Spectroscopy and Femtosecond Dynamics of Type‐II CdTe/CdSe Core–Shell Quantum Dots

Abstract

Syntheses of CdTe/CdSe type‐II quantum dots (QDs) using CdO and CdCl2 as precursors for core and shell, respectively, are reported. Characterization was made via near‐IR interband emission, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDX), and X‐ray diffraction (XRD). Femtosecond fluorescence upconversion measurements on the relaxation dynamics of the CdTe core (in CdTe/CdSe) emission and CdTe/CdSe interband emission reveal that as the size of the core increases from 5.3, 6.1 to 6.9 nm, the rate of photoinduced electron separation decreases from 1.96, 1.44 to 1.07 ×1012 s−1. The finite rates of the initial charge separation are tentatively rationalized by the small electron–phonon coupling, causing weak coupling between the initial and charge‐separated states.

Fast access to core/shell/shell CdTe/CdSe/ZnO quantum dots via magnetic hyperthermia method

“…With increasing amounts of precursors (OA‐CdO and TOP‐Se in this case), evident red shift and PL intensity increase are observed. This red shift accompanying the shell growth has been witnessed in the preparation of type II QDs, indicating the partial leakage of excitons into the shell semiconductor . However, when the molar ratio of Te : Se is 1:8, a distinct blue shift and an increase in trap‐state emission is observed.…”

ChemInform Abstract: Recent Developments in Palladium‐Based Bimetallic Catalysts

“…[37] The role of the additive is to establish at ype II electronic heterojunction in the composite semiconductor supports, whichextend the lifetimeofthermal-or photogenerated excitons owing to the spatial separation of electrons and holes of the support materials with different electronic energyl evels,a ss hown in Scheme 1a. [38][39][40] The accumulated holes, in the form of electron-depleted [O] species, in semiconductor 2o fl ower energy react readily with the atomic Hp roduced by Pd in the proximity to form water because their long dwell time allows the chemicalr eaction to occur.S imultaneously, semiconductor 1a th igher energy facilitates the reduction of cations to the metallic state by their excited electrons (as showni nS cheme1b). In contrast, for ChemCatChem 2015, 7,1998 -2014 www.chemcatchem.org as ingle-phases emiconductor oxide support,t he majority of their excited electrons andh oles (excitons) will recombine rapidly,b lockingf urther reduction processes until high temperature is applied.…”

Type-II Core/Shell Nanowire Heterostructures and Their Photovoltaic Applications

“…To date, the reported type-II heterostructures are mainly based on II-VI and III-V binary semiconductors, such as ZnO/ZnS [41], ZnO/ZnSe [42], ZnO/ZnTe [23], CdSe/CdTe [43], and GaN/GaP [20], as shown in Table 1. Among them, ZnO-based heterostructures attracted more attentions due to its abundant resources and facilitating growth [44].…”