TY - JOUR A1 - Behnke, Thomas A1 - Würth, Christian A1 - Laux, Eva-Maria A1 - Hoffmann, Katrin A1 - Resch-Genger, Ute T1 - Simple strategies towards bright polymer particles via one-step staining procedures JF - Dyes and pigments N2 - In order to develop simple and versatile procedures for the preparation of red emissive particles, various one-step swelling procedures for the loading of fluorophores into nanometer- and micrometer-sized polystyrene particles were systematically assessed. Parameters studied for model dyes from common dye classes include the composition of the swelling medium, dye charge and polarity, dye concentration, and particle surface chemistry. The dye loading procedures were compared based upon the efficiency of dye incorporation, fluorescence intensity, and colloidal stability of the resulting particles as well as the absence of dye leaking as determined by absorption and fluorescence spectroscopy, flow cytometry, and measurements of zeta potentials. In addition, for the first time, the influence of the amount of incorporated dye on the absolute fluorescence quantum yield and brightness of the fluorescent particles was investigated for selected chromophores in differently sized particles using a custom-made calibrated integrating sphere setup. Our results demonstrate the general suitability of these one-step loading procedures for efficient particle staining with neutral, zwitterionic, and charged fluorophores like oxazines, coumarines, squaraines, xanthenes, and cyanines emitting in the visible and near infrared. Dye polarity was identified as a suitable tool to estimate the loading efficiency of fluorophores into these polymer particles. KW - Fluorescence KW - Polystyrene KW - Particles KW - Encapsulation KW - Quantum yield KW - Zeta potential KW - Method KW - Label KW - Particle KW - Polymer KW - Absolute fluorescence quantum yield KW - Fluorophore KW - Dye content KW - Surface groups KW - Size KW - Brightness PY - 2012 DO - https://doi.org/10.1016/j.dyepig.2012.01.021 SN - 0143-7208 SN - 1873-3743 VL - 94 IS - 2 SP - 247 EP - 257 PB - Elsevier Ltd. CY - Kidlington AN - OPUS4-25481 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Priebe, Nsesheye Susan A1 - Schmidt, Wolfram A1 - Rogge, Andreas A1 - Kühne, Hans-Carsten T1 - Performance of rice husk ash as an alternative binder in a modified cementitious system with added superplasticizers JF - Cement and Concrete Composites Journal N2 - Rice husk as (RHA) is an eco-friendly material, which can be used as a supplementary cementitious material (SCM) in cement and concrete. Due to the high water demand for the material, superplasticizers (SPs) are essential to improve the performance. However, the interaction between the SPs and RHA systems is limited. This paper investigates the interaction of the binders with three SPs, i.e. two polycarboxylate ethers (PCEs) and one lignosulphonate (LS). The investigations are performed on blended systems of mortar containing various percentages of RHA and limestone powder (LSP). LSP is used in this research to improve the workability of the mortar. The results from the zeta potential (ZP) shows that the SPs are extremely dependent on the pH of the suspension. At higher pH values such as in a cementitious system, the ZP becomes less negative indicating that the ions in the suspension interact with the carboxyl groups in the backbone of the polymers thus reducing the surface charges of the SP. The mini-slump flow shows that the workability of the blended mortar systems is significantly improved with the addition of SPs. LS systems with increasing RHA is observed to have similar workability as the control mix over time. The compressive strength test results show increased strength for all mortar specimens with added RHA and LSP at later ages. KW - Compressive strength KW - Rice husk ash KW - Superplasticizers KW - Zeta potential KW - Workability PY - 2017 DO - https://doi.org/10.1016/j.cemconcomp.2017.07.014 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 83 SP - 202 EP - 208 PB - Elsevier Ltd. AN - OPUS4-42602 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pütz, E. A1 - Smales, Glen Jacob A1 - Jegel, O. A1 - Emmerling, Franziska A1 - Tremel, W. T1 - Tuning ceria catalysts in aqueous media at the nanoscale: how do surface charge and surface defects determine peroxidase- and haloperoxidase-like reactivity JF - Nanoscale N2 - Designing the shape and size of catalyst particles, and their interfacial charge, at the nanometer scale can radically change their performance. We demonstrate this with ceria nanoparticles. In aqueous media, nanoceria is a functional mimic of haloperoxidases, a group of enzymes that oxidize organic substrates, or of peroxidases that can degrade reactive oxygen species (ROS) such as H2O2 by oxidizing an organic substrate. We show that the chemical activity of CeO2−x nanoparticles in haloperoxidase- and peroxidaselike reactions scales with their active surface area, their surface charge, given by the ζ-potential, and their surface defects (via the Ce3+/Ce4+ ratio). Haloperoxidase-like reactions are controlled through the ζ-potential as they involve the adsorption of charged halide anions to the CeO2 surface, whereas peroxidase-like reactions without charged substrates are controlled through the specific surface area SBET. Mesoporous CeO2−x particles, with large surface areas, were prepared via template-free hydrothermal reactions and characterized by small-angle X-ray scattering. Surface area, ζ-potential and the Ce3+/Ce4+ ratio are controlled in a simple and predictable manner by the synthesis time of the hydrothermal reaction as demonstrated by X-ray photoelectron spectroscopy, sorption and ζ-potential measurements. The surface area increased with synthesis time, whilst the Ce3+/Ce4+ ratio scales inversely with decreasing ζ-potential. In this way the catalytic activity of mesoporous CeO2−x particles could be tailored selectively for haloperoxidase- and peroxidase-like reactions. The ease of tuning the surface properties of mesoporous CeO2x particles by varying the synthesis time makes the synthesis a powerful general tool for the preparation of nanocatalysts according to individual needs. KW - SAXS KW - Ceria KW - Zeta potential PY - 2022 DO - https://doi.org/10.1039/D2NR03172H SP - 1 EP - 12 PB - Royal Society of Chemistry AN - OPUS4-55649 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wäsche, Rolf A1 - Naito, M. A1 - Hackley, V.A. T1 - Experimental study on zeta potential and streaming potential of advanced ceramic powders JF - Powder technology N2 - Zeta potential as measured with the electrokinetic sonic amplitude (ESA) method has been compared to streaming potential as measured with the particle charge detection (PCD) method. The measurements have been carried out on identical suspensions of a-Al2O3, SiC and Si3N4 with a solids volume fraction of 1% and 10%. Zeta potential and streaming potential are related by a linear function. The correlation coefficients for this relationship are better than 0.99 for the suspensions with 1% solids loading. For the suspensions with 10% solids loading, correlation coefficients are slightly lower due to the influence of increasing viscosity. Regardless of lower correlation at the higher solids loading, the isoelectric pH is constant within the limits of accuracy of the pH measurements. KW - Zeta potential KW - Streaming potential KW - Ceramic powders KW - Correlation of measurement PY - 2002 DO - https://doi.org/10.1016/S0032-5910(01)00462-4 SN - 0032-5910 SN - 1873-328X VL - 123 SP - 275 EP - 281 PB - Elsevier CY - Amsterdam AN - OPUS4-1430 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -