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Sample records for femtosecond fluorescence upconversion

  1. Femtosecond broadband fluorescence upconversion spectroscopy: Spectral coverage versus efficiency.

    PubMed

    Gerecke, Mario; Bierhance, Genaro; Gutmann, Michael; Ernsting, Nikolaus P; Rosspeintner, Arnulf

    2016-05-01

    Sum frequency mixing of fluorescence and ∼1300 nm gate pulses, in a thin β-barium borate crystal and non-collinear type II geometry, is quantified as part of a femtosecond fluorimeter [X.-X. Zhang et al., Rev. Sci. Instrum. 82, 063108 (2011)]. For a series of fixed phasematching angles, the upconversion efficiency is measured depending on fluorescence wavelength. Two useful orientations of the crystal are related by rotation around the surface normal. Orientation A has higher efficiency (factor ∼3) compared to B at the cost of some loss of spectral coverage for a given crystal angle. It should be used when subtle changes of an otherwise stationary emission band are to be monitored. With orientation B, the fluorescence range λF > 420-750 nm is covered with a single setting of the crystal and less gate scatter around time zero. The accuracy of determining an instantaneous emission band shape is demonstrated by comparing results from two laboratories. PMID:27250400

  2. 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

  3. Femtosecond fluorescence upconversion studies of excited-state proton-transfer dynamics in 2-(2 '-hydroxyphenyl)benzoxazole (HBO) in liquid solution and DNA

    NASA Astrophysics Data System (ADS)

    Wang, H.; Zhang, H.; Abou-Zied, O. K.; Yu, C.; Romesberg, F. E.; Glasbeek, M.

    2003-01-01

    A femtosecond fluorescence upconversion study is reported for HBO in solution, as well as for HBO incorporated in DNA. The typical time for the excited-state intramolecular proton-transfer reaction of the syn-enol tautomer in solution and in DNA has been determined to be 150 fs. In addition, the lifetimes of the keto, the anti-enol and the 'solvated enol' tautomer forms were determined in protic solvents, aprotic solvents and DNA. Picosecond rise and decay components in the fluorescence transients with characteristic times between 3 and 25 ps are also observed and attributed to the effects of vibrational cooling.

  4. 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.

  5. 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. PMID:27367751

  6. 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

  7. Paper-based microfluidic device with upconversion fluorescence assay.

    PubMed

    He, Mengyuan; Liu, Zhihong

    2013-12-17

    A paper-based microfluidic device with upconversion fluorescence assay (named as UC-μPAD) is proposed. The device is fabricated on a normal office printing sheet with a simple plotting method. Upconversion phosphors (UCPs) tagged with specific probes are spotted to the test zones on the μPAD, followed by the introduction of assay targets. Upconversion fluorescence measurements are directly conducted on the test zones after the completion of the probe-to-target reactions, without any post-treatments. The UC-μPAD features very easy fabrication and operation, simple and fast detection, low cost, and high sensitivity. UC-μPAD is a promising prospect for a clinical point-of-care test. PMID:24308347

  8. 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. PMID:23340955

  9. Ratiometric fluorescent nanosensors for selective detecting cysteine with upconversion luminescence.

    PubMed

    Guan, Yunlong; Qu, Songnan; Li, Bin; Zhang, Liming; Ma, Heping; Zhang, Ligong

    2016-03-15

    Fluorescent sensors based on upconversion (UC) luminescence have been considered as a promising strategy to detect bio-analyte due to their advantages in deep penetration, minimum autofluorescence, and ratiometric fluorescent output. A prototype of nanosensors combined with mesoporous silica coated upconversion nanoparticles (UCNPs) and a fluorescein-based fluorescent probe loaded in pores was therefore designed to detect cysteine (Cys). The silica shell provided loading space for the probe and enabled the nanosensors to disperse in water. In the presence of Cys, the fluorescent probe was transformed into 5(6)-carboxyfluorescein with an emission band centering at 518 nm which was secondarily excited by the light at around 475 nm from NaYF4:Yb(3+), Tm(3+) UCNPs driven by 980 nm near-infrared (NIR) laser. The intensity ratio between green and blue luminescence (I518/I475) grew exponentially with increasing concentrations of Cys over a range of 20-200 μmolL(-1). The response of the nanosensors towards Cys was recognizable with naked eyes by luminescence color change. Evidences suggest that these nanosensors are capable of sensing Cys in aqueous solution and distinguishing Cys from homocysteine (Hcy) with kinetically-controlled selectivity. The system was further employed to detect Cys in human serum and the result was in agreement with it tested by high performance liquid chromatography with acceptable recovery. PMID:26402589

  10. 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. PMID:27236725

  11. 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.

  12. Graphene quantum dots from graphite by liquid exfoliation showing excitation-independent emission, fluorescence upconversion and delayed fluorescence.

    PubMed

    Sarkar, Suprabhat; Gandla, Dayakar; Venkatesh, Yeduru; Bangal, Prakriti Ranjan; Ghosh, Sutapa; Yang, Yang; Misra, Sunil

    2016-08-21

    Facile synthesis of 2-10 nm-sized graphene quantum dots (GQDs) from graphite powder by organic solvent-assisted liquid exfoliation using a sonochemical method is reported in this study. Synthesized GQDs are well dispersed in organic solvents like ethyl acetoacetate (EAA), dimethyl formamide (DMF) and also in water. MALDI-TOF mass spectrometry reveals its selective mass fragmentation. Detailed characterizations by various techniques like X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) confirm the formation of disordered, functional GQDs. Density functional theory (DFT) calculation confirms HOMO-LUMO energy gap variation with changing size and functionalities. Photoluminescence (PL) properties of as-prepared GQDs were studied in detail. The ensemble studies of GQDs showed excellent photoluminescence properties comprising normal and upconverted fluorescence, delayed fluorescence and room-temperature phosphorescence. PL decay dynamics of GQDs has been explored using time-correlated single-photon technique (TCSPC) as well as femtosecond fluorescence upconversion technique. In vitro cytotoxicity study reveals its biocompatibility and high cell viability (>91%) even at high concentration (400 μg mL(-1)) of GQDs in Chinese Hamster Ovary (CHO) cells. PMID:27302411

  13. Ultrafast fluorescence upconversion technique and its applications to proteins.

    PubMed

    Chosrowjan, Haik; Taniguchi, Seiji; Tanaka, Fumio

    2015-08-01

    The basic principles and main characteristics of the ultrafast time-resolved fluorescence upconversion technique (conventional and space-resolved), including requirements for nonlinear crystals, mixing spectral bandwidth, acceptance angle, etc., are presented. Applications to flavoproteins [wild-type (WT) FMN-binding protein and its W32Y, W32A, E13R, E13K, E13Q and E13T mutants] and photoresponsive proteins [WT photoactive yellow protein and its R52Q mutant in solution and as single crystals] are demonstrated. For flavoproteins, investigations elucidating the effects of ionic charges on ultrafast electron transfer (ET) dynamics are summarized. It is shown that replacement of the ionic amino acid Glu13 and the resulting modification of the electrostatic charge distribution in the protein chromphore-binding pocket substantially alters the ultrafast fluorescence quenching dynamics and ET rate in FMN-binding protein. It is concluded that, together with donor-acceptor distances, electrostatic interactions between ionic photoproducts and other ionic groups in the proteins are important factors influencing the ET rates. In WT photoactive yellow protein and the R52Q mutant, ultrafast photoisomerization dynamics of the chromophore (deprotonated trans-p-coumaric acid) in liquid and crystal phases are investigated. It is shown that the primary dynamics in solution and single-crystal phases are quite similar; hence, the photocycle dynamics and structural differences observed at longer time scales arise mostly from the structural restraints imposed by the crystal lattice rigidity versus the flexibility in solution. PMID:25532707

  14. 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. PMID:18596348

  15. Ultrafast Dynamics of Polythiophene with Phenyl Vinylene Branches Studied by Femtosecond Fluorescence Spectroscopy in Solution

    NASA Astrophysics Data System (ADS)

    Chu, Sai-Sai; Gao, Chao; Wang, Shu-Feng; Gong, Qi-Huang

    2011-11-01

    Two polythiophene based polymers, poly[(3-[2-[4-(2-ethyl-hexyloxy)-phenyl]-vinyl]-thiophene)-co-thiophene] (PT1) and poly(3-[2-[4-(2-ethyl-hexyloxy)-phenyl]-vinyl]-thiophene) (PT2), are synthesized and investigated by static, picosecond fluorescence spectroscopies and the femtosecond up-conversion technique in solution. Compared with pristine poly(3-hexylthiophene) (P3HT), PT1 and PT2, in which the main chains are decorated with phenyl vinylene present a ‘camel back’ structure in the absorption spectra. Phenyl vinylene side chains induce a new process of charge transfer, chain twisting motion and defect-induced fluorescence quenching at time scales of 1 ps, 10 ps and 150 ps, respectively.

  16. 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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  19. 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

  20. Microbubble embedded with upconversion nanoparticles as a bimodal contrast agent for fluorescence and ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Jin, Birui; Lin, Min; You, Minli; Zong, Yujin; Wan, Mingxi; Xu, Feng; Duan, Zhenfeng; Lu, Tianjian

    2015-08-01

    Bimodal imaging offers additional imaging signal thus finds wide spread application in clinical diagnostic imaging. Fluorescence/ultrasound bimodal imaging contrast agent using fluorescent dyes or quantum dots for fluorescence signal has emerged as a promising method, which however requires visible light or UV irradiation resulting in photobleaching, photoblinking, auto-fluorescence and limited tissue penetration depth. To surmount these problems, we developed a novel bimodal contrast agent using layer-by-layer assembly of upconversion nanoparticles onto the surface of microbubbles. The resulting microbubbles with average size of 2 μm provide enhanced ultrasound echo for ultrasound imaging and upconversion emission upon near infrared irradiation for fluorescence imaging. The developed bimodal contrast agent holds great potential to be applied in ultrasound target technique for targeted diseases diagnostics and therapy.

  1. Enhanced upconversion luminescence from ZnO/Zn hybrid nanostructures induced on a Zn foil by femtosecond laser ablation.

    PubMed

    Li, Hui; Zhang, Cheng-Yun; Li, Xian-Feng; Xiang, Jin; Tie, Shao-Long; Lan, Sheng

    2015-11-16

    ZnO/Zn hybrid nanostructures including nanowires and nanonets were induced on a Zn foil by using 400-nm femtosecond (fs) laser pulses with a low repetition rate of 1 kHz and duration of 100 fs. The laser fluence was chosen to be slightly above the ablation threshold of Zn. The luminescence of the formed ZnO/Zn hybrid nanostructures was examined by using fs laser pulses with a high repetition rate of 76 MHz and duration of ~130 fs through both single-photon and multiphoton excitation. While the luminescence spectrum under the single-photon excitation exhibited a single peak at ~480 nm, a broadband upconversion luminescence with many ripples was observed under the multiphoton excitation. More interestingly, the upconversion luminescence of the ZnO/Zn hybrid nanostructures was significantly enhanced by the underlying Zn nanostructures which induced strongly localized electric field. The enhancement of the upconversion luminescence was verified by the short lifetime of only ~79 ps observed for the ZnO/Zn hybrid nanostructures, which is nearly one order of magnitude smaller as compared with the luminescence lifetime of the ZnO nanorods synthesized by using the chemical coprecipitation method. The localization of electric field in the ZnO/Zn hybrid nanostructures was confirmed by the numerical simulations based the finite-difference time-domain technique. PMID:26698492

  2. Multifunctional upconversion nanoprobe for tumor fluorescence imaging and near-infrared thermal therapy

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  4. 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.

  5. An upconversion fluorescent resonant energy transfer biosensor for hepatitis B virus (HBV) DNA hybridization detection.

    PubMed

    Zhu, Hao; Lu, Feng; Wu, Xing-Cai; Zhu, Jun-Jie

    2015-11-21

    A novel fluorescent resonant energy transfer (FRET) biosensor was fabricated for the detection of hepatitis B virus (HBV) DNA using poly(ethylenimine) (PEI) modified upconversion nanoparticles (NH2-UCNPs) as energy donor and gold nanoparticles (Au NPs) as acceptor. The PEI modified upconversion nanoparticles were prepared directly with a simple one-pot hydrothermal method, which provides high quality amino-group functionalized UCNPs with uniform morphology and strong upconversion luminescence. Two single-stranded DNA strands, which were partially complementary to each other, were then conjugated with NH2-UCNPs and Au NPs. When DNA conjugated NH2-UCNPs and Au NPs are mixed together, the hybridization between complementary DNA sequences on UCNPs and Au NPs will lead to the quenching of the upconversion luminescence due to the FRET process. Meanwhile, upon the addition of target DNA, Au NPs will leave the surface of the UCNPs and the upconversion luminescence can be restored because of the formation of the more stable double-stranded DNA on the UCNPs. The sensor we fabricated here for target DNA detection shows good sensitivity and high selectivity, which has the potential for clinical applications in the analysis of HBV and other DNA sequences. PMID:26421323

  6. 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

  7. 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. PMID:25322197

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

    PubMed

    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:Yb(3+),Er(3+),Tm(3+) 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. PMID:27102984

  9. Femtosecond laser fluorescence and propagation in very dense potassium vapor.

    PubMed

    Makdisi, Y; Kokaj, J; Afrousheh, K; Nair, R; Mathew, J; Pichler, G

    2013-12-16

    Femtosecond (fs) laser propagation and fluorescence of dense potassium vapor was studied, and the spectral region around the first and the second doublets of the principal series lines of potassium atoms was investigated. In our search we did not observe the conical emission in the far field, although it was previously observed in the case of rubidium. We discuss the possible reason of this unexpected result. The fluorescence spectrum revealed Rb impurity resonance lines in emission due to the collisional redistribution from the K(4p) levels into the Rb(5p) levels. In the forward propagation of 400 nm femtosecond light we observed the molecular band red shifted from potassium second doublet. However, no molecular spectrum was observed when the mode-locked fs laser light was discretely tuned within the wings of the first resonance lines, at 770 nm. PMID:24514609

  10. Optical properties and upconversion fluorescence in Er 3+-doped ZZA glass

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Pita, K.; Buddhudu, S.; Daran, E.; Lam, Y. L.; Liu, X. R.

    2002-08-01

    We report the optical properties and upconversion emissions from the Er 3+ ions in a ZrF 4-based glass system ZrF 4-ZnF 2-AlF 3. Judd-Ofelt intensity parameters ( Ω (t) with t=2,4,6) were obtained by analyzing the room temperature absorption spectrum. Upon 800 nm laser excitation, upconversion fluorescence was observed in blue, green and red regions at both 25 and 300 K. The main mechanism appears to be energy transfer among Er 3+ ions in excited states. The green and red emissions result from a two-step process while the blue one is owing to a three-step energy transfer process.

  11. Efficient green and red fluorescence upconversion in erbium doped new low phonon antimony glasses

    NASA Astrophysics Data System (ADS)

    Som, Tirtha; Karmakar, Basudeb

    2009-02-01

    New K 2O-B 2O 3-Sb 2O 3 (KBS) glass system having low phonon energy (about 600 cm -1) doped with Er 3+ ions has been developed. Infrared reflection spectroscopic (IRRS) studies have been employed to establish its low phonon energy. Ultraviolet-visible-near infrared (UV-vis-NIR) absorption and photoluminescence upconversion properties with special emphasis on the spectrochemistry of the 15K 2O-15B 2O 3-70Sb 2O 3 (mol%) glass have been studied doping with different concentrations (0.1-1.0 wt%) of Er 2O 3. UV-vis-NIR absorption band positions have been justified with quantitative calculation of nephelauxetic parameter and covalent bonding characteristics of the host. NIR to visible upconversion has been investigated by exciting at 798 nm at room temperature. Three upconverted bands originating from the 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2 and 4F 9/2 → 4I 15/2 transitions are found to be centered at 522 (green, very weak), 536 (green, medium) and 645 (red, strong) nm, respectively. These bands have been explained from the evaluation of the absorption, normal (down conversion) fluorescence and excitation spectra. The upconversion processes have been explained by the excited state absorption (ESA), energy transfer (ET), cooperative energy transfer (CET) and cross relaxation (CR) mechanisms involving population of the metastable (storage) energy levels ( 2H 11/2, 4S 3/2 and 4F 9/2) by effects of multiphonon deexcitation and thermal population. It is evident from the IRRS study that the upconversion phenomena are expedited by the low multiphonon relaxation rate in antimony glasses owing to their high intense low phonon energy (602 cm -1) which is very close to that of fluoride glasses (500-600 cm -1). We are the first to report the upconversion fluorescence of Er 3+ ions in KBS antimony glasses.

  12. 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. PMID:19764797

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

    PubMed

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

    2016-08-01

    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 0.2ng·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. PMID:27124091

  14. 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.

  15. 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.

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

    PubMed

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

    2016-07-22

    The paper presents the growth of hexagonal NaYF4:Yb(3+), Tm(3+) nanocrystals with tunable sizes induced by different contents of doped Yb(3+) 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% Yb(3+) ions doped nanoparticles are able to be self-assembled into an ordered inorganic monolayer membrane with a large area of about 10 × 10 μm(2). 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. PMID:27292186

  17. 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. PMID:26722764

  18. 808 nm driven Nd3+-sensitized upconversion nanostructures for photodynamic therapy and simultaneous fluorescence imaging.

    PubMed

    Wang, Dan; Xue, Bin; Kong, Xianggui; Tu, Langping; Liu, Xiaomin; Zhang, Youlin; Chang, Yulei; Luo, Yongshi; Zhao, Huiying; Zhang, Hong

    2015-01-01

    The in vivo biological applications of upconversion nanoparticles (UCNPs) prefer excitation at 700-850 nm, instead of 980 nm, due to the absorption of water. Recent approaches in constructing robust Nd(3+) doped UCNPs with 808 nm excitation properties rely on a thick Nd(3+) sensitized shell. However, for the very important and popular Förster resonance energy transfer (FRET)-based applications, such as photodynamic therapy (PDT) or switchable biosensors, this type of structure has restrictions resulting in a poor energy transfer. In this work, we have designed a NaYF4:Yb/Ho@NaYF4:Nd@NaYF4 core-shell-shell nanostructure. We have proven that this optimal structure balances the robustness of the upconversion emission and the FRET efficiency for FRET-based bioapplications. A proof of the concept was demonstrated for photodynamic therapy and simultaneous fluorescence imaging of HeLa cells triggered by 808 nm light, where low heating and a high PDT efficacy were achieved. PMID:25406514

  19. [The study of up-conversion fluorescence in Er3+:Yb3+ co-doped oxy-fluoride glasses].

    PubMed

    Yang, Xiao-liang; Liu, Zheng-wei; Xiao, Si-guo

    2002-06-01

    Er3+:Yb3+ co-doped oxy-fluoride glasses with composition of (50-x) GeO2.PbF2.WO3.(6 + x) CdF2.1.4Yb2O3.0.6Er2O3 (x = 10,20,30) were prepared. Their up-conversion fluorescence characteristics were investigated under excitation of 930 nm diode laser. Three strong fluorescence bands of Er3+ whose central wavelength lie in 543, 550 and 655 nm have been observed. The maximum phonon energy is obtained by measuring anti-stokes Raman shifts of the samples, and the up-conversion mechanism is briefly discussed. The influences of host materials composition on up-conversion efficiency are also discussed adopting the average electronegative difference and the cationic field strength of the host. It is found that relative small average electronegative difference and large cationic field strength of host benefit to energy up-conversion. PMID:12938302

  20. Synthesis of improved upconversion nanoparticles as ultrasensitive fluorescence probe for mycotoxins.

    PubMed

    Chen, Quansheng; Hu, Weiwei; Sun, Cuicui; Li, Huanhuan; Ouyang, Qin

    2016-09-28

    Rare earth-doped upconversion nanoparticles (UCNPs) have promising potentials in biodetection due to their unique frequency upconverting capability and high detection sensitivity. This paper reports an improved UCNPs-based fluorescence probe for dual-sensing of Aflatoxin B1 (AFB1) and Deoxynivalenol (DON) using a magnetism-induced separation and the specific formation of antibody-targets complex. Herein, the improved UCNPs, which were namely NaYF4:Yb/Ho/Gd and NaYF4:Yb/Tm/Gd, were systematically studied based on the optimization of reaction time, temperature and the concentration of dopant ions with simultaneous phase and size controlled NaYF4 nanoparticles; and the targets were detected using the pattern of competitive combination assay. Under an optimized condition, the advanced fluorescent probes revealed stronger fluorescent properties, broader biological applications and better storage stabilities compared to traditional UCNPs-based ones; and ultrasensitive determinations of AFB1 and DON were achieved under a wide sensing range of 0.001-0.1 ng ml(-1) with the limit of detection (LOD) of 0.001 ng ml(-1). Additionally, the applicability of the improved nanosensor for the detection of mycotoxins was also confirmed in adulterated oil samples. PMID:27619096

  1. Upconversion particles coated with molecularly imprinted polymers as fluorescence probe for detection of clenbuterol.

    PubMed

    Tang, Yiwei; Gao, Ziyuan; Wang, Shuo; Gao, Xue; Gao, Jingwen; Ma, Yong; Liu, Xiuying; Li, Jianrong

    2015-09-15

    A novel fluorescence probe based on upconversion particles, YF3:Yb(3+), Er(3+), coating with molecularly imprinted polymers (MIPs@UCPs) has been synthesized for selective recognition of the analyte clenbuterol (CLB), which was characterized by scan electron microscope and X-ray powder diffraction. The fluorescence of the MIPs@UCPs probe is quenched specifically by CLB, and the effect is much stronger than the NIPs@UCPs (non-imprinting polymers, NIPs). Good linear correlation was obtained for CLB over the concentration range of 5.0-100.0 μg L(-1) with a detection limit of 0.12 μg L(-1) (S/N=3). The developed method was also used in the determination of CLB in water and pork samples, and the recoveries ranged from 81.66% to 102.46% were obtained with relative standard deviation of 2.96-4.98% (n=3). The present study provides a new and general tactics to synthesize MIPs@UCPs fluorescence probe with highly selective recognition ability to the CLB and is desirable for application widely in the near future. PMID:25884733

  2. MMP2-sensing up-conversion nanoparticle for fluorescence biosensing in head and neck cancer cells.

    PubMed

    Chan, Yung-Chieh; Chen, Chieh-Wei; Chan, Ming-Hsien; Chang, Yu-Chan; Chang, Wei-Min; Chi, Li-Hsing; Yu, Hui-Ming; Lin, Yuan-Feng; Tsai, Din Ping; Liu, Ru-Shi; Hsiao, Michael

    2016-06-15

    Upconversion nanoparticles (UCNPs) have extensive biological-applications because of their bio-compatibility, tunable optical properties and their ability to be excited by infrared radiation. Matrix metalloproteinases (MMPs) play important roles in extracellular matrix remodelling; they are usually found to significantly increase during cancer progression, and these increases may lead to poor patient survival. In this study, we produced a biosensor that can be recognized by MMP2 and then be unravelled by the attached quencher to emit visible light. We used 3.5-nm gold nanoparticles as a quencher that absorbed emission from UCNPs at a wavelength of 540 nm. The biosensor consists of an upconversion nanoparticle, MMP2-recognized polypeptides and quenchers. Here, UCNPs consisting of NaYF4:Yb(3+)/Er(3+) were prepared via a high temperature co-precipitation method while protecting the oleic acid ligand. To improve the biocompatibility and modify the UCNPs with a polypeptide, they were coated with a silica shell and further conjugated with MMP-recognizing polypeptides. The polypeptide has two ends of featuring carboxylic and thiol groups that react with UCNPs and AuNPs, and the resulting nanoparticles were referred to as UCNP@p-Au. According to the in vitro cell viability analysis, UCNP@p-Au exhibited little toxicity and biocompatibility in head and neck cancer cells. Cellular uptake studies showed that the MMP-based biosensor was activated by 980-nm irradiation to emit green light. This MMP-based biosensor may serve as sensitive and specific molecular fluorescent probe in biological-applications. PMID:26820361

  3. 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

  4. Upconversion fluorescence resonance energy transfer based biosensor for ultrasensitive detection of matrix metalloproteinase-2 in blood.

    PubMed

    Wang, Yuhui; Shen, Pei; Li, Chunya; Wang, Yanying; Liu, Zhihong

    2012-02-01

    Matrix metalloproteinase-2 (MMP-2) is a very important biomarker in blood. Presently, sensitive and selective determination of MMP-2 directly in blood samples is still a challenging job because of the high complexity of the sample matrix. In this work, we reported a new homogeneous biosensor for MMP-2 based on fluorescence resonance energy transfer (FRET) from upconversion phosphors (UCPs) to carbon nanoparticles (CNPs). A polypeptide chain (NH(2)-GHHYYGPLGVRGC-COOH) comprising both the specific MMP-2 substrate domain (PLGVR) and a π-rich motif (HHYY) was designed and linked to the surface of UCPs at the C terminus. The FRET process was initiated by the π-π interaction between the peptide and CNPs, which thus quenched the fluorescence of the donor. Upon the cleavage of the substrate by the protease at the amide bond between Gly and Val, the donor was separated from the acceptor while the π-rich motif stayed on the acceptor. As a result, the fluorescence of the donor was restored. The fluorescence recovery was found to be proportional to the concentration of MMP-2 within the range from 10-500 pg/mL in an aqueous solution. The quantification limit of this sensor was at least 1 order of magnitude lower than that of other reported assays for MMP-2. The sensor was used to determine the MMP-2 level directly in human plasma and whole blood samples with satisfactory results obtained. Owing to the hypersensitivity of the method, clinical samples of only less than 1 μL were needed for accurate quantification, which can be meaningful in MMP-2-related clinical and bioanalytical applications. PMID:22242647

  5. 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.

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

    PubMed

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

    2016-09-01

    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

  7. 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. PMID:27119377

  8. 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.

  9. Upconversion-induced delayed fluorescence in multicomponent organic systems: Role of Dexter energy transfer

    NASA Astrophysics Data System (ADS)

    Monguzzi, A.; Tubino, R.; Meinardi, F.

    2008-04-01

    The efficiency of the upconversion-induced delayed fluorescence in a solution of multicomponent organic systems is limited by two steps of the overall process: (i) a triplet-triplet energy transfer between a phosphorescent donor and an emitting acceptor, and (ii) a bimolecular acceptor triplet-triplet annihilation generating acceptor singlet excited states from which the high-energy emission takes place. In this work, the energy transfer process has been investigated in a model system constituted by solutions of Pt(II)octaethylporphyrin, which acts as a donor, and 9,10 diphenylanthracene, which acts as an acceptor. At low temperature, the experimental data have been interpreted in the frame of a pure Dexter energy transfer by using the Perrin approximation. A Dexter radius as large as 26.5 Å has been found. At room temperature, the fast diffusion of the molecules in the solution is no longer negligible, which gives rise to a strong increase in the energy transfer rates.

  10. 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)

  11. 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.

  12. Materials Integrating Photochemical Upconversion.

    PubMed

    McCusker, Catherine E; Castellano, Felix N

    2016-04-01

    This review features recent experimental work focused on the preparation and characterization of materials that integrate photochemical upconversion derived from sensitized triplet-triplet annihilation, resulting in the conversion of low energy photons to higher energy light, thereby enabling numerous wavelength-shifting applications. Recent topical developments in upconversion include encapsulating or rigidifying fluid solutions to give them mechanical strength, adapting inert host materials to enable upconversion, and using photoactive materials that incorporate the sensitizer and/or the acceptor. The driving force behind translating photochemical upconversion from solution into hard and soft materials is the incorporation of upconversion into devices and other applications. At present, some of the most promising applications of upconversion materials include imaging and fluorescence microscopy, photoelectrochemical devices, water disinfection, and solar cell enhancement. PMID:27573144

  13. Upconversion fluorescence resonance energy transfer biosensor with aromatic polymer nanospheres as the lable-free energy acceptor.

    PubMed

    Wang, Yuhui; Wu, Zhengjun; Liu, Zhihong

    2013-01-01

    We report a new upconversion fluorescence resonance energy transfer (UC-FRET) biosensor using poly-m-phenylenediamine (PMPD) nanospheres as the energy acceptor in this paper. A single-stranded DNA (ssDNA) tagged with a sulfydryl group at the 5'-terminus was covalently linked to poly(ethylenimine) (PEI) functionalized upconversion phosphors (UCPs, the energy donor). Because of the π-rich electronic structure of PMPD, self-assembly of the donor and the acceptor was achieved through the π-π stacking interaction between ssDNA and PMPD. The fluorescence of the donor was quenched by the acceptor in a PMPD-concentration-dependent manner. A maximum quenching degree of 90% was acquired, which was among the highest levels of all previous reports. Upon the formation of double-stranded DNA (dsDNA) between the target DNA and the probe DNA, the energy acceptor was separated from the donor due to the weakened interaction between dsDNA and PMPD. The fluorescence of UCPs was accordingly restored, and a linear response was obtained with the target concentration ranging from 0.1 to 6.0 nM. The limit of detection was calculated as 0.036 nM, which was a highly competitive sensitivity. The sensor also showed high precision, pronounced specificity, and the applicability to complicated sample matrix (human serum). The UCPs-PMPD FRET sensing platform takes advantages of both the optical merits of the upconversion donors and the superquenching ability and good water-solubility of the aromatic polymer nanoparticles. This study will open the opportunity to develop a new class of UC-FRET biosensors. PMID:23186324

  14. 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. PMID:20940907

  15. 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

  16. Design of poly(ethylene glycol)/streptavidin coimmobilized upconversion nanophosphors and their application to fluorescence biolabeling.

    PubMed

    Kamimura, Masao; Miyamoto, Daisuke; Saito, Yu; Soga, Kohei; Nagasaki, Yukio

    2008-08-19

    Infrared-to-visible upconversion phosphors (i.e., rare earth ion-doped Y2O3 nanoparticles (UNPs)) were synthesized by the homogeneous precipitation method. Because the charge on the erbium (Er) ion-doped Y2O3 (Y2O3:Er) NP (UNP1) surface is positive under neutral conditions, the UNP1 surface was electrostatically PEGylated using negatively charged poly(ethylene glycol)- b-poly(acrylic acid) (PEG- b-PAAc). The adsorption of PEG- b-PAAc was confirmed by Fourier transform infrared (FT-IR) measurements and thermal gravimetric analysis (TGA). The surface charge of the PEGylated UNP1s (PEG-UNP1s) was effectively shielded by the PEGylation. The dispersion stability of the UNP1s was also significantly improved by the PEGylation. The PEG-UNP1s were dispersed over 1 week under physiological conditions as a result of the steric repulsion between the PEG chains on the UNP1 surface. The upconversion emission spectrum of PEG-UNP1s was observed under physiological conditions and was confirmed by near-infrared excited fluorescence microscope observation. Streptavidin (SA)-installed ytterbium (Yb) and Er ion-codoped Y2O3 (Y2O3:Yb,Er) NPs (UNP2s) were prepared by the coimmobilization of PEG- b-PAAc and streptavidin. The PEG/SA coimmobilized UNP2s (PEG/SA-UNP2s) specifically recognized biotinylated antibodies and emitted strong upconversion luminescence upon near-infrared excitation. The obtained PEG/streptavidin coimmobilized UNPs are promising as high-performance near-infrared biolabeling materials. PMID:18652424

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

    PubMed

    Laurenti, Marco; Paez-Perez, Miguel; Algarra, Manuel; Alonso-Cristobal, Paulino; Lopez-Cabarcos, Enrique; Mendez-Gonzalez, Diego; Rubio-Retama, Jorge

    2016-05-25

    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 sp(2) 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

  18. 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.

  19. Ultraviolet femtosecond Kerr-gated wide-field fluorescence microscopy.

    PubMed

    Blake, Jolie C; Nieto-Pescador, Jesus; Li, Zhengxin; Gundlach, Lars

    2016-06-01

    A Kerr-gated microscope capable of imaging ultraviolet luminescence with femtosecond time resolution has been developed. The system allows the spatial, spectral, and temporal measurement of UV-emitting samples. The instrumentation was optimized for emission collection in the UV, resulting in sub 90 fs time resolution of gated signals. ZnO nanowires were used to demonstrate the performance of the instrument. The evolution of the emission from a single nanowire was tracked via ultrafast transient spectroscopy and through sequential imaging. Transient dynamics were extracted from a region of intense emission on a single ZnO nanowire. This technique is a powerful tool capable of contactless ultrafast measurements of charge carrier dynamics in single nanoparticles. PMID:27244389

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

    PubMed Central

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

    2012-01-01

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

  1. Femtosecond lasing from a fluorescent protein in a one dimensional random cavity

    PubMed Central

    Drane, T.M.; Bach, H.; Shapiro, M.; Milner, V.

    2015-01-01

    We present evidence of random lasing from the fluorescent protein DsRed2 embedded in a random one-dimensional cavity. Lasing is achieved when a purified protein solution, placed inside a layered random medium, is optically excited with a femtosecond pump pulse in the direction perpendicular to the plane of random layers. We demonstrate that pumping with ultrashort pulses resulted in a lasing threshold two orders of magnitude lower than that found for nanosecond excitation. PMID:26137388

  2. Femtosecond lasing from a fluorescent protein in a one dimensional random cavity.

    PubMed

    Drane, T M; Bach, H; Shapiro, M; Milner, V

    2015-05-01

    We present evidence of random lasing from the fluorescent protein DsRed2 embedded in a random one-dimensional cavity. Lasing is achieved when a purified protein solution, placed inside a layered random medium, is optically excited with a femtosecond pump pulse in the direction perpendicular to the plane of random layers. We demonstrate that pumping with ultrashort pulses resulted in a lasing threshold two orders of magnitude lower than that found for nanosecond excitation. PMID:26137388

  3. 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. PMID:27134048

  4. A novel upconversion, fluorescence resonance energy transfer biosensor (FRET) for sensitive detection of lead ions in human serum.

    PubMed

    Xu, Sai; Xu, Shihan; Zhu, Yongsheng; Xu, Wen; Zhou, Pingwei; Zhou, Chunyang; Dong, Biao; Song, Hongwei

    2014-11-01

    There has been great progress in the development of fluorescence biosensors based on quantum dots (QDs) for the detection of lead ions. However, most methods are detecting lead ions in aqueous solution rather than in human serum due to the influence of protein autofluorescence in serum excited by visible light. Thus, we developed a novel fluorescence resonance energy transfer (FRET) biosensor by choosing the upconversion NaYF4:Yb(3+)/Tm(3+) nanoparticles as the energy donor and the CdTe QDs as the energy acceptor for lead ion detection. It is the first near infrared (NIR)-excited fluorescent probe for determination of lead ions in serum that is capable of overcoming self-luminescence from serum excitation with visible light. The sensor also shows high selectivity, a low detection limit (80 nm) and good linear Stern-Volmer characteristics (R = 0.996), both in the buffer and serum. This biosensor has great potential for versatile applications in lead ion detection in biological and analytical fields. PMID:25184968

  5. Theoretical analysis of fluorescence signals in filamentation of femtosecond laser pulses in nitrogen molecular gas

    SciTech Connect

    Arevalo, E.; Becker, A.

    2005-10-15

    We study numerically and analytically the role of the combined effect of self-focusing, geometrical focusing, and the plasma defocusing in the formation of the fluorescence signal during the filamentation of a Ti:sapphire laser pulse in nitrogen molecular gas. Results of numerical simulations are used to estimate the number of excited ions in the focal volume, which is proportional to the fluorescence signal. We find good agreement between the theoretical results and the experimental data, showing that such data can be used to get further insight into the effective focal volume during filamentation of femtosecond laser pulses in transparent media.

  6. 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.

  7. 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.

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

    PubMed

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

    2016-03-01

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

  9. 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

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

    PubMed

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

    2014-01-01

    Rare-earth Yb(3+) and Ho(3+) co-doped fluorapatite (FA:Yb(3+)/Ho(3+)) 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 Yb(3+)/Ho(3+) -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:Yb(3+)/Ho(3+) crystals were found to exhibit distinct upconversion fluorescence. The 543- and 654-nm signals in the emission spectra could be assigned, respectively, to the (5)F4 ((5)S2) - (5)I8 and (5)F5 - (5)I8 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:Yb(3+)/Ho(3+) upconversion fluorescent crystals have potential applications in the biomedical field. PMID:24658285

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  12. Influence of laser polarization on plasma fluorescence emission during the femtosecond filamentation in air

    NASA Astrophysics Data System (ADS)

    Shi, Yan; Chen, Anmin; Jiang, Yuanfei; Li, Suyu; Jin, Mingxing

    2016-05-01

    The laser polarization state has a great influence on the plasma fluorescence emission during femtoseond filamentation in air. For the spectral lines from N2, in the case of focusing lens with longer focal length (f=100 cm), due to the impact excitation, circular polarization leads to stronger fluorescence emission when the laser energy is higher than the 'energy threshold' (2.0 mJ). As a lens with shorter focal length (f=40 cm) is used, a similar phenomenon can be observed, however, the 'energy threshold' is much lower, which is lower than 0.8 mJ. For the lines from N2+, especially for the 391 nm one, their emission is stronger in the linear polarization state. The mechanism of plasma fluorescence emission during femtosecond filamentation is discussed based on the analysis of these phenomena, which will be helpful to the remote sensing and spectrum analysis.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    The broad band upconversion luminescence in Yb3+: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 Yb2+ ions and the one at 692 nm could be attributed to the electron-hole recombination process on (Yb2+-F+) 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 Yb3+ to Yb2+ and (Yb2+-F+) centers have been induced by infrared femtosecond laser irradiation in Yb3+:YAG crystal.

  14. 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.

  15. [Upconversion and mid-infrared fluorescence properties of Ho3+/Yb3+ co-doped 50SiO2-50PbF2 glass ceramic].

    PubMed

    Zhang, Xiao-guang; Ren, Guo-zhong; Yang, Huai

    2014-08-01

    In the present paper, the upconversion and mid-infrared fluorescence properties of Ho3+/Yb3+ co-doped 50SiO2- 50PbF2 glass ceramic (GC) were studied. The GC has the following composition (in mol%): 50SiO2-50PbF2-1YbF3-0. 5HoF3. The mixtures of about 10 g were placed in a corundum crucible and melted at 1000 degrees C for 15 min in a SiC electric furnace in air and then poured on a brass plate. The GCs were obtained just by heat treatment at 450 degrees C. The X-ray diffraction pattern of the GC indicates that very small size crystals were precipitated in the precursor glass by heat treatment. The GCs have as high transmittance as glasses. The GCs have higher absorption cross section and narrower absorption peaks compared to the corresponding glasses, indicating that fluoride is doped with Ho ions. The Judd-Ofelt intensity parameters were determined from the absorption spectrum and Judd-Ofelt theory. The omega2 value is 0.17 x 10(-20) cm2 lower than that of fluoride glass ZBLA (2.28 x 10(-20) cm2), because of Ho3+ doping in PbF2 microcrystal. The intense green upconversion light was observed in Ho3+/Yb3+ co-doped 50SiO2-50PbF2 GCs excited by 980 nm laser diode. A main emission band centered around 540 nm (green), and three week emission bands centered around 420 nm(violet), 480 nm (blue), and 650 nm (red) which correspond to the Ho3+ : ((5)F4-->(5)I8) ((5)G-->(5)I8), ((8)K3--(5)I8) and ((5)F5-->(5)I8) transitions, respectively, were simultaneously observed in GCs. Compared with the glass sample, GCs have significantly intension in the green and blue upconversion fluorescence, and not significant change in the red upconversion fluorescence. Those changes are because that Ho ion in GCs locates in lower phonon energy environment than in glasses. Lower phonon energy can make the nonradiative relaxation rate reduce, which improves the green light upconversion efficiency, at the same time reduces the population of the intermediate energy level ((5)I7) of the red light

  16. [Upconversion and mid-infrared fluorescence properties of Ho3+/Yb3+ co-doped 50SiO2-50PbF2 glass ceramic].

    PubMed

    Zhang, Xiao-guang; Ren, Guo-zhong; Yang, Huai

    2014-08-01

    In the present paper, the upconversion and mid-infrared fluorescence properties of Ho3+/Yb3+ co-doped 50SiO2- 50PbF2 glass ceramic (GC) were studied. The GC has the following composition (in mol%): 50SiO2-50PbF2-1YbF3-0. 5HoF3. The mixtures of about 10 g were placed in a corundum crucible and melted at 1000 degrees C for 15 min in a SiC electric furnace in air and then poured on a brass plate. The GCs were obtained just by heat treatment at 450 degrees C. The X-ray diffraction pattern of the GC indicates that very small size crystals were precipitated in the precursor glass by heat treatment. The GCs have as high transmittance as glasses. The GCs have higher absorption cross section and narrower absorption peaks compared to the corresponding glasses, indicating that fluoride is doped with Ho ions. The Judd-Ofelt intensity parameters were determined from the absorption spectrum and Judd-Ofelt theory. The omega2 value is 0.17 x 10(-20) cm2 lower than that of fluoride glass ZBLA (2.28 x 10(-20) cm2), because of Ho3+ doping in PbF2 microcrystal. The intense green upconversion light was observed in Ho3+/Yb3+ co-doped 50SiO2-50PbF2 GCs excited by 980 nm laser diode. A main emission band centered around 540 nm (green), and three week emission bands centered around 420 nm(violet), 480 nm (blue), and 650 nm (red) which correspond to the Ho3+ : ((5)F4-->(5)I8) ((5)G-->(5)I8), ((8)K3--(5)I8) and ((5)F5-->(5)I8) transitions, respectively, were simultaneously observed in GCs. Compared with the glass sample, GCs have significantly intension in the green and blue upconversion fluorescence, and not significant change in the red upconversion fluorescence. Those changes are because that Ho ion in GCs locates in lower phonon energy environment than in glasses. Lower phonon energy can make the nonradiative relaxation rate reduce, which improves the green light upconversion efficiency, at the same time reduces the population of the intermediate energy level ((5)I7) of the red light

  17. 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

  18. 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.

  19. Theoretical description of femtosecond fluorescence depletion spectrum of molecules in solution.

    PubMed

    Niu, Kai; Dong, Li-Qing; Cong, Shu-Lin

    2007-09-28

    A theoretical model used for calculating the fluorescence depletion spectrum (FDS) of molecules in liquids induced by femtosecond pump-probe laser pulses is proposed based on the reduced density matrix theory. The FDS intensity is obtained by calculating the stimulated emission of the excited electronic state. As an application of the theoretical model, the FDS of oxazine 750 (OX-750) molecule in acetone solution is calculated. The simulated FDS agrees with the experimental result of Liu et al. [J. Y. Liu et al., J. Phys. Chem. A 107, 10857 (2003)]. The calculated vibrational relaxation rate is 2.5 ps(-1) for the OX-750 molecule. Vibrational population dynamics and wave packet evolution in the excited state are described in detail. The effect of the probe pulse parameter on the FDS is also discussed. PMID:17902916

  20. 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

  1. Sensitive detection of Porphyromonas gingivalis based on magnetic capture and upconversion fluorescent identification with multifunctional nanospheres.

    PubMed

    Qin, Wei; Zheng, Bin; Yuan, Yuan; Li, Meng; Bai, Yang; Chang, Jin; Wang, Hanjie; Wang, Yonglan

    2016-08-01

    A specific and sensitive detection system was designed to detect Porphyromonas gingivalis, a major periodontal pathogen, in mixed bacterial fluids. This new detection system was based on the use of fluorescent and magnetic encoding nanospheres that were conjugated with monoclonal antibodies specific to P. gingivalis, thus enabling rapid detection of the target bacterium. This strategy simplifies the detection process and improves the sensitivity compared with conventional methods, with a detection limit of approximately 10 colony-forming units (CFU) ml(-1) . This new method shows strong anti-interference ability and excellent selectivity and specificity to detect P. gingivalis in mixed solutions. PMID:27334431

  2. 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. PMID:26337749

  3. Fluorescence-quenching-based homogeneous caspase-3 activity assay using photon upconversion.

    PubMed

    Vuojola, Johanna; Riuttamäki, Terhi; Kulta, Essi; Arppe, Riikka; Soukka, Tero

    2012-05-01

    Caspase proteases are key mediators in apoptosis and thus of great interest in pharmaceutical industry. Enzyme-activity assays are commonly employed in the screening of protease inhibitors that are potential drug candidates. Conventional homogeneous fluorescence-based assays are susceptible to autofluorescence originating from biological material. This background autofluorescence can be eliminated by using upconverting phosphors (UCPs) that emit visible light upon excitation at near-infrared. In the assay energy was transferred from a UCP-donor to a conventional fluorophore acceptor that resided at one end of a caspase-3-specific substrate peptide. Attached to the other end was a quencher molecule that was used to attenuate the acceptor emission through intramolecular energy transfer in an intact peptide. In non-inhibitory conditions the enzyme reaction separated the fluorophore from the quencher and the emission of the fluorophore was recovered. The method was applied for the detection and characterization of a known caspase-3 inhibitor Z-DEVD-FMK, and the assay gave IC(50) values of approximately 13 nM for this inhibitor. We have demonstrated the applicability of UCPs on a fluorescence-quenching-based homogeneous enzyme-activity assay for the detection of caspase-3 inhibitors. The use of near-infrared excitable UCPs enables inexpensive instrumentation and total elimination of autofluorescence, while the use of an internally quenched substrate molecule diminishes the background resulting from radiatively excited acceptor molecules. The reduction of autofluorescence and radiative background result in high signal-to-background ratios (ratios of approximately 100 were obtained). By further utilizing assay miniaturization and signal enhancement in a white microtitration plate, a significant reduction in the reagent consumption can be achieved rendering the assay applicable for high-throughput screening. PMID:22502613

  4. ``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).

  5. 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.

  6. Initial photochemistry of bilirubin probed by femtosecond spectroscopy.

    PubMed

    Zietz, Burkhard; Gillbro, Tomas

    2007-10-18

    Bilirubin is a breakdown product from heme catabolism, and reduced excretion of bilirubin can lead to jaundice. Phototherapy is the most common treatment for neonatal jaundice, a condition frequently encountered in newborn infants. Knowledge of the photochemistry of bilirubin, which is dominated by (ultra)fast components, is necessary for the profound understanding of the processes in phototherapy. Here, we report results from femtosecond fluorescence upconversion measurements on bilirubin and half-bilirubin model compounds, as well as pump-probe absorption measurements on bilirubin. A fast component of ca. 120 fs in the multiexponential fluorescence decay, being only visible in the bilirubin molecule, is interpreted as exciton localization within the molecular halves. The slower components of several hundreds of femtoseconds and a few picoseconds, occurring in bilirubin and the half-bilirubin model, are interpreted as relaxation to a (twisted) intermediate, which decays further with ca. 15 ps to the ground state. PMID:17927274

  7. Intense red upconversion fluorescence emission in NIR-excited erbium-ytterbium doped laponite-derived phosphor

    NASA Astrophysics Data System (ADS)

    da Silva, Andréa F.; Moura, Diógenes S.; Gouveia-Neto, Artur S.; Silva, Elias A., Jr.; Bueno, Luciano A.; Costa, Ernande B.; Azevedo, Eduardo N.

    2011-02-01

    In this report the optical properties and energy-transfer frequency upconversion luminescence of Er3+/Yb3+-codoped laponite-derived powders under 975 nm infrared excitation is investigated. The 75%(laponite):25%(PbF2) samples doped with erbium and ytterbium ions, generated high intensity red emission around 660 nm and lower intensity green emission around 525, and 545 nm. The observed emission signals were examined as a function of the excitation power and annealing temperature. The results indicate that energy-transfer, and excited-state absorption are the major upconversion excitation mechanism for the erbium excited-state red emitting level. The precursor glass samples were also heat treated at annealing temperatures of 300 °C, 400 °C, 500 °C, and 600 °C, for a 2h period. The dependence of the visible upconversion luminescence emission upon the annealing temperature indicated the existence of an optimum temperature which leads to the generation of the most intense and spectrally pure red emission signal.

  8. 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).

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

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Yeh, Alvin T.

    2012-02-01

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

  10. Fluorescence Up-Conversion Studies of [2,2'-Bipyridyl]-3,3'-diol in Octyl-β-d-glucoside and Other Micellar Aggregates.

    PubMed

    Satpathi, Sagar; Gavvala, Krishna; Hazra, Partha

    2015-12-24

    In this present work, excited state double proton transfer dynamics (ESIDPT) of 2,2'-bipyridyl-3,3'-diol (BP(OH)2) molecules has been probed in a nontoxic, biocompatible sugar surfactant assembly, namely, octyl-β-d-glucoside (OBG) micelle with the help of steady state and fluorescence up-conversion techniques. Moreover, the ultrafast double proton transfer dynamics in conventional micelles (SDS, CTAB) and bile salts aggregates have been probed and compared. Interestingly, in all these supramolecular aggregates, the ESIDPT dynamics is found to follow sequential pathway; however, the time-scale of proton transfer dynamics varies from 11 to 30 ps. This difference in proton transfer time scale in different supramolecular aggregates has been explained in terms of accessibility of water molecules in the vicinity of probe. PMID:26613290

  11. ``Smart'' theranostic lanthanide nanoprobes with simultaneous up-conversion fluorescence and tunable T1-T2 magnetic resonance imaging contrast and near-infrared activated photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Das, Gautom Kumar; Vijayaragavan, Vimalan; Xu, Qing Chi; Padmanabhan, Parasuraman; Bhakoo, Kishore K.; Tamil Selvan, Subramanian; Tan, Timothy Thatt Yang

    2014-10-01

    The current work reports a type of ``smart'' lanthanide-based theranostic nanoprobe, NaDyF4:Yb3+/NaGdF4:Yb3+,Er3+, which is able to circumvent the up-converting poisoning effect of Dy3+ ions to give efficient near infrared (980 nm) triggered up-conversion fluorescence, and offers not only excellent dark T2-weighted MR contrast but also tunable bright and T1-weighted MR contrast properties. Due to the efficient up-converted energy transfer from the nanocrystals to chlorin e6 (Ce6) photosensitizers loaded onto the nanocrystals, cytotoxic singlet oxygen was generated and photodynamic therapy was demonstrated. Therefore, the current multifunctional nanocrystals could be potentially useful in various image-guided diagnoses where bright or dark MRI contrast could be selectively tuned to optimize image quality, but also as an efficient and more penetrative near-infrared activated photodynamic therapy agent.The current work reports a type of ``smart'' lanthanide-based theranostic nanoprobe, NaDyF4:Yb3+/NaGdF4:Yb3+,Er3+, which is able to circumvent the up-converting poisoning effect of Dy3+ ions to give efficient near infrared (980 nm) triggered up-conversion fluorescence, and offers not only excellent dark T2-weighted MR contrast but also tunable bright and T1-weighted MR contrast properties. Due to the efficient up-converted energy transfer from the nanocrystals to chlorin e6 (Ce6) photosensitizers loaded onto the nanocrystals, cytotoxic singlet oxygen was generated and photodynamic therapy was demonstrated. Therefore, the current multifunctional nanocrystals could be potentially useful in various image-guided diagnoses where bright or dark MRI contrast could be selectively tuned to optimize image quality, but also as an efficient and more penetrative near-infrared activated photodynamic therapy agent. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01717j

  12. 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.

  13. [An effect enhancement mechanism of up-conversion luminescence--up-conversion sensitization].

    PubMed

    Meng, C; Meng, G; Song, Z

    2001-04-01

    The research of frequency up-conversion has been developed greatly in recent ten years. In order to achieve its applications, it needs to enhance the up-conversion efficiency further greatly, which is the core problem of up-conversion. Because of the specialty of Yb3+ ion energy level, Yb3+ can greatly enhance up-conversion luminescence of co-doped rare earth ion activator through energy transfer. Meanwhile it may not cause the obvious fluorescence quenching. Thus it is very significance to investigate up-conversion sensitization which Yb3+ ion acts as a sensitizer. It is more important that it is quite urgent to combine up-conversion efficiency and material property to develop up-conversion. This paper reviews the proposing and developing process of up-conversion sensitization. The achievement of up-conversion sensitization field especial the originate fruit in indirect up-conversion sensitization obtained by China are introduce emphatically. PMID:12947606

  14. Highly sensitive optical thermometry based on the upconversion fluorescence from Yb3+/Er3+ codoped La2(WO4)3:Yb3+ ,Er3+ phosphor

    NASA Astrophysics Data System (ADS)

    Yang, Yan-min; Mi, Chao

    2013-12-01

    An optical temperature sensor based on Yb3+ and Er3+ codoped La2(WO4)3 phosphor for using in the high temperature region is discussed on the basis of fluorescence intensity ratio (FIR) method. The dependence of temperature on the upconversion green emission was intensive studied when the temperature increased from 300 K to 550 K under the excitation of 971 nm laser diode. The fluorescence intensity ratio of the two green emissions bands centered at 525 nm, 545 nm changed dramatically with the thermal treatment. By analyzing the experimental data according to the FIR method, the result on the thermometric property of La2(WO4)3:Yb3+, Er3+ was obtained and it shows that the sensitivity of La2(WO4)3:Yb3+, Er3+ reached the maximal value of about 0.0097 K-1 at the temperature of 510 K, even when the temperature was as high as 900 K, the sensitivity could still exceed 0.007 K-1. Results indicate that La2(WO4)3:Yb3+, Er3+ has higher sensitivity for thermometry in high temperature area. Owing to its good thermal stability, low synthesis cost and high sensitivity, La2(WO4)3: Yb3+, Er3+ phosphor has potential application in optical temperature sensing.

  15. 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. PMID:22413290

  16. 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. PMID:26761391

  17. NIR-responsive silica-coated NaYbF4:Er/Tm/Ho upconversion fluorescent nanoparticles with tunable emission colors and their applications in immunolabeling and fluorescent imaging of cancer cells

    PubMed Central

    Wang, Meng; Mi, Congcong; Zhang, Yixin; Liu, Jinling; Li, Feng; Mao, Chuanbin; Xu, Shukun

    2009-01-01

    NaYbF4: RE upconversion (UC) fluorescent nanoparticles (NPs) were synthesized with variable rare-earth dopants (RE= Er3+, Tm3+, or Ho3+, or a combination of these ions), from rare-earth stearate precursors in a water-ethanol-oleic acid system by using a two-phase solvothermal method. The NPs were shown to emit visible light such as orange, yellow, green, cyan, blue or pink light in response to near infrared (NIR) irradiation, and their emission colors could be simply tuned by changing either the co-dopant concentration or dopant species. The UC NPs were well-dispersed and spherical with an average size of 15~35 nm. They emitted strong UC fluorescence under the 980 nm NIR excitation. The effects of solvothermal reaction time and temperature on nanoparticle size and phase structure as well as UC fluorescence intensity were systematically studied. Water dispersibility was achieved by forming a silica coat on the surface of the UC NPs. After animo-functionalization, the silica-coated UC NPs were chemically conjugated with the rabbit anti-CEA8 antibody and then used as fluorescent biolabels for the immunolabeling and imaging of HeLa cells. The NIR-responsive multicolor visible light emission of these UC NPs will enable potential applications in biolabeling and multiplexed analysis because NIR light can penetrate tissue as deep as several inches and is safe to human body. PMID:20160878

  18. 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.

  19. Femtosecond, two-photon laser-induced-fluorescence imaging of atomic oxygen in an atmospheric-pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Schmidt, Jacob B.; Sands, Brian L.; Kulatilaka, Waruna D.; Roy, Sukesh; Scofield, James; Gord, James R.

    2015-06-01

    Femtosecond, two-photon-absorption laser-induced-fluorescence (fs-TALIF) spectroscopy is employed to measure space- and time-resolved atomic-oxygen distributions in a nanosecond, repetitively pulsed, externally grounded, atmospheric-pressure plasma jet flowing helium with a variable oxygen admixture. The high-peak-intensity, low-average-energy femtosecond pulses result in increased TALIF signal with reduced photolytic inferences. This allows 2D imaging of absolute atomic-oxygen number densities ranging from 5.8   ×   1015 to 2.0   ×   1012cm-3 using a cooled CCD with an external intensifier. Xenon is used for signal and imaging-system calibrations to quantify the atomic-oxygen fluorescence signal. Initial results highlight a transition in discharge morphology from annular to filamentary, corresponding with a change in plasma chemistry from ozone to atomic oxygen production, as the concentration of oxygen in the feed gas is changed at a fixed voltage-pulse-repetition rate. In this configuration, significant concentrations of reactive oxygen species may be remotely generated by sustaining an active discharge beyond the confines of the dielectric capillary, which may benefit applications that require large concentrations of reactive oxygen species such as material processing or biomedical devices.

  20. 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. PMID:25059168

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

    NASA Astrophysics Data System (ADS)

    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 × 105 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.

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

    PubMed

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

    2016-04-21

    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. PMID:27035265

  3. 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.

  4. 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. PMID:25640213

  5. 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.

  6. 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

  7. Plasmonic modulation of the upconversion fluorescence in NaYF4 :Yb/Tm hexaplate nanocrystals using gold nanoparticles or nanoshells.

    PubMed

    Zhang, Hua; Li, Yujing; Ivanov, Ivan A; Qu, Yongquan; Huang, Yu; Duan, Xiangfeng

    2010-04-01

    Automatic upgrade: attachment of gold nanoparticles (NPs) onto upconversion nanocrystals (NCs) results in plasmonic interactions that lead to a significant enhancement of upconversion emission of more than 2.5. Conversely, formation of a gold shell greatly suppresses the NC emission because of considerable scattering of excitation irradiation (see picture; a=NC before seed attachment; b, c=NC with attached Au NPs; c=NC with Au shell; scale bar=50 nm). PMID:20235253

  8. Correlation of femtosecond wave packets and fluorescence interference in a conjugated polymer: Towards the measurement of site homogeneous dephasing

    NASA Astrophysics Data System (ADS)

    Milota, F.; Sperling, J.; Szöcs, V.; Tortschanoff, A.; Kauffmann, H. F.

    2004-05-01

    Probing electronic femtosecond (fs) coherence among segmental sites that are congested by static and dynamic site disorder and subject to structural relaxation is a big, experimental challenge in the study of photophysics of poly(p-phenylenevinylene). In this work, fs-wave-packet fluorescence interferometry experiments are presented that measure macroscopic coherent kernels and their phase-relaxation in the low-temperature, bottom-state regime of the density-of-states below the migrational threshold energy where downhill site-to-site transfer is marginal. By using freely propagating and tunable 70 fs excitation/probing pulses and employing narrow-band spectral filtering of wave packets, fluorescence interferograms with strongly damped beatings can be observed. The coherences formally follow the in-phase superpositions of two site-optical free-induction-decays and originate from distinct pairs of coherent doorway-states, different in energy and space, each of them being targeted, by two discrete quantum-arrival-states 1α and 1β, via independent, isoenergetic 0→1 fluorescence transitions. The coherent transients are explained as site-to-site polarization beatings, caused by the interference of two fluorescence correlation signals. The numerical analysis of the damping regime, based upon second-order perturbational solutions, reveals the lower limit value of homogeneous dephasing in the range from T2≃100 fs to T2≃200 fs depending on the site-excitation energy of the bottom-states. The experiments enable to look into the formation of the relaxed state as a special molecular process of electron-phonon coupling and hence open-up a quite new perspective in the puzzle of multichromophore optical dynamics and structural relaxation in conjugated polymers.

  9. 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.

  10. 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.

  11. Photolytic-interference-free, femtosecond, two-photon laser-induced fluorescence imaging of atomic oxygen in flames

    NASA Astrophysics Data System (ADS)

    Kulatilaka, Waruna D.; Roy, Sukesh; Jiang, Naibo; Gord, James R.

    2016-02-01

    Ultrashort-pulse lasers are well suited for nonlinear diagnostic techniques such as two-photon laser-induced fluorescence (TPLIF) because the signals generated scale as the laser intensity squared. Furthermore, the broad spectral bandwidths associated with nearly Fourier-transform-limited ultrashort pulses effectively contribute to efficient nonlinear excitation by coupling through a large number of in-phase photon pairs, thereby producing strong fluorescence signals. Additionally, femtosecond (fs)-duration amplified laser systems typically operate at 1-10 kHz repetition rates, enabling high-repetition-rate imaging in dynamic environments. In previous experiments, we have demonstrated utilization of fs pulses for kilohertz (kHz)-rate, interference-free imaging of atomic hydrogen (H) in flames. In the present study, we investigate the utilization of fs-duration pulses to photolytic-interference-free TPLIF imaging of atomic oxygen (O). In TPLIF of O, photodissociation of vibrationally excited carbon dioxide (CO2) is known to be the prominent interference that produces additional O atoms in the medium. We have found that through the use of fs excitation, such interferences can be virtually eliminated in premixed laminar methane flames, which paves the way for two-dimensional imaging of O at kHz data rates. Such measurements can provide critical data for validating complex, multidimensional turbulent-combustion models as well as for investigating flame dynamics in practical combustion devices.

  12. Blue upconversion thulium laser

    SciTech Connect

    Nguyen, D.C.; Faulkner, G.E.; Weber, M.E.; Dulick, M.

    1990-01-01

    Upconversion has been an active area of research for at least two decades, mainly because of its wide ranging applications from infrared quantum counters, visible-emitting phosphors, to upconversion lasers. The upconversion lasers have recently become attractive with the advent of semiconductor laser diodes as the pump source. In an upconversion laser, the laser active ion is excited by internal upconversion of near-ir or red light via multiphoton excitation or cooperative processes and emits anti-Stokes visible light. Since the laser diode output wavelength can be composition turned to match the upconversion laser ion absorption lines, a substantial fraction of the ions can be driven into higher energy levels, thus enhancing the upconversion process. These upconversion solid-state lasers offer a potentially simple and compact source of visible coherent light with semiconductor laser diode excitation. We recently reported a novel upconversion thulium laser that emits blue light at 77 K. In this paper additional data on this 77 K upconversion laser as well as preliminary results on the room temperature upconversion laser are presented. In these demonstrations, dye lasers were used instead of diode lasers because they were more readily available than high power semiconductor laser diodes and their wavelengths could be adjusted easily. 14 refs., 5 figs., 1 tab.

  13. Imaging Electronic Trap States in Perovskite Thin Films with Combined Fluorescence and Femtosecond Transient Absorption Microscopy.

    PubMed

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

    2016-05-01

    Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. The remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps. PMID:27103096

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

    DOE PAGESBeta

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

    2016-04-22

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  16. Remarkable enhancement of upconversion fluorescence and confocal imaging of PMMA Opal/NaYF(4):Yb(3+), Tm(3+)/Er(3+) nanocrystals.

    PubMed

    Yin, Ze; Zhu, Yongsheng; Xu, Wen; Wang, Jing; Xu, Sai; Dong, Biao; Xu, Lin; Zhang, Shuang; Song, Hongwei

    2013-05-01

    Novel PMMA opal photonic crystal/NaYF(4):Yb(3+), Tm(3+)/Er(3+) nanocrystal composites were fabricated and tremendous improvement in upconversion luminescence (UCL) was observed under infrared 980 nm excitation. They were also explored to improve brightness of cell images. PMID:23539518

  17. 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.

  18. 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. PMID:26580697

  19. 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.

  20. 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.

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

    PubMed

    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(-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. PMID:26724012

  2. 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

  3. Plasmon-Enhanced Upconversion.

    PubMed

    Wu, Di M; García-Etxarri, Aitzol; Salleo, Alberto; Dionne, Jennifer A

    2014-11-20

    Upconversion, the conversion of photons from lower to higher energies, is a process that promises applications ranging from high-efficiency photovoltaic and photocatalytic cells to background-free bioimaging and therapeutic probes. Existing upconverting materials, however, remain too inefficient for viable implementation. In this Perspective, we describe the significant improvements in upconversion efficiency that can be achieved using plasmon resonances. As collective oscillations of free electrons, plasmon resonances can be used to enhance both the incident electromagnetic field intensity and the radiative emission rates. To date, this approach has shown upconversion enhancements up to 450×. We discuss both theoretical underpinnings and experimental demonstrations of plasmon-enhanced upconversion, examining the roles of upconverter quantum yield, plasmonic geometry, and plasmon spectral overlap. We also discuss nonoptical consequences of including metal nanostructures near upconverting emitters. The rapidly expanding field of plasmon-enhanced upconversion provides novel fundamental insight into nanoscale light-matter interactions while improving prospects for technological relevance. PMID:26276488

  4. 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. PMID:26089129

  5. [Direct upconversion sensitization luminescence of Tm(0.1)Yb(10.9): oxyfluoride glass].

    PubMed

    Chen, X B; Sawanobori, N; Song, Z F

    2001-12-01

    This paper studied the direct upconversion sensitization luminescence of Tm(0.1)Yb(10.9): oxyfluoride glass pumped by 966 nm diode laser. We found that there are strong 474 nm three-photon upconversion fluorescence of 1G4-->3H6 transition. As well as there are weak 362, 452 and 650 nm three-photon upconversion fluorescence of 1D2-->3H6, 1D2-->3F4, 1G4-->3F4 and 681 nm two-photon upconversion fluorescence of 3F3-->3H6 transitions respectively. Their upconversion mechanism has been analyzed and discussed simply. PMID:12958885

  6. Imaging of the expansion of femtosecond-laser-produced silicon plasma atoms by off-resonant planar laser-induced fluorescence.

    PubMed

    Samek, Ota; Leis, Franz; Margetic, Vanja; Malina, Radomir; Niemax, Kay; Hergenröder, Roland

    2003-10-20

    Planar laser-induced fluorescence measurements were used to investigate the expansion dynamics of a femtosecond laser-induced plasma. Temporally and spatially resolved measurements were performed to monitor the atoms that were ablated from a silicon target. A dye laser (lambda = 288.16 nm) was used to excite fluorescence signals. The radiation of an off-resonant transition (Si 390.55 nm) was observed at different distances from the target surface. This allowed easy detection of the ablated Si atoms without problems caused by scattered laser light. Abel inversion was applied to obtain the radial distribution of the Si atoms. The atom distribution in the plasma shows some peculiarities, depending on the crater depth. PMID:14594057

  7. Ultrafast unequilibrated charge transfer: A new channel in the quenching of fluorescent biological probes

    NASA Astrophysics Data System (ADS)

    Wan, Chaozhi; Xia, Tianbing; Becker, Hans-Christian; Zewail, Ahmed H.

    2005-08-01

    The dynamics of two biological fluorescent probes, 2-aminopurine (Ap) and daunomycin, were studied using both femtosecond transient absorption and fluorescence upconversion techniques. Various Ap-containing structures were investigated in solution: free Ap, non-covalently bonded (with guanine, adenine, and tryptophan) and covalently bonded in DNA constructs (with guanine, 7-deazaguanine, and adenine). The distinct difference of transient absorption and fluorescence dynamics on the ultrafast time scale, and their dependence on free energy change (Δ G), and the abrupt decrease of the initial fluorescence intensity suggest the efficient depopulation by charge transfer from the unequilibrated hot molecules. We provide a model for this possibly general mechanism and obtain the rate constants for charge separation, vibrational relaxation, and charge recombination.

  8. 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

  9. 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.

  10. Investigation of upconversion and downconversion fluorescence emissions from β-NaLn1F{sub 4}:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal disk system

    SciTech Connect

    He, Enjie; Zheng, Hairong; Gao, Wei; Tu, Yinxun; Lu, Ying; Li, Guian

    2013-09-01

    Graphical abstract: Well-defined β-NaLn1F4:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal thin disks with a simple and user-friendly hydrothermal approach by using sodium citrate as a shape modifier. Much stronger UC and DC fluorescence emissions were observed in NaLuF{sub 4}-based hexagonal disks than that for NaYF{sub 4} counterparts. The strength of hypersensitive transitions is mainly attributed to the decrease of local symmetry Ln-F bond lengths in β-NaLuF{sub 4}. It will show a great potential in improving near-infrared conversion efficiency of silicon solar cells and removable sub-micro luminescent platforms. - Highlights: • Regular hexagonal disks (NaLnF{sub 4}) were synthesized by a simple hydrothermal method. • Much stronger UC and DC emissions were observed in NaLuF{sub 4}-based disks. • Stronger fluorescence emissions in NaLuF{sub 4}-based disks were explained reasonably. • NaLuF{sub 4}-based disks can act as a removable luminescent platform for nano-assembly. • NaLuF{sub 4}-based disks can be applied in improving efficiency of solar cells. - Abstract: Uniform hexagonal β-NaLn1F{sub 4}:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) disks were synthesized with hydrothermal method in which the sodium citrate was used as a shape modifier. The experimental observation indicated that both upconversion and downconversion fluorescence emissions were significantly stronger in β-NaLuF{sub 4} than that for β-NaYF{sub 4}. It was found that the stronger hypersensitive transitions were mainly due to the increase of J–O parameter (Ω{sub 2}) in β-NaLuF{sub 4} host, while the stronger insensitive transitions were mainly caused by the stronger overlap of electron cloud that was induced by the decrease of Ln-F bond lengths. Additionally, the larger absorption strength in the near-infrared region is another important factor for the stronger fluorescence emissions. The current research has a great potential in

  11. Upconversion in Nd{sup 3+}-doped glasses: Microscopic theory and spectroscopic measurements

    SciTech Connect

    Oliveira, S. L.; Sousa, D. F. de; Andrade, A. A.; Nunes, L. A. O.; Catunda, T.

    2008-01-15

    In this work, we report a systematic investigation of upconversion losses and their effects on fluorescence quantum efficiency and fractional thermal loading in Nd{sup 3+}-doped fluoride glasses. The energy transfer upconversion ({gamma}{sub up}) parameter, which describes upconversion losses, was experimentally determined using different methods: thermal lens (TL) technique and steady state luminescence (SSL) measurements. Additionally, the upconversion parameter was also obtained from energy transfer models and excited state absorption measurements. The results reveal that the microscopic treatment provided by the energy transfer models is similar to the macroscopic ones achieved from the TL and SSL measurements because similar {gamma}{sub up} parameters were obtained. Besides, the achieved results also point out the migration-assisted energy transfer according to diffusion-limited regime rather than hopping regime as responsible for the upconversion losses in Nd-doped glasses.

  12. Effect of OH - on upconversion luminescence of Er 3+-doped oxyhalide tellurite glasses

    NASA Astrophysics Data System (ADS)

    Xu, Shiqing; Fang, Dawei; Zhang, Zaixuan; Jiang, Zhonghong

    2005-06-01

    The Raman spectra, infrared spectra and upconversion luminescence spectra were studied, and the effect mechanism of OH - groups on the upconversion luminescence of Er 3+-doped oxyhalide tellurite glasses was analyzed. The results show that the phonon energy of lead chloride tellurite (PCT) glass was lower than that of lead fluoride tellurite (PFT) glass, but upconversion luminescence intensity of Er 3+-doped PFT glass was higher than that of Er 3+-doped PCT glass. The analysis considers that it was attributed mainly to the effect of OH - groups. The lower the absorption coefficient of the OH - groups, the higher the fluorescence lifetime of Er 3+, and as a result the higher upconversion luminescence intensity of Er 3+. In this work, the effect of OH - groups on the upconversion luminescence of Er 3+ was bigger than that of the phonon energy.

  13. Plasmon enhancement of luminescence upconversion.

    PubMed

    Park, Wounjhang; Lu, Dawei; Ahn, Sungmo

    2015-05-21

    Frequency conversion has always been an important topic in optics. Nonlinear optics has traditionally focused on frequency conversion based on nonlinear susceptibility but with the recent development of upconversion nanomaterials, luminescence upconversion has begun to receive renewed attention. While upconversion nanomaterials open doors to a wide range of new opportunities, they remain too inefficient for most applications. Incorporating plasmonic nanostructures provides a promising pathway to highly efficient upconversion. Naturally, a plethora of theoretical and experimental studies have been published in recent years, reporting enhancements up to several hundred. It is however difficult to make meaningful comparisons since the plasmonic fields are highly sensitive to the local geometry and excitation condition. Also, many luminescence upconversion processes involve multiple steps via different physical mechanisms and the overall output is often determined by a delicate interplay among them. This review is aimed at offering a comprehensive framework for plasmon enhanced luminescence upconversion. We first present quantum electrodynamics descriptions for all the processes involved in luminescence upconversion, which include absorption, emission, energy transfer and nonradiative transitions. We then present a bird's eye view of published works on plasmon enhanced upconversion, followed by more detailed discussion on comparable classes of nanostructures, the effects of spacer layers and local heating, and the dynamics of the plasmon enhanced upconversion process. Plasmon enhanced upconversion is a challenging and exciting field from the fundamental scientific perspective and also from technological standpoints. It offers an excellent system to study how optical processes are affected by the local photonic environment. This type of research is particularly timely as the plasmonics is placing heavier emphasis on nonlinearity. At the same time, efficient upconversion

  14. Dual-modal fluorescent/magnetic bioprobes based on small sized upconversion nanoparticles of amine-functionalized BaGdF5:Yb/Er

    NASA Astrophysics Data System (ADS)

    Zeng, Songjun; Tsang, Ming-Kiu; Chan, Chi-Fai; Wong, Ka-Leung; Fei, Bin; Hao, Jianhua

    2012-07-01

    A new type of BaGdF5:Yb/Er nanoprobe for dual-modal fluorescent and magnetic resonance imaging (MRI) is demonstrated. Water soluble and amine-functionalized BaGdF5:Yb/Er nanoparticles (NPs) with average size of about 10 nm were synthesized by a facile one-pot hydrothermal method. The in vitro up-converted emission of BaGdF5:Yb/Er NPs is observed in HeLa cells with near-infrared excitation at 980 nm and served as a fluorescent label. In addition, the cytotoxicity assay in HeLa cells shows low cell toxicity of the amine-functionalized BaGdF5:Yb/Er NPs. Moreover, these BaGdF5 NPs exhibit excellent intrinsic paramagnetic properties and enhanced T1-weighted MRI images with increased concentrations of BaGdF5 NPs. Therefore, these results suggest that the amine-functionalized BaGdF5 NPs with an optimized size and low cell toxicity are promising dual-modal bioprobes for optical bioimaging and MRI.A new type of BaGdF5:Yb/Er nanoprobe for dual-modal fluorescent and magnetic resonance imaging (MRI) is demonstrated. Water soluble and amine-functionalized BaGdF5:Yb/Er nanoparticles (NPs) with average size of about 10 nm were synthesized by a facile one-pot hydrothermal method. The in vitro up-converted emission of BaGdF5:Yb/Er NPs is observed in HeLa cells with near-infrared excitation at 980 nm and served as a fluorescent label. In addition, the cytotoxicity assay in HeLa cells shows low cell toxicity of the amine-functionalized BaGdF5:Yb/Er NPs. Moreover, these BaGdF5 NPs exhibit excellent intrinsic paramagnetic properties and enhanced T1-weighted MRI images with increased concentrations of BaGdF5 NPs. Therefore, these results suggest that the amine-functionalized BaGdF5 NPs with an optimized size and low cell toxicity are promising dual-modal bioprobes for optical bioimaging and MRI. Electronic supplementary information (ESI) available: FTIR spectra, EDS, and the simplified energy-level diagrams of Yb3+/Er3+. See DOI: 10.1039/c2nr31294h

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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 3ππ* state than the 3nπ* one lead to a small energy difference between the lowest singlet (S1) and triplet (T1) 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 T1 → S1 pathway in the electroluminescent process.

  17. LDS-750 as a probe of solvation dynamics: a femtosecond time-resolved fluorescence study in liquid aniline

    NASA Astrophysics Data System (ADS)

    Smith, Neil A.; Meech, Stephen R.; Rubtsov, Igor V.; Yoshihara, Keitaro

    1999-04-01

    The dynamics of the fluorescence Stokes shift of the styryl dye LDS-750 have been measured in liquid aniline with sub-100 fs time resolution. The shape of the time-resolved spectra are time dependent, which is not consistent with the predictions of a solvation dynamics mechanism. However, the measured spectral shift correlation function is reasonably well described by the dynamical mean spherical approximation model of solvation dynamics. It is suggested that these observations are consistent if solvent dynamics is the rate controlling process in both solvation of the increased dipole moment of the excited state of LDS-750 and the stabilisation of a distribution of solute conformers in the excited state.

  18. 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. PMID:26111991

  19. Up-conversion luminescence and optical temperature sensing behaviour of Yb3+/Er3+ codoped CaWO4 material

    NASA Astrophysics Data System (ADS)

    Cheng, Xuerui; Yang, Kun; Wang, Jiankun; Yang, Linfu; Cheng, Xiaoshuai

    2016-08-01

    Present article report on structural and optical properties of Er3+/Yb3+ codoped CaWO4 phosphors. Structural properties are explored using XRD and Raman technologies. The upconversion emission has been investigated with 980 nm excitation. The upconversion emission intensity is dependent on the concentrations of Yb3+ ions and reaches a maximum at 7%. Logarithmic plots of power dependencies reveal that the green and red emissions originate from a two-photon upconversion process. Based on the photon energy and the emission spectra, the possible upconversion processes and emission mechanisms are discussed. Finally, the optical temperature sensing properties has been performed using the fluorescence intensity ratio technique based on green upconversion emissions. Its temperature sensitivity is found to be above 0.0025 K-1 in the whole temperature range of 300-540 K, revealing this phosphor to be a promising optical temperature sensing material.

  20. Effect of OH{sup -} on upconversion luminescence of Er{sup 3+}-doped oxyhalide tellurite glasses

    SciTech Connect

    Xu Shiqing . E-mail: shiquingxu75@hotmail.com; Fang Dawei; Zhang Zaixuan; Jiang Zhonghong

    2005-06-15

    The Raman spectra, infrared spectra and upconversion luminescence spectra were studied, and the effect mechanism of OH{sup -} groups on the upconversion luminescence of Er{sup 3+}-doped oxyhalide tellurite glasses was analyzed. The results show that the phonon energy of lead chloride tellurite (PCT) glass was lower than that of lead fluoride tellurite (PFT) glass, but upconversion luminescence intensity of Er{sup 3+}-doped PFT glass was higher than that of Er{sup 3+}-doped PCT glass. The analysis considers that it was attributed mainly to the effect of OH{sup -} groups. The lower the absorption coefficient of the OH{sup -} groups, the higher the fluorescence lifetime of Er{sup 3+}, and as a result the higher upconversion luminescence intensity of Er{sup 3+}. In this work, the effect of OH{sup -} groups on the upconversion luminescence of Er{sup 3+} was bigger than that of the phonon energy.

  1. One-step hydrothermal synthesis of carboxyl-functionalized upconversion phosphors for bioapplications.

    PubMed

    Yang, Jianping; Shen, Dengke; Li, Xiaomin; Li, Wei; Fang, Yin; Wei, Yong; Yao, Chi; Tu, Bo; Zhang, Fan; Zhao, Dongyuan

    2012-10-22

    In this paper, we report a facile one-step hydrothermal method to synthesize phase-, size-, and shape-controlled carboxyl-functionalized rare-earth fluorescence upconversion phosphors by using a small-molecule binary acid, such as malonic acid, oxalic acid, succinic acid, or tartaric acid as capping agent. The crystals, from nano- to microstructures with diverse shapes that include nanospheres, microrods, hexagonal prisms, microtubes, microdisks, polygonal columns, and hexagonal tablets, can be obtained with different reaction times, reaction temperatures, molar ratios of capping agent to sodium hydroxide, and by varying the binary acids. Fourier transform infrared, thermogravimetric analysis, and upconversion luminescence spectra measurements indicate that the synthesized NaYF(4):Yb/Er products with hydrophilic carboxyl-functionalized surface offer efficient upconversion luminescent performance. Furthermore, the antibody/secondary antibody conjugation can be realized by the carboxyl-functionalized surfaces of the upconversion phosphors, thus indicating the potential bioapplications of these kinds of materials. PMID:22996059

  2. Detection of telomerase on upconversion nanoparticle modified cellulose paper.

    PubMed

    Wang, Faming; Li, Wen; Wang, Jiasi; Ren, Jinsong; Qu, Xiaogang

    2015-07-25

    Herein we report a convenient and sensitive method for the detection of telomerase activity based on upconversion nanoparticle (UCNP) modified cellulose paper. Compared with many solution-phase systems, this paper chip is more stable and easily stores the test results. What's more, the low background fluorescence of the UCNPs increases the sensitivity of this method, and the low telomerase levels in different cell lines can clearly be discriminated by the naked eye. PMID:26095724

  3. 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

  4. 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

  5. TPGS-stabilized NaYbF4:Er upconversion nanoparticles for dual-modal fluorescent/CT imaging and anticancer drug delivery to overcome multi-drug resistance.

    PubMed

    Tian, Gan; Zheng, Xiaopeng; Zhang, Xiao; Yin, Wenyan; Yu, Jie; Wang, Dongliang; Zhang, Zhiping; Yang, Xiangliang; Gu, Zhanjun; Zhao, Yuliang

    2015-02-01

    Multi-drug resistance (MDR) is a major cause of failure in cancer chemotherapy. Tocopheryl polyethylene glycol 1000 succinate (TPGS) has been extensively investigated for overcoming MDR in cancer therapy because of its ability to inhibit P-glycoprotein (P-gp). In this work, TPGS was for the first time used as a new surface modifier to functionalize NaYbF4:Er upconversion nanoparticles (UNCPs) and endowed the as-prepared products (TPGS-UCNPs) with excellent water-solubility, P-gp inhibition capability and imaging-guided drug delivery property. After the chemotherapeutic drug (doxorubicin, DOX) loading, the as-formed composites (TPGS-UCNPs-DOX) exhibited potent killing ability for DOX-resistant MCF-7 cells. Flow-cytometric assessment and Western blot assay showed that the TPGS-UCNPs could potently decrease the P-gp expression and facilitate the intracellular drug accumulation, thus achieving MDR reversal. Moreover, considering that UCNPs process efficient upconversion emission and Yb element contained in UCNPs has strong X-ray attenuation ability, the as-obtained composite could also serve as a dual-modal probe for upconversion luminescence (UCL) imaging and X-ray computed tomography (CT) imaging, making them promising for imaging-guided cancer therapy. PMID:25433607

  6. 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.

  7. 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

  8. Tailoring Plasmonic Enhanced Upconversion in Single NaYF4:Yb(3+)/Er(3+) Nanocrystals.

    PubMed

    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:Yb(3+)/Er(3+) 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

  9. 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.

  10. Mid-infrared nonlinear upconversion imaging and sensing

    NASA Astrophysics Data System (ADS)

    Pedersen, Christian; Tidemand-Lichtenberg, Peter

    2016-03-01

    The mid-IR wavelength range is highly relevant for a number of applications related to gas spectroscopy and spectral analysis of complex molecules such as those including CH bounds. The main obstacles for exploitation of mid-IR applications include suitable and affordable mid-IR light sources for excitation of the sample and sensitive mid-IR detectors. With the advent of mid-IR Quantum cascaded lasers and super continuum light sources new possibilities has emerged. However, low-noise, mid-IR (2-15 μm) detection is still challenging requiring cryogenic cooling to gain sensitivities needed for measurements of fluorescence or absorptions signals. Mid-IR upconversion imaging and detection using nonlinear crystals offers good promise as an alternative, sensitive mid-IR imaging and detection technology. In this paper the fundamental properties of upconversion is discussed.

  11. 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.

  12. A general strategy for biocompatible, high-effective upconversion nanocapsules based on triplet-triplet annihilation.

    PubMed

    Liu, Qian; Yin, Baoru; Yang, Tianshe; Yang, Yongchao; Shen, Zhen; Yao, Ping; Li, Fuyou

    2013-04-01

    A general strategy for constructing high-effective upconversion nanocapsules based on triplet-triplet annihilation (TTA) was developed by loading both sensitizer and annihilator into BSA-dextran stabilized oil droplets. This strategy can maintain high translational mobility of the chromophores, avoid luminescence quenching of chromophore by aggregation, and decrease the O2-induced quenching of TTA-based upconversion emission. Pt(II)-tetraphenyl-tetrabenzoporphyrin (PtTPBP) and BODIPY dyes (BDP-G and BDP-Y with the maximal fluorescence emission at 528 and 546 nm, respectively) were chosen as sensitizer/annihilator couples to fabricate green and yellow upconversion luminescent emissive nanocapsules, named UCNC-G and UCNC-Y, respectively. In water under the atmospheric environment, interestingly, UCNC-G and UCNC-Y exhibit intense upconversion luminescence (UCL) emission (λex = 635 nm) with the quantum efficiencies (ΦUCL) of 1.7% and 4.8%, respectively, whereas very weak UCL emission (ΦUCL < 0.1%) was observed for the corresponding previous reported SiO2-coating nanosystems because of aggregation-induced fluorescence quenching of annihilators. Furthermore, application of theses upconversion nanocapsules for high-contrast UCL bioimaging in vivo of living mice without removing the skin was demonstrated under 635-nm excitation with low power density of 12.5 mW cm(-2). PMID:23464990

  13. Photon-avalanche upconversion in thulium-doped lutetium aluminum garnet.

    PubMed

    Patel, D N; Reddy, B R; Nash-Stevenson, S K

    1999-05-20

    Strong blue fluorescence at 487 nm corresponding to the (1)G(4) --> (3)H(6) transition was generated from Tm(3+)-doped lutetium aluminum garnet on excitation with a 618-nm dye laser as a result of a photon-avalanche upconversion mechanism. PMID:18319920

  14. 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…

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Yuan Lei, Dang

    2015-10-01

    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.

  17. 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

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

    PubMed

    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

  19. Optical transitions and visible upconversion in Er3+ doped niobic tellurite glass

    NASA Astrophysics Data System (ADS)

    Lin, Hai; Meredith, Gerald; Jiang, Shibin; Peng, Xiang; Luo, Tao; Peyghambarian, Nasser; Pun, Edwin Yue-Bun

    2003-01-01

    Er3+ doped Nb2O5-TeO2 (NT) glass suitable for developing optical fiber laser and amplifier has been fabricated and characterized. Intense and broad 1.53 μm infrared fluorescence and visible upconversion luminescence were observed under 975 nm diode laser and 798 nm laser excitation. For 1.53 μm emission band, the full width at half-maximum is 51 nm, the fluorescence lifetime is 2.6 ms, and the quantum efficiency is ˜100%. The maximum emission cross section is 8.52×10-21 cm2 at 1.532 μm, and is higher than the values in silicon and phosphate glasses. Under 798 nm excitation, efficient 531, 553, and 670 nm upconversion emissions are due to two-photon absorption processes. The "standardized" efficiency for the green upconversion light is 9.5×10-4, and this value is comparable to that reported for Er3+/Yb3+ codoped fluoride glasses. Intense visible upconversion fluorescence in Er3+ doped NT glass can be used in color display, undersea communication, and infrared sensor.

  20. A new medium for triplet-triplet annihilated upconversion and photocatalytic application.

    PubMed

    Ye, Changqing; Wang, Jingjing; Wang, Xiaomei; Ding, Ping; Liang, Zuoqin; Tao, Xutang

    2016-02-01

    Since the triplet-triplet annihilated upconversion (TTA-UC) materials work efficiently only in degassing organic solvents, it is of significance to find a new medium without toxicity and volatility and that promotes TTA-UC. Here, we firstly reported the effect of an OH-containing medium on low power upconversion and found that in alcohol solvent containing β-cyclodextrin (β-CD), the phosphorescence lifetime (τp) of the sensitizer (PdTPP) and the fluorescence quantum yield (Φf) of the acceptor (DPA) were enhanced with the increase in the number of OH-groups of the medium. A large triplet-triplet quenching constant (kq, 1.91 × 10(9) M(-1) s(-1)) and high upconversion efficiency (ΦUC, ∼ 36%) of PdTPP/DPA were obtained under the excitation of a diode laser (532 nm, 60 mW cm(-2)). Under our green-to-blue upconversion irradiation, in a demonstration experiment the photocurrent was recorded at 0.09 μA cm(-2), resulting from photocatalytic water splitting by a Cd0.7Zn0.3S photoanode and a Pt counter-electrode in a photoelectrochemical cell. The importance of this study suggests that upconversion-powered photoelectrochemistry possesses potential application for hydrogen generation from water under excitation of sun energy. PMID:26580451

  1. An upconversion luminescence nanoprobe for the ultrasensitive detection of hyaluronidase.

    PubMed

    Wang, Zhe; Li, Xiaohua; Song, Yanchao; Li, Lihong; Shi, Wen; Ma, Huimin

    2015-06-01

    A new upconversion luminescence nanoprobe for the detection of hyaluronidase has been developed by coupling the hyaluronic acid-bearing upconversion fluorescence nanoparticles (HA-UCNPs) with poly(m-phenylenediamine) (PMPD) nanospheres via covalent linkage. The nanoprobe alone exhibits an extremely low background signal owing to the effective fluorescence quenching by electron-rich PMPD and the near-infrared excitation characteristic (λex = 980 nm) of HA-UCNPs; upon reaction with hyaluronidase, however, a more than 31-fold fluorescence enhancement is produced. Compared with the corresponding nanosystem assembled via physical adsorption, the prepared nanoprobe shows a largely increased stability and a much higher signal-to-background ratio, which offers an ultrasensitive assay for hyaluronidase, with a detection limit of 0.6 ng/mL. The nanoprobe has been successfully used to determine hyaluronidase in human serum samples from both colorectal cancer patients and healthy people, disclosing that the serum hyaluronidase level in colorectal cancer patients is roughly 3 times higher than that in healthy people. Furthermore, the nanoprobe has also been employed to study the activity change of hyaluronidase affected by different concentrations of arsenate (a potential carcinogen), and the results show that even a low dosage of arsenate (50 μg/L) can raise the activity of hyaluronidase by about one-third, revealing the relationship between arsenate and the enzyme. The proposed method is not only simple but also highly sensitive, making it useful to assay hyaluronidase in relevant clinical samples. PMID:25947627

  2. Photon upconversion with directed emission.

    PubMed

    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

  3. 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.

  4. Photon upconversion in core-shell nanoparticles.

    PubMed

    Chen, Xian; Peng, Denfeng; Ju, Qiang; Wang, Feng

    2015-03-21

    Photon upconversion generally results from a series of successive electronic transitions within complex energy levels of lanthanide ions that are embedded in the lattice of a crystalline solid. In conventional lanthanide-doped upconversion nanoparticles, the dopant ions homogeneously distributed in the host lattice are readily accessible to surface quenchers and lose their excitation energy, giving rise to weak and susceptible emissions. Therefore, present studies on upconversion are mainly focused on core-shell nanoparticles comprising spatially confined dopant ions. By doping upconverting lanthanide ions in the interior of a core-shell nanoparticle, the upconversion emission can be substantially enhanced, and the optical integrity of the nanoparticles can be largely preserved. Optically active shells are also frequently employed to impart multiple functionalities to upconversion nanoparticles. Intriguingly, the core-shell design introduces the possibility of constructing novel upconversion nanoparticles by exploiting the energy exchange interactions across the core-shell interface. In this tutorial review, we highlight recent advances in the development of upconversion core-shell nanoparticles, with particular emphasis on the emerging strategies for regulating the interplay of dopant interactions through core-shell nanostructural engineering that leads to unprecedented upconversion properties. The improved control over photon energy conversion will open up new opportunities for biological and energy applications. PMID:25058157

  5. 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.

  6. 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.

  7. Energy transfer and upconversion in Yb:YAG and Yb:Er:YAG

    SciTech Connect

    Lacovara, P.

    1992-01-01

    Energy transfer and upconversion have been studied in ytterbium, and ytterbium-erbium doped YAG (yttrium-aluminum garnet Y[sub 2]Al[sub 5]O[sub 12]). The energy-transfer probabilities were calculated for Yb-Yb, Yb-Er, and Er-Yb interactions, as well as for Er-Er and Yb-Er upconversion. The transfer of excitation from ytterbium to erbium was found experimentally to be efficient at Er concentrations above about 1%, with an Yb concentration of 6.5%. The Burshtein hopping model for donor migration-assisted transfer was applied to the Yb-Er system for different Er concentrations. Fitting the decay predicted by the Burshtein model to the Yb fluorescence gave a value for the Yb-Er dipole-dipole interaction strength which was in very close agreement with the calculated value, but discrepancies were noted for the donor-donor interaction. Upconversion was observed during pulsed measurements, and studies in detail with intense CW pumping. The Yb-Er upconversion was observed to dominate the Er-Er upconversion in the Yb-Er samples. Values for the Yb-Er and Er-Er ([sup 4]I[sub 1 1/2]) upconversion coefficients were determined from quantitative measurements of the [sup 4]S[sub 3/2] fluorescence which these processes generate, and measurements of the change in [sup 4]I[sub 1 1/2] population with increasing pump density. The quenching of nominally pure Yb:YAG by trace rare-earth impurities was also studied. The time dependence of the Yb fluorescence decay in some high-concentration samples suggested a fast quenching process active at high excited-ion densities, and a slower one at lower excited-ion densities. Study of the cooperative luminescence emitted by excited Yb pairs suggested a quenching mechanism acting preferentially on pairs. Sensitive Ar[sup +]-ion laser-pumped fluorescence measurements showed the presence of high ppm levels of several impurities, including Er, Tm and Cr. Pumping the ytterbium at 940 nm using pulsed and CW lasers revealed Er and Tm upconversion.

  8. Tuning Crystal Phase and Emission Properties of Upconversion Nanocrystals Through Lanthanide Doping.

    PubMed

    Luo, L; Liu, H B; Yao, L L; Dong, G S; Zhang, W; Wang, Y H; Qiu, Z R; Chen, J

    2016-01-01

    Infrared-to-visible upconversion fluorescent nanocrystals of Yb³⁺/Er³⁺-codoped NaYF₄ and Yb³⁺/Er³⁺/Gd³⁺-tridoped NaYF₄ were synthesized using a modified coprecipitation process. X-ray diffraction and transmission electron diffraction scans of the nanocrystals confirmed that Gd³⁺ doping caused a phase transition to occur in the nanocrystals, changing them from a cubic to a hexagonal phase. Hexagonal phase Yb³⁺/Er³⁺/Gd³⁺-tridoped NaYF₄ nanocrystals displayed much stronger and sharper upconversion luminescence, and larger intensity ratios of red over green emissions relative to their cubic phase counterparts. The influence of the crystal phase on the upconversion emission properties was explored by use of excitation power dependence curves, dynamic fluorescence and Raman spectra. The results suggest that the cubic-to-hexagonal phase transition decreases the crystal field symmetry, and then enhances upconversion luminescence intensity by relaxing forbidden selection rules. The conversion into the hexagonal phase also increases the number of phonon modes, and consequently improves the phonon-assisted energy transfer efficiency from Yb³⁺ to Er³⁺, thus facilitating the output of red emissions. PMID:27398498

  9. 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.

  10. 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.

  11. 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

  12. Ultrafast Excited-State Dynamics in the Green Fluorescent Protein Variant S65T/H148D. 2. Unusual Photophysical Properties†

    PubMed Central

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

    2008-01-01

    In the preceding accompanying paper (1), the 1.5 Å resolution crystal structure of GFP variant S65T/H148D is presented and the possible consequences of an unusual short hydrogen bond (≤2.4 Å) between the carboxyl oxygen of Asp148 and phenol oxygen of the chromophore are discussed. In this work, we report the 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 timescale that is faster than the 170 femtosecond 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 timescale 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. We speculate 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. PMID:17918960

  13. Efficient upconversion-pumped continuous wave Er3+:LiLuF4 lasers

    NASA Astrophysics Data System (ADS)

    Moglia, Francesca; Müller, Sebastian; Reichert, Fabian; Metz, Philip W.; Calmano, Thomas; Kränkel, Christian; Heumann, Ernst; Huber, Günter

    2015-04-01

    We report on detailed spectroscopic investigations and efficient visible upconversion laser operation of Er3+:LiLuF4. This material allows for efficient resonant excited-state-absorption (ESA) pumping at 974 nm. Under spectroscopic conditions without external feedback, ESA at the laser wavelength of 552 nm prevails stimulated emission. Under lasing conditions in a resonant cavity, the high intracavity photon density bleaches the ESA at 552 nm, allowing for efficient cw laser operation. We obtained the highest output power of any room-temperature crystalline upconversion laser. The laser achieves a cw output power of 774 mW at a slope efficiency of 19% with respect to the incident pump power delivered by an optically-pumped semiconductor laser. The absorption efficiency of the pump radiation is estimated to be below 50%. To exploit the high confinement in waveguides for this laser, we employed femtosecond-laser pulses to inscribe a cladding of parallel tracks of modified material into Er3+:LiLuF4 crystals. The core material allows for low-loss waveguiding at pump and laser wavelengths. Under Ti:sapphire pumping at 974 nm, the first crystalline upconversion waveguide laser has been realized. We obtained waveguide-laser operation with up to 10 mW of output power at 553 nm.

  14. 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.

  15. Blue-green upconversion laser

    DOEpatents

    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.

  16. 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

  17. Engineered Upconversion Nanoparticles for Resolving Protein Interactions inside Living Cells.

    PubMed

    Drees, Christoph; Raj, Athira Naduviledathu; Kurre, Rainer; Busch, Karin B; Haase, Markus; Piehler, Jacob

    2016-09-12

    Upconversion nanoparticles (UCNPs) convert near-infrared into visible light at much lower excitation densities than those used in classic two-photon absorption microscopy. Here, we engineered <50 nm UCNPs for application as efficient lanthanide resonance energy transfer (LRET) donors inside living cells. By optimizing the dopant concentrations and the core-shell structure for higher excitation densities, we observed enhanced UCNP emission as well as strongly increased sensitized acceptor fluorescence. For the application of these UCNPs in complex biological environments, we developed a biocompatible surface coating functionalized with a nanobody recognizing green fluorescent protein (GFP). Thus, rapid and specific targeting to GFP-tagged fusion proteins in the mitochondrial outer membrane and detection of protein interactions by LRET in living cells was achieved. PMID:27510808

  18. Upconversion, size analysis, and fiber filling of NaYF4: Ho3+, Yb3+ crystals and nanocolloids

    NASA Astrophysics Data System (ADS)

    Patel, Darayas; Lewis, Ashley; Wright, Donald; Velentine, Maucus; Lewis, Danielle; Valentine, Ruben; Sarkisov, Sergey

    2014-03-01

    Nano-colloids and nano-crystals doped with ions of rare-earth elements have recently attracted a lot of attention in the scientific community. This attention is due to unique physical, chemical and optical properties attributed to nanometer size of the particles. They have great potential of being used in applications spanning from new types of lasers, especially blue and UV ones, phosphorous display monitors, optical communications, and fluorescence imaging. In this paper we investigate the near-infrared upconversion luminescence in bulk crystals and nanocolloid filled photonic crystal fiber with ytterbium and holmium co-doped NaYF4 phosphor. The phosphor is prepared by using simple co-precipitation synthetic method. The initially prepared phosphor has very week upconversion fluorescence. The fluorescence significantly increased after the phosphor was annealed at a temperature of 600 °C. Nanocolloids of this phosphor were obtained using 1-propanol as solvent and they were utilized as laser filling medium in photonic crystal fibers. Under 980 nm diode laser excitation very strong upconversion signals were obtained for ytterbium and holmium co-doped phosphor at 541 nm, 646 nm and 751 nm. Pump power emissions, laser ablation and size analysis of the particles was conducted to understand the upconversion mechanisms. The particle sizes of the nanocolloids were analyzed using Atomic Force Microscope and Malvern Zetasizer instrument. The reported nanocolloids are good candidates for fluorescent biosensing applications and also as a new laser filling medium in fiber laser.

  19. 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).

  20. Fluorescence Behaviour of an Aluminium Octacarboxy Phthalocyanine--NaYGdF4:Yb/Er Nanoparticle Conjugate.

    PubMed

    Taylor, Jessica; Litwinski, Christian; Nyokong, Tebello; Antunes, Edith

    2015-05-01

    Using a methanol assisted thermal decomposition approach, sphere shaped NaYGdF4:Yb/Er upconversion nanoparticles (UCNPs) were successfully synthesized. The chemical, spectroscopic and fluorescence properties of the UCNPs were fully characterized. Characteristic upconversion fluorescence emissions were produced by the NPs in the green, red and NIR regions and the NPs were also shown to possess paramagnetic properties. The influence of the UCNPs on the spectroscopic and fluorescence properties of an aluminium octacarboxy phthalocyanine AlOCPc was investigated. Covalent conjugation to an AlOCPc resulted in a large blue shift of the phthalocyanine's Q band, which was accompanied by a decrease in the Pc's fluorescence lifetime in DMSO. By combining the phthalocyanine and upconversion nanoparticle, we present a system capable of multimodal imaging, using both the upconversion nanoparticle's and phthalocyanine's emission, and magnetic resonance imaging (as a result of doping the upconversion nanoparticles with Gd(3+) ions). PMID:25744527

  1. 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. PMID:22252972

  2. Optical transitions of Ho(3+) in oxyfluoride glasses and upconversion luminescence of Ho(3+)/Yb(3+)-codoped oxyfluoride glasses.

    PubMed

    Feng, Li; Wu, Yinsu

    2015-05-01

    Optical properties of Ho(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 Ho(3+)/Yb(3+)-codoped SiO2-BaF2-ZnF2 glasses under 980nm excitation. The effects of composition, concentration of the doping ions, and excitation pump power on the upconversion emissions were also systematically studied. PMID:25703369

  3. 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.

  4. DNA-mediated excitonic upconversion FRET switching

    NASA Astrophysics Data System (ADS)

    Kellis, Donald L.; Rehn, Sarah M.; Cannon, Brittany L.; Davis, Paul H.; Graugnard, Elton; Lee, Jeunghoon; Yurke, Bernard; Knowlton, William B.

    2015-11-01

    Excitonics is a rapidly expanding field of nanophotonics in which the harvesting of photons, ensuing creation and transport of excitons via Förster resonant energy transfer (FRET), and subsequent charge separation or photon emission has led to the demonstration of excitonic wires, switches, Boolean logic and light harvesting antennas for many applications. FRET funnels excitons down an energy gradient resulting in energy loss with each step along the pathway. Conversely, excitonic energy upconversion via upconversion nanoparticles (UCNPs), although currently inefficient, serves as an energy ratchet to boost the exciton energy. Although FRET-based upconversion has been demonstrated, it suffers from low FRET efficiency and lacks the ability to modulate the FRET. We have engineered an upconversion FRET-based switch by combining lanthanide-doped UCNPs and fluorophores that demonstrates excitonic energy upconversion by nearly a factor of 2, an excited state donor to acceptor FRET efficiency of nearly 25%, and an acceptor fluorophore quantum efficiency that is close to unity. These findings offer a promising path for energy upconversion in nanophotonic applications including artificial light harvesting, excitonic circuits, photovoltaics, nanomedicine, and optoelectronics.

  5. Stimuli responsive upconversion luminescence nanomaterials and films for various applications.

    PubMed

    Tsang, Ming-Kiu; Bai, Gongxun; Hao, Jianhua

    2015-03-21

    Upconversion luminescence (UCL) refers to nonlinear optical processes, which can convert near-infrared photons to short-wavelength emission. Recent advances in nanotechnology have contributed to the development of photon upconversion materials as promising new generation candidates of fluorescent bioprobes and spectral converters for biomedical and optoelectronic applications. Apart from the remarkable photoluminescence of the materials under photon excitation, some UCL materials may exhibit intrinsic magnetic, ferroelectric, X-ray absorption properties, and so on. These interesting characteristics provide an opportunity for us to couple a single stimulus or multiple stimuli (electric field, magnetic field, X-ray, electron beam, temperature and pH, etc.) to various types of UCL materials. In this review, we will primarily focus on the stimuli responsive properties of UCL materials beyond light-matter interaction, which can aid both fundamental research and widespread applications of the materials. The mechanisms of the response to various stimuli in the UCL materials are discussed. This article will also highlight recent advances in the development of these materials in response to various stimuli and their applications in multimodal bioimaging, drug delivery and release, electro-optical devices, magnetic, temperature and pH sensors and multiple anti-counterfeiting inks. Lastly, we will present potential directions of future research and challenging issues which arise in expanding the applications of stimuli responsive UCL materials. PMID:25200182

  6. [Study on red up-conversion luminescence of fluoride glasses doped with Er3+, Yb3+ and Tm3+].

    PubMed

    Yan, Lei; Liu, Zheng-wei; Yang, Xiao-liang

    2005-06-01

    When the quality of Er2O3 is 10 times the former, the authors found that its character of up-conversion luminescence is distinct. Then the authors studied the luminescence system of Es3+ /Tm3+, Er3+ /Er3+ and Er3+ /Yb3+ /Tm3+ and their character of upconversion and fluorescence spectrum at 980 nm. In addition, the authors studied the relation between the three systems and the consistency of Er2O3. The authors found that the intensity of green and red light changed with the consistence of Er3+ in the experiment. It's the consistence of Er3+ that is the most causative. The chance is equal for each lanthanonion that makes up the luminescence system in the uniformity matter. With the distance between each pair of lanthanonions in the luminescence system is changed, the luminescence system and the color of the up-conversion luminescence also changed. PMID:16201349

  7. 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

  8. Upconversion Luminescence Properties of Y2Mo4O15: Yb3+, Er3+ by Solid State Combustion Method.

    PubMed

    Jiang, Tao; Xing, Mingming; Fu, Yao; Tian, Ying; Luo, Xixian

    2016-04-01

    The Yb3+ and Er3+ co-doped yttrium molybdenum oxide upconversion phosphors were prepared by the solid state combustion method using urea as fuel at ignition temperature of 550 °C. The upconversion phosphors were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), and photoluminescence spectra XRD results revealed the samples were pure monoclinic Y2Mo4O15 phases when the sintering temperature was 700 °C. SEM micrographs illustrated particle size distribution was almost uniform with an average particle diameter of about 0.5-1.0 µm. The obtained Y2MO4O15: Yb3+, Er3+ presents bright and pure green upconversion luminescence during daylight pumping under 980 nm LD. According to the analysis of upconversion luminescent mechanism, the cross relaxation processes of Er3+ ions restrained the electron population of red emission energy level, which not only increased the green light upconversion emissions fluorescent branching ratio (IGIR = 153:1) but also enhanced the efficiency and purity of green light emissions. PMID:27451756

  9. 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.

  10. Blue emission from Eu2+-doped high silica glass by near-infrared femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Qiao, Yanbo; Chen, Danping; Ren, Jinjun; Wu, Botao; Qiu, Jianrong; Akai, Tomoko

    2008-01-01

    Eu2+-doped high silica glass (HSG) is fabricated by sintering porous glass which is impregnated with europium ions. Eu2+-doped HSG is revealed to yield intense blue emission excited by ultraviolet (UV) light and near-infrared femtosecond laser. The emission profile obtained by UV excitation can be well traced by near-infrared femtosecond laser. The upconversion emission excited by 800 nm femtosecond laser is considered to be related to a two-photon absorption process from the relationship between the integrated intensity and the pump power. A tentative scheme of upconverted blue emission from Eu2+-doped HSG was also proposed. The HSG materials presented herein are expected to find applications in high density optical storage and three-dimensional color displays.

  11. 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. PMID:19322625

  12. Neurotoxin-conjugated upconversion nanoprobes for direct visualization of tumors under near-infrared irradiation.

    PubMed

    Yu, Xue-Feng; Sun, Zhengbo; Li, Min; Xiang, Yang; Wang, Qu-Quan; Tang, Fenfen; Wu, Yingliang; Cao, Zhijian; Li, Wenxin

    2010-11-01

    We report the development of neurotoxin-mediated upconversion nanoprobes for tumor targeting and visualization in living animals. The nanoprobes were synthesized by preparing polyethylenimine-coated hexagonal-phase NaYF(4):Yb,Er/Ce nanoparticles and conjugating them with recombinant chlorotoxin, a typical peptide neurotoxin that could bind with high specificity to many types of cancer cells. Nanoprobes that specifically targeted glioma cells were visualized by laser scanning upconversion fluorescence microscopy. Good probe biocompatibility was displayed with cellular and animal toxicity determinations. Animal studies were performed using Balb-c nude mice injected intravenously with the nanoprobes. The obtained high-contrast images demonstrated highly specific tumor binding and direct tumor visualization with bright red fluorescence under 980-nm near-infrared irradiation. The high sensitivity and high specificity of the neurotoxin-mediated upconversion nanoprobes and the simplification of the required optical device for tumor visualization suggest an approach that may help improve the effectiveness of the diagnostic and therapeutic modalities available for tumor patients. PMID:20728213

  13. Upconverting fluorescent nanoparticles for biodetection and photoactivation

    NASA Astrophysics Data System (ADS)

    Huang, Kai; Li, WenKai; Jayakumar, Muthu Kumara Gnanasammandhan; Zhang, Yong

    2013-03-01

    Fluorophores including fluorescent dyes/proteins and quantum dots (QDs) are used for fluorescence-based imaging and detection. These are based on `downconversion fluorescence' and have several drawbacks: photobleaching, autofluorescence, short tissue penetration depth and tissue photo-damage. Upconversion fluorescent nanoparticles (UCNs) emit detectable photons of higher energy in the short wavelength range upon irradiation with near-infrared (NIR) light based on a process termed `upconversion'. UCNs show absolute photostability, negligible autofluorescence, high penetration depth and minimum photodamage to biological tissues. Lanthanide doped nanocrystals with nearinfrared NIR-to-NIR and/or NIR-to-VIS and/or NIR-to-UV upconversion fluorescence emission have been synthesized. The nanocrystals with small size and tunable multi-color emission have been developed. The emission can be tuned by doping different upconverting lanthanide ions into the nanocrystals. The nanocrystals with core-shell structure have also been prepared to tune the emission color. The surfaces of these nanocrystals have been modified to render them water dispersible and biocompatible. They can be used for ultrasensitive interference-free biodetection because most biomolecules do not have upconversion properties. UCNs are also useful for light based therapy with enhanced efficiency, for example, photoactivation.

  14. 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. PMID:16378753

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

    PubMed

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

    2016-04-13

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

  16. Dual-band pixelless upconversion imaging devices.

    PubMed

    Wu, Le Ke; Hao, Hui Lian; Shen, Wen Zhong; Ariyawansa, Gamini; Perera, A G Unil; Matsik, Steven G

    2007-08-15

    We have proposed a type of mid-infrared (MIR) and far-infrared (FIR) dual-band imaging device, which employs the photon frequency upconversion concept in a GaN/AlGaN MIR and FIR dual-band detector integrated with a GaN/AlGaN violet light emitting diode. On the basis of the photoresponse of single-period GaN/AlGaN dual-band detectors, we present the detailed optimization of multiperiod GaN emitter/AlGaN barrier detectors and their applications to dual-band pixelless upconversion imaging. Satisfying images have been received through the analysis of the modulation transfer function and the upconversion efficiency in the GaN/AlGaN dual-band pixelless upconverters, which exhibit good image resolution, high quantum efficiency, and negligible cross talk. PMID:17700787

  17. [Multiply upconversion emission in oxyfluoride ceramics].

    PubMed

    Xiao, Si-guo; Yang, Xiao-liang; Liu, Zhen-wei

    2003-02-01

    Oxyfluoride ceramics with the host composition of SiO2 and PbF2 have been prepared. X-ray diffraction analysis of the ceramics revealed that fluoride type beta-PbF2 solid solution regions are precipitated in the glass matrix. Rare earth ions in the beta-PbF2 solid solution show highly efficient upconversion performance due to the very small multi-phonon relaxation rates. Eight upconversion emission bands whose central wavelength are 846, 803, 665, 549, 523, 487, 456 and 411 nm have been observed when the sample was excited with 930 nm diode light. Four possible energy transfer processes between Er3+ and Yb3+ cause the electronic population of high energy level of Er3+ and realize the abound upconversion luminescence bands. PMID:12939954

  18. Enhanced UV upconversion emission using plasmonic nanocavities.

    PubMed

    El Halawany, Ahmed; He, Sha; Hodaei, Hossein; Bakry, Ahmed; Razvi, Mir A N; Alshahrie, Ahmed; Johnson, Noah J J; Christodoulides, Demetrios N; Almutairi, Adah; Khajavikhan, Mercedeh

    2016-06-27

    Upconversion of near infrared (NIR) into ultraviolet (UV) radiation could lead to a number of applications in bio-imaging, diagnostics and drug delivery. However, for bare nanoparticles, the conversion efficiency is extremely low. In this work, we experimentally demonstrate strongly enhanced upconversion emission from an ensemble of β-NaYF4:Gd3+/Yb3+/Tm3+ @NaLuF4 core-shell nanoparticles trapped in judiciously designed plasmonic nanocavities. In doing so, different metal platforms and nanostructures are systematically investigated. Our results indicate that using a cross-shape silver nanocavity, a record high enhancement of 170-fold can be obtained in the UV band centered at a wavelength of 345 nm. The observed upconversion efficiency improvement may be attributed to the increased absorption at NIR, the tailored photonic local density of states, and the light out-coupling characteristics of the cavity. PMID:27410563

  19. Luminescence upconversion in colloidal double quantum dots.

    PubMed

    Deutsch, Zvicka; Neeman, Lior; Oron, Dan

    2013-09-01

    Luminescence upconversion nanocrystals capable of converting two low-energy photons into a single photon at a higher energy are sought-after for a variety of applications, including bioimaging and photovoltaic light harvesting. Currently available systems, based on rare-earth-doped dielectrics, are limited in both tunability and absorption cross-section. Here we present colloidal double quantum dots as an alternative nanocrystalline upconversion system, combining the stability of an inorganic crystalline structure with the spectral tunability afforded by quantum confinement. By tailoring its composition and morphology, we form a semiconducting nanostructure in which excited electrons are delocalized over the entire structure, but a double potential well is formed for holes. Upconversion occurs by excitation of an electron in the lower energy transition, followed by intraband absorption of the hole, allowing it to cross the barrier to a higher energy state. An overall conversion efficiency of 0.1% per double excitation event is achieved. PMID:23912060

  20. 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. PMID:26436998

  1. Characterization and modeling of thulium:ZBLAN blue upconversion fiber lasers

    SciTech Connect

    Paschotta, R.; Barber, P.R.; Tropper, A.C.; Hanna, D.C.

    1997-05-01

    We have investigated the performance of blue upconversion fiber lasers based on thulium-doped ZBLAN fiber, operating at 480 nm with a 1140-nm pump. Extensive fluorescence measurements have provided the necessary spectroscopic data to present a computer model that describes the performance of such lasers with good accuracy despite the complicated three-step upconversion mechanism and the influence of ion{endash}ion energy transfer processes. We have identified the mechanisms that populate the levels above the {sup 1}G{sub 4} level and are able to specify the corresponding spectroscopic parameters. We discuss the relevance of these processes to the 480-nm laser performance. Furthermore, we have calculated optimized parameters for such lasers. {copyright} 1997 Optical Society of America

  2. Femtosecond beam science

    NASA Astrophysics Data System (ADS)

    Uesaka, Mitsuru

    1. Introduction -- 2. Femtosecond beam generation. 2.1. Theory and operation of femtosecond terawatt lasers. 2.2. Linear accelerator. 2.3. Synchrotron. 2.4. Laser plasma acceleration. 2.5. Inverse compton scattering x-ray generation. 2.6. Beam slicing by femtosecond laser. 2.7. Free electron lasers. 2.8. Energy recovery linac -- 3. Diagnosis and synchronization. 3.1. Pulse shape diagnostics. 3.2. Synchronization -- 4. Applications. 4.1. Radiation chemistry. 4.2. Time-resolved x-ray diffraction. 4.3. Protein dynamics. 4.4. Molecular dynamics simulation.

  3. Enhancement of the short wavelength upconversion emission in inverse opal photonic crystals.

    PubMed

    Wu, Hangjun; Zhu, Jialun; Yang, Zhengwen; Yan, Dong; Wang, Rongfei; Qiu, Jianbei; Song, Zhiguo; Yu, Xue; Yang, Yong; Zhou, Dacheng; Yin, Zhaoyi

    2014-05-01

    Upconversion luminescence properties of Yb-Tb codoped Bi4Ti3O12 inverse opals have been investigated. The results show that the upconversion emission can be modulated by the photonic band gap. More significantly, in the upconversion inverse opals, the excited-state absorption of Tb3+ is greatly enhanced by the suppression of upconversion spontaneous emissions of the intermediate excited state, and thus the short wavelength upconversion emission from Tb3+ is considerably improved. We believe that the present work will be valuable for not only the foundational study of upconversion emission modifications but also new optical devices in upconversion displays and short wavelength upconversion lasers. PMID:24734648

  4. Up-conversion luminescence from Er3+, Yb3+ co-doped GeO II-PbF II-Nb IIO 5 glass ceramic

    NASA Astrophysics Data System (ADS)

    Lv, Jinwen; Sang, Lanfen; Zhang, Jing; Fu, Xingguo

    2006-01-01

    The paper reports a new up-conversion luminescence material based on Yb 3+, Er 3+ co-doped germanate glass ceramic, the matrix system is GeO II-PbF II-Nb IIO 5. The luminescence characteristics of the Yb3+ , Er3+ co-doped glass ceramic have been studied. The structural properties of the germinate glass ceramic have been analysed by X-ray diffraction. Under the condition of 980nm semiconductor laser pumping, the green fluorescence intensity shows that the existence of niobate components plays an important role for up-conversion luminescence.

  5. 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. PMID:24051289

  6. 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.

  7. Multihydroxy dendritic upconversion nanoparticles with enhanced water dispersibility and surface functionality for bioimaging.

    PubMed

    Zhou, Li; He, Benzhao; Huang, Jiachang; Cheng, Zehong; Xu, Xu; Wei, Chun

    2014-05-28

    Upconversion nanoparticle (UCNP) as a new class of imaging agent is gaining prominence because of its unique optical properties. An ideal UCNP for bioimaging should simultaneously possess fine water dispersibility and favorable functional groups. In this paper, we present a simple but effective method to the synthesis of a UCNP-based nanohybrid bearing a multihydroxy hyperbranched polyglycerol (HPG) shell by the combination of a "grafting from" strategy with a ring-opening polymerization technique. The structure and morphology of the resulting UCNP-g-HPG nanohybrid were characterized in detail by Fourier transform infrared, (1)H NMR, thermogravimetric analysis, and transmission electron microscopy measurements. The results reveal that the amount of grafted HPG associated with the thickness of the HPG shell can be well tuned. UCNP-g-HPG shows high water dispersibility and strong and stable upconversion luminescence. On the basis of its numerous surface hydroxyl groups, UCNP-g-HPG can be tailored by a representative fluorescent dye rhodamine B to afford a UCNP-g-HPG-RB nanohybrid that simultaneously presents upconversion and downconversion luminescence. Preliminary biological studies demonstrate that UCNP-g-HPG shows low cytotoxicity, high luminescent contrast, and deep light penetration depth, posing promising potential for bioimaging applications. PMID:24749852

  8. Converting visible light into UVC: microbial inactivation by Pr(3+)-activated upconversion materials.

    PubMed

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

    2011-04-15

    Herein we report the synthesis and properties of light-activated antimicrobial surfaces composed of lanthanide-doped upconversion luminescent nano- and microcrystalline Y(2)SiO(5). Unlike photocatalytic surfaces, which convert light energy into reactive chemical species, this work describes surfaces that inactivate microorganisms through purely optical mechanisms, wherein incident visible light is partially converted into germicidal UVC radiation. Upconversion phosphors utilizing a Pr(3+) activator ion were synthesized and their visible-to-ultraviolet conversion capabilities were confirmed via photoluminescence spectroscopy. Polycrystalline films were prepared on glass substrates, and the extent of surface microbial inactivation and biofilm inhibition under visible light excitation were investigated. Results show that, under normal visible fluorescent lamp exposure, a sufficient amount of UVC radiation was emitted to inhibit Pseudomonas aeruginosa biofilm formation and to inactivate Bacillus subtilis spores on the dry surfaces. This new application of upconversion luminescence shows for the first time its ability to deter microbial contamination and could potentially lead to new material strategies for disinfection of surfaces and water. PMID:21428395

  9. Photon upconversion with hot carriers in plasmonic systems

    SciTech Connect

    Naik, Gururaj V.; Dionne, Jennifer A.

    2015-09-28

    We propose a scheme of photon upconversion based on harnessing the energy of plasmonic hot carriers. Low-energy photons excite hot electrons and hot holes in a plasmonic nanoparticle, which are then injected into an adjacent semiconductor quantum well where they radiatively recombine to emit a photon of higher energy. We theoretically study the proposed upconversion scheme using Fermi-liquid theory and determine the internal quantum efficiency of upconversion to be as high as 25% in 5 nm silver nanocubes. This upconversion scheme is linear in its operation, does not require coherent illumination, offers spectral tunability, and is more efficient than conventional upconverters.

  10. Photon up-conversion increases biomass yield in Chlorella vulgaris.

    PubMed

    Menon, Kavya R; Jose, Steffi; Suraishkumar, Gadi K

    2014-12-01

    Photon up-conversion, a process whereby lower energy radiations are converted to higher energy levels via the use of appropriate phosphor systems, was employed as a novel strategy for improving microalgal growth and lipid productivity. Photon up-conversion enables the utilization of regions of the solar spectrum, beyond the typical photosynthetically active radiation, that are usually wasted or are damaging to the algae. The effects of up-conversion of red light by two distinct sets of up-conversion phosphors were studied in the model microalgae Chlorella vulgaris. Up-conversion by set 1 phosphors led to a 2.85 fold increase in biomass concentration and a 3.2 fold increase in specific growth rate of the microalgae. While up-conversion by set 2 phosphors resulted in a 30% increase in biomass and 12% increase in specific intracellular neutral lipid, while the specific growth rates were comparable to that of the control. Furthermore, up-conversion resulted in higher levels of specific intracellular reactive oxygen species in C. vulgaris. Up-conversion of red light (654 nm) was shown to improve biomass yields in C. vulgaris. In principle, up-conversion can be used to increase the utilization range of the electromagnetic spectrum for improved cultivation of photosynthetic systems such as plants, algae, and microalgae. PMID:25155721

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

    PubMed

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

    2015-02-01

    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. PMID:25548870

  12. IRRS, UV-Vis-NIR absorption and photoluminescence upconversion in Ho 3+-doped oxyfluorophosphate glasses

    NASA Astrophysics Data System (ADS)

    Karmakar, Basudeb

    2005-09-01

    Infrared reflection spectroscopic (IRRS), ultraviolet-visible-near infrared (UV-Vis-NIR) absorption and photoluminescence upconversion properties with special emphasis on the spectrochemistry of the oxyfluorophosphate (oxide incorporated fluorophosphates) glasses of the Ba(PO 3) 2-AlF 3-CaF 2-SrF 2-MgF 2-Ho 2O 3 system have been studied with different concentrations (0.1, 0.3 and 1.0 mol%) of Ho 2O 3. IRRS spectral band position and intensity of Ho 3+ ion doped oxyfluorophosphate glasses have been discussed in terms of reduced mass and force constant. UV-Vis-NIR absorption band position has been justified with quantitative calculation of nephelauxetic parameter and covalent bonding characteristics of the host. NIR to visible upconversion has been investigated by exciting at 892 nm at room temperature. Three upconverted bands originated from the 5F 3→ 5I 8, ( 5S 2, 5F 4)→ 5I 8 and 5F 5→ 5I 8 transitions have found to be centered at 491 nm (blue, medium), 543 nm (green, very strong) and 658 nm (red, weak), respectively. These bands have been justified from the evaluation of the absorption, normal (down conversion) fluorescence and excitation spectra. The upconversion processes have been explained by the excited state absorption (ESA), energy transfer (ET) and cross relaxation (CR) mechanisms involving population of the metastable (storage) energy levels by multiphonon deexcitation effect. It is evident from the IRRS study that the upconversion phenomena are expedited by the low multiphonon relaxation rate in oxyfluorophosphate glasses owing to their high intense low phonon energy (˜600 cm -1) which is very close to that of fluoride glasses (500-600 cm -1).

  13. 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

  14. 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. PMID:26378771

  15. 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.

  16. 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

  17. 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.

  18. Efficient up-conversion of triplet excitons into a singlet state and its application for organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Endo, Ayataka; Sato, Keigo; Yoshimura, Kazuaki; Kai, Takahiro; Kawada, Atsushi; Miyazaki, Hiroshi; Adachi, Chihaya

    2011-02-01

    A material possessing a very small energy gap between its singlet and triplet excited states, ΔE1-3, which allows efficient up-conversion of triplet excitons into a singlet state and leads to efficient thermally activated delayed fluorescence (TADF), is reported. The compound, 2-biphenyl-4,6-bis(12-phenylindolo[2,3-a] carbazole-11-yl)-1,3,5-triazine, breaks the restriction of a large energy gap, with a ΔE1-3 of just 0.11 eV, while maintaining a high fluorescent radiative decay rate (kr˜107). The intense TADF provides a pathway for highly efficient electroluminescence.

  19. 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.

  20. 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

  1. [High efficiency and low threshold upconversion from IR to red for Er3+ and Tm3+ co-doped fluoride-oxide glass-ceramic].

    PubMed

    Qin, Guan-shi; Qin, Wei-ping; Chen, Bao-jiu; E, Shu-lin; Ge, Zhong-jiu; Ren, Xin-guang; Huang, Shi-hua

    2002-10-01

    In this paper, high efficiency and low threshold upconversion from IR to red is reported, for Er3+ and Tm3+ co-doped fluoride-oxide glass-ceramic under 978 nm LD excitation. The component of sample in experiment is 65GeO2-25NaF-8.5BaF2-1Er2O3-0.5 Tm2O3, and the prepared method is obtained. The upconversion emission spectra under 978 nm LD excitation is measured at room temperature. Analyzing it, we find that introduction of Tm3+ into Er3+ doped system preferentially quenches the green upconversion fluorescence from 4S3/2 level of Er3+ duo to the efficient cross-relaxation of 4I13/2-->4I15/2 (Er): 3H6-->3H4 (Tm) which can significantly reduce the upconversion efficiency from 4I13/2 level to the emitting 4S3/2 level, and the Tm3+ behaves as a good sensitizer of the red upconversion from the 4F9/2 level of Er3+ which is mainly populated by the cross-relaxation of 3H4-->3H6 (Tm): 4I11/2-->4F9/2 (Er). However, at low Er3+ concentration (2 mol%), it is impossible for strong red upconversion. X-ray analysis is done, there are lots of nanocrystallites in MFG glass-ceramic. So we think, this red upconversion is attributed to Er3+ enriched fluoride microcrystallites, which makes the cross-relaxation of 3H4-->3H6 (Tm): 4I11/2-->4F9/2 (Er) more effective, therefore their active optical properties may be optimised. In the end, the relationship between LD working current and intensity of upconversion luminescence is discussed, the results confirm that both red and green upconversion processes are consisted by two photons. PMID:12938407

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

    PubMed Central

    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 Ce3+ 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. PMID:24940173

  3. 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

  4. Hemifusion of cells using femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Katchinskiy, Nir; Godbout, Roseline; Goez, Helly R.; Elezzabi, Abdulhakem Y.

    2015-03-01

    Attachment of single cells via hemifusion of cellular membranes using femtosecond laser pulses is reported in this manuscript. This is a method to attach single cells using sub-10 femtosecond laser pulses, with 800 nm central wavelength delivered from a Ti:Sapphire laser is described. A fluorescent dye, Calcein AM, was used to verify that the cell's cytoplasm did not migrate from a dyed cell to a non-dyed cell, in order to ascertain that the cells did not go through cell-fusion process. An optical tweezer was used in order to assess the mechanical integrity of the attached joint membranes. Hemifusion of cellular membranes was successful without initiating full cell fusion. Attachment efficiency of 95% was achieved, while the cells' viability was preserved. The attachment was performed via the delivery of one to two trains of sub-10 femtosecond laser pulses lasting 15 milliseconds each. An ultrafast reversible destabilization of the phospholipid molecules in the cellular membranes was induced due to a laser-induced ionization process. The inner phospholipid cell membrane remained intact during the attachment procedure, and cells' cytoplasm remained isolated from the surrounding medium. The unbounded inner phospholipid molecules bonded to the nearest free phospholipid molecule, forming a joint cellular membrane at the connection point. The cellular membrane hemifusion technique can potentially provide a platform for the creation of engineered tissue and cell cultures.

  5. G-Quadruplex Supramolecular Assemblies in Photochemical Upconversion.

    PubMed

    Mutsamwira, Saymore; Ainscough, Eric W; Partridge, Ashton C; Derrick, Peter J; Filichev, Vyacheslav V

    2016-07-18

    Parallel, tetramolecular G-quadruplex (G4) DNA possessing TINA monomer, (R)-1-O-[4-(1-pyrenylethynyl)phenylmethyl]glycerol, were synthesised and evaluated in complexes with tris(2,2'-bipyridine)ruthenium(II), [Ru(bpy)3 ](2+) , and the Zn(2+) derivative of 5,10,15,20-tetrakis-(1-methyl-4-pyridyl)-21 H,23H-porphine, ZnTMpyP4. UV/Vis, fluorescence, and circular dichroism (CD) spectroscopy showed that the use of G4-DNA as a template resulted in the effective communication between the ligands and the TINA molecule that was covalently attached to the 5'-end and between T and dG at the 5'-end of the dTG4 T sequence. Only one G4-DNA possessing the TINA molecule at the 5'-end of the dTG4 T sequence was able to yield a green-to-blue photochemical upconversion (PUC, λem =420 nm) in the presence of [Ru(bpy)3 ](2+) upon excitation at 500 nm. Different DNA secondary structures can thus be used in DNA-based assemblies for PUC and the way of attachment of chromophores to DNA plays a pivotal role for the creation of a photosynthetic centre. PMID:27172273

  6. 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

  7. Photoluminescence and upconversion on Ag/CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Ragab, A. E.; Gadallah, A.-S.; Mohamed, M. B.; Azzouz, I. M.

    2014-11-01

    Different sizes of aqueous CdTe QDs have been prepared by microwave via controlling the temperature and time of irradiation. To study the plasmonic effect on CdTe QDs, Silver NPs were prepared by using a chemical reduction method. Structure characterization of the nanocrystals (Ag NPs and CdTe QDs) was determined by transmission electron microscopy “TEM”. For optical characterization, the absorption and photolumincence (PL) spectra were measured. It has been found that there are two opposite behaviors (quenching and enhancement) in the fluorescence spectra based on the spectral coupling strength between Ag NPs and CdTe QDs. When there is strong overlapping, PL enhancement of CdTe QDs has been observed. On the other hand, when the overlapping is weak, the PL quenching was predominant at all Ag NPS concentrations. Input-output PL intensity dependence was also studied. Upconversion photoluminescence with low excitation intensity was observed in our CdTe QDs with a standard spectrofluorometer at excitation wavelength of 800 nm. Thermally assisted surface state mechanism has been proposed to be responsible for the upconverion process.

  8. Bioapplications and biotechnologies of upconversion nanoparticle-based nanosensors.

    PubMed

    Wang, Chengli; Li, Xiaomin; Zhang, Fan

    2016-06-21

    Upconversion nanoparticles (UCNPs), which can emit ultraviolet/visible (UV/Vis) light under near-infrared (NIR) excitation, are regarded as a new generation of nanoprobes because of their unique optical properties, including a virtually zero auto-fluorescence background for the improved signal-to-noise ratio, narrow emission bandwidths and high resistance to photo-bleaching. These properties make UCNPs promising candidates as luminescent bioprobes in biomedicine and biotechnology. In this review, we focus on the recent progress in the development of UCNP-based nanoprobes for biosensing. Firstly, as the FRET process is a widely used method for biosensing to improve the sensitivity, we summarize recent research studies about UCNP-based nanocomposites utilizing the FRET process for biosensing. Different energy acceptors (organic dyes, noble metal nanoparticles, carbon nanomaterials and semiconductor nanomaterials) with their own advantages and limitations are well summarized in this review. Secondly, since UCNPs have been utilized for the detection of different kinds of analytes, we introduce recent research studies about UCNPs for ions, gas molecules, biomolecules and thermal sensing. Finally, we highlight the typical detection techniques and UCNP based devices for bioapplications. PMID:26978012

  9. Femtosecond laser materials processing

    SciTech Connect

    Stuart, B.C.

    1997-02-01

    The use femtosecond pulses for materials processing results in very precise cutting and drilling with high efficiency. Energy deposited in the electrons is not coupled into the bulk during the pulse, resulting in negligible shock or thermal loading to adjacent areas.

  10. Polymer encapsulated upconversion nanoparticle/iron oxide nanocomposites for multimodal imaging and magnetic targeted drug delivery.

    PubMed

    Xu, Huan; Cheng, Liang; Wang, Chao; Ma, Xinxing; Li, Yonggang; Liu, Zhuang

    2011-12-01

    Multimodal imaging and imaging-guided therapies have become a new trend in the current development of cancer theranostics. In this work, we encapsulate hydrophobic upconversion nanoparticles (UCNPs) together with iron oxide nanoparticles (IONPs) by using an amphiphilic block copolymer, poly (styrene-block-allyl alcohol) (PS(16)-b-PAA(10)), via a microemulsion method, obtaining an UC-IO@Polymer multi-functional nanocomposite system. Fluorescent dye and anti-cancer drug molecules can be further loaded inside the UC-IO@Polymer nanocomposite for additional functionalities. Utilizing the Squaraine (SQ) dye loaded nanocomposite (UC-IO@Polymer-SQ), triple-modal upconversion luminescence (UCL)/down-conversion fluorescence (FL)/magnetic resonance (MR) imaging is demonstrated in vitro and in vivo, and also applied for in vivo cancer cell tracking in mice. On the other hand, a chemotherapy drug, doxorubicin, is also loaded into the nanocomposite, forming an UC-IO@Polymer-DOX complex, which enables novel imaging-guided and magnetic targeted drug delivery. Our work provides a method to fabricate a nanocomposite system with highly integrated functionalities for multimodal biomedical imaging and cancer therapy. PMID:21880364

  11. Molecularly imprinted upconversion nanoparticles for highly selective and sensitive sensing of Cytochrome c.

    PubMed

    Guo, Ting; Deng, Qiliang; Fang, Guozhen; Liu, Cuicui; Huang, Xuan; Wang, Shuo

    2015-12-15

    A novel method combined the high selectivity of molecular imprinting technology with the strong fluorescence property of upconversion nanoparticles (UCNPs) for sensing of Cytochrome c (Cyt c) was proposed. The molecularly imprinted material-coated upconversion nanoparticles (UCNPs@MIP) were obtained by in situ coating Cyt c imprinted materials to the surface of the carboxyl modified UCNPs through sol-gel technique. The structure and component of the prepared UCNPs@MIP was investigated by transmission electron microscopy (TEM), power X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDXA) and X-ray photoelectron spectroscopic (XPS). The TEM showed the diameter of UCNPs was 40 nm, and thickness of MIP was 5-10nm. The fluorescence intensity of UCNPs@MIP reduced gradually with the increase of Cyt c concentration. Under optimum conditions, the imprinting factor is 3.19, and the UCNPs@MIP showed selective recognition for Cyt c among other proteins such as bovine serum albumin (BSA) and Lysozyme (Lyz). Therefore, this new method for sensing protein is very promising for future applications. PMID:26176210

  12. Adaptive Femtosecond Quantum Control

    NASA Astrophysics Data System (ADS)

    Gerber, Gustav

    2003-03-01

    Obtaining active control over the dynamics of quantum-mechanical systems is a fascinating perspective in modern physics. A promising tool for this purpose is available with femtosecond laser technologies. The intrinsically broad spectral distribution and the phase function of femtosecond laser pulses can be specifically manipulated by pulse shapers to drive molecular systems coherently into the desired reaction pathways [1]. The approach of adaptive femtosecond quantum control follows the suggestion of Judson and Rabitz [2], in which a computer-controlled pulse shaper is used in combination with a learning algorithm [3] and direct feedback from the experiment to achieve coherent control over quantum-mechanical processes in an automated fashion, without requiring any model for the system's response. This technique can be applied to the control of gas-phase photodissociation processes [4]. Different bond-cleaving reactions can be preferentially selected, resulting in chemically different products. Prior knowledge about molecular Hamiltonians or reaction mechanisms is not required in this automated control loop, and this scheme works for complex systems. Adaptive pulse-shaping techniques can be transferred to the control of photoprocesses in the liquid phase as well, motivated by the wish to achieve control at particle densities high enough for (bimolecular) synthetic-chemical applications. Chemically selective molecular excitation is achieved by many-parameter adaptive quantum control [5], despite the failure of typical single-parameter approaches (such as wavelength control, intensity control, or linear chirp control). This experiment demonstrates that photoprocesses in two different molecular species can be controlled simultaneously. Applications are envisioned in bimolecular reaction control where specific educt molecules could selectively be "activated" for purposes of chemical synthesis. A new technological development further increases the possibilities and

  13. 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

  14. 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

  15. Y2O3:Tm,Yb nanophosphors for correlative upconversion luminescence and cathodoluminescence imaging.

    PubMed

    Fukushima, Shoichiro; Furukawa, Taichi; Niioka, Hirohiko; Ichimiya, Masayoshi; Miyake, Jun; Ashida, Masaaki; Araki, Tsutomu; Hashimoto, Mamoru

    2014-12-01

    We present a phosphor nanoparticle that shows both upconversion luminescence (UCL) and cathodoluminescence (CL). With this particle, low-autofluorescence, deep-tissue and wide-field fluorescence imaging can be achieved with nanometer-order high-spatial-resolution imaging. We synthesized Y2O3:Tm,Yb nanophosphors that emit visible and near-infrared UCL under 980 nm irradiation and blue CL via electron beam excitation. The phosphors were applied to fluorescent imaging of HeLa cells. The photostability of the phosphors was superior to that of a conventional organic dye. We show that after uptake by HeLa cells, the particles can be imaged with SEM and CL contrast in a cellular section. This indicates that correlative UCL and CL imaging of biological samples could be realized. PMID:25146422

  16. Photo-induced electron transfer in a diamino-substituted Ru(bpy)3[PF6]2 complex and its application as a triplet photosensitizer for nitric oxide (NO)-activated triplet-triplet annihilation upconversion.

    PubMed

    Xu, Kejing; Zhao, Jianzhang; Moore, Evan G

    2016-08-01

    A system demonstrating Nitric Oxide (NO) activated Triplet-Triplet Annihilation (TTA) upconversion has been devised, based on a substituted [Ru(II)(bpy)3](PF6)2 complex (bpy = 2,2'-dipyridine) bearing a single 1,2-diaminophenyl moiety as an NO activatable triplet photosensitizer (Ru-1), and 9,10-diphenylanthracene (DPA) as a triplet acceptor/emitter. The excited triplet state of Ru-1 is significantly quenched (ΦT∼ 22%) by a Photoinduced Electron Transfer (PET) reaction, as confirmed by steady state phosphorescence and transient absorption spectroscopy, and hence Ru-1 does not function as a TTA upconversion sensitizer. However, in the presence of NO/O2, the 1,2-diaminophenyl group of Ru-1 is transformed into a benzotriazole. This inhibits PET, and the triplet state quantum yield is increased to ca. 85%, switching on the TTA upconversion process which increases by 10-fold. These processes were studied using a combination of steady state and time-resolved luminescence together with transient absorption spectroscopy on the nanosecond and femtosecond timescales. The energy level of the charge transfer state (CTS) for Ru-1 was also obtained electrochemically, supporting the PET mechanism of triplet state quenching and hence the lack of TTA upconversion with Ru-1. PMID:27387268

  17. 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.

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

    PubMed

    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. PMID:26986473

  19. 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.

  20. 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.

  1. Upconversion studies in Gd2O3:Tm3+/Yb3+ phosphor

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Kumar, K.; Rai, S. B.; Rai, D. K.

    2013-06-01

    The Tm3+/Yb3+ doped Gd2O3 phosphor is prepared through combustion technique and its visible upconversion emission studies are made on 980 nm near infrared excitation. The upconversion studied showed good upconversion emission in blue region (477nm) but the highest emission intensity was observed at 802 nm wavelength. The Tm3+ ion concentration dependence of upconversion emission intensity studies are also done and optimum concentration of Tm3+ ion is found 0.2mol% for blue upconversion. The power dependence studies are also made to know the process of upconversion emission.

  2. 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

  3. Magnetic nanosensor particles in luminescence upconversion capability.

    PubMed

    Wilhelm, Stefan; Hirsch, Thomas; Scheucher, Elisabeth; Mayr, Torsten; Wolfbeis, Otto S

    2011-09-01

    Nanoparticles (NPs) exhibit interesting size-dependent electrical, optical, magnetic, and chemical properties that cannot be observed in their bulk counterparts. The synthesis of NPs (i.e., crystalline particles ranging in size from 1 to 100 nm) has been intensely studied in the past decades. Magnetic nanoparticles (MNPs) form a particularly attractive class of NPs and have found numerous applications such as in magnetic resonance imaging to visualize cancer, cardiovascular, neurological and other diseases. Other uses include drug targeting, tissue imaging, magnetic immobilization, hyperthermia, and magnetic resonance imaging. MNPs, due to their magnetic properties, can be easily separated from (often complex) matrices and manipulated by applying external magnetic field. Near-infrared to visible upconversion luminescent nanoparticles (UCLNPs) form another type of unusual nanoparticles. They are capable of emitting visible light upon NIR light excitation. Lanthanide-doped (Yb, Er) hexagonal NaYF₄ UCLNPs are the most efficient upconversion phosphors known up to now. The use of UCLNPs for in vitro imaging of cancer cells and in vivo imaging in tissues has been demonstrated. UCLNPs show great potential as a new class of luminophores for biological, biomedical, and sensor applications. We are reporting here on our first results on the combination of MNP and UCLNP technology within an ongoing project supported by the DFG and the FWF (Austria). PMID:22022719

  4. Upconversion Nanoparticles for Bioimaging and Regenerative Medicine.

    PubMed

    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

  5. [Femtosecond lenticule extraction (FLEx)].

    PubMed

    Blum, M; Sekundo, W

    2010-10-01

    Starting in 2006 a new "all femto" method of refractive correction for myopia and myopic astigmatism was introduced. This new method was originally introduced as femtosecond lenticule extraction (FLEx) and further developed with a small incision into SMILE (small incision lenticule extraction). To simplify the terminology the manufacturer brought this onto the market in April 2010 as ReLEx (refractive lenticule extraction). In this procedure a lenticule of intrastromal corneal tissue and a flap-like access cut are subsequently cut utilizing the VisuMax® femtosecond system (Carl Zeiss Meditec, Jena, Germany). The lenticule is then manually removed and the flap repositioned (only by FLEx). In approximately 1,000 successful surgical operations only few side effects were found. The number of eyes treated is currently being expanded in order to further standardize this new clinical procedure. PMID:20694728

  6. 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.

  7. Ligand-centred fluorescence and electronic relaxation cascade at vibrational time scales in transition-metal complexes.

    PubMed

    Messina, Fabrizio; Pomarico, Enrico; Silatani, Mahsa; Baranoff, Etienne; Chergui, Majed

    2015-11-19

    Using femtosecond-resolved photoluminescence up-conversion, we report the observation of the fluorescence of the high-lying ligand-centered (LC) electronic state upon 266 nm excitation of an iridium complex, Ir(ppy)3, with a lifetime of 70 ± 10 fs. It is accompanied by a simultaneous emission of all lower-lying electronic states, except the lowest triplet metal-to-ligand charge-transfer ((3)MLCT) state that shows a rise on the same time scale. Thus, we observe the departure, the intermediate steps, and the arrival of the relaxation cascade spanning ∼1.6 eV from the (1)LC state to the lowest (3)MLCT state, which then yields the long-lived luminescence of the molecule. This represents the first measurement of the total relaxation time over an entire cascade of electronic states in a polyatomic molecule. We find that the relaxation cascade proceeds in ≤10 fs, which is faster than some of the highest-frequency modes of the system. We invoke the participation of the latter modes in conical intersections and their overdamping to low-frequency intramolecular modes. On the basis of literature, we also conclude that this behavior is not specific to transition-metal complexes but also applies to organic molecules. PMID:26509329

  8. 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.

  9. 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

    2016-02-10

    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. PMID:26806612

  10. Growth, characterization and upconversion properties of erbium-doped potassium lithium tantalate niobate single crystals under 975 nm laser excitation

    NASA Astrophysics Data System (ADS)

    Zhou, Zhongxiang; Li, Lei; Duan, Qianqian; Feng, Lei; Tian, Hao

    2012-04-01

    Potassium lithium tantalate niobate single crystals doped with erbium ions are grown by top-seeded solution growth method. The crystals are characterized by X-ray diffraction and differential thermal analysis. The refractive indices of the crystal are measured using ellipsometry method and fitted by Sellmeier equation. The as-grown crystals are tetragonal phase tungsten bronze-type structure with Curie temperature of 271.3 °C. Characteristic Er3 + absorption bands are observed from 350 to 1100 nm in ultraviolet-visible-near infrared absorption spectra. These crystals emit brightly green and red upconversion fluorescence under 975 nm LD laser excitation, and the steady state upconversion spectra are obtained at room temperature. The red emission intensity increases as the erbium ions concentration increases in crystals. Processes of excited state absorption and energy transfer are responsible for upconversion luminescence. The emission intensities are quadratic dependences on pump power from pump power dependence analyses and deduction of transition rate equation model.