Qiaoli Yang
Huazhong University of Science and Technology, China
Title: Fluorescent carbon dots based ratiometric pH sensor for direct detection of Escherichia coli O157:H7
Biography
Biography: Qiaoli Yang
Abstract
For sensitive detection of E. coli O157:H7, we report a one-step synthesis of highly water-soluble, biocompatible, fluorescent
and pH-sensitive Carbon Dots (CDs) and their practical application in constructing ratiometric pH sensor. We developed
a simple and easy way to synthesize hydrophilic CDs by the controlled carbonization of sucrose with the help of sulfuric
acid. The as-synthesized CDs are emitting bright green luminescent light without any further treatment, such as passivation.
Detailed fluorescence study showed under the excitation of 410 nm and 350 nm, the ratios of fluorescence intensity (Log[IF410/
IF350]) changed linearly in the range of pH 4.9 to 6.9, in Britton-Robison buffer. As, bacterial growth generally reduces the
pH of the growth medium due to the release of acidic metabolites such as lactic acid, acetic acid and CO2, etc. Based on this
principle, taking advantage of exclusive emission property of the synthesized CDs, they were successfully used for sensing E.
coli O157:H7 growth. While calculating fluorescent intensity of mixture, a linear relationship of E. coli concentration with the
fluorescence intensity (Log[IF410/IF350]) of the mixture was observed. The practical applicability of the synthesized CDs based
ratiometric pH sensor was confirmed to detect E. coli O157:H7 even in real samples like milk and lake water. The Limit of
Detection (LOD) was approximately 1 CFU/mL. In conclusion, the synthesis of our hydrophilic, biocompatible, pH sensitive
and fluorescent CDs and their application for detection of E. coli O157:H7 were all artless, rapid, cheap and efficient practices.