Highlights  Molecular functionalized sensors were elaborated by two steps modification.  Characterization of modified sensors was carried out by ATR-FTIR.  Testing the sensors under gases was performed at room temperature.  Ester modified SnO2 sensor was sensitive and selective to ammonia gas.

Abstract:The development of selective and cheap metal oxide gas sensor at ambient temperature is still a challenging idea. In this study, SnO2 surface functionalization was performed in order to obtain sensitive and selective gas sensor operated at ambient temperature. 3-aminopropyltriethoxysilane (APTES) was used as an intermediate step, followed by functionalization with molecules having acyl chloride with different end functional groups molecules such as alkyl, acid and ester groups. Acid and ester modified sensors are sensitive to ammonia between 0.2 and 10 ppm at room temperature. However, ester modified SnO2 is more selective than acid modified sensor regarding ethanol and carbon monoxide gases.

International audienceSurface functionalization has numerous applications worldwide. Silicon oxide has been a research material of choice. However, tin dioxide (SnO₂) films are employed in many applications especially in gas sensors, and little studied in regard to functionalization. Thus, they were chosen to be functionalized via 3-aminopropyltriethoxysilane (APTES). Different synthesis parameters were tested such as APTES grafting by vapor or liquid phases deposition. In liquid, many parameters were investigated: water presence, reaction times, and APTES concentration. The presence and reactivity of grafted amine-terminated film on SnO₂ were carried out by Alexa Fluor® molecules. In addition, APTES grafting was characterized using attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry techniques. These characterizations showed how synthesis parameters affect the amount and thickness of APTES films. Optimal liquid silanization parameters were determined in order to obtain a saturated SnO₂ surface with APTES molecules. Importantly, the addition of 5 vol% H₂O to the APTES solution provided denser surface coverage, by hydrolyzing the ethoxy groups to silanol. An almost 50% improvement over anhydrous liquid and vapor methods was obtained

The feasibility of room temperature ammonia gas sensors based on tin dioxide (SnO 2 ) functionalization has been demonstrated. 3-aminopropyltriethoxysilane (APTES) was used as an intermediate step, followed by functionalization with molecules having acyl chloride with different end functional groups molecules such as alkyl, acid and ester groups. Modified films were characterized by attenuated total reflectance infra-red spectroscopy (ATR-FTIR). Upon exposure to ammonia gas, the electrical conductance of alkyl, acid and ester modified SnO 2 -APTES increases, whereas other reducing gases such as ethanol, carbon monoxide and acetone show no change in conductance. Furthermore, ester modified SnO 2 is more selective than acid modified sensor regarding ethanol and carbon monoxide gases.