Treatment In Alkaline Solution Research Articles

Surface treatment of GaN nanowires for enhanced photoelectrochemical water-splitting

High-efficiency hydrogen production through photoelectrochemical (PEC) water splitting has emerged as a promising solution to address current global energy challenges. III-nitride semiconductor photoelectrodes with nanostructures have demonstrated great potential in the near future due to their high light absorption, tunable direct band gap, and strong physicochemical stability. However, several issues, including surface trapping centers, surface Fermi level pinning, and surface band bending, need to be addressed. In this work, enhanced photovoltaic properties have been achieved using gallium nitride (GaN) nanowires (NWs) photoelectrodes by adopting an alkaline solution surface treatment method to reduce the surface states. It was found that surface oxides on NWs can be removed by an alkaline solution treatment without changing the surface morphology through X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and other characterization methods. These findings provide new insights to the development of high-efficiency photoelectrodes for new energy source applications.

Alkali assisted water treatment of aluminum promoting the growth of hydrated oxide film for energy conservation

Aluminum anodizing process consumes a lot of energy for ions migration in solid phase. Commonly, the aluminum foil is treated by boiling water to form crystalline γ'-Al2O3 for reducing the energy consumption. In order to improve water treatment, the alkaline buffer solution was used for promoting the growth of hydrated oxide film and contributed to formation of crystalline alumina. As a result, the obtained samples consumed 12.08% less energy during anodizing process compared with that of water treated samples. The hydrated oxide film was detected by means of morphological and electrochemical analysis, which indicated the alkaline treatment promoted generation of hydrated oxide film as well as formed dense anodic oxide film after anodizing. Furthermore, the pretreated samples owned denser anodic oxide film verified by X-ray diffraction and electrochemical analysis, which implied less production of alumina on the same electrical performance. Therefore, the alkaline solution treatment of aluminum/hydrated oxide film has a good prospect for getting rid of the limitation of high energy consumption in electrolytic capacitors industry.

Study of the Resistive Properties of Lead Silicate Glasses after Chemical Impact

The change in the resistive characteristics of lead silicate glasses (LSGs) after treatment in alkaline and acid solutions is studied. It is established that the chemical treatment of glasses and, accordingly, blanks of microchannel plates (MCPs) affects the high-temperature ionic conductivity at a constant activation energy of electrical conductivity. It is shown that the treatment of glasses in NaOH and HF solutions can significantly change the electrical resistance.

Surface Modulation Inducing Bismuth-Rich Surface Composition in BiVO4 for Efficient Photoelectrochemical Water Splitting

Surface engineering affects the photoelectrochemical properties of multinary oxide photoelectrodes. Here, we report a simple alkaline solution treatment of the (010) faceted bismuth vanadate (BiVO4) photoanode to increase the surface ratio of bismuth to vanadium, thus improving the performance of photoelectrochemical water oxidation. This study demonstrates that the preferential vanadium dissolution occurs in an alkaline solution, resulting in a bismuth-rich surface on the outer region of the pristine BiVO4 to afford the formation of homojunction within BiVO4. The homojunction promotes the charge separation efficiency of the treated BiVO4 photoanode to reach an almost ∼100% enhancement at 1.23 VRHE under simulated sunlight. Upon further loading NiFeOx cocatalyst, the maximum applied-bias photon-to-current conversion efficiency (ABPE) of treated BiVO4 photoanode also shows a further 100% enhancement in 0.1 M KPi electrolyte. This study sheds light on the critical role of surface termination/composition on the photoelectrochemical properties of the BiVO4 photoanode. This essential surface property can be modulated through a simple strategy to improve its charge transport for efficient water oxidation.

Physical Quality and Tannin Content of Sorghum (Sorghum bicolor L.) at Different Temperature and Soaking Immersion

This study aimed to evaluate the effect of temperature and the type of immersion solution on the characteristics of the physical quality and tannin content of sorghum seeds. The material used were red sorghum seeds soaked for 24 hours in a neutral and alkaline solution at 30, 45, and 60°C. The parameters observed included moisture content, hardness, tannin content, and brightness of sorghum seeds which were then carried out statistical analysis and further tests with the DMRT method to determine the effect of treatment levels on parameter changes. The results showed that the increase in water content ranged from 28.22 - 32.16% with the highest final water content of 43.49% in the alkaline immersion treatment at 60°C. The value of decreasing hardness of seeds varied from 66.15 to 79.71% with the lowest hardness value of 11.10 Newton. Decreased levels of tannins by 46.98%; 68.13%; and 73.54% in the treatment of neutral solutions at temperature of 30, 45 and 60°C, and 52.30%; 70.74%; and 72.88% in the alkaline solution treatment at temperature of 30, 45 and 60°C. Soaking in the alkaline solution caused a decrease in the lowest brightness level of sorghum seeds compared to soaking at neutral pH at each temperature levels treatment.

A method for ultrafast tissue clearing that preserves fluorescence for multimodal and longitudinal brain imaging

BackgroundTissue-clearing techniques have recently been developed to make tissues transparent for three-dimensional (3D) imaging at different scales, including single-cell resolution. However, current tissue-clearing workflows have several disadvantages, including complex protocols, time-consuming application, and fluorescence quenching. Additionally, they can be used mainly for clearing larger-volume samples, preventing wide and easy applicability in conventional experimental approaches. In this study, we aimed to develop a versatile, fast, and convenient method for clearing thin and semi-thick samples, which can be used for three-dimensional imaging of experimental or even clinical samples.ResultsWe developed an alkaline solution (AKS) containing a combination of 2,2′-thiodiethanol (TDE), DMSO, D-sorbitol, and Tris for tissue clearing, as the alkaline environment is suitable for maintaining the fluorescence of most commonly used fluorescence protein GFP and its variants, and tested its clearing effect on samples from mice and human brains. We assessed the clearing speed, the preservation of fluorescence protein and dyes, and the imaging depth and quality. The results showed that AKS treatment rapidly cleared 300-μm-thick brain slices and 1-mm-thick slices from different organs within 5 min and 1 h, respectively. Moreover, AKS was compatible with a variety of fluorescence proteins and dyes. Most importantly, AKS enhanced the fluorescence of YFP, in contrast to the majority of existing tissue-clearing methods which reduce the fluorescence intensity of fluorescent proteins. Using AKS, we performed long-time high-resolution imaging of weak fluorescent protein-labelled tissues, long-distance fibre tracking, larger-scale 3D imaging and cell counting of the entire brain area, neural circuit tracing, 3D neuromorphic reconstruction, and 3D histopathology imaging.ConclusionsAKS can be used for simple and rapid clearing of samples from mice and human brains and is widely compatible with a variety of fluorescent dyes. Therefore, AKS has great potential to be used as a broad tissue-clearing reagent for biological optical imaging, especially for time-sensitive experiments.

Fabrication of GaN nanowires containing n+-doped top layer by wet processes using electrodeless photo-assisted electrochemical etching and alkaline solution treatment

We attempted to fabricate GaN nanowires by electrodeless photo-assisted electrochemical (PEC) etching and successive alkaline solution treatment. The sample consisting of n+-doped and unintentionally doped GaN grown on a GaN substrate was selectively etched using a Ti mask in a mixed solution of K2S2O8 and KOH under UV light radiation. This specific layer structure required a relatively concentrated KOH solution for etching. The PEC etching resulted in the formation of a tapered cone structure of GaN with its top diameter determined by the mask size. Successive KOH treatment after PEC etching yielded GaN nanowires with diameters of about 220 nm.

Zeolite Produced from Fly Ash by Thermal Treatment in Alkaline Solution and Its Capability to Adsorb Cs(I) and Sr(II) in Aqueous Solution

In this study, we evaluated the efficiency of fly ash (FA) recycling technology, produced from a coal-fired power plant, with the capability to adsorb cesium ion[Cs(I)] and strontium ion [Sr(II)] from aqueous phase. Zeolite was produced from FA by hydrothermal treatment in an alkaline solution. Zeolite 12, 24, and 48 have a Garronite structure. Moreover, the specific surface area of Zeolite was greater than that of FA. Zeolite 12 demonstrated the adsorption capability of Cs(I) and Sr(II) from aqueous phase. Adsorption isotherms data fitted both the Langmuir equation (correlation coefficient: >0.895) and the Freundlich equation (correlation coefficient: >0.881). In addition, the kinetic data fitted the pseudo-second-order model when compared to the pseudo-first-order model. Cs(I) and Sr(II) were selectively adsorbed by Zeolite 12 in complex solution system. Our findings indicate that Zeolite can be produced from FA by hydrothermal treatment in an alkaline solution and shows the capability to adsorb Cs(I) and Sr(II) from aqueous phase. Therefore, Zeolite can be useful adsorbent for purification in water environments.

Synthesis of novel zeolites produced from fly ash by hydrothermal treatment in alkaline solution and its evaluation as an adsorbent for heavy metal removal

In this study, zeolites (FA6, FA12, and FA24) were prepared from JIS Type-II fly ash (FA) by alkaline hydrothermal treatment, and their physicochemical characteristics were investigated. In addition, their adsorption capability for heavy metals ions (Hg2+ and Pb2+) was evaluated. Zeolites have Hydrosodalite and/or Zeolite P structure, and the specific surface area of FA24 was greater than that of FA6 and FA12. A higher amount of heavy metals ions was adsorbed by FA24 than by FA6 and fA12. After adsorption using FA24, the binding energy of Pb2+ was detected, on the other hand, the binding energy of Hg2+ was not detected under our experimental conditions. These results suggest that FA24 surface properties shows a low adsorption capability of Hg2+. In addition, ion exchange with sodium ions in the adsorbent was also related to the adsorption capability of heavy metals ions (correlation coefficient: 0.965–0.973). A pH of approximately 5 was found to be optimal for the adsorption of heavy metals ions under our experimental conditions.

Electrochemical enzymatic biosensor for tyramine based on polymeric matrix derived from 4-mercaptophenylacetic acid

In this paper, we investigated a novel functionalized polymeric film derived from 4-mercaptophenylacetic acid (MPAA). The polymerization was carried out through cyclic voltammetry (CV). Electrochemical, spectroscopic, and morphological analyses were used for characterization. Only acidic medium provided an efficient electrode modification as the electrochemical and morphological profiles obtained from treatment in alkaline solution resembles the unmodified electrode. The electrostatic repulsion between the carboxylate anions in the polymer and ferricyanide probe was verified by the current decrease in CV profiles and by the resistance of charge transfer increase through electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) images showed a complete and homogeneous coverage with a splinter-like morphology. The polymer presents stability under storage conditions until 35 days with no lixiviation during washing steps or loss of activity. The FT-IR measurements confirm the presence of the carboxyl group in the polymer suggesting a polymerization through the sulfur atom, which led to a mechanism proposal. The immobilization of enzyme tyrosinase over this platform and the detection of tyramine were performed successfully. 50 U of the enzyme for 18 h at pH 7.2 was the optimum parameters leading to a limit of detection and limit of quantification of 3.16 μmol L and 10.52 μmol L, respectively. With Kmapp of 62.11 μmol L and a recovery rate of 110.84% in a wine sample, the novel, stable, functionalized material formed over a low-cost electrode is suitable for further electrochemical applications exploiting the chemical reaction of carboxyl groups for biosensor purposing.

One-pot synthesis of microporous Fe2O3/g-C3N4 and its application for efficient removal of phosphate from sewage and polluted seawater

The present work was performed to investigate the effective removal of phosphate from sewage and polluted seawater using microporous Fe2O3/g-C3N4 as the adsorbent. one pot synthesis The adsorbent achieved by direct heating of melamine in the presence of ferric oxalate which not only imposes the porous structure but also acts as a precursor for imbedded Fe2O3 nanoparticles. The removal efficiencies higher than 90% could be obtained in a wide pH range (3–10) and high ionic strength with short equilibrium time of 15 min Adsorption kinetics of phosphate was found to follow a pseudo-second-order kinetic model and adsorption process was well described by the Langmuir isotherm model with adsorption capacity calculated to be 52.5 mg PO43−/g adsorbent. The Fe2O3/g-C3N4 adsorbent could be regenerated easily by a mild alkaline solution treatment. Good adsorption performance, short equilibrium time and effective recyclability make Fe2O3/g-C3N4 a suitable alternative to the well-known adsorbents for removal of phosphate. The efficient removal of phosphate from sewage and polluted seawater in wide pH and ionic strength makes the proposed adsorbent promising for both the removal and recovery of phosphate from complex water and wastewater effluents.

Modifikovanje poliestarske tkanine obradom u alkalnom rastvoru

Modifikovanje poliestarske tkanine obradom u alkalnom rastvoru

Engineering of a Bacillus subtilis Strain Deficient in Cellulase: Application in Degumming of Ramie

Degumming is the most important step before ramie fibers are used in textile industry. Conventional chemical degumming technology with alkaline treatment at high temperature causes critical problems in environment. In addition to multiple degumming enzymes (e.g. pectinases and xylanases), Bacillus subtilis strain 168 can also produce cellulase which brings irreversible damage to ramie fibers. In this study, a strain deficient in cellulase was constructed by insertional inactivation of gene eglS to make it suitable for microbial degumming. Results showed that the cellulase activity was not detected in strain ΔeglS, after 25 h of incubation with strain ΔeglS, the weight loss of the ramie fibers was 20.20 %. Though the residual gum content of ramie fibers obtained in microbial degumming process was 19.67 %, microbial intervention followed by diluted alkaline solution treatment showed lower residual gum content (2.73 %) than chemical degumming (2.96 %). The single fiber breaking strength value of ramie fibers from bio-chemical degumming process reached 27.19 cN, which was the highest of three samples. Moreover, bio-chemical degumming process resulted in a 75 % decrease of alkali dosage as compared with chemical degumming process. This study provides a suggestion to genetically modify wild-type strain in order to protect ramie fibers from cellulase damage, and indicates a sustainable alternative for the traditional chemical degumming in the textile industry.

Effect of lye alkaline solution treatment on engineering properties of oil palm empty fruit bunches (EFB) fiber strengthen foamed concrete

Natural fibers have become attention-grabbing and interesting these days to be employed as an industrial material and structural material for rehabilitating of structures. Nevertheless, the natural fibers to matrix interface interactions with cement matrix remain a key issue in getting the desired mechanical properties. Treatment of natural fibers is crucial in improving matrix to filler adhesion, thus improving its mechanical properties. In this study, oil palm empty fruit bunches (EFB) fiber was studied for use as reinforcement materials for cementitious composites in foamed concrete. The effect of fiber treatment on mechanical properties of EFB fiber reinforced foamed concrete was investigated comprehensively. For lye-treated EFB fibers, these fibers were washed three times with tap water to eliminate unwanted debris, dusts and impurities and dried at room temperature for 48 hours. Lye chemical solution of 2%, 4%, 6%, 8% and 10% wt. concentration were prepared using distilled water and lye chemical pellets. For the 2% wt. concentration, 2 grams of lye chemical was dissolved in 100ml of distilled water which is equivalent to 100 grams. For the 4, 6, 8 and 10% wt. concentrations, 4 grams, 6 grams, 8 grams and 10 grams of lye were dissolved in 100ml of distilled water respectively. The EFB fibers were soaked in the prepared solutions for a period of 24-hours after which they were removed and thoroughly rinsed until a neutral pH of the rinsing solution was attained. A pH meter was used to determine the pH value of the solution after rinsing. Finally, the dried fibers were sealed in a plastic bag before the composite manufacturing to avoid atmospheric moisture contamination. From the results obtained through experimental works, it can be concluded that the lye treatment of the EFB fibers modifies the fibers adequately causing a variation in the axial compression and flexural properties of the foamed concrete. Above all, 6% lye concentration gave better mechanical properties and therefore is considered a better treatment concentration value in the range of 2% to 10% wt. for improving the mechanical properties of EFB reinforced foamed concrete.

Fabrication of calcium phosphate coating on pure magnesium substrate via simple chemical conversion coating: surface properties and corrosion performance evaluations

The main objective of the current work was to fabricate calcium phosphate (CaP) coating on 99.9% purity magnesium, Mg substrate through simple chemical conversion method and evaluated the surface properties and corrosion performance of the coated substrates. The chemical conversion method was done by immersing the samples inside primary phosphating bath and followed by secondary treatment in alkaline solutions. The coated samples from the primary (PRI) and secondary (SEC) coating treatment were analyzed from morphological, topographical, and phase analysis aspects. The corrosion behaviour of the coatings inside simulated body fluid was assessed by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The PRI and SEC coated were composed of dicalcium phosphate dehydrate (DCPD) and hydroxyapatite (HA), respectively. Both of the coatings improved the corrosion resistance of the Mg substrate. The corrosion potentials, Ecorr of the coated samples becomes nobler compared to the bare substrates. EIS shows that the polarization resistance, Rp is improved about 40 and 2 times fold for PRI and SEC compared to the uncoated samples. Furthermore, PRI shows better corrosion resistance compared to SEC due to lower porosity along with thicker and better coating coverage.

Three-dimensional porous carbon frameworks derived from mangosteen peel waste as promising materials for CO2 capture and supercapacitors

Abstract Business costs, environmental and energy concerns have increased interest in biomass materials for the production of porous carbon materials, especially as solid-state adsorbents for CO2 capture or as electrode materials for supercapacitors. We put forward an efficient and scalable approach to convert mangosteen peel (MP) waste into three-dimensional microporous carbon frameworks (3D-MP-CFW) for effective CO2 capture and supercapacitors. The MP waste is first subjected to a controllable hydrothermal treatment in alkaline solution and then a carbonization process. The resultant optimal carbon sample possesses a high surface area up to 1270 m2 g−1 and abundant micropores with fine micropore sizes below 1 nm. The typical sample has a well-tailored open 3D macroporous interconnected network structure, exhibiting an outstanding CO2 capture recyclability and high CO2 capture capacities of 6.93 and 4.77 mmol g−1 at 0 °C and 25 °C (1 bar), respectively. Simultaneously, benefiting from its high surface area and 3D interconnected porous structure, this optimal sample also exhibits a good supercapacitance performance with the specific capacitance of 240 F g−1 (in 6 M KOH, at 1 A g−1) in a three-electrode system. Our simple preparation method presents an efficient way to make promising carbon materials for high-performance CO2 capture and supercapacitors.

Alkali treated Ti3C2Tx MXenes and their dye adsorption performance

To modify the adsorption performance of Ti3C2Tx MXene, we report a facile approach to expand the interlayer spacing of Ti3C2Tx and to tune its surface functional groups by hot alkaline solution treatment. In the treatment, the interlayer spacing of Ti3C2Tx MXene is increased by up to 29% by LiOH, and the surface functional groups are tuned by converting -F to -OH. Among the MXenes, LiOH-Ti3C2Tx and NaOH-Ti3C2Tx can faster adsorb methylene blue (MB) than other MXene adsorbents; NaOH-Ti3C2Tx possesses the highest adsorption capacity (189 mg/g) for MB, which can be ascribed to the cooperation of surface adsorption and intercalation adsorption. The experimental data suggest that the enhanced adsorption toward cationic dyes can be best described by a Langmuir isotherm.

Effect of alkaline treatment on mechanical properties of woven ramie reinforced thermoset composite

Ramie fibres are one of the strongest bast fibres with valuable potential as reinforcement in a composite. In this study, the laminated composite of ramie reinforced plain woven was prepared through hand lay-up process. Prior to moulding, the ramie reinforced woven fabric was treated by soaking the fabric in 5% NaOH solution for 1 hour at room temperature. The effects of alkaline treatment on ramie reinforced woven epoxy resin and ramie reinforced woven unsaturated polyester (UPE) resin were investigated in terms of tensile, flexural, and impact properties. Five samples of both treated ramie (TR) composite and untreated ramie (UR) composite were tested and the results were averaged for comparison with one another. Based on the results obtained, the effects of 5% (w/w) concentration of alkaline solution treatment for 1 hour at room temperature are insignificant to the tensile, flexural, and impact properties. The result of UR and TR composite was compared to the composite for pure epoxy resin and UPE resin. Based on the finding, the data obtained shown no improvement in tensile properties. However, in the case of the flexural properties are enhanced except flexural modulus of the TR-epoxy composite. Impact strength only gets better when reinforcing with the untreated ramie. On overall, the TR ramie have an admirable mechanical when reinforced with the epoxy resin than UPE resin

Investigation of Nanoscale Quasi Pyramid Texture for HIT Solar Cells Using n-type High Performance Multicrystalline Silicon

In this work, an n-type high performance multicrystalline silicon (nHPMC) ingot (τ >1.2 ms) was cast at NTNU. A new method to manufacture nHPMC solar cells with hetero junction solar cell architecture is presented. Texturing of the wafers is performed through silver assisted chemical etching followed by an alkaline solution treatment process. The slight differences of the reactions between the concentration of the alkali solutions and the nanopores on silicon surface has been determined and used to tailor different textures. Alkaline solutions with gradient concentration were developed to improve the surface morphology for HIT solar cells after a silver assisted chemical etching process. A homogeneous texture with quasi pyramid morphology was then obtained through balancing the reflectance and surface properties on nHPMC wafers. This kind of quasi pyramid texture is also a good starting point for the surface passivation during HIT processes. An efficiency of 19.03% has been obtained, demonstrating the potential of using n-type HPMC in the production of cost effective solar cells.

A simple chemical approach to regenerating the strength of thermally damaged glass fibre

Process-induced strength loss is a major technical barrier to the effective reuse of thermally recycled glass fibres in composite applications. We have developed a novel approach to effectively restore strength in glass fibres through treatment in alkaline solutions. Glass fibres were treated at elevated temperature and experienced significant strength loss found typically after thermal recycling processes. Different alkaline treatments were then applied to the thermally damaged fibres in an attempt to restore strength which had been lost as a result of the heat conditioning procedure. Results indicated that these treatments were able to generate considerable fibre strength recovery. The degree of strength regeneration was found to be highly dependent on reaction conditions, which were investigated and optimised. The positive effect of these simple chemical treatments demonstrated great potential for facilitating the reuse of thermally recycled glass fibres in composite applications.