ChemPhysChem

The cover picture illustrates a microfluidic dodecane-in-water emulsion stabilized by the designed peptide surfactant AM1, which forms a cohesive interfacial layer through reversible interaction with Zn^II. Deformed coagulated droplets are stabilized against coalescence in the presence of an elastic interfacial layer, but coalesce rapidly following ZnII chelation with EDTA. A. P. J. Middelberg et al show on page 778 that coalescence rate can be controlled by altering interfacial rheology and hence the dynamics of thin film rupture.

Cool molecules: The cooling of molecules to sub-Kelvin temperatures promises to have a great impact in chemistry and physics. Recently, the first experimental realizations of samples of deeply bound molecules that are approaching the ultracold regime were reported. In this contribution, these interesting results are briefly discussed.

Nonlinearities in atomic vapors allow the production of “entangled images”—beams of light whose transverse light distributions exhibit localized correlations in their unavoidable quantum fluctuations (see picture). These spatially entangled beams may prove useful to reduce the noise in absorption imaging and beam positioning below the quantum noise level, as well as for quantum information applications.

Intramolecular double-hydrogen tunneling in porphycene (see picture) is investigated. Low-temperature conditions are ensured by doping of single molecules into superfluid helium nanodroplets. The investigation of fluorescence excitation and dispersed emission spectra and the highly dissipative environment allows the observation of mode-selective tunneling splitting and reveals a purely concerted tunneling mechanism for all isotopic variants of porphycene.

Reversed photoresponse: Indium tin oxide (ITO)/Au nanoparticle (NP)/TiO₂ electrodes (see picture) exhibit cathodic photocurrents and positive photopotentials under visible light, whereas ITO/TiO₂/Au NP electrodes show an inverted response. This behavior indicates that electron transfer occurs from the plasmon-excited Au NPs to the TiO₂ film. An enhanced O₂ photoreduction activity is found for ITO/Au NP/TiO₂/Pt electrodes.

Polymer conformations: The picture shows instantaneous conformations of product molecules produced in a catalytic reaction at the head of a polymer chain. The extended (left) and collapsed (right) polymers correspond to chains in good and poor solvent conditions, respectively. The product molecule concentration gradient leads to a directed force on the polymer, so that it functions as a self-propelled nanomotor.

Buckypaper-metal composites are prepared by substrate-enhanced electroless deposition of copper onto strips of buckypaper (see picture). Electrical conductivity and mechanical properties of these buckypaper-copper composites at different copper content are investigated. The conductivity is shown to increases by up to 350 %, and the Young's modulus and the ultimate tensile strength of the composites by 282 % and 290 % respectively over pristine buckypaper.

Breaking point: Switchable peptide surfactants are used to demonstrate that the extent of cross-linking in an interfacial surfactant layer can control the rate of emulsion coalescence. Pictured is the rupture of an aqueous thin film where the peptide layer lacks sufficient strength to prevent hole formation, but nonetheless dramatically slows the rate of hole expansion.

The combustion of CH₄ and H₂ in a confined space represents an innovative way to produce heat and power. Burning tests on CH₄/H₂/air mixtures using Pd/NiCrO₄-catalyst-lined SiC monoliths (see picture) show an important reduction of both the ignition temperature and the 100 % conversion temperature in these systems.

Leading light: A series of zinc(II) bis-terpyridine complexes (see picture) is investigated by means of DFT calculations combined with Bader's quantum theory of atoms in molecules. Raman spectroscopy experiments and studies of the electro-optical properties of the complexes in solution and the solid state are also performed to examine their potential as new emissive materials in light-emitting devices.

Looks matter: Generally, the morphology of titania thin films is crucial for their performance, hence much effort is spent to tailor the desired morphology. X-ray scattering enables the monitoring of the crystalline titania layer morphology during build-up of the functional multilayer stack (see Figure). Herein evidence is provided that the morphology is preserved throughout the fabrication process.

Selective DNA detection: The fluorescence, from stable cationic QDs, is quenched by 90% on complexation with modified DNA molecules. The QD–DNA probe is capable of detecting pathogenic DNA fragments at concentrations as low as 200 nM in solution and shows selective fluorescence recovery in the presence of target DNA (see spectrum c in figure) vs noncomplementary DNA (spectrum d).

Positron lifetime spectroscopy serves to determine the void volumes of cucurbituril (CB) capsules, which are not amenable to standard gas adsorption methods. In the case of the host–guest complex Au§CB[7], it also provides evidence of the inclusion of gold nanoparticles in the CB cavity (see space-filling model; Au golden, C gray, H cyan, N blue, O red).

Spin-restricted time-dependent DFT for open-shell systems is used to study the spin multiplicity dependence of nonlinear optical coefficients. Calculations are performed for various spin states of the pyrrole radical (see figure). The results indicate a substantial dependence on spin multiplicity of the NLO properties, which are sensitive to the basis set compared to closed shells at the DFT level of theory.

Molecular dynamics simulations of the structure H (sH) clathrate of tert-butylmethylether show the prevalence of ether–water hydrogen bonding (see picture), absent in the neo-hexane sH clathrate. This affects guest–cage dynamics and host–water dielectric relaxation dynamics. The ¹³C and ¹H NMR relaxation times for both guests are measured, and the differences are explained in terms of guest–host interactions in the two clathrates.

Velocity ion imaging (see figure) is used to analyze the photodissociation mechanism of 1-C₄H₉I (left image) and 2-C₄H₉I (right image) at 266 nm. For 2-C₄H₉I, a new channel for formation of I and I* atoms is observed. It is attributed to the repulsive mode along the CI stretch, coupled with some bending motions.

Vibronic sub-bands in the electronic absorption spectra of symmetrical cyanine dyes (see picture) are attributed to the symmetric CC valence vibration of the polymethine chain in the excited state. The ³J(H,H) coupling constants in the polymethine chain can be used to characterize the bond localization within the chain in the ground state and thus to explain the intensity distribution of the sub-bands.

The right mix: SnO₂:Sb nanocrystals (NCs) can be solubilized into organic solvents with a suitable solvent/surfactant combination to achieve a stable colloid (see picture). A single synthesis route and different solvent/amphiphilic molecule pairs are used to obtain soluble NC colloids, instead of requiring several syntheses to obtain soluble NCs in different solvents.

In a row: Chemical concepts from the spin-polarized conceptual DFT field are used to explain the spectrochemical and nephelauxetic series within a group of ruthenium complexes.