The Effect of CdSe and InP Quantum Dots on the Interaction of ZnO with NO2 under Visible Light Irradiation

Light-Activated Sub-ppm NO2 Detection by Hybrid ZnO/QD Nanomaterials vs. Charge Localization in Core-Shell QD

“…Our previous studies of the photoconductivity and gas sensor properties of nanocrystalline ZnO sensitized with CdSe and InP quantum dots have shown that the periodic backlight mode is more convenient than the constant one (Chizhov et al, 2018). This periodic mode consists in alternation of short (2 min) light on/off periods that leads to the corresponding periodic change in photoconductivity.…”

“…However, for this it is necessary to shift the optical sensitivity of semiconductor oxides from the UV range to longer wavelengths. This can be achieved by creating the defects in the semiconductor matrix (Han et al, 2012(Han et al, , 2013Varechkina et al, 2012;Geng et al, 2013;Zhang et al, 2017) or using the sensitizers that absorb light in the visible range (Peng et al, 2011;Vasiliev et al, 2013;Chizhov et al, 2014Chizhov et al, , 2016Chizhov et al, , 2018Yang et al, 2014;Zhang et al, 2015;Geng et al, 2016a,b;Paolesse et al, 2017;Rumyantseva et al, 2018). In the latter case, the consistency between the energy levels of metal oxide and sensitizer, is the necessary condition ensuring the transfer possibility of photoexcited charge carriers from the sensitizer to the semiconductor matrix (Minami et al, 1998;Ivanov et al, 2007;Kim et al, 2009;Vasiliev et al, 2011;Mordvinova et al, 2014).…”

“…In the latter case, the consistency between the energy levels of metal oxide and sensitizer, is the necessary condition ensuring the transfer possibility of photoexcited charge carriers from the sensitizer to the semiconductor matrix (Minami et al, 1998;Ivanov et al, 2007;Kim et al, 2009;Vasiliev et al, 2011;Mordvinova et al, 2014). A II B VI and A III B V semiconductor quantum dots (QDs) (Vasiliev et al, 2013;Chizhov et al, 2014Chizhov et al, , 2016Chizhov et al, , 2018Yang et al, 2014;Geng et al, 2016a,b) and organic dyes (Peng et al, 2011;Zhang et al, 2015;Paolesse et al, 2017;Rumyantseva et al, 2018) are suitable visible light sensitizers for wide gap semiconductor metal oxides.…”

Photosensitive Organic-Inorganic Hybrid Materials for Room Temperature Gas Sensor Applications

“…Our previous investigations of gas sensor properties of nanocomposites, consisting of a semiconductor oxide matrix and photosensitizers—semiconductor quantum dots, performed under constant and periodic illumination, demonstrated that the latter option is preferable because of long recovery time constants (more than 1 h) necessary to return to the equilibrium resistance under constant illumination [ 35 , 58 ]. In this procedure, the illumination of the sensor element is carried out in a pulsed mode with a short period (2 min “on”–2 min “off”).…”

“…However, this desorption process is a prerequisite for restoring the initial state of the surface and the electrical properties of the sensitive material, providing the formation of a reproducible sensor signal. In our previous works [ 28 , 35 , 58 ], it was demonstrated that the role of illumination consists in the photogeneration of holes that ensure (as in the case of oxygen) the conversion of chemisorbed particles into physically sorbed ones, which can be easily desorbed from the surface of the semiconductor oxide even at room temperature due to thermal fluctuations: …”