Flexible Impedimetric Electronic Nose for High-Accurate Determination of Individual Volatile Organic Compounds by Tuning the Graphene Sensitive Properties

Abstract

We investigated functionalized graphene materials to create highly sensitive sensors for volatile organic compounds (VOCs) such as formaldehyde, methanol, ethanol, acetone, and isopropanol. First, we prepared VOC-sensitive films consisting of mechanically exfoliated graphene (eG) and chemical graphene oxide (GO), which have different concentrations of structural defects. We deposited the films on silver interdigitated electrodes on Kapton substrate and submitted them to thermal treatment. Next, we measured the sensitive properties of the resulting sensors towards specific VOCs by impedance spectroscopy. We obtained the eG- and GO-based electronic nose composed of two eG films- and four GO film-based sensors with variable sensitivity to individual VOCs. The smallest relative change in impedance was 5% for the sensor based on eG film annealed at 180 °C toward 10 ppm formaldehyde, whereas the highest relative change was 257% for the sensor based on two-layers deposited GO film annealed at 200 °C toward 80 ppm ethanol. At 10 ppm VOC, the GO film-based sensors were sensitive enough to distinguish between individual VOCs, which implied excellent selectivity, as confirmed by Principle Component Analysis (PCA). According to a PCA-Support Vector Machine-based signal processing method, the electronic nose provided identification accuracy of 100% for individual VOCs. The proposed electronic nose can be used to detect multiple VOCs selectively because each sensor is sensitive to VOCs and has significant cross-selectivity to others.

Layer-by-Layer Deposited Multi-Modal PDAC/rGO Composite-based Sensors

“…The oxygen-containing functional groups break the ultra-long distance conjugated large π-bonds on the graphene surface, reducing the electron migration rate. The removal of oxygen-containing functional groups, although generating defects, caused the electron migration rate to rebound [10,36]. The formation of defects during the reduction was confirmed here using Raman spectroscopy.…”

“…The effective response of PDAC/GO films to methanol is a combination of PDAC and rGO contributions. The mechanism of the response of rGO to VOC has been explained by filling the defects on the rGO surface, resulting in interrupted long-range charge transport and increased resistance [10]. We note that studied sensors responded well to rising methanol concentration, but it was not the case with acetone.…”

“…For this reason, the research in sensing technologies is very active. For example, different solutions have been found as temperature sensors [7], humidity sensors [8], VOCs sensors [9][10][11], metal ions [12][13], as well as for pesticides and other contaminants [14][15]. In all these applications, sensitive materials based on conductive polymers and carbon materials play very important roles as they are cheap, affordable, and environmentally benign.…”

Wearable Sensors Based on Graphene Nanoplatelets Reinforced Polydimethylsiloxane for Human Motion Monitoring: Analysis of Crack Propagation and Cycling Load Monitoring

“…Furthermore, the development of carbon nanotube (CNT)-based polydimethylsiloxane (PDMS) nanocomposites showed a great potential for the detection of methylparaben (MePRB), a representative preservative for cosmetics [3]. In addition, graphene has been used as a base material for field-effect transistor sensors, showing a high sensitivity [4], and its use for the detection of volatile organic compounds (VOCs) has been also explored, showing its capability for VOCs detection in a selective way [5]. Furthermore, their use as chemiresistors for the detection of NO 2 have been also explored, reaching very high chemi-resistive responses [6].…”

Nanosensor Based on Thermal Gradient and Machine Learning for the Detection of Methanol Adulteration in Alcoholic Beverages and Methanol Poisoning

“…Therefore, chemoresistors are usually joined in arrays called electronic noses, which exploit different materials to obtain good selectivity [ 22 , 23 ]. The interest in electronic noses leads to the study of the most innovative materials, such as graphene and graphene oxide, and the use of algorithms such as the support vector machine (SVM) allows one to obtain good quantitative results [ 24 ]. Most resistive electronic noses use different metal oxides (SnO 2 , ZnO, WO 3 ) and different surface decorations with metal nanoparticles (Ag, Pt, Pd) to obtain good performance also in the detection of ethanol and methanol [ 25 ].…”