Journal of Nanoscience The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. One-Pot Fabrication and Characterization of Silver Nanoparticles Using Solanum lycopersicum: An Eco-Friendly and Potent Control Tool against Rose Aphid, Macrosiphum rosae Tue, 11 Oct 2016 09:23:45 +0000 The espousal of nanotechnology is a current come-up of the present revolution. As we know that the rose aphid, Macrosiphum rosae (Hemiptera: Aphididae), is a key pest on rose plant in Kashmir Valley, India, it exhibits a worldwide distribution. In the present study, we have synthesized biologically silver nanoparticles (Ag NPs) from Solanum lycopersicum and characterized them by UV-vis spectroscopy, TEM, and X-RD analysis. The experiment was performed by leaf dip method. Insecticidal solutions of different Ag NPs concentrations, namely, 200, 300, 400, and 500 ppm, were tested on M. rosae. For assessment purposes, leaves were treated with distilled water (used as control). Aphid mortality data revealed that the Ag NPs were effective at 500 ppm concentration. As the concentration and day’s treatment increased, the aphid mortality rate also increased. There were statistically significant differences in M. rosae mortality between concentrations by LSD at 5%. In wrapping up, the use of Ag NPs in pest control processes will be the most novel eco-friendly approach in the Kashmir Valley, India, in future. Atanu Bhattacharyya, Ram Prasad, Abdul A. Buhroo, Prabha Duraisamy, Insha Yousuf, M. Umadevi, M. R. Bindhu, Marimuthu Govindarajan, and Abdul L. Khanday Copyright © 2016 Atanu Bhattacharyya et al. All rights reserved. In Vitro Cytotoxicity of Nanoparticles: A Comparison between Particle Size and Cell Type Tue, 23 Aug 2016 09:06:28 +0000 The reduction in size of Zinc oxide (ZnO) and Silicon dioxide (SiO2) particles from micron to nano scale offers unique physical characteristics on one hand while making them cytotoxic on other hand. The present study was aimed at comparing cytotoxic effects of ZnO and SiO2 nanoparticles with their micron size and secondary aim was to compare responses of these particles to two different cell types, namely, human lung epithelial cells (L-132) and human monocytes (THP-1). The L-132 and THP-1 cells were exposed to nano and micron size of ZnO and SiO2 particles with different concentrations (5–500 μg/mL) for 24 h, and cytotoxicity was analyzed by MTT assay, live-dead staining, and TC-50 was calculated. ZnO and SiO2 particles showed concentration-dependent cytotoxicity in both cell lines. In size-dependent study, ZnO particles exhibited nearly equal toxicity profile in L-132 cells while in THP-1 cells nano ZnO showed more toxicity than its micron size. The SiO2 particles showed more toxicity in their nano size than micron size in both cell lines. Human monocytes, THP-1 cells, were more sensitive towards the toxicity of both particles than human lung cells, L-132. The results highlight the difference of cytotoxicity between particle sizes and differential sensitivity of cells towards the particles of same composition. In conclusion, ZnO and SiO2 particles exhibited concentration-dependent toxicity, which was more in their nano size than micron counterpart. However, the toxic response varies depending on type of cell exposed due to differential sensitivity. Devashri Sahu, G. M. Kannan, Mukul Tailang, and R. Vijayaraghavan Copyright © 2016 Devashri Sahu et al. All rights reserved. Demonstration of Ultra-Fast Switching in Nanometallic Resistive Switching Memory Devices Mon, 15 Aug 2016 09:53:13 +0000 Interdependency of switching voltage and time creates a dilemma/obstacle for most resistive switching memories, which indicates low switching voltage and ultra-fast switching time cannot be simultaneously achieved. In this paper, an ultra-fast (sub-100 ns) yet low switching voltage resistive switching memory device (“nanometallic ReRAM”) was demonstrated. Experimental switching voltage is found independent of pulse width (intrinsic device property) when the pulse is long but shows abrupt time dependence (“cliff”) as pulse width approaches characteristic time of memory device (extrinsic device property). Both experiment and simulation show that the onset of cliff behavior is dependent on physical device size and parasitic resistance, which is expected to diminish as technology nodes shrink down. We believe this study provides solid evidence that nanometallic resistive switching memory can be reliably operated at low voltage and ultra-fast regime, thus beneficial to future memory technology. Xiang Yang Copyright © 2016 Xiang Yang. All rights reserved. Phase Transformation of Iron Oxide Nanoparticles from Hematite to Maghemite in Presence of Polyethylene Glycol: Application as Corrosion Resistant Nanoparticle Paints Thu, 11 Aug 2016 12:26:25 +0000 This work proposes a simple method for the efficient and rapid synthesis of hematite (α-Fe2O3) nanostructures based on simple heating method under ambient conditions. Polyethylene glycol (PEG) is employed as a structure directing agent in driving the morphology and phase transformation. Typically, Fe2O3 nanoparticles of size below 50 nm were synthesized at temperature around 500°C. The morphology and mechanism of formation of the nanocapsules and then aggregation of nanocapsules to form larger size nanoclusters were studied by scanning electron microscopy and energy dispersive X-ray spectroscopy. Interestingly, this work demonstrates the structural phase transformation of hematite (α-Fe2O3) to maghemite (γ-Fe2O3) upon addition of different amounts of PEG (say 0.066 M, 0.133 M, and 0.2 M) and then heat treating at 500°C. The prepared powders were used in nanoparticle paint preparation and applied as corrosion resistant coatings on iron samples. Polarization studies performed on the paint coatings made out of all the prepared samples showed size-dependent corrosion resistance. As the particle size decreases, the surface area increases and so the corrosion resistance also increases. Pavani Katikaneani, Ajay Kumar Vaddepally, Narender Reddy Tippana, Ramu Banavath, and Srivani Kommu Copyright © 2016 Pavani Katikaneani et al. All rights reserved. Green Route Fabrication of Graphene Oxide Reinforced Polymer Composites with Enhanced Mechanical Properties Wed, 13 Jul 2016 10:00:04 +0000 A facile and “Green” route has been applied to fabricate graphene oxide (GO) reinforced polymer composites utilizing “deionized water” as solvent. The GO was reinforced into water soluble poly(vinyl alcohol) (PVA) and poly-2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS) matrix by ultrasonication followed by mechanical stirring. The incorporation and dispersion of the GO in the polymer matrix were analyzed by XRD, FE-SEM, AFM, FT-IR, and TGA. Further, the FE-SEM and AFM images revealed that the surface roughness and agglomeration of the GO in the polymer matrix increased by increasing its concentration. Ionic exchange capacity, proton conductivity, and tensile texture results showed that the reinforcement of GO in the polymer matrix enhances the physicochemical properties of the host polymer. These PVA/PAMPS/GO nanocomposites showed improved mechanical stability compared to the pristine polymer, because of strong interfacial interactions within the components and homogeneous dispersion of the GO sheets in the PVA/PAMPS matrix. R. Mahendran, D. Sridharan, K. Santhakumar, and G. Gnanasekaran Copyright © 2016 R. Mahendran et al. All rights reserved. On Relation between Porosity of Epitaxial Layer and Quantity of Radiation Defects Generated during Radiation Processing in a Multilayer Structure Sun, 10 Jul 2016 12:40:13 +0000 We analyzed redistribution of radiation defects in a multilayer structure with porous epitaxial layer. The radiation defects were generated during radiation processing. It has been shown that porosity of epitaxial layer gives a possibility to decrease quantity of radiation defects. E. L. Pankratov and E. A. Bulaeva Copyright © 2016 E. L. Pankratov and E. A. Bulaeva. All rights reserved. Importance of Molds for Nanoimprint Lithography: Hard, Soft, and Hybrid Molds Wed, 22 Jun 2016 09:11:08 +0000 Nanoimprint lithography has attracted considerable attention in academic and industrial fields as one of the most prominent lithographic techniques for the fabrication of the nanoscale devices. Effectively controllable shapes of fabricated elements, extremely high resolution, and cost-effectiveness of this especial lithographic system have shown unlimited potential to be utilized for practical applications. In the past decade, many different lithographic techniques have been developed such as electron beam lithography, photolithography, and nanoimprint lithography. Among them, nanoimprint lithography has proven to have not only various advantages that other lithographic techniques have but also potential to minimize the limitations of current lithographic techniques. In this review, we summarize current lithography techniques and, furthermore, investigate the nanoimprint lithography in detail in particular focusing on the types of molds. Nanoimprint lithography can be categorized into three different techniques (hard-mold, soft-mold, and hybrid nanoimprint) depending upon the molds for imprint with different advantages and disadvantages. With numerous studies and improvements, nanoimprint lithography has shown great potential which maximizes its effectiveness in patterning by minimizing its limitations. This technique will surely be the next generation lithographic technique which will open the new paradigm for the patterning and fabrication in nanoscale devices in industry. B. Kwon and Jong H. Kim Copyright © 2016 B. Kwon and Jong H. Kim. All rights reserved. The Role of Ammonia in Synthesis of Silver Nanoparticles in Skim Natural Rubber Latex Wed, 27 Apr 2016 16:12:54 +0000 Silver nanoparticles (AgNPs) were synthesized in skim natural rubber latex, the by-product from concentrated latex production. The role of ammonia was investigated by varying the concentration to be 0.217, 0.362, 0.377, 0.392, and 0.406 wt%. The emergence of AgNPs was detected by UV-visible spectrophotometer and electrical conductivity meter. Upon increasing ammonia concentration, the ABS peak increased to a maximum and slightly shifted to a higher wavelength and then it decreased afterward and slightly shifted to a lower wavelength. The shift of the ABS peak was consistent with the conductivity result. The kinetic model was proposed to explain the competition between the reducing effect and size-controlling effect of ammonia. The reducing effect seemed to dominate in the low range of concentration while the size-controlling effect via the formation of complex ion was important in the higher range. The TEM figures evidently confirmed the effects. Panu Danwanichakul, Thanawat Suwatthanarak, Chidchanok Suwanvisith, and Duangkamol Danwanichakul Copyright © 2016 Panu Danwanichakul et al. All rights reserved. Nickel-Silicon Related Color Center Formed in Nanodiamond Grains under CVD Growth Tue, 15 Dec 2015 12:29:42 +0000 Formation of optical centers in nanodiamond grains with narrow, near-infrared emission at room temperature is one of the most important challenges nowadays. Our aim was to form a metal-related color center through the CVD growth process of nanodiamond. Previously undocumented photoluminescence (PL) system with 865 nm zero-phonon line (ZPL) and 2 nm full width at half maximum (FWHM) was successfully created in nanodiamond grains. According to the detailed analysis of the spectral features of the ZPL and quasilocal modes of the vibronic sideband, a complex center containing Ni and Si atoms could be accounted for these PL features. The inclusion of Ni and Si impurity atoms in the complex optical center was strengthened by micro-Raman spectroscopy performed in the frequency range due to quasilocal vibrations of the vibronic sideband. Sára Tóth, László Himics, and Margit Koós Copyright © 2015 Sára Tóth et al. All rights reserved. Green Synthesis of Silver Nanoparticles Using Leaf Extracts of Clitoria ternatea and Solanum nigrum and Study of Its Antibacterial Effect against Common Nosocomial Pathogens Thu, 09 Apr 2015 13:08:25 +0000 Bionanotechnology has emerged up as integration between biotechnology and nanotechnology for developing biosynthetic and environmental friendly technology for synthesis of nanomaterials. Silver has been known to have effective bactericidal properties for centuries. Nowadays, silver based topical dressings have been widely used as a treatment for infection in burns, open wounds, and chronic ulcer. As the pathogenic organisms are getting evolved day by day due to mutation and gaining antibiotic resistance, an important industrial sector of nanoscience deals with the preparation and study of nanoparticles in antibacterial clothing, burn ointments, and coating for medical device. The size of nanomaterials is much smaller than that of most biological molecules and structures; therefore, nanomaterials can be useful in both in vivo and in vitro biomedical research application. The purpose of the study is to synthesize and characterize the plant mediated silver nanoparticles using Clitoria ternatea and Solanum nigrum. Further investigation of the shape and size of nanoparticle was done by X-ray diffraction and scanning electron microscopic studies. A silver nanoparticle at different concentration was assessed for its antibacterial effect, against various nosocomial pathogens. Narayanaswamy Krithiga, Athimoolam Rajalakshmi, and Ayyavoo Jayachitra Copyright © 2015 Narayanaswamy Krithiga et al. All rights reserved. Charge Density Analysis and Transport Properties of TTF Based Molecular Nanowires: A DFT Approach Wed, 04 Mar 2015 07:28:44 +0000 The present study has been performed to understand the charge density distribution and the electrical characteristics of Au and thiol substituted tetrathiafulvalene (TTF) based molecular nanowire. A quantum chemical calculation has been carried out using DFT method (B3LYP) with the LANL2DZ basis set under various applied electric fields (EFs). The bond topological analysis characterizes the terminal Au–S and S–C bonds as well as all the bonds of central TTF unit of the molecule. The variation of electron density and Laplacian of electron density at the bond critical point of bonds for zero and different applied fields reveal the electron density distribution of the molecule. The molecular conformation, the variation of atomic charges and energy density distribution of the molecule have been analyzed for the various levels of applied EFs. The HOMO-LUMO gap calculated from quantum chemical calculations has been compared with the value calculated from the density of states. The variation of dipole moment due to the polarization effect and the I-V characteristics of the molecule for the various applied EFs have been well discussed. Karuppannan Selvaraju and Poomani Kumaradhas Copyright © 2015 Karuppannan Selvaraju and Poomani Kumaradhas. All rights reserved. A Simple and Facile Solvothermal Synthesis of Hierarchical PbS Microstars with Multidendritic Arms and Their Optical Properties Wed, 11 Feb 2015 14:20:08 +0000 A simple and facile approach was developed in the solvothermal synthesis of hierarchical PbS microstars with multidendritic arms, which were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and photoluminescence (PL) spectroscopy. The morphologies of PbS products were strongly determined by the reaction time and temperature, the ratios of the precursors, and the mixed solvent with various components, and thereby their possible formation mechanism was discussed in some detail. The as-prepared PbS crystals displayed a sharp and strong photoluminescent peak at 437 nm at room temperature. It has potential and practical applications in photoluminescence, photovoltaics, IR photodetectors, electroluminescence, and solar absorbers. Yong-Fang Li, Ming Zhang, Qi-Jing Yang, Feng-Xian Zhang, Mei-Qi Zheng, and Ai-Jun Wang Copyright © 2015 Yong-Fang Li et al. All rights reserved. A Novel Method for Investigating the Casimir Effect on Pull-In Instability of Electrostatically Actuated Fully Clamped Rectangular Nano/Microplates Mon, 09 Feb 2015 14:14:48 +0000 The objective of the present paper is to represent a novel method to investigate the stable and unstable behaviors of fully clamped rectangular nano/microplates under the effects of electrostatic and Casimir pressures. To this end, the governing partial differential equation of equilibrium is considered and reduced to an algebraic equation using a simple and computationally efficient single degree of freedom (SDOF) model through the Galerkin weighted residual method. The linear and undamped mode-shapes of the plate are used in the Galerkin procedure as the weight function which is obtained by the extended Kantorovich method (EKM). The present findings are compared and validated by available empirical and theoretical results in the literature as well as those obtained by finite element (FE) simulation carried out using COMSOL Multiphysics commercial software and excellent agreements between them are observed. Arman Mohsenzadeh, Masoud Tahani, and Amir R. Askari Copyright © 2015 Arman Mohsenzadeh et al. All rights reserved. Size Dependent Optical Nonlinearity and Optical Limiting Properties of Water Soluble CdSe Quantum Dots Wed, 26 Nov 2014 13:04:38 +0000 We present third-order optical nonlinear absorption in CdSe quantum dots (QDs) with particle sizes in the range of 4.16–5.25 nm which has been evaluated by the -scan technique. At an excitation irradiance of 0.54 GW/cm2 the CdSe QDs exhibit reverse saturation indicating a clear nonlinear behavior. Nonlinearity increases with particle size in CdSe QDs within the range of our investigations which in turn depends on the optical band gap. The optical limiting threshold of the QDs varies from 0.35 GW/cm2 to 0.57 GW/cm2 which makes CdSe QDs a promising candidate for reverse-saturable absorption based devices at high laser intensities such as optical limiters. Anju K. Augustine, S. Mathew, P. Radhakrishnan, V. P. N. Nampoori, and M. Kailasnath Copyright © 2014 Anju K. Augustine et al. All rights reserved. Curious Case of Bactericidal Action of ZnO Mon, 17 Nov 2014 06:30:28 +0000 ZnO nanoparticles (NPs) are well known for their bactericidal properties. Various mechanisms are proposed for their bactericidal activity. An ambiguity still prevails to know which mechanism or property is mainly influencing the bactericidal activity of ZnO NPs. The antibacterial properties of ZnO NPs were investigated against both Gram-positive and Gram-negative bacteria. Different ZnO samples with different degrees of surface oxygen vacancies were prepared from ZnO2. The surface oxygen vacancy and thereby reactive oxygen species (ROS) production in aqueous ZnO solution are quantified by photoluminescence (PL) and electron paramagnetic resonance (EPR) spin trapping experiments, respectively. Systematic experiments have been performed to validate a precise antibacterial mechanism of ZnO particle. Somnath Ghosh, R. Gowri Sankar, and V. Vandana Copyright © 2014 Somnath Ghosh et al. All rights reserved. Densification Behaviour and Mechanical Properties of Aluminium Oxide and Cerium Oxide-Doped Yttria Tetragonal Zirconia Polycrystal Ceramics Using Two-Step Sintering Thu, 13 Nov 2014 09:50:37 +0000 The densification behaviour, mechanical properties, and microstructure of high-purity Al2O3 and CeO2-doped Y-TZP with different weight percentage varied from 0.3 to 1 wt% were investigated. The samples were pressed uniaxially at 200 MPa into rectangular bars and discs and pressureless-sintered at temperature ranging between 1250°C and 1450°C for 2 h while the microstructure was characterized with a scanning electron microscope (SEM). Two-step sintering process works well for temperature higher than 1400°C and it created most tetragonal phase arrangement for stable structure to delay ageing through phase transformation. The mechanical properties in terms of bulk density, Young’s modulus, Vickers hardness, and fracture toughness were also measured. The results indicate that the addition of dopants accelerated the densification parameters and reinforced and toughened the obtained bodies. The maximum values for the mechanical properties of the Al2O3 and CeO2-doped Y-TZP ceramics were 6.01, 220 GPa, 13.8 GPa, and 7 MPa for density, Young’s modulus, Vickers hardness, and fracture toughness, respectively, which are higher than those of the doped samples. M. Golieskardi, M. Satgunam, and D. Ragurajan Copyright © 2014 M. Golieskardi et al. All rights reserved. Comparative Study on the Synergistic Action of Differentially Synthesized Silver Nanoparticles with β-Cephem Antibiotics and Chloramphenicol Thu, 13 Nov 2014 08:34:19 +0000 Synergistic activity of cephem antibiotics with silver nanoparticles (Ag NPs) was investigated. Silver nanoparticles were synthesized through biological and chemical method. The combined action of β-lactam cephem antibiotics with both green and chemically synthesized silver nanoparticles enhances the antibacterial activity against wide range of antibiotic resistant pathogens and making them applicable to medical devices and microbial control systems. Synergistic activity of chloramphenicol with silver nanoparticles was also studied. Neethu Hari, Tincy K. Thomas, and A. Jayakumaran Nair Copyright © 2014 Neethu Hari et al. All rights reserved. Enhancement of Field Emission Properties of Carbon Nanotubes by ECR-Plasma Treatment Mon, 27 Oct 2014 09:04:10 +0000 We report a significant improvement in electron field emission property of carbon nanotubes film by using an electron cyclotron resonance plasma treatment. Our research results reveal that plasma treatment can modify the surface morphology and enhance the field emission characteristics of carbon nanotubes. Raman spectra indicate that plasma treated CNTs sample has lesser defects. Before plasma treatment, low current density of 6.5 mA/cm2 at 3.0 V/μm and at a high turn-on field of 2.4 V/μm was observed. ECR plasma treated CNTs showed a high current density of 20.0 mA/cm2 at 3.0 V/μm and at a low of 1.6 V/μm. The calculated enhancement factors are 694 and 8721 for ECR-plasma untreated and treated carbon nanotubes, respectively. We found an increase in the enhancement factor and emission current after the ECR-plasma treatment. This may be attributed to creation of geometrical features through the removal of amorphous carbon and catalyst particles. Javid Ali, Avshish Kumar, Samina Husain, Shama Parveen, Renu Choithrani, Mohammad Zulfequar, Harsh, and Mushahid Husain Copyright © 2014 Javid Ali et al. All rights reserved. Small-Scale Effect on Longitudinal Wave Propagation in Laser-Excited Plates Tue, 21 Oct 2014 00:00:00 +0000 Longitudinal wave propagation in an elastic isotopic laser-excited solid plate with atomic defect (vacancies, interstitials) generation is studied by the nonlocal continuum model. The nonlocal differential constitutive equations of Eringen are used in the formulations. The coupled governing equations for the dynamic of elastic displacement and atomic defect concentration fields are obtained. The frequency equations for the symmetrical and antisymmetrical motions of the plate are found and discussed. Explicit expressions for different characteristics of waves like phase velocity and attenuation (amplification) coefficients are derived. It is shown that coupling between the displacement and defect concentration fields affects the wave dispersion characteristics in the nonlocal elasticity. The dispersion curves of the elastic-diffusion instability are investigated for different pump parameters and larger wave numbers. F. Kh. Mirzade Copyright © 2014 F. Kh. Mirzade. All rights reserved. FTIR and EPR Studies of Nickel Substituted Nanostructured Mn Zn Ferrite Mon, 22 Sep 2014 00:00:00 +0000 The spinel ferrite system is prepared by coprecipitation method. XRD analysis confirms the formation of ferrite phase in all the samples. The FTIR spectra of all the samples show two main absorption bands below 1000 cm−1. FTIR studies reveal cationic exchange between A site and B site. The magnetic moment calculated from EPR studies is lower when compared to the theoretical values. This confirms the existence of noncollinear magnetic structure arising due to spin canting at B site. C. Venkataraju and R. Paulsingh Copyright © 2014 C. Venkataraju and R. Paulsingh. All rights reserved. Landauer-Datta-Lundstrom Generalized Transport Model for Nanoelectronics Wed, 17 Sep 2014 09:25:41 +0000 The Landauer-Datta-Lundstrom electron transport model is briefly summarized. If a band structure is given, the number of conduction modes can be evaluated and if a model for a mean-free-path for backscattering can be established, then the near-equilibrium thermoelectric transport coefficients can be calculated using the final expressions listed below for 1D, 2D, and 3D resistors in ballistic, quasiballistic, and diffusive linear response regimes when there are differences in both voltage and temperature across the device. The final expressions of thermoelectric transport coefficients through the Fermi-Dirac integrals are collected for 1D, 2D, and 3D semiconductors with parabolic band structure and for 2D graphene linear dispersion in ballistic and diffusive regimes with the power law scattering. Yuriy Kruglyak Copyright © 2014 Yuriy Kruglyak. All rights reserved. Growth of Horizontal Nanopillars of CuO on NiO/ITO Surfaces Thu, 28 Aug 2014 09:48:17 +0000 We have demonstrated hydrothermal synthesis of rectangular pillar-like CuO nanostructures at low temperature (~60°C) by selective growth on top of NiO porous structures film deposited using chemical bath deposition method at room temperature using indium tin oxide (ITO) coated glass plate as a substrate. The growth of CuO not only filled the NiO porous structures but also formed the big nanopillars/nanowalls on top of NiO surface. These nanopillars could have significant use in nanoelectronics devices or can also be used as p-type conducting wires. The present study is limited to the surface morphology studies of the thin nanostructured layers of NiO/CuO composite materials. Structural, morphological, and absorption measurement of the CuO/NiO heterojunction were studied using state-of-the-art techniques like X-ray diffraction (XRD), transmission electron microscopy (SEM), atomic force microscopy (AFM), and UV spectroscopy. The CuO nanopillars/nanowalls have the structure in order of (5 ± 1.0) μm × (2.0 ± 0.3) μm; this will help to provide efficient charge transport in between the different semiconducting layers. The energy band gap of NiO and CuO was also calculated based on UV measurements and discussed. Siddharth Joshi, Mrunmaya Mudigere, L. Krishnamurthy, and G. L. Shekar Copyright © 2014 Siddharth Joshi et al. All rights reserved. The Effect of DNA and Sodium Cholate Dispersed Single-Walled Carbon Nanotubes on the Green Algae Chlamydomonas reinhardtii Tue, 26 Aug 2014 00:00:00 +0000 Increasing use of single-walled carbon nanotubes (SWCNTs) will lead to their increased release into the environment. Previous work has shown negative effects of SWCNT on growth and survival of model organisms. The aim of the current study was to determine the effect of SWCNT well-dispersed by either DNA or sodium cholate (SC) on the unicellular green algae Chlamydomonas reinhardtii in stagnant water conditions. Growth measurements were taken up to ten days for algae treated with varied levels of DNA:SWCNT or SC:SWCNT or controls, and chlorophyll content after 10 days was determined. Results show no effect on either growth or chlorophyll content of algae at any concentration or duration. This is in contradiction to prior work showing toxicity of SWCNT to environmental model organisms. Ryan M. Williams, Hannah K. Taylor, Jackson Thomas, Zachary Cox, Bridget D. Dolash, and Letha J. Sooter Copyright © 2014 Ryan M. Williams et al. All rights reserved. Self-Passivation by Fluorine Plasma Treatment and Low-Temperature Annealing in SiGe Nanowires for Biochemical Sensors Wed, 11 Jun 2014 10:37:20 +0000 Nanowires are widely used as highly sensitive sensors for electrical detection of biological and chemical species. Modifying the band structure of strained-Si metal-oxide-semiconductor field-effect transistors by applying the in-plane tensile strain reportedly improves electron and hole mobility. The oxidation-induced Ge condensation increases the Ge fraction in a SiGe-on-insulator (SGOI) and substantially increases hole mobility. However, oxidation increases the number of surface states, resulting in hole mobility degradation. In this work, 3-aminopropyltrimethoxysilane (APTMS) was used as a biochemical reagent. The hydroxyl molecule on the oxide surface was replaced by the methoxy groups of the APTMS molecule. We proposed a surface plasma treatment to improve the electrical properties of SiGe nanowires. Fluorine plasma treatment can result in enhanced rates of thermal oxidation and speed up the formation of a self-passivation oxide layer. Like a capping oxide layer, the self-passivation oxide layer reduces the rate of follow-up oxidation. Preoxidation treatment also improved the sensitivity of SiGe nanowires because the Si-F binding was held at a more stable interface state compared to bare nanowire on the SiGe surface. Additionally, the sensitivity can be further improved by either the N2 plasma posttreatment or the low-temperature postannealing due to the suppression of outdiffusion of Ge and F atoms from the SiGe nanowire surface. Kow-Ming Chang, Chiung-Hui Lai, Chu-Feng Chen, Po-Shen Kuo, Yi-Ming Chen, Tai-Yuan Chang, Allen Jong-Woei Whang, Yi-Lung Lai, Huai-Yi Chen, and Ing-Jar Hsieh Copyright © 2014 Kow-Ming Chang et al. All rights reserved. FTIR and Electrical Study of Dysprosium Doped Cobalt Ferrite Nanoparticles Sun, 18 May 2014 12:46:53 +0000 We have studied the role of Dy3+ doping on the XRD, TEM, FTIR, and dielectric and electrical properties of CoFe2O4 at room temperature. Cubic spinel phase of CoFe2−xDyxO4 ( = 0.00, 0.05, 0.10, and 0.15) was synthesized by using different sintering temperatures (300, 500, 700, and 900°C). The two absorption bands ν1 and ν2 are observed in Fourier transform infrared spectroscopy (FTIR) spectra corresponding to the tetrahedral and octahedral sites, which show signature of spinel structure of the sample. For the sample sintered at 300°C, the dielectric constant is almost unchanged with the frequency at the particular concentrations of = 0.00 and 0.05. Similar result is obtained for the sample sintered at 500°C ( = 0.10, 0.15), 700°C ( = 0.05, 0.10, and 0.15), and 900°C ( = 0.05, 0.10). An increase in the dielectric constant was observed for the undoped cobalt ferrite sintered at 500, 700, and 900°C. The values of electrical resistivity of the materials vary from ~105 to 109 Ω-cm. Hemaunt Kumar, Jitendra Pal Singh, R. C. Srivastava, P. Negi, H. M. Agrawal, and K. Asokan Copyright © 2014 Hemaunt Kumar et al. All rights reserved. Quantifying the Aggregation Factor in Carbon Nanotube Dispersions by Absorption Spectroscopy Tue, 29 Apr 2014 06:23:04 +0000 Absorption spectroscopy in the ultraviolet-visible-near infrared (UV-Vis-NIR) wavelength region has been used to quantify the aggregation factor of single-walled carbon nanotubes (SWCNTs) in liquid media through a series of controlled experiments. SWCNT bundles are dispersed in selected solvents using a calibrated ultrasonicator, which helps in determining the true amount of energy used in the exfoliation process. We also establish the selectivity of the centrifugation process, under the conditions used, in removing the nanotube aggregates as a function of the sonication time and the dispersion solvent. This study, along with the calibration of the sonication process, is shown to be very important for measuring the true aggregation factor of SWCNTs through a modified approach. We also show that the systematic characterization of SWCNT dispersions by optical spectroscopy significantly contributes to the success of dielectrophoresis (DEP) of nanotubes at predefined on-chip positions. The presence of individually dispersed SWCNTs in the dispersions is substantiated by dielectrophoretic assembly and post-DEP electromechanical measurements. Hari Pathangi, Philippe M. Vereecken, Alexander Klekachev, Guido Groeseneken, and Ann Witvrouw Copyright © 2014 Hari Pathangi et al. All rights reserved. Solvent-Mediated Eco-Friendly Synthesis and Characterization of Monodispersed Bimetallic Ag/Pd Nanocomposites for Sensing and Raman Scattering Applications Sun, 13 Apr 2014 13:40:22 +0000 The solvent-mediated eco-friendly monodispersed Ag/Pd bimetallic nanocomposites (BNCs) having thick core and thin shell have been prepared through novel green chemical solvent reduction method. Reducing solvent, dimethyl formamide (DMF) is employed for the controlled green synthesis. Characterization of the synthesized Ag/Pd BNCs has been done by x-ray diffraction (XRD) studies, high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray analysis (EDX), and high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED) pattern. The nature of the interaction of L-cysteine with Ag/Pd BNCs has been studied by using surface plasmon spectroscopy, Fourier transform-infrared spectroscopy (FT-IR), cyclic voltammetry (CV), and theoretical methods. G. Sathiyadevi, B. Loganathan, and B. Karthikeyan Copyright © 2014 G. Sathiyadevi et al. All rights reserved. Modeling Replenishment of Ultrathin Liquid Perfluoropolyether Z Films on Solid Surfaces Using Monte Carlo Simulation Sun, 06 Apr 2014 09:00:05 +0000 Applying the reptation algorithm to a simplified perfluoropolyether Z off-lattice polymer model an NVT Monte Carlo simulation has been performed. Bulk condition has been simulated first to compare the average radius of gyration with the bulk experimental results. Then the model is tested for its ability to describe dynamics. After this, it is applied to observe the replenishment of nanoscale ultrathin liquid films on solid flat carbon surfaces. The replenishment rate for trenches of different widths (8, 12, and 16 nms for several molecular weights) between two films of perfluoropolyether Z from the Monte Carlo simulation is compared to that obtained solving the diffusion equation using the experimental diffusion coefficients of Ma et al. (1999), with room condition in both cases. Replenishment per Monte Carlo cycle seems to be a constant multiple of replenishment per second at least up to 2 nm replenished film thickness of the trenches over the carbon surface. Considerable good agreement has been achieved here between the experimental results and the dynamics of molecules using reptation moves in the ultrathin liquid films on solid surfaces. M. S. Mayeed and T. Kato Copyright © 2014 M. S. Mayeed and T. Kato. All rights reserved. Characterization of Erbium Substituted Yttrium Iron Garnet Films Prepared by Sol-Gel Method Sun, 06 Apr 2014 08:32:49 +0000 Yttrium iron garnet (YIG) thin films substituted erbium ions (Er+3) Er0.4Y2.6Fe5O12 films were prepared by a sol-gel method at different temperatures which varied from 800 to 1000°C for 2 hours in air. Magnetic and microstructural properties of the films were characterized with X-ray diffraction (XRD), the field emission scanning electron microscopy (FESEM), and vibrating sample magnetometer (VSM). The XRD patterns of the sample have only peaks of the garnet structure. The lattice constants decrease, while the particle size increases from 51 to 85 nm as the annealing temperature increases with average in thickness of 300 nm. The saturation magnetization and the coercivity of the samples increased from 26 (emu/cc) and 28 Oe for the film annealed at 800°C to 76 (emu/cc) and 45 Oe for film annealed at 1000°C, respectively. Ramadan E. Shaiboub and N. B. Ibrahim Copyright © 2014 Ramadan E. Shaiboub and N. B. Ibrahim. All rights reserved. Simulations of the Light Scattering Properties of Metal/Oxide Core/Shell Nanospheres Sun, 06 Apr 2014 07:31:34 +0000 Given the importance of the optical properties of metal/dielectric core/shell nanoparticles, in this work we focus our attention on the light scattering properties, within the Mie framework, of some specific categories of these noteworthy nanostructures. In particular, we report theoretical results of angle-dependent light scattering intensity and scattering efficiency for Ag/Ag2O, Al/Al2O2, Cu/Cu2O, Pd/PdO, and Ti/TiO2 core/shell nanoparticles as a function of the core radius/shell thickness ratio and on a relative comparison. The results highlight the light scattering characteristics of these systems as a function of the radius/shell thickness ratio, helping in the choice of the more suitable materials and sizes for specific applications (i.e., dynamic light scattering for biological and molecular recognition, increasing light trapping in thin-film silicon, organic solar cells for achieving a higher photocurrent). F. Ruffino, G. Piccitto, and M. G. Grimaldi Copyright © 2014 F. Ruffino et al. All rights reserved.