In this study, we conducted a one-step photochemical synthesis to produce silver nanoparticles (AgNPs) with irregular morphology. The synthesis process involved the photoconversion of Ag nanoseeds into self-assembled Ag nanostructures of various morphologies using a high-pressure sodium lamp with a wavelength of 589 nm, corresponding to an energy of 2.1 eV. During the synthesis, the color of the colloidal Ag nanoseeds gradually changed as the irradiation time increased, transitioning from yellow to brown, juniper green, basil green, ocean green, aegean blue, and finally to true blue. We characterized the morphological evolution of the resulting AgNPs, as well as their optical properties and aggregation behavior, using transmission electron microscopy, UV-vis spectroscopy, and dynamic light scattering. Furthermore, we evaluated the impact of the self-assembled morphology of the AgNPs on their surface-enhanced Raman scattering efficiency, using R6G as the target analyte. The results revealed that the colloidal AgNPs synthesized under a visible light irradiation time of 1 h consisted of circular nanoplates, hexagonal nanoplates, trapezoid nanoplates, and triangular nanoplates. These colloidal AgNPs exhibited excellent SERS activity when used as an SERS-active substrate in the form of an aqueous solution, enabling the detection of low concentrations of R6G down to 10⁻¹² M.

Background and Aim: Public health and food safety are gaining attention globally. Consumer health can be protected from chemical residues in meat by early detection or screening for antibiotic residues before selling the meat commercially. However, conventional practices are normally applied after slaughtering, which leads to massive business losses. This study aimed to use portable surface-enhanced Raman spectroscopy (SERS) equipped with multivariate curve resolution-alternation least squares (MCR-ALS) to determine the concentrations of enrofloxacin, oxytetracycline, and neomycin concentrations. This approach can overcome the problems of business loss, costs, and time-consumption, and limit of detection (LOD). Materials and Methods: Aqueous solutions of three standard antibiotics (enrofloxacin, oxytetracycline, and neomycin) with different concentrations were prepared, and the LOD for each antibiotic solution was determined using SERS. Extracted pig urine was spiked with enrofloxacin at concentrations of 10, 20, 50, 100, and 10,000 ppm. These solutions were investigated using SERS and MCR-ALS analysis. Urine samples from pigs at 1 and 7 days after enrofloxacin administration were collected and investigated using SERS and MCR-ALS to differentiate the urinary enrofloxacin concentrations. Results: The LOD of enrofloxacin, oxytetracycline, and neomycin in aqueous solutions were 0.5, 2.0, and 100 ppm, respectively. Analysis of enrofloxacin spiking in pig urine samples demonstrated the different concentrations of enrofloxacin at 10, 20, 50, 100, and 10,000 ppm. The LOD of spiking enrofloxacin was 10 ppm, which was 10 times lower than the regulated value. This technique was validated for the first time using urine collected on days 1 and 7 after enrofloxacin administration. The results revealed a higher concentration of enrofloxacin on day 7 than on day 1 due to consecutive administrations. The observed concentration of enrofloxacin was closely correlated with its circulation time and metabolism in pigs. Conclusion: A combination of SERS sensing platform and MCR-ALS is a promising technique for on-farming screening. This platform can increase the efficiency of antibiotic detection in pig urine at lower costs and time. Expansion and fine adjustments of the Raman dataset may be required for individual farms to achieve higher sensitivity.

X-ray photoelectron spectroscopy (XPS) and Spectroscopic Ellipsometry (SE) were used to analyse the effect of oxygen plasma treatment on properties of aluminum oxide thin films. The aluminum oxide films were fabricated using a reactive sputtering system. The as-deposited films were treated with oxygen plasma powered by an RF generator. During the plasma treatment, the pressures were set at 1 x 10^-1 to 1x 10^-2 mbar, while the RF supplied powers at 100 W and 200 W. It was observed that lower plasma powers and higher pressures resulted in smoother films. The O/Al ratio of the films were found to decrease with increasing plasma powers and pressures. The thickness and refractive index of the films were significantly affected by the oxygen plasma treatment process, which could be related to the change in films’ packing density and the etching at the surface.