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In the field of energy storage by high-rate supercapacitors, there has been an upper limit for the total interfacial capacitance of carbon-based materials. This upper limit originates from both quantum and electric double-layer capacitances. Surpassing this limit has been the focus of intense research in this field. Here, we precisely investigate the effect of chemical functional groups and physical confinement on the electrochemical performance of graphene nanoribbons. We present the results of a quasi-one-dimensional single-layer graphene nanoribbon (120 nm in width and ∼100 μm in length) microelectrode fabricated by mechanical exfoliation of graphite, followed by electron beam lithography process and oxygen plasma etching treatment. We directly measure the interfacial capacitance as a function of frequency at different potentials in an aqueous electrolyte using a three-electrode electrochemical system. Electrochemical impedance spectroscopy and cyclic voltammetry tests show an average capacitance of 75...

Introduction: Semiconductor quantum dots (QDs), especially those containing cadmium, have undergone marked improvements and are now widely used nanomaterials in applicable biological fields. However, great concerns exist regarding their toxicity in biomedical applications. Because of the lack of sufficient data regarding the toxicity mechanism of QDs, this study aimed to evaluate the cytotoxicity of three types of QDs: CdTe QDs, high yield CdTe QDs, and CdTe/CdS core/shell QDs on two human breast cancer cell lines MDA-MB468 and MCF-7. Methods: The breast cancer cells were treated with different concentrations of QDs, and cell viability was evaluated via MTT assay. Hoechst staining was applied for observation of morphological changes due to apoptosis. Apoptotic DNA fragmentation was visualized by the agarose gel electrophoresis assay. Flow cytometric annexin V/propidium iodide (PI) measurement was used for apoptosis detection. Results: A significant decrease in cell viability was observed after QDs treatment ( p < 0.05). Apoptotic bodies and chromatin condensation was observed by Hoechst staining. DNA fragmentation assay demonstrated a DNA ladder profile in the exposed cells and also annexin V/PI flow cytometry confirmed apoptosis in a dose-dependent manner. Conclusion: Our results revealed that CdTe, high yield CdTe, and CdTe/CdS core/shell QDs induce apoptosis in breast cancer cell lines in a dose-dependent manner. This study would help realizing the underlying cytotoxicity mechanism, at least partly, of CdTe QDs and may provide information for the development of nanotoxicology and safe use of biological applications of QDs.

Transition metal oxides are being more frequently used as hole injection layer (HIL) in organic light emitting diodes (OLEDs), in place of polymer HILs such as PEDOT:PSS. The very thin films of the metal oxide HILs are usually deposited using vapor deposition, in order to create uniform films. Here, we report OLEDs fabricated using solution processed MoOx films as the HIL and super yellow as the emissive layer. The performance of the devices is comparable to PEDOT:PSS based devices, while the stability tests show the lifetime of MoOx-based devices is 4 × 106 h, about 40 times longer than PEDOT:PSS devices, at typical working condition. X-ray photoelectron spectroscopy (XPS) indicates both Mo5+ and Mo6+ states in the film. The Oxygen vacant MoO3 film shows bandgap states close to valence band, as confirmed by ultraviolet photoelectron spectroscopy and optical absorption. The method show promise for all-solution- processed LEDs utilizing metal oxide HILs.

Growing demands for clean and renewable energy technologies have sparked broad research on the development of highly efficient and stable non-noble metal electrocatalysts for oxygen evolution reaction (OER). In this regard, in the present work a three-dimensional Fe2TiO5/nitrogen-doped graphene (denoted as 3D FTO/NG) hybrid electrocatalyst was synthesized via a facile in-situ process using a hydrothermal method. Structural characterization of the prepared nanocomposite is performed by various techniques e.g. field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) analysis, Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy spectra (XPS), X-ray diffraction (XRD) and Raman spectroscopic methods. A novel binder-free electrode for OER activity has been prepared by coating a 3D FTO/NG onto nickel foam (NF). In particular, the 3D FTO/NG nanocomposite, which is synthesized with in-situ hydrothermal process, exhibited a remarkable OER performance in alkaline media. The prepared electrocatalyst showed a small overpotential of 0.36 V with a Tafel slope of 0.07 V dec−1 at 100 A m−2 with a long-term stability for OER reaction in 1 M KOH. The outstanding OER performance and durability of 3D FTO/NG can be attributed to the synergistic effects originating from NG and FTO in the prepared electrocatalyst, which helps to enhance the conductivity of the nanocomposite. The presence of conductive NG in the prepared 3D nanocomposite can not only improve the mechanical stability, but also facilitate its electron transport. Also, N atoms and FTO provide abundant electrocatalytic active sites, which accelerate evolution of gas bubbles. This work provides a promising approach for synthesis of inexpensive and efficient OER electrocatalysts.

During the past few years, a considerable attention has been devoted to the development of textile- based energy storage devices and wearable electronics applications. In this paper, for the first time, we report a flexible high performance graphene-based supercapacitor using silver fiber fabric as the current collector. The silver fiber fabric offers remarkable advantages such as light weight, mechanical flexibility and ease of integration with electronic textiles, which well-suited for wearable energy storage devices. A new hybrid material of graphene-silver fiber fabric (rGO/SFF) was prepared through a facile electrophoretic deposition of graphene and being used as a binder-free flexible supercapacitor electrode. In order to obtain the optimum condition, the effect of deposition time was investigated and a duration time of 10 minute was selected as an optimum condition. The as-prepared binder-free electrode based on rGO/SFF-10 showed excellent electrochemical performance in the three-electrode configuration using KOH (3 M) as the supporting electrolyte, with the highest capacity of 172 mF/cm2 at 4 mA/cm2 and a capacitance retention of 97% after 5000 charge−discharge cycles. The high performance of rGO/SFF electrode is associated to the superior conductivity, high mechanical flexibility as well as good electrochemical stability of the silver fiber fabrics. The results suggest that the prepared electrode is a promising candidate for wearable energy storage applications due to its advantageous properties and the ease of preparation.

In this study, ethanol gas sensing of PVP fiber membranes based on Quartz Crystal Microbalance (QCM) was investigated. The fibers were deposited on the QCM’s electrodes by electrospinning the viscous blend solutions of PVP. The effects of PVP concentration on morphology of the fibers and their permeability when exposed to ethanol were investigated. Membranes which were prepared using low concentration solutions, contained beads and high packing fibers and showed low permeability. Increase of the PVP concentration to 12 wt% resulted in continuous fine fibers with good permeability. Furthermore, higher PVP concentrations were found to decrease ethanol permeability due to larger fiber radius and lower surface area. Moreover, effects of fibrous layer thickness on gas response was examined. Consequently, optimum amount of PVP concentration and fibrous layer thickness for the best gas response was found.

Hybrid light emitting diodes (HyLED) with a structure of FTO/ZnO/F8BT/MoO 3 /Au/Ag is fabricated and the influence of surface roughness of cathode (FTO/ZnO) is investigated. The roughness of FTO could be decreased from 9.2 nm to 2.2 nm using a mild polishing process. The ZnO film, deposited by spray pyrolysis, functions as an electron injection layer. The roughness of the FTO/ZnO surface is found also highly dependent on the ZnO thickness. For thin ZnO films (20 nm), polishing results in better efficacy and power efficiency of LED devices, with nearly a two times improvement. For thick ZnO films (210 nm), the overall FTO/ZnO roughness is almost independent of the FTO roughness, hence both polished and unpolished substrates exhibit identical performance. Increasing ZnO thickness generally improves the electron injection condition, leading to lower turn on voltage and higher current and power efficiencies. However, for too large ZnO thickness (210 nm) the ohmic loss across the film dominates and deteriorates the performance. While the polished substrates show less device sensitivity to ZnO thickness and better performance at thin ZnO layer, best performance is obtained for unpolished substrates with 110 nm ZnO thickness. Larger interface area of ZnO/F8BT and enhanced electric filed at sharp peaks/valleys could be the reason for better performance of devices with unpolished substrates.

CdSe nanowires were grown in polycarbonate track etched membrane with pore diameter of 80 nm by an electrochemical deposition technique. The mechanism of the growth was studied during the potentiostatic deposition of nanowires. X-ray photoelectron spectroscopy and energy dispersive spectrometry results showed binding of fragments and fraction of atoms for the CdSe nanowires. Microstructure and morphology of synthesized CdSe nanowires were observed by scanning electron microscopy. Optical spectrophotometry technique was used to determine the energy band gap of CdSe nanowires. It was found that the nanowires were resistive in the dark and exhibited a pronounced visible light photoconductivity. Photoconductivity of CdSe nanowire-based nanodevice (an integrated multilayer nanodevice of Cu/CdSe nanowire array/Au thin films) was investigated which indicated an enhanced photoconductive response in contrast to the previously reported results. The photosensitivity of this multilayer nanodevice was found to be about 110, which this sensitivity is one order of magnitude greater than that reported in similar works.

Pd–WO3 nanostructures were incorporated on graphene oxide (GO) and partially reduced graphene oxide (PRGO) sheets using a controlled hydrothermal process to fabricate effective hydrogen gas sensors. Pd–WO3 nanostructures showed ribbon-like morphologies and Pd–WO3/GO presented an irregular nanostructured form, while Pd–WO3/PRGO exhibited a hierarchical nanostructure with a high surface area. Gas sensing properties of thin films of these materials were studied for different hydrogen concentrations (from 20 to 10,000 ppm) at various temperatures (from room temperature to 250 °C). Although adding GO in the Pd–WO3, after hydrothermal process could increase the film conductivity, gas sensitivity was reduced to half, due to lower surface area of the irregular morphology in comparison with the ribbon-like morphology. The Pd–WO3/PRGO films showed an optimum sensitivity (∼10 folds better than the sensitivity of Pd–WO3/GO), and a fast response and recovery time (

We have synthesized ZnxCd1−xS nanocrystals (NCs) using a microwave assisted method. Zn(Ac)2, CdSO4 and Na2S2O3 were used as the precursors and thioglycerol (TG) was used as the capping agent. Na2S2O3 is a photo and heat sensitive material, which supplies S species needed for the reaction upon dissociation. In this facile method, microwave irradiation provides the activation energy for the dissociation of Na2S2O3 in and leads to the formation of ZnxCd1−xS NCs in 2 min. The question that to what extent Zn is incorporated into CdS structure was addressed using UV–Vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Our results showed that the real value of x in ZnxCd1−xS NCs is less than the initial values of Zn. Also we have given evidence indicating the formation of a gradient alloyed structure for ZnxCd1−xS NCs. The NCs sizes were calculated by effective mass approximation, using real calculated x values. Photoluminescence spectra indicated a blue-shift by increasing x value, which is consistent with band gap shift.

The photoanodes of solid state dye sensitized solar cells (ss-DSCs) embedded with different contents of TiO2 hollow spheres (HSs) were prepared and the photovoltaic performances were systematically characterized. TiO2 hollow spheres were synthesized by a facile sacrificial templating method, grounded and added in different ratios to TiO2 nanoparticle (NP) paste, from which composite HS/NP electrodes were fabricated. The composite photoanodes include hollow spheres of 300–700 nm with enhanced light scattering characteristics in visible range which leads to improved light absorption in conventional thin film electrodes of ss-DSC. By optimizing the amount of HSs in the paste, 40% improvement in efficiency was obtained in comparison to ss-DSC utilized pure NP electrodes. By increasing the fraction of HSs in the electrode the current density increased by 56% (from 2.5 to 3.9 mA cm−2). The improved photovoltaic performance of ss-DSC is primarily due to different morphology and altered charged trap distribution in HSs in comparison to NP which leads to significant enhancement in electron transport time and electron lifetime as well as charge collection efficiency and light absorption properties.

As a bi-functional cancer treatment agent, a new hybrid nanostructure is presented which can be used for photothermal therapy by exposure to one order of magnitude lower laser powers compared to similar nanostructures in addition to substantial enhancment in magnetic resonance imaging (MRI) contrast. This gold-iron oxide hybrid nanostructure (GIHN) is synthesized by a cost-effective and high yield water-based approach. The GIHN is sheilded by PEG. Therefore, it shows high hemo and biocompatibility and more than six month stability. Alongside earlier nanostructures, the heat generation rate of GIHN is compareable with surfactnat-capped gold nanorods (GNRs). Two reasons are behind this enhancement: Firstly the distance between GNRs and SPIONs is adjusted in a way that the surface plasmon resonance of the new nanostructure is similar to bare GNRs and secondly the fraction of GNRs is raised in the hybrid nanostructure. GIHN is then applied as a photothermal agent using laser irradiation with power as low as 0.5 W.cm−2 and only 32% of human breast adenocarcinoma cells could survive. The GIHN also acts as a dose-dependent transvers relaxation time (T2) MRI contrast agent. The results show that the GINH can be considered as a good candidate for multimodal photothermal therapy and MRI.

Reduced graphene oxide (RGO) was used to improve the hydrogen sensing properties of Pd and Pt-decorated TiO2 nanoparticles by facile production routes. The TiO2 nanoparticles were synthesized by sol–gel method and coupled on GO sheets via a photoreduction process. The Pd or Pt nanoparticles were decorated on the TiO2/RGO hybrid structures by chemical reduction. X-ray photoelectron spectroscopy demonstrated that GO reduction is done by the TiO2 nanoparticles and Ti–C bonds are formed between the TiO2 and the RGO sheets as well. Gas sensing was studied with different concentrations of hydrogen ranging from 100 to 10,000 ppm at various temperatures. High sensitivity (92%) and fast response time (less than 20 s) at 500 ppm of hydrogen were observed for the sample with low concentration of Pd (2 wt.%) decorated on the TiO2/RGO sample at a relatively low temperature (180 °C). The RGO sheets, by playing scaffold role in these hybrid structures, provide new pathways for gas diffusion and preferential channels for electrical current. Based on the proposed mechanisms, Pd/TiO2/RGO sample indicated better sensing performance compared to the Pt/TiO2/RGO. Greater rate of spill-over effect and dissociation of hydrogen molecules on Pd are considered as possible causes of the enhanced sensitivity in Pd/TiO2/RGO.

A novel approach for particles size separation based on dielectrophoresis (DEP) method is introduced and analyzed both computationally and experimentally. The proposed technique has been utilized for the separation of polystyrene (PS) particles with 8, 6 and 2 μm diameters passing through microchannels with planar electrodes. The performance of the technique has been computationally analyzed using the finite element method (FEM). Considering the structure of the planar electrodes, we propose an approach based on applying an electric potential between one of the global electrodes, and a needle touched the top of the cell suspension. Results of both simulation and experiment show that by applying a proper voltage with 500 kHz frequency, the PS particles with 6 and 8 μm diameters will freeze in the direction of the channel while the smaller particles can pass by and exit from the outlet of the channel. Results have shown that the DEP force exerted on the particles by the middle electrode (needle) is stronger and the separation yield is higher compared with the conventional methods.

The influence of an externally applied bias on photocatalytic performance of crystallized TiO2/Ti nanotubular electrode formed by anodization in fluoride-based electrolyte were investigated and compared to the behavior of multiporous TiO2 electrode. The photoelectrocatalytic oxidation behavior of methanol over the nanotubular electrode has been studied by measuring photocurrent response, potentiodynamic polarization spectroscopy and using electrochemical impedance spectroscopy (EIS). It was found that the photoelectrocatalytic oxidation and the charge transfer rate constant of reaction on TiO2/Ti nanotubular electrode can significantly be increased by applying electrochemical bias. Moreover, based on the results, it was found that the nanotubular TiO2 electrodes have considerably better performance in comparison with porous samples in photoelectrocatalytic performance.

A comparison of X-ray photoemission spectroscopy of Mg doped Cu0.5Tl0.5Ba2Ca1.5Mg0.5Cu3O10−δ and Mg free Cu0.5Tl0.5Ba2Ca2Cu3O10−δ superconductor samples have been made. The main objective of these studies is to see the effect of Mg doping in developing better inter-plane coupling among the CuO2 planes and its effects on the chemical shift of the bonding species. Through these studies it is observed that thallium is in Tl+1 oxidation state in the Cu0.5Tl0.5Ba2O4−δ charge reservoir layer in both Mg doped and Mg free samples, however, the XPS line related to Ba atoms are shifted to higher binding energy side by 0.32 eV in Mg doped sample. This chemical shift is most likely due to presence of Ba atoms in the immediate vicinity of Mg atoms in Cu0.5Tl0.5Ba2(Ca0.5Mg1.5)Cu3O10−δ samples. Moreover, the binding energy of Cu atoms observed in XPS measurements is significantly shifted in magnesium substituted samples, which has provided an unequivocal evidence of enhanced inter-plane coupling. The enhanced inter-plane coupling promotes the enhancement of kF, ξc, VF, and hence the superconductivity parameters.

The high temperature superconductor thin films Cu1−xTlxBa2Ca3Cu4O12−δ (Cu1−xTlx- 1234) are post-annealed in a nitrogen atmosphere. The zero-resistivity critical temperature (Tc(R = 0)) of these thin films is increased from 92.3 to 104 K. The grain size is enhanced and their morphology is improved with the post-annealing. The enlargement of grain size is linked to fluctuation-induced conductivity (FIC) in the light of Aslamazov–Larkin (AL) theory. The FIC measurements have shown that the cross-over of three-dimensional (3D) to two-dimensional (2D) behaviour of fluctuations is shifted to higher temperature values with an increase of post-annealing temperature. These results have shown that the removal of oxygen and the increased grain size are the most likely sources of the increase in the cross-over temperature, T* to higher values.

The X-ray photoemission (XPS) measurements of Cu 1− x Tl x Ba 2 Ca 2 Cu 3− y Zn y O 10− δ ( y = 0, 2.65) superconductors have been performed and compared. These studies revealed that the charge state of thallium in the Cu 0.5 Tl 0.5 Ba 2 O 4− δ charge reservoir layer in Zn doped samples is Tl 1+ , while it is a mix of Tl 1+ and Tl 2+ in Zn free samples. The binding energy of Ba atoms in the Zn doped samples is shifted to higher energy, which when considered along with the presence of Tl 1+ suggested that it more efficiently directed the carriers to ZnO 2 and CuO 2 planes. The evidence of improved inter-plane coupling witnessed in X-ray diffraction is also confirmed by XPS measurements of Ca atoms in the Zn doped samples. The shift of the valance band spectrum in these Zn doped samples to higher energies suggested that the electrons at the top edge of the valance band were tied to a higher binding energy (relative to samples without Zn doping), which most likely resulted in a much lower energy state of the system in the superconducting state. The stronger superconducting state arising out of these effects is witnessed in the form of increased T c ( R = 0), J c and the extent of diamagnetism in the final compound.

X-ray photo-emission spectroscopy (XPS) studies of Cu 1− x Tl x Ba 2 Ca 3 Cu 4 O 12− y superconductor thin films have been carried out for understanding the mechanism of superconductivity and to find out the reasons for the increase of zero resistivity critical temperature T c ( R = 0) with post-annealing in a nitrogen atmosphere. It is observed from these studies that reduction of charge state of thallium is a source of doping of carriers to the CuO 2 planes. The reduced charge state of thallium (i.e. Tl 1+ ) promotes lower oxygen concentration in the charge reservoir layer, which possibly results in movement of electrons to the conducting CuO 2 planes. The higher density of electrons in the CuO 2 planes optimizes the hole concentration “ n p ” in these planes. The reduced charge state of thallium in the Cu 1− x Tl x Ba 2 O 4− δ charge reservoir layer is also supported by a shift of the Ba 3d 5/2 and Ba 3d 3/2 XPS lines to lower binding energies with post-annealing in nitrogen atmosphere. Moreover, the movement of the valance band spectrum to lower binding energies suggested that the electronic density of states changes in the valance band with the post-annealing in nitrogen, which possibly becomes a source of doping of carriers to the CuO 2 planes. The increased doping of electrons to the CuO 2 planes optimizes the Fermi-vector K F and Fermi-velocity V F of the carriers and increases the T c ( R = 0) of final compound.

TiO2 nanofibres were prepared using a templating method with tetraisopropylorthotitanate (TiPT) as a precursor. The preparation comprises liquid phase deposition on cellulose fibres followed by thermal removal of the cellulose template. The obtained TiO2 fibrous substance consists of micron-size fibres with a microstructure of nanofibres. It was demonstrated that nanofibres are basically formed through the aggregation of TiO2 nanoparticles and nanorods into chain structures during the thermal treatment process. The measured surface area of the TiO2 fibres was about 250 m2 g−1. It was shown that the pore size distribution is multi-scale and a fractal morphology was demonstrated with two fractal regimes with dimensions of 1.78 and 2.97 for sizes below and above 7.5 nm, respectively. The crystalline phase of the TiO2 nanofibres, as well as the nanoparticles in the solution, could be controlled by the pH of the solution. A pH of 1.2 resulted in rutile phase, while a pH of 1.8 resulted in anatase phase.

X-ray photoemission spectroscopy (XPS) of Cu 1− x Tl x Ba 2 Ca 2 Cu 3 O 10− δ (Cu 1− x Tl x -1223) superconductors thin films is studied. These films were prepared by amorphous phase epitaxy method on the SrTiO 3 substrate. This compound has Cu 1− x Tl x Ba 2 O 4− δ charge reservoir layer and three CuO 2 planes. The atoms in the CuO 2 planes have strong covalent bonding, while the some of the atoms in Cu 1− x Tl x Ba 2 O 4− δ charge reservoir, such as oxygen (O δ ) have predominantly secondary bonding and could be removed from the unit cell. The deliberate or inadvertent removal of the oxygen from the unit cell may change the charge state of the constituent atoms in the charge reservoir layer. The charge state of the atoms in the unit cell, ultimately determine the carriers concentration, the shape of the Fermi surface and hence control the mechanism of superconductivity. The doping via charge reservoir layer of Cu 1− x Tl x -1223 films had been carried out by post-annealing of the samples in the N 2 atmosphere at 650 °C. It was observed that the critical temperature of thin films increases with the post-annealing at this temperature. In the present studies we have carried out XPS experiments to under stand the mechanism to the microscopic level. It is observed from these studies that before annealing the thallium in Cu 1− x Tl x -1223 superconductor thin films was in Tl 3+ oxidation state, which changes its oxidation state from Tl 3+ to Tl 2+ and Tl 1+ . The changed oxidation state of the thallium increases the density of the carriers in the CuO 2 planes, which increases their Fermi-vector K F and hence their Fermi-velocity v F . These parameters in turn increase the critical temperature of the material. In the present studies the T c ( R = 0) has increased from below 77 K to 92 K with post-annealing in nitrogen atmosphere.

A photochemical approach on the size control of CdS nanoparticles is presented. CdS nanoparticles were grown using the photo-induced reaction of sodium thiosulfate with Cadmium sulfate, in the absence of any surfactant. Particles of 5.5–11 nm were obtained by changing the illumination time. The dark growth of nanoparticles was negligible, however we found by optical scattering measurements that a ripening phenomenon occurs and the size of nanoparticles slightly increases with time.

In this letter a simple procedure to synthesize sodium tungsten oxide nano-thick plates from WO 3 films has been reported. WO 3 films were grown by pulsed-laser deposition method and then heat treated at temperatures up to 560 °C and times up to 120 min. Slide glass was used as both substrate and sodium source simultaneously. XRD analysis revealed presence of an amorphous structure for as-deposited WO 3 films. On the other hand, XRD showed formation of a monoclinic WO 3 structure with annealing in lower temperatures and a triclinic Na 0.5 WO 3.25 structure with annealing at higher temperatures. Intensity of the triclinic phase peaks enhanced drastically by rising annealing temperature and time. SEM results depicted presence of Na 0.5 WO 3.25 nano-thick plates with thickness of about 160 nm and width of about 3 μm. Finally, XPS analysis revealed that heat treatment temperature does not affect tungsten valence state.

In this paper, we have studied the diffusion process of Cu in V2O5 films at room temperature deposited V2O5 (2000??)/Cu/(Si or glass) samples as a function of annealing temperatures in different gas environments. According to our Auger electron spectroscopy, x-ray photoelectron spectroscopy and film resistivity measurements, Cu segregation and accumulation toward the surface of the oxide film were occurred when the vanadium oxide deposited on the Cu buffer layer. The thickness of Cu overlayer was about one monolayer for the deposited samples at room temperature. Annealing treatment at temperatures above 250?C in Ar or N2 (80%) + H2 (20%) environment has enhanced the rate of diffusion process. It is proposed that the diffusion mechanism depends on the nature of applied gases and their pressures.

We present an investigation on the optimisation of solid-state dye sensitized solar cells (SDSCs) comprising mesoporous tin oxide photoanodes infiltrated with poly(3-hexylthiophene-2,5-diyl) (P3HT) hole conductor and sensitized with an organic dye. We chose both the SnO(2) and P3HT for their high charge carrier mobilities and conductivities, but as a result preclude conventional device configurations because of high leakage current and low shunt-resistance. To minimize the "hole leakage current" through the FTO anode, we employed a double compact layer structure, and to minimize "electron leakage current" at the silver cathode, we developed a protocol for depositing an optimal P3HT "capping layer". After optimisation of cell fabrication, the electron lifetime is increased considerably and the solar cells exhibited simulated AM1.5 full sun solar power conversion efficiencies in excess of 1%.

We compare Cu/M/SiO/sub 2/ (M=Cr,V and Ta) multilayers that were deposited on Si substrates. Sample resistance measurements were carried out during annealing in 80% N/sub 2/+20% H/sub 2/, N/sub 2/ and Ar environments. Resistivity measurements, SEM observations, RBS and AES spectroscopies from annealed samples showed good diffusion barrier properties for Cr and V but rather poor properties for Ta buffer layers. This is due to the amorphous nature of Cr films and formation of a continuous Cu overlayer. SEM observation also showed granular structure for Cu/V and Cu/Ta with grain sizes of about 500 and 1000 /spl Aring/ respectively. However, shallow nitrogen implantation in Cu/V samples and DC biasing for Cu/Ta layers during deposition could enhance the adhesion and quality of the copper films. Annealing the samples in a pure nitrogen environment not only improved conductivity but annealing at 500/spl deg/C for 30 minutes also resulted in diffusion of metals towards the Cu surface. Interaction of metals with the nitrogen produces a passive nitride layer. At T=600/spl deg/C, Cu atoms also diffuse to the Si substrate through the Ta layer. In all systems, annealing caused many pinholes of 0.1 /spl mu/m. For technological applications, the mechanism of hole formation should be studied in detail.

The promise of graphene for use as a vapor sensor motivated exploration of the vapor responses of graphene nanomesh (GNM) functionalized with single stranded DNA. Devices detected different vapor types, including carboxylic acids, aldehydes, organophosphates, and explosives. As-fabricated GNM field effect transistors (FETs) had larger vapor responses than standard graphene FETs due to the effect of oxidized edges and lattice defects. DNA-GNM devices discriminated between homologous species with detection limits of a few parts per million, with fast response and recovery. Responses varied significantly when the base sequence of the DNA was changed, making the sensor class an intriguing candidate for use in an electronic nose system.

TiO 2 nanorods, TiO 2 nanorod/TiO 2 nanoparticle and TiO 2 nanorod/ZnO nanoparticle composite structures were integrated as photoanodes in backside illuminated dye-sensitized solar cells (DSSCs). Incorporation of TiO 2 nanoparticles into the bare nanorods increased the dye loading and improved the short-circuit current density ( J sc ) from 2.22 mA/cm 2 to 3.57 mA/cm 2 . ZnO nanoparticles electrochemically grown into the TiO 2 nanorod layer could increase the surface area. Nevertheless, this considerably reduced the J sc to 0.57 mA/cm 2 and consequently cell efficiency. Electrochemical impedance spectroscopy (EIS) results showed that ZnO incorporated samples have better effective diffusion coefficient of electrons in comparison with bare TiO 2 nanorods while the recombination rate of injected electrons to photoanode with electrolyte is near eight times faster than bare TiO 2 nanorods. ZnO incorporated samples showed lower electron density at steady state in the conduction band also. The worse performance of ZnO incorporated samples was attributed to lower electron injection efficiency from excited dye molecules. Monitoring electron transport properties of the cells measured by EIS pointed out the crucial role of electronic structure of composite film components on the performance of cells. Our results showed that EIS technique could be used as an efficient characterization method for precise monitoring of charge transport in nanocomposite photoanodes for DSSCs.

In this paper a new cell structure is introduced to reduce the rate of CdTe corrosion in quantum dot sensitized solar cells (QDSSCs) using electrolyte. In this cell, one electrode is a titania nanorod that was sensitized with CdTe quantum dots as the working electrode. A thin gold layer is sputtered on the electrode to act as a protective layer against the corrosive electrolyte and to passivate the CdTe surface traps which are the main recombination centres in a QDSSC. In addition, a Schottky barrier formed at the interface of Au and CdTe prevents direct electron recombination from the CdTe conduction band with ions. The mechanism of charge transfer and quantum dot regeneration in the presence of gold layer is discussed and our results show that the solar cells made of TiO2/CdTe/Au photoanode have more photostability and a higher fill factor relative to the TiO2/CdTe photoanodes.