Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat Optical properties of nanocomposite fibrous polymer mats containing SbSeI nanowires M. Nowak a , M. Kępińska a , T. Tański b,* , W. Matysiak b , P. Szperlich a , D. Stróż c a Institute of Physics – Center for Science and Education, Silesian University of Technology, Krasińskiego 8 St., 40-019, Katowice, Poland b Institute of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego 18a St., 44-100, Gliwice, Poland c Institute of Material Science, University of Silesia, 75 Pułku Piechoty 1A St., 41-500, Chorzów, Poland ARTICLE INFO Keywords: Mats of nanofibers Polyacrylonitrite nanofibers Antimony selenoiodide Optical parameters Diffusive transmission and reflectance ABSTRACT For the first time, the optical parameters of mats of polymeric, polyacrylonitrite (PAN) nanofibers containing ferroelectric and semiconducting antimony selenoiodide (SbSeI) are presented. The novel material has been made by electrospinning. The SbSeI nanowires, used as the filler, have been prepared sonochemically using elemental Sb, Se and I 2 in the presence of ethanol under ultrasonic irradiation (20 kHz, 565 W/cm 2 ) at 323 K within 2 h. The products have been characterized by using techniques, such as powder X-ray diffraction, scan- ning electron microscopy, energy dispersive X-ray analysis, high-resolution transmission electron microscopy and selected area electron diffraction. The spectral characteristics of diffusive transmission and reflectance of PAN/SbSeI mats have been measured at room temperature to determine absorption and scattering coefficients. The absorption spectrum of PAN/SbSeI has been least square fitted with the theoretical dependence appropriate for the sum of the indirect allowed absorption with an absorption/emission of phonons without excitons and a constant absorption term. The indirect allowed optical energy gap of PAN/SbSeI has the value E gIa = 1.59 (1) eV. 1. Introduction Recently, antimony selenoiodide (SbSeI), one of the chalcohalide ferroelectric semiconductors that belongs to SbSI-type materials [1–4], has been the subject of growing interest due to its optical properties and interesting applications, for example, in X-ray and γ-ray detection [5], in solar cells [6–8], and in optoelectronics [9,10]. It should be noted that a new pathway using 1D SbSeI nanostructures with highly desired properties has been demonstrated [9,10]. While optical properties of bulk SbSeI have been investigated and analyzed in a lot of papers, e.g. [11–16], the absorption characteristics of SbSeI nanowires have been reported only a few times [4,17,18]. The bulk SbSeI crystals are a well-known ferroelectric semi- conductor, possessing a needle-like shape along the [001] axis, coin- ciding with the ferroelectric (polar) c-axis of the orthorhombic cell [1–4]. Such morphology is possibly due to the inherent double chain- type structure of [(SbSeI) ∞ ] 2 and its growth habit. The [(SbSeI) ∞ ] 2 structures consist of two chains related by a twofold screw axis and linked together by short and strong Sb–Se covalent bonds [2,3]. The iodine ions are in ionic bonds with covalently bound bridges (SbSe) + . Crystallization of [(SbSeI) ∞ ] 2 chains tends to occur along the c-axis, favoring the stronger covalent and ionic bonds over the relatively weak, inter-chain van der Waals forces. The aim of this paper is to investigate, for the first time, the optical properties of composite consisting of polymeric, polyacrylonitrite (PAN) nanofibers filled with SbSeI nnanowires. This new material has been made by the electrospinning applying technique used for the fabrication of composite nanofibers filled by semiconductor/dielectric materials [19–21] and composite of mats of PAN/SbSI (antimony sul- foiodide) electrospun nanofibers obtained by the authors [22]. When polymeric nanofibers are spinned, it is convenient to add into them components in the form of ferroelectric and/or piezoelectric nano- particles with very high values of piezoelectric and pyroelectric coef- ficients along their length. Although such opportunity is given by SbSeI, to the best of our knowledge, filling nanofibers with SbSeI has never been reported before. 2. Experimental details The route of preparing PAN/SbSeI nanofibers can be summarized as follows. First of all, the gel of SbSeI was prepared sonically from the constituents (the elements Sb, Se and I 2 ) weighed in a stoichiometric https://doi.org/10.1016/j.optmat.2018.07.012 Received 21 February 2018; Received in revised form 18 June 2018; Accepted 5 July 2018 * Corresponding author. E-mail address: tomasz.tanski@polsl.pl (T. Tański). Optical Materials 84 (2018) 383–388 0925-3467/ © 2018 Elsevier B.V. All rights reserved. T