Assemblies of perylene diimide derivatives with melamine into luminescent hydrogels

We report unique and spontaneous formation of hydrogels of perylene derivatives with melamine. The luminescent gel network is formed by H-type aggregation of the perylene core, supramolecularly cross-linked by melamine units. As a result of controlled aggregation in the extended nanofibers, strong exciton fluorescence emission is observed.     

Metabolism of <Superscript>14</Superscript>C-labelled and non-labelled sulfadiazine after administration to pigs

The behaviour of sulfadiazine (SDZ) and its metabolites was investigated by administering the ¹⁴C-labelled veterinary drug to fattening pigs. The excretion kinetics were determined after daily collection of manure. Two known metabolites, N-acetylsulfadiazine and 4-hydroxysulfadiazine, and two hitherto unidentified minor metabolites were recovered. Various mass spectrometric techniques such as parent, product ion scans and accurate mass measurement were used. The new compounds were identified as N-formylsulfadiazine (For-SDZ) and N-acetyl-4-hydroxysulfadiazine (Ac-4-OH-SDZ). The identification of SDZ, Ac-SDZ and For-SDZ was confirmed by comparison of the spectroscopic and chromatographic data of the synthesized authentic references. The identification of the hydroxylated compounds 4-OH-SDZ and Ac-4-OH-SDZ was performed by MSⁿ, and accurate mass measurements. Only 4% of the administered radioactivity remained in the pig after ten days and SDZ accounted for 44% of the 96% radioactivity excreted. More than 93% of the labelled compounds were detected and identified in the manure. The key analytical problem, namely a high concentration of matrix in sample extracts, was overcome by advanced measurement techniques and with the use of a suitable internal standard. The mean recoveries for all compounds were ≥96%. Linearity was established over a concentration range of 0.5 to 10,000 μg kg⁻¹ manure with a correlation coefficient ≥0.99. The same experiment was carried out simultaneously with non-labelled SDZ to obtain manure for outdoor soil experiments.     

Effect of temperature on adsorption and corrosion inhibition characteristics of gelatin on mild steel in hydrochloric acid medium

Research on Chemical Intermediates - Adsorption characteristics of a water-soluble bio-polymer, gelatin, on mild steel in 1-M hydrochloric acid (HCl) together with its potential corrosion resistive...     

Light Harvesting and Amplification of Emission of Donor Perylene–Acceptor Perylene Aggregates in Aqueous Medium

With the aid of rational design, we have synthesized a pair of water‐soluble donor‐ and acceptor‐type twisted perylene bisimide units, which together form aggregates upon lowering the pH of the medium, providing bright yellow fluorescence. The light‐harvesting efficiency of the co‐assembled system can be tuned by controlling the ratio of donor to acceptor and 98.1 % efficiency has been achieved.     

Isomerization and fluorescence depolarization of merocyanine 540 in polyacrylic acid. Effect of p H

Dynamics of isomerization and fluorescence depolarization of merocyanine 540 (MC540) in an aqueous solution of polyacrylic acid (PAA) have been studied using picosecond time resolved fluorescence spectroscopy. It is observed that the dynamics of isomerization and depolarization are sensitive enough to monitor the uncoiling of PAA at high pH (> 6). At low pH (< 3), when the polymer remains in a hypercoiled form, polymer bound MC540 experiences very high microscopic friction and, hence, the isomerization and depolarization processes are very slow. At high pH (> 6) a polyanion is formed and the polymer assumes an extended configuration due to electrostatic repulsion. At high pH (> 6), the anionic probe MC540 is expelled from the polyanion to bulk water and the dynamics of isomerization and fluorescence depolarization become faster by 12 and 5 times respectively, compared to those at low pH.     

Photoisomerization of merocyanine 540 in polymer-surfactant aggregate

Photoisomerization of merocyanine 540 (MC540) in a polymer-surfactant aggregate is studied using picosecond time resolved emission spectroscopy. The aggregate consists of the polymer, poly(vinylpyrrolidone) (PVP) and the surfactant, sodium dodecyl sulphate (SDS). With increase in the concentration of SDS in an aqueous solution of MC540 containing PVP, the emission quantum yield and lifetime of MC540 increase markedly. This indicates marked retardation in the nonradiative photoisomerization process of MC540, when it binds to the polymer-surfactant aggregate. The critical association concentration of SDS for binding to PVP has been found to be 0.5 mM. This is about 16 times lower than the CMC of SDS in pure water (8 mM).     

An all-organic steroid-D-π-A modular design drives ferroelectricity in supramolecular solids and nano-architectures at RT

Confluence of a modular design approach and self-assembly with a 'steroid-D-π-A' module generates spontaneous polarization in solids and for the first time in nano-architectures constituted from organogels, at room temperature (RT).     

Charge‐Transfer‐Induced Fluorescence Quenching of Anthracene Derivatives and Selective Detection of Picric Acid

2,6‐Divinylpyridine‐appended anthracene derivatives flanked by two alkyl chains at the 9,10‐position of the core have been designed, synthesized, and characterized by NMR, MALDI‐TOF, FTIR, and single‐crystal XRD. These anthracene derivatives are able to recognize picric acid (2,4,6‐trinitrophenol, PA) selectively down to parts per billion (ppb) level in aqueous as well as nonaqueous medium. Fluorescence emission of these derivatives in solution is significantly quenched by adding trace amounts of PA, even in the presence of other competing analogues, such as 2,4‐dinitrophenol (2,4‐DNP), 4‐nitrophenol (NP), nitrobenzene (NB), benzoic acid (BA), and phenol (PH). The high sensitivity of these derivatives toward PA is considered as a combined effect of the proton‐induced intramolecular charge transfer (ICT) as well as electron transfer from the electron‐rich anthracene to the electron‐deficient PA. Moreover, visual detection of PA has been successfully demonstrated in the solid state by using different substrates.     

Synthesis and characterization of cobalt and manganese complexes of indomethacin and comparative study of local analgesic,anti-inflammatory,and anti-ulcerogenic properties

The aim of the study was to synthesize cobalt and manganese complexes of indomethacin and their biological activity screening to uncover. The structures of metal complexes were elucidated by FT-IR, UV-Vis and atomic absorption spectroscopy, X-ray diffraction and calorimetric DSC. Heat radiant tail-flick test for local analgesic activity of cobalt complex of indomethacin in the doses of 50 and 100 μg/mL demonstrated potent local analgesic response. Manganese complex of indomethacin exhibited similar potent of activity at the dose of 100 μg/mL. Anti-inflammatory study of the indomethacin-manganese and indomethacin-cobalt complexes demonstrated their activity (paw edema inhibition of 71.67% at 20 mg/kg dose in the 1 h and 83.33% at 10 mg/kg dose in the 4 h) comparable with the standard diclofenac sodium. Gastrointestinal efficacy of cobalt and manganese complexes was close to that of indomethacin.     

Capillary liquid chromatography and capillary electrochromatography using silica hydride stationary phases

A hydride-based octadecyl stationary phase on both 4.0 and 1.8 microm silica particles is tested in both the capillary LC and the pressurized capillary electrochromatography (pCEC) modes. These two materials are compared to standard C18 stationary phase made by organosilanization and to the hydride material packed into a convention 4.6mm I.D. column. The performance of the capillary columns is evaluated in terms of analysis times for various mixtures as well as efficiency. Of particular interest are the differences between the LC mode where only laminar flow is present and pCEC operation where a flat electrodriven flow profile is superimposed on the parabolic pressurized flow. Differences in performance between columns packed with 4.0 and 1.8 microm particle silica are also evaluated.