Low-temperature Procedure Research Articles

Technology, performance and degradation characteristics of SLS ELA thin film transistors

Low temperature polycrystalline silicon thin film transistors (LTPS poly-Si TFTs) are essential for large area electronics and high performance flat panel displays. In recent years, LTPS TFT performance has substantially increased due to the important breakthroughs in the field of polycrystalline silicon crystallization and also due to the optimization of the process steps that differ from those of typical MOSFETs, mainly because of the requirement for low temperature procedures. In this review we present the electrical characteristics of polycrystalline silicon TFTs, crystallized with different variations of the advanced SLS ELA technique, and the determination of process technological parameters that affect the device performance, in order to further optimize the production of such high performance transistors, in terms of poly-Si microstructure, channel dimensions and topology. Also, the effect of these fabrication parameters on device degradation characteristics is studied, with an attempt to model and predict degradation characteristics.

MICROSTRUCTURAL PROPERTIES OF NC-Si/SiO2 FILMS IN SITU GROWN BY REACTIVE MAGNETRON CO-SPUTTERING

Nanocrystalline silicon embedded in silicon oxide (nc- Si/SiO2 ) films have been in situ grown at a low substrate temperature of 300°C by reactive magnetron co-sputtering of Si and SiO2 targets in a mixed Ar/H2 discharge. The influences of H2 flow rate (F H ) on the microstructural properties of the deposited nc- Si/SiO2 films were investigated. The results of XRD and the deposition rate of nc- Si/SiO2 films show that the introduction of H2 contributes to the growth of nc- Si grains in silicon oxide matrix. With further increasing F H , the average size of nc- Si grains increases and the deposition rate of nc- Si/SiO2 films decreases gradually. Fourier transform infrared spectra analyses reveal that introduction of hydrogen contributes to the phase separation of nc- Si and SiO x in the deposited films. Moreover, the Si–O 4-n Si n(n = 0, 1) concentration of the deposited nc- Si/SiO2 films reduces with the increase of F H , while that of Si – O 4-n Si n(n = 2, 3) concentration increases. These results can be explained by that active hydrogen atoms increase the probability of reducing oxygen from precursor in the plasma and prompting oxygen desorption from the growing surface. This low-temperature procedure for preparing nc- Si/SiO2 films opens up the possibility of fabricating the silicon-based thin-film solar cells onto low-cost glass substrates using nc- Si/SiO2 films.

Carbon silica composites for sulfur dioxide and ammonia adsorption

This work focuses on creating nanoporous carbon silica composites from MCM-41 and two carbon sources, sucrose and furfuryl alcohol. The carbon silica composite with sucrose as the carbon phase was synthesized using a novel low temperature procedure. These novel, biphasic materials were tested for their ability to adsorb two distinct types of gases: sulfur dioxide, an acidic gas, and ammonia, a basic gas. The materials are characterized by XRD, nitrogen adsorption isotherms, high resolution TEM, and TGA. The characterization techniques show that impregnation with the carbon phases does not disrupt the hexagonal mesoporous silica structure. Equilibrium breakthrough results show that the presence of the carbon phase enhances both ammonia and sulfur dioxide adsorption capacities compared to the parent MCM-41 and BPL activated carbon.

Influence of size scale and morphology on antibacterial properties of ZnO powders hydrothemally synthesized using different surface stabilizing agents

Metal oxide nanoparticles represent a new class of important materials that are increasingly being developed for use in research and health-related applications. Although the antibacterial activity and efficiency of bulk zinc oxide were investigated in vitro, the knowledge about the antibacterial activity of ZnO nanoparticles remains deficient. In this study, we have synthesized ZnO particles of different sizes and morphologies with the assistance of different types of surface stabilizing agents – polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and poly (α,γ, l-glutamic acid) (PGA) – through a low-temperature hydrothermal procedure. The characterization of the prepared powders was preformed using X-ray diffraction (XRD) method and field emission scanning electron microscopy (FE SEM), as well as Malvern's Mastersizer instrument for particle size distribution. The specific surface area (SSA) of the ZnO powders was measured by standard Brunauer–Emmett–Teller (BET) technique.The antibacterial behavior of the synthesized ZnO particles was tested against gram-negative and gram-positive bacterial cultures, namely Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. We compared the results of the antibacterial properties of the synthesized ZnO samples with those of the commercial ZnO powder. According to the obtained results, the highest microbial cell reduction rate was recorded for the synthesized ZnO powder consisting of nanospherical particles. In all of the examined samples, ZnO particles demonstrated a significant bacteriostatic activity.

Exploration of MnO2/carbon composites and their application to simultaneous electroanalytical determination of Pb(II) and Cd(II)

We report preparation of MnO2 composites with carbon (Vulcan, graphite, and carbonized nanostructured polyaniline 5-sulfosalicylate) via hydrothermal and low-temperature wet impregnation procedure. All prepared composites were characterized using thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and conductivity measurements, and their characteristics compared. Furthermore, novel micro/nanostructured manganese dioxide/carbon composite based electrodes were tested for simultaneous determination of Pb2+ and Cd2+ as model analytes by anodic stripping voltammetry. The oxidation of the targeted heavy metals at the investigated composite electrodes gave distinctive and well separated peaks with lowest detection limits of 27nM for Pb2+ and 52nM for Cd2+ ions obtained with hydrothermally prepared MnO2/graphite composite based electrode.

Low-Temperature Preparation of Tailored Carbon Nanostructures in Water

The development of low-temperature carbonization procedures promises to provide novel nanostructured carbon materials that are of high current interest in materials science and technology. Here, we report a "wet-chemical" carbonization method that utilizes hexayne amphiphiles as metastable carbon precursors. Nearly perfect control of the nanoscopic morphology was achieved by self-assembly of the precursors into colloidal aggregates with tailored diameter in water. Subsequent carbonization furnished carbon nanocapsules with a carbon microstructure resembling graphite-like amorphous carbon materials.

Growth kinetics on silicon facets during low-temperature crystallization from indium solution

Large-grained Si layers are attractive for cost-effective thin film solar cells. Our experiments using a low-temperature steady-state solution growth procedure for growing Si crystallites on glass show the dominance of Si{111} facets. Recesses observed in the centers of these facets suggest that growth starts at {100} vertices and/or {110} edges and continues rather by spreading of monatomic steps on the {111} facets than by nucleation on these planes. The aim of this paper is to explain the observed morphology by calculation and to find out if the growth can be improved by nucleation on {111} facets. Thermodynamic analysis shows that {100} facets are rough under our growth conditions. Therefore, the calculation of two-dimensional (2D) nucleation is focused on the flat {110}, and {111} facets. The dissolution enthalpy of silicon in indium is used to evaluate the ledge free energy of Wulff-shaped 2D nuclei on both planes. It results, that 2D nucleation takes place on {110} planes already at low degrees of supersaturation. In contrast, the saturated solution would have to be undercooled by 34.2K to explain observed size of grown crystallites by 2D nucleation on {111} planes. Such high degree of supersaturation does not occur in the experiments. Hence, the calculations support the assumed growth model.

The loss of essential oil components induced by the Purge Time in the Pressurized Liquid Extraction (PLE) procedure of Cupressus sempervirens

The influence of different Purge Times on the effectiveness of Pressurized Liquid Extraction (PLE) of volatile oil components from cypress plant matrix (Cupressus sempervirens) was investigated, applying solvents of diverse extraction efficiencies. The obtained results show the decrease of the mass yields of essential oil components as a result of increased Purge Time. The loss of extracted components depends on the extrahent type – the greatest mass yield loss occurred in the case of non-polar solvents, whereas the smallest was found in polar extracts. Comparisons of the PLE method with Sea Sand Disruption Method (SSDM), Matrix Solid-Phase Dispersion Method (MSPD) and Steam Distillation (SD) were performed to assess the method's accuracy. Independent of the solvent and Purge Time applied in the PLE process, the total mass yield was lower than the one obtained for simple, short and relatively cheap low-temperature matrix disruption procedures – MSPD and SSDM. Thus, in the case of volatile oils analysis, the application of these methods is advisable.

Preparation and characterization of a novel hydroxyapatite-wollastonite/silk fibroin composite

A novel hydroxyapatite-wollastonite/silk fibroin (AW/SF) composite was prepared for bone repair and replacement by a modified coprecipitation method. The wollastonite powders introduced in the composite were sintered with full crytallinity and ground to the diameter of 30–50 nm. The FT-IR and XRD analyses showed that the silk fibroin, wollastonite, and hydroxyapatite co-existed in the composite, but the newly formed hydroxyapatite had low crystallinity ascribing to the low temperature procedure. The composite exhibited both higher compressive strength (84.4 MPa) and Barcol hardness (48.5) than the hydroxyapatite/silk fibroin (HA/SF) composite without any wallostonite involved. And the composite in this work showed excellent bioactivities while held in simulated body fluid (SBF).

A simple and efficient multi-residue method based on QuEChERS for pesticides determination in palm oil by liquid chromatography time-of-flight mass spectrometry

In this study, a rapid, specific and sensitive multi-residue method based on acetonitrile extraction followed by dispersive solid-phase extraction (d-SPE) clean-up was implemented and validated for multi-class pesticide residues determination in palm oil for the first time. Liquid-liquid extraction followed by low-temperature precipitation procedure was evaluated in order to study the freezing-out clean-up efficiency to obtain high recovery yield and low co-extract fat residue in the final extract. For clean-up step, d-SPE was carried out using a combination of anhydrous magnesium sulphate (MgSO(4)), primary secondary amine, octadecyl (C(18)) and graphitized carbon black. Recovery study was performed at two concentration levels (10 and 100 ng g(-1)), yielding recovery rates between 74.52% and 97.1% with relative standard deviation values below 10% (n = 6) except diuron. Detection and quantification limits were lower than 5 and 9 ng g(-1), respectively. In addition, soft matrix effects (≤±20%) were observed for most of the studied pesticides except malathion that indicated medium (20-50%) matrix effects. The proposed method was successfully applied to the analysis of suspected palm oil samples.

Application of KZnF3 as a Single Source Precursor for the Synthesis of Nanocrystals of ZnO2:F and ZnO:F; Synthesis, Characterization, Optical, and Photocatalytic Properties

Mixed metal fluoride, KZnF3, possessing a cubic perovskite structure has successfully been employed as a single source precursor for the synthesis of fluoride-doped ZnO2 nanocrystals by a simple low-temperature oxidation procedure. Utilizing the fact that ZnO2 is a precursor for ZnO, F–-doped wurtzite ZnO was readily obtained by a straightforward decomposition procedure. The structure, optical, and photocatalytic properties of doped ZnO2:F and ZnO:F were studied and compared with the undoped ones. The preservation of the cubic pyrite structure of ZnO2 by the inclusion of F–-ions was revealed by the powder X-ray diffraction pattern. Uniform cube morphology of the nanocrystals of ZnO2:F was observed in both the scanning electron microscopy and transmission electron microscopy images with the crystallite size of 20 nm. The IR and Raman spectroscopy analysis implied the absence of any Zn–F direct bonding in ZnO2:F. The high-resolution core level X-ray photoelectron spectroscopy (XPS) spectrum of F 1s observed at 687.9 eV confirmed the presence of fluoride ions in the ZnO2 lattice. By fitting the core level F 1s spectrum, the concentration of the F– ion was found to be 8.6%. A red shift in the excitonic absorption was observed on F– doping in ZnO2. A similar trend was also observed in the band edge emission from the photoluminescence spectrum recorded at 300 K. The intensity of the violet emission in the pure ZnO2 (with a decay time of 18 ns) decreased on F– doping (with a decay time of 13 ns). While ZnO2 nanocrystals efficiently degraded methylene blue (MB) solution under UV radiation and moderately under visible radiation, F–-doped samples showed lesser efficiency for the photo degradation of the MB solution. F–-doped ZnO was obtained by decomposing the ZnO2:F in air at 450 °C for 3 h. The symmetry remained hexagonal on F–-doping as revealed by the powder X-ray diffraction pattern. The intensity of the Raman bands of fluoride-doped ZnO nano powders were in general less as compared to the undoped ZnO, except the one observed at 582 cm–1, which indicated the presence of higher oxygen vacancies in ZnO:F. Core level XPS measurements provided conclusive evidence for the doping of fluorine (6.1%) in ZnO. The band gap value of ZnO:F, estimated from the diffuse reflectance spectrum, was 3.0 eV, and it showed broad visible emission. As a consequence of higher oxygen vacancies, ZnO:F exhibited efficient photocatalytic activity under visible irradiation for the degradation of aqueous MB dye solution.

Mechanosynthesized BiFeO3 Nanoparticles with Highly Reactive Surface and Enhanced Magnetization

A one-step synthesis of nanostructured bismuth ferrite (BiFeO3) via mechanochemical processing of a α-Fe2O3/Bi2O3 mixture at room temperature is reported. The mechanically induced phase evolution of the mixture is followed by XRD and 57Fe Mossbauer spectroscopy. It is shown that the mechanosynthesis of the rhombohedrally distorted perovskite BiFeO3 phase is completed after 12 h. Compared to the traditional synthesis route, the mechanochemical process used here represents a one-step, high-yield, low-temperature, and low-cost procedure for the synthesis of BiFeO3. High-resolution TEM and XRD studies reveal a nonuniform structure of mechanosynthesized BiFeO3 nanoparticles consisting of a crystalline core surrounded by an amorphous surface shell. The latter is found to exhibit an extraordinarily high metastability causing a rapid crystallization of nanoparticles under irradiation with electrons. In situ high-resolution TEM observations of the crystallization clearly show that the heterogeneous processes of nu...

A new method of high-speed cellular protein separation and insight into subcellular compartmentalization of proteins

Transglutaminase (TGM)-2 is a ubiquitous protein with important cellular functions such as regulation of cytoskeleton, cell adhesion, apoptosis, energy metabolism, and stress signaling. We identified several proteins that may interact with TGM-2 through a discovery-based proteomics method via pull down of flag-tagged TGM-2 peptide fragments. The distribution of these potential binding partners of TGM-2 was studied in subcellular fractions separated by density using novel high-speed centricollation technology. Centricollation is a compressed air-driven, low-temperature stepwise ultracentrifugation procedure where low extraction volumes can be processed in a relatively short time in non-denaturing separation conditions with high recovery yield. The fractions were characterized by immunoblots against known organelle markers. The changes in the concentrations of the binding partners were studied in cells expressing short hairpin RNA against TGM-2 (shTG). Desmin, mitochondrial intramembrane cleaving protease (PARL), protein tyrosine kinase (NTRK3), and serine protease (PRSS3) were found to be less concentrated in the 8.5%, 10%, 15%, and 20% sucrose fractions (SFs) from the lysate of shTG cells. The Golgi-associated protein (GOLGA2) was predominantly localized in 15% SF fraction, and in shTG, this shifted to predominantly in the 8.5% SF and showed larger aggregations in the cytosol of cells on immunofluorescent staining compared to control. Based on the relative concentrations of these proteins, we propose how trafficking of such proteins between cellular compartments can occur to regulate cell function. Centricollation is useful for elucidating biological function at the molecular level, especially when combined with traditional cell biology techniques.

Development and validation (according to the 2002/657/EC regulation) of a method to quantify sulfonamides in porcine liver by fast partition at very low temperature and LC-MS/MS.

A novel multi-residue method for the quantification of 15 sulfonamides in porcine liver is described. It involves the application of a liquid-liquid extraction with fast partition at very low temperature (LLE-FPVLT) procedure followed by HPLC-MS/MS (high performance liquid chromatography coupled to tandem mass spectrometry) analysis. By this innovative method, acetonitrile is added to a minced porcine liver sample and the resulting suspension centrifuged and immersed in a container with liquid nitrogen for 15 s. The acetonitrile phase, which remains liquid under these conditions, is isolated, evaporated to dryness, recomposed with formic acid 0.1% v/v, and injected into the liquid chromatograph. The whole analytical procedure was validated according to the European Commission Decision 2002/657/EC and acceptable values (except for sulfanilamide) were obtained for the following parameters: linearity (0.97 < R2 < 0.99), decision limit (107.70 µg kg-1 < CCα < 128.65 µg kg-1), detection capability (115.40 µg kg-1 < CCβ < 157.29 µg kg-1), limit of detection (5.58 µg kg-1 < LOD < 16.75 µg kg-1), limit of quantification (18.41 µg kg-1 < LOQ < 55.26 µg kg-1), accuracy (recovery rates), precision (repeatability, intermediate precision, and measurement uncertainty tests), selectivity, and robustness. Recoveries higher than 70%, at three concentration levels (0.5, 1.0 and 1.5 of the maximum residue limit, MRL), were attained for the majority of the sulfonamides. These very promising results point to the inclusion of the present methodology into the National Residue Control Plan scope of the Ministry of Agriculture, Livestock and Food Supply of Brazil.

Enzyme encapsulation in silica particles prepared using enzyme-assisted sol-gel reactions in ionic liquids

Several studies have demonstrated the use of biomimetic approaches in the synthesis of a variety of inorganic materials. In this study, a low-temperature and natural pH procedure for the synthesis of silica was developed using hydrolytic enzymes. For the preparation of silica particles at room temperature and pH 7, a screening test for enzyme-catalyzing direct hydrolysis and polycondensation of tetraethoxysilane by using 5 types of hydrolases; pepsin, trypsin, esterase, and two lipases were chosen as biocatalysts; moreover, these enzymes can promote the precipitation of silica within 3 days. The 29Si nuclear magnetic resonance (NMR) measurements indicated that the enzyme activity in ionic liquids was higher than that in aqueous buffer solutions, and that the obtained silica particles were highly polycondensed. Under ionic liquid conditions, it was observed that enzymes were effectively encapsulated in the sol–gel silica material. In addition, for siloxane bond formation the catalytic activity of silica–enzyme composites was higher than that of free solution enzymes.

Hydrogen Storage in Irradiated Low-Dimensional Structures

Experimentally, two types of samples (carbon nanotube – CNT, NbSe2) were tested and both irradiated by γ-rays and nonirradiated at two temperature levels — room temperature (293 K) and liquid nitrogen temperature (78 K). The irradiated samples were tested concerning the hydrogen absorption capability, and comparative analysis was done. It has been showed that CNT, NbSe2 are sustainable for irradiation. The increasing (∼15%) of hydrogen sorption-desorption capability for carbon nanotubes after irradiation treatment was demonstrated. Low temperature procedure of hydrogen storing showed the 2.9–3.5 mass% of hydrogen. The increasing of hydrogen storing in NbSe2 has not been observed.

Ecological parameters and disinfection effect of low-temperature laundering in hospitals in Slovenia

The aim of this research was to determine the influence of laundering procedures on the ecological parameters of wastewater and the electric energy consumption. Laundering procedures were simulated in a laboratory washing machine and the parameters temperature, duration and concentration of disinfection agents were varied until the optimal conditions were found for low-temperature laundering while achieving an appropriate disinfection effect with peroxyacetic acid and minimal damages to the textiles. The disinfection effect was determined using standard bioindicators Enterococcus faecium, Staphylococcus aureus, Enterobacter aerogenes and Candida albicans. The optimal low-temperature laundering procedure at 40 °C was then evaluated according to the Slovenian regulations for wastewater reuse and the toxicity of the wastewater on activated sludge as well as the wastewater biodegradability were determined. It was found that an optimal low-temperature laundering procedure at 40 °C decreased the energy consumption while reaching an adequate disinfection effect with somewhat higher dosages of chemicals and with lower damages to the textiles due to lower washing temperatures. The wastewater was found to have a certain level of pollution and was biodegradable and can therefore be treated using biological treatment.

Fabrication of an organic field effect transistor using nano imprinting of Ag inks and semiconducting polymers

A simple and cheap procedure for flexible electronics fabrication was demonstrated by imprinting metallic nanoparticles (NPs) on flexible substrates. Silver NPs with an average diameter of 10 nm were prepared via an improved chemical approach and Ag Np ink was produced in α-terpineol with a concentration up to 15%. Silver micro/nanostructures with a dimension varying from nanometres to microns were produced on a flexible substrate (polyimide) by imprinting the as-prepared silver ink. The fine fluidic properties of an Ag NP/α-terpineol solution and low melting temperatures of silver nanoparticles render a low pressure and low temperature procedure, which is well suited for flexible electronics fabrication. The effects of sintering and mechanical bending on the conductivity of imprinted silver contacts were also investigated. Large area organic field effect transistors (OFET) on flexible substrates were fabricated using an imprinted silver electrode and semiconducting polymer. The OFET with silver electrodes imprinted from our prepared oleic acid stabilized Ag nanoparticle ink show an ideal ohmic contact; therefore, the OFET exhibit high performance (Ion/Ioff ratio: 1 × 103; mobility: 0.071 cm2 V−1 s−1).

Effect of temperature and contact time on Campylobacter jejuni attachment to, and probability of detachment from, stainless steel.

The effect of temperature and contact time on attachment of six Campylobacter jejuni strains to, and probability of their detachment from, stainless steel were determined. Triplicate stainless steel coupons (SSC) were exposed to C. jejuni cell suspensions at 4, 25, 37, and 55 degrees C for 30 min. An increase in temperature enhanced the numbers of cells of all strains of C. jejuni attaching to stainless steel from approximately 4 log/cm(2) at 4 degrees C to approximately 5 log/cm(2) at 55 degrees C. Cells attached to SSC at 4 and 25 degrees C for 30 min were detached by the successive blotting technique on a series of Campylobacter blood-free selective agar plates. The probability of detachment was significantly (P < 0.05) higher at 4 degrees C (> or = 0.219) than at 25 degrees C (> or = 0.111) for five of the six strains tested, suggesting the strength of attachment was weaker at 4 degrees C than at 25 degrees C for these strains. C. jejuni cells were allowed to attach to SSC at 4 degrees C for 1, 15, 30, 45, 60, 120, 180, 240, and 300 min. The numbers of cells attaching to SSC reached approximately 4 log/cm(2) after 1 min of contact and increased slowly thereafter to approximately 5 log/cm(2) after 300 min of contact. The probability of detachment significantly (P < 0.05) decreased from 0.443 after 1 min to 0.134 after 240 min of contact, indicating bacterial attachment was strengthened over time. These data suggest that to reduce the numbers of adhered cells on processing surfaces, low-temperature and early bacterial detachment procedures should be applied.

Comparison of Lung Asbestos Fiber Content in Cancer Subjects with Healthy Individuals with no Known History of Occupational Asbestos Exposure in Korea

To evaluate the effects of environmental asbestos exposure on the inducement of lung cancer, pulmonary asbestos and non-asbestos fiber content was determined in 36 normal Korean subjects and 38 lung cancer subjects with no known occupational history of asbestos exposure. Pulmonary asbestos fiber content was measured by transmission electron microscopy (TEM) with energy-dispersive x-ray analysis after applying a low-temperature ashing procedure. Chrysotile fibers were the major fiber type found in the lungs of the Korean subjects. The asbestos fiber concentrations found in the lungs of normal males (25) and females (11) were 0.26 × 106 fibers/g of dry lung tissue and 0.16 × 106 fibers/g of dry lung tissue, respectively. The asbestos concentrations found in the lungs of cancer subjects were 0.16 × 106 fibers/g of dry lung tissue for 32 males and 0.44 × 106 fibers/g of dry lung tissue for 6 females. No statistical difference was found in pulmonary asbestos content between the normal and lung cancer subjects, whereas a statistical difference was noted between normal and lung cancer subjects with respect to lung non-asbestos content, indicating a potential role for non-asbestos fibers being associated with lung cancer.