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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.

A chemically crosslinked cellulose ester films (MCC-CAD-GA) based on cellulose (MCC), citric acid anhydride (CAD) and l-glutamic acid (l-GA) was successfully prepared via amidation for the adsorption of Cd2+, Co2+, Ni2+, Pb2+ and Cu2+ ions with lower concentration from water. The obtained composites were characterized by FTIR, XRD, elemental analysis and SEM. The results showed that the thermal stability and mechanical strength of MCC-CAD-GA films were enhanced. The adsorption parameters, such as temperature, contact time, adsorbent dose, pH, and initial metal ion concentration were optimized. The adsorption capability of the composite for heavy metal ions was substantially and synergistically improved by adding l-GA into MCC-CAD. The composite films could be recycled and exhibited constant adsorption ability for five successful runs. In addition, the adsorption behavior followed the pseudo-second order kinetic model, and the adsorption isotherms were well described by the Langmuir model. All the results suggested that the MCC-based composite films could be considered as a promising candidate for heavy metal ions treatment. A chemically crosslinked cellulose ester films based on cellulose (MCC), citric acid anhydride (CAD) and l-glutamic acid (l-GA) was successfully prepared via amidation for the adsorption of Cd2+, Co2+, Ni2+, Pb2+ and Cu2+ ions with lower concentration from water. The modified could be recycled and exhibited constant adsorption performance for five successful runs.

Functionalization of microcrystalline cellulose (MCC) with 1,2,3,4-butanetetracarboxylic acid dianhydride (BTCAD) was obtained by esterification reaction. A novel macromolecule cross-linker, MCC-BTCAD-NHS (MBN), was successful prepared through amidation between N-hydroxysuccinimide (NHS) and MCC-BTCAD to modify gelatin films. The reaction between gelatin and MBN was confirmed by the residual free amino test, FTIR, elemental analysis, and XRD spectra. The results indicated that the addition of MBN into gelatin decreased the film degradation ratio and increased its thermal stability, flexibility, hydrophobicity, light barrier performance, and water adsorption ability. In addition, SEM images further proved the successful cross-linking reaction. The particular gelatin film material with excellent performance ended up the limitation of blending modification method for gelatin with natural macromolecule and extended its application in many fields.

Conjugated polymer P, which was synthesized by introducing 9,9-diphenylfluorene and thiophene units into the backbone of poly(fluorenylene ethynylene), showed high sensitivity in detecting nitroaromatics. A double-layer sensor, named P-PS/GEL, was prepared by electrospinning technique using polymer P, polystyrene (PS), and gelatin (GEL). A nanofibrous membrane from the mixture of PS and P as the top layer (P-PS) served as the sensing layer for detecting nitroaromatics (NACs). A gelatin nanofibrous membrane as the bottom layer (GEL) served as porous scaffold for the top layer. Therefore, apart from transferring into the top layer directly from above, the NACs molecules could also approach the top sensing layer through the bottom porous layer. This double-layer conformation greatly improved the permeability of the P-PS layer. As a result, the double-layer sensor exhibited a greater quenching efficiency (Q f) of 75 % than that of the single-layer P-PS (55 %). Importantly, the sensor showed good reversibility of quenching process after being exposed to saturated DNT vapor for 6 cycles.

N-hydroxysuccinimide-activated furandicarboxylic acid (NHS-FDCA), a novel cross-linker, was synthesized to modify gelatin films. The properties of cross-linked gelatin solution was also explored, which showed residual-free amino and viscosity reached best level when mol(NHS-FDCA)/mol(–NH2) ≥1.5. A more homogeneous film was observed by SEM and DSC results exhibited higher decomposition temperature (T d) compared with original films. The degradation test verified better compatibility of modified gelatin films. Finally, the optimization experiment was carried out via free-NH2 and viscosity test.

A series of novel cross-linkers, N-hydroxysuccinimide (NHS)-activated end-bit binary acid (NHS-C4, C5, C6, C8, C10, C14), were synthesised to modify gelatin films and the crosslinking effects were compared. Homogeneous films with the exception of the film crosslinked by NHS-C14 were observed and the thickness was measured using a scanning electron microscope. The section feature influenced by different film-treatment conditions was also recorded. The differential scanning calorimetry results indicated higher thermal stability. The water contact angles confirmed enhanced hydrophobicity. NHS-C6, which was used as a probe crosslinker, exhibited the best crosslinking effect that the content of the free -NH2 achieved was the lowest out of all the crosslinkers. The biodegradation results of gelatin films modified by NHS-C6 exhibited better degradation-resistance and excellent stability. In addition, the optimal experimental conditions were 45°C for 12 h when [NHS-C6]/[-NH2] = 2.5.