Publications

An optimized chemical bath method is applied to obtain well-structured thin films with composition Na0.33V2O5·nH2O (n = 1 and 1.3). The method is based on a controlled precipitation reaction that takes place in the system of sodium metavanadate and diethyl sulfate at 85 °C. The film structure, morphology and the changes occurring during prolonged aging are examined by XRD, IR spectroscopy, TG-DTA, SEM and AFM. The electrochemical and electrochromic properties are studied by cyclic voltammetryand UV–vis spectroscopy. The as-deposited thin films are characterized with high optical transmittance varying between 40 and 70% at the 500 nm visible region in dependence on film thickness. The Na0.33V2O5·nH2O thin films exhibit stable electrochemical cycling combined with relatively high electrochromic activity. The reproducibility of the transmittance variance of 55% after 500 cycles in the electrochromic cell is a promising result for the potential application of Na0.33V2O5·nH2O thin films in electrochromic devices.

This article presents a new safe, cheap and attractive microscale gas generation method that is expected to find place in the primary and secondary schools. Microscale gas generation apparatus consists of plastic syringe, Beral pipette and small plastic or glass test tube on a stand. The pipette has a role of a chemical reactor, which generatesgas and delivers it into a test tube where reaction takes place. Gas generation is based on chemical reaction between liquid substance, which is inserted with syringe and needle into the pipette bulb with liquid or solid substance previously placed in it. A large number of interesting and vivid microscale experiments can be performed using this kind of apparatus and many gases can be generated.

A new chemical bath method for deposition of manganese(II) carbonate thin film on electroconductive FTO glass substrates is designed. The homogeneous thin films with thickness in the range of 70 to 500 nm are deposited at about 98 °C from aqueous solution containing urea and MnCl2. The chemical process is based on a low temperature hydrolysis of the manganese complexes with urea. Three types of films are under consideration: as-deposited, annealed and electrochemically transformed thin films. The structure of the films is studied by XRD, IR and Raman spectroscopy. Electrochemical and optical properties are examined in eight different electrolytes (neutral and alkaline) and the best results are achieved in two component aqueous solution of 0.1 M KNO3 and 0.01 M KOH. It is established that the as-deposited MnCO3film undergoes electrochemically transformation into birnessite-type manganese(IV) oxide films, which exhibit electrochromic color changes (from bright brown to pale yellow and vice versa) with 30% difference in the transmittance of the colored and bleached state at 400 nm.

A new chemical method for fast deposition of electrochromically active thin films of birnessite-type potassium manganese oxide (K0.27MnO2·xH2O) has been developed. The chemical deposition has been performed at room temperature by a reaction of aqueous solutions of potassium permanganate and manganese(II) chloride. The prepared thin films have thickness from 50 to 250 nm depending on the number of the deposition cycles. The composition and the structure of the K-birnessite films are studied by XRD, IR spectroscopy and TG/DTA analyses. Electrochemical studies using four different electrolytes such as aqueous K2SO4, Li2SO4, KNO3, and LiClO4 in PC have been performed. The electrochromic activity has been explored by cyclic voltammetry and VIS spectrometry. The best electrochromic properties are obtained using aqueous KNO3, where the difference in the transmittance at 400 nm between the bleached and colored state is 40% for both as-deposited and annealed films. The obtained data allow the prepared K-birnessite thin films in aqueous KNO3 electrolyte to be proposed as a promising system for electrochromic applications.

A new chemical method for fast deposition of electrochromically active thin films of birnessite-type potassium manganese oxide (K0.27MnO2·xH2O) has been developed. The chemical deposition has been performed at room temperature by a reaction of aqueous solutions of potassium permanganate and manganese(II) chloride. The prepared thin films have thickness from 50 to 250 nm depending on the number of the deposition cycles. The composition and the structure of the K-birnessite films are studied by XRD, IR spectroscopy and TG/DTA analyses. Electrochemical studies using four different electrolytes such as aqueous K2SO4, Li2SO4, KNO3, and LiClO4 in PC have been performed. The electrochromic activity has been explored by cyclic voltammetry and VIS spectrometry. The best electrochromic properties are obtained using aqueous KNO3, where the difference in the transmittance at 400 nm between the bleached and colored state is 40% for both as-deposited and annealed films. The obtained data allow the prepared K-birnessite thin films in aqueous KNO3 electrolyte to be proposed as a promising system for electrochromic applications.