Relative fluorescent efficiency of sodium salicylate between 90 and 800 eV

NASA Technical Reports Server (NTRS)

Angel, G. C.; Samson, J. A. R.; Wiliams, G.

1986-01-01

The relative fluorescent quantum efficiency of sodium salicylate was measured between 90 and 800 eV (138-15 A) by the use of synchrotron radiation. A general increase in efficiency was observed in this spectral range except for abrupt decreases in efficiency at the carbon and oxygen K-edges. Beyond the oxygen K-edge (532 eV) the efficiency increased linearly with the incident photon energy to the limit of the present observations.

The relative fluorescent efficiency of sodium salicylate between 90 and 800 eV

NASA Technical Reports Server (NTRS)

Angel, G. C.; Samson, J. A. R.; Williams, G.

1986-01-01

The relative fluorescent quantum efficiency of sodium salicylate was measured between 90 and 800 eV (138 -15 A) by the use of synchrotron radiation. A general increase in efficiency was observed in this spectral range except for abrupt decreases in efficiency at the carbon and oxygen K-edges. Beyond the oxygen K-edge (532 eV) the efficiency increased linearly with the incident photon energy to the limit of the present observations.

Radioisotopic energy conversion system (RECS): A new radioisotopic power cell, based on nuclear, atomic, and radiation transport principles

NASA Astrophysics Data System (ADS)

Steinfelds, Eric Victor

The topic of this thesis is the development of the Radioisotope Energy Conversion System (RECS) in a project which is utilizing analytical computational assisted design and some experimental Research in the investigation of fluorescers and effective transducers with the appropriate energy range choice for the conversion of energy. It is desirable to increase the efficiency in electrical power from the raw kinetic power available from the radioactive material within radioisotope power generators. A major step in this direction is the development and use of Radioisotope Energy Conversion Systems to supplement and ideally replace Radioactive Thermal Generators (RTG). It is possible to achieve electrical conversion efficiencies exceeding 25% for RECS power devices compared to only 9 percent efficiency for RTG's. The theoretical basis with existent materials for the potential achievability of efficiencies above 25% is documented within this thesis. The fundamental RECS consists of a radioisotope radiative source (C1), a mediating fluorescent gas (C2) which readily absorbs energy from the beta particles (or alpha's) and subsequently emits blue or UV photons, photovoltaic cells (C3) to convert the blue and UV photons into electrical energy [2], and electrical circuitry (C4). Solid State inspired component (C3), due to its theoretical (and attainable) high efficiency, is a large step ahead of the RTG design concept. The radioisotope flux source produces the beta(-) particles or alpha particles. Geometrically, presently, we prefer to have the ambient fluorescent gas surround the radioisotope flux source. Our fluorescer shall be a gas such as Krypton. Our specifically wide band-gap photovoltaic cells shall have gap energies which are slightly less than that of UV photons produced by the fluorescing gas. Diamond and Aluminum Nitride sample materials are good potential choices for photovoltaic cells, as is explained here in. Out of the material examples discussed, the highest electric power to mass ratio is found to be readily attainable with strontium-90 as the radiative source. Krypton-85 is indisputably the most efficient in RECS devices. In the conclusion in chapter VI, suggestions are given on acceptable ways of containing krypton-85 and providing sufficient shielding on deep space probes destined to use krypton-85 powered 'batteries'.

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

Gordon, Kelly L.; Foster, Rebecca; McGowan, Terry

This article for a building trade magazine describes a national design competition for energy efficient lighting sponsored by the U.S. Department of Energy, the American Lighting Association, and the Consortium for Energy Efficiency, with winners announced at ALA's Annual Conference May 14, 2004, in Tucson. The Lighting for Tomorrow competition was the first national lighting fixture design competition focusing on energy-efficient residential lighting. The competition invited fixture manufacturers and designers to come up with beautiful, functional lighting fixtures that also happen to be energy efficient. Fixtures were required to use a ''dedicated'' energy-efficient light source, such as a pin-based fluorescentmore » lamp that cannot be replaced with a screw-in incandescent bulb. Fixtures also had to meet a minimum energy efficiency level that eliminated use of incandescent and halogen lamps, leaving the door open only to fluorescent sources and LEDs. More than 150 paper designs were submitted in the first phase of the competition, in 2003. Of those, 24 finalists were invited to submit working prototypes in 2004, and the winners were announced in May. The Grand Prize of $10,000 went to American Fluorescent of Waukegan, Illinois, for its ''Salem'' chandelier. Some winning fixtures are already available through Lowe's Home Improvement Centers.« less

Solvent-modified ultrafast decay dynamics in conjugated polymer/dye labeled single stranded DNA

NASA Astrophysics Data System (ADS)

Kim, Inhong; Kang, Mijeong; Woo, Han Young; Oh, Jin-Woo; Kyhm, Kwangseuk

2015-07-01

We have investigated that organic solvent (DMSO, dimethyl sulfoxide) modifies energy transfer efficiency between conjugated polymers (donors) and fluorescein-labeled single stranded DNAs (acceptors). In a mixture of buffer and organic solvent, fluorescence of the acceptors is significantly enhanced compared to that of pure water solution. This result can be attributed to change of the donor-acceptor environment such as decreased hydrophobicity of polymers, screening effect of organic solvent molecules, resulting in an enhanced energy transfer efficiency. Time-resolved fluorescence decay of the donors and the acceptors was modelled by considering the competition between the energy harvesting Foerster resonance energy transfer and the energy-wasting quenching. This enables to quantity that the Foerster distance (R0 = 43.3 Å) and resonance energy transfer efficiency (EFRET = 58.7 %) of pure buffer solution become R0 = 38.6 Å and EFRET = 48.0 % when 80% DMSO/buffer mixture is added.

Influence of silver nanoparticles on relaxation processes and efficiency of dipole – dipole energy transfer between dye molecules in polymethylmethacrylate films

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

Bryukhanov, V V; Borkunov, R Yu; Tsarkov, M V

The fluorescence and phosphorescence of dyes in thin polymethylmethacrylate (PMMA) films in the presence of ablated silver nanoparticles has been investigated in a wide temperature range by methods of femtosecond and picosecond laser photoexcitation. The fluorescence and phosphorescence times, as well as spectral and kinetic characteristics of rhodamine 6G (R6G) molecules in PMMA films are measured in a temperature range of 80 – 330 K. The temperature quenching activation energy of the fluorescence of R6G molecules in the presence of ablated silver nanoparticles is found. The vibrational relaxation rate of R6G in PMMA films is estimated, the efficiency of themore » dipole – dipole electron energy transfer between R6G and brilliant green molecules (enhanced by plasmonic interaction with ablated silver nanoparticles) is analysed, and the constants of this energy transfer are determined. (nanophotonics)« less

CH3 NH3 PbBr3 Perovskite Nanocrystals as Efficient Light-Harvesting Antenna for Fluorescence Resonance Energy Transfer.

PubMed

Muthu, Chinnadurai; Vijayan, Anuja; Nair, Vijayakumar C

2017-05-04

Hybrid perovskites have created enormous research interest as a low-cost material for high-performance photovoltaic devices, light-emitting diodes, photodetectors, memory devices and sensors. Perovskite materials in nanocrystal form that display intense luminescence due to the quantum confinement effect were found to be particularly suitable for most of these applications. However, the potential use of perovskite nanocrystals as a light-harvesting antenna for possible applications in artificial photosynthesis systems is not yet explored. In the present work, we study the light-harvesting antenna properties of luminescent methylammonium lead bromide (CH 3 NH 3 PbBr 3 )-based perovskite nanocrystals using fluorescent dyes (rhodamine B, rhodamine 101, and nile red) as energy acceptors. Our studies revealed that CH 3 NH 3 PbBr 3 nanocrystals are an excellent light-harvesting antenna, and efficient fluorescence resonance energy transfer occurs from the nanocrystals to fluorescent dyes. Further, the energy transfer efficiency is found to be highly dependent on the number of anchoring groups and binding ability of the dyes to the surface of the nanocrystals. These observations may have significant implications for perovskite-based light-harvesting devices and their possible use in artificial photosynthesis systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficient triplet harvesting of hybrid white organic light-emitting diodes using thermally activated delayed fluorescence green emitter

NASA Astrophysics Data System (ADS)

Lee, Song Eun; Lee, Ho Won; Baek, Hyun Jung; Yun, Tae Jun; Yun, Geum Jae; Kim, Woo Young; Kim, Young Kwan

2016-10-01

Hybrid white organic light-emitting diodes (WOLEDs) were fabricated by applying triplet harvesting (TH) using a green thermally activated delayed fluorescence (TADF) emitter. The triplet exciton of the green TADF emitter can be upconverted to its singlet state. The TH involved energy transfer of triplet exciton from a blue fluorescent emitter to a green TADF and red phosphorescent emitters, where they can decay radiatively. In addition, the triplet exciton of the green TADF emitter was energy transferred to its singlet state for a reverse intersystem crossing by green emission. Enhanced hybrid WOLEDs were demonstrated using an efficient green TADF emitter combined with red phosphorescent and blue fluorescent emitters. Hybrid WOLEDs were fabricated with various hole-electron recombination zones as changing blue emitting layer thicknesses. Among these, hybrid WOLEDs showed a maximum external quantum efficiency of 11.23%, luminous efficiency of 29.20 cd/A, and a power efficiency of 26.21 lm/W. Moreover, the WOLED exhibited electroluminescence spectra with Commission International de L'Éclairage chromaticity of (0.38, 0.36) at 1000 cd/m2 and a color rendering index of 82 at a practical brightness of 20,000 cd/m2.

Advanced lighting guidelines: 1993. Final report

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

Eley, C.; Tolen, T.M.; Benya, J.R.

1993-12-31

The 1993 Advanced Lighting Guidelines document consists of twelve guidelines that provide an overview of specific lighting technologies and design application techniques utilizing energy-efficient lighting practice. Lighting Design Practice assesses energy-efficient lighting strategies, discusses lighting issues, and explains how to obtain quality lighting design and consulting services. Luminaires and Lighting Systems surveys luminaire equipment designed to take advantage of advanced technology lamp products and includes performance tables that allow for accurate estimation of luminaire light output and power input. The additional ten guidelines -- Computer-Aided Lighting Design, Energy-Efficient Fluorescent Ballasts, Full-Size Fluorescent Lamps, Compact Fluorescent Lamps, Tungsten-Halogen Lamps, Metal Halidemore » and HPS Lamps, Daylighting and Lumen Maintenance, Occupant Sensors, Time Scheduling Systems, and Retrofit Control Technologies -- each provide a product technology overview, discuss current products on the lighting equipment market, and provide application techniques. This document is intended for use by electric utility personnel involved in lighting programs, lighting designers, electrical engineers, architects, lighting manufacturers` representatives, and other lighting professionals.« less

Classic maximum entropy recovery of the average joint distribution of apparent FRET efficiency and fluorescence photons for single-molecule burst measurements.

PubMed

DeVore, Matthew S; Gull, Stephen F; Johnson, Carey K

2012-04-05

We describe a method for analysis of single-molecule Förster resonance energy transfer (FRET) burst measurements using classic maximum entropy. Classic maximum entropy determines the Bayesian inference for the joint probability describing the total fluorescence photons and the apparent FRET efficiency. The method was tested with simulated data and then with DNA labeled with fluorescent dyes. The most probable joint distribution can be marginalized to obtain both the overall distribution of fluorescence photons and the apparent FRET efficiency distribution. This method proves to be ideal for determining the distance distribution of FRET-labeled biomolecules, and it successfully predicts the shape of the recovered distributions.

NIR-Mediated Nanohybrids of Upconversion Nanophosphors and Fluorescent Conjugated Polymers for High-Efficiency Antibacterial Performance Based on Fluorescence Resonance Energy Transfer.

PubMed

Li, Junting; Zhao, Qi; Shi, Feng; Liu, Chenghui; Tang, Yanli

2016-12-01

A novel nanohybrid comprised of upconversion nanophosphors (UCNPs) and fluorescent conjugated polymers (PFVCN) is rationally fabricated. The new UCNP/PFVCN nanohybrids combine the excellent antibacterial ability of PFVCN and the near IR (NIR) absorbing property of UCNPs, which allows for NIR-mediated antibacterial through the effective fluorescence resonance energy transfer from UCNPs to PFVCN accompanied with generation of reactive oxygen species to kill bacteria. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Measuring partial fluorescence yield using filtered detectors.

PubMed

Boyko, T D; Green, R J; Moewes, A; Regier, T Z

2014-07-01

Typically, X-ray absorption near-edge structure measurements aim to probe the linear attenuation coefficient. These measurements are often carried out using partial fluorescence yield techniques that rely on detectors having photon energy discrimination improving the sensitivity and the signal-to-background ratio of the measured spectra. However, measuring the partial fluorescence yield in the soft X-ray regime with reasonable efficiency requires solid-state detectors, which have limitations due to the inherent dead-time while measuring. Alternatively, many of the available detectors that are not energy dispersive do not suffer from photon count rate limitations. A filter placed in front of one of these detectors will make the energy-dependent efficiency non-linear, thereby changing the responsivity of the detector. It is shown that using an array of filtered X-ray detectors is a viable method for measuring soft X-ray partial fluorescence yield spectra without dead-time. The feasibility of this technique is further demonstrated using α-Fe2O3 as an example and it is shown that this detector technology could vastly improve the photon collection efficiency at synchrotrons and that these detectors will allow experiments to be completed with a much lower photon flux reducing X-ray-induced damage.

Bichromophoric dyes for wavelength shifting of dye-protein fluoromodules.

PubMed

Pham, Ha H; Szent-Gyorgyi, Christopher; Brotherton, Wendy L; Schmidt, Brigitte F; Zanotti, Kimberly J; Waggoner, Alan S; Armitage, Bruce A

2015-03-28

Dye-protein fluoromodules consist of fluorogenic dyes and single chain antibody fragments that form brightly fluorescent noncovalent complexes. This report describes two new bichromophoric dyes that extend the range of wavelengths of excitation or emission of existing fluoromodules. In one case, a fluorogenic thiazole orange (TO) was attached to an energy acceptor dye, Cy5. Upon binding to a protein that recognizes TO, red emission due to efficient energy transfer from TO to Cy5 replaces the green emission observed for monochromophoric TO bound to the same protein. Separately, TO was attached to a coumarin that serves as an energy donor. The same green emission is observed for coumarin-TO and TO bound to a protein, but efficient energy transfer allows violet excitation of coumarin-TO, versus longer wavelength, blue excitation of monochromophoric TO. Both bichromophores exhibit low nanomolar KD values for their respective proteins, >95% energy transfer efficiency and high fluorescence quantum yields.

Bichromophoric Dyes for Wavelength Shifting of Dye-Protein Fluoromodules

PubMed Central

Pham, Ha H.; Szent-Gyorgyi, Christopher; Brotherton, Wendy L.; Schmidt, Brigitte F.; Zanotti, Kimberly J.; Waggoner, Alan S.

2015-01-01

Dye-protein fluoromodules consist of fluorogenic dyes and single chain antibody fragments that form brightly fluorescent noncovalent complexes. This report describes two new bichromophoric dyes that extend the range of wavelengths of excitation or emission of existing fluoromodules. In one case, a fluorogenic thiazole orange (TO) was attached to an energy acceptor dye, Cy5. Upon binding to a protein that recognizes TO, red emission due to efficient energy transfer from TO to Cy5 replaces the green emission observed for monochromophoric TO bound to the same protein. Separately, TO was attached to a coumarin that serves as an energy donor. The same green emission is observed for coumarin-TO and TO bound to a protein, but efficient energy transfer allows violet excitation of coumarin-TO, versus longer wavelength, blue excitation of monochromophoric TO. Both bichromophores exhibit low nanomolar KD values for their respective proteins, >95% energy transfer efficiency and high fluorescence quantum yields. PMID:25679477

Interaction and energy transfer studies between bovine serum albumin and CdTe quantum dots conjugates: CdTe QDs as energy acceptor probes.

PubMed

Kotresh, M G; Inamdar, L S; Shivkumar, M A; Adarsh, K S; Jagatap, B N; Mulimani, B G; Advirao, G M; Inamdar, S R

2017-06-01

In this paper, a systematic investigation of the interaction of bovine serum albumin (BSA) with water-soluble CdTe quantum dots (QDs) of two different sizes capped with carboxylic thiols is presented based on steady-state and time-resolved fluorescence measurements. Efficient Förster resonance energy transfer (FRET) was observed to occur from BSA donor to CdTe acceptor as noted from reduction in the fluorescence of BSA and enhanced fluorescence from CdTe QDs. FRET parameters such as Förster distance, spectral overlap integral, FRET rate constant and efficiency were determined. The quenching of BSA fluorescence in aqueous solution observed in the presence of CdTe QDs infers that fluorescence resonance energy transfer is primarily responsible for the quenching phenomenon. Bimolecular quenching constant (k q ) determined at different temperatures and the time-resolved fluorescence data provide additional evidence for this. The binding stoichiometry and various thermodynamic parameters are evaluated by using the van 't Hoff equation. The analysis of the results suggests that the interaction between BSA and CdTe QDs is entropy driven and hydrophobic forces play a key role in the interaction. Binding of QDs significantly shortened the fluorescence lifetime of BSA which is one of the hallmarks of FRET. The effect of size of the QDs on the FRET parameters are discussed in the light of FRET parameters obtained. Copyright © 2016 John Wiley & Sons, Ltd.

Multi-state lasing in self-assembled ring-shaped green fluorescent protein microcavities

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

Dietrich, Christof P., E-mail: cpd3@st-andrews.ac.uk; Höfling, Sven; Gather, Malte C., E-mail: mcg6@st-andrews.ac.uk

2014-12-08

We demonstrate highly efficient lasing from multiple photonic states in microcavities filled with self-assembled rings of recombinant enhanced green fluorescent protein (eGFP) in its solid state form. The lasing regime is achieved at very low excitation energies of 13 nJ and occurs from cavity modes dispersed in both energy and momentum. We attribute the momentum distribution to very efficient scattering of incident light at the surface of the eGFP rings. The distribution of lasing states in energy is induced by the large spectral width of the gain spectrum of recombinant eGFP (FWHM ≅ 25 nm)

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, Alexander M.; Benson, Scott C.

1999-01-01

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, Alexander M.; Benson, Scott C.

1998-01-01

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, Alexander N.; Benson, Scott C.

1995-01-01

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, Alexander N.; Benson, Scott C.

1997-01-01

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated.

Blinking fluorescence of single donor-acceptor pairs: important role of "dark'' states in resonance energy transfer via singlet levels.

PubMed

Osad'ko, I S; Shchukina, A L

2012-06-01

The influence of triplet levels on Förster resonance energy transfer via singlet levels in donor-acceptor (D-A) pairs is studied. Four types of D-A pair are considered: (i) two-level donor and two-level acceptor, (ii) three-level donor and two-level acceptor, (iii) two-level donor and three-level acceptor, and (iv) three-level donor and three-level acceptor. If singlet-triplet transitions in a three-level acceptor molecule are ineffective, the energy transfer efficiency E=I_{A}/(I_{A}+I_{D}), where I_{D} and I_{A} are the average intensities of donor and acceptor fluorescence, can be described by the simple theoretical equation E(F)=FT_{D}/(1+FT_{D}). Here F is the rate of energy transfer, and T_{D} is the donor fluorescence lifetime. In accordance with the last equation, 100% of the donor electronic energy can be transferred to an acceptor molecule at FT_{D}≫1. However, if singlet-triplet transitions in a three-level acceptor molecule are effective, the energy transfer efficiency is described by another theoretical equation, E(F)=F[over ¯](F)T_{D}/[1+F[over ¯](F)T_{D}]. Here F[over ¯](F) is a function of F depending on singlet-triplet transitions in both donor and acceptor molecules. Expressions for the functions F[over ¯](F) are derived. In this case the energy transfer efficiency will be far from 100% even at FT_{D}≫1. The character of the intensity fluctuations of donor and acceptor fluorescence indicates which of the two equations for E(F) should be used to find the value of the rate F. Therefore, random time instants of photon emission in both donor and acceptor fluorescence are calculated by the Monte Carlo method for all four types of D-A pair. Theoretical expressions for start-stop correlators (waiting time distributions) in donor and acceptor fluorescence are derived. The probabilities w_{N}^{D}(t) and w_{N}^{A}(t) of finding N photons of donor and acceptor fluorescence in the time interval t are calculated for various values of the energy transfer rate F and for all four types of D-A pair. Comparison of the calculated D and A fluorescence trajectories with those measured by Weiss and co-workers proves the important role of triplet levels in energy transfer via singlet levels.

Fluorescent material concentration dependency: Förster resonance energy transfer in quasi-solid state DSSCs

NASA Astrophysics Data System (ADS)

Kim, Dong Woo; Jo, Hyun-Jun; Thogiti, Suresh; Yang, Weon Ki; Cheruku, Rajesh; Kim, Jae Hong

2017-05-01

Förster resonance energy transfer (FRET) is critical for wide spectral absorption, an increased dye loading, and photocurrent generation of dye-sensitized solar cells (DSSCs). This process consists of organic fluorescent materials (as an energy donor), and an organic dye (as an energy acceptor on TiO2 surfaces) with quasi-solid electrolyte. The judicious choice of the energy donor and acceptor facilitates a strong spectral overlap between the emission and absorption regions of the fluorescent materials and dye. This FRET process enhances the light-harvesting characteristics of quasi-solid state DSSCs. In this study, DSSCs containing different concentrations (0, 1, and 1.5 wt%) of a fluorescent material (FM) as the energy donor are investigated using FRET. The power conversion efficiency of DSSCs containing FMs in a quasi-solid electrolyte increased by 33% over a pristine cell. The optimized cell fabricated with the quasi-solid state DSSC containing 1.0 wt% FM shows a maximum efficiency of 3.38%, with a short-circuit current density ( J SC ) of 4.32 mA/cm-2, and an open-circuit voltage ( V OC ) of 0.68 V under illumination of simulated solar light (AM 1.5G, 100 mW/cm-2). [Figure not available: see fulltext.

Highly efficient red OLEDs using DCJTB as the dopant and delayed fluorescent exciplex as the host.

PubMed

Zhao, Bo; Zhang, Tianyou; Chu, Bei; Li, Wenlian; Su, Zisheng; Wu, Hairuo; Yan, Xingwu; Jin, Fangming; Gao, Yuan; Liu, Chengyuan

2015-05-29

In this manuscript, we demonstrated a highly efficient DCJTB emission with delayed fluorescent exciplex TCTA:3P-T2T as the host. For the 1.0% DCJTB doped concentration, a maximum luminance, current efficiency, power efficiency and EQE of 22,767 cd m(-2), 22.7 cd A(-1), 21.5 lm W(-1) and 10.15% were achieved, respectively. The device performance is the best compared to either red OLEDs with traditional fluorescent emitter or traditional red phosphor of Ir(piq)3 doped into CBP host. The extraction of so high efficiency can be explained as the efficient triplet excitons up-conversion of TCTA:3P-T2T and the energy transfer from exciplex host singlet state to DCJTB singlet state.

Classic Maximum Entropy Recovery of the Average Joint Distribution of Apparent FRET Efficiency and Fluorescence Photons for Single-molecule Burst Measurements

PubMed Central

DeVore, Matthew S.; Gull, Stephen F.; Johnson, Carey K.

2012-01-01

We describe a method for analysis of single-molecule Förster resonance energy transfer (FRET) burst measurements using classic maximum entropy. Classic maximum entropy determines the Bayesian inference for the joint probability describing the total fluorescence photons and the apparent FRET efficiency. The method was tested with simulated data and then with DNA labeled with fluorescent dyes. The most probable joint distribution can be marginalized to obtain both the overall distribution of fluorescence photons and the apparent FRET efficiency distribution. This method proves to be ideal for determining the distance distribution of FRET-labeled biomolecules, and it successfully predicts the shape of the recovered distributions. PMID:22338694

Highly efficient deep-blue organic light emitting diode with a carbazole based fluorescent emitter

NASA Astrophysics Data System (ADS)

Sahoo, Snehasis; Dubey, Deepak Kumar; Singh, Meenu; Joseph, Vellaichamy; Thomas, K. R. Justin; Jou, Jwo-Huei

2018-04-01

High efficiency deep-blue emission is essential to realize energy-saving, high-quality display and lighting applications. We demonstrate here a deep-blue organic light emitting diode using a novel carbazole based fluorescent emitter 7-[4-(diphenylamino)phenyl]-9-(2-ethylhexyl)-9H-carbazole-2-carbonitrile (JV234). The solution processed resultant device shows a maximum luminance above 1,750 cd m-2 and CIE coordinates (0.15,0.06) with a 1.3 lm W-1 power efficiency, 2.0 cd A-1 current efficiency, and 4.1% external quantum efficiency at 100 cd m-2. The resulting deep-blue emission enables a greater than 100% color saturation. The high efficiency may be attributed to the effective host-to-guest energy transfer, suitable device architecture facilitating balanced carrier injection and low doping concentration preventing efficiency roll-off caused by concentration quenching.

Highly fluorescent carbon dots for visible sensing of doxorubicin release based on efficient nanosurface energy transfer.

PubMed

Wang, Beibei; Wang, Shujun; Wang, Yanfang; Lv, Yan; Wu, Hao; Ma, Xiaojun; Tan, Mingqian

2016-01-01

To prepare fluorescent carbon dots for loading cationic anticancer drug through donor-quenched nanosurface energy transfer in visible sensing of drug release. Highly fluorescent carbon dots (CDs) were prepared by a facile hydrothermal approach from citric acid and o-phenylenediamine. The obtained CDs showed a high quantum yield of 46 % and exhibited good cytocompatibility even at 1 mg/ml. The cationic anticancer drug doxorubicin (DOX) can be loaded onto the negatively charged CDs through electrostatic interactions. Additionally, the fluorescent CDs feature reversible donor-quenched mode nanosurface energy transfer. When loading the energy receptor DOX, the donor CDs' fluorescence was switched "off", while it turned "on" again after DOX release from the surface through endocytic uptake. Most DOX molecules were released from the CDs after 6 h incubation and entered cell nuclear region after 8 h, suggesting the drug delivery system may have potential for visible sensing in drug release.

A comparative study of fluorescent and LED lighting in industrial facilities

NASA Astrophysics Data System (ADS)

Perdahci PhD, C.; Akin BSc, H. C.; Cekic Msc, O.

2018-05-01

Industrial facilities have always been in search for reducing outgoings and minimizing energy consumption. Rapid developments in lighting technology require more energy efficient solutions not only for industries but also for many sectors and for households. Addition of solid-state technology has brought LED lamps into play and with LED lamp usage, efficacy level has reached its current values. Lighting systems which uses fluorescent and LED lamps have become the prior choice for many industrial facilities. This paper presents a comparative study about fluorescent and LED based indoor lighting systems for a warehouse building in an industrial facility in terms of lighting distribution values, colour rendering, power consumption, energy efficiency and visual comfort. Both scenarios have been modelled and simulated by using Relux and photometric data for the luminaires have been gathered by conducting tests and measurements in an accredited laboratory.

In vitro energy transfer in Renilla bioluminescence

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

Ward, W.W.; Cormier, M.J.

1976-09-23

A quantitative study of in vitro energy transfer in a natural biological system is reported. The in vitro bioluminescent oxidation of Renilla (sea pansy) luciferin by luciferase produces a broad, structureless emission, peaking in the blue at 490 nm. In contrast, the live animal produces a structured emission peaking in the green at 509 nm. This difference in emission characteristics is due to the presence, in Renilla, of a green fluorescent protein (GFP). Addition of GFP in vitro sensitizes the oxyluciferin product excited state, resulting in the narrow, structured green emission characteristic of GFP fluorescence (lambda/sub max/ 509 nm). Undermore » conditions of efficient in vitro energy transfer (2.7 x 10/sup -6/ M GFP) the radiative quantum yield (with respect to luciferin) increases 5.7-fold from 5.3% (blue pathway) to 30% (green pathway). The fluorescence quantum yield of the Renilla GFP has been measured as 30%; thus, within the precision of our measurements (15% coefficient of variation) the in vitro energy transfer efficiency is a surprising 100%.« less

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, A.N.; Benson, S.C.

1997-07-08

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated. 4 figs.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, A.M.; Benson, S.C.

1998-06-16

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated. 4 figs.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, A.N.; Benson, S.C.

1995-03-28

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated. 4 figures.

Spatial exciton allocation strategy with reduced energy loss for high-efficiency fluorescent/phosphorescent hybrid white organic light-emitting diodes

DOE PAGES

Zhao, Fangchao; Wei, Ying; Xu, Hui; ...

2017-05-17

Due to the poor operational lifetime of blue phosphorescent dopants and blue thermally activated delayed fluorescent (TADF) materials, hybrid white organic light-emitting diodes (WOLEDs) with conventional blue fluorescent emitters are still preferred for commercial applications in general lighting. However, the improvement in the overall efficiency of hybrid WOLEDs has been limited due to energy losses during the energy transfer process and exciton quenching after the spatial separation of the singlet and triplet excitons. Here we demonstrate the development of a Spatial Exciton Allocation Strategy (SEAS) to achieve close to 100% internal quantum efficiency (IQE) in blue-yellow complementary color hybrid WOLEDs.more » The employed blue fluorophore not only has a resonant triplet level with the yellow phosphor to reduce energy loss during energy transfer processes and triplet–triplet annihilation (TTA), but also has a resonant singlet level with the electron transport layer to extend singlet exciton distribution and enhance both singlet and triplet exciton utilization. Thus, the resulting hybrid WOLEDs exhibited 104 lm W -1 efficacy at 100 cd m -2 and 74 lm W -1 at 1000 cd m -2 with CIE coordinates of (0.42, 0.44) which is warm white and suitable for indoor lighting.« less

Spatial exciton allocation strategy with reduced energy loss for high-efficiency fluorescent/phosphorescent hybrid white organic light-emitting diodes

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

Zhao, Fangchao; Wei, Ying; Xu, Hui

Due to the poor operational lifetime of blue phosphorescent dopants and blue thermally activated delayed fluorescent (TADF) materials, hybrid white organic light-emitting diodes (WOLEDs) with conventional blue fluorescent emitters are still preferred for commercial applications in general lighting. However, the improvement in the overall efficiency of hybrid WOLEDs has been limited due to energy losses during the energy transfer process and exciton quenching after the spatial separation of the singlet and triplet excitons. Here we demonstrate the development of a Spatial Exciton Allocation Strategy (SEAS) to achieve close to 100% internal quantum efficiency (IQE) in blue-yellow complementary color hybrid WOLEDs.more » The employed blue fluorophore not only has a resonant triplet level with the yellow phosphor to reduce energy loss during energy transfer processes and triplet–triplet annihilation (TTA), but also has a resonant singlet level with the electron transport layer to extend singlet exciton distribution and enhance both singlet and triplet exciton utilization. Thus, the resulting hybrid WOLEDs exhibited 104 lm W -1 efficacy at 100 cd m -2 and 74 lm W -1 at 1000 cd m -2 with CIE coordinates of (0.42, 0.44) which is warm white and suitable for indoor lighting.« less

Highly efficient red OLEDs using DCJTB as the dopant and delayed fluorescent exciplex as the host

PubMed Central

Zhao, Bo; Zhang, Tianyou; Chu, Bei; Li, Wenlian; Su, Zisheng; Wu, Hairuo; Yan, Xingwu; Jin, Fangming; Gao, Yuan; Liu, Chengyuan

2015-01-01

In this manuscript, we demonstrated a highly efficient DCJTB emission with delayed fluorescent exciplex TCTA:3P-T2T as the host. For the 1.0% DCJTB doped concentration, a maximum luminance, current efficiency, power efficiency and EQE of 22,767 cd m−2, 22.7 cd A−1, 21.5 lm W−1 and 10.15% were achieved, respectively. The device performance is the best compared to either red OLEDs with traditional fluorescent emitter or traditional red phosphor of Ir(piq)3 doped into CBP host. The extraction of so high efficiency can be explained as the efficient triplet excitons up-conversion of TCTA:3P-T2T and the energy transfer from exciplex host singlet state to DCJTB singlet state. PMID:26023882

Adaptation of light-harvesting functions of unicellular green algae to different light qualities.

PubMed

Ueno, Yoshifumi; Aikawa, Shimpei; Kondo, Akihiko; Akimoto, Seiji

2018-05-28

Oxygenic photosynthetic organisms perform photosynthesis efficiently by distributing captured light energy to photosystems (PSs) at an appropriate balance. Maintaining photosynthetic efficiency under changing light conditions requires modification of light-harvesting and energy-transfer processes. In the current study, we examined how green algae regulate their light-harvesting functions in response to different light qualities. We measured low-temperature time-resolved fluorescence spectra of unicellular green algae Chlamydomonas reinhardtii and Chlorella variabilis cells grown under different light qualities. By observing the delayed fluorescence spectra, we demonstrated that both types of green algae primarily modified the associations between light-harvesting chlorophyll protein complexes (LHCs) and PSs (PSII and PSI). Under blue light, Chlamydomonas transferred more energy from LHC to chlorophyll (Chl) located far from the PSII reaction center, while energy was transferred from LHC to PSI via different energy-transfer pathways in Chlorella. Under green light, both green algae exhibited enhanced energy transfer from LHCs to both PSs. Red light induced fluorescence quenching within PSs in Chlamydomonas and LHCs in Chlorella. In Chlorella, energy transfer from PSII to PSI appears to play an important role in balancing excitation between PSII and PSI.

Kinetics model for the wavelength-dependence of excited-state dynamics of hetero-FRET sensors

NASA Astrophysics Data System (ADS)

Schwarz, Jacob; Leighton, Ryan; Leopold, Hannah J.; Currie, Megan; Boersma, Arnold J.; Sheets, Erin D.; Heikal, Ahmed A.

2017-08-01

Foerster (or fluorescence) resonance energy transfer (FRET) is a powerful tool for investigating protein-protein interactions, in both living cells and in controlled environments. A typical hetero-FRET pair consists of a donor and acceptor tethered together with a linker. The corresponding energy transfer efficiency of a hetero-FRET pair probe depends upon the donor-acceptor distance, relative dipole orientation, and spectral overlap. Because of the sensitivity of the energy transfer efficiency on the donor-acceptor distance, FRET is often referred to as a "molecular ruler". Time-resolved fluorescence approach for measuring the excited-state lifetime of the donor and acceptor emissions is one of the most reliable approaches for quantitative assessment of the energy transfer efficiency in hetero-FRET pairs. In this contribution, we provide an analytical kinetics model that describes the excited-state depopulation of a FRET probe as a means to predicts the time-resolved fluorescence profile as a function of excitation and detection wavelengths. In addition, we used this developed kinetics model to simulate the time-dependence of the excited-state population of both the donor and acceptor. These results should serve as a guide for our ongoing studies of newly developed hetero-FRET sensors (mCerulean3-linker-mCitrine) that are designed specifically for in vivo studies of macromolecular crowding. The same model is applicable to other FRET pairs with the careful consideration of their steady-state spectroscopy and the experimental design for wavelength- dependence of the fluorescence lifetime measurements.

Efficient modulation of optical and electrical properties of X-shaped thermally activated delayed fluorescence emitters by substitution.

PubMed

Fan, Jianzhong; Wang, Xin; Lin, Lili; Wang, Chuankui

2016-08-01

A series of X-shaped thermally activated delayed fluorescence (TADF) emitters are systematically studied by first-principles calculations. Effects of the cyano group adding to the acceptor unit and the hydroxyl group adding to the donor part on the optical and electrical properties are analyzed. It is found that both kinds of groups can efficiently increase the emission wavelength to realize full-color emission. Although they play different roles in modulating the energy level of frontier orbitals, the S-T energy gap, the reorganization energy and transfer integral for different molecules, they can efficiently increase the charge transfer rate and reduce the difference of electron transfer rate and hole transfer rate. These results indicate that these designed strategies are efficient to achieve balanced charge transfer rates and modulate emission colors. By analyzing the energy matching between the TADF emitters and three kinds of hosts, the emission spectra of the 3,5-bis(N-carbazolyl)benzene (mcp) and the absorption spectra of most TADF emitters have a large overlap, which provides helpful information in application of these TADF molecules.

Orientation dependence in fluorescent energy transfer between Cy3 and Cy5 terminally attached to double-stranded nucleic acids

PubMed Central

Iqbal, Asif; Arslan, Sinan; Okumus, Burak; Wilson, Timothy J.; Giraud, Gerard; Norman, David G.; Ha, Taekjip; Lilley, David M. J.

2008-01-01

We have found that the efficiency of fluorescence resonance energy transfer between Cy3 and Cy5 terminally attached to the 5′ ends of a DNA duplex is significantly affected by the relative orientation of the two fluorophores. The cyanine fluorophores are predominantly stacked on the ends of the helix in the manner of an additional base pair, and thus their relative orientation depends on the length of the helix. Observed fluorescence resonance energy transfer (FRET) efficiency depends on the length of the helix, as well as its helical periodicity. By changing the helical geometry from B form double-stranded DNA to A form hybrid RNA/DNA, a marked phase shift occurs in the modulation of FRET efficiency with helix length. Both curves are well explained by the standard geometry of B and A form helices. The observed modulation for both polymers is less than that calculated for a fully rigid attachment of the fluorophores. However, a model involving lateral mobility of the fluorophores on the ends of the helix explains the observed experimental data. This has been further modified to take account of a minor fraction of unstacked fluorophore observed by fluorescent lifetime measurements. Our data unequivocally establish that Förster transfer obeys the orientation dependence as expected for a dipole–dipole interaction. PMID:18676615

Disposal of Energy by UV-B Sunscreens

NASA Astrophysics Data System (ADS)

Nordlund, Thomas; Krishnan, Rajagopal

2008-03-01

Ideal sunscreens absorb dangerous UV light and dispose of the energy safely. ``Safe disposal'' usually means conversion to heat. However, efficient absorption entails a high radiative rate, which implies high energy-transfer and other rates, unless some process intervenes to ``defuse'' the excited state. We studied the excited-state kinetics of three UV-B (290-320 nm) sunscreens by absorption, steady-state and time-resolved fluorescence. Excited-state rate analysis suggests that some sunscreens have low radiative-rate ``dark'' states, in addition to normal excited states.* We deduce dark states when sunscreens of high extinction coefficient do not show lifetimes and total emission consistent with such high radiative rates. A high radiative rate, accompanied by efficient fluorescence emission and/or transfer, may be unfavorable for a sunscreen. In spite of its dark excited state, padimate O shows significant re-emission of light in the UV-A (320-400 nm) and energy transfer to a natural component of excised skin, probably collagen. * Krishnan, R. and T.M. Nordlund (2007) J. Fluoresc. DOI 10.1007/s10895-007-0264-3.

Effect of Clouds on Apertures of Space-based Air Fluorescence Detectors

NASA Technical Reports Server (NTRS)

Sokolsky, P.; Krizmanic, J.

2003-01-01

Space-based ultra-high-energy cosmic ray detectors observe fluorescence light from extensive air showers produced by these particles in the troposphere. Clouds can scatter and absorb this light and produce systematic errors in energy determination and spectrum normalization. We study the possibility of using IR remote sensing data from MODIS and GOES satellites to delimit clear areas of the atmosphere. The efficiency for detecting ultra-high-energy cosmic rays whose showers do not intersect clouds is determined for real, night-time cloud scenes. We use the MODIS SST cloud mask product to define clear pixels for cloud scenes along the equator and use the OWL Monte Carlo to generate showers in the cloud scenes. We find the efficiency for cloud-free showers with closest approach of three pixels to a cloudy pixel is 6.5% exclusive of other factors. We conclude that defining a totally cloud-free aperture reduces the sensitivity of space-based fluorescence detectors to unacceptably small levels.

Excitation energy transfer in europium chelate with doxycycline in the presence of a second ligand in micellar solutions of nonionic surfactants

NASA Astrophysics Data System (ADS)

Smirnova, T. D.; Shtykov, S. N.; Kochubei, V. I.; Khryachkova, E. S.

2011-01-01

The complexation of Eu3+ with doxycycline (DC) antibiotic in the presence of several second ligands and surfactant micelles of different types is studied by the spectrophotometric and luminescence methods. It is found that the efficiency of excitation energy transfer in Eu3+-DC chelate depends on the nature of the second ligand and surfactant micelles. Using thenoyltrifluoroacetone (TTA) as an example, it is shown that the second ligand additionally sensitizes the europium fluorescence, and the possibility of intermediate sensitization of DC and then of europium is shown by the example of 1,10-phenanthroline. In all cases, the excitation energy transfer efficiency was increased due to the so-called antenna effect. The decay kinetics of the sensitized fluorescence of the binary and mixed-ligand chelates in aqueous and micellar solutions of nonionic surfactants is studied and the relative quantum yields and lifetimes of fluorescence are determined.

Excitation-Energy Transfer Paths from Tryptophans to Coordinated Copper Ions in Engineered Azurins: a Source of Observables for Monitoring Protein Structural Changes

NASA Astrophysics Data System (ADS)

Di Rocco, Giulia; Bernini, Fabrizio; Borsari, Marco; Martinelli, Ilaria; Bortolotti, Carlo Augusto; Battistuzzi, Gianantonio; Ranieri, Antonio; Caselli, Monica; Sola, Marco; Ponterini, Glauco

2016-09-01

The intrinsic fluorescence of recombinant proteins offers a powerful tool to detect and characterize structural changes induced by chemical or biological stimuli. We show that metal-ion binding to a hexahistidine tail can significantly broaden the range of such structurally sensitive fluorescence observables. Bipositive metal-ions as Cu2+, Ni2+ and Zn2+ bind 6xHis-tag azurin and its 6xHis-tagged R129W and W48A-R129W mutants with good efficiency and, thereby, quench their intrinsic fluorescence. Due to a much more favourable spectral overlap, the 6xHis-tag/Cu2+ complex(es) are the most efficient quenchers of both W48 and W129 emissions. Based on simple Förster-type dependence of energy-transfer efficiency on donor/acceptor distance, we can trace several excitation-energy transfer paths across the protein structure. Unexpected lifetime components in the azurin 6xHis-tag/Cu2+ complex emission decays reveal underneath complexity in the conformational landscape of these systems. The new tryptophan emission quenching paths provide additional signals for detecting and identifying protein structural changes.

Research on the ultrafast fluorescence property of thylakoid membranes of the wild-type and mutant rice

NASA Astrophysics Data System (ADS)

Ren, Zhao-Yu; Xu, Xiao-Ming; Wang, Shui-Cai; Xin, Yue-Yong; He, Jun-Fang; Hou, Xun

2003-10-01

A high yielding rice variety mutant (Oryza sativa L., Zhenhui 249) with low chlorophyll b (Chl b) has been discovered in natural fields. It has a quality character controlled by a pair of recessive genes (nuclear gene). The partial loss of Chl b in content affects the efficiency of light harvest in a light harvest complex (LHC), thus producing the difference of the exciting energy transfer and the efficiency of photochemistry conversion between the mutant and wild-type rice in photosynthetic unit. The efficiency of utilizing light energy is higher in the mutant than that in the wild-type rice relatively. For further discussion of the above-mentioned difference and learning about the mechanism of the increase in the photochemical efficiency of the mutant, the pico-second resolution fluorescence spectrum measurement with delay-frame-scanning single photon counting technique is adopted. Thylakoid membranes of the mutant and the wild-type rice are excited by an Ar+ laser with a pulse width of 120 ps, repetition rate of 4 MHz and wavelength of 514 nm. Compared with the time and spectrum property of exciting fluorescence, conclusions of those ultrafast dynamic experiments are: 1) The speeds of the exciting energy transferred in photo-system I are faster than that in photo-system II in both samples. 2) The speeds of the exciting energy transfer of mutant sample are faster than those of the wild-type. This might be one of the major reasons why the efficiency of photosynthesis is higher in mutant than that in the wild-type rice.

Comparitive study of fluorescence lifetime quenching of rhodamine 6G by MoS2 and Au-MoS2

NASA Astrophysics Data System (ADS)

Shakya, Jyoti; Kasana, Parath; Mohanty, T.

2018-04-01

Time resolved fluorescence study of Rhodamine 6G (R6G) in the presence of Molybdenum disulfide (MoS2) nanosheets and gold doped MoS2 (Au-MoS2) have been carried out and discussed. We have analyzed the fluorescence decay curves of R6G and it is observed that Au-MoS2 is a better fluorescence lifetime quencher as compare to MoS2 nanosheets. Also, the energy transfer efficiency and energy transfer rate from R6G to MoS2 and Au-MoS2 has been calculated and found higher for Au-MoS2.

Titanium Dioxide/Upconversion Nanoparticles/Cadmium Sulfide Nanofibers Enable Enhanced Full-Spectrum Absorption for Superior Solar Light Driven Photocatalysis.

PubMed

Zhang, Fu; Zhang, Chuan-Ling; Wang, Wan-Ni; Cong, Huai-Ping; Qian, Hai-Sheng

2016-06-22

In this work, we demonstrate an electrospinning technique to fabricate TiO2 /upconversion nanoparticles (UCNPs)/CdS nanofibers on large scale. In addition, the as-prepared TiO2 nanofibers are incorporated with a high population of UCNPs and CdS nanospheres; this results in Förster resonance energy-transfer configurations of the UCNPs, TiO2 , and CdS nanospheres that are in close proximity. Hence, strong fluorescent emissions for the Tm(3+) ions including the (1) G4 →(3) H6 transition are efficiently transferred to TiO2 and the CdS nanoparticles through an energy-transfer process. The as-prepared TiO2 /UCNPs/CdS nanofibers exhibit full-spectrum solar-energy absorption and enable the efficient degradation of organic dyes by fluorescence resonance energy transfer between the UCNPs and TiO2 (or CdS). The UCNPs/TiO2 /CdS nanofibers may also have enhanced energy-transfer efficiency for wide applications in solar cells, bioimaging, photodynamics, and chemotherapy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Triplet exciton confinement for enhanced fluorescent organic light-emitting diodes using a co-host system

NASA Astrophysics Data System (ADS)

Yoo, Han Kyu; Lee, Ho Won; Lee, Song Eun; Kim, Young Kwan; Kim, Se Hyun; Yoon, Seung Soo; Park, Jaehoon

2016-05-01

In this work, the co-host system within an emitting layer (EML) consists of the host and triplet managing (TM) host materials. A set of EML structures was fabricated with various concentrations of the TM host (0, 10, 30, 50, and 70%). The TM host triplet energy level is lower than the energy levels of the host and the guest, which leads to a reduction in the triplet exciton density and the singlet-triplet annihilation of the guest. Blue fluorescent organic light-emitting diodes exhibit a maximum luminous efficiency (LE) and an external quantum efficiency (EQE) of 9.74 cd/A and 4.92%, respectively. In addition, the efficiency roll-off ratios of the LE and the EQE are 14.25 and 13.16%, respectively.

75 FR 14319 - Energy Conservation Standards for Fluorescent Lamp Ballasts: Public Meeting and Availability of...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-24

... Technical Support Document AGENCY: Office of Energy Efficiency and Renewable Energy, Department of Energy. ACTION: Notice of public meeting and availability of preliminary technical support document. SUMMARY: The... products. DOE encourages written comments on these subjects. To inform interested parties and facilitate...

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

Ding, Huanjun; Cho, Hyo-Min; Molloi, Sabee, E-mail: symolloi@uci.edu

Purpose: To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diametermore » of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and −66.33 mV, respectively. The detector’s energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20–45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. Conclusions: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the detector. The proposed x-ray fluorescence technique offers an accurate and efficient way to calibrate the energy response of a photon-counting detector.« less

Optical radiation emissions from compact fluorescent lamps.

PubMed

Khazova, M; O'Hagan, J B

2008-01-01

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

Superior optical nonlinearity of an exceptional fluorescent stilbene dye

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

He, Tingchao; Division of Physics and Applied Physics, Centre for Disruptive Photonic Technologies; Sreejith, Sivaramapanicker

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-harmonicmore » 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.« less

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

Ding, H; Cho, H; Molloi, S

Purpose: To investigate the feasibility of energy response calibration of a Si strip photon-counting detector by using the x-ray fluorescence technique. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on Si strips. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing Ag, I, Ba, and Gd, were placed in small plastic aliquots with a diameter of approximatelymore » 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known energies for materials. The energy resolution was derived from the full width at half maximum (FWHM) of the fluorescence peaks. In addition, the angular dependence of the recorded fluorescence spectra was studied at 30°, 60°, and 120°. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The recorded pulse height was calibrated with respect to photon energy and the gain and offset values were calculated to be 7.0 mV/keV and −69.3 mV, respectively. Negligible variation in energy calibration was observed among the four energy thresholds. The variation among different pixels was estimated to be approximately 1 keV. The energy resolution of the detector was estimated to be 7.9% within the investigated energy range. Conclusion: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the detector. The proposed x-ray fluorescence technique provides an accurate and efficient way to calibrate the energy response of a photon-counting detector.« less

Materials That Enhance Efficiency and Radiation Resistance of Solar Cells

NASA Technical Reports Server (NTRS)

Sun, Xiadong; Wang, Haorong

2012-01-01

A thin layer (approximately 10 microns) of a novel "transparent" fluorescent material is applied to existing solar cells or modules to effectively block and convert UV light, or other lower solar response waveband of solar radiation, to visible or IR light that can be more efficiently used by solar cells for additional photocurrent. Meanwhile, the layer of fluorescent coating material remains fully "transparent" to the visible and IR waveband of solar radiation, resulting in a net gain of solar cell efficiency. This innovation alters the effective solar spectral power distribution to which an existing cell gets exposed, and matches the maximum photovoltaic (PV) response of existing cells. By shifting a low PV response waveband (e.g., UV) of solar radiation to a high PV response waveband (e.g. Vis-Near IR) with novel fluorescent materials that are transparent to other solar-cell sensitive wavebands, electrical output from solar cells will be enhanced. This approach enhances the efficiency of solar cells by converting UV and high-energy particles in space that would otherwise be wasted to visible/IR light. This innovation is a generic technique that can be readily implemented to significantly increase efficiencies of both space and terrestrial solar cells, without incurring much cost, thus bringing a broad base of economical, social, and environmental benefits. The key to this approach is that the "fluorescent" material must be very efficient, and cannot block or attenuate the "desirable" and unconverted" waveband of solar radiation (e.g. Vis-NIR) from reaching the cells. Some nano-phosphors and novel organometallic complex materials have been identified that enhance the energy efficiency on some state-of-the-art commercial silicon and thin-film-based solar cells by over 6%.

Bio-optimized energy transfer in densely packed fluorescent protein enables near-maximal luminescence and solid-state lasers.

PubMed

Gather, Malte C; Yun, Seok Hyun

2014-12-08

Bioluminescent organisms are likely to have an evolutionary drive towards high radiance. As such, bio-optimized materials derived from them hold great promise for photonic applications. Here, we show that biologically produced fluorescent proteins retain their high brightness even at the maximum density in solid state through a special molecular structure that provides optimal balance between high protein concentration and low resonance energy transfer self-quenching. Dried films of green fluorescent protein show low fluorescence quenching (-7 dB) and support strong optical amplification (gnet=22 cm(-1); 96 dB cm(-1)). Using these properties, we demonstrate vertical cavity surface emitting micro-lasers with low threshold (<100 pJ, outperforming organic semiconductor lasers) and self-assembled all-protein ring lasers. Moreover, solid-state blends of different proteins support efficient Förster resonance energy transfer, with sensitivity to intermolecular distance thus allowing all-optical sensing. The design of fluorescent proteins may be exploited for bio-inspired solid-state luminescent molecules or nanoparticles.

Bio-optimized energy transfer in densely packed fluorescent protein enables near-maximal luminescence and solid-state lasers

PubMed Central

Gather, Malte C.; Yun, Seok Hyun

2015-01-01

Bioluminescent organisms are likely to have an evolutionary drive towards high radiance. As such, bio-optimized materials derived from them hold great promise for photonic applications. Here we show that biologically produced fluorescent proteins retain their high brightness even at the maximum density in solid state through a special molecular structure that provides optimal balance between high protein concentration and low resonance energy transfer self-quenching. Dried films of green fluorescent protein show low fluorescence quenching (−7 dB) and support strong optical amplification (gnet = 22 cm−1; 96 dB cm−1). Using these properties, we demonstrate vertical cavity surface emitting micro-lasers with low threshold (<100 pJ, outperforming organic semiconductor lasers) and self-assembled all-protein ring lasers. Moreover, solid-state blends of different proteins support efficient Förster resonance energy transfer, with sensitivity to intermolecular distance thus allowing all-optical sensing. The design of fluorescent proteins may be exploited for bio-inspired solid-state luminescent molecules or nanoparticles. PMID:25483850

Aerosol Generation by Modern Flush Toilets.

PubMed

Johnson, David; Lynch, Robert; Marshall, Charles; Mead, Kenneth; Hirst, Deborah

A microbe-contaminated toilet will produce bioaerosols when flushed. We assessed toilet plume aerosol from high efficiency (HET), pressure-assisted high efficiency (PAT), and flushometer (FOM) toilets with similar bowl water and flush volumes. Total and droplet nuclei "bioaerosols" were assessed. Monodisperse 0.25-1.9- μ m fluorescent microspheres served as microbe surrogates in separate trials in a mockup 5 m 3 water closet (WC). Bowl water seeding was approximately 10 12 particles/mL. Droplet nuclei were sampled onto 0.2- μ m pore size mixed cellulose ester filters beginning 15 min after the flush using open-face cassettes mounted on the WC walls. Pre- and postflush bowl water concentrations were measured. Filter particle counts were analyzed via fluorescent microscopy. Bowl headspace droplet count size distributions were bimodal and similar for all toilet types and flush conditions, with 95% of droplets < 2 μ m diameter and > 99% < 5 μ m. Up to 145,000 droplets were produced per flush, with the high-energy flushometer producing over three times as many as the lower energy PAT and over 12 times as many as the lowest energy HET despite similar flush volumes. The mean numbers of fluorescent droplet nuclei particles aerosolized and remaining airborne also increased with flush energy. Fluorescent droplet nuclei per flush decreased with increasing particle size. These findings suggest two concurrent aerosolization mechanisms-splashing for large droplets and bubble bursting for the fine droplets that form droplet nuclei.

Characterization of energy response for photon-counting detectors using x-ray fluorescence

PubMed Central

Ding, Huanjun; Cho, Hyo-Min; Barber, William C.; Iwanczyk, Jan S.; Molloi, Sabee

2014-01-01

Purpose: To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diameter of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and −66.33 mV, respectively. The detector’s energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20–45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. Conclusions: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the detector. The proposed x-ray fluorescence technique offers an accurate and efficient way to calibrate the energy response of a photon-counting detector. PMID:25471962

Orderly arranged fluorescence dyes as a highly efficient chemiluminescence resonance energy transfer probe for peroxynitrite.

PubMed

Wang, Zhihua; Teng, Xu; Lu, Chao

2015-03-17

Chemiluminescence (CL) probes for reactive oxygen species (ROS) are commonly based on a redox reaction between a CL reagent and ROS, leading to poor selectivity toward a specific ROS. The energy-matching rules in the chemiluminescence resonance energy transfer (CRET) process between a specific ROS donor and a suitable fluorescence dye acceptor is a promising method for the selective detection of ROS. Nevertheless, higher concentrations of fluorescence dyes can lead to the intractable aggregation-caused quenching effect, decreasing the CRET efficiency. In this report, we fabricated an orderly arranged structure of calcein-sodium dodecyl sulfate (SDS) molecules to improve the CRET efficiency between ONOOH* donor and calcein acceptor. Such orderly arranged calcein-SDS composites can distinguish peroxynitrite (ONOO(-)) from a variety of other ROS owing to the energy matching in the CRET process between ONOOH* donor and calcein acceptor. Under the optimal experimental conditions, ONOO(-) could be assayed in the range of 1.0-20.0 μM, and the detection limit for ONOO(-) [signal-to-noise ratio (S/N) = 3] was 0.3 μM. The proposed strategy has been successfully applied in both detecting ONOO(-) in cancer mouse plasma samples and monitoring the generation of ONOO(-) from 3-morpholinosydnonimine (SIN-1). Recoveries from cancer mouse plasma samples were in the range of 96-105%. The success of this work provides a unique opportunity to develop a CL tool to monitor ONOO(-) with high selectivity in a specific manner. Improvement of selectivity and sensitivity of CL probes holds great promise as a strategy for developing a wide range of probes for various ROS by tuning the types of fluorescence dyes.

Development of Functional Fluorescent Molecular Probes for the Detection of Biological Substances

PubMed Central

Suzuki, Yoshio; Yokoyama, Kenji

2015-01-01

This review is confined to sensors that use fluorescence to transmit biochemical information. Fluorescence is, by far, the most frequently exploited phenomenon for chemical sensors and biosensors. Parameters that define the application of such sensors include intensity, decay time, anisotropy, quenching efficiency, and luminescence energy transfer. To achieve selective (bio)molecular recognition based on these fluorescence phenomena, various fluorescent elements such as small organic molecules, enzymes, antibodies, and oligonucleotides have been designed and synthesized over the past decades. This review describes the immense variety of fluorescent probes that have been designed for the recognitions of ions, small and large molecules, and their biological applications in terms of intracellular fluorescent imaging techniques. PMID:26095660

10 CFR 430.3 - Materials incorporated by reference.

Code of Federal Regulations, 2010 CFR

2010-01-01

.... Department of Energy, Office of Energy Efficiency and Renewable Energy, Building Technologies Program, 6th... Standard for Fluorescent Lamps-Instant-start and Cold-Cathode Types-Dimensional and Electrical...-1995 (“ANSI C78.20”), American National Standard for electric lamps—A, G, PS, and Similar Shapes with...

Bright Ideas.

ERIC Educational Resources Information Center

Armstrong, Phil

1999-01-01

Discusses how to upgrade lighting technology in schools to reduce energy consumption and cut operating costs. Explores fixture efficiency using ballast and lamp upgrades and compact fluorescent lights. Other ideas include changing exit signs to ones that use less wattage, improving luminary efficiency through use of reflectors and shielding…

Reversible intermolecular energy transfer between saturated amines and benzene in non-polar solution

NASA Astrophysics Data System (ADS)

Halpern, Arthur M.; Wryzykowska, Krystyna

1981-01-01

Excitation of a mixture of dimethylethylamine (DEMA) and benzene in n-hexane at 222 nm primarily produces excited amine, while at 261 nm excited benzene predominantly results. The fluorescence spectra appreciably overlap. With 222 nm excitation, DEMA fluorescence is quenched by benzene at the diffusion-controlled rate; this quenching results with nearly unit efficiency in sensitized benzene fluorescence. With 261 nm excitation, some sensitized DEMA fluorescence is observed: the rate constant for tins process is ≈ 2.6 × 10 9 M -1 s -1.

Manipulating the Electronic Excited State Energies of Pyrimidine-Based Thermally Activated Delayed Fluorescence Emitters To Realize Efficient Deep-Blue Emission.

PubMed

Komatsu, Ryutaro; Ohsawa, Tatsuya; Sasabe, Hisahiro; Nakao, Kohei; Hayasaka, Yuya; Kido, Junji

2017-02-08

The development of efficient and robust deep-blue emitters is one of the key issues in organic light-emitting devices (OLEDs) for environmentally friendly, large-area displays or general lighting. As a promising technology that realizes 100% conversion from electrons to photons, thermally activated delayed fluorescence (TADF) emitters have attracted considerable attention. However, only a handful of examples of deep-blue TADF emitters have been reported to date, and the emitters generally show large efficiency roll-off at practical luminance over several hundreds to thousands of cd m -2 , most likely because of the long delayed fluorescent lifetime (τ d ). To overcome this problem, we molecularly manipulated the electronic excited state energies of pyrimidine-based TADF emitters to realize deep-blue emission and reduced τ d . We then systematically investigated the relationships among the chemical structure, properties, and device performances. The resultant novel pyrimidine emitters, called Ac-XMHPMs (X = 1, 2, and 3), contain different numbers of bulky methyl substituents at acceptor moieties, increasing the excited singlet (E S ) and triplet state (E T ) energies. Among them, Ac-3MHPM, with a high E T of 2.95 eV, exhibited a high external quantum efficiency (η ext,max ) of 18% and an η ext of 10% at 100 cd m -2 with Commission Internationale de l'Eclairage chromaticity coordinates of (0.16, 0.15). These efficiencies are among the highest values to date for deep-blue TADF OLEDs. Our molecular design strategy provides fundamental guidance to design novel deep-blue TADF emitters.

Fast globally optimal segmentation of cells in fluorescence microscopy images.

PubMed

Bergeest, Jan-Philip; Rohr, Karl

2011-01-01

Accurate and efficient segmentation of cells in fluorescence microscopy images is of central importance for the quantification of protein expression in high-throughput screening applications. We propose a new approach for segmenting cell nuclei which is based on active contours and convex energy functionals. Compared to previous work, our approach determines the global solution. Thus, the approach does not suffer from local minima and the segmentation result does not depend on the initialization. We also suggest a numeric approach for efficiently computing the solution. The performance of our approach has been evaluated using fluorescence microscopy images of different cell types. We have also performed a quantitative comparison with previous segmentation approaches.

Design of ortho-Substituted Donor-Acceptor Molecules as Highly Efficient Green Thermally Activated Delayed Fluorescent Emitters

NASA Astrophysics Data System (ADS)

Cha, Jae-Ryung; Gong, Myoung-Seon; Lee, Tak Jae; Ha, Tae Hoon; Lee, Chil Won

2018-04-01

The ortho-substituted donor-acceptor molecules 2-(4,6-diphenyl-1, 3, 5-triazin-2-yl)- N,Ndiphenylaniline (DPA- o-Trz) and 2-(4,6-diphenyl-1, 3, 5-triazine-2-yl)- N,N-di- p-tolylaniline (MPA- o-Trz) were designed, synthesized, and found to exhibit green fluorescence characteristics. Notably, the singlet-triplet energy gap was less than 0.1 eV, indicating that reverse intersystem crossing gave rise to thermally activated delayed fluorescence (TADF). The organic light-emitting device performance of MPA- o-Trz showed a high external quantum efficiency of 16.3% and good color stability from 0.1 cd/m2 to 5000 cd/m2.

Nearly 100% triplet harvesting in conventional fluorescent dopant-based organic light-emitting devices through energy transfer from exciplex.

PubMed

Liu, Xiao-Ke; Chen, Zhan; Zheng, Cai-Jun; Chen, Miao; Liu, Wei; Zhang, Xiao-Hong; Lee, Chun-Sing

2015-03-25

Nearly 100% triplet harvesting in conventional fluorophor-based organic light-emitting devices is realized through energy transfer from exciplex. The best C545T-doped device using the exciplex host exhibits a maximum current efficiency of 44.0 cd A(-1) , a maximum power efficiency of 46.1 lm W(-1) , and a maximum external quantum efficiency of 14.5%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New anthracene derivatives as triplet acceptors for efficient green-to-blue low-power upconversion.

PubMed

Liang, Zuo-Qin; Sun, Bin; Ye, Chang-Qing; Wang, Xiao-Mei; Tao, Xu-Tang; Wang, Qin-Hua; Ding, Ping; Wang, Bao; Wang, Jing-Jing

2013-10-21

Three new anthracene derivatives [2-chloro-9,10-dip-tolylanthracene (DTACl), 9,10-dip-tolylanthracene-2-carbonitrile (DTACN), and 9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile (DNACN)] were synthesized as triplet acceptors for low-power upconversion. Their linear absorption, single-photon-excited fluorescence, and upconversion fluorescence properties were studied. The acceptors exhibit high fluorescence yields in DMF. Selective excitation of the sensitizer Pd(II)octaethylporphyrin (PdOEP) in solution containing DTACl, DTACN, or DNA-CN at 532 nm with an ultralow excitation power density of 0.5 W cm(-2) results in anti-Stokes blue emission. The maximum upconversion quantum yield (Φ(UC) =17.4%) was obtained for the couple PdOEP/DTACl. In addition, the efficiency of the triplet-triplet energy transfer process was quantitatively studied by quenching experiments. Experimental results revealed that a highly effective acceptor for upconversion should combine high fluorescence quantum yields with efficient quenching of the sensitizer triplet. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diiodobodipy-styrylbodipy Dyads: Preparation and Study of the Intersystem Crossing and Fluorescence Resonance Energy Transfer.

PubMed

Wang, Zhijia; Xie, Yun; Xu, Kejing; Zhao, Jianzhang; Glusac, Ksenija D

2015-07-02

2,6-Diiodobodipy-styrylbodipy dyads were prepared to study the competing intersystem crossing (ISC) and the fluorescence-resonance-energy-transfer (FRET), and its effect on the photophysical property of the dyads. In the dyads, 2,6-diiodobodipy moiety was used as singlet energy donor and the spin converter for triplet state formation, whereas the styrylbodipy was used as singlet and triplet energy acceptors, thus the competition between the ISC and FRET processes is established. The photophysical properties were studied with steady-state UV-vis absorption and fluorescence spectroscopy, electrochemical characterization, and femto/nanosecond time-resolved transient absorption spectroscopies. FRET was confirmed with steady state fluorescence quenching and fluorescence excitation spectra and ultrafast transient absorption spectroscopy (kFRET = 5.0 × 10(10) s(-1)). The singlet oxygen quantum yield (ΦΔ = 0.19) of the dyad was reduced as compared with that of the reference spin converter (2,6-diiodobodipy, ΦΔ = 0.85), thus the ISC was substantially inhibited by FRET. Photoinduced intramolecular electron transfer (ET) was studied by electrochemical data and fluorescence quenching. Intermolecular triplet energy transfer was studied with nanosecond transient absorption spectroscopy as an efficient (ΦTTET = 92%) and fast process (kTTET = 5.2 × 10(4) s(-1)). These results are useful for designing organic triplet photosensitizers and for the study of the photophysical properties.

Aerosol Generation by Modern Flush Toilets

PubMed Central

Johnson, David; Lynch, Robert; Marshall, Charles; Mead, Kenneth; Hirst, Deborah

2015-01-01

A microbe-contaminated toilet will produce bioaerosols when flushed. We assessed toilet plume aerosol from high efficiency (HET), pressure-assisted high efficiency (PAT), and flushometer (FOM) toilets with similar bowl water and flush volumes. Total and droplet nuclei “bioaerosols” were assessed. Monodisperse 0.25–1.9-μm fluorescent microspheres served as microbe surrogates in separate trials in a mockup 5 m3 water closet (WC). Bowl water seeding was approximately 1012 particles/mL. Droplet nuclei were sampled onto 0.2-μm pore size mixed cellulose ester filters beginning 15 min after the flush using open-face cassettes mounted on the WC walls. Pre- and postflush bowl water concentrations were measured. Filter particle counts were analyzed via fluorescent microscopy. Bowl headspace droplet count size distributions were bimodal and similar for all toilet types and flush conditions, with 95% of droplets <2 μm diameter and >99% <5 μm. Up to 145,000 droplets were produced per flush, with the high-energy flushometer producing over three times as many as the lower energy PAT and over 12 times as many as the lowest energy HET despite similar flush volumes. The mean numbers of fluorescent droplet nuclei particles aerosolized and remaining airborne also increased with flush energy. Fluorescent droplet nuclei per flush decreased with increasing particle size. These findings suggest two concurrent aerosolization mechanisms—splashing for large droplets and bubble bursting for the fine droplets that form droplet nuclei. PMID:26635429

76 FR 56661 - Energy Conservation Program: Test Procedures for General Service Fluorescent Lamps, General...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-14

... designed to improve energy efficiency and established the Energy Conservation Program for Consumer Products... prescribed or amended under this section must be reasonably designed to produce test results which measure... conservation standards for GSILs which include for the first time minimum rated lifetime requirements that are...

Temperature measurements of inverse micelles coated in gold nanoparticles using fluorescence

NASA Astrophysics Data System (ADS)

Daley, Chad; Forrest, James A.; Speller, Ryan; William, Toews; McVeigh, Patrick; Emrick, Todd

2009-03-01

When nanoparticles are subject to laser radiation they have the ability to efficiently absorb energy from the beam and transform this energy into heat. Photothermal therapy uses this phenomenon to irreparably damage tissue surrounding nanoparticle conjugates. Despite the promise of this technique, there is no concensus on the damage mechanism or even the local heating. Here we present an experiment designed to measure local temperatures achieved in such processes. Ligand covered Gold nanoparticles are used to stabalize inverse micelles containing fluorescence dye in the water component. The fluorescence intensity being temperature dependent provides us with a means of measuring the temperature of the micelles as a function of time immediately following a laser pulse.

Energy Donor Effect on the Sensing Performance for a Series of FRET-Based Two-Photon Fluorescent Hg2+ Probes

PubMed Central

Zhang, Yujin; Hu, Wei

2017-01-01

Nonlinear optical properties of a series of newly-synthesized molecular fluorescent probes for Hg2+ containing the same acceptor (rhodamine group) are analyzed by using time-dependent density functional theory in combination with analytical response theory. Special emphasis is placed on evolution of the probes’ optical properties in the absence and presence of Hg2+. These compounds show drastic changes in their photoabsorption and photoemission properties when they react with Hg2+, indicating that they are excellent candidates for ratiometric and colorimetric fluorescent chemosensors. Most importantly, the energy donor moiety is found to play a dominant role in sensing performance of these probes. Two-photon absorption cross sections of the compounds are increased with the presence of Hg2+, which theoretically suggests the possibility of the probes to be two-photon fluorescent Hg2+ sensors. Moreover, analysis of molecular orbitals is presented to explore responsive mechanism of the probes, where the fluorescence resonant energy transfer process is theoretically demonstrated. Our results elucidate the available experimental measurements. This work provides guidance for designing efficient two-photon fluorescent probes that are geared towards biological and chemical applications. PMID:28772466

Energy Donor Effect on the Sensing Performance for a Series of FRET-Based Two-Photon Fluorescent Hg2+ Probes.

PubMed

Zhang, Yujin; Hu, Wei

2017-01-25

Nonlinear optical properties of a series of newly-synthesized molecular fluorescent probes for Hg 2+ containing the same acceptor (rhodamine group) are analyzed by using time-dependent density functional theory in combination with analytical response theory. Special emphasis is placed on evolution of the probes' optical properties in the absence and presence of Hg 2+ . These compounds show drastic changes in their photoabsorption and photoemission properties when they react with Hg 2+ , indicating that they are excellent candidates for ratiometric and colorimetric fluorescent chemosensors. Most importantly, the energy donor moiety is found to play a dominant role in sensing performance of these probes. Two-photon absorption cross sections of the compounds are increased with the presence of Hg 2+ , which theoretically suggests the possibility of the probes to be two-photon fluorescent Hg 2+ sensors. Moreover, analysis of molecular orbitals is presented to explore responsive mechanism of the probes, where the fluorescence resonant energy transfer process is theoretically demonstrated. Our results elucidate the available experimental measurements. This work provides guidance for designing efficient two-photon fluorescent probes that are geared towards biological and chemical applications.

Manipulation of Thermally Activated Delayed Fluorescence of Blue Exciplex Emission: Fully Utilizing Exciton Energy for Highly Efficient Organic Light Emitting Diodes with Low Roll-Off.

PubMed

Wang, Zixing; Wang, Hedan; Zhu, Jun; Wu, Peng; Shen, Bowen; Dou, Dehai; Wei, Bin

2017-06-28

The application of exciplex energy has become a unique way to achieve organic light-emitting diodes (OLEDs) with high efficiencies, low turn-on voltage, and low roll-off. Novel δ-carboline derivatives with high triplet energy (T 1 ≈ 2.92 eV) and high glass transition temperature (T g ≈ 153 °C) were employed to manipulate exciplex emissions in this paper. Deep blue (peak at 436 nm) and pure blue (peak at 468 nm) thermally activated delayed fluorescence (TADF) of exciplex OLEDs were demonstrated by utilizing them as emitters with the maximum current efficiency (CE) of 4.64 cd A -1 , power efficiency (PE) of 2.91 lm W -1 , and external quantum efficiency (EQE) of 2.36%. Highly efficient blue phosphorescent OLEDs doped with FIrpic showed a maximum CE of 55.6 cd A -1 , PE of 52.9 lm W -1 , and EQE of 24.6% respectively with very low turn on voltage at 2.7 V. The devices still remain high CE of 46.5 cd A -1 at 100 cd m -2 , 45.4 cd A -1 at 1000 cd m -2 and 42.3 cd A -1 at 5000 cd m -2 with EQE close to 20% indicating low roll-off. Manipulating blue exciplex emissions by chemical structure gives an ideal strategy to fully utilize all exciton energies for lighting of OLEDs.

16 CFR 305.4 - Prohibited acts.

Code of Federal Regulations, 2014 CFR

2014-01-01

... advertisement, with respect to the energy use or efficiency or, in the case of showerheads, faucets, water... showerheads, faucets, water closets and urinals, water use of such product, or cost of energy consumed by such... conditioners, pulse combustion and condensing furnaces, fluorescent lamp ballasts, showerheads, faucets, water...

From Förster resonance energy transfer to coherent resonance energy transfer and back

NASA Astrophysics Data System (ADS)

Clegg, Robert M.; Sener, Melih; Govindjee, .

2010-02-01

Photosynthesis converts solar energy into chemical energy. It provides food and oxygen; and, in the future, it could directly provide bioenergy or renewable energy sources, such as bio-alcohol or hydrogen. To exploit such a highly efficient capture of energy requires an understanding of the fundamental physics. The process is initiated by photon absorption, followed by highly efficient and extremely rapid transfer and trapping of the excitation energy. We first review early fluorescence experiments on in vivo energy transfer, which were undertaken to understand the mechanism of such efficient energy capture. A historical synopsis is given of experiments and interpretations by others that dealt with the question of how energy is transferred from the original location of photon absorption in the photosynthetic antenna system into the reaction centers, where it is converted into useful chemical energy. We conclude by examining the physical basis of some current models concerning the roles of coherent excitons and incoherent hopping in the exceptionally efficient transfer of energy into the reaction center.

Photodynamic therapy potential of thiol-stabilized CdTe quantum dot-group 3A phthalocyanine conjugates (QD-Pc).

PubMed

Tekdaş, Duygu Aydın; Durmuş, Mahmut; Yanık, Hülya; Ahsen, Vefa

2012-07-01

Thiol stabilized CdTe quantum dot (QD) nanoparticles were synthesized in aqueous phase and were used as energy donors to tetra-triethyleneoxythia substituted aluminum, gallium and indium phthalocyanines through fluorescence resonance energy transfer (FRET). Energy transfer occurred from the QDs to phthalocyanines upon photoexcitation of the QDs. An enhancement in efficiency of energy transfer with the nature of the carboxylic thiol stabilizer on the QDs was observed. As a result of the nanoparticle and the phthalocyanine mixing, the photoluminescence efficiency of the phthalocyanine moieties in the mixtures does not strictly follow the quantum yields of the bare phthalocyanines. The photochemistry study of phthalocyanines in the presence of the QDs revealed high singlet oxygen quantum yield, hence the possibility of using QDs in combination with phthalocyanines as photosensitizers in photodynamic therapy of cancer. The fluorescence of the CdTe quantum dots-phthalocyanine conjugates (QDs-Pc) were effectively quenched by addition of 1,4-benzoquinone. Copyright © 2012 Elsevier B.V. All rights reserved.

Comparing colour discrimination and proofreading performance under compact fluorescent and halogen lamp lighting.

PubMed

Mayr, Susanne; Köpper, Maja; Buchner, Axel

2013-01-01

Legislation in many countries has banned inefficient household lighting. Consequently, classic incandescent lamps have to be replaced by more efficient alternatives such as halogen and compact fluorescent lamps (CFL). Alternatives differ in their spectral power distributions, implying colour-rendering differences. Participants performed a colour discrimination task - the Farnsworth-Munsell 100 Hue Test--and a proofreading task under CFL or halogen lighting of comparable correlated colour temperatures at low (70 lx) or high (800 lx) illuminance. Illuminance positively affected colour discrimination and proofreading performance, whereas the light source was only relevant for colour discrimination. Discrimination was impaired with CFL lighting. There were no differences between light sources in terms of self-reported physical discomfort and mood state, but the majority of the participants correctly judged halogen lighting to be more appropriate for discriminating colours. The findings hint at the colour-rendering deficiencies associated with energy-efficient CFLs. In order to compare performance under energy-efficient alternatives of classic incandescent lighting, colour discrimination and proofreading performance was compared under CFL and halogen lighting. Colour discrimination was impaired under CFLs, which hints at the practical drawbacks associated with the reduced colour-rendering properties of energy-efficient CFLs.

Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs

PubMed Central

Furukawa, Taro; Nakanotani, Hajime; Inoue, Munetomo; Adachi, Chihaya

2015-01-01

Recently, triplet harvesting via a thermally activated delayed fluorescence (TADF) process has been established as a realistic route for obtaining ultimate internal electroluminescence (EL) quantum efficiency in organic light-emitting diodes (OLEDs). However, the possibility that the rather long transient lifetime of the triplet excited states would reduce operational stability due to an increased chance for unwarranted chemical reactions has been a concern. Herein, we demonstrate dual enhancement of EL efficiency and operational stability in OLEDs by employing a TADF molecule as an assistant dopant and a fluorescent molecule as an end emitter. The proper combination of assistant dopant and emitter molecules realized a “one-way” rapid Förster energy transfer of singlet excitons from TADF molecules to fluorescent emitters, reducing the number of cycles of intersystem crossing (ISC) and reverse ISC in the TADF molecules and resulting in a significant enhancement of operational stability compared to OLEDs with a TADF molecule as the end emitter. In addition, we found that the presence of this rapid energy transfer significantly suppresses singlet-triplet annihilation. Using this finely-tuned rapid triplet-exciton upconversion scheme, OLED performance and lifetime was greatly improved. PMID:25673259

Spectroscopic investigation of alloyed quantum dot-based FRET to cresyl violet dye.

PubMed

Kotresh, M G; Adarsh, K S; Shivkumar, M A; Mulimani, B G; Savadatti, M I; Inamdar, S R

2016-05-01

Quantum dots (QDs), bright luminescent semiconductor nanoparticles, have found numerous applications ranging from optoelectronics to bioimaging. Here, we present a systematic investigation of fluorescence resonance energy transfer (FRET) from hydrophilic ternary alloyed quantum dots (CdSeS/ZnS) to cresyl violet dye with a view to explore the effect of composition of QD donors on FRET efficiency. Fluorescence emission of QD is controlled by varying the composition of QD without altering the particle size. The results show that quantum yield of the QDs increases with increase in the emission wavelength. The FRET parameters such as spectral overlap J(λ), Förster distance R0, intermolecular distance (r), rate of energy transfer k(T)(r), and transfer efficiency (E) are determined by employing both steady-state and time-resolved fluorescence spectroscopy. Additionally, dynamic quenching is noticed to occur in the present FRET system. Stern-Volmer (K(D)) and bimolecular quenching constants (k(q)) are determined from the Stern-Volmer plot. It is observed that the transfer efficiency follows a linear dependence on the spectral overlap and the quantum yield of the donor as predicted by the Förster theory upon changing the composition of the QD. Copyright © 2015 John Wiley & Sons, Ltd.

High-Performance Fluorescent Organic Light-Emitting Diodes Utilizing an Asymmetric Anthracene Derivative as an Electron-Transporting Material.

PubMed

Zhang, Dongdong; Song, Xiaozeng; Li, Haoyuan; Cai, Minghan; Bin, Zhengyang; Huang, Tianyu; Duan, Lian

2018-05-17

Fluorescent organic light-emitting diodes with thermally activated delayed fluorescent sensitizers (TSF-OLEDs) have aroused wide attention, the power efficiencies of which, however, are limited by the mutual exclusion of high electron-transport mobility and large triplet energy of electron-transporting materials (ETMs). Here, an asymmetric anthracene derivative with electronic properties manipulated by different side groups is developed as an ETM to promote TSF-OLED performances. Multiple intermolecular interactions are observed, leading to a kind of "cable-like packing" in the crystal and favoring the simultaneous realization of high electron-transporting mobility and good exciton-confinement ability, albeit the low triplet energy of the ETM. The optimized TSF-OLEDs exhibit a record-high maximum external quantum efficiency/power efficiency of 24.6%/76.0 lm W -1 , which remain 23.8%/69.0 lm W -1 at a high luminance of even 5000 cd m -2 with an extremely low operation voltage of 3.14 V. This work opens a new paradigm for designing ETMs and also paves the way toward practical application of TSF-OLEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of a High Output Fluorescent Light Module for the Commercial Plant Biotechnology Facility

NASA Technical Reports Server (NTRS)

Turner, Mark; Zhou, Wei-Jia; Doty, Laura (Technical Monitor)

2000-01-01

To maximize the use of available resources provided onboard the International Space Station, the development of an efficient lighting 1 system is critical to the overall performance of the CPBF. Not only is it important to efficiently generate photon energy, but thermal loads on the CPBF Temperature and Humidity Control System must be minimized. By utilizing optical coatings designed to produce highly diffuse reflectance in the visible wavelengths while minimizing reflectance in the infrared region, the design of the fluorescent light module for the CPBF is optimized for maximum photon flux, spatial uniformity and energy efficiency. Since the Fluorescent Light Module must be fully enclosed to meet (ISS) requirements for containment of particulates and toxic materials, heat removal from the lights presented some unique design challenges. By using the Express Rack moderate C, temperature-cooling loop, heat is rejected by means of a liquid/air coolant manifold. Heat transfer to the manifold is performed by conduction using copper fins, by forced air convection using miniature fans, and by radiation using optically selective coatings that absorb in the infrared wavelengths. Using this combination of heat transfer mechanisms builds in redundancy to prevent thermal build up and premature bulb failure.

FRET Sensor for Erythrosine Dye Based on Organic Nanoparticles: Application to Analysis of Food Stuff.

PubMed

Mahajan, Prasad G; Bhopate, Dhanaji P; Kolekar, Govind B; Patil, Shivajirao R

2016-07-01

An aqueous suspension of fluorescent nanoparticles (PHNNPs) of naphthol based fluorescent organic compound 1-[(Z)-(2-phenylhydrazinylidene) methyl] naphthalene -2-ol (PHN) were prepared using reprecipitation method shows bathochromically shifted aggregation induced enhanced emission (AIEE) in the spectral region where erythrosine (ETS) food dye absorbs strongly. The average size of 72.6 nm of aqueous suspension of PHNNPs obtained by Dynamic light scattering results shows a narrow particle size distribution. The negative zeta potential of nano probe (-22.6 mV) responsible to adsorb oppositely charged analyte on its surface and further permit to bind nano probe and analyte within the close distance proximity required for efficient fluorescence resonance energy transfer (FRET) to take place from donor (PHNNPs) to acceptor (ETS). Systematic FRET experiments performed by measuring fluorescence quenching of PHNNPs with successive addition of ETS solution exploited the use of the PHNNPs as a novel nano probe for the detection of ETS in aqueous solution with extremely lower limit of detection equal to 3.6 nM (3.1 ng/mL). The estimation of photo kinetic and thermodynamic parameters such as quenching rate constant, enthalpy change (∆H), Gibbs free energy change (∆G) and entropy change (∆S) was obtained by the quenching results obtained at different constant temperatures which were found to fit the well-known Stern-Volmer relation. The mechanism of binding and fluorescence quenching of PHNNPs by ETS food dye is proposed on the basis of results obtained in photophysical studies, thermodynamic parameter, energy transfer efficiency, critical energy transfer distance (R0) and distance of approach between donor-acceptor molecules (r). The proposed FRET method based on fluorescence quenching of PHNNPs was successfully applied to develop an analytical method for estimation of ETS from food stuffs without interference of other complex ingredients. Graphical Abstract A fluorescent organic nanoprobe developed for the detection of erythrosine (ETS) food dye in aqueous medium based on fluorescence resonance energy transfer (FRET). The FRET process between donor (nanoparticles) and acceptor (ETS dye) arises due to oppositely charge attraction through hydrophobic interactions. The proposed method was successfully applied to quantitative determination of ETS dye in food stuff sample collected from local market.

[Effects of plastic film mulching and rain harvesting modes on chlorophyll fluorescence characteristics, yield and water use efficiency of dryland maize].

PubMed

Li, Shang-Zhong; Fan, Ting-Lu; Wang, Yong; Zhao, Gang; Wang, Lei; Tang, Xiao-Ming; Dang, Yi; Zhao, Hui

2014-02-01

The differences on chlorophyll fluorescence parameters, yield and water use efficiency of dryland maize were compared among full plastic film mulching on double ridges and planting in catchment furrows (FFDRF), half plastic film mulching on double ridges and planting in catchment furrows (HFDRF), plastic film mulching on ridge and planting in film-side (FS), and flat planting with no plastic film mulching (NM) under field conditions in dry highland of Loess Plateau in 2007-2012. The results showed that fluorescence yield (Fo), the maximum fluorescence yield (Fm), light-adapted fluorescence yield when PS II reaction centers were totally open (F), light-adapted fluorescence yield when PS II reaction centers closed (Fm'), the maximal photochemical efficiency of PS II (Fv/Fm), the actual photochemical efficiency of PS II in the light (Phi PS II), the relative electron transport rate (ETR), photochemical quenching (qP) and non-photochemical quenching (qN) in maize leaves of FFDRF were higher than that of control (NM), and the value of 1-qP was lower than that of control, at 13:00, chlorophyll fluorescence parameters values of FFDRF was significantly higher than control, which were increased by 5.3%, 56.8%, 10.7%, 36.3%, 23.6%, 56.7%, 64.4%, 45.5%, 23.6% and -55.6%, respectively, compared with the control. Yield and water use efficiency of FFDRF were the highest in every year no matter dry year, normal year, humid year and hail disaster year. Average yield and water use efficiency of FFDRF were 12,650 kg x hm(-2) and 40.4 kg x mm(-1) x hm(-2) during 2007-2012, increased by 57.8% and 61.6% compared with the control, respectively, and also significantly higher compared with HFDRF and PS. Therefore, it was concluded that FFDRF had significantly increased the efficiency of light energy conversion and improved the production capacity of dryland maize.

Studies on the interaction between 7-(dimethyl amino)-4-(trifluoromethyl)-2H-1-benzopyran-2-one and cadmium sulfide quantum dots

NASA Astrophysics Data System (ADS)

Kuriakose, Alina C.; Pradeep, C.; Nampoori, V. P. N.; Thomas, Sheenu

2018-04-01

Quantum dots (QDs) are well known for their optical properties which differ from those of bulk semiconductors. Herein, we have created an energy transfer platform that combines CdS QDs with a coumarin based dye C485 [7-(dimethyl amino)-4-(trifluoromethyl)-2H-1-benzopyran-2-one]. Spectroscopic studies of energy transfer between the dye donor and CdS QDs as acceptors reveal the occurrence of dynamic quenching. Analysis of the steady-state and time resolved fluorescence measurements of C485 in the presence of CdS QDs infers fluorescence resonance (Förster type) energy transfer (FRET) as responsible for the quenching phenomena. The energy transfer efficiency as well as energy transfer distance for the donor-acceptor pair is calculated using steady-state fluorescence method. Luminescence enhancement of CdS QDs play a critical role in device performance for solar applications and also in the field of biological applications.

High-efficiency in situ resonant inelastic x-ray scattering (iRIXS) endstation at the Advanced Light Source

NASA Astrophysics Data System (ADS)

Qiao, Ruimin; Li, Qinghao; Zhuo, Zengqing; Sallis, Shawn; Fuchs, Oliver; Blum, Monika; Weinhardt, Lothar; Heske, Clemens; Pepper, John; Jones, Michael; Brown, Adam; Spucces, Adrian; Chow, Ken; Smith, Brian; Glans, Per-Anders; Chen, Yanxue; Yan, Shishen; Pan, Feng; Piper, Louis F. J.; Denlinger, Jonathan; Guo, Jinghua; Hussain, Zahid; Chuang, Yi-De; Yang, Wanli

2017-03-01

An endstation with two high-efficiency soft x-ray spectrographs was developed at Beamline 8.0.1 of the Advanced Light Source, Lawrence Berkeley National Laboratory. The endstation is capable of performing soft x-ray absorption spectroscopy, emission spectroscopy, and, in particular, resonant inelastic soft x-ray scattering (RIXS). Two slit-less variable line-spacing grating spectrographs are installed at different detection geometries. The endstation covers the photon energy range from 80 to 1500 eV. For studying transition-metal oxides, the large detection energy window allows a simultaneous collection of x-ray emission spectra with energies ranging from the O K-edge to the Ni L-edge without moving any mechanical components. The record-high efficiency enables the recording of comprehensive two-dimensional RIXS maps with good statistics within a short acquisition time. By virtue of the large energy window and high throughput of the spectrographs, partial fluorescence yield and inverse partial fluorescence yield signals could be obtained for all transition metal L-edges including Mn. Moreover, the different geometries of these two spectrographs (parallel and perpendicular to the horizontal polarization of the beamline) provide contrasts in RIXS features with two different momentum transfers.

Optical tracking of organically modified silica nanoparticles as DNA carriers: A nonviral, nanomedicine approach for gene delivery

NASA Astrophysics Data System (ADS)

Roy, Indrajit; Ohulchanskyy, Tymish Y.; Bharali, Dhruba J.; Pudavar, Haridas E.; Mistretta, Ruth A.; Kaur, Navjot; Prasad, Paras N.

2005-01-01

This article reports a multidisciplinary approach to produce fluorescently labeled organically modified silica nanoparticles as a nonviral vector for gene delivery and biophotonics methods to optically monitor intracellular trafficking and gene transfection. Highly monodispersed, stable aqueous suspensions of organically modified silica nanoparticles, encapsulating fluorescent dyes and surface functionalized by cationic-amino groups, are produced by micellar nanochemistry. Gel-electrophoresis studies reveal that the particles efficiently complex with DNA and protect it from enzymatic digestion of DNase 1. The electrostatic binding of DNA onto the surface of the nanoparticles, due to positively charged amino groups, is also shown by intercalating an appropriate dye into the DNA and observing the Förster (fluorescence) resonance energy transfer between the dye (energy donor) intercalated in DNA on the surface of nanoparticles and a second dye (energy acceptor) inside the nanoparticles. Imaging by fluorescence confocal microscopy shows that cells efficiently take up the nanoparticles in vitro in the cytoplasm, and the nanoparticles deliver DNA to the nucleus. The use of plasmid encoding enhanced GFP allowed us to demonstrate the process of gene transfection in cultured cells. Our work shows that the nanomedicine approach, with nanoparticles acting as a drug-delivery platform combining multiple optical and other types of probes, provides a promising direction for targeted therapy with enhanced efficacy as well as for real-time monitoring of drug action. nonviral vector | ORMOSIL nanoparticles | confocal microscopy

Carbon dot-Au(i)Ag(0) assembly for the construction of an artificial light harvesting system.

PubMed

Jana, Jayasmita; Aditya, Teresa; Pal, Tarasankar

2018-03-06

Artificial light harvesting systems (LHS) with inorganic counterparts are considered to be robust as well as mechanistically simple, where the system follows the donor-acceptor principle with an unchanged structural pattern. Plasmonic gold or silver nanoparticles are mostly chosen as inorganic counterparts to design artificial LHS. To capitalize on its electron accepting capability, Au(i) has been considered in this work for the synergistic stabilization of a system with intriguingly fluorescing silver(0) clusters produced in situ. Thus a stable fluorescent Au(i)Ag(0) assembly is generated with electron accepting capabilities. On the other hand, carbon dots have evolved as new fluorescent probes due to their unique physicochemical properties. Utilizing the simple electronic behavior of carbon dots, an electronic interaction between the fluorescent Au(i)Ag(0) and a carbon dot has been investigated for the construction of a new artificial light harvesting system. This coinage metal assembly allows surface energy transfer where it acts as an acceptor, while the carbon dot behaves as a good donor. The energy transfer efficiency has been calculated experimentally to be significant (81.3%) and the Au(i)Ag(0)-carbon dot assembly paves the way for efficient artificial LHS.

Genetically encoded sensors and fluorescence microscopy for anticancer research

NASA Astrophysics Data System (ADS)

Zagaynova, Elena V.; Shirmanova, Marina V.; Sergeeva, Tatiana F.; Klementieva, Natalia V.; Mishin, Alexander S.; Gavrina, Alena I.; Zlobovskay, Olga A.; Furman, Olga E.; Dudenkova, Varvara V.; Perelman, Gregory S.; Lukina, Maria M.; Lukyanov, Konstantin A.

2017-02-01

Early response of cancer cells to chemical compounds and chemotherapeutic drugs were studied using novel fluorescence tools and microscopy techniques. We applied confocal microscopy, two-photon fluorescence lifetime imaging microscopy and super-resolution localization-based microscopy to assess structural and functional changes in cancer cells in vitro. The dynamics of energy metabolism, intracellular pH, caspase-3 activation during staurosporine-induced apoptosis as well as actin cytoskeleton rearrangements under chemotherapy were evaluated. We have showed that new genetically encoded sensors and advanced fluorescence microscopy methods provide an efficient way for multiparameter analysis of cell activities

Nano-bio assemblies for artificial light harvesting systems

NASA Astrophysics Data System (ADS)

Bain, Dipankar; Maity, Subarna; Patra, Amitava

2018-02-01

Ultrasmall fluorescent gold nanoclusters (Au NCs) have drawn considerable research interest owing to their molecular like properties such as d-sp and sp-sp transitions, and intense fluorescence. Fluorescent Au NCs have especial attraction in biological system owing to their biocompatibility and high photostability. Recently, several strategies have been adapted to design an artificial light-harvesting system using Au NCs for potential applications. Here, we have designed Au nanoclusters based dsDNA (double stranded deoxyribonucleic acid) nano assemblies where the Au nanocluster is covalently attached with Alexa Fluor 488 (A488) dye tagged dsDNA. Investigation reveals that the incorporation of Ag+ into dsDNA enhances the rate of energy transfer from A488 to Au NCs. In addition cadmium telluride quantum dot (CdTe QDs) based Au NCs hybrid material shows the significant enhancement of energy transfer 35% to 83% with changing the capping ligand of Au NCs from glutathione (GSH) to bovine serum albumin (BSA) protein. Another hybrid system is developed using carbon dots and dye encapsulated BSA-protein capped Au NCs for efficient light harvesting system with 83% energy transfer efficiency. Thus, Au NCs base nano bio assemblies may open up new possibilities for the construction of artificial light harvesting system.

LIGHTING FOR READING: DESIGNING AN LED LUMINAIRE FOR HOMES AND OFFICES

EPA Science Inventory

Energy waste from traditional incandescent light bulbs was reduced by fluorescent lamps, but they pose a threat to the environment due to the mercury in each tube and disposal issues. Light emitting diodes (LEDs) provide superior energy efficiency, longer life, toxin-free comp...

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

NASA Astrophysics Data System (ADS)

Zhang, Yue; Zhou, Dejian; He, Junhui

2014-12-01

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

Green Schools Energy Project: A Step-by-Step Manual.

ERIC Educational Resources Information Center

Quigley, Gwen

This publication contains a step-by-step guide for implementing an energy-saving project in local school districts: the installation of newer, more energy-efficient "T-8" fluorescent tube lights in place of "T-12" lights. Eleven steps are explained in detail: (1) find out what kind of lights the school district currently uses;…

Rigidifying fluorescent linkers by metal-organic framework formation for fluorescence blue shift and quantum yield enhancement.

PubMed

Wei, Zhangwen; Gu, Zhi-Yuan; Arvapally, Ravi K; Chen, Ying-Pin; McDougald, Roy N; Ivy, Joshua F; Yakovenko, Andrey A; Feng, Dawei; Omary, Mohammad A; Zhou, Hong-Cai

2014-06-11

We demonstrate that rigidifying the structure of fluorescent linkers by structurally constraining them in metal-organic frameworks (MOFs) to control their conformation effectively tunes the fluorescence energy and enhances the quantum yield. Thus, a new tetraphenylethylene-based zirconium MOF exhibits a deep-blue fluorescent emission at 470 nm with a unity quantum yield (99.9 ± 0.5%) under Ar, representing ca. 3600 cm(-1) blue shift and doubled radiative decay efficiency vs the linker precursor. An anomalous increase in the fluorescence lifetime and relative intensity takes place upon heating the solid MOF from cryogenic to ambient temperatures. The origin of these unusual photoluminescence properties is attributed to twisted linker conformation, intramolecular hindrance, and framework rigidity.

Fluorescence Quenching of Alpha-Fetoprotein by Gold Nanoparticles: Effect of Dielectric Shell on Non-Radiative Decay

NASA Astrophysics Data System (ADS)

Zhu, Jian; Li, Jian-Jun; Wang, A.-Qing; Chen, Yu; Zhao, Jun-Wu

2010-09-01

Fluorescence quenching spectrometry was applied to study the interactions between gold colloidal nanoparticles and alpha-fetoprotein (AFP). Experimental results show that the gold nanoparticles can quench the fluorescence emission of adsorbed AFP effectively. Furthermore, the intensity of fluorescence emission peak decreases monotonously with the increasing gold nanoparticles content. A mechanism based on surface plasmon resonance-induced non-radiative decay was investigated to illuminate the effect of a dielectric shell on the fluorescence quenching ability of gold nanoparticles. The calculation results show that the increasing dielectric shell thickness may improve the monochromaticity of fluorescence quenching. However, high energy transfer efficiency can be obtained within a wide wavelength band by coating a thinner dielectric shell.

pH-Responsive Fluorescence Enhancement in Graphene Oxide-Naphthalimide Nanoconjugates: A Fluorescence Turn-On Sensor for Acetylcholine.

PubMed

Mangalath, Sreejith; Abraham, Silja; Joseph, Joshy

2017-08-22

A pH-sensitive, fluorescence "turn-on" sensor based on a graphene oxide-naphthalimide (GO-NI) nanoconjugate for the detection of acetylcholine (ACh) by monitoring the enzymatic activity of acetylcholinesterase (AChE) in aqueous solution is reported. These nanoconjugates were synthesized by covalently anchoring picolyl-substituted NI derivatives on the GO/reduced GO surface through a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide coupling strategy, and the morphological and photophysical properties were studied in detail. Synergistic effects of π-π interactions between GO and the NI chromophore, and efficient photoinduced electron- and energy-transfer processes, were responsible for the strong quenching of fluorescence of these nanoconjugates, which were perturbed under acidic pH conditions, leading to significant enhancement of fluorescence emission. This nanoconjugate was successfully employed for the efficient sensing of pH changes caused by the enzymatic activity of AChE, thereby demonstrating its utility as a fluorescence turn-on sensor for ACh in the neurophysiological range. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cyclodextrin-enhanced extraction and energy transfer of carcinogens in complex oil environments.

PubMed

Serio, Nicole; Chanthalyma, Chitapom; Prignano, Lindsey; Levine, Mindy

2013-11-27

Reported herein is the use of γ-cyclodextrin for two tandem functions: (a) the extraction of carcinogenic polycyclic aromatic hydrocarbons (PAHs) from oil samples into aqueous solution and (b) the promotion of highly efficient energy transfer from the newly extracted PAHs to a high-quantum-yield fluorophore. The extraction proceeded in moderate to good efficiencies, and the resulting cyclodextrin-promoted energy transfer led to a new, brightly fluorescent signal in aqueous solution. The resulting dual-function system (extraction followed by energy transfer) has significant relevance in the environmental detection and cleanup of oil-spill-related carcinogens.

Annihilation limit of a visible-to-UV photon upconversion composition ascertained from transient absorption kinetics.

PubMed

Deng, Fan; Blumhoff, Jörg; Castellano, Felix N

2013-05-30

Noncoherent sensitized green-to-near-visible upconversion has been achieved utilizing palladium(II) octaethylporphyrin (PdOEP) as the triplet sensitizer and anthracene as the energy acceptor/annihilator in vacuum degassed toluene. Selective 547 nm excitation of PdOEP with incident irradiance as low as 600 μW/cm(2) results in the observation of anthryl fluorescence at higher energy. Stern-Volmer analysis of the dynamic phosphorescence quenching of PdOEP by anthracene possesses an extremely large K(SV) of 810,000 M(-1), yielding a triplet-triplet energy transfer quenching constant of 3.3 × 10(9) M(-1) s(-1). Clear evidence for the subsequent triplet-triplet annihilation (TTA) of anthracene was afforded by numerous experiments, one of the most compelling was an excitation scan illustrating that the Q-band absorption features of PdOEP are solely responsible for sensitizing the anti-Stokes fluorescence. The upconverted emission intensity with respect to the excitation power was shown to vary between quadratic and linear using either coherent or noncoherent light sources, illustrating the expected kinetic limits for the light producing photochemistry under continuous wave illumination. Time-resolved experiments directly comparing the total integrated anthracene intensity/time fluorescence data produced through upconversion (λ(ex) = 547 nm, delayed signal) and with direct excitation (λ(ex) = 355 nm, prompt signal) under conditions where the laser pulse is completely absorbed by the sample reveal annihilation efficiencies of approximately 40%. Similarly, the delayed fluorescence kinetic analysis reported by Schmidt and co-workers (J. Phys. Chem. Lett. 2010, 1, 1795-1799) was used to reveal the maximum possible efficiency from a model red-to-yellow upconverting composition and this treatment was applied to the anthryl triplet absorption decay transients of anthracene measured for the PdOEP/anthracene composition at 430 nm. From this analysis approximately 50% of the anthryl triplets that decay by TTA produce singlet fluorescence, consistent with the notion that annihilation spin statistics does not impose efficiency limits on upconversion photochemistry.

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

NASA Astrophysics Data System (ADS)

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

2015-11-01

Semiconductor nanocrystals exhibit unique fluorescence properties which are tunable in size, shape and composition. The high quantum yield and enhanced stability have led to their use in biomedical imaging and flat panel displays. Here, semiconductor nanorod based inkjet inks are presented, overcoming limitations of the commonly reported quantum dots in printing applications. Fluorescent seeded nanorods were found to be outstanding candidates for fluorescent inks, due to their low particle-particle interactions and negligible self-absorption. This is manifested by insignificant emission shifts upon printing, even in highly concentrated printed layers and by maintenance of a high fluorescence quantum yield, unlike quantum dots which exhibit fluorescence wavelength shifts and quenching effects. This behavior results from the reduced absorption/emission overlap, accompanied by low energy transfer efficiencies between the nanorods as supported by steady state and time resolved fluorescence measurements. The new seeded nanorod inks enable patterning of thin fluorescent layers, for demanding light emission applications such as signage and displays.Semiconductor nanocrystals exhibit unique fluorescence properties which are tunable in size, shape and composition. The high quantum yield and enhanced stability have led to their use in biomedical imaging and flat panel displays. Here, semiconductor nanorod based inkjet inks are presented, overcoming limitations of the commonly reported quantum dots in printing applications. Fluorescent seeded nanorods were found to be outstanding candidates for fluorescent inks, due to their low particle-particle interactions and negligible self-absorption. This is manifested by insignificant emission shifts upon printing, even in highly concentrated printed layers and by maintenance of a high fluorescence quantum yield, unlike quantum dots which exhibit fluorescence wavelength shifts and quenching effects. This behavior results from the reduced absorption/emission overlap, accompanied by low energy transfer efficiencies between the nanorods as supported by steady state and time resolved fluorescence measurements. The new seeded nanorod inks enable patterning of thin fluorescent layers, for demanding light emission applications such as signage and displays. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06248a

Excited state free energy calculations of Cy3 in different environments

NASA Astrophysics Data System (ADS)

Sawangsang, Pilailuk; Buranachai, Chittanon; Punwong, Chutintorn

2015-05-01

Cy3, a cyanine dye, is one of the most widely used dyes in investigating the structure and dynamics of biomolecules by means of fluorescence methods. However, Cy3 fluorescence emission is strongly competed by trans-cis isomerization, whose efficiency is dictated by the isomerization energy barrier and the environment of Cy3. The fluorescence quantum yield of Cy3 is very low when the dye is free in homogeneous solution but it is considerably enhanced in an environment that rigidifies the structure, e.g. when it is attached to a DNA strand. In this work, the barriers for isomerization on the excited state of free Cy3, and Cy3 attached to single- and double-stranded DNA in methanol, are presented. The free energy and subsequently the isomerization barrier calculations are performed using the umbrella sampling technique with the weighted histogram analysis method. The hybrid quantum mechanics/molecular mechanics (QM/MM) approach is employed to provide the potential energy surfaces for the excited state dynamics simulations in umbrella sampling. The semiempirical floating occupation molecular orbital configuration interaction method is used for electronic excited state calculations of the QM region (Cy3). From the free energy calculations, the barrier of Cy3 attached to the single-stranded DNA is highest, in agreement with previously reported experimental results. This is likely due to the stacking interaction between Cy3 and DNA. Such a stacking interaction is likely associated with steric hindrance that prevents the rotation around the conjugated bonds of Cy3. If Cy3 experiences high steric hindrance, it has a higher isomerization barrier and thus the efficiency of fluorescence emission increases.

Absorption-emission optrode and methods of use thereof

DOEpatents

Hirschfeld, T.B.

1990-05-29

A method and apparatus are described for monitoring the physical and chemical properties of a sample fluid by measuring an optical signal generated by a fluorescent substance and modulated by an absorber substance. The emission band of the fluorescent substance overlaps the absorption band of the absorber substance, and the degree of overlap is dependent on the physical and chemical properties of the sample fluid. The fluorescent substance and absorber substance are immobilized on a substrate so that an effective number of molecules thereof are sufficiently close for resonant energy transfer to occur, thereby providing highly efficient modulation of the fluorescent emissions of the fluorescent substance by the absorber substance. 4 figs.

Options for reducing carbon dioxide emissions

NASA Astrophysics Data System (ADS)

Rosenfeld, Arthur H.; Price, Lynn

1992-03-01

Improvements in energy efficiency can significantly reduce the annual growth in greenhouse gas emissions. Such improvements occur when energy intensity is reduced; no reduction in energy services is required. Using the concept of ``cost of conserved energy'' to develop conservation supply curves similar to resource supply curves, researchers consistently find that electricity and natural gas savings of nearly 50% of current consumption are possible for U.S. buildings. Such reductions in energy consumption directly reduce emissions of greenhouse gases. To capture these savings, we must continue to develop energy-efficient technologies and strategies. This paper describes three recent energy-efficient technologies that benefitted from energy conservation research and development (R&D) funding: high-frequency ballasts, compact fluorescent lamps, and low-emissivity windows. Other advanced technologies and strategies of spectrally selective windows, superwindows, electrochromic windows, advanced insulation, low-flow showerheads, improved recessed lamp fixtures, whitening surfaces and planting urban trees, daylighting, and thermal energy storage are also discussed.

Lighting recommendations for the Social Security Administration Frank Hagel Federal Building in Richmond CA

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

Rubinstein, Francis M.

Specific recommendations are made to improve the lighting quality and energy efficiency of the lighting system at the Social Security Administration Frank Hagel Building in Richmond, CA. The main recommendation is to replace the recessed fluorescent lighting system in the general office area with indirect lighting. Indirect lighting will improve lighting quality, will provide an energy efficient solution and will be about the same cost as the direct lighting system originally proposed.

Effect of solvent hydrogen bonding on the photophysical properties of intramolecular charge transfer probe trans-ethyl p-(dimethylamino) cinamate and its derivative

NASA Astrophysics Data System (ADS)

Singh, T. Sanjoy; Moyon, N. S.; Mitra, Sivaprasad

2009-08-01

Intramolecular charge transfer (ICT) behavior of trans-ethyl p-(dimethylamino) cinamate (EDAC) and 4-(dimethylamino) cinnamic acid (DMACA) were studied by steady state absorption and emission, picosecond time-resolved fluorescence experiments in various pure and mixed solvent systems. The large fluorescence spectral shift in more polar solvents indicates an efficient charge transfer from the donor site to the acceptor moiety in the excited state compared to the ground state. The energy for 0,0 transition ( ν0,0) for EDAC shows very good linear correlation with static solvent dielectric property; however, fluorescence emission maximum, stokes shift and fluorescence quantum yield show significant deviation from linearity in polar protic solvents, indicating a large contribution of solvent hydrogen bonding on the excited state relaxation mechanism. A quantitative estimation of contribution from different solvatochromic parameters was made using linear free energy relationship based on Kamlet-Taft equation.

Prime-Color Concept: Lighting for the Future

ERIC Educational Resources Information Center

Modern Schools, 1976

1976-01-01

A major technological breakthrough--the isolation and then combination of narrow bands of blue-violet, pure green, and orange-red energy--has resulted in a highly efficient white fluorescent lamp. (Author/MLF)

Microspectroscopic Study of Liposome-to-cell Interaction Revealed by Förster Resonance Energy Transfer.

PubMed

Yefimova, Svetlana L; Kurilchenko, Irina Yu; Tkacheva, Tatyana N; Kavok, Nataliya S; Todor, Igor N; Lukianova, Nataliya Yu; Chekhun, Vasyl F; Malyukin, Yuriy V

2014-03-01

We report the Förster resonance energy transfer (FRET)-labeling of liposomal vesicles as an effective approach to study in dynamics the interaction of liposomes with living cells of different types (rat hepatocytes, rat bone marrow, mouse fibroblast-like cells and human breast cancer cells) and cell organelles (hepatocyte nuclei). The in vitro experiments were performed using fluorescent microspectroscopic technique. Two fluorescent dyes (DiO as the energy donor and DiI as an acceptor) were preloaded in lipid bilayers of phosphatidylcholine liposomes that ensures the necessary distance between the dyes for effective FRET. The change in time of the donor and acceptor relative fluorescence intensities was used to visualize and trace the liposome-to-cell interaction. We show that FRET-labeling of liposome vesicles allows one to reveal the differences in efficiency and dynamics of these interactions, which are associated with composition, fluidity, and metabolic activity of cell plasma membranes.

Application of CORSIKA Simulation Code to Study Lateral and Longitudinal Distribution of Fluorescence Light in Cosmic Ray Extensive Air Showers

NASA Astrophysics Data System (ADS)

Bagheri, Zahra; Davoudifar, Pantea; Rastegarzadeh, Gohar; Shayan, Milad

2017-03-01

In this paper, we used CORSIKA code to understand the characteristics of cosmic ray induced showers at extremely high energy as a function of energy, detector distance to shower axis, number, and density of secondary charged particles and the nature particle producing the shower. Based on the standard properties of the atmosphere, lateral and longitudinal development of the shower for photons and electrons has been investigated. Fluorescent light has been collected by the detector for protons, helium, oxygen, silicon, calcium and iron primary cosmic rays in different energies. So we have obtained a number of electrons per unit area, distance to the shower axis, shape function of particles density, percentage of fluorescent light, lateral distribution of energy dissipated in the atmosphere and visual field angle of detector as well as size of the shower image. We have also shown that location of highest percentage of fluorescence light is directly proportional to atomic number of elements. Also we have shown when the distance from shower axis increases and the shape function of particles density decreases severely. At the first stages of development, shower axis distance from detector is high and visual field angle is small; then with shower moving toward the Earth, angle increases. Overall, in higher energies, the fluorescent light method has more efficiency. The paper provides standard calibration lines for high energy showers which can be used to determine the nature of the particles.

Quantifying highly efficient incoherent energy transfer in perylene-based multichromophore arrays.

PubMed

Webb, James E A; Chen, Kai; Prasad, Shyamal K K; Wojciechowski, Jonathan P; Falber, Alexander; Thordarson, Pall; Hodgkiss, Justin M

2016-01-21

Multichromophore perylene arrays were designed and synthesized to have extremely efficient resonance energy transfer. Using broadband ultrafast photoluminescence and transient absorption spectroscopies, transfer timescales of approximately 1 picosecond were resolved, corresponding to efficiencies of up to 99.98%. The broadband measurements also revealed spectra corresponding to incoherent transfer between localized states. Polarization resolved spectroscopy was used to measure the dipolar angles between donor and acceptor chromophores, thereby enabling geometric factors to be fixed when assessing the validity of Förster theory in this regime. Förster theory was found to predict the correct magnitude of transfer rates, with measured ∼2-fold deviations consistent with the breakdown of the point-dipole approximation at close approach. The materials presented, along with the novel methods for quantifying ultrahigh energy transfer efficiencies, will be valuable for applications demanding extremely efficient energy transfer, including fluorescent solar concentrators, optical gain, and photonic logic devices.

"siRNA traffic lights": arabino-configured 2'-anchors for fluorescent dyes are key for dual color readout in cell imaging.

PubMed

Steinmeyer, Jeannine; Walter, Heidi-Kristin; Bichelberger, Mathilde A; Schneider, Violetta; Kubař, Tomáš; Rönicke, Franziska; Olshausen, Bettina; Nienhaus, Karin; Nienhaus, Gerd Ulrich; Schepers, Ute; Elstner, Marcus; Wagenknecht, Hans-Achim

2018-05-23

Two fluorescent dyes covalently attached in diagonal interstrand orientation to siRNA undergo energy transfer and thereby enable a dual color fluorescence readout (red/green) for hybridization. Three different structural variations were carried out and compared by their optical properties, including (i) the base surrogate approach with an acyclic linker as a substitute of the 2-deoxyriboside between the phosphodiester bridges, (ii) the 2'-modification of conventional ribofuranosides and (iii) the arabino-configured 2'-modification. The double stranded siRNA with the latter type of modification delivered the best energy transfer efficiency, which was explained by molecular dynamics simulations that showed that the two dyes are more flexible at the arabino-configured sugars compared to the completely stacked situation at the ribo-configured ones. Single molecule fluorescence lifetime measurements indicate their application in fluorescence cell imaging, which reveals a red/green fluorescence contrast in particular for the arabino-configured 2'-modification by the two dyes, which is key for tracking of siRNA transport into HeLa cells.

75 FR 71570 - Energy Conservation Program: Test Procedures for Fluorescent Lamp Ballasts

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-24

... improve energy efficiency. Part A of Title III (42 U.S.C. 6291-6309) establishes the ``Energy Conservation... ballasts (ballasts). (42 U.S.C. 6291(1), (2) and 6292(a)(13)) Under EPCA, the overall program consists... the public an opportunity to present oral and written comments on them. (42 U.S.C. 6293(b)(2)) Finally...

Energy transfer between surface-immobilized light-harvesting chlorophyll a/b complex (LHCII) studied by surface plasmon field-enhanced fluorescence spectroscopy (SPFS).

PubMed

Lauterbach, Rolf; Liu, Jing; Knoll, Wolfgang; Paulsen, Harald

2010-11-16

The major light-harvesting chlorophyll a/b complex (LHCII) of the photosynthetic apparatus in green plants can be viewed as a protein scaffold binding and positioning a large number of pigment molecules that combines rapid and efficient excitation energy transfer with effective protection of its pigments from photobleaching. These properties make LHCII potentially interesting as a light harvester (or a model thereof) in photoelectronic applications. Most of such applications would require the LHCII to be immobilized on a solid surface. In a previous study we showed the immobilization of recombinant LHCII on functionalized gold surfaces via a 6-histidine tag (His tag) in the protein moiety. In this work the occurrence and efficiency of Förster energy transfer between immobilized LHCII on a functionalized surface have been analyzed by surface plasmon field-enhanced fluorescence spectroscopy (SPFS). A near-infrared dye was attached to some but not all of the LHC complexes, serving as an energy acceptor to chlorophylls. Analysis of the energy transfer from chlorophylls to this acceptor dye yielded information about the extent of intercomplex energy transfer between immobilized LHCII.

Optimization of hybrid blue organic light-emitting diodes based on singlet and triplet exciton diffusion length

NASA Astrophysics Data System (ADS)

Lee, Song Eun; Lee, Ho Won; Lee, Jae Woo; Hwang, Kyo Min; Park, Soo Na; Yoon, Seung Soo; Kim, Young Kwan

2015-06-01

The hybrid blue organic light-emitting diodes (HB OLEDs) with triplet harvesting (TH) structures within an emitting layer (EML) are fabricated with fluorescent and phosphorescent EMLs. The TH is to transfer triplet excitons from fluorescence to phosphorescence, where they can decay radiatively. Remarkably, the half-decay lifetime of a hybrid blue device with fluorescent and phosphorescent EML thickness of 5 and 25 nm, measured at an initial luminance of 500 cd/m2, has improved twice than that of using a conventional structure. Additionally, the blue device’s efficiency improved. We attribute this improvement to the efficient triplet excitons energy transfer and the optimized distribution of the EML which depends on singlet and triplet excitons diffusion length that occurs within each the EML.

Thermally activated delayed fluorescence of fluorescein derivative for time-resolved and confocal fluorescence imaging.

PubMed

Xiong, Xiaoqing; Song, Fengling; Wang, Jingyun; Zhang, Yukang; Xue, Yingying; Sun, Liangliang; Jiang, Na; Gao, Pan; Tian, Lu; Peng, Xiaojun

2014-07-09

Compared with fluorescence imaging utilizing fluorophores whose lifetimes are in the order of nanoseconds, time-resolved fluorescence microscopy has more advantages in monitoring target fluorescence. In this work, compound DCF-MPYM, which is based on a fluorescein derivative, showed long-lived luminescence (22.11 μs in deaerated ethanol) and was used in time-resolved fluorescence imaging in living cells. Both nanosecond time-resolved transient difference absorption spectra and time-correlated single-photon counting (TCSPC) were employed to explain the long lifetime of the compound, which is rare in pure organic fluorophores without rare earth metals and heavy atoms. A mechanism of thermally activated delayed fluorescence (TADF) that considers the long wavelength fluorescence, large Stokes shift, and long-lived triplet state of DCF-MPYM was proposed. The energy gap (ΔEST) of DCF-MPYM between the singlet and triplet state was determined to be 28.36 meV by the decay rate of DF as a function of temperature. The ΔE(ST) was small enough to allow efficient intersystem crossing (ISC) and reverse ISC, leading to efficient TADF at room temperature. The straightforward synthesis of DCF-MPYM and wide availability of its starting materials contribute to the excellent potential of the compound to replace luminescent lanthanide complexes in future time-resolved imaging technologies.

Study of protein-probe interaction and protective action of surfactant sodium dodecyl sulphate in urea-denatured HSA using charge transfer fluorescence probe methyl ester of N,N-dimethylamino naphthyl acrylic acid.

PubMed

Mahanta, Subrata; Singh, Rupashree Balia; Guchhait, Nikhil

2009-03-01

We have demonstrated that the intramolecular charge transfer (ICT) probe Methyl ester of N,N-dimethylamino naphthyl acrylic acid (MDMANA) serves as an efficient reporter of the proteinous microenvironment of Human Serum Albumin (HSA). This work reports the binding phenomenon of MDMANA with HSA and spectral modulation thereupon. The extent of binding and free energy change for complexation reaction along with efficient fluorescence resonance energy transfer from Trp-214 of HSA to MDMANA indicates strong binding between probe and protein. Fluorescence anisotropy, red edge excitation shift, acrylamide quenching and time resolved measurements corroborate the binding nature of the probe with protein and predicts that the probe molecule is located at the hydrophobic site of the protein HSA. Due to the strong binding ability of MDMANA with HSA, it is successfully utilized for the study of stabilizing action of anionic surfactant Sodium Dodecyl Sulphate to the unfolding and folding of protein with denaturant urea in concentration range 1M to 9M.

Water-soluble, neutral 3,5-diformyl-BODIPY with extended fluorescence lifetime in a self-healable chitosan hydrogel.

PubMed

Belali, Simin; Emandi, Ganapathi; Cafolla, Atillio A; O'Connell, Barry; Haffner, Benjamin; Möbius, Matthias E; Karimi, Alireza; Senge, Mathias O

2017-11-08

3,5-Diformyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (3,5-diformyl-BODIPY) can be used as an efficient biofunctional cross-linker to generate a new class of chitosan-based hydrogels with fluorescence resonance energy transfer (FRET) dynamics and good solubility in water. The hydrogel was fully characterized by FT-IR, UV-vis, fluorescence, FE-SEM, AFM, rheology and picosecond time-resolved spectroscopic techniques. The self-healing ability was demonstrated by rheological recovery and macroscopic and microscopic observations. The fluorescence lifetime was found to increase in aqueous solution of the BODIPY-chitosan hydrogel compared to the 3,5-diformyl-BODIPY monomer. Calculations based on experimental results such as red-shift and decreased intensity of the emission spectrum of highly dye-concentrated hydrogel in comparison to dilute hydrogels, together with changes in the fluorescence lifetime of the hydrogel at different concentration of dyes, suggest that the BDP-CS hydrogels fluorescence dynamics obey the Förster resonance energy transfer (FRET). Improvements in mechanical and photochemical properties and the acceptable values of BODIPY fluorescence lifetime in the hydrogel matrix indicate the utility of the newly synthesized hydrogels for biomedical applications.

Efficiency of noncoherent photon upconversion by triplet-triplet annihilation: the C60 plus anthanthrene system and the importance of tuning the triplet energies.

PubMed

Sugunan, Sunish K; Greenwald, Chelsea; Paige, Matthew F; Steer, Ronald P

2013-07-03

As part of a continuing effort to find noncoherent photon upconversion (NCPU) systems with improved energy conversion efficiencies, the photophysics of the blue emitter, anthanthrene (An), and the fullerene absorber-sensitizer, C60, have been examined by both steady-state and pulsed laser techniques. An is a promising candidate for NCPU by homomolecular triplet-triplet annihilation (TTA) because its triplet state lies ∼800 cm(-1) below the triplet energy of the C60 donor (thereby improving efficiency by reducing back triplet energy transfer), and its fluorescent singlet state lies in near resonance with double its triplet energy (thus minimizing thermal energy losses in the annihilation process). In fluid solution, efficient triplet-triplet donor-acceptor energy transfer is observed, and rate constants for homomolecular TTA in the An acceptor are estimated to approach the diffusion limit. NCPU is also observed in An + C60 in poly(methylmethacrylate) thin films.

Experimental verification of the kinetic theory of FRET using optical microspectroscopy and obligate oligomers.

PubMed

Patowary, Suparna; Pisterzi, Luca F; Biener, Gabriel; Holz, Jessica D; Oliver, Julie A; Wells, James W; Raicu, Valerică

2015-04-07

Förster resonance energy transfer (FRET) is a nonradiative process for the transfer of energy from an optically excited donor molecule (D) to an acceptor molecule (A) in the ground state. The underlying theory predicting the dependence of the FRET efficiency on the sixth power of the distance between D and A has stood the test of time. In contrast, a comprehensive kinetic-based theory developed recently for FRET efficiencies among multiple donors and acceptors in multimeric arrays has waited for further testing. That theory has been tested in the work described in this article using linked fluorescent proteins located in the cytoplasm and at the plasma membrane of living cells. The cytoplasmic constructs were fused combinations of Cerulean as donor (D), Venus as acceptor (A), and a photo-insensitive molecule (Amber) as a nonfluorescent (N) place holder: namely, NDAN, NDNA, and ADNN duplexes, and the fully fluorescent quadruplex ADAA. The membrane-bound constructs were fused combinations of GFP2 as donor (D) and eYFP as acceptor (A): namely, two fluorescent duplexes (i.e., DA and AD) and a fluorescent triplex (ADA). According to the theory, the FRET efficiency of a multiplex such as ADAA or ADA can be predicted from that of analogs containing a single acceptor (e.g., NDAN, NDNA, and ADNN, or DA and AD, respectively). Relatively small but statistically significant differences were observed between the measured and predicted FRET efficiencies of the two multiplexes. While elucidation of the cause of this mismatch could be a worthy endeavor, the discrepancy does not appear to question the theoretical underpinnings of a large family of FRET-based methods for determining the stoichiometry and quaternary structure of complexes of macromolecules in living cells. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Energy efficiency buildings program

NASA Astrophysics Data System (ADS)

1981-05-01

Progress is reported in developing techniques for auditing the energy performance of buildings. The ventilation of buildings and indoor air quality is discussed from the viewpoint of (1) combustion generated pollutants; (2) organic contaminants; (3) radon emanation, measurements, and control; (4) strategies for the field monitoring of indoor air quality; and (5) mechanical ventilation systems using air-to-air heat exchanges. The development of energy efficient windows to provide optimum daylight with minimal thermal losses in cold weather and minimum thermal gain in hot weather is considered as well as the production of high frequency solid state ballasts for fluorescent lights to provide more efficient lighting at a 25% savings over conventional core ballasts. Data compilation, analysis, and demonstration activities are summarized.

High-efficiency in situ resonant inelastic x-ray scattering (iRIXS) endstation at the Advanced Light Source

DOE PAGES

Qiao, Ruimin; Li, Qinghao; Zhuo, Zengqing; ...

2017-03-17

In this paper, an endstation with two high-efficiency soft x-ray spectrographs was developed at Beamline 8.0.1 of the Advanced Light Source, Lawrence Berkeley National Laboratory. The endstation is capable of performing soft x-ray absorption spectroscopy, emission spectroscopy, and, in particular, resonant inelastic soft x-ray scattering (RIXS). Two slit-less variable line-spacing grating spectrographs are installed at different detection geometries. The endstation covers the photon energy range from 80 to 1500 eV. For studying transition-metal oxides, the large detection energy window allows a simultaneous collection of x-ray emission spectra with energies ranging from the O K-edge to the Ni L-edge without movingmore » any mechanical components. The record-high efficiency enables the recording of comprehensive two-dimensional RIXS maps with good statistics within a short acquisition time. By virtue of the large energy window and high throughput of the spectrographs, partial fluorescence yield and inverse partial fluorescence yield signals could be obtained for all transition metal L-edges including Mn. Finally and moreover, the different geometries of these two spectrographs (parallel and perpendicular to the horizontal polarization of the beamline) provide contrasts in RIXS features with two different momentum transfers.« less

OppoRTUnities Abound

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

Deru, Michael

According to the U.S. Energy Information Administration, HVAC accounts for approximately 38 percent of U.S. commercial buildings' primary energy consumption and a slightly higher percentage of their greenhouse-gas emissions. We have seen incredible gains made with lighting, going from incandescent and T12 fluorescent bulbs to high-efficiency LEDS, but there are even greater advances to be made with HVAC. Gains of 20 percent to 30 percent easily can be made by replacing older degraded equipment with new high-efficiency equipment. Even more savings are possible with an integrated engineering approach yielding optimized system designs combined with highly efficient controls.

Spectral response characterization of CdTe sensors of different pixel size with the IBEX ASIC

NASA Astrophysics Data System (ADS)

Zambon, P.; Radicci, V.; Trueb, P.; Disch, C.; Rissi, M.; Sakhelashvili, T.; Schneebeli, M.; Broennimann, C.

2018-06-01

We characterized the spectral response of CdTe sensors with different pixel sizes - namely 75, 150 and 300 μm - bonded to the latest generation IBEX single photon counting ASIC developed at DECTRIS, to detect monochromatic X-ray energy in the range 10-60 keV. We present a comparison of pulse height spectra recorded for several energies, showing the dependence on the pixel size of the non-trivial atomic fluorescence and charge sharing effects that affect the detector response. The extracted energy resolution, in terms of full width at half maximum or FWHM, ranges from 1.5 to 4 keV according to the pixel size and chip configuration. We devoted a careful analysis to the Quantum Efficiency and to the Spectral Efficiency - a newly-introduced measure that quantifies the impact of fluorescence and escape phenomena on the spectrum integrity in high- Z material based detectors. We then investigated the influence of the photon flux on the aforementioned quantities up to 180 ṡ 106 cts/s/mm2 and 50 ṡ 106 cts/s/mm2 for the 150 μm and 300 μm pixel case, respectively. Finally, we complemented the experimental data with analytical and with Monte Carlo simulations - taking into account the stochastic nature of atomic fluorescence - with an excellent agreement.

Molecular approaches to third generation photovoltaics: photochemical up-conversion

NASA Astrophysics Data System (ADS)

Cheng, Yuen Yap; Fückel, Burkhard; Roberts, Derrick A.; Khoury, Tony; Clady, Rapha"l. G. C. R.; Tayebjee, Murad J. Y.; Piper, Roland; Ekins-Daukes, N. J.; Crossley, Maxwell J.; Schmidt, Timothy W.

2010-08-01

We have investigated a photochemical up-conversion system comprising a molecular mixture of a palladium porphyrin to harvest light, and a polycyclic aromatic hydrocarbon to emit light. The energy of harvested photons is stored as molecular triplet states which then annihilate to bring about up-converted fluorescence. The limiting efficiency of such triplet-triplet annihilation up-conversion has been believed to be 11% for some time. However, by rigorously investigating the kinetics of delayed fluorescence following pulsed excitation, we demonstrate instantaneous annihilation efficiencies exceeding 40%, and limiting efficiencies for the current system of ~60%. We attribute the high efficiencies obtained to the electronic structure of the emitting molecule, which exhibits an exceptionally high T2 molecular state. We utilize the kinetic data obtained to model an up-converting layer irradiated with broadband sunlight, finding that ~3% efficiencies can be obtained with the current system, with this improving dramatically upon optimization of various parameters.

Extended Fluorescent Resonant Energy Transfer in DNA Constructs

NASA Astrophysics Data System (ADS)

Oh, Taeseok

This study investigates the use of surfactants and metal cations for the enhancement of long range fluorescent resonant energy transfer (FRET) and the antenna effect in DNA structures with multiple fluorescent dyes. Double-stranded (ds) DNA structures were formed by hybridization of 21mer DNA oligonucleotides with different arrangements of three fluorescent TAMRA donor dyes with two different complementary 21mer oligonucleotides with one fluorescent TexasRed acceptor dye. In such DNA structures, hydrophobic interactions between the fluorescent dyes in close proximity produces dimerization which along with other quenching mechanisms leads to significant reduction of fluorescent emission properties. Addition of the surfactants Triton X-100, cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) along with sodium cations (Na+) and divalent magnesium cations (Mg 2+) were tested for their ability to reduce quenching of the fluorescent dyes and improve overall fluorescent emission, the long range FRET and the antenna effect properties. When the neutral (uncharged) surfactant Triton X-100 was added to the FRET ds-DNA hybrid structures with three TAMRA donors and one TexasRed acceptor, dye dimerization and emission quenching remained unaffected. However, for the positively charged CTAB surfactant at concentrations of 100 uM or higher, the neutralization of the negatively charged ds-DNA backbone by the cationic surfactant micelles was found to reduce TAMRA dye dimerization and emission quenching and improve TexasRed quantum yield, resulting in much higher FRET efficiencies and an enhanced antenna effect. This improvement is likely due to the CTAB molecules covering or sheathing the fluorescent donor and acceptor dyes which breaks up the dimerized dye complexes and prevents further quenching from interactions with water molecules and guanine bases in the DNA structure. While the negatively charged SDS surfactant alone was not able to reduce dimerization and emission quenching due to repulsive forces between DNA and SDS micelles, the addition of cations such as sodium ions (Na+) and divalent magnesium ions (Mg2+) did lead to a significant reduction in the dimerization and emission quenching resulting in much higher FRET efficiency and an enhanced antenna effect. It appears that when the repulsive electrostatic forces are screened by the cations (Mg2+ in particular), the SDS micelles can approach the FRET ds-DNA structures thereby sheathing or insulating the TAMRA and TexasRed dyes. Overall, the study provides a viable strategy for using combinations of surfactants and cations to reduce adverse fluorescent dye and other quenching mechanisms and improve the overall long distance FRET efficiency and the antenna effect in DNA structures with multi-donor and single acceptor fluorescent dye groups.

UV emissions from low energy artificial light sources.

PubMed

Fenton, Leona; Moseley, Harry

2014-01-01

Energy efficient light sources have been introduced across Europe and many other countries world wide. The most common of these is the Compact Fluorescent Lamp (CFL), which has been shown to emit ultraviolet (UV) radiation. Light Emitting Diodes (LEDs) are an alternative technology that has minimal UV emissions. This brief review summarises the different energy efficient light sources available on the market and compares the UV levels and the subsequent effects on the skin of normal individuals and those who suffer from photodermatoses. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Light Sources and Ballast Circuits

NASA Astrophysics Data System (ADS)

Yorifuji, Takashi; Sakai, Makoto; Yasuda, Takeo; Maehara, Akiyoshi; Okada, Atsunori; Gouriki, Takeshi; Mannami, Tomoaki

According to the machinery statistics by Ministry of Economy, Trade and Industry (METI), the total of domestic light bulb production in 2006 was 1,101 million (88.5% year-on-year). Production for general purpose illumination light bulbs and halogen light bulbs accounted for 122 million (99.2% y/y) and 45 million (96.3% y/y), respectively. The total of fluorescent lamp production was 988 million (114.9%) and the production of general purpose fluorescent lamps excluding backlights accounted for 367 million (101.7% y/y). Further, HID lamp production was 10 million (106.3% y/y). What is noteworthy regarding such lamp production is that, similar to the previous year, the sales volume (amount) of lamps for general illumination exceeded 100% against the previous year, indicating a steady shift to high value added products. Major lighting exhibitions in 2006 included the Light + Building Trade Fair held in Frankfurt in April and the Light Fair International 2006 held in Las Vegas, U.S.A. in May, both of which demonstrated signs of acceleration toward energy saving, high efficiency and resource saving. As for incandescent lamps, products filled with larger atomic weight gases aiming at higher efficiency/longer life are becoming the mainstream. As for new technologies, it was experimentally demonstrated that infrared radiation can be suppressed by processing micro cavities to metal plates made of tungsten, tantalum, etc. For fluorescent lamps, straight and circular fluorescent lamps achieving a longer life/higher luminous flux maintenance factor continued to be widely developed/launched again this year. For compact fluorescent lamps, energy saving/high efficiency products, multifunctional type products combined with LED and new shaped products were launched. As to HID lamps, ceramic metal halide lamps with high efficiency, improved color rendering, longer life and higher luminous flux maintenance factor were commercialized one after another. Numerous studies and analyses, on discharge models were reported. Further, studies on ultra high-pressure mercury lamps as light sources for projectors are becoming the mainstream of HID lamp related researches. For high-pressure sodium lamps, many studies on plant growing and pest control utilizing low insect attracting aspects were also reported in 2006. Additionally, for discharge lamps, the minimum sustaining electric power for arc tubes employed in electrode-less compact fluorescent lamps was investigated. For Hg-free rare-gas fluorescent lamps, a luminance of 10,000cd/m2 was attained by a 1 meter-long external duplex spiral electrode prototype using Xe/Ne barrier discharge. As to startup circuits, the commercialization of energy saving and high value added products mainly associated with fluorescent lamps and HID lamps are becoming common. Further, the miniaturization of startup circuits for self electronic-ballasted lamps has advanced. Speaking of the overall light sources and startup circuits in 2006 and with the enforcement of RoHS in Europe in July, the momentum toward hazardous substance-free and energy saving initiatives has been enhanced from the perspective of protecting the global environment. It is anticipated that similar restrictions will be globally enforced in the future.

Multiexcitation Fluorogenic Labeling of Surface, Intracellular, and Total Protein Pools in Living Cells

PubMed Central

2016-01-01

Malachite green (MG) is a fluorogenic dye that shows fluorescence enhancement upon binding to its engineered cognate protein, a fluorogen activating protein (FAP). Energy transfer donors such as cyanine and rhodamine dyes have been conjugated with MG to modify the spectral properties of the fluorescent complexes, where the donor dyes transfer energy through Förster resonance energy transfer to the MG complex resulting in binding-conditional fluorescence emission in the far-red region. In this article, we use a violet-excitable dye as a donor to sensitize the far-red emission of the MG-FAP complex. Two blue emitting fluorescent coumarin dyes were coupled to MG and evaluated for energy transfer to the MG-FAP complex via its secondary excitation band. 6,8-Difluoro-7-hydroxycoumarin-3-carboxylic acid (Pacific blue, PB) showed the most efficient energy transfer and maximum brightness in the far-red region upon violet (405 nm) excitation. These blue-red (BluR) tandem dyes are spectrally varied from other tandem dyes and are able to produce fluorescence images of the MG-FAP complex with a large Stokes shift (>250 nm). These dyes are cell-permeable and are used to label intracellular proteins. Used together with a cell-impermeable hexa-Cy3-MG (HCM) dye that labels extracellular proteins, we are able to visualize extracellular, intracellular, and total pools of cellular protein using one fluorogenic tag that combines with distinct dyes to effect different spectral characteristics. PMID:27159569

Purple-bacterial photosynthetic reaction centers and quantum-dot hybrid-assemblies in lecithin liposomes and thin films.

PubMed

Lukashev, Eugeny P; Knox, Petr P; Gorokhov, Vladimir V; Grishanova, Nadezda P; Seifullina, Nuranija Kh; Krikunova, Maria; Lokstein, Heiko; Paschenko, Vladimir Z

2016-11-01

Quantum dots (QDs) absorb ultraviolet and long-wavelength visible light energy much more efficiently than natural bacterial light-harvesting proteins and can transfer the excitation energy to photosynthetic reaction centers (RCs). Inclusion of RCs combined with QDs as antennae into liposomes opens new opportunities for using such hybrid systems as a basis for artificial energy-transforming devices that potentially can operate with greater efficiency and stability than devices based only on biological components or inorganic components alone. RCs from Rhodobacter sphaeroides and QDs (CdSe/ZnS with hydrophilic covering) were embedded in lecithin liposomes by extrusion of a solution of multilayer lipid vesicles through a polycarbonate membrane or by dialysis of lipids and proteins dispersed with excess detergent. The efficiency of RC and QD interaction within the liposomes was estimated using fluorescence excitation spectra of the photoactive bacteriochlorophyll of the RCs and by measuring the fluorescence decay kinetics of the QDs. The functional activity of the RCs in hybrid complexes was fully maintained, and their stability was even increased. The efficiency of energy transfer between QDs and RCs and conditions of long-term stability of function of such hybrid complexes in film preparations were investigated as well. It was found that dry films containing RCs and QDs, maintained at atmospheric humidity, are capable of maintaining their functional activity for at least some months as judged by measurements of their spectral characteristics, efficiency of energy transfer from QDs to RCs and RC electron transport activity. Addition of trehalose to the films increases the stability further, especially for films maintained at low humidity. These stable hybrid film structures are promising for further studies towards developing new phototransformation devices for biotechnological applications. Copyright © 2016 Elsevier B.V. All rights reserved.

In vivo fluorescence lifetime tomography of a FRET probe expressed in mouse

PubMed Central

McGinty, James; Stuckey, Daniel W.; Soloviev, Vadim Y.; Laine, Romain; Wylezinska-Arridge, Marzena; Wells, Dominic J.; Arridge, Simon R.; French, Paul M. W.; Hajnal, Joseph V.; Sardini, Alessandro

2011-01-01

Förster resonance energy transfer (FRET) is a powerful biological tool for reading out cell signaling processes. In vivo use of FRET is challenging because of the scattering properties of bulk tissue. By combining diffuse fluorescence tomography with fluorescence lifetime imaging (FLIM), implemented using wide-field time-gated detection of fluorescence excited by ultrashort laser pulses in a tomographic imaging system and applying inverse scattering algorithms, we can reconstruct the three dimensional spatial localization of fluorescence quantum efficiency and lifetime. We demonstrate in vivo spatial mapping of FRET between genetically expressed fluorescent proteins in live mice read out using FLIM. Following transfection by electroporation, mouse hind leg muscles were imaged in vivo and the emission of free donor (eGFP) in the presence of free acceptor (mCherry) could be clearly distinguished from the fluorescence of the donor when directly linked to the acceptor in a tandem (eGFP-mCherry) FRET construct. PMID:21750768

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

Bazalova, M; Ahmad, M; Fahrig, R

Purpose: To evaluate x-ray fluorescence computed tomography induced with proton beams (pXFCT) for imaging of gold contrast agent. Methods: Proton-induced x-ray fluorescence was studied by means of Monte Carlo (MC) simulations using TOPAS, a MC code based on GEANT4. First, proton-induced K-shell and L-shell fluorescence was studied as a function of proton beam energy and 1) depth in water and 2) size of contrast object. Second, pXFCT images of a 2-cm diameter cylindrical phantom with four 5- mm diameter contrast vials and of a 20-cm diameter phantom with 1-cm diameter vials were simulated. Contrast vials were filled with water andmore » water solutions with 1-5% gold per weight. Proton beam energies were varied from 70-250MeV. pXFCT sinograms were generated based on the net number of gold K-shell or L-shell x-rays determined by interpolations from the neighboring 0.5keV energy bins of spectra collected with an idealized 4π detector. pXFCT images were reconstructed with filtered-back projection, and no attenuation correction was applied. Results: Proton induced x-ray fluorescence spectra showed very low background compared to x-ray induced fluorescence. Proton induced L-shell fluorescence had a higher cross-section compared to K-shell fluorescence. Excitation of L-shell fluorescence was most efficient for low-energy protons, i.e. at the Bragg peak. K-shell fluorescence increased with increasing proton beam energy and object size. The 2% and 5% gold contrast vials were accurately reconstructed in K-shell pXFCT images of both the 2-cm and 20-cm diameter phantoms. Small phantom L-shell pXFCT image required attenuation correction and had a higher sensitivity for 70MeV protons compared to 250MeV protons. With attenuation correction, L-shell pXFCT might be a feasible option for imaging of small size (∼2cm) objects. Imaging doses for all simulations were 5-30cGy. Conclusion: Proton induced x-ray fluorescence CT promises to be an alternative quantitative imaging technique to the commonly considered XFCT imaging with x-ray beams.« less

Versatile Molecular Functionalization for Inhibiting Concentration Quenching of Thermally Activated Delayed Fluorescence.

PubMed

Lee, Jiyoung; Aizawa, Naoya; Numata, Masaki; Adachi, Chihaya; Yasuda, Takuma

2017-01-01

Concentration quenching of thermally activated delayed fluorescence is found to be dominated by electron-exchange interactions, as described by the Dexter energy-transfer model. Owing to the short-range nature of the electron-exchange interactions, even a small modulation in the molecular geometric structure drastically affects the concentration-quenching, leading to enhanced solid-state photoluminescence and electroluminescence quantum efficiencies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Grayson, Katie J.; Faries, Kaitlyn M.; Huang, Xia

Photosynthesis uses a limited range of the solar spectrum, so enhancing spectral coverage could improve the efficiency of light capture. Here, we show that a hybrid reaction centre (RC)/yellow fluorescent protein (YFP) complex accelerates photosynthetic growth in the bacterium Rhodobacter sphaeroides. The structure of the RC/YFP-light-harvesting 1 (LH1) complex shows the position of YFP attachment to the RC-H subunit, on the cytoplasmic side of the RC complex. Fluorescence lifetime microscopy of whole cells and ultrafast transient absorption spectroscopy of purified RC/YFP complexes show that the YFP–RC intermolecular distance and spectral overlap between the emission of YFP and the visible-region (Qmore » X) absorption bands of the RC allow energy transfer via a Fo¨rster mechanism, with an efficiency of 40±10%. Finally, this proof-of-principle study demonstrates the feasibility of increasing spectral coverage for harvesting light using non-native genetically-encoded light-absorbers, thereby augmenting energy transfer and trapping in photosynthesis.« less

Photophysical properties gallium octacarboxy phthalocyanines conjugated to CdSe@ZnS quantum dots.

PubMed

Tshangana, Charmaine; Nyokong, Tebello

2015-01-01

L-Glutathione (GSH) capped core CdSe (2.3 nm) and core shell CdSe@ZnS quantum dots (QDs) (3.0 nm and 3.5 nm) were coordinated to gallium octacarboxy phthalocyanine (ClGaPc(COOH)8) to form ClGaPc(COOH)8-QDs conjugates. An efficient transfer of energy from the QDs to the Pcs was demonstrated through Förster resonance energy transfer (FRET), the FRET efficiencies in all cases was above 50%. The photophysical parameters (triplet state and fluorescence quantum yields and lifetimes) were also determined for the conjugates. There was a decrease in the fluorescence lifetimes of ClGaPc(COOH)8 in the presence of all the QDs, due to the heavy atom effect. The triplet quantum yields increased in the conjugates. The lifetimes also became longer for the conjugates compared to Pc alone. Copyright © 2015 Elsevier B.V. All rights reserved.

In vivo imaging of endogenous enzyme activities using luminescent 1,2-dioxetane compounds.

PubMed

Tseng, Jen-Chieh; Kung, Andrew L

2015-06-24

Here we present a non-invasive imaging method for visualizing endogenous enzyme activities in living animals. This optical imaging method is based on an energy transfer principle termed chemically initiated electron exchange luminescence (CIEEL). The light energy is provided by enzymatic activation of metastable 1,2-dioxetane substrates, whose protective groups are removed by hydrolytic enzymes such as β-galactosidase and alkaline phosphatase. In the presence of a nearby fluorescent recipient, the chemical energy within the activated substrate is then transferred via formation of a charge-transfer complex with the fluorophore, a mechanism closely related to glow stick chemistry. Efficient CIEEL energy transfer requires close proximity between the trigger enzyme and the fluorescent recipient. Using cells stained with fluorescent dialkylcarbocyanines as the energy recipients, we demonstrated CIEEL imaging of cellular β-galactosidase or alkaline phosphatase activity. In living animals, we used a similar approach to non-invasively image alkaline phosphatase activity in the peritoneal cavity. In this report, we provide proof-of-concept for CIEEL imaging of in vivo enzymatic activity. In addition, we demonstrate the use of CIEEL energy transfer for visualizing elevated alkaline phosphatase activity associated with tissue inflammation in living animals.

White organic light-emitting diodes with fluorescent tube efficiency.

PubMed

Reineke, Sebastian; Lindner, Frank; Schwartz, Gregor; Seidler, Nico; Walzer, Karsten; Lüssem, Björn; Leo, Karl

2009-05-14

The development of white organic light-emitting diodes (OLEDs) holds great promise for the production of highly efficient large-area light sources. High internal quantum efficiencies for the conversion of electrical energy to light have been realized. Nevertheless, the overall device power efficiencies are still considerably below the 60-70 lumens per watt of fluorescent tubes, which is the current benchmark for novel light sources. Although some reports about highly power-efficient white OLEDs exist, details about structure and the measurement conditions of these structures have not been fully disclosed: the highest power efficiency reported in the scientific literature is 44 lm W(-1) (ref. 7). Here we report an improved OLED structure which reaches fluorescent tube efficiency. By combining a carefully chosen emitter layer with high-refractive-index substrates, and using a periodic outcoupling structure, we achieve a device power efficiency of 90 lm W(-1) at 1,000 candelas per square metre. This efficiency has the potential to be raised to 124 lm W(-1) if the light outcoupling can be further improved. Besides approaching internal quantum efficiency values of one, we have also focused on reducing energetic and ohmic losses that occur during electron-photon conversion. We anticipate that our results will be a starting point for further research, leading to white OLEDs having efficiencies beyond 100 lm W(-1). This could make white-light OLEDs, with their soft area light and high colour-rendering qualities, the light sources of choice for the future.

The "Green Lab": Power Consumption by Commercial Light Bulbs

ERIC Educational Resources Information Center

Einsporn, James A.; Zhou, Andrew F.

2011-01-01

Going "green" is a slogan that is very contemporary, both with industry and in the political arena. Choosing more energy-efficient devices is one way homeowners can "go green." A simple method is to change home lighting from hot incandescent bulbs to compact fluorescent lights (CFLs). But do they really save energy? How do their illuminations…

[Interaction between strychnine and bovine serum albumin].

PubMed

Zhao, Jin; Wang, Zhi; Wu, Qiu-hua; Yang, Xiu-min; Wang, Chun; Hu, Yan-xue

2006-07-01

To study the interaction between strychnine and bovine serum albumin. Fluorescence spectroscopy and ultraviolet spectroscopy were used. The static quenching and the non-radiation energy transfer are the two main reasons to leading the fluorescence quenching of BSA. The apparent combining constants (K(A)) between strychnine and BSA are 3.72 x 10(3) at 27 degrees C, 4.27 x 10(3) at 37 degrees C, 4.47 x 10(3) at 47 degrees C and the combining sites are 1.01 +/- 0.03. The combining distance (r = 3.795 nm) and energy transfer efficiency (E = 0.0338) are obtained by Förster's non-radiation energy transfer mechanism. The interaction between strychnine and BSA was driven mainly by hydrophobic force.

Rapid Global Fitting of Large Fluorescence Lifetime Imaging Microscopy Datasets

PubMed Central

Warren, Sean C.; Margineanu, Anca; Alibhai, Dominic; Kelly, Douglas J.; Talbot, Clifford; Alexandrov, Yuriy; Munro, Ian; Katan, Matilda

2013-01-01

Fluorescence lifetime imaging (FLIM) is widely applied to obtain quantitative information from fluorescence signals, particularly using Förster Resonant Energy Transfer (FRET) measurements to map, for example, protein-protein interactions. Extracting FRET efficiencies or population fractions typically entails fitting data to complex fluorescence decay models but such experiments are frequently photon constrained, particularly for live cell or in vivo imaging, and this leads to unacceptable errors when analysing data on a pixel-wise basis. Lifetimes and population fractions may, however, be more robustly extracted using global analysis to simultaneously fit the fluorescence decay data of all pixels in an image or dataset to a multi-exponential model under the assumption that the lifetime components are invariant across the image (dataset). This approach is often considered to be prohibitively slow and/or computationally expensive but we present here a computationally efficient global analysis algorithm for the analysis of time-correlated single photon counting (TCSPC) or time-gated FLIM data based on variable projection. It makes efficient use of both computer processor and memory resources, requiring less than a minute to analyse time series and multiwell plate datasets with hundreds of FLIM images on standard personal computers. This lifetime analysis takes account of repetitive excitation, including fluorescence photons excited by earlier pulses contributing to the fit, and is able to accommodate time-varying backgrounds and instrument response functions. We demonstrate that this global approach allows us to readily fit time-resolved fluorescence data to complex models including a four-exponential model of a FRET system, for which the FRET efficiencies of the two species of a bi-exponential donor are linked, and polarisation-resolved lifetime data, where a fluorescence intensity and bi-exponential anisotropy decay model is applied to the analysis of live cell homo-FRET data. A software package implementing this algorithm, FLIMfit, is available under an open source licence through the Open Microscopy Environment. PMID:23940626

Charge transfer fluorescence and 34 nm exciton diffusion length in polymers with electron acceptor end traps

DOE PAGES

Zaikowski, Lori; Mauro, Gina; Bird, Matthew; ...

2014-12-22

Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17 to 127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence and DFT descriptions. Quantum yields of CT fluorescence are asmore » large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps the trap depths are 0.06 (p-xylene), 0.13 (THF) and 0.19 eV (CHCl 3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ~50% of the excitons, and that the exciton diffusion length L D =34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. As a result, the efficiency of exciton capture depends on chain length, but not on trap depth, solvent polarity or which trap group is present.« less

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant.

PubMed

Zhang, Tianyou; Zhao, Bo; Chu, Bei; Li, Wenlian; Su, Zisheng; Yan, Xingwu; Liu, Chengyuan; Wu, Hairuo; Gao, Yuan; Jin, Fangming; Hou, Fuhua

2015-05-15

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies.

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant

NASA Astrophysics Data System (ADS)

Zhang, Tianyou; Zhao, Bo; Chu, Bei; Li, Wenlian; Su, Zisheng; Yan, Xingwu; Liu, Chengyuan; Wu, Hairuo; Gao, Yuan; Jin, Fangming; Hou, Fuhua

2015-05-01

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies.

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant

PubMed Central

Zhang, Tianyou; Zhao, Bo; Chu, Bei; Li, Wenlian; Su, Zisheng; Yan, Xingwu; Liu, Chengyuan; Wu, Hairuo; Gao, Yuan; Jin, Fangming; Hou, Fuhua

2015-01-01

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies. PMID:25975371

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

PubMed

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

2015-06-15

This paper reports a novel nanosensor for organophosphorus pesticides based on the fluorescence resonance energy transfer (FRET) between NaYF4:Yb,Er upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs). The detection mechanism is based on the facts that AuNPs quench the fluorescence of UCNPs and organophosphorus pesticides (OPs) inhibit the activity of acetylcholinesterase (AChE) which catalyzes the hydrolysis of acetylthiocholine (ATC) into thiocholine. Under the optimized conditions, the logarithm of the pesticides concentration was proportional to the inhibition efficiency. The detection limits of parathion-methyl, monocrotophos and dimethoate reached 0.67, 23, and 67 ng/L, respectively. Meanwhile, the biosensor shows good sensitivity, stability, and could be successfully applied to detection of OPs in real food samples, suggesting the biosensor has potentially extensive application clinic diagnoses assays. Copyright © 2014 Elsevier B.V. All rights reserved.

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

PubMed

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

2017-07-19

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

Distance distributions of short polypeptides recovered by fluorescence resonance energy transfer in the 10 A domain.

PubMed

Sahoo, Harekrushna; Roccatano, Danilo; Zacharias, Martin; Nau, Werner M

2006-06-28

Fluorescence resonance energy transfer (FRET) between tryptophan (Trp) as donor and 2,3-diazabicyclo[2.2.2]oct-2-ene (Dbo) as acceptor was studied by steady-state and time-resolved fluorescence spectroscopy. The unique feature of this FRET pair is its exceptionally short Förster radius (10 A), which allows one to recover distance distributions in very short structureless peptides. The technique was applied to Trp-(GlySer)n-Dbo-NH2 peptides with n = 0-10, for which the average probe/quencher distance ranged between 8.7 and 13.7 A experimentally (in propylene glycol, analysis according to wormlike chain model) and 8.6-10.2 A theoretically (for n = 0-6, GROMOS96 molecular dynamics simulations). The larger FRET efficiency in steady-state compared to time-resolved fluorescence experiments was attributed to a static quenching component, suggesting that a small but significant part (ca. 10%) of the conformations are already in van der Waals contact when excitation occurs.

Ultrafast fluorescent decay induced by metal-mediated dipole–dipole interaction in two-dimensional molecular aggregates

DOE PAGES

Hu, Qing; Jin, Dafei; Xiao, Jun; ...

2017-09-05

Two-dimensional molecular aggregate (2DMA), a thin sheet of strongly interacting dipole molecules self-assembled at close distance on an ordered lattice, is a fascinating fluorescent material. It is distinctively different from the conventional (single or colloidal) dye molecules and quantum dots. Here, in this paper, we verify that when a 2DMA is placed at a nanometric distance from a metallic substrate, the strong and coherent interaction between the dipoles inside the 2DMA dominates its fluorescent decay at a picosecond timescale. Our streak-camera lifetime measurement and interacting lattice–dipole calculation reveal that the metal-mediated dipole–dipole interaction shortens the fluorescent lifetime to about one-halfmore » and increases the energy dissipation rate by 10 times that expected from the noninteracting single-dipole picture. In conclusion, our finding can enrich our understanding of nanoscale energy transfer in molecular excitonic systems and may designate a unique direction for developing fast and efficient optoelectronic devices.« less

A Leaf-Inspired Luminescent Solar Concentrator for Energy-Efficient Continuous-Flow Photochemistry.

PubMed

Cambié, Dario; Zhao, Fang; Hessel, Volker; Debije, Michael G; Noël, Timothy

2017-01-19

The use of solar light to promote chemical reactions holds significant potential with regard to sustainable energy solutions. While the number of visible light-induced transformations has increased significantly, the use of abundant solar light has been extremely limited. We report a leaf-inspired photomicroreactor that constitutes a merger between luminescent solar concentrators (LSCs) and flow photochemistry to enable green and efficient reactions powered by solar irradiation. This device based on fluorescent dye-doped polydimethylsiloxane collects sunlight, focuses the energy to a narrow wavelength region, and then transports that energy to embedded microchannels where the flowing reactants are converted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

NaEuF4/Au@Ag2S nanoparticles-based fluorescence resonant transfer DNA sensor for ultrasensitive detection of DNA energy.

PubMed

Liu, Yuhong; Zhao, Linlin; Zhang, Jin; Zhang, Jinzha; Zhao, Wenbo; Mao, Chun

2016-12-01

The work investigates a new fluorescence resonance energy transfer (FRET) system using NaEuF 4 nanoparticles (NPs) and Au@Ag 2 S NPs as the energy donor-acceptor pair for the first time. The NaEuF 4 /Au@Ag 2 S NPs-based FRET DNA sensor was constructed with NaEuF 4 NPs as the fluorescence (FL) donor and Au@Ag 2 S core-shell NPs as FL acceptor. In order to find the matching energy acceptor, the amount of AgNO 3 and Na 2 S were controlled in the synthesis process to overlap the absorption spectrum of energy acceptor with the emission spectrum of energy donors. The sensitivity of FRET-based DNA sensor can be enhanced and the self-absorption of ligand as well as the background of signals can be decreased because of Eu 3+ which owns large Stokes shifts and narrow emission bands due to f-f electronic transitions of 4f shell. We obtained the efficient FRET system by studying suitable distance between the donor and acceptor. Then the FRET-based DNA sensor was used for the design of specific and sensitive detection of target DNA and the quenching efficiency (ΔFL/F 0 , ΔFL=F-F 0 ) of FL was logarithmically related to the concentration of the target DNA, ranging from 100aM to 100pM. We can realize an ultrasensitive detection of target DNA with a detection limit of 32 aM. This proposed method was feasible to analyse target DNA in real samples with satisfactory results. Copyright © 2016 Elsevier B.V. All rights reserved.

Energy conservation through more efficient lighting.

PubMed

Maya, J; Grossman, M W; Lagushenko, R; Waymouth, J F

1984-10-26

The efficiency of a mercury-rare gas electrical discharge, which forms the basis of a fluorescent lamp, can be increased about 5 percent simply by increasing the concentration of mercury-196 from 0.146 percent (natural) to about 3 percent. These findings can be implemented immediately without any significant change in the process of manufacturing of this widely used source of illumination, provided that mercury-196 can be obtained economically. The potential energy savings for the United States are estimated to be worth in excess of $200 million per year.

CALiPER Exploratory Study. Recessed Troffer Lighting

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

Miller, N. J.; Royer, M. P.; Poplawski, M. E.

This CALiPER study examines the problems and benefits likely to be encountered with LED products intended to replace linear fluorescent lamps. LED dedicated troffers, replacement tubes, and non-tube retrofit kits were evaluated against fluorescent benchmark troffers in a simulated office space for photometric distribution, uniformity of light on the task surface, suitability of light output, flicker, dimming performance, color quality, power quality, safety and certification issues, ease of installation, energy efficiency, and life-cycle cost.

Intermolecular interaction approach for TADF (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wong, Ken-Tsung

2016-09-01

Materials with thermally activated delayed fluorescence (TADF) have recently emerged as new fluorescent emitters for highly efficient organic light-emitting diodes (OLEDs). Molecule with TADF behavior needs to have a small singlet-triplet energy difference (ΔES-T) that allows the up-conversion from nonradiative triplet state (T1) to radiative singlet state (S1) via reverse intersystem crossing (RISC) process. Generally, molecules with small ΔES-T can be obtained via carefully manipulate the degree of "intramolecular" charge transfer (ICT) between electron-donating and -accepting components, such that the electron exchange energy that contributes to ΔES-T, can be minimized. Alternatively, excited state with small ΔES-T can be feasibly realized via "intermolecular" charge transfer occurring at the interface between spatially separating donor (D) and acceptor (A) molecules. Because the exchange energy decreases as the HOMO-LUMO separation distance increases, theoretically, the intermolecular D/A charge transfer state (or exciplex) should have rather small ΔES-T, leading to efficient TADF. However, it is still a challenge to access highly efficient exciplex systems. This is mainly because exciplex formation is commonly accompanied with a large red shift of emission spectra and long radiative lifetime, which tend to diminish photoluminescence quantum yield (PLQY) as well as electroluminescence (EL) performance. Until now, exciplex-based OLEDs with external quantum efficiency (EQE) above 10% are still limited. By judicious selection of donor and acceptor, the formation of efficient exciplex can be feasibly achieved. In this conference, our recent efforts on highly efficient exciplexes using C3-symmetry triazine acceptors and various donors, and their device characteristics will be presented.

Near-infrared fluorescence imaging using organic dye nanoparticles.

PubMed

Yu, Jia; Zhang, Xiujuan; Hao, Xiaojun; Zhang, Xiaohong; Zhou, Mengjiao; Lee, Chun-Sing; Chen, Xianfeng

2014-03-01

Near-infrared (NIR) fluorescence imaging in the 700-1000 nm wavelength range has been very attractive for early detection of cancers. Conventional NIR dyes often suffer from limitation of low brightness due to self-quenching, insufficient photo- and bioenvironmental stability, and small Stokes shift. Herein, we present a strategy of using small-molecule organic dye nanoparticles (ONPs) to encapsulate NIR dyes to enable efficient fluorescence resonance energy transfer to obtain NIR probes with remarkably enhanced performance for in vitro and in vivo imaging. In our design, host ONPs are used as not only carriers to trap and stabilize NIR dyes, but also light-harvesting agent to transfer energy to NIR dyes to enhance their brightness. In comparison with pure NIR dyes, our organic dye nanoparticles possess almost 50-fold increased brightness, large Stokes shifts (∼250 nm) and dramatically enhanced photostability. With surface modification, these NIR-emissive organic nanoparticles have water-dispersity and size- and fluorescence- stability over pH values from 2 to 10 for almost 60 days. With these superior advantages, these NIR-emissive organic nanoparticles can be used for highly efficient folic-acid aided specific targeting in vivo and ex vivo cellular imaging. Finally, during in vivo imaging, the nanoparticles show negligible toxicity. Overall, the results clearly display a potential application of using the NIR-emissive organic nanoparticles for in vitro and in vivo imaging. Copyright © 2014 Elsevier Ltd. All rights reserved.

Photoinduced changes in photosystem II pigments

NASA Astrophysics Data System (ADS)

Andreeva, Atanaska S.; Busheva, Mira C.; Stoitchkova, Katerina V.; Tzonova, Iren K.

2010-11-01

The photosynthetic apparatus in higher plants performs two seemingly opposing tasks: efficient harvest of sunlight, but also rapid and harmless dissipation of excess light energy as heat to avoid deleterious photodamage. In order to study this process in pigment-protein supercomplexes of photosystem II (PSII), 77 K fluorescence and room temperature resonance Raman (RR) spectroscopy were applied to investigate the changes in structure and spectral properties of the pigments in spinach PSII membranes. The high-light treatment results in a strong quenching of the fluorescence (being largest when the excitation is absorbed by carotenoids) and a red-shift of the main maximum. Decomposition of the fluorescence spectra into four bands revealed intensive quenching of F685 and F695 bands, possible bleaching of chlorophyll a, enhanced extent of light harvesting complexes (LHCII) aggregation and increased energy transfer to aggregated LHCII. The analysis of RR spectra revealed the predominant contribution of ß-carotene (ß-Car) upon 457.8 and 488 nm excitations and lutein (Lut) at 514.5 nm. During prolonged exposure to strong light no significant bleaching of ß-Car and weak photobleaching of Lut is observed. The results will contribute to the efforts to produce more efficient and robust solar cells when exposed to fluctuations in light intensity.

Highly efficient blue and warm white organic light-emitting diodes with a simplified structure

NASA Astrophysics Data System (ADS)

Li, Xiang-Long; Ouyang, Xinhua; Chen, Dongcheng; Cai, Xinyi; Liu, Ming; Ge, Ziyi; Cao, Yong; Su, Shi-Jian

2016-03-01

Two blue fluorescent emitters were utilized to construct simplified organic light-emitting diodes (OLEDs) and the remarkable difference in device performance was carefully illustrated. A maximum current efficiency of 4.84 cd A-1 (corresponding to a quantum efficiency of 4.29%) with a Commission Internationale de l’Eclairage (CIE) coordinate of (0.144, 0.127) was achieved by using N,N-diphenyl-4″-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1, 1‧:4‧, 1″-terphenyl]-4-amine (BBPI) as a non-doped emission layer of the simplified blue OLEDs without carrier-transport layers. In addition, simplified fluorescent/phosphorescent (F/P) hybrid warm white OLEDs without carrier-transport layers were fabricated by utilizing BBPI as (1) the blue emitter and (2) the host of a complementary yellow phosphorescent emitter (PO-01). A maximum current efficiency of 36.8 cd A-1 and a maximum power efficiency of 38.6 lm W-1 were achieved as a result of efficient energy transfer from the host to the guest and good triplet exciton confinement on the phosphorescent molecules. The blue and white OLEDs are among the most efficient simplified fluorescent blue and F/P hybrid white devices, and their performance is even comparable to that of most previously reported complicated multi-layer devices with carrier-transport layers.

A facile approach for cupric ion detection in aqueous media using polyethyleneimine/PMMA core-shell fluorescent nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Jian; Zeng, Fang; Wu, Shuizhu; Su, Junhua; Zhao, Jianqing; Tong, Zhen

2009-09-01

A facile approach was developed to produce a dye-doped core-shell nanoparticle chemosensor for detecting Cu2+ in aqueous media. The core-shell nanoparticle sensor was prepared by a one-step emulsifier-free polymerization, followed by the doping of the fluorescent dye Nile red (9-diethylamino- 5H-benzo[alpha] phenoxazine-5-one, NR) into the particles. For the nanoparticles, the hydrophilic polyethyleneimine (PEI) chain segments serve as the shell and the hydrophobic polymethyl methacrylate (PMMA) constitutes the core of the nanoparticles. The non-toxic and biocompatible PEI chain segments on the nanoparticle surface exhibit a high affinity for Cu2+ ions in aqueous media, and the quenching of the NR fluorescence is observed upon binding of Cu2+ ions. This makes the core-shell nanoparticle system a water-dispersible chemosensor for Cu2+ ion detection. The quenching of fluorescence arises through intraparticle energy transfer (FRET) from the dye in the hydrophobic PMMA core to the Cu2+/PEI complexes on the nanoparticle surface. The energy transfer efficiency for PEI/PMMA particles with different diameters was determined, and it is found that the smaller nanoparticle sample exhibits higher quenching efficiency, and the limit for Cu2+ detection is 1 µM for a nanoparticle sample with a diameter of ~30 nm. The response of the fluorescent nanoparticle towards different metal ions was investigated and the nanoparticle chemosensor displays high selectivity and antidisturbance for the Cu2+ ion among the metal ions examined (Na+, K+, Mg2+, Ca2+, Zn2+, Hg2+, Mn2+, Fe2+, Ni2+, Co2+ and Pb2+). This emulsifier-free, biocompatible and sensitive fluorescent nanoparticle sensor may find applications in cupric ion detection in the biological and environmental areas.

A facile approach for cupric ion detection in aqueous media using polyethyleneimine/PMMA core-shell fluorescent nanoparticles.

PubMed

Chen, Jian; Zeng, Fang; Wu, Shuizhu; Su, Junhua; Zhao, Jianqing; Tong, Zhen

2009-09-09

A facile approach was developed to produce a dye-doped core-shell nanoparticle chemosensor for detecting Cu(2+) in aqueous media. The core-shell nanoparticle sensor was prepared by a one-step emulsifier-free polymerization, followed by the doping of the fluorescent dye Nile red (9-diethylamino- 5H-benzo[alpha] phenoxazine-5-one, NR) into the particles. For the nanoparticles, the hydrophilic polyethyleneimine (PEI) chain segments serve as the shell and the hydrophobic polymethyl methacrylate (PMMA) constitutes the core of the nanoparticles. The non-toxic and biocompatible PEI chain segments on the nanoparticle surface exhibit a high affinity for Cu(2+) ions in aqueous media, and the quenching of the NR fluorescence is observed upon binding of Cu(2+) ions. This makes the core-shell nanoparticle system a water-dispersible chemosensor for Cu(2+) ion detection. The quenching of fluorescence arises through intraparticle energy transfer (FRET) from the dye in the hydrophobic PMMA core to the Cu(2+)/PEI complexes on the nanoparticle surface. The energy transfer efficiency for PEI/PMMA particles with different diameters was determined, and it is found that the smaller nanoparticle sample exhibits higher quenching efficiency, and the limit for Cu(2+) detection is 1 microM for a nanoparticle sample with a diameter of approximately 30 nm. The response of the fluorescent nanoparticle towards different metal ions was investigated and the nanoparticle chemosensor displays high selectivity and antidisturbance for the Cu(2+) ion among the metal ions examined (Na(+), K(+), Mg(2+), Ca(2+), Zn(2+), Hg(2+), Mn(2+), Fe(2+), Ni(2+), Co(2+) and Pb(2+)). This emulsifier-free, biocompatible and sensitive fluorescent nanoparticle sensor may find applications in cupric ion detection in the biological and environmental areas.

Highly Efficient Multiple-Anchored Fluorescent Probe for the Detection of Aniline Vapor Based on Synergistic Effect: Chemical Reaction and PET.

PubMed

Jiao, Zinuo; Zhang, Yu; Xu, Wei; Zhang, Xiangtao; Jiang, Haibo; Wu, Pengcheng; Fu, Yanyan; He, Qingguo; Cao, Huimin; Cheng, Jiangong

2017-05-26

A multiple-anchored fluorescent probe ((((hexane-1,6-diylbis(2,7-bis(4-formyl)-phenyl)-9H-fluorine-9,9-diyl))-bis(hexane-6,1-diyl))-bis(9H-carbazole-9,3,6-triyl))-tetrakis(benzene-4,1-diyl))-tetraformyl-(8FP-2F) with eight aldehyde groups was designed and synthesized. The molecule has four branches and highly twisted structure. Furthermore, it tends to self-assemble into nanospheres, which is beneficial for gaseous analyte penetration and high fluorescence quantum efficiency. Among gaseous analytes, detection of aniline vapor is extraordinarily important in the control of environmental issues and human diseases. Herein, 8FP-2F was introduced to detect aniline vapor with distinguished sensitivity and selectivity via simple Schiff base reaction at room temperature. After exposure to saturate aniline vapor, the 89% fluorescence of 8FP-2F was quenched in 50 s and the detection limit was as low as 3 ppb. Further study showed the suitable HOMO/LUMO energy levels and matched orbital symmetry between probe and aniline molecules ensured chemical reaction and PET process work together. The synergistic effect resulted in a significant sensing performance and fluorescence quenching toward aniline vapor. Moreover, the multiple active sites structure of 8FP-2F means it could be applied for constructing many interesting structures and highly efficient organic optoelectronic functional materials.

Intramolecular fluorescence resonance energy transfer and living cell imaging of novel pyridyltriphenylamine dye

NASA Astrophysics Data System (ADS)

Cao, Duojun; Qian, Ying

2016-07-01

A novel pyridyltriphenylamine-rhodamine dye PTRh and a pyridyltriphenylamine derivative PTO were synthesized and characterized by 1H NMR and HRMS-MALDI-TOF. PTRh performed typical fluorescence resonance energy transfer (FRET) signal from pyridyltriphenylamine to rhodamine along with notable color change from green to rose when interacting with Hg2+ in EtOH/H2O. And PTRh as a ratiometric probe for Hg2+ based on FRET could achieve a very low detection limit of 32 nM and energy transfer efficiency of 83.7% in aqueous organic system. On the other hand, spectra properties of PTO in its aggregates, THF/H2O mixed solution and silica nanoparticles (Si-NPs) dispersed in water were investigated. And the results indicated PTO exhibited bright green fluorescence in solid state, and PTO was successfully encapsulated in silica matrix (30-40 nm), emitting bright blue fluorescence with 11.7% quantum yield. Additionally, living cell imaging experiments demonstrated that PTRh could effectively response to intracellular Hg2+ and PTO-doped Si-NPs were well uptaken by MCF-7 breast cancer cells. It could be concluded that the chromophores are promising materials used as biosensors.

Production mechanism of atomic nitrogen in atmospheric pressure pulsed corona discharge measured using two-photon absorption laser-induced fluorescence

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

Teramoto, Yoshiyuki; Ono, Ryo; Oda, Tetsuji

To study the production mechanism of atomic nitrogen, the temporal profile and spatial distribution of atomic nitrogen are measured in atmospheric pressure pulsed positive corona discharge using two-photon absorption laser-induced fluorescence. The absolute atomic nitrogen density in the streamer filaments is estimated from decay rate of atomic nitrogen in N{sub 2} discharge. The results indicate that the absolute atomic nitrogen density is approximately constant against discharge energy. When the discharge voltage is 21.5 kV, production yield of atomic nitrogen produced by an N{sub 2} discharge pulse is estimated to be 2.9 - 9.8 Multiplication-Sign 10{sup 13} atoms and the energymore » efficiency of atomic nitrogen production is estimated to be about 1.8 - 6.1 Multiplication-Sign 10{sup 16} atoms/J. The energy efficiency of atomic nitrogen production in N{sub 2} discharge is constant against the discharge energy, while that in N{sub 2}/O{sub 2} discharge increases with discharge energy. In the N{sub 2}/O{sub 2} discharge, two-step process of N{sub 2} dissociation plays significant role for atomic nitrogen production.« less

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

Qiao, Ruimin; Li, Qinghao; Zhuo, Zengqing

In this paper, an endstation with two high-efficiency soft x-ray spectrographs was developed at Beamline 8.0.1 of the Advanced Light Source, Lawrence Berkeley National Laboratory. The endstation is capable of performing soft x-ray absorption spectroscopy, emission spectroscopy, and, in particular, resonant inelastic soft x-ray scattering (RIXS). Two slit-less variable line-spacing grating spectrographs are installed at different detection geometries. The endstation covers the photon energy range from 80 to 1500 eV. For studying transition-metal oxides, the large detection energy window allows a simultaneous collection of x-ray emission spectra with energies ranging from the O K-edge to the Ni L-edge without movingmore » any mechanical components. The record-high efficiency enables the recording of comprehensive two-dimensional RIXS maps with good statistics within a short acquisition time. By virtue of the large energy window and high throughput of the spectrographs, partial fluorescence yield and inverse partial fluorescence yield signals could be obtained for all transition metal L-edges including Mn. Finally and moreover, the different geometries of these two spectrographs (parallel and perpendicular to the horizontal polarization of the beamline) provide contrasts in RIXS features with two different momentum transfers.« less

Alterations of pigment composition and their interactions in response to different light conditions in the diatom Chaetoceros gracilis probed by time-resolved fluorescence spectroscopy.

PubMed

Nagao, Ryo; Ueno, Yoshifumi; Yokono, Makio; Shen, Jian-Ren; Akimoto, Seiji

2018-07-01

Maintenance of energy balance under changeable light conditions is an essential function of photosynthetic organisms to achieve efficient photochemical reactions. Among the photosynthetic organisms, diatoms possess light-harvesting fucoxanthin chlorophyll (Chl) a/c-binding protein (FCP) as peripheral antennas. However, how diatoms regulate excitation-energy distribution between FCP and the two photosystem cores during light adaptation is poorly understood. In this study, we examined spectroscopic properties of a marine diatom Chaetoceros gracilis adapted in the dark and at photosynthetic photon flux density at 30 and 300 μmol photons m -2  s -1 . Absorption spectra at 77 K showed significant changes in the Soret region, and 77-K steady-state fluorescence spectra showed significant differences in the spectral shape and relative fluorescence intensity originating from both PSII and PSI, among the cells grown under different light conditions. These results suggest alterations of pigment composition and their interactions under the different light conditions. These alterations affected the excitation-energy dynamics monitored by picosecond time-resolved fluorescence analyses at 77 K significantly. The contributions of Chls having lower energy levels than the reaction center Chls in the two photosystems to the energy dynamics were clearly identified in the three cells but with presumably different roles. These findings provide insights into the regulatory mechanism of excitation-energy balance in diatoms under various light conditions. Copyright © 2018 Elsevier B.V. All rights reserved.

Estimating the distance separating fluorescent protein FRET pairs

PubMed Central

van der Meer, B. Wieb; Blank, Paul S.

2014-01-01

Förster resonance energy transfer (FRET) describes a physical phenomenon widely applied in biomedical research to estimate separations between biological molecules. Routinely, genetic engineering is used to incorporate spectral variants of the green fluorescent protein (GFPs), into cellular expressed proteins. The transfer efficiency or rate of energy transfer between donor and acceptor FPs is then assayed. As appreciable FRET occurs only when donors and acceptors are in close proximity (1–10 nm), the presence of FRET may indicate that the engineered proteins associate as interacting species. For a homogeneous population of FRET pairs the separations between FRET donors and acceptors can be estimated from a measured FRET efficiency if it is assumed that donors and acceptors are randomly oriented and rotate extensively during their excited state (dynamic regime). Unlike typical organic fluorophores, the rotational correlation-times of FPs are typically much longer than their fluorescence lifetime; accordingly FPs are virtually static during their excited state. Thus, estimating separations between FP FRET pairs is problematic. To overcome this obstacle, we present here a simple method for estimating separations between FPs using the experimentally measured average FRET efficiency. This approach assumes that donor and acceptor fluorophores are randomly oriented, but do not rotate during their excited state (static regime). This approach utilizes a Monte-Carlo simulation generated look-up table that allows one to estimate the separation, normalized to the Förster distance, from the average FRET efficiency. Assuming a dynamic regime overestimates the separation significantly (by 10% near 0.5 and 30% near 0.75 efficiencies) compared to assuming a static regime, which is more appropriate for estimates of separations between FPs. PMID:23811334

In-capillary probing of quantum dots and fluorescent protein self-assembly and displacement using Förster resonance energy transfer.

PubMed

Wang, Jianhao; Fan, Jie; Li, Jinchen; Liu, Li; Wang, Jianpeng; Jiang, Pengju; Liu, Xiaoqian; Qiu, Lin

2017-02-01

Herein, a Förster resonance energy transfer system was designed, which consisted of CdSe/ZnS quantum dots donor and mCherry fluorescent protein acceptor. The quantum dots and the mCherry proteins were conjugated to permit Förster resonance energy transfer. Capillary electrophoresis with fluorescence detection was used for the analyses for the described system. The quantum dots and mCherry were sequentially injected into the capillary, while the real-time fluorescence signal of donor and acceptor was simultaneously monitored by two channels with fixed wavelength detectors. An effective separation of complexes from free donor and acceptor was achieved. Results showed quantum dots and hexahistidine tagged mCherry had high affinity and the assembly was affected by His 6 -mCherry/quantum dot molar ratio. The kinetics of the self-assembly was calculated using the Hill equation. The microscopic dissociation constant values for out of- and in-capillary assays were 10.49 and 23.39 μM, respectively. The capillary electrophoresis with fluorescence detection that monitored ligands competition assay further delineated the different binding capacities of histidine containing peptide ligands for binding sites on quantum dots. This work demonstrated a novel approach for the improvement of Förster resonance energy transfer for higher efficiency, increased sensitivity, intuitionistic observation, and low sample requirements of the in-capillary probing system. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and photoluminescence in Yb doped cerium phosphate CePO4

NASA Astrophysics Data System (ADS)

Bhonsule, S. U.; Wankhede, S. P.; Moharil, S. V.

2018-05-01

This paper presents the preparation of CePO4 and Yb doped CePO4 using simple solid state reaction method. PL measurements indicated significant energy transfer from Ce3+ to Yb3+ ions. Further evidence of energy transfer was provided by analysis of Luminescence Decay measurements. Energy transfer efficiency of 50% was obtained for 5%Yb doping. Energy transfer from Ce3+ to Yb3+ ions takes place by Cooperative energy transfer mechanism. Such phosphors can be used in white LED's, Lasers and energy saving fluorescent lamps.

Nd³⁺-Yb³⁺ doped powder for near-infrared optical temperature sensing.

PubMed

Rakov, Nikifor; Maciel, Glauco S

2014-07-01

Er³⁺ doped powders are generally used for fluorescence-based temperature sensing application when near-infrared lasers are the excitation sources of choice. The fluorescence of Er³⁺ is produced by nonlinear (upconversion) processes, which generate strong internal heat. Lowering the excitation power causes drastic reduction of the fluorescence signal, and as a consequence the sensor applicability of Er³⁺ doped powders becomes compromised. Here we propose the use of the downconverted fluorescence of Yb³⁺ produced by efficient energy transfer from Nd³⁺ as an alternative temperature sensing system. Our results are presented for yttrium silicate powders prepared by combustion synthesis.

Synthesis and characterization of novel pyrene-dendronized porphyrins exhibiting efficient fluorescence resonance energy transfer: optical and photophysical properties.

PubMed

Zaragoza-Galán, Gerardo; Fowler, Michael A; Duhamel, Jean; Rein, Regis; Solladié, Nathalie; Rivera, Ernesto

2012-07-31

A novel series of pyrene dendronized porphyrins bearing two and four pyrenyl groups (Py(2)-TMEG1 and Py(4)-TMEG2) were successfully synthesized. First and second generation Fréchet type dendrons (Py(2)-G1OH and Py(4)-G2OH) were prepared from 1-pyrenylbutanol and 3,5-dihydroxybenzyl alcohol. These compounds were further linked to a trimesitylphenylporphyrin containing a butyric acid spacer via an esterification reaction to obtain the desired products. Dendrons and dendronized porphyrins were fully characterized by FTIR and (1)H NMR spectroscopy and their molecular weights were determined by matrix-assisted laser desorption ionization time of flight mass spectrometry. Their optical and photophysical properties were studied by absorption and fluorescence spectroscopies. The formation of dynamic excimers was detected in the pyrene-labeled dendrons, with more excimer being produced in the higher generation dendron. The fluorescence spectra of the pyrene dendronized porphyrins exhibited a significant decrease in the amount of pyrene monomer and excimer emission, jointly with the appearance of a new emission band at 661 nm characteristic of porphyrin emission, an indication that fluorescence resonance energy transfer (FRET) occurred from one of the excited pyrene species to the porphyrin. The FRET efficiency was found to be almost quantitative ranging between 97% and 99% depending on the construct. Model Free analysis of the fluorescence decays acquired with the pyrene monomer, excimer, and porphyrin core established that only residual pyrene excimer formation in the dendrons could occur before FRET from the excited pyrene monomer to the ground-state porphyrin core.

Long-lived efficient delayed fluorescence organic light-emitting diodes using n-type hosts.

PubMed

Cui, Lin-Song; Ruan, Shi-Bin; Bencheikh, Fatima; Nagata, Ryo; Zhang, Lei; Inada, Ko; Nakanotani, Hajime; Liao, Liang-Sheng; Adachi, Chihaya

2017-12-21

Organic light-emitting diodes have become a mainstream display technology because of their desirable features. Third-generation electroluminescent devices that emit light through a mechanism called thermally activated delayed fluorescence are currently garnering much attention. However, unsatisfactory device stability is still an unresolved issue in this field. Here we demonstrate that electron-transporting n-type hosts, which typically include an acceptor moiety in their chemical structure, have the intrinsic ability to balance the charge fluxes and broaden the recombination zone in delayed fluorescence organic electroluminescent devices, while at the same time preventing the formation of high-energy excitons. The n-type hosts lengthen the lifetimes of green and blue delayed fluorescence devices by > 30 and 1000 times, respectively. Our results indicate that n-type hosts are suitable to realize stable delayed fluorescence organic electroluminescent devices.

Quenching of fluorescence of conjugated poly(p-phenylene) polymers by benzil and dimethylaminobenzil molecules

NASA Astrophysics Data System (ADS)

Bagnich, S. A.; Knyukshto, V. N.

2006-11-01

We have studied the mechanisms for quenching of the fluorescence of conjugated poly(p-phenylene) polymers by benzil and dimethylaminobenzil molecules. We have shown that molecules in the diketone series are quenching agents for the fluorescence of the indicated polymers, and can serve as singlet-triplet converters capable of populating the triplet state of the polymer. We have observed that the efficiency of quenching of the fluorescence of the studied polymers depends considerably on the presence of bulky side groups in the polymer or in the activator molecules. Based on analysis of the data obtained, we conclude that in the case of a rigid planar structure for the polymer, a significant contribution to quenching of its fluorescence comes from not only singlet-singlet energy transfer but also charge transfer, leading to formation of intermolecular complexes (exciplexes).

Electroluminescence of fluorescent-phosphorescent organic light-emitting diodes with regular, inverted, and symmetrical structures

NASA Astrophysics Data System (ADS)

Yang, Su-Hua; Shih, Po-Jen; Wu, Wen-Jie

2014-11-01

The influence of the device structure on the electroluminescence (EL) properties of fluorescent-phosphorescent organic light emitting diodes (OLEDs) was demonstrated. Four devices with regular-, inverted-, compensated- and symmetrical-emission layers (EMLs) were prepared. In regular-EML device, DCJTB emission increased when the phosphorescent sensitized EML was thickened. In inverted-EML device, low electron energy barrier at the Bphen/BCzVB interface resulted in weakened blue emission. The compensated-EML device, prepared with a red color-compensated layer, showed a color-tunable broadband white emission. Conversely, device with a quantum-like symmetrical-EML showed a narrow color-temperature range. Stable EL efficiency was obtained from regular, compensated, and symmetrical-EML devices. In contrast, EL efficiency of inverted-EML device rolled off significantly, though it had the highest EL efficiency of 11.4 cd/A.

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

Hu, Qing; Jin, Dafei; Xiao, Jun

Two-dimensional molecular aggregate (2DMA), a thin sheet of strongly interacting dipole molecules self-assembled at close distance on an ordered lattice, is a fascinating fluorescent material. It is distinctively different from the conventional (single or colloidal) dye molecules and quantum dots. Here, in this paper, we verify that when a 2DMA is placed at a nanometric distance from a metallic substrate, the strong and coherent interaction between the dipoles inside the 2DMA dominates its fluorescent decay at a picosecond timescale. Our streak-camera lifetime measurement and interacting lattice–dipole calculation reveal that the metal-mediated dipole–dipole interaction shortens the fluorescent lifetime to about one-halfmore » and increases the energy dissipation rate by 10 times that expected from the noninteracting single-dipole picture. In conclusion, our finding can enrich our understanding of nanoscale energy transfer in molecular excitonic systems and may designate a unique direction for developing fast and efficient optoelectronic devices.« less

Two novel blue phosphorescent host materials containing phenothiazine-5,5-dioxide structure derivatives

PubMed Central

Xie, Feng-Ming; Ou, Qingdong; Zhang, Qiang; Zhang, Jiang-Kun; Dai, Guo-Liang

2018-01-01

Two novel D–A bipolar blue phosphorescent host materials based on phenothiazine-5,5-dioxide: 3-(9H-carbazol-9-yl)-10-ethyl-10H-phenothiazine-5,5-dioxide (CEPDO) and 10-butyl-3-(9H-carbazol-9-yl)-10H-phenothiazine-5,5-dioxide (CBPDO) were synthesized and characterized. The photophysical, electrochemical and thermal properties were systematically investigated. CEPDO and CBPDO not only have a high triplet energy but also show a bipolar behavior. Moreover, their fluorescence emission peaks are in the blue fluorescence region at 408 nm and the fluorescence quantum efficiency (Φ) of CEPDO and CBPDO were 62.5% and 59.7%, respectively. Both CEPDO and CBPDO showed very high thermal stability with decomposition temperatures (T d) of 409 and 396 °C as well as suitable HOMO and LUMO energy levels. This preferable performance suggests that CEPDO and CBPDO are alternative bipolar host materials for the PhOLEDs. PMID:29765467

Probes labelled with energy transfer coupled dyes

DOEpatents

Mathies, R.A.; Glazer, A.; Ju, J.

1997-11-18

Compositions are provided comprising sets of fluorescent labels carrying pairs of donor and acceptor dye molecules, designed for efficient excitation of the donors at a single wavelength and emission from the acceptor in each of the pairs at different wavelengths. The different molecules having different donor-acceptor pairs can be modified to have substantially the same mobility under separation conditions, by varying the distance between the donor and acceptor in a given pair. Particularly, the fluorescent compositions find use as labels in sequencing nucleic acids. 7 figs.

Probes labelled with energy transfer coupled dyes

DOEpatents

Mathies, Richard A.; Glazer, Alexander; Ju, Jingyue

1997-01-01

Compositions are provided comprising sets of fluorescent labels carrying pairs of donor and acceptor dye molecules, designed for efficient excitation of the donors at a single wavelength and emission from the acceptor in each of the pairs at different wavelengths. The different molecules having different donor-acceptor pairs can be modified to have substantially the same mobility under separation conditions, by varying the distance between the donor and acceptor in a given pair. Particularly, the fluorescent compositions find use as labels in sequencing nucleic acids.

Fluorescence turn-on detection of alkaline phosphatase activity based on controlled release of PEI-capped Cu nanoclusters from MnO2 nanosheets.

PubMed

Zhang, Yunyi; Li, Yongxin; Zhang, Cuiyun; Zhang, Qingfeng; Huang, Xinan; Yang, Meiding; Shahzad, Sohail Anjum; Lo, Kenneth Kam-Wing; Yu, Cong; Jiang, Shichun

2017-08-01

A fluorescence turn-on assay for alkaline phosphatase (ALP) activity is developed through the controlled release of polyethyleneimine-capped copper nanoclusters (PEI-capped CuNCs) from the MnO 2 nanosheets. In an aqueous solution, the positively charged PEI-capped CuNCs could be adsorbed onto the surface of the negatively charged MnO 2 nanosheets. Such adsorption through favorable electrostatic interactions could efficiently quench the nanocluster fluorescence emission via resonance energy transfer from the PEI-capped CuNCs to the MnO 2 nanosheets. 2-Phospho-L-ascorbic acid (AAP) could be hydrolyzed to L-ascorbic acid (AA) in the presence of ALP. AA could reduce MnO 2 into Mn 2+ and trigger the disintegration of the MnO 2 nanosheets. As a result, the CuNCs were released and the quenched fluorescence was recovered efficiently. The detection strategy is simple, inexpensive, sensitive, selective, with low toxicity, and has better biocompatibility. The newly fabricated biosensor for ALP activity will potentially make it a robust candidate for numerous biological and biomedical applications.

Resonance Energy Transfer Studies from Derivatives of Thiophene Substituted 1,3,4-Oxadiazoles to Coumarin-334 Dye in Liquid and Dye-Doped Polymer Media

NASA Astrophysics Data System (ADS)

Naik, Lohit; Deshapande, Narahari; Khazi, Imtiyaz Ahamed M.; Malimath, G. H.

2018-02-01

In the present work, we have carried out energy transfer studies using newly synthesised derivatives of thiophene substituted 1,3,4-oxadiazoles namely, 2-(-4-(thiophene-3-yl)phenyl)-5-(5-(thiophene-3-yl)thiophene-2-yl)-1,3,4-oxadiazole [TTO], 2-(-4-(benzo[b]thiophene-2-yl)phenyl)-5-(5-(benzo[b]thiophene-2-yl)-1,3,4-oxadiozole [TBO] and 2-(4-(4-(trifluoromethyl)phenyl)phenyl)-5-(5-(4-(trifluoromethyl)phenyl)thiophen-2-yl)-1,3,4-oxadiazole [TMO] as donors and laser dye coumarin-334 as acceptor in ethanol and dye-doped polymer (poly(methyl methacrylate) (PMMA)) media following steady-state and time-resolved fluorescence methods. Bimolecular quenching constant ( k q), translation diffusion rate parameter ( k d), diffusion length ( D l), critical transfer distance ( R 0), donor- acceptor distance ( r) and energy transfer efficiency ( E T) are calculated. It is observed that, critical transfer distance is more than the diffusion length for all the pairs. Further, bimolecular quenching constant is also more than the translation diffusion rate parameter. Hence, our experimental findings suggest that overall energy transfer is due to Förster resonance energy transfer (FRET) between donor and acceptor in both the media and for all the pairs. In addition, considerable increase in fluorescence intensity and energy transfer efficiency is observed in dye-doped polymer matrix systems as compared to liquid media. This suggests that, these donor-acceptor pairs doped in PMMA matrix may be used for applications such as energy transfer dye lasers (ETDL) to improve the efficiency and photostability, to enhance tunability and for plastic scintillation detectors.

A high-throughput direct fluorescence resonance energy transfer-based assay for analyzing apoptotic proteases using flow cytometry and fluorescence lifetime measurements.

PubMed

Suzuki, Miho; Sakata, Ichiro; Sakai, Takafumi; Tomioka, Hiroaki; Nishigaki, Koichi; Tramier, Marc; Coppey-Moisan, Maïté

2015-12-15

Cytometry is a versatile and powerful method applicable to different fields, particularly pharmacology and biomedical studies. Based on the data obtained, cytometric studies are classified into high-throughput (HTP) or high-content screening (HCS) groups. However, assays combining the advantages of both are required to facilitate research. In this study, we developed a high-throughput system to profile cellular populations in terms of time- or dose-dependent responses to apoptotic stimulations because apoptotic inducers are potent anticancer drugs. We previously established assay systems involving protease to monitor live cells for apoptosis using tunable fluorescence resonance energy transfer (FRET)-based bioprobes. These assays can be used for microscopic analyses or fluorescence-activated cell sorting. In this study, we developed FRET-based bioprobes to detect the activity of the apoptotic markers caspase-3 and caspase-9 via changes in bioprobe fluorescence lifetimes using a flow cytometer for direct estimation of FRET efficiencies. Different patterns of changes in the fluorescence lifetimes of these markers during apoptosis were observed, indicating a relationship between discrete steps in the apoptosis process. The findings demonstrate the feasibility of evaluating collective cellular dynamics during apoptosis. Copyright © 2015 Elsevier Inc. All rights reserved.

Method Of Signal Amplification In Multi-Chromophore Luminescence Sensors

DOEpatents

Levitsky, Igor A.; Krivoshlykov, Sergei G.

2004-02-03

A fluorescence-based method for highly sensitive and selective detection of analyte molecules is proposed. The method employs the energy transfer between two or more fluorescent chromophores in a carefully selected polymer matrix. In one preferred embodiment, signal amplification has been achieved in the fluorescent sensing of dimethyl methylphosphonate (DMMP) using two dyes, 3-aminofluoranthene (AM) and Nile Red (NR), in a hydrogen bond acidic polymer matrix. The selected polymer matrix quenches the fluorescence of both dyes and shifts dye emission and absorption spectra relative to more inert matrices. Upon DMMP sorption, the AM fluorescence shifts to the red at the same time the NR absorption shifts to the blue, resulting in better band overlap and increased energy transfer between chromophores. In another preferred embodiment, the sensitive material is incorporated into an optical fiber system enabling efficient excitation of the dye and collecting the fluorescent signal form the sensitive material on the remote end of the system. The proposed method can be applied to multichromophore luminescence sensor systems incorporating N-chromophores leading to N-fold signal amplification and improved selectivity. The method can be used in all applications where highly sensitive detection of basic gases, such as dimethyl methylphosphonate (DMMP), Sarin, Soman and other chemical warfare agents having basic properties, is required, including environmental monitoring, chemical industry and medicine.

Energy transfer and 2.0 μm emission in Tm{sup 3+}/Ho{sup 3+} co-doped α-NaYF{sub 4} single crystals

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

Feng, Zhigang; Yang, Shuo; Xia, Haiping, E-mail: hpxcm@nbu.edu.cn

2016-04-15

Highlights: • Cubic NaYF{sub 4} single crystals co-doped with ∼1.90 mol% Tm{sup 3+} and various Ho{sup 3+} concentrations were grown by Bridgman method. • The maximum fluorescence lifetime was 23.23 ms for Tm{sup 3+} (1.90 mol%)/Ho{sup 3+} (3.89 mol%) co-doped α-NaYF{sub 4}. • The obtained energy transfer rate (W{sub ET}) and energy transfer efficiency (η) of Tm{sup 3+}:{sup 3}F{sub 4} are 1077 s{sup −1} and 95.0%, respectively. • The maximum emission cross section reached 1.06 × 10{sup −20} cm{sup 2}. - Abstract: Cubic NaYF{sub 4} single crystals co-doped with ∼1.90 mol% Tm{sup 3+} and various Ho{sup 3+} concentrations were grownmore » by Bridgman method. The energy transfer from Tm{sup 3+} to Ho{sup 3+} and the optimum fluorescence emission around 2.04 μm of Ho{sup 3+} ion were investigated based on the measured absorption spectra, emission spectra, emission cross section and decay curves under excitation of 800 nm LD. The emission intensity at 2.04 μm increased with the increase of Ho{sup 3+} concentration from 0.96 mol% to 3.89 mol% when the concentration of Tm{sup 3+} was held constantly at ∼1.90 mol%. Moreover, the maximum emission cross section reached 1.06 × 10{sup −20} cm{sup 2} and the maximum fluorescence lifetime was 23.23 ms for Tm{sup 3+}(1.90 mol%)/Ho{sup 3+}(3.89 mol%) co-doped one. According to the measured lifetime of Tm{sup 3+} single-doped and Tm{sup 3+}/Ho{sup 3+} co-doped samples, the maximum energy transfer efficiency of Tm{sup 3+}:{sup 3}F{sub 4} level was 95.0%. Analysis on the fluorescence dynamics indicated that electric dipole–dipole is dominant for the energy transfer from Tm{sup 3+} to Ho{sup 3+}.« less

78 FR 16443 - Energy Efficiency Program for Consumer Products: Energy Conservation Standards for Ceiling Fans...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-15

... with medium screw base sockets, as well as pin-based sockets. (42 U.S.C. 6295(ff)(2)-(3)) The statute... (including candelabra screw base sockets) by January 1, 2007, and if DOE failed to issue such standards by... standards for light kits with sockets other than medium-screw base or pin-based fluorescent lamps in the CFR...

A highly sensitive and selective aptasensor based on graphene oxide fluorescence resonance energy transfer for the rapid determination of oncoprotein PDGF-BB.

PubMed

Liang, Junfei; Wei, Ran; He, Shuai; Liu, Yikan; Guo, Lin; Li, Lidong

2013-03-21

Oncoprotein platelet derived growth factor-BB (PDGF-BB) is one of the most critical growth factors that regulates tumor growth and division. In this work, a highly sensitive and selective fluorescence resonance energy transfer (FRET) aptasensor for PDGF-BB detection based on the assembly of dye-labeled aptamer and graphene oxide (GO) is developed for the first time. Due to the non-covalent assembly between aptamer and GO, fluorescence quenching of the dye takes place because of FRET. In the presence of PDGF-BB, the binding between aptamer and PDGF-BB will disturb the interaction between aptamer and GO, and release the dye-labeled aptamer from the GO surface, resulting in restoration of the fluorophore fluorescence. Because of the high fluorescence quenching efficiency, unique structure, and electronic properties of GO, the GO aptasensor exhibits extraordinarily high sensitivity. We also demonstrate that two highly related molecular variants of PDGF (AA, AB) can be distinguished from PDGF-BB, which indicates the aptasensor has excellent selectivity. Such an aptasensor opens a rapid, selective and sensitive route for the detection of PDGF-BB and provides a promising strategy for other cancer-related proteins detections.

Augmenting light coverage for photosynthesis through YFP-enhanced charge separation at the Rhodobacter sphaeroides reaction centre

DOE PAGES

Grayson, Katie J.; Faries, Kaitlyn M.; Huang, Xia; ...

2017-01-05

Photosynthesis uses a limited range of the solar spectrum, so enhancing spectral coverage could improve the efficiency of light capture. Here, we show that a hybrid reaction centre (RC)/yellow fluorescent protein (YFP) complex accelerates photosynthetic growth in the bacterium Rhodobacter sphaeroides. The structure of the RC/YFP-light-harvesting 1 (LH1) complex shows the position of YFP attachment to the RC-H subunit, on the cytoplasmic side of the RC complex. Fluorescence lifetime microscopy of whole cells and ultrafast transient absorption spectroscopy of purified RC/YFP complexes show that the YFP–RC intermolecular distance and spectral overlap between the emission of YFP and the visible-region (Qmore » X) absorption bands of the RC allow energy transfer via a Fo¨rster mechanism, with an efficiency of 40±10%. Finally, this proof-of-principle study demonstrates the feasibility of increasing spectral coverage for harvesting light using non-native genetically-encoded light-absorbers, thereby augmenting energy transfer and trapping in photosynthesis.« less

Three-photon excitation source at 1250 nm generated in a dual zero dispersion wavelength nonlinear fiber

DOE PAGES

Domingue, Scott R.; Bartels, Randy A.

2014-12-04

Here, we demonstrate 1250 nm pulses generated in dual-zero dispersion photonic crystal fiber capable of three-photon excitation fluorescence microscopy. The total power conversion efficiency from the 28 fs seed pulse centered at 1075 nm to pulses at 1250 nm, including coupling losses from the nonlinear fiber, is 35%, with up to 67% power conversion efficiency of the fiber coupled light. Frequency-resolved optical gating measurements characterize 1250 nm pulses at 0.6 nJ and 2 nJ, illustrating the change in nonlinear spectral phase accumulation with pulse energy even for nonlinear fiber lengths < 50 mm. The 0.6 nJ pulse has a 26more » fs duration and is the shortest nonlinear fiber derived 1250 nm pulse yet reported (to the best of our knowledge). The short pulse durations and energies make these pulses a viable route to producing light at 1250 nm for multiphoton microscopy, which we we demonstrate here, via a three-photon excitation fluorescence microscope.« less

Detection of Citrus tristeza virus by using fluorescence resonance energy transfer-based biosensor

NASA Astrophysics Data System (ADS)

Shojaei, Taha Roodbar; Salleh, Mohamad Amran Mohd; Sijam, Kamaruzaman; Rahim, Raha Abdul; Mohsenifar, Afshin; Safarnejad, Reza; Tabatabaei, Meisam

2016-12-01

Due to the low titer or uneven distribution of Citrus tristeza virus (CTV) in field samples, detection of CTV by using conventional detection techniques may be difficult. Therefore, in the present work, the cadmium-telluride quantum dots (QDs) was conjugated with a specific antibody against coat protein (CP) of CTV, and the CP were immobilized on the surface of gold nanoparticles (AuNPs) to develop a specific and sensitive fluorescence resonance energy transfer (FRET)-based nanobiosensor for detecting CTV. The maximum FRET efficiency for the developed nano-biosensor was observed at 60% in AuNPs-CP/QDs-Ab ratio of 1:8.5. The designed system showed higher sensitivity and specificity over enzyme linked immunosorbent assay (ELISA) with a limit of detection of 0.13 μg mL- 1 and 93% and 94% sensitivity and specificity, respectively. As designed sensor is rapid, sensitive, specific and efficient in detecting CTV, this could be envisioned for diagnostic applications, surveillance and plant certification program.

Augmenting light coverage for photosynthesis through YFP-enhanced charge separation at the Rhodobacter sphaeroides reaction centre

PubMed Central

Grayson, Katie J.; Faries, Kaitlyn M.; Huang, Xia; Qian, Pu; Dilbeck, Preston; Martin, Elizabeth C.; Hitchcock, Andrew; Vasilev, Cvetelin; Yuen, Jonathan M.; Niedzwiedzki, Dariusz M.; Leggett, Graham J.; Holten, Dewey; Kirmaier, Christine; Neil Hunter, C.

2017-01-01

Photosynthesis uses a limited range of the solar spectrum, so enhancing spectral coverage could improve the efficiency of light capture. Here, we show that a hybrid reaction centre (RC)/yellow fluorescent protein (YFP) complex accelerates photosynthetic growth in the bacterium Rhodobacter sphaeroides. The structure of the RC/YFP-light-harvesting 1 (LH1) complex shows the position of YFP attachment to the RC-H subunit, on the cytoplasmic side of the RC complex. Fluorescence lifetime microscopy of whole cells and ultrafast transient absorption spectroscopy of purified RC/YFP complexes show that the YFP–RC intermolecular distance and spectral overlap between the emission of YFP and the visible-region (QX) absorption bands of the RC allow energy transfer via a Förster mechanism, with an efficiency of 40±10%. This proof-of-principle study demonstrates the feasibility of increasing spectral coverage for harvesting light using non-native genetically-encoded light-absorbers, thereby augmenting energy transfer and trapping in photosynthesis. PMID:28054547

Augmenting light coverage for photosynthesis through YFP-enhanced charge separation at the Rhodobacter sphaeroides reaction centre

NASA Astrophysics Data System (ADS)

Grayson, Katie J.; Faries, Kaitlyn M.; Huang, Xia; Qian, Pu; Dilbeck, Preston; Martin, Elizabeth C.; Hitchcock, Andrew; Vasilev, Cvetelin; Yuen, Jonathan M.; Niedzwiedzki, Dariusz M.; Leggett, Graham J.; Holten, Dewey; Kirmaier, Christine; Neil Hunter, C.

2017-01-01

Photosynthesis uses a limited range of the solar spectrum, so enhancing spectral coverage could improve the efficiency of light capture. Here, we show that a hybrid reaction centre (RC)/yellow fluorescent protein (YFP) complex accelerates photosynthetic growth in the bacterium Rhodobacter sphaeroides. The structure of the RC/YFP-light-harvesting 1 (LH1) complex shows the position of YFP attachment to the RC-H subunit, on the cytoplasmic side of the RC complex. Fluorescence lifetime microscopy of whole cells and ultrafast transient absorption spectroscopy of purified RC/YFP complexes show that the YFP-RC intermolecular distance and spectral overlap between the emission of YFP and the visible-region (QX) absorption bands of the RC allow energy transfer via a Förster mechanism, with an efficiency of 40+/-10%. This proof-of-principle study demonstrates the feasibility of increasing spectral coverage for harvesting light using non-native genetically-encoded light-absorbers, thereby augmenting energy transfer and trapping in photosynthesis.

Is There Excitation Energy Transfer between Different Layers of Stacked Photosystem-II-Containing Thylakoid Membranes?

PubMed

Farooq, Shazia; Chmeliov, Jevgenij; Trinkunas, Gediminas; Valkunas, Leonas; van Amerongen, Herbert

2016-04-07

We have compared picosecond fluorescence decay kinetics for stacked and unstacked photosystem II membranes in order to evaluate the efficiency of excitation energy transfer between the neighboring layers. The measured kinetics were analyzed in terms of a recently developed fluctuating antenna model that provides information about the dimensionality of the studied system. Independently of the stacking state, all preparations exhibited virtually the same value of the apparent dimensionality, d = 1.6. Thus, we conclude that membrane stacking does not affect the efficiency of the delivery of excitation energy toward the reaction centers but ensures a more compact organization of the thylakoid membranes within the chloroplast and separation of photosystems I and II.

Visualization of Stereoselective Supramolecular Polymers by Chirality-Controlled Energy Transfer.

PubMed

Sarkar, Aritra; Dhiman, Shikha; Chalishazar, Aditya; George, Subi J

2017-10-23

Chirality-driven self-sorting is envisaged to efficiently control functional properties in supramolecular materials. However, the challenge arises because of a lack of analytical methods to directly monitor the enantioselectivity of the resulting supramolecular assemblies. Presented herein are two fluorescent core-substituted naphthalene-diimide-based donor and acceptor molecules with minimal structural mismatch and they comprise strong self-recognizing chiral motifs to determine the self-sorting process. As a consequence, stereoselective supramolecular polymerization with an unprecedented chirality control over energy transfer has been achieved. This chirality-controlled energy transfer has been further exploited as an efficient probe to visualize microscopically the chirality driven self-sorting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solvent Dependency in the Quantum Efficiency of 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2, 5- dienylidene) methyl] Aniline Hydrochloride.

PubMed

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

2015-05-01

In the present work dual beam thermal lens technique is used for studying the solvent dependency on the quantum efficiency of a novel dye used for biomedical applications. The role of solvent in the absolute fluorescence quantum yield of 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2, 5- dienylidene) methyl] aniline hydrochloride is studied using thermal lens technique. It is observed that the variation in solvents and its concentration results considerable variations in the fluorescence quantum yield. These variations are due to the non-radiative relaxation of the absorbed energy and because of the different solvent properties. The highest quantum yield of the dye is observed in the polar protic solvent-water.

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

NASA Astrophysics Data System (ADS)

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

2013-12-01

Near-infrared (NIR) fluorescence signals are highly desirable to achieve high resolution in biological imaging. To obtain NIR emission with high brightness, fluorescent nanoparticles (NPs) are synthesized by co-encapsulation of 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenylamino)phenyl)fumaronitrile (TPETPAFN), a luminogen with aggregation-induced emission (AIE) characteristics, and a NIR fluorogen of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] as the encapsulation matrix. The good spectral overlap between the emission of TPETPAFN and the absorption of NIR775 leads to efficient energy transfer, resulting in a 47-fold enhancement of the NIR775 emission intensity upon excitation of TPETPAFN at 510 nm as compared to that upon direct excitation of NIR775 at 760 nm. The obtained fluorescent NPs show sharp NIR emission with a band width of 20 nm, a large Stokes shift of 275 nm, good photostability and low cytotoxicity. In vivo imaging study reveals that the synthesized NPs are able to provide high fluorescence contrast in live animals. The Förster resonance energy transfer strategy overcomes the intrinsic limitation of broad emission spectra for AIE NPs, which opens new opportunities to synthesize organic NPs with high brightness and narrow emission for potential applications in multiplex sensing and imaging.Near-infrared (NIR) fluorescence signals are highly desirable to achieve high resolution in biological imaging. To obtain NIR emission with high brightness, fluorescent nanoparticles (NPs) are synthesized by co-encapsulation of 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenylamino)phenyl)fumaronitrile (TPETPAFN), a luminogen with aggregation-induced emission (AIE) characteristics, and a NIR fluorogen of silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] as the encapsulation matrix. The good spectral overlap between the emission of TPETPAFN and the absorption of NIR775 leads to efficient energy transfer, resulting in a 47-fold enhancement of the NIR775 emission intensity upon excitation of TPETPAFN at 510 nm as compared to that upon direct excitation of NIR775 at 760 nm. The obtained fluorescent NPs show sharp NIR emission with a band width of 20 nm, a large Stokes shift of 275 nm, good photostability and low cytotoxicity. In vivo imaging study reveals that the synthesized NPs are able to provide high fluorescence contrast in live animals. The Förster resonance energy transfer strategy overcomes the intrinsic limitation of broad emission spectra for AIE NPs, which opens new opportunities to synthesize organic NPs with high brightness and narrow emission for potential applications in multiplex sensing and imaging. Electronic supplementary information (ESI) available: Characterization of AIE properties of TPETPAFN, UV-vis spectra of NPs, PL spectra comparison upon excitation at the donor and receptor absorbance maxima, ex vivo fluorescence imaging of mice organs. See DOI: 10.1039/c3nr04243j

Light-energy processing and freezing-tolerance traits in red spruce and black spruce: species and seed-source variation.

PubMed

Major, John E; Barsi, Debby C; Mosseler, Alex; Campbell, Moira; Rajora, Om P

2003-07-01

Red spruce (Picea rubens Sarg.) and black spruce (Picea mariana (Mill.) B.S.P.) are genetically and morphologically similar but ecologically distinct species. We determined intraspecific seed-source and interspecific variation of red spruce and black spruce, from across the near-northern margins of their ranges, for several light-energy processing and freezing-tolerance adaptive traits. Before exposure to low temperature, red spruce had variable fluorescence (Fv) similar to black spruce, but higher photochemical efficiency (Fv/Fm), lower quantum yield, lower chlorophyll fluorescence (%), and higher thermal dissipation efficiency (qN), although the seed-source effect and the seed-source x species interaction were significant only for Fv/Fm. After low-temperature exposure (-40 degrees C), red spruce had significantly lower Fv/Fm, quantum yield and qN than black spruce, but higher chlorophyll fluorescence and relative fluorescence. Species, seed-source effect, and seed-source x species interaction were consistent with predictions based on genetic (e.g., geographic) origins. Multi-temperature exposures (5, -20 and -40 degrees C) often produced significant species and temperature effects, and species x temperature interactions as a result of species-specific responses to temperature exposures. The inherent physiological species-specific adaptations of red spruce and black spruce were largely consistent with a shade-tolerant, late-successional species and an early successional species, respectively. Species differences in physiological adaptations conform to a biological trade-off, probably as a result of natural selection pressure in response to light availability and prevailing temperature gradients.

``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

Determination of sunset yellow in soft drinks based on fluorescence quenching of carbon dots

NASA Astrophysics Data System (ADS)

Yuan, Yusheng; Zhao, Xin; Qiao, Man; Zhu, Jinghui; Liu, Shaopu; Yang, Jidong; Hu, Xiaoli

2016-10-01

Fluorescent carbon dots was prepared by heating N-(2-hydroxyethyl)ethylene diaminetriacetic acid in air. The carbon dots were not only highly soluble in water but also uniform in size, and possessed strong blue fluorescence and excitation wavelength-dependent emission properties with the maximum excitation and emission wavelength at 366 nm and 423 nm, respectively. Food colorant sunset yellow whose excitation and emission wavelength at 303 nm and 430 nm could selectively quench the fluorescence of carbon dots, efficient fluorescent resonance energy transfer between the carbon dots and sunset yellow is achieved. This was exploited to design a method for the determination of sunset yellow in the concentration range from 0.3 to 8.0 μmol L- 1, with a limit of detection (3 σ/k) of 79.6 nmol L- 1. Furthermore the fluorimetric detection method was established and validated for sunset yellow in soft drinks samples with satisfactory results.

Temporal switching of homo-FRET pathways in single-chromophore dimer models of π-conjugated polymers.

PubMed

Stangl, Thomas; Bange, Sebastian; Schmitz, Daniela; Würsch, Dominik; Höger, Sigurd; Vogelsang, Jan; Lupton, John M

2013-01-09

A set of π-conjugated oligomer dimers templated in molecular scaffolds is presented as a model system for studying the interactions between chromophores in conjugated polymers (CPs). Single-molecule spectroscopy was used to reveal energy transfer dynamics between two oligomers in either a parallel or oblique-angle geometry. In particular, the conformation of single molecules embedded in a host matrix was investigated via polarized excitation and emission fluorescence microscopy in combination with fluorescence correlation spectroscopy. While the intramolecular interchromophore conformation was found to have no impact on the fluorescence quantum yield, lifetime, or photon statistics (antibunching), the long-term nonequilibrium dynamics of energy transfer within these bichromophoric systems was accessible by studying the linear dichroism in emission at the single-molecule level, which revealed reversible switching of the emission between the two oligomers. In bulk polymer films, interchromophore coupling promotes the migration of excitation energy to quenching sites. Realizing the presence and dynamics of such interactions is crucial for understanding limitations on the quantum efficiency of larger CP materials.

Pyrimidine-based twisted donor-acceptor delayed fluorescence molecules: a new universal platform for highly efficient blue electroluminescence.

PubMed

Park, In Seob; Komiyama, Hideaki; Yasuda, Takuma

2017-02-01

Deep-blue emitters that can harvest both singlet and triplet excited states to give high electron-to-photon conversion efficiencies are highly desired for applications in full-color displays and white lighting devices based on organic light-emitting diodes (OLEDs). Thermally activated delayed fluorescence (TADF) molecules based on highly twisted donor-acceptor (D-A) configurations are promising emitting dopants for the construction of efficient deep-blue OLEDs. In this study, a simple and versatile D-A system combining acridan-based donors and pyrimidine-based acceptors has been developed as a new platform for high-efficiency deep-blue TADF emitters. The designed pre-twisted acridan-pyrimidine D-A molecules exhibit small singlet-triplet energy splitting and high photoluminescence quantum yields, functioning as efficient deep-blue TADF emitters. The OLEDs utilizing these TADF emitters display bright blue electroluminescence with external quantum efficiencies of up to 20.4%, maximum current efficiencies of 41.7 cd A -1 , maximum power efficiencies of 37.2 lm W -1 , and color coordinates of (0.16, 0.23). The design strategy featuring such acridan-pyrimidine D-A motifs can offer great prospects for further developing high-performance deep-blue TADF emitters and TADF-OLEDs.

Selective Determination of Trinitrotoluene Based on Energy Transfer between Carbon Dots and Gold Nanoparticles.

PubMed

Oskoei, Yones Mosaei; Fattahi, Hassan; Hassanzadeh, Javad; Azar, Ali Mousavi

2016-01-01

A fluorescence resonance energy transfer (FRET) system between carbon dots (C-dots) and amine-capped gold nanoparticles (AuNPs) was developed for the selective determination of 2,4,6-trinitrotoluene (TNT). C-dots have an intrinsic florescence emission depending on their exciting wavelength. In the presence of AuNPs, C-dots adsorb on the Au surfaces, and NPs treat as energy acceptor, which can receive light emitted by C-dots, leading to decrease the fluorescence intensity of C-dots. Furthermore, it is observed that nitroaromatic compounds, especially TNT, could restore this fluorescence due to selective interaction with AuNPs via amine groups, and so releasing the C-dots. Based on this effect, a sensitive and selective fluorescence turn-on probe was designed for the determination of TNT. Some important factors including AuNPs and C-dot concentrations and media pH, which would affect the efficiency of the probe, were optimized. Under the optimum experimental conditions, good linear relationships in the range of 7 - 250 nmol L(-1) TNT with the detection limit of 2.2 nmol L(-1) were obtained. The proposed method was satisfactorily applied to the determination of TNT in the environmental water samples. Compared with previous reports, the developed method has relatively high sensitivity, short analysis time, low cost and ease of operation.

Evidence and mechanism of efficient thermally activated delayed fluorescence promoted by delocalized excited states

PubMed Central

Hosokai, Takuya; Matsuzaki, Hiroyuki; Nakanotani, Hajime; Tokumaru, Katsumi; Tsutsui, Tetsuo; Furube, Akihiro; Nasu, Keirou; Nomura, Hiroko; Yahiro, Masayuki; Adachi, Chihaya

2017-01-01

The design of organic compounds with nearly no gap between the first excited singlet (S1) and triplet (T1) states has been demonstrated to result in an efficient spin-flip transition from the T1 to S1 state, that is, reverse intersystem crossing (RISC), and facilitate light emission as thermally activated delayed fluorescence (TADF). However, many TADF molecules have shown that a relatively appreciable energy difference between the S1 and T1 states (~0.2 eV) could also result in a high RISC rate. We revealed from a comprehensive study of optical properties of TADF molecules that the formation of delocalized states is the key to efficient RISC and identified a chemical template for these materials. In addition, simple structural confinement further enhances RISC by suppressing structural relaxation in the triplet states. Our findings aid in designing advanced organic molecules with a high rate of RISC and, thus, achieving the maximum theoretical electroluminescence efficiency in organic light-emitting diodes. PMID:28508081

Monte Carlo treatment of resonance-radiation imprisonment in fluorescent lamps—revisited

NASA Astrophysics Data System (ADS)

Anderson, James B.

2016-12-01

We reported in 1985 a Monte Carlo treatment of the imprisonment of the 253.7 nm resonance radiation from mercury in the mercury-argon discharge of fluorescent lamps. The calculated spectra of the emitted radiation were found in good agreement with measured spectra. The addition of the isotope mercury-196 to natural mercury was found, also in agreement with experiments, to increase lamp efficiency. In this paper we report the extension of the earlier work with increased accuracy, analysis of photon exit-time distributions, recycling of energy released in quenching, analysis of dynamic similarity for different lamp sizes, variation of Mrozowski transfer rates, prediction and analysis of the hyperfine ultra-violet spectra, and optimization of tailored mercury isotope mixtures for increased lamp efficiency. The spectra were found insensitive to the extent of quenching and recycling. The optimized mixtures were found to increase efficiencies by as much as 5% for several lamp configurations. Optimization without increasing the mercury-196 fraction was found to increase efficiencies by nearly 1% for several configurations.

FRET two-hybrid assay by linearly fitting FRET efficiency to concentration ratio between acceptor and donor

NASA Astrophysics Data System (ADS)

Du, Mengyan; Yang, Fangfang; Mai, Zihao; Qu, Wenfeng; Lin, Fangrui; Wei, Lichun; Chen, Tongsheng

2018-04-01

We here introduce a fluorescence resonance energy transfer (FRET) two-hybrid assay method to measure the maximal donor(D)- and acceptor(A)-centric FRET efficiency (ED,max and EA,max) of the D-A complex and its stoichiometry by linearly fitting the donor-centric FRET efficiency (ED) to the acceptor-to-donor concentration ratio (RC) and acceptor-centric FRET efficiency (EA) to 1/RC, respectively. We performed this method on a wide-field fluorescence microscope for living HepG2 cells co-expressing FRET tandem constructs and free donor/acceptor and obtained correct ED, EA, and stoichiometry values of those tandem constructs. Evaluation on the binding of Bad with Bcl-XL in Hela cells showed that Bad interacted strongly with Bcl-XL to form a Bad-Bcl-XL complex on mitochondria, and one Bad interacted mainly with one Bcl-XL molecule in healthy cells, while with multiple (maybe 2) Bcl-XL molecules in apoptotic cells.

Acute toxicity of excess mercury on the photosynthetic performance of cyanobacterium, S. platensis--assessment by chlorophyll fluorescence analysis.

PubMed

Lu, C M; Chau, C W; Zhang, J H

2000-07-01

Measurement of chlorophyll fluorescence has been shown to be a rapid, non-invasive, and reliable method to assess photosynthetic performance in a changing environment. In this study, acute toxicity of excess Hg on the photosynthetic performance of the cyanobacterium S. platensis, was investigated by use of chlorophyll fluorescence analysis after cells were exposed to excess Hg (up to 20 microM) for 2 h. The results determined from the fast fluorescence kinetics showed that Hg induced a significant increase in the proportion of the Q(B)-non-reducing PSII reaction centers. The fluorescence parameters measured under the steady state of photosynthesis demonstrated that the increase of Hg concentration led to a decrease in the maximal efficiency of PSII photochemistry, the efficiency of excitation energy capture by the open PSII reaction centers, and the quantum yield of PSII electron transport. Mercury also resulted in a decrease in the coefficients of photochemical and non-photochemical quenching. Mercury may have an acute toxicity on cyanobacteria by inhibiting the quantum yield of photosynthesis sensitively and rapidly. Such changes occurred before any other visible damages that may be evaluated by other conventional measurements. Our results also demonstrated that chlorophyll fluorescence analysis can be used as a useful physiological tool to assess early stages of change in photosynthetic performance of algae in response to heavy metal pollution.

A novel method for the rapid detection of benzo(a)pyrene in liquid milk by dimethyl sulfoxide selectively enhanced synchronous fluorescence spectrometry.

PubMed

Lin, Li-Rong; Luo, He-Dong; Li, Xiu-Ying; Li, Na; Zhou, Na; Jia, Yu-Zhu; Liu, Yi-Hong; Li, Yao-Qun

2014-01-01

Based on the high solubility efficiency and strong fluorescence response of benzo(a)pyrene (BaP) in dimethyl sulfoxide in combination with the high-performance derivative constant-energy synchronous fluorescence spectroscopic (DCESFS) technique, a simple, sensitive and economic method was developed for the determination of BaP in liquid milk. This method comprises ultrasound-assisted solvent extraction, solvent replacement and DCESFS detection. No saponification or other tedious clean-up procedures were needed. The recoveries of BaP in different milk samples were greater than 82%. Detection limits in full- and low-fat milk were 0.03 and 0.04 μg kg(-1), respectively.

Method and apparatus for secondary laser pumping by electron beam excitation

DOEpatents

George, E. Victor; Krupke, William F.; Murray, John R.; Powell, Howard T.; Swingle, James C.; Turner, Jr., Charles E.; Rhodes, Charles K.

1978-01-01

An electron beam of energy typically 100 keV excites a fluorescer gas which emits ultraviolet radiation. This radiation excites and drives an adjacent laser gas by optical pumping or photolytic dissociation to produce high efficiency pulses. The invention described herein was made in the course of, or under, United States Energy Research and Development Administration Contract No. W-7405-Eng-48 with the University of California.

Tomographic imaging of flourescence resonance energy transfer in highly light scattering media

NASA Astrophysics Data System (ADS)

Soloviev, Vadim Y.; McGinty, James; Tahir, Khadija B.; Laine, Romain; Stuckey, Daniel W.; Mohan, P. Surya; Hajnal, Joseph V.; Sardini, Alessandro; French, Paul M. W.; Arridge, Simon R.

2010-02-01

Three-dimensional localization of protein conformation changes in turbid media using Förster Resonance Energy Transfer (FRET) was investigated by tomographic fluorescence lifetime imaging (FLIM). FRET occurs when a donor fluorophore, initially in its electronic excited state, transfers energy to an acceptor fluorophore in close proximity through non-radiative dipole-dipole coupling. An acceptor effectively behaves as a quencher of the donor's fluorescence. The quenching process is accompanied by a reduction in the quantum yield and lifetime of the donor fluorophore. Therefore, FRET can be localized by imaging changes in the quantum yield and the fluorescence lifetime of the donor fluorophore. Extending FRET to diffuse optical tomography has potentially important applications such as in vivo studies in small animal. We show that FRET can be localized by reconstructing the quantum yield and lifetime distribution from time-resolved non-invasive boundary measurements of fluorescence and transmitted excitation radiation. Image reconstruction was obtained by an inverse scattering algorithm. Thus we report, to the best of our knowledge, the first tomographic FLIM-FRET imaging in turbid media. The approach is demonstrated by imaging a highly scattering cylindrical phantom concealing two thin wells containing cytosol preparations of HEK293 cells expressing TN-L15, a cytosolic genetically-encoded calcium FRET sensor. A 10mM calcium chloride solution was added to one of the wells to induce a protein conformation change upon binding to TN-L15, resulting in FRET and a corresponding decrease in the donor fluorescence lifetime. The resulting fluorescence lifetime distribution, the quantum efficiency, absorption and scattering coefficients were reconstructed.

Realizing Highly Efficient Solution-Processed Homojunction-Like Sky-Blue OLEDs by Using Thermally Activated Delayed Fluorescent Emitters Featuring an Aggregation-Induced Emission Property.

PubMed

Wu, Kailong; Wang, Zian; Zhan, Lisi; Zhong, Cheng; Gong, Shaolong; Xie, Guohua; Yang, Chuluo

2018-04-05

Two new blue emitters, i.e., bis-[2-(9,9-dimethyl-9,10-dihydroacridine)-phenyl]-sulfone ( o-ACSO2) and bis-[3-(9,9-dimethyl-9,10-dihydroacridine)-phenyl]-sulfone ( m-ACSO2), with reserved fine thermally activated delayed fluorescent (TADF) nature and simply tuned thermal and optoelectronic properties, were synthesized by isomer engineering. The meta-linking compound, i.e., m-ACSO2, obtains the highest photoluminescence quantum yield with a small singlet-triplet energy gap, a moderate delayed fluorescent lifetime, excellent solubility, and neat film homogeneity. Due to its unique aggregation-induced emission (AIE) character, neat film-based heterojunction-like organic light-emitting diodes (OLEDs) are achievable. By inserting an excitonic inert exciton-blocking layer, the PN heterojunction-like emission accompanied by intefacial exciplex was shifted to a homojunction-like channel mainly from the AIE emitter itself, providing a new tactic to generate efficient blue color from neat films. The solution-processed nondoped sky-blue OLED employing m-ACSO2 as emitter with homojunction-like emission achieved a maximum external quantum efficiency of 17.2%. The design strategies presented herein provide practical methods to construct efficient blue TADF dyes and realize high-performance blue TADF devices.

A Wireless Fiber Photometry System Based on a High-Precision CMOS Biosensor With Embedded Continuous-Time Modulation.

PubMed

Khiarak, Mehdi Noormohammadi; Martianova, Ekaterina; Bories, Cyril; Martel, Sylvain; Proulx, Christophe D; De Koninck, Yves; Gosselin, Benoit

2018-06-01

Fluorescence biophotometry measurements require wide dynamic range (DR) and high-sensitivity laboratory apparatus. Indeed, it is often very challenging to accurately resolve the small fluorescence variations in presence of noise and high-background tissue autofluorescence. There is a great need for smaller detectors combining high linearity, high sensitivity, and high-energy efficiency. This paper presents a new biophotometry sensor merging two individual building blocks, namely a low-noise sensing front-end and a order continuous-time modulator (CTSDM), into a single module for enabling high-sensitivity and high energy-efficiency photo-sensing. In particular, a differential CMOS photodetector associated with a differential capacitive transimpedance amplifier-based sensing front-end is merged with an incremental order 1-bit CTSDM to achieve a large DR, low hardware complexity, and high-energy efficiency. The sensor leverages a hardware sharing strategy to simplify the implementation and reduce power consumption. The proposed CMOS biosensor is integrated within a miniature wireless head mountable prototype for enabling biophotometry with a single implantable fiber in the brain of live mice. The proposed biophotometry sensor is implemented in a 0.18- CMOS technology, consuming from a 1.8- supply voltage, while achieving a peak dynamic range of over a 50- input bandwidth, a sensitivity of 24 mV/nW, and a minimum detectable current of 2.46- at a 20- sampling rate.

Simple replacement of violaxanthin by zeaxanthin in LHC-II does not cause chlorophyll fluorescence quenching.

PubMed

Dreuw, Andreas; Wormit, Michael

2008-03-01

Recently, a mechanism for the energy-dependent component (qE) of non-photochemical quenching (NPQ), the fundamental photo-protection mechanism in green plants, has been suggested. Replacement of violaxanthin by zeaxanthin in the binding pocket of the major light harvesting complex LHC-II may be sufficient to invoke efficient chlorophyll fluorescence quenching. Our quantum chemical calculations, however, show that the excited state energies of violaxanthin and zeaxanthin are practically identical when their geometry is constrained to the naturally observed structure of violaxanthin in LHC-II. Therefore, since violaxanthin does not quench LHC-II, zeaxanthin should not either. This theoretical finding is nicely in agreement with experimental results obtained by femtosecond spectroscopy on LHC-II complexes containing violaxanthin or zeaxanthin.

Benzimidazobenzothiazole-based highly-efficient thermally activated delayed fluorescence emitters for organic light-emitting diodes: A quantum-chemical TD-DFT study

NASA Astrophysics Data System (ADS)

Zhu, Qiuling; Wen, Keke; Feng, Songyan; Guo, Xugeng; Zhang, Jinglai

2018-03-01

Based upon two thermally activated delayed fluorescence (TADF) emitters 1 and 2, compounds 3-6 have been designed by replacing the carbazol group with the bis(4-biphenyl)amine one (3 and 4) and introducing the electron-withdrawing CF3 group into the acceptor unit of 3 and 4 (5 and 6). It is found that the present calculations predict comparable but relatively large energy differences (approximate 0.5 eV) between the lowest singlet S1 and triplet T1 states (Δ EST) for the six targeted compounds. In order to explain the highly-efficient TADF behavior observed in compounds 1 and 2, the"triplet reservoir" mechanism has been proposed. In addition, the fluorescence rates of all six compounds are very large, in 107-108 orders of magnitude. According to the present calculations, it is a reasonable assumption that the newly designed compounds 3-6 could be considered as the potential TADF emitters, which needs to be further verified by experimental techniques.

Compressive hyperspectral time-resolved wide-field fluorescence lifetime imaging

NASA Astrophysics Data System (ADS)

Pian, Qi; Yao, Ruoyang; Sinsuebphon, Nattawut; Intes, Xavier

2017-07-01

Spectrally resolved fluorescence lifetime imaging and spatial multiplexing have offered information content and collection-efficiency boosts in microscopy, but efficient implementations for macroscopic applications are still lacking. An imaging platform based on time-resolved structured light and hyperspectral single-pixel detection has been developed to perform quantitative macroscopic fluorescence lifetime imaging (MFLI) over a large field of view (FOV) and multiple spectral bands simultaneously. The system makes use of three digital micromirror device (DMD)-based spatial light modulators (SLMs) to generate spatial optical bases and reconstruct N by N images over 16 spectral channels with a time-resolved capability (∼40 ps temporal resolution) using fewer than N2 optical measurements. We demonstrate the potential of this new imaging platform by quantitatively imaging near-infrared (NIR) Förster resonance energy transfer (FRET) both in vitro and in vivo. The technique is well suited for quantitative hyperspectral lifetime imaging with a high sensitivity and paves the way for many important biomedical applications.

Quantitative fluorescence measurements performed on typical matrix molecules in matrix-assisted laser desorption/ionisation

NASA Astrophysics Data System (ADS)

Allwood, D. A.; Dyer, P. E.

2000-11-01

Fundamental photophysical parameters have been determined for several molecules that are commonly used as matrices, e.g. ferulic acid, within matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Fluorescence quantum efficiencies ( φqe), singlet decay rates ( kl), vibrationless ground-singlet transition energies and average fluorescence wavelengths have been obtained from solid and solution samples by quantitative optical measurements. This new data will assist in modelling calculations of MALDI processes and in highlighting desirable characteristics of MALDI matrices. φqe may be as high as 0.59 whilst the radiative decay rate ( kf) appears to be within the (0.8-4)×10 8 s -1 range. Interestingly, α-cyano-4-hydroxycinnamic acid (α-CHC) has a very low φqe and fast non-radiative decay rate which would imply a rapid and efficient thermalisation of electronic excitation. This is in keeping with observations that α-CHC exhibits low threshold fluences for ion detection and the low fluences at which α-CHC tends to fragment.

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

Cao, Lingyun; Lin, Zekai; Shi, Wenjie

The dimensionality dependency of resonance energy transfer is of great interest due to its importance in understanding energy transfer on cell membranes and in low-dimension nanostructures. Light harvesting two-dimensional metal–organic layers (2D-MOLs) and three-dimensional metal–organic frameworks (3D-MOFs) provide comparative models to study such dimensionality dependence with molecular accuracy. Here we report the construction of 2D-MOLs and 3D-MOFs from a donor ligand 4,4',4''-(benzene-1,3,5-triyl-tris(ethyne-2,1-diyl))tribenzoate (BTE) and a doped acceptor ligand 3,3',3''-nitro-4,4',4''-(benzene-1,3,5-triyl-tris(ethyne-2,1-diyl))tribenzoate (BTE-NO2). These 2D-MOLs and 3D-MOFs are connected by similar hafnium clusters, with key differences in the topology and dimensionality of the metal–ligand connection. Energy transfer from donors to acceptors through themore » 2D-MOL or 3D-MOF skeletons is revealed by measuring and modeling the fluorescence quenching of the donors. We found that energy transfer in 3D-MOFs is more efficient than that in 2D-MOLs, but excitons on 2D-MOLs are more accessible to external quenchers as compared with those in 3D-MOFs. These results not only provide support to theoretical analysis of energy transfer in low dimensions, but also present opportunities to use efficient exciton migration in 2D materials for light-harvesting and fluorescence sensing.« less

A new fluorescent probe for colorimetric and ratiometric detection of sulfur dioxide derivatives in liver cancer cells

NASA Astrophysics Data System (ADS)

Li, Dong-Peng; Wang, Zhao-Yang; Cui, Jie; Wang, Xin; Miao, Jun-Ying; Zhao, Bao-Xiang

2017-03-01

A new ratiometric fluorescent probe was constructed with hemicyanine and 7-nitrobenzofurazan for detection of sulfur dioxide derivatives (HSO3-/SO32-). The ratiometric response mode could be attributed to the efficient FRET (Förster resonance energy transfer) platform. The probe exbihited some desirable properties including fast response (within 2 minutes), good selectivity and high sensitivity. Moreover, the probe could detect endogenous HSO3- in liver cancer cells rather than normal liver cells, implying the diagnosal potential of the probe.

Daylighting with Fluorescent Concentrators and Highly Reflective Silver-Coated Plastic Films: A New Application for New Materials

NASA Astrophysics Data System (ADS)

Zastrow, Armin; Wittwer, Volker

1986-09-01

The interest in efficient daylighting systems has grown recently, due to their potential for saving a considerable amount of electrical energy used for lighting purposes. In this paper we discuss the properties of daylighting systems based on either fluorescent planar concentrators and transparent light guiding plates or light pipes coated with highly reflective silver coated plastic films. Finally we give first results from a demonstration project, daylighting systems in the students' living quarters in Stuttgart-Hohenheim, which is supported by the Commission of the European Communities.

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

PubMed

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

2015-06-01

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

Novel energy relay dyes for high efficiency dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Rahman, Md. Mahbubur; Ko, Min Jae; Lee, Jae-Joon

2015-02-01

4',6-Diamidino-2-phenylindole (DAPI) and Hoechst 33342 (H33342) were used as novel energy relay dyes (ERDs) for an efficient energy transfer to the N719 dye in I-/I3- based liquid-junction dye-sensitized solar cells (DSSCs). The introduction of the ERDs, either as an additive in the electrolyte or as a co-adsorbent, greatly enhanced the power conversion efficiencies (PCEs), mainly because of an increase in short-circuit current density (Jsc). This was attributed to the effects of non-radiative Förster-type excitation energy transfer as well as the radiative (emission)-type fluorescent energy transfer to the sensitizers. The net PCEs for the N719-sensitized DSSCs with DAPI and H33342 were 10.65% and 10.57%, and showed an improvement of 12.2% and 11.4% over control devices, respectively.4',6-Diamidino-2-phenylindole (DAPI) and Hoechst 33342 (H33342) were used as novel energy relay dyes (ERDs) for an efficient energy transfer to the N719 dye in I-/I3- based liquid-junction dye-sensitized solar cells (DSSCs). The introduction of the ERDs, either as an additive in the electrolyte or as a co-adsorbent, greatly enhanced the power conversion efficiencies (PCEs), mainly because of an increase in short-circuit current density (Jsc). This was attributed to the effects of non-radiative Förster-type excitation energy transfer as well as the radiative (emission)-type fluorescent energy transfer to the sensitizers. The net PCEs for the N719-sensitized DSSCs with DAPI and H33342 were 10.65% and 10.57%, and showed an improvement of 12.2% and 11.4% over control devices, respectively. Electronic supplementary information (ESI) available: Details of the materials and instrumentation, device fabrication, measurement and calculations of the quantum yield (Qd), calculations of the Förster radius (R0), optimization of the ERDs mixed with electrolyte according to Type-A strategy; normalized absorption profiles of the N3, Ru505, and Z907 dyes and the emission profiles of DAPI and H33342; J-V characteristics of ERD-incorporated DSSCs sensitized with N3, Ru505, and Z907 (Type-A strategy). See DOI: 10.1039/c4nr06645f

Spectroscopic insights on selfassembly and excited state interactions between rhodamine and phthalocyanine molecules.

PubMed

Geng, Hao; Zhang, Xian-Fu

2015-03-15

The absorption and fluorescence spectra as well as fluorescence lifetimes of tetrasulfonated zinc phthalocyanine ZnPc(SO3Na)4 were measured in the absence and presence of four rhodamine dyes, Rhodamine B (RB), Ethyl rhodamine B (ERB), Rhodamine 6G (R6G), Rhodamine 110 (R110), and Pyronine B (PYB). The ground state complexes of phthalocyanine-(Rhodamine)2 were observed which exhibit new absorption bands. The binding constants are all very large (0.86×10(5)-0.22×10(8) M(-1)), suggesting rhodamine-phthalocyanine pairs are very good combinations for efficient selfassembly. Both the fluorescence intensity and the lifetime values of ZnPc(SO3Na)4 were decreased by the presence of rhodamines. The structural effect of rhodamines on selfassembly is significant. The ground state binding and dynamic quenching capability is PYB>R6G>ERB>RB>R110. The dynamic fluorescence quenching is due to the photoinduced electron transfer (PET). The PET rate constant is very large and in the order of 10(13) M(-1) s(-1), much greater than kf and kic (in the order of 10(8) M(-1) s(-1)), which means that the PET efficiency is almost 100%. Therefore the non-covalent Pc-rhodamine is a very good pair of donor/acceptor for potential efficient solar energy conversion. Copyright © 2014 Elsevier B.V. All rights reserved.

Highly Efficient Full-Color Thermally Activated Delayed Fluorescent Organic Light-Emitting Diodes: Extremely Low Efficiency Roll-Off Utilizing a Host with Small Singlet-Triplet Splitting.

PubMed

Zhang, Dongdong; Zhao, Chongguang; Zhang, Yunge; Song, Xiaozeng; Wei, Pengcheng; Cai, Minghan; Duan, Lian

2017-02-08

Numerous efforts have been devoted to boost the efficiency of thermally activated delayed fluorescence (TADF) devices; however, strategies to suppress the device efficiency roll-off are still in urgent need. Here, a general and effective approach to suppress the efficiency roll-off of TADF devices is proposed, that is, utilizing TADF materials as the hosts for TADF emitters. Bearing small singlet-triplet splitting (ΔE ST ) with donor and acceptor units, TADF materials as the hosts possess the potential to achieve matched frontier energy levels with the adjacent transporting layers, facilitating balanced charge injection as well as bipolar charge transport mobilities beneficial to the balanced charges transportation. Furthermore, an enhanced Förster energy transfer from the host to the dopant can be anticipated, helpful to reduce the exciton concentration. Based on the principles, a new TADF material based on indeno[2,1-b]carbazole/1,3,5-triazin derivation is synthesized and used as the universal host for the full-color TADF devices. Remarkable low efficiency roll-off was achieved with above 90% of the maximum external quantum efficiencies (EQE max 's) maintained even at a brightness of 2000 cd/m 2 , along with EQE max 's of 23.2, 21.0, and 19.2% for orange, green, and sky-blue TADF devices, respectively. Through computational simulation, we identified the suppressed exciton annihilation rates compared with devices adopting conventional hosts. The state-of-the-art low efficiency roll-off of those TADF devices manifests the great potential of such host design strategy, paving an efficient strategy toward their practical application.

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 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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03588k

Investigating the association between photosynthetic efficiency and generation of biophotoelectricity in autotrophic microbial fuel cells

PubMed Central

Ciniciato, Gustavo P. M. K.; Ng, Fong-Lee; Phang, Siew-Moi; Jaafar, Muhammad Musoddiq; Fisher, Adrian C.; Yunus, Kamran; Periasamy, Vengadesh

2016-01-01

Microbial fuel cells operating with autotrophic microorganisms are known as biophotovoltaic devices. It represents a great opportunity for environmentally-friendly power generation using the energy of the sunlight. The efficiency of electricity generation in this novel system is however low. This is partially reflected by the poor understanding of the bioelectrochemical mechanisms behind the electron transfer from these microorganisms to the electrode surface. In this work, we propose a combination of electrochemical and fluorescence techniques, giving emphasis to the pulse amplitude modulation fluorescence. The combination of these two techniques allow us to obtain information that can assist in understanding the electrical response obtained from the generation of electricity through the intrinsic properties related to the photosynthetic efficiency that can be obtained from the fluorescence emitted. These were achieved quantitatively by means of observed changes in four photosynthetic parameters with the bioanode generating electricity. These are the maximum quantum yield (Fv/Fm), alpha (α), light saturation coefficient (Ek) and maximum rate of electron transfer (rETRm). The relationship between the increases in the current density collected by the bioanode to the decrease of the rETRm values in the photosynthetic pathway for the two microorganisms was also discussed. PMID:27502051

Investigating the association between photosynthetic efficiency and generation of biophotoelectricity in autotrophic microbial fuel cells

NASA Astrophysics Data System (ADS)

Ciniciato, Gustavo P. M. K.; Ng, Fong-Lee; Phang, Siew-Moi; Jaafar, Muhammad Musoddiq; Fisher, Adrian C.; Yunus, Kamran; Periasamy, Vengadesh

2016-08-01

Microbial fuel cells operating with autotrophic microorganisms are known as biophotovoltaic devices. It represents a great opportunity for environmentally-friendly power generation using the energy of the sunlight. The efficiency of electricity generation in this novel system is however low. This is partially reflected by the poor understanding of the bioelectrochemical mechanisms behind the electron transfer from these microorganisms to the electrode surface. In this work, we propose a combination of electrochemical and fluorescence techniques, giving emphasis to the pulse amplitude modulation fluorescence. The combination of these two techniques allow us to obtain information that can assist in understanding the electrical response obtained from the generation of electricity through the intrinsic properties related to the photosynthetic efficiency that can be obtained from the fluorescence emitted. These were achieved quantitatively by means of observed changes in four photosynthetic parameters with the bioanode generating electricity. These are the maximum quantum yield (Fv/Fm), alpha (α), light saturation coefficient (Ek) and maximum rate of electron transfer (rETRm). The relationship between the increases in the current density collected by the bioanode to the decrease of the rETRm values in the photosynthetic pathway for the two microorganisms was also discussed.

Fluorescence Quenching of CdSe/ZnS Quantum Dots by Using Black Hole Quencher Molecules Intermediated With Peptide for Biosensing Application.

PubMed

Pillai, Sreenadh Sasidharan; Yukawa, Hiroshi; Onoshima, Daisuke; Biju, Vasudevanpillai; Baba, Yoshinobu

2015-12-17

Quantum dots (QDs) have recently been investigated as fluorescent probes for detecting a very small number of biomolecules and live cells; however, the establishment of molecular imaging technology with on-off control of QD fluorescence remains to be established. Here we have achieved the fluorescence off state of QDs with the conjugation of black hole quencher (BHQ) molecules intermediated with peptide by using streptavidin-QDs585 and biotin-pep-BHQ-1. The fluorescence of streptavidin-QDs585 was decreased by the addition of biotin-pep-BHQ-1 in a dose-dependent manner. It has been suggested that the decrease in QDs585 fluorescence occurred through a Förster resonance energy transfer (FRET) mechanism from the analysis of fluorescence intensity and lifetime of streptavidin-QDs585 and QDs585-pep-BHQ-1. QDs585 fluorescence could be quenched by more than 60% efficiency in this system. The sequence of intermediate peptide (pep) was GPLGVRGK, which can be cleaved by matrix metalloproteinases (MMPs) produced by cancer cells. QDs585-pep-BHQ-1 is thus expected to detect the MMP production by the recovery of QDs585 fluorescence as a new bioanalytical agent for molecular imaging.

Ratiometric Near-Infrared Fluorescent Probes Based On Through-Bond Energy Transfer and π-Conjugation Modulation between Tetraphenylethene and Hemicyanine Moieties for Sensitive Detection of pH Changes in Live Cells.

PubMed

Wang, Jianbo; Xia, Shuai; Bi, Jianheng; Fang, Mingxi; Mazi, Wafa; Zhang, Yibin; Conner, Nathan; Luo, Fen-Tair; Lu, H Peter; Liu, Haiying

2018-04-18

In this paper, we present three ratiometric near-infrared fluorescent probes (A-C) for accurate, ratiometric detection of intracellular pH changes in live cells. Probe A consists of a tetraphenylethene (TPE) donor and near-infrared hemicyanine acceptor in a through-bond energy transfer (TBET) strategy, while probes B and C are composed of TPE and hemicyanine moieties through single and double sp 2 carbon-carbon bond connections in a π-conjugation modulation strategy. The specific targeting of the probes to lysosomes in live cells was achieved by introducing morpholine residues to the hemicyanine moieties to form closed spirolactam ring structures. Probe A shows aggregation-induced emission (AIE) property at neutral or basic pH, while probes B and C lack AIE properties. At basic or neutral pH, the probes only show fluorescence of TPE moieties with closed spirolactam forms of hemicyanine moieties, and effectively avoid blind fluorescence imaging spots, an issue which typical intensity-based pH fluorescent probes encounter. Three probes show ratiometric fluorescence responses to pH changes from 7.0 to 3.0 with TPE fluorescence decreases and hemicyanine fluorescence increases, because acidic pH makes the spirolactam rings open to enhance π-conjugation of hemicyanine moieties. However, probe A shows much more sensitive ratiometric fluorescence responses to pH changes from 7.0 to 3.0 with remarkable ratio increase of TPE fluorescence to hemicyanine fluorescence up to 238-fold than probes B and C because of its high efficiency of energy transfer from TPE donor to the hemicyanine acceptor in the TBET strategy. The probe offers dual Stokes shifts with a large pseudo-Stokes shift of 361 nm and well-defined dual emissions, and allows for colocalization of the imaging readouts of visible and near-infrared fluorescence channels to achieve more precisely double-checked ratiometric fluorescence imaging. These platforms could be employed to develop a variety of novel ratiometric fluorescent probes for accurate detection of different analytes in applications of chemical and biological sensing, imaging, and diagnostics by introducing appropriate sensing ligands to hemicyanine moieties to form on-off spirolactam switches.

Time-resolved tryptophan fluorescence in photosynthetic reaction centers from Rhodobacter sphaeroides

NASA Technical Reports Server (NTRS)

Godik, V. I.; Blankenship, R. E.; Causgrove, T. P.; Woodbury, N.

1993-01-01

Tryptophan fluorescence of reaction centers isolated from Rhodobacter sphaeroides, both stationary and time-resolved, was studied. Fluorescence kinetics were found to fit best a sum of four discrete exponential components. Half of the initial amplitude was due to a component with a lifetime of congruent to 60 ps, belonging to Trp residues, capable of efficient transfer of excitation energy to bacteriochlorophyll molecules of the reaction center. The three other components seem to be emitted by Trp ground-state conformers, unable to participate in such a transfer. Under the influence of intense actinic light, photooxidizing the reaction centers, the yield of stationary fluorescence diminished by congruent to 1.5 times, while the number of the kinetic components and their life times remained practically unchanged. Possible implications of the observed effects for the primary photosynthesis events are considered.

X-ray fluorescence tomographic system design and image reconstruction.

PubMed

Cong, Wenxiang; Shen, Haiou; Cao, Guohua; Liu, Hong; Wang, Ge

2013-01-01

In this paper, we presented a new design of x-ray fluorescence CT imaging system. For detecting fuorescence signals of gold nanoparticles in-vivo, multiple spectroscopic detectors are arranged and rotated orthogonal to an excited region of interest so that a localized scan can be acquired with a maximized efficiency. Excitation filtration was employed to minimize the effects of low-energy x-rays and background scattering for lowering radiation dose to the object. Numerical simulations showed that the radiation dose is less than 300 mGy/second for a complete 30 views tomographic scan; and the sensitivity of 3D fluorescence signal detection is up to 0.2% contrast concentrations of nanoparticles. The x-ray fluorescence computed tomography is an important molecular imaging tool. It can be used directly in samall animal research. It has great translational potential for future clinical applications.

FRET-based glucose monitoring for bioprocessing

NASA Astrophysics Data System (ADS)

Bartolome, Amelita; Smalls-Mantey, Lauren; Lin, Debora; Rao, Govind; Tolosa, Leah

2006-02-01

The glucose-mediated conformational changes in the glucose binding protein (GBP) have been exploited in the development of fluorescence based glucose sensors. The fluorescence response is generated by a polarity sensitive dye attached to a specific site. Such fluorescent sensors respond to submicromolar glucose at diffusion-controlled rates mimicking the wild type. However, such sensors have been limited to in vitro glucose sensing because of the preliminary dye-labeling step. In the study described here, the dye-labeling step is omitted by genetically encoding the GBP with two green fluorescent mutants namely, the green fluorescent protein (GFP) and the yellow fluorescent protein (YFP) in the N- and C-terminal ends, respectively. These two GFP mutants comprise a fluorescence resonance energy transfer (FRET) donor and acceptor pair. Thus, when glucose binds with GBP, the conformational changes affect the FRET efficiency yielding a dose-dependent response. A potential application for this FRET-based glucose biosensor is online glucose sensing in bioprocessing and cell culture. This was demonstrated by the measurement of glucose consumption in yeast fermentation. Further development of this system should yield in vivo measurement of glucose in bioprocesses.

[Study on synthesis and matching degree of energy level of terbium complexes using o-fluoro-benzoic acid as ligand].

PubMed

Tao, Dong-Liang; Zhang, Kun; Zhang, Hong; Cui, Yu-Min; Xu, Yi-Zhuang; Liu, Yu-Hai

2014-04-01

Tb(2-FBA)3 x 2H2O and Tb(2-FBA)3 phen were synthesized using o-fluoro-benzoic acid (2-FBA) as the first ligand, and 1,10-phenanthroline (phen) as the second ligand. Elemental analysis and IR spectra were employed to characterize the molecular composition of the two kinds of lanthanide complexes. The UV absorption spectra with same concentration show that the second ligand phen of Tb(2-FBA)3 phen absorbs the portion of the UV light instead of the first ligand 2-FBA. Liquid fluorescence spectra with same concentration show that the fluorescence intensity of Tb(2-FBA)3 x 2H2O is higher than that of Tb (2-FBA)3 phen. The analytical results show that the energy level of 2-FBA matches the lowest excited state energy level of Tb3+ (5D4) better than that of phen. The O-H oscillation of the crystal water in Tb(2-FBA)3 x 2H2O will greatly consume the absorbed energy by ligands, and cause the fluorescence intensity of Tb(2-FBA)3 x 2H2O significantly decline. The energy level of triplet state of the first ligand 2-FBA corresponding to the absorption peak 273 nm has poor matching degree with the 5D4 energy level of Tb3+. In this case, the emission intensity of Tb(2-FBA)3 x 2H2O is still stronger than that of Tb(2-FBA)3 phen. It illustrates that the energy level of the triplet state of the first ligand 2-FBA corresponding to 252 nm has much better matching degree with the lowest excited state of 5D4 energy level of Tb3+ than that of phen. It is the only way to compensate for energy loss by thermal vibration of water molecules and low energy transfer efficiency for poor matching degree between the energy level of corresponding to 273 nm of the first ligand 2-FBA and 5D4 energy level of Tb3+. By combining UV absorption spectra with fluorescence spectra of lanthanide complexes to qualitatively analyze energy level of ligands, the contribution of different types of ligands to the fluorescence properties can be preliminarily understood.

Fluorescence sensing and photocatalytic properties of a 2D stable and biocompatible Zn(II)-based polymer

NASA Astrophysics Data System (ADS)

Wu, Jian; Li, Bao-Hong; Zhong, Hua-Rui; Qiu, Shuo-Wen; Liang, Yi-Wen; Zhuang, Xiao-Yi; Singh, Amita; Kumar, Abhinav

2018-04-01

A biocompatible metal-organic framework (MOF) [Zn2(TPL)(FA)(OH)(H2O)] (1) (TPL = theophylline and H2FA = fumaric acid) had been chosen which offers an ideal model for the development of fluorescencent chemosensor using simple synthetic protocol. The MOF 1 have been tested as a fluorescent chemosensor against nitro-aromatics (NACs) and it displayed high selectivity for 4-NT over other NACs as evident by the emission spectroscopy. The alleviation in fluorescence intensity of 1 in presence of different NACs have been explained with the help of theoretical calculations which suggested that there is occurrence of both electron and energy transfer processes, in addition to electrostatic interaction between 1 and NACs which may be responsible for the unprecedented selective alleviation in the fluorescence intensity. Also, 1 had been deployed as a photocatalyst for the degradation of methyl violet (MV) and Rhodamine B (Rh B) in aqueous solution under UV irradiation. The photocatalytic results indicated the 1 exhibit 85% photocatalytic efficiency against Rh B in 100 min, while its efficiency against MV was only 50% under the identical experimental conditions. The possible mechanism for the photocatalytic activity has been proposed using density of states (DOS) calculations.

Influence of Donor on the Sensing Performance of a Series of Through-Bond Energy Transfer-Based Two-photon Fluorescent Cu(2+) Probes.

PubMed

Zhang, Yu-Jin; Wang, Xin; Zhou, Yong; Wang, Chuan-Kui

2016-07-01

Optical properties of a series of molecular two-photon fluorescent Cu(2+) probes containing the same acceptor (rhodamine group) are analyzed using time-dependent density functional theory in combination with analytical response theory. Special emphasis is placed on evolution of the probes' optical properties in the presence of Cu(2+) . In this study, the compound with naphthalene as the donor is shown to be excellent ratiometric fluorescent chemosensor, whereas the compound with quinoline derivative as the donor shows off/on-typed colorimetric fluorescent response. For the compound with naphthalimide derivative as the donor, changing the connection between the donor and acceptor can efficiently prevent the fluorescent quenching of the probe both in the absence and presence of Cu(2+) . The donor moiety and the connection between donor and acceptor are thus found to play dominant roles on sensing performance of these probes. Moreover, distributions of molecular orbitals involved in the excitation and emission of the probes are analyzed to explore responsive mechanism of the probes. The through-bond energy transfer process is theoretically demonstrated. Our results are used to elucidate the available experimental measurements. This work is helpful to understand the relationships of structure with optical properties for the studied probes. © 2016 The American Society of Photobiology.

Spatio-temporal imaging of EGF-induced activation of protein kinase A by FRET in living cells

NASA Astrophysics Data System (ADS)

Wang, Jin Jun; Chen, Xiao-Chuan; Xing, Da

2004-07-01

Intracellular molecular interaction is important for the study of cell physiology, yet current relevant methods require fixation or microinjection and lack temporal or spatial resolution. We introduced a new method -- fluorescence resonance energy transfer (FRET) to detect molecular interaction in living cells. On the basis of FRET principle, A-kinase activity reporter (AKAR) protein was designed to consist of the fusions of cyan fluorescent protein (CFP), a phosphoamino acid binding domain, a consensus substrate for protein kinase-A (PKA), and yellow fluorescent protein (YFP). In this study, the designed pAKAR plasmid was used to transfect a human lung cancer cell line (ASTC-a-1). When the AKAR-transfected cells were treated by forskolin (Fsk), we were able to observe the efficient transfer of energy from excited CFP to YFP within the AKAR molecule by fluorescence microcopy, whereas no FRET was detected in the transfected cells without the treatment of Fsk. When the cells were treated by Epidermal growth factor (EGF), the change of FRET was observed at different subcellular locations, reflecting PKA activation inside the cells upon EGF stimulation. The successful design of a fluorescence reporter of PKA activation and its application demonstrated the superiority of this technology in the research of intracellular protein-protein interaction.

An in vitro FRET-based assay for the analysis of SUMO conjugation and isopeptidase cleavage.

PubMed

Stankovic-Valentin, Nicolas; Kozaczkiewicz, Lukasz; Curth, Katja; Melchior, Frauke

2009-01-01

To measure rates of sumoylation and isopeptidase cleavage in vitro, we developed an enzyme assay that is based on fluorescence resonance energy transfer (FRET). FRET is a process by which the excited state energy of a fluorescent donor molecule is transferred to an acceptor molecule. Efficient energy transfer requires very close proximity, and can therefore be used as a read-out for covalent and non-covalent protein interactions. The assay described here uses bacterially expressed and purified YFP-SUMO-1 and CFP-RanGAP1 as model substrates that are covalently coupled in the presence of recombinant SUMO E1 and E2 enzymes and ATP. Reactions of 25 microl volume, set up in 384-wells plates, give sufficient signal for analysis. Consequently, this assay requires very low amounts of recombinant proteins and allows measurement of time courses in high-throughput format.

The role of energy losses in photosynthetic light harvesting

NASA Astrophysics Data System (ADS)

Krüger, T. P. J.; van Grondelle, R.

2017-07-01

Photosynthesis operates at the bottom of the food chain to convert the energy of light into carbohydrates at a remarkable global rate of about 130 TW. Nonetheless, the overall photosynthetic process has a conversion efficiency of a few percent at best, significantly less than bottom-up photovoltaic cells. The primary photosynthetic steps, consisting of light harvesting and charge separation, are often presented as having near-unity quantum efficiency but this holds only true under ideal conditions. In this review, we discuss the importance of energy loss mechanisms to establish robustness in photosynthetic light harvesting. Thermal energy dissipation of light-harvesting complexes (LHCs) in different environments is investigated and the relationships and contrasts between concentration quenching of high pigment concentrations, photoprotection (non-photochemical quenching), quenching due to protein aggregation, and fluorescence blinking are discussed. The role of charge-transfer states in light harvesting and energy dissipation is highlighted and the importance of controlled protein structural disorder to switch the light-harvesting antennae between effective light harvesters and efficient energy quenchers is underscored. The main LHC of plants, LHCII, is used as a prime example.

Reconsideration of the Detection and Fluorescence Mechanism of a Pyrene-Based Chemosensor for TNT.

PubMed

Lu, Meiheng; Zhou, Panwang; Ma, Yinhua; Tang, Zhe; Yang, Yanqiang; Han, Keli

2018-02-08

The rapid detection of chemical explosives is crucial for national security and public safety, and the investigation of sensing mechanisms is important for designing highly efficient chemosensors. This study theoretically investigates the detection and fluorescence mechanism of a newly synthesized pyrene-based chemosensor for the detection of trinitrotoluene (TNT) through density-functional-theory (DFT) and time-dependent density-functional-theory (TDDFT) methods and suggests a different interaction product of the probe and TNT from previously reported ones [ Mosca et al. J. Am. Chem. Soc. 2015 , 137 , 7967 ]. Instead of forming Meisenheimer complexes, the energies of which are beyond those of the reactants, a low-energy product generated by a π-π-stacking interaction is more rational and favorable. The fluorescence-quenching property further confirms that the π-π-stacking product is the predicted one rather than luminescent Meisenheimer complexes. Frontier-molecular-orbital (FMO)-analysis results show that photoinduced electron transfer (PET) is the mechanism underlying the luminescence quenching of the probe upon exposure to TNT.

Beyond superquenching: Hyper-efficient energy transfer from conjugated polymers to gold nanoparticles

PubMed Central

Fan, Chunhai; Wang, Shu; Hong, Janice W.; Bazan, Guillermo C.; Plaxco, Kevin W.; Heeger, Alan J.

2003-01-01

Gold nanoparticles quench the fluorescence of cationic polyfluorene with Stern–Volmer constants (KSV) approaching 1011 M—1, several orders of magnitude larger than any previously reported conjugated polymer–quencher pair and 9–10 orders of magnitude larger than small molecule dye–quencher pairs. The dependence of KSV on ionic strength, charge and conjugation length of the polymer, and the dimensions (and thus optical properties) of the nanoparticles suggests that three factors account for this extraordinary efficiency: (i) amplification of the quenching via rapid internal energy or electron transfer, (ii) electrostatic interactions between the cationic polymer and anionic nanoparticles, and (iii) the ability of gold nanoparticles to quench via efficient energy transfer. As a result of this extraordinarily high KSV, quenching can be observed even at subpicomolar concentrations of nanoparticles, suggesting that the combination of conjugated polymers with these nanomaterials can potentially lead to improved sensitivity in optical biosensors. PMID:12750470

Theoretical Studies on Two-Photon Fluorescent Hg2+ Probes Based on the Coumarin-Rhodamine System.

PubMed

Zhang, Yujin; Leng, Jiancai

2017-07-20

The development of fluorescent sensors for Hg 2+ has attracted much attention due to the well-known adverse effects of mercury on biological health. In the present work, the optical properties of two newly-synthesized Hg 2+ chemosensors based on the coumarin-rhodamine system (named Pro1 and Pro2) were systematically investigated using time-dependent density functional theory. It is shown that Pro1 and Pro2 are effective ratiometric fluorescent Hg 2+ probes, which recognize Hg 2+ by Förster resonance energy transfer and through bond energy transfer mechanisms, respectively. To further understand the mechanisms of the two probes, we have developed an approach to predict the energy transfer rate between the donor and acceptor. Using this approach, it can be inferred that Pro1 has a six times higher energy transfer rate than Pro2. Thus the influence of spacer group between the donor and acceptor on the sensing performance of the probe is demonstrated. Specifically, two-photon absorption properties of these two probes are calculated. We have found that both probes show significant two-photon responses in the near-infrared light region. However, only the maximum two-photon absorption cross section of Pro1 is greatly enhanced with the presence of Hg 2+ , indicating that Pro1 can act as a potential two-photon excited fluorescent probe for Hg 2+ . The theoretical investigations would be helpful to build a relationship between the structure and the optical properties of the probes, providing information on the design of efficient two-photon fluorescent sensors that can be used for biological imaging of Hg 2+ in vivo.

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

NASA Astrophysics Data System (ADS)

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

2014-03-01

Upconversion of infrared radiation into visible light has been investigated for applications in biological imaging and photovoltaics. However, low conversion efficiency due to small absorption cross-section for infrared light (Yb3+) , and slow rate of energy transfer (to Er3+ states) has prevented application of upconversion photoluminescence (UPL) for diffuse sunlight or imaging tissue samples. Here, we utilize resonant surface plasmon polaritons (SPP) waves to enhance UPL in doped-lanthanide nanocrystals. Our analysis indicates that SPP waves not only enhance the electromagnetic field, and hence weak Purcell effect, but also increases the rate of resonant energy transfer from Yb3+ to Er3+ ions by 6 fold. While we do observe strong metal mediated quenching (14 fold) of green fluorescence on flat metal surfaces, the nanostructured metal is resonant in the infrared, and hence enhances the nanocrystal UPL. This strong columbic effect on energy transfer can have important implications for other fluorescent and excitonic systems too.

Plasma-assisted CO2 conversion: optimizing performance via microwave power modulation

NASA Astrophysics Data System (ADS)

Britun, Nikolay; Silva, Tiago; Chen, Guoxing; Godfroid, Thomas; van der Mullen, Joost; Snyders, Rony

2018-04-01

Significant improvement in the energy efficiency of plasma-assisted CO2 conversion is achieved with applied power modulation in a surfaguide microwave discharge. The obtained values of CO2 conversion and energy efficiency are, respectively, 0.23 and 0.33 for a 0.95 CO2  +  0.05 N2 gas mixture. Analysis of the energy relaxation mechanisms shows that power modulation can potentially affect the vibrational-translational energy exchange in plasma. In our case, however, this mechanism does not play a major role, likely due to the low degree of plasma non-equilibrium in the considered pressure range. Instead, the gas residence time in the discharge active zone together with plasma pulse duration are found to be the main factors affecting the CO2 conversion efficiency at low plasma pulse repetition rates. This effect is confirmed experimentally by the in situ time-resolved two-photon absorption laser-induced fluorescence measurements of CO molecular density produced in the discharge as a result of CO2 decomposition.

Economic photoprotection in photosystem II that retains a complete light-harvesting system with slow energy traps

NASA Astrophysics Data System (ADS)

Belgio, Erica; Kapitonova, Ekaterina; Chmeliov, Jevgenij; Duffy, Christopher D. P.; Ungerer, Petra; Valkunas, Leonas; Ruban, Alexander V.

2014-07-01

The light-harvesting antenna of higher plant photosystem II has an intrinsic capability for self-defence against intense sunlight. The thermal dissipation of excess energy can be measured as the non-photochemical quenching of chlorophyll fluorescence. It has recently been proposed that the transition between the light-harvesting and self-defensive modes is associated with a reorganization of light-harvesting complexes. Here we show that despite structural changes, the photosystem II cross-section does not decrease. Our study reveals that the efficiency of energy trapping by the non-photochemical quencher(s) is lower than the efficiency of energy capture by the reaction centres. Consequently, the photoprotective mechanism works effectively for closed rather than open centres. This type of defence preserves the exceptional efficiency of electron transport in a broad range of light intensities, simultaneously ensuring high photosynthetic productivity and, under hazardous light conditions, sufficient photoprotection for both the reaction centre and the light-harvesting pigments of the antenna.

Silver nanowires enhance absorption of poly(3-hexylthiophene)

NASA Astrophysics Data System (ADS)

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

2013-11-01

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

Silver nanowires enhance absorption of poly(3-hexylthiophene)

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

Smolarek, Karolina; Czechowski, Nikodem; Prymaczek, Aneta

2013-11-11

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

Synthesis and systematic evaluation of dark resonance energy transfer (DRET)-based library and its application in cell imaging.

PubMed

Su, Dongdong; Teoh, Chai Lean; Kang, Nam-Young; Yu, Xiaotong; Sahu, Srikanta; Chang, Young-Tae

2015-03-01

In this paper, we report a new strategy for constructing a dye library with large Stokes shifts. By coupling a dark donor with BODIPY acceptors of tunable high quantum yield, a novel dark resonance energy transfer (DRET)-based library, named BNM, has been synthesized. Upon excitation of the dark donor (BDN) at 490 nm, the absorbed energy is transferred to the acceptor (BDM) with high efficiency, which was tunable in a broad range from 557 nm to 716 nm, with a high quantum yield of up to 0.8. It is noteworthy to mention that the majority of the non-radiative energy loss of the donor was converted into the acceptor's fluorescence output with a minimum leak of donor emission. Fluorescence imaging tested in live cells showed that the BNM compounds are cell-permeable and can also be employed for live-cell imaging. This is a new library which can be excited through a dark donor allowing for strong fluorescence emission in a wide range of wavelengths. Thus, the BNM library is well suited for high-throughput screening or multiplex experiments in biological applications by using a single laser excitation source. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2D fluorescence spectroscopy for monitoring ion-exchange membrane based technologies - Reverse electrodialysis (RED).

PubMed

Pawlowski, Sylwin; Galinha, Claudia F; Crespo, João G; Velizarov, Svetlozar

2016-01-01

Reverse electrodialysis (RED) is one of the emerging, membrane-based technologies for harvesting salinity gradient energy. In RED process, fouling is an undesirable operation constraint since it leads to a decrease of the obtainable net power density due to increasing stack electric resistance and pressure drop. Therefore, early fouling detection is one of the main challenges for successful RED technology implementation. In the present study, two-dimensional (2D) fluorescence spectroscopy was used, for the first time, as a tool for fouling monitoring in RED. Fluorescence excitation-emission matrices (EEMs) of ion-exchange membrane surfaces and of natural aqueous streams were acquired during one month of a RED stack operation. Fouling evolvement on the ion-exchange membrane surfaces was successfully followed by 2D fluorescence spectroscopy and quantified using principal components analysis (PCA). Additionally, the efficiency of cleaning strategy was assessed by measuring the membrane fluorescence emission intensity before and after cleaning. The anion-exchange membrane (AEM) surface in contact with river water showed to be significantly affected due to fouling by humic compounds, which were found to cross through the membrane from the lower salinity (river water) to higher salinity (sea water) stream. The results obtained show that the combined approach of using 2D fluorescence spectroscopy and PCA has a high potential for studying fouling development and membrane cleaning efficiency in ion exchange membrane processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Resonance energy transfer: Dye to metal nanoparticles

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

Wari, M. N.; Pujar, G. H.; Inamdar, S. R., E-mail: him-lax3@yahoo.com

2015-06-24

In the present study, surface energy transfer (SET) from Coumarin 540A (C540 A) to Gold nanoparticle (Au) is demonstrated. The observed results show pronounced effect on the photoluminescence intensity and shortening of the lifetime of Coumarin 540A upon interaction with the spherical gold nanoparticle, also there are measured effects on radiative rate of the dye. Experimental results are analyzed with fluorescence resonance energy transfer (FRET) and SET theories. The results obtained from distance-dependent quenching provide experimental evidence that the efficiency curve slope and distance of quenching is best modeled by surface energy transfer process.

Tapping the Unused Potential of Photosynthesis with a Heterologous Electron Sink.

PubMed

Berepiki, Adokiye; Hitchcock, Andrew; Moore, C Mark; Bibby, Thomas S

2016-12-16

Increasing the efficiency of the conversion of light energy to products by photosynthesis represents a grand challenge in biotechnology. Photosynthesis is limited by the carbon-fixing enzyme Rubisco resulting in much of the absorbed energy being wasted as heat or fluorescence or lost as excess reductant via alternative electron dissipation pathways. To harness this wasted reductant, we engineered the model cyanobacterium Synechococcus PCC 7002 to express the mammalian cytochrome P450 CYP1A1 to serve as an artificial electron sink for excess electrons derived from light-catalyzed water-splitting. This improved photosynthetic efficiency by increasing the maximum rate of photosynthetic electron flow by 31.3%. A simple fluorescent assay for CYP1A1 activity demonstrated that the P450 was functional in the absence of its native reductase, that activity was light-dependent and scaled with irradiance. We show for the first time in live cells that photosynthetic reductant can be redirected to power a heterologous cytochrome P450. Furthermore, Synechococcus PCC 7002 expressing CYP1A1 degraded the herbicide atrazine, which is a widespread environmental pollutant.

Energy transfer in a mechanically trapped exciplex.

PubMed

Klosterman, Jeremy K; Iwamura, Munetaka; Tahara, Tahei; Fujita, Makoto

2009-07-15

Host-guest complexes involving M(6)L(4) coordination cages can display unusual photoreactivity, and enclathration of the very large fluorophore bisanthracene resulted in an emissive, mechanically trapped intramolecular exciplex. Mechanically linked intramolecular exciplexes are important for understanding the dependence of energy transfer on donor-acceptor distance, orientation, and electronic coupling but are relatively unexplored. Steady-state and picosecond time-resolved fluorescence measurements have revealed that selective excitation of the encapsulated guest fluorophore results in efficient energy transfer from the excited guest to an emissive host-guest exciplex state.

Optical design of tunnel lighting with white light-emitting diodes.

PubMed

Tsai, Ming-Shiou; Lee, Xuan-Hao; Lo, Yi-Chien; Sun, Ching-Cherng

2014-10-10

This paper presents a tunnel lighting design consisting of a cluster light-emitting diode and a free-form lens. Most of the energy emitted from the proposed luminaire is transmitted onto the surface of the road in front of drivers, and the probability that that energy is emitted directly into drivers' eyes is low. Compared with traditional fluorescent lamps, the proposed luminaire, of which the optical utilization factor, optical efficiency, and uniformity are, respectively, 44%, 92.5%, and 0.72, exhibits favorable performance in energy saving, glare reduction, and traffic safety.

PET and NIR Optical Imaging Using Self-Illuminating 64Cu-Doped Chelator-Free Gold Nanoclusters

PubMed Central

Hu, Hao; Huang, Peng; Weiss, Orit Jacobson; Yan, Xuefeng; Yue, Xuyi; Zhang, Molly Gu; Tang, Yuxia; Nie, Liming; Ma, Ying; Niu, Gang; Wu, Kaichun; Chen, Xiaoyuan

2014-01-01

Self-illuminating fluorescence imaging without autofluorescence background interference has recently aroused more research interests in molecular imaging. Currently, only a few self-illuminating probes were developed, based mainly on toxic quantum dots such as CdSe, CdTe. Herein, we report a novel design of nontoxic self-illuminating gold nanocluster (64Cu-doped AuNCs) for dual-modality positron emission tomography (PET) and near-infrared (NIR) fluorescence imaging based on Cerenkov resonance energy transfer (CRET). PET radionuclide 64Cu was introduced by a chelator-free doping method, which played dual roles as the energy donor and the PET imaging source. Meanwhile, AuNCs acted as the energy acceptor for NIR fluorescence imaging. 64Cu-doped AuNCs exhibited efficient CRET-NIR and PET imaging both in vitro and in vivo. In a U87MG glioblastoma xenograft model, 64Cu-doped AuNCs showed high tumor uptake (14.9%ID/g at 18 h) and produced satisfactory tumor self-illuminating NIR images in the absence of external excitation. This self-illuminating nanocluster with non-toxicity and good biocompatibility can be employed as a novel imaging contrast agent for biomedical applications, especially for molecular imaging. PMID:25224367

PET and NIR optical imaging using self-illuminating (64)Cu-doped chelator-free gold nanoclusters.

PubMed

Hu, Hao; Huang, Peng; Weiss, Orit Jacobson; Yan, Xuefeng; Yue, Xuyi; Zhang, Molly Gu; Tang, Yuxia; Nie, Liming; Ma, Ying; Niu, Gang; Wu, Kaichun; Chen, Xiaoyuan

2014-12-01

Self-illuminating fluorescence imaging without autofluorescence background interference has recently aroused more research interests in molecular imaging. Currently, only a few self-illuminating probes were developed, based mainly on toxic quantum dots such as CdSe, CdTe. Herein, we report a novel design of nontoxic self-illuminating gold nanocluster ((64)Cu-doped AuNCs) for dual-modality positron emission tomography (PET) and near-infrared (NIR) fluorescence imaging based on Cerenkov resonance energy transfer (CRET). PET radionuclide (64)Cu was introduced by a chelator-free doping method, which played dual roles as the energy donor and the PET imaging source. Meanwhile, AuNCs acted as the energy acceptor for NIR fluorescence imaging. (64)Cu-doped AuNCs exhibited efficient CRET-NIR and PET imaging both in vitro and in vivo. In a U87MG glioblastoma xenograft model, (64)Cu-doped AuNCs showed high tumor uptake (14.9 %ID/g at 18 h) and produced satisfactory tumor self-illuminating NIR images in the absence of external excitation. This self-illuminating nanocluster with non-toxicity and good biocompatibility can be employed as a novel imaging contrast agent for biomedical applications, especially for molecular imaging. Published by Elsevier Ltd.

Efficient triplet application in exciplex delayed-fluorescence OLEDs using a reverse intersystem crossing mechanism based on a ΔES-T of around zero.

PubMed

Zhang, Tianyou; Chu, Bei; Li, Wenlian; Su, Zisheng; Peng, Qi Ming; Zhao, Bo; Luo, Yongshi; Jin, Fangming; Yan, Xingwu; Gao, Yuan; Wu, Hairuo; Zhang, Feng; Fan, Di; Wang, Junbo

2014-08-13

We demonstrate highly efficient exciplex delayed-fluorescence organic light-emitting diodes (OLEDs) in which 4,4',4″-tris[3-methylphenyl(phenyl)aminotriphenylamine (m-MTDATA) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were selected as donor and acceptor components, respectively. Our m-MTDATA:Bphen exciplex electroluminescence (EL) mechanism is based on reverse intersystem crossing (RISC) from the triplet to singlet excited states. As a result, an external quantum efficiency (EQE) of 7.79% at 10 mA/cm(2) was observed, which increases by 3.2 and 1.5 times over that reported in Nat. Photonics 2012, 6, 253 and Appl. Phys. Lett. 2012, 101, 023306, respectively. The high EQE would be attributed to a very easy RISC process because the energy difference between the singlet and triplet excited states is almost around zero. The verdict was proven by photoluminescence (PL) rate analysis at different temperatures and time-resolved spectral analysis. Besides, the study of the transient PL process indicates that the presence of an unbalanced charge in exciplex EL devices is responsible for the low EQE and high-efficiency roll-off. When the exciplex devices were placed in a 100 mT magnetic field, the permanently positive magnetoelectroluminescence and magnetoconductivity were observed. The magnetic properties confirm that the efficient exciplex EL only originates from delayed fluorescence via RISC processes but is not related to the triplet-triplet annihilation process.

Magnetic field effect in organic light emitting diodes based on donor-acceptor exciplexes showing thermally activated delayed fluorescence

NASA Astrophysics Data System (ADS)

Baniya, S.; Pang, Z.; Sun, D.; Basel, T.; Zhai, Y.; Kwon, O.; Choi, H.; Vardeny, Z. V.

2016-09-01

A new type of organic light-emitting diode (OLED) has emerged that shows enhanced operational stability and large internal quantum efficiency approaching 100%, which is based on exciplexes in donor-acceptor (D-A) blends having thermally activated delayed fluorescence (TADF) when doped with fluorescent emitters. We have investigated magnetoelectroluminescence (MEL) and magneto-conductivity in such TADF-based OLEDs, as well as magnetophotoluminescence (MPL) in thin films based on the OLEDs active layers, with various fluorescence emitters. We found that both MEL and MPL responses are thermally activated with substantially lower activation energy compared to that in the pristine undoped D-A exciplex host blend. In addition, both MPL and MEL steeply decrease with the emitters' concentration. This indicates the existence of a loss mechanism, whereby the triplet charge-transfer state in the D-A exciplex host blend may directly decay to the lowest, non-emissive triplet state of the additive fluorescent emitter molecules.

A new way towards high-efficiency thermally activated delayed fluorescence devices via external heavy-atom effect

NASA Astrophysics Data System (ADS)

Zhang, Wenzhi; Jin, Jiangjiang; Huang, Zhi; Zhuang, Shaoqing; Wang, Lei

2016-07-01

Thermally activated delayed fluorescence (TADF) mechanism is a significant method that enables the harvesting of both triplet and singlet excitons for emission. However, up to now most efforts have been devoted to dealing with the relation between singlet-triplet splitting (ΔEST) and fluorescence efficiency, while the significance of spin-orbit coupling (SOC) is usually ignored. In this contribution, a new method is developed to realize high-efficiency TADF-based devices through simple device-structure optimizations. By inserting an ultrathin external heavy-atom (EHA) perturber layer in a desired manner, it provides useful means of accelerating the T1 → S1 reverse intersystem crossing (RISC) in TADF molecules without affecting the corresponding S1 → T1 process heavily. Furthermore, this strategy also promotes the utilization of host triplets through Förster mechanism during host → guest energy transfer (ET) processes, which helps to get rid of the solely dependence upon Dexter mechanism. Based on this strategy, we have successfully raised the external quantum efficiency (EQE) in 4CzPN-based devices by nearly 38% in comparison to control devices. These findings provide keen insights into the role of EHA played in TADF-based devices, offering valuable guidelines for utilizing certain TADF dyes which possess high radiative transition rate but relatively inefficient RISC.

Highly Tunable Aptasensing Microarrays with Graphene Oxide Multilayers

NASA Astrophysics Data System (ADS)

Jung, Yun Kyung; Lee, Taemin; Shin, Eeseul; Kim, Byeong-Su

2013-11-01

A highly tunable layer-by-layer (LbL)-assembled graphene oxide (GO) array has been devised for high-throughput multiplex protein sensing. In this array, the fluorescence of different target-bound aptamers labeled with dye is efficiently quenched by GO through fluorescence resonance energy transfer (FRET), and simultaneous multiplex target detection is performed by recovering the quenched fluorescence caused by specific binding between an aptamer and a protein. Thin GO films consisting of 10 bilayers displayed a high quenching ability, yielding over 85% fluorescence quenching with the addition of a 2 μM dye-labeled aptamer. The limit for human thrombin detection in the 6- and 10-bilayered GO array is estimated to be 0.1 and 0.001 nM, respectively, indicating highly tunable nature of LbL assembled GO multilayers in controlling the sensitivity of graphene-based FRET aptasensor. Furthermore, the GO chip could be reused up to four times simply by cleaning it with distilled water.

Selective Killing of Breast Cancer Cells by Doxorubicin-Loaded Fluorescent Gold Nanoclusters: Confocal Microscopy and FRET.

PubMed

Chattoraj, Shyamtanu; Amin, Asif; Jana, Batakrishna; Mohapatra, Saswat; Ghosh, Surajit; Bhattacharyya, Kankan

2016-01-18

Fluorescent gold nanoclusters (AuNCs) capped with lysozymes are used to deliver the anticancer drug doxorubicin to cancer and noncancer cells. Doxorubicin-loaded AuNCs cause the highly selective and efficient killing (90 %) of breast cancer cells (MCF7) (IC50 =155 nm). In contrast, the killing of the noncancer breast cells (MCF10A) by doxorubicin-loaded AuNCs is only 40 % (IC50 =4500 nm). By using a confocal microscope, the fluorescence spectrum and decay of the AuNCs were recorded inside the cell. The fluorescence maxima (at ≈490-515 nm) and lifetime (≈2 ns), of the AuNCs inside the cells correspond to Au10-13 . The intracellular release of doxorubicin from AuNCs is monitored by Förster resonance energy transfer (FRET) imaging. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The study of chemical composition and elemental mappings of colored over-glaze porcelain fired in Qing Dynasty by micro-X-ray fluorescence

NASA Astrophysics Data System (ADS)

Lin, Cheng; Meitian, Li; Youshi, Kim; Changsheng, Fan; Shanghai, Wang; Qiuli, Pan; Zhiguo, Liu; Rongwu, Li

2011-02-01

It is very difficult to measure the chemical composition of colored pigments of over-glaze porcelain by X-ray fluorescence because it contains high concentration of Pb. One of the disadvantages of our polycapillary optics is that it has low transmission efficiency to the high energy X-ray. However, it is beneficial to measure the chemical compositions of rich Pb sample. In this paper, we reported the performances of a tabletop setup of micro-X-ray fluorescence system base on slightly focusing polycapillary and its applications for analysis of rich Pb sample. A piece of Chinese ancient over-glaze porcelain was analyzed by micro-X-ray fluorescence. The experimental results showed that the Cu, Fe and Mn are the major color elements. The possibilities of the process of decorative technology were discussed in this paper, also.

Fluorescent polymeric micelles with aggregation-induced emission properties for monitoring the encapsulation of doxorubicin.

PubMed

Chen, Jen-Ing; Wu, Wen-Chung

2013-05-01

A new type of fluorescent polymeric micelles is developed by self-assembly from a series of amphiphilic block copolymers, poly(ethylene glycol)-b-poly[styrene-co-(2-(1,2,3,4,5-pentaphenyl-1H-silol-1-yloxy)ethyl methacrylate)] [PEG-b-P(S-co-PPSEMA)]. Their capability of loading doxorubicin (DOX) is investigated by monitoring the loading content, encapsulation efficiency, and photophysical properties of micelles. Förster resonance energy transfer from PPSEMA to DOX is observed in DOX-loaded micelles, which can serve as an indication of successful encapsulation of DOX in these micelles. The application of this new type of fluorescent polymeric micelles as a fluorescent probe and an anticancer drug carrier simultaneously is explored by studying the intracellular uptake of DOX-loaded micelles. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

G quadruplex-based FRET probes with the thrombin-binding aptamer (TBA) sequence designed for the efficient fluorometric detection of the potassium ion.

PubMed

Nagatoishi, Satoru; Nojima, Takahiko; Galezowska, Elzbieta; Juskowiak, Bernard; Takenaka, Shigeori

2006-11-01

The dual-labeled oligonucleotide derivative, FAT-0, carrying 6- carboxyfluorescein (FAM) and 6-carboxytetramethylrhodamine (TAMRA) labels at the 5' and 3' termini of the thrombin-binding aptamer (TBA) sequence 5'-GGT TGG TGT GGT TGG-3', and its derivatives, FAT-n (n=3, 5, and 7) with a spacer at the 5'-end of a TBA sequence of T(m)A (m=2, 4, and 6) have been designed and synthesized. These fluorescent probes were developed for monitoring K(+) concentrations in living organisms. Circular dichroism, UV-visible absorption, and fluorescence studies revealed that all FAT-n probes could form intramolecular tetraplex structures after binding K(+). Fluorescence resonance energy transfer and quenching results are discussed taking into account dye-dye contact interactions. The relationship between the fluorescence behavior of the probes and the spacer length in FAT-n was studied in detail and is discussed.

Tween 20-stabilized gold nanoparticles combined with adenosine triphosphate-BODIPY conjugates for the fluorescence detection of adenosine with more than 1000-fold selectivity.

PubMed

Hung, Szu-Ying; Shih, Ya-Chen; Tseng, Wei-Lung

2015-02-01

This study describes the development of a simple, enzyme-free, label-free, sensitive, and selective system for detecting adenosine based on the use of Tween 20-stabilized gold nanoparticles (Tween 20-AuNPs) as an efficient fluorescence quencher for boron dipyrromethene-conjugated adenosine 5'-triphosphate (BODIPY-ATP) and as a recognition element for adenosine. BODIPY-ATP can interact with Tween 20-AuNPs through the coordination between the adenine group of BODIPY-ATP and Au atoms on the NP surface, thereby causing the fluorescence quenching of BODIPY-ATP through the nanometal surface energy transfer (NSET) effect. When adenosine attaches to the NP surface, the attached adenosine exhibits additional electrostatic attraction to BODIPY-ATP. As a result, the presence of adenosine enhances the efficiency of AuNPs in fluorescence quenching of BODIPY-ATP. The AuNP-induced fluorescence quenching of BODIPY-ATP progressively increased with an increase in the concentration of adenosine; the detection limit at a signal-to-noise ratio of 3 for adenosine was determined to be 60nM. The selectivity of the proposed system was more than 1000-fold for adenosine over any adenosine analogs and other nucleotides. The proposed system combined with a phenylboronic acid-containing column was successfully applied to the determination of adenosine in urine. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of fluorescent particle size on the modulation efficiency of ultrasound-modulated fluorescence.

PubMed

Liu, Yuan; Yuan, Baohong; Vignola, Joseph

2012-01-01

To investigate whether the size of fluorescent particles affects the modulation efficiency of ultrasound-modulated fluorescence (UMF), we measured UMF and DC (direct current) signals of the fluorescence emission from four different sized fluorescent particles: (1) three carboxylate-modified fluorescent microspheres (FM) with diameters of 20 nm, 200 nm, and 1.0 µm and (2) streptavidin-conjugated Alexa Fluor 647 with a diameter of approximately 5 nm. The UMF and DC signals were simultaneously measured using a broadband lock-in amplifier and a narrowband amplifier, respectively. The ratio of the UMF strength to the DC signal strength is defined as the modulation efficiency. This modulation efficiency was then used to evaluate the effects of fluorophore size and concentration. Results show that the modulation efficiency was improved by approximately a factor of two when the size of the fluorescent particles is increased from 5 nm to 1 µm. In addition, the linear relationship between the UMF strength and ultrasound pressure (observed in our previous study) were maintained regardless of the fluorescent particle sizes.

Effect of fluorescent particle size on the modulation efficiency of ultrasound-modulated fluorescence

PubMed Central

Liu, Yuan; Yuan, Baohong; Vignola, Joseph

2013-01-01

To investigate whether the size of fluorescent particles affects the modulation efficiency of ultrasound-modulated fluorescence (UMF), we measured UMF and DC (direct current) signals of the fluorescence emission from four different sized fluorescent particles: (1) three carboxylate-modified fluorescent microspheres (FM) with diameters of 20 nm, 200 nm, and 1.0 µm and (2) streptavidin-conjugated Alexa Fluor 647 with a diameter of approximately 5 nm. The UMF and DC signals were simultaneously measured using a broadband lock-in amplifier and a narrowband amplifier, respectively. The ratio of the UMF strength to the DC signal strength is defined as the modulation efficiency. This modulation efficiency was then used to evaluate the effects of fluorophore size and concentration. Results show that the modulation efficiency was improved by approximately a factor of two when the size of the fluorescent particles is increased from 5 nm to 1 µm. In addition, the linear relationship between the UMF strength and ultrasound pressure (observed in our previous study) were maintained regardless of the fluorescent particle sizes. PMID:24179476

Can we Predict Quantum Yields Using Excited State Density Functional Theory for New Families of Fluorescent Dyes?

NASA Astrophysics Data System (ADS)

Kohn, Alexander W.; Lin, Zhou; Shepherd, James J.; Van Voorhis, Troy

2016-06-01

For a fluorescent dye, the quantum yield characterizes the efficiency of energy transfer from the absorbed light to the emitted fluorescence. In the screening among potential families of dyes, those with higher quantum yields are expected to have more advantages. From the perspective of theoreticians, an efficient prediction of the quantum yield using a universal excited state electronic structure theory is in demand but still challenging. The most representative examples for such excited state theory include time-dependent density functional theory (TDDFT) and restricted open-shell Kohn-Sham (ROKS). In the present study, we explore the possibility of predicting the quantum yields for conventional and new families of organic dyes using a combination of TDDFT and ROKS. We focus on radiative (kr) and nonradiative (knr) rates for the decay of the first singlet excited state (S_1) into the ground state (S_0) in accordance with Kasha's rule. M. Kasha, Discuss. Faraday Soc., 9, 14 (1950). For each dye compound, kr is calculated with the S_1-S_0 energy gap and transition dipole moment obtained using ROKS and TDDFT respectively at the relaxed S_1 geometry. Our predicted kr agrees well with the experimental value, so long as the order of energy levels is correctly predicted. Evaluation of knr is less straightforward as multiple processes are involved. Our study focuses on the S_1-T_1 intersystem crossing (ISC) and the S_1-S_0 internal conversion (IC): we investigate the properties that allow us to model the knr value using a Marcus-like expression, such as the Stokes shift, the reorganization energy, and the S_1-T_1 and S_1-S_0 energy gaps. Taking these factors into consideration, we compare our results with those obtained using the actual Marcus theory and provide explanation for discrepancy. T. Kowalczyk, T. Tsuchimochi, L. Top, P.-T. Chen, and T. Van Voorhis, J. Chem. Phys., 138, 164101 (2013). M. Kasha, Discuss. Faraday Soc., 9, 14 (1950).

Red Fluorescent Protein-Aequorin Fusions as Improved Bioluminescent Ca2+ Reporters in Single Cells and Mice

PubMed Central

Bakayan, Adil; Vaquero, Cecilia F.; Picazo, Fernando; Llopis, Juan

2011-01-01

Bioluminescence recording of Ca2+ signals with the photoprotein aequorin does not require radiative energy input and can be measured with a low background and good temporal resolution. Shifting aequorin emission to longer wavelengths occurs naturally in the jellyfish Aequorea victoria by bioluminescence resonance energy transfer (BRET) to the green fluorescent protein (GFP). This process has been reproduced in the molecular fusions GFP-aequorin and monomeric red fluorescent protein (mRFP)-aequorin, but the latter showed limited transfer efficiency. Fusions with strong red emission would facilitate the simultaneous imaging of Ca2+ in various cell compartments. In addition, they would also serve to monitor Ca2+ in living organisms since red light is able to cross animal tissues with less scattering. In this study, aequorin was fused to orange and various red fluorescent proteins to identify the best acceptor in red emission bands. Tandem-dimer Tomato-aequorin (tdTA) showed the highest BRET efficiency (largest energy transfer critical distance R0) and percentage of counts in the red band of all the fusions studied. In addition, red fluorophore maturation of tdTA within cells was faster than that of other fusions. Light output was sufficient to image ATP-induced Ca2+ oscillations in single HeLa cells expressing tdTA. Ca2+ rises caused by depolarization of mouse neuronal cells in primary culture were also recorded, and changes in fine neuronal projections were spatially resolved. Finally, it was also possible to visualize the Ca2+ activity of HeLa cells injected subcutaneously into mice, and Ca2+ signals after depositing recombinant tdTA in muscle or the peritoneal cavity. Here we report that tdTA is the brightest red bioluminescent Ca2+ sensor reported to date and is, therefore, a promising probe to study Ca2+ dynamics in whole organisms or tissues expressing the transgene. PMID:21589654

Simultaneous Single-Molecule Force and Fluorescence Sampling of DNA Nanostructure Conformations Using Magnetic Tweezers.

PubMed

Kemmerich, Felix E; Swoboda, Marko; Kauert, Dominik J; Grieb, M Svea; Hahn, Steffen; Schwarz, Friedrich W; Seidel, Ralf; Schlierf, Michael

2016-01-13

We present a hybrid single-molecule technique combining magnetic tweezers and Förster resonance energy transfer (FRET) measurements. Through applying external forces to a paramagnetic sphere, we induce conformational changes in DNA nanostructures, which are detected in two output channels simultaneously. First, by tracking a magnetic bead with high spatial and temporal resolution, we observe overall DNA length changes along the force axis. Second, the measured FRET efficiency between two fluorescent probes monitors local conformational changes. The synchronized orthogonal readout in different observation channels will facilitate deciphering the complex mechanisms of biomolecular machines.

Feedback quantum control of molecular electronic population transfer

NASA Astrophysics Data System (ADS)

Bardeen, Christopher J.; Yakovlev, Vladislav V.; Wilson, Kent R.; Carpenter, Scott D.; Weber, Peter M.; Warren, Warren S.

1997-11-01

Feedback quantum control, where the sample `teaches' a computer-controlled arbitrary lightform generator to find the optimal light field, is experimentally demonstrated for a molecular system. Femtosecond pulses tailored by a computer-controlled acousto-optic pulse shaper excite fluorescence from laser dye molecules in solution. Fluorescence and laser power are monitored, and the computer uses the experimental data and a genetic algorithm to optimize population transfer from ground to first excited state. Both efficiency (the ratio of excited state population to laser energy) and effectiveness (total excited state population) are optimized. Potential use as an `automated theory tester' is discussed.

Daylighting with Mirror Light Pipes and with Fluorescent Planar Concentrators. First Results from the Demonstration Project Stuttgart-Hohenheim

NASA Astrophysics Data System (ADS)

Zastrow, Armin; Wittwer, Volker

1987-02-01

Efficient daylighting systems have recently attracted increasing interest due to their potential for saving a condiderable amount of electrical energy used for lighting purposes. In this paper we discuss the properties of daylighting systems based on either fluorescent planar concentrators (FPC's) and transparent light guiding plates or light pipes coated with a highly reflective silver coated plastic film (3M Silverlux film). First results on daylighting systems in the students' living quarters in Stuttgart-Hohenheim will be presented. This is a demonstration project which is supported by the Commission of the European Communities.

Gadolinium(III)-sensitized fluorescence of europium in its mixed-metal compounds with trifluroacetate

NASA Astrophysics Data System (ADS)

Kalinovskaya, I. V.; Zadorozhnaya, A. N.

2017-04-01

The fluorescence properties of mixed-metal compounds of Eu(III) and Gd(III) with trifluoroacetic acid, Eu1-хGdx(С2F3O2)3·yD·zH2O, where D - 1,10-phenanthroline, 2,2-dipyridil, diphenylguanidine, x = 0, 0.25, 0.5, or 0.7, were studied. Luminescence spectroscopic evidence and the examination of excitation spectra indicate the occurrence of efficient energy transfer from the gadolinium to the europium ion. The greatest promotion of Eu3+ photoluminescence at 615 nm is observed when Eu:Gd = 1:1.

Differential changes in photosynthetic capacity, 77 K chlorophyll fluorescence and chloroplast ultrastructure between Zn-efficient and Zn-inefficient rice genotypes (Oryza sativa) under low zinc stress.

PubMed

Chen, Wenrong; Yang, Xiaoe; He, Zhenli; Feng, Ying; Hu, Fenghong

2008-01-01

The relationship of zinc (Zn) efficiency in rice to differential tolerance of photosynthetic capacity and chloroplast function to low Zn stress was studied using Zn-efficient (IR8192) and Zn-inefficient (Erjiufeng) rice genotypes (Oryza sativa L.). Zinc deficiency caused extensive declines in leaf chlorophyll (Chl) content, ratios of chl a:b, Pn, Fv/Fm and Fv/Fo, indicating that the intrinsic quantum efficiency of the photosystem II (PSII) units was damaged. A greater decline was observed in the inefficient genotype (Erjiufeng) than the efficient genotype (IR8192). The 77 K chl fluorescence emission spectrum revealed that Zn deficiency blocked energy spillover from PSII to PSI and more excitation energy was distributed to PSII in IR8192 than Erjiufeng. The spectrum of Zn-deficient Erjiufeng was completely disordered, implying that the photosynthetic centers were seriously damaged. Electron microscopy showed that Zn deficiency caused a severe damage to the fine structure of chloroplasts, but IR8192 had a better preserved chloroplast ultrastructure as compared with Erjiufeng. These differences may result from the higher levels of the antioxidant enzyme activities and lower oxidant stress level in IR8192. These results indicate that Zn deficiency decreases leaf photosynthetic capacity primarily by reducing the number of PSII units per unit leaf area, and also reducing the photochemical capacity of the remaining PSII units. Therefore, the maintenance of more efficient photochemical capacity under low Zn stress is a key factor for the high Zn efficiency in rice, which may result from less antioxidant damage caused by low Zn to the chloroplast ultrastructure.

Efficient triplet harvesting by fluorescent molecules through exciplexes for high efficiency organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Park, Young-Seo; Kim, Kwon-Hyeon; Kim, Jang-Joo

2013-04-01

Efficient triplet harvesting from exciplexes by reverse intersystem crossing (RISC) is reported using a fluorescent molecular system composed of the 4,4',4″-tris(N-carbazolyl)-triphenylamine and bis-4,6-(3,5-di-3-pyridylphenyl)-2-methylpyrimidine. The exciplex forming material system shows the efficient delayed fluorescence emission. As a result, almost 100% PL efficiency at 35 K and 10% external quantum efficiency at 195 K are achieved from the exciplex. The delayed fluorescence of the exciplex clearly demonstrates that a significant proportion of the triplet exciplexes is harvested through the RISC.

∼2 μm fluorescence radiative dynamics and energy transfer between Er{sup 3+} and Tm{sup 3+} ions in silicate glass

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

Li, Ming; Liu, Xueqiang; Graduate School of Chinese Academy of Sciences, Beijing 100039

2014-03-01

Graphical abstract: - Highlights: • A Er{sup 3+}/Tm{sup 3+} co-doped silicate glass with good thermal stability (k{sub gl} = 0.402 for STE glass) is prepared. • Efficient ∼2 μm emission is observed under 808 nm and 980 nm laser excitation. • The glass structure and spectroscopic properties are confirmed by optical absorption, IR transmission, Raman and fluorescence studies. • The content of OH groups deceases efficiently after fluorine ions are introduced. • The energy transfer coefficient from Er{sup 3+} to Tm{sup 3+} in STFE glass is 13.39 × 10{sup −40} cm{sup 6}/s. - Abstract: A Er{sup 3+}/Tm{sup 3+} co-doped silicatemore » glass with good thermal stability is prepared by melt-quenching method. An efficient emission of ∼2 μm is observed under different selective laser excitations. The optical absorption and transmission spectra, Raman spectra, and emission spectra are tested to characterize ∼2 μm emission properties of Er{sup 3+}/Tm{sup 3+} co-doped silicate glasses and a reasonable energy transfer mechanism of ∼2 μm emission between Er{sup 3+} and Tm{sup 3+} ions is proposed. Based on the optical absorption spectra, the Judd–Ofelt parameters and radiative properties were calculated. Intense ∼2 μm emission is obtained from Er{sup 3+}/Tm{sup 3+} co-doped silicate glasses due to the efficient energy transfer from Er{sup 3+} to Tm{sup 3+} ions. The energy transfer coefficient from Er{sup 3+} to Tm{sup 3+} ions can reach as high as 13.39 × 10{sup −40} cm{sup 6}/s. In addition, the population of the OH groups is decreased and the ∼2 μm emission is effectively enhanced with fluoride introduction. The emission property, together with good thermal property, indicates that Er{sup 3+}/Tm{sup 3+} co-doped silicate glass is a potential kind of laser glass for efficient ∼2 μm laser.« less

Molecular imprinting ratiometric fluorescence sensor for highly selective and sensitive detection of phycocyanin.

PubMed

Wang, Xiaoyan; Yu, Jialuo; Kang, Qi; Shen, Dazhong; Li, Jinhua; Chen, Lingxin

2016-03-15

A facile strategy was developed to prepare molecular imprinting ratiometric fluorescence sensor for highly selective and sensitive detection of phycocyanin (PC) based on fluorescence resonance energy transfer (FRET), via a sol-gel polymerization process using nitrobenzoxadiazole (NBD) as fluorescent signal source. The ratio of two fluorescence peak emission intensities of NBD and PC was utilized to determine the concentration of PC, which could effectively reduce the background interference and fluctuation of diverse conditions. As a result, this sensor obtained high sensitivity with a low detection limit of 0.14 nM within 6 min, and excellent recognition specificity for PC over its analogues with a high imprinting factor of 9.1. Furthermore, the sensor attained high recoveries in the range of 93.8-110.2% at three spiking levels of PC, with precisions below 4.7% in seawater and lake water samples. The developed sensor strategy demonstrated simplicity, reliability, rapidity, high selectivity and high sensitivity, proving to be a feasible way to develop high efficient fluorescence sensors and thus potentially applicable for ultratrace analysis of complicated matrices. Copyright © 2015 Elsevier B.V. All rights reserved.

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.

The efficiency of light-emitting diode suction traps for the collection of South African livestock-associated Culicoides species.

PubMed

Venter, G J; Boikanyo, S N B; De Beer, C J

2018-06-28

Culicoides biting midges (Diptera: Ceratopogonidae) are vectors of a range of orbiviruses that cause important veterinary diseases such as bluetongue and African horse sickness. The effective monitoring of Culicoides species diversity and abundance, both at livestock and near potential wildlife hosts, is essential for risk management. The Onderstepoort 220-V ultraviolet (UV) light trap is extensively used for this purpose. Reducing its power requirements by fitting low-energy light-emitting diodes (LEDs) can lead to greater flexibility in monitoring. A comparison of the efficiency of the 220-V Onderstepoort trap (8-W fluorescent UV light) with the efficiency of the 220-V or 12-V Onderstepoort traps fitted with red, white, blue or green LEDs or a 12-V fluorescent Onderstepoort trap demonstrated the 220-V Onderstepoort trap to be the most efficient. All the results showed nulliparous Culicoides imicola Kieffer females to be the dominant grouping. Despite the lower numbers collected, 12-V traps can be used in field situations to determine the most abundant species. © 2018 The Royal Entomological Society.

Spectral and laser properties of Er3+/Yb3+/Ce3+ tri-doped Ca3NbGa3Si2O14 crystal at 1.55 µm

NASA Astrophysics Data System (ADS)

Gong, Guoliang; Chen, Yujin; Lin, Yanfu; Huang, Jianhua; Gong, Xinghong; Luo, Zundu; Huang, Yidong

2018-04-01

An Er3+/Yb3+/Ce3+ tri-doped Ca3NbGa3Si2O14 (CNGS) crystal was grown by the Czochralski method. Spectral properties of the crystal, including the polarized absorption and fluorescence spectra, the fluorescence decay, as well as the energy transfer efficiency from Yb3+ to Er3+ were investigated in detail. End-pumped by a 976 nm diode laser, a 1556 nm continuous-wave laser with a maximum output power of 202 mW and a slope efficiency of 11.4% was achieved in the Er,Yb,Ce:CNGS crystal. The results indicate the Er,Yb,Ce:CNGS crystal is a promising 1.55 µm laser gain medium.

Blue Thermally Activated Delayed Fluorescence Polymers with Nonconjugated Backbone and Through-Space Charge Transfer Effect.

PubMed

Shao, Shiyang; Hu, Jun; Wang, Xingdong; Wang, Lixiang; Jing, Xiabin; Wang, Fosong

2017-12-13

We demonstrate novel molecular design for thermally activated delayed fluorescence (TADF) polymers based on a nonconjugated polyethylene backbone with through-space charge transfer effect between pendant electron donor (D) and acceptor (A) units. Different from conventional conjugated D-A polymers with through-bond charge transfer effect, the nonconjugated architecture avoids direct conjugation between D and A units, enabling blue emission. Meanwhile, spatial π-π interaction between the physically separated D and A units results in both small singlet-triplet energy splitting (0.019 eV) and high photoluminescence quantum yield (up to 60% in film state). The resulting polymer with 5 mol % acceptor unit gives efficient blue electroluminescence with Commission Internationale de l'Eclairage coordinates of (0.176, 0.269), together with a high external quantum efficiency of 12.1% and low efficiency roll-off of 4.9% (at 1000 cd m -2 ), which represents the first example of blue TADF nonconjugated polymer.

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

PubMed

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

2014-11-07

The current work reports a type of "smart" lanthanide-based theranostic nanoprobe, NaDyF4:Yb(3+)/NaGdF4:Yb(3+),Er(3+), which is able to circumvent the up-converting poisoning effect of Dy(3+) 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.

Fluorescent biosensor for the detection of hyaluronidase: intensity-based ratiometric sensing and fluorescence lifetime-based sensing using a long lifetime azadioxatriangulenium (ADOTA) fluorophore.

PubMed

Chib, Rahul; Mummert, Mark; Bora, Ilkay; Laursen, Bo W; Shah, Sunil; Pendry, Robert; Gryczynski, Ignacy; Borejdo, Julian; Gryczynski, Zygmunt; Fudala, Rafal

2016-05-01

In this report, we have designed a rapid and sensitive, intensity-based ratiometric sensing as well as lifetime-based sensing probe for the detection of hyaluronidase activity. Hyaluronidase expression is known to be upregulated in various pathological conditions. We have developed a fluorescent probe by heavy labeling of hyaluronic acid with a new orange/red-emitting organic azadioxatriangulenium (ADOTA) fluorophore, which exhibits a long fluorescence lifetime (∼20 ns). The ADOTA fluorophore in water has a peak fluorescence lifetime of ∼20 ns and emission spectra centered at 560 nm. The heavily ADOTA-labeled hyaluronic acid (HA-ADOTA) shows a red shift in the peak emission wavelength (605 nm), a weak fluorescence signal, and a shorter fluorescence lifetime (∼4 ns) due to efficient self-quenching and formation of aggregates. In the presence of hyaluronidase, the brightness and fluorescence lifetime of the sample increase with a blue shift in the peak emission to its original wavelength at 560 nm. The ratio of the fluorescence intensity of the HA-ADOTA probe at 560 and 605 nm can be used as the sensing method for the detection of hyaluronidase. The cleavage of the hyaluronic acid macromolecule reduces the energy migration between ADOTA molecules, as well as the degree of self-quenching and aggregation. This probe can be efficiently used for both intensity-based ratiometric sensing as well as fluorescence lifetime-based sensing of hyaluronidase. The proposed method makes it a rapid and sensitive assay, useful for analyzing levels of hyaluronidase in relevant clinical samples like urine or plasma. Graphical Abstract Scheme showing cleavage of HA-ADOTA probe by hyaluronidase and the change in the emission spectrum of HA-ADOTA probe before and after cleavage by hyaluronidase.

Smart Drug Delivery System-Inspired Enzyme-Linked Immunosorbent Assay Based on Fluorescence Resonance Energy Transfer and Allochroic Effect Induced Dual-Modal Colorimetric and Fluorescent Detection.

PubMed

Miao, Luyang; Zhu, Chengzhou; Jiao, Lei; Li, He; Du, Dan; Lin, Yuehe; Wei, Qin

2018-02-06

Numerous analytical techniques have been undertaken for the detection of protein biomarkers because of their extensive and significant applications in clinical diagnosis, whereas there are few strategies to develop dual-readout immunosensors to achieve more accurate results. To the best of our knowledge, inspired by smart drug delivery system (DDS), a novel pH-responsive modified enzyme-linked immunosorbent assay (ELISA) was innovatively developed for the first time, realizing dual-modal colorimetric and fluorescent detection of cardiac troponin I (cTnI). Curcumin (CUR) was elaborately selected as a reporter molecule, which played the same role of drugs in DDS based on the following considerations: (1) CUR can be used as a kind of pH indicator by the inherited allochroic effect induced by basic pH value; (2) the fluorescence of CUR can be quenched by certain nanocarriers as the acceptor because of the occurrence of fluorescence resonance energy transfer (FRET), while recovered by the stimuli of basic pH value, which can produce "signal-on" fluorescence detection. Three-dimensional MoS 2 nanoflowers (3D-MoS 2 NFs) were employed in immobilizing CUR to constitute a nanoprobe for the determination of cTnI by virtue of good biocompatibility, high absorption capacity, and fluorescence quench efficiency toward CUR. The proposed DDS-inspired ELISA offered dual-modal colorimetric and fluorescent detection of cTnI, thereby meeting the reliable and precise analysis requirements. We believe that the developed dual-readout ELISA will create a new avenue and bring innovative inspirations for biological detections.

Optical Lock-In Detection of FRET Using Synthetic and Genetically Encoded Optical Switches

PubMed Central

Mao, Shu; Benninger, Richard K. P.; Yan, Yuling; Petchprayoon, Chutima; Jackson, David; Easley, Christopher J.; Piston, David W.; Marriott, Gerard

2008-01-01

The Förster resonance energy transfer (FRET) technique is widely used for studying protein interactions within live cells. The effectiveness and sensitivity of determining FRET, however, can be reduced by photobleaching, cross talk, autofluorescence, and unlabeled, endogenous proteins. We present a FRET imaging method using an optical switch probe, Nitrobenzospiropyran (NitroBIPS), which substantially improves the sensitivity of detection to <1% FRET efficiency. Through orthogonal optical control of the colorful merocyanine and colorless spiro states of the NitroBIPS acceptor, donor fluorescence can be measured both in the absence and presence of FRET in the same FRET pair in the same cell. A SNAP-tag approach is used to generate a green fluorescent protein-alkylguaninetransferase fusion protein (GFP-AGT) that is labeled with benzylguanine-NitroBIPS. In vivo imaging studies on this green fluorescent protein-alkylguaninetransferase (GFP-AGT) (NitroBIPS) complex, employing optical lock-in detection of FRET, allow unambiguous resolution of FRET efficiencies below 1%, equivalent to a few percent of donor-tagged proteins in complexes with acceptor-tagged proteins. PMID:18281383

Organic Fluorescent Dyes Supported on Activated Boron Nitride: A Promising Blue Light Excited Phosphors for High-Performance White Light-Emitting Diodes

PubMed Central

Li, Jie; Lin, Jing; Huang, Yang; Xu, Xuewen; Liu, Zhenya; Xue, Yanming; Ding, Xiaoxia; Luo, Han; Jin, Peng; Zhang, Jun; Zou, Jin; Tang, Chengchun

2015-01-01

We report an effective and rare-earth free light conversion material synthesized via a facile fabrication route, in which organic fluorescent dyes, i.e. Rhodamine B (RhB) and fluorescein isothiocyanate (FITC) are embedded into activated boron nitride (αBN) to form a composite phosphor. The composite phosphor shows highly efficient Förster resonance energy transfer and greatly improved thermal stability, and can emit at broad visible wavelengths of 500–650 nm under the 466 nm blue-light excitation. By packaging of the composite phosphors and a blue light-emitting diode (LED) chip with transparent epoxy resin, white LED with excellent thermal conductivity, current stability and optical performance can be realized, i.e. a thermal conductivity of 0.36 W/mk, a Commission Internationale de 1'Eclairage color coordinates of (0.32, 0.34), and a luminous efficiency of 21.6 lm·W−1. Our research opens the door toward to the practical long-life organic fluorescent dyes-based white LEDs. PMID:25682730

Evaluating the binding efficiency of pheromone binding protein with its natural ligand using molecular docking and fluorescence analysis

NASA Astrophysics Data System (ADS)

Ilayaraja, Renganathan; Rajkumar, Ramalingam; Rajesh, Durairaj; Muralidharan, Arumugam Ramachandran; Padmanabhan, Parasuraman; Archunan, Govindaraju

2014-06-01

Chemosignals play a crucial role in social and sexual communication among inter- and intra-species. Chemical cues are bound with protein that is present in the pheromones irrespective of sex are commonly called as pheromone binding protein (PBP). In rats, the pheromone compounds are bound with low molecular lipocalin protein α2u-globulin (α2u). We reported farnesol is a natural endogenous ligand (compound) present in rat preputial gland as a bound volatile compound. In the present study, an attempt has been made through computational method to evaluating the binding efficiency of α2u with the natural ligand (farnesol) and standard fluorescent molecule (2-naphthol). The docking analysis revealed that the binding energy of farnesol and 2-naphthol was almost equal and likely to share some binding pocket of protein. Further, to extrapolate the results generated through computational approach, the α2u protein was purified and subjected to fluorescence titration and binding assay. The results showed that the farnesol is replaced by 2-naphthol with high hydrophobicity of TYR120 in binding sites of α2u providing an acceptable dissociation constant indicating the binding efficiency of α2u. The obtained results are in corroboration with the data made through computational approach.

Boric-Acid-Functional Lanthanide Metal-Organic Frameworks for Selective Ratiometric Fluorescence Detection of Fluoride Ions.

PubMed

Yang, Zhong-Rui; Wang, Man-Man; Wang, Xue-Sheng; Yin, Xue-Bo

2017-02-07

Here, we report that boric acid is used to tune the optical properties of lanthanide metal-organic frameworks (LMOFs) for dual-fluorescence emission and improves the selectivity of LMOFs for the determination of F - ions. The LMOFs are prepared with 5-boronoisophthalic acid (5-bop) and Eu 3+ ions as the precursors. Emission mechanism study indicates that 5-bop is excited with UV photons to produce its triplet state, which then excites Eu 3+ ions for their red emission. This is the general story of the antenna effect, but electron-deficient boric acid decreases the energy transfer efficiency from the triplet state of 5-bop to Eu 3+ ions, so dual emission from both 5-bop and Eu 3+ ions is efficiently excited at the single excitation of 275 nm. Moreover, boric acid is used to identify fluoride specifically as a free accessible site. The ratiometric fluorescent detection of F - ions is validated with the dual emission at single excitation. The LMOFs are very monodisperse, so the determination of aqueous F - ions is easily achieved with high selectivity and a low detection limit (2 μM). For the first time, we reveal that rational selection of functional ligands can improve the sensing efficiency of LMOFs through tuning their optical property and enhancing the selectivity toward targets.

Manganese Deficiency Leads to Genotype-Specific Changes in Fluorescence Induction Kinetics and State Transitions1[C][OA

PubMed Central

Husted, Søren; Laursen, Kristian H.; Hebbern, Christopher A.; Schmidt, Sidsel B.; Pedas, Pai; Haldrup, Anna; Jensen, Poul E.

2009-01-01

Barley (Hordeum vulgare) genotypes display a marked difference in their ability to tolerate growth at low manganese (Mn) concentrations, a phenomenon designated as differential Mn efficiency. Induction of Mn deficiency in two genotypes differing in Mn efficiency led to a decline in the quantum yield efficiency for both, although faster in the Mn-inefficient genotype. Leaf tissue and thylakoid Mn concentrations were reduced under Mn deficiency, but no difference between genotypes was observed and no visual Mn deficiency symptoms were developed. Analysis of the fluorescence induction kinetics revealed that in addition to the usual O-J-I-P steps, clear K and D steps were developed in the Mn-inefficient genotype under Mn deficiency. These marked changes indicated damages to photosystem II (PSII). This was further substantiated by state transition measurements, indicating that the ability of plants to redistribute excitation energy was reduced. The percentage change in state transitions for control plants with normal Mn supply of both genotypes was 9% to 11%. However, in Mn-deficient leaves of the Mn-inefficient genotypes, state transitions were reduced to less than 1%, whereas no change was observed for the Mn-efficient genotypes. Immunoblotting and the chlorophyll a/b ratio confirmed that Mn deficiency in general resulted in a significant reduction in abundance of PSII reaction centers relative to the peripheral antenna. In addition, PSII appeared to be significantly more affected by Mn limitation than PSI. However, the striking genotypic differences observed in Mn-deficient plants, when analyzing state transitions and fluorescence induction kinetics, could not be correlated with specific changes in photosystem proteins. Thus, there is no simple linkage between protein expression and the differential reduction in state transition and fluorescence induction kinetics observed for the genotypes under Mn deficiency. PMID:19369593

A label-free and high-efficient GO-based aptasensor for cancer cells based on cyclic enzymatic signal amplification.

PubMed

Xiao, Kunyi; Liu, Juan; Chen, Hui; Zhang, Song; Kong, Jilie

2017-05-15

A label-free and high-efficient graphene oxide (GO)-based aptasensor was developed for the detection of low quantity cancer cells based on cell-triggered cyclic enzymatic signal amplification (CTCESA). In the absence of target cells, hairpin aptamer probes (HAPs) and dye-labeled linker DNAs stably coexisted in solution, and the fluorescence was quenched by the GO-based FÖrster resonance energy transfer (FRET) process. In the presence of target cells, the specific binding of HAPs with the target cells triggered a conformational alternation, which resulted in linker DNA complementary pairing and cleavage by nicking endonuclease-strand scission cycles. Consequently, more cleaved fragments of linker DNAs with more the terminal labeled dyes could show the enhanced fluorescence because these cleaved DNA fragments hardly combine with GOs and prevent the FRET process. Fluorescence analysis demonstrated that this GO-based aptasensor exhibited selective and sensitive response to the presence of target CCRF-CEM cells in the concentration range from 50 to 10 5 cells. The detection limit of this method was 25 cells, which was approximately 20 times lower than the detection limit of normal fluorescence aptasensors without amplification. With high sensitivity and specificity, it provided a simple and cost-effective approach for early cancer diagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.

Highly Efficient Simplified Single-Emitting-Layer Hybrid WOLEDs with Low Roll-off and Good Color Stability through Enhanced Förster Energy Transfer.

PubMed

Zhang, Dongdong; Cai, Minghan; Zhang, Yunge; Zhang, Deqiang; Duan, Lian

2015-12-30

Single-emitting layer hybrid white organic light-emitting diodes (SEL-hybrid-WOLEDs) usually suffer from low efficiency, significant roll-off, and poor color stability, attributed to the incomplete energy transfer from the triplet states of the blue fluorophores to the phosphors. Here, we demonstrate highly efficient SEL-hybrid-WOLEDs with low roll-off and good color-stability utilizing blue thermally activated delayed fluorescence (TADF) materials as the host emitters. The triplet states of the blue TADF host emitter can be up-converted into its singlet states, and then the energy is transferred to the complementary phosphors through the long-range Förster energy transfer, enhancing the energy transfer from the host to the dopant. Simplified SEL-hybrid-WOLEDs achieve the highest forward-viewing external quantum efficiency (EQE) of 20.8% and power efficiency of 51.2 lm/W with CIE coordinates of (0.398, 0.456) at a luminance of 500 cd/m(2). The device EQE only slightly drops to 19.6% at a practical luminance of 1000 cd/m(2) with a power efficiency of 38.7 lm/W. Furthermore, the spectra of the device are rather stable with the raising voltage. The reason can be assigned to the enhanced Förster energy transfer, wide charge recombination zone, as well as the bipolar charge transporting ability of the host emitter. We believe that our work may shed light on the future development of highly efficient SEL-hybrid-WOLEDs with simultaneous low roll-off and good color stability.

Redox regulation of energy transfer efficiency in antennas of green photosynthetic bacteria

NASA Technical Reports Server (NTRS)

Blankenship, R. E.; Cheng, P.; Causgrove, T. P.; Brune, D. C.; Wang, J.

1993-01-01

The efficiency of energy transfer from the peripheral chlorosome antenna structure to the membrane-bound antenna in green sulfur bacteria depends strongly on the redox potential of the medium. The fluorescence spectra and lifetimes indicate that efficient quenching pathways are induced in the chlorosome at high redox potential. The midpoint redox potential for the induction of this effect in isolated chlorosomes from Chlorobium vibrioforme is -146 mV at pH 7 (vs the normal hydrogen electrode), and the observed midpoint potential (n = 1) decreases by 60 mV per pH unit over the pH range 7-10. Extraction of isolated chlorosomes with hexane has little effect on the redox-induced quenching, indicating that the component(s) responsible for this effect are bound and not readily extractable. We have purified and partially characterized the trimeric water-soluble bacteriochlorophyll a-containing protein from the thermophilic green sulfur bacterium Chlorobium tepidum. This protein is located between the chlorosome and the membrane. Fluorescence spectra of the purified protein indicate that it also contains groups that quench excitations at high redox potential. The results indicate that the energy transfer pathway in green sulfur bacteria is regulated by redox potential. This regulation appears to operate in at least two distinct places in the energy transfer pathway, the oligomeric pigments in the interior of the chlorosome and in the bacteriochlorophyll a protein. The regulatory effect may serve to protect the cell against superoxide-induced damage when oxygen is present. By quenching excitations before they reach the reaction center, reduction and subsequent autooxidation of the low potential electron acceptors found in these organisms is avoided.

Detection of Free Thiols and Fluorescence Response of Phycoerythrin Chromophore after Ultraviolet-B Radiation Stress.

PubMed

Kannaujiya, Vinod K; Sinha, Rajeshwar P

2017-03-01

The chemistry of thiol-chromophore linkage plays a central role in the nature of fluorescence of phycoerythrin (PE). Interaction of thiol and chromophore is crucial for the energy transfer, redox signal and inhibition of oxidative damage. In the present investigation the effects of ultraviolet-B radiation on an emission fluorescence intensity and wavelength shift in PE due to interaction between thiol and chromophore by remarkable strategy of detection technique was studied. Purification of PE was done by using a gel permeation and ion exchange chromatography that yielded a quite high purity index (6.40) in a monomeric (αβ) form. UV-B radiation accelerated the quenching efficiency (24.9 ± 1.52%) by reducing fluorescence emission intensity of thiol linked chromophore after 240 min of UV-B exposure. However, after blocking of transiently released free thiol by N-ethylmaleimide, quenching efficiency was increased (36.8 ± 2.80%) with marked emission wavelength shift towards shorter wavelengths up to 562 nm as compared to 575 nm in control. Emission fluorescence of free thiol was at maximum after 240 min that was detected specifically by monobromobimane (mBrB) molecular probe. The association/dissociation of bilin chromophore was analyzed by SDS- and Native-PAGE that also indicated a complete reduction in emission fluorescence. Our work clearly shows an early detection of free thiols and relative interaction with chromophore after UV-B radiation which might play a significant role in structural and functional integrity of terminal PE.

DNA nanosensor based on biocompatible graphene quantum dots and carbon nanotubes.

PubMed

Qian, Zhao Sheng; Shan, Xiao Yue; Chai, Lu Jing; Ma, Juan Juan; Chen, Jian Rong; Feng, Hui

2014-10-15

An ultrasensitive nanosensor based on fluorescence resonance energy transfer (FRET) between biocompatible graphene quantum dots and carbon nanotubes for DNA detection was reported. We take advantage of good biocompatibility and strong fluorescence of graphene quantum dots, base pairing specificity of DNA and unique fluorescence resonance energy transfer between graphene quantum dots and carbon nanotubes to achieve the analysis of low concentrations of DNA. Graphene quantum dots with high quantum yield up to 0.20 were prepared and served as the fluorophore of DNA probe. FRET process between graphene quantum dots-labeled probe and oxidized carbon nanotubes is easily achieved due to their efficient self-assembly through specific π-π interaction. This nanosensor can distinguish complementary and mismatched nucleic acid sequences with high sensitivity and good reproducibility. The detection method based on this nanosensor possesses a broad linear span of up to 133.0 nM and ultralow detection limit of 0.4 nM. The constructed nanosensor is expected to be highly biocompatible because of all its components with excellent biocompatibility. Copyright © 2014 Elsevier B.V. All rights reserved.

Miniature fiber optic spectrometer-based quantitative fluorescence resonance energy transfer measurement in single living cells.

PubMed

Chai, Liuying; Zhang, Jianwei; Zhang, Lili; Chen, Tongsheng

2015-03-01

Spectral measurement of fluorescence resonance energy transfer (FRET), spFRET, is a widely used FRET quantification method in living cells today. We set up a spectrometer-microscope platform that consists of a miniature fiber optic spectrometer and a widefield fluorescence microscope for the spectral measurement of absolute FRET efficiency (E) and acceptor-to-donor concentration ratio (R(C)) in single living cells. The microscope was used for guiding cells and the spectra were simultaneously detected by the miniature fiber optic spectrometer. Moreover, our platform has independent excitation and emission controllers, so different excitations can share the same emission channel. In addition, we developed a modified spectral FRET quantification method (mlux-FRET) for the multiple donors and multiple acceptors FRET construct (mD∼nA) sample, and we also developed a spectra-based 2-channel acceptor-sensitized FRET quantification method (spE-FRET). We implemented these modified FRET quantification methods on our platform to measure the absolute E and R(C) values of tandem constructs with different acceptor/donor stoichiometries in single living Huh-7 cells.

Spectroscopy and laser action of the "red perylimide dye" in various solvents

NASA Astrophysics Data System (ADS)

Gvishi, R.; Reisfeld, R.; Burshtein, Z.

1993-10-01

Optical properties of the red perylimide laser dye in various solvents are studied. The absorption spectrum exhibits two main bands, in the ranges 480-600 and 400-460 nm, due to the S 0-S 1 and S 0-S 2 transition. The fluorescence spectrum is a mirror image of the S 0-S 1 absorption (shift of ˜ 30-50 nm). The Stokes shift increases with solvent polarity. Such dye-solvent interactions are compared to theoretical predictions. The fluorescence quantum yields approaches unity in all the solvents studied. Laser tunability around 30 nm was obtained each time, covering the spectral range 580-640 nm. This interval is important for medical applications in photodynamic therapy and fluorescence diagnostics. The laser threshold energy varied from 0.35 mJ/pulse in cyclohexane to 1.87 mJ/pulse in methanol, and the slope efficiency from about 6.6% in methanol to 14% in xylenes. The laser output was stable for several hours of operation under an average pump energy of about 20 mJ/pulse at 1 Hz repetition rate, without flow.

Molecular excitonic seesaws.

PubMed

Wilhelm, Philipp; Schedlbauer, Jakob; Hinderer, Florian; Hennen, Daniel; Höger, Sigurd; Vogelsang, Jan; Lupton, John M

2018-04-17

The breaking of molecular symmetry through photoexcitation is a ubiquitous but rather elusive process, which, for example, controls the microscopic efficiency of light harvesting in molecular aggregates. A molecular excitation within a π-conjugated segment will self-localize due to strong coupling to molecular vibrations, locally changing bond alternation in a process which is fundamentally nondeterministic. Probing such symmetry breaking usually relies on polarization-resolved fluorescence, which is most powerful on the level of single molecules. Here, we explore symmetry breaking by designing a large, asymmetric acceptor-donor-acceptor (A 1 -D-A 2 ) complex 10 nm in length, where excitation energy can flow from the donor, a π-conjugated oligomer, to either one of the two boron-dipyrromethene (bodipy) dye acceptors of different color. Fluorescence correlation spectroscopy (FCS) reveals a nondeterministic switching between the energy-transfer pathways from the oligomer to the two acceptor groups on the submillisecond timescale. We conclude that excitation energy transfer, and light harvesting in general, are fundamentally nondeterministic processes, which can be strongly perturbed by external stimuli. A simple demonstration of the relation between exciton localization within the extended π-system and energy transfer to the endcap is given by considering the selectivity of endcap emission through the polarization of the excitation light in triads with bent oligomer backbones. Bending leads to increased localization so that the molecule acquires bichromophoric characteristics in terms of its fluorescence photon statistics.

Distribution of a Glycosylphosphatidylinositol-anchored Protein at the Apical Surface of MDCK Cells Examined at a Resolution of <100 Å Using Imaging Fluorescence Resonance Energy Transfer

PubMed Central

Kenworthy, A.K.; Edidin, M.

1998-01-01

Membrane microdomains (“lipid rafts”) enriched in glycosylphosphatidylinositol (GPI)-anchored proteins, glycosphingolipids, and cholesterol have been implicated in events ranging from membrane trafficking to signal transduction. Although there is biochemical evidence for such membrane microdomains, they have not been visualized by light or electron microscopy. To probe for microdomains enriched in GPI- anchored proteins in intact cell membranes, we used a novel form of digital microscopy, imaging fluorescence resonance energy transfer (FRET), which extends the resolution of fluorescence microscopy to the molecular level (<100 Å). We detected significant energy transfer between donor- and acceptor-labeled antibodies against the GPI-anchored protein 5′ nucleotidase (5′ NT) at the apical membrane of MDCK cells. The efficiency of energy transfer correlated strongly with the surface density of the acceptor-labeled antibody. The FRET data conformed to theoretical predictions for two-dimensional FRET between randomly distributed molecules and were inconsistent with a model in which 5′ NT is constitutively clustered. Though we cannot completely exclude the possibility that some 5′ NT is in clusters, the data imply that most 5′ NT molecules are randomly distributed across the apical surface of MDCK cells. These findings constrain current models for lipid rafts and the membrane organization of GPI-anchored proteins. PMID:9660864

Dynamic Changes of IsiA-Containing Complexes during Long-Term Iron Deficiency in Synechocystis sp. PCC 6803.

PubMed

Ma, Fei; Zhang, Xin; Zhu, Xi; Li, Tianpei; Zhan, Jiao; Chen, Hui; He, Chenliu; Wang, Qiang

2017-01-09

Iron stress-induced protein A (IsiA), a major chlorophyll-binding protein in the thylakoid membrane, is significantly induced under iron deficiency conditions. Using immunoblot analysis and 77 K fluorescence spectroscopy combined with sucrose gradient fractionation, we monitored dynamic changes of IsiA-containing complexes in Synechocystis sp. PCC 6803 during exposure to long-term iron deficiency. Within 3 days of exposure to iron deficiency conditions, the initially induced free IsiA proteins preferentially conjugated to PS I trimer to form IsiA 18 -PS I trimers, which serve as light energy collectors for efficiently transmitting energy to PS I. With prolonged iron deficiency, IsiA proteins assembled either into IsiA aggregates or into two other types of IsiA-PS I supercomplexes, namely IsiA-PS I high fluorescence supercomplex (IHFS) and IsiA-PS I low fluorescence supercomplex (ILFS). Further analysis revealed a role for IsiA as an energy dissipater in the IHFS and as an energy collector in the ILFS. The trimeric structure of PS I mediated by PsaL was found to be indispensable for the formation of IHFS/ILFS. Dynamic changes in IsiA-containing complexes in cyanobacteria during long-term iron deficiency may represent an adaptation to iron limitation stress for flexible light energy distribution, which balances electron transfer between PS I and PS II, thus minimizing photooxidative damage. Copyright © 2017 The Author. Published by Elsevier Inc. All rights reserved.

Balance the Carrier Mobility To Achieve High Performance Exciplex OLED Using a Triazine-Based Acceptor.

PubMed

Hung, Wen-Yi; Chiang, Pin-Yi; Lin, Shih-Wei; Tang, Wei-Chieh; Chen, Yi-Ting; Liu, Shih-Hung; Chou, Pi-Tai; Hung, Yi-Tzu; Wong, Ken-Tsung

2016-02-01

A star-shaped 1,3,5-triazine/cyano hybrid molecule CN-T2T was designed and synthesized as a new electron acceptor for efficient exciplex-based OLED emitter by mixing with a suitable electron donor (Tris-PCz). The CN-T2T/Tris-PCz exciplex emission shows a high ΦPL of 0.53 and a small ΔET-S = -0.59 kcal/mol, affording intrinsically efficient fluorescence and highly efficient exciton up-conversion. The large energy level offsets between Tris-PCz and CN-T2T and the balanced hole and electron mobility of Tris-PCz and CN-T2T, respectively, ensuring sufficient carrier density accumulated in the interface for efficient generation of exciplex excitons. Employing a facile device structure composed as ITO/4% ReO3:Tris-PCz (60 nm)/Tris-PCz (15 nm)/Tris-PCz:CN-T2T(1:1) (25 nm)/CN-T2T (50 nm)/Liq (0.5 nm)/Al (100 nm), in which the electron-hole capture is efficient without additional carrier injection barrier from donor (or acceptor) molecule and carriers mobilities are balanced in the emitting layer, leads to a highly efficient green exciplex OLED with external quantum efficiency (EQE) of 11.9%. The obtained EQE is 18% higher than that of a comparison device using an exciplex exhibiting a comparable ΦPL (0.50), in which TCTA shows similar energy levels but higher hole mobility as compared with Tris-PCz. Our results clearly indicate the significance of mobility balance in governing the efficiency of exciplex-based OLED. Exploiting the Tris-PCz:CN-T2T exciplex as the host, we further demonstrated highly efficient yellow and red fluorescent OLEDs by doping 1 wt % Rubrene and DCJTB as emitter, achieving high EQE of 6.9 and 9.7%, respectively.

Efficient upconversion emission in Ho3+/Nd3+ co-doped oxyfluorosilicate glasses

NASA Astrophysics Data System (ADS)

Devarajulu, G.; Raju, B. Deva Prasad

2018-04-01

We report on an efficient Ho3+ and Ho3+/Nd3+ co-doped oxyfluorosilicate glasses upon excitation with an 808 nm laser diode. The detailed fluorescence have been studied under this excitation source and energy transfer mechanisms in Ho3+/Nd3+ co-doped oxyfluorosilicate glasses. The upconversion peaks at 486, 547 and 596 nm were observed in Nd3+/Ho3+ co-doped sample. The intensity of upconversion emission transitions in Ho3+ depends on the neodymium codopent concentration. These results indicate that Nd3+ ions can be potentially used as sensitizer for Ho3+ ions to stimulate the intense upconversion emission. The energy transfer mechanism between Nd3+ and Ho3+ was analyzed pursuant to the absorption spectra, upconversion spectra and the energy level structures of Nd3+ and Ho3+ ions have been briefly discussed.

Highly efficient phosphorescent, TADF, and fluorescent OLEDs (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kim, Jang-Joo; Kim, Kwon-Hyeon; Moon, Chang-Ki; Shin, Hyun

2016-09-01

High efficiency OLEDs based on phosphorescent, thermally activated delayed fluorescent (TADF) and fluorescent emitters will be presented. We will show that EQEs over 60% is achievable if OLEDs are fabricated using organic semiconductors with the refractive indices of 1.5 and fully horizontal emitting dipoles without any extra light extracting structure. We will also show that reverse intersystem crossing RISC rate plays an important role to reduce the efficiency roll-off in efficient TADF and fluorescent OLEDs and a couple to methods will be presented to increase the RISC rate in the devices.

Electricity savings potentials in the residential sector of Bahrain

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

Akbari, H.; Morsy, M.G.; Al-Baharna, N.S.

1996-08-01

Electricity is the major fuel (over 99%) used in the residential, commercial, and industrial sectors in Bahrain. In 1992, the total annual electricity consumption in Bahrain was 3.45 terawatt-hours (TWh), of which 1.95 TWh (56%) was used in the residential sector, 0.89 TWh (26%) in the commercial sector, and 0.59 TWh (17%) in the industrial sector. Agricultural energy consumption was 0.02 TWh (less than 1%) of the total energy use. In Bahrain, most residences are air conditioned with window units. The air-conditioning electricity use is at least 50% of total annual residential use. The contribution of residential AC to themore » peak power consumption is even more significant, approaching 80% of residential peak power demand. Air-conditioning electricity use in the commercial sector is also significant, about 45% of the annual use and over 60% of peak power demand. This paper presents a cost/benefit analysis of energy-efficient technologies in the residential sector. Technologies studied include: energy-efficient air conditioners, insulating houses, improved infiltration, increasing thermostat settings, efficient refrigerators and freezers, efficient water heaters, efficient clothes washers, and compact fluorescent lights. We conservatively estimate a 32% savings in residential electricity use at an average cost of about 4 fils per kWh. (The subsidized cost of residential electricity is about 12 fils per kWh. 1000 fils = 1 Bahrain Dinar = US$ 2.67). We also discuss major policy options needed for implementation of energy-efficiency technologies.« less

Dual-responsive carbon dot for pH/redox triggered fluorescence imaging with controllable photothermal ablation therapy of cancer.

PubMed

Choi, Cheong A; Lee, Jung Eun; Mazrad, Zihnil Adha Islamy; Kim, Young Kwang; In, Insik; Jeong, Ji Hoon; Park, Sung Young

2018-05-18

We described fluorescence resonance energy transfer for pH/redox-activatable fluorescent carbon dot (FNP) to realize "off-on" switched imaging-guided controllable photothermal therapy (PTT). The FNP is a carbonized self-crosslinked polymer that allows IR825 loading (FNP[IR825]) via hydrophobic interactions in cancer therapy. The capability for fluorescence bioimaging was achieved via the internalization of FNP(IR825) into tumor cells, wherein glutathione (GSH) disulfide bonds were reduced and benzoic imine were cleaved under acidic conditions. The release of IR825 from FNP core in this system can may be used to efficiently control PTT-mediated cancer therapy via its photothermal conversion after near-infrared (NIR) irradiation. The in vitro and in vivo cellular uptake studies revealed the efficient uptake of FNP(IR825) by tumor cells to treat the disease site. Therefore, we demonstrated in mice that our smart nanocarrier could effectively kill tumor cells under exposure to a NIR laser and the particles were biocompatible with various organs. This platform responds sensitively to the exogenous environment inside the cancer cells and may selectively induce the release of PTT-mediated cytotoxicity. Furthermore, this platform may be useful for monitoring the elimination of cancer cells through the fluorescence on/off switch, which can be used for various applications in the field of cancer cell therapy and diagnosis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Three-color confocal Förster (or fluorescence) resonance energy transfer microscopy: Quantitative analysis of protein interactions in the nucleation of actin filaments in live cells.

PubMed

Wallrabe, Horst; Sun, Yuansheng; Fang, Xiaolan; Periasamy, Ammasi; Bloom, George S

2015-06-01

Experiments using live cell 3-color Förster (or fluorescence) resonance energy transfer (FRET) microscopy and corresponding in vitro biochemical reconstitution of the same proteins were conducted to evaluate actin filament nucleation. A novel application of 3-color FRET data is demonstrated, extending the analysis beyond the customary energy-transfer efficiency (E%) calculations. MDCK cells were transfected for coexpression of Teal-N-WASP/Venus-IQGAP1/mRFP1-Rac1, Teal-N-WASP/Venus-IQGAP1/mRFP1-Cdc42, CFP-Rac1/Venus-IQGAP1/mCherry-actin, or CFP-Cdc42/Venus-IQGAP1/mCherry-actin, and with single-label equivalents for spectral bleedthrough correction. Using confirmed E% as an entry point, fluorescence levels and related ratios were correlated at discrete accumulating levels at cell peripheries. Rising ratios of CFP-Rac1:Venus-IQGAP1 were correlated with lower overall actin fluorescence, whereas the CFP-Cdc42:Venus-IQGAP1 ratio correlated with increased actin fluorescence at low ratios, but was neutral at higher ratios. The new FRET analyses also indicated that rising levels of mRFP1-Cdc42 or mRFP1-Rac1, respectively, promoted or suppressed the association of Teal-N-WASP with Venus-IQGAP1. These 3-color FRET assays further support our in vitro results about the role of IQGAP1, Rac1, and Cdc42 in actin nucleation, and the differential impact of Rac1 and Cdc42 on the association of N-WASP with IQGAP1. In addition, this study emphasizes the power of 3-color FRET as a systems biology strategy for simultaneous evaluation of multiple interacting proteins in individual live cells. © 2015 International Society for Advancement of Cytometry.

Soybean stem growth under high-pressure sodium with supplemental blue lighting

NASA Technical Reports Server (NTRS)

Wheeler, R. M.; Mackowiak, C. L.; Sager, J. C.

1991-01-01

To study high-pressure sodium (HPS) lamps used for plant lighting because of their high energy conversion efficiencies, 'McCall' soybean plants were grown for 28 days in growth chambers utilizing HPS lamps, with/without supplemental light from blue phosphor fluorescent lamps. Total photosynthetic photon flux levels, including blue fluorescent, were maintained near 300 or 500 micromol/sq m s. Results indicate that employment of HPS or other blue-deficient sources for lighting at low to moderate photosynthetic photon flux levels may cause abnormal stem elongation, but this can be prevented by the addition of a small amount of supplemental blue light.

Influence of dehydrated nanotubed titanic acid on charge transport and luminescent properties of polymer light-emitting diodes with fluorescent dye

NASA Astrophysics Data System (ADS)

Qian, Lei; Bera, Debasis; Jin, Zhen-Sheng; Du, Zu-Liang; Xu, Zheng; Teng, Feng; Liu, Wei

2007-09-01

In this paper, we discuss the influence of dehydrated nanotubed titanic acid (DNTA) on charge transport and luminescent properties of polymer light-emitting diodes (PLEDs) doped with fluorescent dye. Photoluminescence results confirm the efficient energy transfer from PVK to 4-(dicyanom-ethylene)-2- t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) and tris-(8-hydroxtquinoline) aluminum (Alq 3) in a DNTA-doped device. The device showed lower turn-on voltages and higher charge current by doping with DNTA, which also caused a shift in the exciton's recombination region.

Rose bengal in poly(2-hydroxyethyl methacrylate) thin films: self-quenching by photoactive energy traps

NASA Astrophysics Data System (ADS)

Ezquerra Riega, Sergio D.; Rodríguez, Hernán B.; San Román, Enrique

2017-03-01

The effect of dye concentration on the fluorescence,ΦF, and singlet molecular oxygen,ΦΔ, quantum yields of rose bengal loaded poly(2-hydroxyethyl methacrylate) thin films (∼200 nm thick) was investigated, with the aim of understanding the effect of molecular interactions on the photophysical properties of dyes in crowded constrained environments. Films were characterized by absorption and fluorescence spectroscopy, singlet molecular oxygen (1O2) production was quantified using a chemical monitor, and the triplet decay was determined by laser flash-photolysis. For the monomeric dilute dye, ΦF = 0.05 ± 0.01 and ΦΔ = 0.76 ± 0.14. The effect of humidity and the photostability of the dye were also investigated. Spectral changes in absorption and fluorescence in excess of 0.05 M and concentration self-quenching after 0.01 M are interpreted in the context of a quenching radius model. Calculations of energy migration and trapping rates were performed assuming random distribution of the dye. Best fits of fluorescence quantum yields with concentration are obtained in the whole concentration range with a quenching radius r Q = 1.5 nm, in the order of molecular dimensions. Agreement is obtained only if dimeric traps are considered photoactive, with an observed fluorescence quantum yield ratio ΦF,trap/ΦF,monomer ≈ 0.35. Fluorescent traps are capable of yielding triplet states and 1O2. Results show that the excited state generation efficiency, calculated as the product between the absorption factor and the fluorescence quantum yield, is maximized at around 0.15 M, a very high concentration for random dye distributions. Relevant information for the design of photoactive dyed coatings is provided.

Environmental impacts of lighting technologies - Life cycle assessment and sensitivity analysis

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

Welz, Tobias; Hischier, Roland, E-mail: Roland.Hischier@empa.ch; Hilty, Lorenz M.

2011-04-15

With two regulations, 244/2009 and 245/2009, the European Commission recently put into practice the EuP Directive in the area of lighting devices, aiming to improve energy efficiency in the domestic lighting sector. This article presents a comprehensive life cycle assessment comparison of four different lighting technologies: the tungsten lamp, the halogen lamp, the conventional fluorescent lamp and the compact fluorescent lamp. Taking advantage of the most up-to-date life cycle inventory database available (ecoinvent data version 2.01), all life cycle phases were assessed and the sensitivity of the results for varying assumptions analysed: different qualities of compact fluorescent lamps (production phase),more » different electricity mixes (use phase), and end-of-life scenarios for WEEE recycling versus municipal solid waste incineration (disposal phase). A functional unit of 'one hour of lighting' was defined and the environmental burdens for the whole life cycle for all four lamp types were calculated, showing a clearly lower impact for the two gas-discharge lamps, i.e. the fluorescent and the compact fluorescent lamp. Differences in the product quality of the compact fluorescent lamps reveal to have only a very small effect on the overall environmental performance of this lamp type; a decline of the actual life time of this lamp type doesn't result in a change of the rank order of the results of the here examined four lamp types. It was also shown that the environmental break-even point of the gas-discharge lamps is reached long before the end of their expected life-span. All in all, it can be concluded that a change from today's tungsten lamp technology to a low-energy-consuming technology such as the compact fluorescent lamp results in a substantial environmental benefit.« less

Impact assessment of energy-efficient lighting in patients with lupus erythematosus: a pilot study.

PubMed

Fenton, L; Dawe, R; Ibbotson, S; Ferguson, J; Silburn, S; Moseley, H

2014-03-01

Patients with lupus erythematosus (LE) are often abnormally photosensitive. Ultraviolet (UV) exposure can not only induce cutaneous lesions but may also contribute to systemic flares and disease progression. Various forms of energy-efficient lighting have been shown to emit UV radiation. To determine the effects of these emissions on individuals with LE. This assessment investigated cutaneous responses to repeated exposures from three types of lighting: compact fluorescent lamp (CFL), light-emitting diode (LED) and energy-efficient halogen (EEH). The subjects were 15 patients with LE and a control group of five healthy volunteers. No cutaneous LE lesions were induced by any of the light sources. Delayed skin erythema was induced at the site of CFL irradiation in six of the 15 patients with LE and two of the five healthy subjects. Erythema was increased in severity and more persistent in patients with LE. One patient with LE produced a positive delayed erythema to the EEH. A single patient with LE produced immediate abnormal erythemal responses to the CFL, LED and EEH. Further investigation revealed that this patient also had solar urticaria. All other subjects had negative responses to LED exposure. Compact fluorescent lamps emit UV that can induce skin erythema in both individuals with LE and healthy individuals when situated in close proximity. However, this occurs to a greater extent and is more persistent in patients with LE. EEHs emit UVA that can induce erythema in patients with LE. LEDs provide a safer alternative light source without risk of UV exposure. © 2013 British Association of Dermatologists.

Etching-dependent fluorescence quenching of Ag-dielectric-Au three-layered nanoshells: The effect of inner Ag nanosphere

NASA Astrophysics Data System (ADS)

Zhu, Jian; Xu, Zai-jie; Weng, Guo-jun; Zhao, Jing; Li, Jian-jun; Zhao, Jun-wu

2018-07-01

In this report, Ag-dielectric-Au three-layered nanoshells with controlled inner core size were synthesized. The fluorescence emission of the rhodamine 6G (R6G) could be quenched by the three-layered nanoshells distinctly. What's more, the fluorescence quenching efficiency could be further improved by tuning the etching of inner Ag nanosphere. The maximum fluorescence quenching efficiency is obtained when the separate layer just appears between the inner Ag core and the outer Au shell. Whereas the fluorescence quenching efficiency is weakened when no gaps take place around the inner Ag core or the separate layer is too thick and greater than 13 nm. The fluorescence quenching properties of the Ag-dielectric-Au three-layered nanoshells with different initial sizes of the Ag nanoparticles are also studied. The maximum fluorescence quenching efficiency is obtained when the three-layered nanoshells are synthesized based on the Ag nanoparticles with 60 nm, which is better than others two sizes (42 and 79 nm). Thus we believe that the size of initial Ag nanospheres also greatly affects the optimized fluorescence quenching efficiency. These results about fluorescence quenching properties of Ag-dielectric-Au three-layered nanoshells present a potential for design and fabrication of fluorescence nanosensors based on tuning the geometry of the inner core and the separate layer.

Spectral heterogeneity and carotenoid-to-bacteriochlorophyll energy transfer in LH2 light-harvesting complexes from Allochromatium vinosum.

PubMed

Magdaong, Nikki M; LaFountain, Amy M; Hacking, Kirsty; Niedzwiedzki, Dariusz M; Gibson, George N; Cogdell, Richard J; Frank, Harry A

2016-02-01

Photosynthetic organisms produce a vast array of spectral forms of antenna pigment-protein complexes to harvest solar energy and also to adapt to growth under the variable environmental conditions of light intensity, temperature, and nutrient availability. This behavior is exemplified by Allochromatium (Alc.) vinosum, a photosynthetic purple sulfur bacterium that produces different types of LH2 light-harvesting complexes in response to variations in growth conditions. In the present work, three different spectral forms of LH2 from Alc. vinosum, B800-820, B800-840, and B800-850, were isolated, purified, and examined using steady-state absorption and fluorescence spectroscopy, and ultrafast time-resolved absorption spectroscopy. The pigment composition of the LH2 complexes was analyzed by high-performance liquid chromatography, and all were found to contain five carotenoids: lycopene, anhydrorhodovibrin, spirilloxanthin, rhodopin, and rhodovibrin. Spectral reconstructions of the absorption and fluorescence excitation spectra based on the pigment composition revealed significantly more spectral heterogeneity in these systems compared to LH2 complexes isolated from other species of purple bacteria. The data also revealed the individual carotenoid-to-bacteriochlorophyll energy transfer efficiencies which were correlated with the kinetic data from the ultrafast transient absorption spectroscopic experiments. This series of LH2 complexes allows a systematic exploration of the factors that determine the spectral properties of the bound pigments and control the rate and efficiency of carotenoid-to-bacteriochlorophyll energy transfer.

Screening in crystalline liquids protects energetic carriers in hybrid perovskites

NASA Astrophysics Data System (ADS)

Zhu, Haiming; Miyata, Kiyoshi; Fu, Yongping; Wang, Jue; Joshi, Prakriti; Niesner, Daniel; Williams, Kristopher; Jin, Song; Zhu, Xiaoyang

Hybrid lead halide perovskites exhibit carrier properties that resemble those of pristine nonpolar semiconductors despite static and dynamic disorder, but how carriers are protected from efficient scattering with charged defects and optical phonons is unknown. Here, we reveal the carrier protection mechanism by comparing three single-crystal lead bromide perovskites: CH3NH3PbBr3, CH(NH2)2PbBr3, and CsPbBr3. We observed hot fluorescence emission from energetic carriers with 102 picosecond lifetimes in CH3NH3PbBr3 or CH(NH,SUB>2)2PbBr3, but not in CsPbBr3. The hot fluorescence is correlated with liquid-like molecular reorientational motions, suggesting that dynamic screening protects energetic carriers via solvation or large polaron formation on time scales competitive with that of ultrafast cooling. Similar protections likely exist for band-edge carriers. The long-lived energetic carriers may enable hot-carrier solar cells with efficiencies exceeding the Shockley-Queisser limit. This work was supported by U.S. Department of Energy Grant ER46980, National Science Foundation, Grant DMR 1420634 (MRSEC), and Department of Energy Award DE-FG02-09ER46664.

Investigations regarding the wet decontamination of fluorescent lamp waste using iodine in potassium iodide solutions

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

Tunsu, Cristian, E-mail: tunsu@chalmers.se; Ekberg, Christian; Foreman, Mark

Highlights: • A wet-based decontamination process for fluorescent lamp waste is proposed. • Mercury can be leached using iodine in potassium iodide solution. • The efficiency of the process increases with an increase in leachant concentration. • Selective leaching of mercury from rare earth elements is achieved. • Mercury is furthered recovered using ion exchange, reduction or solvent extraction. - Abstract: With the rising popularity of fluorescent lighting, simple and efficient methods for the decontamination of discarded lamps are needed. Due to their mercury content end-of-life fluorescent lamps are classified as hazardous waste, requiring special treatment for disposal. A simplemore » wet-based decontamination process is required, especially for streams where thermal desorption, a commonly used but energy demanding method, cannot be applied. In this study the potential of a wet-based process using iodine in potassium iodide solution was studied for the recovery of mercury from fluorescent lamp waste. The influence of the leaching agent’s concentration and solid/liquid ratio on the decontamination efficiency was investigated. The leaching behaviour of mercury was studied over time, as well as its recovery from the obtained leachates by means of anion exchange, reduction, and solvent extraction. Dissolution of more than 90% of the contained mercury was achieved using 0.025/0.05 M I{sub 2}/KI solution at 21 °C for two hours. The efficiency of the process increased with an increase in leachant concentration. 97.3 ± 0.6% of the mercury contained was dissolved at 21 °C, in two hours, using a 0.25/0.5 M I{sub 2}/KI solution and a solid to liquid ratio of 10% w/v. Iodine and mercury can be efficiently removed from the leachates using Dowex 1X8 anion exchange resin or reducing agents such as sodium hydrosulphite, allowing the disposal of the obtained solution as non-hazardous industrial wastewater. The extractant CyMe{sub 4}BTBP showed good removal of mercury, with an extraction efficiency of 97.5 ± 0.7% being achieved in a single stage. Better removal of mercury was achieved in a single stage using the extractants Cyanex 302 and Cyanex 923 in kerosene, respectively.« less

Facile synthesis of reduced graphene oxide-gold nanohybrid for potential use in industrial waste-water treatment

NASA Astrophysics Data System (ADS)

Kar, Prasenjit; Sardar, Samim; Liu, Bo; Sreemany, Monjoy; Lemmens, Peter; Ghosh, Srabanti; Pal, Samir Kumar

2016-01-01

Here, we report a facile approach, by the photochemical reduction technique, for in situ synthesis of Au-reduced graphene oxide (Au-RGO) nanohybrids, which demonstrate excellent adsorption capacities and recyclability for a broad range of dyes. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) data confirm the successful synthesis of Au-RGO nanohybrids. The effect of several experimental parameters (temperature and pH) variation can effectively control the dye adsorption capability. Furthermore, kinetic adsorption data reveal that the adsorption process follows a pseudo second-order model. The negative value of Gibbs free energy (ΔG0) confirms spontaneity while the positive enthalpy (ΔH0) indicates the endothermic nature of the adsorption process. Picosecond resolved fluorescence technique unravels the excited state dynamical processes of dye molecules adsorbed on the Au-RGO surface. Time resolved fluorescence quenching of Rh123 after adsorption on Au-RGO nanohybrids indicates efficient energy transfer from Rh123 to Au nanoparticles. A prototype device has been fabricated using Au-RGO nanohybrids on a syringe filter (pore size: 0.220 μm) and the experimental data indicate efficient removal of dyes from waste water with high recyclability. The application of this nanohybrid may lead to the development of an efficient reusable adsorbent in portable water purification.

The use of dendrimers as high-performance shells for round-trip energy transfer: efficient trans-cis photoisomerization from an excited triplet state produced within a dendrimer shell.

PubMed

Miura, Yousuke; Momotake, Atsuya; Takeuchi, Keiichirou; Arai, Tatsuo

2011-01-01

A series of stilbene-cored poly(benzyl ether) dendrimers with benzophenone peripheries were synthesized and their photophysical and photochemical properties were studied. Fluorescence studies revealed that singlet-singlet energy transfer (SSET) from the stilbene core to the benzophenone units took place efficiently in dendrimers of all generations. Similarly, phosphorescence and time-resolved spectroscopic measurements indicated efficient triplet-triplet energy transfer (TTET) from the benzophenone periphery to the stilbene core. Upon excitation at 310 nm, the stilbene core isomerizes via an energy round trip within the dendrimer shell. The quantum yields for the energy round trip (Φ(ERT)), defined as the product of the quantum yields of SSET, intersystem crossing, and TTET (Φ(ERT) = Φ(SS)Φ(isc)Φ(TT)), were extremely high for all generations--99%, 95% and 94% for G1, G2, and G3, respectively--which means that the excitation energy of the dendrimer core was transferred to the dendrimer periphery and back to the core almost quantitatively. The quantum yield for photoisomerization of G1-G3 via an energy round trip was higher than for other stilbene-cored dendrimers, which mainly isomerize from the excited singlet state. Photostability in the dendrimers was also demonstrated and discussed.

Validation of photosynthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus.

PubMed

Dewez, David; Didur, Olivier; Vincent-Héroux, Jonathan; Popovic, Radovan

2008-01-01

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliquus was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystem II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R2>or=0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield (PhiM'), photochemical quenching (qP) and relative photochemical quenching (qP(rel)) values. The cells density was also linearly dependent (R2=0.838) on the relative unquenched fluorescence parameter (UQF(rel)). Non-linear correlation was found (R2=0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF(rel)>PhiM'>qP>qP(rel)>ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants.

Evaluation of the photocatalytic activity of Ln3+-TiO2 nanomaterial using fluorescence technique for real wastewater treatment.

PubMed

Saif, M; Aboul-Fotouh, S M K; El-Molla, S A; Ibrahim, M M; Ismail, L F M

2014-07-15

Evaluation the photocatalytic activity of different Ln(3+) modified TiO2 nanomaterials using fluorescence based technique has rarely been reported. In the present work, xmol Ln(3+) modified TiO2 nanomaterials (Ln = Nd(3+), Sm(3+), Eu(3+), Gd(3+), Dy(3+) and Er(3+) ions; x = 0.005, 0.008, 0.01, 0.02 and 0.03) were synthesized by sol-gel method and characterized using different advanced techniques. The photocatalytic efficiency of the modified TiO2 expressed in the charge carrier separation and OH radicals formation were assigned using TiO2 fluorescence quenching and fluorescence probe methods, respectively. The obtained fluorescence measurements confirm that doping treatment significantly decreases the electron-hole recombination probability in the obtained Ln(3+)/TiO2. Moreover, the rate of OH radicals formation is increased by doping. The highly active nanoparticles (0.02Gd(3+)/TiO2 and 0.01Eu(3+)/TiO2) were applied for industrial wastewater treatment using solar radiation as a renewable energy source. Copyright © 2014 Elsevier B.V. All rights reserved.

Higher-harmonics suppressor for soft x rays

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

Waki, I.; Hirai, Y.; Momose, A.

We have developed an apparatus for suppressing higher harmonics contained in the soft x-ray output beam of grazing-incidence grating monochromators. It consists of eight pairs of total-reflection mirrors. Each pair serves as a low-pass filter with the cutoff energy different from one another. The eight pairs are designed to cover an energy range of 80--1600 eV with an efficiency of harmonic suppression better than 97%, while transmitting more than 50% of the fundamental photons. We have tested its preliminary performance on the soft x-ray beamline BL-8A at the Photon Factory. We present the observed transmission efficiencies and the effects ofmore » the harmonic suppressor on measurements of reflectivity and fluorescence spectra.« less

One-Step Borylation of 1,3-Diaryloxybenzenes Towards Efficient Materials for Organic Light-Emitting Diodes.

PubMed

Hirai, Hiroki; Nakajima, Kiichi; Nakatsuka, Soichiro; Shiren, Kazushi; Ni, Jingping; Nomura, Shintaro; Ikuta, Toshiaki; Hatakeyama, Takuji

2015-11-09

The development of a one-step borylation of 1,3-diaryloxybenzenes, yielding novel boron-containing polycyclic aromatic compounds, is reported. The resulting boron-containing compounds possess high singlet-triplet excitation energies as a result of localized frontier molecular orbitals induced by boron and oxygen. Using these compounds as a host material, we successfully prepared phosphorescent organic light-emitting diodes exhibiting high efficiency and adequate lifetimes. Moreover, using the present one-step borylation, we succeeded in the synthesis of an efficient, thermally activated delayed fluorescence emitter and boron-fused benzo[6]helicene. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluorescent holograms with albumin-acrylamide

NASA Astrophysics Data System (ADS)

Ordóñez-Padilla, M. J.; Olivares-Pérez, A.; Fuentes-Tapia, I.

2014-02-01

We describe fluorescent holograms were made with photosensitive films of albumin (protein) quail, used as modified matrices. Albumin is mixed with acrylamide and eosin Y. Therefore, prepare a photosensitive emulsion and solid hydrated with the ability to phase transmission holograms and volume (VPH). Eosin Y is a fluorescent agent that acts as a photo-sensitizing dye which stimulates the polymerization of acrylamide. To record the interference pattern produced by two waves superimposed on the modified matrix, we use a He-Cd laser. To reconstruct the diffraction pattern is observed with He- Ne laser, λ = 632.8nm, the material is self-developing properties. Measure the diffraction efficiency of the diffracted orders (η[-1, +1]) as a function of exposure energy. We work with various thicknesses and measure the variation of the refractive index using the coupled wave theory of Kogelnik, the holographic gratings meet Bragg condition.

FRET-based binding assay between a fluorescent cAMP analogue and a cyclic nucleotide-binding domain tagged with a CFP.

PubMed

Romero, Francisco; Santana-Calvo, Carmen; Sánchez-Guevara, Yoloxochitl; Nishigaki, Takuya

2017-09-01

The cyclic nucleotide-binding domain (CNBD) functions as a regulatory domain of many proteins involved in cyclic nucleotide signalling. We developed a straightforward and reliable binding assay based on intermolecular fluorescence resonance energy transfer (FRET) between an adenosine-3', 5'-cyclic monophosphate analogue labelled with fluorescein and a recombinant CNBD of human EPAC1 tagged with a cyan fluorescence protein (CFP). The high FRET efficiency of this method (~ 80%) allowed us to perform several types of binding experiments with nanomolar range of sample using conventional equipment. In addition, the CFP tag on the CNBD enabled us to perform a specific binding experiment using an unpurified protein. Considering these advantages, this technique is useful to study poorly characterized CNBDs. © 2017 Federation of European Biochemical Societies.

A new nano-enhanced technology proposed to quantify intracellular detection of radiation-induced metabolic processes.

PubMed

Malak, Henryk; Richmond, Robert; Dicello, J F

2011-02-01

A new approach to intracellular detection and imaging of metabolic processes and pathways is presented that uses surface plasmon resonance to enhance interactions between photon-absorbing metabolites and metal nanoparticles in contact with cells in vitro or in vivo. Photon absorption in the nanoparticles creates plasmon fields, enhancing intrinsic metabolite fluorescence, thereby increasing absorption and emission rates, creating new spectral emission bands, shortening fluorescence lifetimes, becoming more photo-stable and increasing fluorescent resonance energy transfer efficiency. Because the cells remain viable, it is proposed that the method may be used to interrogate cells prior to and after irradiation, with the potential for automated analyses of intracellular interactive pathways associated with radiation exposures at lower doses than existing technologies. The design and concepts of the instrument are presented along with data for unexposed cells.

Surface-confined fluorescence enhancement of Au nanoclusters anchoring to a two-dimensional ultrathin nanosheet toward bioimaging

NASA Astrophysics Data System (ADS)

Tian, Rui; Yan, Dongpeng; Li, Chunyang; Xu, Simin; Liang, Ruizheng; Guo, Lingyan; Wei, Min; Evans, David G.; Duan, Xue

2016-05-01

Gold nanoclusters (Au NCs) as ultrasmall fluorescent nanomaterials possess discrete electronic energy and unique physicochemical properties, but suffer from relatively low quantum yield (QY) which severely affects their application in displays and imaging. To solve this conundrum and obtain highly-efficient fluorescent emission, 2D exfoliated layered double hydroxide (ELDH) nanosheets were employed to localize Au NCs with a density as high as 5.44 × 1013 cm-2, by virtue of the surface confinement effect of ELDH. Both experimental studies and computational simulations testify that the excited electrons of Au NCs are strongly confined by MgAl-ELDH nanosheets, which results in a largely promoted QY as well as prolonged fluorescence lifetime (both ~7 times enhancement). In addition, the as-fabricated Au NC/ELDH hybrid material exhibits excellent imaging properties with good stability and biocompatibility in the intracellular environment. Therefore, this work provides a facile strategy to achieve highly luminescent Au NCs via surface-confined emission enhancement imposed by ultrathin inorganic nanosheets, which can be potentially used in bio-imaging and cell labelling.Gold nanoclusters (Au NCs) as ultrasmall fluorescent nanomaterials possess discrete electronic energy and unique physicochemical properties, but suffer from relatively low quantum yield (QY) which severely affects their application in displays and imaging. To solve this conundrum and obtain highly-efficient fluorescent emission, 2D exfoliated layered double hydroxide (ELDH) nanosheets were employed to localize Au NCs with a density as high as 5.44 × 1013 cm-2, by virtue of the surface confinement effect of ELDH. Both experimental studies and computational simulations testify that the excited electrons of Au NCs are strongly confined by MgAl-ELDH nanosheets, which results in a largely promoted QY as well as prolonged fluorescence lifetime (both ~7 times enhancement). In addition, the as-fabricated Au NC/ELDH hybrid material exhibits excellent imaging properties with good stability and biocompatibility in the intracellular environment. Therefore, this work provides a facile strategy to achieve highly luminescent Au NCs via surface-confined emission enhancement imposed by ultrathin inorganic nanosheets, which can be potentially used in bio-imaging and cell labelling. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01624c

Enhancement of growth and lipid production from microalgae using fluorescent paint under the solar radiation.

PubMed

Seo, Yeong Hwan; Cho, Changsoon; Lee, Jung-Yong; Han, Jong-In

2014-12-01

Solar radiation has intensity that is too high to inhibit microalgae activity and is composed of wide light spectrum including ultraviolet (UV) range which cannot be utilized for microalgae. For these reasons, the modification of solar radiation is required for effective microalgae cultivation, and to do that, fluorescent paint was used for not only blocking excessive solar energy but also converting UV to visible light. With fluorescent aqueous layer, microalgae was protected from photoinhibition and could grow well, but there was difference in growth and lipid accumulation efficiencies depending on the color; maximum dry weight of 1.7 g/L was achieved in red paint, whereas best lipid content of 30% was obtained in blue one. This phenomenon was due to the different light spectrum made by colors. With simple process using fluorescent paint, modification of light was successfully done and allowing microalgae to grow under strong radiation such as solar radiation. Copyright © 2014 Elsevier Ltd. All rights reserved.

A fluorescent probe based on nitrogen doped graphene quantum dots for turn off sensing of explosive and detrimental water pollutant, TNP in aqueous medium

NASA Astrophysics Data System (ADS)

Kaur, Manjot; Mehta, Surinder K.; Kansal, Sushil Kumar

2017-06-01

This paper reports the carbonization assisted green approach for the fabrication of nitrogen doped graphene quantum dots (N-GQDs). The obtained N-GQDs displayed good water dispersibility and stability in the wide pH range. The as synthesized N-GQDs were used as a fluorescent probe for the sensing of explosive 2,4,6-trinitrophenol (TNP) in aqueous medium based on fluorescence resonance energy transfer (FRET), molecular interactions and charge transfer mechanism. The quenching efficiency was found to be linear in proportion to the TNP concentration within the range of 0-16 μM with detection limit (LOD) of 0.92 μM. The presented method was successfully applied to the sensing of TNP in tap and lake water samples with satisfactory results. Thus, N-GQDs were used as a selective, sensitive and turn off fluorescent sensor for the detection of perilous water contaminant i.e. TNP.

A fluorescent probe based on nitrogen doped graphene quantum dots for turn off sensing of explosive and detrimental water pollutant, TNP in aqueous medium.

PubMed

Kaur, Manjot; Mehta, Surinder K; Kansal, Sushil Kumar

2017-06-05

This paper reports the carbonization assisted green approach for the fabrication of nitrogen doped graphene quantum dots (N-GQDs). The obtained N-GQDs displayed good water dispersibility and stability in the wide pH range. The as synthesized N-GQDs were used as a fluorescent probe for the sensing of explosive 2,4,6-trinitrophenol (TNP) in aqueous medium based on fluorescence resonance energy transfer (FRET), molecular interactions and charge transfer mechanism. The quenching efficiency was found to be linear in proportion to the TNP concentration within the range of 0-16μM with detection limit (LOD) of 0.92μM. The presented method was successfully applied to the sensing of TNP in tap and lake water samples with satisfactory results. Thus, N-GQDs were used as a selective, sensitive and turn off fluorescent sensor for the detection of perilous water contaminant i.e. TNP. Copyright © 2017 Elsevier B.V. All rights reserved.

Noncovalent binding of xanthene and phthalocyanine dyes with graphene sheets: the effect of the molecular structure revealed by a photophysical study.

PubMed

Zhang, Xian-Fu; Liu, Su-Ping; Shao, Xiao-Na

2013-09-01

The fluorescence and absorption properties of several xanthene and phthalocyanine dyes were measured in the presence and absence of chemically derived graphene (CDG) sheets. The interaction of pyronine Y (PYY) with graphene sheets was compared with that of rhodamine 6G (R6G) to reveal the effect of the molecular structure. Although the presence of the perpendicular benzene moiety in a R6G or phthalocyanine molecule does cause the difficulty for forming dye-CDG complex and make CDG less efficient in quenching the fluorescence intensity and shortening the fluorescence lifetime, it does not affect the band position of charge transfer absorption, suggesting that no molecular shape change occurred in a dye molecule caused by the interaction with CDG sheets. The spectroscopic and thermodynamic data indicated that the dye-CDG binding is of charge transfer nature, while the dynamic fluorescence quenching is due to photoinduced energy and electron transfer. Copyright © 2013 Elsevier B.V. All rights reserved.

Limits on the maximum attainable efficiency for solid-state lighting

NASA Astrophysics Data System (ADS)

Coltrin, Michael E.; Tsao, Jeffrey Y.; Ohno, Yoshi

2008-03-01

Artificial lighting for general illumination purposes accounts for over 8% of global primary energy consumption. However, the traditional lighting technologies in use today, i.e., incandescent, fluorescent, and high-intensity discharge lamps, are not very efficient, with less than about 25% of the input power being converted to useful light. Solid-state lighting is a rapidly evolving, emerging technology whose efficiency of conversion of electricity to visible white light is likely to approach 50% within the next years. This efficiency is significantly higher than that of traditional lighting technologies, with the potential to enable a marked reduction in the rate of world energy consumption. There is no fundamental physical reason why efficiencies well beyond 50% could not be achieved, which could enable even greater world energy savings. The maximum achievable luminous efficacy for a solid-state lighting source depends on many different physical parameters, for example the color rendering quality that is required, the architecture employed to produce the component light colors that are mixed to produce white, and the efficiency of light sources producing each color component. In this article, we discuss in some detail several approaches to solid-state lighting and the maximum luminous efficacy that could be attained, given various constraints such as those listed above.

Triplet excited state spectra and dynamics of carotenoids from the thermophilic purple photosynthetic bacterium Thermochromatium tepidum

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

Niedzwiedzki, Dariusz; Kobayashi, Masayuki; Blankenship, R. E.

Light-harvesting complex 2 from the anoxygenic phototrophic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption, fluorescence and flash photolysis spectroscopy. Steady-state absorption and fluorescence measurements show that carotenoids play a negligible role as supportive energy donors and transfer excitation to bacteriochlorophyll-a with low energy transfer efficiency of ~30%. HPLC analysis determined that the dominant carotenoids in the complex are rhodopin and spirilloxanthin. Carotenoid excited triplet state formation upon direct (carotenoid) or indirect (bacteriochlorophyll-a Q{sub x} band) excitation shows that carotenoid triplets are mostly localized on spirilloxanthin. In addition, no triplet excitation transfer between carotenoids was observed. Suchmore » specific carotenoid composition and spectroscopic results strongly suggest that this organism optimized carotenoid composition in the light-harvesting complex 2 in order to maximize photoprotective capabilities of carotenoids but subsequently drastically suppressed their supporting role in light-harvesting process.« less

Highly sensitive and selective detection of dopamine using one-pot synthesized highly photoluminescent silicon nanoparticles.

PubMed

Zhang, Xiaodong; Chen, Xiaokai; Kai, Siqi; Wang, Hong-Yin; Yang, Jingjing; Wu, Fu-Gen; Chen, Zhan

2015-03-17

A simple and highly efficient method for dopamine (DA) detection using water-soluble silicon nanoparticles (SiNPs) was reported. The SiNPs with a high quantum yield of 23.6% were synthesized by using a one-pot microwave-assisted method. The fluorescence quenching capability of a variety of molecules on the synthesized SiNPs has been tested; only DA molecules were found to be able to quench the fluorescence of these SiNPs effectively. Therefore, such a quenching effect can be used to selectively detect DA. All other molecules tested have little interference with the dopamine detection, including ascorbic acid, which commonly exists in cells and can possibly affect the dopamine detection. The ratio of the fluorescence intensity difference between the quenched and unquenched cases versus the fluorescence intensity without quenching (ΔI/I) was observed to be linearly proportional to the DA analyte concentration in the range from 0.005 to 10.0 μM, with a detection limit of 0.3 nM (S/N = 3). To the best of our knowledge, this is the lowest limit for DA detection reported so far. The mechanism of fluorescence quenching is attributed to the energy transfer from the SiNPs to the oxidized dopamine molecules through Förster resonance energy transfer. The reported method of SiNP synthesis is very simple and cheap, making the above sensitive and selective DA detection approach using SiNPs practical for many applications.

One pot synthesis of intriguing fluorescent carbon dots for sensing and live cell imaging.

PubMed

Jana, Jayasmita; Ganguly, Mainak; Das, Bodhisatwa; Dhara, Santanu; Negishi, Yuichi; Pal, Tarasankar

2016-04-01

We report a simple one-pot synthesis of highly fluorescent carbon dots (CDs) via modified hydrothermal (MHT) treatment of alkaline solution of dopamine and cysteine. These CDs (λex=320 nm, λem=390 nm, and quantum yield ∼ 5.1%) are of ∼ 2-3 nm in diameter. Further attempt of synthesizing CDs in some common water-miscible solvents ends up the fact that the MHT product from acetone medium is nonfluorescent. However, CDs, produced in aqueous medium, are so stable that they can be dried as a deliverable solid (WCD) without any alteration of fluorescing property if reversibly dispersed in water. Fluorescence of WCD is quenched selectively in acetone. Quenching occurs presumably due to the disruption of radiative recombination along with the hindrance in quantum confinement of the emissive energy traps to the particle surface. Successive quenching of fluorescence of WCD in different acetone concentration admixed in water paves the way to selective acetone sensing (LOD=8.75 × 10(-7) M). The synthesized CDs (in aqueous medium) are cytocompatible and are efficient fluorescent probe for cell imaging. Only living cells are recognized exclusively from fluorescence imaging leaving aside dead cells, while cells are treated with CDs. Copyright © 2015 Elsevier B.V. All rights reserved.

Photosynthetic behavior of woody species under high ozone exposure probed with the JIP-test: a review.

PubMed

Bussotti, Filippo; Strasser, Reto J; Schaub, Marcus

2007-06-01

Visible ozone symptoms on leaves are expressions of physiological mechanisms to cope with oxidative stresses. Often, the symptoms consist of stippling, which corresponds to localized cell death (hypersensitive response, HR), separated from healthy cells by a layer of callose. The HR strategy tends to protect the healthy cells and in most cases the efficiency of chlorophyll to trap energy is not affected. In other cases, the efficiency of leaves to produce biomass declines and the plant loses its photosynthetic apparatus replacing it with a new, more efficient one. Another strategy consists of the production of pigments (anthocyanins), and leaves become reddish. In these cases, the most significant physiological manifestation consists of the enhanced dissipation of energy. These different behavior patterns are reflected in the initial events of photosynthetic activity, and can be monitored with techniques based on the direct fluorescence of chlorophyll a in photosystem II, applying the JIP-test.

CdSe/ZnS quantum dots conjugated with a fluorescein derivative: a FRET-based pH sensor for physiological alkaline conditions.

PubMed

Kurabayashi, Tomokazu; Funaki, Nayuta; Fukuda, Takeshi; Akiyama, Shinnosuke; Suzuki, Miho

2014-01-01

Dual pH-dependent fluorescence peaks from a semiconductor quantum dot (QD) and a pH-dependent fluorescent dye can be measured by irradiating with a single wavelength light, and the pH can be estimated from the ratio of the fluorescent intensity of the two peaks. In this work, ratiometric pH sensing was achieved in an aqueous environment by a fluorescent CdSe/ZnS QD appended with a pH-sensitive organic dye, based on fluorescence resonance energy transfer (FRET). By functionalizing the CdSe/ZnS QD with 5-(and 6)-carboxynaphthofluorescein succinimidyl ester as a pH-dependent fluorescent dye, we succeeded in fabricating sensitive nanocomplexes with a linear response to a broad range of physiological pH levels (7.5-9.5) when excited at 450 nm. We found that a purification process is important for increasing the high-fluorescence intensity ratio of a ratiometric fluorescence pH-sensor, and the fluorescence intensity ratio was improved up to 1.0 at pH 8.0 after the purification process to remove unreacted CdSe/ZnS QDs even though the fluorescence of the dye could not be observed without the purification process. The fluorescence intensity ratio corresponds to the fluorescence intensity of the dye, and this fluorescent dye exhibited pH-dependent fluorescence intensity changes. These facts indicate that the fluorescence intensity ratio linearly increased with increasing pH value of the buffer solution containing the QD and the dye. The FRET efficiencies changed from 0.3 (pH 7.5) to 6.2 (pH 9.5).

Thermo- and light-regulated formation and disintegration of double hydrophilic block copolymer assemblies with tunable fluorescence emissions.

PubMed

Wu, Yonghao; Hu, Huamin; Hu, Jinming; Liu, Tao; Zhang, Guoying; Liu, Shiyong

2013-03-19

We report on thermo- and light-regulated formation and disintegration of double hydrophilic block copolymer (DHBC) micelles associated with tunable fluorescence emissions by employing two types of DHBCs covalently labeled with fluorescence resonance energy transfer (FRET) donor and acceptor moieties, respectively, within the light and temperature dually responsive block. Both DHBCs are molecularly soluble at room temperature in their aqueous mixture, whereas, upon heating to above the critical micellization temperature (CMT, ~31 °C), they coassemble into mixed micelles possessing hydrophilic coronas and mixed cores containing FRET donors and acceptors. Accordingly, the closer spatial proximity between the FRET pair (NBDAE and RhBEA moieties) within micellar cores leads to substantially enhanced FRET efficiency, compared to that in the non-aggregated unimer state. Moreover, upon UV irradiation, the light-reactive moieties undergo light-cleavage reaction and transform into negatively charged carboxylate residues, leading to elevated CMT (∼46 °C). Thus, thermo-induced mixed micelles in the intermediate temperature range (31 °C < T < 46 °C) undergo light-triggered disintegration into unimers, accompanied with the decrease of FRET efficiency. Overall, the coassembly and disassembly occurring in the mixed DHBC solution can be dually regulated by temperature and UV irradiation, and most importantly, these processes can be facilely monitored via changes in FRET efficiency and distinct emission colors.

Discerning the effects of photoinhibition and photoprotection on the rate of oxygen evolution in Arabidopsis leaves.

PubMed

Giovagnetti, Vasco; Ruban, Alexander V

2015-11-01

Higher plants possess a set of interconnected processes to regulate light harvesting. Non-photochemical quenching of chlorophyll a fluorescence (NPQ) is the fastest process activated to protect the photosystem (PS) II from the absorption of excess light energy. However, damage of PSII reaction centers (RCIIs) is often inevitable, a phenomenon known as photoinhibition. Both NPQ and photoinhibition undermine PSII quantum yield (ΦPSII). Recently, we devised a fluorescence-based methodology that uses the coefficient of photochemical quenching measured in the dark following illumination (qPd) to assess the intactness of RCIIs. This procedure enables to express ΦPSII as a function (ƒ) of NPQ and qPd, ΦPSII=ƒ(NPQ,qPd), thus allowing to efficiently discern between the effects of protective NPQ and photoinhibition upon the efficiency of electron transport. In this study, we addressed the relationship between qPd and ΦPSII measured by photosynthetic oxygen evolution in intact leaves of Arabidopsis. We found a linear correlation between qPd and ΦPSII of oxygen evolution (as well as Fv/Fm). This relates to the fact that qPd reflects the onset of photoinhibition. These results further demonstrate the validity of the qPd parameter and underlying theory in quantitatively assessing PSII efficiency solely by using this effective and simple fluorescence technique. Copyright © 2015 Elsevier B.V. All rights reserved.

Purely organic electroluminescent material realizing 100% conversion from electricity to light

PubMed Central

Kaji, Hironori; Suzuki, Hajime; Fukushima, Tatsuya; Shizu, Katsuyuki; Suzuki, Katsuaki; Kubo, Shosei; Komino, Takeshi; Oiwa, Hajime; Suzuki, Furitsu; Wakamiya, Atsushi; Murata, Yasujiro; Adachi, Chihaya

2015-01-01

Efficient organic light-emitting diodes have been developed using emitters containing rare metals, such as platinum and iridium complexes. However, there is an urgent need to develop emitters composed of more abundant materials. Here we show a thermally activated delayed fluorescence material for organic light-emitting diodes, which realizes both approximately 100% photoluminescence quantum yield and approximately 100% up-conversion of the triplet to singlet excited state. The material contains electron-donating diphenylaminocarbazole and electron-accepting triphenyltriazine moieties. The typical trade-off between effective emission and triplet-to-singlet up-conversion is overcome by fine-tuning the highest occupied molecular orbital and lowest unoccupied molecular orbital distributions. The nearly zero singlet–triplet energy gap, smaller than the thermal energy at room temperature, results in an organic light-emitting diode with external quantum efficiency of 29.6%. An external quantum efficiency of 41.5% is obtained when using an out-coupling sheet. The external quantum efficiency is 30.7% even at a high luminance of 3,000 cd m−2. PMID:26477390

Toward the design of alkynylimidazole fluorophores: computational and experimental characterization of spectroscopic features in solution and in poly(methyl methacrylate).

PubMed

Barone, Vincenzo; Bellina, Fabio; Biczysko, Malgorzata; Bloino, Julien; Fornaro, Teresa; Latouche, Camille; Lessi, Marco; Marianetti, Giulia; Minei, Pierpaolo; Panattoni, Alessandro; Pucci, Andrea

2015-10-28

The possibilities offered by organic fluorophores in the preparation of advanced plastic materials have been increased by designing novel alkynylimidazole dyes, featuring different push and pull groups. This new family of fluorescent dyes was synthesized by means of a one-pot sequential bromination-alkynylation of the heteroaromatic core, and their optical properties were investigated in tetrahydrofuran and in poly(methyl methacrylate). An efficient in silico pre-screening scheme was devised as consisting of a step-by-step procedure employing computational methodologies by simulation of electronic spectra within simple vertical energy and more sophisticated vibronic approaches. Such an approach was also extended to efficiently simulate one-photon absorption and emission spectra of the dyes in the polymer environment for their potential application in luminescent solar concentrators. Besides the specific applications of this novel material, the integration of computational and experimental techniques reported here provides an efficient protocol that can be applied to make a selection among similar dye candidates, which constitute the essential responsive part of those fluorescent plastic materials.

Polyproline and the “spectroscopic ruler” revisited with single-molecule fluorescence

PubMed Central

Schuler, Benjamin; Lipman, Everett A.; Steinbach, Peter J.; Kumke, Michael; Eaton, William A.

2005-01-01

To determine whether Förster resonance energy transfer (FRET) measurements can provide quantitative distance information in single-molecule fluorescence experiments on polypeptides, we measured FRET efficiency distributions for donor and acceptor dyes attached to the ends of freely diffusing polyproline molecules of various lengths. The observed mean FRET efficiencies agree with those determined from ensemble lifetime measurements but differ considerably from the values expected from Förster theory, with polyproline treated as a rigid rod. At donor–acceptor distances much less than the Förster radius R0, the observed efficiencies are lower than predicted, whereas at distances comparable to and greater than R0, they are much higher. Two possible contributions to the former are incomplete orientational averaging during the donor lifetime and, because of the large size of the dyes, breakdown of the point-dipole approximation assumed in Förster theory. End-to-end distance distributions and correlation times obtained from Langevin molecular dynamics simulations suggest that the differences for the longer polyproline peptides can be explained by chain bending, which considerably shortens the donor–acceptor distances. PMID:15699337

An efficient core-shell fluorescent silica nanoprobe for ratiometric fluorescence detection of pH in living cells.

PubMed

Fu, Jingni; Ding, Changqin; Zhu, Anwei; Tian, Yang

2016-08-07

Intracellular pH plays a vital role in cell biology, including signal transduction, ion transport and homeostasis. Herein, a ratiometric fluorescent silica probe was developed to detect intracellular pH values. The pH sensitive dye fluorescein isothiocyanate isomer I (FITC), emitting green fluorescence, was hybridized with reference dye rhodamine B (RB), emitting red fluorescence, as a dual-emission fluorophore, in which RB was embedded in a silica core of ∼40 nm diameter. Moreover, to prevent fluorescence resonance energy transfer between FITC and RB, FITC was grafted onto the surface of core-shell silica colloidal particles with a shell thickness of 10-12 nm. The nanoprobe exhibited dual emission bands centered at 517 and 570 nm, under single wavelength excitation of 488 nm. RB encapsulated in silica was inert to pH change and only served as reference signals for providing built-in correction to avoid environmental effects. Moreover, FITC (λem = 517 nm) showed high selectivity toward H(+) against metal ions and amino acids, leading to fluorescence variation upon pH change. Consequently, variations of the two fluorescence intensities (Fgreen/Fred) resulted in a ratiometric pH fluorescent sensor. The specific nanoprobe showed good linearity with pH variation in the range of 6.0-7.8. It can be noted that the fluorescent silica probe demonstrated good water dispersibility, high stability and low cytotoxicity. Accordingly, imaging and biosensing of pH variation was successfully achieved in HeLa cells.

Ratiometric fluorescent sensing of pH values in living cells by dual-fluorophore-labeled i-motif nanoprobes.

PubMed

Huang, Jin; Ying, Le; Yang, Xiaohai; Yang, Yanjing; Quan, Ke; Wang, He; Xie, Nuli; Ou, Min; Zhou, Qifeng; Wang, Kemin

2015-09-01

We designed a new ratiometric fluorescent nanoprobe for sensing pH values in living cells. Briefly, the nanoprobe consists of a gold nanoparticle (AuNP), short single-stranded oligonucleotides, and dual-fluorophore-labeled i-motif sequences. The short oligonucleotides are designed to bind with the i-motif sequences and immobilized on the AuNP surface via Au-S bond. At neutral pH, the dual fluorophores are separated, resulting in very low fluorescence resonance energy transfer (FRET) efficiency. At acidic pH, the i-motif strands fold into a quadruplex structure and leave the AuNP, bringing the dual fluorophores into close proximity, resulting in high FRET efficiency, which could be used as a signal for pH sensing. The nanoprobe possesses abilities of cellular transfection, enzymatic protection, fast response and quantitative pH detection. The in vitro and intracellular applications of the nanoprobe were demonstrated, which showed excellent response in the physiological pH range. Furthermore, our experimental results suggested that the nanoprobe showed excellent spatial and temporal resolution in living cells. We think that the ratiometric sensing strategy could potentially be applied to create a variety of new multicolor sensors for intracellular detection.

Investigation of the optical properties of novel organic macromolecules for solar cell applications

NASA Astrophysics Data System (ADS)

Adegoke, Oluwasegun Oluwasina

The search for renewable energy sources to replace fossil fuel has been a major research focus in the energy sector. The sun, with its vast amount of energy, remains the most abundant and ubiquitous energy source that far exceeds the world energy demand. The ability to effectively capture and convert energy from the sun in the form of photons will be the key to its effective utilization. Organic macromolecules have tremendous potentials to replace and out-perform existing materials, due to their low-cost, ease of tunability, high absorption coefficient and "green" nature. In this dissertation, spectroscopic techniques of steady state absorption and time-resolved fluorescence spectroscopy were used to show the improved absorption of the oligothiophene-functionalized ZnPc through ultrafast energy transfer. ZnPc is known for its chemical and thermal stability. The power conversion efficiency (PCE) in ZnPc-based solar devices is however, very low because of the poor absorption of ZnPc in the 300 - 550 nm region of the solar spectrum. Oligothiophenes have good absorption in the spectral region where the absorption of ZnPc is poor. Other groups of organic compounds that have gained prominence in the study for the design of efficient active materials for photovoltaic cells are the polymers. In the dissertation, different factors which can affect the performance of organic polymers in photovoltaics systems were investigated and analyzed. The effects of the alteration of conjugation, donor-acceptor groups, heteroatoms and alkyl side chains on the photophysical properties and ultimately the performance of organic polymers in organic photovoltaics were investigated. The different effects were investigated using ultrafast spectroscopic techniques which are capable of providing insight of fluorescence decay dynamics at very short times in a time scale of femtosecond. The electronic structure calculations of the polymers were carried out to provide further evidence to the experimental findings. PTB7, which has one of the best power conversion efficiency in organic photovoltaics, was one of the investigated polymers. Other novel organic polymers based on thiophene and furan framework were also considered.

Detection of protease activity by fluorescent protein FRET sensors: from computer simulation to live cells

NASA Astrophysics Data System (ADS)

Goryashchenko, Alexander S.; Khrenova, Maria G.; Savitsky, Alexander P.

2018-04-01

Förster resonance energy transfer (FRET) sensors are widely used for the detection of protease activity in vitro and in vivo. Usually they consist of a FRET pair connected with a polypeptide linker containing a specific cleavage site for the relevant protease. Use of the fluorescent proteins as components of the FRET pair allows genetic encoding of such sensors and solves the problem of their delivery into live cells and animals. There are several ways to improve the properties of such sensors, mainly to increase FRET efficiency and therefore the dynamic range. One of the ways to achieve this is to use a non-fluorescent chromoprotein as an acceptor. Molecular dynamic simulations may assist in the construction of linker structures connecting donor and acceptor molecules. Estimation of the orientation factor κ 2 can be obtained by methods based on quantum theory and combined quantum mechanics/molecular mechanics approaches. The linker can be structured by hydrophobic interactions, bringing it into a closed conformation that shortens the distance between donor and acceptor and, consequently, increases FRET efficiency. We analyzed the effects of different linker structures on the detection of caspase-3 activity using a non-fluorescent acceptor. Also we have constructed the Tb3+- TagRFP sensor in which a complex of the terbium ion and terbium-binding peptide is used as a donor. This allowed us to use the unique property of lanthanide ions—fluorescence lifetime up to milliseconds—to perform measurements with time delay and exclude the nanosecond-order fluorescence. Using our systems as a starting point, by changing the recognition site in the linker it is possible to perform imaging of different protease activity in vitro or in vivo.

P700+- and 3P700-induced quenching of the fluorescence at 760 nm in trimeric Photosystem I complexes from the cyanobacterium Arthrospira platensis.

PubMed

Schlodder, Eberhard; Cetin, Marianne; Byrdin, Martin; Terekhova, Irina V; Karapetyan, Navassard V

2005-01-07

The 5 K absorption spectrum of Photosystem I (PS I) trimers from Arthrospira platensis (old name: Spirulina platensis) exhibits long-wavelength antenna (exciton) states absorbing at 707 nm (called C707) and at 740 nm (called C740). The lowest energy state (C740) fluoresces around 760 nm (F760) at low temperature. The analysis of the spectral properties (peak position and line width) of the lowest energy transition (C740) as a function of temperature within the linear electron-phonon approximation indicates a large optical reorganization energy of approximately 110 cm(-1) and a broad inhomogeneous site distribution characterized by a line width of approximately 115 cm(-1). Linear dichroism (LD) measurements indicate that the transition dipole moment of the red-most state is virtually parallel to the membrane plane. The relative fluorescence yield at 760 nm of PS I with P700 oxidized increases only slightly when the temperature is lowered to 77 K, whereas in the presence of reduced P700 the fluorescence yield increases nearly 40-fold at 77 K as compared to that at room temperature (RT). A fluorescence induction effect could not be resolved at RT. At 77 K the fluorescence yield of PS I trimers frozen in the dark in the presence of sodium ascorbate decreases during illumination by about a factor of 5 due to the irreversible formation of (P700+)F(A/B-) in about 60% of the centers and the reversible accumulation of the longer-lived state (P700+)FX-. The quenching efficiency of different functionally relevant intermediate states of the photochemistry in PS I has been studied. The redox state of the acceptors beyond A(0) does not affect F760. Direct kinetic evidence is presented that the fluorescence at 760 nm is strongly quenched not only by P700+ but also by 3P700. Similar kinetics were observed for flash-induced absorbance changes attributed to the decay of 3P700 or P700+, respectively, and flash-induced fluorescence changes at 760 nm measured under identical conditions. A nonlinear relationship between the variable fluorescence around 760 nm and the [P700red]/[P700total] ratio was derived from titration curves of the absorbance change at 826 nm and the variable fluorescence at 760 nm as a function of the redox potential imposed on the sample solution at room temperature before freezing. The result indicates that the energy exchange between the antennae of different monomers within a PS I trimer stimulates quenching of F760 by P700+.

Evaluation of a High-Performance Solar Home in Loveland, Colorado

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

Hendron, R.; Eastment, M.; Hancock, E.

2006-01-01

Building America (BA) partner McStain Neighborhoods built the Discovery House in Loveland, Colorado, with an extensive package of energy-efficient features, including a high-performance envelope, efficient mechanical systems, a solar water heater integrated with the space-heating system, a heat-recovery ventilator (HRV), and ENERGY STAR? appliances. The National Renewable Energy Laboratory (NREL) and Building Science Consortium (BSC) conducted short-term field-testing and building energy simulations to evaluate the performance of the house. These evaluations are utilized by BA to improve future prototype designs and to identify critical research needs. The Discovery House building envelope and ducts were very tight under normal operating conditions.more » The HRV provided fresh air at a rate of about 75 cfm (35 l/s), consistent with the recommendations of ASHRAE Standard 62.2. The solar hot water system is expected to meet the bulk of the domestic hot water (DHW) load (>83%), but only about 12% of the space-heating load. DOE-2.2 simulations predict whole-house source energy savings of 54% compared to the BA Benchmark [1]. The largest contributors to energy savings beyond McStain's standard practice are the solar water heater, HRV, improved air distribution, high-efficiency boiler, and compact fluorescent lighting package.« less

Evaluation of a High-Performance Solar Home in Loveland, Colorado: Preprint

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

Hendron, R.; Eastment, M.; Hancock, E.

Building America (BA) partner McStain Neighborhoods built the Discovery House in Loveland, Colorado, with an extensive package of energy-efficient features, including a high-performance envelope, efficient mechanical systems, a solar water heater integrated with the space-heating system, a heat-recovery ventilator (HRV), and ENERGY STAR appliances. The National Renewable Energy Laboratory (NREL) and Building Science Consortium (BSC) conducted short-term field-testing and building energy simulations to evaluate the performance of the house. These evaluations are utilized by BA to improve future prototype designs and to identify critical research needs. The Discovery House building envelope and ducts were very tight under normal operating conditions.more » The HRV provided fresh air at a rate of about 35 l/s (75 cfm), consistent with the recommendations of ASHRAE Standard 62.2. The solar hot water system is expected to meet the bulk of the domestic hot water (DHW) load (>83%), but only about 12% of the space-heating load. DOE-2.2 simulations predict whole-house source energy savings of 54% compared to the BA Benchmark. The largest contributors to energy savings beyond McStain's standard practice are the solar water heater, HRV, improved air distribution, high-efficiency boiler, and compact fluorescent lighting package.« less

Energy response calibration of photon-counting detectors using x-ray fluorescence: a feasibility study.

PubMed

Cho, H-M; Ding, H; Ziemer, B P; Molloi, S

2014-12-07

Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using x-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for x-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm(2) in detection area. The angular dependence of x-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded x-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of x-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of x-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic x-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the x-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory.

Energy response calibration of photon-counting detectors using x-ray fluorescence: a feasibility study

NASA Astrophysics Data System (ADS)

Cho, H.-M.; Ding, H.; Ziemer, BP; Molloi, S.

2014-12-01

Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using x-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for x-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3  ×  3 mm2 in detection area. The angular dependence of x-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded x-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of x-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of x-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic x-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the x-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory.

Energy response calibration of photon-counting detectors using X-ray fluorescence: a feasibility study

PubMed Central

Cho, H-M; Ding, H; Ziemer, BP; Molloi, S

2014-01-01

Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using X-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for X-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm2 in detection area. The angular dependence of X-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded X-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of X-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of X-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic X-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the X-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory. PMID:25369288

I'll Save the World from Global Warming--Tomorrow: Using Procrastination Management to Combat Global Warming

ERIC Educational Resources Information Center

Malott, Richard W.

2010-01-01

In the provocatively titled "I'll Save the World from Global Warming--Tomorrow," Dick Malott says that although we all want to do the right thing to help the environment, whether it's buying and installing compact fluorescent light bulbs (CFLs) or replacing an energy-guzzling appliance with a more efficient one, we put it off because there's no…

Effects of oxidants and reductants on the efficiency of excitation transfer in green photosynthetic bacteria

NASA Technical Reports Server (NTRS)

Wang, J.; Brune, D. C.; Blankenship, R. E.

1990-01-01

The efficiency of energy transfer in chlorosome antennas in the green sulfur bacteria Chlorobium vibrioforme and Chlorobium limicola was found to be highly sensitive to the redox potential of the suspension. Energy transfer efficiencies were measured by comparing the absorption spectrum of the bacteriochlorophyll c or d pigments in the chlorosome to the excitation spectrum for fluorescence arising from the chlorosome baseplate and membrane-bound antenna complexes. The efficiency of energy transfer approaches 100% at low redox potentials induced by addition of sodium dithionite or other strong reductants, and is lowered to 10-20% under aerobic conditions or after addition of a variety of membrane-permeable oxidizing agents. The redox effect on energy transfer is observed in whole cells, isolated membranes and purified chlorosomes, indicating that the modulation of energy transfer efficiency arises within the antenna complexes and is not directly mediated by the redox state of the reaction center. It is proposed that chlorosomes contain a component that acts as a highly quenching center in its oxidized state, but is an inefficient quencher when reduced by endogenous or exogenous reductants. This effect may be a control mechanism that prevents cellular damage resulting from reaction of oxygen with reduced low-potential electron acceptors found in the green sulfur bacteria. The redox modulation effect is not observed in the green gliding bacterium Chloroflexus aurantiacus, which contains chlorosomes but does not contain low-potential electron acceptors.

pH-induced vesicle-to-micelle transition in amphiphilic diblock copolymer: investigation by energy transfer between in situ formed polymer embedded gold nanoparticles and fluorescent dye.

PubMed

Maiti, Chiranjit; Banerjee, Rakesh; Maiti, Saikat; Dhara, Dibakar

2015-01-01

The ability to regulate the formation of nanostructures through self-assembly of amphiphilic block copolymers is of immense significance in the field of biology and medicine. In this work, a new block copolymer synthesized by using reversible addition-fragmentation chain transfer (RAFT) polymerization technique from poly(ethylene glycol) monomethyl ether acrylate (PEGMA) and Boc-l-tryptophan acryloyloxyethyl ester (Boc-l-trp-HEA) was found to spontaneously form pH-responsive water-soluble nanostructures after removal of the Boc group. While polymer vesicles or polymerosomes were formed at physiological pH, the micelles were formed at acidic pH (< 5.2), and this facilitated a pH-induced reversible vesicle-to-micelle transition. Formation of these nanostructures was confirmed by different characterization techniques, viz. transmission electron microscopy, dynamic light scattering, and steady-state fluorescence measurements. Further, these vesicles were successfully utilized to reduce HAuCl4 and stabilize the resulting gold nanoparticles (AuNPs). These AuNPs, confined within the hydrophobic shell of the vesicles, could participate in energy transfer process with fluorescent dye molecules encapsulated in the core of the vesicles, thus forming a nanometal surface energy transfer (NSET) pair. Subsequently, following the efficiency of energy transfer between this pair, it was possible to monitor the process of transition from vesicles to micelles. Thus, in this work, we have successfully demonstrated that NSET can be used to follow the transition between nanostructures formed by amphiphilic block copolymers.

Fluorescence Dynamics of a FRET Probe Designed for Crowding Studies.

PubMed

Currie, Megan; Leopold, Hannah; Schwarz, Jacob; Boersma, Arnold J; Sheets, Erin D; Heikal, Ahmed A

2017-06-15

Living cells are crowded with macromolecules and organelles. As a result, there is an urgent need for molecular sensors for quantitative, site-specific assessment of the macromolecular crowding effects on a myriad of biochemical processes toward quantitative cell biology and biophysics. Here we investigate the excited-state dynamics and translational diffusion of a novel FRET sensor (mCerulean-linker-mCitrine) in a buffer (PBS, pH 7.4) at room temperature. Complementary experiments were carried out on free CFP, YFP, and the cleaved FRET probe as controls. The wavelength-dependent fluorescence lifetime measurements of the donor and acceptor in the FRET probe, using the time-correlated single-photon counting technique, indicate an energy transfer efficiency of 6.8 ± 0.9% in PBS, with distinct excited-state dynamics from the recombinant CFP and YFP. The estimated mCerulean-mCitrine distance in this FRET probe is 7.7 ± 0.2 nm. The energy transfer efficiency increases (11.5 ± 0.9%) as the concentration of Ficoll-70 increases over the range of 0-300 g/L with an estimated mCerulean-mCitrine distance of 6.1 ± 0.2 nm. Complementary time-resolved anisotropy measurements suggest that the rotational diffusion of hetero-FRET in PBS is sensitive to the energy transfer from the donor to the acceptor. The results also suggest that the linker, -(GSG) 6 A(EAAAK) 6 A(GSG) 6 A(EAAAK) 6 A(GSG) 6 -, is rather flexible, and the observed rotational dynamics is likely to be due to a segmental mobility of the FRET pairs rather than an overall tumbling motion of a rigid probe. Comparative studies on a new construct of a FRET probe with a shorter, more flexible linker, mCerulean-(GSG) 18 -mCitrine, reveal enhanced energy transfer efficiency. On the millisecond time scale, fluorescence fluctuation analyses of the acceptor (excited at 488 nm) provide a means to examine the translational diffusion coefficient of the FRET probe. The results also suggest that the linker is flexible in this FRET probe, and the observed diffusion coefficient is faster than predicted as compared to the cleaved FRET probe. Our results serve as a point of reference for this FRET probe in a buffer toward its full potential as a sensor for macromolecular crowding in living cells and tissues.

Ligand Assisted Stabilization of Fluorescence Nanoparticles; an Insight on the Fluorescence Characteristics, Dispersion Stability and DNA Loading Efficiency of Nanoparticles.

PubMed

Rhouati, Amina; Hayat, Akhtar; Mishra, Rupesh K; Bueno, Diana; Shahid, Shakir Ahmad; Muñoz, Roberto; Marty, Jean Louis

2016-07-01

This work reports on the ligand assisted stabilization of Fluospheres® carboxylate modified nanoparticles (FCMNPs), and subsequently investigation on the DNA loading capacity and fluorescence response of the modified particles. The designed fluorescence bioconjugate was characterized with enhanced fluorescence characteristics, good stability and large surface area with high DNA loading efficiency. For comparison purpose, bovine serum albumin (BSA) and polyethylene glycol (PEG) with three different length strands were used as cross linkers to modify the particles, and their DNA loading capacity and fluorescence characteristics were investigated. By comparing the performance of the particles, we found that the most improved fluorescence characteristics, enhanced DNA loading and high dispersion stability were obtained, when employing PEG of long spacer arm length. The designed fluorescence bioconjugate was observed to maintain all its characteristics under varying pH over an extended period of time. These types of bioconjugates are in great demand for fluorescence imaging and in vivo fluorescence biomedical application, especially when most of the as synthesized fluorescence particles cannot withstand to varying in vivo physiological conditions with decreases in fluorescence response and DNA loading efficiency.

Dual-Shell Fluorescent Nanoparticles for Self-Monitoring of pH-Responsive Molecule-Releasing in a Visualized Way.

PubMed

Yang, Lingang; Cui, Chuanfeng; Wang, Lingzhi; Lei, Juying; Zhang, Jinlong

2016-07-27

The rational design and controlled synthesis of a smart device with flexibly tailored response ability is all along desirable for bioapplication but long remains a considerable challenge. Here, a pH-stimulated valve system with a visualized "on-off" mode is constructed through a dual-shell fluorescence resonance energy transfer (FRET) strategy. The dual shells refer to carbon dots and fluorescent molecules embedded polymethacrylic acid (F-PMAA) layers successively coating around a SiO2 core (ca. 120 nm), which play the roles as energy donor and acceptor, respectively. The total thickness of the dual-shell in the solid composite is ca. 10 nm. The priorities of this dual-shell FRET nanovalve stem from three facts: (1) the thin shell allows the formation of efficient FRET system without chemical bonding between energy donor and acceptor; (2) the maximum emission wavelength of CD layer is tunable in the range of 400-600 nm, thus providing a flexible energy donor for a wide variety of energy acceptors; (3) the outer F-PMAA shell with a pH-sensitive swelling-shrinking (on-off) behavior functions as a valve for regulating the FRET process. As such, a sensitive and stable pH ratiometric sensor with a working pH range of 3-6 has been built by simply encapsulating pH-responsive fluorescein isothiocyanate (FITC) into PMAA; a pH-dependent swelling-shrinking shuttle carrier with a finely controllable molecule-release behavior has been further fabricated using rhodamine B isothiocyanate (RBITC) as the energy donor and model guest molecule. Significantly, the controlled releasing process is visually self-monitorable.

Influence of quantum dot's quantum yield to chemiluminescent resonance energy transfer.

PubMed

Wang, Hai-Qiao; Li, Yong-Qiang; Wang, Jian-Hao; Xu, Qiao; Li, Xiu-Qing; Zhao, Yuan-Di

2008-03-03

The resonance energy transfer between chemiluminescence donor (luminol-H2O2 system) and quantum dots (QDs, emission at 593 nm) acceptors (CRET) was investigated. The resonance energy transfer efficiencies were compared while the oil soluble QDs, water soluble QDs (modified with thioglycolate) and QD-HRP conjugates were used as acceptor. The fluorescence of QD can be observed in the three cases, indicating that the CRET occurs while QD acceptor in different status was used. The highest CRET efficiency (10.7%) was obtained in the case of oil soluble QDs, and the lowest CRET efficiency (2.7%) was observed in the QD-HRP conjugates case. This result is coincident with the quantum yields of the acceptors (18.3% and 0.4%). The same result was observed in another similar set of experiment, in which the amphiphilic polymer modified QDs (emission at 675 nm) were used. It suggests that the quantum yield of the QD in different status is the crucial factor to the CRET efficiency. Furthermore, the multiplexed CRET between luminol donor and three different sizes QD acceptors was observed simultaneously. This work will offer useful support for improving the CRET studies based on quantum dots.

Use of microgravity to improve the efficiency and power output of Nd-doped laser glasses

NASA Technical Reports Server (NTRS)

Ray, Chandra S.

1992-01-01

The objectives of this research are to: (1) obtain further evidence and understand the science for the reported improvement in chemical homogeneity in glasses prepared in microgravity; and (2) study the feasibility of improving the optical and fluorescence properties, particularly, the limit for Nd(+3) concentration quenching and threshold energy for laser action for laser glasses prepared in microgravity. Attention was directed to ground based investigation whose primary purpose was to determine the suitability and conditions for processing these laser glasses in space. This report describes that the scientific and technical information required for planning flight experiments for these glasses have been obtained, and the preparation for handling and analyzing post flight samples have also been taken. Instruments required for measuring the fluorescence properties of interest have been constructed. The optical and fluorescence properties for the glasses have been measured and made available for comparative property analysis.

Solid State Lighting: A Nanoenabled Case Study in Sustainability

NASA Astrophysics Data System (ADS)

Hicks, Andrea L.

This work uses three household lighting technology options (incandescent, compact fluorescent (CFL), and light emitting diode (LED)) in a nanoenabled case study of artificial lighting. Life cycle assessment (LCA) is used to analyze the environmental impact of three lighting types across all four lifecycle phases: raw materials acquisition, manufacturing, use, and end of life. Using the average United States electricity profile, the use phase is found to have the greatest impact in all nine impact categories defined by TRACI (Tool for the Reduction and Assessment of Chemical and other environmental Impacts). Agent based modeling (ABM) is used to further investigate the use phase with respect to the adoption of energy efficient lighting and the rebound effect. Survey data on the consumer adoption and use of energy efficient lighting technology yields insight into consumer actions and the potential for rebound to occur, and is used to inform the ABM. Based on the results of the ABM analysis it is suggested that regardless of the type of energy efficient lighting, as long as the consumption of light continues to increase, efficiency alone will not reduce energy consumption. Over extended periods of time (~70 years), energy consumption rebounds to levels of pre-efficiency periods. There is a need for policy measures that are coupled with efficiency increases in such a way that energy savings are sustainable. Geographical and temporal variations in electricity profiles and their associated impacts are explored using LCA. It is found that there is the potential for significant variation in the lifetime environmental impact of lighting options based on shifts in the electricity profile. These results suggest the need for effective local policy in coordination with flexible national policy.

Efficient Förster resonance energy transfer in 1,2,3-triazole linked BODIPY-Zn(II) meso-tetraphenylporphyrin donor-acceptor arrays.

PubMed

Leonardi, Matthew J; Topka, Michael R; Dinolfo, Peter H

2012-12-17

Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC) reactivity was successfully employed to synthesize three donor-acceptor energy transfer (EnT) arrays that contain one (Dyad), three (Tetrad) and four (Pentad) 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) donors connected to a Zn-tetraphenylporphyrin acceptor via 1,2,3-triazole linkages. The photophysical properties of the three arrays, along with individual donor and acceptor chromophores, were investigated by UV-vis absorption and emission spectroscopy, fluorescence lifetimes, and density functional theory (DFT) electronic structure modeling. Comparison of the UV-vis absorption spectra and frontier molecular orbitals from DFT calculations of the three arrays with ZnTPP, ZnTTrzlP, and Trzl-BODIPY shows that the electronic structure of the chromophores is essentially unperturbed by the 1,2,3-triazole linkage. Time-dependent DFT (TDDFT) calculations on the Dyad reproduce the absorption spectra in THF and show no evidence of excited state mixing of the donor and acceptor. The BODIPY singlet excited state emission is significantly quenched in all three arrays, consistent with EnT to the porphyrin core, with efficiencies of 95.8, 97.5, and 97.2% for the Dyad, Tetrad, and Pentad, respectively. Fluorescence excitation spectra of the three arrays, measured at the porphyrin emission, mirror the absorption profile of both the porphyrin and BODIPY chromophores and are consistent with the Förster resonance energy transfer (FRET) mechanism. Applying Förster theory to the spectroscopic data of the chromophores gives EnT efficiency estimates that are in close agreement with experimental values, suggesting that the through-space mechanism plays a dominant role in the three arrays.

Non-Constant Learning Rates in Retrospective Experience Curve Analyses and their Correlation to Deployment Programs

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

Wei, Max; Smith, Sarah J.; Sohn, Michael D.

2015-07-16

A key challenge for policy-makers and technology market forecasters is to estimate future technology costs and in particular the rate of cost reduction versus production volume. A related, critical question is what role should state and federal governments have in advancing energy efficient and renewable energy technologies? This work provides retrospective experience curves and learning rates for several energy-related technologies, each of which have a known history of federal and state deployment programs. We derive learning rates for eight technologies including energy efficient lighting technologies, stationary fuel cell systems, and residential solar photovoltaics, and provide an overview and timeline ofmore » historical deployment programs such as state and federal standards and state and national incentive programs for each technology. Piecewise linear regimes are observed in a range of technology experience curves, and public investments or deployment programs are found to be strongly correlated to an increase in learning rate across multiple technologies. A downward bend in the experience curve is found in 5 out of the 8 energy-related technologies presented here (electronic ballasts, magnetic ballasts, compact fluorescent lighting, general service fluorescent lighting, and the installed cost of solar PV). In each of the five downward-bending experience curves, we believe that an increase in the learning rate can be linked to deployment programs to some degree. This work sheds light on the endogenous versus exogenous contributions to technological innovation and highlights the impact of exogenous government sponsored deployment programs. This work can inform future policy investment direction and can shed light on market transformation and technology learning behavior.« less

Rapid protein concentration, efficient fluorescence labeling and purification on a micro/nanofluidics chip.

PubMed

Wang, Chen; Ouyang, Jun; Ye, De-Kai; Xu, Jing-Juan; Chen, Hong-Yuan; Xia, Xing-Hua

2012-08-07

Fluorescence analysis has proved to be a powerful detection technique for achieving single molecule analysis. However, it usually requires the labeling of targets with bright fluorescent tags since most chemicals and biomolecules lack fluorescence. Conventional fluorescence labeling methods require a considerable quantity of biomolecule samples, long reaction times and extensive chromatographic purification procedures. Herein, a micro/nanofluidics device integrating a nanochannel in a microfluidics chip has been designed and fabricated, which achieves rapid protein concentration, fluorescence labeling, and efficient purification of product in a miniaturized and continuous manner. As a demonstration, labeling of the proteins bovine serum albumin (BSA) and IgG with fluorescein isothiocyanate (FITC) is presented. Compared to conventional methods, the present micro/nanofluidics device performs about 10(4)-10(6) times faster BSA labeling with 1.6 times higher yields due to the efficient nanoconfinement effect, improved mass, and heat transfer in the chip device. The results demonstrate that the present micro/nanofluidics device promises rapid and facile fluorescence labeling of small amount of reagents such as proteins, nucleic acids and other biomolecules with high efficiency.

Potassium ions intercalated into g-C3N4-modified TiO2 nanobelts for the enhancement of photocatalytic hydrogen evolution activity under visible-light irradiation

NASA Astrophysics Data System (ADS)

Ma, Jian; Zhou, Wei; Tan, Xin; Yu, Tao

2018-05-01

Solar-to-chemical energy conversion is a challenging photochemical reaction for renewable energy storage. In recent decades, photocatalytic H2 evolution has been studied extensively. TiO2 is a well-established semiconductor in the field of photocatalytic H2 production; however, its low efficiency for solar energy utilization, and high photocarrier recombination rate, restrict its photocatalytic efficiency. Here, a series of K-intercalated g-C3N4-modified TiO2 nanobelts (TCN–Kx) with different dosages of K atoms were fabricated using a hydrothermal method followed by a calcination process. XRD, TEM and XPS tests indicate that a tight interfacial connection is formed between K–g-C3N4 and the TiO2 nanobelts. DFT calculations indicated that K dopants prefer to be at the interlayer sites of g-C3N4, suggesting increased charge transfer efficiency. The H2 production efficiency of the TCN–Kx composite materials from water splitting under visible-light irradiation was clearly improved. Steady fluorescence spectroscopy and photocurrent measurements confirmed that the improvement in photocatalytic H2 production activity was due to the superior charge separation and electron transfer efficiency of TCN–Kx composite materials.

Potassium ions intercalated into g-C3N4-modified TiO2 nanobelts for the enhancement of photocatalytic hydrogen evolution activity under visible-light irradiation.

PubMed

Ma, Jian; Zhou, Wei; Tan, Xin; Yu, Tao

2018-05-25

Solar-to-chemical energy conversion is a challenging photochemical reaction for renewable energy storage. In recent decades, photocatalytic H 2 evolution has been studied extensively. TiO 2 is a well-established semiconductor in the field of photocatalytic H 2 production; however, its low efficiency for solar energy utilization, and high photocarrier recombination rate, restrict its photocatalytic efficiency. Here, a series of K-intercalated g-C 3 N 4 -modified TiO 2 nanobelts (TCN-Kx) with different dosages of K atoms were fabricated using a hydrothermal method followed by a calcination process. XRD, TEM and XPS tests indicate that a tight interfacial connection is formed between K-g-C 3 N 4 and the TiO 2 nanobelts. DFT calculations indicated that K dopants prefer to be at the interlayer sites of g-C 3 N 4 , suggesting increased charge transfer efficiency. The H 2 production efficiency of the TCN-Kx composite materials from water splitting under visible-light irradiation was clearly improved. Steady fluorescence spectroscopy and photocurrent measurements confirmed that the improvement in photocatalytic H 2 production activity was due to the superior charge separation and electron transfer efficiency of TCN-Kx composite materials.

Fluorescence polarization measures energy funneling in single light-harvesting antennas—LH2 vs conjugated polymers

NASA Astrophysics Data System (ADS)

Camacho, Rafael; Tubasum, Sumera; Southall, June; Cogdell, Richard J.; Sforazzini, Giuseppe; Anderson, Harry L.; Pullerits, Tõnu; Scheblykin, Ivan G.

2015-10-01

Numerous approaches have been proposed to mimic natural photosynthesis using artificial antenna systems, such as conjugated polymers (CPs), dendrimers, and J-aggregates. As a result, there is a need to characterize and compare the excitation energy transfer (EET) properties of various natural and artificial antennas. Here we experimentally show that EET in single antennas can be characterized by 2D polarization imaging using the single funnel approximation. This methodology addresses the ability of an individual antenna to transfer its absorbed energy towards a single pool of emissive states, using a single parameter called energy funneling efficiency (ɛ). We studied individual peripheral antennas of purple bacteria (LH2) and single CP chains of 20 nm length. As expected from a perfect antenna, LH2s showed funneling efficiencies close to unity. In contrast, CPs showed lower average funneling efficiencies, greatly varying from molecule to molecule. Cyclodextrin insulation of the conjugated backbone improves EET, increasing the fraction of CPs possessing ɛ = 1. Comparison between LH2s and CPs shows the importance of the protection systems and the protein scaffold of LH2, which keep the chromophores in functional form and at such geometrical arrangement that ensures excellent EET.

Fluorescence polarization measures energy funneling in single light-harvesting antennas--LH2 vs conjugated polymers.

PubMed

Camacho, Rafael; Tubasum, Sumera; Southall, June; Cogdell, Richard J; Sforazzini, Giuseppe; Anderson, Harry L; Pullerits, Tõnu; Scheblykin, Ivan G

2015-10-19

Numerous approaches have been proposed to mimic natural photosynthesis using artificial antenna systems, such as conjugated polymers (CPs), dendrimers, and J-aggregates. As a result, there is a need to characterize and compare the excitation energy transfer (EET) properties of various natural and artificial antennas. Here we experimentally show that EET in single antennas can be characterized by 2D polarization imaging using the single funnel approximation. This methodology addresses the ability of an individual antenna to transfer its absorbed energy towards a single pool of emissive states, using a single parameter called energy funneling efficiency (ε). We studied individual peripheral antennas of purple bacteria (LH2) and single CP chains of 20 nm length. As expected from a perfect antenna, LH2s showed funneling efficiencies close to unity. In contrast, CPs showed lower average funneling efficiencies, greatly varying from molecule to molecule. Cyclodextrin insulation of the conjugated backbone improves EET, increasing the fraction of CPs possessing ε = 1. Comparison between LH2s and CPs shows the importance of the protection systems and the protein scaffold of LH2, which keep the chromophores in functional form and at such geometrical arrangement that ensures excellent EET.

Fluorescence and visual detection of fluoride ions using a photoluminescent graphene oxide paper sensor

NASA Astrophysics Data System (ADS)

Chen, Xiaochun; Yu, Shaoming; Yang, Liang; Wang, Jianping; Jiang, Changlong

2016-07-01

The instant and on-site detection of trace aqueous fluoride ions is still a challenge for environmental monitoring and protection. This work demonstrates a new analytical method and its utility of a paper sensor for visual detection of F- on the basis of the fluorescence resonance energy transfer (FRET) between photoluminescent graphene oxide (GO) and silver nanoparticles (AgNPs) through the formation of cyclic esters between phenylborinic acid and diol. The fluorescence of GO was quenched by the AgNPs, and trace F- can recover the fluorescence of the quenched photoluminescent GO. The increase in fluorescence intensity is proportional to the concentration of F- in the range of 0.05-0.55 nM, along with a limit of detection (LOD) as low as 9.07 pM. Following the sensing mechanism, a paper-based sensor for the visual detection of aqueous F- has been successfully developed. The paper sensor showed high sensitivity for aqueous F-, and the LOD could reach as low as 0.1 μM as observed by the naked eye. The very simple and effective strategy reported here could be extended to the visual detection of a wide range of analytes in the environment by the construction of highly efficient FRET nanoprobes.The instant and on-site detection of trace aqueous fluoride ions is still a challenge for environmental monitoring and protection. This work demonstrates a new analytical method and its utility of a paper sensor for visual detection of F- on the basis of the fluorescence resonance energy transfer (FRET) between photoluminescent graphene oxide (GO) and silver nanoparticles (AgNPs) through the formation of cyclic esters between phenylborinic acid and diol. The fluorescence of GO was quenched by the AgNPs, and trace F- can recover the fluorescence of the quenched photoluminescent GO. The increase in fluorescence intensity is proportional to the concentration of F- in the range of 0.05-0.55 nM, along with a limit of detection (LOD) as low as 9.07 pM. Following the sensing mechanism, a paper-based sensor for the visual detection of aqueous F- has been successfully developed. The paper sensor showed high sensitivity for aqueous F-, and the LOD could reach as low as 0.1 μM as observed by the naked eye. The very simple and effective strategy reported here could be extended to the visual detection of a wide range of analytes in the environment by the construction of highly efficient FRET nanoprobes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02878k

Maximizing fluorescence collection efficiency in multiphoton microscopy

PubMed Central

Zinter, Joseph P.; Levene, Michael J.

2011-01-01

Understanding fluorescence propagation through a multiphoton microscope is of critical importance in designing high performance systems capable of deep tissue imaging. Optical models of a scattering tissue sample and the Olympus 20X 0.95NA microscope objective were used to simulate fluorescence propagation as a function of imaging depth for physiologically relevant scattering parameters. The spatio-angular distribution of fluorescence at the objective back aperture derived from these simulations was used to design a simple, maximally efficient post-objective fluorescence collection system. Monte Carlo simulations corroborated by data from experimental tissue phantoms demonstrate collection efficiency improvements of 50% – 90% over conventional, non-optimized fluorescence collection geometries at large imaging depths. Imaging performance was verified by imaging layer V neurons in mouse cortex to a depth of 850 μm. PMID:21934897

Intramolecular trap formation and Förster energy transfer in the hexapyropheophorbide- a molecular system

NASA Astrophysics Data System (ADS)

Al-Omari, S.

2006-12-01

The photophysical properties of the hexapyropheophorbide- a (P6) compound were studied using both steady-state and time-resolved spectroscopy. It was found that neighboring pyropheophorbide- a (pyroPheo) molecules covalently linked to each other through carbon chains, which could stack. This structural property is the reason for the possibility of formation of two different types of energy traps, which could be resolved experimentally. One of them is formed via face-to-face stacking of two pyroPheo molecules with a direction of the transition dipole moments parallel to each other. The second type of energy trap gives the dominant contribution to the fluorescence signal at a registration wavelength having the oblique geometry or orthogonal direction of the transition dipole moments of the interacting pyroPheo molecules. In any case, the dipole-dipole Förster energy transfer between pyroPheo molecules caused a very fast and efficient delivery of the excitation to a trap. As a result, the fluorescence as well as the singlet oxygen quantum yields of P6 were reduced by four and three times, respectively, compared to those values of the reference bispyrophephorbide- a (P2) compound.

Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers

NASA Astrophysics Data System (ADS)

Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, Sangyoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

2016-09-01

Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble.

Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers

PubMed Central

Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, SangYoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

2016-01-01

Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble. PMID:27641327

Unusual Fluorescent Responses of Morpholine-functionalized Fluorescent Probes to pH via Manipulation of BODIPY’s HOMO and LUMO Energy Orbitals for Intracellular pH Detection

PubMed Central

Zhang, Jingtuo; Yang, Mu; Mazi, Wafa; Adhikari, Kapil; Fang, Mingxi; Xie, Fei; Valenzano, Loredana; Tiwari, Ashutosh; Luo, Fen-Tair; Liu, Haiying

2016-01-01

Three uncommon morpholine-based fluorescent probes (A, B and C) for pH were prepared by introducing morpholine residues to BODIPY dyes at 4,4’- and 2,6-positions, respectively. In contrast to morpholine-based fluorescent probes for pH reported in literature, these fluorescent probes display high fluorescence in a basic condition while they exhibit very weak fluorescence in an acidic condition. The theoretical calculation confirmed that morpholine is unable to function as either an electron donor or an electron acceptor to quench the BODIPY fluorescence in the neutral and basic condition via photo-induced electron transfer (PET) mechanism because the LUMO energy of morpholine is higher than those of the BODIPY dyes while its HOMO energy is lower than those of the BODIPY dyes. However, the protonation of tertiary amines of the morpholine residues in an acidic environment leads to fluorescence quenching of the BODIPY dyes via d-PET mechanism. The fluorescence quenching is because the protonation effectively decreases the LUMO energy which locates between the HOMO and LUMO energies of the BODIPY dyes. Fluorescent probe C with deep-red emission has been successfully used to detect pH changes in mammalian cells. PMID:27547822

Energy efficiency in the U.S. residential sector: An engineering and economic assessment of opportunities for large energy savings and greenhouse gas emissions reductions

NASA Astrophysics Data System (ADS)

Lima de Azevedo, Ines Margarida

Energy efficiency and conservation is a very promising part of a portfolio of the needed strategies to mitigate climate change. Several technologies and energy efficiency measures in the residential sector offer potential for large energy savings. However, while energy efficiency options are currently considered as a means of reducing carbon emissions, there is still large uncertainty about the effect of such measures on overall carbon savings. The first part of this thesis provides a national assessment of the energy efficiency potential in the residential sector under several different scenarios, which include the perspectives of different economic agents (consumers, utilities, ESCOs, and a society). The scenarios also include maximizing energy, electricity or carbon dioxide savings. The second part of this thesis deals with a detailed assessment of the potential for white-light LEDs for energy and carbon dioxide savings in the U.S. commercial and residential sectors. Solid-state lighting shows great promise as a source of efficient, affordable, color-balanced white light. Indeed, assuming market discount rates, the present work demonstrates that white solid-state lighting already has a lower levelized annual cost (LAC) than incandescent bulbs and that it will be lower than that of the most efficient fluorescent bulbs by the end of this decade. However, a large literature indicates that households do not make their decisions in terms of simple expected economic value. The present analysis shows that incorporating the findings from literature on high implicit discount rates from households when performing decisions towards efficient technologies delays the adoption of white LEDs by a couple of years. After a review of the technology, the present work compares the electricity consumption, carbon emissions and cost-effectiveness of current lighting technologies, when accounting for expected performance evolution through 2015. Simulations of lighting electricity consumption and implicit greenhouse gases emissions for the U.S. residential and commercial sectors through 2015 under different policy scenarios (voluntary solid-state lighting adoption, implementation of lighting standards in new construction and rebate programs or equivalent subsidies) are also included.

Experimental feasibility of the airborne measurement of absolute oil fluorescence spectral conversion efficiency

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1983-01-01

Airborne lidar oil spill experiments carried out to determine the practicability of the AOFSCE (absolute oil fluorescence spectral conversion efficiency) computational model are described. The results reveal that the model is suitable over a considerable range of oil film thicknesses provided the fluorescence efficiency of the oil does not approach the minimum detection sensitivity limitations of the lidar system. Separate airborne lidar experiments to demonstrate measurement of the water column Raman conversion efficiency are also conducted to ascertain the ultimate feasibility of converting such relative oil fluorescence to absolute values. Whereas the AOFSCE model is seen as highly promising, further airborne water column Raman conversion efficiency experiments with improved temporal or depth-resolved waveform calibration and software deconvolution techniques are thought necessary for a final determination of suitability.

Far-Red Fluorescent Lipid-Polymer Probes for an Efficient Labeling of Enveloped Viruses.

PubMed

Lacour, William; Adjili, Salim; Blaising, Julie; Favier, Arnaud; Monier, Karine; Mezhoud, Sarra; Ladavière, Catherine; Place, Christophe; Pécheur, Eve-Isabelle; Charreyre, Marie-Thérèse

2016-08-01

Far-red emitting fluorescent lipid probes are desirable to label enveloped viruses, for their efficient tracking by optical microscopy inside autofluorescent cells. Most used probes are rapidly released from membranes, leading to fluorescence signal decay and loss of contrast. Here, water-soluble lipid-polymer probes are synthesized harboring hydrophilic or hydrophobic far-red emitting dyes, and exhibiting enhanced brightness. They efficiently label Hepatitis C Virus pseudotyped particles (HCVpp), more stably and reproducibly than commercial probes, and a strong fluorescence signal is observed with a high contrast. Labeling with such probes do not alter virion morphology, integrity, nor infectivity. Finally, it is shown by fluorescence microscopy that these probes enable efficient tracking of labeled HCVpp inside hepatocarcinoma cells used as model hepatocytes, in spite of their autofluorescence up to 700 nm. These novel fluorescent lipid-polymer probes should therefore enable a better characterization of early stages of infection of autofluorescent cells by enveloped viruses. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Excited-State Proton-Transfer-Induced Trapping Enhances the Fluorescence Emission of a Locked GFP Chromophore

PubMed Central

2016-01-01

The chemical locking of the central single bond in core chromophores of green fluorescent proteins (GFPs) influences their excited-state behavior in a distinct manner. Experimentally, it significantly enhances the fluorescence quantum yield of GFP chromophores with an ortho-hydroxyl group, while it has almost no effect on the photophysics of GFP chromophores with a para-hydroxyl group. To unravel the underlying physical reasons for this different behavior, we report static electronic structure calculations and nonadiabatic dynamics simulations on excited-state intramolecular proton transfer, cis–trans isomerization, and excited-state deactivation in a locked ortho-substituted GFP model chromophore (o-LHBI). On the basis of our previous and present results, we find that the S1 keto species is responsible for the fluorescence emission of the unlocked o-HBI and the locked o-LHBI species. Chemical locking does not change the parts of the S1 and S0 potential energy surfaces relevant to enol–keto tautomerization; hence, in both chromophores, there is an ultrafast excited-state intramolecular proton transfer that takes only 35 fs on average. However, the locking effectively hinders the S1 keto species from approaching the keto S1/S0 conical intersections so that most of trajectories are trapped in the S1 keto region for the entire 2 ps simulation time. Therefore, the fluorescence quantum yield of o-LHBI is enhanced compared with that of unlocked o-HBI, in which the S1 excited-state decay is efficient and ultrafast. In the case of the para-substituted GFP model chromophores p-HBI and p-LHBI, chemical locking hardly affects their efficient excited-state deactivation via cis–trans isomerization; thus, the fluorescence quantum yields in these chromophores remain very low. The insights gained from the present work may help to guide the design of new GFP chromophores with improved fluorescence emission and brightness. PMID:26744782

10 CFR Appendix Q to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Fluorescent Lamp Ballasts

Code of Federal Regulations, 2014 CFR

2014-01-01

... of Fluorescent Lamp Ballasts Q Appendix Q to Subpart B of Part 430 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY CONSERVATION PROGRAM FOR CONSUMER PRODUCTS Test Procedures Pt. 430, Subpt. B, App. Q Appendix Q to Subpart B of Part 430—Uniform Test Method for Measuring the Energy Consumption of Fluorescent...

10 CFR Appendix Q to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Fluorescent Lamp Ballasts

Code of Federal Regulations, 2012 CFR

2012-01-01

... of Fluorescent Lamp Ballasts Q Appendix Q to Subpart B of Part 430 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY CONSERVATION PROGRAM FOR CONSUMER PRODUCTS Test Procedures Pt. 430, Subpt. B, App. Q Appendix Q to Subpart B of Part 430—Uniform Test Method for Measuring the Energy Consumption of Fluorescent...

10 CFR Appendix Q to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Fluorescent Lamp Ballasts

Code of Federal Regulations, 2013 CFR

2013-01-01

... of Fluorescent Lamp Ballasts Q Appendix Q to Subpart B of Part 430 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY CONSERVATION PROGRAM FOR CONSUMER PRODUCTS Test Procedures Pt. 430, Subpt. B, App. Q Appendix Q to Subpart B of Part 430—Uniform Test Method for Measuring the Energy Consumption of Fluorescent...

Comparison of various excitation and detection schemes for dye-doped polymeric whispering gallery mode micro-lasers.

PubMed

Siegle, Tobias; Kellerer, Jonas; Bonenberger, Marielle; Krämmer, Sarah; Klusmann, Carolin; Müller, Marius; Kalt, Heinz

2018-02-05

We compare different excitation and collection configurations based on free-space optics and evanescently coupled tapered fibers for both lasing and fluorescence emission from dye-doped doped polymeric whispering gallery mode (WGM) micro-disk lasers. The focus of the comparison is on the lasing threshold and efficiency of light collection. With the aid of optical fibers, we localize the pump energy to the cavity-mode volume and reduce the necessary pump energy to achieve lasing by two orders of magnitude. When using fibers for detection, the collection efficiency is enhanced by four orders of magnitude compared to a free-space read-out perpendicular to the resonator plane. By enhancing the collection efficiency we are able to record a pronounced modulation of the dye fluorescence under continuous wave (cw) pumping conditions evoked by coupling to the WGMs. Alternatively to fibers as a collection tool, we present a read-out technique based on the detection of in-plane radiated light. We show that this method is especially beneficial in an aqueous environment as well as for size-reduced micro-lasers where radiation is strongly pronounced. Furthermore, we show that this technique allows for the assignment of transverse electric (TE) and transverse magnetic (TM) polarization to the observed fundamental modes in a water environment by performing polarization-dependent photoluminescence (PL) spectroscopy. We emphasize the importance of the polarization determination for sensing applications and verify expected differences in the bulk refractive index sensitivity for TE and TM WGMs experimentally.

Chromophore Isomer Stabilization Is Critical to the Efficient Fluorescence of Cyan Fluorescent Proteins.

PubMed

Gotthard, Guillaume; von Stetten, David; Clavel, Damien; Noirclerc-Savoye, Marjolaine; Royant, Antoine

2017-12-12

ECFP, the first usable cyan fluorescent protein (CFP), was obtained by adapting the tyrosine-based chromophore environment in green fluorescent protein to that of a tryptophan-based one. This first-generation CFP was superseded by the popular Cerulean, CyPet, and SCFP3A that were engineered by rational and random mutagenesis, yet the latter CFPs still exhibit suboptimal properties of pH sensitivity and reversible photobleaching behavior. These flaws were serendipitously corrected in the third-generation CFP mTurquoise and its successors without an obvious rationale. We show here that the evolution process had unexpectedly remodeled the chromophore environment in second-generation CFPs so they would accommodate a different isomer, whose formation is favored by acidic pH or light irradiation and which emits fluorescence much less efficiently. Our results illustrate how fluorescent protein engineering based solely on fluorescence efficiency optimization may affect other photophysical or physicochemical parameters and provide novel insights into the rational evolution of fluorescent proteins with a tryptophan-based chromophore.

Interfacial chemistry and the design of solid-phase nucleic acid hybridization assays using immobilized quantum dots as donors in fluorescence resonance energy transfer.

PubMed

Algar, W Russ; Krull, Ulrich J

2011-01-01

The use of quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET) offer several advantages for the development of multiplexed solid-phase QD-FRET nucleic acid hybridization assays. Designs for multiplexing have been demonstrated, but important challenges remain in the optimization of these systems. In this work, we identify several strategies based on the design of interfacial chemistry for improving sensitivity, obtaining lower limits of detection (LOD) and enabling the regeneration and reuse of solid-phase QD-FRET hybridization assays. FRET-sensitized emission from acceptor dyes associated with hybridization events at immobilized QD donors provides the analytical signal in these assays. The minimization of active sensing area reduces background from QD donor PL and allows the resolution of smaller amounts of acceptor emission, thus lowering the LOD. The association of multiple acceptor dyes with each hybridization event can enhance FRET efficiency, thereby improving sensitivity. Many previous studies have used interfacial protein layers to generate selectivity; however, transient destabilization of these layers is shown to prevent efficient regeneration. To this end, we report a protein-free interfacial chemistry and demonstrate the specific detection of as little as 2 pmol of target, as well as an improved capacity for regeneration.

Interfacial Chemistry and the Design of Solid-Phase Nucleic Acid Hybridization Assays Using Immobilized Quantum Dots as Donors in Fluorescence Resonance Energy Transfer

PubMed Central

Algar, W. Russ; Krull, Ulrich J.

2011-01-01

The use of quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET) offer several advantages for the development of multiplexed solid-phase QD-FRET nucleic acid hybridization assays. Designs for multiplexing have been demonstrated, but important challenges remain in the optimization of these systems. In this work, we identify several strategies based on the design of interfacial chemistry for improving sensitivity, obtaining lower limits of detection (LOD) and enabling the regeneration and reuse of solid-phase QD-FRET hybridization assays. FRET-sensitized emission from acceptor dyes associated with hybridization events at immobilized QD donors provides the analytical signal in these assays. The minimization of active sensing area reduces background from QD donor PL and allows the resolution of smaller amounts of acceptor emission, thus lowering the LOD. The association of multiple acceptor dyes with each hybridization event can enhance FRET efficiency, thereby improving sensitivity. Many previous studies have used interfacial protein layers to generate selectivity; however, transient destabilization of these layers is shown to prevent efficient regeneration. To this end, we report a protein-free interfacial chemistry and demonstrate the specific detection of as little as 2 pmol of target, as well as an improved capacity for regeneration. PMID:22163951

Tar analysis from biomass gasification by means of online fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Baumhakl, Christoph; Karellas, Sotirios

2011-07-01

Optical methods in gas analysis are very valuable mainly due to their non-intrusive character. That gives the possibility to use them for in-situ or online measurements with only optical intervention in the measurement volume. In processes like the gasification of biomass, it is of high importance to monitor the gas quality in order to use the product gas in proper machines for energy production following the restrictions in the gas composition but also improving its quality, which leads to high efficient systems. One of the main problems in the biomass gasification process is the formation of tars. These higher hydrocarbons can lead to problems in the operation of the energy system. Up to date, the state of the art method used widely for the determination of tars is a standardized offline measurement system, the so-called "Tar Protocol". The aim of this work is to describe an innovative, online, optical method for determining the tar content of the product gas by means of fluorescence spectroscopy. This method uses optical sources and detectors that can be found in the market at low cost and therefore it is very attractive, especially for industrial applications where cost efficiency followed by medium to high precision are of high importance.

Nonadiabatic coupling reduces the activation energy in thermally activated delayed fluorescence.

PubMed

Gibson, J; Penfold, T J

2017-03-22

The temperature dependent rate of a thermally activated process is given by the Arrhenius equation. The exponential decrease in the rate with activation energy, which this imposes, strongly promotes processes with small activation barriers. This criterion is one of the most challenging during the design of thermally activated delayed fluorescence (TADF) emitters used in organic light emitting diodes. The small activation energy is usually achieved with donor-acceptor charge transfer complexes. However, this sacrifices the radiative rate and is therefore incommensurate with the high luminescence quantum yields required for applications. Herein we demonstrate that the spin-vibronic mechanism, operative for efficient TADF, overcomes this limitation. Nonadiabatic coupling between the lowest two triplet states give rise to a strong enhancement of the rate of reserve intersystem crossing via a second order mechanism and promotes population transfer between the T 1 to T 2 states. Consequently the rISC mechanism is actually operative between initial and final state exhibiting an energy gap that is smaller than between the T 1 and S 1 states. This contributes to the small activation energies for molecules exhibiting a large optical gap, identifies limitations of the present design procedures and provides a basis from which to construct TADF molecules with simultaneous high radiative and rISC rates.

SR-XFA of uranium-containing materials. A case of Bazhenov formation rocks exploration

NASA Astrophysics Data System (ADS)

Phedorin, M. A.; Bobrov, V. A.; Tchebykin, Ye. P.; Melgunov, M. S.

2000-06-01

When an X-ray fluorescent analysis (XFA) is carried out, errors are possible because fluorescent K-lines of "light" elements and L-lines of some "dark" elements can overlap in energy domain. With certain contents of these elements and insufficient resolution of the spectrometer, this leads to considerable errors of determination. An example is the overlapping of a large number of uranium (U) L-lines and Rb, Nb, Mo K-lines. In this paper a procedure is suggested to correct such overlapping. It was tested on uranium-containing rock samples. These samples represent the oil-producing Bazhenov rock formation, which is characterized by organic matter accumulated in abundance and accompanied by "organophile" elements, including U. The procedure is based on scanning the energy of initial exciting X-radiation. This may be regarded advisable only in the XFA versions that use synchrotron radiation — SR-XFA. As a result of this investigation, geochemical characteristics of the Bazhenov formation rocks are demonstrated and the efficiency of energy scanning procedure in determining both Rb, Nb, Mo and U contents is revealed (using comparison with other methods). The energy scanning procedure also works in the presence of L-lines of some other dark elements (Pb, Th, etc.) in the energy domain of K-lines of As-Mo.

Performance of a two-leaf light use efficiency model for mapping gross primary productivity against remotely sensed sun-induced chlorophyll fluorescence data.

PubMed

Zan, Mei; Zhou, Yanlian; Ju, Weimin; Zhang, Yongguang; Zhang, Leiming; Liu, Yibo

2018-02-01

Estimating terrestrial gross primary production is an important task when studying the carbon cycle. In this study, the ability of a two-leaf light use efficiency model to simulate regional gross primary production in China was validated using satellite Global Ozone Monitoring Instrument - 2 sun-induced chlorophyll fluorescence data. The two-leaf light use efficiency model was used to estimate daily gross primary production in China's terrestrial ecosystems with 500-m resolution for the period from 2007 to 2014. Gross primary production simulated with the two-leaf light use efficiency model was resampled to a spatial resolution of 0.5° and then compared with sun-induced chlorophyll fluorescence. During the study period, sun-induced chlorophyll fluorescence and gross primary production simulated by the two-leaf light use efficiency model exhibited similar spatial and temporal patterns in China. The correlation coefficient between sun-induced chlorophyll fluorescence and monthly gross primary production simulated by the two-leaf light use efficiency model was significant (p<0.05, n=96) in 88.9% of vegetated areas in China (average value 0.78) and varied among vegetation types. The interannual variations in monthly sun-induced chlorophyll fluorescence and gross primary production simulated by the two-leaf light use efficiency model were similar in spring and autumn in most vegetated regions, but dissimilar in winter and summer. The spatial variability of sun-induced chlorophyll fluorescence and gross primary production simulated by the two-leaf light use efficiency model was similar in spring, summer, and autumn. The proportion of spatial variations of sun-induced chlorophyll fluorescence and annual gross primary production simulated by the two-leaf light use efficiency model explained by ranged from 0.76 (2011) to 0.80 (2013) during the study period. Overall, the two-leaf light use efficiency model was capable of capturing spatial and temporal variations in gross primary production in China. However, the model needs further improvement to better simulate gross primary production in summer. Copyright © 2017 Elsevier B.V. All rights reserved.

10 CFR 429.27 - General service fluorescent lamps, general service incandescent lamps, and incandescent reflector...

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 3 2014-01-01 2014-01-01 false General service fluorescent lamps, general service incandescent lamps, and incandescent reflector lamps. 429.27 Section 429.27 Energy DEPARTMENT OF ENERGY ENERGY... EQUIPMENT Certification § 429.27 General service fluorescent lamps, general service incandescent lamps, and...

10 CFR 429.27 - General service fluorescent lamps, general service incandescent lamps, and incandescent reflector...

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 3 2012-01-01 2012-01-01 false General service fluorescent lamps, general service incandescent lamps, and incandescent reflector lamps. 429.27 Section 429.27 Energy DEPARTMENT OF ENERGY ENERGY... EQUIPMENT Certification § 429.27 General service fluorescent lamps, general service incandescent lamps, and...

10 CFR 429.27 - General service fluorescent lamps, general service incandescent lamps, and incandescent reflector...

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 3 2013-01-01 2013-01-01 false General service fluorescent lamps, general service incandescent lamps, and incandescent reflector lamps. 429.27 Section 429.27 Energy DEPARTMENT OF ENERGY ENERGY... EQUIPMENT Certification § 429.27 General service fluorescent lamps, general service incandescent lamps, and...

FRET-based small-molecule fluorescent probes: rational design and bioimaging applications.

PubMed

Yuan, Lin; Lin, Weiying; Zheng, Kaibo; Zhu, Sasa

2013-07-16

Fluorescence imaging has emerged as a powerful tool for monitoring biomolecules within the context of living systems with high spatial and temporal resolution. Researchers have constructed a large number of synthetic intensity-based fluorescent probes for bio-imaging. However, intensity-based fluorescent probes have some limitations: variations in probe concentration, probe environment, and excitation intensity may influence the fluorescence intensity measurements. In principle, the use of ratiometric fluorescent probes can alleviate this shortcoming. Förster resonance energy transfer (FRET) is one of the most widely used sensing mechanisms for ratiometric fluorescent probes. However, the development of synthetic FRET probes with favorable photophysical properties that are also suitable for biological imaging applications remains challenging. In this Account, we review the rational design and biological applications of synthetic FRET probes, focusing primarily on studies from our laboratory. To construct useful FRET probes, it is a pre-requisite to develop a FRET platform with favorable photophysical properties. The design criteria of a FRET platform include (1) well-resolved absorption spectra of the donor and acceptor, (2) well-separated emission spectra of the donor and acceptor, (3) donors and acceptors with comparable brightness, (4) rigid linkers, and (5) near-perfect efficiency in energy transfer. With an efficient FRET platform in hand, it is then necessary to modulate the donor-acceptor distance or spectral overlap integral in an analyte-dependent fashion for development of FRET probes. Herein, we emphasize our most recent progress on the development of FRET probes by spectral overlap integral, in particular by changing the molar absorption coefficient of the donor dyes such as rhodamine dyes, which undergo unique changes in the absorption profiles during the ring-opening and -closing processes. Although partial success has been obtained in design of first-generation rhodamine-based FRET probes via modulation of acceptor molar absorption coefficient, further improvements in terms of versatility, sensitivity, and synthetic accessibility are required. To address these issues with the first-generation rhodamine-based FRET probes, we have proposed a strategy for the design of second-generation probes. As a demonstration, we have developed FRET imaging probes for diverse targets including Cu²⁺, NO, HOCl, cysteine, and H₂O₂. This discussion of the methods for successfully designing synthetic FRET probes underscores the rational basis for further development of new FRET probes as a molecular toolbox for probing and manipulating a wide variety of biomolecules in living systems.

DNA-hosted copper nanoclusters/graphene oxide based fluorescent biosensor for protein kinase activity detection.

PubMed

Wang, Mengke; Lin, Zihan; Liu, Qing; Jiang, Shan; Liu, Hua; Su, Xingguang

2018-07-05

A novel fluorescent biosensor for protein kinase activity (PKA) detection was designed by applying double-strands DNA-hosted copper nanoclusters (dsDNA-CuNCs) and graphene oxide (GO). One DNA strand of the dsDNA consisted of two domains, one domain can hybridize with another complementary DNA strand to stabilize the fluorescent CuNCs and another domain was adenosine 5'-triphosphate (ATP) aptamer. ATP aptamer of the dsDNA-CuNCs would be spontaneously absorbed onto the GO surface through π-π stacking interactions. Thus GO can efficiently quench the fluorescence (FL) of dsDNA-CuNCs through fluorescence resonance energy transfer (FRET). In the present of ATP, ATP specifically combined with ATP aptamer to form ATP-ATP aptamer binding complexes, which had much less affinity to GO, resulting in the fluorescence recovery of the system. Nevertheless, in the presence of PKA, ATP could be translated into ADP and ADP could not combine with ATP aptamer resulting in the fluorescence quenching of dsDNA-CuNCs again. According to the change of the fluorescence signal, PKA activity could be successfully monitored in the range of 0.1-5.0 U mL -1 with a detection limit (LOD) of 0.039 U mL -1 . Besides, the inhibitory effect of H-89 on PKA activity was studied. The sensor was performed for PKA activity detection in cell lysates with satisfactory results. Copyright © 2018 Elsevier B.V. All rights reserved.

Light-emitting diodes as a radiation source for plants

NASA Technical Reports Server (NTRS)

Bula, R. J.; Morrow, R. C.; Tibbitts, T. W.; Barta, D. J.; Ignatius, R. W.; Martin, T. S.

1991-01-01

Development of a more effective radiation source for use in plant-growing facilities would be of significant benefit for both research and commercial crop production applications. An array of light-emitting diodes (LEDs) that produce red radiation, supplemented with a photosynthetic photon flux (PPF) of 30 micromoles s-1 m-2 in the 400- to 500-nm spectral range from blue fluorescent lamps, was used effectively as a radiation source for growing plants. Growth of lettuce (Lactuca sativa L. Grand Rapids') plants maintained under the LED irradiation system at a total PPF of 325 micromoles s-1 m-2 for 21 days was equivalent to that reported in the literature for plants grown for the same time under cool-white fluorescent and incandescent radiation sources. Characteristics of the plants, such as leaf shape, color, and texture, were not different from those found with plants grown under cool-white fluorescent lamps. Estimations of the electrical energy conversion efficiency of a LED system for plant irradiation suggest that it may be as much as twice that published for fluorescent systems.

Fluorescence Ratiometric Assay Strategy for Chemical Transmitter of Living Cells Using H2O2-Sensitive Conjugated Polymers.

PubMed

Wang, Yunxia; Li, Shengliang; Feng, Liheng; Nie, Chenyao; Liu, Libing; Lv, Fengting; Wang, Shu

2015-11-04

A new water-soluble conjugated poly(fluorene-co-phenylene) derivative (PFP-FB) modified with boronate-protected fluorescein (peroxyfluor-1) via PEG linker has been designed and synthesized. In the presence of H2O2, the peroxyfluor-1 group can transform into green fluorescent fluorescein by deprotecting the boronate protecting groups. In this case, upon selective excitation of PFP-FB backbone at 380 nm, efficient fluorescence resonance energy transfer (FRET) from PFP-FB backbone to fluorescein occurs, and accordingly, the fluorescence color of PFP-FB changes from blue to green. Furthermore, the emission color of PFP-FB and the FRET ratio change in a concentration-dependent manner. By taking advantage of PFP-FB, ratiometric detection of choline and acetylcholine (ACh) through cascade enzymatic reactions and further dynamic monitoring of the choline consumption process of cancer cells have been successfully realized. Thus, this new polymer probe promotes the development of enzymatic biosensors and provides a simpler and more effective way for detecting the chemical transmitter of living cells.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

10 CFR Appendix Q1 to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Fluorescent Lamp Ballasts

Code of Federal Regulations, 2014 CFR

2014-01-01

... of Fluorescent Lamp Ballasts Q1 Appendix Q1 to Subpart B of Part 430 Energy DEPARTMENT OF ENERGY... of Fluorescent Lamp Ballasts Comply with Appendix Q1 beginning November 14, 2014. Prior to this date, all fluorescent lamp ballasts shall be tested using the provisions of Appendix Q. 1. Definitions 1.1...

10 CFR Appendix Q1 to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Fluorescent Lamp Ballasts

Code of Federal Regulations, 2013 CFR

2013-01-01

... of Fluorescent Lamp Ballasts Q1 Appendix Q1 to Subpart B of Part 430 Energy DEPARTMENT OF ENERGY... of Fluorescent Lamp Ballasts Comply with Appendix Q1 beginning November 14, 2014. Prior to this date, all fluorescent lamp ballasts shall be tested using the provisions of Appendix Q. 1. Definitions 1.1...

Voltage-dependent dynamic FRET signals from the transverse tubules in mammalian skeletal muscle fibers.

PubMed

DiFranco, Marino; Capote, Joana; Quiñonez, Marbella; Vergara, Julio L

2007-12-01

Two hybrid voltage-sensing systems based on fluorescence resonance energy transfer (FRET) were used to record membrane potential changes in the transverse tubular system (TTS) and surface membranes of adult mice skeletal muscle fibers. Farnesylated EGFP or ECFP (EGFP-F and ECFP-F) were used as immobile FRET donors, and either non-fluorescent (dipicrylamine [DPA]) or fluorescent (oxonol dye DiBAC(4)(5)) lipophilic anions were used as mobile energy acceptors. Flexor digitorum brevis (FDB) muscles were transfected by in vivo electroporation with pEGFP-F and pECFP-F. Farnesylated fluorescent proteins were efficiently expressed in the TTS and surface membranes. Voltage-dependent optical signals resulting from resonance energy transfer from fluorescent proteins to DPA were named QRET transients, to distinguish them from FRET transients recorded using DiBAC(4)(5). The peak DeltaF/F of QRET transients elicited by action potential stimulation is twice larger in fibers expressing ECFP-F as those with EGFP-F (7.1% vs. 3.6%). These data provide a unique experimental demonstration of the importance of the spectral overlap in FRET. The voltage sensitivity of QRET and FRET signals was demonstrated to correspond to the voltage-dependent translocation of the charged acceptors, which manifest as nonlinear components in current records. For DPA, both electrical and QRET data were predicted by radial cable model simulations in which the maximal time constant of charge translocation was 0.6 ms. FRET signals recorded in response to action potentials in fibers stained with DiBAC(4)(5) exhibit DeltaF/F amplitudes as large as 28%, but their rising phase was slower than those of QRET signals. Model simulations require a time constant for charge translocation of 1.6 ms in order to predict current and FRET data. Our results provide the basis for the potential use of lipophilic ions as tools to test for fast voltage-dependent conformational changes of membrane proteins in the TTS.

Amyloid-β Deposits Target Efficient Near-Infrared Fluorescent Probes: Synthesis, in Vitro Evaluation, and in Vivo Imaging.

PubMed

Fu, Hualong; Tu, Peiyu; Zhao, Liu; Dai, Jiapei; Liu, Boli; Cui, Mengchao

2016-02-02

The formation of extracellular amyloid-β (Aβ) plaques is a common molecular change that underlies several debilitating human conditions, including Alzheimer's disease (AD); however, the existing near-infrared (NIR) fluorescent probes for the in vivo detection of Aβ plaques are limited by undesirable fluorescent properties and poor brain kinetics. In this work, we designed, synthesized, and evaluated a new family of efficient NIR probes that target Aβ plaques by incorporating hydroxyethyl groups into the ligand structure. Among these probes, DANIR 8c showed excellent fluorescent properties with an emission maximum above 670 nm upon binding to Aβ aggregates and also displayed a high sensitivity (a 629-fold increase in fluorescence intensity) and affinity (Kd = 14.5 nM). Because of the improved hydrophilicity that was induced by hydroxyls, 8c displayed increased initial brain uptake and a fast washout from the brain, as well as an acceptable biostability in the brain. In vivo NIR fluorescent imaging revealed that 8c could efficiently distinguish between AD transgenic model mice and normal controls. Overall, 8c is an efficient and veritable NIR fluorescent probe for the in vivo detection of Aβ plaques in the brain.

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

PubMed

Yanai, Nobuhiro; Kimizuka, Nobuo

2017-10-17

Photon upconversion based on triplet-triplet annihilation (TTA-UC) has attracted much interest because of its possible applications to renewable energy production and biological fields. In particular, the UC of near-infrared (NIR) light to visible (vis) light is imperative to overcome the Shockley-Queisser limit of single-junction photovoltaic cells, and the efficiency of photocatalytic hydrogen production from water can also be improved with the aid of vis-to-ultraviolet (UV) UC. However, both processes have met limitations in the wavelength range, efficiency, and sensitivity for weak incident light. This Account describes recent breakthroughs that solve these major problems, new triplet sensitization routes to significantly enlarge the range of conversion wavelength by minimizing the energy loss during intersystem crossing (ISC) of triplet sensitizers or bypassing the ISC process. The photochemical processes of TTA-UC in general start with the absorption of longer wavelength incident light by triplet sensitizers, which generate the triplet states via ISC. This ISC inevitably accompanies the energy loss of hundreds of millielectronvolts, which significantly limits the TTA-UC with large anti-Stokes shifts. The small S 1 -T 1 gap of molecules showing thermally activated delayed fluorescence (TADF) allows the sensitization of emitters with the highest T 1 and S 1 energy levels ever employed in TTA-UC, which results in efficient vis-to-UV UC. As alternatives to molecular sensitizers in the NIR region, inorganic nanocrystals with broad NIR absorption bands have recently been shown to work as effective sensitizers for NIR-to-vis TTA-UC. Their small exchange splitting minimizes the energy loss during triplet sensitization. The modification of nanocrystal surfaces with organic acceptors via coordination bonds allows efficient energy transfer between the components and succeeding TTA processes. To remove restrictions on the energy loss during ISC, molecules with direct singlet-to-triplet (S-T) excitation are employed as triplet sensitizers. Although the S-T absorption is spin forbidden, large spin-orbital coupling occurs for appropriately designed metal complexes, which allow S-T absorption in the NIR region with large absorption coefficients. While the triplet lifetime of such S-T absorption sensitizers is often short (less than microsecond), the integration of the molecular sensitizers with emitter assemblies allows facile Dexter energy transfer to the surrounding emitter molecules, leading to efficient NIR-to-vis UC emission through triplet energy migration (TEM) in the condensed state. By judicious modification of the chromophore structures, the first example of NIR-to-blue UC has also been achieved. It is essential to combine these new triplet sensitization routes with an upconverted energy collection (UPCON) approach in molecular assemblies to effectively populate emitter triplets and to overcome remaining issues including back energy transfer. We propose two overall materials designs for the TEM-UPCON strategy, core-shell-shell structures and trilayer structures composed of triplet donor, acceptor, and energy collector. The fusion between triplet science and chemistry of self-assembly would overcome previous difficulties of NIR-to-vis and vis-to-UV TTA-UC toward real-world applications ranging from energy to biology.

Intensity correlation-based calibration of FRET.

PubMed

Bene, László; Ungvári, Tamás; Fedor, Roland; Sasi Szabó, László; Damjanovich, László

2013-11-05

Dual-laser flow cytometric resonance energy transfer (FCET) is a statistically efficient and accurate way of determining proximity relationships for molecules of cells even under living conditions. In the framework of this algorithm, absolute fluorescence resonance energy transfer (FRET) efficiency is determined by the simultaneous measurement of donor-quenching and sensitized emission. A crucial point is the determination of the scaling factor α responsible for balancing the different sensitivities of the donor and acceptor signal channels. The determination of α is not simple, requiring preparation of special samples that are generally different from a double-labeled FRET sample, or by the use of sophisticated statistical estimation (least-squares) procedures. We present an alternative, free-from-spectral-constants approach for the determination of α and the absolute FRET efficiency, by an extension of the presented framework of the FCET algorithm with an analysis of the second moments (variances and covariances) of the detected intensity distributions. A quadratic equation for α is formulated with the intensity fluctuations, which is proved sufficiently robust to give accurate α-values on a cell-by-cell basis in a wide system of conditions using the same double-labeled sample from which the FRET efficiency itself is determined. This seemingly new approach is illustrated by FRET measurements between epitopes of the MHCI receptor on the cell surface of two cell lines, FT and LS174T. The figures show that whereas the common way of α determination fails at large dye-per-protein labeling ratios of mAbs, this presented-as-new approach has sufficient ability to give accurate results. Although introduced in a flow cytometer, the new approach can also be straightforwardly used with fluorescence microscopes. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

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

Halpern, A.M.; Ruggles, C.J.; Zhang, X.K.

Fluorescence spectra and decay curves of dilute solutions (<3 x 10/sup -4/ M) of triethylamine (TEA), tri-n-propylamine (TPA), and 1,4-diazabicyclo(2.2.2)octane (DABCO) in H/sub 2/O- and D/sub 2/O-saturated n-hexane reveal the presence of a complex formed between the electronically excited amine and water. The decay curves, measured between 273 and 323 K (and at 280 and 360 nm; 300 and 400 nm for DABCO), conform to the standard monomer-excimer photokinetic scheme and are analyzed accordingly. These results indicate that the binding energy of the excited TEA-H/sub 2/O complex (B*) is ca. 7.8 kcal/mol, which is larger than that of the ground-statemore » TEA hydrate. B* for the TPA and DABCO-H/sub 2/O complexes is estimated to be ca. 10 and 8.8 kcal/mol, respectively. Stationary-state measurements are consistent with these assignments. The activation energy for the diffusion of water in n-hexane (assumed to be monomeric) appears to be very small (<1 kcal/mol). The decay constants of the three complexes studied are ca. 3.4 x 10/sup 7/ s/sup -1/ for amine-H/sub 2/O and 2.9 x 10/sup 7/ s/sup -1/ for the amine-D/sub 2/O systems. Intrinsic fluorescence quantum efficiencies of the amine-H/sub 2/O complexes are 0.17, 0.23, and 0.28 for TEA, TPA, and DABCO, respectively, at 303 K. A Foerster cycle analysis of the dry and H/sub 2/O-saturated fluorescence spectra of TEA, when taking the ground-state hydrate into account indicates that the repulsion energy of the post-fluorescence (TEA-H/sub 2/O) complex is ca. 10 kcal/mol.« less

Determination of Protein by Fluorescence Enhancement of Curcumin in Lanthanum-Curcumin-Sodium Dodecyl Benzene Sulfonate-Protein System

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

Wang, Feng; Huang, Wei; Zhang, Yunfeng

2011-01-01

We found that the fluorescence intensity of the lanthanum (La(3+))-curcumin (CU) complex can be highly enhanced by proteins in the presence of sodium dodecyl benzene sulphonate (SDBS). Based on this finding, a new fluorimetric method for the determination of protein was developed. Under optimized conditions, the enhanced intensities of fluorescence are quantitatively in proportion to the concentrations of proteins in the range 0.0080-20.0 g mL(-1) for bovine serum albumin (BSA) and 0.00080-20.0 g mL(-1) for human serum albumin (HSA) with excitation of 425 nm, and 0.00020-20.0 g mL(-1) for bovine serum albumin (BSA) and 0.00080-20.0 g mL(-1)for human serum albuminmore » (HSA) with excitation of 280 nm, while corresponding qualitative detection limits (S/N 3) are as low as 5.368, 0.573, 0.049, 0.562 g mL(-1), respectively. Study on reaction mechanism reveals that proteins can bind with La(3+), CU and SDBS through self-assembling function with electrostatic attraction, hydrogen bonding, hydrophobic interaction and van der Waals forces, etc. The proteins form a supermolecular association with multilayer structure, in which La(3+)-CU is clamped between BSA and SDBS. The unique high fluorescence enhancement of CU is resulted through synergic effects of favorable hydrophobic microenvironment provided by BSA and SDBS, and efficient intermolecular energy transfer among BSA, SDBS and CU. In energy transfer process, La(3+) plays a crucial role because it not only shortens the distance between SDBS and CU, but also acts as a "bridge" for transferring the energy from BSA to CU.« less

Structural changes in the cytoplasmic pore of the Kir1.1 channel during pHi-gating probed by FRET.

PubMed

Lee, Jay-Ron; Shieh, Ru-Chi

2009-03-06

Kir1.1 channels are important in maintaining K+ homeostasis in the kidney. Intracellular acidification reversibly closes the Kir1.1 channel and thus decreases K+ secretion. In this study, we used Foster resonance energy transfer (FRET) to determine whether the conformation of the cytoplasmic pore changes in response to intracellular pH (pHi)-gating in Kir1.1 channels fused with enhanced cyan fluorescent protein (ECFP) and enhanced yellow fluorescent protein (EYFP) (ECFP-Kir1.1-EYFP). Because the fluorescence intensities of ECFP and EYFP were affected at pHi < 7.4 where pHi-gating occurs in the ECFP-Kir1.1-EYFP construct, we examined the FRET efficiencies of an ECFP-S219R-EYFP mutant, which is completed closed at pHi 7.4 and open at pHi 10.0. FRET efficiency was increased from 25% to 40% when the pHi was decreased from 10.0 to 7.4. These results suggest that the conformation of the cytoplasmic pore in the Kir1.1 channel changes in response to pHi gating such that the N- and C-termini move apart from each other at pHi 7.4, when the channel is open.

Monitoring apoptosis of TK-GFP-expressing ACC-M cells induced by ACV using FRET technique

NASA Astrophysics Data System (ADS)

Xiong, Tao; Zhang, Zhihong; Lin, Juqiang; Yang, Jie; Zeng, Shaoqun; Luo, Qingming

2006-05-01

Apoptosis is an evolutionary conserved cellular process that plays an important role during development, but it is also involved in tissue homeostasis and in many diseases. To study the characteristics of suicide gene system of the herpes simplex virus thymidine kinase (HSV-tk) gene in tumor cells and explore the apoptosis phenomena in this system and its effect on the human adenoid cystic carcinoma line ACC-M cell, we detected apoptosis of CD3- (ECFP-CRS-DsRed) and TK-GFP-expressing ACC-M (ACC-M-TK-GFP-CD3) cells induced by acyclovir (ACV) using fluorescence resonance energy transfer (FRET) technique. CD3 is a FRET-based indicator for activity of caspase-3, which is composed of an enhanced cyan fluorescent protein, a caspase-3 sensitive linker, and a red fluorescent protein from Discosoma with efficient maturation property. FRET from ECFP to DsRed could be detected in normal ACC-M-TK-GFP-CD3 cells, and the FRET efficient was remarkably decreased and then disappeared during the cells apoptosis induced by ACV. It was due to the activated caspase-3 cleaved the CD3 fusion protein. In this study, the results suggested that the ACV-induced apoptosis of ACC-M-TK-GFP-CD3 cells was through caspase-3 pathway.

Monitoring apoptosis of TK-GFP-expressing ACC-M cells induced by ACV using FRET technique

NASA Astrophysics Data System (ADS)

Xiong, Tao; Zhang, Zhihong; Lin, Juqiang; Yang, Jie; Zeng, Shaoqun; Luo, Qingming

2006-09-01

Apoptosis is an evolutionary conserved cellular process that plays an important role during development, but it is also involved in tissue homeostasis and in many diseases. To study the characteristics of suicide gene system of the herpes simplex virus thymidine kinase (HSV-tk) gene in tumor cells and explore the apoptosis phenomena in this system and its effect on the human adenoid cystic carcinoma line ACC-M cell, we detected apoptosis of CD3- (ECFP-CRS-DsRed) and TK-GFP-expressing ACC-M (ACC-M-TK-GFP-CD3) cells induced by acyclovir (ACV) using fluorescence resonance energy transfer (FRET) technique. CD3 is a FRET-based indicator for activity of caspase-3, which is composed of an enhanced cyan fluorescent protein, a caspase-3 sensitive linker, and a red fluorescent protein from Discosoma with efficient maturation property. FRET from ECFP to DsRed could be detected in normal ACC-M-TK-GFP-CD3 cells, and the FRET efficient was remarkably decreased and then disappeared during the cells apoptosis induced by ACV. It was due to the activated caspase-3 cleaved the CD3 fusion protein. In this study, the results suggested that the AVC-induced apoptosis of ACC-M-TK-GFP-CD3 cells was through caspase-3 pathway.

Microsecond resolved single-molecule FRET time series measurements based on the line confocal optical system combined with hybrid photodetectors.

PubMed

Oikawa, Hiroyuki; Takahashi, Takumi; Kamonprasertsuk, Supawich; Takahashi, Satoshi

2018-01-31

Single-molecule (sm) fluorescence time series measurements based on the line confocal optical system are a powerful strategy for the investigation of the structure, dynamics, and heterogeneity of biological macromolecules. This method enables the detection of more than several thousands of fluorescence photons per millisecond from single fluorophores, implying that the potential time resolution for measurements of the fluorescence resonance energy transfer (FRET) efficiency is 10 μs. However, the necessity of using imaging photodetectors in the method limits the time resolution in the FRET efficiency measurements to approximately 100 μs. In this investigation, a new photodetector called a hybrid photodetector (HPD) was incorporated into the line confocal system to improve the time resolution without sacrificing the length of the time series detection. Among several settings examined, the system based on a slit width of 10 μm and a high-speed counting device made the best of the features of the line confocal optical system and the HPD. This method achieved a time resolution of 10 μs and an observation time of approximately 5 ms in the sm-FRET time series measurements. The developed device was used for the native state of the B domain of protein A.

Tracing the conformational changes in BSA using FRET with environmentally-sensitive squaraine probes

NASA Astrophysics Data System (ADS)

Govor, Iryna V.; Tatarets, Anatoliy L.; Obukhova, Olena M.; Terpetschnig, Ewald A.; Gellerman, Gary; Patsenker, Leonid D.

2016-06-01

A new potential method of detecting the conformational changes in hydrophobic proteins such as bovine serum albumin (BSA) is introduced. The method is based on the change in the Förster resonance energy transfer (FRET) efficiency between protein-sensitive fluorescent probes. As compared to conventional FRET based methods, in this new approach the donor and acceptor dyes are not covalently linked to protein molecules. Performance of the new method is demonstrated using the protein-sensitive squaraine probes Square-634 (donor) and Square-685 (acceptor) to detect the urea-induced conformational changes of BSA. The FRET efficiency between these probes can be considered a more sensitive parameter to trace protein unfolding as compared to the changes in fluorescence intensity of each of these probes. Addition of urea followed by BSA unfolding causes a noticeable decrease in the emission intensities of these probes (factor of 5.6 for Square-634 and 3.0 for Square-685), and the FRET efficiency changes by a factor of up to 17. Compared to the conventional method the new approach therefore demonstrates to be a more sensitive way to detect the conformational changes in BSA.

Portable lamp with dynamically controlled lighting distribution

DOEpatents

Siminovitch, Michael J.; Page, Erik R.

2001-01-01

A double lamp table or floor lamp lighting system has a pair of compact fluorescent lamps (CFLs) arranged vertically with a reflective septum in between. By selectively turning on one or both of the CFLs, down lighting, up lighting, or both up and down lighting is produced. The control system can also vary the light intensity from each CFL. The reflective septum insures that almost all the light produced by each lamp will be directed into the desired light distribution pattern which is selected and easily changed by the user. Planar compact fluorescent lamps, e.g. circular CFLs, particularly oriented horizontally, are preferable. CFLs provide energy efficiency. The lighting system may be designed for the home, hospitality, office or other environments.

Silica nanoparticle-based dual imaging colloidal hybrids: cancer cell imaging and biodistribution

PubMed Central

Lee, Haisung; Sung, Dongkyung; Kim, Jinhoon; Kim, Byung-Tae; Wang, Tuntun; An, Seong Soo A; Seo, Soo-Won; Yi, Dong Kee

2015-01-01

In this study, fluorescent dye-conjugated magnetic resonance (MR) imaging agents were investigated in T mode. Gadolinium-conjugated silica nanoparticles were successfully synthesized for both MR imaging and fluorescence diagnostics. Polyamine and polycarboxyl functional groups were modified chemically on the surface of the silica nanoparticles for efficient conjugation of gadolinium ions. The derived gadolinium-conjugated silica nanoparticles were investigated by zeta potential analysis, transmission electron microscopy, inductively coupled plasma mass spectrometry, and energy dispersive x-ray spectroscopy. MR equipment was used to investigate their use as contrast-enhancing agents in T1 mode under a 9.4 T magnetic field. In addition, we tracked the distribution of the gadolinium-conjugated nanoparticles in both lung cancer cells and organs in mice. PMID:26357472

Carbon "Quantum" Dots for Fluorescence Labeling of Cells.

PubMed

Liu, Jia-Hui; Cao, Li; LeCroy, Gregory E; Wang, Ping; Meziani, Mohammed J; Dong, Yiyang; Liu, Yuanfang; Luo, Pengju G; Sun, Ya-Ping

2015-09-02

The specifically synthesized and selected carbon dots of relatively high fluorescence quantum yields were evaluated in their fluorescence labeling of cells. For the cancer cell lines, the cellular uptake of the carbon dots was generally efficient, resulting in the labeling of the cells with bright fluorescence emissions for both one- and two-photon excitations from predominantly the cell membrane and cytoplasm. In the exploration on labeling the live stem cells, the cellular uptake of the carbon dots was relatively less efficient, though fluorescence emissions could still be adequately detected in the labeled cells, with the emissions again predominantly from the cell membrane and cytoplasm. This combined with the observed more efficient internalization of the same carbon dots by the fixed stem cells might suggest some significant selectivity of the stem cells toward surface functionalities of the carbon dots. The needs and possible strategies for more systematic and comparative studies on the fluorescence labeling of different cells, including especially live stem cells, by carbon dots as a new class of brightly fluorescent probes are discussed.

Controlling photophysical properties of ultrasmall conjugated polymer nanoparticles through polymer chain packing

PubMed Central

Piwoński, Hubert; Michinobu, Tsuyoshi; Habuchi, Satoshi

2017-01-01

Applications of conjugated polymer nanoparticles (Pdots) for imaging and sensing depend on their size, fluorescence brightness and intraparticle energy transfer. The molecular design of conjugated polymers (CPs) has been the main focus of the development of Pdots. Here we demonstrate that proper control of the physical interactions between the chains is as critical as the molecular design. The unique design of twisted CPs and fine-tuning of the reprecipitation conditions allow us to fabricate ultrasmall (3.0–4.5 nm) Pdots with excellent photostability. Extensive photophysical and structural characterization reveals the essential role played by the packing of the polymer chains in the particles in the intraparticle spatial alignment of the emitting sites, which regulate the fluorescence brightness and the intraparticle energy migration efficiency. Our findings enhance understanding of the relationship between chain interactions and the photophysical properties of CP nanomaterials, providing a framework for designing and fabricating functional Pdots for imaging applications. PMID:28508857

LASERS IN MEDICINE: Quantum efficiency of the laser-excited singlet-oxygen-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine

NASA Astrophysics Data System (ADS)

Bashtanov, M. E.; Drozdova, N. N.; Krasnovskii, A. A.

1999-12-01

An investigation was made of the ratios of the intensity Idf of the singlet-oxygen(1O2)-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine (ZnTBPc), with the maximum at λ = 685 nm, to the intensity I1270 of the photosensitised phosphorescence of 1O2 with the maximum at λ = 1270 nm in deuterated benzene when excited with λ = 337 nm nitrogen-laser pulses. Depending on the energy density of the laser radiation (0.25 — 0.7 mJ cm-2) and on the concentration of ZnTBPc (0.06 — 3.4 μM), the ratio of the zero-time intensities of the delayed fluorescence of ZnTBPc and of the singlet-oxygen phosphorescence Idf0/I12700 varied from 0.01 to 0.2 in air-saturated solutions of ZnTBPc. The intensity Idf0 decreased fivefold as a result of saturation with oxygen of air-saturated solutions. The quantum efficiency of the delayed fluorescence was represented by the coefficient α =(Idf0/I12700)kr/(γf[1O2]0[ZnTBPc]), where [1O2]0 is the zero-time concentration of 1O2 after a laser shot; kr is the rate constant of radiative deactivation of 1O2 in the investigated solvent; γf is the quantum yield of the ZnTBPc fluorescence. It was established that in the case of air-saturated solutions of ZnTBPc this coefficient was approximately 200 times less than for metal-free tetra(4-tert-butyl)phthalocyanine and its absolute value was ~2 × 1011 M-2 s-1.

Fluorescence-based characterization of genetically encoded peptides that fold in live cells: progress toward a generic hairpin scaffold

NASA Astrophysics Data System (ADS)

Cheng, Zihao; Campbell, Robert E.

2007-02-01

Binding proteins suitable for expression and high affinity molecular recognition in the cytoplasm or nucleus of live cells have numerous applications in the biological sciences. In an effort to add a new minimal motif to the growing repertoire of validated non-immunoglobulin binding proteins, we have undertaken the development of a generic protein scaffold based on a single β-hairpin that can fold efficiently in the cytoplasm. We have developed a method, based on the measurement of fluorescence resonance energy transfer (FRET) between a genetically fused cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP), that allows the structural stability of recombinant β-hairpin peptides to be rapidly assessed both in vitro and in vivo. We have previously reported the validation of this method when applied to a 16mer tryptophan zipper β-hairpin. We now describe the use of this method to evaluate the potential of a designed 20mer β-hairpin peptide with a 3rd Trp/Trp cross-strand pair to function as a generic protein scaffold. Quantitative analysis of the FRET efficiency, resistance to proteolysis (assayed by loss of FRET), and circular dichroism spectra revealed that the 20mer peptide is significantly more tolerant of destabilizing mutations than the 16mer peptide. Furthermore, we experimentally demonstrate that the in vitro determined β-hairpin stabilities are well correlated with in vivo β-hairpin stabilities as determined by FRET measurements of colonies of live bacteria expressing the recombinant peptides flanked by CFP and YFP. Finally, we report on our progress to develop highly folded 24mer and 28mer β-hairpin peptides through the use of fluorescence-based library screening.

A fluorometric aptasensor for methamphetamine based on fluorescence resonance energy transfer using cobalt oxyhydroxide nanosheets and carbon dots.

PubMed

Saberi, Zeinab; Rezaei, Behzad; Faroukhpour, Hossein; Ensafi, Ali Ashghar

2018-05-17

Cobalt oxyhydroxide (CoOOH) nanosheets are efficient fluorescence quenchers due to their specific optical properties and high surface area. The combination of CoOOH nanosheets and carbon dots (CDs) has not been used in any aptasensor based on fluorescence quenching so far. An aptamer based fluorometric assay is introduced that is making use of fluorescent CDs conjugated to the aptamer against methamphetamine (MTA), and of CoOOH nanosheets which reduce the fluorescence of the CDs as a quencher. The results revealed that the conjugated CDs with aptamers were able to enclose the CoOOH nanosheets. Consequently, fluorescence is quenched. If the aptamer on the CD binds MTA, the CDs are detached from CoOOH nanosheets. As a result, fluorescence is restored proportionally to zhe MTA concentration. The fluorometric limit of detection is 1 nM with a dynamic range from 5 to 156 nM. The method was validated by comparing the results obtained by the new method to those obtained by ion mobility spectroscopy. Theoretical studies showed that the distance between CoOOH nanosheet and C-Ds is approximately 7.6 Å which can illustrate the possibility of FRET phenomenon. The interactions of MTA and the aptamer were investigated using molecular dynamic simulation (MDS). Graphical abstract Carbon dots (C-Ds) were prepared from grape leaves, conjugated to aptamer, and adsorbed on CoOOH nanosheets. So, the fluorescence of C-Ds is quenched. On addition of MTA, fluorescence is restored.

Photo-acoustic spectroscopy and quantum efficiency of Yb{sup 3+} doped alumino silicate glasses

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

Kuhn, Stefan, E-mail: stefan.kuhn84@googlemail.com; Tiegel, Mirko; Herrmann, Andreas

2015-09-14

In this contribution, we analyze the effect of several preparation methods of Yb{sup 3+} doped alumino silicate glasses on their quantum efficiency by using photo-acoustic measurements in comparison to standard measurement methods including the determination via the fluorescence lifetime and an integrating sphere setup. The preparation methods focused on decreasing the OH concentration by means of fluorine-substitution and/or applying dry melting atmospheres, which led to an increase in the measured fluorescence lifetime. However, it was found that the influence of these methods on radiative properties such as the measured fluorescence lifetime alone does not per se give exact information aboutmore » the actual quantum efficiency of the sample. The determination of the quantum efficiency by means of fluorescence lifetime shows inaccuracies when refractive index changing elements such as fluorine are incorporated into the glass. Since fluorine not only eliminates OH from the glass but also increases the “intrinsic” radiative fluorescence lifetime, which is needed to calculate the quantum efficiency, it is difficult to separate lifetime quenching from purely radiative effects. The approach used in this contribution offers a possibility to disentangle radiative from non-radiative properties which is not possible by using fluorescence lifetime measurements alone and allows an accurate determination of the quantum efficiency of a given sample. The comparative determination by an integrating sphere setup leads to the well-known problem of reabsorption which embodies itself in the measurement of too low quantum efficiencies, especially for samples with small quantum efficiencies.« less

Photochemical studies of a fluorescent chlorophyll catabolite--source of bright blue fluorescence in plant tissue and efficient sensitizer of singlet oxygen.

PubMed

Jockusch, Steffen; Turro, Nicholas J; Banala, Srinivas; Kräutler, Bernhard

2014-02-01

Fluorescent chlorophyll catabolites (FCCs) are fleeting intermediates of chlorophyll breakdown, which is seen as an enzyme controlled detoxification process of the chlorophylls in plants. However, some plants accumulate large amounts of persistent FCCs, such as in senescent leaves and in peels of yellow bananas. The photophysical properties of such a persistent FCC (Me-sFCC) were investigated in detail. FCCs absorb in the near UV spectral region and show blue fluorescence (max at 437 nm). The Me-sFCC fluorescence had a quantum yield of 0.21 (lifetime 1.6 ns). Photoexcited Me-sFCC intersystem crosses into the triplet state (quantum yield 0.6) and generates efficiently singlet oxygen (quantum yield 0.59). The efficient generation of singlet oxygen makes fluorescent chlorophyll catabolites phototoxic, but might also be useful as a (stress) signal and for defense of the plant tissue against infection by pathogens.

10 CFR Appendix W to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Medium Base Compact Fluorescent Lamps

Code of Federal Regulations, 2013 CFR

2013-01-01

... “ENERGY STAR Program Requirements for [Compact Fluorescent Lamps] CFLs,” Version dated August 9, 2001... DOE's “ENERGY STAR Program Requirements for [Compact Fluorescent Lamps] CFLs,” Version dated August 9...

Comparison of Test Procedures and Energy Efficiency Criteria in Selected International Standards and Labeling Programs for Clothes Washers, Water Dispensers, Vending Machines and CFLs

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

Fridley, David; Zheng, Nina; Zhou, Nan

Since the late 1970s, energy labeling programs and mandatory energy performance standards have been used in many different countries to improve the efficiency levels of major residential and commercial equipment. As more countries and regions launch programs covering a greater range of products that are traded worldwide, greater attention has been given to harmonizing the specific efficiency criteria in these programs and the test methods for measurements. For example, an international compact fluorescent light (CFL) harmonization initiative was launched in 2006 to focus on collaboration between Australia, China, Europe and North America. Given the long history of standards and labelingmore » programs, most major energy-consuming residential appliances and commercial equipment are already covered under minimum energy performance standards (MEPS) and/or energy labels. For these products, such as clothes washers and CFLs, harmonization may still be possible when national MEPS or labeling thresholds are revised. Greater opportunity for harmonization exists in newer energy-consuming products that are not commonly regulated but are under consideration for new standards and labeling programs. This may include commercial products such as water dispensers and vending machines, which are only covered by MEPS or energy labels in a few countries or regions. As China continues to expand its appliance standards and labeling programs and revise existing standards and labels, it is important to learn from recent international experiences with efficiency criteria and test procedures for the same products. Specifically, various types of standards and labeling programs already exist in North America, Europe and throughout Asia for products in China's 2010 standards and labeling programs, namely clothes washers, water dispensers, vending machines and CFLs. This report thus examines similarities and critical differences in energy efficiency values, test procedure specifications and other technical performance requirements in existing international programs in order to shed light on where Chinese programs currently stands and considerations for their 2010 programs.« less

An Experimental Study of the Fluorescence Spectrum of Cesium Atoms in the Presence of a Buffer Gas

NASA Astrophysics Data System (ADS)

Davydov, V. G.; Kulyasov, V. N.

2018-01-01

A direct experiment is performed to determine the quantum efficiency of a cesium fluorescence filter. The fluorescence spectra of cesium atoms are recorded under excitation of the upper states of the second resonance doublet with a Bell-Bloom cesium lamp. Introduction of different noble gases into the cell with cesium leads to the appearance of additional fluorescence photons. It is found that a fluorescence filter based on atomic cesium vapor with addition of helium in the working cell has the highest efficiency and response rate of all known fluorescence filters based on alkali-metal atomic vapors.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

10 CFR 429.26 - Fluorescent lamp ballasts.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 3 2014-01-01 2014-01-01 false Fluorescent lamp ballasts. 429.26 Section 429.26 Energy... COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.26 Fluorescent lamp ballasts. (a) Sampling plan for selection of units for testing. (1) The requirements of § 429.11 are applicable to fluorescent lamp ballasts...

10 CFR 429.26 - Fluorescent lamp ballasts.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 3 2012-01-01 2012-01-01 false Fluorescent lamp ballasts. 429.26 Section 429.26 Energy... COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.26 Fluorescent lamp ballasts. (a) Sampling plan for selection of units for testing. (1) The requirements of § 429.11 are applicable to fluorescent lamp ballasts...

10 CFR 429.26 - Fluorescent lamp ballasts.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 3 2013-01-01 2013-01-01 false Fluorescent lamp ballasts. 429.26 Section 429.26 Energy... COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.26 Fluorescent lamp ballasts. (a) Sampling plan for selection of units for testing. (1) The requirements of § 429.11 are applicable to fluorescent lamp ballasts...

Maximizing Aggregation of Organic Fluorophores to Prolong Fluorescence Lifetime for Two-Photon Fluorescence Lifetime Imaging.

PubMed

Hu, Wenbo; Guo, Lihong; Bai, Lei; Miao, Xiaofei; Ni, Yun; Wang, Qi; Zhao, Hui; Xie, Meng; Li, Lin; Lu, Xiaomei; Huang, Wei; Fan, Quli

2018-05-28

Two-photon fluorescence lifetime imaging (TP-FLIM) not only permits imaging deep inside the tissues with precise spatial manipulation but also circumvents tissue autofluorescence, holding tremendous promise in molecular imaging. However, the serious lack of suitable contrast agents with long fluorescence lifetime and efficient two-photon absorption (TPA) greatly limits the advance of TP-FLIM. This study reports a simple approach to fabricate water-soluble organic semiconducting nanoparticles [thioxanthone (TXO) NPs] with ultralong fluorescence lifetime and efficient TPA for in vivo TP-FLIM. The approach utilizes the aggregation of a specifically selected thermally activated delayed fluorescence (TADF) fluorophore to prolong its fluorescence lifetime. Encapsulating the TADF fluorophore within an amphiphilic copolymer not only maximizes its aggregation but also obtains TXO NPs with efficient TPA. Importantly, as-prepared TXO NPs exhibit a considerably long fluorescence lifetime at a magnitude of 4.2 µs, which is almost 1000 times larger than that of existing organic contrast agents. Moreover, such long fluorescence lifetime is almost oxygen-inert, readily realizing both in vitro and in vivo TP-FLIM. This work may set valuable guidance for designing organic semiconducting materials with ultralong fluorescence lifetimes to fulfill the potential of FLIM. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impacts of side chain and excess energy on the charge photogeneration dynamics of low-bandgap copolymer-fullerene blends

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

Huo, Ming-Ming, E-mail: hithuomm@163.com; Zhang, Jian-Ping, E-mail: jpzhang@chem.ruc.edu.cn, E-mail: hjhzlz@iccas.ac.cn; Department of Chemistry, Renmin University of China, Beijing 100872

2014-02-28

Primary charge photogeneration dynamics in neat and fullerene-blended films of a pair of alternating benzo[1,2-b:4,5-b{sup ′}]dithiophene (BDT) and thieno[3,4-b]thiophene (TT) copolymers are comparatively studied by using near-infrared, time-resolved absorption (TA) spectroscopy under low excitation photon fluence. PBDTTT-E and PBDTTT-C, differed merely in the respective TT-substituents of ester (-E) and carbonyl (-C), show distinctly different charge photogeneration dynamics. The pair of neat PBDTTT films show exciton lifetimes of ∼0.1 ns and fluorescence quantum yields below 0.2%, as well as prominent excess-energy enhanced exciton dissociation. In addition, PBDTTT-C gives rise to >50% higher P{sup •+} yield than PBDTTT-E does irrespective to themore » excitation photon energy. Both PBDTTT-E:PC{sub 61}BM and PBDTTT-C:PC{sub 61}BM blends show subpicosecond exciton lifetimes and nearly unitary fluorescence quenching efficiency and, with respect to the former blend, the latter one shows substantially higher branching ratio of charge separated (CS) state over interfacial charge transfer (ICT) state, and hence more efficient exciton-to-CS conversion. For PBDTTT-C:PC{sub 61}BM, the ultrafast charge dynamics clearly show the processes of ICT-CS interconversion and P{sup •+} migration, which are possibly influenced by the ICT excess energy. However, such processes are relatively indistinctive in the case of PBDTTT-E:PC{sub 61}BM. The results strongly prove the importance of ICT dissociation in yielding free charges, and are discussed in terms of the film morphology and the precursory solution-phase macromolecular conformation.« less

Efficient up-conversion in Yb:Er:NaT(XO4)2 thermal nanoprobes. Imaging of their distribution in a perfused mouse

PubMed Central

Serrano, María Dolores; Han, Xiumei; Cascales, Concepción; Cantero, Marta; Montoliu, Lluís; Arza, Elvira; Caiolfa, Valeria R.; Zamai, Moreno

2017-01-01

Yb and Er codoped NaT(XO4)2 (T = Y, La, Gd, Lu and X = Mo, W) disordered oxides show a green (Er3+ related) up-conversion (UC) efficiency comparable to that of Yb:Er:β-NaYF4 compound and unless 3 times larger UC ratiometric thermal sensitivity. The similar UC efficiency of Yb:Er doped NaT(XO4)2 and β-NaYF4 compounds allowed testing equal subcutaneous depths of ex-vivo chicken tissue in both cases. This extraordinary behavior for NaT(XO4)2 oxides with large cutoff phonon energy (ħω≈ 920 cm-1) is ascribed to 4F9/2 electron population recycling to higher energy 4G11/2 level by a phonon assisted transition. Crystalline nanoparticles of Yb:Er:NaLu(MoO4)2 have been synthesized by sol-gel with sizes most commonly in the 50–80 nm range, showing a relatively small reduction of the UC efficiency with regards to bulk materials. Fluorescence lifetime and multiphoton imaging microscopies show that these nanoparticles can be efficiently distributed to all body organs of a perfused mouse. PMID:28542327

Nd/sup 3 +/ fluorescence quantum-efficiency measurements with photoacoustics

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

Rosencwaig, A.; Hildum, E.A.

1981-04-01

We have investigated the use of photoacoustic techniques for obtaining absolute values of fluorescence quantum efficiencies in lightly doped Nd/sup 3 +/ laser materials. We have found that surface absorptions play an important role in gas-microphone measurements, and that thermal profiles are important in piezoelectric measurements. We have obtained fluorescence quantum efficiencies for Nd/sup 3 +/ in yttrium aluminum garnet, and in silicate and borate glasses that are in good agreement with lifetime measurements and Judd-Ofelt calculations.

Optical management for efficiency enhancement in hybrid organic-inorganic lead halide perovskite solar cells

PubMed Central

Zhang, Hui; Toudert, Johann

2018-01-01

Abstract In a few years only, solar cells using hybrid organic–inorganic lead halide perovskites as optical absorber have reached record photovoltaic energy conversion efficiencies above 20%. To reach and overcome such values, it is required to tailor both the electrical and optical properties of the device. For a given efficient device, optical optimization overtakes electrical one. Here, we provide a synthetic review of recent works reporting or proposing so-called optical management approaches for improving the efficiency of perovskite solar cells, including the use of anti-reflection coatings at the front substrate surface, the design of optical cavities integrated within the device, the incorporation of plasmonic or dielectric nanostructures into the different layers of the device and the structuration of its internal interfaces. We finally give as outlooks some insights into the less-explored management of the perovskite fluorescence and its potential for enhancing the cell efficiency. PMID:29868146

Derivation of the open-circuit voltage of organic solar cells

NASA Astrophysics Data System (ADS)

Staple, Douglas B.; Oliver, Patricia A. K.; Hill, Ian G.

2014-05-01

Organic photovoltaic cells have improved in efficiency from 1% two decades ago to over 10% today. Continued improvement necessitates a theoretical understanding of the factors determining efficiency. Organic photovoltaic efficiency can be parameterized in terms of open-circuit voltage, short-circuit current, and fill factor. Here we present a theory that explains the dependencies of open-circuit voltage on semiconductor energy levels, light intensity, solar cell and light-source temperatures, charge-carrier recombination, and external fluorescence efficiency. The present theory also explains why recombination at the donor-acceptor heterointerface is a dominant process in heterojunction-based cells. Furthermore, the Carnot efficiency appears, highlighting the connection to basic thermodynamics. The theory presented here is consistent with and builds on the experimental and theoretical observations already in the literature. Crucially, the present theory can be straightforwardly derived in a line-by-line fashion using standard tools from statistical physics.

Energy-cascade organic photovoltaic devices incorporating a host-guest architecture.

PubMed

Menke, S Matthew; Holmes, Russell J

2015-02-04

In planar heterojunction organic photovoltaic devices (OPVs), broad spectral coverage can be realized by incorporating multiple molecular absorbers in an energy-cascade architecture. Here, this approach is combined with a host-guest donor layer architecture previously shown to optimize exciton transport for the fluorescent organic semiconductor boron subphthalocyanine chloride (SubPc) when diluted in an optically transparent host. In order to maximize the absorption efficiency, energy-cascade OPVs that utilize both photoactive host and guest donor materials are examined using the pairing of SubPc and boron subnaphthalocyanine chloride (SubNc), respectively. In a planar heterojunction architecture, excitons generated on the SubPc host rapidly energy transfer to the SubNc guest, where they may migrate toward the dissociating, donor-acceptor interface. Overall, the incorporation of a photoactive host leads to a 13% enhancement in the short-circuit current density and a 20% enhancement in the power conversion efficiency relative to an optimized host-guest OPV combining SubNc with a nonabsorbing host. This work underscores the potential for further design refinements in planar heterojunction OPVs and demonstrates progress toward the effective separation of functionality between constituent OPV materials.

Extraction of information on macromolecular interactions from fluorescence micro-spectroscopy measurements in the presence and absence of FRET.

PubMed

Raicu, Valerică

2018-06-15

Investigations of static or dynamic interactions between proteins or other biological macromolecules in living cells often rely on the use of fluorescent tags with two different colors in conjunction with adequate theoretical descriptions of Förster Resonance Energy Transfer (FRET) and molecular-level micro-spectroscopic technology. One such method based on these general principles is FRET spectrometry, which allows determination of the quaternary structure of biomolecules from cell-level images of the distributions, or spectra of occurrence frequency of FRET efficiencies. Subsequent refinements allowed combining FRET frequency spectra with molecular concentration information, thereby providing the proportion of molecular complexes with various quaternary structures as well as their binding/dissociation energies. In this paper, we build on the mathematical principles underlying FRET spectrometry to propose two new spectrometric methods, which have distinct advantages compared to other methods. One of these methods relies on statistical analysis of color mixing in subpopulations of fluorescently tagged molecules to probe molecular association stoichiometry, while the other exploits the color shift induced by FRET to also derive geometric information in addition to stoichiometry. The appeal of the first method stems from its sheer simplicity, while the strength of the second consists in its ability to provide structural information. Copyright © 2018 Elsevier B.V. All rights reserved.

Multicolor Three-Dimensional Tracking for Single-Molecule Fluorescence Resonance Energy Transfer Measurements

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

Keller, Aaron M.; DeVore, Matthew S.; Stich, Dominik G.

Single-molecule fluorescence resonance energy transfer (smFRET) remains a widely utilized and powerful tool for quantifying heterogeneous interactions and conformational dynamics of biomolecules. However, traditional smFRET experiments either are limited to short observation times (typically less than 1 ms) in the case of “burst” confocal measurements or require surface immobilization which usually has a temporal resolution limited by the camera framing rate. We developed a smFRET 3D tracking microscope that is capable of observing single particles for extended periods of time with high temporal resolution. The confocal tracking microscope utilizes closed-loop feedback to follow the particle in solution by recentering itmore » within two overlapping tetrahedral detection elements, corresponding to donor and acceptor channels. We demonstrated the microscope’s multicolor tracking capability via random walk simulations and experimental tracking of 200 nm fluorescent beads in water with a range of apparent smFRET efficiency values, 0.45-0.69. We also demonstrated the microscope’s capability to track and quantify double-stranded DNA undergoing intramolecular smFRET in a viscous glycerol solution. In future experiments, the smFRET 3D tracking system will be used to study protein conformational dynamics while diffusing in solution and native biological environments with high temporal resolution.« less

Multicolor Three-Dimensional Tracking for Single-Molecule Fluorescence Resonance Energy Transfer Measurements

DOE PAGES

Keller, Aaron M.; DeVore, Matthew S.; Stich, Dominik G.; ...

2018-04-19

Single-molecule fluorescence resonance energy transfer (smFRET) remains a widely utilized and powerful tool for quantifying heterogeneous interactions and conformational dynamics of biomolecules. However, traditional smFRET experiments either are limited to short observation times (typically less than 1 ms) in the case of “burst” confocal measurements or require surface immobilization which usually has a temporal resolution limited by the camera framing rate. We developed a smFRET 3D tracking microscope that is capable of observing single particles for extended periods of time with high temporal resolution. The confocal tracking microscope utilizes closed-loop feedback to follow the particle in solution by recentering itmore » within two overlapping tetrahedral detection elements, corresponding to donor and acceptor channels. We demonstrated the microscope’s multicolor tracking capability via random walk simulations and experimental tracking of 200 nm fluorescent beads in water with a range of apparent smFRET efficiency values, 0.45-0.69. We also demonstrated the microscope’s capability to track and quantify double-stranded DNA undergoing intramolecular smFRET in a viscous glycerol solution. In future experiments, the smFRET 3D tracking system will be used to study protein conformational dynamics while diffusing in solution and native biological environments with high temporal resolution.« less

Extraction of information on macromolecular interactions from fluorescence micro-spectroscopy measurements in the presence and absence of FRET

NASA Astrophysics Data System (ADS)

Raicu, Valerică

2018-06-01

Investigations of static or dynamic interactions between proteins or other biological macromolecules in living cells often rely on the use of fluorescent tags with two different colors in conjunction with adequate theoretical descriptions of Förster Resonance Energy Transfer (FRET) and molecular-level micro-spectroscopic technology. One such method based on these general principles is FRET spectrometry, which allows determination of the quaternary structure of biomolecules from cell-level images of the distributions, or spectra of occurrence frequency of FRET efficiencies. Subsequent refinements allowed combining FRET frequency spectra with molecular concentration information, thereby providing the proportion of molecular complexes with various quaternary structures as well as their binding/dissociation energies. In this paper, we build on the mathematical principles underlying FRET spectrometry to propose two new spectrometric methods, which have distinct advantages compared to other methods. One of these methods relies on statistical analysis of color mixing in subpopulations of fluorescently tagged molecules to probe molecular association stoichiometry, while the other exploits the color shift induced by FRET to also derive geometric information in addition to stoichiometry. The appeal of the first method stems from its sheer simplicity, while the strength of the second consists in its ability to provide structural information.

Spectroscopic and theoretical investigation of conformational changes of proteins by synthesized pyrimidine derivative and its sensitivity towards FRET application

NASA Astrophysics Data System (ADS)

Ghosh, Swadesh; Singharoy, Dipti; Bhattacharya, Subhash Chandra

2018-04-01

Interest in synthesizing and characterizing (IR, NMR and HRMS spectroscopic methods) a pyrimidine based Schiff-base ligand, 2-(2-(Anthracen-9-ylmethylene) hydrazinyl)-4,6-dimethyl pyrimidine (ANHP) has been developed for its application to ascertain the conformational change of protein and sensitivity towards fluorescence resonance energy transfer (FRET) process. Location of ANHP in bovine serum albumin (BSA) and human serum albumin (HSA) proteins environment has been determined using different spectroscopic techniques. Weakly fluorescent ANHP have shown greater protein induced fluorescence enhancement (PIFE) in case of HSA than BSA, though in both cases energy transfer efficiency are almost same but difference in binding constant values encourages us to find the location of ANHP within the complex protein environment. From the FRET parameter and α-helicity change, it has been found that ANHP bound with Trp-214 of HSA and surface Trp-134 of BSA. Conformational changes of proteins have been observed more for HSA than BSA in presence of ANHP, which has confirmed the location of ANHP in both the protein environments. Coupled with experimental studies, molecular docking analysis has also been done to explain the locations and distance dependent FRET process of ANHP in both proteins.

Recent developments in white light emitting diodes

NASA Astrophysics Data System (ADS)

Lohe, P. P.; Nandanwar, D. V.; Belsare, P. D.; Moharil, S. V.

2018-05-01

In the recent years solid state lighting based on LEDs has revolutionized lighting technology. LEDs have many advantages over the conventional lighting based on fluorescent and incandescent lamps such as mercury free, high conversion efficiency of electrical energy into light, long lifetime reliability and ability to use with many types of devices. LEDs have emerged as a new potentially revolutionary technology that could save up to half of energy used for lighting applications. White LEDs would be the most important light source in the future, so much so that this aspect had been highlighted by the Nobel committee during the award of 2014 Nobel Prize for Physics. Recent advancement in the fabrication of GaN chip capable of emitting in blue and near UV region paved way for fabrication of white LED lamps. Mainly there are two approaches used for preparing white emitting solid state lamp. In the first approach blue light (λ=450 nm) emitted from the InGaN LED chip is partially absorbed by the YAG:Ce3+ phosphor coated on it and re-emitted as yellow fluorescence. A white light can be generated by the combination of blue + yellow emission bands. These lamps are already available. But they are suffering from major drawback that their Colour Rendering Index (CRI) is low. In the second approach, white LEDs are made by coating near ultraviolet emitting (360 to 410nm) LED with a mixture of high efficiency red, green and blue emitting phosphors, analogous to the fluorescent lamp. This method yields lamps with better color rendition. Addition of a yellow emitting phosphor improves CRI further. However conversion efficiency is compromised to some extent. Further the cost of near UV emitting chip is very high compared to blue emitting chips. Thus cost and light output wise, near UV chips are much inferior to blue chips. Recently some rare earth activated oxynitrides, silicates, fluorides have emerged as an important family of luminescent materials for white LED application because they can emit visible light strongly under blue light irradiation. These are chemically, thermally and mechanically stable materials with high efficiency to down convert blue radiation into green and red. Efficient white light can be generated by coating these phosphors on blue LED.CRI of white emitting LED lamp can be improved significantly if green and red emitting phosphors are coated on efficient blue emitting LED chips. In this approach CRI will be maintained if appropriate combination of red, green along with blue emission is used. This article reviews some recent developments in phosphors for white light emitting diodes.

Fluorescence polarization measures energy funneling in single light-harvesting antennas—LH2 vs conjugated polymers

PubMed Central

Camacho, Rafael; Tubasum, Sumera; Southall, June; Cogdell, Richard J.; Sforazzini, Giuseppe; Anderson, Harry L.; Pullerits, Tõnu; Scheblykin, Ivan G.

2015-01-01

Numerous approaches have been proposed to mimic natural photosynthesis using artificial antenna systems, such as conjugated polymers (CPs), dendrimers, and J-aggregates. As a result, there is a need to characterize and compare the excitation energy transfer (EET) properties of various natural and artificial antennas. Here we experimentally show that EET in single antennas can be characterized by 2D polarization imaging using the single funnel approximation. This methodology addresses the ability of an individual antenna to transfer its absorbed energy towards a single pool of emissive states, using a single parameter called energy funneling efficiency (ε). We studied individual peripheral antennas of purple bacteria (LH2) and single CP chains of 20 nm length. As expected from a perfect antenna, LH2s showed funneling efficiencies close to unity. In contrast, CPs showed lower average funneling efficiencies, greatly varying from molecule to molecule. Cyclodextrin insulation of the conjugated backbone improves EET, increasing the fraction of CPs possessing ε = 1. Comparison between LH2s and CPs shows the importance of the protection systems and the protein scaffold of LH2, which keep the chromophores in functional form and at such geometrical arrangement that ensures excellent EET. PMID:26478272

Growth and development of Arabidopsis thaliana under single-wavelength red and blue laser light.

PubMed

Ooi, Amanda; Wong, Aloysius; Ng, Tien Khee; Marondedze, Claudius; Gehring, Christoph; Ooi, Boon S

2016-09-23

Indoor horticulture offers a sensible solution for sustainable food production and is becoming increasingly widespread. However, it incurs high energy and cost due to the use of artificial lighting such as high-pressure sodium lamps, fluorescent light or increasingly, the light-emitting diodes (LEDs). The energy efficiency and light quality of currently available horticultural lighting is suboptimal, and therefore less than ideal for sustainable and cost-effective large-scale plant production. Here, we demonstrate the use of high-powered single-wavelength lasers for indoor horticulture. They are highly energy-efficient and can be remotely guided to the site of plant growth, thus reducing on-site heat accumulation. Furthermore, laser beams can be tailored to match the absorption profiles of different plant species. We have developed a prototype laser growth chamber and demonstrate that plants grown under laser illumination can complete a full growth cycle from seed to seed with phenotypes resembling those of plants grown under LEDs reported previously. Importantly, the plants have lower expression of proteins diagnostic for light and radiation stress. The phenotypical, biochemical and proteome data show that the single-wavelength laser light is suitable for plant growth and therefore, potentially able to unlock the advantages of this next generation lighting technology for highly energy-efficient horticulture.

Growth and development of Arabidopsis thaliana under single-wavelength red and blue laser light

PubMed Central

Ooi, Amanda; Wong, Aloysius; Ng, Tien Khee; Marondedze, Claudius; Gehring, Christoph; Ooi, Boon S.

2016-01-01

Indoor horticulture offers a sensible solution for sustainable food production and is becoming increasingly widespread. However, it incurs high energy and cost due to the use of artificial lighting such as high-pressure sodium lamps, fluorescent light or increasingly, the light-emitting diodes (LEDs). The energy efficiency and light quality of currently available horticultural lighting is suboptimal, and therefore less than ideal for sustainable and cost-effective large-scale plant production. Here, we demonstrate the use of high-powered single-wavelength lasers for indoor horticulture. They are highly energy-efficient and can be remotely guided to the site of plant growth, thus reducing on-site heat accumulation. Furthermore, laser beams can be tailored to match the absorption profiles of different plant species. We have developed a prototype laser growth chamber and demonstrate that plants grown under laser illumination can complete a full growth cycle from seed to seed with phenotypes resembling those of plants grown under LEDs reported previously. Importantly, the plants have lower expression of proteins diagnostic for light and radiation stress. The phenotypical, biochemical and proteome data show that the single-wavelength laser light is suitable for plant growth and therefore, potentially able to unlock the advantages of this next generation lighting technology for highly energy-efficient horticulture. PMID:27659906

Design and evaluation of a device for fast multispectral time-resolved fluorescence spectroscopy and imaging

NASA Astrophysics Data System (ADS)

Yankelevich, Diego R.; Ma, Dinglong; Liu, Jing; Sun, Yang; Sun, Yinghua; Bec, Julien; Elson, Daniel S.; Marcu, Laura

2014-03-01

The application of time-resolved fluorescence spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 μm diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and <1 ms per point measurement, respectively, for the detection of tissue autofluorescent components. Organic and biological chromophores with lifetimes that spanned a 0.8-7 ns range were used for system validation, and the measured lifetimes from the organic fluorophores deviated by less than 10% from values reported in the literature. Multi-spectral lifetime images of organic dye solutions contained in glass capillary tubes were recorded by raster scanning the single fiber probe in a 2D plane to validate the system as an imaging tool. The lifetime measurement variability was measured indicating that the system provides reproducible results with a standard deviation smaller than 50 ps. The ms-TRFS is a compact apparatus that makes possible the fast, accurate, and precise multispectral time-resolved fluorescence lifetime measurements of low quantum efficiency sub-nanosecond fluorophores.

Ionoluminescence properties of polystyrene-hosted fluorophore films induced by helium ions of energy 50-350 keV

NASA Astrophysics Data System (ADS)

Chakraborty, Subha; Huang, Mengbing

2017-10-01

We report on measurements and analysis of ionoluminescence properties of pure polystyrene films and polystyrene films doped with four types of fluorophores in low kinetic energies (50-350 keV) of ion irradiation. We have developed a theoretical model to understand the experimentally observed ionoluminescence behaviors in terms of scintillation yield from individual ion tracks, photophysical energy transfer mechanisms, and irradiation-induced defects. A comparison of the model and experimental results suggests that singlet up-conversion resulting from triplet-triplet annihilation processes may be responsible for enhanced singlet emission of the fluorophores at high ion beam flux densities. Energy transfer from the polystyrene matrix to the fluorophore molecules has been identified as an effective pathway to increasing the fluorescence efficiency in the doped scintillator films.

Fat to muscle ratio measurements with dual energy x-ray absorbtiometry

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

Chen, A.; Luo, J.; Wang, A.

Accurate measurement of the fat-to-muscle ratio in animal model is important for obesity research. In addition, an efficient way to measure the fat to muscle ratio in animal model using dual-energy absorptiometry is presented in this paper. A radioactive source exciting x-ray fluorescence from a target material is used to provide the two x-ray energies needed. The x-rays, after transmitting through the sample, are measured with an energy-sensitive Ge detector. Phantoms and specimens were measured. The results showed that the method was sensitive to the fat to muscle ratios with good linearity. A standard deviation of a few percent inmore » the fat to muscle ratio could be observed with the x-ray dose of 0.001 mGy.« less

Fat to muscle ratio measurements with dual energy x-ray absorbtiometry

DOE PAGES

Chen, A.; Luo, J.; Wang, A.; ...

2015-03-14

Accurate measurement of the fat-to-muscle ratio in animal model is important for obesity research. In addition, an efficient way to measure the fat to muscle ratio in animal model using dual-energy absorptiometry is presented in this paper. A radioactive source exciting x-ray fluorescence from a target material is used to provide the two x-ray energies needed. The x-rays, after transmitting through the sample, are measured with an energy-sensitive Ge detector. Phantoms and specimens were measured. The results showed that the method was sensitive to the fat to muscle ratios with good linearity. A standard deviation of a few percent inmore » the fat to muscle ratio could be observed with the x-ray dose of 0.001 mGy.« less

Multispectroscopic and bioimaging approach for the interaction of rhodamine 6G capped gold nanoparticles with bovine serum albumin.

PubMed

Manjubaashini, N; Kesavan, Mookkandi Palsamy; Rajesh, Jegathalaprathaban; Daniel Thangadurai, T

2018-06-01

Binding interaction of Bovine Serum Albumin (BSA) with newly prepared rhodamine 6G-capped gold nanoparticles (Rh6G-Au NPs) under physiological conditions (pH 7.2) was investigated by a wide range of photophysical techniques. Rh6G-Au NPs caused the static quenching of the intrinsic fluorescence of BSA that resulted from the formation of ground-state complex between BSA and Rh6G-Au NPs. The binding constant from fluorescence quenching method (K a  = 1.04 × 10 4  L mol -1 ; LoD = 14.0 μM) is in accordance with apparent association constant (K app  = 1.14 × 10 1  M -1 ), which is obtained from absorption spectral studies. Förster resonance energy transfer (FRET) efficiency between the tryptophan (Trp) residue of BSA and fluorophore of Rh6G-Au NPs during the interaction was calculated to be 90%. The free energy change (ΔG = -23.07 kJ/mol) of BSA-Rh6G-Au NPs complex was calculated based on modified Stern-Volmer Plot. The time-resolved fluorescence analysis confirmed that quenching of BSA follows static mechanism through the formation of ground state complex. Furthermore, synchronous and three-dimensional fluorescence measurement, Raman spectral analysis and Circular Dichroism spectrum results corroborate the strong binding between Rh6G-Au NPs and BSA, which causes the conformational changes on BSA molecule. In addition, fluorescence imaging experiments of BSA in living human breast cancer (HeLa) cells was successfully demonstrated, which articulated the value of Rh6G-Au NPs practical applications in biological systems. Copyright © 2018. Published by Elsevier B.V.

Method for Developing Optical Sensors Using a Synthetic Dye-Fluorescent Protein FRET Pair and Computational Modeling and Assessment.

PubMed

Mitchell, Joshua A; Zhang, William H; Herde, Michel K; Henneberger, Christian; Janovjak, Harald; O'Mara, Megan L; Jackson, Colin J

2017-01-01

Biosensors that exploit Förster resonance energy transfer (FRET) can be used to visualize biological and physiological processes and are capable of providing detailed information in both spatial and temporal dimensions. In a FRET-based biosensor, substrate binding is associated with a change in the relative positions of two fluorophores, leading to a change in FRET efficiency that may be observed in the fluorescence spectrum. As a result, their design requires a ligand-binding protein that exhibits a conformational change upon binding. However, not all ligand-binding proteins produce responsive sensors upon conjugation to fluorescent proteins or dyes, and identifying the optimum locations for the fluorophores often involves labor-intensive iterative design or high-throughput screening. Combining the genetic fusion of a fluorescent protein to the ligand-binding protein with site-specific covalent attachment of a fluorescent dye can allow fine control over the positions of the two fluorophores, allowing the construction of very sensitive sensors. This relies upon the accurate prediction of the locations of the two fluorophores in bound and unbound states. In this chapter, we describe a method for computational identification of dye-attachment sites that allows the use of cysteine modification to attach synthetic dyes that can be paired with a fluorescent protein for the purposes of creating FRET sensors.

FRET study of G-quadruplex forming fluorescent oligonucleotide probes at the lipid monolayer interface.

PubMed

Swiatkowska, Angelika; Kosman, Joanna; Juskowiak, Bernard

2016-01-05

Spectral properties and G-quadruplex folding ability of fluorescent oligonucleotide probes at the cationic dioctadecyldimethylammonium bromide (DODAB) monolayer interface are reported. Two oligonucleotides, a 19-mer bearing thrombin binding aptamer sequence and a 21-mer with human telomeric sequence, were end-labeled with fluorescent groups (FAM and TAMRA) to give FRET probes F19T and F21T, respectively. The probes exhibited abilities to fold into a quadruplex structure and to bind metal cations (Na(+) and K(+)). Fluorescence spectra of G-quadruplex FRET probes at the monolayer interface are reported for the first time. Investigations included film balance measurements (π-A isotherms) and fluorescence spectra recording using a fiber optic accessory interfaced with a spectrofluorimeter. The effect of the presence of DODAB monolayer, metal cations and the surface pressure of monolayer on spectral behavior of FRET probes were examined. Adsorption of probe at the cationic monolayer interface resulted in the FRET signal enhancement even in the absence of metal cations. Variation in the monolayer surface pressure exerted rather modest effect on the spectral properties of probes. The fluorescence energy transfer efficiency of monolayer adsorbed probes increased significantly in the presence of sodium or potassium ion in subphase, which indicated that the probes retained their cation binding properties when adsorbed at the monolayer interface. Copyright © 2015 Elsevier B.V. All rights reserved.

Reversible optical control of cyanine fluorescence in fixed and living cells: optical lock-in detection immunofluorescence imaging microscopy

PubMed Central

Yan, Yuling; Petchprayoon, Chutima; Mao, Shu; Marriott, Gerard

2013-01-01

Optical switch probes undergo rapid and reversible transitions between two distinct states, one of which may fluoresce. This class of probe is used in various super-resolution imaging techniques and in the high-contrast imaging technique of optical lock-in detection (OLID) microscopy. Here, we introduce optimized optical switches for studies in living cells under standard conditions of cell culture. In particular, a highly fluorescent cyanine probe (Cy or Cy3) is directly or indirectly linked to naphthoxazine (NISO), a highly efficient optical switch that undergoes robust, 405/532 nm-driven transitions between a colourless spiro (SP) state and a colourful merocyanine (MC) state. The intensity of Cy fluorescence in these Cy/Cy3-NISO probes is reversibly modulated between a low and high value in SP and MC states, respectively, as a result of Förster resonance energy transfer. Cy/Cy3-NISO probes are targeted to specific proteins in living cells where defined waveforms of Cy3 fluorescence are generated by optical switching of the SP and MC states. Finally, we introduce a new imaging technique (called OLID-immunofluorescence microscopy) that combines optical modulation of Cy3 fluorescence from Cy3/NISO co-labelled antibodies within fixed cells and OLID analysis to significantly improve image contrast in samples having high background or rare antigens. PMID:23267183

Trap formation and energy transfer in the hexapyropheophorbide a - fullerene C 60 hexaadduct molecular system

NASA Astrophysics Data System (ADS)

Ermilov, E. A.; Hackbarth, St.; Al-Omari, S.; Helmreich, M.; Jux, N.; Hirsch, A.; Röder, B.

2005-06-01

The photophysical properties of the novel hexapyropheophorbide a - fullerene hexaadduct (FHP6) compound were studied using both steady-state and time-resolved spectroscopic methods. It was found that neighboring pyropheophorbide a (pyroPheo) molecules covalently linked to one fullerene moiety due to the length and high flexibility of carbon chains could stack with each other. This structural property is the reason for the possibility of formation of two different types of energy traps, which could be resolved experimentally. One of them is formed via face-to-face stacking of two pyroPheo molecules with parallel to each other direction of the transition dipole moments. The second type of energy trap gives the dominant contribution to the fluorescence signal at registration wavelengths having the oblique geometry or orthogonal direction of the transition dipole moments of the interacting pyroPheo molecules. In any case the dipole-dipole resonant Förster energy transfer between pyroPheo molecules coupled to one fullerene moiety caused a very fast and efficient delivery of the excitation to a trap. As result the fluorescence as well as the singlet oxygen quantum yields of FHP6 were reduced three and two times, respectively, compared to those values of the reference bis pyropheophorbide a - fullerene hexaadduct (FHP1) compound.

Characterization of aluminum nitride based films with high resolution X-ray fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Anagnostopoulos, D. F.; Siozios, A.; Patsalas, P.

2018-02-01

X-ray fluorescence spectra of Al based films are measured, using a lab-scale wavelength dispersive flat crystal spectrometer. Various structures of AlN films were studied, like single layered, capped, stratified, nanostructured, crystalline, or amorphous. By optimizing the set-up for enhanced energy resolution and detection efficiency, the measured line shapes of Κα, Kβ, and KLL radiative Auger transitions are shown to be adequately detailed to allow chemical characterization. The chemistry identification is based on the pattern comparison of the emitted line shape from the chemically unknown film and the reference line shapes from standard materials, recorded under identical experimental conditions. The ultimate strength of lab-scale high resolution X-ray fluorescence spectroscopy on film analysis is verified, in cases that ordinary applied techniques like X-ray photoelectron and X-ray diffraction fail, while the characterization refers to the non-destructive determination of the bulk properties of the film and not to its surface, as the probed depth is in the micrometer range.

Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices

NASA Astrophysics Data System (ADS)

Deng, Junquan; Jia, Weiyao; Chen, Yingbing; Liu, Dongyu; Hu, Yeqian; Xiong, Zuhong

2017-03-01

Non-emissive triplet excited states in devices that undergo thermally activated delayed fluorescence (TADF) can be up-converted to singlet excited states via reverse intersystem crossing (RISC), which leads to an enhanced electroluminescence efficiency. Exciton-based fluorescence devices always exhibit a positive magneto-electroluminescence (MEL) because intersystem crossing (ISC) can be suppressed effectively by an external magnetic field. Conversely, TADF devices should exhibit a negative MEL because RISC is suppressed by the external magnetic field. Intriguingly, we observed a positive MEL in TADF devices. Moreover, the sign of the MEL was either positive or negative, and depended on experimental conditions, including doping concentration, current density and temperature. The MEL observed from our TADF devices demonstrated that ISC in the host material and RISC in the guest material coexisted. These competing processes were affected by the experimental conditions, which led to the sign change of the MEL. This work gives important insight into the energy transfer processes and the evolution of excited states in TADF devices.

Atmospheric Fluorescence Yield

NASA Technical Reports Server (NTRS)

Adams, James H., Jr.; Christl, M. J.; Fountain, W. F.; Gregory, J. C.; Martens, K.; Sokolsky, P.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Several existing and planned experiments estimate the energies of ultra-high energy cosmic rays from air showers using the atmospheric fluorescence from these showers. Accurate knowledge of the conversion from atmospheric fluorescence to energy loss by ionizing particles in the atmosphere is key to this technique. In this paper we discuss a small balloon-borne instrument to make the first in situ measurements versus altitude of the atmospheric fluorescence yield. The instrument can also be used in the lab to investigate the dependence of the fluorescence yield in air on temperature, pressure and the concentrations of other gases that present in the atmosphere. The results can be used to explore environmental effects on and improve the accuracy of cosmic ray energy measurements for existing ground-based experiments and future space-based experiments.

Fluorescence and visual detection of fluoride ions using a photoluminescent graphene oxide paper sensor.

PubMed

Chen, Xiaochun; Yu, Shaoming; Yang, Liang; Wang, Jianping; Jiang, Changlong

2016-07-14

The instant and on-site detection of trace aqueous fluoride ions is still a challenge for environmental monitoring and protection. This work demonstrates a new analytical method and its utility of a paper sensor for visual detection of F(-) on the basis of the fluorescence resonance energy transfer (FRET) between photoluminescent graphene oxide (GO) and silver nanoparticles (AgNPs) through the formation of cyclic esters between phenylborinic acid and diol. The fluorescence of GO was quenched by the AgNPs, and trace F(-) can recover the fluorescence of the quenched photoluminescent GO. The increase in fluorescence intensity is proportional to the concentration of F(-) in the range of 0.05-0.55 nM, along with a limit of detection (LOD) as low as 9.07 pM. Following the sensing mechanism, a paper-based sensor for the visual detection of aqueous F(-) has been successfully developed. The paper sensor showed high sensitivity for aqueous F(-), and the LOD could reach as low as 0.1 μM as observed by the naked eye. The very simple and effective strategy reported here could be extended to the visual detection of a wide range of analytes in the environment by the construction of highly efficient FRET nanoprobes.

Light-Induced Fluorescence Modulation of Quantum Dot-Crystal Violet Conjugates: Stochastic Off-On-Off Cycles for Multicolor Patterning and Super-Resolution.

PubMed

Jung, Sungwook; Park, Joonhyuck; Bang, Jiwon; Kim, Jae-Yeol; Kim, Cheolhee; Jeon, Yongmoon; Lee, Seung Hwan; Jin, Ho; Choi, Sukyung; Kim, Bomi; Lee, Woo Jin; Pack, Chan-Gi; Lee, Jong-Bong; Lee, Nam Ki; Kim, Sungjee

2017-06-07

Photoswitching or modulation of quantum dots (QDs) can be promising for many fields that include display, memory, and super-resolution imaging. However, such modulations have mostly relied on photomodulations of conjugated molecules in QD vicinity, which typically require high power of high energy photons at UV. We report a visible light-induced facile modulation route for QD-dye conjugates. QD crystal violets conjugates (QD-CVs) were prepared and the crystal violet (CV) molecules on QD quenched the fluorescence efficiently. The fluorescence of QD-CVs showed a single cycle of emission burst as they go through three stages of (i) initially quenched "off" to (ii) photoactivated "on" as the result of chemical change of CVs induced by photoelectrons from QD and (iii) back to photodarkened "off" by radical-associated reactions. Multicolor on-demand photopatterning was demonstrated using QD-CV solid films. QD-CVs were introduced into cells, and excitation with visible light yielded photomodulation from "off" to "on" and "off" by nearly ten fold. Individual photoluminescence dynamics of QD-CVs was investigated using fluorescence correlation spectroscopy and single QD emission analysis, which revealed temporally stochastic photoactivations and photodarkenings. Exploiting the stochastic fluorescence burst of QD-CVs, simultaneous multicolor super-resolution localizations were demonstrated.

Plasmonic photocatalyst-like fluorescent proteins for generating reactive oxygen species

NASA Astrophysics Data System (ADS)

Leem, Jung Woo; Kim, Seong-Ryul; Choi, Kwang-Ho; Kim, Young L.

2018-03-01

The recent advances in photocatalysis have opened a variety of new possibilities for energy and biomedical applications. In particular, plasmonic photocatalysis using hybridization of semiconductor materials and metal nanoparticles has recently facilitated the rapid progress in enhancing photocatalytic efficiency under visible or solar light. One critical underlying aspect of photocatalysis is that it generates and releases reactive oxygen species (ROS) as intermediate or final products upon light excitation or activation. Although plasmonic photocatalysis overcomes the limitation of UV irradiation, synthesized metal/semiconductor nanomaterial photocatalysts often bring up biohazardous and environmental issues. In this respect, this review article is centered in identifying natural photosensitizing organic materials that can generate similar types of ROS as those of plasmonic photocatalysis. In particular, we propose the idea of plasmonic photocatalyst-like fluorescent proteins for ROS generation under visible light irradiation. We recapitulate fluorescent proteins that have Type I and Type II photosensitization properties in a comparable manner to plasmonic photocatalysis. Plasmonic photocatalysis and protein photosensitization have not yet been compared systemically in terms of ROS photogeneration under visible light, although the phototoxicity and cytotoxicity of some fluorescent proteins are well recognized. A comprehensive understanding of plasmonic photocatalyst-like fluorescent proteins and their potential advantages will lead us to explore new environmental, biomedical, and defense applications.

Development of Highly Fluorescent Materials Based on Thiophenylimidazole Dyes

NASA Technical Reports Server (NTRS)

Santos, Javier; Bu, Xiu R.; Mintz, Eric A.; Meador, Michael A. (Technical Monitor)

2000-01-01

Organic fluorescent materials are expected to find many potential applications in optical devices and photo-functionalized materials. Although many investigations have been focused on heterocyclic compounds such as coumarins, bipyridines, rhodamines, and pyrrole derivatives, little is known for fluorescent imidazole materials. We discovered that one particular class of imidazole derivatives is highly fluorescent. A series of monomeric and polymeric based fluorescent dyes were prepared containing a thiophene unit at the second position of the imidazole ring. Dependence of fluorescence efficiency on parameters such as solvent polarity and substituent groups has been investigated. It was found that a formyl group at the 2-position of the thiophene ring dramatically enhance fluorescence properties. Ion recognition probes indicated their potential as sensor materials. These fluorophores have flexibility for introduction of versatile substituent groups that could improve the fluorescence efficiency and sensor properties.

Determination of the termination efficiency of the transcription terminator using different fluorescent profiles in green fluorescent protein mutants.

PubMed

Nojima, Takahiko; Lin, Angela C; Fujii, Teruo; Endo, Isao

2005-12-01

An approach in determining the intrinsic termination efficiency (%T) of transcription termination using green fluorescent protein (GFP) mutants was developed. This approach utilizes a cassette vector in which the tested terminator is introduced between two GFP mutant genes: an ultraviolet-optimized mutant (GFPuv: F99S, M153T, V163A) and a blue-shifted mutant (BFP: F64L, S65T, T145F). The ratio of the fluorescence intensity of BFP to GFPuv after transcription and translation represents the termination efficiency of the terminator. E. coli ribosomal RNA operon T1 terminator, phage lambda terminator site R2, E. coli tryptophane attenuater were introduced into the vector, and their transcriptional efficiencies were estimated as 89, 79, and 24%, respectively, showing good agreement with published data.

Effect of membrane microheterogeneity and domain size on fluorescence resonance energy transfer.

PubMed

Towles, Kevin B; Brown, Angela C; Wrenn, Steven P; Dan, Nily

2007-07-15

Studies of multicomponent membranes suggest lateral inhomogeneity in the form of membrane domains, but the size of small (nanoscale) domains in situ cannot be determined with current techniques. In this article, we present a model that enables extraction of membrane domain size from time-resolved fluorescence resonance energy transfer (FRET) data. We expand upon a classic approach to the infinite phase separation limit and formulate a model that accounts for the presence of disklike domains of finite dimensions within a two-dimensional infinite planar bilayer. The model was tested against off-lattice Monte Carlo calculations of a model membrane in the liquid-disordered (l(d)) and liquid-ordered (l(o)) coexistence regime. Simulated domain size was varied from 5 to 50 nm, and two fluorophores, preferentially partitioning into opposite phases, were randomly mixed to obtain the simulated time-resolved FRET data. The Monte Carlo data show clear differences in the efficiency of energy transfer as a function of domain size. The model fit of the data yielded good agreement for the domain size, especially in cases where the domain diameter is <20 nm. Thus, data analysis using the proposed model enables measurement of nanoscale membrane domains using time-resolved FRET.

Diurnal Solar Energy Conversion and Photoprotection in Rice Canopies1[OPEN

PubMed Central

Quick, W. Paul; von Caemmerer, Susanne; Furbank, Robert

2017-01-01

Genetic improvement of photosynthetic performance of cereal crops and increasing the efficiency with which solar radiation is converted into biomass has recently become a major focus for crop physiologists and breeders. The pulse amplitude modulated chlorophyll fluorescence technique (PAM) allows quantitative leaf level monitoring of the utilization of energy for photochemical light conversion and photoprotection in natural environments, potentially over the entire crop lifecycle. Here, the diurnal relationship between electron transport rate (ETR) and irradiance was measured in five cultivars of rice (Oryza sativa) in canopy conditions with PAM fluorescence under natural solar radiation. This relationship differed substantially from that observed for conventional short term light response curves measured under controlled actinic light with the same leaves. This difference was characterized by a reduced curvature factor when curve fitting was used to model this diurnal response. The engagement of photoprotective processes in chloroplast electron transport in leaves under canopy solar radiation was shown to be a major contributor to this difference. Genotypic variation in the irradiance at which energy flux into photoprotective dissipation became greater than ETR was observed. Cultivars capable of higher ETR at midrange light intensities were shown to produce greater leaf area over time, estimated by noninvasive imaging. PMID:27895208

Image quality of a pixellated GaAs X-ray detector

NASA Astrophysics Data System (ADS)

Sun, G. C.; Makham, S.; Bourgoin, J. C.; Mauger, A.

2007-02-01

X-ray detection requires materials with large atomic numbers Z in order to absorb the radiation efficiently. In case of X-ray imaging, fluorescence is a limiting factor for the spatial resolution and contrast at energies above the kα threshold. Since both the energy and yield of the fluorescence of a given material increase with the atomic number, there is an optimum value of Z. GaAs, which can now be epitaxially grown as self-supported thick layers to fulfil the requirements for imaging (good homogeneity of the electronic properties) corresponds to this optimum. Image performances obtained with this material are evaluated in terms of line spread function and modulation transfer function, and a comparison with CsI is made. We evaluate the image contrast obtained for a given object contrast with GaAs and CsI detectors, in the photon energy range of medical applications. Finally, we discuss the minimum object size, which can be detected by these detectors in of mammography conditions. This demonstrates that an object of a given size can be detected using a GaAs detector with a dose at least 100 times lower than using a CsI detector.

Optical arc sensor using energy harvesting power source

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

Choi, Kyoo Nam, E-mail: knchoi@inu.ac.kr; Rho, Hee Hyuk, E-mail: rdoubleh0902@inu.ac.kr

Wireless sensors without external power supply gained considerable attention due to convenience both in installation and operation. Optical arc detecting sensor equipping with self sustaining power supply using energy harvesting method was investigated. Continuous energy harvesting method was attempted using thermoelectric generator to supply standby power in micro ampere scale and operating power in mA scale. Peltier module with heat-sink was used for high efficiency electricity generator. Optical arc detecting sensor with hybrid filter showed insensitivity to fluorescent and incandescent lamps under simulated distribution panel condition. Signal processing using integrating function showed selective arc discharge detection capability to different arcmore » energy levels, with a resolution below 17 J energy difference, unaffected by bursting arc waveform. The sensor showed possibility for application to arc discharge detecting sensor in power distribution panel. Also experiment with proposed continuous energy harvesting method using thermoelectric power showed possibility as a self sustainable power source of remote sensor.« less

Optical arc sensor using energy harvesting power source

NASA Astrophysics Data System (ADS)

Choi, Kyoo Nam; Rho, Hee Hyuk

2016-06-01

Wireless sensors without external power supply gained considerable attention due to convenience both in installation and operation. Optical arc detecting sensor equipping with self sustaining power supply using energy harvesting method was investigated. Continuous energy harvesting method was attempted using thermoelectric generator to supply standby power in micro ampere scale and operating power in mA scale. Peltier module with heat-sink was used for high efficiency electricity generator. Optical arc detecting sensor with hybrid filter showed insensitivity to fluorescent and incandescent lamps under simulated distribution panel condition. Signal processing using integrating function showed selective arc discharge detection capability to different arc energy levels, with a resolution below 17J energy difference, unaffected by bursting arc waveform. The sensor showed possibility for application to arc discharge detecting sensor in power distribution panel. Also experiment with proposed continuous energy harvesting method using thermoelectric power showed possibility as a self sustainable power source of remote sensor.

Enhancing the sensitivity of fluorescence correlation spectroscopy by using time-correlated single photon counting.

PubMed

Lamb, D C; Müller, B K; Bräuchle, C

2005-10-01

Fluorescence correlation spectroscopy (FCS) and fluorescence cross-correlation spectroscopy (FCCS) are methods that extract information about a sample from the influence of thermodynamic equilibrium fluctuations on the fluorescence intensity. This method allows dynamic information to be obtained from steady state equilibrium measurements and its popularity has dramatically increased in the last 10 years due to the development of high sensitivity detectors and its combination with confocal microscopy. Using time-correlated single-photon counting (TCSPC) detection and pulsed excitation, information over the duration of the excited state can be extracted and incorporated in the analysis. In this short review, we discuss new methodologies that have recently emerged which incorporated fluorescence lifetime information or TCSPC data in the FCS and FCCS analysis. Time-gated FCS discriminates between which photons are to be incorporated in the analysis dependent upon their arrival time after excitation. This allows for accurate FCS measurements in the presence of fluorescent background, determination of sample homogeneity, and the ability to distinguish between static and dynamic heterogeneities. A similar method, time-resolved FCS can be used to resolve the individual correlation functions from multiple fluorophores through the different fluorescence lifetimes. Pulsed interleaved excitation (PIE) encodes the excitation source into the TCSPC data. PIE can be used to perform dual-channel FCCS with a single detector and allows elimination of spectral cross-talk with dual-channel detection. For samples that undergo fluorescence resonance energy transfer (FRET), quantitative FCCS measurements can be performed in spite of the FRET and the static FRET efficiency can be determined.

Dynamics of energy transfer from lycopene to bacteriochlorophyll in genetically-modified LH2 complexes of Rhodobacter sphaeroides.

PubMed

Hörvin Billsten, H; Herek, J L; Garcia-Asua, G; Hashøj, L; Polívka, T; Hunter, C N; Sundström, V

2002-03-26

LH2 complexes from Rb. sphaeroides were modified genetically so that lycopene, with 11 saturated double bonds, replaced the native carotenoids which contain 10 saturated double bonds. Tuning the S1 level of the carotenoid in LH2 in this way affected the dynamics of energy transfer within LH2, which were investigated using both steady-state and time-resolved techniques. The S1 energy of lycopene in n-hexane was determined to be approximately 12 500 +/- 150 cm(-1), by direct measurement of the S1-S2 transient absorption spectrum using a femtosecond IR-probing technique, thus placing an upper limit on the S1 energy of lycopene in the LH2 complex. Fluorescence emission and excitation spectra demonstrated that energy can be transferred from lycopene to the bacteriochlorophyll molecules within this LH2 complex. The energy-transfer dynamics within the mutant complex were compared to wild-type LH2 from Rb. sphaeroides containing the carotenoid spheroidene and from Rs. molischianum, in which lycopene is the native carotenoid. The results show that the overall efficiency for Crt --> B850 energy transfer is approximately 80% in lyco-LH2 and approximately 95% in WT-LH2 of Rb. sphaeroides. The difference in overall Crt --> BChl transfer efficiency of lyco-LH2 and WT-LH2 mainly relates to the low efficiency of the Crt S(1) --> BChl pathway for complexes containing lycopene, which was 20% in lyco-LH2. These results show that in an LH2 complex where the Crt S1 energy is sufficiently high to provide efficient spectral overlap with both B800 and B850 Q(y) states, energy transfer via the Crt S1 state occurs to both pigments. However, the introduction of lycopene into the Rb. sphaeroides LH2 complex lowers the S1 level of the carotenoid sufficiently to prevent efficient transfer of energy to the B800 Q(y) state, leaving only the Crt S1 --> B850 channel, strongly suggesting that Crt S1 --> BChl energy transfer is controlled by the relative Crt S1 and BChl Q(y) energies.

All the coal in China.

PubMed

Lenssen, N

1993-01-01

China is emerging as a serious producer of carbon emissions from its burning of coal. China contributes 11% of global carbon emissions, which is still less than its population share. Economic reforms are likely to boost emissions. 33% of all fuel burned in China produces useful energy compared to 50-60% in the USA and Japan. Low prices encourage wasteful use. The Chinese government responds to energy shortages by investing scarce capital in building more mines, power plants, and oil wells. It is unlikely that investing in expanding conventional energy supplies will be a viable solution, regardless of the availability of capital to invest, because air pollution threatens life. Particulate suspension is 14 times greater in China than in the USA. 14% of the country is affected by acid rain. Global warming may be affecting the northern drought prone areas. The solutions must involve greater efficiency. Industrial consumption of energy is more than 66% of energy produced. Energy use for a typical steel or cement factory is 7-75% greater per ton than Western countries, i.e., 55-60% efficiency versus 80% in Europe. The inefficiency is due to poor maintenance and operating procedures and old or obsolete technology. The savings in building a compact, fluorescent light bulb factory is compared to the cost of building coal-fired power plants and transmission facilities. Conservation of heat in northern buildings could be accomplished with boiler improvements, insulation, and double- glazed windows. A $3 billion/year investment could yield a cut in energy demand by nearly 50%. The carbon emissions would be reduced from 1.4 billion tons to 1 billion tons in 2025. Between 1980 and 1985 the energy efficiency program was able to reduce growth in energy from 7% to 4% without slowing growth in industrial production. Since 1985, the government has directed expenditures toward expanding the energy supply, which reduced efficiency expenditures from 10% to 6% of total investment. Alternatives are natural gas or solar, wind, biomass, and geothermal energy. Alternatives are natural gas or solar, wind, biomass, and geothermal energy. International lending agencies must now shift their support to renewable resource development and efficiency improvement and education; an example from industrialized countries would also be very persuasive.

Application of fluorescence resonance energy transfer techniques to the study of lectin-binding site distribution on Paramecium primaurelia (Protista, Ciliophora) cell surface.

PubMed

Locatelli, D; Delmonte Corrado, M U; Politi, H; Bottiroli, G

1998-01-01

Fluorescence resonance energy transfer (FRET) is a photophysical phenomenon occurring between the molecules of two fluorochromes with suitable spectral characteristics (donor-acceptor dye pair), and consisting in an excitation energy migration through a non-radiative process. Since the efficiency of the process is strictly dependent on the distance and reciprocal orientation of the donor and acceptor molecules, FRET-based techniques can be successfully applied to the study of biomolecules and cell component organisation and distribution. These techniques have been employed in studying Paramecium primaurelia surface membrane for the reciprocal distribution of N-acetylneuraminic acid (NeuAc) and N-acetylglucosamine (GlcNAc) glycosidic residues, which were found to be involved in mating cell pairing. NeuAc and GlcNAc were detected by their specific binding lectins, Limulus polyphemus agglutinin (LPA) and wheat germ agglutinin (WGA), respectively. Microspectrofluorometric analysis afforded the choice of fluorescein isothiocyanate and Texas red conjugated with LPA and WGA, respectively, as a suitable donor-acceptor couple efficiently activating FRET processes. Studies performed both in solution and in cells allowed to define the experimental conditions favourable for a FRET analysis. The comparative study carried out both on the conjugating-region and the non conjugating region of the surface membrane, indicates that FRET distribution appears quite homogeneous in mating-competent mating type (mt) I, whereas, in mating-competent mt II cells, FRET distribution seems to be preferentially localised on the conjugating-region functionally involved in mating cell pairing. This difference in the distribution of lectin-binding sites is suggested to be related to mating-competence acquisition.

Performance of 'energy efficient' compact fluorescent lamps.

PubMed

Yuen, Gloria S-C; Sproul, Alistair B; Dain, Stephen J

2010-03-01

Compact fluorescent lamps (CFLs) have been heralded as highly energy efficient replacements for incandescent light globes, however, there is some public dissatisfaction with the light output and colour of CFLs. Independent examination of the claims made has not been made. Compliance with the interim Australian/New Zealand Standard has not been established by any independent authority. While the total light output (luminous flux) may meet certain standards, luminous intensity distributions of some designs do differ significantly from the incandescent sources that they are intended to replace. Luminous intensity distribution, luminous flux and spectral energy distribution of CFLs claimed to be equivalent to 75 W incandescent globes and 75 W incandescent globes (pearl and clear) were measured. Luminous flux, luminous efficacy, colour rendering index, correlated colour temperature, wattage and power factor were then calculated and compared with claims made by manufacturers and requirements of the standards. The sources generally complied with the requirements for luminous flux, luminous efficacy, colour rendering index and correlated colour temperature. The claim of 75 W equivalence, which is not regulated in Australia and New Zealand, is justified less than half the time. Luminous intensity distributions of biaxial CFLs are distinctly different from the incandescent lamps they purport to replace. CFLs generally comply with the standards set. The basis on which equivalent wattages are claimed needs to be included in the Australian and New Zealand standard because this is the measure most likely to be relied on by the public. Due to the differences in luminous intensity distribution, CFLs may not necessarily be a direct replacement for incandescent sources without some consideration.

Nerium oleander indirect leaf photosynthesis and light harvesting reductions after clipping injury or Spodoptera eridania herbivory: high sensitivity to injury.

PubMed

Delaney, Kevin J

2012-04-01

Variable indirect photosynthetic rate (P(n)) responses occur on injured leaves after insect herbivory. It is important to understand factors that influence indirect P(n) reductions after injury. The current study examines the relationship between gas exchange and chlorophyll a fluorescence parameters with injury intensity (% single leaf tissue removal) from clipping or Spodoptera eridania Stoll (Noctuidae) herbivory on Nerium oleander L. (Apocynaceae). Two experiments showed intercellular [CO(2)] increases but P(n) and stomatal conductance reductions with increasing injury intensity, suggesting non-stomatal P(n) limitation. Also, P(n) recovery was incomplete at 3d post-injury. This is the first report of a negative exponential P(n) impairment function with leaf injury intensity to suggest high N. oleander leaf sensitivity to indirect P(n) impairment. Negative linear functions occurred between most other gas exchange and chlorophyll a fluorescence parameters with injury intensity. The degree of light harvesting impairment increased with injury intensity via lower (1) photochemical efficiency indicated lower energy transfer efficiency from reaction centers to PSII, (2) photochemical quenching indicated reaction center closure, and (3) electron transport rates indicated less energy traveling through PSII. Future studies can examine additional mechanisms (mesophyll conductance, carbon fixation, and cardenolide induction) to cause N. oleander indirect leaf P(n) reductions after injury. Published by Elsevier Ireland Ltd.

Multiple-photon excitation of nitrogen vacancy centers in diamond

NASA Astrophysics Data System (ADS)

Ji, Peng; Balili, R.; Beaumariage, J.; Mukherjee, S.; Snoke, D.; Dutt, M. V. Gurudev

2018-04-01

We report the observation of multiphoton photoluminescence excitation (PLE) below the resonant energies of nitrogen vacancy (NV) centers in diamond. The quadratic and cubic dependence of the integrated fluorescence intensity as a function of excitation power indicates a two-photon excitation pathway for the NV- charge state and a three-photon process involved for the neutral NV0 charge state, respectively. Comparing the total multiphoton energy with its single-photon equivalent, the PLE spectra follows the absorption spectrum of single photon excitation. We also observed that the efficiency of photoluminescence for different charge states, as well as the decay time constant, was dependent on the excitation wavelength and power.

Conformational Control of Ultrafast Molecular Rotor Property: Tuning Viscosity Sensing Efficiency by Twist Angle Variation.

PubMed

Ghosh, Rajib; Kushwaha, Archana; Das, Dipanwita

2017-09-21

Fluorescent molecular rotors find widespread application in sensing and imaging of microscopic viscosity in complex chemical and biological media. Development of viscosity-sensitive ultrafast molecular rotor (UMR) relies upon the understanding of the excited-state dynamics and their implications for viscosity-dependent fluorescence signaling. Unraveling the structure-property relationship of UMR behavior is of significance toward development of an ultrasensitive fluorescence microviscosity sensor. Herein we show that the ground-state equilibrium conformation has an important role in the ultrafast twisting dynamics of UMRs and consequent viscosity sensing efficiency. Synthesis, photophysics, and ultrafast spectroscopic experiments in conjunction with quantum chemical calculation of a series of UMRs based on dimethylaniline donor and benzimidazolium acceptor with predefined ground-state torsion angle led us to unravel that the ultrafast torsional dynamics around the bond connecting donor and acceptor groups profoundly influences the molecular rotor efficiency. This is the first experimental demonstration of conformational control of small-molecule-based UMR efficiencies which can have wider implication toward development of fluorescence sensors based on the UMR principle. Conformation-controlled UMR efficiency has been shown to exhibit commensurate fluorescence enhancement upon DNA binding.

Photosystem II Water Oxidation: Mechanism, Efficiency and Flux in Diverse Oxygenic Phototrophs

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

Dismukes, Gerard Charles; Ananyev, Gennady; Gates, Colin

In one year, we pursued four aims: 1) extend the VZAD model to allow analysis of PSII chlorophyll fluorescence emission as modulated by interaction with the WOC (partial success); 2) compare the solar energy conversion efficiencies of PSII-WOCs from intact cells, isolated thylakoid membranes and PSII core complexes and crystals from cyanobacterium Thermosynechococcus elongatus (collaboration with Lawrence Berkeley National Laboratory; some success after changing collaborator); 3) determine whether PSIIs can store light energy by pumping protons across the thylakoid membrane (PSII-cyclic electron flow) and how it is regulated within the green alga Chlorella ohadii (collaboration with the Hebrew University ofmore » Jerusalem; some success); and 4) genetically replace the native PSII-D1 protein subunit from a higher plant with two cyanobacterial D1 isoforms to test whether their functional advantages in growth and photoprotection can be transferred (collaboration with Rutgers University; success).« less

Detecting Crop Functional Response to a Heat Wave using Airborne Reflectance and Sun-induced Chlorophyll Fluorescence Measurements

NASA Astrophysics Data System (ADS)

Yang, P.; Van der Tol, C.; Rascher, U.; Damm, A.; Schickling, A.; Verhoef, W.

2016-12-01

This study presents an analysis of airborne measured reflectance (R) and solar-induced chlorophyll fluorescence (SIF) as indicators of high temperature stress in agricultural crops. We used atmospherically corrected R and retrievals of SIF in the O2-A band as obtained from HyPlant data over C3 crops (rapeseed, wheat and barley) and a C4 crop (corn) in Germany before (30th June) and during (2nd July) a heat wave in 2015. The availability of airborne data during this heat wave allowed us to detect fluorescence emission efficiency changes as an indicator of crop photosynthetic performance in response to temperature fluctuations. We found that SIF is affected relatively stronger by heat stress than R. This is according to expectation, because the R spectrum is determined by leaf properties and canopy structure, whereas top-of-canopy (TOC) SIF is also affected by the temperature dependent efficiencies of photochemical and non-photochemical quenching of fluorescence. With the model 'Soil Canopy Observation of Photosynthesis and Energy fluxes (SCOPE), we differentiated leaf optical parameters and canopy structure from the fluorescence quantum emission efficiency (FQE), i.e. the ratio of fluorescence production to light absorption of photosystems. The leaf optical and canopy structure parameters were retrieved from R by inversion of the radiative transfer module 'RTMo' of SCOPE. The retrieved parameters were further used to estimate the FQE from SIF measurements. It appeared that both the leaf water content CW and the FQE responded to the heat wave, but the responses were different for C3 and C4 crops. A slight reduction of CW occurred in C3 crops between the two days, but not in the C4 crop. The reduction of FQE was only significant in C3 crops, and ranged from 18% to 31% for various C3 species. These findings agree with the general knowledge that C4 plants are better adapted to high temperature than C3 plants, and comply with simulations from a biochemical model for C3 and C4 crops in SCOPE. It is concluded that the combination of hyperspectral R and SIF enables the differentiation of long-term and short term responses to heat stress.

Trace vapor detection of hydrogen peroxide: An effective approach to identification of improvised explosive devices

NASA Astrophysics Data System (ADS)

Xu, Miao

Vapor detection has been proven as one of the practical, noninvasive methods suitable for explosives detection among current explosive detection technologies. Optical methods (especially colorimetric and fluorescence spectral methods) are low in cost, provide simple instrumentation alignment, while still maintaining high sensitivity and selectivity, these factors combined facilitate broad field applications. Trace vapor detection of hydrogen peroxide (H2O2) represents an effective approach to noninvasive detection of peroxide-based explosives, though development of such a sensor system with high reliability and sufficient sensitivity (reactivity) still remains challenging. Three vapor sensor systems for H2O2 were proposed and developed in this study, which exploited specific chemical reaction towards H2O2 to ensure the selectivity, and materials surface engineering to afford efficient air sampling. The combination of these features enables expedient, cost effective, reliable detection of peroxide explosives. First, an expedient colorimetric sensor for H2O2 vapor was developed, which utilized the specific interaction between Ti(oxo) and H2O2 to offer a yellow color development. The Ti(oxo) salt can be blended into a cellulose microfibril network to produce tunable interface that can react with H2O2. The vapor detection limit can reach 400 ppb. To further improve the detection sensitivity, a naphthalimide based fluorescence turn-on sensor was designed and developed. The sensor mechanism was based on H2O2-mediated oxidation of a boronate fluorophore, which is nonfluorescent in ICT band, but becomes strongly fluorescent upon conversion into the phenol state. The detection limit of this sensory material was improved to be below 10 ppb. However, some technical factors such as sensor concentration, local environment, and excitation intensity were found difficult to control to make the sensor system sufficiently reproducible. To solve the problem, we developed a ratiometric fluorescence sensor, which allows for dual-band emission monitoring and thus enhances the detection reliability. Moreover, the significant spectral overlap between the fluorescence of the pristine sensor and the absorption of the reacted state enables effective Foster Resonance Energy Transfer (FRET). This FRET process can significantly enhance the fluorescence sensing efficiency in comparison to the normal single-band sensor system, for which the sensing efficiency is solely determined by the stoichiometric conversion of sensor molecules.

Fluorescence energy transfer as a probe for nucleic acid structures and sequences.

PubMed Central

Mergny, J L; Boutorine, A S; Garestier, T; Belloc, F; Rougée, M; Bulychev, N V; Koshkin, A A; Bourson, J; Lebedev, A V; Valeur, B

1994-01-01

The primary or secondary structure of single-stranded nucleic acids has been investigated with fluorescent oligonucleotides, i.e., oligonucleotides covalently linked to a fluorescent dye. Five different chromophores were used: 2-methoxy-6-chloro-9-amino-acridine, coumarin 500, fluorescein, rhodamine and ethidium. The chemical synthesis of derivatized oligonucleotides is described. Hybridization of two fluorescent oligonucleotides to adjacent nucleic acid sequences led to fluorescence excitation energy transfer between the donor and the acceptor dyes. This phenomenon was used to probe primary and secondary structures of DNA fragments and the orientation of oligodeoxynucleotides synthesized with the alpha-anomers of nucleoside units. Fluorescence energy transfer can be used to reveal the formation of hairpin structures and the translocation of genes between two chromosomes. PMID:8152922

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

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

Wu, Tony C.; Congreve, Daniel N.; Baldo, Marc A., E-mail: baldo@mit.edu

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 ismore » 1.1%. Our results demonstrate upconversion in solid state geometries and with non-heavy metal-based sensitizer materials.« less

Light harvesting control in plants.

PubMed

Ruban, Alexander V

2018-05-23

In 1991, my colleagues and I published a hypothesis article that proposed a mechanism that controls light harvesting in plants and protects them against photodamage. The major light harvesting complex, LHCII, was suggested to undergo aggregation upon exposure of the plant to damaging levels of light. Aggregated LHCII was found to be much less efficient in light harvesting, as it promptly dissipated absorbed energy into heat, possessing a very low chlorophyll fluorescence yield. Non-photochemical quenching (NPQ) is a term coined to describe this reduction in chlorophyll fluorescence yield. This article is a story of how the hypothesis that LHCII aggregation is involved in NPQ is developed into a model that is now becoming broadly accepted by the research community. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Single-Molecule Three-Color FRET with Both Negligible Spectral Overlap and Long Observation Time

PubMed Central

Hohng, Sungchul

2010-01-01

Full understanding of complex biological interactions frequently requires multi-color detection capability in doing single-molecule fluorescence resonance energy transfer (FRET) experiments. Existing single-molecule three-color FRET techniques, however, suffer from severe photobleaching of Alexa 488, or its alternative dyes, and have been limitedly used for kinetics studies. In this work, we developed a single-molecule three-color FRET technique based on the Cy3-Cy5-Cy7 dye trio, thus providing enhanced observation time and improved data quality. Because the absorption spectra of three fluorophores are well separated, real-time monitoring of three FRET efficiencies was possible by incorporating the alternating laser excitation (ALEX) technique both in confocal microscopy and in total-internal-reflection fluorescence (TIRF) microscopy. PMID:20808851

Effect of substituent of terpyridines on the in vitro antioxidant, antitubercular, biocidal and fluorescence studies of copper(II) complexes with clioquinol

NASA Astrophysics Data System (ADS)

Kharadi, G. J.

2014-01-01

An octahedral complexes of copper with clioquinol(CQ) and substituted terpyridine have been synthesized. The Cu(II) complexes have been characterized by elemental analyses, thermogravimetric analyses, magnetic moment measurements, FT-IR, electronic, 1H NMR and FAB mass spectra. Antimycobacterial screening of ligand and its copper compound against Mycobacterium tuberculosis shows clear enhancement in the antitubercular activity upon copper complexation. Ferric-reducing anti-oxidant power of all complexes were measured. The fluorescence spectra of complexes show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The antimicrobial efficiency of the complexes were tested on five different microorganisms and showed good biological activity.

The energy spectrum of cosmic rays above 1017.2 eV measured by the fluorescence detectors of the Telescope Array experiment in seven years

NASA Astrophysics Data System (ADS)

Abbasi, R. U.; Abe, M.; Abu-Zayyad, T.; Allen, M.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, W. R.; Fujii, T.; Fukushima, M.; Goto, T.; Hanlon, W.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Honda, K.; Ikeda, D.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kawata, K.; Kido, E.; Kim, H. B.; Kim, J. H.; Kim, J. H.; Kitamura, S.; Kitamura, Y.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lundquist, J. P.; Machida, K.; Martens, K.; Matsuda, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Mukai, Y.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nonaka, T.; Nozato, A.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Shin, H. S.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzawa, T.; Takamura, M.; Takeda, M.; Takeishi, R.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Uchihori, Y.; Udo, S.; Urban, F.; Vasiloff, G.; Wong, T.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yashiro, K.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.

2016-07-01

The Telescope Array (TA) experiment is the largest detector to observe ultra-high-energy cosmic rays in the northern hemisphere. The fluorescence detectors at two stations of TA are newly constructed and have now completed seven years of steady operation. One advantage of monocular analysis of the fluorescence detectors is a lower energy threshold for cosmic rays than that of other techniques like stereoscopic observations or coincidences with the surface detector array, allowing the measurement of an energy spectrum covering three orders of magnitude in energy. Analyzing data collected during those seven years, we report the energy spectrum of cosmic rays covering a broad range of energies above 1017.2eV measured by the fluorescence detectors and a comparison with previously published results.

An Exciplex Host for Deep-Blue Phosphorescent Organic Light-Emitting Diodes.

PubMed

Lim, Hyoungcheol; Shin, Hyun; Kim, Kwon-Hyeon; Yoo, Seung-Jun; Huh, Jin-Suk; Kim, Jang-Joo

2017-11-01

The use of exciplex hosts is attractive for high-performance phosphorescent organic light-emitting diodes (PhOLEDs) and thermally activated delayed fluorescence OLEDs, which have high external quantum efficiency, low driving voltage, and low efficiency roll-off. However, exciplex hosts for deep-blue OLEDs have not yet been reported because of the difficulties in identifying suitable molecules. Here, we report a deep-blue-emitting exciplex system with an exciplex energy of 3.0 eV. It is composed of a carbazole-based hole-transporting material (mCP) and a phosphine-oxide-based electron-transporting material (BM-A10). The blue PhOLEDs exhibited maximum external quantum efficiency of 24% with CIE coordinates of (0.15, 0.21) and longer lifetime than the single host devices.

In Situ Generation and Consumption of H2O2 by Bienzyme-Quantum Dots Bioconjugates for Improved Chemiluminescence Resonance Energy Transfer.

PubMed

Xu, Shuxia; Li, Xianming; Li, Chaobi; Li, Jialin; Zhang, Xinfeng; Wu, Peng; Hou, Xiandeng

2016-06-21

Exploration of quantum dots (QDs) as energy acceptors revolutionizes the current chemiluminescence resonance energy transfer (CRET), since QDs possess large Stokes shifts and high luminescence efficiency. However, the strong and high concentration of oxidant (typically H2O2) needed for luminol chemiluminescence (CL) reaction could cause oxidative quenching to QDs, thereby decreasing the CRET performance. Here we proposed the use of bienzyme-QDs bioconjugate as the energy acceptor for improved CRET sensing. Two enzymes, one for H2O2 generation (oxidase) and another for H2O2 consumption (horseradish peroxidase, HRP), were bioconjugated onto the surface of QDs. The bienzyme allowed fast in situ cascaded H2O2 generation and consumption, thus alleviating fluorescence quenching of QDs. The nanosized QDs accommodate the two enzymes in a nanometric range, and the CL reaction was confined on the surface of QDs accordingly, thereby amplifying the CL reaction rate and improving CRET efficiency. As a result, CRET efficiency of 30-38% was obtained; the highest CRET efficiency by far was obtained using QDs as the energy acceptor. The proposed CRET system could be explored for ultrasensitive sensing of various oxidase substrates (here exemplified with cholesterol, glucose, and benzylamine), allowing for quantitative measurement of a spectrum of metabolites with high sensitivity and specificity. Limits of detection (LOD, 3σ) for cholesterol, glucose, and benzylamine were found to be 0.8, 3.4, and 10 nM, respectively. Furthermore, multiparametric blood analysis (glucose and cholesterol) is demonstrated.

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

PubMed Central

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

2017-01-01

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

FRET-FLIM microscopy

NASA Astrophysics Data System (ADS)

Elangovan, Masilamani; Day, Richard N.; Periasamy, Ammasi

2002-06-01

Visualizing and quantifying protein-protein interactions is a recent trend in biomedical imaging. The current advances in fluorescence microscopy coupled with the development of new fluorescent probes provide the tools to study protein interactions in living specimens. Spectral bleed-through or cross talk is a problem in one- and two-photon microscopy to recognize whether one is observing the sensitized emission or the bleed-through signals. In contrast, FLIM (fluorescence lifetime imaging microscopy) or lifetime measurements are independent of excitation intensity or fluorophore concentration. The combination of FLIM and FRET will provide high spatial (nanometer) and temporal (nanoseconds) resolution when compared to steady state FRET imaging. Importantly, spectral bleed-through is not an issue in FLIM imaging because only the donor fluorophore lifetime is measured. The presence of acceptor molecules within the local environment of the donor that permit energy transfer will influence the fluorescence lifetime of the donor. By measuring the donor lifetime in the presence and the absence of acceptor one can accurately calculate the FRET efficiency and the distance between donor- and acceptor-labeled proteins. Moreover, the FRET-FLIM technique allows monitoring more than one pair of protein interactions in a single living cell.

Lithographically-fabricated channel arrays for confocal x-ray fluorescence microscopy and XAFS

NASA Astrophysics Data System (ADS)

Woll, Arthur R.; Agyeman-Budu, David; Choudhury, Sanjukta; Coulthard, Ian; Finnefrock, Adam C.; Gordon, Robert; Hallin, Emil; Mass, Jennifer

2014-03-01

Confocal X-ray Fluorescence Microscopy (CXRF) employs overlapping focal regions of two x-ray optics—a condenser and collector—to directly probe a 3D volume. The minimum-achievable size of this probe volume is limited by the collector, for which polycapillaries are generally the optic of choice. Recently, we demonstrated an alternative collection optic for CXRF, consisting of an array of micron-scale collimating channels, etched in silicon, and arranged like spokes of a wheel directed towards a single source position. The optic, while successful, had a working distance of only 0.2 mm and exhibited relatively low total collection efficiency, limiting its practical application. Here, we describe a new design in which the collimating channels are formed by a staggered array of pillars whose side-walls taper away from the channel axis. This approach improves both collection efficiency and working distance, while maintaining excellent spatial resolution. We illustrate these improvements with confocal XRF data obtained at the Cornell High Energy Synchrotron Source (CHESS) and the Advanced Photon Source (APS) beamline 20-ID-B.

A water-soluble hybrid material of single-walled carbon nanotubes with an amphiphilic poly(phenyleneethynylene): preparation, characterization, and photovoltaic properties.

PubMed

Mao, Jie; Liu, Qian; Lv, Xin; Liu, Zunfeng; Huang, Yi; Ma, Yanfeng; Chen, Yongsheng; Yin, Shougen

2007-08-01

A novel rigid linear polymer poly(phenyleneethynylene) (PPE) was synthesized and the polymer exhibits good solubility in both water and common organic solvents. The interaction at both ground and excited state between this polymer and single-walled carbon nanotubes (SWNTs) was studied and a water-soluble nano-scale PPE/SWNTs hybrid was fabricated, where the water solubility of SWNTs was enhanced to 1.8 mg/ml. Steady state fluorescence spectra and fluorescence lifetime decay measurements showed that the emissions from PPEs in this hybrid at excited state were efficiently quenched by the attachment of SWNTs, where an efficient energy transfer happened from PPEs to SWNTs as the electron acceptor. Using this hybrid as the active layer we fabricated a photovoltaic cell with the bulk heterojunction configuration, and it showed a photoresponse with an open circuit voltage (Voc) of 105 mV and a short circuit current density (Isc) of 28.7 microA/cm2 under standard AM 1.5 illumination (100 mW/cm2).

Sensitized phosphorescence of benzil-doped ladder-type methyl-poly(para-phenylene)

NASA Astrophysics Data System (ADS)

Bagnich, S. A.; Bässler, H.; Neher, D.

2004-11-01

The delayed luminescence and phosphorescence of ladder-type methyl-poly(para-phenylene) (MeLPPP) doped with benzil at a concentration of 20% by weight has been measured. The introduction of benzil leads to a dramatic reduction of the polymer singlet emission. At the same time, a new band with maximum at 611 nm appears, corresponding to the phosphorescence of MeLPPP. The phosphorescence decay on the short time scale is close to an exponential law with a time decay of 15 ms. This indicates that benzil can efficiently sensitize the phosphorescence of the polymer. In addition, a broad and featureless emission is observed in the delayed luminescence spectra of benzil-doped MeLPPP, which is attributed to an exciplex formed between the polymer host and the dopant. We further observe that the delayed fluorescence is enhanced by the addition of benzil. It is concluded that the delayed fluorescence of benzil-doped MeLPPP is mainly due to the annihilation of triplet excitons on the polymer. Finally, efficient triplet-triplet energy transfer from the benzil-doped polymer to the red-emitting phosphorescent dye Pt(II)octaethylporphyrin is established.

Tailoring of optical properties of fluorescein using green synthesized gold nanoparticles.

PubMed

John, Jisha; Thomas, Lincy; George, Nibu A; Kurian, Achamma; George, Sajan D

2015-06-28

Dye-nanoparticle mixtures hold great promise in biological as well as photonics applications due to their capability to tailor the emission behavior of dye by tuning the nanoparticles parameters. However, as compared to the well-defined dye-nanoparticle distance, studies lack the understanding of homogenous mixtures of dye and nanoparticles. In this work, we investigate the influence of shape and concentration of gold nanoparticles prepared via green synthesis on the optical properties of fluorescein dye in a dye-nanoparticle mixture. We have investigated the radiative path of deexcitation using steady state fluorescence and the non-radiative path is probed using a laser based dual-beam thermal lens technique. The energy transfer efficiency as well as dye-nanoparticle distance is studied using both techniques. Furthermore, we have explored the influence of nanoparticles parameters on the fluorescence quantum yield of fluorescein using the thermal lens technique. The studies indicate that spherical nanoparticles are efficient quenchers while star shaped nanoparticles can probe larger dye-NP distances. The tailoring of dye properties by tuning nanoparticle parameters can be utilized in diverse areas including bioimaging, solar cells, and sensors.

Heavy Atom Effect of Bromine Significantly Enhances Exciton Utilization of Delayed Fluorescence Luminogens.

PubMed

Gan, Shifeng; Hu, Shimin; Li, Xiang-Long; Zeng, Jiajie; Zhang, Dongdong; Huang, Tianyu; Luo, Wenwen; Zhao, Zujin; Duan, Lian; Su, Shi-Jian; Tang, Ben Zhong

2018-05-23

Raising triplet exciton utilization of pure organic luminescent materials is of significant importance for efficiency advancement of organic light-emitting diodes (OLEDs). Herein, by introducing bromine atom(s) onto a typical molecule (bis(carbazol-9-yl)-4,5-dicyanobenzene) with thermally activated delayed fluorescence, we demonstrate that the heavy atom effect of bromine can increase spin-orbit coupling and promote the reverse intersystem crossing, which endow the molecules with more distinct delayed fluorescence. In consequence, the triplet exciton utilization is improved greatly with the increase of bromine atoms, affording apparently advanced external quantum efficiencies of OLEDs. Utilizing the enhancement effect of bromine atoms on delayed fluorescence should be a simple and promising design concept for efficient organic luminogens with high exciton utilization.

The production of consuming less: Energy efficiency, climate change, and light bulbs in North Carolina

NASA Astrophysics Data System (ADS)

Thoyre, Autumn

In this research, I have analyzed the production of consuming less electricity through a case study of promotions of compact fluorescent light bulbs (CFLs). I focused on the CFL because it has been heavily promoted by environmentalists and electricity companies as a key tool for solving climate change, yet such promotions appear counter-intuitive. The magnitude of CFL promotions by environmentalists is surprising because CFLs can only impact less than 1% of U.S. greenhouse gas emissions. CFL promotions by electricity providers are surprising given such companies' normal incentives to sell more of their product. I used political ecological and symbolic interactionist theories, qualitative methods of data collection (including interviews, participant-observation, texts, and images), and a grounded theory analysis to understand this case. My findings suggest that, far from being a self-evident technical entity, energy efficiency is produced as an idea, a part of identities, a resource, and a source of value through social, political, and economic processes. These processes include identity formation and subjectification; gender-coded household labor; and corporate appropriation of household value resulting from environmental governance. I show how environmentalists use CFLs to make and claim neoliberal identities, proposing the concept of green neoliberal identity work as a mechanism through which neoliberal ideologies are translated into practices. I analyze how using this seemingly easy energy efficient technology constitutes labor that is gendered in ways that reflect and reproduce inequalities. I show how electricity companies have used environmental governance to valorize and appropriate home energy efficiency as an accumulation strategy. I conclude by discussing the symbolic power of CFLs, proposing a theory of green obsolescence, and framing the production of energy efficiency as a global production network. I found that promoting energy efficiency involves consuming less energy by consuming more technologies. This research contributes to understandings of how environmentalists become laboring subjects in an era of neoliberalism and how energy companies are responding to the threat of climate change by turning mitigation into an opportunity for profit.

Prediction and design of efficient exciplex emitters for high-efficiency, thermally activated delayed-fluorescence organic light-emitting diodes.

PubMed

Liu, Xiao-Ke; Chen, Zhan; Zheng, Cai-Jun; Liu, Chuan-Lin; Lee, Chun-Sing; Li, Fan; Ou, Xue-Mei; Zhang, Xiao-Hong

2015-04-08

High-efficiency, thermally activated delayed-fluorescence organic light-emitting diodes based on exciplex emitters are demonstrated. The best device, based on a TAPC:DPTPCz emitter, shows a high external quantum efficiency of 15.4%. Strategies for predicting and designing efficient exciplex emitters are also provided. This approach allow prediction and design of efficient exciplex emitters for achieving high-efficiency organic light-emitting diodes, for future use in displays and lighting applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photophysical properties of a novel axially substituted tetra-α-(pentyloxy) Titanium(IV) Phthalocyanine - Hematoxylin

NASA Astrophysics Data System (ADS)

Jiang, Yufeng; Lv, Huafei; Yu, Xinxin; Pan, Sujuan; Zhang, Tiantian; Huang, Yide; Wang, Yuhua; Xie, Shusen; Yang, Hongqin; Peng, Yiru

2017-06-01

Metal phthalocyanines (MPcs) are a very important class of widespread application compounds. They are not only used as dyes but also used as catalysts, data storage, electron charge carriers in photocopiers, photoconductors in chemical sensors, and photo-antenna devices in photosysthesis, photovoltaic cells. A particular application of Pcs is that it was used as a photosensitizers (PS) for treatment of certain cancer by photodynamic therapy of cancer and non-cancer diseases. However, the molecular aggregation of phthalocyanines, which is an intrinsic property of these large π-π conjugated systems, provides an efficient non-radioactive energy relaxation pathway, thereby shortening the excited state lifetimes, and reducing the photosensitizing and target efficiency. To overcome these problems, the introduction of axial ligands to phthalocyanine can prevent the formation of aggregation to some extend. In this paper, hematoxylin axially substituted tetra-α-(pentoxy) titanium (IV) phthalocyanine (TiPc(OC5H11)4-Hematoxylin) were characterized by elemental analysis, IR, 1H NMR, UV-Vis, fluorescence spectra. No obviously Q band change was observed after the hematoxylin was substituted at the peripheral position of substituted phthalocyanine ring. Because of the rigidity structure of the hematoxylin, the fluorescence intensity of hematoxylin peripheral substituted phthalocyanine decreased compared with free substituted phthalocyanines. The fluorescence lifetimes of axially substituted phthalocyanine was fitted to be 3.613 ns. This compound may be considered as a promising photosensitizer for PDT.

Milk caseins as useful vehicle for delivery of dipyridamole drug.

PubMed

Dezhampanah, Hamid; Esmaili, Masoomeh; Hasani, Leila

2018-05-01

The interaction of bovine milk α- and β-caseins as an efficient drug carrier system with Dipyridamole (DIP) was investigated using spectroscopy and molecular docking studies at different temperatures (20-37 °C). FTIR, CD, and fluorescence spectroscopy methods demonstrated that α- and β-caseins interact with DIP molecule mainly via hydrophobic and hydrophilic interactions and change in secondary structure of α- and β-caseins. DIP showed a higher quenching efficiency and binding constant of α-casein than β-casein. There was only one binding site for DIP and it was located on the surface of the protein molecule. The thermodynamic parameters of calculation showed that the binding process occurs spontaneously and demonstrated that α- and β-caseins provide very good binding and entrapment to DIP via hydrogen bonds, Van der Waals forces, and hydrophobic interactions. Fluorescence resonance energy transfer, synchronous fluorescence spectroscopy, and docking study showed that DIP binds to the Trp residues of α- and β-casein molecules with short distances. Docking study showed that DIP molecule made several hydrogen bonds and van der Waals interactions with α- and β-caseins. The study of cell culture and micellar solubility of DIP demonstrated α- and β-caseins relatively the same helping in delivery of DIP. Milk α- and β-caseins are considered as a useful vehicle for the solublization and stabilization of DIP in aqueous solution at natural pH.

Assessing Photosynthesis by Fluorescence Imaging

ERIC Educational Resources Information Center

Saura, Pedro; Quiles, Maria Jose

2011-01-01

This practical paper describes a novel fluorescence imaging experiment to study the three processes of photochemistry, fluorescence and thermal energy dissipation, which compete during the dissipation of excitation energy in photosynthesis. The technique represents a non-invasive tool for revealing and understanding the spatial heterogeneity in…

DNA-length-dependent quenching of fluorescently labeled iron oxide nanoparticles with gold, graphene oxide and MoS2 nanostructures.

PubMed

Balcioglu, Mustafa; Rana, Muhit; Robertson, Neil; Yigit, Mehmet V

2014-08-13

We controlled the fluorescence emission of a fluorescently labeled iron oxide nanoparticle using three different nanomaterials with ultraefficient quenching capabilities. The control over the fluorescence emission was investigated via spacing introduced by the surface-functionalized single-stranded DNA molecules. DNA molecules were conjugated on different templates, either on the surface of the fluorescently labeled iron oxide nanoparticles or gold and nanographene oxide. The efficiency of the quenching was determined and compared with various fluorescently labeled iron oxide nanoparticle and nanoquencher combinations using DNA molecules with three different lengths. We have found that the template for DNA conjugation plays significant role on quenching the fluorescence emission of the fluorescently labeled iron oxide nanoparticles. We have observed that the size of the DNA controls the quenching efficiency when conjugated only on the fluorescently labeled iron oxide nanoparticles by setting a spacer between the surfaces and resulting change in the hydrodynamic size. The quenching efficiency with 12mer, 23mer and 36mer oligonucleotides decreased to 56%, 54% and 53% with gold nanoparticles, 58%, 38% and 32% with nanographene oxide, 46%, 38% and 35% with MoS2, respectively. On the other hand, the presence, not the size, of the DNA molecules on the other surfaces quenched the fluorescence significantly with different degrees. To understand the effect of the mobility of the DNA molecules on the nanoparticle surface, DNA molecules were attached to the surface with two different approaches. Covalently immobilized oligonucleotides decreased the quenching efficiency of nanographene oxide and gold nanoparticles to ∼22% and ∼21%, respectively, whereas noncovalently adsorbed oligonucleotides decreased it to ∼25% and ∼55%, respectively. As a result, we have found that each nanoquencher has a powerful quenching capability against a fluorescent nanoparticle, which can be tuned with surface functionalized DNA molecules.