Adsorptive parameters and influence of hot geometries on the SER(R) S spectra of methylene blue molecules adsorbed on gold nanocolloidal particles

The vibrational signatures of methylene blue (MB) dye molecule have been reported. Complete vibrational assignments of the molecule are presented for the first time. Concentration‐dependent surface enhanced resonance Raman scattering [SER(R) S] spectra of the molecule have been investigated. Fluorescence spectroscopic technique has been applied to explore the concentration of the probe molecule actually adsorbed on the gold nanocolloidal (AuNC) surface. The free energy of adsorption and saturated concentration of MB molecules on AuNC surface are also estimated. Gigantic enhancements ~10⁵–10¹³ orders of magnitude have been recorded for the enhanced Raman bands in the SER(R) S spectra. The possible orientation of the molecule on the AuNC surface and their probable protrusions within the hot spots have been suggested. The hot geometries and correlation between the plasmonic behavior of the nanoparticles and enhancement efficiencies of the SER(R) S band have been mapped with the aid of three‐dimensional finite difference time domain (3D‐FDTD) simulations. Application of soft lithographic technique to engineer the pattern formation of hetero dimeric spherical aggregates will be an interesting field of study in future to enhance the detection limit of this and similar types of dye molecules. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthetic Studies on Ophiobolins1. Synthesis of 1β (H) -3,7α,11β-Trimethyl-CIS-Bicyclo [6.3.0] Undecan-4-One

In our synthetic studies towards ophiobolin F (1), we report here a stereospecific synthesis of 1β(H)-3,7α,llβ-trimethyl-cis bicyclo [6.3.0]undecan-4-one (2) with defined stereochemistry at each of the four contiguous asymmetric centres and particularly with A/B cis ring juncture as present in (1). It may be mentioned here that no synthetic studies towards developing the characteristic ring systems present in ophiobolins have been reported so far.     

A Remote ‘Imidazole’‐Based Ruthenium(II) Para‐Cymene Pre‐catalyst for the Selective Oxidation Reaction of Alkyl Arenes and Alcohols

Herein we disclosed the use of a remote ‘imidazole’‐based precatalyst [(para‐cymene)Ru^II(L)Cl]⁺, C‐1 where L=2‐(4‐substituted‐phenyl)‐1H‐imidazo[4,5‐f]^[1,10] phenanthroline) for the selective oxidation of a variety of alkyl arenes/heteroarenes and alcohols to their corresponding aldehydes or ketones in presence of tert‐butyl hydroperoxide (TBHP). The remote ‘imidazole’ moiety present in the complex facilitates the activation of oxidant and subsequent generation of active species via the release of para‐cymene from C‐1 , which in‐turn was less effective without the ‘imidazole’ moiety. The mechanistic features of C‐1 promoted oxidation of alkyl arenes were also assessed from spectroscopic, kinetic, and few control experiments. The substrate scope for C‐1 promoted oxidation reaction was assessed based on the selective oxidation of 27‐different alkyl arenes/heteroarenes and 25 different alcohols to their corresponding aldehydes/ketones in moderate to good yields.     

Enhancement in MS-based peptide detection by microfluidic free-flow zone electrophoresis

Matrix components are known to significantly alter the ionization of a target analyte in ESI-based measurements particularly when working with complex biological samples. This issue however may be alleviated by extracting the analyte of interest from the original sample into a relatively simple matrix compatible with ESI mass-spectrometric analysis. In this article, we report a microfluidic device that enables such extraction of small peptide molecules into an ESI-compatible solvent stream significantly improving both the sensitivity and reproducibility of the measurements. The reported device realizes this analyte extraction capability based on the free-flow zone electrophoretic fractionation process using a set of internal electrodes placed across the width of the analysis channel. Employing lateral electric fields and separation distances of 75 V/cm and 600 µm, respectively, efficient extraction of the model peptide human angiotensin II was demonstrated allowing a reduction in its detection limit by one to three orders of magnitude using the ESI-MS method. The noted result was obtained in our experiments both for a relatively simple specimen comprising DNA strands and angiotensin II as well as for human serum samples spiked with the same model peptide.     

Copper-catalyzed oxidative synthesis of 2-oxo-acetamidines from one-pot three-component reaction of aryl methyl ketones,secondary amines and anilines

Some novel 2-oxo-acetamidines were synthesized via one-pot three-component reaction of acetophenones, secondary amines and anilines in presence of CuI as catalyst. The reaction involved in a oxidation process of C (sp³)H bonds of acetophenones in presence of air followed by aminations, and products were obtained in good to excellent yields (70–82%) in simple work-up procedure.