Desenvolvimento de "língua eletrônica" nanoestruturada baseada em buckypaper e seu uso para autenticação de bebidas etílicas

Abstract

The development of electronic gadgets has become of great relevance for the detection of fraud in beverages such as wine, as illegal practices involving the addition of exogenous substances such as alcohol and dilution with water pose risks to human health as well as economic impacts. Thus, in this study, Buckypapers (BPs) films were developed based on pure Multi-Walled Carbon Nanotubes (pure-MWCNTs) and functionalized with Carboxylic Acid (COOH-MWCNTs) deposited through vacuum filtration on cellulosic filter paper for application as an element sensor in the analysis of ethylic beverages based grapes and açaí (unadulterated and adulterated with 1.0, 2.5, 5.0, 7.5 and 10% distilled water and ethyl alcohol). The morphological characterization of BPs by Scanning Electron Microscopy indicates the formation of dispersed COOH-MWCNTSs agglomerates on the surface and between the cellulosic fibers of the paper, as well as poor adhesion and non-uniform deposition of highly agglomerated pure-MWCNTs. Electrical resistance measurements were performed as a function of time (R × t) using the two-tip method, at room temperature, adding the analytes to the surface of the sensor element samples using a micropipette. The analysis of the response obtained through normalized relative resistance curves demonstrates a different behavior for BP-COOH-MWCNTs, obtaining a positive variation in the presence of Port and Açaí wines adulterated with water and a negative variation for adulteration with ethyl alcohol. Such behaviors were not observed in the BP-pure-MWCNTs, showing that the responses originate from the polar interactions established between the COOH groups and the adulterant molecules added to the wines, culminating in pronounced performance parameters for the BP-COOH-MWCNTs (response maximum of 5.67 ± 1.82 for unadulterated açaí ethyl beverage and maximum response and recovery times of 37.33 min and 50.58 min for Port wine adulterated with 5.0 and 10% distilled water, respectively). Data processing by PCA showed the ability of BP-COOH-MWCNTs to discriminate and recognize analytes and adulterants, indicating its potential application as a chemoresistive sensor element of low cost, easy handling and real-time response in an “Internet of Things” (IoT) device composing a nanostructured “electronic tongue” for ethyl beverage authentication.