The transport of ionic species through nanochannels plays an important role in the basic research and practical application of nanofluidic devices. Here, a visualized CdSe@ZIF-8/PAA nanochannel membrane was created by employing in situ growth of zeolite imidazole skeleton (ZIF-8) and CdSe quantum dots (CdSe QDs) on a porous anodized aluminum oxide (PAA) membrane surface using CdSe QDs, 2-methylimidazole, and zinc nitrate as the precursor solvents. ZIF-8 is a kind of metal-organic framework, a microporous material that possesses strong metal adsorption capacity. In addition, CdSe quantum dots have fluorescent properties. The nanochannel membrane detects copper ions (Cu2+) by quenching the fluorescence intensity by the interaction between Cu2+ and Se and S atoms. The direct potential of 5 V was applied to achieve Cu2+ enrichment at the nanochannel interface, and the fluorescence change was observed. The CdSe@ZIF-8/PAA nanochannel membrane has a good linear range of concentration (0.01 pM-1 μM) for Cu2+ detection. With the help of nanochannel enrichment, its detection limit reaches 4 fM. In addition, this nanochannel membrane has good selectivity for Cu2+.
Keywords: CdSe quantum dots; enrichment; fluorescence; nanofluidic devices; porous anodized aluminum oxide membrane.