Portable smartphone platform based on tunable chiral fluorescent carbon dots for visual detection of L-Asp and L-Lys

Amino acids are involved in many physiological processes such as neurotransmitter transmission, protein synthesis and immune regulation, which play an indispensable role in life science. However, accurate monitoring of amino acid metabolism still faces a huge challenging due the lack of robust detection approaches. Herein, three-color emission tunable fluorescent carbon dots (CDs) were successfully synthesized by a simple one-step solvothermal treatment using classical precursors. These multi-color CDs exhibited a bright and steady luminescence shifting from blue to red under UV–vis light excitation. Detailed characterization by various precision instruments demonstrated that the unique structure of the prepared polychromatic emission CDs was composed of sp2 hybrid carbon nucleus and part of sp3 hybrid carbon atom. These CDs displayed low cytotoxicity and excellent multi-color cell imaging ability at single wavelength excitation. Moreover, the chiral structure on the surface of the red emissive carbon dots (R-CDs) was well preserved at temperatures far below the melting point of the chiral precursor. Especially, the chiral red emissive CDs (R-L-CDs) as sensitive and selective fluorescent probe could quickly identify L-Aspartic acid (L-Asp) and L-Lysine (L-Lys) in water and biological samples. Additionally, smart phone color recognizer application could realize more accurate visual detection to compensate the defect that the naked eye did not distinguish subtle colors. Therefore, the multi-excitation mode could be effectively shield background interference from complex samples by introducing a self-calibrating reference signal, ensuring accurate and reliable quantitative information, endowing R-L-CDs as a biosensor with far-reaching prospects for further application by binding target analytes.