Synthesis and characterization of glycol ether and oxime modified precursors of niobium(V) for soft transformation to niobia

A glycol ether modified precursor, [Nb{O(CH₂CH₂O)₂}(OPrⁱ)₃] (A) was prepared by the reaction of Nb(OPrⁱ)₅ with O(CH₂CH₂OH)₂ in 1:1 molar ratio in anhydrous benzene. Further reactions of A with a variety of internally functionalized oximes in different molar ratios, yielded heteroleptic complexes of the type, [Nb{O(CH₂CH₂O)₂}(OPrⁱ)_3?n{ON = C(CH₃)(Ar)}_n] (1–9) {where Ar = C₄H₃O-2, n = 1 [1], n = 2 [2], n = 3 [3]; C₄H₃S-2, n = 1 [4], n = 2 [5], n = 3 [6]; C₅H₄N-2, n = 1 [7], n = 2 [8], n = 3 [9]}. All the above derivatives have been characterized by elemental analyses, FT-IR, NMR (¹H, ¹³C {¹H}) and FAB mass studies. Spectral studies of 1–9 suggest the presence of mono- and bi-dentate mode of oxime moieties, in the solution and in the solid states, respectively. FAB mass studies indicate monomeric nature for 3 and dimeric nature for A. TG curves of A and 6 show their low thermal stability. Soft transformation of A and 3 to pure niobia, a and b, respectively have been carried out by sol–gel technique. The XRD patterns of niobia a and b suggest the formation of nano-size crystallites of average size of 10.8 and 19.5 nm, respectively. The XRD patterns also indicate the formation of monoclinic phase of the niobia in both the cases. Absorption spectra of a and b suggest energy band gaps of 4.95 and 4.39 eV, respectively.     

Polycaprolactone composites with TiO(2) for potential nanobiomaterials: tunable properties using different phases

TiO(2) nanoparticles of different phases play a key role in property alteration of nanocomposite fibers. Polycaprolactone (PCL)/TiO(2) composite fibers were prepared using the electrospinning method. Pure anatase and rutile phases were synthesized using the sol-gel route for nanocomposite synthesis. The Effect of nanoparticle phases on crystallinity of fibers and interaction with polymer molecules have been studied using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, morphology through SEM, surface properties using BET method and wetting property of fibers commencing from contact angle measurement. Biocompatibility and biodegradation of hybrid materials have been studied in simulated body fluid (SBF) and phosphate buffer (PBS), respectively. The anatase phase with smaller particle dimensions exhibited significant improvement of most of the properties as compared to composites made of the rutile phase. Better interaction between polymer chain and anatase particle PCL-A nanocomposite fibers leads to better mechanical property and biocompatibility vis-à-vis PCL-R and pristine PCL fibers. Biocompatibility of PCL nanocomposite has been testified through proliferation of fibroblast cell and its adhesion; MTT (3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay demonstrates good proliferation rate for cells on PCL-A nanocomposite fibres.     

Unifying darko-lepto-genesis with scalar triplet inflation

We present a scalar triplet extension of the standard model to unify the origin of inflation with neutrino mass, asymmetric dark matter and leptogenesis. In presence of non-minimal couplings to gravity the scalar triplet, mixed with the standard model Higgs, plays the role of inflaton in the early Universe, while its decay to SM Higgs, lepton and dark matter simultaneously generate an asymmetry in the visible and dark matter sectors. On the other hand, in the low energy effective theory the induced vacuum expectation value of the triplet gives sub-eV Majorana masses to active neutrinos. We investigate the model parameter space leading to successful inflation as well as the observed dark matter to baryon abundance. Assuming the standard model like Higgs mass to be at 125–126 GeV, we found that the mass scale of the scalar triplet to be ?O(10⁹) GeV$?O({10}^9)\text{GeV}$ and its trilinear coupling to doublet Higgs is ?0.09 so that it not only evades the possibility of having a metastable vacuum in the standard model, but also lead to a rich phenomenological consequences as stated above. Moreover, we found that the scalar triplet inflation strongly constrains the quartic couplings, while allowing for a wide range of Yukawa couplings which generate the CP asymmetries in the visible and dark matter sectors.     

Tuning of crystal phase structure in hydrated WO3 nanoparticles under wet chemical conditions and studies on their photochromic properties

Hydrated tungsten oxide nanoparticles have been synthesized using a simple wet chemical method while varying the concentration of HCl. XRD studies show that the variation in HCl concentration from 1 M to 6 M in the reaction results into gradual change in crystal structure of hydrated WO₃ from hexagonal (WO₃·0.33H₂O) to pure orthorhombic (WO₃·H₂O), through a series of samples with mixed phase of the two indifferent ratios. The similar variations in the degree of hydration and phase variations have also been observed from Raman, FTIR and TGA studies. The average crystallite size of the hydrated WO₃ particles was estimated to be ～26 nm from XRD line broadening and AFM studies showed the formation of spherical shaped particles for all the samples. The photochromic studies were carried out on the composite films of these materials in the polymeric matrix of polyvinyl alcohol (PVA) while exposing to UV light. The composite films show interesting variations in the photochromic behavior depending on the crystal structure of hydrated WO₃ filler. The photochromic behavior has been explained on the basis of EPR spectra of hydrated WO₃.     

Novel 3,3′-(alkanediyl)bis-(2,2,2-triaryl-1-oxa-2-stiba-3-azabenzo[d]cyclohex-5-enes)

The hitherto unreported compounds of general structure 3,3′-(alkanediyl)bis-(2,2,2-triaryl-1-oxa-2-stiba-3-azabenzo[d]cyclohex-5-ene) have been synthesized in 48-56% yields by the cyclization of the tetrasodium salt of N,N′-bis(2-hydroxybenzyl)-1,2-diaminoethane(II) or of N,N′-bis(2-hydroxybenzyl)-1,3-diaminopropane(II*) with R₃SbBr₂ (R = phenyl, p-tolyl, or mesityl). The tetrasodium salts were prepared by the reactions of the corresponding amines with sodium hydride. The amines (II and II*), in turn, were obtained by the sodium borohydride reduction of N,N′-bis(salicylidene)-1,2-diaminoethane and N,N′-bis-(salicylidene)-1,3,-diaminopropane, respectively. The heterocyclic compounds are air stable and moisture insensitive. These compounds have been characterized by elemental analyses, molecular weight determinations, and by IR, far IR, ¹H, and ¹³C NMR spectral studies. © 1996 John Wiley & Sons, Inc.