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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.

Uniform hierarchical Ag 3 PO 4 porous microcubes were for the first time synthesized by a one-step reaction at room temperature with the help of the trisodium citrate (Na 3 Cit). The phase, microstructure, morphology, and textural properties of the Ag 3 PO 4 porous microcubes were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and UV-vis diffuse reflectance spectroscopy (DRS). Na 3 Cit played important roles as the structure directing agent, crystal growth modifier and aggregation-orienting agent for the formation of this unique Ag 3 PO 4 microstructure. Ostwald ripening and the self-assembly process were proposed for the possible evolution mechanism based on time-dependent experiments. Importantly, the obtained Ag 3 PO 4 porous microcubes exhibited remarkable enhanced visible-light photocatalytic degradations of an aqueous solution of rhodamine B (RhB), far exceeding that of solid Ag 3 PO 4 sample and commercial P25 powders. The results presented here also provide new insights into porous hierarchical materials as high-performance visible-light photocatalysts and their potential use in environmental protection.

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Nonmetallic plasmonic heterostructure TiO 2 -mesocrystals/WO 3−x -nanowires (TiO 2 -MCs/WO 3−x -NWs) are constructed by coupling mesoporous crystal TiO 2 and plasmonic WO 3−x through a solvothermal procedure. The continuous photoelectron injection from TiO 2 stabilizes the free carrier density and leads to strong surface plasmon resonance (SPR) of WO 3−x , resulting in strong light absorption in the visible and near-infrared region. Photocatalytic hydrogen generation of TiO 2 -MCs/WO 3−x -NWs is attributed to plasmonic hot electrons excited on WO 3−x -NWs under visible light irradiation. However, utilization of injected photoelectrons on WO 3−x -NWs has low efficiency for hydrogen generation and a co-catalyst (Pt) is necessary.TiO 2 -MCs/WO 3−x -NWs are used as co-catalyst free plasmonic photocatalysts for CO 2 reduction, which exhibit much higher activity (16.3 µmol g −1 h −1 ) and selectivity (83%) than TiO 2 -MCs (3.5 µmol g −1 h −1 , 42%) and WO 3−x -NWs (8.0 µmol g −1 h −1 , 64%) for methane generation under UV-vis light irradiation. A photoluminescence study demonstrates the photoelectron injection from TiO 2 to WO 3−x , and the nonmetallic SPR of WO 3−x plays a great role in the highly selective methane generation during CO 2 photoreduction.

Nanoplasmonic sensors are heralding exciting advances as clinical diagnostics as they facilitate label-free, real-time, and ultrasensitive monitoring in a small footprint. But in essence, almost all of them still largely rely on expensive and bulky spectroscopy/imaging instrumentation and methodology, which has become the major impediment for point-of-care (POC) testing implantation. In this context, an ultracompact optical sensor is achieved with direct electrical read-out capacity by combining plasmonic sensing resonance and optical-signal-transducing into a unity integrated device. Benefiting from the convergence of high figure-of-merit (∼190) resonance and hot electron enhanced photoelectric conversions on the near-flat Au-Si nanotrench framework, the device is demonstrated to yield a detection limit on the order of 10–6 RIU in a broadband operating wavelength window (700–1700 nm). Such a compact, silicon process compatible, and ultrasensitive optoelectronic sensing platform holds great potentials for future clinical POC detection and on-chip microspectrometer applications.

Abstract Transition metal dichalcogenides are two-dimensional semiconductors with strong in-plane covalent and weak out-of-plane interactions, resulting in exfoliation into monolayers with atomically thin thickness. This creates a new era for the exploration of two-dimensional physics and device applications. Among them, MoS2 is stable in air and easily available from molybdenite, showing tunable band-gaps in the visible and near-infrared waveband and strong light-matter interactions due to the planar exciton confinement effect. In the single-layer limit, monolayer MoS2 exhibits direct band-gaps and bound excitons, which are fundamentally intriguing for achieving the nanophotonic and optoelectronic applications. In this review, we start from the characterization of monolayer MoS2 in our group and understand the exciton modes, then explore thermal excitons and band renormalization in monolayer MoS2. For nanophotonic applications, the recent progress of nanoscale laser source, exciton-plasmon coupling, photoluminescence manipulation, and the MoS2 integration with nanowires or metasurfaces are overviewed. Because of the benefits brought by the unique electronic and mechanical properties, we also introduce the state of the art of the optoelectronic applications, including photoelectric memory, excitonic transistor, flexible photodetector, and solar cell. The critical applications focused on in this review indicate that MoS2 is a promising material for nanophotonics and optoelectronics.