Thermal Annealing Effect on Structural, Morphological, and Sensor Performance of PANI-Ag-Fe Based Electrochemical E. coli Sensor for Environmental Monitoring

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

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 Ag₂O 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.

A nanocomposite-based electrochemical sensor for non-enzymatic detection of hydrogen peroxide

Hydrogen peroxide (H₂O₂) plays important signaling roles in normal physiology and disease. However, analyzing the actions of H₂O₂ is often impeded by the difficulty in detecting this molecule. Herein, we report a novel nanocomposite-based electrochemical sensor for non-enzymatic detection of H₂O₂. Graphene oxide (GO) was selected as the dopant for the synthesis of polyaniline (PANI), leading to the successful fabrication of a water-soluble and stable GO-PANI composite. GO-PANI was subsequently subject to cyclic voltammetry to generate reduced GO-PANI (rGO-PANI), enhancing the conductivity of the material. Platinum nanoparticles (PtNPs) were then electrodeposited on the surface of the rGO-PANI-modified glassy carbon electrode (GCE) to form an electrochemical H₂O₂ sensor. Compared to previously reported sensors, the rGO-PANI-PtNP/GCE exhibited an expanded linear range, higher sensitivity, and lower detection limit in the quantification of H₂O₂. In addition, the sensor displayed outstanding reproducibility and selectivity in real-sample examination. Our study suggests that the rGO-PANI-PtNP/GCE may have broad utility in H₂O₂ detection under physiological and pathological conditions.