Titanium dioxide/nitrogen-doped graphene-biopolymer based nanocomposite films for pollutant photodegradation and laser desorption ionization mass spectrometry of biomarkers

Titanium dioxide (TiO₂)/nitrogen-doped graphene (NG) nanocomposite is prepared via a solvent-free hydrothermal reaction. The resulting TiO₂/NG materials exhibit a reduction of the band gap energy compared to pristine TiO₂ from 3.27 eV to 2.69 eV. These materials are characterized by scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). To prepare biopolymer films with photocatalytic properties, TiO₂ and NG are mixed with biodegradable chitosan and spin-coated on a silicon wafer. Film roughness and thickness are evaluated by atomic force microscopy (AFM). These films are then tested for ciprofloxacin photodegradation by irradiating with visible light. In comparison to the TiO₂/chitosan films, the addition of NG substantially enhances photodegradation efficiency by up to 34 % upon the addition of 5 % w/w of NG. Furthermore, this film is shown to be a good substrate for biomarker detection using laser desorption ionization mass spectrometry (LDI-MS). In summary, this nanocomposite-biopolymer film provides good photocatalytic activity towards ciprofloxacin degradation and enhances the ionization efficiency of peptide biomarkers in LDI-MS owing to high efficiency of laser absorption/desorption. This nanocomposite film might be useful for environmental-related and medical application.