Redetermination of katayamalite, KLi3Ca7Ti2(SiO3)12(OH)2.

The crystal structure of katayamalite, ideally KLi3Ca7Ti2(SiO3)12(OH)2 (potassium trilithium hepta-calcium dititanium dodeca-silicate di-hydroxide), was previously reported in triclinic symmetry (C-1), with isotropic displacement parameters for all atoms and without the H-atom position [Kato & Murakami (1985 ▶). Mineral. J. 12, 206-217]. The present study redetermines the katayamalite structure with monoclinic symmetry (space group C2/c) based on single-crystal X-ray diffraction data from a sample from the type locality, Iwagi Island, Ehime Prefecture, Japan, with anisotropic displacement parameters for all non-H atoms, and with the H atoms located by difference Fourier analysis. The structure of katayamalite contains a set of six-membered silicate rings inter-connected by sheets of Ca atoms on one side and by an ordered mixture of Li, Ti and K atoms on the other side, forming layers which are stacked normal to (001). From the eight different metal sites, three are located on special positions, viz. one K and one Li atom on twofold rotation axes and one Ca atom on an inversion center. The Raman spectrum of kataymalite shows a band at 3678 cm(-1), similar to that observed for hydroxyl-amphiboles, indicating no or very weak hydrogen bonding.

Pirquitasite, Ag(2)ZnSnS(4).

Pirquitasite, ideally Ag(2)ZnSnS(4) (disilver zinc tin tetra-sulfide), exhibits tetra-gonal symmetry and is a member of the stannite group that has the general formula A(2)BCX(4), with A = Ag, Cu; B = Zn, Cd, Fe, Cu, Hg; C = Sn, Ge, Sb, As; and X = S, Se. In this study, single-crystal X-ray diffraction data are used to determine the structure of pirquitasite from a twinned crystal from the type locality, the Pirquitas deposit, Jujuy Province, Argentina, with anisotropic displacement parameters for all atoms, and a measured composition of (Ag(1.87)Cu(0.13))(Zn(0.61)Fe(0.36)Cd(0.03))SnS(4). One Ag atom is located on Wyckoff site Wyckoff 2a (symmetry -4..), the other Ag atom is statistically disordered with minor amounts of Cu and is located on 2c (-4..), the (Zn, Fe, Cd) site on 2d (-4..), Sn on 2b (-4..), and S on general site 8g. This is the first determination of the crystal structure of pirquitasite, and our data indicate that the space group of pirquitasite is I-4, rather than I-42m as previously suggested. The structure was refined under consideration of twinning by inversion [twin ratio of the components 0.91 (6):0.09 (6)].

Lanthanite-(Nd), Nd2(CO3)3·8H2O.

Lanthanite-(Nd), ideally Nd2(CO3)3·8H2O [dineodymium(III) tricarbonate octa-hydrate], is a member of the lanthanite mineral group characterized by the general formula REE2(CO3)3·8H2O, where REE is a 10-coordinated rare earth element. Based on single-crystal X-ray diffraction of a natural sample from Mitsukoshi, Hizen-cho, Karatsu City, Saga Prefecture, Japan, this study presents the first structure determination of lanthanite-(Nd). Its structure is very similar to that of other members of the lanthanite group. It is composed of infinite sheets made up of corner- and edge-sharing of two NdO10-polyhedra (both with site symmetry ..2) and two carbonate triangles (site symmetries ..2 and 1) parallel to the ab plane, and stacked perpendicular to c. These layers are linked to one another only through hydrogen bonding involving the water mol-ecules.

Integrating Fluorescent Nanodiamonds into Polymeric Microstructures Fabricated by Two-Photon Polymerization.

Nitrogen-vacancy (NV) and other color centers in diamond have attracted much attention as non-photobleaching quantum emitters and quantum sensors. Since microfabrication in bulk diamonds is technically difficult, embedding nanodiamonds with color centers into designed structures is a way to integrate these quantum emitters into photonic devices. In this study, we demonstrate a method to incorporate fluorescent nanodiamonds into engineered microstructures using two-photon polymerization (2PP). We studied the optimal concentration of nanodiamonds in the photoresist to achieve structures with at least one fluorescent NV center and good structural and optical quality. Fluorescence and Raman spectroscopy measurements were used to confirm the presence and location of the nanodiamonds, while absorbance measurements assessed scattering losses at higher concentrations. Our results show the feasibility of fabricating microstructures embedded within fluorescent nanodiamonds via 2PP for photonics and quantum technology applications.

Probing the relationships between molecular conformation and intermolecular contacts in N,N-dibenzyl-N'-(furan-2-carbonyl)thiourea.

In the crystal structure of the title compound, C(20)H(18)N(2)O(2)S, molecules are linked by bifurcated C-H···O hydrogen-bond interactions, giving rise to chains whose links are composed of alternating centrosymmetrically disposed pairs of molecules and characterized by R(2)(2)(10) and R(2)(2)(20) hydrogen-bonding motifs. Also, N-H···S hydrogen bonds form infinite zigzag chains along the [010] direction, which exhibit the C(4) motif. Hirshfeld surface and fingerprint plots were used to explore the intermolecular interactions in the crystal structure. This analysis confirms the important role of C-H···O hydrogen bonds in the molecular conformation and in the crystal structure, providing a potentially useful tool for a full understanding of the intermolecular interactions in acylthiourea derivatives.

Redetermination of durangite, NaAl(AsO(4))F.

The crystal structure of durangite, ideally NaAl(AsO(4))F (chemical name sodium aluminium arsenate fluoride), has been determined previously [Kokkoros (1938). Z. Kristallogr.99, 38-49] using Weissenberg film data without reporting displacement parameters of atoms or a reliability factor. This study reports the redetermination of the structure of durangite using single-crystal X-ray diffraction data from a natural sample with composition (Na(0.95)Li(0.05))(Al(0.91)Fe(3+) (0.07)Mn(3+) (0.02))(AsO(4))(F(0.73)(OH)(0.27)) from the type locality, the Barranca mine, Coneto de Comonfort, Durango, Mexico. Durangite is isostructural with minerals of the titanite group in the space group C2/c. Its structure is characterized by kinked chains of corner-sharing AlO(4)F(2) octa-hedra parallel to the c axis. These chains are cross-linked by isolated AsO(4) tetra-hedra, forming a three-dimensional framework. The Na(+) cation (site symmetry 2) occupies the inter-stitial sites and is coordinated by one F(-) and six O(2-) anions. The AlO(4)F(2) octa-hedron has symmetry -1; it is flattened, with the Al-F bond length [1.8457 (4) Å] shorter than the Al-O bond lengths [1.8913 (8) and 1.9002 (9) Å]. Examination of the Raman spectra for arsenate minerals in the titanite group reveals that the position of the band originating from the As-O symmetric stretching vibrations shifts to lower wavenumbers from durangite, maxwellite [ideally NaFe(AsO(4))F], to tilasite [CaMg(AsO(4))F].

Robertsite, Ca(2)Mn(III) (3)O(2)(PO(4))(3)·3H(2)O.

Robertsite, ideally Ca(2)Mn(3)O(2)(PO(4))(3)·3H(2)O [calcium manganese(III) tris-(orthophosphate) trihydrate], can be associated with the arseniosiderite structural group characterized by the general formula Ca(2)A(3)O(2)(TO(4))(3)·nH(2)O, with A = Fe, Mn; T = As, P; and n = 2 or 3. In this study, single-crystal X-ray diffraction data were used to determine the robertsite structure from a twinned crystal from the type locality, the Tip Top mine, Custer County, South Dakota, USA, and to refine anisotropic displacement parameters for all atoms. The general structural feature of robertsite resembles that of the other two members of the arseniosiderite group, the structures of which have previously been reported. It is characterized by sheets of [MnO(6)] octa-hedra in the form of nine-membered pseudo-trigonal rings. Located at the center of each nine-membered ring is a PO(4) tetra-hedron, and the other eight PO(4) tetra-hedra sandwich the Mn-oxide sheets. The six different Ca(2+) ions are seven-coordinated in form of distorted penta-gonal bipyramids, [CaO(5)(H(2)O)(2)], if Ca-O distances less than 2.85 Šare considered. Along with hydrogen bonding involving the water mol-ecules, they hold the manganese-phosphate sheets together. All nine [MnO(6)] octa-hedra are distorted by the Jahn-Teller effect.

Direct Femtosecond Laser Printing of Silk Fibroin Microstructures.

Fabrication of functional silk fibroin microstructures has extensive applications in biotechnology and photonics. Considerable progress has been made based on lithographic methods and self-assembly approaches. However, most methods require chemical modification of silk fibroin, which restricts the functionalities of the designed materials. At the same time, femtosecond laser-induced forward transfer (fs-LIFT) has been explored as a simple and attractive processing tool for microprinting of high-resolution structures. In this paper, we propose the use of LIFT with fs-pulses for creating high-resolution structures of regenerated silk fibroin (SF). Furthermore, upon adding Eu3+/Tb3+ complexes to SF, we have been able to demonstrate the printing by LIFT of luminescent SF structures with a resolution on the order of 2 µm and without material degradation. This approach provides a facile method for printing well-defined two-dimensional (2D) micropatterns of pure and functionalized SF, which can be used in a wide range of optical and biomedical applications.