SnO₂ “Russian Doll” Octahedra Prepared by Metalorganic Synthesis: A New Structure for Sub‐ppm CO Detection

Abstract

Micrometer-sized hierarchical Sn3 O2 (OH)2 octahedra, which are self-assembled one inside the other, resembling "Russian doll" organization, have been obtained by a metalorganic approach. This synthesis is based on the controlled hydrolysis of [Sn(NMe2 )2 ]2 in the presence of an alkylamine ligand in an organic solvent (THF). The water content of the medium proved to be a key parameter for the formation of these multi-walled octahedra. The resultant structures have been used as gas-sensitive layers on micromachined silicon devices. During in situ heating, Sn3 O2 (OH)2 is oxidized to SnO2 while retaining the initial morphology. The sensors present outstanding dynamic responses at very low CO concentrations (7 % and 67 % resistance variation to 0.25 and 20 ppm CO, respectively, at an operating temperature of 500 °C). This superior gas-sensing performance is closely related to the unique microstructure of the SnO2 multi-walled octahedra.

Hydrolysis of organometallic and metal–amide precursors: synthesis routes to oxo-bridged heterometallic complexes, metal-oxo clusters and metal oxide nanoparticles

“…The reaction of highly Brønsted basic organometallic or metalamide complexes with protic OH groups provides a promising strategy to form a variety of metal-oxo structures ranging from molecular M−O−M' species to nanomaterials. These synthetic routes have enabled the formation of oxo-bridged heterometallic species that act as highly tuned catalysts for polymerisation reactions, 25 and of metal oxide NPs which have found uses in a variety of applications including catalysis, 202 sensing, 195 and antibacterial surfaces. 208 Controlled reactivity with water also allows the formation of partially hydrolysed metal-oxo cluster species.…”

“…203,204 The hydrolytic routes discussed here typically result in hydroxide/water terminated surfaces, as evidenced by spectroscopic techniques. 205 Metal oxide NPs produced by hydrolysis of reactive precursors have found a range of applications including the pseudo-homogeneous catalytic reduction of CO2 to MeOH (ZnO and Cu NPs); 173,202,206,207 polymeric antibacterial surfaces (ZnO); 208, 209 photocatalysts (ZnO); 183, 210 gas sensors (ZnO, 211 SnO 194,195 , CuO 172 ); photoconductive UV detectors (ZnO); 212 and MRI contrast agents (-Fe2O3). 167 The ability to control size, morphology, surface chemistry and ligand coverage has proved very valuable in producing NPs for these applications.…”

Effect of Nanostructured Octahedral SnO2 Added with a Binary Mixture P-Type and N-Type Metal Oxide on CO Detection

“…In this work, all the nanoparticles have been prepared through organometallic synthesis procedures. Firstly, ZnO nanorods have been prepared by the reaction of controlled amounts of water (4 equivalents) on Zinc dicyclohexyl (ZnCy2) placed at 40 °C under argon and in the presence of alkylamines ligands (2 molar equivalents octylamine, OA), according to previously published method [1]. The reaction is left running during 4 days and the resulting nanorods (mean diameter 6 ± 1 nm, mean length 36 ± 19 nm) are washed by several precipitation/dispersion stages with acetone.…”

“…This modification also depends on the quantity of this metal oxide with different percentage of the mass at different operating temperature. In this study, we show the effect of adding different proportions of nanostructured octahedral SnO2 (Figure 1 [1]) to a binary mixture composed by 75% in volume of CuO [2] and 25% of ZnO [3] (Figure 2), on CO detection at different working temperatures. The addition of SnO2 to CuO75%/ZnO25% was used as an intermediate step to improve the adhesion and the chemical functionalization of the surface of CuO75%/ZnO25% for the CO detection between 100 ppm and 1000 ppm at different operating temperatures.…”

Palladium‐Loaded Hierarchical Flower‐like Tin Dioxide Structure as Chemosensor Exhibiting High Ethanol Response in Humid Conditions

“…Although much progress has been made in the studies of SnO 2 as a gas sensor, it continues to be a great challenge to obtain good gas‐sensing performance at low temperatures, which are not favorable for practical applications and reduce the sensor's durability. The addition of noble metals onto the SnO 2 surface has shown to be an effective strategy for reducing the operating temperature and improving other sensing parameters for VOCs, resulting in high responses, enhanced selectivity, and fast response times …”