Excellent Dark/Light Dual-Mode Photoresponsive Activities Based on g-C3N4/CMCh/PVA Nanocomposite Hydrogel Using Electron Beam Radiation Method

Abstract

Photocatalytic technology for inactivating bacteria in water has received much attention. In this study, we reported a dark-light dual-mode sterilized g-C₃N₄/chitosan/poly (vinyl alcohol) hydrogel (g-CP) prepared through freeze-thaw cycling and an in situ electron-beam radiation method. The structures and morphologies of g-CP were confirmed using Fourier infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), solid ultraviolet diffuse reflectance spectroscopy (UV-vis DRS), and Brunauer-Emmett-Teller (BET). Photocatalytic degradation experiments demonstrated that 1 wt% g-CP degraded rhodamine B (RhB) up to 65.92% in 60 min. At the same time, g-CP had good antimicrobial abilities for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) within 4 h. The shapes of g-CP were adjustable (such as bar, cylinder, and cube) and had good mechanical properties and biocompatibility. The tensile and compressive modulus of 2 wt% g-CP were 0.093 MPa and 1.61 MPa, respectively. The Cell Counting Kit-8 (CCK-8) test and Hoechst33342/PI double staining were used to prove that g-CP had good biocompatibility. It is expected to be applied to environmental sewage treatment and wound dressing in the future.

Keywords: cell activity; electron beam radiation method; g-CP hydrogel; photocatalytic antibacterial; photocatalytic degradation.

Figure 1

(a–c) FTIR, XRD, and UV-Vis spectra of the four materials, respectively; (d) the band gap diagram of g-C₃N₄ and 2 wt% g-CP.

Figure 2

(a–d) XPS full spectrum, and C1s, N1s, and O1s spectra of 2wt% g-CP, respectively.

Figure 3

The front and side SEM images of PVA (a,b), CMCh/PVA (c,d), and 2wt% g-CP (e,f) hydrogels.

Figure 4

TEM images of g-C₃N₄ (a–c) and g-CP (d–f).

Figure 5

Nitrogen adsorption–desorption isotherms of PVA (a), CMCh/PVA (b), 2 wt% g-CP (c) hydrogels.

Figure 6

Test diagram of engineering performance. The stress–strain test diagrams of 2 wt% g-CP (a–f); the pictures of different geometric shapes and flexibility test drawings, respectively (g,h).

Figure 7

Performance tests of adsorption and photocatalysis. The fitting curves, the first-order kinetic fitting and second-order kinetic fitting curves of the adsorption capacity, and the time of RhB by three hydrogels, respectively (a–c); the UV absorption spectra of RhB adsorption–photocatalytic degradation by hydrogel with different g-C₃N₄ contents (d–h); free radical trapping diagram of g-CP (i).

Figure 8

Zone of inhibition and photocatalytic antibacterial tests. Inhibition of E. coli and S. aureus by different hydrogels under dark conditions in pictures (1: PVA, 2: CMCh/PVA, 3: g-CP), respectively (a,b); SEM images of g-CP against E. coli at 1 h, 2 h, and 12 h, respectively (c–e); the PVA, CMCh/PVA, and different amounts of g-CP hydrogels on the photocatalytic antibacterial performance of E. coli and S. aureus (f,g).

Figure 9

Cytotoxicity test of 2 wt% g-CP. The MTT assay map of 2 wt% g-CP on L929 cells (a); the toxicity images of 2 wt% g-CP by Hoechst33342/PI cell staining (b).

Scheme 1

Diagram of preparation process (a) and radiation synthesis mechanism of g-CP (b).