Ultrastable and ultrasensitive pH-switchable carbon dots with high quantum yield for water quality identification,glucose detection,and two starch-based solid-state fluorescence materials

It is attractive and encouraging to develop new fluorescent carbon dots(CDs)with excellent optical properties and promising applications prospects.Herein,highly-efficient green emissive CDs(m-CDs)with a high quantum yield(QY)of 71.7%in water are prepared through a facile solvothermal method.Interestingly,the m-CDs exhibit excellent fluorescence stability in the pH range of 1–9.However,the fluorescence intensity of the m-CDs is almost completely quenched as the pH is increased from 9 to 10.The mechanism of the unique pH-responsive behavior is discussed in detail and a plausible mechanism is proposed.Owing to the unique pH-responsive behavior,the m-CDs are used as a on-off fluorescent probe for water quality identification.By combining the reversible pH-ultrasensitive optical properties of the m-CDs in the pH range of 9–10 with the glucose oxidase-mimicking(GOx-mimicking)ability of Au nanoparticles(AuNPs),glucose can be quantitatively detected.Finally,two environment-friendly starch-based solid-state fluorescence materials(powder and film)are developed through green preparation routes.

Water quality characteristics and assessment of Yongding New River by improved comprehensive water quality identification index based on game theory

The Yongding New River is essential for the water supplies of Tianjin.To date,there is no comprehensive report that assesses the year-round water quality of the Yongding New River Main stream.Moreover,little attention has been given to determining a combined weight for improving the traditional comprehensive water quality identification index(ICWQII)by the game theory.Seven water quality parameters were investigated monthly along the main stream of the Yongding New River from May 2018 to April 2019.Organic contaminants and nitrogen pollution were mainly caused by point sources pollution,and the total phosphorus mainly by non-point source pollution.Dramatic spatio-temporal variations of water quality parameters were jointly caused by different pollutant sources and hydrometeorological factors.In terms of this study,an improved comprehensive water quality identification index(ICWQII)based on entropy weight or variation coefficient and traditional CWQII underestimated the water qualities,and an ICWQII based on the superstandard multiple method overvalued the assessments.By contrast,water qualities assessments done with an ICWQII based on the game theory matched perfectly with the practical situation.The ICWQII based on game theory proposed in this study takes into account not only the degree of disorder and variation of water quality data,but also the influence of standard-exceeded pollution indicators,whose results are relatively reasonable.All findings and the ICWQII based on game theory can provide scientific support for decisions related to the water environment management of the Yongding New River and other waters.