Determination of Nitrate and Nitrite by Ion-Selective Electrodes in Relation to Gypsum Formation on Some Travertine Buildings in Polluted Atmosphere of Ankara

Abstract

Gypsum formation on calcareous building stones in the polluted atmosphere of cities is thought to be accelerated by the presence of nitrogen-containing compounds. A reliable method for nitrate and nitrite determinations is proposed and the presence of nitrogen compounds is discussed in relation to their possible influence on gypsum formation. Investigations on nitrate and nitrite determinations with ionselective electrodes have been carried out along with gypsum determinations on the samples taken from altered surfaces of some travertine buildings in Ankara. Interfering effects of the ions which may be present in the matrix studied have been examined and the proper masking solutions for their removal have been introduced. Investigations show that nitrate and nitrite determinations with ion-selective electrodes are reliable, rapid and inexpensive in stone extracts. The sulphate to nitrate ratios in this study vary between 32 and 393. These data are compared with earlier results and the possible effects of nitrogen-containing compounds in gypsum formation are discussed.     

Preparation of glutathione loaded nanoemulsions and testing of hepatoprotective activity on THLE-2 cells

To improve bioavailability and stability of hydrophobic and hydrophilic compounds, nanoemulsions are good alternatives as delivery systems because of their nontoxic and nonirritant nature. Glutathione (GSH) suffers from low stability in water, where its encapsulation in nanoemulsions is a powerful strategy to its stability in aqueous systems. The aim of this study was to obtain nanoemulsions from the hydrophobic/hydrophilic contents of N. sativa seed oil so as to improve GSH stability along with bioavailability of N. sativa seed oil. Then, the prepared nanoemulsions were tested for in vitro hepatoprotective activity against ethanol toxicity. To the best of our knowledge, there is no study on the test of nanoemulsions by the combination of Nigella sativa seed oils and GSH in hepatoprotective activity. Here, nanoemulsions with different contents were prepared using Nigella sativa seed oils. Content analyses and characterisation studies of prepared nanoemulsions were carried out. In order to investigate the protective effects against to ethanol exposure, THLE-2 cells were pretreated with nanoemulsions for 2 h with the maximum benign dose (0.5 mg/mL of nanoemulsions). Ethanol (400 mM) was introduced to pretreated cells and nontreated cells for 48- or 72-h periods, followed by cell viability assay was carried out. Fluorescence microscopy tests revealed the introduction of the nanoemulsions into THLE-2 cells. The findings show that nanoformulations have promising in vitro hepatoprotective effects on the THLE-2 cell line against ethanol exposure.     

Synthesis and characterization of organic dyes containing 4,5-diazafluorene as efficient sensitizers for dye-sensitized solar cells

Two dyes which are 4,5-diazafluoren-9-one-derived diimine ligands and their corresponding Ru(II) bipyridine complexes were synthesized. The structures of all compounds were determined by FTIR, UV–Vis, ¹H-NMR, ¹C-NMR, and MS spectroscopic data. The photovoltaic and electrochemical properties of these compounds were investigated and the applicability in DSSCs as photosensitizers was studied. The photovoltaic cell efficiencies (PCE) of the devices were 0.36–1.26% under simulated AM 1.5 solar irradiation of 100 mW/cm², and the highest open-circuit voltage (V_oc) reached 0.34 V. When comparing the photovoltaic performance of DSSC devices, efficiency increases L2 < L2-Ru < L1 < L1-Ru. The PCE value of 1.26% was obtained with a DSSC based on L1-Ru under AM irradiation (100 mW/cm²). DSSC based on L1-Ru produced efficiency of 1.26%, whereas DSSC-based L1 exhibited the device performance with efficiency of 0.84% under illumination. These results show that the availability of a π-conjugated bridge and a richer electron donor for photovoltaic performance of the DSSC provides increased efficiency.     

Sol–gel derived silver-incorporated titania thin films on glass: bactericidal and photocatalytic activity

Titanium dioxide (TiO₂) and silver-containing TiO₂ (Ag-TiO₂) thin films were prepared on silica pre-coated float glass substrates by a sol–gel spin coating method. The bactericidal activity of the films was determined against Staphylococcus epidermidis under natural and ultraviolet (UV) illumination by four complementary methods; (1) the disk diffusion assay, (2) UV-induced bactericidal test, (3) qualitative Ag ion release in bacteria inoculated agar media and (4) surface topographical examination by laserscan profilometry. Photocatalytic activity of the films was measured through the degradation of stearic acid under UV, solar and visible light conditions. The chemical state and distribution of Ag nanoparticles, as well as the structure of the TiO₂ matrix, and hence the bactericidal and photocatalytic activity, is controlled by post-coating calcination treatment (100–650 °C). Additionally, under any given illumination condition the Ag-incorporated films were found to have superior bactericidal and photocataltyic activity performance compared to TiO₂ thin films. It is shown that with optimized thin film processing parameters, both TiO₂ and Ag-TiO₂ thin films calcined at 450 °C were bactericidal and photocatalytically active.     

The self-activated luminescence of ZnS1−xSex

The self-activated luminescence (SA) of ZnS : I, ZnSe : Cl, ZnSe : A1, and some ZnS_1?xSe_x : Cl single crystals has been investigated at LHeT under excitation with light. The SA-luminescence band has been identified in each case by the temperature dependence and by a direct excitation band resulting in polarized emission. Symmetry C_3v in case of ZnS : I and ZnSe : Cl and symmetry C_s in case of ZnSe : A1 for the SA-centre have been unambiguously revealed from angular dependences of polarization. Thus the nearest neigbour-compensated cation-vacancy has been identified as complex responsible for SA-luminescence.