Navegando por Assunto "Buckypaper"

Agora exibindo 1 - 2 de 2

Acesso aberto (Open Access)
Desenvolvimento de "língua eletrônica" nanoestruturada baseada em buckypaper e seu uso para autenticação de bebidas etílicas
(Universidade Federal do Pará, 2023-03-06) FERREIRA, Luiza de Marilac Pantoja; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637; https://orcid.org/0000-0003-2226-2653; BARBOSA NETO, Newton Martins; http://lattes.cnpq.br/3177694073540758; https://orcid.org/0000-0001-9082-5433
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.
Acesso aberto (Open Access)
Sensor quimiorresistor baseado em nanotubos de carbono para detecção de éter-amina
(Universidade Federal do Pará, 2025-06-25) FERREIRA, Débora Ely Medeiros; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637; HTTPS://ORCID.ORG/0000-0003-2226-2653; CORREA PABÓN, Rosa Elvira; http://lattes.cnpq.br/1410157252579591; https://orcid.org/0000-0002-0635-9095
The development of nanostructured sensors has become highly relevant for the detection of chemical and biological substances, as they require small concentrations and offer easy handling. In the context of detecting and reusing flocculants in iron ore flotation, Buckypapers (BPs) based on functionalized Multi-Walled Carbon Nanotubes (MWCNTs) were employed to serve as sensing elements in the investigation of samples containing deionized water (DW), ether-amine (EA), and salts (AlCl₃, FeO₄·7H₂O, CaCl₂·2H₂O, MgCl₂·6H₂O) at different pH levels. Morphological characterization of the BPs using Scanning Electron Microscopy revealed an aggregated organization of carbon nanotubes (CNTs), which appeared randomly distributed on the phenolic surface. Through chemoresistive testing, electrical resistance measurements over time (R × t) were obtained. The results, based on the sensor response (as a percentage increase) over time (seconds) for three cycles—each with 0.1 μL of the solutions prepared from DW, EA, sodium hydroxide (NaOH), and salts—showed that the sensor was able to distinguish between the solutions and their pH differences. It exhibited specific response (%), response time (s), and recovery time (s) for each solution tested. A notable increase in sensor response was observed with rising pH, with the solution containing 30 ppm EA + salts (pH 9.63) reaching an average response of 20.14%, an average response time of 188.60 s, and an average recovery time of 154.91 s, indicating that the sensor is more sensitive in alkaline environments. Vibrational analysis by Raman spectroscopy revealed sub-bands around the D band resulting from the chemical functionalization and solubilization processes of the MWCNTs, as well as sub-bands near the G band associated with vibrations of the inner and outer nanotube walls. For samples containing EA and salts, the results indicated charge transfer between the ether-amine and the outer layers of the CNTs in the BP. The presence of metallic salts influenced the G band profile, altering electron density and causing local distortions. Principal Component Analysis (PCA) showed that the distribution of scores could distinguish the 30 ppm EA samples with higher pH (9.76 and 10.70) and 30 ppm EA + salts (pH 9.63) from the NaOH samples (pH 9.80 and 10.74) and salt-only samples (pH 4.73 and 9.77), indicating the system's detection and differentiation capability toward ether-amine, NaOH, and salts. Thus, the nanostructured sensor demonstrated relevant results for EA detection and potential application in the industry to recover unutilized EA.