Antibacterial Activity of Graphene Oxide/g-C₃N₄ Composite through Photocatalytic Disinfection under Visible Light

Abstract

Carbon-based nanomaterials have been widely developed into innovative antimicrobial agents due to their advantages of high surface-to-volume ratio, extremely high mechanical strength, and distinct physicochemical properties. Here, the nanocomposite of graphene oxide/graphitic carbon nitride (GO/g-C3N4), a free-metal photocatalyst, was fabricated through sonication at room temperature and its antibacterial activity against Escherichia coli (E. coli) was investigated. The 100 μg/mL GO/g-C3N4 composite was found to kill 97.9% of E. coli after 120 min visible light irradiation, which was further confirmed by fluorescent-based cell membrane integrity assay. Additionally, the holes produced by photocatalysis were confirmed by electron spin resonance (ESR) spectra and trapping experiments to participate in photocatalytic sterilization as principal active species and were further verified by transmission electron microscopy (TEM) and scanning electron microscope (SEM) to lead to the distortion and rupture of cell membrane and finally cell death. Further photoluminescence (PL) spectra, cyclic voltammetry, photocurrent generation, and impedance spectroscopy (EIS) characterization revealed that the introduction of GO contributed to separate photogenerated electrons and prevents the electron–hole pairs of g-C3N4 from recombing to generate more h+, thus directly improving the bactericidal ability of GO/g-C3N4. Reusability assays indicated that the GO/g-C3N4 retained more than 90% of activity after four cycles of use. This study facilitates an in-depth understanding of the mechanism of visible light-driven disinfection and provides an ideal candidate sterilizing agent for treating microbial-contaminated water.

Two‐Dimensional Materials for Antimicrobial Applications: Graphene Materials and Beyond

“…Sun and co-workers introduced GO to g-C 3 N 4 ,w hich not only boosted light absorption but also benefitted the photogenerated electron-hole separation, and led to an increasei nv isible-light-induced bacterial eradication. [189] Furthermore, similar to other 2D materials, the layered structure of g-C 3 N 4 nanosheets are suitable nanoparticle carriers. Because noble-metal NPs can act as electron acceptors that prevent the rapid recombination of the photoexcited electron-hole pairs, and Ag is ak nown antibacterial metal, it was reported by Bing et al that AgNPs-embedded g-C 3 N 4 nanosheets (AgNPs/g-C 3 N 4 ,s ee the TEM image in Figure 16a)s how outstanding antibacterial efficacy and the ability to disperse bacterial biofilms when exposed to visible light (Figure 16b).…”

Two‐dimensional nanomaterials for photocatalytic water disinfection: recent progress and future challenges

“…All these studies have provided meaningful hints for developing novel graphene‐based antibacterial photocatalysts. An increasing amount of progress has been made in combining graphene with diverse semiconductors for water disinfection including Ag 3 PO 4 ‐GO, CdS‐GO, carboxylated GO‐CuS, GO‐g‐C 3 N 4 , Bi 2 MoO 6 ‐GO, etc.…”

“…Besides coupling with Ag‐based materials, another intriguing method to accelerate charge separation in g‐C 3 N 4 is to combine it with graphene oxide . With high light transmittance and conductivity, graphene and its derivatives work as excellent electron sinks, enhancing both light response and electron–hole separation.…”

“…84 Besides coupling with Ag-based materials, another intriguing method to accelerate charge separation in g-C 3 N 4 is to combine it with graphene oxide. 58 With high light transmittance and conductivity, graphene and its derivatives work as excellent electron sinks, enhancing both light response and electron-hole separation. The GO-g-C 3 N 4 hybrid showed remarkably better performance than the pure g-C 3 N 4 towards E. coli inactivation and there was little loss of activity after four rounds of test and recollection.…”

Construction of 3DOM Carbon Nitrides with Quasi‐Honeycomb Structures for Efficient Photocatalytic H2 Production

“…[24,25] Furthermore, the graphenelike architecture composed of a two-dimensional skeleton of tris-triazine linked by a tertiary amine makes g-C 3 N 4 highly steady in different carbon nitride materials and in different chemical conditions (bases, acids or organic solvents). [26][27][28][29] In addition, the bandgap of~2.5 eV corresponding to 460 nm in the visible light scope endows g-C 3 N 4 an excellent visible-light active photocatalyst for hydrogen production and degradation of organic cyanamidic pollutants. [30][31][32] However, the traditional two-dimensional layered g-C 3 N 4 has low photocatalytic activities due to the narrow visible light response range, high recombination probability of electronhole, low quantum efficiency, and small specific surface area.…”