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Fluorescence spectroscopy attracted more and more attention in pesticide residue detection field because of its advantages of non-destructive, non-contact, high speed and no requirement of complex pre-process procedure. However, given that the concentration of the pesticide detected via fluorescence spectroscopy is calculated in accordance with the Beer-Lambert law, this method can only be used to detect samples containing a single kind of pesticide or several kinds of pesticides with completely different fluorescence which is not in accordance with practical cases. In this article, to overcome this disadvantage, back-propagation (BP) neural network algorithm was introduced to detect multiple kinds of pesticides via fluorescence spectroscopy. The results from four kinds of pesticides which are usually used for fruits and vegetables indicated the effectiveness of BP neural network algorithm.

Nickel cobalt sulfides (Ni-Co-S) have been extensive developed as platinum-free counter electrode (CE) materials for dye-sensitized solar cells (DSCs). However, the power conversion efficiency (PCE) of DSCs with Ni-Co-S CEs needs to be further improved by changing crystalline structure of Ni-Co-S. Herein, Ni-Co-S with amorphous structure have been synthesized on fluorine-doped tin oxide (FTO) glass by a potential reversal electrodeposition technique. The morphology of Ni-Co-S films can be controlled through adjusting the molar ratio of Ni and Co ions in the electroplating solution. Ni-Co-S films can be directly applied as low-cost CEs of DSCs. The results demonstrate that Ni-Co-S CEs exhibit excellent electrocatalytic performance for I3− reduction, owing to the synergistic effect and amorphous structure of Ni-Co-S films. Particularly, the DSC based on Ni-Co-S CE with the optimized Ni/Co ratio has achieved the high PCE of 8.18%, which is larger than that of the DSC with platinum (Pt) CE (6.33%).

The femtosecond laser-induced damage characteristics of a novel oxyfluorogallate glass with good mid-infrared property are analyzed in detail and the surface-damage thresholds for single- and multi- pulses ablation are determined and an evident reduction trend is obtained. The nonlinear absorption coefficient measured through the femtosecond laser z-scan method is used to explain the damage mechanism according to the calculation of Keldysh parameter. The ablation characteristics of the oxyfluorogallate glass demonstrated a clear evidence of melting and the ablation rate decreased in the presence of the melting phenomenon. Based on subsequent X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses, the chemistry of the mid-infrared oxyfluorogallate glass appeared to remain constant before and after femtosecond laser ablation. This work provides a reference to manufacture infrared optical devices and is useful in promoting the application of the mid-infrared glass material.

Nickel selenide with the single-phase structure has been widely studied as counterelectrode nanomaterials for dye-sensitized solar cells (DSCs). However, the effect mechanism of the crystalline structure on the electrocatalytic activity is still needed to be explored and analyzed in nickel selenide with hybrid structure. Therefore, NiSe/NiSe2 hybrid nanomaterials are synthesized via a simple solvothermal approach in this work. NiSe/NiSe2 counterelectrodes are constructed by spraying NiSe/NiSe2 hybrid nanomaterials onto fluorine-doped tin oxide glass. The hybrid nanostructure of NiSe/NiSe2 counterelectrodes exhibits the more catalytic active sites, strong charge separation, and transfer ability for the reduction of triiodide owing to the well-controlled crystalline structure of nickel selenide. Therefore, the results from electrochemical measurements prove that the electrocatalytic activity of the optimized NiSe/NiSe2 counterelectrode is higher than that of platinum electrode. As a result, the DSC with the optimized NiSe/NiSe2 counterelectrode yields a remarkable photoelectrical conversion efficiency of 7.78%, which is larger than that of the DSC based on platinum electrode (7.09%). Our research work provides the insight into design and construct of nickel selenide counterelectrodes of DSCs.

A novel flexible metamaterial narrow-band-pass filter is designed and proved to be reliable by both numerical simulations and experimental measurements. The unit cell of the designed structure consists of circle ring resonators on top of a thin dielectric layer backed by a metallic mesh. The investigations on the distribution of the surface current and magnetic field as well as the analysis of the equivalent circuit model reveal that the magnetic resonance response between layers induced by the reverse surface current contributes to the high quality factor band-pass property. Importantly, it is a flexible design with a tunable resonance frequency by just changing the radius of the circle rings and can also be easily extended to have the multi-band-pass property. Moreover, this simplified structure with low duty cycle and ultra-thin thickness is also a symmetric design which is insensitive to the polarization and incident angles. Therefore, such a metamaterial narrow-band-pass filter is of great importance in the practical applications such as filtering and radar stealth, and especially for the conformal structure applications in the infrared and optical window area.