International Journal of Nano Dimension
Volume:11 Issue: 2, Spring 2020

ZnS nanoparticles have been synthesized using various amounts of aqueous Azadirachta Indica (Neem) leaf extract as capping agent and stabilizer. The synthesized nanoparticles were studied by FTIR, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX) and UV-Visible spectroscopy. FTIR spectra shows that the biomolecules such as polyphenols, carboxylic acids, polysaccharide, amino acids and proteins present in the extract are responsible for the binding and stabilizing the synthesized ZnS nanoparticles. Analysis of the XRD data confirms the cubic structure of the synthesized materials with an average particle size of ~2 nm. Using XRD data the microstrain and dislocation density in ZnS crystals have been estimated. The particle size, strain and dislocation density are found to be affected by the amount of the extract used for synthesis. SEM and TEM studies were made to study the morphology and size of the particles. The EDAX spectra confirmed the presence of zinc and sulfur in single nanoparticle. UV-Visible spectra indicated a blue shift in the absorption peak for the extract-capped ZnS materials in comparison to the pure ZnS. The particle size of the ZnS nanoparticles estimated using UV-Visible spectral data along with those obtained from XRD analysis confirms that the green-synthesized ZnS nanoparticles lie in the range of quantum dots. The present study describes a simple, cost effective way of nanoparticle synthesis suitable for large scale production.

The structural and electronic properties of the hydrogenated porous graphene nanoribbons were studied by using density functional theory calculations. The results show that the hydrogenated porous graphene nanoribbons are energetically stable. The effects of ribbon type and ribbon width on the electronic properties of these nanoribbons were investigated. It was found that both armchair and zigzag hydrogenated porous graphene nanoribbons are semiconductors. Their energy band gaps depend on the ribbon width and topological shape of carbon atoms at the edges of the nanoribbons. The band gap of the nanoribbons decreases monotonically with increasing the ribbon width. The semiconducting properties of the hydrogenated porous graphene nanoribbons suggest these ribbons as proper materials for use in future nanoelectronic devices.

Circuit-level implementation of a novel neuron has been discussed in this article. A low-power Activation Function (AF) circuit is introduced in this paper, which is then combined with a highly linear synapse circuit to form the neuron architecture. Designed in Carbon Nanotube Field-Effect Transistor (CNTFET) technology, the proposed structure consumes low power, which makes it suitable for the implementation of high-throughput Neural Networks (NNs). The main advantage of the proposed AF circuit is its higher accuracy for the generation of hyperbolic tangent function compared to the previously reported works. Moreover, the programmability feature for the slope and the position shifting enhances the adaptability of the designed neuron for different types of neural systems, especially Multi-Layer Perceptrons (MLPs). There is also excellent compatibility between the synapse and activation circuits, which illustrates another notable privilege of the proposed neuron. Simulations using HSPICE for CNTFET 32 nm standard process have been carried out for the designed scheme to indicate the correct operation. Based on the results, all of the claimed advantages can be proved clearly while the power dissipation is 6.11µW from the 0.9V power supply. Also, an accuracy of 98% has been achieved for the AF circuit.

The aim of this work was to characterize copper ferrite nanoparticles synthesized via solvothermal method and to investigate the effects of ultrasonic waves on the synthesis efficiency. Crystal structure, functional groups, microstructure, particle size, magnetic properties, specific surface area, porosity distribution and photocatalytic activity of the synthesized nanoparticles were also investigated. Structural analyses revealed that nanostructured copper ferrites with spinel crystal structure have been successfully synthesized via both solvothermal and ultrasonic-assisted solvothermal methods. The powders contained submicron spheres which were consisted of nanoparticles with regular arrangement. The applied ultrasonic wave had significant effect on the shape and size of the spheres, particularly on their specific surface area, but it had no considerable effect on the magnetic properties. All the synthesized powders were superparamagnetic and their band gap energy was about 1.5 eV. High absorption rate is another unique characteristic of the powders so that it can complete the photocatalytic process in less than 10 min. The saturation magnetization of about 47 emu/g, together with negligible coercivity, make the synthesized nanostructured absorbent ideal for magnetic separation processes.

In this study, selenite ions were reduced to selenium nanoparticles using a leaf extract of barley (Hordeum vulgare L.) plants. Characterization of synthesized nanoparticles using Scanning Electron Microscopy (SEM) and UV-visible spectrophotometry indicated the formation of variable size of selenium nanoparticles, suggesting that leaf extract could form polydispersed nanoparticles. Then we used these synthesized selenium nanoparticles to mitigate salt stress in barley plants under hydroponic conditions. Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) analyses suggested that the hydroponically nano-Se application resulted in direct accumulation of Se in the leaves of barley. Shoot growth was negatively affected by salinity levels up to 100 mM, whereas this reduction was mitigated by application of exogenous Se nanoparticles. Our results indicated that high salinity stress decreased the activity of superoxide dismutase (SOD), and enhanced the levels of malondialdehyde (MDA) in the leaves of barley seedlings, whereas application of Se nanoparticles increased total phenolic levels, and also resulted in a significant reduction of MDA (a marker for the ROS-mediated cell membrane damage) contents, which could influence the metabolism and be responsible for the increasing shoot dry weight. These results provided the first evidence that the green Se nanoparticles promote the growth of barley seedlings under salt stress.

Health risk assessment of nanomaterials is a new and important area emerging; obtaining nanoparticles by green synthesis method and performing cytotoxicity, genotoxicity and antimicrobial testing is an important endpoint. In vitro studies for nanoparticles (NPs) obtained by the non-toxic method offer many advantages, such as the study of the bioavailability of nanomaterials to sensitive target cells. It will be useful for investigating the toxic and genotoxic risks associated with nanoparticle exposure. In this study; silver nanoparticles (AgNPs) were synthesized by green synthesis using grape vinegar prepared by ourselves. The resulting Ag NPs were characterized using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) methods and for different AgNPs concentrations in the range of 5-60 nm. The genotoxic effects of AgNPs were investigated using the Sister chromatid exchange (SCE) test and Micronucleus (MN) tests. Furthermore, the antibacterial and antifungal activities of the synthesized compound were tested against some pathogenic bacteria which are causative agents of the disease. As a result; it was found that the synthesized compound showed different degrees of inhibitory effect on the growth of pathogen strains compared to standard antibiotics. The findings are thought to provide clinically useful information in the treatment of many diseases using AgNPs at optimum concentrations (non-genotoxic concentrations).

Functionalized Multi-walled carbon nanotubes (f-MWCNTs) which are modified using nitric acid and sulfuric acid were evaluated to synthesize a uniform nanocomposite via application of TiO2. The f-MWCNTs-TiO2 nanocomposites have been produced via using the chemical simple two-step method. To characterize the structural analysis, scanning electron microscopy (SEM) imaging, ultraviolet-visible (UV-Vis) spectroscopy, and Raman spectroscopy were utilized. The maximum shift of D, G, and 2G-bands of f-MWCNTs were related to 20 wt. % f-MWCNTs in TiO2 nanoparticles. Moreover, an up-shift of 40 cm-1 was recorded for the MWCNTs (G’-band) for 5 wt. % f-MWCNTs. For 20 wt. % f-MWCNTs/TiO2 (G-band) nanocomposites, was determined by 4.7%. By increasing the amount of f-MWCNTs in f-MWCNs/TiO2 nanocomposite, the compressive strain was increased. Among the four bonds, the G’-band behaved differently against increasing f-MWCNTs. The shifting frequency of G-band indicates the strong interaction between f-MWCNTs and TiO2 nanoparticles. The interaction between f-MWCNTs and TiO2 nanoparticles identified by the Gruneisen parameter. Therefore, a mechanism generated for stress transfer at the interface between f-MWCNTs and TiO2 nanoparticles which is indicated in many significant increases obtained in the mechanical and acoustical properties.

Die casting process is used since long, but even today problems like erosion, corrosion, soldering and sticking affect die life. These dies undergo thermal cyclic loads from 70 oC to 600 oC during processing. Physical Vapor Deposition (PVD) hard coating can play an important role in such extreme applications. In the present work, we report the use of Chromium based multilayer CrN/Cr (M-CrN) coatings and multi-component aluminium titanium based AlTiN (M-AlTiN) coatings. The H-13 steel substrate samples were prepared using cathodic arc deposition technique. Structural properties of the coated samples were studied using XRD and SEM techniques. Tribological and mechanical properties of the coatings were studied using Calo-test and Micro-hardness test respectively. Potentiostat technique was used to study the effect of 1 M HCl solution on these coatings. Thermal fatigue (TF) test was conducted by heating the sample to around 600 oC and rapidly cooling it to room temperature imitating the die casting process conditions. After multiple cycles, it was observed that M-AlTiN coated samples outperform M-CrN coated samples in terms of wear, oxidation and adhesion properties. It was observed that formation of oxide layer on the coated surface during the thermal cycling inhibits further oxidation of the coating layer and result in enhanced productivity and efficiency of dies.

Hematite (α-Fe2O3) nanoparticle was synthesized using organometallic compound - ferrocene carboxaldehyde through solventless solid state thermal decomposition technique. The crystal structure, magnetic and morphological properties of the decomposed material were studied using powder X-ray diffraction (XRD), superconducting quantum interference device (SQUID) magnetometry, 57Fe Mössbauer spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) techniques. Structural study confirmed that the synthesized material is hematite with hexagonal phase and good crystallinity. The temperature-dependent magnetization measurement exhibited the Morin transition - the yardstick for hematite formation. Mössbauer spectroscopic study confirmed the purity of phase of the synthesized material. The SEM study observed mostly the agglomerated tiny particles along with some ring-shaped surface structures. The TEM study of the synthesized material showed that the highest distribution of the particles with ~5 nm size. The observed EDX spectra confirmed the existence of Fe and O in the synthesized material. The solid state reaction process leading to hematite on decomposition of ferrocene carboxaldehyde has also been proposed. Present study describes a simple process for the preparation of pure hematite nanoparticle by solventless method.

Ohmic and Schottky contacts are playing a major role in the field of ZnO based electronics device fabrication. It is seen that several works have been reported on metallization scheme, contacts with this semiconducting material. But, the thickness of semiconducting material and the choosing of substrate still remain imperfect and inefficient for advanced IC technology. To estimate contact resistance, the transmission line method (TLM) is found to be more complex. So, Schottky barrier height (SBH) model is considered to obtain at most accuracy to find Ohmic contact parameters. Herein, the investigation of parameters like barrier height, ideality factor and saturation current at room temperature of very low specific resistance Ohmic contact to ZnO using Ti/Al metallization scheme are performed. The thermal evaporation technique is performed for the deposition of ZnO thin film of 200 nm and Ti (100nm) /Al (100nm). Further, using a vacuum furnace, post-annealing treatment is also done at different temperatures (Four samples of 3000C, 4500C, 6000C and 7000C at a time period of 20 minutes for each temperature). Characterization of the contacts are done through current-voltage (I –V) using a semiconductor parameter analyzer. The parameters like barrier height, ideality factor and saturation current of this metallization scheme are extracted from the current-voltage plot. It is considered that the theory of thermionic emission is the fundamental phenomenon behind carrier transport at the interface. After post annealing, a comparative analysis is done and the deviations in the parameters are analyzed from semi-log current versus voltage plot and Richardson plot.