Silver nanoprism synthesis by H₂O₂-triggered shape transformation of silver nanospheres

Abstract

This dissertation presents a novel approach for synthesizing colloidal silver nanoprisms (AgNPrs) with controllable localized surface plasmon resonance (LSPR) via a chemical shape transformation of silver nanospheres (AgNSs) induced by hydrogen peroxide (H₂O₂). The shape conversion was carried out by feeding H₂O₂ solution into a starch-stabilized AgNSs colloid under an ambient condition. Oxidative dissolution and mild reducing action of H₂O₂ under an alkaline condition serve as principal reactions for the conversion process. Initial concentration of AgNSs, mole ratio of H₂O₂:AgNSs, H₂O₂ feed rate, and mixing efficiency are the key parameters for controlling the LSPR wavelengths of AgNPrs as the in-plane dipole plasmon resonance (IPDPR) can be selectively tuned across visible and near infrared regions (i.e., 460–850 nm). AgNPrs exhibited mixed geometries e.g. hexagonal, truncated triangular, and rounded-tip triangular prisms, and circular disk with the average bisector lengths in the range of 30 to 120 nm and the thickness of 10 to 20 nm. Concentrated AgNPrs with a final concentration up to 11 mM can be produced. “Blue” AgNPrs with edge length in the range of 80–120 nm exhibited the antibacterial activities against various tested bacteria with minimum inhibition concentration (MIC) of 5 ppm. They can also be incorporated in moist wound dressing composed of nanobiocellulose fibers. The efficiency of the developed antiseptic wound dressing was clinically approved for the cavity wounds.