Find in Library

Sodium citrate (SC) is sensitive to violet light illumination (VLI) and acts as a weak reductant. Conversely, gold (III) chloride trihydrate (GC) often acts as an oxidant in a redox reaction. In this study, the influences of colored light on the production of gold nanoparticles (AuNPs) in a mixture of gold (III) ions and citrate via VLI and the antibacterial photodynamic inactivation (aPDI) of <i>Escherichia coli</i> (<i>E. coli</i>) are determined under alkaline conditions. The diameter of AuNPs is within the range of 3–15 nm, i.e., their mean diameter is 9 nm; when citrate is mixed with gold (III) ions under VLI, AuNPs are formed via an electron transfer process. Additionally, GC mixed with SC (GCSC) inhibits <i>E. coli</i> more effectively under VLI than it does under blue, green, or red light. GCSC and SC are shown to inhibit <i>E. coli</i> populations by 4.67 and 1.12 logs, respectively, via VLI at 10 W/m² for 60 min under alkaline conditions. GCSC-treated <i>E. coli</i> has a more significant photolytic effect on anionic superoxide radical (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi mathvariant="normal">O</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>•</mo><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula>) formation under VLI, as more <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi mathvariant="normal">O</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>•</mo><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula> is formed within <i>E. coli</i> if the GCSC-treated samples are subjected to VLI. The <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi mathvariant="normal">O</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>•</mo><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula> exhibits a greater effect in a solution of GCSC than that shown by SC alone under VLI treatment. Gold (III) ions in a GCSC system appear to act as an oxidant by facilitating the electron transfer from citrate under VLI and the formation of AuNPs and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi mathvariant="normal">O</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>•</mo><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula> via GCSC photolysis under alkaline conditions. As such, the photolysis of GCSC under VLI is a useful process that can be applied to aPDI.