Resonance Light Scattering Measurements Research Articles

Nitrogen-Doped Carbon Nanodots-Ionogels: Preparation, Characterization, and Radical Scavenging Activity.

Hybrid diimidazolium-based ionogels were obtained by dispersing nitrogen-doped carbon nanodots (NCNDs) in ionic liquid (IL) solutions and by using dicationic organic salts as gelators. The properties of the NCND-ionogels were studied in terms of thermal stability, mechanical strength, morphology, rheological, and microscopic analyses. Insights into the formation of the hybrid soft material were attained from kinetics of sol-gel phase transition and from estimating the size of the aggregates, obtained from opacity and resonance light-scattering measurements. We demonstrate that, on one hand, NCNDs were able to favor the gel formation both in the presence of gelating and nongelating ILs. On the other hand, the gelatinous matrix retains and, in some cases, improves the properties of NCNDs. The NCND-ionogels showed the typical fluorescence emission of the carbon dots and a notable antiradical activity, with higher efficiency as compared to the single components. The presented hybrid materials hold great promise for topical applications in antioxidant fields.

A Study of the Influence of Ionic Liquids Properties on the Kemp Elimination Reaction

The morpholino-induced elimination of 5-nitrobenzisoxazole into the relevant 2-cyano-4-nitrophenolate has been used as a sample reaction in order to investigate molecular properties of some room temperature ionic liquids. The kinetic study was carried out at 298 K by means of spectrophotometric measurements. Ionic liquids, which differ in both their cation and anion properties, were used as solvent systems. In particular, aliphatic (pyrrolidinium, piperidinium, and ammonium) and aromatic (imidazolium and pyridinium) ionic liquids were used. For aromatic cations, imidazolium ions having different hydrogen-bond donor ability or a different alkyl-chain length were taken into account. The anions chosen ([BF(4)(-)], [PF(6)(-)], [SbF(6)(-)], and [NTf(2)(-)]; where NTf(2) = bis(trifluoromethansulfonyl)imide) showed different shape, size, and coordination ability. Solvent parameters of all ionic liquids used were determined by using spectroscopic probes, such as 4-nitroaniline, N,N-diethyl-4-nitroaniline, Nile Red, and Reichardt's dye. Finally, in order to obtain information on the structural organization of the solvent systems, resonance light-scattering measurements were carried out. The collected data provide evidence that ionic liquids are solvent media which exhibit peculiar features, whose effects can be rationalized only considering all parameters affecting their three-dimensional structure.

Interactions of Nile Blue Sulphate with Nucleic Acids as Studied by Resonance Light-Scattering Measurements and Determination of Nucleic Acids at Nanogram Levels

ABSTRACT The interactions of nile blue sulphate (NBS) with nucleic acids, including calf thymus DNA, fish sperm DNA and yeast RNA, were characterized with resonance light-scattering (RLS) measurements by using a common spectrofluorometer. Accordingly a method for the determination of nucleic acids at nanogram levels was established. At pH's of 7.20∼7.60 and ionic strengths lower than 0.012, the interactions of NBS with nucleic acids result in three characteristic RLS peaks at 293.4 nm, 349.4 nm and 560.4 nm. Mechanism study shows that these peaks are ascribed to the long range assembly of NBS on the molecular surface of nucleic acids, which depends on pH, ionic strength and the stranded structure of nucleic acids. A Scatchard plot was constructed by using the RLS data, yielding the assembly number and assembly constant being 6.4 and 7.13x106 mol−1 1 for NBS assembly on the molecular surface of calf thymus DNA. The same parameters are 6.6 and 4.58x106 mol−1 1 for the assembly on that of fish sperm DNA, 3.9 and 1.67x106 mol−1 1 on that of yeast RNA, respectively. Linear relationships were found between the enhanced RLS intensity at 293.4 nm and nucleic acid concentration. If 1.2x10−5 mol I−1 NBS was employed, 0∼0.80 μg ml−1 calf thymus DNA and fish sperm DNA, 0.20∼0.60 μg ml−1 yeast RNA can be determined with the determination limits being 3.2 ng ml−1 for calf thymus DNA, 11.5 ng ml−1 for fish sperm DNA and 38.3 ng ml−1 for yeast RNA, respectively. Four synthetic samples were determined with satisfaction.

Spectral Characteristics of the Aggregation of α,β,γ,δ-Tetrakis(p-sulfophenyl)porphyrin in the Presence of Proteins

Abstract With the aid of absorption, fluorescence, and resonance light-scattering measurements, the aggregation of protonated water-soluble porphyrin, α,β,γ,δ-tetrakis(p-sulfophenyl)porphyrin, [H4tpps4]2−, in the presence of proteins has been characterized. At pH 1.86, proteins dissolved in water can form a positively charged microphase, which can neutralize the negative charges of [H4tpps4]2− distributed in it, leading to the J- and H-aggregation of [H4tpps4]2−. Exciton splitting signals, which are generally associated with the aggregation of porphyrins, as described by molecular-exciton theory, are observed at 436.1 nm on the resonance light-scattering spectra, supporting the porphyrin–porphyrin interactions in the positively charged microphase of proteins. It has been proved that positively charged microphase can protect aggregates of [H4tpps4]2− from water dilution and high temperature.