Microwave-assisted expeditious hydrolysis of isobenzofuranone derivatives using silica supported acid under organic solvent-free conditions

Silica sulfuric acid was found to be an efficient, reusable and environment-friendly catalyst for fast hydrolysis of various isobenzofuranone to corresponding 2-ketomethylquinoline derivatives in a high yield under solvent-free using microwave irradiation. As the activator of silica sulfuric acid the wet SiO₂ was chosen. The reactions in conventional conditions were compared with the microwave assisted reactions. This approach can prove beneficial since the recovery of solvents from conventional reaction systems always results in some losses.     

Remembering Olivier Guillot-Noël

Graphene quantum dots were synthesized by control carbonization of citric acid and utilized for selective determination of dopamine in the presence of ascorbic and uric acids. The prepared graphene quantum dots were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared, ultraviolet–visible and fluorescence spectroscopy. The results revealed that dopamine could quench the fluorescence of graphene quantum dots through a dynamic quenching mechanism. Under the optimized conditions, the linear concentration range was obtained within 0.01–50.0 µM, with the correlation coefficient of 0.9983 and a limit of detection of 8.2 nM. This method does not show any interference with respect to coexisting foreign substances, even at the presence of 500-fold of ascorbic acid and uric acid.     

Nanocomposite hydrogel from grafting of acrylamide onto HPMC using sodium montmorillonite nanoclay and removal of crystal violet dye

Hydrogel nanocomposites were synthesized from grafting of acrylamide onto hydroxypropyl methylcellulose using methylenebisacrylamide crosslinker and sodium montmorillonite (Na-MMt) nanoclay. The effect of nanoclay content on the swelling of nanocomposites was investigated and an optimum swelling capacity was obtained at 12.7 wt% of Na-MMt. The effect of salt solutions on the swelling of nanocomposites revealed that the degree of swelling of samples depends only slightly on the salinity. The structure of nanocomposites was characterized by XRD, SEM, FTIR, and TEM techniques. The XRD and TEM results confirmed the exfoliation of Na-MMt nanoclay in nanocomposite matrix. The morphology of the nanocomposites was characterized by SEM technique and according to the results a loose surface was observed. The nanocomposite hydrogels were evaluated to remove cationic crystal violet dye from water. The investigation of the dye adsorption capacity and rate of nanocomposite hydrogels as a function of Na-MMt content revealed that the both adsorption capacity and rate is enhanced as the nanoclay content is increased in nanocomposite composition. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The best fit to the experimental data was obtained with the Langmuir model.     

Development a robust ionic liquid-based dispersive liquid-liquid microextraction against high concentration of salt combined with flame atomic absorption spectrometry using microsample introduction system for preconcentration and determination of cobalt in water and saline samples

A robust ionic liquid-based method for dispersive liquid-liquid microextraction was developed for the determination of cobalt in saline samples. Its robustness was increased by introducing a common ion of the IL into the sample solution. The concentration of cobalt in the settled phase of the ionic liquid was determined by the FAAS using a homemade microsample injection valve. Under the optimized conditions, the calibration graph was linear in the concentration range from 0.4 to 120 ??g L^?1 with the detection limit of 0.1 ??g L^?1. Accuracy was checked against the ISO standard method. The method was successfully applied to the determination of cobalt in water and saline samples.     

Spectrophotometric determination of ternary mixtures of thiamin, riboflavin and pyridoxal in pharmaceutical and human plasma by least-squares support vector machines.

Ternary mixtures of thiamin, riboflavin and pyridoxal have been simultaneously determined in synthetic and real samples by applications of spectrophotometric and least-squares support vector machines. The calibration graphs were linear in the ranges of 1.0 - 20.0, 1.0 - 10.0 and 1.0 - 20.0 microg ml(-1) with detection limits of 0.6, 0.5 and 0.7 microg ml(-1) for thiamin, riboflavin and pyridoxal, respectively. The experimental calibration matrix was designed with 21 mixtures of these chemicals. The concentrations were varied between calibration graph concentrations of vitamins. The simultaneous determination of these vitamin mixtures by using spectrophotometric methods is a difficult problem, due to spectral interferences. The partial least squares (PLS) modeling and least-squares support vector machines were used for the multivariate calibration of the spectrophotometric data. An excellent model was built using LS-SVM, with low prediction errors and superior performance in relation to PLS. The root mean square errors of prediction (RMSEP) for thiamin, riboflavin and pyridoxal with PLS and LS-SVM were 0.6926, 0.3755, 0.4322 and 0.0421, 0.0318, 0.0457, respectively. The proposed method was satisfactorily applied to the rapid simultaneous determination of thiamin, riboflavin and pyridoxal in commercial pharmaceutical preparations and human plasma samples.     

Acet­amidoxime

The oxime of acet­amide, viz. N‐hydroxy­ethanimid­amide, C₂H₆N₂O, has a complex hydrogen‐bonding arrangement in its crystal structure, featuring one strong O—H⋯N hydrogen bond together with weaker hydrogen bonding involving the amide groups. Conjugation effects lead to atypical distances and angles.     

Developing Novel Fabrication and Optimisation Strategies on Aggregation-Induced Emission Nanoprobe/Polyvinyl Alcohol Hydrogels for Bio-Applications

The current study describes a new technology, effective for readily preparing a fluorescent (FL) nanoprobe-based on hyperbranched polymer (HB) and aggregation-induced emission (AIE) fluorogen with high brightness to ultimately develop FL hydrogels. We prepared the AIE nanoprobe using a microfluidic platform to mix hyperbranched polymers (HB, generations 2, 3, and 4) with AIE (TPE-2BA) under shear stress and different rotation speeds (0–5 K RPM) and explored the FL properties of the AIE nanoprobe. Our results reveal that the use of HB generation 4 exhibits 30-times higher FL intensity compared to the AIE alone and is significantly brighter and more stable compared to those that are prepared using HB generations 3 and 2. In contrast to traditional methods, which are expensive and time-consuming and involve polymerization and post-functionalization to develop FL hyperbranched molecules, our proposed method offers a one-step method to prepare an AIE-HB nanoprobe with excellent FL characteristics. We employed the nanoprobe to fabricate fluorescent injectable bioadhesive gel and a hydrogel microchip based on polyvinyl alcohol (PVA). The addition of borax (50 mM) to the PVA + AIE nanoprobe results in the development of an injectable bioadhesive fluorescent gel with the ability to control AIEgen release for 300 min. When borax concentration increases two times (100 mM), the adhesion stress is more than two times bigger (7.1 mN/mm²) compared to that of gel alone (3.4 mN/mm²). Excellent dimensional stability and cell viability of the fluorescent microchip, along with its enhanced mechanical properties, proposes its potential applications in mechanobiology and understanding the impact of microstructure in cell studies.     

Free volume studies in miscible polymer blend systems

This paper summarises the currently available literature concerned with measurement of free volume in miscible, amorphous polymer blends using positron annihilation lifetime spectroscopy (PALS) which probes excluded volume at the angstrom level. Previously reported data is compared with new data from a range of different blend systems. Miscible blends tend to show a negative deviation of free volume size (and to a lesser degree free volume fraction) on mixing due to the intimacy of packing of the blend component macromolecules. A largely immiscible system is also reported and shows a different behaviour (positive deviation of free volume size) and this is ascribed to additional free volume at the interface.     

1- and 2-D NMR Studies on [Rh6C(CO)14(PPh3)]2−

A complete NMR study involving both 1D and 2D ¹³C-{¹⁰³Rh} and ³¹P-{¹⁰³Rh} HMQC measurements, on [Rh₆C(CO)₁₄(PPh₃)]^2- are reported and discussed, together with the multiple Rh quantum effects found for resonances associated with edge- and face-bridging CO's. As found in [Rh₆C(CO)₁₅]^2-, the carbonyl ligands in [Rh₆C(CO)₁₄(PPh₃)]^2- undergo CO-intermolecular exchange with ¹³CO at different rates; for the edge-bridging CO's, the lower the value of ¹J(Rh–CO), the faster the rate of intermolecular exchange with ¹³CO.