Search

Metal-oxides hold promise as superior plasmonic materials in the mid-infrared compared to metals, although their integration over established material technologies still remains challenging. We demonstrate localized surface plasmons in self-assembled, hemispherical CdZnO metal-oxide nanoparticles on GaAs, as a route to enhance the absorption in mid-infrared photodetectors. In this system, two localized surface plasmon modes are identified at 5.3 and 2.7 μm, which yield an enhancement of the light intensity in the underlying GaAs. In the case of the long-wavelength mode the enhancement is as large as 100 near the interface, and persists at depths down to 50 nm. We show numerically that both modes can be coupled to infrared intersubband transitions in GaAs-based multiple quantum wells, yielding an absorbed power gain as high as 5.5, and allowing light absorption at normal incidence. Experimentally, we demonstrate this coupling in a nanoparticle/multiple quantum well structure, where under p-polarization the intersubband absorption is enhanced by a factor of 2.5 and is still observed under s-polarization, forbidden by the usual absorption selection rules. Thus, the integration of CdZnO on GaAs can help improve the figures of merit of quantum well infrared photodetectors, concept that can be extended to other midinfrared detector technologies.

Despite the successful development of Tokamak nuclear fusion plasma physics devices, commercial power production remains elusive partly due to the severe environments produced during the deuterium-tritium fusion reaction. Nanostructured Ferritic Alloys (NFAs) are candidate structural materials for first-wall/blanket applications. The stainless steels are thermally stable up to 900 °C and remarkably irradiation tolerant. NFAs typically contain a high number density (5x1023/m2) of Y-Ti-O nano-oxides (NOs) with average diameters ≈ 2.5 nm. Most of the smallest NOs are Y2Ti2O7 (YTO) fcc pyrochlore. The NOs impede dislocation climb and glide, stabilize dislocation and grain structures, and trap He in fine-scale bubbles at matrix-NO interfaces. Detailed characterization and analysis of the NO-matrix interfaces is needed to develop first principles and atomic-scale models that are part of multi-scale efforts to predict the behavior of NFAs during processing and in irradiation service environments. YTO-matrix orientation relationships (ORs) are of particular interest because they impact selection of compositions and processing paths, service stability, mechanical properties and irradiation tolerance of NFAs. X-ray absorption spectroscopy (XAS) measurements on embedded NOs are most consistent with Y2Ti2O7, while the slightly larger extracted oxides are primarily consistent with Y2TiO5. A bulk extraction and selective filtration technique was developed to dissolve the ferritic matrix, trap the larger Y2TiO5 oxides, and yield samples well suited for XAS measurements. Further, a 14YWT alloy was annealed to coarsen the NOs, and He implanted to produce bubbles. High resolution transmission electron microscopy shows two dominant ORs (cube-on-edge and cube-on-cube). The smaller NOs are associated with smaller bubbles, while some of the largest NOs (>6 nm) often have two bubbles. Most bubbles nucleate near dislocation cores at {111} NO facets.The second research approach is to study a model bilayer system. For the first time, the dominant deposited Fe-YTO interface ORs are reported. Most Fe grains deposited on {111}YTO have the Nishiyama-Wasserman OR: {110}Fe//{111}YTO and Fe//YTO. The dominant OR for depositions on {100}YTO is: {110}Fe\\{100}YTO and Fe\\YTO. Finally, most Fe grains deposited on {110}YTO show axiotaxial texturing with off-normal {110}Fe planes parallel to off-normal {100}YTO planes. Room temperature He implantation of a Fe-{110}YTO bilayer shows a range of bubble sizes in the Fe film, and larger ~2 nm bubbles at the Fe-YTO interface. In this experiment, He did not diffuse into the YTO. In a second, high temperature implantation, 99.3% of the He remained in the Fe film and interfacial pores, but 0.7% was found in the YTO substrate. The studies performed in this dissertation provide crucial experimental inputs for the development of computational models that accurately predict NFA in-service behavior. The results provide an important step into turning the promise of fusion energy into a reality.

Nanocomposites of metal oxide are considered promising candidates for developing novel gas sensors of exceptional performance. Composite SnO2–Fe2O3 nanoparticles are produced in this work by a modified sole-gel method, and tested for their gas response towards H2S gas in air. The nanoparticles are deposited on a printed substrate with interdigitated electrodes to produce gas sensor devices. Electrical characteristics of the produced devices are tested by means of impedance spectroscopy and revealed an activation energy of 0.13±0.01eV. The sensors exhibit novel characteristics where they are functional at room temperature for low H2S concentration of 2.5 ppm. The practical production process, low power demand, enhanced sensitivity, and low recovery and response times of the fabricated sensors specify their potential for practical implementation for applications of portable gas sensors. Furthermore, the utilization of magnetic nanoparticles enables the recycling of nanocomposites for further applications. This work was supported by Qatar University under grant number, IRCC-2019-003. The Raman, FTIR, TEM, SEM, and EDS measurements were accomplished in the Central Laboratories unit at Qatar University.

Pure, mixed and doped metal oxides (MOX) have attracted great interest for the development of electrical and electrochemical sensors since they are cheaper, faster, easier to operate and capable of online analysis and real-time identification. This review focuses on highly sensitive chemoresistive type sensors based on doped-SnO2, RhO, ZnO-Ca, Smx-CoFe2−xO4 semiconductors used to detect toxic gases (H2, CO, NO2) and volatile organic compounds (VOCs) (e.g., acetone, ethanol) in monitoring of gaseous markers in the breath of patients with specific pathologies and for environmental pollution control. Interesting results about the monitoring of biochemical substances as dopamine, epinephrine, serotonin and glucose have been also reported using electrochemical sensors based on hybrid MOX nanocomposite modified glassy carbon and screen-printed carbon electrodes. The fundamental sensing mechanisms and commercial limitations of the MOX-based electrical and electrochemical sensors are discussed providing research directions to bridge the existing gap between new sensing concepts and real-world analytical applications.

Funder: Aziz Foundation, Funder: Downing College, Cambridge, Funder: Isaac Newton Trust; Id: http://dx.doi.org/10.13039/501100004815, Nickel oxide (NiO x ), a p‐type oxide semiconductor, has gained significant attention due to its versatile and tunable properties. It has become one of the critical materials in wide range of electronics applications, including resistive switching random access memory devices and highly sensitive and selective sensor applications. In addition, the wide band gap and high work function, coupled with the low electron affinity, have made NiO x widely used in emerging optoelectronics and p‐n heterojunctions. The properties of NiO x thin films depend strongly on the deposition method and conditions. Efficient implementation of NiO x in next‐generation devices will require controllable growth and processing methods that can tailor the morphological and electronic properties of the material, but which are also compatible with flexible substrates. In this review, we link together the fundamental properties of NiO x with the chemical processing methods that have been developed to grow the material as thin films, and with its application in electronic devices. We focus solely on thin films, rather than NiO x incorporated with one‐dimensional or two‐dimensional materials. This review starts by discussing how the p‐type nature of NiO x arises and how its stoichiometry affects its electronic and magnetic properties. We discuss the chemical deposition techniques for growing NiO x thin films, including chemical vapor deposition, atomic layer deposition, and a selection of solution processing approaches, and present examples of recent progress made in the implementation of NiO x thin films in devices, both on rigid and flexible substrates. Furthermore, we discuss the remaining challenges and limitations in the deposition of device‐quality NiO x thin films with chemical growth methods. image

Electrosorptive desalination is a very simple and appealing approach to satisfy the increasing demand for drinking water. The large-scale application of this technology calls for the development of easy-to-produce, cheap and highly performing electrode materials and for the identification and tailoring of their most influential properties, as well. Here, biosynthesised bacterial cellulose is used as a carbon precursor for the production of three-dimensional nanostructures endowed with hierarchically porous architecture and different density and type of intrinsic and hetero-atom induced lattice defects. The produced materials exhibit unprecedented desalination capacities for carbon-based electrodes. At an initial concentration of 585 mg L-1 (10 mmol L-1), they are able to remove from 55 to 79 mg g(-1) of salt; as the initial concentration rises to 11.7 g L-1 (200 mmol L-1), their salt adsorption capacity reaches values ranging between 1.03 and 1.35 g g(-1). The results of the thorough material characterisation by complementary techniques evidence that the relative amount of oxygenated surface functional species enhancing the electrode wettability play a crucial role at lower NaCl concentrations, whereas the availability of active non-sp(2) defect sites for adsorption is mainly influential at higher salt concentrations. L.U., M.A.C. and A.E. gratefully thank GIU18/216-UPV/EHU Research Group for the financial support to their work.

In this study, graphene foam/hematite (GF/alpha-Fe2O3) nanowire arrays hetero-structured nanocomposite (HNC) electrode was synthesized in a hierarchical manner where each constituent had its own function. The synthesis of continuous, high crystallinity and intact graphene layers on the surface of Ni foam was carried out via chemical vapor deposition (CVD) and there was no significant deterioration after Ni removal. Acting as an active backing layer, the GF provided a large surface area with high charge transfer capacity, thus facilitating the high electron transfer rate and increased electrochemical response. Hydrothermal synthesis yielded alpha-Fe2O3 nanowires with an average length of 400-450 nm. XPS results showed that the HNC sample was mostly composed of alpha-Fe2O3 phase. Finally, HNC electrode was applied for the construction of an electrochemical glucose biosensor. The increased surface area of the electrode facilitated immobilization of large amounts of glucose oxidase (GOx). Based on the active surface area of the electrode, the limit of detection and sensitivity of the biosensor were calculated to be 71.6 mu M and 20.03 mu AmM(-1)cm(-2), respectively. The high sensitivity and selectivity of HNC for the detection of glucose demonstrated that the synthesized nanocomposite material is a promising material to construct high sensitive biosensors for the detection of biologically relevant molecules. (C) 2021 Elsevier B.V. All rights reserved., Scientific and Technical Research Council of Turkey [TUBITAK] [118M621], This work was supported by the The Scientific and Technical Research Council of Turkey [TUBTAK; grant number: 118M621] .

This work explains the synthesis of an efficient organic hole transporting material based on 4,4'-(5,5'-(thiazolo [5,4-d] thiazole-2,5-diyl) bis(furan-5,2-diyl)) bis(N, N-diphenylaniline) (TP-FTzF-TP) and the replacement of poly (3,4-ethylenedio-xythiophene): poly(styrenesulfonate) (PEDOT:PSS) layer by simple O-2 plasma treatment for perovskite solar cells (PSCs). The introduction of furan spacer groups significantly tuned the absorption and the electrochemical properties of the organic hole transporting material. The ITO(O-2 plasma)/TP-FTzF-TP/CH3NH3PbI3/PC61BM/Au configuration based PSC exhibited a high power conversion efficiency (PCE) of similar to 16.4% which showed a momentous improvement as compared to PCEs of similar to 11.6% and similar to 10.5% achieved by ITO/PEDOT: PSS/TP-FTzF-TP/CH3NH3PbI3/PC61BM/Au and ITO/TP-FTzF-TP/CH3NH3PbI3/PC61BM/Au devices, respectively. The superior performances of PSC were accredited to fast hole injection from the valence band of CH3NH3PbI3 into the suitable HOMO and a high hole mobility of TP-FTzF-TP HTM.

Organic-inorganic hybrid light-emitting diodes (HyLEDs) consist of an organic emission layer in combination with at least one metal oxide charge injection layer, typically in an inverted structure. Low temperature, solution processing of metal oxide charge injection layers is one of the key factors in reducing the manufacture cost of HyLEDs. Herein, we report the use of composite materials, comprising conjugated polyelectrolytes (CPE) and zinc oxide nanoparticles (ZnO NPs), as the electron injection layer (EIL) in highly-efficient, green-light-emitting poly (9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) polymer LEDs that are carefully optimised for use in an inverted HyLED architecture for the first time. The composite CPE:ZnO EILs are processed via a room temperature, one-step, solution deposition and enable superior device performance relative to ZnO NPs on their own. We find that specifically, they (i) improve EIL morphology, reducing surface roughness as well as pin-hole size and density, (ii) induce a favourable vacuum level shift for electron injection by coordinate bonding between the CPE and ZnO constituents, and (iii) reduce interfacial quenching by passivation of ZnO chemical defects caused by oxygen vacancies. This work is also the first demonstration that blending ZnO NPs and CPE supports much faster electroluminescence turn-on times (~7.12 μs) than for traditional ZnO/CPE bilayer devices (~0.4 s) via ‘locking’ of the CPE mobile ions, as well as higher device performance. This demonstrates good suitability for display applications. After optimisation of the EIL composition and the thickness of the F8BT emissive layer, we achieve promising device efficiencies of 16.5 cd/A and 5.4 lm/W for devices with a 1.1 μm thick F8BT layer, which is particularly relevant for potential roll-to-roll fabrication. These results clearly demonstrate the potential that this organic-inorganic composite EIL material has for the realisation of cheap, scalable and highly efficient, printable HyLED devices.

Tungsten (W) is one of the most promising materials to be used in resistive random-access memory electrodes due to its low work function and compatibility with semiconductors, which raises the possibility of device integration, scalability, and low power consumption. However, W has multiple oxidation states that affect device reliability, due to the formation of semistable oxides at the switching interface. W chemical interaction is modulated through the insertion of Al2O3 or Ti interfacial layers. The time-dependent switching kinetics are investigated in transient Set/Reset operations. It is observed that a compact and stoichiometric atomic-layer-deposited Al2O3 barrier layer completely prevents W oxidation, resulting in a sharp current transient. The use of a sputtered Ti buffer layer allows a partial W oxidation, defining a tunable high-resistance state by pulse rise time control. Notable improvements in endurance, power consumption, resistance state stabilization, and cycle-to-cycle and device-to-device variability are reported. Switching kinetics and conductive nanofilament evolution are studied in detail to understand the microscopic effect of the interface modifications. The tunability of multi-HRS states by pulse timing control in Pt/HfO2/Ti/W is in the interest of network and brain-inspired computing applications, adding a degree of freedom in the modulation of its resistance.

We evaluated solid-state sensors (MOS) manufactured using nanostructured tin oxide (SnO2) obtained by different synthesis methods for selectivity, response and repeatability at different operating temperatures and methane concentrations. In addition, Zeolite 13X pellets were placed in front of the sensors to improve CH4 selectivity in the presence of CO2. The palladium doped sensor (1.4% w/w) showed the highest sensitivity at 80 ºC (83%) and shorter response times (16 s), whereas non-doped sensors exhibited the best sensitivity (78%) and response times (14 s) for those with smaller particle size (8 nm). Zeolite 13X pellets proved to be efficient at making the sensor more selective for CH4 in the presence of CO2.

Acetic acid is a potential breath marker for cystic fibrosis and gastroesophageal reflux. Also, it is a key tracer for aroma development in the food industry for chocolate and coffee processing. However, its selective detection down to relevant parts per billion (ppb) concentrations under realistic relative humidity (RH) is most challenging, especially with low-cost sensors. Here, highly porous Y-doped ZnO films for sensing acetic acid down to 10 ppb within 2 min at 90% RH are prepared by single-step flame-aerosol deposition with close control over their composition. X-ray diffraction and energy-dispersive X-ray spectroscopy reveal Y traces inside the ZnO wurtzite nanoparticles assuring small (below 25 nm) and thermally stable crystal sizes even upon annealing at 500 °C for 5 h in air. Separate Y2O3 nanoparticles are formed at elevated Y-contents. At an optimal Y-content of 2.5 mol% and sensing at 350 °C, remarkable selectivities of acetic acid over H2 (200), acetone (15), ethanol (5) and isoprene (3) are obtained. This is attributed to the high surface basicity of Y-doped ZnO featuring up to three orders of magnitude higher acetic acid selectivity than less basic SnO2 and WO3 sensors. Additionally, the influence of RH (10 - 90%) on acetic acid sensing is examined. This sensor is compact and inexpensive, thus promising for integration into hand-held and low-cost food processing or breath monitors., Sensors and Actuators B: Chemical, 327, ISSN:0925-4005

In this article, a unique platform with an organic field-effect transistor (OFET) integrated with metal oxide nanoparticles for sensing of H2S gas is presented. Metal oxide nanoparticles such as SnO2 and ZnO synthesized using herbal techniques were used in the fabrication of OFETs using a bi-layer technique. The as -synthesized nanoparticles were characterized by Field Effect Scanning Electron Microscopy (FESEM), X-ray diffraction (XRD) and UV-vis Spectroscopy (UV-vis) to establish the material properties. We showed that the SnO2 based OFETs displayed better response for H2S at room temperature (25 degrees C) compared to the OFETs fabricated with ZnO. The characterization of the sensors by using extracted electrical parameters like field-effect mobility ([1), On -Current (Ion), threshold voltage (VT) and saturation current (ID]) establish the fact that the SnO2 based OFETs detect H2S gas at room temperature. Plausible mechanisms explaining the H2S gas detection by bi-layer film were discussed. On the other hand, the sensitivity of these OFETs against other reducing gases was less. (C) 2016 Elsevier B.V. All rights reserved.

We explore ultrafast carrier dynamics and interactions of photoexcited carriers with lattice vibrational modes in BiVO4 photoanode material using time-resolved terahertz spectroscopy and first-principles phonon spectrum calculations. We find that photoexcited holes form bound polaron states by introducing lattice distortion that changes phonon spectrum and suppresses the Ag phonon mode associated with opposite motion of Bi and VO4 molecular units. At excitation fluence higher than 1 mJ cm−2 (or 2 × 1015 cm−2 per pulse), lattice distortion due to self-localized holes alters the lattice symmetry and vibrational spectrum, resulting in bleaching of THz absorption by Ag phonons. Concurrently, we observe a short lived population of free carriers which exhibit Drude conductivity with mobility on the order of 200 cm2 V−1 s−1, orders of magnitude higher than typical carrier mobility in BiVO4. The anomalously high carrier mobilities are explained in the framework of a Mott transition. This demonstration of enhanced transport suggests how engineering BiVO4 photoanodes to take advantage of free carrier transport under high excitation conditions may in the future significantly enhance performance of photoelectrochemical devices.

Nanostructured metal oxides and silicates are increasingly applied in catalysis, either as supports or as active species in heterogeneous catalysts, owing to the physicochemical properties that typically distinguish them from bulk oxides, such as higher surface area and a larger fraction of coordinatively unsaturated sites at their surface. Among the different synthetic routes for preparing these oxides, sol-gel is a relatively facile and efficient method. The use of supercritical CO2 (scCO2) in the sol-gel process can be functional to the formation of nanostructured materials. The physical properties of the scCO2 medium can be controlled by adjusting the processing temperature and the pressure of CO2, thus enabling the synthesis conditions to be tuned. This paper provides a review of the studies on the synthesis of oxide nanomaterials via scCO2-assisted sol-gel methods and their catalytic applications. The advantages brought about by scCO2 in the synthesis of oxides are described, and the performance of oxide-based catalysts prepared by scCO2 routes is compared to their counterparts prepared via non-scCO2-assisted methods.

In this paper a charge sense amplifier (CSA) using a 5um In-Ga-Zn-O transistor technology on 15um thick flexible substrate is presented for readout of a 500dpi fingerprint sensor array targeting direct integration with active matrix organic light emitting displays (AMOLED). The CSA achieves a linear input range of 0.8V for rail to rail output at VDD=15V. The CSA comprises of a high gain and stable dual-ended output dual-stage amplifier. The n-type load is driven by a dual-stage buffer and start-up circuit to increase the performance and ensure stability. The amplifier operates down to 6V supply voltage. It achieves 31.17dB DC-gain, 140kHz gain-bandwidth, 53$°$ phase margin and dissipates 87uW at 15V. The footprint of the CSA is 0.3mm2and enables 1fps readout of 1 megapixel 500dpi sensor array. keywords: Thin film transistors,Logic gates,Resistance,amplifier,Dielectrics,igzo,Sensor arrays,Gain,metal-oxide,amoled,dual gate,csa,display,imager,in-panel ispartof: pages:194-197 ispartof: ESSCIRC 2018 - IEEE 44th European Solid State Circuits Conference (ESSCIRC) pages:194-197 ispartof: 44th European Solid State Circuits Conference (ESSCIRC) location:Dresden, Germany date:3 Sep - 6 Sep 2018 status: published

A bilayer WO3 photoelectrode was obtained by radio frequency (RF) plasma sputtering in a reactive 40% O-2/Ar atmosphere by depositing two successive WO3 coatings on a tungsten foil at two different total gas pressures (3 Pa and 1.7 Pa, respectively), followed by calcination at 600 degrees C. Two monolayer samples deposited at each of the two pressures and a bilayer sample deposited at inverted pressures were also prepared. Their photoelectrocatalytic (PEC) activity was evaluated by both Incident Photon-to-Current Efficiency (IPCE) measurements and separate evolution of H-2 and O-2 by water splitting in a two-compartment PEC cell. SEM analysis revealed that the photoanodes have a nanostructured porous double layer surmounting a columnar basement (Staffa-like morphology, after the name of the Scottish island). Mott-Schottky analysis showed that the single layer deposited at 3 Pa has a conduction flat band potential 0.1 V more positive than that deposited at 1.7 Pa. The equivalent n-n heterojunction at the interface of the double-layer creates a built-in electric field that facilitates the photopromoted electron transfer toward the lower lying conduction band material, while the columnar innermost layer introduces percolation paths for efficient electron transport toward the conductive tungsten foil. Both phenomena contribute to decrease the interfacial charge transfer resistance (R-ct) and lead up to a ca. 30% increase in the PEC performance compared to the monolayer and the inverted bilayer coatings and to a 93% faradaic efficiency, which is among the highest reported so far for WO3 photoanodes. Upon methanol addition an outstanding 4-fold photocurrent density increase up to 6.3 mA cm(-2) was attained over the bilayer WO3 photoanode, much larger than the usually observed current doubling effect.

We use conductive atomic force microscopy (CAFM) to study the origin of long-range conductivity in model transparent conductive electrodes composed of networks of reduced graphene oxide (rGOX) and silver nanowires (AgNWs), with nanoscale spatial resolution. Pristine networks of rGOX (1–3 monolayers-thick) and AgNWs exhibit sheet resistances of ∼100–1000 kΩ/□ and 100–900 Ω/□, respectively. When the materials are deposited sequentially to form bilayer rGOX/AgNW electrodes and thermally annealed at 200 °C, the sheet resistance reduces by up to 36% as compared to pristine AgNW networks. CAFM was used to analyze the current spreading in both systems in order to identify the nanoscale phenomena responsible for this effect. For rGOX networks, the low intra-flake conductivity and the inter-flake contact resistance is found to dominate the macroscopic sheet resistance, while for AgNW networks the latter is determined by the density of the inter-AgNW junctions and their associated resistance. In the case of the bilayer rGOX/AgNWs' networks, rGOX flakes are found to form conductive “bridges” between AgNWs. We show that these additional nanoscopic electrical connections are responsible for the enhanced macroscopic conductivity of the bilayer rGOX/AgNW electrodes. Finally, the critical role of thermal annealing on the formation of these nanoscopic connections is discussed. Published version

In this paper, we fabricated p-Co3O4/n-TiO2 heterostructures and investigated their gas sensing properties. The structural and morphological characterization were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy analysis (XPS). The electrical properties of the heterostructure were studied within the temperature range from 293 K to 423 K. Changes in electrical properties and sensing behavior against reducing and oxidizing gases were attributed to the formation of p-n heterojunctions at the Co3O4 and TiO2 interface. In comparison with sensing performed with pristine TiO2 nanotubes (NTs), a significant improvement in H-2 sensing at 200 degrees C was observed, while the sensing response against NO2 decreased for the heterostructures. Additionally, a response against toluene gas, in contrast to pristine TiO2 NTs, appeared in the Co3O4/TiO2 heterostructure samples.

A new procedure for the cosensitization with quantum dots (QDs) and dyes for sensitized solar cells is reported here. Cascade cosensitization of TiO2 electrodes is obtained by the sensitization with CdS QDs and zinc phthalocyanines (ZnPcs), in which ZnPcs containing a sulfur atom are specially designed to produce a cascade injection by direct attachment to QDs. This strategy causes a double synergetic interaction. This is the differentiating point of cascade cosensitization in comparison with other approaches in which dyes with conventional functionalization are anchored to TiO2 electrodes. Cosensitization produces a panchromatic response from the visible to near-IR region already observed with other sensitization strategies. However, cascade cosensitization produces in addition a synergistic interaction between QDs and dye, that it is not merely limited to the complementary light absorption, but dye enhances the efficiency of QD sensitization acting as a passivating agent. The cascade cosensitization concept is demonstrated with using [Co(phen)3]3+/2+ redox electrolyte. The TiO2/CdS QD-ZnPc/[Co(phen)3]3+/2+ sensitized solar cell shows a large improvement of short-circuit photocurrent and open-circuit voltage in comparison with samples just sensitized with QDs. The advent of such cosensitized QD-ZnPc solar cells paves the way to extend the absorbance region of the promising QD-based solar cells and the development of a new family of molecules designed for this purpose. 1) Ministerio de Economía y Competividad 2) Generalitat Valenciana 3) Universitat Jaume I 4) European FEDER funds (CTQ2011-26455, PROMETEO 2012/010, ACOMP/2013/024, ISIC/2012/008, and UJI 12I361.01/1)

Carbon materials such as carbon nanotubes (CNTs), graphene, and reduced graphene oxide (RGO) exhibit unique electrical properties, which are also influenced by the surrounding atmosphere. They are therefore promising sensing materials. Despite the existence of studies reporting the gas-sensing properties of metal oxide (MOx) coated nanostructured carbon, an incomplete understanding of their sensing mechanism remains. Here we report a systematic study on the preparation, characterization, and sensing properties of CNT and RGO composites with SnO2 coating. Atomic layer deposition (ALD) was applied to the conformal coating of the inner and outer walls of CNTs with thin films of SnO2 of various thicknesses, while nonaqueous sol-gel chemistry assisted by microwave heating was used to deposit tin dioxide onto RGO in one step. The sensing properties of SnO2/CNTs and SnO2/RGO heterostructures toward NO2 target gas were investigated as a function of the morphology and density of the metal oxide coating. The general sensing mechanism of carbon-based heterostructures and the role of the various junctions involved are established.

We have synthesized and characterized a series of triphenylamine-based hole-transport materials (HTMs), and studied their function in solid-state dye sensitized solar cells (ss-DSSCs). By increasing the electron-donating strength of functional groups (-H < -Me < -SMe < -OMe) we have systematically shifted the oxidation potential and ensuing photocurrent generation and open-circuit voltage of the solar cells. Correlating the electronic properties of the HTM to the device operation highlights a significant energy offset required between the Dye-HTM highest occupied molecular orbital (HOMO) energy levels. From this study, it is apparent that precise control and tuning of the oxidation potential is a necessity, and usually not achieved with most HTMs developed to date for ss-DSSCs. To significantly increase the efficiency of solid-state DSSCs understanding these properties, and implementing dye-HTM combinations to minimize the required HOMO offset is of central importance. © 2013 The Royal Society of Chemistry.

International audience; During the last decade, an increasing importance has been given to the feedback of mechanical stresses on the chemical diffusion and, further, on corrosion. Many works point the active role of stresses on the material ageing especially on their negative consequences leading to the damaging of structures. Based on a theoretical study and using numerical tools and experimental results our previous works [1,2] on stress/diffusion coupling, highlight the strong influence of stress field on the diffusion process. The aim of the present paper is to describe the influence of some particular morphologies of the metal/oxide interface on both diffusion and oxidation process. The oxidation is assumed to be driven by a mass conservation law (Stefan's law) while the diffusion coefficient of oxygen in metal is locally influenced by the stress field. The stability of a waved-shape interface is studied in both cases: simple diffusion and coupled stress/diffusion process. In this purpose we have developed an original numerical model using a virtual metal/oxide interface of a mono-material with oxygen concentration-dependent parameters, which allows to operate easily with any shape of interface and to use simple finite element meshes. Furthermore, in order to underline in a more obvious way the consequences of mechanical stress on the diffusion process, a particular geometry is studied.

We present an all-solution processed polymer light-emitting diode (PLED) using spincoated zinc oxide (ZnO) and vanadium pentoxide (V2O5) as electron and hole injecting contact, respectively. We compare the performance of these devices to the standard PLED design using PEDOT:PSS as anode and Ba/Al as cathode. We show that the all-solution processed PLEDs have an equal performance as compared to the standard design directly after fabrication. However, the ambient stability of the PLEDs with spincoated transition metal oxide electrodes is exceptionally good in comparison to the standard design. (C) 2012 Elsevier B.V. All rights reserved.

Times Cited: 0 Article English Cited References Count: 36 707sq; Oxide ions in low coordination (O-LC(2-)) Play a major role in adsorption and catalysis properties of CaO powders. They also give specific photoluminescence features that could be used to characterize the distribution of these ions at the molecular level, but up to now, the photoluminescence of defective CaO powders was assigned incompletely. In this study, photoluminescence spectra of defective CaO powders prepared in various ways are recorded at 77 K with unprecedented resolution. A new feature is thus evidenced with an excitation at 320 nm and an emission at 490 nm. Combining infrared and photoluminescence spectroscopies, we show that this feature does not originate from remaining hydroxyl groups, but it completes the set of photoluminescence fingerprints of O-LC(2-) ions on CaO. A revisited assignment of this set is proposed, consistent with the dependence of transition energy on coordination numbers. An application example shows how the photoluminescence spectroscopy can be used as an original tool to compare surface morphologies of CaO samples at the molecular level and under in situ conditions.

A new atomic layer deposition (ALD) process was applied for the homogeneous coating of carbon nanotubes with vanadium oxide. It permits the coating of the inner and outer surface with a highly conformal film of controllable thickness and, hence, the production of high surface area hybrid materials at a so far unprecedented quality. The ALD-coated tubes are used as active component in gas-sensing devices. They show electric responses that are directly related to the peculiar structure, i.e., the p-n heterojunction formed between the support and the film.

PURPOSE. To evaluate the effect of various metal oxides on impact strength (IS), fracture toughness (FT), water sorption (WSP) and solubility (WSL) of heat-cured acrylic resin. MATERIALS AND METHODS. Fifty acrylic resin specimens were fabricated for each test and divided into five groups. Group 1 was the control group and Group 2, 3, 4 and 5 (test groups) included a mixture of 1% TiO2 and 1% Zro(2), 2% Al2O3, 2% TiO2, and 2% ZrO2 by volume, respectively. Rectangular unnotched specimens (50 mm x 6.0 mm x 4.0 mm) were fabricated and drop-tower impact testing machine was used to determine IS. For FT, compact test specimens were fabricated and tests were done with a universal testing machine with a cross-head speed of 5 mm/min. For WSP and WSL, disc-shaped specimens were fabricated and tests were performed in accordance to ISO 1567. ANOVA and Kruskal-Wallis tests were used for statistical analyses. RESULTS. IS and FT values were significantly higher and WSP and WSL values were significantly lower in test groups than in control group (P

The aim of this work is the investigation of the metal-hydride transformation in magnesium (Mg) nanoparticles both as a function of particle size and in response to surface functionalization by clusters of transition metals (TM): Pd, Ni, Ti.Mg nanoparticles were synthesized by the inert-gas condensation technique, which yields single crystals with six-fold symmetry whose average size can be controlled by tuning the inert gas pressure. After the synthesis the nanoparticles were passivated by slow exposure to oxygen, obtaining a core-shell morphology where a metallic core is coated by a MgO shell of about 5 nm thickness.The material structure was investigated by Transmission Electron Microscopy (TEM), also in High Resolution (HRTEM) mode, and by X-Ray Diffraction (XRD). The sorption kinetics were analysed by a volumetric Sievert apparatus, which also allowed for a determination of the activation energies.Small nanoparticles (≈35 nm) display interesting kinetics with gravimetric capacity of 4.5 wt.% at saturation, limited by the oxide fraction. Hydride formation proceeds by one-dimensional growth controlled by diffusion through the hydride, while the reverse transformation to metal involves interface-controlled three-dimensional growth of nuclei formed at constant rate.On the contrary, large nanoparticles (≈450 nm) exhibit very low reactivity due to reduced probability of hydrogen dissociation/recombination and nucleation at the particle surface. For this reason, large nanoparticles were surface-decorated by TM through in situ evaporation in the inert-gas condensation chamber. This procedure results in clusters of 3-4 nm located over a portion of the MgO shell, as shown by XRD and HRTEM on Pd-decorated sample. This treatment results in dramatically improved hydrogen sorption behavior. In fact, previously inert nanoparticles now exhibit of up to 5.6 wt.%.Real-time diffraction studies using Synchrotron Radiation were carried out during hydrogen desorption on the Pd-decorated nanoparticles. We clearly show that a Mg-Pd intermetallic phase is formed after the first heating treatment and takes active part in the transformation.

Localized growth of SnO2 nanowires on top of CMOS compatible micromembranes that incorporate a buried heater and prepatterned interdigitated electrodes has been achieved that presents the advantage that it allows to easily and directly integrate the advantageous properties of quasi-one dimensional structures in an advanced electronic device by a Vapor Liquid Solid (VLS) mechanism. A NWs based sensor of this type is characterized as a low power gas sensor towards NH3 at different temperatures. Stable and reproducible response is obtained, that allows detecting concentrations below the time-weighted average exposure limit for 8h.