Electrochemical Double Layer Capacitors, EDLC, using Cobalt sulfide- Graphene (CoSG) composite electrodes, were fabricated and the storage process was studied. CoSG composite was prepared by a simple chemical route. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Field Emission Scanning Electron microscopy (FESEM) were used to characterized the as prepared composites which indicated formation of Co S phase. Solutions of perfluorosulfonic acid and Polyvinylidene Fluoride (PVDF) were used as electrode binding material. The storage capacitance of the composites were studied in 1M KCl and 6M KOH electrolytes using standard electrochemical techniques like cyclic voltammetry, CV, electrochemical impedance spectroscopy, EIS, and discharge profiles. The capacitance was estimated for various binder concentrations for both the electrolytes. The concentration of perflurosulfonic acid binder of 0.8 wt% and PVDF of 0.04 wt% showed optimized specific capacitances of 657.8 F/gm and 1418.8 F/g, respectively. Some of the problems in storage density in activated carbon, like varying micro or meso pores, poor ion mobility due to varying pore distribution, low electrical conductivity, can be overcome by using Graphene and composites of Graphene. Graphene in various structural nomenclatures have been used by different groups for charge storage. Optimization of the electrode structure in terms of blend percentage, binder content and interface character in the frequency and time domain provides insights to the double layer interface structure.

Nanofiltration technology is being investigated as a cost-effective and environmentally acceptable mechanism of sustaining industrial and public water systems. Nanofiber membranes are part of the family of filtration devices being used to remove inorganics and organics from water systems. This study investigates the use of the natural material, Opuntia ficus-indica (Ofi) cactus mucilage, as a tool for nanofiber membrane filtration. Mucilage is a natural, non-toxic, bio-compatible, biodegradable, inexpensive and abundant material. Mucilage is a clear colorless substance comprised of proteins, mono-saccharides, and polysaccharides. It also contains organic species, which give it the capacity to interact with metals, cations and biological substances promoting flocculation for removing arsenic, bacteria, E. coli, and other particulates from drinking water. This natural material has the potential to be used as a sustainable method for water filtration and contaminant sensing. Therefore, mucilage nanofiber membranes were electrospun with volume ratios of polyvinyl alcohol (PVA) and polystyrene (PS) to mucilage comparing the interaction of non-polar solvents. Atomic Fluorescence Spectrometry (AFS) from PSAnalytical was used to evaluate electrospun nanofiber membranes made from volume ratios ranging from 30:70 to 70:30 of mucilage: polyvinyl alcohol, mucilage: polystyrene-D-limonene, and mucilage: polystyrene–toluene in different proportions. The mucilage nanofiber membranes were used as filtration devices for 50 ppb arsenic solutions. Arsenic, being a toxic substance, acts as a deadly poison in water systems and has plagued societal preservation for centuries. The total arsenic content in the samples were measured before and after treatment. Comparative tests were also performed using 1) coated and non-coated GVWP 0.22 µm and 0.45 µm filters from Millipore and 2) columnar flow through Pasteur glass pipets filled with 0.5 g of pre-washed sand from Fisher Scientific and 0.01 g of mucilage nanofibers. Results show mucilage: polystyrene nanofiber membrane filters were capable of removing arsenic from test solutions, in terms of the percentage of arsenic removed. These data elucidate that mucilage nanofiber membranes have the potential to serve as the basis for the next generation of economically sustainable filtration devices that make use of a natural non-toxic material for sustainable water systems.

Carbon nanotubes come in many varieties, with chemical, mechanical, and electrical properties depending on carbon nanotube (CNT) structural morphology. In order to provide a platform for CNT structural tuning, a membrane reactor was designed and constructed. This reactor provided more intimate gas-catalyst contact by decoupling the carbon feedstock gas from carrier gas in a chemical vapour deposition (CVD) environment using an asymmetric membrane and a macroporous membrane. Growth using this membrane reactor demonstrated normalized yield improvements of ∼300% and ∼1000% for the asymmetric and macroporous membrane cases, respectively, over standard CVD methods. To illustrate the possibility for control, growth variation with time was successfully demonstrated by growing vertically aligned multi-walled CNTs to heights of 0.71 mm, 1.36 mm, and 1.84 mm after growth for 15, 30, and 60 minutes in a commercial thermal CVD reactor. To demonstrate CNT diameter control via catalyst particle size, dip coating and spray coating methods were explored using ferrofluid and Fe(NO3)3 systems. CNT diameter was demonstrated to increase with increasing particle size, yielding CNT like growth with diameters ranging from 15 -150 nm. Demonstration of these dimensions of control coupled with the dramatic efficiency increases over growth in a commercialized CVD reactor establish this new reactor technology as a starting point for further research into CNT structural tuning.

We investigate the crystallization of amorphous Ni–P with near-eutectic composition, fabricated by electroless plating as a 10 µm thick continuous layer. Aiming to understand phase transformations that occur upon heating and, in particular, the microscopic mechanism of crystallization, we combine a variety of complimentary characterization techniques. DSC (differential scanning calorimetry) during isothermal heating reveals the crystallization kinetics. Conventional-, high-resolution-, and analytical TEM (transmission electron microscopy) and TEM-based electron diffraction provide high-spatial-resolution information on phase nucleation and spatial distribution of atom species, particularly the crystallography of the nucleating crystalline phases (Ni3P and Ni) and the spatial distribution of phosphorus in the partially and completely crystallized alloy. Our results indicate that crystallization proceeds by homogeneous nucleation of Ni3P grains. Internally, these exhibit a microstructure of radially oriented subgrains containing Ni nano-platelets in a specific crystallographic OR (orientation relationship) with Ni3P. However, the preferred Ni–Ni3P OR differs from those reported in the literature for similar material. Combining our observation on the structure and microstructure of partially and completely crystallized Ni–P with the observed crystallization kinetics provides a deeper understanding of the microscopic mechanism of crystallization.

We present a concept to increase efficiencies utilizing nonlinear elements integrated with our semiconductor nanowire networks. Demonstrated here is power generation with thermoelectric devices made of two nanowire networks, one silicon and one indium phosphide, grown on a mechanically flexible copper substrate. Electron microscopy was utilized to characterize structural integrity of the nanowire networks. Non-linear current-voltage characteristics were observed, which suggests a new platform to increase maximum electrical power generation for a given temperature gradient.

An inline metal organic chemical vapor deposition system was used to deposit tin sulfide at temperatures >500 °C. Tetramethyltin was used as the tin source and diethyldisulfide as the sulfur source. An overhead injector configuration was used delivering both precursors directly over the substrate. The tin and sulfur precursors were premixed before injection to improve chemical reaction in the gas phase. Growth temperatures 500 – 540 °C were employed producing films with approximate 1:1 stoichiometry of Sn and S detected by energy dispersive x-ray spectroscopy. X-ray diffraction showed there to be mixed phases with Sn2S3 present with SnS.

We present a theoretical approach for modeling electrolyte solutions at interfaces that reaches into the mesoscale while retaining molecular detail. The total Hamiltonian of the system includes interactions arising from density and charge density (ion correlation) fluctuations, direct Coulomb interactions between ions, and at interfaces the image interactions, ion-solid and ion-water dispersion interactions. The model was validated against its ability to reproduce ion activity in 1:1 and 2:1 electrolyte solutions in the 0-2 M concentration range, its ability to capture the ion-specific effect in 1:1 electrolytes at the air-water interface, and solvent structure in a confined environment between hydrophobic surfaces, revealing the central role of ion hydration interactions in specific ion thermodynamic properties in the bulk solutions and at interfaces. The model is readily extensible to treat electrolyte interactions and forces across charged solid-water interfaces.

This work presents the electrochemical behavior of Ag/AgCl electrodes (chloride sensors) in cement paste environment, monitored over a period of 180 days via open circuit potential (OCP) readings and electrochemical impedance spectroscopy (EIS). The EIS response indicates modification of the sensors’ morphology, in particular alteration of the AgCl layers, as a result of continuous chloride penetration into the bulk matrix towards the vicinity of the sensor/cement paste interface. A gradual shift to more cathodic OCP values and stabilization at approximately -1mVSCE to 2mVSCE was observed at the end of the test, reflecting chloride content of 820mM to 930mM in the pore solution surrounding the sensors, which differs 5-10% from the chloride concentration in the external solution. The water soluble chloride content in the cement pate, as destructively measured wet chemically by Volhard method and photometry, was in the range of 1100mM - 1300mM i.e. about 30-50% more than the chloride concentration in the external solution. This difference of maximum 50% in the recorded chloride levels is attributed to the fact that the sensors “read” the average amount of free chloride at the interface sensor/cement paste, while the destructively measured water soluble chloride reflects the average free (with possible contribution of physically bound chloride) in the total volume of analyzed cement paste. It can be concluded that for the conditions of this experiment, more reliable free chloride content is measured via the sensors’ readings. Hence, if chloride thresholds for corrosion initiation are to be determined, the sensors’ readings will be more representative and accurate if compared to destructive water soluble chloride determination.

Half-Heusler MNiSn (M=Ti, Zr, Hf) compounds are well-known, excellent n-type thermoelectric materials. The n-type Seebeck coefficients of ZrNiSn are reduced because of the precipitation of the metallic Heusler ZrNi2Sn phase. An excellent n-type Seebeck coefficient can be converted to p-type based on the vacancy site occupation by the solute Co atoms in the half-Heusler TiNiSn phase as well as ZrNiSn. The Heusler phase precipitates, including their precursor nano-structure in the half-Heusler matrix and the vacancy site occupation of the half-Heusler phase, are regarded as lattice defects based on the crystallographically and thermodynamically close relationship between half-Heusler and Heusler phases.

In this presentation, results of our recent investigations on the role of Ga on Al site in Zr69.5Al7.5-xGaxCu12Ni11 and Ce75Al25-xGax metallic glass compositions will be discussed. Ga like Al is normally expected to be in trivalent state. However, it may go in monovalent state depending on other alloying elements. The rapidly solidified melt spun ribbons of above two alloys gave rise to two important conclusions. The Zr69.5Al7.5-xGaxCu12Ni11 system displayed metallic glass formation in the range of x=0 to 7.5. In this process, we have come out with a new composition of glass without Al corresponding to x=7.5. In contrast to the above, for Ce-Al(Ga) system, we have observed phase separation in glass after dilute substitution of Ga. It seems that such a phase separation in this system cannot be understood in terms of summation of enthalpy of mixing of the various possible binaries in this system. The substitution of Ga in different valence states might have created chemical pressure leading to creation of two types of distinct major clusters. The phase separation may be due to this. This has also given rise to excursion of Ce 4f-states of the alloy. This and aforesaid ‘chemical pressure’ will be corroborated based on results of binary Ce-Al system under pressure by other investigators.

The potential ionic conductors Li2APO4 (A = Na, K) are investigated combining experiments and first principles calculations at the Density Functional Theory level. A high ionic conductivity of 6.5 x10−6 and 1.5 x10−5 S cm−1 at 25 and 70°C, respectively, is found in Nalipoite-Li2NaPO4. For this mixed phosphate the energy barriers to Li motion are calculated. The lower energy barrier (0.7 eV) implies the inter-chain diffusion of Li in the b-c plane. We predict that ionic mobility is enhanced in the isostructural Li2KPO4, with the lowest calculated energy barrier being 0.4 eV.

The BiFeO3/BaTiO3 (BFO/BTO) multilayers were deposited on Pt/Ti/SiO2/Si substrates using sol-gel spin coating technique. The electric and magnetic studies on BFO/BTO multilayer structures were carried out for different number of layers. Enhancement in multiferroic properties were seen for all the prepared multilayers as compared to individual BTO and BFO thin films. Maximum value of ferroelectric polarization 71.18 µC/cm2 and saturation magnetization 69.85 emu/cm3 was obtained for multilayer structure having five layers. The observed enhancement in the multiferroic properties of the multilayer system is due to the increased interfacial stress and multiferroic coupling between the alternating layers.

The present work deals with the production and characterization of metal and bimetallic nanopowders.

The electric explosion wire method for production of metal nanopowders is presented. The method enables to produce both metal and bimetallic nanoparticles (BMNP) with controlled content of metals within one particle. An alternative method to obtain bimetallic nanoparticles is also suggested using a spontaneous electrochemical process from salt solutions. BMNP for both Al-Cu and Al-Ni have been prepared and studied.

The oxidation, ignition and thermal reactivity of the BMNP of Al-Cu and Al-Ni in a simultaneous thermogravimetric (TG) and differential scanning calorimetry (DSC) experiments have been carried out. The microstructure has been characterized with a scanning electron microscope (SEM) and transmission electron microscope (TEM). The phase compositions of the reaction products have been investigated with X-ray diffraction.

By comparing the peak temperature of the first exothermic reaction in DSC and the phase transition temperatures in the respective binary systems, it has been found that for Al-Cu BMNP the melting of an alloy played a pivotal role for the early ignition reaction. The comparison of the reactivity of BMNP with that of aluminum nanoparticles has shown a greater reactivity of BMNP Al-Cu and Al-Ni.

We report on our recent progress in the study of single Dibenzoterrylene (DBT) molecules as single photon sources and nanoscale probes. We consider DBT molecules embedded in thin anthracene films, a system that allows stable single photon emission both at room and at cryogenic temperatures. We investigate the most important optical properties of the DBT:anthracene system as a whole. We then perform a full statistical study of the coupling between single DBT molecules by measuring the lifetimes of DBT both in the coupled and in the uncoupled case. The experimental results are framed into a simple universal scaling model, where the magnitude of coupling depends solely on universal parameters and on the distance d between the single emitter and the graphene monolayer. We apply this model to infer d and provide a proof of principle for a position ruler at the nanoscale [1].

Ultrasensitive biosensors based on bottom gate organic field-effect transistors can be developed by depositing a functional biological (protein) interlayer directly on the silicon oxide gate dielectric and underneath the organic semiconductor film. However, the deposition methods for assembling the protein biological recognition layer can affect the biosensor analytical performances for the target analyte detection. Here, spin-coating and layer-by-layer techniques were considered as different approaches for streptavidin protein deposition. X-ray photoelectron spectroscopy (XPS) was systematically used in the non-destructive parallel angle resolved mode to characterize the multilayer device at each step of its assembly to gain information on elemental depth profiles. Scanning electron and scanning Helium ion microscopies gave information about stacked layer structure and morphology corroborating XPS results.

Ionic piezoresistance, the effect of lattice strain on ionic conductivity, is an important concept that needs to be harnessed to engineer the next generation of fast ionic conductors. To date there have been many reports of strain affecting changes in the level of ionic conductivity in solid electrolytes. The fundamental understanding is, however, still lacking, with limited experimental quantification of the magnitude of the effect. Here, we propose using the ionic piezoresistive coefficient, the constant of proportionality between the strain state and the change in conductivity, as a quantitative measure of this effect and detail a novel technique we have developed to quantify this in high temperature ionically conducting materials.

Droplet interface bilayers (DIBs) are physical lipid bilayers that mimic real membranes in living cells, and they are formed quickly using droplets of water and lipids in oil (Fig. 1A). DIBs allow biomolecular sensing and direct detection of transmembrane proteins or peptides and small molecules such as drugs, anesthetics, or even ions. Cell-free expression systems allow in vitro protein synthesis using actual natural machinery extracted from organisms (Fig. 1B). Previous attempts to combine DIBs with cell-free extracts (CFE) encountered bilayer destabilization due to components in the expression system. This study evaluates incorporation of Promega’s T7 S30 High Yield (HY) Expression system with DIBs to pave the way for future in situ expression of light-activated bacteriorhodopsin (BR) and other complex transmembrane proteins in DIBs. A secondary output includes establishing a method for real-time monitoring and modeling of CF expression reactions using minimal volume. The ability to quantify CF output in such small volumes reduces cost per reaction from $20 to around $0.40, and synthesized protein levels reach tens to hundreds of micrograms per milliliter in less than 1 hour at 37°C.

Organic/inorganic (O/I) composite latexes combine the best attributes of inorganic solids with the processability, lightweight and handling advantages of organic polymers. There are common methods to produce polymer nanocomposites: melt compounding, in-situ polymerization and solution mixing. Emulsion polymerization is an unique chemical process widely used to produce waterborne resins with various colloidal and physicochemical properties. This free radical polymerization process involves emulsification of the relatively hydrophobic monomer in water by an oil-in-water emulsifier, followed by the initiation reaction with a water insoluble initiator. This research focuses on the synthesis and reactions kinetics of polyacrylic latex with the incorporation of various nanospheres (SiO2, TiO2, Al2O3 and Fe2O3), and layered silicate (Bentonite nanoclay) nanoparticles via emulsion polymerization. The influence of nanoparticle concentration on reaction kinetics was also investigated. The results showed that the concentration of nanoparticles has significant influence on the monomer conversion, particle size, coagulum content and viscosity of the emulsion. Furthermore, the nanostructured emulsions were shear thinning, exhibiting a power-law behavior, and the viscosity was influenced by the nanoparticle morphology.

So far we ignore how brain stores memory. Neurons communicate by pulses where the charges are carried between them by ions flowing through channels. Those pulses present a characteristic maximum related to the conformational movements of the channel protein opening and closing. Electrochemical responses from dense gel electrodes of conducting polymers mimic those pulses. Here we proved that the biomimetic pulse includes simultaneously electrical, chemical and conformational information related to the energy stored by the initial conformational packed state of the polymer. This energetic memory increases linearly with the potential used to reduce and pack (write) the initial state: hundreds of different values can be written (stored) in a full reproducible way (multivalent memory). Every state constitutes a chemo-ionic-conformational (CHEMICONF) memory. Each multivalent memory is read and erased by the reverse electrochemical reaction. Crosslinking states produce permanent memories not erased while reading. Developing CHEMICONF memories can provide new hypothesis to reveal brain memory mechanisms.

A review is presented of Synchrotron X-ray Topography and KOH etching studies carried out on n type 4H-SiC offcut substrates before and after homo-epitaxial growth to study defect replication and strain relaxation processes and identify the nucleation sources of both interfacial dislocations (IDs) and half-loop arrays (HLAs) which are known to have a deleterious effect on device performance. We show that these types of defects can nucleate during epilayer growth from: (1) short segments of edge oriented basal plane dislocations (BPDs) in the substrate which are drawn by glide into the epilayer; and (2) segments of half loops of BPD that are attached to the substrate surface prior to growth which also glide into the epilayer. It is shown that the initial motion of the short edge oriented BPD segments that are drawn from the substrate into the epilayer is caused by thermal stress resulting from radial temperature gradients experienced by the wafer whilst in the epi-chamber. This same stress also causes the initial glide of the surface half-loop into the epilayer and through the advancing epilayer surface. These mobile BPD segments provide screw oriented segments that pierce the advancing epilayer surface that initially replicate as the crystal grows. Once critical thickness is reached, according to the Mathews-Blakeslee model [1], these screw segments glide sideways under the action of the mismatch stress leaving IDs and HLAs in their wake. The origin of the mismatch stress is shown to be associated with lattice parameter differences at the growth temperature, arising from the differences in doping concentration between substrate and epilayer.