Internanofiber Spacing Adjustment in the Bundled Nanofibers for Sensitive Fluorescence Detection of Volatile Organic Compounds

In this work, we report the fabrication of hierarchical nanofiber bundles from a perylene monoimide molecule that enable the sensitive detection of various inert volatile organic compounds (VOCs). We demonstrate that the internanofiber spacing of the bundles with appropriate packing interactions can be effectively adjusted by various VOCs, which is in turn translated into the dynamic fluorescence responses. Upon further decreasing the size of the nanofiber bundles, of which the internanofiber spacing is more favorably adjusted, enhanced fluorescence responses to various VOC vapors can be achieved. Our work presents a new protocol, i.e., translating the stimuli-responsive internanofiber spacing into fluorescence responses, to construct novel fluorescence sensors for various hazardous chemical vapors

Gradient FeO_<i>x</i>(PO₄)_<i>y</i> Layer on Hematite Photoanodes: Novel Structure for Efficient Light-Driven Water Oxidation

Hematite has been receiving increasing attention for its application in photoelectrochemical (PEC) water oxidation but usually exhibits poor efficiency. We fabricated a stable gradient-structured FeO_<i>x</i>(PO₄)_<i>y</i> layer on hematite by diffusively incorporating phosphate onto the surface layer of hematite films at a low temperature. X-ray photoelectron spectroscopy depth profile and Fe K-edge grazing-incidence X-ray absorption near-edge structure and extended X-ray absorption fine structure analysis demonstrated the formation of a ∼50 nm overlayer with a gradient phosphorus distribution and structural evolution from the outer surface to the depth. The as-prepared photoanodes showed highly improved PEC water oxidation performance. Up to 8.5-fold enhancement in the photocurrent density at 1.23 V versus reversible hydrogen electrode was achieved relative to the pristine anode. This strategy is applicable for hematite photoanodes prepared by different methods and with different morphologies and structures. The improvement in the water oxidation activity is mainly attributed to the enhanced separation of photogenerated electron–hole pairs, which is derived from the increased hole diffusion length in the gradient-structured overlayer. This work develops a simple and universal method to boost the PEC water oxidation efficiency with versatile hematite photoanodes