ChemPhysChem

On p. 3524 A. Dabirian, P. Hoffmann et al. report on the discovery of chemical vapor deposition (CVD) conditions where both the precursor adsorption and the chemical reaction limit the process. Operating CVD under these conditions has the potential to boost the resolution of laser-assisted CVD processes whereas flux- and desorption-limited conditions appear to be the ideal environment for spatially addressable combinatorial experiments.

The picture shows the temperature-switchable molecular structure of an ionic liquid crystal, confined as a thin film in a porous material. This work is presented on p. 3539 by P. Wasserscheid, J. Libuda, K. Meyer et al.

Shine a light: Synchrotron-based scanning transmission X-ray microspectroscopy (STXM) is reviewed as a tool for in situ examination of polymer microcontainers. The advantages of the STXM technique are highlighted and illustrated with examples of its application to microcapsule and microbubble systems. The picture shows STXM images of air-filled polymer microbubbles in water.

Important interactions: The interactions between two benzene molecules in the parallel orientation are studied by means of crystallographic and computational methods. The results may have interesting applications in the study of systems containing aromatic molecules, including biomolecules and pharmaceuticals. The figure shows the minimum of a benzene dimer at a large offset (optimized geometry with an interaction energy of 2.01 kcal mol⁻¹).

Fast Folding: A combined single-molecule fluorescence resonance energy transfer (smFRET) and microfluidic mixing study reveals that the α-helical subdomain of staphylococcal nuclease (SNase) (see picture) folds about ten times faster than the β-sheet subdomain.

Vibrational circular dichroism spectra allow one to assign the absolute configuration and to monitor the conformational equilibria related to CF₃⋅⋅⋅OH hydrogen bonding of [2.2]paracyclophane with an external stereogenic carbon atom bearing CF₃, OH and H (see picture).

Laser-assisted deposition: The discovery of chemical vapor deposition (CVD) conditions under which the growth rate is a decreasing function of the precursor flux has the potential to boost the resolution of laser-assisted CVD processes whereas flux- and desorption-limited conditions appear to be the ideal environment for spatially addressable combinatorial experiments (see picture).

Better images: A highly sensitive approach for imaging insensitive nuclei, such as silicon-29, using magnetic resonance is presented (see picture, right). Two-dimensional images of natural-abundance silicon-containing solid materials can now be obtained in a reasonable time.

Surfactant-free ZnO quantum dots self-assemble into three-dimensional colloidal crystals in an organic solvent via ionic-strength tuning. The crystalline structure is macroscopically large, transparent, stable and shields UV as bulk ZnO upon solvent removal.

The influence of confinement on the ionic liquid crystal (ILC) [C₁₈C₁Im][OTf] (Im=imidazolium, OTf=trifluoromethanesulfonate) is studied. The ILC is supported on Si-based powders and glasses with pore sizes ranging from 11 to 50 nm. The ILC–supported ionic liquid phase (SILP) materials (see picture) are characterized in terms of their phase-transition temperatures. A contact layer with a thickness of about 2 nm is identified.

The bigger, the stronger: Some azole molecules have the ability to significantly slow down the corrosion of metals. A systematic DFT study is reported with the aim to ascertain how the adsorption characteristics of triazoles evolve as a function of molecular size. According to calculations the molecule–surface bond strength (see picture) increases with increasing molecular size and a sound explanation of why this is so is provided.

Persuasive influence: DFT is used to calculate the Boltzmann-weighted carbon–oxygen and carbon–carbon bond dissociation enthalpies (BDEs) of substituted phenethyl phenyl ethers (PPEs; see picture). Hydrogen bonding between the aliphatic substituents and the ether oxygen in the PPE derivatives has a significant influence on the BDE.

Spin probing thermoresponsive Pluronic triblock copolymers reveals the early onset of static and dynamic inhomogeneities (see picture).

A newly designed magnetic FeNi–Pt nanorod was developed (see picture) by means of growing heterostructured FeNi nanosticks on Pt nanotips. Their reductive reactivity toward chlorinated solvents renders them interesting for application in environmental remediation.

Rationalize to catalyze: The Mo_10−xV_xO_y solid-solution system (0≤x≤10) is studied by electron paramagnetic resonance spectroscopy. Concerning the catalytic activity of this system, the key role of the Mo/V ratio is revealed (see picture). Additionally a quantitative analysis of the [VO²⁺] concentration as a function of the Mo/V ratio allows one to characterize the prevailing defect chemistry.

As easy as pi: The intermolecular interactions in C₆H₆⋅⋅⋅LiX (X=OH, NH₂, F, Cl, Br, NC, CN) complexes were investigated by using second-order Møller–Plesset perturbation theory calculations and quantum theory of “atoms in molecules” studies. The results show that π electrons play a crucial role in the formation of these benzene-containing lithium-bonded complexes (see picture).

Siloxane-based mesogens in which linear and cyclic oligosiloxanes respectively link two and four mesogenic moieties bearing long alkoxy substituents (top left picture) form self-assembled layered structures, such as that depicted top right, which are investigated by techniques such as grazing-incidence small-angle X-ray scattering and atomic force microscopy (bottom left and right, respectively).

Undercover: Carbon nanoparticles have recently emerged as a unique class of optical nanomaterials. This study demonstrates the chromophoric functions of suspended small carbon nanoparticles in harvesting visible photons for the reductive coating of the nanoparticles with silver and gold (see picture) and, as a result, the preparation of unique carbon-metal core–shell nanostructures.

A quartz crystal microbalance method is used for determination of vaporization enthalpies of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids [C_nmim][NTf₂]. In contrast to other data for [C_nmim][NTf₂] reported in the literature, this technique reveals a remarkably linear dependence of the vaporization enthalpies on the chain length n at 298 K (see picture; • this work, other symbols: literature data).

A unified nanothermodynamic model is developed to investigate the predominant factors that determine the lattice thermal conductivity of nanocrystalline, nanoporous, and nanostructured bulk silicon. Comparisons of size-dependent lattice thermal conductivity in these materials are shown in the picture. Through a systematical study, three basic principles are proposed to enhance the thermoelectric performance in nanostructured silicon-based materials.

Amplified emission enhances the sensitivity (50 times more than fluorescence) of optical modulation of emission in a polyfluorene–diarylethene blend. Modulation is obtained through energy transfer from the fluorophore to the photochromic moiety. Experimental measurements and DFT calculations give further information on the underlying physics.

Ways to relax: The dielectric relaxation behavior of D-arabinose–water solutions at different water concentrations and 120–300 K is examined (see picture). Broadband dielectric spectroscopy and FTIR–attenuated total reflectance data validate the hypothesis that above a water content of about x_w=0.20, self-association of water molecules occurs in the aqueous solutions.

No wires required: The nanotube–nanowire transition takes place during both nanotube growth and application. It is observed only in an intermediate chemical dissolution environment. The mechanism is interpreted with a model in terms of stretching and splitting (see picture). The nanowires can be suppressed by surface treatment and those grown for long durations can be removed by ultrasonic cleaning.

Nanoparticle-mediated SERS: The surface-enhanced Raman scattering (SERS) technique was used to characterize the conformational changes of lysozyme adsorbed on octadecanethiol and thiolated PEG monolayers on smooth gold chips (Au-C18 and Au-PEG). The surface roughness required for recording SERS spectra (see picture) was obtained by adding Ag nanoparticles, in the absence of which no Raman signal was detectable.