Ferroelectric C* phase induced in a nematic liquid crystal matrix by a chiral non-mesogenic dopant

We report on a ferroelectric chiral smectic C (C*) phase obtained in a mixture of a nematic liquid crystal (NLC) and a chiral nonmesogenic dopant. The existence of C* phase was proven by calorimetric, dielectric and optical measurements, and also by X-rays analysis. The smectic C* which is obtained in such a way can flow, allowing to restore the ferroelectric liquid crystal layer structure in the electro-optical cells after action of the mechanical stress, as it happens with the cells filled with NLC. The proposed method of obtaining smectic C* material allows us to create innovative electro-optical cell combining the advantages of NLC (mechanical resilience) and smectic C* (high switching speed

Nitrogen control in nanodiamond produced by detonation shock-wave-assisted synthesis

Development of efficient production methods of nanodiamond (ND) particles containing substitutional nitrogen and nitrogen-vacancy (NV) complexes remains an important goal in the nanodiamond community. ND synthesized from explosives is generally not among the preferred candidates for imaging applications owing to lack of optically active particles containing NV centers. In this paper, we have systematically studied representative classes of NDs produced by detonation shock wave conversion of different carbon precursor materials, namely, graphite and a graphite/hexogen mixture into ND, as well as ND produced from different combinations of explosives using different cooling methods (wet or dry cooling). We demonstrate that (i) the N content in nanodiamond particles can be controlled through a correct selection of the carbon precursor material (addition of graphite, explosives composition); (ii) particles larger than approximately 20 nm may contain in situ produced optically active NV centers, and (iii) in ND produced from explosives, NV centers are detected only in ND produced by wet synthesis. ND synthesized from a mixture of graphite/explosive contains the largest amount of NV centers formed during synthesis and thus deserves special attention. © 2011 American Chemical Society

Synthesis, structure and physical characterization of the structural transitions in CePd₃Sn and LaPd₃Sn polymorphs

Abstract Ternary stannides CePd3Sn and LaPd3Sn were synthesized by arc melting the elements. Their crystal structures determined at room temperature revealed a new structure type: sp. gr. Cmcm, Z = 4, a = 4.5160(18) Å, b = 15.878(8) Å, c = 5.396(3) Å for CePd3Sn and a = 4.5187(10) Å, b = 15.961(5) Å, c = 5.451(2) Å for LaPd3Sn. The new type of structure can be presented as built of two types of slabs stacked along the b-axis – CePdSn slab of PbFCl-type and palladium corrugated slab. CePd3Sn and LaPd3Sn undergo reversible crystal structure phase transition at 141 K and 260 K, respectively. The temperature hysteretic behavior through the transition is tracked with electrical resistivity and magnetic susceptibility. Single-crystal X-ray diffraction data at 120 K showed that the low-temperature (LT) polymorph of CePd3Sn crystallizes in the monoclinic structure type, with C2/m space group, Z = 16 and lattice parameters a = 10.8314(7) Å, b = 9.0474(5) Å, c = 15.8725(12) Å, β = 91.325(6)°. LT−CePd3Sn is found to order at low temperature into a putative antiferromagnetic spin structure below 1 K

Nitrogen control in nanodiamond produced by detonation shock-wave-assisted synthesis

Development of efficient production methods of nanodiamond (ND) particles containing substitutional nitrogen and nitrogen-vacancy (NV) complexes remains an important goal in the nanodiamond community. ND synthesized from explosives is generally not among the preferred candidates for imaging applications owing to lack of optically active particles containing NV centers. In this paper, we have systematically studied representative classes of NDs produced by detonation shock wave conversion of different carbon precursor materials, namely, graphite and a graphite/hexogen mixture into ND, as well as ND produced from different combinations of explosives using different cooling methods (wet or dry cooling). We demonstrate that (i) the N content in nanodiamond particles can be controlled through a correct selection of the carbon precursor material (addition of graphite, explosives composition); (ii) particles larger than approximately 20 nm may contain in situ produced optically active NV centers, and (iii) in ND produced from explosives, NV centers are detected only in ND produced by wet synthesis. ND synthesized from a mixture of graphite/explosive contains the largest amount of NV centers formed during synthesis and thus deserves special attention. © 2011 American Chemical Society

Nitrogen control in nanodiamond produced by detonation shock-wave-assisted synthesis

Development of efficient production methods of nanodiamond (ND) particles containing substitutional nitrogen and nitrogen-vacancy (NV) complexes remains an important goal in the nanodiamond community. ND synthesized from explosives is generally not among the preferred candidates for imaging applications owing to lack of optically active particles containing NV centers. In this paper, we have systematically studied representative classes of NDs produced by detonation shock wave conversion of different carbon precursor materials, namely, graphite and a graphite/hexogen mixture into ND, as well as ND produced from different combinations of explosives using different cooling methods (wet or dry cooling). We demonstrate that (i) the N content in nanodiamond particles can be controlled through a correct selection of the carbon precursor material (addition of graphite, explosives composition); (ii) particles larger than approximately 20 nm may contain in situ produced optically active NV centers, and (iii) in ND produced from explosives, NV centers are detected only in ND produced by wet synthesis. ND synthesized from a mixture of graphite/explosive contains the largest amount of NV centers formed during synthesis and thus deserves special attention. © 2011 American Chemical Society

Nitrogen control in nanodiamond produced by detonation shock-wave-assisted synthesis

Development of efficient production methods of nanodiamond (ND) particles containing substitutional nitrogen and nitrogen-vacancy (NV) complexes remains an important goal in the nanodiamond community. ND synthesized from explosives is generally not among the preferred candidates for imaging applications owing to lack of optically active particles containing NV centers. In this paper, we have systematically studied representative classes of NDs produced by detonation shock wave conversion of different carbon precursor materials, namely, graphite and a graphite/hexogen mixture into ND, as well as ND produced from different combinations of explosives using different cooling methods (wet or dry cooling). We demonstrate that (i) the N content in nanodiamond particles can be controlled through a correct selection of the carbon precursor material (addition of graphite, explosives composition); (ii) particles larger than approximately 20 nm may contain in situ produced optically active NV centers, and (iii) in ND produced from explosives, NV centers are detected only in ND produced by wet synthesis. ND synthesized from a mixture of graphite/explosive contains the largest amount of NV centers formed during synthesis and thus deserves special attention. © 2011 American Chemical Society

Order and frustration in liquid-crystalline dendrimers

Abstract. X-ray diffraction has been used to elucidate the structure and phase behavior of several liquidcrystalline dendrimers with a different surface topology of the terminal chains. This includes secondgeneration liquid-crystalline block and statistical dendrimers with mixed aliphatic and mesogenic terminal groups as well as homo-dendrimers of several generations containing only mesogenic end groups. The homodendrimers of generation one to four display a monolayer smectic phase, while the fifth generation shows a more ordered columnar phase. The block-dendrimer of the second generation has a bilayer smectic phase. The precise structure of the lamellar ordering has been determined by X-ray reflectivity from thin films on a substrate. The second-generation statistical dendrimer does not show any mesogenic phase. The observed phase behavior is discussed in terms of the frustration due to competition between the stiff geometry of the dendritic matrix and the close-packing conditions of the terminal chains

Interleukin-1 bedingte Endothelzellaktivierung als Invasionsfaktor beim Urothelkarzinom der Harnblase

X-ray diffraction has been used to elucidate the structure and phase behavior of several liquid-crystalline dendrimers with a different surface topology of the terminal chains. This includes second-generation liquid-crystalline block and statistical dendrimers with mixed aliphatic and mesogenic terminal groups as well as homo-dendrimers of several generations containing only mesogenic end groups. The homo-dendrimers of generation one to four display a monolayer smectic phase, while the fifth generation shows a more ordered columnar phase. The block-dendrimer of the second generation has a bilayer smectic phase. The precise structure of the lamellar ordering has been determined by X-ray reflectivity from thin films on a substrate. The second-generation statistical dendrimer does not show any mesogenic phase. The observed phase behavior is discussed in terms of the frustration due to competition between the stiff geometry of the dendritic matrix and the close-packing conditions of the terminal chains