Current Nanoscience - Volume 14, Issue 5, 2018

Background: Joining nanosized building blocks is a promising approach to fabricate functional nanodevices and nanosystems. Nanojoining approach also helps in integrating these nanodevices and nanosystems for the miniaturization of devices. The nanodevices are mainly fabricated by joining metallic and semiconductor nanowires/nanotubes. Objective: Silicon Carbide Nanowires (SiC-NWs) have become important nanomaterials for future nanoscale devices due to their unique physical properties. Method: In this paper, nanowelding of SiC-NWs has been demonstrated using ion beam technology. SiC-NWs were irradiated by 5 MeV proton beam as per SRIM code simulation. Nanojoining of SiC-NWs was confirmed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Conclusion: Joining of individual SiC-NWs by 5 MeV proton beam irradiation was successfully achieved at the contact point as X-, Y-, II-, and T-shaped welded junctions.

Background: Carbon-coated metal nanoparticle is a kind of unique nuclear-shell material that is the carbon shell filled with metal particles. It has a great promising future in the application as excellent solid lubricants additives, conducting resin, antiradiation material and so on. As a mature technology, the gas detonation method has been widely used to synthesize various nanomaterials. Method: Using copper acetylacetonate as a precursor to provide carbon and different concentrations of argon as a protective medium for the first time, high quality carbon-coated copper nanoparticles (Cu@C) were synthesized in hydrogen and oxygen. X-ray Diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) were employed to characterize the structure, phase and constituent of the Cu@C nanoparticles to investigate the influence of argon concentration on the synthesis. Results: The XRD pattern, Raman spectroscopy and TEM images confirm the effect of Ar on synthesizing Cu@C, especially on particle size. The minimum average size is around 13 nm, and most of the particle size distribution is in 5-10 nm range. When the argon concentration is high, the detonation process of H2 and O2 will be suppressed, which is not conducive to the graphitization. Conclusion: Argon gas has a catalytic effect on the synthesis of high-quality Cu@C, which could significantly reduce the particle size of detonation products; the grain size appears an obvious downtrend with the concentration of argon increasing, but the high concentration of Ar is disadvantageous for the graphitization of carbon shells.

Background: Quercetin (QE) is one of the flavonoids with various biological functions such as anti-oxidation, anti-inflammatory and antitumor. However, the low aqueous solubility and short half-life in the body reduce its in vivo efficacy. Therefore, the appropriate delivery techniques to solve those problems have drawn much attention. In the present study, methoxypolyethylene glycol- poly-DL-lactic acid (MPEG-PLA) nanoparticles loaded with quercetin (QE), called NP, were prepared, and their antitumor characteristics were investigated in vitro and in vivo. Method: NPs were produced by evaporating organic solvent from the organic solvent-water mixture in four formulations. The particle characteristics and in vitro release were examined for the obtained preparations (NP1 – NP4). The antitumor features were investigated in vivo with different administration schedules using mice inoculated subcutaneously with murine Sarcoma 180. In addition, the efficacy of co-administration of NP with a strong antitumor chemotherapeutic agent, irinotecan hydrochloride (CPT-11), was examined. Biodistribution studies were performed using the same animal models. Result: The NP with the higher drug content (0.58 % (w/w)) and gradual release profile, Preparation NP4, were chosen and used as NP in the in vivo studies. NP suppressed tumor growth better than QE solution in various dosing schedules (total dose = 2 mg/kg). In the combination therapy with CPT-11, NP exhibited antitumor efficacy in a nearly additive manner. No decrease in body weight observed with any administration. NP markedly enhanced the systemic distribution and tumor localization. Conclusion: These results indicated that the present NP should promote the efficacy of QE, and might have useful therapeutic potential in the treatment of solid tumors.

Background: Graphitization behavior of diamond has received an increasing interest in nanoscale machining of some hard and brittle materials. Diamond has always been an important and excellent tool material in cutting area. However, the graphitization of the diamond tool is inevitable when it was used in special conditions. It is indicated that the graphitization of diamond crystal has great influence on the wear resistance of diamond cutting tool. The graphitization behavior needs to be investigated extensively in nanoscale with an atomic view. Molecular dynamics simulation provides a useful tool for understanding of the graphitization mechanism of diamond. The investigation on graphitization behavior of single crystal diamond can also provide a useful reference for the application of diamond cutting tool. Materials and Methods: In this paper, a molecular dynamics (MD) diamond crystal model is built to examine the graphitization behavior of diamond under various conditions. The sixfold ring method was employed to identify the structural characteristics of graphite and diamond. The effects of temperature and crystal orientation on the graphitization of diamond have been revealed. Considering the effect of temperature, the anisotropy of diamond graphitization against various crystal planes is presented and discussed carefully. The nano-metric cutting model of diamond tool evaluated by the sixfold ring method also proves the graphitization mechanisms in atomic view. Results: Results indicate that the sixfold ring method is a reliable method to evaluate the graphitization behavior of diamond crystal. There exists a critical temperature of the graphitization of diamond. The results also show that {111} plane is more easy to get graphitization as compared with other crystal planes. However, {100} plane of diamond model presents the highest antigraphitization property. Conclusion: The obtained results have provided the in-depth understanding on the wear of diamond tool in nano-metric machining and underpin the development of diamond cutting tool.

Objective: The purpose of this article is to analyze the effects of different shaped Agnanoparticles on peristaltic flow through curved tube with permeable walls. Method: In the considered endoscope the inner tube is rigid while outer tube experience a sinusoidal wave and both tubes make an annulus. Bricks, cylinders and platelets are different shaped Agnanoparticles. Toroidal coordinate system is used to examine the nature of Ag-nanoparticles mathematically in the curved tube with viscous fluid. Analysis is performed with the consideration of low Reynolds number and long wavelength approximation. Perturbation approximation is used to solve the problem and achieve results for pressure gradient, pressure rise, axial velocity and stream functions. Results: The effects of various parameters such as Grashoff's number, Darcy's number, radius of the endoscope and amplitude ratio on flow variables have been discussed graphically. The contemporary investigation has revealed that the temperature profile shows a decrease for larger shape factor of Ag-nanoparticles. Pressure gradient exhibits higher results with larger Darcy's number. Also trapped bolus tend to have bigger size for greater shape factor. Conclusion: Temperature profile for the nanofluid decreases with the increase in shape factor m of nanoparticles. The trapping phenomena reveal that the size of inner bolus appears larger for platelet nanoparticles as compared to brick and cylinder nanoparticles.

Background: In the last 40 years, scientific efforts were focused on the efficiency improvement in organic photovoltaic devices. Bleaching agents were used to absorb UV light and convert it into lower energy radiation appear as potential candidates for further improvements. The present contribution investigated the effect of adding umbelliferone to poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on its optical and electrical properties. Methods: Characterizations were performed under various umbelliferone concentrations. Fluorescence decay lifetimes were obtained using a MicroTime 200 system (PicoQuant). The UV–vis absorption spectra were obtained with a GE Healthcare Ultrospec 2100 pro Spectrometer. The electrical conductivity measurements as a function of temperature using a cryostat model ARS CS202AE-DMX-1AL. Results: The absorbance increases around 325 nm and decreases in the near infrared s the umbelliferone concentration is increased. It also decreases the absorption in the visible spectrum, concomitantly with a significant increase in the UV region. The electrical conductivity for the umbelliferone doped PEDOT:PSS films display an increase with increasing temperature, but does not follow a linear behavior with the increase of umbelliferone concentration in the films. Conclusion: It was shown that the absorbance displays a redshift in doped samples, while photoluminescence experiments demonstrated that UV light is converted to the visible spectrum more efficiently, which is a desirable feature for photovoltaic devices. Also, the electrical conductivity of PEDOT:PSS is increased for moderate umbelliferone concentrations.

Background: The electrospining of Poly (styrene)/poly(ethylene glycol) blend and prepared electrospun Poly (styrene)/poly(ethylene glycol) are the composite fibers. The Core-shell structured PS-PEG fibers were founded by polarized optical microscope after electrospinning, meanwhile, the mechanism of structure was also discussed. Methods: The Electro-spinning is a facile method to fabricate polymer fibers. The single-step process to fabricate poly (styrene)(PS)/poly(ethylene glycol)(PEG) polymer nano-fiber meshes had been investigated, respectively. The morphology and crystallization behavior of the blend were observed by polarized optical microscopy. Results: The clear phase separation of PEG encapsulating on the PS fiber surface, and the nano-fiber composed of a core-shell structure, furthermore, the core of PS with the shell of PEG were observed, respectively. To increase the compatibility of the PS/PEG blend, Poly (styrene)(PS)-b-poly(ethylene glycol)(PEG), synthesized via atom transfer radical polymerization (ATRP) was introduced. The addition of the PS-b-PEG block copolymer has no negative effect on the electro-spinning process. Conclusion: When the Block copolymer of PS-b-PEG as a compatibilizer was added into the PS/PEG blend, the homogeneous electrospun fibers without phase separation was obtained. The effect of PS-b-PEG block copolymer on electrospinning of PS/PEG blend was analyzed by evaluating the morphology and crystallization behavior of the electrospun fibers. Under polarized optical microscopy analyses suggest that, it can be found that the phase separation between PS and PEG disappears due to the introduction of the compatibilizer. Meanwhile, the core-shell structure of PEG/PS composite fiber was destroyed and PEG evenly dispersed in PS/PEG blend.

Background: Molybdenum disulfide (MoS2) is a transition metal dichalcogenides and has some interesting and promising properties. MoS2 has direct and indirect band gaps depending on its crystalline structure. In addition, its sheets morphology makes it a good candidate for supercapacitor applications. Objective: The aim of this work is to study the effect of MoS2 flakes size on its optical and electrochemical properties. Method: MoS2 with different flakes sizes were prepared by exfoliation method. The exfoliation was performed by sonication of MoS2 powder in N,N-Dimethylformamide followed by different centrifugation speeds. UV-Vis spectra illustrated the optical energy gap was inversely proportional to the MoS2 flakes size. Results: Absorption coefficient values indicated that the exfoliation reduced the number of layers. Symmetric supercapacitor was made from two MoS2 electrodes and tested in 6 M KOH electrolyte. The specific capacitance was found to be dramatically increased with decreasing flakes size (9.5 and 4.5 mF/cm2 for 0.26 and 0.98 μm flakes size, respectively). Conclusion: These findings recommend that MoS2 can be the excellent electrode material for supercapacitor.

Background: It is well known that quantum dot-sensitized solar cells based on nanostructured semiconductor films are considered as a promising alternative to silicon-based solar cells. The aim of this paper is to investigate the structural and morphological properties of CdS/CdSe quantum dot sensitized photoanodes based on nanocrystalline TiO2 thin films considering their performance can reach an efficiency of 2.7%. Methods: TiO2 thin films were prepared on fluorine tin oxide (FTO) glass via the chemical route using commercial Degussa 25 and crystallized at 550°C. Furthermore, a layer of CdS and CdSe nanoparticles was deposited on the titania film by a sequence of successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) methods. After preparation, samples were analyzed using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy for their structural properties and composition. Scanning electron microscopy (SEM) was used to investigate their surface morphology, while energy dispersive X-ray spectrometry (EDS) was used to analyze the sample stoichiometry. Results: The structural properties and morphology of quantum dot sensitized photoanodes revealed that the titania thin films were highly crystalline belonging predominantly in the tetragonalanatase structure, while the CdS/CdS quantum dots were in the cubic phase. Furthermore, scanning electron microscopy (SEM) along with energy dispersive X-Ray mapping EDS showed little contamination. Conclusions: Combined analysis suggests that our preparation route leads to highly crystalline, stoichiometric photoanodes. This plays an important role in the performance of the quantum dot sensitized solar cells.

Background: Controlled drug delivery systems can maintain the concentration of drugs in the exact sites of the body within the optimum range and below the toxicity threshold, improving therapeutic efficacy and reducing toxicity. Mesostructured Cellular Foam (MCF) material is a new promising host for drug delivery systems due to high biocompatibility, in vivo biodegradability and low toxicity. Methods: Ketorolac-Tromethamine/MCF composite was synthesized. The material synthesis and loading of ketorolac-tromethamine into MCF pores were successful as shown by XRD, FTIR, TGA, TEM and textural analyses. Results: We obtained promising results for controlled drug release using the novel MCF material. The application of these materials in KETO release is innovative, achieving an initial high release rate and then maintaining a constant rate at high times. This allows keeping drug concentration within the range of therapeutic efficacy, being highly applicable for the treatment of diseases that need a rapid response. The release of KETO/MCF was compared with other containers of KETO (KETO/SBA-15) and commercial tablets. Conclusion: The best model to fit experimental data was Ritger-Peppas equation. Other models used in this work could not properly explain the controlled drug release of this material. The predominant release of KETO from MCF was non-Fickian diffusion.

Background: LiNi1/3Mn1/3Co1/3O2 derived from the solid-state method suffers from the problem of significant irreversible charge-discharge behavior. To improve the electrochemical performance of LiNi1/3Mn1/3Co1/3O2, there are several important factors, such as starting raw materials, precursor, preparation method and conditions. In this work, the layered LiNi1/3Mn1/3 Co1/3O2 material was prepared by solid-state reaction. By varying the temperature and duration of synthesis thermal treatment, the greater crystallinity and well-ordered layered LiNi1/3Mn1/3Co1/3O2 cathode material has been successfully synthesized. The structural properties, morphology and electrochemical properties of LiNi1/3Mn1/3Co1/3O2 powders have been investigated in detail. Methods: LiNi1/3Co1/3Mn1/3O2 cathode material was synthesized via a high-temperature solid-state method. Stoichiometric amounts of Ni(CH3COO)2•4H2O, Co(CH3COO)2•4H2O, Mn(CH3COO)2• 4H2O, and Li2CO3 as raw materials were homogenized mixed in a ball mill for 8 h at 240 rpm. By varying the temperature and duration of synthesis thermal treatment, LiNi1/3Co1/3Mn1/3O2 cathode materials with different electrochemistry performance were achieved. (a) The effect of the temperature of synthesis thermal treatment on electrochemistry performance of LiNi1/3Co1/3Mn1/3O2 was explored by calcining the above mixed powder at 800°C, 850°C, 900°C, 950°C, and 1000°C for 12 h in air at a rate of 5°C min-1. Then the target product was prepared at last. The obtained compound was named as N-800, N-850, N-900, N-950 and N-1000, respectively. (b) In order to explore the effect of the duration of synthesis thermal treatment on electrochemistry performance of LiNi1/3 Co1/3Mn1/3O2 cathode material, the above mixed raw materials were calcined at 900°C for 4 h, 8 h, 12 h, 16 h and 20 h in air at a rate of 5°C min-1. The obtained compound was named as N-4, N-8, N- 12, N-16 and N-20, respectively. The N-900 and N-12 are the same sample. Results: The cathode material sintered at 900°C for 12 h revealed the best electrochemical performance, with high-capacity and recyclability compared with other materials. Its initial discharge capacity attains 182.4 mAh g-1 at 0.2 C in the voltage range of 2.5-4.6 V, which can be attributed to its greater crystallinity and well-ordered layered structure. Compared with other studies on lithium-ion batteries given in literature, this work provides a sample, optimal and mild synthetic conditions to synthesize the cathode materials with great electrochemistry performance. Conclusion: A greater crystallinity and well-ordered layered LiNi1/3Mn1/3Co1/3O2 powders had been successfully synthesized by mixing raw materials under various temperatures and duration of synthesis thermal treatment. The XRD results indicated the I(003)/I(104) values of N-900 (N-12) is 1.591 larger than 1.2, which illustrates no undesirable cation mixing to be occurred. In this work, from the results of electrochemical property experiments, it can be indicated that the optimal synthesized conditions are 900°C for 12 h. When the calcination temperature is too low and the calcined time is too short, the material is poorly crystalline and has a poor layer structure. When the calcination temperature is too high and the calcined time is too long, lithium salt is evaporated completely during the calcination process resulting in a poor electrochemistry performance.

Background: Poly(d,l-lactide-co-glycolide) (PLGA) based biodegradable nanoparticles are of key interest for the development of controlled release drug delivery systems and for other biomedical applications. It has been reported that PLGA polymers can be converted into colloidal nanoparticulate systems by various techniques, such as emulsification-diffusion, emulsificationevaporation, interfacial deposition, salting out, dialysis and nanoprecipitation. Emulsificationevaporation with water immiscible solvents including dichloromethane and chloroform has been the preferred method for the synthesis of PLGA nanoparticles due to the low boiling point and limited water solubility of these solvents. We and others, however, have found that when water-immiscible solvents are used for the synthesis of PLGA nanoparticles, particle aggregation, non-uniform particle size and multimodal size distribution are commonly encountered problems. This suggests that the synthesis of PLGA nanoparticles using water immiscible solvents is highly sensitive to small procedural variations that affect overall reproducibility. Objective: This study presents a simple and robust procedure for the preparation of PLGA nanoparticles with very small batch to batch variability (<5% variability in size (z-average) as determined by dynamic light scattering). Results: The results showed that the emulsification solvent diffusion method teamed with partially water-miscible solvents, such as ethyl acetate, is a versatile approach for the preparation of PLGA nanoparticles with highly reproducible sizes (between 50 and 400 nm) and zeta potentials (between - 30 and +30 mV), with relatively narrow polydispersity. Conclusion: Emulsification-diffusion with ethyl acetate is, therefore, a more reliable alternative to several existing procedures for the reproducible and refined synthesis of PLGA nanoparticles.