Nanoscience & Nanotechnology-Asia - Volume 10, Issue 5, 2020

The emergence of memristor offers new avenues to look at several potential applications ranging from non-volatile memories to neuromorphic system. A typical sign of the physical memristor device is Pinched Hysteresis Loop. In the aspect of accomplishing this loop with high accuracy, several memristor models have been evolved in the past. Moreover, various mathematical window functions have been developed from the researchers to throw more insight into the memristor model with the accordance of enhancing the degree of nonlinearity, resolving boundary effect and boundary lock. This review portrays a brief description of explored memristor models and window functions. With this, a comprehensive analysis is made to depict the advantages and disadvantages in a more explicit manner. Furthermore, this work exhibits the prevailing properties of memristor and the different types of switching mechanisms. Here, the future perspective of the memristive technology is also explored very well as the memristor has become an innovative candidate in the memory technology over the semiconductor. Memristor-based potential applications such as a fine resolution programmable gain amplifier, synapse, and logic gate are also explained briefly.

Background: The potential use of nanocarriers is being explored rapidly for the targeted delivery of anticancer agents. Curcumin is a natural polyphenolic compound obtained from rhizomes of turmeric, belongs to family Zingiberaceae. It possesses chemopreventive and chemotherapeutic activity with low toxicity in almost all types of cancer. The low solubility and bioavailability of curcumin make it unable to use for the clinical purpose. The necessity of an effective strategy to overcome the limitations of curcumin is responsible for the development of its nanocarriers. Objective: This study is aimed to review the role of curcumin nanocarriers for the treatment of cancer with special emphasis on cellular uptake and in vitro cytotoxicity studies. In addition to this, the effect of various ligand conjugated curcumin nanoparticles on different types of cancer was also studied. Methods: A systematic review was conducted by extensively surfing the PubMed, science direct and other portals to get the latest update on recent development in nanocarriers of curcumin. Results: The current data from recent studies showed that nanocarriers of curcumin resulted in the targeted delivery, higher efficacy, enhanced bioavailability and lower toxicity. The curcumin nanoparticles showed significant inhibitory effects on cancer cells as compared to free curcumin. Conclusion: It can be concluded that bioavailability of curcumin and its cytotoxic effect to cancer cells can be enhanced by the development of curcumin based nanocarriers and it was found to be a potential drug delivery technique for the treatment of cancer.

Introduction: Many nanoformulations have been designed and evaluated for ocular drug delivery system consistently. These nanoformulations are designed for prolonged retention and course time, stable, efficient and reversible drug loading. The ocular bioavailability is very less when the drug is given through topically. Various anatomical and physiological limitations, for example, tear turnover, nasal lachrymal waste, reflex squinting, and visual static and dynamic hindrances cause the challenges and delay the ocular drug permeation because of the limitation that less than 5% dose can reach into the ocular tissues. Different types of Polymeric micelles were prepared to overcome the above challenges. Polymeric nano micelles are prepared by different methods, such as direct dissolution, dialysis method, Oil-in-water emulsion, solvent evaporation, co-solvent evaporation, and freeze-drying method.

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Results: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

Introduction: A numerical study is performed in which the friction factor and forced convection heat transfer is studied for Al2O3 nanoparticle dispersed in water as a base fluid. Methods: Four concentrations of nanofluids in the range of 0-2.5 vol% have been simulated. The Reynolds Number is varied in the range of 100-500 by varying inlet velocity. Cross flow of air is assumed over the pipe with air velocity of 2.2 m/s. Results: The results depict that the friction factor decreases with an increase in flow rate and increases with increase in volume concentration. The maximum deviation for friction factor obtained by simulation from that obtained using Darcy’s relation is about 21.5% for water. Nusselt number increases with increase in Reynolds Number and nanofluid volume concentration with a maximum of 7653.68 W/m2 at a nanoparticle concentration of 2.5% and Reynolds Number of 500. Heat transfer rate enhancement of upto 13.6% is obtained as compared to pure water. The maximum increase in Nusselt Number is about 13.07% for a nanoparticle concentration of 2.5%. Conclusion: The simulation results are compared with established relations obtained by other researchers and there is a good agreement in terms of trends obtained. The deviations from established relations are also depicted.

Introduction: We report here our success in developing a flexible RRAM stack structure by employing a low-cost method. Bare conductive commercial electric paint is used as anode against Stainless Steel (SS) foil deposited with Mn3O4 thin films forming a BCEP/Mn3O4/SS thin film stack to understand the intrinsic non-volatile resistive switching behavior of Mn3O4. Experimental: Thin film Mn3O4 is deposited on a SS (304) foil by means of potential sweep voltammetry by maintaining typical conditions. Interestingly, the pristine device is subjected to an electroforming process which exhibited a digital type bipolar resistive switching characteristics. The study of the conduction mechanism revealed that the resistive switching arises due to local effect occurring in the bulk of Mn3O4, which corresponds to the growth and annihilation of oxygen vacancy nanofilaments, and this is responsible for the change in resistance state of the RRAM between Low Resistance State (LRS) and High Resistance State (HRS) respectively. Results: In order to affirm the reliability and reproducibility of RRAM structure, the memory retention is monitored over 103 s and subsequently, the endurance test is also carried out ensuring the reproducibility over 100 cycles. Conclusion: Owing to the flexible nature of BCEP/Mn3O4/SS Foil RRAM stack structure, it is perceived to be a prime candidate for future non-volatile memory and flexible electronics applications.

Introduction: Pb2+ is a very toxic heavy metal and its pollution to environment is very harmful and to remove its pollution is a very important issue. Methods: In this work, nano Mesocellular Foams (MCF) silica material was synthesized by hydrothermal method in this research. Power X-ray diffraction and scanning electron miccroscopy, etc. were used to characterize the sample. In this paper, the adsorption of heavy metal ion Pb2+ by MCF was studied. Results: The sample showed spherical particles and the morphology was regular. Its average particle diameter was 2.2 μm. Transmission electron microscopic result showed that the structure of the MCF synthesized has honeycomb structure pore channels which are benefitial for adsorbing heavy metal ions. The nitrogen adsorption-desorption experimental results at low temperature of 77 K showed that the adsorption pore diameter of the MCF synthesized was 19.62 nm. The research results showed that when pH value was 4.5, temperature was 25 ± 1°C, the adsorbent material MCF was 0.2000 g:Pb2+ = 5 and the contact time was 40 min, the adsorption effect was the best and the adsorption rate reached 97.16 ± 0.03%, while the adsorption capacity reached 194.32 ± 0.13 mg/g. Conclusion: By studying, it has been found that the adsorption belongs to the quasi-second-order kinetic model, simultaneously, it also fits the Freundlich equation and in accordance with heterogeneous adsorption. The results of adsorption thermodynamics showed that when temperature is 25 ~ 45°C, the adsorption is a spontaneous exothermic reaction, ΔG° is less than zero, the adsorption enthalpy ΔH° is -31.856 kJ/mol and the adsorption entropy change ΔS° is -45.092 J/(mol·K).

Background: Al-doped ZnO thin films are considered as a promising alternative to ITO in optoelectronic applications. In this work, Al-doped ZnO thin films were prepared using sol-gel spin coating technique. Experimental: The optical properties of the films such as refractive index, extinction coefficient, dielectric function and the absorption coefficient were examined using spectroscopic ellipsometry method in the wavelength range of 300 to 900 nm. The effect of Al doping on ZnO thin films with different Al concentrations was significant. Tauc relation was used to estimate the optical band gap energy of the films. Results: The calculated values of band gap energy were obtained between 3.10 to 3.25 eV. Also the fraction of voids was calculated using Aspnes theory. Conclusion: The free carrier concentration value was obtained in the order of 10¹⁹ cm^-3.

Background: The rate-limiting step in the oral absorption of BCS class II drugs is dissolution. Their low solubility is one of the major obstacles in the process of drug development. Dissolution rate can be increased by decreasing the particle size to the nano range, eventually leading to increased bioavailability. Objective: In the present study, glimepiride loaded nanoparticles were prepared to enhance the dissolution rate. The aim of the work was to examine the effect of polymer-drug ratio, solvent-antisolvent ratio and speed of mixing on in vitro release of glimepiride. Methods: Glimepiride is an antidiabetic drug belonging to the BCS class II drugs. The polymeric nanoparticles were formulated according to Box-Behnken Design (BBD) using nanoprecipitation technique. The prepared nanoparticles were evaluated for in vitro drug release, loading capacity, entrapment efficiency, and percentage yield. Results: It was found that NP-8 has maximum in vitro drug release and was selected as an optimized batch. Analysis of Variance (ANOVA) was applied to the in vitro drug release to study the fitness and significance of the model. The batch NP-8 showed 70.34 ± 1.09% in vitro drug release in 0.1 N methanolic HCl and 92.02 ± 1.87% drug release in phosphate buffer pH 7.8. The release data revealed that the nanoparticles followed zero order kinetics. Conclusion: The study revealed that the incorporation of glimepiride into gelucire 50/13 resulted in enhanced dissolution rate.

Objective: In this study, bleached jute yarn was treated with methyl methacrylate and then in situ synthesis of silver nanoparticles were performed. Experimental: Experimental data showed a decrease in tensile strength of treated yarns from 0.91 to 0.78 g/dtex. Afterwards, treated samples were dyed with 1:1 and 1:2 pre-metallised dyes. Results: Methyl methacrylate treated jute yarns exhibited higher color strength (12.55%) and fastness properties as compared to untreated samples. Conclusion: Methyl methacrylate treated and nano-coated jute yarns showed much better color strength (23.96%) and higher color fastness properties towards light and washing.

Background: In this study, the poly(amidoamine) (PAMAM) G-2 dendrimer was applied to the jute yarn. Methods: Untreated and dendrimer treated jute yarns were then dyed with Direct Yellow 24. Thermodynamic parameters of dyed samples, free energy (ΔG°), the enthalpy (ΔH°), and the entropy (ΔS°) were also evaluated. Results: Dendrimer treated jute yarn showed higher dye sorption compare to untreated jute yarn. The values of ΔH° and ΔG° indicated that the sorption process was exothermic and spontaneous at low temperature. Conclusion: Freundlich isotherm was found to be the optimum isotherm for untreated and BET isotherm defined for dendrimer treated jute yarn.

Background: Improvement of conventional heat transfer fluids for achieving higher energy efficiencies in thermal equipment is a key parameter to conserve energy in industries. The heat transfer fluids such as water, oil and ethylene glycol greatly suffer low heat transfer performance in industrial processes. There is a need to develop new types of heat transfer fluids that are more effective in terms of heat transfer performance. Nanofluids enhance thermal conductivity and improve the thermal performance of heat transfer systems. Methods: New titania nanofluid samples consisting of 0.0625 to 1% TiO2 nanoparticles were prepared and characterized. The method of preparation was based on prior precipitation of TiO2 from an ammoniacal solution of pH 9 and calcination at 900°C. Solubilization, homogenization and stabilization of the of the nanoparticles were performed by sonication in the presence of sodium dodecyl sulfate (SDS) anionic surfactant and cetyltrimethylammonium bromide (CTAB) cationic surfactant. Results: This treatment was also utilized to increase the stability and improve the thermal properties of the fluid. Conclusion: Several characterization techniques including measurements of hydrodynamic size distribution, zeta potential, transmission electron microscopy (TEM), viscosity, density, specific heat, thermal conductivity, and sedimentation photo capturing were used to measure and confirm the stability and sedimentation rate of the prepared nanofluids.

Background: With the reducing size of the devices, the leakage power has also increased exponentially in the nano-scale CMOS devices. Several techniques have been devised so far to minimize the leakage power, among which, MTCMOS (power-gating) is the preferred one as it effectively minimizes the leakage power without any complexity in the circuit. However, the power-gating technique suffers from problems like transition noise and delay. In this paper, we proposed a new simple yet effective technique to minimize leakage power in MTCMOS circuits. Objective: The objective of the paper was to propose a new technique which effectively minimizes leakage power in nanoscale power-gated circuits with minimal delay, noise and area requirement so that it can well be implemented in high-speed low-power digital integrated circuits. Methods: A new power-gating structure has been proposed in this paper. The new proposed technique includes three parallel NMOS transistors with variable widths which are functional during the active mode to reduce the on-time delay. A PMOS footer with gate-bias is also connected in parallel with the NMOS footer transistors. The proposed technique has been verified through simulation in 45nm MTCMOS technology to implement a 32 bit adder circuit. Results: The proposed technique offers significant reduction in leakage power, reactivation noise and reactivation energy. The technique reduced the leakage power effectively at room temperature as well as higher temperatures. The reactivation noise produced by the proposed technique minimized by 98.7%, 64.8%, 62.07% and 24.47% as compared to the parallel transistor, variable-width, charge-recycling and the modified-charge recycling techniques respectively at room temperature.The reactivation energy of the proposed technique also minimized by 77.by 77.67%, 55.8%, 45.1%, and 18.32% with respect to the parallel transistor, variable-width, CR and Modified-CR techniques, respectively. Conclusion: The proposed technique offers significant reduction in leakage power, reactivation noise and reactivation energy. The technique reduces the leakage power effectively at room temperature as well as at higher temperatures. Since the delay and area overhead of the proposed structure is minimal, hence it can be easily implemented in high-speed low-power digital circuits.

Objective: This work identifies materials that satisfy refractive index, optical band gap, composition profile, conductivity, hall mobility, carrier type and carrier concentration to utilize them in making thin film photovoltaic cells. Methods: We fabricated phosphorous doped amorphous silicon (n+ aSi:H), boron doped amorphous silicon germanium(p+ aSiGe:H) and intrinsic amorphous silicon (i-aSi:H). A detailed and systematic characterization of the fabricated layers was done. The phosphorous doped amorphous silicon (n+ aSi:H) showed an optical band gap of 1.842 eV and an electron mobility of 295.45 cm²V^-1s^-1. The boron doped amorphous silicon germanium (p+ aSiGe:H) exhibited an optical band gap of 1.74 eV and a hole mobility of 158.353 cm²V^-1s^-1. The intrinsic amorphous silicon (i-aSi:H) has an optical band gap of 1.801 eV. The films of n+ aSi:H, i-aSi:H and p+ aSiGe:H can be utilized for fabricating graded band gap single junction thin film solar cells, as they are semiconducting materials with varying band gaps in the range of 1.74 eV to 1.84 eV. The tailoring of band gap achieved by the proposed material combination has been presented using its energy band diagram. Results: In this work, we are proposing a single junction graded band gap solar cell with aSi:H and aSi- Ge:H alloys of varying doping to achieve grading of band gap, which improves the efficiency while keeping the cell compact and light. Conclusion: As a first step in the validation, we have simulated a thin film solar cell using SCAPS1D simulation software with the measured parameters for each of the layers and found that it successfully performs as solar cell with an efficiency of 14.5%.

Introduction: Clean, safe and potable water with high specifications has been acquired from the red seawater (Suez, Egypt) by utilizing graphene-based chromium oxide (Cr2O3/r-GO) nanocomposites. Experimental: Cr2O3 nanoparticles and Cr2O3/ r-GO nanocomposites have been synthesized from a toxic source (K2CrO7) using the photochemical reduction method where trimethyl ammonium chloride and trisodium citrate working as capping and reducing agents under visible light irradiation. The size, morphology and optical properties have been characterized by Transition Electron Microscopy (TEM), X-ray Diffraction (XRD) and UV-Vis spectrophotometry. Water without salts, lethal metals and no recording micro-organisms were secured in less than 3 hours by utilizing simple distillation in the presence of Cr2O3 nanoparticles with average size 5.0 ± 1.36 nm and Cr2O3/r-GO nanocomposites with average size 3.0 ± 1.69 nm. The evaporation of water was improved due to the productive photothermal change of the Cr2O3 nanoparticles that have two plasmonic bands (423 nm and 576 nm) and the presence of exceptionally highly efficient thermal capacitor, graphene. These Cr2O3/r-GO nanocomposites demonstrated a high gain of temperature and high stability after multiple times of recycling processes. Results: The antimicrobial action of Cr2O3 and Cr2O3/r-GO nanocomposites was examined against Bacillus subtilis (gram positive, G+), Escherichia coli (gram negative, G-), Pseudomonas aeruginosa (gram negative, G-) and Staphylococcus aureus (gram positive, G+). From the results, Cr2O3 nanoparticles showed higher inhibition zone diameters against these microbes than Cr2O3/r-GO nanocomposites. Conclusion: The unique properties, environmental safe, low cost and ease of these composites became them highly efficient alternative in water desalination technology.

Introduction: Solid porous carbon (SPC) with micro-mesopore structures was successfully fabricated from used cigarette filters via carbonization. Experimental: The morphology and structure of the as-prepared porous carbon materials were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Results: This novel carbon material allows the removal of organic pollutants from water. The maximum adsorbed capacity of methylene blue could reach ~185 mg.g-1, which was attributed to the high specific surface area (567.7 m2.g-1) and the micro-mesoporous structure of the samples. Conclusion: Furthermore, when genomic stability was maintained in the solution, SPC was easily extracted. The mechanism for the fabrication of the proposed used cigarette filter is elucidated in this study.