Adsorption at a Carbon Black Microparticle Surface in Aqueous Colloids Probed by Optical Second-Harmonic Generation

Abstract

The surface properties of carbon black microparticles in aqueous solution are characterized through adsorption of a hydrophobic ion (malachite green) monitored by optical second-harmonic generation (SHG). Carbon black particle surfaces with 14 different O/C ratios (from 0.028 to 0.270) have been examined. The adsorption isotherm of MG on the surface of carbon black particles weighing as little as 0.010 g can be measured using SHG measured during continuous titration of the MG molecule into the solution. The SHG data allows determination of the adsorption free energy and reveals coherent interference between the SH fields from the surface-adsorbed MG molecules and the carbon black particle. The change in the coherent interference implies a change of adsorption orientation of MG on surfaces with different O/C ratios. There is strong correlation found between the observed adsorption characteristics and the O/C ratio of the surfaces. Furthermore, MG adsorption isotherms of surfaces with higher O/C ratios appear similar to the ones of surfaces preadsorbed with surfactants that can increase surface hydrophilicity and dispersion in aqueous solution. All observations indicate that particle surfaces with higher O/C ratios appear more hydrophilic. This study demonstrates once again the many advantages of SHG as an effective surface analytical technique of colloidal particles.

Simulation of Micro/Nanopowder Mixing Characteristics for Dry Spray Additive Manufacturing of Li-Ion Battery Electrodes

“…Graphite surface energy measurements can be used to gain insight into the surface energy characteristics of carbon, but it may not be representative of the more commonly used CPA material (Carbon Black) due to its significantly larger size ($10 lm). Previous studies [32][33][34] measuring Carbon Black surface energy show a similar low polar component when compared to graphite, but the dispersive component is typically measured at smaller values in the range of 18-35 mN m À1 . An increase in the Carbon Black polar surface energy component can be achieved through surface modification by way of acid-base treatments as detailed by Park et al [35] where the treatments can be used to obtain a polar surface energy component up to 33.1 mN m À1 [36].…”

“…The dots located on the DEM simulation contour plots (Figs. 4(d) and 4(f)) denote previously measured [21,[31][32][33][34][35][36] surface energy values of carbon materials. They are used to show the expected mixing behavior of common carbon-based CPA materials.…”

Probing the colloidal gold nanoparticle/aqueous interface with second harmonic generation

“…The SHG electric field E SHG is proportional to the population of MG on the nanoparticle surface multiplied by the concentration of nanoparticles, N. In Figure 4, E SHG is normalized to its maximum value found at the isotherm's plateau. E SHG of the nanoparticle sample with no MG added is negligible compared to E SHG at the isotherm's plateau, so possible phase-sensitive interferences [38] are neglected. In the Langmuir model, a key assumption is that the bulk concentration of the solute is not reduced by the solute adsorption to the interface.…”

“…Previous SHG studies on the free adsorption of the triphenyl methane dye, malachite green (MG), to the surface of colloidal polystyrene microparticles has allowed the free energy of adsorption as well as the maximum number of adsorbate sites to be determined [29,30]. This SHG research has since been extended to study the adsorption of molecules to a variety of types and sizes of colloidal polymer microparticles and nanoparticles [31][32][33][34][35], clay [36], TiO 2 [37], and carbon black [38] nanoparticles, oil droplets in water [30], as well as phospholipid liposomes bilayer membranes [39,40]. Related work using SHG to measure the surface electrostatic potential [41] and the surface acidity pK a [42] of nanoparticles has also been achieved.…”

Nonlinear light scattering from clusters and single particles

“…9 Within the past 13 years, a rapidly growing number of publications reported on second-order nonlinear light scattering ͑NLS͒ from small particles to probe their surfaces. Second-harmonic scattering ͑SHS͒ was used to probe ͑elec-tronic͒ transitions on particle surfaces in condensed media [9][10][11][12][13][14][15][16][17][18][19] as well as liposomes in solution. 20 Vibrational sum-frequency scattering ͑SFS͒ was performed to measure the molecular interface structure and its solvent dependence on colloids in solution, [21][22][23] as well as inclusions in biodegradable polymer microspheres.…”