Development of the flow injection method (FIA) for determination the colloidal and ionic silver in water. The newly developed method is based on on-line generation of silver colloids by sodium borohydride (NaBH4). The reaction variables such as the flow rate, length of the mixing coil, volume of the sample loop, concentration and pH of the sodium borohydride, which affect sensitivity were investigated and the experimental setup was optimized. Further improvements in sensigivity of the method were achieved by the use of collinear dual beam thermal lens spectrometric (TLS) detection unit. TLS detection resulted in significant decrease of the limit of detection (LOD) from 50 g/L provided by the transmission mode spectrometry to 1.5 g/L in case of TLS.. The optimized method was applied for the analysis of a drinking water sample provided for the launch of the Automated Transfer Vehicle (ATV) module Jule Verne to the International Space Station (March 9, 2008).
COBISS.SI-ID: 1635323
The goal of this work is to determine the thermo-optical parameters of pure and modified TiO2 thin films (thermal diffusivity and conductivity, optical energy band gap and minority Abstract carrier life time) which were further related to properties determining their photocatalytic activity (surface structure, porosity, volume fraction of introduced atoms). The analysis was performed by the use of photothermal beam deflection spectrometry (PDS) and multiparameter fitting of theoretical dependences to experimental data.
COBISS.SI-ID: 2538747
TiO2 thin films used as photocatalysts in environmental application were studied by beam deflection spectroscopy (BDS) and by atomic force microscopy (AFM). A novel multiparameter theoretical model was developed in order to explain BDS experimental data. The fundamental parameters of examined films: thermal diffusivity, thermal conductivity, and charge transport properties such as the value of energy band gap, carrier life time, concentration and type of dopants, were obtained as results of the modeling of BDS data. With BDS we observed that the material’s thermal conductivity and thermal diffusivity depend also on the porosity and the surface roughness of films. Consequently, we can estimate photocatalytic peformance by measuring the thermal difusivity of films. Furthermore, we found that surface roughness is prone to changes when the film is used as photocatalysts in water purification processes. During purification process the roughness decreases and the photocatlytical performace drops. Moreover, we discovered that the thermal, electrical and morphological properties of photocatalysts films depend on the support to which the TiO2 layer is deposited. These complex relations demonstrate that knowledge of fundamental physical parameters is required in order to improve the photocatalytic performance of TiO2 films. In this view, the BDS measurements offer a tool for noncontact and nondestructive evaluation of thermal and electronic parameters of thin film TiO2 photocatalysts as demonstrated in this work.
COBISS.SI-ID: 2979067
Nanostructured iron(III) oxide deposits are grown by chemical vapor deposition (CVD) at 400−500 °C on Si(100) substrates from Fe(hfa) TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine), yielding the selective formation of α-Fe2O3 or the scarcely studied ε-Fe2O3 polymorphs under suitably optimized preparative conditions. By using Ti(OPri)4 (OPri= iso-propoxy) and water as atomic layer deposition (ALD) precursors, we subsequently functionalized the obtained materials at moderate temperatures ((300 °C) by an ultrathin titanomagnetite (Fe3−xTixO4) overlayer. An extensive multitechnique characterization, aimed at elucidating the system structure, morphology, composition and optical properties, evidenced that the photoactivated hydrophilic and photocatalytic behavior of the synthesized materials is dependent both on iron oxide phase composition and ALD surface modification. The proposed CVD/ALD hybrid synthetic approach candidates itself as a powerful tool for a variety of applications where semiconductor-based nanoarchitectures can benefit from the coupling with an ad hoc surface layer.
COBISS.SI-ID: 2875387
A method for determination of thermooptical, transport and structural parameters of TiO2 based thin films is presented. The measurements were conducted using a beam deflection spectroscopy (BDS) and supporting theoretical analysis performed in the framework of complex geometrical optics providing a novel method of BDS data modeling. It was observed that the material's thermal parameters strongly depend on sample properties determining its photocatalytic activity such as energy band gap, carrier life time, surface structure or porosity. Because of that the fitting procedure of theoretical dependence into experimental data was developed to determine the sample’s thermal parameters, on the basis of which the information about its structure was further found. The obtained results were compared to those based on geometrical and wave optics approaches that are currently widely used for that purpose. It was demonstrated that the choice of proper model for data modeling is a crucial point when performing such type of analysis.
COBISS.SI-ID: 3255803