Optochemical sensors using electrodeposited polyaniline films: Electrical bias enhancement of reflectance response

Autor(es)

Pedroza Dias Mello, Hugo Jose Nogueira ^[1] ; Mulato, Marcelo ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Fac Philosophy Sci & Letters Ribeirao Preto, Dept Phys, BR-14040901 Ribeirao Preto, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: SENSORS AND ACTUATORS B-CHEMICAL; v. 213, p. 195-201, JUL 5 2015.
• Citações Web of Science: 7

Resumo

A bias-enhanced reflective optochemical pH sensor with electrochromic polyaniline is presented. Polyaniline films were prepared by electrodeposition process, controlling the total amount of deposited charge by varying the deposition time. The electrochromic property of polyaniline was the main parameter for sensor development. A quick and easy reflective spectra measurement process was obtained using a handset spectrophotometer in the visible region. A film deposited for 120 min presented a linear response (sensitivity of 25/pH and linearity of 97%) for the integrated reflectance in the green band of the spectrum after insertion in buffer solutions with pH ranging from 2 to 8. The reflectance intensity increased by 92% for the applied bias voltage of 1000 mV. Sensitivity of the sensors increased by about 28% (32/pH) with applied bias voltage of 700 mV, and decreased by about 9% (29/pH) with applied bias voltage of 1000 mV. A corresponding slight decrease in linearity by about 4% (93%) was observed with applied bias voltage of 700 mV, which preserves the linearity value within a good range for use. The linearity decreases by about 20% (78%) with applied bias voltage of 1000 mV. Both facts together indicate the presence of an optimal operation point. The improvement in sensor performance is related to the bias effect over polyaniline protonation/deprotonation. The electrochromic property of the polyaniline films were investigated using the CIE L{*}a{*}b{*} color scale. The data indicated changes from the emeraldine base oxidation state of polyaniline, which is blue, in alkali medium, to the emeraldine salt conducting, which is green, in acid medium. Handset spectrophotometers can be used with PANI optochemical pH sensors working with reflective spectra. (C) 2015 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 14/09562-4 - Biossensores microeletrônicos associados a técnicas eletroquímicas
• Beneficiário: Marcelo Mulato
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 09/09163-4 - Desenvolvimento de microsensores magnéticos tipo fluxgate em tecnologia planar
• Beneficiário: Marcelo Mulato
• Modalidade de apoio: Auxílio à Pesquisa - Regular