Sodium Tungsten Oxide Bronze Nanowires Bundles in Adsorption of Methylene Blue Dye under UV and Visible Light Exposure

This paper describes the analysis and characterization of NayWOx bronze nanowires bundles and evaluation of their effective adsorption of methylene blue dye (MB). The Na-doped WOx bronze nanowires bundles were first synthesized via a simple solvothermal method, which were then fully characterized by using different techniques including TEM, XRD, XPS and UV-Vis, to validate the successful Na+ insertion into the WOx framework. The adsorption activities of the resulting NayWOx bronze nanowires bundles, compared with the undoped WOx form, were investigated by evaluating the adsorption effect on methylene blue under both UV and visible light irradiations. An enhanced adsorption performance of the Na-doped WOx bronze samples was recorded, which demonstrated a 90% of removal efficiency of the MB under different conditions (dark, visible and UV light). Moreover, the NayWOx bronze samples also offered a 4 times better kinetic rate of MB removal than the plain WOx nanowires.

ELECTROCHEMICAL SYNTHESIS OF TUNGSTEN OXIDE BRONZE POWDERS

Химическим анализом установлено, что при электрохимическом восстановлении в расплавах MWO -WO (M - Li, Na, K, Cs,Tl) образуются оксидные вольфрамовые бронзы различного состава и структуры. Изучена зависимость изменения равновесных потенциалов катодных продуктов от температуры и состава расплава. Установлено, что с увеличением содержания щелочного металла в вольфраматных расплавах число зародышей кристаллов уменьшается. Снижение температуры расплава и увеличение катодной плотности тока также приводит к уменьшению размеров зерен катодных осадков, что позволяет получать порошки оксидных вольфрамовых бронз контролируемой дисперсности. Методами рентгеноэлектронной спектроскопии и каналирования были исследованы структура конденсированных в среднем вакууме тонких пленок, а также монокристаллы натрийвольфрамовых бронз электрохимически циклированных в анодном и катодном режимах для получения информации о толщине окрашивающего слоя. Chemical analysis established that during electrochemical reduction in MWO - WO (M - Li, Na, K, Cs,Tl) melts, tungsten oxide bronzes of various compositions and structures are formed. The dependence of the change in the equilibrium potentials of cathode products on the temperature and composition of the melt has been studied. It was found that with an increase in the content of alkali metal in tungsten melts, the number of crystal nuclei decreases. A decrease in the melt temperature and an increase in the cathode current density also lead to a decrease in the grain size of the cathode deposits, which makes it possible to obtain powders of tungsten oxide bronzes of controlled dispersion.

Probing Compositional Order in Atomic Columns: STEM Simulations Beyond the Virtual Crystal Approximation

Taking advantage of recent advances in parallel computing, we studied compositional disorder along metal–oxygen atomic columns in a complex Mo,V-oxide bronze using multislice frozen-phonon calculations. Commonly, the virtual crystal approximation (VCA) is used to model compositional disorder at crystallographic sites in a unit cell for a number of different theoretical and experimental techniques. In the VCA, a weighted linear sum of atomic properties is used to approximate the model structure. When using the VCA, the extracted V content of Mo,V–O columns from experimental high-angle annular dark-field (HAADF) images will be about half the V content estimated from simulations, considering the distinct cation ordering. This discrepancy is larger than the spread of HAADF signals of different configurational orders at a given V concentration, which can be up to 20%. Certain “isophilic” atomic arrangements along the column can be distinguished from more random ones using HAADF-STEM imaging. The trends and ratios of the simulated intensity spreads due to different compositional ordering along 11 M–O columns along the c-axis of the Mo,V oxide bronze qualitatively match those observed in experimental HAADF-STEM data. Instrumental and sample-based noise adds to the variability but does not significantly distort the relative ratios of column intensity variation. We observed that we only required seven random configurations to represent the intensity variations along columns.

Sodium titanium oxide bronze nanoparticles synthesized via concurrent reduction and Na+-doping into TiO2(B)

Topotactic reduction of TiO2(B) with NaBH4 accompanies sodium-ion intercalation and oxygen-deficiency formation, resulting in conductive NaxTiO2−δ bronze nanoparticles.