@article{PerovicZeiningerOschatz2020, author = {Perovic, Milena and Zeininger, Lukas and Oschatz, Martin}, title = {Immobilization of gold-on-carbon catalysts onto perfluorocarbon emulsion droplets to promote oxygen delivery in aqueous phase (D)-glucose oxidation}, series = {ChemCatChem}, volume = {13}, journal = {ChemCatChem}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1867-3880}, doi = {10.1002/cctc.202001590}, pages = {196 -- 201}, year = {2020}, abstract = {The catalytic activity of metal nanoparticles (NPs) supported on porous supports can be controlled by various factors, such as NPs size, shape, or dispersivity, as well as their interaction with the support or the properties of the support material itself. However, these intrinsic properties are not solely responsible for the catalytic behavior of the overall reaction system, as the local environment and surface coverage of the catalyst with reactants, products, intermediates and other invloved species often play a crucial role in catalytic processes as well. Their contribution can be particularly critical in liquid-phase reactions with gaseous reactants that often suffer from low solubiltiy. One example is (D)-glucose oxidation with molecular oxygen over gold nanoparticles supported on porous carbons. The possibility to promote oxygen delivery in such aqueous phase oxidation reactions via the immobilization of heterogenous catalysts onto the interface of perfluorocarbon emulsion droplets is reported here. Gold-on-carbon catalyst particles can stabilize perfluorocarbon droplets in the aqueous phase and the local concentration of the oxidant in the surroundings of the gold nanoparticles accelerates the rate-limiting step of the reaction. Consequently, the reaction rate of a system with the optimal volume fraction of fluorocarbon is higher than a reference emulsion system without fluorocarbon, and the effect is observed even without additional oxygen supply.}, language = {en} } @article{AntoniouPashalidisGessneretal.2011, author = {Antoniou, Stella and Pashalidis, Ioannis and Gessner, Andre and Kumke, Michael Uwe}, title = {Spectroscopic investigations on the effect of humic acid on the formation and solubility of secondary solid phases of Ln(2)(CO3)(3)}, series = {Journal of rare earths}, volume = {29}, journal = {Journal of rare earths}, number = {6}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1002-0721}, doi = {10.1016/S1002-0721(10)60490-5}, pages = {516 -- 521}, year = {2011}, abstract = {The formation of secondary Ln(III) solid phases (e.g., Nd-2(CO3)(3) and Sm-2(CO3)(3)) was studied as a function of the humic acid concentration in 0.1 mol/L NaClO4 aqueous solution in the neutral pH range (5-6.5). The solid phases under investigation were prepared by alkaline precipitation under 100\% CO2 atmosphere and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), time-resolved laser fluorescence spectroscopy (TRLFS), diffuse reflectance ultraviolet-visible (DR-UV-Vis), Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicated that Nd-2(CO3)(3) and Sm-2(CO3)(3) were stable and remained the solubility limiting solid phases even in the presence of increased humic acid concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system, decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurred, the inorganic (Ln(2)(CO3)(3)) and the organic phase (HA), which was adsorbed on the particle surface of the former. Nevertheless, humic acid affected the particle size of the solid phases. Increasing humic acid concentration resulted in decreasing crystallite size of the Nd-2(CO3)(3) and increasing crystallite size of the Sm-2(CO3)(3) solid phase, and affected inversely the solubility of the solid phases. However, this impact on the solid phase properties was expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere.}, language = {en} }