SPECTROFLUORIMETRIC INVESTIGATION OF 2-BENZOPYRYLIUM PERCHLORATES

1,3-Dimethyl-6,7-dimethoxy-2-benzopyrylium perchlorate (1) and its 1-substituted-vinyl, 1-styryl, 1-substituted-styryl derivatives were prepared. The fluorescence properties of fifteen compounds were investigated by pectrofluorimetric method. The 1 and the 1-(substituted-vinyl) derivatives fluoresce intensely. The 1-(3-indolybvinyl)-3-methyl-6,7-dimethoxy-2-benzopyrylium perchlorate (14) shows the most intense fluorescence. The 1-styryl-3-methyl-6,7-dimethoxy-2-benzopyrylium perchlorate (4) fluoresces very weakly. The position of the substituent on the benzene ring and the quality of the substituent have an important influence on the fluorescence. Some investigated derivatives show intensive flourescence in the IR-region. Spectrofluorimetric methods were developed for the determination of eight compounds

Gas Antisolvent Fractionation: a New Method to Obtain Enantiopure Compounds, a Case Study on Mandelic Acid

Micronization processes involving supercritical carbon dioxide are rapid methods to produce fine particles. They also might offer the possibility of using less organic solvent than conventional crystallization methods leading to an environmentally friendlier processing. The separation capabilities of such processes are now demonstrated on the diastereomeric resolution of mandelic acid using (R)-1-phenylethanamine as a resolving agent, utilizing the batch type gas antisolvent fractionation as the separation method. A detailed study was conducted on the effects of the operational parameters pressure (12-20 MPa), temperature (35-55 °C) and co-solvent concentration (33-99 mg/ml). At 12 MPa, 35 °C and 99 mg/ml methanol concentration, a selectivity of 0.52 and a diastereomeric excess of 62% was reached. The same operational parameters were applied during the investigation of the recrystallization-based further purification of the diastereomeric salts, applying the resolving agent in molar equivalent quantity to a non-racemic mixture of mandelic acid. It has been found that the more stable (R)-1-phenylethylammonium-(R)-mandelate salt can be purified to de>98% through four additional recrystallization steps following the initial, half-molar equivalent resolution step

Önszerveződő hibrid filmek előállítása nanoszerkezetű anyagokból = Preparation of self-assembled hybrid films from nanostructured materials

Önszerveződő hibrid nanofilmek előállítását, szerkezeti és optikai tulajdonságait vizsgáltuk különböző kolloidokból felépíthető ultravékony rétegekben. Funkcionált felületű nanorészecskékből szabályozott szerkezetű nanohibrid ultravékony filmeket készítettünk. A félvezető-oxidok közül a cink-oxid részecskéket alkalmaztuk önszerveződő filmek építéséhez és szenzorok előállításához. Réteges szerkezetű nanolamellás rendszerek kiváló önszerveződő tulajdonságokkal rendelkeznek a lamellák anizometrikus dimenziói miatt. A hibrid rétegek további komponensei lehetnek polimerek, peptidek és fehérjék is. Az önrendeződés folyamatát kétdimenziós kísérletekben Langmuir-mérleggel is követtük és jellemeztük a filmek kompresszibilitását. Az ezüst plazmonikus tulajdonságait kihasználva a látható fényben gerjeszthető fotokatalizátorokat készítettünk és azok hatékonyságát fotooxidációs reakciókkal minősítettük. Kvázi-kétdimenziós optikai reflexiós spektroszkópiával tanulmányoztuk a hidrofil és hidrofób nanohibrid filmeket. Funkcionalizált arany részecskékkel gőzök adszorpciójára szenzitív interdigitális szenzorokat fejlesztettünk ki. Aminosavak funkcionalizáló hatását tanulmányoztuk, és a plazmonikus anyagok felületén bekövetkező szorpciós folyamatok alkalmasak az ezüst valamint az arany nanorészecskék felületén megkötött biokolloidok tulajdonságainak optikai jelzésére. Ez a módszer kifejleszthető gyógyszer hatóanyagok megkötésének kvantitatív detektálására protein szupramolekulákra. | Structural and optical properties of self-assembled hybrid nanofilms prepared from different colloids were investigated. The nanohybrid ultrathin films with tailored structure were prepared from functionalized nanoparticles. Semiconductor metal oxide (zinc oxide) nanoparticles were applied for the construction of self assembled films for sensor application. The layered structured nanolamellar systems exhibit excellent self assembled properties because of the anisometric dimensions of the lamellae. Further components of the hybrid layers may also involve polymers, peptides and proteins as well. The self-assembly process was controlled by two dimensional Langmuir-balance measuring the compressibility of the films. The plasmonic properties of silver were exploited for photocatalysis. The catalysts can be excited in visible light and their efficiency in photooxidation reactions was determined. Quasi-two dimensional optical reflection spectroscopy on hydrophilic and hydrophobic nanohybrid films were studied using setup developed in our laboratory. Gold nanoparticles were deposited on interdigital sensor surfaces measuring the vapours adsorption. The effect of surface functionalization by amino acids were also studied. The sorption processes are able to modify the optical signal on the surface of plasmonic materials for biocolloids on plasmonic surfaces. This method can be developed for quantitative characterization of pharmaceutical drug materials binding on supramolecules

Ultrasmall, Ligand-Free Ag Nanoparticles with High Antibacterial Activity Prepared by Pulsed Laser Ablation in Liquid

Since ancient times, silver and its compounds have been known to have a broad spectrum of antimicrobial activities for bacteria, fungi, and viruses. Due to the increasing bacterial resistance to classic antibiotics, the investigations of Ag NPs have increased. Herein, we present the preparation of ligand-free Ag NPs with 3 and 20 nm sizes by applying picosecond laser ablation in liquid at 355 and 1065 nm. Our laser processing system allows a high control on particle sizes. The produced nanoparticles were characterized by means of transmission electron microscopy, UV-Vis spectroscopy, and X-ray diffraction. The size effect on the antibacterial activity of Ag NPs was tested againstE. coliandS. aureus. The growth curves of bacteria were monitored at 0–5 mg/L of Ag NPs by a multimode microplate reader. The size effects as well as the concentration of Ag NPs on their antibacterial activity are discussed

Supercritical carbon dioxide assisted synthesis of ultra-stable sulfur/carbon composite cathodes for Li– S batteries

To mitigate the shuttle effect and enhance the electrical conductivity in lithium battery cathode, the unique characteristics of supercritical CO2 solvent (SC–CO2) and the distinctive porous and layered microstructure of reduced graphene oxide (rGO) are exploited in the fabrication of a high-performance rGO/sulfur composite cathode. Exploiting SC-CO2 technology can realize highly efficient sulfur transfer and precise microstructure regulation of S/C composite cathodes for Li–S batteries. On exposure, due to the sudden pressure release process, the SC-CO2 expands the interlayers of rGO rendering plenty of storage space for small sulfur allotropes in carbon matrices which increases the active sulfur loading. Being a remarkable hydrophobic solvent, the wetting properties of SC-CO2 are excellent, ensuring sulfur dissolution and penetration deep into the voids and interlayers of rGO. This creates intimate contact of sulfur with rGO interlayers, guaranteeing precise sulfur content, uniform sulfur distribution, and strong interaction between sulfur and carbon leading to enhanced electrical conductivity and sulfur utilization efficiency. Another important feature is that the S/C composites can be prepared at room temperature, unlike other conventional techniques which require a higher temperature. Moreover, the product mixture can be separated simply by de-pressuring SC-CO2. Herein, the rGO/sulfur composite cathode prepared on a lab scale showed an initial discharge capacity of 1024 mAh/g at 0.1C rate with capacity retention of 92.2% and coulombic efficiency of 99% even after 200 charge-discharge cycles. The developed cells showed excellent performance (929 mAh/g at 1 C rate) with an ultralow decay of 0.04% per cycle even after 200 charge-discharge cycles. Through this work, we believe that the synergistic effect of SC-CO2 technology and rGO as sulfur host will open up a promising future for the synthesis of efficient S/C composite cathodes with ultra-high cycling stability