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Sample records for femtosecond fluorescence upconversion

  1. Femtosecond broadband fluorescence upconversion spectroscopy: Improved setup and photometric correction

    SciTech Connect

    Zhang, X.-X.; Wuerth, C.; Resch-Genger, U.; Zhao, L.; Ernsting, N. P.; Sajadi, M.

    2011-06-15

    A setup for fluorescence upconversion spectroscopy (FLUPS) is described which has 80 fs temporal response (fwhm) for emission in the spectral range 425-750 nm. Broadband phase matching is achieved with tilted gate pulses at 1340 nm. Background from harmonics of the gate pulse is removed and sensitivity increased compared to previous designs. Photometric calibration of the upconversion process is performed with a set of fluorescent dyes. For Coumarin 153 in methanol the peak position, bandwidth, and asymmetry depending on delay time are reported.

  2. Femtosecond broadband fluorescence upconversion spectroscopy: Improved setup and photometric correction

    NASA Astrophysics Data System (ADS)

    Zhang, X.-X.; Würth, C.; Zhao, L.; Resch-Genger, U.; Ernsting, N. P.; Sajadi, M.

    2011-06-01

    A setup for fluorescence upconversion spectroscopy (FLUPS) is described which has 80 fs temporal response (fwhm) for emission in the spectral range 425-750 nm. Broadband phase matching is achieved with tilted gate pulses at 1340 nm. Background from harmonics of the gate pulse is removed and sensitivity increased compared to previous designs. Photometric calibration of the upconversion process is performed with a set of fluorescent dyes. For Coumarin 153 in methanol the peak position, bandwidth, and asymmetry depending on delay time are reported.

  3. Realizing up-conversion fluorescence tuning in lanthanide-doped nanocrystals by femtosecond pulse shaping method

    PubMed Central

    Zhang, Shian; Yao, Yunhua; Shuwu, Xu; Liu, Pei; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2015-01-01

    The ability to tune color output of nanomaterials is very important for their applications in laser, optoelectronic device, color display and multiplexed biolabeling. Here we first propose a femtosecond pulse shaping technique to realize the up-conversion fluorescence tuning in lanthanide-doped nanocrystals dispersed in the glass. The multiple subpulse formation by a square phase modulation can create different excitation pathways for various up-conversion fluorescence generations. By properly controlling these excitation pathways, the multicolor up-conversion fluorescence can be finely tuned. This color tuning by the femtosecond pulse shaping technique is realized in single material by single-color laser field, which is highly desirable for further applications of the lanthanide-doped nanocrystals. This femtosecond pulse shaping technique opens an opportunity to tune the color output in the lanthanide-doped nanocrystals, which may bring a new revolution in the control of luminescence properties of nanomaterials. PMID:26290391

  4. Femtosecond broadband fluorescence spectroscopy by down- and up-conversion in β-barium borate crystals

    NASA Astrophysics Data System (ADS)

    Sajadi, M.; Quick, M.; Ernsting, N. P.

    2013-10-01

    Broadband transient fluorescence spectroscopy is performed by difference- and sum-frequency generation in β-barium borate crystals at a fixed geometry. Phase matching is spectrally broadened by using (i) 1340 nm gate pulses, (ii) a fluorescence angle of ˜4° extended at the crystal, and (iii) angular dispersion of the fluorescence in a calcite prism. The latter provides 1° angular separation between the two spectral wings of the fluorescence. By combining down- and up-conversion processes, a 26 000 cm-1 wide multiplex window is realized with ˜100 fs time resolution.

  5. Dielectric controlled excited state relaxation pathways of a representative push-pull stilbene: a mechanistic study using femtosecond fluorescence up-conversion technique.

    PubMed

    Rafiq, Shahnawaz; Sen, Pratik

    2013-02-28

    Femtosecond fluorescence up-conversion technique was employed to reinvestigate the intriguing dependence of fluorescence quantum yield of trans-4-dimethylamino-4(')-nitrostilbene (DNS) on dielectric properties of the media. In polar solvents, such as methanol and acetonitrile, the two time components of the fluorescence transients were assigned to intramolecular charge transfer (ICT) dynamics and to the depletion of the ICT state to the ground state via internal conversion along the torsional coordinate of nitro moiety. The viscosity independence of the first time component indicates the absence of any torsional coordinate in the charge transfer process. In slightly polar solvent (carbon tetrachloride) the fluorescence transients show a triple exponential behavior. The first time component was assigned to the formation of the ICT state on a 2 ps time scale. Second time component was assigned to the relaxation of the ICT state via two torsion controlled channels. First channel involves the torsional motion about the central double bond leading to the trans-cis isomerization via a conical intersection or avoided crossing. The other channel contributing to the depopulation of ICT state involves the torsional coordinates of dimethylanilino and∕or nitrophenyl moieties and leads to the formation of a conformationally relaxed state, which subsequently relaxes back to the ground state radiatively, and is responsible for the high fluorescence quantum yield of DNS in slightly polar solvents such as carbon tetrachloride, toluene, etc. The excited singlet state which is having a dominant π-π∗ character may also decay via intersystem crossing to the n-π∗ triplet manifold and thus accounts for the observed triplet yield of the molecule in slightly polar solvents.

  6. Dielectric controlled excited state relaxation pathways of a representative push-pull stilbene: A mechanistic study using femtosecond fluorescence up-conversion technique

    NASA Astrophysics Data System (ADS)

    Rafiq, Shahnawaz; Sen, Pratik

    2013-02-01

    Femtosecond fluorescence up-conversion technique was employed to reinvestigate the intriguing dependence of fluorescence quantum yield of trans-4-dimethylamino-4'-nitrostilbene (DNS) on dielectric properties of the media. In polar solvents, such as methanol and acetonitrile, the two time components of the fluorescence transients were assigned to intramolecular charge transfer (ICT) dynamics and to the depletion of the ICT state to the ground state via internal conversion along the torsional coordinate of nitro moiety. The viscosity independence of the first time component indicates the absence of any torsional coordinate in the charge transfer process. In slightly polar solvent (carbon tetrachloride) the fluorescence transients show a triple exponential behavior. The first time component was assigned to the formation of the ICT state on a 2 ps time scale. Second time component was assigned to the relaxation of the ICT state via two torsion controlled channels. First channel involves the torsional motion about the central double bond leading to the trans-cis isomerization via a conical intersection or avoided crossing. The other channel contributing to the depopulation of ICT state involves the torsional coordinates of dimethylanilino and/or nitrophenyl moieties and leads to the formation of a conformationally relaxed state, which subsequently relaxes back to the ground state radiatively, and is responsible for the high fluorescence quantum yield of DNS in slightly polar solvents such as carbon tetrachloride, toluene, etc. The excited singlet state which is having a dominant π-π* character may also decay via intersystem crossing to the n-π* triplet manifold and thus accounts for the observed triplet yield of the molecule in slightly polar solvents.

  7. Femtosecond Laser-Induced Upconversion Luminescence in Rare-Earth Ions by Nonresonant Multiphoton Absorption.

    PubMed

    Yao, Yunhua; Xu, Cheng; Zheng, Ye; Yang, Chengshuai; Liu, Pei; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong; Zhang, Shian

    2016-07-21

    The upconversion luminescence of rare-earth ions has attracted considerable interest because of its important applications in photoelectric conversion, color display, laser device, multiplexed biolabeling, and security printing. Previous studies mainly explored the upconversion luminescence generation through excited state absorption, energy transfer upconversion, and photon avalanche under the continuous wave laser excitation. Here, we focus on the upconversion luminescence generation through a nonresonant multiphoton absorption by using the intense femtosecond pulsed laser excitation and study the upconversion luminescence intensity control by varying the femtosecond laser phase and polarization. We show that the upconversion luminescence of rare-earth ions under the intense femtosecond laser field excitation is easy to be obtained due to the nonresonant multiphoton absorption through the nonlinear interaction between light and matter, which is not available by the continuous wave laser excitation in previous works. We also show that the upconversion luminescence intensity can be effectively controlled by varying the femtosecond pulsed laser phase and polarization, which can open a new technological opportunity to generate and control the upconversion luminescence of rare-earth ions and also can be further extended to the relevant application areas.

  8. Ultrafast Fluorescence Spectroscopy via Upconversion: Applications to Biophysics

    PubMed Central

    Xu, Jianhua; Knutson, Jay R.

    2012-01-01

    This chapter reviews basic concepts of nonlinear fluorescence upconversion, a technique whose temporal resolution is essentially limited only by the pulse width of the ultrafast laser. Design aspects for upconversion spectrophotofluorometers are discussed, and a recently developed system is described. We discuss applications in biophysics, particularly the measurement of time-resolved fluorescence spectra of proteins (with subpicosecond time resolution). Application of this technique to biophysical problems such as dynamics of tryptophan, peptides, proteins, and nucleic acids is reviewed. PMID:19152860

  9. Three-photon-excited upconversion luminescence of niobium ions doped silicate glass by a femtosecond laser irradiation.

    PubMed

    Zeng, Huidan; Song, Juan; Chen, Danping; Yuan, Shuanglong; Jiang, Xiongwei; Cheng, Ya; Yang, Yunxia; Chen, Guorong

    2008-04-28

    We report on the bluish green upconversion luminescence of niobium ions doped silicate glass by a femtosecond laser irradiation. The dependence of the fluorescence intensity on the pump power density of laser indicates that the conversion of infrared irradiation to visible emission is dominated by three-photon excitation process. We suggest that the charge transfer from O(2-) to Nb(5+) can efficiently contribute to the bluish green emission. The results indicate that transition metal ions without d electrons play an important role in fields of optics when embedded into silicate glass matrix.

  10. Direct observation of up-conversion via femtosecond photoelectron imaging

    NASA Astrophysics Data System (ADS)

    Liu, Yuzhu; Knopp, Gregor; Gerber, Thomas

    2015-10-01

    Ultrafast relaxation dynamics in 2-methylfuran has been investigated by time-resolved photoelectron imaging. An "up" internal conversion from a low-lying state into a higher-lying one has been observed experimentally. Temporal photoelectron kinetic-energy distributions and angular distributions of the photoelectrons are analyzed. In the up-conversion process, the vibrational energy in the initial state is converted to the electronic energy of the final state during the energy transfer. And the time scale for the up-conversion process is estimated by the observed onset delay for the corresponding photoelectron bands.

  11. Upconversion fluorescence immunoassay for imidaclothiz by magnetic nanoparticle separation.

    PubMed

    Hua, Xiude; You, Hongjie; Luo, Peiwen; Tao, Zhexuan; Chen, He; Liu, Fengquan; Wang, Minghua

    2017-10-03

    A sensitive fluorescence immunoassay for the detection of imidaclothiz was established by using magnetic nanoparticles (MNPs) as concentration elements and upconversion nanoparticles (UCNPs) as signal labels. The NaYF4/Yb,Er UCNPs and MNPs were conjugated with imidaclothiz monoclonal antibody and imidaclothiz antigen, respectively. Imidaclothiz could compete with the antigen-conjugated MNPs for binding to the antibody-conjugated UCNPs and resulted in a decreased fluorescence signal when the MNPs were separated by an external magnet. Under the optimal conditions, the concentration of imidaclothiz producing 50% inhibition of the signal (IC50), limit of detection (LOD, IC10), and the linear assay range (IC10-IC90) were 14.59, 0.74, and 0.74-289.30 ng mL(-1), respectively. The immunoassay exhibited no obvious cross-reactivity with analogues of imidaclothiz except for imidacloprid, with 89.2% cross-reactivity. The average recoveries measured in paddy water, pear, soil, peach, rice, tomato, wheat, and pakchoi were 75.7-105.2%, and the relative standard deviations (RSDs) were less than 11.2%. In addition, the results of the immunoassay correlated well with that of high-performance liquid chromatography (HPLC) for authentic samples. Graphical abstract Development of an upconversion fluorescence immunoassay for the detection of imidaclothiz by using antibody-modified upconversion nanoparticles (UCNPs) as the detection probe and antigen-modified magnetic nanoparticles (MNPs) as the capture probe.

  12. Real-time dispersion analyzer of femtosecond laser pulses with use of a spectrally and temporally resolved upconversion technique

    NASA Astrophysics Data System (ADS)

    Rhee, June-Koo; Sosnowski, Thomas S.; Tien, An-Chun; Norris, Theodore B.

    1996-08-01

    We demonstrate a real-time femtosecond-laser-pulse analyzer by using a spectrally and temporally resolved upconversion technique (STRUT) for characterization of the phase and the intensity. The STRUT provides simple but reliable analysis of femtosecond pulses by employing a narrow-bandpass dielectric filter in one arm of a conventional single-shot upconversion autocorrelator and analyzing the spatiotemporal upconversion signal with a monochromator. The resulting spatiotemporal and spatiospectral image presents clear and complete information about femtosecond pulses produced by either oscillators or amplifiers. Characterization of 2-nJ, 60-fs Ti:sapphire oscillator pulses is achieved with 0.5 s data acquisition time and 0.2-s computational time.

  13. Unravelling molecular mechanisms in the fluorescence spectra of doxorubicin in aqueous solution by femtosecond fluorescence spectroscopy.

    PubMed

    Changenet-Barret, Pascale; Gustavsson, Thomas; Markovitsi, Dimitra; Manet, Ilse; Monti, Sandra

    2013-02-28

    Doxorubicin (DOX) is a potent anti-tumoral agent widely used for cancer therapy. Despite numerous studies, the fluorescence properties of DOX, usually exploited for the characterization of the interaction with biological media, have until now led to controversial interpretations, mainly due to self-association of the drug in aqueous solution. We present here the first femtosecond study of DOX based on measurements with the fluorescence up-conversion technique in combination with time-correlated single photon counting using the same laser source. We provide evidence that fluorescence signals of DOX stem from monomers and dimers. DOX dimerization induces a dramatic decrease in the fluorescence quantum yield from 3.9 × 10(-2) to 10(-5) associated with the red shift of the fluorescence spectrum by ~25 nm. While the fluorescence lifetime of the monomer is 1 ns, the dimer fluorescence is found to decay with a lifetime of about 2 ps. In contrast to monomers, the fluorescence anisotropy of dimers is found to be negative. These experimental observations are consistent with an ultrafast internal conversion (<200 fs) between two exciton states, possibly followed by a charge separation process.

  14. A double responsive smart upconversion fluorescence sensing material for glycoprotein.

    PubMed

    Guo, Ting; Deng, Qiliang; Fang, Guozhen; Yun, Yaguang; Hu, Yongjin; Wang, Shuo

    2016-11-15

    A novel strategy was developed to prepare double responsive smart upconversion fluorescence material for highly specific enrichment and sensing of glycoprotein. The novel double responsive smart sensing material was synthesized by choosing Horse radish peroxidase (HRP) as modal protein, the grapheme oxide (GO) as support material, upconversion nanoparticles (UCNPs) as fluorescence signal reporter, N-isopropyl acrylamide (NIPAAM) and 4-vinylphenylboronic acid (VPBA) as functional monomers. The structure and component of smart sensing material was investigated by transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared (FTIR), respectively. These results illustrated the smart sensing material was prepared successfully. The recognition characterizations of smart sensing material were evaluated, and results showed that the fluorescence intensity of smart sensing material was reduced gradually, as the concentration of protein increased, and the smart sensing material showed selective recognition for HRP among other proteins. Furthermore, the recognition ability of the smart sensing material for glycoprotein was regulated by controlling the pH value and temperature. Therefore, this strategy opens up new way to construct smart material for detection of glycoprotein. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Enhancement of 800 nm upconversion emission in a thulium doped tellurite microstructured fiber pumped by a 1560 nm femtosecond fiber laser

    NASA Astrophysics Data System (ADS)

    Jia, Zhixu; Yao, Chuanfei; Wang, Shunbin; Zheng, Kezhi; Xiong, Liangming; Luo, Jie; Lv, Dajuan; Qin, Guanshi; Ohishi, Yasutake; Qin, Weiping

    2016-04-01

    We report enhanced upconversion (UC) fluorescence in Tm3+ doped tellurite microstructured fibers (TDTMFs) fabricated by using a rod-in-tube method. Under the pumping of a 1560 nm femtosecond fiber laser, ultrabroadband supercontinuum light expanding from ˜1050 to ˜2700 nm was generated in a 4 cm long TDTMF. Simultaneously, intense 800 nm UC emission from the 3H4 → 3H6 transition of Tm3+ was observed in the same TDTMF. Compared to that pumped by a 1560 nm continuous wave fiber laser, the UC emission intensity was enhanced by ˜4.1 times. The enhancement was due to the spectral broadening in the TDTMF under the pumping of the 1560 nm femtosecond fiber laser.

  16. Enhancement of 800 nm upconversion emission in a thulium doped tellurite microstructured fiber pumped by a 1560 nm femtosecond fiber laser

    SciTech Connect

    Jia, Zhixu; Zheng, Kezhi; Yao, Chuanfei; Wang, Shunbin; Qin, Guanshi Qin, Weiping; Xiong, Liangming; Luo, Jie; Lv, Dajuan; Ohishi, Yasutake

    2016-04-28

    We report enhanced upconversion (UC) fluorescence in Tm{sup 3+} doped tellurite microstructured fibers (TDTMFs) fabricated by using a rod-in-tube method. Under the pumping of a 1560 nm femtosecond fiber laser, ultrabroadband supercontinuum light expanding from ∼1050 to ∼2700 nm was generated in a 4 cm long TDTMF. Simultaneously, intense 800 nm UC emission from the {sup 3}H{sub 4} → {sup 3}H{sub 6} transition of Tm{sup 3+} was observed in the same TDTMF. Compared to that pumped by a 1560 nm continuous wave fiber laser, the UC emission intensity was enhanced by ∼4.1 times. The enhancement was due to the spectral broadening in the TDTMF under the pumping of the 1560 nm femtosecond fiber laser.

  17. Xanthines Studied via Femtosecond Fluorescence Spectroscopy.

    PubMed

    Changenet-Barret, Pascale; Kovács, Lajos; Markovitsi, Dimitra; Gustavsson, Thomas

    2016-12-03

    Xanthines represent a wide class of compounds closely related to the DNA bases adenine and guanine. Ubiquitous in the human body, they are capable of replacing natural bases in double helices and give rise to four-stranded structures. Although the use of their fluorescence for analytical purposes was proposed, their fluorescence properties have not been properly characterized so far. The present paper reports the first fluorescence study of xanthine solutions relying on femtosecond spectroscopy. Initially, we focus on 3-methylxanthine, showing that this compound exhibits non-exponential fluorescence decays with no significant dependence on the emission wavelength. The fluorescence quantum yield (3 × 10(-4)) and average decay time (0.9 ps) are slightly larger than those found for the DNA bases. Subsequently, we compare the dynamical fluorescence properties of seven mono-, di- and tri-methylated derivatives. Both the fluorescence decays and fluorescence anisotropies vary only weakly with the site and the degree of methylation. These findings are in line with theoretical predictions suggesting the involvement of several conical intersections in the relaxation of the lowest singlet excited state.

  18. 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.

  19. Upconversion fluorescent strip sensor for rapid determination of Vibrio anguillarum

    NASA Astrophysics Data System (ADS)

    Zhao, Peng; Wu, Yuanyuan; Zhu, Yihua; Yang, Xiaoling; Jiang, Xin; Xiao, Jingfan; Zhang, Yuanxing; Li, Chunzhong

    2014-03-01

    Here, we report a simple and ultrasensitive upconversion fluorescent strip sensor based on NaYF4:Yb,Er nanoparticles (NPs) and the lateral flow immunochromatographic assay (LFIA). Carboxyl-modified β-NaYF4:Yb,Er NPs were successfully synthesized by a facile one-pot solvothermal approach, upon further coupling with monoclonal antibody, the resultant UCNPs-antibody conjugates probes were used in LFIA and served as signal vehicles for the fluorescent reporters. V. anguillarum was used as a model analyte to demonstrate the use of this strip sensor. The limit of the detection for the fluorescent strip was determined as 102 CFU mL-1, which is 100 times lower than those displayed by enzyme-linked immunosorbent assays, while the time needed for the detection was only 15 min. Furthermore, no cross-reaction with other eight pathogens was found, indicating the good specificity of the strip. This developed LFIA would offer the potential as a useful tool for the quantification of pathogens analysis in the future.

  20. Intense upconversion fluorescence in Tm 3+/Yb3+ codoped alumina lead borate glasses

    NASA Astrophysics Data System (ADS)

    Krishna Murthy Goud, K.; Shekhar Reddy, M. Chandra; Appa Rao, B.

    2016-09-01

    The Tm3+/Yb3+ codoped alumina lead borate glasses were prepared by the conventional melt quenching technique. Optical absorption and FTIR spectra were recorded. The upconversion fluorescence spectra exhibited weak blue (480 nm) and intense red (660 nm) emissions due to 1G4 → 3H6 and 1G4 → 3H4 transitions, respectively. The results concluded that both emissions are due to three photon absorption process. It has been observed that in the upconversion efficiency increases with the increase in the concentration of Yb3+ ions. The strong red upconversion fluorescence indicate that Tm3+/Yb3+ codoped alumina lead borate glasses can be used as potential host material for upconversion lasers.

  1. Laser polarization and phase control of up-conversion fluorescence in rare-earth ions

    PubMed Central

    Yao, Yunhua; Zhang, Shian; Zhang, Hui; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2014-01-01

    We theoretically and experimentally demonstrate the up-conversion fluorescence control via resonance-mediated two-photon absorption in rare-earth ions by varying both the laser polarization and phase. We show that both the laser polarization and phase can control the up-conversion fluorescence, and the up-conversion fluorescence intensity is decreased when the laser polarization changes from linear through elliptical to circular. We also show that the laser polarization will affect the control efficiency of the up-conversion fluorescence by varying the laser phase, and the circular polarization will reduce the control efficiency. Furthermore, we suggest that the control efficiency by varying the laser polarization and the effect of the laser polarization on the control efficiency by varying the laser phase can be artificially manipulated by controlling the laser spectral bandwidth. This optical control method opens a new opportunity to control the up-conversion fluorescence of rare-earth ions, which may have significant impact on the related applications of rare-earth ions. PMID:25465401

  2. Upconversion: road to El Dorado of the fluorescence world.

    PubMed

    Ong, Li Ching; Gnanasammandhan, Muthu Kumara; Nagarajan, Sounderya; Zhang, Yong

    2010-01-01

    Upconversion nanoparticles (UCNs), in the recent times have attracted attention due to their unique properties, which makes them ideal fluorophores for use in biological applications. There have been various reports on their use for targeted cell imaging, drug and gene delivery and also for diffuse optical tomography. Here we give a brief introduction on what are UCNs and the mechanism of upconversion, followed by a discussion on the biological applications of UCNs and further on what the future holds for UCNs.

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

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

  4. Ultrafast relaxation dynamics of 5,10,15,20-meso-tetrakis pentafluorophenyl porphyrin studied by fluorescence up-conversion and transient absorption spectroscopy.

    PubMed

    Kumar, P Hemant; Venkatesh, Yeduru; Siva, Doddi; Ramakrishna, B; Bangal, Prakriti Ranjan

    2015-02-26

    The ultrafast photophysical characterization of 5,10,15,20-meso-tetrakis pentafluorophenyl porphyrin (H2F20TPP) in 4:1 dichloromethane (DCM) and tetrahydrofuran (THF) solution has been done in the femtosecond-picosecond time domain, by combining fluorescence up-conversion and femtosecond transient absorption spectroscopy. Fluorescence up-conversion studies on H2F20TPP were done demonstrating fluorescence dynamics over the whole spectral range from 440 to 650 nm when excited at 405 nm, 360.5 cm(-1) excess vibrational energy of Soret band (411 nm). Single-exponential decay with ∼160 ± 50 fs lifetime of Soret fluorescence (also called S2 fluorescence or B band fluorescence) at around 440 nm was observed. On going from 440 nm, S2 fluorescence to S1 fluorescence, (Q-band) around 640 nm (wavelength of 0-0 transition in the stationary spectrum), single-exponential fluorescence time profile turns into a multiexponential time profile and it could be resolved critically into five-exponential components. An ultrafast rise component with ∼160 ± 50 fs followed by two decay components: a very fast decay component with 200 ± 50 fs time constant and another relatively slower 1.8 ± 0.5 ps decay component. Next, a very prominent rise component with 105 ± 30 ps lifetime followed by long-lived 10 ns decay component. The initial rise of S1 (Q-band) fluorescence around 640 nm agreed with the decay time of S2 (Soret or B band) fluorescence indicates that internal conversion (IC) from relaxed S2 to vibrationally excited S1 occurs in the ∼160 fs time scale and subsequent very fast decay with 200 fs time constant, which is assigned to be intramolecular vibrational dephasing or redistribution. The 1.8 ps decay component of S1 fluorescence is attributed to be "hot" fluorescence from vibrationally excited S1 state, and it reveals the vibrational relaxation time induced by elastic or quasi-elastic collision with solvent molecules. The 105 ps rise component is the creation time of the

  5. Paper-based upconversion fluorescence resonance energy transfer biosensor for sensitive detection of multiple cancer biomarkers.

    PubMed

    Xu, Sai; Dong, Biao; Zhou, Donglei; Yin, Ze; Cui, Shaobo; Xu, Wen; Chen, Baojiu; Song, Hongwei

    2016-03-22

    A paper-based upconversion fluorescence resonance energy transfer assay device is proposed for sensitive detection of CEA. The device is fabricated on a normal filter paper with simple nano-printing method. Upconversion nanoparticles tagged with specific antibodies are printed to the test zones on the test paper, followed by the introduction of assay antigen. Upconversion fluorescence measurements are directly conducted on the test zones after the antigen-to-antibody reactions. Furthermore, a multi-channel test paper for simultaneous detection of multiple cancer biomarkers was established by the same method and obtained positive results. The device showed high anti-interfere, stability, reproducible and low detection limit (0.89 ng/mL), moreover it is very easy to fabricate and operate, which is a promising prospect for a clinical point-of-care test.

  6. Paper-based upconversion fluorescence resonance energy transfer biosensor for sensitive detection of multiple cancer biomarkers

    PubMed Central

    Xu, Sai; Dong, Biao; Zhou, Donglei; Yin, Ze; Cui, Shaobo; Xu, Wen; Chen, Baojiu; Song, Hongwei

    2016-01-01

    A paper-based upconversion fluorescence resonance energy transfer assay device is proposed for sensitive detection of CEA. The device is fabricated on a normal filter paper with simple nano-printing method. Upconversion nanoparticles tagged with specific antibodies are printed to the test zones on the test paper, followed by the introduction of assay antigen. Upconversion fluorescence measurements are directly conducted on the test zones after the antigen-to-antibody reactions. Furthermore, a multi-channel test paper for simultaneous detection of multiple cancer biomarkers was established by the same method and obtained positive results. The device showed high anti-interfere, stability, reproducible and low detection limit (0.89 ng/mL), moreover it is very easy to fabricate and operate, which is a promising prospect for a clinical point-of-care test. PMID:27001460

  7. Fabrication of fluorescent composite hydrogel using in situ synthesis of upconversion nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Yuqing; Lin, Min; Jin, Guorui; Park, Yong Il; Qiu, Mushu; Zhao, Ying; Yang, Hui; Li, Ang; Lu, Tian Jian

    2017-04-01

    Fluorescent composite hydrogels have found widespread applications, especially in spatial and temporal monitoring of in vivo hydrogel behaviors via the emitting optical signal. However, most existing fluorescent composite hydrogels suffer from limited capability of deep tissue imaging and complicated fabrication routes. We herein report a facile method for fabricating fluorescent composite hydrogels based on the in situ synthesis of NaYF4:Yb, Er upconversion nanoparticles (UCNPs). This approach employs polyacrylamide (PAAm) hydrogels as a template, where the interconnected pores within the hydrogel act as nanoreactors to confine the growth of nanocrystals. We then obtained a fluorescent composite hydrogel exhibiting upconversion fluorescence and enhanced mechanical properties. The fluorescence spectra show that the fluorescence intensity decreases with decreasing size of the UCNPs. We investigated the relationship between the optical properties of the fluorescent composite hydrogel and the incorporated UCNPs based on the morphology, size, and distribution of the UCNPs by using scanning electron microscopy and transmission electron microscopy. In addition, we demonstrated the applicability of the synthesized hydrogel for deep tissue imaging through an in vitro tissue penetration experiment. Compressive and dynamic rheological testing reveal enhanced mechanical properties with increasing UCNP concentration. The fabricated upconversion fluorescent composite hydrogel may pave the way for monitoring the in vivo behavior of biomimetic materials via deep tissue imaging.

  8. Fabrication of fluorescent composite hydrogel using in situ synthesis of upconversion nanoparticles.

    PubMed

    Dong, Yuqing; Lin, Min; Jin, Guorui; Il Park, Yong; Qiu, Mushu; Zhao, Ying; Yang, Hui; Li, Ang; Jian Lu, Tian

    2017-04-28

    Fluorescent composite hydrogels have found widespread applications, especially in spatial and temporal monitoring of in vivo hydrogel behaviors via the emitting optical signal. However, most existing fluorescent composite hydrogels suffer from limited capability of deep tissue imaging and complicated fabrication routes. We herein report a facile method for fabricating fluorescent composite hydrogels based on the in situ synthesis of NaYF4:Yb, Er upconversion nanoparticles (UCNPs). This approach employs polyacrylamide (PAAm) hydrogels as a template, where the interconnected pores within the hydrogel act as nanoreactors to confine the growth of nanocrystals. We then obtained a fluorescent composite hydrogel exhibiting upconversion fluorescence and enhanced mechanical properties. The fluorescence spectra show that the fluorescence intensity decreases with decreasing size of the UCNPs. We investigated the relationship between the optical properties of the fluorescent composite hydrogel and the incorporated UCNPs based on the morphology, size, and distribution of the UCNPs by using scanning electron microscopy and transmission electron microscopy. In addition, we demonstrated the applicability of the synthesized hydrogel for deep tissue imaging through an in vitro tissue penetration experiment. Compressive and dynamic rheological testing reveal enhanced mechanical properties with increasing UCNP concentration. The fabricated upconversion fluorescent composite hydrogel may pave the way for monitoring the in vivo behavior of biomimetic materials via deep tissue imaging.

  9. Wide-bandgap nonlinear crystal LiGaS2 for femtosecond mid-infrared spectroscopy with chirped-pulse upconversion.

    PubMed

    Nakamura, Ryosuke; Inagaki, Yoshizumi; Hata, Hidefumi; Hamada, Norio; Umemura, Nobuhiro; Kamimura, Tomosumi

    2016-11-20

    Femtosecond time-resolved mid-infrared (MIR) spectroscopy based on chirped-pulse upconversion is a promising method for observing molecular vibrational dynamics. A quantitative study on nonlinear media for upconversion is still essential for wide applications, particularly at the frequencies below 2000  cm-1. We evaluate wide-bandgap nonlinear crystals of Li-containing ternary chalcogenides based on their performance as the upconversion medium for femtosecond MIR spectroscopy. The upconversion efficiency is measured as a function of the MIR pulse frequency and the chirped pulse energy. LiGaS2 is found to be an efficient crystal for the upconversion of MIR pulses in a wide frequency range of 1100-2700  cm-1, especially below 2000  cm-1. By using LiGaS2 as an efficient upconversion crystal, we develop a MIR pump-probe spectroscopy system with a spectral resolution of 2.5  cm-1, a time resolution of 0.2 ps, and a probe window of 120  cm-1. Vibrational relaxation dynamics of CO stretching modes of Mn2(CO)10 in cyclohexane and bovine serum albumin in D2O are demonstrated with a high signal-to-noise ratio.

  10. Fluorescence upconversion microbarcodes for multiplexed biological detection: nucleic acid encoding.

    PubMed

    Zhang, Fan; Shi, Qihui; Zhang, Yichi; Shi, Yifeng; Ding, Kunlun; Zhao, Dongyuan; Stucky, Galen D

    2011-09-01

    Fluoride rare-earth-doped upconversion microbarcodes have been successfully developed for multiplexed signaling and nucleic-acid encoding. This kind of novel barcode material can be used for rapid and sensitive analysis of nucleic acids and antigens, which would have many potential applications in clinical, food, and environment detection.

  11. Upconversion fluorescence imaging of cells and small animals using lanthanide doped nanocrystals.

    PubMed

    Chatterjee, Dev K; Rufaihah, Abdul J; Zhang, Yong

    2008-03-01

    Upconversion fluorescence imaging technique with excitation in the near-infrared (NIR) region has been used for imaging of biological cells and tissues. This has several advantages, including absence of photo-damage to living organisms, very low auto-fluorescence, high detection sensitivity, and high light penetration depth in biological tissues. In this report we demonstrate the use of a new upconversion fluorophore, lanthanide doped nanocrystals, for imaging of cells and some deep tissues in animal. Polyethyleneimine (PEI) coated NaYF(4):Yb,Er nanoparticles were synthesized, which produce very strong upconversion fluorescence when excited at 980 nm by a NIR laser. The nanoparticles were shown to be stable in physiologic buffered saline (PBS), non-toxic to bone marrow stem cells, and resistant to photo-bleaching. The nanoparticles delivered into some cell lines or injected intradermally and intramuscularly into some tissues either near the body surface or deep in the body of rats showed visible fluorescence, when exposed to a 980 nm NIR laser. To the best of our knowledge, this represents the first demonstration of use of upconversion fluorophores for cellular and tissue imaging.

  12. Infrared to visible upconversion fluorescence in Yb,Tm:YAG single crystal

    NASA Astrophysics Data System (ADS)

    Xu, Wenwei; Xu, Xiaodong; Wu, Feng; Zhao, Guangjun; Zhao, Zhiwei; Zhou, Guoqing; Xu, Jun

    2007-04-01

    Absorption spectrum from 400 to 2000 nm and upconversion fluorescence spectra under 940 nm pumping of YAG single crystal codoped with 5 at.% Yb3+ and 4 at.% Tm3+ were studied at room temperature. The blue upconversion emission centered at 483 nm corresponds to the transition 1G4 → 3H6, the emission band around 646 nm corresponds to the transition 1G4 → 3F4 of Tm3+. Energy transfer from Yb3+ to Tm3+ is mainly nonradiative and the transfer efficiency was experimentally assessed. The line strengths, transition probabilities and radiative lifetimes of 1G4 level were calculated by using Judd-Ofelt theory. Gain coefficient calculated from spectra shows that the upconversion corresponding with transitions 1G4 → 3H6 in YAG doped with Yb3+ and Tm3+ is potentially useful for blue light output.

  13. Solid state photon upconversion utilizing thermally activated delayed fluorescence molecules as triplet sensitizer

    SciTech Connect

    Wu, Tony C.; Congreve, Daniel N.; Baldo, Marc A.

    2015-07-20

    The ability to upconvert light is useful for a range of applications, from biological imaging to solar cells. But modern technologies have struggled to upconvert incoherent incident light at low intensities. Here, we report solid state photon upconversion employing triplet-triplet exciton annihilation in an organic semiconductor, sensitized by a thermally activated-delayed fluorescence (TADF) dye. Compared to conventional phosphorescent sensitizers, the TADF dye maximizes the wavelength shift in upconversion due to its small singlet-triplet splitting. The efficiency of energy transfer from the TADF dye is 9.1%, and the conversion yield of sensitizer exciton pairs to singlet excitons in the annihilator is 1.1%. Our results demonstrate upconversion in solid state geometries and with non-heavy metal-based sensitizer materials.

  14. A high performance fluorescence switching system triggered electrochemically by Prussian blue with upconversion nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhai, Yiwen; Zhang, Hui; Zhang, Lingling; Dong, Shaojun

    2016-05-01

    A high performance fluorescence switching system triggered electrochemically by Prussian blue with upconversion nanoparticles was proposed. We synthesized a kind of hexagonal monodisperse β-NaYF4:Yb3+,Er3+,Tm3+ upconversion nanoparticle and manipulated the intensity ratio of red emission (at 653 nm) and green emission at (523 and 541 nm) around 2 : 1, in order to match well with the absorption spectrum of Prussian blue. Based on the efficient fluorescence resonance energy transfer and inner-filter effect of the as-synthesized upconversion nanoparticles and Prussian blue, the present fluorescence switching system shows obvious behavior with high fluorescence contrast and good stability. To further extend the application of this system in analysis, sulfite, a kind of important anion in environmental and physiological systems, which could also reduce Prussian blue to Prussian white nanoparticles leading to a decrease of the absorption spectrum, was chosen as the target. And we were able to determine the concentration of sulfite in aqueous solution with a low detection limit and a broad linear relationship.A high performance fluorescence switching system triggered electrochemically by Prussian blue with upconversion nanoparticles was proposed. We synthesized a kind of hexagonal monodisperse β-NaYF4:Yb3+,Er3+,Tm3+ upconversion nanoparticle and manipulated the intensity ratio of red emission (at 653 nm) and green emission at (523 and 541 nm) around 2 : 1, in order to match well with the absorption spectrum of Prussian blue. Based on the efficient fluorescence resonance energy transfer and inner-filter effect of the as-synthesized upconversion nanoparticles and Prussian blue, the present fluorescence switching system shows obvious behavior with high fluorescence contrast and good stability. To further extend the application of this system in analysis, sulfite, a kind of important anion in environmental and physiological systems, which could also reduce Prussian blue to

  15. Broadband up-conversion at subsolar irradiance: triplet-triplet annihilation boosted by fluorescent semiconductor nanocrystals.

    PubMed

    Monguzzi, A; Braga, D; Gandini, M; Holmberg, V C; Kim, D K; Sahu, A; Norris, D J; Meinardi, F

    2014-11-12

    Conventional solar cells exhibit limited efficiencies in part due to their inability to absorb the entire solar spectrum. Sub-band-gap photons are typically lost but could be captured if a material that performs up-conversion, which shifts photon energies higher, is coupled to the device. Recently, molecular chromophores that undergo triplet-triplet annihilation (TTA) have shown promise for efficient up-conversion at low irradiance, suitable for some types of solar cells. However, the molecular systems that have shown the highest up-conversion efficiency to date are ill suited to broadband light harvesting, reducing their applicability. Here we overcome this limitation by combining an organic TTA system with highly fluorescent CdSe semiconductor nanocrystals. Because of their broadband absorption and spectrally narrow, size-tunable fluorescence, the nanocrystals absorb the radiation lost by the TTA chromophores, returning this energy to the up-converter. The resulting nanocrystal-boosted system shows a doubled light-harvesting ability, which allows a green-to-blue conversion efficiency of ∼12.5% under 0.5 suns of incoherent excitation. This record efficiency at subsolar irradiance demonstrates that boosting the TTA by light-emitting nanocrystals can potentially provide a general route for up-conversion for different photovoltaic and photocatalytic applications.

  16. Optical parameters and upconversion fluorescence in Tm3+/Yb3+ codoped tellurite glass

    NASA Astrophysics Data System (ADS)

    Huang, Q. J.; Wang, Q. P.; Chang, J.; Zhang, X. Y.; Liu, Z. J.; Yu, G. Y.

    2010-04-01

    Tm3+/Yb3+ codoped tellurite glass has been prepared. Density, refractive index, optical absorption, Judd-Ofelt parameters and spontaneous transition probabilities of Tm3+ have been measured and calculated, respectively. Intense blue three-photon upconversion fluorescence and S-band (1470 nm) fluorescence were investigated under the excitation of a 980 nm diode laser at room temperature. Judd-Ofelt parameters, strong blue three-photon upcoversion emission of Tm3+ in glass indicate that Tm3+/Yb3+ codoped tellurite glass is a promising blue color upconversion optical and laser material. In addition, experiment results showed the 980 nm laser was more efficient than 808 nm laser when pumping Tm3+/Yb3+ codoped tellurite glass, Tm3+/Yb3+ codoped tellurite glass also could be a promising material for S-band amplification.

  17. Optical parameters and upconversion fluorescence in Tm3+/Yb3+-doped alkali-barium-bismuth-tellurite glasses.

    PubMed

    Lin, Hai; Liu, Ke; Lin, Lin; Hou, Yanyan; Yang, Dianlai; Ma, Tiecheng; Pun, Edwin Yun Bun; An, Qingda; Yu, Jiayou; Tanabe, Setsuhisa

    2006-11-01

    Tm(3+)/Yb(3+)-doped alkali-barium-bismuth-tellurite (LKBBT) glasses have been fabricated and characterized. Density, refractive index, optical absorption, absorption and emission cross-sections of Yb(3+), Judd-Ofelt parameters and spontaneous transition probabilities of Tm(3+) have been measured and calculated, respectively. Intense blue three-photon upconversion fluorescence and near-infrared two-photon upconversion fluorescence were investigated under the excitation of a 980 nm diode laser at room temperature. Wide infrared transmission window, high refractive index and strong blue three-photon upconversion emission of Tm(3+) indicate that Tm(3+)/Yb(3+) co-doped LKBBT glasses are promising upconversion optical and laser materials.

  18. Presence of two emissive minima in the lowest excited state of a push-pull cationic dye unequivocally proved by femtosecond up-conversion spectroscopy and vibronic quantum-mechanical computations.

    PubMed

    Benassi, Enrico; Carlotti, Benedetta; Segado, Mireia; Cesaretti, Alessio; Spalletti, Anna; Elisei, Fausto; Barone, Vincenzo

    2015-05-14

    The long-standing controversy about the presence of two different emissive minima in the lowest excited state of the cationic push-pull dye o-(p-dimethylamino-styryl)-methylpyridinium (DASPMI) was definitively proved through the observation of dual emission, evidenced by both experimental (femtosecond up-conversion measurements) and theoretical (density functional theory calculations) approaches. From the fluorescence up-conversion data of DASPMI in water, the time resolved area normalized spectra (TRANES) were calculated, showing one isoemissive point and therefore revealing the presence of two distinct emissive minima of the excited state potential energy hypersurface with lifetimes of 0.51 and 4.8 ps. These spectroscopic techniques combined with proper data analysis allowed us to discriminate the sub-picosecond emitting state from the occurrence of ultrafast solvation dynamics and to disentangle the overlapping fluorescence (very close in energy) of the two components. Vibronic computations based on TD-DFT potential energy surfaces fully confirm those results and provide deeper insights about the key factors playing a role in determining the overall result. The two emissive minima have different structural and electronic characteristics: on one hand, the locally excited (LE) minimum has a flat geometry and an electric dipole moment smaller than the ground state; on the other hand, the twisted-intramolecular-charge-transfer (TICT) minimum shows a rotation of the methylpyridinium moiety with respect to the rest of the structure, and has an electric dipole moment significantly larger than the ground state.

  19. An ultrasensitive homogeneous aptasensor for kanamycin based on upconversion fluorescence resonance energy transfer.

    PubMed

    Li, Hui; Sun, De-en; Liu, Yajie; Liu, Zhihong

    2014-05-15

    We developed an ultrasensitive fluorescence resonance energy transfer (FRET) aptasensor for kanamycin detection, using upconversion nanoparticles (UCNPs) as the energy donor and graphene as the energy acceptor. Oleic acid modified upconversion nanoparticles were synthesized through a hydrothermal process followed by a ligand exchange with hexanedioic acid. The kanamycin aptamer (5'-NH2-AGATGGGGGTTGAGGCTAAGCCGA-3') was tagged to UCNPs through an EDC-NHS protocol. The π-π stacking interaction between the aptamer and graphene brought UCNPs and graphene in close proximity and hence initiated the FRET process resulting in quenching of UCNPs fluorescence. The addition of kanamycin to the UCNPs-aptamer-graphene complex caused the fluorescence recovery because of the blocking of the energy transfer, which was induced by the conformation change of aptamer into a hairpin structure. A linear calibration was obtained between the fluorescence intensity and the logarithm of kanamycin concentration in the range from 0.01 nM to 3 nM in aqueous buffer solution, with a detection limit of 9 pM. The aptasensor was also applicable in diluted human serum sample with a linear range from 0.03 nM to 3 nM and a detection limit of 18 pM. The aptasensor showed good specificity towards kanamycin without being disturbed by other antibiotics. The ultrahigh sensitivity and pronounced robustness in complicated sample matrix suggested promising prospect of the aptasensor in practical applications.

  20. Sensitivity of laser-induced upconversion fluorescence dynamics to exciting wavelength in Er3+-doped YAG

    NASA Astrophysics Data System (ADS)

    Du, S.; Jiang, L.; Zhang, W.; Gong, W.; Fu, Z.; Dai, Z.

    2011-06-01

    A novel sensitivity of laser-induced upconversion (UC) fluorescence dynamics to the exciting wavelength in Er3+:YAG crystal has been observed. The sensitivities to exciting wavelength variations are only 0.02 and 0.06 nm for 2 G 9/2 and 2 P 3/2 UC luminescence, respectively. The observation of this sensitivity reveals that when a certain level is populated by more than one UC mechanisms, a precise determination of suitable exciting wavelength is crucial because the competition between different UC mechanisms has a sensitive variation with exciting wavelength in near-resonant range.

  1. Femtosecond fluorescence dynamics of rotation-restricted azobenzenophanes: new evidence on the mechanism of trans --> cis photoisomerization of azobenzene.

    PubMed

    Lu, Ying-Chih; Diau, Eric Wei-Guang; Rau, Hermann

    2005-03-17

    The ultrafast relaxation dynamics of two rotation-restricted (azobenzeno-2S-phane and azobenzeno-4S-phane) and one rotation-free (4,4'-dimethylazobenzene) azobenzene derivatives were investigated using femtosecond fluorescence up-conversion on both S(1)(n,pi) and S(2)(pi,pi) excitations. On S(2) excitation, pulse-limited kinetics with a decay coefficient of approximately 100 fs corresponding to ultrafast S(2) --> S(1) relaxation is found to be common for all molecules under investigation regardless of the molecular structure. This indicates that a direct rotational relaxation on the S(2) surface is unfavorable. On S(1) excitation, we observed biphasic fluorescence decay with a femtosecond component attributed to the decay of the Franck-Condon state prepared by excitation and a picosecond component attributed to the deactivation of the relaxed molecule on the S(1) surface. This picosecond component is slowed by at least a factor of 2 for the rotation-restricted 2S-bridged molecule compared to that of the rotation-free molecule; for the even stronger rotation-restricted azobenzeno-4S-phane, the decrease is by a factor of 10. These differences in deactivation suggest that the relaxed states and probably the trajectories for rotation-free and rotation-restricted molecules are different on the S(1) surface, which should be important for the quantum yield of photoisomerization.

  2. Femtosecond fluorescence depolarization study of photosynthetic antenna proteins: observation of ultrafast energy transfer in trimeric C-phycocyanin and allophycocyanin

    NASA Astrophysics Data System (ADS)

    Xie, Sunney; Du, Mei; Mets, Laurens; Fleming, Graham R.

    1992-04-01

    C-phycocyanin (CPC) and Allophycocyanin (APC) are pigment-protein complexes isolated from antenna systems in cyanobacteria. The crystal structure of CPC has recently been solved and APC has a similar structure. CPC and APC have a trimeric structure, monomeric subunits are composed of an (alpha) and (beta) polypeptide chain, each has a tetrapyrrole chromophore chemically bound to position 84. In CPC and APC trimers, the (alpha) 84 and (beta) 84 chromophores in adjacent monomers are in close proximity, forming relatively strong coupled pairs. Calculation of pairwise energy transfer rates using Foerster theory has suggested an extremely fast transfer (> 1 ps-1) between the (alpha) 84 and (beta) 84 pair in CPC. A femtosecond fluorescence up-conversion apparatus was constructed which achieves subhundred femtosecond time resolution. This allows experimental observation of the fast energy transfer process between the (alpha) 84 and (beta) 84 pair in both CPC and APC. There was also a wavelength dependence of the fluorescence depolarization kinetics which is inconsistent with Foerster inductive resonance energy transfer theory.

  3. Distance-dependent plasmon-enhanced fluorescence of upconversion nanoparticles using polyelectrolyte multilayers as tunable spacers.

    PubMed

    Feng, Ai Ling; You, Min Li; Tian, Limei; Singamaneni, Srikanth; Liu, Ming; Duan, Zhenfeng; Lu, Tian Jian; Xu, Feng; Lin, Min

    2015-01-14

    Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted widespread interests in bioapplications due to their unique optical properties by converting near infrared excitation to visible emission. However, relatively low quantum yield prompts a need for developing methods for fluorescence enhancement. Plasmon nanostructures are known to efficiently enhance fluorescence of the surrounding fluorophores by acting as nanoantennae to focus electric field into nano-volume. Here, we reported a novel plasmon-enhanced fluorescence system in which the distance between UCNPs and nanoantennae (gold nanorods, AuNRs) was precisely tuned by using layer-by-layer assembled polyelectrolyte multilayers as spacers. By modulating the aspect ratio of AuNRs, localized surface plasmon resonance (LSPR) wavelength at 980 nm was obtained, matching the native excitation of UCNPs resulting in maximum enhancement of 22.6-fold with 8 nm spacer thickness. These findings provide a unique platform for exploring hybrid nanostructures composed of UCNPs and plasmonic nanostructures in bioimaging applications.

  4. Hybrid lanthanide nanoparticles with paramagnetic shell coated on upconversion fluorescent nanocrystals.

    PubMed

    Li, Zhengquan; Zhang, Yong; Shuter, Borys; Muhammad Idris, Niagara

    2009-10-20

    Nanoparticles comprising of fluorescent probes and MRI contrast agents are highly desirable for biomedical applications due to their ability to be detected at different modes, optically and magnetically. However, most fluorescent probes in such nanoparticles synthesized so far are down-conversion phosphors such as organic dyes and quantum dots, which are known to display many intrinsic limitations. Here, we report a core-shell hybrid lanthanide nanoparticle consisting of an upconverting lanthanide nanocrystal core and a paramagnetic lanthanide complex shell. These nanoparticles are uniform in size, stable in water, and show both high MR relaxivities and upconversion fluorescence, which may have the potential to serve as a versatile imaging tool for smart detection or diagnosis in future biomedical engineering.

  5. Electrospinning fabrication and characterization of magnetic-upconversion fluorescent bifunctional core-shell nanofibers

    NASA Astrophysics Data System (ADS)

    Ma, Qianli; Wang, Jinxian; Dong, Xiangting; Yu, Wensheng; Liu, Guixia

    2014-02-01

    Novel magnetic-upconversion fluorescent bifunctional core-shell nanofibers have been successfully fabricated by coaxial electrospinning technology. NaYF4:Yb3+,Er3+ and Fe3O4 nanoparticles (Nps) were incorporated into polyvinylpyrrolidone (PVP) and electrospun into core-shell nanofibers with Fe3O4/PVP as core and NaYF4:Yb3+,Er3+/PVP as the shell. The morphology and properties of the final products were investigated in detail by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, and fluorescence spectroscopy. The core contained magnetic Nps was ca. 100 nm in diameter, and the shell scattered with NaYF4:Yb3+, Er3+ Nps was ca. 80 nm in thickness. Fluorescence emission peaks of Er3+ in the [Fe3O4/PVP]@[NaYF4:Yb3+,Er3+/PVP] core-shell nanofibers were observed. Compared with Fe3O4/NaYF4:Yb3+,Er3+/PVP composite nanofibers, the luminescent intensity of the [Fe3O4/PVP]@[NaYF4:Yb3+,Er3+/PVP] core-shell nanofibers was much higher, because the Fe3O4 Nps were only distributed in the core of the core-shell nanofibers, thus the manufactured core-shell nanofibers possessed excellent magnetic properties. The new type magnetic-upconversion fluorescent bifunctional [Fe3O4/PVP]@[NaYF4:Yb3+,Er3+/PVP] core-shell nanofibers have many potential applications in display device, nanorobots, protein determination, and target delivery of drug owing to their excellent magnetism and fluorescence.

  6. Quantifying Aflatoxin B1 in peanut oil using fabricating fluorescence probes based on upconversion nanoparticles

    NASA Astrophysics Data System (ADS)

    Sun, Cuicui; Li, Huanhuan; Koidis, Anastasios; Chen, Quansheng

    2016-08-01

    Rare earth doped upconversion nanoparticles convert near-infrared excitation light into visible emission light. Compared to organic fluorophores and semiconducting nanoparticles, upconversion nanoparticles (UCNPs) offer high photochemical stability, sharp emission bandwidths, and large anti-Stokes shifts. Along with the significant light penetration depth and the absence of autofluorescence in biological samples under infrared excitation, these UCNPs have attracted more and more attention on toxin detection and biological labelling. Herein, the fluorescence probe based on UCNPs was developed for quantifying Aflatoxin B1 (AFB1) in peanut oil. Based on a specific immunity format, the detection limit for AFB1 under optimal conditions was obtained as low as 0.2 ng·ml- 1, and in the effective detection range 0.2 to 100 ng·ml- 1, good relationship between fluorescence intensity and AFB1 concentration was achieved under the linear ratios up to 0.90. Moreover, to check the feasibility of these probes on AFB1 measurements in peanut oil, recovery tests have been carried out. A good accuracy rating (93.8%) was obtained in this study. Results showed that the nanoparticles can be successfully applied for sensing AFB1 in peanut oil.

  7. Quantifying Aflatoxin B1 in peanut oil using fabricating fluorescence probes based on upconversion nanoparticles.

    PubMed

    Sun, Cuicui; Li, Huanhuan; Koidis, Anastasios; Chen, Quansheng

    2016-08-05

    Rare earth doped upconversion nanoparticles convert near-infrared excitation light into visible emission light. Compared to organic fluorophores and semiconducting nanoparticles, upconversion nanoparticles (UCNPs) offer high photochemical stability, sharp emission bandwidths, and large anti-Stokes shifts. Along with the significant light penetration depth and the absence of autofluorescence in biological samples under infrared excitation, these UCNPs have attracted more and more attention on toxin detection and biological labelling. Herein, the fluorescence probe based on UCNPs was developed for quantifying Aflatoxin B1 (AFB1) in peanut oil. Based on a specific immunity format, the detection limit for AFB1 under optimal conditions was obtained as low as 0.2ng·ml(-1), and in the effective detection range 0.2 to 100ng·ml(-1), good relationship between fluorescence intensity and AFB1 concentration was achieved under the linear ratios up to 0.90. Moreover, to check the feasibility of these probes on AFB1 measurements in peanut oil, recovery tests have been carried out. A good accuracy rating (93.8%) was obtained in this study. Results showed that the nanoparticles can be successfully applied for sensing AFB1 in peanut oil.

  8. Upconversion nanoparticle-based fluorescence resonance energy transfer assay for organophosphorus pesticides.

    PubMed

    Long, Qian; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2015-06-15

    This paper reports a novel nanosensor for organophosphorus pesticides based on the fluorescence resonance energy transfer (FRET) between NaYF4:Yb,Er upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs). The detection mechanism is based on the facts that AuNPs quench the fluorescence of UCNPs and organophosphorus pesticides (OPs) inhibit the activity of acetylcholinesterase (AChE) which catalyzes the hydrolysis of acetylthiocholine (ATC) into thiocholine. Under the optimized conditions, the logarithm of the pesticides concentration was proportional to the inhibition efficiency. The detection limits of parathion-methyl, monocrotophos and dimethoate reached 0.67, 23, and 67 ng/L, respectively. Meanwhile, the biosensor shows good sensitivity, stability, and could be successfully applied to detection of OPs in real food samples, suggesting the biosensor has potentially extensive application clinic diagnoses assays.

  9. Fluorescence Behaviour and Singlet Oxygen Production of Aluminium Phthalocyanine in the Presence of Upconversion Nanoparticles.

    PubMed

    Watkins, Zane; Taylor, Jessica; D'Souza, Sarah; Britton, Jonathan; Nyokong, Tebello

    2015-09-01

    NaYF4:Yb/Er/Gd upconversion nanoparticles (UCNP) were synthesised and the photoemission stabilised by embedding them in electrospun fibers. The photophysical behaviour of chloro aluminium tetrasulfo phthalocyanine (ClAlTSPc) was studied in the presence of UCNPs when the two are mixed in solution. The fluorescence quantum yield value of ClAlTSPc decreased in the presence of UCNPs due to the heavy atom effect of UCNPs. This effect also resulted in increase in triplet quantum yields for ClAlTSPc in the presence of UCNPs. The fluorescence lifetimes for UCNPs were shortened at 658 nm in the presence of ClAlTSPc when the former was embedded in fiber and suspended in a dimethyl sulfoxide solution of the latter. A clear singlet oxygen generation by ClAlTSPc though Förster resonance energy transfer was demonstrated using a singlet oxygen quencher, 1,3-diphenylisobenzofuran.

  10. Upconversion fluorescence metal-organic frameworks thermo-sensitive imprinted polymer for enrichment and sensing protein.

    PubMed

    Guo, Ting; Deng, Qiliang; Fang, Guozhen; Gu, Dahai; Yang, Yukun; Wang, Shuo

    2016-05-15

    A novel fluorescence material with thermo-sensitive for the enrichment and sensing of protein was successfully prepared by combining molecular imprinting technology with upconversion nanoparticles (UCNPs) and metal-organic frameworks (MOFs). Herein, the UCNPs acted as signal reporter for composite materials because of its excellent fluorescence property and chemical stability. MOFs were introduced to molecularly imprinted polymer (MIP) due to its high specific surface area which increases the rate of mass transfer relative to that of traditional bulk MIP. The thermo-sensitive imprinted material which allows for swelling and shrinking with response to temperature changes was prepared by choosing Bovine hemoglobin (BHB) as the template, N-isopropyl acrylamide (NIPAAM) as the temperature-sensitive functional monomer and N,N-methylenebisacrylamide (MBA) as the cross-linker. The recognition characterizations of imprinted material-coated UCNPs/MOFs (UCNPs/MOFs/MIP) were evaluated, and the results showed that the fluorescence intensity of UCNPs/MOFs/MIP reduced gradually with the increase of BHB concentration. The fluorescence material was response to the temperature. The adsorption capacity was as much as 167.6 mg/g at 28°C and 101.2mg/g at 44°C, which was higher than that of traditional MIP. Therefore, this new fluorescence material for enrichment and sensing protein is very promising for future applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Controllable self-assembly of NaREF4 upconversion nanoparticles and their distinctive fluorescence properties

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoxia; Ni, Yaru; Zhu, Cheng; Fang, Liang; Kou, Jiahui; Lu, Chunhua; Xu, Zhongzi

    2016-07-01

    The paper presents the growth of hexagonal NaYF4:Yb3+, Tm3+ nanocrystals with tunable sizes induced by different contents of doped Yb3+ ions (10%-99.5%) using the thermal decomposition method. These nanoparticles, which have different sizes, are then self-assembled at the interface of cyclohexane and ethylene and transferred onto a normal glass slide. It is found that the size of nanoparticles directs their self-assembly. Due to the appropriate size of 40.5 nm, 15% Yb3+ ions doped nanoparticles are able to be self-assembled into an ordered inorganic monolayer membrane with a large area of about 10 × 10 μm2. More importantly, the obvious short-wave (300-500 nm) fluorescence improvement of the ordered 2D self-assembly structure is observed to be relative to disordered nanoparticles, which is because intrinsic absorption and scattering of upconversion nanoparticles leads to the self-loss of fluorescence, especially the short-wave fluorescence inside the disordered structure, and the relative emission of short-wave fluorescence is reduced. The construction of a 2D self-assembly structure can effectively avoid this and improve the radiated short-wave fluorescence, especially UV photons, and is able to direct the design of new types of solid-state optical materials in many fields.

  12. An upconversion fluorescence resonance energy transfer nanosensor for one step detection of melamine in raw milk.

    PubMed

    Wu, Qiongqiong; Long, Qian; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2015-05-01

    Here we report a nanosensor based on fluorescence resonance energy transfer (FRET) between upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs) for melamine detection. The positively charged UCNPs as donor and the negatively charged AuNPs as acceptor bound together through electrostatic interaction, which caused the fluorescence quenching of UCNPs. Upon addition of melamine, AuNPs were released from the surface of UCNPs and aggregation due to the N-Au interaction between melamine and AuNPs, which results in the fluorescence of UCNPs gradually recovered. Under the optimal conditions including media pH (7.0), the concentration of AuNPs (1.23nM) and incubation time (12min), the fluorescence enhanced efficiency shows a linear response to the melamine concentration ranging from 32.0 to 500nM with a detection limit of 18.0nM. Compared with other fluorescence methods, the fluorimetric nanosensor shows high sensitivity of 0.968, ease of operation and can be used for the determination of melamine in raw milk samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Revisiting the mechanism of nitrogen fluorescence emission induced by femtosecond filament in air

    NASA Astrophysics Data System (ADS)

    Li, Suyu; Jiang, Yuanfei; Chen, Anmin; He, Lanhai; Liu, Dunli; Jin, Mingxing

    2017-03-01

    The backward propagating and side emitted fluorescence during the femtosecond filamentation in air is experimentally investigated in this paper. By comparing the fluorescence emission in the circular and linear polarization states, we find that in the shorter focal length case, the direct ionization of N 2 greatly affects the fluorescence emission behaviors: the fluorescence from N2 + and N 2 is always stronger in the linear and circular polarization cases, respectively. Based on the observation, the emission mechanism of nitrogen fluorescence emission induced by a femtosecond filament is discussed.

  14. Distance-Dependent Plasmon-Enhanced Fluorescence of Upconversion Nanoparticles using Polyelectrolyte Multilayers as Tunable Spacers

    PubMed Central

    Feng, Ai Ling; You, Min Li; Tian, Limei; Singamaneni, Srikanth; Liu, Ming; Duan, Zhenfeng; Lu, Tian Jian; Xu, Feng; Lin, Min

    2015-01-01

    Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted widespread interests in bioapplications due to their unique optical properties by converting near infrared excitation to visible emission. However, relatively low quantum yield prompts a need for developing methods for fluorescence enhancement. Plasmon nanostructures are known to efficiently enhance fluorescence of the surrounding fluorophores by acting as nanoantennae to focus electric field into nano-volume. Here, we reported a novel plasmon-enhanced fluorescence system in which the distance between UCNPs and nanoantennae (gold nanorods, AuNRs) was precisely tuned by using layer-by-layer assembled polyelectrolyte multilayers as spacers. By modulating the aspect ratio of AuNRs, localized surface plasmon resonance (LSPR) wavelength at 980 nm was obtained, matching the native excitation of UCNPs resulting in maximum enhancement of 22.6-fold with 8 nm spacer thickness. These findings provide a unique platform for exploring hybrid nanostructures composed of UCNPs and plasmonic nanostructures in bioimaging applications. PMID:25586238

  15. Electron transfer and solvation in 9,9 '-bianthryl and derivatives: a sub-ps fluorescence upconversion study

    NASA Astrophysics Data System (ADS)

    Jurczok, Martin; Gustavsson, Thomas; Mialocq, Jean-Claude; Rettig, Wolfgang

    2001-08-01

    The time-evolution of the fluorescence spectra of 9,9 '-bianthryl and 9-carbazolyl-anthracene in ethanol and butanol have been studied with subpicosecond time-resolution by the fluorescence upconversion technique. For both compounds, an initial phase (<1 ps) with a structured anthracene-type fluorescence spectrum could be observed which transforms into an unstructured redshifted emission spectrum further shifting to the red on the time scale of the slow component of solvent relaxation. The results are compared to recent transient absorption studies and are interpreted as evidence for a subpicosecond relaxation process (ca 0.4 ps) occurring prior to electron transfer in these compounds.

  16. A cobalt oxyhydroxide-modified upconversion nanosystem for sensitive fluorescence sensing of ascorbic acid in human plasma

    NASA Astrophysics Data System (ADS)

    Cen, Yao; Tang, Jun; Kong, Xiang-Juan; Wu, Shuang; Yuan, Jing; Yu, Ru-Qin; Chu, Xia

    2015-08-01

    Ascorbic acid (AA), a potent antioxidant readily scavenging reactive species, is a crucial micronutrient involved in many biochemical processes. Here, we have developed a cobalt oxyhydroxide (CoOOH)-modified upconversion nanosystem for fluorescence sensing of AA activity in human plasma. The nanosystem consists of upconversion nanoparticles (UCNPs) NaYF4:30% Yb,0.5% Tm@NaYF4, which serve as energy donors, and CoOOH nanoflakes formed on the surface of UCNPs, which act as efficient energy acceptors. The fluorescence resonance energy transfer (FRET) process from the UCNPs to the absorbance of the CoOOH nanoflakes occurs in the nanosystem. The AA-mediated specific redox reaction reduces CoOOH into Co2+, leading to the inhibition of FRET, and resulting in the recovery of upconversion emission spectra. On the basis of these features, the nanosystem can be used for sensing AA activity with sensitivity and selectivity. Moreover, due to the minimizing background interference provided by UCNPs, the nanosystem has been applied to monitoring AA levels in human plasma sample with satisfactory results. The proposed approach may potentially provide an analytical platform for research and clinical diagnosis of AA related diseases.Ascorbic acid (AA), a potent antioxidant readily scavenging reactive species, is a crucial micronutrient involved in many biochemical processes. Here, we have developed a cobalt oxyhydroxide (CoOOH)-modified upconversion nanosystem for fluorescence sensing of AA activity in human plasma. The nanosystem consists of upconversion nanoparticles (UCNPs) NaYF4:30% Yb,0.5% Tm@NaYF4, which serve as energy donors, and CoOOH nanoflakes formed on the surface of UCNPs, which act as efficient energy acceptors. The fluorescence resonance energy transfer (FRET) process from the UCNPs to the absorbance of the CoOOH nanoflakes occurs in the nanosystem. The AA-mediated specific redox reaction reduces CoOOH into Co2+, leading to the inhibition of FRET, and resulting in the

  17. Spatiotemporal control of degenerate multiphoton fluorescence microscopy with delay-tunable femtosecond pulse pairs

    NASA Astrophysics Data System (ADS)

    Das, Dhiman; Bhattacharyya, Indrajit; Goswami, Debabrata

    2016-07-01

    Selective excitation of a particular fluorophore in an ensemble of different fluorophores with overlapping fluorescence spectra is shown to be dependent on the time delay of femtosecond pulse pairs in multiphoton fluorescence microscopy. In particular, the two-photon fluorescence behavior of the Texas Red and DAPI dye pair inside Bovine Pulmonary Artery Endothelial (BPAE) cells depends strongly on the center wavelength of the laser, as well as the delay between two identical laser pulses in one-color femtosecond pulse-pair excitation scheme. Thus, we present a novel design concept using pairs of femtosecond pulses at different central wavelengths and tunable pulse separations for controlling the image contrast between two spatially and spectrally overlapping fluorophores. This femtosecond pulse-pair technique is unique in utilizing the variation of dye dynamics inside biological cells as a contrast mode in microscopy of different fluorophores.

  18. Upconversion fluorescent nanoparticles as a potential tool for in-depth imaging

    NASA Astrophysics Data System (ADS)

    Nagarajan, Sounderya; Zhang, Yong

    2011-09-01

    Upconversion nanoparticles (UCNs) are nanoparticles that are excited in the near infrared (NIR) region with emission in the visible or NIR regions. This makes these particles attractive for use in biological imaging as the NIR light can penetrate the tissue better with minimal absorption/scattering. This paper discusses the study of the depth to which cells can be imaged using these nanoparticles. UCNs with NaYF4 nanocrystals doped with Yb3 + , Er3 + (visible emission)/Yb3 + , Tm3 + (NIR emission) were synthesized and modified with silica enabling their dispersion in water and conjugation of biomolecules to their surface. The size of the sample was characterized using transmission electron microscopy and the fluorescence measured using a fluorescence spectrometer at an excitation of 980 nm. Tissue phantoms were prepared by reported methods to mimic skin/muscle tissue and it was observed that the cells could be imaged up to a depth of 3 mm using the NIR emitting UCNs. Further, the depth of detection was evaluated for UCNs targeted to gap junctions formed between cardiac cells.

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

    PubMed

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

    2016-09-08

    A comprehensive study of ultrafast molecular relaxation processes of isomeric meso-(pyridyl) porphyrins (TpyPs) has been carried out by using femtosecond time-resolved emission and absorption spectroscopic techniques upon pumping at 400 nm, Soret band (B band or S2), in 4:1 dichloromethane (DCM) and tetrahydrofuran (THF) solvent mixture. By combined studies of fluorescence up-conversion, time-correlated single photon counting, and transient absorption spectroscopic techniques, a complete model with different microscopic rate constants associated with elementary processes involved in electronic manifolds has been reported. Besides, a distinct coherent nuclear wave packet motion in Qy state is observed at low-frequency mode, ca. 26 cm(-1) region. Fluorescence up-conversion studies constitute ultrafast time-resolved emission spectra (TRES) over the whole emission range (430-710 nm) starting from S2 state to Qx state via Qy state. Careful analysis of time profiles of up-converted signals at different emission wavelengths helps to reveal detail molecular dynamics. The observed lifetimes are as indicated: A very fast decay component with 80 ± 20 fs observed at ∼435 nm is assigned to the lifetime of S2 (B) state, whereas being a rise component in the region of between 550 and 710 nm emission wavelength pertaining to Qy and Qx states, it is attributed to very fast internal conversion (IC) occurring from B → Qy and B → Qx as well. Two distinct components of Qy emission decay with ∼200-300 fs and ∼1-1.5 ps time constants are due to intramolecular vibrational redistribution (IVR) induced by solute-solvent inelastic collisions and vibrational redistribution induced by solute-solvent elastic collision, respectively. The weighted average of these two decay components is assigned as the characteristic lifetime of Qy, and it ranges between 0.3 and 0.5 ps. An additional ∼20 ± 2 ps rise component is observed in Qx emission, and it is assigned to the formation time of

  20. Nonlinear frequency up-conversion of femtosecond pulses from an erbium fibre laser to the range of 0.8 - 1 {mu}m in silica fibres

    SciTech Connect

    Anashkina, E A; Andrianov, A V; Kim, A V

    2013-03-31

    We consider different mechanisms of nonlinear frequency up-conversion of femtosecond pulses emitted by an erbium fibre system ({lambda} = 1.5 {mu}m) to the range of 0.8 - 1.2 {mu}m in nonlinear silica fibres. The generation efficiency and the centre frequencies of dispersive waves are found as functions of the parameters of the fibre and the input pulse. Simple analytical estimates are obtained for the spectral distribution of the intensity and the frequency shift of a wave packet in the region of normal dispersion during the emission of a high-order soliton under phase matching conditions. In the geometrical optics approximation the frequency shifts are estimated in the interaction of dispersive waves with solitons in various regimes. (extreme light fields and their applications)

  1. Singlet-based photon upconversion in multichromophore organic thin films (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Weingarten, Daniel H.; LaCount, Michael; Rumbles, Garry; van de Lagemaat, Jao; Lusk, Mark T.; Shaheen, Sean E.

    2015-10-01

    Solid-state energy upconversion has many potential applications, from nonlinear photonics and biophotonics to expanding the spectrum available for solar energy harvest. In organic molecular systems, upconversion is frequently done in solution to mitigate aggregation-induced photoluminescence quenching or to facilitate the diffusion of triplet donors in Triplet-Triplet Annihilation (TTA) systems. Here we demonstrate an organic thin film upconversion system utilizing two-photon absorption (TPA) properties to improve upconversion efficiency. In blend films of Stilbene-420 and Rhodamine 6G we observe a tenfold increase in up-converted fluorescence compared to the fluorescence yield of TPA in pristine stilbene films. While TPA normally has quadratic dependence on excitation intensity, these blend films exhibit sub-quadratic intensity dependence, indicating a combination of linear and quadratic upconversion processes and dramatically improving upconversion efficiency at lower excitation intensities. This improvement in intensity dependence allows for relatively efficient upconversion upon excitation by a nanosecond laser pulse, in contrast to the more expensive femtosecond lasers generally required for excitation in TPA microscopy and similar systems. Time-resolved photoluminescence decay measurements reveal that all excited states involved in this upconversion process are singlets, which indicates the potential for reduced energy losses when compared to TTA upconversion systems and their inherent intersystem-crossing energy losses. We observe emission from both the Rhodamine 6G donor molecules and Stilbene-420 acceptor molecules, indicating the presence of prompt fluorescence from the donor as well as upconversion to the acceptor, and FRET losses from acceptor back to donor. By fitting to a kinetic model we extract rates for these competing processes.

  2. A Modified Four-State Model for the "Dual Fluorescence" of N6,N6-Dimethyladenine Derived from Femtosecond Fluorescence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Schwalb, Nina K.; Temps, Friedrich

    2009-07-01

    The radiationless deactivation of the excited electronic states of the dual fluorescence molecule N6,N6-dimethyladenine (DMAde) was investigated using femtosecond time-resolved fluorescence up-conversion spectroscopy. The molecules were studied in solution in water and in dioxane. Fluorescence-time profiles were recorded in the wide wavelength range of 290 ≤ λfl ≤ 650 nm. The excitation wavelengths in the region of the first UV absorption band were tuned from close to the electronic origin (λpump = 294 nm) to excess energies of ˜5400 cm-1 above (λpump = 258 nm). Global fits to the measured curves turned out to reflect distinctive molecular relaxation processes on five well-defined time scales. Sub-100 fs and 0.52(3) ps lifetimes were found to predominate at the shortest UV and blue emission wavelengths in water, 1.5(1) and 3.0(2) ps components at intermediate wavelengths and a 62(1) ps value in the red region of the spectrum (2σ error limits of the last digits in parentheses). In dioxane, these lifetimes changed to ≤0.27 and 0.63(4) ps in the UV, 1.5(1) and 10.9(10) ps in a wide range of intermediate, and 1.40(4) ns at the longest wavelengths. However, little dependence of the respective time constants on λpump was observed, indicating that the ensuing relaxation processes proceed via practically barrierless pathways through conical intersections. Building on the knowledge for the parent molecule adenine (Ade), the observations were rationalized with the help of a modified four-state model for the electronic dynamics in DMAde with the ππ*(La), ππ*(Lb), and nπ* states similar to those in Ade and an intramolecular charge-transfer (ICT) state, which has no counterpart in Ade, responsible for the long-wavelength fluorescence.

  3. Three-dimensional quick response code based on inkjet printing of upconversion fluorescent nanoparticles for drug anti-counterfeiting.

    PubMed

    You, Minli; Lin, Min; Wang, Shurui; Wang, Xuemin; Zhang, Ge; Hong, Yuan; Dong, Yuqing; Jin, Guorui; Xu, Feng

    2016-05-21

    Medicine counterfeiting is a serious issue worldwide, involving potentially devastating health repercussions. Advanced anti-counterfeit technology for drugs has therefore aroused intensive interest. However, existing anti-counterfeit technologies are associated with drawbacks such as the high cost, complex fabrication process, sophisticated operation and incapability in authenticating drug ingredients. In this contribution, we developed a smart phone recognition based upconversion fluorescent three-dimensional (3D) quick response (QR) code for tracking and anti-counterfeiting of drugs. We firstly formulated three colored inks incorporating upconversion nanoparticles with RGB (i.e., red, green and blue) emission colors. Using a modified inkjet printer, we printed a series of colors by precisely regulating the overlap of these three inks. Meanwhile, we developed a multilayer printing and splitting technology, which significantly increases the information storage capacity per unit area. As an example, we directly printed the upconversion fluorescent 3D QR code on the surface of drug capsules. The 3D QR code consisted of three different color layers with each layer encoded by information of different aspects of the drug. A smart phone APP was designed to decode the multicolor 3D QR code, providing the authenticity and related information of drugs. The developed technology possesses merits in terms of low cost, ease of operation, high throughput and high information capacity, thus holds great potential for drug anti-counterfeiting.

  4. Deoxycholate induced tetramer of αA-crystallin and sites of phosphorylation: Fluorescence correlation spectroscopy and femtosecond solvation dynamics

    NASA Astrophysics Data System (ADS)

    Chowdhury, Aritra; Mojumdar, Supratik Sen; Choudhury, Aparajita; Banerjee, Rajat; Das, Kali Pada; Sasmal, Dibyendu Kumar; Bhattacharyya, Kankan

    2012-04-01

    Structure and dynamics of acrylodan labeled αA-crystallin tetramer formed in the presence of a bile salt (sodium deoxycholate, NaDC) has been studied using fluorescence correlation spectroscopy (FCS) and femtosecond up-conversion techniques. Using FCS it is shown that, the diffusion constant (Dt) of the αA-crystallin oligomer (mass ˜800 kDa) increases from ˜35 μm2 s-1 to ˜68 μm2 s-1. This corresponds to a decrease in hydrodynamic radius (rh) from ˜6.9 nm to ˜3.3 nm. This corresponds to about 10-fold decrease in molecular mass to ˜80 kDa and suggests formation of a tetramer (since mass of αA-crystallin monomer is ˜20 kDa). The steady state emission maximum and average solvation time (<τs>) of acrylodan labeled at cysteine 131 position of αA-crystallin is markedly affected on addition of NaDC, while the tryptophan (trp-9) becomes more exposed. This suggests that NaDC binds near the cys-131 and makes the terminal region of αA-crystallin exposed. This may explain the enhanced auto-phosphorylation activity of αA-crystallin near the terminus of the 173 amino acid protein (e.g., at the threonine 13, serine 45, or serine 169 and 172) and suggests that phosphorylation at ser-122 (close to cys-131) is relatively less important.

  5. Mesoporous-silica-coated up-conversion fluorescent nanoparticles for photodynamic therapy.

    PubMed

    Qian, Hai Sheng; Guo, Hui Chen; Ho, Paul Chi-Lui; Mahendran, Ratha; Zhang, Yong

    2009-10-01

    Near-infrared (NIR)-to-visible up-conversion fluorescent nanoparticles have potential to be used for photodynamic therapy (PDT) in deep tissue because NIR light can penetrate thick tissue due to weak absorption in the optical window. Here a uniform layer of mesoporous silica is coated onto NaYF(4) up-converting nanocrystals, with a large surface area of approximately 770 m(2) g(-1) and an average pore size of 2 nm. A photosensitizer, zinc phthalocyanine, is incorporated into the mesoporous silica. Upon excitation by a NIR laser, the nanocrystals convert NIR light to visible light, which further activates the photosensitizer to release reactive singlet oxygen to kill cancer cells. The photosensitizer encapsulated in mesoporous silica is protected from degradation in the harsh biological environment. It is demonstrated that the photosensitizers loaded into the porous silica shell of the nanoparticles are not released out of the silica while they continuously produce singlet oxygen upon excitation by a NIR laser. The nanoparticles are reusable as the photosensitizers encapsulated in the silica are removed by soaking in ethanol.

  6. Efficient holmium-doped fluoride fiber laser emitting 2.1 µm and blue upconversion fluorescence upon excitation at 2 µm.

    PubMed

    Guhur, A; Jackson, S D

    2010-09-13

    We demonstrate a highly efficient and high power Ho(3+)-doped fluoride glass fiber laser that is resonantly pumped with a Tm(3+)-doped silicate glass fiber laser operating at 2.051 µm. The laser operates at 2080 nm and generated 6.66 W at a slope efficiency of 72%. We observe strong visible upconversion fluorescence centered at a variety of wavelengths including 491 nm which results from three sequential energy transfer upconversion processes; the fluorescence to pump energy ratio for this emission is one the largest reported to date.

  7. Sub-picosecond fluorescence spectroscopy of the M intermediate in the photocycle of bacteriorhodopsin by using up-conversion fluorometry

    NASA Astrophysics Data System (ADS)

    Kamiya, Narutoshi; Ohtani, Hiroyuki; Sekikawa, Taro; Kobayashi, Takayoshi

    1999-05-01

    A fluorescence up-conversion method was applied to the measurement of the fluorescence lifetime of the M intermediate with a 13- cis retinal Schiff base. M formed under cw visible light (440-800 nm) irradiation of the purple membrane suspension of Halobacterium salinarum containing diethyl ether or guanidine hydrochloride at 24°C. An excitation source was a frequency-doubled Ti:Sapphire laser (408 nm, 240±10 fs). The 500 nm fluorescence of M was mixed with the fundamental of the laser and converted to UV for detection. The measured lifetimes (0.6 and 0.3 ps in ether and in guanidine, respectively) were shorter than those of protonated all-trans retinal Schiff bases in solution and in apoprotein.

  8. Three-dimensional quick response code based on inkjet printing of upconversion fluorescent nanoparticles for drug anti-counterfeiting

    NASA Astrophysics Data System (ADS)

    You, Minli; Lin, Min; Wang, Shurui; Wang, Xuemin; Zhang, Ge; Hong, Yuan; Dong, Yuqing; Jin, Guorui; Xu, Feng

    2016-05-01

    Medicine counterfeiting is a serious issue worldwide, involving potentially devastating health repercussions. Advanced anti-counterfeit technology for drugs has therefore aroused intensive interest. However, existing anti-counterfeit technologies are associated with drawbacks such as the high cost, complex fabrication process, sophisticated operation and incapability in authenticating drug ingredients. In this contribution, we developed a smart phone recognition based upconversion fluorescent three-dimensional (3D) quick response (QR) code for tracking and anti-counterfeiting of drugs. We firstly formulated three colored inks incorporating upconversion nanoparticles with RGB (i.e., red, green and blue) emission colors. Using a modified inkjet printer, we printed a series of colors by precisely regulating the overlap of these three inks. Meanwhile, we developed a multilayer printing and splitting technology, which significantly increases the information storage capacity per unit area. As an example, we directly printed the upconversion fluorescent 3D QR code on the surface of drug capsules. The 3D QR code consisted of three different color layers with each layer encoded by information of different aspects of the drug. A smart phone APP was designed to decode the multicolor 3D QR code, providing the authenticity and related information of drugs. The developed technology possesses merits in terms of low cost, ease of operation, high throughput and high information capacity, thus holds great potential for drug anti-counterfeiting.Medicine counterfeiting is a serious issue worldwide, involving potentially devastating health repercussions. Advanced anti-counterfeit technology for drugs has therefore aroused intensive interest. However, existing anti-counterfeit technologies are associated with drawbacks such as the high cost, complex fabrication process, sophisticated operation and incapability in authenticating drug ingredients. In this contribution, we developed a

  9. Bifunctional NaGdF4:Yb, Er, Fe nanocrystals with the enhanced upconversion fluorescence

    NASA Astrophysics Data System (ADS)

    Chuai, Xiaohong; Guo, Xingyuan; Liu, Xiaohui; He, Guanghui; Zheng, Kezhi; He, Chunfeng; Qin, Weiping

    2015-06-01

    NaGdF4:Yb, Er nanocrystals doped with Fe3+ were synthesized by a facile hydrothermal method. The upconversion emissions in a broad range from 200 to 700 nm were measured under 980 nm laser excitation. The luminescence intensity can be improved greatly by Fe3+ doping. In addition to the typical upconversion emission of Er3+ ions, the violet emission from Gd3+ is explained by the energy transfer from Er3+ to Gd3+. Powder X-ray diffraction patterns reveal that Fe3+ can enter crystal sites interstitially and substitutionally. The effects of Fe3+ doping on morphology, crystal growth and emission properties of particles are discussed in detailed. Furthermore, these nanocrystals exhibit paramagnetic properties and have the potential applications in bimodal bioimaging in virtue of their upconversion luminescent and paramagnetic properties.

  10. Study of upconversion fluorescence property of novel Er3+/Yb3+ co-doped tellurite glasses.

    PubMed

    Xu, Tie-Feng; Li, Guang-Po; Nie, Qiu-Hua; Shen, Xiang

    2006-06-01

    Er3+/Yb3+ co-doped TeO2-B2O3-Nb2O5-ZnO (TBN) glasses were prepared. The absorption spectra and upconversion luminescence spectra of TBN glasses were measured and analyzed. The upconversion emission bands centered at 530, 546 and 658 nm were observed under the excitation at 975 nm, corresponding to the transitions of 2H11/2-->4I15/2, 4S3/2-->4I15/2 and 4F9/2-->4I15/2 respectively. The ratio of red emission to green emission increases with an increasing of Yb3+ ions concentration. According to the quadratic dependence on excitation power, the possible upconversion mechanisms and processes were discussed.

  11. Synthesis of fluorescent nanocarbons by femtosecond laser induced plasma in liquid

    NASA Astrophysics Data System (ADS)

    Agatsuma, Naoki; Fujimatsu, Yusei; Shimotsuma, Yasuhiko; Sakakura, Masaaki; Miura, Kiyotaka

    2016-07-01

    Fluorescent Carbon nanoparticles (CNPs) with tunable emission are successfully synthesized from the water suspension of graphene oxide by the femtosecond laser irradiation. The luminescence properties were controllable by doping nitrogen into CNPs in the presence of an ammonia molecule. We have also confirmed that CNPs with diamond structure were directly precipitated from the solvent molecules such as cyclohexane.

  12. ATOMIC AND MOLECULAR PHYSICS: Infrared-to-visible and infrared-to-violet upconversion fluorescence of rare earth doped LaF3 nanocrystals

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Qin Wei-, Ping; Di, Wei-Hua; Zhang Ji-, Sen; Cao, Chun-Yan

    2008-09-01

    This paper reports that hexagonal-phase LaF3:Yb0.203+, Er0.023+ and LaF3:Yb0.203+, Tm0.023+ nanocrystals (NCs) were synthesized via a hydrothermal method. The transmission electron microscopy, selected area electron diffraction, powder x-ray diffraction, and thermogravimetric analysis are used to characterize the NCs. Under 980 nm excitation, the Yb3+/Er3+ and Yb3+/Tm3+ codoped NCs colloidal solutions present bright green and blue upconversion fluorescence, respectively. These NCs show efficient infrared-to-violet and infrared-to-visible upconversion. The upconversion fluorescence mechanisms of La F3:Yb0.023+ Er0.023+ and LaF3:Yb0.023+, Tm0.023+ NCs are investigated with a 980-nm diode laser as excitation source.

  13. Laser-induced fluorescence detection of hydroxyl (OH) radical by femtosecond excitation.

    PubMed

    Stauffer, Hans U; Kulatilaka, Waruna D; Gord, James R; Roy, Sukesh

    2011-05-15

    The development of a laser-induced fluorescence detection scheme for probing combustion-relevant species using a high-repetition-rate ultrafast laser is described. A femtosecond laser system with a 1 kHz repetition rate is used to induce fluorescence, following two-photon excitation (TPE), from hydroxyl (OH) radicals that are present in premixed laminar flames. The experimental TPE and one-photon fluorescence spectra resulting from broadband excitation into the (0,0) band of the OH A(2)∑(+)-X(2)Π system are compared to simulated spectra. Additionally, the effects of non-transform-limited femtosecond pulses on TPE efficiency is investigated. © 2011 Optical Society of America

  14. What's new in the proton transfer reaction from pyranine to water? A femtosecond study of the proton transfer dynamics

    SciTech Connect

    Prayer, C.; Gustavsson, T.; Tran-Thi, T.-H.

    1996-04-01

    The proton transfer from excited pyranine to water is studied by the femtosecond fluorescence upconversion technique. It is shown for the first time that the proton transfer reaction in water proceeds by three successive steps: the solvent cage relaxation, the specific solute-solvent hydrogen-bond formation and finally the ion pair dissociation/diffusion.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  16. Enhancement of the Upconversion Emission by Visible-to-Near-Infrared Fluorescent Graphene Quantum Dots for miRNA Detection

    PubMed Central

    2016-01-01

    We developed a sensor for the detection of specific microRNA (miRNA) sequences that was based on graphene quantum dots (GQDs) and ssDNA-UCNP@SiO2. The proposed sensor exploits the interaction between the sp2 carbon atoms of the GQD, mainly π–π stacking, and the DNA nucleobases anchored on the upconversion nanoparticles (UCNPs). This interaction brings the GQD to the surface of the ssDNA-UCNP@SiO2 system, enhancing the upconversion emission. On the other hand, hybridization of the single-stranded DNA (ssDNA) chains anchored on the nanoparticles with their complementary miRNA sequences blocks the capacity of the UCNPs to interact with the GQD through π–π stacking. That gives as result a reduction of the fluorescent enhancement, which is dependent on the concentration of miRNA sequences. This effect was used to create a sensor for miRNA sequences with a detection limit of 10 fM. PMID:27153453

  17. Energy and electron transfer in the photosynthetic reaction center complex of Acidiphilium rubrum containing Zn-bacteriochlorophyll a studied by femtosecond up-conversion spectroscopy.

    PubMed

    Tomi, Tetsuo; Shibata, Yutaka; Ikeda, Yuki; Taniguchi, Seiji; Haik, Chosrowjan; Mataga, Noboru; Shimada, Keizo; Itoh, Shigeru

    2007-01-01

    A photosynthetic reaction center (RC) complex was isolated from a purple bacterium, Acidiphilium rubrum. The RC contains bacteriochlorophyll a containing Zn as a central metal (Zn-BChl a) and bacteriopheophytin a (BPhe a) but no Mg-BChl a. The absorption peaks of the Zn-BChl a dimer (P(Zn)), the accessory Zn-BChl a (B(Zn)), and BPhe a (H) at 4 K in the RC showed peaks at 875, 792, and 753 nm, respectively. These peaks were shorter than the corresponding peaks in Rhodobacter sphaeroides RC that has Mg-BChl a. The kinetics of fluorescence from P(Zn)(*), measured by fluorescence up-conversion, showed the rise and the major decay with time constants of 0.16 and 3.3 ps, respectively. The former represents the energy transfer from B(Zn)(*) to P(Zn), and the latter, the electron transfer from P(Zn) to H. The angle between the transition dipoles of B(Zn) and P(Zn) was estimated to be 36 degrees based on the fluorescence anisotropy. The time constants and the angle are almost equal to those in the Rb. sphaeroides RC. The high efficiency of A. rubrum RC seems to be enabled by the chemical property of Zn-BChl a and by the L168HE modification of the RC protein that modifies P(Zn).

  18. Up-conversion fluorescence "off-on" switch based on heterogeneous core-satellite assembly for thrombin detection.

    PubMed

    Zhao, Xueli; Li, Si; Xu, Liguang; Ma, Wei; Wu, Xiaoling; Kuang, Hua; Wang, Libing; Xu, Chuanlai

    2015-08-15

    NaGdF4: Yb, Er nanoparticles, with up-conversion (UC) fluorescence, were used for the first time to build an "off-on" switch based on Au core-UC satellites for thrombin detection. We fabricated the fluorescence sensor using thrombin aptamer modified Au core and complementary sequence modified UC satellites in liquid phase. With optimized assembled conditions, the yield of Au core-UC satellites achieved 80%. The fluorescence of UC nanoparticles quenched when satellite NP attached to Au core NP. Thrombin aptamer on the surface of Au core would bind to targets when thrombin existed in the system, then UC satellites were released and the quenched fluorescence recovered. The sensor showed high specificity for thrombin compared with other biomolecules and the limit of detection reached 3.5 fg/mL. Application of this sensor to detect targets in human serum also achieved satisfactory results. The purpose of this work was to build an ultrasensitive sensor based on Au core-UC satellites for thrombin detection in human serum to achieve diagnosis of diseases.

  19. Photolytic-interference-free, femtosecond two-photon fluorescence imaging of atomic hydrogen.

    PubMed

    Kulatilaka, Waruna D; Gord, James R; Katta, Viswanath R; Roy, Sukesh

    2012-08-01

    We discuss photolytic-interference-free, high-repetition-rate imaging of reaction intermediates in flames and plasmas using femtosecond (fs) multiphoton excitation. The high peak power of fs pulses enables efficient nonlinear excitation, while the low energy nearly eliminates interfering single-photon photodissociation processes. We demonstrate proof-of-principle, interference-free, two-photon laser-induced fluorescence line imaging of atomic hydrogen in hydrocarbon flames and discuss the method's implications for certain other atomic and molecular species.

  20. Femtosecond fluorescence dynamics of porphyrin in solution and solid films: the effects of aggregation and interfacial electron transfer between porphyrin and TiO2.

    PubMed

    Luo, Liyang; Lo, Chen-Fu; Lin, Ching-Yao; Chang, I-Jy; Diau, Eric Wei-Guang

    2006-01-12

    The excited-state relaxation dynamics of a synthetic porphyrin, ZnCAPEBPP, in solution, coated on a glass substrate as solid films, mixed with PMMA and coated on a glass substrate as solid films, and sensitized on nanocrystalline TiO2 films were investigated by using femtosecond fluorescence up-conversion spectroscopy with excitation in the Soret band, S2. We found that the S2--> S1 electronic relaxation of ZnCAPEBPP in solution and on PMMA films occurs in 910 and 690 fs, respectively, but it becomes extremely rapid, <100 fs, in solid films and TiO2 films due to formation of porphyrin aggregates. When probed in the S1 state of porphyrin, the fluorescence transients of the solid films show a biphasic kinetic feature with the rapid and slow components decaying in 1.9-2.4 and 19-26 ps, respectively. The transients in ZnCAPEBPP/TiO2 films also feature two relaxation processes but they occur on different time scales, 100-300 fs and 0.8-4.1 ps, and contain a small offset. According to the variation of relaxation period as a function of molecular density on a TiO2 surface, we assigned the femtosecond component of the TiO2 films as due to indirect interfacial electron transfer through a phenylethynyl bridge attached to one of four meso positions of the porphyrin ring, and the picosecond component arising from intermolecular energy transfer among porphyrins. The observed variation of aggregate-induced relaxation periods between solid and TiO2 films is due mainly to aggregation of two types: J-type aggregation is dominant in the former case whereas H-type aggregation prevails in the latter case.

  1. Femtosecond two-photon-excited fluorescence of melanin

    NASA Astrophysics Data System (ADS)

    Teuchner, Klaus; Mueller, Susanne; Freyer, Wolfgang; Leupold, Dieter; Altmeyer, Peter; Stuecker, Markus; Hoffmann, Klaus

    2003-02-01

    Spectral and time-resolved fluorescence studies of different eumelanins (natural, synthetic, enzymatic) in solution have been carried out by two-photon excitation at 800 nm, using 80 fs pulses with photon flux densities <= 1027 cm-2.s-1. Whereas all samples show monotonously decreasing absorption between near UV and near IR, their fluorescence behavior indicates strong heterogeneity. With respect to the also measured one-photon excited fluorescence (OPF) of melanin at 400 nm, the overall spectral shape of the two-photon excited fluorescence (TPF) is red-shifted. Both OPF and TPF exhibit three-exponential decay with a shortest component # 200 ps. As is also shown, the fluorescence properties of melanin are dependent on the micro-environment. This allows the hypothesis, that the process of malignant transformation in skin tissue could be reflected in the fluorescence, provided the melanin in skin is selectively excited. The latter is realized by the described stepwise absorption of two 800 nm photons. In this way, indeed characteristic differences between the TPF spectra of healthy tissue, nevus cell nevi and malignant melanoma have been found.

  2. Household Fluorescent Lateral Flow Strip Platform for Sensitive and Quantitative Prognosis of Heart Failure Using Dual-Color Upconversion Nanoparticles.

    PubMed

    You, MinLi; Lin, Min; Gong, Yan; Wang, Shurui; Li, Ang; Ji, Lingyu; Zhao, Haoxiang; Ling, Kai; Wen, Ting; Huang, Yuan; Gao, Dengfeng; Ma, Qiong; Wang, Tingzhong; Ma, Aiqun; Li, Xiaoling; Xu, Feng

    2017-06-27

    Heart failure (HF) is the end-stage of cardiovascular diseases, which is associated with a high mortality rate and high readmission rate. Household early diagnosis and real-time prognosis of HF at bedside are of significant importance. Here, we developed a highly sensitive and quantitative household prognosis platform (termed as UC-LFS platform), integrating a smartphone-based reader with multiplexed upconversion fluorescent lateral flow strip (LFS). Dual-color core-shell upconversion nanoparticles (UCNPs) were synthesized as probes for simultaneously quantifying two target antigens associated with HF, i.e., brain natriuretic peptide (BNP) and suppression of tumorigenicity 2 (ST2). With the fluorescent LFS, we achieved the specific detection of BNP and ST2 antigens in spiked samples with detection limits of 5 pg/mL and 1 ng/mL, respectively, both of which are of one order lower than their clinical cutoff. Subsequently, a smartphone-based portable reader and an analysis app were developed, which could rapidly quantify the result and share prognosis results with doctors. To confirm the usage of UC-LFS platform for clinical samples, we detected 38 clinical serum samples using the platform and successfully detected the minimal concentration of 29.92 ng/mL for ST2 and 17.46 pg/mL for BNP in these clinical samples. Comparing the detection results from FDA approved clinical methods, we obtained a good linear correlation, indicating the practical reliability and stability of our developed UC-LFS platform. Therefore, the developed UC-LFS platform is demonstrated to be highly sensitive and specific for sample-to-answer prognosis of HF, which holds great potential for risk assessment and health monitoring of post-treatment patients at home.

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

    PubMed

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

    2012-09-01

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

  4. Fine tunable red-green upconversion luminescence from glass ceramic containing 5%Er{sup 3+}:NaYF{sub 4} nanocrystals under excitation of two near infrared femtosecond lasers

    SciTech Connect

    Shang, Xiaoying; Cheng, Wenjing; Zhou, Kan; Ma, Jing; Feng, Donghai; Zhang, Shian; Sun, Zhenrong; Jia, Tianqing; Chen, Ping; Qiu, Jianrong

    2014-08-14

    In this paper, we report fine tunable red-green upconversion luminescence of glass ceramic containing 5%Er{sup 3+}: NaYF{sub 4} nanocrystals excited simultaneously by two near infrared femtosecond lasers. When the glass ceramic was irradiated by 800 nm femtosecond laser, weak red emission centered at 670 nm was detected. Bright red light was observed when the fs laser wavelength was tuned to 1490 nm. However, when excited by the two fs lasers simultaneously, the sample emitted bright green light centered at 550 nm, while the red light kept the same intensity. The dependences of the red and the green light intensities on the two pump lasers are much different, which enables us to manipulate the color emission by adjusting the two pump laser intensities, respectively. We present a theoretical model of Er{sup 3+} ions interacting with two fs laser fields, and explain well the experimental results.

  5. Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

    DOE PAGES

    Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole; ...

    2017-06-19

    Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

  6. Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes.

    PubMed

    Phillips, Mark C; Brumfield, Brian E; LaHaye, Nicole; Harilal, Sivanandan S; Hartig, Kyle C; Jovanovic, Igor

    2017-06-19

    We demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from (235)U and (238)U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

  7. Upconversion Nanoparticles and Monodispersed Magnetic Polystyrene Microsphere Based Fluorescence Immunoassay for the Detection of Sulfaquinoxaline in Animal-Derived Foods.

    PubMed

    Hu, Gaoshuang; Sheng, Wei; Zhang, Yan; Wang, Junping; Wu, Xuening; Wang, Shuo

    2016-05-18

    A novel fluorescence immunoassay for detecting sulfaquinoxaline (SQX) in animal-derived foods was developed using NaYF4:Yb/Tm upconversion nanoparticles (UCNPs) conjugated with antibodies as fluorescence signal probes, and monodisperse magnetic polystyrene microspheres (MMPMs) modified with coating antigen as immune-sensing capture probes for trapping and separating the signal probes. Based on a competitive immunoassay format, the detection limit of the proposed method for detecting SQX was 0.1 μg L(-1) in buffer and 0.5 μg kg(-1) in food samples. The recoveries of SQX in spiked samples ranged from 69.80 to 133.00%, with coefficients of variation of 0.24-25.06%. The extraction procedure was fast, simple, and environmentally friendly, requiring no organic solvents. In particular, milk samples can be analyzed directly after simple dilution. This method has appealing properties, such as sensitive fluorescence response, a simple and fast extraction procedure, and environmental friendliness, and could be applied to detecting SQX in animal-derived foods.

  8. Green up-conversion and near-infrared luminescence of femtosecond-laser-written waveguides in Er3+, MgO co-doped nearly stoichiometric LiNbO3 crystal.

    PubMed

    Lv, Jinman; Hao, Xiaotao; Chen, Feng

    2016-10-31

    We report on the green up-conversion and near-infrared (NIR) emission in Er3+, MgO co-doped nearly stoichiometric LiNbO3 waveguides fabricated by femtosecond laser writing. The waveguides with so-called Type I geometry by laser writing support nearly single-mode propagation of light at NIR wavelength of 1.55 μm. In addition, it has been found that the guidance is only along the vertical (i.e., TM) polarization, which is due to the laser-induced positive changes of extraordinary index in the guiding core. The green up-conversion at 550 nm and 528 nm, corresponding to the transitions of 4S3/24I15/2, 2H11/24I15/2, as well as the NIR luminescence emission at C-band centered at 1550 nm under 4I13/24I15/2 transition have been realized in the waveguides, respectively. Our results have shown that the intensities of the guided-wave green up-conversion and NIR emissions are higher than those obtained from the bulk, which may be owing to the enhanced intracavity optical intensities of the waveguide with respect to the bulk.

  9. Manipulation of cellular light from green fluorescent protein by a femtosecond laser

    NASA Astrophysics Data System (ADS)

    He, Hao; Li, Shiyang; Wang, Shaoyang; Hu, Minglie; Cao, Youjia; Wang, Chingyue

    2012-10-01

    Green fluorescent protein (GFP) is one of the most widely studied and exploited proteins in biochemistry and cell biology. It emits fluorescence following optical excitation, which is usually provided by a laser. Here, we report that fluorescence from enhanced GFP can be `turned off' by exposing cells to laser light. A short flash of femtosecond laser light is shown to deplete calcium in the endoplasmic reticulum of cells. Calcium-release-activated calcium channels are then activated by stromal interaction molecule 1 (STIM1). The rise in intracellular Ca2+ depolarizes mitochondria and increases the leakage of reactive oxygen species, which then permanently bleach the GFP. This controllable optical scheme for reactive oxygen species generation can also be used to modulate the photoconversion of GFP fluorescence from green to red emission and provide a mechanism for influencing cellular molecular dynamics.

  10. Efficient upconversion fluorescence in a blue-emitting spirobifluorene-anthracene copolymer doped with low concentrations of Pt(II)octaethylporphyrin.

    PubMed

    Laquai, Frédéric; Wegner, Gerhard; Im, Chan; Büsing, Arne; Heun, Susanne

    2005-08-15

    Upconversion-induced fluorescence in platinum-octaethylporphyrin (PtOEP)-doped thin films of a spirobifluorene-anthracene copolymer has been investigated. Upon exciting in the range of the absorption band (2.31 eV, 537 nm) of the guest molecules, blue fluorescence (2.75 eV, 450 nm) from the spirobifluorene host was observed. The intensity of the upconverted emission was found to be one order of magnitude higher than from a PtOEP doped but anthracene-free spirobifluorene copolymer and than previously reported for metallated porphyrin-doped polyfluorene samples. It is argued that the efficient upconversion originates from the triplet energy transfer from the phosphorescent dopant to the sensitive unit of the host polymer, followed by triplet-triplet annihilation and finally blue emission from the spirobifluorene host polymer backbone.

  11. Efficient upconversion fluorescence in a blue-emitting spirobifluorene-anthracene copolymer doped with low concentrations of Pt(II)octaethylporphyrin

    NASA Astrophysics Data System (ADS)

    Laquai, Frédéric; Wegner, Gerhard; Im, Chan; Büsing, Arne; Heun, Susanne

    2005-08-01

    Upconversion-induced fluorescence in platinum-octaethylporphyrin (PtOEP)-doped thin films of a spirobifluorene-anthracene copolymer has been investigated. Upon exciting in the range of the absorption band (2.31 eV, 537 nm) of the guest molecules, blue fluorescence (2.75 eV, 450 nm) from the spirobifluorene host was observed. The intensity of the upconverted emission was found to be one order of magnitude higher than from a PtOEP doped but anthracene-free spirobifluorene copolymer and than previously reported for metallated porphyrin-doped polyfluorene samples. It is argued that the efficient upconversion originates from the triplet energy transfer from the phosphorescent dopant to the sensitive unit of the host polymer, followed by triplet-triplet annihilation and finally blue emission from the spirobifluorene host polymer backbone.

  12. 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.

  13. Investigation on the structure and upconversion fluorescence of Yb3+/Ho3+ co-doped fluorapatite crystals for potential biomedical applications

    PubMed Central

    Li, Xiyu; Zhu, Jingxian; Man, Zhentao; Ao, Yingfang; Chen, Haifeng

    2014-01-01

    Rare-earth Yb3+ and Ho3+ co-doped fluorapatite (FA:Yb3+/Ho3+) crystals were prepared by hydrothermal synthesis, and their structure, upconversion properties, cell proliferation and imaging were investigated. The synthesized crystals, with a size of 16 by 286 nm, have a hexagonal crystal structure of classic FA and a Ca/Yb/Ho molar ratio of 100/16/2.1. Several reasonable Yb3+/Ho3+ -embedding lattice models along the fluorine channel of the FA crystal cell are proposed for the first time, such as models for (Ca7YbHo©)(PO4)6F2 and (Ca6YbHoNa2)(PO4)6F2. The activated FA:Yb3+/Ho3+ crystals were found to exhibit distinct upconversion fluorescence. The 543- and 654-nm signals in the emission spectra could be assigned, respectively, to the 5F4 (5S2) - 5I8 and 5F5 - 5I8 transitions of holmium via 980-nm near-infrared excitation and the energy transfer of ytterbium. After the surfaces were grafted with hydrophilic dextran, the crystals displayed clear fluorescent cell imaging. Thus, the prepared novel FA:Yb3+/Ho3+ upconversion fluorescent crystals have potential applications in the biomedical field. PMID:24658285

  14. Magnetic and fluorescent Gd2O3:Yb3+/Ln3+ nanoparticles for simultaneous upconversion luminescence/MR dual modal imaging and NIR-induced photodynamic therapy

    PubMed Central

    Liu, Jun; Huang, Long; Tian, Xiumei; Chen, Xiaoming; Shao, Yuanzhi; Xie, Fukang; Chen, Dihu; Li, Li

    2017-01-01

    The development of upconversion nanoparticles (UCNs) for theranostics application is a new strategy toward the accurate diagnosis and efficient treatment of cancer. Here, magnetic and fluorescent lanthanide-doped gadolinium oxide (Gd2O3) UCNs with bright upconversion luminescence (UCL) and high longitudinal relaxivity (r1) are used for simultaneous magnetic resonance imaging (MRI)/UCL dual-modal imaging and photodynamic therapy (PDT). In vitro and in vivo MRI studies show that these products can serve as good MRI contrast agents. The bright upconversion luminescence of the products allows their use as fluorescence nanoprobes for live cells imaging. We also utilized the luminescence-emission capability of the UCNs for the activation of a photosensitizer to achieve significant PDT results. To the best of our knowledge, this study is the first use of lanthanide-doped Gd2O3 UCNs in a theranostics application. This investigation provides a useful platform for the development of Gd2O3-based UCNs for clinical diagnosis, treatment, and imaging-guided therapy of cancer. PMID:28031709

  15. Magnetic and fluorescent Gd2O3:Yb(3+)/Ln(3+) nanoparticles for simultaneous upconversion luminescence/MR dual modal imaging and NIR-induced photodynamic therapy.

    PubMed

    Liu, Jun; Huang, Long; Tian, Xiumei; Chen, Xiaoming; Shao, Yuanzhi; Xie, Fukang; Chen, Dihu; Li, Li

    The development of upconversion nanoparticles (UCNs) for theranostics application is a new strategy toward the accurate diagnosis and efficient treatment of cancer. Here, magnetic and fluorescent lanthanide-doped gadolinium oxide (Gd2O3) UCNs with bright upconversion luminescence (UCL) and high longitudinal relaxivity (r1) are used for simultaneous magnetic resonance imaging (MRI)/UCL dual-modal imaging and photodynamic therapy (PDT). In vitro and in vivo MRI studies show that these products can serve as good MRI contrast agents. The bright upconversion luminescence of the products allows their use as fluorescence nanoprobes for live cells imaging. We also utilized the luminescence-emission capability of the UCNs for the activation of a photosensitizer to achieve significant PDT results. To the best of our knowledge, this study is the first use of lanthanide-doped Gd2O3 UCNs in a theranostics application. This investigation provides a useful platform for the development of Gd2O3-based UCNs for clinical diagnosis, treatment, and imaging-guided therapy of cancer.

  16. Rich stochastic dynamics of co-doped Er:Yb fluorescence upconversion nanoparticles in the presence of thermal, non-conservative, harmonic and optical forces

    NASA Astrophysics Data System (ADS)

    Nome, Rene A.; Sorbello, Cecilia; Jobbágy, Matías; Barja, Beatriz C.; Sanches, Vitor; Cruz, Joyce S.; Aguiar, Vinicius F.

    2017-03-01

    The stochastic dynamics of individual co-doped Er:Yb upconversion nanoparticles (UCNP) were investigated from experiments and simulations. The UCNP were characterized by high-resolution scanning electron microscopy, dynamic light scattering, and zeta potential measurements. Single UCNP measurements were performed by fluorescence upconversion micro-spectroscopy and optical trapping. The mean-square displacement (MSD) from single UCNP exhibited a time-dependent diffusion coefficient which was compared with Brownian dynamics simulations of a viscoelastic model of harmonically bound spheres. Experimental time-dependent two-dimensional trajectories of individual UCNP revealed correlated two-dimensional nanoparticle motion. The measurements were compared with stochastic trajectories calculated in the presence of a non-conservative rotational force field. Overall, the complex interplay of UCNP adhesion, thermal fluctuations and optical forces led to a rich stochastic behavior of these nanoparticles.

  17. Fabricating upconversion fluorescent nanoparticles modified substrate for dynamical control of cancer cells and pathogenic bacteria.

    PubMed

    Li, Huanhuan; Chen, Quansheng; Zhao, Jiewen; Urmila, Khulal

    2016-09-07

    Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted widespread interests in the field of biomedicine because of their unique upconverting capability by converting near infrared (NIR) excitation to visible or ultraviolet (UV) emission. Here, we developed a novel UCNP-based substrate for dynamic capture and release of cancer cells and pathogenic bacteria under NIR-control. The UCNPs harvest NIR light and convert it to ultraviolet light, which subsequently result in the cleavage of photoresponsive linker (PR linker) from the substrate, and on demand allows the release of a captured cell. The results show that after seeding cells for 5 h, the cells were efficiently captured on the surface of the substrate and ˜89.4% of the originally captured S. aureus was released from the surface after exposure to 2 W/cm(2) NIR light for 30 min, and ˜92.1% of HepG2 cells. These findings provide a unique platform for exploring an entirely new application field for this promising luminescent nanomaterial.

  18. Upconverting rare-earth nanoparticles with a paramagnetic lanthanide complex shell for upconversion fluorescent and magnetic resonance dual-modality imaging

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Ji, Lei; Zhang, Bingbo; Yin, Peihao; Qiu, Yanyan; Song, Daqian; Zhou, Juying; Li, Qi

    2013-05-01

    Multi-modal imaging based on multifunctional nanoparticles is a promising alternative approach to improve the sensitivity of early cancer diagnosis. In this study, highly upconverting fluorescence and strong relaxivity rare-earth nanoparticles coated with paramagnetic lanthanide complex shells and polyethylene glycol (PEGylated UCNPs@DTPA-Gd3+) are synthesized as dual-modality imaging contrast agents (CAs) for upconverting fluorescent and magnetic resonance dual-modality imaging. PEGylated UCNPs@DTPA-Gd3+ with sizes in the range of 32-86 nm are colloidally stable. They exhibit higher longitudinal relaxivity and transverse relaxivity in water (r1 and r2 values are 7.4 and 27.8 s-1 per mM Gd3+, respectively) than does commercial Gd-DTPA (r1 and r2 values of 3.7 and 4.6 s-1 per mM Gd3+, respectively). They are found to be biocompatible. In vitro cancer cell imaging shows good imaging contrast of PEGylated UCNPs@DTPA-Gd3+. In vivo upconversion fluorescent imaging and T1-weighted MRI show excellent enhancement of both fluorescent and MR signals in the livers of mice administered PEGylated UCNPs@DTPA-Gd3+. All the experimental results indicate that the synthesized PEGylated UCNPs@DTPA-Gd3+ present great potential for biomedical upconversion of fluorescent and magnetic resonance dual-modality imaging applications.

  19. Femtosecond two-photon laser-induced fluorescence of krypton for high-speed flow imaging.

    PubMed

    Wang, Yejun; Capps, Cade; Kulatilaka, Waruna D

    2017-02-15

    Ultrashort-pulse (femtosecond-duration) two-photon laser-induced fluorescence (fs-TPLIF) of an inert gas tracer krypton (Kr) is investigated. A detailed spectroscopic study of fluorescence channels followed by the 5p'←←4p excitation of Kr at 204.1 nm is reported. The experimental line positions in the 750-840 nm emission region agree well with the NIST Atomic Spectra Database. The present work provides an accurate listing of relative line strengths in this spectral region. In the range of laser pulse energies investigated, a quadratic dependence was observed between the Kr-TPLIF signal and the laser pulse energy. The single-laser-shot 2D TPLIF images recorded in an unsteady jet demonstrate the potential of using fs excitation at 204.1 nm for mixing and flow diagnostic studies using Kr as an inert gas tracer.

  20. Variations in fluorescence quantum yield of basic fuchsin with silver nanoparticles prepared by femtosecond laser ablation.

    PubMed

    Pathrose, Bini; Sahira, H; Nampoori, V P N; Radhakrishnan, P; Mujeeb, A

    2014-07-15

    Nano structured noble metals have very important applications in diverse fields such as photovoltaics, catalysis, electronic and magnetic devices, etc. In the present work, the application of dual beam thermal lens technique is employed for the determination of the absolute fluorescence quantum yield of the triaminotriphenylmethane dye, basic fuchsin in the presence of silver sol is studied. Silver sol is prepared by femtosecond laser ablation. It is observed that the presence of silver sol decreases the fluorescence quantum efficiency. The observed results are in line with the conclusion that the reduction in quantum yield in the quenching region is essentially due to the non-radiative relaxation of the absorbed energy. It is also observed that the presence of silver sol enhances the thermal lens signal which makes its detection easier at any concentration.

  1. Dual-modal upconversion fluorescent/X-ray imaging using ligand-free hexagonal phase NaLuF4:Gd/Yb/Er nanorods for blood vessel visualization.

    PubMed

    Zeng, Songjun; Wang, Haibo; Lu, Wei; Yi, Zhigao; Rao, Ling; Liu, Hongrong; Hao, Jianhua

    2014-03-01

    Visualization of blood vessel of lung can improve the detection of the lung and pulmonary vascular diseases. However, research on visualization of blood vessel of lung using the new generation upconversion nanoprobes is still scarce. Herein, high quality hexagonal phase NaLuF4:Gd/Yb/Er nanorods were synthesized by a simple hydrothermal method through doping Gd(3+). Doping Gd can not only promote the phase transformation from cubic to hexagonal and the shape evolution from microtube to rod-like, but also provide an additional magnetic properties for biomedical application. The as-prepared nanorods were further converted to water solubility by treating with HCl for eliminating the capped oleic acid. The ligand-free nanorods were successfully used for high-contrast upconversion fluorescent bioimaging of HeLa cells. Moreover, the in vivo synergistic upconversion fluorescent and X-ray imaging of nude mice were demonstrated by subcutaneously and intravenously administrated the ligand-free nanorods. The X-ray signals were matched well with the upconversion signal, indicating the successfully synergistic bioimaging. The ex-vivo X-ray and upconversion fluorescent imaging of various organs revealed that the nanorods were mainly accumulated in liver and lung. More importantly, the blood vessel of the lung can be readily visualized when these ligand-free nanorods are intravenously injected. Apart from the synergistic X-ray and upconversion bioimaging, the ligand-free nanorods can also possess excellent paramagnetic property for potential magnetic resonance imaging contrast agent. Our results have demonstrated the enhanced visualization of blood vessel of lung performed by dual-modal bioimaging of X-ray and upconversion fluorescence, revealing the great promise of these nanoprobes in angiography imaging. Such a new technique enables the integration of the two bioimaging techniques by combining their collective strengths and minimizing their shortcomings.

  2. Femtosecond Fluorescence Spectra of Tryptophan in Human γ-Crystallin Mutants: Site-Dependent Ultrafast Quenching

    PubMed Central

    Xu, Jianhua; Chen, Jiejin; Toptygin, Dmitri; Tcherkasskaya, Olga; Callis, Patrik; King, Jonathan; Brand, Ludwig; Knutson, Jay R.

    2012-01-01

    The eye lens crystallin proteins are subject to UV irradiation throughout life, and the photochemistry of damage proceeds through the excited state; thus, their tryptophan (Trp) fluorescence lifetimes are physiologically important properties. The time resolved fluorescence spectra of single Trps in human γD- and γS-crystallins have been measured with both an upconversion spectrophotofluorometer on the 300fs to 100ps time scale, and a time correlated single photon counting apparatus on the 100ps to 10ns time scale, respectively. Three Trps in each wild type protein were replaced by phenylalanine, leading to single-Trp mutants: W68-only and W156-only of HγD- and W72-only and W162-only of HγS-crystallin. These proteins exhibit similar ultrafast signatures: positive definite decay associated spectra (DAS) for 50 – 65ps decay constants that indicate dominance of fast, heterogeneous quenching. The quenched population (judged by amplitude) of this DAS differs among mutants. Trps 68, 156 in human γD- and Trp72 in human γS-crystallin are buried, but water can reach amide oxygen and ring HE1 atoms through narrow channels. QM-MM simulations of quenching by electron transfer predict heterogeneous decay times from 50–500 ps that agree with our experimental results. Further analysis of apparent radiative lifetimes allow us to deduce that substantial subpopulations of Trp are fully quenched in even faster (sub-300 fs) processes for several of the mutants. The quenching of Trp fluorescence of human γD- and γS-crystallin may protect them from ambient light induced photo damage. PMID:19919143

  3. COMPARISON OF FEMTOSECOND AND NANOSECOND TWO PHOTON ABSORPTION LASER INDUCED FLUORESCENCE (TALIF) OF ATOMIC OXYGEN IN ATMOSPHERIC PRESSURE PLASMAS

    DTIC Science & Technology

    2016-08-01

    AFRL-RQ-WP-TR-2016-0118 COMPARISON OF FEMTOSECOND- AND NANOSECOND-TWO-PHOTON-ABSORPTION LASER- INDUCED FLUORESCENCE (TALIF) OF ATOMIC ...LASER-INDUCED FLUORESCENCE (TALIF) OF ATOMIC OXYGEN IN ATMOSPHERIC PRESSURE PLASMAS 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM...copyright protection in the United States. 14. ABSTRACT Absolute number densities of atomic species produced by nanosecond duration, repetitively

  4. Magnetic/upconversion fluorescent NaGdF4:Yb,Er nanoparticle-based dual-modal molecular probes for imaging tiny tumors in vivo.

    PubMed

    Liu, Chunyan; Gao, Zhenyu; Zeng, Jianfeng; Hou, Yi; Fang, Fang; Li, Yilin; Qiao, Ruirui; Shen, Lin; Lei, Hao; Yang, Wensheng; Gao, Mingyuan

    2013-08-27

    Detection of early malignant tumors remains clinically difficult; developing ultrasensitive imaging agents is therefore highly demanded. Owing to the unusual magnetic and optical properties associated with f-electrons, rare-earth elements are very suitable for creating functional materials potentially useful for tumor imaging. Nanometer-sized particles offer such a platform with which versatile unique properties of the rare-earth elements can be integrated. Yet the development of rare-earth nanoparticle-based tumor probes suitable for imaging tiny tumors in vivo remains difficult, which challenges not only the physical properties of the nanoparticles but also the rationality of the probe design. Here we report new approaches for size control synthesis of magnetic/upconversion fluorescent NaGdF4:Yb,Er nanocrystals and their applications for imaging tiny tumors in vivo. By independently varying F(-):Ln(3+) and Na(+):Ln(3+) ratios, the size and shape regulation mechanisms were investigated. By replacing the oleic acid ligand with PEG2000 bearing a maleimide group at one end and two phosphate groups at the other end, PEGylated NaGdF4:Yb,Er nanoparticles with optimized size and upconversion fluorescence were obtained. Accordingly, a dual-modality molecular tumor probe was prepared, as a proof of concept, by covalently attaching antitumor antibody to PEGylated NaGdF4:Yb,Er nanoparticles through a "click" reaction. Systematic investigations on tumor detections, through magnetic resonance imaging and upconversion fluorescence imaging, were carried out to image intraperitoneal tumors and subcutaneous tumors in vivo. Owing to the excellent properties of the molecular probes, tumors smaller than 2 mm was successfully imaged in vivo. In addition, pharmacokinetic studies on differently sized particles were performed to disclose the particle size dependent biodistributions and elimination pathways.

  5. Mechanism and applications of new fluorescent compounds produced by femtosecond laser surgery in biological tissue (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Qu, Jianan Y.; Sun, Qiqi

    2017-02-01

    The single or multi-photon microscopy based on fluorescent labelling and staining is a sensitive and quantitative method that is widely used in molecular biology and medical research for a variety of experimental, analytical, and quality control applications. However, label-free method is highly desirable in biology and medicine when performing long term live imaging of biological system and obtaining instant tissue examination during surgery procedures. Recently, our group found that femtosecond laser surgery turned a variety of biological tissues and protein samples into highly fluorescent substances. The newly formed fluorescent compounds produced during the laser surgery can be excited via single- and two-photon processes over broad wavelength ranges. We developed a combined confocal and two-photon spectroscopic microscope to characterize the fluorescence from the new compound systematically. The structures of the femtosecond laser treated tissue were studied using Raman spectroscopy and transmission electron microscopy. Our study revealed the mechanisms of the fluorescence emission form the new compound. Furthermore, we demonstrated the applications of the fluorescent compounds for instant evaluation of femtosecond laser microsurgery, study of stem cell responses to muscle injury and neuro-regeneration after spinal cord injury.

  6. Fabrication of Ag@SiO(2)@Y(2)O(3):Er nanostructures for bioimaging: tuning of the upconversion fluorescence with silver nanoparticles.

    PubMed

    Zhang, Fan; Braun, Gary B; Shi, Yifeng; Zhang, Yichi; Sun, Xiaohong; Reich, Norbert O; Zhao, Dongyuan; Stucky, Galen

    2010-03-10

    We demonstrated that the nanostructures comprising silver cores and dense layers of Y(2)O(3):Er separated by a silica shell are an excellent model system to study the interaction between upconversion materials and metals in nanoscale. This architecture allows for versatile control of the Y(2)O(3):Er-metal interaction through control of the silica dielectric spacer thickness and the metal-core size. Finally, the nanoparticles are potentially interesting as fluorescent labels in, for instance (single particle), imaging experiments or bioassays which require low background or tissue penetrating wavelengths.

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

    SciTech Connect

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

    2010-11-10

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

  8. Femtosecond laser irradiation of the fluorescent molecules-loaded poly(lactic-co-glycolic acid)

    NASA Astrophysics Data System (ADS)

    Umemoto, Taiga; Shibata, Akimichi; Terakawa, Mitsuhiro

    2017-09-01

    Molecular release from scaffolds is desired for tailoring cell-compatible tissue engineering. Several methods have been proposed to control molecular release, such as annealing, plasma treatment, and laser processing. In this study, we describe the alteration of Rhodamine B (RhB)-loaded poly(lactic-co-glycolic acid) (PLGA) after femtosecond laser irradiation, which was evaluated on the basis of the water absorption and mass remaining. Fluorescence measurement of released RhB molecules revealed the acceleration of the molecular release upon 400-nm laser irradiation, whereas 800-nm laser irradiation did not induce a comparable degree of change compared with non-irradiated samples. The result of the water absorption measurement indicates that the large amount of water absorption of 400-nm laser-irradiated PLGA sample may accelerate the diffusion of the loaded molecules through absorbing water, which resulted in the faster molecular release.

  9. Femtosecond laser inscribed cladding waveguides in Nd:YAG ceramics: fabrication, fluorescence imaging and laser performance.

    PubMed

    Liu, Hongliang; Jia, Yuechen; Vázquez de Aldana, Javier Rodríguez; Jaque, Daniel; Chen, Feng

    2012-08-13

    We report on the fabrication of depressed cladding waveguide lasers in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) ceramics microstructured by femtosecond laser pulses. Full control over the confined light spatial distribution is demonstrated by the fabrication of high contrast waveguides with hexagonal, circular and trapezoidal configurations. The confocal fluorescence measurements of the waveguides reveal that the original luminescence features of Nd3+ ions are well-preserved in the waveguide regions. Under optical pump at 808 nm, cladding waveguides showed continuous wave efficient laser oscillation. The maximum output power obtained at 1064.5 nm is ~181 mW with a slope efficiency as high as 44%, which suggests that the fabricated Nd:YAG ceramic waveguides are promising candidates for efficient integrated laser sources.

  10. Lasing dynamics study by femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy

    NASA Astrophysics Data System (ADS)

    Wei, Dang; Qing, Liao; Peng-Cheng, Mao; Hong-Bing, Fu; Yu-Xiang, Weng

    2016-05-01

    Femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS) is a versatile technique with advantages of high sensitivity, broad detection bandwidth, and intrinsic spectrum correction function. These advantages should benefit the study of coherent emission, such as measurement of lasing dynamics. In this letter, the FNOPAS was used to trace the lasing process in Rhodamine 6G (R6G) solution and organic semiconductor nano-wires. High-quality transient emission spectra and lasing dynamic traces were acquired, which demonstrates the applicability of FNOPAS in the study of lasing dynamics. Our work extends the application scope of the FNOPAS technique. Project supported by the National Natural Science Foundation of China (Grant Nos. 20925313 and 21503066), the Innovation Program of Chinese Academy of Sciences (Grant No. KJCX2-YW-W25), the Postdoctoral Project of Hebei University, China, and the Project of Science and Technology Bureau of Baoding City, China (Grant No. 15ZG029).

  11. Femtosecond laser pulse optimization for multiphoton cytometry and control of fluorescence

    NASA Astrophysics Data System (ADS)

    Tkaczyk, Eric Robert

    This body of work encompasses optimization of near infrared femtosecond laser pulses both for enhancement of flow cytometry as well as adaptive pulse shaping to control fluorescence. A two-photon system for in vivo flow cytometry is demonstrated, which allows noninvasive quantification of circulating cell populations in a single live mouse. We monitor fluorescently-labeled red blood cells for more than two weeks, and are also able to noninvasively measure circulation times of two distinct populations of breast cancer cells simultaneously in a single mouse. We build a custom laser excitation source in the form of an extended cavity mode-locked oscillator, which enables superior detection in whole blood or saline of cell lines expressing fluorescent proteins including the green fluorescent protein (GFP), tdTomato and mPlum. A mathematical model explains unique features of the signals. The ability to distinguish different fluorescent species is central to simultaneous measurement of multiple molecular targets in high throughput applications including the multiphoton flow cytometer. We demonstrate that two dyes which are not distinguishable to one-photon measurements can be differentiated and in fact quantified in mixture via phase-shaped two-photon excitation pulses found by a genetic algorithm. We also selectively enhance or suppress two-photon fluorescence of numerous common dyes with tailored pulse shapes. Using a multiplicative (rather than ratiometric) fitness parameter, we are able to control the fluorescence while maintaining a strong signal. With this method, we control the two-photon fluorescence of the blue fluorescent protein (BFP), which is of particular interest in investigations of protein-protein interactions, and has frustrated previous attempts of control. Implementing an acousto-optic interferometer, we use the same experimental setup to measure two-photon excitation cross-sections of dyes and prove that photon-photon interferences are the

  12. A novel and sensitive fluorescence immunoassay for the detection of fluoroquinolones in animal-derived foods using upconversion nanoparticles as labels.

    PubMed

    Hu, Gaoshuang; Sheng, Wei; Zhang, Yan; Wu, Xuening; Wang, Shuo

    2015-11-01

    A novel fluorescence immunoassay to detect fluoroquinolones in animal-derived foods was developed for the first time by use of upconversion nanoparticles as signal-probe labels. The bioassay system was established by the use of coating-antigen-modified polystyrene particles as immune-sensing probes for separation and anti-norfloxacin monoclonal antibody conjugated with carboxyl-functionalized NaYF4:Yb,Er upconversion nanoparticles which were prepared via a pyrolysis method and a subsequent ligand exchange process as fluorescent-signal probes (emission intensity recorded at 542 nm with excitation at 980 nm). Under optimized conditions, detection of fluoroquinolones was performed easily. The detection limit of this fluorescence immunoassay for norfloxacin, for example, was 10 pg mL(-1), within a wide linear range of 10 pg mL(-1) to 10 ng mL(-1) (R (2)  = 0.9959). For specificity analysis, the data obtained indicate this method could be applied in broad-spectrum detection of fluoroquinolones. The recoveries of norfloxacin-spiked animal-derived foods ranged from 82.37 to 132.22 %, with coefficients of variation of 0.24-25.06 %. The extraction procedure was rapid and simple, especially for milk samples, which could be analyzed directly without any pretreatment. In addition, the results obtained with the method were in good agreement with those obtained with commercial ELISA kits. The fluorescence immunoassay was more sensitive, especially with regard to the detection limit in milk samples (0.01 ng mL(-1) for norfloxacin): it was 50-fold more sensitive than commercial ELISA kits (0.5 ng mL(-1) for norfloxacin). The results show the proposed fluorescence immunoassay was facile, sensitive, and interference free, and is an alternative method for the quantitative detection of fluoroquinolone residues in animal-derived foods.

  13. Facial Layer-by-Layer Engineering of Upconversion Nanoparticles for Gene Delivery: Near-Infrared-Initiated Fluorescence Resonance Energy Transfer Tracking and Overcoming Drug Resistance in Ovarian Cancer.

    PubMed

    Lin, Min; Gao, Yan; Diefenbach, Thomas J; Shen, Jacson K; Hornicek, Francis J; Park, Yong Il; Xu, Feng; Lu, Tian Jian; Amiji, Mansoor; Duan, Zhenfeng

    2017-03-08

    Development of multidrug resistance (MDR) contributes to the majority of treatment failures in clinical chemotherapy. We report facial layer-by-layer engineered upconversion nanoparticles (UCNPs) for near-infrared (NIR)-initiated tracking and delivery of small interfering RNA (siRNA) to enhance chemotherapy efficacy by silencing the MDR1 gene and resensitizing resistant ovarian cancer cells to drug. Layer-by-layer engineered UCNPs were loaded with MDR1 gene-silencing siRNA (MDR1-siRNA) by electrostatic interaction. The delivery vehicle enhances MDR1-siRNA cellular uptake, protects MDR1-siRNA from nuclease degradation, and promotes endosomal escape for silencing the MDR gene. The intrinsic photon upconversion of UCNPs provides an unprecedented opportunity for monitoring intracellular attachment and release of MDR1-siRNA by NIR-initiated fluorescence resonance energy transfer occurs between donor UCNPs and acceptor fluorescence dye-labeled MDR1-siRNA. Enhanced chemotherapeutic efficacy in vitro was demonstrated by cell viability assay. The developed delivery vehicle holds great potential in delivery and imaging-guided tracking of therapeutic gene targets for effective treatment of drug-resistant cancers.

  14. Coupling CARS with multiphoton fluorescence and high harmonic generation imaging modalities using a femtosecond laser source

    NASA Astrophysics Data System (ADS)

    Chen, Hongtao; Slipchenko, Mikhail N.; Zhu, Jiabin; Buhman, Kimberly K.; Cheng, Ji-Xin

    2009-02-01

    Multimodal nonlinear optical imaging has opened new opportunities and becomes a powerful tool for imaging complex tissue samples with inherent 3D spatial resolution.. We present a robust and easy-to-operate approach to add the coherent anti-stokes Raman scattering (CARS) imaging modality to a widely used multiphoton microscope. The laser source composed of a Mai Tai femtosecond laser and an optical parametric oscillator (OPO) offers one-beam, two-beam and three-beam modalities. The Mai Tai output at 790 nm is split into two beams, with 80% of the power being used to pump the OPO. The idler output at 2036 nm from OPO is doubled using a periodically poled lithium niobate (PPLN) crystal. This frequency-doubled idler beam at 1018 nm is sent through a delay line and collinearly combined with the other Mai Tai beam for CARS imaging on a laser-scanning microscope. This Mai Tai beam is also used for multiphoton fluorescence and second harmonic generation (SHG) imaging. The signal output at 1290 nm from OPO is used for SHG and third-harmonic generation (THG) imaging. External detectors are installed for both forward and backward detection, whereas two internal lamda-scan detectors are employed for microspectroscopy analysis. This new system allows vibrationally resonant CARS imaging of lipid bodies, SHG imaging of collagen fibers, and multiphoton fluorescence analysis in fresh tissues. As a preliminary application, the effect of diacylglycerol acyltransferase 1 (DGAT1) deficiency on liver lipid metabolism in mice was investigated.

  15. Femtosecond, two-photon, planar laser-induced fluorescence of carbon monoxide in flames.

    PubMed

    Richardson, Daniel R; Roy, Sukesh; Gord, James R

    2017-02-15

    Two-photon, planar laser-induced fluorescence (TP-PLIF) of carbon monoxide was performed in steady and driven flames using femtosecond (fs) laser pulses at 1 kHz. Excitation radiation at 230.1 nm (full-width at half-maximum bandwidth of 270  cm-1) was used to pump many rovibrational two-photon transitions in the B1+←X1+ system. Visible fluorescence in the range 362-516 nm was captured using an image intensifier and high-speed camera. The signal dependence on excitation energy and wavelength is presented. Photolytic interferences from the ultraviolet laser were explored in a sooting diffusion flame. Using an excitation laser intensity of 1010  W/cm2, negligible photolytic interferences were observed, and PLIF imaging of dynamic flame events was performed at 1 kHz.

  16. Adaptive Control of Two-Photon Excitation of Green Fluorescent Protein with Shaped Femtosecond Pulses

    NASA Astrophysics Data System (ADS)

    Kawano, Hiroyuki; Nabekawa, Yasuo; Suda, Akira; Oishi, Yu; Mizuno, Hideaki; Miyawaki, Atsushi; Midorikawa, Katsumi

    For many years, it has been believed that a Fourier-transform-limited (FTL) laser pulse is the most effective light source for the generation of nonlinear phenomena, since the FTL pulse has the shortest pulse duration, that is, the highest intensity, that can be limited by the spectral width due to the principle of uncertainty. Recently, many reports have been published on the adaptive control of nonlinear phenomena with shaped femtosecond excitation laser pulses [1, 2]. Their reports have shown that the modification of the spectral and temporal phases of excitation pulses can increase or decrease the probabilities and efficiencies of such nonlinear phenomena. This method has been widely applied to studies on the active control of molecular motions or chemical reactions [3,4]. Considering further novel biological applications, we focus on the two-photon excited fluorescence (TPEF) of the green fluorescent protein (GFP) from the jellyfish Aequorea victoria. GFP is spontaneously fluorescent and is relatively nontoxic compared with other organic dyes used as optical markers. Therefore, it has been widely used as a "tag" material for the fluorescence observation of living cells [5]. Two-photon excitation microscopy (TPEM) is a powerful tool for biological real-time observation due to its various advantages, such as a clear contrast, good S/N ratio, and high spatial resolution [7]. From a practical point of view, however, there is a serious problem with TPEM, which is the photobleaching of a dye. The intensity of a fluorescence signal decreases significantly during observation. One of the reasons for this is that the chromophore structure is degraded by intense excitation laser pulses that are required for efficient two-photon excitation. In this study, therefore, we attempted to determine the optimal phase for maximizing the fluorescence efficiency of a GFP variant with excitation laser pulses of minimal intensity. We considered that GFP can be an ideal dye for the

  17. ``Molecular spectrometers'' in the condensed phase: local THz-FIR response from femtosecond fluorescence

    NASA Astrophysics Data System (ADS)

    Ernsting, Nikolaus

    2011-03-01

    We examine dye molecules whose color depends on the polarity of the environment. Following fast optical excitation, their fluorescence band typically red-shifts by 0.5 eV on femtosecond to nanosecond time scales. This ``dynamic Stokes shift'' reflects the joint molecular and environmental reorganisation of the system. Solvation dynamics has been studied for decades in the hope that the dynamics of the environment itself can be extracted. We contribute with two research lines: (1) development of rigid polar solvation probes whose vibrational response is removed from that of water, for example, and (2) fluorescence techniques which measure the dynamic Stokes shifts more precisely. Two results will be shown. The frequency-dependent permittivity ɛ (ω) of water surrounding N-Methyl-6-Quinolone is extracted up to about 100 cm-1 from the time-resolved fluorescence shift R(t). The key consists in an analytical connection ɛ (ω) --> R(t) which is needed for data fitting. Measurements with the cryoprotectant disaccharide trehalose in water serve to establish the method. Its unique feature is locality, i . e . the possibility to measure ɛ (ω) around a supramolecular structure with a covalently connected or embedded probe. THz vibrational activity of a biopolymer is thus measured locally, on the effective length scale for polar solvation, with an embedded molecular probe. For this purpose 2-hydroxy-7-nitro-fluorene was linked into a 13mer duplex opposite an abasic site. The NMR solution structure shows that the fluorene moiety occupies a well-defined position in place of a base-pair. The dynamic Stokes shifts for solution in H2 O and D2 O are quantified. Their difference is much larger than expected for free water, suggesting that only bound water is observed. A weak 26 cm-1 spectral oscillation of the emission band is observed which is not present when the probe is free in solution, and is therefore caused by the supramolecular structure (DNA and hydration water).

  18. 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.

  19. Photoisomerization dynamics of azobenzene in solution with S1 excitation: a femtosecond fluorescence anisotropy study.

    PubMed

    Chang, Chih-Wei; Lu, Ying-Chih; Wang, Tsai-Te; Diau, Eric Wei-Guang

    2004-08-18

    Measurements of anisotropy of femtosecond fluorescence after direct excitation of the S1(n,pi*) state of azobenzene in hexane and ethylene glycol solutions have been carried out to address the controversy about inversion and rotation in the mechanism of photoisomerization. The observed anisotropies in hexane decay to a nonzero asymptotic level with a relaxation period the same as that for slow decay of the corresponding biexponential transient; this effect is attributed to involvement of the out-of-plane CNNC-torsional motion on approach to a twisted conical intersection along the "rotation channel" that depolarizes the original in-plane transition moment. In contrast, when the rotational channel becomes substantially hindered in ethylene glycol, the anisotropies show no discernible decay feature, but the corresponding transients show prominent decays attributed to involvement of in-plane symmetric motions; the latter approach a planar-sloped conical intersection along a "concerted inversion channel" for efficient internal conversion through vibronic coupling. The proposed mechanism is consistent with theoretical calculations and rationalizes both results on quantum yields and ultrafast observations.

  20. New Triplet Sensitization Routes for Photon Upconversion: Thermally Activated Delayed Fluorescence Molecules, Inorganic Nanocrystals, and Singlet-to-Triplet Absorption.

    PubMed

    Yanai, Nobuhiro; Kimizuka, Nobuo

    2017-09-20

    Photon upconversion based on triplet-triplet annihilation (TTA-UC) has attracted much interest because of its possible applications to renewable energy production and biological fields. In particular, the UC of near-infrared (NIR) light to visible (vis) light is imperative to overcome the Shockley-Queisser limit of single-junction photovoltaic cells, and the efficiency of photocatalytic hydrogen production from water can also be improved with the aid of vis-to-ultraviolet (UV) UC. However, both processes have met limitations in the wavelength range, efficiency, and sensitivity for weak incident light. This Account describes recent breakthroughs that solve these major problems, new triplet sensitization routes to significantly enlarge the range of conversion wavelength by minimizing the energy loss during intersystem crossing (ISC) of triplet sensitizers or bypassing the ISC process. The photochemical processes of TTA-UC in general start with the absorption of longer wavelength incident light by triplet sensitizers, which generate the triplet states via ISC. This ISC inevitably accompanies the energy loss of hundreds of millielectronvolts, which significantly limits the TTA-UC with large anti-Stokes shifts. The small S1-T1 gap of molecules showing thermally activated delayed fluorescence (TADF) allows the sensitization of emitters with the highest T1 and S1 energy levels ever employed in TTA-UC, which results in efficient vis-to-UV UC. As alternatives to molecular sensitizers in the NIR region, inorganic nanocrystals with broad NIR absorption bands have recently been shown to work as effective sensitizers for NIR-to-vis TTA-UC. Their small exchange splitting minimizes the energy loss during triplet sensitization. The modification of nanocrystal surfaces with organic acceptors via coordination bonds allows efficient energy transfer between the components and succeeding TTA processes. To remove restrictions on the energy loss during ISC, molecules with direct singlet

  1. Multifunctional nanocomposites of superparamagnetic (Fe3O4) and NIR-responsive rare earth-doped up-conversion fluorescent (NaYF4 : Yb,Er) nanoparticles and their applications in biolabeling and fluorescent imaging of cancer cells

    NASA Astrophysics Data System (ADS)

    Mi, Congcong; Zhang, Jingpu; Gao, Huanyu; Wu, Xianlong; Wang, Meng; Wu, Yingfan; di, Yueqin; Xu, Zhangrun; Mao, Chuanbin; Xu, Shukun

    2010-07-01

    A new kind of magnetic/luminescent multifunctional nanoparticles was synthesized by covalently linking multiple carboxyl-functionalized superparamagnetic Fe3O4 nanoparticles and individual amino-functionalized silica-coated fluorescent NaYF4 : Yb,Er up-conversion nanoparticles (UCNPs). The resultant nanocomposites bear active carboxylic and amino groups on the surface that were proved to be chemically active and useful for further facile bioconjugation with biomolecules. The UCNPs in the nanocomposite particles can emit visible light in response to the irradiation by near infrared (NIR) light, enabling the application of the nanocomposites in bioimaging. X-Ray diffraction, infrared spectroscopy, transmission electron microscopy, luminescence spectroscopy, and magnetometry were applied to characterize the multifunctional nanocomposites. The nanocomposites exhibited good superparamagnetic and excellent green up-conversion photoluminescent properties that can be exploited in magnetic separation and guiding as well as bioimaging. Due to the presence of active functional groups on the nanocomposite surface, the Fe3O4/NaYF4 : Yb,Er magnetic/luminescent nanocomposites were successfully conjugated with a protein called transferrin, which specifically recognizes the transferrin receptors overexpressed on HeLa cells, and can be employed for biolabeling and fluorescent imaging of HeLa cells. Because NIR light can penetrate biological samples with good depth without damaging them and can avoid autofluorescence from them, the presence of both NIR-responsive UCNPs and superparamagnetic nanoparticles in the nanocomposite particles will enable the practical application of the nanocomposites in bioimaging and separation.

  2. Multifunctional nanocomposites of superparamagnetic (Fe3O4) and NIR-responsive rare earth-doped up-conversion fluorescent (NaYF4 : Yb,Er) nanoparticles and their applications in biolabeling and fluorescent imaging of cancer cells.

    PubMed

    Mi, Congcong; Zhang, Jingpu; Gao, Huanyu; Wu, Xianlong; Wang, Meng; Wu, Yingfan; Di, Yueqin; Xu, Zhangrun; Mao, Chuanbin; Xu, Shukun

    2010-07-01

    A new kind of magnetic/luminescent multifunctional nanoparticles was synthesized by covalently linking multiple carboxyl-functionalized superparamagnetic Fe(3)O(4) nanoparticles and individual amino-functionalized silica-coated fluorescent NaYF(4) : Yb,Er up-conversion nanoparticles (UCNPs). The resultant nanocomposites bear active carboxylic and amino groups on the surface that were proved to be chemically active and useful for further facile bioconjugation with biomolecules. The UCNPs in the nanocomposite particles can emit visible light in response to the irradiation by near infrared (NIR) light, enabling the application of the nanocomposites in bioimaging. X-Ray diffraction, infrared spectroscopy, transmission electron microscopy, luminescence spectroscopy, and magnetometry were applied to characterize the multifunctional nanocomposites. The nanocomposites exhibited good superparamagnetic and excellent green up-conversion photoluminescent properties that can be exploited in magnetic separation and guiding as well as bioimaging. Due to the presence of active functional groups on the nanocomposite surface, the Fe(3)O(4)/NaYF(4) : Yb,Er magnetic/luminescent nanocomposites were successfully conjugated with a protein called transferrin, which specifically recognizes the transferrin receptors overexpressed on HeLa cells, and can be employed for biolabeling and fluorescent imaging of HeLa cells. Because NIR light can penetrate biological samples with good depth without damaging them and can avoid autofluorescence from them, the presence of both NIR-responsive UCNPs and superparamagnetic nanoparticles in the nanocomposite particles will enable the practical application of the nanocomposites in bioimaging and separation.

  3. Multifunctional nanocomposites of superparamagnetic (Fe3O4) and NIR-responsive rare earth-doped up-conversion fluorescent (NaYF4 : Yb,Er) nanoparticles and their applications in biolabeling and fluorescent imaging of cancer cells

    PubMed Central

    Mi, Congcong; Zhang, Jingpu; Gao, Huanyu; Wu, Xianlong; Wang, Meng; Wu, Yingfan; Di, Yueqin; Xu, Zhangrun; Mao, Chuanbin; Xu, Shukun

    2011-01-01

    A new kind of magnetic/luminescent multifunctional nanoparticles was synthesized by covalently linking multiple carboxyl-functionalized superparamagnetic Fe3O4 nanoparticles and individual amino-functionalized silica-coated fluorescent NaYF4 : Yb,Er up-conversion nanoparticles (UCNPs). The resultant nanocomposites bear active carboxylic and amino groups on the surface that were proved to be chemically active and useful for further facile bioconjugation with biomolecules. The UCNPs in the nanocomposite particles can emit visible light in response to the irradiation by near infrared (NIR) light, enabling the application of the nanocomposites in bioimaging. X-Ray diffraction, infrared spectroscopy, transmission electron microscopy, luminescence spectroscopy, and magnetometry were applied to characterize the multifunctional nanocomposites. The nanocomposites exhibited good superparamagnetic and excellent green up-conversion photoluminescent properties that can be exploited in magnetic separation and guiding as well as bioimaging. Due to the presence of active functional groups on the nanocomposite surface, the Fe3O4/NaYF4 : Yb,Er magnetic/luminescent nanocomposites were successfully conjugated with a protein called transferrin, which specifically recognizes the transferrin receptors overexpressed on HeLa cells, and can be employed for biolabeling and fluorescent imaging of HeLa cells. Because NIR light can penetrate biological samples with good depth without damaging them and can avoid autofluorescence from them, the presence of both NIR-responsive UCNPs and superparamagnetic nanoparticles in the nanocomposite particles will enable the practical application of the nanocomposites in bioimaging and separation. PMID:20648340

  4. Synthesis of water dispersible hexagonal-phase NaYF4:Yb, Er nanoparticles with high efficient upconversion fluorescence.

    PubMed

    Cui, Yue; Zhao, Suling; Han, Meng; Li, Panlai; Zhang, Ligang; Xu, Zheng

    2014-05-01

    Yb3+ and EP(3+)-codoped hexagonal-phase NaYF4 nanoparticles are synthesized by a simple, safe, and cost-effective method. The results of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) show that the as-synthesized nanoparticles are in good accordance with the standard beta-NaYF4 with an average diameter of 60 nm after silica coating. The upconversion luminescence of prepared material under 980 nm excitation is detected, and the luminescence mechanism is discussed.

  5. Upconversion fluorescence and its thermometric sensitivity of Er3+:Yb3+ co-doped SrF2 powders prepared by combustion synthesis

    NASA Astrophysics Data System (ADS)

    Rakov, Nikifor; Maciel, Glauco S.; Xiao, Mufei

    2014-09-01

    Upconversion fluorescence of co-doped Er3+:Yb3+:SrF2 powders prepared by combustion synthesis was investigated under near-infrared ( λ = 980 nm) continuous wave laser excitation. Surface morphology of the samples and structures of the Er3+:Yb3+:SrF2 powders were studied with scanning electronic microscopy, energy dispersive x-ray, and x-ray powder diffraction. The spectrum of the fluorescence contains bands centered at ~410, ~522, ~545 and ~660 nm, corresponding respectively to transitions from upper levels 2H9/2, 2H11/2, 4S3/2 and 4F9/2 to the ground state 4I15/2, which can be identified as 4 f-4 f transitions from Er3+ excited states. In addition, the fluorescence is found sensitive to the temperature, which suggests that an optical temperature sensor would be feasible. The maximum sensitivity of the proposed sensor was found 0.00396 K-1.

  6. Frequency upconversion and fluorescence intensity ratio method in Yb3+-ion-sensitized Gd2O3:Er3+-Eu3+ phosphors for display and temperature sensing

    NASA Astrophysics Data System (ADS)

    Ranjan, Sushil Kumar; Soni, Abhishek Kumar; Rai, Vineet Kumar

    2017-09-01

    Near infrared (NIR) to visible frequency upconversion emission studies in Er3+-Eu3+/Er3+-Eu3+-Yb3+ co-doped/tri-doped Gd2O3 phosphors prepared by the co-precipitation technique have been explored under 980 nm laser diode radiation. The developed phosphors were characterized with the help of XRD, FE-SEM and FTIR analysis. No upconversion (UC) emission was found in the Eu3+-doped Gd2O3 phosphor. UC emission from Eu3+ ions along with Er3+ ions was observed in Er3+-Eu3+ and Er3+-Eu3+-Yb3+ co-doped/tri-doped phosphors. The UC emission arising from the Er3+ and Eu3+ ions was enhanced several times due to the incorporation of Yb3+ ions. The processes involved in the UC emission were obtained on the basis of the effect of energy transfer/sensitization through the Yb3+ → Er3+ → Eu3+ process. The red/green intensity ratio was improved from 0.16 to 1.50 and 1.01 to 1.50 for Er3+-Eu3+-Yb3+ tri-doped phosphors as compared to the Er3+-doped and Er3+-Yb3+ co-doped phosphors, respectively, at a fixed pump power density. A UC fluorescence intensity ratio (FIR)-based temperature sensing study was performed in the prepared Er3+-Eu3+-Yb3+ tri-doped Gd2O3 phosphors for green upconversion emission bands in the 300 K–443 K temperature range. A maximum sensor sensitivity of about ∼0.0043 K‑1 at 300 K was achieved for the synthesized tri-doped phosphors upon excitation with a 980 nm laser diode. The colour coordinates lying in the green–yellow region are invariant, with variation in pump power density and temperature. The observed results support the utility of the prepared tri-doped phosphors in optical temperature sensing, display devices and NIR to visible upconverters.

  7. Controllable optical modulation of blue/green up-conversion fluorescence from Tm3+ (Er3+) single-doped glass ceramics upon two-step excitation of two-wavelengths

    PubMed Central

    Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

    2017-01-01

    Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8–1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas. PMID:28368041

  8. Controllable optical modulation of blue/green up-conversion fluorescence from Tm3+ (Er3+) single-doped glass ceramics upon two-step excitation of two-wavelengths

    NASA Astrophysics Data System (ADS)

    Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

    2017-04-01

    Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8-1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas.

  9. Controllable optical modulation of blue/green up-conversion fluorescence from Tm(3+) (Er(3+)) single-doped glass ceramics upon two-step excitation of two-wavelengths.

    PubMed

    Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

    2017-04-03

    Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm(3+) (Er(3+)) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8-1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas.

  10. Fluorescent MoS2 Quantum Dots: Ultrasonic Preparation, Up-Conversion and Down-Conversion Bioimaging, and Photodynamic Therapy.

    PubMed

    Dong, Haifeng; Tang, Songsong; Hao, Yansong; Yu, Haizhu; Dai, Wenhao; Zhao, Guifeng; Cao, Yu; Lu, Huiting; Zhang, Xueji; Ju, Huangxian

    2016-02-10

    Small size molybdenum disulfide (MoS2) quantum dots (QDs) with desired optical properties were controllably synthesized by using tetrabutylammonium-assisted ultrasonication of multilayered MoS2 powder via OH-mediated chain-like Mo-S bond cleavage mode. The tunable up-bottom approach of precise fabrication of MoS2 QDs finally enables detailed experimental investigations of their optical properties. The synthesized MoS2 QDs present good down-conversion photoluminescence behaviors and exhibit remarkable up-conversion photoluminescence for bioimaging. The mechanism of the emerging photoluminescence was investigated. Furthermore, superior (1)O2 production ability of MoS2 QDs to commercial photosensitizer PpIX was demonstrated, which has great potential application for photodynamic therapy. These early affording results of tunable synthesis of MoS2 QDs with desired photo properties can lead to application in fields of biomedical and optoelectronics.

  11. Ultraviolet upconversion fluorescence of Er3+ in Yb3+/Er3+-codoped Gd2O3 nanotubes.

    PubMed

    Zheng, Kezhi; Zhao, Dan; Zhang, Daisheng; Liu, Zhenyu; Qin, Weiping

    2011-11-01

    Under 980 nm excitation, room-temperature ultraviolet (UV) upconversion (UC) emissions of Er3+ from the 4G(9/2), 2K(13/2), and 2P(3/2) states were observed in Gd2O3:Yb3+/Er3+ nanotubes, which were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 degrees C. The experimental results exhibited that these UV emissions came from four-photon UC processes. In the Gd2O3:Yb3+/Er3+ nanocrystals, the energy transfers (ETs) from Yb3+ to Er3+ played important roles in populating the high-energy states of Er3+ ions. This material provides a possible candidate for building UV compact solid-state lasers or fiber lasers.

  12. Single and two-photon fluorescence control of Er3+ ions by phase-shaped femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Zhang, Shian; Xu, Shuwu; Ding, Jingxin; Lu, Chenhui; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2014-01-01

    We experimentally demonstrate the control of the single and two-photon fluorescence (SPF and TPF) in Er3+ ions by shaping the femtosecond laser pulse with a π or square phase modulation. With the low laser intensity (8.4 × 1010 W/cm2), SPF keeps a constant while TPF is effectively suppressed by the two control schemes. With the high laser intensity (1.2 × 1013 W/cm2), both SPF and TPF are simultaneously enhanced or suppressed by the π phase modulation, and SPF is enhanced while TPF is effectively suppressed by the square phase modulation. The up/down-conversion fluorescence enhancement, suppression, or tuning by the optical control method can greatly expand its applications in various related fields.

  13. Single and two-photon fluorescence control of Er{sup 3+} ions by phase-shaped femtosecond laser pulse

    SciTech Connect

    Zhang, Shian Ding, Jingxin; Lu, Chenhui; Jia, Tianqing; Sun, Zhenrong; Xu, Shuwu; Qiu, Jianrong

    2014-01-06

    We experimentally demonstrate the control of the single and two-photon fluorescence (SPF and TPF) in Er{sup 3+} ions by shaping the femtosecond laser pulse with a π or square phase modulation. With the low laser intensity (8.4 × 10{sup 10} W/cm{sup 2}), SPF keeps a constant while TPF is effectively suppressed by the two control schemes. With the high laser intensity (1.2 × 10{sup 13} W/cm{sup 2}), both SPF and TPF are simultaneously enhanced or suppressed by the π phase modulation, and SPF is enhanced while TPF is effectively suppressed by the square phase modulation. The up/down-conversion fluorescence enhancement, suppression, or tuning by the optical control method can greatly expand its applications in various related fields.

  14. Coherent photon interference elimination and spectral correction in femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy.

    PubMed

    Dang, Wei; Mao, Pengcheng; Weng, Yuxiang

    2013-07-01

    We report an improved setup of femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS) with a 210 fs temporal response. The system employs a Cassegrain objective to collect and focus fluorescence photons, which eliminates the interference from the coherent photons in the fluorescence amplification by temporal separation of the coherent photons and the fluorescence photons. The gain factor of the Cassegrain objective-assisted FNOPAS is characterized as 1.24 × 10(5) for Rhodamine 6G. Spectral corrections have been performed on the transient fluorescence spectra of Rhodamine 6G and Rhodamine 640 in ethanol by using an intrinsic calibration curve derived from the spectrum of superfluorescence, which is generated from the amplification of the vacuum quantum noise. The validity of spectral correction is illustrated by comparisons of spectral shape and peak wavelength between the corrected transient fluorescence spectra of these two dyes acquired by FNOPAS and their corresponding standard reference spectra collected by the commercial streak camera. The transient fluorescence spectra of the Rhodamine 6G were acquired in an optimized phase match condition, which gives a deviation in the peak wavelength between the retrieved spectrum and the reference spectrum of 1.0 nm, while those of Rhodamine 640 were collected in a non-optimized phase match condition, leading to a deviation in a range of 1.0-3.0 nm. Our results indicate that the improved FNOPAS can be a reliable tool in the measurement of transient fluorescence spectrum for its high temporal resolution and faithfully corrected spectrum.

  15. Dual fluorescence resonance energy transfer assay between tunable upconversion nanoparticles and controlled gold nanoparticles for the simultaneous detection of Pb²⁺ and Hg²⁺.

    PubMed

    Wu, Shijia; Duan, Nuo; Shi, Zhao; Fang, Congcong; Wang, Zhouping

    2014-10-01

    In this work, we presented a novel dual fluorescence resonance energy transfer (FRET) system for the simultaneous detection of Pb(2+) and Hg(2+). This system employed two color upconversion nanoparticles (UCNPs) as the donors, and controlled gold nanoparticles (AuNPs) as the acceptors. The two donor-acceptor pairs were fabricated by hybridizing the aptamers and their corresponding complementary DNA. Thus, the green and red upconversion fluorescence could be quenched because of a good overlap between the UCNPs fluorescence emission and the AuNPs absorption spectrum. In the presence of Pb(2+) and Hg(2+), the aptamers preferred to bind to their corresponding analytes and formed a G-quadruplexes structure for Pb(2+) and the hairpin-like structure for Hg(2+). As a result, the dual FRET was disrupted, and the green and red upconversion fluorescence was restored. Under optimized experimental conditions, the relative fluorescence intensity increased as the metal ion concentrations were increased, allowing for the quantification of Pb(2+) and Hg(2+). The relationships between the fluorescence intensity and plotting logarithms of ion concentrations were linear in the range from 0.1 to 100 nM for Pb(2+) and 0.5 to 500 nM for Hg(2+), and the detection limits of Pb(2+) and Hg(2+) were 50 pM and 150 pM, respectively. As a practical application, the aptasensor was used to monitor Pb(2+) and Hg(2+) levels in naturally contaminated samples and human serum samples. Ultimately, this type of dual FRET could be used to detect other metal ions or contaminants in food safety analysis and environment monitoring.

  16. pH Effect on Two-Photon Cross Section of Highly Fluorescent Dyes Using Femtosecond Two-Photon Induced Fluorescence.

    PubMed

    Makhal, Krishnandu; Goswami, Debabrata

    2017-01-01

    Effect of solution pH on two-photon absorption cross-section of highly fluorescent Coumarin and Rhodamine dyes with high repetition rate femtosecond laser pulses at 780 nm is presented using two-photon induced fluorescence technique. A correspondence in the measured two-photon and single-photon cross-section values is seen when the pH changes from acidic to basic conditions (pH = 2-10) for solutions in 1:1 water-ethanol binary mixture. By plotting changes in the single-photon and two-photon fluorescence in this pH range, the excited state pKa values are found. The ground state pKa values are also affected by the protonation deprotonation equilibrium as a result of variation in pH from acidic to basic, which are characterized by changes in absorbance spectra. Most of these single-photon and two-photon induced fluorescence spectra show characteristic blue shifts. Different fluorescence quantum yields calculated at each pH reflect a change in structure corresponding to their associated properties as a result of acid base equilibrium.

  17. Two-photon excitation spectrum of light-harvesting complex II and fluorescence upconversion after one- and two-photon excitation of the carotenoids

    SciTech Connect

    Walla, P.J.; Yom, J.; Krueger, B.P.; Fleming, G.R.

    2000-05-18

    The two-photon excitation (TPE) spectrum of light-harvesting complex II (LHC II) has been measured in the spectral region of 1,000--1,600 nm, corresponding to one-photon wavelengths of 500--800 nm. The authors observed a band with an origin at {approximately}2 x 660 nm (ca. 15,100 {+-} 300 cm{sup {minus}1}) and a maximum at {approximately}2 x 600 nm. The line shape and origin of this band strongly suggest that the observed signal is due to the two-photon-allowed S{sub 1} state of the energy-transferring carotenoids (Car ) in LHC II. The authors also report the time dependence of the upconverted chlorophyll (Chl) fluorescence after TPE at the maximum of the observed band. Surprisingly, a fast rise of 250 {+-} 50 fs followed by a multiexponential decay on the picosecond time scale was observed. This result provides strong indication that there is a fast energy transfer even from the dipole-forbidden Car S{sub 1} state to the Chl's. The sub picosecond energy transfer from the Car S{sub 1} state is likely a consequence of the large number of energy-accepting Chls in van der Waals contact with the central Car's in LHC II. They also present upconversion data of the Car S{sub 2}, Chl a, and Chl b fluorescence observed after one-photon excitation into the dipole-allowed Car S{sub 2} state. The lifetime of the Car S{sub 2} state is {approximately}120 {+-} 30 fs. With the observed time constants they are able to calculate quantum yields for the different possible pathways contributing to the overall Car to Chl energy transfer in LHC II.

  18. Hexamodal imaging with porphyrin-phospholipid-coated upconversion nanoparticles.

    PubMed

    Rieffel, James; Chen, Feng; Kim, Jeesu; Chen, Guanying; Shao, Wei; Shao, Shuai; Chitgupi, Upendra; Hernandez, Reinier; Graves, Stephen A; Nickles, Robert J; Prasad, Paras N; Kim, Chulhong; Cai, Weibo; Lovell, Jonathan F

    2015-03-11

    Hexamodal imaging using simple nanoparticles is demonstrated. Porphyrin-phospholipids are used to coat upconversion nanoparticles in order to generate a new biocompatible material. The nanoparticles are characterized in vitro and in vivo for imaging via fluorescence, upconversion, positron emission tomography, computed tomography, Cerenkov luminescence, and photoacoustic tomography.

  19. Processing window for femtosecond laser microsurgery and fluorescence imaging of an arterial tissue hosted in a microfluidic chip

    NASA Astrophysics Data System (ADS)

    Karimelahi, Samira; Li, Jianzhao; Herman, Peter R.

    2016-02-01

    We study the exposure limitations of femtosecond laser microsurgery and multiphoton imaging in a microfluidic chip environment, assessing damage thresholds at various interfaces as well as interference from bubble formation in the hosting solution. Both heat accumulation and incubation effects from multipulse laser exposures at 1-MHz repetition rate were evaluated. For demonstration, three microsurgery approaches of laser scribing, percussion drilling and trepanning were applied to arterial walls loaded in vitro in a lab-on-a-chip device. We report that deleterious effects from interface damage and microbubble formation can be avoided to offer laser processing windows for damage-free fluorescence imaging and precise microsurgery of live tissue hosted inside small microfluidic chambers.

  20. Single-layer MoS2 nanosheet grafted upconversion nanoparticles for near-infrared fluorescence imaging-guided deep tissue cancer phototherapy

    NASA Astrophysics Data System (ADS)

    Han, Jianyu; Xia, Hongping; Wu, Yafeng; Kong, Shik Nie; Deivasigamani, Amudha; Xu, Rong; Hui, Kam M.; Kang, Yuejun

    2016-04-01

    A multifunctional nanostructure is prepared by covalently grafting upconversion nanoparticles (UCNPs) with chitosan functionalized MoS2 (MoS2-CS) and folic acid (FA) and then loading phthalocyanine (ZnPc) on the surface of MoS2, which integrates photodynamic therapy (PDT) with photothermal therapy (PTT) and upconversion luminescence imaging into one system for enhanced antitumor efficiency.A multifunctional nanostructure is prepared by covalently grafting upconversion nanoparticles (UCNPs) with chitosan functionalized MoS2 (MoS2-CS) and folic acid (FA) and then loading phthalocyanine (ZnPc) on the surface of MoS2, which integrates photodynamic therapy (PDT) with photothermal therapy (PTT) and upconversion luminescence imaging into one system for enhanced antitumor efficiency. Electronic supplementary information (ESI) available: Experimental details and figures. See DOI: 10.1039/c6nr00150e

  1. Intense 1.54 {mu}m fluorescence of Er{sup 3+}/Yb{sup 3+} codoped phosphate glass and the three-photon phenomenon of near infrared upconversion luminescence

    SciTech Connect

    Luo Lanjun; Song Feng; Yu Xiaochen; Wang Wentao; Ming Chengguo; Han Lin; Yu Yin; Wu Hao; Tian Jianguo

    2010-02-15

    Transparent P{sub 2}O{sub 5}-CaO-Na{sub 2}O glasses codoped with Er{sup 3+} and Yb{sup 3+} ions were fabricated by high-temperature melting technique. Strong near infrared and visible upconversion luminescence were observed under 975 nm laser diode excitation, and the luminescence processes were explained in details. For 1.54 {mu}m band, the calculated peak emission cross sections is 1.04x10{sup -20} cm{sup 2}, and it is better than that in germinate, tellurite, silicate, and other phosphate glasses. The near infrared upconversion emission around 828 nm contains two-photon and three-photon processes, and it is attributed to the transition {sup 4}S{sub 3/2}{yields}{sup 4}I{sub 13/2}, which enhances the population of the upper level for 1.54 {mu}m laser emission and reduces the energy loss due to upconversion. Efficient near infrared fluorescence indicates Er{sup 3+}/Yb{sup 3+} codoped phosphate glass is a promising laser and amplifier material.

  2. Valence state change and defect centers induced by infrared femtosecond laser in Yb:YAG crystals

    SciTech Connect

    Wang, Xinshun Liu, Yang; Zhao, Panjuan; Guo, Zhongyi; Li, Yan; Qu, Shiliang

    2015-04-21

    The broad band upconversion luminescence in Yb{sup 3+}:YAG crystal has been observed in experiments under the irradiation of focused infrared femtosecond laser. The dependence of the fluorescence intensity on the pump power shows that the upconversion luminescence is due to simultaneous two-photon absorption process, which indicates that the broad emission bands at 365 and 463 nm could be assigned to the 5d → 4f transitions of Yb{sup 2+} ions and the one at 692 nm could be attributed to the electron-hole recombination process on (Yb{sup 2+}-F{sup +}) centers. The absorption spectra of the Yb:YAG crystal samples before and after femtosecond laser irradiation, and after further annealing reveal that permanent valence state change of Yb ions from Yb{sup 3+} to Yb{sup 2+} and (Yb{sup 2+}-F{sup +}) centers have been induced by infrared femtosecond laser irradiation in Yb{sup 3+}:YAG crystal.

  3. Up-Conversion Intersystem Crossing Rates in Organic Emitters for Thermally Activated Delayed Fluorescence: Impact of the Nature of Singlet vs Triplet Excited States.

    PubMed

    Samanta, Pralok K; Kim, Dongwook; Coropceanu, Veaceslav; Brédas, Jean-Luc

    2017-03-22

    The rates for up-conversion intersystem crossing (UISC) from the T1 state to the S1 state are calculated for a series of organic emitters with an emphasis on thermally activated delayed fluorescence (TADF) materials. Both the spin-orbit coupling and the energy difference between the S1 and T1 states (ΔEST) are evaluated, at the density functional theory (DFT) and time-dependent DFT levels. The calculated UISC rates and ΔEST values are found to be in good agreement with available experimental data. Our results underline that small ΔEST values and sizable spin-orbit coupling matrix elements have to be simultaneously realized in order to facilitate UISC and ultimately TADF. Importantly, the spatial separation of the highest occupied and lowest unoccupied molecular orbitals of the emitter, a widely accepted strategy for the design of TADF molecules, does not necessarily lead to a sufficient reduction in ΔEST; in fact, either a significant charge-transfer (CT) contribution to the T1 state or a minimal energy difference between the local-excitation and charge-transfer triplet states is required to achieve a small ΔEST. Also, having S1 and T1 states of a different nature is found to strongly enhance spin-orbit coupling, which is consistent with the El-Sayed rule for ISC rates. Overall, our results indicate that having either similar energies for the local-excitation and charge-transfer triplet states or the right balance between a substantial CT contribution to T1 and somewhat different natures of the S1 and T1 states, paves the way toward UISC enhancement and thus TADF efficiency improvement.

  4. Imaging electronic trap states in perovskite thin films with combined fluorescence and femtosecond transient absorption microscopy

    DOE PAGES

    Xiao, Kai; Ma, Ying -Zhong; Simpson, Mary Jane; ...

    2016-04-22

    Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. Themore » remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Furthermore, detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps.« less

  5. Imaging electronic trap states in perovskite thin films with combined fluorescence and femtosecond transient absorption microscopy

    SciTech Connect

    Xiao, Kai; Ma, Ying -Zhong; Simpson, Mary Jane; Doughty, Benjamin; Yang, Bin

    2016-04-22

    Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. The remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Furthermore, detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps.

  6. Imaging electronic trap states in perovskite thin films with combined fluorescence and femtosecond transient absorption microscopy

    SciTech Connect

    Xiao, Kai; Ma, Ying -Zhong; Simpson, Mary Jane; Doughty, Benjamin; Yang, Bin

    2016-04-22

    Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. The remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Furthermore, detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps.

  7. Superior optical nonlinearity of an exceptional fluorescent stilbene dye

    SciTech Connect

    He, Tingchao; Sreejith, Sivaramapanicker; Zhao, Yanli; Gao, Yang; Grimsdale, Andrew C.; Lin, Xiaodong E-mail: hdsun@ntu.edu.sg; Sun, Handong E-mail: hdsun@ntu.edu.sg

    2015-03-16

    Strong multiphoton absorption and harmonic generation in organic fluorescent chromophores are, respectively, significant in many fields of research. However, most of fluorescent chromophores fall short of the full potential due to the absence of the combination of such different nonlinear upconversion behaviors. Here, we demonstrate that an exceptional fluorescent stilbene dye could exhibit efficient two- and three-photon absorption under the excitation of femtosecond pulses in solution phase. Benefiting from its biocompatibility and strong excited state absorption behavior, in vitro two-photon bioimaging and superior optical limiting have been exploited, respectively. Simultaneously, the chromophore could generate efficient three-photon excited fluorescence and third-harmonic generation (THG) when dispersed into PMMA film, circumventing the limitations of classical fluorescent chromophores. Such chromophore may find application in the production of coherent light sources of higher photon energy. Moreover, the combination of three-photon excited fluorescence and THG can be used in tandem to provide complementary information in biomedical studies.

  8. Superior optical nonlinearity of an exceptional fluorescent stilbene dye

    NASA Astrophysics Data System (ADS)

    He, Tingchao; Sreejith, Sivaramapanicker; Gao, Yang; Grimsdale, Andrew C.; Zhao, Yanli; Lin, Xiaodong; Sun, Handong

    2015-03-01

    Strong multiphoton absorption and harmonic generation in organic fluorescent chromophores are, respectively, significant in many fields of research. However, most of fluorescent chromophores fall short of the full potential due to the absence of the combination of such different nonlinear upconversion behaviors. Here, we demonstrate that an exceptional fluorescent stilbene dye could exhibit efficient two- and three-photon absorption under the excitation of femtosecond pulses in solution phase. Benefiting from its biocompatibility and strong excited state absorption behavior, in vitro two-photon bioimaging and superior optical limiting have been exploited, respectively. Simultaneously, the chromophore could generate efficient three-photon excited fluorescence and third-harmonic generation (THG) when dispersed into PMMA film, circumventing the limitations of classical fluorescent chromophores. Such chromophore may find application in the production of coherent light sources of higher photon energy. Moreover, the combination of three-photon excited fluorescence and THG can be used in tandem to provide complementary information in biomedical studies.

  9. Enhanced two-photon absorption and fluorescence upconversion in Thioflavin T micelle-type aggregates in glycerol/water solution

    NASA Astrophysics Data System (ADS)

    Donnelly, Julie; Vesga, Yuly; Hernandez, Florencio E.

    2016-09-01

    In this article, we report the systematic characterization of the two-photon absorption of ThT in different mixtures of glycerol/water solution. The relationships of TPA peak position and amplitude revealed a dependence on particle size suggesting that the curious trend observed in TPA with changing glycerol content can be attributed to the presence of micelle-type aggregates. Consequently, the relatively strong TPA cross-section (δTPA = 300 GM) obtained in 8.75% glycerol/water solutions could be attributed to the immobilization of dye molecules and the strong coupling of the molecular transition dipoles in micelle-type aggregates. This enhancement of TPA, in addition to the already reported significant fluorescence quantum yield of ThT attached to brain tissue, is expected to boost the application of this compound for in vitro and perhaps in vivo high resolution multiphoton bioimaging of amyloids in brain tissue.

  10. Excited-state dynamics of bacteriorhodopsin probed by broadband femtosecond fluorescence spectroscopy.

    PubMed

    Schmidt, B; Sobotta, C; Heinz, B; Laimgruber, S; Braun, M; Gilch, P

    2005-01-07

    The impact of varying excitation densities (approximately 0.3 to approximately 40 photons per molecule) on the ultrafast fluorescence dynamics of bacteriorhodopsin has been studied in a wide spectral range (630-900 nm). For low excitation densities, the fluorescence dynamics can be approximated biexponentially with time constants of <0.15 and approximately 0.45 ps. The spectrum associated with the fastest time constant peaks at 650 nm, while the 0.45 ps component is most prominent at 750 nm. Superimposed on these kinetics is a shift of the fluorescence maximum with time (dynamic Stokes shift). Higher excitation densities alter the time constants and their amplitudes. These changes are assigned to multi-photon absorptions.

  11. Integrated femtosecond stimulated Raman scattering and two-photon fluorescence imaging of subcellular lipid and vesicular structures

    NASA Astrophysics Data System (ADS)

    Li, Xuesong; Lam, Wen Jiun; Cao, Zhe; Hao, Yan; Sun, Qiqi; He, Sicong; Mak, Ho Yi; Qu, Jianan Y.

    2015-11-01

    The primary goal of this study is to demonstrate that stimulated Raman scattering (SRS) as a new imaging modality can be integrated into a femtosecond (fs) nonlinear optical (NLO) microscope system. The fs sources of high pulse peak power are routinely used in multimodal nonlinear microscopy to enable efficient excitation of multiple NLO signals. However, with fs excitations, the SRS imaging of subcellular lipid and vesicular structures encounters significant interference from proteins due to poor spectral resolution and a lack of chemical specificity, respectively. We developed a unique NLO microscope of fs excitation that enables rapid acquisition of SRS and multiple two-photon excited fluorescence (TPEF) signals. In the in vivo imaging of transgenic C. elegans animals, we discovered that by cross-filtering false positive lipid signals based on the TPEF signals from tryptophan-bearing endogenous proteins and lysosome-related organelles, the imaging system produced highly accurate assignment of SRS signals to lipid. Furthermore, we demonstrated that the multimodal NLO microscope system could sequentially image lipid structure/content and organelles, such as mitochondria, lysosomes, and the endoplasmic reticulum, which are intricately linked to lipid metabolism.

  12. Integrated femtosecond stimulated Raman scattering and two-photon fluorescence imaging of subcellular lipid and vesicular structures.

    PubMed

    Li, Xuesong; Lam, Wen Jiun; Cao, Zhe; Hao, Yan; Sun, Qiqi; He, Sicong; Mak, Ho Yi; Qu, Jianan Y

    2015-11-01

    The primary goal of this study is to demonstrate that stimulated Raman scattering (SRS) as a new imaging modality can be integrated into a femtosecond (fs) nonlinear optical (NLO) microscope system. The fs sources of high pulse peak power are routinely used in multimodal nonlinear microscopy to enable efficient excitation of multiple NLO signals. However, with fs excitations, the SRS imaging of subcellular lipid and vesicular structures encounters significant interference from proteins due to poor spectral resolution and a lack of chemical specificity, respectively. We developed a unique NLO microscope of fs excitation that enables rapid acquisition of SRS and multiple two-photon excited fluorescence (TPEF) signals. In the in vivo imaging of transgenic C. elegans animals, we discovered that by cross-filtering false positive lipid signals based on the TPEF signals from tryptophan-bearing endogenous proteins and lysosome-related organelles, the imaging system produced highly accurate assignment of SRS signals to lipid. Furthermore, we demonstrated that the multimodal NLO microscope system could sequentially image lipid structure/content and organelles, such as mitochondria, lysosomes, and the endoplasmic reticulum, which are intricately linked to lipid metabolism.

  13. Primary light-induced reaction steps of reversibly photoswitchable fluorescent protein Padron0.9 investigated by femtosecond spectroscopy.

    PubMed

    Walter, Arne; Andresen, Martin; Jakobs, Stefan; Schroeder, Jörg; Schwarzer, Dirk

    2015-04-23

    The reversible photoswitching of the photochromic fluorescent protein Padron0.9 involves a cis-trans isomerization of the chromophore. Both isomers are subjected to a protonation equilibrium between a neutral and a deprotonated form. The observed pH dependent absorption spectra require at least two protonating groups in the chromophore environment modulating its proton affinity. Using femtosecond transient absorption spectroscopy, we elucidate the primary reaction steps of selectively excited chromophore species. Employing kinetic and spectral modeling of the time dependent transients, we identify intermediate states and their spectra. Excitation of the deprotonated trans species is followed by excited state relaxation and internal conversion to a hot ground state on a time scale of 1.1-6.5 ps. As the switching yield is very low (Φtrans→cis = 0.0003 ± 0.0001), direct formation of the cis isomer in the time-resolved experiment is not observed. The reverse switching route involves excitation of the neutral cis chromophore. A strong H/D isotope effect reveals the initial reaction step to be an excited state proton transfer with a rate constant of kH = (1.7 ps)(-1) (kD = (8.6 ps)(-1)) competing with internal conversion (kic = (4.5 ps)(-1)). The deprotonated excited cis intermediate relaxes to the well-known long-lived fluorescent species (kr = (24 ps)(-1)). The switching quantum yield is determined to be low as well, Φcis→trans = 0.02 ± 0.01. Excitation of both the neutral and deprotonated cis chromophores is followed by a ground state proton transfer reaction partially re-establishing the disturbed ground state equilibrium within 1.6 ps (deuterated species: 5.6 ps). The incomplete equilibration reveals an inhomogeneous population of deprotonated cis species which equilibrate on different time scales.

  14. Local environment inside a novel aromatic micelle investigated by steady-state and femtosecond fluorescence spectroscopy of an encapsulated solvatochromic probe.

    PubMed

    Sartin, Matthew M; Kondo, Kei; Yoshizawa, Michito; Takeuchi, Satoshi; Tahara, Tahei

    2016-12-21

    The local environment within a recently developed anthracene-shelled micelle (ASM), which is a micelle-like nanocapsule composed of anthracene-embedded amphiphiles, was investigated by steady-state and time-resolved spectroscopy of an encapsulated solvatochromic fluorescent probe molecule, coumarin 153 (C153). The absorption maximum of encapsulated C153 (452 nm) is more red-shifted than that of free C153 in water, indicating a highly polar environment inside the micelle. Despite this, the fluorescence Stokes shift of encapsulated C153 (∼3700 cm(-1)) is substantially smaller than that of free C153 in water. Femtosecond time-resolved broadband fluorescence measurements further showed that the dynamic Stokes shift is completed within 1 ps, revealing that the reorganization of the micelle interior following photoexcitation of the C153 probe is characterized by a sub-picosecond, limited-amplitude response. The femtosecond fluorescence anisotropy data showed that the orientational diffusion of the host-guest complex is slower (860 ps) than that of the empty micelle (510 ps), suggesting that the micelle structure is flexible enough to expand when the guest molecule is accommodated and that the micelle rotates with the encapsulated guest molecule. This softness of the micelles further allows some of them to simultaneously encapsulate two C153 molecules, as evidenced by the appearance of blue-shifted, H-dimer-like absorption and fluorescence bands. Based on these steady-state and femtosecond time-resolved spectroscopic data, we discuss the electronic state of C153 and micelle structure as well as the host-guest interaction in this novel flexible synthetic nanocapsule.

  15. Multi-channel lock-in amplifier assisted femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy with efficient rejection of superfluorescence background

    SciTech Connect

    Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang

    2015-12-15

    Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300–1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10{sup −5}M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process.

  16. Multi-channel lock-in amplifier assisted femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy with efficient rejection of superfluorescence background

    NASA Astrophysics Data System (ADS)

    Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang

    2015-12-01

    Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300-1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10-5M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process.

  17. Upconversion Spectrophotofluorometry

    PubMed Central

    Biesso, Arianna; Xu, Jianhua; Knutson, Jay R.

    2014-01-01

    As the other chapters attest, sensitivity of fluorescent molecules to their local environment has created powerful tools in the study of molecular biology, particularly in the study of protein, DNA, and lipid dynamics. Surprisingly, even events faster than the nanosecond lifetimes of fluorophores are important in protein function, and in particular, events lasting just a few ps reflect on water motion and the coupled dynamics of proteins. These ultrafast phenomena can best be studied by using the same laser that excites fluorescence to also “strobe” the emission, providing sub-picosecond time slices of the action. We explain the strobing “upconversion” technique and some limits on its execution. PMID:24108631

  18. Photo-annealing effect of gamma-irradiated erbium-doped fibre by femtosecond pulsed laser

    NASA Astrophysics Data System (ADS)

    Hsiung Chang, Sheng; Liu, Ren-Young; Lin, Chu-En; Chou, Fong-In; Tai, Chao-Yi; Chen, Chii-Chang

    2013-12-01

    In this work, a photo-annealing effect of gamma-irradiated erbium-doped glass fibre is investigated. Two commercial erbium-doped fibres (EDFs) with different doping concentrations were sealed inside a chamber with a cobalt-60 gamma source for 6 h to give an accumulated dose of 3.18 kGy. A tunable femtosecond pulsed laser with a repetition rate of 80 MHz was then used to pump EDF to generate 1550 nm fluorescence and green up-conversion emission, resulting in the annealing effect of the gamma-irradiated EDF. The fluorescence power of gamma-irradiated EDF with a moderate level of doping was almost returned to the initial state by photo-annealing, unlike that of a heavily doped EDF. This finding may facilitate the development of anti-irradiated superfluorescence fibre source for space navigation.

  19. Synthesis of NIR-Responsive NaYF₄:Yb,Er Upconversion Fluorescent Nanoparticles Using an Optimized Solvothermal Method and Their Applications in Enhanced Development of Latent Fingerprints on Various Smooth Substrates.

    PubMed

    Wang, Meng; Zhu, Ye; Mao, Chuanbin

    2015-06-30

    Fingerprints at crime scenes are usually latent. The powder-dusting method is the most commonly used procedure for developing latent fingerprints in forensic science. However, the traditional powder-dusting method has characteristics of low sensitivity, low contrast, high background noise, and high autofluorescence interference. To overcome the drawbacks faced by the traditional method, we first optimized an oleic acid-based solvothermal approach for the synthesis of NaYF4:Yb,Er fluorescent upconversion nanoparticles (UCNPs) with the highest possible fluorescence intensity under near-infrared (NIR) irradiation. To optimize the synthesis, we studied the effects of the reaction time, reaction temperature, and volume of oleic acid on the size, phase composition, and UC fluorescence intensity of the UCNPs. We then used the resultant UCNPs to fluorescently label the fingerprints on various smooth substrates to improve the development of latent fingerprints because the UCNPs could undergo excitation under 980 nm NIR light to emit visible light. Latent fingerprints on three major types of smooth substrates were studied, including those with a single background color (transparent glass, white ceramic tiles, and black marbles), with multiple background colors (marbles with different complex surface patterns) and with strong background autofluorescence (note papers, Chinese paper money, and plastic plates). Compared with fingerprint development using traditional powders such as bronze powder, magnetic powder, and green fluorescent powder, our development procedure using UCNPs is facile and exhibits very high sensitivity, high contrast, low background interference, and low autofluorescence interference. This work shows that UCNPs synthesized under optimized conditions are a versatile fluorescent label for the facile development of fingerprints and can find their practical applications in forensic sciences.

  20. PEGylated NaLuF4: Yb/Er upconversion nanophosphors for in vivo synergistic fluorescence/X-ray bioimaging and long-lasting, real-time tracking.

    PubMed

    Yi, Zhigao; Lu, Wei; Xu, Yaru; Yang, Jing; Deng, Li; Qian, Chao; Zeng, Tianmei; Wang, Haibo; Rao, Ling; Liu, Hongrong; Zeng, Songjun

    2014-12-01

    Simultaneous in vivo luminescence and X-ray bioimaging in a tissue or animal integrates the advantages of each single-modal imaging technology, and will find widespread application in biological and clinical fields. However, synergistic dual-modal bioimaging that utilizes a new generation of upconversion nanoprobes is still limited. In addition, investigations concentrated on in vivo biodistribution of these nanoprobes may contribute to diagnosis and treatment, but long-term in vivo tracking based on these nanoprobes is rarely reported. In this work, water-soluble NaLuF4: Yb/Er nanophosphors were prepared through modified one-pot simultaneous synthesis and surface modification method. Owing to the outstanding upconverting emissions and large X-ray absorption coefficient/K-edge value of Lu and doped Yb ions, the obtained nanoprobes were successfully used as luminescent nanoprobes and X-ray contrast agents for in vivo synergistic upconversion luminescence and X-ray bioimaging. The in vivo biodistribution of these nanoprobes were observed, and the results based on long-term tracking reveal that the as-prepared nanoprobes first aggregated in the lung of the mouse, transferred to the liver, and finally moved to the spleen. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. High efficiency upconversion nanophosphors for high-contrast bioimaging

    NASA Astrophysics Data System (ADS)

    Alkahtani, Masfer H.; Alghannam, Fahad S.; Sanchez, Carlos; Gomes, Carmen L.; Liang, Hong; Hemmer, Philip R.

    2016-12-01

    Upconversion nanoparticles (UCNPs) are of interest because they allow suppression of tissue autofluorescence and are therefore visible deep inside biological tissue. Compared to upconversion dyes, UCNPs have a lower pump intensity threshold, better photostability, and less toxicity. Recently, YVO4: Er+3, Yb+3 nanoparticles were shown to exhibit strong up-conversion luminescence with a relatively low 10 kW cm-2 excitation intensity even in water, which makes them excellent bio-imaging candidates. Herein, we investigate their use as internal probes in insects by injecting YVO4 : Er+3, Yb+3 nanoparticles into fire ants as a biological model, and obtain 2D optical images with 980 nm illumination. High-contrast images with high signal-to-noise ratio are observed by detecting the up-conversion fluorescence as the excitation laser is scanned.

  2. High efficiency upconversion nanophosphors for high-contrast bioimaging.

    PubMed

    Alkahtani, Masfer H; Alghannam, Fahad S; Sanchez, Carlos; Gomes, Carmen L; Liang, Hong; Hemmer, Philip R

    2016-12-02

    Upconversion nanoparticles (UCNPs) are of interest because they allow suppression of tissue autofluorescence and are therefore visible deep inside biological tissue. Compared to upconversion dyes, UCNPs have a lower pump intensity threshold, better photostability, and less toxicity. Recently, YVO4: Er(+3), Yb(+3) nanoparticles were shown to exhibit strong up-conversion luminescence with a relatively low 10 kW cm(-2) excitation intensity even in water, which makes them excellent bio-imaging candidates. Herein, we investigate their use as internal probes in insects by injecting YVO4 : Er(+3), Yb(+3) nanoparticles into fire ants as a biological model, and obtain 2D optical images with 980 nm illumination. High-contrast images with high signal-to-noise ratio are observed by detecting the up-conversion fluorescence as the excitation laser is scanned.

  3. Upconversion color tunability and white light generation in Tm 3+/Ho 3+/Yb 3+ doped aluminum germanate glasses

    NASA Astrophysics Data System (ADS)

    Gong, Hua; Yang, Dianlai; Zhao, Xin; Yun Bun Pun, Edwin; Lin, Hai

    2010-02-01

    Tm 3+/Ho 3+/Yb 3+ triply doped aluminum germanate glasses exhibiting multicolor upconversion fluorescences have been fabricated and characterized. Efficient three-photon blue upconversion emission of Tm 3+ and two-photon green and red upconversion fluorescences of Ho 3+ have been observed. The strong red emission of Ho 3+, which is more than eight times higher than that of the green emission, is desirable in achieving high color rendering index. By varying the excitation power of the 974 nm wavelength laser diode, a series of white fluorescences with a large range of correlated color temperature ( CCT) was obtained, and the fluorescence colors can be tuned from yellowish white to warm white, pure white, cool white, and bluish white with different CCT. The upconversion color tunability via pump power adjustment will promote the development of three-dimensional solid-state displays and upconversion illumination devices.

  4. Upconversion of rare Earth nanomaterials.

    PubMed

    Sun, Ling-Dong; Dong, Hao; Zhang, Pei-Zhi; Yan, Chun-Hua

    2015-04-01

    Rare earth nanomaterials, which feature long-lived intermediate energy levels and intraconfigurational 4f-4f transitions, are promising supporters for photon upconversion. Owing to their unique optical properties, rare earth upconversion nanomaterials have found applications in bioimaging, theranostics, photovoltaic devices, and photochemical reactions. Here, we review recent advances in the photon upconversion processes of these nanomaterials. We start by considering energy transfer models involved in the study of upconversion emissions, as well as well-established synthesis strategies to control the size and shape of rare earth upconversion nanomaterials. Progress in engineering energy transfer pathways, which play a dominant role in determining upconversion emission outputs, is then discussed. Lastly, representative optical applications of these materials are considered. The aim of this review is to provide inspiration for researchers to explore novel upconversion nanomaterials and extended optical applications.

  5. Upconversion in solar cells

    PubMed Central

    2013-01-01

    The possibility to tune chemical and physical properties in nanosized materials has a strong impact on a variety of technologies, including photovoltaics. One of the prominent research areas of nanomaterials for photovoltaics involves spectral conversion. Modification of the spectrum requires down- and/or upconversion or downshifting of the spectrum, meaning that the energy of photons is modified to either lower (down) or higher (up) energy. Nanostructures such as quantum dots, luminescent dye molecules, and lanthanide-doped glasses are capable of absorbing photons at a certain wavelength and emitting photons at a different (shorter or longer) wavelength. We will discuss upconversion by lanthanide compounds in various host materials and will further demonstrate upconversion to work for thin-film silicon solar cells. PMID:23413889

  6. Multifunctional polyoxometalates-modified upconversion nanoparticles: integration of electrochromic devices and antioxidants detection.

    PubMed

    Zhai, Yanling; Zhu, Chengzhou; Ren, Jiangtao; Wang, Erkang; Dong, Shaojun

    2013-03-25

    We report a novel design, based on a combination of lanthanide-doped upconversion nanoparticles and polyoxometalates, for electrically controlled fluorescence switches and sensitive detection of antioxidants in aqueous solution.

  7. Simultaneous synthesis and amine-functionalization of single-phase BaYF5:Yb/Er nanoprobe for dual-modal in vivo upconversion fluorescence and long-lasting X-ray computed tomography imaging

    NASA Astrophysics Data System (ADS)

    Liu, Hongrong; Lu, Wei; Wang, Haibo; Rao, Ling; Yi, Zhigao; Zeng, Songjun; Hao, Jianhua

    2013-06-01

    In this work, we developed a novel and biocompatible dual-modal nanoprobe based on single-phase amine-functionalized BaYF5:Yb/Er nanoparticles (NPs) for upconversion (UC) fluorescence and in vivo computed X-ray tomography (CT) bioimaging for the first time. High-quality water-soluble amine-functionalized BaYF5:Yb/Er NPs with an average size of 24 nm were synthesized by a facile environmentally friendly hydrothermal method for simultaneous synthesis and surface functionalization. Structure investigation based on the Rietveld refinement method revealed that the as-synthesized BaYF5:Yb/Er NPs present a cubic phase structure, which differs from the previously reported tetragonal structure. Under 980 nm excitation, high-contrast green and red UC emissions were observed from HeLa cells incubated with these amine-functionalized NPs. The UC spectra measured from the NPs incubated with HeLa cells presented only green and red UC emissions without any autofluorescence, further revealing that these NPs are ideal candidates for fluorescent bioimaging. In addition, the cell cytotoxicity test showed low cell toxicity of these NPs. These amine-functionalized NPs were also successfully used as CT agents for in vivo CT imaging because of the efficient X-ray absorption efficiency of Ba and doped Yb ions. A prolonged (2 h) signal enhancement of the spleen in a mouse was observed in CT imaging, which can improve the detection of splenic diseases. More importantly, the simultaneous X-ray and UC in vivo bioimaging was demonstrated in a nude mouse for the first time, indicating the as-prepared UCNPs can be successfully used as dual-modal bioprobes. These results demonstrate that BaYF5:Yb/Er NPs are ideal nanoprobes for dual-modal fluorescent/CT bioimaging with low cytotoxicity, non-autofluorescence, and enhanced detection of the spleen.

  8. Simultaneous synthesis and amine-functionalization of single-phase BaYF5:Yb/Er nanoprobe for dual-modal in vivo upconversion fluorescence and long-lasting X-ray computed tomography imaging.

    PubMed

    Liu, Hongrong; Lu, Wei; Wang, Haibo; Rao, Ling; Yi, Zhigao; Zeng, Songjun; Hao, Jianhua

    2013-07-07

    In this work, we developed a novel and biocompatible dual-modal nanoprobe based on single-phase amine-functionalized BaYF5:Yb/Er nanoparticles (NPs) for upconversion (UC) fluorescence and in vivo computed X-ray tomography (CT) bioimaging for the first time. High-quality water-soluble amine-functionalized BaYF5:Yb/Er NPs with an average size of 24 nm were synthesized by a facile environmentally friendly hydrothermal method for simultaneous synthesis and surface functionalization. Structure investigation based on the Rietveld refinement method revealed that the as-synthesized BaYF5:Yb/Er NPs present a cubic phase structure, which differs from the previously reported tetragonal structure. Under 980 nm excitation, high-contrast green and red UC emissions were observed from HeLa cells incubated with these amine-functionalized NPs. The UC spectra measured from the NPs incubated with HeLa cells presented only green and red UC emissions without any autofluorescence, further revealing that these NPs are ideal candidates for fluorescent bioimaging. In addition, the cell cytotoxicity test showed low cell toxicity of these NPs. These amine-functionalized NPs were also successfully used as CT agents for in vivo CT imaging because of the efficient X-ray absorption efficiency of Ba and doped Yb ions. A prolonged (2 h) signal enhancement of the spleen in a mouse was observed in CT imaging, which can improve the detection of splenic diseases. More importantly, the simultaneous X-ray and UC in vivo bioimaging was demonstrated in a nude mouse for the first time, indicating the as-prepared UCNPs can be successfully used as dual-modal bioprobes. These results demonstrate that BaYF5:Yb/Er NPs are ideal nanoprobes for dual-modal fluorescent/CT bioimaging with low cytotoxicity, non-autofluorescence, and enhanced detection of the spleen.

  9. Ultraviolet C upconversion fluorescence of trivalent erbium in BaGd2ZnO5 phosphor excited by a visible commercial light-emitting diode.

    PubMed

    Yang, Yanmin; Mi, Chao; Su, Xianyuan; Jiao, Fuyun; Liu, Linlin; Zhang, Jiao; Yu, Fang; Li, Xiaodong; Liu, Yanzhou; Mai, Yaohua

    2014-04-01

    Multiple ultraviolet (UV) emission bands have been obtained in Er3+ doped BaGd2ZnO5 phosphor under the excitation of a 532 nm solid-state laser, and the emission peaks at 217, 254, 278, 296, 314, 348, 374 and 394 nm were determined to stem from the high-energy states 4D(1/2), 4D(7/2), 2H(9/2), 2P(1/2), 2P(3/2), 4G(7/2), 4G(11/2), 4H(9/2) of trivalent erbium, respectively. Some UV emission bands in the UVC region can be observed when the sample was excited by commercial green (529 nm) and blue (460 nm) LED. In view of the small size, low-drive voltage and price of LED, UVC upconversion phosphor BaGd2ZnO5:Er3+ excited by visible LED has potential application in environmental sciences.

  10. Multiple temperature effects on up-conversion fluorescences of Er{sup 3+}-Y b{sup 3+}-Mo{sup 6+} codoped TiO{sub 2} and high thermal sensitivity

    SciTech Connect

    Cao, B. S.; Wu, J. L.; Wang, X. H.; He, Y. Y.; Feng, Z. Q.; Dong, B. E-mail: bscao@dlnu.edu.cn; Rino, L.

    2015-08-15

    We report multiple temperature effects on green and red up-conversion emissions in Er{sup 3+}-Y b{sup 3+}-Mo{sup 6+} codoped TiO{sub 2} phosphors. With increasing temperature, the decrease of the red emission from {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2}, the increase of green emission from {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} and another unchanged green emission from {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} were simultaneously observed, which are explained by steady-state rate equations analysis. Due to different evolution with temperature of the two green emissions, higher thermal sensitivity of optical thermal sensor was obtained based on the transitions with the largest fluorescence intensity ratio. Two parameters, maximum theoretical sensitivity (S{sub max}) and optimum operating temperature (T{sub max}) are given to describe thermal sensing properties of the produced sensors. The intensity ratio and energy difference ΔE of a pair of energy levels are two main factors for the sensitivity and accuracy of sensors, which should be referred to design sensors with optimized sensing properties.

  11. Femtosecond time-resolved energy transfer from CdSe nanoparticles to phthalocyanines

    NASA Astrophysics Data System (ADS)

    Dayal, S.; Królicki, R.; Lou, Y.; Qiu, X.; Berlin, J. C.; Kenney, M. E.; Burda, C.

    2006-07-01

    The first real-time observation of the early events during energy transfer from a photoexcited CdSe nanoparticle to an attached phthalocyanine molecule are presented in terms of a femtosecond spectroscopic pump-probe study of the energy transfer in conjugates of CdSe nanoparticles (NPs) and silicon phthalocyanines (Pcs) with 120 fs time resolution. Four different silicon phthalocyanines have been conjugated to CdSe NPs. All of these have proven potential for photodynamic therapy (PDT). In such NP-Pc conjugates efficient energy transfer (ET) from CdSe NPs to Pcs occurs upon selective photoexcitation of the NP moiety. Spectral analysis as well as time-resolved fluorescence up-conversion measurements revealed the structure and dynamics of the investigated conjugates. Femtosecond transient differential absorption (TDA) spectroscopy was used for the investigation of the non-radiative carrier and ET dynamics. The formation of excitons, trapped carriers states, as well as stimulated emission was monitored in the TDA spectra and the corresponding lifetimes of these states were recorded. The time component for energy transfer was found to be between 15 and 35 ps. The ET efficiencies are found to be 20-70% for the four Pc conjugates, according to fluorescence quenching experiments. Moreover, as a result of the conjugation between NP and the Pcs the photoluminescence efficiency of the Pc moieties in the conjugates do not strictly follow the quantum yields of the bare phthalocyanines.

  12. Excited state structural events of a dual-emission fluorescent protein biosensor for Ca²⁺ imaging studied by femtosecond stimulated Raman spectroscopy.

    PubMed

    Wang, Yanli; Tang, Longteng; Liu, Weimin; Zhao, Yongxin; Oscar, Breland G; Campbell, Robert E; Fang, Chong

    2015-02-12

    Fluorescent proteins (FPs) are luminescent biomolecules that emit characteristic hues upon irradiation. A group of calmodulin (CaM)-green FP (GFP) chimeras have been previously engineered to enable the optical detection of calcium ions (Ca(2+)). We investigate one of these genetically encoded Ca(2+) biosensors for optical imaging (GECOs), GEM-GECO1, which fluoresces green without Ca(2+) but blue with Ca(2+), using femtosecond stimulated Raman spectroscopy (FSRS). The time-resolved FSRS data (<800 cm(-1)) reveal that initial structural evolution following 400 nm photoexcitation involves small-scale coherent proton motions on both ends of the chromophore two-ring system with a <250 fs time constant. Upon Ca(2+) binding, the chromophore adopts a more twisted conformation in the protein pocket with increased hydrophobicity, which inhibits excited-state proton transfer (ESPT) by effectively trapping the protonated chromophore in S1. Both the chromophore photoacidity and local environment form the ultrafast structural dynamics basis for the dual-emission properties of GEM-GECO1. Its photochemical transformations along multidimensional reaction coordinates are evinced by distinct stages of FSRS spectral evolution, particularly related to the ∼460 and 504 cm(-1) modes. The direct observation of lower frequency modes provides crucial information about the nuclear motions preceding ESPT, which enriches our understanding of photochemistry and enables the rational design of new biosensors.

  13. A bis-cyclometalated iridium complex as a benchmark sensitizer for efficient visible-to-UV photon upconversion.

    PubMed

    Duan, Pengfei; Yanai, Nobuhiro; Kimizuka, Nobuo

    2014-11-07

    To resolve the biggest problem in visible-to-UV photon upconversion based on sensitized triplet-triplet annihilation-the quenching of upconverted fluorescence by sensitizers-we discovered a superior sensitizer with less UV absorption intensity that enables highly efficient, low-power (0.78 mW cm(-2)) visible-to-UV upconversion.

  14. Size control and vacuum-ultraviolet fluorescence of nanosized KMgF3 single crystals prepared using femtosecond laser pulses.

    PubMed

    Muramatsu, Sotaro; Yanagihara, Masahiro; Asaka, Toru; Ono, Shingo; Nagami, Tomohito; Fukuda, Kentaro; Suyama, Toshihisa; Yokota, Yuui; Yanagida, Takayuki; Yoshikawa, Akira

    2016-01-01

    We fabricated nanosized KMgF3 single crystals via a dry pulsed laser ablation process using femtosecond laser pulses. The sizes, shapes, and crystallographic properties of the crystals were evaluated by transmission electron microscopy (TEM). Almost all of the particles were spherical with diameters of less than 100 nm, and they were not highly agglomerated. Selected-area electron diffraction and high-resolution TEM analyses showed that the particles were single crystals. Particle diameter was controlled within a wide range by adjusting the Ar ambient gas pressure. Under low gas pressures (1 and 10 Pa), relatively small particles (primarily 10 nm or less) were observed with a high number density. With increasing pressure, the mean diameter increased and the number density drastically decreased. Vacuum-ultraviolet cathodoluminescence was observed at 140-230 nm with blue shift and broadening of spectrum.

  15. Size control and vacuum-ultraviolet fluorescence of nanosized KMgF3 single crystals prepared using femtosecond laser pulses

    PubMed Central

    Muramatsu, Sotaro; Yanagihara, Masahiro; Asaka, Toru; Ono, Shingo; Nagami, Tomohito; Fukuda, Kentaro; Suyama, Toshihisa; Yokota, Yuui; Yanagida, Takayuki; Yoshikawa, Akira

    2016-01-01

    Abstract We fabricated nanosized KMgF3 single crystals via a dry pulsed laser ablation process using femtosecond laser pulses. The sizes, shapes, and crystallographic properties of the crystals were evaluated by transmission electron microscopy (TEM). Almost all of the particles were spherical with diameters of less than 100 nm, and they were not highly agglomerated. Selected-area electron diffraction and high-resolution TEM analyses showed that the particles were single crystals. Particle diameter was controlled within a wide range by adjusting the Ar ambient gas pressure. Under low gas pressures (1 and 10 Pa), relatively small particles (primarily 10 nm or less) were observed with a high number density. With increasing pressure, the mean diameter increased and the number density drastically decreased. Vacuum-ultraviolet cathodoluminescence was observed at 140–230 nm with blue shift and broadening of spectrum. PMID:27877915

  16. Ultrafast Electron Transfer in Complexes of Doxorubicin with Human Telomeric G-Quadruplexes and GC Duplexes Probed by Femtosecond Fluorescence Spectroscopy.

    PubMed

    Changenet-Barret, Pascale; Gustavsson, Thomas; Markovitsi, Dimitra; Manet, Ilse

    2016-05-04

    Doxorubicin (DOX) is a natural anthracycline widely used in chemotherapy; its combined application as a chemotherapeutic and photodynamic agent has been recently proposed. In this context, understanding the photoinduced properties of DOX complexes with nucleic acids is crucial. Herein, the study of photoinduced electron transfer in DOX-DNA complexes by femtosecond fluorescence spectroscopy is reported. The behaviour of complexes with two model DNA structures, a G-quadruplex (G4) formed by the human telomeric sequence (Tel21) and a d(GC) duplex, is compared. The DOX affinity for these two sequences is similar. Although both 1:1 and 2:1 stoichiometries have been reported for DOX-G4 complexes, only 1:1 complexes form with the duplex. The steady-state absorption indicates a strong binding interaction with the duplex due to drug intercalation between the GC base pairs. In contrast, the interaction of DOX with Tel21 is much weaker and arises from drug binding on the G4 external faces at two independent binding sites. As observed for DOX-d(GC) complexes, fluorescence of the drug in the first binding site of Tel21 exhibits decays within a few picoseconds following a biphasic pattern; this is attributed to the existence of two drug conformations. The fluorescence of the drug in the second binding site of Tel21 shows slower decays within 150 ps. These timescales are consistent with electron transfer from the guanines to the excited drug, as favoured by the lower oxidation potential of the stacked guanines of G4 with respect to those in the duplex. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Excited-state dynamics of dGMP measured by steady-state and femtosecond fluorescence spectroscopy.

    PubMed

    Miannay, Francois-Alexandre; Gustavsson, Thomas; Banyasz, Akos; Markovitsi, Dimitra

    2010-03-11

    The room-temperature fluorescence of 2'-deoxyguanosine 5'-monophosphate (dGMP) in aqueous solution is studied by steady-state and time-resolved fluorescence spectroscopy. The steady-state fluorescence spectrum of dGMP shows one band centered at 334 nm but has an extraordinary long red tail, extending beyond 700 nm. Both the fluorescence quantum yield and the relative weight of the 334 nm peak increase with the excitation wavelength. The initial fluorescence anisotropy after excitation at 267 nm is lower than 0.2 for all emission wavelengths, indicating an ultrafast S(2) --> S(1) internal conversion. The fluorescence decays depend strongly on the emission wavelength, getting longer with the wavelength. A rise time of 100-150 fs was observed for wavelengths longer than 450 nm, in accordance with a gradual red shift of the time-resolved spectra. The results are discussed in terms of a relaxation occurring mainly on the lowest excited (1)pi pi*-state surface toward a conical intersection with the ground state, in line with recent theoretical predictions. Our results show that the excited-state population undergoes a substantial "spreading out" before reaching the CI, explaining the complex dynamics observed.

  18. High-efficiency simultaneous three-photon absorption upconversion luminescence of a terbium-doped germanate glass

    NASA Astrophysics Data System (ADS)

    Zhang, Liaolin; Yang, Runlan; Zou, Hui; Shen, Xiao; Zheng, Jiajin; Wei, Wei

    2016-12-01

    In this paper, high-efficiency green upconversion luminescence from a terbium (Tb3+)-doped germanate glass is reported. The upconversion luminescence involved a simultaneous three-photon absorption process. Compared with an emission spectrum excited at 377 nm, the upconversion luminescence bands of Tb3+ pumped by an fs laser showed a slight red-shift. This was ascribed to the redistribution of glass composition when the glass sample was exposed to the high-intensity laser, which results in the aggregation of Tb3+ around the laser-exposed focal region, which in turn results in the slight red-shift of luminescence. The upconversion luminescence intensities at 540, 590, and 620 nm strongly depended on the polarization angle of the femtosecond laser, which was ascribed to the different transmittances of a half-wavelength plate at different polarization angles, which results in the regularity change in fs laser power.

  19. Optical transitions and frequency upconversion emission of Er 3+ions in novel lead-bismuthate glass

    NASA Astrophysics Data System (ADS)

    Sun, Hongtao; Dai, Shixun; Zhang, Debao; Xu, Shiqing; Zhang, Junjie; Hu, Lili; Jiang, Zhonghong

    2004-12-01

    Er 3+-doped strontiam lead bismuth glass for developing upconversion lasers has been fabricated and characterized. The Judd-Ofelt analysis was performed on the absorption spectrum and the transition probabilities, excited state lifetimes, and the fluorescence branching ratios were calculated and discussed. Under 975 nm excitation, intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H→4I, 4S→4I, and 4F→4I, respectively, were observed. The upconversion mechanisms are discussed based on the energy matching and quadratic dependence on excitation power, and the dominant mechanisms are excited state absorption and energy transfer upconversion for the green and red emissions.

  20. Photon upconversion sensitized by a Ru(II)-pyrenyl chromophore

    PubMed Central

    Deng, Fan; Lazorski, Megan S.; Castellano, Felix N.

    2015-01-01

    The near-visible-to-blue singlet fluorescence of anthracene sensitized by a ruthenium chromophore with a long-lived triplet-excited state, [Ru(5-pyrenyl-1,10-phenanthroline)3](PF6)2, in acetonitrile was investigated. Low intensity non-coherent green light was used to selectively excite the sensitizer in the presence of micromolar concentrations of anthracene generating anti-Stokes, singlet fluorescence in the latter, even with incident power densities below 500 μW cm−2. The resultant data are consistent with photon upconversion proceeding from sensitized triplet–triplet annihilation (TTA) of the anthracene acceptor molecules, confirmed through transient absorption spectroscopy as well as static and dynamic photoluminescence experiments. Additionally, quadratic-to-linear incident power regimes for the upconversion process were identified for this composition under monochromatic 488 nm excitation, consistent with a sensitized TTA mechanism ultimately producing the anti-Stokes emission characteristic of anthracene singlet fluorescence. PMID:25987571

  1. The origin of radiationless conversion of the excited state in the kindling fluorescent protein (KFP): femtosecond studies and quantum modeling

    NASA Astrophysics Data System (ADS)

    Shelaev, I.; Mironov, V.; Rusanov, A.; Gostev, F.; Bochenkova, A.; Sarkisov, O.; Nemukhin, A.; Savitsky, A.

    2011-06-01

    The Ala143Gly variant of the chromoprotein asCP from the sea anemony Anemonia sulcata, called the kindling fluorescent protein (KFP), is a promising candidate for the development of novel subdiffraction method of fluorescent microscopy. The pump-probe method with the delay times between the pump and probe pulses up to 5 ps was applied to study dynamics of the primary processes upon excitation of KFP. The differential absorption spectra at 80 fs delay showed the absorption peak in the range 450-510 nm with the maximum wavelength at 490 nm, which diminished almost twice by intensity by 400 fs and practically disappeared by 1.5 ps. The quantum calculations showed that upon photo-excitation of KFP to the first excited state S1, the fast radiationless relaxation occurred to the ground state S0 due to rotation of the phenolic fragment of the chromophore.

  2. Blue upconversion thulium laser

    NASA Astrophysics Data System (ADS)

    Nguyen, Dinh C.; Faulkner, George E.; Weber, Michael E.; Dulick, Michael

    1990-04-01

    We report a blue emission upconversion solid-state laser based on Tm3+:YLF. Under double resonance excitation at 780.8 nm (near-ir) and 648.8 nm (red), the Tm3+ ion is sequentially excited from the 3H6 ground state to the 1D2 excited state through the 3H4 intermediate level. The laser output at 450 and 453 nm corresponds to the 1D2 -> 3F4 transitions of Tm3+ ions in YLF.

  3. Thermally activated delayed fluorescence from {sup 3}nπ* to {sup 1}nπ* up-conversion and its application to organic light-emitting diodes

    SciTech Connect

    Li, Jie; Zhang, Qisheng; Nomura, Hiroko; Miyazaki, Hiroshi; Adachi, Chihaya

    2014-07-07

    Intense nπ* fluorescence from a nitrogen-rich heterocyclic compound, 2,5,8-tris(4-fluoro-3-methylphenyl)-1,3,4,6,7,9,9b-heptaazaphenalene (HAP-3MF), is demonstrated. The overlap-forbidden nature of the nπ* transition and the higher energy of the {sup 3}ππ* state than the {sup 3}nπ* one lead to a small energy difference between the lowest singlet (S{sub 1}) and triplet (T{sub 1}) excited states of HAP-3MF. Green-emitting HAP-3MF has a moderate photoluminescence quantum yield of 0.26 in both toluene and doped film. However, an organic light-emitting diode containing HAP-3MF achieved a high external quantum efficiency of 6.0%, indicating that HAP-3MF harvests singlet excitons through a thermally activated T{sub 1} → S{sub 1} pathway in the electroluminescent process.

  4. Towards biosensing of arteriosclerotic nanoplaque formation using femtosecond spectroscopy.

    PubMed

    Rodríguez, M; Lindinger, A; Ernsting, N P; Malmsten, M; Siegel, G

    2007-04-01

    The ultrafast dynamics of proteoheparan sulfate (HS-PG) in Krebs blood substitute solution was measured using femtosecond transient absorption spectroscopy after UV excitation. Interacting with blood lipoproteins and Ca(2+) ions, the proteoglycan HS-PG is the key component of the so-called nanoplaque, the earliest stage in atherogenesis. Since tryptophan (Trp) residues are the main optically active parts of HS-PG, analogous measurements were performed on bare Trp in Krebs solution. The comparison reveals distinct differences to main characteristics of the HS-PG broadband absorption spectra. Analyzing the Trp spectra, we show that the results from transient absorption spectroscopy resemble the time constants of the chromophore ultrafast solvation dynamics that have been found by another group using fluorescence up-conversion techniques. Yet, the broadband transient absorption provides more details about the molecular dynamics, including stimulated emission, excited state absorption and resonant energy transfer. Furthermore, the absorption long time dynamics upon adding Ca(2+) to the HS-PG probe were investigated by transient absorption spectroscopy and by surface force and ellipsometry investigations. Notably, a Ca(2+)-induced conformational change responsible for arteriosclerotic nanoplaque formation was detected. Slight differences, which are only visible as broad spectral features in the sub-picosecond time scale, provide a first insight into the molecular formation of nanoplaques in blood vessels, which may yield a better understanding of the genesis of arteriosclerosis.

  5. Femtosecond, two-photon-absorption, laser-induced-fluorescence (fs-TALIF) imaging of atomic hydrogen and oxygen in non-equilibrium plasmas

    NASA Astrophysics Data System (ADS)

    Schmidt, Jacob B.; Roy, Sukesh; Kulatilaka, Waruna D.; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.; Gord, James R.

    2017-01-01

    Femtosecond, two-photon-absorption laser-induced fluorescence (fs-TALIF) is employed to measure space- and time-resolved distributions of atomic hydrogen and oxygen in moderate-pressure, non-equilibrium, nanosecond-duration pulsed-discharge plasmas. Temporally and spatially resolved hydrogen and oxygen TALIF images are obtained over a range of low-temperature plasmas in mixtures of helium and argon at 100 Torr total pressure. The high-peak-intensity, low-average-energy fs pulses combined with the increased spectral bandwidth compared to traditional ns-duration laser pulses provide a large number of photon pairs that are responsible for the two-photon excitation, which results in an enhanced TALIF signal. Krypton and xenon TALIF are used for quantitative calibration of the hydrogen and oxygen concentrations, respectively, with similar excitation schemes being employed. This enables 2D collection of atomic-hydrogen and -oxygen TALIF signals with absolute number densities ranging from 2  ×  1012 cm-3 to 6  ×  1015 cm-3 and 1  ×  1013 cm-3 to 3  ×  1016 cm-3, respectively. These 2D images are the first application of TALIF imaging in moderate-pressure plasma discharges. 1D self-consistent modeling predictions show agreement with experimental results within the estimated experimental error of 25%. The present results can be used to further the development of higher fidelity kinetic models while quantifying plasma-source characteristics.

  6. Resonance Energy Transfer in Upconversion Nanoplatforms for Selective Biodetection.

    PubMed

    Su, Qianqian; Feng, Wei; Yang, Dongpeng; Li, Fuyou

    2017-01-17

    Resonance energy transfer (RET) describes the process that energy is transferred from an excited donor to an acceptor molecule, leading to a reduction in the fluorescence emission intensity of the donor and an increase in that of the acceptor. By this technique, measurements with the good sensitivity can be made about distance within 1 to 10 nm under physiological conditions. For this reason, the RET technique has been widely used in polymer science, biochemistry, and structural biology. Recently, a number of RET systems incorporated with nanoparticles, such as quantum dots, gold nanoparticles, and upconversion nanoparticles, have been developed. These nanocrystals retain their optical superiority and can act as either a donor or a quencher, thereby enhancing the performance of RET systems and providing more opportunities in excitation wavelength selection. Notably, lanthanide-doped upconversion nanophosphors (UCNPs) have attracted considerable attention due to their inherent advantages of large anti-Stoke shifts, long luminescence lifetimes, and absence of autofluorescence under low energy near-infrared (NIR) light excitation. These nanoparticles are promising for the biodetection of various types of analytes. Undoubtedly, the developments of those applications usually rely on resonance energy transfer, which could be regarded as a flexible technology to mediate energy transfer from upconversion phosphor to acceptor for the design of luminescent functional nanoplatforms. Currently, researchers have developed many RET-based upconversion nanosystems (RET-UCNP) that respond to specific changes in the biological environments. Specifically, small organic molecules, biological molecules, metal-organic complexes, or inorganic nanoparticles were carefully selected and bound to the surface of upconversion nanoparticles for the preparation of RET-UCNP nanosystems. Benefiting from the advantage and versatility offered by this technology, the research of RET

  7. Synthesis and characterization of visible-to-UVC upconversion antimicrobial ceramics.

    PubMed

    Cates, Stephanie L; Cates, Ezra L; Cho, Min; Kim, Jae-Hong

    2014-02-18

    The objective of this study was to develop visible-to-ultraviolet C (UVC) upconversion ceramic materials, which inactivate surface-borne microbes through frequency amplification of ambient visible light. Ceramics were formed by high-temperature sintering of compacted yttrium silicate powders doped with Pr(3+) and Li(+). In comparison to previously reported upconversion surface coatings, the ceramics were significantly more durable and had greater upconversion efficiency under both laser and low-power visible light excitation. The antimicrobial activity of the surfaces under diffuse fluorescent light was assessed by measuring the inactivation of Bacillus subtilis spores, the rate of which was nearly 4 times higher for ceramic materials compared to the previously reported films. Enhanced UVC emissions were attributed to increased material thickness as well as increased crystallite size in the ceramics. These results represent significant advancement of upconversion surfaces for sustainable, light-activated disinfection applications.

  8. Multifunctional Upconversion-Magnetic Hybrid Nanostructured Materials: Synthesis and Bioapplications

    PubMed Central

    Li, Xiaomin; Zhao, Dongyuan; Zhang, Fan

    2013-01-01

    The combination of nanotechnology and biology has developed into an emerging research area: nano-biotechnology. Upconversion nanoparticles (UCNPs) have attracted a great deal of attention in bioapplications due to their high chemical stability, low toxicity, and high signal-to-noise ratio. Magnetic nanoparticles (MNPs) are also well-established nanomaterials that offer controlled size, ability to be manipulated externally, and enhancement of contrast in magnetic resonance imaging (MRI). As a result, these nanoparticles could have many applications in biology and medicine, including protein purification, drug delivery, and medical imaging. Because of the potential benefits of multimodal functionality in biomedical applications, researchers would like to design and fabricate multifunctional upconversion-magnetic hybrid nanostructured materials. The hybrid nanostructures, which combine UCNPs with MNPs, exhibit upconversion fluorescence alongside superparamagnetism property. Such structures could provide a platform for enhanced bioimaging and controlled drug delivery. We expect that the combination of unique structural characteristics and integrated functions of multifunctional upconversion-magnetic nanoparticles will attract increasing research interest and could lead to new opportunities in nano-bioapplications. PMID:23650477

  9. Fluorescence kinetics of Trp-Trp dipeptide and its derivatives in water via ultrafast fluorescence spectroscopy.

    PubMed

    Jia, Menghui; Yi, Hua; Chang, Mengfang; Cao, Xiaodan; Li, Lei; Zhou, Zhongneng; Pan, Haifeng; Chen, Yan; Zhang, Sanjun; Xu, Jianhua

    2015-08-01

    Ultrafast fluorescence dynamics of Tryptophan-Tryptophan (Trp-Trp/Trp2) dipeptide and its derivatives in water have been investigated using a picosecond resolved time correlated single photon counting (TCSPC) apparatus together with a femtosecond resolved upconversion spectrophotofluorometer. The fluorescence decay profiles at multiple wavelengths were fitted by a global analysis technique. Nanosecond fluorescence kinetics of Trp2, N-tert-butyl carbonyl oxygen-N'-aldehyde group-l-tryptophan-l-tryptophan (NBTrp2), l-tryptophan-l-tryptophan methyl ester (Trp2Me), and N-acetyl-l-tryptophan-l-tryptophan methyl ester (NATrp2Me) exhibit multi-exponential decays with the average lifetimes of 1.99, 3.04, 0.72 and 1.22ns, respectively. Due to the intramolecular interaction between two Trp residues, the "water relaxation" lifetime was observed around 4ps, and it is noticed that Trp2 and its derivatives also exhibit a new decay with a lifetime of ∼100ps, while single-Trp fluorescence decay in dipeptides/proteins shows 20-30ps. The intramolecular interaction lifetime constants of Trp2, NBTrp2, Trp2Me and NATrp2Me were then calculated to be 3.64, 0.93, 11.52 and 2.40ns, respectively. Candidate mechanisms (including heterogeneity, solvent relaxation, quasi static self-quenching or ET/PT quenching) have been discussed.

  10. Ultraviolet and visible upconversion luminescence of Tm(0.1)Yb(5):FOV oxyfluoride nanophase vitroceramics

    NASA Astrophysics Data System (ADS)

    Chen, Xiaobo; Song, Zengfu; Wu, Jinguang; Sawanoboi, N.; Ohtsuka, M.; Li, Yongliang; Zhou, Jing; Wang, Ce; Liu, Jinying; Tian, Qiang; Sun, Ping; Jing, Hongmei

    2008-12-01

    The ultraviolet upconversion luminescence of Tm3+ ions sensitized by Yb3+ ions in oxyfluoride nanophase vitroceramics when excited by a 975 nm diode laser was studied. An ultraviolet upconversion luminescence line positioned at 363.6 nm was found. It was attributed to the fluorescence transition of 1D2→3H6 of Tm3+ ion. Several visible upconversion luminescence lines at 450.7 nm, (477.0 nm, 462.5 nm), 648.5 nm, (680.5 nm, 699.5 nm) and (777.2 nm, 800.7 nm) were also found, which result respectively from the fluorescence transitions of 1D2→3F4, 1G4→3H6, 1G4→3F4, 3F3→3H6 and 3H4→3H6 of Tm3+ ion. The careful measurement and analysis of the variation of upconversion luminescence intensity F as a function of the 975 nm pumping laser power P prove that the upconversion luminescence of 1D2 state is partly a five-photon upconversion luminescence, and the upconversion luminescence of 1G4 state and 3H4 state are respectively the three-photon and two-photon upconversion luminescence. The theoretical analysis suggested that the upconversion mechanism of the 363.6 nm 1D2→3H6 upconversion luminescence is partly the cross energy transfer of {3H4(Tm3+), 3F4(Tm3+), 1G4(Tm3+)→1D2(Tm3+)} and {1G4(Tm3+)→3F4(Tm3+), 3H4(Tm3+)→1D2(Tm3+)} between Tm3+ ions. In addition, the upconversion luminescence of 1G4 and 3H4 state results respectively from the sequential energy transfer {2F5/2(Yb3+)→2F7/2(Yb3+), 3H4(Tm3+)→1G4(Tm3+)} and {2F5/2(Yb3+) →2F7/2(Yb3+), 3F4(Tm3+)→3F2(Tm3+)} from Yb3+ ions to Tm3+ ions.

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

    PubMed

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

    2008-09-11

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

  12. Preservation of fluorescence and Raman gain in the buried channel waveguides in neodymium-doped KGd(WO{sub 4}){sub 2}(Nd:KGW) by femtosecond laser writing

    SciTech Connect

    Liu Xiaoyu; Qu Shiliang; Tan Yang; Chen Feng

    2011-02-20

    We report on the preservation of fluorescence and Raman gain in low-repetition-rate femtosecond laser written buried channel waveguides in neodymium-doped KGd(WO{sub 4}){sub 2}. The propagation loss index, profile reconstruction, and calculation of the modal intensity distribution by the beam propagation method of the waveguide are presented. Microluminescence spectra of the waveguides show that the fluorescence properties of Nd{sup 3+} ions are not significantly affected by the waveguide formation processing, which indicates a fairly good potential for further laser actions in a compact device. Micro-Raman spectra are also performed to reveal the preservation of the characteristic 768 and 901 cm{sup -1} Raman mode intensities in the guiding regions.

  13. Upconversion luminescence from CdSe nanoparticles.

    PubMed

    Chen, Wei; Joly, Alan G; McCready, David E

    2005-06-08

    Efficient upconversion luminescence has been observed from CdSe nanoparticles ranging in size from 2.5 to 6 nm. The upconversion luminescence exhibits a near-quadratic laser power dependence. Emissions from both excitons and trap states are observed in the upconversion and photoluminescence spectra, and in the upconversion luminescence the emission from the trap states is enhanced relative to the trap-state emission in the photoluminescence. The upconversion decay lifetimes are slightly longer than the photoluminescence decay lifetimes. Time-resolved spectral measurements indicate that this is due to the involvement of long decay components from surface or trap states. Both the photoluminescence and upconversion luminescence decrease in intensity with increasing temperature due mainly to thermal quenching. All the observations indicate that trap states work as emitters rather than as intermediate states for upconversion luminescence and that two-photon absorption is the likely excitation mechanism.

  14. Upconversion nanoparticles and their composite nanostructures for biomedical imaging and cancer therapy

    NASA Astrophysics Data System (ADS)

    Cheng, Liang; Wang, Chao; Liu, Zhuang

    2012-12-01

    Upconversion nanoparticles (UCNPs), particularly lanthanide-doped nanocrystals, which emit high energy photons under excitation by the near-infrared (NIR) light, have found potential applications in many different fields, including biomedicine. Compared with traditional down-conversion fluorescence imaging, the NIR light excited upconversion luminescence (UCL) imaging relying on UCNPs exhibits improved tissue penetration depth, higher photochemical stability, and is free of auto-fluorescence background, which promises biomedical imaging with high sensitivity. On the other hand, the unique upconversion process of UCNPs may be utilized to activate photosensitive therapeutic agents for applications in cancer treatment. Moreover, the integration of UCNPs with other functional nanostructures could result in the obtained nanocomposites having highly enriched functionalities, useful in imaging-guided cancer therapies. This review article will focus on the biomedical imaging and cancer therapy applications of UCNPs and their nanocomposites, and discuss recent advances and future prospects in this emerging field.

  15. Tailoring Plasmonic Enhanced Upconversion in Single NaYF4:Yb3+/Er3+ Nanocrystals

    PubMed Central

    Wang, Ya-Lan; Mohammadi Estakhri, Nasim; Johnson, Amber; Li, Hai-Yang; Xu, Li-Xiang; Zhang, Zhenyu; Alù, Andrea; Wang, Qu-Quan; Shih, Chih-Kang (Ken)

    2015-01-01

    By using silver nanoplatelets with a widely tunable localized surface plasmon resonance (LSPR), and their corresponding local field enhancement, here we show large manipulation of plasmonic enhanced upconversion in NaYF4:Yb3+/Er3+ nanocrystals at the single particle level. In particular, we show that when the plasmonic resonance of silver nanolplatelets is tuned to 656 nm, matching the emission wavelength, an upconversion enhancement factor ~5 is obtained. However, when the plasmonic resonance is tuned to 980 nm, matching the nanocrystal absorption wavelength, we achieve an enhancement factor of ~22 folds. The precise geometric arrangement between fluorescent nanoparticles and silver nanoplatelets allows us to make, for the first time, a comparative analysis between experimental results and numerical simulations, yielding a quantitative agreement at the single particle level. Such a comparison lays the foundations for a rational design of hybrid metal-fluorescent nanocrystals to harness the upconversion enhancement for biosensing and light harvesting applications. PMID:25976870

  16. Sodium yttrium fluoride based upconversion nano phosphors for biosensing

    NASA Astrophysics Data System (ADS)

    Parameswaran Nampi, Padmaja; Varma, Harikrishna; Biju, P. R.; Kakkar, Tarun; Jose, Gin; Saha, Sikha; Millner, Paul

    2015-06-01

    In the present study, NaYF4-Yb3+/Er3+ having the composition NaYF4-18%Yb3+/2%Er3+ and NaYF4-20%Yb3+/2%Er3+ with and without the addition of PVP (polyvinyl pyrolidone) have been synthesised by a solution method using NaF, yttrium nitrate, ytterbium nitrate and erbium nitrate as precursors. Upconversion spectra of prepared nanomaterial under 980 nm laser excitation have been studied. The variation in upconversion spectra with new born calf serum and myoglobin has been studied. Myoglobin (Mb) may be helpful when used in conjunction with other cardiac markers for rapid determination of acute myocardial ischemia, especially in patients with a typical chest pain or nonspecific ECG changes. The variation of UC fluorescence with addition of Mb indicates the suitability of using NaYF4 based UC nanoparticles in cardiac marker detection. The detailed study is currently under progress.

  17. Use of upconverting fluorescent nanoparticles for bioimaging

    NASA Astrophysics Data System (ADS)

    Chatterjee, Dev K.; Zhang, Yong

    2012-02-01

    Lanthanide doped nanocrystals with upconversion fluorescence emission have been synthesized. The surface of these nanocrystals are modified to render them water dispersible and biocompatible. Use of these nanocrystals for bioimaging introduces many advantages, for example, minimum photo-damage to biological samples, weak auto-fluorescence, high detection sensitivity, high light penetration depth, etc. Here, we use upconversion nanocrystals to label cancer cells and demonstrate confocal imaging of the labeled cells implanted in mouse muscle.

  18. Monolithic blue upconversion fiber laser

    NASA Astrophysics Data System (ADS)

    Gaebler, Volker; Eichler, Hans J.

    2002-06-01

    We report a monolithic low threshold 482nm Tm:ZBLAN upconversion fiber laser. The laser cavity consists of a directly coated single-mode fluoride fiber. The vapor deposit coatings significantly reduce the coupling losses and are suitable to be pumped by laser diodes. The laser operation and threshold characteristics have been investigated. The output stability and beam quality was tested.

  19. Remarkable effects of solvent and substitution on the photo-dynamics of cytosine: a femtosecond broadband time-resolved fluorescence and transient absorption study.

    PubMed

    Ma, Chensheng; Cheng, Chopen Chan-Wut; Chan, Chris Tsz-Leung; Chan, Ruth Chau-Ting; Kwok, Wai-Ming

    2015-07-15

    Cytosine (Cyt) among all the nucleic acid bases features the most complex and least understood nonradiative deactivation, a process that is crucially important for its photostability. Herein, the excited state dynamics of Cyt and a series of its N1- and C5-derivatives, including the full set of Cyt nucleosides and nucleotides in DNA and RNA and the nucleosides of 5-methyl cytosine, 5-methylcytidine and 2'-deoxy-5-methylcytidine, have been investigated in water and in methanol employing femtosecond broadband time-resolved fluorescence coupled with fs transient absorption spectroscopy. The results reveal remarkable state-specific effects of the substitution and solvent in tuning distinctively the timescales and pathways of the nonradiative decays. For Cyt and the N1-derivatives, the nonradiative deactivations occur in a common two-state process through three channels, two from the light-absorbing ππ* state with respectively the sub-picosecond (∼0.2 ps) and the picosecond (∼1.5 ps) time constant, and the third is due to an optically dark nπ* state with the lifetime ranging from several to hundreds of picoseconds depending on solvents and substitutions. Compared to Cyt, the presence of the ribose or deoxyribose moiety at the N1 position of N1-derivatives facilitates the formation of the nπ* at the sub-picosecond timescale and at the same time increases its lifetime by ∼4-6 times in both water and methanol. In sharp contrast, the existence of the methyl group at the C5 position of the C5-derivatives eliminates completely the sub-picosecond ππ* channel and the channel due to the nπ*, but on the other hand slows down the decay of the ππ* state which after relaxation exhibits a single time constant of ∼4.1 to ∼7.6 ps depending on solvents. Varying the solvent from water to methanol accelerates only slightly the decay of the ππ* state in all the compounds; while for Cyt and its N1-derivatives, this change of solvent also retards strongly the n

  20. Photochemical Upconversion: A Physical or Inorganic Chemistry Experiment for Undergraduates Using a Conventional Fluorimeter

    ERIC Educational Resources Information Center

    Wilke, Bryn M.; Castellano, Felix N.

    2013-01-01

    Photochemical upconversion is a regenerative process that transforms lower-energy photons into higher-energy light through two sequential bimolecular reactions, triplet sensitization of an appropriate acceptor followed by singlet fluorescence producing triplet-triplet annihilation derived from two energized acceptors. This laboratory directly…

  1. Photochemical Upconversion: A Physical or Inorganic Chemistry Experiment for Undergraduates Using a Conventional Fluorimeter

    ERIC Educational Resources Information Center

    Wilke, Bryn M.; Castellano, Felix N.

    2013-01-01

    Photochemical upconversion is a regenerative process that transforms lower-energy photons into higher-energy light through two sequential bimolecular reactions, triplet sensitization of an appropriate acceptor followed by singlet fluorescence producing triplet-triplet annihilation derived from two energized acceptors. This laboratory directly…

  2. Ultrafast mid-infrared spectroscopy by chirped pulse upconversion in 1800-1000cm(-1) region.

    PubMed

    Zhu, Jingyi; Mathes, Tilo; Stahl, Andreas D; Kennis, John T M; Groot, Marie Louise

    2012-05-07

    Broadband femtosecond mid-infrared pulses can be converted into the visible spectral region by chirped pulse upconversion. We report here the upconversion of pump probe transient signals in the frequency region below 1800cm(-1), using the nonlinear optical crystal AgGaGeS4, realizing an important expansion of the application range of this method. Experiments were demonstrated with a slab of GaAs, in which the upconverted signals cover a window of 120cm(-1), with 1.5cm(-1) resolution. In experiments on the BLUF photoreceptor Slr1694, signals below 1 milliOD were well resolved after baseline correction. Possibilities for further optimization of the method are discussed. We conclude that this method is an attractive alternative for the traditional MCT arrays used in most mid-infrared pump probe experiments.

  3. Upconversion processes in Yb-sensitized Tm:ZBLAN

    SciTech Connect

    Carrig, T.J.; Cockroft, N.J.

    1996-10-01

    A spectroscopic study of 22 rare-earth-ion doped ZBLAN (fluorozirconate) glass was done to study feasibility of sensitizing Tm:ZBLAN with Yb to facilitate development of an efficient, conveniently pumped blue upconversion fiber laser. it was found that, under single-color pumping, 480 nm emission from Tm{sup 3+} was strongest when Yb,Tm:ZBLAN is excited at 975 nm; the strongest blue blue emission was obtained from a glass sample with 2.0 wt% Yb + 0.3 wt% Tm. Also, for weak 975 nm pump intensities, strength of blue upconversion emission can be greatly enhanced by simultaneously pumping at 785 nm. This increased upconversion efficiency is due to reduced number of energy transfer steps needed to populate the Tm{sup 3+} {sup 1}G{sub 4} energy level. Measurements of fluorescence lifetimes vs dopant concentration were also made for Yb{sup 3+}, Tm{sup 3+}, and Pr{sup 3+} transitions in ZBLAN in order to better characterize concentration quenching effects. Energy transfer between Tm{sup 3+} and Pr{sup 3+} in ZBLAN is also described.

  4. Femtosecond upconverted photocurrent spectroscopy of InAs quantum nanostructures

    SciTech Connect

    Yamada, Yasuhiro; Tex, David M.; Kanemitsu, Yoshihiko; Kamiya, Itaru

    2015-07-06

    The carrier upconversion dynamics in InAs quantum nanostructures are studied for intermediate-band solar-cell applications via ultrafast photoluminescence and photocurrent (PC) spectroscopy based on femtosecond excitation correlation (FEC) techniques. Strong upconverted PC-FEC signals are observed under resonant excitation of quantum well islands (QWIs), which are a few monolayer-thick InAs quantum nanostructures. The PC-FEC signal typically decays within a few hundred picoseconds at room temperature, which corresponds to the carrier lifetime in QWIs. The photoexcited electron and hole lifetimes in InAs QWIs are evaluated as functions of temperature and laser fluence. Our results provide solid evidence for electron–hole–hole Auger process, dominating the carrier upconversion in InAs QWIs at room temperature.

  5. Photophysical properties of new bis-perylene dyads for potential upconversion use

    NASA Astrophysics Data System (ADS)

    Ribas, Marcos R.; Steer, Ronald P.; Rüther, Ricardo

    2014-06-01

    Two new bis-perylenes, BPC with a meta-disubstituted benzene linker, and BPD with a p,p‧-disubstituted biphenyl linker, have been synthesized and their photophysical parameters measured. Their singlet and triplet energies decrease incrementally in the order perylene, BPC, BPD, making them ideally matched with C60 for triplet-triplet energy transfer in sensitized photon upconversion schemes. Following photosensitization by triplet C60, BPC exhibits strong fluorescence upconversion by triplet-triplet annihilation, indicating that these bis-perylene dyads (and the multimers that can be constructed from them) will be interesting candidates for use in organic devices such as bulk-heterojunction and dye-sensitized solar cells employing non-coherent photon upconversion.

  6. Simultaneous excitation and emission enhancements in upconversion luminescence using plasmonic double-resonant gold nanorods

    PubMed Central

    Liu, Xin; Yuan Lei, Dang

    2015-01-01

    The geometry and dimension of a gold nanorod (GNR) are optimally designed to enhance the fluorescence intensity of a lanthanide-doped upconversion nanocrystal placed in close proximity to the GNR. A systematic study of the electromagnetic interaction between the upconversion emitter of three energy levels and the GNR shows that the enhancement effect arising from localized electric field-induced absorption can be balanced by the negative effect of electronic transition from an intermediate state to the ground state of the emitter. The dependence of fluorescence enhancement on the emitter-GNR separation is investigated, and the results demonstrate a maximum enhancement factor of 120 folds and 160 folds at emission wavelengths 650 and 540 nm, respectively. This is achieved at the emitter-GNR separation ranging from 5 to 15 nm, depending on the initial quantum efficiency of the emitter. The modified upconversion luminescence behavior by adjusting the aspect ratio of the GNR and the relative position of the emitter indicates the dominate role of excitation process in the total fluorescence enhancement. These findings are of great importance for rationally designing composite nanostructures of metal nanoparticles and upconversion nanocrystals with maximized plasmonic enhancement for bioimaging and sensing applications. PMID:26468686

  7. Mesoporous silica encapsulating upconversion luminescence rare-earth fluoride nanorods for secondary excitation.

    PubMed

    Yang, Jianping; Deng, Yonghui; Wu, Qingling; Zhou, Jing; Bao, Haifeng; Li, Qiang; Zhang, Fan; Li, Fuyou; Tu, Bo; Zhao, Dongyuan

    2010-06-01

    Mesoporous silica encapsulating upconversion luminescence NaYF(4) nanorods with uniform core-shell structures have been successfully synthesized by the surfactant-assistant sol-gel process. The thickness of ordered mesoporous silica shells can be adjusted from 50 to 95 nm by varying the amount of hydrolyzed silicate oligomer precursors from tetraethyl orthosilicate (TEOS), which further influences the BET surface area, pore volume, and the luminescence intensity. After coated with mesoporous silica shells, the hydrophobic nanorods is rendered to hydropholic simultaneously. The obtained beta-NaYF(4)@SiO(2)@mSiO(2) core-shell nanorods possess high surface area (71.2-196 m(2) g(-1)), pore volume (0.07-0.17 cm(3) g(-1)), uniform pore size distribution (2.3 nm), and accessible channels. Furthermore, the uniform core-shell nanorods show strong upconversion luminescence property similar to the hexagonal upconversion cores. The open mesopores can not only provide convenient transmission channels but also offer the huge location for accommodation of large molecules, such as fluorescent dyes and quantum dots. The secondary-excitation fluorescence of Rhodamine B is generated from the upconversion rare-earth fluoride nanorods cores to the fluorescent dyes loaded in the mesoporous silica shells.

  8. Photon upconversion with directed emission

    PubMed Central

    Börjesson, K.; Rudquist, P.; Gray, V.; Moth-Poulsen, K.

    2016-01-01

    Photon upconversion has the potential to increase the efficiency of single bandgap solar cells beyond the Shockley Queisser limit. Efficient light management is an important point in this context. Here we demonstrate that the direction of upconverted emission can be controlled in a reversible way, by embedding anthracene derivatives together with palladium porphyrin in a liquid crystalline matrix. The system is employed in a triplet-triplet annihilation photon upconversion scheme demonstrating controlled switching of directional anti Stokes emission. Using this approach an emission ratio of 0.37 between the axial and longitudinal emission directions and a directivity of 1.52 is achieved, reasonably close to the theoretical maximal value of 2 obtained from a perfectly oriented sample. The system can be switched for multiple cycles without any visible degradation and the speed of switching is only limited by the intrinsic rate of alignment of the liquid crystalline matrix. PMID:27573539

  9. Photon upconversion with directed emission

    NASA Astrophysics Data System (ADS)

    Börjesson, K.; Rudquist, P.; Gray, V.; Moth-Poulsen, K.

    2016-08-01

    Photon upconversion has the potential to increase the efficiency of single bandgap solar cells beyond the Shockley Queisser limit. Efficient light management is an important point in this context. Here we demonstrate that the direction of upconverted emission can be controlled in a reversible way, by embedding anthracene derivatives together with palladium porphyrin in a liquid crystalline matrix. The system is employed in a triplet-triplet annihilation photon upconversion scheme demonstrating controlled switching of directional anti Stokes emission. Using this approach an emission ratio of 0.37 between the axial and longitudinal emission directions and a directivity of 1.52 is achieved, reasonably close to the theoretical maximal value of 2 obtained from a perfectly oriented sample. The system can be switched for multiple cycles without any visible degradation and the speed of switching is only limited by the intrinsic rate of alignment of the liquid crystalline matrix.

  10. Femtosecond to nanosecond dynamics of 2,2'-bipyridine-3,3'-diol inside the nano-cavities of molecular containers.

    PubMed

    Gavvala, Krishna; Sengupta, Abhigyan; Koninti, Raj Kumar; Hazra, Partha

    2014-01-21

    Femtosecond fluorescence upconversion measurements are employed to elucidate the mechanism of ultrafast double proton transfer dynamics of BP(OH)2 inside molecular containers (cucurbit[7]uril (CB7) and β-cyclodextrin (β-CD)). Femtosecond up-converted signals of BP(OH)2 in water consist of growth followed by a long decay component (~650 ps). The appearance of the growth component (~35 ps) in the up-converted signal indicates the presence of a two-step sequential proton transfer process of BP(OH)2 in water. Surprisingly, the up-converted signal of BP(OH)2 inside the CB7 nano-cavity does not exhibit any growth component characteristic of a two-step sequential process. Interestingly, the growth component exists inside the nano-cavity of β-CD (having similar cavity size as that of CB7), inferring the presence of a two-step sequential process of PT inside the β-CD nano-cavity. The different features of PT dynamics of BP(OH)2 in the above mentioned two macrocyclic hosts may be attributed to the presence and absence of water solvation network surrounding the BP(OH)2 inside the nano-cavities of β-CD and CB7, respectively. Finally, docking and DFT calculations have been employed in deciphering the molecular pictures of the interactions between BP(OH)2 and the macrocyclic host.

  11. Upconversion photon quantification of holmium and erbium ions in waveguide-adaptive germanate glasses

    NASA Astrophysics Data System (ADS)

    Zhu, C. L.; Pun, E. Y. B.; Wang, Z. Q.; Lin, H.

    2017-02-01

    Visible upconversion photons have been quantified precisely in Ho3+/Yb3+ and Er3+/Yb3+ doped waveguide-adaptive aluminum germanate (NMAG) glasses, and effective red and green upconversion emissions generated from Ho3+ and Er3+ were illustrated in contrast. The emission photon numbers are identified as a positive correlation with the laser power densities, and stronger dominance of red emission in the Ho3+/Yb3+ doped NMAG glasses and more effectiveness of photon generation in Er3+/Yb3+ doped case were proved. When the power density is 1227 W/cm2, the absolute quantum yields for red and green (660 and 548 nm) upconversion fluorescences are derived to be 2.41 × 10-5 and 0.17 × 10-5 in Ho3+/Yb3+ doped NMAG glasses, and the ones (665 and 548 nm) in Er3+/Yb3+ doped NMAG glasses are 4.26 × 10-5 and 1.44 × 10-5. The macroscopic quantization of red and green upconversion emissions in Ho3+/Yb3+ and Er3+/Yb3+ doped waveguide-adaptive NMAG glasses provides the original referenced data for developing upconversion waveguide-typed irradiation light sources.

  12. Infrared Signal Detection by Upconversion Technique

    NASA Technical Reports Server (NTRS)

    Wong, Teh-Hwa; Yu, Jirong; Bai, Yingxin; Johnson, William E.

    2014-01-01

    We demonstrated up-conversion assisted detection of a 2.05-micron signal by using a bulk periodically poled Lithium niobate crystal. The 94% intrinsic up-conversion efficiency and 22.58% overall detection efficiency at pW level of 2.05-micron was achieved.

  13. Development, applications, and future of infrared upconversion

    NASA Technical Reports Server (NTRS)

    Gurski, T. R.

    1976-01-01

    Infrared upconversion is a technique that converts linearly polarized infrared photons to photons of higher frequency. The technique can be applied advantageously to the detection of IR radiation because the upconverted signal can be detected by photon-counting devices available for the visible spectral region. In addition, unlike presently available IR detectors, an upconversion device can provide sensitivity to IR radiation without the need for cryogenic cooling. Infrared upconversion was first demonstrated in 1961. By 1974, approximately 100% quantum conversion efficiency and a bandwidth of 1.81 microns had been attained. Photometric detection of IR radiation from various astronomical objects had also been demonstrated. Research is presently under way on the application of upconversion to astronomical spectroscopy and to imaging. The major drawback to the upconversion technique is the sheer bulk of the apparatus involved. It is anticipated that this problem can be overcome by applying the developing technology of integrated optics.

  14. Construction of a femtosecond laser microsurgery system

    PubMed Central

    Steinmeyer, Joseph D; Gilleland, Cody L; Pardo-Martin, Carlos; Angel, Matthew; Rohde, Christopher B; Scott, Mark A; Yanik, Mehmet Fatih

    2014-01-01

    Femtosecond laser microsurgery is a powerful method for studying cellular function, neural circuits, neuronal injury and neuronal regeneration because of its capability to selectively ablate sub-micron targets in vitro and in vivo with minimal damage to the surrounding tissue. Here, we present a step-by-step protocol for constructing a femtosecond laser microsurgery setup for use with a widely available compound fluorescence microscope. The protocol begins with the assembly and alignment of beam-conditioning optics at the output of a femtosecond laser. Then a dichroic mount is assembled and installed to direct the laser beam into the objective lens of a standard inverted microscope. Finally, the laser is focused on the image plane of the microscope to allow simultaneous surgery and fluorescence imaging. We illustrate the use of this setup by presenting axotomy in Caenorhabditis elegans as an example. This protocol can be completed in 2 d. PMID:20203659

  15. The dependence of the ultrafast relaxation kinetics of the S(2) and S(1) states in beta-carotene homologs and lycopene on conjugation length studied by femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies.

    PubMed

    Kosumi, Daisuke; Fujiwara, Masazumi; Fujii, Ritsuko; Cogdell, Richard J; Hashimoto, Hideki; Yoshizawa, Masayuki

    2009-06-07

    The ultrafast relaxation kinetics of all-trans-beta-carotene homologs with varying numbers of conjugated double bonds n(n=7-15) and lycopene (n=11) has been investigated using femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies, both carried out under identical excitation conditions. The nonradiative relaxation rates of the optically allowed S(2)(1(1)B(u) (+)) state were precisely determined by the time-resolved fluorescence. The kinetics of the optically forbidden S(1)(2(1)A(g) (-)) state were observed by the time-resolved absorption measurements. The dependence of the S(1) relaxation rates upon the conjugation length is adequately described by application of the energy gap law. In contrast to this, the nonradiative relaxation rates of S(2) have a minimum at n=9 and show a reverse energy gap law dependence for values of n above 11. This anomalous behavior of the S(2) relaxation rates can be explained by the presence of an intermediate state (here called the S(x) state) located between the S(2) and S(1) states at large values of n (such as n=11). The presence of such an intermediate state would then result in the following sequential relaxation pathway S(2)-->S(x)-->S(1)-->S(0). A model based on conical intersections between the potential energy curves of these excited singlet states can readily explain the measured relationships between the decay rates and the energy gaps.

  16. The dependence of the ultrafast relaxation kinetics of the S2 and S1 states in β-carotene homologs and lycopene on conjugation length studied by femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies

    NASA Astrophysics Data System (ADS)

    Kosumi, Daisuke; Fujiwara, Masazumi; Fujii, Ritsuko; Cogdell, Richard J.; Hashimoto, Hideki; Yoshizawa, Masayuki

    2009-06-01

    The ultrafast relaxation kinetics of all-trans-β-carotene homologs with varying numbers of conjugated double bonds n(n =7-15) and lycopene (n =11) has been investigated using femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies, both carried out under identical excitation conditions. The nonradiative relaxation rates of the optically allowed S2(1Bu+1) state were precisely determined by the time-resolved fluorescence. The kinetics of the optically forbidden S1(2Ag-1) state were observed by the time-resolved absorption measurements. The dependence of the S1 relaxation rates upon the conjugation length is adequately described by application of the energy gap law. In contrast to this, the nonradiative relaxation rates of S2 have a minimum at n =9 and show a reverse energy gap law dependence for values of n above 11. This anomalous behavior of the S2 relaxation rates can be explained by the presence of an intermediate state (here called the Sx state) located between the S2 and S1 states at large values of n (such as n =11). The presence of such an intermediate state would then result in the following sequential relaxation pathway S2→Sx→S1→S0. A model based on conical intersections between the potential energy curves of these excited singlet states can readily explain the measured relationships between the decay rates and the energy gaps.

  17. Superresolved femtosecond laser nanosurgery of cells

    PubMed Central

    Pospiech, Matthias; Emons, Moritz; Kuetemeyer, Kai; Heisterkamp, Alexander; Morgner, Uwe

    2011-01-01

    We report on femtosecond nanosurgery of fluorescently labeled structures in cells with a spatially superresolved laser beam. The focal spot width is reduced using phase filtering applied with a programmable phase modulator. A comprehensive statistical analysis of the resulting cuts demonstrates an achievable average resolution enhancement of 30 %. PMID:21339872

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

  20. Blue-green upconversion laser

    DOEpatents

    Nguyen, D.C.; Faulkner, G.E.

    1990-08-14

    A blue-green laser (450--550 nm) uses a host crystal doped with Tm[sup 3+]. The Tm[sup 3+] is excited through upconversion by a red pumping laser and an IR pumping laser to a state which transitions to a relatively lower energy level through emissions in the blue-green band, e.g., 450.20 nm at 75 K. The exciting laser may be tunable dye lasers or may be solid-state semiconductor laser, e.g., GaAlAs and InGaAlP. 3 figs.

  1. Blue-green upconversion laser

    SciTech Connect

    Nguyen, Dinh C.; Faulkner, George E.

    1990-01-01

    A blue-green laser (450-550 nm) uses a host crystal doped with Tm.sup.3+. The Tm.sup.+ is excited through upconversion by a red pumping laser and an IR pumping laser to a state which transitions to a relatively lower energy level through emissions in the blue-green band, e.g., 450.20 nm at 75 K. The exciting laser may be tunable dye lasers or may be solid-state semiconductor laser, e.g., GaAlAs and InGaAlP.

  2. Gold nanorod plasmonic upconversion microlaser.

    PubMed

    Shi, Ce; Soltani, Soheil; Armani, Andrea M

    2013-01-01

    Plasmonic-photonic interactions have stimulated significant interdisciplinary interest, leading to rapid innovations in solar design and biosensors. However, the development of an optically pumped plasmonic laser has failed to keep pace due to the difficulty of integrating a plasmonic gain material with a suitable pump source. In the present work, we develop a method for coating high quality factor toroidal optical cavities with gold nanorods, forming a photonic-plasmonic laser. By leveraging the two-photon upconversion capability of the nanorods, lasing at 581 nm with a 20 μW threshold is demonstrated.

  3. Femtosecond spectral holography

    SciTech Connect

    Weiner, A.M.; Leaird, D.E.; Reitze, D.H.; Paek, E.G. )

    1992-10-01

    Storage, recall, and processing of shaped femtosecond waveforms are achieved by performing spectral holography within a femtosecond pulse shaping apparatus. Time reversal, as well as correlation and convolution, of femtosecond temporal signals is demonstrated. Applications of this technique to matched filtering, dispersion compensation, encryption and decoding, and femtosecond waveform synthesis are also discussed. The work extends the powerful principles of holographic signal processing, which have been used extensively for pattern recognition and filtering of two-dimensional spatial signals, to the femtosecond time domain. 44 refs.

  4. Femtosecond spectral holography

    NASA Astrophysics Data System (ADS)

    Weiner, Andrew M.; Leaird, Daniel E.; Reitze, David H.; Paek, Eung G.

    1992-10-01

    Storage, recall, and processing of shaped femtosecond waveforms are achieved by performing spectral holography within a femtosecond pulse shaping apparatus. Time reversal, as well as correlation and convolution, of femtosecond temporal signals is demonstrated. Applications of this technique to matched filtering, dispersion compensation, encryption and decoding, and femtosecond waveform synthesis are also discussed. The work extends the powerful principles of holographic signal processing, which have been used extensively for pattern recognition and filtering of two-dimensional spatial signals, to the femtosecond time domain.

  5. Up-conversion luminescence polarization control in Er3+-doped NaYF4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Hui, Zhang; Yun-Hua, Yao; Shi-An, Zhang; Chen-Hui, Lu; Zhen-Rong, Sun

    2016-02-01

    We propose a femtosecond laser polarization modulation scheme to control the up-conversion (UC) luminescence in Er3+-doped NaYF4 nanocrystals dispersed in the silicate glass. We show that the UC luminescence can be suppressed when the laser polarization is changed from linear through elliptical to circular, and the higher repetition rate will yield the lower control efficiency. We theoretically analyze the physical control mechanism of the UC luminescence polarization modulation by considering on- and near-resonant two-photon absorption, energy transfer up-conversion, and excited state absorption, and show that the polarization control mainly comes from the contribution of near-resonant two-photon absorption. Furthermore, we propose a method to improve the polarization control efficiency of UC luminescence in rare-earth ions by applying a two-color femtosecond laser field. Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 11304396), the National Natural Science Foundation of China (Grant Nos. 11474096 and 51132004), and the Shanghai Municipal Science and Technology Commission, China (Grant No. 14JC1401500).

  6. Controlling upconversion nanocrystals for emerging applications

    NASA Astrophysics Data System (ADS)

    Zhou, Bo; Shi, Bingyang; Jin, Dayong; Liu, Xiaogang

    2015-11-01

    Lanthanide-doped upconversion nanocrystals enable anti-Stokes emission with pump intensities several orders of magnitude lower than required by conventional nonlinear optical techniques. Their exceptional properties, namely large anti-Stokes shifts, sharp emission spectra and long excited-state lifetimes, have led to a diversity of applications. Here, we review upconversion nanocrystals from the perspective of fundamental concepts and examine the technical challenges in relation to emission colour tuning and luminescence enhancement. In particular, we highlight the advances in functionalization strategies that enable the broad utility of upconversion nanocrystals for multimodal imaging, cancer therapy, volumetric displays and photonics.

  7. Controlling upconversion nanocrystals for emerging applications.

    PubMed

    Zhou, Bo; Shi, Bingyang; Jin, Dayong; Liu, Xiaogang

    2015-11-01

    Lanthanide-doped upconversion nanocrystals enable anti-Stokes emission with pump intensities several orders of magnitude lower than required by conventional nonlinear optical techniques. Their exceptional properties, namely large anti-Stokes shifts, sharp emission spectra and long excited-state lifetimes, have led to a diversity of applications. Here, we review upconversion nanocrystals from the perspective of fundamental concepts and examine the technical challenges in relation to emission colour tuning and luminescence enhancement. In particular, we highlight the advances in functionalization strategies that enable the broad utility of upconversion nanocrystals for multimodal imaging, cancer therapy, volumetric displays and photonics.

  8. Study on up-conversion emissions of Yb 3+/Tm 3+ co-doped GdF 3 and NaGdF 4

    NASA Astrophysics Data System (ADS)

    Cao, Chunyan; Qin, Weiping; Zhang, Jisen

    2010-02-01

    The Yb 3+/Tm 3+ co-doped GdF 3 and NaGdF 4 samples were synthesized through a combination method of a co-precipitation and an argon atmosphere annealing procedures. X-ray diffraction analysis indicated that the Yb 3+/Tm 3+ co-doped GdF 3 sample crystallized well and was orthorhombic phase, and the Yb 3+/Tm 3+ co-doped NaGdF 4 sample was hexagonal phase. With a 980-nm semiconductor continuous wave laser diode as the excitation source, the up-conversion emission spectra of the two samples in the wavelength range of 240-510 nm were recorded. In the up-conversion emissions of the samples, Yb 3+ transferred energies to Tm 3+ resulting in their ultraviolet, violet, and blue up-conversion emissions. And, Tm 3+ simultaneously transferred energies to Gd 3+, which finally resulted in ultraviolet up-conversion emissions of Gd 3+. The study on the excitation power dependence of up-conversion fluorescence intensity indicated that there were multi-photon (three-, four-, five-, and six-) processes in the up-conversion emissions of the samples. And the up-conversion emissions of Gd 3+ and Tm 3+ in the Yb 3+/Tm 3+ co-doped GdF 3 and NaGdF 4 samples were compared studied, too.

  9. Upconversion Nanoparticles: Synthesis, Surface Modification, and Biological Applications

    PubMed Central

    Wang, Meng; Abbineni, Gopal; Clevenger, April; Mao, Chuanbin; Xu, Shukun

    2011-01-01

    New generation fluorophores, also termed upconversion nanoparticles (UCNPs), have the ability to convert near infrared radiations with lower energy into visible radiations with higher energy via a non-linear optical process. Recently, these UCNPs have evolved as alternative fluorescent labels to traditional fluorophores, showing great potential for imaging and biodetection assays in both in vitro and in vivo applications. UCNPs exhibit unique luminescent properties, including high penetration depth into tissues, low background signals, large Stokes shifts, sharp emission bands, and high resistance to photo-bleaching, making UCNPs an attractive alternative source for overcoming current limitations in traditional fluorescent probes. In this review, we discuss the recent progress in the synthesis and surface modification of rare earth doped UCNPs with a specific focus on their biological applications. PMID:21419877

  10. Upconversion nanoparticles based FRET aptasensor for rapid and ultrasenstive bacteria detection.

    PubMed

    Jin, Birui; Wang, Shurui; Lin, Min; Jin, Ying; Zhang, Shujing; Cui, Xingye; Gong, Yan; Li, Ang; Xu, Feng; Lu, Tian Jian

    2017-04-15

    Pathogenic bacteria cause serious harm to human health, which calls for the development of advanced detection methods. Herein, we developed a novel detection platform based on fluorescence resonance energy transfer (FRET) for rapid, ultrasensitive and specific bacteria detection, where gold nanoparticles (AuNPs, acceptor) were conjugated with aptamers while upconversion nanoparticles (UCNPs, donor) were functionalized with corresponding complementary DNA (cDNA). The spectral overlap between UCNPs fluorescence emission and AuNPs absorption enables the occurrence of FRET when hybridizing the targeted aptamer and cDNA, causing upconversion fluorescence quenching. In the presence of target bacteria, the aptamers preferentially bind to bacteria forming a three-dimensional structure and thereby dissociate UCNPs-cDNA from AuNPs-aptamers, resulting in the recovery of upconversion fluorescence. Using the UCNPs based FRET aptasensor, we successfully detected Escherichia coli ATCC 8739 (as a model analyte) with a detection range of 5-10(6)cfu/mL and detection limit of 3cfu/mL. The aptasensor was further used to detect E. coli in real food and water samples (e.g., tap/pond water, milk) within 20min. The novel UCNPs based FRET aptasensor could be used to detect a broad range of targets from whole cells to metal ions by using different aptamer sequences, holding great potential in environmental monitoring, medical diagnostics and food safety analysis.

  11. Femtosecond-Pulsed Plasmonic Nanotweezers

    PubMed Central

    Roxworthy, Brian J.; Toussaint, Kimani C.

    2012-01-01

    We demonstrate for the first time plasmonic nanotweezers based on Au bowtie nanoantenna arrays (BNAs) that utilize a femtosecond-pulsed input source to enhance trapping of both Rayleigh and Mie particles. Using ultra-low input power densities, we demonstrate that the high-peak powers associated with a femtosecond source augment the trap stiffness to 2x that of nanotweezers employing a continuous-wave source, and 5x that of conventional tweezers using a femtosecond source. We show that for trapped fluorescent microparticles the two-photon response is enhanced by 2x in comparison to the response without nanoantennas. We also demonstrate tweezing of 80-nm diameter Ag nanoparticles, and observe an enhancement of the second-harmonic signal of ~3.5x for the combined nanoparticle-BNA system compared to the bare BNAs. Finally, under select illumination conditions, fusing of Ag nanoparticles to the BNAs is observed which holds potential for in situ fabrication of three-dimensional, bimetallic nanoantennas. PMID:22993686

  12. Sensitive Infrared Signal Detection by Upconversion Technique

    NASA Technical Reports Server (NTRS)

    Wong, Teh-Hwa; Yu, Jirong; Bai, Yingxin; Johnson, William; Chen, Songsheng; Petros, Mulugeta; Singh, Upendra N.

    2014-01-01

    We demonstrated upconversion assisted detection of a 2.05-micron signal by sum frequency generation to generate a 700-nm light using a bulk periodically poled lithium niobate crystal. The achieved 94% intrinsic upconversion efficiency and 22.58% overall detection efficiency at a pW level of 2.05 micron pave the path to detect extremely weak infrared (IR) signals for remote sensing applications.

  13. Plasmon-enhanced energy transfer for improved upconversion of infrared radiation in doped-lanthanide nanocrystals.

    PubMed

    Sun, Qi-C; Mundoor, Haridas; Ribot, Josep C; Singh, Vivek; Smalyukh, Ivan I; Nagpal, Prashant

    2014-01-08

    Upconversion of infrared radiation into visible light has been investigated for applications in photovoltaics and biological imaging. However, low conversion efficiency due to small absorption cross-section for infrared light (Yb(3+)), and slow rate of energy transfer (to Er(3+) states) has prevented application of upconversion photoluminescence (UPL) for diffuse sunlight or imaging tissue samples. Here, we utilize resonant surface plasmon polaritons (SPP) waves to enhance UPL in doped-lanthanide nanocrystals. Our analysis indicates that SPP waves not only enhance the electromagnetic field, and hence weak Purcell effect, but also increase the rate of resonant energy transfer from Yb(3+) to Er(3+) ions by 6 fold. While we do observe strong metal mediated quenching (14-fold) of green fluorescence on flat metal surfaces, the nanostructured metal is resonant in the infrared and hence enhances the nanocrystal UPL. This strong Coulombic effect on energy transfer can have important implications for other fluorescent and excitonic systems too.

  14. Controlled synthesis of uniform and monodisperse upconversion core/mesoporous silica shell nanocomposites for bimodal imaging.

    PubMed

    Liu, Jianan; Bu, Wenbo; Zhang, Shengjian; Chen, Feng; Xing, Huaiyong; Pan, Limin; Zhou, Liangping; Peng, Weijun; Shi, Jianlin

    2012-02-20

    Here we report the design and controlled synthesis of monodisperse and precisely size-controllable UCNP@mSiO(2) nanocomposites smaller than 50 nm by directly coating a mesoporous silica shell (mSiO(2)) on upconversion nanocrystals NaYF(4):Tm/Yb/Gd (UCNPs), which can be used as near-infrared fluorescence and magnetic resonance imaging (MRI) agents and a platform for drug delivery as well. Some key steps such as transferring hydrophobic UCNPs to the water phase by using cetyltrimethylammonium bromide (CTAB), removal of the excess amount of CTAB, and temperature-controlled ultrasonication treatment should be adopted and carefully monitored to obtain uniform upconversion core/mesoporous silica shell nanocomposites. The excellent performance of the core-shell-structured nanocomposite in near-infrared fluorescence and magnetic resonance imaging was also demonstrated. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. All-or-none switching of photon upconversion in self-assembled organogel systems.

    PubMed

    Duan, Pengfei; Asthana, Deepak; Nakashima, Takuya; Kawai, Tsuyoshi; Yanai, Nobuhiro; Kimizuka, Nobuo

    2017-02-22

    Aggregation-induced photon upconversion (iPUC) based on a triplet-triplet annihilation (TTA) process is successfully developed via controlled self-assembly of donor-acceptor pairs in organogel nanoassemblies. Although segregation of donor from acceptor assemblies has been an outstanding problem in TTA-based UC and iPUC, we resolved this issue by modifying both the triplet donor and aggregation induced emission (AIE)-type acceptor with glutamate-based self-assembling moieties. These donors and acceptors co-assemble to form organogels without segregation. Interestingly, these donor-acceptor binary gels show upconversion at room temperature but the upconversion phenomena were lost upon dissolution of the gels on heating. The observed changes in TTA-UC emission were thermally reversible, reflecting the controlled assembly/disassembly of the binary molecular systems. The observed on/off ratio of UC emission was much higher than that of the aggregation-induced fluorescence of the acceptor, which highlights the important role of iPUC, i.e., multi-exciton TTA for photoluminescence switching. This work bridges iPUC and supramolecular chemistry and provides a new strategy for designing stimuli-responsive upconversion systems.

  16. Femtosecond Laser Filamentation for Atmospheric Sensing

    PubMed Central

    Xu, Huai Liang; Chin, See Leang

    2011-01-01

    Powerful femtosecond laser pulses propagating in transparent materials result in the formation of self-guided structures called filaments. Such filamentation in air can be controlled to occur at a distance as far as a few kilometers, making it ideally suited for remote sensing of pollutants in the atmosphere. On the one hand, the high intensity inside the filaments can induce the fragmentation of all matters in the path of filaments, resulting in the emission of characteristic fluorescence spectra (fingerprints) from the excited fragments, which can be used for the identification of various substances including chemical and biological species. On the other hand, along with the femtosecond laser filamentation, white-light supercontinuum emission in the infrared to UV range is generated, which can be used as an ideal light source for absorption Lidar. In this paper, we present an overview of recent progress concerning remote sensing of the atmosphere using femtosecond laser filamentation. PMID:22346566

  17. Upconversion in Er3+-doped Bi2O3-Li2O-BaO-PbO tertiary glass.

    PubMed

    Tripathi, Garima; Rai, Vineet Kumar; Rai, D K; Rai, S B

    2007-04-01

    Radiative properties of Er3+-doped tertiary bismuth glass has been analyzed by the Judd-Ofelt theory. NIR to visible upconversion in the Er3+-doped glass has been reported. The mechanism for the upconversion is explained on the basis of quadratic dependence on excitation power and on the energy-matching scheme. Energy transfer is noted as the dominant process including the long-lived 4I11/2 level as the intermediate state for the green and red upconversion emissions. The effect of temperature on the fluorescence intensity of the two bands due to 2H11/2-->4I15/2 and 4S3/2-->4I15/2 transitions as well as on the transitions due to Stark components of the 4S3/2 level have been monitored and it is concluded that their intensity ratio may serve as better temperature sensing device.

  18. Blue upconversion luminescence in 12 CaO·7 Al 2O 3:Tm 3 + /Yb 3 + polycrystals

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Liu, Liang; Sun, Jinchao; Qian, Yannan; Zhang, Yushen; Xu, Yanling

    2012-03-01

    The effect of Yb 3 + concentration on the fluorescence of 12 CaO·7 Al 2O 3:Tm 3 + /Yb 3 + polycrystals is investigated. Under the excitation of 980 nm laser, the strong blue (477 nm) emission band is observed and attributed to 1G 4 → 3H 6 of Tm 3 + . The ratio of blue to red emission increases with the increasing of Yb 3 + and remains constant at 10 mol% Yb 3 + . The pump dependence and upconversion mechanisms show that the two-photon cooperative upconversion process is responsible for the enhancement of the blue upconversion emission. The Commission Internationale de l'eclairage chromaticity coordinates (x, y) illustrate that the 12 CaO·7 Al 2O 3:1 mol% Tm 3 + /10 mol% Yb 3 + can emit high-purity blue light.

  19. Optical temperature sensor through infrared excited blue upconversion emission in Tm3 +/Yb3 + codoped Y2O3

    NASA Astrophysics Data System (ADS)

    Li, Dongyu; Wang, Yuxiao; Zhang, Xueru; Yang, Kun; Liu, Lu; Song, Yinglin

    2012-04-01

    An analysis of the intense blue upconversion emission at 476 and 488 nm in Tm3 +/Yb3 + codoped Y2O3 under excitation power density of 86.7 W/cm2 available from a diode laser emitting at 976 nm, has been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive blue upconversion emission at 476 and 488 nm in this material was recorded in the temperature range from 303 to 753 K. The maximum sensitivity derived from the FIR technique of the blue upconversion emission is approximately 0.0035 K- 1. The results imply that Tm3 +/Yb3 + codoped Y2O3 is a potential candidate for the optical temperature sensor.

  20. Hypoxic condition-selective upconversion via triplet-triplet annihilation based on POSS-core dendrimer complexes.

    PubMed

    Tanaka, Kazuo; Okada, Hiroshi; Ohashi, Wataru; Jeon, Jong-Hwan; Inafuku, Kenichi; Chujo, Yoshiki

    2013-05-15

    The influence on the efficiencies of the triplet-triplet annihilation (TTA)-supported upconversion by oxygen under biomimetic conditions was investigated. From the solution containing the dendrimer complexes based on polyhedral oligomeric silsesquioxane (POSS)-core dendrimer with the Pt complex of octaethylporphyrin (PtOEP) and anthracene in PBS, the fluorescence emission of anthracene depending on the dissolved oxygen (DO) concentrations via the TTA-supported upconversion was obtained with the excitation light at 540 nm. In particular, we observed strong emission only under hypoxic conditions. In addition, it was found that the emission intensity via TTA-supported upconversion can be reversibly regulated by the DO concentrations in the solution. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Non-invasive tracking of hydrogel degradation using upconversion nanoparticles.

    PubMed

    Dong, Yuqing; Jin, Guorui; Ji, Changchun; He, Rongyan; Lin, Min; Zhao, Xin; Li, Ang; Lu, Tian Jian; Xu, Feng

    2017-06-01

    Tracking the distribution and degradation of hydrogels in vivo is important for various applications including tissue engineering and drug delivery. Among various imaging modalities, fluorescence imaging has attracted intensive attention due to their high sensitivity, low cost and easy operation. Particularly, upconversion nanoparticles (UCNPs) that emit visible lights upon near-infrared (NIR) light excitation as tracking probes are promising in deciphering the fate of hydrogels after transplantation. Herein, we reported a facile and non-invasive in vivo hydrogel tracking method using UCNPs, where the degradation of hydrogels was determined using the decrease in fluorescence intensity from the UCNPs encapsulated in the hydrogels. We found that the change in the fluorescence intensity from the UCNPs was well consistent with that of the fluorescein isothiocyanate (FITC) covalently conjugated to hydrogels and also with the weight change of the hydrogels, suggesting the accuracy of the UCNPs in tracking the degradation of hydrogels. Furthermore, the in vivo fluorescence signals were only observed from the UCNPs instead of FITC after implantation for 7days due to the deep tissue penetration of UCNPs, demonstrating the capability of UCNPs in longitudinal, consecutive and non-invasive monitoring the in vivo degradation of hydrogels without causing any damage to the major organs (heart, lung, liver and kidney) of model rats. This study thus paves the way for monitoring the in vivo behaviors of biomimetic materials via deep tissue imaging with great clinical translation potentials. Long-term noninvasive in vivo tracking of the distribution and degradation of biodegradable hydrogels using fluorescent probes is important in tissue regeneration and drug delivery. Unlike the widely used fluorescent dyes and quantum dots (QDs) that suffer from photobleaching and undesired toxicity, upconversion nanoparticles (UCNPs) with high stability, deep tissue penetration as tracking probes

  2. Dopant distribution in a Tm(3+)-Yb(3+) codoped silica based glass ceramic: an infrared-laser induced upconversion study.

    PubMed

    Lahoz, F; Martin, I R; Mendez-Ramos, J; Nunez, P

    2004-04-01

    The optically active dopant distribution in a Tm(3+)-Yb(3+) doped silica based glass ceramic sample has been investigated. A systematic analysis of the upconversion fluorescence of the Tm(3+)-Yb(3+) codoped glass and glass ceramic has been performed at room temperature. Tm(3+) and Yb(3+) single doped glass and glass ceramics have also been included in the study. Upon infrared excitation at 790 nm into the (3)H(4) level of the Tm(3+) ions a blue upconversion emission is observed, which is drastically increased in the Yb(3+) codoped samples. A rate equation model confirmed the energy transfer upconversion mechanism. Based on these results, the temporal dynamic curves of the levels involved in the upconversion process, (3)H(4), (2)F(5/2), and (1)G(4) were interpreted in the glass ceramic samples. The contribution of the optically active Tm(3+) and Yb(3+) ions in the crystalline and in the vitreous phase of the glass ceramic was distinguished and the ratio of Tm(3+) ions in the crystalline phase could be quantified for the 1 mol % Tm(3+)-2.5 mol % Yb(3+) glass ceramic. A surprising result was obtained for that concentration: the main contribution to the upconversion emission of the glass ceramic is due to Tm(3+)-Yb(3+) ions in the vitreous phase.

  3. Two-photon spectral fluorescence lifetime and second-harmonic generation imaging of the porcine cornea with a 12-femtosecond laser microscope.

    PubMed

    Batista, Ana; Breunig, Hans Georg; Uchugonova, Aisada; Morgado, António Miguel; König, Karsten

    2016-03-01

    Five dimensional microscopy with a 12-fs laser scanning microscope based on spectrally resolved two-photon autofluorescence lifetime and second-harmonic generation (SHG) imaging was used to characterize all layers of the porcine cornea. This setup allowed the simultaneous excitation of both metabolic cofactors, NAD(P)H and flavins, and their discrimination based on their spectral emission properties and fluorescence decay characteristics. Furthermore, the architecture of the stromal collagen fibrils was assessed by SHG imaging in both forward and backward directions. Information on the metabolic state and the tissue architecture of the porcine cornea were obtained with subcellular resolution, and high temporal and spectral resolutions.

  4. Two-photon spectral fluorescence lifetime and second-harmonic generation imaging of the porcine cornea with a 12-femtosecond laser microscope

    NASA Astrophysics Data System (ADS)

    Batista, Ana; Breunig, Hans Georg; Uchugonova, Aisada; Morgado, António Miguel; König, Karsten

    2016-03-01

    Five dimensional microscopy with a 12-fs laser scanning microscope based on spectrally resolved two-photon autofluorescence lifetime and second-harmonic generation (SHG) imaging was used to characterize all layers of the porcine cornea. This setup allowed the simultaneous excitation of both metabolic cofactors, NAD(P)H and flavins, and their discrimination based on their spectral emission properties and fluorescence decay characteristics. Furthermore, the architecture of the stromal collagen fibrils was assessed by SHG imaging in both forward and backward directions. Information on the metabolic state and the tissue architecture of the porcine cornea were obtained with subcellular resolution, and high temporal and spectral resolutions.

  5. A femtosecond study of photoinduced electron transfer from dimethylaniline to coumarin dyes in a cetyltrimethylammonium bromide micelle

    SciTech Connect

    Ghosh, Subhadip; Sahu, Kalyanasis; Mondal, Sudip Kumar; Sen, Pratik; Bhattacharyya, Kankan

    2006-08-07

    Ultrafast photoinduced electron transfer (PET) from N,N-dimethylaniline to coumarin dyes in cetyltrimethylammonium bromide (CTAB) micelle is studied using femtosecond upconversion spectroscopy. The rate of PET in a CTAB micelle is found to be highly nonexponential with components much faster ({approx}10 ps) than the slow components of solvation dynamics. The ultrafast components of electron transfer exhibits a bell-shaped dependence on the free energy change which is similar to the Marcus inversion.

  6. The characteristic saturation phenomenon of upconversion luminescence in holmium ytterbium-co-doped oxyfluoride glass Ho(0.1)Yb(5):FOG

    NASA Astrophysics Data System (ADS)

    Chen, Xiaobo; Song, Zengfu; Sawanobori, Naruhito; Ohtsuka, Masaaki; Li, Xiaowen; Wang, Yafei; Xu, Xiaoling; He, Chenjuan; Ma, Hui; Chen, Ying; Zhu, Jianyang

    2008-11-01

    The upconversion luminescence of holmium Ho 3+ ion sensitized by ytterbium Yb 3+ ion in Ho 3+Yb 3+-co-doped oxyfluoride glass Ho(0.1)Yb(5):FOG is investigated in this paper. A plenty of upconversion luminescence lines are measured out. The upconversion mechanism of Ho(0.1)Yb(5):FOG, when excited by 960 nm laser, is the energy transfer from Yb 3+ to Ho 3+ ion. A very weak 795.5 nm common photoemission fluorescence is detected, which is recognized as the 5I 4→ 5I 8 fluorescence transition based on careful measurement, calculation and analysis. And moreover, a novel characteristic upconversion luminescence saturation phenomenon is found. It is that the log F-log P curve of upconversion fluorescence vs. pumping laser power is a straight line, and meanwhile the slopes of these double-logarithmic F- P plots are smaller than normal multi-photon relation clearly. When pumping laser spot is increased, the slopes of these double logarithmic F- P plots could be enhanced noticeably from small value to near the normal multi-photon relation value. The mechanism of this characteristic saturation phenomenon is the energy expansion resulted from energy resonant migration among Yb 3+ ions.

  7. Dispersing upconversion nanocrystals in a single silicon microtube

    PubMed Central

    Li, Hanyang; Wang, Yan; Li, Hui; Zhang, Yundong; Yang, Jun

    2016-01-01

    Nanocrystals of Ln3+ (Ln = Yb, Tm and Ho) doped β-NaLuF4 with average diameter about 200 nm are dispersed in silica-based microtube (MT) by a simple flame heating method. The fabricated microtube has a diameter range from 2 μm to 30 μm and lengths up to hundreds microns. The fluorescence of upconversion nanocrystals (UCNCs) can propagate along a single MT and couple into another MT through evanescent field. The guiding performance of the single UCNCs doped MT is measured to prove that it can be used as an active waveguide. Moreover, optical temperature sensing based on the single UCNCs-MT is also demonstrated, and the sensitivity of UCNCs-MT is significantly enough for thermometry applications in the range of 298–383 K. PMID:27779210

  8. Amplified Photon Upconversion by Photonic Shell of Cholesteric Liquid Crystals.

    PubMed

    Kang, Ji-Hwan; Kim, Shin-Hyun; Fernandez-Nieves, Alberto; Reichmanis, Elsa

    2017-04-26

    As an effective platform to exploit triplet-triplet-annihilation-based photon upconversion (TTA-UC), microcapsules composed of a fluidic UC core and photonic shell are microfluidically prepared using a triple emulsion as the template. The photonic shell consists of cholesteric liquid crystals (CLCs) with a periodic helical structure, exhibiting a photonic band gap. Combined with planar anchoring at the boundaries, the shell serves as a resonance cavity for TTA-UC emission and enables spectral tuning of the UC under low-power-density excitation. The CLC shell can be stabilized by introducing a polymerizable mesogen in the LC host. Because of the microcapsule spherical symmetry, spontaneous emission of the delayed fluorescence is omnidirectionally amplified at the edge of the stop band. These results demonstrate the range of opportunities provided by TTA-UC systems for the future design of low-threshold photonic devices.

  9. Autofluorescence-free in vivo multicolor imaging using upconversion fluoride nanocrystals.

    PubMed

    Tian, Zhen; Chen, Guanying; Li, Xiang; Liang, Huijuan; Li, Yuanshi; Zhang, Zhiguo; Tian, Ye

    2010-07-01

    Non-invasive fluorescence imaging is an important technique in biology. However, detection of traditional biomarker emissions is accompanied by a high background signal. In this study we examined whether upconversion sodium yttrium fluoride (NaYF(4)) nanocrystals were suitable for autofluorescence-free multicolor fluorescence imaging in a living animal. Tissue autofluorescence was induced with a 405 nm light source, then rats were subjected to injection of fluorescein isothiocyanate (FITC), cadmium selenide/zinc sulfide (CdSe/ZnS) quantum dots (QDs), or NaYF(4):ytterbium/thulium (Yb(3+)/Tm(3+)), NaYF(4):Yb(3+)/holmium (Ho(3+)), and NaYF(4):Yb(3+)/Ho(3+)/cerium (Ce(3+)) nanocrystals. Imaging with NaYF(4) nanocrystals (974 nm laser) completely removed the high tissue autofluorescence, in marked contrast to imaging with FITC and QDs (405 nm light). Optical imaging experiments demonstrated that multiple biological targets and organs could be imaged at the same time using multicolor NaYF(4) upconversion nanocrystals under a single excitation wavelength (974 nm). These data demonstrated the proof-of-principle that autofluorescence-free multicolor imaging using near-infrared to visible upconversion of NaYF(4) nanocrystals excited by laser can be performed in a living animal.

  10. Intense upconversion luminescence and effect of local environment for Tm3+/Yb3+ co-doped novel TeO2-BiCl3 glass system.

    PubMed

    Wang, Guonian; Dai, Shixun; Zhang, Junjie; Wen, Lei; Yang, Jianhu; Jiang, Zhonghong

    2006-05-15

    We present the results of a study that uses theoretical and experimental methods to investigate the characteristics of the upconversion luminescence of Tm3+/Yb3+ codoped TeO2-BiCl3 glass system as a function of the BiCl3 fraction. These glasses are potentially important in the design of upconversion fiber lasers. Effect of local environment around Tm3+ on upconversion fluorescence intensity was analyzed by theoretical calculations. The structure and spectroscopic properties were investigated in the experiments by measuring the Raman spectra, IR transmission spectra, and absorption and fluorescence intensities at room temperature. The results indicate that blue luminescence quantum efficiency increases with increasing BiCl3 content from 10 to 60 mol%, which were interpreted by the increase of asymmetry of glass structure, decrease of phonon energy and removing of OH- groups.

  11. Recent advances in lanthanide-doped upconversion nanomaterials: synthesis, nanostructures and surface modification

    NASA Astrophysics Data System (ADS)

    Qiu, Peiyu; Zhou, Na; Chen, Hengyu; Zhang, Chunlei; Gao, Guo; Cui, Daxiang

    2013-11-01

    Owing to their unique photo-physical properties, rare-earth ions-doped upconversion nanoparticles (UCNPs) have attracted extensive attention in recent years. UCNPs have many special merits, such as a long luminescence lifetime, narrow emission band widths, high quantum yields and low toxicity, which allows their potential applications in bio-medical field, biological luminescent labels and drug delivery carriers. Compared with traditional fluorescence labels exited by UV (ultraviolet), such as organic dyes and quantum dots, UCNPs can transfer near-infrared (NIR) light into visible light, which is commonly called upconversion luminescence (UCL). This paper reviews the recent advances of several typical synthesis methods of UCNPs in detail as well as the fabrication and optimization of the particle morphology, and the latest advances of UCNPs for multimode imaging, surface passivation and functionalization are also described.

  12. Tuning the Upconversion Luminescence Lifetimes of KYb2 F7 :Ho(3+) Nanocrystals for Optical Multiplexing.

    PubMed

    Ding, Mingye; Chen, Daqin; Ma, Danyang; Liu, Peng; Song, Kaixin; Lu, Hongwei; Ji, Zhenguo

    2015-12-21

    Conventional luminescent color coding is limited by spectral overlap and the interference of background fluorescence, thus restricting the number of distinguishable identities that can be used in practice. Here, we demonstrate the possibility of generating diverse time-domain codes, specially designed for a single emission band, using lanthanide-doped upconversion nanocrystals. Based on the knowledge of concentration quenching, the upconversion luminescence kinetics of KYb2 F7 : Ho(3+) nanocrystals can be precisely controlled by modifying the dopant concentration of Ho(3+) ions, resulting in a tunable emission lifetime from 75.8 to 1944.5 μs, which suggests the practicality of these time-domain codes for optical multiplexing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Recent advances in lanthanide-doped upconversion nanomaterials: synthesis, nanostructures and surface modification.

    PubMed

    Qiu, Peiyu; Zhou, Na; Chen, Hengyu; Zhang, Chunlei; Gao, Guo; Cui, Daxiang

    2013-12-07

    Owing to their unique photo-physical properties, rare-earth ions-doped upconversion nanoparticles (UCNPs) have attracted extensive attention in recent years. UCNPs have many special merits, such as a long luminescence lifetime, narrow emission band widths, high quantum yields and low toxicity, which allows their potential applications in bio-medical field, biological luminescent labels and drug delivery carriers. Compared with traditional fluorescence labels exited by UV (ultraviolet), such as organic dyes and quantum dots, UCNPs can transfer near-infrared (NIR) light into visible light, which is commonly called upconversion luminescence (UCL). This paper reviews the recent advances of several typical synthesis methods of UCNPs in detail as well as the fabrication and optimization of the particle morphology, and the latest advances of UCNPs for multimode imaging, surface passivation and functionalization are also described.

  14. Ultrafast excited-state dynamics in the green fluorescent protein variant S65T/H148D. 2. Unusual photophysical properties.

    PubMed

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

    2007-10-30

    In the preceding accompanying paper [Shu, X., et al. (2007) Biochemistry 46, 12005-12013], the 1.5 A resolution crystal structure of green fluorescent protein (GFP) variant S65T/H148D is presented, and the possible consequences of an unusual short hydrogen bond (femtosecond time-resolved emission of this variant at pH 5.6 by ultrafast fluorescence upconversion spectroscopy. Following excitation at 400 nm, green fluorescence is observed at 510 nm with a rise on a time scale that is faster than the 170 fs instrument response. Time-resolved emission spectra at 140 K also exhibit the immediate appearance of green fluorescence, and this extremely fast process is hardly affected by deuteration of exchangeable protons. These results appear to be dramatically different from those of wild-type GFP, in which the green fluorescence at 508 nm is produced on the picosecond time scale as a result of excited-state proton transfer from the state that is excited at 400 nm. The unique features observed in S65T/H148D and apparent ultrafast excited-state proton transfer are discussed in light of evidence for multiple states underlying the band at around 415 nm, as suggested by steady-state fluorescence spectra. The behavior of these different states may explain the novel photophysical properties observed for this GFP variant, including the ultrafast green fluorescence and the absence of completely matched decay in blue fluorescence. It is speculated that two different orientations of the Asp introduced at position 148, not distinguishable by chromatography, mass spectrometry, or X-ray crystallography, give rise to the two functionally distinct populations.

  15. Nano-photonic chemical sensor using rare-earth upconversion phosphors

    NASA Astrophysics Data System (ADS)

    Patel, Darayas N.; Blockmon, Avery; Ochieng, Vanesa; Sarkisov, Sergey S.; Darwish, Abdalla M.; Sarkisov, Avedik S.

    2017-02-01

    The objective of the paper was to demonstrate feasibility of a chemical (ammonia) sensor using dye-doped polymer nanocomposite with upconversion phosphor nano-particles. The micro-crystalline powder of upconversion rare-earth phosphor NaYF4:Yb3+, Er3+ was synthesized using a simple wet process followed up by baking in open air. The powder was reduced into nano-colloid with 100-nm nano-particles using the ball milling process. The nano-colloid was added to the solution of polymer poly(methyl methacrylate) known as PMMA. Additionally, a pH indicator dye (Phenol Red or Bromothymol Blue) was dissolved in polymer solution. The dye-doped polymer nanocomposite films were deposited on substrates using the dipping process followed by baking in order to evaporate the solvent. The deposited nano-photonic sensor film had bright green upconversion fluorescence with a spectral peak at 540 nm attributed to the nano-photonic rare-earth phosphor pumped with a 980 nm infrared diode laser. The spectrum of green emission matched the absorption band of the indicator dye exposed to ammonia. When the film was exposed to ammonia, it demonstrated an optical response in the form of the drop of intensity of green radiation measured with a silicon photodiode power meter. The sensitivity of the developed chemical sensor was close to 0.4% ammonia in air, and the response time was close to 5 minutes.

  16. Up-conversion processes in Yb-sensitized Tm:ZBLAN

    NASA Astrophysics Data System (ADS)

    Carrig, Timothy J.; Cockroft, Nigel J.

    1996-11-01

    A systematic spectroscopic study of 22 rate-earth-ion doped ZBLAN glass samples was conducted to investigate the feasibility of sensitizing Tm:ZBLAN with Yb to facilitate the development of an efficient and conveniently pumped blue upconversion fiber laser. It was determined that, under conditions of single-color pumping, 480 nm emission from Tm3+ is strongest when Yb, Tm:ZBLAN is excited at a wavelength of approximately 975 nm. In this case, the strongest blue emission was obtained from a ZBLAN glass sample with a nominal dopant concentration of approximately 2.0 wt percent Yb + 0.3 wt percent Tm. Additionally, it was demonstrated that for weak 975 nm pump intensities, the strength of the blue upconversion emission can be greatly enhanced by simultaneously pumping at approximately 785 nm. This increase in upconversion efficiency is due to a reduction in the number of energy transfer steps needed to populate the Tm3+ 1G4 energy level. Measurements of fluorescence lifetimes as a function of dopant concentration wee also made for Yb3+, and Pr3+ transitions in ZBLAN in order to better characterize concentration quenching effects. Energy transfer between Tm3+ and Pr3+ in ZBLAN is also described.

  17. Optical temperature sensing properties of Yb3+/Er3+ codoped LaF3 upconversion phosphor

    NASA Astrophysics Data System (ADS)

    Cheng, Xuerui; Ma, Xiaochun; Zhang, Huanjun; Ren, Yufen; Zhu, Kunkun

    2017-09-01

    The structural and optical properties of Er3+/Yb3+ codoped LaF3 phosphors are investigated using X-ray diffraction (XRD) and upconversion luminescence spectra. The result shows that the hexagonal phase of LaF3 keep stability at temperature lower than 800 °C in air condition and will be oxidized to be LaOF at higher temperature. Its upconversion emission intensity varies with the doping concentrations of Yb3+ ions and reaches a maximum at around 7 mol% Yb3+. The power-dependent luminescence reveals the possible emission mechanisms and the corresponding upconversion processes. Furthermore, the optical temperature sensing properties of LaF3: Er3+/Yb3+ are studied based on the fluorescence intensity ratio (FIR) technique for two thermally coupled levels (2H11/2 and 4S3/2) of Er3+. The maximum sensitivity is found to be about 0.00157 K-1 at 386 K, revealing this phosphor to be a promising prototype for applications in optical temperature sensing.

  18. Particle-size Dependent Förster Resonance Energy Transfer from Upconversion Nanoparticles to Organic Dyes.

    PubMed

    Muhr, Verena; Würth, Christian; Kraft, Marco; Buchner, Markus; Resch-Genger, Ute; Baeumner, Antje J; Hirsch, Thomas

    2017-03-22

    Upconversion nanoparticles (UCNPs) are attractive candidates for energy transfer-based analytical applications. In contrast to classical donor-acceptor pairs, these particles contain many emitting lanthanide ions together with numerous acceptor dye molecules at different distances to each other, strongly depending on the particle diameter. UCNPs with precisely controlled sizes between 10 and 43 nm were prepared and functionalized with rose bengal and sulforhodamine B by a ligand exchange procedure. Time-resolved studies of the upconversion luminescence of the UCNP donor revealed a considerable shortening of the donor lifetime as a clear hint for Förster resonance energy transfer (FRET). FRET was most pronounced for 21 nm-sized UCNPs, yielding a FRET efficiency of 60%. At larger surface-to-volume ratios the FRET efficiency decreased by an increasing competition of non-radiative surface deactivation. Such dye-UCNP architectures can also provide an elegant way to shift the UCNP emission color, since the fluorescence intensity of the organic dyes excited by FRET was comparable to that of the upconversion emission of smaller particles.

  19. Monitoring Delamination of Thermal Barrier Coatings by Near-Infrared and Upconversion Luminescence Imaging

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Martin, R. E.; Singh, Jogender; Wolfe, Doug E.

    2008-01-01

    Previous work has demonstrated that TBC delamination can be monitored by incorporating a thin luminescent sublayer that produces greatly increased luminescence intensity from delaminated regions of the TBC. Initial efforts utilized visible-wavelength luminescence from either europium or erbium doped sublayers. This approach exhibited good sensitivity to delamination of electron-beam physical-vapor-deposited (EB-PVD) TBCs, but limited sensitivity to delamination of the more highly scattering plasma-sprayed TBCs due to stronger optical scattering and to interference by luminescence from rare-earth impurities. These difficulties have now been overcome by new strategies employing near-infrared (NIR) and upconversion luminescence imaging. NIR luminescence at 1550 nm was produced in an erbium plus ytterbium co-doped yttria-stabilized zirconia (YSZ) luminescent sublayer using 980-nm excitation. Compared to visible-wavelength luminescence, these NIR emission and excitation wavelengths are much more weakly scattered by the TBC and therefore show much improved depth-probing capabilities. In addition, two-photon upconversion luminescence excitation at 980 nm wavelength produces luminescence emission at 562 nm with near-zero fluorescence background and exceptional contrast for delamination indication. The ability to detect TBC delamination produced by Rockwell indentation and by furnace cycling is demonstrated for both EB-PVD and plasma-sprayed TBCs. The relative strengths of the NIR and upconversion luminescence methods for monitoring TBC delamination are discussed.

  20. Optical transitions of Tm3+ in oxyfluoride glasses and compositional and thermal effect on upconversion luminescence of Tm3+/Yb3+-codoped oxyfluoride glasses.

    PubMed

    Feng, Li; Wu, Yinsu; Liu, Zhuo; Guo, Tao

    2014-01-24

    Optical properties of Tm(3+)-doped SiO2-BaF2-ZnF2 glasses have been investigated on the basis of the Judd-Ofelt theory. Judd-Ofelt intensity parameters, radiative transition probabilities, fluorescence branching ratios and radiative lifetimes have been calculated for different glass compositions. Upconversion emissions were observed in Tm(3+)/Yb(3+)-codoped SiO2-BaF2-ZnF2 glasses under 980 nm excitation. The effects of composition, concentration of the doping ions, temperature, and excitation pump power on the upconversion emissions were also systematically studied. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Low temperature sensing behavior of upconversion luminescence in Er3+/Yb3+ codoped PLZT transparent ceramic

    NASA Astrophysics Data System (ADS)

    Feng, Zhuohong; Lin, Lin; Wang, ZheZhe; Zheng, Zhiqiang

    2017-09-01

    In this paper, low temperature sensing characteristic of upconversion luminescence in Er3+/Yb3+ codoped lead-lanthanum zirconate-titanate ferroelectric ceramics (PLZT) was investigated by fluorescence intensity ratios (FIRs). The upconversion emissions at 539 nm, 564 nm and 666 nm were observed from 10 K to 320 K by exciting at 980 nm. These emissions were assigned to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively. The temperature dependent emission intensities of upconversion luminescence were analyzed, from which the thermal excitation processes among the three levels system of 2H11/2, 4S3/2 and 4F9/2 were discovered. Based on this, the FIRs of 539 nm to 666 nm, 539 nm to 564 nm are studied, and the variation trends of them agree with the Boltzmann distribution of thermal coupled in the temperature range of 140-320 K. The temperature sensitivity of intensity ratio of 539 nm to 666 nm is 21.84×10-4 K-1 at 320 K, which is about 4 times than that of 539 nm to 564 nm. The temperature sensing performance can be improved by high valued ΔE of thermal coupled levels (TCLs). This paper shows that 2H11/2 and 4F9/2 of Er3+ are TCLs in PLZT, and the upconversion luminescence of Er3+/Yb3+ codoped PLZT transparent ceramic have a potential application in low temperature sensing above 140 K.

  2. Homogeneous assay for whole blood folate using photon upconversion.

    PubMed

    Arppe, Riikka; Mattsson, Leena; Korpi, Krista; Blom, Sami; Wang, Qi; Riuttamäki, Terhi; Soukka, Tero

    2015-02-03

    Red blood cell folate is measured for folate deficiency diagnosis, because it reflects the long-term folate level in tissues, whereas serum folate only represents the dietary intake. Direct homogeneous assay from whole blood would be ideal but conventional fluorescence techniques in blood suffer from high background and strong absorption of light at ultraviolet and visible wavelengths. In this study, a new photon upconversion-based homogeneous assay for whole blood folate is introduced based on resonance energy transfer from upconverting nanophosphor donor coated with folate binding protein to a near-infrared fluorescent acceptor dye conjugated to folate analogue. The sensitized acceptor emission is measured at 740 nm upon 980 nm excitation. Thus, optically transparent wavelengths are utilized for both donor excitation and sensitized acceptor emission to minimize the sample absorption, and anti-Stokes detection completely eliminates the Stokes-shifted autofluorescence. The IC50 value of the assay was 6.0 nM and the limit of detection (LOD) was 1 nM. The measurable concentration range was 2 orders of magnitude between 1.0-100 nM, corresponding to 40-4000 nM folate in the whole blood sample. Recoveries of added folic acid were 112%-114%. A good correlation was found when compared to a competitive heterogeneous assay based on the DELFIA-technology. The introduced assay provides a simple and fast method for whole blood folate measurement.

  3. Micromachining using femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Toenshoff, Hans K.; Ostendorf, Andreas; Nolte, Stefan; Korte, Frank; Bauer, Thorsten

    2000-11-01

    Femtosecond laser systems have been proved to be effective tools for high precision micro-machining. Almost all solid materials can be processed with high precision. The dependence on material properties like thermal conductivity, transparency, heat- or shock sensitivity is strongly reduced and no significant influence on the remaining bulk material is observed after ablation using femtosecond laser pulses. In contrast to conventional laser processing, where the achievable precision is reduced due to a formed liquid phase causing burr formation, the achievable precision using femtosecond pulses is only limited by the diffraction of the used optics. Potential applications of this technique, aincluding the structuring of biodegradable polymers for cardiovascular implants, so-called stents, as well as high precision machining of transparent materials are presented.

  4. LOW POWER UPCONVERSION FOR SOLAR FUELS PHOTOCHEMISTRY

    SciTech Connect

    Castellano, Felix N.

    2013-08-05

    Earth abundant copper(I) diimine complexes represent a renewable and economically feasible alternative to commonly used heavy metal containing chromophores. In the metal-to-ligand charge transfer (MLCT) excited state, copper(I) diimine complexes typically undergo a significant structural rearrangement, leading to molecules with large Stokes shifts and very short excited state lifetimes, thereby limiting their usefulness as sensitizers in bimolecular electron and triplet energy transfer reactions. Strategically placed bulky substituents on the coordinating phenanthroline ligands have proven useful in restricting the transiently produced excited state Jahn-Teller distortion, leading to longer-lived excited states. By combining bulky sec-butyl groups in the 2- and 9- positions with methyl groups in the 3-,4-, 7-, and 8- positions, a remarkably long-lived (2.8 μs in DCM) copper(I) bis-phenanthroline complex, [Cu(dsbtmp)2]+, has been synthesized and characterized. Unlike other copper(I) diimine complexes, [Cu(dsbtmp)2]+ also retains a μs lifetime in coordinating solvents such as acetonitrile and water as a result of the cooperative sterics inherent in the molecular design. Preliminary results on the use of this complex in hydrogen-forming homogeneous photocatalysis is presented. Photon upconversion based on sensitized triplet-triplet annihilation (TTA) represents a photochemical means to generate high-energy photons (or high-energy chemical products) from low-energy excitation, having potential applications in solar energy conversion and solar fuels producing devices. For the first time, synthetically facile and earth abundant Cu(I) MLCT sensitizers have been successfully incorporated into two distinct photochemical upconversion schemes, affording both red-to-green and orange-to-blue wavelength conversions. Preliminary results on aqueous-based photochemical upconversion as well as intramolecular Sn(IV) porphyrins containing axially coordinated aromatic hydrocarbon

  5. Recent advances in synthesis and surface modification of lanthanide-doped upconversion nanoparticles for biomedical applications.

    PubMed

    Lin, Min; Zhao, Ying; Wang, ShuQi; Liu, Ming; Duan, ZhenFeng; Chen, YongMei; Li, Fei; Xu, Feng; Lu, TianJian

    2012-01-01

    Lanthanide (Ln)-doped upconversion nanoparticles (UCNPs) with appropriate surface modification can be used for a wide range of biomedical applications such as bio-detection, cancer therapy, bio-labeling, fluorescence imaging, magnetic resonance imaging and drug delivery. The upconversion phenomenon exhibited by Ln-doped UCNPs renders them tremendous advantages in biological applications over other types of fluorescent materials (e.g., organic dyes, fluorescent proteins, gold nanoparticles, quantum dots, and luminescent transition metal complexes) for: (i) enhanced tissue penetration depths achieved by near-infrared (NIR) excitation; (ii) improved stability against photobleaching, photoblinking and photochemical degradation; (iii) non-photodamaging to DNA/RNA due to lower excitation light energy; (iv) lower cytotoxicity; and (v) higher detection sensitivity. Ln-doped UCNPs are therefore attracting increasing attentions in recent years. In this review, we present recent advances in the synthesis of Ln-doped UCNPs and their surface modification, as well as their emerging applications in biomedicine. The future prospects of Ln-doped UCNPs for biomedical applications are also discussed.

  6. Femtosecond optical pulse amplification

    NASA Astrophysics Data System (ADS)

    Knox, Wayne H.

    1988-02-01

    A number of techniques have been developed for amplification of optical pulses of approximately 100-fs duration. These amplifiers span a wide range of operating parameters from kilowatt to gigawatt peak powers and from 10 Hz to megahertz repetition rates. Amplification of femtosecond pulses has also been demonstrated at several wavelengths including visible, near-infrared, and ultraviolet regions. Several problems arise when amplifying short optical pulses to very high intensities. The problems are discussed and the state of the art of femtosecond optical pulse amplification is reviewed.

  7. Infrared to visible upconversion of Er(3+) doped in a chloride matrix

    NASA Astrophysics Data System (ADS)

    Ohwaki, Junichi; Wang, Yuhu

    1992-10-01

    The preparation of a new kind Er(3+)-doped infrared excitable phosphor (IEP), obtained with the chloride powder phosphor system YCl3-ErCl3-PbCl2-KCl, is reported, and the fluorescence characteristics of the new IEP are described. The IR-to-visible conversion efficiency of the Er(+)-doped chloride IEP was found to be higher by more than one order of magnitude than that of commercially available fluoride IEPs. A strong upconversion fluorescence at 496 nm due to the 4F7/2-4I15/2 transition was observed in the chloride phosphor under 0.972 micron laser diode excitation. Under 1.52 micron laser diode excitation, a specimen containing 20 mol pct Er(3+) dopant emitted bright green luminescence; the fluorescence lines at 410 nm, 550 nm, and 660 nm reached their respective intensities of 48, 20, and 9 times those of conventional Er(3+)-doped fluoride.

  8. Upconversion Nanomaterials: Synthesis, Mechanism, and Applications in Sensing

    PubMed Central

    Chen, Jiao; Zhao, Julia Xiaojun

    2012-01-01

    Upconversion is an optical process that involves the conversion of lower-energy photons into higher-energy photons. It has been extensively studied since mid-1960s and widely applied in optical devices. Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences. The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis. The main difference between upconversion nanoparticles and other nanomaterials is that they can emit visible light under near infrared irradiation. The near infrared irradiation leads to low autofluorescence, less scattering and absorption, and deep penetration in biological samples. In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing. PMID:22736958

  9. Upconversion nanomaterials: synthesis, mechanism, and applications in sensing.

    PubMed

    Chen, Jiao; Zhao, Julia Xiaojun

    2012-01-01

    Upconversion is an optical process that involves the conversion of lower-energy photons into higher-energy photons. It has been extensively studied since mid-1960s and widely applied in optical devices. Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences. The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis. The main difference between upconversion nanoparticles and other nanomaterials is that they can emit visible light under near infrared irradiation. The near infrared irradiation leads to low autofluorescence, less scattering and absorption, and deep penetration in biological samples. In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

  10. Application of upconversion detection to pulsed CO2 lidar

    NASA Technical Reports Server (NTRS)

    Itabe, T.; Bufton, J. L.

    1982-01-01

    In this paper the application of an upconversion detector to pulsed CO2 lidar is investigated. In this device a nonlinear IR crystal would be used to convert 10-micron lidar radiation into the visible region for conventional detection with a photomultiplier tube. A pulsed CO2 lidar can be substantially improved with an upconversion detector configured for rejection of thermal background radiation using a narrowband filter for the upconverted signal or a cold filter front end. The sensitivity of the upconversion detector with the narrowband visible wavelength filter is estimated to be 2 orders of magnitude better than that of the usual direct detection diode. The cold filter can improve upconversion detection to nearly the signal-shot limit. These upconversion detectors are not limited by speckle noise as is a pulsed heterodyne detector.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  12. High-resolution spectroscopy with a femtosecond laser frequency comb.

    PubMed

    Gerginov, V; Tanner, C E; Diddams, S A; Bartels, A; Hollberg, L

    2005-07-01

    The output of a mode-locked femtosecond laser is used for precision single-photon spectroscopy of 133Cs in an atomic beam. By changing the laser's repetition rate, the cesium D1 (6s 2S(1/2)-->6p 2P(1/2)) and D2 (6s 2S(1/2)-->6p 2P(3/2)) transitions are detected and the optical frequencies are measured with accuracy similar to that obtained with a cw laser. Control of the femtosecond laser repetition rate by use of the atomic fluorescence is also implemented, thus realizing a simple cesium optical clock.

  13. Photon upconversion sensitized nanoprobes for sensing and imaging of pH

    NASA Astrophysics Data System (ADS)

    Arppe, Riikka; Näreoja, Tuomas; Nylund, Sami; Mattsson, Leena; Koho, Sami; Rosenholm, Jessica M.; Soukka, Tero; Schäferling, Michael

    2014-05-01

    Acidic pH inside cells indicates cellular dysfunctions such as cancer. Therefore, the development of optical pH sensors for measuring and imaging intracellular pH is a demanding challenge. The available pH-sensitive probes are vulnerable to e.g. photobleaching or autofluorescence background in biological materials. Our approach circumvents these problems due to near infrared excitation and upconversion photoluminescence. We introduce a nanosensor based on upconversion resonance energy transfer (UC-RET) between an upconverting nanoparticle (UCNP) and a fluorogenic pH-dependent dye pHrodo™ Red that was covalently bound to the aminosilane surface of the nanoparticles. The sensitized fluorescence of the pHrodo™ Red dye increases strongly with decreasing pH. By referencing the pH-dependent emission of pHrodo™ Red with the pH-insensitive upconversion photoluminescence of the UCNP, we developed a pH-sensor which exhibits a dynamic range from pH 7.2 to 2.5. The applicability of the introduced pH nanosensor for pH imaging was demonstrated by imaging the two emission wavelengths of the nanoprobe in living HeLa cells with a confocal fluorescence microscope upon 980 nm excitation. This demonstrates that the presented pH-nanoprobe can be used as an intracellular pH-sensor due to the unique features of UCNPs: excitation with deeply penetrating near-infrared light, high photostability, lack of autofluorescence and biocompatibility due to an aminosilane coating.Acidic pH inside cells indicates cellular dysfunctions such as cancer. Therefore, the development of optical pH sensors for measuring and imaging intracellular pH is a demanding challenge. The available pH-sensitive probes are vulnerable to e.g. photobleaching or autofluorescence background in biological materials. Our approach circumvents these problems due to near infrared excitation and upconversion photoluminescence. We introduce a nanosensor based on upconversion resonance energy transfer (UC-RET) between an

  14. Preparation of Gd2O2S: Yb3+, Er3+, Tm3+ sub-micro phosphors by sulfurization of the oxides derived from sol-gel method and the upconversion luminescence properties

    NASA Astrophysics Data System (ADS)

    Wang, Nengli; Liu, Zuojie; Tong, Huanzhe; Zhang, Xiyan; Bai, Zhaohui

    2017-07-01

    Yb3+, Er3+ and Tm3+ co-doped Gd2O2S sub-micro phosphors were synthesized by solid-state sulfurization of the oxide powders derived from sol-gel method. The crystal structure, morphology and upconversion luminescence properties of the phosphors were characterized by x-ray diffraction, scanning electron microscopic and fluorescence spectrum analysis methods. The phosphors exhibited typical hexagonal Gd2O2S phase when sulfurized at 800 °C for 2 h. Under the excitation of 980 nm laser diode, the Gd2O2S: Yb3+, Er3+, Tm3+ phosphors displayed distinct blue, green and red upconversion emissions centered at 481, 546 and 669 nm, respectively. The Gd2O2S phosphors using acetic acid as a chelating agent in the sol-gel process had the optimal upconversion emission property. The upconversion mechanism analysis revealed that the two-photon absorption was mainly responsible for the green and red upconversion emission of Er3+ ions, and the three-photon absorption was responsible for the blue upconversion emission of Tm3+ ions in the Gd2O2S: Yb3+, Er3+, Tm3+ phosphors.

  15. Optical Temperature Sensor Through Upconversion Emission from the Er3+ Doped SrBi8Ti7O27 Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zou, Hua; Wang, Xusheng; Hu, Yifeng; Zhu, Xiaoqing; Sui, Yongxing; Song, Zhitang

    2016-06-01

    Er doped SrBi8Ti7O27 (SBT) ferroelectric ceramics were prepared by a solid-state reaction technique. By Er doping, the intensive green upconversion emissions were recorded under 980 nm diode laser excitation with 20 mW. The fluorescence spectrum was investigated in the temperature range of 150-580 K. By the fluorescence intensity ratio technique, the green emission band was studied as a function of temperature with a maximum sensing sensitivity of 0.0028 at 510 K. These results indicate that the Er doped SBT ferroelectric ceramics are promising multifunctional sensing materials.

  16. Bioinspired near-infrared-excited sensing platform for in vitro antioxidant capacity assay based on upconversion nanoparticles and a dopamine-melanin hybrid system.

    PubMed

    Wang, Dong; Chen, Chuan; Ke, Xuebin; Kang, Ning; Shen, Yuqing; Liu, Yongliang; Zhou, Xi; Wang, Hongjun; Chen, Changqing; Ren, Lei

    2015-02-11

    A novel core-shell structure based on upconversion fluorescent nanoparticles (UCNPs) and dopamine-melanin has been developed for evaluation of the antioxidant capacity of biological fluids. In this approach, dopamine-melanin nanoshells facilely formed on the surface of UCNPs act as ultraefficient quenchers for upconversion fluorescence, contributing to a photoinduced electron-transfer mechanism. This spontaneous oxidative polymerization of the dopamine-induced quenching effect could be effectively prevented by the presence of various antioxidants (typically biothiols, ascorbic acid (Vitamin C), and Trolox). The chemical response of the UCNPs@dopamine-melanin hybrid system exhibited great selectivity and sensitivity toward antioxidants relative to other compounds at 100-fold higher concentration. A satisfactory correlation was established between the ratio of the "anti-quenching" fluorescence intensity and the concentration of antioxidants. Besides the response of the upconversion fluorescence signal, a specific evaluation process for antioxidants could be visualized by the color change from colorless to dark gray accompanied by the spontaneous oxidation of dopamine. The near-infrared (NIR)-excited UCNP-based antioxidant capacity assay platform was further used to evaluate the antioxidant capacity of cell extracts and human plasma, and satisfactory sensitivity, repeatability, and recovery rate were obtained. This approach features easy preparation, fluorescence/visual dual mode detection, high specificity to antioxidants, and enhanced sensitivity with NIR excitation, showing great potential for screening and quantitative evaluation of antioxidants in biological systems.

  17. Reduced erbium-doped ceria nanoparticles: one nano-host applicable for simultaneous optical down- and up-conversions.

    PubMed

    Shehata, Nader; Meehan, Kathleen; Hassounah, Ibrahim; Hudait, Mantu; Jain, Nikhil; Clavel, Michael; Elhelw, Sarah; Madi, Nabil

    2014-01-01

    This paper introduces a new synthesis procedure to form erbium-doped ceria nanoparticles (EDC NPs) that can act as an optical medium for both up-conversion and down-conversion in the same time. This synthesis process results qualitatively in a high concentration of Ce(3+) ions required to obtain high fluorescence efficiency in the down-conversion process. Simultaneously, the synthesized nanoparticles contain the molecular energy levels of erbium that are required for up-conversion. Therefore, the synthesized EDC NPs can emit visible light when excited with either UV or IR photons. This opens new opportunities for applications where emission of light via both up- and down-conversions from a single nanomaterial is desired such as solar cells and bio-imaging.

  18. Quantitative Imaging of Single Upconversion Nanoparticles in Biological Tissue

    PubMed Central

    Nadort, Annemarie; Sreenivasan, Varun K. A.; Song, Zhen; Grebenik, Ekaterina A.; Nechaev, Andrei V.; Semchishen, Vladimir A.; Panchenko, Vladislav Y.; Zvyagin, Andrei V.

    2013-01-01

    The unique luminescent properties of new-generation synthetic nanomaterials, upconversion nanoparticles (UCNPs), enabled high-contrast optical biomedical imaging by suppressing the crowded background of biological tissue autofluorescence and evading high tissue absorption. This raised high expectations on the UCNP utilities for intracellular and deep tissue imaging, such as whole animal imaging. At the same time, the critical nonlinear dependence of the UCNP luminescence on the excitation intensity results in dramatic signal reduction at (∼1 cm) depth in biological tissue. Here, we report on the experimental and theoretical investigation of this trade-off aiming at the identification of optimal application niches of UCNPs e.g. biological liquids and subsurface tissue layers. As an example of such applications, we report on single UCNP imaging through a layer of hemolyzed blood. To extend this result towards in vivo applications, we quantified the optical properties of single UCNPs and theoretically analyzed the prospects of single-particle detectability in live scattering and absorbing bio-tissue using a human skin model. The model predicts that a single 70-nm UCNP would be detectable at skin depths up to 400 µm, unlike a hardly detectable single fluorescent (fluorescein) dye molecule. UCNP-assisted imaging in the ballistic regime thus allows for excellent applications niches, where high sensitivity is the key requirement. PMID:23691012

  19. Folic acid-functionalized up-conversion nanoparticles: toxicity studies in vivo and in vitro and targeted imaging applications

    NASA Astrophysics Data System (ADS)

    Sun, Lining; Wei, Zuwu; Chen, Haige; Liu, Jinliang; Guo, Jianjian; Cao, Ming; Wen, Tieqiao; Shi, Liyi

    2014-07-01

    Folate receptors (FRs) are overexpressed on a variety of human cancer cells and tissues, including cancers of the breast, ovaries, endometrium, and brain. This over-expression of FRs can be used to target folate-linked imaging specifically to FR-expressing tumors. Fluorescence is emerging as a powerful new modality for molecular imaging in both the diagnosis and treatment of disease. Combining innovative molecular biology and chemistry, we prepared three kinds of folate-targeted up-conversion nanoparticles as imaging agents (UCNC-FA: UCNC-Er-FA, UCNC-Tm-FA, and UCNC-Er,Tm-FA). In vivo and in vitro toxicity studies showed that these nanoparticles have both good biocompatibility and low toxicity. Moreover, the up-conversion luminescence imaging indicated that they have good targeting to HeLa cells and can therefore serve as potential fluorescent contrast agents.Folate receptors (FRs) are overexpressed on a variety of human cancer cells and tissues, including cancers of the breast, ovaries, endometrium, and brain. This over-expression of FRs can be used to target folate-linked imaging specifically to FR-expressing tumors. Fluorescence is emerging as a powerful new modality for molecular imaging in both the diagnosis and treatment of disease. Combining innovative molecular biology and chemistry, we prepared three kinds of folate-targeted up-conversion nanoparticles as imaging agents (UCNC-FA: UCNC-Er-FA, UCNC-Tm-FA, and UCNC-Er,Tm-FA). In vivo and in vitro toxicity studies showed that these nanoparticles have both good biocompatibility and low toxicity. Moreover, the up-conversion luminescence imaging indicated that they have good targeting to HeLa cells and can therefore serve as potential fluorescent contrast agents. Electronic supplementary information (ESI) available: Up-conversion luminescence spectra of UCNC-Er and UCNC-Er-FA, UCNC-Tm and UCNC-Tm-FA. Confocal luminescence imaging data collected as a series along the Z optical axis. See DOI: 10.1039/c4nr02312a

  20. Femtosecond optical engineering

    NASA Astrophysics Data System (ADS)

    Li, Peng

    The last a few decades have witnessed the rapid progress of ultrafast optics, which has been driving the technology revolutions in scientific research and engineering applications. For instance, several recent Nobel Prize winners have made their discoveries using femtosecond optics applications in physics, chemistry and biomedicine. This dissertation covers three important applications of ultrafast femtosecond lasers. First, we study the single particle scattering spectroscopy using supercontinuum white light tweezers. We have developed supercontinuum white light optical tweezers by using the ultrabroad band supercontinuum (SC) generated in highly nonlinear photonic crystal fibers pumped by ultrafast laser pulses and for the first time studied the scattering spectra in tightly focused supercontinuum. When the scatterer is of spherical shape, we describe modeling based on Mie's scattering theory and angular spectrum decomposition. For the non-spherical-shaped scatterers, when the size of the scatterer is small or the refractive index of the scatterer is close to the surrounding medium, another modeling based on Born approximation and Green's function is derived. The calculation results are provided as well. This work has built the foundation to understand optical scattering spectroscopy of single particles in the supercontinuum white light optical tweezers and further application to probe the single particle's physical and chemical properties via the linear and nonlinear optical scattering spectra, which can lead to many important applications particularly in nanoparticle characterization and sensing. The second part of this dissertation is dedicated to the study of the femtosecond pulse beam shaping. For femtosecond laser pulses, which cover bandwidths of tens of nanometers, the performance of beam-shaping a Gaussian beam into a flat-topped rectangular intensity profile is discussed for a practical realization. In the meantime, the convergence of the improved

  1. Mechanisms of low-power noncoherent photon upconversion in metalloporphyrin-organic blue emitter systems in solution.

    PubMed

    Sugunan, Sunish K; Tripathy, Umakanta; Brunet, Sophie M K; Paige, Matthew F; Steer, Ronald P

    2009-07-30

    The mechanisms of noncoherent photon upconversion that involve triplet-triplet annihilation (TTA) in solution have been investigated for two model systems. ZnTPP (meso-tetraphenylporphine zinc) is used as the model visible light-absorbing metalloporphyrin because its S(1) fluorescence intensity can be used to monitor the initial rate of porphyrin triplet state production and because its S(2) fluorescence intensity can be used as a direct measure of the rate of porphyrin TTA. When perylene, which has a triplet energy lower than that of ZnTPP, is added as a signaling blue emitter (BE), the mechanism of photon upconversion involves triplet energy transfer from the porphyrin to the BE followed by TTA in the BE to form the fluorescent perylene S(1) state. The kinetics of this process have been characterized and are unremarkable. When coumarin 343 (C343), which has photophysical properties similar to those of perylene except that it has a much higher triplet energy than ZnTPP, is added as the signaling BE, emission from the ZnTPP S(2) state is quenched and fluorescence from the C343 grows in. Contrary to previous suggestions, the mechanism of photon upconversion in this system does not involve singlet energy transfer from the porphyrin S(2) state to the BE. Instead, ground-state C343 complexes with the ZnTPP triplet to form a triplet exciplex, which then undergoes TTA with a second ZnTPP triplet to give the fluorescent state of the BE in a three-center process.

  2. Surgical applications of femtosecond lasers.

    PubMed

    Chung, Samuel H; Mazur, Eric

    2009-10-01

    Femtosecond laser ablation permits non-invasive surgeries in the bulk of a sample with submicrometer resolution. We briefly review the history of optical surgery techniques and the experimental background of femtosecond laser ablation. Next, we present several clinical applications, including dental surgery and eye surgery. We then summarize research applications, encompassing cell and tissue studies, research on C. elegans, and studies in zebrafish. We conclude by discussing future trends of femtosecond laser systems and some possible application directions.

  3. Non-collinear upconversion of infrared light.

    PubMed

    Pedersen, Christian; Hu, Qi; Høgstedt, Lasse; Tidemand-Lichtenberg, Peter; Dam, Jeppe Seidelin

    2014-11-17

    Two dimensional mid-infrared upconversion imaging provides unique spectral and spatial information showing good potential for mid-infrared spectroscopy and hyperspectral imaging. However, to extract spectral or spatial information from the upconverted images an elaborate model is needed, which includes non-collinear interaction. We derive here a general theory providing the far field of the upconverted light when two arbitrary fields interact inside a nonlinear crystal. Theoretical predictions are experimentally verified for incoherent radiation and subsequently applied to previously published data with good agreement.

  4. Hybrid upconversion nanomaterials for optogenetic neuronal control

    NASA Astrophysics Data System (ADS)

    Shah, Shreyas; Liu, Jing-Jing; Pasquale, Nicholas; Lai, Jinping; McGowan, Heather; Pang, Zhiping P.; Lee, Ki-Bum

    2015-10-01

    Nanotechnology-based approaches offer the chemical control required to develop precision tools suitable for applications in neuroscience. We report a novel approach employing hybrid upconversion nanomaterials, combined with the photoresponsive ion channel channelrhodopsin-2 (ChR2), to achieve near-infrared light (NIR)-mediated optogenetic control of neuronal activity. Current optogenetic methodologies rely on using visible light (e.g. 470 nm blue light), which tends to exhibit high scattering and low tissue penetration, to activate ChR2. In contrast, our approach enables the use of 980 nm NIR light, which addresses the short-comings of visible light as an excitation source. This was facilitated by embedding upconversion nanomaterials, which can convert NIR light to blue luminescence, into polymeric scaffolds. These hybrid nanomaterial scaffolds allowed for NIR-mediated neuronal stimulation, with comparable efficiency as that of 470 nm blue light. Our platform was optimized for NIR-mediated optogenetic control by balancing multiple physicochemical properties of the nanomaterial (e.g. size, morphology, structure, emission spectra, concentration), thus providing an early demonstration of rationally-designing nanomaterial-based strategies for advanced neural applications.Nanotechnology-based approaches offer the chemical control required to develop precision tools suitable for applications in neuroscience. We report a novel approach employing hybrid upconversion nanomaterials, combined with the photoresponsive ion channel channelrhodopsin-2 (ChR2), to achieve near-infrared light (NIR)-mediated optogenetic control of neuronal activity. Current optogenetic methodologies rely on using visible light (e.g. 470 nm blue light), which tends to exhibit high scattering and low tissue penetration, to activate ChR2. In contrast, our approach enables the use of 980 nm NIR light, which addresses the short-comings of visible light as an excitation source. This was facilitated by

  5. Solar upconversion with plasmonic hot carriers

    NASA Astrophysics Data System (ADS)

    Dionne, Jennifer A.

    Upconversion of sub-bandgap photons is a promising approach to exceed the Shockley-Queisser limit in solar technologies. Placed behind a solar cell, upconverting materials convert lower-energy photons transmitted through the cell to higher-energy above-bandgap photons that can then be absorbed by the cell and contribute to photocurrent. Because the upconverter is electrically isolated from the active cell, it need not be current-matched to the cell, nor will it add mid-gap recombination pathways. Calculations have indicated that single-junction cell efficiencies can exceed 44% upon addition of an upconverter - a significant improvement over the maximum cell efficiency of 30% without an upconverter. However, due to the low quantum efficiencies and narrow absorption bandwidths of existing upconverters, such significant cell improvements have yet to be observed experimentally. In this presentation, we will describe an entirely new solar upconverting scheme based on hot-carrier injection from a plasmonic absorber to an adjacent semiconductor. The plasmonic system both induces upconversion based on injection of hot-electrons and hot-holes and also enhances light-matter interactions. Low-energy photons incident on a plasmonic particle generate hot electrons and hot holes, which are injected into a semiconducting quantum well and subsequently radiatively recombine. Importantly, the bandgap of the quantum well can be higher than the energy of the incident photon, enabling emission of a higher-energy photon than that absorbed. First, we present analytic calculations showing that efficiencies as high as 25% are possible, significantly higher than existing solid-state upconverters, which are only 2-5% efficient. We also describe how further improvements in the efficiency are possible by employing materials and geometries that allow for more efficient carrier injection. Then, we describe experiments on InGaN/GaN quantum wells decorated with Au disks. On their own, the In

  6. Femtosecond laser materials processing

    NASA Astrophysics Data System (ADS)

    Banks, Paul S.; Stuart, Brent C.; Komashko, Aleksey M.; Feit, Michael D.; Rubenchik, Alexander M.; Perry, Michael D.

    2000-05-01

    The use of femtosecond lasers allows materials processing of practically any material with extremely high precision and minimal collateral damage. Advantages over conventional laser machining (using pulses longer than a few tens of picoseconds) are realized by depositing the laser energy into the electrons of the material on a time scale short compared to the transfer time of this energy to the bulk of the material, resulting in increased ablation efficiency and negligible shock or thermal stress. The improvement in the morphology by using femtosecond pulses rather than nanosecond pulses has been studied in numerous materials from biological materials to dielectrics to metals. During the drilling process, we have observed the onset of small channels which drill faster than the surrounding material.

  7. Femtosecond Laser Materials Processing

    SciTech Connect

    Banks, P.S.; Stuart, B.C.; Komashko, A.M.; Feit, M.D.; Rubenchik, A.M.; Perry, M.D.

    2000-03-06

    The use of femtosecond lasers allows materials processing of practically any material with extremely high precision and minimal collateral damage. Advantages over conventional laser machining (using pulses longer than a few tens of picoseconds) are realized by depositing the laser energy into the electrons of the material on a time scale short compared to the transfer time of this energy to the bulk of the material, resulting in increased ablation efficiency and negligible shock or thermal stress. The improvement in the morphology by using femtosecond pulses rather than nanosecond pulses has been studied in numerous materials from biologic materials to dielectrics to metals. During the drilling process, we have observed the onset of small channels which drill faster than the surrounding material.

  8. Co-doping of glasses with rare earth ions and metallic nanoparticles for frequency up-conversion

    NASA Astrophysics Data System (ADS)

    Wackerow, S.; Seifert, G.

    2010-05-01

    We explore different approaches to achieve co-doping of glasses with rare earth ions and metallic nanoparticles, and to manipulate the spectral position of the particles' surface plasmon resonance. The final goal is to find a composite material with improved efficiency of frequency up-conversion of light for photovoltaic applications. The potential for improvement has been shown by theoretical calculations predicting that absorption and emission probabilities of the ions can be enhanced when the plasmon resonance of the nanoparticles is close to the respective transition frequency of the ions. In this work we demonstrate the sequential co-doping of glasses already containing rare-earth ions with Ag nanoparticles, as well as implantation of rare-earth ions in glasses which already contained metallic nanoparticles. It could also be demonstrated that the surface plasmon resonance of the created particles can be tuned by femtosecond laser induced shape transformation of the Ag clusters.

  9. Lanthanide upconversion luminescence at the nanoscale: fundamentals and optical properties

    NASA Astrophysics Data System (ADS)

    Nadort, Annemarie; Zhao, Jiangbo; Goldys, Ewa M.

    2016-07-01

    Upconversion photoluminescence is a nonlinear effect where multiple lower energy excitation photons produce higher energy emission photons. This fundamentally interesting process has many applications in biomedical imaging, light source and display technology, and solar energy harvesting. In this review we discuss the underlying physical principles and their modelling using rate equations. We discuss how the understanding of photophysical processes enabled a strategic influence over the optical properties of upconversion especially in rationally designed materials. We subsequently present an overview of recent experimental strategies to control and optimize the optical properties of upconversion nanoparticles, focussing on their emission spectral properties and brightness.

  10. Femtosecond laser materials processing

    SciTech Connect

    Stuart, B. C., LLNL

    1998-06-02

    Femtosecond lasers enable materials processing of most any material with extremely high precision and negligible shock or thermal loading to the surrounding area Applications ranging from drilling teeth to cutting explosives to making high-aspect ratio cuts in metals with no heat-affected zone are made possible by this technology For material removal at reasonable rates, we developed a fully computer-controlled 15-Watt average power, 100-fs laser machining system.

  11. Femtosecond laser materials processing

    SciTech Connect

    Stuart, B

    1998-08-05

    Femtosecond lasers enable materials processing of most any material with extremely high precision and negligible shock or thermal loading to the surrounding area. Applications ranging from drilling teeth to cutting explosives to precision cuts in composites are possible by using this technology. For material removal at reasonable rates, we have developed a fully computer-controlled 15-Watt average power, 100-fs laser machining system.

  12. Femtosecond Optical Tweezers

    NASA Astrophysics Data System (ADS)

    Peng, Jiahui; Wang, Lei; Sokolov, Alexei

    2004-10-01

    Optical tweezers has drawn much attention of people since recent years, which shows great advantages on biological applications due to quite straightforward ideas and simple configurations. Optical tweezers rely upon the extremely high gradient in the electric field produced near the beam waist of a tightly focused laser beam, which creates a force sufficient to trap micron-sized dielectric particles in three dimensions.(J.E. Molloy and M.J. Padgett, Light, Action: Optical Tweezers, Contemporary P)hysics, 43 241 (2002). We applied a femtosecond laser on optical tweezers as light source and got successfully ``optical trapping'' and ``optical tweezers.'' Further, due to the characters of short pulse width and extremely high intensity of laser, femtosecond optical tweezers may direct us to new optics field. Under such strong intensity many non-linear optical phenomena could be observable, such like optical Kerr effect, stimulated Raman effect and so on. Our work will shows that it may be applied into the recently proposed FAST CAR (Femtosecond Adaptive Spectroscopic Techniques for Coherent Anti-Stokes Raman Spectroscopy) by M. Scully et. al.(M. O. Scully, G. W. Kattawar, R. P. Lucht, T. Opatrny, H. Pilloff, A. Rebane, A. V. Sokolov, and M. S. Zubairy, ``FAST CARS: Engineering a Laser Spectroscopic Technique for Rapid Identification of Bacterial Spores,'' Proceedings of NASE (2002).)

  13. Optical gene transfer by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Konig, Karsten; Riemann, Iris; Tirlapur, Uday K.

    2003-07-01

    Targeted transfection of cells is an important technique for gene therapy and related biomedical applications. We delineate how high-intensity (1012 W/cm2) near-infrared (NIR) 80 MHz nanojoule femtosecond laser pulses can create highly localised membrane perforations within a minute focal volume, enabling non-invasive direct transfection of mammalian cells with DNA. We suspended Chinese hamster ovarian (CHO), rat kangaroo kidney epithelial (PtK2) and rat fibroblast cells in 0.5 ml culture medium in a sterile miniaturized cell chamber (JenLab GmbH, Jena, Germany) containing 0.2 μg plasmid DNA vector pEGFP-N1 (4.7 kb), which codes for green fluorescent protein (GFP). The NIR laser beam was introduced into a femtosecond laser scanning microscope (JenLab GmbH, Jena, Germany; focussed on the edge of the cell membrane of a target cell for 16 ms. The integration and expression efficiency of EGFP were assessed in situ by two-photon fluorescence-lifetime imaging using time-correlated single photon counting. The unique capability to transfer foreign DNA safely and efficiently into specific cell types (including stem cells), circumventing mechanical, electrical or chemical means, will have many applications, such as targeted gene therapy and DNA vaccination.

  14. Recent Advance of Biological Molecular Imaging Based on Lanthanide-Doped Upconversion-Luminescent Nanomaterials

    PubMed Central

    Min, Yuanzeng; Li, Jinming; Liu, Fang; Padmanabhan, Parasuraman; Yeow, Edwin K. L.; Xing, Bengang

    2014-01-01

    Lanthanide-doped upconversion-luminescent nanoparticles (UCNPs), which can be excited by near-infrared (NIR) laser irradiation to emit multiplex light, have been proven to be very useful for in vitro and in vivo molecular imaging studies. In comparison with the conventionally used down-conversion fluorescence imaging strategies, the NIR light excited luminescence of UCNPs displays high photostability, low cytotoxicity, little background auto-fluorescence, which allows for deep tissue penetration, making them attractive as contrast agents for biomedical imaging applications. In this review, we will mainly focus on the latest development of a new type of lanthanide-doped UCNP material and its main applications for in vitro and in vivo molecular imaging and we will also discuss the challenges and future perspectives.

  15. Energy transfer upconversion in ? and ? doped ? crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao; Jouart, Jean-Pierre; Mary, Gérard

    1998-01-01

    A comparative spectroscopic study for 0953-8984/10/2/027/img10 and 0953-8984/10/2/027/img11 doped 0953-8984/10/2/027/img12 crystals has been realised at liquid nitrogen temperature. The 0953-8984/10/2/027/img10 single-doped sample shows principally blue emission corresponding to the 0953-8984/10/2/027/img14 transition, whereas the 0953-8984/10/2/027/img11 codoped sample gives rise to a very efficient green emission which is ascribed to the 0953-8984/10/2/027/img16 transition. The total integrated upconversion emission intensity (including blue and green emissions) for the codoped crystal is three times more intense than that of the 0953-8984/10/2/027/img10 doped one, while the ratio for green emission rises to 27. The green emission in the codoped sample results mainly from the 0953-8984/10/2/027/img18 mixed centre, whereas the blue emission is essentially due to the 0953-8984/10/2/027/img19 pair. Two energy transfer upconversion mechanisms have been proposed and are discussed in the paper.

  16. Hybrid upconversion nanomaterials for optogenetic neuronal control.

    PubMed

    Shah, Shreyas; Liu, Jing-Jing; Pasquale, Nicholas; Lai, Jinping; McGowan, Heather; Pang, Zhiping P; Lee, Ki-Bum

    2015-10-28

    Nanotechnology-based approaches offer the chemical control required to develop precision tools suitable for applications in neuroscience. We report a novel approach employing hybrid upconversion nanomaterials, combined with the photoresponsive ion channel channelrhodopsin-2 (ChR2), to achieve near-infrared light (NIR)-mediated optogenetic control of neuronal activity. Current optogenetic methodologies rely on using visible light (e.g. 470 nm blue light), which tends to exhibit high scattering and low tissue penetration, to activate ChR2. In contrast, our approach enables the use of 980 nm NIR light, which addresses the short-comings of visible light as an excitation source. This was facilitated by embedding upconversion nanomaterials, which can convert NIR light to blue luminescence, into polymeric scaffolds. These hybrid nanomaterial scaffolds allowed for NIR-mediated neuronal stimulation, with comparable efficiency as that of 470 nm blue light. Our platform was optimized for NIR-mediated optogenetic control by balancing multiple physicochemical properties of the nanomaterial (e.g. size, morphology, structure, emission spectra, concentration), thus providing an early demonstration of rationally-designing nanomaterial-based strategies for advanced neural applications.

  17. Upconversion Nanoparticles for Bioimaging and Regenerative Medicine

    PubMed Central

    González-Béjar, María; Francés-Soriano, Laura; Pérez-Prieto, Julia

    2016-01-01

    Nanomaterials are proving useful for regenerative medicine in combination with stem cell therapy. Nanoparticles (NPs) can be administrated and targeted to desired tissues or organs and subsequently be used in non-invasive real-time visualization and tracking of cells by means of different imaging techniques, can act as therapeutic agent nanocarriers, and can also serve as scaffolds to guide the growth of new tissue. NPs can be of different chemical nature, such as gold, iron oxide, cadmium selenide, and carbon, and have the potential to be used in regenerative medicine. However, there are still many issues to be solved, such as toxicity, stability, and resident time. Upconversion NPs have relevant properties such as (i) low toxicity, (ii) capability to absorb light in an optical region where absorption in tissues is minimal and penetration is optimal (note they can also be designed to emit in the near-infrared region), and (iii) they can be used in multiplexing and multimodal imaging. An overview on the potentiality of upconversion materials in regenerative medicine is given. PMID:27379231

  18. Advances in femtosecond laser technology

    PubMed Central

    Callou, Thais Pinheiro; Garcia, Renato; Mukai, Adriana; Giacomin, Natalia T; de Souza, Rodrigo Guimarães; Bechara, Samir J

    2016-01-01

    Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. PMID:27143847

  19. Amplified stimulated emission in upconversion nanoparticles for super-resolution nanoscopy

    NASA Astrophysics Data System (ADS)

    Liu, Yujia; Lu, Yiqing; Yang, Xusan; Zheng, Xianlin; Wen, Shihui; Wang, Fan; Vidal, Xavier; Zhao, Jiangbo; Liu, Deming; Zhou, Zhiguang; Ma, Chenshuo; Zhou, Jiajia; Piper, James A.; Xi, Peng; Jin, Dayong

    2017-02-01

    Lanthanide-doped glasses and crystals are attractive for laser applications because the metastable energy levels of the trivalent lanthanide ions facilitate the establishment of population inversion and amplified stimulated emission at relatively low pump power. At the nanometre scale, lanthanide-doped upconversion nanoparticles (UCNPs) can now be made with precisely controlled phase, dimension and doping level. When excited in the near-infrared, these UCNPs emit stable, bright visible luminescence at a variety of selectable wavelengths, with single-nanoparticle sensitivity, which makes them suitable for advanced luminescence microscopy applications. Here we show that UCNPs doped with high concentrations of thulium ions (Tm3+), excited at a wavelength of 980 nanometres, can readily establish a population inversion on their intermediate metastable 3H4 level: the reduced inter-emitter distance at high Tm3+ doping concentration leads to intense cross-relaxation, inducing a photon-avalanche-like effect that rapidly populates the metastable 3H4 level, resulting in population inversion relative to the 3H6 ground level within a single nanoparticle. As a result, illumination by a laser at 808 nanometres, matching the upconversion band of the 3H4 → 3H6 transition, can trigger amplified stimulated emission to discharge the 3H4 intermediate level, so that the upconversion pathway to generate blue luminescence can be optically inhibited. We harness these properties to realize low-power super-resolution stimulated emission depletion (STED) microscopy and achieve nanometre-scale optical resolution (nanoscopy), imaging single UCNPs; the resolution is 28 nanometres, that is, 1/36th of the wavelength. These engineered nanocrystals offer saturation intensity two orders of magnitude lower than those of fluorescent probes currently employed in stimulated emission depletion microscopy, suggesting a new way of alleviating the square-root law that typically limits the

  20. Photon Upconversion Through Tb(3+) -Mediated Interfacial Energy Transfer.

    PubMed

    Zhou, Bo; Yang, Weifeng; Han, Sanyang; Sun, Qiang; Liu, Xiaogang

    2015-10-28

    A strategy of interfacial energy transfer upconversion is demonstrated through the use of a terbium (Tb(3+) ) dopant as energy donor or energy migrator in core-shell-structured nanocrystals. This mechanistic investigation presents a new pathway for photon upconversion, and, more importantly, contributes to the better control of energy transfer at the nanometer length scale. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Silver nanoclusters emitting weak NIR fluorescence biomineralized by BSA

    NASA Astrophysics Data System (ADS)

    Li, Baoshun; Li, Jianjun; Zhao, Junwu

    2015-01-01

    Noble metal (e.g., gold and silver) nanomaterials possess unique physical and chemical properties. In present work, silver nanoclusters (also known as silver quantum clusters or silver quantum dots) were synthesized by bovine serum albumin (BSA) biomineralization. The synthesized silver nanoclusters were characterized by UV-VIS absorption spectroscopy, fluorescence spectroscopy, upconversion emission spectroscopy, TEM, HRTEM and FTIR spectroscopy. TEM results showed that the average size of the silver nanoclusters was 2.23 nm. Fluorescence results showed that these silver nanoclusters could emit weak near-infrared (NIR) fluorescence (the central emission wavelength being about 765 nm). And the central excitation wavelength was about 395 nm, in the UV spectral region. These silver nanoclusters showed an extraordinarily large gap (about 370 nm) between the central excitation wavelength and central emission wavelength. In addition, it was found that these silver nanoclusters possess upconversion emission property. Upconversion emission results showed that the upconversion emission spectrum of the silver nanoclusters agreed well with their normal fluorescence emission spectrum. The synthesized silver nanoclusters showed high stability in aqueous solution and it was considered that they might be confined in BSA molecules. It was found that silver nanoclusters might enhance and broaden the absorption of proteins, and the protein absorption peak showed an obvious red shift (being 7 nm) after the formation of silver nanoclusters.

  2. Enhanced upconversion luminescence through core/shell structures and its application for detecting organic dyes in opaque fishes.

    PubMed

    Hu, Pan; Wu, Xiaofeng; Hu, Shigang; Chen, Zenghui; Yan, Huanyuan; Xi, Zaifang; Yu, Yi; Dai, Gangtao; Liu, Yunxin

    2016-02-01

    Here, we report the enhanced upconversion luminescence of NaLuF4:18%Yb(3+),2%Er(3+) through core/shell structures. Among NaYF4, NaGdF4, and NaLuF4 shells, the first one presents the highest efficiency. These upconversion fluorescent nanoprobes with an oleic acid/PEG hybrid ligand can efficiently capture Rhodamine B (RB) and sodium fluorescein (SF) in opaque fishes to present their residues in vivo through luminescence resonant energy transfer (LRET) processes. It can be confirmed based on LRET technology that no RB is absorbed by opaque fishes after incubating in the aqueous solution of 1 μg ml(-1) RB for one day, while SF residue can be obviously detected after incubating in the aqueous solution of 1 μg ml(-1) SF for one day. The merit of this LRET technology with the upconversion nanoparticle (UCNP) donor is ascribed to the deep penetration depth of the infrared pumping laser and high signal to noise ratio.

  3. Fluorophore discrimination by tracing quantum interference in fluorescence microscopy

    SciTech Connect

    De, Arijit Kumar; Roy, Debjit; Goswami, Debabrata

    2011-01-15

    We show fluorescence-detected quantum interference in a microscope setup and demonstrate selective enhancement or suppression of fluorophores using femtosecond pulse-pair excitation with periodic modulation of the interpulse phase.

  4. Nile Red Derivative-Modified Nanostructure for Upconversion Luminescence Sensing and Intracellular Detection of Fe(3+) and MR Imaging.

    PubMed

    Wei, Ruoyan; Wei, Zuwu; Sun, Lining; Zhang, Jin Z; Liu, Jinliang; Ge, Xiaoqian; Shi, Liyi

    2016-01-13

    Iron ion (Fe(3+)) which is the physiologically most abundant and versatile transition metal in biological systems, has been closely related to many certain cancers, metabolism, and dysfunction of organs, such as the liver, heart, and pancreas. In this Research Article, a novel Nile red derivative (NRD) fluorescent probe was synthesized and, in conjunction with polymer-modified core-shell upconversion nanoparticles (UCNPs), demonstrated in the detection of Fe(3+) ion with high sensitivity and selectivity. The core-shell UCNPs were surface modified using a synthesized PEGylated amphiphilic polymer (C18PMH-mPEG), and the resulting mPEG modified core-shell UCNPs (mPEG-UCNPs) show good water solubility. The overall Fe(3+)-responsive upconversion luminescence nanostructure was fabricated by linking the NRD to the mPEG-UCNPs, denoted as mPEG-UCNPs-NRD. In the nanostructure, the core-shell UCNPs, NaYF4:Yb,Er,Tm@NaGdF4, serve as the energy donor while the Fe(3+)-responsive NRD as the energy acceptor, which leads to efficient luminescence resonance energy transfer (LRET). The mPEG-UCNPs-NRD nanostructure shows high selectivity and sensitivity for detecting Fe(3+) in water. In addition, benefited from the good biocompatibility, the nanostructure was successfully applied for detecting Fe(3+) in living cells based on upconversion luminescence (UCL) from the UCNPs. Furthermore, the doped Gd(3+) ion in the UCNPs endows the mPEG-UCNPs-NRD nanostructure with effective T1 signal enhancement, making it a potential magnetic resonance imaging (MRI) contrast agent. This work demonstrates a simple yet powerful strategy to combine metal ion sensing with multimodal bioimaging based on upconversion luminescence for biomedical applications.

  5. Fabrication and upconversion luminescence properties of YF3:Er3+ hollow nanofibers via monoaxial electrospinning combined with fluorination method.

    PubMed

    Li, Dan; Dong, Xiangting; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

    2014-06-01

    YF3:Er3+ hollow nanofibers were successfully fabricated via fluorination of the relevant Y2O3:Er3+ hollow nanofibers which were obtained by calcining the electrospun PVP/[Y(NO3)3 + Er(NO3)3] composite nanofibers. The morphology and properties of the products were investigated in detail by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and fluorescence spectrometer. YF3:Er3+ hollow nanofibers were pure orthorhombic phase with space group Pnma and were hollow-centered structure with the mean diameter of 172 +/- 23 nm, and YF3:Er3+ hollow nanofibers were composed of nanoparticles with the diameter ranging from 30 nm to 50 nm. Upconversion emission spectrum analysis manifested that YF3:Er3+ hollow nanofibers emitted strong green and weak red upconversion emission centering at 524 nm, 543 nm and 653 nm, respectively. The green emissions and the red emission were respectively originated from 2H11/2/4S3/2 --> 4I15/2 and 4F9/2 --> 4I15/2 energy levels transitions of the Er3+ ions. Moreover, the emitting colors of YF3:Er3+ hollow nanofibers were located in the green region in CIE chromaticity coordinates diagram. The luminescent intensity of YF3:Er3+ hollow nanofibers was increased remarkably with the increasing doping concentration of Er3+ ions. The possible formation mechanism of YF3:Er3+ upconversion luminescence hollow nanofibers was also discussed. This preparation technique could be applied to prepare other rare earth fluoride upconversion luminescence hollow nanofibers.

  6. Upconversion luminescence behavior of single nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhou, Jiajia; Xu, Shiqing; Zhang, Junjie; Qiu, Jianrong

    2015-09-01

    Upconversion nanoparticles (UCNPs) have made a significant and valuable contribution to materials science, photophysics, and biomedicine due to their specific spectroscopic characteristics. However, the ensemble spectroscopy of UCNPs is limited because of the electronic behavior in average effect, which ignores the fact that these nanoparticles are heterogeneous. With regards to the research focus on heterogeneous intrinsic structures, unique photophysical phenomena, and advanced applications, the optical characterization of single UCNPs have been promoted to the frontier development of the UCNPs community. In this review, we give an overview of the importance of single UCNPs characterization, typical principles of UC, and single particle detection methods. Considerable emphasis is placed on the specific spectroscopic study of single UCNPs, which shows fantastic photophysical phenomena beyond ensemble measurement. Parallel efforts are devoted to the current applications of single UCNPs.

  7. Dualistic temperature sensing in Er3 +/Yb3 + doped CaMoO4 upconversion phosphor

    NASA Astrophysics Data System (ADS)

    Sinha, Shriya; Mahata, Manoj Kumar; Kumar, Kaushal; Tiwari, S. P.; Rai, V. K.

    2017-02-01

    Temperature sensing performance of Er3 +/Yb3 + doped CaMoO4 phosphor prepared via polyol method is reported herein. The X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy are done to confirm the phase, structure and purity of the synthesized phosphor. The infrared to green upconversion emission is investigated using 980 nm diode laser excitation along with its dependence on input pump power and external temperature. The temperature dependent fluorescence intensity ratio of two upconversion emission bands assigned to 2H11/2 → 4I15/2 (530 nm) and 4S3/2 → 4I15/2 (552 nm) transitions has shown two distinct slopes in the studied temperature range - 300 to 760 K and therefore, dual nature of temperature sensitivity is observed in this phosphor. This phenomenon in rare earth doped materials is either scarcely reported or overlooked. The material has shown higher sensitivity in the high temperature region (535 K < T < 760 K) with a maximum of 7.21 × 10- 3 K- 1 at 535 K. The results indicate potential of CaMoO4: Er3 +/Yb3 + phosphor in high temperature thermometry.

  8. Enhancing the Imaging and Biosafety of Upconversion Nanoparticles through Phosphonate Coating

    PubMed Central

    Li, Ruibin; Ji, Zhaoxia; Dong, Juyao; Chang, Chong Hyun; Wang, Xiang; Sun, Bingbing; Wang, Meiying; Liao, Yu-Pei; Zink, Jeffrey I.; Nel, Andre E.; Xia, Tian

    2015-01-01

    Upconversion nanoparticles (UCNPs), which are generated by doping with rare earth (RE) metals, are increasingly used for bio-imaging because of the advantages they hold over conventional fluorophores. However, because pristine RE nanoparticles (NPs) are unstable in acidic physiological fluids (e.g., lysosomes), leading to intracellular phosphate complexation with the possibility of the lysosomal injury, it is important to ensure that UCNPs are safe designed. In this study, we used commercially available NaYF4: Er/Yb UCNPs to study their stability in lysosomes and simulated lysosomal fluid. We demonstrate that phosphate complexation leads to REPO4 deposition on the particle surfaces and morphological transformation. This leads to a decline in upconversion fluorescence efficiency as well as inducing pro-inflammatory effects at cellular level and in the intact lung. In order to preserve the imaging properties of the UCNPs as well as improve their safety, we experimented with a series of phosphonate chemical moieties to passivate particle surfaces through the strong coordination of the organophosphates with RE atoms. Particle screening and physicochemical characterization revealed that ethylenediaminetetra methylenephosphonic acid (EDTMP) surface coating provides the most stable UCNPs, which maintain their imaging intensity and do not induce pro-inflammatory effects in vitro and in vivo. In summary, phosphonate coating presents a safer design method that preserves and improves the bio-imaging properties of UCNPs, thereby enhancing their biological use. PMID:25727446

  9. Dualistic temperature sensing in Er(3+)/Yb(3+) doped CaMoO4 upconversion phosphor.

    PubMed

    Sinha, Shriya; Mahata, Manoj Kumar; Kumar, Kaushal; Tiwari, S P; Rai, V K

    2017-02-15

    Temperature sensing performance of Er(3+)/Yb(3+) doped CaMoO4 phosphor prepared via polyol method is reported herein. The X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy are done to confirm the phase, structure and purity of the synthesized phosphor. The infrared to green upconversion emission is investigated using 980nm diode laser excitation along with its dependence on input pump power and external temperature. The temperature dependent fluorescence intensity ratio of two upconversion emission bands assigned to (2)H11/2→(4)I15/2 (530nm) and (4)S3/2→(4)I15/2 (552nm) transitions has shown two distinct slopes in the studied temperature range - 300 to 760K and therefore, dual nature of temperature sensitivity is observed in this phosphor. This phenomenon in rare earth doped materials is either scarcely reported or overlooked. The material has shown higher sensitivity in the high temperature region (535K

  10. Upconversion properties of Er3+-doped oxyfluoride glass-ceramics containing SrF2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Kesavulu, C. R.; Kiran Kumar, K.; Jayasankar, C. K.

    2014-03-01

    Er3+-doped oxyfluoride glass and glass-ceramics containing SrF2 nanocrystals have been prepared and investigated their spectroscopic and luminescence properties. The formation of SrF2 nanocrystals in glass-ceramics were confirmed by Xray diffraction (XRD) and transmission electron microscopy (TEM). Judd-Ofelt parameters have been evaluated from absorption spectra of the Er3+-doped glass, which in turn used to predict radiative properties for the fluorescent levels of Er3+ ions. The intensities of both Stokes and upconversion (anti-Stokes) emissions significantly increase with increase of the size of the fluoride crystals in the glass matrix. The mechanism of green and red upconversion emissions have been ascribed to two photon processes. The lifetime of the 4S3/2 level of the Er3+ ions in glass-ceramics is found to be slightly higher than that of the counter glass, which may be due to the incorporation of Er3+ ions into the low phonon sites of SrF2 nanocrystals.

  11. Accurate Quantitative Sensing of Intracellular pH based on Self-ratiometric Upconversion Luminescent Nanoprobe

    PubMed Central

    Li, Cuixia; Zuo, Jing; Zhang, Li; Chang, Yulei; Zhang, Youlin; Tu, Langping; Liu, Xiaomin; Xue, Bin; Li, Qiqing; Zhao, Huiying; Zhang, Hong; Kong, Xianggui

    2016-01-01

    Accurate quantitation of intracellular pH (pHi) is of great importance in revealing the cellular activities and early warning of diseases. A series of fluorescence-based nano-bioprobes composed of different nanoparticles or/and dye pairs have already been developed for pHi sensing. Till now, biological auto-fluorescence background upon UV-Vis excitation and severe photo-bleaching of dyes are the two main factors impeding the accurate quantitative detection of pHi. Herein, we have developed a self-ratiometric luminescence nanoprobe based on förster resonant energy transfer (FRET) for probing pHi, in which pH-sensitive fluorescein isothiocyanate (FITC) and upconversion nanoparticles (UCNPs) were served as energy acceptor and donor, respectively. Under 980 nm excitation, upconversion emission bands at 475 nm and 645 nm of NaYF4:Yb3+, Tm3+ UCNPs were used as pHi response and self-ratiometric reference signal, respectively. This direct quantitative sensing approach has circumvented the traditional software-based subsequent processing of images which may lead to relatively large uncertainty of the results. Due to efficient FRET and fluorescence background free, a highly-sensitive and accurate sensing has been achieved, featured by 3.56 per unit change in pHi value 3.0–7.0 with deviation less than 0.43. This approach shall facilitate the researches in pHi related areas and development of the intracellular drug delivery systems. PMID:27934889

  12. Accurate Quantitative Sensing of Intracellular pH based on Self-ratiometric Upconversion Luminescent Nanoprobe

    NASA Astrophysics Data System (ADS)

    Li, Cuixia; Zuo, Jing; Zhang, Li; Chang, Yulei; Zhang, Youlin; Tu, Langping; Liu, Xiaomin; Xue, Bin; Li, Qiqing; Zhao, Huiying; Zhang, Hong; Kong, Xianggui

    2016-12-01

    Accurate quantitation of intracellular pH (pHi) is of great importance in revealing the cellular activities and early warning of diseases. A series of fluorescence-based nano-bioprobes composed of different nanoparticles or/and dye pairs have already been developed for pHi sensing. Till now, biological auto-fluorescence background upon UV-Vis excitation and severe photo-bleaching of dyes are the two main factors impeding the accurate quantitative detection of pHi. Herein, we have developed a self-ratiometric luminescence nanoprobe based on förster resonant energy transfer (FRET) for probing pHi, in which pH-sensitive fluorescein isothiocyanate (FITC) and upconversion nanoparticles (UCNPs) were served as energy acceptor and donor, respectively. Under 980 nm excitation, upconversion emission bands at 475 nm and 645 nm of NaYF4:Yb3+, Tm3+ UCNPs were used as pHi response and self-ratiometric reference signal, respectively. This direct quantitative sensing approach has circumvented the traditional software-based subsequent processing of images which may lead to relatively large uncertainty of the results. Due to efficient FRET and fluorescence background free, a highly-sensitive and accurate sensing has been achieved, featured by 3.56 per unit change in pHi value 3.0–7.0 with deviation less than 0.43. This approach shall facilitate the researches in pHi related areas and development of the intracellular drug delivery systems.

  13. Thermal effects and upconversion in the Er3+:YAG solid-state heat-capacity laser

    NASA Astrophysics Data System (ADS)

    Eichhorn, Marc

    2010-10-01

    Although seen as nearly being impossible to realize, a quasi-three-level laser medium can be used in heat-capacity operation. In this operation mode, the laser medium is not cooled during lasing in order to avoid strong thermal lensing, which, in actively cooled operation, would result in a low beam quality or would even destabilize the laser cavity. Thus, in heat-capacity mode, the laser medium will substantially heat up during operation, which will cause an increase in re-absorption for a quasi-three-level laser medium, resulting in a general drop in output power over time. However, laser power, temperature rise, fluorescence and inversion are coupled by the temperaturedependent spectroscopic properties of the laser medium in a complex way. This paper presents an investigation on these thermal effects and upconversion in the resonantly pumped Er3+:YAG solid-state heat-capacity laser (SSHCL) system. These effects are important for the scaling properties on this laser towards medium- or high-energy systems, and to obtain a good beam quality from the laser itself. It is shown that the expected power drop of this quasi-three-level medium due to the rise in crystal temperature is very low, allowing for high-power operation on substantial time scales. The experimental results and the theoretical background will be explained in detail. The effect of fluorescence re-absorption on the laser properties, especially on threshold and laser efficiency will also be discussed. This fluorescence re-pumping, applicable in general to a large variety of lasers, can drastically increase the output power and thus laser efficiency at a given pump power. Up to 125 W and 89 J in 2 s are achieved using optimized doping levels for upconversion reduction.

  14. Dynamics of the higher lying excited states of cyanine dyes. An ultrafast fluorescence study.

    PubMed

    Guarin, Cesar A; Villabona-Monsalve, Juan P; López-Arteaga, Rafael; Peon, Jorge

    2013-06-20

    The electronic relaxation dynamics of the second singlet excited states of several cyanine dyes was studied through the femtosecond fluorescence up-conversion technique. Our interest in these molecules comes from the potential applications of systems with upper excited singlet states with a long lifetime, which can include electron and energy transfer from the higher lying singlets after one- or two-photon absorption. We studied three series of cyanines with 4-quinolyl, 2-quinolyl, or benzothiazolyl type end groups, each with varying sp(2) carbon conjugation lengths in the methinic bridge. The dynamics after electronic excitation to singlet states above the fluorescent state vary significantly as a function of cyanine structure and conjugation length. In particular, for the 4-quinolyl series the cyanine with an intermediate conjugation length (three methinic carbons) has the slowest S2 decays with lifetimes of 5.4 ps in ethanol and 6.6 ps in ethylene glycol. On the other hand, we observed that the 2-quinolyl family has S2 decay times in the subpicosecond range independent of the conjugation length between the end groups. The slowest internal conversion was observed for the benzothiazolyl type cyanine with five methinic carbons, with an S2 lifetime of 17.3 ps in ethanol. For the planar cyanines of this study we observed for the first time a clear systematic trend in the S2 decay times which closely follow the energy gap law. It was also demonstrated that a slow S2 decay is as well observed upon excitation through degenerate two-photon absorption with near-IR pulses. The present study isolates the most important variables for the design of cyanines with long S2 lifetimes.

  15. An Nd3+-sensitized upconversion nanophosphor modified with a cyanine dye for the ratiometric upconversion luminescence bioimaging of hypochlorite

    NASA Astrophysics Data System (ADS)

    Zou, Xianmei; Liu, Yi; Zhu, Xingjun; Chen, Min; Yao, Liming; Feng, Wei; Li, Fuyou

    2015-02-01

    Excessive or misplaced production of ClO- in living systems is usually associated with many human diseases. Therefore, it is of great importance to develop an effective and sensitive method to detect ClO- in living systems. Herein, we designed an 808 nm excited upconversion luminescence nanosystem, composed of the Nd3+-sensitized core-shell upconversion nanophosphor NaYF4:30%Yb,1%Nd,0.5%Er@NaYF4:20%Nd, which serves as an energy donor, and the ClO--responsive cyanine dye hCy3, which acts as an energy acceptor, for ratiometric upconversion luminescence (UCL) monitoring of ClO-. The detection limit of ClO- for this nanoprobe in aqueous solution is 27 ppb and the nanoprobe was successfully used to detect the ClO- in the living cells by ratiometric upconversion luminescence. Importantly, the nanoprobe realized the detection of ClO- in a mouse model of arthritis, which produced an excess of ROS, under 808 nm irradiation in vivo. The excitation laser efficiently reduced the heating effect, compared to the commonly used 980 nm laser for upconversion systems.Excessive or misplaced production of ClO- in living systems is usually associated with many human diseases. Therefore, it is of great importance to develop an effective and sensitive method to detect ClO- in living systems. Herein, we designed an 808 nm excited upconversion luminescence nanosystem, composed of the Nd3+-sensitized core-shell upconversion nanophosphor NaYF4:30%Yb,1%Nd,0.5%Er@NaYF4:20%Nd, which serves as an energy donor, and the ClO--responsive cyanine dye hCy3, which acts as an energy acceptor, for ratiometric upconversion luminescence (UCL) monitoring of ClO-. The detection limit of ClO- for this nanoprobe in aqueous solution is 27 ppb and the nanoprobe was successfully used to detect the ClO- in the living cells by ratiometric upconversion luminescence. Importantly, the nanoprobe realized the detection of ClO- in a mouse model of arthritis, which produced an excess of ROS, under 808 nm irradiation in

  16. Theory of femtosecond stimulated Raman spectroscopy

    PubMed Central

    Lee, Soo-Y.; Zhang, Donghui; McCamant, David W.; Kukura, Philipp; Mathies, Richard A.

    2005-01-01

    Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique that produces high-resolution (time-resolved) vibrational spectra from either the ground or excited electronic states of molecules, free from background fluorescence. FSRS uses simultaneously a narrow bandwidth ∼1 – 3 ps Raman pump pulse with a continuum ∼30– 50 fs Stokes probe pulse to produce sharp Raman gains, at positions corresponding to vibrational transitions in the sample, riding on top of the continuum Stokes probe spectrum. When FSRS is preceded by a femtosecond actinic pump pulse that initiates the photochemistry of interest, time-resolved Raman spectroscopy can be carried out. We present two theoretical approaches to FSRS: one is based on a coupling of Raman pump and probe light waves with the vibrations in the medium, and another is a quantum-mechanical description. The latter approach is used to discuss the conditions of applicability and limitations of the coupled-wave description. Extension of the quantum-mechanical description to the case where the Raman pump beam is on resonance with an excited electronic state, as well as when FSRS is used to probe a nonstationary vibrational wave packet prepared by an actinic pump pulse, is also discussed. PMID:15303930

  17. Monitoring femtosecond laser microscopic photothermolysis with multimodal microscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Huang, Yimei; Lui, Harvey; Zhao, Jianhua; McLean, David I.; Zeng, Haishan

    2016-02-01

    Photothermolysis induced by femtosecond (fs) lasers may be a promising modality in dermatology because of its advantages of high precision due to multiphoton absorption and deeper penetration due to the use of near infrared wavelengths. Although multiphoton absorption nonlinear effects are capable of precision targeting, the femtosecond laser photothermolysis could still have effects beyond the targeted area if a sufficiently high dose of laser light is used. Such unintended effects could be minimized by real time monitoring photothermolysis during the treatment. Targeted photothermolytic treatment of ex vivo mouse skin dermis was performed with tightly focused fs laser beams. Images of reflectance confocal microscopy (RCM), second harmonic generation (SHG), and two-photon fluorescence (TPF) of the mouse skins were obtained with integrated multimodal microscopy before, during, and after the laser treatment. The RCM, SHG, and TPF signal intensities of the treatment areas changed after high power femtosecond laser irradiation. The intensities of the RCM and SHG signals decreased when the tissue was damaged, while the intensity of the TPF signal increased when the photothermolysis was achieved. Moreover, the TPF signal was more susceptible to the degree of the photothermolysis than the RCM and SHG signals. The results suggested that multimodal microscopy is a potentially useful tool to monitor and assess the femtosecond laser treatment of the skin to achieve microscopic photothermolysis with high precision.

  18. Fabrication of a novel nanocomposite Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er for large enhancement upconversion luminescence.

    PubMed

    Yin, Dongguang; Cao, Xianzhang; Zhang, Lu; Tang, Jingxiu; Huang, Wenfeng; Han, Yanlin; Wu, Minghong

    2015-06-28

    Upconversion nanocrystals have a lot of advantages over other fluorescent materials. However, their applications are still limited due to their comparatively low upconversion luminescence (UCL). In the present study, a novel nanocomposite of Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er for enhancing UCL was fabricated successfully, and its morphology, crystalline phase, composition, and fluorescent property were investigated. It is interesting to find that the Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er and Ag@SiO2-NaLuF4:Yb,Gd,Er nanocomposites showed high UCL enhancements of 52- and 10-fold compared to the control of Ag-free nanocomposite SiO2-NaLuF4:Yb,Gd,Er, respectively. The enhancement of 52-fold is greater than those reported in our previous studies and some papers. Moreover, the measured life times of the Ag-presented nanocrystals were longer than that of Ag-absent counterparts. These enhancements of UCL can be ascribed to the effect of metal-enhanced fluorescence, which is caused by the enhancement of the local electric field. The UCL intensity of Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er was 5.2-fold higher than that of Ag@SiO2-NaLuF4:Yb,Gd,Er, indicating that graphene presented in the fabricated nanocomposite structure favors metal-enhanced UCL. The small-sized Ag nanoparticles anchored on the graphene sheet mutually enhanced each other's polarizability and surface plasmon resonance, resulting in a big metal-enhanced UCL. This study provides a new strategy for effectively enhancing the UCL of upconversion nanocrystals. The enhancement potentially increases the overall upconversion nanocrystal detectability for highly sensitive biological, medical, and optical detections.

  19. Femtosecond Stimulated Raman Spectroscopy.

    PubMed

    Dietze, Daniel R; Mathies, Richard A

    2016-05-04

    Femtosecond stimulated Raman spectroscopy (FSRS) is an ultrafast nonlinear optical technique that provides vibrational structural information with high temporal (sub-50 fs) precision and high spectral (10 cm(-1) ) resolution. Since the first full demonstration of its capabilities ≈15 years ago, FSRS has evolved into a mature technique, giving deep insights into chemical and biochemical reaction dynamics that would be inaccessible with any other technique. It is now being routinely applied to virtually all possible photochemical reactions and systems spanning from single molecules in solution to thin films, bulk crystals and macromolecular proteins. This review starts with an historic overview and discusses the theoretical and experimental concepts behind this technology. Emphasis is put on the current state-of-the-art experimental realization and several variations of FSRS that have been developed. The unique capabilities of FSRS are illustrated through a comprehensive presentation of experiments to date followed by prospects.

  20. CdSe/AsS core-shell quantum dots: preparation and two-photon fluorescence.

    PubMed

    Wang, Junzhong; Lin, Ming; Yan, Yongli; Wang, Zhe; Ho, Paul C; Loh, Kian Ping

    2009-08-19

    Arsenic(II) sulfide (AsS)-coated CdSe core-shell nanocrystals can be prepared by a cluster-complex deposition approach under mild conditions. At 60 degrees C, growth of an AsS shell onto a CdSe nanocrystal can be realized through the crystallization of a cluster complex of AsS/butylamine in a mixed solvent of isopropanol/chloroform. The new, type I core-shell nanocrystal exhibits markedly enhanced one-photon fluorescence as well two-photon upconversion fluorescence. The nanocrystals can be used for infrared-excited upconversion cellular labeling.

  1. Upconversion luminescence and mechanisms of Tm(3+)/Yb(3+)-codoped oxyhalide tellurite glasses.

    PubMed

    Xu, Shiqing; Fang, Dawei; Zhang, Zaixuan; Jiang, Zhonghong

    2005-11-01

    To obtain efficient blue upconversion laser glasses, upconversion luminescence and mechanisms of Tm(3+)/Yb(3+)-codoped oxyhalide tellurite glasses were investigated under 980 nm excitation. The results showed that upconversion blue and red emission intensities of Tm(3+) first increase, reach its maximum at Tm(2)O(3)%=0.1 mol %, and then decrease with increasing Tm(2)O(3) content. The effect of Tm(2)O(3) content on upconversion intensity is discussed, and possible effect mechanisms are evaluated. The investigated results were conducing to increase upconversion luminescence efficiency of Tm(3+).

  2. Photon upconversion for thin film solar cells

    NASA Astrophysics Data System (ADS)

    de Wild, J.

    2012-09-01

    In this research one of the many possible methods to increase the efficiency of solar cells is described. The method investigated is based on adapting the solar light in such a way that the solar cell can convert more light into electricity. The part of the solar spectrum that is adapted is the part that cannot be absorbed by the solar cells, because the photon energy is too low. This conversion of light is done by so called upconversion, which means that lower energy photons are converted into higher energy photons that can be absorbed by the solar cell. The upconverters used in this thesis are those based on lanthanide ions doped in crystalline hosts. Lanthanide ions have very specific absorption and emission lines, which means that by choosing an appropriate ion one can convert any arbitrary wavelength. One of the most important aspects when one wants to apply upconverters onto solar cells is the light intensity necessary for efficient conversion. Because the upconversion process requires two photons to make a new, higher energy photon, the conversion process is non-linearly dependent on the light intensity. This is the main limitation for practical applications. Therefore, next to applying upconverters onto solar cells also more fundamental questions are addressed in this thesis, for instance, the question what determines efficient conversion. At first the upconverter materials in different hosts are characterized and investigated. The host material influences non-radiative decays, the absorption strength, the lifetime and the energy transfer rate between the lanthanide ions. By investigating two upconverter hosts with small differences (α and β-NaYF4 doped with Er3+ and Yb3+), we have tried to investigate the origin of the difference in upconversion efficiency. For this, emission and absorption spectra are measured under the same conditions and concentrations of the lanthanide ions. Also the absorption strength on the upconverter efficiency is investigated

  3. One-step solvothermal synthesis of targetable optomagnetic upconversion nanoparticles for in vivo bimodal imaging.

    PubMed

    Wang, Xu; Chen, Jia-Tong; Zhu, Haomiao; Chen, Xueyuan; Yan, Xiu-Ping

    2013-11-05

    Bionanoparticles and nanostructures with high biocompatibility and stability, low toxicity, diversification of imaging modality, and specificity of targeting to desired organs or cells are of great interest in nanobiology and medicine. However, integrating all of these desired features into a single bionanoparticle, which can be applied to biomedical applications and eventually in clinical prediagnosis and therapy, is still a challenge. We herein report a facile one-step solvothermal approach to fabricate targetable and biocompatible β-NaYF4:Yb,Gd,Tm upconversion nanoparticles (UCNPs) with bimodal-signals (near-infrared (NIR) fluorescence and magnetic resonance (MR) signals) using hyaluronic acid (HA) as a multifunctional molecule. The prepared UCNPs with low toxicity are successfully applied for in vitro and in vivo targeted tumor imaging. The developed biomimetic surface modification approach for the synthesis of biomolecule-guided multifunctional UCNPs holds great potential applications in medical diagnostics and therapy.

  4. Three-dimensional micro-printing of temperature sensors based on up-conversion luminescence

    NASA Astrophysics Data System (ADS)

    Wickberg, Andreas; Mueller, Jonathan B.; Mange, Yatin J.; Fischer, Joachim; Nann, Thomas; Wegener, Martin

    2015-03-01

    The pronounced temperature dependence of up-conversion luminescence from nanoparticles doped with rare-earth elements enables local temperature measurements. By mixing these nanoparticles into a commercially available photoresist containing the low-fluorescence photo-initiator Irgacure 369, and by using three-dimensional direct laser writing, we show that micrometer sized local temperature sensors can be positioned lithographically as desired. Positioning is possible in pre-structured environments, e.g., within buried microfluidic channels or on optical or electronic chips. We use the latter as an example and demonstrate the measurement for both free space and waveguide-coupled excitation and detection. For the free space setting, we achieve a temperature standard deviation of 0.5 K at a time resolution of 1 s.

  5. Three-dimensional micro-printing of temperature sensors based on up-conversion luminescence

    SciTech Connect

    Wickberg, Andreas; Mueller, Jonathan B.; Mange, Yatin J.; Nann, Thomas; Fischer, Joachim; Wegener, Martin

    2015-03-30

    The pronounced temperature dependence of up-conversion luminescence from nanoparticles doped with rare-earth elements enables local temperature measurements. By mixing these nanoparticles into a commercially available photoresist containing the low-fluorescence photo-initiator Irgacure 369, and by using three-dimensional direct laser writing, we show that micrometer sized local temperature sensors can be positioned lithographically as desired. Positioning is possible in pre-structured environments, e.g., within buried microfluidic channels or on optical or electronic chips. We use the latter as an example and demonstrate the measurement for both free space and waveguide-coupled excitation and detection. For the free space setting, we achieve a temperature standard deviation of 0.5 K at a time resolution of 1 s.

  6. Phase and Size Controllable Synthesis of NaYbF4 Nanocrystals in Oleic Acid/ Ionic Liquid Two-Phase System for Targeted Fluorescent Imaging of Gastric Cancer

    PubMed Central

    Pan, Liyuan; He, Meng; Ma, Jiebing; Tang, Wei; Gao, Guo; He, Rong; Su, Haichuan; Cui, Daxiang

    2013-01-01

    Upconversion nanocrystals with small size and strong fluorescent signals own great potential in applications such as biomolecule-labeling, in vivo tracking and molecular imaging. Herein we reported that NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with small size and strong fluorescent signals were controllably synthesized by oleic acid (OA)/ ionic liquid (IL) two-phase system for targeted fluorescent imaging of gastric cancer in vivo. The optimal synthesis condition of NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals by OA/IL two-phase system was established, adding more metal ion such as Na+ ion could facilitate the size control and crystal-phase transition, more importantly, markedly enhancing fluorescent intensity of beta-phase nanocrystals compared with traditional methods. Alpha-phase NaYbF4, 2%Tm upconversion nanocrystals with less than 10nm in diameter and beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with 30 nm or so in diameter and strong fluorescent signals were obtained, these synthesized nanocrystals exhibited very low cytotoxicity. Folic acid-conjugated silica-modified beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals were prepared, could actively target gastric cancer tissues implanted into nude mice in vivo, and realized targeted fluorescent imaging. Folic acid-conjugated silica-modified NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals show great potential in applications such as targeted near infared radiation fluorescent imaging, magnetic resonance imaging and targeted therapy of gastric cancer in the near future. PMID:23471455

  7. High-efficiency infrared-to-visible upconversion of Er3 + in BaCl2

    NASA Astrophysics Data System (ADS)

    Wang, Yuhu; Ohwaki, Junichi

    1993-07-01

    Highly efficient infrared-to-visible upconversion has been observed in Er3+-doped BaCl2 phosphors. The composition optimized for maximum green emission was around 25ErCl3 (mol %), which contains 5-15 mol % more active Er3+ ions than those in the conventional Er3+-doped fluoride phosphors. Pumped by a 0.8 μm laser diode with a power density of ˜3 W/cm2, chloride (25ErCl3-75BaCl2) shows a very bright green emission with the intensity being two orders of magnitude larger than that of the commercially available IR sensor card on which an optimized fluoride phosphor Y0.8Er0.2F3 is pasted. A 0.97 μm laser diode excitation on the chloride yielded blue (0.49 μm), green (0.55 μm), and red (0.66 μm) fluorescences, visually exhibited as a bright greenish-white emission. The visible fluorescence excited by 0.8, 0.97, or 1.5 μm laser diodes shows quadratic or cubic dependencies on the excitation power over the entire power range for the chlorides but lower dependences for the fluoride. The differences in the upconversion characteristics between the chlorides and fluoride are discussed in terms of the rate equations and attributed principally to the different Er3+...Er3+ interionic energy transfer probability and the different multiphonon decay rate from the excited states of Er3+ in these matrices.

  8. Enhancing Solar Cell Efficiency Using Photon Upconversion Materials

    PubMed Central

    Shang, Yunfei; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

    2015-01-01

    Photovoltaic cells are able to convert sunlight into electricity, providing enough of the most abundant and cleanest energy to cover our energy needs. However, the efficiency of current photovoltaics is significantly impeded by the transmission loss of sub-band-gap photons. Photon upconversion is a promising route to circumvent this problem by converting these transmitted sub-band-gap photons into above-band-gap light, where solar cells typically have high quantum efficiency. Here, we summarize recent progress on varying types of efficient upconversion materials as well as their outstanding uses in a series of solar cells, including silicon solar cells (crystalline and amorphous), gallium arsenide (GaAs) solar cells, dye-sensitized solar cells, and other types of solar cells. The challenge and prospect of upconversion materials for photovoltaic applications are also discussed. PMID:28347095

  9. Energy upconversion in holmium doped lead-germano-tellurite glass

    SciTech Connect

    Kamma, Indumathi; Reddy, B. Rami

    2010-06-15

    Holmium doped lead-germano-tellurite glass was prepared by the melt quenching technique. The Judd-Ofelt intensity parameters were estimated as {Omega}{sub 2}=7.6x10{sup -20}, {Omega}{sub 4}=12.9x10{sup -20}, and {Omega}{sub 6}=2.5x10{sup -20} cm{sup 2}. Radiative transition probabilities and lifetimes were also determined for some of the levels. Room temperature upconversion emissions have been observed from Ho{sup 3+} at 497 nm under 532 nm laser excitation, and at 557 and 668 nm under 762 nm laser excitation. The upconversion emission mechanisms were found to be due to a step wise excitation process. Upconversion emission intensity enhanced in a heat treated glass.

  10. Experimental demonstration of photon upconversion via cooperative energy pooling

    DOE PAGES

    Weingarten, Daniel H.; LaCount, Michael D.; van de Lagemaat, Jao; ...

    2017-03-15

    Photon upconversion is a fundamental interaction of light and matter that has applications in fields ranging from bioimaging to microfabrication. However, all photon upconversion methods demonstrated thus far involve challenging aspects, including requirements of high excitation intensities, degradation in ambient air, requirements of exotic materials or phases, or involvement of inherent energy loss processes. Here we experimentally demonstrate a mechanism of photon upconversion in a thin film, binary mixture of organic chromophores that provides a pathway to overcoming the aforementioned disadvantages. This singlet-based process, called Cooperative Energy Pooling (CEP), utilizes a sensitizer-acceptor design in which multiple photoexcited sensitizers resonantly andmore » simultaneously transfer their energies to a higher-energy state on a single acceptor. Data from this proof-of-concept implementation is fit by a proposed model of the CEP process. As a result, design guidelines are presented to facilitate further research and development of more optimized CEP systems.« less

  11. Low Power Upconversion Mixer for Medical Remote Sensing

    PubMed Central

    Lioe, De Xing; Shafie, Suhaidi; Tan, Gim Heng

    2014-01-01

    This work presents the design of a low power upconversion mixer adapted in medical remote sensing such as wireless endoscopy application. The proposed upconversion mixer operates in ISM band of 433 MHz. With the carrier power of −5 dBm, the proposed mixer has an output inferred 1 dB compression point of −0.5 dBm with a corresponding output third-order intercept point (OIP3) of 7.1 dBm. The design of the upconversion mixer is realized on CMOS 0.13 μm platform, with a current consumption of 594 μA at supply voltage headroom of 1.2 V. PMID:25133266

  12. Enhancing Solar Cell Efficiency Using Photon Upconversion Materials.

    PubMed

    Shang, Yunfei; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

    2015-10-27

    Photovoltaic cells are able to convert sunlight into electricity, providing enough of the most abundant and cleanest energy to cover our energy needs. However, the efficiency of current photovoltaics is significantly impeded by the transmission loss of sub-band-gap photons. Photon upconversion is a promising route to circumvent this problem by converting these transmitted sub-band-gap photons into above-band-gap light, where solar cells typically have high quantum efficiency. Here, we summarize recent progress on varying types of efficient upconversion materials as well as their outstanding uses in a series of solar cells, including silicon solar cells (crystalline and amorphous), gallium arsenide (GaAs) solar cells, dye-sensitized solar cells, and other types of solar cells. The challenge and prospect of upconversion materials for photovoltaic applications are also discussed.

  13. Experimental demonstration of photon upconversion via cooperative energy pooling

    PubMed Central

    Weingarten, Daniel H.; LaCount, Michael D.; van de Lagemaat, Jao; Rumbles, Garry; Lusk, Mark T.; Shaheen, Sean E.

    2017-01-01

    Photon upconversion is a fundamental interaction of light and matter that has applications in fields ranging from bioimaging to microfabrication. However, all photon upconversion methods demonstrated thus far involve challenging aspects, including requirements of high excitation intensities, degradation in ambient air, requirements of exotic materials or phases, or involvement of inherent energy loss processes. Here we experimentally demonstrate a mechanism of photon upconversion in a thin film, binary mixture of organic chromophores that provides a pathway to overcoming the aforementioned disadvantages. This singlet-based process, called Cooperative Energy Pooling (CEP), utilizes a sensitizer-acceptor design in which multiple photoexcited sensitizers resonantly and simultaneously transfer their energies to a higher-energy state on a single acceptor. Data from this proof-of-concept implementation is fit by a proposed model of the CEP process. Design guidelines are presented to facilitate further research and development of more optimized CEP systems. PMID:28294129

  14. Experimental demonstration of photon upconversion via cooperative energy pooling

    NASA Astrophysics Data System (ADS)

    Weingarten, Daniel H.; Lacount, Michael D.; van de Lagemaat, Jao; Rumbles, Garry; Lusk, Mark T.; Shaheen, Sean E.

    2017-03-01

    Photon upconversion is a fundamental interaction of light and matter that has applications in fields ranging from bioimaging to microfabrication. However, all photon upconversion methods demonstrated thus far involve challenging aspects, including requirements of high excitation intensities, degradation in ambient air, requirements of exotic materials or phases, or involvement of inherent energy loss processes. Here we experimentally demonstrate a mechanism of photon upconversion in a thin film, binary mixture of organic chromophores that provides a pathway to overcoming the aforementioned disadvantages. This singlet-based process, called Cooperative Energy Pooling (CEP), utilizes a sensitizer-acceptor design in which multiple photoexcited sensitizers resonantly and simultaneously transfer their energies to a higher-energy state on a single acceptor. Data from this proof-of-concept implementation is fit by a proposed model of the CEP process. Design guidelines are presented to facilitate further research and development of more optimized CEP systems.

  15. Experimental demonstration of photon upconversion via cooperative energy pooling.

    PubMed

    Weingarten, Daniel H; LaCount, Michael D; van de Lagemaat, Jao; Rumbles, Garry; Lusk, Mark T; Shaheen, Sean E

    2017-03-15

    Photon upconversion is a fundamental interaction of light and matter that has applications in fields ranging from bioimaging to microfabrication. However, all photon upconversion methods demonstrated thus far involve challenging aspects, including requirements of high excitation intensities, degradation in ambient air, requirements of exotic materials or phases, or involvement of inherent energy loss processes. Here we experimentally demonstrate a mechanism of photon upconversion in a thin film, binary mixture of organic chromophores that provides a pathway to overcoming the aforementioned disadvantages. This singlet-based process, called Cooperative Energy Pooling (CEP), utilizes a sensitizer-acceptor design in which multiple photoexcited sensitizers resonantly and simultaneously transfer their energies to a higher-energy state on a single acceptor. Data from this proof-of-concept implementation is fit by a proposed model of the CEP process. Design guidelines are presented to facilitate further research and development of more optimized CEP systems.

  16. Femtosecond broadband stimulated Raman spectroscopy: Apparatus and methods

    PubMed Central

    McCamant, David W.; Kukura, Philipp; Yoon, Sangwoon; Mathies, Richard A.

    2005-01-01

    The laser, detection system, and methods that enable femtosecond broadband stimulated Raman spectroscopy (FSRS) are presented in detail. FSRS is a unique tool for obtaining high time resolution (<100 fs) vibrational spectra with an instrument response limited frequency resolution of <10 cm–1. A titanium:Sapphire-based laser system produces the three different pulses needed for FSRS: (1) A femtosecond visible actinic pump that initiates the photochemistry, (2) a narrow bandwidth picosecond Raman pump that provides the energy reservoir for amplification of the probe, and (3) a femtosecond continuum probe that is amplified at Raman resonances shifted from the Raman pump. The dependence of the stimulated Raman signal on experimental parameters is explored, demonstrating the expected exponential increase in Raman intensity with concentration, pathlength, and Raman pump power. Raman spectra collected under different electronic resonance conditions using highly fluorescent samples highlight the fluorescence rejection capabilities of FSRS. Data are also presented illustrating our ability: (i) To obtain spectra when there is a large transient absorption change by using a shifted excitation difference technique and (ii) to obtain high time resolution vibrational spectra of transient electronic states. PMID:17183413

  17. Optical high temperature sensor based on enhanced green upconversion emissions in Er3+-Yb3+-Li+ codoped TiO2 powders.

    PubMed

    Cao, B S; He, Y Y; Sun, Y; Song, M; Dong, B

    2011-11-01

    The Er3+-Yb3+-Li+ codoped TiO2 powders have been prepared by sol-gel method. The strong enhancement of green and red upconversion emissions were obtained for Er3+-Yb3+ codoped TiO2 by additional Li+ codoping and investigated using 976 nm semiconductor laser diode excitation. The enhanced upconversion emissions by the addition of Li+ resulted from the formation of Li compound with lower crystal field symmetry. The fluorescence intensity ratio (FIR) of green upconversion emissions from the transitions of 2H(11/2) --> 4I(15/2) and 4S(3/2) --> 4I(15/2) of Er3+ in the Er3+-Yb3+-Li+ codoped TiO2 has been studied as a function of temperature in the range of 300-925 K, and the maximum sensitivity was determined to be 0.0025 K(-1). Er3+-Yb3+-Li+ codoped TiO2 material with the highest operating temperature up to 925 K, has higher temperature sensitivity and fluorescence efficiency being a promising candidate for applications in optical high temperature sensor.

  18. Fabrication and evaluation of chitosan/NaYF4:Yb(3+)/Tm(3+) upconversion nanoparticles composite beads based on the gelling of Pickering emulsion droplets.

    PubMed

    Yan, Huiqiong; Chen, Xiuqiong; Shi, Jia; Shi, Zaifeng; Sun, Wei; Lin, Qiang; Wang, Xianghui; Dai, Zihao

    2017-02-01

    The rare earth ion doped upconversion nanoparticles (UCNPs) synthesized by hydrophobic organic ligands possess poor solubility and low fluorescence quantum yield in aqueous media. To conquer this issue, NaYF4:Yb(3+)/Tm(3+) UCNPs, synthesized by a hydrothermal method, were coated with F127 and then assembled with chitosan to fabricate the chitosan/NaYF4:Yb(3+)/Tm(3+) composite beads (CS/NaYF4:Yb(3+)/Tm(3+) CBs) by Pickering emulsion system. The characterization results revealed that the as-synthesized NaYF4:Yb(3+)/Tm(3+) UCNPs with an average size of 20nm exhibited spherical morphology, high crystallinity and characteristic emission upconversion fluorescence with an overall blue color output. The NaYF4:Yb(3+)/Tm(3+) UCNPs were successfully conjugated on the surface of chitosan beads by the gelling of emulsion droplets. The resultant CS/NaYF4:Yb(3+)/Tm(3+) CBs showed good upconversion luminescent property, drug-loading capacity, release performance and excellent biocompatibility, exhibiting great potentials in targeted drug delivery and tissue engineering with potential tracking capability and lasting release performance.

  19. Femtosecond transient photoluminescence of the substituted poly(diphenylacetulene)s.

    NASA Astrophysics Data System (ADS)

    Piskun, N. V.; Wang, D. K.; Lim, H.; Epstein, A. J.; Vanwoerkom, L. D.; Gustafson, T. L.

    2000-03-01

    We present the results of a femtosecond transient photoluminescence (PL) study of solutions of two derivatives of substituted poly(diphenylacetylene) using an up-conversion technique. n-Butyl (nBu) and p-carbazole (Cz) substituted poly(diphenylacetylene), PDPA-nBu and PDPA-Cz respectively, have band gaps determined by maxima in the slope of absorption vs. energy of 2.75 eV and 2.63 eV. The steady state emission peaks are at 2.4 eV for PDPA-nBu and at 2.3 eV for PDPA-Cz respectively. The PL peak for PDPA-Cz is red shifted in comparison to the PL peak for PDPA-nBu. Roles of phenyl groups, electron donating effect of the carbazole side units and planarity of the backbone are discussed. Exciting at 3.1 eV, the fs PL shows a faster decay for PDPA-Cz than that for PDPA-nBu, in accord with the decrease of PL quantum efficiency of PDPA-Cz. The 200 fs - 80 ps PL(t) agrees with ~1 ns lifetime. The PDPA-Cz has larger red shift in the 0.2-20 ps time frame. The origin of that shift will be discussed. This work is supported in part by ONR.

  20. Filamentation assisted generation of tunable multicolored femtosecond sidebands based on cascaded four-wave mixing

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Liu, Jun; Li, Fangjia; Shen, Xiong; Li, Ruxin

    2015-05-01

    Tunable intense multicolored femtosecond sidebands are generated in a 0.1 mm-thick sapphire plate based on cascaded four-wave mixing (CFWM) by using a spectrally broadened pulse from filamentation in air and a 806 nm fundamental pulse from a Ti:sapphire laser amplifier. By using the filamentation to extend the spectrum of one incident pulse, the experimental setup is compact and inexpensive. Furthermore, the spectra of the sidebands can be conveniently tuned by varying the input power for the filamentation generation, and even the second-order frequency upconversion sideband can maintain its output power higher than 0.2 mW during the process of tuning. The generated sidebands are observed with a spectral range from 500 to 950 nm, and each spectrum has a full width half maximum (FWHM) bandwidth above 37 nm, which have potential applications in ultrafast spectroscopy and microscopy.

  1. Frequency up-conversion in Lasing Without Inversion

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar

    2014-12-01

    It is well known that in a three-level lambda system, spontaneous emission decay rate on the lasing transition must be smaller than or equal to the decay rate on the driving transition in order to observe LWI. Since spontaneous emission rate is proportional to cube of the corresponding transition frequency, satisfying the above condition requires the frequency of lasing transition to be smaller than the driving transitions frequency. In other words, according to this condition, frequency upconversion is not possible with LWI. The main theme of this article is to suggest the possibilty of frequency upconversion in LWI by overcoming the condition described above.

  2. An experimental design approach for hydrothermal synthesis of NaYF4: Yb3+, Tm3+ upconversion microcrystal: UV emission optimization

    NASA Astrophysics Data System (ADS)

    Kaviani Darani, Masoume; Bastani, Saeed; Ghahari, Mehdi; Kardar, Pooneh

    2015-11-01

    Ultraviolet (UV) emissions of hydrothermally synthesized NaYF4: Yb3+, Tm3+ upconversion crystals were optimized using the response surface methodology experimental design. In these experimental designs, 9 runs, two factors namely (1) Tm3+ ion concentration, and (2) pH value were investigated using 3 different ligands. Introducing UV upconversion emissions as responses, their intensity were separately maximized. Analytical methods such as XRD, SEM, and FTIR could be used to study crystal structure, morphology, and fluorescent spectroscopy in order to obtain luminescence properties. From the photo-luminescence spectra, emissions centered at 347, 364, 452, 478, 648 and 803 nm were observed. Some results show that increasing each DOE factor up to an optimum value resulted in an increase in emission intensity, followed by reduction. To optimize UV emission, as a final result to the UV emission optimization, each design had a suggestion.

  3. Clean synthesis of YOF:Er3+, Yb3+ upconversion colloidal nanoparticles in water through liquid phase pulsed laser ablation for imaging applications

    NASA Astrophysics Data System (ADS)

    Anjana, R.; Kurias, K. M.; Jayaraj, M. K.

    2017-10-01

    Upconversion luminescent nanomaterials have great outlook towards imaging applications. These materials have high chemical and thermal stability, low auto fluorescence, high photo stability and IR excitation does not cause photo damage to living cells and penetrate deeply into tissue. Most of the reported nanoparticles are synthesized through chemical methods in which surface modification is needed for dispersing nanoparticles in water. In this paper we report clean and simple synthesis of upconversion luminescent yttrium oxyfluoride (YOF) nanoparticles through laser ablation in deionized water. YOF:Er3+, Yb3+ pellets were used for ablation. Er3+ is the emission centre Yb3+ is the sensitizer. Obtained colloidal solution is transparent to day light and showing red emission on exciting with 980 nm IR laser. By controlling ablation parameters particles of size less than 10 nm dispersed uniformly in water can be obtained through this surfactant free method. The synthesized nanoparticles can be used for cell imaging.

  4. Nanoparticle fluorescence based technology for biological applications.

    PubMed

    Chen, Wei

    2008-03-01

    Fluorescence is widely used in biological detection and imaging. The emerging luminescent nanoparticles or quantum dots provide a new type of biological agents that can improve these applications. The advantages of luminescent nanoparticles for biological applications include their high quantum yield, color availability, good photo-stability, large surface-to-volume ratio, surface functionality, and small size. In this review article, we first introduce quantum size confinement, photoluminescence and upconversion luminescence of nanoparticles, then describe the preparation and conjugation of water soluble nanoparticles and introduce the applications of luminescence nanoparticles for in vitro and in vivo imaging, fluorescence resonance energy based detection, and the applications of luminescence nanoparticles for photodynamic activation.

  5. Direct femtosecond laser waveguide writing inside zinc phosphate glass.

    PubMed

    Fletcher, Luke B; Witcher, Jon J; Troy, Neil; Reis, Signo T; Brow, Richard K; Krol, Denise M

    2011-04-25

    We report the relationship between the initial glass composition and the resulting microstructural changes after direct femtosecond laser waveguide writing with a 1 kHz repetition rate Ti:sapphire laser system. A zinc polyphosphate glass composition with an oxygen to phosphorus ratio of 3.25 has demonstrated positive refractive index changes induced inside the focal volume of a focusing microscope objective for laser pulse energies that can achieve intensities above the modification threshold. The permanent photo-induced changes can be used for direct fabrication of optical waveguides using single scan writing techniques. Changes to the localized glass network structure that produce positive changes in the refractive index of zinc phosphate glasses upon femtosecond laser irradiation have been studied using scanning confocal micro-Raman and fluorescence spectroscopy.

  6. Visible and near infra-red up-conversion in Tm3+/Yb3+ co-doped silica fibers under 980 nm excitation.

    PubMed

    Simpson, D A; Gibbs, W E; Collins, S F; Blanc, W; Dussardier, B; Monnom, G; Peterka, P; Baxter, G W

    2008-09-01

    The spectroscopic properties of Tm(3+)/Yb(3+) co-doped silica fibers under excitation at 980 nm are reported. Three distinct up-conversion fluorescence bands were observed in the visible to near infra-red regions. The blue and red fluorescence bands at 475 and 650 nm, respectively, were found to originate from the (1)G(4) level of Tm(3+). A three step up-conversion process was established as the populating mechanism for these fluorescence bands. The fluorescence band at 800 nm was found to originate from two possible transitions in Tm(3+); one being the transition from the (3)H(4) to (3)H(6) manifold which was found to dominate at low pump powers; the other being the transition from the (1)G(4) to (3)H(6) level which dominates at higher pump powers. The fluorescence lifetime of the (3)H(4) and (3)F(4) levels of Tm(3+) and (2)F(5/2) level of Yb(3+) were studied as a function of Yb(3+) concentration, with no significant energy back transfer from Tm(3+) to Yb(3+) observed.

  7. Investigation on up-conversion luminescence properties of novel transparent Ho3+-Tm3+-Yb3+ co-doped oxyfluoride glass ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-bo; Han, Wan-lei; Xu, Fang; Song, Ying-lin

    2011-06-01

    In the present letter, the transparent oxyfluoride glass ceramics containing Ho3+-Tm3+-Yb3+:NaYF4 were successfully prepared by melt-quenching at 1400°C and subsequent heating at 650-680°C for 1~2 hours . X-ray diffraction (XRD) with Cu Kα radiation (λ=0.154nm) investigation revealed that NaYF4 nano-crystals in the glass ceramics was fabricated. Their sizes were determined by Sherrer's equation. The emission spectra red green and blue up-conversion (UC) under 980nm laser diode (LD) pumping and absorption spectra were measured. Luminescence measurements confirmed the partition of RE ions in nano-crystals NaYF4. The blue red and green UC radiations correspond to the transitions 1G4-3H6, 1G4-3H4 of Tm3+, 5F4, 5S2-5I8, 5F5-5I8, of Ho3+ ions, respectively. This is similar to that in Tm3+-Yb3+ and/or Ho3+-Yb3+ co-doped glass ceramics. To obtain upconversion fluorescence mechanisms, upconversion fluorescence intensity versus LD pump power were analyzed in view of energy levels of rare earth. Up-conversion mechanisms were discussed and the ratio between red, green and blue UC emission bands was found to be varied as a function of temperature of heat treatment and pump power. This result could be mainly attributed to the cross-relaxation between Ho3+ ions. The excellent optical properties and its convenient, low-cost synthesis of the present glass ceramic imply that it is an excellent substitution material for the unobtainable bulk NaYF4 crystal and may have potentially applications in tunable visible laser or many other fields.

  8. Femtosecond photography lessons

    NASA Astrophysics Data System (ADS)

    Fanchenko, S. D.

    1999-06-01

    Antic scientists, sailors, warriors, physician, etc. were perceiving the space by means of their eye vision system. Nowadays the same people use eyeglasses, telescopes, microscopes, image converters. All these devices fit the necessary magnification, intensification gain and image spectrum to the eyes. The human brain is processing the image data offered to him in a format pertaining to eyes. Hence, the cognition of images can be regarded as a direct measurement. As to the time scale converters, they turned out to be harder done as compared with the spatial scale converters. Hence, the development of the high-speed photography (HSP) continues for more than a hundred and fifty years. The recent pico- femtosecond HSP branch sprang up in 1949 at the Kurchatov Institute -- its cradle. All about the HSP had been advertised. Instead of reprinting what is already well known, it makes sense to emphasize some instructive lessons drawn from past experience. Also it is tempting to look a bit into the high-speed photography future.

  9. Fluorescence lifetime analyses reveal how the high light-responsive protein LHCSR3 transforms PSII light-harvesting complexes into an energy-dissipative state.

    PubMed

    Kim, Eunchul; Akimoto, Seiji; Tokutsu, Ryutaro; Yokono, Makio; Minagawa, Jun

    2017-09-27

    In green algae, light-harvesting complex stress-related 3 (LHCSR3) is responsible for the pH-dependent dissipation of absorbed light energy, a function vital for survival under high-light conditions. LHCSR3 binds the photosystem II and light-harvesting complex II (PSII-LHCII) supercomplex and transforms it into an energy-dissipative form under acidic conditions, but the molecular mechanism remains unclear. Here we show that in the green alga Chlamydomonas reinhardtii, LHCSR3 modulates the excitation energy flow and dissipates the excitation energy within the light-harvesting complexes of the PSII supercomplex. Using fluorescence decay-associated spectra analysis, we found that, when the PSII supercomplex is associated with LHCSR3 under high-light conditions, excitation energy transfer from light-harvesting complexes to the chlorophyll-binding protein CP43 is selectively inhibited compared with that to CP47, preventing excess excitation energy from overloading the reaction center. By analyzing femtosecond upconversion fluorescence kinetics, we further found that pH- and LHCSR3-dependent quenching of the PSII-LHCII-LHCSR3 supercomplex is accompanied by a fluorescence emission centered at 684 nm, with a decay time constant of 18.6 ps, which is equivalent to the rise time constant of the lutein radical cation generated within a chlorophyll-lutein heterodimer. These results suggest a mechanism in which LHCSR3 transforms the PSII supercomplex into an energy-dissipative state and provide critical insight into the molecular events and characteristics in LHCSR3-dependent energy quenching. Copyright © 2017, The American Society for Biochemistry and Molecular Biology.

  10. Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs

    PubMed Central

    Furukawa, Taro; Nakanotani, Hajime; Inoue, Munetomo; Adachi, Chihaya

    2015-01-01

    Recently, triplet harvesting via a thermally activated delayed fluorescence (TADF) process has been established as a realistic route for obtaining ultimate internal electroluminescence (EL) quantum efficiency in organic light-emitting diodes (OLEDs). However, the possibility that the rather long transient lifetime of the triplet excited states would reduce operational stability due to an increased chance for unwarranted chemical reactions has been a concern. Herein, we demonstrate dual enhancement of EL efficiency and operational stability in OLEDs by employing a TADF molecule as an assistant dopant and a fluorescent molecule as an end emitter. The proper combination of assistant dopant and emitter molecules realized a “one-way” rapid Förster energy transfer of singlet excitons from TADF molecules to fluorescent emitters, reducing the number of cycles of intersystem crossing (ISC) and reverse ISC in the TADF molecules and resulting in a significant enhancement of operational stability compared to OLEDs with a TADF molecule as the end emitter. In addition, we found that the presence of this rapid energy transfer significantly suppresses singlet-triplet annihilation. Using this finely-tuned rapid triplet-exciton upconversion scheme, OLED performance and lifetime was greatly improved. PMID:25673259

  11. Microfluidic cell counter with embedded optical fibers fabricated by femtosecond laser ablation and anodic bonding.

    PubMed

    Schafer, Dawn; Gibson, Emily A; Salim, Evan A; Palmer, Amy E; Jimenez, Ralph; Squier, Jeff

    2009-04-13

    A simple fabrication technique to create all silicon/glass microfluidic devices is demonstrated using femtosecond laser ablation and anodic bonding. In a first application, we constructed a cell counting device based on small angle light scattering. The counter featured embedded optical fibers for multiangle excitation and detection of scattered light and/or fluorescence. The performance of the microfluidic cell counter was benchmarked against a commercial fluorescence-activated cell sorter.

  12. Microfluidic cell counter with embedded optical fibers fabricated by femtosecond laser ablation and anodic bonding

    PubMed Central

    Schafer, Dawn; Gibson, Emily A.; Salim, Evan A.; Palmer, Amy E.; Jimenez, Ralph; Squier, Jeff

    2011-01-01

    A simple fabrication technique to create all silicon/glass microfluidic devices is demonstrated using femtosecond laser ablation and anodic bonding. In a first application, we constructed a cell counting device based on small angle light scattering. The counter featured embedded optical fibers for multiangle excitation and detection of scattered light and/or fluorescence. The performance of the microfluidic cell counter was benchmarked against a commercial fluorescence-activated cell sorter. PMID:19365429

  13. Noncontact microsurgery of cell membranes using femtosecond laser pulses for optoinjection of specified substances into cells

    SciTech Connect

    Il'ina, I V; Ovchinnikov, A V; Chefonov, O V; Sitnikov, D S; Agranat, Mikhail B; Mikaelyan, A S

    2013-04-30

    IR femtosecond laser pulses were used for microsurgery of a cell membrane aimed at local and short-duration change in its permeability and injection of specified extracellular substances into the cells. The possibility of noncontact laser delivery of the propidium iodide fluorescent dye and the pEGFP plasmid, encoding the green fluorescent protein, into the cells with preservation of the cell viability was demonstrated. (extreme light fields and their applications)

  14. Femtosecond optomagnetism in dielectric antiferromagnets

    NASA Astrophysics Data System (ADS)

    Bossini, D.; Rasing, Th

    2017-02-01

    Optical femtosecond manipulation of magnetic order is attractive for the development of new concepts for ultrafast magnetic recording. Theoretical and experimental investigations in this research area aim at establishing a physical understanding of magnetic media in light-induced non-equilibrium states. Such a quest requires one to adjust the theory of magnetism, since the thermodynamical concepts of elementary excitations and spin alignment determined by the exchange interaction are not applicable on the femtosecond time-scale after the photo-excitation. Here we report some key milestones concerning the femtosecond optical control of spins in dielectric antiferromagnets, whose spin dynamics is by nature faster than that of ferromagnets and can be triggered even without any laser heating. The recent progress of the opto-magnetic effect in the sub-wavelength regime makes this exciting research area even more promising, in terms of both fundamental breakthroughs and technological perspectives.

  15. Transition Metal-Involved Photon Upconversion.

    PubMed

    Ye, Shi; Song, En-Hai; Zhang, Qin-Yuan

    2016-12-01

    Upconversion (UC) luminescence of lanthanide ions (Ln(3+)) has been extensively investigated for several decades and is a constant research hotspot owing to its fundamental significance and widespread applications. In contrast to the multiple and fixed UC emissions of Ln(3+), transition metal (TM) ions, e.g., Mn(2+), usually possess a single broadband emission due to its 3d(5) electronic configuration. Wavelength-tuneable single UC emission can be achieved in some TM ion-activated systems ascribed to the susceptibility of d electrons to the chemical environment, which is appealing in molecular sensing and lighting. Moreover, the UC emissions of Ln(3+) can be modulated by TM ions (specifically d-block element ions with unfilled d orbitals), which benefits from the specific metastable energy levels of Ln(3+) owing to the well-shielded 4f electrons and tuneable energy levels of the TM ions. The electric versatility of d(0) ion-containing hosts (d(0) normally viewed as charged anion groups, such as MoO6(6-) and TiO4(4-)) may also have a strong influence on the electric dipole transition of Ln(3+), resulting in multifunctional properties of modulated UC emission and electrical behaviour, such as ferroelectricity and oxide-ion conductivity. This review focuses on recent advances in the room temperature (RT) UC of TM ions, the UC of Ln(3+) tuned by TM or d(0) ions, and the UC of d(0) ion-centred groups, as well as their potential applications in bioimaging, solar cells and multifunctional devices.

  16. Transition Metal‐Involved Photon Upconversion

    PubMed Central

    Song, En‐Hai

    2016-01-01

    Upconversion (UC) luminescence of lanthanide ions (Ln3+) has been extensively investigated for several decades and is a constant research hotspot owing to its fundamental significance and widespread applications. In contrast to the multiple and fixed UC emissions of Ln3+, transition metal (TM) ions, e.g., Mn2+, usually possess a single broadband emission due to its 3d 5 electronic configuration. Wavelength‐tuneable single UC emission can be achieved in some TM ion‐activated systems ascribed to the susceptibility of d electrons to the chemical environment, which is appealing in molecular sensing and lighting. Moreover, the UC emissions of Ln3+ can be modulated by TM ions (specifically d‐block element ions with unfilled d orbitals), which benefits from the specific metastable energy levels of Ln3+ owing to the well‐shielded 4f electrons and tuneable energy levels of the TM ions. The electric versatility of d 0 ion‐containing hosts (d 0 normally viewed as charged anion groups, such as MoO6 6‐ and TiO4 4‐) may also have a strong influence on the electric dipole transition of Ln3+, resulting in multifunctional properties of modulated UC emission and electrical behaviour, such as ferroelectricity and oxide‐ion conductivity. This review focuses on recent advances in the room temperature (RT) UC of TM ions, the UC of Ln3+ tuned by TM or d 0 ions, and the UC of d 0 ion‐centred groups, as well as their potential applications in bioimaging, solar cells and multifunctional devices. PMID:27981015

  17. Two-step photon up-conversion solar cells

    PubMed Central

    Asahi, Shigeo; Teranishi, Haruyuki; Kusaki, Kazuki; Kaizu, Toshiyuki; Kita, Takashi

    2017-01-01

    Reducing the transmission loss for below-gap photons is a straightforward way to break the limit of the energy-conversion efficiency of solar cells (SCs). The up-conversion of below-gap photons is very promising for generating additional photocurrent. Here we propose a two-step photon up-conversion SC with a hetero-interface comprising different bandgaps of Al0.3Ga0.7As and GaAs. The below-gap photons for Al0.3Ga0.7As excite GaAs and generate electrons at the hetero-interface. The accumulated electrons at the hetero-interface are pumped upwards into the Al0.3Ga0.7As barrier by below-gap photons for GaAs. Efficient two-step photon up-conversion is achieved by introducing InAs quantum dots at the hetero-interface. We observe not only a dramatic increase in the additional photocurrent, which exceeds the reported values by approximately two orders of magnitude, but also an increase in the photovoltage. These results suggest that the two-step photon up-conversion SC has a high potential for implementation in the next-generation high-efficiency SCs. PMID:28382945

  18. Two-step photon up-conversion solar cells.

    PubMed

    Asahi, Shigeo; Teranishi, Haruyuki; Kusaki, Kazuki; Kaizu, Toshiyuki; Kita, Takashi

    2017-04-06

    Reducing the transmission loss for below-gap photons is a straightforward way to break the limit of the energy-conversion efficiency of solar cells (SCs). The up-conversion of below-gap photons is very promising for generating additional photocurrent. Here we propose a two-step photon up-conversion SC with a hetero-interface comprising different bandgaps of Al0.3Ga0.7As and GaAs. The below-gap photons for Al0.3Ga0.7As excite GaAs and generate electrons at the hetero-interface. The accumulated electrons at the hetero-interface are pumped upwards into the Al0.3Ga0.7As barrier by below-gap photons for GaAs. Efficient two-step photon up-conversion is achieved by introducing InAs quantum dots at the hetero-interface. We observe not only a dramatic increase in the additional photocurrent, which exceeds the reported values by approximately two orders of magnitude, but also an increase in the photovoltage. These results suggest that the two-step photon up-conversion SC has a high potential for implementation in the next-generation high-efficiency SCs.

  19. Development of Pressure sensing Particles through SERS and Upconversion

    NASA Astrophysics Data System (ADS)

    Widejko, Ryan; Wang, Fenglin; Anker, Jeff

    2012-03-01

    With the increasing distance of space travel, there is a critical need for non-invasive point-of-care diagnostic techniques. According to the NASA Human Research Roadmap, the ``lack of non-invasive diagnostic imaging capability and techniques to diagnose identified Exploration Medical Conditions involving internal body parts,'' is a critical capability gap for long distance space travel. To address this gap, we developed a novel technique for non-invasive monitoring of strain on implanted devices. We constructed a prototype tension-indicating washer with an upconversion spectrum that depended upon strain. The washer was made of a polydimethylsiloxane (PDMS) mixture with upconversion particles embedded in it. This mixture was cured onto a lenticular lens. Methylene blue dye solution was sealed between the lenticular lens and PDMS so that pressure on the washer displaced the dye and uncovered the upconversion particles. We also began work on a tension-indicating screw based upon surface enhanced Raman spectroscopy (SERS). Future work for this project is to quantitatively correlate the spectral intensity with pressure, further develop SERS washers, and construct SERS and/or upconversion screws or bolts. Non-invasive tension-indicating devices and techniques such as these can be applied to orthopedics, used as a general technique for measuring micro-strain, verifying proper assembly of equipment, and observing/studying bolt loosening.

  20. Ultrasensitive Detection of Prostate-Specific Antigen and Thrombin Based on Gold-Upconversion Nanoparticle Assembled Pyramids.

    PubMed

    Hao, Tiantian; Wu, Xiaoling; Xu, Liguang; Liu, Liqiang; Ma, Wei; Kuang, Hua; Xu, Chuanlai

    2017-03-29

    Self-assembled nanostructures have been used for the detection of numerous cancer biomarkers. In this study, a gold-upconversion-nanoparticle (Au-UCNP) pyramid based on aptamers is fabricated to simultaneously detect thrombin and prostate-specific antigen (PSA) using surface-enhanced Raman scattering (SERS) and fluorescence, respectively. The higher the concentration of thrombin, the lower the intensity of SERS. PSA connected with the PSA aptamer leads to an increase in fluorescence intensity. The limit of detection of thrombin and PSA reaches 57 × 10(-18) and 0.032 × 10(-18) m, respectively. In addition, the pyramid also exhibits great target specificity. The results of human serum target detection demonstrate that the Au-UCNP pyramid is an excellent choice for the quantitative determination of cancer biomarkers, and is feasible for the early diagnosis of cancer.

  1. Deep-penetrating photodynamic therapy with KillerRed mediated by upconversion nanoparticles.

    PubMed

    Liang, Liuen; Lu, Yiqing; Zhang, Run; Care, Andrew; Ortega, Tiago A; Deyev, Sergey M; Qian, Yi; Zvyagin, Andrei V

    2017-03-15

    The fluorescent protein KillerRed, a new type of biological photosensitizer, is considered as a promising substitute for current synthetic photosensitizes used in photodynamic therapy (PDT). However, broad application of this photosensitiser in treating deep-seated lesions is challenging due to the limited tissue penetration of the excitation light with the wavelength falling in the visible spectral range. To overcome this challenge, we employ upconversion nanoparticles (UCNPs) that are able to convert deep-penetrating near infrared (NIR) light to green light to excite KillerRed locally, followed by the generation of reactive oxygen species (ROS) to kill tumour cells under centimetre-thick tissue. The photosensitizing bio-nanohybrids, KillerRed-UCNPs, are fabricated through covalent conjugation of KillerRed and UCNPs. The resulting KillerRed-UCNPs exhibit excellent colloidal stability in biological buffers and low cytotoxicity in the dark. Cross-comparison between the conventional KillerRed and UCNP-mediated KillerRed PDT demonstrated superiority of KillerRed-UCNPs photosensitizing by NIR irradiation, manifested by the fact that ∼70% PDT efficacy was achieved at 1-cm tissue depth, whereas that of the conventional KillerRed dropped to ∼7%. KillerRed is a protein photosensitizer that holds promise as an alternative for the existing hydrophobic photosensitizers that are widely used in clinical photodynamic therapy (PDT). However, applications of KillerRed to deep-seated tumours are limited by the insufficient penetration depth of the excitation light in highly scattering and absorbing biological tissues. Herein, we reported the deployment of upconversion nanoparticles (UCNPs) to enhance the treatment depth of KillerRed by converting the deep-penetrating near-infrared (NIR) light to upconversion photoluminescence and activating the PDT effect of KillerRed under deep tissues. This work demonstrated clear potential of UCNPs as the NIR-to-visible light converter to

  2. Holographic vector-wave femtosecond laser processing

    NASA Astrophysics Data System (ADS)

    Hayasaki, Yoshio; Hasegawa, Satoshi

    2016-03-01

    Arbitrary and variable beam shaping of femtosecond pulses by a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM) have been applied to femtosecond laser processing. The holographic femtosecond laser processing has been widely used in many applications such as two-photon polymerization, optical waveguide fabrication, fabrication of volume phase gratings in polymers, and surface nanostructuring. A vector wave that has a spatial distribution of polarization states control of femtosecond pulses gives good performances for the femtosecond laser processing. In this paper, an in- system optimization of a CGH for massively-parallel femtosecond laser processing, a dynamic control of spatial spectral dispersion to improve the focal spot shape, and the holographic vector-wave femtosecond laser processing are demonstrated.

  3. In vivo 808 nm image-guided photodynamic therapy based on an upconversion theranostic nanoplatform

    NASA Astrophysics Data System (ADS)

    Liu, Xiaomin; Que, Ivo; Kong, Xianggui; Zhang, Youlin; Tu, Langping; Chang, Yulei; Wang, Tong Tong; Chan, Alan; Löwik, Clemens W. G. M.; Zhang, Hong

    2015-09-01

    A new strategy for efficient in vivo image-guided photodynamic therapy (PDT) has been demonstrated utilizing a ligand-exchange constructed upconversion-C60 nanophotosensitizer. This theranostic platform is superior to the currently reported nanophotosensitizers in (i) directly bonding photosensitizer C60 to the surface of upconversion nanoparticles (UCNPs) by a smart ligand-exchange strategy, which greatly shortened the energy transfer distance and enhanced the 1O2 production, resulting in the improvement of the therapeutic effect; (ii) realizing in vivo NIR 808 nm image-guided PDT with both excitation (980 nm) and emission (808 nm) light falling in the biological window of tissues, which minimized auto-fluorescence, reduced light scatting and improved the imaging contrast and depth, and thus guaranteed noninvasive diagnostic accuracy. In vivo and ex vivo tests demonstrated its favorable bio-distribution, tumor-selectivity and high therapeutic efficacy. Owing to the effective ligand exchange strategy and the excellent intrinsic photophysical properties of C60, 1O2 production yield was improved, suggesting that a low 980 nm irradiation dosage (351 J cm-2) and a short treatment time (15 min) were sufficient to perform NIR (980 nm) to NIR (808 nm) image-guided PDT. Our work enriches the understanding of UCNP-based PDT nanophotosensitizers and highlights their potential use in future NIR image-guided noninvasive deep cancer therapy.A new strategy for efficient in vivo image-guided photodynamic therapy (PDT) has been demonstrated utilizing a ligand-exchange constructed upconversion-C60 nanophotosensitizer. This theranostic platform is superior to the currently reported nanophotosensitizers in (i) directly bonding photosensitizer C60 to the surface of upconversion nanoparticles (UCNPs) by a smart ligand-exchange strategy, which greatly shortened the energy transfer distance and enhanced the 1O2 production, resulting in the improvement of the therapeutic effect; (ii

  4. Near diffraction limited mid-IR spectromicroscopy using frequency upconversion

    NASA Astrophysics Data System (ADS)

    Sanders, Nicolai; Dam, Jeppe Seidelin; Tidemand-Lichtenberg, Peter; Pedersen, Christian

    2014-02-01

    Mid-infrared microscopy and spectroscopy is interesting due to its medical, biological and chemical applications. Spectromicroscopy can be used for histopathology, sample analysis and diagnosis. The ability to do spectromicroscopy in the 2.5 to 4.5 μm wavelength range where many organic molecules have their fundamental vibrations, with the addition of sufficient spectroscopic resolution to resolve these bands, can e.g. potentially allow for diagnostics without the need for staining of the sample. On a longer timeframe, mid-IR spectromicroscopy has the potential for in-vivo diagnostics, combining morphological and spectral imaging. Recent developments in nonlinear frequency upconversion, have demonstrated the potential to perform both imaging and spectroscopy in the mid-IR range at unparalleled low levels of illumination, the low upconversion detector noise being orders of magnitude below competing technologies. With these applications in mind, we have incorporated microscopy optics into an image upconversion system, achieving near diffraction limited spatial resolution in the 3 μm range. Spectroscopic information is further acquired by appropriate control of the phase match condition of the upconversion process. Multispectral images for a region of interest can be obtained by XY-scanning this region of interest within the field of view of the mid-IR upconversion system. Thus, the whole region of interest can be imaged with all available converter wavelengths, and the spectral representation becomes equal for all points in the image. In addition, the range of converted/imaged wavelengths can be tuned continuously by changing the temperature of the crystal, or discretely by using a different poling channel in the PPLN crystal.

  5. Blue Upconversion Luminescence in Tm3+/Yb3+ Codoped CaWO4 Polycrystals

    NASA Astrophysics Data System (ADS)

    Xu, Yan-Ling; Wang, Yun-Long; Shi, Lian-Sheng; Tan, Xiang

    2013-08-01

    We investigate the upconversion emission of CaWO4:Tm3+/Yb3+ polycrystals prepared by the high-temperature solid-state method. The crystal structure of the polycrystals is characterized by means of x-ray diffraction. Under the excitation of a 980 nm continuous wave diode laser, the samples show intense blue upconversion emissions centered at 473 nm, corresponding to the 1G4→3H6 transition of Tm3+. The dependence of the upconversion emission intensity on the pump power of a laser diode is measured, and the results indicate that the two-photon and three-photon processes contribute simultaneously to the blue upconversion emissions. The possible multi-photon upconversion process and upconversion mechanisms are discussed.

  6. Dye-Sensitized Core/Active Shell Upconversion Nanoparticles for Optogenetics and Bioimaging Applications.

    PubMed

    Wu, Xiang; Zhang, Yuanwei; Takle, Kendra; Bilsel, Osman; Li, Zhanjun; Lee, Hyungseok; Zhang, Zijiao; Li, Dongsheng; Fan, Wei; Duan, Chunying; Chan, Emory M; Lois, Carlos; Xiang, Yang; Han, Gang

    2016-01-26

    Near-infrared (NIR) dye-sensitized upconversion nanoparticles (UCNPs) can broaden the absorption range and boost upconversion efficiency of UCNPs. Here, we achieved significantly enhanced upconversion luminescence in dye-sensitized core/active shell UCNPs via the doping of ytterbium ions (Yb(3+)) in the UCNP shell, which bridged the energy transfer from the dye to the UCNP core. As a result, we synergized the two most practical upconversion booster effectors (dye-sensitizing and core/shell enhancement) to amplify upconversion efficiency. We demonstrated two biomedical applications using these UCNPs. By using dye-sensitized core/active shell UCNP embedded poly(methyl methacrylate) polymer implantable systems, we successfully shifted the optogenetic neuron excitation window to a biocompatible and deep tissue penetrable 800 nm wavelength. Furthermore, UCNPs were water-solubilized with Pluronic F127 with high upconversion efficiency and can be imaged in a mouse model.

  7. Dye-Sensitized Core/Active Shell Upconversion Nanoparticles for Optogenetics and Bioimaging Applications

    DOE PAGES

    Wu, Xiang; Zhang, Yuanwei; Takle, Kendra; ...

    2016-01-06

    A near-infrared (NIR) dye-sensitized upconversion nanoparticles (UCNPs) can broaden the absorption range and boost upconversion efficiency of UCNPs. We achieved significantly enhanced upconversion luminescence in dye-sensitized core/active shell UCNPs via the doping of ytterbium ions (Yb 3+ ) in the UCNP shell, which bridged the energy transfer from the dye to the UCNP core. As a result, we synergized the two most practical upconversion booster effectors (dye-sensitizing and core/shell enhancement) to amplify upconversion efficiency. We also demonstrated two biomedical applications using these UCNPs. By using dye-sensitized core/active shell UCNP embedded poly(methyl methacrylate) polymer implantable systems, we successfully shifted the optogeneticmore » neuron excitation window to a biocompatible and deep tissue penetrable 800 nm wavelength. Furthermore, UCNPs were water-solubilized with Pluronic F127 with high upconversion efficiency and can be imaged in a mouse model.« less

  8. Dye-Sensitized Core/Active Shell Upconversion Nanoparticles for Optogenetics and Bioimaging Applications

    SciTech Connect

    Wu, Xiang; Zhang, Yuanwei; Takle, Kendra; Bilsel, Osman; Li, Zhanjun; Lee, Hyungseok; Zhang, Zijiao; Li, Dongsheng; Fan, Wei; Duan, Chunying; Chan, Emory M.; Lois, Carlos; Xiang, Yang; Han, Gang

    2016-01-06

    A near-infrared (NIR) dye-sensitized upconversion nanoparticles (UCNPs) can broaden the absorption range and boost upconversion efficiency of UCNPs. We achieved significantly enhanced upconversion luminescence in dye-sensitized core/active shell UCNPs via the doping of ytterbium ions (Yb 3+ ) in the UCNP shell, which bridged the energy transfer from the dye to the UCNP core. As a result, we synergized the two most practical upconversion booster effectors (dye-sensitizing and core/shell enhancement) to amplify upconversion efficiency. We also demonstrated two biomedical applications using these UCNPs. By using dye-sensitized core/active shell UCNP embedded poly(methyl methacrylate) polymer implantable systems, we successfully shifted the optogenetic neuron excitation window to a biocompatible and deep tissue penetrable 800 nm wavelength. Furthermore, UCNPs were water-solubilized with Pluronic F127 with high upconversion efficiency and can be imaged in a mouse model.

  9. Advances in the theoretical understanding of photon upconversion in rare-earth activated nanophosphors.

    PubMed

    Liu, Guokui

    2015-03-21

    Photon upconversion in rare earth activated phosphors involves multiple mechanisms of electronic transitions. Stepwise optical excitation, energy transfer, and various nonlinear and collective light-matter interaction processes act together to convert low-energy photons into short-wavelength light emission. Upconversion luminescence from nanomaterials exhibits additional size and surface dependencies. A fundamental understanding of the overall performance of an upconversion system requires basic theories on the spectroscopic properties of solids containing rare earth ions. This review article surveys the recent progress in the theoretical interpretations of the spectroscopic characteristics and luminescence dynamics of photon upconversion in rare earth activated phosphors. The primary aspects of upconversion processes, including energy level splitting, transition probability, line broadening, non-radiative relaxation and energy transfer, are covered with an emphasis on interpreting experimental observations. Theoretical models and methods for analyzing nano-phenomena in upconversion are introduced with detailed discussions on recently reported experimental results.

  10. Preparation and up-conversion luminescence properties of LaOBr:Yb3+/Er3+ nanofibers via electrospinning.

    PubMed

    Ma, Wenwen; Yu, Wensheng; Dong, Xiangting; Wang, Jinxian; Liu, Guixia

    2014-11-01

    LaOBr:Yb(3+)/Er(3+) nanofibers were synthesized for the first time by calcinating electrospun PVP/[La(NO3)3 + Er(NO3)3 + Yb(NO3)3 + NH4 Br] composites. The morphology and properties of the final products were investigated in detail using scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffractometry (XRD) and fluorescence spectroscopy. The results indicate that LaOBr:Yb(3+)/Er(3+) nanofibers are tetragonal in structure with a space group of P4/nmm. The diameter of LaOBr:Yb(3+)/Er(3+) nanofibers is ~ 147 nm. Under the excitation of a 980-nm diode laser, LaOBr:Yb(3+)/Er(3+) nanofibers emit strong green and red up-conversion emission centering at 519, 541 and 667 nm, ascribed to the (2)H11/2, (4)S3/2 → (4) I(15/2) and (4)F9/2 → (4)I(15/2) energy-level transitions of Er(3+) ions, respectively. The up-conversion luminescent mechanism of LaOBr:Yb(3+)/Er(3+) nanofibers is advanced. Moreover, near-infrared emission of LaOBr:Yb(3+)/Er(3+) nanofibers is obtained under the excitation of a 532-nm laser. The formation mechanism of LaOBr:Yb(3+)/Er(3+) nanofibers is proposed. LaOBr:Yb(3+)/Er(3+) nanofibers could be important up-conversion luminescent materials. Copyright © 2014 John Wiley & Sons, Ltd.

  11. Ophthalmic applications of femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Kurtz, Ron M.; Spooner, Greg J. R.; Sletten, Karin R.; Yen, Kimberly G.; Sayegh, Samir I.; Loesel, Frieder H.; Horvath, Christopher; Liu, HsiaoHua; Elner, Victor; Cabrera, Delia; Muenier, Marie-Helene; Sacks, Zachary S.; Juhasz, Tibor; Miller, Doug L.; Williams, A. R.

    1999-06-01

    We investigated three potential femtosecond laser ophthalmic procedures: intrastromal refractive surgery, transcleral photodisruptive glaucoma surgery and photodisruptive ultrasonic lens surgery. A highly reliable, all-solid-state system was used to investigate tissue effects and demonstrate clinical practicality. Compared with longer duration pulses, femtosecond laser-tissue interactions are characterized by smaller and more deterministic photodisruptive energy thresholds, smaller shock wave and cavitation bubble sizes. Scanning a 5 (mu) spot below the target tissue surface produced contiguous tissue effects. Various scanning patterns were used to evaluate the efficacy, safety, and stability of three intrastromal refractive procedures in animal eyes: corneal flap cutting, keratomileusis, and intrastromal vision correction (IVC). Superior dissection and surface quality results were obtained for the lamellar procedures. IVC in rabbits revealed consistent, stable pachymetric changes, without significant inflammation or corneal transparency degradation. Transcleral photodisruption was evaluated as a noninvasive method for creating partial thickness scleral channels to reduce elevated intraocular pressure associated with glaucoma. Photodisruption at the internal scleral surface was demonstrated by focusing through tissue in vitro without collateral damage. Femtosecond photodisruptions nucleated ultrasonically driven cavitation to demonstrate non-invasive destruction of in vitro lens tissue. We conclude that femtosecond lasers may enable practical novel ophthalmic procedures, offering advantages over current techniques.

  12. Femtosecond laser corneal refractive surgery

    NASA Astrophysics Data System (ADS)

    Kurtz, Ron M.; Spooner, Greg J. R.; Sletten, Karin R.; Yen, Kimberly G.; Sayegh, Samir I.; Loesel, Frieder H.; Horvath, Christopher; Liu, HsiaoHua; Elner, Victor; Cabrera, Delia; Muenier, Marie-Helene; Sacks, Zachary S.; Juhasz, Tibor

    1999-06-01

    We evaluated the efficacy, safety, and stability of femtosecond laser intrastromal refractive procedures in ex vivo and in vivo models. When compared with longer pulsewidth nanosecond or picosecond laser pulses, femtosecond laser-tissue interactions are characterized by significantly smaller and more deterministic photodisruptive energy thresholds, as well as reduced shock waves and smaller cavitation bubbles. We utilized a highly reliable, all-solid-state femtosecond laser system for all studies to demonstrate clinical practicality. Contiguous tissue effects were achieved by scanning a 5 μm focused laser spot below the corneal surface at pulse energies of approximately 2 - 4 microjoules. A variety of scanning patterns was used to perform three prototype procedures in animal eyes; corneal flap cutting, keratomileusis, and intrastromal vision correction. Superior dissection and surface quality results were obtained for lamellar procedures (corneal flap cutting and keratomileusis). Preliminary in vivo evaluation of intrastromal vision correction in a rabbit model revealed consistent and stable pachymetry changes, without significant inflammation or loss of corneal transparency. We conclude that femtosecond laser technology may be able to perform a variety of corneal refractive procedures with high precision, offering advantages over current mechanical and laser devices and techniques.

  13. Influence of Yb3+ concentration on the upconversion luminescence of oxyfluoride material doped with Er3+

    NASA Astrophysics Data System (ADS)

    Zhao, Suling; Xu, Zheng; Wang, Lihui; Wageh, S.

    2010-02-01

    In this paper, a new upconversion luminescent material co-doped with Erbium and Ytterbium is reported. The upconversion luminescence transition routes and related properties are studied. The results show that the absorption and emission intensities under excitation of 980 nm laser increase with the increase of the Yb3+ concentration. The red emission is stronger than the green emission. The energy transfer process plays an important role in the upconversion mechanism.

  14. Observation of bistable upconversion emission in Tm,Yb codoped yttria nanocrystal

    NASA Astrophysics Data System (ADS)

    Li, L.; Li, H.; Zhang, X. L.; Peng, Y. F.; Nie, M.; Jiang, B.; Zhang, X. W.; Li, R. M.

    2010-11-01

    Nonlinear upconversion emission properties in Tm and Yb codoped yttria nanocrystal have been studied under 973 nm laser excitation. Intrinsic bistability and hysteresis have been observed for the bright blue upconversion luminescence of Tm3+ ions at room temperature. The mechanism of the Tm3+ bistable emission is mainly related to laser-induced local thermal effects which cause the enhancement of sequential multi-photon energy transfer upconversion of Yb3+-Tm3+ pairs.

  15. Enhancement of femtosecond laser-induced nucleation of protein in a gel solution

    NASA Astrophysics Data System (ADS)

    Murai, Ryota; Yoshikawa, Hiroshi Y.; Takahashi, Yoshinori; Maruyama, Mihoko; Sugiyama, Shigeru; Sazaki, Gen; Adachi, Hiroaki; Takano, Kazufumi; Matsumura, Hiroyoshi; Murakami, Satoshi; Inoue, Tsuyoshi; Mori, Yusuke

    2010-01-01

    We found that the use of a gel solution with agarose enhanced femtosecond laser-induced nucleation and produced hen egg white lysozyme crystals at three to five times lower supersaturation than those by the femtosecond laser or agarose alone. The fast fluorescence imaging of the protein in the gel solution revealed that cavitation bubbles created high-concentration regions at the focal point, which could be the trigger for protein nucleation. The lower diffusions of protein molecules in agarose gel retained the high-concentration regions for a longer time, and facilitated the nucleation.

  16. Plastic optofluidic chip fabricated by femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Martínez Vázquez, R.; Eaton, S. M.; Cerullo, G.; Ramponi, R.; Osellame, R.

    2012-03-01

    We have fabricated entirely by femtosecond micromachining a plastic optofluidic chip with integrated microfluidics and optical excitation/detection. First a microfluidic channel and two fiber grooves were ablated on one surface of the PMMA substrate. In order to collect and focus the fluorescence signal onto a detector, two binary Fresnel lenses were micromachined on the back surface of the substrate. The operatio of the integrated optofluidic chip was demonstrated by filling the channel with different Rhodamine 6G solution, and a limit of detection of 50 nM was achieved.

  17. Dual-Mode Luminescent Nanopaper Based on Ultrathin g-C3N4 Nanosheets Grafted with Rare-Earth Upconversion Nanoparticles.

    PubMed

    Zhao, Yafei; Wei, Ruoyan; Feng, Xin; Sun, Lining; Liu, Panpan; Su, Yongxiang; Shi, Liyi

    2016-08-24

    Ultrathin graphite-like carbon nitride (g-C3N4) nanosheets have attracted considerable attention due to the enhanced intrinsic photoabsorption and photoresponse with respect to bulk g-C3N4. For the first time, a dual-mode of down- and upconversion luminescent g-C3N4 nanopaper with high optical transparency and mechanical robustness was successfully fabricated through a simple thermal evaporation process using chitosan as a green cross-linking agent. The dual-mode of down- and upconversion fluorescence emission originated from the amino terminated ultrathin g-C3N4 nanosheets functionalized with carboxylic acid modified multicolored rare-earth upconversion nanoparticles (cit-UCNPs) via EDC/NHS coupling chemistry. The homogeneously distributed cit-UCNPs@g-C3N4 nanoconjugates with excellent hydrophilicity displayed good film-forming ability and structural integrity; thus, the photoluminescence of each ingredient was substantially maintained. Results indicated that the freestanding chitosan cross-linked cit-UCNPs@g-C3N4 luminescent nanopaper possessed high transmittance, excellent mechanical properties, and remarkable dual-mode emission. The smart design of high performance luminescent nanopaper based on ultrathin g-C3N4 nanosheets grafted with multicolored UCNPs offers a potential strategy to immobilize other multifunctional luminescent materials for easily recognizable and hardly replicable anticounterfeiting fields.

  18. Structural morphology, upconversion luminescence and optical thermometric sensing behavior of Y2O3:Er(3+)/Yb(3+) nano-crystalline phosphor.

    PubMed

    Joshi, C; Dwivedi, A; Rai, S B

    2014-08-14

    Infrared-to-visible upconverting rare earths Er(3+)/Yb(3+) co-doped Y2O3 nano-crystalline phosphor samples have been prepared by solution combustion method followed by post-heat treatment at higher temperatures. A slight increase in average crystallite size has been found on calcinations verified by X-ray analysis. Transmission electron microscopy (TEM) confirms the nano-crystalline nature of the as-prepared and calcinated samples. Fourier transform infrared (FTIR) analysis shows the structural changes in as-prepared and calcinated samples. Upconversion and downconversion emission recorded using 976 and 532 nm laser sources clearly demonstrates a better luminescence properties in the calcinated samples as compared to as-prepared sample. Upconversion emission has been quantified in terms of standard chromaticity diagram (CIE) showing a shift in overall upconversion emission of as-prepared and calcinated samples. Temperature sensing behaviour of this material has also been investigated by measurement of fluorescence intensity ratio (FIR) of various signals in green emission in the temperature range of 315 to 555 K under 976 nm laser excitation. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Synthesis and upconversion luminescence properties of YF3:Yb3+/Er3+ hollow nanofibers derived from Y2O3:Yb3+/Er3+ hollow nanofibers

    NASA Astrophysics Data System (ADS)

    Li, Dan; Dong, Xiangting; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

    2013-06-01

    YF3:Yb3+/Er3+ hollow nanofibers were successfully fabricated via fluorination of the relevant Y2O3:Yb3+/Er3+ hollow nanofibers which were obtained by calcining the electrospun PVP/[Y(NO3)3 + Yb(NO3)3 + Er(NO3)3] composite nanofibers. The morphology and properties of the products were investigated in detail by X-ray diffraction, scanning electron microscope, transmission electron microscope, and fluorescence spectrometer. YF3:Yb3+/Er3+ hollow nanofibers were pure orthorhombic phase with space group Pnma and were hollow-centered structure with mean diameter of 174 ± 22 nm, and YF3:Yb3+/Er3+ hollow nanofibers are composed of nanoparticles with size in the range of 30-60 nm. Upconversion emission spectrum analysis manifested that YF3:Yb3+/Er3+ hollow nanofibers emitted strong green and weak red upconversion emissions centering at 523, 545, and 654 nm, respectively. The green and red emissions were, respectively, originated from 2H11/2/4S3/2 → 4I15/2 and 4F9/2 → 4Il5/2 energy levels transitions of the Er3+ ions. Moreover, the emitting colors of YF3:Yb3+/Er3+ hollow nanofibers were located in the green region in CIE chromaticity coordinates diagram. This preparation technique could be applied to prepare other rare earth fluoride upconversion luminescence hollow nanofibers.

  20. Different dynamics of ultraviolet upconversion in Tm3+:ZBLAN glass under blue laser excitation

    NASA Astrophysics Data System (ADS)

    Yang, Haigui; Gao, Jinsong

    2013-10-01

    Ultraviolet upconversion luminescence around 292 nm, 350 nm and 363 nm in Tm3+:ZBLAN glass was observed clearly by pulsed excitation at 464 nm. Upconversion dynamics was discussed in detail by an analysis of the measured intensity dependence, decay curves and excitation spectra of upconversion luminescence, from which it was clarified that upconversion luminescence around 292 nm and 350 nm from 1I6 level was attributed to excited state absorption, while that around 363 nm from 1D2 level was attributed to energy transfer process.

  1. Comprehensive studies on an overall proton transfer cycle of the ortho-green fluorescent protein chromophore.

    PubMed

    Hsieh, Cheng-Chih; Chou, Pi-Tai; Shih, Chun-Wei; Chuang, Wei-Ti; Chung, Min-Wen; Lee, Junghwa; Joo, Taiha

    2011-03-09

    Initiated by excited-state intramolecular proton transfer (ESIPT) reaction, an overall reaction cycle of 4-(2-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (o-HBDI), an analogue of the core chromophore of the green fluorescent protein (GFP), has been investigated. In contrast to the native GFP core, 4-(4-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (p-HBDI), which requires hydrogen-bonding relay to accomplish proton transfer in vivo, o-HBDI possesses a seven-membered-ring intramolecular hydrogen bond and thus provides an ideal system for mimicking an intrinsic proton-transfer reaction. Upon excitation, ESIPT takes place in o-HBDI, resulting in a ∼600 nm proton-transfer tautomer emission. The o-HBDI tautomer emission, resolved by fluorescence upconversion, is comprised of an instantaneous rise to a few hundred femtosecond oscillation in the early relaxation stage. Frequency analysis derived from ultrashort pulse gives two low-frequency vibrations at 115 and 236 cm(-1), corresponding to skeletal deformation motions associated with the hydrogen bond. The results further conclude that ESIPT in o-HBDI is essentially triggered by low-frequency motions and may be barrierless along the reaction coordinate. Femtosecond UV/vis transient absorption spectra also provide supplementary evidence for the structural evolution during the reaction. In CH(3)CN, an instant rise of a 530 nm transient is resolved, which then undergoes 7.8 ps decay, accompanied by the growth of a rather long-lived 580 nm transient species. It is thus concluded that following ESIPT the cis-proton transfer isomer undergoes cis-trans-isomerization. The results of viscosity-dependent dynamics are in favor of the one-bond-flip mechanism, which is in contrast to the volume-conserving isomerization behavior for cis-stilbene and p-HBDI. Further confirmation is given by the picosecond-femtosecond transient IR absorption spectra, where several new and long-lived IR bands in the range of 1400

  2. Application of femtosecond-laser induced nanostructures in optical memory.

    PubMed

    Shimotsuma, Yasuhiko; Sakakura, Masaaki; Miura, Kiyotaka; Qiu, Jiarong; Kazansky, Peter G; Fujita, Koji; Hirao, Kazuyuki

    2007-01-01

    The femtosecond laser induced micro- and nanostructures for the application to the three-dimensional optical data storage are investigated. We have observed the increase of refractive index due to local densification and atomic defect generation, and demonstrated the real time observation of photothermal effect after the femtosecond laser irradiation inside a glass by the transient lens (TrL) method. The TrL signal showed a damped oscillation with about an 800 ps period. The essential feature of the oscillation can be reproduced by the pressure wave creation and propagation to the outward direction from the irradiated region. The simulation based on elastodynamics has shown that a large thermoelastic stress is relaxed by the generation of the pressure wave. In the case of soda-lime glass, the velocity of the pressure wave is almost same as the longitudinal sound velocity at room temperature (5.8 microm/ns). We have also observed the localized photo-reduction of Sm3+ to Sm2+ inside a transparent and colorless Sm(3+)-doped borate glass. Photoluminescence spectra showed that some the Sm3+ ions in the focal spot within the glass sample were reduced to Sm2+ ions after femtosecond laser irradiation. A photo-reduction bit of 200 nm in three-dimensions can be recorded with a femtosecond laser and readout clearly by detecting the fluorescence excited by Ar+ laser (lambda = 488 nm). A photo-reduction bit can be also erased by photo-oxidation with a cw Ar+ laser (lambda = 514.5 nm). Since photo-reduction bits can be spaced 150 nm apart in a layer within glass, a memory capacity of as high as 1 Tbit can be achieved in a glass piece with dimensions of 10 mm x 10 mm x 1 mm. We have also demonstrated the first observation of the polarization-dependent periodic nanostructure formation by the interference between femtosecond laser light and electron acoustic waves. The observed nanostructures are the smallest embedded structures ever created by light. The period of self

  3. Two-photon excitation of dyes in a polymer matrix by femtosecond pulses from a Ti:sapphire laser

    SciTech Connect

    Meshalkin, Yu P; Myachin, A Yu; Bakhareva, S S; Svetlichnyi, Valerii A; Kopylova, T N; Reznichenko, A V; Dolotov, S M; Ponomarenko, E P

    2003-09-30

    Two-photon fluorescence was observed for 18 organic dyes in a polymethyl methacrylate (PMMA) matrix excited by a femtosecond Ti:sapphire laser. The product of the cross section for two-photon absorption by the quantum yield of fluorescence (two-photon fluorescence cross section) is estimated by comparing it with fluorescence of Rhodamine 6G in ethanol. Using this parameter, dyes are selected that exhibit the most intense fluorescence in PMMA and their concentrations in PMMA are optimised. Coumarin and rhodamine dyes in polymer matrices are proposed for using as visualisers of femtosecond radiation of a Ti:sapphire laser and as detectors in self-triggering systems. (active media. lasers)

  4. Synthesis of Gd2O3:Ho3+/Yb3+ upconversion nanoparticles for latent fingermark detection on difficult surfaces

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Tiwari, S. P.; Singh, A. K.; Kumar, K.

    2016-07-01

    Infrared to visible upconversion fluorescent nanoparticles of Gd2O3 codoped with Ho3+/Yb3+ ions are synthesized via thermal decomposition process. The X-ray diffraction analysis of as-synthesized nanoparticles and annealed sample at 1000 °C has shown body-centered cubic phase of Gd2O3. The synthesized phosphor has shown intense green emission upon 980-nm excitation. High-contrast latent fingermarks on some difficult semi-porous and non-porous surfaces under 980-nm diode laser excitation were developed through powder dusting and colloidal solution spraying techniques and the results are compared with the commercial green luminescent fingermark powder. The latent fingermarks were developed on transparent (biological glass slides), single-color (aluminum foil) and multicolor (plywood, plastic bottle and book cover page) background surfaces. The present study depicts that the upconversion-based latent fingermarks detection using Gd2O3:Ho3+/Yb3+ phosphor material is suitable over the other conventional powders and has potential for practical applications in forensic science.

  5. NIR to NIR upconversion in KYb2F7: RE3+ (RE = Tm, Er) nanoparticles for biological imaging

    NASA Astrophysics Data System (ADS)

    Pedraza, F.; Yust, B.; Tsin, A.; Sardar, D.

    2014-03-01

    Until recently, many contrast agents widely used in biological imaging have absorbed and emitted in the visible region, limiting their usefulness for deeper tissue imaging. In order to push the boundaries of deep tissue imaging with non-ionizing radiation, contrast agents in the near infrared (NIR) regime, which is not strongly absorbed or scattered by most tissues, are being sought after. Upconverting nanoparticles (UCNPs) are attractive candidates since their upconversion emission is tunable with a very narrow bandwidth and they do not photobleach or blink. The upconversion produced by the nanoparticles can be tailored for NIR to NIR by carefully choosing the lanthanide dopants and dopant ratios such as KYb2F7: RE3+ (RE = Tm, Er). Spectroscopic characterization was done by analyzing absorption, fluorescence, and quantum yield data. In order to study the toxicity of the nanoparticles Monkey Retinal Endothelial Cells (MREC) were cultivated in 24 well plates and then treated with nanoparticles at different concentrations in triplicate to obtain the optimal concentration for in vivo experiments. It will be shown that these UCNPs do not elicit a strong toxic response such as quantum dots and some noble metal nanoparticles. 3-D optical slices of nanoparticle treated fibroblast cells were imaged using a confocal microscope where the nucleus and cytoplasm were stained with DAPI and Alexa Fluor respectively. These results presented support the initial assumption, which suggests that KYb2F7: RE3+ would be excellent candidates for NIR contrast agents.

  6. Intense ultraviolet and blue upconversion emissions in Yb 3+-Tm 3+ codoped stoichiometric Y 7O 6F 9 powder

    NASA Astrophysics Data System (ADS)

    Ma, Mo; Xu, Changfu; Yang, Liwen; Ren, Guozhong; Lin, Jianguo; Yang, Qibin

    2011-09-01

    Stoichiometric Y 7O 6F 9 powder codoped with Yb 3+-Tm 3+ was synthesized via co-precipitation and subsequent calcining route. The results of X-ray diffraction and transmission electron microscopy reveal that when the calcining temperature is beyond 800 °C, orthorhombic YF 3 nanoparticles can be completely oxidized into orthorhombic Y 7O 6F 9 powder. Under the excitation of a 980 nm laser, Y 7O 6F 9 powder exhibits multicolor UC emission in regions spanning the UV to the NIR. In addition, the upconversion emission intensities of YF 3, Y 7O 6F 9 and Y 2O 3 powders were compared under the same dopant condition (Yb/Tm=5/0.5 mol%). The low phonon energy revealed by Raman spectra helped to understand the high efficient upconversion emission of Y 7O 6F 9 and the main phonon vibration of Y 7O 6F 9 lies at 472 cm -1, which is far lower that of Y 2O 3 (at 708 cm -1). Our results indicate that orthorhombic rare earth ions doped Y 7O 6F 9 is an efficient matrix for UV and blue UC emission, and has potential applications in color displays, anti-counterfeiting and multicolor fluorescent labels.

  7. One-pot template-free synthesis of NaYF4 upconversion hollow nanospheres for bioimaging and drug delivery.

    PubMed

    Tian, Gan; Duan, Longsheng; Zhang, Xiao; Yin, Wenyan; Yan, Liang; Zhou, Liangjun; Liu, Xiaodong; Zheng, Xiaopeng; Li, Jinxia; Gu, Zhanjun; Zhao, Yuliang

    2014-06-01

    Hollow-structured nanomaterials with fluorescent properties are extremely attractive for image-guided cancer therapy. In this paper, sub-100 nm and hydrophilic NaYF4 upconversion (UC) hollow nanospheres (HNSs) with multicolor UC luminescence and drug-delivery properties were successfully prepared by a facile one-pot template-free hydrothermal route using polyetherimide (PEI) polymer as the stabilizing agent. XRD, SEM, TEM, and N2-adsorption/desorption were used to characterize the as-obtained products. The growth mechanism of the HNSs has been systematically investigated on the basis of the Ostwald ripening. Under 980 nm excitation, UC emissions of HNSs can be tuned by a simple change of the concentration or combination of various upconverters. As a result, the PEI-coated HNSs could be used as efficient probes for in vitro upconversion luminescence (UCL) cell imaging. Furthermore, a doxorubicin storage/release behavior and cancer-cell-killing ability investigation reveal that the product has the potential to be a drug carrier for cancer therapy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. A femtosecond stimulated Raman loss (fSRL) microscope for highly sensitive bond-selective imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Delong; Slipchenko, Mikhail N.; Yue, Shuhua; Li, Junjie; Cheng, Ji-Xin

    2011-03-01

    We demonstrate nonlinear vibrational imaging of isolated Raman bands by detecting femtosecond pulse stimulated Raman loss. Femtosecond pulse excitation produces a stimulated Raman loss signal that is 12 times larger than what picosecond pulse excitation produces. The strong signal allowed real-time, bond-selective imaging of deuterated palmitic acid-d31 inside live cells, and 3D sectioning of fat storage in live C. elegans. With the high peak power provided by femtosecond pulses, this system is highly compatible with other nonlinear optical modalities such as two-photon excited fluorescence. With most of the excitation power contributed by the Stokes beam in the 1.0 - 1.2 μm wavelength range, photodamage of biological samples was not observed.

  9. Processes Affecting the Variability of Fluorescence Signals from Benthic Targets in Shallow Waters

    DTIC Science & Technology

    1998-09-30

    were completed to study fluorescence lifetimes from model targets such as zooxanthellae cultivated from Aiptasia, Porites, Montipora, Cassiopea, and...analysis of zooxanthellae isolated from coral samples. We examined fluorescence lifetimes from benthic targets using femtosecond laser based Single...a temporal resolution 5 ps. The laser set-up was employed for laboratory studies of fluorescence lifetimes from model targets such as zooxanthellae

  10. Oxyfluoroborate host glass for upconversion application: phonon energy calculation

    NASA Astrophysics Data System (ADS)

    Abdel-Baki, Manal; El-Diasty, Fouad

    2016-04-01

    Reducing the glass phonon energy is an essential procedure to achieve high efficient radiative upconversion process. The degree of covalence of chemical bonds is responsible for the high oscillator strength of intracenter transitions in rare-earth ions. So, conversion covalent to ionic glass character is proposed as a structure-sensitive criterion that controls the phonon energy of the glasses. A series of oxyfluoro aluminum-borate host glasses used for upconversion application is prepared by the conventional melt-quenching technique. Through lithium oxide substitution by lithium fluoride, the ionic-covalent property of Li+ ion successes to regulate the band gap energies of the studied glasses. Furthermore, a new method to determine the glass phonon energy is offered.

  11. Subwavelength imaging through ion-beam-induced upconversion

    PubMed Central

    Mi, Zhaohong; Zhang, Yuhai; Vanga, Sudheer Kumar; Chen, Ce-Belle; Tan, Hong Qi; Watt, Frank; Liu, Xiaogang; Bettiol, Andrew A.

    2015-01-01

    The combination of an optical microscope and a luminescent probe plays a pivotal role in biological imaging because it allows for probing subcellular structures. However, the optical resolutions are largely constrained by Abbe's diffraction limit, and the common dye probes often suffer from photobleaching. Here we present a new method for subwavelength imaging by combining lanthanide-doped upconversion nanocrystals with the ionoluminescence imaging technique. We experimentally observed that the ion beam can be used as a new form of excitation source to induce photon upconversion in lanthanide-doped nanocrystals. This approach enables luminescence imaging and simultaneous mapping of cellular structures with a spatial resolution of sub-30 nm. PMID:26560858

  12. Functionalized Upconversion Nanoparticles: Versatile Nanoplatforms for Translational Research

    PubMed Central

    Chen, Feng; Bu, Wenbo; Cai, Weibo; Shi, Jianlin

    2013-01-01

    The design, application, and translation of targeted multimodality molecular imaging probes based on nanotechnology has attracted increasing attentions during the last decade and will continue to play vital roles in cancer diagnosis and personalized medicine. With the growing awareness of drawbacks of traditional organic dyes and quantum dots, biocompatible lanthanide ion doped upconversion nanoparticles have emerged as promising candidates for clinically translatable imaging probes, owing to their unique features that are suitable for future targeted multimodal imaging in living subjects. In this review, we summarized the recent advances in the field of functionalized upconversion nanoparticles (f-UCNP) for biological imaging and therapy in vivo, and discussed the future research directions, obstacles ahead, and the potential use of f-UCNP in translational research. PMID:24206131

  13. Upconversion imaging using an all-fiber supercontinuum source.

    PubMed

    Huot, Laurent; Moselund, Peter Morten; Tidemand-Lichtenberg, Peter; Leick, Lasse; Pedersen, Christian

    2016-06-01

    In this Letter, the first demonstration, to the best of our knowledge, of pulsed upconversion imaging using supercontinuum light is presented. A mid-infrared (IR) imaging system was built by combining a mid-IR supercontinuum source emitting between 1.8 and 2.6 μm with upconversion detection. The infrared signal is used to probe a sample and mixed with a synchronized 1550 nm laser pulse inside a lithium niobate (LiNbO3) crystal. The signal is thus upconverted to the 860-970 nm range and acquired on a standard silicon CCD array at a rate of 22 frames per second. In our implementation, spatial features in the sample plane as small as 55 μm could be resolved.

  14. Time-resolved up-conversion of entangled photon pairs.

    PubMed

    O'Donnell, Kevin A; U'Ren, Alfred B

    2009-09-18

    In the process of spontaneous parametric down-conversion, photons from a pump field are converted to signal and idler photon pairs in a nonlinear crystal. The reversed process, or up-conversion of these pairs back to single photons in a second crystal, is also possible. Here, we present experimental measurements of the up-conversion rate with a controlled time delay introduced between the signal and idler photons. As a function of delay, this rate presents a full width at half maximum of 27.9 fs under our experimental conditions, and we further demonstrate that group delay dispersion of the photon pairs broadens this width. These observations are in close agreement with our calculations, thus demonstrating an ultrafast, nonclassical correlation between the signal and idler waves.

  15. Femtosecond laser in laser in situ keratomileusis

    PubMed Central

    Salomão, Marcella Q.; Wilson, Steven E.

    2014-01-01

    Flap creation is a critical step in laser in situ keratomileusis (LASIK). Efforts to improve the safety and predictability of the lamellar incision have fostered the development of femtosecond lasers. Several advantages of the femtosecond laser over mechanical microkeratomes have been reported in LASIK surgery. In this article, we review common considerations in management and complications of this step in femtosecond laser–LASIK and concentrate primarily on the IntraLase laser because most published studies relate to this instrument. PMID:20494777

  16. All-inorganic colloidal upconversion quantum dots (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Oron, Dan; Teitelboim, Ayelet

    2017-02-01

    Upconversion (UC) is a nonlinear process in which two, or more, long wavelength photons are converted to a shorter wavelength photon. This process is based on sequential absorption of two or more photons, involving metastable, long lived intermediate energy states, thus is not restricted to ultrashort pulsed excitation. Hence, requirements for UC processes are long lived excited states, a ladder like arrangement of energy levels and a mechanism inhibiting cooling of the hot charge carrier. UC holds great promise for bioimaging, enabling to perform multiphoton imaging in scattering specimen at very low powers. Rare-earth-doped nanocrystals, the most commonly used ones for UC, typically require a minimal particle diameter of several tens of nanometers and have a limited action spectrum. Here, we present a novel luminescence upconversion nano-system based on colloidal semiconductor double quantum dots, consisting of a NIR-absorbing component and a visible emitting component separated by a tunneling barrier in a spherical onion-like geometry. These dual near-infrared and visible core/shell/shell PbSe/CdSe/CdS nanocrystals are shown to efficiently upconvert a broad range of NIR wavelengths up to 1.2 microns to visible emission at room temperature, covering a spectral range where there are practically no alternative upconversion systems. The particle diameter is less than ten nanometers, and the synthesis enables versatility and tunability of both the visible emission color and the NIR absorption edge. The physical mechanism for upconversion in this type of structures, as well as potential advances and extensions on this system will be discussed.

  17. Dental optical tomography with upconversion nanoparticles—a feasibility study

    NASA Astrophysics Data System (ADS)

    Long, Feixiao; Intes, Xavier

    2017-06-01

    Upconversion nanoparticles (UCNPs) have the unique ability to emit multiple colors upon excitation by near-infrared (NIR) light. Herein, we investigate the potential use of UCNPs as contrast agents for dental optical tomography, with a focus on monitoring the status of fillings after dental restoration. The potential of performing tomographic imaging using UCNP emission of visible or NIR light is established. This in silico and ex vivo study paves the way toward employing UCNPs as theranostic agents for dental applications.

  18. Synthesis and upconversion luminescence of NaYF4:Yb, Tm/TiO2 core/shell nanoparticles with controllable shell thickness.

    PubMed

    Zhang, Daisheng; Zhao, Dan; Zheng, Kezhi; Liu, Ning; Qin, Weiping

    2011-11-01

    NaYF4:Yb, Tm/TiO2 core/shell nanoparticles were synthesized by a two-step method. First, the NaYF4:Yb, Tm nanocrystals were prepared using solvothermal technology; then, TiO2 shells were deposited on the nanocrystals by the hydrolysis of titanium ethoxide (TEOT) to form core/shell structures. By controlling the reaction time, we can adjust the thickness of TiO2 shell and thereby the weight percentage of TiO2 in the core/shell nanoparticles. The effect of shell thickness on the upconversion fluorescence of NaYF4:Yb, Tm nanocrystals was investigated in detail.

  19. Femtosecond Photon-Counting Receiver

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.; Rambo, Timothy M.; Yang, Guangning; Lu, Wei; Numata, Kenji

    2016-01-01

    An optical correlation receiver is described that provides ultra-precise distance and/or time-pulse-width measurements even for weak (single photons) and short (femtosecond) optical signals. A new type of optical correlation receiver uses a fourth-order (intensity) interferometer to provide micron distance measurements even for weak (single photons) and short (femtosecond) optical signals. The optical correlator uses a low-noise-integrating detector that can resolve photon number. The correlation (range as a function of path delay) is calculated from the variance of the photon number of the difference of the optical signals on the two detectors. Our preliminary proof-of principle data (using a short-pulse diode laser transmitter) demonstrates tens of microns precision.

  20. Femtosecond single-electron diffraction

    PubMed Central

    Lahme, S.; Kealhofer, C.; Krausz, F.; Baum, P.

    2014-01-01

    Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration. PMID:26798778

  1. Femtosecond photon-counting receiver

    NASA Astrophysics Data System (ADS)

    Krainak, Michael A.; Rambo, Timothy M.; Yang, Guangning; Lu, Wei; Numata, Kenji

    2016-05-01

    An optical correlation receiver is described that provides ultra-precise distance and/or time/pulsewidth measurements even for weak (single photons) and short (femtosecond) optical signals. A new type of optical correlation receiver uses a fourth-order (intensity) interferometer to provide micron distance measurements even for weak (single photons) and short (femtosecond) optical signals. The optical correlator uses a low-noise-integrating detector that can resolve photon number. The correlation (range as a function of path delay) is calculated from the variance of the photon number of the difference of the optical signals on the two detectors. Our preliminary proof-of principle data (using a short-pulse diode laser transmitter) demonstrates tens of microns precision.

  2. Femtosecond Photon-Counting Receiver

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.; Rambo, Timothy M.; Yang, Guangning; Lu, Wei; Numata, Kenji

    2016-01-01

    An optical correlation receiver is described that provides ultra-precise distance and/or time/pulse-width measurements even for weak (single photons) and short (femtosecond) optical signals. A new type of optical correlation receiver uses a fourth-order (intensity) interferometer to provide micron distance measurements even for weak (single photons) and short (femtosecond) optical signals. The optical correlator uses a low-noise-integrating detector that can resolve photon number. The correlation (range as a function of path delay) is calculated from the variance of the photon number of the difference of the optical signals on the two detectors. Our preliminary proof-of principle data (using a short-pulse diode laser transmitter) demonstrates tens of microns precision.

  3. Excitonic luminescence upconversion in a two-dimensional semiconductor

    SciTech Connect

    Jones, Aaron M.; Yu, Hongyi; Schaibley, John R.; Yan, Jiaqiang; Mandrus, David G.; Taniguchi, Takashi; Watanabe, Kenji; Dery, Hanan; Yao, Wang; Xu, Xiaodong

    2015-12-21

    Photon upconversion is an elementary light-matter interaction process in which an absorbed photon is re-emitted at higher frequency after extracting energy from the medium. Furthermore, this phenomenon lies at the heart of optical refrigeration in solids(1), where upconversion relies on anti-Stokes processes enabled either by rare-earth impurities(2) or exciton-phonon coupling(3). We demonstrate a luminescence upconversion process from a negatively charged exciton to a neutral exciton resonance in monolayer WSe2, producing spontaneous anti-Stokes emission with an energy gain of 30 meV. Polarization-resolved measurements find this process to be valley selective, unique to monolayer semiconductors(4). Since the charged exciton binding energy(5) closely matches the 31 meV A(1)' optical phonon(6-9), we ascribe the spontaneous excitonic anti-Stokes to doubly resonant Raman scattering, where the incident and outgoing photons are in resonance with the charged and neutral excitons, respectively. Additionally, we resolve a charged exciton doublet with a 7 meV splitting, probably induced by exchange interactions, and show that anti-Stokes scattering is efficient only when exciting the doublet peak resonant with the phonon, further confirming the excitonic doubly resonant picture.

  4. Excitonic luminescence upconversion in a two-dimensional semiconductor

    DOE PAGES

    Jones, Aaron M.; Yu, Hongyi; Schaibley, John R.; ...

    2015-12-21

    Photon upconversion is an elementary light-matter interaction process in which an absorbed photon is re-emitted at higher frequency after extracting energy from the medium. Furthermore, this phenomenon lies at the heart of optical refrigeration in solids(1), where upconversion relies on anti-Stokes processes enabled either by rare-earth impurities(2) or exciton-phonon coupling(3). We demonstrate a luminescence upconversion process from a negatively charged exciton to a neutral exciton resonance in monolayer WSe2, producing spontaneous anti-Stokes emission with an energy gain of 30 meV. Polarization-resolved measurements find this process to be valley selective, unique to monolayer semiconductors(4). Since the charged exciton binding energy(5) closelymore » matches the 31 meV A(1)' optical phonon(6-9), we ascribe the spontaneous excitonic anti-Stokes to doubly resonant Raman scattering, where the incident and outgoing photons are in resonance with the charged and neutral excitons, respectively. Additionally, we resolve a charged exciton doublet with a 7 meV splitting, probably induced by exchange interactions, and show that anti-Stokes scattering is efficient only when exciting the doublet peak resonant with the phonon, further confirming the excitonic doubly resonant picture.« less

  5. Confining energy migration in upconversion nanoparticles towards deep ultraviolet lasing

    PubMed Central

    Chen, Xian; Jin, Limin; Kong, Wei; Sun, Tianying; Zhang, Wenfei; Liu, Xinhong; Fan, Jun; Yu, Siu Fung; Wang, Feng

    2016-01-01

    Manipulating particle size is a powerful means of creating unprecedented optical properties in metals and semiconductors. Here we report an insulator system composed of NaYbF4:Tm in which size effect can be harnessed to enhance multiphoton upconversion. Our mechanistic investigations suggest that the phenomenon stems from spatial confinement of energy migration in nanosized structures. We show that confining energy migration constitutes a general and versatile strategy to manipulating multiphoton upconversion, demonstrating an efficient five-photon upconversion emission of Tm3+ in a stoichiometric Yb lattice without suffering from concentration quenching. The high emission intensity is unambiguously substantiated by realizing room-temperature lasing emission at around 311 nm after 980-nm pumping, recording an optical gain two orders of magnitude larger than that of a conventional Yb/Tm-based system operating at 650 nm. Our findings thus highlight the viability of realizing diode-pumped lasing in deep ultraviolet regime for various practical applications. PMID:26739352

  6. Upconversion imaging using short-wave infrared picosecond pulses.

    PubMed

    Mathez, Morgan; Rodrigo, Peter John; Tidemand-Lichtenberg, Peter; Pedersen, Christian

    2017-02-01

    To the best of our knowledge, we present the first demonstration of short-wavelength infrared image upconversion that employs intense picosecond signal and pump beams. We use a fiber laser that emits a signal beam at 1877 nm and a pump beam at 1550 nm-both with a pulse width of 1 ps and a pulse repetition rate of 21.7 MHz. Due to synchronization of high peak-power pulses, efficient upconversion is achieved in a single-pass setup that employs a bulk lithium niobate crystal. Optimizing the temporal overlap of the pulses for high upconversion efficiency enables us to exploit a relatively large pump beam diameter to upconvert a wider range of signal spatial frequencies in the crystal. The 1877 nm signal is converted into 849 nm-enabling an image to be acquired by a silicon CCD camera. The measured size of the smallest resolvable element of this imaging system is consistent with the value predicted by an improved model that considers the combined image blurring effect due to finite pump beam size, thick nonlinear crystal, and polychromatic infrared illumination.

  7. Structural characterizations and intense green upconversion emission in Yb3+, Pr3+ co-doped Y2O3 nano-phosphor.

    PubMed

    Yadav, R S; Verma, R K; Bahadur, A; Rai, S B

    2015-02-25

    We report the structural and optical properties of Yb(3+), Pr(3+) co-doped Y2O3 nano-phosphor synthesized through solution combustion method. The structural studies reveal the nano-crystalline structure of the sample. The energy dispersive spectroscopy (EDS) measurements confirm the presence of Y, O, Pr and Yb elements in the sample. Fourier transform infrared studies show the vibrational features of the samples. The fluorescence spectra of the samples have been monitored on excitation with 976 nm and the intense green upconversion emission observed at 552 nm is due to (3)P0→(3)H5 electronic transition. The concentration of Pr(3+) ion in the sample is optimized and the fluorescence intensity is maximum at 0.08 mol% of Pr(3+). The power dependence studies reveal the involvement of two photons in the emission process. The possible mechanism of upconversion has been discussed on the basis of schematic energy level diagram. The sample annealed at higher temperature enhances the fluorescence intensity up to 8 times and this enhancement is discussed in terms of the removal of optical quenching centers. The nano-phosphor can be applicable in the field of display devices and green laser.

  8. High contrast in vivo bioimaging using multiphoton upconversion in novel rare-earth-doped fluoride upconversion nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Guanying; Yang, Chunhui; Prasad, Paras N.

    2013-02-01

    Upconversion in rare-earth ions is a sequential multiphoton process that efficiently converts two or more low-energy photons, which are generally near infrared (NIR) light, to produce anti-Stokes emission of a higher energy photon (e.g., NIR, visible, ultraviolet) using continuous-wave (cw) diode laser excitation. Here, we show the engineering of novel, efficient, and biocompatible NIRin-to-NIRout upconversion nanoparticles for biomedical imaging with both excitation and emission being within the "optical transparency window" of tissues. The small animal whole-body imaging with exceptional contrast (signal-to-noise ratio of 310) was shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles. An imaging depth as deep as 3.2-cm was successfully demonstrated using thick animal tissue (pork) under cw laser excitation at 980 nm.

  9. Cataract surgery with femtosecond lasers.

    PubMed

    Alió, Jorge L

    2011-07-01

    Cataract surgery with femtosecond lasers is approaching its practical application in ophthalmology. These lasers, working in the near infrared wavelength (1030 nm) can penetrate the transparent and even opaque tissues of the anterior segment of the eye, with limitations related to vessels and mineral opacities. Femtosecond lasers, guided by image systems can precisely outline the anatomy of the anterior segment of the eye, acting in a very precise way, performing corneal incisions, capsulorhexis, softening and breaking of the nucleus, which are essential steps in cataract surgery. In this article we summarize the four technologies available and approaching commercial application in the coming future. The main differences between the systems are based on the diagnostic imaging techniques, which might either be based on optical coherence tomography or the Scheimpflug principles. One model (the Technolas Femtec 520 F custom lens, 20/10 Perfect Vision), offers the possibility of combined use in corneal and intraocular surgery. While clinical studies are being performed with all of them, and most probably becoming available on the market during 2011 and 2012, the main problem of this emerging technology is its practical application as the increase in costs will affect their availability in the market of cataract surgery. Research is needed to confirm the practicality and the advantages of femtosecond laser cataract surgery over conventional surgery. Meanwhile, a new path for the future of cataract surgery is opening.

  10. Cornea surgery with nanojoule femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Wang, Bagui; Riemann, Iris; Kobow, Jens

    2005-04-01

    We report on a novel optical method for (i) flap-generation in LASIK procedures as well as (ii) for flap-free intrastromal refractive surgery based on nanojoule femtosecond laser pulses. The near infrared 200 fs pulses for multiphoton ablation have been provided by ultracompact turn-key MHz laser resonators. LASIK flaps and intracorneal cavities have been realized with high precision within living New Zealand rabbits using the system FemtoCutO (JenLab GmbH, Jena, Germany) at 800 nm laser wavelength. Using low-energy sub-2 nJ laser pulses, collateral damage due to photodisruptive and self-focusing effects was avoided. The laser ablation system consists of fast galvoscanners, focusing optics of high numerical aperture as well as a sensitive imaging system and provides also the possibility of 3D multiphoton imaging of fluorescent cellular organelles and SHG signals from collagen. Multiphoton tomography of the cornea was used to determine the exact intratissue beam position and to visualize intraocular post-laser effects. The wound healing process has been investigated up to 90 days after instrastromal laser ablation by histological analysis. Regeneration of damaged collagen structures and the migration of inflammation cells have been detected.

  11. Bi-Plasma Interactions on Femtosecond Time-Scales

    SciTech Connect

    Not Available

    2011-06-22

    Ultrafast THz radiation has important applications in materials science studies, such as characterizing transport properties, studying the vibrational response of materials, and in recent years, controlling materials and elucidating their response in intense electromagnetic fields. THz fields can be generated in a lab setting using various plasma-based techniques. This study seeks to examine the interaction of two plasmas in order to better understand the fundamental physics associated with femtosecond filamentation processes and to achieve more efficient THz generation in a lab setting. The intensity of fluorescence in the region of overlap was measured as a function of polarization, power, and relative time delay of the two plasma-generating laser beams. Results of time dependent intensity studies indicate strikingly similar behaviors across polarizations and power levels; a sudden intensity spike was observed at time-zero, followed by a secondary maxima and subsequent decay to the initial plasma intensity. Dependence of the intensity on the power through either beam arm was also observed. Spectral studies of the enhanced emission were also carried out. Although this physical phenomenon is still not fully understood, future studies, including further spectral analysis of the fluorescence overlap, could yield new insight into the ultrafast processes occurring at the intersection of femtosecond filaments, and would provide a better understanding of the mechanisms for enhanced THz production.

  12. Photodegradation and photocuring in the operation of a blue upconversion fiber laser

    SciTech Connect

    Qin Guanshi; Huang Shenghong; Feng Yan; Shirakawa, A.; Musha, M.; Ueda, Ken-ichi

    2005-06-15

    Photodegradation and photocuring effects were investigated in the operation of a Tm{sup 3+}-doped blue upconversion fiber laser. Our experimental results indicate that a competition between photodegradation and photocuring greatly affects the maximum output power of a blue upconversion fiber laser.

  13. Laser diode pumped 106 mW blue upconversion fiber laser

    NASA Astrophysics Data System (ADS)

    Sanders, S.; Waarts, R. G.; Mehuys, D. G.; Welch, D. F.

    1995-09-01

    A laser diode pumped Tm3+-doped ZBLAN fiber upconversion laser is demonstrated with blue output power levels up to 106 mW. Differential optical-to-optical conversion efficiencies up to 30% are measured with respect to pump power coupled into the upconversion fiber. A single spatial mode blue output beam is demonstrated, with an M2 value of 1.4.

  14. Energy up-conversion and trapping: Dynamics of 5f states of Bk sup 4+ in CeF sub 4

    SciTech Connect

    Liu, G.K.; Beitz, J.V.

    1991-01-01

    Energy transfer mechanisms of excited 5f states of Bk{sup 4+} (0.05 atom %) in CeF{sub 4} containing circa 0.95 atom % Cf{sup 4+} have been investigated at 4 K. The observed anti-Stokes fluorescence arises from both up-conversion and two-photon excitation. Nonexponential decays of Stokes fluorescence are ascribed to both excitation-excitation annihilation and site-dependent trapping processes and, therefore, are not describable by the Inokuti-Hirayama or exciton annihilation models. Based on the Forster-Dexter energy transfer theory, a new model is developed to fit the observed fluorescence decay data. 16 refs., 3 figs.

  15. IR-stimulated visible fluorescence in pink and brown diamond.

    PubMed

    Byrne, K S; Chapman, J G; Luiten, A N

    2014-03-19

    Irradiation of natural pink and brown diamond by middle-ultraviolet light (photon energy ϵ ≥ 4.1 eV ) is seen to induce anomalous fluorescence phenomena at N3 defect centres (structure N3-V). When diamonds primed in this fashion are subsequently exposed to infrared light (even with a delay of many hours), a transient burst of blue N3 fluorescence is observed. The dependence of this IR-triggered fluorescence on pump wavelength and intensity suggest that this fluorescence phenomena is intrinsically related to pink diamond photochromism. An energy transfer process between N3 defects and other defect species can account for both the UV-induced fluorescence intensity changes, and the apparent optical upconversion of IR light. From this standpoint, we consider the implications of this N3 fluorescence behaviour for the current understanding of pink diamond photochromism kinetics.

  16. Lanthanide-doped upconversion materials: emerging applications for photovoltaics and photocatalysis.

    PubMed

    Yang, Weifeng; Li, Xiyan; Chi, Dongzhi; Zhang, Hongjie; Liu, Xiaogang

    2014-12-05

    Photovoltaics and photocatalysis are two significant applications of clean and sustainable solar energy, albeit constrained by their inability to harvest the infrared spectrum of solar radiation. Lanthanide-doped materials are particularly promising in this regard, with tunable absorption in the infrared region and the ability to convert the long-wavelength excitation into shorter-wavelength light output through an upconversion process. In this review, we highlight the emerging applications of lanthanide-doped upconversion materials in the areas of photovoltaics and photocatalysis. We attempt to elucidate the fundamental physical principles that govern the energy conversion by the upconversion materials. In addition, we intend to draw attention to recent technologies in upconversion nanomaterials integrated with photovoltaic and photocatalytic devices. This review also provides a useful guide to materials synthesis and optoelectronic device fabrication based on lanthanide-doped upconversion materials.

  17. Compositional and thermal effect on upconversion luminescence of Ho 3+/Yb 3+-codoped oxyfluoride glasses

    NASA Astrophysics Data System (ADS)

    Feng, Li; Su, Qiang; Li, Yan; Zheng, Chunrui; Wang, Cheng; Du, Hongli

    2009-07-01

    The upconversion luminescence properties of Ho 3+/Yb 3+-codoped SiO 2-BaF 2-ZnF 2 glasses were investigated upon excitation with 980 nm diode laser. The visible emission bands centered at 546 and 661 nm correspond to 5F 4, 5S 2 → 5I 8 and 5F 5 → 5I 8 transitions were observed. The effect of composition and temperature on the upconversion emission intensity was examined. It was found that the upconversion emission signals decrease with increasing ZnF 2 content and temperature. The dependence of the upconversion emission intensity upon the excitation power was also examined, and the upconversion mechanisms were discussed.

  18. Effects of chloride introduction on up-conversion luminescence in Tm3+ -doped tellurite glasses.

    PubMed

    Xu, Shiqing; Yang, Zhongmin; Wang, Guonian; Zhang, Junjie; Dai, Shixun; Hu, Lili; Jiang, Zhonghong

    2004-11-01

    Blue up-conversion luminescence properties in Tm3+ -doped lead chloride tellurite glasses have been studied under 980 nm excitation. The intense blue and relatively weak red emissions centered at 476 and 649 nm corresponding to the transitions 1G4 --> 3H6 and 1G4 --> 3H4 of Tm3+, respectively, are simultaneously observed at room temperature. The effect of PbCl2 on up-conversion intensity is observed and discussed, and possible up-conversion mechanisms are evaluated. The intense blue up-conversion luminescence of Tm3+ -doped lead chloride tellurite glasses may be a potentially useful material for developing up-conversion optical devices.

  19. Infrared upconversion as a means of seeing in the dark. [based on nonlinear crystal optics

    NASA Technical Reports Server (NTRS)

    Gurski, T. R.

    1975-01-01

    A new approach to seeing in the dark is described which is based on the principles of nonlinear optics employing a crystal such as lithium iodate. A nonlinear optical device capable of producing photons at higher frequencies from lower-frequency incident light is shown to upconvert infrared light directly into visible light. The major advantages of the infrared upconversion process is that it permits the infrared signal to be detected by photon-counting devices presently available for the visible spectral region, and that it can provide sensitivity to infrared radiation without the need for cryogenic cooling of the detector used. Early works on infrared upconversion are reviewed. The development of applications is discussed as to astronomical spectroscopy and infrared image upconversion involving either angular or positional resolution elements. The demonstration of infrared upconversion in rectangular waveguides of single-crystal GaAs by Anderson et al. (1971) indicates future possibilities in upconversion by the use of integrated optics devices.

  20. A novel upconversion@polydopamine core@shell nanoparticle based aptameric biosensor for biosensing and imaging of cytochrome c inside living cells.

    PubMed

    Ma, Lina; Liu, Fuyao; Lei, Zhen; Wang, Zhenxin

    2017-01-15

    Herein, a novel upconversion@polydopamine core@shell nanoparticle (termed as UCNP@PDA NP) -based aptameric biosensor has been fabricated for the quantitative analysis of cytochrome c (Cyt c) inside living cells, which comprises an UCNP@PDA NP, acting as an internal reference and fluorescence quenching agent, and Cy3 modified aptamer enabling ratiometric quantitative Cyt c measurement. After the hybridization of Cy3 labeled aptamer with amino-terminated single DNA on the UCNP@PDA NP surface (termed as UCNP@PDA@AP), the fluorescence of Cy3 can be efficiently quenched by the PDA shell. With the spontaneous cellular uptake of UCNP@PDA@AP, the Cyt c aptamer dissociates from UCNP@PDA NP surface through formation of aptamer-Cyt c complex, resulting in concomitant activation of the Cy3 fluorescence. High amount of Cyt c leads to high fluorescence emission, enabling direct visualization/measurement of the Cyt c by fluorescence microscopy/spectroscopy. The steady upconversion luminescent (UCL) signals can be employed not only for intracellular imaging, but also as an internal reference for evaluating intracellular Cyt c amount using the ratio of fluorescence intensity of Cy3 with the UCL intensity of UCNP. The UCNP@PDA@AP shows a reasonable detection limit (20nM) and large dynamic range (50nM to 10μM, which covers the literature reported values (1-10μM) for cytosolic Cyt c in apoptotic cells) for detecting Cyt c in buffer with excellent selectivity. In addition, the UCNP@PDA@AP has been successfully used to monitor etoposide induced intracellular releasing of Cyt c, providing the possibility for cell-based screening of apoptosis-inducing drugs. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Facile and high spatial resolution ratio-metric luminescence thermal mapping in microfluidics by near infrared excited upconversion nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Cao, Wenbin; Li, Shunbo; Wen, Weijia

    2016-02-01

    A local area temperature monitor is important for precise control of chemical and biological processes in microfluidics. In this work, we developed a facile method to realize micron spatial resolution of temperature mapping in a microfluidic channel quickly and cost effectively. Based on the temperature dependent fluorescence emission of NaYF4:Yb3+, Er3+ upconversion nanoparticles (UCNPs) under near-infrared irradiation, ratio-metric imaging of UCNPs doped polydimethylsiloxane can map detailed temperature distribution in the channel. Unlike some reported strategies that utilize temperature sensitive organic dye (such as Rhodamine) to achieve thermal sensing, our method is highly chemically inert and physically stable without any performance degradation in long term operation. Moreover, this method can be easily scaled up or down, since the spatial and temperature resolution is determined by an optical imaging system. Our method supplied a simple and efficient solution for temperature mapping on a heterogeneous surface where usage of an infrared thermal camera was limited.

  2. Characterization of conjugates of NaYF4:Yb,Er,Gd upconversion nanoparticle with aluminium phthalocyanines

    NASA Astrophysics Data System (ADS)

    Watkins, Zane; Uddin, Imran; Britton, Jonathan; Nyokong, Tebello

    2017-02-01

    NaYF4:Er/Yb/Gd upconversion nanoparticles (UCNP) capped with amino groups were covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). There was a decrease in the intensity of fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to Förster resonance energy transfer (FRET). FRET efficiencies of 18% and 21% for ClAlTSPc and ClAlTCPc, respectively, were obtained. Oxygen generation by ClAlTSPc following FRET was proved.

  3. Micromachining of Silicon Carbide using femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Farsari, M.; Filippidis, G.; Zoppel, S.; Reider, G. A.; Fotakis, C.

    2007-04-01

    We have demonstrated micromachining of bulk 3C silicon carbide (3C- SiC) wafers by employing 1028nm wavelength femtosecond laser pulses of energy less than 10 nJ directly from a femtosecond laser oscillator, thus eliminating the need for an amplified system and increasing the micromachining speed by more than four orders of magnitude.

  4. Synthesis of fluorescent carbon nanoparticles directly from active carbon via a one-step ultrasonic treatment

    SciTech Connect

    Li, Haitao; He, Xiaodie; Liu, Yang; Yu, Hang; Kang, Zhenhui; Lee, Shuit-Tong

    2011-01-15

    Water-soluble fluorescent carbon nanoparticles were synthesized directly from active carbon by a one-step hydrogen peroxide-assisted ultrasonic treatment. The carbon nanoparticles were characterized by transmission electron microscopy, optical fluorescent microscopy, fluorescent spectroscopy, Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometer. The results showed that the surface of carbon nanoparticles was rich of hydroxyl groups resulting in high hydrophilicity. The carbon nanoparticles could emit bright and colorful photoluminescence covering the entire visible-to-near infrared spectral range. Furthermore, these carbon nanoparticles also had excellent up-conversion fluorescent properties.

  5. Upconversion Nanoparticles for Security Printing and CdSe QDs for Drug Delivery Applications

    NASA Astrophysics Data System (ADS)

    Baride, Aravind

    Upconversion is an anti-Stokes luminescence process, in which NIR excitation results in visible emission. Lanthanide ions, such as Yb3+ , Er3+ and Tm3+ ions, doped in beta-NaYF 4 crystals exhibit upconversion. Doped NaYF4 nanocrystals retain the bulk-like upconversion property in colloidal dispersions. The doping composition influences both the spectral output and efficiency of the upconversion emission. Red, green and blue primary color upconversion ink formulations were prepared using upconversion nanoparticles. We optimized the Er/Tm doping composition to produce spectrally pure red emitting nanoparticles. RGB upconversion inks were printed on various substrates and chromaticity of the printed features was investigated. Upconversion inks printed on substrates are not visible to the naked eye under ambient conditions, but the printed features appear upon 980 nm excitation. The upconversion inks, because of covertness, have numerous security printing and anti-counterfeiting applications. Colors produced by combinations of primary colors involving blue are excitation power density dependent. We evaluated the relation between the print density, excitation power density and chromaticity of the prints. In addition to NIR-to-visible inks, we also developed NIR-to-NIR inks for security printing systems. Spectrally pure NIR-to-NIR (980nm-to-800nm) emission was achieved by optimization of Yb/Tm doping composition. We demonstrated excitation and capture of NIR-to-NIR images from upconversion prints coated with NIR transparent materials. The upconversion inks described so far were prepared in non-polar ink bases. We also prepared upconversion inks in polar solvent bases. As synthesized nanoparticles are capped with oleic acid ligands. Polar solvent dispersibility of the nanoparticles was achieved by post-synthetic ligand exchange techniques. Polar-solvent-based upconversion inks were printed with a piezo inkjet and a thermal inkjet printer. In a second project, we

  6. Time-Resolved Down-Conversion of 2-Aminopurine in a DNA Hairpin: Fluorescence Anisotropy and Solvent Effects

    NASA Astrophysics Data System (ADS)

    Tourón Touceda, Patricia; Gelot, Thomas; Crégut, Olivier; Léonard, Jérémie; Haacke, Stefan

    2013-03-01

    Femtosecond fluorescence anisotropy decay measured by type II difference frequency generation provides new insight into the local structural dynamics of ΔP(-)PBS fragments of the HIV- 1 DNA primary binding sequence, labeled with 2-aminopurine.

  7. Near-infrared-emitting colloidal Ag2S quantum dots exhibiting upconversion luminescence

    NASA Astrophysics Data System (ADS)

    Zhang, Yanyan; Jiang, Danyu; Yang, Wei; Wang, Dandan; Zheng, Huiping; Du, Yuansheng; Li, Xi; Li, Qiang

    2017-02-01

    Ag2S quantum dots (QDs) coated with thioglycolic acid (Ag2S QDs-TGA) have been synthesized in an organic solvent via a stepwise addition of reagents. When excited by a 980 nm laser, the near-infrared-emitting colloidal Ag2S QDs-TGA exhibit upconversion luminescence (UCL). The observed photoluminescence (PL) was attributed to the presence of ligand-modified Ag2S on the QD surfaces. Hence, upon dilution of the solution, the PL intensity initially increased before subsequently decreasing, accompanied by a blue shift in the PL spectra. The PL phenomena can be attributed to the increase in the amount of ligand-modified Ag2S on the QD surfaces upon dilution, which in turn affected the fluorescence resonance energy transfer (FRET) and re-emission of the surface energy level. The relations between the emission intensity of Ag2S QDs-TGA and the excitation power are investigated, and the results confirm that the UCL in Ag2S QDs-TGA can be ascribed to a two-photon-assisted absorption process via a real energy state.

  8. Upconversion Nanoparticle-Based Förster Resonance Energy Transfer for Detecting DNA Methylation

    PubMed Central

    Kim, Seockjune; Hwang, Sang-Hyun; Im, Su-Gyeong; Lee, Min-Ki; Lee, Chang-Hun; Son, Sang Jun; Oh, Heung-Bum

    2016-01-01

    Aberrant methylation of a crucial CpG island is the main mechanism for the inactivation of CDKN2A in the early stages of carcinogenesis. Therefore, the detection of DNA methylation with high sensitivity and specificity is important, and various detection methods have been developed. Recently, upconversion nanoparticles (UCNPs) have been found to display a high signal-to-noise ratio and no photobleaching, making them useful for diagnostic applications. In this pilot study, we applied UCNPs to the detection of CDKN2A methylation and evaluated the feasibility of this system for use in molecular diagnostics. DNA PCR was performed using biotinylated primers, and the PCR amplicon was then intercalated with SYTOX Orange dye, followed by incubation with streptavidin-conjugated UCNPs. Fluorescence detection of the Förster resonance energy transfer (FRET) of the UCNPs (MS-UC-FRET) was then performed, and the results were compared to those from real-time PCR (RQ-PCR) and pyrosequencing. Detection by MS-UC-FRET was more sensitive than that by either RQ-PCR or pyrosequencing. Our results confirmed the success of our MS-UC-FRET system for detecting DNA methylation and demonstrated the potential application of this system in molecular diagnostics. PMID:27517925

  9. Upconversion effective enhancement by producing various coordination surroundings of rare-Earth ions.

    PubMed

    Huang, Qingming; Yu, Han; Ma, En; Zhang, Xinqi; Cao, Wenbing; Yang, Chengang; Yu, Jianchang

    2015-03-16

    In this manuscript, we present a simple route to enhance upconversion (UC) emission by producing two different coordination sites of trivalent cations in a matrix material and adjusting crystal field asymmetry by Hf(4+) co-doping. A cubic phase, Y3.2Al0.32Yb0.4Er0.08F12, with these structural characteristics was synthesized successfully by introducing a small ion (Al(3+)) into YF3. X-ray diffraction (XRD), nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), X-ray spectroscopy (XPS), and fluorescence spectrophotometry (FS) were employed for its crystalline structure and luminescent property analysis. As a result, the coordination environments of the rare-earth ions were varied more obviously than a hexagonal NaYF4 matrix with the same Hf(4+) co-doping concentration, with vertical comparison, UC luminescent intensities of cubic Y3.2Al0.32Yb0.4Er0.08F12 were largely enhanced (∼32-80 times greater than that of different band emissions), while the maximum enhancement of hexagonal NaYF4 was by a factor of ∼12. According to our experimental results, the mechanism has been demonstrated involving the crystalline structure, crystal field asymmetry, luminescence lifetime, hypersensitive transition, and so on. The study may be helpful for the design and fabrication of high-performance UC materials.

  10. Dual-Color Emissive Upconversion Nanocapsules for Differential Cancer Bioimaging In Vivo.

    PubMed

    Kwon, Oh Seok; Song, Hyun Seok; Conde, João; Kim, Hyoung-Il; Artzi, Natalie; Kim, Jae-Hong

    2016-01-26

    Early diagnosis of tumor malignancy is crucial for timely cancer treatment aimed at imparting desired clinical outcomes. The traditional fluorescence-based imaging is unfortunately faced with challenges such as low tissue penetration and background autofluorescence. Upconversion (UC)-based bioimaging can overcome these limitations as their excitation occurs at lower frequencies and the emission at higher frequencies. In this study, multifunctional silica-based nanocapsules were synthesized to encapsulate two distinct triplet-triplet annihilation UC chromophore pairs. Each nanocapsule emits different colors, blue or green, following a red light excitation. These nanocapsules were further conjugated with either antibodies or peptides to selectively target breast or colon cancer cells, respectively. Both in vitro and in vivo experimental results herein demonstrate cancer-specific and differential-color imaging from single wavelength excitation as well as far greater accumulation at targeted tumor sites than that due to the enhanced permeability and retention effect. This approach can be used to host a variety of chromophore pairs for various tumor-specific, color-coding scenarios and can be employed for diagnosis of a wide range of cancer types within the heterogeneous tumor microenvironment.

  11. Effective cancer targeting and imaging using macrophage membrane-camouflaged upconversion nanoparticles.

    PubMed

    Rao, Lang; He, Zhaobo; Meng, Qian-Fang; Zhou, Ziyao; Bu, Lin-Lin; Guo, Shi-Shang; Liu, Wei; Zhao, Xing-Zhong

    2017-02-01

    Upconversion nanoparticles (UCNPs), with fascinating optical and chemical features, are a promising new generation of fluorescent probes. Although UCNPs have been widely used in diagnosis and therapy, there is an unmet need for a simple and effective surface engineering method that can produce cancer-targeting UCNPs. Here, we show that by coating particles with macrophage membranes, it becomes possible to utilize the adhesion between macrophages and cancer cells for effective cancer targeting. Natural macrophage membranes along with their associated membrane proteins were reconstructed into vesicles and then coated onto synthetic UCNPs. The resulting macrophage membrane-camouflaged particles (MM-UCNPs) exhibited effective cancer targeting capability inherited from the source cells and were further used for enhanced in vivo cancer imaging. Finally, the blood biochemistry, hematology testing and histology analysis results suggested a good in vivo biocompatibility of MM-UCNPs. The combination of synthetic nanoparticles with biomimetic cell membranes embodies a novel design strategy toward developing biocompatible nanoprobes for potential clinical applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 521-530, 2017.

  12. Energy transfer and upconversion of Sm3+ ions in YAlO3

    NASA Astrophysics Data System (ADS)

    Malinowski, M.; Kaczkan, M.; Turczyński, S.

    2017-01-01

    Sm3+ doped YAlO3 (YAP) single crystals were prepared by the micro-pulling down method. Emission spectra as well as luminescence decay curves for these crystals were recorded at temperatures ranging from 10 K to 300 K. Based on the low temperature spectra the energies of the Stark levels for several multiplets were determined. The fluorescence decay curves have been measured as a function of concentration and temperature and are found to exhibit single exponential nature at lowest concentration of 0.1 at.% but are strongly non-exponential at concentrations above 1 at.%. This concentration quenching of the Sm3+ ion emission was ascribed to resonant cross-relaxation. The non-exponential decay rates were successfully fitted to Inokuti-Hirayama model for s = 6 indicating that the nature of the energy transfer process among the Sm3+ ions is of electric dipole-dipole type. Cross-relaxation rates were experimentally determined as a function of activator concentration and used to evaluate and to model the decays. The critical distances and energy transfer microparameter for the transfer processes were given. After pulsed 925-975 nm infra-red excitation upconverted yellow-orange emission has been generated at room temperature in Sm3+:YAP crystals. Dynamics of the involved excited states have been analyzed and the responsible upconversion mechanism was proposed to be energy transfer.

  13. Paramagnetism and improved upconversion luminescence properties of NaYF4:Yb,Er/NaGdF4 nanocomposites synthesized by a boiling water seed-mediated route

    NASA Astrophysics Data System (ADS)

    Yang, Chao-Qing; Li, Ao-Ju; Guo, Wei; Tian, Peng-Hua; Yu, Xiao-Long; Liu, Zhong-Xin; Cao, Yang; Sun, Zhong-Liang

    2016-03-01

    In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form α-NaYF4:Yb, Er nuclei. Then prepared sample is heated at elevated temperature to improve the fluorescence intensity, and next a NaGdF4 shell grows on the surface of NaYF4 nuclei. NaYF4:Yb,Er/NaGdF4 core-shell structured upconversion nanoparticles (CSUCNPs) have been successfully synthesized by above route. The use of boiling water decreases the cubic-to-hexagonal phase transition temperature of NaYF4:Yb,Er to 350°C and increases its upconversion (UC) luminescence intensity. A heterogeneous NaGdF4 epitaxially growing on the surface of Ln3+-doped NaYF4 not only improves UC luminescence, but also creates a paramagnetic shell, which can be used as contrast agents in magnetic resonance imaging (MRI). The solution of CSUCNPs shows bright green UC fluorescence under the excitation at 980 nm in a power density only about 50 mW·cm-2. A broad spectrum with a dominant resonance at g of about 2 is observed by the electron paramagnetic resonance (EPR) spectrum of CSUCNPs. Above properties suggest that the obtained CSUCNPs could be potential candidates for dual-mode optical/magnetic bioapplications.

  14. Structural and optical properties of thermal decomposition assisted Gd2O3:Ho3 +/Yb3 + upconversion phosphor annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Tiwari, S. P.; Kumar, K.; Rai, V. K.

    2016-10-01

    The infrared to visible upconversion fluorescent nanoparticles of Ho3 +/Yb3 + codoped Gd2O3 phosphor is synthesized via thermal decomposition route. The as-synthesized sample was annealed at 800, 1000 and 1200 °C for 3 h and then structural and optical properties were studied. The Rietveld refinement of X-ray diffraction (XRD) data was analyzed to probe the effect of Ho3 +/Yb3 + dopant on the structural parameters of Gd2O3 host. The upconversion emission spectra of as-synthesized and annealed samples are compared using 980 nm diode laser excitation and five emission bands noticed at 490, 539, 550, 667 and 757 nm corresponding to the 5F3 → 5I8, 5F4 → 5I8, 5S2 → 5I8,5F5 → 5I8 and 5I4 → 5I8 manifolds, respectively. The local temperature induced by laser light is also calculated. The fluorescence intensity ratio (FIR) of two thermally coupled transitions 5F4 → 5I8 and 5S2 → 5I8 is plotted against the sample temperature and sensor sensitivity of sample is calculated.

  15. Current Advances in Lanthanide‐Doped Upconversion Nanostructures for Detection and Bioapplication

    PubMed Central

    Chen, Cailing

    2016-01-01

    Along with the development of science and technology, lanthanide‐doped upconversion nanostructures as a new type of materials have taken their place in the field of nanomaterials. Upconversion luminescence is a nonlinear optical phenomenon, which absorbs two or more photons and emits one photon. Compared with traditional luminescence materials, upconversion nanostructures have many advantages, such as weak background interference, long lifetime, low excitation energy, and strong tissue penetration. These interesting nanostructures can be applied in anticounterfeit, solar cell, detection, bioimaging, therapy, and so on. This review is focused on the current advances in lanthanide‐doped upconversion nanostructures, covering not only basic luminescence mechanism, synthesis, and modification methods but also the design and fabrication of upconversion nanostructures, like core–shell nanoparticles or nanocomposites. At last, this review emphasizes the application of upconversion nanostructure in detection and bioimaging and therapy. Learning more about the advances of upconversion nanostructures can help us better exploit their excellent performance and use them in practice. PMID:27840794

  16. Optical detection of terahertz using nonlinear parametric upconversion.

    PubMed

    Khan, M Jalal; Chen, Jerry C; Kaushik, Sumanth

    2008-12-01

    We extend our work to perform sensitive, room-temperature optical detection of terahertz (THz) by using nonlinear parametric upconversion. THz radiation at 700 GHz is mixed with pump light at 1,550 nm in a bulk GaAs crystal to generate an idler wave at 1,555.6 nm. The idler is separated, coupled into optical fiber, and detected using a gated Geiger-mode avalanche photodiode. The resulting THz detector has a power sensitivity of 4.5 pW/Hz and a timing resolution of 1 ns.

  17. Z-scan Measurement of Upconversion in Er:YAG

    DTIC Science & Technology

    2010-12-01

    of each manifold, e.g.   22414313212121 NCWNWNWNNfNfh I td Nd upae    . (1) Here, N1 (N2) is the population of the 4I15/2 (4I13/2...manifold, I is the laser intensity,  is the absolute cross section, fa ( fe ) is the probability that an ion in the 4I15/2 (4I13/2) manifold is in a...sublevel that can absorb (emit) a laser photon, Wij is the relaxation rate from level i to level j, and Cup is the upconversion coefficient. Also

  18. Study of upconversion in PCFs with high erbium concentration

    NASA Astrophysics Data System (ADS)

    Berdejo, Víctor; Vallés, Juan A.; Rebolledo, Miguel Á.; Diez, Antonio; Martin, Juan C.; Sanchez-Martin, José A.; Álvarez, José M.; Andrés, Miguel V.

    2011-09-01

    We report on a comparison of characterization techniques for high concentration erbium-doped photonic crystal fibres (PCFs). A highly erbium-doped-silica PCF was fabricated and an amplifier based on the PCF was built. Then, measurements on the amplifier output optical powers were carried out. To model the amplifier, three different formalisms were assumed for the Er3+-ion upconversion mechanism and the numerical results were fitted to the experimental ones. The sets of best-fit parameters are compared and the use of these techniques for active PCF characterisation is discussed.

  19. Dual channel fluorescence engineering on the nano-patterened metamaterial (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wu, Huijun; Tseng, Ming Lun; Tsai, Wei Yi; Chen, Ting-Yu; Chien, Yihsin; Chang, Yun-Chorng; Tsai, Din Ping

    2016-09-01

    Upconversion fluorescence from Lanthanide-doped nanocrystals has attracted widespread interests because of its greatly potential applications in various fields, such as photonic crystal lasers, material science, biological therapy, and so on. However, the relatively low quantum yield (typically < 5%) is the major limitation for upconversion nanocrystals. Meanwhile, in addition to the chemical methods, plasmonic structures have been adopted as another strategy to improve the radiation efficiency and control the relaxation process of the upcovnersion nanocrystals. We designed the anti-symmetric split ring resonators with various periods and the fishnet structures. The surface plasmon resonance peaks of the structure shift as the periods varies. For example, in a multi-layered plamsonic metasurface with the period of 250nm, both the electric and magnetic modes could be generated simultaneously when excited by the incident light with proper polarization. This plasmonic structure provides two different channels for the enhancement of upconversion fluorescence. The resonance peak of 650nm is magnetic resonance mode, while the peak of 980nm is electric resonance mode. The resonance peak of 980nm coincides with the absorption band of the Lanthanide-dopoed nanocrystal, and the peak of 650nm matches with its emission band. We found that the upconversion fluorescence intensity could be enhanced more than 10 times when the electric resonance frequency of the metasurface matches with the absorption band of the upconversion nanocrystals, while the magnetic mode overlaps with its emission band. This is due to the local density of optical states was significantly enhanced by the plasmonic metasurface. The detailed results and mechanism will be discussed.

  20. Near-Infrared-Triggered Photodynamic Therapy toward Breast Cancer Cells Using Dendrimer-Functionalized Upconversion Nanoparticles.

    PubMed

    Wang, Bing-Yen; Liao, Ming-Liang; Hong, Guan-Ci; Chang, Wen-Wei; Chu, Chih-Chien

    2017-09-11

    Water-soluble upconversion nanoparticles (UCNPs) that exhibit significant ultraviolet, blue, and red emissions under 980-nm laser excitation were successfully synthesized for performing near infrared (NIR)-triggered photodynamic therapy (PDT). The lanthanide-doped UCNPs bearing oleate ligands were first exchanged by citrates to generate polyanionic surfaces and then sequentially encapsulated with NH₂-terminated poly(amido amine) (PAMAM) dendrimers (G4) and chlorine6 (Ce6) using a layer-by-layer (LBL) absorption strategy. Transmission electron microscopy and X-ray diffraction analysis confirm that the hybrid UCNPs possess a polygonal morphology with an average dimension of 16.0 ± 2.1 nm and α-phase crystallinity. A simple calculation derived through thermogravimetric analysis revealed that one polycationic G4 dendrimer could be firmly accommodated by approximately 150 polyanionic citrates through multivalent interactions. Moreover, zeta potential measurements indicated that the LBL fabrication results in the hybrid nanoparticles with positively charged surfaces originated from these dendrimers, which assist the cellular uptake in biological specimens. The cytotoxic singlet oxygen based on the photosensitization of the adsorbed Ce6 through the upconversion emissions can be readily accumulated by increasing the irradiation time of the incident lasers. Compared with that of 660-nm lasers, NIR-laser excitation exhibits optimized in vitro PDT effects toward human breast cancer MCF-7 cells cultured in the tumorspheres, and less than 40% of cells survived under a low Ce6 dosage of 2.5 × 10(-7) M. Fluorescence microscopy analysis indicated that the NIR-driven PDT causes more effective destruction of the cells located inside spheres that exhibit significant cancer stem cell or progenitor cell properties. Moreover, an in vivo assessment based on immunohistochemical analysis for a 4T1 tumor-bearing mouse model confirmed the effective inhibition of cancer cell

  1. Control of multiphoton molecular excitation with shaped femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Xu, Bingwei

    The work presented in this dissertation describes the use of shaped femtosecond laser pulses to control the outcome of nonlinear optical process and thus to achieve the selectivity for multiphoton molecular transitions. This research could lead to applications in various fields including nonlinear optical spectroscopy, chemical identification, biological imaging, communications, photodynamic therapy, etc. In order to realize accurate pulse shaping of the femtosecond laser pulses, it is essential to measure and correct the spectral phase distortion of such pulses. A method called multiphoton intrapulse interference phase scan is used to do so throughout this dissertation. This method is highly accurate and reproducible, and has been proved in this work to be compatible with any femtosecond pulses regardless of bandwidth, intensity and repetition rate of the laser. The phase control of several quasi-octave laser sources is demonstrated in this dissertation, with the generation of 4.3 fs and 5.9 fs pulses that reach the theoretically predicted transform-limited pulse duration. The excellent phase control achieved also guarantees the reproducibility for selective multiphoton excitations by accurate phase and/or amplitude shaping. Selective two-photon excitation, stimulated Raman scattering and coherent anti-Stokes Raman scattering with a single broadband laser source are demonstrated in this dissertation. Pulse shaping is used to achieve a fast and robust approach to measure the two-photon excitation spectrum from fluorescent molecules, which provide important information for two-photon biological imaging. The selective excitation concept is also applied in the field of remote chemical identification. Detection of characteristic Raman lines for several chemicals using a single beam coherent anti-Stokes Raman scattering spectroscopy from a 12 meter standoff distance is shown, providing a promising approach to standoff detection of chemicals, hazardous contaminations

  2. Core-shell hybrid upconversion nanoparticles carrying stable nitroxide radicals as potential multifunctional nanoprobes for upconversion luminescence and magnetic resonance dual-modality imaging

    NASA Astrophysics Data System (ADS)

    Chen, Chuan; Kang, Ning; Xu, Ting; Wang, Dong; Ren, Lei; Guo, Xiangqun

    2015-03-01

    Nitroxide radicals, such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and its derivatives, have recently been used as contrast agents for magnetic resonance imaging (MRI) and electron paramagnetic resonance imaging (EPRI). However, their rapid one-electron bioreduction to diamagnetic N-hydroxy species when administered intravenously has limited their use in in vivo applications. In this article, a new approach of silica coating for carrying stable radicals was proposed. A 4-carboxyl-TEMPO nitroxide radical was covalently linked with 3-aminopropyl-trimethoxysilane to produce a silanizing TEMPO radical. Utilizing a facile reaction based on the copolymerization of silanizing TEMPO radicals with tetraethyl orthosilicate in reverse microemulsion, a TEMPO radicals doped SiO2 nanostructure was synthesized and coated on the surface of NaYF4:Yb,Er/NaYF4 upconversion nanoparticles (UCNPs) to generate a novel multifunctional nanoprobe, PEGylated UCNP@TEMPO@SiO2 for upconversion luminescence (UCL) and magnetic resonance dual-modality imaging. The electron spin resonance (ESR) signals generated by the TEMPO@SiO2 show an enhanced reduction resistance property for a period of time of up to 1 h, even in the presence of 5 mM ascorbic acid. The longitudinal relaxivity of PEGylated UCNPs@TEMPO@SiO2 nanocomposites is about 10 times stronger than that for free TEMPO radicals. The core-shell NaYF4:Yb,Er/NaYF4 UCNPs synthesized by this modified user-friendly one-pot solvothermal strategy show a significant enhancement of UCL emission of up to 60 times more than the core NaYF4:Yb,Er. Furthermore, the PEGylated UCNP@TEMPO@SiO2 nanocomposites were further used as multifunctional nanoprobes to explore their performance in the UCL imaging of living cells and T1-weighted MRI in vitro and in vivo.Nitroxide radicals, such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and its derivatives, have recently been used as contrast agents for magnetic resonance imaging (MRI) and electron

  3. Towards sub-femtosecond emission

    NASA Astrophysics Data System (ADS)

    Bach, Roger; Hansen, Peter; Batelaan, Herman; Hilbert, Shawn

    2010-03-01

    To manipulate femtosecond pulses of electrons new electron optical elements are needed. For example, if a source has a lower limit in the duration of the electron pulses that it generates, then aan electron optical element that can reduce the pulse duration could be useful. An example of this is the proposed ``temporal lens '' [1]. To detect the short electron pulses one also needs new elements. Attempts to use the ponderomotive interaction between the electron pulse and a second laser pulse will be presented [2]. Alternatively, we have started to explore a plasmonics structure provided by the Capasso group to make a fast electron switch. This has the potential to be useful both for switching, shaping and detecting the electron pulse. Finally, the experimental parameters and detection ideas for quantum degeneracy will be discussed. [1] S. Hilbert, B. Barwick, K. Uiterwaal, H. Batelaan, A. Zewail, ``Temporal lenses for attosecond and femtosecond electron pulses'', Proceedings of the National Academy of Sciences, p. 10558, vol. 106, (2009). [2] L. Kreminskaya, C. Corder, V. Engquist, O. Golovin, P. Hansen, H. Batelaan, A. I. Khizhnyak, G. A. Swartzlander, Jr., ``Laser Beam Shaping: Donut Mode Formation by Interference.'' Laser Beam Shaping X (Proceedings Volume) Proceedings of SPIE Volume: 7430.

  4. Temperature Dependence of Triplet–Triplet Annihilation Upconversion in Phospholipid Membranes

    PubMed Central

    2017-01-01

    Understanding the temperature dependency of triplet–triplet annihilation upconversion (TTA-UC) is important for optimizing biological applications of upconversion. Here the temperature dependency of red-to-blue TTA-UC is reported in a variety of neutral PEGylated phospholipid liposomes. In these systems a delicate balance between lateral diffusion rate of the dyes, annihilator aggregation, and sensitizer self-quenching leads to a volcano plot, with the maximum upconversion intensity occurring near the main order–disorder transition temperature of the lipid membrane. PMID:28059523

  5. Rare-earth ion doped up-conversion materials for photovoltaic applications.

    PubMed

    Wang, Hai-Qiao; Batentschuk, Miroslaw; Osvet, Andres; Pinna, Luigi; Brabec, Christoph J

    2011-06-17

    With the aim of utilizing the infrared region of solar radiation to improve solar cell performance, significant progress, including theoretical analysis and experimental achievement, has been made in the field of up-conversion for photovoltaic applications. This Research News article reviews recent progress in the development of rear-earth (RE) ion doped up-conversion materials for solar cell applications. In addition, new trends for RE-ion-doped phosphors are briefly discussed, among them trivalent RE-ion-doped up-conversion materials for organic solar cell applications.

  6. Preparation and Upconversion Emission Modification of Crystalline Colloidal Arrays and Rare Earth Fluoride Microcrystal Composites

    PubMed Central

    Liao, Jiayan; Yang, Zhengwen; Sun, Jinbo; Lai, Shenfeng; Shao, Bo; Li, Jun; Qiu, Jianbei; Song, Zhiguo; Yang, Yong

    2015-01-01

    In this paper, highly ordered crystalline colloidal arrays containing rare earth fluoride microcrystals were fabricated. The upconversion emission property of rare earth fluoride microcrystals in crystalline colloidal arrays was studied and modified. A significant suppression and enhancement of the upconversion emission from the rare earth fluorides can be observed in the regions of the photonic band gap and its band edge, respectively. The suppression or enhancement factor was shown to be related to the ordered degree of the crystalline colloidal arrays and is critical in the preparation of upconversion displays and low-threshold lasers. PMID:25560045

  7. Upconversion luminescence in BaMoO4:Pr3+ phosphor for display devices

    NASA Astrophysics Data System (ADS)

    Soni, Abhishek Kumar; Rai, Vineet Kumar

    2015-08-01

    The frequency upconversion is an important nonlinear optical property by which near infrared light is converted into the visible light. The BaMoO4:Pr3+ powder phosphor has been synthesized by solid state reaction method. The upconversion emission bands are recorded under the excitation of 808 nm diode laser. The phase formation of the prepared phosphor has been identified by powder X-ray diffraction (XRD) technique. The upconversion emission mechanism and colour coordinate have been explained by using energy level and CIE (International Commission on Illumination) chromaticity diagram study, respectively.

  8. Infrared upconversion for astronomical applications. [laser applications to astronomical spectroscopy of infrared spectra

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Kostiuk, T.; Ogilvie, K. W.

    1975-01-01

    The performance of an upconversion system is examined for observation of astronomical sources in the low to middle infrared spectral range. Theoretical values for the performance parameters of an upconversion system for astronomical observations are evaluated in view of the conversion efficiencies, spectral resolution, field of view, minimum detectable source brightness and source flux. Experimental results of blackbody measurements and molecular absorption spectrum measurements using a lithium niobate upconverter with an argon-ion laser as the pump are presented. Estimates of the expected optimum sensitivity of an upconversion device which may be built with the presently available components are given.

  9. Femtosecond-irradiation-induced refractive-index changes and channel waveguiding in bulk Ti{sup 3+}:Sapphire

    SciTech Connect

    Apostolopoulos, V.; Laversenne, L.; Colomb, T.; Depeursinge, C.; Salathe, R.P.; Pollnau, M.; Osellame, R.; Cerullo, G.; Laporta, P.

    2004-08-16

    We have employed femtosecond laser writing in order to induce refractive-index changes and waveguides in Ti{sup 3+}-doped sapphire. Doping the sapphire crystal with an appropriate ion significantly reduces the threshold for creating structural changes, thus enabling the writing of waveguide structures. Passive and active buried channel waveguiding is demonstrated and images of the guided modes, propagation-loss values, fluorescence spectra, and output efficiencies are presented. The guiding area is located around the laser-damaged region, indicating that the guiding effect is stress induced. Refractive-index changes are measured by digital holography. Proper active doping should enable femtosecond processing and waveguide writing in various crystalline materials.

  10. High-power femtosecond pulse generation in a passively mode-locked Nd:SrLaAlO4 laser

    NASA Astrophysics Data System (ADS)

    Liu, Shan-De; Dong, Lu-Lu; Zheng, Li-He; Berkowski, Marek; Su, Liang-Bi; Ren, Ting-Qi; Peng, Yan-Dong; Hou, Jia; Zhang, Bai-Tao; He, Jing-Liang

    2016-07-01

    A high optical quality Nd:SrLaAlO4 (Nd:SLA) crystal was grown using the Czochralski method and showed broad fluorescence spectrum with a full width at half maximum value of 34 nm, which is beneficial for generating femtosecond laser pulses. A stable diode-pumped passively mode-locked femtosecond Nd:SLA laser with 458 fs pulse duration was achieved for the first time at a central wavelength of 1077.9 nm. The average output power of the continuous-wave mode-locked laser was 520 mW and the repetition rate was 78.5 MHz.

  11. Femtosecond multiphoton ionization of ammonia clusters

    SciTech Connect

    Wei, S.; Purnell, J.; Buzza, S.A.; Stanley, R.J.; Castleman, A.W. Jr. )

    1992-12-15

    Herein, we report on femtosecond time-resolved experiments in ammonia clusters. The mechanisms of their ionization and the subsequent formation of the protonated ammonia cluster ions are studied using a femtosecond pump-probe technique at 620 nm. It is found that an intermediate corresponding to [ital C][prime] states of the monomer is responsible for the ionization of ammonia clusters. Femtosecond pump--probe studies show that the lifetime of the intermediate to the formation of the protonated cluster ions (NH[sub 3])[sub [ital n

  12. Low phase noise microwave extraction from femtosecond laser by frequency conversion pair and IF-domain processing.

    PubMed

    Dai, Yitang; Cen, Qizhuang; Wang, Lei; Zhou, Yue; Yin, Feifei; Dai, Jian; Li, Jianqiang; Xu, Kun

    2015-12-14

    Extraction of a microwave component from a low-time-jitter femtosecond pulse train has been attractive for current generation of spectrally pure microwave. In order to avoid the transfer from the optical amplitude noise to microwave phase noise (AM-PM), we propose to down-convert the target component to intermediate frequency (IF) before the opto-electronic conversion. Due to the much lower carrier frequency, the AM-PM is greatly suppressed. The target is then recovered by up-conversion with the same microwave local oscillation (LO). As long as the time delay of the second LO matches that of the IF carrier, the phase noise of the LO shows no impact on the extraction process. The residual noise of the proposed extraction is analyzed in theory, which is also experimentally demonstrated as averagely around -155 dBc/Hz under offset frequency larger than 1 kHz when 10-GHz tone is extracted from a home-made femtosecond fiber laser. Large tunable extraction from 1 GHz to 10 GHz is also reported.

  13. Highly efficient Yb3+/Tm3+ co-doped NaYF4 nanotubes: Synthesis and intense ultraviolet to infrared up-conversion luminescence

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Y.; Wang, Y.; Deng, J. Q.; Wang, J.; Ni, S. C.

    2014-02-01

    Nanocrystals of up-conversion (UC) phosphor Yb3+/Tm3+ co-doped NaYF4 are prepared by a facile hydrothermal method using oleic acid as a stabilizing agent. The as-prepared nanocrystals are of hexagonal phase, and have tube-like morphology and strong ultraviolet (UV) and blue UC fluorescence intensity, which have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectroscopy. The effect of Yb3+ concentration on the UC emission properties is also analyzed. Our results reveal that the intensity of emission peaks can be controlled by varying the Yb3+ concentration and these NaYF4 nanotubes are highly efficient host material. The as-prepared NaYF4 nanotubes show potential applications in UV compact solid state lasers and multi-channel fluorescent label.

  14. Mercaptopropionic acid-capped Mn2+:ZnSe/ZnO quantum dots with both downconversion and upconversion emissions for bioimaging applications†

    PubMed Central

    Zhao, Bingxia; Yao, Yulian; Yang, Kai; Rong, Pengfei; Huang, Peng; An, Xiao; Li, Zhiming; Chen, Xiaoyuan

    2015-01-01

    Doped quantum dots (d-dots) can serve as fluorescent biosensors and biolabels for biological applications. Our study describes a synthesis of mercaptopropionic acid (MPA)-capped Mn2+:ZnSe/ZnO d-dots through a facile, cost-efficient hydrothermal route. The as-prepared water-soluble d-dots exhibit strong emission at ca. 580 nm, with a photoluminescence quantum yield (PLQY) as high as 31%, which is the highest value reported to date for such particles prepared via an aqueous route. They also exhibit upconversion emission when excited at 800 nm. With an overall diameter of around 6.7 nm, the d-dots could gain access to the cell nucleus without any surface decoration, demonstrating their promising broad applications as fluorescent labels. PMID:25189675

  15. A femtosecond Raman generator for long wavelength two-photon and third harmonic generation imaging

    NASA Astrophysics Data System (ADS)

    Trägârdh, J.; Schniete, J.; Parsons, M.; McConnell, G.

    2016-12-01

    We demonstrate a femtosecond single pass Raman generator based on an YVO4 crystal pumped by a high energy fiber laser at a wavelength of 1064 nm and a repetition rate of 1 MHz. The Raman generator shifts the pump wavelength to 1175 nm, in a broadband spectrum, making it suitable for multi-photon microscopy. We use the Raman generator for third harmonic generation imaging of live plant specimens as well as for two-photon fluorescence imaging of red fluorescent protein expressing HeLa cells. We demonstrate that the photo-damage to a live specimen is low.

  16. Ti:Sapphire micro-structures by femtosecond laser inscription: Guiding and luminescence properties

    NASA Astrophysics Data System (ADS)

    Ren, Yingying; Jiao, Yang; Vázquez de Aldana, Javier R.; Chen, Feng

    2016-08-01

    We report on the fabrication of buried cladding waveguides with different diameters in a Ti:Sapphire crystal by femtosecond laser inscription. The propagation properties are studied, showing that the cladding waveguides could support near- to mid-infrared waveguiding at both TE and TM polarizations. Confocal micro-photoluminescence experiments reveal that the original fluorescence properties in the waveguide region are very well preserved, while it suffers from a strong quenching at the centers of laser induced filaments. Broadband waveguide fluorescence emissions with high efficiency are realized, indicating the application of the cladding waveguides in Ti:Sapphire as compact broadband luminescence sources in biomedical fields.

  17. Frequency Up-Conversion Photon-Type Terahertz Imager

    NASA Astrophysics Data System (ADS)

    Fu, Z. L.; Gu, L. L.; Guo, X. G.; Tan, Z. Y.; Wan, W. J.; Zhou, T.; Shao, D. X.; Zhang, R.; Cao, J. C.

    2016-05-01

    Terahertz imaging has many important potential applications. Due to the failure of Si readout integrated circuits (ROICs) and the thermal mismatch between the photo-detector arrays and the ROICs at temperatures below 40 K, there are big technical challenges to construct terahertz photo-type focal plane arrays. In this work, we report pixel-less photo-type terahertz imagers based on the frequency up-conversion technique. The devices are composed of terahertz quantum-well photo-detectors (QWPs) and near-infrared (NIR) light emitting diodes (LEDs) which are grown in sequence on the same substrates using molecular beam epitaxy. In such an integrated QWP-LED device, photocurrent in the QWP drives the LED to emit NIR light. By optimizing the structural parameters of the QWP-LED, the QWP part and the LED part both work well. The maximum values of the internal and external energy up-conversion efficiencies are around 20% and 0.5%. A laser spot of a homemade terahertz quantum cascade laser is imaged by the QWP-LED together with a commercial Si camera. The pixel-less imaging results show that the image blurring induced by the transverse spreading of photocurrent is negligible. The demonstrated pixel-less imaging opens a new way to realize high performance terahertz imaging devices.

  18. Photon correlation in single-photon frequency upconversion.

    PubMed

    Gu, Xiaorong; Huang, Kun; Pan, Haifeng; Wu, E; Zeng, Heping

    2012-01-30

    We experimentally investigated the intensity cross-correlation between the upconverted photons and the unconverted photons in the single-photon frequency upconversion process with multi-longitudinal mode pump and signal sources. In theoretical analysis, with this multi-longitudinal mode of both signal and pump sources system, the properties of the signal photons could also be maintained as in the single-mode frequency upconversion system. Experimentally, based on the conversion efficiency of 80.5%, the joint probability of simultaneously detecting at upconverted and unconverted photons showed an anti-correlation as a function of conversion efficiency which indicated the upconverted photons were one-to-one from the signal photons. While due to the coherent state of the signal photons, the intensity cross-correlation function g(2)(0) was shown to be equal to unity at any conversion efficiency, agreeing with the theoretical prediction. This study will benefit the high-speed wavelength-tunable quantum state translation or photonic quantum interface together with the mature frequency tuning or longitudinal mode selection techniques.

  19. Solar-Pumping Upconversion of Interfacial Coordination Nanoparticles

    PubMed Central

    Ishii, Ayumi; Hasegawa, Miki

    2017-01-01

    An interfacial coordination nanoparticle successfully exhibited an upconversion blue emission excited by very low-power light irradiation, such as sunlight. The interfacial complex was composed of Yb ions and indigo dye, which formed a nano-ordered thin shell layer on a Tm2O3 nanoparticle. At the surface of the Tm2O3 particle, the indigo dye can be excited by non-laser excitation at 640 nm, following the intramolecular energy transfer from the indigo dye to the Yb ions. Additionally, the excitation energy of the Yb ion was upconverted to the blue emission of the Tm ion at 475 nm. This upconversion blue emission was achieved by excitation with a CW Xe lamp at an excitation power of 0.14 mW/cm2, which is significantly lower than the solar irradiation power of 1.4 mW/cm2 at 640 ± 5 nm. PMID:28134295

  20. Frequency Up-Conversion Photon-Type Terahertz Imager

    PubMed Central

    Fu, Z. L.; Gu, L. L.; Guo, X. G.; Tan, Z. Y.; Wan, W. J.; Zhou, T.; Shao, D. X.; Zhang, R.; Cao, J. C.

    2016-01-01

    Terahertz imaging has many important potential applications. Due to the failure of Si readout integrated circuits (ROICs) and the thermal mismatch between the photo-detector arrays and the ROICs at temperatures below 40 K, there are big technical challenges to construct terahertz photo-type focal plane arrays. In this work, we report pixel-less photo-type terahertz imagers based on the frequency up-conversion technique. The devices are composed of terahertz quantum-well photo-detectors (QWPs) and near-infrared (NIR) light emitting diodes (LEDs) which are grown in sequence on the same substrates using molecular beam epitaxy. In such an integrated QWP-LED device, photocurrent in the QWP drives the LED to emit NIR light. By optimizing the structural parameters of the QWP-LED, the QWP part and the LED part both work well. The maximum values of the internal and external energy up-conversion efficiencies are around 20% and 0.5%. A laser spot of a homemade terahertz quantum cascade laser is imaged by the QWP-LED together with a commercial Si camera. The pixel-less imaging results show that the image blurring induced by the transverse spreading of photocurrent is negligible. The demonstrated pixel-less imaging opens a new way to realize high performance terahertz imaging devices. PMID:27147281

  1. Solar-Pumping Upconversion of Interfacial Coordination Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ishii, Ayumi; Hasegawa, Miki

    2017-01-01

    An interfacial coordination nanoparticle successfully exhibited an upconversion blue emission excited by very low-power light irradiation, such as sunlight. The interfacial complex was composed of Yb ions and indigo dye, which formed a nano-ordered thin shell layer on a Tm2O3 nanoparticle. At the surface of the Tm2O3 particle, the indigo dye can be excited by non-laser excitation at 640 nm, following the intramolecular energy transfer from the indigo dye to the Yb ions. Additionally, the excitation energy of the Yb ion was upconverted to the blue emission of the Tm ion at 475 nm. This upconversion blue emission was achieved by excitation with a CW Xe lamp at an excitation power of 0.14 mW/cm2, which is significantly lower than the solar irradiation power of 1.4 mW/cm2 at 640 ± 5 nm.

  2. Dye-sensitized lanthanide-doped upconversion nanoparticles.

    PubMed

    Wang, Xindong; Valiev, Rashid R; Ohulchanskyy, Tymish Y; Ågren, Hans; Yang, Chunhui; Chen, Guanying

    2017-07-17

    Lanthanide-doped upconversion nanoparticles (UCNPs) are promising for applications as wide as biological imaging, multimodal imaging, photodynamic therapy, volumetric displays, and solar cells. Yet, the weak and narrow absorption of lanthanide ions poses a fundamental limit of UCNPs to withhold their brightness, creating a long-standing hurdle for the field. Dye-sensitized UCNPs are emerging to address this performance-limiting problem, yielding up to thousands-fold brighter luminescence than conventional UCNPs without dye sensitization. In their configuration, organic dyes with spectrally broad and intense absorption are anchored to the surface of UCNPs to harvest the excitation light energy, which is then transferred via Förster and/or Dexter mechanisms across the organic/inorganic interface to the lanthanides incorporated in UCNPs (with or devoid of a shell) to empower efficient upconversion. This tutorial review highlights recent progress in the development of dye sensitized UCNPs, with an emphasis on the theory of energy transfer, the geometric classification of the dye sensitized core and core/shell nanocrystals, and their emerging photonic and biophotonic applications. Opportunities and challenges offered by dye sensitized UCNPs are also discussed.

  3. Programmable femtosecond laser pulses in the ultraviolet

    SciTech Connect

    Hacker, M.; Feurer, T.; Sauerbrey, R.; Lucza, T.; Szabo, G.

    2001-06-01

    Using a combination of a zero-dispersion compressor and spectrally compensated sum-frequency generation, we have produced amplitude-modulated femtosecond pulses in the UV at 200 nm. {copyright} 2001 Optical Society of America

  4. Femtosecond Lasers and Corneal Surgical Procedures.

    PubMed

    Marino, Gustavo K; Santhiago, Marcony R; Wilson, Steven E

    2017-01-01

    Our purpose is to present a broad review about the principles, early history, evolution, applications, and complications of femtosecond lasers used in refractive and nonrefractive corneal surgical procedures. Femtosecond laser technology added not only safety, precision, and reproducibility to established corneal surgical procedures such as laser in situ keratomileusis (LASIK) and astigmatic keratotomy, but it also introduced new promising concepts such as the intrastromal lenticule procedures with refractive lenticule extraction (ReLEx). Over time, the refinements in laser optics and the overall design of femtosecond laser platforms led to it becoming an essential tool for corneal surgeons. In conclusion, femtosecond laser is a heavily utilized tool in refractive and nonrefractive corneal surgical procedures, and further technological advances are likely to expand its applications. Copyright 2017 Asia-Pacific Academy of Ophthalmology.

  5. REVIEW: Optical frequency standards and femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Baklanov, E. V.; Pokasov, P. V.

    2003-05-01

    A review is presented of the state of the art in a new direction in quantum electronics based on the use of femtosecond lasers for precision frequency measurements and the development of optical frequency and time standards.

  6. Chemical aerosol detection using femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Alexander, Dennis R.; Rohlfs, Mark L.; Stauffer, John C.

    1997-07-01

    Many chemical warfare agents are dispersed as small aerosol particles. In the past, most electro-optical excitation and detection schemes have used continuous or pulsed lasers with pulse lengths ranging from nanoseconds to microseconds. In this paper, we present interesting ongoing new results on femtosecond imaging and on the time dependent solutions to the scattering problem of a femtosecond laser pulse interacting with a single small aerosol particle. Results are presented for various incident pulse lengths. Experimental imaging results using femtosecond pulses indicate that the diffraction rings present when using nanosecond laser pulses for imaging are greatly reduced when femtosecond laser pulses are used. Results are presented in terms of the internal fields as a function of time and the optical size parameter.

  7. Blue and white upconversion emissions of rare-earth ions-doped oxyfluoride phosphors

    NASA Astrophysics Data System (ADS)

    Pang, Tao; Cao, Wanghe; Xing, Mingming; Feng, Wei; Xu, Shujing

    2010-05-01

    A blue emitting upconversion phosphor based on Yb 3+ and Tm 3+ codoped oxyfluoride is reported. Under the excitation of a single 980 nm diode laser with the power density of 5.56 W/cm 2, the upconversion luminescence brightness can reaches to 13053 mcd/m 2, which is much stronger than that of commercial Y 2O 2S:Yb, Tm phosphors (8194 mcd/m 2). The research of upconversion mechanism indicates that cooperating sensitization dominates the emissions at 479 and 645 nm, while the emission at 454 nm results from the combination of cooperating sensitization and phonon-assisted energy transfer from Yb 3+ to Tm 3+. Also, bright upconversion white light is obtained by tri-doping of Er 3+, Tm 3+ and Yb 3+. Because the blue (main emission at 479 nm), green and red emissions are two-photon process, the white light is not sensitive to the pumping power.

  8. Recent emergence of photon upconversion based on triplet energy migration in molecular assemblies.

    PubMed

    Yanai, Nobuhiro; Kimizuka, Nobuo

    2016-04-07

    An emerging field of triplet energy migration-based photon upconversion (TEM-UC) is reviewed. Highly efficient photon upconversion has been realized in a wide range of chromophore assemblies, such as non-solvent liquids, ionic liquids, amorphous solids, gels, supramolecular assemblies, molecular crystals, and metal-organic frameworks (MOFs). The control over their assembly structures allows for unexpected air-stability and maximum upconversion quantum yield at weak solar irradiance that has never been achieved by the conventional molecular diffusion-based mechanism. The introduction of the "self-assembly" concept offers a new perspective in photon upconversion research and triplet exciton science, which show promise for numerous applications ranging from solar energy conversion to chemical biology.

  9. Upconversion emission of erbium-doped lanthanum oxysulfide powders for temperature sensing

    NASA Astrophysics Data System (ADS)

    Balda, Rolindes; Hakmeh, Noha; Merdrignac-Conanec, Odile; Arriandiaga, M. Angeles; Fernandez, Joaquin

    2017-02-01

    In this work we report a detailed spectroscopic study of the near-infrared to visible upconversion luminescence in Erdoped lanthanum oxysulfide crystal powders after excitation of level 4I9/2. The analysis of the decay curves of the upconversion emission indicates that energy transfer upconversion is the main mechanism responsible for the green (4S3/2) and red (4F9/2) upconversion luminescence. The temperature dependence of the green upconverted emission from the two thermally coupled 2H11/2 and 4S3/2 levels has been analyzed in the 230 K- 300 K temperature range in order to check its availability as a temperature sensor.

  10. Recent Progress in 808 nm Excited Upconversion Nanomaterials as Multifunctional Nanoprobes for Visualized Theranostics in Cancers.

    PubMed

    Zeng, Leyong; Wu, Di; Tian, Ying; Pan, Yuanwei; Wu, Aiguo; Zhang, Jinchao; Lu, Guangming

    2017-03-20

    Near-infrared (NIR) light responsive nanomaterials have attracted considerable attention due to their location in the biological window. Especially, lanthanide-doped nanomaterials exhibit unique upconversion luminescence (UCL) properties with low background interference and long luminescence lifetime, which makes them promising in imaging diagnosis of cancers. Compared with traditional upconversion nanomaterials excited by 980 nm laser, 808 nm excitation can overcome the disadvantages of high heating effect and weak penetration depth induced by excitation source. Therefore, developing 808 nm excited upconversion nanoprobes will be important for the in vivo bio-imaging and visualized theranostics of tumors in deep-tissue. In the review paper, we systematically summarized the synthesis strategy and luminescence modulation of Nd3+-sensitized upconversion nanomaterials under 808 nm excitation, discussed the influence of excitation source on heating effect and penetration depth, and particularly focused on their applications in UCL imaging, multi-modal imaging and imaging-guided therapy of cancers.

  11. Gold and Hairpin DNA Functionalization of Upconversion Nanocrystals for Imaging and In Vivo Drug Delivery.

    PubMed

    Han, Sanyang; Samanta, Animesh; Xie, Xiaoji; Huang, Ling; Peng, Juanjuan; Park, Sung Jin; Teh, Daniel Boon Loong; Choi, Yongdoo; Chang, Young-Tae; All, Angelo Homayoun; Yang, Yanmei; Xing, Bengang; Liu, Xiaogang

    2017-03-10

    Although multifunctional upconversion imaging probes have recently attracted considerable interest in biomedical research, there are currently few methods for stabilizing these luminescent nanoprobes with oligonucleotides in biological systems. Herein, a method to robustly disperse upconversion nanoprobes in physiological buffers based on rational design and synthesis of nanoconjugates comprising hairpin-DNA-modified gold nanoparticles is presented. This approach imparts the upconversion nanoprobes with excellent biocompatibility and circumvents the problem of particle agglomeration. By combining single-band anti-Stokes near-infrared emission and the photothermal effect mediated by the coupling of gold to upconversion nanoparticles, a simple, versatile nanoparticulate system for simultaneous deep-tissue imaging and drug molecule release in vivo is demonstrated.

  12. Up-conversion and Photoluminescence in Er3+ Single Crystal MgAl-spinel

    NASA Astrophysics Data System (ADS)

    Mironova-Ulmane, N.; Sarakovskis, A.; Skvortsova, V.

    Traditional and up-conversion luminescence of MgAl2O4 single crystal doped with erbium ions obtained by the Verneuil method has been investigated. The time resolved spectral measurements of the green and red up-conversion luminescence bands show that a build-up part is present in the up-conversion luminescence kinetics. This means that energy transfer process is involved in the creation of the luminescence. Considering rather small concentration of Er3+ in the material (0.12 mass %), the expected up-conversion mechanism should be excited state absorption since the average distance between erbium ions is high. The above-mentioned considerations suggest that clustering of the activator ions is present in the material, which is supported by SEM analysis.

  13. Photoemission using femtosecond laser pulses

    SciTech Connect

    Srinivasan-Rao, T.; Tsang, T.; Fischer, J.

    1991-10-01

    Successful operation of short wavelength FEL requires an electron bunch of current >100 A and normalized emittance < 1 mm-mrad. Recent experiments show that RF guns with photocathodes as the electron source may be the ideal candidate for achieving these parameters. To reduce the emittance growth due to space charge and RF dynamics effects, the gun may have to operate at high field gradient (hence at high RF frequency) and a spot size small compared to the aperture. This may necessitate the laser pulse duration to be in the subpicosecond regime to reduce the energy spread. We will present the behavior of metal photocathodes upon irradiation with femtosecond laser beams, comparison of linear and nonlinear photoemission, and scalability to high currents. Theoretical estimate of the intrinsic emittance at the photocathode in the presence of the anomalous heating of the electrons, and the tolerance on the surface roughness of the cathode material will be discussed.

  14. High energy femtosecond pulse compression

    NASA Astrophysics Data System (ADS)

    Lassonde, Philippe; Mironov, Sergey; Fourmaux, Sylvain; Payeur, Stéphane; Khazanov, Efim; Sergeev, Alexander; Kieffer, Jean-Claude; Mourou, Gerard

    2016-07-01

    An original method for retrieving the Kerr nonlinear index was proposed and implemented for TF12 heavy flint glass. Then, a defocusing lens made of this highly nonlinear glass was used to generate an almost constant spectral broadening across a Gaussian beam profile. The lens was designed with spherical curvatures chosen in order to match the laser beam profile, such that the product of the thickness with intensity is constant. This solid-state optics in combination with chirped mirrors was used to decrease the pulse duration at the output of a terawatt-class femtosecond laser. We demonstrated compression of a 33 fs pulse to 16 fs with 170 mJ energy.

  15. Generation of Femtosecond Electron Pulses

    SciTech Connect

    Jinamoon, V.; Kusoljariyakul, K.; Rimjaem, S.; Saisut, J.; Thongbai, C.; Vilaithong, T.; Rhodes, M.W.; Wichaisirimongkol, P.; Chumphongphan, S.; Wiedemann, H.; /SLAC, SSRL

    2005-05-09

    At the Fast Neutron Research Facility (FNRF), Chiang Mai University (Thailand), the SURIYA project has been established aiming to produce femtosecond electron pulses utilizing a combination of an S-band thermionic rf gun and a magnetic bunch compressor ({alpha}-magnet). A specially designed rf-gun has been constructed to obtain optimum beam characteristics for the best bunch compression. Simulation results show that bunch lengths as short as about 50 fs rms can be expected at the experimental station. The electron bunch lengths will be determined using autocorrelation of coherent transition radiation (TR) through a Michelson interferometer. The paper discusses beam dynamics studies, design, fabrication and cold tests of the rf-gun as well as presents the project current status and forth-coming experiments.

  16. 2 micron femtosecond fiber laser

    DOEpatents

    Liu, Jian; Wan, Peng; Yang, Lihmei

    2014-07-29

    Methods and systems for generating femtosecond fiber laser pulses are disclose, including generating a signal laser pulse from a seed laser oscillator; using a first amplifier stage comprising an input and an output, wherein the signal laser pulse is coupled into the input of the first stage amplifier and the output of the first amplifier stage emits an amplified and stretched signal laser pulse; using an amplifier chain comprising an input and an output, wherein the amplified and stretched signal laser pulse from the output of the first amplifier stage is coupled into the input of the amplifier chain and the output of the amplifier chain emits a further amplified, stretched signal laser pulse. Other embodiments are described and claimed.

  17. Efficient upconversion polymer-inorganic nanocomposite thin film emitters prepared by the double beam matrix assisted pulsed laser evaporation (DB-MAPLE)

    NASA Astrophysics Data System (ADS)

    Darwish, Abdalla M.; Burkett, Allan; Blackwell, Ashley; Taylor, Keylantra; Walker, Vernell; Sarkisov, Sergey; Koplitz, Brent

    2014-09-01

    We report on fabrication and investigation of optical and morphological properties of highly efficient (a quantum yield of 1%) upconversion polymer-inorganic nanocomposite thin film emitters prepared by the new technique of double beam matrix assisted pulsed laser evaporation (DB-MAPLE). Polymer poly(methyl methacrylate) (PMMA) host was evaporated on a silicon substrate using a 1064-nm pulsed laser beam using a target made of frozen (to the temperature of liquid nitrogen) solution of PMMA in chlorobenzene. Concurrently, the second 532-nm pulsed beam from the same laser was used to impregnate the polymer host with the inorganic nanoparticulate made of the rare earth upconversion compounds NaYF4: Yb3+, Er3+, NaYF4: Yb3+, Ho3+, and NaYF4: Yb3+, Tm3+. The compounds were initially synthesized using the wet process, baked, and compressed in solid pellet targets. The proposed DB-MAPLE method has the advantage of making highly homogeneous nanocomposite films with precise control of the doping rate due to the optimized overlapping of the plumes produced by the ablation of the organic and inorganic target with the infrared and visible laser beams respectively. X-ray diffraction, electron and atomic force microscopy, and optical fluorescence spectroscopy indicated that the inorganic nanoparticulate preserved its crystalline structure and upconversion properties (strong emission in green, red, and blue bands upon illumination with 980-nm laser diode) after being transferred from the target in the polymer nanocomposite film. The produced films can be used in applications varying from the efficiency enhancement of the photovoltaic cells, optical sensors and biomarkers to anti-counterfeit labels.

  18. Optofluidic integrated cell sorter fabricated by femtosecond lasers.

    PubMed

    Bragheri, F; Minzioni, P; Martinez Vazquez, R; Bellini, N; Paiè, P; Mondello, C; Ramponi, R; Cristiani, I; Osellame, R

    2012-10-07

    The main trend in optofluidics is currently towards full integration of the devices, thus improving automation, compactness and portability. In this respect femtosecond laser microfabrication is a very powerful technology given its capability of producing both optical waveguides and microfluidic channels. The current challenge in biology is the possibility to perform bioassays at the single cell level to unravel the hidden complexity in nominally homogeneous populations. Here we report on a new device implementing a fully integrated fluorescence-activated cell sorter. This non-invasive device is specifically designed to operate with a limited amount of cells but with a very high selectivity in the sorting process. Characterization of the device with beads and validation with human cells are presented.

  19. Exciton Mobility in Organic Photovoltaic Heterojunctions from Femtosecond Stimulated Raman.

    PubMed

    Hoffman, David P; Leblebici, Sibel Y; Schwartzberg, Adam M; Mathies, Richard A

    2015-08-06

    Exciton mobility is crucial to organic photovoltaic (OPV) efficiency, but accurate, quantitative measures and therefore precise understanding of this process are currently lacking. Here, we exploit the unique capabilities of femtosecond stimulated Raman spectroscopy (FSRS) to disentangle the signatures of the bulk and interfacial donor response in a bulk heterojunction composed of poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and phenyl-C61-butyric acid methyl ester (PCBM). Surprisingly, we find that donor excitons are very mobile for the first ∼300 fs following excitation (before thermalization) even though their overall lifetime is significantly longer (170 ps). A sharp decrease in mobility occurs after the system relaxes out of the Franck-Condon (FC) region. From this observation we predict that any polymer lacking a significant resonance Raman effect and fluorescence Stokes shift, indicating slow FC relaxation and small reorganization energy, will make an efficient OPV material.

  20. Very low threshold green lasing in microspheres by up-conversion of IR photons

    NASA Astrophysics Data System (ADS)

    von Klitzing, W.; Jahier, E.; Long, R.; Lissillour, F.; Lefèvre-Seguin, V.; Hare, J.; Raimond, J.-M.; Haroche, S.

    2000-04-01

    A green up-conversion laser is demonstrated in a 120 µm diameter microsphere of Er 3+-doped ZBLAN at room temperature. Lasing occurs around 540 nm with a 801 nm diode laser pump. The lasing threshold of only 30 µW of absorbed power is over two orders of magnitude lower than the lowest previously observed in IR-visible up-conversion lasing (Funk D S et al 1997 Electron. Lett. 33 1958-60).

  1. Internal upconversion and doubling of an optical parametric oscillator to extend the tuning range.

    NASA Technical Reports Server (NTRS)

    Campillo, A. J.

    1972-01-01

    Efficient extension of the tuning range of a 1.09-1.95-micron parametric oscillator to 0.435-0.975 microns by upconversion and doubling internally to the oscillator cavity is reported. Unlike previously studied external mixing, internal upconversion and doubling yielded uniform powers of 30 and 60 kW, respectively, over the entire extended tuning range with an unfocused 2-mm ruby laser pump beam of 750 kW.-

  2. Z-scan Measurement of the Upconversion Coefficient in Er:YAG

    DTIC Science & Technology

    2009-09-01

    technique for measuring the upconversion coefficient that uses the same continuous wave (CW) source that is used to pump an Er:YAG laser . We find that...The schematic for the experimental setup is shown in figure 2. A 5-MHz linewidth distributed feedback Bragg (DFB) laser diode is temperature tuned...Conclusions In an Er:YAG laser operating at 1645 nm, no upconversion would ideally take place, and the pump photons would have a 1:1 ratio with emitted

  3. Preparation of ZnO nanoparticles showing upconversion luminescence through simple chemical method

    SciTech Connect

    Anjana, R.; Subha, P. P.; Markose, Kurias K.; Jayaraj, M. K.

    2016-05-23

    Upconversion luminescence is an interesting area while considering its applications in a vast variety of fields. Rare earth ions like erbium is the most studied and efficient candidate for achieving upconversion. Erbium and ytterbium co-doped ZnO nanoparticles were prepared through co-precipitation method. A strong red emission has been obtained while exciting with 980 nm laser. Dependence of luminescence emission colour on ytterbium concentration has been studied.

  4. Live cell opto-injection by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Baumgart, J.; Bintig, W.; Ngezahayo, A.; Ertmer, W.; Lubatschowski, H.; Heisterkamp, A.

    2007-02-01

    Fluorescence imaging of cells and cell organelles requires labeling by fluorophores. The labeling of living cells is often done by transfection of fluorescent proteins. Viral vectors are transferring the DNA into the cell. To avoid the use of viruses, it is possible to perforate the cell membrane for example by electro-shocks, the so called electroporation, so that the fluorescent proteins can diffuse into the cell. This method causes cell death in up to 50% of the treated cells because the damage of the outer membrane is too large. A less lethal perforation of the cell membrane with high efficiency can be realized by femtosecond (fs) laser pulses. Transient pores are created by focusing the laser beam for some milliseconds on the membrane. Through this pore, the proteins can enter into the cell. This was demonstrated in a proof of principle experiment for a few cells, but it is essential to develop an opto-perforation system for large numbers of cells in order to obtain statistically significant samples for biological experiments. The relationship between pulse energy, irradiation time, repetition rate and efficacy of the transfer of a chromophor into the cells as well as the viability of the cells was analysed. The cell viability was observed up to 90 minutes after manipulation.

  5. Pulse energy dependence of subcellular dissection by femtosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Heisterkamp, A.; Maxwell, I. Z.; Mazur, E.; Underwood, J. M.; Nickerson, J. A.; Kumar, S.; Ingber, D. E.

    2005-01-01

    Precise dissection of cells with ultrashort laser pulses requires a clear understanding of how the onset and extent of ablation (i.e., the removal of material) depends on pulse energy. We carried out a systematic study of the energy dependence of the plasma-mediated ablation of fluorescently-labeled subcellular structures in the cytoskeleton and nuclei of fixed endothelial cells using femtosecond, near-infrared laser pulses focused through a high-numerical aperture objective lens (1.4 NA). We find that the energy threshold for photobleaching lies between 0.9 and 1.7 nJ. By comparing the changes in fluorescence with the actual material loss determined by electron microscopy, we find that the threshold for true material ablation is about 20% higher than the photobleaching threshold. This information makes it possible to use the fluorescence to determine the onset of true material ablation without resorting to electron microscopy. We confirm the precision of this technique by severing a single microtubule without disrupting the neighboring microtubules, less than 1 micrometer away. c2005 Optical Society of America.

  6. Upconversion white-light emission in Ho3+/Yb3+/Tm3+ tridoped LiNbO3 single crystal.

    PubMed

    Xing, Lili; Wu, Xiaohong; Wang, Rui; Xu, Wei; Qian, Yannan

    2012-09-01

    Ho3+/Yb3+/Tm3+ tridoped LiNbO3 single crystal exhibiting intense upconversion white light under 980 nm excitation has been successfully fabricated by the Czochralski method. The tridoped LiNbO3 single crystal offers power dependent color tuning properties by simply changing excitation power. Efficient three-photon blue upconversion emission and two-photon green and red upconversion emissions have been observed. In addition, the red emission of Ho3+ originates dominantly from the nonradiative decay of green emission. The LiNbO3 with upconversion white light will be a potential laser candidate material.

  7. Femtosecond solvation dynamics in a neat ionic liquid and ionic liquid microemulsion: excitation wavelength dependence.

    PubMed

    Adhikari, Aniruddha; Sahu, Kalyanasis; Dey, Shantanu; Ghosh, Subhadip; Mandal, Ujjwal; Bhattacharyya, Kankan

    2007-11-08

    Solvation dynamics in a neat ionic liquid, 1-pentyl-3-methyl-imidazolium tetra-flouroborate ([pmim][BF4]) and its microemulsion in Triton X-100 (TX-100)/benzene is studied using femtosecond up-conversion. In both the neat ionic liquid and the microemulsion, the solvation dynamics is found to depend on excitation wavelength (lambda(ex)). The lambda(ex) dependence is attributed to structural heterogeneity in neat ionic liquid (IL) and in IL microemulsion. In neat IL, the heterogeneity arises from clustering of the pentyl groups which are surrounded by a network of cation and anions. Such a nanostructural organization is predicted in many recent simulations and observed recently in an X-ray diffraction study. In an IL microemulsion, the surfactant (TX-100) molecules aggregate in form of a nonpolar peripheral shell around the polar pool of IL. The micro-environment in such an assembly varies drastically over a short distance. The dynamic solvent shift (and average solvation time) in neat IL as well as in IL microemulsions decreases markedly as lambda(ex) increases from 375 to 435 nm. In a [pmim][BF4]/water/TX-100/benzene quaternary microemulsion, the solvation dynamics is slower than that in a microemulsion without water. This is ascribed to the smaller size of the water containing microemulsion. The anisotropy decay in an IL microemulsion is found to be faster than that in neat IL.

  8. Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

    NASA Astrophysics Data System (ADS)

    Linz, Norbert; Freidank, Sebastian; Liang, Xiao-Xuan; Vogel, Alfred

    2016-07-01

    The wavelength dependence of the threshold for femtosecond optical breakdown in water provides information on the interplay of multiphoton, tunneling, and avalanche ionization and is of interest for parameter selection in laser surgery. We measured the bubble threshold from ultraviolet to near-infrared wavelengths and found a continuous decrease of the irradiance threshold with increasing wavelength λ . Results are compared to the predictions of a numerical model that assumes a band gap of 9.5 eV and considers the existence of a separate initiation channel via excitation of valence band electrons into a solvated state followed by rapid upconversion into the conduction band. Fits to experimental data yield an electron collision time of ≈1 fs and an estimate for the capacity of the initiation channel. Using that collision time, the breakdown dynamics were explored up to λ = 2 μ m . The irradiance threshold first continues to decrease but levels out for wavelengths longer than 1.3 μ m . This opens promising perspectives for laser surgery at wavelengths around 1.3 and 1.7 μ m , which are attractive because of their large penetration depth into scattering tissues.

  9. Enhanced up-conversion and temperature-sensing behaviour of Er(3+) and Yb(3+) co-doped Y2Ti2O7 by incorporation of Li(+) ions.

    PubMed

    Singh, B P; Parchur, A K; Ningthoujam, R S; Ramakrishna, P V; Singh, S; Singh, P; Rai, S B; Maalej, R

    2014-11-07

    Y2Ti2O7:Er(3+)/Yb(3+) (EYYTO) phosphors co-doped with Li(+) ions were synthesized by a conventional solid-state ceramic method. X-ray diffraction studies show that all the Li(+) co-doped EYYTO samples are highly crystalline in nature with pyrochlore face centred cubic structure. X-ray photon spectroscopy studies reveal that the incorporation of Li(+) ions creates the defects and/or vacancies associated with the sample surface. The effect of Li(+) ions on the photoluminescence up-conversion intensity of EYYTO was studied in detail. The up-conversion study under ∼976 nm excitation for different concentrations of Li(+) ions showed that the green and red band intensities were significantly enhanced. The 2 at% Li(+) ion co-doped EYYTO samples showed nearly 15- and 8-fold enhancements in green and red band up-converted intensities compared to Li(+) ion free EYYTO. The process involved in the up-conversion emission was evaluated in detail by pump power dependence, the energy level diagram, and decay analysis. The incorporation of Li(+) ions modified the crystal field around the Er(3+) ions, thus improving the up-conversion intensity. To investigate the sensing application of the synthesized phosphor materials, temperature-sensing performance was evaluated using the fluorescence intensity ratio technique. Appreciable temperature sensitivity was obtained using the synthesized phosphor material, indicating its applicability as a high-temperature-sensing probe. The maximum sensitivity was found to be 0.0067 K(-1) at 363 K.

  10. Up-conversion cell imaging and pH-induced thermally controlled drug release from NaYF4/Yb3+/Er3+@hydrogel core-shell hybrid microspheres.

    PubMed

    Dai, Yunlu; Ma, Ping'an; Cheng, Ziyong; Kang, Xiaojiao; Zhang, Xiao; Hou, Zhiyao; Li, Chunxia; Yang, Dongmei; Zhai, Xuefeng; Lin, Jun

    2012-04-24

    In this study, we report a new controlled release system based on up-conversion luminescent microspheres of NaYF(4):Yb(3+)/Er(3+) coated with the smart hydrogel poly[(N-isopropylacrylamide)-co-(methacrylic acid)] (P(NIPAM-co-MAA)) (prepared using 5 mol % of MAA) shell. The hybrid microspheres show bright up-conversion fluorescence under 980 nm laser excitation, and turbidity measurements show that the low critical solution temperature of the polymer shell is thermo- and pH-dependent. We have exploited the hybrid microspheres as carriers for Doxorubicin hydrochloride (DOX) due to its stimuli-responsive property as well as good biocompatibility via MTT assay. It is found that the drug release behavior is pH-triggered thermally sensitive. Changing the pH to mildly acidic condition at physiological temperature deforms the structure of the shell, causing the release of a large number of DOX from the microspheres. The drug-loaded microspheres exhibit an obvious cytotoxic effect on SKOV3 ovarian cancer cells. The endocytosis process of drug-loaded microspheres is observed using confocal laser scanning microscopy and up-conversion luminescence microscopy. Meanwhile, the as-prepared NaYF(4):Yb(3+)/Er(3+)@SiO(2)@P(NIPAM-co-MAA) microspheres can be used as a luminescent probe for cell imaging. In addition, the extent of drug release can be monitored by the change of up-conversion emission intensity. These pH-induced thermally controlled drug release systems have potential to be used for in vivo bioimaging and cancer therapy by the pH of the microenvironment changing from 7.4 (normal physiological environment) to acidic microenvironments (such as endosome and lysosome compartments) owing to endocytosis.

  11. Multiphoton fluorescence lifetime imaging of human hair.

    PubMed

    Ehlers, Alexander; Riemann, Iris; Stark, Martin; König, Karsten

    2007-02-01

    In vivo and in vitro multiphoton imaging was used to perform high resolution optical sectioning of human hair by nonlinear excitation of endogenous as well as exogenous fluorophores. Multiphoton fluorescence lifetime imaging (FLIM) based on time-resolved single photon counting and near-infrared femtosecond laser pulse excitation was employed to analyze the various fluorescent hair components. Time-resolved multiphoton imaging of intratissue pigments has the potential (i) to identify endogenous keratin and melanin, (ii) to obtain information on intrahair dye accumulation, (iii) to study bleaching effects, and (iv) to monitor the intratissue diffusion of pharmaceutical and cosmetical components along hair shafts.

  12. Rhodamine-modified upconversion nanophosphors for ratiometric detection of hypochlorous acid in aqueous solution and living cells.

    PubMed

    Zhou, Yi; Pei, Wenbo; Wang, Chenyuan; Zhu, Jixin; Wu, Jiansheng; Yan, Qinyu; Huang, Ling; Huang, Wei; Yao, Cheng; Loo, Joachim Say Chye; Zhang, Qichun

    2014-09-10

    Hypochlorous acid (HOCl), a reactive oxygen species (ROS) produced by myeloperoxidase (MPO) enzyme-mediated peroxidation of chloride ions, acts as a key microbicidal agent in immune systems. However, misregulated production of HOCl could damage host tissues and cause many inflammation-related diseases. Due to its biological importance, many efforts have been focused on developing fluorescent probes to image HOCl in living system. Compared with those conventional fluorescent probes, up-conversion luminescence (UCL) detection system has been proven to exhibit a lot of advantages including no photo-bleaching, higher light penetration depth, no autofluorescence and less damage to biosamples. Herein, we report a novel water-soluble organic-nano detection system based on rhodamine-modified UCNPs for UCL-sensing HOCl. Upon the interaction with HOCl, the green UCL emission intensity in the detection system were gradually decreased, but the emissions in the NIR region almost have no change, which is very important for the ratiometric UCL detection of HOCl in aqueous solution. More importantly, RBH1-UCNPs could be used for the ratiometric UCL visualization of HOCl released by MPO-mediated peroxidation of chloride ions in living cells. This organic-nano system could be further developed into a novel next-generation imaging technique for bio-imaging HOCl in living system without background noise.

  13. Quantum frequency up-conversion of continuous variable entangled states

    SciTech Connect

    Liu, Wenyuan; Wang, Ning; Li, Zongyang; Li, Yongmin

    2015-12-07

    We demonstrate experimentally quantum frequency up-conversion of a continuous variable entangled optical field via sum-frequency-generation process. The two-color entangled state initially entangled at 806 and 1518 nm with an amplitude quadrature difference squeezing of 3.2 dB and phase quadrature sum squeezing of 3.1 dB is converted to a new entangled state at 530 and 1518 nm with the amplitude quadrature difference squeezing of 1.7 dB and phase quadrature sum squeezing of 1.8 dB. Our implementation enables the observation of entanglement between two light fields spanning approximately 1.5 octaves in optical frequency. The presented scheme is robust to the excess amplitude and phase noises of the pump field, making it a practical building block for quantum information processing and communication networks.

  14. Photon avalanche up-conversion in holmium doped fluoride glasses

    SciTech Connect

    Chen, Y.H.; Liu, G.K.; Beitz, J.V.; Jie Wang

    1996-08-01

    Photon avalanche green up-conversion emission centered at 545 nm has been observed in Ho{sup 3+} doped and Ho{sup 3+}, Tm{sup 3+} co-doped ZrF{sub 4}-based fluoride glasses when excited near 585 nm which is off resonance with any ground state absorption bands of either Ho{sup 3+} or Tm{sup 3+} ions. Detailed spectral measurements and analysis suggest that the 545 nm emission occurs from the {sup 5}S{sub 2},{sup 5}F{sub 4} states of Ho{sup 3+} that are populated by excited state absorption from the {sup 5}I{sub 7} state of Ho{sup 3+}. Strong cross-relaxation that efficiently populates the {sup 5}I{sub 7} state makes the photon avalanche process possible in this system.

  15. Erasing distinguishability using quantum frequency up-conversion.

    PubMed

    Takesue, Hiroki

    2008-10-24

    The frequency distinguishability of two single photons was successfully erased using single photon frequency up-conversion. A frequency nondegenerate photon pair generated via spontaneous four-wave mixing in a dispersion shifted fiber was used to emulate two telecom-band single photons that were in the same temporal mode but in different frequency modes. The frequencies of these photons were converted to the same frequency by using the sum-frequency generation process in periodically poled lithium niobate waveguides, while maintaining their temporal indistinguishability. As a result, the two converted photons exhibited a nonclassical dip in a Hong-Ou-Mandel quantum interference experiment. The present scheme will add flexibility to networking quantum information systems that use photons with various wavelengths.

  16. Ultra-broadband mid-wave-IR upconversion detection.

    PubMed

    Barh, Ajanta; Pedersen, Christian; Tidemand-Lichtenberg, Peter

    2017-04-15

    In this Letter, we demonstrate efficient room temperature detection of ultra-broadband mid-wave-infrared (MWIR) light with an almost flat response over more than 1200 nm, exploiting an efficient nonlinear upconversion technique. Black-body radiation from a hot soldering iron rod is used as the IR test source. Placing a 20 mm long periodically poled lithium niobate crystal in a compact intra-cavity setup (>20  W CW pump at 1064 nm), MWIR wavelengths ranging from 3.6 to 4.85 μm are upconverted to near-infrared (NIR) wavelengths (820-870 nm). The NIR light is detected using a standard low-noise silicon-based camera/grating spectrometer. The proposed technique allows high conversion efficiency over a wider bandwidth without any need for a shorter crystal length. Different analytical predictions and numerical simulations are performed a priori to support the experimental demonstrations.

  17. Single Particle Investigations of the Photophysics and Applications of Upconversion Nanoparticles

    NASA Astrophysics Data System (ADS)

    Green, Kory Kevin

    Upconversion nanoparticles doped with rare earth ions represent a relatively efficient medium for converting light from infrared to visible. Although upconversion nanoparticles perform this conversion at higher efficiencies than alternative materials, their utility remains tempered by the low cross section of Erbium ions. Efforts to improve this efficiency have been employed through modification of the host medium of the rare earth ions or to increase their optical cross section by increasing local excitation fields through plasmonic coupling. In order to accurately quantify the effect of modification on emission enhancement, single particle composite structures are used as opposed to ensemble measurements. In addition, finite element modeling was performed in order to 1) predict the effect of potential modifications to excitation and emission enhancement as well as 2) to quantify the level of enhancement provided by optimization of a single type of modification. My work is focused on enhancing the excitation and emission processes in ucponversion nanoparticles through modification of their local environment. I aim to develop bright, efficient, and functional upconverting single nanoparticles that potentially can be used in applications such as biological tracking. First I will demonstrate this enhancement by coating upconversion nanoparticles in a thin gold shell and quantifying the effect of coupling local surface plasmon resonances into the active energy states in the rare earth ions. The presence of local surface plasmons will increase the density of incoming excitation fields thereby enhancing the absorption of the rare earth ions in the upconversion nanoparticles. In addition, these local surface plasmon resonances provide an increased local density of optical energy states which will improve energy transfer and emission efficiency of the upconverting nanoparticles. In addition, an easily generated geometry is presented to increase the density of excitation

  18. Plasmon-enhanced light harvesting of chlorophylls on near-percolating silver films via one-photon anti-Stokes upconversion.

    PubMed

    Wang, Ya-Lan; Nan, Fan; Liu, Xiao-Li; Zhou, Li; Peng, Xiao-Niu; Zhou, Zhang-Kai; Yu, Ying; Hao, Zhong-Hua; Wu, Yan; Zhang, Wei; Wang, Qu-Quan; Zhang, Zhenyu

    2013-01-01

    There exists a wealth of means of efficient utilization of solar energy in nature, with photosynthesis of chlorophylls as a prime example. Separately, artificially structured plasmonic materials are versatile in light harvesting and energy conversion. Using a simple and scalable design of near-percolating silver nanostructures, we demonstrate that the light-harvesting efficiency of chlorophylls can be drastically enhanced by tuning the plasmon frequency of the constituent silver nanoparticles to coincide with the maximal photon flux of sunlight. In particular, we show that the photon upconversion efficiency can be readily enhanced by over 20 folds, with the room-temperature fluorescence quantum yield increased by a factor of 2.63. The underlying mechanism for the upconversion enhancement is attributed to a one-electron-per-photon anti-Stokes process, involving absorption of a characteristic phonon mode of the chlorophylls. These findings suggest that chlorophylls can serve as molecular building blocks for high-efficiency light harvesting and solar energy conversion.

  19. Effects of Upconversion Nanoparticles on Polymerase Chain Reaction

    PubMed Central

    Hwang, Sang-Hyun; Im, Su-Gyeong; Hah, Sang Soo; Cong, Vu Thanh; Lee, Eun Jeong; Lee, Yeon-Su; Lee, Geon Kook

    2013-01-01

    Nanoparticles (NPs) are attractive materials owing to their physical and electrochemical properties, which make them extremely useful in diagnostic applications. Photon upconversion is the phenomenon where high-energy photons are emitted upon excitation of low-energy photons. Nucleic acids detection based on upconversion nanoparticles (UCNPs), which display a high signal-to-noise ratio and no photobleaching, has been widely applied. We evaluated whether UCNPs can improve polymerase chain reaction (PCR) specificity and affect PCR amplification. The effects of UCNPs with a diameter size of 40, 70, and 250 nm were evaluated using 3 PCR kits (AccuPower PCR PreMix, AmpliTaq Gold 360 Master Mix, and HotStarTaq Plus Master Mix) and 3 real-time PCR kits (AccuPower GreenStar qPCR PreMix, SYBR Green PCR Master Mix, and QuantiTect SYBR Green PCR Kit). Quantum dots were used for comparison with the UCNPs. In the presence of an appropriate concentration of UCNPs, PCR specificity was optimized. UCNPs of 40-nm size improved PCR specificity more effectively than did UCNPs sized 70 or 250 nm. As the size and concentrations of the UCNPs were increased, PCR amplification was more severely inhibited. At lower annealing temperatures (25°C–45°C), addition of the 40 nm UCNP (1 µg/µL) to the PCR reagent produced specific PCR products without nonspecific sequence amplification. Therefore, UCNPs of different sizes, with different DNA polymerases used in the commercial kits, showed different inhibitory effects on PCR amplification. These results demonstrate that optimization of UCNPs, added to reaction mixtures at appropriate concentrations, can improve PCR specificity. However, the mechanism underlining UCNPs effect on PCR remains unclear and will require further investigation. PMID:24039935

  20. Upconversion nanoparticles with a strong acid-resistant capping

    NASA Astrophysics Data System (ADS)

    Recalde, Ileana; Estebanez, Nestor; Francés-Soriano, Laura; Liras, Marta; González-Béjar, María; Pérez-Prieto, Julia

    2016-03-01

    Water-dispersible upconversion nanoparticles (β-NaYF4:Yb3+,Er3+, UCNP) coated with a thin shell of a biocompatible copolymer comprising 2-hydroxyethylmethacrylate (HEMA) and 2-acrylamido-2-methyl-1-propanesulphonsulphonic acid (AMPS), which we will term COP, have been prepared by multidentate grafting. This capping is remarkably resistant to strong acidic conditions as low as pH 2. The additional functionality of the smart UCNP@COP nanosystem has been proved by its association to a well-known photosensitizer (namely, methylene blue, MB). The green-to-red emission ratio of the UC@COP@MB nanohybrid exhibits excellent linear dependence in the 7 to 2 pH range as a consequence of the release of the dye as the pH decreases.Water-dispersible upconversion nanoparticles (β-NaYF4:Yb3+,Er3+, UCNP) coated with a thin shell of a biocompatible copolymer comprising 2-hydroxyethylmethacrylate (HEMA) and 2-acrylamido-2-methyl-1-propanesulphonsulphonic acid (AMPS), which we will term COP, have been prepared by multidentate grafting. This capping is remarkably resistant to strong acidic conditions as low as pH 2. The additional functionality of the smart UCNP@COP nanosystem has been proved by its association to a well-known photosensitizer (namely, methylene blue, MB). The green-to-red emission ratio of the UC@COP@MB nanohybrid exhibits excellent linear dependence in the 7 to 2 pH range as a consequence of the release of the dye as the pH decreases. Electronic supplementary information (ESI) available: Additional spectra and data of HEMA, AMPS, COP, UCNP@oleate, UCNP@COP, and UCNP@COP@MB. See DOI: 10.1039/c5nr06653k