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[Lecture Notes in Networks and Systems] Advances in Engineering Research and Application Volume 63 (Proceedings of the International Conference, ICERA 2018) || Near-Infrared Emitting Type-II CdTe/CdSe Core/Shell Nanocrystals: Synthesis and Optical Properties
摘要： Type-II CdTe/CdSe core/shell (C/S) nanocrystals (NCs) have been synthesized with 1-octadecane (ODE) by chemical methods. The formation of type-II C/S structures were clari?ed by spectro-metric techniques of UV–vis absorption, photoluminescence (PL) and Raman scattering (RS). Observation results from X-ray diffraction (XRD) reveal that both CdTe core and type-II CdTe/CdSe C/S NCs crystallize in the cubic phase with zinc-blende structure. By changing CdSe shell thicknesses from 1 to 4ML, the PL peaks of CdTe/CdSe C/S NCs could be adjusted from 801 nm to 871 nm (in near-infrared), respectively. These results prove that the partial separation of photoexcited carriers is dependent strongly on the shell thicknesses. As increasing the excitation power, the PL peaks of CdTe/CdSe NCs move towards high energy and increase with a third root of the excitation power. These observations have been explained by the band bending (BB) effect, which is resulting from the spatially separated photoexcited carriers in type-II C/S NCs.
关键词： Spatially separated,Type-II CdTe/CdSe,Photoluminescence,Nanocrystals
更新于2025-09-23 15:21:01
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Highly Efficient Near-Infrared Light-Emitting Diodes Based on Chloride Treated CdTe/CdSe Type-II Quantum Dots
摘要： Quantum dot light-emitting diodes (QLEDs) have been considered as the most promising candidate of light sources for the new generation display and solid-state lighting applications. Especially, the performance of visible QLEDs based on II-VI quantum dots (QDs) has satisfied the requirements of the above applications. However, the lag far optoelectronic properties of the corresponding near-infrared (NIR) QLEDs still behind the visible ones. Here, we demonstrated the highly efficient NIR QLEDs based on chloride treated CdTe/CdSe type-II QDs. The maximum radiant emittance and peak external quantum efficiency (EQE) increased by 24.5 and 26.3%, up to 66 mW/cm2 and 7.2% for the corresponding devices based on the chloride treated CdTe/CdSe QDs with the PL peak located at 788 nm, respectively, compared with those of devices before chloride treatment. Remarkably, the EQE of > 5% can be sustained at the current density of 0.3–250 mA/cm2 after the chloride treatment. Compared with NIR LEDs based on transition metal complex, the efficiency roll-off has been suppressed to some extent for chloride treated CdTe/CdSe based NIR QLEDs. Based on the optimized conditions, the peak EQE of 7.4, 5.0, and 1.8% can be obtained for other devices based on chloride treated CdTe/CdSe with PL peak of 744, 852, and 910 nm, respectively. This improved performance can be mainly attributed to the chloride surface ligand that not only increases the carrier mobility and reduces the carrier accumulation, but also increases the probability of electron-hole radiative efficiency within QD layers.
关键词： QD,CdTe/CdSe,chloride,near-infrared,electroluminescence
更新于2025-09-23 15:19:57
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Signal-switchable lab-on-paper photoelectrochemical aptasensing system integrated triple-helix molecular switch with charge separation and recombination regime of type-II CdTe@CdSe core-shell quantum dots
摘要： Herein, a new “on-off-on” signal switch system combined triple helix molecular switch with efficient charge separation and transfer between different sensitization units was designed for the ultrasensitive photoelectrochemical (PEC) determination of prostate-specific antigen (PSA). Concretely, the initial “signal-on” state was obtained via the cascaded sensitization structure consisting of type-II CdTe@CdSe core-shell quantum dots (QDs), CdS QDs, and ZnO nanotubes, which were assembled on Au nanoparticles modified paper fibers with the aid of signal transduction probe (STP). Thereinto, the type-II CdTe@CdSe QDs with hole-localizing core and electron-localizing shell could enable the ultrafast charge transfer and retard the charge recombination, magnifying the initial photocurrent response and preserving the high efficiency of signal-switchable PEC aptasensing system. Subsequently, the PSA aptamer (PSA-Apt) modified with gold nanoparticles (GNPs) was introduced by the hybridization of PSA-Apt with STP and the hairpin configuration of STP changed from closed to open state, forming a triple-helix structure. Hence, the CdTe@CdSe QDs labeled on the terminal of STP moved away from the electrode surface while the GNPs kept attached close to it. The proposed aptasensor turned to “signal-off” state because of the dual inhibition of vanished cosensitization effect and signal quenching effect of GNPs. Upon the target recognition, the triple-helix structure was perturbed with the formation of DNA-protein complex and the recovery of STP hairpin structure, resulting in the second “switch-on” state. Based on the target-induced photocurrent enhancement, the proposed PEC aptasensor was utilized for the determination of PSA with high sensitivity, persuasive selectivity, and excellent stability.
关键词： Prostate-specific antigen,Type-II CdTe@CdSe QDs,Signal-switchable,Triple helix molecular switch,Photoelectrochemical
更新于2025-09-19 17:13:59
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Synthesis, characterization and the photoinduced electron-transfer energetics of CdTe/CdSe type-II core/shell quantum dots
摘要： The CdTe/CdSe type-II core/shell quantum dots (QDs) were chemically synthesized in a noncoordinating solvent. The optical properties and structures of the synthesized QDs were characterized by absorption spectroscopy (Abs), photoluminescence (PL) spectroscopy, PL-decay lifetime, X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The PL peak of the CdTe/CdSe core/shell QDs could be tuned from 698 nm (1.77 eV) to 780 nm (1.59 eV) by changing the thickness of CdSe shell and fixing the size of CdTe core. The PL quantum yields (QYs) of these QDs were from 14.1% to 31.7% and their full width at half maximum (FWHM) of PL peaks was kept below 0.12 eV during the growth process of CdSe shell on CdTe core. Compared to CdTe cores, the CdTe/CdSe type-II core/shell QDs have much longer PL decay times, up to ~100 ns. Based on Marcus theory, the charge transfer (CT) of CdTe/CdSe 1-5 monolayers (MLs) type-II core/shell QDs has been studied and the effects of quantum confinement on the structure parameters have been revealed. The reorganization energies (RE) of the CdTe/CdSe (1-5 ML) type-II core/shell QDs for the electron transfer (ET) were in the range from 60 meV to 106 meV and was found that ET takes place in the Marcus inverted region (-?G0 ET > λCT) which is typical for these QDs.
关键词： core/shell,reorganization energy,type-II quantum dots,spatial separations,CdTe/CdSe
更新于2025-09-19 17:13:59