Quantum dots (QDs) are nanomaterials with high area/volume and unique optical and electronic properties, including tunable fluorescence emission, high photoluminescence, and photochemical stability. QDs find applications in photocatalysis, solar cells, drug carriers, and sensors, among others.<br/><br/>As chemical sensors for heavy metals detection, QDs offer selectivity and low detection limits. Soils in northeast of Colombia, a region characterized by mountainous ranges and cacao crops, display high concentrations of bioavailable Cd. The presence of Cd in cacao crops negatively impacts the commercialization of Colombian cacao beans in international markets due to recent restrictions imposed by the EU Codex Alimentarius stipulating a range of 0.1 - 0.8 ppm for Cd in food. The constrains related to Cd concentrations in food are due to the toxic nature of this metal and its potential bioaccumulation in the human body through the food chain.<br/><br/>In this study, we tested the photochemical properties of thioglycerol (TG)-functionalized CdSe QDs for the selective detection of Cd in standard solutions and aqueous soil extracts [MYCM1] using UV-Vis and fluorescence spectroscopy. The QDs Cd sensing performance in terms of detection limit, selectivity, reusability, stability, and effect of pH were also investigated. The CdSe QDs were dispersed onto TEMPO-cellulose nanofibers to avoid aggregation, promote stabilization, and obtain a versatile material for future use in a portable sensing device. The composite structure, morphology, and physicochemical properties were determined using XRD, SEM, XPS, EDS, and IR-ATR.

Sensing trace levels of Cd in soils with CdSe quantum dots immobilized on cellulose nanofibers

ACS Spring 2022

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