Unreacted Residues Research Articles

Advances and challenges in designing active site environments in zeolites for Brønsted acid catalysis.

Zeolites contain proton active sites in diverse void environments that stabilize the reactive intermediates and transition states formed in converting hydrocarbons and oxygenates to chemicals and energy carriers. The catalytic diversity that exists among active sites in voids of varying sizes and shapes, even within a given zeolite topology, has motivated research efforts to position and quantify active sites within distinct voids (synthesis-structure) and to link active site environment to catalytic behavior (structure-reactivity). This Feature Article describes advances and challenges in controlling the position of framework Al centers and associated protons within distinct voids during zeolite synthesis or post-synthetic modification, in identifying and quantifying distinct active site environments using characterization techniques, and in determining the influence of active site environments on catalysis. During zeolite synthesis, organic structure directing agents (SDAs) influence Al substitution at distinct lattice positions via intermolecular interactions (e.g., electrostatics, hydrogen bonding) that depend on the size, structure, and charge distribution of organic SDAs and their mobility when confined within zeolitic voids. Complementary post-synthetic strategies to alter intrapore active site distributions include the selective removal of protons by differently-sized titrants or unreactive organic residues and the selective exchange of framework heteroatoms of different reactivities, but remain limited to certain zeolite frameworks. The ability to identify and quantify active sites within distinct intrapore environments depends on the resolution with which a given characterization technique can distinguish Al T-site positions or proton environments in a given zeolite framework. For proton sites in external unconfined environments, various (post-)synthetic strategies exist to control their amounts, with quantitative methods to distinguish them from internal sites that largely depend on using stoichiometric or catalytic probes that only interact with external sites. Protons in different environments influence reactivity by preferentially stabilizing larger transition states over smaller precursor states and influence selectivity by preferentially stabilizing or destabilizing competing transition states of varying sizes that share a common precursor state. We highlight opportunities to address challenges encountered in the design of active site environments in zeolites by closely integrating precise (post-)synthetic methods, validated characterization techniques, well-defined kinetic probes, and properly calibrated theoretical models. Further advances in understanding the molecular details that underlie synthesis-structure-reactivity relationships for active site environments in zeolite catalysis can accelerate the predictive design of tailored zeolites for desired catalytic transformations.

Mineralogy of the 1.45 Ga Wafangzi manganese deposit in North China: Implications for pulsed Mesoproterozoic oxygenation events

Abstract Ancient manganese (Mn) deposits are primarily characterized by the presence of Mn(II) carbonates that likely formed by the diagenetic reduction of precursor Mn(IV) oxides. As such, Precambrian sedimentary Mn deposits have been used as a line of evidence for the evolution of oxygen in Earth’s surface environments. However, recent studies have shown that these Mn(II)-carbonates have the ability to directly accumulate within anoxic water columns, where free oxygen does not play a role in their formation. This alternative pathway casts uncertainty on the robustness of using ancient Mn deposits to constrain the redox fabric of the past marine water columns. Here, we investigate the Wafangzi Mn and Fe ore deposit from the 1.45 billion-year-old Tieling Formation, North China. The deposit contains Mn(II, III) mineral phases (hausmannite, braunite) as inclusions, or unreacted residues, trapped within Mn(II) carbonate (Ca-rhodochrosite). Some nodules and oolites of Mn(II) and Fe(II)-carbonate phases are also present and display a banded structure with concentric rings. Mn(III) oxide (manganite) is present in a paragenetic assemblage along with hematite and replacement textures with braunite. The negative carbon isotope composition (δ13C, –7‰ to –4‰) from Mn(II) carbonate samples in the Wafangzi Mn deposit which are distinct from that of contemporaneous seawater (~0‰), along with petrographic and speciation analyses, collectively suggest that the Mn(II, III)- and Fe(II)-bearing mineral phases formed through the diagenetic reduction of primary Mn(IV)/Fe(III) minerals coupled to the oxidation of organic matter. Therefore, the Wafangzi Mn deposit suggests the presence of sufficiently oxygenated marine waters, overlying anoxic ferruginous deeper waters with a transitional manganous water layer that could have driven the redox cycling of Mn, Fe, and C. Given the contemporaneous economic Mn deposits in the 1.45 Ga Ullawarra Formation in Western Australia, our findings imply the existence of a transient, and perhaps widespread, pulsed oxygenation event in the mid-Proterozoic oceans.

Напрямки удосконалення технологій конверсії вугілля в синтетичні рідкі палива

Modern technologies for producing synthetic liquid fuels from coal include pyrolysis, hydrogenation, gasification, followed by synthesis of the final products by the Fischer-Tropsch process or via methanol. In pyrolysis, liquid fuels are obtained as by-products and their yield is usually no more than a few percent. A negative feature of hydrogenation is the formation of a significant amount (up to 40 %) of small, unreactive residue, the efficient use of which poses a significant scientific and technical challenge. The gas produced by coal gasification always contains more carbon monoxide CO than hydrogen, which is due to the need to ensure the heat balance of the process. At the same time, to be used in chemical syntheses, the hydrogen content in the gas should be several times higher than CO. To ensure the required Н2:СО ratio, part of the carbon contained in the feed coal is oxidised to carbon dioxide in an exothermic process. This improves the ratio in the resulting synthesis gas, but leads to irrational consumption of some carbon, reduces gas yield and ultimately increases the consumption factor of raw materials for the final product and worsens the technical and economic performance of the production. Therefore, obtaining additional hydrogen to improve the composition of synthesis gas is relevant. Until recently, however, the main way to produce hydrogen in industry was through the conversion of natural gas methane, which is unacceptable in today’s environment. The production of hydrogen from coke oven gas, where its content is about 60 % (by volume), by short-cycle adsorption is also unpromising, due to the several-fold decrease in coke production in Ukraine and, consequently, the almost complete absence of free coke oven gas resources. Therefore, it is important to introduce other industrial methods of hydrogen production. Keywords coal, synthetic liquid fuels, gasification, Fischer-Tropsch synthesis, hydrogen. Corresponding author: V.V. Shulga, e-mail: ko@ukhin.org.ua

Effect of blending ratio of biofuel from used cooking oil with Dexlite

Indonesia is committed to accelerating the clean energy transition through the biodiesel policy to achieve net zero emission. The commitment to use palm oil as a biofuel base material will support Indonesia in achieving its energy security and energy mix target of 23% in 2025. This article discussed the characteristics of the blended fuel between biofuel from used cooking oil and Dexlite from PERTAMINA products. The blending process is carried out with the biofuel: Dexlite ratio as follows: 5:95, 10:90, 15:85 20:80, 25:75 and 30:70. The results revealed that the best experiments for acid number were obtained at the B5 blending ratio of 0.039 mgKOH/(g sample), saponification number at the B5 blending ratio of 1.066 mgKOH/(g sample), flash point at the B20 blending ratio at a temperature of 101°C, 90% distillation at the B10 blending ratio at a temperature of 213°C, and the density at the blending ratio B15 is 837 kg/m3. From these results, only the density parameter does not meet the biodiesel quality standards based on SNI 7182:2015. These results indicate that the addition of 30% biofuel to Dexlite can still be used as a fuel for diesel vehicles by applying a better washing method for KOH catalyst residue and unreacted methanol residue.

A facile healing of two-step deposited MAPbI3 perovskite on TiO2 nanorod through dynamic methylamine treatment

The highly crystalline TiO2 nanorod as an underlying electron transport layer in perovskite solar cell has gained much attention due to its directional charge transport, better carrier extraction and enhanced light scattering. However, the morphology of perovskite film is critical to the photovoltaic performance, which makes it challenging to realize a high-quality perovskite film readily on an uneven nanorod-shaped underlying layer. In this regard, we develop a facile strategy to modify the two-step deposited methylammonium lead iodide (MAPbI3) film, deposited on hydrothermally synthesized TiO2 nanorod, by rapidly introducing methylamine vapor during the rotation, which enables another control to film planarization via a shear force induced by air flow, to investigate the influence of methylamine (MA) healing on such perovskite solar devices. The morphology and porosity of PbI2 on nanorod-based TiO2 are systemically studied by controlling the mixed solvent effect of dimethylformamide and dimethyl sulfoxide to satisfy a preferred PbI2 for the two-step deposited perovskite using TiO2 nanorod. The performance of such two-step deposited perovskite film after the developed MA treatment can be further improved, which suggests the occurrence of liquified MAPbI3 during the rotation to provide the positive healing effect on the film smoothness, pore infiltration, and unreacted PbI2 residues. The perovskite film after a long MA treatment is found to suffer from the formation of more defects or disorders than the defect tolerance in MAPbI3, which outweighs the healing advantages. Such a trend highlights the importance of delicately optimizing the developed MA treatment process, which can possibly achieve a high-performance perovskite solar cell of using two-step deposited MAPbI3 on TiO2 NR.

Потенційна небезпека УФ-фарб в процесі друкування пакувань для харчової і фармацевтичної продукції

The article is devoted to the problem of the potential danger of UV-inks with radical mechanism of photoinitiated polymerization during printing and operation of packages for food and pharmaceutical products. Pointing to the high level of environmental friendliness of the technology the use of UV-inks, which do not contain volatile organic solvents, their problem is noted application due to the possible migration of components from the ink layer and accordingly the risk of product contamination during packaging. An analysis of the processes occurring during the reaction was carried out radical polymerization, the reasons for the migration of printing ink components and by-products as a result of undergoing photoinitiated polymerization in aerobic conditions Accordingly, small amounts of unreacted components remain embedded in a three-dimensional polymer mesh and constitute the bulk of those components which can freely diffuse from the ink layer. The factors as the reason were analyzed refusal to use some types of oligomers, monomers and photoinitiators for the creation photopolymerizable ink compositions. Unreacted component residues, diffusing and mixing, depending on the chemical structure, can have a toxic or carcinogenic effect on living organisms. The analysis made it possible to classify ways of minimizing migration components of UV-inks when printing packages, namely, ways to minimize migration. The properties of UV-inks components can be divided into two types: chemical and physical. At the chemical method is a careful selection of UV-inks components and introduction synergists, and in the case of physical - compliance with technological regimes, reduction the concentration of oxygen both in the atmosphere and in the liquid composition by creating an inert gas environment and the creation of effective barriers by lamination.

Impact-Initiation Sensitivity of High-Temperature PTFE-Al-W Reactive Materials

Drop-weight tests were conducted to investigate the impact-initiation sensitivity of high-temperature PTFE-Al-W reactive materials. The test results show that the impact-initiation sensitivity of the materials more than doubles with increasing the sample temperature from 25 to 350 °C. Combined with the impact-induced initiation process recorded by high-speed video and the difference between reacted and unreacted residues, the crack-induced initiation mechanism was revealed. The rapid propagation of crack provides a high-temperature and aerobic environment where Al reacts violently to PTFE, which induces the initiation. Moreover, the influence of sample temperature on the sensitivity was discussed and analyzed. The analysis results indicate that the sensitivity shows a temperature interval effect, and 127 and 327 °C are the interval boundaries where the sensitivity changes significantly. The sensitivity may leaps at 127 °C and increases more rapidly in the temperature interval from 127 to 327 °C, but hardly changes after the temperature reaches 327 °C.

Calcium oxide derived from eggshells supported on titanium oxide green catalysts for lignin hydrogenolysis under supercritical alcohol solvents

Catalytic depolymerization of lignin has been investigated in the presence of egg shell derived CaO/TiO2 catalysts. Reaction was carried out for different reaction temperatures (250, 280 and 310 °C) at different reaction holding time at presence of N2 and H2 gas under ethanol, methanol and water solvent. Highest bio-oil yield was found with CaO/TiO2-800 catalyst in ethanol solvent under N2 (74.8 wt%), and H2 (82.8 wt%) environment compared to the water solvent. Under hydrogen environment very less amount of unreacted residue was produced. Bio-oil analysis showed that in under nitrogen environment catalytic depolymerization of lignin produced alkyl phenolic monomer compounds 68.0% with methoxy phenolic compounds 24.0%. Interestingly hydrogen promoted the deoxygenating and hydrogenation reaction which produced higher cyclohexane compounds 38.2% and aromatic hydrocarbon 19%. This is suggesting that the effectively breaking of β-O-4 bond by the catalysts which has an excellence character for the industrial application. Elemental analysis shows that hydrogen enhanced the bio-oil quality compared to the nitrogen environment. This work introduces new perspectives for the efficient production of functional compounds from lignin assisted by egg shell derived green catalysts.

The research on hydro-raffinates from the co-hydrogenation process in terms of mono- and diacylglycerols content determination

In this work, the possibilities of using the GC-FID gas chromatography technique for determination of mono- and diacylglycerols content in the stream from the co-hydrogenation of rapeseed oil and middle distillates were investigated. Products from this process are planned to be increasingly used in the future as a new biocomponent of fuel for diesel engines. Before introducing new types of fuel components, it is necessary to test them in detail, especially in terms of residues of the fat raw material. The Regulation of the Minister of Climate of June 24, 2020 on the content of biocomponents formed as a result of co-hydrogenation indicates that the level of biomass conversion is determined on the basis of the content of triacylglycerols in the hydro-raffinate. Hence, on the basis of this determination, it is possible to assess the correctness of the co-hydrogenation process. However, other fatty components may be present in the product of this process in the form of unreacted residues. Therefore, it seems justified to carry out studies on other trace components of fatty origin in the hydro-treating material, due to the introduction of various plant materials together with petroleum hydrocarbons into the co-hydrogenation process. Due to the lack of available standardized methodologies for testing this type of products, a review of the literature was made regarding the possibility of using analytical techniques including gas and liquid chromatography to determine content of the so-called mono- and dicylglycerols, being residues of the fatty raw material, in various types of matrices, including vegetable oils and fatty acid methyl esters. In the case of examining the content of mono- and diacylglycerols in the product from the co-hydrogenation process, it was necessary to use the technique of liquid chromatography for the first-step concentration of the substances of interest. This technique made it possible to separate the sample matrix and concentrate the components to be determined prior to gas chromatographic analysis. Due to the complicated matrix of samples and the low required level of quantification, it was necessary to select appropriate conditions for removing the matrix using the classical liquid chromatography technique. A proprietary methodology for testing the content of mono- and diacylglycerols in the hydro-raffinate was developed, which was used to test selected samples of real hydro-raffinates from the co-HVO and HVO co-hydrogenation process. The ability to detect these trace fat components at a low level was indicated – as low as 2 mg/kg. The obtained sensitivity of the method allowed for additional qualitative assessment of this type of co-hydrogenation products, which are gradually gaining importance on the European market of liquid fuels.

Cytocompatibility of Modified Silk Fibroin with Glycidyl Methacrylate for Tissue Engineering and Biomedical Applications.

Hydrogel with chemical modification has been used for 3D printing in the biomedical field of cell and tissue-based regeneration because it provides a good cellular microenvironment and mechanical supportive ability. As a scaffold and a matrix, hydrogel itself has to be modified chemically and physically to form a β-sheet crosslinking structure for the strength of the biomaterials. These chemical modifications could affect the biological damage done to encapsulated cells or surrounding tissues due to unreacted chemical residues. Biological assessment, including assessment of the cytocompatibility of hydrogel in clinical trials, must involve testing with cytotoxicity, irritation, and sensitization. Here, we modified silk fibroin and glycidyl methacrylate (Silk-GMA) and evaluated the physical characterizations, residual chemical detection, and the biological effect of residual GMA depending on dialysis periods. Silk-GMA depending on each dialysis period had a typical β-sheet structure in the characterization analysis and residual GMA decreased from dialysis day 1. Moreover, cell proliferation and viability rate gradually increased; additionally, necrotic and apoptotic cells decreased from dialysis day 2. These results indicate that the dialysis periods during chemical modification of natural polymer are important for removing unreacted chemical residues and for the potential application of the manufacturing standardization for chemically modified hydrogel for the clinical transplantation for tissue engineering and biomedical applications.

Development of chitosan membrane using non-toxic crosslinkers for potential wound dressing applications

There is a myriad of ways to crosslink hydrogel wound dressings; however, they require additional steps to remove the residue of the crosslinking agents, or their byproducts in biological environments are toxic. In this study, we studied and characterized the crosslinking of the chitosan hydrogels by various dicarboxylic acids, including oxalic acid, adipic acid, and sebacic acid under vacuum at 90 °C. The concentrations of the crosslinkers in the crosslinked hydrogels are tolerable for the cells, and the membranes can be used after crosslinking without complicated additional steps to remove the unreacted residues. The molar ratio of the crosslinkers was calculated based on the stoichiometry of the chitosan amine groups. Attenuated total reflectance Fourier transform infrared spectroscopy revealed amide linkage formation between amine groups of the chitosan and carboxyl groups of the dicarboxylic acids at 90 °C. The results showed that the chitosan membranes crosslinked with oxalic acid had higher Young's modulus (~ 1042 N/mm2) and ultimate tensile strength (~ 75 N/mm2) in comparison with the other dicarboxylic acids. Moreover, the membranes crosslinked with oxalic acid showed a weight loss of ~ 5.4% after 24 h at double-distilled water, which was drastically lower than that of the others. Thus, oxalic acid was selected as the most effective crosslinker. Cell viability assay, using mouse fibroblast (L929) cells, was conducted on the mechanically optimized membranes. The fibroblast cells successfully attached and spread well on the surface of the membranes. In conclusion, the obtained results suggested oxalic acid as an effective and non-toxic crosslinker for chitosan-based membranes for wound dressing applications.

Хемилюминесцентный метод определения несимметричного диметилгидразина в водных объектах

Для оперативного контроля качества водных сред предложен хемилюминесцентный метод количественного определения несимметричного диметилгидразина (НДМГ) в водных объектах. В основе метода анализа НДМГ лежит определение расхода окислителя на нейтрализацию исследуемого вещества. В качестве окислителя использован перманганат калия, подкисленный концентрированной серной кислотой до рН = 1-2. На первом этапе перманганат калия реагирует с НДМГ, далее количество непрореагировавшего окислителя измеряется в ходе его реакции с люминолом методом хемилюминесценции. По результатам изменения интенсивности излучения света в реакции хемилюминесценции определяется концентрация окислителя в реакционной смеси, что позволяет количественно определить содержание НДМГ в пробе. Концентрацию НДМГ определяют по максимальной интенсивности свечения в системе люминол - подкисленный перманганат калия. Показано, что предлагаемый метод превосходит по точности измерений традиционный фотоколориметрический метод определения НДМГ. При этом хемилюминесцентная реакция позволяет значительно сократить продолжительность снятия показаний и ускорить обработку данных (продолжительность измерений не превышает 2,5 мин), т.е. обеспечить экспресс-анализ НДМГ в растворах в полевых условиях и в мобильных лабораториях. A chemiluminescence mediated procedure for quantitative determination of unsymmetrical dimethyl hydrazine (UDMH) in water bodies is proposed which can be applied for prompt quality control of aqueous media. The UDMH analysis is based on determining an oxidizing agent uptake required for neutralization of the analyzed compound. Potassium permanganate acidified with concentrated sulfuric acid for pH value adjustment up to 1-2 is used as the oxidizing agent. The first step of the procedure involves interaction of potassium permanganate with UDMH followed by chemiluminescence reaction of unreacted oxidant residues with luminol. Measurements of changes in the intensity of light emission in the chemiluminescence reaction are performed for determination of concentration of the oxidizing agent in the reaction mixture, which provides quantitative determination of UDMH content in the sample. The concentration of UDMH is calculated from maximum luminous intensity in the luminol - acidified potassium permanganate system. The proposed method has demonstrated a superior accuracy as compared to the traditional photocolorimetric method for determining UDMH. Moreover, the chemiluminescent reaction allows to reduce significantly the duration of the analytical procedure and accelerates the data processing (the average time of measurement does not exceed 2.5 minutes), i.e. provides express-analysis of UDMH in aqueous solutions, in particular, in the field conditions and mobile laboratories.

Development and validation of the enzymatic kinetic photometric procedure for determination of residual quantities of dequalinium chloride on the surface of the pharmaceutical equipment

Aim. To develop and validate the new enzymatic kinetic photometric procedure for analysis of dequalinium chloride based on application of enzymatic acetylcholine hydrolysis to determine the residual quantities of dequalinium chloride while monitoring the completeness of cleaning of the pharmaceutical equipment.Results and discussion. The optimal conditions for the enzymatic reaction course were determined – the order of mixing and the concentration of acetylcholine (0.05 mg/mL), cholinesterase (0.4 mg/mL), hydrogen peroxide (10 %) and p-phenetedine (1 %), the time of the reaction mixture maintaining (20 min), pH (8.35), the effect of the nature of the buffer solution. Validation of the procedure developed was carried out – the application range of the procedure was proposed (40–160 % in the normalized coordinates, the maximum acceptable concentration of dequalinium chloride in washes from the pharmaceutical equipment хcrit = 0.5 μg/mL), the number of concentration levels (n = 7); the order of their location within the application range, taking these data into account the maximum acceptable uncertainty of the procedure (maxΔx = 3.05 %) and the acceptability criteria for linear dependence parameters, systematic and random errors were calculated. The validation characteristics of the procedure developed were shown to correspond to the acceptability criteria calculated. The degree of extraction of dequalinium chloride from swabs with flushing from the pharmaceutical equipment was determined.Experimental part. The residual quantities of dequalinium chloride on the surface of the pharmaceutical equipment were determined by the degree of inhibition of the enzymatic reaction assessed by the unreacted residue of the substrate of the biochemical reaction, such as acetylcholine. The residual quantities of acetylcholine in the reaction mixture was determined by the kinetic photometric method by the indicator reaction of p-phenetidine oxidation with peracetic acid (formed during the auxiliary perhydrolysis reaction when adding an excess of hydrogen peroxide to the reaction mixture) in the way of registering the light absorbance of the resulting reaction product – azoxifenetole (λmax = 358 nm) for a definite period of time.Conclusions. The enzymatic kinetic photometric procedure has been developed to determine the residual quantities of dequalinium chloride on the surface of the pharmaceutical equipment after its cleaning. The procedure developed has been validated by such parameters as linearity, accuracy, precision and the limit of quantification

Recycling of rare earth elements from FeNdB-Magnets via solid-state chlorination

Recycling of rare earths from magnetic alloys such as Fe14Nd2B is a widely studied field of research. However, with rare earth metal prices falling, leaching of magnet materials with mineral acids has become economically unfeasible. In order to circumvent high expenditures, solid-state chlorination offers an attractive alternative. Chlorination takes place via partial decomposition of NH4Cl at temperatures between 225 and 325 °C. Subsequently, dry HCl gas reacts with the magnet material in a rotary kiln to form water-soluble metal chlorides, which are dissolved in an acetic acid buffer medium. Here, spent Fe14Nd2B-magnets from a wind turbine served as starting material. For the first time, the solid-state chlorination process was optimised with the aid of statistical experimental design considering binary factor correlations. The global optimum was determined by varying the amount of NH4Cl, temperature, residence time and buffer mass in the subsequent leaching step. The maximum rare earth yield amounted to 84.1%. For dissolving rare earths quantitatively, the unreacted residue requires recirculation. In this respect, solid-state chlorination was compared to an optimised state-of-the-art process employing hydrochloric acid for digestion. The solid-state chlorination process was found to be superior in that consumption of chemicals was reduced by 45%, no costs for neutralisation incur and chemical costs were decreased by at least 51%.

Self-Assembly of Pentacene on Sub-nm Scale Surface Roughness-Controlled Gate Dielectrics

Surface roughness (Rq) of dielectric materials plays an important role in the ordering and charge-carrier transport of organic semiconductors, and is directly involved in the development of nuclei and crystal grains on a surface. To investigate the effect of Rq-controlled dielectrics with similar surface energy (γ) on the development of nuclei and crystal grain, a series of triethoxysilane-terminated polystyrene (PSTES) polymers with different molecular weights (MW) values is synthesized using reversible addition-fragmentation chain transfer polymerization. The different MW PS-TES films are spun-cast on a hydroxyl (-OH)-rich SiO2 dielectric surface, and chemically coupled with -OH moieties at 110 °C. Some films are also rinsed with an excess of toluene to remove unreacted polymer residue, increasing the average Rq values of the treated SiO2 surfaces. The resulting polymer-treated dielectrics show similar surface energy values of 41.6-42.5 mJ m-2 but different Rq values ranging from 0.29 to 1.07 nm. On the nanoscale roughness-controlled dielectric surfaces, 40-nm-thick pentacene films show discernible types of crystal grains with different phases, shapes, sizes, and ordering, all of which significantly affect charge-carrier transport along π-conjugated semiconductors in organic field-effect transistors (OFETs). Pentacene OFETs show large variations in field-effect mobility (μFET) from 0.89 to 0.19 cm2 V-1 s-1. Specifically, at Rq=0.40 nm the μFET value suddenly decreases to 0.30 cm2 V-1 s-1. On polymer treated SiO2 dielectrics with an Rq value greater than 0.40 nm, polymorphic, less-ordered, and smaller grains of pentacene containing large number of charge trap sites developed, resulting in significantly degraded charge-carrier transport along the intra- and inter-grains in OFETs, in comparison to the well-ordered grains on smooth polymer-treated surfaces (Rq<0.40 nm).

Comparison of residual styrene monomer determination of pharmaceutical materials packed with polystyrene using gas chromatography and ultraviolet/visible spectrophotometer

Background: Plastics such as plastic wrapping are an integral part of today’s society. Plastics are made by polymerization of styrene monomers. If the polymerization reaction is not perfect, then there will be unreacted monomer residues. Although styrene is still considered harmless, if there is a metabolic process will form styrene oxide that can cause effects that are carcinogenic. Aims and Objectives: This study aims to determine the residue of pharmaceutical styrene materials packed with polystyrene using gas chromatography (GC) and ultraviolet (UV)/visible spectrophotometers which are usually available in chemical analysis laboratories. Materials and Methods: Orientation of analysis method was performed using latex polystyrene sample. Styrene monomer analysis was performed using a GC and UV/visible spectrophotometer. Then a comparative study was conducted on both methods. Once this method was accepted, it was applied to a polystyrene-containing sample obtained from the market. Styrene was isolated from the sample; then, both methods were tested and compared. Results: Using polystyrene latex sample and varying column temperature, for GC, the optimum condition was obtained at column temperature 110°C, detector temperature 200°C, and temperature of injector 200°C. Using the packing column, we got a repeatability of 96.67%, PRECISION test of 2.81%, 96.49% recovery test, and a detection limit of 0.25 ppm. For the quantitative test of latex polystyrene samples, the average residual content obtained was 0.276%. When using GC with a capillary column, used column DB-17 at 110°C, detector, and injector temperature at 200°C, the average content of styrene residue was 0.278%. When using the spectrophotometer UV/visible, λ maximum at 280.5 nm, the reliability, assay, recovery test, and detection limits were 94.83%, 4.36%, 93.72% and 0.30 ppm, respectively. The residual styrene results obtained with this instrument was an average of 0.271%. Using variance analysis with the fixed model for all three methods (GC with the capillary column, GC with packing column, and spectrophotometer UV/visible) obtained H0 hypothesis was rejected so that it was continued with Duncan test with the result of all three methods could be used for analysis of styrene residue. The result of average analysis for beverage sample with Spectrophotometer UV/visible method was 0.0220%, packed column GC was 0.0221% packing, and capillary column GC of 0.0.223%. For medication samples in each instruments were found 0.0239%, 0.0241%, and 0.0242%, whereas for food samples obtained 0.0236%, 0.0238%, and 0.0239%. Conclusions: A GC method with either a packing column or a capillary column and a spectrophotometer UV/visible could be used to analyze the residual styrene monomer of a polystyrene-grade pharmaceutical sample. The best analysis could use GC with a capillary column. It is recommended to use differential scanning calorimetry and thermogravimetric analysis, if available, as well as infrared spectrophotometer to obtain a cheaper and better method.

Atomic layer deposition of molybdenum disulfide films using MoF6 and H2S

Molybdenum sulfide films were grown by atomic layer deposition on silicon and fused silica substrates using molybdenum hexafluoride (MoF6) and hydrogen sulfide at 200 °C. In situ quartz crystal microbalance (QCM) measurements confirmed linear growth at 0.46 Å/cycle and self-limiting chemistry for both precursors. Analysis of the QCM step shapes indicated that MoS2 is the reaction product, and this finding is supported by x-ray photoelectron spectroscopy measurements showing that Mo is predominantly in the Mo(IV) state. However, Raman spectroscopy and x-ray diffraction measurements failed to identify crystalline MoS2 in the as-deposited films, and this might result from unreacted MoFx residues in the films. Annealing the films at 350 °C in a hydrogen rich environment yielded crystalline MoS2 and reduced the F concentration in the films. Optical transmission measurements yielded a bandgap of 1.3 eV. Finally, the authors observed that the MoS2 growth per cycle was accelerated when a fraction of the MoF6 pulses were substituted with diethyl zinc.

Analysis of Influence of Foaming Mixture Components on Structure and Properties of Foam Glass

It is recommended to use high-quality thermal insulation materials to increase the energy efficiency of buildings. One of the best thermal insulation materials is foam glass - durable, porous material that is resistant to almost any effect of substance. Glass foaming is a complex process depending on the foaming mode and the initial mixture composition. This paper discusses the influence of all components of the mixture – glass powder, foaming agent, enveloping material and water - on the foam glass structure. It was determined that glass powder is the basis of the future material. A foaming agent forms a gas phase in the process of thermal decomposition. This aforementioned gas foams the viscous glass mass. The unreacted residue thus changes a colour of the material. The enveloping agent slows the foaming agent decomposition preventing its premature burning out and, in addition, helps to accelerate the sintering of glass particles. The introduction of water reduces the viscosity of the foaming mixture making it evenly distributed and also promotes the formation of water gas that additionally foams the glass mass. The optimal composition for producing the foam glass with the density of 150 kg/m3 is defined according to the results of the research.

Key factors regulating protein carbonylation by α,β unsaturated carbonyls: A structural study based on a retrospective meta-analysis

Protein carbonylation represents one of the most important oxidative-based modifications involving nucleophilic amino acids and affecting protein folding and function. Protein carbonylation is induced by electrophilic carbonyl species and is an highly selective process since few nucleophilic residues are carbonylated within each protein. While considering the great interest for protein carbonylation, few studies investigated the factors which render a nucleophilic residue susceptible to carbonylation. Hence, the present study is aimed to delve into the factors which modulate the reactivity of cysteine, histidine and lysine residues towards α,β unsaturated carbonyls by a retrospective analysis of the available studies which identified the adducted residues for proteins, the structure of which was resolved. Such an analysis involved different parameters including exposure, nucleophilicity, surrounding residues and capacity to attract carbonyl species (as derived by docking simulations). The obtained results allowed a meaningful clustering of the analyzed proteins suggesting that on average carbonylation selectivity increases with protein size. The comparison between adducted and unreactive residues revealed differences in all monitored parameters which are markedly more pronounced for cysteines compared to lysines and histidines. Overall, these results suggest that cysteine's carbonylation is a finely (and reasonably purposely) modulated process, while the carbonylation of lysines and histidines seems to be a fairly random event in which limited differences influence their reactivity.

Highly stable semi-transparent CH3NH3PbI3 sandwich type perovskite solar sub-module with neutral color

∼10% semi-transparent neutral color sandwich type CH3NH3PbI3 (MAPbI3) perovskite sub-module (active area = 25 cm2) with UV cross-linked polystyrene passivation layer showed ∼2.8% degradation of initial efficiency after continuous light soaking of 1 Sun for 1000 h at 55 °C. Due to the role of island-morphology-MAPbI3 as selective UV-cut mask, the UV curable monomeric compounds on the island-morphology-MAPbI3/blocking TiO2/F-doped tin oxide substrate could be selectively cross-linked polymerized by exposure of UV light and consequently the UV cured passivation layer could be reproducibly deposited in the gaps between perovskite islands after simple washing of unreacted residue. The degree of cross-linking was controlled by adjusting the concentration of divinylbezene cross-linker in the UV curable monomeric compounds from 1 to 7 mol% and eventually 5 mol% sample showed the best power conversion efficiency of 11.58% for forward scan condition and 11.95% for reverse scan condition (active area = 1 cm2, geometric fill factor = 100%, average = 10.28 ± 0.96% for 40 samples: average visible transmittance = 20.1%). When the active area of the MAPbI3 perovskite sub-module increases to 1 → 25 → 100 cm2, the power conversion efficiency was slightly decreased to 11.95 → 10.16 → 7.08% at 1 Sun condition.