Development of a novel fluorescence spectroscopy based method using layered double hydroxides to study degradation of E. coli in water

Layered double hydroxides (LDHs) belong to a class of 2D nanomaterials having metallic ions of varying valences and interlayer spacing as in brucite. Since their discovery, they are being used everywhere. However, their biomedical properties are the most explored as they exhibit advantages like biodegradability, biocompatibility, and ease of making composites. In this research, two types of LDHs i.e. Mg - Al and Zn - Al LDHs are synthesized via hydrothermal route. Two types of doping; Gd and Yb, are done to create Gd - Mg - Al, Gd - Zn - Al, Yb - Mg - Al and Yb - Zn - Al. After synthesis, LDHs are characterized by X-ray Diffraction, Scanning Electron Microscopy, Dynamic Light Scattering, Energy dispersive X-ray Spectroscopy, and UV-vis spectroscopy. Average length for LDHs was found out to be in the range of 275-467 nm whereas thickness was in between 67 nm and 135 nm via SEM. Hydrodynamic size came out to be between 331 nm and 1720 nm for all samples. Absorption wavelength for all samples was between 251 and 261 nm. A novel antibacterial approach utilizing LDHs was introduced, employing antibacterial photodynamic treatment. The results were quantified using fluorescence spectroscopy, taking tryptophan peak as bacterial indicator at 270 nm excitation. Spectra recorded in 285-550 nm range showed considerable bacterial degradation, notably with Yb - Zn - Al LDHs. The efficacy was further tested with Colony Forming Units. Notably, all synthesized particles outperformed UV light alone, demonstrating their versatility as photocatalysts for bacterial inactivation. This pioneering method provides a unique and effective strategy for antibacterial treatment.