Monolayer of PDDA/graphene/PDDA/H(2)PtCl(6) is fabricated on conductive glass using electrostatic layer-by-layer self-assembly technique, which is then converted to graphene/Pt monolayer for use as counter electrode in dye-sensitized solar cell (DSSC). As compared to the sputtered Pt counter electrode, the self-assembled monolayer reduces the Pt amount by about 1000-fold but exhibits comparable photovoltaic performance. This finding provides a new route to fabrication of cheap and efficient counter electrodes for flow-line production of DSSCs.

Highly uniform and transparent polyaniline (PANI) electrodes that can be used as counter electrodes in dye-sensitized solar cells (DSSCs) were prepared by a facile in situ polymerization method. They were used to fabricate a novel bifacially active transparent DSSC, which showed conversion efficiencies of 6.54 and 4.26% corresponding to front- and rear-side illumination, respectively. Meanwhile, the efficiency of the same photoanode employing a Pt counter electrode was 6.69%. Compared to conventional Pt-based DSSCs, the design of the bifacial DSSC fabricated in this work would help to bring down the cost of energy production due to the lower cost of the materials and the higher power-generating efficiency of such devices for their capabilities of utilizing the light from both sides. These promising results highlight the potential application of PANI in cost-effective, transparent DSSCs.

We report a simple method to prepare hierarchically structured TiO(2) spheres (HS-TiO(2)), using an electrostatic spray technique, that are utilized for photoelectrodes of highly efficient dye-sensitized solar cells (DSSCs). This method has an advantage to remove the synthesis steps in conventional sol-gel method to form nano-sized spheres of TiO(2) nanoclusters. The fine dispersion of commercially available nanocrystalline TiO(2) particles (P25, Degussa) in EtOH without surfactants and additives is electro-sprayed directly onto a fluorine-dopoed tin-oxide (FTO) substrate for DSSC photoelectrodes. The DSSCs of HS-TiO(2) photoelectrodes show high energy conversion efficiency over 10% under illumination of light at 100 mW cm(-2), AM1.5 global. It is concluded from frequency-dependent measurements that the faster electron diffusion coefficient and longer lifetime of HS-TiO(2) than those in nonstructured TiO(2) contribute to the enhanced efficiency in DSSCs.

High-performance, room-temperature (RT), solid-state dye-sensitized solar cells (DSSCs) were fabricated using hierarchically structured TiO₂ nanofiber (HS-NF) electrodes and plastic crystal (PC)-based solid-state electrolytes. The electrospun HS-NF photoelectrodes possessed a unique morphology in which submicrometer-scale core fibers are interconnected and the nanorods are dendrited onto the fibers. This nanorod-in-nanofiber morphology yielded porosity at both the mesopore and macropore level. The macropores, steming from the interfiber space, afforded high pore volumes to facilitate the infiltration of the PC electrolytes, whereas the mesoporous nanorod dendrites offered high surface area for enhanced dye loading. The solid-state DSSCs using HS-NFs (DSSC-NF) demonstrated improved power conversion efficiency (PCE) compared to conventional TiO₂ nanoparticle (NP) based DSSCs (DSSC-NP). The improved performance (>2-fold) of the DSSC-NFs was due to the reduced internal series resistance (R(s)) and the enhanced charge recombination lifetime (τ(r)) determined by electrochemical impedance spectroscopy and intensity modulated photocurrent/photovoltage spectroscopy. The easy penetration of the PC electrolytes into HS-NF layers via the macropores reduces R(s) significantly, improving the fill factor (FF) of the resulting DSSC-NFs. The τ(r) difference between the DSSC-NF and DSSC-NP in the PC electrolytes was extraordinary (~14 times) compared to reported results in conventional organic liquid electrolytes. The optimized PCE of DSSC-NF using the PC electrolytes was 6.54, 7.69, and 7.93% at the light intensity of 100, 50, and 30 mW cm⁻², respectively, with increased charge collection efficiency (>40%). This is the best performing RT solid-state DSSC using a PC electrolyte. Considering the fact that most reported quasi-solid state or nonvolatile electrolytes require higher iodine contents for efficient ion transport, our HS-NFs are a promising morphology for such electrolytes that have limited ion mass transport.

Restriction factors, such as the retroviral complementary DNA deaminase APOBEC3G, are cellular proteins that dominantly block virus replication. The AIDS virus, human immunodeficiency virus type 1 (HIV-1), produces the accessory factor Vif, which counteracts the host's antiviral defence by hijacking a ubiquitin ligase complex, containing CUL5, ELOC, ELOB and a RING-box protein, and targeting APOBEC3G for degradation. Here we reveal, using an affinity tag/purification mass spectrometry approach, that Vif additionally recruits the transcription cofactor CBF-β to this ubiquitin ligase complex. CBF-β, which normally functions in concert with RUNX DNA binding proteins, allows the reconstitution of a recombinant six-protein assembly that elicits specific polyubiquitination activity with APOBEC3G, but not the related deaminase APOBEC3A. Using RNA knockdown and genetic complementation studies, we also demonstrate that CBF-β is required for Vif-mediated degradation of APOBEC3G and therefore for preserving HIV-1 infectivity. Finally, simian immunodeficiency virus (SIV) Vif also binds to and requires CBF-β to degrade rhesus macaque APOBEC3G, indicating functional conservation. Methods of disrupting the CBF-β-Vif interaction might enable HIV-1 restriction and provide a supplement to current antiviral therapies that primarily target viral proteins.

Polymer based field effect transistors are fabricated using the gas-assisted spray technique, and their performance is considerably improved when an efficient solvent-assisted post-treatment method, solvent sprayed overlayer (SSO), is used. The SSO method is a unique treatment that can effectively facilitate chain packing to increase crystallinity within the sprayed polymer layers, which inherently have a kinetically trapped amorphous chain morphology with lack of crystallinity due to rapid solvent evaporation. The device performance was notably improved after SSO treatment including an order of magnitude increase in charge mobility. The device performance was drastically improved after SSO relative to conventional post-treatment, thermal annealing (TA). This occurred because SSO can re-arrange the polymer chains into a dominantly edge-on crystal orientation, which is preferential for charge transport, whereas TA increases the crystallinity without re-arrangement of the crystal orientation resulting in a complex of edge-on and face-on. The development of edge-on crystal domains after SSO within the active layers was responsible for the significant improvement in performance. The SSO is a simple and effective post-treatment method which validates the use of spray process and holds promise for use in other high-throughput processes for OFETs fabrication.

Nanoparticles meet nanotubes! Direct synthesis of TiN nanoparticles in a three-dimensional network of few-walled carbon nanotubes (FWCNTs) was achieved by using mesoporous graphitic carbon nitride (C(3) N(4)) as both a hard template and a nitrogen source. The TiN/FWCNT composite showed high performance for the oxygen reduction reaction in acidic media.

N-doped porous carbon produced via chemical activation of polypyrrole functionalized graphene sheets shows selective adsorption of CO(2)(4.3 mmol g(-1)) over N(2)(0.27 mmol g(-1)) at 298 K. The potential for large scale production and facile regeneration makes this material useful for industrial applications.

A previously healthy 54-year-old man complained of progressive voice changes. A firm subglottic polypoid mass was located at the right posterior site, as seen on fiberoptic laryngoscopy, with a distinctly narrowed subglottic space being seen on neck computed tomography, and there were multiple opacities from the cricoid cartilage to the tracheal rings. Resection was done under general anesthesia. The mass-like elevated lesion showed enchondral ossification of the laryngeal cartilage just beneath the squamous metaplastic surface epithelium. The vocal cord mobility was normal. Compared with the computed tomography and the laryngoscopic examination, the polypoid mass-like elevation corresponded to a ossified vocal process of the right arytenoid cartilage. To date, clinically symptomatic ossification of the laryngeal cartilages has presented with foreign body-like impaction. The present case is a rare case of ossification of the laryngeal cartilage that masqueraded as a subglottic polypoid mass. The ossification of laryngeal cartilage is part of the normal aging process, but a tumor-like mass at the airway related with voice changes, like was seen in the present case, is rare. Albeit rare, clinicians and radiologists should be aware that this heterotopic ossification may mimic a polypoid mass-like presentation as well as the accompanying symptoms.

We present a combined experimental and computational study that probes the thermoelectric and electrical transport properties of molecular junctions. Experiments were performed on junctions created by trapping aromatic molecules between gold electrodes. The end groups (-SH,-NC) of the aromatic molecules were systematically varied to study the effect of contact coupling strength and contact chemistry. When the coupling of the molecule with one of the electrodes was reduced by switching the terminal chemistry from -SH to -H, the electrical conductance of molecular junctions decreased by an order of magnitude, whereas the thermopower varied by only a few percent. This has been predicted computationally in the past and is experimentally demonstrated for the first time. Further, our experiments and computational modeling indicate the prospect of tuning thermoelectric properties at the molecular scale. In particular, the thiol-terminated aromatic molecular junctions revealed a positive thermopower that increased linearly with length. This positive thermopower is associated with charge transport primarily through the highest occupied molecular orbital, as shown by our computational results. In contrast, a negative thermopower was observed for a corresponding molecular junction terminated by an isocyanide group due to charge transport primarily through the lowest unoccupied molecular orbital.

Submicroscale SiC fiber mats were prepared by the electrospinning of an oil-in-water(O/W) precursor emulsion, a subsequent thermal curing treatment, and calcination at 1600 °C. Low-molecular-weight PCS micelles entrapped within an aqueous PVP matrix played an important role in forming the continuous and dense core structure, resulting in pure SiC fibers. The manipulation of SiC fiber diameters could be obtained via control of the micellar PCS concentration (10-30 wt %), enabling the production of dense and highly crystallized SiC fiber architectures with diameters ranging from 200 to 350 nm.

Deposition of nanostructures such as carbon nanotubes on Si wafers to make heterojunction structures is a promising route toward high efficiency solar cells with reduced cost. Here, we show a significant enhancement in the cell characteristics and power conversion efficiency by growing a silicon oxide layer at the interface between the nanotube film and Si substrate. The cell efficiency increases steadily from 0.5% without interfacial oxide to 8.8% with an optimal oxide thickness of about 1 nm. This systematic study reveals that formation of an oxide layer switches charge transport from thermionic emission to a mixture of thermionic emission and tunneling and improves overall diode properties, which are critical factors for tailoring the cell behavior. By controlled formation and removal of interfacial oxide, we demonstrate oscillation of the cell parameters between two extreme states, where the cell efficiency can be reversibly altered by a factor of 500. Our results suggest that the oxide layer plays an important role in Si-based photovoltaics, and it might be utilized to tune the cell performance in various nanostructure-Si heterojunction structures.

We used Ti meshes for both the photoanodes and counter electrodes of dye-sensitized solar cells (DSSCs) to improve the flexibility and conductivity of the electrodes. These mesh type electrodes showed good transparency and high bendability when subjected to an external force. We demonstrated the advantages of cells using such electrodes compared to traditional transparent conducting oxide based electrodes and back side illuminated DSSCs, such as low sheet resistance, elevated photo-induced current and enhanced sunlight utilization. Nanotube layers of different thicknesses were investigated to determine their effect on the photovoltaic parameters of the cell. The overall efficiency of the best cells was approximately 5.3% under standard air mass 1.5 global (AM 1.5 G) solar conditions. Furthermore, the DSSCs showed an efficiency of approximately 3.15% due to the all Ti-mesh type electrodes even after illumination from the back side.

Low-cost transparent counter electrodes (CEs) for efficient dye-sensitized solar cells (DSSCs) are prepared by using nanohybrids of carbon nanotube (CNT)-supported platinum nanoparticles as highly active catalysts. The nanohybrids, synthesized by an ionic-liquid-assisted sonochemical method, are directly deposited on either rigid glass or flexible plastic substrates by a facile electrospray method for operation as CEs. Their electrochemical performances are examined by cyclic voltammetry, current density-voltage characteristics, and electrochemical impedance spectroscopy (EIS) measurements. The CNT/Pt hybrid films exhibit high electrocatalytic activity for I(-)/I(3)(-) with a weak dependence on film thickness. A transparent CNT/Pt hybrid CE film about 100 nm thick with a transparency of about 70 %(at 550 nm) can result in a high power conversion efficiency (η) of over 8.5 %, which is comparable to that of pyrolysis platinum-based DSSCs, but lower cost. Furthermore, DSSC based on flexible CNT/Pt hybrid CE using indium-doped tin oxide-coated polyethylene terephthalate as the substrate also exhibits η=8.43 % with J(sc)=16.85 mA cm(-2), V(oc)=780 mV, and FF=0.64, and this shows great potential in developing highly efficient flexible DSSCs.

Vertically aligned single-walled carbon nanotubes (VASWCNTs) have been successfully transferred onto transparent conducting oxide glass and implemented as efficient low-cost, platinum-free counter electrode in sulfide -mediated dye-sensitized solar cells (DSCs), featuring notably improved electrocatalytic activity toward thiolate/disulfide redox shuttle over conventional Pt counter electrodes. Impressively, device with VASWCNTs counter electrode demonstrates a high fill factor of 0.68 and power conversion efficiency up to 5.25%, which is significantly higher than 0.56 and 3.49% for that with a conventional Pt electrode. Moreover, VASWCNTs counter electrode produces a charge transfer resistance of only 21.22 Ω towards aqueous polysulfide electrolyte commonly applied in quantum dots-sensitized solar cells (QDSCs), which is several orders of magnitude lower than that of a typical Pt electrode. Therefore, VASWCNTs counter electrodes are believed to be a versatile candidate for further improvement of the power conversion efficiency of other iodine-free redox couple based DSCs and polysulfide electrolyte based QDSCs.

ABSTRACT: High-efficient fibrous dye-sensitized solar cell with carbon nanotube (CNT) thin films as counter electrodes has been reported. The CNT films were fabricated by coating CNT paste or spraying CNT suspension solution on Ti wires. A fluorine tin oxide-coated CNT underlayer was used to improve the adherence of the CNT layer on Ti substrate for sprayed samples. The charge transfer catalytic behavior of fibrous CNT/Ti counter electrodes to the iodide/triiodide redox pair was carefully studied by electrochemical impedance and current-voltage measurement. The catalytic activity can be enhanced by increasing the amount of CNT loading on substrate. Both the efficiencies of fibrous dye-sensitized solar cells using paste coated and sprayed CNT films as counter electrodes are comparative to that using Pt wires, indicating the feasibility of CNT/Ti wires as fibrous counter electrode for superseding Pt wires.

Metal wires suffer from corrosion in fiber-shaped dye-sensitized solar cells (DSSCs). We report herein that stable, ultrastrong, and highly flexible aligned carbon nanotube fibers can be used not only as catalytic counter electrodes but also as conductive materials to support dye-loaded TiO(2) nanoparticles in DSSCs. The power conversion efficiency of this fiber solar cell can achieve 2.94%. These solar power fibers, exhibiting power conversion efficiency independent of incident light angle and cell length, can be woven into textiles via a convenient weaving technology.

We report the preparation of highly interconnected ordered mesoporous carbon-carbon nanotube nanocomposites which show Pt-like dye-sensitized solar cell (DSSC) efficiency and remarkable long-term durability as DSSC counter electrodes.

To overcome the intrinsic shortcomings of the traditional iodide-triiodide redox couple and pursue a further performance improvement, intense efforts have been made to exploit alternative redox shuttles in dye-sensitized solar cells (DSCs). Herein, we report an energetic and kinetic view of DSCs when the iodine electrolyte is substituted with its thiolate counterpart and identify that a conventional platinum counter electrode presents low catalytic activity for the thiolate electrolyte, featuring a high charge transfer resistance found at the platinized fluorine-doped tin oxide (FTO). We employ conductive carbon black with several polymers to fabricate highly active composite catalysts for thiolate regeneration. The use of a highly active conductive carbon black and polymerized 3,4-ethylenedioxythiophene composition as a counter electrode combined with a high-absorptivity ruthenium dye C106 sensitized titania film has generated a DSC with an organic thiolated electrolyte, exhibiting an overall power conversion efficiency of 7.6% under AM1.5G full sunlight.

We investigated the fabrication of inverse opal carbon counter electrodes using a colloidal templating method for DSSCs. Specifically, bare inverse opal carbon, mesopore-incoporated inverse opal carbon and graphitized inverse opal carbon were synthesized and stably dispersed in ethanol solution for spray coating on a FTO substrate. The thickness of the electrode was controlled by the number of coatings, and the average relative thickness evaluated by measuring the transmittance spectrum. The effect of the counter electrode thickness on the photovoltaic performance of the DSSCs was investigated and analyzed by interfacial charge transfer resistance (RCT) under EIS measurement. The effect of the surface area and conductivity of the inverse opal was also investigated by considering the increase in surface area due to the mesopore in the inverse opal carbon and conductivity by graphitization of the carbon matrix. The results showed that the FF and thereby the efficiency of DSSCs was increased as the electrode thickness increased. Consequently, the larger FF and thereby the greater efficiency of the DSSCs was achieved for mIOC and gIOC compared to IOC, which was attributed to the lower RCT. Finally, compared to a conventional Pt counter electrode, the inverse opal-based carbon showed comparable efficiency upon application to DSSCs.

We report on the multiwall carbon nanotube application as energy conversion material to fabricate thin film solar cells, with nanotubes acting as photogeneration sites as well as charge separators, collectors and carrier transporters. The device consists of a semitransparent thin film of nanotubes coating a n-type crystalline silicon substrate. Under illumination electron-hole (e-h) pairs, generated in the nanotubes and in the silicon substrate underneath, are split and charges are transported through the nanotubes (electrons) and the n-Si (holes). We found that a suitable thickness of the nanotube thin film, high density of Schottky junctions between nanotubes and n-Si and lowest number of nanotube walls are all fundamental parameters to improve the device incident photon to electron conversion efficiency. Multiwall carbon nanotubes have been synthesized by chemical vapour deposition in an ultra high vacuum chamber by evaporating a given amount of iron at room temperature and then exposing the substrate kept at 800 degrees C at acetylene gas. The amount of deposited iron is found to directly affect the nanotube size distribution (inner and outer diameter) and therefore the number of walls of the nanotubes.