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/CoO 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 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.

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 MCoO (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 NaBH. After calcination, these nanofibers as precursors were easily transformed into the corresponding hierarchical nanosheets-constructed MCoO nanotubes. By applying a photocatalyst, the resultant MCoO nanotubes, particularly the CuCoO nanotubes, exhibited high photocatalytic activity and cycle stability toward water oxidation reaction with O generation rates of 51.1 mmol g h 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.

Developing a facile and reliable strategy for detecting cancer cells in early stages in aqueous systems remains a challenge, although this strategy is crucial in biomedicine. Here, a green approach is proposed for synthesis of MnCo2O4 nanotubes. The resulting nanotubes have been shown to have peroxidase activity that catalyzes the oxidation of 3,3′,5,5′-tertamethylbenzidine (TMB) by O2, resulting in a typical color reaction from colorless to blue. Moreover, such nanotubes exhibit excellent catalytic properties for the decomposition of H2O2 into O2, resulting in a significant increase in pressure in the bottle. Thus, a new sensor system using MnCo2O4 nanotubes as an artificial peroxidase, generating O2 as pressure signal, and TMB as a color change reporter molecule for dual-mode pressure-based (pressuremeter) and colorimetric (naked eye) detection of cancer cells was established. By using folic acid (FA) as a recognition element, a total of 50 folate receptor (FR) positive cancerous cells can be distinguished by naked-eye observation and pressuremeter. The clinical applicability of such a dual-mode strategy has been tested in detecting cancer cells in serum samples. We envisaged that such a dual-signal readout dual-mode strategy based on MnCo2O4 nanotubes offers a promising biosensing platform for early clinical diagnosis.

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 CuFeSe@Au heterostructured nanosheet with an amorphous core and a crystalline shell based on the reversed growth of Au nanosheets on the CuFeSe frameworks under near-infrared (NIR) illumination. The nanosheet exhibits strong absorbance in the NIR region, and the valence band top of CuFeSe@Au nanosheets is higher than the oxidation potential of O/HO. Owing to the unique structural features, the resulting nanosheets show excellent photocatalytic activity and high stability toward water oxidation with an O generation rate up to 3.48 mmol h g 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.