Precise control of the size, shape, and composition of nanocrystals will be required to fully explore and utilize unique properties of nanomaterials with a broad range. In this manuscript we have designed colloidal QD chains, using carboxyl-modified red fluorescent cadmium telluride (CdTe), which were self-assembled by the mediation of trithiocyanuric acid (TTCA). Furthermore, a ratiometric fluorescent sensor with dual-emissions was constructed by mixing the QD chains with blue fluorescent carbon dots (CDs) for the visual ultrasensitive detection of As(III) in environmental water. In the process of As3+ detection, it could react with the third sulfydryl, which resulted in the agglomeration of QD chains and quenching of the red emission of the QDs, while the blue fluorescent CDs were insensitive to the analyte. So the variation of fluorescence intensity ratios produces an obvious change of the fluorescence color from fushia to blue, which can be conveniently observed by the naked eye under a UV lamp without any complicated instrumentation. The LOD of this ratiometric fluorescent probe could reach as low as 1 ppb, which is much lower than the maximum level of 10 ppb As3+ in drinking water stipulated by WHO. Following the sensing mechanism, a paper-based sensor has been prepared by printing the ratiometric probe on filter paper, which provides a convenient and simple approach for the visual detection of As3+. Therefore, the very simple and effective strategy reported here could be extended to the visual detection of a wide range of analytes in the environment by the construction of highly efficient ratiometric nanoprobes.
Aggregation-induced quenching (ACQ) in carbon nanodots (CNDs) impede their applications in solid devices. Herein, the concept of alternating quantum dot (QD) chains was proposed to overcome the common issue of fluorescence quenching in CNDs; in this study, CNDs and ZnO QDs were interlinked to form carbon-ZnO alternating quantum dot chains (CZA-QDCs), which overcame the ACQ of CNDs and hence ensured efficient full-spectrum fluorescence for white light-emitting devices (WLEDs) without excessive blue emission. Under the excitation of 365 nm lines, white emission resulting from the combination of blue emission from the CNDs and yellow emission from the ZnO QDs has been achieved from these powders. The quantum efficiency of the CZA-QDC powders can reach 49% and remain stable for two months. By coating the powders onto an ultraviolet chip as phosphors, WLEDs with a luminous efficiency of 20.1 lm W−1, color coordinate of (0.30, 0.35), correlated color temperature of 5205 K, and a color rendering index of 84 have been fabricated. Due to the relatively high abundance and eco-friendly characteristics of both carbon and ZnO, the results reported herein may provide a promising alternative to fluorescent phosphors that are widely used in WLEDs.
危险品化学品经营许可证（带存储）