Designing Photocatalytic Nanostructured Antibacterial Surfaces: Why Is Black Silica Better than Black Silicon?

Singh, J and Jadhav, S and Avasthi, S and Sen, P (2020) Designing Photocatalytic Nanostructured Antibacterial Surfaces: Why Is Black Silica Better than Black Silicon? In: ACS Applied Materials and Interfaces, 12 (18). pp. 20202-20213.

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Abstract

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. © 2020 American Chemical Society.

Item Type:	Journal Article
Publication:	ACS Applied Materials and Interfaces
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to American Chemical Society.
Keywords:	Aromatic compounds; Aspect ratio; Light; Light absorption; Nanostructured materials; Photocatalytic activity; Silica; Silicon; Silicon oxides; Titanium dioxide, Antibacterial surfaces; Extinction coefficients; High extinction coefficients; Methylene blue degradations; Nanostructured surface; Optoelectrical properties; Photocatalytic materials; Photocatalytic surfaces, Nanopillars, antiinfective agent; hydroxyl radical; methylene blue; nanomaterial; oxygen; silicon; silicon dioxide; titanium; titanium dioxide; water, catalysis; chemistry; drug effect; Escherichia coli; light; microbial sensitivity test; oxidation reduction reaction; radiation response; surface property, Anti-Bacterial Agents; Catalysis; Escherichia coli; Hydroxyl Radical; Light; Methylene Blue; Microbial Sensitivity Tests; Nanostructures; Oxidation-Reduction; Oxygen; Silicon; Silicon Dioxide; Surface Properties; Titanium; Water
Department/Centre:	Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited:	06 Feb 2023 08:54
Last Modified:	06 Feb 2023 08:54
URI:	https://eprints.iisc.ac.in/id/eprint/79902

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