Urinary tract infections, especially catheter-associated urinary tract infections (CAUTIs), are the most common type of nosocomial infections. Patients with chronic indwelling urinary catheters have a higher risk of infection due to biofilm formation on the urinary catheter surface. Therefore, in this work, a novel, cost-effective antimicrobial urinary catheter was developed using green technology. Silver nanoparticles (AgNPs) synthesized from Mon Thong durian rind waste were used as an antimicrobial agent for the prevention of infection. Flavonoids, phenolic compounds, and glucose extracted from durian rind were used as a reducing agent to reduce the Ag⁺ dissolved in AgNO₃ solution to form non-aggregated AgNPs under light irradiation. The AgNPs were simultaneously synthesized and coated on the inner and outer surfaces of silicone indwelling urinary catheters using the dip coating method. The results showed that the antimicrobial urinary catheter fabricated using a 0.3 mM AgNO₃ concentration and 48 h coating time gave the highest antibacterial activity. The as-prepared spherical AgNPs with an average diameter of 9.1 ± 0.4 nm formed on catheter surfaces in a monolayer approximately 1.3 µm thick corresponding to a 0.712 mg/cm² silver content. The AgNP layer was found to damage and almost completely inhibit the growth of Escherichia coli cells with antibacterial activity by 91%, equivalent to the commercial, high-price antimicrobial urinary catheter. The cumulative amount of silver released from the coated catheter through artificial urine over 10 days was about 0.040 µg/mL, which is less than the silver content that causes tissue and organ toxicity at 44 µg/mL. Thus, we concluded that the developed antimicrobial urinary catheter was useful in reducing the risk of infectious complications in patients with indwelling catheters.

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.

The performance of a metal-enhanced fluorescence (MEF) substrate is fundamentally based on the orientation of the metal nanostructures on a solid substrate. In particular, two-dimensional (2D) periodic metallic nanostructures exhibit a strong confinement of the electric field between adjacent nanopatterns due to localized surface plasmon resonance (LSPR), leading to stronger fluorescence intensity enhancement. The use of vertical vibration-assisted convective deposition, a novel, simple, and highly cost-effective technique for preparing the 2D periodic nanostructure of colloidal particles with high uniformity, was therefore proposed in this work. The influences of vertical vibration amplitude and frequency on the structure of thin colloidal film, especially its uniformity, monolayer, and hexagonal close-packed (HCP) arrangement, were also investigated. It was found that the vibration amplitude affected film uniformity, whereas the vibration frequency promoted the colloidal particles to align themselves into defect-free HCP nanostructures. Furthermore, the results showed that the self-assembled 2D periodic arrays of monodisperse colloidal particles were employed as an excellent template for a Au thin-film coating in order to fabricate an efficient MEF substrate. The developed MEF substrate provided a strong plasmonic fluorescence enhancement, with a detection limit for rhodamine 6G as low as 10⁻⁹ M. This novel approach could be advantageous in further applications in the area of plasmonic sensing platforms.