Presently, chemical agents remain the main antimildew agents for bamboo, which has a certain negative impact on the environment and human health. Therefore, it is urgent to develop new environment-friendly antimildew agents for bamboo. Here, citral, an environment-friendly natural antibacterial agent, was used as an antimildew agent for bamboo. The orthogonal test was used to explore the effects of citral concentration, impregnation pressure, and pressurization time on the drug loading capacity of treated bamboo strips. The effect of antimildew-treated bamboo strips on bamboo mold was also discussed. Furthermore, the Fourier transform infrared spectroscopy and ultraviolet spectrophotometer were used to investigate the distribution of citral in bamboo strips. Results showed that the optimum technological parameters of citral mildew-proof treatment of bamboo were as follows: citral concentration: 0.795 mg/ml, impregnation pressure: 0.3 MPa, and pressurization time: 90 min. Also, citral was easy to volatilize, which decreased the citral content of bamboo strips after vacuum drying and showed the trend of a lower surface layer and a higher inner layer. The concentration of citral therefore had a significant effect on the drug loading of the antimildew-treated bamboo strips. Thus, it was difficult to achieve effective prevention and control of bamboo mold when bamboo strips were impregnated with a lower concentration of citral solution. When the concentration of citral reached 200 mg/ml, the prevention and antimold efficiency of antimildew bamboo strips reached over 100%. This study will provide references for the development and application of environment-friendly natural antibacterial agents in the field of bamboo mildew prevention.

Inorganic−organic donor−acceptor hybrid compounds are an emerging class of multifunctional crystalline materials with well-defined structures built from semiconductive inorganic and organic components. Perylenediimides (PDIs) are a prominent class of electron-deficient organic dyes, which can undergo consecutive photoinduced electron transfers to generate doublet excitedstate radical anions for photoredox-inert chemical bonds. Thus, this is an excellent organic component for building hybrid materials to study the structure−property relationships in organic synthesis. In this context, three molecular structure modified PDI-based hybrid materials, (Me 4 -PDI) 2 •SiW 12 O 40 (1), (Me 4 -Cl 4 -PDI) 2 • SiW 12 O 40 (2), and (Me 4 -Br 2 -PDI) 1.5 •HSiW 12 O 40 (3), were studied. By the introduction of different substituent groups at the bay positions, these three hybrid materials were successfully fabricated to investigate the impact of substituent groups on the photocatalytic activity. As expected, all PDI-based hybrid materials easily underwent consecutive photoexcitation to obtain their excited-state radical anions. However, experimental and theoretical analyses showed that these obtained excited-state radical anions displayed unusual bay-substituent-group-dependent photocatalytic conversion activities for the iodoperfluoroalkylation of alkenes and oxidative coupling of amines. Higher conversion yields were obtained for complexes 1 and 3 (bay-unsubstituted and Br-substituted PDI hybrid materials, respectively), and lower conversion was observed for complex 2 (Cl-substituted PDI hybrid material), which is attributed to the excited-state SOMO-1 energies of the PDI radical anions. The structure−property relationship established in this work provides insights for the further exploration of baysubstituted PDI hybrid materials in other small-molecule photocatalytic transformations.

To reduce the amount of citral used without reducing the antimildew performance of bamboo, the citral compound preparation process, the distribution of the compound in bamboo, and its antimildew performance were investigated using the Oxford cup method, Fourier-transform infrared spectroscopy, and ultraviolet spectrophotometry. The results revealed that the combination of citral with cinnamaldehyde or thymol may lead to partial chemical reactions, which may change the chemical structure of citral and affect its bacteriostatic properties. The bacteriostatic properties of the citraldehyde thymol compound against common molds of bamboo were considerably superior to those of the citral cinnamaldehyde compound. The limonaldehyde thymol compound showed a low distribution trend outside and vice versa inside in the treated bamboo. The citral thymol compound exhibited good antimildew performance at a concentration of 200 mg/mL. The citral thymol compound could reduce the amount of citral by approximately 67 mg/mL without reducing the antimildew performance of bamboo.

In order to reduce the oxidative degradation of citral, our research group modified citral with the natural antioxidant from tea polyphenols and applied it to bamboo processing to enhance the anti-mold effect of bamboo, but its application to the bamboo treatment process and the anti-mold effect is still not clear. For this reason, in this paper, the tea polyphenol-modified citral anti-mildew treatment of bamboo as well as the anti-mildew properties of bamboo were explored using the orthogonal testing method and a UV-vis spectrophotometer. The results showed that when the concentration of tea polyphenol-modified citral reached 175 mg mL−1 and above, the efficacy of the anti-mildew treated bamboo against common molds reached 100%; the improved anti-mildew treatment process parameters for bamboo were as follows: impregnation pressure 0.6 MPa, impregnation time 150 min, and tea polyphenol-modified citral concentration 200 mg mL−1. Following the tea polyphenol-modified citral anti-mildew treatment of bamboo, not only did it improve the anti-mildew properties of the bamboo materials, but it also added a fresh lemon fragrance without altering the original colour, microstructure, and chemical properties of the bamboo materials.

In the present study, the sustained-release system loading citral was synthesised by using PNIPAm nanohydrogel as a carrier and analysed its drug-release kinetics and mechanism. Four release models, namely zero-order, first-order, Higuchi, and Peppas, were employed to fit the experimental data, and the underlying action mechanism was analysed. The optimised system was applied to treat a bamboo mould, followed by assessment of the mould-proof performance. Our experimental results revealed that the release kinetics equation of the system conformed to the first order; the higher the external temperature, the better the match was. In the release process, PNIPAm demonstrated a good protection and sustained-release effect on citral. Under the pressure of 0.5 MPa, immersion time of 120 min, and the system concentration ratio of 1, the optimal drug-loading parameters were obtained using the slow-release system with the best release parameters. Compared to the other conditions, bamboos treated with pressure impregnation demonstrated a better control effect on bamboo mould, while the control effect on Penicillium citrinum, Trichoderma viride, Aspergillus niger, and mixed mould was 100% after 28 days. Moreover, the structure and colour of bamboo remained unchanged during the entire process of mould control.