Higher polythionic acids – the precursors for formation of thallium sulphide layers on polyethylene surface

Abstract

The method of thallium sulphide thin films deposition on low density polyethylene (LDPE), based on applying solutions of higher polythionic acids (H2SnO6, n = 21, 33, 45) was developed and investigated. The concentration of sulphur in LDPE film increases with the increase of temperature of higher polythionic acid solution and its sulphurity , as well as the duration of retention of LDPE in its solution is prolonged.. The sulphur concentration in the PE film under the same duration of sulphurisation and repetition of treatment cycles insignificantly changes. When the sulphurised LDPE was treated with thallium Tl(I) salt solution, the sulphur present in the polymer reacts with thallium ions and the layers of thallium sulphides, TlxSy, of different composition are formed. Stoichiometric composition of the layer changes from Tl0.1S to Tl2.6S. The amount of thallium increases in sulphide layers when the number of the cycles of LDPE sulphurisation in H2S33O6 solution and treatment of sulphurised polymer with Tl(I) salt solution is increased. The stoichiometric composition of TlxSy coats of one treatment cycle samples changes from Tl0.5S to Tl1.1S, X-ray diffraction analysis of the polyethylene, treated with the solution of higher polythionic acid, H2S33O6, and then with Tl(I) salt solution, confirmed the premise that on the LDPE surface the layers of thallium sulphides, TlxSy, are formed. Five phases of thallium sulphides were identified: TlS, Tl2S, Tl2S2, Tl4S3 and Tl2S5. The TlS phase prevailed in diffractograms. Chemical and phase composition of TlxSy layers surface (up to 1 nm depth) is identified by X-ray photo-electronic spectroscopy analysis. The analysis data confirmed that the compounds of TlS, Tl2S, Tl2SO4, Tl(OH)3, S8 and Tl2O3 are formed on the surface of the layers. Morphology of thallium sulphides layers and mechanism of their formation is determined by means of scanning atomic force and electronic microscopy. Two processes take place during the formation of layer: desorption of sulphur and reaction of thallium ions from thallium(I) salt solution with the sulphur present on the LDPE surface. The layer of thallium sulphides is forming on the surface of sulphur layer. Deposition of thallium sulfide films from the solution of higher polythionic acid on the LDPE films no homogeneous, separated island type morphology. Identified regularities let purposively choose the conditions for sulphurisation of LDPE films by using the solution of higher polythionic acid as the agent of polymer sulphurisation in order to compose the layers of thallium sulphides, TlxSy, of desired chemical and phasic composition on the surface of this polymer by means of sorption-diffusion method.

Patobulintas ir tyrinėtas talio sulfidų plonų sluoksnių nusodinimo ant žemo tankio polietileno (LDPE), naudojant aukštųjų politionato rūgščių (H2SnO6, n = 21, 33, 45) tirpalus, metodas. Sieros koncentracija LDPE plėvelėse didėja didinant rūgšties tirpalo temperatūrą, jos sieringumą ir išlaikymo tirpale trukmę. Kai sierintas polimeras veikiamas Tl(I) tirpalu, siera, esanti polimere, reaguoja su talio jonais, susidaro skirtingos sudėties talio sulfidų TlxSy sluoksniai. Rentgeno struktūrinė analizė LDPE patvirtino TlxSy sluoksnių susidarymą. Identifikuotos penkios talio sulfidų fazės: TlS, Tl2S, Tl2S2 , Tl4S3 ir Tl2S5 . TlS fazė dominuoja sluoksniuose. Cheminė ir fazinė TlxSy sluoksnių sudėtis taip pat identifikuota rentgeno fotoelektronine spektroskopija. Ji parodė, kad sudarytuose sluoksniuose yra TlS, Tl2S, Tl2SO4 , Tl(OH)3 , S8 ir Tl2O3 junginių. Talio sulfidų sluoksnių ir jų susidarymo mechanizmas nustatyti atominės jėgos mikroskopijos metodu, kuris parodė, kad vyksta du procesai – sieros desorbcija ir talio druskos tirpalo sąveika su siera LDPE paviršiuje. Talio sulfidų sluoksniai nėra homogeniški, t. y. atskirų salelių pavidalo. Sudarant norimos cheminės ir fazinės sudėties talio sulfidų sluoksnius sorbciniu-difuziniu metodu nustatyti dėsningumai įgalina tikslingai parinkti LDPE plėvelių sierinimo, naudojant aukštąsias politionato rūgštis, sąlygas.