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Graphene oxide (GO)-Ag(3)PO(4) nanocomposites synthesized through a facile solution approach via electrostatic interaction were investigated as excellent photocatalysts for the degradation of rhodamine B (RhB) under visible light irradiation. SEM and TEM observations indicate that Ag(3)PO(4) nanospheres of ~120 nm in diameter were well dispersed and anchored onto the exfoliated GO sheets. The characterizations of FTIR and Raman demonstrated the existence of strong charge interactions between GO sheets and Ag(3)PO(4) nanospheres. As compared to Ag(3)PO(4) nanospheres alone, the attachments of GO sheets led to a band gap narrowing (2.10 eV) and a strong absorbance in the near infrared region (NIR). The photoluminescence (PL) analysis indicates a more efficient separation of electron-hole pairs in the GO-Ag(3)PO(4) nanocomposites. Notably, the incorporation of GO sheets not only significantly enhances the photocatalytic activity but also improves the structural stability of Ag(3)PO(4). The positive synergistic effects between Ag(3)PO(4) nanospheres and GO sheets are proposed to contribute to the improved photocatalytic properties. A possible photocatalytic mechanism of the GO-Ag(3)PO(4) nanocomposites was assumed as well. The integration of these advantages enables such GO-Ag(3)PO(4) hybrid material to be a nice photocatalyst for broad applications in a sewage treatment system.

Upconversion fluorescence has triggered extensive efforts in the past decade because of its superior physicochemical features and great potential in biomedical and biophotonic studies. However, practical applications of upconversion fluorescence are often hindered by its relatively low luminescence efficiency (<1%). Here, we employ a living yeast or human cell as a natural bio-microlens to enhance the upconversion fluorescence. The natural bio-microlens, which was stably trapped on a fiber probe, could concentrate the excitation light into a subwavelength region so that the upconversion fluorescence of core-shell NaYF:Yb/Tm nanoparticles was enhanced by 2 orders of magnitude. As a benefit of the fluorescence enhancement, single-cell imaging and real-time detection of the labeled pathogenic bacteria, such as Escherichia coli and Staphylococcus aureus, were successfully achieved in the dark fields. This biocompatible, sensitive, and miniature approach could provide a promising powerful tool for biological imaging, biophotonic sensing, and single-cell analysis.