JOURNAL OF NANOSTRUCTURES
Year:2019 | Volume:9 | Issue:3|Papers Count:20

Silver nanostructures as an effective antibacterial materials were synthesized via three various hydrothermal, sono-chemical and microwave methods using water as a green solvent. Then Chitosan-Ag polymer based nanocomposites were made by a fast chemical procedure. The influence of power, temperature and time on the morphology and particle size of the products was investigated. Scanning electron microscopy (SEM) approved that mono-disperse nanoparticles were achieved using all three procedures. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy confirmed preparation of pure products. The antibacterial behaviour of Chitosan-Ag nanocomposites was evaluated using degradation of E coli bacteria. The results show a nanocomposite with applicable antibacterial performance in burn wounds.

In recent years, the availability and use of various antibiotics and antimicrobial agents have resulted in increase of drug resistant pathogens. Therefore, scientist’ s attention has been diverted to find a suitable replacement for antimicrobial treatment. Graphene (G), as a two-dimensional (2D) carbon-based nanomaterials (CBNs) has a unique physicochemical properties including thermal, optical and electrically conductive activities along with high surface-to-volume ratio and mechanical strength. Also, they have gained significant attention in biomedical application, such as regenerative medicine and drug delivery carriers. With the emergent of nanomaterials over the past decades, there has been a growing interest in using GBNs to develop new antifungal and antimicrobial nanomaterials due to their diverse antifungal and bactericidal mechanisms and relatively low cytotoxicity towards mammalian cells. Numerous reviews on GBNs are available with different perspective. In this review, we summarized the latest progresses towards an understanding of the antifungal and antibacterial properties of GBNs for developing a new antifungal and antibacterial materials

In this study, BaZr1-xCoxO3 nanoparticles, x = 0. 00, 0. 04, 0. 06, 0. 08, 0. 10 and 0. 20, are synthesized through co-precipitation method. Therefore, structural, optical and magnetic properties have been investigated. The cubic perovskite structure is confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic measurements. The average crystallite size and micro strain are calculated by Williamson-hall analysis and they have been found to increase by increasing Co 2+ content. More emphasis is given for the calculation of the optical parameters from UV– visible absorption spectra. The optical bandgap is found to be decreasing; on the other hand Urbach energy increases with the increase in Co 2+ content. The refractive index of the samples obeys the singleoscillator model and the dispersion parameters such as single oscillator energy, dispersion energy, and lattice dielectric constant are calculated and their variations with Co 2+ content are reported. The undoped BaZrO3 nanoparticles exhibit unexpected superparamagnetic behavior and ferromagnetic hysteresis at room temperature for BaZr1-xCoxO3, x=0. 10 and 0. 20. With increasing in Co 2+ content, the concentration of oxygen vacancies increases and as a result the magnetic properties are improved. Thus, the most significant result of the present work is the modification of optical constants and the improvement of magnetic properties of BaZrO3 nanoparticles by partial Co 2+ substitution.

DNA-based nano-biosensors are emerging scope in the field of biosensors. Many synthetic single stranded functional DNAs have been applied for development of such sensors, recently. Immobilization of DNA oligonucleotides on the surface of gold nanoparticles is a key step in the development of most colorimetric nano-biosensors. The bound DNA is usually thiolated and forms Au-S covalent bond to the surface of gold nanoparticles. To this endeavor, the DNA must get reduced prior to immobilization. There are a variety of approaches for reduction of thiolated DNAs that mostly employ Dithiothreitol (DTT). DTT-based DNA reduction is not always complete and the sulfhydryl DNA (DSH) is not the sole product of the reaction. The results of the reduction of a thiolated DNA with DTT is analyzed in this paper with high performance liquid chromatography (HPLC) in order to find an optimal condition for DTT based reduction. Finally, the optimal condition is compared to TCEPbased reduction for the efficiency of DNA immobilization on the surface of gold nanoparticles.

The Fe nanowires were prepared by Ac electrodeposition method. The two steps anodized aluminum oxides (alumina) were used as templates for electrodeposition of magnetic nanowires. Sulfuric acid was used to anodize aluminum. The pours diameter and growth rate of alumina were investigated. The FeSO4 electrolyte was used for growth of nanowires. The prepared magnetic nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDX), and vibrating sample magnetometer (VSM).

In the present research, the primary crystallization kinetics of the amorphous Fe85. 3B11P3Cu0. 7 alloy was analyzed using non-isothermal DSC measurements. The average and local activation energies, Ea, were determined by different isokinetic and isoconversional methods. The results obtained for activation energy in this research, show that due to the complexity of the primary crystallization process in this alloy, isoconversional methods are more suitable than the isokinetic ones. The Avrami exponents lie between about 1 and 2 in a wide temperature range of 370˂ T≤ 410˚ C. This indicates that one dimensional growth of nuclei with a decreasing rate of nucleation is the main mechanism during nonisothermal primary crystallization process of the amorphous Fe85. 3B11P3Cu0. 7 alloy which is a new finding for this alloy. Study of magnetic properties in the amorphous and nanocrystalline states revealed that annealing the amorphous ribbons at 440˚ C for 10 minutes gives rise to a significant increase in saturation magnetization, Ms, i. e. from 144 in as-spun to 201 emu/g in annealed states. This amount of Ms makes this material a good candidate for different applications, especially in transformer cores.

Multiwall carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) with contents ranging from 1 to 10 phr (part per hundred parts of rubber) were selected and then characterized to reinforce acrylonitrile butadiene rubber (NBR) based composites. Fabrication of nanocomposites were done by a novel procedure and structural analysis along with variety of mechanical and chemical tests, according to the standard methods, were implemented to evaluate their properties. As a result, cure conditions, mechanical, and chemical properties of fabricated nanocomposites were further improved and optimized. The NBR nanocomposite containing 10 phr of MWCNTs devotes the best performance in curing time (13. 3 % reduction), shore A hardness (36. 4 % improvement), compression set (12. 2 % reduction) and swelling rate in methyl ethyl ketone solvent (by the amount of 120 %) than those of other prepared nanocomposites and as a result, this nanocomposite was proposed as a material with the best improved properties for further industrial applications. However, 1 and 5 phr contents of MWCNTs were found to be optimum values of nanofillers to be added to the NBR in case of tensile strength and elongation at break properties.

In the present study, silver nanoparticles were synthesized by decomposition of AgNO3 via gelcasting. Methacrylamide was used as a low toxic monomer for gel formation. Effect of monomer content (MAM), crosslinker to monomer ratio (MBAM/MAM), silver salt to monomer ratio (AgNO3/MAM), duration of calcination, and temperature of calcination were investigated to optimize the size of nanoparticles. Taguchi method was applied to study the effect of gelcasting parameters on the size of silver nanoparticles. Mentioned parameters were surveyed at four levels and based on the Taguchi method 16 experiments were carried out. Silver nanoparticles were characterized, and average particle sizes were measured by SEM analysis. By using the signal to noise ratio (S/N) analysis of the results, it is revealed that monomer content is the most effective parameter on size of particles. Also, optimal values of monomer content, cross-linker to monomer ratio, silver salt to monomer ratio, duration of calcination and temperature of calcination for the minimum particle size were found to be 4. 25 g (in 20 g water), 1: 3, 1: 15, 6 h and 650⁰ C, respectively. An evaluation test was performed with the optimal value of parameters, and suitable agreement between the prediction and experimental results was observed.

Microwave assisted facile one-step approach was adopted to prepare mono-dispersed silver sulfide nanoparticles. The structures of the synthesized Ag2S nanoparticles were confirmed by Fourier-transform infrared spectroscopy (FT-IR), diffuse reflectance UV-vis spectroscopy (DRS), X-ray diffractometer (XRD), energy dispersive X-ray analysis (EDX) and transmission electron microscope (TEM). The prepared Ag2S nanoparti-cles (NPs) were successfully used as a heterogeneous catalyst in the onepot three-component coupling reaction of aldehydes, amines and alkynes (A 3-coupling) toward propargylamines. In this protocol, both aromatic and aliphatic aldehydes and secondary amines were reacted with terminal alkynes in the presence of Ag2S NPs at low catalytic loading (0. 5 mol %) that led to the rapid and efficient formation of propargylamines with good to excellent yields. The A 3-coupling reaction occurred effectively at 80 o C under solvent-free conditions. The catalyst is easy to prepare and is perfectly stable under the reaction conditions. Also, the Ag2S NPs catalyst can be easily recovered and reused several times and exhibited higher catalytic activity than other some commercially catalysts.

Highly meso-porous Pt contained γ-Al2O3 nanostructure was prepared by a combined sol gel-pyrolysis method in the presence of polyvinylpyrrolidone and Pluronic p123 as surfactant. The surface of the prepared nanostructure was decorated with 1-Butyl-3-methylimidazolium hexafluorophosphate ([BMM]PF6) ionic liquid to enhance the sorption capacity and prevent the poisoning of the catalytic active sites. The catalyst was characterized by X-ray diffraction powder (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX), and Brunauer– Emmett– Teller surface analysis (BET) methods. The XRD pattern and the results of elemental analysis well confirmed the crystalline phase of gamma-alumina and the presence of Pt nanoparticles on the surface. Decolorization of Anazolene Sodium (AS) dye compound as a typical wastewater was carried out using H2O2 as oxidative agent and the results showed that the prepared nanostructure had promising catalytic activity. The results of the recycling experiments showed that [BMIM]PF6/Pt/γ-Al2O3 is more promising than Pt/γ-Al2O3 which points out the role of ionic liquid layer on the surface.

The adsorption behavior of hydrogen for synthesized graphitic carbon nitride (g-C3 N4 ) and graphene oxide nanosheets was compared. The structure of the prepared g-C3 N4 and graphene oxide samples were studied using TEM, FT-IR spectroscopy and surface area analysis. Textural results of the prepared nanosheets show that the surface area, total pore volume, and average internal diameter of g-C3 N4 and graphene oxide samples are similar. The hydrogen adsorption isotherms at 298 K, up to 22 bar pressures were as Type III and the maximum hydrogen storage capacities at 22 bar and 296 K were 1. 06 and 1. 27 mmol/g for graphite oxide and g-C3 N4 samples, respectively. The adsorption results were fitted by Freundlich model, which was related to reversible multilayer adsorption on non-uniform surface active sites with different affinities of both g-C3 N4 and graphene oxide adsorbents. Isosteric heat of adsorption of hydrogen on the graphene oxide varies from 8. 6 kJ. mol-1 (at low hydrogen uptake) to 4. 3 kJ. mol-1. These results are the range of 10. 1 to 4. 8 kJ. mol-1 for the prepared g-C3 N4 sample at same hydrogen uptake. The results show that the interaction between hydrogen molecules and tri-s-triazine units in g-C3 N4 structure are stronger than carbon atoms in graphene oxide structure.

In this paper, new various morphologies of boron carbide were successfully synthesized using carbon black, activated carbon and boron oxide precursors as well as using cobalt nanoparticles as catalysts. Almost the whole morphology of synthesized boron carbide are consisted of smooth nanowires and nanobelts. With decreasing the carbon black particles size from 29 nm to 13 nm (29, 23, 17 and 13), the synthesis efficiency of nanowires and nanobelts are increased. With increasing the temperature from 1500 ° C to 1700 ° C, the amounts of nanowires and nanobelts are decreased and the amounts of nano particles and synthesizing the nanoworms are increased. By placing the catalyst nanoparticles on the crucible lid and being subjected to the argon gas flow, new morphologies of boron carbide are appeared (flower-shaped and needle-shaped are synthesized by using carbon black and activated carbon, respectively). The argon gas flow creates new branches on the main wires. The specimens were characterized by the X-ray diffraction and a scanning electron microscopy.

In this study at first, in laboratory, three types of vanadium oxide were produced by using porous graphene and amine framework in hydrothermal method nanostructures such as: vanadium oxide-octadecyl amine- graphene, vanadium oxide-dodecyl amine-graphene and vanadium oxide – aniline-graphene (V-ODA-G، V-DDA-G، V-A-G). Then their structures and functions in propane dehydrogenation reactions were studied and productivity and efficiency of these catalysts in mentioned reactions were compared with each other. In order to notice and compare the structures and properties of synthesized catalysts, some methods such as Field Emission Scanning Electron Microscope (FE-SEM), X Ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA), Fourier Transform Infrared Spectrometry (FTIR), Gas Chromatography (GC) have been used. The obtained results show that vanadium oxide nanostructures have great opportunities to be oxidatively dehydrogenation (ODH) and make sciences explore the use of porous grapheme as catalysts for propane oxidative dehydrogenation.

In this paper, polymer grafted nickel-doped iron oxide nanoparticles are fabricated via an easy, one-step and fast electrochemical procedure. In the deposition experiments, iron(II) chloride hexahydrate, iron(III) nitrate nonahydrate, nickel chloride hexahydrate, and dextran were used as the bath composition. Dextran grafted nickel-doped iron oxides (DEX/NiSPIOs) were synthesized with applying direct current (dc) of 10 mA cm – 2. The magnetite crystal phase, nano-size, Ni doped content, and dextran grafting onto SPIOs were verified through X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. Magnetic evaluation through vibrating-sample magnetometer (VSM) proved that the DEX/Ni-SPIOs product have superparamagnetic behavior with exhibiting the high saturation magnetization and negligible Ms and Hci values. Based on the obtained results, it was confirmed that the prepared dextran grafted Ni-SPIOs have suitable physico-chemical and magnetic properties for both therapeutic and diagnostic aims.

In this study, palladium nano-particles were electrodeposited galvanostatically on carbon black powder (Vulcan XC-72R). The catalytic activity for electro-oxidation of ethanol and methanol in alkaline media were studied by cyclic voltammetry and linear sweep voltammetry techniques. The results indicated that the electro-oxidation of ethanol and methanol strongly depends on adsorbed species on the electrocatalyst layer. Effects of ethanol, methanol and KOH concentration on the electrocatalytic properties of the synthesized electrocatalysts during electro-oxidation reactions were evaluated by linear sweep voltammetry with various scan rates. The overall rate equations for ethanol electro-oxidation and methanol electro-oxidation on Palladium /Vulcan in alkaline media were developed. It has been shown that the Pd-C particles with mass loading of 0. 11 mg cm – 2 have superior catalytic activity. Finally, two overall rate equations were developed for EOR and MOR.

Reduced graphene oxide(rGO)– silver(Ag) nanocomposites have been prepared by using solution based facile one-pot synthesis process. The reaction process involves high-temperature liquid-phase exfoliation of graphite oxide and silver acetate in presence of N-N’ dimethylformamide (DMF) solvent, resulting in simultaneous formation of rGO as well as Ag nanoparticles. Different nanocomposites have been prepared by varying the ratio of graphite oxide and Ag ions during the reaction. The crystal structure, chemical structure, morphology, and photoluminescence properties have been investigated by using powder X-Ray Diffraction (XRD), Raman spectroscopy, Fourier Transform InfraRed spectroscopy (FTIR), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and Photo Luminescence (PL) spectroscopy techniques respectively. The microscopic studies reveal a uniform distribution of silver nanoparticles of size ~ 200 nm on to graphene layers. Further, average defect distance in the graphene layers was estimated to be 11 nm from Raman peak ratio in these nanocomposites. These nanocomposites showed luminescent emission around 410 nm and intensity of emission enhanced significantly for the nanocomposites comprising more silver nanoparticles, which may be due to resonant energy transfer between Ag metal and rGO.

ZnS nanoparticles (NPs) doped with Ag, Cu, and AgCu were synthesized using hydrothermal method in water solution. The NPS are characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy scanning (EDX), scanning electron microscopy (SEM) and dynamic light scattering (DLS). The produced NPs have approximately hexagonal structure and a cubic zinc blended structure. The size distribution of NPs has a medium around 10 nm. Optical properties of these NPs were investigated using photo luminescence (PL) spectra, that show the samples exhibit reasonable optical properties for scintillation applications. The produced NPs were mixed with methyl methacrylate and dimethylformamide to prepare a very thin layer of a nanocomposite that is uniformly coated on a substrate of Plexiglas. Response of the layers under alpha particles irradiation using a photomultiplier tube and a multichannel analyzer indicates that the doped ZnS NPs have reasonable scintillation response that capable them to be used in developing a low-cost and free-size structure of alpha particles detectors.

Radiotherapy consisting of external beam radiotherapy (EBRT) and internal radioisotope therapy (RIT) has a wide application for treating cancer as clinical trials. This study provides some conditions to prove that tungsten oxide nanoparticles (WO3) is a radio sensitizer. The peripheral blood mononuclear cells (PBMCs) were used to calculate inhibitory concentration (IC). The AGS cell line exposed the concentration of 89. 6 µ g/mL (IC20) WO3 nanoparticles that was optimal and its radio sensitization was examined in megavoltage photons radiation of 6 MV x-rays. The sensitivity enhancement ratio (SER) and dose enhancement factor (DEF) was determined 1. 24 and 1. 68 respectively. We described the mechanisms of creating WO3 nanoparticles toxicity and genotoxicity in different concentrations on AGS cell line. The mean size of WO3 NPs by transmission electron microscopy was measured 31. 89± 3. 82 nm. Tungsten oxide Nanoparticles cause to reduce cell viability, remove membrane and damage to DNA. There was a meaningful increasing in damages to DNA and proliferation cell potency and also significantly reducing cell viability in concentrations more than 100 µ g/mL.

In this paper, BaLaxGdxFe12-2xO19 (x=0. 2, 0. 4, 0. 6 and 0. 8) were synthesized via sol-gel auto-combustion method. Fourier transform infrared spectroscopy (FTIR) of samples was represented that the bands at 400 and 500 cm-1 were related to the formation of hexaferrite phase. The (x-ray diffraction) XRD patterns were matched exactly with the structure of barium hexaferrite. (Field emission scanning electron microscopy) FESEM were represented the hexagonal shapes of all products. Magnetic analysis of barium hexaferrite were investigated by (vibrating sample magnetometer) VSM. The saturation magnetization of all samples decreased by increasing dopant ’ s substitution due to the different occupation sites of dopants instead of Fe 3+ (64 to 36. 56 emu/g) in the hexaferrite structure. The coercivity increased because of its reverse relation with saturation magnetization (5010 to 5500 Oe). Microwave absorption properties of samples was investigated by (vector network analyzer) VNA. The maximum value of reflection loss was-7. 8 db at 10. 4 GHz frequency in 3mm thickness for x=0. 4 sample.

Nowadays, a lot of efforts have been applied to find an appropriate catalyst for generating hydrogen from NaBH4. Hence in the current study, various nanostructures of TiO2 were employed to obtain an insight into how the different support catalysts effect on the hydrolysis rate of NaBH4. For this aim, disordered filaments (DF-NTs) and ordered free-standing TiO2 nanotubes (FS-NTs) were fabricated via hydrothermal and chemical-assisted twostep anodization methods, respectively. The physical and chemical features of catalysts were analyzed using FESEM, XRD, FTIR and BET analysis, respectively. The results showed, TiO2 itself has catalytic activity and the H2 generation rate by FS-NTs was 1. 67 and 5. 26 times more than the generation rate by DF-NTs and spherical TiO2 nanoparticles, respectively. This premier catalytic behavior of FS-NTs can be ascribed to its high surface area (112. 77 m 2 /g) and ordered arrangement of the nanotubes which allows reagents to be easily transferred to the active sites. The kinetic study revealed that hydrolysis of NaBH4 using the catalyst of FS-TNs is a first-order reaction regarding catalyst amount, while it is a zero-order reaction regarding the NaBH4 level. Moreover, the reusability results exhibited that FS-TNs has good durability and performance even up to the Fifth run.