One-pot aqueous phase growth of biocompatible 15-130 nm gold nanoparticles stabilized with bidentate PEG

We describe a new, single pot, aqueous phase method for synthesizing water soluble gold nanoparticles (AuNPs) over a size range of 15-130 nm. Poly(ethylene glycol)-appended thioctic acid ligands were used to control the growth rates and stabilize the AuNPs. Critical factors that enable the controlled growth of the AuNPs over this size range include the pH, the choice of reducing agent, the reaction temperature and the sequential addition of gold precursor and ligand with specific ligand-to-gold ratios. We describe the synthetic procedure in detail. Optical and structural characterization of the AuNPs was accomplished using UV-vis absorption spectroscopy, dynamic light scattering, and transmission and scanning electron microscopy.     

COSMO-RS Based Predictions for the Extraction of Lignin from Lignocellulosic Biomass Using Ionic Liquids: Effect of Cation and Anion Combination

A total of 34 cations belonging to 6 classes and 34 anions resulting in 1156 possible combinations are screened using the quantum chemical based COSMO-RS (COnductor-like Screening MOdel for Real Solvents) model. The Hildebrand solubility parameter (?? _H) is calculated using the predicted infinite dilution activity coefficient (?? ^??) of lignin in ionic liquids at 303.15 K. Initial benchmarking is performed by predicting the Hildebrand solubility parameter of lignin in ionic liquids. Comparison with literature values involving 12 ILs gives the average root mean square deviation (RMS) as 10.15?%. Except for anions based on hexafluorophosphate [PF₆], bis(oxalato(2)borate) [BOB], tetracyanoborate [B(CN)₄] and bis(trifluoromethylsulfonyl)amide [BTA], all the cation?Canion combinations have calculated solubility parameters equal to that of lignin at 303.15 K, indicating high solubilities for lignin.     

Dendrimer building toolkit: Model building and characterization of various dendrimer architectures

We have developed a graphical user interface based dendrimer builder toolkit (DBT) which can be used to generate the dendrimer configuration of desired generation for various dendrimer architectures. The validation of structures generated by this tool was carried out by studying the structural properties of two well known classes of dendrimers: ethylenediamine cored poly(amidoamine) (PAMAM) dendrimer, diaminobutyl cored poly(propylene imine) (PPI) dendrimer. Using full atomistic molecular dynamics (MD) simulation we have calculated the radius of gyration, shape tensor and monomer density distribution for PAMAM and PPI dendrimer at neutral and high pH. A good agreement between the available simulation and experimental (small angle X‐ray and neutron scattering; SAXS, SANS) results and calculated radius of gyration was observed. With this validation we have used DBT to build another new class of nitrogen cored poly(propyl ether imine) dendrimer and study it's structural features using all atomistic MD simulation. DBT is a versatile tool and can be easily used to generate other dendrimer structures with different chemistry and topology. The use of general amber force field to describe the intra‐molecular interactions allows us to integrate this tool easily with the widely used molecular dynamics software AMBER. This makes our tool a very useful utility which can help to facilitate the study of dendrimer interaction with nucleic acids, protein and lipid bilayer for various biological applications. © 2012 Wiley Periodicals, Inc.