China
Africa
Explore chapters and articles related to this topic
Novel CMP for Next-Generation Devices
Published in Ungyu Paik, Jea-Gun Park, Nanoparticle Engineering for Chemical-Mechanical Planarization, 2019
Figure 6.20a shows the polishing rate of NGST film as a function of the tetramethylammonium hydroxide (TMAH) concentration. Without TMAH in the slurry, the polishing rate was 6 nm/min. With the TMAH addition, however, the NGST polishing rate drastically increased up to 242 nm/min at a TMAH concentration of 0.12 wt%. This striking difference in the polishing rates with and without TMAH resulted from the chemical reactions between the NGST film and the TMAH, which we explain later in detail. Beyond a TMAH concentration of 0.12 wt%, however, the polishing rate of NGST slightly decreased. This behavior was related to the way that TMAH effectively influences chemical reactions at the NGST film surface, such as hydrophobic or hydrophilic interactions. The characteristics of the reaction of TMAH with the NGST film surface can be estimated from the surface tension by measuring the contact angle. In general, wettability can be quantitatively evaluated in terms of the spreading coefficient, which is the energy difference between the solid substrate and the contacting liquid phase. The interaction of the interfacial tensions at the liquid–vapor–solid junction is described by the Young equation as follows: () cosθ=rSV−rSLrLV
Light-Emitting Polymers
Published in Zhigang Rick Li, Organic Light-Emitting Materials and Devices, 2017
Shidi Xun, Dmitrii F. Perepichka, Igor F. Perepichka, Hong Meng, Fred Wudl
Polyelectrolyte 659: The bis(sulfonium) salt 658 (600 mg, 1.08 mmol) was dissolved in 25 ml distilled water. The solution was filtered through a glass frit and placed in a 100 ml round-bottom flask. An equal volume of pentane was added to the flask, and the two-phase system was cooled to 0°C under argon. A solution of tetramethylammonium hydroxide was also cooled to 0°C under argon and pentane. Both solutions were thoroughly purged with argon gas for 1 h. Then, the base (0.47 ml, 1.30 mmol) was added swiftly by syringe. The polymerization was allowed to proceed for 1 h at 0°C. The excess base was neutralized with 6 M HCl solution to a phenolphthalein end point. The resulting yellow–green solution was dialyzed against distilled water (Spectropore 1 filters, Mw cutoff 6000–8000) for 3 days to give a uniform green solution. This solution can be used to cast films, which are soluble in methanol but insoluble in THF and CHCl3. This material is appropriate for conversion to polyether 660.
Morphology and Microstructure of MXene
Published in Zuzeng Qin, Tongming Su, Hongbing Ji, MXene-Based Photocatalysts, 2022
Nongfeng Huang, Zuzeng Qin, Hongbing Ji
There are other ways to avoid using HF for etching, and the most promising one may be electrochemical synthesis (Verger et al. 2019). MXene (Ti2CTx) prepared by dilute HCl electrochemical etching is a safer and milder method than the traditional HF etching method. Its structure and surface properties will be changed with the change of electrochemical etching conditions. The parent phase is treated in an HCl, or ammonium chloride, or tetramethylammonium hydroxide (TMAOH) electrolyte to remove the Al. Yang (Yang et al. 2018) obtained more than 90% of Ti3C2Tx single-layer and double-layer high yields from Ti3AlC2 using binary water electrolytes, a process that has also been successfully applied to produce other Mxenes, such as V2CTx and Cr2CTx. In addition, it has effectively solved the long-standing problem of high concentration of HF and showed its potential as a general preparation method for MXene. On the other hand, MXene synthesized by the nonelectrochemical etching method can reach 25 μm and has a flower-like structure (Pang et al. 2019), showed in Figure 3.3. Other methods, including hydrothermal synthesis to produce Ti3C2Tx (Li et al. 2018), and synthetic first nitride Ti4N3Tx in molten salt of LiF, NaF, and KF (Urbankowski et al. 2016), and fully Cl-terminated Ti3C2Cl2 and Ti2CCl2 MXene were synthesized in ZnCl2 Lewis acidic molten salt (Yu et al. 2019), are also used for synthesizing the MXene.
Potentially toxic elements (PTEs) in coffee: a comprehensive review of toxicity, prevalence, and analytical techniques
Published in International Journal of Environmental Health Research, 2022
Neda Mollakhalili-Meybodi, Sima Tahmouzi, Fardin Javanmardi, Amene Nematollahi, Amin Mousavi Khaneghah
Regarding developing alternative sample preparation methods, food chemists and analysts eagerly seek alternative methodologies that do not require complete decomposition of the sample (Trindade et al. 2020). Researchers propose microwave/ultrasound-assisted acid digestion, slurry sampling, and direct solid sampling as alternatives to conventional sample preparation methods that will postpone adverse effects caused by traditional sample preparation. The use of tetramethylammonium hydroxide, an alkaline solution of tetramethylammonium hydroxide, has been proposed as a simple strategy for the solubilization of instant coffee (Ribeiro et al. 2003). The method is validated for the total quantification of Ca, Cu, Fe, Mg, Mn, Na, P, Se, Sn, and Zn using ICP-OES. The potential of using 0.36 mol L-1 HNO3 solution and the solubilization in aqua regia has also been determined by (Asfaw and Wibetoe 2005) to quantify Se, Ca, Mg, K, P, S, and Zn elements by ICP-OES using a dual-mode sample introduction system (MSIS) in different beverages like instant coffee and also (Szymczycha-Madeja et al. 2015) with accuracy, precision and recovery in the range of 1.9–4.7%, 0.5–0.86%, and 93.5–103% respectively. Besides the solubilization method, dilution and centrifugation have also been used to quantify instant coffee elements (Oliveira et al. 2012). This preparation method is reliable for quantifying Ca, Mg, K, Na, Fe, Mn, Cr, and Ni using high-resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS) and graphite furnace atomic absorption spectrometry (HR-CS-GFAAS).
Nanomaterials for sustainable remediation of chemical contaminants in water and soil
Published in Critical Reviews in Environmental Science and Technology, 2022
Raj Mukhopadhyay, Binoy Sarkar, Eakalak Khan, Daniel S. Alessi, Jayanta Kumar Biswas, K. M. Manjaiah, Miharu Eguchi, Kevin C. W. Wu, Yusuke Yamauchi, Yong Sik Ok
Toxicity of the NPs in water, particularly Fe NPs (e.g., nZVI), also depends on the mixing and dispersing agents present. There may be residual NPs in water even after pollutant removal is complete (Peeters et al., 2016). The dispersion of Fe NPs with tetramethylammonium hydroxide (TMAH) resulted in a slower settling of the iron aggregates. In Milli-Q and forest spring waters treated with Fe NPs and dispersed by TMAH, the nano iron remained in solution for a day after the treatment, which represented a residual effect and may pose a threat to aquatic ecosystems (Peeters et al., 2016). Likewise, during the use of nano-TiO2 in aqueous systems, a combination of humic acid and HCO3- increased the release of Ti in water. Olabarrieta et al. (2018) reported that the nano-TiO2 rejection rate was generally above 95% in a low-pressure membrane filtration pilot plant, and 2.3 g of the NPs could be released when treating 31 m3 of tap water with 2 mg/L nano-TiO2.
Surface properties and doxorubicin delivery in mixed systems comprising a natural rosin-based ester tertiary amine and an anionic surfactant
Published in Journal of Dispersion Science and Technology, 2019
Chao Tian, Yuanli Liang, Haixia Lin, Jie Song, Qi Li, Rui Li, Chunrui Han
In order to determine the purity of RETAS, we tested the GC-MS of RETAS (A) and rosin acid raw material (B) as contrast as shown in the Figure 2. The molecular weight of RETAS is 739.39 and the molecular weight is not permitted more than 600 in GC-MS test. So, the GC-MS of RETAS was carried out by the method of literature.[9] RETAS was methyl etherified by tetramethylammonium hydroxide (TMAH). The reaction of RETAS with TMAH is shown in Figure 2A. Compounds a-g are the main methyl etherified productions of RETAS. Compounds b-d are the three dimethylesters of maleic rosin (MR) and e-g are the three monomethylesters of MR. The compound h would be reacted to be i [bis (2-(Dimethylamino) ethyl) ether] as shown in Figure 3B at the high temperature process of GC-MS. So, the main productions were a (trimethylester of MR), b-d (dimethylester of MR), e-g (monomethylester of MR) and h [bis (2-(Dimethylamino) ethyl) ether]. The main productions and their percent were shown in Table 1. We showed the mass spectrum (MS) and standard MS spectra of main compounds in Figure 4A and 4B. All MS of a-i compounds and unreacted raw materials (corresponding to peak 1 and 2 in Figure 2) well correspond to the standard MS spectra. The unreacted raw materials (peak1 and 2) are isopimaric acid and dehydroabietic acid. Compounds a-i are the productions of methyl etherified RETAS by TMAH. The most production is a, trimethylester of MR, and its percent is 41.7%. The peak area percent of a-i is 81.2%. So, the purity of RETAS is about 81.2% by analyzing GC-MS in detail.