A rapid, ultrasensitive and convenient fluorescence measurement technology based on the enhancement of the fluorescence intensity resulting from the interaction of functionalized CdSe/CdS quantum dots （QDs） with bov...A rapid, ultrasensitive and convenient fluorescence measurement technology based on the enhancement of the fluorescence intensity resulting from the interaction of functionalized CdSe/CdS quantum dots （QDs） with bov/ne serum albumin （BSA） was proposed. The citrate-stabilized CdSe/CdS （QDs） were synthesized by using Se powder and Na2S as precursors instead of any pyrophoric organometallic precursors. The modified CdSe/CdS QDs are brighter and more stable against photobleaching in comparison with organic fluorophores. At pH 7.0, the fluorescence signal of CdSe/CdS is enhanced by increasing the concentration of BSA in the range of 0.1-10 μg/mL, and the low detection limit is 0.06 μg/mL. A linear relationship between the enhanced fluorescence peak intensity （△F） and BSA concentration （c） is established using equation △F=50.7c＋16.4 （R=0.996 36）. Results of determination for BSA in three synthetic samples are identical with the true values, and the recovery （98.9%-102.4%） and relative standard deviation （RSD, 1.8%-2.5%） are satisfactory.展开更多
A new and convenient route is developed to synthesize CdSe and core-shell CdSe/CdS quantum dots（QDs） in aqueous solution.The gaseous precursors,H2Se and H2S,generated on-line by reducing SeO 3 2à with NaBH 4 an...A new and convenient route is developed to synthesize CdSe and core-shell CdSe/CdS quantum dots（QDs） in aqueous solution.The gaseous precursors,H2Se and H2S,generated on-line by reducing SeO 3 2à with NaBH 4 and the reaction between Na 2 S and diluted H2SO 4,are used to form high-quality CdSe and CdSe/CdS QDs,respectively.The synthesized water-soluble CdSe and CdSe/CdS QDs possess high quantum yield（3% and 20%） and narrow full-width-at-half-maximum（43 nm and 38 nm）.The synthesis process is easily reproducible with simple apparatus and low-toxic chemicals,and can be readily extended to the large-scale aqueous synthesis of QDs.展开更多
Toxicities of CdSe and CdSe/CdS quantum dots （QDs） synthesized by ultrasound-assisted methods were investigated in vitro and in vivo. Five human cell lines were used to assess the cytotoxicity of as-prepared CdSe an...Toxicities of CdSe and CdSe/CdS quantum dots （QDs） synthesized by ultrasound-assisted methods were investigated in vitro and in vivo. Five human cell lines were used to assess the cytotoxicity of as-prepared CdSe and CdSe/CdS by assays of MTT viability, red blood cell hemolysis, flow cytometry, and fluorescence imaging. The results show that these QDs may be cytotoxic by their influence in S and G2 phases in cell cycles. The cytotoxicity of QDs depends on both the physicochemical properties and related to target cells.展开更多
The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe...The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe technique. By selectively exciting the core and shell carrier, the dynamics are studied in detail. Carrier relaxation is found faster in the conduction band of the CdS shell （about 130 fs） than that in the conduction band of the CdSe core （about 400 fs）. From the experiments it is distinctly demonstrated the existence of the defect states in the interface between the CdSe core and the CdS shell, indicating that ultrafast spectroscopy might be a suitable tool in studying interface and surface morphology properties in nanosystems.展开更多
This work demonstrated the feasibility of detecting hydrocortisone in cosmetics using a novel CdSe/CdS quan- tum dots-based competitive fluoroimmunoassay with magnetic core/shell Fe3Oa/Au nanoparticles （MCFN） as sol...This work demonstrated the feasibility of detecting hydrocortisone in cosmetics using a novel CdSe/CdS quan- tum dots-based competitive fluoroimmunoassay with magnetic core/shell Fe3Oa/Au nanoparticles （MCFN） as solid carriers. Hydrocortisone antigen was labeled with the synthesized core/shell CdSe/CdS quantum dots （QDs） to form the antigen-QDs conjugate. Meanwhile, hydrocortisone antibody was incubated with MCFN and the immobilized antibody was obtained. The immobilized antibody was then mixed sequentially with hydrocortisone and a slightly excess amount of the QDs-labeled hydrocortisone antigen, allowing their competition for binding with the antibody immobilized on MCFN. The bound hydrocortisone and the antigen-QDs conjugates on MCFN were removed subsequently after the mixture was applied to a magnetic force. The analyte concentration was obtained by measuring the fluorescence intensity of the unbound hydrocortisone antigen-QDs conjugates. The proposed method was characterized by simplicity, rapidity, and high sensitivity with a wide linear working range of 0.5 to 15000 pg·mL^-1 and a low detection limit of 0.5 pg.mL^- 1. The proposed method was successfully applied to the determination of hydrocortisone in cosmetics with satisfactory results.展开更多
The rapid recombination of photogenerated carriers poses a significant limitation on the use of CdS quantum dots(QDs)in photocatalysis.Herein,the construction of a novel S-scheme heterojunction between cubic-phase CdS...The rapid recombination of photogenerated carriers poses a significant limitation on the use of CdS quantum dots(QDs)in photocatalysis.Herein,the construction of a novel S-scheme heterojunction between cubic-phase CdS QDs and hollow nanotube In_(2)O_(3)is successfully achieved using an electrostatic self-assembly method.Under visible light irradiation,all CdS-In_(2)O_(3)composites exhibit higher hydrogen evolution efficiency compared to pure CdS QDs.Notably,the photocatalytic H_(2)evolution rate of the optimal CdS-7%In_(2)O_(3)composite is determined to be 2258.59μmol g^(−1)h^(−1),approximately 12.3 times higher than that of pure CdS.The cyclic test indicates that the CdS-In_(2)O_(3)composite maintains considerable activity even after 5 cycles,indicating its excellent stability.In situ X-ray photoelectron spectroscopy and density functional theory calculations confirm that carrier migration in CdS-In_(2)O_(3)composites adheres to a typical S-scheme heterojunction mechanism.Additionally,a series of characterizations demonstrate that the formation of S-scheme heterojunctions between In_(2)O_(3)and CdS inhibits charge recombination and accelerates the separation and migration of photogenerated carriers in the CdS QDs,thus achieving enhanced photocatalytic performance.This work elucidates the pivotal role of S-scheme heterojunctions in photocatalytic H_(2)production and offers novel insights into the construction of effective composite photocatalysts.展开更多
Water-soluble CdSe quantum dots(QDs) were synthesized in aqueous solution with thioglycollic acid as stabilizer.CdSe QDswere characterized using Transmission electron microscopy(TEM),UV-Vis absorption spectrum(UV-Vis)...Water-soluble CdSe quantum dots(QDs) were synthesized in aqueous solution with thioglycollic acid as stabilizer.CdSe QDswere characterized using Transmission electron microscopy(TEM),UV-Vis absorption spectrum(UV-Vis) and fluorescence spectra(FL).The characterization results indicate that as-synthesized CdSe QD was uniform at about 3.5 nm.展开更多
CdSe quantum dots(QDs)hybridized with graphene oxide(GO)are synthesized by a facile chemical precipitation method.The absorption of the CdSe/GO nanocomposite is increased with a significantblue shift with respect to C...CdSe quantum dots(QDs)hybridized with graphene oxide(GO)are synthesized by a facile chemical precipitation method.The absorption of the CdSe/GO nanocomposite is increased with a significantblue shift with respect to CdSe QDs.The specific surface area of the CdSe/GO nanocomposite is10.4m2/g,which is higher than that of CdSe QDs(5m2/g).The PL intensity of the CdSe/GO nanocomposite is lower than that of the CdSe QDs owing to the inhibition of the recombination of electron‐hole pairs in the composite.In Raman analysis,the two bands of the CdSe/GO nanocomposite are shifted to higher wavenumbers with respect to graphene oxide,which is attributed to electron injection that is induced by CdSe QDs into graphene oxide.Using the Brilliant Green dye,the photocatalytic reduction efficiency of CdSe QDs and the CdSe/GO nanocomposite under sunlight irradiation for90min are approximately81.9%and95.5%,respectively.The calculated photodegradation rate constants for CdSe QDs and the CdSe/GO nanocomposite are0.0190min–1and0.0345min–1,respectively.The enhanced photocatalytic activity of the CdSe/GO nanocomposite can be attributed to the high specific surface area and the reduction of electron‐hole pair recombination because of the introduction of graphene oxide.展开更多
Fabrication of well-designed heterojunctions is an extraordinarily attractive pathway for boosting the photocatalytic activity toward CO_(2) photoreduction.Herein,a novel kind of na nosheet-based intercalation hybrid ...Fabrication of well-designed heterojunctions is an extraordinarily attractive pathway for boosting the photocatalytic activity toward CO_(2) photoreduction.Herein,a novel kind of na nosheet-based intercalation hybrid coupled with CdSe quantum dots(QDs) was successfully fabricated by a facile solvothermal method and served as photocatalyst for full-spectrum-light-driven CO_(2) reduction.Ultra-small CdSe QDs were rationally in-situ introduced and coupled with lamellar ZnSe-intercalation hybrid nanosheet,resulting in the formation of CdSe Q.Ds/ZnSe hybrid heterojunction.Significantly,the concentration of Cd^(2+) could change directly the crystallinity and micromorphology of ZnSe intercalation hybrid,which in turn would impact on the photocatalysis activity.The optimized CdSe QDs/ZnSe hybrid-5 composite demonstrated a considerable CO yield rate of the 25.6 μmol g^(-1) h^(-1) without any additional cocatalysts or sacrificial agents assisting,making it one of the best reported performance toward CO_(2) photoreduction under full-spectrum light.The elevated CO_(2) photoreduction activity could be attributed to the special surface heterojunction,leading to improving the ability of light absorption and promoting the separation/transfer of photogenerated carriers.This present study developed a new strategy for designing inorganic-organic heterojunctions with enhanced photocatalyst for CO_(2) photoreduction and provided an available way to simultaneously mitigate the greenhouse effect and alleviate energy shortage pressure.展开更多
This paper reported an efficient and rapid method to produce highly monodispersed CdSe quantum dots (QDs), in which the traditional trioctylphosphine oxide (TOPO) was replaced by paraffin liquid as solvent and oleic a...This paper reported an efficient and rapid method to produce highly monodispersed CdSe quantum dots (QDs), in which the traditional trioctylphosphine oxide (TOPO) was replaced by paraffin liquid as solvent and oleic acid as the reacting media. The experimental conditions and the properties of QDs had been studied in detail. The resulting samples were confirmed of uniform size distribution with transmission electronic microscopy (TEM), while UV-vis absorption and photoluminescence (PL) spectra clearly indicated that such synthesized QDs had good fluorescence properties.展开更多
CdSe quantum dots (QDs) (2 - 3 nm) were synthesized by chemical precipitation method. Optical and structure properties of the products were investigated by scanning tunneling microscope (STM), X-ray diffraction (XRD),...CdSe quantum dots (QDs) (2 - 3 nm) were synthesized by chemical precipitation method. Optical and structure properties of the products were investigated by scanning tunneling microscope (STM), X-ray diffraction (XRD), and ultra violet-visible (UV-Vis) spectrophotometer. The results show that high-quality cubic CdSe QDs were obtained. It is also obtained that temperature is one of the most important factors the affect on the particle size and optical properties of the prepared QDs samples.展开更多
CdSe quantum dot sensitized solar cells （QDSCs） modified with graphene quantum dots （GQDs） have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage （Voc） of the...CdSe quantum dot sensitized solar cells （QDSCs） modified with graphene quantum dots （GQDs） have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage （Voc） of the modified QDSCs was approximately 0.04 V higher than that of plain CdSe QDSCs, consequently improving the photovoltaic performance of the resulting QDSCs. Served as a novel coating on the CdSe QD sensitized photoanode, GQDs played a vital role in improving Voc due to the suppressed charge recombination which has been confirmed by electron impedance spectroscopy as well as transient photovoltage decay measure- ments. Moreover, different adsorption sequences, concentration and deposition time of GQDs have also been systematically investigated to boost the power conversion efficiency （PCE） of CdSe QDSCs. After the coating of CdSe with GQDs, the resulting champion CdSe QDSCs exhibited an improved PCE of 6.59% under AM 1.5G full one sun illumination.展开更多
The interaction of CdSe quantum dots （QDs） with bovine serum albumin （BSA） has been investigated with ultraviolet visible absorption spectroscopy （UVAS）. It was found that the absorption intensity of CdSe QDs si...The interaction of CdSe quantum dots （QDs） with bovine serum albumin （BSA） has been investigated with ultraviolet visible absorption spectroscopy （UVAS）. It was found that the absorption intensity of CdSe QDs significantly decreased after adding BSA solution, showing that CdSe QDs were bonded to BSA. The binding molar ratio was 1：1 and the binding constant was 9.7 × 10^6 L mol^-1.展开更多
This work mainly investigated the influences of some factors, such as, synthesis methods, precursor alteraatives, and vacuum heat-treating process, etc, on the fluorescent characteristics of the semiconductor quantum ...This work mainly investigated the influences of some factors, such as, synthesis methods, precursor alteraatives, and vacuum heat-treating process, etc, on the fluorescent characteristics of the semiconductor quantum dots synthesized by aqueous phase. The research results indicate that the fluorescent characteristic of water- solution sample prepared from Na2 SO3 precursor was sensitive to water bath heating time, and specially, its photohuninescence spectrum shows the unique phenomenon of double excitation and emission peaks. Meanwhile, the fluorescent characteristic of water- solution sample prepared from NaBH4 precursor is slightly influenced by water bath heating time, and the sugface of CdSe quantum dots could be passivated by the excessive amount of NaBH4 precursor, which results in the effective decrease of surface traps and great enhancement of quantum yield. Furthermore, the fluorescent emission peaks of samples could be sharpened by vacuum heat-treating process, with its spectral full width at half of maximum （FWHM） around 30- 40 run, so the emission peaks become redshifi, of which the intensity greatly increases.展开更多
Poly(organophosphazenes) have potential applications in making water-soluble and biocompatible quantum dots (QDs) due to their wide variety of properties. The CdSe QDs of green emission and the core-shell CdSe/ZnS QDs...Poly(organophosphazenes) have potential applications in making water-soluble and biocompatible quantum dots (QDs) due to their wide variety of properties. The CdSe QDs of green emission and the core-shell CdSe/ZnS QDs of red emission were prepared. Subsequently the trioctylphosphine oxide-stabilized CdSe/ZnS QDs were transferred from chloroform into water through a ligand exchange process with poly(glycino amino acid)phosphazenes, which can be obtained from the saponification of poly (glycino amino ester)phosphazenes at room temperature. The resulting QDs-polymer nanocomposite particles can form colloidally stable suspensions in water and exhibit good photostability.展开更多
Colloidal CdSe quantum dots(QDs)are promising materials for solar cells because of their simple preparation pro-cess and compatibility with flexible substrates.The QD radiative recombination lifetime has attracted eno...Colloidal CdSe quantum dots(QDs)are promising materials for solar cells because of their simple preparation pro-cess and compatibility with flexible substrates.The QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery electrodes.However,the scaling law for the exciton radiative lifetime in CdSe QDs is still a puzzle.This article presents a novel explanation that recon-ciles this controversy.Our calculations agree with the experimental measurements of all three divergent trends in a broadened energy window.Further,we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton states.Each of the contradictory size-dependent patterns reflects this trend in a specific size range.As the optical band gap increases,the radiative lifetime decreases in larger QDs,increases in smaller QDs,and is weakly depend-ent on size in the intermediate energy region.This study addresses the inconsistencies in the scaling law of the exciton life-time and gives a unified interpretation over a widened framework.Moreover,it provides valuable guidance for carrier separa-tion in the thin film solar cell of CdSe QDs.展开更多
Widespread usage of engineered metallic quantum dots(QDs)within consumer products has evoked a need to assess their fate within environmental systems.QDs are mixed-metal nanocrystals that often include Cd2+which poses...Widespread usage of engineered metallic quantum dots(QDs)within consumer products has evoked a need to assess their fate within environmental systems.QDs are mixed-metal nanocrystals that often include Cd2+which poses a health risk as a nanocrystal or when leached into water.The goal of this work is to study the long-term metal cation leaching behavior and the factors affecting the dissolution processes of mercaptopropionic acid(MPA)capped CdSe/ZnS QDs in aphotic conditions.QD suspensions were prepared in different water conditions,and release of Zn2+and Cd2+cations were monitored over time by size exclusion chromatography-inductively coupled plasm a-mass spectrometry.In most conditions with dissolved 02 present,the ZnS shell degraded fairly rapidly over^1 week,while some of the CdSe core remained up to 80 days.Additional MPA,Zn2+,and Cd2+temporarily delayed dissolution,indicating a moderate role for capping agent detachment and mineral solubility.The presence of H2 O2 and the ligand ethylenediaminetetraacetate accelerated dissolution,while NOM had no kinetic effect.No dissolution of CdSe core was observed when 02 was absent or when QDs formed aggregates at higher concentrations with 02 present.The shrinking particle model with product layer diffusion control best describes Zn2+and Cd2+dissolution kinetics.The longevity of QDs in their nanocrystal form appears to be partly controlled by environmental conditions,with anoxic,aphotic environments preserving the core mineral phase,and oxidants or complexing ligands promoting shell and core mineral dissolution.展开更多
The optical properties of CdSe/ZnS quantum dots(QDs)embedded in polydimethylsiloxane(PDMS)flexible materials after irradiated withγ-rays were studied.As an embedding matrix,PDMS exhibits the advantage of high radiati...The optical properties of CdSe/ZnS quantum dots(QDs)embedded in polydimethylsiloxane(PDMS)flexible materials after irradiated withγ-rays were studied.As an embedding matrix,PDMS exhibits the advantage of high radiation hardness.The luminescence spectra and fluorescence lifetime of the irradiated and unirradiated samples were tested.The fluorescence intensity of QDs decreases with the increase of the irradiation dose according to the result of luminescence spectra.The fluorescence intensity of the QDs decreases by 80%after irradiation with a dose of 1 kGy,but the position of the emission peak and the spectral shape of the QDs remain consistent before and after irradiation.In addition,the fluorescence lifetime of QDs is shortened after irradiation.Based on the fluorescence response of QDs to the irradiation ofγ-rays and combined with flexible materials,our work provides a theoretical basis for the application of QDs as a new wearable dosimeter.展开更多
Room-temperature negative differential resistance （NDR） has been observed in different types of organic materials. However, detailed study on the influence of the organic material on NDR performance is still scarce....Room-temperature negative differential resistance （NDR） has been observed in different types of organic materials. However, detailed study on the influence of the organic material on NDR performance is still scarce. In this work, room-temperature NDR ＆ observed when CdSe quantum dot （QD） modified ITO is used as the electrode. Furthermore, material dependence of the NDR performance is observed by selecting materials with different charge transporting properties as the active layer, respectively. A peak-to-valley current ratio up to 9 is observed. It is demonstrated that the injection barrier between ITO and the organic active layer plays a decisive role for the device NDR performance. The influence of the aggregation state of CdSe QDs on the NDR performance is also studied, which indicates that the NDR is caused by the resonant tunneling process in the ITO/CdSe QD/organic active layer structure.展开更多
基金Project(50772133) supported by the National Natural Science Foundation of China
文摘A rapid, ultrasensitive and convenient fluorescence measurement technology based on the enhancement of the fluorescence intensity resulting from the interaction of functionalized CdSe/CdS quantum dots （QDs） with bov/ne serum albumin （BSA） was proposed. The citrate-stabilized CdSe/CdS （QDs） were synthesized by using Se powder and Na2S as precursors instead of any pyrophoric organometallic precursors. The modified CdSe/CdS QDs are brighter and more stable against photobleaching in comparison with organic fluorophores. At pH 7.0, the fluorescence signal of CdSe/CdS is enhanced by increasing the concentration of BSA in the range of 0.1-10 μg/mL, and the low detection limit is 0.06 μg/mL. A linear relationship between the enhanced fluorescence peak intensity （△F） and BSA concentration （c） is established using equation △F=50.7c＋16.4 （R=0.996 36）. Results of determination for BSA in three synthetic samples are identical with the true values, and the recovery （98.9%-102.4%） and relative standard deviation （RSD, 1.8%-2.5%） are satisfactory.
文摘A new and convenient route is developed to synthesize CdSe and core-shell CdSe/CdS quantum dots（QDs） in aqueous solution.The gaseous precursors,H2Se and H2S,generated on-line by reducing SeO 3 2à with NaBH 4 and the reaction between Na 2 S and diluted H2SO 4,are used to form high-quality CdSe and CdSe/CdS QDs,respectively.The synthesized water-soluble CdSe and CdSe/CdS QDs possess high quantum yield（3% and 20%） and narrow full-width-at-half-maximum（43 nm and 38 nm）.The synthesis process is easily reproducible with simple apparatus and low-toxic chemicals,and can be readily extended to the large-scale aqueous synthesis of QDs.
基金supported by National Natural Science Foundation of China(No.60976004)Shanghai Municipal Commission for Science and Technology(No.09JC1405300)
文摘Toxicities of CdSe and CdSe/CdS quantum dots （QDs） synthesized by ultrasound-assisted methods were investigated in vitro and in vivo. Five human cell lines were used to assess the cytotoxicity of as-prepared CdSe and CdSe/CdS by assays of MTT viability, red blood cell hemolysis, flow cytometry, and fluorescence imaging. The results show that these QDs may be cytotoxic by their influence in S and G2 phases in cell cycles. The cytotoxicity of QDs depends on both the physicochemical properties and related to target cells.
基金This work was supported by the National Natural Science Foundation of China （No.11074003） and the Key Program of Educational Commission of Anhui Province of China （No.KJ2010AI32）. For the help of Prof. J. L. Zhao at Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences in sample preparation is greatly appreciated.
文摘The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe technique. By selectively exciting the core and shell carrier, the dynamics are studied in detail. Carrier relaxation is found faster in the conduction band of the CdS shell （about 130 fs） than that in the conduction band of the CdSe core （about 400 fs）. From the experiments it is distinctly demonstrated the existence of the defect states in the interface between the CdSe core and the CdS shell, indicating that ultrafast spectroscopy might be a suitable tool in studying interface and surface morphology properties in nanosystems.
基金Project supported by the National Natural Science Foundation of China （Nos. 20345006 and 20575043）.
文摘This work demonstrated the feasibility of detecting hydrocortisone in cosmetics using a novel CdSe/CdS quan- tum dots-based competitive fluoroimmunoassay with magnetic core/shell Fe3Oa/Au nanoparticles （MCFN） as solid carriers. Hydrocortisone antigen was labeled with the synthesized core/shell CdSe/CdS quantum dots （QDs） to form the antigen-QDs conjugate. Meanwhile, hydrocortisone antibody was incubated with MCFN and the immobilized antibody was obtained. The immobilized antibody was then mixed sequentially with hydrocortisone and a slightly excess amount of the QDs-labeled hydrocortisone antigen, allowing their competition for binding with the antibody immobilized on MCFN. The bound hydrocortisone and the antigen-QDs conjugates on MCFN were removed subsequently after the mixture was applied to a magnetic force. The analyte concentration was obtained by measuring the fluorescence intensity of the unbound hydrocortisone antigen-QDs conjugates. The proposed method was characterized by simplicity, rapidity, and high sensitivity with a wide linear working range of 0.5 to 15000 pg·mL^-1 and a low detection limit of 0.5 pg.mL^- 1. The proposed method was successfully applied to the determination of hydrocortisone in cosmetics with satisfactory results.
文摘The rapid recombination of photogenerated carriers poses a significant limitation on the use of CdS quantum dots(QDs)in photocatalysis.Herein,the construction of a novel S-scheme heterojunction between cubic-phase CdS QDs and hollow nanotube In_(2)O_(3)is successfully achieved using an electrostatic self-assembly method.Under visible light irradiation,all CdS-In_(2)O_(3)composites exhibit higher hydrogen evolution efficiency compared to pure CdS QDs.Notably,the photocatalytic H_(2)evolution rate of the optimal CdS-7%In_(2)O_(3)composite is determined to be 2258.59μmol g^(−1)h^(−1),approximately 12.3 times higher than that of pure CdS.The cyclic test indicates that the CdS-In_(2)O_(3)composite maintains considerable activity even after 5 cycles,indicating its excellent stability.In situ X-ray photoelectron spectroscopy and density functional theory calculations confirm that carrier migration in CdS-In_(2)O_(3)composites adheres to a typical S-scheme heterojunction mechanism.Additionally,a series of characterizations demonstrate that the formation of S-scheme heterojunctions between In_(2)O_(3)and CdS inhibits charge recombination and accelerates the separation and migration of photogenerated carriers in the CdS QDs,thus achieving enhanced photocatalytic performance.This work elucidates the pivotal role of S-scheme heterojunctions in photocatalytic H_(2)production and offers novel insights into the construction of effective composite photocatalysts.
文摘Water-soluble CdSe quantum dots(QDs) were synthesized in aqueous solution with thioglycollic acid as stabilizer.CdSe QDswere characterized using Transmission electron microscopy(TEM),UV-Vis absorption spectrum(UV-Vis) and fluorescence spectra(FL).The characterization results indicate that as-synthesized CdSe QD was uniform at about 3.5 nm.
基金supported by the National Natural Science Foundation of China(51774259)Engineering Research Center of Nano-Geo Materials of Ministry of Education(NGM2017KF004 and NGM2017KF012)~~
文摘CdSe quantum dots(QDs)hybridized with graphene oxide(GO)are synthesized by a facile chemical precipitation method.The absorption of the CdSe/GO nanocomposite is increased with a significantblue shift with respect to CdSe QDs.The specific surface area of the CdSe/GO nanocomposite is10.4m2/g,which is higher than that of CdSe QDs(5m2/g).The PL intensity of the CdSe/GO nanocomposite is lower than that of the CdSe QDs owing to the inhibition of the recombination of electron‐hole pairs in the composite.In Raman analysis,the two bands of the CdSe/GO nanocomposite are shifted to higher wavenumbers with respect to graphene oxide,which is attributed to electron injection that is induced by CdSe QDs into graphene oxide.Using the Brilliant Green dye,the photocatalytic reduction efficiency of CdSe QDs and the CdSe/GO nanocomposite under sunlight irradiation for90min are approximately81.9%and95.5%,respectively.The calculated photodegradation rate constants for CdSe QDs and the CdSe/GO nanocomposite are0.0190min–1and0.0345min–1,respectively.The enhanced photocatalytic activity of the CdSe/GO nanocomposite can be attributed to the high specific surface area and the reduction of electron‐hole pair recombination because of the introduction of graphene oxide.
基金supported by the National Natural Science Foundation of China (Nos.51902266 and 22002185)the Fundamental Research Funds for the Central Universities (Nos.310201QD0410 and 3102019ZD0403)+2 种基金the Natural Science Foundation of Beijing (No.2204100)Natural Science Foundation of Shaanxi (No.2020JQ-143)supported by the Research Fund of the State Key Laboratory of Solidification Processing (NPU),China (No.2019-TS-12)。
文摘Fabrication of well-designed heterojunctions is an extraordinarily attractive pathway for boosting the photocatalytic activity toward CO_(2) photoreduction.Herein,a novel kind of na nosheet-based intercalation hybrid coupled with CdSe quantum dots(QDs) was successfully fabricated by a facile solvothermal method and served as photocatalyst for full-spectrum-light-driven CO_(2) reduction.Ultra-small CdSe QDs were rationally in-situ introduced and coupled with lamellar ZnSe-intercalation hybrid nanosheet,resulting in the formation of CdSe Q.Ds/ZnSe hybrid heterojunction.Significantly,the concentration of Cd^(2+) could change directly the crystallinity and micromorphology of ZnSe intercalation hybrid,which in turn would impact on the photocatalysis activity.The optimized CdSe QDs/ZnSe hybrid-5 composite demonstrated a considerable CO yield rate of the 25.6 μmol g^(-1) h^(-1) without any additional cocatalysts or sacrificial agents assisting,making it one of the best reported performance toward CO_(2) photoreduction under full-spectrum light.The elevated CO_(2) photoreduction activity could be attributed to the special surface heterojunction,leading to improving the ability of light absorption and promoting the separation/transfer of photogenerated carriers.This present study developed a new strategy for designing inorganic-organic heterojunctions with enhanced photocatalyst for CO_(2) photoreduction and provided an available way to simultaneously mitigate the greenhouse effect and alleviate energy shortage pressure.
基金Project supported by the National Natural Science Foundation of China (No. 30672017)the Swedish Foundation for Strategic Research (SSF)
文摘This paper reported an efficient and rapid method to produce highly monodispersed CdSe quantum dots (QDs), in which the traditional trioctylphosphine oxide (TOPO) was replaced by paraffin liquid as solvent and oleic acid as the reacting media. The experimental conditions and the properties of QDs had been studied in detail. The resulting samples were confirmed of uniform size distribution with transmission electronic microscopy (TEM), while UV-vis absorption and photoluminescence (PL) spectra clearly indicated that such synthesized QDs had good fluorescence properties.
文摘CdSe quantum dots (QDs) (2 - 3 nm) were synthesized by chemical precipitation method. Optical and structure properties of the products were investigated by scanning tunneling microscope (STM), X-ray diffraction (XRD), and ultra violet-visible (UV-Vis) spectrophotometer. The results show that high-quality cubic CdSe QDs were obtained. It is also obtained that temperature is one of the most important factors the affect on the particle size and optical properties of the prepared QDs samples.
基金supported by the National Natural Science Foundation of China (21175043,91233102)the Fundamental Research Funds for the Central Universities for financial support
文摘CdSe quantum dot sensitized solar cells （QDSCs） modified with graphene quantum dots （GQDs） have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage （Voc） of the modified QDSCs was approximately 0.04 V higher than that of plain CdSe QDSCs, consequently improving the photovoltaic performance of the resulting QDSCs. Served as a novel coating on the CdSe QD sensitized photoanode, GQDs played a vital role in improving Voc due to the suppressed charge recombination which has been confirmed by electron impedance spectroscopy as well as transient photovoltage decay measure- ments. Moreover, different adsorption sequences, concentration and deposition time of GQDs have also been systematically investigated to boost the power conversion efficiency （PCE） of CdSe QDSCs. After the coating of CdSe with GQDs, the resulting champion CdSe QDSCs exhibited an improved PCE of 6.59% under AM 1.5G full one sun illumination.
文摘The interaction of CdSe quantum dots （QDs） with bovine serum albumin （BSA） has been investigated with ultraviolet visible absorption spectroscopy （UVAS）. It was found that the absorption intensity of CdSe QDs significantly decreased after adding BSA solution, showing that CdSe QDs were bonded to BSA. The binding molar ratio was 1：1 and the binding constant was 9.7 × 10^6 L mol^-1.
文摘This work mainly investigated the influences of some factors, such as, synthesis methods, precursor alteraatives, and vacuum heat-treating process, etc, on the fluorescent characteristics of the semiconductor quantum dots synthesized by aqueous phase. The research results indicate that the fluorescent characteristic of water- solution sample prepared from Na2 SO3 precursor was sensitive to water bath heating time, and specially, its photohuninescence spectrum shows the unique phenomenon of double excitation and emission peaks. Meanwhile, the fluorescent characteristic of water- solution sample prepared from NaBH4 precursor is slightly influenced by water bath heating time, and the sugface of CdSe quantum dots could be passivated by the excessive amount of NaBH4 precursor, which results in the effective decrease of surface traps and great enhancement of quantum yield. Furthermore, the fluorescent emission peaks of samples could be sharpened by vacuum heat-treating process, with its spectral full width at half of maximum （FWHM） around 30- 40 run, so the emission peaks become redshifi, of which the intensity greatly increases.
基金Project(2006CB601005) supported by the National Basic Research Program of Chinaproject(200331) supported by the National Excellent Doctoral Dissertations of Chinaproject(Q5009001200801) supported by the Post-Doctoral Science and Technology Foundation from Beijing University of Technology
文摘Poly(organophosphazenes) have potential applications in making water-soluble and biocompatible quantum dots (QDs) due to their wide variety of properties. The CdSe QDs of green emission and the core-shell CdSe/ZnS QDs of red emission were prepared. Subsequently the trioctylphosphine oxide-stabilized CdSe/ZnS QDs were transferred from chloroform into water through a ligand exchange process with poly(glycino amino acid)phosphazenes, which can be obtained from the saponification of poly (glycino amino ester)phosphazenes at room temperature. The resulting QDs-polymer nanocomposite particles can form colloidally stable suspensions in water and exhibit good photostability.
基金supported by the National Key Research and Development Program of China under Grant No.2021YFB2800304.
文摘Colloidal CdSe quantum dots(QDs)are promising materials for solar cells because of their simple preparation pro-cess and compatibility with flexible substrates.The QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery electrodes.However,the scaling law for the exciton radiative lifetime in CdSe QDs is still a puzzle.This article presents a novel explanation that recon-ciles this controversy.Our calculations agree with the experimental measurements of all three divergent trends in a broadened energy window.Further,we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton states.Each of the contradictory size-dependent patterns reflects this trend in a specific size range.As the optical band gap increases,the radiative lifetime decreases in larger QDs,increases in smaller QDs,and is weakly depend-ent on size in the intermediate energy region.This study addresses the inconsistencies in the scaling law of the exciton life-time and gives a unified interpretation over a widened framework.Moreover,it provides valuable guidance for carrier separa-tion in the thin film solar cell of CdSe QDs.
基金financially supported by the United States National Science Foundation(grant number CBET-1254245)
文摘Widespread usage of engineered metallic quantum dots(QDs)within consumer products has evoked a need to assess their fate within environmental systems.QDs are mixed-metal nanocrystals that often include Cd2+which poses a health risk as a nanocrystal or when leached into water.The goal of this work is to study the long-term metal cation leaching behavior and the factors affecting the dissolution processes of mercaptopropionic acid(MPA)capped CdSe/ZnS QDs in aphotic conditions.QD suspensions were prepared in different water conditions,and release of Zn2+and Cd2+cations were monitored over time by size exclusion chromatography-inductively coupled plasm a-mass spectrometry.In most conditions with dissolved 02 present,the ZnS shell degraded fairly rapidly over^1 week,while some of the CdSe core remained up to 80 days.Additional MPA,Zn2+,and Cd2+temporarily delayed dissolution,indicating a moderate role for capping agent detachment and mineral solubility.The presence of H2 O2 and the ligand ethylenediaminetetraacetate accelerated dissolution,while NOM had no kinetic effect.No dissolution of CdSe core was observed when 02 was absent or when QDs formed aggregates at higher concentrations with 02 present.The shrinking particle model with product layer diffusion control best describes Zn2+and Cd2+dissolution kinetics.The longevity of QDs in their nanocrystal form appears to be partly controlled by environmental conditions,with anoxic,aphotic environments preserving the core mineral phase,and oxidants or complexing ligands promoting shell and core mineral dissolution.
基金National Natural Science Foundation of China(No.51775522)Scientific and Technologial Innovation Programs of Higher Education Institutions in Shanxi Province(No.2020L0638)+2 种基金Shanxi Province Key Laboratory of Quantum Sensing and Precision Measurement(No.201905D121001)Shanxi“1331 Project”Key Subjects ConstructionApplied Basic Research Program in Shanxi Province(Nos.201901D211203,201801D221230)。
文摘The optical properties of CdSe/ZnS quantum dots(QDs)embedded in polydimethylsiloxane(PDMS)flexible materials after irradiated withγ-rays were studied.As an embedding matrix,PDMS exhibits the advantage of high radiation hardness.The luminescence spectra and fluorescence lifetime of the irradiated and unirradiated samples were tested.The fluorescence intensity of QDs decreases with the increase of the irradiation dose according to the result of luminescence spectra.The fluorescence intensity of the QDs decreases by 80%after irradiation with a dose of 1 kGy,but the position of the emission peak and the spectral shape of the QDs remain consistent before and after irradiation.In addition,the fluorescence lifetime of QDs is shortened after irradiation.Based on the fluorescence response of QDs to the irradiation ofγ-rays and combined with flexible materials,our work provides a theoretical basis for the application of QDs as a new wearable dosimeter.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61106123 and 61275034the National Basic Research Program of China under Grant No 2013CB328705
文摘Room-temperature negative differential resistance （NDR） has been observed in different types of organic materials. However, detailed study on the influence of the organic material on NDR performance is still scarce. In this work, room-temperature NDR ＆ observed when CdSe quantum dot （QD） modified ITO is used as the electrode. Furthermore, material dependence of the NDR performance is observed by selecting materials with different charge transporting properties as the active layer, respectively. A peak-to-valley current ratio up to 9 is observed. It is demonstrated that the injection barrier between ITO and the organic active layer plays a decisive role for the device NDR performance. The influence of the aggregation state of CdSe QDs on the NDR performance is also studied, which indicates that the NDR is caused by the resonant tunneling process in the ITO/CdSe QD/organic active layer structure.
