The efficiency of photocatalytic antibacterial surfaces is limited by the absorption of light in it. Light absorption in photocatalytic surfaces can be enhanced by structuring it, leading to increased generation of reactive oxygen species (ROS) and hence improved bactericidal efficacy. A second, more passive methodology to kill bacteria involves the use of sharp nanostructures that mechanically disrupt the bacterial membrane. Recently, these two mechanisms were combined to form photoactive nanostructured surfaces with better antibacterial efficacy. However, the design rules for fabricating the optimal photoactive nanostructured surfaces have not been articulated. Here we show that for optimal performance it is very important to account for optoelectrical properties and geometry of the photoactive coating and the underlying pillar. We show that TiO2-coated nanopillars arrays made of SiO2, a material with a low extinction coefficient, have 73% higher bactericidal efficacies than those made of Si, a material with a high extinction coefficient. The finite element method (FEM) shows that despite the higher absorption in higher aspect ratio nanopillars, their performance is not always better. The concentration of bulk ROS saturates around 5 μm. For taller pillars, the improvement in surface ROS concentration is minimal due to the diffusion bottleneck. Simulation results corroborate with the experimentally observed methylene blue degradation and bacterial count measurements and provide an explanation of the observed phenomenon. The guidelines for designing these optically activated photocatalyst nanopillars can be extended to other photocatalytic material after adjusting for their respective properties.

No abstract

No abstract

No abstract

Antimicrobial peptides have been demonstrated to display an immediate response to a large set of pathogenic activity against viruses, bacteria, and fungi by virtue of their local binding with phospholipid phosphatidylserines to exert cytotoxic effect. Plasmonic nanostructures are particularly appealing in medical diagnostics and therapeutics owing to their biocompatibility and ease of surface modification. The current article reports a development of ε‐poly‐l‐lysine modified gold nanorod (PLL‐AuNR) Raman‐active system that can be used to target pathogenic bacteria along with rapid monitoring of antimicrobial action from environmental samples. Result indicates a remarkable change in Raman enhancement factor from 1.49 × 104 to 2.17 × 107 after addition of Salmonella, Bacillus subtilis, and Escherichia coli bacteria in PLL‐AuNR colloid, enabling a large optical window to monitor the process of pathogenic action. Antimicrobial assay with PLL‐AuNR reveals significantly high cytotoxic values of ~92% in E. coli, ~90% in B. subtilis, and ~87% in Salmonella compared with their respective responses in bare PLL, which shows ~37% in E. coli, ~32% in B. subtilis, and ~27% in Salmonella, which proportionally collaborates with change in surface‐enhanced Raman spectroscopy (SERS) intensity beyond 10 min of incubation time. Major experimental design parameters and possible mechanism that relates unusual plasmonic enhancement and antimicrobial action of PLL‐AuNR system have also been discussed.