Luminescence of nanostructured potassium sulfate crystals $ Marat Myrzakhmet n , Gulzipa Sataeva, Seitzhan Yessengali, Galiya Kuralbayeva Eurasian National University, 5 Munaitpasov Street, Astana 010008, Kazakhstan article info Article history: Received 22 October 2014 Received in revised form 9 May 2015 Accepted 28 May 2015 Available online 6 June 2015 abstract The implementation technique of potassium sulfate was developed in a three-dimensional opal lattice by sedimentation method from solution. Samples of potassium sulfate–thallium-opal composites were obtained. Degree of pore filling of opal matrix controlled in two ways: (1) increase in mass of the sample and (2) the shift of the maximum in the optical absorption spectrum filled with potassium sulfate– thallium samples relative to the initial opal matrices. The results obtained by the two methods were similar. The luminescence of the composites was studied. Optimal conditions for the synthesis of opals filled with nanocrystals were identified in terms of getting the maximum luminescence intensity. & 2015 Elsevier B.V. All rights reserved. 1. Introduction One of the most widely used recent methods of synthesis of nanostructures are the so-called method of "soft chemistry" that allows to create a wide range of nanomaterials in solutions using controlled phase formation and crystallization processes (colloidal synthesis, sol–gel method, synthesis in microemulsions) target self-assembly of nano-objects into ordered 2D and 3D assemblies (template synthesis aimed sedimentation, convection self-assem- bly) [1]. Such systems become demanding in the information processing. The development of technologies is required for manufacturing to broadcasting/excitation devices, photo-detectors and light-controlled logic gates. On the other hand, such nanomorphological systems can arise by self-organization, which is the case of naturally occurring material with properties of photonic crystal-precious opal. As a result of long-term research and experiments, carried out in var- ious laboratories of the world, various methods for artificial synthesis of this mineral have been developed. The technology of producing opal matrixes with regular packs is developed highly most fully for silicon dioxide (SiO 2 ). On this basis the three-dimensional characteristic nanocomposites with nanoscale structure are obtained. These structures provide a photonic material properties and formed a whole branch of research in the field of opal photonic crystals [3]. Nanocomposites using the precious opal host were created by filling its regular nanocavities by precious metals, nanocrystals of semiconductors and nanocrystals of crystalline phosphors on the basis of rare-earth ions [1]. So far the ionic nanocrystals with tetrahedrally-coordinated anions or cations have not been used for such a purpose. Tl-doped K 2 SO 4 could be suitable for such a purpose. It is interesting to research the optical properties with decreasing size of crystals (size effects). To do this, we used the pores of opal matrices. Such structures provide photonic material properties and formed an entire branch of research in the field of opal photonic crystals. Previously, we have not seen in the litera- ture to use as a second component of the nanocomposite the ion nanocrystals with tetrahedral anions. 2. Experiment We worked on technological methods of synthesis of opal matrices with the necessary physical and chemical characteristics and predetermined optical properties. The process of obtaining opal matrices can be divided into several stages. At the first stage we performed the hydrolysis of tetraethoxysilane (TEOS) in a hydroalcoholic solution, in one case with an acidic catalyst (nitric acid), and the other catalyst we used an aqueous solution of ammonia, i.e. an alkaline catalyst. It should be noted that the mechanisms of the processes of hydrolysis and condensation in these cases are different. Let us consider the obtaining of sol–gel matrices using TEOS. Ratio of the starting components are in the following ranges: S 2 N 5 OH:H 2 O:H þ /OH À ¼ (1–3):(1–3):(2–4):(0,05–0,2). Then we placed a solution in plastic dishes of various sizes and shapes with subsequent sealing. Gelation process took 20–24 h. Then, the resultant gel suspension of the latex particles, we were separated by centrifugation (4000 rev/min for 10 min). The resulting pre- cipitate was washed off several times with ethyl alcohol and Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence http://dx.doi.org/10.1016/j.jlumin.2015.05.063 0022-2313/& 2015 Elsevier B.V. All rights reserved. ☆ The 17th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter (ICL2014). n Corresponding author. Tel./fax: þ7 7172701247. E-mail address: myrzakh@gmail.com (M. Myrzakhmet). Journal of Luminescence 169 (2016) 804–806