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). For optimization of the performance,
we develop three types of sensors based on as-fabricated Si nanowires,
nanowires treated with hydrofluoric acid (HF), and nanowires decorated
with silver (Ag) nanoparticles. The fabricated sensors exhibit good
performance governed by the sensitivity of the nanoscale Schottky
barriers at the interface between the golden pads and Si nanowires.
The best results on sensitivity are obtained with untreated Si nanowires
providing a detection limit at the level of 4 μmol·L–1 and resistive sensitivities of 0.8% per μmol·L–1 for HCl and 4 μmol·L–1, −0.2% per μmol·L–1 for NH3, correspondingly. Treatment with HF stimulates the surface
oxidation providing higher density of the adsorption sites and found
promising for the detection with the analyte content up to 1000 μmol·L–1. In the end, we study the sensor response upon simultaneous
exposure under NH3 and HCl vapors using developed approach
for the EIS data analysis involving characterization of the sensor
response with two parametersresistance and EIS frequency corresponding
to the change in the operation regime. Due to the use of two parameters
simultaneously, this approach is found as a pathway for qualitative
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.
Zinc oxide and zinc stannate nanowires were synthesized by hydrothermal method. Zinc oxide nanowires were doped by iodine. The formation of multicomponent and doped oxides was studied by X-ray photoelectron spectroscopy. It was found that formation of zinc stannate from zinc oxide nanowires occurs in 1 hour. The percentage of OH-groups increases on the surface of zinc oxide nanowires as a result of doping by iodine.
Наноструктуры станната цинка были синтезированы гидротермальным методом, в качестве исходных материалов были использованы наностержни оксида цинка. Образование многокомпонентных оксидов было исследовано с помощью рентгеновской фотоэлектронной спектроскопии. Установлено, что в процессе гидротермального синтеза происходит постепенное встраивание ионов олова в кристаллическую решетку наностержней оксида цинка и замещение ионов цинка. с образованием наноструктур станната цинка. Исследование влияния времени синтеза на химический состав поверхности полученных образцов показало, что формирование станната цинка происходит через 1 час, что подтверждается изменением энергий связи цинка и кислорода. При более длительном синтезе происходит разрушение наноструктур станната цинка, оксидов цинка и олова на поверхности образца практически не наблюдается.
Zinc stannate nanostructures were synthesized by hydrothermal method, and zinc oxide nanorods were used as starting materials. Formation of multicomponent oxides was studied by using the X-ray photoelectron spectroscopy. It was found that tin ions are gradually embedded in the crystal lattice of zinc oxide nanorods and replaced zinc ions during hydrothermal synthesis with the formation of zinc stannate nanostructures. The study of the synthesis time effect on the surface chemical composition of the prepared samples has shown formation of zinc stannate after 1 hour, that is confirmed by changes in the binding energies of zinc and oxygen. With a longer synthesis, zinc stannate nanostructures collapsed, thus zinc and tin oxides are practically not observed on the sample surface.
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