Effects of cold atmospheric plasma treatment on the morphological and optical properties of plasmonic silver nanoparticles

Abstract

The use of plasma processes in nanomaterial synthesis is limited by a lack of understanding of the effects of plasma treatment on the morphology and other properties. Here, we studied the effects of atmospheric plasma treatment on the morphology and optical properties of Ag nanoparticles. The Ag nanoparticles were deposited on substrates by injecting an aerosol into flowing argon gas and then treated with a low-temperature atmospheric plasma jet. After plasma treatment, the mean Ag nanoparticle diameter reduced to an average of 5 nm, which was accompanied by a blue shift of ∼70 nm in the peak of the surface plasmon resonance; these results are similar to those obtained by thermal treatment at elevated temperatures. The reduction in nanoparticle size is explained by the redox reaction that occurs on the nanoparticle surface, which is evident from the presence of AgO and Ag 2 O Raman peaks in the treated sample. The surface charge changed as a result of plasma treatment, as indicated by a large change in the zeta potential from +25.1 ± 4 mV for the untreated sample to −25.9 ± 6 mV after 15 min of plasma treatment. Surface-enhanced Raman spectroscopy of the plasma-treated films was carried out with the fluorescent dye Rhodamine 6 G, which showed a ∼120-fold enhancement in the signal intensity relative to the untreated substrates. We, therefore, conclude that cold-plasma treatment modified the surface morphology of the Ag nanoparticles, thereby enhancing their optical properties. This technique could be applied to a wide range of nanoparticle systems used in biosensing applications.

Plasma-Induced Enhancement in Electronic Properties of Gold Nanoparticles: Application in Electrochemical Biosensing of Cortisol

“…29,30 In our earlier work published in 2020, we have systematically studied the interaction of the plasma species with metal nanoparticles. 19 The plasma was characterized by optical emission spectroscopy (OES) to investigate the energy of the reactive species such as oxygen, hydrogen, nitrogen, argon, and free electrons. These reactive species interacted with the surface of the NPs and removed the surface citrate capping of AuNPs.…”

“…The removal of citrate capping induced the redox reaction on the AuNP surface and modified the arrangement and surface roughness. 19 The redox reaction that was induced by plasma treatment resulted in the size reduction of NPs. The SERS response of the plasmatreated AuNPs (Figure 5) evidenced the removal of citrate capping and surface oxide formation.…”

“…The energy required for the Au oxidation reaction to happen was 1.42 V. 32 However, the energy provided in plasma treatment was around 1eV, which explained the broader size distribution and partial surface oxide formation. 19 The optical emission spectra (OES) was carried out to characterize the plasma and to investigate the species present. There were a few oxygen species present in the plasma.…”

“…The downstream plasma jet contains energetic electrons as well as reactive ion species, which are responsible for the surface plasma chemistry. , In our earlier work published in 2020, we have systematically studied the interaction of the plasma species with metal nanoparticles . The plasma was characterized by optical emission spectroscopy (OES) to investigate the energy of the reactive species such as oxygen, hydrogen, nitrogen, argon, and free electrons.…”

Recent developments in cold plasma‐based enzyme activity (browning, cell wall degradation, and antioxidant) in fruits and vegetables

“…The plasma retains the transferred energy as a cloud of active particles for a short period. These active particles can react with fruit and vegetable materials in the plasma, moving their stored energy into enzymes (Sonawane et al., 2020). These reactive species cause the enzyme inactivation by impeding the coenzyme and/or substrate from binding and, subsequently, the catalysis step.…”