Quantification of purine basis in their mixtures at femto-molar concentration levels using FT-SERS

Surface-enhanced Raman scattering spectroscopy represents one of the unique techniques for studying nanoscale objects, and its distinctive properties can be used in the process of further analysis. The careful evaluation of the particular influence of selected key-role experimental parameters (e.g. pH value of measured sample mixture, size and distribution of used nanoparticles) and the influence of reduction agent used in the process of formation of desired nanoparticle objects presents an important task in the further study of surface-enhanced Raman scattering effect. A broad study of these experimental parameters was performed in this paper. The main aim of the presented work was to a demonstrate an application potential of selected experimental conditions in the determination of three purine bases: adenine, xanthine, and hypoxanthine. The resulting limits of detection are at femtomolar concentration levels for all three studied compounds

Capillary isotachophoresis for separation of silver nanoparticles according to size

Capillary isotachophoresis (ITP) was used for the separation of Ag nanoparticles according to their size. For this purpose, ethanol–water dispersions of Ag nanoparticles stabilized by gelatin were prepared. The ITP separations were performed in a column-coupling system filled with two electrolytes with a pH of leading electrolytes of 7.1 (system I – LE: 10 mM HNO3, ε-aminocaproic acid, TE: 10 mM caproic acid) and 4.5 (system II – LE: 10 mM HNO3, imidazole, TE: 5 mM 2-(N-morpholino)ethanesulfonic acid). In both electrolyte systems the four main peak-mode zones of Ag nanoparticles migrating at zone boundaries were identified, however, the better separation was achieved by the system II. The Ag nanoparticle dispersions were also examined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The zeta potential and thickness of gelatin double layers adsorbed on the nanoparticles were found to depend on pH. The TEM analysis revealed four size fractions of 4 nm, 10 nm, 16 nm and 22 nm, which correspond to the zones separated by ITP. Other migration zones of the electrolyte systems, such as impurities and/or products of the nanoparticle synthesis, served as spacers and separated the peak zones of the Ag nanoparticles.Web of Science573591365913

Nanocomposite of montmorillonite and silver nanoparticles: Characterization and application in catalytic reduction of 4-nitrophenol

Silver ions previously intercalated into a montmorillonite (MMT) interlayer were reduced by sodium borohydride forming a nanocomposite of MMT and silver nanoparticles (Ag–MMT) with no other stabilizing additives. Within 360 min no coagulation of an aqueous Ag–MMT dispersion was observed. However, after 24 h the coagulation was indicated by a red shift of absorption maximum from 408 nm to 434 nm and by broadening of the absorbance band. The nanocomposite was characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and measurements of specific surface area (SSA). It contained 4.94 wt. % of silver. Ag nanoparticles with an average size of 6.9 nm were located on the external MMT surface, mostly in its pores. Ag–MMT was used as a catalyst for reduction of 4-nitrophenol with sodium borohydride forming 4-aminophenol. After 30 s the reaction kinetics changed from zero order to first order, which was explained by means of the Langmuir–Hinshelwood model. The whole reduction was completed after 290 s. During this time min. 95 wt. % of Ag nanoparticles stayed fixed on the MMT support.Web of Science1402-349849

Hydrogenation of CO2 on Nanostructured Cu/FeOx Catalysts: The Effect of Morphology and Cu Load on Selectivity

The aim of this work was to study the influence of copper content and particle morphology on the performance of Cu/FeOx catalysts in the gas-phase conversion of CO2 with hydrogen. All four investigated catalysts with a copper content between 0 and 5 wt% were found highly efficient, with CO2 conversion reaching 36.8%, and their selectivity towards C1 versus C2-C4, C2-C4=, and C5+ products was dependent on catalyst composition, morphology, and temperature. The observed range of products is different from those observed for catalysts with similar composition but synthesized using other precursors and chemistries, which yield different morphologies. The findings presented in this paper indicate potential new ways of tuning the morphology and composition of iron-oxide-based particles, ultimately yielding catalyst compositions and morphologies with variable catalytic performances