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Energy Transfer between Tm-Doped Upconverting Nanoparticles and a Small Organic Dye with Large Stokes Shift
摘要： Lanthanide-doped upconverting nanoparticles (UCNP) are being extensively studied for bioapplications due to their unique photoluminescence properties and low toxicity. Interest in RET applications involving UCNP is also increasing, but due to factors such as large sizes, ion emission distributions within the particles, and complicated energy transfer processes within the UCNP, there are still many questions to be answered. In this study, four types of core and core-shell NaYF4-based UCNP co-doped with Yb3+ and Tm3+ as sensitizer and activator, respectively, were investigated as donors for the Methyl 5-(8-decanoylbenzo[1,2-d:4,5-d']bis([1,3]dioxole)-4-yl)-5-oxopentanoate (DBD-6) dye. The possibility of resonance energy transfer (RET) between UCNP and the DBD-6 attached to their surface was demonstrated based on the comparison of luminescence intensities, band ratios, and decay kinetics. The architecture of UCNP influenced both the luminescence properties and the energy transfer to the dye: UCNP with an inert shell were the brightest, but their RET efficiency was the lowest (17%). Nanoparticles with Tm3+ only in the shell have revealed the highest RET efficiencies (up to 51%) despite the compromised luminescence due to surface quenching.
关键词： time-resolved luminescence,core shell UCNP,DBD dye,resonance energy transfer
更新于2025-09-23 15:22:29
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A large Stokes shift fluorescent protein constructed from the fusion of the red fluorescent mCherry and far-red fluorescent BDFP1.6
摘要： While phycobiliproteins are organized as the phycobilisomes, they can harvest orange, red and/or far-red lights for photosynthesis in cyanobacteria and red algae, phycobiliproteins in the phycobilisome cores such as allophycocyanins absorb far-red light for funneling the energy to the reaction centers. Therefore, the allophycocyanin subunits have been engineered as far-red fluorescent proteins such as BDFP1.6. However, most current fluorescent probes have small Stokes shifts, which limits their applications in multicolor bioimaging. mCherry is an excellent fluorescent protein that has maximal emittance in the red spectral range and high fluorescence quantum yield, thus can be used as a donor for energy transfer to the far-red acceptor such as BDFP1.6 via F?rster resonance energy transfer. In this study, mCherry was fused with BDFP1.6, which results in a highly bright far-red fluorescent protein, BDFP2.0, of a large Stokes shift (~79 nm). The excitation energy was absorbed maximally at 587 nm by mCherry and transferred to BDFP1.6 efficiently, thus emitting strong far-red fluorescence maximally at 666 nm. The effective brightness of BDFP2.0 in mammalian cells was 4.2-fold higher than iRFP670 that is reported as the brightest far-red fluorescent protein. The large Stokes shift of BDFP2.0 facilitates multicolor bioimaging. Therefore, BDFP2.0 can not only well bio-label mammalian including human cells, but also well bio-label the various intracellular components in dual-color imaging.
关键词： biliverdin,energy transfer,allophycocyanin,Phycobiliprotein,bioimaging,fluorescence
更新于2025-09-23 15:22:29
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A photochromic benzothiadiazole-diarylethene with tuneable on-off fluorescence modulation
摘要： Organic molecules with photoswitchable emission properties are of interest in the optical devices field. We present herein in-solution studies for two dimethoxy-DTE-fluorophore-conjugates with carboxylic acid anchor group attachable to semiconductor surfaces (DTE-BODIPY and BTD-DTE). Both conjugates show almost quantitative reversible photoisomerization between open (OF) and closed form (CF). With excitation of the fluorophores, both conjugates emit fluorescence with highly solvent dependent OFs (BTD-DTE > DTE-BODIPY) and minor solvent dependent CFs. In the polar solvent MeCN for BTD-DTE a TICT state is clearly observed, which will be located in the twisted conjugated structure of the benzoic acid-BTD-fluorophore-methoxy thiophene unit. BTD-DTE shows positive solvatofluorochromism with decrease of fluorescence quantum yields by increasing Δf verified in Lippert-Mataga plots. This leads to solvent dependent on-off/off-on (CF-OF) emission modulation by FRET with well-separated emission bands for BTD-DTE.
关键词： Diarylethenes,Photochromism,Solvatochromism,Fluorescence,Energy transfer
更新于2025-09-23 15:22:29
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A far-red FRET fluorescent probe for ratiometric detection of l-cysteine based on carbon dots and N-acetyl-l-cysteine-capped gold nanoparticles
摘要： A novel far-red fluorescence resonance energy transfer (FRET) fluorescenct probe for ratiometric detection of L-cysteine (L-Cys) has been designed. The system was established a FRET assembly by positively charged carbon dots (CDs) and negatively charged N-acetyl-L-cysteine capped gold nanoparticles (NAC-AuNPs). The fluorescence of CDs at 539 nm could be effectively quenched in the presence of NAC-AuNPs owing to FRET process, while the emission of NAC-AuNPs at 630 nm was appeared. Subsequently, the interactions between L-Cys and NAC-AuNPs resulted in the decreased emission intensity of NAC-AuNPs, but the emission intensity of CDs kept almost constant due to the continuous FRET efficiency. The ratio of emission intensities at 539 and 630 nm (I539/I630) exhibited a linear correlation to the L-Cys concentration in the range of 1.0-110 μM with the detection limit of 0.16 μM. Moreover, this far-red ratiometric sensor also revealed excellent selectivity toward L-Cys over other amino acids, which showed very high potential in the practical application for diagnosing of cysteine-related disease.
关键词： Fluorescence resonance energy transfer,gold nanoparticles,L-cysteine,Carbon dots
更新于2025-09-23 15:22:29
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Photoluminescence Characteristics of Sm3+-doped LnBWO6 (Ln=La, Gd and Y) as New Orange-red Phosphors
摘要： A series of Sm3+-doped LnBWO6 (Ln=La, Gd and Y) phosphors with orange-red light emitting in pure phase were prepared by high temperature solid-state process. The crystal structure, photoluminescence properties, decay lifetimes and thermal stability properties of those as-prepared samples were investigated. Those phosphors can be efficiently excited by near-UV and blue light and emitted orange-red luminescence with color coordinates (0.622, 0.377). Among those LnBWO6 (Ln=La, Gd and Y) hosts, the emission intensities of Sm3+-doped LaBWO6 are the strongest ones. The optimum doping concentration and critical energy transfer distance of Sm3+ ions in LaBWO6 were determined. The fluorescence concentration quenching mechanism was attributed to the dipole-dipole interaction between the Sm3+ ions. The fluorescent thermal quenching studies showed Sm3+ doped LaBWO6 had high thermal-stable properties. The present work suggested that Sm3+-doped LnBWO6 (Ln=La, Gd and Y) as orange-red phosphors exhibited potential application in white LED.
关键词： red phosphors,concentration quenching,energy transfer,white LEDs,luminescent properties
更新于2025-09-23 15:22:29
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Role of electron and hole centers in energy transfer in BaBrI crystals
摘要： In this paper we study a role of F-centers, hole centers and excitons in energy transfer in Eu-doped BaBrI crystals. Optical absorption spectra, thermally stimulated (TSL) and photostimulated (PSL) luminescence in wide temperature range 7-300 K are studied in undoped and doped with different concentrations of Eu ions BaBrI crystals. Based on experimental and calculated results two possible energy tranfer processes from host to Eu2+ ions are established.
关键词： energy transfer,thermoluminescence,alkali earth halides,scintillators,bromide,iodide,F-center,photostimulated luminescence
更新于2025-09-23 15:22:29
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White-light emissive upconversion nanoparticles for visual and colorimetric determination of the pesticide thiram
摘要： The authors describe the use of white-light emitting upconversion nanoparticles (WL-UCNPs) for visual detection of the pesticide thiram. The method is demonstrated to undergo a better discernable color change upon target binding. The WL-UCNPs are modified with the lead(II)-dithizone complex which acts as the energy acceptor and recognition unit. This leads to quenching of the blue (475 nm) and green (545 nm) emissions of the WL-UCNPs, while the red emission (650 nm) remains unaffected. Upon addition of thiram, the quenched emissions are recovered, with a linear signal increase in the range from 2 nM to 20 nM of thiram and a limit of detection of 0.26 nM. The nanoprobe was further integrated into a test paper for visual detection. The concentration-dependent color change that varies from red to cyan and bluish violet and then to white can be visually distinguished.
关键词： Lead-dithizone complex,Color-differentiation,Upconversional nanoprobe,Test paper,Energy transfer
更新于2025-09-23 15:22:29
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Intense red emission and two-way energy transfer in Sm3+, Eu3+ co-doped NaLa(WO4)2 phosphors
摘要： NaLa(WO4)2 phosphors with various Eu3+ and Sm3+ concentrations were prepared via a molten salt method. The structure and luminescent properties of the prepared samples were analyzed by the X-ray diffraction (XRD) and fluorescence spectrophotometer. The results show that the crystal phase of all the prepared samples is single tetragonal crystal structure. The energy transfer type between Eu3+ ions is proved to be the exchange interaction and the electron-phonon coupling is weak. With the increase of the Sm3+ concentration, the energy transfer from Sm3+ to Eu3+ in NaLa(WO4)2:0.15Eu3+,xSm3+ is transformed from Eu3+ to Sm3+, and the mechanism for energy transfer is given.
关键词： Nanophosphor powders NaLa(WO4)2: xEu3+ ySm3+,Electron-phonon coupling,Photoluminescence,Energy transfer
更新于2025-09-23 15:21:21
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Theoretical Model of Exciton States and Ultra-fast Energy Transfer in Heliobacterial Type-I Homodimeric Reaction Center
摘要： A simple theoretical model of exciton dynamics was proposed to interpret the fast excitation energy transfer process in the Type-I homodimeric reaction center of Heliobacterium modesticaldum (hRC); this structure was recently identified and shown to resemble that of the plant/cyanobacterial photosystem I (PSI) reaction center. The exciton state model, which mainly relies on the geometries of 54 bacteriochlorophyll (BChl) g, 4 BChl-g′ and 2 chlorophyll (Chl) a on hRC and assumes constant site energy values for the pigments, reproduced the absorption spectrum of hRC rather well. The model also enabled numerical analysis of the exciton dynamics on hRC, which can be compared with the decay-associated spectra obtained by the laser spectroscopy experiments. The model indicates that the stronger transition-dipole moment on BChl-g contributes to the faster energy transfer due to the higher coherency of the delocalized exciton states on hRC compared to that on PSI that arranges Chl-a at almost homologous locations.
关键词： chlorophyll,photosystem I,bacteriochlorophyll,exciton dynamics,energy transfer,reaction center
更新于2025-09-23 15:21:21
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Effect of Eu3+ ions on optical and fluorescence studies of Nd3+ ions doped zinc-lithium fluoroborate glasses
摘要： Nd3+ single and Nd3+/Eu3+ co-doped ZnF2-LiF-Na2CO3-Bi2O3-H3BO3, zinc lithium fluoroborate (ZLFNBiB) glasses with good optical properties have been prepared by high temperature melt-quenching method. The single and co-doped samples exhibiting emission bands centered at 874, 1058 and 1330 nm under the excitation of 808 nm laser diode (LD). The photoluminescence spectra for co-doped glasses were recorded under the 394 and 464 nm of xenon lamp as excitation sources. The Judd-Ofelt intensity parameters were calculated from optical absorption spectrum and radiative parameters from the emission spectrum of 0.5 mol% of Nd3+ doped glass. The large stimulated emission cross-section and branching ratio values are evaluated and compared with the other Nd3+ doped systems, the energy transfer from Eu3+ to Nd3+ ions is observed and thoroughly discussed from NIR emission spectra (λexc = 394 nm) of co-doped glasses. The decay profiles are recorded for all the concentrations of co-doped samples and the experimental lifetimes (τexp) were obtained from the decay profiles. The binding energy and Urbach energy values of prepared glass samples were calculated and discussed.
关键词： Spectroscopic properties,Fluorescence,Energy transfer,Lifetime.,Nd3+/Eu3+-co-doped glasses
更新于2025-09-23 15:21:21