Three-dimensional surface-enhanced Raman scattering (SERS) substrates usually provide more hot spots in the excitation light beam and higher sensitivity when compared with the two-dimensional counterpart. Here a simple approach is presented for the fabrication of arrays of Ag-nanoparticles decorated TiO₂ nanotubes. Arrays of ZnO nanorods were fabricated in advance by a hydrothermal method. Then TiO₂ nanotube arrays were achieved by immersing the arrays of ZnO nanorods in an aqueous solution of (NH₄)₂TiF₆ for 1.5 h. Vertically aligned TiO₂ nanotube arrays were modified with dense Ag nanoparticles by Ag mirror reaction. High density of Ag nanoparticles decorated on the fabricated TiO₂ nanotubes provide plenty of hotspots for Raman enhancement. In addition, the fabricated array of Ag nanoparticles modified TiO₂ nanotubes can serve as a reusable SERS substrate because of the photocatalytic activity of the TiO₂ nanotubes. The SERS substrate adsorbed with analyte molecules can realize self-cleaning in deionized water after UV irradiation for 2.5 h. The sensitivity of the fabricated SERS substrate was investigated by the detection of organic dye molecules. The detectable concentration limits of rhodamine 6G (R6G), malachite green (MG) and methylene blue (MB) were found to be 10⁻¹² M, 10⁻⁹ M and 10⁻⁸ M, respectively. The enhancement factor (EF) of the three-dimensional SERS substrate was estimated to be as high as ∼1.4×10⁸. Therefore, the prepared Ag nanoparticles modified TiO₂ nanotube arrays have promising potentials to be applied to rapid and trace SERS detection of organic chemicals.

Straw burning is a long-term environmental problem in China’s agricultural production. At present, China relies mainly on satellite remote sensing positioning and manual patrol to detect straw burning, which are inefficient. Due to the development of machine learning, target detection technology can be used for the detection of straw burning, but the current research does not take into account the various scenarios of straw burning and the deployment of object detection models. Therefore, a lightweight network based on depthwise separable convolution and channel attention mechanisms is proposed to detect straw-burning smoke at a remote distance. Various regional and crop-burning smoke datasets were collected to make the algorithm more robust. The lightweight network was applied to automatically identify and detect straw-burning smoke in surveillance videos. The experiment showed that the amount of light network parameter was only 4.76 M, and the calculation performance was only 11.2 Gflops. For the intelligent detection of straw-burning smoke, performance verification accuracy was improved by 2.4% compared with Yolov5s. Meanwhile, the detection speed on the embedded Jetson Xavier NX device can reach 28.65 FPS, which is 24.67% better than the Yolov5s. This study proposes a lightweight target detection network, providing a possible method for developing low-cost, rapid straw-burning smoke detection equipment.

Porous noble metal nanomaterials can be employed to construct sensitive surface-enhanced Raman scattering (SERS) substrates, because the plasmonic nanopores and nanogaps of the porous materials can provide a larger number of hotspots, and can also serve as containers of analyte molecules. However, the fabrication processes of nanoporous noble metal are generally complicated. Here, a facile method is presented to prepare nanoporous Ag nanoparticles-decorated Ag₇O₈NO₃ micro-pyramids, which are fabricated through the chemical reduction of the electrodeposited Ag₇O₈NO₃ micro-pyramids using NaBH₄. The Ag₇O₈NO₃ micro-pyramids are fabricated by electrodeposition by using a simple aqueous solution of AgNO₃ as electrolyte. Then, porous Ag-decorated Ag₇O₈NO₃ micro-pyramids are achieved by the chemical reduction of the surface of the electrodeposited Ag₇O₈NO₃ micro-pyramids with NaBH₄. The high-density nanopores and nanogaps of the fabricated nanoporous Ag can provide plenty of hot spots for Raman enhancement. Additionally, the nanopores have an effective capacity to trap and enrich analytes. Using rhodamine 6G (R6G) as a probe molecule, the SERS performance of the fabricated SERS substrate has been investigated. It is found that a limit of detection (LOD) ~1.0 × 10⁻¹⁵ M can be achieved for R6G. Then, the SERS substrates are employed to detect dye molecule (crystal violet) and pesticide (thiram), and their LODs are calculated down to 9.6 × 10⁻¹³ M and 1.3 × 10⁻¹⁵ M, respectively. The enhancement factor of the fabricated SERS substrate is estimated to be as high as 5.6 × 10⁸. Therefore, the nanoporous Ag-decorated Ag₇O₈NO₃ micro-pyramids have shown promising application in the sensitive SERS detection of organic molecules.

Plasmonic metal nanostructures have been widely applied in photodetectors for the enhanced light response range and sensitivity. In contrast, photodetection based on surface plasmon effect of the emerging plasmonic nonmetals has not been investigated. Here, single nonmetal plasmonic WO_3−x nanosheets were used as the sensing material for UV–Vis–NIR broad spectral photodetectors. The plasmonic WO_3−x nanosheets were synthesized by solvothermal and follow-up thermal treatment in a hydrogen-containing atmosphere, which exhibited a localized surface plasmon resonance (LSPR) band centered at 899 nm with broad spectral absorption spanned from UV to NIR. Then photodetectors fabricated facilely by depositing Au electrodes on a film of WO_3−x nanosheets showed sensitive response for the regulation of conductance through the plasmonic hot free charge carriers. The responsivity and detectivity were 52 mA/W and 1.46 × 10⁸ Jones under an incident light with a wavelength of 980 nm with an ultralow bias of 0.01 V, and went up to 538 mA/W and 4.75 × 10⁸ Jones under 0.1 V. The results demonstrate the great potential of nonmetal plasmonic materials for photodetection.