Silver nanoparticles supported on carbon nanotube carpets: influence of surface functionalization

Abstract

The effectiveness of nanoparticle-based functional devices depends strongly on the surface morphology and area of the support. An emerging powerful approach of increasing the available surface area without decreasing strength or increasing bulk is to attach arrays of suitable nanotubes on the surface, and to attach the necessary nanoparticles to them. Earlier publications by this team have shown that carpet-like arrays of carbon nanotubes (CNT) can be successfully grown on a variety of larger carbon substrates such as graphite, foams and fabric, which offer hierarchical multiscale supporting architecture suitable for the attachment of silver nanoparticles (AgNPs). A limiting factor of pure CNT arrays in fluid-based applications is their hydrophobicity, which can reduce the percolation of an aqueous medium through individual nanotubes. Previous studies have demonstrated that the treatment of CNT carpets with dry (oxygen) plasma can induce reversible wettability, and treatment with wet (sol-gel) coating can impart permanent wettability. In this paper, we report the influence of such treatments on the attachment of AgNPs, and their effectiveness in water disinfection treatments. Both types of hydrophilic surface treatments show an increase in silver loading on the CNT carpets. Oxygenplasma treated surfaces (O-CNTs) show fine and densely packed AgNP, whereas silica-coated nanotubes (silica-CNTs) show uneven clusters of AgNPs. However, O-CNT surfaces lose their hydrophilicity during AgNP deposition, whereas silica-CNT surfaces remain hydrophilic. This difference significantly impacts the antibacterial effectiveness of these materials, as tested in simulated water containing Gram negative Escherichia coli (E. coli, JM109). AgNPs on silicacoated CNT substrates showed significantly higher reduction rates of E. coli compared to AgNPs on plasma-treated CNT substrates, despite the finer and better dispersed AgNP distribution in the latter. These results provide important insights into different aspects of surface modification approaches that can control the wettability of CNT carpets, and their applicability in water treatment applications.

Wettability tailoring of nanotube carpets: morphology-chemistry synergy for hydrophobic–hydrophilic cycling

“…Some aspects of surface wettability in these materials, and their inuence on uid-based applications have also been discussed more recently. 33,34 It was shown that CNT carpets, as fabricated, are free from detectable defects and impurities, and tend to be super-hydrophobic. They can be made permanently hydrophilic with liquid phase silica coatings and temporarily hydrophilic through microwave plasma treatments.…”

In Situ Synthesis of Silver Nanoparticles on the Polyelectrolyte-Coated Sericin/PVA Film for Enhanced Antibacterial Application

“…The water contact angle was hardly changed before and after AgNPs modification, indicating that AgNPs modification did not affect the hydrophilicity of PEMs-SS/PVA film. Karumuri et al have reported that water contact angle has slightly gone down with AgNPs deposition, but the small difference does not affect the hydrophilicity [ 51 ].…”

Recent Advances in the Disinfection of Water Using Nanoscale Antimicrobial Materials

“…In addition, Gunawan et al decorated a polyacrylonitrile (PAN) hollow fiber membrane with Ag/MWCNTs (Figure F), and the resulting membrane with well‐dispersed Ag nanoparticles (Figure G) increased the hydrophilicity of MWCNTs, yielding a huge improvement in disinfection performance . Karumuri et al concluded that surface modification approaches (oxygen‐plasma treatment and liquid‐phase silica coating) could affect the distribution, growth, and deposition densities of Ag NPs on CNTs and tune the wettability of CNTs . Reports have shown that SWCNTs exhibit antibacterial properties via direct contact with bacteria (Figure H,I) .…”