Experimental design applied to spin coating of 2D colloidal crystal masks: a relevant method?

Monolayers of colloidal spheres are used as masks in nanosphere lithography (NSL) for the selective deposition of nanostructured layers. Several methods exist for the formation of self-organized particle monolayers, among which spin coating appears to be very promising. However, a spin coating process is defined by several parameters like several ramps, rotation speeds, and durations. All parameters influence the spreading and drying of the droplet containing the particles. Moreover, scientists are confronted with the formation of numerous defects in spin coated layers, limiting well-ordered areas to a few micrometers squared. So far, empiricism has mainly ruled the world of nanoparticle self-organization by spin coating, and much of the literature is experimentally based. Therefore, the development of experimental protocols to control the ordering of particles is a major goal for further progress in NSL. We applied experimental design to spin coating, to evaluate the efficiency of this method to extract and model the relationships between the experimental parameters and the degree of ordering in the particles monolayers. A set of experiments was generated by the MODDE software and applied to the spin coating of latex suspension (diameter 490 nm). We calculated the ordering by a homemade image analysis tool. The results of partial least squares (PLS) modeling show that the proposed mathematical model only fits data from strictly monolayers but is not predictive for new sets of parameters. We submitted the data to principal component analysis (PCA) that was able to explain 91% of the results when based on strictly monolayered samples. PCA shows that the ordering was positively correlated to the ramp time and negatively correlated to the first rotation speed. We obtain large defect-free domains with the best set of parameters tested in this study. This protocol leads to areas of 200 μm(2), which has never been reported so far.     

Remarkably high catalytic activity of the Ru(III)(edta)/H2O2 system towards degradation of the azo-dye Orange II

The Ru(III)(edta)/H(2)O(2) system (edta(4-) = ethylenediaminetretaacetate) was found to degrade the azo-dye Orange II at remarkably high efficiency under ambient conditions. Catalytic degradation of the dye was studied by using rapid-scan spectrophotometry as a function of [H(2)O(2)], [Orange II] and pH. Spectral analyses and kinetic data point towards a catalytic pathway involving the rapid formation of [Ru(III)(edta)(OOH)](2-) followed by the immediate subsequent degradation of Orange II prior to the conversion of [Ru(III)(edta)(OOH)](2-) to [Ru(IV)(edta)(OH)](-) and [Ru(V)(edta)(O)](-)via homolysis and heterolysis of the O-O bond, respectively. The higher oxidation state Ru(IV) and Ru(V) complexes react three orders of magnitude slower with Orange II than the Ru(III)-hydroperoxo complex. In comparison to biological oxygen transfer reactions, the Ru(edta) complexes show the reactivity order Compound 0 ? Compounds I and II.     

Thermodynamic and kinetic studies on the interaction of Ru(III)(edta) with NO in an ionic liquid

The aim of this study was to determine rate constants for the release of NO from an iron(II) nitrosyl complex dissolved in a typical imidazolium-based ionic liquid, [emim][dca], using an NO trapping technique combined with stopped-flow measurements. The anionic component of the selected ionic liquid, viz. [dca] (dicyanamide), was found to coordinate to the Ru(III)(edta) complex used as trapping agent, and hindered its successful application. Further investigations in aqueous solution revealed thermodynamic and kinetic data for the formation of the [Ru(III)(edta)(dca)](2-) complex and its reaction with NO to form the corresponding nitrosyl complex. The results obtained under conditions similar to those in the ionic liquid indicated a much slower formation of the nitrosyl complex in [emim][dca] compared to that reported for the formation of this complex in aqueous medium.     

Ion-specific hydration effects: Extending the Poisson-Boltzmann theory

In aqueous solutions, dissolved ions interact strongly with the surrounding water and surfaces, thereby modifying solution properties in an ion-specific manner. These ion-hydration interactions can be accounted for theoretically on a mean-field level by including phenomenological terms in the free energy that correspond to the most dominant ion-specific interactions. Minimizing this free energy leads to modified Poisson-Boltzmann equations with appropriate boundary conditions. Here, we review how this strategy has been used to predict some of the ways ion-specific effects can modify the forces acting within and between charged interfaces immersed in salt solutions.     

Gossip in Organizations

Three hypotheses about the effects of different informal social network structures on gossip behavior are developed and tested. Gossip is defined as a conversation about a third person who is not participating in the conversation. Having analyzed the costs and benefits of gossip, we prefer the coalition hypothesis.~It states that gossip will flourish in social networks that have a relatively large number of coalition triads, that is ego and alter having a good relationship amongst themselves and both having a bad relationship with tertius, the object of gossip. Two rivalling hypotheses are developed. The constraint hypothesis predicts that the inclination towards gossip is greater, the larger the number of structural holes in the personal network of the gossipmonger.~The closure hypothesis predicts that more gossip will be found in networks with a large number of closed triads, that is where both gossipmonger and listener have a good relationship with the absent third person. The hypotheses are tested using a newly developed instrument to measure gossip behavior and network data from six work organizations and six school classes. The data support the coalition hypothesis and do not support the two rivalling hypotheses.