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Competing interests The authors declare that they have no competing interests. Authors’ contributions THM and JKT wrote this manuscript. SMC, YCL, and TYC carried out the preparation of the samples. TCW, LWJ, and WW carried out the current–voltage measurements. WRC, ITT and CJH carried out the EIS and IPCE measurements. All authors read and approved the final manuscript.”
“Background Cuprous oxide (Cu2O) is a p-type semiconductor metal oxide with a direct band gap of approximately 2.17 eV [1, 2]. Due to its unique optical, electrical, and magnetic properties [3–5] and other properties such as simplicity

and low cost of preparation, nontoxic nature, and abundance, it has attracted great Forskolin manufacturer attention and has been widely applied in solar selleck energy conversion [6], photocatalysis [7], sensors [8], and antibacterials [9]. The fundamental properties of micro/nanostructure semiconductors are found to be dependent on their architectures, including geometry, morphology, and hierarchical structures [10–12]. Therefore, great efforts have been devoted to artificially control the morphology of Cu2O micro/nanocrystals in the past several years [13]. Different Cu2O nanoarchitectures have been synthesized, such as nanowhiskers [14], nanowires [11], nanocubes [15], nanorods [16], nanospheres [17], and nanoflowers [18]; Cu2O flower/grass-like three-dimensional nanoarchitectures (FGLNAs) with relatively large surface area have received particular attention and are expected to display significant semiconductor properties. Various methods have been reported to synthesize Cu2O nanoflowers, such as pulse electrodeposition [19], polyol process [20], and solution-phase route [21]. However, up to now, all the fabrication methods of Cu2O flower-like architectures are complex and costly. Recently, we proposed a novel method using thermal

oxidation with participation of catalyst and humidity to fabricate three-dimensional Cu2O FGLNAs (Hu LJ, Ju Y, Chen MJ, Hosoi A, and Arai S, unpublished observations). In the present paper, the growth mechanism of Cu2O FGLNAs affected by Progesterone the surface conditions of different substrates was investigated in detail. The effect of surface stresses on the growth of FGLNAs – in unpolished Cu foil, polished Cu foil, and Cu film specimens before thermal oxidation – was analyzed. The effects of grain size and surface roughness of polished Cu foil specimens and Cu film specimens before heating were also studied. Methods Two categories of specimens were prepared. One was made of a commercial Cu-113421 sheet (99.96% purity) with a thickness of 0.30 mm, which was cut into a square size of 6 × 6 mm2.