Xi Zhang

A general one-pot solvothermal process was explored to prepare BiOX (X = Cl, Br, I) powders by employing ethylene glycol as the solvent. The as-prepared BiOX powders were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV−vis diffuse reflectance spectroscopy, and nitrogen sorption. The resulting BiOX samples were phase-pure and of hierarchical microspheres consisting of nanoplates. The band gaps of the as-prepared powders were estimated to about 3.22, 2.64, and 1.77 eV for BiOCl, BiOBr, and BiOI, respectively. On the basis of characterization results, we proposed a possible process for the growth of hierarchical BiOX nanoplate microspheres. Moreover, we evaluated their photocatalytic activities on the degradation of methyl orange and compared them with TiO2 (Degussa, P25) under UV−vis light irradiation and C-doped TiO2 under visible light (λ > 420 nm) irradiation, respectively. It was found that all the BiOX samples were photocatalytically active and BiOI exhibited excellent activity under both UV−vis and visible light irradiation. The resulting hierarchical BiOX nanoplate microspheres are very promising photocatalysts for degrading organic pollutants and other applications.

Super-resolution fluorescence microscopy is distinct among nanoscale imaging tools in its ability to image protein dynamics in living cells. Structured illumination microscopy (SIM) stands out in this regard because of its high speed and low illumination intensities, but typically offers only a twofold resolution gain. We extended the resolution of live-cell SIM through two approaches: ultrahigh numerical aperture SIM at 84-nanometer lateral resolution for more than 100 multicolor frames, and nonlinear SIM with patterned activation at 45- to 62-nanometer resolution for approximately 20 to 40 frames. We applied these approaches to image dynamics near the plasma membrane of spatially resolved assemblies of clathrin and caveolin, Rab5a in early endosomes, and α-actinin, often in relationship to cortical actin. In addition, we examined mitochondria, actin, and the Golgi apparatus dynamics in three dimensions.

BiOI/TiO2 heterostructures with different Bi to Ti molar ratios were synthesized through a simple soft-chemical method at a temperature as low as 80 °C. The as-prepared powders were characterized by X-ray powder diffraction, electron microscopy, UV−vis diffuse reflectance spectroscopy, nitrogen sorption, and X-ray photoelectron spectroscopy. The photocatalytic activities of these BiOI/TiO2 heterostructures were evaluated on the degradation of methyl orange under visible-light irradiation (λ > 420 nm). The results revealed that the BiOI/TiO2 heterostructures exhibited much higher photocatalytic activities than pure BiOI and TiO2, respectively, and 50%BiOI/TiO2 showed the best activity among all these heterostructured photocatalysts. Surface photovoltage spectroscopy and transient photovoltage measurements were used to confirm the formation of heterojunction and probe charge transfer between BiOI and TiO2. The visible-light photocatalytic activity enhancement of BiOI/TiO2 heterostructures could be attributed to its strong absorption in the visible region and low recombination rate of the electron−hole pairs because of the heterojunction formed between BiOI and TiO2.

In this study, ZnO/BiOI heterostructures were synthesized by a facile chemical bath method at low temperature. Control of the morphology and constituents of the ZnO/BiOI heterostructures was realized by simply tuning the Bi/Zn molar ratios. The resulting ZnO/BiOI heterostructures exhibited high photocatalytic activity in the degradation of methyl orange under visible-light irradiation. The high photocatalytic activity of the ZnO/BiOI heterostructures was first attributed to their high surface area. Surface photovoltage spectroscopy and transient photovoltage measurements revealed that the photoinduced charge-transfer property of p-type BiOI could be improved greatly by coupling with n-type ZnO. The heterojunction at the interface between the BiOI and ZnO could efficiently reduce the recombination of photoinduced electron–hole pairs to increase the lifetime of charge carriers by 15 times and thus enhance the photocatalytic activity of the ZnO/BiOI heterostructures, in addition to the high surface area. This study reveals that the heterostructure construction between two different semiconductors plays a very important role in determining the dynamic properties of their photogenerated charge carriers and their photocatalytic properties.

Foreign nonmetal or metal element doping has been widely used to tailor the electronic and band structures of wide band gap binary oxide semiconductor photocatalysts, extending their absorption edges into the visible light range for better utilization of solar light. Besides doping with foreign elements, self-doping can also tune the electronic and band structures of semiconductor photocatalysts but only limited to binary metal oxides, such as oxygen-deficient TiOx (x < 2). In this study, we demonstrate that self-doping is able to tune the electronic and band structures of ternary semiconductor photocatalysts and thus significantly enhance their photocatalytic activities by utilizing BiOI as the example. Density functional theory calculations revealed that iodine self-doping could effectively tune the electronic structures of BiOI. Motivated by the calculations, iodine self-doped bismuth oxyiodide photocatalysts were synthesized with a soft chemical method to illustrate this band structure tailoring approach. Experimental results confirmed that self-doping could change the electronic structures to intrinsically improve the optical absorption property and charge transfer ability, thus enhancing the photocatalytic activity of ternary semiconductors. Meanwhile, the intense absorption with a steep absorption edge of self-doped ternary semiconductors is different from that of foreign elements doped TiO2 with discrete bands, confirming this is a novel electronic and band structure tuning method. This successful band structure tailoring example of ternary semiconductors suggests the self-doping strategy could be general to develop novel visible light driven ternary photocatalysts with enhanced performances.