Multifunctional Self-Doped Nanocrystal Thin-Film Transistor Sensors

Abstract

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.

Transformation of Colloidal Quantum Dot: From Intraband Transition to Localized Surface Plasmon Resonance

“…To be concrete, a loss in the MWIR emission intensity reveals how the excitonic intraband transition is gradually mixed with the LSPRs in the self-doped nanocrystal. Thus, we performed the mid-IR intraband PL measurement for the Ag 2 Se CQDs with various sizes. ,, Since the photoexcitation wavelength of 532 nm is shorter than that of the bandgap transition, the overall mechanism inevitably involves the electron in the VB that eventually recombines with the hole at 1S e state (Figure b) …”

“…Thus, we performed the mid-IR intraband PL measurement for the Ag 2 Se CQDs with various sizes. 7,45,46 Since the photoexcitation wavelength of 532 nm is shorter than that of the bandgap transition, the overall mechanism inevitably involves the electron in the VB that eventually recombines with the hole at 1S e state (Figure 5b). 47 Due to the loss in the excitonic character with an increase of the nanocrystal size, the intraband PL intensity is substantially attenuated as observed in Figure 5a.…”

Mercury Chalcogenide Quantum Dots: Material Perspective for Device Integration

“…Nevertheless, many researchers have attempted to integrate HgSe NCs into devices by exploiting their infrared intraband absorption. 29,34,39,47,[118][119][120] Table 2 summarizes the main synthetic processes used to grow HgSe NCs. The first synthesis of nanosized HgSe involved nearly cluster-sized materials.…”

A Review of Phototransistors Using Metal Oxide Semiconductors: Research Progress and Future Directions

“…Researchers have recently attempted to use phototransistors in the field of biotechnology. [ 140 ] Park et al. presented phototransistor arrays with QD/IGZO hybrid structures using QD materials of PbS, CdSe, and CdS, and attempted to apply the sensor arrays to biotechnology.…”