Nanoscience & Nanotechnology-Asia - Volume 10, Issue 1, 2020

By far the most important members of carbon-based materials family, are graphene, Carbon Nanotube (CNT) and Carbon Nanohorn (CNH). Thanks to their outstanding features and effective applications, have been broadly researched in recent times. Numerous ways have been proposed to synthesize graphene, CNT and CNH. This paper presents an overview of approaches to graphene, CNT and CNH synthesis, properties and applications. Most of the ways to create graphene is related to Hummer's method. Thanks to the exclusive electrical and thermal properties of graphene, it has been applied to build batteries, gas and vapor sensors, and elimination of numerous pollutants from water. Also, this review involves the conventional definition of the carbon nanotubes growth mechanism. Undoubtedly, an expert interpretation of nanotube growth at the atomic scale is one of the major challenges to improve nanotubes bulk synthesis procedure. In fact, a controlled growth may lead to get the ideal form of nanotube. Moreover, carbon nanohorn is a new member of single-graphene tubules family with a diameter of 3-6 nm and a length 35-45 nm. According to the latest reports, a new fluid including carbon nanohorns and ethylene glycol can be used for solar energy applications. Carbon nanohorns have an important role in increasing sunlight absorption as for the pure base fluid. Nanohorn spectral characteristics are far more interesting than those of amorphous carbon for the exclusive application. They can be used in important industries such as gas sensors, drug delivery, detecting some food borne contaminants.

Introduction: Transferosomes also known as ultra-deformable liposomes were introduced by Gregor Cevc in 1990. These are deformable vesicles that transport drug across the skin, which is the best route of drug delivery because skin is the largest human organ with 3 kg total weight and a surface area of 1.5-2.0 m2. Methods: Transferosomes are able to efficiently deliver low as well as high molecular weight drug across the skin in terms of quantity and depth. Various methods used for the preparation of transferosomes such as thin film hydration method, reverse phase evaporation method, vortex/sonication method, ethanol injection method and freeze thaw method. Results: The prepared transferosomal preparation will be evaluated for particle shape and size, entrapment efficiency, stability study, penetration ability and skin permeation study. In vitro release studies are to be performed using a specific dissolution medium. Conclusion: Ultra deformable liposomes can be used for delivery of different drugs e.g. analgesic, anesthetic, corticosteroids, anticancer, sex hormone, insulin, gap junction protein, and albumin.

Background: Tunability in resonance wavelength and the enhancement of the electromagnetic field intensities around the surface are two unique properties which make metal as a plasmonic material. A theoretical investigation on the LSPR and field enhancement for heterogeneous dimer–trimer metallic nanostructure by constituting Al and Au as two different plamsonic materials has been studied. Since electrons in Al exhibit free behavior for LSPR of Au, therefore, they influence the electric field magnitude generated by Au LSPR. Methods: The electromagnetic simulations reported in this paper were performed using the FDTD Solutions (version 7.5.1), a product of Lumerical Solutions Inc., Vancouver, Canada. We adopted a cubic Yee cell of 1 nm side and a time step Δt= 1.31•10-18 s, bounded by Courant condition. Results: The extinction spectrum shows LSPR peak over UV-visible region for isotropic nanostructure which shifts to NIR region for anisotropic shape nanostructure. The spherical shape hetero dimer nanostructure shows enhancement factor ~ 3.9 X 105 whereas it increases to ~ 6.2 X 106 for anisotropic shape at 610 nm. The field distribution corresponding to the trimer nanostructure reveals a large dipolar field distribution on each of the three nanoparticles, oscillating approximately in-phase. The spherical shape Al-Au-Al shows enhancement factor ~ 8.5 X 106 at 571 nm. The anisotropic shape increase the enhancement factor to ~ 2.4 X 107 at peak wavelength 700 nm i.e. tuning the plasmon wavelength towards NIR region. Conclusion: The tunability in plasmon wavelength and field enhancement factor has been evaluated for heterogeneous nanostructure over wider spectrum range i.e. DUV-Visible-NIR using Au-Al dimer and trimer nanostructure. The isotropic shape Au-Al hetero nanostructure shows larger enhancement in the UV-visible region, whereas the anisotropic shape nanostructure contributes towards the NIR region.

Background: The estimation of glucose level in the blood serum, has been widely used as a clinical indicator of diabetes. Optical and electrochemical sensing of glucose widely uses Glucose Oxidase (GOD) enzyme, as the catalyst for glucose oxidation, which releases hydrogen peroxide (H2O2). Optical biosensors are superior to their electrochemical counter-parts as they are resistant to electromagnetic interference, easier to fabricate into a microdevice and require low power supply. The quantum-dot-based biosensors work on the phenomenon of fluorescence quenching following the release of H2O2. Methods: The CdSe nanoparticles are prepared in two series by room-temperature microemulsion method. In series A, only AOT surfactant is used to synthesize spherical CdSe nanoparticles. In series B, the mixed surfactant system of AOT and lecithin is used to synthesize anisotropic CdSe. The morphology and crystallography is studied as the CdSe shape changes from spherical to rod-like. As the CdSe nanoparticles are studied from spherical to rod-like morphology, the transducing sensitivity of these nanoparticles is evaluated with respect to glucose biosensing. The effects of size and shape are studied, based on the fluorescence quenching by H2O2 solutions. The sensitivity of proposed nanoparticles, is evaluated as a function of size, shape, surface area and number concentration of CdSe nanoparticles. Results: The spherical CdSe nanoparticles are found to increase in size as R(water-to-surfactant ratio) is increased from 4 to 12, in series A. Also, the aspect ratio of CdSe nanoparticle is found to increase from 4.2 to 12.8 as the ratio of AOT to lecithin is varied from 1:0.5 to 1:3. The decrease in sensitivity index is seen with increasing surface area for both series A and B. The sensitivity is decreasing again with increasing maximum dimension of the CdSe nanoparticle in the dispersion. While the trend is reverse in case of the number concentration for CdSe nanoparticles synthesized in series B. Conclusion: From the data presented, it can be safely concluded that the sensitivity indices for series A are better than those for series B, for the same values of a) the total surface area of CdSe nanoparticles, b) total number concentration, and c) maximum dimension of CdSe nanoparticles. Also, the single surfactant system (series A) is simple, cheaper and more reproducible to synthesize the CdSe nanosheres, as compared with the mixed surfactant system forming CdSe quantum rods (series B). With these points, it is reasonable to report that CdSe spherical QDs are better candidates for glucose biosensing, as compared to CdSe quantum rods.

Background: The quandary of antimicrobial resistance is rapidly becoming a cause for global concern. Meanwhile, green biological synthesis of silver nanoparticles is being extensively studied for their antibacterial properties. However, in the dearth of appropriate and substantial evidence, the development of Green Silver Nanoparticles (GSNPs) as the antibacterial drug is impeded. Objective: The present study aims at surfacing the mechanism behind the inhibitory actions of GSNPs against both gram-positive and gram-negative bacteria. Methods: Silver nanoparticles were fabricated using the peels of Citrus Sinensis and Punica granatum and characterized using UV-Vis Spectrophotometer, XRD, FTIR, SEM and TEM. The GSNPs were further scrutinized for their antibacterial properties against Gran negative Escherichia coli and grampositive Listeria monocytogenes and confirmed using FC analysis. Further multiple parameters were investigated for deciphering the mechanism of antibacterial action. Results: The results reveal the fabrication of 14-60 nm polydispersed GSNPs having 96% inhibition potential against both the test bacteria. Deposition of GSNPs on the bacterial surface resulting in pit formation in the bacterial cell wall and membrane causing leaking of cellular components and deactivation of bacterial enzymes were observed in the present study. Conclusion: The study proves that contrary to earlier investigations, GSNPs prepared using orange and pomegranate peels are effective against both gram positive and gram negative bacteria and may thus be used for the development of antibacterial therapies, subjected to further investigation.

Introduction: Foodborne diseases are caused by consuming contaminated foods and/or beverages. Methods: Traditional detection methods for foodborne bacteria are sluggish and laborious. In this study, room temperature voltammetric sensors with low cost, specific, rapid and easy detection were fabricated using Polyaniline (PANI) and silver (Ag) nanoparticles. PANI films were coated on to the Indium Tin Oxide (ITO) glass substrate using electrochemical deposition technique. PANI surface was modified using Ag nanoparticles prepared by reduction method as Ag is one of the most powerful disinfectants against microbes. Both surface electron microscopy (SEM), X-ray diffraction (XRD) technique revealed the presence of Ag nanoparticles in the composites. The peaks observed in Fourier Transform Infrared Spectroscopy (FTIR) and optical absorption spectra are characteristics to PANI/Ag nanocomposites. Results: The antibacterial activities of the PANI/Ag nanocomposites were evaluated against Escherichia coli (E. Coli) (NCIM 2065), Staphylococcus aureus (S. aureus) (NCIM 2079) and Bacillus cereus (B. cereus) (NCIM 2106) using disk diffusion method. The composites showed better antibacterial activity due to the presence of Ag in comparison to pure PANI films. Conclusion: The sensor current for composites was found to increase with the presence of all the microbes. The sensitivity of the sensor was higher for E. coli bacteria among the other bacterial strains.

Introduction: Raloxifene Hydrochloride (RXL), a BCS class II drug, is used for the treatment of invasive breast cancer and osteoporosis in post menopausal women. Even though the drug is highly efficient, it shows poor bioavailability of 2% when administered orally. The aim of the study was to develop, statistically optimize, and characterize Raloxifene Hydrochloride loaded Nanostructured Lipid Carriers (NLC) for transdermal delivery to overcome the bioavailability issue. Methods: The RXL-NLC’s were developed using glyceryl behenate (Compritol® 888 ATO), glyceryl monostearate (GMS), and capric triglyceride (Miglyol® 810) as solid and liquid lipids, and Polysorbate 80 (Tween 80) and cremophor EL were used as surfactants and co-surfactant. A response surface methodology was applied for the optimization of NLC, using Box-Behnken experimental design. Amount of the drug, tween 80 and polyethoxylated castor oil (cremophor EL), each at three levels, were selected as independent variables, while particle size and polydispersity index were identified as dependent variables. The optimized batch was characterized for Particle size (79.8 nm±3), Polydispersity index (0.229±0.05), Zeta potential (-12.3±5) and Entrapment efficiency (79.14%±5). Surface morphology of the NLC’s were studied using Transmission Electron microscopy (TEM) and the shift in the endotherm of Differential scanning calorimetry confirmed the entrapment of the drug within NLC. In vitro drug release studies were performed using dialysis bag (12000-14000 Da) method. The optimized NLC dispersion was then incorporated into gel and characterized for gel uniformity, spreadability, pH, viscosity and drug content. Results: In vivo skin penetration study was carried out by tape stripping method, which showed increase in penetration when incorporated into nanogel as compared to plain drug gel. Conclusion: Based on the above result it can be concluded that transdermal delivery of NLC’s can be a superior alternative for orally low bioavailable drugs such as RXL which undergoes rapid first pass metabolism.

Introduction: The unique properties of carbon nanotubes trigger a lot of ideas to study the ability of the material in many fields. Experimental: The research started with the preparation of cobalt catalyst by using the sol-gel method, which used cobalt acetate tetrahydrate and 2-amino ethanol solvent, followed by the actual growth of carbon nanotube by using the prepared catalyst in alcohol catalytic CVD. Results: The crystal structure, microstructure, and size of particles of the resulting cobalt-based powders were characterized by using X-ray Diffraction, Optical Microscopy, and Particle Size Analyzer, followed by, carbon nanotube growth at 700, 750, 800, and 850°C, where other parameters were fixed in order to determine the effect of CVD processing and temperature on the quality of resulting carbonbased materials. The graphitic structure of the carbon-based materials was analyzed by using Raman Spectroscopy. Conclusion: It was found that the optimum CVD processing temperature was 850°C with IG/ID ratio of 1.052.

Background: Glancing Angle Deposition (GLAD) provides oblique deposition and substrate motion to engineer thin film microstructures in three dimensions on nano scale. Using this technique zigzag, chevrons, staircase, post, helical and various type of nanostructures including 3-D multilayers can be obtained from various metals with controllable morphologies. The aim of the study is to increase surface porosity and junction using GLAD method area for thin film solar cells and therefore to increase p-n junction area. This provides efficient charge separation and strong light absorption. Methods: Glancing angle deposition using e-beam evaporation technique has been employed to create 3- D silicon nano-structures on the surface. Al and Ag contact layers were deposited by thermal evaporation technique. Hole-conductor polymer PEDOT: PSS was spin coated onto n type silicon thin film. Reflectance spectra were measured using UV-VIS spectroscopy. Scanning electron microscopy was used to image surface and cross-section with and without PEDOT: PSS. Also, transmission spectra of PEDOT: PSS was measured using UV-VIS spectroscopy. Surface wettability properties and contact angles of silicon samples were measured by contact angle measurement with water. Results: Columnar structures possess less reflection compared to the flat surface depending on surface porosity. This phenomenon shows that these structures can be used as anti-reflection coatings for solar cells and optical devices to decrease reflectivity and increase light harvesting with higher efficiency. Contact angle decreases when surface roughness increases therefore we can see that columnar structures are more hydrophilic compared to dense films. Flat silicon has 98° contact angle while columnar structures have 71° and 61°. PEDOT: PSS exhibits high transparency in the range from 200 to 1100 nm of wavelength of light, which resembles to solar radiation inside the atmosphere. Also, SEM images of the samples show that silicon columnar structures form better contact with PEDOT: PSS than flat surface. Conclusion: GLAD technique has been used to achieve homogenous rough surface by e-beam evaporation. Both cross-sectional and top-view SEM images show that columnar structures have higher porosity than flat surfaces. The response of UV-VIS spectroscopy shows that columnar structures have less reflection due to highly porous surface. With increasing incident flux angle, antireflection property of the surfaces was enhanced by surpassing the surface reflection. Due to the reduced hydrophobicity of porous structures, organic polymer can be distributed homogenously in between the columnar structures with increased p-n junction interface area. PEDOT: PSS is highly conductive, and it is highly transparent material in the range of the wavelength typically seen in the solar radiation. This makes it easier for light to reach to Si interface to generate electrons and holes. These results provide better understanding of Si- based heterojunction solar cells efficiency improvement with surface modification. This study also shows dependency of optical and electrical activity to surface geometry and surface porosity.

Background: Investigating the bioactivity of nanoscale materials against microorganisms give a comprehensive, proactive understanding of nanomaterial toxicity and explore their potential for applications. Methods: The aim of this study is to assess the changes in the mycelium growth and proteomics for filamentous fungi Aspergillus niger (A. niger) caused by palladium nanoparticles (Pd NPs). In this study, quantitative analysis of the mycelium growth and protein content of A. niger upon incubation with different concentrations of Pd NPs (0-1350 ng/mL) were reported. Matrix Assisted Laser Desorption/ Ionization Mass Spectrometry (MALDI-MS) was also used to analyze the changes of the proteins content of A. niger in different medium using two different matrices; α-cyano-4-hydroxycinnamic acid (CHCA), and sinapinic acid (SA). We found that Pd NPs decrease the mycelium growth of A. niger. Results: The protein contents are increased at low concentrations of Pd NPs, while it decreases with high concentration. MALDI-MS results show change of the protein contents for A. niger upon incubation with Pd NPs. Mycelia biomass decreases at high concentration of Pd NPs. Conclusion: The biological activity of Pd NPs depends on their concentration and cell culture medium. These new findings may add valuable information about the cytotoxicity of Pd NPs.

Background: ZnO nanofoam cluster was deposited on ZnO nanowires using SiO2/Si substrate. Nanocrystalline ZnO nanofoam cluster was grown on Chemical Bath Deposition (CBD) grown ZnO nanowires by consecutive immersion (50 times) of the sample into Sodium Zincate (Na2ZnO2) bath (0.125M) kept at room temperature and into the de-ionized (DI) water maintained at 80oC. Methods: Sodium Zincate was prepared by reacting Zinc Sulphate (ZnSO4) and excess Sodium Hydroxide (NaOH) in aqueous solution. By simple Chemical Bath Deposition (CBD) technique ZnO nanowires of length of 1-1.5 μm with diameter 2-3 nm were deposited on SiO2 coated <100> p-Si substrate. The ZnO nanofoam cluster area was found to be ~(0.5 x 0.5) μm2. After structural and morphological characterizations by FESEM, EDX and AFM, the sensor was tested for three different H2 concentrations (0.1, 0.5 and 1%) taking N2 as carrier gas at four different operating temperatures (50ºC, 75ºC, 100ºC and 125ºC). Results: The sensor offered ~98% response magnitude at very low operating temperature 100ºC at 1000 ppm H2 gas with very fast response time (16 sec) and recovery time (52 sec). The unique structure of nanofoam covers multidimensional area having more molecular surface interactions thus permitting better response in gas sensing. The I-V characteristics was studied to indicate ohmic nature of the silver contacts for four operating temperatures with 1% hydrogen in N2 and it was also observed that amplitude of current is higher with the presence of H2. Conclusion: Finally the stability study of the H2 sensor was also done in presence of carrier gas (N2) over a span of 24 hours (6 hr daily).