Near-infrared-light mediated ratiometric luminescent sensor for multimode visualized assays of explosives.

The development of a portable and easy-to-use device for the detection of explosives with high sensitivity and selectivity is in high demand for homeland security and public safety. In this study, we demonstrate miniaturized devices depending on the upconversion ratiometric luminescent probe for point-of-care (POC) assay of explosives with the naked-eye. When the PEI-coated upconversion nanoparticles (UCNPs) selectively bonded to 2,4,6-trinitrotoluene (TNT) explosives by the formation of Meisenheimer complex, the formed of UCNP-Meisenheimer complexes show turned visible multicolor upconversion luminescence (UCL) on account of TNT-modulating Förster resonance energy transfer process under near-infrared excitation. With UCL emission at 808 nm as internal standard and ratiometric UCL at 477 nm to that at 808 nm (I477/I808) as output signal, the probe can simultaneously meet the accuracy for TNT explosives quantitative analysis. In addition, this easy-to-use visual technique provides a powerful tool for convenient POC assay of rapid explosives identification.

High-Performance Electrochemical Catalysts Based on Three-Dimensional Porous Architecture with Conductive Interconnected Networks.

The electrochemical applications of traditional carbon nanomaterials such as carbon nanotubes (CNTs) and graphene (G) powders are significantly impeded by their poor three-dimensional (3D) conductivity and lack of hierarchical porous structure. Here, we have constructed a 3D highly conductive CNTs networks and further combined it with mesoporous carbon (mC) for the creation of a core-shell structured (CNT@mC) composite sponge that featured 3D conductivity and hierarchical porous structure. In the composite sponge, interconnected CNTs efficiently eliminates the contact resistance and the hierarchical pores significantly facilitate the mass transport. The electron transfer rates, electroactive surface area and catalytic activity of the CNT@mC composite sponge based catalysts were tested in the direct methanol fuel cells (DMFCs) and electrochemical sensors. In DMFCs, the Pd nanoparticles deposited CNT@mC showed significantly improved catalytic activity and methanol oxidization current. As for amperometric sensing of endocrine disrupting compounds (EDCs), CNT@mC-based catalyst gave a liner range from 10 nM to 1 mM for bisphenol A (BPA) detection and showed great promise for simultaneous detection of multiple EDCs. BPA recovery from environmental water further indicated the potential practical applications of the sensor for BPA detection. Finally, the electrochemical performance of CNT@mC were also investigated in impedimetric sensors. Good selectivity was obtained in impedimetric sensing of BPA and the detection limit was measured to be 0.3 nM. This study highlighted the exceptional electrochemical properties of the CNT@mC composite sponge enabled by its 3D conductivity and hierarchical porous structure. The strategy described may further pave a way for the creation of novel functional materials through integrating multiple superior properties into a single nanostructure for future clean energy technologies and environmental monitoring systems.

Near-Infrared Light Manipulated Chemoselective Reductions Enabled by an Upconversional Supersandwich Nanostructure.

Core-satellite is one of the most powerful superstructures since it leads to enhanced or completely new properties through compatible combination of each component. Here we create a novel ceria-based core-shell-satellite supersandwich structure with near-infrared (NIR) light manipulated catalytic activity by integrating the upconversion luminescent and catalytic functionality of CeO2 nanoparticles. Specifically, lanthanide-doped octahedral CeO2 nanoparticles (o-CeO2) are coated with silica layer (o-CeO2@SiO2) to enhance their luminescence intensity. The pH-dependent catalytic active cubic CeO2 nanoparticles (c-CeO2) are then assembled on the surface of o-CeO2@SiO2 to form the supersandwich structure (o-CeO2@SiO2@c-CeO2) following a classic chemical reaction. The upconversion quantum yield of o-CeO2 in this nanostructure can be nearly doubled. Furthermore, under NIR light irradiation, the o-CeO2@SiO2@c-CeO2 supersandwich structure based composite catalyst displays superior catalytic activity in selective reduction of aromatic nitro compounds to corresponding azo compounds, and the composite photocatalyst can be easily recycled for several times without significant loss of catalytic activity. This strategy may serve as a universal method for the construction of multifunctional nanostructures and shed light on the green chemistry for chemical synthesis.