Electronic excitations and lattice dynamics of coordinatively "unsaturated" complex transition metal compounds.

Single crystal polarized Raman and infrared spectra of the series Na(5)[MO(2)][X] with M = Co(I), Ni(I), and Cu(I) and X = S(2-) and CO(3)(2-), are reported. All phonon modes are assigned to the lattice eigenmodes based on the group theory analysis and first principles lattice dynamics calculations. The energies of the fundamental symmetric and asymmetric vibrations of the [MO(2)](3-) complex are discussed on the basis of their electronic structure and variation in M-O interatomic distances. Electronic Raman scattering and luminescence are observed for the magnetic members of the series (Co(I), d(8), and Ni(I), d(9)). Ligand field theory is employed to account for the electronic effects which originate from states split by spin-orbit coupling.

Gold-silver alloy nanoshells: a new candidate for nanotherapeutics and diagnostics.

We have developed novel gold-silver alloy nanoshells as magnetic resonance imaging (MRI) dual T1 (positive) and T2 (negative) contrast agents as an alternative to typical gadolinium (Gd)-based contrast agents. Specifically, we have doped iron oxide nanoparticles with Gd ions and sequestered the ions within the core by coating the nanoparticles with an alloy of gold and silver. Thus, these nanoparticles are very innovative and have the potential to overcome toxicities related to renal clearance of contrast agents such as nephrogenic systemic fibrosis. The morphology of the attained nanoparticles was characterized by XRD which demonstrated the successful incorporation of Gd(III) ions into the structure of the magnetite, with no major alterations of the spinel structure, as well as the growth of the gold-silver alloy shells. This was supported by TEM, ICP-AES, and SEM/EDS data. The nanoshells showed a saturation magnetization of 38 emu/g because of the presence of Gd ions within the crystalline structure with r1 and r2 values of 0.0119 and 0.9229 mL mg-1 s-1, respectively (Au:Ag alloy = 1:1). T1- and T2-weighted images of the nanoshells showed that these agents can both increase the surrounding water proton signals in the T1-weighted image and reduce the signal in T2-weighted images. The as-synthesized nanoparticles exhibited strong absorption in the range of 600-800 nm, their optical properties being strongly dependent upon the thickness of the gold-silver alloy shell. Thus, these nanoshells have the potential to be utilized for tumor cell ablation because of their absorption as well as an imaging agent.

Synthesis, crystal structure, and physical properties of BaAg2Cu[VO4]2: a new member of the S = 1/2 triangular lattice.

By application of flux growth methods in combination with redox reactions, single crystals of BaAg(2)Cu[VO(4)](2) can be synthesized. A new structure type (triclinic, P1, Z = 2, a = 5.448(2) Å, b = 5.632(3) Å, c = 14.393(6) Å, α = 94.038(9)°, ß = 90.347(6)°, and γ = 118.195(5)°) has been found and will be described here. Structure-properties relationships have been investigated by spectroscopic methods (IR, UV-vis-NIR, ESR) and the electronic structure will be discussed within the angular-overlap model (AOM) for Cu(2+). Furthermore, we present the magnetization and specific heat data for BaAg(2)Cu[VO(4)](2) representing a Heisenberg spin system with exclusive super-super exchange (SSE) on a frustrated magnetic triangular lattice. Considerable antiferromagnetic (AFM) low-dimensional interaction is evident, and ferromagnetic-like long-range order sets in at ≈0.7 K.