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Decoration of carbon dots over hydrogen peroxide treated graphitic carbon nitride: Exceptional photocatalytic performance in removal of different contaminants under visible light
摘要： The development of novel photocatalysts with considerable activity for completely removal of different pollutants from the environment is a dominating goal of modern chemistry. In this study, carbon dots (CDs) were adhered to the graphitic carbon nitride activated by hydrogen peroxide (ag-C3N4) to fabricate photocatalysts with exceptional ability upon visible-light illumination. Interestingly, the BET surface area, visible-light absorption characteristics, and electron-hole separation yield of the pristine g-C3N4 were improved after activation with H2O2 and decoration of CDs. The binary nanocomposite was used for degradation of MB, RhB, fuchsine, and phenol and photoreduction of Cr(VI) under visible light. The nanocomposite exhibited excellent photocatalytic performance with 100% removal of RhB in 60 min, which is almost 34.7 folds as premier as the pristine g-C3N4. Reactive species scavenging measurements displayed that ?O2?, ?OH, and h+ had significant roles for photodegradation of RhB. The possible mechanism was proposed regarding how activation with H2O2 and decoration of CDs improved the photocatalytic performance of g-C3N4. Also, stability of the composite was characterized through cyclic photocatalytic tests.
关键词： Graphitic carbon nitride,g-C3N4/CDs,Hydrogen peroxide treated g-C3N4,Visible-light-active photocatalyst
更新于2025-09-19 17:15:36
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One-pot hydrothermal synthesis of nitrogen and sulfur co-doped carbon dots and their application for sensitive detection of curcumin and temperature
摘要： In this study, excitation-independent emission nitrogen and sulfur co-doped fluorescence carbon dots (N,S-CDs) was fabricated by using a simple and efficient one-step hydrothermal treatment with sodium citrate and thiourea as precursor. We found that the obtained N,S-CDs displayed excellent optical properties and emitted strong blue fluorescence under the 365 nm UV lamp. The relative quantum yield was as high as 26.9% using quinine sulfate as reference. The fluorescence of N,S-CDs could be effectively quenched when curcumin(CM) was added into the solution based on the inner filter effect (IFE). The as-prepared N,S-CDs without any modification could be as switch-off fluorescent probe for fluorescence turn-off detection of CM in the range of 0.15–18.0 μmol L?1 with the detection limit of about 0.04 μmol L?1. Moreover, the as-prepared N,S-CDs were successfully employed to the detection of CM in urine samples with satisfactory results. Noticeably, the N,S-CDs showed a distinct temperature-sensitive feature and used to construct fluorescent temperature sensor. Therefore, a convenient approach was proposed that N,S-CDs could be used as a fluorescent probe for rapid and sensitive detection of curcumin and temperature.
关键词： N,S-CDs,Curcumin,Fluorescent sensor,Temperature,Inner filter effect
更新于2025-09-19 17:15:36
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Alloyed Pd Ni hollow nanoparticles as cocatalyst of CdS for improved photocatalytic activity toward hydrogen production
摘要： Photocatalytic hydrogen evolution has been regarded as an efficient method for H2 production, in which the cocatalysts play a crucial role. In this work, two-dimensional (2D) snow-flake CdS was synthesized via a solvothermal method. PdeNi hollow alloy with different compositions were synthesized by a galvanic replacement method, and decorated on CdS surface. The structural microscopic and spectroscopic analysis demonstrated that the formation of PdNi hollow nanoparticles (HNPs) and the decoration of PdNi HNPs on CdS (PdNi/CdS). Photocatalytic hydrogen evolution reaction was performed under visible light irradiation (l ≥ 420 nm). Pd1Ni1/CdS exhibited higher photocatalytic H2 generation rate about 54 mmol/h/g with a quantum efficiency of 63.97% at 420 nm, which was 1.7-fold higher than that of Pd/CdS (32.4 mmol/h/g). The high photocatalytic performance for Pd1Ni1/CdS was mainly attributed to the strong interaction between Pd1Ni1 HNPs and CdS, and the formation of unique hollow structure of PdNi alloy with porous nature which provided more active sites for H2 evolution. Additionally, the synergistic effect between Pd and Ni, as well as the 2D morphology of CdS enhance the mobility of photo-generated charge carriers which minimize their recombination in turn enhance the photocurrent and photocatalytic performance of solar water splitting reaction.
关键词： PdNi hollow NPs,Hydrogen production,Photocatalyst,CdS
更新于2025-09-19 17:15:36
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Controllable design of double metal oxide (NiCo2O4) modified CdS for efficient photocatalytic hydrogen production
摘要： In the present work, we have successfully synthesized a kind of high efficiency NiCo2O4/CdS composite photocatalyst by using hydrothermal method and high temperature calcination. With the addition of NiCo2O4, hydrogen evolution has been greatly improved by successfully adjusting electron transport routes. For the composite catalyst, the maximum number of hydrogen evolution under visible light irradiation for 5 hours reached 549 μmol. Under this phenomenon, the hydrogen production rate of the corresponding composite catalysts reached 10980 μmol.g-1.h-1. The hydrogen production rate of composite catalysts is 5.1 times that of pure CdS under the same conditions. In addition, there is no significant decrease in the photocatalytic activity of the composite catalyst even after 5 cycles of photocatalytic hydrogen production. These phenomena indicate that the introduction of NiCo2O4 inhibits the photo-corrosion of CdS itself and enhances the hydrogen production activity while ensuring the stability of the catalyst. Regarding the physical properties of the NiCo2O4/CdS composite catalyst, we use XRD, SEM, TEM, XPS, BET and UV-vis to study the related of characterization. In photoelectron and hole transport mechanisms, we have studied the catalysts by photoluminescence spectroscopy, transient photocurrent and photoelectrochemical experiments. The introduction of NiCo2O4 increases the active site of the composite catalyst, which facilitates the separation of photogenerated electrons and holes, and accelerates the transfer of electrons.
关键词： Controllable design,CdS,NiCo2O4,Hydrogen production.
更新于2025-09-19 17:15:36
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Preparing CdS QDs in sodium alginate gel: realizing water-solubility and stimuli-responsiveness of QDs in an integrative way
摘要： Quantum dots (QDs) were of great interest due to the excellent fluorescence property and have been widely studied. Comparing with the typical organometallic synthetic routes and hydrothermal method that were usually carried out under high temperature, colloidal template could be used for preparing QDs in mild conditions and have gained increasing attention. In this prospect, hydrogel was an ideal colloidal template for preparation of QDs in aqueous medium while the related study for in-situ preparation of QDs in gel and the consequent functionalization of QDs was in demand. In this paper, we proposed a two-step method to prepare CdS QDs in sodium alginate (SA) gel which showed effective constraint in uniform size distribution of QDs. Without extra ligands introduction, the prepared CdS-SA QDs showed responsiveness to pH and detectability to Fe3+ which provide a simplified way for functionalization of QDs. The CdS-SA QDs showed good biocompatibility and stability in a certain concentration which indicated the application prospect of the CdS-SA QDs in fields of biological labeling and environmental sensor.
关键词： gel,stimuli responsiveness,pH,Sodium alginate,CdS QDs
更新于2025-09-19 17:15:36
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A remarkable effect of Pr doping on key optoelectrical properties of CdS thin films prepared using spray pyrolysis technique for high-performance photodetector applications
摘要： High-quality thin film-based photodetectors containing praseodymium doped cadmium sulfide (Pr:CdS) were fabricated through spray pyrolysis and studied for various opto-electrical applications. Field emission electron microscopy (FE-SEM) revealed that the prepared films were highly compacted with an extremely fine nanostructure without any pinhole or crack. X-ray diffraction and FT-Raman spectroscopy studies confirmed the single hexagonal phase of all the films. The crystallite size was found to lie between 19 and 32 nm. Optical spectroscopy revealed that the fabricated films have low absorbance and high transmittance (in range of 70–80%). The energy gap was found to lie in the range of 2.40–2.44 eV. The PL spectra contained an intense green emission band at ~531 ± 5 nm (2.33 eV), and its intensity was enhanced by increasing the Pr doping content in CdS. The dark and photo currents of CdS increased by approximately 950 and 42 times, respectively with the addition of 5.0 wt.% Pr. The responsivity (R) and specific detectivity (D*) were remarkably enhanced to 2.71 AW-1 and 6.9×1011 Jones, respectively, for the 5.0 wt.% Pr:CdS film. The external quantum efficiency (EQE) of 5 wt.% Pr:CdS films was 43 times that of pure CdS films, and the on/off ratio was 3.95 × 102 for 5.0 wt.% Pr:CdS film. Its high R, D*, and EQE values, and photo-switching behavior make Pr:CdS a good contender for high quality photodetector applications.
关键词： responsivity,external quantum efficiency,detectivity,CdS and Pr: CdS films,opto-electrical properties
更新于2025-09-19 17:13:59
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Quantification of the Photon Absorption, Scattering, and On-resonance Emission Properties of CdSe/CdS Core/Shell Quantum Dots: Effect of Shell Geometry and Volumes
摘要： Reliable quantification of the optical properties of fluorescent quantum dots (QDs) is critical for their photo-chemical, -physical, and -biological applications. Presented herein is the experimental quantification of photon scattering, absorption, and on-resonance-fluorescence (ORF) activities of CdSe/CdS core/shell fluorescent QDs as a function of the shell sizes and geometries. Four spherical QDs (SQDs) with different diameters and four rod-like QDs (RQDs) with different aspect ratios (ARs) have been analyzed using UV-vis, fluorescence, and the recent polarized resonance synchronous spectroscopic (PRS2) methods. All quantum dots are simultaneous absorbers and scatterers in the UV-vis wavelength region, and they all exhibit strong ORF emission in the wavelength regions where the QDs both absorb and emit. The absorption and scattering cross-sections of the CdS shell are linearly and quadratically, respectively, proportional to the shell volume for both the SQDs and RQDs. However, the effects of CdS shell coating on the core optical properties are different between SQDs and RQDs. For RQDs, increasing the CdS shell volume through the length elongation has no effect on either the peak wavelength or intensity of the CdSe core UV-vis absorption and ORF, but it reduces the QD fluorescence depolarization. In contrast, increasing CdS shell volume in the SQDs induces red-shift in the CdSe core peak UV-vis absorption and ORF wavelengths, and increases their peak cross-sections, but it has no effect on the SQD fluorescence depolarization. The RQD ORF cross-sections and quantum yields are significantly higher than their respective counterparts for the SQDs with similar particle sizes (volumes). While these new insights should be significant for the QD design, characterization, and applications, the methodology presented in this work is directly applicable for quantifying the optical activities of optically complex materials where the common UV-vis spectrometry and fluorescence spectroscopy are inadequate.
关键词： quantum dots,CdSe/CdS,photon absorption,shell geometry,scattering,shell volumes,on-resonance fluorescence
更新于2025-09-19 17:13:59
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Spectral converters for CdSa??CdTe solar cell
摘要： Among thin film solar cells, CdSeCdTe solar cell is one of the earliest and most successful devise owing to high absorption co-efficient of CdTe for the solar radiations. However, the conversion efficiency drops drastically below 500 nm due to the absorption in the CdS window layer. Down shifting of 350e500 nm solar radiations is expected to overcome this drawback. It is suggested that Cr3t activators can provide efficient absorption of radiations in near ultraviolet (nUV)-visible region and emission around 700 nm. Synthesis and photoluminescence (PL) characterization of several such phosphors is described. Cr3t exhibits efficient luminescence in aluminate hosts Al5GeO9.5, SrMgAl10O17:Cr, SrMgAl10O17:Eu,Cr which could be easily prepared by combustion synthesis. In oxidic hosts prepared by conventional solid state reaction; Li2Mg3SnO6:Mn4t, emission is obtained close to 700 nm where the CdSeCdTe solar cell has good response. BaAl2Si2O8:Sm2t, and BaB8O13:Sm2t were also prepared by solid state reaction. These phosphors exhibited line emission close to 700 nm and excitation over broad spectra range. All these phosphors were characterized using XRD, photoluminescence (PL) and lifetime measurements. PL spectra are analysed in terms of Racah parameters. The PL characteristics of these phosphors are compared and it is shown that Cr3t doped phosphors possess unwanted excitation beyond 500 nm while Mn4t doped samples show good response either in nUV or in blue region but not both. BaAl2Si2O8:Sm2t has optimum properties among the phosphors studied. It is suitable as a spectral converter for CdSeCdTe solar cell.
关键词： Photoluminescence,Mn4t,CdS-CdTe solar cell,Cr3t,Sm2t
更新于2025-09-19 17:13:59
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CdSe@CdS Dot@Platelet Nanocrystals: Controlled Epitaxy, Mono-Exponential Decay of Two-Dimensional Exciton, and Non-Blinking Photoluminescence of Single Nanocrystal
摘要： Wurtzite CdSe@CdS dot@platelet nanocrystals—a dot-shaped CdSe nanocrystal encased within an epitaxially-grown CdS nanoplatelet—are controllably synthesized with nearly monodisperse size/shape distribution and outstanding photoluminescence (PL) properties. The excellent size/shape control with their lateral to thickness dimension ratio up to 3 to 1 is achieved by systematically studying the synthetic parameters, which results in a simple, tunable yet reproducible epitaxy scheme. This special type of core/shell nanocrystals possess two-dimensional emission dipole with the ab plane of the wurtzite structure. While their near-unity PL quantum yield and mono-exponential PL decay dynamics are at the same level of the-state-of-art CdSe/CdS core/shell nanocrystals in dot shape, CdSe@CdS dot@platelet nanocrystals possess ~2 orders of magnitude lower probability for initiating PL blinking at single-nanocrystal level than the dot-shaped counterparts do.
关键词： dot@platelet nanocrystals,non-blinking,photoluminescence,CdSe@CdS,epitaxy
更新于2025-09-19 17:13:59
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Study on the Stability of Unpackaged CdS/CdTe Solar Cells with Different Structures
摘要： In this work, the stability of unpackaged CdTe solar cells with di?erent con?gurations was investigated according to the International Electrotechnical Commission IEC 61215-2016. The measurements of thermal cycling from -40°C to +85°C and 24-hour temperature cycling from -40°C to +85°C were carried out in CdS/CdTe solar cells with structures of FTO/CdS/CdTe/Au, FTO/CdS/CdTe/back contact/Au, and FTO/MZO/CdS/CdTe/back contact/Au, respectively. The performances of these cells before and after the thermal aging experiments were investigated by using light and dark I‐V together with C‐V. The results reveal varied performance degradation before and after thermal aging in the cells with di?erent structures. Among these, the most deteriorated device is the one without back contact (BC), whose e?ciency decreased by 25.12% after thermal cycling accompanying an obvious roll-over phenomenon when forward bias was greater than open circuit voltage. On the contrary, the reduction in the e?ciency was about 16.80% in the case cells with BC, and the roll-over phenomenon was not so signi?cant. Furthermore, for the devices with optimized front contact of FTO/MZO, the thermal stability was improved obviously. Interestingly, short-circuit current density associated with the carrier concentration of cells remained relatively small variations compared with the change of Voc and ?ll factor. All the results indicated that an e?cient back contact layer and an optimized front electrode were the indispensable structural elements to attain high stabilization in the CdS/CdTe solar cells.
关键词： front electrode,thermal cycling,back contact,CdS/CdTe solar cells,stability
更新于2025-09-19 17:13:59