Synthesis of thiodiazole copper microcapsules and release behavior of inhibiting R. solanacearum

Microcapsules are one of the most useful devices to reduce the dosage of pesticides and prolong the duration of the active ingredient in target crops. In this study, thiadiazole copper (TDC) microcapsules were synthesized by in situ polymerization using poly(urea-formaldehyde) and characterized by field emission scanning electron microscopy, laser diffraction analysis, 3D optical microscopy, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy. The effects of pH and temperature on the release of TDC were characterized by UV-visible absorption spectroscopy. The relationship between the micromechanical behavior of the microcapsules and release of TDC was studied by nanoindentation tests. The particle size distributions of the microcapsules (10-530 mm) were controlled by different reaction parameters. The microcapsules were stable below 220 degrees C, as determined by TGA. The release kinetics indicated that the higher the temperature, the faster the release rate. The TDC microcapsules were sensitive to pH, and the fastest release rate was observed at pH 4.0. The maximum load, hardness, and Young's modulus under the same displacement conditions decreased during the release. Water swelling was the major reason for TDC release from the microcapsules. The pot experiments confirmed that the microcapsules exhibited long-term sustained release of TDC, thereby protecting the tobacco from R. solanacearum.