Fig. 4: Ultrasound-induced reversible control over availability of organocatalyst for hydrolysis reaction in aqueous media.

a A schematic of catalyst availability in the presence and absence of ultrasound stimulus in HEPES buffer containing Ca⁺² ion, b, c FESEM micrograph of Im-Alg based material - before (b) and after (c) application of ultrasound in presence of Ca²⁺ ions, d conversion of pNPA in ambient conditions (blank, black square), in presence of ultrasound stimulus (purple hexagon), and in presence of Im-Alg and ultrasound stimulus (blue triangle), e conversion of DNPA in ambient conditions (blank, black square), in presence of ultrasound stimulus (purple hexagon), and in presence of Im-Alg and ultrasound stimulus (blue triangle), f conversion of pNPB in ambient conditions (blank, black square), in presence of ultrasound stimulus (purple hexagon), and in presence of Im-Alg and ultrasound stimulus (blue triangle). Ultrasound was employed during the course of the reaction at specific time for 5 min (ultrasound ON, shaded area) and ultrasound remain OFF for the remaining time. Markers indicates the experimental data. Error bars are based on standard errors in duplicate runs. The lines are to guide the eyes.