Nanosize Dimensions Research Articles

Synergistic bifunctional catalyst design based on perovskite oxide nanoparticles and intertwined carbon nanotubes for rechargeable zinc-air battery applications.

Advanced morphology of intertwined core-corona structured bifunctional catalyst (IT-CCBC) is introduced where perovskite lanthanum nickel oxide nanoparticles (LaNiO3 NP) are encapsulated by high surface area network of nitrogen-doped carbon nanotubes (NCNT) to produce highly active and durable bifunctional catalyst for rechargeable metal-air battery applications. The unique composite morphology of IT-CCBC not only enhances the charge transport property by providing rapid electron-conduction pathway but also facilitates in diffusion of hydroxyl and oxygen reactants through the highly porous framework. Confirmed by electrochemical half-cell testing, IT-CCBC in fact exhibits very strong synergy between LaNiO3 NP and NCNT demonstrating bifunctionality with significantly improved catalytic activities of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Furthermore, when compared to the state-of-art catalysts, IT-CCBC outperforms Pt/C and Ir/C in terms of ORR and OER, respectively, and shows improved electrochemical stability compared to them after cycle degradation testing. The practicality of the catalyst is corroborated by testing in a realistic rechargeable zinc-air battery utilizing atmospheric air in ambient conditions, where IT-CCBC demonstrates superior charge and discharge voltages and long-term cycle stability with virtually no battery voltage fading. These improved electrochemical properties of the catalyst are attributed to the nanosized dimensions of LaNiO3 NP controlled by simple hydrothermal technique, which enables prolific growth of and encapsulation by highly porous NCNT network. The excellent electrochemical results presented in this study highlight IT-CCBC as highly efficient and commercially viable bifunctional catalyst for rechargeable metal-air battery applications.

Nanostructured V2O5 Cathode for Rechargeable Mg-Ion Batteries

Introduction Rechargeable battery systems with different transporting ions are an alternative choice to Li batteries that can expand and diversify the existing energy storage market. Magnesium batteries are the most promising technology to achieve substantially greater energy density than Li-ion batteries, due to their divalent nature (two electron redox couple). Furthermore, because of its “green” character Mg is environmentally friendly, with high natural abundance in the Earth’s crust (13.9% as compared to 0.0007 % for Li), and atmospheric stability.The current quest for new cathode materials for rechargeable Mg batteries is focused on intercalation compounds exhibiting high working potential and capacity1. When transporting ions have much larger diameter or charge than the host metal ion, segregation of transporting and host metal ions in the crystalline structure is forseable. In this case deintercalation will lead to the collapse of the crystalline structure and breaking of electric conductance. Therefore, our approach to achieving magnesium intercalation is to use nanoscale material that have adjustable d spacing and two-dimensional layered structure that can to control polarizability of Mg2+ions and accommodate large charge/volume changes.Nanostructured electrode materials represent one of the most attractive strategies to dramatically enhance battery performance. Short diffusion length associated with the nanosized dimensions effectively reduces the distance that ions and electrons must travel during cycling. Their large surface area increases the contact area between electrode and electrolyte and hence the number of active sites for electrode reactions, which in turn reduces electrode polarization loss and improves power density, energy efficiency, and usable energy.Nanostructured bilayered V2O5 is highly efficient 3 V cathode material for ambient temperature sodium ion batteries2. It shows superb performance: theoretical reversible capacity for Na2V2O5 stochiometry of 250 mAh/g, excellent rate capability and cycle life, as well as high energy and power densities. Preliminary results show that it is possible to extend the reversible ion-insertion chemistry of nanostructured layered V2O5 beyond lithium and larger in size Na+ ions to those with higher charge: Mg2+ions. Results and Discussion As–prepared nanostructured bilayered V2O5 cathode is synthesized in the charged state. To provide source enrichment, prior to assembling into full Mg-ion cell, it was necessary to pre-condition V2O5 cathode (intercalate with Mg2+ ions). Half-cells were discharged galvanostatically at 20mA down to and 0.01 V versus Mg/ Mg2+, respectively, using an automated Maccor battery tester at ambient temperature. As shown in Figure 1., upon electrochemical pre-condition (Mg-ion half cell) the X-ray edge energy for vanadium is shifted toward the lower energy as a consequence of a vanadium reduction due to Mg intercalation. Pre-edge peak is proportional to the octahedral symmetry of the vanadium sites and its decrease upon transporting ion intercalation is due to modification of vanadium local environment into more ordered, symmetric structure. Based on the main-edge peak position and comparison with Na-ion half cell we estimate 1 Mg is incorporated in the V2O5 structure (V5+ is reduced to V4+). It was previously shown that the V5+ was reduced to V4+ when discharged to 1.5V versus Na/ Na+ (Na-ion half cell)2. As a result of this electrochemical pre-condition we created Mg-rich V2O5 cathodes that were able to provide source of Mg-ions in full-cell. Furthermore, we employed HRTEM, X-Ray fluorescence (XRF) imaging and classical molecular dynamics simulations to understand the role of environment in the intercalation processes of Mg-ions into V2O5cathode. Conclusions We have developed high-voltage nanostructured V2O5 cathode for Mg-ion rechargeable batteries that can operate in commercial electrolytes. Our results emphasize the importance of tailoring nanoarchitecture of electrode materials and open up new opportunities for rechargeable Mg batteries. In the near future, we plan using the combined experimental and theoretical approach to guide our efforts to increase the Mg enrichment to reach the ultimate goal of inserting 2 Mg-ions/V2O5. Acknowledgement. This work was supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by DOE, Office of Science, Basic Energy Science (BES). Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, and Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. References (1) On the Way to Rechargeable Mg Batteries: The Challenge of New Cathode Materials, E. Levi, Y. Gofer, and D. Aurbach, Chem. Mater. 2010, 22, 860–868.(2) Vanadium Oxide Electrodes for Rechargeable Sodium-Ion Batteries, Sanja Tepavcevic, Hui Xiong, Vojislav R. Stamenkovic, Xiaobing Zuo, Mahalingam Balasubramanian, Vitali B. Prakapenka, Christopher S. Johnson, and Tijana Rajh, Nanostructured Bilayered ACS Nano, 2012, 6 (1), 530–538.

In Vivo Evaluation of the Pulmonary Toxicity of Cellulose Nanocrystals: A Renewable and Sustainable Nanomaterial of the Future.

The use of cellulose as building blocks for the development of novel functional materials is rapidly growing. Cellulose nanocrystals (CNC), with advantageous chemical and mechanical properties, have gained prominence in a number of applications, such as in nanofillers in polymer composites, building materials, cosmetics, food, and the drug industry. Therefore, it becomes critical to evaluate the potential health effects associated with CNC exposures. The objective of this study was to compare pulmonary outcomes caused by exposure of C57BL/6 mice to two different processed forms of CNC derived from wood, i.e., CNCS (10 wt %; gel/suspension) and CNCP (powder), and compare to asbestos induced responses. Pharyngeal aspiration with CNCS and CNCP was found to facilitate innate inflammatory response assessed by an increase in leukocytes and eosinophils recovered by bronchoalveolar lavage (BAL). Biomarkers of tissue damage were elevated to a higher extent in mice exposed to CNCP. Compared to CNCP, CNCS caused a significant increase in the accumulation of oxidatively modified proteins. The up-regulation of inflammatory cytokines was higher in the lungs after CNCS treatments. Most importantly, CNCP materials were significantly longer than CNCS. Taken together, our data suggests that particle morphology and nanosize dimensions of CNCs, regardless of the same source, may be critical factors affecting the type of innate immune inflammatory responses. Because various processes have been developed for producing highly sophisticated nanocellulose materials, detailed assessment of specific health outcomes with respect to their physical-structural-chemical properties is highly warranted.

Nanocellulose from Diseased Coconut Wood Biomass

Cellulose is the most widespread biopolymer on earth. In biosynthesis, cellulose polymers aggregate to form substructures, microfibrils, which in turn aggregate to form cellulose fibers. By applying effective methods these fibers can be disintegrated into cellulose substructures with micro- or nano-size dimensions. This article covers some aspects related to the sources of cellulose micro- and nanofibers and the most important methods for their isolation. One of these methods, acid hydrolysis, was experimentally used to obtain cellulose nano-fibers from diseased coconut wood biomass. They were studied by Thermogravimetric analysis (TGA), X-ray diffractometer (XRD) and Scanning electrom microscope (SEM).
 The ‘Replanting and Rejuvenation of Coconut Gardens’ was the sponsored scheme of the Coconut Development Board with an objective to eliminate all disease- affected coconut palms in eight districts of Kerala state in India. The main components of the scheme included cutting and removal of all old, unproductive and disease-hit palms followed by a replanting exercise. The present work was carried out under the Board sponsored project entitled “Diversified uses of diseased coconut wood”.

Nano-size effects on the nature of bonding in Y2Sn2O7: EXAFS and Raman spectroscopic investigations

Nature of bonding around Y3+ and Sn4+ ions in Y2Sn2O7 phase, both in the bulk and in nanosize dimensions, were investigated by yttrium K edge EXAFS measurement, Raman spectroscopy and theoretical calculations based on density functional theory (DFT). From the investigations it is established that Y–O bond is more covalent in nanoparticles of Y2Sn2O7, compared to bulk Y2Sn2O7. Asymmetric electron density distribution around Sn4+ in nanoparticles of Y2Sn2O7, compared to bulk, leads to the improvement in the Raman activities of bending and stretching vibrational modes of Y–O, Y–O–Sn and Sn–O linkages.

Receptor mediated cellular uptake of low molecular weight dendritic polyglycerols.

The development of effective polymer-based nanocarriers which are able to target diseased tissues still remains a great challenge in current research. Dendritic polyglycerols have emerged as novel polymeric scaffolds that have demonstrated a great potential for diverse biomedical applications. These architectures have already proven their usefulness in therapeutic approaches related to multivalency, given by the synergy between the nanosized dimensions combined with the high density of functional groups. However, a continuous effort is necessary to modify and tailor polyglycerol architectures to fit the future demands of biomedical applications. The present work deals with the development of a general synthetic strategy that allows the linkage of low molecular weight dendritic polyglycerols to fluorescent dyes and cell targeting ligands. The receptor mediated cellular uptake of the polyglycerol conjugates highlight their potential to acts as new targeted nanocarriers that should be able to decrease non-specific cellular uptake.

Sintering Conditions for Al2(WO4)3High-Dense Ceramic

Al2(WO4)3 nanoparticles with average particles size of 20, 90 and 200 nm are sintered by two methods: cold pressing with additional sintering at di erent temperatures and time durations and hot pressure sintering. Density, particles size dimensions and anisometricity are tested. The results show that optimal initial nanosized dimensions and an optimal pressing condition are needed to obtain compact ceramic. Hot pressure method gives possibilities of a ceramic with a density in order of 99.8% to be received, which possesses some level of transparency.

Giant Chemo-Resistance of SnO disk-like structures

Single crystalline SnO micro-disks, synthesized by a carbothermal reduction process, exhibited a nearly 1000-fold increase in resistance upon exposure to 100ppm of NO2 without addition of catalysts or dopants nor the existence of nano-sized dimensions. Moreover, the SnO displayed a greater than 100-fold selectivity to NO2 over potential interferents including CO, H2 and CH4. The high sensor signal and exceptional selectivity for this novel sensor material are attributed to the existence of a high density of active lone pair electrons on the exposed (001) planes of the single crystalline SnO disks. This, thereby, identifies new means, not utilizing nano-dimensions, to achieve high gas sensitivity.

The effects of supercritical CO2 formulations on the removal of high-dose ion-implanted photoresists

Highlights3wt.% EH-3 and TMN-3 are chosen to form scCO2 microemulsions.2vol.% DMSO and IPA can enhance HDI PR efficiency by 75.5% and 64.2%.DMSO and EH-3 show a positive synergistic effect on the stripping efficiency.scCO2 density tuned by temperature and pressure affects HDI PR stripping behavior.100% Removal efficiency is achieved at 60?C and 25MPa for 20min. A new effective method for high-dose ion-implanted photoresist (HDI PR) stripping is reported based on supercritical CO2 (scCO2) microemulsions consisting of branched hydrocarbon surfactant 2-ethylhexanol polyoxyethylene-polyoxypropylene (EH-3) and co-solvent dimethylsulfoxide (DMSO). The optimized concentrations of EH-3 and DMSO in scCO2 were 3wt.% and 2vol.%, respectively, and the weight ratio of H2O and EH-3 is 1:1. The HDI PRs containing crust layers were removed in the scCO2 microemulsions at 10-25MPa and 40-80?C for 20min. The results revealed that the stripping efficiency of HDI PR increased with the pressure and temperature (T) when T is lower than 60?C. The removal efficiency of 96.8% was achieved at 60?C and 20MPa and then it gradually decreased as T higher than 60?C due to the lower scCO2 density at higher T. Magnetic agitation was favorable for the HDI PR removal. The optimum stripping parameters were determined to be 60?C and 25MPa for 20min at which 100% removal efficiency was achieved in EH-3/DMSO/scCO2 microemulsions. This environmentally benign method provides a promising alternative to effectively strip HDI PR for devices with nano-sized feature dimensions in microelectronic processing.

Carbon Nanotubes in Cancer Treatment: A Preliminary <i>In Vitro</i> Study Using Neuroblastoma Cells

Carbon nanotubes (CNTs) were reported to cause severe toxicity in in vivo and in vitro studies. On the other hand, CNTs has the potential as a mechanism for drug delivery across the blood brain barrier due to its nano-sized dimensions. The present preliminary study examined the cytotoxic effect of CNTs in serum-free and serum-containing EMEM medium on neuroblastoma cells growth. The MTS assay showed that CNTs did not cause any cytotoxicity at concentrations below 0.1 mg/mL at 24 and 48 h incubation in serum-containing EMEM medium. This finding suggested that below 0.1 mg/mL, CNTs can be used as a mechanism for drug delivery for the treatment of neuronal cancer. However, CNTs showed slighty toxic towards neuroblastoma cells at concentration 0.1 mg/ml at 48h incubation in serum-free EMEM medium. This finding indicates that the present of serum play a role for toxicity effect of CNTs in cells.

Nanoscale bacteriophage biosensors beyond phage display.

Bacteriophages are traditionally used for the development of phage display technology. Recently, their nanosized dimensions and ease with which genetic modifications can be made to their structure and function have put them in the spotlight towards their use in a variety of biosensors. In particular, the expression of any protein or peptide on the extraluminal surface of bacteriophages is possible by genetically engineering the genome. In addition, the relatively short replication time of bacteriophages offers researchers the ability to generate mass quantities of any given bacteriophage-based biosensor. Coupled with the emergence of various biomarkers in the clinic as a means to determine pathophysiological states, the development of current and novel technologies for their detection and quantification is imperative. In this review, we categorize bacteriophages by their morphology into M13-based filamentous bacteriophages and T4- or T7-based icosahedral bacteriophages, and examine how such advantages are utilized across a variety of biosensors. In essence, we take a comprehensive approach towards recent trends in bacteriophage-based biosensor applications and discuss their outlook with regards to the field of biotechnology.

High-Density Ceramics of Al<sub>2-x</sub>Me<sub>x</sub> (WO<sub>4</sub>)<sub>3</sub>, (Me = Sc or In) Solid Solutions

Al2-xMex(WO4)3, (Me is Sc or In; x varies from 0 to 2) ceramics are sintered by two methods: 1) cold pressing with subsequent sintering at different temperatures and durations and 2) hot pressure sintering. The row materials are nanoparticles with average particle size of 20, 90 and 200 nm obtained by co-precipitation method. Density, particle size and anisometricity of the obtained ceramics are tested. The results show that optimal initial nanosized dimensions and optimal pressing conditions are needed to obtain compact ceramics. The hot pressure method provides possibilities for obtaining ceramics with a density of about 99.8%. These ceramics possess some level of transparency.

A new nanospray drying method for the preparation of nicergoline pure nanoparticles

Three different batches of pure nanoparticles (NPs) of nicergoline (NIC) were prepared by spray drying a water:ethanol solution by a new Nano Spray Dryer Buchi B-90. Spherical pure NPs were obtained, and several analytical techniques such as differential scanning calorimetry and X-ray powder diffractometry permitted to assess their amorphous character. A comparison of the solubility, intrinsic dissolution, and drug release of original particles and pure amorphous NPs were determined, revealing an interesting improvement of biopharmaceutical properties of amorphous NPs, due to both amorphous properties and nanosize dimensions. Since in a previous work, the high-thermodynamic stability of amorphous NIC was demonstrated, this study is addressed toward the formulation of NIC as pure amorphous NPs.

Autonomous movement of platinum-loaded stomatocytes

Polymer stomatocytes are bowl-shaped structures of nanosize dimensions formed by the controlled deformation of polymer vesicles. The stable nanocavity and strict control of the opening are ideal for the physical entrapment of nanoparticles which, when catalytically active, can turn the stomatocyte morphology into a nanoreactor. Herein we report an approach to generate autonomous movement of the polymer stomatocytes by selectively entrapping catalytically active platinum nanoparticles within their nanocavities and subsequently using catalysis as a driving force for movement. Hydrogen peroxide is free to access the inner stomatocyte cavity, where it is decomposed by the active catalyst (the entrapped platinum nanoparticles) into oxygen and water. This generates a rapid discharge, which induces thrust and directional movement. The design of the platinum-loaded stomatocytes resembles a miniature monopropellant rocket engine, in which the controlled opening of the stomatocytes directs the expulsion of the decomposition products away from the reaction chamber (inner stomatocyte cavity).

Platinum nano particles dispersed in alumina

We report the propane dehydrogenation behavior of catalysts prepared using wet impregnation method that immobilize Pt nano cluster on the alumina surface. The immobilization of the metal particles and their nano size dimensions were demonstrated by transmission electron microscopy. Selectivity to propylene for these catalysts is comparable to those obtained over industrial Pt catalysts, yet the resistance to deactivation by carbon poisoning is much greater for our catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts on γ-alumina than of catalysts supported onθ-alumina.

Evaluation of bulk and surfaces absorption edge energy of sol-gel-dip-coating SnO2 thin films

The absorption edge and the bandgap transition of sol-gel-dip-coating SnO2 thin films, deposited on quartz substrates, are evaluated from optical absorption data and temperature dependent photoconductivity spectra. Structural properties of these films help the interpretation of bandgap transition nature, since the obtained nanosized dimensions of crystallites are determinant on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110) and (101) surfaces are also presented, calculated by means of density functional theory applied to periodic calculations at B3LYP hybrid functional level. Experimentally obtained absorption edge is compared to the calculated energy band diagrams of bulk and (110) and (101) surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101) surface, which presents direct bandgap transition.

Investigation on Fabrication of W-Cu Nanocomposite via a Thermochemical Co-Precipitation Method and its Consolidation Behavior

W-25%Cu nanocomposite was produced via a thermochemical co-precipitation procedure. Copper nitrate and sodium tungstate salts were used as Cu and W containing precursors respectively. Aqueous solutions of these salts were reacted under controlled pH condition prepared by ammonia addition and the resulting precipitates were then calcined at 450oC and hydrogen reduced at 800oC. The products of each step were characterized by XRD and Electron Microscope. Using a basic medium with a pH of 13 which caused the formation of complex Cu(NH3)42+ was found to provide suitable condition for precipitation of nanosized composite powders. Cu2WO4(OH)2 and CuWO4.2H2O as raw precipitates, CuWO4-x , CuO, and WO3 as calcined powders, and W-Cu reduced composite powders, all were seen to keep nanosize dimensions through high temperature treatments of fabrication. Sintering of the reduced powders at the temperature of 1150oC led in a density of about 98% theoretical density.

Coating dielectric substrates by plasma-reduction of metallic ions in solvents

Abstract We demonstrate herein the coating of dielectric surfaces with metallic thin films using the plasma-reduction of metallic ions such as HAuCl 4 , AgNO 3 , H 2 PtCl 6 , PdCl 2 , Ni(NO 3 ) 2 and Co(NO 3 ) 2 in solutions. Stable plasma was formed using 12 MHz/18 W and 2.45 GHz/900 W plasma generators and was confined in a Pyrex vacuum chamber with an inert gas environment. Depending on the controlled parameters, the fabricated films are either continuous or granular with grains of nano-size dimensions. All samples were chemically analyzed using X-ray diffraction analysis, and were morphologically observed using High Resolution Electron Beam microscopy. As an example of their electrical conductivity, Van der Pauw resistivity measurements were carried out for a gold layer at a wide temperature range. The smooth resistivity signal spreading at this range indicates that the conductive layer is stable and electrically continuous. An estimation of the adhesion of the deposited films was conducted by resistance measurements, followed by an ultrasonic bath treatment. Our results indicate no change in the resistance after this treatment, namely, a good adhesion of metallic particles to the glass surface has been achieved. The fact that this method is fast, simple, and low in cost (compared to other methods like sputtering or cvd), and can be applied for coating flat, rough, and porous surfaces can indicate its importance in future applications.

Hybrid Organic/Inorganic UV‐Cured Acrylic Films with Hydrophobic Surface Properties

AbstractHybrid organic/inorganic acrylic nanostructured films were prepared by a UV/thermal dual‐curing process. The role of a fluorinated hydroxyl acrylate monomer (AF) as coupling agent was investigated. Increased Tg values and modulus of the dual‐cured films were achieved by increasing the TEOS inorganic precursor. The coupling agent deeply modified the surface properties of the cured films: the formation of hybrid films characterized by high hydrophobicity together with an increase on surface hardness was achieved. TEM analysis clearly evidenced the reducing of the nanosize dimensions of the inorganic silica domains by increasing the coupling agent content in the photocurable formulation.magnified image

Preparation and characterization of the transparent [formula omitted] nanocomposite mirror film for the infrared region by sol–gel method

Transparent mirror coated, SiO 2–Ag/PV P nanocomposites were prepared on the Pyrex glass slides by dip-coating technique. Embedding of the silver (Ag) nanoparticles on silica modified polyvinyl pyrrolidone (PVP) was performed by the sol–gel method. As prepared transparent mirror coated SiO 2–Ag/PV P nanocomposite films were finally characterized for surface morphology, chemistry, and nano size dimensions using various advanced analytical techniques including, UV visible, Fourier transform, infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), dispersive x-ray analaysis (EDAX) and transmission electron microscopy (TEM) analysis. It was found that all the prepared samples were almost uniform particles of Ag nanospheres of 7–8 nm diameters arranged as double paralleled nanowires with an average length of 200–450 nm and diameters of around 20–25 nm.