Showing papers by "Yang Yang published in 2010"

A One-Step, Solvothermal Reduction Method for Producing Reduced Graphene Oxide Dispersions in Organic Solvents

Abstract: Refluxing graphene oxide (GO) in N-methyl-2-pyrrolidinone (NMP) results in deoxygenation and reduction to yield a stable colloidal dispersion. The solvothermal reduction is accompanied by a color change from light brown to black. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images of the product confirm the presence of single sheets of the solvothermally reduced graphene oxide (SRGO). X-ray photoelectron spectroscopy (XPS) of SRGO indicates a significant increase in intensity of the C═C bond character, while the oxygen content decreases markedly after the reduction is complete. X-ray diffraction analysis of SRGO shows a single broad peak at 26.24° 2θ (3.4 A), confirming the presence of graphitic stacking of reduced sheets. SRGO sheets are redispersible in a variety of organic solvents, which may hold promise as an acceptor material for bulk heterojunction photovoltaic cells, or electromagnetic interference shielding applications.

Interface investigation and engineering – achieving high performance polymer photovoltaic devices

Abstract: The contact between the polymer active layer and the electrode is one the most critical interfaces in polymer solar cells. In this article, we report the progress of interface engineering in polymer solar cell research, where the multiple functions of the interfacial materials will be discussed. The vertical composition profile in polymer:fullerene blends is an emerging topic, and the interlayer effect on the vertical phase separation and device performance will be highlighted. We also discuss the energy level alignment at the bulk heterojunction (BHJ) interface, with the aim of providing a better understanding towards the route of high efficiency polymer solar cells.

A Polybenzo[1,2‐b:4,5‐b′]dithiophene Derivative with Deep HOMO Level and Its Application in High‐Performance Polymer Solar Cells

Abstract: Although there is a consensus on the development of solar energy as a green energy resource, the importance of development of the polymer solar cell (PSC) has only been realized in recent years owing to its advantages of low cost and flexibility in large-area applications. Bulk heterojunction (BHJ) type polymer solar cells now play a leading role in realizing high power conversion efficiency (PCE). The development of new polymer materials to further improve the efficiencies of BHJ-type PSCs will accelerate their commercial application. At present, P3HT-PCBM-based PSCs (P3HT= poly(3-hexylthiophene), PCBM=methanofullerene (6,6)-phenyl-C61-butyric acid methyl ester) have exhibited high efficiencies of 4–5%. However, the narrow absorption spectrum of P3HT in 300–650 nm is one of the main hindrances to the further improvement of the efficiencies of P3HT-based devices. To overcome this problem, some low-band-gap polymer materials as donors have been synthesized successfully and applied to photovoltaic devices. Large short-circuit current density (Jsc) and higher efficiencies have been demonstrated using this strategy. In spite of the high Jsc achievable with low-band-gap polymers, the device performance suffers owing to the low open-circuit voltage (Voc) of 0.5–0.7 V. According to published models and experimental results, theVoc of a PSC is closely related to the offset between energy levels of the highest occupied molecular orbital (HOMO) of the donor and lowest unoccupied molecular orbital (LUMO) of the acceptor. Thus, to enhance the opencircuit voltage of these devices, some building blocks with lower-lying HOMOs should be introduced in donor molecules to lower their HOMO levels. Polyfluorene and its derivatives are a well-known class of wide-band-gap organic semiconducting materials. Many donor polymers containing fluorene on the main chain were reported to show lower HOMO levels and correspondingly exhibited higher open-circuit voltages. However, the wider band gaps of these polymers resulted in lower values of Jsc and consequently lower efficiencies. To enhance the efficiency, there is a need for a low-band-gap polymers that can have a high Voc. Few polymers with high open-circuit voltages (above 0.8 V) and consequently high PCEs (above 5%) have been reported to date, except for two kinds of polymers, poly[(2,7silafluorene)-alt-(4,7-di-2-thienyl-2,1,3-benzothiadiazole)] (PSiFDBT) and poly[N-9’’-heptadecanyl-2,7-carbazole-alt5,5-(4’,7’-di-2-thienyl-benzothiadiazole) (PCDTBT), both of which contain a fluorene unit in the polymer main chain. Considering the similarity in the molecular structures of PSiFDBTand PCDTBTwith analogous fluorene units in both of their main chains, it is necessary to explore new molecular structures with favorable characteristics for higher opencircuit voltages and conversion efficiencies. Recently, some benzo[1,2-b :4,5-b’]dithiophene-containing polymers were applied to field-effect transistor (FET) and PSC devices (Table 1). 6, 7] A high mobility of 0.15–

Carrier aggregation for LTE-advanced mobile communication systems

Abstract: In order to achieve up to 1 Gb/s peak data rate in future IMT-Advanced mobile systems, carrier aggregation technology is introduced by the 3GPP to support very-high-data-rate transmissions over wide frequency bandwidths (e.g., up to 100 MHz) in its new LTE-Advanced standards. This article first gives a brief review of continuous and non-continuous CA techniques, followed by two data aggregation schemes in physical and medium access control layers. Some technical challenges for implementing CA technique in LTE-Advanced systems, with the requirements of backward compatibility to LTE systems, are highlighted and discussed. Possible technical solutions for the asymmetric CA problem, control signaling design, handover control, and guard band setting are reviewed. Simulation results show Doppler frequency shift has only limited impact on data transmission performance over wide frequency bands in a high-speed mobile environment when the component carriers are time synchronized. The frequency aliasing will generate much more interference between adjacent component carriers and therefore greatly degrades the bit error rate performance of downlink data transmissions.

Silicon Atom Substitution Enhances Interchain Packing in a Thiophene-Based Polymer System

Abstract: A new silole-containing low bandgap polymer is synthesized by replacing the 5-position carbon of PCPDTBT with a silicon atom (PSBTBT). Through experiments and computational calculations, we show that the material properties, particular the packing of polymer chains, can be altered significantly. As a result, the polymer changes from amorphous to highly crystalline with the replacement of the silicon atom.

Highly efficient tandem polymer photovoltaic cells

Abstract: A tandem polymer photovoltaic device includes a first bulk hetero-junction polymer semiconductor layer, a second bulk hetero-junction polymer semiconductor layer spaced apart from the first bulk hetero-junction polymer semiconductor layer, and a metal-semiconductor layer between and in contact with the first and second bulk hetero junction polymer semiconductor layers. The first and second bulk hetero-junction polymer semiconductor layers have complementary photon absorption spectra.

Higher moments of net proton multiplicity distributions at RHIC.

Abstract: 200 GeV corresponding to baryon chemical potentials (mu(B)) between 200 and 20 MeV. Our measurements of the products kappa sigma(2) and S sigma, which can be related to theoretical calculations sensitive to baryon number susceptibilities and long-range correlations, are constant as functions of collision centrality. We compare these products with results from lattice QCD and various models without a critical point and study the root s(NN) dependence of kappa sigma(2). From the measurements at the three beam energies, we find no evidence for a critical point in the QCD phase diagram for mu(B) below 200 MeV.

Self-configuration and self-optimization for LTE networks

Abstract: With the rapid growth of mobile communications, deployment and maintenance of cellular mobile networks are becoming more and more complex, time consuming, and expensive. In order to meet the requirements of network operators and service providers, the telecommunication industry and international standardization bodies have recently paid intensive attention to the research and development of self-organizing networks. In this article we first introduce both the market and technological perspectives for SONs. Then we focus on the self-configuration procedure and illustrate a self-booting mechanism for a newly added evolved NodeB without a dedicated backhaul interface. Finally, mobility load balancing as one of the most important selfoptimization issues for Long Term Evolution networks is discussed, and a distributed MLB algorithm with low handover cost is proposed and evaluated.

Self-assembled 3D BiOCl hierarchitectures: tunable synthesis and characterization

Abstract: 3D hierarchitectures (HAs) of BiOCl composed of 2D nanosheets, which intercross with each other, have been successfully synthesized by a template-free solvothermal method at 160 °C for 12 h. The morphology and compositional characteristics of the 3D HAs were investigated by various techniques. On the basis of characterization results, the growth of such 3D HAs has been proposed as an Ostwald ripening process followed by self-assembly. The growth and self-assembly of BiOCl nanosheets could be readily tuned with the molar ratio of urea to BiCl3·5H2O, which brought different morphologies and microstructures to the final products. The specific surface area and porosity of the 3D hierarchitectured (HAd) BiOCl also were investigated by using nitrogen adsorption and desorption isotherms. UV–vis spectra reveal that the band gap energies of the 3D HAs can be tuned from 3.05 eV to 3.32 eV. The as-prepared 3D HAd BiOCl showed much higher photocatalytic activity than that of the reported in the literature, which was evaluated by the degradation of Rhodamine-B (RhB) dye under ultraviolet light irradiation.

Energy efficiency metrics for green wireless communications

Abstract: Recently the concern on energy efficiency in wireless communications has been growing rapidly as energy consumption increasingly becomes a global environment problem. Lots of research and development efforts have been spent in wireless industry, aiming for energy efficient solutions which lead to green wireless communications. In this paper we provide a brief overview on those efforts, with an emphasis on introducing energy efficiency metrics. Since energy efficiency metrics are indicators of efficiency, understanding those metrics provides us a better view on how energy efficiency can be achieved in wireless systems/networks. Observing energy is a concern at every corner of a wireless system/network, we describe those metrics from at component, equipment and system/networks level, respectively. From our observation, energy efficiency metrics for components and equipments have been well established. However, studied for system/network level solutions and metrics deserve more attention. We believe new energy efficient architecture and associated metrics will be the key for the energy consumption problem in wireless industry.

Wireless sensor and actuator networks: Enabling the nervous system of the active aircraft

Abstract: The ever increasing volume of air transport necessitates new technologies to be adopted by the flight industry to fulfill the requirements of safety, security, affordability, and environmental friendliness while still meeting the growing demand. What we need to achieve this goal is a new type of aircraft cruise control, interconnecting all the onboard active control systems and making more accurate control decisions than is currently possible, thus improving overall flight efficiency. Active Aircraft envisions such a nervous system of distributed wireless sensor and actuator network components, enabling the early detection of potential problems and quick, accurate reactions to these. As part of this vision, WSANs deployed on aircraft wings help reduce aerodynamic drag and significantly reduce fuel consumption. In this article we first describe this conceptual change in aircraft control technology. We then introduce a WSAN application to reduce skin friction drag and a network topology to enable it. In our application WSANs form virtual flap arrays on the wings to measure the skin friction in real time and to react using synthetic jet actuators, which suck and expel air on the wing to reduce the friction. The Active Aircraft vision imposes stringent performance requirements on the underlying WSAN communication algorithms. The medium access control and routing protocols, in particular, must meet the quality of service criteria set by active control applications. Thus, we also present the application characteristics of Active Aircraft and raise the issue of design considerations with regard to the communication protocols.

Effect of Carbon Chain Length in the Substituent of PCBM-like Molecules on Their Photovoltaic Properties

Abstract: A series of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)-like fullerene derivatives with the butyl chain in PCBM changing from 3 to 7 carbon atoms, respectively (F1–F5), are designed and synthesized to investigate the relationship between photovoltaic properties and the molecular structure of fullerene derivative acceptors. F2 with a butyl chain is PCBM itself for comparison. Electrochemical, optical, electron mobility, morphology, and photovoltaic properties of the molecules are characterized, and the effect of the alkyl chain length on their properties is investigated. Although there is little difference in the absorption spectra and LUMO energy levels of F1–F5, an interesting effect of the alkyl chain length on the photovoltaic properties is observed. For the polymer solar cells (PSCs) based on P3HT as donor and F1–F5, respectively, as acceptors, the photovoltaic behavior of the P3HT/F1 and P3HT/F4 systems are similar to or a little better than that of the P3HT/PCBM device with power conversion efficiencies (PCEs) above 3.5%, while the performances of P3HT/F3 and P3HT/F5-based solar cells are poorer, with PCE values below 3.0%. The phenomenon is explained by the effect of the alkyl chain length on the absorption spectra, fluorescence quenching degree, electron mobility, and morphology of the P3HT/F1–F5 (1:1, w/w) blend films.

High-Efficiency Polymer Tandem Solar Cells with Three-Terminal Structure

Abstract: Figure 1. a) Two diodes connected in parallel with the anodes of the two diodes connected together and the cathodes connected together. b) Schematic of the three-terminal device and the dotted squares on Polymer solar cells are a promising alternative to future photovoltaic applications due to various advantages such as low cost and ease of processing. Ever since the invention of bulk heterojunctions (BHJs) utilizing a blend of donor polymer and acceptor fullerene derivative, there have been increasing efforts to enhance the power-conversion efficiency (PCE) of polymer solar cells. However, narrow absorption range and low carrier mobility of polymer solar cells limit the thickness of the active layer and, hence, the absorption efficiency. One of the strategies to increase its efficiency is to make use of tandem architectures. In a two-terminal tandem solar cell, two subcells with complementary absorption bands are connected in series through an interlayer that acts as a recombination zone for electrons from one subcell and holes from the other. The series connection leads to summation of the open-circuit voltage (VOC); however, the overall current is limited by the subcell that delivers the smaller photocurrent. Therefore, the photocurrentmatching criterion between the two subcells must be satisfied for efficient working of a two-terminal tandem cell. Because of the current-matching criterion, the two subcells might not be readily incorporated into a tandem cell under their optimal conditions. An ideal tandem structure would consist of two subcells that operate separately, so that the efficiency of the tandem cell is simply the sum of the efficiencies of the two subcells. To circumvent the challenge of photocurrent matching in the two-terminal architecture, two solar cells can be stacked together to form a four-terminal tandem cell. In this case, the two cells can be connected either in series, to add up the VOC, or connected in parallel (shown in Fig. 1a) to add up the short-circuit current (JSC). However, in these devices, considerable optical losses are encountered because of the presence of an additional indium tin oxide (ITO)-coated glass substrate and semitransparent metal electrode that compensates for the gain from absorption. In this manuscript, tandem structures with a three-terminal (3T) configuration are demonstrated, as seen in Figure 1b, in which two subcells are connected in parallel through a transparent conducting interlayer that acts as a common electrode to the two subcells. The advantage of this structure is that it is convenient to characterize the two subcells independently as well as when connected in parallel. If two subcells with similarVOC are used, they can be connected in parallel to sum the JSC without

Synthesis of Magnetite Nanooctahedra and Their Magnetic Field-Induced Two-/Three-Dimensional Superstructure

Abstract: In this work, we report a robust wet-chemical route to synthesize monosized octahedron-shaped magnetite (Fe3O4) nanoparticles with average sizes ranging from 8 to ∼430 nm In other words, we are able to adjust the magnetic properties of the as-synthesized nanoparticles from superparamagnetic to single-domain to multidomain ferrimagnetic regimes We also demonstrate a simple solvent-evaporation assembly process to obtain either 2D monolayer or 3D microrod superstructures made of 21 nm-sized nanooctahedra by applying a weak magnetic field (∼006 T) in the horizontal or vertical direction, respectively The as-obtained 2D monolayer assembly not only exhibits a long-range translational order (hexagonal close packing) but also has a high degree of crystallographic orientational order (⟨111⟩ texture normal to the substrate) Large-area assemblies (up to 10 × 10 μm) can be formed on various substrates, for example, silicon substrates and carbon films of transmission electron microscopy copper grids, as demonstra

Multi-source/component spray coating for polymer solar cells.

Abstract: A multi-source/component spray coating process to fabricate the photoactive layers in polymer solar cells is demonstrated. Well-defined domains consisting of polymer:fullerene heterojunctions are constructed in ambient conditions using an alternating spray deposition method. This approach preserves the integrity of the layer morphology while forming an interpenetrating donor (D)/acceptor (A) network to facilitate charge transport. The formation of multi-component films without the prerequisite of a common solvent overcomes the limitations in conventional solution processes for polymer solar cells and enables us to process a wide spectrum of materials. Polymer solar cells based on poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester spray-coated using this alternating deposition method deliver a power conversion efficiency of 2.8%, which is comparable to their blend solution counterparts. More importantly, this approach offers the versatility to independently select the optimal solvents for th...

Low temperature silicon dioxide by thermal atomic layer deposition: Investigation of material properties

Abstract: SiO2 is the most widely used dielectric material but its growth or deposition involves high thermal budgets or suffers from shadowing effects. The low-temperature method presented here (150 °C) for the preparation of SiO2 by thermal atomic layer deposition (ALD) provides perfect uniformity and surface coverage even into nanoscale pores, which may well suit recent demands in nanoelectronics and nanotechnology. The ALD reaction based on 3-aminopropyltriethoxysilane, water, and ozone provides outstanding SiO2 quality and is free of catalysts or corrosive by-products. A variety of optical, structural, and electrical properties are investigated by means of infrared spectroscopy, UV-Vis spectroscopy, secondary ion mass spectrometry, capacitance-voltage and current-voltage measurements, electron spin resonance, Rutherford backscattering, elastic recoil detection analysis, atomic force microscopy, and variable angle spectroscopic ellipsometry. Many features, such as the optical constants (n, k) and optical transm...

Alternating Copolymers of Carbazole and Triphenylamine with Conjugated Side Chain Attaching Acceptor Groups: Synthesis and Photovoltaic Application

Abstract: Four alternating copolymers of carbazole (Cz) and triphenylamine (TPA) with thienylene-vinylene (TV) conjugated side chain containing different acceptor end groups of aldehyde (PCzTPA−TVCHO), monocyano (PCzTPA−TVCN) dicyano (PCzTPA−TVDCN), and 1,3-diethyl-2-thiobarbituric acid (PCzTPA−TVDT), have been designed and synthesized. The structures and properties of the main chain donor-side chain acceptor D−A copolymers were fully characterized. Through changing the acceptor group attached to the TV conjugated side chain on TPA, the electronic properties and energy levels of the copolymers were effectively tuned. The effect of substituent on the electronic structures of the copolymers was also studied by molecular simulation. These results indicate that it is a simple and effective approach to tune the bandgap in a conjugated polymer by attaching an acceptor end group on the conjugated side chains. PCzTPA−TVCN, PCzTPA−TVDCN, and PCzTPA−TVDT were used as donor in polymer solar cells; the device based on PCzTPA−T...

Field test of wavelength-saving quantum key distribution network

Abstract: We propose a wavelength-saving topology of a quantum key distribution (QKD) network based on passive optical elements, and we report on the field test of this network on commercial telecom optical fiber at the frequency of 20MHz. In this network, five nodes are supported with two wavelengths, and every two nodes can share secure keys directly at the same time. We also characterized the insertion loss and cross talk effects on the point-to-point QKD system after introducing this QKD network.

Performance Analysis of Selective Opportunistic Spectrum Access With Traffic Prediction

Abstract: In cognitive radio (CR) networks, the ability to capture a frequency slot for transmission in an idle channel has a significant impact on the spectrum efficiency and quality of service (QoS) of a secondary user (SU). The radio frequency (RF) front-ends of an SU have limited bandwidth for spectrum sensing with the target frequency bands dispersed in a discontinuous manner. This results in the SU having to sense multiple target frequency bands in a short period of time before selecting an appropriate idle channel for transmission. This paper addresses this technical challenge by proposing a selective opportunistic spectrum access (SOSA) scheme. With the aid of statistical data and traffic prediction techniques, our SOSA scheme can estimate the probability of a channel appearing idle based on the statistics and choose the best spectrum-sensing order to maximize spectrum efficiency and maintain an SU's connection. By means of doing so, this SOSA scheme can preserve the QoS of an SU while improving the system efficiency. In contrast to previous work, we consider the practical issues encountered by an SU in a wireless environment, such as discontinuous target frequency bands and limited spectrum-sensing ability. We examine the spectrum-sensing scheme in terms of packet loss ratio (PLR) and throughput. The simulation results show that the proposed SOSA scheme can decrease the probability of packet losses in the discontinuous spectrum environment and improve the spectrum efficiency.

Harnessing battery recovery effect in wireless sensor networks: Experiments and analysis

Abstract: Many applications of wireless sensor networks rely on batteries. But most batteries are not simple energy reservoirs, and can exhibit battery recovery effect. That is, the deliverable energy in a battery can be self-replenished, if left idling for sufficient time. As a viable approach for energy optimisation, we made several contributions towards harnessing battery recovery effect in sensor networks. 1) We empirically examine the gain of battery runtime of sensor devices due to battery recovery effect, and affirm its significant benefit in sensor networks. We also observe a saturation threshold, beyond which more idle time will contribute only little to battery recovery. 2) Based on our experiments, we propose a Markov chain model to capture battery recovery considering saturation threshold and random sensing activities, by which we can study the effectiveness of duty cycling and buffering. 3) We devise a simple distributed duty cycle scheme to take advantage of battery recovery using pseudo-random sequences, and analyse its trade-off between the induced latency of data delivery and duty cycle rates.

Origin of Radiation-Induced Degradation in Polymer Solar Cells

Abstract: Polymer solar cells have been shown to degrade under X-rays Here, in situ polymer photovoltaic performance and recombination lifetimes are measured and it is found that charge accumulation is the primary reason for degradation of solar cells This is affected by the mixing ratio of donor and acceptor in the bulk heterojunction Both a quantitative understanding and the physical model of the degradation mechanism are presented Understanding of the degradation mechanism is extended in polymer donor-acceptor bulk heterojunction systems to propose a material combination for making radiation hard diodes that can find important application in fields ranging from memory arrays to organic X-ray detectors for medical imaging

Surface patterning on periodicity of femtosecond laser-induced ripples

Abstract: Properties of femtosecond laser-induced ripples on patterned metal surfaces are investigated through using a crossed two-step line-scribing method. It is found that the ripple periodicity tends to decrease with larger surface roughness but increase with higher laser fluence. For the increased roughness, the change in ripple periodicity becomes more sensitive to the incident laser fluence. A cut-off surface roughness that prevents from altering the ripple periodicity is also revealed to increase with the lower laser fluence. These phenomena are discussed in the view of surface plasmon polaritons in the laser-induced plasma and the modified dielectric constant of the roughened surfaces.

HARNESSING BATTERY RECOVERY EFFECT IN WIRELESS SENSOR NETWORKS: EXPERIMENTS AND ANALYSIS Research Title

Abstract: -Many applications of wireless sensor networks rely on batteries. But most batteries are not simple energy reservoirs, and can exhibit battery recovery effect. That is, the deliverable energy in a battery can be self-replenished, if left idling for sufficient time. As a viable approach for energy optimisation, we made several contributions towards harnessing battery recovery effect in sensor networks. 1) We empirically examine the gain of battery runtime of sensor devices due to battery recovery effect, and affirm its significant benefit in sensor networks. \Ve also observe a saturation threshold, beyond which more idle time will contribute only little to battery recovery. 2) Based on our experiments, we propose a Markov chain model to capture battery recovery considering saturation threshold and random sensing activities, by which we can study the effectiveness of duty cycling and buffering, 3) We devise a simple distributed duty cycle scheme to take advantage of battery recovery using pseudo-random sequences, and analyse its trade-oil" between the induced latency of data delivery and duty cycle rates,

Detection and identification of potential biomarkers of breast cancer

Abstract: Noninvasive and convenient biomarkers for early diagnosis of breast cancer remain an urgent need. The aim of this study was to discover and identify potential protein biomarkers specific for breast cancer. Two hundred and eighty-two (282) serum samples with 124 breast cancer and 158 controls were randomly divided into a training set and a blind-testing set. Serum proteomic profiles were analyzed using SELDI-TOF-MS. Candidate biomarkers were purified by HPLC, identified by LC-MS/MS and validated using ProteinChip immunoassays and western blot technique. A total of 3 peaks (m/z with 6,630, 8,139 and 8,942 Da) were screened out by support vector machine to construct the classification model with high discriminatory power in the training set. The sensitivity and specificity of the model were 96.45 and 94.87%, respectively, in the blind-testing set. The candidate biomarker with m/z of 6,630 Da was found to be down-regulated in breast cancer patients, and was identified as apolipoprotein C-I. Another two candidate biomarkers (8,139, 8,942 Da) were found up-regulated in breast cancer and identified as C-terminal-truncated form of C3a and complement component C3a, respectively. In addition, the level of apolipoprotein C-I progressively decreased with the clinical stages I, II, III and IV, and the expression of C-terminal-truncated form of C3a and complement component C3a gradually increased in higher stages. We have identified a set of biomarkers that could discriminate breast cancer from non-cancer controls. An efficient strategy, including SELDI-TOF-MS analysis, HPLC purification, MALDI-TOF-MS trace and LC-MS/MS identification, has been proved very successful.

Controllable synthesis and luminescent properties of novel erythrocyte-like CaMoO4 hierarchical nanostructures via a simple surfactant-free hydrothermal route.

Abstract: Synthesis of metal molybdates (XMoO4, X = Ca, Sr, Ba) have received much attention recently because of their interesting structural and luminescent properties. Here novel erythrocyte-like CaMoO4 hierarchical nanostructures are synthesized via a simple surfactant-free hydrothermal route. The formation of the calcium molybdate erythrocytes is controllable through adjusting the fundamental experimental parameters including reaction time, temperature and DMAc to H2O ratio. The as-synthesized products are characterized using X-ray powder diffraction, scanning electron microscopy, Brunauer–Emmett–Teller and transmission electron microscopy. The results show that the nucleation and growth of the novel erythrocyte-like CaMoO4 hierarchical nanostructures are governed by an oriented attachment growth mechanism. The luminescent properties of the CaMoO4 erythrocytes are then studied using a spectrophotometer and the erythrocyte-like CaMoO4 nanostructures display a strong blue emission. This study provides an easy surfactant-free synthetic route for the controllable construction of inorganic materials with high hierarchy in the absence of any surfactants.

Versatile solution for growing thin films of conducting polymers.

Abstract: The method employed for depositing nanostructures of conducting polymers dictates potential uses in a variety of applications such as organic solar cells, light-emitting diodes, electrochromics, and sensors. A simple and scalable film fabrication technique that allows reproducible control of thickness, and morphological homogeneity at the nanoscale, is an attractive option for industrial applications. Here we demonstrate that under the proper conditions of volume, doping, and polymer concentration, films consisting of monolayers of conducting polymer nanofibers such as polyaniline, polythiophene, and poly(3-hexylthiophene) can be produced in a matter of seconds. A thermodynamically driven solution-based process leads to the growth of transparent thin films of interfacially adsorbed nanofibers. High quality transparent thin films are deposited at ambient conditions on virtually any substrate. This inexpensive process uses solutions that are recyclable and affords a new technique in the field of conducting polymers for coating large substrate areas.

Polymer:metal nanoparticle devices with electrode-sensitive bipolar resistive switchings and their application as nonvolatile memory devices

Abstract: Devices with a polystyrene film blended with gold nanoparticles capped with conjugated 2-naphthalenethiol exhibited electrode-sensitive bipolar resistive switchings. The resistances of the two states could be different by almost three orders of magnitude, and the devices could be switched between the two states for numerous times. Thus, these devices can be used as nonvolatile memory devices. The resistive switching voltage is related to the work function of the electrode. The electrode sensitivity of the resistive switchings is attributed to the contact potential at the contact of gold nanoparticles and electrode arising from charge transfer between them.