Challenges in Nano and Micro Scale Science and Technology
Volume:11 Issue: 2, Summer-Autumn 2023

In this research, membranes based on polyvinyl alcohol polymer were surface modified using graphene oxide nanostructures, and the effect of this layering on the performance and properties of the membrane was investigated and evaluated. Graphene oxide nanostructures were produced using a non-thermal plasma jet. The surface morphology and hydrophilicity of prepared membranes were studied using the AFM, SEM, FTIR, and CA analyses. The analyses showed a rougher surface with more hydrophilicity for the modified membranes than the pure PVA membrane. Also, the separation performance of membranes using a cross-flow filtration system was investigated for different salt solutions. The modified nanofiltration membrane with graphene oxide, showed good separation performance for Na2SO4 and NaCl salts, 94% and 38%, respectively. On the other hand, the high-water flux for the two salts mentioned above, 60 L/m2.h and 73 L/m2.h respectively, was obtained for the modified nanofiltration membrane with graphene oxide. In sum, this study shows that the separation performance of nanofiltration membranes can be effectively improved by adjusting the different factors in the groups that changed the graphene oxide surface. Also, membranes modified using graphene oxide nanostructures have more suitable antibacterial properties compared to other unmodified membranes.

The main goal and innovation of this study is to analyze the effects of the configuration of the walls and their orientation (parallel or perpendicular to the flow direction) on the behavior of the thermal properties of the fluid. So, in this paper, the effects of shape, size, and surfaces wettability of nanochannel with a focus on walls configuration on the thermal conductivity of fluid are investigated. Equilibrium molecular dynamics simulation is used for this purpose. Two parallel plates, a square cross-sectional nanochannel, and a rectangular cross-sectional nanochannel are examined as three different nanochannel shapes. According to results, the shape and size of the nanochannel are a significant factor in thermal conductivity, which is caused by the effect of walls on the mobility and arrangement of fluid atoms in the nanochannel. The walls have a negative effect in terms of the mobility of atoms, but in terms of the arrangement of the atoms, they have opposite effects depending on their orientation (perpendicular or parallel to the desired direction). As a result, in a same channel height, square channels have a higher thermal conductivity than slit channels, since the side walls affect thermal conductivity positively. The results also indicate that with the increase in the wettability of the nanochannel surfaces, the thermal conductivity decreases. In this case, fluid thermal conductivity is more affected by the walls.

In this paper, a numerical strategy is presented to analyze the bending and buckling responses of aluminum composite plates (ACPs) reinforced by nano-scale silicon carbide and micro-scale discontinuous fiber-like silicon carbide. First, the equivalent mechanical properties of multiscale fillers-reinforced ACPs are predicted using a nested micromechanics-based approach. It is considered that discontinuous fibers are randomly dispersed into the hybrid material system. Thereafter, the finite element (FE) method is employed to evaluate the bending and buckling characteristics of hybrid ACPs. The influences of volume fraction of nano-filler, aspect ratio, alignment and volume fraction of micro-filler, shape and thickness of the plate on the ACP structural responses are examined. The results indicate that reinforcing the metal-based structures by nano/micro multiscale silicon carbide fillers significantly improves their load bearing capacity. The hybrid ACPs with higher volume fractions of multiscale fillers possess larger critical buckling loads. It is observed that by (i) increasing the aspect ratio, and (ii) aligning discontinuous fiber-like silicon carbide, the critical buckling load of ACP is increased, while its maximum deflection is decreased.

Undoped and Strontium doped ZnO thin films were deposited by pulse laser deposition whose average crystallite size lies within the range of 38–53 nm. The deposited film's structure showed that the films crystallized in hexagonal wurtzite structure. The band gap was originating to be 3.31 and 3.20 eV for undoped ZnO and Sr doped ZnO thin films, respectively due to the lattice distortion and creation of active imperfections in the ZnO lattice. The photoluminescence emissions confirmed the presence of defects related to oxygen vacancies and zinc interstitials. SEM images revealed plate-like morphology with hexagonal shape regardless of the sizes. The sensing results revealed that ZnO doped 3% Strontium exhibited the highest response, achieving 41 % at 50 ppm ethanol at an operating temperature of 352 °C. The electrical sheet resistance per square area of undoped ZnO and Sr doped ZnO thin films was obtained to be 4.5×10^(+7) Ω/sq and 7.0×10^(+7) Ω/sq, respectively. ZnO thin films have been studied extensively for electronics and optoelectronic applications..

Food samples are facing enormous challenges from contaminants of heavy metal ions that are released into the environment by long-term industrial and agricultural activities. One of the most hazardous environmental pollutants is cadmium ions (Cd(II), Cd2+) because of their high toxicity and long-term stability. Heavy metal ions tend to enter into human body by the food chain and cause liver damage, nervous system diseases, as well as kidney. Since the trace of Cd2+ excess to its limit is very hazardous a sensitive determination method for cadmium ions is very important. One of the methods for monitoring cadmium heavy metal ions is electrochemical technique. The techniques based on modified electrodes can act as efficient method for sensitive analysis of Cd2+ in real samples. Among the different modifiers, carbon nanotubes (CNTs) have been used broadly over the last two decades for various potential applications in electrode modification systems. CNTs due to the tubular structures are one of the most valuable modifiers because of their distinct features for instance inertness, porous structure, low density, and affinity for pollutants. In the present work, modified electrochemical sensors based on CNTs were reported to show their potential as active materials for sensitive detection of Cd2+ in food complicated samples.

Guanine, a purine base in deoxyribonucleic acid (DNA), has a low redox potential, making it susceptible to oxidation and contributing to DNA damage and mutations. In the current study, a new polymer nanocomposite consisting of nickel oxide-Mobile crystalline material-41 (NiO-MCM-41) nanocomposites and poly(5-sulfosalicylic acid) (PSSA) was prepared by electropolymerization for modification of the graphite/glassy carbon electrode (Gr/GCE) surface and sensitive measurement of the guanine. The synthesized nanocomposite was identified and confirmed by FE-SEM, EDX and FT-IR techniques. The electrochemical behavior of guanine on the surface of the PSSA/NiO-MCM-41/Gr/GCE was analyzed in optimal conditions using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The proposed modified electrode achieved a satisfactory dynamic range between the anodic peak current and the concentration of guanine, with a linear range of 0.001–36 µM, a sensitivity of 0.977 µA/µM, and the detection limit (LOD) was determined to be 0.5 nM (signal/noise = 3). This sensor was successfully used in the determination of guanine in the real sample of fish sperm’s DNA.