Size control of Au@Cu₂O octahedra for excellent photocatalytic performance

Abstract

Due to its intrinsic structure and characteristics, small size and monodispersity, control of singlecrystalline Cu 2 O polyhedra in aqueous media is a challenge, which is important to overcome to achieve enhanced photocatalytic activity. Here, we use heterogeneous nucleation, rather than homogeneous nucleation, of Cu 2 O with gold nanorods as seeds to realize subsequent uniform crystal growth. We obtained nearly monodisperse octahedral Au@Cu 2 O nanocrystals with single-crystalline shells, which are distinct from the pentagonal column-shaped structures previously described. Due to the fact that one Au@Cu 2 O holds only one Au nanorod, two formulas were deduced for convenient size control of the Cu 2 O shell. The formulas were calculated by adjusting the amount of Au rods that are relatively quantified. The formula also allows the size of the final product to be predicted when a given amount of gold seeds are employed. The experimental results agree well with the calculated data. The result of larger surface area and improved charge separation from core-shell interaction, made five samples of different sizes exhibit excellent photocatalytic activity toward MO degradation. The synthetic strategy reported here provides a clue to monodispersity and size control of core-shell nanocrystals, which is useful in developing new catalysts with better performance that are urgently needed in the fields of both science and technology.

Processing and luminescence properties of Ce:Y3Al5O12 and Eu:Y3Al5O12 ceramics for white-light applications

“…The XRD data were analyzed by applying the Rietveld method and confirmed the formation of YAG (cubic symmetry, space group Ia-3d) in both samples. The calculated lattice parameters, a ¼12.001(2)Å, are in agreement with those reported in the literature [18][19][20][21], while the Rietveld refined parameters (R wp ¼19.7 and 16.7 and R exp ¼4.94 and 5.96, for Ce:YAG and Eu:YAG samples, respectively) attest the feasibility of the refinement model in this case. Since the amount of dopants is very low, significant structural distortions could not be observed.…”

“…Furthermore, the sol-gel process involves chemicals sensitive to the environment that make the experiments difficult to be carefully handled. Besides these wet-chemical routes, high-energy ball milling was successfully employed to prepare YAG at temperatures in the range of 1000-1200 1C [18][19][20][21]. In fact, Sakurai and Guo [21] reported the formation of Ce doped YAG as a side result of an investigation of mechanosynthesis of Y 1 À x Ce x AlO 3 , which exhibits a promising optical response to X-Ray irradiation.…”

“…In fact, Sakurai and Guo [21] reported the formation of Ce doped YAG as a side result of an investigation of mechanosynthesis of Y 1 À x Ce x AlO 3 , which exhibits a promising optical response to X-Ray irradiation. Kong et al [20] have obtained YAG powders by milling oxide precursors for long times (12 h) and calcining at temperatures ranging from 900 to 1500 1C for 2 h. Huang et al [18] have synthesized YAG powders by milling precursors also for long times (20 h), and calcining temperatures in the same temperature range.…”

“…Such specific features have entailed the use of this material as solid-state lasers, scintillators, field emission displays (FED), plasma display panels (PDP), and electroluminescent devices (ELD) [13][14][15][16]. YAG single-crystals are normally fabricated by the Czochralski method under extremely severe growth conditions that difficult obtaining large-size crystals [17][18][19][20]. Compared to YAG single-crystal counterpart, polycrystalline YAG ceramics have excellent possibilities for future applications owing to low cost, easy fabrication, high dopant concentration and mass production [18].…”

TEMPLATE STRATEGY FOR THE SYNTHESIS OF Cu2O–Pt HIERARCHICAL HETEROSTRUCTURES FOR THE DEGRADATION OF METHYLENE BLUE

“…Cu 2 O is a p-type semiconductor with a direct bandgap of 2.17 eV, and it has a maximum theoretical solar conversion e±ciency of À12% in a single layer photovoltaic cell. 7,8 As a result of the special properties, Cu 2 O has been considered as the promising material with potential applications in chemical reaction catalysis, 9 photocalysis, 10,11 gas sensors, 12 solar energy conversion, 13 templates, 14À17 antibacterial activity, 18 metalÀinsulatorÀmetal resistive switching memory, 19 cancer therapeutic agent. In the past decade, numerous scienti¯c workers have paid great attention to the development of the noble metal-Cu 2 O, 20 meanwhile, to understand the mechanism of the progress within the reaction.…”