Coordination-driven self-assembly directs a single-crystal-to-single-crystal transformation that exhibits photocontrolled fluorescence

Coordination-driven self-assembly is employed to direct a single-crystal-to-single-crystal [2 + 2] photodimerization that exhibits tunable fluorescence.     

The firefighter problem for graphs of maximum degree three

We show that the firefighter problem is NP-complete for trees of maximum degree three, but in P for graphs of maximum degree three if the fire breaks out at a vertex of degree at most two.     

Determination of metal ion content of beverages and estimation of target hazard quotients: a comparative study

Background  

Considerable research has been directed towards the roles of metal ions in nutrition with metal ion toxicity attracting particular attention. The aim of this study is to measure the levels of metal ions found in selected beverages (red wine, stout and apple juice) and to determine their potential detrimental effects via calculation of the Target Hazard Quotients (THQ) for 250 mL daily consumption.     

Resorcinol-templated synthesis of a cofacial terpyridine in crystalline π-stacked columns

A resorcinol achieves a templated stereospecific and near-quantitative synthesis of a cofacial terpyridine in the solid state. The solid-state synthesis occurs in one-dimensional π-stacked columns with reactivities highly sensitive to peripheral groups attached to the template.     

Site-directed regiocontrolled synthesis of a 'head-to-head' photodimer via a single-crystal-to-single-crystal transformation involving a linear template

Co-crystallisation of 1,8-naphthalenedicarboxylic acid (1,8-nap) with trans-1-(3-pyridyl)-2-(4-pyridyl)ethylene (3,4-bpe) gives a discrete molecular solid-state assembly, 2(3,4-bpe).2(1,8-nap) 1, that is held together by four O-H...N hydrogen bonds wherein the diacid directs a regiocontrolled [2 + 2] photodimerization; the reaction occurs by way of a single-crystal-to-single-crystal transformation.     

Contact line motion and dynamic wetting of nanofluid solutions

The effect that nanoparticles play in the spreading of nanofluids dynamically wetting and dewetting solid substrates is investigated experimentally, using 'drop shape' analysis technique to analyse aluminium-ethanol contact lines advancing and receding over hydrophobic Teflon-AF coated substrates. Results obtained from the advancing/receding contact line analysis show that the nanoparticles in the vicinity of the three-phase contact line enhance the dynamic wetting behaviour of aluminium-ethanol nanofluids for concentrations up to approximately 1% concentration by weight. Two mechanisms were identified as a potential reason for the observed enhancement in spreading of nanofluids: structural disjoining pressure and friction reduction due to nanoparticle adsorption on the solid surface. The observed 'lubricating effect' that the nanoparticles seem to be inducing is similar to the 'superspreading' effect for surfactant solutions spreading on hydrophobic surfaces, up to a concentration (weight) of approximately 1%, could be a result of the predicted enhanced wetting behaviour. Indeed, Trokhymchuk et al. [Langmuir, 2001, 17, 4940] observed a solid-like ordering of nanoparticles in the vicinity of the three-phase contact line, leading to an increased pressure in the fluid 'wedge'. This increased pressure leads to a pressure gradient which causes the nanofluids to exhibit enhanced wetting characteristics. Another possible cause for the observed increase in advancing/receding contact line velocity could be deposition of nanoparticles on the solid surface in the vicinity of the three-phase contact line resulting in the nanofluid effectively advancing over aluminium rather than Teflon-AF, or the contact line 'rolling' over nanoparticles at the three-phase contact line due to sphericity of nanoparticles. For either of these to be the case, the nanoparticle effect at the three-phase contact line would have to be enhanced for the lower concentration in the same way that it would have to be for the increased pressure in the fluid 'wedge'.