Origin of surface trap states in CdS quantum dots: relationship between size dependent photoluminescence and sulfur vacancy trap states

Veamatahau, Aisea; Jiang, Bo; Seifert, Tom S.; Makuta, Satoshi; Latham, Kay; Kanehara, Masayuki; Teranishi, Toshiharu; Tachibana, Yasuhiro

doi:10.1039/c4cp04761c

Cited by 224 publications

(184 citation statements)

References 59 publications

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“…In both cases, band edge (excitonic transition) emissions were not detected and the radiative emissions were associated with point and surface defects. 29,30 The quantum yield of the CdS and ZnS nanoconjugates was estimated to be ~1% and 2%, respectively, which is in good agreement with reports published about QDs synthesized using low temperatures and aqueous colloidal routes.…”

supporting

confidence: 76%

“…The spin-orbit components (Cd 3d 5/2 and Cd 3d 3/2 ) are separated by a binding energy interval of ~6.7 eV. 29,32,33 In Figure 1D, the peaks at 1,022.0 eV and 1,044.9 eV correspond to the Zn 2p 3/2 and Zn 2p 1/2 levels, respectively, which are generally assigned to Zn-S bonding in ZnS. The difference between the binding energies of Zn 2p 1/2 and Zn 2p 3/2 is 23.0 eV, which is in agreement with literature.…”

mentioning

confidence: 99%

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Surface biofunctionalized CdS and ZnS quantum dot nanoconjugates for nanomedicine and oncology: to be or not to be nanotoxic?

Mansur¹,

Mansur²,

Carvalho³

et al. 2016

IJN

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Herein, for the first time, we demonstrated that novel biofunctionalized semiconductor nanomaterials made of Cd-containing fluorescent quantum dot nanoconjugates with the surface capped by an aminopolysaccharide are not biologically safe for clinical applications. Conversely, the ZnS-based nanoconjugates proved to be noncytotoxic, considering all the parameters investigated. The results of in vitro cytotoxicity were remarkably dependent on the chemical composition of quantum dot (CdS or ZnS), the nature of the cell (human cancerous and embryonic types), and the concentration and time period of exposure to these nanomaterials, caused by the effects of Cd 2+ on the complex nanotoxicity pathways involved in cellular uptake. Unexpectedly, no decisive evidence of nanotoxicity of CdS and ZnS conjugates was observed in vivo using intravenous injections in BALB/c mice for 30 days, with minor localized fluorescence detected in liver tissue specimens. Therefore, these results proved that CdS nanoconjugates could pose an excessive threat for clinical applications due to unpredicted and uncorrelated in vitro and in vivo responses caused by highly toxic cadmium ions at biointerfaces. On the contrary, ZnS nanoconjugates proved that the “safe by design” concept used in this research (ie, biocompatible core–shell nanostructures) could benefit a plethora of applications in nanomedicine and oncology.

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supporting

confidence: 76%

mentioning

confidence: 99%

Surface biofunctionalized CdS and ZnS quantum dot nanoconjugates for nanomedicine and oncology: to be or not to be nanotoxic?

Mansur¹,

Mansur²,

Carvalho³

et al. 2016

IJN

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“…Colloidal CdS QDs were synthesized by one pot synthesis method previously described [23]. The size of the synthesized QD is 4.3 nm.…”

Section: Synthesis Of Cds Qds (For Pre-synthesis Method)mentioning

confidence: 99%

“…Figure 4 shows comparison of photoluminescence spectrum of PSM-CdS/TiO 2 with that of PSM-CdS/Al 2 O 3 . The spectra show characteristic photoluminescence peaks around 480 and 720 nm, indicative of emission originated from the exciton and the surface trap states of the CdS QD, respectively [23]. Since the Al 2 O 3 is an insulator, no electron injection is expected from the CdS, and thus PSM-CdS/Al 2 O 3 can be employed as a control sample to assess the electron injection reaction.…”

Section: Solar Cell Performancementioning

confidence: 99%

Electron Injection from a CdS Quantum Dot to a TiO<sub>2</sub> Conduction Band as an Efficiency Limiting Process: Comparison of QD Depositions between SILAR and Linker Assisted Attachment

Lee

Makuta

Sukarasep

et al. 2016

J. Photopol. Sci. Technol.

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Sensitization of TiO 2 by semiconductor quantum dots (QDs) initiates a primary charge separation in semiconductor quantum dot sensitized solar cells (QDSSCs), and thus is a key fundamental process controlling their solar cell performance. However, despite extensive researches on QD deposition methods, correlation between the solar cell performance and charge transfer dynamics modulated by the different deposition method has rarely been studied. Here, we demonstrate influence of a CdS QD deposition method on their solar cell performance and charge transfer dynamics. Two deposition methods, (i) in-situ QD synthesis directly on the TiO2 surface using a Successive Ionic Layer Adsorption and Reaction (SILAR) method, SILAR-CdS/TiO 2 , and (ii) linker assisted attachment of pre-synthesized QDs on the TiO 2 surface, PSM-CdS/TiO 2 , were investigated. The electron injection efficiency of SILAR-CdS/TiO 2 is estimated to be 96%, while that of PSM-CdS/TiO 2 is 40~50%. The charge recombination dynamics are similar for both films. Therefore, the QDSSC efficiency is essentially controlled by the electron injection process from a CdS QD to the TiO 2 conduction band.

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“…The large shift in the emission peak with respect to the band gap together with peak broadening is attributable to trap state emission, owing to sulfur rich or metal vacancies defect sites near to the valence band. 21 …”

Section: Characterization Of Cds Quantum Dots Surface Passivated By Tmentioning

confidence: 99%

Rapid Photoluminescence Quenching Based Detection of Cu2+ in Aqueous Medium by CdS Quantum Dots Surface Passivated by Thiourea

Kumar

Dutta

2017

ANAL. SCI.

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Presented here is a simple yet rapid and efficient analytical method for visual as well as spectroscopic method for sensing of trace concentrations of Cu 2+ ions in aqueous medium by systematic photoluminescence quenching of a highly water soluble probe made of CdS quantum dots surface modified by thiourea. The salient features of this work describe rapid detection (2 min equilibration time) of Cu 2+ ions at wider linear concentration range (0.025 -10 mg/L) corresponding to a sensitivity of 2.81(mg/L) -1 and limit of quantification of 47.3 μg/L, respectively, suitable for Cu 2+ sensing in drinking water and ground water. Further, the detection of Cu 2+ ion was free from most interfering cations and anions, except for minor interference from Cr 3+ , Hg 2+ and Pb 2+. The robustness of our probe for Cu 2+ sensing is demonstrated from efficient Cu 2+ spike recovery analysis in groundwater and river water samples.

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Origin of surface trap states in CdS quantum dots: relationship between size dependent photoluminescence and sulfur vacancy trap states

Cited by 224 publications

References 59 publications

Surface biofunctionalized CdS and ZnS quantum dot nanoconjugates for nanomedicine and oncology: to be or not to be nanotoxic?

Surface biofunctionalized CdS and ZnS quantum dot nanoconjugates for nanomedicine and oncology: to be or not to be nanotoxic?

Electron Injection from a CdS Quantum Dot to a TiO<sub>2</sub> Conduction Band as an Efficiency Limiting Process: Comparison of QD Depositions between SILAR and Linker Assisted Attachment

Rapid Photoluminescence Quenching Based Detection of Cu2+ in Aqueous Medium by CdS Quantum Dots Surface Passivated by Thiourea

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