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Abstract Spectral technology is theoretically effective in diagnosing N stress in maize (Zea mays L.), but its application is affected by varietal differences. In this study, the responses to N stress, leaf N spectral diagnostic models and the differences between two maize varieties were analysed. The variety “Jiyu 5817” exhibited a greater response to different N stresses at the 12-leaf stage (V12), while “Zhengdan 958” displayed a greater response in the silking stage (R1). Correlation analysis showed that the spectral bands more sensitive to leaf N content were 548–556 nm and 706–721 nm at the V12 stage in “Jiyu 5817” and 760–1142 nm at the R1 stage in “Zhengdan 958”. An N spectral diagnostic model that considers the varietal effect improves the model fit and root mean square error (RMSE) with respect to the model without it by 10.6% and 29.2%, respectively. It was concluded that the V12 stage for “Jiyu 5817” and the R1 stage for “Zhengdan 958” were the best diagnostic stages and were more sensitive to N stress, which can further guide fertilization decision-making in precision fertilization.

The detection of toxic metals is indispensable for water safety. In this paper, a small molecule of aggregation-induced emission (AIE) with barbiturate group was synthesized. It combined with mercury ions to form a stable metal complex so as to enhance the color of the solution to achieve the visualization of ion detection. The fluorescent molecule showed good selectivity and anti-interference ability and had a low detection limit (DL = 22.27 nM) for mercury ion.

A double-layered sensor was prepared by an electrospinning method using pyrene, polystyrene, and gelatine to prepare a pyrenepolystyrene/gelatin/glass device for the determination of nitroaromatics. The pyrene-polystyrene top layer, which was an electronspun membrane from a mixture of the starting materials in 3:1 N, N-dimethylformaide:tetrahydrofuan, served as the sensing layer for detecting 2,4-dinitrotoluene. The bottom layer was the gelatin electrospun membrane that served as an intermediate between the top layer and the glass slide. The dinitrotoluene analyte was transferred into the sensing layer above and below due to the porosity of the gelatin layer. With a large number of hydroxyl and amino groups, the gelatin layer formed hydrogen bonds with the 2,4-dinitrotoluene molecules, which caused the enrichment of the analyte around the gelatin layer. Additionally, single-layer pyrenepolystyrene/glass sensor was also prepared for control measurements. The quenching efficiency of the pyrene-polystyrene/gelatin/glass sensor was 76.7% at equilibrium obtained within 6 minutes, while the monolayer sensor pyrene-polystyrene/glass device provided 65.8% quenching efficiency within 6 minutes. The gelatin layer played an important role in the superior performance of the double-layered sensor. [ABSTRACT FROM AUTHOR]

A hyperbranched conjugated polymer (P), as well as its repeating units (M), have been synthesized based on 2,4,6-trimethyl-s-triazine and formylcarbazole. Compared with M, P exhibits much stronger fluorescence and a larger Stern--Volmer constant (KSV) in response to DNT, indicating a fluorescence signal amplification effect in the hyperbranched conjugated polymer P. [ABSTRACT FROM AUTHOR]