Iranian Journal of Materials Science and Engineering

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The principal goal of this research is to produce a CrN/Cu multilayer coating and a CrN single-layer
coating and also compare their electrochemical and antibacterial behavior. In this investigation, the coatings were
applied to the stainless steel substrate by cathodic arc evaporation a sub-division of physical vapor deposition
(CAE-PVD). The present phases were characterized and the thickness of the coatings was measured using X-ray
diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. Rockwell-C tester was
used to evaluate the adhesion quality. Also, to evaluate the mechanical properties of the coatings such as modulus
of elasticity and hardness, a nanoindentation test was used and the indentation effect and coating topography were
evaluated using atomic force microscopy (AFM). Studying the electrochemical behavior of the coatings was done
using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests in Ringer's
solution. The results of EIS tests showed that the CrN coating had higher polarization resistance in comparison to
the CrN/Cu coating and an increasing trend of polarization resistance related to both coatings was identified by
rising the time of immersion. Also, using the PDP curves, the CrN and CrN/Cu coating current densities were
estimated at 1.835×10-8 and 2.088×10-8, respectively. The antibacterial activity of CrN and CrN/Cu coatings was
evaluated by the spot-inoculation method. The results of the antibacterial test indicated that compared to CrN
coating, CrN/Cu coating had a better impact on the control of the bacteria growth.

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Drug-resistance among bacteria is a concerning issue in medical field. Silver nanoparticles (AgNPs) are one of the promising novel nano-antibiotics. In the present study, AgNPs were synthesized using cell-free extract of Acinetobacter sp. challenged with silver nitrate. Preliminary observations done using UV-Vis spectrophotometry at 420 nm. Complete reduction of silver ions to AgNPs was confirmed through cyclic voltammetry. Electron microscopy revealed formation of spherical shaped nanoparticles of size upto 20 nm. These AgNPs were furthr used to determine their effect on activity of various antibiotics against pathogenic bacteria such as Neisseria and Xanthomonas. Higher antibacterial activity of AgNPs was observed against Gram-negative bacteria. Enhanced antibacterial action of AgNPs was observed with selected beta-lactam antibiotics producing upto 3-fold increase in area of zone of inhibition. On exposure to AgNPs, the minimum inhibitory concentration and minimum bactericidal concentration of antibiotics were lowered by upto 2000 times indicating potential synergistic action of AgNPs. This study clearly signifies that the drug, proved to be inefficient due to bacterial resistance, could be made functional again in presence of AgNPs. This will help in development of novel antibacterial formulations containing antibiotics and nanoparticles to combat multiple drug-resistance in microorganisms.

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Researchers are increasingly focusing on green synthesis methods for silver nanoparticles due to their cost-effectiveness and reduced environmental impact. In this study, we utilized an edible bird's nest (EBN), a valuable economic resource, as the primary material for synthesizing silver nanoparticles using only water as the solvent. Metabolite profiling of the EBN extract was conducted using LC-QTOF-MS in positive mode (ESI+), revealing the presence of lipids, glycosides, peptides, polysaccharides, and disaccharides. Upon the addition of silver nitrate to the aqueous EBN extract, noticeable color changes from transparent to brown indicated the successful formation of AgNPs. Subsequent characterization of these silver nanoparticles involved UV-Visible spectroscopy, which revealed an absorption peak at 421 nm. Further characterization was carried out using FESEM, ATR-FTIR spectroscopy, and EDX analysis. The involvement of phenolic agents, proteins, and amino acids in reducing the silver particles was confirmed. The synthesized nanoparticles exhibited a spherical shape, and a particle size ranging from 10 to 20 nm. The presence of elemental silver was confirmed by a strong, intense peak around 3 keV in the EDX spectrum. To assess their potential, the antibacterial properties of the silver nanoparticles against Escherichia coli and Staphylococcus aureus were evaluated using the agar diffusion method.
 

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Nanomaterials have significantly transformed multiple scientific and technological fields due to their exceptional properties, which result from their quantum confinement effects and high surface-to-volume ratios. Among these materials, zinc oxide (ZnO) and titanium dioxide (TiO₂) nanoparticles have attracted considerable interest because of their diverse applications.
In this study, TiO₂-ZnO nanocomposites were synthesized using varying calcination times of 1, 1.5, 2, 2.5, and 3 hours. Characterization of fabricated samples through X-ray diffraction (XRD)‌ spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDXS) confirmed the successful fabrication of the nanocomposites. In this regard, XRD analysis revealed anatase TiO₂ and hexagonal wurtzite ZnO phases. Raman spectroscopy also supported these findings, identifying characteristic peaks of both TiO₂ and ZnO.
The calcination time had a minimal effect on the crystal structures and also morphology of the nanocomposites, which gave rise to its negligible impact on optical properties and biological activities of the samples. Optical properties assessed by means of UV-visible and photoluminescence (PL) spectroscopy showed consistent band gap absorption and emission profiles across all samples, among which the nanocomposite calcined for 1 hour exhibited the best optical properties.

The sample prepared at 1 hour not only showed the most favorable optical properties, but also demonstrated significant antibacterial, antifungal, and cytotoxic activities, which make it suitable for various applications. In this regard, a reduction of more than 99.9% occurred in the number of Escherichia coli and Staphylococcus aureus bacteria and also Candida albicans fungus by using TiO₂-ZnO nanocomposite. Besides, addition of 500 µg/ml of nanocomposite decreased the cell viability to 34.47%, which signifies its high cytotoxicity activity.

 

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The copper oxide nanoparticles were synthesized using a precipitation method, recognized for its significance in antibacterial applications. This study reports the synthesis of pure CuO and CuO:Cd nanoparticles at two different concentrations, and explores their structural properties and antibacterial activity. The structural characteristics of the prepared powders were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Raman spectra were also examined using a 543 nm laser wavelength. XRD analysis confirmed that the as-synthesized samples exhibit a face-centered monoclinic structure, with crystallite size decreasing as dopant concentration increases, as estimated using the Scherrer method. The obtained crystallite sizes ranged from 7.13 to 11.72 nm, likely due to the larger atomic radius of Cd compared to Cu. The major Raman lines observed included Au2 (156 cm^-1), Ag (∼294 cm^-1), Bu2 (∼598 cm^-1), and lines at 1100 cm^-1 and 1420 cm^-1. The antibacterial activity of the synthesized CuO and CuO:Cd specimens was evaluated using the Kirby-Bauer disk diffusion method against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. The antibacterial activity increased with higher Cd concentrations and smaller particle sizes, resulting in larger inhibition zones and higher percentage inhibition ratios for both types of bacteria.
The copper oxide nanoparticles were synthesized using a precipitation method, recognized for its significance in antibacterial applications. This study reports the synthesis of pure CuO and CuO:Cd nanoparticles at two different concentrations, and explores their structural properties and antibacterial activity. The structural characteristics of the prepared powders were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Raman spectra were also examined using a 543 nm laser wavelength. XRD analysis confirmed that the as-synthesized samples exhibit a face-centered monoclinic structure, with crystallite size decreasing as dopant concentration increases, as estimated using the Scherrer method. The obtained crystallite sizes ranged from 7.13 to 11.72 nm, likely due to the larger atomic radius of Cd compared to Cu. The major Raman lines observed included Au2 (156 cm^-1), Ag (∼294 cm^-1), Bu2 (∼598 cm^-1), and lines at 1100 cm^-1 and 1420 cm^-1. The antibacterial activity of the synthesized CuO and CuO:Cd specimens was evaluated using the Kirby-Bauer disk diffusion method against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. The antibacterial activity increased with higher Cd concentrations and smaller particle sizes, resulting in larger inhibition zones and higher percentage inhibition ratios for both types of bacteria.
 

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Despite being an effective material for food packaging, chitosan (CS) exhibited poor ductility when processed into film, which restricted its use in this industry. In this study, composite films with enhanced properties were developed by incorporating polyvinyl alcohol (PVA) into CS through a simple solution casting method. The effects of different PVA/CS weight ratios (70:30, 50:50, and 30:70 w/w) on the morphology, mechanical properties, antibacterial activity, and soil degradation of the composite films were analyzed. Compared to the pristine PVA film, increasing the CS content in the PVA/CS composite film enhanced thickness, stiffness, roughness, antibacterial efficiency, and degradation rate, while reducing tensile strength and elongation at break. Fourier transform infrared (FTIR) spectroscopy revealed the highest intermolecular interactions in the PVA/CS composite film with 70:30 w/w. Antibacterial activity tests and soil burial analysis demonstrated that the PVA:70/CS:30 composite exhibited significantly higher antibacterial activity toward Escherichia coli and Bacillus subtilis bacteria as opposed to PVA film, along with a moderate degradation rate of 76.76% following 30 days soil burial, effectively balancing biodegradability and material integrity. These findings suggest that the PVA:70/CS:30 composite is a promising alternative for sustainable and functional biodegradable packaging solutions.