摘要 :
Alloyed semiconductor quantum dots (QDs) enriched the synthetic routes for engineering materials with unique structural and optical properties. High-quality thiol-stabilized CdTe_xSe_(1-x) alloyed QDs were synthesized through a fa...
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Alloyed semiconductor quantum dots (QDs) enriched the synthetic routes for engineering materials with unique structural and optical properties. High-quality thiol-stabilized CdTe_xSe_(1-x) alloyed QDs were synthesized through a facile and economic hydrothermal method at 120 C, a relatively low temperature. These water-soluble QDs were prepared using different capping agents including 3-mercaptopropionic acid (MPA) and L-cysteine (L-Cys). The photoluminescence (PL) intensity and stability of L-Cys-capped CdTe_xSe_(1-x) QDs were found to be higher than that of MPA-stabilized ones. The molar ratios of Se-to-Te upon preparation were adjusted for investigating the effect of composition on the properties of the resulting QDs. We also investigated the effect of the pH value of the reaction solution on the growth kinetics of the alloyed CdTe_xSe_(1-x) QDs. The resulting CdTe_xSe_(1-x) QDs were characterized by UV-vis absorbance and PL spectroscopy, powder X-ray diffraction, and transmission electron microscopy. Being coated with a CdS inorganic shell, the PL intensity and stability of the CdTe_xSe_(1-x)/CdS core-shell QDs were drastically enhanced, accompanied by the red-shift of the PL peak wavelength. Owing to the unique optical properties, the QDs hold great potential for application and have to be further exploited.
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Considerable attention has been paid to designing graphene based hybrid materials for developing new light-harvesting systems. Here, we have synthesized CdTeSe alloy nanorods and modified the surface of CdTeSe nanorods by porphyri...
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Considerable attention has been paid to designing graphene based hybrid materials for developing new light-harvesting systems. Here, we have synthesized CdTeSe alloy nanorods and modified the surface of CdTeSe nanorods by porphyrin molecules to attach to graphene surface through pi-pi stacking. In this CdTeSe nanorod-porphyrin-graphene hybrid system, porphyrin acts as an antenna material which harvests light and consequently transfers electrons to the adjacent conduction band of nanorods and finally to reduced graphene oxide (RGO). An ultrafast spectroscopic study suggests that the rate of electron transfer from porphyrin to RGO via conduction band of CdTeSe nanorods is 17.4 x 10(-2) ps(-1). It is to be noted that this ternary hybrid system exhibits 240-fold enhancement of photocurrent under visible light irradiation which reveals that this new type of graphene based inorganic and organic hybrid system is very promising for solar light harvesting.
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In this study, a molecular dynamics (MD) study has been performed on composition and temperature dependences of mechanical properties of CdTe1-xSex (x = 0.25, 0.50 and 0.75) nanowires with a diameter of 6.93 nm. The simulation res...
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In this study, a molecular dynamics (MD) study has been performed on composition and temperature dependences of mechanical properties of CdTe1-xSex (x = 0.25, 0.50 and 0.75) nanowires with a diameter of 6.93 nm. The simulation results show that CdTe0.75Se0.25 nanowire seems to be more ductile, whereas CdTe0.25Se0.75 nanowire seems to be more brittle at 1 K. Moreover, the temperature and composition exert significant effects on the mechanical properties of CdTeSe nanowires under stretching. We conclude that the dominancy of Se atoms yields a higher stability and strength at the lower temperature of 1 K, whilst it is the same for the nanowires with both higher Te and Se contents at the higher temperature of 300 K. The radial distribution functions (RDFs) have also been calculated for the CdTeSe nanowires based on the pair separation distance at 1 and 300 K.
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Miniaturization and integration of lasers have been a hot topic in recent years. Colloidal quantum dots (CQDS) can be used as laser gain media because of their high luminous efficiency and low threshold. Compact distributed Bragg ...
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Miniaturization and integration of lasers have been a hot topic in recent years. Colloidal quantum dots (CQDS) can be used as laser gain media because of their high luminous efficiency and low threshold. Compact distributed Bragg reflector (DBR) combined with CQDs is used to construct micro laser. In this paper, CdTeSe/ZnS core-shell CQDs were prepared by aqueous synthesis. DBR was fabricated by magnetron sputtering using SiO2 and TiO2 through reasonable design of their thickness and repetition cycle number. CQDs were dropped on the surface of DBR to form a low-cost small-scale surface particle laser (SPL). The output emission of 770 nm and 824 nm dual wavelength laser is realized. The threshold is 11 mW/cm2 and the bandwidth is 1 nm. The micro integrated laser with high intensity and Narrow bandwidth near infrared emission has been completed.
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Abstract A rarely studied transformation in colloidal ternary magic‐size clusters (MSCs) is addressed. We report the first observation of the transformation from ternary CdTeSe MSC‐399 to MSC‐422, which occurs at room temperatu...
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Abstract A rarely studied transformation in colloidal ternary magic‐size clusters (MSCs) is addressed. We report the first observation of the transformation from ternary CdTeSe MSC‐399 to MSC‐422, which occurs at room temperature. These two MSC types display sharp optical absorption resonances at 399 and 422?nm, respectively, and are related in that they are quasi isomers, together with their counterpart precursor compounds (PCs). Binary CdTe and CdSe samples were prepared in the prenucleation stage also called the induction period (IP). After they were mixed and placed in a mixture of toluene and octylamine, the transformation was found to take place and to be assisted by the addition of the CdSe IP sample. A binary IP sample contains corresponding binary PCs and monomers (Mo) and fragments (Fr). We argue that the transformation pathway is enabled by the corresponding ternary PCs, involving the substitution reaction, namely CdTeSe PC‐399 + CdSe (Mo/Fr)‐1 ? CdTeSe PC‐422 + CdSe (Mo/Fr)‐2. The present study provides an in‐depth understanding of the formation characteristics of the MSCs.
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Tunable and dual emission Cu2+-doped CdTe1-xSex alloy nanocrystals (NCs) were successfully synthesized by the wet chemical method. The morphology and chemical compositions of the synthesized NCs were assessed by transmission elect...
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Tunable and dual emission Cu2+-doped CdTe1-xSex alloy nanocrystals (NCs) were successfully synthesized by the wet chemical method. The morphology and chemical compositions of the synthesized NCs were assessed by transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The structural and optical properties were characterized by X-ray diffraction (XRD), absorption spectroscopy (Abs), photo-luminescence (PL) spectroscopy, PL-decay lifetime. With the Cu2+ dopant concentration in the range of 0.5-5% and x of 0.5 in the precursors, the fabricated Cu2+-doped CdTe1-xSex NCs exhibited the dual emissions in the visible window at about 665 nm and near infrared window ranging from 830 to 840 nm which correspond to the excitonic emission of CdTe1-xSex NCs and Cu2+ dopant ions, respectively. With the increase in dopant concentration, the fluorescence lifetime of Cu-doped CdTe0.5Se0.5 NCs significantly improved (up to mu s) and the lattice constant of NCs decreased. By varying x from 0 to 1.0, both excitonic and dopant emissions of Cu-doped CdTe1-xSex NCs could be tuned in a wild range from 758 to 563 nm and from 918 to 748 nm, respectively. Interestingly, the crystal structure of these NCs changed gradually from the zinc blende (ZB) to wurtzite (WZ) structure when x increased. The results revealed that the dual emission, fluorescence lifetime and crystal structure of the Cu-doped NCs could be controlled by varying dopant concentration and chemical composition of the host.
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A lattice thermal expansion study of cubic CdTe_(0.9)Se_(0.1) solid solution was carried out by high temperature X-ray powder diffraction technique (HTXRD) from room temperature to 773 K. An analytical least squares method for pre...
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A lattice thermal expansion study of cubic CdTe_(0.9)Se_(0.1) solid solution was carried out by high temperature X-ray powder diffraction technique (HTXRD) from room temperature to 773 K. An analytical least squares method for precise determination of the lattice constant for cubic crystals using a standard reference material as an external standard 20-calibrant was used in this investigation. The best estimated value of the lattice constant (a) for CdTe_(0.9)Se_(0.1) was determined to be 6.441 (2) A at 298 K. This value gradually increased to 6.457 (2) A at 773 K. A similar trend was observed in the unit cell volume, which increased from 267.2(2) A~3 to 269.3(2) A~3 as the temperature changed from RT to 773 K. The thermal expansion coefficient was found to be 3.91 X 10~(-6) K~(-1) at 298 K and continuously increased to 9.73 X 10~(-6) K~(-1) at 773 K.
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This work presents the results on the fabrication, structural and optical properties of CdTeSe/ZnTe and CdTeSe/ZnSe n monolayers (ML) (with n = 0,1,2,4 and 6 being the nominal shell monolayer thickness) ternary alloyed core/shell ...
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This work presents the results on the fabrication, structural and optical properties of CdTeSe/ZnTe and CdTeSe/ZnSe n monolayers (ML) (with n = 0,1,2,4 and 6 being the nominal shell monolayer thickness) ternary alloyed core/shell quantum dots (QDs). Transmission electron microscopy has been used to observe the shape and size of the QDs. These QDs crystallize at the zinc-blende phase. Raman scattering has been used to characterize the CdTeSe QDs' alloy composition in the fabrication and coating processes. The Raman spectrum of CdTeSe QDs, in the frequency range from 100 cm(-1) to 300 cm(-1), is a composite band with two peaks at 160 cm(-1) and 192 cm(-1). When the thickness of the ZnTe shell is 4 ML, the peak of the Raman spectrum only appears at 160 cm(-1). For the ZnSe 4 ML shell, the peak only appears at similar to 200 cm(-1). This shows that the nature of the CdTeSe QDs is either CdTe-rich or CdSe-rich depending on the shell of each sample. The shell thickness of 2 ML does not change the ternary core QDs' crystalline phase. The absorption and photoluminescence spectra show that the absorption and emission bands can be shifted to 900 nm, depending on each ternary alloyed QD core/shell sample. This near-infrared spectrum region is suitable for applications in solar cells.
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Highly panchromatic luminescent CdTexSe1-x, alloy quantum dots (QDs) with emissions from blue to red regions are synthesized using a one-step method in aqueous solution with 3-mercaptopropionic acid (3-MPA) as stabilizer. The stru...
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Highly panchromatic luminescent CdTexSe1-x, alloy quantum dots (QDs) with emissions from blue to red regions are synthesized using a one-step method in aqueous solution with 3-mercaptopropionic acid (3-MPA) as stabilizer. The structure, shape, and spectral properties of these alloy QDs are investigated. The structure of the obtained CdTexSe1-x QDs is consistent with the zinc-blende crystal structure, with a nearly spherical shape having diameter of 4-7 nm. The CdTexSe1-x QDs exhibit an absorbance wavelength ranging from 460 nm to 700 nm, and the maximum quantum yield (QY) approaches 28% for CdTe0.5Se0.5 alloy QDs with a reflux time of 0.5 h. The emission wavelength of CdTexSe1-x QDs can be continuously tuned from 500 nm to 720 nm by controlling the size and composition of the alloy QDs, indicating their potential use in semiconductor-sensitized solar cells. (C) 2015 Elsevier GmbH. All rights reserved.
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High quality ternary-alloyed CdTeSe quantum dots (QDs) have been synthesized via a simple one-pot approach in aqueous phase. CdTeSe QDs show an average size of 3.0 nm with good crystallinity, excellent monodispersity and relativel...
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High quality ternary-alloyed CdTeSe quantum dots (QDs) have been synthesized via a simple one-pot approach in aqueous phase. CdTeSe QDs show an average size of 3.0 nm with good crystallinity, excellent monodispersity and relatively narrow size distribution. TiO2 nanotubes (TNTs) were prepared by hydrothermal method with larger specific surface area (364.2 m(2) g(-1)), and CdTeSe@TNTs were synthesized by in situ process. The absorption edge of CdTeSe@TNTs is red shifted significantly toward 697 nm. After sensitized with CdTeSe, the photoluminescence (PL) emission of CdTeSe@TNTs is significantly quenched, and the fluorescence lifetime of the composites is drastically decayed from 105.82 ns to 0.13 ns with a high photoinduced electron transfer rate (k(et) = 7.98 x 10(9)s(-1)) because of their high matchable lattice constant. In addition, under visible-light irradiation, the photocatalytic efficiency of rhodamine B (RhB) with CdTeSe@TNTs reaches 90% for 80 min. And the photocatalytic reaction rate constant for CdTeSe@TNTs is 0.0272 min(-1), which is 5.4 and 3.4 times larger than that of pure TNTs and CdTeSe QDs, respectively. It is due to the broad visible absorption of CdTeSe@TNTs and the faster photoinduced electron transfer from CdTeSe QDs to TNTs. (C) 2016 Elsevier B.V. All rights reserved.
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