Search results for "Stability"
showing 10 items of 3085 documents
HAPPY Dyes as Light Amplification Media in Thin Films
2021
A series of 1Hamorphous tri-phenyl pyridine (HAPPY) dyes have been synthesized from luminescent triphenyl-group-containing 2-methyl-6-styryl-substituted-4H-pyran-4-ylidene derivatives in reactions with benzylamine and investigated for suitability as solution-processable light-emitting medium components in thin films for amplified spontaneous emission (ASE). Conversion of a 4H-pyrane ring into a 1H-pyridine fragment enables aggregation-induced emission enhancement (AIEE) behavior in the target products and slightly increases thermal stability, glass transition temperatures, and ASE efficiency with PLQY up to 15% and ASE thresholds as low as 46 μJ/cm2 in neat spin-cast films, although thermal…
Glass-forming non-symmetric bis-styryl-DWK-type dyes for infra-red radiation amplification systems
2019
Abstract A series of D-π-A type organic dyes with bulky triphenylmethyl moiety containing 2,6-bis-(4-substituted)styryl-4H-pyran-4-ylidene donor (D) fragments and different electron acceptors (A) were synthesized and investigated, mostly for potential applications in organic solid-state lasers as infra-red (IR) radiation amplification medium. Dye glass transition temperature is above 99 °C with thermal stability in the region from 173 °C to 326 °C which was slightly influenced by the electron acceptor fragment attached to the 4H-pyrane ring in 4-position. Introducing substituents in 4-position within one of the styryl-fragments with stronger electron withdrawing properties decreased ASE exc…
Introduction to MIP synthesis, characteristics and analytical application
2019
Abstract One of the trends in analytical chemistry is associated with designing and developing new types of sample preparation techniques, which might significantly increase the efficiency and selectivity of the analytes isolation or/and preconcentration process. One of the most widely employed solutions is selective sorption materials, defined as molecularly imprinted polymers (MIPs), as well as the sorbents with the molecular fingerprint. Due to their simple preparation protocol, mechanical, thermal and chemical stability and selectivity, MIPs have found application as a stationary phase in separation techniques such as liquid chromatography or capillary electrophoresis, in electrochemica…
Hydrolysis of (CH3)Hg+ in Different Ionic Media: Salt Effects and Complex Formation
1998
The hydrolysis of monomethylmercury(II) was studied potentiometrically, in NaNO3, Na2SO4, and NaCl aqueous solution, in a wide range of ionic strengths (NaNO3, 0 ≤ I ≤ 3.25; Na2SO4, 0 ≤ I ≤ 1; NaCl, 0 ≤ I ≤ 3 mol dm-3) and at t = 25 °C. For the reaction (CH3)Hg+ = (CH3)Hg(OH)° + H+, we found log K1 = −4.528 (I = 0 mol dm-3). The species [(CH3)Hg]2(OH)+ was also found, with log β2 = −2.15. Monomethylmercury(II) forms quite strong complexes with Cl- (log K = 5.45, I = 0 mol dm-3) and SO42- (log K = 2.64, I = 0 mol dm-3). The dependence on ionic strength of formation constants was considered by using a Debye−Huckel type equation. Hydrolysis and complex formation constants (at different ionic s…
Chemical and pharmaceutical evaluation of the relationship between triazole linkers and pore size on cyclodextrin–calixarene nanosponges used as carr…
2016
Mixed cyclodextrin–calixarene nanosponges were used to prepare some composites with the well known polyphenolic bioactive compounds quercetin and silibinin. The composites were characterized by means of different techniques (UV-vis, FT-IR, microcalorimetry, thermogravimetry), in order to assess their loading and thermal stability. The kinetics of release of the bioactive molecules into aqueous solution were studied at two different pH values (1.0, 6.4), which mimic typical physiological conditions. Finally the possible antiproliferative effects in vitro were assayed towards three triple negative breast cancer cell lines (SUM 149, SUM 159 and MDA-MB-23). Our results point out the role assume…
Stability−Charge and Stability−Structure Relationships in the Binding of Dicarboxylic Ligands by Open-Chain Polyammonium Cations
2000
The stability of complexes formed by 5 dicarboxylic ligands with 11 open-chain polyammonium cations (40 systems) was studied potentiometrically, in aqueous solution, at 25 °C. In all the systems ALHr species (A = amine, L = dicarboxylic ligand, r = 1 ... n; diamines n = 3, triamines n = 4, tetraamines n = 4 or 5) were found. Formation constants for the various complexes studied in this work, together with data for the analogous systems previously studied (20 systems), were examined as a function of charges involved in the formation reaction and of the structure of both the dicarboxylic ligand and the polyammonium cation. Structure generally has little effect on stability, while charges play…
A Facile Approach for Transferring Hydrophobic Magnetic Nanoparticles into Water-Soluble Particles
2008
A novel, easy and high-efficient method is described for transferring hydrophobic magnetic Fe 3 O 4 nanoparticles from organic to aqueous solution by wrapping a thermo-responsive and photocrosslinkable poly(N-isopropylacrylamide) (PNIPAm) terpolymer around the particles. The wrapping procedure is introduced by the co-nonsolvent transition of PNIPAm in the mixing solvent and the polymer can dissolve in water carrying Fe 3 O 4 nanoparticles by noncovalent interaction. The temperature-dependant and magnetic properties of the water-soluble particles are characterized in this paper.
Palladium(II) sequestration by phytate in aqueous solution. Speciation analysis and ionic medium effects.
2010
Environmental context.In the last 20 years, the demand for palladium and other platinum-group elements has intensified, causing a significant increase in their concentration in the environment, with particular accumulation in urban areas. Knowledge about Pd2+ speciation in aqueous media is fundamental for the understanding of its biological and environmental activity in contaminated areas. Phytic acid appears to be a good sequestering agent towards Pd2+ under various conditions, indicating its potential use in the remediation of contaminated sites. Abstract. Palladium(II) speciation in the presence of phytate (Phy12–) was studied by H+ ion selective electrode (ISE) potentiometry at 25°C in…
Speciation of tin(II) in aqueous solution: thermodynamic and spectroscopic study of simple and mixed hydroxocarboxylate complexes
2013
This contribution reports the results of potentiometric and Mossbauer investigations on the formation, stability, and structure of binary and ternary mono- and binuclear complexes of Sn2+ with three hydroxocarboxylic ligands (namely L = tartrate, malate, and citrate) and chloride at T = 298.15 K in different ionic media and ionic strengths (0.15 and 1.00 mol dm−3 in NaCl(aq) and 1.00 mol dm−3 in NaNO3(aq)). The stability constants of various simple Sn i H j L (2+−) and mixed Sn i H j L k Cl (2+−−) species obtained in the different experimental conditions are reported, and various speciation diagrams of the simple and mixed systems are shown in different conditions. The sequestering ability …
Speciation of Low Molecular Weight Carboxylic Ligands in Natural Fluids: Protonation Constants and Association with Major Components of Seawater of O…
1999
Abstract The interaction of oxydiacetate and citrate with the major components of seawater has been studied potentiometrically, at 25°C, in an artificial seawater (containing Na+, K+, Ca2+, Mg2+, Cl− and SO42−) at different salinities (5–45‰). Apparent protonation constants were calculated, from potentiometric data, and estimated, using an appropriate complex formation model. Formation constants of complexes formed by oxydiacetate and citrate and the cation of seawater (the inorganic content of seawater being considered as a single 1 : 1 salt) were determined. The single salt approximation for the major inorganic components of seawater, which is a good tool in estimating the mean strength o…