ABSTRACT
Hierarchical nanosheets-assembled nanotubes are of great interest for their unique physicochemical properties as well as their potential applications in a variety of fields. However, the synthesis of hierarchical mixed transition-metal oxides-based nanosheets-assembled nanotubes for highly efficient photocatalytic oxygen evolution is rarely reported. Herein, a simple and versatile approach was developed to synthesize hierarchical nanosheets-constructed MCo2O4 (M = Ni, Cu, Zn) nanotubes. Core-shell polyacrylonitrile (PAN)/M-cobalt hydroxide ultrathin nanosheet composite nanofibers were first synthesized by hydroxylation reaction between PAN/M-cobalt acetate hydroxide precursors and NaBH4. After calcination, these nanofibers as precursors were easily transformed into the corresponding hierarchical nanosheets-constructed MCo2O4 nanotubes. By applying a photocatalyst, the resultant MCo2O4 nanotubes, particularly the CuCo2O4 nanotubes, exhibited high photocatalytic activity and cycle stability toward water oxidation reaction with O2 generation rates of 51.1 mmol g-1 h-1 under visible light irradiation, which is higher than most reported catalysts. This approach is very versatile and can be applied to synthesize other hierarchical multi-element oxides-based nanosheets-constructed nanotubes for advanced applications.
ABSTRACT
Although substantial efforts have been made toward the synthesis of noble metal-semiconductor heteronanostructures, direct in situ synthesis of two-dimensional (2D) core-shell semiconductor@noble metal heterostructured nanosheets remains largely unexplored. Herein, we report the synthesis of a novel 2D core-shell CuFeSe2@Au heterostructured nanosheet with an amorphous core and a crystalline shell based on the reversed growth of Au nanosheets on the CuFeSe2 frameworks under near-infrared (NIR) illumination. The nanosheet exhibits strong absorbance in the NIR region, and the valence band top of CuFeSe2@Au nanosheets is higher than the oxidation potential of O2/H2O. Owing to the unique structural features, the resulting nanosheets show excellent photocatalytic activity and high stability toward water oxidation with an O2 generation rate up to 3.48 mmol h-1 g-1 compared to those of the constituent materials under NIR light irradiation (λ > 850 nm). This work brings new opportunities to prepare 2D core-shell semiconductor@noble metal heterostructured nanosheets, which can be applied as photocatalysts toward water splitting and solar energy conversion at long wavelengths.
ABSTRACT
Portable, low-cost, and quantitative detection of cancer cells at home and in the field has the potential to revolutionize medical diagnostics. We first report the design and synthesis of highly efficient folic-acid-conjugated hydrogen-generation tube-in-tube CuO/Co3O4 heterojunction nanofibers for highly sensitive and rapid recognition of cancer cells through a pressure signal under visible-light irradiation. The resultant nanofibers can dramatically enhance the hydrogen-generation activity of ammonia borane under visible-light irradiation. Such hydrogen-generation reaction can translate a molecular recognition event between folic acid and folate receptor to measurable pressure signal readout through a low-cost and portable pressure meter for target cancer cell detection. Limits of detection (LODs) down to 50 cells mL-1 in only 15 min can be achieved. This result is superior to those of the other reported methods, indicating the superiority of the new pressure-based sensor in terms of sensitivity. The present study establishes the pressure meter as a useful tool for early clinical point-of-care cancer diagnosis.
