Finely Tuned SnO₂ Nanoparticles for Efficient Detection of Reducing and Oxidizing Gases: The Influence of Alkali Metal Cation on Gas-Sensing Properties

Abstract

Tin dioxide (SnO2) nanoparticles were straightforwardly synthesized using an easily scaled-up liquid route that involves the hydrothermal treatment, either under acidic or basic conditions, of a commercial tin dioxide particle suspension including potassium counterions. After further thermal post-treatment, the nanomaterials have been thoroughly characterized by Fourier transform infrared and Raman spectroscopy, powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen sorption porosimetry. Varying pH conditions and temperature of the thermal treatment provided cassiterite SnO2 nanoparticles with crystallite sizes ranging from 7.3 to 9.7 nm and Brunauer–Emmett–Teller surface areas ranging from 61 to 106 m2·g–1, acidic conditions favoring potassium cation removal. Upon exposure to a reducing gas (H2, CO, and volatile organic compounds such as ethanol and acetone) or oxidizing gas (NO2), layers of these SnO2 nanoparticles led to highly sensitive, reversible, and reproducible responses. The sensing results were discussed in regard to the crystallite size, specific area, valence band energy, Debye length, and chemical composition. Results highlight the impact of the counterion residuals, which affect the gas-sensing performance to an extent much higher than that of size and surface area effects. Tin dioxide nanoparticles prepared under acidic conditions and calcined in air showed the best sensing performances because of lower amount of potassium cations and higher crystallinity, despite the lower surface area.

Designing SnO2 Nanostructure-Based Sensors with Tailored Selectivity toward Propanol and Ethanol Vapors

“…The response recovery times were calculated as the time intervals between the time at which the response has achieved 90% of its maximum and the time at which it has decreased to 10% of its maximum. 12…”

Morphological Effects in SnO2 Chemiresistors for Ethanol Detection: A Review in Terms of Central Performances and Outliers

“…Other remarkable responses have been reported for different nanoparticle networks with no hierarchical organization [16,40,55,86]. Visually extrapolating the calibration curves of the reported materials allows to compare layers tested in different concentration ranges.…”

“…The band diagram in the two regimes is schematically reported in Figure 2. Schematic representation of the energy band diagram in a spherical grain of diameter t in the regional depletion regime (a), in which the grain diameter is larger than two times the depletion layer W (t > 2W), and in the volume depletion regime (b), in which 2W > t. Adapted with permission from [40]. Copyright (2018) American Chemical Society.…”

Recent Progress of Nanostructured Sensing Materials from 0D to 3D: Overview of Structure–Property‐Application Relationship for Gas Sensors

“…prepared finely tuned SnO 2 nanoparticles and studied the influence of alkali metal cation (potassium residuals) on gas sensing properties. [ 81 ] They found that the surface area and Debye length of SnO 2 are not dominant factors in gas sensitivity. SnO 2 samples that were synthesized under acidic conditions and calcined in air obtained the best sensing performances because of a lower amount of potassium residuals and higher crystallinity.…”