Controlled Synthesis And Characterization Of Colloidal In-doped ZnO Nanocrystals

Herein we report a rational synthetic strategy of high-quality monodisperse colloidal In doped ZnO nanocrystals. Hot-injection method based on alcoholysis of metal carboxylate in the noncoordinating solvent by one-step ester elimination reaction was developed.The main results are as follows:1. Firstly, we synthesized Indium stereate (In(St)3) and Indium2-ethylhexanoate (In(Et)3) based on ligand replacement reactions. The as-prepared precursors were characterized by FTIR and TGA, which demonstrated the successful synthetic procedures.2. We studied the reaction pathways of In(St)3and In(Et)3.The results indicated that In(St)3were readily undergo hydrolysis reactions, which may lead to the formation of the dopant phase. In addition, ZnO and In2O3nanocrystals were synthesized by using precursors of zinc stereate (Zn(St)2) and zinc2-ethylhexanoate (Zn(Et)2), In(St)3and In(Et)3, respectively. The relative reactivities of these precursors were quantitatively characterized by FTIR. We found that the reactivities of the precursor may impact the morphologies and sizes of the resulting nanocrystals.3. We selected In(Et)3, Zn(St)2and Zn(Et)2, as precursors to synthesize10%In-Doped ZnO. Regading the precursor combination of In(Et)3and Zn(Et)2, cubic In2O3phase can be distinguished from the wurzite structure of ZnO in the XRD profiles. This result suggest that the relatively reactivity of cationic precursors are critical in terms of achving high quality doped nanocrystals.4. Based on the results shown in part2and3, we selected Indium2-ethylhexanoate, which exhibit lower reactivity than zinc stearate in the alcoholysis route, as the dopant precursor. The synthetic scheme led to successful doping with high concentrations of indium without segregation of dopant phases. In doped ZnO nanocrystals with different Indium concentrations were prepared. TEM, XRD, UV-Vis, ICP-AES were used to characterize the morphological, structural, optical, chemical properties of as-prepared In-ZnO nanocrystals. The doped nanocrystals maintained wurzite structure when the content of indium was as high as30%, The optical band-gap of the In-ZnO nanocrystals can be tuned from3.38eV to3.48eV. 5.10%In-doped ZnO nanocrystals were taken as an example to characterize the optical property and crystal structure by UV-Vis-NIR, HRTEM and ED. Localized surface plasmon absorption features in the near-infrared range due to a high concentration of free elecrons, were observed in the UV-Vis-NIR absorption spectrua of the as-synthesized In-doped ZnO nanocrystals, indicating that indium occupy substitutional sites in host lattices. We also conducted etching experiments on the In-doped ZnO nanocrystals, suggesting that the indium content was higher at the center of the doped nanocrystals..