Persistence of nematic liquid crystalline phase in a polyfluorene‐based organic semiconductor: A high pressure study

The role of high pressure on a low molecular weight nematic liquid crystalline organic semiconductor, ethyl‐hexyl substituted polyfluorene (PF2/6) is investigated using photoluminescence (PL), Raman scattering, and X‐ray scattering studies at pressures from 1 to 8 GPa. The PL and the Raman data under pressure are consistent with each other with no abrupt changes in the pressure coefficients of PL or Raman peaks. The PL energies redshift and broaden, consistent with both enhanced intra‐ and interchain interactions. The Raman peak positions yield pressure coefficients similar to other phenyl based π‐conjugated polymers. The broadening of a doublet peak in the 1135 cm^?1 region indicates a more planar backbone conformation with increasing pressure. X‐ray scattering indicates that the torsion angle between adjacent repeats reduces with increasing pressure and reverts back with decompression. The intermolecular structure is weakly ordered (frozen nematic) and essentially maintained with increasing pressure, in contrast to a high molecular weight PF2/6. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1014–1023     

Biosynthetic Approaches towards the Design of Artificial Hydrogen-Evolution Catalysts

Hydrogen is a clean and sustainable form of fuel that can minimize our heavy dependence on fossil fuels as the primary energy source. The need of finding greener ways to generate H₂ gas has ignited interest in the research community to synthesize catalysts that can produce H₂ by the reduction of H⁺. The natural H₂ producing enzymes hydrogenases have served as an inspiration to produce catalytic metal centers akin to these native enzymes. In this article we describe recent advances in the design of a unique class of artificial hydrogen evolving catalysts that combine the features of the active site metal(s) surrounded by a polypeptide component. The examples of these biosynthetic catalysts discussed here include i) assemblies of synthetic cofactors with native proteins; ii) peptide-appended synthetic complexes; iii) substitution of native cofactors with non-native cofactors; iv) metal substitution from rubredoxin; and v) a reengineered Cu storage protein into a Ni binding protein. Aspects of key design considerations in the construction of these artificial biocatalysts and insights gained into their chemical reactivity are discussed.     

A sensitive RP-HPLC method for estimation of artemether from polymeric nanoparticles after pre-column acid treatment using UV-visible detector

Abstract

Artemether; a sesquiterpene lactone is widely used for the treatment of malaria as artemisinin-based combination therapy (ACT). The present work involves the development and validation of sensitive reversed-phase high-performance liquid chromatography (RP-HPLC) method for quantification of artemether (ART) in polymeric nanoparticles. ART was transformed to α, β-unsaturated decalones by pre-column acid treatment to enhance the sensitivity of chromophoric group lacking ART for quantification by HPLC-UV. Waters Spherisorb^® 5?µm ODS(C18) column (4.6*250?mm) with gradient elution by mobile phase comprising of ACN and PBS (10?mM; pH 6.0) was used to separate acid-treated ART. The analysis was carried at λ_max of 253?nm with 20?min and 20?µL run time and injection volume, respectively. The method was found to be linear in the concentration range of 0.5–10?µg mL^?1 with 0.09?µg mL^?1 and 0.27?µg mL^?1 as LOD and LOQ respectively. Further, the method was also found to be specific for ART in presence of blank polymeric nanoparticles, accurate (% average recovery rate 101.7?±?1.68%), precise (RSD <2%), and robust. The method was successfully used to determine % entrapment efficiency and in vitro release of ART-loaded polymeric nanoparticles with HPLC using a UV-visible detector.     

Extraction of p-Coumaric Acid and Ferulic Acid Using Surfactant-Based Aqueous Two-Phase System

Ferulic acid (FA) and p-coumaric acid (pCA) are high-value products that can be obtained by alkaline hydrolysis of lignocellulose. Present work explores the potential of surfactant-based cloud-point extraction (CPE) for FA and pCA extraction from corn cob hydrolysate. More than 90 % (w/w) extraction of both FA and pCA was achieved from model system with L92. The partition coefficient of FA and pCA in L92 aqueous phase system was 35 and 55, respectively. A significant enrichment (8–10-fold) of both FA and pCA was achieved in surfactant-rich phase. Furthermore, the downstream process volume was reduced by 10 to 13 times. Optimized conditions (5 %?v/v?L92 and pH 3.0) resulted into 85 and 89 % extraction of FA and p-CA, respectively, from alkaline corn cob hydrolysate. Biocompatibility tests were carried out for L92 for ethanol fermentation and found to be biocompatible. Thus, the new surfactant-based CPE system not only concentrated FA and pCA but also reduced the process volume significantly. Further, aqueous phase containing sugars can be used for ethanol fermentation.