Studies of the synthesis and thermochemistry of coordinatively unsaturated chelate complexes (eta 5-C5Me5)IrL2 (L2 = TsNCH2CH2NTs, TsNCH2CO2, CO2CO2)

A comparative synthetic, structural, and thermochemical study on a series of chelate complexes containing the fragment (eta 5-C5Me5)Ir [(eta 5-C5Me5)Ir(TsNCH2CH2NTs) (1), (eta 5-C5Me5)Ir(TsNCH2CO2) (2), (eta 5-C5Me5)Ir(CO2CO2) (3)] was performed to clarify the roles of carboxylato and sulfonamido ligands. Whereas 1 and 2 are monomeric in solution and in the solid state, 3 appears to exist as an oligomer or polymer, (3)n, which can be broken up by addition of a ligand L such as a phosphine, CO, or 2-methoxypyridine to form (eta 5-C5Me5)Ir(L)(CO2CO2) (6). The synthesis of (3)n from [(eta 5-C5Me5)IrCl(mu-Cl)]2 required the use of silver oxalate in CH3CN, but if other solvents were used, the bridging oxalato complex (eta 5-C5Me5)IrCl(mu-eta 2-eta 2-C2O4)ClIr(eta 5-C5Me5) (7) was obtained and identified by X-ray diffraction. Enthalpies for reaction of THF-soluble monomers 1 and 2 with PMe3 were determined to be -28.7(0.5) and -28.5(0.4) kcal mol-1, respectively. The oligomerization behavior of 3 may be a result of reduced sigma- or pi-donation of carboxylato ligands compared to N-tosylamido ligands, because the values for nu CO in oxalato and bissulfonamido complexes 6-CO and (eta 5-C5Me5)Ir(CO)(TsNCH2CH2NTs) (4-CO) were 2064 and 2042 cm-1, respectively.     

Effective Drug Therapies from Functional,Macromolecular Building Blocks with a Biomimetic Design

Summary: The development of suitable delivery systems for intracellular delivery of proteins, peptides and other bioactive materials opens the possibility to establish refined strategies for small drug delivery, gene delivery and vaccination. We present the assembly of advanced drug delivery systems from tailored building blocks to scaffolds and bioactive cargos to afford targeting and transport across biological barriers. In particular, the utilization of novel molecular transporter will advance the bioavailability of small and macromolecular drugs that show targeted intracellular delivery.     

Effect of vanadium doping on electrochemical performance of LiMnPO4 for lithium-ion batteries

A series of LiMn_1-x V _x PO₄ samples have been synthesized successfully via a conventional solid-state reaction method. The active materials are characterized by x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. The electrochemical performances of the samples are tested using cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge measurement techniques. It is confirmed that the samples are in single phase when the content of vanadium (x) is lower than 0.05. If that content is higher than 0.1, the samples are shown to contain an additional conductive phase of Li₃V₂(PO₄)₃. The vanadium doping significantly enhances the electrochemical properties of LiMnPO₄. It is underlined that the optimal ratio for a low-vanadium doping with the best electrochemical performance is 0.1 and this material exhibits a corresponding initial charge and discharge capacity of 98.9 and 98.1 mAh g^?1 at 0.1 C under 50 °C. The capacity retention is higher than 99 % after 30 cycles. The dramatic electrochemical improvement of the LiMnPO₄ samples is ascribed to the strengthened ability of lithium-ion diffusion and enhanced electronic conductivity for the V-doped samples.     

Surface nitridation induced high electrochemical performance of Li4Ti5O12 using urea as a nitrogen source

Surface nitridation of the Li₄Ti₅O₁₂ particles was carried out by thermal treatment with urea as the nitrogen source in a controllable manner. The titanium nitride (TiN) was formed in the well-dispersed zones on the surface of the Li₄Ti₅O₁₂ particles, depending on the coverage of the nitride. The surface TiN formed led to a great improvement of the conductivity of the oxide. The extent of the surface nitridation exhibited a large effect on electrochemical behaviors of the Li₄Ti₅O₁₂ particles, with the Li₄Ti₅O₁₂/TiN composite (prepared using 6 % urea) providing the best initial capacity and rate capability. Thus, the electrochemical performance of the Li₄Ti₅O₁₂ particles can be achieved by optimizing surface nitridation of the oxide. The chemically inert TiN occupied the surface sites of the Li₄Ti₅O₁₂ particles which may have prevented the electrolyte from decomposition and stabilized the surface structure of the Li₄Ti₅O₁₂ particles, endowing the oxide with excellent cycleability     

Radiative corrections to positronium decay

In this work a method for calculating radiative corrections to positronium decay is presented that is direct, and allows for a systematic extension applicable to the calculation of corrections beyond the first [o(α)] correction. An expression for the decay amplitude in terms of the Bethe-Salpeter wavefunction is employed. The Bethe-Salpeter wavefunction is evaluated perturbatively in a scheme having a lowest-order bound state equation that is exactly soluble. The decay amplitude is evaluated in Coulomb gauge, without the introduction of a photon mass. One-loop renormalization in Coulomb gauge is shown to be consistent. Using this method the known analytic result for the o(α) correction to the parapositronium decay rate is obtained. The same method is applied to orthopositronium, and the existing theoretical discrepancy in the value of the o(α) correction to the decay rate is resolved. This o(α) correction is obtained with an error which corresponds to an uncertainty in the total rate much smaller than α²Γ_LO (where Γ_LO is the lowest-order rate). Also, the o(α) correction to the differential decay rate is computed for the first time.     

Model independent relations for baryons as solitons in mesonic theories

We derive model-independent relations for SU(2) and SU(3) chiral solitons. These relations depend only on the soliton picture of baryons and therefore are a test of the 1/N expansion. In the two-flavor case we discuss the magnetic moment and the electric quadrupole transition of the Δ. In SU(3) we discuss magnetic moments, including SU(3) breaking effects and 1/N corrections.     

Electrochemistry on Paper‐based Analytical Devices: A Review

Even though they were introduced less than a decade ago, electrochemical paper‐based devices (ePADs) have attracted widespread attention because of their inherent advantages in many applications. ePADs combine the advantages of microfluidic paper‐based devices (low cost, ease of use, equipment free pumping, etc.) for sample handling and processing with the advantages of sensitive and selective detection provided by electrochemistry. As a result, ePADs provide simplicity, portability, reproducibility, low cost and high selectivity and sensitivity for analytical measurements in a variety of applications ranging from clinical diagnostics to environmental sensing. Herein, recent advances in ePAD development and application are reviewed, focusing on electrode fabrication techniques and examples of applications specially focused on environmental monitoring, biological applications and clinical assays. Finally, a summary and prospective directions for ePAD research are also provided.