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
CdS and CdS/ZnS quantum dots were synthesized by the microemulsion method in sulfosuccinic acid bis(2-ethylhexyl)ester sodium salt(AOT) surfactant reverse micelles containing water.The products were characterized by U...CdS and CdS/ZnS quantum dots were synthesized by the microemulsion method in sulfosuccinic acid bis(2-ethylhexyl)ester sodium salt(AOT) surfactant reverse micelles containing water.The products were characterized by UV-Vis spectrometer,transmission electronmicroscopy(TEM),energy dispersive X-ray spectroscope(EDX)and photoluminescence(PL) spectroscope.The diameter of CdS/ZnS nanoparticle was obvious larger than that of CdS nanoparticle.The diameter of the nanoparticle was estimated,which was confirmed by the images of TEM.The existence of core-shell structure was established by the result of energy dispersive X-ray analysis.PL studies of the samples showed that the luminescence from CdS was enhanced by the ZnS shell.A possible reason was that the ZnS shell reduced the number of defects on the surface of CdS quantum dots,which were assumed to act as centers for radiation-free recombination.展开更多
We have developed a simple one-step process for synthesis of ternary quantum dots(ZnCdSe,MgCdSe) with photoluminescence wavelengths ranging from the red to the blue region of the visible spectrum.The primary aim of th...We have developed a simple one-step process for synthesis of ternary quantum dots(ZnCdSe,MgCdSe) with photoluminescence wavelengths ranging from the red to the blue region of the visible spectrum.The primary aim of this work was to develop a synthesis for the preparation of Cd-containing quantum dots using a Cd precursor with lower toxicity than those used in common syntheses. This synthesis makes use of Cd(acac)_2 which is significantly less toxic than precursors such as CdO and CdCl_2. We have studied the effect of solvent boiling point, precursors and reaction time on the photoluminescence properties of the ternary quantum dots. Ternary quantum dots synthesized from Cd(acac)_2 in low boiling point solvents have photoluminescence wavelengths in the blue region, while those synthesized in high boiling point solvents have photoluminescence wavelengths in the red region.展开更多
A novel chemiluminescence（CL） performance of CdTe/CdS/ZnS quantum dots（QDs） with periodate（KIO_4） was studied.Effects of concentration and pH on the CL system were investigated.Electron spin resonance（ESR） and...A novel chemiluminescence（CL） performance of CdTe/CdS/ZnS quantum dots（QDs） with periodate（KIO_4） was studied.Effects of concentration and pH on the CL system were investigated.Electron spin resonance（ESR） and the effects of radical scavenger analysis were employed for identification of intermediate species.The CL spectra for this system showed only one maximum emission peak centered around 620 nm,which was similar with photoluminescence（PL） spectra of CdTe/CdS/ZnS QDs.The CL of CdTe/CdS/ZnS QDs was induced by direct chemical oxidation and the possible mechanism could be explained by radiative recombination of injected holes and electrons.This investigation not only provided new sight into the optical characteristics of CdTe/CdS/ZnS QDs,but also broadened their potential optical utilizations.展开更多
The synthesis of graphene-semiconductor nanocomposites has attracted increasing attention due to their interesting optoelectronic properties.However the synthesis of such nanocomposites,with decorated particles well d...The synthesis of graphene-semiconductor nanocomposites has attracted increasing attention due to their interesting optoelectronic properties.However the synthesis of such nanocomposites,with decorated particles well dispersed on graphene,is still a great challenge.This work reports a facile,one-step,solvothermal method for the synthesis of graphene-CdS and graphene-ZnS quantum dot nanocomposites directly from graphene oxide,with CdS and ZnS very well dispersed on the graphene nanosheets.Photoluminescence measurements showed that the integration of CdS and ZnS with graphene significantly decreases their photoluminescence.Transient photovoltage studies revealed that the graphene-CdS nanocomposite exhibits a very unexpected strong positive photovoltaic response,while separate samples of graphene and CdS quantum dots(QDs)of a similar size do not show any photovoltaic response.展开更多
The transformation of quantum dots(QDs)by organisms has attracted broad attention but remains unclear.Understanding of the metabolites helps to reveal the transformation pathway of QDs.Cd containingmetallothionein(MT)...The transformation of quantum dots(QDs)by organisms has attracted broad attention but remains unclear.Understanding of the metabolites helps to reveal the transformation pathway of QDs.Cd containingmetallothionein(MT)are the main species formed by Cd released from CdSe QDs in HepG2 cells,while speciation analysis of Cd containing MTs remains a challenge because MTs has several subisoforms and can bind with several metals.Herein,we built a hyphenated platform for speciation analysis of QDs in HepG2 cells after treatment with CdSe/ZnS QDs.The Cd-containing MTs were separated in reversed phase high performance liquid chromatography(RP-HPLC)and subsequently online detected by inductively coupled plasma mass spectrometry(ICP-MS)and electrospray ionization quadrupole time-of-flight mass spectrometry(ESI-Q-TOF-MS)parallelly.Four groups of Cd-containing metabolites were found by detecting Cd in ICP-MS.Their structures were identified in ESI-Q-TOF-MS and further confirmed with standards of four subisoforms of MT,including N-terminal acetylation MT2a,N-terminal acetylation MT1e,N-terminal acetylation MT1g and MT1m.Each group of them contains various stoichiometry of Cd/Zn.The metabolites of QDs remain same while the concentrations of each metabolite and its stoichiometry of Cd/Zn vary for different incubation concentration/time.This work provides a new parallel hyphenation technique of HPLC-ICP-MS/ESI-MS with high separation resolution and powerful detection ability,and the obtained results provide detailed metabolism information of QDs in HepG2 cells after treatment of CdSe/ZnS QDs,contributing to deep exploration of the functional mechanisms of QDs in organisms.展开更多
This work reports on a smartphone-based quantitative POCT system which consists of a paper-based microarray chip,a homemade LEGO dark-box,and a smartphone installed with custom-designed FChip-APP,for on-site quantitat...This work reports on a smartphone-based quantitative POCT system which consists of a paper-based microarray chip,a homemade LEGO dark-box,and a smartphone installed with custom-designed FChip-APP,for on-site quantitation of Fe^(3+),Vitamin 12(VB12),and folic acid(FA).Collection and automatic analysis of fluorescence turn-off response of three kinds of fluorescent nanoprobes which are coated onto filter papers by a smartphone-based device is the principle behind this study.The POCT system exhibits good analytical performance for multiplexed analysis of Fe^(3+),VB_(12)and FA with a wide linear range(Fe^(3+),1.0–14.0μg mL^(-1)(R^(2)=0.983);VB_(12),1.35–40.0μg mL^(-1)(R^(2)=0.991);FA,2.0–26.0μg mL^(-1)(R^(2)=0.994))and low detection limit(Fe^(3+),0.35μg mL^(-1);VB12,0.47μg mL^(-1);FA,0.56μg mL^(-1)).The cost and weight of the whole system are~$220 and~600 g per set,highlighting its cost-eff ectiveness and portability.The simple operation procedures and user-friendly interface of the FChip-APP validate the ease-of-use feature of the reported system.This versatile smartphonebased quantitative POCT system provides a cost-eff ective and easy-of-use method for screening the context-specific causes of anemia and thus its eff ective interventions in the future,especially in resource-limited areas.展开更多
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.
文摘CdS and CdS/ZnS quantum dots were synthesized by the microemulsion method in sulfosuccinic acid bis(2-ethylhexyl)ester sodium salt(AOT) surfactant reverse micelles containing water.The products were characterized by UV-Vis spectrometer,transmission electronmicroscopy(TEM),energy dispersive X-ray spectroscope(EDX)and photoluminescence(PL) spectroscope.The diameter of CdS/ZnS nanoparticle was obvious larger than that of CdS nanoparticle.The diameter of the nanoparticle was estimated,which was confirmed by the images of TEM.The existence of core-shell structure was established by the result of energy dispersive X-ray analysis.PL studies of the samples showed that the luminescence from CdS was enhanced by the ZnS shell.A possible reason was that the ZnS shell reduced the number of defects on the surface of CdS quantum dots,which were assumed to act as centers for radiation-free recombination.
基金CIT (Carnegie Institute of Technology)ICES (Institute of Complex Engineered System) for the financial support of this work
文摘We have developed a simple one-step process for synthesis of ternary quantum dots(ZnCdSe,MgCdSe) with photoluminescence wavelengths ranging from the red to the blue region of the visible spectrum.The primary aim of this work was to develop a synthesis for the preparation of Cd-containing quantum dots using a Cd precursor with lower toxicity than those used in common syntheses. This synthesis makes use of Cd(acac)_2 which is significantly less toxic than precursors such as CdO and CdCl_2. We have studied the effect of solvent boiling point, precursors and reaction time on the photoluminescence properties of the ternary quantum dots. Ternary quantum dots synthesized from Cd(acac)_2 in low boiling point solvents have photoluminescence wavelengths in the blue region, while those synthesized in high boiling point solvents have photoluminescence wavelengths in the red region.
基金supported by the National Natural Science Foundation of China(Nos.81373373,21435002,21227006)
文摘A novel chemiluminescence（CL） performance of CdTe/CdS/ZnS quantum dots（QDs） with periodate（KIO_4） was studied.Effects of concentration and pH on the CL system were investigated.Electron spin resonance（ESR） and the effects of radical scavenger analysis were employed for identification of intermediate species.The CL spectra for this system showed only one maximum emission peak centered around 620 nm,which was similar with photoluminescence（PL） spectra of CdTe/CdS/ZnS QDs.The CL of CdTe/CdS/ZnS QDs was induced by direct chemical oxidation and the possible mechanism could be explained by radiative recombination of injected holes and electrons.This investigation not only provided new sight into the optical characteristics of CdTe/CdS/ZnS QDs,but also broadened their potential optical utilizations.
基金This work was supported by the National Natural Science Foundation of China(No.20820102037)the 973 Project(Nos.2009CB930100 and 2010CB933600)+1 种基金Dr.Ping Wang gratefully acknowledges partial financial support from the China Postdoctoral Science Foundation(No.20090461047)973 Project(No.2007CB613303).
文摘The synthesis of graphene-semiconductor nanocomposites has attracted increasing attention due to their interesting optoelectronic properties.However the synthesis of such nanocomposites,with decorated particles well dispersed on graphene,is still a great challenge.This work reports a facile,one-step,solvothermal method for the synthesis of graphene-CdS and graphene-ZnS quantum dot nanocomposites directly from graphene oxide,with CdS and ZnS very well dispersed on the graphene nanosheets.Photoluminescence measurements showed that the integration of CdS and ZnS with graphene significantly decreases their photoluminescence.Transient photovoltage studies revealed that the graphene-CdS nanocomposite exhibits a very unexpected strong positive photovoltaic response,while separate samples of graphene and CdS quantum dots(QDs)of a similar size do not show any photovoltaic response.
基金The financial support from the National Natural Science Foundation of China(Nos.21575107,21775113,21575108)the Science Fund for Creative Research Groups of NSFC(No.20921062)the Fundamental Research Funds for the Central Universities(No.114009)。
文摘The transformation of quantum dots(QDs)by organisms has attracted broad attention but remains unclear.Understanding of the metabolites helps to reveal the transformation pathway of QDs.Cd containingmetallothionein(MT)are the main species formed by Cd released from CdSe QDs in HepG2 cells,while speciation analysis of Cd containing MTs remains a challenge because MTs has several subisoforms and can bind with several metals.Herein,we built a hyphenated platform for speciation analysis of QDs in HepG2 cells after treatment with CdSe/ZnS QDs.The Cd-containing MTs were separated in reversed phase high performance liquid chromatography(RP-HPLC)and subsequently online detected by inductively coupled plasma mass spectrometry(ICP-MS)and electrospray ionization quadrupole time-of-flight mass spectrometry(ESI-Q-TOF-MS)parallelly.Four groups of Cd-containing metabolites were found by detecting Cd in ICP-MS.Their structures were identified in ESI-Q-TOF-MS and further confirmed with standards of four subisoforms of MT,including N-terminal acetylation MT2a,N-terminal acetylation MT1e,N-terminal acetylation MT1g and MT1m.Each group of them contains various stoichiometry of Cd/Zn.The metabolites of QDs remain same while the concentrations of each metabolite and its stoichiometry of Cd/Zn vary for different incubation concentration/time.This work provides a new parallel hyphenation technique of HPLC-ICP-MS/ESI-MS with high separation resolution and powerful detection ability,and the obtained results provide detailed metabolism information of QDs in HepG2 cells after treatment of CdSe/ZnS QDs,contributing to deep exploration of the functional mechanisms of QDs in organisms.
基金The financial support from Science and Technology Project of Guangzhou(201803020026)Guangdong Provincial Key Laboratory of Sensing Technology and Biomedical Instruments(2020B1212060077)Guangdong Natural Science Foundation(S2017A030313076,2020A1515010661)
文摘This work reports on a smartphone-based quantitative POCT system which consists of a paper-based microarray chip,a homemade LEGO dark-box,and a smartphone installed with custom-designed FChip-APP,for on-site quantitation of Fe^(3+),Vitamin 12(VB12),and folic acid(FA).Collection and automatic analysis of fluorescence turn-off response of three kinds of fluorescent nanoprobes which are coated onto filter papers by a smartphone-based device is the principle behind this study.The POCT system exhibits good analytical performance for multiplexed analysis of Fe^(3+),VB_(12)and FA with a wide linear range(Fe^(3+),1.0–14.0μg mL^(-1)(R^(2)=0.983);VB_(12),1.35–40.0μg mL^(-1)(R^(2)=0.991);FA,2.0–26.0μg mL^(-1)(R^(2)=0.994))and low detection limit(Fe^(3+),0.35μg mL^(-1);VB12,0.47μg mL^(-1);FA,0.56μg mL^(-1)).The cost and weight of the whole system are~$220 and~600 g per set,highlighting its cost-eff ectiveness and portability.The simple operation procedures and user-friendly interface of the FChip-APP validate the ease-of-use feature of the reported system.This versatile smartphonebased quantitative POCT system provides a cost-eff ective and easy-of-use method for screening the context-specific causes of anemia and thus its eff ective interventions in the future,especially in resource-limited areas.
