Tetramethylammonium Hydroxide Research Articles

Reproducible Superinsulation Materials: Organosilica-Based Hybrid Aerogels with Flexibility Control

In this study, we report highly crosslinked hybrid aerogels with an organic backbone based on vinylmethyldimethoxysilane (VMDMS) with tuneable properties. For an improved and highly reproducible synthesis, a prepolymer based on 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D4V4) and VMDMS as monomers was prepared and purified. Di-tert-butylperoxide (DTBP) concentrations of 1 mol% initiate the radical polymerization of the mentioned monomers to achieve high yields of polymers. After purification, the obtained viscous polyorganosilane precursor could be reproducibly crosslinked with dimethyldimethoxysilane (DMDMS) or methyltrimethoxysilane (MTMS) to form gels in benzylic alcohol (BzOH), water (H2O) and tetramethylammonium hydroxide (TMAOH). Whereas freeze-drying these silica-based hybrid aerogels led to high thermal conductivity (>20 mW m−1K−1) and very fragile materials, useful aerogels were obtained via solvent exchange and supercritical drying with CO2. The DMDMS-based aerogels exhibit enhanced compressibility (31% at 7 kPa) and low thermal conductivity (16.5 mW m−1K−1) with densities around (0.111 g cm−3). The use of MTMS results in aerogels with lower compressibility (21% at 7 kPa) and higher density (0.124 g cm−3) but excellent insulating properties (14.8 mW m−1K−1).

Quartz crystal microbalance analysis of effects of surfactants on dissolution kinetics of poly(4-hydroxystyrene) partially protected with t-butoxycarbonyl group

Abstract Surfactants comprise water-repellent and water-attracting moieties and have been used to improve the lithographic performance of resist materials. However, the effects of surfactants on the dissolution kinetics of these materials are still unclear. In this study, the effects of surfactants on the dissolution kinetics of partially-protected poly(4-hydroxystyrene) (PHS) in 0.26 N tetramethylammonium hydroxide aqueous solution was investigated using a quartz crystal microbalance method. Anionic (sodium n-octanonate, sodium 1-hexanesulfonate, n-dodecylbenzenesulfonic acid, and sodium n-dodecyl sulfate), cationic (methylamine hydrochloride, dodecyltrimethylammonium chloride, and 30% ammonium lauryl sulfate solution), nonionic (sorbitan monooleate, polyoxyethylene(23)lauryl ether, and polyoxyethylene(10)hydrogenated castor oil), and amphoteric (35% lauryl dimethylaminoacetic acid solution) surfactants were examined. The surfactant significantly affected the dissolution kinetics of the PHS films. The surfactant effects were significantly reduced by protecting the hydroxyl groups of PHS. The effect of the surfactant on the dissolution kinetics depended on the surfactant rather than on the surfactant type.

Polarity control and crystalline quality improvement of AlN thin films grown on Si(111) substrates by molecular beam epitaxy

We attain N-polar and Al-polar AlN thin films on Si(111) substrates by plasma-assisted molecular beam epitaxy. The polarity of AlN epilayers has been validated by wet chemical etching using tetramethylammonium hydroxide and by the direct cross-sectional observation of atomic stacking under high-angle annular dark-field scanning transmission electron microscopy. For the 290 nm-thick as-grown N-polar AlN epilayer, x-ray diffraction (XRD) (002) and (102) ω rocking curve peak full width half maximums (FWHMs) are 475 and 1177 arcsec, and the surface mean square roughness (RMS) is 0.30 nm. We flipped the polarity using the metal-flux-modulation-epitaxy (MME) strategy. The MME strategy promotes anti-phase boundaries (APBs) on the {22¯01} crystalline planes instead of commonly observed lateral planar APBs in AlN epilayers. Merging of the tilted APBs at ∼50 nm leads to a complete Al-polar surface. For the 180 nm-thick Al-polar AlN epilayer, XRD (002) and (102) peak FWHMs are 1505 and 2380 arcsec, and the surface RMS is 1.41 nm. Strain analysis by XRD and Raman spectroscopy indicates a uniform tensile strain of 0.160% across the N-polar AlN epilayer surface and a strain distribution of 0.113%–1.16% through the epilayer. In contrast, the Al-polar AlN epilayer exhibits a much broader tensile strain distribution of 0.482%–2.406% along the growth direction, potentially due to the interaction of polarity inversion and strain relaxation.

Insight into the responses of the anammox granular sludge system to tetramethylammonium hydroxide (TMAH) during chip wastewater treatment

Tetramethylammonium hydroxide (TMAH), an extensively utilized photoresist developer, is frequently present in ammonium-rich wastewater from semiconductor manufacturing, and its substantial ecotoxicity should not be underestimated. This study systematically investigated the effects of TMAH on the anammox granular sludge (AnGS) system and elucidated its inhibitory mechanisms. The results demonstrated that the median inhibitory concentration of TMAH for anammox was 84.85 mg/L. The nitrogen removal performance of the system was significantly decreased after long-term exposure to TMAH (0–200 mg/L) for 30 days (p < 0.05), but it showed adaptability to certain concentrations (≤50 mg/L). Concurrently, the stability of the granules decreased dramatically, resulting in the breakdown of AnGS. Further investigations indicated that TMAH exposure increased the secretion of extracellular polymeric substances but weakened their defense function. The increase in reactive oxygen species resulted in damage to the cell membrane. Reduced activity of anammox bacteria, impeded electron transfer, and changes in enzyme activity suggested that TMAH affected the metabolic activity. Microbiological analysis revealed that TMAH caused a decrease in the abundance of anammox bacteria and a weakening of symbiotic interactions within the microbial community. These results provide valuable guidance for the AnGS system application in chip wastewater treatment.

Unveiling the generation of mesoporous MFI zeolites with one-dimensional fins in the assistance from small quaternary ammonium cation and its application in propane aromatization

In this work, a kind of ZSM-5 zeolite with one-dimensional fins growing along the [010] direction has been successfully synthesized utilizing both tetrapropylammonium hydroxide (TPAOH) and tetramethylammonium hydroxide (TMAOH) as co-templates. With the aid of molecular dynamic simulations and a series of experimental evidences, the formation mechanism of the one-dimensional feature is determined to arise from the synergic effects between TPA+ and TMA+. Two TPA+ and three TMA+ would co-exist in a unit MFI cell at a certain crystallization period depending on the composition of zeolite and precursor, and this configuration ensures a minimum stabilization energy required for the growth along [010] direction. Investigations manifest these needle-like fins with diameters of ca. 60 nm could function as pseudo nano crystals and introduce additional pores ranging from 10 to 90 nm, which effectively promotes the diffusion capability and substantially improves the catalytic performance in propane aromatization.

Enhanced solar hydrogen evolution by laminated integration of n+p-SiIP/TiO2/Pt inverted pyramid black Si photocathode

The nano/microstructuring of silicon (Si) via chemical methods has garnered significant attention due to its excellent light-trapping capabilities across a wide spectral range. Current research has predominantly focused on the synthesis of pyramidal-shaped microtextures, which enable two reflections on the surface, while largely overlooking the superior light-trapping potential of inverted pyramid silicon (SiIP) microtextures, which theoretically allow for three reflections. Moreover, there has been limited investigation into the application of inverted pyramid black silicon for solar-driven hydrogen evolution. This study reports the synthesis of uniformly arranged inverted pyramid-textured black silicon using the copper-assisted chemical etching (Cu-ACE) method to enhance the efficiency of solar-driven water splitting for hydrogen production. The formation mechanism and the influence of copper-localized surface plasmon resonance (Cu-LSPR) from Cu nanoparticle (NP) byproducts on photoelectrochemical (PEC) activity were systematically analyzed. To reduce sidewall defects and minimize photogenerated carrier recombination, the surface of the SiIP was treated with tetramethylammonium hydroxide (TMAH). A vertical PN junction was developed through ion implantation to reduce the external bias of the SiIP. Additionally, a uniform TiO₂ antireflective layer was deposited via atomic layer deposition (ALD), reducing the average reflectance of the SiIP-T4 to 5.78 % over the 300–1100 nm wavelength range. MoSₓ and Pt NPs were electrodeposited to improve the fill factor and enhance HER kinetics. With optimized catalyst loading, the n+p-SiIP-T4/TiO₂/Pt 80 mC electrode achieved a photocurrent density of 8.0 mA cm−2 at 0 V vs. RHE, an applied bias photon-to-current efficiency (ABPE) of 0.93 % at 0.24 V vs. RHE, and a double-layer capacitance (Cdl) of 91 μF cm−2. The onset potential (Von) was positively shifted by ∼1.13 V to 0.49 V vs. RHE compared to a SiIP photocathode, and the photocathode operated continuously at 0 V vs. RHE for 27 h in an acidic electrolyte. These results demonstrate that SiIP has significant potential for PEC hydrogen evolution, with further performance optimization achievable through structural and surface engineering.

Re-evaluation of the reduced heart weights in male rats in a 28-day oral repeated-dose toxicity study of tetramethylammonium hydroxide

We recently conducted a detailed hazard assessment of tetramethylammonium hydroxide (TMAH), a priority chemical substance under the Japan Chemical Substances Control Law. During this assessment, there was debate regarding the reduced heart weight observed in the treated male groups in the 28-day rat oral repeated-dose toxicity study. This finding was not observed in females in this study and in both sexes of oral toxicity studies for tetramethylammonium chloride (TMAC) or tetramethylammonium hydrogen phthalate (TMAHP). Unpublished individual data from the oral TMAH developmental and reproductive toxicity (DART) screening study were also obtained; no effect on heart weight was observed. In addition, background data on rat heart weight from six 28-day oral toxicity studies conducted in the same facility, year, strain, age, and breeder as the TMAH study were obtained from the Japan Existing Chemical Substances Database (JECDB). These investigations suggest that the statistically significant lower heart weight in the treated males in the 28-day toxicity study is likely caused by an incidental skewing of individuals with heavier heart weights toward control male groups and is not due to TMAH treatment. Thus, it is worthwhile to include as much relevant data as possible to confirm or refute unexpected findings in toxicity studies.

Dicationic salt of β-alkyl substituted sapphyrin-type porphyrinoid: Acid-basic properties, thermal stability and quantum-chemical calculations

The UV-Vis spectra of the dicationic salt of 2,3,7,13,17,18,18,22,23-octamethyl-8,12-diethylsapphyrin {H5β-Me8Et2Sap[Formula: see text](Cl[Formula: see text]} in solutions with different polarity and acid-basic properties have been investigated. The tautomeric and acid-base equilibria of H5β-Me8Et2Sap[Formula: see text](Cl[Formula: see text] in the presence of organic bases have been examined by spectrophotometric titration. It was demonstrated that an addition of small amounts of 1,8-diazabicyclo[5.4.0]undecene (DBU) and tetramethylammonium hydroxide (Me4NOH) dissolved in methylene chloride (DCM) and MeOH, respectively results in a stepwise detachment of two protons from the basic nitrogen atoms of the macrocycle, with no anionic forms of sapphyrin being registered. The results obtained were supported using quantum-chemical calculations (DFT, B3LYP, cc-pVDZ including NBO analysis). The interactions of 2,3,7,13,17,18,18,22,23-octamethyl-8,12-diethylsapphyrin (H3β-Me8Et2Sap) with a series of compounds of different acidity and basicity were studied and the formation of very weak hydrogen bond of H3β-Me8Et2Sap as NH-acid with N,N-dimethylformamide (DMF) molecule with the value of the interaction energy (E[Formula: see text] equal -16.40 kJ/mol was revealed. The low acidity of bonds NH in the sapphyrin molecule was confirmed on the base of thermogravimetric data obtained for the solid samples of H5β-Me8Et2Sap[Formula: see text](Cl[Formula: see text] evaporated from DMF and DCM concentrated solutions.

Determination of tetramethylammonium hydroxide in air using ion chromatography or ultra-performance liquid chromatography - high-resolution mass spectrometry

Tetramethylammonium hydroxide (TMAH) is extensively utilized in the semiconductor and optoelectronic industries, serving as either a developer or an etchant. TMAH possesses acute toxicity and alkaline corrosiveness, having caused several fatal and injurious accidents in Taiwan. However, there is currently a lack of methods available for assessing TMAH exposure. This study developed a method involving sampling with quartz fiber filters followed by ultrasonic agitation in 10 mL mobile phase, filtering, and analysis using either ion chromatography (IC) or ultra-performance liquid chromatography - high-resolution mass spectrometry (UPLC-HRMS). Utilizing the characteristics of HRMS, the compound analyzed was identified as tetramethylammonium ion (TMA+) through mass spectrometry analysis. The method exhibits excellent trapping capacity and recovery rate. The linear range of TMA+ for IC is 0.3 to 100 μg/mL, with a correlation coefficient of R = 0.9998. The linear range of TMA+ for UPLC-HRMS is 0.002 to 1 μg/mL, with a correlation coefficient of R = 0.996. The recovery rates for IC and HRMS were 116.6% and 90.6%, with corresponding coefficient of variation (CV) of 2.25% and 3.53%, respectively. Samples can be stored at room temperature for 28 days. Verification of this method was conducted at the TMAH factory, and the air concentrations measured in the TMAH filling area were 3.29 and 4.75 μg/m3 from IC and UPLC-HRMS, respectively. This method will be applied in the on-site analysis of occupational hazards for operators in chemical plants, technology factories, and recycling plants, aiming to evaluate risk values to protect the safety and health of workers and prevent occupational diseases.

Application of an ozone-activated peroxymonosulfate process to effectively degrade tetramethylammonium hydroxide (TMAH) in semiconductor wastewater

In this study, ozone-activated peroxymonosulfate (O3/PMS) was used to remove tetramethylammonium hydroxide (TMAH) from artificial semiconductor wastewater. The rate constant for the O3/PMS process was approximately 14.4 times higher than that for the process employing only O3. This was attributed to the explosive production of hydroxyl radicals (•OH) in the process, the contribution of which was confirmed using a scavenger test. The degradation efficiencies were the highest at pH 7.0 (1.80 × 10−2 min−1) and 40 °C (2.18 × 10−2 min−1). Alkalinity and humic acid, which are potent scavengers of •OH, significantly reduced the degradation of TMAH. Remarkably, removal efficiencies of 64.4 % for TMAH and 43.7 % for the total organic carbon (TOC) were achieved at a relatively high initial concentration of 100 μM. However, approximately 27 % of the nitrogen was converted to the final byproducts, NH4+ and NO3−, indicating that a considerable number of nitrogen fragments remained as intermediates. Degradation pathways and intermediates were proposed based on the spectrometry data. Given that the toxicity of the demethylated intermediates was roughly 20–30 times lower than that of TMAH, the acute toxicity to A. fischeri was reduced by approximately half (46.4 ± 2.57 %). The results of this study demonstrated the substantial potential of the O3/PMS process for treating wastewater containing TMAH.

The application of unsupervised machine learning for the elucidation of the burial effect of lignin in peatland: Case of TMAH thermochemolysis

Lignin is one of the major components of organic macromolecules in peatland. Analysis of lignin in sediments is considered as a valuable tool for understanding peat vegetation as well as carbon cycle. It provides valuable perspectives on different sides such as occurrence of various vegetation types and the extent of decay in terrestrial organic material. Thermochemolysis technique using tetramethyl ammonium hydroxide (TMAH) was used for lignin analysis, in an ombrotrophic peatland. It specifically breaks of O-aryl bonds followed by methylation of the lignin components yielding phenolic subunits. Several discrepancies exist between TMAH thermochemolysis findings and those obtained from previous investigations with CuO oxidation. This could be explained by the specific pool of aryl ether, specifically targeted by the thermochemolysis, with discarding of C-C bonds. Hence, this would show the capacity of TMAH thermochemolysis to cleave oxidised lignin leaving lignin of fresh and preserved organic matter intact. The TMAH thermochemolysis method's efficiency in molecular characterization and lignin degradation was evaluated using principal component analysis (PCA). PCA reduced dimensionality and redundancy of component contributions, with the first two principal components accounting for 70.33 % of the total variance. PCA has reinforced the selectively of the thermochemolytic approach in targeting O-aryl bonds while maintaining C-C bonding of polyphenolic sub-units. Hence, two distinct oxidation phases: recent (acrotelm and mesotelm) and older (catotelm) have been revealed. PCA was applied to diagenetic and source vegetation proxies, revealing strong agreement among variables which is supported by the use of molecular ratios as indicators of organic matter source and dynamics in a peat core.

Relationship between the surface free energy of underlayers and the dissolution kinetics of poly(4-hydroxystyrene) partially protected by t-butoxycarbonyl groups in tetramethylammonium hydroxide aqueous developer

In the lithography used for the high-volume production of semiconductor devices, the photoresist film becomes thin with the reduction in pattern size to prevent the pattern collapse due to the surface tension of rinsing liquids. The interfacial effect becomes strong with the reduction in photoresist film thickness. In the development process, it is of importance to clarify the relationship between the photoresist and the underlayer for fine patterning. In this study, the dissolution kinetics of poly(4-hydroxystyrene) (PHS) partially protected by t-butoxycarbonyl (t-Boc) groups in tetramethylammonium hydroxide (TMAH) aqueous solution was found to be related to the surface free energy of the underlayer. The attenuation rate of developer viscosity first decreased and then increased with the polar-to-dispersion component ratio. An inflection point with the lowest rate existed. The TMAH concentration affected not only the attenuation rate but also the ratio of polar to dispersion components at the minimum attenuation rate.

Effect of Triton X-100 surfactant and agitation on tetramethylammonium hydroxide wet etching for microneedle fabrication

Solid silicon (Si) microneedles have many applications such as skin pretreatment to form micrometer-sized holes in the skin surface in transdermal drug delivery systems. Wet etching based on tetramethylammonium hydroxide (TMAH) is an efficient method to fabricate solid microneedles. However, it is challenging to increase the density of microneedle arrays due to the faster lateral etching than the vertical etching that requires a large initial mask size. In this work, we used wet etching based on TMAH to fabricate solid Si microneedles. One kind of nonionic surfactant, Triton X-100, was introduced into the TMAH solution to suppress the lateral etching. When Triton X-100 was added into TMAH for a given etching condition, the maximum height (attained right before the mask fell off) of microneedles could reach ∼230 μm for 600 μm square-shaped mask size and 700 μm array period, compared to microneedles of maximum 152 μm height for the same mask size and period without surfactant addition. Correspondingly, when the target heights of microneedles were the same as ∼230 μm, denser (down to 700 μm period, 600 μm mask size) microneedle arrays were achieved with the help of Triton X-100, in comparison to arrays down to 900 μm period (800 μm mask size) without surfactant addition. Furthermore, agitation by a magnetic stirring bar is important for the fabrication of dense solid Si microneedle arrays based on TMAH. The microneedle structures were rhombic pyramid in shape with Triton X-100 and agitation. But microneedle structures obtained with Triton X-100 yet without agitation were octagonal pyramid in shape with a much less steep side surface.

External quantum efficiency enhancement of GaN-based blue LEDs by treating their full-M-sided hexagonal mesa with TMAH solution.

In recent years, III-Nitride-based micro light-emitting diodes (micro-LEDs) have emerged in many fields and gained more attention. However, fabricating high-efficiency micro-LEDs still remains a challenge due to the presence of sidewall damage. In this study, a GaN-based single blue micro-LED with a full-M-sided hexagonal mesa was prepared. The mesa has a circumradius of 10 µm and was treated with a tetramethylammonium hydroxide (TMAH) solution. Experimental results show that the sidewall defects introduced by dry etching damage act as non-radiative recombination centers and greatly impair the performance of the device. By constructing a full-M-sided hexagonal structure and soaking in a TMAH solution, the etching damage on the sidewall can be eliminated to the greatest extent, thereby reducing sidewall defects. In consequence, the peak EQE of the devices treated with the TMAH solution exceeded 10% at low current density, an increase of 9% compared with the untreated samples. This work provides, to our knowledge, a new approach to improving the efficiency of GaN-based micro-LEDs.

Enhancing Slurry Stability and Surface Flatness of Silicon Wafers through Organic Amine-Catalyzed Synthesis Silica Sol.

The stability of slurries used for chemical mechanical polishing (CMP) is a crucial concern in industrial chip production, influencing both the quality and cost-effectiveness of polishing fluids. In silicon wafer polishing, the conventional use of commercial neutral silica sol combined with organic bases often leads to slurry instability. To address this issue, this study proposes organic amines-specifically ethanolamine (MEA), ethylenediamine (EDA), and tetramethylammonium hydroxide (TMAOH)-as catalysts for synthesizing alkaline silica sol tailored for silicon wafer polishing fluids. Sol-gel experiments and zeta potential measurements demonstrate the efficacy of this approach in enhancing the stability of silica sol. The quantitative analysis of surface hydroxyl groups reveals a direct correlation between enhanced stability and increased hydroxyl content. The application of the alkaline silica sol in silicon wafer polishing fluids improves polishing rates and enhances surface flatness according to atomic force microscopy (AFM). In addition, electrochemical experiments validate the capability of this polishing solution to mitigate corrosion on silicon wafer surfaces. These findings hold significant implications for the advancement of chemical mechanical polishing techniques in the field of integrated circuit fabrication.

Preparation of novel ACMO-AA/PVDF composite membrane by one-step process and its application in removal of heavy metal ions from aqueous solutions

In this study, a simple one-step process was used to fabricate a high-efficiency 4-acryloylmorpholine-acrylic acid/polyvinylidene fluoride (ACMO-AA/PVDF) composite membrane for the adsorption of heavy metal ions. The initiation phase involved the use of the strong organic base tetramethylammonium hydroxide (TMAH) to facilitate the partial dehydrofluorination of PVDF, thereby yielding a reactive CC bond. Following this, undesirable residuals and by-products of TMAH were removed through a thermal treatment process. Subsequently, an ACMO and AA, both possessing distinctive functional groups, onto the active CC bond took place in-situ. The use of a suitable initiator (AIBN) and crosslinking agent (MBA) facilitated the copolymerization process, culminating in the production of the ACMO-AA/PVDF composite membrane with excellent capability for the adsorption of heavy metal ions. Performance evaluations confirmed the membrane high efficiency in Pb2+ removal with complete removal realized at initial Pb2+ concentrations of ≤50 mg·L–1 and presenting a maximum adsorption capacity of 1214.75 mg·g–1, as described by the Langmuir model. In complex environments with co-existing metal ions such as Cu2+, Hg2+, and Cd2+, at an each initial concentration of up to 50 mg·L–1, the membrane exhibited a Pb2+ removal rate of 93.81 %, and Hg2+ and Cu2+ removal rates of 93.75 % and 92.93 %, respectively. The results of surface morphological and microstructural analyses showed that the principal adsorption mechanism is chemical chelation. Furthermore, the membrane exhibited sustainable usability, retaining its structural integrity and adsorption efficacy over multiple regeneration cycles. This indicates that the ACMO-AA/PVDF composite membrane is a viable candidate for deep decontamination processes involving Pb2+, Hg2+, and Cu2+ in environmental remediation applications.

Impacts and effectiveness of sidewall treatment on the spatially resolved optical properties and efficiency enhancement for GaN-based blue and green micro-LEDs

InGaN-based micro-light-emitting diodes (micro-LEDs) are crucial for efficient full-color micro-displays, but suffer from severe degradation of external quantum efficiency (EQE) with size reduction. In this study, the impacts of chemical treatment on the sidewall condition and the EQE of the 10 μm InGaN-based blue and green micro-LEDs were demonstrated. The sidewall treatment can effectively alleviate the residual damage caused by dry etching and suppress the nonradiative recombination, facilitating the achievement of high internal quantum efficiency (IQE). Nevertheless, the sidewall light extraction of the micro-LEDs with smoother sidewall morphology after tetramethylammonium hydroxide (TMAH) treatment is lower than those with rough and prismatic sidewall surface. By utilizing microscopic hyperspectral imaging, the difference in chromatic properties between the inner region and the whole micro-LED caused by dry etching can hinder the stability of chromatic properties of InGaN-based blue micro-LEDs, which can be alleviated by sidewall treatment. The optimal duration for TMAH treatment is obtained as 10 min for both blue and green micro-LEDs, which is the consequence of the compromise between sidewall light extraction efficiency (LEE) and IQE, whereas the improvement of IQE by sidewall treatment for green micro-LEDs is less significant compared to that for blue ones, which can be attributed to the higher dislocation density and recombination via localized states of green InGaN micro-LEDs. This work demonstrates the evolution of IQE and LEE for blue and green micro-LEDs with different sidewall treatment strategies to achieving the ultimate EQE.

Synthesis and characterization of ZnO quantum dot-functionalized mesoporous nanocarriers for controlled drug delivery

In this study, ZnO quantum dots (ZnO@QDs) were synthesized and functionalized with 2nd generation poly amido amine (2GPD) using 3-amino-propyl tri-methoxy silane as the initiator core, facilitated by tetramethylammonium hydroxide (TMAH) to enhance stability against oleate coating. Concurrently, a mesoporous substrate with a unique morphology was developed as a drug reservoir for doxorubicin loading. ZnO quantum dots displayed photoluminescence radiation, with dimensions ranging from 5 to 7 nm and exhibiting spherical morphology. The cubic structure of the synthesized mesoporous nanocatalysts was also confirmed. Brunauer-Emmett-Teller analysis indicated a multidimensional porous structure of the nanocarriers, while zeta potential analysis showed a stable system (approximately −9.6 mV). Fourier transform infrared spectroscopy, X-ray diffraction, and energy dispersive spectroscopy corroborated these findings. Drug release studies demonstrated sustained release under acidic conditions (pH 5.5), with an efficiency of approximately 94 %. These results highlight the potential applications of this nanosystem for controlled drug delivery, underscoring its practical implications in the field of nanotechnology.

Rejection of PFAS and priority co-contaminants in semiconductor fabrication wastewater by nanofiltration membranes

Use of high-pressure membranes is an effective means for removal of per-and polyfluoroalkyl substances (PFAS) that is less sensitive than adsorption processes to variable water quality and specific PFAS structure. This study evaluated the use of nanofiltration (NF) membranes for the removal of PFAS and industry relevant co-contaminants in semiconductor fabrication (fab) wastewater. Initial experiments using a flat sheet filtration cell determined that the NF90 (tight NF) membrane provided superior performance compared to the NF270 (loose NF) membrane, with NF90 rejection values exceeding 97 % for all PFAS evaluated, including the ultrashort trifluoromethane sulfonic acid (TFMS). Cationic fab co-contaminants diaryliodonium (DIA), triphenylsulfonium (TPS), and tetramethylammonium hydroxide (TMAH) were not as highly rejected as anionic PFAS likely due to electrostatic effects. A spiral wound NF90 module was then used in a pilot system to treat a lab solution containing PFAS and co-contaminants and fab wastewater effluent. Treatment of the fab wastewater, containing high concentrations of perfluorocarboxylic acids (PFCAs), including trifluoroacetic acid (TFA: 96,413 ng/L), perfluoropropanoic acid (PFPrA: 11,796 ng/L), and perfluorobutanoic acid (PFBA: 504 ng/L), resulted in ≥92 % rejection of all PFAS while achieving 90 % water recovery in a semi-batch configuration. These findings demonstrate nanofiltration as a promising technology option for incorporation in treatment trains targeting PFAS removal from wastewater matrices.

Dissolution dynamics of partially protected poly(4-hydroxystyrene) in organic developers investigated by a quartz crystal microbalance (QCM) method

Poly(4-hydroxystyrene) (PHS) molecules in solid films are connected to each other through polar and nonpolar molecular interaction and hydrogen bonds. Although the dissociation of phenolic hydroxyl groups plays a major role in the dissolution of PHS films in tetramethylammonium hydroxide (TMAH) aqueous developer, it is important to clarify the effects of other interactions. In this study, we investigated the dissolution dynamics of partially protected PHS in organic developer by a quartz crystal microbalance method to deepen the fundamental understanding of the dissolution dynamics of chemically amplified resists. The dissolution dynamics in the solvents, in which the phenolic hydroxyl groups are hardly dissociated, was measured. In a 50 vol% methanol aqueous developer, a large swelling was observed. By decreasing the polarity of the developer, the dissolution dynamics was significantly changed. In the hexyl acetate, the dissolution kinetics of PHS films became similar to that in TMAH aqueous developer although the dissolution mechanism is different.