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1Si nanowire-based Schottky sensors for selective sensing of NH3 and HCl via impedance spectroscopy
V. Kondratev1*, A. Bolshakov1
1- Laboratory of Functional Nanomaterials, Center for Photonics and 2D Materials, Moscow Institute of Physics and Technology, 9 Institutskiy Lane, 141701 Dolgoprudny, Russia
This work is aimed at the development of a highly sensitive silicon (Si)-based sensor allowing for the selective detection and analysis of liquid solution compositions containing ammonia (NH3) and hydrochloric acid (HCl) in an indirect manner using electrochemical impedance spectroscopy (EIS). The best sensitivity results were obtained with Si nanowires based Schottky Sensors, which provided a detection limit of 4 ^molL-1 and resistive sensitivities of 0.8% per ^molL-1 for HCl and 4 pmol-L"1, -0.2% per ^molL-1 for NH3, respectively. Treatment with HF stimulated Si nanowires surface oxidation and increased the density of adsorption sites, making it promising for detecting analyte concentrations up to 1000 ^molL-1. Schematic of the Si nanowire-based schottky sensors operation is shown in Fig.l.
The experimental data were confirmed via density functional theory (DFT) modeling of the processes of adsorption and redox interaction between ammonia and hydrochloric acid molecules and the surface of silicon nanowires.
Finally, the sensor response was studied when exposed to NH3 and HCl vapors simultaneously. Also, the approach for the EIS data analysis involving characterization of the sensor response with two parameters - resistance and EIS frequency corresponding to the change in the operation regime was developed. Due to the use of two parameters simultaneously, this approach is found as a pathway for qualitative and quantitative analysis of the gas mixture composition using only one sensor.
The results of the work shed light on the development of feasible highly sensitive sensors for health monitoring, allowing for selective mixed analytes detection [1].
[1] V.M. Kondratev, E.A. Vyacheslavova, T. Shugabaev, D.A. Kirilenko, A. Kuznetsov, S.A. Kadinskaya, Z.V. Shomakhov, A.I. Baranov, S.S. Nalimova, V.A. Moshnikov, A.S. Gudovskikh, A.D. Bolshakov, Si Nanowire-Based Schottky Sensors for Selective Sensing of NH3 and HCl via Impedance Spectroscopy, ACS Applied Nanomaterials 2023 6 (13), 11513-11523.
Figure 1 - Schematic of the Si nanowire-based Schottky sensors operation.
