A promising temperature sensor based on all-quantum-dot multilayer via layer-by-layer self-assembled method

摘要

This study describes the fabrication, performance and characterization of a luminescence temperature sensor based on ordered all-quantum-dot (QD) multilayers.Highly photoluminescent and stable CdSe/ZnS core-shell QDs modified with two types of surface functional groups (-NH2 and -COOH) were prepared via aqueous route. Ordered thin films (film-A), based on alternate assembly of CdSe/ZnS-COOH (negatively charged) and CdSe/ZnS-NH2 (positively charged), were fabricated through electrostatic layer-by-layer (LBL) self-assembly technique. The temperature-dependent fluorescent properties of film-A (temperature-dependent photoluminescence; transient spectroscopy) were compared with that of a QD-polymer film (PDDA-CdSe/ZnS-COOH films; film-B) also prepared using electrostatic LBL self -assembly. Compared with film-B, film-A showed significant temperature sensitivity and fluorescence lifetime over the range 50-300 K. In addition, structural characterization of CdSe/ZnS-COOH and CdSe/ZnS-NH2 QDs were symmetrically characterized by transmission electron microscope (TEM) and the average diameters of the two QDs were both around 4.2 nm. The two functional groups (-COOH and -NH2) were confirmed by X-ray photoelectron spectroscopy (XPS). The results suggested that ordered all-QD multilayer films may have good potential in applications requiring sensors for optical thermometry.