On-Paper Synthesis of Silver Nanoparticles for Antibacterial Applications

This chapter provides a new concept and strategic approach to optimising use of AgNPs in practical applications without compromising their excellent functionalities. Direct, in situ synthesis of AgNPs, called on-paper synthesis, is successfully achieved by using a paper matrix composed of ceramic fibers as a main framework and ZnO whiskers as a selective support for AgNPs via a simple soaking treatment with AgNO3 solution. As-prepared AgNPs@ZnO paper with the appearance of flexible cardboard is convenient for a wide range of practical uses, and demonstrates excellent antibacterial performance against both Gram-negative E. coli and Gram-positive B. subtilis, with much greater efficacy than paper composites containing either ionic Ag or commercial crystalline Ag microparticles. Thus, this method provides highly-functional AgNPs in a form that can be easily handled, and will open up a new avenue for promoting the effective use of AgNPs in practical applications. On-paper synthesis has broad applications and can be extended to a diverse array of metal NPs. CuNPs are successfully synthesized from an aqueous solution of Cu(NO3)2, and CuNPs@ZnO paper offers exceptional catalytic performance in the methanol reforming process for hydrogen production. AuNPs@ZnO paper, which is prepared from HAuCl4 complex as a precursor, can mediate the complete conversion of CO to CO2 at room temperature. Thus the novel on-paper synthesis approach allows us to design a variety of nanomaterials containing metal NPs that maintain their original excellent functionality, and metal NPs@paper composites with convenience in handling are expected to be promising materials in a wide range of future applications. Such a new concept for practical immobilization of metal NPs will break new ground in metal NPs engineering fields.