Gas-Sensitivity Of Nano-composite Materials Of SnO₂and TiO₂under Ultraviolet Light

It becomes more attractive that nano-matel oxide of TiO₂and SnO₂isproposed as a novel gas-sensing material, using in boardband semiconductorproduction. Although there were many reports on examination of volatilityorganic componds （shortened as VOCs） by TiO₂or SnO₂, it was still littledisscusion of VOCs determinations by composite material of the two,especially under ultraviolet light （UV） irradiation. In this work, thegas-sensitivity elements were prepared with complex materials consisted ofnano-matel oxide of TiO₂-SnO₂by using a method of sol-gel. In addition, theeffects of ultraviolet light with different wave lengths on gas-sensitivity ofmaterial elements to tree kinds of gases （carbinol, ethanol and acetone） werestudied. And the results were shown as follows.（1） The crystal grain size of prepared composite material with TiO₂-SnO₂is between6nm and8nm, while the particle size of the material is rangedfrom170nm to350nm. The pattern of the particle is homogeneous andregular globular shape. With the content of TiO₂declines, the particle size isgradually increased.（2） With the same composite ratio of TiO₂and SnO₂as12to1, thesensitivity of composite material mixed with Ag+is obviously perior to theone without Ag+. Not only is gas-sensitivity evaluated, but also a selectivity tocarbinol, ethanol and acetone at different temperature is found individually bythis adulteration. The sensitivity of composite material with Ag+doped in to600ppm carbinol reach to45.8at320℃, while the one without Ag+arrives to21.5, only occupying47.6%of the former. To ethanol of600ppm, thesensitivity of composite material （Sn:Ti=12:1） without Ag+as65.7is38% of the one doped with Ag+as25.2at320℃. To acetone of800ppm, thesensitivity of composite material （Sn:Ti=12:1） without Ag+as63.5is83%of the one doped with Ag+as52.7at320℃, which is less distinction thanthose of to carbinol and to ethanol.（3） Different gas-sensitivities of prepared materials to the three gaseswere represented at the conditions of no UV irradiation, of313nm UVirradiation and of365nm UV irradiation. As to carbinol, the maximalsensitivity is obtained as53.6with UV of313nm at the conditiontions thatgas concentration, component of material and working temperature are600ppm, Sn:Ti=19:1within Ag+and280℃, respectively, which is1.9timesof the value tested under the same conditions only without UV irradiation. Asto ethanol, the highest sensitivity is60.6with UV of365nm at the conditionsthat gas concentration, component of material and working temperature are800ppm, Sn:Ti=19:1without Ag+and280℃, respectively, which is1.5times of the one gained under the same conditions only without UVirradiation. That is to say, the sensitivity of the material to some VOCs can beenhanced in certain extent by UV irradiation. As to acetone, however, themaximum of sensitivity is provided from element4#（Sn:Ti=12:1withinAg⁺） of800ppm at240℃with no UV irradiation, which shows a unexpectedirradiation result.（4） The working temperature with UV irradiation is much lower than thatof without UV irradiation when arriving to the same sensitivity. Namely, itcan be decreased by UV irradiation in certain extent. For example, during theexamination of carbinol at600ppm, the working temperature is high to280℃without UV, correspondingly the sensitivity of element1#（Sn:Ti=7:1,withou Ag+） is about2.4, while the result with UV is only120℃at the sameconditions. Compared with240℃by no UV irradiation in experiments of testing600ppm ethanol using by element2#（Sn:Ti=7:1）, the workingtemperature with UV of365nm is low to160℃which is significantly lowerthan the former when corresponding sensitivities of the both two states areapproximately15.8.All the above indicated that, there is a fine sensitivity of nona-compositematerial with TiO₂-SnO₂to VOCs such as carbinol, ethanol and acetone,which can be ultilized in a certain formidable circumstance containing toxicor/and inflammable gases. Besides, with ultraviolet light exsting, thegas-sensitivity of the material is increased and the working temperature of thematerial is desreased. Therefore, it may be the most probability of gasexamination at room temperature by irradiating nona-metal films sensor withultraviolet light, which holds a great protential for study and application.