Intermolecular photoinduced electron transfer (PeT) has found a wide range of photoelectronic utility. One of the most notable examples includes the natural photosynthesis, where PeT between chlorophyll and quinone triggers photon-to-chemical energy conversion. We observed that phosphorescent Ir(III) complexes exhibited efficient PeT to trigger a cascade of catalytic intermolecular electron transfer among electrochemically active molecules. To establish the photoelectronic utility of PeT, a series of cyclometalated Ir(III) complexes were prepared and evaluated for photoelectrocatalytic conversion of dithienylethene (DTE) compounds. Selective photoexcitation of the Ir(III) complexes facilitated ultrafast PeT from DTE. The oxidative PeT initiated electrocatalytic cycloreversion of DTE, yielding one order of magnitude enhancement in quantum yields relative to direct photochromic conversion.

The present investigation involves the synthesis of chitosan based composite sponges in view of their applications in wound dressing, antibacterial and haemostatic. A facile CO2 bubbles template freeze-drying method was developed for the fabrication of macroporous chitosan- poly(vinyl alcohol) (PVA) composite sponges with a typical porosity of 50% and pore size of 100-300 µm. The composite sponges show a high water absorption rate up to 60 times of its weight and a water vapor transmission rate of 30 ∼ 70g/m2 • h. Effects of the content of cross-linking agent and PVA on mechanical properties and moisture permeability were examined. Improved strength and flexibility of the chitosan sponges were observed with the presence of PVA. Further, the antibacterial and haemostatic activities have been demonstrated. The Chitosan/PVA sponges of high liquid absorption, appropriate moisture permeability, excellent antimicrobial and haemostatic activities have a great potential for wound dressing applications.

The electron transport properties of ultra-scaled amorphous phase change material (PCM) GeTe are studied using non-equilibrium Green’s function (NEGF). The inelastic electron-phonon scattering is included using Born approximation. It is shown that, in ultra-scaled PCM device with 6 nm channel length, less than 4% of the energy carried by the incident electrons from the source is transferred to the atomic lattice before reaching the drain, indicating that the electron transport is largely elastic. Our simulation results show that the inelastic electron-phonon scattering, which plays an important role to excite trapped electrons in bulk PCM devices, exerts very limited influence on the current density value and the shape of current-voltage curve of ultra-scaled PCM devices. The analysis reveals that the Poole-Frenkel law and the Ohm’s law, which are the governing physical mechanisms of the bulk PCM devices, cease to be valid in the ultra-scaled PCM devices.

In this study electrochemical and surface analysis were carried out in order to provide preliminary information to diagnose the state of conservation of two bronze bells from two Colonial religious building from San Francisco de Campeche City: The Cathedral of Nuestra Señora de la Purísima Concepción and the Ex-temple of San José. Small corroded bronze samples were retired from each bell and analyzed by using optical microscopy in order to observe the distribution of the oxides over metal surface. Complementary XRD analysis was used to identify crystalline phases formed as a consequence of bells interaction with the urban tropical environment of this city. Electrochemical techniques such as linear polarization resistance (Rp) and potentiodynamic curve (CP) were conducted “in situ” in order to evaluate the behavior of bell bronze patinas under the action of two artificial solutions that recreate typical electrolyte formed over corroded metal surfaces in urban environments.

Detailed structural studies of two lithiated metal oxides, Li2CuO2 and nanoscale LiCoO2, have been carried out using ex situ high-energy X-ray diffraction (XRD) and in situ X-ray absorption spectroscopy (XAS) with the objective of understanding structural changes that might cause capacity loss during cycling. XRD on the cuprate was studied at various states of charge and phase composition, and the bulk state was determined by Rietveld refinement and pair density function (PDF) analysis. Results showed a largely irreversible structural change of the material upon oxidation of Cu2+ as well as CuO formation. The in-situ XAS of the LiCoO2 was analyzed through a difference method to extract the changes in the local structure that occur upon cycling in both the near edge (XANES) and extended region (EXAFS). Results suggest that cycling causes site exchange of the Co and Li ions near the surface of the nanoscale LiCoO2.

This study investigates Sr surface segregation behavior and phase formation in La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), a commonly used cathode material for solid oxide fuel cells (SOFCs). (100)-oriented LSCF thin films were deposited on (110)-oriented NdGaO3 (NGO) substrates by Pulsed Laser Deposition (PLD). The samples were annealed in atmospheres with various CO2 partial pressures at 800°C. Using the synchrotron technique of Total Reflection X-ray Fluorescence (TXRF), surface segregation in these thin films were quantified. The morphological changes at the surface were examined by AFM studies. The kinetics and thermodynamics of the segregation are discussed.

Graphene nanoplatelets (GNPs) functionalised with platinum were explored as the active material in a high specific surface area ink. The ink had a transmission at 550nm (T550) = 85% and a charge transfer resistance (Rct) of 6Ω/cm2. Although the Rct is higher than required for laboratory cells having a Jsc of 20mA/cm2 under 1 sun test conditions it is sufficient for industrially produced reverse devices, especially when utilised for indoor applications where light conditions will be lower than 100W/m2. This was demonstrated by reverse illuminated DSC efficiencies with flexible cathodes which were equivalent to cells with sputtered platinum catalysts when subjected to 300W/m2 lighting or less. A modification to the ink, suitable for catalysing a Co2+/3+ electrolyte having an Rct of 2Ω/cm2 and T550= 85% was undertaken. This demonstrates potential for use in high efficiency cobalt mediated DSCs. The work shows that printed graphene catalysts are a versatile low cost replacement to sputtered platinum in reverse illuminated DSCs for dye sensitised solar cells.

Among the exceptional properties of isolated individual carbon nanotubes (CNTs), exceptional thermal conductivity along their axis has been demonstrated, However they have also shown poor thermal transfer between adjacent CNTs. Thick bundles of aligned CNTs have been used as heat pipes, but the thermal input and output power densities are the same, providing no heat spreading effect. We demonstrate the use of energetic argon ion beams to join overlapping CNTs in a thin film to form an interpenetrating network with an isotropic thermal conductivity of 2150 W/m K. Such thin films may be used as heat spreaders to enlarge the thermal footprint of laser diodes and CPU chips, for example, for enhanced cooling. At higher ion energies and fluence, the CNTs appear to collapse and reform, aligned parallel to the ion beam axis, and form dense high aspect ratio tapered structures. The high surface area of these structures lends themselves to applications in energy storage, for example. We consider the mechanisms of energetic ion interaction with CNTs and junction formation of two overlapping CNTs during the subsequent self-healing process, as well as the formation of high aspect ratio structures under more extreme conditions

Over 2000 micro-X-Ray Fluorescence (μ-XRF) measurements of iron gall inks were collected at the General Archive of the Nation in Mexico (Archivo General de la Nación, AGN). The portable X-Ray system SANDRA permitted detection of common elements present in all iron gall inks (e.g. Ca, Fe, S, etc.) as well as characteristic traces and impurities (e.g. Cu, Ni, Zn, Pb, etc). The documents in the data set originate from all over Mexico and are dated between the 16th and 19th centuries. All manuscripts were well preserved.

Extensive statistical processing of the relative X-Ray intensities revealed common features in groups of documents with the same provenance. Among the findings, there is a progressive trend to complex mixtures from the beginning of the 16th century to the 17th. A reverse trend was observed for the following century. Zinc, lead and seldom arsenic, chromium and mercury seem characteristic for northern areas whereas manganese seems common to the vast majority of studied inks.

As a general concern in conservation research, special attention was addressed to copper, as it is known to have additive effects to the degradation of cellulose. This metal seems fairly common to Mexican inks, especially during 18th century.

To the best of our knowledge, this is the first examination taken to such a large number of inks. This study contributes to the more-focused development of suitable treatments that tailor specific needs, since they are to be based on of ink’s composition. It sets a precedent for the study of these inks in the Americas and allows conservators and historians to gain further insight into the history of their usage in Mexico.

Optical control is a reversible and convenient technology, able to be measured in real-time, which makes it excellent for application to microfluidic, biomechanical, and electro-mechanical devices. These advantages are especially attractive for photo-responsive materials. In this study, we developed a new photo-responsive, electrostrictive material from a composite material made by mixing a dielectric polymer P(VDF-TrFE-CFE) and an organic photoconductive material TiOPc. The photo-responsibility of the material has been validated by corresponding actuators. We found that under white light illumination, deformation will increase which can be attributed to a decrease in the TiOPc impedance. We identified that the optimal TiOPc concentration for actuator applications is 10% P(VDF-TrFE-CFE)/TiOPc. Moreover, controlling the fluid flow within the capillary tube through light illumination also validated the photo-responsive actuator. Our results show that the mechanism and the photo-responsive material can be used to pursue further study on light controlling microfluidic, and related electro-mechanical devices.

Imidazoles present a tunable, versatile and economical platform for the development of novel liquid solvents and polymer membranes for CO2 capture. An overview of our studies in this area is presented, with emphasis on characterization of structure-property relationships in imidazole-based materials through both experimental and computational studies. To this end, a growing library of systematically varied imidazole compounds has been synthesized using only commercial available starting materials and straightforward reactions. Using this library of compounds, we have sought to understand and develop predictive models for thermophysical properties relating to process design, including: density, viscosity, vapor pressure, pKa and CO2 absorption capacity. Furthermore, we have discovered that imidazoles are stable in the presence of SO2 and can form reversible 1:1 adducts, which can be beneficial as SO2 is typically present at ppm levels alongside CO2 in flue gas from coal-fired power plants.

The electronic band structures of the hydrogenated graphene-like materials, graphane, silicane, and germanane, under tensile strains are calculated using first-principles calculation. The imposed tensile strain is in either the armchair or zigzag direction in the honeycomb lattice. It is found that the band gap of graphane gradually increases with the increase of the strain, whereas the band gaps of silicane and germanane decrease with the increase of the strain. There is little effect of the direction of the imposed strain on such strain dependences.

We designed and constructed a drop-on-demand (DOD) droplet dispenser using the piezo inkjet technique that is simple to construct and operate and makes use of readily available components. The droplet dispenser can be easily fitted with cost effective glass nozzles and can be readily tuned to produce consistent drop sizes. The dynamics of the droplet motion are obtained using a calibrated analog video imaging system. We observed very high accelerations for the ejected droplets that corroborate with the applied drive pulse amplitudes. The acceleration measured, near the ejection nozzle, was many times the acceleration of gravity with the largest value of 34g’s. We successfully dispensed glycol water solutions and aqueous suspensions of titanium oxide nanoparticles, with values greater than 10 in the measured pH. For the inkjet droplets deposited on smooth gold/chromium substrates (±3nm surface roughness variation), we observed the well-known coffee ring effect using optical microscopy and nanoparticle morphology using an atomic force microscope.

Interest in patterned polymer-based flexible nanodevices and sub-100 nm metal and transparent conducting nanostructured electrodes have led us to modify the traditional nanoimprint lithography technique to enable fabrication of an array of sub-100 nm diameter electrode structures. Transparent conducting electrodes (TCOs) are fabricated by coating one or multiple TCO layers of choice on top of a polymer nanostructured scaffold of appropriate dimension. By optimizing the thickness of each of these layers one may tune and optimize the trade-off between the conductivity and transparency of the sample. Incorporation of plasmonic materials such as Ag leads to interplay of localized and tunable surface plasmon resonances within the TCO structures. At plasmon resonance the reflection of the sample is minimized and absorption in the TCO structures dominates. Experimental and simulated reflection spectra of these structures are in good agreement, including the appearance of sharp spectral features that are absent in a simple planar analog. The simulated Brewster angle of the nanopillars decreases compared to the planar reference sample by up to 10-13 degrees depending on the height of the pillars and indicates a reduced effective refractive index. The depolarization factor obtained by ellipsometry is about 0.05, as anticipated for ellipsoidal pillars.

Shape Memory Alloys (SMA) metallic materials that change their mechanical and physical properties with temperature variation and mechanical loading, surprising engineers and researchers. In this way, one can develop thermomechanical actuators capable, for example, of generating force by blocking the shape recovery or change the natural frequency of a mechanical system by blocking resonance. The processing of these SMA are countless, each one with its specific limitation and particularity. This study aims to evaluate the influence of rapid solidification of a Ni-Ti SMA that is originally manufactured by Vacuum Induction Melting (VIM) and reprocessed by Plasma Melting (PM) followed by injection molding into different metal molds (steel, brass, aluminum and copper). The influence of such a processing is analyzed through Differential Scanning Calorimetry (DSC) and Electrical Resistance as a function of Temperature (ERT) to determine the effects on transformation temperatures. The results demonstrate that by using the copper mold one can provide greater uniformity of the material properties. Thus, there is the possibility of obtaining different kinds of SMA mini-actuators by PM injection in a copper mold and that includes different shapes and sizes that can be studied further.

We develop a program (within MATLAB software environment) to numerically simulate current-voltage characteristics of a bilayer organic light-emitting diode (OLED). The program is based on the Poole-Frenkel and Schottky continuous quantum models which take into account the geometry of thin films and their emission parameters in the calculation of charge carrier and current density in organic materials. Simulations are performed for OLEDs with A/EML/C and A/HIL/EML/C architectures where A=anode, HIL=hole injection layer, EML=emissive layer and C=cathode. For EML we assume MEH-PPV and MDMO-PPV derivatives of poly-para-phenylene-vinylene (PPV) polymer semiconductor, and for HIL we use PEDOT:PSS. The results of simulation are compared with experimental results obtained from actual OLED devices constructed in our laboratory. For comparison we also use the commercial software SimOLED to simulate the devices under similar architectures. We find in general a fair agreement between the simulated and measured behavior except for a few orders of magnitude difference in the current.

In the study of grain boundary migration of metallic materials using molecular dynamics simulation (MDS), grain boundary mobilities and activation energies are often found to be different from experimentally observed values. To reconcile the discrepancies, tremendous effort has been made to replicate experiment conditions in MDS, e.g.as low a driving force as possible, near zero grain boundary velocity. In the present study, we propose an analytic method that removes effects from non-physical conditions such as high driving force or high temperature. The analytic model presumes that two types of rate limiting events coexist during grain boundary migration. Kinetics parameters, such as activation energies, of the rare events are different and therefore should be modeled separately. Activation energies from this model are closer to experiment than previously reported values. Further, by analyzing the evolution of atomic structures, these two types of rate limiting events correspond to shear coupled migration and grain boundary sliding mechanisms, respectively.

Structure prediction for novel materials requires computationally inexpensive lattice relaxation methods. Prediction of the band gap and excited state properties depends on the accuracy of the relaxations and the sensitivity of the band edges to structural parameters. We examine the relaxation performance of common relaxation methods for several members of the type IB3-V-VI4 copper chalcogenide semiconductors, which have become of recent interest for potential photovoltaic and thermoelectric applications. These materials are members of a larger family of materials, composed of type IB and type VI elements and additional elements acting as cations, which contains structures as complex as Cu12Sb4S13 (tetrahedrite) and may benefit from materials prediction studies. Examining Cu3PS4, Cu3PSe4, Cu3AsS4, and Cu3AsSe4, we find that relaxation induced structural errors cause subsequently calculated band gap values E g to deviate by as much as 0.6 eV from values obtained using experimentally determined structures. Using the HSE06 hybrid functional we find that the complex V/VI* anti-bonding character of the conduction band minimum creates a band gap sensitivity of order 10 eV/Å to the mean V-VI distance 〈V-VI〉. A weaker correlation between E g and 〈IB-VI〉 exists due to the Cu-d/Ch-p* character of the valence band maximum (Ch = S, Se). Type IB-III-VI2 materials are known to have similar properties and we include CuInSe2, CuAlS2, and CuAlSe2. Regarding structural relaxation accuracy, we find that GGA+U and meta-GGA functional MS2 typically perform better than GGA (PBE) or PBEsol, but not as well as the much more expensive HSE functional.