A tandem photoelectrochemical water splitting cell consisting of CuBi2O4 and BiVO4 synthesized from a single Bi4O5I2 nanosheet template.

We report on a simple and facile synthetic approach for preparing both a CuBi2O4 photocathode and BiVO4 photoanode from a single Bi4O5I2 nanosheet template. A nanosheet structured Bi4O5I2 (nanoBi4O5I2) template, solvothermally deposited on a conducting glass substrate, can be converted to a textured CuBi2O4 photocathode and a BiVO4 photoanode with coral-like nanostructure by drop-casting a copper ion-containing and a vanadium ion-containing solution, respectively, with a follow-up heat treatment. UV-vis absorption spectra and Mott-Schottky analyses confirm CuBi2O4 and BiVO4 have well-suited band gaps for absorbing a large portion of visible light and complementary band structures for proton reduction and water oxidation, respectively. A photoelectrochemical tandem cell, consisting of a cobalt based catalyst modified CuBi2O4 photocathode and a cobalt based catalyst modified BiVO4 photoanode shows promising photoelectrochemical properties towards water splitting, and can be operated without an external bias. Factors limiting the performance of the tandem cell are also discussed.

Fabrication of a novel partially dissolving polymer microneedle patch for transdermal drug delivery.

Polymer microneedles (MNs) have gained increasing attention as a minimally invasive method for efficiently delivering drugs and vaccines in a patient-friendly manner. Herein, an easy and mild process with O2 plasma treatment was used to fabricate polyvinylpyrrolidone (PVP)-polyvinyl alcohol (PVA) MN patches, and efficient, sustained transdermal delivery was achieved. The diffusion rate of the entrained molecules could be controlled by adjusting the ratio of PVP-PVA. Optical coherence tomography was used to monitor the in vitro penetration in real time and to measure the penetration depth. Rhodamine 6G and fluorescein isothiocyanate-labeled bovine serum albumin (BSA-FITC) were used to explore the potential for using partially dissolving MNs as a transdermal delivery device. Confocal microscopy images revealed that the model drug can gradually diffuse from the puncture sites to a deeper depth. The drug-release profile also demonstrated that the PVP-PVA MNs can provide a successful and sustained release and that the transdermal delivery rate was regulated by the PVP-PVA ratio. Furthermore, the two-stage processing strategy developed in this study provides a simple and easy method for localizing the drug in the needle. The partially dissolving MNs developed in this study may serve as a promising device for controlled drug release and for biological storage applications.