Formation and Dissolution of Twin ZnO Nanostructures Promoted by Water and Control over Their Emitting Properties

Abstract

By using ZnO as a model system, the formation of twinned nanostructures has been investigated under microwave irradiation, exploiting experimental conditions ranging from purely solvothermal when N,N-dimethylformamide was used, to purely hydrothermal when water was the solvent. A progressive increase in size, elongation and roughness of the surface was observed with increasing water content in the solvent mixture. Particular attention was paid to the reactivity of the ZnO surfaces towards dissolution. Our results show that the formation of twinned nanorods is a dynamic process and that the coupling interphase itself is highly reactive. Consequently, the twinned rods undergo a number of complex dissolution processes that are responsible for the appearance of a wide distribution of defects either on the surface or inside the structure. Poly(N-vinyl pyrrolidone) influences the photoluminescent properties of the as-synthesised materials and allows control of the ratio of the intensity of the UV and visible emission.

Defects in ZnO nanoparticles laser-ablated in water–ethanol mixtures at different pressures

“…Various nanostructures of ZnO have been synthesized via solvothermal approaches, 3,6,7,11) CVD, 6,15) microwave irradiation, 19) as well as laser ablation in liquid (LAL) media, 4,5,16,17,[20][21][22][23][24][25][26][27] to name just a few techniques. The latter method, LAL, has recently become a very convenient, simple and versatile approach to prepare diverse nanomaterials at the laboratory scale.…”

Accelerated microwave-assisted hydrothermal/solvothermal processing: Fundamentals, morphologies, and applications

“…The use of microwave radiation provides a rapid and homogeneous heating of solution, in addition to possibly assisting in the alignment of the atomic planes by dipole rotation. Recent literature shows that materials grown by MAH/S occur via OA [40,69,97,98]. Some reaction conditions, morphology and nucleation/growth mechanisms for metal oxides/ hydroxides are summarized in Table 2.…”

Controllable Growth of Unique Three-Dimensional Layered Basic Zinc Salt/ZnO Binary Structure

“…28 Among them, a few of the ZnO crystals consist of the asymmetrical twinned hexagonal rods, which has been reported in forming ZnO by varying additives. 39,42,43 With increasing hydrothermal time, LBZS completely disappears and only hexagonal ZnO microrods with more smooth surfaces and uniform dimensions are obtained after Ostwald ripening 44 (Figure 3g 1 −h 2 ). SEM clearly shows the dynamic evolution process of the growth of LBZS and its transformation to ZnO, in which the LBZS/ZnO binary structure could be obtained by carefully controlling the reaction time, suggesting that the ZnO formation proceeds via a stepwise reaction as Zn(DDAB) 2 → LBZS → LBZS/ZnO → ZnO.…”