Journal of Nano Structures
Volume:10 Issue: 2, Spring 2020

Gold nanostar particles were synthesized using seed-mediated method. Au-seed was synthesized with the diameter of approximately 3 nm and a considerably low STDEV of less than 1 nm. Then, different amount of Au seed was introduced into the growth solution of nanostars and the influence of the changes in concentration of Au seed on the growth process was investigated. The size of gold nanostars increased with decreasing the concentration of Au seeds. We further extended this method to enable size-control of gold nanostars from approximately 70 nm to 140 nm in size. Also the longer branch length caused red shifting of resonant plasmonic peaks in the absorption spectra of the sample with the lower amount of Au seed. Thanks to this method, we could control size, and spikes of gold nanostars and the obtained results broaden the concept of the formation and morphology of gold nanostars. The plasmon band shift was attributed to variations in branch numbers, and overall star size.

Scanningelectron microscopy (SEM) has been utilized  to examine  the morphology and topography alterations  in the surface of Poly(Lactic Acid)(PLA) fabrics due to UV/Ozoneirradiation. In the past decade, a growing attention in the usage of “Green Techniques” in industrial applications has been observed owing to many benefits such as low impurities and their relatively low cost to substitute the conventional processes.The effects of UV/Ozone irradiation along  with the pretreatments with distilled water, hydrogen peroxide, and hydrogen peroxide/sodium silicate solutions on the surface morphology of the PLA fibers by means of SEM were investigated and the images were compared with that of virgin untreated samples.The observations presented dramatically increase in insurface roughness andsurface area of the samples after the treatment. Nano-size roughening (827 nm) has been clearly observed on the samples. The changes in morphology mainly surface roughness and surface area, on the PLA fabrics surface due to UV/Ozone irradiation seem to be due mainly to the intensified etching effect of the UV/Ozone process and these alterations maximized by the pretreatment of the fabrics with the hydrogen peroxide/sodium silicate solution.

First-principle calculations have been investigated to study the adsorption of the molecules (SO2, CO, NH3, CO2, NO2, and NO) on the surface of mono boron (B) B-doped and dual B-doped graphene sheets to explore their potential applications as sensors. Our findings indicate that the adsorption of (CO and NH3) on B-doped graphene and (CO and SO2) on dual B-doped graphene are weak physisorption with adsorption energy between (0.128 to 0.810) eV. However, the adsorption of (CO2, NO2, SO2, and NO) on B-doped graphene and (CO2, NH3, NO and NO2) on dual B-doped graphene are strong chemisorption. The strong interaction of (CO2, NO2, SO2, and NO) on B-doped graphene and (CO2, NH3, NO and NO2) on dual B-doped graphene demonstrating that B-doped graphene and dual B-doped graphene could catalyse or activate, suggesting the possibility of B-doped graphene and dual B-doped graphene as a catalyst. Moreover, the energy gap of B-doped graphene and dual B-doped graphene is opened upon adsorption of (CO, CO2, NH3, NO, NO2 and SO2) in various ways. Our calculations demonstrate the feasibility of B-doped graphene may be a good sensor for (CO and NH3) and dual B-doped graphene could be a good sensor for (CO and SO2).

5-fluorouracil is a widely used anticancer drug with many side effects on humans, and hence its analysis in biological samples is very important. Accordingly, a novel sensitive electrochemical approach was fabricated by incorporating graphene quantum dots (GCD) and 1-butylpyridinium bromide (BPBr) in the formulation of a carbon paste electrode (GQD/BPBr/CPE). The GQD was synthesized and characterized TEM method and results confirmed them as being spherical with D~ of 5.0 nm. The applicability of the GQD/BPBr/CPE in voltammetric analysis of 5-fluorouracil was evaluated. The relations of oxidation currents and potentials of 5-fluorouracil with pH at the surface of GQD/BPBr/CPE were investigated and the results confirmed the involvement of electrons and protons in the electro-oxidation mechanism of 5-fluorouracil. In square wave voltammetry (SWV) analyses, the GQD/BPBr/CPE showed good sensitivity for 5-fluorouracil over a wide linear range of 0.001–400 μΜ and a detection limit of 0.5 nΜ was achieved. The GQD/BPBr/CPE was successfully applied for the determination of 5-fluorouracil in pharmaceutical samples and acceptable results were obtained.

In this work, NdFeO3 nanoparticles were synthesized through a simple co-precipitation method. The formation of NdFeO3 particles was verified by X-ray powder diffraction, infrared spectroscopy, vibrating sample magnetometer, and transmission electron microscopy analysis. Polyaniline and chitosan were employed as proper support for production of metal nanoparticles. Novel Pt-NFO/PA-CH nanocomposite was fabricated by immobilization of Pt nanoparticles on the PA-CH support in the presence of NdFeO3 nanoparticles. The prepared nanocomposite was characterized by transmission electron microscopy and X-ray powder diffraction analysis. The catalytic performance of the Pt-NFO/PA-CH nanocomposite was evaluated for electro-oxidation of methanol through CO stripping voltammetry, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Durability of the Pt-NFO/PA-CH catalyst was investigated and the effects of several factors such as temperature, scan rate, and methanol concentration were studied for methanol oxidation. Enhanced catalytic performance of Pt-NFO/PA-CH nanocatalyst compared to Pt/PA-CH catalyst recommends its application for methanol electro-oxidation in direct methanol fuel cells.

The modified glassy carbon electrode (GCE) was prepared with 6-amino-4-(3,4-dihydroxyphenyl)-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (pyrazole derivative (AMPC)) and functionalized multi-walled carbon nanotubes. In this research, electrocatalytic activity of nanocomposite (AMPC/MWCNTs) has been studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CHA) methods. The electrocatalytic properties of the AMPC/MWCNTs nanocomposite for cysteine oxidation was considerably enhanced as compared to only AMPC. The kinetic parameters including the electron transfer coefficient (α) and the heterogeneous constant rate (k’) for oxidation of cysteine was studied by CV method. The diffusion coefficient of cysteine was calculated with aid of chronoamperometry (D=9.51×10-6 cm2/s). The AMPC/MWCNTs modified electrode shows a linear response to cysteine in the range of 0.7 nM to 200.0 µM with detection limit of 0.16 nM. Also, differential pulse voltammetry was applied for the simultaneous determination of cysteine (CYS) and paracetamol (or acetaminophen, AC). Finally, the modified electrode was used for the detection of CYS and AC in human serums (real samples). The sensor produced good sensitivity, selectivity, reproducibility and stability features.

The present study aimed to evaluate the effect of surfactant composition on the physical properties of nanostructured lipid carriers (NLCs) containing wheat germ oil (WGO) and to investigate the influence of both surfactant composition and pH on the oxidative stability of WGO encapsulated within the NLCs. The results showed that the smallest particle size (52.7 nm) was related to the NLC with the poloxamer-to-lipid ratio of 1:1 (Polox-NLC-1). Polox-NLC-1 not only showed good stability during storage, but also indicated a suitable physical structure from differential scanning calorimetry (DSC) analysis. The oxidative stability results indicated that the NLCs were more successful than O/W emulsion in protecting the WGO from oxidation. Additionally, the oxidative stability of the NLC with the poloxamer-to-lipid ratio of 2:1 (Polox-NLC-2) looked promising. Furthermore, NLCs prepared with the surfactant of poloxamer as a non-ionic surfactant had greater oxidative stability at high pH, and NLC prepared with sodium dodecyl sulfate (SDS) as an ionic surfactant had greater oxidative stability at low pH. These findings indicated that NLC could be an effective delivery and protection system for the WGO as a source of bioactive compounds.

Three chitosan (CS), polyethylene glycol (PEG) and polylactic acid (PLA) nanocomposite systems containing SiO2 nanoparticles and water molecules were designed by molecular dynamics (MD) simulations to deliver pipobromane (PIP) anticancer drug in order to discover the most appropriate drug delivery system (DDS) in aqueous medium which was analogous to the human body. The density for the CS matrix was 1.25 g/cm3 but it was decreased to 1.16 g/cm3 in PLA and 1.02 g/cm3 in PEG. The potential energies of the CS, PLA and PEG DDSs were near 195000, 3700 and –4600 kcal/mol while their related non-bond energies were around 14000, –150 and –6150 kcal/mol, respectively, indicating the PEG composite had the most negative energies whereas the most positive values belonged to the CS system. The CS system revealed the greatest fractional free volume (FFV) of 77.232% but PLA offered the smallest FFV (65.804%). The radial distribution function (RDF) data displayed that the PIP molecules had strongest H-bond interactions with the CS chains which reflected the drug molecules would diffuse the slowest inside the CS nanocomposite. The diffusion coefficients for the PLA, PEG and CS systems were equal to 0.0183×10–4, 0.0163×10–4 and 0.0154×10–4 cm2/s, respectively approving the slowest drug diffusion was happened in the CS cell which certified the most controlled and sustained drug delivery.

In this work, activated carbon (AC) derived from biomass wastes was implemented as electrode materials in supercapacitor application. This study has adopted rubber seed shell (RSS) wastes to derive AC via pyrolysis process. Meanwhile, reduced graphene oxide (rGO) was used as an additive material in order to study the effect of the rGO in capacitive behavior. The synthesized rGO was successfully produced through the electrochemical exfoliation method then further chemically reduced the solution using hydrazine hydrate. Four different electrodes were fabricated using a spin coating method to investigate the effect of added rGO to the capacitive behavior. One sample of AC/polyvinyl alcohol (PVA) as reference was prepared with ratio 2:8. Meanwhile, the three samples were prepared with different volumes of rGO. A series of techniques to characterize the morphological and structural properties of the samples have been carried out using field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX), atomic force microscopy (AFM), and Brunauer-Emmett-Teller (BET) surface analysis. Based on the cyclic measurements, AC/PVA/rGO2 showed the lowest resistivity which was 3.74 and consequently enhanced at least 10 orders in capacitive performance as compared to bare AC/PVA. Therefore, the capability of small amount rGO in enhancing the capacitive behavior paves the way for versatile practical applications in the electronic field.

In order to improve photocatalytic activities of the pure anatase TiO2 under UV and visible light irradiations, a novel and efficient N-doped TiO2 photocatalyst was prepared by sol-gel method. N-doped titania is prepared using the various nitrogen sources such as: triethylamine, N,N,N’,N’-tetramethylethane-1,2-diamine, ethyldiamine, 1,2-phenylenediamine, propanolamine, and propylenediamine and then the effect of these source on properties of products was investigated. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectra (DRS), energy dispersive spectrometry (EDS) and Fourier transform infrared (FT-IR) techniques. Results indicate that the shifting of absorption edge to visible region compare to the pure TiO2, reducing average size of the TiO2 crystallites, enhancing of lattice distortion of Ti, effective separation of photo-induced electron and hole pair, and improvement of pollutant decomposition under UV and visible light irradiations are due to doping of N in titania. The photocatalytic activities of N-doped TiO2 nanoparticles were evaluated using the photodegradation of methyl orange (MO) under the irradiation of UV and visible light and it confirmed that the photocatalytic activity of N-TiO2 is better than the pure TiO2. By comparing the photocatalytic activities of the N-TiO2 with different nitrogen sources, triethylamine with 2 molar ratio was chosen as the optimum.

In this work, a novel Silicon on Insulator (SOI) MOSFET is proposed and investigated. The drain and source electrode structures are optimized to enhance ON-current while global device temperature and hot carrier injection are decreased. In addition, to create an effective heat passage from channel to outside of the device, a silicon region has embedded in the buried oxide. In order to reduce the device leakage current and controlling the threshold voltage, a p-type retrograde doping is introduced into channel region. Since the air has the least permittivity among materials, it can be utilized to decrease the device parasitic capacitances. Based on this, an air gap is embedded in the buried oxide near the silicon to improve RF performance of the device. Because the source and drain electrodes are embedded in and over the silicon film in the source and drain regions, we called this structure EEIOS-SOI MOSFET. “EEIOS” stands for “Embedded Electrodes In and Over the Silicon film”. During this work, EEIOS-SOI MOSFET is compared with a conventional SOI MOSFET and another SOI MOSFET with just Embedded Electrodes In the Silicon Film (EEIS-SOI). EEIS-SOI presents better electrical figure of merits including lower subthreshold slope and lower leakage current in simulations. An immense investigation among these devices shows that EEIOS-SOI MOSFET has better transconductance, lower gate injection leakage current and lower temperature related to DC parameters and higher cut off frequency, gain bandwidth product and unilateral power gain related to AC figures of merits compared to its counterparts.

Hydroxypropyl starch was synthesized by modified sago starch with hydroxypropylation reaction. Hydroxypropyl starch nanoparticles with mean particle sizes of 110 nm are obtained by controlled precipitation through the drop-wise addition of dissolved hydroxypropyl starch solution into excess absolute ethanol. Piperine was loaded onto hydroxypropyl starch nanoparticles and native starch nanoparticles via the in-situ nanoprecipitation process. Hydroxypropyl starch nanoparticles exhibited higher piperine loading capacity as compared to native starch nanoparticles with the maximum loading capacity of 0.46 and 0.33 mg.mg-1, respectively. Piperine was release from hydroxypropyl starch nanoparticles in a slow and sustained manner at pH 1.2 over the period of 24 hours. Whereas piperine was completely released from native starch nanoparticles within 16 hours.

The present study reports synthesis of MOWS2 nanocomposite followed by its characterization using energy dispersive X-ray spectroscopy (EDS), X-Ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Chronoamperometry (CHA), differential pulse voltammetry (DPV), and cyclic voltammetry (CV) have been used to examine electro-chemical behaviors of sulfite on MOWS2 nanocomposite modified SPE. Electro-chemical specification indicated very good electro-catalytic activities and surface area impact of MOWS2 nanocomposite. Oxidation signals of sulfite on MOWS2/SPE has been considerably increased in comparison to the bare SPE. Within optimum conditions, quantification of sulfite might range between 0.08 to 700.0 µM with a small determination limit of 0.02 µM based on S/N=3.The impact of scan rates has been explored. Finally, the MOWS2/SPE has been employed for detection of sulfite in real specimens. In general, an easy experimental method for manufacturing MOWS2 nanocomposite has been suggested that takes advantage of selectivity, reproducibility, and sensitivity toward electro-active specimens, as well as biological matrices.

To discuss the potential role of the support for iridium catalyst, we have proceeded to prepare a series of supported catalysts with the same active phase content, but different silica content, to elucidate the changes in surface structure and the reaction process of hydrous hydrazine decomposition on catalyst. The obtained iridium catalysts contained 20 wt% of nanoparticles dispersed on spherical mesoporous alumina and aluminosilicate supports for hydrogen generation from hydrous hydrazine. Iridium nanoparticles with different morphologies and diameters could be produced over the catalyst supports depending on its nature. The iridium catalysts were characterized by some techniques such as XRD, FESEM, BET, TGA, H2-TPR, and mechanical properties. The type of catalyst support played an important role in the effectiveness of the catalyst particles, leading to different activities for hydrazine monohydrate decomposition. Under the given test conditions, the performance of the catalyst was better when using alumina granular as the catalyst support than when using aluminosilicate granular. Since the aluminosilicate support was less reactive than the alumina, hydrogen selectivity was relatively small; consequently, the reaction rate was lower when using the aluminosilicate support than when using the alumina support.

In the present investigation, a systematic study on the dependence of chelating agents on the size control of silver phosphate Ag3PO4 powders is presented. The effect of two different capping-ligands (monoethanolamine (MEA) and oleylamine (OLA) as amino-additives) is studied using sol-gel route. Structural and morphological characterization techniques were used to quantify the particles size and molecular bonding. Results show that oleylamine as a chelating agent is more efficient in controlling the size of the as-synthesized nanoparticles, especially in low concentration of Ag+ precursor related to its long alkyl-chain preventing nuclei assemblage. This argument is confirmed by energy interaction calculation between Ag+ cations and oleylamine molecules using Molecular Dynamics Simulations. Finally, this investigation clearly demonstrates that the ratio between amino-additives (MEA and OLA) and Ag+ is the key-parameter that controls the crystalline growth of Ag3PO4 particles thus leading to nanometric size.

Polyhedral Oligomeric Silsesquioxanes (POSSs) are a class of hybrid structures synthesized through hydrolytic condensation (Sol-Gel method) of trifunctional silane monomers under specific conditions. Octavinyl silsesquioxane (OVS) nanostructures are comprised of a rigid inorganic silica core surrounded by vinyl functional groups with an under-developed synthesis procedure. Generally, POSS morphology, yield and crystallinity depend strongly on synthesis conditions such as solvent type, synthesis temperature, sequence of reagents addition, water/monomer molar ratio, etc. In this study, effect of solvent properties on the formation of OVS compounds, their morphology and crystallite size was studied under specific conditions. Finally, n-pentanol and butanol as the most efficient solvents were suggested according to solvent characteristics, theoretical background reported in previous studies and experimental results. Different characterization techniques such as XRD to investigate crystallinity and crystallite size, FE-SEM and TEM to determine the morphology, EDX to identify elemental and chemical composition, C-NMR and 1H-NMR to confirm the attachment of vinyl groups and FTIR to define chemical bonds, were employed to confirm the formation of the as-prepared structure. Based on the results, butanol and n-pentanol represent the best results regarding crystallinity and size by optimizing other influential parameters.

Microwave absorbing materials are usually designed to solve protection against electromagnetic interference in wireless communication systems and high frequency circuit mechanisms. In this research polystyrene (PS) nanocomposites containing various nano-fillers were successfully synthesized. The novelty of this work is comparing of three various nanostructures: non-metallic conductive graphene oxide, magnetic Fe3O4 and semi-conductor zinc oxide were used as additive. The effect of different fillers loading and homogenizer speed on the reflection loss (RL) amount and electromagnetic wave absorption was investigated. In order to investigate particle size and morphology of the nanostructures the scanning electron microscopy (SEM) was used. The frequency range of 5-8 GHz was employed in the investigation of electromagnetic wave absorption properties of nanocomposites using a vector network analyzer and eventually their absorption properties were analyzed and compared. The results indicate that graphene oxide has substantial effect on absorption in compare with the other nanocomposite samples. Increase of homogenizer speed led to a dispersion improvement of nanostructures and absorption. Therefore, the broadening of the microwave absorption band-width is attributed to the suitable dispersion of nanostructures in polymeric matrix.

The mesoporous ZrFe2O4 nanocauliflowers were synthesized via the solvothermal method. The core-shell ZrFe2O4@SiO2 nanocomposite was successfully prepared by a simple wet route using tetraethylorthosilicate, then modified with (3-aminopropyl)triethoxisilan (APTES) as linker and tetrakis(4-carboxyphenyl)porphyrin (TCPP) as agent for light harvesting, to fabricate ZrFe2O4@SiO2-NH-TCPP nanocomposite. The characterizations of samples were done by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), nitrogen adsorption and desorption isotherms (BET), vibrating sample magnetometer (VSM), diffuse reflectance spectroscopy (DRS) and fluorescence spectroscopy. The prepared samples were applied as photocatalyst to remove of methyl orange (MO) under visible LED light irradiation. The obtained results showed that the presence of SiO2 and TCPP decreased the size of particles and improve the photocatalytic activity of samples, too, led to increase of photodegradation of MO. The final fabricated nanocomposite (ZrFe2O4@SiO2-NH-TCPP) could degrade MO about 100% under only 10 W visible LED irradiation and be separated easily by an external magnetic field.

TiO2 nano-particles were used in electroless plating bath to obtain Ni/P/nano-composite coatings. The coatings were heat treated at 200, 400, 600 and 700 oC and their chemical and physical properties were investigated and it was found that 400 oC was the optimum temperature for the heat treatment of the coatings. The micro-hardness test of coatings showed that the composite coatings, which contain TiO2 nano-particles, exhibit better properties of microhardness. X-ray diffraction (XRD) analysis indicated that at 400 oC, Ni3P phase is formed, and when the heating temperature is 600 oC the presence of TiO2 particles is seen. We have used scanning Electron Microscopy (SEM) to measure the surface morphology of the composite and plane deposits. Weight loss measurement, Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization Spectroscopy were utilized to study the corrosion resistance of coatings in 3.5 %wt NaCl solution. Corrosion resistance experiments indicated that presence of TiO2 nano particles in the electroless coatings matrix improved the corrosion resistance of the coatings. Heat-treatment improved the corrosion resistance of the coatings up to 400 oC but heating above 400 oC caused a decrease in corrosion resistance. Wear behavior of the samples indicated that presence of TiO2 particles improve the wear resistance.

The antifungal properties of ZnO were implemented in the real handicraft and showed promising results for the value addition of local products by sun-screen and fungi protections. The inhibition of Aspergillus sp. growth on tube sedge basketry by zinc oxide (ZnO) was demonstrated. ZnO nanoparticles synthesized with chitosan capping agents were analyzed by X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectrophotometry and thermogravimetric analysis (TGA). The crystallite size consistent with electron microscope images and surface area of ZnO were dependent on the amounts of chitosan. ZnO exhibited a large ultraviolet (UV) absorbance in an entire 200-400 nm range when large crystallites agglomerated into bulky aggregates. In the case of small amounts of chitosan used, small crystallites tending to agglomerate in close contacts enhanced antifungal activity on pieces of tube sedge basketry. The fungi inhibition by this chitosan-modified ZnO was attributed to the stress response in fungal hyphae and generation of hydrogen peroxide.