One-Pot Hydrothermal Synthesis of mSiO₂-N-CDs with High Solid-State Photoluminescence as a Fluorescent Probe for...

An effective fluorescent probe (mSiO₂-N-CDs) was prepared by embedding N-CDs into mesoporous silica via a simple one-pot hydrothermal reaction and applied to the detection of dopamine (DA). Mesoporous silica not only provided a skeleton to prevent the aggregation of N-CDs but also a medium for the centrifugal collection of N-CDs, avoiding the need for dialysis and freeze-drying. The formation process, phase composition, morphology, and luminescence properties of the composite were studied in detail. The synthesized mSiO₂-N-CDs possessed spherical morphology, a smooth surface, and a diameter of approximately 150 nm. The fluorescence results indicated that mSiO₂-N-CDs emitted intense blue color fluorescence at 465 nm under the optimal excitation of 370 nm. Because the mesoporous silica effectively inhibited the self-quenching caused by the aggregation of N-CDs, the quantum yield of solid mSiO₂-N-CDs powder reached 32.5%. Furthermore, the emission intensity of the solid mSiO₂-N-CDs remained constant for 28 days. The good sensitivity and selectivity of mSiO₂-N-CDs for DA enabled the establishment of a rapid, simple, and sensitive DA detection method. The linear range was 0-50 µM and the limit of detection was calculated to be 107 nM. This method was used for the determination of DA in urine, with recovery rates ranging between 98% and 100.8%. In addition, the sensing mechanism was characterized by fluorescence lifetime decay and UV-VIS spectral analysis.