Low Temperature Synthesis of Cu₂O Crystals: Shape Evolution and Growth Mechanism

Abstract

An interesting shape evolution of Cu2O crystals, that is, from cubes, truncated octahedra, octahedra, and finally to nanospheres was first realized in high yield by reducing the copper−citrate complex solution with glucose. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) techniques were employed to characterize the samples. We elucidate the important parameters (including poly (vinyl pyrrolidone) (PVP) concentration, reaction time, and reaction temperature) responsible for the shape-controlled synthesis of Cu2O crystals. The possible formation mechanism for the products with various architectures is presented, which is mainly based on the variation of the ratio (R) of the growth rates along the ⟨100⟩ and ⟨111⟩ direction. In addition, the effect of the low supersaturation on the formation of star-shaped samples with six symmetric branches is also taken into account. This polymer-mediated method should be readily extended to the controlled synthesis of other metal oxides and the proposed growth model could also be used to explain and direct the growth of crystals with a cubic structure.

Synthesis of Monodisperse Lanthanum Hydroxide Nanoparticles and Nanorods by Sonochemical Method

“…For lanthanum hydroxide nanorods, the intensity ratio between the (100) and the (110) diffractions is 0.85, and between the (100) and the (101) diffractions is 1.19 which is significantly smaller than the conventional bulk intensity ratios (1.38 and 2.12, respectively) and lanthanum hydroxide nanoparticles ratios. This trend reveal that there is a direct relation between XRD patterns and shape of nanostructures because preferential growth of one face cause formation of specific shape and in the case of La(OH) 3 this preferential growth along the [100] direction forms 1D structure [35][36][37]. Figure 2 shows TEM image of lanthanum hydroxide nanorods, sample no.…”

Bismuth tungstate nano/microstructures: Controllable morphologies, growth mechanism and photocatalytic properties

“…In recent years, the morphology and size controlled synthesis of materials have attracted much attention due to their unique chemical and physical properties that are relevant to the shape and size [1][2][3][4][5][6]. Considerable efforts have been devoted to synthesize novel nano-and microstructured materials with various morphologies, such as low-dimensional structures (e.g., rods [7], wires [8,9], belts [10], tubes [11]) and hierarchical structures (e.g., branches [12], urchins [13], hollow spheres [14,15]), for their specific properties and corresponding potential applications.…”

Shape evolution of antimony oxychloride from sheaf-like to quasi-wafer structures

“…77-1584). The intensity ratio of the reflection peaks represents a well established approach used to discuss the crystal orientation against the standard powder XRD pattern [13,14]. Based on our detailed analysis, we observed that the intensity ratio between the (020) and (031) diffraction peaks gradually changed with different shapes obtained for samples in different concentrations of NaOH.…”