Accurate ethanol determination in Chinese Baijiu based on red-emitted carbon quantum dots (CQDs) and a simple pH correction.

The quality control of Baijiu is necessary including ethanol content. In this work, red-emitted carbon quantum dots based on p-phenylenediamine (PPD-CQDs) were fabricated for accurate determination of ethanol in Baijiu. The good linear response of PPD-CQDs to ethanol-water solution (E-Ws; 20-80 vol%) offered the potential for ethanol determination in practice. However, further application of this procedure to Baijiu resulted in a certain deviation. After excluding interference from most of the ingredients involved, a simple pH correction on Baijiu made application of the process practicable. The red-emission of PPD-CQDs supported analysis of Baijiu with different flavors and ethanol monitoring. Therefore, a quick-response fluorescence method was established for Baijiu ethanol determination; this method can be applied to the many varieties of Chinese Baijiu available and also has potential for use in other alcoholic beverages.

A smart ratiometric fluoresence and colorimetry dual-responsive sensor for morin determination based on the complex between carbon quantum dots and polyethyleneimine.

As a representative flavonoid, morin exhibits multi-biological activities, but its abuse endangers human health. Developing advanced technology for morin determination is urgently needed. In this study, a dual-responsive approach was reported for morin based on the complexing of carbon quantum dots (CQDs) and polyethyleneimine (PEI). The CQDs were fabricated via an improved hydrothermal method employing tyrosine and malic acid. Binding with PEI induced an 8-fold emission enhancement and a slight red-shift to 445 nm of CQDs because of the complexing of PEI and CQDs. Further morin introduction led to the blue emission (445 nm) quenching of CQDs-PEI and a yellow emission (560 nm) generation, which contributed a ratiometric fluorescence approach for morin determination between 2.0 and 32 µM, with a limit of detection (LOD) of 45 nM. Meanwhile, under sunlight the color of CQDs-PEI became yellow upon morin addition, which developed a colorimetric method for morin determination in a wide range between 2.0 and 100 µM (LOD = 69 nM). The developed dual-responsive method either displayed accurate results for morin in diluted human and bovine serum, being potential for actual sample analysis. Finally, a visual detection based on the smartphone was constructed and applied for the real-time determination of morin.