Three-dimensional open-framework zinc phosphates with the structure-directing organic amines acting as ligands

Two new three-dimensional zinc phosphates I, [NH(CH2)2NH2 (CH2)2NH3]2+[Zn5(PO4)4]2- and II, [CN5H6]+ [Zn2(PO4)(HPO4]-, where the structure-directing organic amine acts as a ligand, have been synthesized hydrothermally. Crystal data for I : a=27.071(2), b=5.215(1), c=17.920(1) Å, β =130.3(1)°; U=1930.9(3) Å3; space group=Cc (no. 9) ; Z=4; M=811.01; Dcalc=2.789 g cm-3; MoKα and for II : a=8.089(1), b=12.771(1), c=10.067(1) Å, β=105.3(1)°; U=1000.3(2) Å3; space group=P21/n (no. 14) ; Z=4; M=409.8; Dcalc=2.713 g cm-3; MoKα. Compound I is novel in the sense that it is dominated by the presence of a large number of three-coordinated oxygen atoms (25%), leading to the formation of inÐnite Zn-O-Zn chains. The presence of a distorted bipyramidal ZnO3N2 unit as well as a 2-membered ring in II is noteworthy. These structures are formed by the networking of ZnO4, ZnO3N, PO4 and ZnO3N2 moieties, leading to the formation of three-dimensional structures possessing channels with I forming a 10-membered one-dimensional channel system and II forming two 8-membered channels

A zinc phosphate oxalate with phosphate layers pillared by the oxalate units

An open-framework phosphate oxalate of zinc, of composition [NH3(CH2)3NH3][Zn6(PO4)4(C2O4)], 1, has been synthesized, for the first time, employing hydrothermal methods in the presence of ethylenediamine. The structure comprises a network of Zn(1)O5, Zn(2)O4, Zn(3)O5 polyhedra and PO4 tetrahedra connected through their vertices forming neutral layers bridged by the oxalate units, giving one-dimensional channels. The presence of Zn in tetrahedral, trigonal-bipyramidal and square-pyramidal coordinations, and the formation of neutral layers, are noteworthy features

A novel open-framework zinc phosphate with intersecting helical channels

A new open-framework zinc phosphate, possessing two interpenetrating 8-membered helical channels, has been synthesized under mild hydrothermal conditions

Open-framework zinc and cobalt phosphates synthesized by the tributylphosphate route

By employing tributylphosphate as the source of phosphorus, several open-framework zinc and cobalt phosphates have been prepared hydrothermally. Of the three new zinc phosphates [C6N2H18][Zn(HPO4)2], I, has a linear chain structure while [C4N2H14][Zn5(PO4)4(H2O)], II, [NH4][H3O][Zn4(PO4)3]2·H2O, III, have three-dimensional structures. Of the three new cobalt phosphates described, [C5N2H14][Co(HPO4)2], IV, and [C5N2H14][Co(HPO4)2], V, have linear chain structures, while [C4N2H12]3 [Co2(OH)(HPO4)3]2, VI, has a complex double chain structure. The study shows that the use of the organophosphate yields a variety of architectures of metal phosphates

Magnetic Behavior in RRhX (R = rare earths; X=B, C) Compounds

We report on the magnetic behavior of RRhB (R = La, Ce, Pr, Nd, Gd, Tb and Tm) and RRhC (R = La, Ce, Pr and Gd) compounds crystallizing in the cubic perovskite type structure with space group Pm3m. The heat capacity data on Pauli-paramagnetic LaRhB and LaRhC indicate a high frequency vibrating motion of boron and carbon atoms in the unit cell. Ce is in -like nonmagnetic state in both the compounds. Pr compounds show a dominant crystal field effect with a nonmagnetic singlet ground state in PrRhB and a nonmagnetic quadrupolar doublet in PrRhC. Compounds with other rare earths order ferromagnetically at low temperatures except TmRhB in which the zero field evolution of magnetic interactions is relatively more complicated. The electrical resistivity of GdRhB decreases with increasing temperature in the paramagnetic state in the vicinity of T, which is rarely seen in ferromagnets. The behavior is discussed to be arising due to the short range spin fluctuation and a possible contribution from Fermi surface geometry.Comment: 14 Figs and a text fil

Evaluation of Guava (Psidium guajava L.) Varieties and Standardization of Recipe for Nectar Preparation

The nectar prepared from guava variety L-49 had highest ascorbic acid, pH and non-reducing sugar. The recipe with 20 per cent pulp, 0.3 per cent acidity and 17°Brix (TSS) recorded highest organoleptic score. The acidity, TSS, total and reducing sugar of nectar showed an increasing trend during the progress of storage upto five months under ambient conditions. However, these chemical constituents did not change markedly until five months of storage as compared to fresh nectar at the time of preparation

A new route for the synthesis of open-framework metal phosphates using organophosphates

Use of tributylphosphate, an organophosphate, as the phosphorus source in place of phosphoric acid, has enabled the synthesis of several new open-framework zinc(II) and cobalt(II) phosphates, under solvothermal conditions

Synthesis of Silver Nanostructures and their Application in Highly Sensitive SERS Sensors

A comparison of Surface Enhanced Raman Scattering (SERS) activity of chemically synthesised silver nanostructures with different shapes is reported. The silver nanostructures of cubical, prism and wire like morphology were synthesised using chemical synthesis route and utilised as SERS substrates. The sensors were fabricated by spin coating these materials over a Silicon or glass substrate. The fabricated sensors were used to analyse response with two different analytes, 4-Mercaptobenzoic acid and Rhodamine 6G under different concentrations. The signal enhancement was compared with a silver coated thin film over glass substrate and it was observed that the enhancement of the order of 103 is achieved. The nanowire performed better than the other forms of silver and gave a higher signal enhancement for all the analytes as compared to other nanostructures. The fabricated sensors may be useful for various applications including explosive and biowarfare agent detection

Enhanced Room Temperature Coefficient of Resistance and Magneto-resistance of Ag-added La0.7Ca0.3-xBaxMnO3 Composites

In this paper we report an enhanced temperature coefficient of resistance (TCR) close to room temperature in La0.7Ca0.3-xBaxMnO3 + Agy (x = 0.10, 0.15 and y = 0.0 to 0.40) (LCBMO+Ag) composite manganites. The observed enhancement of TCR is attributed to the grain growth and opening of new conducting channels in the composites. Ag addition has also been found to enhance intra-granular magneto-resistance. Inter-granular MR, however, is seen to decrease with Ag addition. The enhanced TCR and MR at / near room temperature open up the possibility of the use of such materials as infrared bolometric and magnetic field sensors respectively.Comment: 22 pages of Text + Figs:comments/suggestions([email protected]