Tin dioxide

Tin dioxide, an n-type semiconductor with a wide bandgap (3.6 eV at 300 K), has been widely studied as a sensor, a (photo)electrode material and in oxidation reactions for depollution. The performance of tin(iv) oxide is closely linked to structural features, such as nanosized crystallites, surface-to-volume ratio and surface electronic properties. The incentive for carbon-dioxide transformation into value-added products led to examination of the electroreduction of carbon dioxide at different cathodes. It has been recognised that the faradic yield and selectivity to carbon monoxide, methane, methanol, and formic acid rely upon the nature of the cathode and pH. ° Tin(iv) oxide, as cathode, was found to be selective in formate formation at pH = 10.2 with a faradic yield of 67%, whereas copper is selective for methane and ethene, and gold and silver for carbon monoxide. Nano-tin(iv) oxide has been shown to be active and selective in the carboigrlation of methanol to dimethyl carbonate at 150 °C and 20 MPa pressure. The catalyst was recyclable and its activity and selectivity compare with that of soluble organotins (see Section 21.5). 

These are experimental results from, on the one hand, a study on tin dioxide and, on the other, a study on nickel oxide. 

These two materials are studied here under different oxygen pressure values and either have or have not been subjected to some gaseous treatments. 

Particularly used as the sensitive element in gas sensors, this material has been the subjeet of a large number of investigations in the thermodesorption field. 

This presentation will foeus more specifically on the effect the presence of adsorbed sulfur dioxide has on the binding energies of the hydroxyl groups present on the tin oxide s surfaee. 

The experiments were eondueted on two types of sintered samples. These two samples differ from one another in respect of a sulfur dioxide gaseous treatment that was eondueted upon one, but not the others, at 500°C for 15 minutes. 

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The common ore of tin is tinstone or cassiterite. Sn02, found in Cornwall and in Germany and other countries. The price of tin has risen so sharply in recent years that previously disregarded deposits in Cornwall are now being re-examined. Tin is obtained from the tin dioxide, Sn02, by reducing it with coal in a reverbatory furnace ... 

Construction In tin dioxide semiconductor sensors, the sensing material is small sintered particles. For the sensor current flow, particle boundaries form potential energy barriers, which act as a random barrier netw ork. Different types t)f semiconductor gas sensors are shown in Fig. 13..54. 

Zion-saum, m. list of tin, selvedge, -allure, /. stannic acid, -saureonhydrid, n. stannic anhydride, tin dioxide, -schlich, m. (Ores) tin slimes, fine tin. -schrei, m. = 2Unngeschrei. -seife, /. (Mining) stream tin. -soda, /. sodium stannate. -staub, m. tin dust, -stein, m. tinstone, cassiterite. -sulfid, n. tin sulfide, specif, stannic sulfide, tin(IV) sulfide. -BuUocyanid, 1. tin thiocyanate, specif. 

Fluctuating Gap Model Fowler-Nordheim fluorine-doped tin dioxide full width at half maximum geminate pair... 

Stannic Oxide (White Tin Oxide, Tin Dioxide, Stannic Anhydride, Flowers of Tin Stannic Acid, Cassiterite). Sn02, mw 150.69, white powd, mp 1127°, bp 1800-1900° (subl), d 6.95 g/cc. Sol in coned sulfuric and coned hydrochloric acids, si sol in hot coned aq KOH or NaOH. Prepn is by reacting Sn with coned nitric acid (d 1.41 g/cc) on a w bath forming 0-stannic acid. The 0-stannic acid is then heated to a red heat and converted to Sn02. It is used as a chemical reagent and (see above) as an antifouling, flash and barrel wear reducing additive in propints... 

First chemical test measurements have been conducted with the array chip. Figure 6.19 shows the results that have been obtained simultaneously from three microhotplates coated with different tin-dioxide-based materials at operation temperatures of 280 °C and 330 °C in humidified air (40% relative humidity at 22 °C). The first microhotplate (pHPl) is covered with a Pd-doped Sn02 layer (0.2wt% Pd), which is optimized for CO-detection, whereas the sensitive layer on microhotplate 3 contains 3 wt% Pd, which renders this material more responsive to CH4. The material on microhotplate 2 is pure tin oxide, which is known to be sensitive to NO2. Therefore, the electrodes on microhotplate 2 do not measure any significant response upon exposure to CO or methane. The digital register values can be converted to resistance values by taking into account the resistor bias currents [147,148]. The calculated baseline resistance of microhotplate 1 is approximately 47 kQ, that of hotplate 2 is 370 kQ and the material on hotplate 3 features a rather large resistance of nearly 1MQ. 

As it is evident from Fig. 6.19, the responses of the three sensitive materials to the test gases CO and CH4 are very different. The lightly Pd-doped (0.2%) tin dioxide shows large responses to CO, and very small responses to CH4, whereas the heavily Pd-doped (3%) tin oxide exhibits comparably smaller responses to CO, but also... 

Synonyms stannic oxide tin dioxide tin peroxide white tin oxide stannic anhydride flowers of tin... 

The self-assembly of an imprinted layer on the surface of a transducer was realized through the adsorption of the template on gold, Si02, or ln02 surfaces followed by treatment with an alkylthiol or organosilane (Hirsch et al. 2003). The first example of this type of sensor was reported in 1987 by Tabushi and coworkers (1987). Octadecylchlorosilane was chemisorbed in the presence of n-hexadecane onto tin dioxide or silicon dioxide for electrochemical detection of phylloquinone, menaqui-none, topopherol, cholesterol, and adamantane. Another MlP-based sensor was... 

Eguren M, Tascon-Garcia ML, Vazquez-Barbado MD, Sanchez-Batanero P (1988) Study of electrochemical behavior of solid tin dioxide using a carbon paste electrode. Electrochim Acta 33, 1009-1011. 

Considering the stoichiometry of the salt, the only feasible arrangement is with C.N.qj- 3, C.N4n-. = 6 tin dioxide assumes theTiOz or rutile structure of Fig. 4.4. Note that the radius ratio would allow three more tin(IV) ions in the coordination sphere of the oxide ion, but the stoichiometry forbids it One final example is K20 ... 

Both mechanisms explain the decrease of the resistance with the formation of a rooted or an isolated hydroxyl group out of an O2" of the lattice. In both cases it is assumed that the bonding to the Sn does not contribute to the concentration of free charge carriers, which implies that not all the surface tin atoms are in oxidation state +4 because otherwise the formation of the Sn—OH bond would need an electron from the conduction band. This assumption is reasonable because tin has two stable oxidation states, +2 and +4, and the most stable surface of tin dioxide, (110), can easily be conditioned to show atoms with both oxidation states. Furthermore it is known that defects like vacancies are an essential factor for the performance of Sn02 gas sensors and it probably is not realistic to base a mechanism on the situation on a perfect surface. Emiroglu et al. (2001) and Harbeck et al. (2003) proved the formation of rooted and isolated hydroxyl group on the Sn02 surface in the presence of water, so the final result is clear even if the exact mechanism still allows for speculation. 

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