One-step biosynthesis of a bilayered graphene oxide embedded bacterial nanocellulose hydrogel for versatile photothermal membrane applications

We introduce the facile one-step biosynthesis of a bilayer structured hydrogel composite of reduced-graphene oxide (rGO) and bacterial nanocellulose (BNC) for multiple photothermal water treatment applications. One-step in situ biosynthesis of a bilayered hydrogel was achieved via modification of BNC growth medium supplemented with an optimized concentration of corn steep liquor as a growth enhancer. A two-stage, growth rate-controlled formation mechanism for the bilayer structure was revealed. The final cleaned and freeze-dried reduced-GO embedded BNC bilayer membrane enables versatile applications such as filtration (tested using gold nanoparticles, Escherichia coli cells, and plasmid DNA), photothermal disinfection of entrapped E. coli, and solar water evaporation. Comparable particle rejection (up to approximate to 4 nm) and water flux (146 L h(-1) m(-2)) to ultrafiltration were observed. Entrapment and photothermal inactivation of E. coli cells were accomplished within 10 min of solar exposure (one sun). Such treatment can potentially suppress membrane biofouling. The steam generation capacity was 1.96 kg m(-2) h(-1). Our simple and scalable approach opens a new path for biosynthesis of nanostructured materials for environmental and biomedical applications.

Automated summary

This study introduces a facile one-step biosynthesis method for a bilayer structured hydrogel composed of reduced-graphene oxide (rGO) and bacterial nanocellulose (BNC) for various photothermal water treatment applications. The bilayer hydrogel was synthesized by modifying the BNC growth medium with an optimized concentration of corn steep liquor, which acted as a growth enhancer. The resulting rGO-BNC bilayer membrane showed comparable performance with ultrafiltration in terms of particle rejection and water flux, and also demonstrated efficient filtration, photothermal disinfection, and solar water evaporation.