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A photochromic sensing platform composing of emeraldine salt of polyaniline (ES-PANI) and titanium dioxide nanoparticles (TiO2NPs) for visual detection of trace copper was developed. Under ultraviolet light irradiation, the greenish ES-PANI could be oxidized to dark blue pernigraniline salt by the photo-generated hole of excited TiO2NPs. In the presence of Cu2+, a light yellow leucoemeraldine salt was visually observed. The overall mechanism of color change was verified to be corresponding to the different redox states of PANI regulated by Cu species during the photochromic process. By integrating the advantages of both photoelectric property and visual detection, the redox reaction-based sensing mechanism led to a good sensitivity and high selectivity in detection of Cu2+with the limit of detection of 0.4 μM. Besides the naked eyes, two color recognition methods including reading mean green intensities in Photoshop and recording ultraviolet absorbance in microplate reader were also studied. This method was successfully applied to Cu2+detection in human hair, and satisfactory recoveries were achieved. More significantly, this sensing platform was really simple, low-cost and able to detect an array of analytes within several minutes without requiring sophisticated equipment. This photoelectron-regulated colorimetric strategy provides a novel concept for the design of visual sensing platform, and can develop the portable test kits for rapid detection in clinical diagnosis.

InGaO3(ZnO)m(m= 3, 5) nanowires with perfect superlattice structures were synthesized via a catalyst-assisted vapor−liquid−solid (VLS) growth mechanism. Different from In2O3(ZnO)mnanowires maintaining wurtzite structure, the InGaO3(ZnO)m(m= 3, 5) superlattice nanowires have a monoclinic crystal structure. High resolution transmission electron microscopy (HRTEM) indicates that the nanowires have an axial superlattice structure, which consists of an In−O layer and In, Ga/Zn−O layers stacking alternately along the nanowire length. The period of a InGaO3(ZnO)3nanowire consists of four atom layers, which is the shortest period in quasi-one-dimensional superlattice structures.