Journal of Nano Research Vol. 64

Abstract: In this paper, a numerical procedure is proposed for analyzing the effects of length scale parameter, external electric field, angular speed and nonlocal parameter on the free vibration of a functionally graded piezoelectric cylindrical nanoshell. Nonlocal strain gradient theory (NSGT) is employed to study Eringen’s size-dependent effect and the length scale parameter. This new proposed method can be considered as a combination of Eringen’s nonlocal model and classical strain gradient theory. The obtained results show that this model can be used reliably for small-scale systems. The effects of boundary conditions, applied voltage, nonlocal parameter, rotational speed and length scale parameter on natural frequencies are presented. Compared to other elasticity theories, NSGT achieves the highest natural frequency and critical rotational speed and also a wider stability region. Doubling and tripling the length scale increases the natural frequency by approximately 1.8 and 2.6 times, respectively; while doubling and tripling the nonlocal parameter value reduces the natural frequency by approximately 1.2 and 1.4 times, respectively. Therefore, the natural frequency is more sensitive to the length scale parameter than the nonlocal parameter. Finally, it was shown that the critical angular speed goes up by increasing the length scale parameter, applied voltage, or nonlocal parameter.

Abstract: Curcumin is a phytochemical compound extracted from the rhizomes of the plant Curcuma longa and shows intrinsic anti-cancer properties. Its medical application remains limited due to its extremely low water solubility and bioavailability. Addressing this problem, drug delivery systems based on nano-scale technology have emerged. Among the advanced techniques, the self-nano-emulsifying drug delivery system (SNEDDS) has been considered as an ideal method to enhance the oral absorption and bioavailability of poorly water-soluble drugs. The objectives of present study are to prepare a formulation of nanoemulsion containing curcuminoids of natural origin, assess its micro properties, stabilities and evaluate the in vitro cytotoxic activity against some cancer cells using tetrazolium dye MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo- lium bromide] (MTT assay). Measurement results showed that the curcumin nanoemulsion was successfully synthesized with typical mean droplet sizes from 9 to 11 nm, and revealed an excellent stability over time. Curcumin in a nanoemulsion was more stable than unencapsulated curcumin. In vitro experiments on cytotoxic activities against Hela, HepG2 and H460 cancer cell lines indicated that the prepared curcumin nanoemulsion effectively inhibited the growth of all three cell lines with IC50 values of 8.6 µM, 14.5 µM and 5.3 µM respectively. Results of this study suggest that curcumin nanoemulsion can be considered as novel and promising chemo-preventive and therapeutic drug in treatment of cancer, and it may supply some useful ideas in developing anticancer drugs for further in vivo studies.

Abstract: Anatase/brookite nanocomposites were fabricated by the classical method of hydrolysis, additionally using hydrothermal treatment of preformed titanium dioxide sol with tetrabutyl orthotitanate. The influence of hydrothermal processing the buffer solution of TiO₂ synthesis on the average particle sizes, specific surface area, pore sizes distributions, optical and photocatalytic properties investigated by X-ray diffraction, low-temperature nitrogen adsorption and UV-Vis spectroscopy. It has been determined that the hydrothermal treatment of pre-prepared titania sol as hydrolysis product leads to rutile formation after annealing at 400°C. Respective model of forming anatase/brookite/rutile nanocomposites was proposed. The changes of bang gap energy of TiO₂ were observed and explained by effect of change phase composition and particles size of nanocomposite particles. Methylene blue (MB) photo-oxidation reactions using titanium dioxide nanocomposite were analyzed. Maximal photocatalytic activity of MB oxidation was detected for material with the ratio of the titania phases (anatase : brookite : rutile – 2 : 2 : 1). Synergistic effect between crystallinity, phase ratio, morphology of oxide material, band gap and photocatalytic activity in the anatase/brookite nanocomposites was established.

Abstract: Vibration problem of variable cross-sectional nanorods have been investigated. Analytical solutions have been determined for the variable cross-sectional nanorods for a family of cross-sectional variation. Cross-sectional area variation has been assumed as power function of the axial coordinate. Nonlocal governing equation of motion has been obtained as a second order linear differential equation. Bessel functions have been used in analytical solution of the governing differential equation. Effect of nonlocal and area variation power parameters on dynamics of nanorods have been analyzed. Mode shapes of nanorod have been depicted in various cases and boundary conditions. Present results could be useful at design of atomic force microscope’s probe tip selection.

Abstract: This study presents the analytical solutions of free vibration analysis of simply supported nanoplate FG porous using nonlocal high order shear deformation plate theory. This theory contains four unknowns without the use of shear correction factors unlike the others. The objective of this article is to develop a model to use the function f (z) on vibration and the natural frequencies of functionally graded nanoplates nonlocal to study the effect of the various parameters. The validity of the theory is shown by comparing the present results with obtained with those reported in the literature. The effects of various parameters are all discussed.

Abstract: The influence of velocity slip and thermal radiation effects on the magnetohydrodynamic hybrid Cu-Al₂O₃/water nanofluid flow over a permeable stretching sheet is reported in this paper. The similarity transformation is adopted to reduce the partial differential equations to the ordinary differential equations. Exact analytical method is implemented to solve the problem. Maple program is used to facilitate the calculation process. The new additional effects which are the velocity slip and thermal radiation effects are considered towards the model to scrutinize the impacts. The effects of various parameters towards the velocity and temperature profiles are demonstrated through graphs, meanwhile the skin friction coefficient and the local Nusselt number are exhibited through the tabulation of data. The existence of velocity slip reduced the velocity profile but enhanced the temperature profile. The thermal radiation effect has increased the temperature profile. The heat transfer rate are enhanced for the case of hybrid nanofluid compared to the mono nanofluid.

Abstract: Improving the charge transfer of quantum dots and the electron transport layer can greatly improve the efficiency of quantum dot sensitized solar cells (QDSSC). In this work, we used the ligand exchange method to improve the electron transfer efficiency between CdSe QDs and electron transport layer. The short chain-ligand containing disulfide bond and benzene ring conjugated structure was selected as the surface ligand of CdSe QDs. Because of its unique disulfide bond and conjugated structure, the stability and electron transfer efficiency of QDs in TiO₂ layer can be effectively improved. The surface ligand has good stability and the ability to promote charge transfer, which can effectively improve the efficiency of QDSSC. By characterizing of fluorescence performance and the analysis of fluorescence lifetime, the surface of this ligand behaves fluorescence quenching phenomenon and life decay phenomenon after modification. Furthermore, photovoltaic devices constructed by the as-prepared dithiocarbamate functionalization of CdSe@TiO₂ have also been assembled with the highest PCE of 5.22%.

Abstract: Herein, this study shows three different synthesis of gold nanoparticles with various nano-shapes and an investigation of the correlation between nano-shapes and electrochemical effects on dopamine oxidation. To synthesize nano-shaped gold nanoparticles green reducing sources such as rose extract, glucose, and pomegranate juice were used. Thereby, three different gold nanoparticles were synthesized. In order to examine nanoparticle shapes microscopic and spectroscopic characterizations of nanoparticles were carried out. Subsequently the effects of shapes on electrochemical probes and dopamine were accomplished. As a result, it was confirmed that the shapes of the same metal nanoparticles had different effects on electrochemical experiments.

Abstract: The paper introduces an analytical model for gate all around (GAA) or Surrounding Gate Metal Oxide Semiconductor Field Effect Transistor (SG-MOSFET) inclusive of quantum mechanical effects. The classical oxide capacitance is replaced by the capacitance incorporating quantum effects by including the centroid parameter. The quantum variant of inversion charge distribution function, inversion layer capacitance, drain current, and transconductance expressions are modeled by employing this model. The established analytical model results agree with the simulated results, verifying these models' validity and providing theoretical supports for designing and applying these novel devices.

Abstract: This paper presents an analytical model for ultra scaled symmetric double gate (SDG) nanowire junctionless field effect transistor (JLFET), which includes charge quantization in all the regions of operation. This model is based on a first-order correction for the confined energies obtained by solving the Schrodinger’s equation. The model is able to predict the quantum mechanical effects (QME) on the surface potential, drain current and transconductance for a highly doped and extremely thin silicon layer of thickness down to 4nm. The results obtained are validated by comparing with GENIUS 3D TCAD quantum simulations.