افشین پوراحمد

Rice husk is an agricultural by-product material comprising about 22% of the weight of rice. Even though some of this husk is converted into end products such as feedstock and adsorbent most is burnt openly, causing environmental and health problems especially in poor and developing countries. Therefore, it is very important to find pathways to fully utilize the rice husk.

In this study, the fabrication and characterization of ZSM-12 zeolite using rice husk ash as an alternative cheap silica source, and synthesis and characterization of magnesium oxide nanoparticles in ZSM-12 matrix by solid state reaction and ion exchange methods is reported. Disk diffusion method and MIC were used to evaluate the antimicrobial activity of nanoparticles on gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) strains of bacteria compared to standard commercial antibiotic disks.

Synthesized samples were evaluated using X-ray diffraction, scanning electron microscopy, energy dispersive X-Ray spectroscopy and transmission electron microscopy. XRD results revealed diffraction peaks for each of the two compounds in the MgO/ZSM-12 nanocomposite.

Transmission electron microscopy image of nanocomposite indicated that nanoparticles size of MgO is ~ 35 nm. Nanocomposite exhibited antibacterial activity with minimal inhibitory concentration of 96 µg/mL against E. coli and S. aureus.

Zeolite Y, MIL-53, and zeolite – MOF nanocomposite were synthesized. Synthesized samples were evaluated using X-ray diffraction, scanning electron microscopy, energy dispersive X-Ray spectroscopy and transmission electron microscopy. The XRD profiles of the zeolite Y /MIL-53 nanoporous coordination polymer nanocomposite depicted diffraction peaks that had been ascribed to individual MIL-53 MOF and zeolite Y. Based on the transmission electron microscopy result of the nanocomposite, it was determined that the compound was synthesized with a core-shell structure. TEM image of the consisted of two regions. One dark region related to Zeolite Y with a diameter of about 500 nm and light part with an average diameter of 60 nm that related to the MIL-53 shell. The EDX spectra of the core@shell sample show that the nanocomposite contained O, C, Al, Na, and Si elements. In this research, disk diffusion method and MIC were used to evaluate the antibacterial activity of prepared samples on gram-negative (E. coli and Pseudomonas aeruginosa) and gram-positive (S. aureus) compared to standard commercial antibiotic disks. Nanocomposite exhibited antibacterial activity with minimal inhibitory concentration of 55 µg/mL against E. coli, Pseudomonas aeruginosa and S. aureus.

The fabrication and characterization of ZSM-5 zeolite using rice husk ash as an alternative cheap silica source is reported. Rice husk, combusted at 700 ºC for the production of amorphous silica, has been used for the preparation of RHA-ZSM-5 zeolite.MgO nanoparticles were synthesized in the RHA-ZSM-5 matrix with a solid-state reaction method and calcined at 300°C. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Transmission electron microscopy, and scanning electron microscopy. XRD results revealed diffraction peaks for each of the two compounds in the nanocomposite. In the FT-IR spectra, all bands in the nanocomposite sample show a shift concerning that of the matrix, indicating that the MgO is incorporated in the matrix. Transmission electron microscopy images showed small particles belong to MgO nanoparticles with a maximum diameter of 26 nm.

In this work, core SiO2 –shell CuS nanostructures have beendeveloped using a simple wet chemical route. X-ray diffraction analysis XRD, diffuse reflectance spectroscopy DRS, scanning electron microscopy SEM, transmission electron microscopy TEM, EDS and fourier transform infrared FT-IR were used to characterize the products.The morphological studies revealed theuniformity in size distribution with core size of 250 nm andshell thickness of 7.5-17 nm. The structural studies indicate hexagonal structure of covellite CuS shell with no other trace for impurities in the crystalstructure. This CuS layer exhibit the band gap energy of3.1 eV, due to quantum confinement and numerousdefects presence.Photocatalytic activity of nanocomposites was studied for degradation of Methylene Blue MB under visible light. Several parameters were examined, catalyst amount 0.1–1 g L-1, pH 1–13 and initial concentration of MB 0.96–10 ppm. The extent of degradation was estimated from the residual concentration by spectrophotometrically.]]>

The investigation of the antibacterial activity of nanomaterials has regained importance due to increasing bacterial resistance to antibiotics. Inorganic antibacterial materials have several advantages over traditionally used organic agents; like chemical stability, thermal resistance, safety to the user, long lasting action period, etc. In this research, antibacterial properties of graphene - zinc oxide nanoparticles nanocomposite was evaluated for gram-positive (S. aureus) and gram-negative (E. coli and Pseudomonas aeruginosa) bacteria.
Material & The current study demonstrates homogenous decorating of zinc oxide nanoparticles (NPs) onto graphene oxide (GO) surface via simple chemical method.
Disk diffusion method and MIC were used to evaluate the antibacterial activity of ZnO nanoparticles on S. aureus, E. coli and Pseudomonas aeruginosa compared to standard commercial antibiotic disks.
XRD results revealed diffraction peaks for each of the two compounds in the nanocomposite. The XRD studies showed that the synthesized ZnO NPs have hexagonal wurtzite structure. It was found that GO addition induces a decrease in crystallite size. Average size of the ZnO NPs was estimated by transmission electron microscopy around 20 nm. ZnO nanoparticles showed bactericidal effects on Gram-positive and Gram-negative bacteria. The improved antibacterial activity of ZnO nanoparticles compared to its microparticles was related to the surface area enhancement in the nanoparticles.
The novel nanocomposite exhibits excellent antibacterial activity against gram-positive (S. aureus) and gram-negative (E. coli and Pseudomonas aeruginosa) bacteria.

The fabrication and characterization of mesoporous material using rice straw ash as an alternative cheap silica source is reported. Rice straw, combusted at 500 ºC for the production of amorphous silica, has been used for the preparation of mesoporous material. Magnesium oxide nanoparticles were successfully synthesized in mesoporous matrix through a solid state reaction method. The synthesized samples were characterized by XRD, FTIR, SEM and TEM. Disk diffusion method and MIC were used to evaluate the antimicrobial activity of nanoparticles on S. aureus and E. coli compared to standard commercial antibiotic disks. XRD results reveal diffraction peaks for each of the two compounds in the nanocomposite. The XRD studies show that the synthesized MgO nanoparticles have cubic structure. Transmission electron microscopy images showed small particles belong to magnesium oxide nanoparticles with maximum diameter 19 nm.

Microbial contamination is a great threat to human health. Studies have shown that antimicrobial compounds made from a variety of NPs have high antimicrobial activity. The potential effects of nanostructured metal oxides on the reduction of microbial contaminants are well established. The present study aimed to investigate the antimicrobial activities of magnesium oxide nanoparticles in zeolite matrix on Gram-positive and Gram-negative bacteria.
MgO nanoparticles were successfully synthesized from Mg (NO3)2.6H2O in large mordenite matrix through a solid state reaction method. The synthesized samples were characterized by XRD, FTIR, SEM and TEM. Disk diffusion method and MIC were used to evaluate the antimicrobial activity of MgO nanoparticles on Staphylococcus aureus and Escherichia coli compared to commercial antibiotic disks.
XRD results reveal diffraction peaks for each of the two compounds in the nanocomposite. The XRD studies show that the synthesized magnesium oxide NPs have cubic structure. Average size of the NPs was estimated by transmission electron microscopy around 14 nm. Based on the results, these nanoparticles have antimicrobial activity against selected bacteria.
MgO indicate strong antibacterial activity related to alkalinity and active oxygen species. MgO nanoparticles damage the cell membrane and then cause the leakage of intracellular contents which in turn lead to death of the bacterial cells.

Zeolites are crystalline aluminosilicates with a well-defined microporous structure. Depending on their structure and composition, zeolites are widely used as sorbents, detergents, ion-exchangers, heterogeneous catalyst and especially as host for metal oxide or metal nanostructures. Silver oxide (Ag2O), an intrinsic p-type semiconductor with band gap1.46eV, has been widely investigated as an essential material for potential practical applications in antibacterial material, photocatalysis, silver-oxide batteries, and gas sensing. In this study, the spherical structure of Ag2O NPs was synthesized in the Large Mordenite matrix. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and Scanning electron microscopy (SEM). TEM images show small spherical nanoparticles belong to Ag2O nanoparticles with mean diameter 2–14 nm. The antibacterial activity of Ag2O/Large Mordenite nanocomposite was tested against Gram- negative (E. coli) and Gram- positive (S. aureus) bacteria and compared with standard antibiotics.

Drug resistance, particularly methicillin resistant in Staphylococcus aureus strain is a major worldwide public health concern. The present study aimed to synthetize selenium nanoparticles, investigate its antibacterial effect and its ability to be used as ampicillin nanocarrier.
Selenium nanoparticles were synthetized via chemical regeneration of sodium selenite by L-systein amino acid. Loading of ampicillin on the surface of selenium nanoparticles was done by gradual addition of antibiotic to nanoparticle solution and continuous shaking. Then this attachment was investigated by using UV-Vis spectroscopy, XRD and scanning electron microscope. Antibacterial properties of produced selenium nanoparticles and antibiotic loaded selenium nanoparticles against standard strain of S. aureus and 10 methicillin resistant S. aureus strains were tested by disc diffusion method. Minimum inhibitory concentration (MIC) of bacterial growth was determined by broth macrodilution method.
The produced selenium nanoparticles showed antibacterial effect against all strains of S. aureus. Loading of ampicillin on the surface of selenium nanoparticles enhanced the antimicrobial activity of this drug. The mean MIC of selenium nanoparticles against S. aureus strains ranged between 7.8-62.5 µg/mL free form of ampicillin between 62.5- 250 and ampicillin bound to nanoparticles was 7.8-7.8 μg / mL. These values for standard strain of Staphylococcus aureus strains were 7.8, 31.2 and 3.9 μg / mL, respectively. Loading of ampicillin on the surface of selenium nanoparticles enhanced the MIC against methicillin resistant S. aureus.
The obtained results confirmed antibacterial activity of selenium nanoparticles. Enhancing the antibacterial activity of antibiotics loaded on the surface of nanoparticles, increases the possibility of application of these drugs especially for the elimination of hard-to-heal infective diseases.