Polypyrrole-coated nanocellulose for solar steam generation: A multi-surface photothermal ink with antibacterial and antifouling properties.

Solar energy-based steam generation holds immense potential to tackle the problem of 1.1 billion people lacking access to freshwater and 2.7 billion experiencing freshwater scarcity at least one month a year. Efficient, portable, and universal photothermal materials are required for popularity of solar-driven evaporation systems. Herein, a facile one-pot process based on solution-processed vapor phase polymerization is adopted to fabricate polypyrrole-coated cellulose nanocrystals (CNC-PPy). The CNC-PPy dispersed in water is used as an ink (CNC-PPy ink) to create photothermal layers. The developed ink is readily laminated on diverse substrates utilizing a common paintbrush that firmly attached without any delamination after drying. The optimized cellulose membrane (6 coating cycles) presents an excellent evaporation rate of 1.96 Kg m-2 h-1 with corresponding light-to-vapor efficiency of 88.92 % at 1 sun. In addition, the CNC-PPy display excellent antibacterial and antifouling properties in powder and laminated forms against E. coli and S. aureus.

Tannic acid-mediated rapid layer-by-layer deposited non-leaching silver nanoparticles hybridized cellulose membranes for point-of-use water disinfection.

Gravity driven water filtration is a commonly used process of removing microorganism from the contaminated water. However, the existing strategies involve prolonged synthesis and toxic reducing agent for immobilization of silver nanoparticles (AgNPs) on cellulose membranes that are not suitable for routine handling. We have developed a non-toxic and environmentally benign method using TA mediated silver salt layer-by-layer (LbL) in-situ reduction method. Our LbL method exhibited the properties of controlled size and uniform distribution of in-site AgNPs on the surface of the membranes. The LbL deposited AgNPs hybrid membranes displayed an excellent antibacterial activity which have been validated through an efficient bacterial filtration performance against the Escherichia coli (E. coli). The present method for developing hybrid membranes offered a simple, rapid, low-cost, sustainable, and large-scale fabrication for bacterial filtration which could be used for the point-of-use applications, particularly at resource-limited and remote areas.

Water-Stable Flexible Nanocellulose Chiral Nematic Films through Acid Vapor Cross-Linked Glutaraldehyde for Chiral Nematic Templating.

Cellulose nanocrystals (CNCs) have drawn considerable attention for their use in optical and sensor applications due to their appealing properties of chiral nematic photonic structures. However, the flexibility and water instability of neat CNC chiral nematic films are questionable and compromise their outstanding properties. We propose a room-temperature process for fabricating flexible, water-stable chiral nematic CNC films. Aqueous glutaraldehyde (GA) was first mixed with CNCs, and then free-standing films were formed by evaporation-induced self-assembly. The chiral nematic dry films that formed were then exposed to hydrochloric acid vapor for subsequent GA cross-linking with CNCs. The GA cross-linked CNC films had a highly ordered chiral nematic organization. The enhanced water stability of the films was demonstrated by using GA cross-linked CNC films as freestanding template substrates for conducting polymers (polypyrrole) and metal oxides (iron oxide) to form flexible chiral nematic photonic hybrids.