Titanium nitride was recommended as pH-sensitive materials to fabricate pH sensors. The TiN electrode studied in this paper showed a linear response in the pH range of 11-14 with a response slope of -60 mV/pH. The cor...Titanium nitride was recommended as pH-sensitive materials to fabricate pH sensors. The TiN electrode studied in this paper showed a linear response in the pH range of 11-14 with a response slope of -60 mV/pH. The correlation coefficient was 0.998. The response time of the electrode was about 1 min. It exhibits some advantages over the glass pH electrode in more rigid structure and better selectivity toward cations of alkali metals, effectively overcoming the interference of Na + in high pH solution. No interferences from commonly accompanying cations and anions were observed. The electrode also showed a high stability and a good reproducibility. The potential drift was less than 2 mV as measured in pH 13.5 and 14 solution for 2 h. When the electrode was alternately measured in the solution of pH 13.5 and 14 solution, the relative standard deviation estimated for six measurements were about 0.27% and 0.29%, respectively. In addition, the electrode was performed excellently in corrosion medium containing F -. The lifetime of the electrode was over 3 months.展开更多
Ultrasound assisted electrocatalytic process was used for enhancing decomposition efficiency of organic compounds. In this paper, the effect of ultrasonic frequency, ultrasonic intensity and pH value on 3-chlorophenol...Ultrasound assisted electrocatalytic process was used for enhancing decomposition efficiency of organic compounds. In this paper, the effect of ultrasonic frequency, ultrasonic intensity and pH value on 3-chlorophenol decomposition were studied. It was found that 3-chlorophenol in aqueous solution can be markedly decomposed by ultrasound assisted electrocatalytic process. The rate of decomposition increased with the increase of frequency, and low frequency is proper in the ultrasound assisted electrocatalytic system. The removal of 3-chlorophenol increased visibly with the increase of ultrasonic intensity until the intensity of 1.56 W/cm2. Alkaline condition is beneficial to 3-chlorophenol decomposition, the rate at pH 9.08 was higher than pH 2.48 and 6.85. The major intermediate formed during 3-chlorophenol decomposition was 2-chloro-pbenzoquinone, which was readily decomposed by ultrasound assisted electrocatalytic process.展开更多
The Escherichia coli strain DH42 is sensitive to high osmolarity in an alkaline medium. Using mini-Tn5 mutagenesis, construction of mutant strains by homologous recombination and subcloning of DNA fragment techniques,...The Escherichia coli strain DH42 is sensitive to high osmolarity in an alkaline medium. Using mini-Tn5 mutagenesis, construction of mutant strains by homologous recombination and subcloning of DNA fragment techniques, gene ompC was identified as the key factor that, once disrupted, caused osmosis-sensitivity of E. coli strain DH42 grown in an alkaline medium. Through P1 transduction, a mutant strain, D9 （W3110 ompC：kan）, was constructed and growth comparison was performed between DH42 and D9 under different pHs and salt concentrations. The result showed that ompC was necessarily required for hyperosmotic adaptation of E. coli in the alkaline medium.展开更多
A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reac...A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reaction. In this work, based on theoretic calculation and experimental study on 7-hydroxy-2-（quinolin-2-ylmethylene） malonic acid, we demonstrated that QMA as a Michael acceptor is acid-activatable, i.e., it works only in solutions at pH〈7, and the lower the pH of solutions is, the higher reactivity QMA has. In alkaline solution, the malonate QMA[-2H＋]2- cannot react with both RSand RSH. In contrast, 2-（quinolin-2- ylmethylene） malonic ester （QME）, the ester of QMA, reveal a contrary pH effect on its sensing reaction, that is, it can sense thiols in alkaline solutions but not in acidic solutions, like a normal base-catalysed Michael addition. The values of activation enthalpies from theoretic calculation support the above sensing behavior of two probes under different pH conditions. In acidic solutions, the protonated QMA is more highly reactive towards electrophilic attack over its other ionized states in neutral and alkaline solutions, and so can react with lowly reactive RSH. In contrast, there is a big energy barrier in the interaction of QME with RSH （acidic solutions）, and the reaction of QME with the highly reactive nucleophile RS- is a low activation energy process （in alkaline solutions）. Theoretic calculation reveals that the sensing reaction of QMA undergoes a 1,4-addition process with neutral thiols （RSH）, and a 1,2-addition pathway for the sensing reaction of QME with RS-. Therefore, the sensing reaction of QMA is an acid-catalysed Michael addition via a 1,4-addition, and a normal base-catalysed Michael addition via a 1,2-addition.展开更多
文摘Titanium nitride was recommended as pH-sensitive materials to fabricate pH sensors. The TiN electrode studied in this paper showed a linear response in the pH range of 11-14 with a response slope of -60 mV/pH. The correlation coefficient was 0.998. The response time of the electrode was about 1 min. It exhibits some advantages over the glass pH electrode in more rigid structure and better selectivity toward cations of alkali metals, effectively overcoming the interference of Na + in high pH solution. No interferences from commonly accompanying cations and anions were observed. The electrode also showed a high stability and a good reproducibility. The potential drift was less than 2 mV as measured in pH 13.5 and 14 solution for 2 h. When the electrode was alternately measured in the solution of pH 13.5 and 14 solution, the relative standard deviation estimated for six measurements were about 0.27% and 0.29%, respectively. In addition, the electrode was performed excellently in corrosion medium containing F -. The lifetime of the electrode was over 3 months.
文摘Ultrasound assisted electrocatalytic process was used for enhancing decomposition efficiency of organic compounds. In this paper, the effect of ultrasonic frequency, ultrasonic intensity and pH value on 3-chlorophenol decomposition were studied. It was found that 3-chlorophenol in aqueous solution can be markedly decomposed by ultrasound assisted electrocatalytic process. The rate of decomposition increased with the increase of frequency, and low frequency is proper in the ultrasound assisted electrocatalytic system. The removal of 3-chlorophenol increased visibly with the increase of ultrasonic intensity until the intensity of 1.56 W/cm2. Alkaline condition is beneficial to 3-chlorophenol decomposition, the rate at pH 9.08 was higher than pH 2.48 and 6.85. The major intermediate formed during 3-chlorophenol decomposition was 2-chloro-pbenzoquinone, which was readily decomposed by ultrasound assisted electrocatalytic process.
文摘The Escherichia coli strain DH42 is sensitive to high osmolarity in an alkaline medium. Using mini-Tn5 mutagenesis, construction of mutant strains by homologous recombination and subcloning of DNA fragment techniques, gene ompC was identified as the key factor that, once disrupted, caused osmosis-sensitivity of E. coli strain DH42 grown in an alkaline medium. Through P1 transduction, a mutant strain, D9 （W3110 ompC：kan）, was constructed and growth comparison was performed between DH42 and D9 under different pHs and salt concentrations. The result showed that ompC was necessarily required for hyperosmotic adaptation of E. coli in the alkaline medium.
基金This work is supported by the National Natural Science Foundation of China （No.21272224）, the Open Research Fund of State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University （No.201410）, and the Open Research Fund of Key Laboratory of Advanced Scientific Computation, Xihua University （No.szjj2013-024）.
文摘A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reaction. In this work, based on theoretic calculation and experimental study on 7-hydroxy-2-（quinolin-2-ylmethylene） malonic acid, we demonstrated that QMA as a Michael acceptor is acid-activatable, i.e., it works only in solutions at pH〈7, and the lower the pH of solutions is, the higher reactivity QMA has. In alkaline solution, the malonate QMA[-2H＋]2- cannot react with both RSand RSH. In contrast, 2-（quinolin-2- ylmethylene） malonic ester （QME）, the ester of QMA, reveal a contrary pH effect on its sensing reaction, that is, it can sense thiols in alkaline solutions but not in acidic solutions, like a normal base-catalysed Michael addition. The values of activation enthalpies from theoretic calculation support the above sensing behavior of two probes under different pH conditions. In acidic solutions, the protonated QMA is more highly reactive towards electrophilic attack over its other ionized states in neutral and alkaline solutions, and so can react with lowly reactive RSH. In contrast, there is a big energy barrier in the interaction of QME with RSH （acidic solutions）, and the reaction of QME with the highly reactive nucleophile RS- is a low activation energy process （in alkaline solutions）. Theoretic calculation reveals that the sensing reaction of QMA undergoes a 1,4-addition process with neutral thiols （RSH）, and a 1,2-addition pathway for the sensing reaction of QME with RS-. Therefore, the sensing reaction of QMA is an acid-catalysed Michael addition via a 1,4-addition, and a normal base-catalysed Michael addition via a 1,2-addition.
