Journal of Applied Sciences and Nanotechnology

In this study, mesoporous silica nanoparticles (MSNs) with a hexagonal structure and large surface area were synthesized via a sol-gel method. The properties of the synthesized MCM-41 catalyst were characterized using BET, EDX, XRD, and FTIR analyses. The results showed that the MCM-41 had a high surface area of 966 m2/g and large pore volume of about 0.91 cm3/g. Sunflower oil was converted to biodiesel in a batch reactor at different temperatures (40, 50, 60 °C), methanol-to-oil molar ratios (6:1, 9:1, 12:1), catalyst loadings (0.7, 0.9, 1.25 wt%), and reaction times (up to 80 min) using the prepared catalyst under atmospheric pressure. The biodiesel yield was found to reduce when the reaction time exceeded 1 hour despite maintaining the catalyst. The maximum biodiesel yield of 45% was obtained under optimal conditions of a 9:1 methanol-to-oil ratio, 1.25 wt% catalyst loading, 60 °C temperature, and 60 min reaction time. GC-MS analysis characterized the biodiesel composition and properties. The synthesized biodiesel showed improved properties compared to conventional fuels, with linoleic acid methyl ester (C17H34O2, 25.93%) as the main component. The MCM-41 catalyst exhibited remarkable catalytic activity and could be recovered, regenerated, and reused, reducing reaction costs. This makes it a potential alternative to homogeneous catalysts that complicate product separation.

In scientific research, the search for cost-efficient and scalable functional materials for substantial and practical applications is necessary. Therefore, metallic materials at the nanoscale represent a rapidly growing area of research, especially as plasmonic materials in the field of surface-enhanced Raman scattering (SERS). In this study, the potential of copper nanowires (CuNWs) and palladium nanoparticles (PdNPs) as thin films on the porous silicon (PS) surface was investigated and compared. Their parameters as plasmonic SERS sensing materials were investigated by detecting sodium nitrite (NaNO2) molecules as the analyzing material. CuNWs and PdNPs were locally deposited on the PS substrate by the immersion method to synthesize Cu/PS and Pd/PS SERS sensors. The successful fabrication of these sensors was confirmed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), and Raman measurements. The results show that the nanostructures of the metallic thin films are evenly distributed on the PS surface and that hot spot areas have formed in between. The Raman peaks of NaNO2 were effectively detected even at extremely low concentration values. Therefore, CuNWs and PdNPs were integrated with PS in the SERS to improve the detection process. Excellent detection of (510-6) M NaNO2 concentration was achieved with the Cu/PS and Pd/PS SERS sensors with high amplification factors of (0.43108) and (0.11108), respectively.

In this work, room temperature laser ablation with an iron target in water was used to create iron oxide nanoparticles (IONPs) with a different number of pulses (100, 200, 300, 400 and 500) at a constant energy of 200 mJ. The colloidal solutions of the IONPs were studied and the effects of the number of pulses on the properties were investigated by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), ultraviolet-visible spectroscopy (UV-VIS) and photoluminescence (PL). The FTIR spectra showed that the synthesised IONPs were formed, and the peaks appeared between (500-600) cm-1. FESEM images showed that the IONPs have hemispherical structures and become spherical with increasing laser pulses. They also exhibited a small aggregation due to electrostatic forces. The UV-VIS results showed that the IONPs had an absorption shoulder at 300-400 nm, which increased with the laser pulses. The PL spectra of the IONPs showed strong, sharp peaks in the UV region at 370 nm, the intensity of which increased with increasing pulse duration, while the density of the nanoparticles in the solution increased. In addition, the antibacterial activities were evaluated using an agar well diffusion assay against Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), Streptococcus mutans (S. mutans) and Acinetobacter baumannii (A. baumannii). The result showed that the IONPs have good antibacterial activity, which increased with the laser pulses due to the increased concentration of IONPs. A hemolysis and in vitro toxicity test also evaluated the compatibility with human blood on red blood cells.

Refractory ceramics were produced using silicon carbide (SiC) as the main component in combination with different weight percentages of Iraqi white kaolin (20%, 40%, 60% and 80%). Two different weight percentages of alumina (5% and 10%) were then added to each SiC-kaolin mixture. The samples were effectively mixed, molded, dried and fired at 1300 °C. The structural and physical properties were measured, including X-ray diffraction, apparent porosity, water absorption and thermal conductivity. X-ray diffraction showed that the addition of Al2O3 to the SiC-kaolin composite increased the mullite phase by interacting with the excess silica formed during the firing of kaolin or with the silica formed during the oxidation of SiC. The increase in kaolin content in the composite without alumina was accompanied by a decrease in physical properties, as the apparent porosity decreased from 30.17% to 17.95% and the water absorption from 16.31% to 7.07%. The addition of 80 wt.% kaolin led to a decrease in thermal conductivity from 35 to 15 W/m.K. The addition of 10 wt% Al2O3 also reduced the apparent porosity and water absorption to 13.85% and 5.33% respectively for the (SiC-20 wt% kaolin) sample. The apparent porosity and water absorption of the sample (SiC-80 wt% kaolin) with 10 wt% Al2O3 reached the lowest values of 9.44% and 3.55%, respectively. The thermal conductivity decreased from 15 to 12 W/m.K. This study found that adding alumina improves refractory efficiency due to its high melting point, making it ideal for high-temperature applications.

In this study, cadmium oxide (CdO) was prepared by pulsed laser ablation in liquid (PLAL). The morphological structure and optical properties of the prepared CdO were determined by various analytical techniques, including SEM, AFM and XRD. The SEM images obtained showed that the prepared film exhibited cluster-like cubic structures. The AFM images showed a homogeneous and very uniform surface. In addition, XRD analysis revealed that the prepared film had a grain size of about 20 nm. The optical properties of the fabricated film showed an increase in absorbance values with a simultaneous increase in wavelength. The maximum value was measured at 340 nm, and the measured optical energy gap was about 2.55 electron volts (eV). The solar cell was produced by depositing a CdO film on the porous silicon. The fabricated solar cell achieved an efficiency of 0.16%. Therefore, the CdO film from this work could be an important factor for the development of gas sensors and solar cells. In addition, other powerful analytical techniques were performed in this study, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL) observations.