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A wide bandgap, an enhanced piezoelectric coefficient, and low dielectric permittivity are some of the outstanding properties that have made ScxAl1−xN a promising material in numerous MEMS and optoelectronics applications. One of the substantial challenges of fabricating ScxAl1−xN devices is its difficulty in etching, specifically with higher scandium concentration. In this work, we have developed an experimental approach with high temperature annealing followed by a wet etching process using tetramethyl ammonium hydroxide (TMAH), which maintains etching uniformity across various Sc compositions. The experimental results of etching approximately 730 nm of ScxAl1−xN (x = 0.125, 0.20, 0.40) thin films show that the etch rate decreases with increasing scandium content. Nevertheless, sidewall verticality of 85°~90° (±0.2°) was maintained for all Sc compositions. Based on these experimental outcomes, it is anticipated that this etching procedure will be advantageous in the fabrication of acoustic, photonic, and piezoelectric devices.

MXenes are a large family of two-dimensional materials that have attracted attention across many fields due to their desirable optoelectronic, biological, mechanical and chemical properties. There currently exist many synthesis procedures that lead to differences in flake size, defects and surface chemistry, which in turn affect their properties. Herein, we describe the steps to synthesize Ti 3 C 2 T x —the most important and widely used MXene, from a Ti 3 AlC 2 MAX phase precursor. The procedure contains three main sections: synthesis of Ti 3 AlC 2 MAX, wet chemical etching of the MAX in hydrofluoric acid/HCl solution to yield multilayer Ti 3 C 2 T x and its delamination into single-layer flakes. Three delamination options are described; these use LiCl, tertiary amines (tetramethyl ammonium hydroxide/ tetrabutyl ammonium hydroxide) and dimethylsulfoxide respectively. These procedures can be adapted for the synthesis of MXenes beyond Ti 3 C 2 T x . The MAX phase synthesis takes about 1 week, with the etching and delamination each requiring 2 d. This protocol requires users to have experience working with hydrofluoric acid, and it is recommended that users have experience with wet chemistry and centrifugation; characterization techniques such as X-ray diffraction and particle size analysis are also essential for the success of the protocol. While alternative synthesis methods, such as minimally intensive layer delamination, are desirable for certain MXenes (such as Ti 2 CT x ) or specific applications, this protocol aims to standardize the more commonly used hydrofluoric acid/HCl etching method, which produces Ti 3 C 2 T x with minimal concentration of defects and the highest conductivity and serves as a guideline for those working with MXenes for the first time. Key points MXenes are two-dimensional materials, the best known of which is Ti 3 C 2 T x . Many diverse and unique properties have been described for MXenes, but it is difficult to compare the data because their physical characteristics depend on their synthesis. This protocol provides a detailed guideline for the synthesis of a Ti 3 AlC 2 MAX phase precursor, wet chemical etching of MAX to yield multilayer Ti 3 C 2 T x and its delamination into single-layer flakes. MXenes are two-dimensional materials with diverse optoelectronic, biological, mechanical and chemical properties. This protocol describes how to prepare single-layer flakes of Ti 3 C 2 T x , the most important and widely used MXene, from a Ti 3 AlC 2 MAX phase precursor.

High-performance thermal insulators represented by aerogels are regarded as one of the most promising materials for energy savings. However, significantly low mechanical strength has been a barrier for aerogels to be utilized in various social domains such as houses, buildings, and industrial plants. Here, we report a synthetic strategy to realize highly transparent aerogels with unusually high bending flexibility based on poly(methylsilsesquioxane) (PMSQ) network. We have constructed mesoscopic fine fiber-like structures of various sizes in PMSQ gels by the combination of phase separation suppression by tetramethylammonium hydroxide (TMAOH) and mesoscopic fiber-like assembly by nonionic poly(ethylene oxide)- b -poly(propylene oxide)- b -poly(ethylene oxide) (PEO- b -PPO- b -PEO) type surfactant. The optimized mesoscale structures of PMSQ gels have realized highly transparent and resilient monolithic aerogels with much high bendability compared to those reported in previous works. This work will provide a way to highly insulating materials with glasslike transparency and high mechanical flexibility. Aerogels are mechanically friable despite their attractive properties such as visible-light transparency and low thermal conductivity. Here the authors show mechanically flexible, highly transparent aerogels based on fiber-like pore skeletons.

The formation of gas hydrates is a major issue during the operation of oil and gas pipelines, because gas hydrates cause plugging, thereby disrupting the normal oil and gas flows. A solution is to inject gas hydrate inhibitors such as ionic liquids. Contrary to classical inhibitors, ionic liquids act both as thermodynamic inhibitors and hydrate inhibitors, and as anti-agglomerates. Imidazolium-based ionic liquids have been found efficient for the inhibition of CO2 and CH4 hydrates. For CO2 gas hydrates, N-ethyl-N-methylmorpholinium bromide showed an average depression temperature of 1.72 K at 10 wt% concentration. The induction time of 1-ethyl-3-methyl imidazolium bromide is 36.3 h for CO2 hydrates at 1 wt% concentration. For CH4 hydrates, 1-ethyl-3-methyl-imidazolium chloride showed average depression temperature of 4.80 K at 40 wt%. For mixed gas hydrates of CO2 and CH4, only quaternary ammonium salts have been studied. Tetramethyl ammonium hydroxide shifted the hydrate liquid vapour equilibrium to 1.56 K at 10 wt%, while tetrabutylammonium hydroxide showed an induction time of 0.74 h at 1 wt% concentration.

Engineered iron oxide nanoparticles (IONPs) have potential applications in agriculture, but their effects vary depending on their composition, concentration, and plant species. In this study, we investigated the biological effects of iron oxide nanoparticles stabilized with tetramethylammonium hydroxide (TMA-IONPs) on Zea mays (corn). The nanoparticles were characterized by transmission and scanning electron microscopy (TEM, SEM), revealing an average diameter of 10.78 nm, and by ATR-FTIR spectroscopy, which confirmed TMA binding and colloidal stability in an aqueous medium. Corn seeds were germinated directly in aqueous solutions of TMA-IONPs at six concentrations ranging from 7.6 to 45.6 mg/L. Seedlings were grown under controlled environmental conditions, and all analyses were performed on day seven of seedling development. The following parameters were assessed: germination rate; seedling growth (shoot and root length); chlorophyll content; antioxidant enzyme activity (catalase and peroxidase); and mitotic index in root meristematic cells. Concentrations up to 45.6 mg/L significantly enhanced germination, biomass accumulation, chlorophyll biosynthesis, and enzymatic antioxidant activity. The highest mitotic index was observed at 38 mg/L with a low incidence of chromosomal aberrations. These findings suggest that low concentrations of TMA-IONPs promote corn seedling growth by stimulating cell division and modulating oxidative stress response. Further research is required to assess the broader agricultural potential and safety of these nanoparticle formulations.

Extractions methods based on ultrapure water, tetramethylammonium hydroxide (TMAH), and tetrasodium pyrophosphate (TSPP) were applied to faeces collected from two in vivo experiments of pigs and chickens fed with a silver-based nanomaterial to study the fate and speciation of silver. For TMAH extraction, cysteine and CaCl 2 were used to evaluate their stabilization effect on the silver forms. The analytical techniques single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS), hydrodynamic chromatography hyphenated to ICP-MS (HDC-ICP-MS) and asymmetric flow field flow fractionation coupled to ICP-MS (AF4-ICP-MS) were applied to the simultaneous detection of particulate and dissolved silver. Results have shown that water extraction was a suitable option to assess the environmental release of silver, with percentages of 3 and 9% for faeces of pigs and chickens, respectively. The use of TMAH extraction combined with SP-ICP-MS analysis was useful to characterize Ag-containing particles (less than 1%). Both stabilizers, cysteine and CaCl 2 , have a similar effect on silver nanoparticle preservation for chicken faeces, whereas cysteine-Triton was better for pig samples. In any case, silver extraction efficiency with TMAH was low (39–42%) for both types of faeces due to a matrix effect. TSPP followed by ICP-MS enabled the fractionation of the silver in the faeces, with silver sulphide (41%) and ionic silver (62%) being the most abundant fractions. Graphical Abstract

The magnetic Fe 3 O 4 was synthesized by using a one-step solvothermal method. Then, anhydrous ethanol as a solvent, tetramethyl ammonium hydroxide (TMAOH) as an auxiliary agent, tetraethyl orthosilicate (TEOS) as a silicon source, and (3-aminopropyl) triethoxysilane (APTES) as amino source were used to prepare Fe 3 O 4 @mSiO 2 -NH 2 by using the sol-gel method. Uniform design U14*(14 5 ) and the response surface method (RSM) were used to optimize the synthesis ratio. According to the results of TEM, SEM, N 2 adsorption–desorption test, VSM, and XRD, it found that the best coating effect obtained when the relative molar ratio of TMAOH:TEOS:APTES:Fe 3 O 4 was 5:4:6:0.45. The results of EDS and elemental analysis confirmed the success of amino group coating; VSM magnetization after surface modification was 32 emu/g; BET results show that specific surface area is 236 m 2 /g, size 5 nm, and the pore volume is 0.126 cm 3 /g. The removal of Cu 2+ , Zn 2+ , and Pb 2+ by Fe 3 O 4 @mSiO 2 -NH 2 was studied at the optimal initial pH value 6 of the adsorption test system. The isothermal adsorption results show that the Langmuir model and Redlich–Peterson model are more suitable than the Freundlich model to describe the adsorption behavior, and Cu 2+ , Zn 2+ , and Pb 2+ adsorption is mainly single molecular layer. The maximum adsorption capacity qm of the Langmuir model for Cu 2+ , Zn 2+ , and Pb 2+ removal was 48.04 mg/g, 41.31 mg/g, and 62.17 mg/g, respectively. The adsorption kinetic rates of Cu 2+ , Zn 2+ , and Pb 2+ on Fe 3 O 4 @mSiO 2 -NH 2 relatively more suitable for pseudo-second-order kinetic model, i.e., R 2 , were ranged between 0.995 and 0.999, and the suitable reaction time was 60 min. These results proved that Fe 3 O 4 @m-SiO 2 -NH 2 prepared by using this method is easy to synthesize, has easy recovery, is ecofriendly, and can be potential adsorbent for Cu 2+ , Zn 2+ , and Pb 2+ removal.

The microelectronics industry wastewater is attracting the scientific community and industry attention due to the high amount of organic and inorganic pollutants produced. Pollutants in microelectronic wastewater are considered qualitative contaminants, found in low concentrations but present with high risks to the environment and public health. The current paper highlights the most common pollutants in microelectronics wastewater and discusses the recent treatment technologies used to remove these contaminates. The review process was conducted based on the identification and screening of microelectronic wastewater and the principle of contaminant detection reported in previous research literature. It appears that tetramethylammonium hydroxide and ammonium are the major organic compounds in microelectronic wastewater, while heavy metals are among the inorganic pollutants with high environmental toxicity. The membrane filtration is the most efficient method for removing the pollutants (more than 90%) and producing ultrapure water. However, wastewater should be subjected to primary treatment using chemical and biological methods before undergoing the ultrafiltration process. The zero-discharge concept is more applicable in the microelectronics industries due to the stringent regulations associated with these industries. Microelectronic sludge represents the main challenge in wastewater recycling, while advanced treatment methods have been suggested for sludge treatment. More effort is required to recycle microelectronics owing to the high prices related to the disposal of these solids’ wastes.

Environmental pollution is becoming one of the most important global problems. Understanding the main factors affecting accumulation of toxic trace elements in consumed crops is of particular value. Unfortunately, possible toxicity of many trace elements is still poorly studied. The development of measures on identification of new potentially toxic trace elements is critical for high quality and safety of food. In the research, we performed greenhouse pot experiments with two major crops, wheat and barley, that were grown in the soil contaminated with bromides of ammonium and neodymium. The concentrations of elements in the plants and soil were determined by ICP-MS/ICP-OES after leaching the samples with tetramethyl ammonium hydroxide. Additionally, variations in the biomasses and concentrations of pigments in the plant leaves were studied. Although wheat and barley are botanically similar and were grown under the same conditions, concentrations of several elements in the plants were rather different. Both wheat and barley were capable of accumulating high concentrations of bromine (Br) when the plants grow in the soil contaminated with this trace element, but demonstrated different response on the soil contamination. The Br concentrations were always higher in barley, while the concentrations of pigments in barley leaves were lower than in leaves of wheat. During first days, biomass of the plants grown in the soil contaminated with bromides was slightly lower than biomass of the wheat and barley grown in uncontaminated soil. However, with time the bromides exhibited positive effect on the plant biomass.

Among various protein-containing biomass wastes, waste animal wool, poultry feather, and human hair are considered one of the most important renewable sources of keratin. Animal wool and human hair are utilized for the production of several products. However, the substantial quantity of short fibers that are inappropriate for spinning and being unusable is thrown away as waste resulting in significant environmental issues in terms of their accumulation in water bodies resulting in obstruction of waterways and other related problems. Similarly, poultry wastes, especially waste chicken feathers (WCF) are dumped or burnt or used as low-value fertilizer in certain applications. The purpose of this research is to develop an efficient method that can extract the recoverable keratin from various wastes and effectively utilize the spent solvent in the extraction process. Herein suitability of an aqueous solution of quaternary ammonium hydroxide known as tetramethyl ammonium hydroxide (TMAOH, 25% w/w in water) to solubilize these protein wastes and extract keratin from them was investigated. The solvent could solubilize ca. 39–44% w/w of waste animal wool (WAW), 19–25% of waste human hair (WHH), and 55–60% of WCF. Crude keratin with ca. 19–20%, 35–37%, and 69–74% were isolated from WAW, WHH, and WCF, respectively. The chemical and structural stability of keratin thus isolated was established. The recovered TMAOH, insoluble WAW, and WCF were found to be nontoxic to soil microbes. The recovered TMAOH thus generated after isolation of keratin was used for green gram ( Vigna radiata ) seed treatment, and a substantial increase in the height (4–12%) and weight (9–58%) of the plants was observed. Treating biomass waste as a source of high-value compounds may minimize environmental impact by reducing the waste load.