One step synthesis of Ag nanoparticles incorporated PVA nanocomposite via plasma reduction route

Abstract

PVA/Ag nanocomposite films were synthesized via a one-step plasma-solution reduction method with varying processing times. Following synthesis, the PVA/Ag NP solutions were cast to form films, which were subsequently characterized by TEM, XRD, FTIR, XPS, UV-Vis, and Raman spectroscopy. Antimicrobial activity was evaluated using an agar diffusion test. TEM analysis confirmed the presence of Ag NPs with diverse sizes and shapes, averaging around 16.1 nm. XRD analysis showed a distinct peak at 2θ = 38°, corresponding to the Ag (111) plane in films synthesized at 10, 15, and 20 min, indicating the formation of crystalline Ag NPs. XPS results demonstrated an increased O/C ratio in plasma-synthesized PVA/Ag nanocomposite films, along with a new peak at 369.15 eV attributed to the Ag 3d orbital, confirming the presence of Ag NPs within the PVA matrix. FTIR spectra further suggested the formation of coordinate bonds between Ag NPs and PVA polymer chains. UV-Vis analysis revealed a localized surface plasmon resonance (LSPR) peak at approximately 425 nm, with a redshift to 445 nm at a longer processing time (20 min). This suggests alterations in NP size or interaction with the matrix. The optical bandgap of PVA/AgNP films decreased with longer plasma processing time, accompanied by increased film opacity. Raman analysis highlighted the potential use of PVA/Ag NP films (synthesized at 5 min) as substrates for surface-enhanced Raman spectroscopy (SERS). The PVA/Ag NP composite synthesized at a plasma processing time of 20 min exhibited considerable antibacterial activity against S. aureus and C. albicans. Also, the percentage of biofilm inhibition of S. aureus was 65%, compared to the control. Collectively, these findings suggest that plasma-synthesized PVA/Ag NP nanocomposite films are promising candidates for various applications, including optical devices, food packaging, SERS, and wound dressings.

Keywords: Ag NPs; Antimicrobial properties; Nanocomposites; Opacity; Optical energy gap; PVA; SERS; XPS.

Fig. 1

(a) Optical emission spectrum of atmospheric-pressure Ar plasma, (b) Plasma treatment of the PVA/AgNO₃ solution mixture, and (c) Photograph of the PVA/AgNPs composite film.

Fig. 2

The XRD spectra of pristine PVA and PVA/AgNPs composites synthesized by plasma at different plasma processing times.

Fig. 3

(a) TEM image and (b) size distributions of AgNPs for PVA/AgNPs sample synthesised by plasma at a processing time of 20 min.

Fig. 4

The FTIR spectra of pristine PVA and PVA/AgNPs composites synthesized by plasma at different plasma processing times.

Fig. 5

UV/VIS spectra of pristine PVA and PVA/AgNPs composites synthesized by plasma at different plasma processing times.

Fig. 6

Variation of (α E)^1/2 (a) and (α E)² (b) with the photon energy for pristine PVA and PVA/AgNPs composites synthesized by plasma at different plasma processing times.

Fig. 7

(a) Survey spectra of pristine PVA and PVA/Ag (20 min) samples, (b) C 1s spectrum of PVA and (c) C 1s of PVA/Ag (20 min) samples.

Fig. 8

High resolution spectra of (a) Ag 3d for PVA/Ag (20 min) sample, (b) O 1s spectrum of PVA and (c) O1s of PVA/Ag (20 min) samples.

Fig. 9

Raman spectra of (a) pristine PVA and PVA/AgNPs films synthesized via plasma irradiation for (b) 2 min, (c) 5 min, (d) 15 min and (e) 20 min.

Fig. 10

Antimicrobial activity of the pristine PVA and the plasma synthesized PVA/AgNPs against (a) S. aureus and (b) Candia albicans. 1 is the pristine PVA, and 2, 3, 4, 5, and 6 are PVA/AgNPs samples synthesized by plasma at plasma processing times of 2, 5, 10, 15, and 20 min, respectively.

Fig. 11

Anti-biofilm formation by S. aureus by the pristine PVA and PVA/AgNPs samples synthesized via plasma at plasma processing times of 20 min.