Preparation and characterization of indole-3-butyric acid nanospheres for improving its stability and utilization

Indole-3-butyric acid (IBA) is an efficient plant growth regulator for promoting germination and the formation of rooting of various plants. Since it is unstable and presents the low utilization ratio, there is a compelling need to design an environmentally friendly formulation for IBA, which can reduce the loss of degradation and improve its utilization. Nano-sized controlled-release formulations can provide better durability and penetrate through the plant epidermis to efficiently deliver the agrochemicals to the target tissues. In this work, a kind of novel nano controlled-release formulation was prepared by conjugating the IBA and 3-glycidoxypropyltrimethoxysilane (GPTMS) through a covalent cross-linking reaction, and subsequently hydrolyzation and poly condensation with tetraethoxysilane. The resulting nanospheres were characterized by Fourier transform infrared spectroscopy, ultraviolet spectrophotometry, scanning electron microscope, and thermal gravity analysis. The results showed that the obtained nanospheres had a remarkable loading efficiency of IBA (about 43% w/w). The formation of covalent between IBA and GPTMS enabled the nanospheres with a good chemical stability that could protect against photo-degradation effectively. The released rate of the IBA from nanospheres was related to the temperature, pH value. With increased temperature as well as acidity and alkality, the release of the IBA was sped up. The IBA could also be released effectively from IBA-silica nanospheres by esterase, and the sustainable release characteristics of IBA-silica nanospheres were in conformity with the Ritger and Peppas equation. The IBA-silica nanospheres displayed excellent dual stimuli-responsive properties under esterase and weak acid conditions, and could obviously promote the growth of root and bud of pea. Thus, the IBA silica nano spheres prepared by covalent cross-linking reaction have a good potential application as a controlled-release formulation and environmentally-friendly plant growth regulator.