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Keywords:

  • Rhamnolipid;
  • ZnS nanoparticles;
  • biosynthesis;
  • biosurfactant;
  • photoluminescence;
  • biocompatibility

Abstract

Background

This paper reports a facile eco-friendly route for biosynthesis of rhamnolipid biosurfactant capped zinc sulphide (ZnS) nanoparticles (NPs), its structural characterization, biocompatibility, cytotoxicity assessment and its applicability as a nanophotocatalyst for textile azo dye degradation.

Results

Homogeneous, water soluble, stable and polydisperse 10–15 nm sized ZnS NPs were synthesized with rhamnolipid biosurfactant that served the dual role of capping and stabilizing agent. The as-prepared ZnS NPs retained photoluminescence intensity and showed an obvious blue shift compared with normal ZnS crystallites of micrometer scale. XRD analysis confirmed crystallinity and SEM and TEM images revealed spherical particles. Unchanged cell viability of adult rat (Rattus norvegicus) hepatocytes for biosurfactant capped ZnS were observed while conventional ZnS NPs showed dose and time-dependent cytotoxicity. Specifically, rhamnolipid capping induced less oxidative stress, lipid peroxidation and perturbation in total glutathione (GSH). Maximum Direct brown MR dye degradation of 96 and 94% was obtained under UV irradiation for 180 min using SDS and biosurfactant capped ZnS NPs, respectively, at pH 11.0 and 25°C.

Conclusion

The results elucidated the significance of biocompatible and biodegradable rhamnolipids as an effective and inexpensive capping and stabilizing agent for developing stable and biocompatible ZnS NPs as nanophotocatalyst in the textile industry and for wastewater and effluents treatment.