Konstantinos E. Papathanasiou

Divalent metal vinylphosphonate layered materials: compositional variability, structural peculiarities, dehydration behavior, and photoluminescent properties

A family of M-VP (M = Ni, Co, Cd, Mn, Zn, Fe, Cu, Pb; VP = vinylphosphonate) and M-PVP (M = Co, Cd; PVP = phenylvinylphosphonate) materials have been synthesized by hydrothermal methods and characterized by FT-IR, elemental analysis, and thermogravimetric analysis (TGA). Their structures were determined either by single crystal X-ray crystallography or from laboratory X-ray powder diffraction data. The crystal structure of some M-VP and M-PVP materials is two-dimensional (2D) layered, with the organic groups (vinyl or phenylvinyl) protruding into the interlamellar space. However, the Pb-VP and Cu-VP materials show dramatically different structural features. The porous, three-dimensional (3D) structure of Pb-VP contains the Pb center in a pentagonal pyramid. A Cu-VP variant of the common 2D layered structure shows a very peculiar structure. The structure of the material is 2D with the layers based upon three crystallographically distinct Cu atoms; an octahedrally coordinated Cu(2+) atom, a square planar Cu(2+) atom and a Cu(+) atom. The latter has an unusual co-ordination environment as it is 3-coordinated to two oxygen atoms with the third bond across the double bond of the vinyl group. Metal-coordinated water loss was studied by TGA and thermodiffractometry. The rehydration of the anhydrous phases to give the initial phase takes place rapidly for Cd-PVP but it takes several days for Co-PVP. The M-VP materials exhibit variable dehydration-rehydration behavior, with most of them losing crystallinity during the process.

Crystal engineering in confined spaces. A novel method to grow crystalline metal phosphonates in alginate gel systems

In this paper we report a crystal growth method for metal phosphonate frameworks in alginate gels. It consists of a metal-containing alginate gel, in which a solution of phosphonate ligand is slowly diffused. Crystals of metal phosphonate products are formed inside the gel. We have applied this for a variety of metal ions (alkaline-earth metals, transition metals and lanthanides) and a number of polyphosphonic acid and mixed carboxy/phosphonic acid ligands.

CMOS RF noise, scaling, and compact modeling for RFIC design

This work presents an analysis of high frequency noise and linearity performance of a 90 nm CMOS process. Measurements are performed for a wide range of nominal gate lengths and bias points at high frequency. Modeling is based on the EKV3 compact model in Spectre RF circuit simulator from Cadence. The model shows correct scalability for noise and linearity accounting for short channel effects (SCEs), such as velocity saturation (VS) and channel length modulation (CLM). Results are presented versus a common measure of channel inversion level, named inversion coefficient. Optimum performance is shown to gradually shift from higher to lower levels of moderate inversion, when scaling from 240 nm to 100 nm. The same trend is observed from investigating the transconductance frequency product (TFP) of a common-source (CS) LNA for technology nodes ranging from 180 nm to 22 nm.

Luminescent and Proton Conducting Lanthanide Coordination Networks Based On a Zwitterionic Tripodal Triphosphonate

The synthesis, structural characterization, luminescence properties, and proton conduction performance of a new family of isostructural cationic 2D layered compounds are reported. These have the general formula [Ln(H4NMP)(H2O)2]Cl·2H2O [Ln = La(3+), Pr(3+), Sm(3+), Eu(3+), Gd(3+), Tb(3+), Dy(3+), Ho(3+), H6NMP = nitrilotris(methylphosphonic acid)], and contain Cl(-) as the counterion. In the case of Ce(3+), a 1D derivative, [Ce2(H3NMP)2(H2O)4]·4.5H2O, isostructural with the known lanthanum compound has been isolated by simply crystallization at room temperature. The octa-coordinated environment of Ln(3+) in 2D compounds is composed by six oxygen atoms from three different ligands and two oxygens from each bound water. Two of the three phosphonate groups act as both chelating and bridging linkers, while the third phosphonate group acts solely as a bridging moiety. The materials are stable at low relative humidity at less at 170 °C. However, at high relative humidity transform to other chloride-free phases, including the 1D structure. The proton conductivity of the 1D materials varies in a wide range, the highest values corresponding to the La derivative (σ ≈ 2 × 10(-3) S·cm(-1) at RH 95% and 80 °C). A lower proton conductivity, 3 × 10(-4) S·cm(-1), was measured for [Gd(H4NMP)(H2O)2]Cl·2H2O at 80 °C, which remains stable under the work conditions used. Absorption and luminescence spectra were recorded for selected [Ln(H4NMP)(H2O)2]Cl·2H2O compounds. In all of them, the observed transitions are attributed solely to f-f transitions of the lanthanide ions present, as the H4NMP(2-) organic group has no measurable absorption or luminescence properties.

Smart, programmable and responsive injectable hydrogels for controlled release of cargo osteoporosis drugs

Easy-to-prepare drug delivery systems, based on smart, silica gels have been synthesized, characterized, and studied as hosts in the controlled release of bisphosphonates. They exhibit variable release rates and final % release, depending on the nature of bisphosphonate (side-chain length, hydro-philicity/-phobicity, water-solubility), cations present, pH and temperature. These gels are robust, injectable, re-loadable and re-usable.

Moderate inversion: Analog and RF benchmarking with the EKV3 compact model

In this paper the validity of the EKV3 advanced compact MOSFET model is verified with DC and RF measurements of a 90 nm CMOS low-power (LP) process. The model is capable of describing the edge conduction effect, mainly occurring in moderate levels of channel inversion. Non-linearities are extracted from DC measurements and the robustness of the model is also proven, in terms of RF figures of merit (FoM) suitable for RFIC design, for both n- and p-type MOS devices.

Silica-Based Polymeric Gels as Platforms for Delivery of Phosphonate Pharmaceutics

This chapter focuses on polymeric gel drug delivery systems used for initial immobilization and subsequent controlled release of active pharmaceutical ingredients. The primary focus is on phosphonate-based drugs, which are extensively used for a variety of medicinal applications and pathological conditions. Their most recognizable use is for osteoporosis drugs with the common names: medronate, chlodronate, etidronate, alendronate, zoledronate, obadronate, ibandronate, neridronate, etc. Herein, we present a concise literature overview of this research field, presenting research results on immobilization of phosphonates onto silica-based polymeric gels, with the goal to achieve controlled release of these ingredients into biological fluids.