Environmental pollution is one of the worldwide issues, consequently, there is a vital demand to detect and monitor the pollutants which contribute to health problems. Various volatile organic compounds (VOC) are directly responsible for environmental pollutions. In fact, organic pollutants are largely used in industries and every day VOC's emissions are released by the industries to the environment. Among VOC, ethanol is the most common organic pollutant which affects the environment and human health. The detection and quantification of ethanol is urgent for the air quality monitoring and for the quality control of food as well as for breath tests [1-2]. Metal oxide nanostructures are commonly used as chemical sensors for the detection of ethanol in the 10-50 ppm range but all these materials operate at high temperature. Currently developed ethanol sensors operating at room temperature (RT) are capable to detect ethanol at high concentration levels, in a range of 10000 - 50000 ppm [3]. Therefore, the development of ethanol sensor, operating at RT, is a challenge for the research community. In this framework, we present an ethanol device based on a graphene-like (GL) layers, operating at RT. Graphene and graphene related materials (GRM) have been widely explored for the fabrication of gas sensors because of their high conductivity, large specific surface areas, high stability, controllable thickness and tunable performances [4]. Graphene-like (GL) layers are a recently developed carbon-based material [5, 6] and belongs to the graphene related materials (GRM) family. Recently, GL layers have been produced under mild conditions and in aqueous environment through a two steps oxidation/reduction method starting from a nanostructured carbon black. [5-6]. The GL layers undergo to self-assembling in thin film on surfaces after drying, driven by the instauration of hydrophobic interactions between the graphenic layers, as typically observed in reduced graphite oxide. Thanks to the presence of residual oxygen functional groups, mainly carboxylic groups, as confirmed by X-ray Photoemission Spectroscopy (XPS, Fig. 1 a)), atomically flat self-assembly over large areas is enabled at low pH (AFM, Fig. 1 b)). For the fabrication of the sensing layer, 500 ?L of a 1mg/mL GL suspension at pH 3.7 were then deposited onto interdigitated electrodes patterned onto alumina substrate (Fig. 2 a)) and allowed to dry in order to assure morphological uniformity of the dried film. The device was introduced into the gas testing chamber and exposed to 50 ppm of ethanol at RT in dry N2, setting the voltage at 1 V. The sensing mechanism is based on the change of the electrical conductivity induced by the adsorption or desorption of molecules on the surface [7]. From the literature, pristine graphene emerges as totally insensitive to ethanol; surprisingly, GL material is responsive to this analyte, exhibiting a conductance variation equal to 3% (Fig. 2 b)). This result is even more astonishing when compared to the detection limits of other devices operating at RT, reported in the literature [3]. The explanation might lie in the presence of residual oxygen functional groups, mainly carboxylic groups. To investigate in depth this aspect, morphological and structural analyses are currently ongoing. References [1] S. B. Khan, M. Faisal, M. M. Rahman and A. Jamal, Sci. Tot. Environ. 409, 2011, pp. 2987-2992. [2] Han, Sun-Kee and Hang-Sik Shin, International Journal of Hydrogen Energy, 29, 2004, pp. 569-577. [3] A. Aziz, H. N. Lim, S. H. Girei, M. H. Yaacob, M. A. Mahdi, N. M. Huang, A. Pandikumar, Sensors and Actuators B: Chemical 206, 2015, pp. 119-125. [4] M. Inagaki, Carbon, 50, 2012, pp. 3247-3266. [5] M. Alfè, V. Gargiulo, R. Di Capua, F. Chiarella, J.-N. Rouzaud, A. Vergara and Anna Ciajolo, ACS Appl. Mater. Interfaces, 4, 2012, pp. 4491-4498. [6] M. Alfè, V. Gargiulo, R. Di Capua, Applied Surface Science 353, 2015, pp. 628-635. [7] O. Leenaerts, B. Partoens and F.M. Peeters, Phys. Rev. B, 77, 2008, 125416.
GRAPHENE-LIKE SENSING FILM FOR ETHANOL DETECTION
M Alfè;V Gargiulo;
2016
Abstract
Environmental pollution is one of the worldwide issues, consequently, there is a vital demand to detect and monitor the pollutants which contribute to health problems. Various volatile organic compounds (VOC) are directly responsible for environmental pollutions. In fact, organic pollutants are largely used in industries and every day VOC's emissions are released by the industries to the environment. Among VOC, ethanol is the most common organic pollutant which affects the environment and human health. The detection and quantification of ethanol is urgent for the air quality monitoring and for the quality control of food as well as for breath tests [1-2]. Metal oxide nanostructures are commonly used as chemical sensors for the detection of ethanol in the 10-50 ppm range but all these materials operate at high temperature. Currently developed ethanol sensors operating at room temperature (RT) are capable to detect ethanol at high concentration levels, in a range of 10000 - 50000 ppm [3]. Therefore, the development of ethanol sensor, operating at RT, is a challenge for the research community. In this framework, we present an ethanol device based on a graphene-like (GL) layers, operating at RT. Graphene and graphene related materials (GRM) have been widely explored for the fabrication of gas sensors because of their high conductivity, large specific surface areas, high stability, controllable thickness and tunable performances [4]. Graphene-like (GL) layers are a recently developed carbon-based material [5, 6] and belongs to the graphene related materials (GRM) family. Recently, GL layers have been produced under mild conditions and in aqueous environment through a two steps oxidation/reduction method starting from a nanostructured carbon black. [5-6]. The GL layers undergo to self-assembling in thin film on surfaces after drying, driven by the instauration of hydrophobic interactions between the graphenic layers, as typically observed in reduced graphite oxide. Thanks to the presence of residual oxygen functional groups, mainly carboxylic groups, as confirmed by X-ray Photoemission Spectroscopy (XPS, Fig. 1 a)), atomically flat self-assembly over large areas is enabled at low pH (AFM, Fig. 1 b)). For the fabrication of the sensing layer, 500 ?L of a 1mg/mL GL suspension at pH 3.7 were then deposited onto interdigitated electrodes patterned onto alumina substrate (Fig. 2 a)) and allowed to dry in order to assure morphological uniformity of the dried film. The device was introduced into the gas testing chamber and exposed to 50 ppm of ethanol at RT in dry N2, setting the voltage at 1 V. The sensing mechanism is based on the change of the electrical conductivity induced by the adsorption or desorption of molecules on the surface [7]. From the literature, pristine graphene emerges as totally insensitive to ethanol; surprisingly, GL material is responsive to this analyte, exhibiting a conductance variation equal to 3% (Fig. 2 b)). This result is even more astonishing when compared to the detection limits of other devices operating at RT, reported in the literature [3]. The explanation might lie in the presence of residual oxygen functional groups, mainly carboxylic groups. To investigate in depth this aspect, morphological and structural analyses are currently ongoing. References [1] S. B. Khan, M. Faisal, M. M. Rahman and A. Jamal, Sci. Tot. Environ. 409, 2011, pp. 2987-2992. [2] Han, Sun-Kee and Hang-Sik Shin, International Journal of Hydrogen Energy, 29, 2004, pp. 569-577. [3] A. Aziz, H. N. Lim, S. H. Girei, M. H. Yaacob, M. A. Mahdi, N. M. Huang, A. Pandikumar, Sensors and Actuators B: Chemical 206, 2015, pp. 119-125. [4] M. Inagaki, Carbon, 50, 2012, pp. 3247-3266. [5] M. Alfè, V. Gargiulo, R. Di Capua, F. Chiarella, J.-N. Rouzaud, A. Vergara and Anna Ciajolo, ACS Appl. Mater. Interfaces, 4, 2012, pp. 4491-4498. [6] M. Alfè, V. Gargiulo, R. Di Capua, Applied Surface Science 353, 2015, pp. 628-635. [7] O. Leenaerts, B. Partoens and F.M. Peeters, Phys. Rev. B, 77, 2008, 125416.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
