Browse
Submit Data
Databases
API
Help

Dataset Information

25 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Aerobic Conditions Enhance the Photocatalytic Stability of CdS/CdO_x Quantum Dots.

ABSTRACT: Photocatalytic H₂ production through water splitting represents an attractive route to generate a renewable fuel. These systems are typically limited to anaerobic conditions due to the inhibiting effects of O₂ . Here, we report that sacrificial H₂ evolution with CdS quantum dots does not necessarily suffer from O₂ inhibition and can even be stabilised under aerobic conditions. The introduction of O₂ prevents a key inactivation pathway of CdS (over-accumulation of metallic Cd and particle agglomeration) and thereby affords particles with higher stability. These findings represent a possibility to exploit the O₂ reduction reaction to inhibit deactivation, rather than catalysis, offering a strategy to stabilise photocatalysts that suffer from similar degradation reactions.

SUBMITTER: Wakerley DW

PROVIDER: S-EPMC6348374 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Aerobic Conditions Enhance the Photocatalytic Stability of CdS/CdOx Quantum Dots.

Wakerley David W DW Ly Khoa H KH Kornienko Nikolay N Orchard Katherine L KL Kuehnel Moritz F MF Reisner Erwin E

Chemistry (Weinheim an der Bergstrasse, Germany) 20180627 69

Photocatalytic H2 production through water splitting represents an attractive route to generate a renewable fuel. These systems are typically limited to anaerobic conditions due to the inhibiting effects of O2 . Here, we report that sacrificial H2 evolution with CdS quantum dots does not necessarily suffer from O2 inhibition and can even be stabilised under aerobic conditions. The introduction of O2 prevents a key inactivation pathway of CdS ...[more]

PMID: 29750379

Similar Datasets

Quasi-type II CuInS2/CdS core/shell quantum dots.

Project description:Ternary chalcopyrite CuInS2 quantum dots (QDs) have been extensively studied in recent years as an alternative to conventional QDs for solar energy conversion applications. However, compared with the well-established photophysics in prototypical CdSe QDs, much less is known about the excited properties of CuInS2 QDs. In this work, using ultrafast spectroscopy, we showed that both conduction band (CB) edge electrons and copper vacancy (VCu) localized holes were susceptible to surface trappings in CuInS2 QDs. These trap states could be effectively passivated by forming quasi-type II CuInS2/CdS core/shell QDs, leading to a single-exciton (with electrons delocalized among CuInS2/CdS CB and holes localized in VCu) half lifetime of as long as 450 ns. Because of reduced electron-hole overlap in quasi-type II QDs, Auger recombination of multiple excitons was also suppressed and the bi-exciton lifetime was prolonged to 42 ps in CuInS2/CdS QDs from 10 ps in CuInS2 QDs. These demonstrated advantages, including passivated trap states, long single and multiple exciton lifetimes, suggest that quasi-type II CuInS2/CdS QDs are promising materials for photovoltaic and photocatalytic applications.

| S-EPMC5975837 | biostudies-literature

Strategy for Encapsulation of CdS Quantum Dots into Zeolitic Imidazole Frameworks for Photocatalytic Activity.

Project description:Encapsulating CdS quantum dots (QDs) into zeolitic imidazole framework-8 (ZIF-8) can offer several advantages for photocatalysis. Various types of capping agents have been used to encapsulate QDs into ZIF-8 nanopores. An effective method for encapsulating CdS QDs into ZIF-8 is to use 2-mercaptoimidazole as the capping agent. This is because 2-mercaptoimidazole is similar to the imidazolate ligands of ZIFs and can used for capping active species with simultaneous encapsulation during the crystal growth of ZIF-8. Compared to other widely used capping agents such as polyvinylpyrrolidone (PVP), using 2-mercaptoimidazole for encapsulating CdS QDs into ZIF-8 revealed photocatalytic effects along with the molecular sieving effect when using differently sized molecular redox mediators such as methyl viologen (MV2+) and diquat (DQ2+).

| S-EPMC7764424 | biostudies-literature

Imidazolium-modification enhances photocatalytic CO2 reduction on ZnSe quantum dots.

Project description:Colloidal photocatalysts can utilize solar light for the conversion of CO2 to carbon-based fuels, but controlling the product selectivity for CO2 reduction remains challenging, in particular in aqueous solution. Here, we present an organic surface modification strategy to tune the product selectivity of colloidal ZnSe quantum dots (QDs) towards photocatalytic CO2 reduction even in the absence of transition metal co-catalysts. Besides H2, imidazolium-modified ZnSe QDs evolve up to 2.4 mmolCO gZnSe -1 (TONQD > 370) after 10 h of visible light irradiation (AM 1.5G, λ > 400 nm) in aqueous ascorbate solution with a CO-selectivity of up to 20%. This represents a four-fold increase in CO-formation yield and 13-fold increase in CO-selectivity compared to non-functionalized ZnSe QDs. The binding of the thiolated imidazolium ligand to the QD surface is characterized quantitatively using 1H-NMR spectroscopy and isothermal titration calorimetry, revealing that a subset of 12 to 17 ligands interacts strongly with the QDs. Transient absorption spectroscopy reveals an influence of the ligand on the intrinsic charge carrier dynamics through passivating Zn surface sites. Density functional theory calculations indicate that the imidazolium capping ligand plays a key role in stabilizing the surface-bound *CO2 - intermediate, increasing the yield and selectivity toward CO production. Overall, this work unveils a powerful tool of using organic capping ligands to modify the chemical environment on colloids, thus enabling control over the product selectivity within photocatalyzed CO2 reduction.

| S-EPMC8261709 | biostudies-literature

Photocatalytic activity of CdS and Ag(2)S quantum dots deposited on poly(amidoamine) functionalized carbon nanotubes.

Project description:Two novel ternary nanocatalysts, f-MWCNTs-CdS and f-MWCNTs-Ag(2)S were successfully constructed by covalent grafting of fourth generation (G4) hyperbranched, crosslinked poly(amidoamine) (PAMAM) to carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) and subsequent deposition of CdS or Ag(2)S quantum dots (QDs). The structural transformation, surface potential, and morphology of functionalized MWCNTs (f-MWCNTs) and nanocatalysts were characterized by UV-vis spectrophotometer, Fourier transform infrared spectroscopy, powder X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and energy dispersive spectroscopy. Transmission electron microscopy reveals the effective anchoring of QDs on f-MWCNTs. The catalytic activity of nanocatalysts was evaluated by photodegradation of methyl orange under illumination of UV light. The coupling of MWCNTs, PAMAM and CdS or Ag(2)S QDs significantly enhanced the catalytic efficiency of nanocatalysts. The rate constants for degradation of methyl orange in presence of nanocatalysts were calculated using the Langmuir-Hinshelwood model. Overall, the excellence in photodegradation was accomplished by hybridizing f-MWCNTs with CdS or Ag(2)S.

| S-EPMC3259686 | biostudies-literature

CsPbBr3/CdS Core/Shell Structure Quantum Dots for Inverted Light-Emitting Diodes Application.

Project description:Novel CsPbBr3/CdS core/shell structure quantum dots (QDs) were successfully synthesized using a facile hot-injection method. The corresponding CsPbBr3/CdS QDs based light-emitting diodes (QLEDs) were further prepared, which demonstrated the maximum luminance of 354 cd/m2 and an external quantum efficiency (EQE) of 0.4% with the current efficiency (CE) of 0.3 cd/A. Moreover, the optoelectronic performance of the CsPbBr3/CdS QDs based QLEDs exhibited a comparable enhancement in contrast to the pure CsPbBr3 QDs based QLEDs. Hypothetically, the novel CsPbBr3/CdS structure QDs introduced one new route for advanced light emission applications of perovskite materials.

| S-EPMC6640208 | biostudies-literature

Directed Energy Transfer from Monolayer WS2 to Near-Infrared Emitting PbS-CdS Quantum Dots.

Project description:Heterostructures of two-dimensional (2D) transition metal dichalcogenides (TMDs) and inorganic semiconducting zero-dimensional (0D) quantum dots (QDs) offer useful charge and energy transfer pathways, which could form the basis of future optoelectronic devices. To date, most have focused on charge transfer and energy transfer from QDs to TMDs, that is, from 0D to 2D. Here, we present a study of the energy transfer process from a 2D to 0D material, specifically exploring energy transfer from monolayer tungsten disulfide (WS2) to near-infrared emitting lead sulfide-cadmium sulfide (PbS-CdS) QDs. The high absorption cross section of WS2 in the visible region combined with the potentially high photoluminescence (PL) efficiency of PbS QD systems makes this an interesting donor-acceptor system that can effectively use the WS2 as an antenna and the QD as a tunable emitter, in this case, downshifting the emission energy over hundreds of millielectron volts. We study the energy transfer process using photoluminescence excitation and PL microscopy and show that 58% of the QD PL arises due to energy transfer from the WS2. Time-resolved photoluminescence microscopy studies show that the energy transfer process is faster than the intrinsic PL quenching by trap states in the WS2, thus allowing for efficient energy transfer. Our results establish that QDs could be used as tunable and high PL efficiency emitters to modify the emission properties of TMDs. Such TMD-QD heterostructures could have applications in light-emitting technologies or artificial light-harvesting systems or be used to read out the state of TMD devices optically in various logic and computing applications.

| S-EPMC8155326 | biostudies-literature

Modifying SnS2 With Carbon Quantum Dots to Improve Photocatalytic Performance for Cr(VI) Reduction.

Project description:The photoreduction for hazardous Cr(VI) in industrial wastewater has been considered a "green" approach with low-cost and easy-to-go operation. SnS2 is a promising narrow bandgap photocatalyst, but its low charge carrier separation efficiency should be solved first. In this work, N-doped carbon quantum dots (CQDs) were prepared and loaded onto SnS2 nanoparticles via an in situ method. The resulting composite samples (NC@SnS2) were characterized, and their photocatalytic performance was discussed. SnS2 nanoparticles were obtained as hexagonal ones with a bandgap of 2.19 eV. The optimal doping level for NC@SnS2 was citric acid: urea:SnS2 = 1.2 mmol:1.8 mmol:3.0 mmol. It showed an average diameter of 40 nm and improved photocatalytic performance, compared to pure SnS2, following a pseudo-first-order reaction with a kinetic rate constant of 0.1144 min-1. Over 97% of Cr(VI) was photo-reduced after 30 min. It was confirmed that modification of SnS2 with CQDs can not only improve the light-harvesting ability but also stimulate the charge separation, which therefore can enhance the photoreactivity of SnS2 toward Cr(VI) reduction. The excellent stability of NC@SnS2 indicates that it is promising to be practically used in industrial wastewater purification.

| S-EPMC9257045 | biostudies-literature

New Understanding on Photocatalytic Mechanism of Nitrogen-Doped Graphene Quantum Dots-Decorated BiVO4 Nanojunction Photocatalysts.

Project description:Bismuth vanadate (BiVO4) is a promising candidate as a visible-light-driven photocatalyst in the aspect of practical applications. To investigate the origin of active species from BiVO4 and understand the influence of the variations of the photocatalytic process, comparative studies on zero-dimensional nitrogen-doped graphene quantum dot (NGQD)-decorated BiVO4 have been carried out for methylene blue photodegradation. It was found that the hydroxyl group-rich NGQD surface and the established heterojunction structure between NGQDs and BiVO4 were greatly beneficial for the conversion of the •OH radical. With NGQD decoration, the dominant oxidant species for NGQDs/BiVO4 were confirmed to be •OH and H2O2, rather than holes originating from the valence band of unmodified BiVO4. The synergistic photocatalytic mechanism with respect to the interfacial charge transport and the conversion of active species was proposed. The achievement of the controllable active species significantly altering the activity may be applied for different photocatalytic reactions.

| S-EPMC6641612 | biostudies-literature

The Size Effect of TiO2 Hollow Microspheres on Photovoltaic Performance of ZnS/CdS Quantum Dots Sensitized Solar Cell.

Project description:Size controllable TiO2 hollow microspheres (HMS) were synthesized by a carbonaceous spheres (CS) template method. Based on TiO2 HMS, the ZnS/CdS quantum dots (QDs) were loaded to form a ZnS/CdS@TiO2 HMS photoanode for quantum dots sensitized solar cell (QDSSC). The size effects of TiO2 HMS on photovoltaic performance were investigated, and showed that TiO2 HMS with sizes ~560 nm produced the best short-circuit current density (Jsc) of 8.02 mA cm-2 and highest power conversion efficiency (PCE) of 1.83%, showing a better photovoltaic performance than any other QDSSCs based on TiO2 HMS with size ~330 nm, ~400 nm, and ~700 nm. The improvement of photovoltaic performance based on ~560 nm TiO2 HMS which can be ascribed to the enhanced light harvesting efficiency caused by multiple light reflection and strong light scattering of TiO2 HMS. The ultraviolet-visible (UV-vis) spectra and incident photo to the current conversion efficiency (IPCE) test results confirmed that the size of TiO2 HMS has an obvious effect on light harvesting efficiency. A further application of ~560 nm TiO2 HMS in ZnS/PbS/CdS QDSSC can improve the PCE to 2.73%, showing that TiO2 HMS has wide applicability in the design of QDSSCs.

| S-EPMC6566662 | biostudies-literature

Dynamics of Intermittent Delayed Emission in Single CdSe/CdS Quantum Dots.

Project description:Bright and fast fluorescence makes semiconductor nanocrystals, or quantum dots (QDs), appealing for applications ranging from biomedical research to display screens. However, a few percent of their fluorescence intensity is surprisingly slow. Research into this "delayed emission" has been scarce, despite undesired consequences for some applications and potential opportunities for others. Here, we characterize the dynamics of delayed emission exhibited by individual CdSe/CdS core/shell QDs and correlate these with changes in the emission spectrum. The delayed-emission intensity from a single QD fluctuates strongly during an experiment of several minutes and is thus not always "on", implying that control over delayed emission may be possible. Periods of bright delayed emission correlate with red-shifted emission spectra. This behavior is consistent with exciton polarization by fluctuating electric fields due to diffusing surface charges, which have been known to cause spectral diffusion in QDs. Our findings thus provide a stepping stone for future efforts to control delayed emission.

| S-EPMC7309328 | biostudies-literature