S-layer proteins of various lattice-forming types are the most abundant protein by mass on earth. They form the outermost cell crystalline component in a broad range of bacteria and archaea. They are porous monomolecular layer with unit cell size in tens of nanometers. These monomer proteins are capable of forming self-assembled mono- or double layers. Isolated from cell surfaces or through recombinant protein production, they are able to form ordered 2D crystal lattice on a variety of non-cellular surfaces. We study S-layer SbpA protein, which is found in mesophilic organism Lysinibacillus sphaericus with square lattice crystallinity. The recombinant SbpA (rSbpA) can be genetically modified and expressed in E. coli in different truncated forms. Using both the wtSpbA and truncated rSbpA, we reproduced the unique two-dimensional self-assembly pattern on several solid or flexible surfaces of interests towards electronic devices. By surface modification we can promote the self-assembly of SbpA on low affinity substrates. This enables a potential mean of creating complex functional bio-nanostructure. Delicate control of the self-assembly processes of S-layer on surfaces also serves the prerequisite of building the supramolecular structure as bio-electronic platform through protein fusing. Understanding of the electrical response from s-layer proteins provides a bridge between biological systems and electronic devices. Scale-up production and understanding the detailed interaction of the S-layer interface will likely be useful for nanobiotechnology and synthetic biology.

In this work we report the electrodeposition parameters of Sn-graphene films in aqueous solutions and silicon films in propylene carbonate. The galvanostatic electrodeposition of tin-graphene films from a sulfate-based acidic solution on copper substrates has been studied evaluating the effect of stirring on the morphology and the electrochemical performance. SEM analysis of films deposited galvanostatically at -10 mA.cm−2 for 20 minutes at 25 °C reveals that electrodeposition is suitable to generate continuous and homogeneous films with thickness values in the micrometer range. XRD analysis shows many intermetallic Cu-Sn crystalline phases are formed, as opposed to a pure amorphous tin layer. So far, electrochemical characterization has only been performed over a short number of charge-discharge cycles. The galvanostatic electrodeposition of silicon from propylene carbonate in galvanostatic mode has been carried out, but is currently extremely challenging to obtain continuous and homogeneous films. The XRD characterization has suggested the possible presence of amorphous phases in the films deposited at -1.0 mA.cm-2 for 30 minutes at 25 °C.

Piezoelectric semiconductors (PS) nanofibers, which simultaneously exhibit piezoelectricity and unique electric conductive behavior, have huge applications in sensors, energy harvesters, and piezoelectric field effect transistors. Electromechanical fields and charge carrier in PS nanofibers can be effectively controlled by a mechanical force. One-dimensional linear equations for PS nanofibers, which are suitable for small axial force and small electron concentration perturbation, are presented. Analytical expressions for the electromechanical fields and electron concentration in the fiber are obtained. Numerical results show that the electromechanical fields near the two ends are sensitive to the initial electron concentration and the applied axial force.

Physics forms the core of any Materials Science Programme at undergraduate level. Knowing the properties of materials is fundamental to developing and designing new materials and new applications for known materials.

“Physical Physics” is a physics education approach which is an innovative and promising instruction model that integrates physical activity with mechanics and material properties. It aims to significantly enhance the learning experience and to illustrate how physics works, while allowing students to be active participants and take ownership of the learning process. It has been successfully piloted with undergraduate students studying mechanics on a Games Development Programme. It is a structured guided learning approach which provides a scaffold for learners to develop their problem solving skills.

The objective of having applied physics on a programme is to introduce students to the mathematical world. Today students view the world through smart devices. By incorporating student recorded videos into the laboratory experience the student can visualise the mathematical world. Sitting in a classroom learning about material properties does not easily facilitate an understanding of mathematical equations as mapping to a physical reality. In order to get the students motivated and immersed in the real mathematical and physical world, an approach which makes them think about the cause and effect of actions is used. Incorporating physical action with physics enables students to assimilate knowledge and adopt an action problem solving approach to the physics concept. This is an integrated approach that requires synthesis of information from various sources in order to accomplish the task. As a transferable skill, this will ensure that the material scientists will be visionary in their approach to real life problems.

Progress in ultrafast terahertz (THz) communications has been limited due to the lack of picosecond switchable modulators with sufficient modulation depth. Gallium arsenide nanowires are ideal candidates for THz modulators as they absorb THz radiation, only when photoexcited – giving the potential for picosecend speed switching and high modulation depth. By embedding the nanowires in a polymer matrix and laminating together several nanowire–polymer films, we increase the areal density of nanowires, resulting in greater modulation of THz radiation. In this paper, we compare PDMS and Parylene C polymers for nanowire encapsulation and show that a high modulation depth is possible using Parylene C due to its thinness and its ability to be laminated. We characterize the modulator behavior and switching speed using optical pump–THz probe spectroscopy, and demonstrate a parylene–nanowire THz modulator with 13.5% modulation depth and 1ps switching speed.

In this work, calcium fluoride (CaF2) and Tb3+-doped calcium fluoride (CaF2:Tb3+) thin films were prepared by electrochemical methods. According to EDS and XRD results, CaF2 thin films undergo through a phase transformation from cubic CaF2:Tb3+ to NaTbF4 when Tb3+ concentration in the electrolytic bath is increased. So that, peaks showed a very clear shifting towards lower angles. On the other hand, optical absorption results showed the typical range of transparency from IR to UV, and from photoluminescence (PL) spectra results it can be observed that it is possible to identify the f-f transition of Tb3+. The PL at low temperature allows finding the quenching concentration when the PL intensity decreases at the highest doping concentration value. However, the results also showed that the transition of Tb3+ does not seem to be affected by the coexistence of the secondary phases such as cubic NaTbF4. In the case of RE-doped CaF2 thin films materials, they can be used with a double purpose for solar cell applications, not only as antireflecting coating, but also as a host for lanthanide doping for down conversion of light. These properties could be very useful for photovoltaic applications, so that the spectral range of light conversion could be increased to achieve higher conversion efficiency values.

This article reports investigation of the effects of high-rate stochastic micro-mechanics on the produced particulate size distribution during ball milling of reactive bimetallic foils (nanoheaters), by experimental and computational modeling. In particular, Ni-Al foils are ball-milled at various load charges, revolution rates and process durations, and the resulting particulate geometries are characterized by micrograph statistical analysis. Numerical simulation of the evolving particulate structure is based on coalescence and fragmentation of flexible monometallic ellipsoidal primitives, impacted by milling balls and vial walls with kinetic theory-based kinematics. Particulates are constrained by discrete compliant and continuum media and undergo conceptual ideal elastic transformations modeled by strain energy methods, and recast into inelastic frictional and plasticity-driven welding and fracture events. Finally the theoretical model predictions of particulate size distribution are validated against laboratory microscopy observations.

Ag7Fe3(P2O7)4 is a 3D structured material which has been recently studied as a possible cathode material for lithium batteries. Notably, Na7Fe3(P2O7)4 is reported to be a fast-ion conductor, yet poor electrical conductor. Here, partial replacement of Na+ for Ag+ yielded Na2Ag5Fe3(P2O7)4 pyrophosphate framework where the formation of Ag metal is proposed to increase the intrinsic low electrical conductivity of this polyanion electrode. Specifically, the Ag5Na2Fe3(P2O7)4 -Ag composite is synthesized via chemical reduction of Ag7Fe3(P2O7)4 using NaBH4. The occupancy of Ag+ and Na+ in each site was determined via Rietveld analysis of the diffraction pattern. Electrochemistry of the Ag5Na2Fe3(P2O7)4 -Ag metal composite was explored with voltammetry and galvanostatic charge/discharge cycling. The Ag5Na2Fe3(P2O7)4 -Ag metal composite electrodes displayed good rate capability assisted by the presence of Ag metal from the chemical reduction and in-situ electrochemical formation of a Ag conductive network.

We present the first detailed structure-function study of a photoconducting ionic porphyrin supermolecular assembly, fabricated from tetra(N-methyl-4-pyridyl)porphyrin (TMPyP) and tetra(4-sulfonatophenyl)porphyrin (TSPP) in a 1:1 stoichiometric ratio. Rod like crystals large enough for single crystal diffraction studies were grown by utilizing a nucleation and growth model described in our previous work. The unit cell of the TMPyP:TSPP crystals is monoclinic P21/c and the cell constants are a = 8.3049(11) Å, b = 16.413(2) Å, c = 29.185(3) Å, β = 92.477(9)°. These crystals have smooth well defined facets and their internal structure consists of highly organized molecular columns of alternating porphyrin cations and anions that are stacked face to face. For the first time crystal morphology (habit) of an ionic porphyrin solid is predicted by using the crystal structure data and applying attachment energy (AE) model. The predicted habit is in good agreement with the experimental structural morphology observed in AFM and SEM images of the TMPyP:TSPP crystalline solid. The TMPyP:TSPP crystals are non-conducting in the dark and are photoconducting. The photoconductive response is significantly faster with excitation in the Q-band (Red) than with excitation in the Soret band (blue). DFT calculations were performed to determine their electronic band structure and density of states. The TMPyP:TSPP crystalline system is a useful model structure that combine the elements of molecular organization and morphology along with theory and correlate them with electronic and optical electronic properties.

The composite Li-ion battery anode material of Fe2SiO4, Fe3O4, Fe3C (Fe-Si-O) and carbon nanotubes was prepared by a simple one-step reaction between ferrocene and tetraethyl orthosilicate. When cycled at 100 mA g-1, this material exhibited ever-increasing capacities and reached 588 mAh g-1 at the 280th cycle. At 500 mA g-1, a reversible capacity of 350 mAh g-1 was retained for 600 cycles. Compared with Fe3O4 materials, the Fe-Si-O/CNT exhibited superior long-term high-rate performance, which could mainly result from its enhanced stability and conductivities by introducing silicates and CNTs during the one-step synthesis.

Geopolymers are recently developed ceramic materials produced by alkaline activation of thermally activated natural materials such as metakaolin. Due to their promising application in the field of structural components, the presence of a piezoresistive effect is a very useful property for such materials because it allows the real time self-monitoring of civil infrastructures. As observed for cement-based materials, the use of a conductive filler can enhance the piezoresistive response by avoiding measuring issues related to the electrical polarization. In this work we present preliminary results about the piezoresistive characterization of a metakaolin based geopolymeric mortar filled with graphene nanoplatelets. Composites with different graphene weight concentrations (0, 0.1, 0.5, 1%) were produced and the gauge factor (the ratio between the electrical resistance variation and the imposed strain) was calculated by means of dynamic four-probe resistance measurements. Very high gauge factor values (in the range of 1000-2000) were recorded and they can vary according to the dispersion quality of the graphene nanoplatelets into the ceramic matrix.

Copper-alumina and copper-silica aerogels formed by impregnation of a copper(II) salt into an alumina or silica wet gel before supercritical extraction have been found to contain copper in multiple oxidation states: Cu0, Cu+1 and Cu+2. These aerogels are effective at catalyzing the reduction of NO and the oxidation of HCs and CO under conditions similar to those found in automotive three way catalysts. In this work we have developed a preparation method incorporating Cu0, Cu+1 and Cu+2 nanoparticles directly into silica aerogels. Nanoparticles in the form of (a) Cu0 nanorods (100 nm diameter, 10-20 μm length); (b) Cu+1 nanoparticles (350 nm diameter); and (c) Cu+2 nanoparticles (25-55 nm diameter) were added (0.5-15% by weight) to separate precursor mixtures consisting of tetramethyl orthosilicate, methanol, water and ammonia. These precursor mixtures were then processed using a rapid supercritical extraction (RSCE) method to form aerogels. The resulting aerogels show evidence of nanoparticles dispersed throughout the silica aerogel structure. Addition of Cu+1 and Cu+2 nanoparticles decreases the surface area of the aerogels significantly. X-Ray diffraction shows that regardless of initial oxidation state of the nanoparticles, crystalline Cu0 is detected after RSCE processing to 290 °C. Following heat treatment at 700 °C, crystalline Cu+2 is detected. The copper containing silica aerogels are found to be catalytically active with light-off temperatures (50% conversion) for NO and CO at 400 °C in three-way catalytic applications.

The simultaneous capability of high-strain deformation and high shape recovery ratio constitutes a great challenge in design of the shape-memory polymers. Here we report on poly(carbonate-urea-urethane)s (PCUUs) synthesized by a precursor route, based on oligo(alkylene carbonate) diols, L-lysine diisocyanate (LDI), and water vapor. When programed with a strain of ε prog = 800%, the PCUU networks exhibited a one-way shape-memory effect (1W-SME) with excellent shape fixity (> 97%) and shape recovery (> 99%) ratios. The switching temperatures (T sw) varied between 50 and 56 °C and correlated to the melting transitions of the switching domains. The obtained PCUUs capable of high-strain are interesting candidate materials for degradable biomaterials as required in smart medical devices.

Starting in 2007, a portable, hand-held X-ray fluorescence spectrometer was used to elementally analyze and determine the geological source of obsidian artifacts in the Mediterranean, effectively replacing the instruments used in my previous research studies - INAA, LA-ICP-MS, ED-XRF and an electron microprobe with WDS. Approximately 400 geological obsidian samples from the Mediterranean area, and 8500 obsidian artifacts from prehistoric sites in Italy, France, Croatia, Malta, Tunisia, Greece, Cyprus, Turkey, Israel, and Egypt have been analyzed non-destructively by pXRF. Overall, the pXRF can distinguish all of the individual sources, based on the composition of Fe and trace elements Rb, Sr, Y, Zr, and Nb, as well as assign most artifacts to specific subsources and thus addressing archaeological research hypotheses about trade and exchange in many different time periods.

Samples of Ni57-xNdxFe18Ga25 with x=2 and 4 were prepared in ribbon form by rapid quenching via melt spinning route. The samples were analyzed by X-ray diffraction (XRD), magnetic measurements and Mössbauer spectroscopy, both in the as-quenched form and after thermal annealing at 900 oC for 2 min and 400 °C for 2 hours. For x=2 the Nd atoms are completely dissolved in the Ni-Fe-Ga matrix, while for x=4 the additional occurrence of the secondary 2:17 phase could be resolved. These findings were supported by the analysis of hyperfine magnetic field distributions obtained from the non-linear least-squares fitting of the Mössbauer spectra.

Cold atmospheric pressure plasma has been intensively studied due to growing interest in biomedical applications. For example, it has been revealed that the plasma-irradiated cell culture medium (PAM: Plasma Activated Medium) shows antitumor effect as well as the direct plasma treatment. Long-lived reactive oxygen and nitrogen species (RONS), such as hydrogen peroxide (H2O2), nitrite (NO2-), and nitrate (NO3-), are considered as a main product in PAM. Therefore, investigation of the production characteristics of RONS in PAM with different experimental parameters is important. Here, we focused on humidification of feed gas (argon or helium) and effect of gap between the nozzle of the plasma jet and liquid surface. As a result, H2O2 concentration was increased by humidification of both feed gases. However, the concentration of NO2- and NO3- was decreased by the humidification of helium. In addition, the remarkable effect of the humidification on H2O2 production was observed when the plasma jet was in contact with the liquid surface.

The use of ceria abrasives in the chemical mechanical polishing (CMP) of glass allows us to prepare extremely smooth surfaces because it aides both the chemical and mechanical aspects of the polishing process. The mechanism of CMP has remained vague, but the redox of Ce4+/Ce3+ would play a major role for the formation of hydration layer by the chemical factors of CMP. This redox accompanies the process of the charge transfer at glass/slurry interface. Electron charge carrier would be important role in chemical polishing if the redox reaction occurs during polishing. We then prepared the polishing model that it is possible to estimate slurry resistivity and the interfacial area specific resistance (ASR). The effects of abrasive compositions and slurry solution on chemical factor of CMP were investigated to clarify CMP mechanism. The hydration layer forms as a result of the shear stress during polishing but is independent of polishing loads. The amount of hydration layer as well as removal rate was increasing with increasing lanthanum concentration dissolved in ceria lattice. Small amount addition of NH4NO3 increase electron charge carrier density in slurry and improves removal rate, but excess addition inhibited hydration reaction by steric hindrance.

SiO2-MgF2/TiO2 double-layer films with antireflective, self-cleaning and adherent properties were prepared by spin-coating SiO2-MgF2 and TiO2 sol on glass substrate successively and subsequently being calcined at 250°C. The optical and structural properties of films have been investigated by visible spectrophotometer and field emission scanning electron microscope, respectively. At the same time, self-cleaning property generated from superhydrophilicity and photocatalysis was obtained. The results indicated that the as-prepared SiO2-MgF2/TiO2 double-layer films show a maximum increase in transmittance near 520 nm wavelength of 2.8% and photocatalytic property with the R value of 4.7(JIS R 1703–2).It has been demonstrated that high transmittance, self-cleaning and adherent composite has been obtained by a simple sol–gel route presenting good potential to be applied on photovoltaics systems.

Given the lack of satisfying treatments for consolidating marble affected by thermally induced grain detachment (the so-called "sugaring"), the use of aqueous solutions of diammonium hydrogen phosphate (DAP) has recently been proposed. The idea is to form a new binding mineral (hydroxyapatite, HAP) as the reaction product between the DAP solution and the calcitic substrate. In this study, we investigated the effects of adding small quantities of ethanol (EtOH) to the DAP solution, with the aim of favoring HAP formation. The results of the study indicate that, when a 0.1 M DAP and 0.1 mM CaCl2 solution in 10 vol% EtOH is used, complete coverage of marble surface with a crack-free coating with reduced porosity is achieved (whereas no coating is formed without EtOH addition). This is thought to be a consequence of the weakening of hydration shells of phosphate ions in the DAP solution, thanks to the presence of ethanol molecules. When used to restore mechanical properties of weathered marble, the treatment with 10 vol% EtOH was found to significantly improve the dynamic elastic modulus after a single application and to completely restore it after a second application.

Light collection efficiency and specific molecular detection are crucial factors for the performance of bio-chemical molecule sensors. In this paper, the low optical-reflection silicon (Si) substrates which combine reduced optical reflectivity by light trapping effect and high Raman enhancement ability of gold nanoparticles (Au-NPs) coated textured Si substrates are investigated for surface-enhanced Raman scattering (SERS). A fast, single-step and highly controllable nanosecond (ns) laser processing technique is employed to fabricate textured Si substrates under ambient conditions. Parallel arrays of micro-pyramids are fabricated on Si surface by direct laser writing two-dimensional structures. SEM micrographs clearly show well-ordered surface features in the form of micro-pyramid shape with well-defined sharp tips on the laser processed Si substrates. The aggregation of Si micro/nanoparticles on Si surface forms nanocavities and nanogaps and further enhances the surface roughness in order to minimize the optical reflection. The low optical reflection Si substrates exhibit optical reflection below 15% over a broad wavelength range from 300 nm to 1200 nm. The textured Si substrates with high signal reproducibility are successfully applied as SERS substrates to detect a very small concentration of Rhodamine B molecules with an average enhancement factor of the order of ∼107. The low optical reflection and SERS signal amplification are also altered by the variation of laser pulse energy resulting into low optical reflection and high SERS signal intensity over the entire laser-patterned area. The effect of surface roughness on water contact angle was studied after the modification with Polydimethylsiloxane (PDMS), the surfaces show perfect superhydrophobicity with almost no water adhesion. This approach provides a novel high-speed and cost-effective method for fabricating SERS substrate with micro/nano-scale surfaces roughness and low optical reflection for high Raman signal enhancement.