Multi-Stimuli-Responsive Organogel Based on Bisthiourea Compounds for The Removal of Selected Organic Dyes

The self-assembly of a series of bisthiourea containing amino acid side chains has been studied in a large range of organic solvents. Self-assembly is driven mainly by hydrogen bonding groups of thiourea and amino acids moieties. Of all the synthesized compounds, only bisthiourea with alanine side chains, 3.5 formed thermoreversible gel in 50:3 dichloromethane:water mixture at minimum gel concentration of 0.5%. SEM micrographs of the gel showed the formation of entangled cross-linked fibres. The addition of anions such as Cl¯, F¯ and AcO¯ disrupted the gel network of 3.5 thus inducing the gel-sol transition. To investigate the ability of the bisthiourea to form metallogel, metal ions such as Co2+, Cu2+, Ni2+ and Pb2+ were introduced, however, none of them induce the formation of metallogel. In particular, the gels show good performance in the absorption of bromocresol green and Eriochrome black-T at 75% and 61% efficiency, respectively within 24 hours. The good dye absorption properties of gel 3.5 render the potential of bisthiourea gels as new dye absorption materials, which show significant benefit for water pollution treatment.