Journal of Applied Sciences and Nanotechnology

This study investigates the effects of pulsed Nd:YAG laser annealing at a wavelength of 532 nm on the photoconductivity properties of cadmium sulfide (CdS) thin films prepared by thermal evaporation. In addition, measurements at room temperature showed an ohmic behavior in the voltage-current characteristics of the CdS thin films. It was observed that after laser irradiation, the photosensitivity of the film increased due to the improved crystallinity and decreased defect density of the thin films, as shown by the increase in the ratio of light to dark current (Iph/Id) from 0.35 to 0.42. The photocurrent also follows the relationship (Iph∝FγI), with γ-values of 1.037 and 1.047 after annealing due to monomolecular recombination, reduced grain boundaries and enhanced recrystallization. The spectral response peaked at 585 nm, which corresponds to the optical band gap of the CdS thin film. The transient photoconductivity, which describes the time-dependent change in the electrical conductivity of the material when exposed to light, was measured and showed significantly increased decay rates. The differential lifetime (τd) decreased from (90.8 sec) to (39.2 sec) after Nd:YAG laser annealing, which can be attributed to a lower density of defect states and an improvement in film quality. The results highlight the ability of Nd:YAG laser annealing to maximize the photonic and electronic properties of CdS thin films through structural and carrier recombination dynamics, increasing their use in optoelectronic devices.

New approaches have been developed to combat bacterial infections because of the growing threat of antibiotic-resistant bacteria. Gold colloidal nanoparticles and their applications as antibacterial agents have shown promising strategies due to these properties. The properties of nanoparticles, including size, shape, and surface charge, play an essential role in determining antibacterial activity. Pulsed laser ablation in a liquid medium was utilized to produce gold nanoparticles, an environmentally friendly method. Gold NPs were produced in ultrapure water. Experimental research was done to determine the impact of the number of laser pulses on the nanoparticles' size, shape, and concentration. Surface plasmon resonance (SPR) peaks for gold nanoparticles were detected by UV–visible spectroscopy at approximately 525 nm in the visible region. Transmission electron microscopy (TEM) showed the appearance of spherical nanoparticles with an average size of 20 to 80 nm. For gold nanoparticles, increasing laser pulses from 100 to 250 pulses while maintaining the fixed energy of the laser at 600 mJ reduced the average nanoparticle size. S. mutans were isolated to study and evaluate the antibacterial effects of AuNP substances using the suitable diffusion method. The antibacterial examination revealed valuable results for gold nanoparticles, which showed a more significant effect on bacteria at high concentrations. The best results were found for the sample prepared at the highest concentration at 250 pulses. Toxicity assessments of the materials revealed low toxicity levels of this material, confirming their safety for human use.

In this work, several types of plasmonic sensors were prepared by different methods (ion reduction method and wet-chemical KOH route) to detect the ultralow anti-CIPRO concentration using AgNPs/PSi SERS-active substrate with AgNPs concentration. The process was optimized to be very effective in detecting CIPRO and to have a high amplification factor (EF). For the deposition of AgNPs with a concentration of 5×10-3 M and the maximum density of hotspot areas, a nanocrystalline silicon sample prepared by the KOH method and an ion reduction technique before etching was used. We tested an AgNPs/PSi SERS substrate, which showed better performance in detecting the CIPRO antibiotic over a range of doses (10-7-10-13 M). XRD, EDX, FESEM and SERS were used to analyze the PSi samples and the AgNP/PSi chemical sensors. The results of the AgNPs/PSi SERS substrates from both methods showed that the ion reduction process was more effective in detecting the CIPRO antibiotics at their lowest concentrations. It was found that the highest EF at salt concentrations of 5×10-3M was 6.3×1012 for the pre-etching method, compared with 7.78×1010 for the KOH method under the same conditions. The results showed that the proposed AgNPs/PSi SERS substrate is an effective method to find CIPRO even at low concentrations, and that CIPRO was localized approximately near the surface. This approach is considered a revolutionary work that has the potential to modify the plasmonic properties of metallic NPs for SERS applications.

In this study, Fe₂O₃ nanoparticles were synthesized by a hydrothermal method using chitosan extract and ferric chloride (FeCl₃) as precursor at 150 °C. The hydrothermal approach provides precise control over the size and morphology of the nanoparticles by promoting the decomposition and crystallization of the precursors near their evaporation temperatures. The aim of this study was to quantify the antibacterial activity of the nanoparticles to regulate the production of Fe₂O₃ NPs. The optical and structural properties of Fe₂O₃ nanoparticles (NPs) were investigated and tested using various techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL). The crystal size and hexagonal structure of Fe₂O₃ NPs in the range of 10 to 25 nm were determined by XRD. In addition, FESEM images were used for measurement. The morphology and particle size of the Fe₂O₃ NPs, which is between 15.63 and 56.84 nm due to the aggregation of the nanoparticles. The UV-visible spectra were used to calculate the direct and indirect optical band gap versus hν of the Fe₂O₃ NPs prepared by the hydrothermal method from chitosan extract NPs. These are 3.8 eV and 3.6 eV, respectively. The band edge emission of Fe₂O₃ NPs was about 2.57 eV as measured by photoluminescence (PL) spectroscopy. Inhibition zones of 40 mm in size were observed for Staphylococcus aureus and Escherichia coli.

The current work focuses on assessing flexural properties, and water uptake of polymeric composites prepared using various reinforcements. These additives consist of kaolinite nano clays and rock wool (RW). In addition to a polymer blend that consists of epoxy and polyester resins as the matrix. The castings were made using a hand lay-up approach. Nanoclay (NC) was added in weight fractions of 5% and 7%, together with RW added in a volume fraction of 10% as reinforcement. The impact test was employed to decide the optimum mixing ratio of the polymer blend that used as a matrix. From the results the blend consisting of 80 wt.% epoxy and 20 wt.% polyester has the highest impact strength value. Thermal analysis was done using differential scanning calorimetry (DSC) as a characterization method to assess the miscibility of the polymer blend. The polyester/epoxy blend showed the maximum flexural strength, which determined as (57.4) MPa. While the hybrid reinforcement using NC (5 wt.%) and RW (10%) lowered the flexural strength to 16.53 MPa. From the water absorption test results showed that, in addition to the standard concentration, the type of material also affects water, in addition to the ratios of its components. Finally, DSC results revealed the presence of two different glass transition temperatures, which indicates that the epoxy/polyester blend is immiscible and there are two distinct phases in this matrix.