Fabrication And Application Of CdTe Quantum Dots/Polyelectrolyte Multilayer Films

Semiconductor quantum dots (QDs) have drawn widespread attention and exploited in a variety of multicolor imaging for bio-sample, vivo tissue and bio-fluorescence probe, especially in fluorescence sensors in the past decade. In the synthesis approaches of quantum dots, the aqueous syntheses are easier controlled, higher repeated, lower cost. It is easily to modify the surface of QDs with different functional groups using the aqueous syntheses. QDs provide robust and stable signal intensity, narrow emission spectra, and the broad emission wavelength which can be turned continuously by changing the size and component of the QD particles.In this work, CdTe quantum dots (QDs)/polyelectrolyte multilayer films (QDMF) were assembled by layer-by-layer (LBL) deposition of oppositely charged CdTe QDs and poly(dimethyldiallylemmonium chloride) (PDDA). Based on the fluorescence quenching of CdTe quantum dots (QDs)/polyelectrolyte multilayer films, a novel method for the direct detection of gaseous formaldehyde (QDMF) was proposed in this paper. Formaldehyde can quench the fluorescence of CdTe QDs multilayer films effectively. Under the optimization conditions, the fluorescence intensity of QDs decreased linearly with the increase of formaldehyde concentration in the range of 5–500 ppb. The detection limit for formaldehyde was 1 ppb. The quenching mechanism of CdTe QDs multilayer films by formaldehyde was also studied in detail. This proposed approach was simple, rapid and had excellent selectivity and sensitivity for the detection of gaseous formaldehydeCdTe quantum dots (QDs)/polyelectrolyte multilayer films were also used as sensors for paraoxon detection. Paraoxon can enhance the fluorescence intensity of CdTe QDs multilayer films effectively. Enhancements of photoluminescence of QDs is most likely due to the passivation of surface traps by ligand groups (P=O group of paraoxon). Under the optimization conditions, the fluorescence intensity of QDs multilayer films increased linearly with the increase of paraoxon concentration in the range of 5-200 ppb. The detection limit for paraoxon was 2 ppb. This approach was simple, rapid and had excellent selectivity and sensitivity for the detection of organophosphates.