Current Nanoscience - Volume 16, Issue 6, 2020

Most current modern devices have micro dimensions. For engineers and manufacturers, it is now possible to manufacture completely remote devices in a modern way. To determine the critical points in measuring the dimensions for the manufacturing of devices, which is achieved in practice and at an appropriate cost, numerous studies have been conducted around the world. Researchers have attempted to develop a pragmatic approach to interface various nanoscale devices together and to study their focal points and disadvantages. The objective of this study is to focus on modern trends in the manufacturing of nanoscale devices. These trends are divided into the following five sections: development of tribotronic devices, nanodevice fabrication using two-dimensional materials, fabrication using carbon nanotubes (CNTs), on-chip nanodevice fabrication, and nanodevices based on photonics. In this study, the views on these trends and how to effectively apply them in the future are presented. To enhance the structure and features of nanowires inside a scanning tunneling microscope (STM) scanner, a novel view about the structure of nanowire is presented. These nanowires demonstrate unique metal properties that enable them to operate in multiple environments with high efficiency. Using these nanowires inside an STM scanner can improve their ability to withstand high pressure because their metal properties minimize the chances of breakage.

Background: Cucurbit[n]uril (CB[n], n=5, 6, 7, 8 and 10#137;is a type of macrocyclic compounds formed by n glycerol units and 2n methylene. The different sizes of the cavity lead to the different chemical characteristics of CB[n]. Therefore, it is very important to distinguish and detect CB[n]. Methods: At room temperature, Rhodamine B was added to a gold nanoparticles solution. The above mixture was respectively mixed with different concentrations of Cucurbituril[n] or β-cyclodextrin solutions. The fluorescence spectra and ultraviolet-visible spectra of samples were determined. Results: It was found that 1.2nM gold nanoparticles could quench the fluorescence of 1μM Rhodamine B completely. After adding a certain amount of Cucurbituril[7], the fluorescence intensity of Rhodamine B was restored. Compared with other macrocyclic compounds, such as Cucurbituril[5], Cucurbituril[6] and β-cyclodextrin, we found that this method had unique selectivity for Cucurbituril[ 7]. Under the optimal conditions, the fluorescence recovery efficiency was linearly proportional to the concentration of Cucurbituril[7] in the range of 0.8-8 μg·mL^-1. The detection limit was 0.21 μg·mL^-1. Conclusion: The research established an effective and practical FRET-based detection method for CB[7] with RhB as a donor and the gold nanoparticles as the acceptor. The system had unique and extensive selectivity for CB[7].

Background: The lipid-drug conjugate nanoparticles (LDC NPs), amongst other lipidbased nanoparticles, are the most accepted ones for the oral delivery of both hydrophilic and hydrophobic drugs with poor bioavailability. Besides, the LDC NPs show altered physicochemical properties of the drug and have the potential applications in targeting the drug to a specific organ. Objective: To synthesize hydrophilic Valacyclovir (VACV)-stearic acid (SA) and lipophilic Acyclovir (ACV)-stearic acid conjugates (VACV-SAC and ACV-SAC), and develop their nanoparticles (VACV-LDC-NPs and ACV-LDC-NPs) for improved intestinal permeability. Methods: Both VACV-SAC and ACV-SAC were synthesized and confirmed using FTIR, NMR, and DSC techniques and characterized for assay. The lipid drug conjugate nanoparticles (LDC NPs) were prepared using cold high-pressure homogenization technique and characterized for drug content, mean particle size, zeta potential, ex vivo gut permeability using rat gut sac model, and Caco-2 cell permeability. Results: The FTIR, NMR, and DSC results confirmed the successful synthesis of LDCs. The assay of VACV-SAC and ACV-SAC was found to be 51.48±5.6% and 41.2±6.2%, respectively. The VACV-LDC-NPs and ACV-LDC-NPs showed %EE of 99.10±6.71% and 86.84±5.32%, the mean particle size of 338.7±8nm and 251.3±7nm and zeta potential of -10.8±2.31mV and -11.2±3.52mV respectively. About 91±5.2% of VACV and 84±6.5% of ACV were found permeated across the rat intestine after 480 minutes from their respective NPs. Furthermore, VACV-LDC-NPs and ACVLDC- NPs displayed a significantly higher permeability coefficient (61.5x10^-6 and 59.8x10^-6 cm/s, respectively) than their plain solutions. Conclusion: The obtained remarkable permeability characteristics indicate developed LDC NPs are the potential, promising and translational approaches for effective oral delivery of poorly bioavailable hydrophilic and lipophilic drugs. Furthermore, this approach may result in moderately to significantly enhanced oral bioavailability of hydrophilic drugs as the conjugation results in amphiphilic molecules, which are further absorbed through different mechanisms across the intestinal mucosa (mainly through passive diffusion mechanism).

Background: Despite great hopes for small interfering RNA (siRNA)-based gene therapies, restrictions, including the presence of nucleases, reticuloendothelial system and undesired electrostatic interactions between nucleic acids and the cell membrane, limit the success of these approaches. In the last few decades, non-viral nucleic acid delivery vectors in nanosize with high biocompatibility, low toxicity and proton sponge effect have emerged as magic bullets to overcome these drawbacks. Objective: This study aimed to develop poly(2-hydroxyethyl methacrylate) (pHEMA)-chitosan nanoparticles (PCNp), and to transfect green fluorescent protein (GFP)-silencing siRNA (GsiR) in vitro. Methods: Firstly, PCNp displaying core-shell structure were synthesized and thereafter GsiR was encapsulated into the core of PCNp. The synthesized PCNp with/without GsiR were characterized using ultraviolet-visible (UV-vis)-spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, thermal decomposition, atomic force microscopy (AFM), scanning electron microscopy (SEM), zeta potential and dynamic light scattering (DLS) measurements. Encapsulation of siRNA into the pHEMA core coated with chitosan shell was demonstrated using fluorescence and FTIR spectroscopy. Results: The surface charges of PCNp and PCNp-GsiR were found to be +39.5 and +40.2, respectively. In DLS analysis, an insignificant shift in the Z-average diameter of PCNp was observed from 109 nm to 133 nm using the encapsulation of GsiR. In comparison to other studied nanomaterials and a commercial transfection reagent, our findings suggest a promising GFP-silencing effect of 45%. Conclusion: To our knowledge, we have obtained comparable silencing activity with the other studied equivalents despite using the lowest concentration of siRNA in existing literature.

Background: This study used Electrical Spark Discharge Method (ESDM) to fabricate the nano-Au, nano-Ag and nano-Cu colloid. The spark wears down the surface of the electrodes and gets nano-metal particles at standard temperature and pressure and without adding any other chemical materials in the deionized water. Methods: The nano-metal particles are examined by UV-Visible Spectroscopy, Zetasizer, Transmission Electron Microscope, and Energy Dispersive X-ray Analysis and are proven to be nano-metal colloid. Under the comparison of different parameters (discharge pulse width, HV, Ip), the size of nano-metal particles increases with the level of Ip. Results: Under the experiment of light or dark, most of the Absorbance of the nano-Au and nano-Ag colloid is higher than that of the environment under strong light irradiation as long as it is prepared in a pure black environment. The nano-Au and nano-Ag colloid prepared by ESDM have a zeta potential exceeding the absolute value of 30 mV, no matter which parameter is applied or whether there is illumination or not. Conclusion: It represents a good suspension stability of the nano-Au and nano-Ag colloid, but the nano-Cu colloid does not have this feature. The suspension stability is not good.

Background: Researchers working in the field of nanofluid have done many studies on the thermophysical properties of nanofluids. Among these studies, the number of studies on specific heat is rather limited. In the study of the heat transfer performance of nanofluids, it is essential to raise the number of specific heat studies, whose subject is one of the important thermophysical properties. Objective: The authors aimed to measure the specific heat values of Al2O3/water, Cu/water nanofluids and Al2O3-Cu/water hybrid nanofluids using the DTA procedure, and compare the results with those frequently used in the literature. In addition, this study focuses on the effect of temperature and volume concentration on specific heat. Methods: The two-step method was tried to have nanofluids. The pure water selected as the base fluid was mixed with the Al2O3 and Cu nanoparticles and Arabic Gum as the surfactant, firstly mixed in the magnetic stirrer for half an hour. It was then homogenized for 6 hours in the ultrasonic homogenizer. Results: After the experiments, the specific heat of nanofluids and hybrid nanofluid were compared and the temperature and volume concentration of specific heat were investigated. Then, the experimental results obtained for all three fluids were compared with the two frequently used correlations in the literature. Conclusion: Specific heat capacity increased with increasing temperature, and decreased with increasing volume concentration for three tested nanofluids. Cu/water has the lowest specific heat capacity among all tested fluids. Experimental specific heat capacity measurement results are compared by using the models developed by Pak and Cho and Xuan and Roetzel. According to experimental results, these correlations can predict experimental results within the range of ±1%.

Background: The solidification of metals is usually initiated by heterogeneous nucleation, which, however, is less controllable due to the unexpected impurities. In this study, the nucleation behavior of micro- and nano-sized Bi droplets embedded in the Cu matrix, where well-identified catalyst interfaces were introduced, was studied. Objective: This paper demonstrated the nucleation behavior of the nano-sized Bi droplets embedded in the Cu matrix to determine the nucleation sites and contact angle. Methods: Cu-20Bi (wt. %) melt-spun ribbons consisting of numerous micro- and nano-sized Bi droplets embedded in the Cu matrix were prepared. Based on the structure characterization by transmission electron microscopy (TEM), the nucleation behavior of these embedded Bi droplets was demonstrated by nanocalorimetry. Results: The orientation relationship between the nano-sized Bi droplets and the Cu matrix was determined. The undercooling of the nano-sized Bi droplets with the cooling rate was more stable than that of the micro-sized Bi droplets, and a nucleation contact angle of 72° was obtained. Conclusion: The undercooling increases with the reduction of droplet size. The nucleation of the Bi droplets is significantly affected by their interfacial structure with the Cu matrix. Compared with hexagonal Zn, the Cu matrix with face-centered cubic structure has a less catalytic effect on the nucleation of Bi.

Background: Recently, molecular electronics have attracted the attention of many researchers, both theoretically and applied electronics. Nanostructures have significant thermal properties, which is why they are considered as good options for designing a new generation of integrated electronic devices. Objective: In this paper, the focus is on the thermoelectric properties of the molecular junction points with the electrodes. The influence of the number of atom contacts was also investigated on the thermoelectric properties of molecule located between two electrodes metallic. Therefore, the thermoelectric characteristics of the B12 N12 molecule are investigated. Methods: For this purpose, the Green’s function theory as well as mapping technique approach with the wide-band approximation and also the inelastic behaviour is considered for the electron-phonon interactions. Results: It has been observed that the largest values of the total part of conductance as well as its elastic (G^maxe,n) depend on the number of atom contacts and are arranged as: G^maxe,6 > G^maxe,1 > G^maxe,4. Furthermore, the largest values of the electronic thermal conductance, i.e. K^maxp are seen to be in the order of K^maxp,4< K^maxp,1< K^maxp,6 that the number of main peaks increases in four-atom contacts at (E < Ef). Conclusion: Furthermore, it is represented that the thermal conductance shows an oscillatory behavior which is significantly affected by the number of atom contacts.

Background: During chemotherapy, drugs can damage cancer cells’ DNA and cytomembrane structure, and then induce cell death. However, autophagy can increase the chemotherapy resistance of cancer cells, reducing the effect of chemotherapy. Objective: To block the autophagic flux in cancer cells, it is vital to enhance the anti-cancer efficacy of chemotherapy drugs; for this purpose, we test the gadolinium oxide nanoparticles (Gd2O3 NPs)’ effect on autophagy. Methods: The cytotoxicity of Gd2O3 NPs on HeLa cells was evaluated by a (4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide assay. Then, monodasylcadaverine staining, immunofluorescence, immunoblot, and apoptosis assay were conducted to evaluate the effect of Gd2O3 NPs on autophagy and efficacy of chemotherapy drugs in human ovarian cancer cells. Results: We found that Gd2O3 NPs, which have great potential for use as a contrast agent in magnetic resonance imaging, could block the late stage of autophagic flux in a dose-dependent manner and then cause autophagosome accumulation in HeLa cells. When co-treated with 8 μg/mL Gd2O3 NPs and 5 μg/mL cisplatin, the number of dead HeLa cells increased by about 20% compared with cisplatin alone. We observed the same phenomenon in cisplatin-resistant COC1/DDP cells. Conclusion: We conclude that Gd2O3 NPs can block the late stage of autophagic flux and enhance the cytotoxicity of chemotherapeutic drugs in human ovarian cancer cells. Thus, the nanoparticles have significant potential for use in both diagnosis and therapy of solid tumor.

Background: This study used molecular dynamics simulations to investigate the wetting properties of a droplet on copper surfaces with different nanostructures to determine the influence of the structural parameter and roughness factor on the wetting properties. Methods: The simulation results show that the structural parameter h/b can determine the wetting transition of droplets on surfaces. In addition, the critical structural parameter values are 1.5, 1.5, 2.08 and 2.24 for the square pillar, cylinder, frustum and cone nanostructures, respectively. Due to the restriction of the wedge surface on water molecules, the effect of the wedge surface is not the same when the theoretical gap and height of the nanostructures are changed on different surfaces. Results and Discussion: For the square pillar and the cylinder surfaces, when changing the height or the theoretical gap of the nanostructure, the wedge angle is always the same and is 90°, so the effect of the wedge surface is unchanged for water molecules. For the frustum and the cone surfaces, the wedge angle does not change when the theoretical gap of the nanostructure is changed but when the height of the nanostructure is changed, the wedge angle gradually increases but does not exceed 90° resulting in the restriction of the wedge surface on water molecules gradually increasing. Therefore, for the same height and theoretical gap, the contact angle of the frustum and the cone surfaces is larger than that of the square pillar surfaces and cylinder surfaces due to the effect of the wedge surface. It is also observed that the increased roughness factor helps increase the contact angle of the droplet. Conclusion: We propose that the wetting properties of the nanostructure surface can be controlled by the structural parameter associated with the surface roughness.

Background: In nano-size α-Fe2O3 particles, the Morin transition temperature was reported to be suppressed. This suppression of the TM in nano-size α-Fe2O3 was suggested to be due to high internal strain and to the enhanced role of surface spins because of the enhanced surface to volume ratio. It was reported that for nanoparticles of diameters less than 20 nm, no Morin transition was observed and the antiferromagnetic phase disappears. In addition, annealing of samples was reported to result in both an increase of TM and a sharper transition which were attributed to the reduction in defects, crystal growth, or both. Objective: In this work, we investigated the role of applied magnetic field in TM, the extent of the Morin transition, thermal hysteresis, and the spin-flop field in synthetic α-Fe2O3 nanoparticles of diameter around 20 nm. Methods: Hematite nanoparticles were synthesized using the sol-gel method. Morphology and structural studies of the particles were done using TEM, and XRD, respectively. The XRD patterns confirm that the particles are hematite with a very small maghemite phase. The average size of the nanoparticles is estimated from both TEM images and XRD patterns to be around 20 nm. The magnetization versus temperature measurements were conducted upon heating from 5 K to 400 K and cooling down back to 5 K at several applied fields between 50 Oe and 500 Oe. Magnetization versus magnetic field measurements between -5 T and +5 T were conducted at several temperatures in the temperature range of 2-300 K. Results: We report three significant findings in these hematite nanoparticles. Firstly, we report the occurrence of Morin transition in hematite nanoparticles of such size. Secondly, we report the slight field dependence of Morin transition temperature. Thirdly, we report the strong temperature dependence of the spin-flop. Zero-field-cooled magnetization versus temperature measurements were conducted at several applied magnetic fields. Conclusion: From the magnetization versus temperature curves, Morin transition was observed to occur in all applied fields at Morin transition temperature, TM which is around 250 K with slight field dependence. From the magnetization versus magnetic field curves, spin-flop in the antiferromagnetic state was observed and found to be strongly temperature dependent. The results are discussed in terms of three components of the magnetic phase in our sample. These are the paramagnetic, soft ferromagnetic, and hard ferromagnetic components.

Background: The active layer not only must have a strong light absorption in the visible spectrum but must also be sufficient for charge carrier transport to the electrodes. Electrons in conducting polymer transport by hopping between different energy levels resulted in much lower charge mobility. Therefore, the thickness of the active layer must be limited, so the separated charge can reach the corresponding electrodes without recombination. However, a thin active layer has weaker light absorption, resulting in the low photogenerated current in organic solar cell devices. Furthermore, buffer layers usually have high charge mobility, which in turn would enhance the transportation of charge from the active layer to electrodes. Metal oxides have been studied to be used as a cathode buffer layer, such as titanium dioxide (TiO2), zinc oxide (ZnO), etc. Objective: In this work, behaviors of the photon-electrical characteristics with variation in thickness of the active (poly(3-hexylthiophene-2,5-diyl) and phenyl-C61 butyric acid methyl ester blend) and buffer (zinc oxide) layers were investigated. Methods: The influences of the thickness of the active and buffer layers on characteristic parameters of organic solar cells were investigated by solving the drift and diffusion equation with the photogenerated current given by the Hetch equation. Results: The optimum thickness was obtained around 100 nm and below 10 nm for the active and the ZnO buffer layers, respectively. Conclusion: Thinner active layer resulted in lower photocurrent due to poor light absorption while at 150 nm thick and above, PCE of the device reduced rapidly because of the high recombination rate of photogenerated electron-hole pairs. ZnO buffer layer was used as an electron transport layer and a hole blocking layer in order to improve the cell’s performance. The addition of ZnO enhanced the PCE up to 2.48 times higher than the conventional device.

Background: Hydroxyapatite is similar to bone mineral in chemical composition and has good biocompatibility with host tissue and bone. Objective: This work aims to tailor the mechanical and dielectric properties of hydroxyapatite with zinc substitution, to improve the wearability of implant and accelerate the healing process. Methods: Pure and zinc incorporated hydroxyapatite Ca10(PO4)6(OH)2 samples have been successfully prepared by means of the chemical precipitation method. Results: The results showed that hydroxyapatite(Hap) having a hexagonal structure was the major phase identified in all the samples. It was found that the secondary phase of β-tricalcium phosphate (β-TCP) formed due to the addition of zinc, resulting in biphasic structure BCP (Hap + β-TCP). A minor phase of ZnO also formed for a higher concentration of Zn (Zn ≥ 2mol%) doping. It was found that the Zn incorporation to Hap enhanced both mechanical and dielectric properties without altering the bioactive properties. The microhardness increased up to 0.87 GPa for Zn concentration equal to 1.5mol%, which is comparable to the human bone ~0.3 - 0.9 GPa. The dielectric properties evaluated in the study showed that 1.5 mol% Zn doped hydroxyapatite had the highest dielectric constant. Higher values of dielectric constant at low frequencies signify its importance in healing processes and bone growth due to polarization of the material under the influence of the electric field. Conclusion: Sample Z1.5, having 1.5 mol% Zn doping, showed the most optimized properties suitable for bone regeneration applications.

Background: The addition of nanofillers to polymers for enhanced performance is delivering more interesting applications for aerospace, aeronautic industries, and other numerous nanotechnical applications. Objective: The aim was, therefore, to examine the role of graphene nanopowder on the thermal stability and conductivity of the poly(vinyl alcohol)/poly(vinyl pyrrolidone) (PVA/PVP) polymer nanocomposites. Methods: In this work, graphene nanofillers were incorporated into the PVA/PVP polymer blended by solution mixing for the preparation of nanocomposite films. Results: Results showed that increasing graphene ratio improved thermal conductivity up to 330%, moreover enhancing hardness shore A up to 16.3% compared to pure PVA/PVP blend polymer. TGA analysis confirmed that the PVA/PVP and graphene network showed good thermal stability. Conclusion: From the present findings, it is proved that PVA/PVP blends have profound effects on thermal stability that cannot be attained by using individual counterparts. The property of the nanocomposite depends on the host blend, morphology, and interfacial characteristics.

Background: Nowadays, microbial infections are considered the most important causes of morbidity and mortality. Various microorganisms including biofilm-forming bacteria reported playing a crucial role in such public health concerns. On the other hand, the inefficacy of conventional antimicrobial agents due to various reasons including drug resistance creates a need for the development of effective drug molecules. In this context, nanoparticles can be promisingly used in the management of all such concerns. Objective: The study aimed to evaluate antibacterial and biofilm removal efficacy of various metal nanoparticles against biofilm-forming bacteria. Methods: Various metal nanoparticles including silver (AgNPs), copper (CuNPs) and zinc oxide (ZnONPs) were synthesized from plant leaf extracts of Punica granatum, Citrus medica, and Annona squamosa, respectively. Results: Thus synthesized nanoparticles were evaluated for their antibacterial and biofilm removal efficacies against Enterococcus gallinarum, Staphylococcus haemolyticus, Enterobacter aerogenes, and Salmonella enterica serovar Typhi to propose a promising approach towards management of such pathogens. In vitro antibacterial study demonstrated that AgNPs showed the maximum efficacy against all the test bacteria followed by CuNPs and ZnONPs. Conclusion: Our results indicate that the metal nanoparticles can be effectively used for the removal of biofilm and also as antimicrobial agents for the management of microbial pathogens responsible for dreadful infections.

Background: Advancement in wireless communication technology has raised today’s living standards but has consequently led to the problems of electromagnetic (EM) air pollution as well as spectrum congestion particularly in radio frequency band. To overcome the traffic congestion problem in lower bands, terahertz frequency bands are explored but EM pollution still persists as a global issue, which can be addressed by a tunable microwave absorber. At THz frequencies, 2-D nanostructured graphene has been observed to be less lossy than using other materials and further finds its most interesting applications on account of the plasmonic mode supported by graphene resulting in extreme device miniaturization. At micro and mm-waves, graphene is resistive, hence it can be electronically controlled, ensuring its suitability for the design of tunable microwave absorber. Objective: Designing of a frequency reconfigurable or frequency tunable absorber is the prime objective of the current work. Two-dimensional graphene absorber has been proposed here having inherent bandgap tunability property, which means the electromagnetic properties of graphene can be controlled via varying external bias potential. Methods: The numerical modelling of graphene microwave absorber utilizing bulk graphene backed by glass and perfect electric conductor layer is reported in this paper. Finite element Method (FEM) based high frequency structure simulator (HFSS) platform is used to simulate the graphene absorber model. The whole structure is placed into a rectangular waveguide with two ports for absorber excitation. Results: The variation of electromagnetic properties of graphene absorber is achieved by changing bias potential and further the absorption tunability for the designed absorber is investigated in the range from 2 GHz to 18 GHz. From reflection coefficient curves, it is authenticated that -72.6 dB reflection coefficient dip is obtained at 14 GHz for 5 volt bias potential, which shifts to higher side of frequency as the potential changes from 5 volts to 25 volts. Conclusion: The results show that by increasing bias potential, absorption coefficient shifts to higher frequency and proves to be a tunable wideband absorber whose resonant frequency can be changed from one value to another without changing thickness or material properties of absorber, thus it can effectively incorporate with antenna substrate or surface of radar.

Background: This article presents a micro beam, fabricated using digital light processing (DLP), one of the additive manufacturing methods. The fabrication process is based on the projection micro stereolithography method. Objective: The micro beam, which can move in one direction (y-axis), was designed according to the specified criteria and fabricated. In the experiments carried out during the fabrication process, it showed the effect of the support structures on the fabrication of the micro beam. Methods: For the characterization process, the micro beam connected to the probe station is connected to a circuit board with cables attached to the electrical pads. The image processing algorithm has been developed to detect the displacement of the micro beam as a result of the characterization processes. The operating voltage was increased from 0V to 2V and incremented until fracture and deterioration in the structure of the micro beam were observed. Results: The micro beam was able to withstand distortion and breaks up to a maximum voltage of 10V. When 12V voltage was applied to the micro beam, fractures occurred in the arm. As a result of the characterization process, the maximum displacement of the micro beam was measured as 2.32 μm at 10V voltage. Conclusion: The characterization results indicated the usability of the image processing algorithm in 3D technology.