Organic semiconductor technology paves the way to low cost lightweight, flexible, printable electronics circuits and sensors. A novel lateral multilayer organic semiconductor photosensor is fabricated using small molecule organic semiconductor. A specialized interface layer is introduced between the metal electrodes and the organic semiconductor layer. The interface layer material is a large band gap and low electronic conductivity material. The use of interface layer limits the charge injection from the electrodes to the organic semiconductor and overall improves the photosensor dark current performance with an additional advantage to apply high voltage for improved collection. This design has low dark current with high photo-to-dark current ratio and can be set to high bias mode of operation.

Lateral interdigitated photodetector, with bottom contact Metal Semiconductor Metal (MSM) is fabricated consisting of interface layer and organic semiconductor bilayer. Small molecule organic semiconductor 3,4,9,10 perylenetetracarboxylic bisbenzimidazole (PTCBI) and Copper-Phthalocyanine (CuPc) are used as the active bilayer, where as polyamide forms the interface layer. Current through the sensor is measured in both dark and in light (wavelength 400nm). The dark current density in a 1mm2 photosensor area with 5μm lateral electrode spacing at 10V/μm measured equal to 10-5mA/cm2 and a photocurrent density of 10-3 mA/cm2 under 0.3mW/cm2 incident optical power. The photo to dark current ratio is measured to be equal to ∼103.

This photosensor has an application in large area imaging for example portable lightweight detectors. Other applications of this sensor include indirect medial imaging and as a biosensor in UV Spectroscopy study of bacteria cultures.

Hematite (α-Fe2O3) nanoparticles were diffused of two different shapes (spherical and cubical) in PEDOT:PSS matrices below the percolation threshold. Increases in conductivity within a distinct range in concentration were observed in the dark and under simulated solar illumination. The effect was ascribed to a generalized Poole-Frenkel effect in conjunction with basic properties of heterojunctions and electrostatic dipoles, and verified through data fitting. A difference in behaviour between sphere- and cube-based nanocomposites was also observed.

An introductory materials science course has been traditionally taught at Texas A&M University - like at many other universities - through lectures with minimal active student involvement. With this approach, most students just reproduce what they are given and accept it without any challenge or question. The authors have redesigned this course to include an active learning component. While the course consists of lecture-based classes during regular teaching hours to keep the essence of traditional teaching, the authors incorporated a research experience to their class in order to engage students and encourage them to apply the content seen in class to real-word problems with a higher level of expertise. The aim of the study was to discover the effectiveness of the authors’ redesign. We hypothesized that the research experience would facilitate the learning of knowledge content and the enthusiasm for the chosen field of study, i. e. engineering. The results reveal that students in the experimental condition consistently show a greater gain in knowledge, but there is no sufficient evidence suggesting that the research experience increase the student’s enthusiasm to be an engineer.

We investigate structural and magnetic properties of Co thin-film electrodes used in a new type of spin quantum cross (SQC) devices, in which a strong stray magnetic field could be generated between the both edges of magnetic thin-film electrodes. We also calculate the stray field between the two edges of Co thin-film electrodes in SQC devices and discuss the possibility to novel spintronics devices. As a result of magnetic force microscopy (MFM) observations, the stray fields are generated from the Co edges, and they are uniformly distributed. This result indicates that magnetic single-domain structures can be formed. This is consistent with the result obtained by magneto-optical Kerr effect (MOKE). The theoretical calculation reveals that the stray field exhibits as high as 7000 Oe under the condition that the distance between the two Co edges is 5 nm and the Co thickness is 19 nm. These results indicate that SQC devices utilizing stray fields can be expected as novel spintronics devices, such as spin filtering devices and beyond CMOS switching devices.

Silicon is emerging as a very attractive anode material for lithium ion batteries due to its low discharge potential, natural abundance, and high theoretical capacity of 4200 mAh/g, more than ten times that of graphite (372 mAh/g). This high charge capacity is the result of silicon’s ability to incorporate 4.4 lithium atoms per silicon atom; however, the incorporation of lithium also leads to a 300-400% volume expansion during charging, which can cause pulverization of the material and loss of access to the silicon. The architecture of the anode must therefore be able to adapt to this volume increase. Here we present a layered carbon nanotube and silicon nanoparticle electrode structure, fabricated using directed assembly techniques. The porous carbon nanotube layers maintain electrical connectivity through the active material and increase the surface area of the current collector. Using this architecture, we obtain an initial capacity in excess of 4000 mAh/g, as well as increased power and energy density as compared to anodes fabricated using the standard procedure of slurry casting.

Carbon nanotubes (CNTs) have been shown to be a viable conductive additive in Li-Ion batteries [1]. By using CNTs battery life, energy, and power capability can all be improved over carbon black, the traditional conductive additive. A significantly smaller weight percentage (5% CNTs) is needed to get the same conductivity as 20% carbon black. Many of the previous efforts found that a combination of conductive additives was most advantageous [2]. Unfortunately many of these efforts did not attend to the unique challenge that dispersing nanotubes presents and used non-optimal methods to disperse CNTs (e.g. ball milling) [3,4]. With poor dispersion a stable and resilient conductive network in the cathode is hard to form with CNTs alone. Here we investigate the formation of LiFePO₄ with CNTs using a polyol process synthesis.

Multi-walled nanofibers with their outstanding properties have found expanding applications on drug delivery systems, biosensors, self-healing materials and many other state-of-the-art technologies. This work investigates the fabrication and morphological control of multi-walled structured electrospun polymeric nanofibers by multi-axial electrospinning system. This process is based on a nozzle allowing multi-axial extrusion of different fluids with concentric orders. Two spinnable polymers of poly(methyl methacrylate) and polyacrylamide are chosen for the fabrication of middle and outer walls of co-axial hollow nanofibers, respectively. Hansen’s solubility parameters are used to systematically optimize the solvent selection for each layer and control the degree of miscibility of layers with the purpose of tailoring the final wall morphology of nanofibers. Characterization studies are performed by Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, Fourier Transform Infrared Spectroscopy, and Thermal Gravimetric Analyzer.

We wish to propose an impedance spectroscopic method for the quality control of contact lenses by measuring the pore resistance. Silicone hydrogels are excellent materials for use as contact lenses and their on eye performance is dependent on salt intrusion characteristics which are related to the pore resistance and water uptake. When the contact lenses are placed on the eye, they are expected to permeate ions and molecules to maintain ocular health. The hydrogel pores control the permeability and can be viewed as a quality control parameter. Two models are considered here: in one, the contact lenses are considered as strong rigid films with no permeability. In another, the hydrogels are having ionic permeability. We designed a silicone hydrogel contact lens attachment holder that is amenable for electrochemical impedance measurements. The electrochemical impedance measurements were carried out in an inert medium of 0.1 M Na2SO4. The impedance measurement experimental parameters used were a) AC potential 10 mV rms b) frequency range 0.1-210 kHz and c) open circuit potential of 0.207 V. The impedance variation with frequency was constructed for a number of hydrogels. The ideally acceptable silicone hydrogel contact lenses showed an impedance change with frequency in a sigmoidal fashion with a characteristic phase angle (acceptable in the range of 70-75o). The hydrogel pore resistances for the acceptable contact lenses are in the range of 4.5-11 kΩ. When the impedance showed a linear decrease or no well defined phase angle, the contact lens is considered acting as an insulator-a test for rejection. A test of the model was done with several acceptable contact lenses in the market. This study revealed interesting aspects of the influence of pulsating electric field on the silicone hydrogels.

Recently there have been reports of hot carrier thermoelectric response in nanostructured materials like graphene and MoS. We report observing that thermoelectric nanowire junctions detect light. In these experiments we employed devices composed of bismuth nanowire arrays which are capped with a transparent indium tin oxide electrode. The incident surface features very low optical reflectivity and enhanced light trapping. The unique attributes of the thermoelectric arrays are the combination of strong temporal and optical wavelength dependences of the photocurrent. Under infrared illumination, the signal can be completely described by “quasi-equilibrium” thermoelectric effects considering cooling rates given by heat diffusion through the array. The thermal diffusivity is found to be less (by a factor of 3.5) than in the bulk, a result that we discuss in terms of phonon confinement effects. In addition to a thermoelectric response, under visible illumination, we observe a photovoltaic response.

Lead-free, piezoelectric (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films were epitaxially grown onto (100) SrTiO3 substrate via pulsed laser deposition. The effects of post-annealing temperature on the crystal phases, mosaic spread, and chemical composition of the deposited (Na,K)NbO3 and (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films were analyzed. Results indicate the epitaxial growth of (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films deposited at an oxygen pressure (PO2) of ≥40 Pa and substrate temperature (Ts) of 800°C. The alkaline-deficiency could be suppressed in the (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films deposited at PO2 ≥ 70 Pa. AFM profile of the (Na,K)NbO3 post-annealed at 1000°C indicates the epitaxial growth of film with atomically flat step-terrace structure, while that of the (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 film post-annealed at 1200°C shows relatively smooth surface with step-terrace structure and several cubic crystals. It was also found that the preferential evaporation of alkaline components could be suppressed by annealing under covered substrate condition.

The effect of compositional changes on the glass forming ability of Mg alloys containing Y was studied. Four rapidly-solidified Mg-alloys were investigated: Mg91Y7.5La1.5, Mg85Y12La3, Mg86Y9.5Cu2.5La2 and Mg82Y11La4Eu3. XRD and DSC spectra revealed that the Mg86Y9.5Cu2.5La2 was the most amorphous out of the investigated alloys. A model based on a spinodal-like decomposition of a supercooled liquid alloy was developed. The model provides qualitative and quantitative explanation for the variation in glass forming ability.

This article deals with the development of autoclaved composites (AC) with nanostructured additive (NSA) and reports on the beneficial effects of NSA in autoclaved lime-silica mixtures.

Based on the results of X-ray diffraction and electron microscopy investigation, the effects of hydrothermal conditions on the mechanisms of lime-silica interaction are revealed. It is demonstrated that the addition of NSA intensifies the formation of the C-S-H phase, reduces the quantities of amorphous phases and enables the formation of low-base calcium hydrosilicates (11Å-tobermorite and xonotlite).

The physical and mechanical properties of autoclaved composites with NSA are investigated and optimized. The reported research demonstrates the feasibility of NSA application to improve the performance of autoclaved materials.

Form-finding describes the process of finding a stable equilibrium shape for a structure under a specific set of loading for a set of boundary conditions. Both physical (experimental) and numerical (computational) form-finding methods have been employed by structural engineers and architects for the design of shape-resistant structures: structures whose behavior depends mostly on their global spatial configuration and less on the properties of their individual components. The shape of dielectric elastomer minimum energy structures (DEMES) depends on the equilibrium between the pre-stressed elastomeric membrane and its inextensible frame. Therefore, DEMES can be modeled and analyzed using structural form-finding techniques. We applied dynamic relaxation (DR), a well-established explicit and efficient numerical form-finding and analysis method, to simulate DEMES equilibrium shapes and predict the elastic energy of DEMES. The DR-DEMES model shows generally good agreement with its physical implementation counterpart, as it captures the equilibrium shape and also the elastic energy in function of shape. However, we found that the numerical and the physical models differ in the pre-stress that is required to obtain a specific equilibrium shape. Therefore, in this study we introduce hyper-elasticity in the DR-DEMES model. With this refinement in physical parameters the DR-DEMES model approaches the pre-stress state of the physical DEMES implementation more closely, while it maintains the computational efficiency of the form-finding approach. We conclude that dynamic relaxation, with its low computational cost, is a powerful tool for the design of novel DEMES applications.

We present results of theoretical and experimental studies of whispering-gallery modes in optical microdisk resonators interacting with subwavelength dielectric particles. We predict theoretically and confirm by direct observations that, contrary to the generally accepted models, both peaks of the particle-induced doublet of resonances are red shifted with respect to the position of the initial resonance.

Molecular Dynamics simulation are employed to investigate the structures and mechanical behavior of both symmetric and asymmetric Σ5[0 0 1] tilt grain boundaries (GBs) of copper bicrystal under uniaxial tension and shear deformation. Simulation results indicate that the Σ5 asymmetric GBs can facet into their corresponding symmetric GB structures. The maximum tensile stress of symmetric GBs is higher than the asymmetric ones at both 10 K and 300 K, which suggests the symmetric GBs may have a more stable boundary structures. All the Σ5 GBs investigate in this study can migrate under the shear deformation with different velocity. The migration of Σ5 symmetric GBs is realized by uniform displacement of local atoms and rotation of the atomic group in “E” structural unit, while for the asymmetric GBs, the migration is identified to be a diffusion-related process result from local atoms shuffling.

III-V on Si multijunction solar cells represent an alternative to traditional compound III-V multijunction cells as a promising way to achieve high efficiencies. A theoretical study on the energy yield of GaAs/Si tandem solar cells is performed to assess the performance potential and sensitivity to spectral variations. Recorded time-dependent spectral irradiance data in two locations (Singapore and Denver) were used. We found that a 4-terminal contact scheme with thick top cell confers distinctive advantages over a 2-terminal scheme, giving a yield potential 21% higher than the 2-terminal scheme in Singapore and 17% higher in Denver. The theoretical energy yield benefit of a 4-terminal device emphasizes the need for further technology development in this design space.

The United Kingdom aims to decarbonize its national electricity generation in order to transition to a low carbon economy. Solar, wind, hydro and thermal energy conversion are renewable alternatives to fossil fuels and are currently being explored that may form part of the future generation mix of the country.

How does materials scientist's work addressing energy research challenges for solar and storage (for example) translate into the adoption of new technology? How appropriate are the technology usage visions of the scientists? How can technology users better inform the materials science motivations? This report will focus on how a multidisciplinary team of researchers from the Universities of Sheffield and University of Durham, community members and industry representatives are jointly developing renewable energy projects to try to answer these and other questions. The history of the project will be presented as well as the methodology used to collaboratively engage the community participants.

This work is supported by a grant provided by the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom.

A facile and novel method of fabricating large-area-patterned monolayer of polytetrafluoroethylene(PTFE) nanoparticles was achieved using surface charge induced colloidal deposition. Chemical processes of amination and hydroxylation were used to make the silicon substrates positively and negatively charged, respectively, while the PTFE colloidal nanoparticles were anisotropic and negatively charged. After colloidal deposition, an ordered monolayer with microholes was formed on the amination surface, while an island-like monolayer was achieved on the hydroxylation surface. Both of the two kinds of monolayers were as large as 1.5 square centimeters. It is worth pointing out that these large-area-patterned monolayers were fabricated without any templates and the whole process only took several hours. The formation mechanism of the different structures can be generally attributed to the cooperation and competition of three-body, two-body and particle-wall interactions. It is believed that the interesting patterned monolayer formation mechanism, high production efficiency, good adaptability and quality will make this novel method attractive.

This work focuses on the effect of gamma-ray radiation conditions on the stimuli-responsive of polypropylene (PP) films and silicone (SR) rubber substrates grafted with N-vinylcaprolactam (NVCL) and acrylic acid (AAc). PP films and SR rubber were weighed and placed into glass ampoules and exposed to 60Co γ-source in the presence of air at room temperature, at dose rate around 12 kGy h-1 and dose between 5 and 70 kGy. Solutions of NVCL and AAc (1/1, v/v), 50 % monomer concentration (v/v) in toluene were added to the samples, the ampoules were degassed by repeated freeze-thaw cycles (5 times per 20 min) and sealed. The ampoules were heated at 60 or 70 °C at reaction time per 12 h. To extract the residual monomer and homopolymer formed during the grafting, the samples were soaked in ethanol for 24 h and then in distilled water, followed by drying under vacuum to constant weight. The values of grafting percentage achieved at a given irradiation dose were higher for SR than for PP. Samples where characterized by FTIR-ATR, DSC, swelling, LCST, and pH critical point.