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Selective, robust and cost-effective chemical sensors for detecting small volatile-organic compounds (VOCs) have widespread applications in industry, healthcare and environmental monitoring. Here we design a Pt(II) pincer-type material with selective absorptive and emissive responses to methanol and water. The yellow anhydrous form converts reversibly on a subsecond timescale to a red hydrate in the presence of parts-per-thousand levels of atmospheric water vapour. Exposure to methanol induces a similarly-rapid and reversible colour change to a blue methanol solvate. Stable smart coatings on glass demonstrate robust switching over 104 cycles, and flexible microporous polymer membranes incorporating microcrystals of the complex show identical vapochromic behaviour. The rapid vapochromic response can be rationalised from the crystal structure, and in combination with quantumchemical modelling, we provide a complete microscopic picture of the switching mechanism. We discuss how this multiscale design approach can be used to obtain new compounds with tailored VOC selectivity and spectral responses. [ABSTRACT FROM AUTHOR]

The crystal structure of the mineral zdenekite NaPbCu[sub 5](AsO[sub 4])[sub 4]Cl · 5H[sub 2]O was established (Bruker SMART CCD diffractometer, synchrotron radiation, λ = 0.6843 Å, R = 0.096 for 1356 reflections). Single-crystal X-ray diffraction study demonstrated that zdenekite belongs to the monoclinic system with the unit-cell parameters a = 10.023(7) Å, b = 19.55(1) Å, c = 10.023(6) Å, β = 90.02(1)°, sp. gr. P2[sub 1]/n, Z = 4. The structure consists of polyhedral layers parallel to the (010) plane. These layers are formed by Cuφ[sub 5] polyhedra (φ = O, Cl, H[sub 2]O) and AsO[sub 4] tetrahedra. Distorted Na octahedra and Pb 7-vertex polyhedra and H[sub 2]O molecules coordinated to these metal atoms are located between the layers. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The crystal structure of strontium hilgardite, CaSr[B[sub 5]O[sub 9]]C1 H[sub 2]O, was established by the method of X-ray diffraction analysis (synchrotron radiation; diffractometer equipped with a position-sensitive detector; λ = 0.688 Å; 3191 reflections with F > 4σ(F); R = 0.045 in the anisotropic approximation). The triclinic unitcell parameters are as follows: a = 6.5732(6) Å, b = 6.4445(6) Å, c = 6.3693(6) Å, α = 60.995(2)°, β = 61.257(2)°, γ= 77.191(2)° sp. gr. P1; Z= 1. The Ca and Sr atoms were found to be disordered over two positions. The structures of strontium hilgardite and hilgardite-1A differ in the configurations of the seven-vertex Sr- and Ca(2)-polyhedra. The structure solved in this work is consistent with two series of borates studied previously. One of these groups involves pentaborates with different degrees of hydration of borate complexes, and the second group includes Sr-containing borates. [ABSTRACT FROM AUTHOR]

Presents research which effected phase-contrast imaging of the domain structure of a ferroelectric material, lithium niobate. Impact of a varying refractive index across a wavefront; Effect of lattice distortions; Creation of a periodically domain-inverted structure; Lattice distortion across the domain walls; Usefulness of the phase-contrast imaging technique.