Scientia Iranica
Volume:24 Issue: 3, 2017

Electromechanical nanothermometers are instruments that work on the basis of the van der Waals (vdW) potential energy and interaction force of their constituent carbon nanotubes (CNTs). The CNT-based nanothermometers have two different configurations, namely telescope and shuttle configurations. In this article, based on the Lennard-Jones potential function together with the continuum approximation, first the vdW potential energy and interaction force for a telescope configuration with finite CNTs are derived, which have not been obtained in the previous works. Thereafter, by employing the interaction force, the equation of motion between constituent CNTs are solved. Subsequently, a new semi-analytical expression is obtained which enables one to precisely evaluate the oscillation frequency. By employing the given formulae, effects of different system parameters on the vdW interactions and oscillation frequency are shown.

Temperature dependent, delay, power dissipation and power delay product (PDP), in single walled carbon nanotube (SWCNT) bundle interconnect have been analyzed. Thermally aware circuit model for metallic SWCNT bundle is presented. The results are compared with those of currently used copper interconnects at 22nm technology node. It is seen that delay, power dissipation and PDP of SWCNT bundle interconnect increase with rise in temperature from 300K to 450K at different interconnect lengths from 100µm to 1000µm . It is also observed that, with rise in temperature, SWCNT bundle has a lower delay than that of copper for all interconnect lengths whereas reverse is true for power dissipation. In addition, with rise in temperature from 300K to 450K, for interconnect lengths at 100µm and 400µm SWCNT bundle has lower PDP compared to copper interconnects whereas reverse is true for interconnect lengths at 700µm and 1000µm. Moreover, relative average improvement in delay, power and PDP using thermally aware model in comparison with temperature independent model is estimated. Based on simulation results, the thermally aware model of SWCNT bundle achieved improvement in delay, power and PDP estimation accuracy of about 22.44%, 7.59% and 31.96% on average.

In the present study, various higher order shear deformation beam theories (HSDTs) applied in order to achieve an the exact analytical solution of bending, buckling, and free vibration of functionally graded (FG) nanobeam lying on the Winkler and Pasternak elastic foundations. HSDTs are thosein which the effect of transverse shear strains is included.The displacement field of these theories involves a quadratic variation of transverseshear strains and stresses, hence this hypothesis leads to the diminishing of transverse shearstresses at the top and bottom surfaces of a beam. Thus, necessarily there is noneed to use shear correction factors in the HSDTs. Nanobeam has been made of FG materials in which the properties of this material are changed through in the thickness of nanobeam according to the power law distribution. Hamilton`s principle is used to derive equation of motions and the related boundary conditions of simply supported nanobeam. The present study shows that the stability and vibration behavior of FG nanobeam are extremely dependent on the Winkler and Pasternak elastic foundation, gradient index, aspect ratio, and nonlocal parameter. For controlling the stability and vibration of nano-structure, it can be considered that the Winkler-Pasternak foundation as a smart medium gathered with nanobeam. The obtained results of the present study might be useful in the advanced field of micro/nano electromechanical systems.

One of the major challenges facing researchers of tissue engineering is scaffold design with desirable physical and mechanical properties for growth and proliferation of cells and tissue formation. In this paper, firstly, β-tricalcium phosphate (β-TCP) nano powders with particle size of 50-70 nm were synthesized using a simple sol–gel route with calcium nitrate and potassium dihydrogenphosphate as calcium and phosphorus precursors, respectively. Then the porous ceramic scaffold containing 40, 50 and 60wt% of nβ-TCP was prepared by the polyurethane sponge replication method. The scaffolds were coated with P3HB for 30 s and 1 min in order to increase the scaffold’s mechanical properties. XRD, XRF, SEM, TEM and FT-IR were used in order to study the phase and element structure, morphology, particle size and determination of functional groups, respectively. Based on the results of compressive strength and porosimetry tests, the most appropriate type of scaffold is 50 wt% of nβ-TCP immersed for 30 sec in P3HB with 75% porosity in 200-600 μm, with a compressive strength of 1.09 MPa and a compressive modulus of 33MPa, which can be utilized in bone tissue engineering.

The surface plasmon resonance (SPR) properties in the petahertz (1015 Hz) frequency range for monolayer graphene nanosheet and graphene nanopore are investigated using discrete dipole approximation method. We calculate graphene refractive indices by using first principal density functional theory. The near-field enhancement produced by plasmon for these structures is studied by employing finite-difference-time-domain method. For graphene nanosheets, energy of the SPR peak drops with the increase of the sheet length. Also, for graphene nanopores smaller than 5 nm in length, increasing the pore diameter decreases energy of the SPR peak and for some length values like 6 nm, this energy value is raised. For larger sheets (e.g. 8 nm), SPR peak is rather unchanged by variations of the pore diameter. The SPR is used to detect nanoscale objects such as gold, silver, copper, rhodium and aluminium oxide. If nanoscale particles are inserted into the graphene nanopore, 0.195 to 0.474 eV shift in the SPR spectra appears. Type of the presented nanoparticle can be clearly determined by measuring the energy shifts in the SPR spectra. Our results show that petahertz-frequency plasmon in graphene nanopore can be used as a nanoscale-object detection methodology.

A facile two-step systematic plan of action was used for preparation of nanocomposite of reduced graphene oxide (RGO) doped poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) decorated with nickelnanoparticles (NiNPs) onto a glassy carbon electrode (GCE). Composites of PEDOT:PSS and RGO have been prepared by mixing of each component solution and have been fabricated as a beneficial substrate for NiNPs. NiNPs were electrodeposited on the PEDOT-RGO support by applying constant potential to nickel ions solutions. Then, Ni/PEDOT-RGO/GCE employed as efficient electro catalyst for electro oxidation of urea. The electrocatalytic properties of Ni NPs/PEDOT-RGO modified glassy carbon electrode toward the oxidation ofurea was analyzed by cyclic voltammetry (CV) and chronoamperometry (CA). Such studies evidenced the high electro catalytic activity of Ni NPs and mixed PEDOT-RGO, which is mainly ascribed to the good electrochemical activity of PEDOT-RGO composites and the well-dispersed NiNPs on the surface of PEDOT-RGO composite.

Combined eff ects of hydrodynamic partial slip, thermal radiation due to solar energy, and nanoparticles volume fraction on natural convection and entropy generation of atmospheric ultra ne aerosols sample enclosed within a two-sided lid-driven cavity are studied numerically in the present contribution. Partial slip e ect is taken into account along the two horizontal moving walls, and thermal radiation is considered......

The purpose of this study was to evaluate the antibacterial activity and cytotoxicity of copper-doped (Cu45SBG) and copper-free bioactive glass (45SBG) nanopowders. The antibacterial effect was studied using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus)bacteria. The BG nanopowders were synthesized by the sol-gel technique. Theywere characterized by various techniques and their cytotoxicity was evaluated by MTT assay. Chemical compositions of BGs were as the same as predicted compositions. The size of the BGs with an amorphous structure was measured around 100 nm. Both BG nanopowders have no antibacterial effect at broth concentrations less than 12.5 mg/ml. They demonstrated the similar antibacterial activity on E. coli with the minimum bactericidal concentration (MBC) of 12.5 mg/ml. Cu45SBG nanopowders with the MBC of 25 mg/ml were more efficient on S. aureous bacteria than 45SBG nanopowders with the MBC of 50 mg/ml. Cu45SBG showed much more cytotoxicity than 45SBG. The latter, demonstrated similar cells viability to the control. It was concluded that overcome cytotoxic effect, Cu content of BGs nanopowders must be lower than the amount which was used in this research. Therefore, 45SBG nanopowders with considerable antibacterial activity could be used as a good candidate for biomedical applications.

In this paper, zinc oxide (ZnO), copper oxide (CuO) and titanium oxide (TiO2) nanoparticles were prepared using sol-gel method. The structural properties of these nanoparticles were characterized using X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). SEM images revealed that the average size of zinc oxide, copper oxide and titanium oxide nanoparticles to be about 37 nm, 86 nm and 50 nm, respectively. Then, nano-composites of metal oxide were produced by Polyvinyl Alcohol (PVA). The antibacterial activity of zinc oxide, copper oxide and titanium oxide nano-composites against human pathogenic bacteria, mainly Escherichia coli HB101 (gram-negative) have been studied using drop test during the time period of 15 minutes, 30 minutes, 1 hour, 2 hours, 12 hours and 24 hours generated reviews.According to the results obtained with the nano-composite zinc oxide nanoparticles exhibit highest antibacterial properties.

In the presence of elastic planar strain distributions, electronic properties of molybdenum disul de (MoS2) monolayer are investigated within Density Functional Theory (DFT) calculations as implemented in SIESTA package. Three types of planar strain are considered with some di erent intensity values, and uniaxial strain along the armchair and zigzag directions as well as biaxial strain. We present a systematic study of the strained MoS2 monolayer by focusing on the calculation of Total Density Of State (TDOS), Partial Density Of State (PDOS), electron charge density, and electrostatic potential using post processing tools. In most cases, the states due to Mo atoms have dominant association in the TDOS close to the Fermi level of MoS2 monolayer under strain. As a consequence of the strain, S atom takes electron from Mo atom and becomes negatively charged. In addition, the tensile and compressive strains introduce the charge polarization in two opposite directions per three types of strain for both sheets, which is in line with the experimental study. As another important result, the strain-induced charge polarization is proportional to the intensity value of strain.