# Tailored TiO2 Nanoparticles for Broad-Spectrum Antibiofilm Applications: A Systematic Comparison of Structural and Functional Properties of Carbon- and Nitrogen-Doped TiO2 Nanoparticles

## TL;DR

This study compares carbon- and nitrogen-doped TiO2 nanoparticles for their ability to destroy bacterial biofilms under visible light.

## Contribution

The paper provides a systematic comparison of the structural and functional properties of carbon- and nitrogen-doped TiO2 nanoparticles for antibiofilm applications.

## Key findings

- Carbon doping reduced the band gap more significantly than nitrogen doping, enhancing visible light absorption and ROS generation.
- Carbon-doped TiO2 nanoparticles showed 1.5-fold higher antibiofilm activity against S. aureus and E. coli under visible light.
- Gram-negative bacteria were less susceptible due to their outer membrane limiting ROS penetration.

## Abstract

Nonmetal doping extends the photocatalytic
response of
TiO2 nanoparticles (NPs) into the visible light region;
however,
systematic evaluations of how specific dopants influence their antimicrobial
performance remain limited. In this study, we present a direct comparison
of carbon-doped TiO2 (C-TiO2) and nitrogen-doped
TiO2 (N-TiO2) NPs synthesized via a sol–gel
method. Structural and optoelectronic properties were characterized
by powder X-ray diffraction (p-XRD), transmission electron microscopy
(TEM), attenuated total reflectance Fourier transform infrared spectroscopy
(ATR-FTIR), UV–vis diffuse reflectance spectroscopy (UV–vis
DRS), and X-ray photoelectron spectroscopy (XPS), confirming dopant
incorporation and band gap narrowing. Carbon doping resulted in a
more pronounced band gap reduction (2.66 eV compared with 3.09 eV
for N-TiO2), which correlated with stronger visible light
absorption and increased reactive oxygen species (ROS) generation.
Under visible light irradiation, C-TiO2 NPs achieved 80%
eradication of Staphylococcus aureus biofilms and 69% eradication of Escherichia coli biofilms, corresponding to a ∼1.5-fold higher antibiofilm
activity relative to N-TiO2 NPs. Differences in bacterial
susceptibility were associated with cell envelope architecture, in
which the outer phospholipid membrane of Gram-negative Escherichia coli likely limited ROS penetration and
contributed to lower eradication efficiency compared with Gram-positive Staphylococcus aureus. These findings demonstrate
that dopant selection directly modulates photocatalytic functionality
and identify C-TiO2 NPs as a broad-spectrum antimicrobial
material. The results have implications for the rational design of
TiO2-based nanomaterials in antimicrobial photodynamic
therapy (aPDT), indoor building environments where pathogen control
is essential, environmental remediation, and the development of next-generation
self-disinfecting surfaces.