Tunable device properties of free-standing inorganic/organic flexible hybrid structures obtained by exfoliation

We report the fabrication of free-standing flexible inorganic/organic hybrid structures by exfoliating ZnO nanostructured films from the flat indium tin oxide (ITO)/silicon/sapphire substrates using poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). Strong interaction between ZnO and PEDOT: PSS and the thermomechanical response of PEDOT: PSS are the key issues for the exfoliation to prevail. The performance of the free-standing hybrid structures as rectifiers and photodetectors is better as compared to ITO supported hybrid structures. It is also shown that device properties of hybrid structures can be tuned by using different electrode materials. (C) 2012 American Institute of Physics. http://dx.doi.org/10.1063/1.4729550]

Accommodating Unwelcome Guests in Inorganic Layered Hosts: Inclusion of Chloranil in a Layered Double Hydroxide

The host-guest chemistry of most inorganic layered solids is limited to ion-exchange reactions. The guest species are either cations or anions to compensate for the charge deficit, either positive or negative, of the inorganic layers. Here, we outline a strategy to include neutral molecules like ortho- and para-chloranil, that are known to be good acceptors in donor-acceptor or charge-transfer complexes, within the galleries of a layered solid. We have succeeded in including neutral ortho- and para-chloranil molecules within the galleries of an Mg-Al layered double hydroxide (LDH) by using charge-transfer interactions with preintercalated p-aminobenzoate ions as the driving force. The p-aminobenzoate ions are introduced in the Mg-Al LDH via ion exchange. The intercalated LDH can adsorb ortho- and para-chloranil from chloroform solutions by forming charge-transfer complexes with the p-aminobenzoate anions present in the galleries. We use X-ray diffraction, spectroscopy, and molecular dynamics simulations to establish the nature of interactions and arrangement of the charge-transfer complex within the galleries of the layered double hydroxide.

Mechanistic Aspects for the Formation of Copper Dimer Bridged by Phosphonic Acid and Extending Its Dimensionality by Organic and Inorganic Linkers: Synthesis, Structural Characterization, Magnetic Properties, and Theoretical Studies

Six new copper metal complexes with formulas Cu(H2O)(2,2'-bpy) (H2L)](2) center dot H4L center dot 4 H2O (1), {Cu(H2O)(2,2'-bpy)-(H3L)}(2)(H2L)]center dot 2H(2)O (2), Cu(H2O)(1,10-phen)(H2L)](2)center dot 6H(2)O (3), Cu(2,2'-bpy)(H2L)](n)center dot nH(2)O (4), Cu(1,10-phen)(H2L)](n)center dot 3nH(2)O (5), and {Cu(2,2'-bpy)(MoO3)}(2)(L)](n)center dot 2nH(2)O (6) have been synthesized starting from p-xylylenediphosphonic acid (H4L) and 2,2'-bipyridine (2,2'-bpy) or 1,10-phenanthroline (1,10-phen) as secondary linkers and characterized by single crystal X-ray diffraction analysis, IR spectroscopy, and thermogravimetric (TG) analysis. All the complexes were synthesized by hydrothermal methods. A dinuclear motif (Cu-dimer) bridged by phosphonic acid represents a new class of simple building unit (SBU) in the construction of coordination architectures in metal phosphonate chemistry. The initial pH of the reaction mixture induced by the secondary linker plays an important role in the formation of the molecular phosphonates 1, 2, and 3. Temperature dependent hydrothermal synthesis of the compounds 1, 2, and 3 reveals the mechanism of the self assembly of the compounds based on the solubility of the phosphonic acid H4L. Two-dimensional coordination polymers 4, 5, and 6, which are formed by increasing the pH of the reaction mixture, comprise Cu-dimers as nodes, organic (H2L) and inorganic (Mo4O12) ligands as linkers. The void space-areas, created by the (4,4) connected nets in compounds 4 and 5, are occupied by lattice water molecules. Thus compounds 4 and 5 have the potential to accommodate guest species/molecules. Variable temperature magnetic studies of the compounds 3, 4, 5, and 6 reveal the antiferromagnetic interactions between the two Cu(II) ions in the eight membered ring, observed in their crystal structures. A density functional theory (DFT) calculation correlates the conformation of the Cu-dimer ring with the magnitude of the exchange parameter based on the torsion angle of the conformation.

A 12 V Substrate-Integrated PbO2-Activated Carbon Asymmetric Hybrid Ultracapacitor with Silica-Gel-Based Inorganic-Polymer Electrolyte

A 12 V Substrate-Integrated PbO2-Activated Carbon hybrid ultracapacitor (SI-PbO2-AC HUCs) with silica-gel sulfuric acid electrolyte is developed and performance tested. The performance of the silica-gel based hybrid ultracapacitor is compared with flooded and AGM-based HUCs. These HUCs comprise substrate-integrated PbO2 (SI-PbO2) as positive electrodes and high surface-area activated carbon with dense graphite-sheet substrate as negative electrodes. 12 V SI-PbO2-AC HUCs with flooded, AGM and gel electrolytes are found to have capacitance values of 308 F, 184 F, and 269 F at C-rate and can be pulse charged and discharged for 100,000 cycles with only a nominal decrease in their capacitance values. The best performance is exhibited by gel-electrolyte HUCs.

Advanced multifunctional inorganic nanostructured oxides for controlled release and sensing

ADVANCED MULTIFUNCTIONAL INORGANIC NANOSTRUCTURED OXIDES FOR CONTROLLED RELEASE AND SENSING. We demonstrate here certain examples of multifunctional nanostructured oxidematerials for biotechnological and environmental applications.Various in-house synthesized homogeneous nanostructured viz.mesoporous and nanotubes silica and titania have been employed for controlled drug delivery and electrochemical biosensing applications. Confinement of macromolecules such as proteins studied via electrochemical, thermal and spectroscopic methods showed no detrimental effect on native protein structure and function, thus suggesting effective utility of oxide nanostructures as bio-encapsulators. Multi-functionalitywas demonstrated via employing similar nanostructures for sensing organic water pollutants e.g. textile dyes.

YGa1-xMnxO3: A novel purple inorganic pigment

A purple inorganic pigment, YGa1-xMnxO3 (0 < x <= 0.10), based on hexagonal YGaO3 is reported here. The metastable series of oxides were prepared by a sol-gel technique where the dried gels, obtained from aqueous solutions of metal nitrate-citric acid mixtures, were calcined for a short duration in a preheated furnace around 850 degrees C. The purple colour of the oxides arises from the specific trigonal bipyramidal ligand field around Mn-III in a YGaO3 host. Other hexagonal RGaO3 hosts for R = Lu, Tm and Ho substituted with Mn-III also produce similar purple coloured materials.

Polyvinylbutyral based hybrid organic/inorganic films as a moisture barrier material

Flexible and thermally stable, freestanding hybrid organic/inorganic based polymer-composite films have been fabricated using a simple solution casting method. Polyvinylbutyral and amine functionalized mesoporous silica were used to synthesize the composite. An additional polyol-''tripentaerythritol''-component was also used to increase the -OH group content in the composite matrix. The moisture permeability of the composites was investigated by following a calcium degradation test protocol. This showed a reduction in the moisture permeability with the increase in functionalized silica loadings in the matrix. A reduction in permeability was observed for the composites as compared to the neat polymer film. The thermal and mechanical properties of these composites were also investigated by various techniques like thermogravimetric analysis, differential scanning calorimetry, tensile experiments, and dynamic mechanical analysis. It was observed that these properties detonate with the increase in the functionalized silica content and hence an optimized loading is required in order to retain critical properties. This deterioration is due to the aggregation of the fillers in the matrix. Furthermore, the films were used to encapsulate P3HT (poly 3 hexyl thiophene) based organic Schottky structured diodes, and the diode characteristics under accelerated aging conditions were studied. The weathered diodes, encapsulated with composite film showed an improvement in the lifetime as compared to neat polymer film. The initial investigation of these films suggests that they can be used as a moisture barrier layer for organic electronics encapsulation application.

Exploring the color of transition metal ions in irregular coordination geometries: new colored inorganic oxides based on the spiroffite structure, Zn2-xMxTe3O8 (M = Co, Ni, Cu)

We describe the synthesis, crystal structures, and optical absorption spectra of transition metal substituted spiroffite derivatives, Zn2-xMxTe3O8 (M-II = Co, Ni, Cu; 0 < x <= 1.0). The oxides are readily synthesized by solid state reaction of stoichiometric mixtures of the constituent binaries at 620 degrees C. Reitveld refinement of the crystal structures from powder X-ray diffraction (XRD) data shows that the Zn/MO6 octahedra are strongly distorted, as in the parent Zn2Te3O8 structure, consisting of five relatively short Zn/M-II-O bonds (1.898-2.236 angstrom) and one longer Zn/M-II-O bond (2.356-2.519 angstrom). We have interpreted the unique colors and the optical absorption/diffuse reflectance spectra of Zn2-xMxTe3O8 in the visible, in terms of the observed/irregular coordination geometry of the Zn/M-II-O chromophores. We could not however prepare the fully substituted M2Te3O8 (M-II = Co, Ni, Cu) by the direct solid state reaction method. Density Functional Theory (DFT) modeling of the electronic structure of both the parent and the transition metal substituted derivatives provides new insights into the bonding and the role of transition metals toward the origin of color in these materials. We believe that transition metal substituted spiroffites Zn2-xMxTe3O8 reported here suggest new directions for the development of colored inorganic materials/pigments featuring irregular/distorted oxygen coordination polyhedra around transition metal ions.

Seeded-growth, nanocrystal-fusion, ion-exchange and inorganic-ligand mediated formation of semiconductor-based colloidal heterostructured nanocrystals

This article highlights different synthetic strategies for the preparation of colloidal heterostructured nanocrystals, where at least one component of the constituent nanostructure is a semiconductor. Growth of shell material on a core nanocrystal acting as a seed for heterogeneous nucleation of the shell has been discussed. This seeded-growth technique, being one of the most heavily explored mechanisms, has already been discussed in many other excellent review articles. However, here our discussion has been focused differently based on composition (semiconductor@semiconductor, magnet@semiconductor, metal@semiconductor and vice versa), shape anisotropy of the shell growth, and synthetic methodology such as one-step vs. multi-step. The relatively less explored strategy of preparing heterostructures via colloidal sintering of different nanostructures, known as nanocrystal-fusion, has been reviewed here. The ion-exchange strategy, which has recently attracted huge research interest, where compositional tuning of nanocrystals can be achieved by exchanging either the cation or anion of a nanocrystal, has also been discussed. Specifically, controlled partial ion exchange has been critically reviewed as a viable synthetic strategy for the fabrication of heterostructures. Notably, we have also included the very recent methodology of utilizing inorganic ligands for the fabrication of heterostructured colloidal nanocrystals. This unique strategy of inorganic ligands has appeared as a new frontier for the synthesis of heterostructures and is reviewed in detail here for the first time. In all these cases, recent developments have been discussed with greater detail to add upon the existing reviews on this broad topic of semiconductor-based colloidal heterostructured nanocrystals.

Nanocomposite Based Organic-Inorganic Cu3BiS3 High Sensitive Hybrid Photonic Devices

We report the synthesis and application Cu3BiS3 nanorods in infrared photodectection. Cu3BiS3 nano rods were characterized structurally, optically and electrically. The detailed IR photodectection properties in terms of photo response were demonstrated with IA lamp and 1064 nm laser illuminations. The rapid photocurrent time constants followed by the slower components, resulting due to the defect states. The photo detecting properties for different concentrations of nanorods blended with the conjugate polymer devices were demonstrated. Further the photocurrent was enhanced to threefold increase from 3.47 x 10(-7) A to 2.37 x 10(-3) A at 1 V for 10 mg nanorods embedded in the polymer device. Responsivity of hybrid device was enhanced from 0.0158 NW to 102 NW. The detailed trap assisted space charge transport properties were studied considering the different regimes. Hence Cu3BiS3 can be a promising candidate in the nano switchable near IA photodetectors.

Organic-inorganic hybrid PtCo nanoparticle with high electrocatalytic activity and durability for oxygen reduction

In Pt-transition metal (TM) alloy catalysts, the electron transfer from the TM to Pt is retarded owing to the inevitable oxidation of the TM surface by oxygen. In addition, acidic electrolytes such as those employed in fuel cells accelerate the dissolution of the surface TM oxide, which leads to catalyst degradation. Herein, we propose a novel synthesis strategy that selectively modifies the electronic structure of surface Co atoms with N-containing polymers, resulting in highly active and durable PtCo nanoparticle catalysts useful for the oxygen reduction reaction (ORR). The polymer, which is functionalized on carbon black, selectively interacts with the Co precursor, resulting in Co-N bond formation on the PtCo nanoparticle surface. Electron transfer from Co to Pt in the PtCo nanoparticles modified by the polymer is enhanced by the increase in the difference in electronegativity between Pt and Co compared with that in bare PtCo nanoparticles with the TM surface oxides. In addition, the dissolution of Co and Pt is prevented by the selective passivation of surface Co atoms and the decrease in the O-binding energy of surface Pt atoms. As a result, the catalytic activity and durability of PtCo nanoparticles for the ORR are significantly improved by the electronic ensemble effects. The proposed organic/inorganic hybrid concept will provide new insights into the tuning of nanomaterials consisting of heterogeneous metallic elements for various electrochemical and chemical applications.

All Inorganic Spin-Coated Nanoparticle-Based Capacitive Memory Devices

We demonstrate all inorganic, robust, cost-effective, spin-coated, two-terminal capacitive memory metal-oxide nanoparticle-oxide-semiconductor devices with cadmium telluride nanoparticles sandwiched between aluminum oxide phosphate layers to form the dielectric memory stack. Using a novel high-speed circuit to decouple reading and writing, experimentally measured memory windows, programming voltages, retention times, and endurance are comparable with or better than the two-terminal memory devices realized using other fabrication techniques.

Impacts of inorganic turbidity on diquat efficacy against Egeria densa

In clear water, diquat [6,7-dihydrodipyrido (1,2-1a:2',1'-c) pyrazinediium dibromide] provides excellent submersed Plant control at low concentrations, such as <0.5 mg active ingredient (ai) L-1: however. turbid water conditions can interfere with the activity and effectiveness of this herbicide. Little work has been done to examine what ranges of turbidity caused by different Suspended sediment types affect diquat efficacy against a target species. A growth chamber study was conducted rising diquat against the submersed macrophyte -egeria (Egeria densa Planch.) under a range Of turbid conditions. Two materials were used to create turbid beater conditions: 100% bentonite clay for a "worst-case" scenario and a natural partial-clav (20% clay). Results indicated that a high rate of diquat (2 mg ai L-1) controlled egeria under relatively low levels of turbidity (5-10 NTU) using bentonite clay: however. higher levels (25 to 50 NTU) of turbidity essentially blocked effectiveness of diquat when applied at all rates tested (0.5. 1, 2 mg ai L-1). When using a natural partial-clay sediment, rates of 1 to 2 mg ai L-1 diquat provided good control of egeria in moderately turbid water (15 NTU). Additional evaluations rising different clay types would be useful to determine the effect of inorganic turbidity oil diquat efficacy.

In situ measurement of dissolved inorganic carbon speciation in natural waters, pH, pC02, TA, & TC02, Honolulu, Hawaii, February 16-18, 2005: workshop proceedings

The Alliance for Coastal Technology (ACT) convened a workshop on the in situ measurement of dissolved inorganic carbon species in natural waters in Honolulu, Hawaii, on February 16, 17, and 18, 2005. The workshop was designed to summarize existing technologies for measuring the abundance and speciation of dissolved inorganic carbon and to make strategic recommendations for future development and application of these technologies to coastal research and management. The workshop was not focused on any specific technology, however, most of the attention of the workshop was on in situ pC02 sensors given their recent development and use on moorings for the measurement of global carbon fluxes. In addition, the problems and limitations arising from the long-term deployment of systems designed for the measurement of pH, total dissolved inorganic carbon (DIC), and total alkalinity (TA) were discussed. Participants included researchers involved in carbon biogeochemistry, industry representatives, and coastal resource managers. The primary questions asked during the workshop were: I. What are the major impediments to transform presently used shipboard pC02 measurement systems for use on cost-eficient moorings? 2. What are the major technical hurdles for the in situ measurement of TA and DIC? 3. What specific information do we need to coordinate efforts for proof of concept' testing of existing and new technologies, inter-calibration of those technologies, better software development, and more precise knowledge quantzjjing the geochemistry of dissolved inoeanic carbon species in order to develop an observing system for dissolved inorganic carbon? Based on the discussion resulting from these three questions, the following statements were made: Statement No. 1 Cost-effective, self-contained technologies for making long-term, accurate measurements of the partial pressure of C02 gas in water already exist and at present are ready for deployment on moorings in coastal observing systems. Statement No. 2 Cost-effective, self-contained systems for the measurement of pH, TA, and DIC are still needed to both fully define the carbonate chemistry of coastal waters and the fluxes of carbon between major biogeochemical compartments (e.g., air-sea, shelf-slope, water column-sediment, etc.). (pdf contains 23 pages)