Core–Shell Quantum Dot-Based Honeycomb Films on Capillary Walls for Rapid In Situ Ascorbic Acid Detection

The rapid, portable, and in situ measurement of the ascorbic acid (AA) solution remains a challenge, and there is no suitable way to achieve multiscale regulation of the measurement range and sensitivity. In this work, water-soluble CdTe, CdTe/CdSe, and CdTe/CdSe/ZnS quantum dots (QDs) were used as fluorescence probes (FPs), and the specific sensitivity of photoluminescence (PL) intensity and AA were used as a detection indicator. By changing the concentration of the FP and the type of core–shell structure, multiscale regulation of the measurement range and sensitivity was realized. The same FP with distinct sensitivity in different measurement ranges is ingeniously realized by double-layer core–shell CdTe/CdSe/ZnS with type II-I band gap transition, which greatly expanded the application fields. The maximum measurement range was 0–27 μM and the minimum detection limit was 0.014 μM for three FP systems. The capillary sensor with a honeycomb QD film attached to the inner wall was prepared by drying at room temperature, high-temperature heating, and laser processing, which greatly increased the contact area between the QDs and AA and reduced the measurement time. Furthermore, the microfluidic system was used to precisely control the deposition area and position of the film, the concentration of the FP was adjusted and the deposition status of the film was observed in real time, so as to achieve real-time in situ rapid detection of the four concentration orders of the AA solution. This work is of great significance for the rapid, portable, multifield, and in situ real-time detection in the field of biomolecule detection.