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This study reports the use ofa natural deep eutectic solvent (NADES) with hollow fiber-microporous membrane liquid-liquid microextraction (HF-MMLLE) for the multiclass determination of 11 compounds classified as emerging contaminantsin water. Different deep eutectic solvents were synthetized and Thymol: Camphor (1:1 molar fraction) wasused as extraction solvent. The Thymol:Camphor was impregnated into the polypropylene membrane porous for 10 min, replacing commonly used solvents (ex. hexane and octanol). The optimized parameters were obtained by multi and univariate models. Extractions were carried out for 50 min using 1.5 mL of water sample at pH 6 and without addition of salt while desorption was made in a mixture of acetone: methanol (3:1, v/v) for 15 min. Separation/quantification was conducted by HPLC with a diode array detection (DAD)and calibration curves were obtained for each analyte. Determination coefficients higher than 0.9906 and limits of detection ranged from 0.3 to 6.1 µg L−1. Intraday precision (n = 3) ranged from 1.6 to 18.4% and inter day from 5.0 to 21.3%. Relative recoveries were performed in tap and stream water and ranged from 64 to 123%.

A water-soluble nanocarrier for a photo-activated CO releasing moiety (photoCORM) that can be triggered with NIR excitation is described. This has an upconversion nanoparticle core encapsulated by an amphiphilic polymer imparting both water solubility and a hydrophobic interior containing the photoCORM trans-Mn(bpy)(PPh3)2(CO)2. Such an ensemble offers a unique strategy for CO delivery to biological targets.

We describe a new strategy for triggering the photochemical release of caged carbon monoxide (CO) in aerobic media using long-wavelength visible and near-infrared (NIR) light. The dinuclear rhenium-manganese carbonyl complexes (CO)5ReMn(CO)3(L), where L = phenanthroline (1), bipyridine (2), biquinoline (3), or phenanthrolinecarboxaldehyde (4), each show a strong metal-metal-bond-to-ligand (σMM → πL*) charge-transfer absorption band at longer wavelengths. Photolysis with deep-red (1 and 2) or NIR (3 and 4) light leads to homolytic cleavage of the Re-Mn bonds to give mononuclear metal radicals. In the absence of trapping agents, these radicals primarily recombine to reform dinuclear complexes. In oxygenated media, however, the radicals react with dioxygen to form species much more labile toward CO release via secondary thermal and/or photochemical reactions. Conjugation of 4, with an amine-terminated poly(ethylene glycol) oligomer, gives a water-soluble derivative with similar photochemistry. In this context, we discuss the potential applications of these dinuclear complexes as visible/NIR-light-photoactivated CO-releasing moieties (photoCORMs).

The water-soluble rhenium(I) complex fac-[Re(bpy)(CO)(3)(thp)](+) (1) [CF(3)SO(3)(-) salt; bpy = 2,2'-bipyridine, thp = tris(hydroxymethyl)phosphine] is both strongly luminescent and photoactive toward carbon monoxide release. It is stable in aerated aqueous media, is incorporated into cells from the human prostatic carcinoma cell line PPC-1, and shows no apparent cytotoxicity. Furthermore, the solvated Re(I) photoproduct of CO release (2) is also luminescent, a feature that allows one to track the transformation of 1 to 2 inside such cells using confocal fluorescence microscopy. In this context, 1 is a very promising candidate as a photoactivated CO releasing moiety (photoCORM) with potential therapeutic applications.

The potential therapeutic effects of carbon monoxide in several disease states, and new methodologies for CO delivery to specific targets is a topic of growing interest in mammalian physiology. Here we provide an overview of recent efforts in this laboratory regarding several types of carbonyl complexes of the group 6 metal and of those in other laboratories that are focused on developing photochemical techniques for such CO delivery. Photo-activated carbon monoxide releasing moieties (photoCORMs) based on manganese, iron and group 6 metals are described.

We describe a new strategy for triggering the photochemical release of caged carbon monoxide (CO) in aerobic media using long-wavelength visible and near-infrared (NIR) light. The dinuclear rhenium–manganese carbonyl complexes (CO)5ReMn(CO)3(L), where L = phenanthroline (1), bipyridine (2), biquinoline (3), or phenanthrolinecarboxaldehyde (4), each show a strong metal–metal-bond-to-ligand (σMM → πL*) charge-transfer absorption band at longer wavelengths. Photolysis with deep-red (1 and 2) or NIR (3 and 4) light leads to homolytic cleavage of the Re–Mn bonds to give mononuclear metal radicals. In the absence of trapping agents, these radicals primarily recombine to reform dinuclear complexes. In oxygenated media, however, the radicals react with dioxygen to form species much more labile toward CO release via secondary thermal and/or photochemical reactions. Conjugation of 4, with an amine-terminated poly(ethylene glycol) oligomer, gives a water-soluble derivative with similar photochemistry. In this contex...

We examined how first year students (10th grade) of Greek Senior High School could conceptualize the influence of the molecular weight of saturated fatty acids on the melting and the freezing point, during the 'change of phase' phenomenon using the Microcomputer-Based Laboratory (MBL) system. Students had to freeze a melted substance, observing at the same time the change of its temperature and trying to explain the temperature vs time curve. They used different saturated fatty acids in order to understand how the molecular weight of each organic acid affects the melting – freezing point. Data about the students' conceptualizations was collected using three methods: videotape recordings, field notes and supplementary semi-structured interviews. The analysis of the students' responses to the same questions before and after the experiments showed statistically significant differences on their responses in every case. After the experiments there was a clear increase of correct responses concerning the freezing point of the saturated fatty acids, the relation of the freezing point to the molecular weight and the description of this relation.

The kinetics of calcite (CaCO(3)) crystallization on calcite seed crystals in the presence of taurine was investigated by the constant composition method. The presence of taurine (4 x 10(- 5)- 4 x 10(-4)M) in the supersaturated solutions lead to calcite crystals with a characteristic discontinuous planes of growth and poor habit, as compared to the hombohedral morphology of the seed crystals. The acceleration effect of taurine on the crystal growth rate was 17-96%. The apparent order of the crystal growth was found to be 2.0+/- 0.2 typical for a surface diffusion-controlled spiral growth processes.

In this work, the feasibility to develop micelle carriers of griseofulvin based on PLA-PEG copolymers was investigated. With the use of the dialysis method of micelle formation, the micellization behavior of a range of PLA(X)-PEG(5) copolymers was investigated. At copolymer concentrations in the organic solvent 10-20 mg/mL, stable micelles with 100% yield could only be prepared from PLA(X)-PEG(5) copolymers with molar composition in the range 50-70% PEG. The copolymers exhibited sufficiently low CMC to provide stable micelles in vivo. The loading capacity of PLA(4)-PEG(5) micelles with griseofulvin was 6.5 mg of drug/1 g of copolymer. The release of griseofulvin from the PLA-PEG micelles in vitro in phosphate-buffered saline (PBS) was sustained over 30 days. No burst effect was observed. Analysis of the release kinetics suggested that the release was erosion-controlled. The release profile was biphasic. Micelle degradation data in PBS indicated that the second phase of release was induced by copolymer degradation. The PLA-PEG micelles of griseofulvin were stable in simulated gastric and intestinal fluids for a long-enough time for oral application. Overall, the PLA-PEG micelles have suitable properties to be considered as potential oral or topical formulations of griseofulvin, provided that the drug-loading capacity of the micelles is sufficiently improved.

The effect of sodium alginate on the crystal growth of hydroxyapatite (HAP) was investigated at sustained supersaturation by the constant composition technique. Sodium alginate was found to inhibit HAP crystal growth at low concentrations and reduced the crystal growth rates by 42–86% for inhibitor concentrations of 2.1 × 10− 7–12.6 × 10− 7 mol/l. The inhibition effect on the crystal growth rate may be explained possibly through adsorption onto the active growth sites. A detailed kinetics analysis suggested a Langmuir-type adsorption of the alginate on HAP surface and a value of 1.63 × 107 l/mol was obtained for the affinity constant of sodium alginate for the surface of HAP. The apparent order for the crystallization reaction was determined to be approximately 2, thus suggesting a surface diffusion controlled spiral growth mechanism.

Flash and continuous photolysis studies of (μ-pdt)[Fe(CO)(3)](2) under excess CO were conducted in coordinating and noncoordinating solvents. The back-reaction of CO with the photoproduct showed second-order kinetics with k(CO) values of 1.0 × 10(8), 3.4 × 10(6), 1.2 × 10(6), and 0.90 M(-1) s(-1) in hexanes, benzene, toluene, and THF, respectively. These data indicate a solvent-coordinated intermediate as one photoproduct, but other long-lived species were also apparent.

Carbon disulfide (CS2) is thought to be a biologically relevant molecule that, upon reacting with amines, forms dithiocarbamates, which disrupt nuclear factor κB mediated tumor growth. To insure careful control we have designed a photocatalytic system whereby CS2 uncaged from the surface of binary chalcogenide cadmium selenide (CdSe) nanocrystalline quantum dots (QD). This is achieved through a hole transfer process to 1,1-dithiooxalate (DTO) adsorbed to the nanoparticle surface after exciting the QD with visible and near UV light. An analogous photoreaction occurs with the t-butyl- DTO ester. We have also synthesized an octyl-DTO ester through an acetylation and a subsequent sulfur replacement reaction with chloride substituents. These esters provide a modular system where the photochemical breakdown of the DTO compound could release additional therapeutics. Currently, we are working to synthesize a dye-functionalized DTO ester to further understand this photochemical process and product distribution. Th...

The crystal growth of hydroxyapatite (HAP), the thermodynamically most stable calcium phosphate phase at 37°C, pH 7.40 and ionic strength 0.15 M in the presence of ferrocene complexes has been investigated by the constant composition technique. The kinetic results showed a surface diffusion controlled mechanism. The presence of ferricenium salts inhibited the crystal growth of HAP possibly through adsorption onto the active growth sites for crystal growth. The kinetic results favored a Langmuir-type isotherm, suggesting a high affinity of ferricenium salts for HAP.

The precipitation and dissolution processes of the iron phosphate system may be of particular interest for the mechanism of phosphorus binding in the soils. The system of Fe(NO3)3–H3PO4–H2O was investigated at pH 2.00 and 25°C. At high supersaturations a crystalline phase of the formula Fe(H2PO4)(HPO4) · xH2O forms spontaneously at rates strongly dependent on the solution supersaturation. The solubility product of the spontaneously precipitating phase was found. Seeding of stable supersaturated solutions with the spontaneously precipitating solid resulted in ferric phosphate dihydrate overgrowth, with a second-order dependence of the rate on the relative solution supersaturation, suggesting a surface diffusion – controlled mechanism.

Full Paper: The critical concentration c** which separates the regime of extremely dilute solutions from that of dilute solutions of polymers was studies in the static state and in flowing solution. This concentration is lower when determined by UV measurements in the static compared to the critical concentration determined in the dynamic state using viscosimetry. The influence of the molecular mass of the polymer and of thetemperature on the critical concentration was studied. Further arguments are presented wich can be made in favor of the assumption that in the critical concentration c** entanglement emerge between the macromolecular chains.

A new viscometric method, which consists of plotting the inverse of the intrinsic viscosity versus the inverse of the square root of the molecular mass (Dondos and Staikos, Colloid Polym. Sci. , 1995, 273 , 62) has been applied for the determination of the statistical segment length of a poly(p-phenylene) ribbon-type polymer (Me-LPPP). The same method has also been applied to determine the statistical segment length of other wormlike polymers with viscometric data taken from the literature. The values of the statistical segments obtained using this new method are in close agreement with the values obtained from other methods.

The critical overlapping concentration c * has been studied in the dynamic state (by viscometry) and in the static state (by light scattering). An increase of the shear rate of the solution provokes an increase of c * in the case of linear polymers. In the case of a highly branched polymer the shear rate has no influence on its critical concentration. The scaling law between c * and the molecular mass for a given polymer—solvent system presents two different exponents, depending on the molecular mass region of the polymer.

When viscometry is used, a crossover phenomenon is observed separating the dilute solutions into extremely dilute solutions and dilute solutions. The critical concentration c**, determined from this crossover phenomenon, strongly depends on the shear rate in the solution. At very high values of shear rate the critical concentration c** becomes very low and depends only on the contour length of the elongated chains of different polymers. An increase of the temperature induces an increase of c** because the relaxation time of the chains decreases. If a polymer adopts a rodlike conformation (in a given solvent at a given temperature) the excluded volume of its chains increases and its critical concentration c** decreases.

Carbon disulfide, a potentially therapeutic small molecule, is generated via oxidative cleavage of 1,1-dithiooxalate (DTO) photosensitized by CdSe quantum dots (QDs). Irradiation of DTO-QD conjugates leads to λirrindependent photooxidation with a quantum yield of ∼4% in aerated pH 9 buffer solution that drops sharply in deaerated solution. Excess DTO is similarly decomposed, indicating labile exchange at the QD surfaces and a photocatalytic cycle. Analogous photoreaction occurs with the O-tert-butyl estertBuDTO in nonaqueous media. We propose that oxidation is initiated by hole transfer from photoexcited QD to surface DTO and that these substrates are a promising class of photocleavable ligands for modifying QD surface coordination. © 2013 American Chemical Society.

A relation is proposed which yields the occupied volume by macromolecular chains in solution. The experimental verification of the model is carried out by a viscometric study of the ternary system polymer A/polymer B/solvent. More precisely the viscometric study permits the determination of the critical concentration c** corresponding to the incipient overlap of spherical coils.

A viscometric study is presented using ternary systems polymer-1/polymer-2/solvent. The variation of the reduced viscosity of the polymer mixture with the total concentration shows two crossover points corresponding to the two critical concentrations of polymers C∗∗ and C∗. The influences of the temperature and of the hydrodynamic volume of the polymers on the critical concentrations are also presented.

A very sharp crossover is observed in the variation of the reduced viscosity ηsp/c as a function of the concentration c for mixtures of 1:1 by weight mixtures of polystyrene and poly(methylmethacrylate) in benzene at 20°C and a 1:1 by weight mixture of poly(ethylene glycol) and polystyrene in benzene at 20°C. The crossover is attributed to the critical to the concentration of the two respective polymers in the solution and its sharpness is due to the incompatibility between the two different polymers.

The incompatibility of different couples of polymers is correlated with the dipole moment of these polymers. It is shown that when the dipole moment of a polymer A is very close to the dipole moment of a polymer B the incompatibility of the mixture polymer A-polymer B is very low. In the contrary a mixture polymer A-polymer B presents a high incompatibility when the dipole moment of the polymer A is too different from the dipole moment of the polymer B.