Dual-mode sensor array based on silica-coated carbon dots with tunable fluorescence and phosphorescence for discrimination and detection of monoamine neurotransmitters.

Detection and discrimination of monoamine neurotransmitters (MNTs) are critical for early diagnosis but remain a substantial challenge due to their similar molecular structures and the complex interferences from biological sample matrices. Herein, dual-mode (fluorescence/phosphorescence) sensor arrays based on silica-coated carbon dots (CDs@SiO) were developed for discrimination and detection of multiple MNTs. The synthesized CDs@SiO displayed dual fluorescence (395 nm) and phosphorescence (520 nm) emission, enabling a one-component dual-mode sensor array for discrimination of catecholamines (100 % accuracy). The CDs-RhB@SiO nanocomposites, prepared by co-confining CDs and rhodamine B (RhB) in silica, exhibited orange fluorescence (585 nm) and red phosphorescence (600 nm). This structure enables efficient FRET (77.4 %) from CDs to RhB, yielding long-wavelength phosphorescence. Subsequently, a two-component four-channel sensor array utilizing CDs@SiO and CDs-RhB@SiO was developed. By leveraging distinct fluorescence λ = 395/585 nm and phosphorescence λ = 520/600 nm signals, the sensor array achieved precise discrimination (100 % accuracy) and quantitative detection of multiple MNTs with a low detection limit of 1.25 μM. This work provides a strategy to develop multimode sensor arrays with low background interference, demonstrating promise as a proof-of-concept platform that may support early diagnostic applications.