Hydrothermal Synthesis of ZnO Microspheres and Hexagonal Microrods with Sheetlike and Platelike Nanostructures

Abstract

Unusual ZnO microspheres constructed of interconnected sheetlike nanostructures were prepared by the hydrothermal synthesis approach. These microspheres possess high surface areas (28.9 m(2)/g) and are amorphous. Trisodium citrate plays a key role in directing the formation of these microstructures. By increasing the reaction time, these microspheres gradually dissolved to form short hexagonal microrods with stacked nanoplate or nanosheet structure. The microrods were also formed under the influence of trisodium citrate. They are crystalline and show a strong (002) X-ray diffraction peak of wurtzite ZnO structure. Both microsphere and microrod samples show near-band-edge emission at approximately 385 nm, but only the microrod sample exhibits yellow luminescence at approximately 560 nm. Due to their high surface areas, these ZnO microstructures were examined for their ability to photodecompose phenol. The as-prepared samples did not display photocatalytic activity due to possible surface adsorption of solution species. However, microspheres with heat treatment to 300 degrees C can substantially enhance the photodecomposition of phenol under direct sunlight irradiation and still maintain their high surface area nanosheet structure.

Direct evidence of ZnO morphology modification via the selective adsorption of ZnO-binding peptides

“…1. The non-ZnO gel-like precipitates collected after 24 hours (t 20 C ¼ 24 h) appeared to be continuous sheets with rough surfaces (Fig. 2a) as opposed to hexagonal ZnO crystals obtained at 65 C (Fig.…”

“…39,76,89-93 Since ZnO was not detected at 20 C, for simplicity, the reaction time is quoted as the reaction duration at 65 C in all following sections, i.e. total reaction time of 25 hours and 48 hours are described as t 65 C ¼ 1 h and t 65 C ¼ 24 h respectively.…”

“…In addition, the coprecipitation of G-12 and GT-16 strongly correlated (quantitatively) with the reduction of crystal dimension growth rate. In many instances the presence of capping agents such as DBCP, [22][23][24][25] citrate ions, 19,20,75 hydroxyl ions, 13 etc. has been shown to reduce the aspect ratio of ZnO crystals.…”

“…The most commonly used approach is that involving SDAs ranging from simple molecules, such as amines [13][14][15][16] and anionic species, [17][18][19][20][21] to polymers (DBCP, [22][23][24][25][26][27][28][29] PVP, [30][31][32][33][34][35][36][37][38][39][40][41][42] PAM, 29 and PAH 43 ) and biomolecules. [44][45][46][47][48][49][50][51][52] The SDAs have been shown to affect the morphology of ZnO by imposition of effects on nucleation and/or growth of the crystals.…”

Form Emerges from Formless Entities: Temperature‐Induced Self‐Assembly and Growth of ZnO Nanoparticles into Zeptoliter Bowls and Troughs

“…[13] The properties of ZnO are closely related to its microstructures, particularly its crystal size, orientation, and morphology. [14] Though a variety of ZnO nano-and microstructures of various shapes have been obtained by solid-vapor phase growth (SVG), [15][16][17][18][19][20][21] microemulsion, [22] and hydrothermal methods, [23] bowl and triangular trough-shaped structures, to the best of our knowledge, have not been reported so far. We also demonstrate herein that the ZnO bowls and rings thus obtained can be used as a template to make metal or metal oxide replicas.…”