Abstract
Excellent luminescent materials are essential for high-performance fluorescent nanosensors. Here, a new-type self-calibrated humidity sensor has been established through monitoring the fluorescent color change of carbon dots (CDs) confined in sodium hydroxide (CDs@NaOH). The CDs are prepared by a facile and rapid microwave assisted heating method using citric acid, urea, and NaOH as precursors. The confinement effect from NaOH has reduced the nonradiative transition and suppressed the aggregation-induced quenching of the CDs in solid. Compared with other sensors based on CD fluorescent visualization, the sensor has good linearity and wide humidity detection range from 6.9% to 95.4%. With the increased relative humidity, the fluorescence color of the sensor change from green to blue. The proposed sensing mechanism is due to the breaking and reforming of hydrogen bonds and proton transfer occurring at the CD-NaOH matrix interfaces. This finding suggests a potential role for the spatial confinement effect and may provide an avenue for developing highly sensitive humidity readouts.
Probing DNA sequences in solution with a monomer-excimer fluorescence color change