shown that 1Lb-1La inversion occurred under the conditions of our experiment. The two-photon absorption predominantly populated the 1La state at all excitation wavelengths but in the 287-289 nm area which contained an absorption hump of the 1Lb state 0-0 origin. The components of the two-photon excitation tensor S were analyzed giving important information on the principal tensor axes and absorption symmetry. The results obtained are in a good agreement with the results reported by other groups. The lifetime τf and the rotation correlation time τrot showed no explicit dependence on the effective excitation wavelength. Their calculated weighted average values were found to be τf = 3.83 ± 0.14 ns and τrot = 0.74 ± 0.06 ns.

  1. Biocompound detection through fluorescence excitation-emission matrix analysis

    NASA Astrophysics Data System (ADS)

    Twede, David R.; Sanders, Lee C.; Wagner, Michael L.

    2004-01-01

    The excitation-emission matrix (EEM) is the luminescence spectral emission intensity of fluorescent compounds as a function of the excitation wavelength. EEMs offer the promise of an additional degree of information for enhanced compound detection and identification. Veridian has collected pure-component EEMs of amino acids (Trp, Phe, Tyr), Bacillus globigii (bg), Bacillus thuringiensis (bt,), and selected backgrounds. Also collected were EEMs of mixtures of amino acids and of bg in solution with a few backgrounds. The EEMs of pure components and mixtures were analyzed for phenomenology and for potential methods of unmixing and identifying the constituents of EEMs having mixed components of a similar nature.

  2. Biocompound detection through fluorescence excitation-emission matrix analysis

    NASA Astrophysics Data System (ADS)

    Twede, David R.; Sanders, Lee C.; Wagner, Michael L.

    2003-12-01

    The excitation-emission matrix (EEM) is the luminescence spectral emission intensity of fluorescent compounds as a function of the excitation wavelength. EEMs offer the promise of an additional degree of information for enhanced compound detection and identification. Veridian has collected pure-component EEMs of amino acids (Trp, Phe, Tyr), Bacillus globigii (bg), Bacillus thuringiensis (bt,), and selected backgrounds. Also collected were EEMs of mixtures of amino acids and of bg in solution with a few backgrounds. The EEMs of pure components and mixtures were analyzed for phenomenology and for potential methods of unmixing and identifying the constituents of EEMs having mixed components of a similar nature.

  3. Hyperspectral fluorescence imaging with multi wavelength LED excitation

    NASA Astrophysics Data System (ADS)

    Luthman, A. Siri; Dumitru, Sebastian; Quirós-Gonzalez, Isabel; Bohndiek, Sarah E.

    2016-04-01

    Hyperspectral imaging (HSI) can combine morphological and molecular information, yielding potential for real-time and high throughput multiplexed fluorescent contrast agent imaging. Multiplexed readout from targets, such as cell surface receptors overexpressed in cancer cells, could improve both sensitivity and specificity of tumor identification. There remains, however, a need for compact and cost effective implementations of the technology. We have implemented a low-cost wide-field multiplexed fluorescence imaging system, which combines LED excitation at 590, 655 and 740 nm with a compact commercial solid state HSI system operating in the range 600 - 1000 nm. A key challenge for using reflectance-based HSI is the separation of contrast agent fluorescence from the reflectance of the excitation light. Here, we illustrate how it is possible to address this challenge in software, using two offline reflectance removal methods, prior to least-squares spectral unmixing. We made a quantitative comparison of the methods using data acquired from dilutions of contrast agents prepared in well-plates. We then established the capability of our HSI system for non-invasive in vivo fluorescence imaging in small animals using the optimal reflectance removal method. The HSI presented here enables quantitative unmixing of at least four fluorescent contrast agents (Alexa Fluor 610, 647, 700 and 750) simultaneously in living mice. A successful unmixing of the four fluorescent contrast agents was possible both using the pure contrast agents and with mixtures. The system could in principle also be applied to imaging of ex vivo tissue or intraoperative imaging in a clinical setting. These data suggest a promising approach for developing clinical applications of HSI based on multiplexed fluorescence contrast agent imaging.

  4. Excitation of emission lines by fluorescence and recombination in IC 418

    NASA Astrophysics Data System (ADS)

    Escalante, Vladimir; Morisset, Cristophe; Georgiev, Leonid

    2012-08-01

    We predict intensities of lines of CII, NI, NII, OI and OII and compare them with a deep spectroscopic survey of IC 418 to test the effect of excitation of nebular emission lines by continuum fluorescence of starlight. Our calculations use a nebular model and a synthetic spectrum of its central star to take into account excitation of the lines by continuum fluorescence and recombination. The NII spectrum is mostly produced by fluorescence due to the low excitation conditions of the nebula, but many CII and OII lines have more excitation by fluorescence than recombination. In the neutral envelope, the NI permitted lines are excited by fluorescence, and almost all the OI lines are excited by recombination. Electron excitation produces the forbidden optical lines of OI, but continuum fluorescence excites most of the NI forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to explore the photodissociation region of a nebula.

  5. Atomic Absorption, Atomic Fluorescence, and Flame Emission Spectrometry.

    ERIC Educational Resources Information Center

    Horlick, Gary

    1984-01-01

    This review is presented in six sections. Sections focus on literature related to: (1) developments in instrumentation, measurement techniques, and procedures; (2) performance studies of flames and electrothermal atomizers; (3) applications of atomic absorption spectrometry; (4) analytical comparisons; (5) atomic fluorescence spectrometry; and (6)…

  6. Near-infrared spark source excitation for fluorescence lifetime measurements

    NASA Astrophysics Data System (ADS)

    Birch, D. J. S.; Hungerford, G.; Imhof, R. E.

    1991-10-01

    We have extended the range of excitation wavelengths from spark sources used in single photon timing fluorometry into the near infrared by means of the all-metal coaxial flashlamp filled with an argon-hydrogen gas mixture. At 750 nm this mixture gives ˜15 times the intensity available from pure hydrogen for a comparable pulse duration. Measurements are demonstrated by using the laser dye IR-140 in acetone, for which a fluorescence lifetime of 1.20 ns is recorded.

  7. Laser-excited fluorescence spectra of atomic uranium

    SciTech Connect

    Wang Songyue; Jin Changtai; Shen Mingtao; Wang Xiulan

    1987-05-01

    Using a dc-supply hollow-cathode lamp as a source of uranium vapor and a rhodamine 6G dye laser to excite the vapor optically, it was simple and convenient to detect fluorescence from uranium atoms at 753.393, 763.175, and 763.954 nm. We give a detailed discussion of how we eliminated the intense background emissions, which were principally due to the lamp.

  8. Topographic mapping of subsurface fluorescent structures in tissue using multiwavelength excitation

    PubMed Central

    Kim, Anthony; Roy, Mathieu; Dadani, Farhan N.; Wilson, Brian C.

    2010-01-01

    Different colors of visible light penetrate to varying depths in tissue due to the wavelength dependence of tissue optical absorption and elastic scattering. We exploit this to map the contour of the closest surface of a buried fluorescent object. This uses a novel algorithm based on the diffusion theory description of light propagation in tissue at each excitation wavelength to derive metrics that define the depth of the top surface of the object. The algorithm was validated using a tissue-simulating phantom. It was then demonstrated in vivo by subsurface brain tumor topography in a rodent model, using the fluorescence signal from protoporphyrin IX that is preferentially synthesized within malignant cells following systemic application of aminolevulinic acid. Comparisons to histomorphometry in the brain post mortem show the spatial accuracy of the technique. This method has potential for fluorescence image-guided tumor surgery, as well as other biomedical and nonbiological applications in subsurface sensing. PMID:21198200

  9. Temperature profile of a stoichiometric ch4/N2O flame from laser excited fluorescence measurements on OH

    SciTech Connect

    Anderson, W.R.; Decker, L.J.; Kotlar, A.J.

    1982-07-01

    The temperature profile of a stoichiometric CH/sub 4//N/sub 2/O flame over a porous plug, atmospheric-pressure burner has been measured using laser excited fluorescence of the OH radical. The technique of rotationally resolved fluorescence excitation scans was extended to the (1,1) vibrational band of the A doublet sigma plus - X doublet pi system to avoid problems of laser beam depletion and self-absorption encountered by this group and previous workers using the (O,O) band. Absorption spectra were obtained in addition to fluorescence spectra. A least squares curve-fitting technique which accounts for the various types of line broadening was developed and applied to two absorption lines in the (O,O) band. The resulting temperature profile is compared to that from fluorescence data reduced using Boltzmann plots. The more complicated curve-fitting approach was later applied to five lines in the spectrum using several combinations of fluorescence and absorption data. Results of all the aforementioned methods were compared to those from OH band reversal and N2 vibrational Raman measurements at the same point in the post flame gases. Excellent agreement was achieved. The results are discussed with emphasis on both the fluorescence diagnostics and the characteristics of the CH/sub 4//N/sub 2/O flame on the porous-plug burner.

  10. Multi-color femtosecond source for simultaneous excitation of multiple fluorescent proteins in two-photon fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Liu, Tzu-Ming; Wu, Juwell; Horton, Nicholas G.; Lin, Charles P.; Xu, Chris

    2013-02-01

    Simultaneous imaging of cells expressing multiple fluorescent proteins (FPs) is of particular interest in applications such as mapping neural circuits, tracking multiple immune cell populations, etc. To visualize both in vivo and ex vivo tissue morphology and physiology at a cellular level deep within scattering tissues, two-photon fluorescence microscopy (2PM) is a powerful tool that has found wide applications. However, simultaneous imaging of multiple FPs with 2PM is greatly hampered by the lack of proper ultrafast lasers offering multi-color femtosecond pulses, each targeting the two-photon absorption peak of a different FP. Here we demonstrate simultaneous two-photon fluorescence excitation of RFP, YFP, and CFP in human melanoma cells engineered to express a "rainbow" pallet of colors, using a novel fiber-based source with energetic, three-color femtosecond pulses. The three-color pulses, centered at 775 nm, 864 nm and 950 nm, are obtained through second harmonic generation of the 1550 nm pump laser and SHG of the solitons at 1728 nm and 1900 nm generated through soliton self-frequency shift (SSFS) of the pump laser in a large-mode-area (LMA) fiber. The resulting wavelengths are well matched to the two-photon absorption peaks of the three FPs for efficient excitation. Our results demonstrate that multi-color femtosecond pulse generation using SSFS and a turn-key, fiber-based femtosecond laser can fulfill the requirements for simultaneous imaging of multiple FPs in 2PM, opening new opportunities for a wide range of biological applications where non-invasive, high-resolution imaging of multiple fluorescent indicators is required.

  11. Laser line illumination scheme allowing the reduction of background signal and the correction of absorption heterogeneities effects for fluorescence reflectance imaging.

    PubMed

    Fantoni, Frédéric; Hervé, Lionel; Poher, Vincent; Gioux, Sylvain; Mars, Jérôme I; Dinten, Jean-Marc

    2015-10-01

    Intraoperative fluorescence imaging in reflectance geometry is an attractive imaging modality as it allows to noninvasively monitor the fluorescence targeted tumors located below the tissue surface. Some drawbacks of this technique are the background fluorescence decreasing the contrast and absorption heterogeneities leading to misinterpretations concerning fluorescence concentrations. We propose a correction technique based on a laser line scanning illumination scheme. We scan the medium with the laser line and acquire, at each position of the line, both fluorescence and excitation images. We then use the finding that there is a relationship between the excitation intensity profile and the background fluorescence one to predict the amount of signal to subtract from the fluorescence images to get a better contrast. As the light absorption information is contained both in fluorescence and excitation images, this method also permits us to correct the effects of absorption heterogeneities. This technique has been validated on simulations and experimentally. Fluorescent inclusions are observed in several configurations at depths ranging from 1 mm to 1 cm. Results obtained with this technique are compared with those obtained with a classical wide-field detection scheme for contrast enhancement and with the fluorescence by an excitation ratio approach for absorption correction. PMID:26442963

  12. The photophysics of phenylenevinylene oligomers and self-absorption of their fluorescence in polymer films.

    PubMed

    Winch, Nicola M; Smith, Gerald J; Breukers, Robert D; Bhuiyan, Delower H; Kay, Andrew J; Smith, Trevor A; Ghiggino, Kenneth P; Raymond, Sebastiampillai G

    The fluorescence spectra, quantum yields and lifetimes of a series of alkoxy-substituted phenylenevinylene molecules, which serve as short chain oligomer models for poly(p-phenylenevinylene), have been determined in fluid solvents and in a high viscosity polymer matrix. The effects of solvent polarity and a high viscosity molecular environment on the fluorescence yields and spectral shapes have been established. Alkoxy group substitution on the phenyl ring moieties of the molecules has an important effect on the vibronic structures and profiles of the absorption spectra. This was interpreted in terms of hot-band, ground to excited singlet state transitions from energetically closely-spaced torsional vibrational levels of the vinylene double bond in the ground state. The shapes of the absorption bands affect the overlaps of the absorption and fluorescence spectra. This has been quantified as the probability of fluorescence reabsorption in solid polymer films as a function of pathlength. This is an important determinant of the efficacies of these compounds for "harvesting" solar energy in luminescent solar concentrator systems. The reabsorption probabilities of these compounds are lower for all pathlengths than those determined in the same polymer film for the fluorophores, perylene and perylene diimide, which have been considered for concentrating spatially diffuse sunlight. PMID:27480331

  13. Electronic excited states of guanine-cytosine hairpins and duplexes studied by fluorescence spectroscopy.

    PubMed

    Brazard, Johanna; Thazhathveetil, Arun K; Vayá, Ignacio; Lewis, Frederick D; Gustavsson, Thomas; Markovitsi, Dimitra

    2013-08-01

    Guanine-cytosine hairpins, containing a hexaethylene glycol bridge, are studied by steady-state fluorescence spectroscopy and time-correlated single photon counting; their properties are compared to those of duplexes with the same sequence. It is shown that, both in hairpins and in duplexes, base pairing induces quenching of the ππ* fluorescence, the quantum yield decreasing by at least two orders of magnitude. When the size of the systems increases from two to ten base pairs, a fluorescent component decaying on the nanosecond time-scale appears at energy higher than that stemming from the bright states of non-interacting mono-nucleotides (ca. 330 nm). For ten base pairs, this new fluorescence forms a well-defined band peaking at 305 nm. Its intensity is about 20% higher for the hairpin compared to the duplex. Its position (red-shifted by 1600 cm(-1)) and width (broader by 1800 cm(-1) FWHM) differ from those observed for large duplexes containing 1000 base pairs, suggesting the involvement of electronic coupling. Fluorescence anisotropy reveals that the excited states responsible for high energy emission are not populated directly upon photon absorption but are reached during a relaxation process. They are assigned to charge transfer states. According to the emerging picture, the amplitude of conformational motions determines whether instantaneous deactivation to the ground state or emission from charge transfer states will take place, while ππ* fluorescence is associated to imperfect base-pairing. PMID:23736116

  14. Remote excitation fluorescence correlation spectroscopy using silver nanowires

    NASA Astrophysics Data System (ADS)

    Su, Liang; Yuan, Haifeng; Lu, Gang; Hofkens, Johan; Roeffaers, Maarten; Uji-i, Hiroshi

    2014-11-01

    Fluorescence correlation spectroscopy (FCS), a powerful tool to resolve local properties, dynamical process of molecules, rotational and translational diffusion motions, relies on the fluctuations of florescence observables in the observation volume. In the case of rare transition events or small dynamical fluctuations, FCS requires few molecules or even single molecules in the observation volume at a time to minimize the background signals. Metal nanoparticle which possess unique localized surface plasmon resonance (LSPR) have been used to reduce the observation volume down to sub-diffraction limited scale while maintain at high analyst concentration up to tens of micromolar. Nevertheless, the applications of functionalized nanoparticles in living cell are limited due to the continuous diffusion after cell uptake, which makes it difficult to target the region of interests in the cell. In this work, we demonstrate the use of silver nanowires for remote excitation FCS on fluorescent molecules in solution. By using propagation surface plasmon polaritons (SPPs) which supported by the silver nanowire to excite the fluorescence, both illumination and observation volume can be reduced simultaneously. In such a way, less perturbation is induced to the target region, and this will broaden the application scope of silver nanowire as tip in single cell endoscopy.

  15. Local excitation and collection in polymeric fluorescent microstructures

    NASA Astrophysics Data System (ADS)

    Henrique, Franciele Renata; Mendonca, Cleber Renato

    2016-04-01

    Integrated photonics has gained attention in recent years due to its wide range of applications which span from biology to optical communications. The use of polymer-based platforms for photonic devices is of great interest because organic compounds can be easily incorporated to polymers, enabling modifications to the system physical properties. The two-photon polymerization technique has emerged as an interesting tool for the production of three-dimensional polymeric microstructures. However, for their further incorporation in photonic devices it is necessary to develop methods to perform optical excitation and signal collection on such microstructures. With such purpose, we demonstrate approaches to perform local excitation and collection in polymeric microstructures doped with fluorescent dyes, employing tapered fibers. The obtained results indicate that fiber tapers are suitable to couple light in and out of fluorescent polymeric microstructures, paving the way for their incorporation in photonic devices. We also show that microstructures doped with more than one dye can be used as built-in broadband light sources to photonic circuits and their emission spectrum can be tuned by the right choice of the excitation position.

  16. A fluorescent benzothiazole probe with efficient two-photon absorption

    NASA Astrophysics Data System (ADS)

    Echevarria, Lorenzo; Moreno, Iván; Camacho, José; Salazar, Mary Carmen; Hernández, Antonio

    2012-11-01

    In this work, we report the two-photon absorption of 2-[4-(dimethylamino)phenyl]-1,3-benzothiazole-6-carbonitrile (DBC) in DMSO solution pumping at 779 nm with a 10 ns pulse laser-Nd:YAG system. The obtained two-photon absorption cross-section in DBC (407 ± 18 GM) is considerably high. Because DBC is a novel compound and have high values of fluorescence quantum yield, this result is expected to have an impact in biomolecules detection, diagnosis and treatment of cancer. Similar structures have previously been reported to show remarkable antitumour effects.

  17. Simulations of fluorescence solvatochromism in substituted PPV oligomers from excited state molecular dynamics with implicit solvent

    SciTech Connect

    Bjorgaard, J. A.; Nelson, T.; Kalinin, K.; Kuzmenko, V.; Velizhanin, K. A.; Tretiak, S.

    2015-04-28

    In this study, an efficient method of treating solvent effects in excited state molecular dynamics (ESMD) is implemented and tested by exploring the solvatochromic effects in substituted p-phenylene vinylene oligomers. A continuum solvent model is used which has very little computational overhead. This allows simulations of ESMD with solvent effects on the scale of hundreds of picoseconds for systems of up to hundreds of atoms. At these time scales, solvatochromic shifts in fluoresence spectra can be described. Solvatochromic shifts in absorption and fluorescence spectra from ESMD are compared with time-dependent density functional theory calculations and experiments.

  18. Order in supported phospholipid monolayers detected by the dichroism of fluorescence excited with polarized evanescent illumination.

    PubMed Central

    Thompson, N. L.; McConnell, H. M.; Burhardt, T. P.

    1984-01-01

    A technique is described and demonstrated for measuring the orientation distribution of fluorescent molecules in a two-dimensional system. A laser beam is totally internally reflected at the interface between a glass slide and an aqueous solution, which creates a thin layer of evanescent illumination that excites fluorescent molecules near the interface. Molecules with absorption dipoles at different tilts from the normal to the interface are preferentially excited when the laser polarization is rotated. Approximately one-half of the emitted fluorescence is collected with an inverted microscope using a high-aperture objective. The fluorescence vs. polarization curve yields the value of an order parameter that is related to the orientation distribution of absorption dipoles. This technique is applied to phospholipid monolayers made at an air/water interface and transferred to hydrophobic glass microscope slides. Dipalmitoylphosphatidylcholine monolayers were doped with 2 mol% phosphatidylethanolamine labeled with the fluorescent moiety nitrobenzoxadiazole, either on an acyl chain or on the head group. The measured value of the order parameter for the head-labeled probe decreases as a function of the surface pressure at which the monolayer is transferred to the slide, as the surface pressure increases from 10 to 40 dyne/cm. The measured value of the order parameter for the chain-labeled probe is high for all coating pressures. These results can be interpreted in terms of probe partitioning into coexistent fluid and solid domains. Dimyristoylphosphatidylcholine monolayers were doped with 2 mol% chain-labeled phosphatidylethanolamine, either free or covalently conjugated to a small peptide. In these monolayers, the measured value of the order parameter is high at all pressures. The technique presented here may also prove useful for measuring the orientation distribution of proteins bound to or embedded in a planar model membrane. PMID:6518254

  19. Polymer filters for ultraviolet-excited integrated fluorescence sensing

    NASA Astrophysics Data System (ADS)

    Dandin, Marc; Abshire, Pamela; Smela, Elisabeth

    2012-09-01

    Optical filters for blocking ultraviolet (UV) light were fabricated by doping various polymer hosts with a UV absorbing chromophore. The polymers were polydimethylsiloxane (PDMS), a silicone elastomer frequently used in microfluidics, SU-8, a photopatternable epoxy, and Humiseal 1B66, an acrylic coating used for moisture protection of integrated circuits. The chromophore was 2-(2‧-hydroxy-5‧-methylphenyl) benzotriazole (BTA), which has a high extinction coefficient between 300 nm and 400 nm. We demonstrate filters 5 µm thick that exhibit high ultraviolet rejection (nearly -40 dB at 342 nm) yet pass visible light (near 0 dB above 400 nm), making them ideal for ultraviolet-excited fluorescence sensing within microsystems. The absorbance of the BTA depended on the host polymer. These filters are promising for integrated fluorescence spectroscopy in bioanalytical platforms because they can be patterned by dry etching, molding or exposure to ultraviolet light.

  20. Absorption and Transport of Fluorescent Brighteners by Microorganisms

    PubMed Central

    Darken, Marjorie A.

    1962-01-01

    The absorption of brighteners by living cells and their transport to subsequent growth is described. Brighteners are highly fluorescent, ultraviolet-absorbing compounds which appear to be essentially nontoxic, stable biological markers. They have been effectively absorbed by growing cultures of bacteria, yeasts, actinomycetes, and higher fungi, with active growth centers evidencing the greatest flourescence. Images FIG. 2 FIG. 3 FIG. 4 FIG. 5 FIG. 6 FIG. 7 FIG. 8 FIG. 9 FIG. 10-11 PMID:14025111

  1. Laser-excited confocal-fluorescence gel scanner

    SciTech Connect

    Mathies, R.A.; Scherer, J.R.; Quesada, M.A. ); Rye, H.S.; Glazer, A.N. )

    1994-04-01

    A high-sensitivity, laser-excited, confocal-fluorescence scanner has been developed for the detection of fluorescently labeled nucleic acids separated on slab gels. The gel is placed on a motor-driven, two-dimensional scan stage and raster scanned past the optical detection system. The 488-nm argon ion laser beam is introduced into the confocal optical system at a long-pass dichroic beam splitter and focused within the gel to an [similar to]2 [mu]m diameter spot by a high-numerical aperture microscope objective. The resulting fluorescence is gathered by the objective, passed back through the first long-pass beam splitter, and relayed to a second dichroic beam splitter that separates the red and green emissions. The fluorescence is then focused on confocal spatial filters to reduce stray and scattered light, passed through spectral filters, and detected with photomultipliers. The resulting signals are amplified, filtered, and digitized for display on a computer. This system can detect as little as 5[times]10[sup [minus]12] M fluorescein, the resolution as operated is 160 [mu]m, and it can scan a 6 cm[times]6 cm gel using a scan rate of 4 cm/s in 12 min. The detection of DNA on slab gels, two-color DNA fragment sizing, and microtiter plate scanning are presented to illustrate some of the possible applications of this apparatus.

  2. Fluorescent vibration-rotation excitation of cometary C2

    NASA Technical Reports Server (NTRS)

    Gredel, Roland; Van Dishoeck, Ewine F.; Black, John H.

    1989-01-01

    The statistical equilibrium equations that determine the population densities of the energy levels in cometary C2 molecules due to fluorescent excitation are examined in detail. The adopted model and molecular parameters are discussed, and a theoretical estimate is made of the two intercombination transition moments. From the theoretical population densities in the various rotational levels, flux ratios and synthetic emission profiles are calculated as functions of the a 3Pi(u) - X 1Sigma(g)+ and the c 3Sigma(u)+ - X 3Sigma(g)+ intercombination transition moments. The influence of each of these two transitions separately on the vibrational and rotational excitation temperatures is investigated. The observed emission spectra of the (0,0) Swan band in Comet Halley are presented and compared to the synthetic profiles.

  3. Excited-state dynamics of Si-rhodamine and its aggregates: versatile fluorophores for NIR absorption.

    PubMed

    Kim, Sooyeon; Fujitsuka, Mamoru; Miyata, Mikiji; Majima, Tetsuro

    2016-01-21

    Since it was first reported in 2008, great attention has been paid to Si-rhodamine (SiR) because of its far-red to near-infrared (NIR) absorption/fluorescence and suitability for high-resolution in vivo imaging. However, properties of SiR in the excited state have not been reported, even though they are directly related to its fluorescence. In the present study, the properties of SiR monomers in the excited states are thoroughly characterized for the first time. Moreover, by replacing a phenyl moiety of SiR with a 4-(9-anthryl)phenylene group (SiR-An), we prepared H- and J-aggregates of SiR in the aqueous solution, and succeeded in monitoring exciton formation and annihilation in the aggregates. Interestingly, the relative exciton population in the SiR J-aggregate increases as the excitation power becomes stronger, which is unusual considering that the substantial exciton-exciton annihilation process occurs as more excitons are generated. The results obtained in the present study suggest high versatility of SiR not only as a red fluorophore in the cutting-edge microscopic techniques but also as a NIR absorber in the light harvesting system. PMID:26692043

  4. Fluorescence Excitation-Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter

    USGS Publications Warehouse

    Chen, W.; Westerhoff, P.; Leenheer, J.A.; Booksh, K.

    2003-01-01

    Excitation-emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the >10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation-emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation-emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (??i,n). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet-visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 hydrophobic or hydrophilic acid, neutral, and base DOM fractions plus nonfractionated DOM from wastewater effluents and rivers in the southwestern United States. DOM fractions fluoresced in one or more EEM regions. The highest cumulative EEM volume (??T,n = ????i,n) was observed for hydrophobic neutral DOM fractions, followed by lower ??T,n values for hydrophobic acid, base, and hydrophilic acid DOM fractions, respectively. An extracted wastewater biomass DOM sample contained aromatic protein- and humic-like material and was characteristic of bacterial-soluble microbial products. Aromatic carbon and the presence of specific aromatic compounds (as indicated by solid-state 13C NMR and FTIR data) resulted in EEMs that aided in differentiating wastewater effluent DOM from drinking water DOM.

  5. Two-step excitation and blue fluorescence under continuous-wave pumping in Nd:YLF

    NASA Technical Reports Server (NTRS)

    Fan, T. Y.; Byer, Robert L.

    1986-01-01

    Near-UV and blue fluorescence from the 4D3/2 and 4D5/2 manifolds in Nd:YLF has been observed at room temperature under CW pumping by a rhodamine 590 dye laser. Excitation to these manifolds is attributed to two-step excitation involving excited-state absorption from the 4F3/2 metastable level. A similar phenomenon has also been observed in Nd:YAG and Nd:glass. The effective excited-state absorption cross section is measured to be (2 + or - 1) x 10 to the -20th sq cm at 587.4 nm in the pi polarization, and the peak effective stimulated emission cross section is measured to be 5 x 10 to the -20th sq cm at 411.7 nm, also in the pi polarization. Estimated laser threshold at 411.7 nm for two-step pumping at 587.4 nm is 70 mW.

  6. Fluorescence of molecular hydrogen excited by solar extreme-ultraviolet radiation

    NASA Technical Reports Server (NTRS)

    Feldman, P. D.; Fastie, W. G.

    1973-01-01

    During trans-earth coast, the Apollo 17 ultraviolet spectrometer was scheduled to make observations of the far ultraviolet background in selected regions of the sky. In the course of one of these observations, the spacecraft fuel cells were routinely purged of excess hydrogen and water vapor. The ultraviolet fluorescence spectrum of the purged molecular hydrogen excited by solar extreme ultraviolet radiation is interpreted by absorption of solar L-beta and L-gamma radiation in the nearly resonant (6, 0) and (11, 0) Lyman bands. The results are deemed significant for ultraviolet spectroscopic investigations of the atmospheres of the moon and planets since Lyman-band fluorescence provides an unambiguous means of identification of molecular hydrogen in upper atmospheres.

  7. Thermochromic Absorption, Fluorescence Band Shifts and Dipole Moments of BADAN and ACRYLODAN

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2002-08-01

    Using the thermochromic shift method of absorption and fluorescence bands, the electric dipole moments in the ground (μg) and excited (μe) state are simultaneously determined for BADAN (6-bromoacetyl-2-dimethylamino-naphtalene) and ACRYLODAN (6-acrylolyl-2-dimethylamino-naphtalene) in ethyl acetate. For these compounds the same ratio μe/μg = 2.9 was found, which is similar to that of PRODAN (6-propionyl-2-dimethylamino-naphtalene). The estimated empirical Onsager radii afor BADAN and ACRYLODAN are the same, and they are somewhat smaller than the calculated geometrical values.

  8. Determination of optimal excitation and emission wavebands for detection of defect cherry tomato by using fluorescence emission and excitation matrix

    NASA Astrophysics Data System (ADS)

    Baek, In-Suck; Cho, Byoung-Kwan; Kim, Moon S.; Kim, Young-Sik

    2013-05-01

    Fluorescence imaging technique has been widely used for quality and safety measurements of agro-food materials. Fluorescence emission intensities of target materials are influenced by wavelengths of excitation sources. Hence, selection of a proper excitation wavelength is an important factor in differentiating target materials effectively. In this study, optimal fluorescence excitation wavelength was determined on the basis of fluorescence emission intensity of defect and sound areas of cherry tomatoes. The result showed that fluorescence responses of defect and sound surfaces of cherry tomatoes were most significantly separated with the excitation light wavelength range between 400 and 410 nm. Fluorescence images of defect cherry tomatoes were acquired with the LEDs with the central wavelength of 410 nm as the excitation source to verify the detection efficiency of cherry tomato defects. The resultant fluorescence images showed that the defects were discriminated from sound areas on cherry tomatoes with above 98% accuracy. This study shows that high power LEDs as the excitation source for fluorescence imaging are suitable for defect detection of cherry tomatoes.

  9. Absorption and Fluorescence Properties of Chromophoric Dissolved Organic Matter Produced by Algae.

    PubMed

    Peng, Tong; Lu, Xiao-lan; Su, Rong-guo; Zhang, Dong-mei

    2015-09-01

    Four kinds of diatom (Chaetoceros curvisetus, Phaeodactylum tricornutum, Nitzschia closterium f. minutissima and Navicula halophile) and two kinds of dinoflagellates (Prorocentrum donghaiense and Gymnodinium) were cultured under laboratory conditions. Variations of optical properties of chromophoric dissolved organic matter (CDOM) were studied with absorption and fluorescence excitation-emission matrix spectroscopy(EEM) during growth of marine microalgae in incubation experiment. Absorption spectrum revealed absorption coefficient a(355) (CDOM absorption coefficients at 355 nm) of 6 kinds of marine microalgae above increased by 64.8%, 242.3%, 535.1%, 903.2%, 836% and 196.4%, respectively. Simultaneously, the absorption spectral slope (Sg), determined between 270 and 350 nm, representing the size of molecular weight of CDOM and humic-like composition, decreased by 8.7%, 34.6%, 39.4%, 53.1%, 46.7%, and 35.7%, respectively. Applying parallel factor analysis (PARAFAC) together with EEM got four components of CDOM: C1(Ex/Em=350(260) nm/450 nm), C2 (Ex/Em=260(430) nm/525 nm), C3 (Ex/Em=325 nm/400 nm) and C4(Ex/Em=275 nm/325 nm), which were relative to three humic-like and one protein-like fluorescent components of Nitzschia closterium f. minutissima and Navicula halophile. In incubation experiment, fluorescence intensity of these four components during growth of Nitzschia closterium f. minutissima increased by, respectively, 8.68, 24.9, 7.19 and 39.8 times, and those of Navicula halophile increased by 2.64, 0.07, 4.39 and 12.4 times, respectively. Significant relationships were found between the fluorescence intensity of four components of CDOM, a(355) and Sg. All results demonstrated that both content and molecular weight of CDOM produced by diatom and dinoflagellate studied in incubation experiment increased, but these two parameters changed more obviously of the diatom than those of dinoflagellate; the proportion of humic-like components in the composition of CDOM

  10. Excitation-Selectable Nanoprobe for Tumor Fluorescence Imaging and Near-Infrared Thermal Therapy.

    PubMed

    Wei, Yanchun; Chen, Qun; Wu, Baoyan; Xing, Da

    2016-01-01

    The combination of diagnostics and therapeutics is growing rapidly in cancer treatment. Here, using upconversion nanoparticles coated with chitosan conjugated with a targeting molecule and loaded with indocyanine green (ICG), we develop an excitation-selectable nanoprobe with highly integrated functionalities, including the emission of visible and near-infrared (NIR) light, strong optical absorption in the NIR region and high photostability. After intravenous injection in tumor bearing mice, the nanoprobes target to the tumor vascular system. NIR lasers (980 and 808 nm) are then selectively applied to the mice. The results show that the emitted upconversion fluorescence and NIR fluorescence can be used in a complementary manner for high signal/noise ratio and sensitive tumor imaging for more precise tumor localization. Highly effective photothermal therapy is realized using 808 nm laser irradiation, and the upconversion fluorescence at 654 nm can be used for monitoring treatment effect during the thermal therapy. In summary, using the nanoprobes, outstanding therapeutic efficacy could be realized through flexible excitation control, precise tumor localization, highly effective photothermal conversion and real-time treatment monitoring. The nanofabrication strategy highlights the promise of nanoparticles in cancer theranostics. PMID:27301175

  11. Polarized fluorescence and absorption of macroscopically aligned Light Harvesting Complex II.

    PubMed Central

    van Amerongen, H; Kwa, S L; van Bolhuis, B M; van Grondelle, R

    1994-01-01

    Polarized absorption and fluorescence measurements have been performed at 77 K on isotropic and anisotropic preparations of trimeric Light Harvesting Complex II (LHC-II) from spinach. The results enable a decomposition of the absorption spectrum into components parallel and perpendicular to the trimeric plane. For the first time, it is shown quantitatively that the strong absorption band around 676 nm is polarized essentially parallel to the plane of the trimer, i.e., the average angle between the corresponding transition dipole moments and this plane is at most 12 degrees. The different absorption bands for LHC-II should not be considered as corresponding to individual pigments but to collective excitations of different pigments. Nevertheless, the average angle between the Qy transition dipole moments of all chlorophyll a pigments in LHC-II and the trimeric plane could be determined and was found to be 17.5 degrees +/- 2.5 degrees. For the chlorophyll b pigments, this angle is significantly larger (close to 35 degrees). At 77 K, most of the fluorescence stems from a weak band above 676 nm and the corresponding transition dipole moments are oriented further out of plane than the dipole moments corresponding to the 676-nm band. The results are shown to be of crucial significance for understanding the relation between the LHC-II structure and its spectroscopy. PMID:7948696

  12. Spectral analysis on origination of the bands at 437 nm and 475.5 nm of chlorophyll fluorescence excitation spectrum in Arabidopsis chloroplasts.

    PubMed

    Zeng, Lizhang; Wang, Yongqiang; Zhou, Jun

    2016-05-01

    Chlorophyll fluorescence has been often used as an intrinsic optical molecular probe to study photosynthesis. In this study, the origin of bands at 437 and 475.5 nm in the chlorophyll fluorescence excitation spectrum for emission at 685 nm in Arabidopsis chloroplasts was investigated using various optical analysis methods. The results revealed that this fluorescence excitation spectrum was related to the absorption characteristics of pigment molecules in PSII complexes. Moreover, the excitation band centred at 475.5 nm had a blue shift, but the excitation band at 437 nm changed relatively less due to induction of non-photochemical quenching (NPQ). Furthermore, fluorescence emission spectra showed that this blue shift occurred when excitation energy transfer from both chlorophyll b (Chl b) and carotenoids (Cars) to chlorophyll a (Chl a) was blocked. These results demonstrate that the excitation band at 437 nm was mainly contributed by Chl a, while the excitation band at 475.5 nm was mainly contributed by Chl b and Cars. The chlorophyll fluorescence excitation spectrum, therefore, could serve as a useful tool to describe specific characteristics of light absorption and energy transfer between light-harvesting pigments. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26358732

  13. Solvent dependence of two-photon absorption spectra of the enhanced green fluorescent protein (eGFP) chromophore

    NASA Astrophysics Data System (ADS)

    Hosoi, Haruko; Tayama, Ryo; Takeuchi, Satoshi; Tahara, Tahei

    2015-06-01

    Two-photon absorption spectra of 4‧-hydroxybenzylidene-2,3-dimethylimidazolinone, a model chromophore of enhanced green fluorescent protein (eGFP), were measured in various solvents. The two-photon absorption band of its anionic form is markedly blue-shifted from the corresponding one-photon absorption band in all solvents. Moreover, the magnitude of the blue shift varies largely depending on the solvent, which does not accord with the assignment of the two-photon absorption band to the transitions to the vibrationally excited S1 state. Our finding is readily rationalized by considering overlapping contributions of the S1 ← S0 and S2 ← S0 transitions, suggesting the involvement of the S2 state also in two-photon fluorescence of eGFP.

  14. Fluorescent Ag nanoclusters prepared in aqueous poly(acrylic acid-co-maleic acid) solutions: a spectroscopic study of their excited state dynamics, size and local environment.

    PubMed

    Dandapat, Manika; Mandal, Debabrata

    2016-01-28

    Stable, fluorescent Ag nanoclusters were prepared in aqueous solutions of Na(+) salt of the carboxylate-rich polymer poly(acrylic acid-co-maleic acid) under brief spells of UV irradiation. The nanoclusters were nearly spherical, with diameters within 1.90 ± 0.50 nm, but displayed a prominent red edge excitation shift (REES) of fluorescence upon exciting within the visible absorption band, indicating heterogeneity of energy level distributions. Spectroscopic studies revealed that irrespective of whether the nanoclusters are excited in their UV or visible absorption bands, their fluorescence always ensues from the same manifold of emissive states, with a broad range of fluorescence lifetimes from ∼150 fs to 1 ns. PMID:26700465

  15. Two-color two-photon excited fluorescence of indole: Determination of wavelength-dependent molecular parameters

    SciTech Connect

    Herbrich, Sebastian; Al-Hadhuri, Tawfik; Gericke, Karl-Heinz; Shternin, Peter S. Vasyutinskii, Oleg S.; Smolin, Andrey G.

    2015-01-14

    We present a detailed study of two-color two-photon excited fluorescence in indole dissolved in propylene glycol. Femtosecond excitation pulses at effective wavelengths from 268 to 293.33 nm were used to populate the two lowest indole excited states {sup 1}L{sub a} and {sup 1}L{sub b} and polarized fluorescence was then detected. All seven molecular parameters and the two-photon polarization ratio Ω containing information on two-photon absorption dynamics, molecular lifetime τ{sub f}, and rotation correlation time τ{sub rot} have been determined from experiment and analyzed as a function of the excitation wavelength. The analysis of the experimental data has shown that {sup 1}L{sub b}–{sup 1}L{sub a} inversion occurred under the conditions of our experiment. The two-photon absorption predominantly populated the {sup 1}L{sub a} state at all excitation wavelengths but in the 287–289 nm area which contained an absorption hump of the {sup 1}L{sub b} state 0-0 origin. The components of the two-photon excitation tensor S were analyzed giving important information on the principal tensor axes and absorption symmetry. The results obtained are in a good agreement with the results reported by other groups. The lifetime τ{sub f} and the rotation correlation time τ{sub rot} showed no explicit dependence on the effective excitation wavelength. Their calculated weighted average values were found to be τ{sub f} = 3.83 ± 0.14 ns and τ{sub rot} = 0.74 ± 0.06 ns.

  16. Fluorescence-excitation and Emission Spectroscopy on Single FMO Complexes

    PubMed Central

    Löhner, Alexander; Ashraf , Khuram; Cogdell, Richard J.; Köhler, Jürgen

    2016-01-01

    In green-sulfur bacteria sunlight is absorbed by antenna structures termed chlorosomes, and transferred to the RC via the Fenna-Matthews-Olson (FMO) complex. FMO consists of three monomers arranged in C3 symmetry where each monomer accommodates eight Bacteriochlorophyll a (BChl a) molecules. It was the first pigment-protein complex for which the structure has been determined with high resolution and since then this complex has been the subject of numerous studies both experimentally and theoretically. Here we report about fluorescence-excitation spectroscopy as well as emission spectroscopy from individual FMO complexes at low temperatures. The individual FMO complexes are subjected to very fast spectral fluctuations smearing out any possible different information from the ensemble data that were recorded under the same experimental conditions. In other words, on the time scales that are experimentally accessible by single-molecule techniques, the FMO complex exhibits ergodic behaviour. PMID:27545197

  17. Tissue fluorescence origins evaluation using excitation-emission matrices

    NASA Astrophysics Data System (ADS)

    Zhelyazkova, A.; Borisova, E.; Angelova, L.; Pavlova, E.; Keremedchiev, M.; Avramov, L.

    2015-01-01

    Autofluorescence has been proven to be a very sensitive, accurate, noninvasive method for detection of early pathological changes in tissues. This optical method has the potential to provide a real-time diagnosis of different benign, dysplastic and malignant tissue pathologies. We obtain tissue samples after surgical excision of preliminary clinically diagnosed tumours. Ethical approval for our investigations is received from Ethical Committee of University Hospital "Queen Jiovanna-ISUL" - Sofia, where the samples will be obtained as well. The investigations presented in this report are based on ex vivo measurements of excitation-emission matrices (EEM) for normal and neoplastic human tissue samples with various cutaneous malignant and dysplastic lesions, as well for gastrointestinal tract (GIT) normal mucosa, polyps and carcinoma. The origins of the endogenous fluorescence are found and the differences observed are discussed from the point of view of their diagnostic value and correlation with the morphological and biochemical changes occurred during the tumour development.

  18. Fluorescence-excitation and Emission Spectroscopy on Single FMO Complexes.

    PubMed

    Löhner, Alexander; Ashraf, Khuram; Cogdell, Richard J; Köhler, Jürgen

    2016-01-01

    In green-sulfur bacteria sunlight is absorbed by antenna structures termed chlorosomes, and transferred to the RC via the Fenna-Matthews-Olson (FMO) complex. FMO consists of three monomers arranged in C3 symmetry where each monomer accommodates eight Bacteriochlorophyll a (BChl a) molecules. It was the first pigment-protein complex for which the structure has been determined with high resolution and since then this complex has been the subject of numerous studies both experimentally and theoretically. Here we report about fluorescence-excitation spectroscopy as well as emission spectroscopy from individual FMO complexes at low temperatures. The individual FMO complexes are subjected to very fast spectral fluctuations smearing out any possible different information from the ensemble data that were recorded under the same experimental conditions. In other words, on the time scales that are experimentally accessible by single-molecule techniques, the FMO complex exhibits ergodic behaviour. PMID:27545197

  19. Excited-state absorption of pump radiation as a loss mechanism in solid-state lasers

    SciTech Connect

    Kliewer, M.L.; Powell, R.C.

    1989-08-01

    The characteristics of optical pumping dynamics occuring in laser-pumped rare earth-doped, solid-state laser materials were investigated by using a tunable alexandrite laser to pump Y3Al5O12:Nd(3+) in an optical cavity. It was found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelength resulting in low slope efficiencies, intense fluorescence emission is observed form the sample in the blue-green spectral region. This is attributed to the excited state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process will be an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  20. Excited state absorption of pump radiation as a loss mechanism in solid-state lasers

    NASA Technical Reports Server (NTRS)

    Kliewer, Michael L.; Powell, Richard C.

    1989-01-01

    The characteristics of optical pumping dynamics in laser-pumped, rare-earth-doped, solid-state laser materials are investigated by using a tunable alexandrite laser to pump Y3Al5O12:Nd(3+) in an optical cavity. It is found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelengths resulting in low slope efficiencies, intense fluorescence emission is observed from the sample in the blue-green spectral region. This is attributed to the excited-state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process is an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  1. Excited state absorption of pump radiation as a loss mechanism in solid-state lasers

    SciTech Connect

    Kliewer, M.L.; Powell, R.C.

    1989-08-01

    The characteristics of optical pumping dynamics occurring in laser-pumped rare earth-doped, solid-state laser materials were investigated by using a tunable alexandrite laser to pump Y/sub 3/Al/sub 5/O/sub 12/:Nd/sup 3+/ in an optical cavity. It was found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelengths resulting in low slope efficiencies, intense fluorescence emission is observed from the sample in the blue-green spectral region. This is attributed to the excited state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process will be an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  2. Two-color excitation system for fluorescence detection in DNA sequencing by capillary array electrophoresis.

    PubMed

    Xue, Gang; Yeung, Edward S

    2002-05-01

    Two computer-controlled galvanometer scanners are adapted for two-dimensional step scanning across a 96-capillary array for laser-induced fluorescence detection. 488 nm and 514 nm laser lines from the same Ar(+) laser were alternately coupled for two-color excitation in each capillary. The signal at a single photomultiplier tube is temporally sorted to distinguish among the capillaries and the excitation wavelengths. Based on the differences in absorption spectra for the dyes, the peak-height ratios in the 488 nm and 514 nm excitation electropherograms were used for peak identification for multiplexed capillary electrophoresis. Successful base calling for 24-capillary DNA sequencing was achieved to 450 bp with 99% accuracy. Advantages include the efficient utilization of light due to the high duty-cycle of step scan, good detection performance due to the reduction of stray light, ruggedness due to the small mass of the galvanometer mirror, low cost due to the simplicity of components and flexibility due to the independent paths for excitation and emission. PMID:12116160

  3. Two-photon excitation of nitric oxide fluorescence as a temperature indicator in unsteady gas-dynamic processes

    NASA Technical Reports Server (NTRS)

    Mckenzie, R. L.; Gross, K. P.

    1980-01-01

    A laser induced fluorescence technique, suitable for measuring fluctuating temperatures in cold turbulent flows containing very low concentrations of nitric oxide is described. Temperatures below 300 K may be resolved with signal to noise ratios greater than 50 to 1 using high peak power, tunable dye lasers. The method relies on the two photon excitation of selected ro-vibronic transitions. The analysis includes the effects of fluorescence quenching and shows the technique to be effective at all densities below ambient. Signal to noise ratio estimates are based on a preliminary measurement of the two photon absorptivity for a selected rotational transition in the NO gamma (0,0) band.

  4. Nonlinear reconstruction of absorption and fluorescence contrast from measured diffuse transmittance and reflectance of a compressed-breast-simulating phantom

    SciTech Connect

    Ziegler, Ronny; Nielsen, Tim; Koehler, Thomas; Grosenick, Dirk; Steinkellner, Oliver; Hagen, Axel; Macdonald, Rainer; Rinneberg, Herbert

    2009-08-20

    We report on the nonlinear reconstruction of local absorption and fluorescence contrast in tissuelike scattering media from measured time-domain diffuse reflectance and transmittance of laser as well as laser-excited fluorescence radiation. Measurements were taken at selected source-detector offsets using slablike diffusely scattering and fluorescent phantoms containing fluorescent heterogeneities. Such measurements simulate in vivo data that would be obtained employing a scanning, time-domain fluorescence mammograph, where the breast is gently compressed between two parallel glass plates, and source and detector optical fibers scan synchronously at various source-detector offsets, allowing the recording of laser and fluorescence mammograms. The diffusion equations modeling the propagation of the laser and fluorescence radiation were solved in frequency domain by the finite element method simultaneously for several modulation frequencies using Fourier transformation and preprocessed experimental data. To reconstruct the concentration of the fluorescent contrast agent, the Born approximation including higher-order reconstructed photon densities at the excitation wavelength was used. Axial resolution was determined that can be achieved by various detection schemes. We show that remission measurements increase the depth resolution significantly.

  5. Fluorescence depolarization of rhodamine 6G in glycerol: a photon-counting test of three-dimensional excitation transport theory

    SciTech Connect

    Anfinrud, P.A.; Hart, D.E.; Hedstrom, J.F.; Struve, W.S.

    1986-05-22

    Time-correlated photon counting has been used to measure fluorescence concentration depolarization for rhodamine 6G in glycerol. The excitation transport theory developed by Gochanour, Andersen, and Fayer yields good approximations to the experimental decay profiles over the concentration range 1.7 x 10/sup -4/ to 2.4 x 10/sup -3/ M. Although the differences between optimized theoretical and experimental profiles are fractionally small, they are readily characterized under present counting statistics. They prove to be dominated by experimental artifacts, arising from excitation trapping by rhodamine 6G aggregates and from self-absorption in solution cells thicker than approx. 10 ..mu..m.

  6. Two-photon excited fluorescence enhancement with broadband versus tunable femtosecond laser pulse excitation

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Yeh, Alvin T.

    2012-02-01

    The inverse relationship between two-photon excited fluorescence (TPEF) and laser pulse duration suggests that two-photon microscopy (TPM) performance may be improved by decreasing pulse duration. However, for ultrashort pulses of sub-10 femtosecond (fs) in duration, its spectrum contains the effective gain bandwidth of Ti:Sapphire and its central wavelength is no longer tunable. An experimental study was performed to explore this apparent tradeoff between untuned sub-10 fs transform-limited pulse (TLP) and tunable 140 fs pulse for TPEF. Enhancement factors of 1.6, 6.7, and 5.2 are measured for Indo-1, FITC, and TRITC excited by sub-10 fs TLP compared with 140 fs pulse tuned to the two-photon excitation (TPE) maxima at 730 nm, 800 nm, and 840 nm, respectively. Both degenerate (v1=v2) and nondegenerate (v1≠v2) mixing of sub-10 fs TLP spectral components result in its broad second-harmonic (SH) power spectrum and high spectral density, which can effectively compensate for the lack of central wavelength tuning and lead to large overlap with dye TPE spectra for TPEF enhancements. These pulse properties were also exploited for demonstrating its potential applications in multicolor imaging with TPM.

  7. Deconvolution of C-phycocyanin beta-84 and beta-155 chromophore absorption and fluorescence spectra of cyanobacterium Mastigocladus laminosus.

    PubMed Central

    Demidov, A A; Mimuro, M

    1995-01-01

    Absorption and fluorescence spectra of the C-phycocyanin beta-subunit were quantitatively deconvoluted into component spectra of the beta-84 and beta-155 chromophores. The deconvolution procedure was based on a theoretical treatment of polarization properties. Four kinds of spectra (absorption, emission, emission polarization, and excitation polarization) measured on C-phycocyanin isolated from the cyanobacterium Mastigocladus laminosus were used as the experimental data set. Without any assumption of spectral shape, the absorption and fluorescence spectra of both chromophores were unambiguously resolved and their fluorescence quantum yields were evaluated. By combining the spectra of the alpha-subunit, independently measured, with the resolved spectra of the beta-subunit, the fluorescence and fluorescence polarization spectra and the fluorescence quantum yield of the monomer were estimated; they agree with experimental values to within an acceptable error. Further, the matrix of energy transfer rates in the monomer was estimated; it gave a significantly different result (by up to 40%) from previously estimated ones. PMID:7787035

  8. Serial Femtosecond Crystallography and Ultrafast Absorption Spectroscopy of the Photoswitchable Fluorescent Protein IrisFP.

    PubMed

    Colletier, Jacques-Philippe; Sliwa, Michel; Gallat, François-Xavier; Sugahara, Michihiro; Guillon, Virginia; Schirò, Giorgio; Coquelle, Nicolas; Woodhouse, Joyce; Roux, Laure; Gotthard, Guillaume; Royant, Antoine; Uriarte, Lucas Martinez; Ruckebusch, Cyril; Joti, Yasumasa; Byrdin, Martin; Mizohata, Eiichi; Nango, Eriko; Tanaka, Tomoyuki; Tono, Kensuke; Yabashi, Makina; Adam, Virgile; Cammarata, Marco; Schlichting, Ilme; Bourgeois, Dominique; Weik, Martin

    2016-03-01

    Reversibly photoswitchable fluorescent proteins find growing applications in cell biology, yet mechanistic details, in particular on the ultrafast photochemical time scale, remain unknown. We employed time-resolved pump-probe absorption spectroscopy on the reversibly photoswitchable fluorescent protein IrisFP in solution to study photoswitching from the nonfluorescent (off) to the fluorescent (on) state. Evidence is provided for the existence of several intermediate states on the pico- and microsecond time scales that are attributed to chromophore isomerization and proton transfer, respectively. Kinetic modeling favors a sequential mechanism with the existence of two excited state intermediates with lifetimes of 2 and 15 ps, the second of which controls the photoswitching quantum yield. In order to support that IrisFP is suited for time-resolved experiments aiming at a structural characterization of these ps intermediates, we used serial femtosecond crystallography at an X-ray free electron laser and solved the structure of IrisFP in its on state. Sample consumption was minimized by embedding crystals in mineral grease, in which they remain photoswitchable. Our spectroscopic and structural results pave the way for time-resolved serial femtosecond crystallography aiming at characterizing the structure of ultrafast intermediates in reversibly photoswitchable fluorescent proteins. PMID:26866390

  9. [Influence of the Experiment Energy Dispersive X-Ray Fluorescence Measurement of Uranium by Different Excitation Source].

    PubMed

    Xiong, Chao; Ge, Liang-quan; Liu, Duan; Zhang, Qing-xian; Gu, Yi; Luo, Yao-yao; Zhao, Jian-kun

    2016-03-01

    Aiming at the self-excitation effect on the interference of measurements which exist in the process of Energy dispersive X-ray fluorescence method for uranium measurement. To solve the problem of radioactive isotopes only used as excitation source in determination of uranium. Utilizing the micro X-ray tube to test Self-excitation effect to get a comparison of the results obtained by three different uranium ore samples--109 Cd, 241 Am and Mirco X-ray tube. The results showed that self-excitation effect produced the area measure of characteristic X-ray peak is less than 1% of active condition, also the interference of measurements can be negligible. Photoelectric effect cross-section excited by 109 Cd is higher, corresponding fluorescence yield is higher than excited by 241 Am as well due to characteristics X-ray energy of 109 Cd, 22.11 & 24.95 KeV adjacent to absorption edge energy of L(α), 21.75 KeV, based on the above, excitation efficiency by 109 Cd is higher than 241 Am; The fact that measurement error excited by 241 Am is significantly greater than by 109 Cd is mainly due to peak region overlap between L energy peaks of uranium and Scattering peak of 241 Am, 26.35 keV, These factors above caused the background of measured Spectrum higher; The error between the uranium content in ore samples which the X-ray tube as the excitation source and the chemical analysis results is within 10%. Conclusion: This paper come to the conclusion that the technical quality of uranium measurement used X-ray tube as excitation source is superior to that in radioactive source excitation mode. PMID:27400534

  10. Laser excited fluorescence in the cesium-xenon excimer and the cesium dimer

    NASA Technical Reports Server (NTRS)

    Exton, R. J.; Snow, W. L.; Hillard, M. E.

    1978-01-01

    Argon ion laser lines are used to excite fluorescence in a mixture of cesium and xenon. Excimer band fluorescence is observed at higher pressures (about 1 atm) while at lower pressures (several torr) a diffuse fluorescence due to the cesium dimer is observed whose character changes with exciting wavelength. The excimer fluorescence is shown to be directly related to the location of the exciting wavelength within previously measured Cs/Xe line shapes. This fact suggests that the excimer systems may be efficiently pumped through these line shapes. Qualitative energy-level schemes are proposed to explain the observations in both the excimer and dimer systems.

  11. Spectral fluorescent properties of tissues in vivo with excitation in the red wavelength range

    NASA Astrophysics Data System (ADS)

    Stratonnikov, Alexander A.; Loschenov, Victor B.; Klimov, D. V.; Edinac, N. E.; Wolnukhin, V. A.; Strashkevich, I. A.

    1997-12-01

    The spectral fluorescence analysis is a promising method for differential tissue diagnostic. Usually the UV and visible light is used for fluorescence excitation with emission registration in the visible wavelength range. The light penetration length in this wavelength range is very small allowing one to analyze only the surface region of the tissue. Here we present the tissue fluorescent spectra in vivo excited in the red wavelength region. As excitation light source we used compact He-Ne laser (632.8 nm) and observed the fluorescence in 650 - 800 nm spectral range. The various tissues including normal skin, psoriasis, tumors, necrosis as well as photosensitized tissues have been measured.

  12. Twisting in the excited state of an N-methylpyridinium fluorescent dye modulated by nano-heterogeneous micellar systems.

    PubMed

    Cesaretti, A; Carlotti, B; Gentili, P L; Germani, R; Spalletti, A; Elisei, F

    2016-04-13

    A push-pull N-methylpyridinium fluorescent dye with a pyrenyl group as the electron-donor portion was investigated within the nano-heterogeneous media provided by some micellar systems. The molecule was studied by stationary and time-resolved spectroscopic techniques in spherical micellar solutions and viscoelastic hydrogels, in order to throw light on the role played by twisting in its excited state deactivation. As proven by femtosecond fluorescence up-conversion and transient absorption experiments, the excited state dynamics of the molecule is ruled by charge transfer and twisting processes, which, from the locally excited (LE) state initially populated upon excitation, progressively lead to twisted (TICT) and planar (PICT) intramolecular charge transfer states. The inclusion within micellar aggregates was found to slow down and/or limit the rotation of the molecule with respect to what had previously been observed in water, while its confinement within the hydrophobic domains of the gel matrixes prevents any molecular torsion. The increasing viscosity of the medium, when passing from water to micellar systems, implies that the detected steady-state fluorescence comes from an excited state which is not fully relaxed, as is the case with the TICT state in micelles or the LE state in hydrogels, where the detected emission changes its usual orange colour to yellow. PMID:26982966

  13. Laser excited confocal microscope fluorescence scanner and method

    DOEpatents

    Mathies, Richard A.; Peck, Konan

    1992-01-01

    A fluorescent scanner for scanning the fluorescence from a fluorescence labeled separated sample on a sample carrier including a confocal microscope for illuminating a predetermined volume of the sample carrier and/or receiving and processing fluorescence emissions from said volume to provide a display of the separated sample.

  14. Laser excited confocal microscope fluorescence scanner and method

    DOEpatents

    Mathies, R.A.; Peck, K.

    1992-02-25

    A fluorescent scanner is designed for scanning the fluorescence from a fluorescence labeled separated sample on a sample carrier. The scanner includes a confocal microscope for illuminating a predetermined volume of the sample carrier and/or receiving and processing fluorescence emissions from the volume to provide a display of the separated sample. 8 figs.

  15. Laser-induced fluorescence of formaldehyde in combustion using third harmonic Nd:YAG laser excitation.

    PubMed

    Brackmann, Christian; Nygren, Jenny; Bai, Xiao; Li, Zhongshan; Bladh, Henrik; Axelsson, Boman; Denbratt, Ingemar; Koopmans, Lucien; Bengtsson, Per-Erik; Aldén, Marcus

    2003-12-01

    Formaldehyde (CH2O) is an important intermediate species in combustion processes and it can through laser-induced fluorescence measurements be used for instantaneous flame front detection. The present study has focussed on the use of the third harmonic of a Nd:YAG laser at 355 nm as excitation wavelength for formaldehyde, and different dimethyl ether (C2H6O) flames were used as sources of formaldehyde in the experiments. The investigations included studies of the overlap between the laser profile and the absorption lines of formaldehyde, saturation effects and the potential occurrence of laser-induced photochemistry. The technique was applied for detection of formaldehyde in an internal combustion engine operated both as a spark ignition engine and as a homogenous charge compression ignition engine. PMID:14607232

  16. Optimization strategies for a fluorescent dye with bimodal excitation spectra: application to semiautomated proteomics

    NASA Astrophysics Data System (ADS)

    Patton, Wayne F.; Berggren, Kiera N.; Lopez, Mary F.

    2001-04-01

    Facilities engaged in proteome analysis differ significantly in the degree that they implement automated systems for high-throughput protein characterization. Though automated workstation environments are becoming more routine in the biotechnology and pharmaceutical sectors of industry, university-based laboratories often perform these tasks manually, submitting protein spots excised from polyacrylamide gels to institutional core facilities for identification. For broad compatibility with imaging platforms, an optimized fluorescent dye developed for proteomics applications should be designed taking into account that laser scanners use visible light excitation and that charge-coupled device camera systems and gas discharge transilluminators rely upon UV excitation. The luminescent ruthenium metal complex, SYPRO Ruby protein gel stain, is compatible with a variety of excitation sources since it displays intense UV (280 nm) and visible (470 nm) absorption maxima. Localization is achieved by noncovalent, electrostatic and hydrophobic binding of dye to proteins, with signal being detected at 610 nm. Since proteins are not covalently modified by the dye, compatibility with downstream microchemical characterization techniques such as matrix-assisted laser desorption/ionization-mass spectrometry is assured. Protocols have been devised for optimizing fluorophore intensity. SYPRO Ruby dye outperforms alternatives such as silver staining in terms of quantitative capabilities, compatibility with mass spectrometry and ease of integration into automated work environments.

  17. Excitation of emission lines by fluorescence and recombination in IC 418

    NASA Astrophysics Data System (ADS)

    Escalante, V.; Morisset, C.; Georgiev, L.

    2012-11-01

    We compare calculated intensities of lines of C II, N I, N II, O I and O II with a published deep spectroscopic survey of IC 418. Our calculations use a self-consistent nebular model and a synthetic spectrum of the central star atmosphere to take into account line excitation by continuum fluorescence and electron recombination. We found that the N II spectrum of the s, p and most d states is excited by fluorescence due to the low-excitation conditions of the nebula. Many C II and O II lines have significant amount of excitation by fluorescence. Recombination excites all the lines from the f and g states and most O II lines. In the neutral-ionized boundary, the N I quartet and O I triplet dipole-allowed lines are excited by fluorescence, while the quintet O I lines are excited by recombination. Electron excitation produces the forbidden optical lines of O I, and continuum fluorescence enhances the N I forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to explore the inner boundary of the photodissociation region of the nebula.

  18. Rational design of a fluorescent NADPH derivative imaging constitutive nitric-oxide synthases upon two-photon excitation

    PubMed Central

    Li, Yun; Wang, Huan; Tarus, Bogdan; Perez, Miguel Romero; Morellato, Laurence; Henry, Etienne; Berka, Vladimir; Tsai, Ah-Lim; Ramassamy, Booma; Dhimane, Hamid; Dessy, Chantal; Tauc, Patrick; Boucher, Jean-Luc; Deprez, Eric; Slama-Schwok, Anny

    2012-01-01

    We report the structure-based design and synthesis of a unique NOS inhibitor, called nanoshutter NS1, with two-photon absorption properties. NS1 targets the NADPH site of NOS by a nucleotide moiety mimicking NADPH linked to a conjugated push–pull chromophore with nonlinear absorption properties. Because NS1 could not provide reducing equivalents to the protein and competed with NADPH binding, it efficiently inhibited NOS catalysis. NS1 became fluorescent once bound to NOS with an excellent signal-to-noise ratio because of two-photon excitation avoiding interference from the flavin–autofluorescence and because free NS1 was not fluorescent in aqueous solutions. NS1 fluorescence enhancement was selective for constitutive NOS in vitro, in particular for endothelial NOS (eNOS). Molecular dynamics simulations suggested that two variable residues among NOS isoforms induced differences in binding of NS1 and in local solvation around NS1 nitro group, consistent with changes of NS1 fluorescence yield. NS1 colocalized with eNOS in living human umbilical vein endothelial cells. Thus, NS1 constitutes a unique class of eNOS probe with two-photon excitation in the 800–950-nm range, with great perspectives for eNOS imaging in living tissues. PMID:22802674

  19. Determination of the Residual Anthracene Concentration in Cultures of Haloalkalitolerant Actinomycetes by Excitation Fluorescence, Emission Fluorescence, and Synchronous Fluorescence: Comparative Study.

    PubMed

    Lara-Severino, Reyna Del Carmen; Camacho-López, Miguel Ángel; García-Macedo, Jessica Marlene; Gómez-Oliván, Leobardo M; Sandoval-Trujillo, Ángel H; Isaac-Olive, Keila; Ramírez-Durán, Ninfa

    2016-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are compounds that can be quantified by fluorescence due to their high quantum yield. Haloalkalitolerant bacteria tolerate wide concentration ranges of NaCl and pH. They are potentially useful in the PAHs bioremediation of saline environments. However, it is known that salinity of the sample affects fluorescence signal regardless of the method. The objective of this work was to carry out a comparative study based on the sensitivity, linearity, and detection limits of the excitation, emission, and synchronous fluorescence methods, during the quantification of the residual anthracene concentration from the following haloalkalitolerant actinomycetes cultures Kocuria rosea, Kocuria palustris, Microbacterium testaceum, and 4 strains of Nocardia farcinica, in order to establish the proper fluorescence method to study the PAHs biodegrading capacity of haloalkalitolerant actinobacteria. The study demonstrated statistical differences among the strains and among the fluorescence methods regarding the anthracene residual concentration. The results showed that excitation and emission fluorescence methods performed very similarly but sensitivity in excitation fluorescence is slightly higher. Synchronous fluorescence using Δλ = 150 nm is not the most convenient method. Therefore we propose the excitation fluorescence as the fluorescence method to be used in the study of the PAHs biodegrading capacity of haloalkalitolerant actinomycetes. PMID:26925294

  20. Determination of the Residual Anthracene Concentration in Cultures of Haloalkalitolerant Actinomycetes by Excitation Fluorescence, Emission Fluorescence, and Synchronous Fluorescence: Comparative Study

    PubMed Central

    Lara-Severino, Reyna del Carmen; Camacho-López, Miguel Ángel; García-Macedo, Jessica Marlene; Gómez-Oliván, Leobardo M.; Sandoval-Trujillo, Ángel H.; Isaac-Olive, Keila; Ramírez-Durán, Ninfa

    2016-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are compounds that can be quantified by fluorescence due to their high quantum yield. Haloalkalitolerant bacteria tolerate wide concentration ranges of NaCl and pH. They are potentially useful in the PAHs bioremediation of saline environments. However, it is known that salinity of the sample affects fluorescence signal regardless of the method. The objective of this work was to carry out a comparative study based on the sensitivity, linearity, and detection limits of the excitation, emission, and synchronous fluorescence methods, during the quantification of the residual anthracene concentration from the following haloalkalitolerant actinomycetes cultures Kocuria rosea, Kocuria palustris, Microbacterium testaceum, and 4 strains of Nocardia farcinica, in order to establish the proper fluorescence method to study the PAHs biodegrading capacity of haloalkalitolerant actinobacteria. The study demonstrated statistical differences among the strains and among the fluorescence methods regarding the anthracene residual concentration. The results showed that excitation and emission fluorescence methods performed very similarly but sensitivity in excitation fluorescence is slightly higher. Synchronous fluorescence using Δλ = 150 nm is not the most convenient method. Therefore we propose the excitation fluorescence as the fluorescence method to be used in the study of the PAHs biodegrading capacity of haloalkalitolerant actinomycetes. PMID:26925294

  1. Three-color femtosecond source for simultaneous excitation of three fluorescent proteins in two-photon fluorescence microscopy

    PubMed Central

    Wang, Ke; Liu, Tzu-Ming; Wu, Juwell; Horton, Nicholas G.; Lin, Charles P.; Xu, Chris

    2012-01-01

    We demonstrate a fiber-based, three-color femtosecond source for simultaneous imaging of three fluorescent proteins (FPs) using two-photon fluorescence microscopy (2PM). The three excitation wavelengths at 775 nm, 864 nm and 950 nm, are obtained through second harmonic generation (SHG) of the 1550-nm pump laser and the 1728-nm and 1900-nm solitons generated through soliton self-frequency shift (SSFS) in a large-mode-area (LMA) fiber. These energetic pulses are well matched to the two-photon excitation peaks of red, cyan and yellow fluorescent proteins (TagRFPs, TagCFPs, and TagYFPs) for efficient excitation. We demonstrate simultaneous 2PM of human melanoma cells expressing a “rainbow” combination of these three fluorescent proteins. PMID:23024893

  2. Laser-excited fluorescence for measuring atmospheric pollution

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.

    1975-01-01

    System measures amount of given pollutant at specific location. Infrared laser aimed at location has wavelength that will cause molecules of pollutant to fluoresce. Detector separates fluorescence from other radiation and measures its intensity to indicate concentration of pollutant.

  3. Solvent-induced multicolour fluorescence of amino-substituted 2,3-naphthalimides studied by fluorescence and transient absorption measurements.

    PubMed

    Fujii, Mayu; Namba, Misa; Yamaji, Minoru; Okamoto, Hideki

    2016-07-01

    A series of amino-2,3-naphthalimide derivatives having the amino functionality at 1-, 5- and 6-positions (, and , respectively) were prepared, and their photophysical properties were systematically investigated based on the measurements of steady-state absorption and fluorescence spectra, fluorescence lifetimes as well as transient absorption spectra. The s efficiently fluoresced in solution, and the emission spectra appreciably shifted depending on the solvent polarity. displayed only a slight fluorescence red-shift upon increasing the solvent polarity. In contrast, and showed marked positive solvatofluorochromism with large Stokes shifts displaying multicolour fluorescence; the fluorescence colours of and varied from violet-blue in hexane to orange-red in methanol. and , thus, serve as micro-environment responding fluorophores. In methanol, the intensity of the fluorescence emission band of and significantly reduced. Based on the fluorescence quantum yields and lifetimes, and transient absorption measurements, it has been revealed that internal conversion from the S1 state of s to the ground state was accelerated by the protic medium, resulting in a reduction in their fluorescence efficiency, while intersystem crossing from the S1 state to a triplet state was not responsible for the decrease of fluorescence intensity. PMID:27251860

  4. Optimal fluorescence excitation wavelengths for detection of squamous intra-epithelial neoplasia: results from an animal model

    NASA Astrophysics Data System (ADS)

    Coghlan, Lezlee; Utzinger, Urs; Drezek, Rebekah A.; Heintzelmann, Doug; Zuluaga, Andres F.; Brookner, Carrie; Richards-Kortum, Rebecca R.; Gimenez-Conti, Irma; Follen, Michele

    2000-12-01

    Using the hamster cheek pouch carcinogenesis model, we explore which fluorescence excitation wavelengths are useful for the detection of neoplasia. 42 hamsters were treated with DMBA to induce carcinogenesis, and 20 control animals were treated only with mineral oil. Fluorescence excitation emission matrices were measured from the cheek pouches of the hamsters weekly. Results showed increased fluorescence near 350-370 nm and 410 nm excitation and decreased fluorescence near 450-470 nm excitation with neoplasia. The optimal diagnostic excitation wavelengths identified using this model - 350-370 nm excitation and 400-450 nm excitation - are similar to those identified for detection of human oral cavity neoplasia.

  5. Polarization-induced control of two-photon excited fluorescence in a chiral polybinaphthyl

    NASA Astrophysics Data System (ADS)

    Zeng, Yi; Wang, Changshun; Zhao, Fuli; Huang, Xiaobo; Cheng, Yixiang

    2011-08-01

    The fluorescence behavior of a chiral polybinaphthyl excited with 100fs800nm laser pulses was investigated in tetrahydrofuran solution. The peak fluorescence intensity versus the input irradiance was measured to meet a square dependence, giving evidence for two-photon excited fluorescence (TPF). The variations of the TPF intensity were found to be strongly modulated by the different polarized incident lights and tightly depend on the linearly polarized component of the incident light. Furthermore, combining with the characteristics of chiral molecules, the two-photon polarization ratio was studied to reveal the symmetry of the involved excited states.

  6. Invited Review Article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy

    PubMed Central

    Carriles, Ramón; Schafer, Dawn N.; Sheetz, Kraig E.; Field, Jeffrey J.; Cisek, Richard; Barzda, Virginijus; Sylvester, Anne W.; Squier, Jeffrey A.

    2009-01-01

    We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences. PMID:19725639

  7. New Approaches for Correction of Interlayer Absorption Effects in X-ray Fluorescence Imaging of Paintings.

    PubMed

    Wróbel, Paweł M; Frączek, Piotr; Lankosz, Marek

    2016-02-01

    The X-ray fluorescence imaging technique allows not only the imaging itself but also the identification of the hidden paint layers what makes it much more versatile as compared with X-ray radiography. One of the main disadvantages of the former method is the fact that the characteristic X-rays from the deeper paint layers are absorbed in the covering layers. This effect is manifested by some artifacts that impede a proper interpretation of the acquired images. In this work, it is shown that the methodology for correction of the interlayer absorption effects can be extended to the case of polychromatic excitation. Additionally, a new approach for determination of the optimal correction parameters has also been presented. The methodology was verified using either the test painting or the mock-up painting both measured with a table-top micro-XRF setup. PMID:26708500

  8. pH Measurement Using Dual-Wavelength Fluorescent Ratio by Two-Photon Excitation for Mitochondrial Activity

    NASA Astrophysics Data System (ADS)

    Kanazashi, Yasuaki; Li, Yongbo; Onojima, Takumi; Iwami, Kentaro; Ohta, Yoshihiro; Umeda, Norihiro

    2012-11-01

    A mitochondrion has a pH gradient between the two sides of its inner membrane in order to produce adenosine triphosphate (ATP). Because ATP depletion causes numerous diseases, the measurement of the pH value around the mitochondrion is expected to clarify the mechanism of these diseases. In this study, a dual-wavelength pH-sensitive dye was excited by two-photon absorption initiated using a femtosecond pulse laser. In addition, fluorescence from the dye was directly collected from the fluorescent point using the collection-mode probe of a scanning near-field optical microscope. By this proposed method, a pH calibration curve was obtained from the fluorescent intensity ratio of the dye solution, and temporal pH variations with 0.1 s time resolution following the addition of acid were observed. Moreover, mitochondrial activity on the basis of the pH changes was successfully observed in three different mitochondrial densities.

  9. Dipolar relaxation within the protein matrix of the green fluorescent protein: a red edge excitation shift study.

    PubMed

    Haldar, Sourav; Chattopadhyay, Amitabha

    2007-12-27

    The fluorophore in green fluorescent protein (GFP) is localized in a highly constrained environment, protected from the bulk solvent by the barrel-shaped protein matrix. We have used the wavelength-selective fluorescence approach (red edge excitation shift, REES) to monitor solvent (environment) dynamics around the fluorophore in enhanced green fluorescent protein (EGFP) under various conditions. Our results show that EGFP displays REES in buffer and glycerol, i.e., the fluorescence emission maxima exhibit a progressive shift toward the red edge, as the excitation wavelength is shifted toward the red edge of the absorption spectrum. Interestingly, EGFP displays REES when incorporated in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT), independent of the hydration state. We interpret the observed REES to the constrained environment experienced by the EGFP fluorophore in the rigid protein matrix, rather than to the dynamics of the bulk solvent. These results are supported by the temperature dependence of REES and characteristic wavelength-dependent changes in fluorescence anisotropy. PMID:18052368

  10. OH(A-X) fluorescence from photodissociative excitation of HO2 at 157.5 nm

    NASA Technical Reports Server (NTRS)

    Suto, M.; Ye, C.; Mitchell, M. J.; Lee, L. C.

    1988-01-01

    The OH(A-X) fluorescence from photodissociative excitation of HO2 by F2 laser photons (157.5 nm) was observed and compared with the OH fluorescence spectra of H2O2 and the O2+CH3OH mixture. The rotational population distributions of OH(A) were obtained from the fluorescence spectra. The most populated levels are J = 4 for photodissociative excitation of HO2, J = 20 for H2O2, and J = 21 for the O2+CH3OH mixture. The fluorescence from the gas mixture is attributed to the O + H recombination for which the atoms are produced from photodissociation of parent molecules.

  11. CF2 and CFCl fluorescence from VUV excitation of C2F3Cl

    NASA Technical Reports Server (NTRS)

    Nee, J. B.; Wang, Xiuyan; Suto, Masako; Lee, L. C.

    1987-01-01

    The photoexcitation process of the C2F3Cl molecule was investigated in the 106-230-nm region using synchrotron radiation as a light source. Photoabsorption and fluorescence cross sections were measured and used to determine the fluorescence quantum yield. Fluorescence yield starts to appear at 170 nm and increases to about 2 percent at 155 nm. The fluorescence spectra were dispersed to identify the emitting species. The (A-X) systems of CFCl (at excitation wavelengths 155 and 123.9 nm) and CF2 (at 123.9 nm) are observed. The dissociation processes that produced these excited species are discussed.

  12. Polychromatic excitation improves detection limits in total reflection X-ray fluorescence analysis compared with monochromatic excitation.

    PubMed

    Kunimura, Shinsuke; Kawai, Jun

    2010-08-01

    Detection limits obtained by a portable total reflection X-ray fluorescence (TXRF) spectrometer with or without a monochromator are compared. A 1 W X-ray tube (tube voltage: 20 kV) is used in this spectrometer. Polychromatic excitation improves the detection limits in TXRF analysis with the low power X-ray tube compared with monochromatic excitation. A detection limit of 26 pg is achieved for Co when using the weak polychromatic X-rays. PMID:20535410

  13. Two-photon microscopy of living cells by simultaneously exciting multiple endogenous fluorophores and fluorescent proteins

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Li, Dong; Qu, Jianan Y.

    2010-02-01

    Endogenous fluorophores, such as reduced nicotinamide adenine dinucleotide (NADH), keratin, and tryptophan, have been used as contrast agents for imaging metabolism and morphology of living cells and tissues. Multilabeling which maps the distribution of different targets is an indispensable technique in many biomedical and biochemical studies. Therefore, two-photon excitation fluorescence (TPEF) microscopy of endogenous fluorophores combining with in vivo fluorescence labeling techniques such as genetically encoded fluorescent protein could be a powerful tool for imaging living cells and tissues. However, the challenge is that the excitation and emission wavelengths of these endogenous fluorophores and fluorescence labels are very different. A multi-color ultrafast source is required for the excitation of multiple fluorescence molecules. In this study, we developed a two-photon imaging system with excitations from the pump femtosecond laser and the selected Supercontinuum generated from a photonic crystal fiber (PCF). Multiple endogenous fluorophores and fluorescent proteins such as NADH, tryptophan, green fluorescent protein (GFP), and yellow fluorescent protein (YFP) were excited in their optimal wavelengths alternately or simultaneously. A time- and spectral-resolved detection system was used to record the TPEF signals. This detection technique separated the TPEF signals from multiple sources in time and spectral domains. Cellular organelles such as nucleus, mitochondria, microtubule and Endoplasmic Reticulum (ER), were clearly revealed in the TPEF images.

  14. Time-resolved multicolor two-photon excitation fluorescence microscopy of cells and tissues

    NASA Astrophysics Data System (ADS)

    Zheng, Wei

    2014-11-01

    Multilabeling which maps the distribution of different targets is an indispensable technique in many biochemical and biophysical studies. Two-photon excitation fluorescence (TPEF) microscopy of endogenous fluorophores combining with conventional fluorescence labeling techniques such as genetically encoded fluorescent protein (FP) and fluorescent dyes staining could be a powerful tool for imaging living cells. However, the challenge is that the excitation and emission wavelength of these endogenous fluorophores and fluorescent labels are very different. A multi-color ultrafast source is required for the excitation of multiple fluorescence molecules. In this study, we developed a two-photon imaging system with excitations from the pump femtosecond laser and the selected supercontinuum generated from a photonic crystal fiber (PCF). Multiple endogenous fluorophores, fluorescent proteins and fluorescent dyes were excited in their optimal wavelengths simultaneously. A time- and spectral-resolved detection system was used to record the TPEF signals. This detection technique separated the TPEF signals from multiple sources in time and wavelength domains. Cellular organelles such as nucleus, mitochondria, microtubule and endoplasmic reticulum, were clearly revealed in the TPEF images. The simultaneous imaging of multiple fluorophores of cells will greatly aid the study of sub-cellular compartments and protein localization.

  15. Fluorescence excitation-emission matrix characterization of river waters impacted by a tissue mill effluent.

    PubMed

    Baker, Andy

    2002-04-01

    Fluorescence excitation-emission matrix (EEM) spectrophotometry was applied to five neighboring rivers, including one that is impacted by wastewater from a large tissue mill, to determine if fluorescence spectrophotometry could be used to differentiate between the river waters. River water samples from both the tissue mill effluent and the impacted river, the Park Burn, exhibited significantly higher fluorescence intensity than the other sites. This fluorescence was dominated by tryptophan fluorescence and a fluorescence center possibly due to the presence of fluorescent whitening agents. In contrast, the three other rivers exhibited lower fluorescence intensities typical of river systems with tryptophan (sewage), humic-like (peat derived color), and fulvic-like (natural organic matter) sources. It is suggested that fluorescence EEM spectrophotometry has the potential to provide a useful tool for pollution detection, monitoring, and control of paper industry impacts on river systems. PMID:11999038

  16. Optimization of the design of a multiple-photon excitation laser scanning fluorescence imaging system

    NASA Astrophysics Data System (ADS)

    Wokosin, David L.; White, John G.

    1997-04-01

    Multi-photon (two or more photon) excitation imaging offers three significant advantages compared to laser-scanning confocal fluorescence microscopy for 3-D and 4-D fluorescence microscopy: considerable reduction in total sample excitation, increased depth penetration, and increased detection sensitivity. All-solid-state ultra-fast lasers offer tremendous potential for affordable, reliable, 'turn-key' multi-photon excitation sources. We have been developing a multi-photon system that utilizes an all-solid- state Nd:YLF excitation source. We have been evaluating the potential of this source for biological microscopy and have been optimizing system parameters for this application area. We have found that the 1047 nm radiation from these lasers can excite by two-photon fluorescence many commonly used fluorophores that are normally excited from blue to yellow light. In addition, we have found that this wavelength readily excites several normally UV excited fluorophores by the mechanism of three-photon excitation. The Nd:YLF laser has proven reliable in operation with nearly 6000 hours logged without significant loss of power. However, the original system produced rather long pulses for multi-photon excitation (300 fs) and a beam shape that was not ideal. We have recently commissioned the development of an improved pulse compressor from the manufacturers that gives narrower pulses (120 fs), improved beam shape, and a smaller insertion loss. This optimized excitation system has 6 times more potential two-photon excited fluorescence and 22 times more potential three-photon excited fluorescence than the prototype system. In addition, by optimizing coatings in the excitation and signal paths, we have improved the descanned detection sensitivity by 20% for two-photon excited fluorescence and 315% for three-photon excited fluorescence. The excitation optical transfer efficiency (1047 nm) of our imaging system is currently 60% to the back aperture of the objective. The

  17. Two-photon excitation with pico-second fluorescence lifetime imaging to detect nuclear association of flavanols.

    PubMed

    Mueller-Harvey, Irene; Feucht, Walter; Polster, Juergen; Trnková, Lucie; Burgos, Pierre; Parker, Anthony W; Botchway, Stanley W

    2012-03-16

    Two-photon excitation enabled for the first time the observation and measurement of excited state fluorescence lifetimes from three flavanols in solution, which were ~1.0 ns for catechin and epicatechin, but <45 ps for epigallocatechin gallate (EGCG). The shorter lifetime for EGCG is in line with a lower fluorescence quantum yield of 0.003 compared to catechin (0.015) and epicatechin (0.018). In vivo experiments with onion cells demonstrated that tryptophan and quercetin, which tend to be major contributors of background fluorescence in plant cells, have sufficiently low cross sections for two-photon excitation at 630 nm and therefore do not interfere with detection of externally added or endogenous flavanols in Allium cepa or Taxus baccata cells. Applying two-photon excitation to flavanols enabled 3-D fluorescence lifetime imaging microscopy and showed that added EGCG penetrated the whole nucleus of onion cells. Interestingly, EGCG and catechin showed different lifetime behaviour when bound to the nucleus: EGCG lifetime increased from <45 to 200 ps, whilst catechin lifetime decreased from 1.0 ns to 500 ps. Semi-quantitative measurements revealed that the relative ratios of EGCG concentrations in nucleoli associated vesicles: nucleus: cytoplasm were ca. 100:10:1. Solution experiments with catechin, epicatechin and histone proteins provided preliminary evidence, via the appearance of a second lifetime (τ(2)=1.9-3.1 ns), that both flavanols may be interacting with histone proteins. We conclude that there is significant nuclear absorption of flavanols. This advanced imaging using two-photon excitation and biophysical techniques described here will prove valuable for probing the intracellular trafficking and functions of flavanols, such as EGCG, which is the major flavanol of green tea. PMID:22340533

  18. Extending single molecule fluorescence observation time by amplitude-modulated excitation

    PubMed Central

    Kisley, Lydia; Chang, Wei-Shun; Cooper, David; Mansur, Andrea P; Landes, Christy F

    2014-01-01

    We present a hardware-based method that can improve single molecule fluorophore observation time by up to 1500% and super-localization by 47% for the experimental conditions used. The excitation was modulated using an acousto-optic modulator (AOM) synchronized to the data acquisition and inherent data conversion time of the detector. The observation time and precision in super-localization of four commonly used fluorophores were compared under modulated and traditional continuous excitation, including direct total internal reflectance excitation of Alexa 555 and Cy3, non-radiative Förster resonance energy transfer (FRET) excited Cy5, and direct epi-fluorescence wide field excitation of Rhodamine 6G. The proposed amplitude-modulated excitation does not perturb the chemical makeup of the system or sacrifice signal and is compatible with multiple types of fluorophores. Amplitude-modulated excitation has practical applications for any fluorescent study utilizing an instrumental setup with time-delayed detectors. PMID:24587894

  19. Vibrationally Resolved Absorption and Fluorescence Spectra of Firefly Luciferin: A Theoretical Simulation in the Gas Phase and in Solution.

    PubMed

    Cheng, Yuan-Yuan; Liu, Ya-Jun

    2016-07-01

    Firefly bioluminescence has been applied in several fields. However, the absorption and fluorescence spectra of the substrate, luciferin, have not been observed at the vibrational level. In this study, the vibrationally resolved absorption and fluorescence spectra of firefly luciferin (neutral form LH2 , phenolate ion form LH(-) and dianion form L(2-) ) are simulated using the density functional method and convoluted by a Gaussian function, with displacement, distortion and Duschinsky effects in the framework of the Franck-Condon approximation. Both neutral and anionic forms of the luciferin are considered in the gas phase and in solution. The simulated spectra have desired band maxima with the experimental ones. The vibronic structure analysis reveals that the features of the most contributive vibrational modes coincide with the key geometry-changing region during transition between the ground state and the first singlet excited state. PMID:27165852

  20. Exciting fluorescence compounds on an optical fiber's side surface with a liquid core waveguide.

    PubMed

    Ray, Jason C; Almas, Muhammad S; Tao, Shiquan

    2016-01-01

    A new fiber optic fluorescence spectroscopic method using a liquid core waveguide (LCW) as an excitation element has been developed for detecting a fluorescence compound absorbed on an optical fiber's surface. A laser light beam was coupled into a multimode optical fiber. The distal end of the fiber was inserted into an LCW. The diverging light emerging from the fiber's end was collected and guided within the LCW. A tapered optical fiber was inserted into the LCW from the other side. Laser light traveling in the LCW evenly illuminates the tapered fiber surface and excites fluorescence molecules absorbed on the tapered fiber's surface. Fluorescence light emitted from the tapered fiber surface was collected with the fiber itself and delivered through the fiber to an optical fiber compatible spectrometer for detection. This new technique provides an efficient way for evenly exciting fluorescence compounds absorbed on an optical fiber's surface. PMID:26696168

  1. Photoacoustic imaging of a near-infrared fluorescent marker based on dual wavelength pump-probe excitation

    NASA Astrophysics Data System (ADS)

    Märk, Julia; Theiss, Christoph; Schmitt, Franz-Josef; Laufer, Jan

    2014-03-01

    Photoacoustic imaging has been used to determine the spatial distribution of fluorophores, such as exogenous dyes and genetically expressed proteins, from images acquired in phantoms and in vivo. Most methods involve the acquisition of multiwavelength images and rely on differences in the absorption spectra of the tissue chromophores to estimate the spatial distribution and abundance of the latter using spectral decomposition techniques, such as model based inversion schemes. However, the inversion of 3-D images can be computationally expensive. Experimental approaches to localising contrast agents may therefore be useful, especially if quantification is not essential. This work aims to develop a method for determining the spatial distribution of a near-infrared fluorescent cell marker from images acquired using dual wavelength excitation. The excitation wavelengths coincided with the absorption and emission spectrum of the fluorophore. The contrast mechanism relies on reducing the excited state lifetime of the fluorophore by inducing stimulated emission. This changes the amount of energy thermalized by the fluorophore, and hence the photoacoustic signal amplitude. Since this is not observed in endogenous chromophores, the background may be removed by subtracting two images acquired with and without pulse delay between the pump and probe pulses. To characterise the fluorophore, the signal amplitude is measured in a cuvette as a function of pulse delay, concentration, and fluence. The spatial distribution of the fluorophore is determined from images acquired in realistic tissue phantoms. This method may be suitable for in vivo applications, such as imaging of exogenous or genetically expressed fluorescent cell markers.

  2. Optical nonlinearities in hyperbranched polyyne studied by two-photon excited fluorescence and third-harmonic generation spectroscopy

    NASA Astrophysics Data System (ADS)

    Castro-Beltran, R.; Ramos-Ortiz, G.; Jim, C. K. W.; Maldonado, J. L.; Häußler, M.; Peralta-Dominguez, D.; Meneses-Nava, M. A.; Barbosa-Garcia, O.; Tang, B. Z.

    2009-10-01

    The nonlinear optical properties of a hyperbranched polyyne ( hb-Polyyne) have been measured at infrared wavelengths by using femtosecond and nanosecond pulsed excitation. This hyperbranched polyyne exhibited strong and intrinsic (simultaneous) two-photon absorption and upconverted blue fluorescent emission under femtosecond excitation around 800 nm. The hb-Polyyne in chloroform solution is characterized by a large two-photon absorption cross section of 9068 GM (1 GM=10-50 cm4 s) and a fluorescence quantum yield of 0.57. On the other hand, by third-harmonic generation (THG) spectroscopy with nanosecond excitation, the measured third-order nonlinear susceptibility χ (3) for solid films of hb-Polyyne ranged from 2.4×10-11 to 6.1×10-11 esu in the spectral range of 1100-1600 nm, with results comparable to the values exhibited by the well-known conjugated polymer MEH:PPV, but with a much better transparency for visible wavelengths.

  3. Deeper Insight into Fluorescence-Excitation of Molecules by Light

    ERIC Educational Resources Information Center

    Wahab, M. Farooq; Gore, Gordon R.

    2013-01-01

    In a recent issue of "TPT," Gordon Gore made interesting observations about the red or yellow fluorescence when laser beams are passed through olive oil. With the excellent visuals contained in that article, we present a pictorial explanation of the questions that were raised in Ref 1 ("Fun with Fluorescence in Olive Oil,"…

  4. Noninvasive fluorescence excitation spectroscopy for the diagnosis of oral neoplasia in vivo

    NASA Astrophysics Data System (ADS)

    Ebenezar, Jeyasingh; Ganesan, Singaravelu; Aruna, Prakasarao; Muralinaidu, Radhakrishnan; Renganathan, Kannan; Saraswathy, Thillai Rajasekaran

    2012-09-01

    Fluorescence excitation spectroscopy (FES) is an emerging approach to cancer detection. The goal of this pilot study is to evaluate the diagnostic potential of FES technique for the detection and characterization of normal and cancerous oral lesions in vivo. Fluorescence excitation (FE) spectra from oral mucosa were recorded in the spectral range of 340 to 600 nm at 635 nm emission using a fiberoptic probe spectrofluorometer to obtain spectra from the buccal mucosa of 30 sites of 15 healthy volunteers and 15 sites of 10 cancerous patients. Significant FE spectral differences were observed between normal and well differentiated squamous cell carcinoma (WDSCC) oral lesions. The FE spectra of healthy volunteers consists of a broad emission band around 440 to 470 nm, whereas in WDSCC lesions, a new primary peak was seen at 410 nm with secondary peaks observed at 505, 540, and 580 nm due to the accumulation of porphyrins in oral lesions. The FE spectral bands of the WDSCC lesions resemble the typical absorption spectra of a porphyrin. Three potential ratios (I410/I505, I410/I540, and I410/I580) were calculated from the FE spectra and used as input variables for a stepwise linear discriminant analysis (SLDA) for normal and WDSCC groups. Leave-one-out (LOO) method of cross-validation was performed to check the reliability on spectral data for tissue characterization. The diagnostic sensitivity and specificity were determined for normal and WDSCC lesions from the scatter plot of the discriminant function scores. It was observed that diagnostic algorithm based on discriminant function scores obtained by SLDA-LOO method was able to distinguish WDSCC from normal lesions with a sensitivity of 100% and specificity of 100%. Results of the pilot study demonstrate that the FE spectral changes due to porphyrin have a good diagnostic potential; therefore, porphyrin can be used as a native tumor marker.

  5. o-nitrobenzyl photolabile protecting groups with red-shifted absorption: syntheses and uncaging cross-sections for one- and two-photon excitation.

    PubMed

    Aujard, Isabelle; Benbrahim, Chouaha; Gouget, Marine; Ruel, Odile; Baudin, Jean-Bernard; Neveu, Pierre; Jullien, Ludovic

    2006-09-01

    We evaluated the o-nitrobenzyl platform for designing photolabile protecting groups with red-shifted absorption that could be photolyzed upon one- and two-photon excitation. Several synthetic pathways to build different conjugated o-nitrobenzyl backbones, as well as to vary the benzylic position, are reported. Relative to the reference 4,5-dimethoxy-2-nitrobenzyl group, several o-nitrobenzyl derivatives exhibit a large and red-shifted one-photon absorption within the near-UV range. Uncaging after one-photon excitation was studied by measuring UV-visible absorption and steady-state fluorescence emission on model caged ethers and esters. In the whole series investigated, the caged substrates were released cleanly upon photolysis. Quantum yields of uncaging after one-photon absorption lie within the 0.1-1 % range. We observed that these drop as the maximum wavelength absorption of the o-nitrobenzyl protecting group is increased. A new method based on fluorescence correlation spectroscopy (FCS) after two-photon excitation was used to measure the action uncaging cross section for two-photon excitation. The series of o-nitrobenzyl caged fluorescent coumarins investigated exhibit values within the 0.1-0.01 Goeppert-Mayer (GM) range. Such results are in line with the low quantum yields of uncaging associated with cross-sections of 1-50 GM for two-photon absorption. Although the cross-sections for one- and two-photon absorption of o-nitrobenzyl photolabile protecting groups can be readily improved, we emphasize the difficulty in enlarging the corresponding action uncaging cross-sections in view of the observed trend of their quantum yield of uncaging. PMID:16763952

  6. Hyperspectral imaging fluorescence excitation scanning for detecting colorectal cancer: pilot study

    NASA Astrophysics Data System (ADS)

    Leavesley, Silas J.; Wheeler, Mikayla; Lopez, Carmen; Baker, Thomas; Favreau, Peter F.; Rich, Thomas C.; Rider, Paul F.; Boudreaux, Carole W.

    2016-03-01

    Optical spectroscopy and hyperspectral imaging have shown the theoretical potential to discriminate between cancerous and non-cancerous tissue with high sensitivity and specificity. To date, these techniques have not been able to be effectively translated to endoscope platforms. Hyperspectral imaging of the fluorescence excitation spectrum represents a new technology that may be well-suited for endoscopic implementation. However, the feasibility of detecting differences between normal and cancerous mucosa using fluorescence excitation-scanning hyperspectral imaging has not been evaluated. The objective of this pilot study was to evaluate the changes in the fluorescence excitation spectrum of resected specimen pairs of colorectal adenocarcinoma and normal colorectal mucosa. Patients being treated for colorectal adenocarcinoma were enrolled. Representative adenocarcinoma and normal colonic mucosa specimens were collected from each case. Specimens were flash frozen in liquid nitrogen. Adenocarcinoma was confirmed by histologic evaluation of H&E permanent sections. Hyperspectral image data of the fluorescence excitation of adenocarcinoma and surrounding normal tissue were acquired using a custom microscope configuration previously developed in our lab. Results demonstrated consistent spectral differences between normal and cancerous tissues over the fluorescence excitation spectral range of 390-450 nm. We conclude that fluorescence excitation-scanning hyperspectral imaging may offer an alternative approach for differentiating adenocarcinoma and surrounding normal mucosa of the colon. Future work will focus on expanding the number of specimen pairs analyzed and will utilize fresh tissues where possible, as flash freezing and reconstituting tissues may have altered the autofluorescence properties.

  7. Taking the spectral overlap between excitation and emission spectra of fluorescent materials into account with Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Leyre, Sven; Ryckaert, Jana; Acuna, Paula; Audenaert, Jan; Meuret, Youri; Hofkens, Johan; Durinck, Guy; Deconinck, Geert; Hanselaer, Peter

    2014-05-01

    Monte Carlo ray tracing is an important simulation tool in applications where fluorescence is present, e.g. in bio-medical applications and in the design of luminaires and luminescent solar concentrators. A frequently used ray tracing procedure for fluorescence is the `dual stage' approach. In this approach, first, all sources are traced through the system and the rays absorbed in the fluorescent components are stored. Next, the emission from the fluorescent components is traced. This approach does not allow for subsequent re-absorption and re-emission effects in fluorescent materials with a spectral overlap between excitation and emission spectra. In this work, a `multi stage' ray tracing procedure for the simulation of luminescence is presented. Herein, wavelengths are traced from short to long separately and no distinction is made regarding the origin of emission (either a fluorescent component or a source). The presented approach can be easily implemented in existing commercial ray tracing software thus reducing the programming efforts for the new ray tracing algorithm and taking advantage of the strength of the selected ray tracing package concerning the modelling of complex geometrical systems. Both techniques are compared to investigate the influence of the selected ray tracing approach on the efficiency and colour prediction of a remote phosphor LED module.

  8. Enhanced energy transfer in respiratory-deficient endothelial cells probed by microscopic fluorescence excitation spectroscopy

    NASA Astrophysics Data System (ADS)

    Schneckenburger, Herbert; Gschwend, Michael H.; Bauer, Manfred; Strauss, Wolfgang S. L.; Steiner, Rudolf W.

    1996-12-01

    Mitochondrial malfunction may be concomitant with changes of the redox states of the coenzymes nicotinamide adenine dinucleotide (NAD+/NADH), as well as flavin.mononucleotide or dinucleotide. The intrinsic fluorescence of these coenzymes was therefore proposed to be a measure of malfunction. Since mitochondrial fluorescence is strongly superposed by autofluorescence from various cytoplasmatic fluorophores, cultivated endothelial cells were incubated with the mitochondrial marker rhodamine 123 (R123), and after excitation of flavin molecules, energy transfer to R123 was investigated. Due to spectral overlap of flavin and R123 fluorescence, energy transfer flavin yields R123 could not be detected from their emission spectra. Therefore, the method of microscopic fluorescence excitation spectroscopy was established. When detecting R123 fluorescence, excitation maxima at 370 - 390 nm and 420-460 nm were assigned to flavins, whereas a pronounced excitation band at 465 - 490 nm was attributed to R123. Therefore, excitation at 475 nm reflected the intracellular concentration of R123, whereas excitation at 385 nm reflected flavin excitation with a subsequent energy transfer to R123 molecules. An enhanced energy transfer after inhibition of specific enzyme complexes of the respiratory chain is discussed in the present article.

  9. Multi-Channel Hyperspectral Fluorescence Detection Excited by Coupled Plasmon-Waveguide Resonance

    PubMed Central

    Du, Chan; Liu, Le; Zhang, Lin; Guo, Jun; Guo, Jihua; Ma, Hui; He, Yonghong

    2013-01-01

    We propose in this paper a biosensor scheme based on coupled plasmon-waveguide resonance (CPWR) excited fluorescence spectroscopy. A symmetrical structure that offers higher surface electric field strengths, longer surface propagation lengths and depths is developed to support guided waveguide modes for the efficient excitation of fluorescence. The optimal parameters for the sensor films are theoretically and experimentally investigated, leading to a detection limit of 0.1 nM (for a Cy5 solution). Multiplex analysis possible with the fluorescence detection is further advanced by employing the hyperspectral fluorescence technique to record the full spectra for every pixel on the sample plane. We demonstrate experimentally that highly overlapping fluorescence (Cy5 and Dylight680) can be distinguished and ratios of different emission sources can be determined accurately. This biosensor shows great potential for multiplex detections of fluorescence analytes. PMID:24129023

  10. Moving Towards a Technical Specification for Fluorescence Excitation-Emission Mapping and Absorbance Analysis of Colored Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Gilmore, A. M.

    2010-12-01

    Colored dissolved organic matter (CDOM) measurements with fluorescence and absorbance are important for evaluating a wide variety natural and industrial water sources. However, uncertainties and ambiguities continue to be propagated regarding interpretation of CDOM spectral data due to the variety of instruments, sampling chemistry conditions and types of analysis algorithms. Recent efforts have focused on standardization and interlaboratory comparisons of CDOM samples with respect to preparation, spectroscopic evaluation and mathematical analysis. This study deals with correlating absorbance and fluorescence data measured with the same sample to minimize interlaboratory variation. The theoretical significance of true simultaneous acquisition of the corrected (NIST Traceable) absorbance spectrum and fluorescence excitation spectral profile and excitation emission map is discussed as a means to provide the least ambiguous spectral data. Key issues considered are the variations introduced by ‘serial’ acquisitions of absorbance and fluorescence data. Variation can be caused by the different light-exposure history (especially UV) in the instruments, dissolved oxygen content associated with temperature changes and oxidation kinetics of the CDOM and in many cases concentration- and pH-related changes associated with diluting and pH buffering of the CDOM sample, respectively. Concentration changes in CDOM can be associated with optical anomalies including self-quenching and -absorption which systematically alter the fluorescence spectrum. Clearly, monitoring the absorbance and fluorescence simultaneously would deal with the above sampling variations and facilitate correcting the absorbance based fluorescence anomalies. The proposed method(s) described will be discussed in view of their potential to serve as the basis for an international technical specification in terms of the optical instrument and sampling conditions for CDOM analysis and reporting.

  11. Fluorescence from Pearls under N2 Laser Excitation and Its Application to Distinction of Mother Oysters

    NASA Astrophysics Data System (ADS)

    Miyoshi, Tadaki; Matsuda, Yasunori; Komatsu, Hiroshi

    1986-10-01

    Fluorescence spectra of pearls of Pinctada fucata (Japan’s Akoya oyster) and Pinctada maxima (white lip oyster) have been measured in order to distinguish species of the mother oyster which produce that pearl. A distinction is possible for these pearls using the difference in the fluorescence spectra under N2 laser excitation.

  12. Capillary Electrophoresis and Fluorescence Excitation-Emission Matrix Characterization of Soil Mobile and Calcium Humates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Capillary electrophoresis (CE) and Excitation-emission matrix (EEM) fluorescence spectroscopy have been used in natural organic matter (NOM) studies. The mutual relevance of data collected from each of the two methods provides novel insight into the correlation of complex NOM fluorescence spectra to...

  13. Tracking of mercury ions in living cells with a fluorescent chemodosimeter under single- or two-photon excitation.

    PubMed

    Lu, Zhou-Jun; Wang, Pei-Nan; Zhang, Yu; Chen, Ji-Yao; Zhen, Shen; Leng, Bing; Tian, He

    2007-08-01

    Tracking of Hg2+ in solutions as well as in living cells was conducted with a fluorescent chemodosimeter by measuring the spectral shift of its fluorescence under single- or two-photon excitation. The spectral hypsochromic shifts of this chemodosimeter when reacting with Hg2+ were found to be about 50 nm in acetonitrile/water solutions and 32 nm in Euglena gracilis 277 living cells. This chemodosimeter shows high sensitivity and selectivity, and is not influenced by the pH values. It can signal Hg2+ in solutions down to the ppb range under either single-photon excitation (SPE) at 405 nm or two-photon excitation (TPE) at 800 nm. However, with low cellular chemodosimeter concentrations, the SPE spectra were disturbed by the auto-fluorescence from the native fluorophore in the cell, while the TPE spectra were still of high quality since the two-photon absorption cross section of this chemodosimeter is much larger than that of the native fluorophores in the cell. PMID:17683744

  14. Conjugated Polymer-Based Hybrid Nanoparticles with Two-Photon Excitation and Near-Infrared Emission Features for Fluorescence Bioimaging within the Biological Window.

    PubMed

    Lv, Yanlin; Liu, Peng; Ding, Hui; Wu, Yishi; Yan, Yongli; Liu, Heng; Wang, Xuefei; Huang, Fei; Zhao, Yongsheng; Tian, Zhiyuan

    2015-09-23

    Hybrid fluorescent nanoparticles (NPs) capable of fluorescing near-infrared (NIR) light (centered ∼730 nm) upon excitation of 800 nm laser light were constructed. A new type of conjugated polymer with two-photon excited fluorescence (TPEF) feature, P-F8-DPSB, was used as the NIR-light harvesting component and the energy donor while a NIR fluorescent dye, DPA-PR-PDI, was used as the energy acceptor and the NIR-light emitting component for the construction of the fluorescent NPs. The hybrid NPs possess δ value up to 2.3 × 10(6) GM per particle upon excitation of 800 nm pulse laser. The excellent two-photon absorption (TPA) property of the conjugated polymer component, together with its high fluorescence quantum yield (ϕ) up to 45% and the efficient energy transfer from the conjugated polymer to NIR-emitting fluorophore with efficiency up to 90%, imparted the hybrid NPs with TPEF-based NIR-input-NIR-output fluorescence imaging ability with penetration depth up to 1200 μm. The practicability of the hybrid NPs for fluorescence imaging in Hela cells was validated. PMID:26340609

  15. Short-range ordered photonic structures of lamellae-forming diblock copolymers for excitation-regulated fluorescence enhancement

    NASA Astrophysics Data System (ADS)

    Kim, Se Hee; Kim, Ki-Se; Char, Kookheon; Yoo, Seong Il; Sohn, Byeong-Hyeok

    2016-05-01

    Photonic crystals can be represented by periodic nanostructures with alternating refractive indices, which create artificial stop bands with the appearance of colors. In this regard, nanodomains of block copolymers and the corresponding structural colors have been intensively studied in the past. However, the practical application of photonic crystals of block copolymers has been limited to a large degree because of the presence of large defects and grain boundaries in the nanodomains of block copolymers. The present study focuses on the alternative opportunity of short-range ordered nanodomains of block copolymers for fluorescence enhancement, which also has a direct relevance to the development of fluorescence sensors or detectors. The enhancement mechanism was found to be interconnected with the excitation process rather than the alternation of the decay kinetics. In particular, we demonstrate that randomly oriented, but regular grains of lamellae of polystyrene-block-polyisoprene, PS-b-PI, diblock copolymers and their blend with PS homopolymers can behave as Bragg mirrors to induce multiple reflections of the excitation source inside the photonic structures. This process in turn significantly increases the effective absorption of the given fluorophores inside the polymeric photonic structures to amplify the fluorescence signal.Photonic crystals can be represented by periodic nanostructures with alternating refractive indices, which create artificial stop bands with the appearance of colors. In this regard, nanodomains of block copolymers and the corresponding structural colors have been intensively studied in the past. However, the practical application of photonic crystals of block copolymers has been limited to a large degree because of the presence of large defects and grain boundaries in the nanodomains of block copolymers. The present study focuses on the alternative opportunity of short-range ordered nanodomains of block copolymers for fluorescence

  16. Ultrafast Excited-State Dynamics in the Green Fluorescent Protein Variant S65T/H148D 1. Mutagenesis and Structural Studies†

    PubMed Central

    Shu, Xiaokun; Kallio, Karen; Shi, Xinghua; Abbyad, Paul; Kanchanawong, Pakorn; Childs, William; Boxer, Steven G.; Remington, S. James

    2008-01-01

    Wild type green fluorescent protein (wt-GFP) and the variant S65T/H148D each exhibit two absorption bands, A and B, which are associated with the protonated and deprotonated chromophores respectively. Excitation of either band leads to green emission. In wt-GFP, excitation of band A (~390 nm) leads to green emission with a rise time of 10–15 picoseconds, due to excited state proton transfer (ESPT) from the chromophore hydroxyl group to an acceptor. This process produces an anionic excited state intermediate I* that subsequently emits a green photon. In the variant S65T/H148D, the A band absorbance maximum is red-shifted to ~415 nm and as detailed in the accompanying papers (1, 2), when the A band is excited, green fluorescence appears with rise time shorter than the instrument time resolution (~170 fs). Based on steady state spectroscopy and high resolution crystal structures of several variants described herein, we propose that in S65T/H148D, the red shift of absorption band A and the ultrafast appearance of green fluorescence upon excitation of band A is due to a very short (≤ 2.4 Å), and possibly low barrier, hydrogen bond between the chromophore hydroxyl and introduced Asp148. PMID:17918959

  17. The effects of refractive index heterogeneity within kidney tissue on multiphoton fluorescence excitation microscopy.

    PubMed

    Young, P A; Clendenon, S G; Byars, J M; Dunn, K W

    2011-05-01

    Although multiphoton fluorescence excitation microscopy has improved the depth at which useful fluorescence images can be collected in biological tissues, the reach of multiphoton fluorescence excitation microscopy is nonetheless limited by tissue scattering and spherical aberration. Scattering can be reduced in fixed samples by mounting in a medium whose refractive index closely matches that of the fixed material. Using optical 'clearing', the effects of refractive index heterogeneity on signal attenuation with depth are investigated. Quantitative measurements show that by mounting kidney tissue in a high refractive index medium, less than 50% of signal attenuates in 100 μm of depth. PMID:21118239

  18. Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Cheng, Yan; Chini, Michael; Wang, Xiaowei; González-Castrillo, Alberto; Palacios, Alicia; Argenti, Luca; Martín, Fernando; Chang, Zenghu

    2016-08-01

    Attosecond science promises to allow new forms of quantum control in which a broadband isolated attosecond pulse excites a molecular wave packet consisting of a coherent superposition of multiple excited electronic states. This electronic excitation triggers nuclear motion on the molecular manifold of potential energy surfaces and can result in permanent rearrangement of the constituent atoms. Here, we demonstrate attosecond transient absorption spectroscopy (ATAS) as a viable probe of the electronic and nuclear dynamics initiated in excited states of a neutral molecule by a broadband vacuum ultraviolet pulse. Owing to the high spectral and temporal resolution of ATAS, we are able to reconstruct the time evolution of a vibrational wave packet within the excited B'Σ1u+ electronic state of H2 via the laser-perturbed transient absorption spectrum.

  19. New aspects concerning the energy transfer in carotenoids by measuring intracavity absorption spectra and delayed fluorescence

    NASA Astrophysics Data System (ADS)

    Bettermann, Hans; Bouschen, Werner; Ulrich, Lars; Domnick, Gabriele; Martin, H. D.

    1999-05-01

    The first excited singlet state and the lower energetic triplet states of carotenoids are considered to be involved in the light-harvesting as well as in the photochemical protection of cells, respectively. For this reason, the symmetry-forbidden S 0-S 1 (1 1A g-2 1A g) transitions and the multiplicity-forbidden S 0-T 2 (1 1A g-2 3A g) transition of the model carotenoid 8,13-dimethyl-2,2,19,19-tetramethoxy-icosa-4,6,8,10,12,14,16-heptaene-3,18-dione were investigated by intracavity absorption spectroscopy from low-concentrated ethanolic solutions. Both transitions are shaped by promoting modes caused by Herzberg-Teller coupling and the sequence of these modes allows the precise determination of the non-visible S 0-S 1 (0-0)- and S 0-T 2 (0-0)-transitions. The assignments of the singlet-triplet transitions were additionally supported by measuring delayed fluorescence from crystalline samples by directly exciting vibronic triplet states. The vibronic coupling is promoted by C-H bending vibrations of the chain and mainly by deformation modes of the terminating groups of the carotenoid.

  20. Single-molecule detection using continuous wave excitation of two-photon fluorescence

    NASA Astrophysics Data System (ADS)

    Hou, Ximiao; Cheng, Wei

    2011-08-01

    Two-photon fluorescence (TPF) is one of the most important discoveries for biological imaging. Although a cw laser is known to excite TPF, its application in TPF imaging has been very limited due to the perceived low efficiency of excitation. Here we directly excited fluorophores with an IR cw laser used for optical trapping and achieved single-molecule fluorescence sensitivity: discrete stepwise photobleaching of enhanced green fluorescent proteins was observed. The single-molecule fluorescence intensity analysis and on-time distribution strongly indicate that a cw laser can generate TPF detectable at the single-molecule level, and thus opens the door to single-molecule TPF imaging using cw lasers.

  1. Describing two-photon absorptivity of fluorescent proteins with a new vibronic coupling mechanism.

    PubMed

    Drobizhev, M; Makarov, N S; Tillo, S E; Hughes, T E; Rebane, A

    2012-02-01

    Fluorescent proteins (FPs) are widely used in two-photon microscopy as genetically encoded probes. Understanding the physical basics of their two-photon absorption (2PA) properties is therefore crucial for creation of two-photon brighter mutants. On the other hand, it can give us better insight into molecular interactions of the FP chromophore with a complex protein environment. It is known that, compared to the one-photon absorption spectrum, where the pure electronic transition is the strongest, the 2PA spectrum of a number of FPs is dominated by a vibronic transition. The physical mechanism of such intensity redistribution is not understood. Here, we present a new physical model that explains this effect through the "Herzberg-Teller"-type vibronic coupling of the difference between the permanent dipole moments in the ground and excited states (Δμ) to the bond-length-alternating coordinate. This model also enables us to quantitatively describe a large variability of the 2PA peak intensity in a series of red FPs with the same chromophore through the interference between the "Herzberg-Teller" and Franck-Condon terms. PMID:22224830

  2. Laser-excitation atomic fluorescence spectroscopy in a helium microwave-induced plasma

    NASA Astrophysics Data System (ADS)

    Schroeder, Timothy S.

    The focus of this dissertation is to report the first documented coupling of helium microwave induced plasmas (MIPs) to laser excitation atomic fluorescence spectroscopy. The ability to effectively produce intense atomic emission from both metal and nonmetal analytes gives helium microwave induced plasmas a greater flexibility than the more commonly utilized argon inductively coupled plasma (ICP). Originally designed as an element selective detector for non-aqueous chromatography applications at low applied powers (<100W), the helium microwave plasma has been applied to aqueous sample determinations at higher applied powers (>500 W). The helium MIP has been shown to be a very powerful analytical atomic spectroscopy tool. The development of the pulsed dye laser offered an improved method of excitation in the field of atomic fluorescence. The use of laser excitation for atomic fluorescence was a logical successor to the conventional excitation methods involving hollow cathode lamps and continuum sources. The highly intense, directional, and monochromatic nature of laser radiation results in an increased population of atomic species in excited electronic states where atomic fluorescence can occur. The application of laser excitation atomic fluorescence to the analysis of metals in a helium microwave induced plasma with ultrasonic sample nebulization was the initial focus of this work. Experimental conditions and results are included for the aqueous characterization of manganese, lead, thallium, and iron in the helium MIP- LEAFS system. These results are compared to previous laser excitation atomic fluorescence experimentation. The effect of matrix interferences on the analytical fluorescence signal was also investigated for each element. The advantage of helium MIPs over argon ICPs in the determination of nonmetals in solution indicates that the helium MIP is an excellent candidate for laser excitation atomic fluorescence experiments involving nonmetals such as

  3. Statistical image segmentation for the detection of skin lesion borders in UV fluorescence excitation

    NASA Astrophysics Data System (ADS)

    Ortega-Martinez, Antonio; Padilla-Martinez, Juan Pablo; Franco, Walfre

    2016-04-01

    The skin contains several fluorescent molecules or fluorophores that serve as markers of structure, function and composition. UV fluorescence excitation photography is a simple and effective way to image specific intrinsic fluorophores, such as the one ascribed to tryptophan which emits at a wavelength of 345 nm upon excitation at 295 nm, and is a marker of cellular proliferation. Earlier, we built a clinical UV photography system to image cellular proliferation. In some samples, the naturally low intensity of the fluorescence can make it difficult to separate the fluorescence of cells in higher proliferation states from background fluorescence and other imaging artifacts -- like electronic noise. In this work, we describe a statistical image segmentation method to separate the fluorescence of interest. Statistical image segmentation is based on image averaging, background subtraction and pixel statistics. This method allows to better quantify the intensity and surface distributions of fluorescence, which in turn simplify the detection of borders. Using this method we delineated the borders of highly-proliferative skin conditions and diseases, in particular, allergic contact dermatitis, psoriatic lesions and basal cell carcinoma. Segmented images clearly define lesion borders. UV fluorescence excitation photography along with statistical image segmentation may serve as a quick and simple diagnostic tool for clinicians.

  4. Two-photon excited fluorescence microscopy application for ex vivo investigation of ocular fundus samples

    NASA Astrophysics Data System (ADS)

    Peters, Sven; Hammer, Martin; Schweitzer, Dietrich

    2011-07-01

    Two-photon excited fluorescence (TPEF) imaging of ocular tissue has recently become a promising tool in ophthalmology for diagnostic and research purposes. The feasibility and the advantages of TPEF imaging, namely deeper tissue penetration and improved high-resolution imaging of microstructures, have been demonstrated lately using human ocular samples. The autofluorescence properties of endogenous fluorophores in ocular fundus tissue are well known from spectrophotometric analysis. But fluorophores, especially when it comes to fluorescence lifetime, typically display a dependence of their fluorescence properties on local environmental parameters. Hence, a more detailed investigation of ocular fundus autofluorescence ideally in vivo is of utmost interest. The aim of this study is to determine space-resolved the stationary and time-resolved fluorescence properties of endogenous fluorophores in ex vivo porcine ocular fundus samples by means of two-photon excited fluorescence spectrum and lifetime imaging microscopy (FSIM/FLIM). By our first results, we characterized the autofluorescence of individual anatomical structures of porcine retina samples excited at 760 nm. The fluorescence properties of almost all investigated retinal layers are relatively homogenous. But as previously unknown, ganglion cell bodies show a significantly shorter fluorescence lifetime compared to the adjacent mueller cells. Since all retinal layers exhibit bi-exponential autofluorescence decays, we were able to achieve a more precise characterization of fluorescence properties of endogenous fluorophores compared to a present in vivo FLIM approach by confocal scanning laser ophthalmoscope (cSLO).

  5. The Fe XI-excited fluorescent cascade in Ne IV

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Kastner, S. O.

    1990-01-01

    A theoretical spectroscopic investigation of the fluorescent cascade to be expected in nitrogen-like Ne IV, when it is resonantly photoexcited by Fe XI in the solar atmosphere, symbiotic stars, or novae, is described. Primary and secondary cascade intensities are obtained as functions of photoexcitation rate, and expected absolute intensities in the solar atmosphere are derived on the basis of observed Fe XI and Ne EUV emission. Comparisons between the spatially resolved solar situation and spatially unresolved stellar cases of cataclysmic variables, in which these ions have been found to coexist, are made. An interesting possibility of periodic time-dependent fluorescence exists for the binary cataclysmics.

  6. Photochemistry on surfaces: Fluorescence emission of monomers and dimers and triplet state absorption of acridine orange adsorbed on microcrystalline cellulose

    NASA Astrophysics Data System (ADS)

    Wilkinson, F.; Worrall, D. R.; Ferreira, L. F. Vieira

    1992-02-01

    Prompt fluorescence as well as delayed fluorescence emission of acridine orange was detected at room temperature from samples where this dye is adsorbed on microcrystalline cellulose. Ground state absorption studies provided evidence for dimer formation of the dye when adsorbed on cellulose, and the equilibrium constant for dimerisation was determined as 1.6±0.1 × 10 6mol -1g. At low loadings of acridine orange on cellulose (<1 μmol g -1) the fluorescence emission is mainly due to the monomer and is similar to that observed in ethanolic solutions where little aggregation occurs, and peaks at 530 nm. A linear dependence of the fluorescence intensity on the amount of light absorbed by the dye was established for these "diluted" samples. However, at higher loadings (>20 μmol g -1), the fluorescence intensity decreases, and the emission is broad with its maximum at 620 nm, and is mainly due to the dimer. By assuming that the excited monomer and dimer of acridine orange are the only emitting species, it was possible to determine the fluorescence quantum yields for these two species when adsorbed on microcrystalline cellulose as 0.95±0.05 and 0.40±0.10, respectively. Pulsed emission studies at room temperature in the millisecond time-range also revealed monomer and dimer emissions on this longer time-scale. These are shown to be due to thermally activated delayed fluorescence arising from the triplet states of monomer and dimer acridine orange as confirmed by diffuse reflectance transient absorption studies.

  7. Atomic-fluorescence analysis of materials using a lamp-pumped dye LZhI laser as an excitation source

    SciTech Connect

    Denisov, L.K.; Loshin, A.F.; Nikiforov, V.G.; Sterlyadkina, E.A.

    1987-12-01

    The use of frequency-tunable dye lasers in atomic-fluorescence analysis has made it possible to lower significantly the limits of detection for most elements. In this work the commercially produced lamp-pumped dye lasers of the type LZhI were used as the excitation source, which made it possible, first of all, to simplify the design of the atomic-fluorescence spectrometer by eliminating the frequency doubling of the laser radiation and, second, to study the analytical possibilities of commercially produced dye lasers with microsecond lasing. The authors studied solutions of sodium, barium, potassium, calcium, nickel, cobalt, copper, and molybdenum salts. These elements were chosen based on the fact that they have absorption lines with different degrees of intensity in the region of generation of the most efficient rhodamine 6G dye laser.

  8. Encapsulation of 3-hydroxyflavone in γ-cyclodextrin nanocavities: Excited state proton transfer fluorescence and molecular docking studies

    NASA Astrophysics Data System (ADS)

    Pahari, Biswapathik; Chakraborty, Sandipan; Sengupta, Pradeep K.

    2011-12-01

    Steady state and time resolved fluorescence spectroscopy have been used to explore the confinement of 3-hydroxyflavone (3HF), (a bioactive flavonol) in γ-cyclodextrin (γ-CDx) nanocavities in aqueous medium. With increasing concentrations of γ-CDx, dramatic enhancements occur in the intensity and anisotropy of the excited state intramolecular proton transfer (ESIPT) tautomer fluorescence of 3HF. These observations indicate that 3HF readily enters the relatively hydrophobic cavity of γ-CDx, where the chromone ring is well shielded from external H-bonding perturbation effects, thus facilitates the ESIPT process. Additionally, appearance of induced circular dichroism (ICD) bands is noted in the absorption region of 3HF, which further confirms the inclusion process. Docking calculations suggest that hydrogen bonding interactions are involved in the formation of the inclusion complex.

  9. Saturable absorption and two-photon absorption of 1,2,5-thiadiazolo[3,4-g]quinoxaline based derivatives with near-infrared fluorescence

    NASA Astrophysics Data System (ADS)

    Du, Yabing; Lin, Xiaodong; Jia, Tingjian; Dong, Jun

    2015-03-01

    Organic molecules with near-infrared (NIR) fluorescence are extremely interesting for the applications in nonlinear optical devices and bioimaging. However, such kind of materials have been relatively rarely studied. In this work, the nonlinear optical properties of 1,2,5-thiadiazolo[3,4-g]quinoxaline based derivatives with NIR fluorescence emission have been investigated for the first time. Under the excitation of femtosecond pulses at 532 nm, the chromophore with dithienyl as donor (TQ2) presents saturable absorption (SA) behavior, while no SA has been observed in the derivative with biphenyl (TQ1) as donor. Moreover, TQ2 exhibits much larger two-photon absorption (TPA) cross-sections with strong NIR fluorescence in the second biological window. The larger nonlinear optical properties of TQ2 is due to the introduction of stronger electron-donating group (dithienyl) and the resultant enhanced intramolecular charge transfer properties. At the end, TPA based optical limiting behaviors of the molecules are demonstrated in THF solutions, thanks to their large solubility and strong TPA.

  10. Deeper Insight into Fluorescence--Excitation of Molecules by Light

    NASA Astrophysics Data System (ADS)

    Wahab, M. Farooq; Gore, Gordon R.

    2013-05-01

    In a recent issue of TPT, Gordon Gore made interesting observations about the red or yellow fluorescence when laser beams are passed through olive oil. With the excellent visuals contained in that article, we present a pictorial explanation of the questions that were raised in Ref 1.

  11. Biocompatible glutathione capped gold clusters as one- and two-photon excitation fluorescence contrast agents for live cells imaging.

    PubMed

    Polavarapu, Lakshminarayana; Manna, Manoj; Xu, Qing-Hua

    2011-02-01

    The one- and two-photon excitation emission properties of water soluble glutathione monolayer protected gold clusters were investigated. Strong two-photon emission was observed from the gold clusters. The two-photon absorption cross section of these gold clusters in water was deduced from the z-scan measurement to be 189 740 GM, which is much higher compared to organic fluorescent dyes and quantum dots. These gold clusters also showed high photo-stability. The MTT assay showed that these gold clusters have low toxicity even at high concentrations. We have successfully demonstrated their applications for both one and two-photon excitation live cell imaging. The exceptional properties of these gold clusters make them a promising alternative for one- and two-photon bio-imaging and other nonlinear optical applications. PMID:20944843

  12. UV-Excited Fluorescence of Rocks in Gale Crater, Mars

    NASA Astrophysics Data System (ADS)

    Fisk, M. R.; Pommerenck, J.; Watkins-Brandt, K.; Edgett, K. S.; Minitti, M. E.; Hardgrove, C. J.; Popa, R.; Goetz, W.; Cloutis, E.; Nixon, B.; Kennedy, M. R.; Treiman, A. H.

    2015-12-01

    Curiosity, the Mars Science Laboratory rover, landed in Gale crater in 2012. The Mars Hand Lens Imager (MAHLI), located on Curiosity's robotic arm, can be placed as close as 0.2 cm from targets. At this distance it has a pixel scale of ~13 µm/pixel. MAHLI usually images in daylight, but light emitting diodes (LEDs) located around the lens make nighttime imaging possible. Two of the six LEDs produce 365 nm long wave UV and near-UV light and small amounts of green and red light. On Mars MAHLI has taken images of UV-illuminated rocks, drill tailings, and a fluorescent calibration standard. In a lab test bed we took images of UV-illuminated terrestrial minerals. The test bed UV LEDs are equivalent to those on MAHLI. Fluorescence in the test bed was inferred when the color of the mineral in UV light was shifted from the color of the reflected incident UV light on non-fluorescing targets. We demonstrate this shift with terrestrial minerals: willemite (ZnSiO4) is green, fluorite (CaF2) is blue, fluorapatite (Ca5(PO4)3F) is yellow, and (some) calcites are red (Figure). Bassanite (CaSO4•½H2O) has been identified in sedimentary rock in Gale, and under long wave UV illumination, terrestrial bassanite fluoresces blue. In addition to bassanite, fluorite and apatite are candidate minerals in Gale crater. Portions of a bassanite-bearing target in Gale appear to fluoresce blue under MAHLI UV illumination. Adjacent to the bassanite is a dark mineral that yields a signal with more blue and less red and green than the bassanite suggesting a second fluorescing mineral. If these findings are supported by additional MAHLI and test bed measurements, then this will be the first fluorescence detection of its kind on Mars. This will be a step toward using UV light for the detection of organic compounds as has been proposed for the Mars 2020 mission.

  13. Highly selective population of two excited states in nonresonant two-photon absorption

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Zhang, Shi-An; Sun, Zhen-Rong

    2011-08-01

    A nonresonant two-photon absorption process can be manipulated by tailoring the ultra-short laser pulse. In this paper, we theoretically demonstrate a highly selective population of two excited states in the nonresonant two-photon absorption process by rationally designing a spectral phase distribution. Our results show that one excited state is maximally populated while the other state population is widely tunable from zero to the maximum value. We believe that the theoretical results may play an important role in the selective population of a more complex nonlinear process comprising nonresonant two-photon absorption, such as resonance-mediated (2+1)-three-photon absorption and (2+1)-resonant multiphoton ionization.

  14. Light-induced changes in the absorption spectrum of bacteriorhodopsin under two-wavelength excitation

    NASA Astrophysics Data System (ADS)

    Koklyushkin, A. V.; Korolev, A. E.

    2004-09-01

    The results of spectrophotometric measurements of nonlinear light-induced changes in the absorption spectrum of bacteriorhodopsin D96N occurring upon simultaneous excitation at the wavelengths 633 and 441 nm in the excitation intensity range typical for recording of dynamic holograms are presented. The quantitative conditions under which the action of the radiation at one wavelength reduces the change in the optical density caused by the radiation at the other wavelength are determined.

  15. Hybridization assay based on evanescent fluorescence excitation and collection

    NASA Astrophysics Data System (ADS)

    Sumner, James J.; Mmerole, Robert U.; Stratis-Cullum, Dimitra N.; Yi, Hyunmin; Bentley, William E.; Gillespie, James B.

    2003-08-01

    There is a great need for high throughput and sensitive sensors for genetic analysis. These sensors can be used for varied purposes from monitoring gene expression in organims to speciation of possible pathogens. Consequently, an instrument capable of these tasks would be a great benefit for food and water safety, medical diagnostics and defense of military and civilian populations from biological threats. This work examines the development of a hybridization-based biosensor using a novel tapered fiber optic rpobe. The immobilization of single-stranded, synthetic ologinucleotides utilizing aminoproplytriethoxysilane and glutaraldehyde was implemented on the fiber optic sensor. Hybridization takes place with a complementary analyte sequence followed by a fluorescent, labeled signaling probe to form a sandwich assay. Following hybridization, the fiber is interrogated with a diode laser source and the resulting fluorescence signal is detected using a miniature spectrometer.

  16. Two-photon excited fluorescent chemosensor for homogeneous determination of copper(II) in aqueous media and complicated biological matrix.

    PubMed

    Liu, Lingzhi; Dong, Xiaohu; Xiao, Yan; Lian, Wenlong; Liu, Zhihong

    2011-05-21

    In the present work, a two-photon excited fluorescent chemosensor for Cu(2+) was prepared. The probe was constructed on the basis of internal charge transfer (ICT) principle with macrocyclic dioxotetraamine as the Cu(2+) receptor. The good water-solubility of the molecule enabled recognition and assay of Cu(2+) ions in biological media. The photophysical properties of the chemosensor were investigated in detail, exhibiting favorable fluorescence quantum yield and moderate two-photon absorption cross-section. The studies on binding thermodynamics demonstrated the formation of 1 : 1 complex between the chemosensor and Cu(2+) and an association constant of ca. 1.04 × 10(5) M(-1). Due to the rational design of the molecular structure, the sensor was highly specific to Cu(2+), which ensured high selectivity in Cu(2+) determination. Upon Cu(2+) binding, the intramolecular charge-transfer extent within the chromophore was weakened resulting in a remarkable quenching of fluorescence, based on which quantitative determination of Cu(2+) was performed. Good linearity was obtained between the fluorescence quenching value and Cu(2+) concentration ranging from 0.04 to 2.0 μM in aqueous solution. Benefiting from the merits of two-photon excitation, the chemosensor was free of interference from background luminescence in serum. A homogeneous quantitative determination of Cu(2+) was achieved in the serum medium with a linear range of 0.04 to 2.0 μM. Considering the structural flexibility of the sensor, this work also opens up the possibility to construct other two-photon excited chemosensors for direct homogeneous assay of various molecules/ions in complicated biological sample matrices. PMID:21416097

  17. Broadband transient absorption spectroscopy with 1- and 2-photon excitations: Relaxation paths and cross sections of a triphenylamine dye in solution

    SciTech Connect

    Moreno, J.; Dobryakov, A. L.; Hecht, S. E-mail: skovale@chemie.hu-berlin.de; Kovalenko, S. A. E-mail: skovale@chemie.hu-berlin.de; Ioffe, I. N.; Granovsky, A. A.

    2015-07-14

    1-photon (382 nm) and 2-photon (752 nm) excitations to the S{sub 1} state are applied to record and compare transient absorption spectra of a push-pull triphenylamine (TrP) dye in solution. After 1-photon excitation, ultrafast vibrational and structural molecular relaxations are detected on a 0.1 ps time scale in nonpolar hexane, while in polar acetonitrile, the spectral evolution is dominated by dipolar solvation. Upon 2-photon excitation, transient spectra in hexane reveal an unexpected growth of stimulated emission (SE) and excited-state absorption (ESA) bands. The behavior is explained by strong population transfer S{sub 1} → S{sub n} due to resonant absorption of a third pump photon. Subsequent S{sub n} → S{sub 1} internal conversion (with τ{sub 1} = 1 ps) prepares a very hot S{sub 1} state which cools down with τ{sub 2} = 13 ps. The pump pulse energy dependence proves the 2-photon origin of the bleach signal. At the same time, SE and ESA are strongly affected by higher-order pump absorptions that should be taken into account in nonlinear fluorescence applications. The 2-photon excitation cross sections σ{sup (2)} = 32 ⋅ 10{sup −50} cm{sup 4} s at 752 nm are evaluated from the bleach signal.

  18. Broadband transient absorption spectroscopy with 1- and 2-photon excitations: Relaxation paths and cross sections of a triphenylamine dye in solution

    NASA Astrophysics Data System (ADS)

    Moreno, J.; Dobryakov, A. L.; Ioffe, I. N.; Granovsky, A. A.; Hecht, S.; Kovalenko, S. A.

    2015-07-01

    1-photon (382 nm) and 2-photon (752 nm) excitations to the S1 state are applied to record and compare transient absorption spectra of a push-pull triphenylamine (TrP) dye in solution. After 1-photon excitation, ultrafast vibrational and structural molecular relaxations are detected on a 0.1 ps time scale in nonpolar hexane, while in polar acetonitrile, the spectral evolution is dominated by dipolar solvation. Upon 2-photon excitation, transient spectra in hexane reveal an unexpected growth of stimulated emission (SE) and excited-state absorption (ESA) bands. The behavior is explained by strong population transfer S1 → Sn due to resonant absorption of a third pump photon. Subsequent Sn → S1 internal conversion (with τ1 = 1 ps) prepares a very hot S1 state which cools down with τ2 = 13 ps. The pump pulse energy dependence proves the 2-photon origin of the bleach signal. At the same time, SE and ESA are strongly affected by higher-order pump absorptions that should be taken into account in nonlinear fluorescence applications. The 2-photon excitation cross sections σ(2) = 32 ṡ 10-50 cm4 s at 752 nm are evaluated from the bleach signal.

  19. Boron Difluoride Curcuminoid Fluorophores with Enhanced Two-Photon Excited Fluorescence Emission and Versatile Living-Cell Imaging Properties.

    PubMed

    Kamada, Kenji; Namikawa, Tomotaka; Senatore, Sébastien; Matthews, Cédric; Lenne, Pierre-François; Maury, Olivier; Andraud, Chantal; Ponce-Vargas, Miguel; Le Guennic, Boris; Jacquemin, Denis; Agbo, Peter; An, Dahlia D; Gauny, Stacey S; Liu, Xin; Abergel, Rebecca J; Fages, Frédéric; D'Aléo, Anthony

    2016-04-01

    The synthesis of boron difluoride complexes of a series of curcuminoid derivatives containing various donor end groups is described. Time-dependent (TD)-DFT calculations confirm the charge-transfer character of the second lowest-energy transition band and ascribe the lowest energy band to a "cyanine-like" transition. Photophysical studies reveal that tuning the donor strength of the end groups allows covering a broad spectral range, from the visible to the NIR region, of the UV-visible absorption and fluorescence spectra. Two-photon-excited fluorescence and Z-scan techniques prove that an increase in the donor strength or in the rigidity of the backbone results in a considerable increase in the two-photon cross section, reaching 5000 GM, with predominant two-photon absorption from the S0-S2 charge-transfer transition. Direct comparisons with the hemicurcuminoid derivatives show that the two-photon active band for the curcuminoid derivatives has the same intramolecular charge-transfer character and therefore arises from a dipolar structure. Overall, this structure-relationship study allows the optimization of the two-photon brightness (i.e., 400-900 GM) with one dye that emits in the NIR region of the spectrum. In addition, these dyes demonstrate high intracellular uptake efficiency in Cos7 cells with emission in the visible region, which is further improved by using porous silica nanoparticles as dye vehicles for the imaging of two mammalian carcinoma cells type based on NIR fluorescence emission. PMID:26919627

  20. Excited-state absorption of a bipyridyl platinum(II) complex with alkynyl-benzothiazolylfluorene units.

    PubMed

    Pritchett, Timothy M; Sun, Wenfang; Zhang, Bingguang; Ferry, Michael J; Li, Yunjing; Haley, Joy E; Mackie, David M; Shensky, William; Mott, Andrew G

    2010-05-01

    The singlet excited-state lifetime of a bipyridyl platinum(II) complex containing two alkynyl-benzothiazolylfluorene units was determined to be 145+/-105 ps by fitting femtosecond transient difference absorption data, and the triplet quantum yield was measured to be 0.14. A ground-state absorption cross section of 6.1 x 10(-19) cm(2) at 532 nm was deduced from UV-visible absorption data. Excited-state absorption cross sections of (6.7+/-0.1) x 10(-17) cm(2) (singlet) and (4.6+/-0.1) x 10(-16) cm(2) (triplet) were obtained by using a five-level dynamic model to fit open-aperture Z scans at picosecond and nanosecond pulse widths and a variety of pulse energies. For this complex, the ratio of the triplet excited-state absorption cross section to the ground-state absorption cross section--long used as a figure of merit for reverse saturable absorbers--thus stands at 754, to our knowledge the largest ever reported at 532 nm wavelength. PMID:20436550

  1. Two-photon excited fluorescence microendoscopic imaging using a GRIN lens

    NASA Astrophysics Data System (ADS)

    Yan, Wei; Peng, Xiao; Lin, Danying; Wang, Qi; Gao, Jian; Zhou, Jie; Ye, Tong; Qu, Junle; Niu, Hanben

    2015-03-01

    With the rapid development of life sciences, there is an increasing demand for intravital fluorescence imaging of small animals. However, large dimensions and limited working distances of objective lenses in traditional fluorescence microscopes have limited the imaging applications mostly to superficial tissues. To overcome this disadvantage, researchers have developed the graded-index (GRIN) probes with small diameters for imaging internal organs of small animals in a minimally invasive fashion. Here, we present the development of a fluorescence endoscopic imaging system based on a GRIN lens using two-photon excitation. Experimental results showed that this system could perform dynamic fluorescence microendoscopic imaging and monitor the blood flow in anesthetized living mice using two-photon excitation.

  2. Fluorescent excitation transfer immunoassay for the determination of spinosyn A in water.

    PubMed

    Lee, M; Walt, D R; Nugent, P

    1999-07-01

    A fluorescent excitation transfer immunoassay for spinosyn A, a fermentation derived insect control agent, has been developed and applied to the analysis of tap water and wastewater effluent from manufacturing plants. Fluorescein (F) and tetramethylrhodamine (TMR) were chosen as donor and quencher, respectively, for the excitation transfer. Fluorescence quenching was observed from the binding of F-labeled antigen to TMR-labeled antibody. By employing nonlabeled antigen in a competitive immunoassay format, we reversed fluorescence quenching. The assay provides a limit of detection of 0. 01 ppb and a working range of 0.05-1 ppb and allows for the rapid determination of spinosyn A in water with recovery values ranging from 96% to 120%. With the exploitation of the small size of optical fibers, fluorescence from an assay volume of 24 microL could be measured without special vessels. PMID:10552562

  3. CF2 and CFCl fluorescence from VUV excitation of C2F3Cl

    NASA Technical Reports Server (NTRS)

    Nee, J. B.; Wang, Xiuyan; Suto, Masako; Lee, Long C.

    1986-01-01

    The photoexcitation process of C2F3Cl molecule was investigated in the 106 to 230 nm region using synchrotron radiation as a light source. Photoabsorption and fluorescence cross sections were measured and used to determine the fluorescence quantum yield. Fluorescence yield starts to appear at 170 nm and increases to about 2% at 155 nm. The fluorescence spectra were dispersed to identify the emitting species. At the excitation wavelength of 155 nm, the emission system is CFCl (Hermitian conjugate of A - Hermitian conjugate of X), and at 123.9 nm, both the CF2 (Hermitian conjugate of A - Hermitian conjugate of X) and CFCl (Hermitian conjugate of A - Hermitian conjugate of X) systems are observed. The dissociation processes that produced these excited species are discussed.

  4. Diagnostics of a see-through hollow cathode discharge by emission, absorption, and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Taylor, Nicholas

    Atomic line filters have been suggested to be attractive in areas of Doppler velocimetry, resonance fluorescence detection, and resonance ionization detection. They are based on the resonant absorption of photons by an atomic vapor, and allow all other radiation to pass. This allows the detection of very low levels of light superimposed on a large optical background. Several elements have been studied for use as atomic line filters, such as the alkali metals, alkaline earths, and thallium. As previously recognized, thallium is especially attractive since the 535.046 nm metastable transition overlaps with the second harmonic output of an Nd:La2Be2O 5 (BEL) laser (1070 nm). This makes thallium ideal for certain applications as an atomic line filter. Recently a see-through hollow cathode lamp, or galvatron (Hamamatsu), was made commercially available. The galvatron geometry is unique compared to traditional hollow cathode lamps since the cathode and cell are oriented in a T-shape, with the cathode bored completely through to allow the propagation of a light source through the cathode. This allows multi-step excitation of the atomic vapor, not easily accomplished with a traditional hollow cathode lamp. The advantages that a galvatron offers over conventional atomic reservoirs make it an attractive candidate for the application as an atomic line filter; however, little spectroscopic data have been found in the literature. For this reason, Doppler temperatures, number densities, quantum efficiencies, and lifetimes have been determined in order to characterize this atomic reservoir as a potential atomic line filter. These parameters are determined by use of various spectroscopic techniques which include emission, absorption, time-resolved fluorescence, and time-resolved laser-induced saturated fluorescence spectroscopy. From these measurements, it has been demonstrated that a galvatron is an attractive atomic reservoir for applications as an atomic line filter. The

  5. Ultralow detection limits for an organic dye determined by fluorescence spectroscopy with laser diode excitation

    SciTech Connect

    Johnson, P.A.; Barber, T.E.; Smith, B.W.; Winefordner, J.D. )

    1989-04-15

    Fluorescence of IR-140, a laser dye in methanol solution, is excited by a semiconductor laser diode. Analytical figures of merit are compared for three different instrumental configurations, with the dye measured in a cuvette, a liquid jet, and a compact instrument. The best limit of detection, 46,000 molecules, was achieved with a liquid jet. Linear dynamic range was 6 orders of magnitude. The laser diode operates in the near-infrared region, resulting in low background fluorescence.

  6. Construction, figures of merit, and testing of a single-cell fluorescence excitation spectroscopy system

    PubMed Central

    Hill, Laura S.; Richardson, Tammi L.; Profeta, Luisa T. M.; Shaw, Timothy J.; Hintz, Christopher J.; Twining, Benjamin S.; Lawrenz, Evelyn; Myrick, Michael L.

    2010-01-01

    Characterization of phytoplankton community composition is critical to understanding the ecology and biogeochemistry of the oceans. One approach to taxonomic characterization takes advantage of differing pigmentation between algal taxa and thus differences in fluorescence excitation spectra. Analyses of bulk water samples, however, may be confounded by interference from chromophoric dissolved organic matter or suspended particulate matter. Here, we describe an instrument that uses a laser trap based on a Nikon TE2000-U microscope to position individual phytoplankton cells for confocal fluorescence excitation spectroscopy, thus avoiding interference from the surrounding medium. Quantitative measurements of optical power give data in the form of photons emitted per photon of exposure for an individual phytoplankton cell. Residence times for individual phytoplankton in the instrument can be as long as several minutes with no substantial change in their fluorescence excitation spectra. The laser trap was found to generate two-photon fluorescence from the organisms so a modification was made to release the trap momentarily during data acquisition. Typical signal levels for an individual cell are in the range of 106 photons∕s of fluorescence using a monochromated 75 W Xe arc lamp excitation source with a 2% transmission neutral density filter. PMID:20113077

  7. Fluorescence excitation enhancement by Bloch surface wave in all-polymer one-dimensional photonic structure

    SciTech Connect

    Fornasari, L.; Floris, F.; Patrini, M.; Guizzetti, G.; Marabelli, F.; Canazza, G.; Comoretto, D.

    2014-08-04

    We demonstrate photoluminescence excitation enhancement in an all-polymer flexible one-dimensional photonic crystal structure capped with a fluorescent organic ultrathin film. When optical matching conditions between the excitation beam and the Bloch Surface Wave mode supported by the photonic structure are achieved, a ten times enhancement of the photoluminescence is observed. We notice that in these systems luminescence signal reinforcement is achieved by increasing the pump efficiency with no need of spectral resonance to the emission of the chosen fluorophore. All these features make these systems suitable candidates for easy, flexible, and cheap fluorescent sensing.

  8. An experimental study of the electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles and their electrosynthesized polymers

    NASA Astrophysics Data System (ADS)

    Diaw, A. K. D.; Gningue-Sall, D.; Yassar, A.; Brochon, J.-C.; Henry, E.; Aaron, J.-J.

    2015-01-01

    Electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles (N-PhPys), including HOPhPy, MeOPhPy, ThPhPy, PhDPy, DPhDPy, PyPhThThPhPy, and their available, electrosynthesized polymers were investigated. Electronic absorption spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (ΦF) and lifetimes (τF), and other photophysical parameters of these N-PhPy derivatives and their polymers were measured in DMF, DMSO diluted solutions and/or solid state at room temperature. The electronic absorption spectra of N-PhPy derivatives and their polymers included one to several bands, located in the 270-395 nm region, according to the p-phenyl substituent electron-donating effect and conjugated heteroaromatic system length. The fluorescence excitation spectra were characterized by one broad main peak, with, in most cases, one (or more) poorly resolved shoulder (s), appearing in the 270-405 nm region, and their emission spectra were generally constituted of several bands located in the 330-480 nm region. No significant shift of the absorption, fluorescence excitation and emission spectra wavelengths was found upon going from the monomers to the corresponding polymers. ΦF values were high, varying between 0.11 and 0.63, according to the nature of substituents(s) and to the conjugated system extension. Fluorescence decays were mono-exponential for the monomers and poly-exponential for PyPhThThPhPy and for polymers. τF values were relatively short (0.35-5.17 ns), and markedly decreased with the electron-donor character of the phenyl group p-substituent and the conjugated system extension.

  9. An experimental study of the electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles and their electrosynthesized polymers.

    PubMed

    Diaw, A K D; Gningue-Sall, D; Yassar, A; Brochon, J-C; Henry, E; Aaron, J-J

    2015-01-25

    Electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles (N-PhPys), including HOPhPy, MeOPhPy, ThPhPy, PhDPy, DPhDPy, PyPhThThPhPy, and their available, electrosynthesized polymers were investigated. Electronic absorption spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (ΦF) and lifetimes (τF), and other photophysical parameters of these N-PhPy derivatives and their polymers were measured in DMF, DMSO diluted solutions and/or solid state at room temperature. The electronic absorption spectra of N-PhPy derivatives and their polymers included one to several bands, located in the 270-395 nm region, according to the p-phenyl substituent electron-donating effect and conjugated heteroaromatic system length. The fluorescence excitation spectra were characterized by one broad main peak, with, in most cases, one (or more) poorly resolved shoulder (s), appearing in the 270-405 nm region, and their emission spectra were generally constituted of several bands located in the 330-480 nm region. No significant shift of the absorption, fluorescence excitation and emission spectra wavelengths was found upon going from the monomers to the corresponding polymers. ΦF values were high, varying between 0.11 and 0.63, according to the nature of substituents(s) and to the conjugated system extension. Fluorescence decays were mono-exponential for the monomers and poly-exponential for PyPhThThPhPy and for polymers. τF values were relatively short (0.35-5.17 ns), and markedly decreased with the electron-donor character of the phenyl group p-substituent and the conjugated system extension. PMID:25173528

  10. Absorption and Luminescence Studies of Some Highly Fluorescent Derivatives of Vitamin B1; Solvent and pH Effects

    NASA Astrophysics Data System (ADS)

    Marciniak, B.; Koput, J.; Kozubek, H.

    1990-08-01

    The influence of solvent on the UV-visible absorption and luminescence spectra of some highly fluorescent vitamin B1 derivatives, the products of the reaction of N-methylated vitamin B1 with cytidine (I), adenosine (II) and 2-amino-4-methylpyridine (III) is studied. Spectroscopic manifestations of protonation of I and II are also investigated using a semiempirical INDO/S CI method. Singlet and triplet energy levels of the free ion and several protonated species are calculated, and transition energies and oscillator strengths are compared with the experimental spectra. Calculated charge densities on heteroatoms in the ground and excited singlet and triplet states are correlated with changes of the experimental pKa values with excitation. The results for I and II are compared with those for the trimethylated pyrichrominium ion (III) previously studied

  11. Integrated optic/nanofluidic fluorescent detection device with plasmonic excitation

    NASA Astrophysics Data System (ADS)

    Varsanik, J. S.; Bernstein, J. J.

    2013-09-01

    Integrated optic/microfluidic devices have proven to be useful tools in many sensing applications. However, the resolution and sensitivity of existing devices is limited by the processes and materials chosen for their fabrication. A procedure for the production of a new family of low-noise, high-resolution integrated microfluidic optical detection devices is presented, along with results from a prototype device. The device architecture is presented, highlighting design choices made in fluidics and optical integration to minimize scattered light. Diffused waveguides were fabricated, characterized, and modeled. A plasmonic resonator is designed, simulated, and integrated into the system to achieve electric field enhancement and localization to sub-micron dimensions. The device was tested to demonstrate both field enhancement and localization. The procedure that was developed enables the creation of integrated devices capable of high-resolution detection of fluorescent samples. The interrogation region was 200 nm long in the direction of flow, achieving sub-wavelength resolution in an integrated device. Furthermore, discrete fluorescent particles 20 nm in diameter were individually detected, demonstrating the high resolution and sensitivity capabilities of this family of devices.

  12. Fluorescence excitation by enhanced plasmon upconversion under continuous wave illumination

    NASA Astrophysics Data System (ADS)

    Tasgin, Mehmet Emre; Salakhutdinov, Ildar; Kendziora, Dania; Abak, Musa Kurtulus; Turkpence, Deniz; Piantanida, Luca; Fruk, Ljiljana; Lazzarino, Marco; Bek, Alpan

    2016-09-01

    We demonstrate effective background-free continuous wave nonlinear optical excitation of molecules that are sandwiched between asymmetrically constructed plasmonic gold nanoparticle clusters. We observe that near infrared photons are converted to visible photons through efficient plasmonic second harmonic generation. Our theoretical model and simulations demonstrate that Fano resonances may be responsible for being able to observe nonlinear conversion using a continuous wave light source. We show that nonlinearity enhancement of plasmonic nanostructures via coupled quantum mechanical oscillators such as molecules can be several orders larger as compared to their classical counterparts.

  13. Study of excitation transfer in laser dye mixtures by direct measurement of fluorescence lifetime

    NASA Technical Reports Server (NTRS)

    Lin, C.; Dienes, A.

    1973-01-01

    By directly measuring the donor fluorescence lifetime as a function of acceptor concentration in the laser dye mixture Rhodamine 6G-Cresyl violet, we found that the Stern-Volmer relation is obeyed, from which the rate of excitation transfer is determined. The experimental results indicate that the dominant mechanism responsible for the efficient excitation transfer is that of resonance transfer due to long range dipole-dipole interaction.

  14. Multispectral fluorescence lifetime imaging of feces-contaminated apples by time-resolved laser-induced fluorescence imaging system with tunable excitation wavelengths

    NASA Astrophysics Data System (ADS)

    Kim, Moon S.; Cho, Byoung-Kwan; Lefcourt, Alan M.; Chen, Yud-Ren; Kang, Sukwon

    2008-04-01

    We recently developed a time-resolved multispectral laser-induced fluorescence (LIF) imaging system capable of tunable wavelengths in the visible region for sample excitation and nanosecond-scale characterizations of fluorescence responses (lifetime imaging). Time-dependent fluorescence decay characteristics and fluorescence lifetime imaging of apples artificially contaminated with a range of diluted cow feces were investigated at 670 and 685 nm emission bands obtained by 418, 530, and 630 nm excitations. The results demonstrated that a 670 nm emission with a 418 nm excitation provided the greatest difference in time-dependent fluorescence responses between the apples and feces-treated spots. The versatilities of the time-resolved LIF imaging system, including fluorescence lifetime imaging of a relatively large biological object in a multispectral excitation-emission wavelength domain, were demonstrated.

  15. A novel non-fluorescent excited state intramolecular proton transfer phenomenon induced by intramolecular hydrogen bonds: an experimental and theoretical investigation

    PubMed Central

    Yin, Hang; Li, Hui; Xia, Guomin; Ruan, Chengyan; Shi, Ying; Wang, Hongming; Jin, Mingxing; Ding, Dajun

    2016-01-01

    Two molecules, 1-hydroxypyrene-2-carbaldehyde (HP) and 1-methoxypyrene-2-carbaldehyde (MP) were explored. We investigated their photophysical properties, using experimental transient absorption and theoretical density functional theory/time-dependent density functional theory (DFT/TDDFT). HP and MP have similar geometric conformations but exhibit entirely different photophysical properties upon excitation into the S1 state. In contrast to traditional excited state intramolecular proton transfer (ESIPT) in molecules that exhibit either single or dual fluorescence, HP has an unusual non-fluorescent property. Specifically, the ultrafast ESIPT process occurs in 158 fs and is followed by an intersystem crossing (ISC) component of 11.38 ps. In contrast to HP, MP undergoes only an 8 ps timescale process, which was attributed to interactions between solute and solvent. We concluded that this difference arises from intramolecular hydrogen bonds (IMHBs), which induce drastic structural alterntion upon excitation. PMID:26790961

  16. Two-photon-excited fluorescence resonance energy transfer in an aqueous system of CdTe quantum dots and Rhodamine B

    SciTech Connect

    Li, Muye; Lu, Peixiang; Li, Fang He, Zhicong; Zhang, Junpei; Han, Junbo

    2014-12-21

    Two-photon excited fluorescence resonance energy transfer (FRET) between CdTe quantum dots with different emission peaks and Rhodamine B in aqueous solution are investigated both experimentally and theoretically. The photoluminescence and lifetime are measured using a time-resolved fluorescence test system. The two-photon excited FRET efficiency is found to increase as the degree of spectral overlap of the emission spectrum of CdTe and the absorption spectrum of Rhodamine B increases, which is due to the increase of Forster radius of the sample. Moreover, FRET efficiency increases when the ratio of acceptor/donor concentration increases. The two-photon excited FRET efficiency was found to reach 40%.

  17. Cutaneous melanin exhibiting fluorescence emission under near-infrared light excitation.

    PubMed

    Huang, Zhiwei; Zeng, Haishan; Hamzavi, Iltefat; Alajlan, Abdulmajeed; Tan, Eileen; McLean, David I; Lui, Harvey

    2006-01-01

    Under ultraviolet and visible light excitation, melanin is essentially a nonfluorescent substance. This work reports our study on near-infrared (NIR) fluorescence properties of melanins, and explores potential applications of NIR fluorescence techniques for evaluating skin disorders involving melanin. The NIR fluorescence spectrum is obtained using a fiber optic NIR spectrometer under 785-nm laser excitation. In vitro measurements are performed on synthetic dihydroxyphenylalanine (DOPA) melanin, melanin extracted from Sepia ink sacs, human hair, animal fur, and bird feathers. Paired spectral comparisons of white and black skin appendages show that melanization of hair, fur, or feathers more than doubles the NIR fluorescence. In vivo NIR autofluorescence of normal dorsal and volar forearm skin of 52 volunteers is measured. Dorsal forearm skin, which is darker than volar skin, exhibits significantly greater NIR fluorescence. Patients with vitiligo (n=4), compound nevus (n=3), nevus of Ota (n=1), superficial spreading melanoma (n=3), and postinflammatory hyperpigmentation (n=1) are also evaluated. NIR fluorescence is greater within the lesion than the surrounding normal skin for all these conditions except vitiligo, where the converse was true. The observed melanin NIR fluorescence provides a new approach to in vitro and in vivo melanin detection and quantification that may be particularly useful for evaluating pigmented skin lesions. PMID:16822060

  18. Shape of the absorption and fluorescence spectra of condensed phases and transition energies.

    PubMed

    Lagos, Miguel; Paredes, Rodrigo

    2014-11-13

    General integral expressions for the temperature-dependent profile of the spectral lines of photon absorption and emission by atomic or molecular species in a condensed environment are derived with no other hypothesis than: (a) The acoustic vibrational modes of the condensed host medium constitute the thermodynamic energy reservoir at a given constant temperature, and local electronic transitions modifying the equilibrium configuration of the surroundings are multiphonon events, regardless of the magnitude of the transition energy. (b) Electron-phonon coupling is linear in the variations of the bond length. The purpose is to develop a theoretical tool for the analysis of the spectra, allowing us to grasp highly accurate information from fitting the theoretical line shape function to experiment, including those spectra displaying wide features. The method is illustrated by applying it to two dyes, Lucifer Yellow CH and Coumarin 1, which display fluorescence maxima of 0.41 and 0.51 eV fwhm. Fitting the theoretical curves to the spectra indicates that the neat excitation energies are 2.58 eV ± 2.5% and 3.00 eV ± 2.0%, respectively. PMID:25321927

  19. Effect of gold nanoparticles on the fluorescence excitation spectrum of α-fetoprotein: Local environment dependent fluorescence quenching

    NASA Astrophysics Data System (ADS)

    Li, Jian-jun; Chen, Yu; Wang, A.-qing; Zhu, Jian; Zhao, Jun-wu

    2011-01-01

    The effect of colloid gold nanoparticles (AuNPs) on the fluorescence excitation spectrum of α-fetoprotein (AFP) has been investigated experimentally. The excitation spectral peaks of AFP with low concentration from 0.01 ng ml -1 to 12 ng ml -1 increase monotonically with increasing of AFP concentration. When some gold colloids were added to the AFP solution, the excitation peak at 285 nm decreases distinctly. By comparing the excitation peak intensity of AFP solution with gold colloids and without gold colloids at different AFP concentrations, the quenching effect from gold nanoparticle was more effective at lower AFP concentration. So the range of concentration from 0.01 ng ml -1 to 0.09 ng ml -1 will be the potential range of applications because of the higher sensitivity. The physical origin based on local field effect was investigated to illuminate this local environment dependent fluorescence quenching. The changing extent of quenching with different AFP concentrations can be attributed to the nonlinear decreasing of the local field factor of gold nanoparticles as a function of environmental dielectric constant.

  20. Video-rate two-photon excited fluorescence lifetime imaging system with interleaved digitization

    PubMed Central

    Dow, Ximeng Y.; Sullivan, Shane Z.; Muir, Ryan D.; Simpson, Garth J.

    2016-01-01

    A fast (up to video rate) two-photon excited fluorescence lifetime imaging system based on interleaved digitization is demonstrated. The system is compatible with existing beam-scanning microscopes with minor electronics and software modification. Proof-of-concept demonstrations were performed using laser dyes and biological tissue. PMID:26176453

  1. Video-rate two-photon excited fluorescence lifetime imaging system with interleaved digitization.

    PubMed

    Dow, Ximeng Y; Sullivan, Shane Z; Muir, Ryan D; Simpson, Garth J

    2015-07-15

    A fast (up to video rate) two-photon excited fluorescence lifetime imaging system based on interleaved digitization is demonstrated. The system is compatible with existing beam-scanning microscopes with minor electronics and software modification. Proof-of-concept demonstrations were performed using laser dyes and biological tissue. PMID:26176453

  2. The Effective of Different Excitation Wavelengths on the Identification of Plant Species Based on Fluorescence LIDAR

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Gong, Wei; Shi, Shuo; Du, Lin; Sun, Jia; Song, Shalei

    2016-06-01

    Laser-induced fluorescence (LIF) served as an active technology has been widely used in many field, and it is closely related to excitation wavelength (EW). The objective of this investigation is to discuss the performance of different EWs of LIF LiDAR in identifying plant species. In this study, the 355, 460 and 556 nm lasers were utilized to excite the leaf fluorescence and the fluorescence spectra were measured by using the LIF LiDAR system built in the laboratory. Subsequently, the principal component analysis (PCA) with the help of support vector machine (SVM) was utilized to analyse fluorescence spectra. For the three EWs, the overall identification rates of the six plant species were 80 %, 83.3 % and 90 %. Experimental results demonstrated that 556 nm excitation light source is superior to 355 and 460 nm for the classification of the plant species for the same genus in this study. Thus, an appropriate excitation wavelength should be considered when the LIF LiDAR was utilized in the field of remote sensing based on the LIF technology.

  3. Magnetic fluorescent lamp having reduced ultraviolet self-absorption

    DOEpatents

    Berman, Samuel M.; Richardson, Robert W.

    1985-01-01

    The radiant emission of a mercury-argon discharge in a fluorescent lamp assembly (10) is enhanced by providing means (30) for establishing a magnetic field with lines of force along the path of electron flow through the bulb (12) of the lamp assembly, to provide Zeeman splitting of the ultraviolet spectral line. Optimum results are obtained when the magnetic field strength causes a Zeeman splitting of approximately 1.7 times the thermal line width.

  4. Absorption and luminescence excitation spectra of ClF in the Vac UV region

    NASA Astrophysics Data System (ADS)

    Alekseev, Vadim A.; Schwentner, Nikolaus

    2010-07-01

    Absorption and luminescence excitation spectra of ClF are recorded in the vacuum ultraviolet employing synchrotron radiation. A broad band (120-130 nm) due to transition to the ion-pair state E(0 +) and sparse transitions to Rydberg states are observed. All Rydberg states are predissociated and their excitation yields no luminescence. Perturbations by the 4 sσ1Π 1 and 4p π1Σ + Rydberg states result in characteristic dips in the E(0 +) state luminescence excitation spectrum. Excitation above the Cl∗ + F dissociation threshold results in luminescence from ion-pair states of ClF or Cl 2 populated in reaction of Cl∗ with ClF or Cl 2.

  5. Two-Photon Excitation of a Plasmonic Nanoswitch Monitored by Single-Molecule Fluorescence Microscopy.

    PubMed

    Impellizzeri, Stefania; Simoncelli, Sabrina; Hodgson, Gregory K; Lanterna, Anabel E; McTiernan, Christopher D; Raymo, Françisco M; Aramendia, Pedro F; Scaiano, Juan C

    2016-05-17

    Visible-light excitation of the surface plasmon band of silver nanoplates can effectively localize and concentrate the incident electromagnetic field enhancing the photochemical performance of organic molecules. Herein, the first single-molecule study of the plasmon-assisted isomerization of a photochrome-fluorophore dyad, designed to switch between a nonfluorescent and a fluorescent state in response to the photochromic transformation, is reported. The photochemistry of the switchable assembly, consisting of a photochromic benzooxazine chemically conjugated to a coumarin moiety, is examined in real time with total internal reflection fluorescence microscopy in the presence of silver nanoplates excited with a 633 nm laser. The metallic nanostructures significantly enhance the visible light-induced performance of the photoconversion, which normally requires ultraviolet excitation. The resulting ring-open isomer is strongly fluorescent and can also be excited at 633 nm. These stochastic emission events are used to monitor photochromic activation and show quadratic dependence on incident power. The utilization of a single laser wavelength for both photochromic activation and excitation effectively mimics a pseudo two-colours system. PMID:27060994

  6. Quantum counter for correcting fluorescence excitation spectra at 320- to 800-nm wavelengths.

    PubMed

    Nothnagel, E A

    1987-05-15

    A procedure for recording corrected fluorescence excitation spectra to wavelengths as long as 800 nm is described. The procedure involves the use of a commercial spectrofluorometer, which is modified by substituting 1,1',3,3,3',3'-hexamethylindotricarbocyanine perchlorate in place of rhodamine B as the quantum counter dye. This modification is applicable to spectrofluorometers supplied by several different manufacturers and can be accomplished by a user having only modest technical skills. A study of the fluorescence excitation spectrum of bacteriochlorophyll a is presented as an illustration of the use of the procedure. The procedure will be valuable in biological and biochemical studies that involve the use of long-wavelength fluorescent probes of either natural or synthetic origin. PMID:3619023

  7. Two-photon excited fluorescence lifetime imaging microscopy for FRET study on protein interactions

    NASA Astrophysics Data System (ADS)

    Qu, Junle; Lin, Ziyang; Liu, Lixin; Guo, Xuan; Chen, Danni; Niu, Hanben

    2005-01-01

    Two-photon excited fluorescence lifetime imaging (2P-FLIM) provides a more direct and precise approach to fluorescence resonance energy transfer (FRET), which allows studying the dynamic behavior of protein-protein interactions in living cells. In this paper, we describe the combination of a Leica TCS SP2 laser scanning microscope and a time-correlated single photon counting (TCSPC) lifetime imaging module developed by Becker & Hickl for two-photon excited fluorescence lifetime imaging. This 2P-FLIM system was used for FRET study on the interaction of heat shock protein hsp27 with p38 MAP kinase in the single living cell. Results show that the reduction in donor (CFP) lifetime in the presence of acceptor (YFP) reveals interactions between the two proteins.

  8. Multifocal multiphoton excitation and time correlated single photon counting detection for 3-D fluorescence lifetime imaging.

    PubMed

    Kumar, S; Dunsby, C; De Beule, P A A; Owen, D M; Anand, U; Lanigan, P M P; Benninger, R K P; Davis, D M; Neil, M A A; Anand, P; Benham, C; Naylor, A; French, P M W

    2007-10-01

    We report a multifocal multiphoton time-correlated single photon counting (TCSPC) fluorescence lifetime imaging (FLIM) microscope system that uses a 16 channel multi-anode PMT detector. Multiphoton excitation minimizes out-of-focus photobleaching, multifocal excitation reduces non-linear in-plane photobleaching effects and TCSPC electronics provide photon-efficient detection of the fluorescence decay profile. TCSPC detection is less prone to bleaching- and movement-induced artefacts compared to wide-field time-gated or frequency-domain FLIM. This microscope is therefore capable of acquiring 3-D FLIM images at significantly increased speeds compared to single beam multiphoton microscopy and we demonstrate this with live cells expressing a GFP tagged protein. We also apply this system to time-lapse FLIM of NAD(P)H autofluorescence in single live cells and report measurements on the change in the fluorescence decay profile following the application of a known metabolic inhibitor. PMID:19550524

  9. Ultrafast Excited State Relaxation of a Metalloporphyrin Revealed by Femtosecond X-ray Absorption Spectroscopy.

    PubMed

    Shelby, Megan L; Lestrange, Patrick J; Jackson, Nicholas E; Haldrup, Kristoffer; Mara, Michael W; Stickrath, Andrew B; Zhu, Diling; Lemke, Henrik T; Chollet, Matthieu; Hoffman, Brian M; Li, Xiaosong; Chen, Lin X

    2016-07-20

    Photoexcited Nickel(II) tetramesitylporphyrin (NiTMP), like many open-shell metalloporphyrins, relaxes rapidly through multiple electronic states following an initial porphyrin-based excitation, some involving metal centered electronic configuration changes that could be harnessed catalytically before excited state relaxation. While a NiTMP excited state present at 100 ps was previously identified by X-ray transient absorption (XTA) spectroscopy at a synchrotron source as a relaxed (d,d) state, the lowest energy excited state (J. Am. Chem. Soc., 2007, 129, 9616 and Chem. Sci., 2010, 1, 642), structural dynamics before thermalization were not resolved due to the ∼100 ps duration of the available X-ray probe pulse. Using the femtosecond (fs) X-ray pulses of the Linac Coherent Light Source (LCLS), the Ni center electronic configuration from the initial excited state to the relaxed (d,d) state has been obtained via ultrafast Ni K-edge XANES (X-ray absorption near edge structure) on a time scale from hundreds of femtoseconds to 100 ps. This enabled the identification of a short-lived Ni(I) species aided by time-dependent density functional theory (TDDFT) methods. Computed electronic and nuclear structure for critical excited electronic states in the relaxation pathway characterize the dependence of the complex's geometry on the electron occupation of the 3d orbitals. Calculated XANES transitions for these excited states assign a short-lived transient signal to the spectroscopic signature of the Ni(I) species, resulting from intramolecular charge transfer on a time scale that has eluded previous synchrotron studies. These combined results enable us to examine the excited state structural dynamics of NiTMP prior to thermal relaxation and to capture intermediates of potential photocatalytic significance. PMID:27286410

  10. Decomposing the First Absorption Band of OCS Using Photofragment Excitation Spectroscopy.

    PubMed

    Toulson, Benjamin W; Murray, Craig

    2016-09-01

    Photofragment excitation spectra of carbonyl sulfide (OCS) have been recorded from 212-260 nm by state-selectively probing either electronically excited S((1)D) or ground state S((3)P) photolysis products via 2 + 1 resonance-enhanced multiphoton ionization. Probing the major S((1)D) product results in a broad, unstructured action spectrum that reproduces the overall shape of the first absorption band. In contrast, spectra obtained probing S((3)P) products display prominent resonances superimposed on a broad continuum; the resonances correspond to the diffuse vibrational structure observed in the conventional absorption spectrum. The vibrational structure is assigned to four progressions, each dominated by the C-S stretch, ν1, following direct excitation to quasi-bound singlet and triplet states. The S((3)PJ) products are formed with a near-statistical population distribution over the J = 2, 1, and 0 spin-orbit levels across the wavelength range investigated. Although a minor contributor to the S atom yield near the peak of the absorption cross section, the relative yield of S((3)P) increases significantly at longer wavelengths. The experimental measurements validate recent theoretical work characterizing the electronic states responsible for the first absorption band by Schmidt and co-workers. PMID:27552402

  11. Two-photon-induced excited-state absorption in high-index fibers

    NASA Astrophysics Data System (ADS)

    Shensky, William M., III; Cohanoschi, Ion; Sevian, Armen; Hagan, David J.; Van Stryland, Eric W.

    2004-06-01

    We have studied the nonlinear optical properties of a high-index (n = 1.82) glass that is used as the core material in a commercially available fiber optic inverter, which is a coherent fiber bundle twisted 180 degrees to produce an inverted image. We have determined through open aperture Z-scan the two-photon absorption coefficient of the glass to be 0.8 cm/GW using 23 ps pulses (FWHM) at 532 nm, far from the linear absorption edge of 320 nm. For 5 ns (FWHM) pulses the nonlinear absorption is much larger, and is dominated by two-photon induced excited-state absorption. These effects contribute to the nanosecond optical limiting response that we have observed for the inverter using an F/5 focusing geometry.

  12. Determination of the in vivo redox potential using roGFP and fluorescence spectra obtained from one-wavelength excitation

    NASA Astrophysics Data System (ADS)

    Wierer, S.; Elgass, K.; Bieker, S.; Zentgraf, U.; Meixner, A. J.; Schleifenbaum, F.

    2011-02-01

    The analysis of molecular processes in living (plant) cells such as signal transduction, DNA replication, carbon metabolism and senescence has been revolutionized by the use of green fluorescent protein (GFP) and its variants as specific cellular markers. Many cell biological processes are accompanied by changes in the intracellular redox potential. To monitor the redox potential, a redox-sensitive mutant of GFP (roGFP) was created, which shows changes in its optical properties in response to changes in the redox state of its surrounding medium. For a quantitative analysis in living systems, it is essential to know the optical properties of roGFP in vitro. Therefore, we applied spectrally resolved fluorescence spectroscopy on purified roGFP exposed to different redox potentials to determine shifts in both the absorption and the emission spectra of roGFP. Based on these in vitro findings, we introduce a new approach using one-wavelength excitation to use roGFP for the in vivo analysis of cell biological processes. We demonstrate the ability this technique by investigating chloroplast-located Grx1-roGFP2 expressing Arabidopsis thaliana cells as example for dynamically moving intracellular compartments. This is not possible with the two-wavelength excitation technique established so far, which hampers a quantitative analysis of highly mobile samples due to the time delay between the two measurements and the consequential displacement of the investigated area.

  13. Bioaerosol detection and classification using dual excitation wavelength laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Jonsson, Per; Wästerby, Pär.; Gradmark, Per-Åke; Hedborg, Julia; Larsson, Anders; Landström, Lars

    2015-05-01

    We present results obtained by a detection system designed to measure laser-induced fluorescence from individual aerosol particles using dual excitation wavelengths. The aerosol is sampled from ambient air and via a 1 mm diameter nozzle, surrounded by a sheath air flow, confined into a particle beam. A continuous wave blue laser at 404 nm is focused on the aerosol beam and two photomultiplier tubes monitor the presence of individual particles by simultaneous measuring the scattered light and any induced fluorescence. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser at 263 nm and the corresponding fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channel photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 250 to 800 nm. In the present report, data were measured on different monodisperse reference aerosols, simulants of biological warfare agents, and different interference aerosol particles, e.g. pollen. In the analysis of the experimental data, i.e., the time-resolved scattered and fluorescence signals from 404 nm c.w. light excitation and the fluorescence spectra obtained by a pulsed 263 nm laser source, we use multivariate data analysis methods to classify each individual aerosol particle.

  14. Picosecond time-resolved absorption and fluorescence dynamics in the artificial bacteriorhodopsin pigment BR6.11.

    PubMed Central

    Brack, T. L.; Delaney, J. K.; Atkinson, G. H.; Albeck, A.; Sheves, M.; Ottolenghi, M.

    1993-01-01

    The picosecond molecular dynamics in an artificial bacteriorhodopsin (BR) pigment containing a structurally modified all-trans retinal chromphore with a six-membered ring bridging the C11=C12-C13 positions (BR6.11) are measured by picosecond transient absorption and picosecond time-resolved fluorescence spectroscopy. Time-dependent intensity and spectral changes in absorption in the 570-650-nm region are monitored for delays as long as 5 ns after the 7-ps, 573-nm excitation of BR6.11. Two intermediates, J6.11 and K6.11/1, both with enhanced absorption to the red (> 600 nm) of the BR6.11 spectrum are observed within approximately 50 ps. The J6.11 intermediate decays with a time constant of 12 +/- 3 ps to form K6.11/1. The K6.11/1 intermediate decays with an approximately 100-ps time constant to form a third intermediate, K6.11/2, which is observed through diminished 650-nm absorption (relative to that of K6.11/1). No other transient absorption changes are found during the remainder of the initial 5-ns period of the BR6.11 photoreaction. Fluorescence in the 650-900-nm region is observed from BR6.11, K6.11/1, and K6.11/2, but no emission assignable to J6.11 is found. The BR6.11 fluroescence spectrum has a approximately 725-nm maximum which is blue-shifted by approximately 15 nm relative to that of native BR-570 and is 4.2 +/- 1.5 times larger in intensity (same sample optical density). No differences in the profile of the fluorescence spectra of BR6.11 and the intermediates K6.11/1 and K6.11/2 are observed. Following ground-state depletion of the BR6.11 population, the time-resolved fluroescence intensity monitored at 725 nm increases with two time constants, 12 +/- 3 and approximately 100 ps, both of which correlate well with changes in the picosecond transient absorption data. The resonance Raman spectrum of ground-state BR6.11, measured with low-energy, 560-nm excitation, is significantly different from the spectrum of native BR-570, thus confirming that the

  15. Rapid prototyping of electrochromatography chips for improved two-photon excited fluorescence detection.

    PubMed

    Hackl, Claudia; Beyreiss, Reinhild; Geissler, David; Jezierski, Stefan; Belder, Detlev

    2014-04-15

    In the present study, we introduce two-photon excitation at 532 nm for label-free fluorescence detection in chip electrochromatography. Two-photon excitation at 532 nm offers a promising alternative to one-photon excitation at 266 nm, as it enables the use of economic chip materials instead of fused silica. In order to demonstrate these benefits, one-photon and two-photon induced fluorescence detection are compared in different chip layouts and materials with respect to the achievable sensitivity in the detection of polycyclic aromatic hydrocarbons (PAHs). Customized chromatography chips with cover or bottom slides of different material and thickness are produced by means of a rapid prototyping method based on liquid-phase lithography. The design of thin bottom chips (180 μm) enables the use of high-performance immersion objectives with low working distances, which allows one to exploit the full potential of two-photon excitation for a sensitive detection. The developed method is applied for label-free analysis of PAHs separated on a polymer monolith inside polymer glass sandwich chips made from fused silica or soda-lime glass. The obtained limits of detection range from 40 nM to 1.95 μM, with similar sensitivities in fused silica thin bottom chips for one-photon and two-photon excitation. In deep-UV non- or less-transparent devices two-photon excitation is mandatory for label-free detection of aromatics with high sensitivity. PMID:24666258

  16. Multi-excitation near infrared (NIR) spectral fluorescence imaging using organic fluorophores

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hisataka; Koyama, Yoshinori; Barrett, Tristan; Hama, Yukihiro; Choyke, Peter L.

    2008-02-01

    The ability to obtain multi-color fluorescent imaging in vivo simultaneously using multi-targeted imaging probes could be of potential benefit from both a research and a clinical perspective. However, the simultaneous acquisition of more than 2 separate organic fluorophores usually requires more than one excitation source, since a single excitation source may not optimally excite all the fluorophores. In this study, we employed a multi-excitation approach in order to acquire optimized images with multiple near infrared (NIR) organic fluorophores at the same time. Using 3 sets of excitation filters (595+/-20nm, 640+/-25nm, 688+/-17nm) to acquire 3 distinct spectra and spectral unmixing software (CRi, Woburn, MA), it was possible to resolve the emission spectra of each of the NIR fluorophores using commercial software (Nuance, CRi, Woburn, MA) To demonstrate the utility of this approach 2 mouse models were investigated; In one model, mice bearing four implanted malignancies were injected with a cocktail of 3 fluorescently labeled monoclonal antibodies, each with its own distinct NIR fluorophore. In the second model five different lymph node drainage basins were imaged with 5-color dendrimer-based lymphatic imaging agents tagged with 5 different NIR fluorophores. We successfully detected each of the targeted tumors in the first model and all of the lymph nodes by their distinct color in the second model; neither of which would have been possible using the single excitation method. In conclusion, multi-excitation NIR spectral fluorescence imaging is feasible in a reasonable time frame and opens the possibility for in vivo immunohistochemical imaging (IHCi).

  17. Photothermal measurement of absorption and scattering losses in thin films excited by surface plasmons.

    PubMed

    Domené, Esteban A; Balzarotti, Francisco; Bragas, Andrea V; Martínez, Oscar E

    2009-12-15

    We present a novel noncontact, photothermal technique, based on the focus error signal of a commercial CD pickup head that allows direct determination of absorption in thin films. Combined with extinction methods, this technique yields the scattering contribution to the losses. Surface plasmon polaritons are excited using the Kretschmann configuration in thin Au films of varying thickness. By measuring the extinction and absorption simultaneously, it is shown that dielectric constants and thickness retrieval leads to inconsistencies if the model does not account for scattering. PMID:20016617

  18. Environment-sensitive quinolone demonstrating long-lived fluorescence and unusually slow excited-state intramolecular proton transfer kinetics

    NASA Astrophysics Data System (ADS)

    Zamotaiev, O. M.; Shvadchak, V.; Sych, T. P.; Melnychuk, N. A.; Yushchenko, D.; Mely, Y.; Pivovarenko, V. G.

    2016-09-01

    A new small fluorescent dye based on 3-hydroxybenzo[g]quinolone, a benzo-analogue of Pseudomonas quinolone signal species, has been synthesized. The dye demonstrates interesting optical properties, with absorption in the visible region, two band emission due to an excited-state intramolecular proton transfer (ESIPT) reaction and high fluorescence quantum yield in both protic and aprotic media. Time-resolved fluorescence spectroscopy shows that the ESIPT reaction time is unusually long (up to 8 ns), indicating that both forward and backward ESIPT reactions are very slow in comparison to other 3-hydroxyquinolones. In spite of these slow rate constants, the ESIPT reaction was found to show a reversible character as a result of the very long lifetimes of both N* and T* forms (up to 16 ns). The ESIPT reaction rate is mainly controlled by the hydrogen bond donor ability in protic solvents and the polarity in aprotic solvents. Using large unilamellar vesicles and giant unilamellar vesicles of different lipid compositions, the probe was shown to preferentially label liquid disordered phases.

  19. Two-photon excited fluorescence of the lens for the diagnosis of presbyopia

    NASA Astrophysics Data System (ADS)

    Steiner, R.; Kessler, M.; Fugger, O.; Dolp, F.; Russ, D.

    2009-09-01

    Presbyopia is a wide spread phenomenon in elder people and is caused by the hardening of the lens in human eyes. Research is performed to make such lenses again more flexible by application of geometrically optimised cuts through the lens with a femtosecond-laser. Different protein agglomerations are responsible for the flexibility reduction of the lens. Two-photon excited fluorescence of the lens can be used as a diagnostic tool to localise such protein accumulations. In in-vitro experiments with human cataract lenses and also lenses of the Philly-mouse it could be demonstrated that with age the fluorescence increases as presbyopia proceeds. The distribution of the fluorescing compounds are not homogeneous but rather cloudy. Discrimination of the compounds by fluorescence lifetime measurements in relation of the depth in the lens is possible.

  20. Two-Photon Excited Fluorescence Imaging of Endogenous Contrast in a Mouse Model of Ovarian Cancer

    PubMed Central

    Watson, Jennifer M.; Marion, Samuel L.; Rice, Photini F.; Utzinger, Urs; Brewer, Molly A.; Hoyer, Patricia B.; Barton, Jennifer K.

    2015-01-01

    Background and Objective Ovarian cancer has an extremely high mortality rate resulting from poor understanding of the disease. In order to aid understanding of disease etiology and progression, we identify the endogenous fluorophores present in a mouse model of ovarian cancer and describe changes in fluorophore abundance and distribution with age and disease. Study Design/Materials and Methods A mouse model of ovarian cancer was created by dosing with 4-vinylcyclohexene diepoxide, which induces follicular apoptosis (simulating menopause), and 7,12-dimethylbenz[a]anthracene, a known carcinogen. Imaging of ovarian tissue was completed ex vivo with a multiphoton microscope using excitation wavelength of 780 nm and emission collection from 405 to 505 nm. Two-photon excited fluorescence images and corresponding histologic sections with selective stains were used to identify endogenous fluorophores. Results The majority of collected fluorescence emission was attributed to NADH and lipofuscin, with additional contributions from collagen and elastin. Dim cellular fluorescence from NADH did not show observable changes with age. Changes in ovarian morphology with disease development frequently caused increased fluorescence contributions from collagen and adipose tissue-associated NADH. Lipofuscin fluorescence was much brighter than NADH fluorescence and increased as a function of both age and disease. Conclusions Our finding of NADH fluorescence patterns similar to that seen previously in human ovary, combined with the observation of lipofuscin accumulation with age and disease also seen in human organs, suggests that the findings from this model may be relevant to human ovarian disease. Increased lipofuscin fluorescence might be used as an indicator of disease in the ovary and this finding warrants further study. PMID:23362124

  1. Excitation-dependent visible fluorescence in decameric nanoparticles with monoacylglycerol cluster chromophores.

    PubMed

    Lee, Kwang-Ming; Cheng, Wan-Yin; Chen, Cheng-Yu; Shyue, Jing-Jong; Nieh, Chih-Chun; Chou, Chen-Fu; Lee, Jia-Rong; Lee, Ya-Yun; Cheng, Chih-Yang; Chang, Sarah Y; Yang, Thomas C; Cheng, Mei-Ching; Lin, Bi-Yun

    2013-01-01

    Organic fluorescent nanoparticles, excitation-dependent photoluminescence, hydrogen-bonded clusters and lysobisphosphatidic acid are four interesting individual topics in materials and biological sciences. They have attracted much attention not only because of their unique properties and important applications, but also because the nature of their intriguing phenomena remained unclear. Here we report a new type of organic fluorescent nanoparticles with intense blue and excitation-dependent visible fluorescence in the range of 410-620 nm. The nanoparticles are composed of ten bis(monoacylglycerol)bisphenol-A molecules and the self-assembly occurs only in elevated concentrations of 2-monoacylglycerol via radical-catalysed 3,2-acyl migration from 3-monoacylglycerol in neat conditions. The excitation-dependent fluorescence behaviour is caused by chromophores composed of hydrogen-bonded monoacylglycerol clusters, which are linked by an extensive hydrogen-bonding network between the ester carbonyl groups and the protons of the alcohols with collective proton motion and HO···C=O (n→π) interactions. PMID:23443572

  2. Role of excited state solvent fluctuations on time-dependent fluorescence Stokes shift

    SciTech Connect

    Li, Tanping E-mail: revatik@lsu.edu; Kumar, Revati E-mail: revatik@lsu.edu

    2015-11-07

    We explore the connection between the solvation dynamics of a chromophore upon photon excitation and equilibrium fluctuations of the solvent. Using molecular dynamics simulations, fluorescence Stokes shift for the tryptophan in Staphylococcus nuclease was examined using both nonequilibrium calculations and linear response theory. When the perturbed and unperturbed surfaces exhibit different solvent equilibrium fluctuations, the linear response approach on the former surface shows agreement with the nonequilibrium process. This agreement is excellent when the perturbed surface exhibits Gaussian statistics and qualitative in the case of an isomerization induced non-Gaussian statistics. However, the linear response theory on the unperturbed surface breaks down even in the presence of Gaussian fluctuations. Experiments also provide evidence of the connection between the excited state solvent fluctuations and the total fluorescence shift. These observations indicate that the equilibrium statistics on the excited state surface characterize the relaxation dynamics of the fluorescence Stokes shift. Our studies specifically analyze the Gaussian fluctuations of the solvent in the complex protein environment and further confirm the role of solvent fluctuations on the excited state surface. The results are consistent with previous investigations, found in the literature, of solutes dissolved in liquids.

  3. Role of excited state solvent fluctuations on time-dependent fluorescence Stokes shift

    NASA Astrophysics Data System (ADS)

    Li, Tanping; Kumar, Revati

    2015-11-01

    We explore the connection between the solvation dynamics of a chromophore upon photon excitation and equilibrium fluctuations of the solvent. Using molecular dynamics simulations, fluorescence Stokes shift for the tryptophan in Staphylococcus nuclease was examined using both nonequilibrium calculations and linear response theory. When the perturbed and unperturbed surfaces exhibit different solvent equilibrium fluctuations, the linear response approach on the former surface shows agreement with the nonequilibrium process. This agreement is excellent when the perturbed surface exhibits Gaussian statistics and qualitative in the case of an isomerization induced non-Gaussian statistics. However, the linear response theory on the unperturbed surface breaks down even in the presence of Gaussian fluctuations. Experiments also provide evidence of the connection between the excited state solvent fluctuations and the total fluorescence shift. These observations indicate that the equilibrium statistics on the excited state surface characterize the relaxation dynamics of the fluorescence Stokes shift. Our studies specifically analyze the Gaussian fluctuations of the solvent in the complex protein environment and further confirm the role of solvent fluctuations on the excited state surface. The results are consistent with previous investigations, found in the literature, of solutes dissolved in liquids.

  4. Toward Fourier interferometry fluorescence excitation/emission imaging of malignant cells combined with photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Kohen, Elli; Hirschberg, Joseph G.; Berry, John P.; Ozkutuk, Nuri; Ornek, Ceren; Monti, Marco; Leblanc, Roger M.; Schachtschabel, Dietrich O.; Haroon, Sumaira

    2003-10-01

    Dual excitation fluorescence imaging has been used as a first step towards multi-wavelength excitation/emission fluorescence spectral imaging. Target cells are transformed keratinocytes, and other osteosarcoma, human breast and color cancer cells. Mitochondrial membrane potential probes, e.g. TMRM (tetramethylrhodamine methyl ester), Mitotracker Green (Molecular Probes, Inc., Eugene OR,USA; a recently synthesized mitochondrial oxygen probe, [PRE,P1"- pyrene butyl)-2-rhodamine ester] allow dual excitation in the UV plus in teh blue-green spectral regions. Also, using the natural endogenous probe NAD(P)H, preliminary results indicate mitochondrial responses to metabolic challenges (e.g. glucose addition), plus changes in mitochonrial distribution and morphology. In terms of application to biomedicine (for diagnostiscs, prognostsics and drug trials) three parameters have been selected in addition to the natural probe NAD(P)H, i.e. vital fluorescence probing of mitochondria, lysosomes and Golgi apparatus. It is hoped that such a multiparameter approach will allow malignant cell characterization and grading. A new area being introduced is the use of similar methodology for biotechnical applications such as the study of the hydrogen-producing alga Chlamydomonas Reinhardtii, and possible agricultural applications, such as Saccharomyces yeast for oenology. Complementation by Photoacoustic Microscopy is also contemplated, to study the internal conversion component which follows the excitation by photons.

  5. Self-absorption Effects on Alpha-Induced Atmospheric Nitrogen Fluorescence Yield

    SciTech Connect

    Bachelor, Paula P.; Jordan, David V.; Harper, Warren W.; Cannon, Bret D.; Finn, Erin C.

    2009-12-01

    Nitrogen fluorescence induced by alpha, beta and gamma radiation can be used to detect the presence of radioactive contamination in the environment. Successful measurement of fluorescence yield involves a number of factors, including: known fluorescence signal rate during the measurement; the effective alpha spectrum of the radioactive sources used in the measurement; optical attenuation length of the fluorescence signal in air during the measurement; the absolute throughput of the instrumentation; calibration of the instrumentation; and radiation transport modeling of the "effective" array exposure rate given the spectrum of the alpha particles. Field testing of optical instrumentation was conducted to measure the nitrogen fluorescence yield from the alpha radiation generated from americium-241 (241Am) decay. The 241Am test sources were prepared by direct evaporation of ~1 mCi in nitric acid solution, and some solids were visible on the surface of the sources. A laboratory study was conducted with lower activities of 241Am to determine whether the presence of solids on the surface of the sources prepared both by direct evaporation and by electrodeposition onto stainless steel disks produced sufficient self-absorption to cause a decrease in expected fluorescence. Alpha spectroscopy was used to determine the apparent activity of the sources versus the known activity deposited on the surface. Results from the self-absorption laboratory studies were used to correct the activity values in the model and calculate the nitrogen fluorescence generated by the 241Am during the field experiments.

  6. Excitation-emission matrices measurements of human cutaneous lesions: tool for fluorescence origin

    NASA Astrophysics Data System (ADS)

    Zhelyazkova, A.; Borisova, E.; Angelova, L.; Pavlova, E.; Keremedchiev, M.

    2013-11-01

    The light induced fluorescence (LIF) technique has the potential of providing real-time diagnosis of malignant and premalignant skin tissue; however, human skin is a multilayered and inhomogeneous organ with different optical properties that complicate the analysis of cutaneous fluorescence spectra. In spite of the difficulties related to the detection and analysis of fluorescent data from skin lesions, this technique is among the most widely applied techniques in laboratorial and pre-clinical investigations for early skin neoplasia diagnosis. The important point is to evaluate all sources of intrinsic fluorescence and find any significant alterations distinguishing the normal skin from a cancerous state of the tissue; this would make the autofluorescence signal obtained useful for the development of a non-invasive diagnostic tool for the dermatological practice. Our investigations presented here were based on ex vivo point-by-point measurements of excitation-emission matrices (EEM) from excised tumor lesions and the surrounding skin taken during the daily clinical practice of Queen Jiovanna- ISUL University Hospital, Sofia, the local Ethical Committee's approval having already been obtained. The fluorescence emission was measured between 300 nm and 800 nm using excitation in the 280-440 nm spectral range. In the process of excitation-emission matrices (EEM) measurements we could establish the origin of the autofluorescence and the compounds related by assigning the excitation and emission maxima obtained during the experiments. The EEM were compared for normal human skin, basal cell carcinoma, squamous cell carcinoma, benign nevi and malignant melanoma lesions to obtain information for the most common skin malignancies and their precursors. The main spectral features and the applicability of the technique of autofluorescent spectroscopy of human skin in general as an initial diagnostic tool are discussed as well.

  7. Excitation-emission matrices (EEMs) and synchronous fluorescence spectroscopy (SFS) investigations of gastrointestinal tissues

    NASA Astrophysics Data System (ADS)

    Genova, Ts.; Borisova, E.; Zhelyazkova, Al.; Semyachkina-Glushkovskaya, O.; Penkov, N.; Keremedchiev, M.; Vladimirov, B.; Avramov, L.

    2015-01-01

    In this report we will present our recent investigations of the fluorescence properties of lower part gastrointestinal tissues using excitation-emission matrix and synchronous fluorescence spectroscopy measurement modalities. The spectral peculiarities observed will be discussed and the endogenous sources of the fluorescence signal will be addressed. For these fluorescence spectroscopy measurements the FluoroLog 3 system (HORIBA Jobin Yvon, France) was used. It consists of a Xe lamp (300 W, 200-650 nm), a double mono-chromators, and a PMT detector with a work region at 220- 850 nm. Autofluorescence signals were detected in the form of excitation-emission matrices for the samples of normal mucosa, dysphasia and colon carcinoma and specific spectral features for each tissue were found. Autofluorescence signals from the same samples are observed through synchronous fluorescence spectroscopy, which is a novel promising modality for fluorescence spectroscopy measurements of bio-samples. It is one of the most powerful techniques for multicomponent analysis, because of its sensitivity. In the SFS regime, the fluorescence signal is recorded while both excitation λexc and emission wavelengths λem are simultaneously scanned. A constant wavelength interval is maintained between the λexc and λem wavelengths throughout the spectrum. The resulted fluorescence spectrum shows narrower peak widths, in comparison with EEMs, which are easier for identification and minimizes the chance for false determinations or pretermission of specific spectral feature. This modality is also faster, than EEMs, a much smaller number of data points are required.1 In our measurements we use constant wavelength interval Δλ in the region of 10-200 nm. Measurements are carried out in the terms of finding Δλ, which results in a spectrum with most specific spectral features for comparison with spectral characteristics observed in EEMs. Implementing synchronous fluorescence spectroscopy in optical

  8. [Laser fluorescence excited spectrum of NO via alpha2sigma<--chi2pi transition].

    PubMed

    Zhang, Lian-shui; Zhang, Gui-yin; Zhao, Xiao-hui; Yang, Xiao-dong; Li, Yi

    2004-06-01

    Two-photon fluorescence excited spectrum of NO induced by Nd: YAG laser pumped optical parameter generator/amplifier as excitation source was obtained in the range of 420-472 nm. With this technique, the structure of the energy levels of NO molecule in alpha2sigma electronic state was investigated. The peaks of the spectrum were attributed to alpha2sigma(v' = 0,1)<--chi2pi(v" = 0) transition. The near square dependence of fluorescence signal on the laser intensity indicates a two-photon process. The ground-vibrational-state oscillation frequency and the force constant of alpha2sigma state were calculated. The fluorescence lifetime of alpha2sigma(v' = 0) state under the pressure of 266 Pa was also obtained by measuring fluorescence decay curve of alpha2sigma(v' = 0) states. It is about 53.76 ns. Fitting the curve of the fluorescence radiant lifetime versus pressure, the spontaneous radiant lifetimes and the rate coefficient of nonradiative transition relaxation of alpha2sigma(v' = 0,1) states were deduced. PMID:15766171

  9. Fluorescence and excited state dynamics of the deprotonated Schiff base retinal in proteorhodopsin.

    PubMed

    Bühl, Elena; Braun, Markus; Lakatos, Andrea; Glaubitz, Clemens; Wachtveitl, Josef

    2015-09-01

    The UV light absorbing species of proteorhodopsin with deprotonated Schiff base retinal was investigated using steady-state fluorescence and femtosecond pump-probe spectroscopy. Compared to the all-trans retinal with protonated Schiff base, the deprotonated chromophore absorbs at 365 nm and exhibits a blue-shifted fluorescence spectrum. The unusually long-lived excited state decays bi-exponentially with time constants of 8 ps and 130 ps to form a deprotonated 13-cis retinal as the primary photo-product. PMID:26083266

  10. Steady state fluorescence spectroscopic characterization of normal and diabetic urine at selective excitation wavelength 280 nm

    NASA Astrophysics Data System (ADS)

    Kesavan, Anjana; Pachaiappan, Rekha; Aruna, Prakasa Rao; Ganesan, Singaravelu

    2016-03-01

    Urine is considered diagnostically important for tits native fluorophores and they vary in their distribution, concentration and physiochemical properties, depending upon the metabolic condition of the subject. In this study, we have made an attempt, to characterize the urine of normal subject and diabetic patients under medication by native fluorescence spectroscopy at 280 nm excitation. Further, the fluorescence data were analyzed employing the multivariate statistical method linear discriminant analysis (LDA) using leave one out cross validation method. The results were promising in discriminating diabetic urine from that of normal urine. This study in future may be extended to check the feasibility in ruling out the coexisting disorders such as cancer.

  11. Non-invasive intravital imaging of cellular differentiation with a bright red-excitable fluorescent protein

    PubMed Central

    Chu, Jun; Haynes, Russell D; Corbel, Stéphane Y; Li, Pengpeng; González-González, Emilio; Burg, John S; Ataie, Niloufar J; Lam, Amy J; Cranfill, Paula J; Baird, Michelle A; Davidson, Michael W; Ng, Ho-Leung; Garcia, K Christopher; Contag, Christopher H; Shen, Kang; Blau, Helen M; Lin, Michael Z

    2014-01-01

    A method for non-invasive visualization of genetically labelled cells in animal disease models with micron-level resolution would greatly facilitate development of cell-based therapies. Imaging of fluorescent proteins (FPs) using red excitation light in the “optical window” above 600 nm is one potential method for visualizing implanted cells. However, previous efforts to engineer FPs with peak excitation beyond 600 nm have resulted in undesirable reductions in brightness. Here we report three new red-excitable monomeric FPs obtained by structure-guided mutagenesis of mNeptune, previously the brightest monomeric FP when excited beyond 600 nm. Two of these, mNeptune2 and mNeptune2.5, demonstrate improved maturation and brighter fluorescence, while the third, mCardinal, has a red-shifted excitation spectrum without reduction in brightness. We show that mCardinal can be used to non-invasively and longitudinally visualize the differentiation of myoblasts and stem cells into myocytes in living mice with high anatomical detail. PMID:24633408

  12. Excited state absorption in chromium doped Li2B4O7 glass

    NASA Astrophysics Data System (ADS)

    Koepke, Cz; Wisniewski, K.; Grinberg, M.; Majchrowski, A.; Han, T. P. J.

    2001-03-01

    Excited state absorption (ESA) measurements of the Cr:Li2B4O7 glass (Cr:LBO-glass) along with preliminary interpretation are presented. The presence of chromium in its tri- (d3) and hexa- (d0) valence states is observed. Both Cr3+ and Cr6+ ions appear to contribute in the de-excitation processes and can be attributed in the ESA spectra under excitation wavelengths at 308 nm, 488 nm, 515 nm and 610 nm. The ESA spectra detected with UV excitation have been interpreted in terms of transitions in the framework of the Cr5+O- centre, which forms after charge-transfer-type absorption in the [CrO4]2- group. Assumption of the double-electron state of the 3d22p4 electronic configuration together with crystal-field-split states of the 3d12p5 configuration allowed us to reproduce the obtained ESA spectra. The ESA spectra of the Cr3+ ions have different characteristics and are related to transitions to the conduction band.

  13. Two-photon absorption of fluorescent protein chromophores incorporating non-canonical amino acids: TD-DFT screening and classical dynamics.

    PubMed

    Alaraby Salem, M; Brown, Alex

    2015-10-14

    Two-photon spectroscopy of fluorescent proteins is a powerful bio-imaging tool characterized by deep tissue penetration and little damage. However, two-photon spectroscopy has lower sensitivity than one-photon microscopy alternatives and hence a protein with a large two-photon absorption cross-section is needed. We use time-dependent density functional theory (TD-DFT) at the B3LYP/6-31+G(d,p) level of theory to screen twenty-two possible chromophores that can be formed upon replacing the amino-acid Tyr66 that forms the green fluorescent protein (GFP) chromophore with a non-canonical amino acid. A proposed chromophore with a nitro substituent was found to have a large two-photon absorption cross-section (29 GM) compared to other fluorescent protein chromophores as determined at the same level of theory. Classical molecular dynamics are then performed on a nitro-modified fluorescent protein to test its stability and study the effect of the conformational flexibility of the chromophore on its two-photon absorption cross-section. The theoretical results show that the large cross-section is primarily due to the difference between the permanent dipole moments of the excited and ground states of the nitro-modified chromophore. This large difference is maintained through the various conformations assumed by the chromophore in the protein cavity. The nitro-derived protein appears to be very promising as a two-photon absorption probe. PMID:26370051

  14. [The measurement and analysis of visible-absorption spectrum and fluorescence spectrum of lycopene].

    PubMed

    Yang, Xiao-zhan; Li, Ping; Dai, Song-hui; Wu, Da-cheng; Li, Rui-xia; Yang, Jian-hui; Xiao, Hai-bo

    2005-11-01

    Using ICCD spectral detection system, the absorbency of lycopene-carbon bisulfide solution with different concentration was measured, and the result shows that in a specified range the absorption rule of lycopene solution agrees with Lambert-Beer Law. Absorption spectral wavelength shifts were measured respectively when lycopene was dissolved in acetone, normal hexane, petroleum ether, benzene, ethyl acetate, and carbon bisulfide, and comparing to acetone, different red-shift appeared when lycopene was dissolved in benzene, ethyl acetate, and carbon bisulfide when water was added in lycopene-acetone solution, t he absorbency of lycopene dropped, the fine structure of absorption spectrum became indistinct, and a new absorption peak appeared in UV. The reason for these phenomena is that the solvent molecule had different effect on lycopene molecule when lycopene was dissolved in different solvent. Using fluorecence spectrophotometer, fluorescence spectra of lycopene in different concentrations were collected, and the results show that the fluorescence spectra of lycopene were mainly in 500-680 nm. When concentration was lower than 50 microg x mL(-1), the fluorescence intensity linearly increased with increasing concentration, and when concentration was higher than 60 microg x mL(-1), the fluorescence intensity dropped because of the interaction between lycopene molecules. PMID:16499057

  15. One-photon and two-photon excited fluorescence microscopies based on polarization-control: Applications to tip-enhanced microscopy

    NASA Astrophysics Data System (ADS)

    Hayazawa, Norihiko; Furusawa, Kentaro; Taguchi, Atsushi; Kawata, Satoshi

    2009-12-01

    One-photon and two-photon excited fluorescence microscopies using either radial or azimuthal polarization have been developed and applied to the imaging of quantum dots. In both cases (one-photon and two-photon excitations), the fluorescence image profile of each quantum dot is in good agreement with the electric field intensity distribution of a tightly focused spot using a high numerical aperture objective lens. While this polarization dependence of the absorption/emission of quantum dots (or other dye molecules) is useful for characterizing the orientation of the quantum dots, most of the biological applications that employ quantum dots or dye molecules as labels require the information describing not only the orientation but also the precise position of each dot. In order to improve the sensing accuracy of the dot's position, we employ a modified near-field fluorescence microscopy system that utilizes a tip-enhancement technique and radially polarized two-photon excitations. For the tip enhancement, a commercially available silicon cantilever tip has been successfully utilized instead of metallic tips, as the latter tip can drastically quench the near-field fluorescence. Our tip-enhanced two-photon excited fluorescence microscopy technique enables visualization of the quantum dots distributed on a cover slip beyond the diffraction limit of light. We demonstrate that our approach is advantageous not only due to its high spatial resolution but also due to its high sensitivity by showing that the fluorescence signal is not detectable without the aid of the tip enhancement in some cases.

  16. Absorption-Ablation-Excitation Mechanism of Laser-Cluster Interactions in a Nanoaerosol System

    NASA Astrophysics Data System (ADS)

    Ren, Yihua; Li, Shuiqing; Zhang, Yiyang; Tse, Stephen D.; Long, Marshall B.

    2015-03-01

    The absorption-ablation-excitation mechanism in laser-cluster interactions is investigated by measuring Rayleigh scattering of aerosol clusters along with atomic emission from phase-selective laser-induced breakdown spectroscopy. For 532 nm excitation, as the laser intensity increases beyond 0.16 GW /cm2 , the scattering cross section of TiO2 clusters begins to decrease, concurrent with the onset of atomic emission of Ti, indicating a scattering-to-ablation transition and the formation of nanoplasmas. With 1064 nm laser excitation, the atomic emissions are more than one order of magnitude weaker than that at 532 nm, indicating that the thermal effect is not the main mechanism. To better clarify the process, time-resolved measurements of scattering signals are examined for different excitation laser intensities. For increasing laser intensity, the cross section of clusters decreases during a single pulse, evincing the shorter ablation delay time and larger ratios of ablation clusters. Assessment of the electron energy distribution during the ablation process is conducted by nondimensionalizing the Fokker-Planck equation, with analogous Strouhal SlE , Peclet PeE , and Damköhler DaE numbers defined to characterize the laser-induced aerothermochemical environment. For conditions where SlE≫1 , PeE≫1 , and DaE≪1 , the electrons are excited to the conduction band by two-photon absorption, then relax to the bottom of the conduction band by electron energy loss to the lattice, and finally serve as the energy transfer media between laser field and lattice. The relationship between delay time and excitation intensity is well correlated by this simplified model with quasisteady assumption.

  17. Absorption-ablation-excitation mechanism of laser-cluster interactions in a nanoaerosol system.

    PubMed

    Ren, Yihua; Li, Shuiqing; Zhang, Yiyang; Tse, Stephen D; Long, Marshall B

    2015-03-01

    The absorption-ablation-excitation mechanism in laser-cluster interactions is investigated by measuring Rayleigh scattering of aerosol clusters along with atomic emission from phase-selective laser-induced breakdown spectroscopy. For 532 nm excitation, as the laser intensity increases beyond 0.16  GW/cm^{2}, the scattering cross section of TiO_{2} clusters begins to decrease, concurrent with the onset of atomic emission of Ti, indicating a scattering-to-ablation transition and the formation of nanoplasmas. With 1064 nm laser excitation, the atomic emissions are more than one order of magnitude weaker than that at 532 nm, indicating that the thermal effect is not the main mechanism. To better clarify the process, time-resolved measurements of scattering signals are examined for different excitation laser intensities. For increasing laser intensity, the cross section of clusters decreases during a single pulse, evincing the shorter ablation delay time and larger ratios of ablation clusters. Assessment of the electron energy distribution during the ablation process is conducted by nondimensionalizing the Fokker-Planck equation, with analogous Strouhal Sl_{E}, Peclet Pe_{E}, and Damköhler Da_{E} numbers defined to characterize the laser-induced aerothermochemical environment. For conditions where Sl_{E}≫1, Pe_{E}≫1, and Da_{E}≪1, the electrons are excited to the conduction band by two-photon absorption, then relax to the bottom of the conduction band by electron energy loss to the lattice, and finally serve as the energy transfer media between laser field and lattice. The relationship between delay time and excitation intensity is well correlated by this simplified model with quasisteady assumption. PMID:25793812

  18. Electronic excited states responsible for dimer formation upon UV absorption directly by thymine strands: joint experimental and theoretical study.

    PubMed

    Banyasz, Akos; Douki, Thierry; Improta, Roberto; Gustavsson, Thomas; Onidas, Delphine; Vayá, Ignacio; Perron, Marion; Markovitsi, Dimitra

    2012-09-12

    The study addresses interconnected issues related to two major types of cycloadditions between adjacent thymines in DNA leading to cyclobutane dimers (T<>Ts) and (6-4) adducts. Experimental results are obtained for the single strand (dT)(20) by steady-state and time-resolved optical spectroscopy, as well as by HPLC coupled to mass spectrometry. Calculations are carried out for the dinucleoside monophosphate in water using the TD-M052X method and including the polarizable continuum model; the reliability of TD-M052X is checked against CASPT2 calculations regarding the behavior of two stacked thymines in the gas phase. It is shown that irradiation at the main absorption band leads to cyclobutane dimers (T<>Ts) and (6-4) adducts via different electronic excited states. T<>Ts are formed via (1)ππ* excitons; [2 + 2] dimerization proceeds along a barrierless path, in line with the constant quantum yield (0.05) with the irradiation wavelength, the contribution of the (3)ππ* state to this reaction being less than 10%. The formation of oxetane, the reaction intermediate leading to (6-4) adducts, occurs via charge transfer excited states involving two stacked thymines, whose fingerprint is detected in the fluorescence spectra; it involves an energy barrier explaining the important decrease in the quantum yield of (6-4) adducts with the irradiation wavelength. PMID:22894169

  19. Parallel excitation-emission multiplexed fluorescence lifetime confocal microscopy for live cell imaging

    PubMed Central

    Zhao, Ming; Li, Yu; Peng, Leilei

    2014-01-01

    We present a novel excitation-emission multiplexed fluorescence lifetime microscopy (FLIM) method that surpasses current FLIM techniques in multiplexing capability. The method employs Fourier multiplexing to simultaneously acquire confocal fluorescence lifetime images of multiple excitation wavelength and emission color combinations at 44,000 pixels/sec. The system is built with low-cost CW laser sources and standard PMTs with versatile spectral configuration, which can be implemented as an add-on to commercial confocal microscopes. The Fourier lifetime confocal method allows fast multiplexed FLIM imaging, which makes it possible to monitor multiple biological processes in live cells. The low cost and compatibility with commercial systems could also make multiplexed FLIM more accessible to biological research community. PMID:24921725

  20. Experimental recovery of intrinsic fluorescence and fluorophore concentration in the presence of hemoglobin: spectral effect of scattering and absorption on fluorescence

    NASA Astrophysics Data System (ADS)

    Du Le, Vinh Nguyen; Patterson, Michael S.; Farrell, Thomas J.; Hayward, Joseph E.; Fang, Qiyin

    2015-12-01

    The ability to recover the intrinsic fluorescence of biological fluorophores is crucial to accurately identify the fluorophores and quantify their concentrations in the media. Although some studies have successfully retrieved the fluorescence spectral shape of known fluorophores, the techniques usually came with heavy computation costs and did not apply for strongly absorptive media, and the intrinsic fluorescence intensity and fluorophore concentration were not recovered. In this communication, an experimental approach was presented to recover intrinsic fluorescence and concentration of fluorescein in the presence of hemoglobin (Hb). The results indicated that the method was efficient in recovering the intrinsic fluorescence peak and fluorophore concentration with an error of 3% and 10%, respectively. The results also suggested that chromophores with irregular absorption spectra (e.g., Hb) have more profound effects on fluorescence spectral shape than chromophores with monotonic absorption and scattering spectra (e.g., black India ink and polystyrene microspheres).

  1. Dual excitation ratiometric fluorescent pH sensor for noninvasive bioprocess monitoring: development and application.

    PubMed

    Kermis, Haley R; Kostov, Yordan; Harms, Peter; Rao, Govind

    2002-01-01

    The development and application of a fluorescent excitation-ratiometric, noninvasive pH sensor for continuous on-line fermentation monitoring is presented. The ratiometric approach is robust and insensitive to factors such as source intensity, photobleaching, or orientation of the patch, and since measurements can be made with external instrumentation and without direct contact with the patch, detection is completely noninvasive. The fluorescent dye 8-hydroxy-1,3,6-pyrene trisulfonic acid was immobilized onto Dowex strongly basic anion-exchange resin, which was subsequently entrapped into a proton-permeable hydrogel layer. The sensor layer was polymerized directly onto a white microfiltration membrane backing that provided an optical barrier to the fluorescence and scatter of the fermentation medium. The ratio of emission intensity at 515 nm excited at 468 nm to that excited at 408 nm correlated well with the pH of clear buffers, over the pH range of 6-9. The sensor responded rapidly (<9 min) and reversibly to changes in the solution pH with high precision. The sterilizable HPTS sensor was used for on-line pH monitoring of an E. coli fermentation. The output from the indwelling sensor patch was always in good agreement with the pH recorded off-line with an ISFET probe, with a maximum discrepancy of 0.05 pH units. The sensor is easily adaptable to closed-loop feedback control systems. PMID:12363356

  2. Photosystem II Does Not Possess a Simple Excitation Energy Funnel: Time-Resolved Fluorescence Spectroscopy Meets Theory

    PubMed Central

    2013-01-01

    The experimentally obtained time-resolved fluorescence spectra of photosystem II (PS II) core complexes, purified from a thermophilic cyanobacterium Thermosynechococcus vulcanus, at 5–180 K are compared with simulations. Dynamic localization effects of excitons are treated implicitly by introducing exciton domains of strongly coupled pigments. Exciton relaxations within a domain and exciton transfers between domains are treated on the basis of Redfield theory and generalized Förster theory, respectively. The excitonic couplings between the pigments are calculated by a quantum chemical/electrostatic method (Poisson-TrEsp). Starting with previously published values, a refined set of site energies of the pigments is obtained through optimization cycles of the fits of stationary optical spectra of PS II. Satisfactorily agreement between the experimental and simulated spectra is obtained for the absorption spectrum including its temperature dependence and the linear dichroism spectrum of PS II core complexes (PS II-CC). Furthermore, the refined site energies well reproduce the temperature dependence of the time-resolved fluorescence spectrum of PS II-CC, which is characterized by the emergence of a 695 nm fluorescence peak upon cooling down to 77 K and the decrease of its relative intensity upon further cooling below 77 K. The blue shift of the fluorescence band upon cooling below 77 K is explained by the existence of two red-shifted chlorophyll pools emitting at around 685 and 695 nm. The former pool is assigned to Chl45 or Chl43 in CP43 (Chl numbering according to the nomenclature of Loll et al. Nature2005, 438, 1040) while the latter is assigned to Chl29 in CP47. The 695 nm emitting chlorophyll is suggested to attract excitations from the peripheral light-harvesting complexes and might also be involved in photoprotection. PMID:23537277

  3. Spoilage of foods monitored by native fluorescence spectroscopy with selective excitation wavelength

    NASA Astrophysics Data System (ADS)

    Pu, Yang; Wang, Wubao; Alfano, Robert R.

    2015-03-01

    The modern food processing and storage environments require the real-time monitoring and rapid microbiological testing. Optical spectroscopy with selective excitation wavelengths can be the basis of a novel, rapid, reagent less, noncontact and non-destructive technique for monitoring the food spoilage. The native fluorescence spectra of muscle foods stored at 2-4°C (in refrigerator) and 20-24°C (in room temperature) were measured as a function of time with a selective excitation wavelength of 340nm. The contributions of the principal molecular components to the native fluorescence spectra of meat were measured spectra of each fluorophore: collagen, reduced nicotinamide adenine dinucleotide (NADH), and flavin. The responsible components were extracted using a method namely Multivariate Curve Resolution with Alternating Least-Squares (MCR-ALS). The native fluorescence combined with MCR-ALS can be used directly on the surface of meat to produce biochemically interpretable "fingerprints", which reflects the microbial spoilage of foods involved with the metabolic processes. The results show that with time elapse, the emission from NADH in meat stored at 24°C increases much faster than that at 4°C. This is because multiplying of microorganisms and catabolism are accompanied by the generation of NADH. This study presents changes of relative content of NADH may be used as criterion for detection of spoilage degree of meat using native fluorescence spectroscopy.

  4. Freshness estimation of intact frozen fish using fluorescence spectroscopy and chemometrics of excitation-emission matrix.

    PubMed

    ElMasry, Gamal; Nagai, Hiroto; Moria, Keisuke; Nakazawa, Naho; Tsuta, Mizuki; Sugiyama, Junichi; Okazaki, Emiko; Nakauchi, Shigeki

    2015-10-01

    The current study attempted to provide a convenient, non-invasive and time-saving method to estimate the freshness of intact horse mackerel (Trachurus japonicus) fish in a frozen state using autofluorescence spectroscopy in tandem with multivariate analysis of fluorescence excitation-emission matrices (EEM). The extracted fluorescence data from different freshness conditions were pretreated, masked and reorganized to resolve fish fluorescence spectra from overlapping signals and scattering profiles for detecting and characterizing freshness changes. The real freshness values of the examined fish samples were then traditionally determined by the hard chemical analysis using the high performance liquid chromatography (HPLC) method and expressed as K-values. The fluorescence EEM data and the real freshness values were modeled using partial least square (PLS) regression and a novel algorithm was proposed to identify the ideal combinations of excitation and emission wavelengths being used as perfect predictors. The results revealed that freshness of frozen fish could be accurately predicted with R(2) of 0.89 and root mean square error estimated by cross validation (RMSECV) of 9.66%. This work substantially demonstrated that the autofluorescence spectroscopy associated with the proposed technical approaches has a high potential in non-destructive sensing of fish freshness in the frozen state. PMID:26078142

  5. Excited-State Intramolecular Proton Transfer in a Blue Fluorescence Chromophore Induces Dual Emission.

    PubMed

    Wu, Dan; Guo, Wei-Wei; Liu, Xiang-Yang; Cui, Ganglong

    2016-08-01

    Compared with green fluorescence protein (GFP) chromophores, the recently synthesized blue fluorescence protein (BFP) chromophore variant presents intriguing photochemical properties, for example, dual fluorescence emission, enhanced fluorescence quantum yield, and ultra-slow excited-state intramolecular proton transfer (ESIPT; J. Phys. Chem. Lett., 2014, 5, 92); however, its photochemical mechanism is still elusive. Herein we have employed the CASSCF and CASPT2 methods to study the mechanistic photochemistry of a truncated BFP chromophore variant in the S0 and S1 states. Based on the optimized minima, conical intersections, and minimum-energy paths (ESIPT, photoisomerization, and deactivation), we have found that the system has two competitive S1 relaxation pathways from the Franck-Condon point of the BFP chromophore variant. One is the ESIPT path to generate an S1 tautomer that exhibits a large Stokes shift in experiments. The generated S1 tautomer can further evolve toward the nearby S1 /S0 conical intersection and then jumps down to the S0 state. The other is the photoisomerization path along the rotation of the central double bond. Along this path, the S1 system runs into an S1 /S0 conical intersection region and eventually hops to the S0 state. The two energetically allowed S1 excited-state deactivation pathways are responsible for the in-part loss of fluorescence quantum yield. The considerable S1 ESIPT barrier and the sizable barriers that separate the S1 tautomers from the S1 /S0 conical intersections make these two tautomers establish a kinetic equilibrium in the S1 state, which thus results in dual fluorescence emission. PMID:27128380

  6. Femtosecond single optical fiber tweezers enabled two-photon fluorescence excitation of trapped microscopic objects

    NASA Astrophysics Data System (ADS)

    Mishra, Yogeshwar N.; Pinto, Mervyn; Ingle, Ninad; Mohanty, Samarendra K.

    2011-03-01

    Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber femto second optical tweezers and its use in two-photon fluorescence (TPF) excitation of trapped fluorescent particles. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Trapping depth of few cm was achieved inside colloidal sample with TPF from the trapped particle being visible to the naked eye. Furthermore, the fiber optic trapping was so stable that the trapped particle could be moved in 3D even by holding the fiber in hand and slow maneuvering of the same. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. The theoretical simulation of fiber optical microbeam profiles emerging from the axicon tip and trapping force estimations was found to be in good agreement with the experimentally observed stiffness and TPF patterns. Apart from miniaturization capability into lab-on- a-chip micro-fluidic devices, the proposed non-invasive micro axicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting and ablation as well as for two-photon fluorescence excitation of motile sample which will revolutionize biophysics and research in material science.

  7. [Microsecond Pulsed Hollow Cathode Lamp as Enhanced Excitation Source of Hydride Generation Atomic Fluorescence Spectrometry].

    PubMed

    Zhang, Shuo

    2015-09-01

    The spectral, electrical and atomic fluorescence characteristics of As, Se, Sb and Pb hollow cathode lamps (HCLs) powered by a laboratory-built high current microsecond pulse (HCMP) power supply were studied, and the feasibility of using HCMP-HCLs as the excitation source of hydride generation atomic fluorescence spectrometry (HG-AFS) was evaluated. Under the HCMP power supply mode, the As, Se, Sb, Pb HCLs can maintain stable glow discharge at frequency of 100~1000 Hz, pulse width of 4.0~20 μs and pulse current up to 4.0 A. Relationship between the intensity of characteristic emission lines and HCMP power supply parameters, such as pulse current, power supply voltage, pulse width and frequency, was studied in detail. Compared with the conventional pulsed (CP) HCLs used in commercial AFS instruments, HCMP-HCLs have a narrower pulse width and much stronger pulse current. Under the optimized HCMP power supply parameters, the intensity of atomic emission lines of As, Se, Sb HCLs had sharp enhancement and that indicated their capacity of being a novel HG-AFS excitation source. However, the attenuation of atomic lines and enhancement of ionic lines negated such feasibility of HCMP-Pb HCL. Then the HG-AFS analytical capability of using the HCMP-As/Se/Sb HCLs excitation source was established and results showed that the HCMP-HCL is a promising excitation source for HG-AFS. PMID:26669140

  8. Wide field of view two-photon excited fluorescence imaging, theory and applications

    NASA Astrophysics Data System (ADS)

    Stoltzfus, Caleb Ray

    Two-photon excited fluorescence (2PEF) is a unique photophysical process that has benefited many diverse areas of science. Imaging the 2PEF signal offers numerous intrinsic benefits, including low background scattering, high sample photo-stability, and high excitation selectivity. The 2PEF signal has a nonlinear dependence on excitation intensity, which has proven to be extremely useful for high resolution, three dimensional microscopy. This same nonlinear dependence, in conjunction with the typically low probability of two-photons being simultaneously absorbed, also makes 2PEF imaging difficult to scale, leaving most two-photon microscopes with a field of view (FOV) limited to less than a few mm2. This effectively limits the benefits of the unique properties of 2PEF imaging to microscopic applications. This dissertation explores the development and application of a wide FOV 2PEF imaging technique, where a FOV as large as 10 cm2 is achieved by increasing the peak photon flux of the excitation source, and expanding the illumination region. The use of this imaging technique for the in depth characterization and optimization of fluorescent proteins (FPs), as well as taking high contrast images of fingermarks is described. This new wide FOV 2PEF imaging technique greatly expands the usefulness of the unique photophysical properties of 2PEF and allows for sensitive, high contrast 2PEF imaging on a much larger scale than was previously possible.

  9. Excitation-emission matrix fluorescence coupled to chemometrics for the exploration of essential oils.

    PubMed

    Mbogning Feudjio, William; Ghalila, Hassen; Nsangou, Mama; Mbesse Kongbonga, Yvon G; Majdi, Youssef

    2014-12-01

    Excitation-emission matrix fluorescence (EEMF) coupled to chemometrics was used to explore essential oils (EOs). The spectrofluorometer was designed with basic and inexpensive materials and was accompanied by appropriate tools for data pre-treatment. Excitation wavelengths varied between 320 nm and 600 nm while emission wavelengths were from 340 nm to 700 nm. Excitation-emission matrix (EEM) spectra of EOs presented different features, revealing the presence of varying fluorophores. EOs from the same species but from different origins presented almost the same spectra, showing the possibility that EEM spectra could be used as additional parameters in the standardisation of EOs. With the aid of unfold principal component analysis (UPCA), resemblances obtained by spectral analysis of EOs were confirmed. A five components parallel factor analysis (PARAFAC) model was used to find the profiles of fluorophores in EOs. One of those components was associated to chlorophyll a. PMID:25159392

  10. Two-photon fluorescence excitation spectroscopy by pulse shaping ultrabroad-bandwidth femtosecond laser pulses

    SciTech Connect

    Xu Bingwei; Coello, Yves; Lozovoy, Vadim V.; Dantus, Marcos

    2010-11-10

    A fast and automated approach to measuring two-photon fluorescence excitation (TPE) spectra of fluorophores with high resolution ({approx}2 nm ) by pulse shaping ultrabroad-bandwidth femtosecond laser pulses is demonstrated. Selective excitation in the range of 675-990 nm was achieved by imposing a series of specially designed phase and amplitude masks on the excitation pulses using a pulse shaper. The method eliminates the need for laser tuning and is, thus, suitable for non-laser-expert use. The TPE spectrum of Fluorescein was compared with independent measurements and the spectra of the pH-sensitive dye 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) in acidic and basic environments were measured for the first time using this approach.

  11. Excitation spectroscopy in multispectral optical fluorescence tomography: methodology, feasibility, and computer simulation studies

    PubMed Central

    Chaudhari, Abhijit J; Ahn, Sangtae; Levenson, Richard; Badawi, Ramsey D; Cherry, Simon R; Leahy, Richard M

    2009-01-01

    Molecular probes used for in vivo Optical Fluorescence Tomography (OFT) studies in small animals are typically chosen such that their emission spectra lie in the 680–850 nm wavelength range. This is because tissue attenuation in this spectral band is relatively low, allowing optical photons even from deep sites in tissue to reach the animal surface, and consequently be detected by a CCD camera. The wavelength dependence of tissue optical properties within the 680–850 nm band can be exploited for emitted light by measuring fluorescent data via multispectral approaches and incorporating the spectral dependence of these optical properties into the OFT inverse problem - that of reconstructing underlying 3D fluorescent probe distributions from optical data collected on the animal surface. However, in the aforementioned spectral band, due to only small variations in the tissue optical properties, multispectral emission data, though superior for image reconstruction compared to achromatic data, tend to be somewhat redundant. A different spectral approach for OFT is to capitalize on the larger variations in the optical properties of tissue for excitation photons than for the emission photons by using excitation at multiple wavelengths as a means of decoding source depth in tissue. The full potential of spectral approaches in OFT can be realized by a synergistic combination of these two approaches, that is, exciting the underlying fluorescent probe at multiple wavelengths and measuring emission data multispectrally. In this paper, we describe a method that incorporates both excitation as well as emission spectral information into the OFT inverse problem. We describe a linear algebraic formulation of the multiple wavelength illumination - multispectral detection (MWI-MD) forward model for OFT and compare it to models that use only excitation at multiple wavelengths or those that use only multispectral detection techniques. This study is carried out in a realistic

  12. Phase Reconstruction of Strong-Field Excited Systems by Transient-Absorption Spectroscopy.

    PubMed

    Liu, Zuoye; Cavaletto, Stefano M; Ott, Christian; Meyer, Kristina; Mi, Yonghao; Harman, Zoltán; Keitel, Christoph H; Pfeifer, Thomas

    2015-07-17

    The evolution of a V-type three-level system is studied, whose two resonances are coherently excited and coupled by two ultrashort laser pump and probe pulses, separated by a varying time delay. We relate the quantum dynamics of the excited multilevel system to the absorption spectrum of the transmitted probe pulse. In particular, by analyzing the quantum evolution of the system, we interpret how atomic phases are differently encoded in the time-delay-dependent spectral absorption profiles when the pump pulse either precedes or follows the probe pulse. This scheme is experimentally applied to atomic Rb, whose fine-structure-split 5s  (2)S{1/2}→5p(2)P{1/2} and 5s(2)S_{1/2}→5p(2)P{3/2} transitions are driven by the combined action of a pump pulse of variable intensity and a delayed probe pulse. The provided understanding of the relationship between quantum phases and absorption spectra represents an important step towards full time-dependent phase reconstruction (quantum holography) of bound-state wave packets in strong-field light-matter interactions with atoms, molecules, and solids. PMID:26230787

  13. In situ phytoplankton absorption, fluorescence emission, and particulate backscattering spectra determined from reflectance

    NASA Technical Reports Server (NTRS)

    Roesler, Collin S.; Pery, Mary Jane

    1995-01-01

    An inverse model was developed to extract the absortion and scattering (elastic and inelastic) properties of oceanic constituents from surface spectral reflectance measurements. In particular, phytoplankton spectral absorption coefficients, solar-stimulated chlorophyll a fluorescence spectra, and particle backscattering spectra were modeled. The model was tested on 35 reflectance spectra obtained from irradiance measurements in optically diverse ocean waters (0.07 to 25.35 mg/cu m range in surface chlorophyll a concentrations). The universality of the model was demonstrated by the accurate estimation of the spectral phytoplankton absorption coefficents over a range of 3 orders of magnitude (rho = 0.94 at 500 nm). Under most oceanic conditions (chlorophyll a less than 3 mg/cu m) the percent difference between measured and modeled phytoplankton absorption coefficents was less than 35%. Spectral variations in measured phytoplankton absorption spectra were well predicted by the inverse model. Modeled volume fluorescence was weakly correlated with measured chl a; fluorescence quantum yield varied from 0.008 to 0.09 as a function of environment and incident irradiance. Modeled particle backscattering coefficients were linearly related to total particle cross section over a twentyfold range in backscattering coefficents (rho = 0.996, n = 12).

  14. Transient absorption dynamics of sterically congested Cu(I) MLCT excited states.

    PubMed

    Garakyaraghi, Sofia; Danilov, Evgeny O; McCusker, Catherine E; Castellano, Felix N

    2015-04-01

    Subpicosecond through supra-nanosecond transient absorption dynamics of the homoleptic Cu(I) metal-to-ligand charge transfer (MLCT) photosensitizers including the benchmark [Cu(dmp)2](+) (dmp =2,9-dimethyl-1,10-phenanthroline) chromophore, as well as [Cu(dsbp)2](+) (dsbp =2,9-di(sec-butyl)-1,10-phenanthroline and [Cu(dsbtmp)2](+) (dsbtmp =2,9-di(sec-butyl)-3,4,7,8-tetramethyl-1,10-phenanthroline) were investigated in dichloromethane and tetrahydrofuran solutions. Visible and near-IR spectroelectrochemical measurements of the singly reduced [Cu(dsbp)2](+) and [Cu(dsbtmp)2](+) species were determined in tetrahydrofuran, allowing for the identification of redox-specific phenanthroline-based radical anion spectroscopic signatures prevalent in the respective transient absorption experiments. This study utilized four different excitation wavelengths (418, 470, 500, and 530 nm) to elucidate dynamics on ultrafast times scales spanning probe wavelengths ranging from the UV to the near-IR (350 to 1450 nm). With the current time resolution of ∼150 fs, initial excited state decay in all three compounds was found to be independent of excitation wavelength. Not surprisingly, there was little to no observed influence of solvent in the initial stages of excited state decay in any of these molecules including [Cu(dmp)2](+), consistent with results from previous investigators. The combined experimental data revealed two ranges of time constants observed on short time scales in all three MLCT chromophores and both components lengthen as a function of structure in the following manner: [Cu(dsbtmp)2](+) < [Cu(dsbp)2](+) < [Cu(dmp)2](+). The molecule with the most inhibited potential for distortion, [Cu(dsbtmp)2](+), possessed the fastest ultrafast dynamics as well as the longest excited state lifetimes in both solvents. These results are consistent with a small degree of excited state distortion, rapid intersystem crossing, and weak vibronic coupling to the ground state. The

  15. [Atomic/ionic fluorescence in microwave plasma torch discharge with excitation of high current and microsecond pulsed hollow cathode lamp: Ca atomic/ionic fluorescence spectrometry].

    PubMed

    Gong, Zhen-bin; Liang, Feng; Yang, Peng-yuan; Jin, Qin-han; Huang, Ben-li

    2002-02-01

    A system of atomic and ionic fluorescence spectrometry in microwave plasma torch (MPT) discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL) has been developed. The operation conditions for Ca atomic and ionic fluorescence spectrometry have been optimized. Compared with atomic fluorescence spectrometry (AFS) in argon microwave induced plasma (MIP) and MPT with the excitation of direct current and conventional pulsed HCL, the system with HCMP HCL excitation can improve AFS and ionic fluorescence spectrometry (IFS) detection limits in MPT atomizer and ionizer. Detection limits (3 sigma) with HCMP HCL-MPT-AFS/IFS are 10.1 ng.mL-1 for Ca I 422.7 nm, 14.6 ng.mL-1 for Ca II 393.4 nm, and 37.4 ng.mL-1 for Ca II 396.8 nm, respectively. PMID:12940030

  16. Experimental and theoretical comparison between absorption, total electron yield, and fluorescence spectra of rare-earth M{sub 5} edges

    SciTech Connect

    Pompa, M.; Flank, A.M.; Lagarde, P.; Rife, J.C.; Stekhin, I.; Nakazawa, M.; Ogasawara, H.; Kotani, A.

    1997-07-01

    Besides the now well-known self-absorption effect, several phenomena related to the multiplet structure of the intermediate state may occur which render x-ray fluorescence different from the true absorption in 3d transition metals at the L edge and at the M{sub 4,5} edges of rare earths. Special selection rules of the radiative de-excitation process play an important role there. We have measured the absorption coefficient of thin films of lanthanum, samarium, and thulium deposited on an aluminum foil, at room temperature, through the simultaneous detection of the transmission, total electron yield, and 150-eV bandwidth fluorescence yield. The latter result shows differences as compared to the other two, and exhibits polarization effects depending upon the angle between incident and outgoing photons. The resonant x-ray fluorescence spectrum is calculated using an atomic model, and then integrated over the emitted energy, to predict the fluorescence yield spectrum. Very good agreement is obtained between the theory and experiment. {copyright} {ital 1997} {ital The American Physical Society}

  17. Characterization of dissolved organic matter in fogwater by excitation-emission matrix fluorescence spectroscopy

    USGS Publications Warehouse

    Birdwell, J.E.; Valsaraj, K.T.

    2010-01-01

    Dissolved organic matter (DOM) present in fogwater samples collected in southeastern Louisiana and central-eastern China has been characterized using excitation-emission matrix fluorescence spectroscopy. The goal of the study was to illustrate the utility of fluorescence for obtaining information on the large fraction of organic carbon in fogwaters (typically >40% by weight) that defies characterization in terms of specific chemical compounds without the difficulty inherent in obtaining sufficient fogwater volume to isolate DOM for assessment using other spectroscopic and chemical analyses. Based on the findings of previous studies using other characterization methods, it was anticipated that the unidentified organic carbon fraction would have characteristic peaks associated with humic substances and fluorescent amino acids. Both humic- and protein-like fluorophores were observed in the fogwater spectra and fluorescence-derived indices for the fogwater had similar values to those of soil and sediment porewater. Greater biological character was observed in samples with higher organic carbon concentrations. Fogwaters are shown to contain a mixture of terrestrially- and microbially-derived fluorescent organic material, which is expected to be derived from an array of different sources, such as suspended soil and dust particles, biogenic emissions and organic substances generated by atmospheric processes. The fluorescence results indicate that much of the unidentified organic carbon present in fogwater can be represented by humic-like and biologically-derived substances similar to those present in other aquatic systems, though it should be noted that fluorescent signatures representative of DOM produced by atmospheric processing of organic aerosols may be contributing to or masked by humic-like fluorophores. ?? 2010.

  18. Characterization of dissolved organic matter in fogwater by excitation-emission matrix fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Birdwell, Justin E.; Valsaraj, Kalliat T.

    Dissolved organic matter (DOM) present in fogwater samples collected in southeastern Louisiana and central-eastern China has been characterized using excitation-emission matrix fluorescence spectroscopy. The goal of the study was to illustrate the utility of fluorescence for obtaining information on the large fraction of organic carbon in fogwaters (typically >40% by weight) that defies characterization in terms of specific chemical compounds without the difficulty inherent in obtaining sufficient fogwater volume to isolate DOM for assessment using other spectroscopic and chemical analyses. Based on the findings of previous studies using other characterization methods, it was anticipated that the unidentified organic carbon fraction would have characteristic peaks associated with humic substances and fluorescent amino acids. Both humic- and protein-like fluorophores were observed in the fogwater spectra and fluorescence-derived indices for the fogwater had similar values to those of soil and sediment porewater. Greater biological character was observed in samples with higher organic carbon concentrations. Fogwaters are shown to contain a mixture of terrestrially- and microbially-derived fluorescent organic material, which is expected to be derived from an array of different sources, such as suspended soil and dust particles, biogenic emissions and organic substances generated by atmospheric processes. The fluorescence results indicate that much of the unidentified organic carbon present in fogwater can be represented by humic-like and biologically-derived substances similar to those present in other aquatic systems, though it should be noted that fluorescent signatures representative of DOM produced by atmospheric processing of organic aerosols may be contributing to or masked by humic-like fluorophores.

  19. Excited-state absorption in the lasing wavelength region of Alexandrite

    SciTech Connect

    Shand, M.L.; Walling, J.C.

    1982-07-01

    The excited-state absorption cross section sigma/sub 2/ /sub a/ (E) in the gain wavelength region of alexandrite has been determined and is shown to limit the vibronic laser range at both high and low energy. The maximum in vibronic laser emission is due to a minimum in sigma/sub 2/ /sub a/ (E) near 13 000 cm/sup -1/. sigma/sub 2/ /sub a/ (E) is less than 10/sup -20/ cm/sup 2/ between 12 000 and 14 000 cm/sup -1/.

  20. A high resolution x-ray fluorescence spectrometer for near edge absorption studies

    SciTech Connect

    Stojanoff, V.; Hamalainen, K.; Siddons, D.P.; Hastings, J.B.; Berman, L.E.; Cramer, S.; Smith, G.

    1991-01-01

    A high resolution fluorescence spectrometer using a Johann geometry in a back scattering arrangement was developed. The spectrometer, with a resolution of 0.3 eV at 6.5 keV, combined with an incident beam, with a resolution of 0.7 eV, form the basis of a high resolution instrument for measuring x-ray absorption spectra. The advantages of the instrument are illustrated with the near edge absorption spectrum of dysprosium nitrate. 10 refs., 4 figs.

  1. A high resolution x-ray fluorescence spectrometer for near edge absorption studies

    SciTech Connect

    Stojanoff, V.; Hamalainen, K.; Siddons, D.P.; Hastings, J.B.; Berman, L.E.; Cramer, S.; Smith, G.

    1991-12-31

    A high resolution fluorescence spectrometer using a Johann geometry in a back scattering arrangement was developed. The spectrometer, with a resolution of 0.3 eV at 6.5 keV, combined with an incident beam, with a resolution of 0.7 eV, form the basis of a high resolution instrument for measuring x-ray absorption spectra. The advantages of the instrument are illustrated with the near edge absorption spectrum of dysprosium nitrate. 10 refs., 4 figs.

  2. Comparison of Cherenkov excited fluorescence and phosphorescence molecular sensing from tissue with external beam irradiation.

    PubMed

    Lin, Huiyun; Zhang, Rongxiao; Gunn, Jason R; Esipova, Tatiana V; Vinogradov, Sergei; Gladstone, David J; Jarvis, Lesley A; Pogue, Brian W

    2016-05-21

    Ionizing radiation delivered by a medical linear accelerator (LINAC) generates Cherenkov emission within the treated tissue. A fraction of this light, in the 600-900 nm wavelength region, propagates through centimeters of tissue and can be used to excite optical probes in vivo, enabling molecular sensing of tissue analytes. The success of isolating the emission signal from this Cherenkov excitation background is dependent on key factors such as: (i) the Stokes shift of the probe spectra; (ii) the excited state lifetime; (iii) the probe concentration; (iv) the depth below the tissue surface; and (v) the radiation dose used. Previous studies have exclusively focused on imaging phosphorescent dyes, rather than fluorescent dyes. However there are only a few biologically important phosphorescent dyes and yet in comparison there are thousands of biologically relevant fluorescent dyes. So in this study the focus was a study of efficacy of Cherenkov-excited luminescence using fluorescent commercial near-infrared probes, IRDye 680RD, IRDye 700DX, and IRDye 800CW, and comparing them to the well characterized phosphorescent probe Oxyphor PtG4, an oxygen sensitive dye. Each probe was excited by Cherenkov light from a 6 MV external radiation beam, and measured in continuous wave or time-gated modes. The detection was performed by spectrally resolving the luminescence signals, and measuring them with spectrometer-based separation on an ICCD detector. The results demonstrate that IRDye 700DX and PtG4 allowed for the maximal signal to noise ratio. In the case of the phosphorescent probe, PtG4, with emission decays on the microsecond (μs) time scale, time-gated acquisition was possible, and it allowed for higher efficacy in terms of the probe concentration and detection depth. Phantoms containing the probe at 5 mm depth could be detected at concentrations down to the nanoMolar range, and at depths into the tissue simulating phantom near 3 cm. In vivo studies showed that 5

  3. Comparison of Cherenkov excited fluorescence and phosphorescence molecular sensing from tissue with external beam irradiation

    NASA Astrophysics Data System (ADS)

    Lin, Huiyun; Zhang, Rongxiao; Gunn, Jason R.; Esipova, Tatiana V.; Vinogradov, Sergei; Gladstone, David J.; Jarvis, Lesley A.; Pogue, Brian W.

    2016-05-01

    Ionizing radiation delivered by a medical linear accelerator (LINAC) generates Cherenkov emission within the treated tissue. A fraction of this light, in the 600–900 nm wavelength region, propagates through centimeters of tissue and can be used to excite optical probes in vivo, enabling molecular sensing of tissue analytes. The success of isolating the emission signal from this Cherenkov excitation background is dependent on key factors such as: (i) the Stokes shift of the probe spectra; (ii) the excited state lifetime; (iii) the probe concentration; (iv) the depth below the tissue surface; and (v) the radiation dose used. Previous studies have exclusively focused on imaging phosphorescent dyes, rather than fluorescent dyes. However there are only a few biologically important phosphorescent dyes and yet in comparison there are thousands of biologically relevant fluorescent dyes. So in this study the focus was a study of efficacy of Cherenkov-excited luminescence using fluorescent commercial near-infrared probes, IRDye 680RD, IRDye 700DX, and IRDye 800CW, and comparing them to the well characterized phosphorescent probe Oxyphor PtG4, an oxygen sensitive dye. Each probe was excited by Cherenkov light from a 6 MV external radiation beam, and measured in continuous wave or time-gated modes. The detection was performed by spectrally resolving the luminescence signals, and measuring them with spectrometer-based separation on an ICCD detector. The results demonstrate that IRDye 700DX and PtG4 allowed for the maximal signal to noise ratio. In the case of the phosphorescent probe, PtG4, with emission decays on the microsecond (μs) time scale, time-gated acquisition was possible, and it allowed for higher efficacy in terms of the probe concentration and detection depth. Phantoms containing the probe at 5 mm depth could be detected at concentrations down to the nanoMolar range, and at depths into the tissue simulating phantom near 3 cm. In vivo studies showed that 5

  4. Fluorescence spectroscopy using excitation and emission matrix for quantification of tissue native fluorophores and cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Wu, Binlin; Gayen, S. K.; Xu, M.

    2014-03-01

    Native fluorescence spectrum of normal and cancerous human prostate tissues is studied to distinguish between normal and cancerous tissues, and cancerous tissues at different cancer grade. The tissue samples were obtained from Cooperative Human Tissue Network (CHTN) and National Disease Research Interchange(NDRI). An excitation and emission matrix (EEM) was generated for each tissue sample by acquiring native fluorescence spectrum of the sample using multiple excitation wavelengths. The non-negative matrix factorization algorithm was used to generate fluorescence EEMs that correspond to the fluorophores in biological tissues, including tryptophan, collagen, elastin, nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD) and the background paraffin. We hypothesize that, as a consequence of metabolic changes associated with the development of cancer, the concentrations of NADH and FAD are different in normal and cancerous tissues, and also different for different cancer grades. We used the ratio of the abundances of FAD and NADH to distinguish between normal and cancerous tissues, and the tissue cancer grade. The FAD-to-NADH ratio was found to be the highest for normal tissue and decreased as the cancer grade increased.

  5. Fluorescence excitation-emission matrix spectroscopy as a tool for determining quality of sparkling wines.

    PubMed

    Elcoroaristizabal, Saioa; Callejón, Raquel M; Amigo, Jose M; Ocaña-González, Juan A; Morales, M Lourdes; Ubeda, Cristina

    2016-09-01

    Browning in sparkling wines was assessed by the use of excitation-emission fluorescence spectroscopy combined with PARAllel FACtor analysis (PARAFAC). Four different cava sparkling wines were monitored during an accelerated browning process and subsequently storage. Fluorescence changes observed during the accelerated browning process were monitored and compared with other conventional parameters: absorbance at 420nm (A420) and the content of 5-hydroxymethyl-2-furfural (5-HMF). A high similarity of the spectral profiles for all sparkling wines analyzed was observed, being explained by a four component PARAFAC model. A high correlation between the third PARAFAC factor (465/530nm) and the commonly used non-enzymatic browning indicators was observed. The fourth PARAFAC factor (280/380nm) gives us also information about the browning process following a first order kinetic reaction. Hence, excitation-emission fluorescence spectroscopy, together with PARAFAC, provides a faster alternative for browning monitoring to conventional methods, as well as useful key indicators for quality control. PMID:27041327

  6. A Step Beyond BRET: Fluorescence by Unbound Excitation from Luminescence (FUEL)

    PubMed Central

    Dragavon, Joseph; Sinow, Carolyn; Holland, Alexandra D.; Rekiki, Abdessalem; Theodorou, Ioanna; Samson, Chelsea; Blazquez, Samantha; Rogers, Kelly L.; Tournebize, Régis; Shorte, Spencer L.

    2014-01-01

    Fluorescence by Unbound Excitation from Luminescence (FUEL) is a radiative excitation-emission process that produces increased signal and contrast enhancement in vitro and in vivo. FUEL shares many of the same underlying principles as Bioluminescence Resonance Energy Transfer (BRET), yet greatly differs in the acceptable working distances between the luminescent source and the fluorescent entity. While BRET is effectively limited to a maximum of 2 times the Förster radius, commonly less than 14 nm, FUEL can occur at distances up to µm or even cm in the absence of an optical absorber. Here we expand upon the foundation and applicability of FUEL by reviewing the relevant principles behind the phenomenon and demonstrate its compatibility with a wide variety of fluorophores and fluorescent nanoparticles. Further, the utility of antibody-targeted FUEL is explored. The examples shown here provide evidence that FUEL can be utilized for applications where BRET is not possible, filling the spatial void that exists between BRET and traditional whole animal imaging. PMID:24894759

  7. Use of image analysis to estimate anthocyanin and UV-excited fluorescent phenolic compound levels in strawberry fruit

    PubMed Central

    Yoshioka, Yosuke; Nakayama, Masayoshi; Noguchi, Yuji; Horie, Hideki

    2013-01-01

    Strawberry is rich in anthocyanins, which are responsible for the red color, and contains several colorless phenolic compounds. Among the colorless phenolic compounds, some, such as hydroxycinammic acid derivatives, emit blue-green fluorescence when excited with ultraviolet (UV) light. Here, we investigated the effectiveness of image analyses for estimating the levels of anthocyanins and UV-excited fluorescent phenolic compounds in fruit. The fruit skin and cut surface of 12 cultivars were photographed under visible and UV light conditions; colors were evaluated based on the color components of images. The levels of anthocyanins and UV-excited fluorescent compounds in each fruit were also evaluated by spectrophotometric and high performance liquid chromatography (HPLC) analyses, respectively and relationships between these levels and the image data were investigated. Red depth of the fruits differed greatly among the cultivars and anthocyanin content was well estimated based on the color values of the cut surface images. Strong UV-excited fluorescence was observed on the cut surfaces of several cultivars, and the grayscale values of the UV-excited fluorescence images were markedly correlated with the levels of those fluorescent compounds as evaluated by HPLC analysis. These results indicate that image analyses can select promising genotypes rich in anthocyanins and fluorescent phenolic compounds. PMID:23853516

  8. Dicyanostilbene-derived two-photon fluorescence dyes with large two-photon absorption cross sections

    NASA Astrophysics Data System (ADS)

    Huang, Chibao; Lin, Changhua; Ren, Anxiang; Yang, Nianfa

    2011-12-01

    Four dicyanostilbene-derived two-photon fluorescence (TPF) dyes were synthesized as the model compounds to systematically study the effect of the dicyano and the terminal substituent on the two-photon absorption (TPA). These four compounds ( DSO, DCY, DTO and DPH) exhibit very large two-photon absorption cross sections ( δ). DCY (A- π-A) with the terminal cyano group has especially high fluorescence quantum yield (0.71) and relatively large δ (1480 GM), while DPH (D- π-A) with the substitutedamino group at its terminus possesses the largest δ (2800 GM) and the longest emission wavelength (620 nm). The idealest terminal substituent should not be the alkoxy group but the substitutedamino group. This class of dicyanostilbene dyes possess small molecule size, large δ (830-2800 GM), long-wavelength emission (459-620 nm) and large Stokes shift (80-206 nm), and are ideal chromophores for TPF labels and probes.

  9. Relationship of CDOM fluorescence and absorption on the South West Florida Shelf

    NASA Astrophysics Data System (ADS)

    Conmy, R. N.; Coble, P. G.; Hastings, R. H.

    2005-12-01

    The WFS is a complex subtropical coastal region affected by multiple river systems. In recent years, the southern portion of the shelf has been the focus of much study due to the initiation of persistent harmful algal blooms. During this time, great effort has been put forth in collecting seasonal measurements of CDOM (Colored Dissolved Organic Matter) inherent optical properties via in situ and discrete sampling techniques. This sizeable dataset now allows for establishing robust regional relationships of CDOM fluorescence and absorption. Discussed here will be factors affecting that relationship and how it covaries with chlorophyll and DOC (Dissolve Organic Carbon). This relationship also demonstrates the potential for using in situ CDOM fluorescence measurements from moored locations to provide reliable CDOM absorption values for current bio-optical models.

  10. Simultaneous Two-Photon Absorption to Gerade Excited Singlet States of Diphenylacetylene and Diphenylbutadiyne Using Optical-Probing Photoacoustic Spectroscopy.

    PubMed

    Isozaki, Tasuku; Oba, Hikari; Ikoma, Tadaaki; Suzuki, Tadashi

    2016-08-11

    Simultaneous two-photon absorption to one-photon forbidden electronically excited states of diphenylacetylene (DPA) and diphenylbutadiyne (DPB) was investigated by means of highly sensitive optical-probing photoacoustic spectroscopy. The incident laser power dependencies on photoacoustic signal intensity indicate that the signals are dominated by the two-photon absorption regime. Two-photon absorption is responsible for transitions to gerade excited states based on the selection rule. The two-photon absorption bands observed in the heat action spectra were assigned with the aid of quantum chemical calculations. The relative magnitude of the two-photon absorption cross sections of DPA and DPB was estimated, and the larger two-photon absorption cross section of DPB was related to the resonance effect with the red-shifted one-photon allowed 1(1)B1u ← 1(1)Ag transition of DPB. PMID:27410388

  11. Highly-sensitive Eu3+ ratiometric thermometers based on excited state absorption with predictable calibration

    NASA Astrophysics Data System (ADS)

    Souza, Adelmo S.; Nunes, Luiz A. O.; Silva, Ivan G. N.; Oliveira, Fernando A. M.; da Luz, Leonis L.; Brito, Hermi F.; Felinto, Maria C. F. C.; Ferreira, Rute A. S.; Júnior, Severino A.; Carlos, Luís D.; Malta, Oscar L.

    2016-02-01

    Temperature measurements ranging from a few degrees to a few hundreds of Kelvin are of great interest in the fields of nanomedicine and nanotechnology. Here, we report a new ratiometric luminescent thermometer using thermally excited state absorption of the Eu3+ ion. The thermometer is based on the simple Eu3+ energy level structure and can operate between 180 and 323 K with a relative sensitivity ranging from 0.7 to 1.7% K-1. The thermometric parameter is defined as the ratio between the emission intensities of the 5D0 --> 7F4 transition when the 5D0 emitting level is excited through the 7F2 (physiological range) or 7F1 (down to 180 K) level. Nano and microcrystals of Y2O3:Eu3+ were chosen as a proof of concept of the operational principles in which both excitation and detection are within the first biological transparent window. A novel and of paramount importance aspect is that the calibration factor can be calculated from the Eu3+ emission spectrum avoiding the need for new calibration procedures whenever the thermometer operates in different media.Temperature measurements ranging from a few degrees to a few hundreds of Kelvin are of great interest in the fields of nanomedicine and nanotechnology. Here, we report a new ratiometric luminescent thermometer using thermally excited state absorption of the Eu3+ ion. The thermometer is based on the simple Eu3+ energy level structure and can operate between 180 and 323 K with a relative sensitivity ranging from 0.7 to 1.7% K-1. The thermometric parameter is defined as the ratio between the emission intensities of the 5D0 --> 7F4 transition when the 5D0 emitting level is excited through the 7F2 (physiological range) or 7F1 (down to 180 K) level. Nano and microcrystals of Y2O3:Eu3+ were chosen as a proof of concept of the operational principles in which both excitation and detection are within the first biological transparent window. A novel and of paramount importance aspect is that the calibration factor can be

  12. Dual-wavelength excitation to reduce background fluorescence for fluorescence spectroscopic quantitation of erythrocyte zinc protoporphyrin-IX and protoporphyrin-IX from whole blood and oral mucosa

    NASA Astrophysics Data System (ADS)

    Hennig, Georg; Vogeser, Michael; Holdt, Lesca M.; Homann, Christian; Großmann, Michael; Stepp, Herbert; Gruber, Christian; Erdogan, Ilknur; Hasmüller, Stephan; Hasbargen, Uwe; Brittenham, Gary M.

    2014-02-01

    Erythrocyte zinc protoporphyrin-IX (ZnPP) and protoporphyrin-IX (PPIX) accumulate in a variety of disorders that restrict or disrupt the biosynthesis of heme, including iron deficiency and various porphyrias. We describe a reagent-free spectroscopic method based on dual-wavelength excitation that can measure simultaneously both ZnPP and PPIX fluorescence from unwashed whole blood while virtually eliminating background fluorescence. We further aim to quantify ZnPP and PPIX non-invasively from the intact oral mucosa using dual-wavelength excitation to reduce the strong tissue background fluorescence while retaining the faint porphyrin fluorescence signal originating from erythrocytes. Fluorescence spectroscopic measurements were made on 35 diluted EDTA blood samples using a custom front-face fluorometer. The difference spectrum between fluorescence at 425 nm and 407 nm excitation effectively eliminated background autofluorescence while retaining the characteristic porphyrin peaks. These peaks were evaluated quantitatively and the results compared to a reference HPLC-kit method. A modified instrument using a single 1000 μm fiber for light delivery and detection was used to record fluorescence spectra from oral mucosa. For blood measurements, the ZnPP and PPIX fluorescence intensities from the difference spectra correlated well with the reference method (ZnPP: Spearman's rho rs = 0.943, p < 0.0001; PPIX: rs = 0.959, p < 0.0001). In difference spectra from oral mucosa, background fluorescence was reduced significantly, while porphyrin signals remained observable. The dual-wavelength excitation method evaluates quantitatively the ZnPP/heme and PPIX/heme ratios from unwashed whole blood, simplifying clinical laboratory measurements. The difference technique reduces the background fluorescence from measurements on oral mucosa, allowing for future non-invasive quantitation of erythrocyte ZnPP and PPIX.

  13. Facile synthesis of carbon dots in an immiscible system with excitation-independent emission and thermally activated delayed fluorescence.

    PubMed

    Hou, Juan; Wang, Long; Zhang, Ping; Xu, Yuan; Ding, Lan

    2015-12-28

    Herein, we present a one-pot microwave-assisted preparative method for water-soluble carbon dots (CDs) in an immiscible system. CDs demonstrated uniform morphology, high quantum yield and excitation-independent fluorescence emission. Moreover, we first reported the observation of thermally activated delayed fluorescence from CDs. PMID:26498875

  14. Complexes trans-Pt(BODIPY)X(PEt3)2: excitation energy-dependent fluorescence and phosphorescence emissions, oxygen sensing and photocatalysis.

    PubMed

    Irmler, Peter; Winter, Rainer F

    2016-06-21

    We report on five new complexes with the general formula trans-Pt(BODIPY)X(PEt3)2 (), where the platinum(ii) ion is σ-bonded to a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacen-8-yl (BODIPY) and an anionic ligand X(-) (X(-) = Cl(-), I(-), NO2(-), NCS(-), CH3(-)). All five complexes were characterized by multinuclear NMR, electronic absorption and luminescence spectroscopy and by X-ray diffraction analysis. Four of these complexes show efficient intersystem crossing (ISC) from an excited singlet state to a BODIPY-centred T1 state and exhibit dual fluorescence and phosphorescence emission from the BODIPY ligand. In , the fluorescence is almost completely quenched, whereas the phosphorescence quantum yield reaches a value of 40%. The rate of ISC and the ratio of phosphorescence to fluorescence emissions depend on the excitation wavelength (i.e. on which specific transition is excited). The performance of these complexes as one-component oxygen sensors and their photocatalytic activities were tested by Stern-Volmer quenching experiments and by monitoring the oxidation of 1,5-dihydroxynaphthalene with (1)O2 generated from the long-lived triplet state of the sensitizer by triplet-triplet annihilation with (3)O2. Exceptionally high (1)O2 generation quantum yields of up to near unity were obtained. PMID:27255789

  15. Near infrared excited micro-Raman spectra of 4:1 methanol-ethanol mixture and ruby fluorescence at high pressure

    NASA Astrophysics Data System (ADS)

    Wang, X. B.; Shen, Z. X.; Tang, S. H.; Kuok, M. H.

    1999-06-01

    Near infrared (NIR) lasers, as a new excitation source for Raman spectroscopy, has shown its unique advantages and is being increasingly used for some special samples, such as those emitting strong fluorescence in the visible region. This article focuses on some issues related to high-pressure micro-Raman spectroscopy using NIR excitation source. The Raman spectra of 4:1 methanol-ethanol mixture (4:1 M-E) show a linear variation in both Raman shifts and linewidths under pressure up to 18 GPa. This result is useful in distinguishing Raman scattering of samples from that of the alcohol mixture, an extensively used pressure-transmitting medium. The R1 fluorescence in the red region induced by two-photon absorption of the NIR laser is strong enough to be used as pressure scale. The frequency and line width of the R1 lines are very sensitive to pressure change and the glass transition of the pressure medium. Our results manifest that it is reliable and convenient to use NIR induced two-photon excited fluorescence of ruby for both pressure calibration and distribution of pressure in the 4:1 M-E pressure transmitting medium.

  16. Investigation of features of processes Raman and fluorescence sea water depending on the time characteristics of the excitation radiation

    NASA Astrophysics Data System (ADS)

    Mayor, A. Yu.; Bukin, O. A.; Proschenko, D. Yu.; Golik, S. S.

    2015-11-01

    The forms and intensities of Raman lines and chlorophyll A fluorescence have been researched when excited at 532 nm, depending on the duration of the pulses of the exciting radiation. The duration of continuous operation ranged from emission to 120 fs.

  17. Fluorescent optical position sensor

    DOEpatents

    Weiss, Jonathan D.

    2005-11-15

    A fluorescent optical position sensor and method of operation. A small excitation source side-pumps a localized region of fluorescence at an unknown position along a fluorescent waveguide. As the fluorescent light travels down the waveguide, the intensity of fluorescent light decreases due to absorption. By measuring with one (or two) photodetectors the attenuated intensity of fluorescent light emitted from one (or both) ends of the waveguide, the position of the excitation source relative to the waveguide can be determined by comparing the measured light intensity to a calibrated response curve or mathematical model. Alternatively, excitation light can be pumped into an end of the waveguide, which generates an exponentially-decaying continuous source of fluorescent light along the length of the waveguide. The position of a photodetector oriented to view the side of the waveguide can be uniquely determined by measuring the intensity of the fluorescent light emitted radially at that location.

  18. Single excitation-emission fluorescence spectrum (EEF) for determination of cetane improver in diesel fuel

    NASA Astrophysics Data System (ADS)

    Insausti, Matías; Fernández Band, Beatriz S.

    2015-04-01

    A highly sensitive spectrofluorimetric method has been developed for the determination of 2-ethylhexyl nitrate in diesel fuel. Usually, this compound is used as an additive in order to improve cetane number. The analytical method consists in building the chemometric model as a first step. Then, it is possible to quantify the analyte with only recording a single excitation-emission fluorescence spectrum (EEF), whose data are introduced in the chemometric model above mentioned. Another important characteristic of this method is that the fuel sample was used without any pre-treatment for EEF. This work provides an interest improvement to fluorescence techniques using the rapid and easily applicable EEF approach to analyze such complex matrices. Exploding EEF was the key to a successful determination, obtaining a detection limit of 0.00434% (v/v) and a limit of quantification of 0.01446% (v/v).

  19. Eliminating Unwanted Far-Field Excitation in Objective-Type TIRF. Part II. Combined Evanescent-Wave Excitation and Supercritical-Angle Fluorescence Detection Improves Optical Sectioning

    PubMed Central

    Brunstein, Maia; Hérault, Karine; Oheim, Martin

    2014-01-01

    Azimuthal beam scanning makes evanescent-wave (EW) excitation isotropic, thereby producing total internal reflection fluorescence (TIRF) images that are evenly lit. However, beam spinning does not fundamentally address the problem of propagating excitation light that is contaminating objective-type TIRF. Far-field excitation depends more on the specific objective than on cell scattering. As a consequence, the excitation impurities in objective-type TIRF are only weakly affected by changes of azimuthal or polar beam angle. These are the main results of the first part of this study (Eliminating unwanted far-field excitation in objective-type TIRF. Pt.1. Identifying sources of nonevanescent excitation light). This second part focuses on exactly where up beam in the illumination system stray light is generated that gives rise to nonevanescent components in TIRF. Using dark-field imaging of scattered excitation light we pinpoint the objective, intermediate lenses and, particularly, the beam scanner as the major sources of stray excitation. We study how adhesion-molecule coating and astrocytes or BON cells grown on the coverslip surface modify the dark-field signal. On flat and weakly scattering cells, most background comes from stray reflections produced far from the sample plane, in the beam scanner and the objective lens. On thick, optically dense cells roughly half of the scatter is generated by the sample itself. We finally show that combining objective-type EW excitation with supercritical-angle fluorescence (SAF) detection efficiently rejects the fluorescence originating from deeper sample regions. We demonstrate that SAF improves the surface selectivity of TIRF, even at shallow penetration depths. The coplanar microscopy scheme presented here merges the benefits of beam spinning EW excitation and SAF detection and provides the conditions for quantitative wide-field imaging of fluorophore dynamics at or near the plasma membrane. PMID:24606929

  20. Two-photon excited fluorescence lifetime imaging and spectroscopy of melanins in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Krasieva, Tatiana B.; Stringari, Chiara; Liu, Feng; Sun, Chung-Ho; Kong, Yu; Balu, Mihaela; Meyskens, Frank L.; Gratton, Enrico; Tromberg, Bruce J.

    2013-03-01

    Changes in the amounts of cellular eumelanin and pheomelanin have been associated with carcinogenesis. The goal of this work is to develop methods based on two-photon-excited-fluorescence (TPEF) for measuring relative concentrations of these compounds. We acquire TPEF emission spectra (λex=1000 nm) of melanin in vitro from melanoma cells, hair specimens, and in vivo from healthy volunteers. We find that the pheomelanin emission peaks at approximately 615 to 625 nm and eumelanin exhibits a broad maximum at 640 to 680 nm. Based on these data we define an optical melanin index (OMI) as the ratio of fluorescence intensities at 645 and 615 nm. The measured OMI for the MNT-1 melanoma cell line is 1.6±0.22 while the Mc1R gene knockdown lines MNT-46 and MNT-62 show substantially greater pheomelanin production (OMI=0.5±0.05 and 0.17±0.03, respectively). The measured values are in good agreement with chemistry-based melanin extraction methods. In order to better separate melanin fluorescence from other intrinsic fluorophores, we perform fluorescence lifetime imaging microscopy of in vitro specimens. The relative concentrations of keratin, eumelanin, and pheomelanin components are resolved using a phasor approach for analyzing lifetime data. Our results suggest that a noninvasive TPEF index based on spectra and lifetime could potentially be used for rapid melanin ratio characterization both in vitro and in vivo.

  1. Label-free in vivo imaging of human leukocytes using two-photon excited endogenous fluorescence

    NASA Astrophysics Data System (ADS)

    Zeng, Yan; Yan, Bo; Sun, Qiqi; Teh, Seng Khoon; Zhang, Wei; Wen, Zilong; Qu, Jianan Y.

    2013-04-01

    We demonstrate that two-photon excited endogenous fluorescence enables label-free morphological and functional imaging of various human blood cells. Specifically, we achieved distinctive morphological contrast to visualize morphology of important leukocytes, such as polymorphonuclear structure of granulocyte and mononuclear feature of agranulocyte, through the employment of the reduced nicotinamide adenine dinucleotide (NADH) fluorescence signals. In addition, NADH fluorescence images clearly reveal the morphological transformation process of neutrophils during disease-causing bacterial infection. Our findings also show that time-resolved NADH fluorescence can be potentially used for functional imaging of the phagocytosis of pathogens by leukocytes (neutrophils) in vivo. In particular, we found that free-to-bound NADH ratios measured in infected neutrophils increased significantly, which is consistent with a previous study that the energy consumed in the phagocytosis of neutrophils is mainly generated through the glycolysis pathway that leads to the accumulation of free NADH. Future work will focus on further developing and applying label-free imaging technology to investigate leukocyte-related diseases and disorders.

  2. Continuous flow real-time PCR device using multi-channel fluorescence excitation and detection.

    PubMed

    Hatch, Andrew C; Ray, Tathagata; Lintecum, Kelly; Youngbull, Cody

    2014-02-01

    High throughput automation is greatly enhanced using techniques that employ conveyor belt strategies with un-interrupted streams of flow. We have developed a 'conveyor belt' analog for high throughput real-time quantitative Polymerase Chain Reaction (qPCR) using droplet emulsion technology. We developed a low power, portable device that employs LED and fiber optic fluorescence excitation in conjunction with a continuous flow thermal cycler to achieve multi-channel fluorescence detection for real-time fluorescence measurements. Continuously streaming fluid plugs or droplets pass through tubing wrapped around a two-temperature zone thermal block with each wrap of tubing fluorescently coupled to a 64-channel multi-anode PMT. This work demonstrates real-time qPCR of 0.1-10 μL droplets or fluid plugs over a range of 7 orders of magnitude concentration from 1 × 10(1) to 1 × 10(7). The real-time qPCR analysis allows dynamic range quantification as high as 1 × 10(7) copies per 10 μL reaction, with PCR efficiencies within the range of 90-110% based on serial dilution assays and a limit of detection of 10 copies per rxn. The combined functionality of continuous flow, low power thermal cycling, high throughput sample processing, and real-time qPCR improves the rates at which biological or environmental samples can be continuously sampled and analyzed. PMID:24297040

  3. Structural and dynamical aspects of skin studied by multiphoton excitation fluorescence microscopy-based methods.

    PubMed

    Bloksgaard, Maria; Brewer, Jonathan; Bagatolli, Luis A

    2013-12-18

    This mini-review reports on applications of particular multiphoton excitation microscopy-based methodologies employed in our laboratory to study skin. These approaches allow in-depth optical sectioning of the tissue, providing spatially resolved information on specific fluorescence probes' parameters. Specifically, by applying these methods, spatially resolved maps of water dipolar relaxation (generalized polarization function using the 6-lauroyl-2-(N,N-dimethylamino)naphthale probe), activity of protons (fluorescence lifetime imaging using a proton sensitive fluorescence probe--2,7-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein) and diffusion coefficients of distinct fluorescence probes (raster imaging correlation spectroscopy) can be obtained from different regions of the tissue. Comparative studies of different tissue strata, but also between equivalent regions of normal and abnormal excised skin, including applications of fluctuation correlation spectroscopy on transdermal penetration of liposomes are presented and discussed. The data from the different studies reported reveal the intrinsic heterogeneity of skin and also prove these strategies to be powerful noninvasive tools to explore structural and dynamical aspects of the tissue. PMID:23608611

  4. In vivo Diagnosis of Cervical Intraepithelial Neoplasia Using 337-nm- Excited Laser-Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Ramanujam, N.; Mitchell, M. F.; Mahadevan, A.; Warren, S.; Thomsen, S.; Silva, E.; Richards-Kortum, R.

    1994-10-01

    Laser-induced fluorescence at 337-nm excitation was used in vivo to differentiate neoplastic [cervical intraepithelial neoplasia (CIN)], nonneoplastic abnormal (inflammation and human papilloma viral infection), and normal cervical tissues. A colposcope (low-magnification microscope used to view the cervix with reflected light) was used to identify 66 normal and 49 abnormal (5 inflammation, 21 human papilloma virus infection, and 23 CIN) sites on the cervix in 28 patients. These sites were then interrogated spectroscopically. A two-stage algorithm was developed to diagnose CIN. The first stage differentiated histologically abnormal tissues from colposcopically normal tissues with a sensitivity, specificity, and positive predictive value of 92%, 90%, and 88%, respectively. The second stage differentiated preneoplastic and neoplastic tissues from nonneoplastic abnormal tissues with a sensitivity, specificity, and positive predictive value of 87%, 73%, and 74%, respectively. Spectroscopic differences were consistent with a decrease in the absolute contribution of collagen fluorescence, an increase in the absolute contribution of oxyhemoglobin attenuation, and an increase in the relative contribution of reduced nicotinamide dinucleotide phosphate [NAD(P)H] fluorescence as tissue progresses from normal to abnormal in the same patient. These results suggest that in vivo fluorescence spectroscopy of the cervix can be used to diagnose CIN at colposcopy.

  5. Fluorescence-based calculus detection using a 405-nm excitation wavelength

    NASA Astrophysics Data System (ADS)

    Brede, O.; Schelle, F.; Krueger, S.; Oehme, B.; Dehn, C.; Frentzen, M.; Braun, A.

    2011-03-01

    The aim of this study was to assess the difference of fluorescence signals of cement and calculus using a 405 nm excitation wavelength. A total number of 20 freshly extracted teeth was used. The light source used for this study was a blue LED with a wavelength of 405nm. For each tooth the spectra of calculus and cementum were measured separately. Fluorescence light was collimated into an optical fibre and spectrally analyzed using an echelle spectrometer (aryelle 200, Lasertechnik Berlin, Germany) with an additionally bandpass (fgb 67, Edmund Industrial Optics, Karlsruhe, Germany). From these 40 measurements the median values were calculated over the whole spectrum, leading to two different median spectra, one for calculus and one for cementum. For further statistical analysis we defined 8 areas of interest (AOI) in wavelength regions, showing remarkable differences in signal strength. In 7 AOIs the intensity of the calculus spectrum differed statistically significant from the intensity of the cementum spectrum (p < 0.05). A spectral difference could be shown between calculus and cement between 600nm and 700nm. Thus, we can conclude that fluorescence of calculus shows a significant difference to the fluorescence of cement. A differentiation over the intensity is possible as well as over the spectrum. Using a wavelength of 405nm, it is possible to distinguish between calculus and cement. These results could be used for further devices to develop a method for feedback controlled calculus removal.

  6. Two-photon excited fluorescence lifetime imaging and spectroscopy of melanins in vitro and in vivo

    PubMed Central

    Krasieva, Tatiana B.; Stringari, Chiara; Liu, Feng; Sun, Chung-Ho; Kong, Yu; Balu, Mihaela; Meyskens, Frank L.; Gratton, Enrico

    2012-01-01

    Abstract. Changes in the amounts of cellular eumelanin and pheomelanin have been associated with carcinogenesis. The goal of this work is to develop methods based on two-photon-excited-fluorescence (TPEF) for measuring relative concentrations of these compounds. We acquire TPEF emission spectra (λex=1000  nm) of melanin in vitro from melanoma cells, hair specimens, and in vivo from healthy volunteers. We find that the pheomelanin emission peaks at approximately 615 to 625 nm and eumelanin exhibits a broad maximum at 640 to 680 nm. Based on these data we define an optical melanin index (OMI) as the ratio of fluorescence intensities at 645 and 615 nm. The measured OMI for the MNT-1 melanoma cell line is 1.6±0.22 while the Mc1R gene knockdown lines MNT-46 and MNT-62 show substantially greater pheomelanin production (OMI=0.5±0.05 and 0.17±0.03, respectively). The measured values are in good agreement with chemistry-based melanin extraction methods. In order to better separate melanin fluorescence from other intrinsic fluorophores, we perform fluorescence lifetime imaging microscopy of in vitro specimens. The relative concentrations of keratin, eumelanin, and pheomelanin components are resolved using a phasor approach for analyzing lifetime data. Our results suggest that a noninvasive TPEF index based on spectra and lifetime could potentially be used for rapid melanin ratio characterization both in vitro and in vivo. PMID:23235925

  7. Fluorescence polarization of helium negative-ion resonances excited by polarized electron impact

    NASA Astrophysics Data System (ADS)

    Maseberg, J. W.; Gay, T. J.

    2006-12-01

    We have investigated helium (1s3d) 3D → (1s2p) 3P (588 nm) fluorescence produced by electron impact excitation in the vicinity of the (2s22p) 2P and (2s2p2) 2D negative-ion resonances at 57.2 and 58.3 eV, respectively. In contrast to previous work, we use spin-polarized incident electrons and report the relative Stokes parameters P1, P2 and P3 in the 55-60 eV region. Our failure to see discernable resonance effects in P2 indicates that even though the lifetime of these resonances is significant (~10 fs), magnetic forces acting on the temporarily captured electron are small. Resonant structures in the values of P1 and P3 are observed because the polarization contributions of resonant states are generally different than those from direct excitation of the 3 3D state.

  8. Signal reduction in fluorescence imaging using radio frequency-multiplexed excitation by compressed sensing

    NASA Astrophysics Data System (ADS)

    Chan, Antony C. S.; Lam, Edmund Y.; Tsia, Kevin K.

    2014-11-01

    Fluorescence imaging using radio frequency-multiplexed excitation (FIRE) has emerged to enable an order-of-magnitude higher frame rate than the current technologies. Similar to all high-speed realtime imaging modalities, FIRE inherently generates massive image data continuously. While this technology entails high-throughput data sampling, processing, and storage in real-time, strategies in data compression on the fly is also beneficial. We here report that it is feasible to exploit the radio frequency-multiplexed excitation scheme in FIRE for implementing compressed sensing (CS) without any modification of the FIRE system. We numerically demonstrate that CS-FIRE can reduce the effective data rate by 95% without severe degradation of image quality.

  9. Upper atmospheric probing by resonance fluorescence excited by tunable laser radiation.

    NASA Technical Reports Server (NTRS)

    Saunders, A. R.; Mumola, P. B.

    1972-01-01

    Consideration of the application of the measurement of resonance fluorescence radiation excited by tunable laser radiation to the detection of atomic, molecular, and ionic species in the upper atmosphere. The species considered are N2, N2(+), NO, NO(+), O2(+), CO, CO(+), CH, Na, K, and Ca. Calculations of the resonance scattering cross sections, photon returns, and signal-to-noise ratios are given for these species for a range of conditions. Based on a probing altitude of 100 km, the detections of N2, NO, CO, CH, O2, and the trace metals appear feasible with state-of-the-art systems and within the concentration range present in the atmosphere.

  10. Comments on laser-excited fluorescence of the hydroxyl radical: Relaxation coefficients at atmospheric pressure, appendix 5

    NASA Technical Reports Server (NTRS)

    Wang, C. C.

    1983-01-01

    The lifetime of the excited state of a atom or molecule is often determined from the rate of fluorescence decay originating as a function of buffer gas pressure, an accurate determination is made of the rates of collision induced transitions away from the excited state. Deconvolution can in principle be employed to resolve fluorescence times shorter than the response times of the system. However, attainable reproducibility and accuracy in actual experiments usually set a limit beyond which no meaningful results are expected. Prudence thus dictates that the results of deconvolution be viewed with extreme caution whenever fluorescence time much shorter than the response of times of the system are indicated.

  11. Fluorescence detection of single molecules using pulsed near-field optical excitation and time correlated photon counting

    SciTech Connect

    Ambrose, W.P.; Goodwin, P.M.; Martin, J.C.; Keller, R.A.

    1994-03-01

    Pulsed excitation, time correlated single photon counting and time gated detection are used in near-field optical microscopy to enhance fluorescence images and measure the fluorescence lifetimes of single molecules of Rhodamine 6G on silica surfaces. Time gated detection is used to reject prompt scattered background and to improve the image signal to noise ratio. The excited state lifetime of a single Rhodamine 6G molecule is found to depend on the position of the near-field probe. We attribute the lifetime variations to spontaneous emission rate alterations by the fluorescence reflected from and quenching by the aluminum coated probe.

  12. Excited state dipole moments of chloroanilines and chlorophenols from solvatochromic shifts in electronic absorption spectra: Support for the concept of excited state group moments

    NASA Astrophysics Data System (ADS)

    Prabhumirashi, L. S.; Satpute, R. S.

    The dipole moments of isomeric o-, m- and p-chloroanilines and chlorophenols in electronically excited L a and L b states are estimated from solvent induced polarization shifts in electronic absorption spectra. It is observed that μ e( L a) > μ e( L b) > μ g, which is consistent with the general theory of polarization red shift. The μ es are found to be approximately co-linear with the corresponding μ gs. The concept of group moments is extended to aromatic molecules in excited states. This approach is found to be useful in understanding correlations among the excited states of mono- and disubstituted benzenes.

  13. Highly-sensitive Eu(3+) ratiometric thermometers based on excited state absorption with predictable calibration.

    PubMed

    Souza, Adelmo S; Nunes, Luiz A O; Silva, Ivan G N; Oliveira, Fernando A M; da Luz, Leonis L; Brito, Hermi F; Felinto, Maria C F C; Ferreira, Rute A S; Júnior, Severino A; Carlos, Luís D; Malta, Oscar L

    2016-03-01

    Temperature measurements ranging from a few degrees to a few hundreds of Kelvin are of great interest in the fields of nanomedicine and nanotechnology. Here, we report a new ratiometric luminescent thermometer using thermally excited state absorption of the Eu(3+) ion. The thermometer is based on the simple Eu(3+) energy level structure and can operate between 180 and 323 K with a relative sensitivity ranging from 0.7 to 1.7% K(-1). The thermometric parameter is defined as the ratio between the emission intensities of the (5)D0 → (7)F4 transition when the (5)D0 emitting level is excited through the (7)F2 (physiological range) or (7)F1 (down to 180 K) level. Nano and microcrystals of Y2O3:Eu(3+) were chosen as a proof of concept of the operational principles in which both excitation and detection are within the first biological transparent window. A novel and of paramount importance aspect is that the calibration factor can be calculated from the Eu(3+) emission spectrum avoiding the need for new calibration procedures whenever the thermometer operates in different media. PMID:26883124

  14. Electronically excited states of DNA oligonucleotides with disordered base sequences studied by fluorescence spectroscopy.

    PubMed

    Vayá, Ignacio; Brazard, Johanna; Gustavsson, Thomas; Markovitsi, Dimitra

    2012-11-01

    DNA double-stranded oligomers are studied by steady-state and time-resolved fluorescence spectroscopy from the femtosecond to the nanosecond time-scale, following excitation at 267 nm. It is shown that emission arises from three types of excited states. (i) Bright ππ* states emitting around 330 nm and decaying on the sub-picosecond time-scale with an average lifetime of ca. 0.4 ps and a quantum yield lower than 4 × 10(-6). (ii) Excimers/exciplexes emitting around 430 nm and decaying on the sub-nanosecond time-scale. (iii) Excited states emitting mainly at short wavelengths (λ < 330 nm) and decaying on the nanosecond time-scale, possibly correlated to GC pairs. The properties of the examined duplexes, exhibiting significant disorder with respect to the nearest neighbour base sequence, are radically different than those of the much longer and disordered calf thymus DNA. Such behaviour suggests that long range and/or sequence effects play a key role in the fate of excitation energy. PMID:23034563

  15. Ultraviolet emission and excitation fluorescence spectroscopic characterization of DMBA-treated Swiss Albino mice skin carcinogenesis for measuring tissue transformation

    NASA Astrophysics Data System (ADS)

    Aruna, Prakasa R.; Hemamalini, Srinivasan; Ebenezar, Jeyasingh; Ganesan, Singaravelu

    2002-05-01

    The ultraviolet fluorescence emission spectra of skin tissues under different pathological conditions were measured at 280nm excitation. At this excitation wavelength, the normal skin showed a primary peak emission at 352nm and this primary peak emission from neoplastic skin shows a blue shift with respect to normal tissue. This blue shift increases as the stage of abnormality increases and it is maximum (19nm) for well-differentiated squamous cell carcinoma. This alteration is further confirmed from fluorescence excitation spectra of the tissues for 340nm emission. The study concludes that the change in the emission of tryptophan around 340nm may be due to partial unfolding of protein.

  16. Time-Dependent Density Functional Theory Study of Low-Lying Absorption and Fluorescence Band Shapes for Phenylene-Containing Oligoacenes.

    PubMed

    Jun, Ye

    2015-12-24

    Low-lying band shapes of absorption and fluorescence spectra for a member of a newly synthesized family of phenylene-containing oligoacenes (POA 6) reported in J. Am. Chem. Soc. 2012 , 134 , 15351 are studied theoretically with two different approaches with TIPS-anthracene as a comparison. Underlying photophysics and exciton-phonon interactions in both molecules are investigated in details with the aid of the time-dependent density functional theory and multimode Brownian oscillator model. The first two low-lying excited-states of POA 6 were found to exhibit excitation characteristics spanning entire conjugated backbone despite the presence of antiaromatic phenylene section. Absorption and fluorescence spectra calculated from both time-dependent density functional theory and multimode Brownian oscillator model are shown to reach good agreement with experimental ones. The coupling between phonon modes and optical transitions is generally weak as suggested by the multimode Brownian oscillator model. Broader peaks of POA 6 spectra are found to relate to stronger coupling between low frequency phonon modes such as backbone twisting (with frequency <300 cm(-1)) and optical transitions. Furthermore, POA 6 exhibits weaker exciton-phonon coupling for the phonon modes above 1000 cm(-1) compared to TIPS-anthracene owing to extended conjugated backbone. A significant coupling between an in-plane breathing mode localized around the antiaromatic phenylene segment with frequency at 1687 cm(-1) and optical transitions for the first two excited-states of POA 6 is also observed. PMID:26611665

  17. Fluorenyl porphyrins for combined two-photon excited fluorescence and photosensitization

    NASA Astrophysics Data System (ADS)

    Mongin, Olivier; Hugues, Vincent; Blanchard-Desce, Mireille; Merhi, Areej; Drouet, Samuel; Yao, Dandan; Paul-Roth, Christine

    2015-04-01

    The two-photon absorption (2PA), the luminescence and the photosensitization properties of porphyrin-cored fluorenyl dendrimers and meso-substituted fluorenylporphyrin monomer, dimer and trimer are described. In comparison with model tetraphenylporphyrin, these compounds combine enhanced (non-resonant) 2PA cross-sections in the near infrared and enhanced fluorescence quantum yields, together with maintained singlet oxygen generation quantum yields. 'Semi-disconnection' between fluorenyl groups and porphyrins (i.e. direct meso substitution) proved to be more efficient than non-conjugated systems (based on efficient FRET between fluorenyl antennae and porphyrins). These results are of interest for combined two-photon imaging and photodynamic therapy.

  18. Ratiometric fluorescent chemosensor for fluoride ion based on inhibition of excited state intramolecular proton transfer

    NASA Astrophysics Data System (ADS)

    Gupta, Akul Sen; Paul, Kamaldeep; Luxami, Vijay

    2015-03-01

    ESIPT based benzimidazole derivative has been synthesized and investigated their photophysical behavior towards various anions. The probe 2 has been used for selective estimation of F- ions as compared to other anions and signaled the binding event through formation of new absorption band at 360 nm and emission band at 420 nm. The probe 2 showed fluorescence behavior towards fluoride ions through hydrogen bonding interactions and restricted the ESIPT emission at 540 nm from OH to nitrogen of benzimidazole moiety to release its enol emission at 420 nm.

  19. Determination of K shell absorption jump factors and jump ratios in the elements between Tm( Z = 69) and Os( Z = 76) by measuring K shell fluorescence parameters

    NASA Astrophysics Data System (ADS)

    Kaya, N.; Tıraşoğlu, E.; Apaydın, G.

    2008-04-01

    The K shell absorption jump factors and jump ratios have been measured in the elements between Tm ( Z = 69) and Os( Z = 76) without having any mass attenuation coefficient at the upper and lower energy branch of the K absorption edge. The jump factors and jump ratios for these elements have been determined by measuring K shell fluorescence parameters such as the total atomic absorption cross-sections, the K α X-ray production cross-sections, the intensity ratio of the K β and K α X-rays and the K shell fluorescence yields. We have performed the measurements for the calculations of these values in attenuation and direct excitation experimental geometry. The K X-ray photons are excited in the target using 123.6 keV gamma-rays from a strong 57Co source, and detected with an Ultra-LEGe solid state detector with a resolution 0.15 keV at 5.9 keV. The measured values have been compared with theoretical and others' experimental values. The results have been plotted versus atomic number.

  20. Towards the understanding at the molecular level of the structured-water absorption and fluorescence spectra: a fingerprint of π-stacked water

    NASA Astrophysics Data System (ADS)

    Segarra-Martí, Javier; Coto, Pedro B.; Rubio, Mercedes; Roca-Sanjuán, Daniel; Merchán, Manuela

    2013-07-01

    An intriguing absorption peak around ∼270 nm (4.59 eV) has been recurrently recorded in aqueous solutions of salts, sugars, amino acids, in the free-solute zone (exclusion zone) adjacent to various hydrophilic surfaces, as well as a transient in the conversion process of ice to water. The corresponding associated fluorescence has been observed in the interval 480-490 nm (2.58-2.53 eV). The spectroscopic features have been related to the presence of structured water but its nature remains incompletely understood. On the basis of high-level ab initio computations, the main absorption feature of structured water is assigned to the presence of two π-stacked ground-state water molecules, preferably non-hydrogen bonded, at relatively short intermolecular distances (around 2 Å). The lowest singlet excited state is characterised by an equilibrium distance of around 2 Å with a vertical absorption transition predicted at 4.5 eV. The excited π-stacked dimer has a large binding energy (∼1 eV). Therefore, near-ultraviolet light may favour the formation of structured water. Two relaxed side-hydrated π-stacked water molecules (a relaxed tetramer) constitute the smallest unique excimer-type fluorescent moiety consistent with the available experimental data.

  1. Excitation laser energy dependence of surface-enhanced fluorescence showing plasmon-induced ultrafast electronic dynamics in dye molecules

    NASA Astrophysics Data System (ADS)

    Itoh, Tamitake; Yamamoto, Yuko S.; Tamaru, Hiroharu; Biju, Vasudevanpillai; Murase, Norio; Ozaki, Yukihiro

    2013-06-01

    We find unique properties accompanying surface-enhanced fluorescence (SEF) from dye molecules adsorbed on Ag nanoparticle aggregates, which generate surface-enhanced Raman scattering. The properties are observed in excitation laser energy dependence of SEF after excluding plasmonic spectral modulation in SEF. The unique properties are large blue shifts of fluorescence spectra, deviation of ratios between anti-Stokes SEF intensity and Stokes from those of normal fluorescence, super-broadening of Stokes spectra, and returning to original fluorescence by lower energy excitation. We elucidate that these properties are induced by electromagnetic enhancement of radiative decay rates exceeding the vibrational relaxation rates within an electronic excited state, which suggests that molecular electronic dynamics in strong plasmonic fields can be largely deviated from that in free space.

  2. Substituent and Solvent Effects on Excited State Charge Transfer Behavior of Highly Fluorescent Dyes Containing Thiophenylimidazole-Based Aldehydes

    NASA Technical Reports Server (NTRS)

    Santos, Javier; Bu, Xiu R.; Mintz, Eric A.

    2001-01-01

    The excited state charge transfer for a series of highly fluorescent dyes containing thiophenylimidazole moiety was investigated. These systems follow the Twisted Intramolecular Charge Transfer (TICT) model. Dual fluorescence was observed for each substituted dye. X-ray structures analysis reveals a twisted ground state geometry for the donor substituted aryl on the 4 and 5 position at the imidazole ring. The excited state charge transfer was modeled by a linear solvation energy relationship using Taft's pi and Dimroth's E(sub T)(30) as solvent parameters. There is linear relation between the energy of the fluorescence transition and solvent polarity. The degree of stabilization of the excited state charge transfer was found to be consistent with the intramolecular molecular charge transfer. Excited dipole moment was studied by utilizing the solvatochromic shift method.

  3. Fluorescence and UV/VIS absorption spectroscopy studies on polymer blend films for photovoltaics

    NASA Astrophysics Data System (ADS)

    van Stam, Jan; Lindqvist, Camilla; Hansson, Rickard; Ericsson, Leif; Moons, Ellen

    2015-08-01

    The quinoxaline-based polymer TQ1 (poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5- diyl]) is a promising candidate as electron donor in organic solar cells. In combination with the electron acceptor [6,6]- phenyl-C71- butyric acid methyl ester (PC70BM), TQ1 has resulted in solar cells with power conversion efficiencies of 7 %. We have studied TQ1 films, with and without PC70BM, spin-casted from different solvents, by fluorescence spectroscopy and UV/VIS absorption spectroscopy. We used chloroform (CF), chlorobenzene (CB), and odichlorobenzene (o-DCB) as solvents for the coating solutions and 1-chloronaphthalene (CN) as solvent additive. CN addition has been shown to enhance photo-conversion efficiency of these solar cells. Phase-separation causes lateral domain formation in the films and the domain size depends on the solvent . These morphological differences coincide with changes in the spectroscopic patterns of the films. From a spectroscopic point of view, TQ1 acts as fluorescent probe and PC70BM as quencher. The degree of fluorescence quenching is coupled to the morphology through the distance between TQ1 and PC70BM. Furthermore, if using a bad solvent for PC70BM, morphological regions rich in the fullerene yield emission characteristic for aggregated PC70BM. Clear differences were found, comparing the TQ1:PC70BM blend films casted from different solvents and at different ratios between the donor and acceptor. The morphology also influences the UV/VIS absorption spectra, yielding further information on the composition. The results show that fluorescence and UV/VIS absorption spectroscopy can be used to detect aggregation in blended films and that these methods extend the morphological information beyond the scale accessible with microscopy.

  4. Absorption spectra and spectral-kinetic characteristics of the fluorescence of Sanguinarine in complexes with polyelectrolytes and DNA

    NASA Astrophysics Data System (ADS)

    Motevich, I. G.; Strekal, N. D.; Nowicky, J. W.; Maskevich, S. A.

    2010-07-01

    The absorption spectra and stationary and time resolved fluorescence spectra of the isoquinoline alkaloid sanguinarine are studied in aqueous media and during interactions with synthetic polyelectrolytes (polystyrene sulfonate and polyallylamine) and a natural polyelectrolyte (DNA).

  5. Ultrafast Excited-State Dynamics of 6-Azauracil Studied by Femtosecond Transient Absorption Spectroscopy.

    PubMed

    Hua, XinZhong; Hua, LinQiang; Liu, XiaoJun

    2015-12-31

    The excited-state dynamics of 6-azauracil in different solvents have been studied using femtosecond transient absorption spectroscopy. The molecule is populated to the S2 state with a pump pulse at 264 nm. Broad-band white light continuum which covers from 320 to 600 nm is used as the probe. With a global fitting analysis of the measured transient spectra, three decay time constants, i.e., <0.3, 5.2 ± 0.1, and >1000 ps, are directly obtained in the solvent of acetonitrile. These newly observed lifetime constants are important in clarifying its decay dynamics as well as in providing a criterion for the ultrafast dynamics simulations in 6-azauracil using quantum chemical theories. In combination with previous theoretical works, the main decay channel is proposed: the initially populated S2 decays to S1 through internal conversion in <0.3 ps, followed by an intersystem crossing from S1 to T1 in 5.2 ± 0.1 ps. The >1000 ps component is due to the decay of the T1 state. A comparison of the excited-state dynamics in different solvents reveals that the decay from S1 to T1 shows a clear dependence on the polarity of the solvents. With higher polarity, the S1 excited state decays faster. This observation is in line with the prediction by Etinski et al. [ Phys. Chem. Chem. Phys. 2010 , 12 , 15665 - 15671 ], where a blue-shift of the T1 state potential energy surface leading to an increase of the intersystem crossing rate was proposed. With the new information obtained in the present measurement, a clearer picture of the decay dynamics of 6-azauracil on the S2 excited state is provided. PMID:26689220

  6. Video-rate scanning two-photon excitation fluorescence microscopy and ratio imaging with cameleons.

    PubMed

    Fan, G Y; Fujisaki, H; Miyawaki, A; Tsay, R K; Tsien, R Y; Ellisman, M H

    1999-05-01

    A video-rate (30 frames/s) scanning two-photon excitation microscope has been successfully tested. The microscope, based on a Nikon RCM 8000, incorporates a femtosecond pulsed laser with wavelength tunable from 690 to 1050 nm, prechirper optics for laser pulse-width compression, resonant galvanometer for video-rate point scanning, and a pair of nonconfocal detectors for fast emission ratioing. An increase in fluorescent emission of 1.75-fold is consistently obtained with the use of the prechirper optics. The nonconfocal detectors provide another 2.25-fold increase in detection efficiency. Ratio imaging and optical sectioning can therefore be performed more efficiently without confocal optics. Faster frame rates, at 60, 120, and 240 frames/s, can be achieved with proportionally reduced scan lines per frame. Useful two-photon images can be acquired at video rate with a laser power as low as 2.7 mW at specimen with the genetically modified green fluorescent proteins. Preliminary results obtained using this system confirm that the yellow "cameleons" exhibit similar optical properties as under one-photon excitation conditions. Dynamic two-photon images of cardiac myocytes and ratio images of yellow cameleon-2.1, -3.1, and -3.1nu are also presented. PMID:10233058

  7. Excited State Proton Transfer in the Red Fluorescent Protein mKeima

    PubMed Central

    Henderson, J. Nathan; Osborn, Maire F.; Koon, Nayden; Gepshtein, Rinat; Huppert, Dan; Remington, S. James

    2009-01-01

    mKeima is an unusual monomeric red fluorescent protein (λemmax ~620 nm) that is maximally excited in the blue (λexmax ~440 nm). The large Stokes shift suggests that the chromophore is normally protonated. A 1.63 Å resolution structure of mKeima reveals the chromophore to be imbedded in a novel hydrogen bond network, different than in GFP, which could support proton transfer from the chromophore hydroxyl, via Ser142, to Asp157. At low temperatures the emission contains a green component (λemmax ~535 nm), enhanced by deuterium substitution, presumably resulting from reduced proton transfer efficiency. Ultrafast pump/probe studies reveal a rising component in the 610 nm emission with lifetime ~4 ps, characterizing the rate of proton transfer. Mutation of Asp157 to neutral Asn changes the chromophore resting charge state to anionic (λexmax ~565 nm, λemmax ~620 nm). Thus, excited state proton transfer (ESPT) explains the large Stokes shift. This work unambiguously characterizes green emission from the protonated acylimine chromophore of red fluorescent proteins. PMID:19708654

  8. Increased signals from short-wavelength-excited fluorescent molecules using sub-Ti:Sapphire wavelengths

    PubMed Central

    NORRIS, G; AMOR, R; DEMPSTER, J; AMOS, W B; MCCONNELL, G

    2012-01-01

    We report the use of an all-solid-state ultrashort pulsed source specifically for two-photon microscopy at wavelengths shorter than those of the conventional Ti:Sapphire laser. Our approach involves sum–frequency mixing of the output from an optical parametric oscillator (λ= 1400–1640 nm) synchronously pumped by a Yb-doped fibre laser (λ= 1064 nm), with the residual pump radiation. This generated an fs-pulsed output tunable in the red spectral region (λ= 620–636 nm, ∼150 mW, 405 fs, 80 MHz, M2∼ 1.3). We demonstrate the performance of our ultrashort pulsed system using fluorescently labelled and autofluorescent tissue, and compare with conventional Ti:Sapphire excitation. We observe a more than 3-fold increase in fluorescence signal intensity using our visible laser source in comparison with the Ti:Sapphire laser for two-photon excitation at equal illumination peak powers of 1.16 kW or less. PMID:23078118

  9. Combined analysis of intracellular calcium with dual excitation fluorescence photometry and imaging

    NASA Astrophysics Data System (ADS)

    Uttenweiler, Dietmar; Wojciechowski, Reinhold; Makabe, Makoto; Veigel, Claudia; Fink, Rainer H.

    1995-10-01

    We have developed an integrated microscopy system combining fast dual-excitation fluorescence photometry and digital image analysis with high spatial resolution, based mainly on standard components. With the combination of these well-established techniques in one setup it is possible to monitor intracellular calcium with both sufficiently high temporal and high spatial resolution on the same preparation for many biological applications. Our system consists of a commercially available dual-excitation photometric system, an attached ICCD camera, and a frame grabber board. With this integrated setup one can easily switch between the fast photometric mode and the imaging mode. We used the system to record Fura-2 calcium images (340/380 nm ratios), which were correlated with the faster spot measurements and were analyzed by means of image processing. As an example for its application we reconstructed caffeine-induced calcium transient released from the sarcoplasmic reticulum of isolated and permeabilized skeletal muscle fiber preparations. Such a combined technique will also be important for cellular studies using other fluorescence indicators. Additionally, the described system has an external trigger facility that enables combination with other cell physiological methods, e.g., electrophysiological techniques.

  10. Absorption and fluorescence of alexandrite and of titanium in sapphire and glass

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.; Hess, R. V.; Buoncristiani, A. M.

    1985-01-01

    The fluorescence and absorption data for titanium in crystalline sapphire and titanium doped into two silicate and one phosphate glass structures are analyzed. It is observed that the Ti-doped silicate glass sample exhibits no absorption related to the Ti(III) ion, the Ti-doped phosphate glass is deep blue, the absorption line width of the glass samples are a factor of two larger than that of sapphire, and the absorption peak for the Ti in the glass shifted about 100 nm to the red from the Ti:sapphire absorption peak. This shift reveals that the Ti(III) ion is sensitive to the crystalline environment and not to the glass environment. The photoluminescence spectra for Ti-doped sapphire and alexandrite are compared. It is detected that the Ti:sapphire exhibits a broader spectrum than that for alexandrite with a peak at 750 nm. The three zero phonon transitions of Ti:Al2O3 at liquid nitrogen temperatures are studied.

  11. Optimization of optical limiting devices based on excited-state absorption.

    PubMed

    Xia, T; Hagan, D J; Dogariu, A; Said, A A; Van Stryland, E W

    1997-06-20

    Limiting devices protect sensitive optical elements from laser-induced damage (LID). Passive devices use focusing optics to concentrate the light through a nonlinear optical (NLO) element (or elements) to reduce the limiting threshold. Unfortunately, these NLO elements may themselves undergo LID for high inputs, restricting the useful dynamic range (DR). Recently, efforts at optimizing this DR have focused on distributing the NLO material along the propagation path z of a focused beam, resulting in different portions of the device (in z) exhibiting NLO response at different inputs. For example, nonlinear absorbers closer to the lens, i.e., upstream, protect device elements downstream near the focal plane. This results in an undesirable increase in the threshold, although the lowest threshold is always obtained with the final element at focus. Thus there is a compromise between DR and threshold. This compromise is determined by the material. We concentrate on reverse saturable absorber (RSA) materials (molecules exhibiting larger excited-state than ground-state absorption). We look at both tandem devices and devices in which the concentration of the NLO material is allowed to spatially vary in z. These latter devices require solid-state hosts. The damage threshold of currently available solid-state hosts is too low to allow known RSA materials to reach their maximum absorption, which occurs when all molecules are in their excited state. This is demonstrated by approximate analytical methods as well as by a full numerical solution of the nonlinear wave propagation equation over extremely large distances in z (up to 10(3)Z(0), where Z(0) is the Rayleigh range of the focused beam). The numerical calculations, based on a one-dimensional fast Fourier transform, indicate that proper inclusion of diffraction reduces the effectiveness of reverse saturable absorption for limiting, sometimes by more than a factor of 10. Liquid-based devices have higher damage thresholds

  12. Problems affecting performance of the fluorescent treponemal antibody-absorption test for syphilis.

    PubMed Central

    Hunter, E F; Adams, M R; Orrison, L H; Pender, B J; Larsen, S A

    1979-01-01

    Immunofluorescent staining of Treponema pallidum was studied to clarify the effect of three factors on the results of the fluorescent treponemal antibody-absorption test: (i) heat inactivation of sera at 56 degrees C for 30 min before testing, (ii) use of multicircle slides, and (iii) tungsten illumination to visualize and assess unstained treponemes on reactive as well as nonreactive smears. It was found that serum inactivation before testing was not necessary for detection of immunoglobin G antibody, but an immunoglobulin M prozone was detected in unheated serum. On multicircle slides, it was demonstrated that a false-positive reaction could be obtained in 30 s at 37 and 25 degrees C if a smear where a nonreactive serum had been placed was crossed by a strongly reactive serum from another circle. Tungsten illumination proved necessary for correct assessment of unstained treponemes on all fluorescent treponemal antibody-aborption test smears, reactive or nonreactive. The possible role of these factors in incorrect fluorescent treponemal antibody-absorption test results is discussed. PMID:372219

  13. Picosecond time-resolved fluorescence studies on excitation energy transfer in a histidine 117 mutant of the D2 protein of photosystem II in Synechocystis 6803.

    PubMed

    Vasil'ev, S; Bruce, D

    2000-11-21

    The role of the peripheral reaction center chlorophyll a molecule associated with His117 of the D2 polypeptide in photosystem II was investigated in Synechocystis sp. PCC 6803 using a combination of steady state, pump-probe, and picosecond time-resolved fluorescence spectroscopy. Data were obtained from intact cells and isolated thylakoid membranes of a control mutant and a D2-H117T mutant, both of which lacked photosystem I. Excitation energy transfer and trapping were investigated by analyzing the data with a kinetic model that used an exact numerical solution of the Pauli master equation, taking into account available photosystem II spectral and structural information. The results of our kinetic analysis revealed the observed difference in excited-state dynamics between the H117T mutant and the control to be consistent with a retardation of the rate of excitation energy transfer from the peripheral chlorophyll of D2 (Chl at His117) to the electron-transfer pigments and an increase of the rate constant for charge recombination in the H117T mutant. The kinetic model was able to account for the experimentally observed changes in absorption cross section and fluorescence decay kinetics between the control and mutant by invoking changes in only these two rate constants. The results rule out quenching of excitation by a chlorophyll cation radical as a mechanism responsible for the lower efficiency of excitation energy utilization in the H117T mutant. Our work also demonstrates the importance of the chlorophyll associated with His117 of the D2 protein for excitation energy transfer to the PSII electron-transfer pigments and for the effective stabilization of the primary radical pair. PMID:11087370

  14. Differences in excitation energy transfer of Arthrospira platensis cells grown in seawater medium and freshwater medium, probed by time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Arba, Muhammad; Aikawa, Shimpei; Niki, Kenta; Yokono, Makio; Kondo, Akihiko; Akimoto, Seiji

    2013-11-01

    Excitation energy transfer of Arthrospira platensis cells grown in f/2 medium (a high salinity medium) and SOT medium (a control) was investigated by steady-state and time-resolved spectroscopies. Growth in f/2 medium induced changes in absorption and fluorescence spectra as well as in the energy transfer pathways. Excitation energy captured by phycobilisome (PBS) was transferred directly to photosystem (PS) I, instead of being first transferred to an intermediate (PBS → PSII → PSI), as observed in SOT medium. The respiration rate increased while photosynthetic rate reduced in f/2 medium. Possible causes of the differences in light-harvesting and energy-transfer processes between the two media are discussed.

  15. Fluorescence in air excited by electrons from a 90Sr source

    NASA Astrophysics Data System (ADS)

    Sakaki, N.; Watanabe, Y.; Nagano, M.; Kobayakawa, K.

    2008-11-01

    The air fluorescence technique is used to observe ultra-high energy cosmic rays (UHECRs). In this technique, fluorescence from air excited by electrons within an extensive air shower (EAS) under various pressure and temperature conditions is detected by a telescope. The primary energy of the UHECR is estimated from the amount of fluorescence. Since ground-based experiments, such as Fly's Eye, HiRes, Auger, Telescope Array, are carried out at high altitudes, the effects of water vapor may be negligible and the photon yields in dry air, which we have measured and reported so far, will be applicable. However, in case of space-based experiments such as JEM-EUSO, most events will be observed above the sea. Photon yields in moist air are measured with a 90Sr β source and compared to those in dry air at wavelengths of 337, 358 and 391 nm. The presence of water vapor considerably reduces the photon yield. The decrease in the photon yield in moist air should be taken into account to interpret the longitudinal development of EASs near the sea surface, although the effects around the shower maximum for most showers might be small.

  16. Temperature and bath gas composition dependence of effective fluorescence lifetimes of toluene excited at 266 nm

    NASA Astrophysics Data System (ADS)

    Faust, S.; Dreier, T.; Schulz, C.

    2011-05-01

    Time-resolved fluorescence spectra of gas-phase toluene upon picosecond excitation at 266 nm were investigated as a function of temperature (296-1074 K) and bath gas composition (varying amounts of N 2, O 2, and CO 2) at 1 bar total pressure with a temporal resolution of 50 ps. In the investigated temperature range the effective fluorescence lifetime drops with increasing temperature from 46 ± 3 ns to 0.05 ± 0.01 ns in N 2 and CO 2. In the presence of O 2 at constant temperature the lifetimes also decrease significantly (e.g., from 46 ± 3 ns without O 2 to 0.63 ± 0.05 ns in air at room temperature), whereas lifetimes are independent on the CO 2 concentration. The implications of the results for the existing phenomenological model of predicting temporally integrated fluorescence intensities in toluene [W. Koban, J.D. Koch, R.K. Hanson, C. Schulz, Appl. Phys. B 80 (2005) 777] are discussed.

  17. Diagnosis of basal cell carcinoma by two photon excited fluorescence combined with lifetime imaging

    NASA Astrophysics Data System (ADS)

    Fan, Shunping; Peng, Xiao; Liu, Lixin; Liu, Shaoxiong; Lu, Yuan; Qu, Junle

    2014-02-01

    Basal cell carcinoma (BCC) is the most common type of human skin cancer. The traditional diagnostic procedure of BCC is histological examination with haematoxylin and eosin staining of the tissue biopsy. In order to reduce complexity of the diagnosis procedure, a number of noninvasive optical methods have been applied in skin examination, for example, multiphoton tomography (MPT) and fluorescence lifetime imaging microscopy (FLIM). In this study, we explored two-photon optical tomography of human skin specimens using two-photon excited autofluorescence imaging and FLIM. There are a number of naturally endogenous fluorophores in skin sample, such as keratin, melanin, collagen, elastin, flavin and porphyrin. Confocal microscopy was used to obtain structures of the sample. Properties of epidermic and cancer cells were characterized by fluorescence emission spectra, as well as fluorescence lifetime imaging. Our results show that two-photon autofluorescence lifetime imaging can provide accurate optical biopsies with subcellular resolution and is potentially a quantitative optical diagnostic method in skin cancer diagnosis.

  18. Production and excitation-emission fluorescence properties of colored dissolved organic matter from marine tropical species

    NASA Astrophysics Data System (ADS)

    Mendoza, W. G.; Zika, R. G.

    2009-12-01

    Colored dissolved organic matter (CDOM) plays an important key role in the photochemistry and biogeochemical cycling of carbon in the coastal region. Their distribution can vary in space and time due to supply of CDOM from different sources. To determine properties of fluorescence-CDOM produced by various marine tropical species, two species from each of the different marine communities were examined after incubation in the dark for forty-nine (49) days: seagrasses-Enhalus acoroides (EA), Thalassia testudinium (TT); corals-Pocillopora cylindrical (PC), Seriatopora hystrix (SH) ; mangroves- Avicennia marina (AM), Sonneratia alba (SA); brown algae-Hormophysa cuneiformis (HC), Sargassum sp.(SS). Average CDOM production is highest from mangrove species (218 QSU/g-sample/day), followed by seagrass (42 QSU/g-sample/day), brown alga (26 QSU/g-sample/day) then corals (19 QSU/g-sample/day).The fluorescence maximum at 312; 380-420 nm emission-excitation pair appears to be present in all species that is an identified humic-like signature. These results suggest that the production of the fluorescent CDOM fraction is a common phenomenon of tropical marine species and as such constitutes a major part of the marine CDOM pool in coastal regions.

  19. Source-corrected two-photon excited fluorescence measurements between 700 and 880 nm

    SciTech Connect

    Fisher, W.G.; Wachter, E.A.; Lytle, F.E.; Armas, M.; Seaton, C.

    1998-04-01

    Passively mode-locked titanium:sapphire (Ti:S) lasers are capable of generating a high-frequency train of transform-limited subpico-second pulses, producing peak powers near 10{sup 5}thinspW at moderate average powers. The low energy per pulse ({lt}20 nJ) permits low fluence levels to be maintained in tightly focused beams, reducing the possibility of saturating fluorescence transitions. These properties, combined with a wavelength tunability from approximately 700 nm to 1 {mu}m, provide excellent opportunities for studying simultaneous two-photon excitation (TPE). However, pulse formation is very sensitive to a variety of intracavity parameters, including group velocity dispersion compensation, which leads to wavelength-dependent pulse profiles as the wavelength is scanned. This wavelength dependence can seriously distort band shapes and apparent peak heights during collection of two-photon spectral data. Since two-photon excited fluorescence is proportional to the product of the peak and average powers, it is not possible to obtain source-independent spectra by using average power correction schemes alone. Continuous-wave, single-mode lasers can be used to generate source-independent two-photon data, but these sources are four to five orders of magnitude less efficient than the mode-locked Ti:S laser and are not practical for general two-photon measurements. Hence, a continuous-wave, single-mode Ti:S laser has been used to collect a source-independent excitation spectrum for the laser dye Coumarin 480. This spectrum may be used to correct data collected with multimode sources; this possibility is demonstrated by using a simple ratiometric method to collect accurate TPE spectra with the mode-locked Ti:S laser. An approximate value of the two-photon cross section for Coumarin 480 is also given. {copyright} {ital 1998} {ital Society for Applied Spectroscopy}

  20. Integrated OLED as excitation light source in fluorescent lateral flow immunoassays.

    PubMed

    Venkatraman, Vishak; Steckl, Andrew J

    2015-12-15

    The integration of organic light emitting diodes (OLEDs) as excitation light sources for quantum dot-based fluorescent lateral flow immunoassay systems (LFIA) was investigated. This approach has the potential to deliver a sensitive visible detection scheme for low-cost, disposable lab-on-chip point-of-care (POC) diagnosis system. Thin film phosphorescent green OLEDs fabricated on plastic substrates were integrated on-chip to excite the test line of a quantum dot-based LFIA (QD-LFIA). OLEDs were fabricated by sequential deposition of organic thin films (total of ~100 nm) onto ITO-coated PET substrates. CdSe/ZnS QDs emitting at 655 nm and Au nanoparticles (NP - 10 nm size) conjugated antibodies were used for the fluorescence QD-LFIA and conventional reflection-mode Au NP-LFIA, respectively. Thin plastic color light filters were integrated for filtering the excitation light source and, thereby, increasing the contrast of the emitted light for optimized visual detection. Integration of the OLED and color filters with the analytical membrane was achieved using adhesive techniques facilitated by the planar nature of the layers, which suggests possible large scale manufacturing using roll-to-roll processing. Gray scale analysis from digital images captured with a digital camera was used to quantify the visual sensitivity. The signal intensity, signal-to-noise ratio (SNR) and the limit of detection (LOD) of OLED integrated QD-LFIAs were compared to Au NP LFIAs. OLED QD-LFIA exhibited superior performance in all signal aspects: 7-8× higher signal intensity and SNR, and a 7× lower LOD of 3 nM (measured at S/N=3). These results demonstrate the potential of OLED-integrated in LFIA devices for obtaining sensitive, fast and low-cost POC diagnostics. PMID:26134292

  1. Selective two-photon absorptive resonance femtosecond-laser electronic-excitation tagging velocimetry.

    PubMed

    Jiang, Naibo; Halls, Benjamin R; Stauffer, Hans U; Danehy, Paul M; Gord, James R; Roy, Sukesh

    2016-05-15

    Selective two-photon absorptive resonance femtosecond-laser electronic-excitation tagging (STARFLEET), a nonseeded ultrafast-laser-based velocimetry technique, is demonstrated in reactive and nonreactive flows. STARFLEET is pumped via a two-photon resonance in N2 using 202.25 nm 100 fs light. STARFLEET greatly reduces the per-pulse energy required (30 μJ/pulse) to generate the signature FLEET emission compared to the conventional FLEET technique (1.1 mJ/pulse). This reduction in laser energy results in less energy deposited in the flow, which allows for reduced flow perturbations (reactive and nonreactive), increased thermometric accuracy, and less severe damage to materials. Velocity measurements conducted in a free jet of N2 and in a premixed flame show good agreement with theoretical velocities, and further demonstrate the significantly less intrusive nature of STARFLEET. PMID:27176968

  2. Anomalously Broad Diffuse Interstellar Bands and Excited CH+ Absorption in the Spectrum of Herschel 36

    NASA Astrophysics Data System (ADS)

    York, D. G.; Dahlstrom, J.; Welty, D. E.; Oka, T.; Hobbs, L. M.; Johnson, S.; Friedman, S. D.; Jiang, Z.; Rachford, B. L.; Snow, T. P.; Sherman, R.; Sonnentrucker, P.

    2014-02-01

    Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 Å are found in absorption along the line of sight to Herschel 36, an O star system next to the bright Hourglass nebula of the Hii region Messier 8. Excited lines of CH and CH+ are seen as well. We show that the region is very compact and itemize other anomalies of the gas. An infrared-bright star within 400 AU is noted. The combination of these effects produces anomalous DIBs, interpreted by Oka et al. (2013, see also this volume) as being caused predominantly by infrared pumping of rotational levels of relatively small molecules.

  3. Site-selective excitation and polarized absorption and emission spectra of trivalent thulium and erbium in strontium fluorapatite

    SciTech Connect

    Gruber, J.B.; Wright, A.O.; Seltzer, M.D.; Zandi, B.; Merkle, L.D.; Hutchinson, J.A.; Morrison, C.A.; Allik, T.H.; Chai, B.H.

    1997-05-01

    Polarized fluorescence spectra produced by site-selective excitation and conventional polarized absorption spectra were obtained for Tm{sup 3+} and Er{sup 3+} ions individually incorporated into single crystals of strontium fluorapatite, Sr{sub 5}(PO{sub 4}){sub 3}F. Substitution of the trivalent rare earth ion for divalent strontium was achieved by passive charge compensation during Czochralski growth of the fluorapatite crystals. Spectra were obtained between 1780 and 345 nm at temperatures from 4 K to room temperature on crystals having the hexagonal structure [P6{sub 3}/m(C{sub 6h}{sup 2})]. The polarized fluorescence spectra due to transitions from multiplet manifolds of Tm{sup 3+}(4f{sup 12}), including {sup 1}D{sub 2}, {sup 1}G{sub 4}, and {sup 3}H{sub 4} to manifolds {sup 3}H{sub 6} (the ground-state manifold), {sup 3}F{sub 4}, {sup 3}H{sub 5}, {sup 3}H{sub 4}, and {sup 3}F{sub 3} were analyzed for the details of the crystal-field splitting of the manifolds. Fluorescence lifetimes were measured for Tm{sup 3+} transitions from {sup 1}D{sub 2}, {sup 1}G{sub 4}, and {sup 3}H{sub 4} at room temperature and from {sup 1}G{sub 4} at 16 K. Results of the analysis indicate that the majority of Tm{sup 3+} ions occupy sites having C{sub s} symmetry. A point-charge lattice-sum calculation was made in which the crystal-field components, A{sub nm}, were determined assuming that trivalent thulium replaces divalent strontium in the metal site having C{sub s} symmetry. Results support the conclusion that the nearest-neighbor fluoride (F{sup {minus}}) is replaced by divalent oxygen (O{sup 2{minus}}), thus preserving overall charge neutrality and local symmetry. Crystal-field splitting calculations predict energy levels in agreement with experimental data. By varying the crystal-field parameters, B{sub nm}, we obtained a rms difference of 7cm{sup {minus}1} between 43 calculated and experimental Stark levels for Tm{sup 3+}(4f{sup 12}) in Tm:SFAP. (Abstract Truncated)

  4. Investigating ligand-receptor interactions at bilayer surface using electronic absorption spectroscopy and Fluorescence Resonance Energy Transfer

    PubMed Central

    Dogra, Navneet; Li, Xuelian; Kohli, Punit

    2012-01-01

    We investigate interactions between receptors and ligands at bilayer surface of polydiacetylene (PDA) liposomal nanoparticles using changes in electronic absorption spectroscopy and Fluorescence Resonance Energy Transfer (FRET). We study the effect of mode of linkage (covalent versus non-covalent) between the receptor and liposome bilayer. We also examine the effect of size dependent interactions between liposome and analyte through electronic absorption and FRET responses. Glucose (receptor) molecules were either covalently or non-covalently attached at the bilayer of nanoparticles, and they provided selectivity for molecular interactions between glucose and glycoprotein ligands of E. coli. The receptor-ligand interactions between glucose and ligand on E. Coli surface induced stress on conjugated PDA chain which resulted in changes (blue to red) in the absorption spectrum of PDA. The changes in electronic absorbance also led to changes in FRET efficiency between conjugated PDA chains (acceptor) and fluorophores (Sulphorhodamine-101) (donor) attached to the bilayer surface. Interestingly, we did not find significant differences in UV-Vis and FRET responses for covalently- and non-covalently-bound glucose to liposomes following their interactions with E. Coli. We attributed these results to close proximity of glucose receptor molecules to the liposome bilayer surface such that induced stress were similar in both the cases. We also found that PDA emission from direct excitation mechanism was ~ 2 - 10 times larger than that of FRET based response. These differences in emission signals were attributed to three major reasons: non-specific interactions between E. Coli and liposomes; size differences between analyte and liposomes; and a much higher PDA concentration with respect to sulpho-rhodamine (SR-101). We have proposed a model to explain our experimental observations. Our fundamental studies reported here will help in enhancing our knowledge regarding interactions

  5. The excitation energy transfer in the trimeric fucoxanthin-chlorophyll protein from Cyclotella meneghiniana analyzed by polarized transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Gildenhoff, Nina; Herz, Julia; Gundermann, Kathi; Büchel, Claudia; Wachtveitl, Josef

    2010-07-01

    Polarized transient absorption spectroscopy has been applied to study the carotenoid to chlorophyll excitation energy transfer in the trimeric fucoxanthin-chlorophyll protein FCPa of the centric diatom Cyclotella meneghiniana. We examined the transfer pathways after excitation in the main carotenoid band (S 0 → S 2 transition) with two excitation wavelengths that address either red fucoxanthins only or blue fucoxanthins and the xanthophyll cycle pigments. We were able to identify different transition dipole moments for the S 1 and the ICT state, which are assumed to be a single coupled state that transfers excitation energy to chlorophyll a. Furthermore we obtained different transition dipole moments for the first excited state S 1 of fucoxanthin depending on the excitation wavelength.

  6. Excited-State Absorption from Real-Time Time-Dependent Density Functional Theory: Optical Limiting in Zinc Phthalocyanine.

    PubMed

    Fischer, Sean A; Cramer, Christopher J; Govind, Niranjan

    2016-04-01

    Optical-limiting materials are capable of attenuating light to protect delicate equipment from high-intensity light sources. Phthalocyanines have attracted a lot of attention for optical-limiting applications due to their versatility and large nonlinear absorption. With excited-state absorption (ESA) being the primary mechanism for optical limiting behavior in phthalocyanines, the ability to tune the optical absorption of ground and excited states in phthalocyanines would allow for the development of advanced optical limiters. We recently developed a method for the calculation of ESA based on real-time time-dependent density functional theory propagation of an excited-state density. In this work, we apply the approach to zinc phthalocyanine, demonstrating the ability of our method to efficiently identify the optical limiting potential of a molecular complex. PMID:27007445

  7. Quantitative photoabsorption and fluorescence study of HCl in vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Nee, J. B.; Suto, M.; Lee, L. C.

    1986-01-01

    The photoabsorption and fluorescence cross sections of HCl were measured in the 106-185 nm region. Sharp absorption bands appear at wavelengths shorter than 135 nm, and fluorescence occurs at several excited states. The fluorescence cross sections are generally quite small, indicating that the excited states are strongly predissociative. The molecular processes for producing the VUV and UV fluorescences are investigated, and the Rydberg characteristics of the strong absorption bands are discussed.

  8. Do fluorescence and transient absorption probe the same intramolecular charge transfer state of 4-(dimethylamino)benzonitrile?

    SciTech Connect

    Gustavsson, Thomas; Fujiwara, Takashige; Lim, Edward C.

    2009-07-21

    We present here the results of time-resolved absorption and emission experiments for 4-(dimethylamino)benzonitrile in solution, which suggest that the fluorescent intramolecular charge transfer (ICT) state may differ from the twisted ICT (TICT) state observed in transient absorption.

  9. Dressing effects in the attosecond transient absorption spectra of doubly excited states in helium

    NASA Astrophysics Data System (ADS)

    Argenti, L.; Jiménez-Galán, Á.; Marante, C.; Ott, C.; Pfeifer, T.; Martín, F.

    2015-06-01

    Strong-field manipulation of autoionizing states is a crucial aspect of electronic quantum control. Recent measurements of the attosecond transient absorption spectrum (ATAS) of helium dressed by a few-cycle visible pulse [C. Ott et al., Nature (London) 516, 374 (2014), 10.1038/nature14026] provide evidence of the inversion of Fano profiles. With the support of accurate ab initio calculations that reproduce the results of the latter experiment, here we investigate the new physics that arise from ATAS when the laser intensity is increased. In particular, we show that (i) previously unnoticed signatures of the dark 2 p21S doubly excited state are observed in the experimental spectrum, (ii) inversion of Fano profiles is predicted to be periodic in the laser intensity, and (iii) the ac Stark shift of the higher terms in the s p2,n + autoionizing series exceeds the ponderomotive energy, which is the result of a genuine two-electron contribution to the polarization of the excited atom.

  10. Excitations, optical absorption spectra, and optical excitonic gaps of heterofullerenes. I. C60, C59N+, and C48N12: theory and experiment.

    PubMed

    Xie, Rui-Hua; Bryant, Garnett W; Sun, Guangyu; Nicklaus, Marc C; Heringer, David; Frauenheim, Th; Manaa, M Riad; Smith, Vedene H; Araki, Yasuyuki; Ito, Osamu

    2004-03-15

    Low-energy excitations and optical absorption spectrum of C(60) are computed by using time-dependent (TD) Hartree-Fock, TD-density functional theory (TD-DFT), TD DFT-based tight-binding (TD-DFT-TB), and a semiempirical Zerner intermediate neglect of diatomic differential overlap method. A detailed comparison of experiment and theory for the excitation energies, optical gap, and absorption spectrum of C(60) is presented. It is found that electron correlations and correlation of excitations play important roles in accurately assigning the spectral features of C(60), and that the TD-DFT method with nonhybrid functionals or a local spin density approximation leads to more accurate excitation energies than with hybrid functionals. The level of agreement between theory and experiment for C(60) justifies similar calculations of the excitations and optical absorption spectrum of a monomeric azafullerene cation C(59)N(+), to serve as a spectroscopy reference for the characterization of carborane anion salts. Although it is an isoelectronic analogue to C(60), C(59)N(+) exhibits distinguishing spectral features different from C(60): (1) the first singlet is dipole-allowed and the optical gap is redshifted by 1.44 eV; (2) several weaker absorption maxima occur in the visible region; (3) the transient triplet-triplet absorption at 1.60 eV (775 nm) is much broader and the decay of the triplet state is much faster. The calculated spectra of C(59)N(+) characterize and explain well the measured ultraviolet-visible (UV-vis) and transient absorption spectra of the carborane anion salt [C(59)N][Ag(CB(11)H(6)Cl(6))(2)] [Kim et al., J. Am. Chem. Soc. 125, 4024 (2003)]. For the most stable isomer of C(48)N(12), we predict that the first singlet is dipole-allowed, the optical gap is redshifted by 1.22 eV relative to that of C(60), and optical absorption maxima occur at 585, 528, 443, 363, 340, 314, and 303 nm. We point out that the characterization of the UV-vis and transient absorption

  11. Fluorescence excitation involving multiple electron transition states of N{sub 2} and CO{sub 2}

    SciTech Connect

    Wu, C.Y.R.; Chen, F.Z.; Hung, T.; Judge, D.L.

    1997-04-01

    The electronic states and electronic structures of N{sub 2} and CO{sub 2} in the 8-50 eV energy region have been studied extensively both experimentally and theoretically. In the energy region higher than 25 eV there exists many electronic states including multiple electron transition (MET) states which are responsible for producing most of the dissociative photoionization products. The electronic states at energies higher than 50 eV have been mainly determined by Auger spectroscopy, double charge transfer, photofragment spectroscopy and ion-ion coincidence spectroscopy. The absorption and ionization spectra of these molecules at energies higher than 50 eV mainly show a monotonic decrease in cross section values and exhibit structureless features. The decay channels of MET and Rydberg (or superexcited) states include autoionization, ionization, dissociative ionization, predissociation, and dissociation while those of single ion and multiple ion states may involve predissociation. and dissociation processes. The study of fluorescence specifically probes electronically excited species resulting from the above-mentioned decay channels and provides information for understanding the competition among these channels.

  12. Intermediate Coupling For Core-Level Excited States: Consequences For X-Ray Absorption Spectroscopy

    SciTech Connect

    Bagus, Paul S.; Sassi, Michel JPC; Rosso, Kevin M.

    2015-04-15

    The origin of the complex NEXAFS features of X-Ray Absorption, XAS, spectra in transition metal complexes is analyzed and interpreted in terms of the angular momentum coupling of the open shell electrons. Especially for excited configurations where a core-electron is promoted to an open valence shell, the angular momentum coupling is intermediate between the two limits of Russell- Saunders, RS, coupling where spin-orbit splitting of the electron shells is neglected and j-j coupling where this splitting is taken as dominant. The XAS intensities can be understood in terms of two factors: (1) The dipole selection rules that give the allowed excited RS multiplets and (2) The contributions of these allowed multiplets to the wavefunctions of the intermediate coupled levels. It is shown that the origin of the complex XAS spectra is due to the distribution of the RS allowed multiplets over several different intermediate coupled excited levels. The specific case that is analyzed is the L2,3 edge XAS of an Fe3+ cation, because this cation allows a focus on the angular momentum coupling to the exclusion of other effects; e.g., chemical bonding. Arguments are made that the properties identified for this atomic case are relevant for more complex materials. The analysis is based on the properties of fully relativistic, ab initio, many-body wavefunctions for the initial and final states of the XAS process. The wavefunction properties considered include the composition of the wavefunctions in terms of RS multiplets and the occupations of the spin-orbit split open shells; the latter vividly show whether the coupling is j-j or not.

  13. Excited state electron distribution and role of the terminal amine in acidic and basic tryptophan dipeptide fluorescence

    NASA Astrophysics Data System (ADS)

    Eisenberg, Azaria S.; Nathan, Moshe; Juszczak, Laura J.

    2016-08-01

    The results of quantum yield (QY) study of tryptophanyl glutamate (Trp-Glu), tryptophanyl lysine (Trp-Lys) and lysinyl tryptophan (Lys-Trp) dipeptides over the pH range, 1.5-13, show that the charge state of the N-terminal amine, and not the nominal molecular charge determines the QY. When the terminal amine is protonated, QY is low (10-2) for all three dipeptides. As the terminal amine cation is found proximal to the indole ring in Trp-Glu and Trp-Lys conformers but not in those for Lys-Trp, its effect may lie only in the partitioning of energy between nonradiative processes, not on QY reduction. QY is also low when both the N-terminal amine and indole amine are deprotonated. These two low QY states can be distinguished by fluorescence lifetime measurement. Molecular dynamics simulation shows that the Chi 1 conformers persist for tens of nanoseconds such that 100-101 ns lifetimes may be associated with individual Chi 1 conformers. The ground state electron density or isosurface of high QY (0.30) 3-methyindole has a uniform electron density over the indole ring as do the higher QY Trp dipeptide conformers. This validates the association of ground state isosurfaces with QY. Excited state orbitals from calculated high intensity, low energy absorption transitions are typically centered over the indole ring for higher QY dipeptide species and off the ring in lower QY species. Thus excited state orbitals substantiate the earlier finding that the ground state isosurface charge density pattern on the indole ring can be predictive of QY.

  14. Enhancement of light absorption in polyazomethines due to plasmon excitation on randomly distributed metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Wróbel, P.; Antosiewicz, T. J.; Stefaniuk, T.; Ciesielski, A.; Iwan, A.; Wronkowska, A. A.; Wronkowski, A.; Szoplik, T.

    2015-05-01

    In photovoltaic devices, metal nanoparticles embedded in a semiconductor layer allow the enhancement of solar-toelectric energy conversion efficiency due to enhanced light absorption via a prolonged optical path, enhanced electric fields near the metallic inclusions, direct injection of hot electrons, or local heating. Here we pursue the first two avenues. In the first, light scattered at an angle beyond the critical angle for reflection is coupled into the semiconductor layer and confined within such planar waveguide up to possible exciton generation. In the second, light is trapped by the excitation of localized surface plasmons on metal nanoparticles leading to enhanced near-field plasmon-exciton coupling at the peak of the plasmon resonance. We report on results of a numerical experiment on light absorption in polymer- (fullerene derivative) blends, using the 3D FDTD method, where exact optical parameters of the materials involved are taken from our recent measurements. In simulations we investigate light absorption in randomly distributed metal nanoparticles dispersed in polyazomethine-(fullerene derivative) blends, which serve as active layers in bulkheterojunction polymer solar cells. In the study Ag and Al nanoparticles of different diameters and fill factors are diffused in two air-stable aromatic polyazomethines with different chemical structures (abbreviated S9POF and S15POF) mixed with phenyl-C61-butyric acid methyl ester (PCBM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The mixtures are spin coated on a 100 nm thick Al layer deposited on a fused silica substrate. Optical constants of the active layers are taken from spectroscopic ellipsometry and reflectance measurements using a rotating analyzer type ellipsometer with auto-retarder performed in the wavelength range from 225 nm to 2200 nm. The permittivities of Ag and Al particles of diameters from 20 to 60 nm are assumed to be equal to those measured on 100 to 200 nm thick metal films.

  15. A method for tuning the excitation wavelength of an LED light source during fluorescence-based cystoscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Lindvold, Lars R.; Hermannn, Gregers G.

    2016-02-01

    In clinical applications of fluorescence-guided endoscopy of the bladder (cystoscopy) it can be observed that the contrast in light from autofluorescence and from photodynamic diagnosis (PDD) varies from patient to patient. To compensate for this effect, a new method is presented for tuning the wavelength of a LED-based light source during fluorescence guided endoscopy of the bladder i.e. photodynamic diagnosis of bladder tumours. In the present embodiment, the wavelength of the LED source, developed in our laboratory, can be tuned to vary the excitation wavelength of both the sensitised fluorescence in the tumours (PDD) as well as the native fluorescence of the bladder mucosa and blood vessels. The contrast of the image observed through the CCD-camera attached to the cystoscope is thereby increased. In this way, patient to patient variations in autofluorescence and in sensitised fluorescence of tumours can be compensated for during fluorescence-guided cystoscopy in the clinic.

  16. Influence of Oil-in-Water Emulsions on Fluorescence Properties as Observed by Excitation-Emission Spectra

    NASA Astrophysics Data System (ADS)

    Baszanowska, E.; Zielinski, O.; Otremba, Z.; Toczek, H.

    2013-10-01

    Oil poses a major threat to marine ecosystems. This work describes a set of studies focused on introducing an efficient method for the identification of oil in the form of oil emulsions through fluorescence spectra analyses. Hence the concept of classification of oil pollution in seawater based on fluorescence spectroscopy using a high sensitive fluorimeter [1] suitable for laboratory and in situ measurements is introduced. We consider that this approach, in the future, will make it possible to collect specific fluorescence information allowing us to build a base of the oil standards. Here we examined excitation-emission fluorescence spectra (EEMs) of water containing oil-in-water emulsion prepared artificially under laboratory conditions. Water polluted with oil-in-water emulsion was studied with the objective to estimate differences in three-dimensional fluorescence spectra. Studies included various types of oils and oil concentrations. Essential differences in fluorescence spectra for various oils are indicated.

  17. Picosecond kinetic absorption and fluorescence studies of bovine rhodopsin with a fixed 11-ene.

    PubMed Central

    Buchert, J; Stefancic, V; Doukas, A G; Alfano, R R; Callender, R H; Pande, J; Akita, H; Balogh-Nair, V; Nakanishi, K

    1983-01-01

    A synthetic retinal having a fixed 11-cis geometry has been used to prepare a nonbleachable analogue of bovine rhodopsin. Marked differences in the picosecond absorption and fluorescence behavior of this analogue at room temperature, compared with that of natural rhodopsin, were observed. This not only indicates that the 11-cis to trans isomerization of the retinal moiety is the crucial primary event in the photolysis of rhodopsin, but also it establishes that this isomerization must occur on the picosecond time scale or faster. PMID:6626668

  18. Surface extended x-ray absorption fine structure of low-Z absorbates using fluorescence detection

    SciTech Connect

    Stoehr, J.; Kollin, E.B.; Fischer, D.A.; Hastings, J.B.; Zaera, F.; Sette, F.

    1985-05-01

    Comparison of x-ray fluorescence yield (FY) and electron yield surface extended x-ray absorption fine structure spectra above the S K-edge for c(2 x 2) S on Ni(100) reveals an order of magnitude higher sensitivity of the FY technique. Using FY detection, thiophene (C/sub 4/H/sub 4/S) chemisorption on Ni(100) is studied with S coverages down to 0.08 monolayer. The molecule dissociates at temperatures as low as 100K by interaction with fourfold hollow Ni sites. Blocking of these sites by oxygen leaves the molecule intact.

  19. Time-dependent excitation and ionization modelling of absorption-line variability due to GRB 080310

    NASA Astrophysics Data System (ADS)

    Vreeswijk, P. M.; Ledoux, C.; Raassen, A. J. J.; Smette, A.; De Cia, A.; Woźniak, P. R.; Fox, A. J.; Vestrand, W. T.; Jakobsson, P.

    2013-01-01

    We model the time-variable absorption of Fe II, Fe III, Si II, C II and Cr II detected in Ultraviolet and Visual Echelle Spectrograph (UVES) spectra of gamma-ray burst (GRB) 080310, with the afterglow radiation exciting and ionizing the interstellar medium in the host galaxy at a redshift of z = 2.42743. To estimate the rest-frame afterglow brightness as a function of time, we use a combination of the optical VRI photometry obtained by the RAPTOR-T telescope array, which is presented in this paper, and Swift's X-Ray Telescope (XRT) observations. Excitation alone, which has been successfully applied for a handful of other GRBs, fails to describe the observed column density evolution in the case of GRB 080310. Inclusion of ionization is required to explain the column density decrease of all observed Fe II levels (including the ground state 6D9/2) and increase of the Fe III 7S3 level. The large population of ions in this latter level (up to 10% of all Fe III) can only be explained through ionization of Fe II, as a large fraction of the ionized Fe II ions (we calculate 31% using the Flexible Atomic and Cowan codes) initially populate the 7S3 level of Fe III rather than the ground state. This channel for producing a significant Fe III 7S3 level population may be relevant for other objects in which absorption lines from this level, the UV34 triplet, are observed, such as broad absorption line (BAL) quasars and η Carinae. This provides conclusive evidence for time-variable ionization in the circumburst medium, which to date has not been convincingly detected. However, the best-fit distance of the neutral absorbing cloud to the GRB is 200-400 pc, i.e. similar to GRB-absorber distance estimates for GRBs without any evidence for ionization. We find that the presence of time-varying ionization in GRB 080310 is likely due to a combination of the super-solar iron abundance ([Fe/H] = +0.2) and the low H I column density (log N(H i) = 18.7) in the host of GRB 080310. Finally

  20. Two-photon excited fluorescence in praseodymium doped fibre and its application in distributed optical fibre sensing of temperature

    NASA Astrophysics Data System (ADS)

    Dalzell, Craig J.; Han, Thomas P. J.; Ruddock, Ivan S.

    2011-05-01

    Distributed temperature sensing based on time-correlated two-photon excited fluorescence (TPF) in doped fibre is described. Counter-propagating laser pulses generate a TPF flash at the position of overlap which is scanned along the fibre by a variable relative time delay. The flash is detected and analysed at one end. With the fluorescence power being completely independent of excitation pulse duration and temporal profile, the sensor does not require ultrashort excitation pulses for operation. There is potential for high spatial resolution as the length of the sensed region depends only on pulse duration. TPF is reported in bulk glass doped with rare earths and in doped single-mode fibre. The suitability of fluorescence transitions for sensing is discussed taking into account the temperature dependence of the decay times, the location of the terminating energy level relative to the ground state, and the option of non-degenerate TPF.

  1. Standing-wave-excited multiplanar fluorescence in a laser scanning microscope reveals 3D information on red blood cells

    PubMed Central

    Amor, Rumelo; Mahajan, Sumeet; Amos, William Bradshaw; McConnell, Gail

    2014-01-01

    Standing-wave excitation of fluorescence is highly desirable in optical microscopy because it improves the axial resolution. We demonstrate here that multiplanar excitation of fluorescence by a standing wave can be produced in a single-spot laser scanning microscope by placing a plane reflector close to the specimen. We report here a variation in the intensity of fluorescence of successive planes related to the Stokes shift of the dye. We show by the use of dyes specific for the cell membrane how standing-wave excitation can be exploited to generate precise contour maps of the surface membrane of red blood cells, with an axial resolution of ≈90 nm. The method, which requires only the addition of a plane mirror to an existing confocal laser scanning microscope, may well prove useful in studying diseases which involve the red cell membrane, such as malaria. PMID:25483987

  2. Standing-wave-excited multiplanar fluorescence in a laser scanning microscope reveals 3D information on red blood cells

    NASA Astrophysics Data System (ADS)

    Amor, Rumelo; Mahajan, Sumeet; Amos, William Bradshaw; McConnell, Gail

    2014-12-01

    Standing-wave excitation of fluorescence is highly desirable in optical microscopy because it improves the axial resolution. We demonstrate here that multiplanar excitation of fluorescence by a standing wave can be produced in a single-spot laser scanning microscope by placing a plane reflector close to the specimen. We report here a variation in the intensity of fluorescence of successive planes related to the Stokes shift of the dye. We show by the use of dyes specific for the cell membrane how standing-wave excitation can be exploited to generate precise contour maps of the surface membrane of red blood cells, with an axial resolution of ~90 nm. The method, which requires only the addition of a plane mirror to an existing confocal laser scanning microscope, may well prove useful in studying diseases which involve the red cell membrane, such as malaria.

  3. Simulating One-Photon Absorption and Resonance Raman Scattering Spectra Using Analytical Excited State Energy Gradients within Time-Dependent Density Functional Theory

    SciTech Connect

    Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus J. J.; Jensen, Lasse

    2013-12-10

    A parallel implementation of analytical time-dependent density functional theory gradients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids, and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G, and a molecular host–guest complex (TTFcCBPQT4+). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host–guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experimental data for most exchange-correlation functionals. Finally, however, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.

  4. Study on discrimination of oral cancer from normal using blood plasma based on fluorescence steady and excited state at excitation wavelength 280 nm

    NASA Astrophysics Data System (ADS)

    Rekha, Pachaiappan; Aruna, Prakasa Rao; Ganesan, Singaravelu

    2016-03-01

    Many research works based on fluorescence spectroscopy have proven its potential in the diagnosis of various diseases using the spectral signatures of the native key fluorophores such as tryptophan, tyrosine, collagen, NADH, FAD and porphyrin. These fluorophores distribution, concentration and their conformation may be changed depending upon the pathological and metabolic conditions of cells and tissues. In this study, we have made an attempt to characterize the blood plasma of normal subject and oral cancer patients by native fluorescence spectroscopy at 280 nm excitation. Further, the fluorescence data were analyzed by employing the multivariate statistical method - linear discriminant analyses (LDA) using leaves one out cross validation method. The results illustrate the potential of fluorescence spectroscopy technique in the diagnosis of oral cancer using blood plasma.

  5. The use of ultraviolet excitation of native fluorescence for identifying biomarkers in halite crystals

    NASA Astrophysics Data System (ADS)

    Mormile, Melanie R.; Storrie-Lombardi, Michael

    2005-09-01

    Recent findings by the NASA's Mars Exploration Rovers and ESA's Mars Express indicate that during an earlier era in the planets' evolution, evaporation of surface water may have left behind vast evaporite deposits1,2,3. This makes the possibility of finding biological material preserved in halite inclusions most intriguing4. The retrieval and characterization of microorganisms from ancient halite crystals5,6 suggests that it might be possible to locate their remains as biomarkers or even living cells from evaporites sampled from extraterrestrial environments. However, before this is possible, techniques for the detection of bacterial cells or biomolecules in halite and other evaporite crystals need further refining. Specifically, contamination must be minimized and quantified during the microbial analysis of such crystals. Aseptic techniques that allow for the direct extraction of fluid brines from micron to millimeter size inclusions significantly reduce the possibility for contamination. However, even with extreme precautions, the possibility for contamination cannot be entirely eliminated, particularly when culture-based methods are employed. We have elicited native fluorescence from a variety of biomolecules, including the aromatic amino acids and nucleic acids, by laser excitation at 248 and 224 nm from haloarchaea and haloarchaea residues trapped in halite. Energy to each sample, (positive control crystals with Halobacteria salinarum and bacteria-free negative control crystals), was 80 microwatts at 224 nm and 25 microwatts at 248 nm. A 30 s exposure of the inclusions within the positive control elicited easily detectable fluorescence while there was no response from the negative control crystals during the same exposure. Analysis of halite crystals sampled from the Waste Isolation Pilot Plant, Carlsbad, New Mexico yielded similar results. To minimize microbial damage from the high-energy 224-248 nm beams and to make the technique more widely available to the

  6. ICPBC and C12-ICPBC: two new red emitting, fluorescent Ca2+ indicators excited with visible light.

    PubMed

    Roussakis, Emmanuel; Liepouri, Fotini; Nifli, Artemissia-Phoebe; Castanas, Elias; Deligeorgiev, Todor G; Katerinopoulos, Haralambos E

    2006-01-01

    Two new, visible-excited and red-emitting fluorescent Ca(2+) indicators were synthesized and the spectral profiles of their free and Ca(2+) bound forms were studied. The fluorescent properties of these probes are due to the extended conjugation of the chromeno[3',2':3,4]pyrido[1,2a][1,3]benzimidazole chromophore incorporated in their BAPTA-type, Ca(2+) chelating structure. The compounds, namely ICPBC and its N-dodecyl analog C12-ICPBC exhibit Ca(2+) dissociation constants of 7.7 and 18.0 microM, respectively. The fluorescence spectra of the probes showed a clear shift in excitation wavelength maxima upon Ca(2+) binding along with a large Stokes shift and changes in fluorescence intensity, indicating their potential use as Ca(2+) indicators. The ability of ICPBC to trace high calcium spikes was tested in the human HepG2 cell line with positive results. PMID:16236357

  7. Excited-State Proton-Transfer-Induced Trapping Enhances the Fluorescence Emission of a Locked GFP Chromophore

    PubMed Central

    2016-01-01

    The chemical locking of the central single bond in core chromophores of green fluorescent proteins (GFPs) influences their excited-state behavior in a distinct manner. Experimentally, it significantly enhances the fluorescence quantum yield of GFP chromophores with an ortho-hydroxyl group, while it has almost no effect on the photophysics of GFP chromophores with a para-hydroxyl group. To unravel the underlying physical reasons for this different behavior, we report static electronic structure calculations and nonadiabatic dynamics simulations on excited-state intramolecular proton transfer, cis–trans isomerization, and excited-state deactivation in a locked ortho-substituted GFP model chromophore (o-LHBI). On the basis of our previous and present results, we find that the S1 keto species is responsible for the fluorescence emission of the unlocked o-HBI and the locked o-LHBI species. Chemical locking does not change the parts of the S1 and S0 potential energy surfaces relevant to enol–keto tautomerization; hence, in both chromophores, there is an ultrafast excited-state intramolecular proton transfer that takes only 35 fs on average. However, the locking effectively hinders the S1 keto species from approaching the keto S1/S0 conical intersections so that most of trajectories are trapped in the S1 keto region for the entire 2 ps simulation time. Therefore, the fluorescence quantum yield of o-LHBI is enhanced compared with that of unlocked o-HBI, in which the S1 excited-state decay is efficient and ultrafast. In the case of the para-substituted GFP model chromophores p-HBI and p-LHBI, chemical locking hardly affects their efficient excited-state deactivation via cis–trans isomerization; thus, the fluorescence quantum yields in these chromophores remain very low. The insights gained from the present work may help to guide the design of new GFP chromophores with improved fluorescence emission and brightness. PMID:26744782

  8. Imaging electronic trap states in perovskite thin films with combined fluorescence and femtosecond transient absorption microscopy

    DOE PAGESBeta

    Xiao, Kai; Ma, Ying -Zhong; Simpson, Mary Jane; Doughty, Benjamin; Yang, Bin

    2016-04-22

    Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. Themore » remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Furthermore, detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps.« less

  9. Imaging Electronic Trap States in Perovskite Thin Films with Combined Fluorescence and Femtosecond Transient Absorption Microscopy.

    PubMed

    Simpson, Mary Jane; Doughty, Benjamin; Yang, Bin; Xiao, Kai; Ma, Ying-Zhong

    2016-05-01

    Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. The remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps. PMID:27103096

  10. Development of laser excited atomic fluorescence and ionization methods. Final technical progress report, May 1, 1988--December 31, 1991

    SciTech Connect

    Winefordner, J.D.

    1991-12-31

    Progress report: May 1, 1988 to December 31, 1991. The research supported by DE-FG05-88ER13881 during the past (nearly) 3 years can be divided into the following four categories: (1) theoretical considerations of the ultimate detection powers of laser fluorescence and laser ionization methods; (2) experimental evaluation of laser excited atomic fluorescence; (3) fundamental studies of atomic and molecular parameters in flames and plasmas; (4) other studies.

  11. Fluorescence from excitation of CH4, CH3OH and CH3SH by extreme vacuum ultraviolet radiation

    NASA Technical Reports Server (NTRS)

    Ma, Guang; Suto, Masako; Lee, L. C.

    1990-01-01

    The photoabsorption and fluorescence cross sections of CH4, CH3OH, and CH3SH were measured in the wavelength regions of 52-106, 48-106, and 48-106 nm, respectively. The fluorescence spectra were dispersed to identify the emitting species. Emissions from the excited species of H(asterisk) and CH(asterisk) are commonly observed for all three molecules. Emission from the excited CH2(asterisk) is observed from CH4, OH(asterisk) from CH3OH and CS(asterisk) from CH3SH. The photoexcitation processes that may produce the observed emission bands are discussed.

  12. Technical Note: Dissolved organic matter fluorescence - a finite mixture approach to deconvolve excitation-emission matrices

    NASA Astrophysics Data System (ADS)

    Butturini, A.; Ejarque, E.

    2013-09-01

    The analysis of the shape of excitation-emission matrices (EEMs) is a relevant tool for exploring the origin, transport and fate of dissolved organic matter (DOM) in aquatic ecosystems. Within this context, the decomposition of EEMs is acquiring a notable relevance. A simple mathematical algorithm that automatically deconvolves individual EEMs is described, creating new possibilities for the comparison of DOM fluorescence properties and EEMs that are very different from each other. A mixture model approach is adopted to decompose complex surfaces into sub-peaks. The laplacian operator and the Nelder-Mead optimisation algorithm are implemented to individuate and automatically locate potential peaks in the EEM landscape. The EEMs of a simple artificial mixture of fluorophores and DOM samples collected in a Mediterranean river are used to describe the model application and to illustrate a strategy that optimises the search for the optimal output.

  13. Technical Note: Dissolved organic matter fluorescence - a finite mixture approach to deconvolve excitation-emission matrices

    NASA Astrophysics Data System (ADS)

    Butturini, A.; Ejarque, E.

    2013-03-01

    The analysis of the shape of excitation-emission matrices (EEMs) is a relevant tool for exploring the origin, transport and fate of dissolved organic matter (DOM) in aquatic ecosystems. Within this context, the decomposition of EEMs is acquiring a notable relevance. A simple mathematical algorithm that automatically deconvolves single EEM is described, creating new possibilities for the comparison of DOM fluorescence properties and EEMs that are very different from each other. A mixture model approach is adopted to decompose complex surfaces into sub-peaks. The laplacian operator and the Nelder-Mead optimization algorithm are implemented to individuate and automatically locate potential peaks in the EEM landscape. A small heterogeneous data set of 21 EEMs from a human-impacted Mediterranean river is used to describe the model application and to illustrate a strategy that optimises the search for the optimal output.

  14. Coherence gated wavefront sensorless adaptive optics for two photon excited fluorescence retinal imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Jian, Yifan; Cua, Michelle; Bonora, Stefano; Pugh, Edward N.; Zawadzki, Robert J.; Sarunic, Marinko V.

    2016-03-01

    We present a novel system for adaptive optics two photon imaging. We utilize the bandwidth of the femtosecond excitation beam to perform coherence gated imaging (OCT) of the sample. The location of the focus is directly observable in the cross sectional OCT images, and adjusted to the desired depth plane. Next, using real time volumetric OCT, we perform Wavefront Sensorless Adaptive Optics (WSAO) aberration correction using a multi-element adaptive lens capable of correcting up to 4th order Zernike polynomials. The aberration correction is performed based on an image quality metric, for example intensity. The optimization time is limited only by the OCT acquisition rate, and takes ~30s. Following aberration correction, two photon fluorescence images are acquired, and compared to results without adaptive optics correction. This technique is promising for multiphoton imaging in multi-layered, scattering samples such as eye and brain, in which traditional wavefront sensing and guide-star sensorless adaptive optics approaches may not be suitable.

  15. A tube-excited x-ray fluorescence spectrometer for use in small-diameter boreholes

    SciTech Connect

    Reeves, J.H.; Arthur, R.J.; Brodzinski, R.L.; Shepard, C.L.

    1995-04-01

    A portable in-situ x-ray fluorescence analytical system that uses an x-ray tube excitation source and a cooled Si(Li) spectrometer for detecting characteristic emission x rays has been developed for use in small-diameter wells and boreholes. The 15-watt, iron-anode x-ray tube operates up to 30 kV. Three wells at the Sandia National Laboratory Chemical Waste Landfill, lined with 76 {mu} thick polyethylene, were logged specifically for Cr contamination. Detection limits below 50 ppM were achieved with counting intervals of 600 seconds and with the Si(Li) detector operating at 450-eV resolution (full width at half maximum [FWHM] for the Mn K-alpha x ray).

  16. Imaging of surgical margin in pancreatic metastasis using two-photon excited fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Jing; Hong, Zhipeng; Chen, Hong; Chen, Youting; Xu, Yahao; Zhu, Xiaoqin; Zhuo, Shuangmu; Shi, Zheng; Chen, Jianxin

    2014-09-01

    Two-photon excited fluorescence (TPEF) microscopy, has become a powerful tool for imaging unstained tissue samples at subcellular level in biomedical research. The purpose of this study was to determine whether TPEF imaging of histological sections without H-E staining can be used to identify the boundary between normal pancreas and pancreatic metastasis from renal cell carcinoma (RCC). The typical features such as the significant increase of cancerous nests, the absence of pancreatic ductal, the appearance of cancer cells were observed to present the boundary between normal pancreas and pancreatic metastasis from RCC. These results correlated well with the corresponding histological outcomes. With the advent of clinically miniaturized TPEF microscopy and integrative endoscopy, TPEF microscopy has the potential application on surgical location of pancreatic metastasis from RCC in the near future.

  17. Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation

    PubMed Central

    Zipfel, Warren R.; Williams, Rebecca M.; Christie, Richard; Nikitin, Alexander Yu; Hyman, Bradley T.; Webb, Watt W.

    2003-01-01

    Multicolor nonlinear microscopy of living tissue using two- and three-photon-excited intrinsic fluorescence combined with second harmonic generation by supermolecular structures produces images with the resolution and detail of standard histology without the use of exogenous stains. Imaging of intrinsic indicators within tissue, such as nicotinamide adenine dinucleotide, retinol, indoleamines, and collagen provides crucial information for physiology and pathology. The efficient application of multiphoton microscopy to intrinsic imaging requires knowledge of the nonlinear optical properties of specific cell and tissue components. Here we compile and demonstrate applications involving a range of intrinsic molecules and molecular assemblies that enable direct visualization of tissue morphology, cell metabolism, and disease states such as Alzheimer's disease and cancer. PMID:12756303

  18. Fluorescence excitation and propagation through brain phantom gelatins: measurements and potential applications

    SciTech Connect

    Allison, Stephen W; Gillies, George

    2010-01-01

    We have investigated the utility of 0.6% agarose gels as surrogate materials for brain tissues in optical propagation studies for possible diagnostic and therapeutic applications. Centimeter-scale layers of the gel exhibited a Beer's law attenuation factor, , of 0.2 mm 1 for incident illumination via a pulsed LED (100 Hz) at 405 nm. This result was different by only about a factor of 3 from the effective penetration depth at similar wavelengths through in vitro samples of the gray (cortical) matter of human brain, as measured by others. Then, films of the thermographic phosphors La2O2S:Eu, Mg4FGeO6:Mn, YAG:Cr and variants of the latter were formed on aluminum substrates and the fluorescence of these samples was stimulated and observed through layers of the gel up to 4 cm thick. In all cases, the fluorescence was easily excited and distinguishable above the background. The results demonstrate that this gel might serve as an inexpensive and robust test bed for exploratory studies of neurological modalities involving propagation of optical signals within brain tissues.

  19. Triggered Excited-State Intramolecular Proton Transfer Fluorescence for Selective Triplex DNA Recognition.

    PubMed

    Wang, Ying; Hu, Yuehua; Wu, Tao; Zhou, Xiaoshun; Shao, Yong

    2015-12-01

    The triplex DNA has received much interest due to its various applications in gene regulation, molecular switch, and sensor development. However, realizing a highly selective recognition using a fluorescence probe specific only for the triplex topology is still a great challenge. Herein, we found that relative to the structural analogues of natural robinetin, myricetin, quercetin, kaempferol, morin, rutin, baicalin, luteolin, naringenin, genistein, chrysin, galangin, isorhamnetin, and several synthetic flavonoids, fisetin (FIS) is the brightest emitter when targeting the triplex DNA in contrast to binding with ss-DNA, ds-DNA (with or without an abasic site), i-motif, and DNA/RNA G-quadruplexes. Only the triplex association triggers the FIS green fluorescence that is relaxed from the tautomer favorable for excited-state intramolecular proton transfer (ESIPT). FIS can stabilize the triplex structure and primarily interact with the two terminals of the triplex via a 2:1 binding mode. This work demonstrates the potential of FIS as a DNA structure-selective switch-on ESIPT probe when evolving the triplex-forming oligonucleotides and developing the novel triplex-based sensors and switches. PMID:26556582

  20. Optimized streak-camera system: wide excitation range and extended time scale for fluorescence lifetime measurement

    NASA Astrophysics Data System (ADS)

    Graf, Urs; Buehler, Christof; Betz, Michael; Zuber, Herbert; Anliker, M.

    1994-08-01

    A new versatile system for the measurement of time-resolved fluorescence emission spectra of biomolecules is presented. Frequency doubling and tripling of a Ti:Sapphire laser allows excitation over a wide wavelength range. The influence of increasing the spectral resolution on the time resolution has been investigated. System performance can be optimized for best resolution in the spectral or time domain, respectively. System performance can be optimized for best resolution in the spectral or time domain, respectively. The currently achieved temporal resolution is 6 psec, and the best spectral resolution is 3 nm. Long fluorescence decays can be resolved with optimal time resolution by way of taking into account the flyback of the streak camera. With the system described, the core complex ((alpha) (beta) )3APCLC8.9 of the phycobilisome from the photosynthetic cyanobacteria Mastigocladus laminosus has been analyzed. Lifetime analysis clearly demonstrated the influence of the linker polypeptide on the phycobiliprotein complex and the identity of native and reconstituted complex.

  1. Effect of Solvation on Electron Detachment and Excitation Energies of a Green Fluorescent Protein Chromophore Variant.

    PubMed

    Bose, Samik; Chakrabarty, Suman; Ghosh, Debashree

    2016-05-19

    Hybrid quantum mechanics/molecular mechanics (QM/MM) is applied to the fluorinated green fluorescent protein (GFP) chromophore (DFHBDI) in its deprotonated form to understand the solvatochromic shifts in its vertical detachment energy (VDE) and vertical excitation energy (VEE). This variant of the GFP chromophore becomes fluorescent in an RNA environment and has a wide range of applications in biomedical and biochemical fields. From microsolvation studies, we benchmark (with respect to full QM) the accuracy of our QM/MM calculations with effective fragment potential (EFP) as the MM method of choice. We show that while the solvatochromic shift in the VEE is minimal (0.1 eV blue shift) and its polarization component is only 0.03 eV, the effect of the solvent on the VDE is quite large (3.85 eV). We also show by accurate calculations on the solvatochromic shift of the VDE that polarization accounts for ∼0.23 eV and therefore cannot be neglected. The effect of the counterions on the VDE of the deprotonated chromophore in solvation is studied in detail, and a charge-smearing scheme is suggested for charged chromophores. PMID:27116477

  2. Fluorescence excitation and propagation through brain phantom gelatins: measurements and potential applications

    NASA Astrophysics Data System (ADS)

    Allison, S. W.; Gillies, G. T.

    2010-08-01

    We have investigated the utility of 0.6% agarose gels as surrogate materials for brain tissues in optical propagation studies for possible diagnostic and therapeutic applications. Centimeter-scale layers of the gel exhibited a Beer's law attenuation factor, δ, of ≈0.2 mm-1 for incident illumination via a pulsed LED (100 Hz) at 405 nm. This result was different by only about a factor of 3 from the effective penetration depth at similar wavelengths through in vitro samples of the gray (cortical) matter of human brain, as measured by others. Then, films of the thermographic phosphors La2O2S:Eu, Mg4FGeO6:Mn, YAG:Cr and variants of the latter were formed on aluminum substrates and the fluorescence of these samples was stimulated and observed through layers of the gel up to 4 cm thick. In all cases, the fluorescence was easily excited and distinguishable above the background. The results demonstrate that this gel might serve as an inexpensive and robust test bed for exploratory studies of neurological modalities involving propagation of optical signals within brain tissues.

  3. Large two-photon absorption cross sections of hemiporphyrazines in the excited state: the multiphoton absorption process of hemiporphyrazines with different central metals.

    PubMed

    Dini, Danilo; Calvete, Mario J F; Hanack, Michael; Amendola, Vincenzo; Meneghetti, Moreno

    2008-09-17

    A series of five hemiporphyrazines (Hps) with different coordinating central atoms (H2, GeCl2, InCl, Pt, Pb), and the acyclic derivative 1,3-bis-(6'-amino-4'-butoxy-2'-pyridylimino)-1,3-dihydroisoindoline have been synthesized and their multiphoton absorption properties examined at the second harmonic frequency of the Nd:YAG laser in the nanosecond time regime. Metal-free and platinum Hps display saturation of optical transmittance within incident fluence values of 6 J cm(-2). Comparison with other similar molecular structures like phthalocyanines and related molecules shows that Hps are strong nonlinear absorbers. The experimental curves of nonlinear transmission at 532 nm have been fitted by means of a three-level model with the occurrence of simultaneous two-photon absorption from an excited state. In the sole case of the InCl complex we found that a five-level model is needed because of the participation of triplet states. Contrary to phthalocyanines, naphthalocyanines, and porphyrins, a heavy central atom does not improve the nonlinear absorption properties since a different excited states dynamic is involved. The large nonlinear absorption of Hps combined with the very small absorption in the visible spectral range makes these molecules a very interesting class of molecules for nonlinear optical applications. PMID:18722439

  4. Single-molecule spectroscopy and femtosecond transient absorption studies on the excitation energy transfer process in ApcE(1-240) dimers.

    PubMed

    Long, Saran; Zhou, Meng; Tang, Kun; Zeng, Xiao-Li; Niu, Yingli; Guo, Qianjin; Zhao, Kai-Hong; Xia, Andong

    2015-05-28

    ApcE(1-240) dimers with one intrinsic phycocyanobilin (PCB) chromophore in each monomer that is truncated from the core-membrane linker (ApcE) of phycobilisomes (PBS) in Nostoc sp. PCC 7120 show a sharp and significantly red-shifted absorption. Two explanations either conformation-dependent Förster resonance energy transfer (FRET) or the strong exciton coupling limit have been proposed for red-shifted absorption. This is a classic example of the special pair in the photosynthetic light harvesting proteins, but the mechanism of this interaction is still a matter of intense debate. We report the studies using single-molecule and transient absorption spectra on the interaction in the special pair of ApcE dimers. Our results demonstrate the presence of conformation-dependent FRET between the two PCB chromophores in ApcE dimers. The broad distributions of fluorescence intensities, lifetimes and polarization difference from single-molecule measurements reveal the heterogeneity of local protein-pigment environments in ApcE dimers, where the same molecular structures but different protein environments are the main reason for the two PCB chromophores with different spectral properties. The excitation energy transfer rate between the donor and the acceptor about (110 ps)(-1) is determined from transient absorption measurements. The red-shifted absorption in ApcE dimers could result from more extending conformation, which shows another type of absorption redshift that does not depend on strong exciton coupling. The results here stress the importance of conformation-controlled spectral properties of the chemically identical chromophores, which could be a general feature to control energy/electron transfer, widely existing in the light harvesting complexes. PMID:25925197

  5. Molecular probes for two-photon excited fluorescence and second harmonic generation imaging of biological membranes

    NASA Astrophysics Data System (ADS)

    Porres, Laurent; Mongin, Olivier; Bhatthula, Bharath K. G.; Blanchard-Desce, Mireille H.; Ventelon, Lionel; Moreaux, Laurent; Pons, T.; Mertz, Jerome

    2002-11-01

    Novel microscopies based on nonlinear optical (NLO) phenomena are attracting increasing interest in the biology community owing to their potentialities in the area of real-time, non-damaging imaging of biological systems. In particular, second-harmonic generation (SHG) and two-photon excited fluorescence (TPEF) are NLO phenomena that scale with excitation intensity squared, and thus give rise to an intrinsic 3-dimensional resolution when used in microscopic imaging. In this perspective, we have implemented a molecular engineering approach toward NLO-probes specifically designed for SHG and/or TPEF imaging of cellular membranes. We have designed nanoscale rod-like fluorophores showing very large TPEF cross-sections in the visible red, outperforming standard fluorophores such as fluorescein by up to two orders of magnitude. Bolaamphiphilic derivatives combining high TPEF cross-sections and affinity for cellular membranes were prepared. Their incorporation into model or cell membranes can be monitored by TPEF microscopy. Amphiphilic push-pull chromophores showing both high TPA and SHG cross-sections in the near-IR region were designed as NLO-probes for imaging of biological membranes by simultaneous SHG and TPEF microscopy. These NLO-phores offer intriguing potentialities for imaging of fundamental biological processes such as adhesion, fusion or for reporting of membrane electrical potentials.

  6. Spectral fluorescence signature techniques and absorption measurements for continuous monitoring of biofuel-producing microalgae cultures

    NASA Astrophysics Data System (ADS)

    Martín de la Cruz, M. C.; Gonzalez Vilas, L.; Yarovenko, N.; Spyrakos, E.; Torres Palenzuela, J. M.

    2013-08-01

    Biofuel production from microalgae can be both sustainable and economically viable. Particularly in the case of algal growth in wastewater an extra benefit is the removal or biotransformation of pollutants from these types of waters. A continuous monitoring system of the microalgae status and the concentration of different wastewater contaminants could be of great help in the biomass production and the water characterisation. In this study we present a system where spectral fluorescence signature (SFS) techniques are used along with absorption measurements to monitor microalgae cultures in wastewater and other mediums. This system aims to optimise the microalgae production for biofuel applications or other uses and was developed and tested in prototype indoor photo-bioreactors at the University of Vigo. SFS techniques were applied using the fluorescence analyser INSTAND-SCREENER developed by Laser Diagnostic Instruments AS. INSTAND-SCREENER permits wavelength scanning in two modes, one in UV and another in VIS. In parallel, it permits the on-line monitoring and rapid analysis of both water quality and phytoplankton status without prior treatment of the sample. Considering that different contaminants and microalgae features (density, status etc.) have different spectral signatures of fluorescence and absorption properties, it is possible to characterise them developing classification libraries. Several algorithms were used for the classification. The implementation of this system in an outdoor raceway reactor in a Spanish wastewater treatment plant is also discussed. This study was part of the Project EnerBioAlgae (http://www.enerbioalgae.com/), which was funded by the Interreg SUDOE and led by the University of Vigo.

  7. Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an atmospheric pressure air plasma jet

    NASA Astrophysics Data System (ADS)

    Conway, J.; Gogna, G. S.; Gaman, C.; Turner, M. M.; Daniels, S.

    2016-08-01

    Atomic oxygen number density [O] is measured in an air atmospheric pressure plasma jet (APPJ) using two-photon absorption laser induced fluorescence (TALIF). Gas flow is fixed at 8 slpm, the RF power coupled into the plasma jet varied between 5 W and 20 W, and the resulting changes in atomic oxygen density measured. Photolysis of molecular oxygen is employed to allow in situ calibration of the TALIF system. During calibration, O2 photo-dissociation and two-photon excitation of the resulting oxygen atoms are achieved within the same laser pulse. The atomic oxygen density produced by photolysis is time varying and spatially non-uniform which needs to be corrected for to calibrate the TALIF system for measurement of atomic oxygen density in plasma. Knowledge of the laser pulse intensity I 0(t), wavelength, and focal spot size allows correction factors to be determined using a rate equation model. Atomic oxygen is used for calibration and measurement, so the laser intensity can be increased outside the TALIF quadratic laser power dependence region without affecting the calibration reliability as the laser power dependence will still be the same for both. The atomic O density results obtained are not directly benchmarked against other known density measurement techniques. The results show that the plasma jet atomic oxygen content increases as the RF power coupled into the plasma increases.

  8. All-Optical Switching in Bacteriorhodopsin Based on Excited-State Absorption

    NASA Astrophysics Data System (ADS)

    Roy, Sukhdev

    2008-03-01

    Switching light with light is of tremendous importance for both fundamental and applied science. The advent of nano-bio-photonics has led to the design, synthesis and characterization of novel biomolecules that exhibit an efficient nonlinear optical response, which can be utilized for designing all-optical biomolecular switches. Bacteriorhodopsin (bR) protein found in the purple membrane of Halobacterium halobium has been the focus of intense research due to its unique properties that can also be tailored by physical, chemical and genetic engineering techniques to suit desired applications. The talk would focus on our recent results on all-optical switching in bR and its mutants, based on excited-state absorption, using the pump-probe technique. We would discuss the all-optical control of various features of the switching characteristics such as switching contrast, switching time, switching pump intensity, switched probe profile and phase, and relative phase-shift. Optimized conditions for all-optical switching that include optimized values of the small-signal absorption coefficient (for cw case), the pump pulse width and concentration for maximum switching contrast (for pulsed case), would be presented. We would discuss the desired optimal spectral and kinetic properties for device applications. We would also discuss the application of all-optical switching to design low power all-optical computing devices, such as, spatial light modulators, logic gates and multiplexers and compare their performance with other natural photoreceptors such as pharaonis phoborhodopsin, proteorhodopsin, photoactive yellow protein and the blue light plant photoreceptor phototropin.

  9. A two photon absorption laser induced fluorescence diagnostic for fusion plasmas

    SciTech Connect

    Magee, R. M.; Galante, M. E.; McCarren, D.; Scime, E. E.; Boivin, R. L.; Brooks, N. H.; Groebner, R. J.; Hill, D. N.; Porter, G. D.

    2012-10-15

    The quality of plasma produced in a magnetic confinement fusion device is influenced to a large extent by the neutral gas surrounding the plasma. The plasma is fueled by the ionization of neutrals, and charge exchange interactions between edge neutrals and plasma ions are a sink of energy and momentum. Here we describe a diagnostic capable of measuring the spatial distribution of neutral gas in a magnetically confined fusion plasma. A high intensity (5 MW/cm{sup 2}), narrow bandwidth (0.1 cm{sup -1}) laser is injected into a hydrogen plasma to excite the Lyman {beta} transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer {alpha} emission, is proportional to the number of particles with a given velocity. Calibration is performed in situ by filling the chamber to a known pressure of neutral krypton and exciting a transition close in wavelength to that used in hydrogen. We present details of the calibration procedure, including a technique for identifying saturation broadening, measurements of the neutral density profile in a hydrogen helicon plasma, and discuss the application of the diagnostic to plasmas in the DIII-D tokamak.

  10. Trapping and two-photon fluorescence excitation of microscopic objects using ultrafast single-fiber optical tweezers

    NASA Astrophysics Data System (ADS)

    Mishra, Yogeshwar N.; Ingle, Ninad; Mohanty, Samarendra K.

    2011-10-01

    Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber ultrafast optical tweezers and its use in simultaneous two-photon fluorescence (TPF) excitation of trapped fluorescent microscopic objects. Using this method, trapping depth of a few centimeters was achieved inside a colloidal sample with TPF from the trapped particle being visible to the naked eye. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of the axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Furthermore, the stability of the fiber optic trapping was confirmed by holding and maneuvering the fiber by hand so as to move the trapped fluorescent particle in three dimensions. Apart from miniaturization capability into lab-on-a-chip microfluidic devices, the proposed noninvasive microaxicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting, and ablation, as well as for two-photon fluorescence excitation of a motile sample.

  11. 5-HT spatial distribution imaging with multiphoton excitation of 5-HT correlative visible fluorescence in live cells

    NASA Astrophysics Data System (ADS)

    Zhang, Zhihong; Zeng, Shaoqun; Liu, Yafeng; Zhou, Wei; Chen, Tongsheng; Luo, Qingming

    2002-04-01

    The autofluorescence of 5-Hydroxytryptamine (5-HT) loaded rat mucosal mast cells (RBL-2H3 cells) is imaged with multiphoton excitation laser scanning microscope (MPELSM). 5-HT correlative visible fluorescence (Fco-vis) excited with 740-nm multiphoton excitation is observed in live cells for the first time, and the generating mechanism of 5-HT Fco-vis is studied. The spatial distribution of 5-HT in live cells is imaged at high spatial resolution in our experiment, which provides a new way to study the correlation between 5-HT spatial distribution and content, and the cellular functional state in live tissue or cells.

  12. Detection limits of 405 nm and 633 nm excited PpIX fluorescence for brain tumor detection during stereotactic biopsy

    NASA Astrophysics Data System (ADS)

    Markwardt, Niklas; Götz, Marcus; Haj-Hosseini, Neda; Hollnburger, Bastian; Sroka, Ronald; Stepp, Herbert; Zelenkov, Petr; Rühm, Adrian

    2016-04-01

    5-aminolevulinic-acid-(5-ALA)-induced protoporphyrin IX (PpIX) fluorescence may be used to improve stereotactic brain tumor biopsies. In this study, the sensitivity of PpIX-based tumor detection has been investigated for two potential excitation wavelengths (405 nm, 633 nm). Using a 200 μm fiber in contact with semi-infinite optical phantoms containing ink and Lipovenös, PpIX detection limits of 4.0 nM and 200 nM (relating to 1 mW excitation power) were determined for 405 nm and 633 nm excitation, respectively. Hence, typical PpIX concentrations in glioblastomas of a few μM should be well detectable with both wavelengths. Additionally, blood layers of selected thicknesses were placed between fiber and phantom. Red excitation was shown to be considerably less affected by blood interference: A 50 μm blood layer, for instance, blocked the 405- nm-excited fluorescence completely, but reduced the 633-nm-excited signal by less than 50%. Ray tracing simulations demonstrated that - without blood layer - the sensitivity advantage of 405 nm rises for decreasing fluorescent volume from 50-fold to a maximum of 100-fold. However, at a tumor volume of 1 mm3, which is a typical biopsy sample size, the 633-nm-excited fluorescence signal is only reduced by about 10%. Further simulations revealed that with increasing fiber-tumor distance, the signal drops faster for 405 nm. This reduces the risk of detecting tumor tissue outside the needle's coverage, but diminishes the overlap between optically and mechanically sampled volumes. While 405 nm generally offers a higher sensitivity, 633 nm is more sensitive to distant tumors and considerably superior in case of blood-covered tumor tissue.

  13. Excitation Dependence of Photoinduced Absorption (PA) in Π-Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Zhai, Yaxin; Basel, Tek; Vardeny, Z. Valy

    2014-03-01

    In order to study the process of singlet fission (SF), where a singlet exciton decomposes into a pair of triplets S0 +S1 -->T1 +T1 , we have investigated the excitation dependence of the photoinduced absorption band of triplet exciton (EXPA) and photoluminescence (EXPL) in various luminescent and non-luminescent π-conjugated polymers. We found that the EXPA spectrum of luminescent polymers is composed of two steps, showing that two different channels are operative for triplet photogeneration. One process starts at the optical gap and has flat response similar to that of the EXPL spectrum. We therefore identify this process as due to intersystem crossing from the lowest lying singlet exciton. Whereas the second process with an onset at E ~ 2ET , where ET is the triplet energy is due to singlet fission of hot excitons. We also found that the EXPA spectrum of some non luminescent polymers is different from that of the luminescent polymers. Supported in part by the NSF-MRSEC program at the University of Utah.

  14. Atmospheric radical production by excitation of vibrational overtones via absorption of visible light

    NASA Astrophysics Data System (ADS)

    Donaldson, D. J.; Frost, G. J.; Rosenlof, K. H.; Tuck, A. F.; Vaida, V.

    1997-11-01

    We present calculations using a radiative transfer model which predict that in the lower stratosphere at high zenith angles, significant enhancements to the photodissociation rates of HNO3 and HNO4 can result from visible wavelength excitation of OH overtone vibrations containing sufficient energy to cleave the O-O and N-O bonds. The results indicate that atmospheric chromophores such as HONO2, HO2NO2 and H2O2, could make a potentially significant contribution to the production of HOx and NOx. Calculating the relative importance of their effect requires better knowledge of the absolute absorption cross sections, both for vibrational overtones and in the near UV. Stratospheric air masses in which this process could be important are those that experience lengthy exposure at high solar zenith angles: the outer regions of the polar winter vortex and the polar summer anticyclone. We note that the general mechanism may have application elsewhere, such as in the atmospheres of other planets and in generating the diffuse interstellar bands associated with molecular clouds.

  15. In vivo micro-vascular imaging and flow cytometry in zebrafish using two-photon excited endogenous fluorescence

    PubMed Central

    Zeng, Yan; Yan, Bo; Sun, Qiqi; He, Sicong; Jiang, Jun; Wen, Zilong; Qu, Jianan Y.

    2014-01-01

    Zebrafish has rapidly evolved as a powerful vertebrate model organism for studying human diseases. Here we first demonstrate a new label-free approach for in vivo imaging of microvasculature, based on the recent discovery and detailed characterization of the two-photon excited endogenous fluorescence in the blood plasma of zebrafish. In particular, three-dimensional reconstruction of the microvascular networks was achieved with the depth-resolved two-photon excitation fluorescence (TPEF) imaging. Secondly, the blood flow images, obtained by perpendicularly scanning the focal point across the blood vessel, provided accurate information for characterizing the hemodynamics of the circulatory system. The endogenous fluorescent signals of reduced nicotinamide adenine dinucleotide (NADH) enabled visualization of the circulating granulocytes (neutrophils) in the blood vessel. The development of acute sterile inflammation could be detected by the quantitative counting of circulating neutrophils. Finally, we found that by utilizing a short wavelength excitation at 650 nm, the commonly used fluorescent proteins, such as GFP and DsRed, could be efficiently excited together with the endogenous fluorophores to achieve four-color TPEF imaging of the vascular structures and blood cells. The results demonstrated that the multi-color imaging could potentially yield multiple view angles of important processes in living biological systems. PMID:24688803

  16. Excitation and propagation of X-ray fluorescence through thin devices with hollowed ordered structures: comparison of experimental and theoretical spectra.

    PubMed

    Mazuritskiy, M I; Dabagov, S B; Marcelli, A; Lerer, A M; Dziedzic-Kocurek, K

    2016-01-01

    The lack of models describing the propagation of X-rays in waveguides and the interference mechanism between incident and reflected radiation waves hamper the understanding and the control of wave propagation phenomena occurring in many real systems. Here, experimental spectra collected at the exit of microchannel plates (MCPs) under the total X-ray reflection condition are presented. The results are discussed in the framework of a theoretical model in which the wave propagation is enhanced by the presence of a transition layer at the surface. The angular distributions of the propagating radiation at the exit of these MCPs with microchannels of ∼3 µm diameter will also be presented and discussed. These spectra show contributions associated with the reflection of the primary monochromatic beam and with the fluorescence radiation originating from the excitation of atoms composing the surface of the microchannel. The soft X-ray fluorescence spectra collected at the exit of microcapillaries were analyzed in the framework of a wave approximation while diffraction contributions observed at the exit of these hollow X-ray waveguides have been calculated using the Fraunhofer diffraction model for waves in the far-field domain. Data collected at the Si L-edge show that in glassy MCPs the fluorescence radiation can be detected only when the energy of the primary monochromatic radiation is above the absorption edge for grazing angles higher than half of the critical angle of the total reflection phenomenon. Experimental data and simulations of the propagating radiation represent a clear experimental confirmation of the channeling phenomenon of the excited fluorescence radiation inside a medium and point out that a high transmission can be obtained in waveguide optics for parameters relevant to X-ray imaging. PMID:26698074

  17. Excited-state structural dynamics of a dual-emission calmodulin-green fluorescent protein sensor for calcium ion imaging.

    PubMed

    Oscar, Breland G; Liu, Weimin; Zhao, Yongxin; Tang, Longteng; Wang, Yanli; Campbell, Robert E; Fang, Chong

    2014-07-15

    Fluorescent proteins (FPs) have played a pivotal role in bioimaging and advancing biomedicine. The versatile fluorescence from engineered, genetically encodable FP variants greatly enhances cellular imaging capabilities, which are dictated by excited-state structural dynamics of the embedded chromophore inside the protein pocket. Visualization of the molecular choreography of the photoexcited chromophore requires a spectroscopic technique capable of resolving atomic motions on the intrinsic timescale of femtosecond to picosecond. We use femtosecond stimulated Raman spectroscopy to study the excited-state conformational dynamics of a recently developed FP-calmodulin biosensor, GEM-GECO1, for calcium ion (Ca(2+)) sensing. This study reveals that, in the absence of Ca(2+), the dominant skeletal motion is a ∼ 170 cm(-1) phenol-ring in-plane rocking that facilitates excited-state proton transfer (ESPT) with a time constant of ∼ 30 ps (6 times slower than wild-type GFP) to reach the green fluorescent state. The functional relevance of the motion is corroborated by molecular dynamics simulations. Upon Ca(2+) binding, this in-plane rocking motion diminishes, and blue emission from a trapped photoexcited neutral chromophore dominates because ESPT is inhibited. Fluorescence properties of site-specific protein mutants lend further support to functional roles of key residues including proline 377 in modulating the H-bonding network and fluorescence outcome. These crucial structural dynamics insights will aid rational design in bioengineering to generate versatile, robust, and more sensitive optical sensors to detect Ca(2+) in physiologically relevant environments. PMID:24987121

  18. Nitric oxide γ band fluorescent scattering and self-absorption in the mesosphere and lower thermosphere

    NASA Astrophysics Data System (ADS)

    Stevens, Michael H.

    1995-08-01

    The fluorescent scattering of UV sunlight and self-absorption by the nitric oxide (NO) γ bands between 2000-2500 Å are quantified for the purpose of inferring NO density profiles as a function of altitude in the mesosphere and above. Rotational line emission rate factors and cross sections are calculated at a variety of temperatures. The observed variation of the solar spectrum across the γ bands and its effect on emission rate factors are explored by using irradiance measurements that resolve features down to 0.1 Å. The model also includes quenching by O2 and N2, multiple scattering, temperature effects, attenuation of the solar irradiance by O2 and ozone, and self-absorption with the summation of adjacent rotational features. Results indicate that for resonant γ bands, the rotational structure in emission is not symmetric to that in absorption so that as self-absorption increases the shape of the observed emission envelope changes. For γ(1,0) this is largely characterized by an increase in the integrated emission observed longward of 2151 Å compared to shortward. It is found that solar irradiances measured at 0.1 Å resolution decrease the calculated γ(1,0) and γ(0,0) band emission rate factors by less than 3% compared to those measured at 2 Å resolution. However, more Fraunhofer structure included in the calculation is reflected in the relative intensities of the rotational features. It is also found that extinction of the solar irradiance by ozone and quenching by O2 rapidly reduce the γ(1,0) emission rate factor with decreasing altitude below 60 km.

  19. Laser-excited fluorescence of rare earth elements in fluorite: Initial observations with a laser Raman microprobe

    USGS Publications Warehouse

    Burruss, R.C.; Ging, T.G.; Eppinger, R.G.; Samson, a.M.

    1992-01-01

    Fluorescence emission spectra of three samples of fluorite containing 226-867 ppm total rare earth elements (REE) were excited by visible and ultraviolet wavelength lines of an argon ion laser and recorded with a Raman microprobe spectrometer system. Narrow emission lines ( 0.9 for Eu2+ and 0.99 for Er3+. Detection limits for three micrometer spots are about 0.01 ppm Eu2+ and 0.07 ppm Er3+. These limits are less than chondrite abundance for Eu and Er, demonstrating the potential microprobe analytical applications of laser-excited fluorescence of REE in fluorite. However, application of this technique to common rock-forming minerals may be hampered by competition between fluorescence emission and radiationless energy transfer processes involving lattice phonons. ?? 1992.

  20. Identification of biological molecules in situ at high resolution via the fluorescence excited by a scanning electron beam.

    PubMed Central

    Hough, P V; McKinney, W R; Ledbeter, M C; Pollack, R E; Moos, H W

    1976-01-01

    Proteins, nucleic acids, and fluorescein-conjugated antibody are shown to be identifidable in situ via the fluorescence excited by the focused electron beam of a canning electron microscope. A molecular species is identified by its characteristic fluorescence spectrum and by a characteristic alteration of the spectrum with time under the electron beam. Primary protein fluorescence is relatively rapidly destroyed by the beam, but protein photoproduct fluorescence is more rugged and will in some cases permit detection of small numbers of protein molecules. Nucleic acid fluorescence is extremely long-lived and will permit detection of small numbers of nucleic acid residues. The theoretical resolution limit for localization of a particular molecular species -- about 20 A--is determined by the known maximum distance for molecular excitation by fast electrons. Drect extapolation from an observed resolution of 900 A in the localization of nucleic acid using a low-efficiency detector leads to an experimental resolution limit of less than 60 A. Fluorescence is strongly quenched by residual water in the specimen. Similar quenching is produced by some macromolecular associations and so may serve to localize such associations. Images PMID:768980

  1. Monitor RNA synthesis in live cell nuclei by using two-photon excited fluorescence lifetime imaging microscopy

    NASA Astrophysics Data System (ADS)

    Peng, Xiao; Lin, Danying; Wang, Yan; Qi, Jing; Yan, Wei; Qu, Junle

    2015-03-01

    Probing of local molecular environment in cells is of significant value in creating a fundamental understanding of cellular processes and molecular profiles of diseases, as well as studying drug cell interactions. In order to investigate the dynamically changing in subcellular environment during RNA synthesis, we applied two-photon excited fluorescence lifetime imaging microscopy (FLIM) method to monitor the green fluorescent protein (GFP) fused nuclear protein ASF/SF2. The fluorescence lifetime of fluorophore is known to be in inverse correlation with a local refractive index, and thus fluorescence lifetimes of GFP fusions provide real-time information of the molecular environment of ASF/SF2- GFP. The FLIM results showed continuous and significant fluctuations of fluorescence lifetimes of the fluorescent protein fusions in live HeLa cells under physiological conditions. The fluctuations of fluorescence lifetime values indicated the variations of activities of RNA polymerases. Moreover, treatment with pharmacological drugs inhibiting RNA polymerase activities led to irreversible decreases of fluorescence lifetime values. In summary, our study of FLIM imaging of GFP fusion proteins has provided a sensitive and real-time method to investigate RNA synthesis in live cell nuclei.

  2. Interconfigurational absorption and two-photon excitation spectra of PtCl sub 6 sub 2 minus -containing crystals

    SciTech Connect

    Yoo, Ryong, K.; Keiderling, T.A. )

    1990-10-18

    Low-temperature absorption and two-photon excitation spectra of complexes containing PtCl{sub 6}{sup 2{minus}} are presented and discussed. One-photon absorption spectra with moderately well resolved vibronic structure were obtained for PtCl{sub 6}{sup 2{minus}} in dilute mixed crystals. The data show that a transition to a low-lying interconfigurational state is located at {approximately} 18,000 cm{sup {minus}1} in the spectral frequency region below the first absorption transition previously assigned by others. This transition cannot be unambiguously assigned. If it corresponds to the same excited state responsible for the PtCl{sub 6}{sup 2{minus}} emission spectrum, this would lead to a partial reassignment of the excited states from that of earlier work. Ligand field calculations consistent with such a reassignment are presented. The two-photon excitation (TPE) spectra of the mixed Cs{sub 2}ZrCl{sub 6}:PtCl{sub 6}{sup 2{minus}} and pure K{sub 2}PtCl{sub 6} (at 77 K), measured with an improved spectrometer, show a noticeable improvement in signal-to-noise ratio compared to the previously reported TPE spectra of K{sub 2}PtCl{sub 6} and are assigned to higher energy d-d transitions.

  3. Absorption, fluorescence, and acid-base equilibria of rhodamines in micellar media of sodium dodecyl sulfate.

    PubMed

    Obukhova, Elena N; Mchedlov-Petrossyan, Nikolay O; Vodolazkaya, Natalya A; Patsenker, Leonid D; Doroshenko, Andrey O; Marynin, Andriy I; Krasovitskii, Boris M

    2017-01-01

    Rhodamine dyes are widely used as molecular probes in different fields of science. The aim of this paper was to ascertain to what extent the structural peculiarities of the compounds influence their absorption, emission, and acid-base properties under unified conditions. The acid-base dissociation (HR(+)⇄R+H(+)) of a series of rhodamine dyes was studied in sodium n-dodecylsulfate micellar solutions. In this media, the form R exists as a zwitterion R(±). The indices of apparent ionization constants of fifteen rhodamine cations HR(+) with different substituents in the xanthene moiety vary within the range of pKa(app)=5.04 to 5.53. The distinct dependence of emission of rhodamines bound to micelles on pH of bulk water opens the possibility of using them as fluorescent interfacial acid-base indicators. PMID:27423469

  4. Energy transfer in the inhomogeneously broadened core antenna of purple bacteria: a simultaneous fit of low-intensity picosecond absorption and fluorescence kinetics.

    PubMed Central

    Pullerits, T; Visscher, K J; Hess, S; Sundström, V; Freiberg, A; Timpmann, K; van Grondelle, R

    1994-01-01

    The excited state decay kinetics of chromatophores of the purple photosynthetic bacterium Rhodospirillum rubrum have been recorded at 77 K using picosecond absorption difference spectroscopy under strict annihilation free conditions. The kinetics are shown to be strongly detection wavelength dependent. A simultaneous kinetic modeling of these experiments together with earlier fluorescence kinetics by numerical integration of the appropriate master equation is performed. This model, which accounts for the spectral inhomogeneity of the core light-harvesting antenna of photosynthetic purple bacteria, reveals three qualitatively distinct stages of excitation transfer with different time scales. At first a fast transfer to a local energy minimum takes place (approximately 1 ps). This is followed by a much slower transfer between different energy minima (10-30 ps). The third component corresponds to the excitation transfer to the reaction center, which depends on its state (60 and 200 ps for open and closed, respectively) and seems also to be the bottleneck in the overall trapping time. An acceptable correspondence between theoretical and experimental decay kinetics is achieved at 77 K and at room temperature by assuming that the width of the inhomogeneous broadening is 10-15 nm and the mean residence time of the excitation in the antenna lattice site is 2-3 ps. PMID:8130341

  5. Two-photon excited fluorescence spectroscopy and imaging of melanin in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Krasieva, Tatiana B.; Liu, Feng; Sun, Chung-Ho; Kong, Yu; Balu, Mihaela; Meyskens, Frank L.; Tromberg, Bruce J.

    2012-03-01

    The ability to detect early melanoma non-invasively would improve clinical outcome and reduce mortality. Recent advances in two-photon excited fluorescence (TPEF) in vivo microscopy offer a powerful tool in early malignant melanoma diagnostics. The goal of this work was to develop a TPEF optical index for measuring relative concentrations of eumelanin and pheomelanin since ex vivo studies show that changes in this ratio have been associated with malignant transformation. We acquired TPEF emission spectra (λex=1000 nm) of melanin from several specimens, including human hair, malignant melanoma cell lines, and normal melanocytes and keratinocytes in different skin layers (epidermis, papillary dermis) in five healthy volunteers in vivo. We found that the pheomelanin emission peaks at around 620 nm and is blue-shifted from the eumelanin with broad maximum at 640-680nm. We defined "optical melanin index" (OMI) as a ratio of fluorescence signal intensities measured at 645 nm and 615nm. The measured OMI for a melanoma cell line MNT-1 was 1.6+/-0.2. The MNT-46 and MNT-62 lines (Mc1R gene knockdown) showed an anticipated change in melanins production ratio and had OMI of 0.55+/-0.05 and 0.17+/-0.02, respectively, which strongly correlated with HPLC data obtained for these lines. Average OMI measured for basal cells layers (melanocytes and keratinocytes) in normal human skin type I, II-III (not tanned and tanned) in vivo was 0.5, 1.05 and 1.16 respectively. We could not dependably detect the presence of pheomelanin in highly pigmented skin type V-VI. These data suggest that a non-invasive TPEF index could potentially be used for rapid melanin ratio characterization both in vitro and in vivo, including pigmented lesions.

  6. Optimal Spectral Regions For Laser Excited Fluorescence Diagnostics For Point Of Care Application

    NASA Astrophysics Data System (ADS)

    Vaitkuviene, A.; Gėgžna, V.; Varanius, D.; Vaitkus, J.

    2011-09-01

    The tissue fluorescence gives the response of light emitting molecule signature, and characterizes the cell composition and peculiarities of metabolism. Both are useful for the biomedical diagnostics, as reported in previous our and others works. The present work demonstrates the results of application of laser excited autofluorescence for diagnostics of pathology in genital tissues, and the feasibility for the bedside at "point of care—off lab" application. A portable device using the USB spectrophotometer, micro laser (355 nm Nd:YAG, 0,5 ns pulse, repetition rate 10 kHz, output power 15 mW), three channel optical fiber and computer with diagnostic program was designed and ready for clinical trial to be used for cytology and biopsy specimen on site diagnostics, and for the endoscopy/puncture procedures. The biopsy and cytology samples, as well as intervertebral disc specimen were evaluated by pathology experts and the fluorescence spectra were investigated in the fresh and preserved specimens. The spectra were recorded in the spectral range 350-900 nm. At the initial stage the Gaussian components of spectra were found and the Mann-Whitney test was used for the groups' differentiation and the spectral regions for optimal diagnostics purpose were found. Then a formal dividing of spectra in the components or the definite width bands, where the main difference of the different group spectra was observed, was used to compare these groups. The ROC analysis based diagnostic algorithms were created for medical prognosis. The positive prognostic values and negative prediction values were determined for cervical Liquid PAP smear supernatant sediment diagnosis of being Cervicitis and Norma versus CIN2+. In a case of intervertebral disc the analysis allows to get the additional information about the disc degeneration status. All these results demonstrated an efficiency of the proposed procedure and the designed device could be tested at the point-of-care site or for

  7. Quantitative Decoupling of Excited-State Absorption Cross Section and Population via Pump-Probe Spectroscopy with a Strong Probe

    NASA Astrophysics Data System (ADS)

    Barker, Alex J.; Hodgkiss, Justin M.

    2015-08-01

    Photoinduced absorption signals measured by transient absorption spectroscopy are typically proportional to the product of absorption cross section (σ ) and excited-state density (N ). We show that this approximation does not hold at high probe-pulse intensities, and introduce the use of probe-intensity-dependent spectroscopy to decouple the two parameters. The singlet excited-state (S1→S2) absorption cross section of the conjugated polymer F8BT is measured to be 1.6 ×10-16 cm2±40 % at 800 nm and 3.7×10 -16 cm2±30 % at 900 nm, with no variation over the time window surveyed. The robustness of these parameters is established by observing that only N scales with excitation fluence and time delay, and conversely only σ is dependent on probe wavelength. The technique may be useful for quantifying salient parameters in many systems, such as branching yields in systems exhibiting singlet fission or triplet production, or cross sections required for photophysical models.

  8. First-principles calculation of ground and excited-state absorption spectra of ruby and alexandrite considering lattice relaxation

    NASA Astrophysics Data System (ADS)

    Watanabe, Shinta; Sasaki, Tomomi; Taniguchi, Rie; Ishii, Takugo; Ogasawara, Kazuyoshi

    2009-02-01

    We performed first-principles calculations of multiplet structures and the corresponding ground-state absorption and excited-state absorption spectra for ruby (Cr3+:α-Al2O3) and alexandrite (Cr3+:BeAl2O4) which included lattice relaxation. The lattice relaxation was estimated using the first-principles total energy and molecular-dynamics method of the CASTEP code. The multiplet structure and absorption spectra were calculated using the configuration-interaction method based on density-functional calculations. For both ruby and alexandrite, the theoretical absorption spectra, which were already in reasonable agreement with experimental spectra, were further improved by consideration of lattice relaxation. In the case of ruby, the peak positions and peak intensities were improved through the use of models with relaxations of 11 or more atoms. For alexandrite, the polarization dependence of the U band was significantly improved, even by a model with a relaxation of only seven atoms.

  9. Base pairing enhances fluorescence and favors cyclobutane dimer formation induced upon absorption of UVA radiation by DNA.

    PubMed

    Banyasz, Akos; Vayá, Ignacio; Changenet-Barret, Pascale; Gustavsson, Thomas; Douki, Thierry; Markovitsi, Dimitra

    2011-04-13

    The photochemical properties of the DNA duplex (dA)(20)·(dT)(20) are compared with those of the parent single strands. It is shown that base pairing increases the probability of absorbing UVA photons, probably due to the formation of charge-transfer states. UVA excitation induces fluorescence peaking at ∼420 nm and decaying on the nanosecond time scale. The fluorescence quantum yield, the fluorescence lifetime, and the quantum yield for cyclobutane dimer formation increase upon base pairing. Such behavior contrasts with that of the UVC-induced processes. PMID:21417388

  10. Fluorescence Excitation Models of Ammonia and Amidogen Radical (NH2) in Comets: Application to Comet C/2004 Q2 (Machholz)

    NASA Technical Reports Server (NTRS)

    Kawakita, Hideyo; Mumma, Michael J.

    2011-01-01

    Ammonia is a major reservoir of nitrogen atoms in cometary materials. However, detections of ammonia in comets are rare, with several achieved at radio wavelengths. A few more detections were obtained through near-infrared observations (around the 3 m wavelength region), but moderate relative velocity shifts are required to separate emission lines of cometary ammonia from telluric absorption lines in the 3 micron wavelength region. On the other hand, the amidogen radical (NH2 -- a photodissociation product of ammonia in the coma) also shows rovibrational emission lines in the 3 micron wavelength region. Thus, gas production rates for ammonia can be determined from the rovibrational emission lines of ammonia (directly) and amidogen radical (indirectly) simultaneously in the near-infrared. In this article, we present new fluorescence excitation models for cometary ammonia and amidogen radical in the near-infrared, and we apply these models to the near-infrared high-dispersion spectra of comet C/2004 Q2 (Machholz) to determine the mixing ratio of ammonia to water in the comet. Based on direct detection of NH3 lines, the mixing ratio of NH3/H2O is 0.46% +/- 0.03% in C/2004 Q2 (Machholz), in agreement with other results. The mixing ratio of ammonia determined from the NH2 observations (0.31% -- 0.79%) is consistent but has relatively larger error, owing to uncertainty in the photodissociation rates of ammonia. At the present level of accuracy, we confirm that NH3 could be the sole parent of NH2 in this comet.

  11. Airborne intercomparison of vacuum ultraviolet fluorescence and tunable diode laser absorption measurements of tropospheric carbon monoxide

    NASA Astrophysics Data System (ADS)

    Holloway, John S.; Jakoubek, Roger O.; Parrish, David D.; Gerbig, Christoph; Volz-Thomas, Andreas; Schmitgen, Sandra; Fried, Alan; Wert, Brian; Henry, Bruce; Drummond, James R.

    2000-01-01

    During the fall 1997 North Atlantic Regional Experiment (NARE 97), two separate intercomparisons of aircraft-based carbon monoxide measurement instrumentation were conducted. On September 2, CO measurements were simultaneously made aboard the National Oceanic and Atmospheric Administration (NOAA) WP-3 by vacuum ultraviolet (VUV) fluorescence and by tunable diode laser absorption spectroscopy (TDLAS). On September 18, an intercomparison flight was conducted between two separate instruments, both employing the VUV fluorescence method, on the NOAA WP-3 and the U.K. Meteorological Office C-130 Hercules. The results indicate that both of the VUV fluorescence instruments and the TDLAS system are capable of measuring ambient CO accurately and precisely with no apparent interferences in 5 s. The accuracy of the measurements, based upon three independent calibration systems, is indicated by the agreement to within 11% with systematic offsets of less than 1 ppbv. In addition, one of the groups participated in the Measurement of Air Pollution From Satellite (MAPS) intercomparison [Novelli et al., 1998] with a different measurement technique but very similar calibration system, and agreed with the accepted analysis to within 5%. The precision of the measurements is indicated by the variability of the ratio of simultaneous measurements from the separate instruments. This variability is consistent with the estimated precisions of 1.5 ppbv and 2.2 ppbv for the 5 s average results of the C-130 and the WP-3 instruments, respectively, and indicates a precision of approximately 3.6% for the TDLAS instrument. The excellent agreement of the instruments in both intercomparisons demonstrates that significant interferences in the measurements are absent in air masses that ranged from 7 km in the midtroposphere to boundary layer conditions including subtropical marine air and continental outflow with embedded urban plumes. The intercomparison of the two VUV instruments that differed widely

  12. pH-Induced changes in electronic absorption and fluorescence spectra of phenazine derivatives

    NASA Astrophysics Data System (ADS)

    Ryazanova, O. A.; Voloshin, I. M.; Makitruk, V. L.; Zozulya, V. N.; Karachevtsev, V. A.

    2007-04-01

    The visible electronic absorption and fluorescence spectra as well as fluorescence polarization degrees of imidazo-[4,5-d]-phenazine (F1), 2-methylimidazo-[4,5-d]-phenazine (F2), 2-trifluoridemethylimidazo-[4,5-d]-phenazine (F3), 1,2,3-triazole-[4,5-d]-phenazine (F4) and their glycosides, imidazo-[4,5-d]-phenazine-N1-β- D-ribofuranoside (F1rib), 1,2,3-triazole-[4,5-d]-phenazine-N1-β- D-glucopyranoside (F4gl), were investigated in aqueous buffered solutions over the pH range of 0-12, where the spectral transformations were found to be reversible. The effects of protonation and deprotonation on spectral properties of these dyes were studied. We have determined the ranges of pH, where individual ionic species are predominant. In aqueous buffered solutions the fluorescence was found only for neutral species of F1, F1rib, F2, and F4gl dyes, whereas for the ionic forms of these dyes, as well as for F3 and F4 ones, the fluorescence has not been detected. The concentrational deprotonation p Ka values were evaluated from experimental data. It was shown that donor-acceptor properties of the substituent group in the second position of the pentagonal ring substantially affect the values of the deprotonation constants and the character of protonation for chromophore. The substitution of a hydrogen atom in the NH-group by the sugar residue blocks the formation of the anionic species, and results in enhancement of the dye emission intensity. The steep emission dependence for F1 and F1rib over pH range of 0-7 with intensities ratio of IpH 7/ IpH 1 = 60 allows us to propose them as possible indicator dyes in luminescence based pH sensors for investigation of processes accompanied by acidification, e.g. as gastric pH-sensors. A comparative analysis of the studied dyes has shown that F4gl is the most promising compound to be used as a fluorescent probe for investigation of molecular hybridization of nucleic acids.

  13. Absorption and fluorescence characteristics of chromophoric dissolved organic matter in the Yangtze Estuary.

    PubMed

    Sun, Qiyuan; Wang, Chao; Wang, Peifang; Hou, Jun; Ao, Yanhui

    2014-03-01

    The Yangtze Estuary is heavily influenced by coast-continent geochemical processes and anthropogenic activity; thus, the source and distribution of chromophoric dissolved organic matter (CDOM) in the estuary are strongly impacted by these processes. Here, a series of samples were collected from across the Yangtze Estuary to investigate the source and spatial dynamics of CDOM and its components throughout the system. Three indices (a(355), spectral slope, and fluorescence) were then calculated and interpreted. The results indicated that the distribution of CDOM was dominated by allochthonous input, conservative mixing, and phase transfer. The contribution of biogenic CDOM to total CDOM increased with salinity, and three individual CDOM components were identified upon fluorescence excitation emission matrix spectroscopy and parallel factor analysis of the water samples: C1, corresponding to humic substance-like CDOM, C2, corresponding to tryptophan-like CDOM, and C3, corresponding to tyrosine-like CDOM. C1 primarily originated from a terrestrial source, C2 had widespread origins, none of which played a dominant role, and C3 mainly originated from allochthonous input in the medium salinity area. Unexpectedly, no marine humic-like component was found in the surface water of the Yangtze Estuary, possibly because turbidity decreased the depth of sunlight penetration, limiting production of this component. PMID:24243263

  14. Heavy Metals Effect on Cyanobacteria Synechocystis aquatilis Study Using Absorption, Fluorescence, Flow Cytometry, and Photothermal Measurements

    NASA Astrophysics Data System (ADS)

    Dudkowiak, A.; Olejarz, B.; Łukasiewicz, J.; Banaszek, J.; Sikora, J.; Wiktorowicz, K.

    2011-04-01

    The toxic effect of six heavy metals on cyanobacteria Synechocystis aquatilis was studied by absorption, fluorescence, flow cytometry, and photothermal measurements. This study indicates that at the concentration used, the cyanobacteria are more sensitive to silver, copper, and mercury than to cadmium, lead, and zinc metals. Disregarding the decrease in the yields of the related radiative processes caused by photochemical processes and/or damage to phycobilisomes, no changes were detected in the efficiency of thermal deactivation processes within a few microseconds, which can indicate the lack of disturbances in the photosynthetic light reaction and the lack of damage to the photosystem caused by the heavy metal ions in the concentrations used. The results demonstrate that the relative values of fluorescence yield as well as promptly generated heat calculated for the metal-affected and unaffected (reference) bacteria are sensitive indicators of environmental pollution with heavy metal ions, whereas the complementary methods proposed could be used as a noninvasive and fast procedure for in vivo assessment of their toxicity.

  15. Determination of mercury distribution inside spent compact fluorescent lamps by atomic absorption spectrometry

    SciTech Connect

    Rey-Raap, Natalia

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer New treatments for CFL are required considering the aim of Directive 202/96/CE. Black-Right-Pointing-Pointer It is shown that most of the mercury introduced into a CFL is in the phosphor powder. Black-Right-Pointing-Pointer Experimental conditions for microwave-assisted sample digestion followed by AAS measurements are described. Black-Right-Pointing-Pointer By washing the glass it is possible to reduce the concentration below legal limits. - Abstract: In this study, spent compact fluorescent lamps were characterized to determine the distribution of mercury. The procedure used in this research allowed mercury to be extracted in the vapor phase, from the phosphor powder, and the glass matrix. Mercury concentration in the three phases was determined by the method known as cold vapor atomic absorption spectrometry. Median values obtained in the study showed that a compact fluorescent lamp contained 24.52 {+-} 0.4 ppb of mercury in the vapor phase, 204.16 {+-} 8.9 ppb of mercury in the phosphor powder, and 18.74 {+-} 0.5 ppb of mercury in the glass matrix. There are differences in mercury concentration between the lamps since the year of manufacture or the hours of operation affect both mercury content and its distribution. The 85.76% of the mercury introduced into a compact fluorescent lamp becomes a component of the phosphor powder, while more than 13.66% is diffused through the glass matrix. By washing and eliminating all phosphor powder attached to the glass surface it is possible to classified the glass as a non-hazardous waste.

  16. Excitations, optical absorption spectra, and optical excitonic gaps of heterofullerenes: I. C60, C59N+ and C48N12

    SciTech Connect

    Xie, R; Bryant, G W; Sun, G; C.Nicklaus, M; Heringer, D; Frauenheim, T; Manaa, M R; Smith, Jr., V H; Araki, Y; Ito, O

    2003-10-02

    Low-energy excitations and optical absorption spectrum of C{sub 60} are computed by using time-dependent (TD) Hartree-Fock (HF), TD-density functional theory (TD-DFT), TD-DFT-based tight-binding (TD-DFT-TB) and a semiempirical ZINDO method. A detailed comparison of experiment and theory for the excitation energies, optical gap and absorption spectrum of C{sub 60} is presented. It is found that electron correlations and collective effects of exciton pairs play important roles in assigning accurately the spectral features of C{sub 60} and the TD-DFT method with non-hybrid functionals or a local spin density approximation leads to more accurate excitation energies than with hybrid functionals. The level of agreement between theory and experiment for C{sub 60} justifies similar calculations of the excitations and optical absorption spectrum of a monomeric azafullerene cation C{sub 59}N{sup +} exhibits distinguishing spectral features different from C{sub 60}: (1) the first singlet is dipole-allowed and the optical gap is redshifted by 1.44 eV; (2) several weaker absorption maxima occur in the visible region; (3) the transient triplet-triplet absorption at 1.60 eV (775 nm) is much broader and the decay of the triplet state is much faster. The calculated spectra of C{sub 59}N{sup +} characterize and explain well our measured ultraviolet-visible (UV-vis) and transient absorption spectra of the carborane anion salt [C{sub 59}N][Ag(CB{sub 11}H{sub 6}Cl{sub 6}){sub 2}]. For the most stable isomer of C{sub 48}N{sub 12}, we predict that the first singlet is dipole-allowed, the optical gap is redshifted by 1.22 eV relative to that of C{sub 60}, and optical absorption maxima occur at 585, 528, 443, 363, 340, 314 and 303 nm. We point out that the characterization of the UV-vis and transient absorption spectra of C{sub 48}N{sub 12} isomers is helpful in distinguishing the isomer structures required for applications in molecular electronics. For C{sub 59}N{sup +} and C{sub 48}N

  17. Seasonal characterization of CDOM for lakes in semiarid regions of Northeast China using excitation-emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC)

    NASA Astrophysics Data System (ADS)

    Zhao, Ying; Song, Kaishan; Wen, Zhidan; Li, Lin; Zang, Shuying; Shao, Tiantian; Li, Sijia; Du, Jia

    2016-03-01

    The seasonal characteristics of fluorescent components in chromophoric dissolved organic matter (CDOM) for lakes in the semiarid region of Northeast China were examined by excitation-emission matrix (EEM) spectra and parallel factor analysis (PARAFAC). Two humic-like (C1 and C2) and protein-like (C3 and C4) components were identified using PARAFAC. The average fluorescence intensity of the four components differed under seasonal variation from June and August 2013 to February and April 2014. Components 1 and 2 exhibited a strong linear correlation (R2 = 0.628). Significantly positive linear relationships between CDOM absorption coefficients a(254) (R2 = 0.72, 0.46, p < 0.01), a(280) (R2 = 0.77, 0.47, p < 0.01), a(350) (R2 = 0.76, 0.78, p < 0.01) and Fmax for two humic-like components (C1 and C2) were exhibited, respectively. A significant relationship (R2 = 0.930) was found between salinity and dissolved organic carbon (DOC). However, almost no obvious correlation was found between salinity and EEM-PARAFAC-extracted components except for C3 (R2 = 0.469). Results from this investigation demonstrate that the EEM-PARAFAC technique can be used to evaluate the seasonal dynamics of CDOM fluorescent components for inland waters in the semiarid regions of Northeast China, and to quantify CDOM components for other waters with similar environmental conditions.

  18. Two-photon excited transient absorption in poly(9,9'-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine)

    NASA Astrophysics Data System (ADS)

    Zhang, Xinping; Xia, Yajun; Silva, Carlos; Friend, Richard H.

    2006-06-01

    We investigate femtosecond transient absorption in the visible range in a solution sample of poly(9,9'-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine), TFB, using two-photon excitation at 800 nm (1.55 eV). A rapid probe absorbing process taking place within the temporal overlap between the pump and probe pulses was observed in the whole visible spectral range (430 nm to 700 nm), which resulted from the combination of a transition from 1A g to mA g via absorbing one pump and one probe photon and a further transition from mA g to nB u state due to the pump-induced transient population on mA g. A long-lived slow process following the rapid one is interpreted as a combination of 1B u absorption for transitions to a higher-lying state of kA g and charge absorption. These excitation and absorption channels, as well as the mechanisms of charge separation, were resolved and evaluated quantitatively by the pump-intensity dependence of the transient absorption dynamics.

  19. Temperature-dependent excitonic photoluminescence excited by two-photon absorption in perovskite CsPbBr_3 quantum dots

    NASA Astrophysics Data System (ADS)

    Wei, Ke; Xu, Zhongjie; Chen, Runze; Zheng, Xin; Cheng, Xiangai; Jiang, Tian

    2016-08-01

    Recently lead halide nanocrystals (quantum dots) have been reported with potential for photovoltaic and optoelectronic applications due to their excellent luminescent properties. Herein excitonic photoluminescence (PL) excited by two-photon absorption in perovskite CsPbBr3 quantum dots (QDs) have been studied across a broad temperature range from 80K to 380K. Two-photon absorption has been investigated with absorption coefficient up to 0.085 cm/GW at room temperature. Moreover, the photoluminescence excited by two-photon absorption shows a linear blue-shift (0.25meV/K) below temperature of ~220K and turned steady with fluctuation below 1nm (4.4meV) for higher temperature up to 380K. These phenomena are distinctly different from general red-shift of semiconductor and can be explained by the competition between lattice expansion and electron-phonon couplling.Our results reveal the strong nonlinear absorption and temperature-independent chromaticity in a large temperature range from 220K to 380K in the CsPbX3 QDs, which will offer new opportunities in nonlinear photonics, light-harvesting and light-emitting devices.

  20. Picosecond excite-and-probe absorption measurement of the 4T2 state nonradiative lifetime in ruby

    NASA Technical Reports Server (NTRS)

    Gayen, S. K.; Wang, W. B.; Petricevic, V.; Dorsinville, R.; Alfano, R. R.

    1985-01-01

    In a picosecond excite-and-probe absorption measurement, a 527-nm picosecond pulse excites the 4T2 state of the Cr(3+) ion in ruby and a 3.4-micron picosecond probe pulse monitors the growth and decay of population in the 2E state as a function of pump-probe delay. From the growth of population in the metastable 2E state, an upper limit of 7 ps for the nonradiative lifetime of the 4T2 state is determined.

  1. Fluorescence excitation and emission spectroscopy on single MEH-PPV chains at low temperature.

    PubMed

    Feist, Florian A; Basché, Thomas

    2008-08-14

    Fluorescence emission and excitation spectra of single MEH-PPV polymer molecules dispersed in thin PMMA films have been recorded at 1.2 and 20 K. We observe single as well as multichromophore emission in single chain emission spectra, whereby the relative fractions depend on the two different molecular weights (50 and 350 kDa) studied. The molecular weight also affects the distribution of peak emission maxima, which is monomodal (bimodal) for the low (high) molecular weight. The appearance of an additional "red" subpopulation for the high molecular weight sample is attributed to interactions of multiple chromophores from a sufficiently flexible single chain. The comparison of emission spectra appearing in the "blue" as well as "red" subpopulations suggests that these intrachain interactions rather lead to ground-state aggregates than excimers. Independent of the molecular weight, large variations in spectral shape and apparent line width in the emission spectra have been observed. Occasionally, we find very narrow purely electronic zero-phonon lines both in emission and in excitation spectra, with line widths down to the instrumental resolution. In accordance with earlier literature data it is argued that linear electron-phonon coupling should be quite strong for MEH-PPV in PMMA, leading to only a small fraction of chromophores exhibiting zero-phonon lines. In addition, spectral diffusion, which manifests itself by several time-dependent line shifting and broadening phenomena, contributes to the substantial variations of spectral shapes. Excitation experiments with particularly stable chromophores provide an upper limit for the optical line width (approximately 0.1 cm(-1)), which at 1.2 K can actually approach the lifetime-limited homogeneous width. Raising the temperature to 20 K leads to line broadening and typically, to disappearance of zero-phonon lines. The failure to observe zero-phonon lines of chromophores supposedly serving as donors in intramolecular

  2. Excited-State-Proton-Transfer-Triggered Fluorescence Resonance Energy Transfer: from 2-Naphthylamine to Phenosafranin

    NASA Astrophysics Data System (ADS)

    Ghosh, Debanjana; Bose, Debosreeta; Sarkar, Deboleena; Chattopadhyay, Nitin

    2009-09-01

    Excited-state proton transfer (ESPT) and fluorescence resonance energy transfer (FRET) have been linearly coupled leading to an efficient pH-sensitive energy transfer from 2-naphthylamine (2NA) to a potentially bioactive cationic phenazinium dye, phenosafranin (PSF). The prototropic product produced exclusively from the photoexcited 2NA in the presence of added alkali serves as the donor for the energy transfer process. The energy transfer process is turned on at pH ≥ 12, whereas the process is turned off at a pH lower than that. Within the range of pH 12 to 13, the energy transfer efficiency (E) has been shown to follow a linear relation with the solution pH establishing the governing role of pH of the solution on the energy transfer process. The energy transfer follows a long-range dipole-dipole interaction mechanism. The critical energy transfer distance (R0) and the distance between the acceptor and the donor (r) have been determined for the ESPT-promoted FRET process at an optimum pH of 13. The present study involving the coupled processes is simple but has its implication due to its potential to be exploited for designing a pH-sensitive molecular switch.

  3. Focused fluorescence excitation with time-reversed ultrasonically encoded light and imaging in thick scattering media

    NASA Astrophysics Data System (ADS)

    Lai, Puxiang; Suzuki, Yuta; Xu, Xiao; Wang, Lihong V.

    2013-07-01

    Scattering dominates light propagation in biological tissue, and therefore restricts both resolution and penetration depth in optical imaging within thick tissue. As photons travel into the diffusive regime, typically 1 mm beneath human skin, their trajectories transition from ballistic to diffusive due to the increased number of scattering events, which makes it impossible to focus, much less track, photon paths. Consequently, imaging methods that rely on controlled light illumination are ineffective in deep tissue. This problem has recently been addressed by a novel method capable of dynamically focusing light in thick scattering media via time reversal of ultrasonically encoded (TRUE) diffused light. Here, using photorefractive materials as phase conjugate mirrors, we show a direct visualization and dynamic control of optical focusing with this light delivery method, and demonstrate its application for focused fluorescence excitation and imaging in thick turbid media. These abilities are increasingly critical for understanding the dynamic interactions of light with biological matter and processes at different system levels, as well as their applications for biomedical diagnosis and therapy.

  4. Ultrafast fluorescence resonance energy transfer in a reverse micelle: Excitation wavelength dependence

    NASA Astrophysics Data System (ADS)

    Mondal, Sudip Kumar; Ghosh, Subhadip; Sahu, Kalyanasis; Mandal, Ujjwal; Bhattacharyya, Kankan

    2006-12-01

    Fluorescence resonance energy transfer (FRET) from coumarin 480 (C480) to fluorescein 548 (F548) in a sodium dioctyl sulfosuccinate (AOT) reverse micelle is studied by picosecond and femtosecond emission spectroscopy. In bulk water, at the low concentration of the donor (C480) and the acceptor (F548), no FRET is observed. However, when the donor (C480) and the acceptor (F548) are confined in a AOT reverse micelle very fast FRET is observed. The time constants of FRET were obtained from the rise time of the emission of the acceptor (F548). In a AOT microemulsion, FRET is found to occur in multiple time scales—3, 200, and 2700ps. The 3ps component is assigned to FRET in the water pool of the reverse micelle with a donor-acceptor distance, 16Å. The 200ps component corresponds to a donor-acceptor distance of 30Å and is ascribed to the negatively charged acceptor inside the water pool and the neutral donor inside the alkyl chains of AOT. The very long 2700ps component may arise due to FRET from a donor outside the micelle to an acceptor inside the water pool and also from diffusion of the donor from bulk heptane to the reverse micelle. With increase in the excitation wavelength from 375to405nm the relative contribution of the FRET due to C480 in the AOT reverse micelle (the 3 and 200ps components) increases.

  5. Ultrafast fluorescence resonance energy transfer in a reverse micelle: excitation wavelength dependence.

    PubMed

    Mondal, Sudip Kumar; Ghosh, Subhadip; Sahu, Kalyanasis; Mandal, Ujjwal; Bhattacharyya, Kankan

    2006-12-14

    Fluorescence resonance energy transfer (FRET) from coumarin 480 (C480) to fluorescein 548 (F548) in a sodium dioctyl sulfosuccinate (AOT) reverse micelle is studied by picosecond and femtosecond emission spectroscopy. In bulk water, at the low concentration of the donor (C480) and the acceptor (F548), no FRET is observed. However, when the donor (C480) and the acceptor (F548) are confined in a AOT reverse micelle very fast FRET is observed. The time constants of FRET were obtained from the rise time of the emission of the acceptor (F548). In a AOT microemulsion, FRET is found to occur in multiple time scales--3, 200, and 2700 ps. The 3 ps component is assigned to FRET in the water pool of the reverse micelle with a donor-acceptor distance, 16 A. The 200 ps component corresponds to a donor-acceptor distance of 30 A and is ascribed to the negatively charged acceptor inside the water pool and the neutral donor inside the alkyl chains of AOT. The very long 2700 ps component may arise due to FRET from a donor outside the micelle to an acceptor inside the water pool and also from diffusion of the donor from bulk heptane to the reverse micelle. With increase in the excitation wavelength from 375 to 405 nm the relative contribution of the FRET due to C480 in the AOT reverse micelle (the 3 and 200 ps components) increases. PMID:17176157

  6. The correction fluorescence inner filter effect using a single excitation and dual-emission fiber optic probe.

    PubMed

    Zeng, Li-Hua; Wang, Cong; Wang, Tan; Li, Dao-Liang

    2016-09-21

    A significant disadvantage of fluorometry is the inner filter effect when the fluorophore concentration is high. A new simple fiber-optic probe was made to measure the concentration of fluorescent solutions. The proposed probe consists of one excitation fiber and two emission fibers. One emission fiber is parallel to the excitation fiber, and the other has a tilted angle with the excitation fiber. A numerical model was used to optimize the tilted angle and distance of the three fibers. There was a linear relationship between the fluorophore concentration and the ratio of the fluorescence intensity of the two emission fibers. Using our homemade probe, we measured Eosin Y, fluorescein and quinine sulfate solutions. The linear range of Eosin Y solution was up to 500 μM, which was approximately 7 times the range measured with a single emission probe. The results of fluorescein and quinine sulfate solutions also showed that the fluorescence intensity ratio method could correct the inner filter effect. The experimental results also indicated that the probe is robust when the excitation light fluctuates. PMID:27334633

  7. Synthesis, crystal structure and DFT studies of a dual fluorescent ketamine: Structural changes in the ground and excited states

    NASA Astrophysics Data System (ADS)

    Latha, V.; Balakrishnan, C.; Neelakantan, M. A.

    2015-07-01

    A fluorescent probe 2Z,2‧Z-3,3‧-(4,4‧-methylenebis(4,1-phenylene) bis(azanediyl))bis (1,3-diphenylprop-2-en-1-one) (L) was synthesized and characterized by IR, 1H NMR, ESI-mass, UV-visible and fluorescence spectral techniques. The single crystal analysis illustrates the existence of L in ketamine form. The crystal structure is stabilized by intramolecular and intermolecular hydrogen bonding. The thermal stability of L was studied by TG analysis. The fluorescence spectrum of L shows dual emission, and is due to excited state intramolecular proton transfer (ESIPT) process. This is supported by the high Stokes shift value. Electronic structure calculations of L in the ground and excited state have been carried out using DFT and TD-DFT at B3LYP/6-31G (d,p) level, respectively. The vibrational spectrum was computed at this level and compared with experimental values. Major orbital contributions for the electronic transitions were assigned with the help of TD-DFT. The changes in the Mulliken charge, bond lengths and bond angles between the ground and excited states of the tautomers demonstrate that twisted intramolecular charge transfer (TICT) process occurs along with ESIPT in the excited state.

  8. Microwave-assisted synthesis of water-soluble, fluorescent gold nanoclusters capped with small organic molecules and a revealing fluorescence and X-ray absorption study

    NASA Astrophysics Data System (ADS)

    Helmbrecht, C.; Lützenkirchen-Hecht, D.; Frank, W.

    2015-03-01

    Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES spectra in comparison to several gold references, optically transparent fluorescent AuNC are predicted to be ligand-stabilized Au5+ species. Additionally, their near edge structure compared with analogous results of polynuclear clusters known from the literature discloses an increasing intensity of the feature close to the absorption edge with decreasing cluster size. As a result, a linear relationship between the cluster size and the X-ray absorption coefficient can be established for the first time.Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES

  9. One-Dimensional Fluorescent Silicon Nanorods Featuring Ultrahigh Photostability, Favorable Biocompatibility, and Excitation Wavelength-Dependent Emission Spectra.

    PubMed

    Song, Bin; Zhong, Yiling; Wu, Sicong; Chu, Binbin; Su, Yuanyuan; He, Yao

    2016-04-13

    We herein report a kind of one-dimensional biocompatible fluorescent silicon nanorods (SiNRs) with tunable lengths ranging ∼100-250 nm, which can be facilely prepared through one-pot microwave synthesis. In addition to the strong fluorescence (quantum yield value: ∼15%) and negligible toxicity, the resultant SiNRs exhibit excitation wavelength-dependent photoluminescence whose maximum emission wavelength ranges from ∼450 to ∼600 nm under serial excitation wavelengths from 390 to 560 nm, providing feasibility for multicolor biological imaging. More significantly, the SiNRs are ultrahighly photostable, preserving strong and nearly unchanged fluorescence under 400 min high-power UV irradiation, which is in sharp contrast to severe fluorescence quenching of organic dyes (e.g., FITC) or II-VI quantum dots (QDs) (e.g., CdTe QDs and CdSe/ZnS QDs) within 15 or 160 min UV treatment under the same experiment conditions, respectively. Taking advantage of these attractive merits, we further exploit the SiNRs as a novel type of color converters for the construction of white light-emitting diodes (LED), which is the first proof-of-concept demonstration of LED device fabricated using the one-dimensional fluorescent silicon nanostructures. PMID:27010956

  10. Fluorescence excitation and emission spectra of ALA-induced protoporphyrin IX in normal and tumoral tissue of the human bladder

    NASA Astrophysics Data System (ADS)

    Forrer, Martin; Glanzmann, Thomas M.; Mizeret, Jerome C.; Braichotte, Daniel; Wagnieres, Georges A.; van den Bergh, Hubert; Jichlinski, Patrice; Leisinger, Hans-Juerg

    1995-01-01

    In vivo spectrofluorometric analysis represents a tool to obtain information about fluorophore distribution in tissue. Based on a Peltier-cooled CCD we designed a fluorescence excitation and emission spectrograph which allows to obtain tissue spectra endoscopically and in a clinical environment. Clinical studies were performed on patients with positive cytology or tumor recurrence in the urinary bladder. Patients received a 50 ml instillation of 3% ALA solution at pH 5.5 during 3 to 4 hours and underwent a normal white light cystoscopic examination together with light induced fluorescence photodetection at 5 to 8 hours after the beginning of the instillation. Local fluorescence measurements with a single fiber were performed before photodetection. These showed fluorescence ratios between tumor and normal tissue of 1.5 to 20 with the strongest ratios for exophytic papillary tumors. Fluorescence excitation between 380 nm and 450 nm revealed that the higher Protoporphyrin IX (PPIX) signal on tumor tissue is accompanied by a decrease of the autofluorescence at the emission wavelength of 500 nm.

  11. Time-resolved fluorescence spectroscopy of matrix-isolated silver atoms after pulsed excitation of inner-shell transitions

    NASA Astrophysics Data System (ADS)

    Hebert, T.; Wiggenhauser, H.; Schriever, U.; Kolb, D. M.

    1990-02-01

    The energy dissipation in matrix-isolated silver atoms after pulsed vacuum ultraviolet (VUV) excitation of 4d-5p transitions has been studied by time-resolved fluorescence spectroscopy. The decay behavior of the various fluorescence bands has been analyzed and a model for the relaxation process proposed within the framework of a two-dimensional configuration-coordinate diagram. If minute quantities of Ag2 are present in the matrix, the analysis requires consideration of energy transfer between silver atoms and dimers.

  12. A new visibly-excited fluorescent component in latent fingerprint residue induced by gaseous electrical discharge.

    PubMed

    Davies, L M; Jones, N E; Brennan, J S; Bramble, S K

    2000-11-01

    A technique that exposes fingerprint residue to a gaseous electrical discharge in nitrogen followed by treatment with ammonium hydrogen carbonate vapors to produce fluorescence is investigated. Particular attention is made to fluorescence observed via laser illumination at 514 nm. Insight into the nature of the fluorescent components is achieved through the use of thin-layer chromatography (TLC) of fingerprint residue. Results reported indicate the fluorescence observed is from previously non-fluorescent fractions of the fingerprint residue, and TLC results point towards lipid derivatives as a possible source of the fluorescence. PMID:11110185

  13. Attosecond XUV absorption spectroscopy of doubly excited states in helium atoms dressed by a time-delayed femtosecond infrared laser

    NASA Astrophysics Data System (ADS)

    Yang, Z. Q.; Ye, D. F.; Ding, Thomas; Pfeifer, Thomas; Fu, L. B.

    2015-01-01

    In the present paper, we investigate the time-resolved transient absorption spectroscopy of doubly excited states of helium atoms by solving the time-dependent two-electron Schrödinger equation numerically based on a one-dimensional model. The helium atoms are subjected to an extreme ultraviolet (XUV) attosecond pulse and a time-delayed infrared (IR) few-cycle laser pulse. A superposition of doubly excited states populated by the XUV pulse is identified, which interferes with the direct ionization pathway leading to Fano resonance profiles in the photoabsorption spectrum. In the presence of an IR laser, however, the Fano line profiles are strongly modified: A shifting, splitting, and broadening of the original absorption lines is observed when the XUV attosecond pulse and infrared few-cycle laser pulse overlap in time, which is in good agreement with recent experimental results. At certain time delays, we observe symmetric Lorentz, inverted Fano profiles, and even negative absorption cross sections indicating that the XUV light can be amplified during the interaction with atoms. We further prove that the above pictures are general for different doubly excited states by suitably varying the frequency of the IR field to coherently couple the corresponding states.

  14. Excitation-resolved wide-field fluorescence imaging of indocyanine green visualizes the microenvironment properties in vivo via solvatochromic shift (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Cho, Jaedu; Kim, Chang-Seok; Gulsen, Gultekin

    2016-03-01

    Near-infrared fluorescence imaging (NIRF) is a powerful wide-field optical imaging tool that has a potential to visualize molecular-specific exogenous fluorescence agents, such as FDA approved Indocyanine Green (ICG), in thick tissue. Indeed, ICG is sensitive to biochemical environment such that it can be used to detect micro- or macroscopic environmental changes in tissue by solvatochromic shift that is defined by the dependence of absorption and emission spectra with the solvent polarity. For example, dimethyl sulfoxide (DMSO) is a very powerful drug carrier that can penetrate biological barriers such as the skin, the membranes, and the blood-brain-barrier. In presence of DMSO, ICG in tissue shows the excitation blue shift. However, NIRF imaging of microenvironment dependent changes of ICG has been challenging for the following reasons. First, the Stoke's shift of ICG is too small to separate the excitation and emission spectra easily. Second, the solvatochromic shift of ICG is too small to be detected by conventional NIRF techniques. Last but not least, the multiple scattering in tissue degrades not only the spatial information but also the spectral contents by the red-shift. We developed a wavelength-swept laser-based NIRF system that can resolve the excitation shift of ICG in tissue such that DMSO can be indirectly visualized. We plan to conduct an in-vivo lymph-node drug-delivery study in a mouse model to show feasibility of the indirect imaging of the drug-carrier with the wavelength-swept-laser based NIRF system.

  15. A benzo-15-crown-5-modifying ratiometric-absorption and fluorescent OFF-ON chemosensor for Cu(2.).

    PubMed

    Chen, Yuting; Wang, Xinxin; Wang, Kaili; Zhang, Xiuling

    2016-05-15

    One new benzo-15-crown-5-modifying fluorene Schiff base (FBC), together with the CN-linked fluorene-3,4-dimethoxybenzene (FBDMO) and fluorene-benzene (FB) references, has been designed and facilely synthesized. The binding of Cu(2+) with nitrogen atom of CN moiety in these three compounds can inhibit the photo-induced electronic transition process and induce the ratiometric-absorption and fluorescent OFF-ON response to Cu(2+). Whereas the employment of benzo-15-crown-5 moiety in FBC as additional binding platform for Cu(2+) not only amplifies the fluorescent enhancement of FBCvia preventing the isomerization of CN moiety, but also endows this compound high selectivity and rapid response towards Cu(2+) over the references FB and FBDMO. These results render FBC highly sensitive ratiometric-absorption and fluorescent OFF-ON detecting potential for Cu(2+) with the detection limit of 3.91×10(-6)M. PMID:26971023

  16. A benzo-15-crown-5-modifying ratiometric-absorption and fluorescent OFF-ON chemosensor for Cu2 +

    NASA Astrophysics Data System (ADS)

    Chen, Yuting; Wang, Xinxin; Wang, Kaili; Zhang, Xiuling

    2016-05-01

    One new benzo-15-crown-5-modifying fluorene Schiff base (FBC), together with the Cdbnd N-linked fluorene-3,4-dimethoxybenzene (FBDMO) and fluorene-benzene (FB) references, has been designed and facilely synthesized. The binding of Cu2 + with nitrogen atom of Cdbnd N moiety in these three compounds can inhibit the photo-induced electronic transition process and induce the ratiometric-absorption and fluorescent OFF-ON response to Cu2 +. Whereas the employment of benzo-15-crown-5 moiety in FBC as additional binding platform for Cu2 + not only amplifies the fluorescent enhancement of FBCvia preventing the isomerization of Cdbnd N moiety, but also endows this compound high selectivity and rapid response towards Cu2 + over the references FB and FBDMO. These results render FBC highly sensitive ratiometric-absorption and fluorescent OFF-ON detecting potential for Cu2 + with the detection limit of 3.91 × 10- 6 M.

  17. Intercomparison of OH Radical Measurements by Long-Path Absorption and Laser Induced Fluorescence in the Atmosphere Simulation Chamber SAPHIR

    NASA Astrophysics Data System (ADS)

    Dorn, H.-P.; Brauers, T.; Greif, J.; Häseler, R.; Hofzumahaus, A.; Holland, F.; Rupp, L.

    2003-04-01

    A striking advantage of the SAPHIR chamber is the availability of two spectroscopic detection instruments for OH radicals: Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS). Both instruments have already been compared in 1994 during the field measurement campaign POPCORN. They agreed well with a correlation coefficient of r=0.90 and a weighted linear fit with a slope of 1.09 +- 0.12. However, OH measurements in the simulation chamber differ significantly from measurements in ambient air. While DOAS measures OH as an integral value along the central longitudinal axis of SAPHIR, LIF samples the air locally and close (2 cm) to the floor of the chamber. Thus, the LIF measurements might be possibly affected by local concentration gradients caused by insufficient mixing of the chamber air or by deposition to the wall. On the other hand, if turbulent mixing of the chamber air is weak and high concentrations of ozone are used in experiments, the DOAS instrument might be subject to artificial formation of OH radicals in the air volume which is illuminated by the detection laser. This interference results from laser induced photolysis of ozone and the subsequent reaction of water vapor with the excited oxygen atoms formed. Thus it is of decisive importance to compare OH measurements from both instruments in order to investigate potential disturbing effects due to the specific sampling properties of both instruments within SAPHIR. We report on OH measurements accomplished simultaneously with both instruments using different trace gas compositions and experimental conditions.

  18. Study of nonlinear optical absorption properties of Sb2Se3 nanoparticles in the nanosecond and femtosecond excitation regime

    NASA Astrophysics Data System (ADS)

    Molli, Muralikrishna; Pradhan, Prabin; Dutta, Devarun; Jayaraman, Aditya; Bhat Kademane, Abhijit; Muthukumar, V. Sai; Kamisetti, Venkataramaniah; Philip, Reji

    2016-05-01

    In this work, we report for the first time, the nonlinear optical absorption properties of antimony selenide (Sb2Se3) nanoparticles synthesized through solvothermal route. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies revealed that the nanoparticles are in the range of 10-40 nm. Elemental analysis was performed using EDAX. The nanosecond optical limiting effect was characterized by using fluence-dependent transmittance measurements with 15-ns laser pulses at 532 and 1064 nm excitation wavelengths. Mechanistically, effective two-photon (2PA) absorption and nonlinear scattering processes were the dominant nonlinear processes at both the wavelengths. At 800 nm excitation in the femtosecond regime (100 fs), the nonlinear optical absorption was found to be a three-photon (3PA) process. Both 2PA and 3PA processes were explained using the band structure and density of states of Sb2Se3 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered to have optical power-limiting applications in the visible range.

  19. Excited-state absorption and third-order optical nonlinearities in symmetric π-electron organic molecules

    NASA Astrophysics Data System (ADS)

    Williams, G. R. J.

    1996-07-01

    Excited-State Absorption (ESA), Two-Photon Absorption (TPA) and the third-order polarizability γ(ω;ω,ω, - ω) have been investigated for a model dichloride derivative of a symmetrically substituted benzylidene analine (SBAC), using a multielectron configuration-interaction procedure. The calculations indicate that SBAC exhibits ESA across the visible region of the spectrum, but that it is not as extensive as for molecules such as the phthalocyanines. The magnitude of the third-order polarizability is dominated by resonance enhancement from a very strong A g → B u one-photon absorption. The calculated off-resonance value for γ(ω;ω,ω, - ω) suggests that SBAC is a potential candidate for ultrafast switching applications.

  20. Projection imaging of photon beams using Čerenkov-excited fluorescence

    NASA Astrophysics Data System (ADS)

    Glaser, Adam K.; Davis, Scott C.; Voigt, William H. A.; Zhang, Rongxiao; Pogue, Brian W.; Gladstone, David J.

    2013-02-01

    Full 3D beam profiling and quality assurance (QA) of therapeutic megavoltage linear accelerator (LINAC) x-ray photon beams is not routinely performed due to the slow point-by-point measurement nature of conventional scanning ionization chamber systems. In this study we explore a novel optical-based dose imaging approach using a standard commercial camera, water tank, and fluorescent dye, which when excited by the Čerenkov emission induced by the radiation beam, allows 2D projection imaging in a fast timeframe, potentially leading toward 3D tomographic beam profiling. Detailed analysis was carried out to optimize the imaging parameters in the experimental setup. The results demonstrate that the captured images are linear with delivered dose, independent of dose rate, and comparison of experimentally captured images to a reference dose distribution for a 4 × 4 cm2 6 MV x-ray photon beam yielded results with improved accuracy over a previous study which used direct imaging and Monte Carlo calibration of the Čerenkov emission itself. The agreement with the reference dose distribution was within 1-2% in the lateral direction, and ±3% in the depth direction. The study was restricted to single 2D image projection, with the eventual goal of creating full 3D profiles after tomographic reconstruction from multiple projections. Given the increasingly complex advances in radiation therapy, and the increased emphasis on patient-specific treatment plans, further refinement of the technique could prove to be an important tool for fast and robust QA of x-ray photon LINAC beams.

  1. Projection imaging of photon beams using Čerenkov-excited fluorescence.

    PubMed

    Glaser, Adam K; Davis, Scott C; Voigt, William H A; Zhang, Rongxiao; Pogue, Brian W; Gladstone, David J

    2013-02-01

    Full 3D beam profiling and quality assurance (QA) of therapeutic megavoltage linear accelerator (LINAC) x-ray photon beams is not routinely performed due to the slow point-by-point measurement nature of conventional scanning ionization chamber systems. In this study we explore a novel optical-based dose imaging approach using a standard commercial camera, water tank, and fluorescent dye, which when excited by the Čerenkov emission induced by the radiation beam, allows 2D projection imaging in a fast timeframe, potentially leading toward 3D tomographic beam profiling. Detailed analysis was carried out to optimize the imaging parameters in the experimental setup. The results demonstrate that the captured images are linear with delivered dose, independent of dose rate, and comparison of experimentally captured images to a reference dose distribution for a 4 × 4 cm(2) 6 MV x-ray photon beam yielded results with improved accuracy over a previous study which used direct imaging and Monte Carlo calibration of the Čerenkov emission itself. The agreement with the reference dose distribution was within 1-2% in the lateral direction, and ±3% in the depth direction. The study was restricted to single 2D image projection, with the eventual goal of creating full 3D profiles after tomographic reconstruction from multiple projections. Given the increasingly complex advances in radiation therapy, and the increased emphasis on patient-specific treatment plans, further refinement of the technique could prove to be an important tool for fast and robust QA of x-ray photon LINAC beams. PMID:23318469

  2. Projection imaging of photon beams using Čerenkov-excited fluorescence

    PubMed Central

    Glaser, Adam K.; Davis, Scott C.; Voigt, William H.A.; Zhang, Rongxiao; Pogue, Brian W.; Gladstone, David J.

    2013-01-01

    Full 3D beam profiling and quality assurance (QA) of therapeutic megavoltage linear accelerator (LINAC) x-ray photon beams is not routinely performed due to the slow point-by-point measurement nature of conventional scanning ionization chamber systems. In this study we explore a novel optical-based dose imaging approach using a standard commercial camera, water tank, and fluorescent dye, which when excited by the Čerenkov emission induced by the radiation beam, allows 2D projection imaging in a fast timeframe, potentially leading towards 3D tomographic beam profiling. Detailed analysis was done to optimize the imaging parameters in the experimental setup. The results demonstrate that the captured images are linear with delivered dose, independent of dose rate, and comparison of experimentally captured images to a reference dose distribution for a 4×4 cm 6 MV x-ray photon beam yielded results with improved accuracy over a previous study which used direct imaging and Monte Carlo calibration of the Čerenkov emission itself. The agreement with the reference dose distribution was within 1-2% in the lateral direction, and ± 3 % in the depth direction. The study was restricted to single 2D image projection, with the eventual goal of creating full 3D profiles after tomographic reconstruction from multiple projections. Given the increasingly complex advances in radiation therapy, and the increased emphasis on patient-specific treatment plans, further refinement of the technique could prove to be an important tool for fast and robust QA of x-ray photon LINAC beams. PMID:23318469

  3. Calculation and interpretation of vibronic absorption and fluorescence spectra of the first electronic nπ* transitions of pyridine and pyrimidine

    NASA Astrophysics Data System (ADS)

    Ten, G. N.; Kadrov, D. M.; Berezin, M. K.; Baranov, V. I.

    2014-11-01

    We have calculated vibronic spectra of the first electronic nπ* transitions of pyridine and pyrimidine in the isolated state using the DFT method in the Franck-Condon approximation. Vibrational spectra for the ground and excited states have been calculated in the anharmonic approximation, which allowed us to refine the assignment of normal vibrations of pyridine and pyrimidine. We have done a complete interpretation of the vibrational structure of the absorption and fluorescence spectra of pyridine and pyrimidine. It has been shown that Fermi resonances between fundamental and combination vibrations and overtones 12 and 16 b + 4, 6 a and 2 × 16 b affect the formation of the vibrational structure of electronic spectra of pyrimidine. Good agreement between calculated and experimental spectra confirms the correctness of the models of the two molecules in their ground and excited states, which makes it possible to use the models in further investigations of various properties of these molecules in electronically excited states, e.g., tautomerism of pyrimidine bases of nucleic acids.

  4. Combined system for high-time-resolution dual-excitation fluorescence photometry and fluorescence imaging of calcium transients in single normal and diseased skeletal muscle fibers

    NASA Astrophysics Data System (ADS)

    Uttenweiler, Dietmar; Wojciechowski, Reinhold; Makabe, Makoto; Veigel, Claudia; Fink, Rainer H.

    1994-12-01

    Fast photometric measurements and video-imaging of fluorescent indicators both are powerful tools in measuring the intracellular free calcium concentration of muscle and many other cells. as photometric systems yield a high temporal resolution, calcium imaging systems have high spatial but significantly reduced temporal resolution. Therefore we have developed an integrated system combining both methods and based mostly on standard components. As a common, sensitive Ca2+- indicator we used the fluorescent probe Fura-2, which is alternatingly excited for ratio measurements at 340/380 nm. We used a commercially available dual excitation photometric system (OSP-3; Olympus) for attaching a CCD-camera and a frame grabber board. To achieve the synchronization we had to design circuitries for external triggering, synchronization and accurate control of the filter changer, which we added to the system. Additionally, the software for a triggered image acquisition was developed. With this integrated setup one can easily switch between the fast photometric mode (ratio frequency 100 Hz) and the imaging mode (ratio frequency 4.17 Hz). The calcium images are correlated with the 25 times faster spot measurements and are analyzed by means of image processing. With this combined system we study release and uptake of calcium ions of normal and diseased skeletal muscle from mdx mice. Such a system will also be important for other cellular studies in which fluorescence indicators are used to monitor similar time dependent alterations as well as changes in cellular distributions of calcium.

  5. Biological membrane modeling with a liquid/liquid interface. Probing mobility and environment with total internal reflection excited fluorescence.

    PubMed Central

    Morrison, L E; Weber, G

    1987-01-01

    Total internal reflection of exciting light, in combination with fluorescence intensity and polarization measurements, was used to selectively study fluorescent compounds adsorbed to the interface region between two immiscible liquids. A fluorometer was constructed which provided excitation at variable angles of incidence and allowed sensitive detection of polarized fluorescence emitted from the interface. The compound 4,4'-bis-1-phenylamino-8-naphthalenesulfonate (bis-ANS) was examined at a decalin/water interface and was found to possess remarkable affinity for the interface region with the bulk of the adsorbed molecule residing in the decalin phase. The adsorbed fluorophore displayed an apparent hindered rotation in the plane of the interface with a rotational diffusion coefficient 3- to 12-fold lower than that expected for bis-ANS in solution. While other dyes examined were not found to be significantly surface active, the addition of cationic surfactant sufficed to induce adsorption of the anionic fluorophore 1-aminonaphthalene-3,6,8-trisulfonic acid. This fluoropore was found to reside in an aqueous environment when bound to the interface, and it also exhibited hindered rotation in the plane of the interface. As the concentrations of the dyes were increased, both adsorbed dyes exhibited polarization reductions consistent with excitation energy transfer. Adsorption of bis-ANS was reversed by addition of bovine serum albumin. The membrane protein cytochrome b5 was found not to bind at the decalin/water interface, indicating that interaction with lipid is required for its adherence to biological membranes. PMID:3651556

  6. The ultraviolet continuum and the fluorescent H2 lines in low-excitation Herbig-Haro objects

    NASA Technical Reports Server (NTRS)

    Boehm, K. H.; Scott, D. M.; Solf, J.

    1991-01-01

    Long-exposure IUE observations are used here to determine the spatial distribution of the fluorescent H2 line emission in the low-excitation objects HH 43 and HH 47. In HH 43, the spatial distribution of the fluorescent H2 line emission has a width equal to or smaller than the width of the point-spread function of IUE, while both the short-wavelength UV continuum and the optical forbidden S II lines show distributions which are wider by more than a factor of two. In HH 47, the results are qualitatively analogous, but the differences between the fluorescent HH 23 emission distribution on the one hand, and the UV continuum and optical forbidden S II distribution on the other, are smaller. These distributions indicate that the appropriate conditions for the formation of fluorscent H2 lines are fulfilled only in rather narrow regions for these low-excitation objects. A continuous energy distribution in HH 43 and HH 47 is found which differs only slightly from that in the high-excitation objects HH 1 and HH 2.

  7. Thermally activated delayed fluorescence as a cycling process between excited singlet and triplet states: Application to the fullerenes

    NASA Astrophysics Data System (ADS)

    Baleizão, Carlos; Berberan-Santos, Mário N.

    2007-05-01

    In efficient thermally activated delayed fluorescence (TADF) the excited chromophore alternates randomly between the singlet and triplet manifolds a large number of times before emission occurs. In this work, the average number of cycles n¯ is obtained and is shown to have a simple experimental meaning: n¯+1 is the intensification factor of the prompt fluorescence intensity, owing to the occurrence of TADF. A new method of data analysis for the determination of the quantum yield of triplet formation, combining steady-state and time-resolved data in a single plot, is also presented. Application of the theoretical results to the TADF of [70]fullerenes shows a general good agreement between different methods of fluorescence analysis and allows the determination of several photophysical parameters.

  8. Light, Molecules, Action: Broadband UV-visible transient absorption studies of excited state dynamics in photoactive molecules

    NASA Astrophysics Data System (ADS)

    Sension, Roseanne

    2015-03-01

    Broadband UV-visible transient absorption spectroscopy provides a powerful tool for the investigation of the dynamics of electronically excited molecules in the condensed phase. It is now possible to obtain transient spectra on a routine basis spanning the range from <300 nm to >800 nm with femtosecond time resolution. We have used this method to study the excited state dynamics and internal conversion of a range of molecular systems with potential application as optically powered molecular devices. The cyclohexadiene ring-opening reaction is the basis of a class of important optical switches and of the biological synthesis of previtamin D3. The ring-opening reaction is ultrafast, occurring on a picosecond to subpicosecond times scale depending on the substituents around the ring. These have a significant influence on the dynamics and electronic structure of the electronically excited molecule. The results of a series of transient absorption studies as a function of chromophore substitution and environment will be presented. The cis-trans isomerization of polyene molecules, especially substituted stilbenes, provides another important class of functional molecular transformations. Again the excited state dynamics can be ultrafast with photochemistry controlled by details of the curve crossings and conical intersections. Finally the photochemistry of the even more complex set of cobalamin chromophores with a photoalabile C-Co bond has been proposed as a tool for spatio-temporal control of molecule delivery including drug delivery. Broadband transient absorption spectroscopy has been used to investigate the ultrafast electronic dynamics of a range of cobalamin compounds with comparison to detailed theoretical calculations. The results of these studies will be presented.

  9. Calibration approach for fluorescence lifetime determination for applications using time-gated detection and finite pulse width excitation.

    PubMed

    Keller, Scott B; Dudley, Jonathan A; Binzel, Katherine; Jasensky, Joshua; de Pedro, Hector Michael; Frey, Eric W; Urayama, Paul

    2008-10-15

    Time-gated techniques are useful for the rapid sampling of excited-state (fluorescence) emission decays in the time domain. Gated detectors coupled with bright, economical, nanosecond-pulsed light sources like flashlamps and nitrogen lasers are an attractive combination for bioanalytical and biomedical applications. Here we present a calibration approach for lifetime determination that is noniterative and that does not assume a negligible instrument response function (i.e., a negligible excitation pulse width) as does most current rapid lifetime determination approaches. Analogous to a transducer-based sensor, signals from fluorophores of known lifetime (0.5-12 ns) serve as calibration references. A fast avalanche photodiode and a GHz-bandwidth digital oscilloscope is used to detect transient emission from reference samples excited using a nitrogen laser. We find that the normalized time-integrated emission signal is proportional to the lifetime, which can be determined with good reproducibility (typically <100 ps) even for data with poor signal-to-noise ratios ( approximately 20). Results are in good agreement with simulations. Additionally, a new time-gating scheme for fluorescence lifetime imaging applications is proposed. In conclusion, a calibration-based approach is a valuable analysis tool for the rapid determination of lifetime in applications using time-gated detection and finite pulse width excitation. PMID:18798652

  10. An orange fluorescent protein with a large Stokes shift for single-excitation multicolor FCCS and FRET imaging

    PubMed Central

    Shcherbakova, Daria M.; Hink, Mark A.; Joosen, Linda; Gadella, Theodorus W. J.; Verkhusha, Vladislav V.

    2012-01-01

    Multicolor imaging based on genetically-encoded fluorescent proteins (FPs) is a powerful approach to study several dynamic processes in a live cell. We report a monomeric orange FP with a large Stokes shift (LSS), called LSSmOrange (excitation/emission at 437/572 nm), which fills up an existing spectral gap between the green-yellow and red LSSFPs. Brightness of LSSmOrange is 5-fold larger than that of the brightest red LSSFP and similar to the green-yellow LSS-FPs. LSSmOrange allows numerous multicolor applications using a single excitation wavelength that was not possible before. Using LSSmOrange we developed a four-color single-laser fluorescence cross-correlation spectroscopy, solely based on FPs. The quadruple cross-correlation combined with photon counting histogram techniques allowed quantitative single-molecule analysis of the particles labeled with four FPs. LSSmOrange was further applied to simultaneously image two Förster resonance energy transfer pairs, one of which is the commonly used CFP-YFP pair, with a single excitation laser. The combination of LSSmOrange-mKate2 and CFP-YFP biosensors enabled imaging of apoptotic activity and calcium fluctuations in real time. The LSSmOrange mutagenesis, low-temperature and isotope effect studies revealed a proton relay for the excited state proton transfer responsible for the LSS phenotype. PMID:22486524

  11. A multi-channel monolithic Ge detector system for fluorescence x-ray absorption spectroscopy

    SciTech Connect

    Bucher, J.J.; Allen, P.G.; Edelstein, N.M.; Shuh, D.K.; Madden, N.W.; Cork, C.; Luke, P.; Pehl, D.; Malone, D.

    1995-03-01

    Construction and performance of a monolithic quad-pixel Ge detector for fluorescence x-ray absorption spectroscopy (XAS) at synchrotron radiation sources are described. The detector semiconductor element has an active surface area of 4.0 cm{sup 2} which is electrically separated into four 1.0 cm{sup 2} pixels, with little interfacial dead volume. Spatial response of the array shows that cross-talk between adjacent pixels is < 10% for 5.9 keV photons that fall within 0.5 mm of the pixel boundaries. The detector electronics system uses pre-amplifiers built at LBNL with commercial Tennelec Model TC 244 amplifiers. Using an {sup 55}Fe test source (MnK{sub {alpha}}, 5.9 keV), energy resolution of better than 200 eV is achieved with a 4 {mu}sec peaking time. At 0.5 {mu}sec peaking time, pulse pileup results in a 75% throughput efficiency for an incoming count rate of 100 kHz. Initial XAS fluoresncece measurements at the beamline 4 wiggler end stations at SSRL show that the detector system has several advantages over commercial x-ray spectrometers for low-concentration counting.

  12. Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide

    NASA Astrophysics Data System (ADS)

    Degueldre, Claude; Cozzo, Cedric; Martin, Matthias; Grolimund, Daniel; Mieszczynski, Cyprian

    2013-06-01

    Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regard to their environment and the coolant. In this work the study of the atomic structure and next-neighbour environment of Am in the (Pu,U)O2 lattice in an irradiated (60 MW d kg-1) MOX sample was performed employing micro-X-ray fluorescence (µ-XRF) and micro-X-ray absorption fine structure (µ-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Am (˜0.66 wt%) are determined from the experimental data gained for the irradiated fuel material examined in its peripheral zone (rim) of the fuel. In the irradiated sample Am builds up as Am3+ species within an [AmO8]13- coordination environment (e.g. >90%) and no (<10%) Am(IV) or (V) can be detected in the rim zone. The occurrence of americium dioxide is avoided by the redox buffering activity of the uranium dioxide matrix.

  13. Study of nonlinear optical absorption properties of V2O5 nanoparticles in the femtosecond excitation regime

    NASA Astrophysics Data System (ADS)

    Molli, Muralikrishna; Bhat Kademane, Abhijit; Pradhan, Prabin; Sai Muthukumar, V.

    2016-08-01

    In this work, we report for the first time, the nonlinear optical absorption properties of vanadium pentoxide (V2O5) nanoparticles in the femtosecond excitation regime. V2O5 nanoparticles were synthesized through solution combustion technique. The as-synthesized samples were further characterized using XRD, FESEM, EDAX, TEM and UV-visible spectroscopy. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies showed the size of the nanoparticles to be ~200 nm. Open-aperture z-scan technique was employed to study the nonlinear optical absorption behavior of the synthesized samples using a 100-fs laser pulses at 800 nm from a regeneratively amplified Ti: sapphire laser. The mechanism of nonlinear absorption was found to be a three-photon absorption process which was explained using the density of states of V2O5 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered for optical-power-limiting applications.

  14. Superior optical nonlinearity of an exceptional fluorescent stilbene dye

    SciTech Connect

    He, Tingchao; Sreejith, Sivaramapanicker; Zhao, Yanli; Gao, Yang; Grimsdale, Andrew C.; Lin, Xiaodong E-mail: hdsun@ntu.edu.sg; Sun, Handong E-mail: hdsun@ntu.edu.sg

    2015-03-16

    Strong multiphoton absorption and harmonic generation in organic fluorescent chromophores are, respectively, significant in many fields of research. However, most of fluorescent chromophores fall short of the full potential due to the absence of the combination of such different nonlinear upconversion behaviors. Here, we demonstrate that an exceptional fluorescent stilbene dye could exhibit efficient two- and three-photon absorption under the excitation of femtosecond pulses in solution phase. Benefiting from its biocompatibility and strong excited state absorption behavior, in vitro two-photon bioimaging and superior optical limiting have been exploited, respectively. Simultaneously, the chromophore could generate efficient three-photon excited fluorescence and third-harmonic generation (THG) when dispersed into PMMA film, circumventing the limitations of classical fluorescent chromophores. Such chromophore may find application in the production of coherent light sources of higher photon energy. Moreover, the combination of three-photon excited fluorescence and THG can be used in tandem to provide complementary information in biomedical studies.

  15. Photodynamic cancer therapy: fluorescence localization and light absorption spectra of chlorophyll-derived photosensitizers inside cancer cells

    NASA Astrophysics Data System (ADS)

    Moser, Joerg G.; Rueck, Angelika C.; Schwarzmaier, Hans-Joachim; Westphal-Frosch, Christel

    1992-07-01

    The first prerequisite for an optimum effect of photodynamic therapy with chlorophyll- derived photosensitizers is irradiation at the S1 absorption maximum in the red spectral region. This absorption maximum changes its position due to molecular association by 20 to 100 nm depending on the subcellular environment, and must be determined by direct absorption spectrometry in the region of subcellular sensitizer localization. Fluorescence- intensifying video microscopy allows for localization of the sensitizer storage site at or near the Galgi apparatus of OAT 75 small-cell lung carcinoma cells. The absorption maximum at 760 nm taken from spectra of single cells and cell layers determines the postulated optimum condition for dye laser irradiation with bacteriopheophorbide-a-methyl-ester as the sensitizer.

  16. Fluorescence yields from photodissociative excitation of chloromethanes by vacuum ultraviolet radiation

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Suto, Masako

    1987-01-01

    The photoabsorption and fluorescence cross sections of chloromethanes were measured in the 105-220 nm region using synchrotron radiation as a light source. The fluorescence threshold for CCl4 is at 152 nm with a maximum yield of 3 percent at 113 nm. The fluorescence results from the CCl2(A-X) system. For CHCl3, the fluorescence threshold is at 155 nm with a maximum yield of 0.6 percent at 110 nm. For CH2Cl2, the threshold is at 137 nm with a maximum yield of 0.35 percent at 107 nm. The fluorescence yield of CH3Cl is very small with an upper limit of 0.02 percent. The photodissociation processes are discussed in accord with the fluorescence data observed. Vibrational structures in CHCl3 and CH3Cl2 are observed and classified into progressions.

  17. Acceptor and Excitation Density Dependence of the Ultrafast Polaron Absorption Signal in Donor-Acceptor Organic Solar Cell Blends.

    PubMed

    Zarrabi, Nasim; Burn, Paul L; Meredith, Paul; Shaw, Paul E

    2016-07-21

    Transient absorption spectroscopy on organic semiconductor blends for solar cells typically shows efficient charge generation within ∼100 fs, accounting for the majority of the charge carriers. In this Letter, we show using transient absorption spectroscopy on blends containing a broad range of acceptor content (0.01-50% by weight) that the rise of the polaron signal is dependent on the acceptor concentration. For low acceptor content (<10% by weight), the polaron signal rises gradually over ∼1 ps with most polarons generated after 200 fs, while for higher acceptor concentrations (>10%) most polarons are generated within 200 fs. The rise time in blends with low acceptor content was also found to be sensitive to the pump fluence, decreasing with increasing excitation density. These results indicate that the sub-100 fs rise of the polaron signal is a natural consequence of both the high acceptor concentrations in many donor-acceptor blends and the high excitation densities needed for transient absorption spectroscopy, which results in a short average distance between the exciton and the donor-acceptor interface. PMID:27355877

  18. Electrochemical immobilization of Fluorescent labelled probe molecules on a FTO surface for affinity detection based on photo-excited current

    NASA Astrophysics Data System (ADS)

    Haruyama, Tetsuya; Wakabayashi, Ryo; Cho, Takeshi; Matsuyama, Sho-taro

    2011-10-01

    Photo-excited current can be generated at a molecular interface between a photo-excited molecules and a semi-conductive material in appropriate condition. The system has been recognized for promoting photo-energy devices such as an organic dye sensitized solar-cell. The photo-current generated reactions are totally dependent on the interfacial energy reactions, which are in a highly fluctuated interfacial environment. The authors investigated the photo-excited current reaction to develop a smart affinity detection method. However, in order to perform both an affinity reaction and a photo-excited current reaction at a molecular interface, ordered fabrications of the functional (affinity, photo-excitation, etc.) molecules layer on a semi-conductive surface is required. In the present research, we would like to present the fabrication and functional performance of photo-excited current-based affinity assay device and its application for detection of endocrine disrupting chemicals. On the FTO surface, fluorescent pigment labelled affinity peptide was immobilized through the EC tag (electrochemical-tag) method. The modified FTO produced a current when it was irradiated with diode laser light. However, the photo current decreased drastically when estrogen (ES) coexisted in the reaction solution. In this case, immobilized affinity probe molecules formed a complex with ES and estrogen receptor (ER). The result strongly suggests that the photo-excited current transduction between probe molecule-labelled cyanine pigment and the FTO surface was partly inhibited by a complex that formed at the affinity oligo-peptide region in a probe molecule on the FTO electrode. The bound bulky complex may act as an impediment to perform smooth transduction of photo-excited current in the molecular interface. The present system is new type of photo-reaction-based analysis. This system can be used to perform simple high-sensitive homogeneous assays.

  19. Graphene quantum dots from graphite by liquid exfoliation showing excitation-independent emission, fluorescence upconversion and delayed fluorescence.

    PubMed

    Sarkar, Suprabhat; Gandla, Dayakar; Venkatesh, Yeduru; Bangal, Prakriti Ranjan; Ghosh, Sutapa; Yang, Yang; Misra, Sunil

    2016-08-21

    Facile synthesis of 2-10 nm-sized graphene quantum dots (GQDs) from graphite powder by organic solvent-assisted liquid exfoliation using a sonochemical method is reported in this study. Synthesized GQDs are well dispersed in organic solvents like ethyl acetoacetate (EAA), dimethyl formamide (DMF) and also in water. MALDI-TOF mass spectrometry reveals its selective mass fragmentation. Detailed characterizations by various techniques like X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) confirm the formation of disordered, functional GQDs. Density functional theory (DFT) calculation confirms HOMO-LUMO energy gap variation with changing size and functionalities. Photoluminescence (PL) properties of as-prepared GQDs were studied in detail. The ensemble studies of GQDs showed excellent photoluminescence properties comprising normal and upconverted fluorescence, delayed fluorescence and room-temperature phosphorescence. PL decay dynamics of GQDs has been explored using time-correlated single-photon technique (TCSPC) as well as femtosecond fluorescence upconversion technique. In vitro cytotoxicity study reveals its biocompatibility and high cell viability (>91%) even at high concentration (400 μg mL(-1)) of GQDs in Chinese Hamster Ovary (CHO) cells. PMID:27302411

  20. [Vermicomposting of different organic materials and three-dimensional excitation emission matrix fluorescence spectroscopic characterization of their dissolved organic matter].

    PubMed

    Yang, Wei; Wang, Dong-sheng; Liu, Man-qiang; Hu, Feng; Li, Hui-xin; Huang, Zhong-yang; Chang, Yi-jun; Jiao, Jia-guo

    2015-10-01

    In this experiment, different proportions of the cattle manure, tea-leaf, herb and mushroom residues, were used as food for earthworm (Eisenia fetida) to study the growth of the earth-worm. Then the characteristics and transformation of nutrient content and three-dimensional excitation emission matrix fluorescence (3DEEM) of dissolved organic matter (DOM) during vermistabilization were investigated by means of chemical and spectroscopic methods. The result showed that the mixture of different ratios of cattle manure with herb residue, and cattle manure with tea-leaf were conducive to the growth of earthworm, while the materials compounded with mushroom residue inhibited the growth of earthworm. With the increasing time of verimcomposting, the pH in vermicompost tended to be circumneutral and weakly acidic, and there were increases in electrical conductivity, and the contents of total nitrogen, total phosphorus, available nitrogen, and available phosphorus, while the total potassium and available potassium increased first and then decreased, and the organic matter content decreased. 3DEEM and fluorescence regional integration results indicated that, the fluorescence of protein-like fluorescence peaks declined significantly, while the intensity of humic-like fluorescence peak increased significantly in DOM. Vermicomposting process might change the compositions of DOM with elevated concentrations of humic acid and fulvic acid in the organics. In all, this study suggested the suitability of 3DEEM for monitoring the organics transformation and assessing the maturity in the vermicomposting. PMID:26995929

  1. Fluorescence Excitation Spectra of Photo-Fragmented Nitrobenzene Using a Picosecond Laser: Potential Evidence for no Produced by Two Distinct Channels.

    NASA Astrophysics Data System (ADS)

    Lue, Christopher J.; Tanjaroon, Chakree; Johnson, J. Bruce; Reeve, Scott W.; Allen, Susan D.

    2013-06-01

    Upon absorption of a UV photon, nitrobenzene can dissociate into C_6H_5O and NO through two different mechanisms. Evidence for these mechanisms was obtained from velocity map imaging (VMI) studies and theoretical calculations. VMI experiments showed NO produced with two distinct rotational distributions, which the calculations explained as a fast and a slow channel for NO production. We have recorded high resolution fluorescence excitation spectra of the NO resulting from photo-fragmented nitrobenzene using a pulsed picosecond tunable laser (pulse width ≈ 15 ps) by means of a two-color process. In the two-color process, photons of a particular energy dissociated the nitrobenzene while photons of a different energy probed the A^2Σ^+← X^2Π_{(1/2,3/2)} NO band system between 225-260 nm. This laser system allowed us to vary the delay between the photolysis and excitation pulses. At longer delays (>1 ns), we observed an increase in the population of NO, which may be evidence that at least two photolysis channels produce NO. We present the spectra we recorded at various photolysis/probe delays ranging from 0.025 to 1.5 ns. The spectral subtraction method we used to observe the production increase is introduced. Hause, M. L.; Herath, N.; Zhu, R.; Lin, M. C. and Suits, A. G. Nat Chem, Nature Publishing Group, 2011, 3, 932-937

  2. High-speed laser-induced fluorescence and spark plug absorption sensor diagnostics for mixing and combustion studies in engines.

    PubMed

    Cundy, Michael; Schucht, Torsten; Thiele, Olaf; Sick, Volker

    2009-02-01

    Simultaneous high-speed in-cylinder measurements of laser-induced fluorescence of biacetyl as a fuel tracer and mid-infrared broadband absorption of fuel and combustion products (water and carbon dioxide) using a spark plug probe are compared in an optical engine. The study addresses uncertainties and the applicability of absorption measurements at a location slightly offset to the spark plug when information about mixing at the spark plug is desired. Absorbance profiles reflect important engine operation events, such as valve opening and closing, mixing, combustion, and outgassing from crevices. PMID:19183588

  3. Characterization of CDOM from urban waters in Northern-Northeastern China using excitation-emission matrix fluorescence and parallel factor analysis.

    PubMed

    Zhao, Ying; Song, Kaishan; Li, Sijia; Ma, Jianhang; Wen, Zhidan

    2016-08-01

    Chromophoric dissolved organic matter (CDOM) plays an important role in aquatic systems, but high concentrations of organic materials are considered pollutants. The fluorescent component characteristics of CDOM in urban waters sampled from Northern and Northeastern China were examined by excitation-emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) to investigate the source and compositional changes of CDOM on both space and pollution levels. One humic-like (C1), one tryptophan-like component (C2), and one tyrosine-like component (C3) were identified by PARAFAC. Mean fluorescence intensities of the three CDOM components varied spatially and by pollution level in cities of Northern and Northeastern China during July-August, 2013 and 2014. Principal components analysis (PCA) was conducted to identify the relative distribution of all water samples. Cluster analysis (CA) was also used to categorize the samples into groups of similar pollution levels within a study area. Strong positive linear relationships were revealed between the CDOM absorption coefficients a(254) (R (2) = 0.89, p < 0.01); a(355) (R (2) = 0.94, p < 0.01); and the fluorescence intensity (F max) for the humic-like C1 component. A positive linear relationship (R (2) = 0.77) was also exhibited between dissolved organic carbon (DOC) and the F max for the humic-like C1 component, but a relatively weak correlation (R (2) = 0.56) was detected between DOC and the F max for the tryptophan-like component (C2). A strong positive correlation was observed between the F max for the tryptophan-like component (C2) and total nitrogen (TN) (R (2) = 0.78), but moderate correlations were observed with ammonium-N (NH4-N) (R (2) = 0.68), and chemical oxygen demand (CODMn) (R (2) = 0.52). Therefore, the fluorescence intensities of CDOM components can be applied to monitor water quality in real time compared to that of traditional approaches. These results demonstrate

  4. Seasonal characterization of CDOM for lakes in semi-arid regions of Northeast China using excitation-emission matrices fluorescence and parallel factor analysis (EEM-PARAFAC)

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Song, K.; Wen, Z.; Li, L.; Zang, S.; Shao, T.; Li, S.; Du, J.

    2015-04-01

    The seasonal characteristics of fluorescence components in CDOM for lakes in the semi-arid region of Northeast China were examined by excitation-emission matrices fluorescence and parallel factor analysis (EEM-PARAFAC). Two humic-like peaks C1 (Ex/Em = 230, 300/425 nm) and C2 (Ex/Em = 255, 350/460 nm) and two protein-like B (Ex/Em = 220, 275/320 nm) and T (Ex/Em = 225, 290/360 nm) peaks were identified using PARAFAC. The average fluorescence intensity of the four components differed with seasonal variation from June and August 2013 to February and April 2014. The total fluorescence intensity significantly varied from 2.54 ± 0.68 nm-1 in June to the mean value 1.93 ± 0.70 nm-1 in August 2013, and then increased to 2.34 ± 0.92 nm-1 in February and reduced to the lowest 1.57 ± 0.55 nm-1 in April 2014. In general, the fluorescence intensity was dominated by peak C1, indicating that most part of CDOM for inland waters being investigated in this study was originated from phytoplankton degradation. The lowest C2 represents only a small portion of CDOM from terrestrial imported organic matter to water bodies through rainwash and soil leaching. The two protein-like intensities (B and T) formed in situ through microbial activity have almost the same intensity. Especially, in August 2013 and February 2014, the two protein-like peaks showed obviously difference from other seasons and the highest C1 (1.02 nm-1) was present in February 2014. Components 1 and 2 exhibited strong linear correlation (R2 = 0.633). There were significantly positive linear relationships between CDOM absorption coefficients a(254) (R2 = 0.72, 0.46, p < 0.01), a(280) (R2 = 0.77, 0.47, p < 0.01), a(350) (R2 = 0.76, 0.78, p < 0.01) and Fmax for two humic-like components (C1 and C2), respectively. A close relationship (R2 = 0.931) was found between salinity and DOC. However, almost no obvious correlation was found between salinity and EEM-PARAFAC extracted components except for C3 (R2 = 0.469). Results

  5. Atomic Resolution Mapping of the Excited-State Electronic Structure of Cu2O with Time-Resolved X-Ray Absorption Spectroscopy

    SciTech Connect

    Hillyard, Patrick B.; Kuchibhatla, Satyanarayana V N T; Glover, T. E.; Hertlein, M. P.; Huse, N.; Nachimuthu, Ponnusamy; Saraf, Laxmikant V.; Thevuthasan, Suntharampillai; Gaffney, Kelly J.

    2009-09-29

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that that the conduction band and valence band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  6. Atomic resolution mapping of the excited-state electronic structure of Cu2O with time-resolved x-ray absorption spectroscopy

    SciTech Connect

    Hillyard, P. W.; Kuchibhatla, S. V. N. T.; Glover, T. E.; Hertlein, M. P.; Huse, Nils; Nachimuthu, P.; Saraf, L. V.; Thevuthasan, S.; Gaffney, K. J.

    2010-05-02

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that the conduction-band and valence-band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  7. Absorption and fluorescence characteristics of rainwater CDOM and contribution to Lake Taihu, China

    NASA Astrophysics Data System (ADS)

    Zhang, Yunlin; Gao, Guang; Shi, Kun; Niu, Cheng; Zhou, Yongqiang; Qin, Boqiang; Liu, Xiaohan

    2014-12-01

    We characterized the composition and sources of chromophoric dissolved organic matter (CDOM) in rainwater, and assessed the relative contribution of rainwater CDOM to lake water in Lake Taihu based on rainwater collected during 35 rainfall events in 2012. Chemical analysis, ultraviolet-visible absorbance, and three-dimensional fluorescence spectroscopy were used to characterize CDOM. The CDOM absorption coefficient at 254 nm (a254) had a significant seasonal variation, with a mean of 3.67 ± 1.69 m-1 in the wet season (from April to early August), which was significantly lower than the means in the two dry seasons (8.26 ± 2.94 m-1 from January to March, and 7.60 ± 3.80 m-1 from late August to December). The mean humification index and the mean index of recent autochthonous contribution were 0.74 ± 0.48 and 1.31 ± 0.35, respectively, indicating that rainwater CDOM was dominated by an atmospheric microbial origin component. We identified four fluorescence components using parallel factor analysis modeling in the rainwater CDOM, i.e., two protein-like components (C1 and C2) and two fulvic-like components (C3 and C4), which had characteristics similar to those of protein and humic-like substances, respectively. The a254 was significantly and positively (p < 0.001) correlated with each of the five nutrient parameters: total dissolved nitrogen (r2 = 0.76), ammonium (r2 = 0.65), nitrate (r2 = 0.36), total dissolved phosphorus (r2 = 0.55), and phosphate (r2 = 0.50) showing the tightly coupling between CDOM and nutrients. Based on the deposition of the rainwater CDOM and the storage of the CDOM in Lake Taihu, the annual relative contribution of rainwater CDOM to the lake water was 11.7% in 2012. The results showed the important effect of wet deposition on CDOM sources in Lake Taihu, which is located in a region with severe air pollution in the Yangtze River Delta.

  8. Triplet excited electronic state switching induced by hydrogen bonding: A transient absorption spectroscopy and time-dependent DFT study.

    PubMed

    Ravi Kumar, Venkatraman; Ariese, Freek; Umapathy, Siva

    2016-03-21

    The solvent plays a decisive role in the photochemistry and photophysics of aromatic ketones. Xanthone (XT) is one such aromatic ketone and its triplet-triplet (T-T) absorption spectra show intriguing solvatochromic behavior. Also, the reactivity of XT towards H-atom abstraction shows an unprecedented decrease in protic solvents relative to aprotic solvents. Therefore, a comprehensive solvatochromic analysis of the triplet-triplet absorption spectra of XT was carried out in conjunction with time dependent density functional theory using the ad hoc explicit solvent model approach. A detailed solvatochromic analysis of the T-T absorption bands of XT suggests that the hydrogen bonding interactions are different in the corresponding triplet excited states. Furthermore, the contributions of non-specific and hydrogen bonding interactions towards differential solvation of the triplet states in protic solvents were found to be of equal magnitude. The frontier molecular orbital and electron density difference analysis of the T1 and T2 states of XT indicates that the charge redistribution in these states leads to intermolecular hydrogen bond strengthening and weakening, respectively, relative to the S0 state. This is further supported by the vertical excitation energy calculations of the XT-methanol supra-molecular complex. The intermolecular hydrogen bonding potential energy curves obtained for this complex in the S0, T1, and T2 states support the model. In summary, we propose that the different hydrogen bonding mechanisms exhibited by the two lowest triplet excited states of XT result in a decreasing role of the nπ(∗) triplet state, and are thus responsible for its reduced reactivity towards H-atom abstraction in protic solvents. PMID:27004870

  9. Triplet excited electronic state switching induced by hydrogen bonding: A transient absorption spectroscopy and time-dependent DFT study

    NASA Astrophysics Data System (ADS)

    Ravi Kumar, Venkatraman; Ariese, Freek; Umapathy, Siva

    2016-03-01

    The solvent plays a decisive role in the photochemistry and photophysics of aromatic ketones. Xanthone (XT) is one such aromatic ketone and its triplet-triplet (T-T) absorption spectra show intriguing solvatochromic behavior. Also, the reactivity of XT towards H-atom abstraction shows an unprecedented decrease in protic solvents relative to aprotic solvents. Therefore, a comprehensive solvatochromic analysis of the triplet-triplet absorption spectra of XT was carried out in conjunction with time dependent density functional theory using the ad hoc explicit solvent model approach. A detailed solvatochromic analysis of the T-T absorption bands of XT suggests that the hydrogen bonding interactions are different in the corresponding triplet excited states. Furthermore, the contributions of non-specific and hydrogen bonding interactions towards differential solvation of the triplet states in protic solvents were found to be of equal magnitude. The frontier molecular orbital and electron density difference analysis of the T1 and T2 states of XT indicates that the charge redistribution in these states leads to intermolecular hydrogen bond strengthening and weakening, respectively, relative to the S0 state. This is further supported by the vertical excitation energy calculations of the XT-methanol supra-molecular complex. The intermolecular hydrogen bonding potential energy curves obtained for this complex in the S0, T1, and T2 states support the model. In summary, we propose that the different hydrogen bonding mechanisms exhibited by the two lowest triplet excited states of XT result in a decreasing role of the nπ∗ triplet state, and are thus responsible for its reduced reactivity towards H-atom abstraction in protic solvents.

  10. Self-trapping and excited state absorption in fluorene homo-polymer and copolymers with benzothiadiazole and tri-phenylamine.

    PubMed

    Denis, Jean-Christophe; Ruseckas, Arvydas; Hedley, Gordon J; Matheson, Andrew B; Paterson, Martin J; Turnbull, Graham A; Samuel, Ifor D W; Galbraith, Ian

    2016-08-01

    Excited state absorption (ESA) is studied using time-dependent density functional theory and compared with experiments performed in dilute solutions. The molecules investigated are a fluorene pentamer, polyfluorene F8, the alternating F8 copolymer with benzothiadiazole F8BT, and two blue-emitting random copolymers F8PFB and F8TFB. Calculated and measured spectra show qualitatively comparable results. The ESA cross-section of co-polymers at its maximum is about three times lower than that of F8. The ESA spectra are found to change little upon structural relaxation of the excited state, or change in the order of sub-units in a co-polymer, for all studied molecules. In all these molecules, the strongest ESA transition is found to arise from the same electronic process, exhibiting a reversal of the charge parity. In addition, F8PFB and F8TFB are found to possess almost identical electronic behaviour. PMID:27439750

  11. Theoretical study of Raman chirped adiabatic passage by X-ray absorption spectroscopy: Highly excited electronic states and rotational effects

    SciTech Connect

    Engin, Selma; Sisourat, Nicolas Selles, Patricia; Taïeb, Richard; Carniato, Stéphane

    2014-06-21

    Raman Chirped Adiabatic Passage (RCAP) is an efficient method to climb the vibrational ladder of molecules. It was shown on the example of fixed-in-space HCl molecule that selective vibrational excitation can thus be achieved by RCAP and that population transfer can be followed by X-ray Photoelectron spectroscopy [S. Engin, N. Sisourat, P. Selles, R. Taïeb, and S. Carniato, Chem. Phys. Lett. 535, 192–195 (2012)]. Here, in a more detailed analysis of the process, we investigate the effects of highly excited electronic states and of molecular rotation on the efficiency of RCAP. Furthermore, we propose an alternative spectroscopic way to monitor the transfer by means of X-ray absorption spectra.

  12. Laser-Induced Fluorescence in Gaseous [I[subscript]2] Excited with a Green Laser Pointer

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2007-01-01

    A green laser pointer could be used in a flashy demonstration of laser-induced fluorescence in the gas phase by directing the beam of the laser through a cell containing [I[subscript]2] at its room temperature vapor pressure. The experiment could be used to provide valuable insight into the requirements for laser-induced fluorescence (LIF) and the…

  13. Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide

    SciTech Connect

    Degueldre, Claude Cozzo, Cedric; Martin, Matthias; Grolimund, Daniel; Mieszczynski, Cyprian

    2013-06-01

    Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regard to their environment and the coolant. In this work the study of the atomic structure and next-neighbour environment of Am in the (Pu,U)O₂ lattice in an irradiated (60 MW d kg⁻¹) MOX sample was performed employing micro-X-ray fluorescence (µ-XRF) and micro-X-ray absorption fine structure (µ-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Am (~0.66 wt%) are determined from the experimental data gained for the irradiated fuel material examined in its peripheral zone (rim) of the fuel. In the irradiated sample Am builds up as Am³⁺ species within an [AmO₈]¹³⁻ coordination environment (e.g. >90%) and no (<10%) Am(IV) or (V) can be detected in the rim zone. The occurrence of americium dioxide is avoided by the redox buffering activity of the uranium dioxide matrix. - Graphical abstract: Americium LIII XAFS spectra recorded for the irradiated MOX sub-sample in the rim zone for a 300 μm×300 μm beam size area investigated over six scans of 4 h. The records remain constant during multi-scan. The analysis of the XAFS signal shows that Am is found as trivalent in the UO₂ matrix. This analytical work shall open the door of very challenging analysis (speciation of fission product and actinides) in irradiated nuclear fuels. - Highlights: • Americium was characterized by microX-ray absorption spectroscopy in irradiated MOX fuel. • The americium redox state as determined from XAS data of irradiated fuel material was Am(III). • In the sample, the Am³⁺ face an AmO₈¹³⁻coordination environment in the (Pu,U)O₂ matrix. • The americium dioxide is reduced by the uranium dioxide matrix.

  14. Electronic absorption spectra and solvatochromic shifts by the vertical excitation model: solvated clusters and molecular dynamics sampling.

    PubMed

    Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G

    2015-01-22

    A physically realistic treatment of solvatochromic shifts in liquid-phase electronic absorption spectra requires a proper account for various short- and long-range equilibrium and nonequilibrium solute-solvent interactions. The present article demonstrates that such a treatment can be accomplished using a mixed discrete-continuum approach based on the two-time-scale self-consistent state-specific vertical excitation model (called VEM) for electronic excitation in solution. We apply this mixed approach in combination with time-dependent density functional theory to compute UV/vis absorption spectra in solution for the n → π* ((1)A2) transition for acetone in methanol and in water, the π → π* ((1)A1) transition for para-nitroaniline (PNA) in methanol and in water, the n → π* ((1)B1) transition for pyridine in water, and the n → π* ((1)B1) transition for pyrimidine in water. Hydrogen bonding and first-solvation-shell-specific complexation are included by means of explicit solvent molecules, and solute-solvent dispersion is included by using the solvation model with state-specific polarizability (SMSSP). Geometries of microsolvated clusters were treated in two different ways, (i) using single liquid-phase global-minimum solute-solvent clusters containing up to two explicit solvent molecules and (ii) using solute-solvent cluster snapshots derived from molecular dynamics (MD) trajectories. The calculations in water involve using VEM/TDDFT excitation energies and oscillator strengths computed over 200 MD-derived solute-solvent clusters and convoluted with Gaussian functions. We also calculate ground- and excited-state dipole moments for interpretation. We find that inclusion of explicit solvent molecules generally improves the agreement with experiment and can be recommended as a way to include the effect of hydrogen bonding in solvatochromic shifts. PMID:25159827

  15. A reagentless enzymatic fluorescent biosensor for glucose based on upconverting glasses, as excitation source, and chemically modified glucose oxidase.

    PubMed

    Del Barrio, Melisa; Cases, Rafael; Cebolla, Vicente; Hirsch, Thomas; de Marcos, Susana; Wilhelm, Stefan; Galbán, Javier

    2016-11-01

    Upon near-infrared excitation Tm(3+)+Yb(3+) doped fluorohafnate glasses present upconversion properties and emit visible light. This property permits to use these glasses (UCG) as excitation sources for fluorescent optical biosensors. Taking this into account, in this work a fluorescent biosensor for glucose determination is designed and evaluated. The biosensor combines the UCG and the fluorescence of the enzyme glucose oxidase chemically modified with a fluorescein derivative (GOx-FS), whose intensity is modified during the enzymatic reaction with glucose. Optical parameters have been optimized and a mathematical model describing the behavior of the analytical signal is suggested. Working in FIA mode, the biosensor responds to glucose concentrations up to, at least, 15mM with a limit of detection of 1.9mM. The biosensor has a minimum lifetime of 9 days and has been applied to glucose determination in drinks. The applicability of the sensor was tested by glucose determination in two fruit juices. PMID:27591654

  16. Nondestructive Total Excitation-Emission Fluorescence Microscopy Combined with Multi-Way Chemometric Analysis for Visually Indistinguishable Single Fiber Discrimination.

    PubMed

    Muñoz de la Peña, Arsenio; Mujumdar, Nirvani; Heider, Emily C; Goicoechea, Hector C; Muñoz de la Peña, David; Campiglia, Andres D

    2016-03-01

    The potential of total excitation-emission fluorescence microscopy combined with multiway chemometric analysis was investigated for the nondestructive forensic analysis of textile fibers. The four pairs of visually indistinguishable fibers consisted of nylon 361 dyed with acid yellow 17 and acid yellow 23, acetate satin 105B dyed with disperse blue 3 and disperse blue 14, polyester 777 dyed with disperse red 1 and disperse red 19, and acrylic 864 dyed with basic green 1 and basic green 4. Excitation emission matrices were recorded with the aid of an inverted microscope and a commercial spectrofluorimeter. The full information content of excitation-emission matrices was processed with the aid of unsupervised parallel factor analysis (PARAFAC), PARAFAC supervised by linear discriminant analysis (LDA), and discriminant unfolded partial least-squares (DU-PLS). The ability of the latter algorithm to classify the four pairs of fibers demonstrates the advantage of using the multidimensionality of fluorescence data formats for the nondestructive analysis of forensic fiber evidence. PMID:26861578

  17. Two photon absorption laser induced fluorescence measurements of neutral density in a helicon plasma

    SciTech Connect

    Galante, M. E.; Magee, R. M.; Scime, E. E.

    2014-05-15

    We have developed a new diagnostic based on two-photon absorption laser induced fluorescence (TALIF). We use a high intensity (5 MW/cm{sup 2}), narrow bandwidth (0.1 cm{sup −1}) laser to probe the ground state of neutral hydrogen, deuterium and krypton with spatial resolution better than 0.2 cm, a time resolution of 10 ns, and a measurement cadence of 20 Hz. Here, we describe proof-of-principle measurements in a helicon plasma source that demonstrate the TALIF diagnostic is capable of measuring neutral densities spanning four orders of magnitude; comparable to the edge neutral gradients predicted in the DIII-D tokamak pedestal. The measurements are performed in hydrogen and deuterium plasmas and absolute calibration is accomplished through TALIF measurements in neutral krypton. The optical configuration employed is confocal, i.e., both light injection and collection are accomplished with a single lens through a single optical port in the vacuum vessel. The wavelength resolution of the diagnostic is sufficient to separate hydrogen and deuterium spectra and we present measurements from mixed hydrogen and deuterium plasmas that demonstrate isotopic abundance measurements are feasible. Time resolved measurements also allow us to explore the evolution of the neutral hydrogen density and temperature and effects of wall recycling. We find that the atomic neutral density grows rapidly at the initiation of the discharge, reaching the steady-state value within 1 ms. Additionally, we find that neutral hydrogen atoms are born with 0.08 eV temperatures, not 2 eV as is typically assumed.

  18. Forensic analysis of laser printed ink by X-ray fluorescence and laser-excited plume fluorescence.

    PubMed

    Chu, Po-Chun; Cai, Bruno Yue; Tsoi, Yeuk Ki; Yuen, Ronald; Leung, Kelvin S Y; Cheung, Nai-Ho

    2013-05-01

    We demonstrated a minimally destructive two-tier approach for multielement forensic analysis of laser-printed ink. The printed document was first screened using a portable-X-ray fluorescence (XRF) probe. If the results were not conclusive, a laser microprobe was then deployed. The laser probe was based on a two-pulse scheme: the first laser pulse ablated a thin layer of the printed ink; the second laser pulse at 193 nm induced multianalytes in the desorbed ink to fluoresce. We analyzed four brands of black toners. The toners were printed on paper in the form of patches or letters or overprinted on another ink. The XRF probe could sort the four brands if the printed letters were larger than font 20. It could not tell the printing sequence in the case of overprints. The laser probe was more discriminatory; it could sort the toner brands and reveal the overprint sequence regardless of font size while the sampled area was not visibly different from neighboring areas even under the microscope. In terms of general analytical performance, the laser probe featured tens of micrometer lateral resolution and tens to hundreds of nm depth resolution and atto-mole mass detection limits. It could handle samples of arbitrary size and shape and was air compatible, and no sample pretreatment was necessary. It will prove useful whenever high-resolution and high sensitivity 3D elemental mapping is required. PMID:23570307

  19. Study on the interaction between fluoroquinolones and erythrosine by absorption, fluorescence and resonance Rayleigh scattering spectra and their application

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Liu, Zhongfang; Liu, Jiangtao; Liu, Shaopu; Shen, Wei

    2008-03-01

    In pH 4.4-4.5 Britton-Robinson (BR) buffer solution, fluoroquinolone antibiotics (FLQs) including ciprofloxacin (CIP), norfloxacin (NOR), levofloxacin (LEV) and lomefloxacin (LOM) could react with erythrosine (Ery) to form 1:1 ion-association complexes, which not only resulted in the changes of the absorption spectra and the quenching of fluorescence, but also resulted in the great enhancement of resonance Rayleigh scattering (RRS). These offered some indications of the determination of fluoroquinolone antibiotics by spectrophotometric, fluorescence and resonance Rayleigh scattering methods. The detection limits for fluoroquinolone antibiotics were in the range of 0.097-0.265 μg/mL for absorption methods, 0.022-0.100 μg/mL for fluorophotometry and 0.014-0.027 μg/mL for RRS method, respectively. Among them, the RRS method had the highest sensitivity. In this work, the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions and the properties of the analytical chemistry were investigated. The methods have been successfully applied to determination of some fluoroquinolone antibiotics in human urine samples and tablets. Taking CIP-Ery system as an example, the charge distribution, the enthalpy of formation and the mean polarizability were calculated by density function theory (DFT) method. In addition, the reasons for the enhancement of scattering spectra were discussed.

  20. Intense red upconversion fluorescence emission in NIR-excited erbium-ytterbium doped laponite-derived phosphor

    NASA Astrophysics Data System (ADS)

    da Silva, Andréa F.; Moura, Diógenes S.; Gouveia-Neto, Artur S.; Silva, Elias A., Jr.; Bueno, Luciano A.; Costa, Ernande B.; Azevedo, Eduardo N.

    2011-02-01

    In this report the optical properties and energy-transfer frequency upconversion luminescence of Er3+/Yb3+-codoped laponite-derived powders under 975 nm infrared excitation is investigated. The 75%(laponite):25%(PbF2) samples doped with erbium and ytterbium ions, generated high intensity red emission around 660 nm and lower intensity green emission around 525, and 545 nm. The observed emission signals were examined as a function of the excitation power and annealing temperature. The results indicate that energy-transfer, and excited-state absorption are the major upconversion excitation mechanism for the erbium excited-state red emitting level. The precursor glass samples were also heat treated at annealing temperatures of 300 °C, 400 °C, 500 °C, and 600 °C, for a 2h period. The dependence of the visible upconversion luminescence emission upon the annealing temperature indicated the existence of an optimum temperature which leads to the generation of the most intense and spectrally pure red emission signal.