Associate Professor Dr
Ji Ha Lee
Institute for Fiber Engineering and Science (IFES), Shinshu University, Tokida 3-15-1, Ueda 386-8567, Japan
Title: UV-Activated Photoresponsive Hydrogels for Controlled and Targeted Pesticide Release
The widespread use of pesticide spraying in modern agriculture raises serious environmental concerns, including water pollution, soil contamination, and ecological disturbance. To address these issues, stimuli-responsive gel-based pesticide carriers have emerged as a promising approach for reducing chemical loss while maintaining effective pest control. In this study, we developed a UV-activated photoresponsive supramolecular hydrogel composed of azobenzene-4,4′-dicarboxylic acid (ADA), hexadecyltrimethylammonium bromide (CTAB), and the pesticide thiamethoxam (TMX). The gel was formed through the self-assembly of ADA and CTAB in aqueous solution, followed by encapsulation of TMX. We investigated the structural, mechanical, and optical properties of the gel to understand its suitability as a controlled-release carrier. SEM analysis revealed a three-dimensional fibrous network capable of incorporating TMX, while rheological measurements indicated tunable mechanical strength depending on CTAB/ADA concentration. UV–visible spectroscopy confirmed reversible cis–trans photoisomerization of the azobenzene moieties under 365 nm irradiation, leading to gel–sol transition and enabling light-triggered pesticide release. In addition, the foliar wettability of the gel was evaluated by contact angle measurements on cabbage, Chinese cabbage, and lettuce leaves. The gel exhibited improved wettability after UV irradiation, attributed to structural rearrangement and partial gel dissolution. Such enhanced dispersibility is expected to reduce pesticide runoff and increase adhesion efficiency on leaf surfaces. Overall, this work demonstrates that UV-responsive supramolecular hydrogels provide a promising platform for environmentally conscious pesticide delivery. Their photo-triggered sol transition, tunable wettability, and effective encapsulation suggest strong potential for next-generation smart agricultural formulations.
Biography of the presenting author
Ji Ha Lee received her Ph.D. in Chemistry from Gyeongsang National University, South Korea, in February 2015 under the supervision of Prof. Jong Hwa Jung. Following her doctoral studies, she joined the University of Kitakyushu in Japan as a postdoctoral researcher (2015–2020), where she worked with Prof. Kazuo Sakurai on supramolecular assembly and structure analysis, including synchrotron-based SAXS characterization.In 2020, she was appointed Assistant Professor in the Chemical Engineering Program at Hiroshima University, where she established research programs focused on biomolecular hydrogels, drug delivery materials, and functional soft matter. Since 2024, she has been serving as an Associate Professor at the Institute for Fiber Engineering and Science, Shinshu University, Japan. Her current research centers on supramolecular gels, molecular recognition, nanofiber–hydrogel hybrid systems, and stimuli-responsive materials for biomedical and agricultural applications.
Presenting author details
Full name: Ji Ha Lee
Contact number: +81-268-21-5571
Email: leejiha@shinshu-u.ac.jp