Large Surface Energy Research Articles

ROLE OF NANOTECHNOLOGY IN REDUCING POLLUTION

Looking at the Nano scale has stimulated the development and use of novel and costeffective technologies for remediation, pollution detection, catalysis and others. Nanotechnology is defined as the creation of functional materials, devices and systems through control of matter on the nanometer (1-100 nm) length scale and the exploitation of novel properties and phenomena developed at that scale. Environmental nanotechnology is considered to play a key role in the shaping of current environmental engineering and science. Nanotechnology is an upcoming technology that can provide solution for combating pollution by controlling shape and size of materials at the Nano scale. This review provides comprehensive information regarding the role of nanotechnology in pollution control at three different steps viz. Source reduction or pollution prevention, remediation or degradation of pollutants and sensing of pollutants. Due to its large surface area and high surface energy, the nanoparticles have the ability to absorb large amount of pollutants or catalyze reactions at a much faster rate, thus reducing energy consumption during degradation or helps in preventing release of contaminants. Pollution prevention by nanotechnology refers on the one hand to a reduction in the use of raw materials, water or other resources and the elimination or reduction of waste and on the other hand to more efficient use of energy or involvement in energy production. The Nano size of the particles also make it possible to reach otherwise inaccessible areas and hence promote in-situ remediation rather than ex-situ remediation. The ability of the nanoparticles to be coated with various ligands and control of surface area to volume ratio by changing the shape of the nanoparticle Nanotechnology and the environment – is it therefore a Janus-faced relationship. There is the huge hope that Nano technological applications and products will lead to a cleaner and healthier environmentrticles enables the design of sensors with high selectivity, sensitivity and specificity.

Carrier free inhaled dry powder of budesonide tailored by supercritical fluid particle design

Budesonide (BUD) is a potent inhaled corticosteroid widely used for treatment of asthma and chronic obstructive pulmonary disease (COPD). The aim of the present study was to develop carrier free inhaled dry powder containing only BUD using supercritical fluid particle design (SCF PD) technique. The powder was perpetrated using the proprietary apparatus of SCF PD-Lab and characterized in terms of crystal behavior, surface property and suitability for pulmonary delivery. SCF PD-BUD powder shown itself large specific area and lower surface energy measured by iGC-SEA, and the aerodynamic performances relative to the milled powder and the marketed Pulmicort® powder was considerably improved, the pulmonary deposition rate increased substantially up to FPF<5μm=32.9% which was comparable to the Pulmicort® powder of FPF<5μm=28.4%. The proprietary SCF PD technique was capable of simultaneously tailoring particle size, morphology and physical properties toward an enhancing aerodynamic performance and pulmonary deposition rate of the carrier free inhaled dry powder.

Differences in adsorption of anionic surfactant AOT by calcium oxalate: Effect of crystal size and crystalline phase

The adsorption of anionic surfactant sodium diisooctyl sulfosuccinate(AOT) onto calcium oxalate monohydrate(COM) and dihydrate(COD) with sizes of 50, 100 nm, 1, 3 and 10 µm was comparatively studied to simulate the interaction between urinary crystallites and urine components. The adsorption quantity of different concentrations of AOT onto COD and COM with different sizes was detected using a UV-Vis spectrophotometer. The crystalline phase transition of COM and COD before and after adsorption was analyzed by X-ray powder diffraction and Fourier transform infrared spectrometry. The zeta potential of the crystal surface after adsorption of different concentrations of AOT was measured using a zeta potential analyzer. The adsorption quantity of AOT on COM and COD with different sizes was ranked in the following order: 50 nm>100 nm>1 µm>3 µm>10 µm. The adsorption quantity of COM was greater than that of COD with the same size because the density of the positive charges on the COM surface was higher than that on COD surface. With the increase of AOT concentration, the adsorption curves of the large-sized COM and COD(3 and 10 µm) were S-type, whereas the adsorption curves of the small-sized COM and COD(50 nm, 100 nm and 1 µm) were linear. The adsorption capacities of small-sized COM and COD were much greater than those of the 3 and 10 µm crystals. On the basis of the above results, we proposed a molecular model to summarize the absorption of AOT onto COM and COD crystals. Small crystals exhibit a large specific surface area and high surface energy. Thus, their adsorption capacities are stronger than those of large crystals. Overall, this study implied that small crystals can easily absorb anionic molecules in urine and may easily adhere to a negatively charged cell surface, thereby increasing the severity of cell injury.

Diketopyrrolopyrrole‐based Conjugated Polymers Bearing Branched Oligo(Ethylene Glycol) Side Chains for Photovoltaic Devices

AbstractConjugated polymers are essential for solution‐processable organic opto‐electronic devices. In contrast to the great efforts on developing new conjugated polymer backbones, research on developing side chains is rare. Herein, we report branched oligo(ethylene glycol) (OEG) as side chains of conjugated polymers. Compared with typical alkyl side chains, branched OEG side chains endowed the resulting conjugated polymers with a smaller π‐π stacking distance, higher hole mobility, smaller optical band gap, higher dielectric constant, and larger surface energy. Moreover, the conjugated polymers with branched OEG side chains exhibited outstanding photovoltaic performance in polymer solar cells. A power conversion efficiency of 5.37 % with near‐infrared photoresponse was demonstrated and the device performance could be insensitive to the active layer thickness.

Diketopyrrolopyrrole-based Conjugated Polymers Bearing Branched Oligo(Ethylene Glycol) Side Chains for Photovoltaic Devices.

Conjugated polymers are essential for solution-processable organic opto-electronic devices. In contrast to the great efforts on developing new conjugated polymer backbones, research on developing side chains is rare. Herein, we report branched oligo(ethylene glycol) (OEG) as side chains of conjugated polymers. Compared with typical alkyl side chains, branched OEG side chains endowed the resulting conjugated polymers with a smaller π-π stacking distance, higher hole mobility, smaller optical band gap, higher dielectric constant, and larger surface energy. Moreover, the conjugated polymers with branched OEG side chains exhibited outstanding photovoltaic performance in polymer solar cells. A power conversion efficiency of 5.37 % with near-infrared photoresponse was demonstrated and the device performance could be insensitive to the active layer thickness.

Gold-Platinum Nanostructures Formed By Thermal Dewetting

Introduction Bimetallic core-shell nanoparticles, including Au-Pt nanoparticles (NPs), exhibit interesting electrocatalytic properties for fuel cell reactions.1 For this application, the ability to control the size of the NPs, as well as their composition and surface crystallinity, has been shown to be important to enhance the utilization efficiency of the catalysts.2 NP arrays have been previously achieved by fabrication methods such as “top-down” or “bottom-up” approaches, which typically involve lithography and self-assembly, respectively. Top-down methods are often costly and time consuming, while bottom-up methods suffer from poor long range (> µm) order. The present study has focused on the formation of bimetallic nanostructures on Ta templates, where the large surface energy difference between a metallic thin film (Au and Pt) and the air-formed oxide on the Ta surface cause the dewetting of a sputter-coated metallic film to form NPs. This approach has been previously used to form Au NPs of controllable size, with a linear relationship observed between the metal film thickness prior to dewetting and the NP diameter.3 Here, we have attempted to form useful Au/Pt nanostructures and the electrochemistry of these materials, formed using a range of fabrication conditions, will be discussed in detail. Methods and Results Solid-state dewetting of thin metal films on oxide substrates is a known method of fabricating metal NP arrays over relatively large dimensions (e.g., cm2) without requiring costly lithography processes.4,5 Recent work in our group has demonstrated the ability to form ordered Au NP arrays on Ta templates, which are covered by a thin, air-formed Ta oxide film. This was achieved by the sputter-deposition of a thin film (3-4 nm) of Au, followed by thermal annealing at 450 oC for 30 minutes.4 This method was then adapted to form Au-Pt nanostructures, where two metal films (3-4 nm each of Au and Pt) were sequentially sputtered (Au then Pt, or Pt then Au) on chemically polished Ta templates, and then thermally annealed at 450 oC or 600 oC for 90 minutes. These Au-Pt nanostructures were characterized by FESEM (field emission scanning electron microscopy) to determine the extent of dewetting. It was observed that higher annealing temperatures of 600 oC (well below the melting point of both Au and Pt) were needed to further dewet the thin metal films (Figure 1 (a) and (b)), as heating at 450 oC was only able to partially dewet these Au-Pt films (Figure 1 (c) and (d)). The electrochemical behaviour of these bimetallic nanostructures was investigated by cyclic voltammetry (CV) in 0.5 M H2SO4 solution and then compared to the response from the individual Au vs. Pt thin films. The CVs show that the bimetallic thin films (before annealing) exhibit characteristics of both metals, indicating that the second sputter-coated metal does not form a conformal coating on the first sputter-coated film. After annealing at 450 oC, the CVs exhibit only Au characteristics, regardless of the deposition sequence. This suggests that, regardless of the order of sputter-coating, Au is coating the Pt structures after thermal annealing (i.e., these are Pt@Au nanostructures), in contrast to the Pt enrichment observed at the surface of Au@Pt core-shell NPs, formed by the electrochemical reduction of ionic precursors in solution. The characteristics of the nanostructures were shown to be optimized by varying the fabrication conditions (film thickness and annealing conditions), which also aided in understanding the mechanism of dewetting of these thin bimetallic films. Acknowledgements We gratefully acknowledge financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC). References Luo, J.; Maye, M.M.; Kariuki, N.N.; Wang, L.; Njoki, P.; Lin, Y.; Schadt, M.; Naslund, H.R.; Zhong, C.J. Catal. Today. 2005, 17, 291-297.Ataee-Esfahani, H.; Wang, L.; Nemoto, Y.; Yamauchi, Y. Chem. Mater. 2010, 22, 6310-6318.Kojima, Y.; Kato, T. Nanotechnology . 2008, 19, 255605.El-Sayed, H. A.; Molero, H. M.; Birss, V. I. Nanotechnology. 2012, 23, 435602.Wang, D.; Schaff, P. J.Mater.Sci: Mater Electron. 2011, 22,1067-1070. Figure 1

Effects of deposition temperature and quenching rate on the surface morphology and magnetic properties of FePt/TiN films

FePt thin films have been deposited on Si substrate with a TiN buffer layer. The effects of deposition temperature and the quenching rate on the magnetic properties and microstructure of the FePt/TiN films have been investigated. Out-of-plane anisotropy can be achieved for the film deposited at room temperature followed by annealing at 600°C and quenching in air. It is observed that a small fraction of L10-FePt in the room temperature deposited film is well-aligned in the perpendicular direction which is due to the large surface energy of the TiN buffer layer, which contracts the lattice of L10-FePt during the ordering process. However, by increasing the deposition temperature from room temperature to 450°C, both the L10-ordering parameter and the in-plane anisotropy can be enhanced. The microstructure and phase structural results indicate that a high quenching rate is beneficial to refine the FePt grains despite the high deposition temperature. The highest in-plane coercivity (915.6kA/m) is obtained by depositing at 300°C and quenching in air. However, when the film is deposited at 300°C followed by quenching in ice water, the average FePt grain size dramatically decreases to 22nm and the in-plane coercivity still maintains at about 875.8kA/m. The results indicate that the high rate quenching can effectively separate the grains and result in the high coercivity due to the reduced exchange coupling effect.

Ag Nanoparticles Supported on Yttria-Stabilized Zirconia: A Synergistic System within Redox Environments

In this work, we report a distinctive dynamic sintering-free redox behavior of Ag nanoparticles (AgNPs) on 30 nm thick yttria-stabilized zirconia (YSZ) films. The material system demonstrates reversible 200 nm shifts in the plasmonic spectra with an unprecedented particle phase/size/morphology oscillation during cyclic redox reactions in air and hydrogen/air at 300–400 °C. This is in significant contrast to the minor changes more commonly observed for AgNPs on quartz. It was found that the ionically active YSZ has a strong tendency to drive AgNPs to oxidize under oxidizing conditions, and upon surface oxidation a large differential surface energy is built up, forcing the core/shell particles to migrate and coalesce toward a lower system free energy. Most strikingly, once switched to a mixture of H2 and air, the previously formed large dewetted metal-core/thick oxide-shell particles collapse, and new small Ag nanoparticles quickly form and remain in a highly dispersed and sintering-free state on YSZ. This is found to likely be due to catalytic production of water over the material system, which plays a key role in the dynamic redox activities. It is hypothesized that the small metallic particle regeneration and sinter-free behavior take place through a four-step process resulting from the synergistic behavior of AgNPs supported on YSZ within a redox environment: (I) production of a local humid environment via catalytic reactions of H2 and O2 mostly at the triple-phase boundary, (II) dissolution of Ag+ from both reduced Ag and the AgOx shell, (III) collapse and spillover of the AgOx shell/water layer with Ag ions onto the hydrous YSZ surface, and (IV) reduction, diffusion, nucleation, and growth to new small metallic AgNPs with a dynamic equilibrium quickly reached. The findings behind this novel system could set up an avenue for a new concept of catalysts operating in a self-controlled dynamic regime for governing chemical reactions via metal and ceramic synergized catalysis with high activities and stabilities.

Water governance challenges presented by nanotechnologies: tracking, identifying and quantifying nanomaterials (the ultimate disparate source) in our waterways

Nanotechnologies are considered an enabling technology, as they enhance the functioning of a wide range of products and processes. They are increasingly appearing in consumer products, including sun creams, socks and outdoor paints, resulting in the potential for direct access of nanomaterials (NMs) into wastewater and the environment. As such, they could be considered as the ultimate disparate source, with multiple products and multiple routes into the environment, as well as numerous transformation pathways, such that the final form may bear little resemblance to the initially produced form. NMs thus represent a significant governance and regulatory challenge, for a number of reasons, related to their small size, which makes detection challenging, especially against a background of naturally occurring nanoscale entities (clay and sediment particles, etc.), and their large surface area and high surface energy which leads to very dynamic behaviour and a strong tendency to interact with (bind) anything they come into contact with. Some initial considerations of regulatory issues related to Registration, Evaluation and Authorization of Chemicals, the Water Framework Directive, and the potential for benign-by-design approaches exploiting the potential for recovery or recycling of NMs at the design phase are presented, aimed at reducing the risk of unintentional accumulation of NMs in our waterways.

Investigating with P,V,T-Calorimetry the Large Surface Energies Developed by Lyophobic Porous Solids upon Intrusion/Extrusion of Non-Wetting Liquids

Investigating with <i>P</i>,<i>V</i>,<i>T</i>-Calorimetry the Large Surface Energies Developed by Lyophobic Porous Solids upon Intrusion/Extrusion of Non-Wetting Liquids

Effect of enhanced interfacial reaction on the microstructure, phase transformation and mechanical property of Ni–Mn–Ga particles/Mg composites

Abstract This study investigated the microstructure, phase transformation and mechanical property of Ni–Mn–Ga particles/Mg composites with a strong interfacial reaction between the particles and the matrix. The strong interfacial reaction was related to the large surface area and energy per unit volume of the flaky shape Ni–Mn–Ga particles that favors the reaction between the particles and matrix. The martensitic transformation behavior was largely weakened due to the interfacial reactions and thus the reduced volume fraction of Ni–Mn–Ga particles. The composites exhibited a much improved compressive strength and ductility in comparison with that of the Ni–Mn–Ga alloy. The compressive plasticity of the composites was decreased when the Ni–Mn–Ga particle content exceeded 40 wt%. In comparison with the Mg-composites with large size Ni–Mn–Ga particles, the composites with small size particles would have a much stronger interfacial reactions, which was detrimental to the phase transformation and mechanical ductility of the composites. The investigation results in this article could provide a reference for the design and preparation of the particles reinforced metal matrix functional composites.

Resonance Raman spectroscopic study for radial vibrational modes in ultra‐thin walled TiO2 nanotubes

The study reports the observation of radial vibrational modes in ultra‐thin walled anatase TiO2 nanotube powders grown by rapid breakdown anodization technique using resonant Raman spectroscopic study. The as‐grown tubes in the anatase phase are around 2–5 nm in wall thickness, 15–18 nm in diameter and few microns in length. The Eg(ν1,ν5,ν6) phonon modes with molecular vibrations in the radial direction are predominant in the resonance Raman spectroscopy using 325 nm He–Cd excitation. Multi‐phonons including overtones and combinational modes of Eg(ν1,ν5,ν6) are abundantly observed. Fröhlich interaction owing to electron–phonon coupling in the resonance Raman spectroscopy of ultra‐thin wall nanotubes is responsible for the observation of radial vibrational modes. Finite size with large surface energy in these nanotubes energetically favor only one mode, B1g(ν4) with unidirectional molecular vibrations in the parallel configuration out of the three Raman modes with molecular vibration normal to the radial modes. Enhanced specific heat with increasing temperatures in these nanotubes as compared to that reported for nanoparticles of similar diameter may possibly be related to the presence of the prominent radial mode along with other energetic phonon mode. The findings elucidate the understanding of total energy landscape for TiO2 nanotubes. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Observation of piezoelectricity in free-standing monolayer MoS₂.

Piezoelectricity allows precise and robust conversion between electricity and mechanical force, and arises from the broken inversion symmetry in the atomic structure. Reducing the dimensionality of bulk materials has been suggested to enhance piezoelectricity. However, when the thickness of a material approaches a single molecular layer, the large surface energy can cause piezoelectric structures to be thermodynamically unstable. Transition-metal dichalcogenides can retain their atomic structures down to the single-layer limit without lattice reconstruction, even under ambient conditions. Recent calculations have predicted the existence of piezoelectricity in these two-dimensional crystals due to their broken inversion symmetry. Here, we report experimental evidence of piezoelectricity in a free-standing single layer of molybdenum disulphide (MoS₂) and a measured piezoelectric coefficient of e₁₁ = 2.9 × 10(-10) C m(-1). The measurement of the intrinsic piezoelectricity in such free-standing crystals is free from substrate effects such as doping and parasitic charges. We observed a finite and zero piezoelectric response in MoS₂ in odd and even number of layers, respectively, in sharp contrast to bulk piezoelectric materials. This oscillation is due to the breaking and recovery of the inversion symmetry of the two-dimensional crystal. Through the angular dependence of electromechanical coupling, we determined the two-dimensional crystal orientation. The piezoelectricity discovered in this single molecular membrane promises new applications in low-power logic switches for computing and ultrasensitive biological sensors scaled down to a single atomic unit cell.

A Top Coat with Solvent Annealing Enables Perpendicular Orientation of Sub‐10 nm Microdomains in Si‐Containing Block Copolymer Thin Films

Achieving sub‐10 nm high‐aspect‐ratio patterns from diblock copolymer self‐assembly requires both a high interaction parameter (χ, which is determined by the incompatibility between the two blocks) and a perpendicular orientation of microdomains. However, these two conditions are extremely difficult to achieve simultaneously because the blocks in a high‐χ copolymer typically have very different surface energies, favoring in‐plane microdomain orientations. A fully perpendicular orientation of a high‐χ block copolymer, poly(styrene‐block‐dimethylsiloxane) (PS‐b‐PDMS) is realized here using partially hydrolyzed polyvinyl alcohol (PVA) top coats with a solvent annealing process, despite the large surface energy differences between PS and PDMS. The PVA top coat on the block copolymer films under a solvent vapor atmosphere significantly reduces the interfacial energy difference between two blocks at the top surface and provides sufficient solvent concentration gradient in the through‐thickness direction and appropriate solvent evaporation rates within the film to promote a perpendicular microdomain orientation. The effects of interfacial energy differences and the swellability of PVA top coats controlled by the degree of hydrolysis on the orientation of micro­domains are examined. The thickness of the BCP film and top coats also affects the orientation of the BCP film.

Evaluation of dispersion degree of nanoparticles in TiO2/epoxy resin nanocomposites

The purpose of this study was to evaluate the dispersion degree of particles using a nanoindentation test for titanium oxide nanoparticles/epoxy resin nanocomposites. Thus, the effects of the particle size and weight fraction, dispersion agent, and position of the sample on the modulus and degree of particle dispersion in the nanocomposites were investigated. As a result, the dispersion degree of large particles was found to be better than that of smaller particles in composites. It could be found that the aggregation or agglomeration of small particles with large surface energy occurred more easily in nanocomposites because of the large specific surface area. The moduli of the upper side of the film-shaped sample obtained from a nanoindentation test were low scattering, while the values for the bottom side were high scattering. Thus, the dispersion situation of the nanoparticles on the upper side of film-shaped samples could be considered to be better than that for the bottom side. This could be concluded due to the non-uniform nanoparticle dispersion in the same sample. The modulus obtained from nanoindentation test increased slightly with the content of nanoparticles and increased with the indented depth for the same sample. The latter is presumably due to the increase in the accumulated particles facing the indenter with the indented depth. The nanoindentation test was found to be a useful method to evaluate the dispersion status of nanoparticles in nanocomposites.

MECHANOCHEMICAL SYNTHESIS OF NiO NANOPARTICLES: INSIGHT INTO THE NATURE OF PREFERRED GROWTH ORIENTATION

Nickel oxide ( NiO ) nanoparticles were synthesized by calcination at 400°C to 700°C for 8 h of the precursor obtained via mechanochemical reaction of Ni ( NO 3)2 ⋅ 6 H 2 O with citric acid as a dispersant. The nanoparticles were characterized by thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The kinetics of different surfaces of the nanocrystals under nonisothermal conditions was investigated. The activation energies for different lattice planes of NiO nanoparticles were determined using the Arrhenius equation, revealing their preferred orientation. The growth of NiO obeyed the general theory that nanoparticles with the largest surface energy tend to form. XRD data reveal that the NiO nanoparticles possess preferred (111) or (200) orientations that reflect their complex activity. The nature of preferred growth orientation was found to be negative diffusion activity among different lattice surfaces, which indicates that oxygen atoms diffuse from low oxygen concentration on the lattice surface to high concentration on the lattice surface.

Effect of UV-Ozone Treatment on the Performance of ZnO TFTs Fabricated by RF Sputtering Deposition Technique

In this paper, bottom-gate thin-film transistors (TFTs) with zinc oxide (ZnO) channels were grown on Si substrates with an SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dielectric layer via the radio-frequency sputtering technique. The ZnO films were then subjected to 16 min of ultraviolet (UV)-ozone treatment, which resulted in fewer oxygen vacancies, enhanced crystallization, lower strain, lower surface roughness, and higher thin-film density, as well as improved surface energy and adhesion properties of the gallium zinc oxide source/drain electrodes. The UV-ozone 16-min ZnO active layer TFT with the preferable resistivity values by Hall measurement results. The optimal UV-ozone treatment time (16 min) led to the smallest full-width at half-maximum (0.4138°), smallest strain (2.61 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ), highest thin-film density (5.78 g/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ), lowest surface roughness (1.75 nm), and largest surface energy (65.3 mJ/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). The saturation mobility, subthreshold voltage, ON/OFF current ratio, and trap density of the ZnO TFTs with optimal UV-ozone treatment were 4.54 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , 0.28 V/decade, 2.02 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> , and 2.61 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , respectively, indicating the potential of this structure to be applied to large-area flat-panel displays.

Effect of desiccant characteristics on the properties of PS/zeolite functional packaging materials

Desiccant composites were prepared from a polystyrene homopolymer (PS) and a high impact copolymer (HIPS). Five zeolites were used as adsorbents, which included the A and X types frequently used in industrial practice. Composites containing zeolites up to 50 vol% were homogenized in an internal mixer and then compression molded to 1 mm thick plates. The results proved that the water adsorption capacity of zeolites depends on the total volume of the pores, whereas the rate of adsorption on thermodynamics, on the equilibrium constant of adsorption. On the other hand, zeolite characteristics influence the moisture adsorption of the composites only marginally; adsorption capacity is determined by zeolite content, whereas the rate of adsorption is determined by the properties of the polymer. Composites prepared with X type zeolites have somewhat smaller water adsorption capacity than those containing their A type counterparts. The dispersion of the zeolite is good both in PS and in HIPS composites. Mechanical properties are excellent mainly because of the good interfacial adhesion between the components. Because of their larger surface energy, composites containing X type zeolites have larger viscosity and they reinforce the polymer more than A type desiccants. Matrix characteristics influence mainly application related properties; reinforcement and ductility is better in HIPS than in PS composites. POLYM. COMPOS., 35:2112–2120, 2014. © 2014 Society of Plastics Engineers

Comparison of physical and electrical properties of GZO/ZnO buffer layer and GZO as source and drain electrodes of α-IGZO thin-film transistors

In this research, top-gate bottom-contact thin-film transistors (TFTs) made with amorphous indium gallium zinc oxide (α-IGZO) active layers were grown using the radio-frequency sputtering technique. Two kinds of source and drain (S/D) electrodes, namely bi-layer GZO/100-nm ZnO buffer layer/Corning 1737 and single-layer GZO/Corning 1737, used in the TFT devices and the electric characteristics of the devices were compared. To explain the differences in the TFT performances with these different S/D electrodes, X-ray reflectivity (XRR) and contact angles were measured. The α-IGZO TFT with the bi-layer GZO/100-nm ZnO buffer layer structure as S/D electrodes exhibited superior device performance compared to that of the TFT with a single-layer GZO structure, with a higher thin film density (5.94g/cm3), lower surface roughness (0.817nm), and larger surface energy (62.07mJ/m2) and better adhesion properties of neighboring α-IGZO films. In addition, the mechanisms responsible for the GZO/100-nm ZnO buffer layer/Corning 1737 structure S/D electrodes improving the device characteristics were systematically investigated. The α-IGZO TFT saturation mobility, subthreshold voltage, on/off current ratio, and the trap density of the GZO/100-nm ZnO buffer layer/Corning 1737 S/D electrodes were 13.5cm2V−1S−1, 0.43V/decade, 3.56×107, and 5.65×1012eV−1cm−2, respectively, indicating the potential of this bi-layer structure to be applied to large-area flat-panel displays.

X-ray reflectivity and surface energy analyses of the physical and electrical properties of α-IGZO/GZO double active layer thin film transistors

In this research, bottom-gate thin film transistors (TFTs) of amorphous indium gallium zinc oxide (α-IGZO)-based active layers were grown by the radio-frequency sputtering technique. The device characteristics of two kinds of TFT structures, namely α-IGZO/GZO double active layer TFT and α-IGZO single active layer TFT, were compared. To explain the differences in the TFT performances of these different structures, X-ray reflectivity (XRR) and contact angles of the active layer were measured. The α-IGZO/GZO double active layer TFT exhibits superior device performance as compared to the other TFT structure because of its highest thin film density (5.87g/cm3), lowest surface roughness (1.89nm), and largest surface energy (60.07mJ/m2). Also, the mechanisms of this double active layer to improve the device characteristics were systematically investigated. The improved saturation mobility, sub-threshold voltage, on/off current ratio, and trap density of the α-IGZO/GZO double active layer TFT were 18.92cm2V−1S−1, 0.33V/decade, 1.33×108, and 4.25×1012eV−1cm−2, respectively, indicating the potential of this structure to be applied on large-area-flat-panel displays.