Suppression of gold nanoparticle agglomeration and its separation via nylon membranes

Using Sparfloxacin-Capped Gold Nanoparticles to Modify a Screen-Printed Carbon Electrode Sensor for Ethanol Determination

Alcohol is a dangerous substance causing global mortality and health issues, including mental health problems. Regular alcohol consumption can lead to depression, anxiety, cognitive decline, and increased risk of alcohol-related disorders. Thus, monitoring ethanol levels in biological samples could contribute to maintaining good health. Herein, we developed an electrochemical sensor for the determination of ethanol in human salivary samples. Initially, the tetra-chloroauric acid (HAuCl4) was chemically reduced using sparfloxacin (Sp) which also served as a stabilizing agent for the gold nanoparticles (AuNPs). As-prepared Sp-AuNPs were comprehensively characterized and confirmed by UV-visible spectroscopy, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and elemental mapping analysis. The average particle size (~25 nm) and surface charge (negative) of Sp-AuNPs were determined by using dynamic light scattering (DLS) and Zeta potential measurements. An activated screen-printed carbon electrode (A-SPE) was modified using Sp-AuNPs dispersion, which exhibited greater electrocatalytic activity and sensitivity for ethanol (EtOH) oxidation in 0.1 M sodium hydroxide (NaOH) as studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). DPV showed a linear response for EtOH from 25 µM to 350 µM with the lowest limit of detection (LOD) of 0.55 µM. Reproducibility and repeatability studies revealed that the Sp-AuNPs/A-SPEs were highly stable and very sensitive to EtOH detection. Additionally, the successful electrochemical determination of EtOH in a saliva sample was carried out. The recovery rate of EtOH spiked in the saliva sample was found to be 99.6%. Thus, the incorporation of Sp-AuNPs within sensors could provide new possibilities in the development of ethanol sensors with an improved level of precision and accuracy.

Novel PVDF-PVP Hollow Fiber Membrane Augmented with TiO2 Nanoparticles: Preparation, Characterization and Application for Copper Removal from Leachate

High proportion of copper has become a global challenge owing to its negative impact on the environment and public health complications. The present study focuses on the fabrication of a polyvinylidene fluoride (PVDF)-polyvinyl pyrrolidone (PVP) fiber membrane incorporated with varying loading (0, 0.5, 1.0, 1.5, and 2.0 wt%) of titanium dioxide (TiO₂) nanoparticles via phase inversion technique to achieve hydrophilicity along with high selectivity for copper removal. The developed fibers were characterized based on scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), permeability, porosity, zeta potential, and contact angle. The improved membrane (with 1.0 wt% TiO₂) concentration recorded the maximum flux (223 L/m²·h) and copper rejection (98.18%). Similarly, 1.0 wt% concentration of TiO₂ nanoparticles made the membrane matrix more hydrophilic with the least contact angle of 50.01°. The maximum copper adsorption capacity of 69.68 mg/g was attained at 1.0 wt% TiO₂ concentration. The experimental data of adsorption capacity were best fitted to the Freundlich isotherm model with R² value of 0.99573. The hybrid membrane developed in this study has considerably eliminated copper from leachate and the concentration of copper in the permeate was substantially reduced to 0.044 mg/L, which is below standard discharge threshold.

Utilization of Nano-TiO2 as an Influential Additive for Complementing Separation Performance of a Hybrid PVDF-PVP Hollow Fiber: Boron Removal from Leachate

The continuous increase in anthropogenic activities resulting in an increase in boron concentration in the environment is becoming a serious threat to public health and the ecosystem. In this regard, a hybrid polyvinylidene fluoride (PVDF)-polyvinyl pyrrolidone (PVP) hollow fiber was synthesized with hydrophilic nano-titanium oxide (TiO₂) at varied loadings of 0, 0.5, 1.0, 1.5, and 2.0 wt% using the phase inversion technique. The resultant membranes were characterized in terms of Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), contact angle, porosity, and zeta potential. The permeability flux was assessed using both pure water and leachate; also, rejection performance was evaluated based on boron removal from the leachate. The results revealed that the membrane with 1.0 wt% loading had the highest flux alongside an upturn in boron rejection percentage of 223 L/m²·h and 94.39%, respectively. In addition, the lowest contact angle of 50.01° was recorded with 1.0 wt% TiO₂ loading, and this implies that it is the most hydrophilic. Throughout the experiment cycles, the fiber with 1.0 wt% TiO₂ loading demonstrated a high flux recovery varying between 92.82% and 76.26% after 9 h filtration time. The physicochemical analysis of the permeate revealed that the boron concentration was significantly reduced to 0.43 mg/L, which is far lower than the discharge limit of 1.0 mg/L.