Research On Preparation And Properties Of Carbon-encapsulated Quantum Dot Nanohybrids

Low dimensional carbon nanomaterials have large surface area and good electrical conductivity, and therfore they are extensively used as an electrode material. Because of affluent surface defects of quantum dots, electron-hole pairs generated by photoexcitation can be quickly recombined on their surface. In this paper, ZnO and CdSe quantum dot-encapsulated carbon hybrid nanomaterials are synthesized by low-temperature combustion method, where triethanolamine is used as a complexing agent. Photogenerated holes generated by illuminating ZnO and CdSe quantum dots easily transfer to carbon materials under the action of built-in electric field, and therfore photoexcited electron-hole pairs can be effectively separated. On this basis, phase analysis, morphology and structure characterization of ZnO/C and CdSe/C hybrid nanomaterials are carried out, and electrical transport, photoelectricity, piezoresistive properties are researched. The main results are as follows:1. SEM image analysis indicates that ZnO/C hybrid nanostructures are mainly composed of sheet structure and CdSe/C hybrids mostly consist in belt-like structure. As seen from HRTEM, ZnO and CdSe quantum dots are uniformly embedded in the carbon nanomaterials with the formation of a good hybrid structure at the nanosize level.2. The results of electrical transport experiments show that ZnO/C and CdSe/C hybrid nanomaterials are p-type semiconductor materials. Carrier mobility of ZnO/C hybrid nanosheets is 924.7 cm2V-1S-1 and hole concentration is 2.192 * 1014 cm-3. The carrier mobility of CdSe / C hybrid nanoribelts can reach 2.719 * 103 cm2V-1S-1 and the hole concentration is 2.197 * 1014 cm-3.3. The results of photoelectric experiments show that the ZnO/C hybrid nanosheet-based photodetectors have strong spectral response to the intrinsic bandgap, and furthermore other wavelength light such as ultraviolet and visible light also show a relatively weak responsivity. Currents may reduce to almost zero under illuminating with 980 nm infrared light or heating to the temperature higher than 30 °C. Thermosensitive factor is high up to-54440. The results of piezoresistive expemients show the devices have high piezoresistive repeatability and sensitivity. The resistance ratios are up to 1: 22 and 8: 1 under maximum compressive strain and tensile strain, respectively. Besides, the devices exhibit a certain piezoresistance-related storage properties under tensile strain.4. The results of photoelectric experiments show that CdSe/C hybrid nanobelt-based photodetectors have apparent responses to the light with wavelengh from 200 to 900 nm. Especially for 840 and 890 nm infrared light, their response is more obvious.