Optical oxygen sensing by MPA-capped CdTe quantum dots immobilized in mesoporous silica

Abstract

A novel nanocomposite luminescent material was prepared by taking advantage of the versatile wet impregnation method for the dispersion of CdTe quantum dots (QDs) into mesoporous silica host matrix and thus providing great interaction between oxygen and QDs, with potential application in an optical oxygen sensor. The optical/spectroscopic properties of the QDs suspended in aqueous media and incorporated in mesoporous silica were evaluated as a function of aging time, temperature variation and oxygen concentration. Luminescence quenching studies were carried out for both QDs suspended in solution and loaded into the silica matrix, in the presence of varying O 2 concentration. By Stern-Volmer plot analysis, obtained at different temperatures, it was possible to verify the existence of two types of emission quenching mechanisms for CdTe QDs. After aging for 120 days at room temperature, the QDs in colloidal suspension displayed a small red-shifted emission, which was interpreted as a decreased bandgap energy owing to the increase in the nanocrystal size. In contrast, the emission spectrum of CdTe QDs loaded into the mesoporous SiO 2 matrix remained unchanged after aging for the same time at ambient temperature. The presented results will contribute to the discernment of oxygen quenching mechanisms and chemical stability of optical sensors based on CdTe QDs.

Highly stable fluorescent probe based on mesoporous silica coated quantum dots for sensitive and selective detection of Cd2+

“…As a prominent strategy for modification of QDs, silica encapsulation has been widely used in the construction of FRET systems [22]. In fact, the silica shell gives QDs stability, biocompatibility, and versatile surface chemistry, yet reduces the activity of core, and thus lead to a poor sensing sensitivity in detection [23][24][25]. To overcome the contradiction between stability and sensitivity, mesoporous silica shell with large surface area, high pore volumes and highdensity functional groups on surface has been studied [26][27][28][29].…”