# Synthesis and Features of Luminescent Bromo- and Iodohectorite Nanolay Materials
## Materials and Methods
### Characterization  
The crystal structure and purity of the Br-Hec and I-Hec were investigated by X-ray powder diffraction (XPD) measurements at room temperature (RT) with a Huber G670 Guinier camera (Huber, Rimsting, Germany), using an image plate detector and Cu K\({}_{\alpha 1}\) radiation. The crystallite size was calculated with the Scherrer formula [23; 24; 25].  
The chemical bonds formed at the molecular level of both nanoclays were studied with FTIR measurements. The spectra were determined at RT in the range of 400-4000 cm\({}^{-1}\) using a Bruker Vertex 70 spectrometer (Bruker Optics Scandinavia AB, Solna, Sweden) equipped with a RT-DLaTGS detector and a VideoMVPT Diamond ATR accessory. For each spectrum, a total of 320 interferograms were co-added using 4 cm\({}^{-1}\) as resolution. For the diamond as internal reflection element in the attenuated total reflection (ATR) method, the limitation is as follows: intrinsic absorption from approximately 2300 to 1800 cm\({}^{-1}\) limits its usefulness in this region (gives in this range only 5% transmission).  
The qualitative compositions of the Br- and I-Hec were analysed through X-ray fluorescence spectroscopy (XRF) with a Panalytical Epsilon 1 apparatus (Panalytical, Almelo, The Netherlands), using Ag K\({}_{\alpha}\) radiation (22.16 keV), and a high-resolution Si drift detector (with a typical energy resolution of 135 eV at 5.9 keV/1000 cps).  
The chemical environment around the Si\({}^{\text{IV}}\) cations of the Br-Hec and I-Hec was studied with solid-state \({}^{29}\)Si MAS NMR spectroscopy. The spectra were recorded for 24 h at room temperature with a Bruker AV400 spectrometer (Bruker, Fallanden, Switzerland) using a 10,000 Hz spinning rate and a 60 s relaxation time. The parts per million scale was calibrated against tetramethylsilane (TMS) at 0.00 ppm, designated by the equipment.  
The surface area and porosity of both nanoclays were determined by nitrogen sorption at 77 K, measured through a TriStar 3000 apparatus (Micromerities, Norcross, GA, USA). The surface area was calculated with the Brunauer-Emmett-Teller (BET) method [26]. The volume of the mesopores was estimated using the total adsorbed amount at a relative pressure \(p/p^{0}=0.97\)[27].  
The thermal stability of the Br-Hec and I-Hec was studied with a TA Instruments SDT Q600 simultaneous TGA-DSC apparatus (TA Instruments, New Castle, DE, USA). Approximately 20 mg of each material was heated from 25 to 1000 \({}^{\circ}\)C in flowing N\({}_{2}\) (rate flow: 100 cm\({}^{3}\) min\({}^{-1}\), heating rate: 10 \({}^{\circ}\)C min\({}^{-1}\)). An empty aluminum oxide crucible was used as the reference material, and similar crucibles were used as sample pans.  
The visual appearance of both materials was recorded with photos taken with a Canon EOS 60 D camera (Canon, Tokyo, Japan), which has 18 megapixel resolution and 5.3 fps shooting speed. The emission and excitation spectra as well as luminescence decay curves were measured at RT with an Agilent Varian Cary Eclipse spectrophotometer (Agilent, Santa Clara, CA, USA), using a 150 W Xe lamp as the excitation source.