In situ synthesis of fluorescent silicon nanodots for determination of total carbohydrates in a paper microfluidic device combined with laser prepared graphene heater

We report a simple, rapid, low-resource and one-step method for formation of fluorescent silicon nanodots (SNDs) in a microfluidic paper-based analytical device (mu PAD) incorporated in a reusable, portable and flexible heater for determination of total carbohydrates. The synthesis of SNDs is based on the redox reaction between (3-aminopropyl) triethoxysilane (APTS) reagent and carbohydrates, which act as a reducer. The graphene-based heater was fabricated by laser ablation of Kapton polyimide. Thereby, the developed system heat the mu PAD during the synthesis of SNDs at 80 degrees C for 30 min. The blue emitting SNDs formed have an emission peak wavelength at 475 nm. We used a digital camera and smartphone for the quantitative analysis of total carbohydrates expressed such as index of glucose or fructose with grey scale value as the analytical parameter. Under the optimal conditions, the method has a low detection limit (0.80 mu M for glucose and 0.51 mu M for fructose, respectively), and a linear response (10-200 mu M for glucose and 10-100 mu M for fructose). The method has been applied to the determination of glucose in biological fluids (serum and urine samples). In addition, determination of total carbohydrates in commercial juices and teas have been carried out.

Automated summary

This study developed a simple, rapid, low-resource method for the formation of fluorescent silicon nanodots in a microfluidic paper-based analytical device (mu PAD) for determination of total carbohydrates. A graphene-based heater fabricated by laser ablation of Kapton polyimide was used to heat the mu PAD during the synthesis process of blue emitting silicon nanodots. The method showed low detection limits and linear responses for glucose and fructose, and was successfully applied in biological fluids and commercial juice and tea samples.