Accelerated naked-eye identification of cations using non-plasmonic amplification by functionalized GQDs: A novel photochemical microfluidic sensor for environmental/mineral analysis using Lab-on-paper technology

This study describes the synthesis of various types of thiolated-graphene quantum dots (GQDs) for the simultaneous multi-sensing of heavy metal ions using one-droplet microfluidic paper-based analytical devices (OD mu PADs). For the first time, functionalized GQDs were synthesized and stabilized on the surface of hydrophobic fiber-glass with simple manufacturing and assembly strategy towards colorimetric chemosensing of ions including iron, copper, cobalt, mercury, chrome, manganese, and nickel. For this purpose, GQDs are functionalized by various organic species including cysteamine, decanethiol, and mercaptopropionic acid (MPA) towards specific electrostatic interaction with metal ions of Fe (II), Cu (II), Co(II), Hg (II), Mn (II), and Ni (II). Therefore, an innovative GQDs-based miniaturized chemo-system was proposed for the environmental analysis. Additionally, the results were confirmed using fluorescence spectrometry as an optical detection method. Finally, this simple and efficient colorimetric platform was used for facile metal ions detection in human urine models, and environmental fluids, which can provide a commercial device for sensing contaminants by non-professional users in biomedical/environmental mixture. As an economical technique, this platform presents a mix-and-sense system without dye (as a side substance) or chemical treatments. The low instrumental requirements, the color uniformity, and the disposability of OD-mu PADs approve the commercial application of the engineered ionchemosensor.

Automated summary

This study successfully synthesized various types of thiolated-graphene quantum dots (GQDs) and utilized them in a one-droplet microfluidic paper-based analytical device for the simultaneous multi-sensing of heavy metal ions. The GQDs were functionalized and stabilized on the surface of hydrophobic fiber-glass, enabling colorimetric chemosensing of ions including iron, copper, cobalt, mercury, chrome, manganese, and nickel. The results were confirmed using fluorescence spectrometry, and the platform showed potential for facile metal ion detection in human urine models and environmental fluids.