Chitosan modified with a polydentate crosslinker for metal‐ion adsorption

Extensive study of solution properties of sodium hyaluronate including about 140 samples and covering broad molar mass range was carried out by classical viscometry using an Ubbelohde capillary viscometer and by combination of size‐exclusion chromatography with a multi‐angle light scattering detector and an on‐line viscometer. The study also involved critical overview of literature data of Mark‐Houwink relation for sodium hyaluronate. Continuous decrease of the Mark‐Houwink exponent with increasing molar mass to the values markedly lower than those typical of linear random coils in thermodynamically good solvents was observed. This fact was attributed to branched molecular structure of hyaluronic acid as a result of unknown side reactions during the manufacturing process. The molar mass dependence of the second virial coefficient was determined and proved aqueous salt solutions to be thermodynamically good solvents for sodium hyaluronate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effective sensitization of Eu3+ ions on Eu3+/Nd3+ co-doped multicomponent borosilicate glasses for visible and NIR luminescence applications

Eu³⁺/Nd³⁺ co-doped multicomponent borosilicate glasses (ND1E: 10BaO +10ZnF₂+10K₂O +20SiO₂+(49-x) B₂O₃+1Nd₂O₃+xEu₂O₃) were prepared by conventional melting and rapid quench technique to evaluate the effect of Eu³⁺ ions in the Nd³⁺ doped glasses. Thermal stability, structural and spectroscopic characteristics of the ND1E glasses were investigated by using DSC, XRD, FTIR, Optical absorption, excitation and emission measurements. The Judd – Ofelt (JO) analysis is implemented to the absorption spectrum of the prepared glassy matrix in order to identify their potential applicability in lasing devices. Enhancement of ⁷F₀ → ⁵L₆ band (394 nm) with the increasing concentration of Eu³⁺ ion in the Nd³⁺ excitation spectra (λ_emi = 1060 nm) reveals the possibility of obtaining the characteristic fluorescence spectra of Nd³⁺ ion with the typical excitation wavelengths (Nd³⁺ = 584 nm and Eu³⁺ = 394 nm) of both rare earth ions and it is further verified from the emission spectrum. This interesting luminescence effect of showing excellent visible and NIR emission under 394 nm excitation mainly attributes the energy transfer mechanism between the RE³⁺ ions and the reason underlying this effect is discussed in detail with the help of partial energy level diagram. Energy transfer efficiency between the Eu³⁺ and Nd³⁺ ions were evaluated by using the radiative lifetimes of the prepared glasses. Also, a comparison of radiative properties and lasing characteristics of Eu³⁺/Nd³⁺ co-doped glasses with other Nd³⁺ glasses are reported. The emission intensities were characterized using CIE chromaticity diagram and the observed CIE coordinates shows a shift towards reddish – orange region with the increase in Eu³⁺ concentration. The quantum efficiency of the prepared glasses was determined experimentally. The obtained results suggest that the ND1E glassy system can be considered as a potential candidate for visible and NIR luminescence applications.     

Simple, selective and sensitive spectrophotometric determination of fenitrothion using novel chromogenic reagent

A facile, rapid and sensitive spectrophotometric method was developed for the determination of fenitrothion in its formulations, water, food grain and agriculture soil samples with newly synthesised reagent. The method was based on the alkaline hydrolysis of fenitrothion pesticide and resultant hydrolysed product of fenitrothion was coupled with diazotised 4,4'-methylene-bis-(p-amino-3'-hydroxybenzanilide) in basic medium to give orange coloured product having lambdamax 480 nm. The formation of coloured derivatives with the coupling agent is instantaneous and stable for 48 h. Beer's law was obeyed in the concentration range of 0.1-19.0 microg ml(-1). The proposed method is sensitive, easy to operate and permitted the determination of fenitrothion with a detection limits of 0.085 microg ml(-1). The experimental results indicate that the procedure can eliminate the fundamental interferences caused by other pesticides and non-target ions, which made these methods more sensitive and selective. The method was applicable to the determination of fenitrothion residue in water, food grain and soil samples up to ng level.     

Hyaluronic acid microneedles-laden collagen cryogel plugs for ocular drug delivery

Particle loaded hydrogels have shown to provide prolonged delivery of drug in a controlled manner. We propose that embedding drug-loaded hyaluronic acid (HA) microneedles in supermacroporous collagen type-I (Col-I) cryogel plugs may enhance the hydration and provide prolonged release of drug for ocular diseases. In this study, we have fabricated Col-I cryogel and HA-microneedles embedded Col-I cryogel at sub-zero temperature using 4S-arm Star-PEG as a crosslinker. The fabricated novel Col-I cryogels have shown supermacroporous morphology with solvent uptake capacity of nearly 90% due to large pore volume and high interconnectivity. These features of the cryogel enable the release the drug in a controlled and sustained manner. The fabricated cryogels have demonstrated nearly 50% degradation in simulated tear fluid within 15 days of duration. Moreover, the microneedles incorporated cryogels have shown prolonged release of required therapeutic concentration of drug that may satisfy the present dire need for antibacterial drug delivery in eyes. The variation in the drug release kinetics from Col-I cryogel and HA-microneedles-laden-Col-I cryogels have been studied in different release media (PBS and Simulated tear fluid).     

A comparative evaluation on the spectroscopic characteristics of Sm3+/Pr3+-doped fluoroborosilicate glasses for photonic applications

Journal of Materials Science: Materials in Electronics - The current study focuses on a comparative investigation of the luminescent properties of fluoroborosilicate glasses doped with the two...