Vol.:(0123456789) SN Applied Sciences (2020) 2:1849 | https://doi.org/10.1007/s42452-020-03662-6 Research Article Correlation of photocatalytic activity and defects generated in Ca 2+ ‑based heterojunctions Ubirajara Coleto Jr 1,2  · Rafael A. C. Amoresi 3  · Chrystopher A. M. Pereira 1  · Bruna W. Schmidt 1  · Isabela M. Iani 1  · Alexandre Z. Simões 3  · Elias S. Monteiro 1  · Elson Longo 4  · Maria A. Zaghete 1  · Leinig A. Perazolli 1 Received: 10 July 2020 / Accepted: 12 October 2020 / Published online: 21 October 2020 © Springer Nature Switzerland AG 2020 Abstract In this work a new semiconductor based on calcium heterojunction (CaO/CaTiO 3 ) was evaluated to the optical properties correlated to crystalline lattice defects. The heterojunctions of the semiconductor were prepared by the sol–gel route and its formation was confrmed by the intimate contact inter face between crystalline phases. Morphology and elemental composition of the nanometric heterojunction were evaluated. Chemical environment and composition of the surface were used to determine the oxidation state of the material constituents. The electronic structure was evaluated and the relationship among band gap energy, photoluminescent emission energy, and photocatalytic activity of the materials was demonstrated. Oxygen vacancies located on the surface promoted photoluminescent spectra emission in the green wavelength, making them more photoactive than those defects that emitted in the red region. The use of active species scavenger indicated that the photogenerated species with the greatest photocatalytic action was the superoxide radical. This study has developed calcium heterojunctions for application as photocatalysts, demonstrating the importance of the defects generated in the production of heterojunctions and the activity of photogenerated species, studied using scavengers. Keywords Heterojunctions · Structural defects · Oxygen vacancies · Photocatalysis · Scavenger 1 Introduction It is extremely important for new devices to evaluate how the defects present in a crystalline lattice of semiconduc- tor oxides infuence the most diverse properties (electri- cal, optical, sensor, magnetic). Studies have shown that the composition of perovskite doping applied to the solar cell improves its performance due to the trapping of defects on the surface of the materials [1, 2]. In the same sense, materials applied to the anti-reflective coating have shown their performance is related not only to the composition but also to the type of defect generated in the structure [3–5]. Among the numerous applications, the photocatalytic also has features closely related to the presence of defects. In the fght against increasing water pollution, environmental remediation by photocatalysis has been a focus of the scientifc community [6–8]. Highly photoactive materials that act in water decontamination have structural defects such as oxygen vacancies [9–13]. One way to generate structural defects is through the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42452-020-03662-6) contains supplementary material, which is available to authorized users. * Ubirajara Coleto Jr , biracoleto@ifsp.edu.br | 1 LIEC - Chemistry Institute, São Paulo State University - UNESP, Araraquara, SP 14800-060, Brazil. 2 Department of Chemistry, Federal Institute of São Paulo - IFSP, Catanduva, SP 15808-305, Brazil. 3 Faculty of Engineering of Guaratinguetá, UNESP, Guaratinguetá, SP 12516-410, Brazil. 4 LIEC - Department of Chemistry, São Carlos Federal University - UFSCar, São Carlos, SP 13565-905, Brazil.