Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (LaxAl1-xOy) grown by spray pyrolysis in ambient atmosphere at 440 C. The structural, electronic, optical, morphological, and electrical properties of the LaxAl1-xOy films and devices as a function ofthe lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As deposited LaAlOy dielectrics exhibit a wide band gap (6.18eV), high dielectric constant (k~16),low roughness (1.9 nm), and very low leakage currents (106, subthreshold swing of 650 mV dec-11, and electron mobility of 12 cm2 V-1 s-1

Tailoring Ca-Based Nanoparticles by Polyol Process for Use as Nematicidals and pH Adjusters in Agriculture

The remarkable progress in nanotechnology has extended the application of inorganic nanoparticles (NPs) in the agriculture sector, as both economically sustainable and environmentally sound alternatives. Root knot nematodes are undoubtedly a foremost problem of agriculture, and research strives to develop effective materials to tackle this issue. Herein, the microwave-assisted selective polyol synthesis of different compositions of Ca-based NPs, Ca(OH)2, Ca(OH)2/CaCO3, and CaCO3 is reported and the products were evaluated as nematicides and pH adjusters. Two precursors (CaCl2 and Ca(NO3)2) and three polyols (1,2-propylene glycol (PG), tetraethylene glycol (TEG), polyethylene glycol (PEG 8000)) that differ in their redox potential have been utilized to provide selectivity over composition. On the basis of the utilized polyols, NPs are produced as inorganic/organic hybrid formulations with a biocompatible organic coating that provides increased colloidal stability and controlled release of active components. Characterization of NPs has been carried out by XRD, TGA, FTIR, TEM, and pH-metry. Each composition exhibited different pH changing ability, an essential feature for agrochemical applications. The in vitro nematicidal activity of Ca(OH)2, Ca(OH)2/CaCO3, and CaCO3NPs was evaluated on second stage juveniles (J2) of two Meloidogyne species (Meloidogyne incognita and Meloidogyne javanica) based on nematode paralysis experiments. Results unveiled nematicidal activity for all evaluated Ca-based NPs, while Ca(OH)2 and CaCO3 NPs appeared to be the most and the least effective ones, respectively. The nematicidal effect appears to be boosted by the release of [OH]- anions, as indicated by pH-metric measurements, displaying the crucial role of [OH]- anions in their nematicidal activity

Fabrication and examination of oxidation resistance of zinc coated copper and brass components by chemical deposition

n this work, the structure and the oxidation resistance of Zn deposited Cu and brass metallic components are examined. The deposition was accomplished with pack cementation chemical deposition. The examination of the samples was performed with electron microscopy and X-ray diffraction analysis. It was found that coatings on Cu substrate consist of two layers with different Zn concentrations, while coatings on brass were single layered with almost constant Zn concentration. The presence of distinct Zn—Cu phases was revealed in both cases. The subjection of the as coated samples together with the uncoated substrates in air at 400ºC showed that both Zn coated samples have enhanced resistivity in such atmospheres, as most of the coating remained mostly unoxidised, and the substrates were fully protected. On the contrary, the bare substrates appear to have undergone severe damage as brittle oxides were formed on their surface.Publicad

Self-assembled plasmonic templates produced by microwave annealing: applications to surface-enhanced Raman scattering

Perhaps the simplest method for creating metal nanoparticles on a substrate is by driving their self-assembly with the thermal annealing of a thin metal film. By properly tuning the annealing parameters one hopes to discover a recipe that allows the pre-determined design of the NP arrangement. However, thermal treatment is known for detrimental effects and is not really the manufacturer's route of choice when it comes to large-scale applications. An alternative method is the use of microwave annealing, a method that has never been applied for metal processing, due to the high reflectance of microwave radiation at the surface of a metal. However, in this work we challenge the widely used nanostructuring methods by proving the microwave's annealing ability to produce plasmonic templates, out of extremely thin metal films, by simply using a domestic microwave oven apparatus. We show that this process is generic and independent of the deposition method used for the metal and we further quantify the suitability of these plasmonic templates for use in surface-enhanced Raman scattering applications

Solution processed SnO2:Sb transparent conductive oxide as an alternative to indium tin oxide for applications in organic light emitting diodes

Here we present the deposition of antimony-doped tin oxide thin films using the ambient spray pyrolysis technique and demonstrate their implementation as transparent electrodes (anodes) in red, green and blue Organic Light emitting diodes. The films were spray coated at 380 oC from SnCl4 and SbCl3 solution blends in methanol and ∼230 nm thick films were investigated by means of x-ray diffraction, AFM, UV-Vis absorption spectroscopy, 4-point probe, Hall Effect and Kelvin Probe. It was found that for optimum antimony doping in the precursor solution of ∼2 wt%, the as-deposited ATO films exhibit excellent characteristics such as low surface roughness of RRMS∼6.3 nm, high work function (∼ -5.03 eV), wide direct band gap (∼4.2 eV), high transparency in the visible spectrum in excess of 85 % on glass, low sheet resistivity (∼32 Ohms/sq), high charge carrier concentration (∼6.35 × 10^20 cm-3) and carrier mobility of ∼32 cm2 V-1 s-1. Furthermore, the electrical and optical performance i.e. the turn on voltage and external quantum efficiency of red, green and blue OLEDs fabricated on optimized SnO2:Sb films were identical to those of OLEDs fabricated on commercially available ITO (Rs∼15 Ohms/sq) and were found to be in excess of 11 %, 0.3 % and 13 % for red, green and blue OLEDs respectivel

Laser-driven structural modifications and diffusion phenomena of plasmonic AlN/Ag stratified films

Laser annealing (LA) of AlN/Ag multilayers was proven to be an effective process to control the structure and dispersion of Ag into the AlN resulting in intense coloration via the localized surface plasmon resonance, which is of particular importance for decorative applications. In this work we present a study of the structural changes occurring in various AlN/Ag multilayers after LA, in an effort to establish firm knowledge of the diffusion and re-nucleation mechanisms that occur during the laser process. We investigate the effect of the basic LA parameters, such as the laser wavelength (193 and 248 nm), fluence (400–700 mJ/cm2), pressure (1 and 10 Bar) and number of pulses (1 and 2) and we show that the main processes is the Ag particle enhancement close to the film surface as a result of additive outidiffusion Ag and the formation of nanoparticles of varying size

Sub-surface laser nanostructuring in stratified metal/dielectric media: a versatile platform towards flexible, durable and large-scale plasmonic writing

Laser nanostructuring of pure ultrathin metal layers or ceramic/metal composite thin films has emerged as a promising route for the fabrication of plasmonic patterns with applications in information storage, cryptography, and security tagging. However, the environmental sensitivity of pure Ag layers and the complexity of ceramic/metal composite film growth hinder the implementation of this technology to large-scale production, as well as its combination with flexible substrates. In the present work we investigate an alternative pathway, namely, starting from non-plasmonic multilayer metal/dielectric layers, whose growth is compatible with large scale production such as in-line sputtering and roll-to-roll deposition, which are then transformed into plasmonic templates by single-shot UV-laser annealing (LA). This entirely cold, large-scale process leads to a subsurface nanoconstruction involving plasmonic Ag nanoparticles (NPs) embedded in a hard and inert dielectric matrix on top of both rigid and flexible substrates. The subsurface encapsulation of Ag NPs provides durability and long-term stability, while the cold character of LA suits the use of sensitive flexible substrates. The morphology of the final composite film depends primarily on the nanocrystalline character of the dielectric host and its thermal conductivity. We demonstrate the emergence of a localized surface plasmon resonance, and its tunability depending on the applied fluence and environmental pressure. The results are well explained by theoretical photothermal modeling. Overall, our findings qualify the proposed process as an excellent candidate for versatile, large-scale optical encoding applications. Keywords : Ceramic materials; Composite films; Environmental technology; Film growth; Film preparation; Multilayer films; Multilayers; Nanocrystals; Optical data processing; Plasmons; Silver; Substrates; Surface plasmon resonance; Thin films; Ultrathin films, Laser annealing; Localised surface plasmon resonance; Multi-layer thin film; Nano-structuring; Plasmonics, Nanocomposite film

Polymer Light‐Emitting Transistors With Charge‐Carrier Mobilities Exceeding 1 cm2 V−1 s−1

The vast majority of conjugated polymer-based light emitting field-effect transistors (LEFETs) are characterized by low charge carrier mobilities typically in the range 10-5 to 10-3 cm2 V-1 s-1 range. Fast carrier transport is a highly desirable characteristic for high frequency LEFET operation and, potentially, for use in electrically-pumped lasers. Unfortunately, high mobility organic semiconductors are often characterised by strong intermolecular π-π interactions that reduce luminescence. Development of new materials and/or device concepts that overcome this hurdle are therefore required. We report single organic semiconductor layer, light-emitting transistors that combine the highest hole mobilities reported to date for any polymer-based LEFET, with encouraging light emission characteristics. We achieve this in a single polymer layer LEFET, which was further enhanced through the use of a small-molecule/conjugated polymer blend system that possesses a film microstructure which supports enhanced charge carrier mobility (3.2 cm2 V-1 s-1) and promising light emission characteristics (1600 cd m-2) as compared to polymer-only based LEFETs. This simple approach represents an attractive strategy to further advance the performance of solution-processed LEFETs

Enhanced detoxification of Cr6+ by Shewanella oneidensis via adsorption on spherical and flower-like manganese ferrite nanostructures

Maximizing the safe removal of hexavalent chromium (Cr6+) from waste streams is an increasing demand due to the environmental, economic and health benefits. The integrated adsorption and bio-reduction method can be applied for the elimination of the highly toxic Cr6+ and its detoxification. This work describes a synthetic method for achieving the best chemical composition of spherical and flower-like manganese ferrite (MnxFe3-xO4) nanostructures (NS) for Cr6+ adsorption. We selected NS with the highest adsorption performance to study its efficiency in the extracellular reduction of Cr6+ into a trivalent state (Cr3+) by Shewanella oneidensis (S. oneidensis) MR-1. MnxFe3-xO4 NS were prepared by a polyol solvothermal synthesis process. They were characterised by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), dynamic light scattering (DLS) and Fourier transform-infrared (FTIR) spectroscopy. The elemental composition of MnxFe3-xO4 was evaluated by inductively coupled plasma atomic emission spectroscopy. Our results reveal that the oxidation state of the manganese precursor significantly affects the Cr6+ adsorption efficiency of MnxFe3-xO4 NS. The best adsorption capacity for Cr6+ is 16.8 ± 1.6 mg Cr6+/g by the spherical Mn0.22+Fe2.83+O4 nanoparticles at pH 7, which is 1.4 times higher than that of Mn0.8Fe2.2O4 nanoflowers. This was attributed to the relative excess of divalent manganese in Mn0.22+Fe2.83+O4 based on our XPS analysis. The lethal concentration of Cr6+ for S. oneidensis MR-1 was 60 mg L-1 (determined by flow cytometry). The addition of Mn0.22+Fe2.83+O4 nanoparticles to S. oneidensis MR-1 enhanced the bio-reduction of Cr6+ 2.66 times compared to the presence of the bacteria alone. This work provides a cost-effective method for the removal of Cr6+ with a minimum amount of sludge production

Synthesis and biological evaluation of PEGylated CuO nanoparticles

There is a growing field of research into the physicochemical properties of metal oxide nanoparticles (NPs) and their potential use against tumor formation, development and progression. Coated NPs with biocompatible surfactants can be incorporated into the natural metabolic pathway of the body and specifically favor delivery to the targeted cancerous cells versus normal cells. Polyethylene glycol (PEG) is an FDA approved, biocompatible synthetic polymer and PEGylated NPs are regarded as “stealth” nanoparticles, which are not recognized by the immune system. Herein, PEGylated cupric oxide nanoparticles (CuO NPs) with either PEG 1000 or PEG 8000 were hydrothermally prepared upon properly adjusting the reaction conditions. Depending on the reaction time CuO NPs in the range of core sizes 11–20 nm were formed, while hydrodynamic sizes substantially varied (330–1120 nm) with improved colloidal stability in PBS. The anticancer activity of the NPs was evaluated on human cervical carcinoma HeLa cells by using human immortalized embryonic kidney 293 FT cells as a control. Viability assays (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT) revealed that CuO NPs could selectively reduce viability of tumor cells (IC50 values 11.91–25.78 μg/mL). Reactive oxygen species (ROS) production, cell membrane damage and apoptotic DNA laddering were also evident by nitroblue tetrazolium (NBT) reduction, lactate dehydrogenase (LDH) release assays and DNA electrophoresis, respectively. CuO NPs strongly inhibited lipoxygenase (LOX) enzymatic activity with IC50 values 4–5.9 μg/mL, highlighting in that manner their anti-inflammatory activity