Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Carbon-based electrode loaded with Y-doped SrTiO 3 perovskite as support for enzyme immobilization in biosensors E. Rosa Silva a,b,* , J.V. Nicolini c , L. Yamauchi Jr. a , T.M. Machado a , M. Curi d , J.G. Furtado b , A.R. Secchi a , H.C. Ferraz a a Chemical Engineering Program, COPPE, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro, Brazil b Electrical Energy Research Center, CEPEL, 21941-911, Rio de Janeiro, Brazil c Chemical Engineering Department, Universidade Federal Rural do Rio de Janeiro, 23890-000, Seropédica, Brazil d School of Chemistry and Food, Universidade Federal do Rio Grande, 96203-000, Rio Grande, Brazil ARTICLE INFO Keywords: Electrical properties Perovskites Sensors Electrodes ABSTRACT Many studies have been presented Y-doped SrTiO 3 as a potential alternative material for electrical, electro- chemical and chemical applications due to its mixed (ionic and electronic) conduction and its morphological characteristics. In this work, 8% mol yttrium doped SrTiO 3 (YST08) was used to assemble a Horseradish per- oxidase (HRP) biosensor aiming at hydrogen peroxide (H 2 O 2 ) detection. The perovskite was characterized by X- ray diffraction (XRD), Brunauer–Emmett–Teller N 2 physisorption (BET), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS); and, after HRP immobilization, by zeta potential, atomic force microscopy (AFM), cyclic voltammetry, Fourier-transform infrared spectroscopy (FTIR), and chron- oamperometry. The structure presented a low specific surface area due to particle agglomeration as a result of the elevated temperature of calcination. This characteristic was ratified by SEM analysis, which also demon- strated regular and well-rounded grains. Zeta potential results suggest successful HRP immobilization on YST08 surface because of the resemblance of zeta potential of immobilized sample and free HRP. FTIR spectra and AFM micrographs confirm a homogenous HRP adsorption due to functional groups identification and surface topo- graphy changes. YST08 + HRP electrode proved to be efficient in sensing H 2 O 2 in different scan rates and background electrolytes under electrochemical evaluation. Results also showed that the process is surface- controlled, exhibiting a low reduction potential for H 2 O 2 around -0.31 V at pH = 7. The YST08 matrix was effective to the diffusion mechanisms presenting a detection limit of 14.97 μM; and increases the enzyme long- term activity, retaining 14.97% of specific capacity after 180 days. 1. Introduction Perovskite oxides are a large family of compounds with general formula ABO 3 , where A and B represent cations, (A atoms are larger than B in most stable perovskites) and O represents oxygen atoms [1]. One of the most important perovskite materials is strontium titanate (SrTiO 3 ), a semiconductor with mixed ionic-electronic conductivity that can be improved by doping processes with rare-earth or transition metal elements. Different cations can be used to dope perovskites such as Nb 5+ [2], Y 3+ [3], and La 3+ [4], creating extrinsic semiconductors with a predominance of electrons carriers (n-type) or Co 3+ , Fe 3+ [5], and Cr 3+ [6], generating extrinsic semiconductors with hole carriers predominance (p-type). Due to the nature of the chemical bonds be- tween Sr +2 , Ti +3 /Ti +4 [7] and O -2 , oxygen vacancies, its mixed conductivity and its large band gap, pure and doped strontium titanate can be applied in several areas as: solid oxide fuel cells [8], gas sensors [9,10], catalysts [11,12], capacitors [13,14] and great potential of using in the biosensing field [15]. Immobilization of enzymes on a solid support to prepare biosensors should be able to preserve the enzyme secondary structure and con- formation. Furthermore, it should provide a biocompatible and inert environment, besides allowing substrate and product to diffuse to/from the active site [16–18]. The objective of biosensors is the detection of different compounds such as glucose [15], cholesterol [19], bacterial substances [20], nucleic acids [21] and hydrogen peroxide (H 2 O 2 )[22]. This last one has been arousing the interest of many researchers because H 2 O 2 is coproduced in many biochemical reactions catalyzed by oxi- doreductase enzymes (such as glucose oxidase) [23] and it is considered https://doi.org/10.1016/j.ceramint.2019.10.077 Received 13 August 2019; Received in revised form 26 September 2019; Accepted 9 October 2019 * Corresponding author. Chemical Engineering Program, COPPE, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro, Brazil. E-mail address: eduardosilva@peq.coppe.ufrj.br (E. Rosa Silva). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: E. Rosa Silva, et al., Ceramics International, https://doi.org/10.1016/j.ceramint.2019.10.077