RESUMEN

The immunoglobulin E (IgE) level in serum is an important factor in the examination of allergy. Ferrocene (Fc)-modified self-assembled monolayers (SAMs) were placed on an indium tin oxide (ITO) electrode as a sensing layer for the detection of human IgE. The Fc moiety in the SAMs facilitated the electron transfer through the organic SAMs layer and electrocatalytic signal amplification. The electrochemical measurement was accomplished after the sandwich type immobilization of the receptor antibody, target human IgE, and enzyme conjugated secondary antibody. The enzyme product, p-aminophenol, was quantitatively analyzed by redox cycling via Fc. In addition, the electrochemical impedance spectroscopy (EIS) was investigated for the detection of IgE. The limit of detection (LOD), limit of quantification (LOQ), and dynamic range of the electrochemical sensor were 3 IU/mL, 10 IU/mL, and from 10 IU/mL to 100 IU/mL, respectively.

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RESUMEN

Self-doping in nanocrystals allows accessing higher quantum states. The electrons occupying the lowest energy state of the conduction band form a metastable state that is very sensitive to the electrostatic potential of the surface. Here, we demonstrate that the high charge sensitivity of the self-doped HgSe colloidal quantum dot solid can be used for sensing three different targets with different phases through self-doped HgSe nanocrystal/ZnO thin-film transistors: the environmental gases (CO2 gas, NO gas, and H2S gas); mid-IR photon; and biothiol (l-cysteine) molecules. The self-doped quantum dot solid detects the targets through different mechanisms. The physisorption of the CO2 gas and the NO gas molecules, and the mid-IR photodetection show reversible processes, whereas the chemisorption of l-cysteine biothiol and H2S gas molecules shows irreversible processes. Considering the quenching of mid-IR intraband photoluminescence of the HgSe colloidal quantum dot solid by the vibrational mode of the CO2 gas molecule, sensing the CO2 gas could be involved in the electronic-to-vibrational energy transfer. The target molecules are quantitatively analyzed, and the limits of detection for CO2 and l-cysteine are 250 ppm and 10 nM, respectively, which are comparable to the performance of commercial detectors.