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Fabrication of Remarkably Bright QD Densely-Embedded Silica Nanoparticle
摘要： We developed a synthesis method for silica-coated quantum dot (QD)-densely-embedded silica nanoparticle (Si@D-QD@Si NP) with remarkably brighter fluorescence by increasing the number of QDs on silica NPs. Si@D-QD@Si NPs exhibited a narrow size distribution and a high signal reproducibility. Red, green, and blue Si@D-QD@Si NPs were successfully fabricated and characterized. The Si@D-QD@Si NP carried 2.4 times more QDs than previously reported silica-coated QD-embedded silica NP (Si@QD@Si NP). The quantum yield of Si@D-QD@Si NPs was slightly higher than Si@QD@Si NPs. The red Si@D-QD@Si NPs showed approximately 26.6%, the green Si@D-QD@Si NP 36.2%, and the blue Si@D-QD@Si NP 39.3% higher fluorescence intensity compared to the corresponding Si@QD@Si NPs. This result implied that the particles can be used at bio-field with a higher sensitive detection.
关键词： Quantum dot,Quantum yield,Fluorescence,Silica coating,Silica nanoparticle
更新于2025-09-23 15:23:52
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High Quantum Yield Single-Band Green Upconversion in La <sub/>2</sub> O <sub/>3</sub> :Yb <sup>3+</sup> , Ho <sup>3+</sup> Microcrystals for Anticounterfeiting and Plastic Recycling
摘要： Single-band green upconversion (UC) with high green purity and color stability is urgently required for plastic recycling and anticounterfeiting. However, it is very difficult to obtain single-band green emission for benchmark Yb3+/Er3+ activated UC materials (such as NaYF4:Yb3+,Er3+) due to the strong accompanying red UC. Herein, highly efficient and stable single-band green UC is reported in La2O3:Yb3+/Ho3+ (LYH) microcrystals with record high absolute UC quantum yield (UCQY) of 2.6% for single-band green UC. LYH yields pure green UC with large and stable intensity ratio, IGreen/IRed ≈ 18. LYH presents not only higher UCQY for a single-band green UC but also much more pure and stable green UC than the benchmark UC materials such as NaYF4:Yb3+,Er3+ and Gd2O2S:Yb3+,Er3+. These results suggest that the newly developed LYH can, in principle, be promising for anticounterfeiting and plastic recycling. Its proof-of-concept is demonstrated as a security label based on a transparent institute logo.
关键词： anticounterfeiting,high UC quantum yield,plastic recycling,upconversion materials,pure green UC
更新于2025-09-23 15:23:52
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Photochemical multivariate curve resolution models for the investigation of photochromic systems under continuous irradiation
摘要： We propose a multivariate curve resolution approach for the investigation of photochromic systems using UV-Visible spectroscopy. The incorporation of photochemical hard-models as constraints in multivariate curve resolution alternating least squares (MCR-ALS) allows extracting reaction quantum yields in situations where a complete knowledge of the system is not available. We apply this approach to the study of the photochromism of CMTE (cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene) under continuous monochromatic irradiation. The mechanism, involving 3 species and 2 reversible reactions, is written and translated into a kinetic constraint that can be applied to the concentration profiles within ALS. First, ambiguity of the solution obtained for photochemical model(s) is calculated and discussed for single set analysis. Multiset analysis is then proposed combining data obtained under different irradiation wavelengths to provide more reliable results. Finally, the photochemical reactivity of CMTE is widely unraveled, and some description of the mechanism observed under irradiation at 365 nm is given.
关键词： Multivariate curve resolution,Quantum yield,Hard-soft modelling,Parameter ambiguity,Photochemical reaction
更新于2025-09-23 15:23:52
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One-pot three-component synthesis and photophysical properties of highly fluorescent novel 4-alkyl-3-aryl-2,6-dicyanoanilines by using tris(hydroxymethyl)aminomethane as a catalyst
摘要： Novel 4-alkyl-3-aryl-2,6-dicyanoanilines were synthesized by a multi-component one-step reaction of aromatic aldehyde, malononitrile and aliphatic aldehyde using tris(hydroxymethyl)aminomethane (THAM) as a catalyst under microwave (MW) irradiation or conventional heating. The optimized reaction condition involved use of 2.5 equivalents of THAM under MW irradiation at 140 W using 20 % MW power for 5 min or conventional heating at 80 °C for 8 h in dimethylformamide. The photophysical properties including λmax, quantum yield and Stokes’ shifts of newly synthesized molecules were studied. All compounds exhibited quantum yield in the range of 0.04 to 0.52 with respect to standard quinine sulphate having quantum yield 0.54. The Stokes’ shifts of all compounds were found in the range of 41-105 nm. The current strategy provides operationally simple protocol using THAM as a catalyst to synthesize 4-alkyl-3-aryl-2,6-dicyanoanilines with diverse structural features to make them available for exploration of their photophysical as well as biological applications.
关键词： Fluorescent,Quantum Yield,Tris(hydroxymethyl)aminomethane,Microwave,Malononitrile,Dicyanoanilnes
更新于2025-09-23 15:23:52
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Optimizing one-dimensional TiO2 for photocatalytic hydrogen production from a water-ethanol mixture and other electron donors
摘要： This work is focused on synthesizing and employing one-dimensional (1D) titanium dioxide (TiO2) for hydrogen (H2) production. Based on using electron donors (EDs) (ethanol, methanol, formic acid and 1,2,3 propanetriol), the increased H2 production, when compared to P25 TiO2 nanoparticles, was due to the large specific surface area (SSA) and enhanced electron mobility of 1D TiO2. The impact of the 1D TiO2 synthesis reaction conditions (temperature, NaOH concentration and the TiO2 precursor concentration) on the photocatalytic H2 production rate was evaluated using a 3-factor 3-level Box Behnken design (BBD). The BBD model demonstrated that the temperature and the NaOH concentration significantly affected the 1D TiO2 phase structure, crystal size, SSA, bandgap and the photocatalytic H2 production rate. The phase structure and crystal size of 1D TiO2 were key factors affecting the H2 production rate. 1D TiO2 containing an anatase phase with a mean crystal size of 20.1±0.2 nm was synthesized at 126oC, 15 M NaOH and 49 g·L-1 TiO2. The maximum H2 production rate of 475±12 μmol·h-1 (quantum efficiency (ε) = 20.2±0.5%) for the 1D TiO2 sample was significantly enhanced when compared to commercial TiO2 P25. The H2 production rate for the optimized 1D TiO2 was significantly enhanced by decorating the structure with Pt and Au. Hydrothermal synthesized of 1D TiO2 provided an efficient and low cost method for producing H2 from ethanol, methanol, formic acid and 1,2,3 propanetriol.
关键词： hydrogen production,hydrothermal,1D titanium dioxide,TiO2-B,anatase,photocatalyst,quantum yield
更新于2025-09-23 15:23:52
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Blue Electrogenerated Chemiluminescence from Halide Perovskite Nanocrystals
摘要： Electrogenerated chemiluminescence (ECL) has been extensively used in ultrasensitive electroanalysis because it can be generated electrochemically without using expensive optics and light sources. Visible ECL emission can be obtained with a reasonable quantum yield and stability. Blue ECL is rare and often suffers from stability and poor quantum efficiency. Blue ECL emission at 473 nm from organometallic halide perovskite nanocrystals (PNCs), CH3NH3PbCl1.08Br1.92, is reported here for the first time using tripropylamine (TPrA) as co-reactant. The blue ECL emission peak resembles its photoluminescence peak position. In addition to this blue emission peak, the ECL spectra of CH3NH3PbCl1.08Br1.92 PNCs also showed a broad ECL peak at 745 nm. Generation of the second ECL peak at 745 nm from CH3NH3PbCl1.08Br1.92 PNCs was can be explained by the existence of surface trap states on as-synthesized PNC due to incomplete surface passivation. Halide anion tunability of ECL emission from CH3NH3PbX3 (X: Cl, Br, I) PNCs is also demonstrated. The fluorescence microscopy image of single PNC and stability of selected single PNCs are presented in this with simultaneous acquisition of fluorescence spectra using 405-nm laser excitation. The photoluminescence (PL) decay was described by PL lifetime (τ) of 1.2 ns. The effect of the addition of surfactants (oleic acid and n-octylamine) on the fluorescence intensity and stability of CH3NH3PbCl1.08Br1.92 PNCs is also discussed.
关键词： Surfactants,Blue light emission,ECL (electrogenerated chemiluminescence),Photoluminescence (PL),Perovskite nanocrystals (PNCs),Photoluminescence quantum yield (PLQY)
更新于2025-09-23 15:23:52
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Broadband Emission in Hybrid Organic–Inorganic Halides of Group 12 Metals
摘要： We report syntheses, crystal and electronic structures, and characterization of three new hybrid organic?inorganic halides (R)ZnBr3(DMSO), (R)2CdBr4·DMSO, and (R)CdI3(DMSO) (where (R) = C6(CH3)5CH2N(CH3)3, and DMSO = dimethyl sulfoxide). The compounds can be conveniently prepared as single crystals and bulk polycrystalline powders using a DMSO?methanol solvent system. On the basis of the single-crystal X-ray diffraction results carried out at room temperature and 100 K, all compounds have zero-dimensional (0D) crystal structures featuring alternating layers of bulky organic cations and molecular inorganic anions based on a tetrahedral coordination around group 12 metal cations. The presence of discrete molecular building blocks in the 0D structures results in localized charges and tunable room-temperature light emission, including white light for (R)ZnBr3(DMSO), bluish-white light for (R)2CdBr4·DMSO, and green for (R)CdI3(DMSO). The highest photoluminescence quantum yield (PLQY) value of 3.07% was measured for (R)ZnBr3(DMSO), which emits cold white light based on the calculated correlated color temperature (CCT) of 11,044 K. All compounds exhibit fast photoluminescence lifetimes on the timescale of tens of nanoseconds, consistent with the fast luminescence decay observed in π-conjugated organic molecules. Temperature dependence photoluminescence study showed the appearance of additional peaks around 550 nm, resulting from the organic salt emission. Density functional theory calculations show that the incorporation of both the low-gap aromatic molecule R and the relatively electropositive Zn and Cd metals can lead to exciton localization at the aromatic molecular cations, which act as luminescence centers.
关键词： zero-dimensional structures,broadband emission,group 12 metals,exciton localization,photoluminescence quantum yield,hybrid organic?inorganic halides
更新于2025-09-23 15:23:52
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Synthesis, characterization and photophysical properties of a new class of pyrene substituted 1,3,4-oxadiazole derivatives
摘要： We have designed and synthesized a series of a new class of pyrene substituted 1,3,4- oxadiazole derivatives (abbreviated as 3(a-e)) through palladium catalyzed Suzuki-Miyaura cross coupling reaction. The chemical structures of the probes were characterized by using analytical techniques namely 1H NMR, 13C NMR, FT-IR and GC-MS. The novel bipolar molecules consist of pyrene as an electron donor unit (D) and electron-deficient 1,3,4-oxadiazole as an acceptor unit (A) linked via extending π conjugation through a phenyl spacer with para linkages (D-π-A). Intramolecular charge transfer is improved by structure-property relationship. The detailed photophysical/solvatochromic properties of newly synthesized derivatives have been studied employing steady state spectroscopic techniques. The photophysical studies revealed that compounds emit strong indigo-blue fluorescence and efficient blue emission extending into blue-green in solid phase with high quantum yields. Thermal and morphological stabilities of the derivatives were studied employing DSC and TGA measurements. In addition, density functional theory (DFT) computations have been carried out to demonstrate various intramolecular interactions that cause the stabilization of the compound leading to its optoelectronic applications. The highest occupied molecular orbital energy (HOMOs), lowest unoccupied molecular orbital energy (LUMOs), the energy bandgap, chemical hardness (η), softness (δ), electronegativity (χ) and chemical potential (μ) were computed with the help of frontier molecular orbitals. The results were compared and discussed with the experimental results. The results demonstrate that the novel pyrene containing oxadiazole derivatives could be used as small organic molecules for multifunctional organic light-emitting devices (OLED)/optoelectronic devices.
关键词： Intramolecular charge transfer (ICT),1,3,4-Oxadiazole,Quantum yield,Pyrene,Density functional theory
更新于2025-09-23 15:23:52
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Reducing aggregation caused quenching effect through co-assembly of PAH chromophores and molecular barriers
摘要： The features of well-conjugated and planar aromatic structures make π-conjugated luminescent materials suffer from aggregation caused quenching (ACQ) effect when used in solid or aggregated states, which greatly impedes their applications in optoelectronic devices and biological applications. Herein, we reduce the ACQ effect by demonstrating a facile and low cost method to co-assemble polycyclic aromatic hydrocarbon (PAH) chromophores and octafluoronaphthalene together. Significantly, the solid photoluminescence quantum yield (PLQYs) for the as-resulted four micro/nanococrystals are enhanced by 254%, 235%, 474 and 582%, respectively. Protection from hydrophilic polymer chains (P123 (PEO20-PPO70-PEO20)) endows the cocrystals with superb dispersibility in water. More importantly, profiting from the above-mentioned highly improved properties, nano-cocrystals present good biocompatibility and considerable cell imaging performance. This research provides a simple method to enhance the emission, biocompatibility and cellular permeability of common chromophores, which may open more avenues for the applications of originally non- or poor fluorescent PAHs.
关键词： cocrystals,aggregation caused quenching,bioimaging,polycyclic aromatic hydrocarbon,photoluminescence quantum yield
更新于2025-09-23 15:23:52
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Model To Determine a Distinct Rate Constant for Carrier Multiplication from Experiments
摘要： Carrier multiplication (CM) is the process in which multiple electron?hole pairs are created upon absorption of a single photon in a semiconductor. CM by an initially hot charge carrier occurs in competition with cooling by phonon emission, with the respective rates determining the CM e?ciency. Up until now, CM rates have only been calculated theoretically. We show for the ?rst time how to extract a distinct CM rate constant from experimental data of the relaxation time of hot charge carriers and the yield of CM. We illustrate this method for PbSe quantum dots. Additionally, we provide a simpli?ed method using an estimated energy loss rate to estimate the CM rate constant just above the onset of CM, when detailed experimental data of the relaxation time is missing.
关键词： carrier multiplication,quantum yield,quantum dots,semiconductor,electron?hole pairs
更新于2025-09-23 15:22:29