Absolute luminescence quantum yield for nanosized carbon particles in water as a function of excitation wavelength

Advanced fluorescence analysis within the wide range of excitation wavelengths from 230 to 510 nm accompanied with chromatography was used to study natural chromophoric dissolved organic matter (CDOM) from three freshwater Karelian lakes. The influence of excitation wavelength (λex) on fluorescence quantum yield and emission maximum position was determined. The CDOM fluorescence quantum yield has reached a minimum at λex∼270–280 nm and a maximum at λex∼340–360 nm. It was monotonously decreasing after 370 nm towards longer excitation wavelengths. Analytical reversed-phase high-performance liquid chromatography with multiwavelength fluorescence detector characterized distribution of fluorophores between hydrophilic/hydrophobic CDOM parts. This technique revealed “hidden” protein-like fluorophores for some CDOM fractions, in spite of the absence of protein-like fluorescence in the initial CDOM samples. The humic-like fluorescence was documented for all hydrophilic and hydrophobic CDOM chromatographic peaks, and its intensity was decreasing along with peaks’ hydrophobicity. On contrary, the protein-like fluorescence was found only in the hydrophobic peaks, and its intensity was increasing along with peaks’ hydrophobicity. This work provides new data on the CDOM optical properties consistent with the formation of supramolecular assemblies controlled by association of low-molecular size components. In addition, these data are very useful for understanding the CDOM function in the environment.

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Two-Photon–NIR-II Antimicrobial Graphene-Nanoagent for Ultraviolet–NIR Imaging and Photoinactivation

10.21203/rs.3.rs-519688/v1 ◽

2021 ◽

Author(s):

WEN-SHUO KUO ◽

Chia-Yuan Chang ◽

Ping-Ching Wu ◽

Jiu-Yao Wang

Keyword(s):

Photodynamic Therapy ◽

Quantum Yield ◽

Chemical Modification ◽

Near Infrared ◽

Photon Absorption ◽

Excitation Wavelength ◽

Strong Electron ◽

Two Photon ◽

Photon Excitation ◽

Two Photon Excitation

Abstract BackgroundNitrogen doping and amino-group functionalization, which result in strong electron donation, can be achieved through chemical modification. Large π-conjugated systems of graphene quantum dot (GQD)-based materials acting as electron donors can be chemically manipulated with low two-photon excitation energy in a short photoexcitation time for improving the charge transfer efficiency of sorted nitrogen-doped amino acid–functionalized GQDs (sorted amino-N-GQDs). ResultsIn this study, a self-developed femtosecond Ti-sapphire laser optical system (222.7 nJ pixel−1 with 100-170 scans, approximately 0.65-1.11 s of total effective exposure times; excitation wavelength: 960 nm in the near-infrared II region) was used for chemical modification. The sorted amino-N-GQDs exhibited enhanced two-photon absorption, post-two-photon excitation stability, two-photon excitation cross-section, and two-photon luminescence through the radiative pathway. The lifetime and quantum yield of the sorted amino-N-GQDs decreased and increased, respectively. Furthermore, the sorted amino-N-GQDs exhibited excitation-wavelength-independent photoluminescence in the near-infrared region and generated reactive oxygen species after two-photon excitation. An increase in the size of the sorted amino-N-GQDs boosted photochemical and electrochemical efficacy and resulted in high photoluminescence quantum yield and highly efficient two-photon photodynamic therapy. ConclusionThe sorted dots can be used in two-photon contrast probes for tracking and localizing analytes during two-photon imaging in a biological environment and for conducting two-photon photodynamic therapy for eliminating infectious microbes.

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Diverse Coordination Numbers and Geometries in Pyridyl Adducts of Lanthanide(III) Complexes Based on β-Diketonate

Inorganics ◽

10.3390/inorganics9100074 ◽

2021 ◽

Vol 9 (10) ◽

pp. 74

Author(s):

Franz A. Mautner ◽

Florian Bierbaumer ◽

Roland C. Fischer ◽

Ana Torvisco ◽

Ramon Vicente ◽

...

Keyword(s):

Rare Earth ◽

Solid State ◽

Quantum Yield ◽

Rare Earth Complexes ◽

Luminescence Spectra ◽

Excitation Wavelength ◽

Coordination Numbers ◽

State Luminescence

Ten mononuclear rare earth complexes of formula [La(btfa)3(H2O)2] (1), [La(btfa)3(4,4′-Mt2bipy)] (2), [La(btfa)3(4,4′-Me2bipy)2] (3), [La(btfa)3(5,5′-Me2bipy)2] (4), [La(btfa)3(terpy)] (5), [La(btfa)3(phen)(EtOH)] (6), [La(btfa)3(4,4′-Me2bipy)(EtOH)] (7), [La(btfa)3(2-benzpy)(MeOH)] (8), [Tb(btfa)3(4,4′-Me2bipy)] (9) and (Hpy)[Eu(btfa)4] (10), where btfa = 4,4,4-trifuoro-1-phenylbutane-1,3-dionato anion, 4,4′-Mt2bipy = 4,4′-dimethoxy-2,2′-bipyridine, 4,4′-Me2bipy = 4,4′-dimethyl-2,2′-bipyridine, 5,5′-Me2bipy = 5,5′-dimethyl-2,2′-bipyridine, terpy = 2,2′:6′,2′-terpyridine, phen = 1,10-phenathroline, 2-benzpy = 2-(2-pyridyl)benzimidazole, Hpy = pyridiniumH+ cation) have been synthesized and structurally characterized. The complexes display coordination numbers (CN) eight for 1, 2, 9, 10, nine for 5, 6, 7, 8 and ten for 3 and 4. The solid-state luminescence spectra of Tb-9 and Eu-10 complexes showed the same characteristic bands predicted from the Tb(III) and Eu(III) ions. The Overall Quantum Yield measured (ϕTOT) at the excitation wavelength of 371 nm for both compounds yielded 1.04% for 9 and up to 34.56% for 10.

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Synthesis of CdS-Capped CdSe Nanocrystals without any Poisonous Materials

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.981.806 ◽

2014 ◽

Vol 981 ◽

pp. 806-809

Author(s):

Wu Lei Zhou ◽

Tuo Cai ◽

Yun Chen ◽

Xuan Lin Chen ◽

Yu Qiu Qu ◽

...

Keyword(s):

Aqueous Solution ◽

Quantum Yield ◽

Aqueous Medium ◽

Laser Irradiation ◽

Absorption Spectroscopy ◽

Photoluminescence Spectroscopy ◽

Luminescence Quantum Yield ◽

Cdse Nanocrystals ◽

Core Shell ◽

Photo Stability

CdS-capped CdSe nanocrystals (NCs) which show high luminescence quantum yield are synthesized without any Poisonous Materials in aqueous solution. The synthesis in an aqueous medium without any poisonous materials is attached importance to. The absorption spectroscopy and photoluminescence spectroscopy are employed to analyze the NCs. It takes 78s that the intensity decreases to the half for bare CdSe NCs, but 442s for CdSe/CdS core/shell NCs. The photo stability of CdSe NCs under 325nm laser irradiation is enhanced greatly after CdS overcoating.

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Gold Doping of Silver Nanoclusters: A 26-Fold Enhancement in the Luminescence Quantum Yield

Angewandte Chemie ◽

10.1002/ange.201600267 ◽

2016 ◽

Vol 128 (19) ◽

pp. 5843-5847 ◽

Cited By ~ 36

Author(s):

Giada Soldan ◽

Maha A. Aljuhani ◽

Megalamane S. Bootharaju ◽

Lina G. AbdulHalim ◽

Manas R. Parida ◽

...

Keyword(s):

Quantum Yield ◽

Silver Nanoclusters ◽

Luminescence Quantum Yield ◽

Gold Doping

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Synthesis and luminescence properties of colloidal lanthanide doped YVO4

MRS Proceedings ◽

10.1557/proc-667-g4.5 ◽

2001 ◽

Vol 667 ◽

Cited By ~ 6

Author(s):

Arnaud Huignard ◽

Thierry Gacoin ◽

Frédéric Chaput ◽

Jean-Pierre Boilot ◽

Patrick Aschehoug ◽

...

Keyword(s):

Quantum Yield ◽

Room Temperature ◽

Sol Gel ◽

Precursor Solution ◽

Silica Matrix ◽

Luminescence Quantum Yield ◽

Colloidal Solutions ◽

Silicon Alkoxide ◽

Crystalline Defects ◽

Hydroxylated Surface

ABSTRACTAqueous colloidal solutions of well dispersed YVO4:Ln (Ln = Eu, Nd) nanoparticles are synthesized through precipitation reactions at room temperature. In the case of YVO4:Eu, a luminescence quantum yield of 15% is found, which is not as high as in the bulk due to the existence of residual crystalline defects and nonradiative relaxations from the hydroxylated surface. Appropriate hydrothermal annealing and deuteration of the surface allow to rise the yield up to 38%. Incorporation of the nanocrystals into a transparent silica matrix is achieved through preliminary coating of the particles with a functionnalized silicon alkoxide and further dispersion into a sol-gel precursor solution. Such sol-gel materials doped with YVO4:Nd nanocrystals are transparent and exhibit the typical emission at 1.06 μm of the Nd3+ ion.

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Magnetron-Sputtered Polytetrafluoroethylene-Stabilized Silver Nanoisland Surface for Surface-Enhanced Fluorescence

Nanomaterials ◽

10.3390/nano10040773 ◽

2020 ◽

Vol 10 (4) ◽

pp. 773 ◽

Cited By ~ 1

Author(s):

Martin Šubr ◽

Petr Praus ◽

Anna Kuzminova ◽

Eva Kočišová ◽

Ondřej Kylián ◽

...

Keyword(s):

Quantum Yield ◽

Radiative Decay ◽

Adsorbed Layer ◽

Localized Surface Plasmon ◽

Homogeneous Layer ◽

Excitation Wavelength ◽

Sessile Droplet ◽

Enhanced Fluorescence ◽

Surface Enhanced Fluorescence ◽

Surface Enhanced

Surface-enhanced fluorescence (SEF) requires the absorption/emission band of the fluorophore, the localized surface plasmon resonance (LSPR) of the nanostructure and the excitation wavelength to fall in the same (or very close) spectral range. In this paper, we monitor the SEF intensity and lifetime dependence of riboflavin (vitamin B2) adsorbed on a spacer-modified Ag substrate with respect to the thickness of the spacer. The substrates were formed by silver nanoislands deposited onto magnetron-sputtered polytetrafluoroethylene (ms-PTFE). The spacer was formed by the ms-PTFE layer with the thickness ranging from ~5 to 25 nm. The riboflavin dissolved in dimethylsulfoxide (DMSO) at a 10 µM concentration forms, at the ms-PTFE surface, a homogeneous layer of adsorbed molecules corresponding to a monomolecular layer. The microspectroscopic measurements of the adsorbed layer were performed through a sessile droplet; our study has shown the advantages and limitations of this approach. Time-resolved fluorescence enabled us to determine the enhanced fluorescence quantum yield due to the shortening of the radiative decay in the vicinity of the plasmonic surface. For the 5 nm ms-PTFE layer possessing the largest (estimated 4×) fluorescence enhancement, the quantum yield was increased 2.3×.

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