Absorption and fluorescence spectra of heterocyclic isomers from long-range-corrected density functional theory in polarizable continuum approach.

PubMed

Kityk, Andriy V

2012-03-22

Long-range-corrected (LC) DFT/TDDFT methods may provide adequate description of ground and excited state properties; however, accuracy of such an approach depends much on a range separation (exchange screening) representing adjustable model parameter. Its relation to a size or specific of molecular systems has been explored in numerous studies, whereas the effect of solvent environment is usually ignored during the evaluation of state properties. To benchmark and assess the quality of the LC-DFT/TDDFT formalism, we report the optical absorption and fluorescence emission energies of organic heterocyclic isomers, DPIPQ and PTNA, calculated by LC-BLYP DFT/TDDFT method in the polarizable continuum (PCM) approach. The calculations are compared with the optical absorption and fluorescence spectra measured in organic solvents of different polarity. Despite a considerable structural difference, both dyes exhibit quite similar range separations being somewhat different for the optical absorption and fluorescence emission processes. Properly parametrized LC-BLYP xc-potential well reproduces basic features of the optical absorption spectra including the electronic transitions to higher excited states. The DFT/TDDFT/PCM analysis correctly predicts the solvation trends although solvatochromic shifts of the electronic transition energies appear to be evidently underestimated in most cases, especially for the fluorescence emission. Considering the discrepancy between the experiment and theory, evaluated state dipole moments and solvation corrections to the exchange screening are analyzed. The results of the present study emphasize the importance of a solvent-dependent range separation in DFT/TDDFT/PCM calculations for investigating excited state properties. © 2012 American Chemical Society

Two-Photon Excitation, Fluorescence Microscopy, and Quantitative Measurement of Two-Photon Absorption Cross Sections

NASA Astrophysics Data System (ADS)

DeArmond, Fredrick Michael

As optical microscopy techniques continue to improve, most notably the development of super-resolution optical microscopy which garnered the Nobel Prize in Chemistry in 2014, renewed emphasis has been placed on the development and use of fluorescence microscopy techniques. Of particular note is a renewed interest in multiphoton excitation due to a number of inherent properties of the technique including simplified optical filtering, increased sample penetration, and inherently confocal operation. With this renewed interest in multiphoton fluorescence microscopy, comes an increased demand for robust non-linear fluorescent markers, and characterization of the associated tool set. These factors have led to an experimental setup to allow a systematized approach for identifying and characterizing properties of fluorescent probes in the hopes that the tool set will provide researchers with additional information to guide their efforts in developing novel fluorophores suitable for use in advanced optical microscopy techniques as well as identifying trends for their synthesis. Hardware was setup around a software control system previously developed. Three experimental tool sets were set up, characterized, and applied over the course of this work. These tools include scanning multiphoton fluorescence microscope with single molecule sensitivity, an interferometric autocorrelator for precise determination of the bandwidth and pulse width of the ultrafast Titanium Sapphire excitation source, and a simplified fluorescence microscope for the measurement of two-photon absorption cross sections. Resulting values for two-photon absorption cross sections and two-photon absorption action cross sections for two standardized fluorophores, four commercially available fluorophores, and ten novel fluorophores are presented as well as absorption and emission spectra.

Compact characterization of liquid absorption and emission spectra using linear variable filters integrated with a CMOS imaging camera

NASA Astrophysics Data System (ADS)

Wan, Yuhang; Carlson, John A.; Kesler, Benjamin A.; Peng, Wang; Su, Patrick; Al-Mulla, Saoud A.; Lim, Sung Jun; Smith, Andrew M.; Dallesasse, John M.; Cunningham, Brian T.

2016-07-01

A compact analysis platform for detecting liquid absorption and emission spectra using a set of optical linear variable filters atop a CMOS image sensor is presented. The working spectral range of the analysis platform can be extended without a reduction in spectral resolution by utilizing multiple linear variable filters with different wavelength ranges on the same CMOS sensor. With optical setup reconfiguration, its capability to measure both absorption and fluorescence emission is demonstrated. Quantitative detection of fluorescence emission down to 0.28 nM for quantum dot dispersions and 32 ng/mL for near-infrared dyes has been demonstrated on a single platform over a wide spectral range, as well as an absorption-based water quality test, showing the versatility of the system across liquid solutions for different emission and absorption bands. Comparison with a commercially available portable spectrometer and an optical spectrum analyzer shows our system has an improved signal-to-noise ratio and acceptable spectral resolution for discrimination of emission spectra, and characterization of colored liquid’s absorption characteristics generated by common biomolecular assays. This simple, compact, and versatile analysis platform demonstrates a path towards an integrated optical device that can be utilized for a wide variety of applications in point-of-use testing and point-of-care diagnostics.

Compact characterization of liquid absorption and emission spectra using linear variable filters integrated with a CMOS imaging camera.

PubMed

Wan, Yuhang; Carlson, John A; Kesler, Benjamin A; Peng, Wang; Su, Patrick; Al-Mulla, Saoud A; Lim, Sung Jun; Smith, Andrew M; Dallesasse, John M; Cunningham, Brian T

2016-07-08

A compact analysis platform for detecting liquid absorption and emission spectra using a set of optical linear variable filters atop a CMOS image sensor is presented. The working spectral range of the analysis platform can be extended without a reduction in spectral resolution by utilizing multiple linear variable filters with different wavelength ranges on the same CMOS sensor. With optical setup reconfiguration, its capability to measure both absorption and fluorescence emission is demonstrated. Quantitative detection of fluorescence emission down to 0.28 nM for quantum dot dispersions and 32 ng/mL for near-infrared dyes has been demonstrated on a single platform over a wide spectral range, as well as an absorption-based water quality test, showing the versatility of the system across liquid solutions for different emission and absorption bands. Comparison with a commercially available portable spectrometer and an optical spectrum analyzer shows our system has an improved signal-to-noise ratio and acceptable spectral resolution for discrimination of emission spectra, and characterization of colored liquid's absorption characteristics generated by common biomolecular assays. This simple, compact, and versatile analysis platform demonstrates a path towards an integrated optical device that can be utilized for a wide variety of applications in point-of-use testing and point-of-care diagnostics.

Ag@Aggregation-induced emission dye core/shell nanostructures with enhanced one- and two-photon fluorescence

NASA Astrophysics Data System (ADS)

Wang, Cheng; Li, Yang; Xu, Qiujin; Luo, Liang

2017-10-01

Combining plasmonic nanostructures with two-photon fluorescence materials is a promising way to significantly enhance two-photon fluorescence. Ag@1,4-bis(2-cyano-2-phenylethenyl) benzene (BCPEB) core/shell nanostructures were fabricated by simply incubating the isolated Ag nanoparticles with BCPEB microrods in ethanol. BCPEB was chosen as the fluorescent organic molecule owing to the aggregation-induced-emission (AIE) nature which would reduce the emission loss as being practically applied in solid phase. By utilizing the match of the extinction spectrum of Ag nanoparticles and BCPEB's absorption band, the target Ag@BCPEB core/shell nanostructures showed an enhanced one-photon (12×) fluorescence, integrating with SERS signal as well. Moreover, the resultant second harmonic generation of Ag nanoparticles under two-photon excitation also well matched with the absorption band of BCPEB, and significant enhanced two-photon (17×) fluorescence was obtained. The confocal images of NIH-3T3 cells with these nanostructures under one- and two-photon excitation showed good contrast and brightness for bio-imaging.

Numerical Modeling of Fluorescence Emission Energy Dispersion in Luminescent Solar Concentrator

NASA Astrophysics Data System (ADS)

Li, Lanfang; Sheng, Xing; Rogers, John; Nuzzo, Ralph

2013-03-01

We present a numerical modeling method and the corresponding experimental results, to address fluorescence emission dispersion for applications such as luminescent solar concentrator and light emitting diode color correction. Previously established modeling methods utilized a statistic-thermodynamic theory (Kenard-Stepnov etc.) that required a thorough understanding of the free energy landscape of the fluorophores. Some more recent work used an empirical approximation of the measured emission energy dispersion profile without considering anti-Stokes shifting during absorption and emission. In this work we present a technique for modeling fluorescence absorption and emission that utilizes the experimentally measured spectrum and approximates the observable Frank-Condon vibronic states as a continuum and takes into account thermodynamic energy relaxation by allowing thermal fluctuations. This new approximation method relaxes the requirement for knowledge of the fluorophore system and reduces demand on computing resources while still capturing the essence of physical process. We present simulation results of the energy distribution of emitted photons and compare them with experimental results with good agreement in terms of peak red-shift and intensity attenuation in a luminescent solar concentrator. This work is supported by the DOE `Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under grant DE-SC0001293.

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. Copyright © 2014 Elsevier B.V. All rights reserved.

Absorption and emission spectroscopic characterisation of combined wildtype LOV1-LOV2 domain of phot from Chlamydomonas reinhardtii.

PubMed

Song, S-H; Dick, B; Zirak, P; Penzkofer, A; Schiereis, T; Hegemann, P

2005-10-03

An absorption and emission spectroscopic characterisation of the combined wild-type LOV1-LOV2 domain string (abbreviated LOV1/2) of phot from the green alga Chlamydomonas reinhardtii is carried out at pH 8. A LOV1/2-MBP fusion protein (MBP=maltose binding protein) and LOV1/2 with a His-tag at the C-terminus (LOV1/2-His) expressed in an Escherichia coli strain are investigated. Blue-light photo-excitation generates a non-fluorescent intermediate photoproduct (flavin-C(4a)-cysteinyl adduct with absorption peak at 390 nm). The photo-cycle dynamics is studied by dark-state absorption and fluorescence measurement, by following the temporal absorption and emission changes under blue and violet light exposure, and by measuring the temporal absorption and fluorescence recovery after light exposure. The fluorescence quantum yield, phi(F), of the dark adapted samples is phi(F)(LOV1/2-His) approximately 0.15 and phi(F)(LOV1/2-MBP) approximately 0.17. A bi-exponential absorption recovery after light exposure with a fast (in the several 10-s range) and a slow component (in the near 10-min range) are resolved. The quantum yield of photo-adduct formation, phi(Ad), is extracted from excitation intensity dependent absorption measurements. It decreases somewhat with rising excitation intensity. The behaviour of the combined wildtype LOV1-LOV2 double domains is compared with the behaviour of the separate LOV1 and LOV2 domains.

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.

Compact characterization of liquid absorption and emission spectra using linear variable filters integrated with a CMOS imaging camera

PubMed Central

Wan, Yuhang; Carlson, John A.; Kesler, Benjamin A.; Peng, Wang; Su, Patrick; Al-Mulla, Saoud A.; Lim, Sung Jun; Smith, Andrew M.; Dallesasse, John M.; Cunningham, Brian T.

2016-01-01

A compact analysis platform for detecting liquid absorption and emission spectra using a set of optical linear variable filters atop a CMOS image sensor is presented. The working spectral range of the analysis platform can be extended without a reduction in spectral resolution by utilizing multiple linear variable filters with different wavelength ranges on the same CMOS sensor. With optical setup reconfiguration, its capability to measure both absorption and fluorescence emission is demonstrated. Quantitative detection of fluorescence emission down to 0.28 nM for quantum dot dispersions and 32 ng/mL for near-infrared dyes has been demonstrated on a single platform over a wide spectral range, as well as an absorption-based water quality test, showing the versatility of the system across liquid solutions for different emission and absorption bands. Comparison with a commercially available portable spectrometer and an optical spectrum analyzer shows our system has an improved signal-to-noise ratio and acceptable spectral resolution for discrimination of emission spectra, and characterization of colored liquid’s absorption characteristics generated by common biomolecular assays. This simple, compact, and versatile analysis platform demonstrates a path towards an integrated optical device that can be utilized for a wide variety of applications in point-of-use testing and point-of-care diagnostics. PMID:27389070

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

Seasonal variability in CDOM absorption and fluorescence properties in the Barataria Basin, Louisiana, USA.

PubMed

Singh, Shatrughan; D'Sa, Eurico; Swenson, Erick

2010-01-01

Absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) along a 124 km transect in the Barataria Basin, a large estuary located in Louisiana, USA, were investigated during high and low flow periods of the Mississippi River in the spring and winter of 2008-2009. Mean CDOM absorption at 355 nm from the marine to the freshwater end member stations ranged from (3.25 +/- 0.56) to (20.76 +/- 2.43) m(-1) for the three month high flow period whereas it varied from (1.48 +/- 1.08) to (25.45 +/- 7.03) m(-1) for the same stations during low flow period. Corresponding salinity values at these stations indicated the influence of river and shelf exchanges in the lower basin and precipitation and runoff in the upper basin. An inverse relationship of CDOM absorbance and fluorescence with salinity observed in the basin could be a useful indicator of salinity. CDOM fluorescence also varied over a large range showing an approximately 8 to 12-fold increase between the marine and freshwater end members for the two flow seasons. Excitation-emission matrix spectral plots indicated the presence of various fluorescence components with highest being the A-peak, lowest the T-peak, and the C and M-peaks showing similar trends along the transect. During low flow season the A/C ratio were well correlated with station locations indicating increased terrestrial influence towards the upper basin. CDOM absorption and fluorescence at 355 nm were highly correlated and independent of CDOM sources suggesting that fluorescence could be used to characterize CDOM in the basin.

Direct and Indirect Electron Emission from the Green Fluorescent Protein Chromophore

NASA Astrophysics Data System (ADS)

Toker, Y.; Rahbek, D. B.; Klærke, B.; Bochenkova, A. V.; Andersen, L. H.

2012-09-01

Photoelectron spectra of the deprotonated green fluorescent protein chromophore have been measured in the gas phase at several wavelengths within and beyond the S0-S1 photoabsorption band of the molecule. The vertical detachment energy (VDE) was determined to be 2.68±0.1eV. The data show that the first electronically excited state is bound in the Franck-Condon region, and that electron emission proceeds through an indirect (resonant) electron-emission channel within the corresponding absorption band.

Absorption and fluorescence properties of colored dissolved organic matter in the Ross Sea during austral summer

NASA Astrophysics Data System (ADS)

D'Sa, E. J.; Kim, H. C.; Ha, S. Y.

2016-12-01

Colored dissolved organic matter (CDOM) spectral absorption and excitation-emission matrix (EEMs) fluorescence with parallel factor analysis (PARAFAC) were examined in the Ross Sea during a survey conducted on board the R/V Araon in the austral summer of 14/15. CDOM absorption at 355 nm ranged from 0.06 to 1.14 m-1 while spectral slope S calculated between 275-295 nm wavelength ranged from 18.83 to 33.32 µm-1 with water masses playing an important role in its variability. Spectral slope S decreased with increasing CDOM absorption indicating the strong role of photo-oxidation on CDOM abundance during the summer. PARAFAC analysis of EEM data identified two humic-like (terrestrial and marine-like) and a protein-like (tryptophan-like) component. The two humic-like components were well correlated with little variability spatially and across the water column ( 0-100 m) likely indicating more refractory material. The protein-like fluorescent component was relatively quite variable supporting the autochthonous production of this fluorescent component in the highly productive Ross Sea waters.

Donor-acceptor-pair emission in fluorescent 4H-SiC grown by PVT method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xi, E-mail: liuxi@mail.sic.ac.cn; Zhuo, Shi-Yi; Gao, Pan

Fluorescent SiC, which contains donor and acceptor impurities with optimum concentrations, can work as a phosphor for visible light emission by donor-acceptor-pair (DAP) recombination. In this work, 3 inch N-B-Al co-doped fluorescent 4H-SiC crystals are prepared by PVT method. The p-type fluorescent 4H-SiC with low aluminum doping concentration can show intensive yellow-green fluorescence at room temperature. N-B DAP peak wavelength shifts from 578nm to 525nm and weak N-Al DAP emission occurred 403/420 nm quenches, when the temperature increases from 4K to 298K. The aluminum doping induces higher defect concentration in the fluorescent crystal and decreases optical transmissivity of the crystalmore » in the visible light range. It triggers more non-radiative recombination and light absorption losses in the crystal.« less

Absorption and emission spectroscopic characterisation of 8-amino-riboflavin

NASA Astrophysics Data System (ADS)

Tyagi, A.; Zirak, P.; Penzkofer, A.; Mathes, T.; Hegemann, P.; Mack, M.; Ghisla, S.

2009-10-01

The flavin dye 8-amino-8-demethyl- D-riboflavin (AF) in the solvents water, DMSO, methanol, and chloroform/DMSO was studied by absorption and fluorescence spectroscopy. The first absorption band is red-shifted compared to riboflavin, and blue-shifted compared to roseoflavin (8-dimethylamino-8-demethyl-D-riboflavin). The fluorescence quantum yield of AF in the studied solvents varies between 20% and 50%. The fluorescence lifetimes were found to be in the 2-5 ns range. AF is well soluble in DMSO, weakly soluble in water and methanol, and practically insoluble in chloroform. The limited solubility causes AF aggregation, which was seen in differences between measured absorption spectra and fluorescence excitation spectra. Light scattering in the dye absorption region is discussed and approximate absorption cross-section spectra are determined from the combined measurement of transmission and fluorescence excitation spectra. The photo-stability of AF was studied by prolonged light exposure. The photo-degradation routes of AF are discussed.

Near-infrared fluorescence amplified organic nanoparticles with aggregation-induced emission characteristics for in vivo imaging

NASA Astrophysics Data System (ADS)

Geng, Junlong; Zhu, Zhenshu; Qin, Wei; Ma, Lin; Hu, Yong; Gurzadyan, Gagik G.; Tang, Ben Zhong; Liu, Bin

2013-12-01

Near-infrared (NIR) fluorescence signals are highly desirable to achieve high resolution in biological imaging. To obtain NIR emission with high brightness, fluorescent nanoparticles (NPs) are synthesized by co-encapsulation of 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenylamino)phenyl)fumaronitrile (TPETPAFN), a luminogen with aggregation-induced emission (AIE) characteristics, and a NIR fluorogen of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] as the encapsulation matrix. The good spectral overlap between the emission of TPETPAFN and the absorption of NIR775 leads to efficient energy transfer, resulting in a 47-fold enhancement of the NIR775 emission intensity upon excitation of TPETPAFN at 510 nm as compared to that upon direct excitation of NIR775 at 760 nm. The obtained fluorescent NPs show sharp NIR emission with a band width of 20 nm, a large Stokes shift of 275 nm, good photostability and low cytotoxicity. In vivo imaging study reveals that the synthesized NPs are able to provide high fluorescence contrast in live animals. The Förster resonance energy transfer strategy overcomes the intrinsic limitation of broad emission spectra for AIE NPs, which opens new opportunities to synthesize organic NPs with high brightness and narrow emission for potential applications in multiplex sensing and imaging.Near-infrared (NIR) fluorescence signals are highly desirable to achieve high resolution in biological imaging. To obtain NIR emission with high brightness, fluorescent nanoparticles (NPs) are synthesized by co-encapsulation of 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenylamino)phenyl)fumaronitrile (TPETPAFN), a luminogen with aggregation-induced emission (AIE) characteristics, and a NIR fluorogen of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000

Measurement of two-photon-absorption spectra through nonlinear fluorescence produced by a line-shaped excitation beam.

PubMed

Hasani, E; Parravicini, J; Tartara, L; Tomaselli, A; Tomassini, D

2018-05-01

We propose an innovative experimental approach to estimate the two-photon absorption (TPA) spectrum of a fluorescent material. Our method develops the standard indirect fluorescence-based method for the TPA measurement by employing a line-shaped excitation beam, generating a line-shaped fluorescence emission. Such a configuration, which requires a relatively high amount of optical power, permits to have a greatly increased fluorescence signal, thus avoiding the photon counterdetection devices usually used in these measurements, and allowing to employ detectors such as charge-coupled device (CCD) cameras. The method is finally tested on a fluorescent isothiocyanate sample, whose TPA spectrum, which is measured with the proposed technique, is compared with the TPA spectra reported in the literature, confirming the validity of our experimental approach. © 2018 The Authors Journal of Microscopy © 2018 Royal Microscopical Society.

Studies of Time-Resolved Fluorescence Spectroscopy and Resolved Absorption Spectra of Nucleic Acid Components.

NASA Astrophysics Data System (ADS)

Fu, Yingxian

1993-01-01

There is considerable uncertainty about dynamic aspects of the photophysics of the adenylyl chromophore, stemming from the discordant values reported for the room temperature fluorescence lifetimes (tau_1 = 5 ps, tau_2 = 330 ps for 9MeAde; tau_1 = 290 ps, tau_2 = 4.17 ns for ATP). Spectra reported in conjunction with these lifetimes create difficulties in assignment of emission. To clarify this situation I have investigated the fluorescence decay times and time -resolved emission spectra of adenylyl compounds under a variety of conditions (concentration, pH, solvent) using sub-ns laser excitation at 265 nm together with gated fast sampling (100 ps) detection and signal averaging. Multi -component decays and spectra are observed in aqueous solution. Major slow components (tau = 4.4 +/- 0.2 ns) with emission maxima at 380 nm are found for all components at pH 1.1 and for ATP at pH 4.4. At pH 7 a fast component (<100 ps) predominates. There is no marked evidence for a concentration dependence, the oscillator strengths are 10^ {-3}-10^{-5} and transitions must be classified as weakly forbidden. Single component emission is observed in acetonitrile and ethanol. The UV absorption spectra of biomolecules d(CG) and polyd(GC)cdotpolyd(GC) exhibit the different hypochromic effects due to different interactions between guanosine(G) and cytidine(C) in stacked form. The present work has been carried out to explain this quantitatively. To approach this problem the absorption spectra of G and C have been resolved into gaussian components using the PeakFit program. The absorption spectra (220-310 nm) of d(CG) and polyd(GC)cdotpolyd(GC) have been fitted with gaussian components of G and C (in the order of increasing energy, G1 and G2, and C1, C2 and C3, respectively), and the contribution to both spectra from individual gaussians is estimated in terms of oscillator strengths. The fitting results suggest that the small hypochromism in absorption spectrum of d(CG) may be attributed

Determination of total x-ray absorption coefficient using non-resonant x-ray emission

PubMed Central

Achkar, A. J.; Regier, T. Z.; Monkman, E. J.; Shen, K. M.; Hawthorn, D. G.

2011-01-01

An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that is both bulk sensitive and free of saturation effects. Here we show that the angle dependence of IPFY can provide a measure directly proportional to the total x-ray absorption coefficient, µ(E). In contrast, fluorescence yield (FY) and electron yield (EY) spectra are offset and/or distorted from µ(E) by an unknown and difficult to measure amount. Moreover, our measurement can determine µ(E) in absolute units with no free parameters by scaling to µ(E) at the non-resonant emission energy. We demonstrate this technique with measurements on NiO and NdGaO3. Determining µ(E) across edge-steps enables the use of XAS as a non-destructive measure of material composition. In NdGaO3, we also demonstrate the utility of IPFY for insulating samples, where neither EY or FY provide reliable spectra due to sample charging and self-absorption effects, respectively. PMID:22355697

[Chromophoric dissolved organic matter absorption characteristics with relation to fluorescence in typical macrophyte, algae lake zones of Lake Taihu].

PubMed

Zhang, Yun-lin; Qin, Bo-qiang; Ma, Rong-hua; Zhu, Guang-wei; Zhang, Lu; Chen, Wei-min

2005-03-01

Chromophoric dissolved organic matter (CDOM) represents one of the primary light-absorbing species in natural waters and plays a critical in determining the aquatic light field. CDOM shows a featureless absorption spectrum that increases exponentially with decreasing wavelength, which limits the penetration of biologically damaging UV-B radiation (wavelength from 280 to 320 nm) in the water column, thus shielding aquatic organisms. CDOM absorption measurements and their relationship with dissolved organic carbon (DOC), and fluorescence are presented in typical macrophyte and algae lake zone of Lake Taihu based on a field investigation in April in 2004 and lab analysis. Absorption spectral of CDOM was measured from 240 to 800 nm using a Shimadzu UV-2401PC UV-Vis recording spectrophotometer. Fluorescence with an excitation wavelength of 355 nm, an emission wavelength of 450 nm is measured using a Shimadzu 5301 spectrofluorometer. Concentrations of DOC ranged from 6.3 to 17.2 mg/L with an average of 9.08 +/- 2.66 mg/L. CDOM absorption coefficients at 280 nm and 355 nm were in the range of 11.2 - 32.6 m(-1) (average 17.46m(-1) +/- 5.75 m(-1) and 2.4 - 8.3 m(-1) (average 4.17m(-1) +/- 1.47 m(-l)), respectively. The values of the DOC-specific absorption coefficient at 355 nm ranged from 0.31 to 0.64 L x (mg x m)-1. Fluorescence emission at 450 nm, excited at 355 nm, had a mean value of 1.32nm(-1) +/- 0.84 nm(-1). A significant lake zone difference is found in DOC concentration, CDOM absorption coefficient and fluorescence, but not in DOC-specific absorption coefficient and spectral slope coefficient. This regional distribution pattern is in agreement with the location of sources of yellow substance: highest concentrations close to river mouth under the influence of river inflow, lower values in East Lake Taihu. The values of algae lake zone are obvious larger than those of macrophyte lake zone. In Meiliang Bay, CDOM absorption, DOC concentration and fluorescence tend to

Combined "dual" absorption and fluorescence smartphone spectrometers.

PubMed

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

2015-04-15

A combined "dual" absorption and fluorescence smartphone spectrometer is demonstrated. The optical sources used in the system are the white flash LED of the smartphone and an orthogonally positioned and interchangeable UV (λ_ex=370  nm) and blue (λ_ex=450  nm) LED. The dispersive element is a low-cost, nano-imprinted diffraction grating coated with Au. Detection over a 300 nm span with 0.42 nm/pixel resolution was carried out with the camera CMOS chip. By integrating the blue and UV excitation sources into the white LED circuitry, the entire system is self-contained within a 3D printed case and powered from the smartphone battery; the design can be scaled to add further excitation sources. Using a customized app, acquisition of absorption and fluorescence spectra are demonstrated using a blue-absorbing and green-emitting pH-sensitive amino-naphthalimide-based fluorescent probe and a UV-absorbing and blue-emitting Zn²⁺-sensitive fluoro-ionophore.

Absorption and Emission of the Apigenin and Luteolin Flavonoids: A TDDFT Investigation

NASA Astrophysics Data System (ADS)

Amat, Anna; Clementi, Catia; de Angelis, Filippo; Sgamellotti, Antonio; Fantacci, Simona

2009-09-01

The absorption and emission properties of the two components of the yellow color extracted from weld (Reseda luteola L.), apigenin and luteolin, have been extensively investigated by means of DFT and TDDFT calculations. Our calculations reproduce the absorption spectra of both flavonoids in good agreement with the experimental data and allow us to assign the transitions giving rise to the main spectral features. For apigenin, we have also computed the electronic spectrum of the monodeprotonated species, providing a rationale for the red-shift of the experimental spectrum with increasing pH. The fluorescence emission of both apigenin and luteolin has then been investigated. Excited-state TDDFT geometry optimizations have highlighted an excited-state intramolecular proton transfer (ESIPT) from the 5-hydroxyl to the 4-carbonyl oxygen of the substituted benzopyrone moiety. By computing the potential energy curves at the ground and excited states as a function of an approximate proton transfer coordinate for apigenin, we have been able to trace an ESIPT pathway and thus explain the double emission observed experimentally.

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

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 (UV(220) and UV(254)), 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, UV(220), C3 and C1 exhibited the highest correlation coefficients with BOD, COD, and TN concentrations, respectively. Multiple regression analysis using UV(220) and C3 demonstrated the enhancement of the prediction capability for TN.

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

USDA-ARS?s Scientific Manuscript database

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-...

QUASARS PROBING QUASARS. IV. JOINT CONSTRAINTS ON THE CIRCUMGALACTIC MEDIUM FROM ABSORPTION AND EMISSION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hennawi, Joseph F.; Prochaska, J. Xavier, E-mail: xavier@ucolick.org

2013-03-20

We have constructed a sample of 29 close projected quasar pairs where the background quasar spectrum reveals absorption from optically thick H I gas associated with the foreground quasar. These unique sightlines allow us to study the quasar circumgalactic medium (CGM) in absorption and emission simultaneously, because the background quasar pinpoints large concentrations of gas where Ly{alpha} emission, resulting from quasar-powered fluorescence, resonant Ly{alpha} scattering, and/or cooling radiation, is expected. A sensitive search (1{sigma} surface-brightness limits of SB{sub Ly{alpha}}{approx_equal}3 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2} arcsec{sup -2}) for diffuse Ly{alpha} emission in the environments of the foreground (predominantlymore » radio-quiet) quasars is conducted using Gemini/GMOS and Keck/LRIS slit spectroscopy. We fail to detect large-scale {approx}100 kpc Ly{alpha} emission, either at the location of the optically thick absorbers or in the foreground quasar halos, in all cases except a single system. We interpret these non-detections as evidence that the gas detected in absorption is shadowed from the quasar UV radiation due to obscuration effects, which are frequently invoked in unified models of active galactic nuclei. Small-scale R {approx}< 50 kpc extended Ly{alpha} nebulosities are detected in 34% of our sample, which are likely the high-redshift analogs of the extended emission-line regions (EELRs) commonly observed around low-redshift (z < 0.5) quasars. This may be fluorescent recombination radiation from a population of very dense clouds with a low covering fraction illuminated by the quasar. We also detect a compact high rest-frame equivalent width (W{sub Ly{alpha}} > 50 A) Ly{alpha}-emitter with luminosity L{sub Ly{alpha}} = 2.1 {+-} 0.32 Multiplication-Sign 10{sup 41} erg s{sup -1} at small impact parameter R = 134 kpc from one foreground quasar, and argue that it is more likely to result from quasar

A borane-bithiophene-BODIPY triad: intriguing tricolor emission and selective fluorescence response towards fluoride ions.

PubMed

Sarkar, Samir Kumar; Thilagar, Pakkirisamy

2013-10-04

The structure and photophysical properties of a new triad (borane–bithiophene–BODIPY) 1 have been investigated. Triad 1 exhibits unprecedented tricolour emission when excited at the borane centred high energy absorption band and also acts as a selective fluorescent and colorimetric sensor for fluoride ions with ratiometric response. The experimental results are supported by computational studies.

Coherent fluorescence emission by using hybrid photonic–plasmonic crystals

PubMed Central

Shi, Lei; Yuan, Xiaowen; Zhang, Yafeng; Hakala, Tommi; Yin, Shaoyu; Han, Dezhuan; Zhu, Xiaolong; Zhang, Bo; Liu, Xiaohan; Törmä, Päivi; Lu, Wei; Zi, Jian

2014-01-01

The spatial and temporal coherence of the fluorescence emission controlled by a quasi-two-dimensional hybrid photonic–plasmonic crystal structure covered with a thin fluorescent-molecular-doped dielectric film is investigated experimentally. A simple theoretical model to describe how a confined quasi-two-dimensional optical mode may induce coherent fluorescence emission is also presented. Concerning the spatial coherence, it is experimentally observed that the coherence area in the plane of the light source is in excess of 49 μm2, which results in enhanced directional fluorescence emission. Concerning temporal coherence, the obtained coherence time is 4 times longer than that of the normal fluorescence emission in vacuum. Moreover, a Young's double-slit interference experiment is performed to directly confirm the spatially coherent emission. This smoking gun proof of spatial coherence is reported here for the first time for the optical-mode-modified emission. PMID:25793015

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.

Absorption and emission spectroscopic characteristics of dipterex and its molecularly imprinted recognition: A TD-DFT investigation

NASA Astrophysics Data System (ADS)

Cheng, Xueli; Li, Liqing; Zhao, Yanyun; Wang, Chang'an

2016-05-01

By using G09 program package, the absorption and fluorescence/phosphorescence spectra of dipterex were explored, and its spectroscopic characters were altered by methacrylic acid (MAA) as the imprinted molecule. The TD-DFT results revealed that: (1) All absorption and emission excitations of dipterex are assigned to the nσ∗ transition; (2) without MAA as imprinted molecule, one of the dipterex Csbnd Cl bonds is extended significantly and dipterex is almost destroyed in transition states; (3) dipterex is connected to methacrylic acid via two hydrogen bonds; (4) for the dipterex-MAA complex, the electronic excitation (ππ∗ excitation) in absorption spectra is dominated by the configuration HOMO → LUMO.

Cryptography based on the absorption/emission features of multicolor semiconductor nanocrystal quantum dots.

PubMed

Zhou, Ming; Chang, Shoude; Grover, Chander

2004-06-28

Further to the optical coding based on fluorescent semiconductor quantum dots (QDs), a concept of using mixtures of multiple single-color QDs for creating highly secret cryptograms based on their absorption/emission properties was demonstrated. The key to readout of the optical codes is a group of excitation lights with the predetermined wavelengths programmed in a secret manner. The cryptograms can be printed on the surfaces of different objects such as valuable documents for security purposes.

Optical absorption and fluorescence spectroscopy studies of Artepillin C, the major component of green propolis

NASA Astrophysics Data System (ADS)

Camuri, Isamara Julia; Costa, Adriano Batista; Ito, Amando Siuiti; Pazin, Wallance Moreira

2018-06-01

The bioactivity of propolis against several pathogens is well established, leading to the extensive consumption of that bee product to prevent diseases. Brazilian green propolis, collected by the species Apis mellifera, is one of the most consumed in the world. The chemical composition of green propolis is complex and it has been shown that it displays antioxidant, antimicrobial, anti-inflammatory and antitumor activities, especially due to the high content of Artepillin C. The molecule is a derivative of cinnamic acid with two prenylated groups, responsible for the improvement of the affinity of the compound for lipophilic environment. A carboxylic group (COOH) is also present in the molecule, making it a pH-sensitive compound and the pH-dependent structure of Artepillin C, may modulate its biological activity related to interactions with the cellular membrane of organisms and tissues. Molecular properties of Artepillin C on aqueous solution were examined by optical absorption, steady state and time-resolved fluorescence spectroscopies. Acid-base titration based on the spectral position of the near UV absorption band, resulted in the pKa value of 4.65 for the carboxylic group in Artepillin C. In acidic pH, below the pKa value, an absorption band raised around 350 nm at Artepillin C concentration above 50 μM, due to aggregation of the molecule. In neutral pH, with excitation at 310 nm, Artepillin C presents dual emission at 400 and 450 nm. In pH close to the pKa, the optical spectra show contribution from both protonated and deprotonated species. A three-exponential function was necessary to fit the intensity decays at the different pHs, dominated by a very short lifetime component, around 0.060 ns. The fast decay resulted in emission before fluorescence depolarization, and in values of fluorescence anisotropy higher than could be expected for monomeric forms of the compound. The results give fundamental knowledge about the protonation-deprotonation state of the

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).

Particle sensing with confined optical field enhanced fluorescence emission (Cofefe).

PubMed

Kenison, John P; Fast, Alexander; Matthews, Brandon M; Corn, Robert M; Potma, Eric Olaf

2018-05-14

We describe the development and performance of a new type of optical sensor suitable for registering the binding/dissociation of nanoscopic particles near a gold sensing surface. The method shares similarities with surface plasmon resonance microscopy but uses a completely different optical signature for reading out binding events. This new optical read-out mechanism, which we call confined optical field enhanced fluorescence emission (Cofefe), uses pulsed surface plasmon polariton fields at the gold/liquid interface that give rise to confined optical fields upon binding of the target particle to the gold surface. The confined near-fields are sufficient to induce two-photon absorption in the gold sensor surface near the binding site. Subsequent radiative recombination of the electron-hole pairs in the gold produces fluorescence emission, which can be captured by a camera in the far-field. Bound nanoparticles show up as bright confined spots against a dark background on the camera. We show that the Cofefe sensor is capable of detecting gold and silicon nanoparticles, as well as polymer nanospheres and sub-μm lipid droplets in a label-free manner with average illumination powers of less than 10 μW/μm 2 .

Fluorescence and absorption spectroscopy for warm dense matter studies and ICF plasma diagnostics

NASA Astrophysics Data System (ADS)

Hansen, Stephanie

2017-10-01

The burning core of an inertial confinement fusion (ICF) plasma at stagnation is surrounded by a shell of warm, dense matter whose properties are difficult both to model (due to a complex interplay of thermal, degeneracy, and strong coupling effects) and to diagnose (due to low emissivity and high opacity). We demonstrate a promising technique to study the warm dense shells of ICF plasmas based on the fluorescence emission of dopants or impurities in the shell material. This emission, which is driven by x-rays produced in the hot core, exhibits signature changes in response to compression and heating. High-resolution measurements of absorption and fluorescence features can refine our understanding of the electronic structure of material under high compression, improve our models of density-driven phenomena such as ionization potential depression and plasma polarization shifts, and help diagnose shell density, temperature, mass distribution, and residual motion in ICF plasmas at stagnation. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. This work was supported by the U.S. Department of Energy, Office of Science Early Career Research Program, Office of Fusion Energy Sciences under FWP-14-017426.

Spectroscopic studies, fluorescence quenching by molecular oxygen and amplified spontaneous emission of 1,4-bis [2-(2-pyridyl) vinyl] benzene (P2VB) diolefinic laser dye

NASA Astrophysics Data System (ADS)

El-Daly, Samy A.; Ebeid, E. M.

2014-04-01

The UV-visible electronic absorption spectra, molar absorptivity, fluorescence spectra, fluorescence quantum yield and excited state lifetime of 1,4-bis [2-(2-pyridyl) vinyl] benzene P2VB were measured in different solvents. The fluorescence quenching of P2VB by molecular oxygen was also studied using lifetime measurements. A 2 × 10-4 mol dm-3 solution of P2VB in dimethyl formamide (DMF) gave amplified spontaneous emission (ASE) in blue spectral region with emission maximum at 420 nm upon pumping by 337.1 nitrogen laser pulse. The photochemical quantum yields (ϕc) of trans-cis photoisomerization of P2VB were calculated in different organic solvents. The photoreactivity of P2VB are also studied PMMA matrix.

Photochemical synthesis and photophysical properties of coumarins bearing extended polyaromatic rings studied by emission and transient absorption measurements.

PubMed

Yamaji, Minoru; Hakoda, Yuma; Okamoto, Hideki; Tani, Fumito

2017-04-12

We prepared a variety of coumarin derivatives having expanded π-electron systems along the direction crossing the C 3 -C 4 bond of the coumarin skeleton via a photochemical cyclization process and investigated their photophysical features as a function of the number (n) of the added benzene rings based on emission and transient absorption measurements. Upon increasing n, the fluorescence quantum yields of the π-extended coumarins increased. Expanding the π-electron system on the C 3 -C 4 bond of the coumarin skeleton was found to be efficient for increasing the fluorescence ability more than that on the C 7 -C 8 bond. Introducing the methoxy group at the 7-position was also efficient for enhancing the fluorescence quantum yield and rate of the expanded coumarins. The non-radiative process from the fluorescence state was not substantially influenced by the expanded π-electron system. The competitive process with the fluorescence was found to be intersystem crossing to the triplet state based on the observations of the triplet-triplet absorption. The effects of the expanded π-electron systems on the fluorescence ability were investigated with the aid of TD-DFT calculations.

Photostable fluorescent organic dots with aggregation-induced emission (AIE dots) for noninvasive long-term cell tracing

NASA Astrophysics Data System (ADS)

Li, Kai; Qin, Wei; Ding, Dan; Tomczak, Nikodem; Geng, Junlong; Liu, Rongrong; Liu, Jianzhao; Zhang, Xinhai; Liu, Hongwei; Liu, Bin; Tang, Ben Zhong

2013-01-01

Long-term noninvasive cell tracing by fluorescent probes is of great importance to life science and biomedical engineering. For example, understanding genesis, development, invasion and metastasis of cancerous cells and monitoring tissue regeneration after stem cell transplantation require continual tracing of the biological processes by cytocompatible fluorescent probes over a long period of time. In this work, we successfully developed organic far-red/near-infrared dots with aggregation-induced emission (AIE dots) and demonstrated their utilities as long-term cell trackers. The high emission efficiency, large absorptivity, excellent biocompatibility, and strong photobleaching resistance of the AIE dots functionalized by cell penetrating peptides derived from transactivator of transcription proteins ensured outstanding long-term noninvasive in vitro and in vivo cell tracing. The organic AIE dots outperform their counterparts of inorganic quantum dots, opening a new avenue in the development of fluorescent probes for following biological processes such as carcinogenesis.

Kα X-Ray Emission Spectra and K X-Ray Absorption-Edge Structures of Fluorine in 3d Transition-Metal Difluorides

NASA Astrophysics Data System (ADS)

Sugiura, Chikara

1991-08-01

The fluorine Kα emission spectra in fluorescence from a series of 3d transition-metal difluorides MF2 (M=Mn, Fe, Co, Ni, Cu and Zn) have been measured with a high-resolution two-crystal vacuum spectrometer. It is shown that the observed FWHM of the Kα1,2 emission band is closely related to the difference in the electronegativity between the metal and fluorine atoms. The measured emission spectra are presented along with the UPS or XPS spectra of the valence bands and the fluorine K absorption spectra of the metal difluorides, reported previously. The structures at the fluorine K absorption edges are interpreted in terms of a molecular orbital (MO) model.

Development of Thermally Stable and Highly Fluorescent IR Dyes

NASA Technical Reports Server (NTRS)

Bu, Xiu R.

2004-01-01

Fluorophores are the core component in various optical applications such as sensors and probes. Fluorphores with low-energy or long wavelength emission, in particular, in NIR region, possess advantages of low interference and high sensitivity. In this study, we has explored several classes of imidazole-based compounds for NIR fluorescent properties and concluded: (1) thiazole-based imidazole compounds are fluorescent; (2) emission energy is tunable by additional donor groups; (3) they also possess impressive two- photon absorption properties; and (4) fluorescence emission can be induced by two- photon input. This report summarizes (1) synthesis of new series of fluorophore; (2) impact of electron-withdrawing groups on fluorescent property; (3) unique property of two-photon absorption; and (4) on-going development.

Inkjet printed fluorescent nanorod layers exhibit superior optical performance over quantum dots

NASA Astrophysics Data System (ADS)

Halivni, Shira; Shemesh, Shay; Waiskopf, Nir; Vinetsky, Yelena; Magdassi, Shlomo; Banin, Uri

2015-11-01

Semiconductor nanocrystals exhibit unique fluorescence properties which are tunable in size, shape and composition. The high quantum yield and enhanced stability have led to their use in biomedical imaging and flat panel displays. Here, semiconductor nanorod based inkjet inks are presented, overcoming limitations of the commonly reported quantum dots in printing applications. Fluorescent seeded nanorods were found to be outstanding candidates for fluorescent inks, due to their low particle-particle interactions and negligible self-absorption. This is manifested by insignificant emission shifts upon printing, even in highly concentrated printed layers and by maintenance of a high fluorescence quantum yield, unlike quantum dots which exhibit fluorescence wavelength shifts and quenching effects. This behavior results from the reduced absorption/emission overlap, accompanied by low energy transfer efficiencies between the nanorods as supported by steady state and time resolved fluorescence measurements. The new seeded nanorod inks enable patterning of thin fluorescent layers, for demanding light emission applications such as signage and displays.Semiconductor nanocrystals exhibit unique fluorescence properties which are tunable in size, shape and composition. The high quantum yield and enhanced stability have led to their use in biomedical imaging and flat panel displays. Here, semiconductor nanorod based inkjet inks are presented, overcoming limitations of the commonly reported quantum dots in printing applications. Fluorescent seeded nanorods were found to be outstanding candidates for fluorescent inks, due to their low particle-particle interactions and negligible self-absorption. This is manifested by insignificant emission shifts upon printing, even in highly concentrated printed layers and by maintenance of a high fluorescence quantum yield, unlike quantum dots which exhibit fluorescence wavelength shifts and quenching effects. This behavior results from the

Fluorescence emission of disperse Red 1 in solution at room temperature.

PubMed

Toro, Carlos; Thibert, Arthur; De Boni, Leonardo; Masunov, Artëm E; Hernández, Florencio E

2008-01-24

In this article, we report the fluorescence emission of Disperse Red 1 in solution at room temperature and pumping at 532 nm with a 25 mW diode laser. We have measured its fluorescence quantum yield in methanol, ethylene glycol, glycerol, and phenol obtaining values as high as 10(-3) in the aliphatic alcohols. The excitation spectra of Disperse Red 1 in all four solvents as well as its excitation anisotropy in glycerol are presented. Applying a Gaussian decomposition method to the absorption spectra along with the support from the excitation spectra, the positions of the different transitions in this pseudo-stilbene azobenzene dye were determined. Solvatochromic and isomerization constraint effects are discussed. Calculations using density functional theory at TD-B3LYP/6-31G*//HF/6-31G* level were performed to interpret the experimental observations.

Solvent effects on the fluorescence and effective three-photon absorption of a Zn(II)-[meso-tetrakis(4-octyloxyphenyl)porphyrin

NASA Astrophysics Data System (ADS)

Wan, Yong; Xue, Yuxiong; Sheng, Ning; Rui, Guanghao; Lv, Changgui; He, Jun; Gu, Bing; Cui, Yiping

2018-06-01

The fluorescence and effective three-photon absorption (3PA) properties of Zn(II)-[meso-tetrakis(4-octyloxyphenyl)porphyrin] (labeled Zn(II)-porphyrin) dissolved in three different polar solvents were systematically investigated. The electrochemical and photophysical properties of Zn(II)-porphyrin were investigated by 1H NMR spectra, IR spectra, mass spectroscopy, and electronic absorption spectra. The fluorescence emission of Zn(II)-porphyrin in three different solvents excited at the wavelengths of 420 nm (Soret band) and 550 nm (Q-band) were analyzed. By performing Z-scan experiments with femtosecond laser pulses at a wavelength of 800 nm, the effective 3PA process of Zn(II)-porphyrin in three different solvents was observed and the underlying mechanism was discussed in detail. It is found that the fluorescence spectra slightly depend on the polarity of the solvent. Interestingly, the effective 3PA properties of Zn(II)-porphyrin strongly depend on the solvent polarity. The lower the solvent polarity is, the larger effective 3PA cross-section is. Low polar solvents are beneficial to applications of Zn(II)-porphyrin in optical limiting, photodynamic therapy, etc.

Fluorescence Spectroscopy Applied to Monitoring Biodiesel Degradation: Correlation with Acid Value and UV Absorption Analyses.

PubMed

Vasconcelos, Maydla Dos Santos; Passos, Wilson Espíndola; Lescanos, Caroline Honaiser; Pires de Oliveira, Ivan; Trindade, Magno Aparecido Gonçalves; Caires, Anderson Rodrigues Lima; Muzzi, Rozanna Marques

2018-01-01

The techniques used to monitor the quality of the biodiesel are intensely discussed in the literature, partly because of the different oil sources and their intrinsic physicochemical characteristics. This study aimed to monitor the thermal degradation of the fatty acid methyl esters of Sesamum indicum L. and Raphanus sativus L. biodiesels (SILB and RSLB, resp.). The results showed that both biodiesels present a high content of unsaturated fatty acids, ∼84% (SILB) and ∼90% (RSLB). The SILB had a high content of polyunsaturated linoleic fatty acid (18  :  2), about 49%, and the oleic monounsaturated (18  :  1), ∼34%. On the other hand, RSLB presented a considerable content of linolenic fatty acid (18  :  3), ∼11%. The biodiesel samples were thermal degraded at 110°C for 48 hours, and acid value, UV absorption, and fluorescence spectroscopy analysis were carried out. The results revealed that both absorption and fluorescence presented a correlation with acid value as a function of degradation time by monitoring absorptions at 232 and 270 nm as well as the emission at 424 nm. Although the obtained correlation is not completely linear, a direct correlation was observed in both cases, revealing that both properties can be potentially used for monitoring the biodiesel degradation.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bachelor, Paula P.; Jordan, David V.; Harper, Warren W.

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 measuremore » 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.« less

Photoacoustic emission from fluorescent nanodiamonds enhanced with gold nanoparticles

PubMed Central

Zhang, Bailin; Fang, Chia-Yi; Chang, Cheng-Chun; Peterson, Ralph; Maswadi, Saher; Glickman, Randolph D.; Chang, Huan-Cheng; Ye, Jing Yong

2012-01-01

Fluorescent nanodiamonds (FNDs) have drawn much attention in recent years for biomedical imaging applications due to their desired physical properties including excellent photostability, high biocompatibility, extended far-red fluorescence emission, and ease of surface functionalization. Here we explore a new feature of FNDs, i.e. their photoacoustic emission capability, which may lead to potential applications of using FNDs as a dual imaging contrast agent for combined fluorescence and photoacoustic imaging modalities. We observed significant enhancement of photoacoustic emission from FNDs when they were conjugated with gold nanoparticles (GNPs). PMID:22808436

Photoacoustic emission from fluorescent nanodiamonds enhanced with gold nanoparticles.

PubMed

Zhang, Bailin; Fang, Chia-Yi; Chang, Cheng-Chun; Peterson, Ralph; Maswadi, Saher; Glickman, Randolph D; Chang, Huan-Cheng; Ye, Jing Yong

2012-07-01

Fluorescent nanodiamonds (FNDs) have drawn much attention in recent years for biomedical imaging applications due to their desired physical properties including excellent photostability, high biocompatibility, extended far-red fluorescence emission, and ease of surface functionalization. Here we explore a new feature of FNDs, i.e. their photoacoustic emission capability, which may lead to potential applications of using FNDs as a dual imaging contrast agent for combined fluorescence and photoacoustic imaging modalities. We observed significant enhancement of photoacoustic emission from FNDs when they were conjugated with gold nanoparticles (GNPs).

Pixel-based absorption correction for dual-tracer fluorescence imaging of receptor binding potential

PubMed Central

Kanick, Stephen C.; Tichauer, Kenneth M.; Gunn, Jason; Samkoe, Kimberley S.; Pogue, Brian W.

2014-01-01

Ratiometric approaches to quantifying molecular concentrations have been used for decades in microscopy, but have rarely been exploited in vivo until recently. One dual-tracer approach can utilize an untargeted reference tracer to account for non-specific uptake of a receptor-targeted tracer, and ultimately estimate receptor binding potential quantitatively. However, interpretation of the relative dynamic distribution kinetics is confounded by differences in local tissue absorption at the wavelengths used for each tracer. This study simulated the influence of absorption on fluorescence emission intensity and depth sensitivity at typical near-infrared fluorophore wavelength bands near 700 and 800 nm in mouse skin in order to correct for these tissue optical differences in signal detection. Changes in blood volume [1-3%] and hemoglobin oxygen saturation [0-100%] were demonstrated to introduce substantial distortions to receptor binding estimates (error > 30%), whereas sampled depth was relatively insensitive to wavelength (error < 6%). In response, a pixel-by-pixel normalization of tracer inputs immediately post-injection was found to account for spatial heterogeneities in local absorption properties. Application of the pixel-based normalization method to an in vivo imaging study demonstrated significant improvement, as compared with a reference tissue normalization approach. PMID:25360349

Absorption, fluorescence, and acid-base equilibria of rhodamines in micellar media of sodium dodecyl sulfate

NASA Astrophysics Data System (ADS)

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 pKaapp = 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.

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

PubMed

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

1993-08-01

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

Effects of substituents in silyl groups on the absorption, fluorescence and structural properties of 1,3,6,8-tetrasilylpyrenes.

PubMed

Maeda, Hajime; Suzuki, Tsubasa; Segi, Masahito

2018-05-09

1,3,6,8-Tetrasilylpyrenes and related germyl and stannyl derivatives were synthesized, and their absorption and fluorescence spectroscopic and structural properties were elucidated. The results show that the UV-vis absorption maxima of these substances in CH2Cl2 solutions shift to longer wavelengths as the size of the alkyl groups and numbers of phenyl groups on silicon increase. Fluorescence quantum yields of tetrasilylpyrenes in cyclohexane are larger than that of pyrene, and a pentamethyldisilyl derivative has an emission efficiency of 0.79. Except in the case of the SiMe2H derivative, excimer emission was not observed in concentrated solutions of these substances. The SiMe2H and SiMe3 derivatives were shown to form CT complexes with tetracyanoethylene in CH2Cl2 solutions. The calculated energy barriers for rotation of the silyl groups about the Si-C bond increase as the steric bulk of the silyl group increases. 29Si NMR chemical shifts were found to depend on the sizes of the alkyl groups and numbers of phenyl groups. Data arising from theoretical calculations suggest that the silyl groups act as electron-donating groups, and the donating ability of the groups decreases in the order SiR3 > GeR3 > SnR3.

Method for accurate quantitation of background tissue optical properties in the presence of emission from a strong fluorescence marker

NASA Astrophysics Data System (ADS)

Bravo, Jaime; Davis, Scott C.; Roberts, David W.; Paulsen, Keith D.; Kanick, Stephen C.

2015-03-01

Quantification of targeted fluorescence markers during neurosurgery has the potential to improve and standardize surgical distinction between normal and cancerous tissues. However, quantitative analysis of marker fluorescence is complicated by tissue background absorption and scattering properties. Correction algorithms that transform raw fluorescence intensity into quantitative units, independent of absorption and scattering, require a paired measurement of localized white light reflectance to provide estimates of the optical properties. This study focuses on the unique problem of developing a spectral analysis algorithm to extract tissue absorption and scattering properties from white light spectra that contain contributions from both elastically scattered photons and fluorescence emission from a strong fluorophore (i.e. fluorescein). A fiber-optic reflectance device was used to perform measurements in a small set of optical phantoms, constructed with Intralipid (1% lipid), whole blood (1% volume fraction) and fluorescein (0.16-10 μg/mL). Results show that the novel spectral analysis algorithm yields accurate estimates of tissue parameters independent of fluorescein concentration, with relative errors of blood volume fraction, blood oxygenation fraction (BOF), and the reduced scattering coefficient (at 521 nm) of <7%, <1%, and <22%, respectively. These data represent a first step towards quantification of fluorescein in tissue in vivo.

Absorption and emission properties of photonic crystals and metamaterials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Lili

We study the emission and absorption properties of photonic crystals and metamaterials using Comsol Multiphysics and Ansoft HFSS as simulation tools. We calculate the emission properties of metallic designs using drude model and the results illustrate that an appropriate termination of the surface of the metallic structure can significantly increase the absorption and therefore the thermal emissivity. We investigate the spontaneous emission rate modifications that occur for emitters inside two-dimensional photonic crystals and find the isotropic and directional emissions with respect to different frequencies as we have expected.

Absorption and fluorescence spectroscopic characterization of BLUF domain of AppA from Rhodobacter sphaeroides

NASA Astrophysics Data System (ADS)

Zirak, P.; Penzkofer, A.; Schiereis, T.; Hegemann, P.; Jung, A.; Schlichting, I.

2005-08-01

The BLUF domain of the transcriptional anti-repressor protein AppA from the non-sulfur anoxyphototrophic purple bacterium Rhodobacter sphaeroides was characterized by absorption and emission spectroscopy. The BLUF domain constructs AppA 148 (consisting of amino-acid residues 1-148) and AppA 126 (amino-acid residues 1-126) are investigated. The cofactor of the investigated domains is found to consist of a mixture of the flavins riboflavin, FMN, and FAD. The dark-adapted domains exist in two different active receptor conformations (receptor states) with different sub-nanosecond fluorescence lifetimes (BLUF r,f and BLUF r,sl) and a small non-interacting conformation (BLUF nc). The active receptor conformations are transformed to putative signalling states (BLUF s,f and BLUF s,sl) of low fluorescence efficiency and picosecond fluorescence lifetime by blue-light excitation (light-adapted domains). In the dark at room temperature both signalling states recover back to the initial receptor states with a time constant of about 17 min. A quantum yield of signalling state formation of about 25% was determined by intensity dependent transmission measurements. A photo-cycle scheme is presented including photo-induced charge transfer complex formation, charge recombination, and protein binding pocket reorganisation.

Quantitative calculations of fluorescence polarization and absorption anisotropy kinetics of double- and triple-chromophore complexes with energy transfer.

PubMed Central

Demidov, A A

1994-01-01

A new method is presented for calculation of the fluorescence depolarization and kinetics of absorption anisotropy for molecular complexes with a limited number of chromophores. The method considers absorption and emission of light by both chromophores, and also energy transfer between them, with regard to their mutual orientations. The chromophores in each individual complex are rigidly positioned. The complexes are randomly distributed and oriented in space, and there is no energy transfer between them. The new "practical" formula for absorption anisotropy and fluorescence depolarization kinetics, P(t) = [3B(t) - 1 + 2A(t)]/[3 + B(t) + 4A(t)], is derived both for double- and triple-chromophore complexes with delta-pulse excitation. The parameter B(t) is given by (a) B(t) = cos2(theta) for double-chromophore complexes, and (b) B(t) = q12(t)cos2(theta 12) + q13(t)-cos2(theta 13) + q23(t)cos2(theta 23) for triple-chromophore complexes, where q12(t) + q13(t) + q23(t) = 1. Here theta ij are the angles between the chromophore transition dipole moments in the individual molecular complex. The parameters qij(t) and A(t) are dependent on chromophore spectroscopic features and on the rates of energy transfer. PMID:7696461

Emission wavelength tuning of fluorescence by fine structural control of optical metamaterials with Fano resonance

PubMed Central

Moritake, Y.; Kanamori, Y.; Hane, K.

2016-01-01

We demonstrated fine emission wavelength tuning of quantum dot (QD) fluorescence by fine structural control of optical metamaterials with Fano resonance. An asymmetric-double-bar (ADB), which was composed of only two bars with slightly different bar lengths, was used to obtain Fano resonance in the optical region. By changing the short bar length of ADB structures with high dimensional accuracy in the order of 10 nm, resonant wavelengths of Fano resonance were controlled from 1296 to 1416 nm. Fluorescence of QDs embedded in a polymer layer on ADB metamaterials were modified due to coupling to Fano resonance and fine tuning from 1350 to 1376 nm was observed. Wavelength tuning of modified fluorescence was reproduced by analysis using absorption peaks of Fano resonance. Tuning range of modified fluorescence became narrow, which was interpreted by a simple Gaussian model and resulted from comparable FWHM in QD fluorescence and Fano resonant peaks. The results will help the design and fabrication of metamaterial devices with fluorophores such as light sources and biomarkers. PMID:27622503

Photometric and fluorometric continuous kinetic assay of acid phosphatases with new substrates possessing longwave absorption and emission maxima.

PubMed

Koller, E; Wolfbeis, O S

1984-11-15

A direct and continuous kinetic method for the photometric and fluorometric determination of various acid phosphatases is described. It is based on new coumarin-derived phosphates, which after enzymatic hydrolysis undergo dissociation to form intensely colored and strongly fluorescent phenolate anions. The latter have absorption maxima ranging from 385 to 505 nm, and fluorescence maxima between 470 and 595 nm. The new substrates were compared with respect to their rate of enzymatic hydrolysis, optimum pH, and detection limits of acid phosphatase from potato and wheat germ. Detection limits of 0.001 unit/ml were found by photometry, and as low as 0.00006 unit/ml by fluorometry. The principal advantages of the new substrates over existing ones are longwave absorptions and emissions, large Stokes shifts, and the low pKa values of the corresponding phenols, thus allowing a direct and continuous assay of acid phosphatase even in weakly acidic solutions.

Dendritic copper phthalocyanine with aggregation induced blue emission and solid-state fluorescence

NASA Astrophysics Data System (ADS)

Wang, Jiayi; Pan, Lin; Zhou, Xuefei; Jia, Kun; Liu, Xiaobo

2016-09-01

In this work, dendritic copper phthalocyanine (CuPc) showing obvious aggregation induced emission (AIE) and strong solid-state fluorescence was synthesized. It was found that synthesized CuPc can be easily solubilized in polar aprotic solvent, where no fluorescence signal was detected. Interestingly, both the CuPc aggregates in solution and solid-state powder exhibited strong fluorescence emission around 480 nm, which should be attributed to the restriction of intramolecular rotation as rationalized in aggregation induced emission framework. Meanwhile the obvious crystalline enhanced solid-state fluorescent emission is observed for CuPc powder.

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.

Laser induced fluorescence of dental caries

NASA Technical Reports Server (NTRS)

Albin, S.; Byvik, C. E.; Buoncristiani, A. M.

1988-01-01

Significant differences between the optical spectra taken from sound regions of teeth and carious regions have been observed. These differences appear both in absorption and in laser induced fluorescence spectra. Excitation by the 488 nm line of an argon ion laser beam showed a peak in the emission intensity around 553 nm for the sound dental material while the emission peak from the carious region was red-shifted by approximately 40 nm. The relative absorption of carious region was significantly higher at 488 nm; however its fluorescence intensity peak was lower by an order of magnitude compared to the sound tooth. Implications of these results for a safe, reliable and early detection of dental caries are discussed.

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

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.

Life cycle analysis of greenhouse gas emissions for fluorescent lamps in mainland China.

PubMed

Chen, Sha; Zhang, Jiaxing; Kim, Junbeum

2017-01-01

China is the world's largest emitter of carbon dioxide, and it is also one of the largest fluorescent lamp consuming and producing country in the world. However, there are few studies evaluating greenhouse gas (GHG) emissions of fluorescent lamps in China. This analysis compared GHG emissions of compact fluorescent lamps with linear fluorescent lamps using life cycle assessment method in China's national conditions. The GHG emissions of fluorescent lamps from their manufacture to the final disposal phase on the national level of China were also quantified. The results indicate that the use phase dominates the GHG emissions for both lamps. Linear fluorescent lamp is a better source of light compared to compact fluorescent lamp with respect to GHG emissions. The analysis found that in 2011, China generated around 710.90milliontons CO 2 -eq associated with fluorescent lamps. The raw material production and use phases accounted for major GHG emissions. More than half of GHG emissions during the domestic production were embodied in the exported lamps in recent years. This urges the government to take necessary measures that lead to more environmental friendly production, consumption and trade patterns. Copyright © 2016 Elsevier B.V. All rights reserved.

Leaf Level Chlorophyll Fluorescence Emission Spectra: Narrow Band versus Full 650-800 nm Retrievals

NASA Astrophysics Data System (ADS)

Middleton, E.; Zhang, Q.; Campbell, P. K.; Huemmrich, K. F.; Corp, L.; Cheng, Y.

2012-12-01

Recently, chlorophyll fluorescence (ChlF) retrievals in narrow spectral regions (< 1 nm, between 750-770 nm) of the near infrared (NIR) region of Earth's reflected radiation have been achieved from satellites, including the Japanese GOSAT and the European Space Agency's Sciamachy/Envisat. However, these retrievals sample the total full-spectrum ChlF and are made at non-optimal wavelengths since they are not located at the peak fluorescence emission features. We wish to estimate the total full-spectrum ChlF based on emissions obtained at selected wavelengths. For this, we drew upon leaf emission spectra measured on corn leaves obtained from a USDA experimental cornfield in MD (USA). These emission spectra were determined for the adaxial and abaxial (i.e., top and underside) surfaces of leaves measured throughout the 2008 and 2011 growing seasons (n>400) using a laboratory instrument (Fluorolog-3, Horiba Scientific, USA), recorded in either 1 nm or 5 nm increments with monochromatic excitation wavelengths of either 532 or 420 nm. The total ChlF signal was computed as the area under the continuous spectral emission curves, summing the emission intensities (counts per second) per waveband. The individual narrow (1 or 5 nm) waveband emission intensities were linearly related to full emission values, with variable success across the spectrum. Equations were developed to estimate total ChlF from these individual wavebands. Here, we report the results for the average adaxial/abaxial emissions. Very strong relationships were achieved for the relatively high fluorescence intensities at the red chlorophyll peak, centered at 685 nm (r2= 0.98, RMSE = 5.53 x 107 photons/s) and in the nearby O2-B atmospheric absorption feature centered at 688 nm (r2 = 0.94, RMSE = 4.04 x 107), as well as in the far-red peak centered at 740 nm (r2=0.94, RMSE = 5.98 x107). Very good retrieval success occurred for the O2-A atmospheric absorption feature on the declining NIR shoulder centered at 760

Low light CMOS contact imager with an integrated poly-acrylic emission filter for fluorescence detection.

PubMed

Dattner, Yonathan; Yadid-Pecht, Orly

2010-01-01

This study presents the fabrication of a low cost poly-acrylic acid (PAA) based emission filter integrated with a low light CMOS contact imager for fluorescence detection. The process involves the use of PAA as an adhesive for the emission filter. The poly-acrylic solution was chosen due its optical transparent properties, adhesive properties, miscibility with polar protic solvents and most importantly its bio-compatibility with a biological environment. The emission filter, also known as an absorption filter, involves dissolving an absorbing specimen in a polar protic solvent and mixing it with the PAA to uniformly bond the absorbing specimen and harden the filter. The PAA is optically transparent in solid form and therefore does not contribute to the absorbance of light in the visible spectrum. Many combinations of absorbing specimen and polar protic solvents can be derived, yielding different filter characteristics in different parts of the spectrum. We report a specific combination as a first example of implementation of our technology. The filter reported has excitation in the green spectrum and emission in the red spectrum, utilizing the increased quantum efficiency of the photo sensitive sensor array. The thickness of the filter (20 μm) was chosen by calculating the desired SNR using Beer-Lambert's law for liquids, Quantum Yield of the fluorophore and the Quantum Efficiency of the sensor array. The filters promising characteristics make it suitable for low light fluorescence detection. The filter was integrated with a fully functional low noise, low light CMOS contact imager and experimental results using fluorescence polystyrene micro-spheres are presented.

Absorption into fluorescence. A method to sense biologically relevant gas molecules

NASA Astrophysics Data System (ADS)

Strianese, Maria; Varriale, Antonio; Staiano, Maria; Pellecchia, Claudio; D'Auria, Sabato

2011-01-01

In this work we present an innovative optical sensing methodology based on the use of biomolecules as molecular gating nano-systems. Here, as an example, we report on the detection ofanalytes related to climate change. In particular, we focused our attention on the detection ofnitric oxide (NO) and oxygen (O2). Our methodology builds on the possibility of modulating the excitation intensity of a fluorescent probe used as a transducer and a sensor molecule whose absorption is strongly affected by the binding of an analyte of interest used as a filter. The two simple conditions that have to be fulfilled for the method to work are: (a) the absorption spectrum of the sensor placed inside the cuvette, and acting as the recognition element for the analyte of interest, should strongly change upon the binding of the analyte and (b) the fluorescence dye transducer should exhibit an excitation band which overlaps with one or more absorption bands of the sensor. The absorption band of the sensor affected by the binding of the specific analyte should overlap with the excitation band of the transducer. The high sensitivity of fluorescence detection combined with the use of proteins as highly selective sensors makes this method a powerful basis for the development of a new generation of analytical assays. Proof-of-principle results showing that cytochrome c peroxidase (CcP) for NO detection and myoglobin (Mb) for O2 detection can be successfully used by exploiting our new methodology are reported. The proposed technology can be easily expanded to the determination of different target analytes.

Fluorescent measurements in whole blood and plasma using red-emitting dyes

NASA Astrophysics Data System (ADS)

Abugo, Omoefe O.; Herman, Petr; Lakowicz, Joseph R.

2000-04-01

We have determined the fluorescence characteristics of albumin blue 670 and Rhodamine 800 in plasma and blood in order to test the feasibility of making direct fluorescence sensing measurements in blood. These dyes were used because of their absorption in the red/NIR where absorption by hemoglobin is minimized. Front face illumination and detection was used to minimize absorption and scattering during measurement. Fluorescence emission was observed for these dyes in plasma and blood. Attenuation of the fluorescence emission was observed in blood because of hemoglobin absorption. Using frequency domain fluorometry, we recovered the expected lifetime parameters for both dyes in blood and plasma. We were able to quantify HSA concentrations using changes in the mean lifetime of AB670, a dye previously shown to bind preferentially to HSA. Rh800 concentrations in plasma and blood were also determined using modulation sensing. Anisotropy measurements revealed high Anisotropy for these dyes in plasma and blood. It also showed an increase in the anisotropy of AB670 with increase in HSA concentration in the presence of red blood cells. These results indicate that qualitative and quantitative fluorescence measurements can be made directly in blood without the need to process the blood.

Red Fluorescent Line Emission from Hydrogen Molecules in Diffuse Molecular Clouds

NASA Technical Reports Server (NTRS)

Neufeld, David A.; Spaans, Marco

1996-01-01

We have modeled the fluorescent pumping of electronic and vibrational emissions of molecular hydrogen (H2) within diffuse molecular clouds that are illuminated by ultraviolet continuum radiation. Fluorescent line intensities are predicted for transitions at ultraviolet, infrared, and red visible wavelengths as functions of the gas density, the visual extinction through the cloud, and the intensity of the incident UV continuum radiation. The observed intensity in each fluorescent transition is roughly proportional to the integrated rate of H2 photodissociation along the line of sight. Although the most luminous fluorescent emissions detectable from ground-based observatories lie at near-infrared wavelengths, we argue that the lower sky brightness at visible wavelengths makes the red fluorescent transitions a particularly sensitive probe. Fabry-Perot spectrographs of the type that have been designed to observe very faint diffuse Ha emissions are soon expected to yield sensitivities that will be adequate to detect H2 vibrational emissions from molecular clouds that are exposed to ultraviolet radiation no stronger than the mean radiation field within the Galaxy. Observations of red H2 fluorescent emission together with cospatial 21 cm H I observations could serve as a valuable probe of the gas density in diffuse molecular clouds.

Quantitative X-ray fluorescence computed tomography for low-Z samples using an iterative absorption correction algorithm

NASA Astrophysics Data System (ADS)

Huang, Rong; Limburg, Karin; Rohtla, Mehis

2017-05-01

X-ray fluorescence computed tomography is often used to measure trace element distributions within low-Z samples, using algorithms capable of X-ray absorption correction when sample self-absorption is not negligible. Its reconstruction is more complicated compared to transmission tomography, and therefore not widely used. We describe in this paper a very practical iterative method that uses widely available transmission tomography reconstruction software for fluorescence tomography. With this method, sample self-absorption can be corrected not only for the absorption within the measured layer but also for the absorption by material beyond that layer. By combining tomography with analysis for scanning X-ray fluorescence microscopy, absolute concentrations of trace elements can be obtained. By using widely shared software, we not only minimized the coding, took advantage of computing efficiency of fast Fourier transform in transmission tomography software, but also thereby accessed well-developed data processing tools coming with well-known and reliable software packages. The convergence of the iterations was also carefully studied for fluorescence of different attenuation lengths. As an example, fish eye lenses could provide valuable information about fish life-history and endured environmental conditions. Given the lens's spherical shape and sometimes the short distance from sample to detector for detecting low concentration trace elements, its tomography data are affected by absorption related to material beyond the measured layer but can be reconstructed well with our method. Fish eye lens tomography results are compared with sliced lens 2D fluorescence mapping with good agreement, and with tomography providing better spatial resolution.

Interpretation of the fluorescence signatures from vegetation

NASA Astrophysics Data System (ADS)

Buschmann, C.

Vegetation emits fluorescence as part of the energy taken up by absorption %of solar radiation from UV to the visible. This fluorescence consists of light with low intensity (only few percents of the reflected light) emitted from the leaves. The fluorescence emission of a green leaf is characterized by four bands with maxima in the blue (440 nm), green (520 nm), red (690 nm) and far red (740 nm) spectral region. The intensity of fluorescence in the maxima of the emission spectrum varies depending on the following six basic parameters which must be taken into account for the interpretation of fluorescence signatures from vegetation: (a) content of the fluorophores (ferulic acid, chlorophyll a), (b) temperature of the leaf, (c) penetration of excitation light into the leaf, (d) emission of fluorescence from the leaf (re-absorption inside the leaf tissue), (e) photosynthetic activity of the leaf, (f) non-radiative decay (heat production) parallel to the fluorescence The ratios between the intensities of the maxima (F440/F690, F440/F520, F690/F740) are used as characteristic fluorescence parameter. The wide range of changes of these ratios caused by differences in the leaf tissue (aerial interspaces, variegated/homogeneous green leaves), various types of stress (UV, photoinhibition, sun exposure, heat, water deficiency, N-deficiency) and chemicals (inhibitors, fertilizers) can be explained by changes of the six basic parameters. It will be shown that the interpretation of the fluorescence signatures, in most cases, must be based on a complex consideration of more than one of the basic parameters.

[Study of the Detecting System of CH4 and SO2 Based on Spectral Absorption Method and UV Fluorescence Method].

PubMed

Wang, Shu-tao; Wang, Zhi-fang; Liu, Ming-hua; Wei, Meng; Chen, Dong-ying; Wang, Xing-long

2016-01-01

According to the spectral absorption characteristics of polluting gases and fluorescence characteristics, a time-division multiplexing detection system is designed. Through this system we can detect Methane (CH4) and sulfur dioxide (SO2) by using spectral absorption method and the SO2 can be detected by using UV fluorescence method. The system consists of four parts: a combination of a light source which could be switched, the common optical path, the air chamber and the signal processing section. The spectral absorption characteristics and fluorescence characteristics are measured first. Then the experiment of detecting CH4 and SO2 through spectral absorption method and the experiment of detecting SO2 through UV fluorescence method are conducted, respectively. Through measuring characteristics of spectral absorption and fluorescence, we get excitation wavelengths of SO2 and CH4 measured by spectral absorption method at the absorption peak are 280 nm and 1.64 μm, respectively, and the optimal excitation wavelength of SO2 measured by UV fluorescence method is 220 nm. we acquire the linear relation between the concentration of CH4 and relative intensity and the linear relation between the concentration of SO2 and output voltage after conducting the experiment of spectral absorption method, and the linearity are 98.7%, 99.2% respectively. Through the experiment of UV fluorescence method we acquire that the relation between the concentration of SO2 and the voltage is linear, and the linearity is 99.5%. Research shows that the system is able to be applied to detect the polluted gas by absorption spectrum method and UV fluorescence method. Combing these two measurement methods decreases the costing and the volume, and this system can also be used to measure the other gases. Such system has a certain value of application.

Fluorescence detection of organic molecules in the Jovian atmosphere

NASA Technical Reports Server (NTRS)

Levine, J. S.; Rogowski, R. S.

1975-01-01

A search for fluorescent emission due to the presence of possible organic molecules in the Jovian atmosphere is described. We first consider natural Jovian fluorescent emission excited by precipitating auroral particles. Due to our lack of knowledge of the Jovian precipitating particle energies and fluxes we next consider fluorescent emission excited by a laser system aboard a Jupiter spacecraft. Laser-induced fluorescence is routinely used to monitor trace constituents and pollutants in the terrestrial atmosphere. Several spacecraft laser systems are currently under development. Our calculations indicate that laser-induced fluorescent detection is approximately two orders of magnitude more sensitive than rocket ultraviolet measurements of possible Jovian absorption features at 2600 A that have been attributed to the presence of adenine or benzene.

Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Geon Joon, E-mail: gjlee@kw.ac.kr; Sim, Geon Bo; Choi, Eun Ha

To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated watermore » (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.« less

Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Lee, Geon Joon; Sim, Geon Bo; Choi, Eun Ha; Kwon, Young-Wan; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

2015-01-01

To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

Study of the Many Fluorescent Lines and the Absorption Variability in GX 301-2 with XMM-Newton

NASA Technical Reports Server (NTRS)

Fuerst, F.; Suchy, S.; Kreykenbohm, I.; Barragan, L.; Wilms, J.; Pottschmidt, K.; Caballero, I.; Kretschmar, P.; Ferrigno, C.; Rothschild, R. E.

2011-01-01

We present an in-depth study of the High Mass X-ray Binary (HMXB) GX 301-2 during its pre-periastron flare using data from the XMM-Newton satellite. The energy spectrum shows a power law continuum absorbed by a large equivalent hydrogen column on the order of 10(exp 24)/ sq cm and a prominent Fe K-alpha fluorescent emission line. Besides the Fe K-alpha line, evidence for Fe K-Beta, Ni K-alpha, Ni K-Beta, S K-alpha, Ar K-alpha, Ca K-alpha, and Cr K-alpha fluorescent lines is found. The observed line strengths are consistent with fluorescence in a cold absorber. This is the first time that Cr K-alpha is seen in emission in the X-ray spectrum of a HMXB. In addition to the modulation by the strong pulse period of approx 685 sec the source is highly variable and shows different states of activity. We perform time-resolved as well as pulse-to-pulse resolved spectroscopy to investigate differences between these states of activity. We find that fluorescent line fluxes are strongly variable and generally follow the overall flux. The N-H value is variable by a factor of 2, but not correlated to continuum normalization. We find an interval of low flux in the light curve in which the pulsations cease almost completely, without any indication of an increasing absorption column. We investigate this dip in detail and argue that it is most likely that during the dip the accretion ceased and the afterglow of the fluorescent iron accounted for the main portion of the X-ray flux. A similar dip was found earlier in RXTE data, and we compare our findings to these results.

Optimization via specific fluorescence brightness of a receptor-targeted probe for optical imaging and positron emission tomography of sentinel lymph nodes

PubMed Central

Qin, Zhengtao; Hall, David J.; Liss, Michael A.; Hoh, Carl K.; Kane, Christopher J.; Wallace, Anne M.

2013-01-01

Abstract. The optical properties of a receptor-targeted probe designed for dual-modality mapping of the sentinel lymph node (SLN) was optimized. Specific fluorescence brightness was used as the design criterion, which was defined as the fluorescence brightness per mole of the contrast agent. Adjusting the molar ratio of the coupling reactants, IRDye 800CW-NHS-ester and tilmanocept, enabled us to control the number of fluorescent molecules attached to each tilmanocept, which was quantified by H1 nuclear magnetic resonance spectroscopy. Quantum yields and molar absorptivities were measured for unconjugated IRDye 800CW and IRDye 800CW-tilmanocept (800CW-tilmanocept) preparations at 0.7, 1.5, 2.3, 2.9, and 3.8 dyes per tilmanocept. Specific fluorescence brightness was calculated by multiplication of the quantum yield by the molar absorptivity and the number of dyes per tilmanocept. It predicted that the preparation with 2.3 dyes per tilmanocept would exhibit the brightest signal, which was confirmed by fluorescence intensity measurements using three optical imaging systems. When radiolabeled with Ga68 and injected into the footpads of mice, the probe identified SLNs by both fluorescence and positron emission tomography (PET) while maintaining high percent extraction by the SLN. These studies demonstrated the feasibility of 800CW-tilmanocept for multimodal SLN mapping via fluorescence and PET–computed tomography imaging. PMID:23958947

Experimental assessment of fluorescence microscopy signal enhancement by stimulated emission

NASA Astrophysics Data System (ADS)

Dake, Fumihiro; Yazawa, Hiroki

2017-10-01

The quantity of photons generated during fluorescence microscopy is principally determined by the quantum yield of the fluorescence dyes and the optical power of the excitation beam. However, even though low quantum yields can produce poor images, it is challenging to tune this parameter, while increasing the power of the excitation beam often results in photodamage. Here, we propose the use of stimulated emission (SE) as a means of enhancing both the signal intensity and signal-to-noise ratio during confocal fluorescence microscopy. This work experimentally confirmed that both these factors can be enhanced by SE radiation, through generating a greater number of photons than are associated with the standard fluorescence signal. We also propose the concept of stimulated emission enhancing fluorescence (SEEF) microscopy, which employs both the SE and fluorescence signals, and demonstrate that the intensity of an SEEF signal is greater than those of the individual SE and fluorescence signals.

On the uncertainty in single molecule fluorescent lifetime and energy emission measurements

NASA Technical Reports Server (NTRS)

Brown, Emery N.; Zhang, Zhenhua; Mccollom, Alex D.

1995-01-01

Time-correlated single photon counting has recently been combined with mode-locked picosecond pulsed excitation to measure the fluorescent lifetimes and energy emissions of single molecules in a flow stream. Maximum likelihood (ML) and least square methods agree and are optimal when the number of detected photons is large however, in single molecule fluorescence experiments the number of detected photons can be less than 20, 67% of those can be noise and the detection time is restricted to 10 nanoseconds. Under the assumption that the photon signal and background noise are two independent inhomogeneous poisson processes, we derive the exact joint arrival time probably density of the photons collected in a single counting experiment performed in the presence of background noise. The model obviates the need to bin experimental data for analysis, and makes it possible to analyze formally the effect of background noise on the photon detection experiment using both ML or Bayesian methods. For both methods we derive the joint and marginal probability densities of the fluorescent lifetime and fluorescent emission. the ML and Bayesian methods are compared in an analysis of simulated single molecule fluorescence experiments of Rhodamine 110 using different combinations of expected background nose and expected fluorescence emission. While both the ML or Bayesian procedures perform well for analyzing fluorescence emissions, the Bayesian methods provide more realistic measures of uncertainty in the fluorescent lifetimes. The Bayesian methods would be especially useful for measuring uncertainty in fluorescent lifetime estimates in current single molecule flow stream experiments where the expected fluorescence emission is low. Both the ML and Bayesian algorithms can be automated for applications in molecular biology.

On the Uncertainty in Single Molecule Fluorescent Lifetime and Energy Emission Measurements

NASA Technical Reports Server (NTRS)

Brown, Emery N.; Zhang, Zhenhua; McCollom, Alex D.

1996-01-01

Time-correlated single photon counting has recently been combined with mode-locked picosecond pulsed excitation to measure the fluorescent lifetimes and energy emissions of single molecules in a flow stream. Maximum likelihood (ML) and least squares methods agree and are optimal when the number of detected photons is large, however, in single molecule fluorescence experiments the number of detected photons can be less than 20, 67 percent of those can be noise, and the detection time is restricted to 10 nanoseconds. Under the assumption that the photon signal and background noise are two independent inhomogeneous Poisson processes, we derive the exact joint arrival time probability density of the photons collected in a single counting experiment performed in the presence of background noise. The model obviates the need to bin experimental data for analysis, and makes it possible to analyze formally the effect of background noise on the photon detection experiment using both ML or Bayesian methods. For both methods we derive the joint and marginal probability densities of the fluorescent lifetime and fluorescent emission. The ML and Bayesian methods are compared in an analysis of simulated single molecule fluorescence experiments of Rhodamine 110 using different combinations of expected background noise and expected fluorescence emission. While both the ML or Bayesian procedures perform well for analyzing fluorescence emissions, the Bayesian methods provide more realistic measures of uncertainty in the fluorescent lifetimes. The Bayesian methods would be especially useful for measuring uncertainty in fluorescent lifetime estimates in current single molecule flow stream experiments where the expected fluorescence emission is low. Both the ML and Bayesian algorithms can be automated for applications in molecular biology.

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

[Laser Induced Fluorescence Spectroscopic Analysis of Aromatics from One Ring to Four Rings].

PubMed

Zhang, Peng; Liu, Hai-feng; Yue, Zong-yu; Chen, Bei-ling; Yao, Ming-fa

2015-06-01

In order to distinguish small aromatics preferably, a Nd : YAG Laser was used to supply an excitation laser, which was adjusted to 0.085 J x cm(-2) at 266 nm. Benzene, toluene, naphthalene, phenanthrene, anthracene, pyrene and chrysene were used as the representative of different rings aromatics. The fluorescence emission spectra were researched for each aromatic hydrocarbon and mixtures by Laser induced fluorescence (LIF). Results showed that the rings number determined the fluorescence emission spectra, and the structure with same rings number did not affect the emission fluorescence spectrum ranges. This was due to the fact that the absorption efficiency difference at 266 nm resulted in that the fluorescence intensities of each aromatic hydrocarbon with same rings number were different and the fluorescence intensities difference were more apparently with aromatic ring number increasing. When the absorption efficiency was similar at 266 nm and the concentrations of each aromatic hydrocarbon were same, the fluorescence intensities were increased with aromatic ring number increasing. With aromatic ring number increasing, the fluorescence spectrum and emission peak wavelength were all red-shifted from ultraviolet to visible and the fluorescence spectrum range was also wider as the absorption efficiency was similar. The fluorescence emission spectra from one to four rings could be discriminated in the following wavelengths, 275 to 320 nm, 320 to 375 nm, 375 to 425 nm, 425 to 556 nm, respectively. It can be used for distinguish the type of the polycyclic aromatic hydrocarbons (PAHs) as it exists in single type. As PAHs are usually exist in a variety of different rings number at the same time, the results for each aromatic hydrocarbon may not apply to the aromatic hydrocarbon mixtures. For the aromatic hydrocarbon mixtures, results showed that the one- or two-ring PAHs in mixtures could not be detected by fluorescence as three- or four-ring PAHs existed in mixture

Airborne interferometer for atmospheric emission and solar absorption.

PubMed

Keith, D W; Dykema, J A; Hu, H; Lapson, L; Anderson, J G

2001-10-20

The interferometer for emission and solar absorption (INTESA) is an infrared spectrometer designed to study radiative transfer in the troposphere and lower stratosphere from a NASA ER-2 aircraft. The Fourier-transform spectrometer (FTS) operates from 0.7 to 50 mum with a resolution of 0.7 cm(-1). The FTS observes atmospheric thermal emission from multiple angles above and below the aircraft. A heliostat permits measurement of solar absorption spectra. INTESA's calibration system includes three blackbodies to permit in-flight assessment of radiometric error. Results suggest that the in-flight radiometric accuracy is ~0.5 K in the mid-infrared.

Spectrally selective fluorescence imaging of Chlorobaculum tepidum reaction centers conjugated to chelator-modified silver nanowires.

PubMed

Kowalska, Dorota; Szalkowski, Marcin; Ashraf, Khuram; Grzelak, Justyna; Lokstein, Heiko; Niedziolka-Jonsson, Joanna; Cogdell, Richard; Mackowski, Sebastian

2018-03-01

A polyhistidine tag (His-tag) present on Chlorobaculum tepidum reaction centers (RCs) was used to immobilize photosynthetic complexes on a silver nanowire (AgNW) modified with nickel-chelating nitrilo-triacetic acid (Ni-NTA). The optical properties of conjugated nanostructures were studied using wide-field and confocal fluorescence microscopy. Plasmonic enhancement of RCs conjugated to AgNWs was observed as their fluorescence intensity dependence on the excitation wavelength does not follow the excitation spectrum of RC complexes in solution. The strongest effect of plasmonic interactions on the emission intensity of RCs coincides with the absorption spectrum of AgNWs and is observed for excitation into the carotenoid absorption. From the absence of fluorescence decay shortening, we attribute the emission enhancement to increase of absorption in RC complexes.

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.

Vanishing absorption and blueshifted emission in FeLoBAL quasars

NASA Astrophysics Data System (ADS)

Rafiee, Alireza; Pirkola, Patrik; Hall, Patrick B.; Galati, Natalee; Rogerson, Jesse; Ameri, Abtin

2016-07-01

We study the dramatic decrease in iron absorption strength in the iron low-ionization broad absorption line quasar SDSS J084133.15+200525.8. We report on the continued weakening of absorption in the prototype of this class of variable broad absorption line quasar, FBQS J140806.2+305448. We also report a third example of this class, SDSS J123103.70+392903.6; unlike the other two examples, it has undergone an increase in observed continuum brightness (at 3000 Å rest frame) as well as a decrease in iron absorption strength. These changes could be caused by absorber transverse motion or by ionization variability. We note that the Mg II and UV Fe II lines in several FeLoBAL quasars are blueshifted by thousands of km s-1 relative to the H β emission line peak. We suggest that such emission arises in the outflowing winds normally seen only in absorption.

Absorption properties and graphitic carbon emission factors of forest fire aerosols

Treesearch

E.M. Patterson; Charles K. McMahon; D.E. Ward

1986-01-01

Abstract. Data on the optical absorption properties (expressed as a specific absorption, Ba) of the smoke emissions from fires with forest fuels have been determined for a series of low-intensity field fires and a series of laboratory scale fires. The B, data have been used to estimate the emission factors for graphitic...

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

Thermal emission and absorption of radiation in finite inverted-opal photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Florescu, Marian; Stimpson, Andrew J.; Lee, Hwang

We study theoretically the optical properties of a finite inverted-opal photonic crystal. The light-matter interaction is strongly affected by the presence of the three-dimensional photonic crystal and the alterations of the light emission and absorption processes can be used to suppress or enhance the thermal emissivity and absorptivity of the dielectric structure. We investigate the influence of the absorption present in the system on the relevant band edge frequencies that control the optical response of the photonic crystal. Our study reveals that the absorption processes cause spectral broadening and shifting of the band edge optical resonances, and determine a strongmore » reduction of the photonic band gap spectral range. Using the angular and spectral dependence of the band edge frequencies for stop bands along different directions, we argue that by matching the blackbody emission spectrum peak with a prescribed maximum of the absorption coefficient, it is possible to achieve an angle-sensitive enhancement of the thermal emission/absorption of radiation. This result opens a way to realize a frequency-sensitive and angle-sensitive photonic crystal absorbers/emitters.« less

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.

Modification of fluorescence and optical properties of Rhodamine B dye doped PVA/Chitosan polymer blend films

NASA Astrophysics Data System (ADS)

Padmakumari, R.; Ravindrachary, V.; Mahantesha, B. K.; Sagar, Rohan N.; Sahanakumari, R.; Bhajantri, R. F.

2018-05-01

Pure and Rhodamine B doped Poly (vinyl alcohol)/Chitosan composite films are prepared using solution casting method. Fourier transforms infrared spectra (FTIR), Ultraviolet-Visible (UV-Vis), fluorescence studies were used to characterize the prepared polymer films. The FT-IR results show that the appearance of new peaks along with shift in peak positions indicates the interaction of Rhodamine B with PVA-CS blend. Optical absorption edge, band gap and activation energy were determined from UV-Visible studies. The optical absorption edge increases, band gap decreases and activation energy increases with dopant concentration respectively. The corresponding emission spectra were studied using fluorescence spectroscopy. From the fluorescence study the quenching phenomena are observed in emission wavelength range of 607nm-613nm upon excitation with absorption maxima 443nm.

Pathological changes in Alzheimer"s brain evaluated with fluorescence emission analysis (FEA)

NASA Astrophysics Data System (ADS)

Christov, Alexander; Ottman, Todd; Grammas, Paula

2004-07-01

Development of AD is associated with cerebrovascular deposition of amyloid beta (Aβ) as well as a progressive increase in vasular collagen content. Both AΒ and collagen are naturally fluorescent compounds when exposed to UV light. We analyzed autofluorescence emitted from brain tissue samples and isolated brain resistance vessels harvested postmortem from patients with Alzheimer's disease (AD) and age-matched controls. Fluorescence emission, excited at 355 nm with an Nd:YAG laser, was measured using a fiber-optic based fluorescence spectroscopic system for tissue analysis. Significantly higher values of fluorescence emission intensity (P<0.001) in the spectral region from 465 to 490 nm were detected in brain resistance vessel samples from AD patients compared to the normal individuals. Results from western blot analysis showed elevated levels of type I and type III collagen, and reduced levels of type IV collagen in resistance vessels from AD patients, compared to control samples. In addition, using direct scanning of the cortical suface for fluoresxcence emission by the laser-induced fluorescence spectroscopy system we detected a significantly (P<0.05) higher level of apoptosis in AD brain tissue compared to age-matched controls. Fluorescence emission analysis (FEA) appears to be a sensitive technique for detecting structural changes in AD brain tissue.

Terahertz-Radiation-Enhanced Emission of Fluorescence from Gas Plasma

NASA Astrophysics Data System (ADS)

Liu, Jingle; Zhang, X.-C.

2009-12-01

We report the study of femtosecond laser-induced air plasma fluorescence under the illumination of terahertz (THz) pulses. Semiclassical modeling and experimental verification indicate that time-resolved THz radiation-enhanced emission of fluorescence is dominated by the electron kinetics and the electron-impact excitation of gas molecules or ions. We demonstrate that the temporal waveform of the THz field could be retrieved from the transient enhanced fluorescence, making omnidirectional, coherent detection available for THz time-domain spectroscopy.

Quantitative Measurement of Protease-Activity with Correction of Probe Delivery and Tissue Absorption Effects

PubMed Central

Salthouse, Christopher D.; Reynolds, Fred; Tam, Jenny M.; Josephson, Lee; Mahmood, Umar

2009-01-01

Proteases play important roles in a variety of pathologies from heart disease to cancer. Quantitative measurement of protease activity is possible using a novel spectrally matched dual fluorophore probe and a small animal lifetime imager. The recorded fluorescence from an activatable fluorophore, one that changes its fluorescent amplitude after biological target interaction, is also influenced by other factors including imaging probe delivery and optical tissue absorption of excitation and emission light. Fluorescence from a second spectrally matched constant (non-activatable) fluorophore on each nanoparticle platform can be used to correct for both probe delivery and tissue absorption. The fluorescence from each fluorophore is separated using fluorescence lifetime methods. PMID:20161242

Optical radiation emissions from compact fluorescent lamps.

PubMed

Khazova, M; O'Hagan, J B

2008-01-01

There is a drive to energy efficiency to mitigate climate change. To meet this challenge, the UK Government has proposed phasing out incandescent lamps by the end of 2011 and replacing them with energy efficient fluorescent lighting, including compact fluorescent lamps (CFLs) with integrated ballasts. This paper presents a summary of an assessment conducted by the Health Protection Agency in March 2008 to evaluate the optical radiation emissions of CFLs currently available in the UK consumer market. The study concluded that the UV emissions from a significant percentage of the tested CFLs with single envelopes may result in foreseeable overexposure of the skin when these lamps are used in desk or task lighting applications. The optical output of all tested CFLs, in addition to high-frequency modulation, had a 100-Hz envelope with modulation in excess of 15%. This degree of modulation may be linked to a number of adverse effects.

High resolution x-ray fluorescence spectroscopy - a new technique for site- and spin-selectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xin

1996-12-01

X-ray spectroscopy has long been used to elucidate electronic and structural information of molecules. One of the weaknesses of x-ray absorption is its sensitivity to all of the atoms of a particular element in a sample. Through out this thesis, a new technique for enhancing the site- and spin-selectivity of the x-ray absorption has been developed. By high resolution fluorescence detection, the chemical sensitivity of K emission spectra can be used to identify oxidation and spin states; it can also be used to facilitate site-selective X-ray Absorption Near Edge Structure (XANES) and site-selective Extended X-ray Absorption Fine Structure (EXAFS). Themore » spin polarization in K fluorescence could be used to generate spin selective XANES or spin-polarized EXAFS, which provides a new measure of the spin density, or the nature of magnetic neighboring atoms. Finally, dramatic line-sharpening effects by the combination of absorption and emission processes allow observation of structure that is normally unobservable. All these unique characters can enormously simplify a complex x-ray spectrum. Applications of this novel technique have generated information from various transition-metal model compounds to metalloproteins. The absorption and emission spectra by high resolution fluorescence detection are interdependent. The ligand field multiplet model has been used for the analysis of K{alpha} and K{beta} emission spectra. First demonstration on different chemical states of Fe compounds has shown the applicability of site selectivity and spin polarization. Different interatomic distances of the same element in different chemical forms have been detected using site-selective EXAFS.« less

Organic light-emitting device with a phosphor-sensitized fluorescent emission layer

DOEpatents

Forrest, Stephen [Ann Arbor, MI; Kanno, Hiroshi [Osaka, JP

2009-08-25

The present invention relates to organic light emitting devices (OLEDs), and more specifically to OLEDS that emit light using a combination of fluorescent emitters and phosphorescent emitters. The emissive region of the devices of the present invention comprise at least one phosphor-sensitized layer which has a combined emission from a phosphorescent emitter and a fluorescent emitter. In preferred embodiments, the invention relates to white-emitting OLEDS (WOLEDs).

Fluorescence emission induced by the femtosecond filament transmitting through the butane/air flame

NASA Astrophysics Data System (ADS)

Li, Suyu; Li, Yanhua; Shi, Zhe; Sui, Laizhi; Li, He; Li, Qingyi; Chen, Anmin; Jiang, Yuanfei; Jin, Mingxing

2018-01-01

We measure the backward fluorescence spectra generated by the femtosecond filament transmitting through the butane/air flame, and study the fluorescence emission from combustion intermediates (CN, CH and C2 radicals), air (mainly N2 and N2+). It is found that the fluorescence emission from combustion intermediates, N2 and N2+ shows difference when the femtosecond filament transmits through different parts of the butane/air flame, and we attempt to analyze it in this paper. This study demonstrates that the filament-induced fluorescence technique can be utilized to sense the combustion intermediates.

Composite fluorescent nanoparticles for biomedical imaging.

PubMed

Pansare, Vikram J; Bruzek, Matthew J; Adamson, Douglas H; Anthony, John; Prud'homme, Robert K

2014-04-01

In the rapidly expanding field of biomedical imaging, there is a need for nontoxic, photostable, and nonquenching fluorophores for fluorescent imaging. We have successfully encapsulated a new, extremely hydrophobic, pentacene-based fluorescent dye within polymeric nanoparticles (NPs) or nanocarriers (NCs) via the Flash NanoPrecipitation (FNP) process. Nanoparticles and dye-loaded micelles were formulated by FNP and characterized by dynamic light scattering, fluorescence spectroscopy, UV-VIS absorbance spectroscopy, and confocal microscopy. These fluorescent particles were loaded from less than 1% to 78% by weight core loading and the fluorescence maximum was found to be at 2.3 wt.%. The particles were also stably formed at 2.3% core loading from 20 up to 250 nm in diameter with per-particle fluorescence scaling linearly with the NC core volume. The major absorption peaks are at 458, 575, and 625 nm, and the major emission peaks at 635 and 695 nm. In solution, the Et-TP5 dye displays a strong concentration-dependent ratio of the emission intensities of the first two emission peaks, whereas in the nanoparticle core the spectrum is independent of concentration over the entire concentration range. A model of the fluorescence quenching was consistent with Förster resonant energy transfer as the cause of the quenching observed for Et-TP5. The Förster radius calculated from the absorption and emission spectra of Et-TP5 is 4.1 nm, whereas the average dye spacing in the particles at the maximum fluorescence is 3.9 nm. We have successfully encapsulated Et-TP5, a pentacene derivative dye previously only used in light-emitting diode applications, within NCs via the FNP process. The extreme hydrophobicity of the dye keeps it encapsulated in the NC core, its extended pentacene structure gives it relatively long wavelength emission at 695 nm, and the pentacene structure, without oxygen or nitrogen atoms in its core, makes it highly resistant to photobleaching. Its bulky side

Solvent induced fluorescence enhancement of graphene oxide studied by ultrafast spectroscopy

NASA Astrophysics Data System (ADS)

Zhao, Litao; Chen, Jinquan; He, Xiaoxiao; Yu, Xiantong; Yan, Shujun; Zhang, Sanjun; Pan, Haifeng; Xu, Jianhua

2018-05-01

Femtosecond transient absorption (TA) spectroscopy combined with picosecond time resolved fluorescence (TRF) were used to reveal the fluorescence kinetics of graphene oxide (GO) in water, ethanol and water-ethanol mixtures. Size-independent fluorescence of GO were observed in water, and pH-dependent fluorescence spectra could be fitted well by a triple emission relaxation with peaks around 440 nm, 500 nm, and 590 nm respectively. The results indicate that polycyclic aromatic hydrocarbons (PAHs) linked by oxygen-containing functional groups dominate GO's fluorescence emission. GO's fluorescence quantum yield was measured to be 2.8% in ethanol but 1.2% in water. The three decay components fluorescence decay, as well as the transient absorption dynamics with an offset, confirmed this solvent induced fluorescence enhancement. GO's Raman spectral signals showed that GO in ethanol has a smaller average size of PAHs than that of GO in water. Therefore, besides other enhancement effects reported in literatures, we proposed that solvents could also change the size of PAHs, resulting in a photoluminescence enhancement. Our experimental data demonstrates that GO's quantum yield could be up to 2.8% in water and 8.4% in ethanol and this observation may help ones to improve GO's photoluminescence efficiency as well as its applications in solution.

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.

[Seasonal variation in the absorption and fluorescence characteristics of CDOM in downstream of Liaohe River].

PubMed

Shao, Tian-Tian; Zhao, Ying; Song, Kai-Shan; Du, Jia; Ding, Zhi

2014-10-01

Chromophoric dissolved organic matter (CDOM), which is an important part of dissolved organic matter (DOM), is considered as the largest storage of dissolved organic carbon in the aquatic environment. Liaohe River is the seventh largest river in China with annual runoff of 1.48 billion m3. As a result, studying on CDOM of Liaohe River is very important in estimating the organic carbon flux into sea. Seasonal optical characteristics of CDOM in the downstream of Liaohe River were investigated using absorbance spectroscopy and fluorescence excitation-emission matrices (EEMs). CDOM absorption coefficient at 355 nm [aCDOM (355)] in spring was lower than that in autumn and winter while low molecular weight substances were found in autumn and high molecular weight substances in spring based on the absorption coefficient and absorption slope (S) of CDOM. Samples in different seasons all exhibited fairly strong protein-like fluorophore (fluorophore B and fluorophore T) in the EEMs but the values showed apparent temporal variations. Based on the analysis of the relationships between different fluorophores, strong correlations (R2 > 0. 9) were observed between fluorophore A and C in spring, fluorophore B and T in autumn and winter, which illustrated that they had similar CDOM originalsources. However, a weak relationship (R2 = 0.21) was found between fluorophore B and T in spring, demonstrating the complexity and diversity of CDOM sources. Starting from autumn to winter and the subsequent spring, humic-like fluorophores exhibited enhanced fluorescent intensity, which could be ascribed to exogenous input. Furthermore, linear relationship between aCDOM (355) and Fn (355) in different seasons was examined in the study, and the strongest relationship was obtained in winter (R2 = 0.75), followed by autumn (R2 = 0.48) and spring (R2 = 0.01). This study indicated that fluorophore B in autumn and winter (R = 0.66; R = 0.89) as well as humic-like fluorophores (A and C, R = 0.74; R = 0

Violet and blue light-induced green fluorescence emissions from dental caries.

PubMed

Shakibaie, F; Walsh, L J

2016-12-01

The objective of this laboratory study was to compare violet and visible blue LED light-elicited green fluorescence emissions from enamel and dentine in healthy or carious states. Microscopic digital photography was undertaken using violet and blue LED illumination (405 nm and 455 nm wavelengths) of tooth surfaces, which were photographed through a custom-made stack of green compensating filters which removed the excitation light and allowed green fluorescence emissions to pass. Green channel pixel data were analysed. Dry sound enamel and sound root surfaces showed strong green fluorescence when excited by violet or blue lights. Regions of cavitated dental caries gave lower green fluorescence, and this was similar whether the dentine in the lesions was the same colour as normal dentine or was darkly coloured. The presence of saliva on the surface did not significantly change the green fluorescence, while the presence of blood diluted in saliva depressed green fluorescence. Using violet or blue illumination in combination with green compensating filters could potentially aid in the assessment of areas of mineral loss. © 2016 Australian Dental Association.

Designing an anion-functionalized fluorescent ionic liquid as an efficient and reversible turn-off sensor for detecting SO2.

PubMed

Che, Siying; Dao, Rina; Zhang, Weidong; Lv, Xiaoyu; Li, Haoran; Wang, Congmin

2017-03-30

A novel anion-functionalized fluorescent ionic liquid was designed and prepared, which was capable of capturing sulphur dioxide with high capacity and could also be used as a good colorimetric and fluorescent SO 2 sensor. Compared to conventional fluorescent sensors, this fluorescent ionic liquid did not undergo aggregation-caused quenching or aggregation-induced emission, and the fluorescence was quenched when exposed to SO 2 , and the fluorescence would quench when exposed to SO 2 . The experimental absorption, spectroscopic investigation, and quantum chemical calculations indicated that the quenching of the fluorescence originated from SO 2 physical absorption, not chemical absorption. Furthermore, this fluorescent ionic liquid exhibited high selectivity, good quantification, and excellent reversibility for SO 2 detection, and showed potential for an excellent liquid sensor.

A case study on the myth of emission from aliphatic amides

NASA Astrophysics Data System (ADS)

Singh, Avinash Kumar; Das, Sreyashi; Datta, Anindya

2016-12-01

For several decades, aliphatic amidic compounds have been believed to be emissive. We report that this contention is incorrect and that the anomalous emission from amides originates in fluorescent impurities generated during their synthesis. In order to make this point, we have synthesized fluorescent compounds and have compared the absorption spectra with excitation spectra.

Potential mercury emissions from fluorescent lamps production and obsolescence in mainland China.

PubMed

Tan, Quanyin; Li, Jinhui

2016-01-01

The use of fluorescent lamps has expanded rapidly all over the world in recent years, because of their energy-saving capability. Consequently, however, mercury emissions from production, breakage, and discard of the lamps are drawing increasing concern from the public. This article focuses on evaluating the amount of mercury used for fluorescent lamp production, as well as the potential mercury emissions during production and breakage, in mainland China. It is expected to provide a comprehensive understanding about the risks present in the mercury from fluorescent lamps, and to know about the impacts of the policies on fluorescent lamps after their implementation. It is estimated that, in 2020, mercury consumption will be about 11.30-15.69 tonnes, a significant reduction of 34.9%-37.4% from that used in 2013, owing to improvement in mercury dosing dosage technology and tighter limitations on mercury content in fluorescent lamps. With these improvements, the amount of mercury remaining in fluorescent lamps and released during production is estimated to be 10.71-14.86 and 0.59-0.83 tonnes, respectively; the mercury released from waste fluorescent lamps is estimated to be about 5.37-7.59 tonnes. Also, a significant reduction to the mercury emission can be expected when a collection and treatment system is well established and conducted in the future. © The Author(s) 2015.

Organic Dots Based on AIEgens for Two-Photon Fluorescence Bioimaging.

PubMed

Lou, Xiaoding; Zhao, Zujin; Tang, Ben Zhong

2016-12-01

Two-photon fluorescence imaging technique is a powerful bioanalytical approach in terms of high photostability, low photodamage, high spatiotemporal resolution. Recently, fluorescent organic dots comprised of organic emissive cores and a polymeric matrix are emerging as promising contrast reagents for two-photon fluorescence imaging, owing to their numerous merits of high and tunable fluorescence, good biocompatibility, strong photobleaching resistance, and multiple surface functionality. The emissive core is crucial for organic dots to get high brightness but many conventional chromophores often encounter a severe problem of fluorescence quenching when they form aggregates. To solve this problem, fluorogens featuring aggregation-induced emission (AIE) can fluoresce strongly in aggregates, and thus become ideal candidates for fluorescent organic dots. In addition, two-photon absorption property of the dots can be readily improved by just increase loading contents of AIE fluorogen (AIEgen). Hence, organic dots based on AIEgens have exhibited excellent performances in two-photon fluorescence in vitro cellular imaging, and in vivo vascular architecture visualization of mouse skin, muscle, brain and skull bone. In view of the rapid advances in this important research field, here, we highlight representative fluorescent organic dots with an emissive core of AIEgen aggregate, and discuss their great potential in bioimaging applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Light emitting diode excitation emission matrix fluorescence spectroscopy.

PubMed

Hart, Sean J; JiJi, Renée D

2002-12-01

An excitation emission matrix (EEM) fluorescence instrument has been developed using a linear array of light emitting diodes (LED). The wavelengths covered extend from the upper UV through the visible spectrum: 370-640 nm. Using an LED array to excite fluorescence emission at multiple excitation wavelengths is a low-cost alternative to an expensive high power lamp and imaging spectrograph. The LED-EEM system is a departure from other EEM spectroscopy systems in that LEDs often have broad excitation ranges which may overlap with neighboring channels. The LED array can be considered a hybrid between a spectroscopic and sensor system, as the broad LED excitation range produces a partially selective optical measurement. The instrument has been tested and characterized using fluorescent dyes: limits of detection (LOD) for 9,10-bis(phenylethynyl)-anthracene and rhodamine B were in the mid parts-per-trillion range; detection limits for the other compounds were in the low parts-per-billion range (< 5 ppb). The LED-EEMs were analyzed using parallel factor analysis (PARAFAC), which allowed the mathematical resolution of the individual contributions of the mono- and dianion fluorescein tautomers a priori. Correct identification and quantitation of six fluorescent dyes in two to six component mixtures (concentrations between 12.5 and 500 ppb) has been achieved with root mean squared errors of prediction (RMSEP) of less than 4.0 ppb for all components.

Aequorea green fluorescent protein analysis by flow cytometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ropp, J.D.; Cuthbertson, R.A.; Donahue, C.J.

The isolation and expression of the cDNA for the green fluorescent protein (GFP) from the bioluminescent jellyfish Aequorea victoria has highlighted its potential use as a marker for gene expression in a variety of cell types. The longer wavelength peak (470 nm) of GFP`s bimodal absorption spectrum better matches standard fluorescein filter sets; however, it has a considerably lower amplitude than the major absorption peak at 395. In an effort to increase the sensitivity of GFP with routinely available instrumentation, Heim et al. have generated a GFP mutant (serine-65 to threonine; S65T-GFP) which possesses a single absorption peak centered atmore » 490 nm. We have constructed this mutant in order to determine whether it or wild-type GFP (wt-GFP) afforded greater sensitivity when excited near their respective absorption maxima. Using the conventionally available 488 nm and ultraviolet (UV) laser lines from the argon ion laser as well as the 407 nm line from a krypton ion laser with enhanced violet emission, we were able to closely match the absorption maxima of both the S65T and wild-type forms of Aequorea GFP and analyze differences in fluorescence intensity of transiently transfected 293 cells with flow cytometry. The highest fluorescence signal was observed with 488 nm excitation of S65T-GFP relative to all other laser line/GFP pairs. The wt-GFP fluorescence intensity, in contrast, was significantly higher at 407 nm relative to either 488 nm or UV. These results were consistent with parallel spectrofluorometric analysis of the emission spectrum for wt-GFP and S65T- GFP. The relative contribution of cellular autofluorescence at each wavelength was also investigated and shown to be significantly reduced at 407 nm relative to either UV or 488 nm. 29 refs., 5 figs.« less

Selective detection of Mg2+ ions via enhanced fluorescence emission using Au–DNA nanocomposites

PubMed Central

Basu, Tanushree; Rana, Khyati; Das, Niranjan

2017-01-01

The biophysical properties of DNA-modified Au nanoparticles (AuNPs) have attracted a great deal of research interest for various applications in biosensing. AuNPs have strong binding capability to the phosphate and sugar groups in DNA, rendering unique physicochemical properties for detection of metal ions. The formation of Au–DNA nanocomposites is evident from the observed changes in the optical absorption, plasmon band, zeta potential, DLS particle size distribution, as well as TEM and AFM surface morphology analysis. Circular dichroism studies also revealed that DNA-functionalized AuNP binding caused a conformational change in the DNA structure. Due to the size and shape dependent plasmonic interactions of AuNPs (33–78 nm) with DNA, the resultant Au–DNA nanocomposites (NCs) exhibit superior fluorescence emission due to chemical binding with Ca2+, Fe2+ and Mg2+ ions. A significant increase in fluorescence emission (λex = 260 nm) of Au–DNA NCs was observed after selectively binding with Mg2+ ions (20–800 ppm) in an aqueous solution where a minimum of 100 ppm Mg2+ ions was detected based on the linearity of concentration versus fluorescence intensity curve (λem = 400 nm). The effectiveness of Au–DNA nanocomposites was further verified by comparing the known concentration (50–120 ppm) of Mg2+ ions in synthetic tap water and a real life sample of Gelusil (300–360 ppm Mg2+), a widely used antacid medicine. Therefore, this method could be a sensitive tool for the estimation of water hardness after careful preparation of a suitably designed Au–DNA nanostructure. PMID:28487819

Visualizing BPA by molecularly imprinted ratiometric fluorescence sensor based on dual emission nanoparticles.

PubMed

Lu, Hongzhi; Xu, Shoufang

2017-06-15

Construction of ratiometric fluorescent probe often involved in tedious multistep preparation or complicated coupling or chemical modification process. The emergence of dual emission fluorescent nanoparticles would simplify the construction process and avoids the tedious chemical coupling. Herein, we reported a facile strategy to prepare ratiometric fluorescence molecularly imprinted sensor based on dual emission nanoparticles (d-NPs) which comprised of carbon dots and gold nanoclusters for detection of Bisphenol A (BPA). D-NPs emission at 460nm and 580nm were first prepared by seed growth co-microwave method using gold nanoparticles as seeds and glucose as precursor for carbon dots. When they were applied to propose ratiometric fluorescence molecularly imprinted sensor, the preparation process was simplified, and the sensitivity of sensor was improved with detection limit of 29nM, and visualizing BPA was feasible based on the distinguish fluorescence color change. The feasibility of the developed method in real samples was successfully evaluated through the analysis of BPA in water samples with satisfactory recoveries of 95.9-98.9% and recoveries ranging from 92.6% to 98.6% in canned food samples. When detection BPA in positive feeding bottles, the results agree well with those obtained by accredited method. The developed method proposed in this work to prepare ratiometric fluorescence molecularly imprinted sensor based on dual emission nanoparticles proved to be a convenient, reliable and practical way to prepared high sensitive and selective fluorescence sensors. Copyright © 2017 Elsevier B.V. All rights reserved.

Photophysical parameters and fluorescence quenching of 7-diethylaminocoumarin (DEAC) laser dye

NASA Astrophysics Data System (ADS)

El-Mossalamy, E. H.; Obaid, A. Y.; El-Daly, S. A.

2011-10-01

The optical properties including electronic absorption spectrum, emission spectrum, fluorescence quantum yield, and dipole moment of electronic transition of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. Both electronic absorption and fluorescence spectra are red shifted as the polarity of the medium increases, indicating that the dipole moment of molecule increases on excitation. The fluorescence quantum yield of DEAC decreases as the polarity of solvent increases, a result of the role of solvent polarity in stabilization of the twisting of the intramolecular charge transfer (TICT) in excited state, which is a non-emissive state, as well as hydrogen bonding with the hetero-atom of dye. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles, the intensity increases as the concentration of surfactant increases, and an abrupt change in emission intensity is observed at critical micelle concentration (CMC) of surfactant. 2×10 -3 mol dm -3 of DEAC gives laser emission in the blue region on pumping with nitrogen laser ( λex=337.1 nm). The laser parameters such as tuning range, gain coefficient ( α), emission cross section ( σe), and half-life energy have been calculated in different solvents, namely acetone, dioxane , ethanol, and dimethyforamide (DMF). The photoreactivity of DEAC has been studied in CCl 4 at a wavelength of 366 nm. The values of photochemical yield ( ϕc) and rate constant ( k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE), and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC is also studied using fluorescence measurements in acetonitrile (CH 3CN); from fluorescence quenching study we assume the possible electron transfer from excited donor DEAC to organic acceptor forming non-emissive exciplex.

Differential Absorption Lidar (DIAL) Measurements of Landfill Methane Emissions

NASA Astrophysics Data System (ADS)

Innocenti, Fabrizio; Robinson, Rod; Gardiner, Tom; Finlayson, Andrew; Connor, Andy

2017-04-01

DIFFERENTIAL ABSORPTION LIDAR (DIAL) MEASURMENTS OF LANDFILL METHANE EMISSIONS F. INNOCENTI *, R.A. ROBINSON *, T.D. GARDINER, A. FINLAYSON *, A. CONNOR* * National Physical Laboratory (NPL), Hampton Road, Teddington, Middlesex, TW11 0LW, United Kingdom Methane is one of the most important gaseous hydrocarbon species for both industrial and environmental reasons. Understanding and quantifying methane emissions to atmosphere is an important element of climate change research. Range-resolved infrared Differential Absorption Lidar (DIAL) measurements provide the means to map and quantify a wide range of different methane sources. DIAL is a powerful technique that can be used to track and quantify plumes emitted from area emission sources such as landfill sites, waste water treatment plants and petrochemical plants. By using lidar (light detection and ranging), the DIAL technique is able to make remote range-resolved single-ended measurements of the actual distribution of target gases in the atmosphere, with no disruption to normal site operational activities. DIAL provides 3D mapping of emission concentrations and quantification of emission rates for a wide range of target gases such as methane. The NPL DIAL laser source is operated alternately at two similar wavelengths. One of these, termed the "on-resonant wavelength", is chosen to be at a wavelength which is absorbed by the target species. The other, the "off-resonant wavelength", is chosen to be at a nearby wavelength which is not absorbed significantly by the target species. The two wavelengths are chosen to be close, so that the atmospheric scattering properties are the same for both wavelengths. They are also chosen so that any differential absorption due to other atmospheric species are minimised. Any measured difference in the returned signals is therefore due to absorption by the target gas. In the typical DIAL measurement configuration the mobile DIAL facility is positioned downwind of the area being

Diphenylacrylonitrile-connected BODIPY dyes: fluorescence enhancement based on dark and AIE resonance energy transfer.

PubMed

Lin, Liangbin; Lin, Xiaoru; Guo, Hongyu; Yang, Fafu

2017-07-19

This study focuses on the construction of novel diphenylacrylonitrile-connected BODIPY dyes with high fluorescence in both solution and an aggregated state by combining DRET and FRET processes in a single donor-acceptor system. The first BODIPY derivatives with one, two, or three AIE-active diphenylacrylonitrile groups were designed and synthesized in moderate yields. Strong fluorescence emissions were observed in the THF solution under excitation at the absorption wavelength of non-emissive diphenylacrylonitrile chromophores, implying the existence of the DRET process between the dark diphenylacrylonitrile donor and the emissive BODIPY acceptor. In the THF/H 2 O solution, the fluorescence intensity of the novel BODIPY derivatives gradually increased under excitation at the absorption wavelength of diphenylacrylonitrile chromophores, suggesting a FRET process between diphenylacrylonitrile and BODIPY moieties. A greater number of diphenylacrylonitrile units led to higher energy-transfer efficiencies. The pseudo-Stokes shift for both DRET and FRET processes was as large as 190 nm.

Naturally occurring fluorescence in frogs

PubMed Central

Taboada, Carlos; Brunetti, Andrés E.; Pedron, Federico N.; Carnevale Neto, Fausto; Estrin, Darío A.; Bari, Sara E.; Chemes, Lucía B.; Peporine Lopes, Norberto; Lagorio, María G.

2017-01-01

Fluorescence, the absorption of short-wavelength electromagnetic radiation reemitted at longer wavelengths, has been suggested to play several biological roles in metazoans. This phenomenon is uncommon in tetrapods, being restricted mostly to parrots and marine turtles. We report fluorescence in amphibians, in the tree frog Hypsiboas punctatus, showing that fluorescence in living frogs is produced by a combination of lymph and glandular emission, with pigmentary cell filtering in the skin. The chemical origin of fluorescence was traced to a class of fluorescent compounds derived from dihydroisoquinolinone, here named hyloins. We show that fluorescence contributes 18−29% of the total emerging light under twilight and nocturnal scenarios, largely enhancing brightness of the individuals and matching the sensitivity of night vision in amphibians. These results introduce an unprecedented source of pigmentation in amphibians and highlight the potential relevance of fluorescence in visual perception in terrestrial environments. PMID:28289227

Solvatochromic fluorescence characteristics of cinnamoyl pyrone derivatives

NASA Astrophysics Data System (ADS)

Benosmane, Nadjib; Boutemeur, Baya; Hamdi, Safouane M.; Hamdi, Maamar; Silva, Artur S. M.

2017-12-01

The solvatochromic fluorescence behavior of cinnamoyl pyrone derivatives has been studied in several polar and non-polar solvents. The fluorescence spectra of these compounds exhibit red shift from its absorption spectra and present an excellent correlation with solvent polarity. Cinnamoyl pyrones show a significant spectral shift in fluorescence emission as a function of water composition in binary aqueous solutions mixture. This change is due to the specific intermolecular hydrogen bonding of cinnamoyl pyrones with a molecules of water, due to the deactivation of the lowest excited singlet state of these compounds. The relative quantum yields are calculated. It is found that the quantum yields of the cinnamoyl pyrones vary with the change in the solvent polarity indicating the dependency of fluorescence properties on the solvent nature. It has been observed that the addition of water and pH medium can affect the fluorescence properties of cinnamoyl pyrones in ethanol. This study exhibited that due to the solvent sensitive emission, cinnamoyl pyrone derivatives are a good compound to be used as fluorescence probes.

Influence of moisturizer and relative humidity on human emissions of fluorescent biological aerosol particles.

PubMed

Zhou, J; Fang, W; Cao, Q; Yang, L; Chang, V W-C; Nazaroff, W W

2017-05-01

Utilizing the ultraviolet light-induced fluorescence (UV-LIF) measurement technique as embodied in the Waveband Integrated Bioaerosol Sensor (WIBS-4A), we evaluated the fluorescent particle emissions associated with human shedding while walking in a chamber. The mean emission rates of supermicron (1-10 μm) fluorescent particles were in the range 6.8-7.5 million particles per person-h (~0.3 mg per person-h) across three participants, for conditions when the relative humidity was 60%-70% and no moisturizer was applied after showering. The fluorescent particles displayed a lognormal distribution with the geometric mean diameter in the range 2.5-4 μm and exhibited asymmetry factors that increased with particle size. Use of moisturizer was associated with changes in number and mass emission rates, size distribution, and particle shape. Emission rates were lower when the relative humidity was reduced, but these differences were not statistically significant. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Light emission from compound eye with conformal fluorescent coating

NASA Astrophysics Data System (ADS)

Martín-Palma, Raúl J.; Miller, Amy E.; Pulsifer, Drew P.; Lakhtakia, Akhlesh

2015-03-01

Compound eyes of insects are attractive biological systems for engineered biomimicry as artificial sources of light, given their characteristic wide angular field of view. A blowfly eye was coated with a thin conformal fluorescent film, with the aim of achieving wide field-of-view emission. Experimental results showed that the coated eye emitted visible light and that the intensity showed a weaker angular dependence than a fluorescent thin film deposited on a flat surface.

Saturated virtual fluorescence emission difference microscopy based on detector array

NASA Astrophysics Data System (ADS)

Liu, Shaocong; Sun, Shiyi; Kuang, Cuifang; Ge, Baoliang; Wang, Wensheng; Liu, Xu

2017-07-01

Virtual fluorescence emission difference microscopy (vFED) has been proposed recently to enhance the lateral resolution of confocal microscopy with a detector array, implemented by scanning a doughnut-shaped pattern. Theoretically, the resolution can be enhanced by around 1.3-fold compared with that in confocal microscopy. For further improvement of the resolving ability of vFED, a novel method is presented utilizing fluorescence saturation for super-resolution imaging, which we called saturated virtual fluorescence emission difference microscopy (svFED). With a point detector array, matched solid and hollow point spread functions (PSF) can be obtained by photon reassignment, and the difference results between them can be used to boost the transverse resolution. Results show that the diffraction barrier can be surpassed by at least 34% compared with that in vFED and the resolution is around 2-fold higher than that in confocal microscopy.

Some fluorescence properties of dimethylaminochalcone and its novel cyclic analogues

NASA Astrophysics Data System (ADS)

Tomečková, Vladimíra; Poškrobová, Martina; Štefanišinová, Miroslava; Perjési, Pál

2009-12-01

This paper demonstrates the basic character (polarity, solubility, colour, absorption and fluorescence quantum yield) of synthetic dimethylaminochalcone ( 1) and its cyclic analogues measured in toluene, chloroform, dimethylsulfoxide and ethanol, which have been studied by absorption and fluorescence spectroscopy. The biologically active dye 4'-dimethylaminochalcone ( 1b) and its less flexible analogues 4-dimethylaminoindanone ( 2b), -tetralone ( 3b), and -benzosuberone ( 4b) are lipophilic molecules that displayed the best solubility in toluene and chloroform. The highest fluorescence and quantum yields of compounds 1 and 2 have been obtained in DMSO and chloroform. Quenching effect of fluorescence compounds ( 1- 4) has been studied in the mixture of the most polar organic solvents DMSO and water. In the presence of water, fluorescence of compound 1 has been quenched the best from all studied chalcones and emission maxima of molecules 1- 4 have been shifted to the longer wavelengths. Quenching effect of fluorescence by water was in order 1 > 2 > 3 > 4.

Light absorption properties and radiative effects of primary organic aerosol emissions

DOE PAGES

Lu, Zifeng; Streets, David G.; Winijkul, Ekbordin; ...

2015-03-26

Organic aerosols (OAs) in the atmosphere affect Earth’s energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called “brown carbon” (BrC) component. However, the absorptivities of OAs are not represented or are poorly represented in current climate and chemical transport models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (k OA, the fundamental optical parameter determining the particle’s absorptivity) andmore » their uncertainties for the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parametrize the k OA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, indicating that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based k OA profiles are incorporated into a global carbonaceous aerosol emission inventory, and the integrated k OA values of sectoral and total POA emissions are presented. The results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ~27% reduction in the amount of the net global average POA cooling compared to results from the nonabsorbing assumption.« less

One trinucleus dimethine cyanine dye: Experimental and theoretical studies on molecular structure as well as absorption and fluorescence properties

NASA Astrophysics Data System (ADS)

Zhang, D. D.; Wang, L. Y.; Su, J. J.; Zhang, X. F.; Lei, Y. B.; Zhai, G. H.; Wen, Z. Y.

2013-05-01

A kind of trinucleus dimethine cyanine dye: 1-methyl-2,6-bis[2-(furan-2-yl)vinyl]pyridinium iodide (1) was synthesized and characterized by 1H NMR, 13C NMR, IR, MS, UV-Vis spectroscopy and elemental analysis. The crystals of dye 1, obtained from slow evaporation of solvent acetone, crystallized in the triclinic space group P - 1 with a = 9.6501(16) Å, b = 10.2308(17) Å, c = 10.7341(17) Å, V = 887.2(3) Å3, and Z = 2 (at 298(2) K), and it was stabilized by the hydrogen bonds and intermolecular face-to-face π⋯π aromatic stacking interactions. Crystallographic, IR, 1H NMR and UV-Vis data of dye 1 were compared with the results of density functional theory (DFT) method, and the calculated molecular geometries, vibrational bands, 1H NMR chemical shifts and UV-Vis maximum absorption were consistent with the experimental results. The fluorescence spectra were predicted in four different solvents with CIS/PCM methods. Compared with experimental values, the absolute deviations of emission maxima were -17.4 nm in chloroform, 6.3 nm in DMSO, 4.9 nm in methanol, and 6.8 nm in water, respectively. And the experimental fluorescence spectra were nicely reproduced by the simulated fluorescence spectra for each solvent.

First-principle study of phosphors for white-LED applications : absorption and emission energies for Ce- and Eu-doped hosts.

NASA Astrophysics Data System (ADS)

Gonze, Xavier; Jia, Yongchao; Miglio, Anna; Giantomassi, Matteo; Ponce, Samuel; Mikami, Masayoshi

After the invasion of compact fluorescent lamps, white LED lighting is becoming a major contender in ecofriendly light sources, with a combination of yellow-, green- and/or red-emitting phosphors partly absorbing the blue light emitted by an InGaN LED. After introducing the semi-empirical Dorenbos model for 4f' 5d transition energies of rare earth ions, I present a first-principle study of two dozen compounds, pristine as well as doped with Ce3+ or Eu2+ ions, in view of explaining their different emission color. The neutral excitation of the ions is simulated through a constrained density functional theory method coupled with a delta SCF analysis of total energies, yielding absorption energies. Then, atomic positions in the excited state are relaxed, yielding emission energies and Stokes shifts, and identification of luminescent centers. In case of the Ce doped materials, the first-principle approach matches experimental data within 0.3 eV for both absorption and emission energies, covering a range of values between 2.0 eV and 5.0 eV, and provides Stokes shifts within 30%, with two exceptions. This is significantly better than the semi-empirical Dorenbos model. A similar analysis is performed for Eu-doped materials, also examining the thermal quenching of two oxynitride hosts. The work was supported by the FRS-FNRS Belgium (PDR Grant T.0238.13 - AIXPHO).

SU-F-J-46: Feasibility of Cerenkov Emission for Absorption Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oraiqat, I; Rehemtulla, A; Lam, K

2016-06-15

Purpose: Cerenkov emission (CE) is a promising tool for online tumor microenvironment interrogation and targeting during radiotherapy. In this work, we utilize CE generated during radiotherapy as a broadband excitation source for real-time absorption spectroscopy. We demonstrate the feasibility of CE spectroscopy using a controlled experiment of materials with known emission/absorption properties. Methods: A water tank is irradiated with 20 MeV electron beam to induce Cerenkov emission. Food coloring dyes (Yellow #5, Red #40, and Blue #1), which have known emission/absorption properties were added to the water tank with increasing concentration (1 drop (0.05 mL), 2 drops, and 4 dropsmore » from a dispenser bottle). The signal is collected using a condensing lens which is coupled into a 20m optical fiber that is fed into a spectrometer that measures the emitted spectra. The resulting spectra from water/food coloring dye solutions were normalized by the reference spectrum, which is the Cerenkov spectrum of pure water, correcting for both the nonlinearity of the broadband Cerenkov emission spectrum as well as the non-uniform spectral response of the spectrometer. The emitted spectra were then converted into absorbance and their characteristics were analyzed. Results: The food coloring dye had a drastic change on the Cerenkov emission, shifting its wavelength according to its visible color. The collected spectra showed various absorbance peaks which agrees with tabulated peak positions of the dyes added within 0.3% for yellow, 1.7% for red, and 0.16% for blue. The CE peak heights proportionally increased as the dye concentration is increased. Conclusion: This work shows the potential for real-time functional spectroscopy using Cerenkov emission during radiotherapy. It was demonstrated that molecule identification as well as relative concentration can be extracted from the Cerenkov emission color shift.« less

Characterization of CDOM of river waters in China using fluorescence excitation-emission matrix and regional integration techniques

NASA Astrophysics Data System (ADS)

Zhao, Ying; Song, Kaishan; Shang, Yingxin; Shao, Tiantian; Wen, Zhidan; Lv, Lili

2017-08-01

The spatial characteristics of fluorescent dissolved organic matter (FDOM) components in river waters in China were first examined by excitation-emission matrix spectra and fluorescence regional integration (FRI) with the data collected during September to November between 2013 and 2015. One tyrosine-like (R1), one tryptophan-like (R2), one fulvic-like (R3), one microbial protein-like (R4), and one humic-like (R5) components have been identified by FRI method. Principal component analysis (PCA) was conducted to assess variations in the five FDOM components (FRί (ί = 1, 2, 3, 4, and 5)) and the humification index for all 194 river water samples. The average fluorescence intensities of the five fluorescent components and the total fluorescence intensities FSUM differed under spatial variation among the seven major river basins (Songhua, Liao, Hai, Yellow and Huai, Yangtze, Pearl, and Inflow Rivers) in China. When all the river water samples were pooled together, the fulvic-like FR3 and the humic-like FR5 showed a strong positive linear relationship (R2 = 0.90, n = 194), indicating that the two allochthonous FDOM components R3 and R5 may originate from similar sources. There is a moderate strong positive correlation between the tryptophan-like FR2 and the microbial protein-like FR4 (R2 = 0.71, n = 194), suggesting that parts of two autochthonous FDOM components R2 and R4 are likely from some common sources. However, the total allochthonous substance FR(3+5) and the total autochthonous substances FR(1+2+4) exhibited a weak correlation (R2 = 0.40, n = 194). Significant positive linear relationships between FR3 (R2 = 0.69, n = 194), FR5 (R2 = 0.79, n = 194), and chromophoric DOM (CDOM) absorption coefficient a(254) were observed, which demonstrated that the CDOM absorption was dominated by the allochthonous FDOM components R3 and R5.

Modeling Far-UV Fluorescent Emission Features of Warm Molecular Hydrogen in the Inner Regions of Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Hoadley, Keri; France, Kevin

2015-01-01

Probing the surviving molecular gas within the inner regions of protoplanetary disks (PPDs) around T Tauri stars (1 - 10 Myr) provides insight into the conditions in which planet formation and migration occurs while the gas disk is still present. We model observed far ultraviolet (FUV) molecular hydrogen (H₂) fluorescent emission lines that originate within the inner regions (< 10 AU) of 9 well-studied Classic T Tauri stars, using the Hubble Space Telescope Cosmic Origins Spectrograph (COS), to explore the physical structure of the molecular disk at different PPD dust evolutionary stages. We created a 2D radiative transfer model that estimates the density and temperature distributions of warm, inner radial H₂ (T > 1500 K) with a set of 6 free parameters and produces a data cube of expected emission line profiles that describe the physical structure of the inner molecular disk atmosphere. By comparing the modeled emission lines with COS H₂ fluorescence emission features, we estimate the physical structure of the molecular disk atmosphere for each target with the set of free parameters that best replicate the observed lines. First results suggest that, for all dust evolutionary stages of disks considered, ground-state H₂ populations are described by a roughly constant temperature T(H₂) = 2500 +/- 1000 K. Possible evolution of the density structure of the H₂ atmosphere between intact and depleting dust disks may be distinguishable, but large errors in the inferred best-fit parameter sets prevent us from making this conclusion. Further improvements to the modeling framework and statistical comparison in determining the best-fit model-to-data parameter sets are ongoing, beginning with improvements to the radiative transfer model and use of up-to-date HI Lyman α absorption optical depths (see McJunkin in posters) to better estimate disk structural parameters. Once improvements are implemented, we will investigate the possible presence of a molecular wind

Highly Sensitive Ratiometric Fluorescent Sensor for Trinitrotoluene Based on the Inner Filter Effect between Gold Nanoparticles and Fluorescent Nanoparticles.

PubMed

Lu, Hongzhi; Quan, Shuai; Xu, Shoufang

2017-11-08

In this work, we developed a simple and sensitive ratiometric fluorescent assay for sensing trinitrotoluene (TNT) based on the inner filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent nanoparticles (RFNs), which was designed by hybridizing green emissive carbon dots (CDs) and red emissive quantum dots (QDs) into a silica sphere as a fluorophore pair. AuNPs in their dispersion state can be a powerful absorber to quench CDs, while the aggregated AuNPs can quench QDs in the IFE-based fluorescent assays as a result of complementary overlap between the absorption spectrum of AuNPs and emission spectrum of RFNs. As a result of the fact that TNT can induce the aggregation of AuNPs, with the addition of TNT, the fluorescent of QDs can be quenched, while the fluorescent of CDs would be recovered. Then, ratiometric fluorescent detection of TNT is feasible. The present IFE-based ratiometric fluorescent sensor can detect TNT ranging from 0.1 to 270 nM, with a detection limit of 0.029 nM. In addition, the developed method was successfully applied to investigate TNT in water and soil samples with satisfactory recoveries ranging from 95 to 103%, with precision below 4.5%. The simple sensing approach proposed here could improve the sensitivity of colorimetric analysis by changing the ultraviolet analysis to ratiometric fluorescent analysis and promote the development of a dual-mode detection system.

Dual-emissive quantum dots for multispectral intraoperative fluorescence imaging.

PubMed

Chin, Patrick T K; Buckle, Tessa; Aguirre de Miguel, Arantxa; Meskers, Stefan C J; Janssen, René A J; van Leeuwen, Fijs W B

2010-09-01

Fluorescence molecular imaging is rapidly increasing its popularity in image guided surgery applications. To help develop its full surgical potential it remains a challenge to generate dual-emissive imaging agents that allow for combined visible assessment and sensitive camera based imaging. To this end, we now describe multispectral InP/ZnS quantum dots (QDs) that exhibit a bright visible green/yellow exciton emission combined with a long-lived far red defect emission. The intensity of the latter emission was enhanced by X-ray irradiation and allows for: 1) inverted QD density dependent defect emission intensity, showing improved efficacies at lower QD densities, and 2) detection without direct illumination and interference from autofluorescence. Copyright 2010 Elsevier Ltd. All rights reserved.

Optimization-Based Approach for Joint X-Ray Fluorescence and Transmission Tomographic Inversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di, Zichao; Leyffer, Sven; Wild, Stefan M.

2016-01-01

Fluorescence tomographic reconstruction, based on the detection of photons coming from fluorescent emission, can be used for revealing the internal elemental composition of a sample. On the other hand, conventional X-ray transmission tomography can be used for reconstructing the spatial distribution of the absorption coefficient inside a sample. In this work, we integrate both X-ray fluorescence and X-ray transmission data modalities and formulate a nonlinear optimization-based approach for reconstruction of the elemental composition of a given object. This model provides a simultaneous reconstruction of both the quantitative spatial distribution of all elements and the absorption effect in the sample. Mathematicallymore » speaking, we show that compared with the single-modality inversion (i.e., the X-ray transmission or fluorescence alone), the joint inversion provides a better-posed problem, which implies a better recovery. Therefore, the challenges in X-ray fluorescence tomography arising mainly from the effects of self-absorption in the sample are partially mitigated. The use of this technique is demonstrated on the reconstruction of several synthetic samples.« less

SPATIAL DISTRIBUTIONS OF ABSORPTION, LOCAL SUPPRESSION, AND EMISSIVITY REDUCTION OF SOLAR ACOUSTIC WAVES IN MAGNETIC REGIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chou, D.-Y.; Yang, M.-H.; Zhao Hui

Observed acoustic power in magnetic regions is lower than the quiet Sun because of absorption, emissivity reduction, and local suppression of solar acoustic waves in magnetic regions. In the previous studies, we have developed a method to measure the coefficients of absorption, emissivity reduction, and local suppression of sunspots. In this study, we go one step further to measure the spatial distributions of three coefficients in two active regions, NOAA 9055 and 9057. The maps of absorption, emissivity reduction, and local suppression coefficients correlate with the magnetic map, including plage regions, except the emissivity reduction coefficient of NOAA 9055 wheremore » the emissivity reduction coefficient is too weak and lost among the noise.« less

Spatial photosensitizer fluorescence emission predictive analysis for photodynamic therapy monitoring applied to a skin disease

NASA Astrophysics Data System (ADS)

Salas-García, Irene; Fanjul-Vélez, Félix; Arce-Diego, José Luis

2012-03-01

The development of Photodynamic Therapy (PDT) predictive models has become a valuable tool for an optimal treatment planning, monitoring and dosimetry adjustment. A few attempts have achieved a quite complete characterization of the complex photochemical and photophysical processes involved, even taking into account superficial fluorescence in the target tissue. The present work is devoted to the application of a predictive PDT model to obtain fluorescence tomography information during PDT when applied to a skin disease. The model takes into account the optical radiation distribution, a non-homogeneous topical photosensitizer distribution, the time dependent photochemical interaction and the photosensitizer fluorescence emission. The results show the spatial evolution of the photosensitizer fluorescence emission and the amount of singlet oxygen produced during PDT. The depth dependent photosensitizer fluorescence emission obtained is essential to estimate the spatial photosensitizer concentration and its degradation due to photobleaching. As a consequence the proposed approach could be used to predict the photosensitizer fluorescence tomographic measurements during PDT. The singlet oxygen prediction could also be employed as a valuable tool to predict the short term treatment outcome.

Image scanning fluorescence emission difference microscopy based on a detector array.

PubMed

Li, Y; Liu, S; Liu, D; Sun, S; Kuang, C; Ding, Z; Liu, X

2017-06-01

We propose a novel imaging method that enables the enhancement of three-dimensional resolution of confocal microscopy significantly and achieve experimentally a new fluorescence emission difference method for the first time, based on the parallel detection with a detector array. Following the principles of photon reassignment in image scanning microscopy, images captured by the detector array were arranged. And by selecting appropriate reassign patterns, the imaging result with enhanced resolution can be achieved with the method of fluorescence emission difference. Two specific methods are proposed in this paper, showing that the difference between an image scanning microscopy image and a confocal image will achieve an improvement of transverse resolution by approximately 43% compared with that in confocal microscopy, and the axial resolution can also be enhanced by at least 22% experimentally and 35% theoretically. Moreover, the methods presented in this paper can improve the lateral resolution by around 10% than fluorescence emission difference and 15% than Airyscan. The mechanism of our methods is verified by numerical simulations and experimental results, and it has significant potential in biomedical applications. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Strategy for sensor based on fluorescence emission red shift of conjugated polymers: applications in pH response and enzyme activity detection.

PubMed

Tang, Yanli; Liu, Yue; Cao, Ali

2013-01-15

A new strategy was developed and applied in monitoring pH response and enzyme activity based on fluorescence emission red shift (FERS) of the conjugated polymer PPP-OR10 induced by the inner filter effect (IFE) of nitrobenzene derivatives. Neutral poly(p-phenylenes) functionalized with oligo(oxyethylene) side chains (PPP-OR10) was designed and synthesized by the Suzuki cross-coupling reaction. Nitrobenzene derivatives display different light absorption activities in the acidic or basic form due to adopting different electron-transition types. When environmental pH is higher than their pK(a) values, nitrobenzene derivatives exhibit strong absorbance around 400 nm, which is close to the maximal emission of polymer PPP-OR10. As a result, the maximal emission wavelength of PPP-OR10/nitrobenzene derivatives red shifts with the pH value increasing. Apparently, the IFE plays a very important role in this case. A new method has been designed that takes advantage of this pH-sensitive platform to sensor α-chymotrypsin (ChT) based on the IFE of p-nitroaniline, since the absorption spectrum of p-nitroaniline, the ChT-hydrolyzed product of N-benzoyl-L-tyrosine-p-nitroaniline (BTNA), overlaps with the emission spectrum of PPP-OR10. In addition, the present approach can detect α-chymotrypsin with a detection limit of 0.1 μM, which is lower than that of the corresponding absorption spectroscopy method. Furthermore, the pH response and enzyme detections can be carried out in 10% serum, which makes this new FERS-based strategy promising in applications in more complex conditions and a broader field.

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.

Heat generation and light scattering of green fluorescent protein-like pigments in coral tissue

NASA Astrophysics Data System (ADS)

Lyndby, Niclas H.; Kühl, Michael; Wangpraseurt, Daniel

2016-05-01

Green fluorescent protein (GFP)-like pigments have been proposed to have beneficial effects on coral photobiology. Here, we investigated the relationships between green fluorescence, coral heating and tissue optics for the massive coral Dipsastraea sp. (previously Favia sp.). We used microsensors to measure tissue scalar irradiance and temperature along with hyperspectral imaging and combined imaging of variable chlorophyll fluorescence and green fluorescence. Green fluorescence correlated positively with coral heating and scalar irradiance enhancement at the tissue surface. Coral tissue heating saturated for maximal levels of green fluorescence. The action spectrum of coral surface heating revealed that heating was highest under red (peaking at 680 nm) irradiance. Scalar irradiance enhancement in coral tissue was highest when illuminated with blue light, but up to 62% (for the case of highest green fluorescence) of this photon enhancement was due to green fluorescence emission. We suggest that GFP-like pigments scatter the incident radiation, which enhances light absorption and heating of the coral. However, heating saturates, because intense light scattering reduces the vertical penetration depth through the tissue eventually leading to reduced light absorption at high fluorescent pigment density. We conclude that fluorescent pigments can have a central role in modulating coral light absorption and heating.

Evanescent excitation and emission in fluorescence microscopy.

PubMed

Axelrod, Daniel

2013-04-02

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. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Synthesis and spectral properties of Methyl-Phenyl pyrazoloquinoxaline fluorescence emitters: Experiment and DFT/TDDFT calculations

NASA Astrophysics Data System (ADS)

Gąsiorski, P.; Matusiewicz, M.; Gondek, E.; Uchacz, T.; Wojtasik, K.; Danel, A.; Shchur, Ya.; Kityk, A. V.

2018-01-01

Paper reports the synthesis and spectroscopic studies of two novel 1-Methyl-3-phenyl-1H-pyrazolo[3,4-b]quinoxaline (PQX) derivatives with 6-substituted methyl (MeMPPQX) or methoxy (MeOMPPQX) side groups. The optical absorption and fluorescence emission spectra are recorded in solvents of different polarity. Steady state and time-resolved spectroscopy provide photophysical characterization of MeMPPQX and MeOMPPQX dyes as materials for potential luminescence or electroluminescence applications. Measured optical absorption and fluorescence emission spectra are compared with quantum-chemical DFT/TDDFT calculations using long-range corrected xc-functionals, LRC-BLYP and CAM-B3LYP in combination with self-consistent reaction field model based on linear response (LR), state specific (SS) or corrected linear response (CLR) solvations. Performances of relevant theoretical models and approaches are compared. The reparameterized LRC-BLYP functional (ω = 0.231 Bohr-1) in combination with CLR solvation provides most accurate prediction of both excitation and emission energies. The MeMPPQX and MeOMPPQX dyes represent efficient fluorescence emitters in blue-green region of the visible spectra.

Impact of oxygen chemistry on the emission and fluorescence spectroscopy of laser ablation plumes

NASA Astrophysics Data System (ADS)

Hartig, K. C.; Brumfield, B. E.; Phillips, M. C.; Harilal, S. S.

2017-09-01

Oxygen present in the ambient gas medium may affect both laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) emission through a reduction of emission intensity and persistence. In this study, an evaluation is made on the role of oxygen in the ambient environment under atmospheric pressure conditions in LIBS and laser ablation (LA)-LIF emission. To generate plasmas, 1064 nm, 10 ns pulses were focused on an aluminum alloy sample. LIF was performed by frequency scanning a CW laser over the 396.15 nm (3s24s 2S1/2 → 3s23p 2P°3/2) Al I transition. Time-resolved emission and fluorescence signals were recorded to evaluate the variation in emission intensity caused by the presence of oxygen. The oxygen partial pressure (po) in the atmospheric pressure environment using N2 as the makeup gas was varied from 0 to 400 Torr O2. 2D-fluorescence spectroscopy images were obtained for various oxygen concentrations for simultaneous evaluation of the emission and excitation spectral features. Results showed that the presence of oxygen in the ambient environment reduces the persistence of the LIBS and LIF emission through an oxidation process that depletes the density of atomic species within the resulting laser-produced plasma (LPP) plume.

Efficiency of the intermolecular interaction of salicylic acid neutral form and monoanion with Cd2 + ion studied by methods of absorption and fluorescence

NASA Astrophysics Data System (ADS)

Lavrik, N. L.; Mulloev, N. U.

2018-02-01

The methods of absorption and fluorescence were used to study the efficiency of the interaction between salicylic acid derivatives SAD (neutral SA form and SA monoanion) and Cd2 + ions (in CdBr2 salt) within the range pH = 1.5 ÷ 8. The efficiency was determined from the change in both the absorption band contour and the fluorescence intensity of various SAD forms. It has been established that depending on the SAD form, the addition of CdBr2 to a starting solution leads to the formation of additional absorption for both the shorter wave lengths in the absorption spectrum of the neutral form (at pH < 3) and the longer wave lengths in the absorption spectrum for the HSal- monoanion (at pH > 4). In the fluorescence spectra, the intensity was observed to increase for the neutral SAD form (at pH < 3) and to decrease for the HSal- monoanion (at pH > 4) after addition of CdBr2. The spectral changes were interpreted in the framework of common notions about the effect of three physicochemical factors that determine the interaction between the SAD and the Cd2 + ion and affect the parameters of absorption and fluorescence spectra. These factors are: (1) the decrease in pH after addition of CdBr2 to the SAD solution, (2) the decrease in the efficiency of the H-bonding of SAD molecules to the water ones, and (3) the existence of electrostatic ion-ion interaction between the HSal- monoanion and the Cd2 + ion. The bimolecular fluorescence quenching constants Kq of HSal- monoanion fluorescence quenching by the Cd2 + ion appeared to be substantially less than those of the quenching which would follow either the dynamic (diffusion) or the concentration (static) mechanisms.

Coherent stimulated light emission (lasing) in covalently linked chlorophyll dimers

PubMed Central

Hindman, James C.; Kugel, Roger; Wasielewski, Michael R.; Katz, Joseph J.

1978-01-01

The covalently linked chlorophyll a dimer exhibits remarkably different properties in the folded and open configurations. In the folded configuration the absorption maximum is at 695 nm and the fluorescence maximum is at 730 nm. Laser output at 733 and 735 nm is obtained for solutions in wet benzene and 0.1 M ethanol/toluene, respectively. Measurements of fluorescence lineshapes, made with a transverse excited atmospheric (TEA) nitrogen laser for excitation, show the lifetime shortening associated with stimulated emission resulting from appreciable concentrations of molecules in S1 excited states. In contrast, the open dimer has absorption and fluorescence spectra essentially the same as those of chlorophyll a monomer. Unlike either the folded dimer or chlorophyll a monomer, the open dimer shows no laser emission or fluorescene lifetime shortening. It does not appear that the behavior of the open dimer can be explained in terms of excimer or triplet formation or by nonradiative decay processes. It is suggested that absorption of the exciting radiation by S1, leading to the formation of an exciplex or charge transfer state, may be involved. Significantly, no large changes in fluorescence quantum yield or fluorescence lifetime are observed for these dimers as compared to monomer chlorophyll. This suggests that concentration quenching and lifetime shortening in condensed chlorophyll systems involve more than the simple proximity of two chlorophyll molecules. Images PMID:16592524

Chlorophyll fluorescence emission as a reporter on cold tolerance in Arabidopsis thaliana accessions

PubMed Central

Mishra, Anamika; Höermiller, Imke I; Heyer, Arnd G; Nedbal, Ladislav

2011-01-01

Non-invasive, high-throughput screening methods are valuable tools in breeding for abiotic stress tolerance in plants. Optical signals such as chlorophyll fluorescence emission can be instrumental in developing new screening techniques. In order to examine the potential of chlorophyll fluorescence to reveal plant tolerance to low temperatures, we used a collection of nine Arabidopsis thaliana accessions and compared their fluorescence features with cold tolerance quantified by the well established electrolyte leakage method on detached leaves. We found that, during progressive cooling, the minimal chlorophyll fluorescence emission rose strongly and that this rise was highly dependent on the cold tolerance of the accessions. Maximum quantum yield of PSII photochemistry and steady state fluorescence normalized to minimal fluorescence were also highly correlated to the cold tolerance measured by the electrolyte leakage method. In order to further increase the capacity of the fluorescence detection to reveal the low temperature tolerance, we applied combinatorial imaging that employs plant classification based on multiple fluorescence features. We found that this method, by including the resolving power of several fluorescence features, can be well employed to detect cold tolerance already at mild sub-zero temperatures. Therefore, there is no need to freeze the screened plants to the largely damaging temperatures of around −15°C. This, together with the method's easy applicability, represents a major advantage of the fluorescence technique over the conventional electrolyte leakage method. PMID:21427532

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.

Fluorescence and absorption properties of chromophoric dissolved organic matter (CDOM) in coastal surface waters of the Northwestern Mediterranean Sea (Bay of Marseilles, France)

NASA Astrophysics Data System (ADS)

Para, J.; Coble, P. G.; Charrière, B.; Tedetti, M.; Fontana, C.; Sempéré, R.

2010-07-01

Seawater samples were collected in surface waters (2 and 5 m depths) of the Bay of Marseilles (Northwestern Mediterranean Sea; 5°17'30'' E, 43°14'30'' N) during one year from November 2007 to December 2008 and studied for total organic carbon (TOC) as well as chromophoric dissolved organic matter (CDOM) optical properties (absorbance and fluorescence). The annual mean value of surface CDOM absorption coefficient at 350 nm [aCDOM(350)] was very low (0.10 ± 0.02 m-1) with in comparison to values usually found in coastal waters, and no significant seasonal trend in aCDOM(350) could be determined. By contrast, the spectral slope of CDOM absorption (SCDOM) was significantly higher (0.023 ± 0.003 nm-1) in summer than in fall and winter periods (0.017 ± 0.002 nm-1), reflecting either CDOM photobleaching or production in surface waters during stratified sunny periods. The CDOM fluorescence, assessed through excitation emission matrices (EEMs), was dominated by protein-like component (peak T; 1.30-21.94 QSU) and marine humic-like component (peak M; 0.55-5.82 QSU), while terrestrial humic-like fluorescence (peak C; 0.34-2.99 QSU) remained very low. This reflected a dominance of relatively fresh material from biological origin within the CDOM fluorescent pool. At the end of summer, surface CDOM fluorescence was very low and strongly blue shifted, reinforcing the hypothesis of CDOM photobleaching. Our results suggested that unusual Rhône River plume eastward intrusion events may reach Marseilles Bay within 2-3 days and induce local phytoplankton blooms and subsequent fluorescent CDOM production (peaks M and T) without adding terrestrial fluorescence signatures (peak C). Besides Rhône River plumes, mixing events of the entire water column injected humic (peaks C and M) CDOM from the bottom into the surface and thus appeared also as an important source of CDOM in surface waters of the Marseilles Bay. Therefore, the assessment of CDOM optical properties, within the

Polarization Multiplexing of Fluorescent Emission Using Multiresonant Plasmonic Antennas.

PubMed

De Leo, Eva; Cocina, Ario; Tiwari, Preksha; Poulikakos, Lisa V; Marqués-Gallego, Patricia; le Feber, Boris; Norris, David J; Prins, Ferry

2017-12-26

Combining the ability to localize electromagnetic fields at the nanoscale with a directional response, plasmonic antennas offer an effective strategy to shape the far-field pattern of coupled emitters. Here, we introduce a family of directional multiresonant antennas that allows for polarization-resolved spectral identification of fluorescent emission. The geometry consists of a central aperture surrounded by concentric polygonal corrugations. By varying the periodicity of each axis of the polygon individually, this structure can support multiple resonances that provide independent control over emission directionality for multiple wavelengths. Moreover, since each resonant wavelength is directly mapped to a specific polarization orientation, spectral information can be encoded in the polarization state of the out-scattered beam. To demonstrate the potential of such structures in enabling simplified detection schemes and additional functionalities in sensing and imaging applications, we use the central subwavelength aperture as a built-in nanocuvette and manipulate the fluorescent response of colloidal-quantum-dot emitters coupled to the multiresonant antenna.

Polarization Multiplexing of Fluorescent Emission Using Multiresonant Plasmonic Antennas

PubMed Central

2017-01-01

Combining the ability to localize electromagnetic fields at the nanoscale with a directional response, plasmonic antennas offer an effective strategy to shape the far-field pattern of coupled emitters. Here, we introduce a family of directional multiresonant antennas that allows for polarization-resolved spectral identification of fluorescent emission. The geometry consists of a central aperture surrounded by concentric polygonal corrugations. By varying the periodicity of each axis of the polygon individually, this structure can support multiple resonances that provide independent control over emission directionality for multiple wavelengths. Moreover, since each resonant wavelength is directly mapped to a specific polarization orientation, spectral information can be encoded in the polarization state of the out-scattered beam. To demonstrate the potential of such structures in enabling simplified detection schemes and additional functionalities in sensing and imaging applications, we use the central subwavelength aperture as a built-in nanocuvette and manipulate the fluorescent response of colloidal-quantum-dot emitters coupled to the multiresonant antenna. PMID:29161502

Hyperspectral small animal fluorescence imaging: spectral selection imaging

NASA Astrophysics Data System (ADS)

Leavesley, Silas; Jiang, Yanan; Patsekin, Valery; Hall, Heidi; Vizard, Douglas; Robinson, J. Paul

2008-02-01

Molecular imaging is a rapidly growing area of research, fueled by needs in pharmaceutical drug-development for methods for high-throughput screening, pre-clinical and clinical screening for visualizing tumor growth and drug targeting, and a growing number of applications in the molecular biology fields. Small animal fluorescence imaging employs fluorescent probes to target molecular events in vivo, with a large number of molecular targeting probes readily available. The ease at which new targeting compounds can be developed, the short acquisition times, and the low cost (compared to microCT, MRI, or PET) makes fluorescence imaging attractive. However, small animal fluorescence imaging suffers from high optical scattering, absorption, and autofluorescence. Much of these problems can be overcome through multispectral imaging techniques, which collect images at different fluorescence emission wavelengths, followed by analysis, classification, and spectral deconvolution methods to isolate signals from fluorescence emission. We present an alternative to the current method, using hyperspectral excitation scanning (spectral selection imaging), a technique that allows excitation at any wavelength in the visible and near-infrared wavelength range. In many cases, excitation imaging may be more effective at identifying specific fluorescence signals because of the higher complexity of the fluorophore excitation spectrum. Because the excitation is filtered and not the emission, the resolution limit and image shift imposed by acousto-optic tunable filters have no effect on imager performance. We will discuss design of the imager, optimizing the imager for use in small animal fluorescence imaging, and application of spectral analysis and classification methods for identifying specific fluorescence signals.

Concentration Dependence of Gold Nanoparticles for Fluorescence Enhancement

NASA Astrophysics Data System (ADS)

Solomon, Joel; Wittmershaus, Bruce

Noble metal nanoparticles possess a unique property known as surface plasmon resonance in which the conduction electrons oscillate due to incoming light, dramatically increasing their absorption and scattering of light. The oscillating electrons create a varying electric field that can affect nearby molecules. The fluorescence and photostability of fluorophores can be enhanced significantly when they are near plasmonic nanoparticles. This effect is called metal enhanced fluorescence (MEF). MEF from two fluorescence organic dyes, Lucifer Yellow CH and Riboflavin, was measured with different concentrations of 50-nm colloidal gold nanoparticles (Au-NP). The concentration range of Au-NP was varied from 2.5 to 250 pM. To maximize the interaction, the dyes were chosen so their emission spectra had considerable overlap with the absorption spectra of the Au-NP, which is common in MEF studies. If the dye molecules are too close to the surface of Au-NP, fluorescence quenching can occur instead of MEF. To try to observe this difference, silica-coated Au-NP were compared to citrate-based Au-NP; however, fluorescence quenching was observed with both Au-NP. This material is based upon work supported by the National Science Foundation under Grant Number NSF-ECCS-1306157.

Aggregation induced emission enhancement (AIEE) characteristics of quinoline based compound - A versatile fluorescent probe for pH, Fe(III) ion, BSA binding and optical cell imaging

NASA Astrophysics Data System (ADS)

Manikandan, Irulappan; Chang, Chien-Huei; Chen, Chia-Ling; Sathish, Veerasamy; Li, Wen-Shan; Malathi, Mahalingam

2017-07-01

Novel benzimidazoquinoline derivative (AVT) was synthesized through a substitution reaction and characterized by various spectral techniques. Analyzing the optical properties of AVT under absorption and emission spectral studies in different environments exclusively with respect to solvents and pH, intriguing characteristics viz. aggregation induced emission enhancement (AIEE) in the THF solvent and 'On-Off' pH sensing were found at neutral pH. Sensing nature of AVT with diverse metal ions and bovine serum albumin (BSA) was also studied. Among the metal ions, Fe3 + ion alone tunes the fluorescence intensity of AVT probe in aqueous medium from ;turn-on; to ;turn-off; through ligand (probe) to metal charge transfer (LMCT) mechanism. The probe AVT in aqueous medium interacts strongly with BSA due to Fluorescence Resonance Energy Transfer (FRET) and the conformational change in BSA was further analyzed using synchronous fluorescence techniques. Docking study of AVT with BSA reveals that the active site of binding is tryptophan residue which is also supported by the experimental results. Interestingly, fluorescent AVT probe in cells was examined through cellular imaging studies using BT-549 and MDA-MB-231 cells. Thus, the single molecule probe based detection of multiple species and stimuli were described.

Advances in engineering of fluorescent proteins and photoactivatable proteins with red emission.

PubMed

Piatkevich, Kiryl D; Verkhusha, Vladislav V

2010-02-01

Monomeric fluorescent proteins of different colors are widely used to study behavior and targeting of proteins in living cells. Fluorescent proteins that irreversibly change their spectral properties in response to light irradiation of a specific wavelength, or photoactivate, have become increasingly popular to image intracellular dynamics and superresolution protein localization. Until recently, however, no optimized monomeric red fluorescent proteins and red photoactivatable proteins have been available. Furthermore, monomeric fluorescent proteins, which change emission from blue to red simply with time, so-called fluorescent timers, were developed to study protein age and turnover. Understanding of chemical mechanisms of the chromophore maturation or photoactivation into a red form will further advance engineering of fluorescent timers and photoactivatable proteins with enhanced and novel properties. 2009 Elsevier Ltd. All rights reserved.

Absorption and fluorescence properties of the eastern Bering Sea in the summer with special reference to the influence of a Cold Pool

NASA Astrophysics Data System (ADS)

D'Sa, E. J.; Goes, J. I.; Gomes, H.; Mouw, C.

2013-12-01

The absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) are reported for the inner shelf, slope waters and outer shelf regions of the eastern Bering Sea during the summer of 2008, when a warm, thermally stratified surface mixed layer lay over a Cold Pool (< 2 °C) that occupied the entire middle shelf. CDOM absorption at 355 nm (ag355) and its spectral slope (S) in conjunction with excitation emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) revealed large variability in the characteristics of CDOM in different regions of the Bering Sea. PARAFAC analysis aided in the identification of three humic-like (components 1, 2 and 5) and two protein-like (a tyrosine-like component 3, and a tryptophan-like component 4) components. In the extensive shelf region, average absorption coefficients at 355 nm (ag355 m-1) and DOC concentrations (μM) were highest in the inner shelf (0.342 ± 0.11 m-1, 92.67 ± 14.60 μM) and lower in the middle (0.226 ± 0.05 m-1, 78.38 ± 10.64 μM) and outer (0.176 ± 0.05 m-1, 80.73 ± 18.11 μM) shelves, respectively. Mean spectral slopes S were elevated in the middle shelf (24.38 ± 2.25 μm-1) especially in the surface waters (26.87 ± 2.39 μm-1) indicating high rates of photodegradation in the highly stratified surface mixed layer, which intensified northwards in the northern middle shelf likely contributing to greater light penetration and to phytoplankton blooms at deeper depths. The fluorescent humic-like components 1, 2, and 5 were most elevated in the inner shelf most likely from riverine inputs. Measurements at depth in slope waters (> 250 m) revealed low values of ag355 (0.155 ± 0.03 m-1) and S (15.45 ± 1.78 μm-1) indicative of microbial degradation of CDOM in deep waters. DOC concentrations, however were not significantly different suggesting CDOM sources and sinks to be uncoupled from DOC. Along the productive "green belt" in the outer shelf/slope region, absorption and

Redox-responsive nanoparticles with Aggregation-Induced Emission (AIE) characteristic for fluorescence imaging.

PubMed

Cheng, Weiren; Wang, Guan; Pan, Xiaoyong; Zhang, Yong; Tang, Ben Zhong; Liu, Ye

2014-08-01

The redox environment between intracellular compartments and extracellular matrix is significantly different, and the cellular redox homeostasis determines many physiological functions. Here, redox-responsive nanoparticles with aggregation-induced emission (AIE) characteristic for fluorescence imaging are developed by encapsulation of fluorophore with redox "turn-on" AIE characteristic, TPE-MI, into the micelles of poly(ethylene glycol) (PEG)- and cholesterol (CE)-conjugated disulfide containing poly(amido amine)s. The redox-responsive fluorescence profiles of the nanoparticles are investigated after reaction with glutathione (GSH). The encapsulation of TPE-MI in micelles leads to a higher efficiency and red shift in emission, and the fluorescence intensity of the nanoparticles increases with the concentration of GSH. Confocal microscopy imaging shows that the nanoparticles can provide obvious contrast between the intracellular compartments and the extracellular matrix in MCF-7 and HepG2 cells. So the nanoparticles with PEG shells and low cytotoxicity are promising to provide fluorescence bioimaging with a high contrast and for differentiation of cellular redox environment. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser Induced Fluorescence Spectroscopy of Neutral and Ionized Polycyclic Aromatic Hydrocarbons in the Cosmic Simulation Chamber

NASA Technical Reports Server (NTRS)

Bejaoui, Salma; Salama, Farid; Contreras, Cesar; Sciamma O'Brien, Ella; Foing, Bernard; Pascale, Ehrenfreund

2015-01-01

Polycyclic aromatic hydrocarbon (PAH) molecules are considered the best carriers to account for the ubiquitous infrared emission bands. PAHs have also been proposed as candidates to explain the diffuse interstellar bands (DIBs), a series of absorption features seen on the interstellar extinction curve and are plausible carriers for the extended red emission (ERE), a photoluminescent process associated with a wide variety of interstellar environments. Extensive efforts have been devoted over the past two decades to characterize the physical and chemical properties of PAH molecules and ions in space. Absorption spectra of PAH molecules and ions trapped in solid matrices have been compared to the DIBs. Absorption spectra of several cold, isolated gas-phase PAHs have also been measured under experimental conditions that mimic the interstellar conditions. The purpose of this study is to provide a new dimension to the existing spectroscopic database of neutral and single ionized PAHs that is largely based on absorption spectra by adding emission spectroscopy data. The measurements are based on the laser induced fluorescence (LIF) technique and are performed with the Pulsed Discharge Nozzle (PDN) of the COSmIC laboratory facility at NASA Ames laboratory. The PDN generates a plasma in a free supersonic jet expansion to simulate the physical and the chemical conditions in interstellar environments. We focus, here, on the fluorescence spectra of large neutral PAHs and their cations where there is a lack of fluorescence spectroscopy data. The astronomical implications of the data (e.g., ERE) are examined.

Measurement of fluorophore concentrations and fluorescence quantum yield in tissue-simulating phantoms using three diffusion models of steady-state spatially resolved fluorescence.

PubMed

Diamond, Kevin R; Farrell, Thomas J; Patterson, Michael S

2003-12-21

Steady-state diffusion theory models of fluorescence in tissue have been investigated for recovering fluorophore concentrations and fluorescence quantum yield. Spatially resolved fluorescence, excitation and emission reflectance Carlo simulations, and measured using a multi-fibre probe on tissue-simulating phantoms containing either aluminium phthalocyanine tetrasulfonate (AlPcS4), Photofrin meso-tetra-(4-sulfonatophenyl)-porphine dihydrochloride The accuracy of the fluorophore concentration and fluorescence quantum yield recovered by three different models of spatially resolved fluorescence were compared. The models were based on: (a) weighted difference of the excitation and emission reflectance, (b) fluorescence due to a point excitation source or (c) fluorescence due to a pencil beam excitation source. When literature values for the fluorescence quantum yield were used for each of the fluorophores, the fluorophore absorption coefficient (and hence concentration) at the excitation wavelength (mu(a,x,f)) was recovered with a root-mean-square accuracy of 11.4% using the point source model of fluorescence and 8.0% using the more complicated pencil beam excitation model. The accuracy was calculated over a broad range of optical properties and fluorophore concentrations. The weighted difference of reflectance model performed poorly, with a root-mean-square error in concentration of about 50%. Monte Carlo simulations suggest that there are some situations where the weighted difference of reflectance is as accurate as the other two models, although this was not confirmed experimentally. Estimates of the fluorescence quantum yield in multiple scattering media were also made by determining mu(a,x,f) independently from the fitted absorption spectrum and applying the various diffusion theory models. The fluorescence quantum yields for AlPcS4 and TPPS4 were calculated to be 0.59 +/- 0.03 and 0.121 +/- 0.001 respectively using the point source model, and 0.63 +/- 0.03 and 0

[Fluorescence excitation-emission matrix spectroscopy of CDOM from Yundang Lagoon and its indication for organic pollution].

PubMed

Zhuo, Jian-Fu; Guo, Wei-Dong; Deng, Xun; Zhang, Zhi-Ying; Xu, Jing; Huang, Ling-Feng

2010-06-01

Fluorescence excitation-emission matrix spectroscopy (EEMs) combined with absorption spectroscopy were applied to study the optical properties of CDOM samples from highly-polluted Yundang Lagoon in Xiamen in order to demonstrate the feasibility of using these spectral properties as a tracer of the degree of organic pollution in similar polluted coastal waters. Surface water samples were collected from 13 stations 4 times during April and May, 2008. Parallel factor analysis (PARAFAC) model was used to resolve the EEMs of CDOM. Five separate fluorescent components were identified, including two humic-like components (C1: 240, 325/422 nm; C5: 260, 380/474 nm), two protein-like components (C2: 225, 275/350 nm; C4: 240, 300/354 nm) and one xenobiotic-like component (C3: 225/342 nm), which could be used as a good tracer for the input of the anthropogenic organic, pollutants. The concentrations of component C3 and dissolved organic carbon (DOC) are much higher near the inlet of sewage discharge, demonstrating that the discharge of surrounding sewage is a major source of organic pollutants in Yundang Lagoon. CDOM absorption coefficient alpha (280) and the score of humic-like component C1 showed significant linear relationships with COD(Mn), and a strong positive correlation was also found between the score of protein-like component C2 and BOD5. This suggested that the optical properties of CDOM may provide a fast in-situ way to monitor the variation of the water quality in Yundang Lagoon and that of similar polluted coastal waters.

Deletion mapping of the Aequorea victoria green fluorescent protein.

PubMed

Dopf, J; Horiagon, T M

1996-01-01

Aequorea victoria green fluorescent protein (GFP) is a promising fluorescent marker which is active in a diverse array of prokaryotic and eukaryotic organisms. A key feature underlying the versatility of GFP is its capacity to undergo heterocyclic chromophore formation by cyclization of a tripeptide present in its primary sequence and thereby acquiring fluorescent activity in a variety of intracellular environments. In order to define further the primary structure requirements for chromophore formation and fluorescence in GFP, a series of N- and C-terminal GFP deletion variant expression vectors were created using the polymerase chain reaction. Scanning spectrofluorometric analyses of crude soluble protein extracts derived from eleven GFP expression constructs revealed that amino acid (aa) residues 2-232, of a total of 238 aa in the native protein, were required for the characteristic emission and absorption spectra of native GFP. Heterocyclic chromophore formation was assayed by comparing the absorption spectrum of GFP deletion variants over the 300-500-nm range to the absorption spectra of full-length GFP and GFP deletion variants missing the chromophore substrate domain from the primary sequence. GFP deletion variants lacking fluorescent activity showed no evidence of heterocyclic ring structure formation when the soluble extracts of their bacterial expression hosts were studied at pH 7.9. These observations suggest that the primary structure requirements for the fluorescent activity of GFP are relatively extensive and are compatible with the view that much of the primary structure serves an autocatalytic function.

FIRST CONNECTION BETWEEN COLD GAS IN EMISSION AND ABSORPTION: CO EMISSION FROM A GALAXY–QUASAR PAIR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neeleman, Marcel; Prochaska, J. Xavier; Zwaan, Martin A.

2016-04-01

We present the first detection of molecular emission from a galaxy selected to be near a projected background quasar using the Atacama Large Millimeter/submillimeter Array (ALMA). The ALMA detection of CO(1−0) emission from the z = 0.101 galaxy toward quasar PKS 0439–433 is coincident with its stellar disk and yields a molecular gas mass of M{sub mol} ≈ 4.2 × 10{sup 9} M{sub ⊙} (for a Galactic CO-to-H{sub 2} conversion factor), larger than the upper limit on its atomic gas mass. We resolve the CO velocity field, obtaining a rotational velocity of 134 ± 11 km s{sup −1} and a resultant dynamical mass of ≥4 × 10{sup 10} M{sub ⊙}.more » Despite its high metallicity and large molecular mass, the z = 0.101 galaxy has a low star formation rate, implying a large gas consumption timescale, larger than that typical of late-type galaxies. Most of the molecular gas is hence likely to be in a diffuse extended phase, rather than in dense molecular clouds. By combining the results of emission and absorption studies, we find that the strongest molecular absorption component toward the quasar cannot arise from the molecular disk, but is likely to arise from diffuse gas in the galaxy’s circumgalactic medium. Our results emphasize the potential of combining molecular and stellar emission line studies with optical absorption line studies to achieve a more complete picture of the gas within and surrounding high-redshift galaxies.« less

Emission spectra profiling of fluorescent proteins in living plant cells

PubMed Central

2013-01-01

Background Fluorescence imaging at high spectral resolution allows the simultaneous recording of multiple fluorophores without switching optical filters, which is especially useful for time-lapse analysis of living cells. The collected emission spectra can be used to distinguish fluorophores by a computation analysis called linear unmixing. The availability of accurate reference spectra for different fluorophores is crucial for this type of analysis. The reference spectra used by plant cell biologists are in most cases derived from the analysis of fluorescent proteins in solution or produced in animal cells, although these spectra are influenced by both the cellular environment and the components of the optical system. For instance, plant cells contain various autofluorescent compounds, such as cell wall polymers and chlorophyll, that affect the spectral detection of some fluorophores. Therefore, it is important to acquire both reference and experimental spectra under the same biological conditions and through the same imaging systems. Results Entry clones (pENTR) of fluorescent proteins (FPs) were constructed in order to create C- or N-terminal protein fusions with the MultiSite Gateway recombination technology. The emission spectra for eight FPs, fused C-terminally to the A- or B-type cyclin dependent kinases (CDKA;1 and CDKB1;1) and transiently expressed in epidermal cells of tobacco (Nicotiana benthamiana), were determined by using the Olympus FluoView™ FV1000 Confocal Laser Scanning Microscope. These experimental spectra were then used in unmixing experiments in order to separate the emission of fluorophores with overlapping spectral properties in living plant cells. Conclusions Spectral imaging and linear unmixing have a great potential for efficient multicolor detection in living plant cells. The emission spectra for eight of the most commonly used FPs were obtained in epidermal cells of tobacco leaves and used in unmixing experiments. The generated set of

Absolute intensity measurements of impurity emissions in a shock tunnel and their consequences for laser-induced fluorescence experiments

NASA Technical Reports Server (NTRS)

Palma, P. C.; Houwing, A. F. P.; Sandeman, R. J.

1993-01-01

Absolute intensity measurements of impurity emissions in a shock tunnel nozzle flow are presented. The impurity emission intensities were measured with a photomultiplier and optical multichannel analyzer and calibrated against an intensity standard. The various metallic contaminants were identified and their intensities measured in the spectral regions 290 to 330 nm and 375 to 385 nm. A comparison with calculated fluorescence intensities for predissociated laser-induced fluorescence signals is made. It is found that the emission background is negligible for most fluorescence experiments.

Enhanced eumelanin emission by stepwise three-photon excitation

NASA Astrophysics Data System (ADS)

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

2011-03-01

Eumelanin fluorescence from Sepia officinalis and black human hair was activated with near-infrared radiation and multiphoton excitation. A third order multiphoton absorption by a step-wise process appears to be the underlying mechanism. The activation was caused by a photochemical process since it could not be reproduced by simple heating. Both fluorescence and brightfield imaging indicate the near-infrared irradiation caused photodamage to the eumelanin and the activated emission originated from the photodamaged region. At least two different components with about thousand-fold enhanced fluorescence were activated and could be distinguished by their excitation properties. One component was excited with wavelengths in the visible region and exhibited linear absorption dependence. The second component could be excited with near-infrared wavelengths and had a third order dependence on the laser power. The third order dependence is explained by a step-wise excited state absorption (ESA) process since it could be observed equally with the CW and femtosecond lasers. The new method for photoactivating the eumelanin fluorescence was used to map the melanin content in human hair.

Photobleaching response of different sources of chromophoric dissolved organic matter exposed to natural solar radiation using absorption and excitation-emission matrix spectra.

PubMed

Zhang, Yunlin; Liu, Xiaohan; Osburn, Christopher L; Wang, Mingzhu; Qin, Boqiang; Zhou, Yongqiang

2013-01-01

CDOM biogeochemical cycle is driven by several physical and biological processes such as river input, biogeneration and photobleaching that act as primary sinks and sources of CDOM. Watershed-derived allochthonous (WDA) and phytoplankton-derived autochthonous (PDA) CDOM were exposed to 9 days of natural solar radiation to assess the photobleaching response of different CDOM sources, using absorption and fluorescence (excitation-emission matrix) spectroscopy. Our results showed a marked decrease in total dissolved nitrogen (TDN) concentration under natural sunlight exposure for both WDA and PDA CDOM, indicating photoproduction of ammonium from TDN. In contrast, photobleaching caused a marked increase in total dissolved phosphorus (TDP) concentration for both WDA and PDA CDOM. Thus TDN:TDP ratios decreased significantly both for WDA and PDA CDOM, which partially explained the seasonal dynamic of TDN:TDP ratio in Lake Taihu. Photobleaching rate of CDOM absorption a(254), was 0.032 m/MJ for WDA CDOM and 0.051 m/MJ for PDA CDOM from days 0-9, indicating that phototransformations were initially more rapid for the newly produced CDOM from phytoplankton than for the river CDOM. Extrapolation of these values to the field indicated that 3.9%-5.1% CDOM at the water surface was photobleached and mineralized every day in summer in Lake Taihu. Photobleaching caused the increase of spectral slope, spectral slope ratio and molecular size, indicating the CDOM mean molecular weight decrease which was favorable to further microbial degradation of mineralization. Three fluorescent components were validated in parallel factor analysis models calculated separately for WDA and PDA CDOM. Our study suggests that the humic-like fluorescence materials could be rapidly and easily photobleached for WDA and PDA CDOM, but the protein-like fluorescence materials was not photobleached and even increased from the transformation of the humic-like fluorescence substance to the protein

Photobleaching Response of Different Sources of Chromophoric Dissolved Organic Matter Exposed to Natural Solar Radiation Using Absorption and Excitation–Emission Matrix Spectra

PubMed Central

Zhang, Yunlin; Liu, Xiaohan; Osburn, Christopher L.; Wang, Mingzhu; Qin, Boqiang; Zhou, Yongqiang

2013-01-01

CDOM biogeochemical cycle is driven by several physical and biological processes such as river input, biogeneration and photobleaching that act as primary sinks and sources of CDOM. Watershed-derived allochthonous (WDA) and phytoplankton-derived autochthonous (PDA) CDOM were exposed to 9 days of natural solar radiation to assess the photobleaching response of different CDOM sources, using absorption and fluorescence (excitation-emission matrix) spectroscopy. Our results showed a marked decrease in total dissolved nitrogen (TDN) concentration under natural sunlight exposure for both WDA and PDA CDOM, indicating photoproduction of ammonium from TDN. In contrast, photobleaching caused a marked increase in total dissolved phosphorus (TDP) concentration for both WDA and PDA CDOM. Thus TDN∶TDP ratios decreased significantly both for WDA and PDA CDOM, which partially explained the seasonal dynamic of TDN∶TDP ratio in Lake Taihu. Photobleaching rate of CDOM absorption a(254), was 0.032 m/MJ for WDA CDOM and 0.051 m/MJ for PDA CDOM from days 0–9, indicating that phototransformations were initially more rapid for the newly produced CDOM from phytoplankton than for the river CDOM. Extrapolation of these values to the field indicated that 3.9%–5.1% CDOM at the water surface was photobleached and mineralized every day in summer in Lake Taihu. Photobleaching caused the increase of spectral slope, spectral slope ratio and molecular size, indicating the CDOM mean molecular weight decrease which was favorable to further microbial degradation of mineralization. Three fluorescent components were validated in parallel factor analysis models calculated separately for WDA and PDA CDOM. Our study suggests that the humic-like fluorescence materials could be rapidly and easily photobleached for WDA and PDA CDOM, but the protein-like fluorescence materials was not photobleached and even increased from the transformation of the humic-like fluorescence substance to the protein

Chromophoric dissolved organic matter (CDOM) variability in Barataria Basin using excitation-emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC).

PubMed

Singh, Shatrughan; D'Sa, Eurico J; Swenson, Erick M

2010-07-15

Chromophoric dissolved organic matter (CDOM) variability in Barataria Basin, Louisiana, USA,was examined by excitation emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC). CDOM optical properties of absorption and fluorescence at 355nm along an axial transect (36 stations) during March, April, and May 2008 showed an increasing trend from the marine end member to the upper basin with mean CDOM absorption of 11.06 + or - 5.01, 10.05 + or - 4.23, 11.67 + or - 6.03 (m(-)(1)) and fluorescence 0.80 + or - 0.37, 0.78 + or - 0.39, 0.75 + or - 0.51 (RU), respectively. PARAFAC analysis identified two terrestrial humic-like (component 1 and 2), one non-humic like (component 3), and one soil derived humic acid like (component 4) components. The spatial variation of the components showed an increasing trend from station 1 (near the mouth of basin) to station 36 (end member of bay; upper basin). Deviations from this increasing trend were observed at a bayou channel with very high chlorophyll-a concentrations especially for component 3 in May 2008 that suggested autochthonous production of CDOM. The variability of components with salinity indicated conservative mixing along the middle part of the transect. Component 1 and 4 were found to be relatively constant, while components 2 and 3 revealed an inverse relationship for the sampling period. Total organic carbon showed increasing trend for each of the components. An increase in humification and a decrease in fluorescence indices along the transect indicated an increase in terrestrial derived organic matter and reduced microbial activity from lower to upper basin. The use of these indices along with PARAFAC results improved dissolved organic matter characterization in the Barataria Basin. Copyright 2010 Elsevier B.V. All rights reserved.

Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for Bisphenol A

NASA Astrophysics Data System (ADS)

Xiang, Guo-Qiang; Ren, Yue; Xia, Yin; Mao, Wenjie; Fan, Chao; Guo, Si-Yu; Wang, Pan-Pan; Yang, Deng-Hui; He, Lijun; Jiang, Xiuming

2017-04-01

A simple and effective strategy for designing a ratiometric fluorescent nanosensor is described in this work. A carbon dots (CDs) based dual-emission nanosensor for Bisphenol A (BPA) was prepared by coating CDs on the surface of dye-doped silica nanoparticles. The fluorescence of dual-emission silica nanoparticles was quenched in hydrochloric acid by potassium bromate (KBrO3) oxidation; BPA inhibited KBrO3 oxidation, resulting in the ratiometric fluorescence response of dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated and optimized. The detection limit of this nanosensor was 0.80 ng mL- 1 with a linear range from 10 to 500 ng mL- 1. This was applied successfully to determine BPA in the leached solution of different plastic products with satisfactory results.

A-TEEMTM, a new molecular fingerprinting technique: simultaneous absorbance-transmission and fluorescence excitation-emission matrix method

NASA Astrophysics Data System (ADS)

Quatela, Alessia; Gilmore, Adam M.; Steege Gall, Karen E.; Sandros, Marinella; Csatorday, Karoly; Siemiarczuk, Alex; (Ben Yang, Boqian; Camenen, Loïc

2018-04-01

We investigate the new simultaneous absorbance-transmission and fluorescence excitation-emission matrix method for rapid and effective characterization of the varying components from a mixture. The absorbance-transmission and fluorescence excitation-emission matrix method uniquely facilitates correction of fluorescence inner-filter effects to yield quantitative fluorescence spectral information that is largely independent of component concentration. This is significant because it allows one to effectively monitor quantitative component changes using multivariate methods and to generate and evaluate spectral libraries. We present the use of this novel instrument in different fields: i.e. tracking changes in complex mixtures including natural water, wine as well as monitoring stability and aggregation of hormones for biotherapeutics.

Temperature dependence of the hydrated electron's excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy

NASA Astrophysics Data System (ADS)

Farr, Erik P.; Zho, Chen-Chen; Challa, Jagannadha R.; Schwartz, Benjamin J.

2017-08-01

The structure of the hydrated electron, particularly whether it exists primarily within a cavity or encompasses interior water molecules, has been the subject of much recent debate. In Paper I [C.-C. Zho et al., J. Chem. Phys. 147, 074503 (2017)], we found that mixed quantum/classical simulations with cavity and non-cavity pseudopotentials gave different predictions for the temperature dependence of the rate of the photoexcited hydrated electron's relaxation back to the ground state. In this paper, we measure the ultrafast transient absorption spectroscopy of the photoexcited hydrated electron as a function of temperature to confront the predictions of our simulations. The ultrafast spectroscopy clearly shows faster relaxation dynamics at higher temperatures. In particular, the transient absorption data show a clear excess bleach beyond that of the equilibrium hydrated electron's ground-state absorption that can only be explained by stimulated emission. This stimulated emission component, which is consistent with the experimentally known fluorescence spectrum of the hydrated electron, decreases in both amplitude and lifetime as the temperature is increased. We use a kinetic model to globally fit the temperature-dependent transient absorption data at multiple temperatures ranging from 0 to 45 °C. We find the room-temperature lifetime of the excited-state hydrated electron to be 137 ±40 fs, in close agreement with recent time-resolved photoelectron spectroscopy (TRPES) experiments and in strong support of the "non-adiabatic" picture of the hydrated electron's excited-state relaxation. Moreover, we find that the excited-state lifetime is strongly temperature dependent, changing by slightly more than a factor of two over the 45 °C temperature range explored. This temperature dependence of the lifetime, along with a faster rate of ground-state cooling with increasing bulk temperature, should be directly observable by future TRPES experiments. Our data also suggest

Analysis of synthetic derivatives of peptide hormones by capillary zone electrophoresis and micellar electrokinetic chromatography with ultraviolet-absorption and laser-induced fluorescence detection.

PubMed

Solínová, Veronika; Kasicka, Václav; Koval, Dusan; Barth, Tomislav; Ciencialová, Alice; Záková, Lenka

2004-08-25

Capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) were used for the analysis of new synthetic derivatives of hypophysis neurohormones--vasopressin and oxytocin, and pancreatic hormone--human insulin (HI) and its octapeptide fragment, derivatized by fluorescent probe, 4-chloro-7-nitrobenzo[1,2,5]oxadiazol (NBD). The suitable composition of background electrolytes (BGEs) was selected on the basis of calculated pH dependence of effective charge of analyzed peptides. Basic ionogenic peptides were analyzed by CZE in the acidic BGE composed of 100 mM H3PO4, 50 mM Tris, pH 2.25. The ionogenic peptides with fluorescent label, NBD, were analyzed in 0.5 M acetic acid, pH 2.5. The best MEKC separation of non-ionogenic peptides was achieved in alkaline BGE, 20 mM Tris, 5 mM H3PO4, with micellar pseudophase formed by 50 mM sodium dodecylsulfate (SDS), pH 8.8. Selected characteristics (noise, detectability of substance, sensitivity of detector) of the UV-absorption detectors (single wavelength detector, multiple-wavelength photodiode array detector (PDA), both of them operating at constant wavelength 206 nm) and laser-induced fluorescence (LIF) detector (excitation/emission wavelength 488/520 nm) were determined. The detectability of peptides in the single wavelength detector was 1.3-6.0 micromol dm(-3) and in the PDA detector 1.6-3.1 micromol dm(-3). The LIF detection was more sensitive, the applied concentration of NBD derivative of insulin fragment in CZE analysis with LIF detection was three orders lower than in CZE with UV-absorption detector, and the detectability of this peptide was improved to 15.8 nmol dm(-3).

Endogenous fluorescence emission of the ovary

NASA Astrophysics Data System (ADS)

Utzinger, Urs; Kirkpatrick, Nathaniel D.; Drezek, Rebekah A.; Brewer, Molly A.

2005-03-01

Epithelial ovarian cancer has the highest mortality rate among the gynecologic cancers. Early detection would significantly improve survival and quality of life of women at increased risk to develop ovarian cancer. We have constructed a device to investigate endogenous signals of the ovarian tissue surface in the UV C to visible range and describe our initial investigation of the use of optical spectroscopy to characterize the condition of the ovary. We have acquired data from more than 33 patients. A table top spectroscopy system was used to collect endogenous fluorescence with a fiberoptic probe that is compatible with endoscopic techniques. Samples were broken into five groups: Normal-Low Risk (for developing ovarian cancer) Normal-High Risk, Benign, and Cancer. Rigorous statistical analysis was applied to the data using variance tests for direct intensity versus diagnostic group comparisons and principal component analysis (PCA) to study the variance of the whole data set. We conclude that the diagnostically most useful excitation wavelengths are located in the UV. Furthermore, our results indicate that UV B and C are most useful. A safety analysis indicates that UV-C imaging can be conducted at exposure levels below safety thresholds. We found that fluorescence excited in the UV-C and UV-B range increases from benign to normal to cancerous tissues. This is in contrast to the emission created with UV-A excitation which decreased in the same order. We hypothesize that an increase of protein production and a decrease of fluorescence contributions of the extracellular matrix could explain this behavior. Variance analysis also identified fluctuation of fluorescence at 320/380 which is associated with collagen cross link residues. Small differences were observed between the group at high risk and normal risk for ovarian cancer. High risk samples deviated towards the cancer group and low risk samples towards benign group.

Absorption and fluorescence properties of chromophoric dissolved organic matter: implications for the monitoring of water quality in a large subtropical reservoir.

PubMed

Liu, Xiaohan; Zhang, Yunlin; Shi, Kun; Zhu, Guangwei; Xu, Hai; Zhu, Mengyuan

2014-12-01

The development of techniques for real-time monitoring of water quality is of great importance for effectively managing inland water resources. In this study, we first analyzed the absorption and fluorescence properties in a large subtropical reservoir and then used a chromophoric dissolved organic matter (CDOM) fluorescence monitoring sensor to predict several water quality parameters including the total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), dissolved organic carbon (DOC), and CDOM fluorescence parallel factor analysis (PARAFAC) components in the reservoir. The CDOM absorption coefficient at 254 nm (a(254)), the humic-like component (C1), and the tryptophan-like component (C3) decreased significantly along a gradient from the northwest to the lake center, northeast, southwest, and southeast region in the reservoir. However, no significant spatial difference was found for the tyrosine-like component (C2), which contributed only four marked peaks. A highly significant linear correlation was found between the a(254) and CDOM concentration measured using the CDOM fluorescence sensor (r(2) = 0.865, n = 76, p < 0.001), indicating that CDOM concentrations could act as a proxy for the CDOM absorption coefficient measured in the laboratory. Significant correlations were also found between the CDOM concentration and TN, TP, COD, DOC, and the maximum fluorescence intensity of C1, suggesting that the real-time monitoring of CDOM concentrations could be used to predict these water quality parameters and trace the humic-like fluorescence substance in clear aquatic ecosystems with DOC <2 mg/L and total suspended matter (TSM) concentrations <15 mg/L. These results demonstrate that the CDOM fluorescence sensor is a useful tool for on-line water quality monitoring if the empirical relationship between the CDOM concentration measured using the CDOM fluorescence sensor and the water quality parameters is calibrated and validated.

Silver nanowires enhance absorption of poly(3-hexylthiophene)

NASA Astrophysics Data System (ADS)

Smolarek, Karolina; Ebenhoch, Bernd; Czechowski, Nikodem; Prymaczek, Aneta; Twardowska, Magdalena; Samuel, Ifor D. W.; Mackowski, Sebastian

2013-11-01

Results of optical spectroscopy reveal strong influence of plasmon excitations in silver nanowires on the fluorescence properties of poly(3-hexylthiophene) (P3HT), which is one of the building blocks of organic solar cells. For the structure where a conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) was used as a spacer in order to minimize effects associated with non-radiative energy transfer from P3HT to metallic nanoparticles, we demonstrate over two-fold increase of the fluorescence intensity. Results of time-resolved fluorescence indicate that the enhancement of emission intensity can be attributed to increased absorption of P3HT. Our findings are a step towards improving the efficiency of organic solar cells through incorporation of plasmonic nanostructures.

Silver nanowires enhance absorption of poly(3-hexylthiophene)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smolarek, Karolina; Czechowski, Nikodem; Prymaczek, Aneta

2013-11-11

Results of optical spectroscopy reveal strong influence of plasmon excitations in silver nanowires on the fluorescence properties of poly(3-hexylthiophene) (P3HT), which is one of the building blocks of organic solar cells. For the structure where a conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) was used as a spacer in order to minimize effects associated with non-radiative energy transfer from P3HT to metallic nanoparticles, we demonstrate over two-fold increase of the fluorescence intensity. Results of time-resolved fluorescence indicate that the enhancement of emission intensity can be attributed to increased absorption of P3HT. Our findings are a step towards improving the efficiency of organic solar cellsmore » through incorporation of plasmonic nanostructures.« less

Evaluating the effect of local pH on fluorescence emissions from oral bacteria of the genus Prevotella

NASA Astrophysics Data System (ADS)

Hope, Christopher K.; Higham, Susan M.

2016-08-01

A number of anaerobic oral bacteria, notably Prevotellaceae, exhibit red fluorescence when excited by short-wavelength visible light due to their accumulation of porphyrins, particularly protoporphyrin IX. pH affects the fluorescence of abiotic preparations of porphyrins due to transformations in speciation between monomers, higher aggregates, and dimers. To elucidate whether the porphyrin speciation phenomenon could be manifested within a microbiological system, suspensions of Prevotella intermedia and Prevotella nigrescens were examined by fluorescence spectrophotometry while being titrated against NaOH. The initial pH of the samples was <6, which was then raised toward the maximum found within a diseased periodontal pocket, being ˜pH 8.7. The intensity of the fluorescence emissions increased between 600 and 650 nm with increasing pH. Peak fluorescence emissions occurred at 635±1 nm with a second emission peak developing with increasing pH at 622 nm. A linear relationship was demonstrated between pH and the log10 ratio of 635:622 nm excitation fluorescence intensities. These findings suggest that the pH range found within the oral cavity could affect the fluorescence of oral bacteria in vivo, which may in turn have connotations for any clinical diagnoses that may be inferred from dental plaque fluorescence.

Plasmonic beaming and active control over fluorescent emission.

PubMed

Jun, Young Chul; Huang, Kevin C Y; Brongersma, Mark L

2011-01-01

Nanometallic optical antennas are rapidly gaining popularity in applications that require exquisite control over light concentration and emission processes. The search is on for high-performance antennas that offer facile integration on chips. Here we demonstrate a new, easily fabricated optical antenna design that achieves an unprecedented level of control over fluorescent emission by combining concepts from plasmonics, radiative decay engineering and optical beaming. The antenna consists of a nanoscale plasmonic cavity filled with quantum dots coupled to a miniature grating structure that can be engineered to produce one or more highly collimated beams. Electromagnetic simulations and confocal microscopy were used to visualize the beaming process. The metals defining the plasmonic cavity can be utilized to electrically control the emission intensity and wavelength. These findings facilitate the realization of a new class of active optical antennas for use in new optical sources and a wide range of nanoscale optical spectroscopy applications.

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

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

PubMed

Zhao, Ming; Li, Yu; Peng, Leilei

2014-05-05

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.

Measurements of trace constituents from atmospheric infrared emission and absorption spectra, a feasibility study

NASA Technical Reports Server (NTRS)

Goldman, A.; Williams, W. J.; Murcray, D. G.

1974-01-01

The feasibility of detecting eight trace constituents (CH4, HCl, HF, HNO3, NH3, NO, NO2 and SO2) against the rest of the atmospheric background at various altitudes from infrared emission and absorption atmospheric spectra was studied. Line-by-line calculations and observational data were used to establish features that can be observed in the atmospheric spectrum due to each trace constituent. Model calculations were made for experimental conditions which approximately represent state of the art emission and absorption spectrometers.

Determination of K shell absorption jump factors and jump ratios of 3d transition metals by measuring K shell fluorescence parameters.

PubMed

Kaçal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

2015-01-01

Energy dispersive X-ray fluorescence technique (EDXRF) has been employed for measuring K-shell absorption jump factors and jump ratios for Ti, Cr, Fe, Co, Ni and Cu elements. The jump factors and jump ratios for these elements were determined by measuring K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to-Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using a Cd-109 radioactive point source and an Si(Li) detector in direct excitation and transmission experimental geometry. The measured values for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature. Copyright © 2014 Elsevier Ltd. All rights reserved.

Simultaneous control of emission localization and two-photon absorption efficiency in dissymmetrical chromophores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tretiak, Sergei

2009-01-01

The aim of the present work is to demonstrate that combined spectral tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two novel series of structurally related chromophores have been designed and studied: a first series based on rod-like quadrupolar chromophores bearing different electron-donating (D) end groups and a second series based on three-branched octupolar chromophores built from a trigonal donating moiety and bearing various acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of themore » linear and nonlinear optical properties of dissymmetric chromophores compared to their symmetrical counterparts. In both types of systems (i.e. quadrupoles and octupoles) experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution between the different D and A moieties within the multipolar structure (i.e. concerted intramolecular charge transfer). In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moieties due to fast excitation localization after excitation prior to emission. Hence control of emission characteristics (polarization and emission spectrum) in addition to localization can be achieved by controlled introduction of electronic dissymmetry (i.e. replacement of one of the D or A end-groups by a slightly stronger D{prime} or A{prime} units). Interestingly dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route strategy allowing major TPA enhancement in multipolar structures due to

Improvement of LOD in Fluorescence Detection with Spectrally Nonuniform Background by Optimization of Emission Filtering.

PubMed

Galievsky, Victor A; Stasheuski, Alexander S; Krylov, Sergey N

2017-10-17

The limit-of-detection (LOD) in analytical instruments with fluorescence detection can be improved by reducing noise of optical background. Efficiently reducing optical background noise in systems with spectrally nonuniform background requires complex optimization of an emission filter-the main element of spectral filtration. Here, we introduce a filter-optimization method, which utilizes an expression for the signal-to-noise ratio (SNR) as a function of (i) all noise components (dark, shot, and flicker), (ii) emission spectrum of the analyte, (iii) emission spectrum of the optical background, and (iv) transmittance spectrum of the emission filter. In essence, the noise components and the emission spectra are determined experimentally and substituted into the expression. This leaves a single variable-the transmittance spectrum of the filter-which is optimized numerically by maximizing SNR. Maximizing SNR provides an accurate way of filter optimization, while a previously used approach based on maximizing a signal-to-background ratio (SBR) is the approximation that can lead to much poorer LOD specifically in detection of fluorescently labeled biomolecules. The proposed filter-optimization method will be an indispensable tool for developing new and improving existing fluorescence-detection systems aiming at ultimately low LOD.

Excitation-emission matrices and synchronous fluorescence spectroscopy for the diagnosis of gastrointestinal cancers

NASA Astrophysics Data System (ADS)

Genova, Ts; Borisova, E.; Penkov, N.; Vladimirov, B.; Zhelyazkova, A.; Avramov, L.

2016-06-01

We report the development of an improved fluorescence technique for cancer diagnostics in the gastrointestinal tract. We investigate the fluorescence of ex vivo colorectal (cancerous and healthy) tissue samples using excitation-emission matrix (EEM) and synchronous fluorescence spectroscopy (SFS) steady-state approaches. The obtained results are processed for revealing characteristic fluorescence spectral features with a valuable diagnostic meaning. The main tissue fluorophores, contributing to the observed fluorescence, are tyrosine, tryptophan, NADH, FAD, collagen and elastin. Based on the results of the Mann-Whitney test as useful parameters for differentiation of gastrointestinal cancer from normal mucosa, we suggest using excitation wavelengths in the range 300 - 360 nm for fluorescence spectroscopy and wavelengths intervals of 60 nm and 90 nm for SFS.

Seasonal variation in chromophoric dissolved organic matter and relationships among fluorescent components, absorption coefficients and dissolved organic carbon in the Bohai Sea, the Yellow Sea and the East China Sea

NASA Astrophysics Data System (ADS)

Zhu, Wen-Zhuo; Zhang, Hong-Hai; Zhang, Jing; Yang, Gui-Peng

2018-04-01

The absorption coefficient and fluorescent components of chromophoric dissolved organic matter (CDOM) in the Bohai Sea (BS), Yellow Sea (YS), and East China Sea (ECS) in spring and autumn were analyzed in this study. Excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC) identified three components, namely, humic-like C1, tyrosine-like C2 and tryptophan-like C3. The seasonal variations in the vertical patterns of the CDOM absorption coefficient (aCDOM(355)) and fluorescent components were influenced by the seasonal water mass except for the terrestrial input. The relationship between aCDOM(355) and dissolved organic matter (DOC) was attributed to their own mixing behavior. The correlation of the fluorescent components with DOC was disturbed by other non-conservative processes during the export of CDOM to the open ocean. The different chemical compositions and origins of DOC and CDOM led to variability in carbon-specific CDOM absorption (a*CDOM(355)) and fluorescent component ratios (ICn/IC1). The relationship between a*CDOM(355) and aCDOM(355) demonstrated that dissolved organic matter (DOM) in the BS, but not in the ECS, highly contributed non-absorbing DOC to the total DOC concentration. The photodegradation of dominant terrestrially derived CDOM in the ECS contributed to the positive relationship between a*CDOM(355) and ICn/IC1. By contrast, the abundant autochthonous CDOM in the YS was negatively correlated with ICn/IC1 in autumn. Our established box models showed that water exchange is a potentially important source of the aromatic components in the BS, YS, and ECS. Hence, the seasonal variations in water exchange might contribute to the variability of CDOM chemical composition in the BS, YS, and ECS, and significantly influence the structure and function of their ecosystems.

Annealed silver-island films for applications in metal-enhanced fluorescence: interpretation in terms of radiating plasmons.

PubMed

Aslan, Kadir; Leonenko, Zoya; Lakowicz, Joseph R; Geddes, Chris D

2005-09-01

The effects of thermally annealed silver island films have been studied with regard to their potential applicability in applications of metal-enhanced fluorescence, an emerging tool in nano-biotechnology. Silver island films were thermally annealed between 75 and 250 degrees C for several hours. As a function of both time and annealing temperature, the surface plasmon band at approximately 420 nm both diminished and was blue shifted. These changes in plasmon resonance have been characterized using both absorption measurements, as well as topographically using Atomic Force Microscopy. Subsequently, the net changes in plasmon absorption are interpreted as the silver island films becoming spherical and growing in height, as well as an increased spacing between the particles. Interestingly, when the annealed surfaces are coated with a fluorescein-labeled protein, significant enhancements in fluorescence are observed, scaling with annealing temperature and time. These observations strongly support our recent hypothesis that the extent of metal-enhanced fluorescence is due to the ability of surface plasmons to radiate coupled fluorophore fluorescence. Given that the extinction spectrum of the silvered films is comprised of both an absorption and scattering component, and that these components are proportional to the diameter cubed and to the sixth power, respectively, then larger structures are expected to have a greater scattering contribution to their extinction spectrum and, therefore, more efficiently radiate coupled fluorophore emission. Subsequently, we have been able to correlate our increases in fluorescence emission with an increased particle size, providing strong experiment evidence for our recently reported metal-enhanced fluorescence, facilitated by radiating plasmons hypothesis.

Emission shaping in fluorescent proteins: role of electrostatics and π-stacking.

PubMed

Park, Jae Woo; Rhee, Young Min

2016-02-07

For many decades, simulating the excited state properties of complex systems has been an intriguing but daunting task due to its high computational cost. Here, we apply molecular dynamics based techniques with interpolated potential energy surfaces toward calculating fluorescence spectra of the green fluorescent protein (GFP) and its variants in a statistically meaningful manner. With the GFP, we show that the diverse electrostatic tuning can shape the emission features in many different ways. By computationally modulating the electrostatic interactions between the chromophore phenoxy oxygen and its nearby residues, we demonstrate that we indeed can shift the emission to the blue or to the red side in a predictable manner. We rationalize the shifting effects of individual residues in the GFP based on the responses of both the adiabatic and the diabatic electronic states of the chromophore. We next exhibit that the yellow emitting variant, the Thr203Tyr mutant, generates changes in the electrostatic interactions and an additional π-stacking interaction. These combined effects indeed induce a red shift to emit the fluorescence into the yellow region. With the series of demonstrations, we suggest that our approach can provide sound rationales and useful insights in understanding different responses of various fluorescent complexes, which may be helpful in designing new light emitting proteins and other related systems in future studies.

Light-induced flickering of DsRed provides evidence for distinct and interconvertible fluorescent states.

PubMed Central

Malvezzi-Campeggi, F; Jahnz, M; Heinze, K G; Dittrich, P; Schwille, P

2001-01-01

Green fluorescent protein (GFP) from jellyfish Aequorea victoria, the powerful genetically encoded tag presently available in a variety of mutants featuring blue to yellow emission, has found a red-emitting counterpart. The recently cloned red fluorescent protein DsRed, isolated from Discosoma corals (), with its emission maximum at 583 nm, appears to be the long awaited tool for multi-color applications in fluorescence-based biological research. Studying the emission dynamics of DsRed by fluorescence correlation spectroscopy (FCS), it can be verified that this protein exhibits strong light-dependent flickering similar to what is observed in several yellow-shifted mutants of GFP. FCS data recorded at different intensities and excitation wavelengths suggest that DsRed appears under equilibrated conditions in at minimum three interconvertible states, apparently fluorescent with different excitation and emission properties. Light absorption induces transitions and/or cycling between these states on time scales of several tens to several hundreds of microseconds, dependent on excitation intensity. With increasing intensity, the emission maximum of the static fluorescence continuously shifts to the red, implying that at least one state emitting at longer wavelength is preferably populated at higher light levels. In close resemblance to GFP, this light-induced dynamic behavior implies that the chromophore is subject to conformational rearrangements upon population of the excited state. PMID:11509387

Gold nanoclusters as contrast agents for fluorescent and X-ray dual-modality imaging.

PubMed

Zhang, Aili; Tu, Yu; Qin, Songbing; Li, Yan; Zhou, Juying; Chen, Na; Lu, Qiang; Zhang, Bingbo

2012-04-15

Multimodal imaging technique is an alternative approach to improve sensitivity of early cancer diagnosis. In this study, highly fluorescent and strong X-ray absorption coefficient gold nanoclusters (Au NCs) are synthesized as dual-modality imaging contrast agents (CAs) for fluorescent and X-ray dual-modality imaging. The experimental results show that the as-prepared Au NCs are well constructed with ultrasmall sizes, reliable fluorescent emission, high computed tomography (CT) value and fine biocompatibility. In vivo imaging results indicate that the obtained Au NCs are capable of fluorescent and X-ray enhanced imaging. Copyright © 2012 Elsevier Inc. All rights reserved.

Absorption and emission spectroscopic characterization of blue-light receptor Slr1694 from Synechocystis sp. PCC6803.

PubMed

Zirak, P; Penzkofer, A; Lehmpfuhl, C; Mathes, T; Hegemann, P

2007-01-03

The BLUF protein Slr1694 from the cyanobacterium Synechocystis sp. PCC6803 is characterized by absorption and emission spectroscopy. Slr1694 expressed from E. coli which non-covalently binds FAD, FMN, and riboflavin (called Slr1694(I)), and reconstituted Slr1694 which dominantly contains FAD (called Slr1694(II)) are investigated. The receptor conformation of Slr1694 (dark adapted form Slr1694(r)) is transformed to the putative signalling state (light adapted form Slr1694(s)) with red-shifted absorption and decreased fluorescence efficiency by blue-light excitation. In the dark at 22 degrees C, the signalling state recovers back to the initial receptor state with a time constants of about 14.2s for Slr1694(I) and 17s for Slr1694(II). Quantum yields of signalling state formation of approximately 0.63+/-0.07 for both Slr1694(I) and Slr1694(II) were determined by transient transmission measurements and intensity dependent steady-state transmission measurements. Extended blue-light excitation causes some bound flavin conversion to the hydroquinone form and some photo-degradation, both with low quantum efficiency. The flavin-hydroquinone re-oxidizes slowly back (time constant 5-9 min) to the initial flavoquinone form in the dark. A photo-cycle dynamics scheme is presented.

Development of a Time Domain Fluorimeter for Fluorescent Lifetime Multiplexing Analysis

PubMed Central

Weissleder, Ralph; Mahmood, Umar

2009-01-01

We show that a portable, inexpensive USB-powered time domain fluorimeter (TDF) and analysis scheme were developed for use in evaluating a new class of fluorescent lifetime multiplexed dyes. Fluorescent proteins, organic dyes, and quantum dots allow the labeling of more and more individual features within biological systems, but the wide absorption and emission spectra of these fluorophores limit the number of distinct processes which may be simultaneously imaged using spectral separation alone. By additionally separating reporters in a second dimension, fluorescent lifetime multiplexing provides a means to multiply the number of available imaging channels. PMID:19830273

Infrared fluorescence from PAHs in the laboratory

NASA Technical Reports Server (NTRS)

Cherchneff, Isabelle; Barker, John R.

1989-01-01

Several celestial objects, including UV rich regions of planetary and reflection nebulae, stars, H II regions, and extragalactic sources, are characterized by the unidentified infrared emission bands (UIR bands). A few years ago, it was proposed that polycyclic aromatic hydrocarbon species (PAHs) are responsible for most of the UIR bands. This hypothesis is based on a spectrum analysis of the observed features. Comparisons of observed IR spectra with lab absorption spectra of PAHs support the PAH hypothesis. An example spectrum is represented, where the Orion Bar 3.3 micron spectrum is compared with the absorption frequencies of the PAHs Chrysene, Pyrene, and Coronene. The laser excited 3.3 micron emission spectrum is presented from a gas phase PAH (azulen). The infrared fluorescence theory (IRF) is briefly explained, followed by a description of the experimental apparatus, a report of the results, and discussion.

Origin of chlorophyll fluorescence in plants at 55-75 degrees C.

PubMed

Ilík, Petr; Kouril, Roman; Kruk, Jerzy; Myśliwa-Kurdziel, Beata; Popelková, Hana; Strzałka, Kazimierz; Naus, Jan

2003-01-01

The origin of heat-induced chlorophyll fluorescence rise that appears at about 55-60 degrees C during linear heating of leaves, chloroplasts or thylakoids (especially with a reduced content of grana thylakoids) was studied. This fluorescence rise was earlier attributed to photosystem I (PSI) emission. Our data show that the fluorescence rise originates from chlorophyll a (Chl a) molecules released from chlorophyll-containing protein complexes denaturing at 55-60 degrees C. This conclusion results mainly from Chl a fluorescence lifetime measurements with barley leaves of different Chl a content and absorption and emission spectra measurements with barley leaves preheated to selected temperatures. These data, supported by measurements of liposomes with different Chl a/lipid ratios, suggest that the released Chl a is dissolved in lipids of thylakoid membranes and that with increasing Chl a content in the lipid phase, the released Chl a tends to form low-fluorescing aggregates. This is probably the reason for the suppressed fluorescence rise at 55-60 degrees C and the decreasing fluorescence course at 60-75 degrees C, which are observable during linear heating of plant material with a high Chl a/lipid ratio (e.g. green leaves, grana thylakoids, isolated PSII particles).

Deriving chlorophyll fluorescence emissions of vegetation canopies from high resolution field reflectance spectra

NASA Astrophysics Data System (ADS)

Middleton, Elizabeth M.; Corp, Lawrence A.; Daughtry, Craig S.; Entcheva Campbell, Petya K.; Butcher, L. Maryn

2005-11-01

Fluorescence of foliage in the laboratory has proven more rigorous than reflectance for correlation to plant physiology. Especially useful are emissions produced from two stable red and far-red chlorophyll fluorescence (ChlF) peaks centered at 685 nm and 735 nm. Methods have been developed elsewhere to extract steady state solar induced fluorescence (SIF) from apparent reflectance of vegetation canopies/landscapes using the Fraunhofer Line Depth (FLD) principal. Our study utilized these methods in conjunction with field-acquired high spectral resolution canopy reflectance spectra obtained in 2004 and 2005 over corn crops and small tree plots of three deciduous species (red maple, tulip poplar, sweet gum). Leaf level measurements were also made of foliage which included ChlF, photosynthesis, and leaf constituents (photosynthetic pigment, carbon (C), and nitrogen (N) contents). As part of ongoing experiments, measurements were made on N application plots within corn (280, 140, 70, and 0 kg N/ha) and tree (0, 37.5, 75, 112.5, 150 kg N /ha) sites at the USDA/Agriculture Research Service in Beltsville, MD. SIF intensities for ChlF were derived directly from canopy reflectance spectra in specific narrow- band regions associated with atmospheric oxygen absorption features centered at 688 and 760 nm. The red/far-red SIF ratio (SIFratio) derived from these field reflectance spectra successfully discriminated foliar pigment ratios altered by N application rates in both corn crops. This ratio was also positively correlated to the C/N ratio at leaf and canopy levels, for the available corn data (e.g., 2004). No consistent N treatment or species differences in SIF were detected in the tree foliage, but additional 2005 data are forthcoming. This study has relevance to future passive satellite remote sensing approaches to monitoring C dynamics from space.

Recoilless Nuclear Resonance Absorption of Gamma Radiation

NASA Astrophysics Data System (ADS)

Mössbauer, Rudolf L.

It is a high distinction to be permitted to address you on the subject of recoilless nuclear resonance absorption of gamma radiation. The methods used in this special branch of experimental physics have recently found acceptance in many areas of science. I take the liberty to confine myself essentially to the work which I was able to carry out in the years 1955-1958 at the Max Planck Institute in Heidelberg, and which finally led to establishment of the field of recoilless nuclear resonance absorption. Many investigators shared in the preparations of the basis for the research we are concerned with in this lecture. As early as the middle of the last century Stokes observed, in the case of fluorite, the phenomenon now known as fluorescence - namely, that solids, liquids, and gases under certain conditions partially absorb incident electromagnetic radiation which immediately is reradiated. A special case is the so-called resonance fluorescence, a phenomenon in which the re-emitted and the incident radiation both are of the same wavelength. The resonance fluorescence of the yellow D lines of sodium in sodium vapour is a particularly notable and exhaustively studied example. In this optical type of resonance fluorescence, light sources are used in which the atoms undergo transitions from excited states to their ground states (Fig. 1.1). The light quanta emitted in these transitions (A → B) are used to initiate the inverse process of resonance absorption in the atoms of an absorber which are identical with the radiating atoms. The atoms of the absorber undergo a transition here from the ground state (B) to the excited state (A), from which they again return to the ground state, after a certain time delay, by emission of fluorescent light.

A Monte Carlo study of fluorescence generation probability in a two-layered tissue model

NASA Astrophysics Data System (ADS)

Milej, Daniel; Gerega, Anna; Wabnitz, Heidrun; Liebert, Adam

2014-03-01

It was recently reported that the time-resolved measurement of diffuse reflectance and/or fluorescence during injection of an optical contrast agent may constitute a basis for a technique to assess cerebral perfusion. In this paper, we present results of Monte Carlo simulations of the propagation of excitation photons and tracking of fluorescence photons in a two-layered tissue model mimicking intra- and extracerebral tissue compartments. Spatial 3D distributions of the probability that the photons were converted from excitation to emission wavelength in a defined voxel of the medium (generation probability) during their travel between source and detector were obtained for different optical properties in intra- and extracerebral tissue compartments. It was noted that the spatial distribution of the generation probability depends on the distribution of the fluorophore in the medium and is influenced by the absorption of the medium and of the fluorophore at excitation and emission wavelengths. Simulations were also carried out for realistic time courses of the dye concentration in both layers. The results of the study show that the knowledge of the absorption properties of the medium at excitation and emission wavelengths is essential for the interpretation of the time-resolved fluorescence signals measured on the surface of the head.

Absorption and emission spectroscopic characterization of BLUF protein Slr1694 from Synechocystis sp. PCC6803 with roseoflavin cofactor.

PubMed

Zirak, P; Penzkofer, A; Mathes, T; Hegemann, P

2009-11-09

The wild-type BLUF protein Slr1694 from Synechocystis sp. PCC6803 (BLUF=blue-light sensor using FAD) has flavin adenosine dinucleotide (FAD) as natural cofactor. This light sensor causes positive phototaxis of the marine cyanobacterium. In this study the FAD cofactor of the wild-type Slr1694 was replaced by roseoflavin (RoF) and the roseoflavin derivatives RoFMN and RoFAD during heterologous expression in a riboflavin auxotrophic E. coli strain. An absorption and emission spectroscopic characterization of the cofactor-exchanged-Slr1694 (RoSlr) was carried out both under dark conditions and under illuminated conditions. The behaviour of RoF embedded in RoSlr in aqueous solution at pH 8 is compared with the behaviour of RoF in aqueous solution. The fluorescence of RoF and RoSlr is quenched by photo-induced twisted intra-molecular charge transfer at room temperature with stronger effect for RoF. The fluorescence quenching is diminished at liquid nitrogen temperature. Light exposure of RoSlr causes irreversible conversion of the protein embedded roseoflavins to 8-methylamino-flavins, 8-dimethylamino-lumichrome and 8-methylamino-lumichrome.

Long wavelength fluorescence based biosensors for in vivo continuous monitoring of metabolites

NASA Astrophysics Data System (ADS)

Thomas, Joseph; Ambroise, Arounaguiry; Birchfield, Kara; Cai, Wensheng; Sandmann, Christian; Singh, Sarabjit; Weidemaier, Kristin; Pitner, J. Bruce

2006-02-01

The early stage development studies of novel implantable continuous metabolite sensor systems for glucose, lactate and fatty acids are discussed. These sensors utilize non-enzymatic "reagentless" sensor systems based on NIR fluorophore-labeled binding proteins. For in vivo applications, NIR fluorescence based systems (beyond 600 nm) have the added benefit of reduced interference from background scattering, tissue and serum absorption and cell auto-fluorescence. The long wavelength emission facilitates implanted sensor disks to transmit fluorescence to an external reader through wireless connections and the resulting fluorescence signals can be correlated to metabolite concentrations. We have developed a prototype optical system that uses a bifurcated optical fiber to transmit excitation and read emission at the surface of the skin. With this system, fluorescence signals were read over time through animal skin. The changes in glucose concentration were studied using immobilized sensor proteins and were compared to non-immobilized sensors in solution. For sensors in solution, no response delay was observed. For immobilized systems, the fluorescence response showed a delay corresponding to the diffusion time for the metabolite to equilibrate within the sensor.

Remote sensing of methane emissions by combining optical similitude absorption spectroscopy (OSAS) and lidar

NASA Astrophysics Data System (ADS)

Galtier, Sandrine; Anselmo, Christophe; Welschinger, Jean-Yves; Cariou, Jean-Pierre; Sivignon, Jean-François; Miffre, Alain; Rairoux, Patrick

2018-04-01

Monitoring the emission of gases is difficult to achieve in industrial sites and in environments presenting poor infrastructures. Hence, robust methodologies should be developed and coupled to Lidar technology to allow remote sensing of gas emission. OSAS is a new methodology to evaluate gas concentration emission from spectrally integrated differential absorption measurements. Proof of concept of OSAS-Lidar for CH4 emission monitoring is here presented.

Fluorescent Nanodiamonds in Biomedical Applications.

PubMed

Mitura, Katarzyna Anna; Włodarczyk, Elżbieta

2018-04-18

Nanoparticles have an extended surface and a large surface area, which is the ratio of the size of the surfacearea to the volume. A functionalized surface can give rise to more modifications and therefore allows this nanomaterial to have new properties. Fluorescent molecules contain fluorophore, which is capable of being excited via the absorption of light energy at a specific wavelength and subsequently emitting radiation energy of a longer wavelength. A chemically modified surface of nanodiamond (ND; by carboxylation) demonstrated biocompatibility with DNA, cytochrome C, and antigens. In turn, fluorescent nanodiamonds (FNDs) belong to a group of new nanomaterials. Their surface can be modified by joining functional groups such as carboxyl, hydroxyl, or amino, after which they can be employed as a fluorescence agent. Their fluorescent properties result from defects in the crystal lattice. FNDs reach dimensions of 4-100 nm, have attributes such as photostability, long fluorescence lifetimes (10 ns), and fluorescence emission between 600 and 700 nm. They are also nontoxic, chemically inert, biocompatible, and environmentally harmless. The main purpose of this article was to present the medical applications of various types of modified NDs.

Effects of alcohols on fluorescence intensity and color of a discharged-obelin-based biomarker.

PubMed

Alieva, Roza R; Belogurova, Nadezhda V; Petrova, Alena S; Kudryasheva, Nadezhda S

2014-05-01

Photoproteins are responsible for bioluminescence of marine coelenterates; bioluminescent and fluorescent biomarkers based on photoproteins are useful for monitoring of calcium-dependent processes in medical investigations. Here, we present the analysis of intensity and color of light-induced fluorescence of Ca(2+)-discharged photoprotein obelin in the presence of alcohols (ethanol and glycerol). Complex obelin spectra obtained at different concentrations of the alcohols at 350- and 280-nm excitation (corresponding to polypeptide-bound coelenteramide and tryptophan absorption regions) were deconvoluted into Gaussian components; fluorescent intensity and contributions of the components to experimental spectra were analyzed. Five Gaussian components were found in different spectral regions-ultraviolet (tryptophan emission), blue-green (coelenteramide emission), and red (hypothetical indole-coelenteramide exciplex emission). Inhibition coefficients and contributions of the components to experimental fluorescent spectra showed that presence of alcohols increased contributions of ultraviolet, violet, and red components, but decreased contributions of components in the blue-green region. The effects were related to (1) changes of proton transfer efficiency in fluorescent S*1 state of coelenteramide in the obelin active center and (2) formation of indole-coelenteramide exciplex at 280-nm photoexcitation. The data show that variation of fluorescence color and intensity in the presence of alcohols and dependence of emission spectra on excitation wavelength should be considered while applying the discharged obelin as a fluorescence biomarker.

Detection of intaoral lesions using a fluorescence camera

NASA Astrophysics Data System (ADS)

Thoms, Michael

2006-02-01

Optical methods for the detection of carious lesions, calculus and plaque have the advantage of being minimally invasive. The use of endogeneous fluorescence markers like porphyrins could simplify the application of fluorescence techniques in the dental practice. It is known that porphyrins are produced by some of the bacterial species that are present in the oral cavity. Since porphyrins have an excitation band at about 400nm they have the potential to be used as fluorescent markers of locations in the oral cavity where the production of bacteria is out of the limits of healthy regions. Further, modern and efficient GaN-based semiconductor diodes emit light in this spectral range and thus make the implementation of fluorescence sensors with excitation at this wavelength easy. Carious lesions, calculus and plaque have been measured using a self build fluorescence camera using GaN-diodes for illumination at 405nm. Further, emission spectra under this excitation were recorded. For the latter purpose freshly extracted teeth were used. It has been found that already in the case of an initial carious lesion red porphyrin-fluorescence is emitted whereas it is absent in healthy enamel. In already brown coloured carious lesions the emission bands of porphyrin are present but the observed overall fluorescence intensity is lower, probably due to the absorption of the fluorescence by the carious defect itself. In dental calculus, dental plaque and subgingival concrements porphyrin originated luminescence was found as well. Since in these cases the emission spectra differ slightly it can be concluded that they originate from different types of porphyrins and thus also from different bacteria. These results show that this fluorescence technique can be a promising method to diagnose carious lesions, calculus and plaque.

Infrared molecular emissions from comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Mumma, M. J.

1983-01-01

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued.

Tricolor emission of a fluorescent heteroditopic ligand over a concentration gradient of zinc(II) ions.

PubMed

Sreenath, Kesavapillai; Clark, Ronald J; Zhu, Lei

2012-09-21

The internal charge transfer (ICT) type fluoroionophore arylvinyl-bipy (bipy = 2,2'-bipyridyl) is covalently tethered to the spirolactam form of rhodamine to afford fluorescent heteroditopic ligand 4. Compound 4 can be excited in the visible region, the emission of which undergoes sequential bathochromic shifts over an increasing concentration gradient of Zn(ClO(4))(2) in acetonitrile. Coordination of Zn(2+) stabilizes the ICT excited state of the arylvinyl-bipy component of 4, leading to the first emission color shift from blue to green. At sufficiently high concentrations of Zn(ClO(4))(2), the nonfluorescent spirolactam component of 4 is transformed to the fluorescent rhodamine, which turns the emission color from green to orange via intramolecular fluorescence resonance energy transfer (FRET) from the Zn(2+)-bound arylvinyl-bipy fluorophore to rhodamine. While this work offers a new design of ratiometric chemosensors, in which sequential analyte-induced emission band shifts result in the sampling of multiple colors at different concentration ranges (i.e., from blue to green to orange as [Zn(2+)] increases in the current case), it also reveals the nuances of rhodamine spirolactam chemistry that have not been sufficiently addressed in the published literature. These issues include the ability of rhodamine spirolactam as a fluorescence quencher via electron transfer, and the slow kinetics of spirolactam ring-opening effected by Zn(2+) coordination under pH neutral aqueous conditions.

Chlorophyll Fluorescence Emissions of Vegetation Canopies From High Resolution Field Reflectance Spectra

NASA Technical Reports Server (NTRS)

Middleton, E. M.; Corp, L. A.; Daughtry, C. S. T.; Campbell, P. K. Entcheva

2006-01-01

A two-year experiment was performed on corn (Zea mays L.) crops under nitrogen (N) fertilization regimes to examine the use of hyperspectral canopy reflectance information for estimating chlorophyll fluorescence (ChlF) and vegetation production. Fluorescence of foliage in the laboratory has proven more rigorous than reflectance for correlation to plant physiology. Especially useful are emissions produced from two stable red and far-red chlorophyll ChlF peaks centered at 685V10 nm and 735V5 nm. Methods have been developed elsewhere to extract steady state solar induced fluorescence (SF) from apparent reflectance of vegetation canopies/landscapes using the Fraunhofer Line Depth (FLD) principal. Our study utilized these methods in conjunction with field-acquired high spectral resolution canopy reflectance spectra obtained in 2004 and 2005 over corn crops, as part of an ongoing multi-year experiment at the USDA/Agriculture Research Service in Beltsville, MD. A spectroradiometer (ASD-FR Fieldspec Pro, Analytical Spectral Devices, Inc., Boulder, CO) was used to measure canopy radiances 1 m above plant canopies with a 22deg field of view and a 0deg nadir view zenith angle. Canopy and plant measurements were made at the R3 grain fill reproductive stage on 3-4 replicate N application plots provided seasonal inputs of 280, 140, 70, and 28 kg N/ha. Leaf level measurements were also made which included ChlF, photosynthesis, and leaf constituents (photosynthetic pigment, carbon (C), and N contents). Crop yields were determined at harvest. SIF intensities for ChlF were derived directly from canopy reflectance spectra in specific narrowband regions associated with atmospheric oxygen absorption features centered at 688 and 760 nm. The red/far-red S F ratio derived from these field reflectance spectra successfully discriminated foliar pigment levels (e.g., total chlorophyll, Chl) associated with N application rates in both corn crops. This canopy-level spectral ratio was also

Effect of silver nanoparticles on the fluorescence of Pb2+ and compositional dependence of Sm3+ fluorescence in borate glasses

NASA Astrophysics Data System (ADS)

Olumoroti, Akinloluwa T.

Borate glasses have been widely studied due to their good optical and mechanical properties. Lead and bismuth (PbO/Bi2O 3:B2O3) borate glasses belong to a family of heavy metal oxide (HMO) glasses which are well known to be chemically durable, stable against atmospheric moisture, have low melting temperatures and good corrosion resistance. The first part of this work deals with lead borate glasses with silver nanoparticles (NPs) introduced into the glass matrix. Transmission electron microscopy characterization is done to verify the nucleation of NPs. Fluorescence and optical absorption experiments are then carried out after different heat treatment duration to investigate the influence of silver NPs on the optical properties of lead (Pb2+) by comparing with a glass sample without silver NPs. Optical absorption experiments show that a well-defined surface plasmon resonance (SPR) peak due to Ag NPs can be observed only for samples that were annealed for 36 hrs. Pb2+ fluorescence spectra reveal that the presence of silver NPs creates new emission centers for Pb2+ ions by altering their chemical environment. The second part of the work involves the use of samarium (a rare earth ion) as a dopant in lead and bismuth borate glasses. The concentration of samarium (Sm3+) is fixed and the base glass composition is varied. The goal is to investigate the compositional dependence of optical properties of samarium in the base glass (PbO/Bi2O3:B 2O3). Optical absorption spectra have been collected and the oscillator strength of each transition - including the hypersensitive - is obtained. The Optical absorption edge is found to shift toward lower energies with increasing PbO/Bi2O3 concentration. Both the oscillator strength and the peak position of the hypersensitive transition show significant variation with glass composition. Strong interaction between Sm3+ ions and Pb2+/Bi3+ ions can also be seen from the variations in the fluorescence emission properties of Sm3+ as a

Enhanced Fluorescence Emission of Me-ADOTA+ by Self-Assembled Silver Nanoparticles on a Gold Film

PubMed Central

Sørensen, Thomas J.; Laursen, Bo W.; Luchowski, Rafal; Shtoyko, Tanya; Akopova, Irina; Gryczynski, Zygmunt; Gryczynski, Ignacy

2009-01-01

We report a multi-fold enhancement of the fluorescence of methyl-azadioxatriangulenium chloride (Me-ADOTA•Cl) in PVA deposited on a 50 nm thick gold mirror carrying an evaporation induced self-assembly of colloidal silver nanoparticles (Ag-SACs). The average measured increase in fluorescence emission of about 50-fold is accompanied by hot spots with a local enhancement in brigthness close to 200. The long lifetime of the dye allows for the first direct determination of the correlation between the enhancement of emission intensity and the decrease in fluorescence lifetime. The Ag-SACs surface preparation and observed enhancements are highly reproducible. We believe that these robust plasmonic surfaces will find use in sensing platforms for ultrasensitive detection. PMID:20161182

A new high selective and sensitive turn-on fluorescent and ratiometric absorption chemosensor for Cu2+ based on benzimidazole in aqueous solution and its application in live cell.

PubMed

Bing, Qijing; Wang, Lin; Li, Donglin; Wang, Guang

2018-09-05

A new benzimidazole base turn-on fluorescent and ratiometric absorption chemosensor (L) bearing bidentate ligand for detection of Cu 2+ was designed and synthesized. Fluorescence and UV-vis spectra studies demonstrated that L can detect Cu 2+ ions in aqueous solution using fluorescence enhancement and ratiometric absorption sensing over a wide pH range. Both fluorescent and ratiometric absorption sensing of L for Cu 2+ possessed high selectivity and sensitivity over other competitive metal ions and had low detection limit. Job's plot, mass spectra and DFT calculation indicated the sensing mechanism is the complex formation between L and Cu 2+ with 1:2 stoichiometry. Fluorescence images of HepG2 in the absence and presence of Cu 2+ displayed L had cell permeability and detection ability for Cu 2+ in live cells. Copyright © 2018 Elsevier B.V. All rights reserved.

Chip-scale fluorescence microscope based on a silo-filter complementary metal-oxide semiconductor image sensor.

PubMed

Ah Lee, Seung; Ou, Xiaoze; Lee, J Eugene; Yang, Changhuei

2013-06-01

We demonstrate a silo-filter (SF) complementary metal-oxide semiconductor (CMOS) image sensor for a chip-scale fluorescence microscope. The extruded pixel design with metal walls between neighboring pixels guides fluorescence emission through the thick absorptive filter to the photodiode of a pixel. Our prototype device achieves 13 μm resolution over a wide field of view (4.8 mm × 4.4 mm). We demonstrate bright-field and fluorescence longitudinal imaging of living cells in a compact, low-cost configuration.

X-ray Absorption and Emission Spectroscopy of CrIII (Hydr)Oxides: Analysis of the K-Pre-Edge Region

NASA Astrophysics Data System (ADS)

Frommer, Jakob; Nachtegaal, Maarten; Czekaj, Izabela; Weng, Tsu-Chien; Kretzschmar, Ruben

2009-10-01

Pre-edge spectral features below the main X-ray absorption K-edge of transition metals show a pronounced chemical sensitivity and are promising sources of structural information. Nevertheless, the use of pre-edge analysis in applied research is limited because of the lack of definite theoretical peak-assignments. The aim of this study was to determine the factors affecting the chromium K-pre-edge features in trivalent chromium-bearing oxides and oxyhydroxides. The selected phases varied in the degree of octahedral polymerization and the degree of iron-for-chromium substitution in the crystal structure. We investigated the pre-edge fine structure by means of high-energy-resolution fluorescence detected X-ray absorption spectroscopy and by 1s2p resonant X-ray emission spectroscopy. Multiplet theory and full multiple-scattering calculations were used to analyze the experimental data. We show that the chromium K-pre-edge contains localized and nonlocalized transitions. Contributions arising from nonlocalized metal-metal transitions are sensitive to the nearest metal type and to the linkage mode between neighboring metal octahedra. Analyzing these transitions opens up new opportunities for investigating the local coordination environment of chromium in poorly ordered solids of environmental relevance.

Fluorescence and absorption properties of chromophoric dissolved organic matter (CDOM) in coastal surface waters of the northwestern Mediterranean Sea, influence of the Rhône River

NASA Astrophysics Data System (ADS)

Para, J.; Coble, P. G.; Charrière, B.; Tedetti, M.; Fontana, C.; Sempéré, R.

2010-12-01

Seawater samples were collected monthly in surface waters (2 and 5 m depths) of the Bay of Marseilles (northwestern Mediterranean Sea; 5°17'30" E, 43°14'30" N) during one year from November 2007 to December 2008 and studied for total organic carbon (TOC) as well as chromophoric dissolved organic matter (CDOM) optical properties (absorbance and fluorescence). The annual mean value of surface CDOM absorption coefficient at 350 nm [aCDOM(350)] was very low (0.10 ± 0.02 m-1) in comparison to values usually found in coastal waters, and no significant seasonal trend in aCDOM(350) could be determined. By contrast, the spectral slope of CDOM absorption (SCDOM) was significantly higher (0.023 ± 0.003 nm-1) in summer than in fall and winter periods (0.017 ± 0.002 nm-1), reflecting either CDOM photobleaching or production in surface waters during stratified sunny periods. The CDOM fluorescence, assessed through excitation emission matrices (EEMs), was dominated by protein-like component (peak T; 1.30-21.94 QSU) and marine humic-like component (peak M; 0.55-5.82 QSU), while terrestrial humic-like fluorescence (peak C; 0.34-2.99 QSU) remained very low. This reflected a dominance of relatively fresh material from biological origin within the CDOM fluorescent pool. At the end of summer, surface CDOM fluorescence was very low and strongly blue shifted, reinforcing the hypothesis of CDOM photobleaching. Our results suggested that unusual Rhône River plume eastward intrusion events might reach Marseilles Bay within 2-3 days and induce local phytoplankton blooms and subsequent fluorescent CDOM production (peaks M and T) without adding terrestrial fluorescence signatures (peaks C and A). Besides Rhône River plumes, mixing events of the entire water column injected relative aged (peaks C and M) CDOM from the bottom into the surface and thus appeared also as an important source of CDOM in surface waters of the Marseilles Bay. Therefore, the assessment of CDOM optical properties

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.

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.

Differentiation of ocular fundus fluorophores by fluorescence lifetime imaging using multiple excitation and emission wavelengths

NASA Astrophysics Data System (ADS)

Hammer, M.; Schweitzer, D.; Schenke, S.; Becker, W.; Bergmann, A.

2006-10-01

Ocular fundus autofluorescence imaging has been introduced into clinical diagnostics recently. It is in use for the observation of the age pigment lipofuscin, a precursor of age - related macular degeneration (AMD). But other fluorophores may be of interest too: The redox pair FAD - FADH II provides information on the retinal energy metabolism, advanced glycation end products (AGE) indicate protein glycation associated with pathologic processes in diabetes as well as AMD, and alterations in the fluorescence of collagen and elastin in connective tissue give us the opportunity to observe fibrosis by fluorescence imaging. This, however, needs techniques able to differentiate particular fluorophores despite limited permissible ocular exposure as well as excitation wavelength (limited by the transmission of the human ocular lens to >400 nm). We present an ophthalmic laser scanning system (SLO), equipped with picosecond laser diodes (FWHM 100 ps, 446 nm or 468 nm respectively) and time correlated single photon counting (TCSPC) in two emission bands (500 - 560 nm and 560 - 700 nm). The decays were fitted by a bi-exponential model. Fluorescence spectra were measured by a fluorescence spectrometer fluorolog. Upon excitation at 446 nm, the fluorescence of AGE, FAD, and lipofuscin were found to peak at 503 nm, 525 nm, and 600 nm respectively. Accordingly, the statistical distribution of the fluorescence decay times was found to depend on the different excitation wavelengths and emission bands used. The use of multiple excitation and emission wavelengths in conjunction with fluorescence lifetime imaging allows us to discriminate between intrinsic fluorophores of the ocular fundus. Taken together with our knowledge on the anatomical structure of the fundus, these findings suggest an association of the short, middle and long fluorescence decay time to the retinal pigment epithelium, the retina, and connective tissue respectively.

Theoretical studies on absorption, emission, and resonance Raman spectra of Coumarin 343 isomers

NASA Astrophysics Data System (ADS)

Wu, Wenpeng; Cao, Zexing; Zhao, Yi

2012-03-01

The vibrationally resolved spectral method and quantum chemical calculations are employed to reveal the structural and spectral properties of Coumarin 343 (C343), an ideal candidate for organic dye photosensitizers, in vacuum and solution. The results manifest that the ground-state energies are dominantly determined by different placements of hydrogen atom in carboxylic group of C343 conformations. Compared to those in vacuum, the electronic absorption spectra in methanol solvent show a hyperchromic property together with the redshift and blueshift for the neutral C343 isomers and their deprotonated anions, respectively. From the absorption, emission, and resonance Raman spectra, it is found that the maximal absorption and emission come from low-frequency modes whereas the high-frequency modes have high Raman activities. The detailed spectra are further analyzed for the identification of the conformers and understanding the potential charge transfer mechanism in their photovoltaic applications.

Selective two-photon absorption in carbon dots: a piece of the photoluminescence emission puzzle.

PubMed

Santos, Carla I M; Mariz, Inês F A; Pinto, Sandra N; Gonçalves, Gil; Bdikin, Igor; Marques, Paula A A P; Neves, Maria Graça P M S; Martinho, José M G; Maçôas, Ermelinda M S

2018-06-22

Carbon nanodots (Cdots) are now emerging as promising nonlinear fluorophores for applications in biological environments. A thorough and systematic approach to the two-photon induced emission of Cdots that could provide design guidelines to control their nonlinear emission properties is still missing. In this work, we address the nonlinear optical spectroscopy of Cdots prepared by controlled chemical cutting of graphene oxide (GO). The two-photon absorption in the 700-1000 nm region and the corresponding emission spectrum are carefully investigated. The highest two-photon absorption cross-section estimated was 130 GM at 720 nm. This value is comparable with the one reported for graphene nanoribbons with push-pull architecture. The emission spectrum depends on the excitation mode. At the same excitation energy, nonlinear excitation results in excitation-wavelength independent emission, while upon linear excitation the emission is excitation-wavelength dependent. The biphotonic interaction seems to be selective towards sp2 clusters bearing electron donor and acceptor groups found in push-pull architectures. Both linear and nonlinear emission can be understood based on the existence of isolated sp2 clusters involved in π-π stacking interactions with clusters in adjacent layers.

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

2016-03-03

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.

Decomposition of the fluorescence spectra of two FAD molecules in electron-transferring flavoprotein from Megasphaera elsdenii.

PubMed

Sato, Kyosuke; Nishina, Yasuzo; Shiga, Kiyoshi

2013-07-01

Electron-transferring flavoprotein (ETF) from Megasphaera elsdenii contains two FAD molecules, FAD-1 and FAD-2. FAD-2 shows an unusual absorption spectrum with a 400-nm peak. In contrast, ETFs from other sources such as pig contain one FAD and one AMP with the FAD showing a typical flavin absorption spectrum with 380- and 440-nm peaks. It is presumed that FAD-2 is the counterpart of the FAD in other ETFs. In this study, the FAD-1 and FAD-2 fluorescence spectra were determined by titration of FAD-1-bound ETF with FAD using excitation-emission matrix (EEM) fluorescence spectroscopy. The EEM data were globally analysed, and the FAD fluorescence spectra were calculated from the principal components using their respective absorption spectra. The FAD-2 fluorescence spectrum was different from that of pig ETF, which is more intense and blue-shifted. AMP-free pig ETF in acidic solution, which has a comparable absorption spectrum to FAD-2, also had a similar fluorescence spectrum. This result suggests that FAD-2 in M. elsdenii ETF and the FAD in acidic AMP-free pig ETF share a common microenvironment. A review of published ETF fluorescence spectra led to the speculation that the majority of ETF molecules in solution are in the conformation depicted by the crystal structure.

Emission and absorption x-ray edges of Li

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callcott, T A; Arakawa, E T; Ederer, D L

1977-01-01

Measurements of the K X-ray absorption and emission edges of Li are reported. They were made with the same spectrometer at the NBS storage ring and serve to establish a 0.1 eV separation between the edges with no possibility of instrument calibration error. These results are compared with recent theories of Almbladh and Mahan describing the effects of incomplete phonon relaxation about the core hole. It is concluded that these theories give a satisfactory explanation of the data.

Metal plasmon-coupled fluorescence imaging and label free coenzyme detection in cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jian, E-mail: jian@cfs.bioment.umaryland.edu; Fu, Yi; Li, Ge

2012-08-31

Highlights: Black-Right-Pointing-Pointer Metal nanoparticle for fluorescence cell imaging. Black-Right-Pointing-Pointer Non-invasive emission detection of coenzyme in cell on time-resolved confocal microscope. Black-Right-Pointing-Pointer Near-field interaction of flavin adenine dinucleotide with silver substrate. Black-Right-Pointing-Pointer Isolation of emissions by coenzymes from cellular autofluorescence on fluorescence cell imaging. -- Abstract: Flavin adenine dinucleotide (FAD) is a key metabolite in cellular energy conversion. Flavin can also bind with some enzymes in the metabolic pathway and the binding sites may be changed due to the disease progression. Thus, there is interest on studying its expression level, distribution, and redox state within the cells. FAD is naturally fluorescent,more » but it has a modest extinction coefficient and quantum yield. Hence the intrinsic emission from FAD is generally too weak to be isolated distinctly from the cellular backgrounds in fluorescence cell imaging. In this article, the metal nanostructures on the glass coverslips were used as substrates to measure FAD in cells. Particulate silver films were fabricated with an optical resonance near the absorption and the emission wavelengths of FAD which can lead to efficient coupling interactions. As a result, the emission intensity and quantum yield by FAD were greatly increased and the lifetime was dramatically shortened resulting in less interference from the longer lived cellular background. This feature may overcome the technical limits that hinder the direct observation of intrinsically fluorescent coenzymes in the cells by fluorescence microscopy. Fluorescence cell imaging on the metallic particle substrates may provide a non-invasive strategy for collecting the information of coenzymes in cells.« less

The extreme wings of atomic emission and absorption lines. [in low pressure gases

NASA Technical Reports Server (NTRS)

Dalgarno, A.; Sando, K. M.

1973-01-01

Consideration of the extreme wings of atomic and molecular emission and absorption lines in low pressure gases. Classical and semiclassical results are compared with accurate quantal calculations of the self-broadening of Lyman-alpha in the hydrogen absorption spectrum that arises from quasimolecular transition. The results of classical, quantal, and semiclassical calculations of the absorption coefficient in the red wing are shown for temperatures of 500, 200, and 100 K. The semiclassical and quantal spectra agree well in shape at 500 K. Various other findings are discused.

Computer Reconstruction of Plant Growth and Chlorophyll Fluorescence Emission in Three Spatial Dimensions

PubMed Central

Bellasio, Chandra; Olejníčková, Julie; Tesař, Radek; Šebela, David; Nedbal, Ladislav

2012-01-01

Plant leaves grow and change their orientation as well their emission of chlorophyll fluorescence in time. All these dynamic plant properties can be semi-automatically monitored by a 3D imaging system that generates plant models by the method of coded light illumination, fluorescence imaging and computer 3D reconstruction. Here, we describe the essentials of the method, as well as the system hardware. We show that the technique can reconstruct, with a high fidelity, the leaf size, the leaf angle and the plant height. The method fails with wilted plants when leaves overlap obscuring their true area. This effect, naturally, also interferes when the method is applied to measure plant growth under water stress. The method is, however, very potent in capturing the plant dynamics under mild stress and without stress. The 3D reconstruction is also highly effective in correcting geometrical factors that distort measurements of chlorophyll fluorescence emission of naturally positioned plant leaves. PMID:22368511

Computer reconstruction of plant growth and chlorophyll fluorescence emission in three spatial dimensions.

PubMed

Bellasio, Chandra; Olejníčková, Julie; Tesař, Radek; Sebela, David; Nedbal, Ladislav

2012-01-01

Plant leaves grow and change their orientation as well their emission of chlorophyll fluorescence in time. All these dynamic plant properties can be semi-automatically monitored by a 3D imaging system that generates plant models by the method of coded light illumination, fluorescence imaging and computer 3D reconstruction. Here, we describe the essentials of the method, as well as the system hardware. We show that the technique can reconstruct, with a high fidelity, the leaf size, the leaf angle and the plant height. The method fails with wilted plants when leaves overlap obscuring their true area. This effect, naturally, also interferes when the method is applied to measure plant growth under water stress. The method is, however, very potent in capturing the plant dynamics under mild stress and without stress. The 3D reconstruction is also highly effective in correcting geometrical factors that distort measurements of chlorophyll fluorescence emission of naturally positioned plant leaves.

Fibre Optic Temperature Sensors Using Fluorescent Phenomena.

NASA Astrophysics Data System (ADS)

Selli, Raman Kumar

Available from UMI in association with The British Library. A number of fibre optic sensors based on fluorescent phenomena using low cost electronic and optical filtering techniques, for temperature sensing applications are described and discussed. The initial device developed uses the absorption edge change of an optical glass to monitor changes in temperature with a second wavelength reference channel being generated from a fluorescent material, neodymium doped in glass. This device demonstrates the working of the self-referencing principle in a practical device tested over the temperature range of -60^circ C to 200^circC. This initial device was improved by incorporating a microprocessor and by modifying the processing electronic circuitry. An alternative probe was constructed which used a second fibre placed along-side the addressing fibre in contrast to the original device where the fibre is placed at the opposite end of the addressing fibre. A device based on the same principle but with different absorption glasses and a different fluorescent medium, crystalline ruby, was also examined. This device operated at a lower wavelength region compared to the infra -red working region of the first device. This work illustrated the need to make an appropriate choice of sensor absorption glass so that the cheaper indicator type LEDs, which operated at lower wavelengths, may be used. Ruby is a fluorescent material which is characterized by each emission wavelength having its own temperature characteristics. The integrated energy output over the complete emission spectrum is independent of temperature. This provided a means of generating a reference from the complete spectrum while a small frequency band gave a temperature dependent output. This characteristic of ruby was used to develop a temperature measuring device. A final system which utilises the temperature dependent decay-time emission properties of crystalline ruby was developed. In this case the ruby was

Measurement of temperature profiles in flames by emission-absorption spectroscopy

NASA Technical Reports Server (NTRS)

Simmons, F. S.; Arnold, C. B.; Lindquist, G. H.

1972-01-01

An investigation was conducted to explore the use of infrared and ultraviolet emission-absorption spectroscopy for determination of temperature profiles in flames. Spectral radiances and absorptances were measured in the 2.7-micron H2O band and the 3064-A OH band in H2/O2 flames for several temperature profiles which were directly measured by a sodium line-reversal technique. The temperature profiles, determined by inversion of the infrared and ultraviolet spectra, showed an average disagreement with line-reversal measurements of 50 K for the infrared and 200 K for the ultraviolet at a temperature of 2600 K. The reasons for these discrepancies are discussed in some detail.

Optical filters for wavelength selection in fluorescence instrumentation.

PubMed

Erdogan, Turan

2011-04-01

Fluorescence imaging and analysis techniques have become ubiquitous in life science research, and they are poised to play an equally vital role in in vitro diagnostics (IVD) in the future. Optical filters are crucial for nearly all fluorescence microscopes and instruments, not only to provide the obvious function of spectral control, but also to ensure the highest possible detection sensitivity and imaging resolution. Filters make it possible for the sample to "see" light within only the absorption band, and the detector to "see" light within only the emission band. Without filters, the detector would not be able to distinguish the desired fluorescence from scattered excitation light and autofluorescence from the sample, substrate, and other optics in the system. Today the vast majority of fluorescence instruments, including the widely popular fluorescence microscope, use thin-film interference filters to control the spectra of the excitation and emission light. Hence, this unit emphasizes thin-film filters. After briefly introducing different types of thin-film filters and how they are made, the unit describes in detail different optical filter configurations in fluorescence instruments, including both single-color and multicolor imaging systems. Several key properties of thin-film filters, which can significantly affect optical system performance, are then described. In the final section, tunable optical filters are also addressed in a relative comparison.

Calculated emission rates for barium releases in space

NASA Technical Reports Server (NTRS)

Stenbaek-Nielsen, H. C.

1989-01-01

The optical emissions from barium releases in space are caused by resonance and fluorescent scattering of sunlight. Emission rates for the dominant ion and neutral lines are calculated assuming the release to be optically thin and the barium to be in radiative equilibrium with the solar radiation. The solar spectrum has deep Fraunhofer absorption lines at the primary barium ion resonances. A velocity component toward or away from the sun will Doppler shift the emission lines relative to the absorption lines and the emission rates will increase many-fold over the rest value. The Doppler brightening is important in shaped charge or satellite releases where the barium is injected at high velocities. Emission rates as a function of velocity are calculated for the 4554, 4934, 5854, 6142 and 6497 A ion emission lines and the dominant neutral line at 5535 A. Results are presented for injection parallel to the ambient magnetic field, B, and for injection at an angle to B.

Biocompatible near-infrared fluorescent nanoparticles for macro and microscopic in vivo functional bioimaging

PubMed Central

Chu, Liliang; Wang, Shaowei; Li, Kanghui; Xi, Wang; Zhao, Xinyuan; Qian, Jun

2014-01-01

Near-infrared (NIR) imaging technology has been widely used for biomedical research and applications, since it can achieve deep penetration in biological tissues due to less absorption and scattering of NIR light. In our research, polymer nanoparticles with NIR fluorophores doped were synthesized. The morphology, absorption/emission features and chemical stability of the fluorescent nanoparticles were characterized, separately. NIR fluorescent nanoparticles were then utilized as bright optical probes for macro in vivo imaging of mice, including sentinel lymph node (SLN) mapping, as well as distribution and excretion monitoring of nanoparticles in animal body. Furthermore, we applied the NIR fluorescent nanoparticles in in vivo microscopic bioimaging via a confocal microscope. Under the 635 nm-CW excitation, the blood vessel architecture in the ear and the brain of mice, which were administered with nanoparticles, was visualized very clearly. The imaging depth of our one-photon microscopy, which was assisted with NIR fluorescent nanoprobes, can reach as deep as 500 μm. Our experiments show that NIR fluorescent nanoparticles have great potentials in various deep-tissue imaging applications. PMID:25426331

Approximate description of Stokes shifts in ICT fluorescence emission

NASA Astrophysics Data System (ADS)

Saielli, Giacomo; Braun, David; Polimeno, Antonino; Nordio, Pier Luigi

1996-07-01

The time-resolved emission spectrum of a dual fluorescent prototype system like DMABN is associated with an intramolecular adiabatic charge-transfer reaction and the simultaneous relaxation of the polarization coordinate describing the dynamic behaviour of the polar solvent. The dynamic Stokes shift of the frequency maximum of the long-wavelength emission band related to the charge-transfer (CT) state towards the red region is interpreted as a consequence of a kinetic pathway which deviates from steepest descent to the CT state, the rate-determining step being the solvent relaxation. The present stochastic treatment is based on the assumption that internal and solvent coordinates could be described separately, neglecting coupling elements in the case of slow solvent relaxation.

Emission turn-on and solubility turn-off in conjugated polymers: one- and two-photon-induced removal of fluorescence-quenching solubilizing groups.

PubMed

Schelkle, Korwin M; Becht, Steffy; Faraji, Shirin; Petzoldt, Martin; Müllen, Klaus; Buckup, Tiago; Dreuw, Andreas; Motzkus, Marcus; Hamburger, Manuel

2015-01-01

The synthesis of highly efficient two-photon uncaging groups and their potential use in functional conjugated polymers for post-polymerization modification are reported. Careful structural design of the employed nitrophenethyl caging groups allows to efficiently induce bond scission by a two-photon process through a combination of exceptionally high two-photon absorption cross-sections and high reaction quantum yields. Furthermore, π-conjugated polyfluorenes are functionalized with these photocleavable side groups and it is possible to alter their emission properties and solubility behavior by simple light irradiation. Cleavage of side groups leads to a turn-on of the fluorescence while solubility of the π-conjugated materials is drastically reduced. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectral and photophysical properties of intramolecular charge transfer fluorescence probe: 4'-Dimethylamino-2,5-dihydroxychalcone

NASA Astrophysics Data System (ADS)

Xu, Zhicheng; Bai, Guan; Dong, Chuan

2005-12-01

The spectral and photophysical properties of a new intramolecular charge transfer (ICT) probe, namely 4'-dimethylamino-2,5-dihydroxychalcone (DMADHC) were studied in different solvents by using steady-state absorption and emission spectroscopy. Whereas the absorption spectrum undergoes minor change with increasing polarity of the solvents, the fluorescence spectrum experiences a distinct bathochromic shift in the band position and the fluorescence quantum yield increases reaching a maximum before decrease with increasing the solvent polarity. The magnitude of change in the dipole moment was calculated based on the Lippert-Mataga equation. These results give the evidence about the intramolecular charge transfer character in the emitting singlet state of this compound.

Spectral and photophysical properties of intramolecular charge transfer fluorescence probe: 4'-dimethylamino-2,5-dihydroxychalcone.

PubMed

Xu, Zhicheng; Bai, Guan; Dong, Chuan

2005-12-01

The spectral and photophysical properties of a new intramolecular charge transfer (ICT) probe, namely 4'-dimethylamino-2,5-dihydroxychalcone (DMADHC) were studied in different solvents by using steady-state absorption and emission spectroscopy. Whereas the absorption spectrum undergoes minor change with increasing polarity of the solvents, the fluorescence spectrum experiences a distinct bathochromic shift in the band position and the fluorescence quantum yield increases reaching a maximum before decrease with increasing the solvent polarity. The magnitude of change in the dipole moment was calculated based on the Lippert-Mataga equation. These results give the evidence about the intramolecular charge transfer character in the emitting singlet state of this compound.

Facile and green synthesis of fluorescent carbon dots with tunable emission for sensors and cells imaging.

PubMed

Diao, Haipeng; Li, Tingting; Zhang, Rong; Kang, Yu; Liu, Wen; Cui, Yanhua; Wei, Shuangyan; Wang, Ning; Li, Lihong; Wang, Haojiang; Niu, Weifen; Sun, Tijian

2018-07-05

Most carbon dots (CDs) conventional fabrication approaches produce single colored fluorescent materials, different methods are required to synthesize distinct carbon dots for specific optical applications. Herein, using one-pot hydrothermal treatment of Syringa obtata Lindl, a facile, low-cost and green assay is achieved in the controllable synthesis of blue and green fluorescent carbon dots. The fluorescent emission of CDs can be well-tuned by adding sodium hydroxide in the precursor solution. Blue fluorescent CDs are applied to Fe 3+ sensing with a low detection limit of 0.11 μM of linear range from 0.5 to 80 μM, and then further extended to analysis river water samples. Green fluorescent CDs can be applied to pH detection, which show a remarkable linear enhancement in the green fluorescence emission region when the pH is increased from 1.98 to 8.95. Eventually, the detection of Fe 3+ and pH are applied for the living cells fluorescent images in MCF-7 cells are achieved successfully, indicating as-synthesized CDs potential toward diverse application as promising candidate. Copyright © 2018 Elsevier B.V. All rights reserved.

High resolution measurements of solar induced chlorophyll fluorescence in the Fraunhofer oxigen bands

NASA Astrophysics Data System (ADS)

Mazzoni, M.; Agati, G.; Cecchi, G.; Toci, G.; Mazzinghi, P.

2017-11-01

Spectra of solar radiance reflected by leaves close to the Fraunhofer bands show the net contribution of chlorophyll fluorescence emission which adds to the reflected solar spectra. In a laboratory experiment, a low stray light, high resolution, 0.85 m double monochromator was used to filter radiation living leaves still attached to the plant in correspondence of the 687 nm and 760 nm O2 absorption bands. Reference spectra from a non fluorescent white reference were also acquired. Acquisition was performed by a Microchannel plate (MCP) intensified diode array with 512 elements. A fit of the spectral data outside the absorption lines allowed to retrieve the spectral base-line as a function of wavelength for the reference panel and the leaf. Reflectance functions were determined extending the Plascyck equation system to all the resolved lines of the oxygen absorption bands and using the base-lines for the continuum values. Fluorescence was deduced from the same equation system, using both the measured leaf and reference radiance spectra and the leaf reflectance fitting function.

Variation of fluorescence spectroscopy during the menstrual cycle

NASA Astrophysics Data System (ADS)

Macaulay, Calum; Richards-Kortum, Rebecca; Utzinger, Urs; Fedyk, Amanda; Neely Atkinson, E.; Cox, Dennis; Follen, Michele

2002-06-01

Cervical autofluorescence has been demonstrated to have potential for real-time diagnosis. Inter-patient and intra-patient variations in fluorescence intensity have been measured. Inter-patient measurements may vary by a factor of ten, while intra-patient measurements may vary by a factor of two. Age and menopausal status have been demonstrated to account for some of the variations, while race and smoking have not. In order to explore in detail the role of the menstrual cycle in intra-patient variation, a study was designed to measure fluorescence excitation emission matrices (EEMs) in patients daily throughout one cycle. Ten patients with a history of normal menstrual cycles and normal Papanicolaou smears underwent daily measurements of fluorescence EEMs from three colposcopically normal sites throughout one menstrual cycle. Changes in signals from porphyrin, NADH, and FAD fluorescence and blood absorption were noted when the data was viewed in a graphical format. Visually interpreted features of the EEMs in this graphical format did not appear to correlate with the day of the menstrual cycle with the exception that blood absorption features were more prominent during the menstrual phase (during which bleeding occurs), suggesting that measurements during the menstrual phase should be avoided. Variations in cycle date likely do not account for inter- or intra-patient variations.

Determination of mercury distribution inside spent compact fluorescent lamps by atomic absorption spectrometry.

PubMed

Rey-Raap, Natalia; Gallardo, Antonio

2012-05-01

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±0.4ppb of mercury in the vapor phase, 204.16±8.9ppb of mercury in the phosphor powder, and 18.74±0.5ppb 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. Copyright © 2011 Elsevier Ltd. All rights reserved.

Infrared molecular emissions from comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Mumma, M. J.

1984-01-01

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued. Previously announced in STAR as N83-30344

Carbon dots based dual-emission silica nanoparticles as ratiometric fluorescent probe for nitrite determination in food samples.

PubMed

Xiang, Guoqiang; Wang, Yule; Zhang, Heng; Fan, Huanhuan; Fan, Lu; He, Lijun; Jiang, Xiuming; Zhao, Wenjie

2018-09-15

In this work, a simple and effective strategy for designing a ratiometric fluorescent nanosensor was described. A carbon dots (CDs) based dual-emission nanosensor for nitrite was prepared by coating the CDs on to dye-doped silica nanoparticles. Dual-emission silica nanoparticles fluorescence was quenched in sulfuric acid using potassium bromate (KBrO 3 ). The nitrite present catalyzed the KBrO 3 oxidation, resulting in ratiometric fluorescence response of the dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated. Under optimized conditions, the limit of detection was 1.0 ng mL -1 and the linear range 10-160 ng mL -1 . Furthermore, the sensor was suitable for nitrite determination in different food samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

Superresolution fluorescence imaging by pump-probe setup using repetitive stimulated transition process

NASA Astrophysics Data System (ADS)

Dake, Fumihiro; Fukutake, Naoki; Hayashi, Seri; Taki, Yusuke

2018-02-01

We proposed superresolution nonlinear fluorescence microscopy with pump-probe setup that utilizes repetitive stimulated absorption and stimulated emission caused by two-color laser beams. The resulting nonlinear fluorescence that undergoes such a repetitive stimulated transition is detectable as a signal via the lock-in technique. As the nonlinear fluorescence signal is produced by the multi-ply combination of incident beams, the optical resolution can be improved. A theoretical model of the nonlinear optical process is provided using rate equations, which offers phenomenological interpretation of nonlinear fluorescence and estimation of the signal properties. The proposed method is demonstrated as having the scalability of optical resolution. Theoretical resolution and bead image are also estimated to validate the experimental result.

Suppression of Kasha's rule as a mechanism for fluorescent molecular rotors and aggregation-induced emission

NASA Astrophysics Data System (ADS)

Qian, Hai; Cousins, Morgan E.; Horak, Erik H.; Wakefield, Audrey; Liptak, Matthew D.; Aprahamian, Ivan

2017-01-01

Although there are some proposed explanations for aggregation-induced emission, a phenomenon with applications that range from biosensors to organic light-emitting diodes, current understanding of the quantum-mechanical origin of this photophysical behaviour is limited. To address this issue, we assessed the emission properties of a series of BF2-hydrazone-based dyes as a function of solvent viscosity. These molecules turned out to be highly efficient fluorescent molecular rotors. This property, in addition to them being aggregation-induced emission luminogens, enabled us to probe deeper into their emission mechanism. Time-dependent density functional theory calculations and experimental results showed that the emission is not from the S1 state, as predicted from Kasha's rule, but from a higher energy (>S1) state. Furthermore, we found that suppression of internal conversion to the dark S1 state by restricting the rotor rotation enhances fluorescence, which leads to the proposal that suppression of Kasha's rule is the photophysical mechanism responsible for emission in both viscous solution and the solid state.

Absorption and emission behaviour of trans- p-coumaric acid in aqueous solutions and some organic solvents

NASA Astrophysics Data System (ADS)

Putschögl, M.; Zirak, P.; Penzkofer, A.

2008-01-01

The absorption and fluorescence behaviour of trans- p-coumaric acid ( trans-4-hydroxycinnamic acid) is investigated in buffered aqueous solution over a wide range from pH 1 to pH 12, in un-buffered water, and in some organic solvents. Absorption cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and degrees of fluorescence polarisation are measured. p-Coumaric acid exists in different ionic forms in aqueous solution depending on the pH. There is an equilibrium between the neutral form ( p-CAH 2) and the single anionic form ( p-CAH -) at low pH (p Kna ≈ 4.9), and between the single anionic and the double anionic form ( p-CA 2-) at high pH (p Kaa ≈ 9.35). In the organic solvents studied trans- p-coumaric acid is dissolved in its neutral form. The fluorescence quantum yield of trans- p-coumaric acid in aqueous solution is ϕF ≈ 1.4 × 10 -4 for the neutral and the single anionic form, while it is ϕF ≈ 1.3 × 10 -3 for the double anionic form. For trans- p-coumaric acid in organic solvents fluorescence quantum yields in the range from 4.8 × 10 -5 (acetonitrile) to 1.5 × 10 -4 (glycerol) were measured. The fluorescence spectra are 7700-10,000 cm -1 Stokes shifted in aqueous solution, and 5400-8200 cm -1 Stokes shifted in the studied organic solvents. Decay paths responsible for the low fluorescence quantum yields are discussed (photo-isomerisation and internal conversion for p-CA 2-, solvent-assisted intra-molecular charge-transfer or ππ ∗ to nπ ∗ transfer and internal conversion for p-CAH 2 and p-CAH -). The solvent dependence of the first ππ ∗ electronic transition frequency and of the fluorescence Stokes shift of p-CAH 2 is discussed in terms of polar solute-solvent interaction effects. Thereby the ground-state and excite-state molecular dipole moments are extracted.

Transient Fluorescence Spectroscopy and laser induced fluorescence lifetimes of terbium doped dipicolinic acid

NASA Astrophysics Data System (ADS)

Makoui, Anali

We have investigated the use of deep UV laser induced fluorescence for the sensitive detection and spectroscopic lifetime studies of terbium doped dipicolinic acid (DPA-Tb) and used this to study the optical characteristics of DPA which is a chemical surrounding most bacterial spores. Background absorption spectra, fluorescence spectra, and Excitation Emission Matrix (EEM) spectra were made of the DPA-Tb complex, using both fixed 266 nm wavelength and tunable (220 nm--280 nm) UV laser excitations. Of importance, the fluorescence lifetimes of the four main fluorescence peaks (488 nm, 543 nm, 581 nm, and 618 nm) of the DPA-Tb complex have been measured for the first time to our knowledge. The lifetimes of all the fluorescing lines have been measured as a function of DPA-Tb concentration, solvent pH, and solvent composition, including that for the weakest fluorescing line of DPA-Tb at 618 nm. In addition, a new spectroscopic lifetime measurement technique, which we call "Transient Fluorescence Spectroscopy", was developed. In this technique, a weak, quasi-CW, amplitude modulated UV laser (8.5 kHz) was used to measure the lifetimes of the fluorescence lines, and yields insight into energy transfer and excitation lifetimes within the system. This technique is especially useful when a high power laser is not either available or not suitable. In the latter case, this would be when a high power pulsed deep-UV laser could produce bleaching or destruction of the biological specimen. In addition, this technique simulated the excitation and fluorescence emission of the DPA-Tb using a 4-level energy model, and solved the dynamic transient rate equations to predict the temporal behavior of the DPA-Tb emitted fluorescence. Excellent agreement between the experiments and the simulation were found. This technique has the potential to provide a more accurate value for the fluorescence lifetime values. In addition, with the use of asymmetric excitation waveforms, the dynamic

Dual fluorescence of N-phenylanthranilic acid: Effect of solvents, pH and beta-cyclodextrin.

PubMed

Rajendiran, N; Balasubramanian, T

2007-11-01

Spectral characteristics of N-phenylanthranilic acid (NPAA) have been studied in different solvents, pH and beta-cyclodextrin (beta-CD) and compared with anthranilic acid (2-aminobenzoic acid, 2ABA). In all solvents a dual fluorescence is observed in NPAA, whereas 2ABA gives single emission. Combining the results observed in the absorption, fluorescence emission and fluorescence excitation spectra, it is found that strong intramolecular hydrogen bonding (IHB) interactions present in NPAA molecule. The inclusion complex of NPAA with beta-CD is analysed by UV-vis, fluorimetry, FT-IR, (1)H NMR, scanning electron microscope and AM 1 method. The above spectral studies show that NPAA forms a 1:1 inclusion complex with beta-CD and COOH group present in the beta-CD cavity. A mechanism is proposed to explain the inclusion process.

Dual fluorescence of N-phenylanthranilic acid: Effect of solvents, pH and β-cyclodextrin

NASA Astrophysics Data System (ADS)

Rajendiran, N.; Balasubramanian, T.

2007-11-01

Spectral characteristics of N-phenylanthranilic acid (NPAA) have been studied in different solvents, pH and β-cyclodextrin (β-CD) and compared with anthranilic acid (2-aminobenzoic acid, 2ABA). In all solvents a dual fluorescence is observed in NPAA, whereas 2ABA gives single emission. Combining the results observed in the absorption, fluorescence emission and fluorescence excitation spectra, it is found that strong intramolecular hydrogen bonding (IHB) interactions present in NPAA molecule. The inclusion complex of NPAA with β-CD is analysed by UV-vis, fluorimetry, FT-IR, 1H NMR, scanning electron microscope and AM 1 method. The above spectral studies show that NPAA forms a 1:1 inclusion complex with β-CD and COOH group present in the β-CD cavity. A mechanism is proposed to explain the inclusion process.

FRET Studies Between CdTe Capped by Small-Molecule Ligands and Fluorescent Protein

NASA Astrophysics Data System (ADS)

Zhang, Yue; Zhou, Dejian; He, Junhui

2014-12-01

Water-soluble luminescent semiconductor nanocrystals also known as quantum dots (QDs) that have prominent photostability, wide absorption cross sections and tunable narrow emission, have been shown as promising probes in immunoassays. QDs are often used as donors in fluorescence resonance energy transfer (FRET) based sensors using organic dyes or fluorescent proteins as acceptors. Here, the FRET between a QD donor and fluorescent protein acceptors has been studied. The fluorescent protein (FP)mCherry appended with a hexa-histidine-tag could effectively self-assemble onto CdTe to produce small donor-acceptor distances and hence highly efficient FRET (efficiency > 80%) at relatively low FP:CdTe copy numbers (ca.1). Using the Förster dipole-dipole interaction formula, the Förster radius (R0) and respective donor-acceptor distances for the CdTe-FP FRET systems have been calculated. The binding constants (Kd) of the QD-FP systems have also been evaluated by the emission spectra.

Carbazole-based BODIPYs with ethynyl substituents at the boron center: solid-state excimer fluorescence in the VIS/NIR region.

PubMed

Maeda, Chihiro; Nagahata, Keiji; Ema, Tadashi

2017-09-26

Carbazole-based BODIPYs 1-6 with several different substituents at the boron atom site were synthesized. These dyes fluoresced in the solid state, and 3a with phenylethynyl groups exhibited a red-shifted and broad fluorescence spectrum, which suggested an excimer emission. Its derivatives 3b-n were synthesized, and the relationship between the solid-state emission and crystal packing was investigated. The X-ray crystal structures revealed cofacial dimers that might form excimers. From the structural optimization results, we found that the introduction of mesityl groups hindered intermolecular access and led to reduced interactions between the dimers. In addition, the red-shifted excimer fluorescence suppressed self-absorption, and dyes with ethynyl groups showed solid-state fluorescence in the vis/NIR region.

Viscosity and medium effects on the fluorescence and photochemical behaviour of some aryl chalcones

NASA Astrophysics Data System (ADS)

Ebeid, El-Zeiny M.; Abdel-Kader, Mahmood H.; Issa, Raafat M.; El-Daly, Samy A.

1988-05-01

The emission, excitation and absorption spectra toghether with the fluorescence and photochemical quantum yields of some chalcone derivatives have been studied in organic solvents and micellar and microemulsion media. Both 4-[2-(2-pyridyl)ethenyl] ( I) and 4-[2-(4-pyridyl)ethenyl ( II) chalcones show large positive solvatochromic effects. The fluorescence quantum yields increase substantially as the medium viscosity increases with a subsequent decrease in the photochemical quatum yield. Compounds I and II undergo excited-state molecular aggregation in concentrated solutions giving excimer-like emission that coincides with emission from crystalline samples. The enthalpies of photoassociation have been estimated. The chalcone derivative I acts as an efficient quencher of the fluorescence of the laser dye 1,4-bis (β-pyridyl-2-vinyl)benzene via a long-range mechanism. The excited-state lifetimes of both I and II are short and at 20°C their τ values are less than 800 ps.

Imaging the environment of green fluorescent protein.

PubMed Central

Suhling, Klaus; Siegel, Jan; Phillips, David; French, Paul M W; Lévêque-Fort, Sandrine; Webb, Stephen E D; Davis, Daniel M

2002-01-01

An emerging theme in cell biology is that cell surface receptors need to be considered as part of supramolecular complexes of proteins and lipids facilitating specific receptor conformations and distinct distributions, e.g., at the immunological synapse. Thus, a new goal is to develop bioimaging that not only locates proteins in live cells but can also probe their environment. Such a technique is demonstrated here using fluorescence lifetime imaging of green fluorescent protein (GFP). We first show, by time-correlated single-photon counting, that the fluorescence decay of GFP depends on the local refractive index. This is in agreement with the Strickler Berg formula, relating the Einstein A and B coefficients for absorption and spontaneous emission in molecules. We then quantitatively image, by wide-field time-gated fluorescence lifetime imaging, the refractive index of the environment of GFP. This novel approach paves the way for imaging the biophysical environment of specific GFP-tagged proteins in live cells. PMID:12496126

Robust and economical multi-sample, multi-wavelength UV/vis absorption and fluorescence detector for biological and chemical contamination

NASA Astrophysics Data System (ADS)

Lu, Peter J.; Hoehl, Melanie M.; Macarthur, James B.; Sims, Peter A.; Ma, Hongshen; Slocum, Alexander H.

2012-09-01

We present a portable multi-channel, multi-sample UV/vis absorption and fluorescence detection device, which has no moving parts, can operate wirelessly and on batteries, interfaces with smart mobile phones or tablets, and has the sensitivity of commercial instruments costing an order of magnitude more. We use UV absorption to measure the concentration of ethylene glycol in water solutions at all levels above those deemed unsafe by the United States Food and Drug Administration; in addition we use fluorescence to measure the concentration of d-glucose. Both wavelengths can be used concurrently to increase measurement robustness and increase detection sensitivity. Our small robust economical device can be deployed in the absence of laboratory infrastructure, and therefore may find applications immediately following natural disasters, and in more general deployment for much broader-based testing of food, agricultural and household products to prevent outbreaks of poisoning and disease.

Alteration of fluorescent protein spectroscopic properties upon cryoprotection.

PubMed

von Stetten, David; Batot, Gaëlle O; Noirclerc-Savoye, Marjolaine; Royant, Antoine

2012-11-01

Cryoprotection of a protein crystal by addition of small-molecule compounds may sometimes affect the structure of its active site. The spectroscopic and structural effects of the two cryoprotectants glycerol and ethylene glycol on the cyan fluorescent protein Cerulean were investigated. While glycerol had almost no noticeable effect, ethylene glycol was shown to induce a systematic red shift of the UV-vis absorption and fluorescence emission spectra. Additionally, ethylene glycol molecules were shown to enter the core of the protein, with one of them binding in close vicinity to the chromophore, which provides a sound explanation for the observed spectroscopic changes. These results highlight the need to systematically record spectroscopic data on crystals of light-absorbing proteins and reinforce the notion that fluorescent proteins must not been seen as rigid structures.

Synthesis, Luminescent Properties of aza-Boron-Diquinomethene Difluoride Complexes and Their Application for Fluorescent Security Inks.

PubMed

Gu, Long; Liu, Rui; Shi, Hong; Wang, Qiang; Song, Guangliang; Zhu, Xiaolin; Yuan, Shidong; Zhu, Hongjun

2016-03-01

Two aza-boron-diquinomethene (aza-BODIQU) complexes bearing phenyl and carbazyl substituents were synthesized and characterized. Their photophysical properties were investigated systematically via spectroscopic and theoretical methods. Both complexes exhibit strong (1)π-π* transition absorptions (λ(abs) = 400-540 nm) and intense fluorescent emissions (λ(em) = 440-600 nm, Φ(PL) = 0.93 and 0.78) in CH2Cl2 solution and in solid state at room temperature. Compared to the complex with phenyl groups, the complex bearing carbazyl groups shows significant bathochromic shift in both absorption and emission. This could be attributed to the larger π-electron conjugation of the carbazole unit and intramolecular charge transfer feature from carbazole to aza-BODIQU component. In addition, the complexes exhibit intense photoluminescence and good stability on antacid, anti-alkali and stability in printing ink samples, which makes them potential dopants for the application of fluorescent security inks.

Compensation of optical heterogeneity-induced artifacts in fluorescence molecular tomography: theory and in vivo validation

NASA Astrophysics Data System (ADS)

Mohajerani, Pouyan; Adibi, Ali; Kempner, Joshua; Yared, Wael

2009-05-01

We present a method for reduction of image artifacts induced by the optical heterogeneities of tissue in fluorescence molecular tomography (FMT) through identification and compensation of image regions that evidence propagation of emission light through thin or low-absorption tunnels in tissue. The light tunneled as such contributes to the emission image as spurious components that might substantially overwhelm the desirable fluorescence emanating from the targeted lesions. The proposed method makes use of the strong spatial correlation between the emission and excitation images to estimate the tunneled components and yield a residual image that mainly consists of the signal due to the desirable fluorescence. This residual image is further refined using a coincidence mask constructed for each excitation-emission image pair. The coincidence mask is essentially a map of the ``hot spots'' that occur in both excitation and emission images, as such areas are often associated with tunneled emission. In vivo studies are performed on a human colon adenocarcinoma xenograft tumor model with subcutaneous tumors and a murine breast adenocarcinoma model with aggressive tumor cell metastasis and growth in the lungs. Results demonstrate significant improvements in the reconstructions achieved by the proposed method.

Interstellar absorption in the Mg II resonance line k2 and h2 emissions

NASA Technical Reports Server (NTRS)

Boehm-Vitense, E.

1981-01-01

High-resolution (0.2 A) IUE spectra for the long wavelength range (1800-3000 A) have been studied. It is shown that narrow interstellar Mg II lines are seen in the center of the k2 and h2 emissions from nearby stars with large rotational velocities. For all observed stars, the radial velocity of the central k3 absorption component in the rest system of the star is strongly correlated with the mirror image of the radial velocity of the stars; this shows that a major fraction if not all of the k3 absorption is due to interstellar absorption in the solar neighborhood. The violet to red asymmetry of the k2 emission also correlates with the radial velocities of the star; this shows that the shift of k3 is due to the velocity shift of the local interstellar cloud with respect to the star.

Highly selective and sensitive nanoprobes for cyanide based on gold nanoclusters with red fluorescence emission

NASA Astrophysics Data System (ADS)

Zhang, Guomei; Qiao, Yunyun; Xu, Ting; Zhang, Caihong; Zhang, Yan; Shi, Lihong; Shuang, Shaomin; Dong, Chuan

2015-07-01

We report a novel and environmentally friendly fluorescent probe for detecting the cyanide ion (CN-) using l-amino acid oxidase (LAAOx)-protected Au nanoclusters (LAAOx@AuNCs) with red emission. The fluorescence-based sensing behaviour of LAAOx@AuNCs towards anions was investigated in buffered aqueous media. Among the anions studied, CN- was found to effectively quench the fluorescence emission of AuNCs based on CN- induced Au core decomposition. Excellent sensitivity and selectivity toward the detection of CN- in aqueous solution were observed. The CN- detection limit was determined to be approximately 180 nM, which is 15 times lower than the maximum level (2700 nM) of CN- in drinking water permitted by the World Health Organization (WHO). A linear relationship between the fluorescence intensity and CN- concentration was observed in two ranges of CN- concentration, including 3.2 × 10-6 to 3.4 × 10-5 mol L-1 and 3.81 × 10-5 to 1.04 × 10-4 mol L-1. The high sensitivity and selectivity to CN- among the 17 types of anions make the AuNCs good candidates for use in fluorescent nanoprobes of CN-.

Terahertz absorption and emission upon the photoionization of acceptors in uniaxially stressed silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhukavin, R. Kh., E-mail: zhur@ipmras.ru; Kovalevsky, K. A.; Orlov, M. L.

2016-11-15

Experimental data on the spontaneous emission and absorption modulation in boron-doped silicon under CO{sub 2} laser excitation depending on the uniaxial stress applied along the [001] and [011] crystallographic directions are presented. Room-temperature radiation is used as the probe radiation. Low stress (less than 0.5 kbar) is shown to reduce losses in the terahertz region by 20%. The main contribution to absorption modulation at zero and low stress is made by A{sup +} centers. Intersubband free hole transitions additionally contribute to terahertz absorption at higher stress. These contributions can be minimized by compensation.

A new screening method for flunitrazepam in vodka and tequila by fluorescence spectroscopy.

PubMed

Leesakul, Nararak; Pongampai, Sirintip; Kanatharana, Proespichaya; Sudkeaw, Pravit; Tantirungrotechai, Yuthana; Buranachai, Chittanon

2013-01-01

A new screening method for flunitrazepam in colourless alcoholic beverages based on a spectroscopic technique is proposed. Absorption and steady-state fluorescence of flunitrazepam and its protonated form with various acids were investigated. The redshift of the wavelength of maximum absorption was distinctively observed in protonated flunitrazepam. An emissive fluorescence at 472 nm was detected in colourless spirits (vodka and tequila) at room temperature. 2-M perchloric acid was the most appropriated proton source. By using electron ionization mass spectrometry and time-dependent density functional theory calculations, the possible structure of protonated flunitrazepam was identified to be 2-nitro-N-methylacridone, an acridone derivative as opposed to 2-methylamino-5-nitro-2'-fluorobenzophenone, a benzophenone derivative. Copyright © 2012 John Wiley & Sons, Ltd.

Theoretical design and investigation of 1,8-naphthalimide-based two-photon fluorescent probes for detecting cytochrome P450 1A with separated fluorescence signal.

PubMed

Zhang, Chun; Ren, Ai-Min; Guo, Jing-Fu; Wang, Dan; Yu, Li-Ying

2018-05-16

As a type of enzyme with a terminal oxygen, the CYP1A subfamily possesses the ability to catalyze the reactions of many environmental toxins, endogenous substrates and clinical drugs. The development of efficient methods for the rapid and real-time detection of CYP1A enzyme activity in complex biological systems is of considerable significance for identifying potential abnormalities in these cancer-related enzymes. With this goal, we firstly provided a series of 1,8-naphthalimide-based two-photon fluorescent chromophores with large two-photon absorption (TPA) cross-sections (500-7000 GM) and remarkable changes in fluorescence spectra upon recognizing the CYP1A enzyme from its theoretical aspect. Moreover, we have thoroughly studied the effects of cyclic acceptor (dichlorobenzene and benzothiadiazole) and donor (fluorene and carbazole) groups on the one-photon absorption (OPA), TPA, and fluorescence properties of CYP1A enzyme probes and the corresponding reaction products. The connection of a heterocycle as the donor group to a 1,8-naphthalimide-based molecule to form a D-π-A-π-D-type electronic structure can effectively cause red shifts in the absorption and emission wavelengths to facilitate bioimaging in the near infrared (NIR) region, which is attributed to the lower transition energy, larger transition dipole moment and amount of transferred charge. Docking analysis suggests that the two-photon fluorescent probes NCMN-3 and NCMN-5 that were designed will guarantee and achieve excellent selectivity for the CYP1A enzyme.

Differential Absorption Lidar Measurements of Fugitive Benzene Emissions

NASA Astrophysics Data System (ADS)

Robinson, R. A.; Innocenti, F.; Helmore, J.; Gardiner, T.; Finlayson, A.; Connor, A.

2016-12-01

The Differential Absorption Lidar (DIAL) technique is based on the optical analogue of radar; lidar (light detection and ranging). It provides the capability to remotely measure the concentration and spatial distribution of compounds in the atmosphere. The ability to scan the optical measurement beam throughout the atmosphere enables pollutant concentrations to be mapped, and emission fluxes to be determined when combined with wind data. The NPL DIAL systems can operate in the UV and infrared spectral, enabling the measurement of a range of air pollutants and GHGs including hazardous air pollutants such as benzene. The mobile ground based DIAL systems developed at NPL for pollution monitoring have been used for over 25 years. They have been deployed for routine monitoring, emission factor studies, research investigations and targeted monitoring campaigns. More recently the NPL DIAL has been used in studies to validate other monitoring techniques. In support of this capability, NPL have developed a portable, configurable controlled release system (CRF) able to simulate emissions from typical sources. This has been developed to enable the validation and assessment of fugitive emission monitoring techniques. Following a brief summary of the technique, we outline recent developments in the use of DIAL for monitoring fugitive and diffuse emissions, including the development of a European Standard Method for fugitive emission monitoring. We will present the results of a number of validation exercises using the CRF presenting an update on the performance of DIAL for emission quantification and discuss the wider validation of novel technologies. We will report on recent measurements of the emissions of benzene from industrial sites including a large scale emissions monitoring study carried out by the South Coast Air Quality Management District (SCAQMD) and will report on the measurement of emissions from petrochemical facilities and examine an example of the identification

Optimal optical filters of fluorescence excitation and emission for poultry fecal detection

USDA-ARS?s Scientific Manuscript database

Purpose: An analytic method to design excitation and emission filters of a multispectral fluorescence imaging system is proposed and was demonstrated in an application to poultry fecal inspection. Methods: A mathematical model of a multispectral imaging system is proposed and its system parameters, ...

A dual-emission and large Stokes shift fluorescence probe for real-time discrimination of ROS/RNS and imaging in live cells.

PubMed

Guo, Ting; Cui, Lei; Shen, Jiaoning; Wang, Rui; Zhu, Weiping; Xu, Yufang; Qian, Xuhong

2013-03-04

A novel dual-emission fluorescence probe has been developed for specific and sensitive detection of hypochlorite (ClO(-)). Upon addition of ClO(-), significant changes in fluorescence emission intensity at two discrete wavelengths were observed. Meanwhile OONO(-) led to only a single-channel fluorescence enhancement. This feature makes it a clear advantage in distinguishing ClO(-), RNS from other ROS.

Fluorescence kinetics of emission from a small finite volume of a biological system

NASA Astrophysics Data System (ADS)

Dagen, A. J.; Alfano, R. R.; Zilinskas, B. A.; Swenberg, C. E.

1985-07-01

The fluorescence decay, apparent quantum yield and transmission from chromophores constrained to a microscopic volume using a single picosecond laser excitation were measured as a function of incident intensity. The β subunit of phycoeryhthrin aggregate isolated from the photosynthetic antenna system of Nostoc sp. was selected since it contains only four chromophores in a volume of less than 5.6×10 4 Å 3. The non-exponential fluorescence decay profiles were intensity independent for the intensity range studied (5 × 10 13 - 2 × 10 15 photon cm -2 per pulse). The apparent decrease in the relative fluorescence quantum yield and increase of the relative transmission with increasing excitation intensity is attributed to the combined effects of ground state depletion and upper excited state absorption. Evidence suggests that exciton annihilation is absent within isolated β subunits.

Molecules for Fluorescence Detection of Specific Chemicals

NASA Technical Reports Server (NTRS)

Fedor, Steve

2008-01-01

A family of fluorescent dye molecules has been developed for use in on-off fluorescence detection of specific chemicals. By themselves, these molecules do not fluoresce. However, when exposed to certain chemical analytes in liquid or vapor forms, they do fluoresce (see figure). These compounds are amenable to fixation on or in a variety of substrates for use in fluorescence-based detection devices: they can be chemically modified to anchor them to porous or non-porous solid supports or can be incorporated into polymer films. Potential applications for these compounds include detection of chemical warfare agents, sensing of acidity or alkalinity, and fluorescent tagging of proteins in pharmaceutical research and development. These molecules could also be exploited for use as two-photon materials for photodynamic therapy in the treatment of certain cancers and other diseases. A molecule in this family consists of a fluorescent core (such as an anthracene or pyrene) attached to two end groups that, when the dye is excited by absorption of light, transfer an electron to the core, thereby quenching the fluorescence. The end groups can be engineered so that they react chemically with certain analytes. Upon reaction, electrons on the end groups are no longer available for transfer to the core and, consequently, the fluorescence from the core is no longer quenched. The chemoselectivity of these molecules can be changed by changing the end groups. For example, aniline end groups afford a capability for sensing acids or acid halides (including those contained in chemical warfare agents). Pyridine or bipyridyl end groups would enable sensing of metal ions. Other chemicals that can be selectively detected through suitable choice of end groups include glucose and proteins. Moreover, the fluorescent cores can be changed to alter light-absorption and -emission characteristics: anthracene cores fluoresce at wavelengths around 500 nm, whereas perylene cores absorb and emit at

Detection of iron atoms by emission spectroscopy and laser-induced fluorescence in solid propellant flames.

PubMed

Vilmart, G; Dorval, N; Orain, M; Lambert, D; Devillers, R; Fabignon, Y; Attal-Tretout, B; Bresson, A

2018-05-10

Planar laser-induced fluorescence on atomic iron is investigated in this paper, and a measurement strategy is proposed to monitor the fluorescence of iron atoms with good sensitivity. A model is proposed to fit the experimental fluorescence spectra, and good agreement is found between simulated and experimental spectra. Emission and laser-induced fluorescence measurements are performed in the flames of ammonium perchlorate composite propellants containing iron-based catalysts. A fluorescence signal from iron atoms after excitation at 248 nm is observed for the first time in propellant flames. Images of the spatial distribution of iron atoms are recorded in the flame in which turbulent structures are generated. Iron fluorescence is detected up to 1.0 MPa, which opens the way to application in propellant combustion.

Oscillations of absorption of a probe picosecond light pulse caused by its interaction with stimulated picosecond emission of GaAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ageeva, N. N.; Bronevoi, I. L., E-mail: bil@cplire.ru; Zabegaev, D. N.

2015-04-15

The self-modulation of absorption of a picosecond light pulse was observed earlier [1] in a thin (∼1-μm thick) GaAs layer pumped by a high-power picosecond pulse. Analysis of the characteristics of this self-modulation predicted [5] that the dependences of the probe pulse absorption on the pump pulse energy and picosecond delay between pump and probe pulses should be self-modulated by oscillations. Such self-modulation was experimentally observed in this work. Under certain conditions, absorption oscillations proved to be a function of part of the energy of picosecond stimulated emission of GaAs lying above a certain threshold in the region where themore » emission front overlapped the probe pulse front. Absorption oscillations are similar to self-modulation of the GaAs emission characteristics observed earlier [4]. This suggests that the self-modulation of absorption and emission is determined by the same type of interaction of light pulses in the active medium, the physical mechanism of which has yet to be determined.« less

Ratiometric fluorescent detection of chromium(VI) in real samples based on dual emissive carbon dots.

PubMed

Ma, Yunxia; Chen, Yonglei; Liu, Juanjuan; Han, Yangxia; Ma, Sudai; Chen, Xingguo

2018-08-01

As we know, hexavalent chromium (Cr(VI)) was usually used as an additive to improve the color fastness during the printing and dyeing process, and thus posing tremendous threat to our health and living quality. In this work, the dual emissive carbon dots (DECDs) were synthesized through hydrothermal treatment of m-aminophenol and oxalic acid. The obtained DECDs not only exhibited dual emission fluorescence peaks (430 nm, 510 nm) under the single excitation wavelength of 380 nm, but also possessed good water solubility and excellent fluorescence stability. A ratiometric fluorescent method for the determination of Cr(VI) was developed using the DECDs as a probe. Under the optimal conditions, a linear range was obtained from 2 to 300 μM with a limit of detection of 0.4 μM. Furthermore, the proposed ratiometric fluorescent method was applied to the analysis of Cr(VI) in textile, steel, industrial wastewater and chromium residue samples with satisfactory recoveries (88.4-106.8%). Copyright © 2018 Elsevier B.V. All rights reserved.

Combined optical resolution photoacoustic and fluorescence micro-endoscopy

NASA Astrophysics Data System (ADS)

Shao, Peng; Shi, Wei; Hajireza, Parsin; Zemp, Roger J.

2012-02-01

We present a new micro-endoscopy system combining real-time C-scan optical-resolution photoacoustic micro-endoscopy (OR-PAME), and a high-resolution fluorescence micro-endoscopy system for visualizing fluorescently labeled cellular components and optically absorbing microvasculature simultaneously. With a diode-pumped 532-nm fiber laser, the OR-PAM sub-system is capable of imaging with a resolution of ~ 7μm. The fluorescence sub-system consists of a diode laser with 445 nm-centered emissions as the light source, an objective lens and a CCD camera. Proflavine, a FDA approved drug for human use, is used as the fluorescent contrast agent by topical application. The fluorescence system does not require any mechanical scanning. The scanning laser and the diode laser light source share the same light path within an optical fiber bundle containing 30,000 individual single mode fibers. The absorption of Proflavine at 532 nm is low, which mitigates absorption bleaching of the contrast agent by the photoacoustic excitation source. We demonstrate imaging in live murine models. The system is able to provide cellular morphology with cellular resolution co-registered with the structural and functional information given by OR-PAM. Therefore, the system has the potential to serve as a virtual biopsy technique, helping researchers and clinicians visualize angiogenesis, effects of anti-cancer drugs on both cells and the microcirculation, as well as aid in the study of other diseases.

Characterizing chromophoric dissolved organic matter in Lake Tianmuhu and its catchment basin using excitation-emission matrix fluorescence and parallel factor analysis.

PubMed

Zhang, Yunlin; Yin, Yan; Feng, Longqing; Zhu, Guangwei; Shi, Zhiqiang; Liu, Xiaohan; Zhang, Yuanzhi

2011-10-15

Chromophoric dissolved organic matter (CDOM) is an important optically active substance that transports nutrients, heavy metals, and other pollutants from terrestrial to aquatic systems and is used as a measure of water quality. To investigate how the source and composition of CDOM changes in both space and time, we used chemical, spectroscopic, and fluorescence analyses to characterize CDOM in Lake Tianmuhu (a drinking water source) and its catchment in China. Parallel factor analysis (PARAFAC) identified three individual fluorophore moieties that were attributed to humic-like and protein-like materials in 224 water samples collected between December 2008 and September 2009. The upstream rivers contained significantly higher concentrations of CDOM than did the lake water (a(350) of 4.27±2.51 and 2.32±0.59 m(-1), respectively), indicating that the rivers carried a substantial load of organic matter to the lake. Of the three main rivers that flow into Lake Tianmuhu, the Pingqiao River brought in the most CDOM from the catchment to the lake. CDOM absorption and the microbial and terrestrial humic-like components, but not the protein-like component, were significantly higher in the wet season than in other seasons, indicating that the frequency of rainfall and runoff could significantly impact the quantity and quality of CDOM collected from the catchment. The different relationships between the maximum fluorescence intensities of the three PARAFAC components, CDOM absorption, and chemical oxygen demand (COD) concentration in riverine and lake water indicated the difference in the composition of CDOM between Lake Tianmuhu and the rivers that feed it. This study demonstrates the utility of combining excitation-emission matrix fluorescence and PARAFAC to study CDOM dynamics in inland waters. Copyright © 2011 Elsevier Ltd. All rights reserved.

Photon upconversion in homogeneous fluorescence-based bioanalytical assays.

PubMed

Soukka, Tero; Rantanen, Terhi; Kuningas, Katri

2008-01-01

Upconverting phosphors (UCPs) are very attractive reporters for fluorescence resonance energy transfer (FRET)-based bioanalytical assays. The large anti-Stokes shift and capability to convert near-infrared to visible light via sequential absorption of multiple photons enable complete elimination of autofluorescence, which commonly impairs the performance of fluorescence-based assays. UCPs are ideal donors for FRET, because their very narrow-banded emission allows measurement of the sensitized acceptor emission, in principle, without any crosstalk from the donor emission at a wavelength just tens of nanometers from the emission peak of the donor. In addition, acceptor dyes emitting at visible wavelengths are essentially not excited by near-infrared, which further emphasizes the unique potential of upconversion FRET (UC-FRET). These characteristics result in favorable assay performance using detection instrumentation based on epifluorometer configuration and laser diode excitation. Although UC-FRET is a recently emerged technology, it has already been applied in both immunoassays and nucleic acid hybridization assays. The technology is also compatible with optically difficult biological samples, such as whole blood. Significant advances in assay performance are expected using upconverting lanthanide-doped nanocrystals, which are currently under extensive research. UC-FRET, similarly to other fluorescence techniques based on resonance energy transfer, is strongly distance dependent and may have limited applicability, for example in sandwich-type assays for large biomolecules, such as viruses. In this article, we summarize the essentials of UC-FRET, describe its current applications, and outline the expectations for its future potential.

Nanoparticle-enhanced fluorescence emission for non-separation assays of carbohydrates using a boronic acid-alizarin complex.

PubMed

Li, Qianjin; Kamra, Tripta; Ye, Lei

2016-03-04

Addition of crosslinked polymer nanoparticles into a solution of a 3-nitrophenylboronic acid-alizarin complex leads to significant enhancement of fluorescence emission. Using the nanoparticle-enhanced boronic acid-alizarin system has improved greatly the sensitivity and extended the dynamic range of separation-free fluorescence assays for carbohydrates.

CONTROL OF SULFUR EMISSIONS FROM OIL SHALE RETORTING USING SPEND SHALE ABSORPTION

EPA Science Inventory

The paper gives results of a detailed engineering evaluation of the potential for using an absorption on spent shale process (ASSP) for controlling sulfur emissions from oil shale plants. The evaluation analyzes the potential effectiveness and cost of absorbing SO2 on combusted s...

Time-resolved polarization imaging by pump-probe (stimulated emission) fluorescence microscopy.

PubMed Central

Buehler, C; Dong, C Y; So, P T; French, T; Gratton, E

2000-01-01

We report the application of pump-probe fluorescence microscopy in time-resolved polarization imaging. We derived the equations governing the pump-probe stimulated emission process and characterized the pump and probe laser power levels for signal saturation. Our emphasis is to use this novel methodology to image polarization properties of fluorophores across entire cells. As a feasibility study, we imaged a 15-microm orange latex sphere and found that there is depolarization that is possibly due to energy transfer among fluorescent molecules inside the sphere. We also imaged a mouse fibroblast labeled with CellTracker Orange CMTMR (5-(and-6)-(((4-chloromethyl)benzoyl)amino)tetramethyl-rhodamine). We observed that Orange CMTMR complexed with gluthathione rotates fast, indicating the relatively low fluid-phase viscosity of the cytoplasmic microenvironment as seen by Orange CMTMR. The measured rotational correlation time ranged from approximately 30 to approximately 150 ps. This work demonstrates the effectiveness of stimulated emission measurements in acquiring high-resolution, time-resolved polarization information across the entire cell. PMID:10866979

Masked-backlighter technique used to simultaneously image x-ray absorption and x-ray emission from an inertial confinement fusion plasma.

PubMed

Marshall, F J; Radha, P B

2014-11-01

A method to simultaneously image both the absorption and the self-emission of an imploding inertial confinement fusion plasma has been demonstrated on the OMEGA Laser System. The technique involves the use of a high-Z backlighter, half of which is covered with a low-Z material, and a high-speed x-ray framing camera aligned to capture images backlit by this masked backlighter. Two strips of the four-strip framing camera record images backlit by the high-Z portion of the backlighter, while the other two strips record images aligned with the low-Z portion of the backlighter. The emission from the low-Z material is effectively eliminated by a high-Z filter positioned in front of the framing camera, limiting the detected backlighter emission to that of the principal emission line of the high-Z material. As a result, half of the images are of self-emission from the plasma and the other half are of self-emission plus the backlighter. The advantage of this technique is that the self-emission simultaneous with backlighter absorption is independently measured from a nearby direction. The absorption occurs only in the high-Z backlit frames and is either spatially separated from the emission or the self-emission is suppressed by filtering, or by using a backlighter much brighter than the self-emission, or by subtraction. The masked-backlighter technique has been used on the OMEGA Laser System to simultaneously measure the emission profiles and the absorption profiles of polar-driven implosions.

Stacking the Cosmic Web in fluorescent Ly α emission with MUSE

NASA Astrophysics Data System (ADS)

Gallego, Sofia G.; Cantalupo, Sebastiano; Lilly, Simon; Marino, Raffaella Anna; Pezzulli, Gabriele; Schaye, Joop; Wisotzki, Lutz; Bacon, Roland; Inami, Hanae; Akhlaghi, Mohammad; Tacchella, Sandro; Richard, Johan; Bouche, Nicolas F.; Steinmetz, Matthias; Carollo, Marcella

2018-04-01

Cosmological simulations suggest that most of the matter in the Universe is distributed along filaments connecting galaxies. Illuminated by the cosmic UV background (UVB), these structures are expected to glow in fluorescent Ly α emission with a surface brightness (SB) that is well below current limits for individual detections. Here, we perform a stacking analysis of the deepest MUSE/VLT data using three-dimensional regions (subcubes) with orientations determined by the position of neighbouring Ly α galaxies at 3 < z < 4. Our method increase the probability of detecting filamentary Ly α emission, provided that these structures are Lyman-limit systems (LLSs). By stacking 390 oriented subcubes we reach a 2σ sensitivity level of SB ≈ 0.44 × 10-20 erg s-1 cm-2 arcsec-2 in an aperture of 1 arcsec2 × 6.25 Å, three times below the expected fluorescent Ly α signal from the Haardt & Madau UVB at z ˜ 3.5. No detectable emission is found on intergalactic scales, implying that at least two thirds of our subcubes do not contain oriented LLSs. On the other hand, significant emission is detected in the circumgalactic medium (CGM) in the direction of the neighbours. The signal is stronger for galaxies with a larger number of neighbours and appears to be independent of any other galaxy properties. We estimate that preferentially oriented satellite galaxies cannot contribute significantly to this signal, suggesting instead that gas densities in the CGM are typically larger in the direction of neighbouring galaxies on cosmological scales.

Bias and uncertainty in the absorption emission measurement of atomic sodium density in the SSME exit plane

NASA Technical Reports Server (NTRS)

Bauman, Leslie E.

1990-01-01

The measurement of atomic sodium concentration in the TTB 019 firing of April 1990 is significant in that it represents the first measurement of density at the exit plane of the space shuttle main engine. The knowledge of the sodium density, combined with the certainty that the exit plane of the plume is optically thin at the sodium D-line wavelengths, provides essential information for evaluation of diagnostic techniques using sodium atoms, such as resonant Doppler velocimetry for temperature, pressure, and velocity through high resolution fluorescent lineshape analysis. The technique used for the sodium atom line transmission (SALT) measurements is that of resonant absorption emission using a hollow cathode lamp as the reference source. Through the use of two-dimensional kinetic (TDK) predictions of temperature and density for the flight engine case and radiative transfer calculations, this line-of-sight spectrally integrated transmission indicates a sodium atom concentration, i.e., mole fraction, of 0.91e-10. The subject of this paper is the assumptions and measurement uncertainties tied into the calculation. Because of the narrow shape of the source emission, the uncertainties in the absorption profile could introduce considerable bias in the measurement. The following were investigated: (1) the inclusion of hyperfine splitting of the D-lines in the calculation; (2) the use of the flight engine predictions of plume temperature and density versus those for the large throat engine; (3) the assumption of a Gaussian, i.e., Doppler, distribution for the source radiance with a temperature of 400 K; (4) the use of atomic collisional shift and width values for the work by Jongerius; and (5) a Doppler shift for a 7 degree outward velocity vector at the plume edge. Also included in the study was the bias introduced by an uncertainty in the measurement of the D1/D2 line ratio in the source.

Plasmonically amplified fluorescence bioassay with microarray format

NASA Astrophysics Data System (ADS)

Gogalic, S.; Hageneder, S.; Ctortecka, C.; Bauch, M.; Khan, I.; Preininger, Claudia; Sauer, U.; Dostalek, J.

2015-05-01

Plasmonic amplification of fluorescence signal in bioassays with microarray detection format is reported. A crossed relief diffraction grating was designed to couple an excitation laser beam to surface plasmons at the wavelength overlapping with the absorption and emission bands of fluorophore Dy647 that was used as a label. The surface of periodically corrugated sensor chip was coated with surface plasmon-supporting gold layer and a thin SU8 polymer film carrying epoxy groups. These groups were employed for the covalent immobilization of capture antibodies at arrays of spots. The plasmonic amplification of fluorescence signal on the developed microarray chip was tested by using interleukin 8 sandwich immunoassay. The readout was performed ex situ after drying the chip by using a commercial scanner with high numerical aperture collecting lens. Obtained results reveal the enhancement of fluorescence signal by a factor of 5 when compared to a regular glass chip.

What Quasars Really Look Like: Unification of the Emission and Absorption Line Regions

NASA Technical Reports Server (NTRS)

Elvis, Martin

2000-01-01

We propose a simple unifying structure for the inner regions of quasars and AGN. This empirically derived model links together the broad absorption line (BALS), the narrow UV/X-ray ionized absorbers, the BELR, and the 5 Compton scattering/fluorescing regions into a single structure. The model also suggests an alternative origin for the large-scale bi-conical outflows. Some other potential implications of this structure are discussed.

A Green Fluorescent Protein with Photoswitchable Emission from the Deep Sea

PubMed Central

Vogt, Alexander; D'Angelo, Cecilia; Oswald, Franz; Denzel, Andrea; Mazel, Charles H.; Matz, Mikhail V.; Ivanchenko, Sergey; Nienhaus, G. Ulrich; Wiedenmann, Jörg

2008-01-01

A colorful variety of fluorescent proteins (FPs) from marine invertebrates are utilized as genetically encoded markers for live cell imaging. The increased demand for advanced imaging techniques drives a continuous search for FPs with new and improved properties. Many useful FPs have been isolated from species adapted to sun-flooded habitats such as tropical coral reefs. It has yet remained unknown if species expressing green fluorescent protein (GFP)-like proteins also exist in the darkness of the deep sea. Using a submarine-based and -operated fluorescence detection system in the Gulf of Mexico, we discovered ceriantharians emitting bright green fluorescence in depths between 500 and 600 m and identified a GFP, named cerFP505, with bright fluorescence emission peaking at 505 nm. Spectroscopic studies showed that ∼15% of the protein bulk feature reversible ON/OFF photoswitching that can be induced by alternating irradiation with blue und near-UV light. Despite being derived from an animal adapted to essentially complete darkness and low temperatures, cerFP505 maturation in living mammalian cells at 37°C, its brightness and photostability are comparable to those of EGFP and cmFP512 from shallow water species. Therefore, our findings disclose the deep sea as a potential source of GFP-like molecular marker proteins. PMID:19018285

Porphyrin synthesized from cashew nut shell liquid as part of a novel superparamagnetic fluorescence nanosystem

NASA Astrophysics Data System (ADS)

Clemente, C. S.; Ribeiro, V. G. P.; Sousa, J. E. A.; Maia, F. J. N.; Barreto, A. C. H.; Andrade, N. F.; Denardin, J. C.; Mele, G.; Carbone, L.; Mazzetto, S. E.; Fechine, P. B. A.

2013-06-01

Magnetic Fe3O4 nanoparticles with average size approximately 11 nm were first oleic acid coated to interact with the meso-porphyrin derivative from CNSL. This procedure produced a novel superparamagnetic fluorescent nanosystem (SFN) linked by van der Waals interactions. This system was characterized by transmission electron microscope, infrared spectroscopy, thermogravimetric analysis, magnetic measurements, UV-Vis absorption, and fluorescence emission measurements. These results showed that SFN has good thermal stability, excellent magnetization, and nanosized dimensions ( 13 nm). It exhibited emission peaks at 668 and 725 nm with a maximum emission at 467 nm of excitation wavelength. The type of interaction between porphyrin and magnetic nanoparticles allowed to obtain a material with interesting optical properties which might be used as an imaging agent for contrast in cells as well as heterogeneous photocatalysis.

Quantification of zinc-porphyrin in dry-cured ham products by spectroscopic methods Comparison of absorption, fluorescence and X-ray fluorescence spectroscopy.

PubMed

Laursen, Kristoffer; Adamsen, Christina E; Laursen, Jens; Olsen, Karsten; Møller, Jens K S

2008-03-01

Zinc-protoporphyrin (Zn-pp), which has been identified as the major pigment in certain dry-cured meat products, was extracted with acetone/water (75%) and isolated from the following meat products: Parma ham, Iberian ham and dry-cured ham with added nitrite. The quantification of Zn-pp by electron absorption, fluorescence and X-ray fluorescence (XRF) spectroscopy was compared (concentration range used [Zn-pp]=0.8-9.7μM). All three hams were found to contain Zn-pp, and the results show no significant difference among the content of Zn-pp quantified by fluorescence, absorbance and X-ray fluorescence spectroscopy for Parma ham and Iberian ham. All three methods can be used for quantification of Zn-pp in acetone/water extracts of different ham types if the content is higher than 1.0ppm. For dry-cured ham with added nitrite, XRF was not applicable due to the low content of Zn-pp (<0.1ppm). In addition, XRF spectroscopy provides further information regarding other trace elements and can therefore be advantageous in this aspect. This study also focused on XRF determination of Fe in the extracts and as no detectable Fe was found in the three types of ham extracts investigated (limit of detection; Fe⩽1.8ppm), it allows the conclusion that iron containing pigments, e.g., heme, do not contribute to the noticeable red colour observed in some of the extracts.

Azadioxatriangulenium: exploring the effect of a 20 ns fluorescence lifetime in fluorescence anisotropy measurements

NASA Astrophysics Data System (ADS)

Bogh, Sidsel A.; Bora, Ilkay; Rosenberg, Martin; Thyrhaug, Erling; Laursen, Bo W.; Just Sørensen, Thomas

2015-12-01

Azaoxatriangulenium (ADOTA) has been shown to be highly emissive despite a moderate molar absorption coefficient of the primary electronic transition. As a result, the fluorescence lifetime is ~20 ns, longer than all commonly used red fluorescent organic probes. The electronic transitions in ADOTA are highly polarised (r 0  =  0.38), which in combination with the long fluorescence lifetime extents the size-range of biomolecular weights that can be detected in fluorescence polarisation-based experiments. Here, the rotational dynamics of bovine serum albumin (BSA) are monitored with three different ADOTA derivatives, differing only in constitution of the reactive linker. A detailed study of the degree of labelling, the steady-state anisotropy, and the time-resolved anisotropy of the three different ADOTA-BSA conjugates are reported. The fluorescence quantum yields (ϕ fl) of the free dyes in PBS solution are determined to be ~55%, which is reduced to ~20% in the ADOTA-BSA conjugates. Despite the reduction in ϕ fl, a ~20 ns intensity averaged lifetime is maintained, allowing for the rotational dynamics of BSA to be monitored for up to 100 ns. Thus, ADOTA can be used in fluorescence polarisation assays to fill the gap between commonly used organic dyes and the long luminescence lifetime transition metal complexes. This allows for efficient steady-state fluorescence polarisation assays for detecting binding of analytes with molecular weights of up to 100 kDa.

Hydrophobic-carbon-dot-based dual-emission micelle for ratiometric fluorescence biosensing and imaging of Cu2+ in liver cells.

PubMed

Lu, Linlin; Feng, Chongchong; Xu, Jie; Wang, Fengyang; Yu, Haijun; Xu, Zhiai; Zhang, Wen

2017-06-15

Copper is closely related to liver damage, therefore, it is essential to develop a simple and sensitive strategy to detect copper ions (Cu 2+ ) in liver cells. A hydrophobic carbon dots (HCDs)-based dual-emission fluorescent probe for Cu 2+ was prepared by encapsulating HCDs in micelles formed by self-assembly of amphiphilic polymer DSPE-PEG and tetrakis (4-carboxyphenyl) porphyrin (TCPP)-modified DSPE-PEG. The obtained probe showed characteristic fluorescence emissions of HCDs and TCPP with large emission shift of 170nm with single-wavelength excitation. In the presence of Cu 2+ , the fluorescence of TCPP was quenched and that of HCDs remained unchanged, displaying ratiometric fluorescence response to Cu 2+ . The developed probe exhibited high sensitivity (detection limit down to 36nM) and selectivity to Cu 2+ over other substances, and the probe was used to image the changes of Cu 2+ level in liver cells successfully. Copyright © 2017 Elsevier B.V. All rights reserved.

[A novel method for extracting leaf-level solar-induced fluorescence of typical crops under Cu stress].

PubMed

Qu, Ying; Liu, Su-hong; Li, Xiao-wen

2012-05-01

The leaf-level solar-induced fluorescence changes when the typical crops are under Cu stress, which can be considered as a sensitive indicator to estimate the stress level. In the present study, wheat (Triticum aestivum L.), pea (Pisum sativum L.) and Chinese cabbage (Brassica campestris L.) were selected and cultured with copper solutions or copper polluted soil with different Cu stress. The apparent reflectance of leaves was measured by an ASD Fieldspec spectrometer and an integrating sphere. As the apparent reflectance was seldom affected by the fluorescence emission at 580-650 and 800-1000 nm, so the apparent solar-induced fluorescence can be separated from the apparent reflectance based on PROSPECT model. The re-absorption effect of chlorophyll was corrected by three methods, called GM (Gitelson et al.'s model), AM (Agati et al.'s model) and LM (Lagorio et al.'s model). After the re-absorption correction, the solar-induced fluorescence under different Cu stress was obtained, and a positive relationship was found between the height of far RED fluorescence (FRF) and the copper contents in leaves.

Feasibility of airborne detection of laser-induced fluorescence emissions from green terrestrial plants

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.; Yungel, J. K.

1983-01-01

The present investigation provides a demonstration of the feasibility of the airborne detection of the laser-induced fluorescence spectral emissions from living terrestrial grasses, shrubs, and trees using existing levels of lidar technology. Airborne studies were performed to ascertain system requirements necessary to detect laser-induced fluorescence from living terrestrial plants, to assess the practical acquisition of useful single-shot laser-induced fluorescence (LIF) waveforms over vegetative canopies, and to determine the comparative suitability of laser system, airborne platform, and terrestrial environmental parameters. The field experiment was conducted on May 3, 1982, over the northern portion of Wallops Island, VA. Attention is given to airborne lidar results and the description of laboratory investigations.

Radiation Force Caused by Scattering, Absorption, and Emission of Light by Nonspherical Particles

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Hansen, James E. (Technical Monitor)

2001-01-01

General formulas for computing the radiation force exerted on arbitrarily oriented and arbitrarily shaped nonspherical particles due to scattering, absorption, and emission of electromagnetic radiation are derived. For randomly oriented particles with a plane of symmetry, the formula for the average radiation force caused by the particle response to external illumination reduces to the standard Debye formula derived from the Lorenz-Mie theory, whereas the average radiation force caused by emission vanishes.

Construction of a ratiometric fluorescent probe with an extremely large emission shift for imaging hypochlorite in living cells

NASA Astrophysics Data System (ADS)

Song, Xuezhen; Dong, Baoli; Kong, Xiuqi; Wang, Chao; Zhang, Nan; Lin, Weiying

2018-01-01

Hypochlorite is one of the important reactive oxygen species (ROS) and plays critical roles in many biologically vital processes. Herein, we present a unique ratiometric fluorescent probe (CBP) with an extremely large emission shift for detecting hypochlorite in living cells. Utilizing positively charged α,β-unsaturated carbonyl group as the reaction site, the probe CBP itself exhibited near-infrared (NIR) fluorescence at 662 nm, and can display strong blue fluorescence at 456 nm when responded to hypochlorite. Notably, the extremely large emission shift of 206 nm could enable the precise measurement of the fluorescence peak intensities and ratios. CBP showed high sensitivity, excellent selectivity, desirable performance at physiological pH, and low cytotoxicity. The bioimaging experiments demonstrate the biological application of CBP for the ratiometric imaging of hypochlorite in living cells.

Coherent nonlinear optical imaging: beyond fluorescence microscopy.

PubMed

Min, Wei; Freudiger, Christian W; Lu, Sijia; Xie, X Sunney

2011-01-01

The quest for ultrahigh detection sensitivity with spectroscopic contrasts other than fluorescence has led to various novel approaches to optical microscopy of biological systems. Coherent nonlinear optical imaging, especially the recently developed nonlinear dissipation microscopy (including stimulated Raman scattering and two-photon absorption) and pump-probe microscopy (including excited-state absorption, stimulated emission, and ground-state depletion), provides new image contrasts for nonfluorescent species. Thanks to the high-frequency modulation transfer scheme, these imaging techniques exhibit superb detection sensitivity. By directly interrogating vibrational and/or electronic energy levels of molecules, they offer high molecular specificity. Here we review the underlying principles and excitation and detection schemes, as well as exemplary biomedical applications of this emerging class of molecular imaging techniques.

Effects of solvent polarity on the absorption and fluorescence spectra of chlorogenic acid and caffeic acid compounds: determination of the dipole moments.

PubMed

Belay, Abebe; Libnedengel, Ermias; Kim, Hyung Kook; Hwang, Yoon-Hwae

2016-02-01

The effects of solvent polarity on absorption and fluorescence spectra of biologically active compounds (chlorogenic acid (CGA) and caffeic acids (CA)) have been investigated. In both spectra pronounced solvatochromic effects were observed with shift of emission peaks larger than the corresponding UV-vis electronic absorption spectra. From solvatochromic theory the ground and excited-state dipole moments were determined experimentally and theoretically. The differences between the excited and ground state dipole moment determined by Bakhshiev, Kawski-Chamma-Viallet and Reichardt equations are quite similar. The ground and excited-state dipole moments were determined by theoretical quantum chemical calculation using density function theory (DFT) method (Gaussian 09) and were also similar to the experimental results. The HOMO-LUMO energy band gaps for CGA and CFA were calculated and found to be 4.1119 and 1.8732 eV respectively. The results also indicated the CGA molecule is more stable than that of CFA. It was also observed that in both compounds the excited state possesses a higher dipole moment than that of the ground state. This confirms that the excited state of the hydroxycinnamic compounds is more polarized than that of the ground state and therefore is more sensitive to the solvent. Copyright © 2015 John Wiley & Sons, Ltd.

Synthesis and fluorescence properties of some difluoroboron β-diketonate complexes and composite containing PMMA

NASA Astrophysics Data System (ADS)

Xing, Dongye; Hou, Yanjun; Niu, Haijun

2018-03-01

A series of difluoroboron β-diketonate complexes, containing the indon-β-diketonate ligand carrying methyl or methoxyl substituents was synthesized. The crystal structures of the complexes were confirmed by single crystal X-ray diffraction studies. The fluorescence properties of compounds were studied in solution state, solid state and on PMMA polymer matrix. The photophysical data of compounds 2a-2d exhibited strong fluorescence and photostability under the ultraviolet light (Hg lamp). The complex 2b showed higher fluorescence intensity in solution state as compared to other complexes of the series. The complexes 2c and 2d showed higher fluorescence intensity in the solid state, which are ascribed to the stronger π-π interactions between ligands in the solid state. The introduction of methoxyl or methyl groups on the benzene rings enhanced the absorption intensity, emission intensity, quantum yields and fluorescence lifetimes due to their electron-donating nature. Furthermore, the complex 2b was doped into the PMMA to produce hybrid materials, where the PMMA matrix acted as sensitizer for the central boron ion to enhance the fluorescence emission intensity and quantum yields.

Optically-Enhanced, Near-IR, Silver Cluster Emission Altered by Single Base Changes in the DNA Template

PubMed Central

Fan, Chaoyang; Story, Sandra P.; Sengupta, Bidisha; Sartin, Matthew; Hsiang, Jung-Cheng; Perry, Joseph W.

2011-01-01

Few-atom silver clusters harbored by DNA are promising fluorophores due to their high molecular brightness along with their long- and short-term photostability. Furthermore, their emission rate can be enhanced when co-illuminated with low-energy light that optically depopulates the fluorescence-limiting dark state. The photophysical basis for this effect is evaluated for two near infrared-emitting clusters. Clusters emitting at ~800 nm form with C3AC3AC3TC3A and C3AC3AC3GC3A and both exhibit a trap state with λmax ~ 840 nm and an absorption cross section of 5–6 × 10−16 cm2/molec that can be optically depopulated. Transient absorption spectra, complemented by fluorescence correlation spectroscopy studies, show that the dark state has an inherent lifetime of 3–4 μs and that absorption from this state is accompanied by photoinduced crossover back to the emissive manifold of states with an action cross section of ~2 × 10−18 cm2/molec. Relative to C3AC3AC3TC3A, C3AC3AC3GC3A produces a longer-lived trap state and permits more facile passage back to the emissive manifold. With the C3AC3AC3AC3G template, a spectrally distinct cluster forms having emission at ~900 nm and its trap state has a ~four-fold shorter lifetime. These studies of optically-gated fluorescence bolster the critical role of the nucleobases on both the formation and excited state dynamics of these highly emissive metallic clusters. PMID:21568292

pH-Dependent Optical Properties of Synthetic Fluorescent Imidazoles

PubMed Central

Berezin, Mikhail Y.; Kao, Jeff; Achilefu, Samuel

2010-01-01

An imidazole moiety is often found as an integral part of fluorophores in a variety of fluorescent proteins and many such proteins possess pH dependent light emission. In contrast, synthetic fluorescent compounds with incorporated imidazoles are rare and have not been studied as pH probes. In this report, the richness of imidazole optical properties, including pH sensitivity, was demonstrated via a novel imidazole-based fluorophore 1H-imidazol-5-yl-vinyl-benz[e]indolium. Three species corresponding to protonated, neutral and deprotonated imidazoles were identified in the broad range of pH 1-12. The absorption and emission bands of each species were assigned by comparative spectral analysis with synthesized mono- and di-N-methylated fluorescent imidazole analogues. pKa analysis in the ground and the excited states showed photoacidic properties of the fluorescent imidazoles due to the excited state proton transfer (ESPT). This effect was negligible for substituted imidazoles. The assessment of a pH sensitive center in the imidazole ring revealed the switching of the pH sensitive centers from 1-N in the ground state to 3-N in the excited state. The effect was attributed to the unique kind of the excited state charge transfer (ESCT) resulting in a positive charge swapping between two nitrogens. PMID:19212987

Theoretical Analysis of Optical Absorption and Emission in Mixed Noble Metal Nanoclusters.

PubMed

Day, Paul N; Pachter, Ruth; Nguyen, Kiet A

2018-04-26

In this work, we studied theoretically two hybrid gold-silver clusters, which were reported to have dual-band emission, using density functional theory (DFT) and linear and quadratic response time-dependent DFT (TDDFT). Hybrid functionals were found to successfully predict absorption and emission, although explanation of the NIR emission from the larger cluster (cluster 1) requires significant vibrational excitation in the final state. For the smaller cluster (cluster 2), the Δ H(0-0) value calculated for the T1 → S0 transition, using the PBE0 functional, is in good agreement with the measured NIR emission, and the calculated T2 → S0 value is in fair agreement with the measured visible emission. The calculated T1 → S0 phosphorescence Δ H(0-0) for cluster 1 is close to the measured visible emission energy. In order for the calculated phosphorescence for cluster 1 to agree with the intense NIR emission reported experimentally, the vibrational energy of the final state (S0) is required to be about 0.7 eV greater than the zero-point vibrational energy.

Investigation of formalin influence over hard and soft biological tissues fluorescent spectra in vitro

NASA Astrophysics Data System (ADS)

Borisova, E.; Uzunov, Tz.; Vladimirov, B.; Avramov, L.

2007-05-01

In order to investigate the formalin influence over fluorescence properties of hard and soft biological tissues during conservation, emission spectra have been registered. Nitrogen laser at 337 nm and light-emitting diode with maximum at 405 nm have been used as excitation sources. For investigation of formalin influence over hard tissues, an experiment was made on teeth samples. Sound teeth were demineralized with a phosphoric acid for 10 seconds to obtain enamel structure near to the tooth lesion, and were fixed in formalin. Before and after teeth treatment spectra from the areas of interest were detected. There were not observed changes in the shape of the teeth spectra, related to the introduction of formalin fluorescence. Samples from mucosa of esophagus and stomach, where initially an ALA/Protoporphyrin IX diagnosis was applied, were used as soft tissue specimens. After fluorescent diagnosis in vivo biopsy samples were obtained from normal and cancerous areas and were conserved in formalin. Initially, spectrum observed has one autofluorescence maximum from the mucous tissue at 500-600 nm and secondary maxima from the protoporphyrin fluorescence at 635 nm and 720 nm, as well as pronounced minima at 540 and 575 nm related to hemoglobin absorption. After formalin conservation hemoglobin absorption was strongly reduced that increases mucous emission signal in green-yellow spectral region. Simultaneously the maxima at 635 nm and 720 nm were reduced. As conclusion we could say that formalin has negligible influence over fluorescence spectra of conserved hard tissues and has more pronounced influence over fluorescence spectra obtained in the case of soft tissue conservation, which has to be taking into account in measurements in vitro.

Model-independent analysis of the orientation of fluorescent probes with restricted mobility in muscle fibers.

PubMed Central

Dale, R E; Hopkins, S C; an der Heide, U A; Marszałek, T; Irving, M; Goldman, Y E

1999-01-01

The orientation of proteins in ordered biological samples can be investigated using steady-state polarized fluorescence from probes conjugated to the protein. A general limitation of this approach is that the probes typically exhibit rapid orientational motion ("wobble") with respect to the protein backbone. Here we present a method for characterizing the extent of this wobble and for removing its effects from the available information about the static orientational distribution of the probes. The analysis depends on four assumptions: 1) the probe wobble is fast compared with the nanosecond time scale of its excited-state decay; 2) the orientational distributions of the absorption and emission transition dipole moments are cylindrically symmetrical about a common axis c fixed in the protein; 3) protein motions are negligible during the excited-state decay; 4) the distribution of c is cylindrically symmetrical about the director of the experimental sample. In a muscle fiber, the director is the fiber axis, F. All of the information on the orientational order of the probe that is available from measurements of linearly polarized fluorescence is contained in five independent polarized fluorescence intensities measured with excitation and emission polarizers parallel or perpendicular to F and with the propagation axis of the detected fluorescence parallel or perpendicular to that of the excitation. The analysis then yields the average second-rank and fourth-rank order parameters ( and ) of the angular distribution of c relative to F, and and , the average second-rank order parameters of the angular distribution for wobble of the absorption and emission transition dipole moments relative to c. The method can also be applied to other cylindrically ordered systems such as oriented lipid bilayer membranes and to processes slower than fluorescence that may be observed using longer-lived optically excited states. PMID:10049341

Highly photostable near-infrared fluorescent pH indicators and sensors based on BF2-chelated tetraarylazadipyrromethene dyes.

PubMed

Jokic, Tijana; Borisov, Sergey M; Saf, Robert; Nielsen, Daniel A; Kühl, Michael; Klimant, Ingo

2012-08-07

In this study, a series of new BF(2)-chelated tetraarylazadipyrromethane dyes are synthesized and are shown to be suitable for the preparation of on/off photoinduced electron transfer modulated fluorescent sensors. The new indicators are noncovalently entrapped in polyurethane hydrogel D4 and feature absorption maxima in the range 660-710 nm and fluorescence emission maxima at 680-740 nm. Indicators have high molar absorption coefficients of ~80,000 M(-1) cm(-1), good quantum yields (up to 20%), excellent photostability and low cross-sensitivity to the ionic strength. pK(a) values of indicators are determined from absorbance and fluorescence measurements and range from 7 to 11, depending on the substitution pattern of electron-donating and -withdrawing functionalities. Therefore, the new indicators are suitable for exploitation and adaptation in a diverse range of analytical applications. Apparent pK(a) values in sensor films derived from fluorescence data show 0.5-1 pH units lower values in comparison with those derived from the absorption data due to Förster resonance energy transfer from protonated to deprotonated form. A dual-lifetime referenced sensor is prepared, and application for monitoring of pH in corals is demonstrated.

Deep-red to near-infrared fluorescent dyes: Synthesis, photophysical properties, and application in cell imaging

NASA Astrophysics Data System (ADS)

Li, Qi; Liu, Weimin; Wu, Jiasheng; Zhou, Bingjiang; Niu, Guangle; Zhang, Hongyan; Ge, Jiechao; Wang, Pengfei

2016-07-01

More and more attention has been paid to the design of new fluorescent imaging agents with good photostability and water solubility, especially those with emissions in the deep-red and near-infrared regions. In this work, we designed and synthesized four novel fluorescent dyes with deep-red or NIR fluorescence by hybridizing coumarin and pyronin moieties based on our previous work. Introduction of carboxylic acid in the dyes not only imparted the dyes with water solubility but also provided a versatile sensing platform for designing the fluorescent probes and sensors of biomolecules. The photophysical properties of these new dyes were investigated through absorption and fluorescence spectroscopy. Cell imaging experiments showed that esterification products could selectively stain lysosomes with good photostability, thereby indicating that they could be useful in the development of fluorescent probes for bioimaging.

Visual Understanding of Light Absorption and Waveguiding in Standing Nanowires with 3D Fluorescence Confocal Microscopy

PubMed Central

2017-01-01

Semiconductor nanowires are promising building blocks for next-generation photonics. Indirect proofs of large absorption cross sections have been reported in nanostructures with subwavelength diameters, an effect that is even more prominent in vertically standing nanowires. In this work we provide a three-dimensional map of the light around vertical GaAs nanowires standing on a substrate by using fluorescence confocal microscopy, where the strong long-range disruption of the light path along the nanowire is illustrated. We find that the actual long-distance perturbation is much larger in size than calculated extinction cross sections. While the size of the perturbation remains similar, the intensity of the interaction changes dramatically over the visible spectrum. Numerical simulations allow us to distinguish the effects of scattering and absorption in the nanowire leading to these phenomena. This work provides a visual understanding of light absorption in semiconductor nanowire structures, which is of high interest for solar energy conversion applications. PMID:28966933

Visual Understanding of Light Absorption and Waveguiding in Standing Nanowires with 3D Fluorescence Confocal Microscopy.

PubMed

Frederiksen, Rune; Tutuncuoglu, Gozde; Matteini, Federico; Martinez, Karen L; Fontcuberta I Morral, Anna; Alarcon-Llado, Esther

2017-09-20

Semiconductor nanowires are promising building blocks for next-generation photonics. Indirect proofs of large absorption cross sections have been reported in nanostructures with subwavelength diameters, an effect that is even more prominent in vertically standing nanowires. In this work we provide a three-dimensional map of the light around vertical GaAs nanowires standing on a substrate by using fluorescence confocal microscopy, where the strong long-range disruption of the light path along the nanowire is illustrated. We find that the actual long-distance perturbation is much larger in size than calculated extinction cross sections. While the size of the perturbation remains similar, the intensity of the interaction changes dramatically over the visible spectrum. Numerical simulations allow us to distinguish the effects of scattering and absorption in the nanowire leading to these phenomena. This work provides a visual understanding of light absorption in semiconductor nanowire structures, which is of high interest for solar energy conversion applications.

The absorption, fluorescence and phosphorescence spectra of α and β-F, Cl, Br-naphthalenes in crystalline matrixes at 77 K

NASA Astrophysics Data System (ADS)

Iliescu, T.; Milea, I.; Abdolrahman, P. M.

1984-03-01

The paper studies the absorption, fluorescence and phosphorescence spectra of α and β-F, Cl, Br-naphtalenes (α, β-F, Cl,BrN) in different matrixes at 77 K and different concentrations. From these spectra one obtaines the vibrational frequences.

Indocyanine green fluorescence in second near-infrared (NIR-II) window

PubMed Central

Bhavane, Rohan; Ghaghada, Ketan B.; Vasudevan, Sanjeev A.; Kaay, Alexander; Annapragada, Ananth

2017-01-01

Indocyanine green (ICG), a FDA approved near infrared (NIR) fluorescent agent, is used in the clinic for a variety of applications including lymphangiography, intra-operative lymph node identification, tumor imaging, superficial vascular imaging, and marking ischemic tissues. These applications operate in the so-called “NIR-I” window (700–900 nm). Recently, imaging in the “NIR-II” window (1000–1700 nm) has attracted attention since, at longer wavelengths, photon absorption, and scattering effects by tissue components are reduced, making it possible to image deeper into the underlying tissue. Agents for NIR-II imaging are, however, still in pre-clinical development. In this study, we investigated ICG as a NIR-II dye. The absorbance and NIR-II fluorescence emission of ICG were measured in different media (PBS, plasma and ethanol) for a range of ICG concentrations. In vitro and in vivo testing were performed using a custom-built spectral NIR assembly to facilitate simultaneous imaging in NIR-I and NIR-II window. In vitro studies using ICG were performed using capillary tubes (as a simulation of blood vessels) embedded in Intralipid solution and tissue phantoms to evaluate depth of tissue penetration in NIR-I and NIR-II window. In vivo imaging using ICG was performed in nude mice to evaluate vascular visualization in the hind limb in the NIR-I and II windows. Contrast-to-noise ratios (CNR) were calculated for comparison of image quality in NIR-I and NIR-II window. ICG exhibited significant fluorescence emission in the NIR-II window and this emission (similar to the absorption profile) is substantially affected by the environment of the ICG molecules. In vivo imaging further confirmed the utility of ICG as a fluorescent dye in the NIR-II domain, with the CNR values being ~2 times those in the NIR-I window. The availability of an FDA approved imaging agent could accelerate the clinical translation of NIR-II imaging technology. PMID:29121078

Multifunctional PHPMA-Derived Polymer for Ratiometric pH Sensing, Fluorescence Imaging, and Magnetic Resonance Imaging.

PubMed

Su, Fengyu; Agarwal, Shubhangi; Pan, Tingting; Qiao, Yuan; Zhang, Liqiang; Shi, Zhengwei; Kong, Xiangxing; Day, Kevin; Chen, Meiwan; Meldrum, Deirdre; Kodibagkar, Vikram D; Tian, Yanqing

2018-01-17

In this paper, we report synthesis and characterization of a novel multimodality (MRI/fluorescence) probe for pH sensing and imaging. A multifunctional polymer was derived from poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) and integrated with a naphthalimide-based-ratiometric fluorescence probe and a gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex (Gd-DOTA complex). The polymer was characterized using UV-vis absorption spectrophotometry, fluorescence spectrofluorophotometry, magnetic resonance imaging (MRI), and confocal microscopy for optical and MRI-based pH sensing and cellular imaging. In vitro labeling of macrophage J774 and esophageal CP-A cell lines shows the polymer's ability to be internalized in the cells. The transverse relaxation time (T 2 ) of the polymer was observed to be pH-dependent, whereas the spin-lattice relaxation time (T 1 ) was not. The pH probe in the polymer shows a strong fluorescence-based ratiometric pH response with emission window changes, exhibiting blue emission under acidic conditions and green emission under basic conditions, respectively. This study provides new materials with multimodalities for pH sensing and imaging.

Emission factors and light absorption properties of brown carbon from household coal combustion in China

NASA Astrophysics Data System (ADS)

Sun, Jianzhong; Zhi, Guorui; Hitzenberger, Regina; Chen, Yingjun; Tian, Chongguo; Zhang, Yayun; Feng, Yanli; Cheng, Miaomiao; Zhang, Yuzhe; Cai, Jing; Chen, Feng; Qiu, Yiqin; Jiang, Zhiming; Li, Jun; Zhang, Gan; Mo, Yangzhi

2017-04-01

Brown carbon (BrC) draws increasing attention due to its effects on climate and other environmental factors. In China, household coal burned for heating and cooking purposes releases huge amounts of carbonaceous particles every year; however, BrC emissions have rarely been estimated in a persuasive manner due to the unavailable emission characteristics. Here, seven coals jointly covering geological maturity from low to high were burned in four typical stoves as both chunk and briquette styles. The optical integrating sphere (IS) method was applied to measure the emission factors (EFs) of BrC and black carbon (BC) via an iterative process using the different spectral dependence of light absorption for BrC and BC and using humic acid sodium salt (HASS) and carbon black (CarB) as reference materials. The following results have been found: (i) the average EFs of BrC for anthracite coal chunks and briquettes are 1.08 ± 0.80 and 1.52 ± 0.16 g kg-1, respectively, and those for bituminous coal chunks and briquettes are 8.59 ± 2.70 and 4.01 ± 2.19 g kg-1, respectively, reflecting a more significant decline in BrC EFs for bituminous coals than for anthracites due to briquetting. (ii) The BrC EF peaks at the middle of coal's geological maturity, displaying a bell-shaped curve between EF and volatile matter (Vdaf). (iii) The calculated BrC emissions from China's residential coal burning amounted to 592 Gg (1 Gg = 109 g) in 2013, which is nearly half of China's total BC emissions. (iv) The absorption Ångström exponents (AAEs) of all coal briquettes are higher than those of coal chunks, indicating that the measure of coal briquetting increases the BrC / BC emission ratio and thus offsets some of the climate cooling effect of briquetting. (v) In the scenario of current household coal burning in China, solar light absorption by BrC (350-850 nm in this study) accounts for more than a quarter (0.265) of the total absorption. This implies the significance of BrC to climate

Laser Ablated Carbon Nanodots for Light Emission.

PubMed

Reyes, Delfino; Camacho, Marco; Camacho, Miguel; Mayorga, Miguel; Weathers, Duncan; Salamo, Greg; Wang, Zhiming; Neogi, Arup

2016-12-01

The synthesis of fluorescent carbon dots-like nanostructures (CNDs) obtained through the laser ablation of a carbon solid target in liquid environment is reported. The ablation process was induced in acetone with laser pulses of 1064, 532, and 355 nm under different irradiation times. Close-spherical amorphous CNDs with sizes between 5 and 20 nm, whose abundance strongly depends on the ablation parameters were investigated using electron microscopy and was confirmed using absorption and emission spectroscopies. The π- π* electronic transition at 3.76 eV dominates the absorption for all the CNDs species synthesized under different irradiation conditions. The light emission is most efficient due to excitation at 3.54 eV with the photoluminescence intensity centered at 3.23 eV. The light emission from the CNDs is most efficient due to ablation at 355 nm. The emission wavelength of the CNDs can be tuned from the near-UV to the green wavelength region by controlling the ablation time and modifying the ablation and excitation laser wavelength.

Synchronous fluorescence spectroscopic study of solvatochromic curcumin dye

NASA Astrophysics Data System (ADS)

Patra, Digambara; Barakat, Christelle

2011-09-01

Curcumin, the main yellow bioactive component of turmeric, has recently acquired attention by chemists due its wide range of potential biological applications as an antioxidant, an anti-inflammatory, and an anti-carcinogenic agent. This molecule fluoresces weakly and poorly soluble in water. In this detailed study of curcumin in thirteen different solvents, both the absorption and fluorescence spectra of curcumin was found to be broad, however, a narrower and simple synchronous fluorescence spectrum of curcumin was obtained at Δ λ = 10-20 nm. Lippert-Mataga plot of curcumin in different solvents illustrated two sets of linearity which is consistent with the plot of Stokes' shift vs. the ET30. When Stokes's shift in wavenumber scale was replaced by synchronous fluorescence maximum in nanometer scale, the solvent polarity dependency measured by λSFSmax vs. Lippert-Mataga plot or ET30 values offered similar trends as measured via Stokes' shift for protic and aprotic solvents for curcumin. Better linear correlation of λSFSmax vs. π* scale of solvent polarity was found compared to λabsmax or λemmax or Stokes' shift measurements. In Stokes' shift measurement both absorption/excitation as well as emission (fluorescence) spectra are required to compute the Stokes' shift in wavenumber scale, but measurement could be done in a very fast and simple way by taking a single scan of SFS avoiding calculation and obtain information about polarity of the solvent. Curcumin decay properties in all the solvents could be fitted well to a double-exponential decay function.

Synchronous fluorescence spectroscopic study of solvatochromic curcumin dye.

PubMed

Patra, Digambara; Barakat, Christelle

2011-09-01

Curcumin, the main yellow bioactive component of turmeric, has recently acquired attention by chemists due its wide range of potential biological applications as an antioxidant, an anti-inflammatory, and an anti-carcinogenic agent. This molecule fluoresces weakly and poorly soluble in water. In this detailed study of curcumin in thirteen different solvents, both the absorption and fluorescence spectra of curcumin was found to be broad, however, a narrower and simple synchronous fluorescence spectrum of curcumin was obtained at Δλ=10-20 nm. Lippert-Mataga plot of curcumin in different solvents illustrated two sets of linearity which is consistent with the plot of Stokes' shift vs. the ET30. When Stokes's shift in wavenumber scale was replaced by synchronous fluorescence maximum in nanometer scale, the solvent polarity dependency measured by λSFSmax vs. Lippert-Mataga plot or ET30 values offered similar trends as measured via Stokes' shift for protic and aprotic solvents for curcumin. Better linear correlation of λSFSmax vs. π* scale of solvent polarity was found compared to λabsmax or λemmax or Stokes' shift measurements. In Stokes' shift measurement both absorption/excitation as well as emission (fluorescence) spectra are required to compute the Stokes' shift in wavenumber scale, but measurement could be done in a very fast and simple way by taking a single scan of SFS avoiding calculation and obtain information about polarity of the solvent. Curcumin decay properties in all the solvents could be fitted well to a double-exponential decay function. Copyright © 2011 Elsevier B.V. All rights reserved.

Marine fluorescence from high spectrally resolved satellite measurements

NASA Astrophysics Data System (ADS)

Wolanin, Aleksandra; Dinter, Tilman; Rozanov, Vladimir; Noël, Stefan; Vountas, Marco; Burrows, John P.; Bracher, Astrid

2014-05-01

When chlorophyll molecules absorb light, most of this energy is transformed into chemical energy in a process of photosynthesis. However, a fraction of the energy absorbed is reemitted as fluorescence. As a result of its relationship to photosynthetic e?ciency, information about chlorophyll fluorescence can be used to assess the physiological state of phytoplankton (Falkowski and Kolber,1995). In-situ measurements of chlorophyll fluorescence are widespread in physiological and ecophysiological studies. When retrieved from space, chlorophyll fluorescence can improve our knowledge of global biogeochemical cycles and phytoplankton productivity (Behrenfeld et al., 2009; Huot et al., 2013) by providing high coverage and periodicity. So far, the only satellite retrieval of sun-induced marine fluorescence, Fluorescence Line Height (FLH), was designed for MODIS (Abbott and Letelier, 1999), and later also applied to the similar sensor MERIS (Gower et al., 2004). However, it could so far not be evaluated on global scale. Here, we present a different approach to observe marine chlorophyll fluorescence, based on the Differential Optical Absorption Spectroscopy (DOAS) technique (Perner and Platt, 1979) applied to the hyperspectral data from Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) and Global Ozone Monitoring Experiment-2 (GOME-2). Since fluorescence, as a trans-spectral process, leads to the shift of the wavelength of the radiation, it can be observed in the filling-in of Fraunhofer lines. In our retrieval, we evaluate the filling-in of the Zeeman triplet Fraunhofer line FeI at 684.3 nm, which is located very close to the emission peak of marine fluorescence (~685 nm). In order to conduct the chlorophyll fluorescence retrieval with the DOAS method, we calculated the reference spectra for chlorophyll fluorescence, based on simulations performed with the coupled ocean-atmosphere radiative transfer model SCIATRAN (Rozanov et al., 2014

[Characterizing chromophoric dissolved organic matter (CDOM) in Lake Honghu, Lake Donghu and Lake Liangzihu using excitation-emission matrices (EEMs) fluorescence and parallel factor analysis (PARAFAC)].

PubMed

Zhou, Yong-Qiang; Zhang, Yun-Lin; Niu, Cheng; Wang, Ming-Zhu

2013-12-01

Little is known about DOM characteristics in medium to large sized lakes located in the middle and lower reaches of Yangtze River, like Lake Honghu, Lake Donghu and Lake Liangzihu. Absorption, fluorescence and composition characteristics of chromophoric dissolved organic matter (CDOM) are presented using the absorption spectroscopy, the excitation-emission ma trices (EEMs) fluorescence and parallel factor analysis (PARAFAC) model based on the data collected in Sep-Oct. 2007 including 15, 9 and 10 samplings in Lake Honghu, Lake Donghu and Lake Liangzihu, respectively. CDOM absorption coefficient at 350 nm a(350) coefficient in Lake Honghu was significantly higher than those in Lake Donghu and Lake Liangzihu (t-test, p< 0. 001). A significant negative correlation was found between CDOM spectral slope in the wavelength range of 280-500 nm (S280-500) and a(350) (R2 =0. 781, p<0. 001). The mean value of S280-500 in Lake Honghu was significantly lower than those in Lake Donghu (t-test, pfluorescent components (C3, C4) were identified by PARAFAC model, among which significant positive correlations were found between C1 and C2 (R2 =0. 884, p<0. 001), C3 and C4 (R2 =0. 677, p<0.001), respectively, suggesting that the sources of the two humic-like components as well as the two protein-like components were similar. However, no significant correlation has been found between those 4 fluorescent components and DOC concentration. Th e fluorescenceindices of FI255 (HIX), Fl265, FI310 (BIX) and Fl370 in Lake Donghu were all significantly higher than those in Lake Liangzihu (t-test, p <0.05) and Lake Honghu (t-test, p<0. 01), indicating that the eutrophication status in Lake Donghu was higher than Lake Honghu and Lake Liangzihu.

A novel reaction-based colorimetric and ratiometric fluorescent sensor for cyanide anion with a large emission shift and high selectivity.

PubMed

Wang, Shaodan; Fei, Xiaoliang; Guo, Jing; Yang, Qingbiao; Li, Yaoxian; Song, Yan

2016-01-01

A hybrid carbazole-hemicyanine dye (Cac) has been developed as a novel colorimetric and ratiometric fluorescent sensor for cyanide detection. Upon treatment with cyanide, Cac displayed a remarkable fluorescence ratiometric response, with the emission wavelength displaying a very large emission shift (214 nm). The detection of cyanide was performed via the nucleophilic addition of cyanide anion to the indolium group of the sensor, which resulted in the blocking of the intramolecular charge transfer (ICT) process in the sensor, inducing a ratiometric fluorescence change and simultaneously an obvious color change. Furthermore, competitive anions did not showed any significant changes both in color and emission intensity ratio (I381/I595), indicating the high selectivity of the sensor to CN(-). Copyright © 2015 Elsevier B.V. All rights reserved.

Selective detection of Co2+ by fluorescent nano probe: Diagnostic approach for analysis of environmental samples and biological activities

NASA Astrophysics Data System (ADS)

Mahajan, Prasad G.; Dige, Nilam C.; Desai, Netaji K.; Patil, Shivajirao R.; Kondalkar, Vijay V.; Hong, Seong-Karp; Lee, Ki Hwan

2018-06-01

Nowadays scientist over the world are engaging to put forth improved methods to detect metal ion in an aqueous medium based on fluorescence studies. A simple, selective and sensitive method was proposed for detection of Co2+ ion using fluorescent organic nanoparticles. We synthesized a fluorescent small molecule viz. 4,4‧-{benzene-1,4-diylbis-[(Z)methylylidenenitrilo]}dibenzoic acid (BMBA) to explore its suitability as sensor for Co2+ ion and biocompatibility in form of nanoparticles. Fluorescence nanoparticles (BMBANPs) prepared by simple reprecipitation method. Aggregation induced enhanced emission of BMBANPs exhibits the narrower particle size of 68 nm and sphere shape morphology. The selective fluorescence quenching was observed by addition of Co2+ and does not affected by presence of other coexisting ion solutions. The photo-physical properties, viz. UV-absorption, fluorescence emission, and lifetime measurements are in support of ligand-metal interaction followed by static fluorescence quenching phenomenon in emission of BMBANPs. Finally, we develop a simple analytical method for selective and sensitive determination of Co2+ ion in environmental samples. The cell culture E. coli, Bacillus sps., and M. tuberculosis H37RV strain in the vicinity of BMBANPs indicates virtuous anti-bacterial and anti-tuberculosis activity which is of additional novel application shown by prepared nanoparticles.

Polycyclic aromatic hydrocarbons in biomass-burning emissions and their contribution to light absorption and aerosol toxicity.

PubMed

Samburova, Vera; Connolly, Jessica; Gyawali, Madhu; Yatavelli, Reddy L N; Watts, Adam C; Chakrabarty, Rajan K; Zielinska, Barbara; Moosmüller, Hans; Khlystov, Andrey

2016-10-15

In recent years, brown carbon (BrC) has been shown to be an important contributor to light absorption by biomass-burning atmospheric aerosols in the blue and near-ultraviolet (UV) part of the solar spectrum. Emission factors and optical properties of 113 polycyclic aromatic hydrocarbons (PAHs) were determined for combustion of five globally important fuels: Alaskan, Siberian, and Florida swamp peat, cheatgrass (Bromus tectorum), and ponderosa pine (Pinus ponderosa) needles. The emission factors of total analyzed PAHs were between 1.9±0.43.0±0.6 and 9.6±1.2-42.2±5.4mgPAHkg(-1)fuel for particle- and gas phase, respectively. Spectrophotometric analysis of the identified PAHs showed that perinaphthenone, methylpyrenes, and pyrene contributed the most to the total PAH light absorption with 17.2%, 3.3 to 10.5%, and 7.6% of the total particle-phase PAH absorptivity averaged over analyzed emissions from the fuels. In the gas phase, the top three PAH contributors to BrC were acenaphthylene (32.6%), anthracene (8.2%), and 2,4,5-trimethylnaphthalene (8.0%). Overall, the identified PAHs were responsible for 0.087-0.16% (0.13% on average) and 0.033-0.15% (0.11% on average) of the total light absorption by dichloromethane-acetone extracts of particle and gas emissions, respectively. Toxic equivalency factor (TEF) analysis of 16 PAHs prioritized by the United States Environmental Protection Agency (EPA) showed that benzo(a)pyrene contributed the most to the PAH carcinogenic potency of particle phase emissions (61.8-67.4% to the total carcinogenic potency of Σ16EPA PAHs), while naphthalene played the major role in carcinogenicity of the gas phase PAHs in the biomass-burning emission analyzed here (35.4-46.0% to the total carcinogenic potency of Σ16EPA PAHs). The 16 EPA-prioritized PAHs contributed only 22.1±6.2% to total particle and 23.4±11% to total gas phase PAH mass, thus toxic properties of biomass-burning PAH emissions are most likely underestimated. Copyright �

A dual-selective fluorescent probe for GSH and Cys detection: Emission and pH dependent selectivity.

PubMed

Tang, Yunqiang; Jin, Longyi; Yin, Bingzhu

2017-11-15

A novel fluorescent probe 1 based on acridine orange was developed for the selective detection and bioimaging of biothiols. The probe exhibits higher selectivity and turn-on fluorescence response to cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) than to other amino acids. Importantly, the probe responds to GSH and Cys/Hcy with distinct fluorescence emissions in PBS buffer at pH of 7.4. The Cys/Hcy-triggered tandem S N Ar-rearrangement reaction and GSH-induced S N Ar reaction with the probe led to the corresponding amino-acridinium and thio-acridinium dyes, respectively, which can discriminate GSH from Cys/Hcy through different emission channels. Interestingly, Cys finishes the tandem reaction with the probe and subsequently forms amino-acridinium and Hcy/GSH induces S N Ar reaction with the probe to form thio-acridiniums at weakly acidic conditions (pH 6.0), enabling Cys to be discriminated from Hcy/GSH at different emissions. Finally, we demonstrated that probe 1 can selectively probe GSH over Cys and Hcy or Cys over GSH and Hcy in HeLa cells through multicolor imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

Thioflavin T as an efficient fluorescence sensor for selective recognition of RNA G-quadruplexes

NASA Astrophysics Data System (ADS)

Xu, Shujuan; Li, Qian; Xiang, Junfeng; Yang, Qianfan; Sun, Hongxia; Guan, Aijiao; Wang, Lixia; Liu, Yan; Yu, Lijia; Shi, Yunhua; Chen, Hongbo; Tang, Yalin

2016-04-01

RNA G-quadruplexes (G4s) play important roles in translational regulation, mRNA processing events and gene expression. Therefore, a fluorescent probe that is capable of efficiently recognizing RNA G-quadruplex structures among other RNA forms is highly desirable. In this study, a water-soluble fluorogenic dye (i.e., Thioflavin T (ThT)) was employed to recognize RNA G-quadruplex structures using UV-Vis absorption spectra, fluorescence spectra and emission lifetime experiments. By stacking on the G-tetrad, the ThT probe exhibited highly specific recognition of RNA G-quadruplex structures with striking fluorescence enhancement compared with other RNA forms. The specific binding demonstrates that ThT is an efficient fluorescence sensor that can distinguish G4 and non-G4 RNA structures.

Direct observation of single layer graphene oxide reduction through spatially resolved, single sheet absorption/emission microscopy.

PubMed

Sokolov, Denis A; Morozov, Yurii V; McDonald, Matthew P; Vietmeyer, Felix; Hodak, Jose H; Kuno, Masaru

2014-06-11

Laser reduction of graphene oxide (GO) offers unique opportunities for the rapid, nonchemical production of graphene. By tuning relevant reduction parameters, the band gap and conductivity of reduced GO can be precisely controlled. In situ monitoring of single layer GO reduction is therefore essential. In this report, we show the direct observation of laser-induced, single layer GO reduction through correlated changes to its absorption and emission. Absorption/emission movies illustrate the initial stages of single layer GO reduction, its transition to reduced-GO (rGO) as well as its subsequent decomposition upon prolonged laser illumination. These studies reveal GO's photoreduction life cycle and through it native GO/rGO absorption coefficients, their intrasheet distributions as well as their spatial heterogeneities. Extracted absorption coefficients for unreduced GO are α405 nm ≈ 6.5 ± 1.1 × 10(4) cm(-1), α520 nm ≈ 2.1 ± 0.4 × 10(4) cm(-1), and α640 nm ≈ 1.1 ± 0.3 × 10(4) cm(-1) while corresponding rGO α-values are α405 nm ≈ 21.6 ± 0.6 × 10(4) cm(-1), α520 nm ≈ 16.9 ± 0.4 × 10(4) cm(-1), and α640 nm ≈ 14.5 ± 0.4 × 10(4) cm(-1). More importantly, the correlated absorption/emission imaging provides us with unprecedented insight into GO's underlying photoreduction mechanism, given our ability to spatially resolve its kinetics and to connect local rate constants to activation energies. On a broader level, the developed absorption imaging is general and can be applied toward investigating the optical properties of other two-dimensional materials, especially those that are nonemissive and are invisible to current single molecule optical techniques.

Broadband two-photon absorption cross sections of benzothiazole derivatives and benzobisthiazolium salts

NASA Astrophysics Data System (ADS)

Noskovičova, Eva; Lorenc, Dušan; Magdolen, Peter; Sigmundová, Ivica; Zahradník, Pavol; Velič, Dušan

2018-05-01

Two-photon absorption (TPA) cross sections of conjugated donor-π-acceptor dipolar structures containing benzothiazole or benzobisthiazolium moieties are determined in a broad spectral range from 700 nm to 1000 nm using two-photon induced fluorescence technique. The TPA cross section values range from 150 GM to 4600 GM. The largest values are observed in near-infrared region. The dipolar derivative of benzothiazole has the largest TPA cross section of 4600 GM at wavelength of 890 nm. A combination of the large TPA in the near-infrared region and the high emission quantum yield makes these compounds excellent candidates for two-photon fluorescence microscopy.

Absorption and fluorescence properties of chromophoric dissolved organic matter of the eastern Bering Sea in the summer with special reference to the influence of a cold pool

NASA Astrophysics Data System (ADS)

D'Sa, E. J.; Goes, J. I.; Gomes, H.; Mouw, C.

2014-06-01

The absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) are reported for the inner shelf, slope waters and outer shelf regions of the eastern Bering Sea during the summer of 2008, when a warm, thermally stratified surface mixed layer lay over a cold pool (< 2 °C) that occupied the entire middle shelf. CDOM absorption at 355 nm (ag355) and its spectral slope (S) in conjunction with excitation-emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) revealed large variability in the characteristics of CDOM in different regions of the Bering Sea. PARAFAC analysis aided in the identification of three humic-like (components one, two and five) and two protein-like (a tyrosine-like component three, and a tryptophan-like component four) components. In the extensive shelf region, average absorption coefficients at 355 nm (ag355, m-1) and DOC concentrations (μM) were highest in the inner shelf (0.342 ± 0.11 m-1, 92.67 ± 14.60 μM) and lower in the middle (0.226 ± 0.05 m-1, 78.38 ± 10.64 μM) and outer (0.185 ± 0.05 m-1, 79.24 ± 18.01 μM) shelves, respectively. DOC concentrations, however were not significantly different, suggesting CDOM sources and sinks to be uncoupled from DOC. Mean spectral slopes S were elevated in the middle shelf (24.38 ± 2.25 μm-1) especially in the surface waters (26.87 ± 2.39 μm-1) indicating high rates of photodegradation in the highly stratified surface mixed layer, which intensified northwards in the northern middle shelf likely contributing to greater light penetration and to phytoplankton blooms at deeper depths. The fluorescent humic-like components one, two, and five were most elevated in the inner shelf most likely from riverine inputs. Along the productive "green belt" in the outer shelf/slope region, absorption and fluorescence properties indicated the presence of fresh and degraded autochthonous DOM. Near the Unimak Pass region of the Aleutian Islands, low DOC and ag355

Internal standards in fluorescent X-ray spectroscopy1 1 Publication authorized by the Director, U.S. Geological Survey.

USGS Publications Warehouse

Adler, I.; Axelrod, J.M.

1955-01-01

The use of internal standards in the analysis of ores and minerals of widely-varying matrix by means of fluorescent X-ray spectroscopy is frequently the most practical approach. Internal standards correct for absorption and enhancement effects except when an absorption edge falls between the comparison lines or a very strong emission line falls between the absorption edges responsible for the comparison lines. Particle size variations may introduce substantial errors. One method of coping with the particle size problem is grinding the sample with an added abrasive. ?? 1955.

In vitro fluorescence measurements and Monte Carlo simulation of laser irradiation propagation in porcine skin tissue.

PubMed

Drakaki, E; Makropoulou, M; Serafetinides, A A

2008-07-01

In dermatology, the in vivo spectral fluorescence measurements of human skin can serve as a valuable supplement to standard non-invasive techniques for diagnosing various skin diseases. However, quantitative analysis of the fluorescence spectra is complicated by the fact that skin is a complex multi-layered and inhomogeneous organ, with varied optical properties and biophysical characteristics. In this work, we recorded, in vitro, the laser-induced fluorescence emission signals of healthy porcine skin, one of the animals, which is considered as one of the most common models for investigations related to medical diagnostics of human cutaneous tissues. Differences were observed in the form and intensity of the fluorescence signal of the porcine skin, which can be attributed to the different concentrations of the native fluorophores and the variable physical and biological conditions of the skin tissue. As the light transport in the tissue target is directly influencing the absorption and the fluorescence emission signals, we performed Monte Carlo simulation of the light distribution in a five-layer model of human skin tissue, with a pulsed ultraviolet laser beam.

Solvatochromism and preferential solvation of 1,4-dihydroxy-2,3-dimethyl-9,10-anthraquinone by UV-vis absorption and laser-induced fluorescence measurements

NASA Astrophysics Data System (ADS)

Sasirekha, V.; Vanelle, P.; Terme, T.; Ramakrishnan, V.

2008-12-01

Solvation characteristics of 1,4-dihydroxy-2,3-dimethyl-9,10-anthraquinone ( 1) in pure and binary solvent mixtures have been studied by UV-vis absorption spectroscopy and laser-induced fluorescence techniques. The binary solvent mixtures used as CCl 4 (tetrachloromethane)-DMF ( N, N-dimethylformamide), AN (acetonitrile)-DMSO (dimethylsulfoxide), CHCl 3 (chloroform)-DMSO, CHCl 3-MeOH (methanol), and MeOH-DMSO. The longest wavelength band of 1 has been studied in pure solvents as well as in binary solvent mixtures as a function of the bulk mole fraction. The Vis absorption band maxima show an unusual blue shift with increasing solvent polarity. The emission maxima of 1 show changes with varying the pure solvents and the composition in the case of binary solvent mixtures. Non-ideal solvation characteristics are observed in all binary solvent mixtures. It has been observed that the quantity [ ν-(Xν+Xν)] serves as a measure of the extent of preferential solvation, where ν˜ and X are the position of band maximum in wavenumbers (cm -1) and the bulk mole fraction values, respectively. The preferential solvation parameters local mole fraction ( X2L), solvation index ( δs2), and exchange constant ( k12) are evaluated.

A turn-on fluorescence chemosensor based on a tripodal amine [tris(pyrrolyl-α-methyl)amine]-rhodamine conjugate for the selective detection of zinc ions.

PubMed

Balamurugan, Rathinam; Chang, Wen-I; Zhang, Yandison; Fitriyani, Sri; Liu, Jui-Hsiang

2016-09-21

A novel tetradendate ligand derived from a tris(pyrrolyl-α-methyl)amine (H3tpa) and rhodamine-based conjugate (PR) has been designed for use as a sensor, synthesized and characterized spectroscopically. PR {(tris(5-rhodamineiminopyrrol-2-ylmethyl)amine)} serves as a selective colorimetric as well as a fluorescent chemosensor for Zn(2+) in acetonitrile/water (1 : 1, v/v). In the presence of Zn(2+), PR exhibited obvious absorption (558 nm) and emission (577 nm) peaks whose intensity increased along with increasing Zn(2+) concentrations. Titration experiments revealed that a large excess of Zn(2+) was required to saturate the absorption (λmax) and emission intensities. Upon the addition of 1000 equivalents of Zn(2+), the fluorescence intensity of the PR underwent an ∼500-fold increase (Φf = 0.34) with the emission maximum at 580 nm. These kinetics studies demonstrated that the absorption and emission changes were proportional to the Zn(2+) concentration. The color of the solution changed from colorless to a dark pink color. The fluorescence of the PR-Zn(2+) complex can be reversibly restored by using ammonium water or by heating. Competitive ion tests revealed that the intensity of PR-Zn(2+) was not suppressed by excess amounts of other metal ions. The counter anions did not exert obvious influences on the absorption and emission profiles. (1)H-NMR and FT-IR spectroscopic investigations of PR and PR-Zn(2+) revealed that the pyrrole motifs, -C[double bond, length as m-dash]N- groups and spirolactam of rhodamine B are capable of coordinating cation guest species. Because each arm of the tripodal ligand tautomerizes independently, only moderate fluorescence enhancement could be seen until all three -C[double bond, length as m-dash]N- groups were coordinated by zinc, which may be due to the spirolactam ring opening mechanism of the rhodamine unit. Once all three -C[double bond, length as m-dash]N- groups were locked by coordinating with excess of Zn(2+), the

Spatial variability of oceanic phycoerythrin spectral types derived from airborne laser-induced fluorescence emissions

NASA Astrophysics Data System (ADS)

Hoge, Frank E.; Wright, C. Wayne; Kana, Todd M.; Swift, Robert N.; Yungel, James K.

1998-07-01

We report spatial variability of oceanic phycoerythrin spectral types detected by means of a blue spectral shift in airborne laser-induced fluorescence emission. The blue shift of the phycoerythrobilin fluorescence is known from laboratory studies to be induced by phycourobilin chromophore substitution at phycoerythrobilin chromophore sites in some strains of phycoerythrin-containing marine cyanobacteria. The airborne 532-nm laser-induced phycoerythrin fluorescence of the upper oceanic volume showed distinct segregation of cyanobacterial chromophore types in a flight transect from coastal water to the Sargasso Sea in the western North Atlantic. High phycourobilin levels were restricted to the oceanic (oligotrophic) end of the flight transect, in agreement with historical ship findings. These remotely observed phycoerythrin spectral fluorescence shifts have the potential to permit rapid, wide-area studies of the spatial variability of spectrally distinct cyanobacteria, especially across interfacial regions of coastal and oceanic water masses. Airborne laser-induced phytoplankton spectral fluorescence observations also further the development of satellite algorithms for passive detection of phytoplankton pigments. Optical modifications to the NASA Airborne Oceanographic Lidar are briefly described that permitted observation of the fluorescence spectral shifts.

Two-photon absorption laser-induced fluorescence measurements of atomic nitrogen in a radio-frequency atmospheric-pressure plasma jet

NASA Astrophysics Data System (ADS)

Wagenaars, E.; Gans, T.; O'Connell, D.; Niemi, K.

2012-08-01

The first direct measurements of atomic nitrogen species in a radio-frequency atmospheric-pressure plasma jet (APPJ) are presented. Atomic nitrogen radicals play a key role in new plasma medicine applications of APPJs. The measurements were performed with a two-photon absorption laser-induced fluorescence diagnostic, using 206.65 nm laser photons for the excitation of ground-state N atoms and observing fluorescence light around 744 nm. The APPJ was run with a helium gas flow of 1 slm and varying small admixtures of molecular nitrogen of 0-0.7 vol%. A maximum in the measured N concentration was observed for an admixture of 0.25 vol% N2.

A DNA-Encapsulated and Fluorescent Ag 10 6+ Cluster with a Distinct Metal-Like Core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petty, Jeffrey T.; Ganguly, Mainak; Rankine, Ian J.

Silver cluster–DNA complexes are optical chromophores, and pairs of these conjugates can be toggled from fluorescently dim to bright states using DNA hybridization. This paper highlights spectral and structural differences for a specific cluster pair. We have previously characterized a cluster with low emission and violet absorption that forms a compact structure with single-stranded oligonucleotides. We now consider its counterpart with blue absorption and strong green emission. This cluster develops with a single-stranded/duplex DNA construct and is favored by low silver concentrations with ≲8 Ag+:DNA, an oxygen atmosphere, and neutral pH. The resulting cluster displays key signatures of a molecularmore » metal with well-defined absorption/emission bands at 490/550 nm, and with a fluorescence quantum yield of 15% and lifetime of 2.4 ns. The molecular cluster conjugates with the larger DNA host because it chromatographically elutes with the DNA and it exhibits circular dichroism. The silver cluster is identified as Ag106+ using two modes of mass spectrometry and elemental analysis. Our key finding is that it adopts a low-dimensional shape, as determined from a Ag K-edge extended X-ray absorption fine structure analysis. The Ag0 in this oxidized cluster segregates from the Ag+ via a sparse number of metal-like bonds and a denser network of silver–DNA bonds. This structure contrasts with the compact, octahedral-like shape of the violet counterpart to the blue cluster, which is also a Ag106+ species. We consider that the blue- and violet-absorbing clusters may be isomers with shapes that are controlled by the secondary structures of their DNA templates.« less

Research of the fluorescence detection apparatus for nutrients

NASA Astrophysics Data System (ADS)

Wang, Yu; Yan, Huimin; Ni, Xuxiang; Xu, Xiaoyi; Chen, Shibing

2015-10-01

The research of the multifunctional analyzer of Clinical Nutrition, which integrates the absorbance, luminescence, fluorescence and other optical detection methods, can overcome the functional limitations of a single technology on human nutrition analysis, and realize a rapid and accurate analysis of the nutrients. This article focuses on the design of fluorescence detection module that uses a photomultiplier tube(PMT) to detect weak fluorescence, and utilizes the single photon counting method to measure the fluorescence intensity, and then according to the relationship between the fluorescent marker and fluorescence intensity, the concentration of the analyte can be derived. Using fluorescein isothiocyanate(FITC, the most widely used fluorescein currently)to mark antibodies in the experiment, therefore, according to the maximum absorption wavelength and the maximum emission wavelength of the fluorescein isothiocyanate, to select the appropriate filters to set up the optical path. In addition, the fluorescence detection apparatus proposed in this paper uses an aspherical lens with large numerical aperture, in order to improve the capacity of signal acquisition more effectively, and the selective adoption of flexible optical fiber can realize a compact opto-mechanical structure, which is also conducive to the miniaturization of the device. The experimental results show that this apparatus has a high sensitivity, can be used for the detection and analysis of human nutrition.

Real-time monitoring of river water quality using in-line continuous acquisition of fluorescence excitation and emission matrices

NASA Astrophysics Data System (ADS)

Carstea, E.; Baker, A.; Johnson, R.; Reynolds, D. M.

2009-12-01

In-line fluorescence EEM monitoring has been performed over an eleven-day period for Bournbrook River, Birmingham, UK. River water was diverted to a portable laboratory via a continuous flow pump and filter system. Fluorescence excitation-emission matrices data was recorded every 3 minutes using a flow cell (1cm pathlength) coupled to a fiber optic probe. This real-time fluorescence EEM data (Excitation, 225-400 nm at 5 nm steps, emission, 280-500 nm at 2 nm steps) was collected 'in-line'and directly compared with the spectrophotometric properties and physical and chemical parameters of river water samples collected off-line at known time intervals. Over the monitoring period, minor pollution pulses from cross connections were detected and identified hourly along with a random diesel pollution event. This work addresses the practicalities of measuring and detecting fluorescence EEM in the field and discusses the potential of this technological approach for further understanding important hydrological and biogeochemical processes. Problems associated with fouling and system failure are also reported. Example of the data generated from the continuous fluorescence EEM monitoring.

Laser Induced Fluorescence Spectroscopy of Neutral and Ionized Polycyclic Aromatic Hydrocarbons in a Cosmic Simulation Chamber

NASA Astrophysics Data System (ADS)

Bejaoui, Salma; Salama, Farid

2015-08-01

Polycyclic aromatic hydrocarbon (PAH) molecules are considered the best carriers to account for the ubiquitous infrared emission bands. PAHs have also been proposed as candidates to explain the diffuse interstellar bands (DIBs), a series of absorption features seen on the interstellar extinction curve and are plausible carriers for the extended red emission (ERE), a photoluminescent process associated with a wide variety of interstellar environments. Extensive efforts have been devoted over the past two decades to characterize the physical and chemical properties of PAH molecules and ions in space. Absorption spectra of PAH molecules and ions trapped in solid matrices have been compared to the DIBs [1, 2]. Absorption spectra of several cold, isolated gas-phase PAHs have also been measured under experimental conditions that mimic the interstellar conditions [see 3 for a review]. The purpose of this study is to provide a new dimension to the existing spectroscopic database of neutral and single ionized PAHs that is largely based on absorption spectra by adding emission spectroscopy data. The measurements are based on the laser-induced fluorescence (LIF) technique [4] and are performed with the Pulsed Discharge Nozzle (PDN) of the COSmIC laboratory facility at NASA Ames laboratory. The PDN generates plasma in a free supersonic jet expansion to simulate the physical and the chemical conditions in interstellar environments. We focus, here, on the fluorescence spectra of large neutral PAHs and their cations where there is a lack of fluorescence spectroscopy data. The astronomical implications of the data (e.g., ERE) are examinedReferences[1] F. Salama, E. Bakes, L.J. Allamandola, A.G.G.M. Tielens, Astrophys. J., 458 (1996) p.621[2] F. Salama, The ISO Revolution, EDP Sciences, Les Ulis, France (1999) p.65[3] Salama F., In Organic Matter in Space, IAU Symposium 251, Kwok & Sandford Eds.Cambridge University Press,4, S251,(2008), p. 357 (2008) and references therein.[4

Raman scattering and red fluorescence in the photochemical transformation of dry tryptophan particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Chih Wei; Schwab, Mark; Hill, Steven C.

Tryptophan is a fluorescent amino acid common in proteins. Its absorption is largest for wavelengths λ ≲ 290 nm and its fluorescence emissions peak around 300–350 nm, depending upon the local environment. Here we report the observation of red fluorescence near 600 nm emerging from 488-nm continuous-wave (CW) laser photoexcitation of dry tryptophan (Trp) particles. With an excitation intensity below 0.5 kW/cm 2, dry Trp particles yield distinctive Raman scattering peaks in the presence of relatively weak and spectrally broad emissions with λ ~500–700 nm, allowing estimation of particle temperature at low excitation intensities. When the photoexcitation intensity is increasedmore » to 1 kW/cm 2 or more for a few minutes, fluorescence intensity dramatically increases by more than two orders of magnitude. The fluorescence continues to increase in intensity and gradually shift to the red when photoexcitation intensity and the duration of exposure are increased. The resulting products absorb at visible wavelengths and generate red fluorescence with λ ~ 650–800 nm with 633-nm CW laser excitation. In conclusion, we attribute the emergence of orange and red fluorescence in the Trp products to a photochemical transformation that is instigated by weak optical transitions to triplet states in Trp with 488-nm excitation and which may be expedited by a photothermal effect.« less

Raman scattering and red fluorescence in the photochemical transformation of dry tryptophan particles.

PubMed

Lai, Chih Wei; Schwab, Mark; Hill, Steven C; Santarpia, Joshua; Pan, Yong-Le

2016-05-30

Tryptophan is a fluorescent amino acid common in proteins. Its absorption is largest for wavelengths λ ≲ 290 nm and its fluorescence emissions peak around 300-350 nm, depending upon the local environment. Here we report the observation of red fluorescence near 600 nm emerging from 488-nm continuous-wave (CW) laser photoexcitation of dry tryptophan (Trp) particles. With an excitation intensity below 0.5 kW/cm², dry Trp particles yield distinctive Raman scattering peaks in the presence of relatively weak and spectrally broad emissions with λ ∼500-700 nm, allowing estimation of particle temperature at low excitation intensities. When the photoexcitation intensity is increased to 1 kW/cm² or more for a few minutes, fluorescence intensity dramatically increases by more than two orders of magnitude. The fluorescence continues to increase in intensity and gradually shift to the red when photoexcitation intensity and the duration of exposure are increased. The resulting products absorb at visible wavelengths and generate red fluorescence with λ ∼ 650-800 nm with 633-nm CW laser excitation. We attribute the emergence of orange and red fluorescence in the Trp products to a photochemical transformation that is instigated by weak optical transitions to triplet states in Trp with 488-nm excitation and which may be expedited by a photothermal effect.

Raman scattering and red fluorescence in the photochemical transformation of dry tryptophan particles

DOE PAGES

Lai, Chih Wei; Schwab, Mark; Hill, Steven C.; ...

2016-05-19

Tryptophan is a fluorescent amino acid common in proteins. Its absorption is largest for wavelengths λ ≲ 290 nm and its fluorescence emissions peak around 300–350 nm, depending upon the local environment. Here we report the observation of red fluorescence near 600 nm emerging from 488-nm continuous-wave (CW) laser photoexcitation of dry tryptophan (Trp) particles. With an excitation intensity below 0.5 kW/cm 2, dry Trp particles yield distinctive Raman scattering peaks in the presence of relatively weak and spectrally broad emissions with λ ~500–700 nm, allowing estimation of particle temperature at low excitation intensities. When the photoexcitation intensity is increasedmore » to 1 kW/cm 2 or more for a few minutes, fluorescence intensity dramatically increases by more than two orders of magnitude. The fluorescence continues to increase in intensity and gradually shift to the red when photoexcitation intensity and the duration of exposure are increased. The resulting products absorb at visible wavelengths and generate red fluorescence with λ ~ 650–800 nm with 633-nm CW laser excitation. In conclusion, we attribute the emergence of orange and red fluorescence in the Trp products to a photochemical transformation that is instigated by weak optical transitions to triplet states in Trp with 488-nm excitation and which may be expedited by a photothermal effect.« less

Laser-Induced Photofragmentation Fluorescence Imaging of Alkali Compounds in Flames.

PubMed

Leffler, Tomas; Brackmann, Christian; Aldén, Marcus; Li, Zhongshan

2017-06-01

Laser-induced photofragmentation fluorescence has been investigated for the imaging of alkali compounds in premixed laminar methane-air flames. An ArF excimer laser, providing pulses of wavelength 193 nm, was used to photodissociate KCl, KOH, and NaCl molecules in the post-flame region and fluorescence from the excited atomic alkali fragment was detected. Fluorescence emission spectra showed distinct lines of the alkali atoms allowing for efficient background filtering. Temperature data from Rayleigh scattering measurements together with simulations of potassium chemistry presented in literature allowed for conclusions on the relative contributions of potassium species KOH and KCl to the detected signal. Experimental approaches for separate measurements of these components are discussed. Signal power dependence and calculated fractions of dissociated molecules indicate the saturation of the photolysis process, independent on absorption cross-section, under the experimental conditions. Quantitative KCl concentrations up to 30 parts per million (ppm) were evaluated from the fluorescence data and showed good agreement with results from ultraviolet absorption measurements. Detection limits for KCl photofragmentation fluorescence imaging of 0.5 and 1.0 ppm were determined for averaged and single-shot data, respectively. Moreover, simultaneous imaging of KCl and NaCl was demonstrated using a stereoscope with filters. The results indicate that the photofragmentation method can be employed for detailed studies of alkali chemistry in laboratory flames for validation of chemical kinetic mechanisms crucial for efficient biomass fuel utilization.

Quantitative frequency-domain fluorescence spectroscopy in tissues and tissue-like media

NASA Astrophysics Data System (ADS)

Cerussi, Albert Edward

1999-09-01

In the never-ending quest for improved medical technology at lower cost, modern near-infrared optical spectroscopy offers the possibility of inexpensive technology for quantitative and non-invasive diagnoses. Hemoglobin is the dominant chromophore in the 700-900 nm spectral region and as such it allows for the optical assessment of hemoglobin concentration and tissue oxygenation by absorption spectroscopy. However, there are many other important physiologically relevant compounds or physiological states that cannot be effectively sensed via optical methods because of poor optical contrast. In such cases, contrast enhancements are required. Fluorescence spectroscopy is an attractive component of optical tissue spectroscopy. Exogenous fluorophores, as well as some endogenous ones, may furnish the desperately needed sensitivity and specificity that is lacking in near-infrared optical tissue spectroscopy. The main focus of this thesis was to investigate the generation and propagation of fluorescence photons inside tissues and tissue-like media (i.e., scattering dominated media). The standard concepts of fluorescence spectroscopy have been incorporated into a diffusion-based picture that is sometimes referred to as photon migration. The novelty of this work lies in the successful quantitative recovery of fluorescence lifetimes, absolute fluorescence quantum yields, fluorophore concentrations, emission spectra, and both scattering and absorption coefficients at the emission wavelength from a tissue-like medium. All of these parameters are sensitive to the fluorophore local environment and hence are indicators of the tissue's physiological state. One application demonstrating the capabilities of frequency-domain lifetime spectroscopy in tissue-like media is a study of the binding of ethidium bromide to bovine leukocytes in fresh milk. Ethidium bromide is a fluorescent dye that is commonly used to label DNA, and hence visualize chromosomes in cells. The lifetime of

A Method for Eliminating Beam Steering Error for the Modulated Absorption-Emission Thermometry Technique

DTIC Science & Technology

2014-01-01

broadened and merged. It is also suitable for environments where broadband emitters such as soot are present. Radiometric measurements in general can be...emitters such as soot are present. Radiometric measurements in general can be made with very high accuracy. The international temperature scale (ITS...by a fitting to a model. In the case of sooting flames, the emissivity is a result of the nearly black absorption and emission features of soot

A ratiometric fluorescent probe for hydrophobic proteins in aqueous solution based on aggregation-induced emission.

PubMed

Peng, Lu; Wei, Ruirui; Li, Kai; Zhou, Zhaojuan; Song, Panshu; Tong, Aijun

2013-04-07

A novel fluorescent probe 1 is reported here with ratiometric response to hydrophobic proteins (casein) or proteins with hydrophobic pockets (BSA, HSA) through hydrophobic interaction. Probe 1 underwent deprotonation in aqueous solution at pH 7.4 and emitted blue fluorescence at 436 nm. Upon the addition of BSA, HSA or casein, the aggregation-induced emission fluorescence of 1 at 518 nm was turned on. The fluorescence intensity ratio, I518/I436 was linearly related to the concentrations of these proteins. The detection limits for BSA, HSA and casein based on IUPAC (CDL = 3Sb m(-1)) were 16.2 μg mL(-1), 10.5 μg mL(-1) and 5.7 μg mL(-1), respectively.

Molecular hydrogen fluorescence and accretion in far-ultraviolet spectra of classical T Tauri stars

NASA Astrophysics Data System (ADS)

Herczeg, Gregory J.

2005-11-01

Far-ultraviolet spectra of classical T Tauri stars reveal accretion, outflows, and H 2 fluorescence. The E140M echelle spectrograph on HST /STIS and the FUSE satellite offer high spectral resolution and broad wavelength coverage, and enables our unique and detailed analysis of the H 2 lines. A strong and broad Lya emission line excites warm H 2 into many levels of the B and C electronic states, from which we can detect as many as 200 H 2 emission lines. These H2 lines are narrow and often asymmetric, with excess blueshifted emission that can extend to 100 km s -1 from some sources. The fluorescent H 2 emission probes diverse environments around CTTSs. High spectral and spatial resolution are essential for identifying the location and studying the kinematics of the gas, which constrain the origin of the H 2 emission. Several other spectral characteristics, including absorption of H2 emission by the wind and H 2 absorption lines, also provide valuable diagnostics of the origin of this emission. The H 2 emission is most likely produced at the surface of a circumstellar disk in some sources, but is produced by outflows from other sources. DF Tau appears to show H 2 emission from both a disk and an outflow. The excitation of H 2 can be determined from relative line strengths by measuring self-absorption in lines with low-energy lower levels, or by reconstructing the Lya profile incident upon the warm H 2 using the total flux from a single upper level and the opacity in the pumping transition. Based on those diagnostics and the rich H 2 spectrum of TW Hya, the H 2 at the warm disk surface has a column density of log N (H 2 ) = [Special characters omitted.] , a temperature T = [Special characters omitted.] K, and a filling factor of H 2 , as seen by the source of Lya emission, of 0.25 +/- 0.08 (all 2s error bars). The total FUV luminosity from CTTSs ranges from 2 x 10 -3 to 3 x 10 -2 [Special characters omitted.] , much of which is in the Lya line. With the exception of

Size-dependent fluorescence of bioaerosols: Mathematical model using fluorescing and absorbing molecules in bacteria

DOE PAGES

Hill, Steven C.; Williamson, Chatt C.; Doughty, David C.; ...

2015-02-02

This paper uses a mathematical model of fluorescent biological particles composed of bacteria and/or proteins (mostly as in Hill et al., 2013 [23]) to investigate the size-dependence of the total fluorescence emitted in all directions. The model applies to particles which have negligible reabsorption of fluorescence within the particle. The specific particles modeled here are composed of ovalbumin and of a generic Bacillus. The particles need not be spherical, and in some cases need not be homogeneous. However, the results calculated in this paper are for spherical homogeneous particles. Light absorbing and fluorescing molecules included in the model are aminomore » acids, nucleic acids, and several coenzymes. Here the excitation wavelength is 266 nm. The emission range, 300 to 370 nm, encompasses the fluorescence of tryptophan. The fluorescence cross section (C F) is calculated and compared with one set of published measured values. We investigate power law (Ad y) approximations to C F, where d is diameter, and A and y are parameters adjusted to fit the data, and examine how y varies with d and composition, including the fraction as water. The particle's fluorescence efficiency (Q F=C F/geometric-cross-section) can be written for homogeneous particles as Q absR F, where Q abs is the absorption efficiency, and R F, the fraction of the absorbed light emitted as fluorescence, is independent of size and shape. When Q F is plotted vs. m id or mi(m r-1)d, where m=m r+im i is the complex refractive index, the plots for different fractions of water in the particle tend to overlap.« less

Evaluation of potential emission spectra for the reliable classification of fluorescently coded materials

NASA Astrophysics Data System (ADS)

Brunner, Siegfried; Kargel, Christian

2011-06-01

The conservation and efficient use of natural and especially strategic resources like oil and water have become global issues, which increasingly initiate environmental and political activities for comprehensive recycling programs. To effectively reutilize oil-based materials necessary in many industrial fields (e.g. chemical and pharmaceutical industry, automotive, packaging), appropriate methods for a fast and highly reliable automated material identification are required. One non-contacting, color- and shape-independent new technique that eliminates the shortcomings of existing methods is to label materials like plastics with certain combinations of fluorescent markers ("optical codes", "optical fingerprints") incorporated during manufacture. Since time-resolved measurements are complex (and expensive), fluorescent markers must be designed that possess unique spectral signatures. The number of identifiable materials increases with the number of fluorescent markers that can be reliably distinguished within the limited wavelength band available. In this article we shall investigate the reliable detection and classification of fluorescent markers with specific fluorescence emission spectra. These simulated spectra are modeled based on realistic fluorescence spectra acquired from material samples using a modern VNIR spectral imaging system. In order to maximize the number of materials that can be reliably identified, we evaluate the performance of 8 classification algorithms based on different spectral similarity measures. The results help guide the design of appropriate fluorescent markers, optical sensors and the overall measurement system.

Hydrological and Biogeochemical Controls on Absorption and Fluorescence of Dissolved Organic Matter in the Northern South China Sea

NASA Astrophysics Data System (ADS)

Wang, Chao; Guo, Weidong; Li, Yan; Stubbins, Aron; Li, Yizhen; Song, Guodong; Wang, Lei; Cheng, Yuanyue

2017-12-01

The Kuroshio intrusion from the West Philippine Sea (WPS) and mesoscale eddies are important hydrological features in the northern South China Sea (SCS). In this study, absorption and fluorescence of dissolved organic matter (CDOM and FDOM) were determined to assess the impact of these hydrological features on DOM dynamics in the SCS. DOM in the upper 100 m of the northern SCS had higher absorption, fluorescence, and degree of humification than in the Kuroshio Current of the WPS. The results of an isopycnal mixing model showed that CDOM and humic-like FDOM inventories in the upper 100 m of the SCS were modulated by the Kuroshio intrusion. However, protein-like FDOM was influenced by in situ processes. This basic trend was modified by mesoscale eddies, three of which were encountered during the fieldwork (one warm eddy and two cold eddies). DOM optical properties inside the warm eddy resembled those of DOM in the WPS, indicating that warm eddies could derive from the Kuroshio Current through Luzon Strait. DOM at the center of cold eddies was enriched in humic-like fluorescence and had lower spectral slopes than in eddy-free waters, suggesting inputs of humic-rich DOM from upwelling and enhanced productivity inside the eddy. Excess CDOM and FDOM in northern SCS intermediate water led to export to the Pacific Ocean interior, potentially delivering refractory carbon to the deep ocean. This study demonstrated that DOM optical properties are promising tools to study active marginal sea-open ocean interactions.

One-pot and ultrafast synthesis of nitrogen and phosphorus co-doped carbon dots possessing bright dual wavelength fluorescence emission

NASA Astrophysics Data System (ADS)

Sun, Xiangcheng; Brückner, Christian; Lei, Yu

2015-10-01

Very brief microwave heating of aniline, ethylene diamine, and phosphoric acid in water at ambient pressure generated nitrogen and phosphorus co-doped carbon dots (N,P-CDs) that exhibit bright dual blue (centred at 450 nm; 51% quantum yield) and green (centred at 510 nm, 38% quantum yield) fluorescence emission bands. The N,P-CDs were characterized using TEM, XRD, XPS, IR, UV-vis, and fluorescence spectroscopy, demonstrating their partially crystalline carbon, partially amorphous structures, and the incorporation of O, N, and P into the carbogenic scaffold. The N,P-CDs demonstrated excitation-dependent and nearly pH-independent emission properties. The unique dual emission properties lay the foundation for the use of N,P-CDs in ratiometric sensing applications.Very brief microwave heating of aniline, ethylene diamine, and phosphoric acid in water at ambient pressure generated nitrogen and phosphorus co-doped carbon dots (N,P-CDs) that exhibit bright dual blue (centred at 450 nm; 51% quantum yield) and green (centred at 510 nm, 38% quantum yield) fluorescence emission bands. The N,P-CDs were characterized using TEM, XRD, XPS, IR, UV-vis, and fluorescence spectroscopy, demonstrating their partially crystalline carbon, partially amorphous structures, and the incorporation of O, N, and P into the carbogenic scaffold. The N,P-CDs demonstrated excitation-dependent and nearly pH-independent emission properties. The unique dual emission properties lay the foundation for the use of N,P-CDs in ratiometric sensing applications. Electronic supplementary information (ESI) available: Detailed experimental section, XRD, FTIR, explosive sensing and the applications results. See DOI: 10.1039/c5nr05549k

Proton triggered emission and selective sensing of picric acid by the fluorescent aggregates of 6,7-dimethyl-2,3-bis-(2-pyridyl)-quinoxaline.

PubMed

Mazumdar, Prativa; Maity, Samir; Shyamal, Milan; Das, Debasish; Sahoo, Gobinda Prasad; Misra, Ajay

2016-03-14

A heteroatom containing organic fluorophore 6,7-dimethyl-2,3-bis-(2-pyridyl)-quinoxaline (BPQ) is weakly emissive in solution but its emission properties are highly enhanced in the aggregated state due to the restriction of intramolecular rotation (RIR) and large amplitude vibrational modes, demonstrating the phenomenon, aggregation induced emission enhancement (AIEE). It has strong proton capture capability, allowing reversible fluorescence switching in basic and acidic medium and the emission color changes from blue to green in the aggregated state through protonation. It has been explained as a competition between intramolecular charge transfers (ICTs) and the AIEE phenomena at a lower pH range (pH ∼1-4). Such behavior enables it as a fluorescent pH sensor for detection in acidic and basic medium. Morphologies of the particles are characterized using optical and field emission scanning electron microscopic (FESEM) studies. The turn off fluorescence properties of aggregated BPQ have been utilized for the selective detection of picric acid and the fluorescence quenching is explained due to ground state complexation with a strong quenching constant, 7.81 × 10(4) M(-1).

Bifunctional Diaminoterephthalate Fluorescent Dye as Probe for Cross-Linking Proteins.

PubMed

Wallisch, Melanie; Sulmann, Stefan; Koch, Karl-Wilhelm; Christoffers, Jens

2017-05-11

Diaminoterephthalates are fluorescent dyes and define scaffolds, which can be orthogonally functionalized at their two carboxylate residues with functional residues bearing task specific reactive groups. The synthesis of monofunctionalized dyes with thiol groups for surface binding, an azide for click chemistry, and a biotinoylated congener for streptavidin binding is reported. Two bifunctionalized dyes were prepared: One with an azide for click chemistry and a biotin for streptavidin binding, the other with a maleimide for reaction with thiol and a cyclooctyne moiety for ligation with copper-free click chemistry. In general, the compounds are red to orange, fluorescent materials with an absorption at about 450 nm and an emission at 560 nm with quantum yields between 2-41 %. Of particular interest is the maleimide-functionalized compound, which shows low fluorescence quantum yield (2 %) by itself. After addition of a thiol, the fluorescence is "turned on"; quantum yield 41 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Far-ultraviolet Fluorescent Molecular Hydrogen Emission Map of the Milky Way Galaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jo, Young-Soo; Min, Kyoung-Wook; Seon, Kwang-Il

We present the far-ultraviolet (FUV) fluorescent molecular hydrogen (H{sub 2}) emission map of the Milky Way Galaxy obtained with FIMS/SPEAR covering ∼76% of the sky. The extinction-corrected intensity of the fluorescent H{sub 2} emission has a strong linear correlation with the well-known tracers of the cold interstellar medium (ISM), including color excess E(B–V) , neutral hydrogen column density N (H i), and H α emission. The all-sky H{sub 2} column density map was also obtained using a simple photodissociation region model and interstellar radiation fields derived from UV star catalogs. We estimated the fraction of H{sub 2} ( f {submore » H2}) and the gas-to-dust ratio (GDR) of the diffuse ISM. The f {sub H2} gradually increases from <1% at optically thin regions where E(B–V) < 0.1 to ∼50% for E(B–V)  = 3. The estimated GDR is ∼5.1 × 10{sup 21} atoms cm{sup −2} mag{sup −1}, in agreement with the standard value of 5.8 × 10{sup 21} atoms cm{sup −2} mag{sup −1}.« less

Reduced Fluorescent Protein Switching Fatigue by Binding-Induced Emissive State Stabilization

PubMed Central

Dedecker, Peter

2017-01-01

Reversibly switchable fluorescent proteins (RSFPs) enable advanced fluorescence imaging, though the performance of this imaging crucially depends on the properties of the labels. We report on the use of an existing small binding peptide, named Enhancer, to modulate the spectroscopic properties of the recently developed rsGreen series of RSFPs. Fusion constructs of Enhancer with rsGreen1 and rsGreenF revealed an increased molecular brightness and pH stability, although expression in living E. coli or HeLa cells resulted in a decrease of the overall emission. Surprisingly, Enhancer binding also increased off-switching speed and resistance to switching fatigue. Further investigation suggested that the RSFPs can interconvert between fast- and slow-switching emissive states, with the overall protein population gradually converting to the slow-switching state through irradiation. The Enhancer modulates the spectroscopic properties of both states, but also preferentially stabilizes the fast-switching state, supporting the increased fatigue resistance. This work demonstrates how the photo-physical properties of RSFPs can be influenced by their binding to other small proteins, which opens up new horizons for applications that may require such modulation. Furthermore, we provide new insights into the photoswitching kinetics that should be of general consideration when developing new RSFPs with improved or different photochromic properties. PMID:28930199

Highly Photostable Near-Infrared Fluorescent pH Indicators and Sensors Based on BF2-Chelated Tetraarylazadipyrromethene Dyes

PubMed Central

2012-01-01

In this study, a series of new BF2-chelated tetraarylazadipyrromethane dyes are synthesized and are shown to be suitable for the preparation of on/off photoinduced electron transfer modulated fluorescent sensors. The new indicators are noncovalently entrapped in polyurethane hydrogel D4 and feature absorption maxima in the range 660–710 nm and fluorescence emission maxima at 680–740 nm. Indicators have high molar absorption coefficients of ∼80 000 M–1 cm–1, good quantum yields (up to 20%), excellent photostability and low cross-sensitivity to the ionic strength. pKa values of indicators are determined from absorbance and fluorescence measurements and range from 7 to 11, depending on the substitution pattern of electron-donating and -withdrawing functionalities. Therefore, the new indicators are suitable for exploitation and adaptation in a diverse range of analytical applications. Apparent pKa values in sensor films derived from fluorescence data show 0.5–1 pH units lower values in comparison with those derived from the absorption data due to Förster resonance energy transfer from protonated to deprotonated form. A dual-lifetime referenced sensor is prepared, and application for monitoring of pH in corals is demonstrated. PMID:22738322

High-performance hybrid white organic light-emitting devices without interlayer between fluorescent and phosphorescent emissive regions.

PubMed

Sun, Ning; Wang, Qi; Zhao, Yongbiao; Chen, Yonghua; Yang, Dezhi; Zhao, Fangchao; Chen, Jiangshan; Ma, Dongge

2014-03-12

By using mixed hosts with bipolar transport properties for blue emissive layers, a novel phosphorescence/fluorescence hybrid white OLED without using an interlayer between the fluorescent and phosphorescent regions is demonstrated. The peak EQE of the device is 19.0% and remains as high as 17.0% at the practical brightness of 1000 cd m(-2) . © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ag-protein plasmonic architectures for surface plasmon-coupled emission enhancements and Fabry-Perot mode-coupled directional fluorescence emission

NASA Astrophysics Data System (ADS)

Badiya, Pradeep Kumar; Patnaik, Sai Gourang; Srinivasan, Venkatesh; Reddy, Narendra; Manohar, Chelli Sai; Vedarajan, Raman; Mastumi, Noriyoshi; Belliraj, Siva Kumar; Ramamurthy, Sai Sathish

2017-10-01

We report the use of silver decorated plant proteins as spacer material for augmented surface plasmon-coupled emission (120-fold enhancement) and plasmon-enhanced Raman scattering. We extracted several proteins from different plant sources [Triticum aestivum (TA), Aegle marmelos (AM), Ricinus communis (RC), Jatropha curcas (JC) and Simarouba glauca (SG)] followed by evaluation of their optical properties and simulations to rationalize observed surface plasmon resonance. Since the properties exhibited by protein thin films is currently gaining research interest, we have also carried out simulation studies with Ag-protein biocomposites as spacer materials in metal-dielectric-metal planar microcavity architecture for guided emission of Fabry-Perot mode-coupled fluorescence.

Controlling photophysics of styrylnaphthalimides through TICT, fluorescence and E,Z-photoisomerization interplay.

PubMed

Panchenko, Pavel A; Arkhipova, Antonina N; Fedorova, Olga A; Fedorov, Yuri V; Zakharko, Marina A; Arkhipov, Dmitry E; Jonusauskas, Gediminas

2017-01-04

The photophysical properties of naphthalimide dyes NI1-3 with electron releasing 4-methoxy- (NI1), 3,4-dimethoxystyryl- (NI2) and dimethylaminostyryl (NI3) groups are examined in a variety of protic and aprotic solvents. All compounds demonstrate positive solvatochromism in the steady-state absorption and fluorescence spectra. The analysis of the dependence of the Stokes shift on the polarity of the solvent using the Lippert-Mataga equation allowed us to determine the change in the dipole moment upon excitation. The obtained data correspond to the formation of highly polar charge transfer states. Based on the transient absorption spectra and time-resolved fluorescence measurements, the presence of two different emissive states was definitely proved. The primarily formed planar Local Excited (LE) state dominates in non-polar solvents like cyclohexane and toluene where it relaxes mostly through fluorescence and E,Z-isomerisation pathways. In polar solvents, an alternative relaxation channel emerges that consists of twisting around single bond between styryl and naphthalimide fragments, which leads to the formation of a Twisted Intramolecular Charge Transfer (TICT) state. The factors affecting the fluorescence of TICT states are discussed. The observed spectral effects are rationalized using quantum-chemical calculations, X-ray data and NMR spectroscopy.

Structure of fluorescent metal clusters on a DNA template.

NASA Astrophysics Data System (ADS)

Vdovichev, A. A.; Sych, T. S.; Reveguk, Z. V.; Smirnova, A. A.; Maksimov, D. A.; Ramazanov, R. R.; Kononov, A. I.

2016-08-01

Luminescent metal clusters are a subject of growing interest in recent years due to their bright emission from visible to near infrared range. Detailed structure of the fluorescent complexes of Ag and other metal clusters with ligands still remains a challenging task. In this joint experimental and theoretical study we synthesized Ag-DNA complexes on a DNA oligonucleotide emitting in violet- green spectral range. The structure of DNA template was determined by means of various spectral measurements (CD, MS, XPS). Comparison of the experimental fluorescent excitation spectra and calculated absorption spectra for different QM/MM optimized structures allowed us to determine the detailed structure of the green cluster containing three silver atoms in the stem of the DNA hairpin structure stabilized by cytosine-Ag+-cytosine bonds.

Synthesis, spectral behaviour and photophysics of donor-acceptor kind of chalcones: Excited state intramolecular charge transfer and fluorescence quenching studies

NASA Astrophysics Data System (ADS)

Pannipara, Mehboobali; Asiri, Abdullah M.; Alamry, Khalid A.; Arshad, Muhammad N.; El-Daly, Samy A.

2015-02-01

The spectral and photophysical properties of two chalcones containing electron donating and accepting groups with intramolecular charge transfer characteristics were synthesized and characterized by 1H NMR, 13C NMR and X-ray crystallography. Both compounds show very strong solvent polarity dependent changes in their photophysical characteristics, namely, remarkable red shift in the emission spectra with increasing solvent polarity, large change in Stokes shift, significant reduction in the fluorescence quantum yield; indicating that the fluorescence states of these compounds are of intramolecular charge transfer (ICT) character. The solvent effect on the photophysical parameters such as singlet absorption, molar absorptivity, oscillator strength, dipole moment, fluorescence spectra, and fluorescence quantum yield of both compounds have been investigated comprehensively. For both dyes, Lippert-Mataga and Reichardt's correlations were used to estimate the difference between the excited and ground state dipole moments (Δμ). The interactions of dyes with colloidal silver nanoparticles (Ag NPs) were also studied in ethanol using steady state fluorescence quenching measurements. The fluorescence quenching data reveal that dynamic quenching and energy transfer play a major role in the fluorescence quenching of dyes by Ag NPs.

Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for vanadium(V) detection in mineral water samples

NASA Astrophysics Data System (ADS)

He, Lijun; Zhang, Heng; Fan, Huanhuan; Jiang, Xiuming; Zhao, Wenjie; Xiang, Guo Qiang

2018-01-01

Herein, we propose a simple and effective strategy for designing a ratiometric fluorescent nanosensor. We designed and developed a carbon dots (CDs) based dual-emission nanosensor for vanadium(V) by coating the surface of dye-doped silica nanoparticles with CDs. The fluorescence of dual-emission silica nanoparticles was quenched in acetic acid through potassium bromate (KBrO3) oxidation. V(V) could catalyze KBrO3 oxidation reaction process, resulting in the ratiometric fluorescence quenching of dual-emission silica nanoparticles. We investigated several important parameters affecting the performance of the nanosensor. Under the optimized conditions, the detection limit of this nanosensor reached 1.1 ng mL- 1 and the linear range from 10 to 800 ng mL- 1. Furthermore, we found that the sensor was suitable for determination of V(V) in different mineral water samples with satisfactory results.

Absorption and fluorescence spectroscopic characterisation of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry)

NASA Astrophysics Data System (ADS)

Shirdel, J.; Zirak, P.; Penzkofer, A.; Breitkreuz, H.; Wolf, E.

2008-09-01

The absorption and fluorescence behaviour of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry) in a pH 8 aqueous buffer solution is studied. The flavin adenine dinucleotide (FAD) cofactor of dCry is identified to be present in its oxidized form (FAD ox), and the 5,10-methenyltetrahydrofolate (MTHF) cofactor is found to be hydrolyzed and oxidized to 10-formyldihydrofolate (10-FDHF). The absorption and the fluorescence behaviour of dCry is investigated in the dark-adapted (receptor) state, the light-adapted (signalling) state, and under long-time violet light exposure. Photo-excitation of FAD ox in dCry causes a reductive electron transfer to the formation of anionic FAD semiquinone (FAD rad - ), and photo-excitation of the generated FAD rad - causes an oxidative electron transfer to the back formation of FAD ox. In light adapted dCry a photo-induced equilibrium between FAD ox and FAD rad - exists. The photo-cycle dynamics of signalling state formation and recovery is discussed. Quantum yields of photo-induced signalling state formation of about 0.2 and of photo-induced back-conversion of about 0.2 are determined. A recovery of FAD rad - to FAD ox in the dark with a time constant of 1.6 min at room temperature is found.

Fluorescence lifetime spectroscopy in multiple-scattering environments: an application to biotechnology

NASA Astrophysics Data System (ADS)

Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio

1999-07-01

Over the past few years, there has been significant research activity devoted to the application of fluorescence spectroscopy to strongly scattering media, where photons propagate diffusely. Much of this activity focused on fluorescence as a source of contrast enhancement in optical tomography. Our efforts have emphasized the quantitative recovery of fluorescence parameters for spectroscopy. Using a frequency-domain diffusion-based model, we have successfully recovered the lifetime, the absolute quantum yield, the fluorophore concentration, and the emission spectrum of the fluorophore, as well as the absorption and the reduced scattering coefficients at the emission wavelength of the medium in different measurements. In this contribution, we present a sensitive monitor of the binding between ethidium bromide and bovine cells in fresh milk. The spectroscopic contrast was the approximately tenfold increase in the ethidium bromide lifetime upon binding to DNA. The measurement clearly demonstrated that we could quantitatively measure the density of cells in the milk, which is an application vital to the tremendous economic burden of bovine subclinical mastitis detection. Furthermore, we may in principle use the spirit of this technique as a quantitative monitor of the binding of fluorescent drugs inside tissues. This is a first step towards lifetime spectroscopy in tissues.

Fluorenyl benzothiadiazole and benzoselenadiazole near-IR fluorescent probes for two-photon fluorescence imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Belfield, Kevin D.; Yao, Sheng; Kim, Bosung; Yue, Xiling

2016-03-01

Imaging biological samples with two-photon fluorescence (2PF) microscopy has the unique advantage of resulting high contrast 3D resolution subcellular image that can reach up to several millimeters depth. 2PF probes that absorb and emit at near IR region need to be developed. Two-photon excitation (2PE) wavelengths are less concerned as 2PE uses wavelengths doubles the absorption wavelength of the probe, which means 2PE wavelengths for probes even with absorption at visible wavelength will fall into NIR region. Therefore, probes that fluoresce at near IR region with high quantum yields are needed. A series of dyes based on 5-thienyl-2, 1, 3-benzothiadiazole and 5-thienyl-2, 1, 3-benzoselenadiazole core were synthesized as near infrared two-photon fluorophores. Fluorescence maxima wavelengths as long as 714 nm and fluorescence quantum yields as high as 0.67 were achieved. The fluorescence quantum yields of the dyes were nearly constant, regardless of solvents polarity. These diazoles exhibited large Stokes shift (<114nm), high two-photon absorption cross sections (up to 2,800 GM), and high two-photon fluorescence figure of merit (FM , 1.04×10-2 GM). Cells incubated on a 3D scaffold with one of the new probes (encapsulated in Pluronic micelles) exhibited bright fluorescence, enabling 3D two-photon fluorescence imaging to a depth of 100 µm.

Application of fluorescence spectroscopy and imaging in the detection of a photosensitizer in photodynamic therapy

NASA Astrophysics Data System (ADS)

Zang, Lixin; Zhao, Huimin; Zhang, Zhiguo; Cao, Wenwu

2017-02-01

Photodynamic therapy (PDT) is currently an advanced optical technology in medical applications. However, the application of PDT is limited by the detection of photosensitizers. This work focuses on the application of fluorescence spectroscopy and imaging in the detection of an effective photosenzitizer, hematoporphyrin monomethyl ether (HMME). Optical properties of HMME were measured and analyzed based on its absorption and fluorescence spectra. The production mechanism of its fluorescence emission was analyzed. The detection device for HMME based on fluorescence spectroscopy was designed. Ratiometric method was applied to eliminate the influence of intensity change of excitation sources, fluctuates of excitation sources and photo detectors, and background emissions. The detection limit of this device is 6 μg/L, and it was successfully applied to the diagnosis of the metabolism of HMME in the esophageal cancer cells. To overcome the limitation of the point measurement using fluorescence spectroscopy, a two-dimensional (2D) fluorescence imaging system was established. The algorithm of the 2D fluorescence imaging system is deduced according to the fluorescence ratiometric method using bandpass filters. The method of multiple pixel point addition (MPPA) was used to eliminate fluctuates of signals. Using the method of MPPA, SNR was improved by about 30 times. The detection limit of this imaging system is 1.9 μg/L. Our systems can be used in the detection of porphyrins to improve the PDT effect.

Application of excitation and emission matrix fluorescence (EEM) and UV-vis absorption to monitor the characteristics of Alizarin Red S (ARS) during electro-Fenton degradation process.

PubMed

Lai, Bo; Zhou, Yuexi; Wang, Juling; Yang, Zhishan; Chen, Zhiqiang

2013-11-01

Oxidative degradation of Alizarin Red S (ARS) in aqueous solutions by using electro-Fenton was studied. At first, effect of operating parameters such as current density, aeration rate and initial pH on the degradation of ARS were studied by using UV-vis spectrum, respectively. Then, under the optimal operating conditions (current density: 10.0mAcm(-2), aeration rate: 1000mLmin(-1), initial pH: 2.8), the identification of degradation products of ARS was carried out by using GC-MS and HPLC, meanwhile its degradation pathway was proposed according to the intermediates. Considering the location, intensity and intensity ratio of fluorescence center peak of the ARS in aqueous solution, a convenient and quick monitoring method by using excitation-emission matrix fluorescence spectrum technology was developed to monitor the degradation degree of ARS through electro-Fenton process. Furthermore, it is suggested that the developed method would be promising for the quick analysis and evaluation of the degradation degree of the pollutants with π-conjugated system. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fluorescent magnetic hybrid nanoprobe for multimodal bioimaging

PubMed Central

Bright, Vanessa

2011-01-01

A fluorescent magnetic hybrid imaging nanoprobe (HINP) was fabricated by conjugation of superparamagnetic Fe3O4 nanoparticles and visible light-emitting (~600 nm) fluorescent CdTe/CdS quantum dots (QDs). The assembly strategy used the covalent linking of the oxidized dextran shell of magnetic particles to the glutathione ligands of QDs. Synthesized HINP formed stable water-soluble colloidal dispersions. The structure and properties of the particles were characterized by transmission electron and atomic force microscopy, energy dispersive X-ray analysis and inductively coupled plasma optical emission spectroscopy, dynamic light scattering analysis, optical absorption and photoluminescence spectroscopy, and fluorescent imaging. The luminescence imaging region of the nanoprobe was extended to the near-infrared (NIR) (~800 nm) by conjugation of superparamagnetic nanoparticles with synthesized CdHgTe/CdS QDs. Cadmium, mercury based QDs in HINP can be easily replaced by novel water soluble glutathione stabilized AgInS2/ZnS QDs to present a new class of cadmium-free multimodal imaging agents. Observed NIR photoluminescence of fluorescent magnetic nanocomposites supports their use for bioimaging. The developed HINP provides dual-imaging channels for simultaneous optical and magnetic resonance imaging. PMID:21597146

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.

Fe II fluorescence and anomalous C IV doublet intensities in symbiotic novae

NASA Technical Reports Server (NTRS)

Michalitsianos, A. G.; Kafatos, M.; Meier, S. R.

1992-01-01

The variation of absolute intensities of Bowen-excited Fe II emission in the symbiotic stars RR Tel, RX Pup, and AG Peg is examined. The C IV doublet intensity ratios in RR Tel were not anomalous between 1979 and 1989, and the ratio had typical values within the optically thin range. The intensity of individual Fe II Bowen-excited lines is correlated with the C IV 1548.2 A flux, suggesting the presence of a foreground Fe II region in which fluorescent-excited material responds to flux variations of C IV 1548.2 A. In RX Pup the combined fluxes of Fe II Bowen-pumped lines can account for an appreciable fraction of the flux deficit in the C IV 1548.2 A line when the C IV doublet ratio is less than the optically thick limit of unity. The Fe II Bowen lines in RX Pup exhibit a velocity range from 0 to 80 km/s, where several strong Fe II emission lines correspond to deep absorption structure in the C IV 1548.2 A line profile. In AG Peg and C IV 1548.2 A flux deficit cannot be explained by Fe II fluorescent absorption alone when the C IV doublet ratio anomaly is at an extreme.

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.

Ongoing advances in quantitative PpIX fluorescence guided intracranial tumor resection (Conference Presentation)

NASA Astrophysics Data System (ADS)

Olson, Jonathan D.; Kanick, Stephen C.; Bravo, Jaime J.; Roberts, David W.; Paulsen, Keith D.

2016-03-01

Aminolevulinc-acid induced protoporphyrin IX (ALA-PpIX) is being investigated as a biomarker to guide neurosurgical resection of brain tumors. ALA-PpIX fluorescence can be observed visually in the surgical field; however, raw fluorescence emissions can be distorted by factors other than the fluorophore concentration. Specifically, fluorescence emissions are mixed with autofluorescence and attenuated by background absorption and scattering properties of the tissue. Recent work at Dartmouth has developed advanced fluorescence detection approaches that return quantitative assessments of PpIX concentration, which are independent of background optical properties. The quantitative fluorescence imaging (qFI) approach has increased sensitivity to residual disease within the resection cavity at the end of surgery that was not visible to the naked eye through the operating microscope. This presentation outlines clinical observations made during an ongoing investigation of ALA-PpIX based guidance of tumor resection. PpIX fluorescence measurements made in a wide-field hyperspectral imaging approach are co-registered with point-assessment using a fiber optic probe. Data show variations in the measured PpIX accumulation among different clinical tumor grades (i.e. high grade glioma, low grade glioma), types (i.e. primary tumors. metastases) and normal structures of interest (e.g. normal cortex, hippocampus). These results highlight the contrast enhancement and underscore the potential clinical benefit offered from quantitative measurements of PpIX concentration during resection of intracranial tumors.

A two photon absorption laser induced fluorescence diagnostic for fusion plasmas.

PubMed

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

2012-10-01

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(2)), narrow bandwidth (0.1 cm(-1)) laser is injected into a hydrogen plasma to excite the Lyman β transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer α 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.

A two photon absorption laser induced fluorescence diagnostic for fusion plasmasa)

NASA Astrophysics Data System (ADS)

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.

2012-10-01

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/cm2), narrow bandwidth (0.1 cm-1) laser is injected into a hydrogen plasma to excite the Lyman β transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer α 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.

Dual emission fluorescent silver nanoclusters for sensitive detection of the biological coenzyme NAD+/NADH.

PubMed

Yuan, Yufeng; Huang, Kehan; Chang, Mengfang; Qin, Cuifang; Zhang, Sanjun; Pan, Haifeng; Chen, Yan; Xu, Jianhua

2016-02-01

Fluorescent silver nanoclusters (Ag NCs) displaying dual-excitation and dual-emission properties have been developed for the specific detection of NAD(+) (nicotinamide adenine dinucleotide, oxidized form). With the increase of NAD(+) concentrations, the longer wavelength emission (with the peak at 550 nm) was gradually quenched due to the strong interactions between the NAD(+) and Ag NCs, whereas the shorter wavelength emission (peaking at 395 nm) was linearly enhanced. More important, the dual-emission intensity ratio (I395/I550), fitting by a single-exponential decay function, can efficiently detect various NAD(+) levels from 100 to 4000 μM, as well as label NAD(+)/NADH (reduced form of NAD) ratios in the range of 1-50. Copyright © 2015 Elsevier Inc. All rights reserved.

Multiphoton-gated cycloreversion reaction of a fluorescent diarylethene derivative as revealed by transient absorption spectroscopy.

PubMed

Nagasaka, Tatsuhiro; Kunishi, Tomohiro; Sotome, Hikaru; Koga, Masafumi; Morimoto, Masakazu; Irie, Masahiro; Miyasaka, Hiroshi

2018-06-07

The one- and two-photon cycloreversion reactions of a fluorescent diarylethene derivative with oxidized benzothiophene moieties were investigated by means of ultrafast laser spectroscopy. Femtosecond transient absorption spectroscopy under the one-photon excitation condition revealed that the excited closed-ring isomer is simply deactivated into the initial ground state with a time constant of 2.6 ns without remarkable cycloreversion, the results of which are consistent with the very low cycloreversion reaction yield (<10-5) under steady-state light irradiation. On the other hand, an efficient cycloreversion reaction was observed under irradiation with a picosecond laser pulse at 532 nm. The excitation intensity dependence of the cycloreversion reaction indicates that a highly excited state attained by the stepwise two-photon absorption is responsible for the marked increase of the cycloreversion reaction, and the quantum yield at the highly excited state was estimated to be 0.018 from quantitative analysis, indicating that the reaction is enhanced by a factor of >1800.

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

Metal-Enhanced Fluorescence from Nanoparticulate Zinc Films

PubMed Central

Aslan, Kadir; Previte, Michael J.R.; Zhang, Yongxia; Geddes, Chris D.

2009-01-01

A detailed study of metal-enhanced fluorescence (MEF) from fluorophores in the blue-to- red spectral region placed in close proximity to thermally evaporated zinc nanostructured films is reported. The zinc nanostructured films were deposited onto glass microscope slides as individual particles and were 1–10 nm in height and 20–100 nm in width, as characterized by Atomic Force Microscopy. The surface plasmon resonance peak of the zinc nanostructured films was ≈ 400 nm. Finite-difference time-domain calculations for single and multiple nanostructures organized in a staggered fashion on a solid support predict, as expected, that the electric fields are concentrated both around and between the nanostructures. Additionally, Mie scattering calculations show that the absorption and scattering components of the extinction spectrum are dominant in the UV and visible spectral ranges, respectively. Enhanced fluorescence emission accompanied by no significant changes in excited state lifetimes of fluorophores with emission wavelengths in the visible blue-to-red spectral range near-to zinc nanostructured films were observed, implying that MEF from zinc nanostructured films is mostly due to an electric field enhancement effect. PMID:19946356

Ultraviolet continuum and H2 fluorescent emission in Herbig-Haro objects 43 and 47

NASA Technical Reports Server (NTRS)

Schwartz, R. D.

1983-01-01

IUE short wavelength spectra are presented for the low excitation Herbig-Haro objects HH 43 and HH 47. In the former, several emission lines in the Lyman band of H2 from an excited state are observed which are due to fluorescence from the H Ly-alpha line pumping a lower state (that is in turn excited by a low-velocity shock wave). No evidence of highly ionized gas emission is found in the UV spectra, and both objects exhibit a UV continuum which peaks in the vicinity of 1500 A and is probably caused by H two-photon emission enhanced by low velocity shock collisional excitation.

Studies on interaction of an intramolecular charge transfer fluorescence probe: 4'-dimethylamino-2,5-dihydroxychalcone with DNA.

PubMed

Xu, Zhicheng; Bai, Guan; Dong, Chuan

2005-10-15

The interaction of a new intramolecular charge transfer probe, namely 4'-dimethylamino-2,5-dihydroxychalcone (DMADHC), with calf thymus DNA has been studied. Compared to the spectral characteristics of the free form in aqueous solution, the fluorescence of DMADHC enhanced dramatically accompanying a blueshift of the emission maxima in the presence of DNA. The absorption and fluorescence spectra, salt concentration effect, KI quenching, fluorescence polarization, and DNA denaturation experiments were given. These results give evidence that the DMADHC molecule is inserted into the base-stacking domain of the DNA double helix. The intrinsic binding constant and the binding site number were estimated. The analytical characteristics were also given.

The influence of surface plasmons on fluorescence of the dye Lumogen F red 300 in condensed phase

NASA Astrophysics Data System (ADS)

Reisfeld, Renata; Levchenko, Viktoria

2017-01-01

The paper is divided to two parts one is a short description of scientific activity of Georges Boulon and my long standing friendship with him, the second part consists of the new findings of increasing fluorescence by surface plasmons studies performed recently in Jerusalem. We describe the synthesis of copper nanoparticles and their incorporation into polyvinylpyrrolidone and into sol-gel matrix co-doped with the fluorescent dye Lumogen F Red 300. The absorption and emission spectra of samples undoped and co-doped with nanoparticles reveal the increase of fluorescence of the dye in presence of copper nanoparticles. The phenomenon arises from scattered light by the nanoparticles.

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

[The research of UV-responsive sensitivity enhancement of fluorescent coating films by MgF2 layer].

PubMed

Lu, Zhong-Rong; Ni, Zheng-Ji; Tao, Chun-Xian; Hong, Rui-Jin; Zhang, Da-Wei; Huang, Yuan-Shen

2014-03-01

A low cost and less complicated expansion approach of wavelength responses with a Lumogen phosphor coating was adopted, as they increased the quantum efficiency of CCD and CMOS detectors in ultra-violet by absorbing UV light and then re emitting visible light. In this paper, the sensitivity enhancement of fluorescence coatings was studied by adding an anti-reflection film or barrier film to reduce the loss of the scattering and reflection on the incident interface. The Lumogen and MgF2/Lumogen film were deposited on quartz glasses by physical vacuum deposition. The surface morphology, transmittance spectrum, reflectance spectrum and fluorescence emission spectrum were obtained by atomic force microscope (AFM), spectrophotometer and fluorescence spectrometer, respectively. The results indicated that MgF2 film had obvious positive effect on reducing scattering and reflection loss in 500-700 nm, and enhancing the absorption of Lumogen coating in ultraviolet spectrum. Meanwhile, the fluorescent emission intensity had a substantial increase by smoothing the film surface and thus reducing the light scattering. At the same time, the MgF2 layer could protect Lumogen coating from damaging and contamination, which give a prolong lifetime of the UV-responsive CCD sensors with fluorescent coatings.

Enhanced emission of nile red fluorescent nanoparticles embedded in hybrid sol-gel glasses.

PubMed

Ferrer, Maria L; del Monte, Francisco

2005-01-13

Highly fluorescent Nile Red (NR) nanoparticles embedded in a hybrid sol-gel glass are reported. The crystallite growth within the confined system created by the porous hybrid matrix results in NR nanoparticles of averaged dimensions below 36 nm. The preparation process allows for the control of both the conformation adopted by single NR molecules prior to aggregation (e.g., near planar) and the configuration of the aggregates (e.g., oblique with phi < 54.7 degrees) prior to their assembly in the supramolecular architecture which ultimately forms the nanoparticles. The full preservation of the fluorescent configuration of the aggregates in the nanoparticles is confirmed through the application of the exciton theory, and it is responsible for the significant increase of the fluorescence emission intensity (e.g., up to 525- and 70-fold as compared to that obtained for single NR molecules embedded in pure and hybrid silica glasses, respectively).

Calculated hydroxyl A2 sigma --> X2 pi (0, 0) band emission rate factors applicable to atmospheric spectroscopy

NASA Technical Reports Server (NTRS)

Cageao, R. P.; Ha, Y. L.; Jiang, Y.; Morgan, M. F.; Yung, Y. L.; Sander, S. P.

1997-01-01

A calculation of the A2 sigma --> X2 pi (0, 0) band emission rate factors and line center absorption cross sections of OH applicable to its measurement using solar resonant fluorescence in the terrestrial atmosphere is presented in this paper. The most accurate available line parameters have been used. Special consideration has been given to the solar input flux because of its highly structured Fraunhofer spectrum. The calculation for the OH atmospheric emission rate factor in the solar resonant fluorescent case is described in detail with examples and intermediate results. Results of this calculation of OH emission rate factors for individual rotational lines are on average 30% lower than the values obtained in an earlier work.

A fluorescent chemosensor for Zn(II). Exciplex formation in solution and the solid state.

PubMed

Bencini, Andrea; Berni, Emanuela; Bianchi, Antonio; Fornasari, Patrizia; Giorgi, Claudia; Lima, Joao C; Lodeiro, Carlos; Melo, Maria J; de Melo, J Seixas; Parola, Antonio Jorge; Pina, Fernando; Pina, Joao; Valtancoli, Barbara

2004-07-21

The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthrolinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm(-3) NMe(4)Cl H(2)O-MeCN (1:1, v/v) solution at 298.1 +/- 0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular pi-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (I(Exc)/I(M)), the activation energy for the exciplex formation (E(a)) and the binding energy of the exciplex (-DeltaH) were determined. The crystal structure of the [ZnLBr](ClO(4)).H(2)O compound was resolved, showing that in the solid state both intra- and inter-molecular pi-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no pi-stacking (full overlap of the pi-electron cloud of the two chromophores - anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of pi-stacking complexes or to exciplex emission in solution.

Temperature dependence of the Urbach optical absorption edge: A theory of multiple phonon absorption and emission sidebands

NASA Astrophysics Data System (ADS)

Grein, C. H.; John, Sajeev

1989-01-01

The optical absorption coefficient for subgap electronic transitions in crystalline and disordered semiconductors is calculated by first-principles means with use of a variational principle based on the Feynman path-integral representation of the transition amplitude. This incorporates the synergetic interplay of static disorder and the nonadiabatic quantum dynamics of the coupled electron-phonon system. Over photon-energy ranges of experimental interest, this method predicts accurate linear exponential Urbach behavior of the absorption coefficient. At finite temperatures the nonlinear electron-phonon interaction gives rise to multiple phonon emission and absorption sidebands which accompany the optically induced electronic transition. These sidebands dominate the absorption in the Urbach regime and account for the temperature dependence of the Urbach slope and energy gap. The physical picture which emerges is that the phonons absorbed from the heat bath are then reemitted into a dynamical polaronlike potential well which localizes the electron. At zero temperature we recover the usual polaron theory. At high temperatures the calculated tail is qualitatively similar to that of a static Gaussian random potential. This leads to a linear relationship between the Urbach slope and the downshift of the extrapolated continuum band edge as well as a temperature-independent Urbach focus. At very low temperatures, deviations from these rules are predicted arising from the true quantum dynamics of the lattice. Excellent agreement is found with experimental data on c-Si, a-Si:H, a-As2Se3, and a-As2S3. Results are compared with a simple physical argument based on the most-probable-potential-well method.

LASER BIOLOGY AND MEDICINE: Application of laser fluorimetry for determining the influence of a single amino-acid substitution on the individual photophysical parameters of a fluorescent form of a fluorescent protein mRFP1

NASA Astrophysics Data System (ADS)

Banishev, A. A.; Vrzheshch, E. P.; Shirshin, E. A.

2009-03-01

Individual photophysical parameters of the chromophore of a fluorescent protein mRFP1 and its two mutants (amino-acid substitution at position 66 - mRFP1/ Q66C and mRFP1/Q66S proteins) are determined. For this purpose, apart from conventional methods of fluorimetry and spectrophotometry, nonlinear laser fluorimetry is used. It is shown that the individual extinction coefficients of the chromophore of proteins correlate (correlation coefficient above 0.9) with the volume of the substituted amino-acid residue at position 66 (similar to the positions of the absorption, fluorescence excitation and emission maxima).

The influence of visible light and inorganic pigments on fluorescence excitation emission spectra of egg-, casein- and collagen-based painting media

NASA Astrophysics Data System (ADS)

Nevin, A.; Anglos, D.; Cather, S.; Burnstock, A.

2008-07-01

Spectrofluorimetric analysis of proteinaceous binding media is particularly promising because proteins employed in paintings are often fluorescent and media from different sources have significantly different fluorescence spectral profiles. Protein-based binding media derived from eggs, milk and animal tissue have been used for painting and for conservation, but their analysis using non-destructive techniques is complicated by interferences with pigments, their degradation and their low concentration. Changes in the fluorescence excitation emission spectra of films of binding media following artificial ageing to an equivalent of 50 and 100 years of museum lighting include the reduction of bands ascribed to tyrosine, tryptophan and Maillard reaction products and an increase in fluorescent photodegradation. Fluorescence of naturally aged paint is dependent on the nature of the pigment present and, with egg-based media, in comparison with un-pigmented films, emissions ascribed to amino acids are more pronounced.

Molecular and structural characterization of New Red and Erythrosine by fluorescence polarization spectroscopy

NASA Astrophysics Data System (ADS)

Zhu, Chun; Du, Jia-Meng; Zhao, Jin-Chen; Zhu, Tuo; Chen, Guo-Qing

2017-07-01

The fundamental and the fluorescence anisotropies of New Red and Erythrosine were measured. The intersection angles between the absorption and the emission dipole moments for New Red and Erythrosine are 4.44∘ and 23.26∘, respectively. The average angle shift of the emission dipole moment of New Red is 3.91∘ during the lifetime of the excited state. This indicates that it has a bifurcated linear structure with weak rotational capacity. The average angle shift of the emission dipole moment of Erythrosine is 9.25∘, indicating that it has a partial planar structure and is easier to rotate. The spatial ground state structures were simulated with Gaussian 09.

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

Ratiometric Fluorescent Detection of Pb2+ by FRET-Based Phthalocyanine-Porphyrin Dyads.

PubMed

Zhang, Dongli; Zhu, Mengliang; Zhao, Luyang; Zhang, Jinghui; Wang, Kang; Qi, Dongdong; Zhou, Yang; Bian, Yongzhong; Jiang, Jianzhuang

2017-12-04

Sensitive and selective detection of Pb 2+ is a very worthwhile endeavor in terms of both human health and environmental protection, as the heavy metal is fairly ubiquitous and highly toxic. In this study, we designed phthalocyanine-porphyrin (Pc-Por) heterodyads, namely, H 2 Pc-α-ZnPor (1) and H 2 Pc-β-ZnPor (2), by connecting a zinc(II) porphyrin moiety to the nonperipheral (α) or peripheral (β) position of a metal-free phthalocyanine moiety. Upon excitation at the porphyrin Soret region (420 nm), both of the dyads exhibited not only a porphyrin emission (605 nm) but also a phthalocyanine emission (ca. 700 nm), indicating the occurrence of intramolecular fluorescence resonance energy transfer (FRET) processes from the porphyrin donor to the phthalocyanine acceptor. The dyads can selectively bind Pb 2+ in the phthalocyanine core leading to a red shift of the phthalocyanine absorption and thus a decrease of spectral overlap between the porphyrin emission and phthalocyanine absorption, which in turn suppresses the intramolecular FRET. In addition, the binding of Pb 2+ can highly quench the emission of phthalocyanine by heavy-metal ion effects. The synergistic coupled functions endow the dyads with remarkable ratiometric fluorescent responses at two distinct wavelengths (F 605 /F 703 for 1 and F 605 /F 700 for 2). The emission intensity ratio increased as a linear function to the concentration of Pb 2+ in the range of 0-4.0 μM, whereas the detection limits were determined to be 3.4 × 10 -9 and 2.2 × 10 -8 M for 1 and 2, respectively. Furthermore, by comparative study of 1 and 2, the effects of distance and relative orientation between Pc and ZnPor fluorophores on the FRET efficiency and sensing performance were highlighted, which is helpful for further optimizing such FRET systems.

A supramolecular approach to fabricate highly emissive smart materials

PubMed Central

Liu, Kai; Yao, Yuxing; Kang, Yuetong; Liu, Yu; Han, Yuchun; Wang, Yilin; Li, Zhibo; Zhang, Xi

2013-01-01

The aromatic chromophores, for example, perylene diimides (PDIs) are well known for their desirable absorption and emission properties. However, their stacking nature hinders the exploitation of these properties and further applications. To fabricate emissive aggregates or solid-state materials, it has been common practice to decrease the degree of stacking of PDIs by incorporating substituents into the parent aromatic ring. However, such practice often involves difficultorganic synthesis with multiple steps. A supramolecular approach is established here to fabricate highly fluorescent and responsive soft materials, which has greatly decreases the number of required synthetic steps and also allows for a system with switchable photophysical properties. The highly fluorescent smart material exhibits great adaptivity and can be used as a supramolecular sensor for the rapid detection of spermine with high sensitivity and selectivity, which is crucial for the early diagnosis of malignant tumors. PMID:23917964

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation.

PubMed

Moix, Jeremy M; Ma, Jian; Cao, Jianshu

2015-03-07

A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters.

Stable and Size-Tunable Aggregation-Induced Emission Nanoparticles Encapsulated with Nanographene Oxide and Applications in Three-Photon Fluorescence Bioimaging.

PubMed

Zhu, Zhenfeng; Qian, Jun; Zhao, Xinyuan; Qin, Wei; Hu, Rongrong; Zhang, Hequn; Li, Dongyu; Xu, Zhengping; Tang, Ben Zhong; He, Sailing

2016-01-26

Organic fluorescent dyes with high quantum yield are widely applied in bioimaging and biosensing. However, most of them suffer from a severe effect called aggregation-caused quenching (ACQ), which means that their fluorescence is quenched at high molecular concentrations or in the aggregation state. Aggregation-induced emission (AIE) is a diametrically opposite phenomenon to ACQ, and luminogens with this feature can effectively solve this problem. Graphene oxide has been utilized as a quencher for many fluorescent dyes, based on which biosensing can be achieved. However, using graphene oxide as a surface modification agent of fluorescent nanoparticles is seldom reported. In this article, we used nanographene oxide (NGO) to encapsulate fluorescent nanoparticles, which consisted of a type of AIE dye named TPE-TPA-FN (TTF). NGO significantly improved the stability of nanoparticles in aqueous dispersion. In addition, this method could control the size of nanoparticles' flexibly as well as increase their emission efficiency. We then used the NGO-modified TTF nanoparticles to achieve three-photon fluorescence bioimaging. The architecture of ear blood vessels in mice and the distribution of nanoparticles in zebrafish could be observed clearly. Furthermore, we extended this method to other AIE luminogens and showed it was widely feasible.

Silole-Based Red Fluorescent Organic Dots for Bright Two-Photon Fluorescence In vitro Cell and In vivo Blood Vessel Imaging.

PubMed

Chen, Bin; Feng, Guangxue; He, Bairong; Goh, Chiching; Xu, Shidang; Ramos-Ortiz, Gabriel; Aparicio-Ixta, Laura; Zhou, Jian; Ng, Laiguan; Zhao, Zujin; Liu, Bin; Tang, Ben Zhong

2016-02-10

Robust luminescent dyes with efficient two-photon fluorescence are highly desirable for biological imaging applications, but those suitable for organic dots fabrication are still rare because of aggregation-caused quenching. In this work, a red fluorescent silole, 2,5-bis[5-(dimesitylboranyl)thiophen-2-yl]-1-methyl-1,3,4-triphenylsilole ((MesB)2 DTTPS), is synthesized and characterized. (MesB)2 DTTPS exhibits enhanced fluorescence efficiency in nanoaggregates, indicative of aggregation-enhanced emission (AEE). The organic dots fabricated by encapsulating (MesB)2 DTTPS within lipid-PEG show red fluorescence peaking at 598 nm and a high fluorescence quantum yield of 32%. Upon excitation at 820 nm, the dots show a large two-photon absorption cross section of 3.43 × 10(5) GM, which yields a two-photon action cross section of 1.09 × 10(5) GM. These (MesB)2 DTTPS dots show good biocompatibility and are successfully applied to one-photon and two-photon fluorescence imaging of MCF-7 cells and two-photon in vivo visualization of the blood vascular of mouse muscle in a high-contrast and noninvasive manner. Moreover, the 3D blood vasculature located at the mouse ear skin with a depth of over 100 μm can also be visualized clearly, providing the spatiotemporal information about the whole blood vascular network. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.