Catalytic evaluation and in vitro bacterial inactivation of graphitic carbon nitride/carbon sphere doped bismuth oxide quantum dots with evidential in silico analysis

Abstract

Herein, Bi₂O₃ quantum dots (QDs) have been synthesized and doped with various concentrations of graphitic carbon nitride (g-C₃N₄) and a fixed amount of carbon spheres (CS) using a co-precipitation technique. XRD analysis confirmed the presence of monoclinic structure along the space group P2₁/c and C2/c. Various functional groups and characteristic peaks of (Bi-O) were identified using FTIR spectra. QDs morphology of Bi₂O₃ showed agglomeration with higher amounts of g-C₃N₄ by TEM analysis. HR-TEM determined the variation in the d-spacing which increased with increasing dopants. These doping agents were employed to reduce the exciting recombination rate of Bi₂O₃ QDs by providing more active sites which enhance antibacterial activity. Notably, (6 wt%) g-C₃N₄/CS-doped Bi₂O₃ exhibited considerable antimicrobial potential in opposition to E. coli at higher values of concentrations relative to ciprofloxacin. The (3 wt%) g-C₃N₄/CS-doped Bi₂O₃ exhibits the highest catalytic potential (97.67%) against RhB in a neutral medium. The compound g-C₃N₄/CS-Bi₂O₃ has been suggested as a potential inhibitor of β-lactamase_{E. coli} and DNA gyrase_{E. coli} based on the findings of a molecular docking study that was in better agreement with in vitro bactericidal activity.

Fig. 1. (a and b) Synthesis of g-C₃N₄ and CS doped Bi₂O₃ QDs.

Fig. 2. (a) XRD patterns, (b) FTIR spectra of pure and (3 and 6 wt%) g-C₃N₄/CS-doped Bi₂O₃ and (c–e) SAED images of pristine and CS-Bi₂O₃ and (3 wt%) g-C₃N₄ doped Bi₂O₃.

Fig. 3. (a) UV-vis reflectance spectra (b) PL spectra of Bi₂O₃, CS-Bi₂O₃ (3 wt%) g-C₃N₄/CS-Bi₂O₃ and (6 wt%) g-C₃N₄/CS-Bi₂O₃ respectively.

Fig. 4. TEM images of (a) Bi₂O₃ (b) CS-Bi₂O₃ (c) (3 wt%) g-C₃N₄/CS-doped Bi₂O₃ (d) (6 wt%) g-C₃N₄/CS-doped Bi₂O₃ QDs.

Fig. 5. Catalytic activity of pristine and (3, 6 wt%) g-C₃N₄/CS-Bi₂O₃ in (a) neutral medium (b) basic medium, and (c) acidic medium.

Fig. 6. Binding interaction pattern of (a) superimposed complexes, (b) Bi₂O_3, (c) CS-Bi₂O_3, and (d) g-C₃N₄/CS-Bi₂O₃ QDs inside active pocket of β-lactamase_E. coli.

Fig. 7. Binding interaction pattern of (a) superimposed complexes, (b) Bi₂O₃, (c) CS-Bi₂O₃ and (d) g-C₃N₄/CS-Bi₂O₃ QDs inside active pocket of DNA Gyrase_E. coli.