José L. Bourdelande

Characterization of Edible Oils Using Total Luminescence Spectroscopy

Total luminescence spectroscopy was used to characterise and differentiate edible oils and additionally, to control one of the major problems in the oil quality—the effect of thermal and photo-oxidation. We studied several vegetable oils available on the Polish market, including soybean, rapeseed, corn, sunflower, linseed and olive oils. Total luminescence spectroscopy measurements were performed using two different sample geometries: front-face for pure oil samples and right-angle for transparent samples, diluted in n-hexane. All the samples studied as n-hexane solutions exhibit an intense peak, which appears at 320 nm in emission and 290 nm in excitation, attributed to tocopherols. Some of the oils exhibit a second long-wavelength peak, appearing at 670 nm in emission and 405 nm in excitation, belonging to pigments of the chlorophyll group. Additional bands were present in the intermediate range of excitation and emission wavelengths; however, the compounds responsible for this emission were not identified. The front-face spectra for pure oils included chlorophyll peaks for most samples, and some additional peaks in the intermediate range, while the tocopherol peaks were comparatively less intense. The results presented demonstrate the capability of the total luminescence techniques to characterise and differentiate vegetable oil products, and additionally, to characterize the effect of thermal and photo-oxidation on such products. In the photo-oxidation experiments, special attention was paid to possible involvement of singlet oxygen. Experiments were done to monitor the highly specific O2 (1Δg) → O2(3Σ−) singlet oxygen emission at 1270 nm. Thus, total luminescence spectroscopy presents an interesting alternative to time-consuming and expensive techniques such as gas or liquid chromatography, mass spectrometry and other methods requiring wet chemistry steps.

Influence of Light and Oxygen on the Color Stability of Five Calcium Silicate–based Materials

INTRODUCTION Difficult handling, long setting time, and potential discoloration are important drawbacks of white mineral trioxide aggregate (WMTA). The development of Biodentine, a recently developed calcium silicate-based material (CSM), has overcome some of these shortcomings; however, there are no available data on its color stability. A previous study showed that WMTA discolors under light irradiation in an oxygen-free environment. The present study evaluated the influence of light irradiation and oxygen on the color stability of 5 CSMs. METHODS Fifteen samples of 5 CSMs (ProRoot WMTA, Angelus WMTA, White Portland Cement [PC], PC with bismuth oxide, and Biodentine) were divided into 5 groups. Each group was exposed to different oxygen and light conditions. A spectrophotometer was used to determine the color of each specimen at 0, 120 seconds, and 5 days. Data were analyzed by using analysis of variance and Tukey honestly significant difference test. RESULTS The materials PC with bismuth oxide, Angelus WMTA, and ProRoot WMTA showed dark discoloration after light irradiation in an oxygen-free environment, which was statistically significantly different from Biodentine and PC. In groups that were exposed to no light irradiation or to an oxygen atmosphere, all materials showed color stability over time, and no significant differences were observed among them. PC and Biodentine maintained color stability in all conditions over time and showed no significant differences. CONCLUSIONS The combination of light and anaerobic conditions (similar to those in clinical situations) results in differences in color of the tested CSMs during a period of 5 days, of which Biodentine and PC demonstrated color stability.

Photophysical properties of lumichromes in water.

The photophysics of lumichrome, 1-methyllumichrome, and lumiflavin in water solutions have been investigated. Fluorescence lifetimes of 2.7 and 2.2 ns were observed for lumichrome and 1-methyllumichrome, respectively, the corresponding triplet state lifetimes of 17 and 18 micros have been obtained from the transient absorption spectra. Evidence for long lived species with absorption maxima near 450 nm and lifetimes of ca. 400 micros has been found in the transient absorption spectra of both lumichromes. Quantum yields for the sensitised production of singlet oxygen, phi(Delta), are 0.36 and 0.41 for lumichrome and 1-methyllumichrome, respectively, in D(2)O.

[2+2] Photocycloaddition of homochiral 2(5H)-furanones to alkenes. First step for an efficient and diastereoselective synthesis of (+)- and (−)-grandisol

Abstract The [2+2] photocycloaddition of homochiral 5-alkyl-2( 5H )-furanones to alkenes is studied in order to evaluate the influence of the stereogenie centre to induce facial diastereoselectivity. The major cycloadduct could be transformed, eventually, in (+)-grandisol, The existence of a charge-transfer complex between the furanone and electron rich substituted alkenes as well as the formation of a predominant conformation in 5-oxyalkylfuranones due to n-π interactions are discussed.

A novel phosphine sulphide functionalized polymer for the selective separation of Pd(II) and Au(III) from base metals

Abstract Two new insoluble extractant systems based on a derivated polystyrene have been prepared for the separation and recovery of precious metals. This functional polymer has been obtained by the incorporation of a phosphine sulphide on the Merrifield polymer. This incorporation has been made by either direct attachment to the polymer or through on alkyl chain as spacer between the polymeric backbone and the phosphine sulphide unit. The spacer consists of a tris-ethoxylated chain to provide hydrophilic properties. Adsorption of metals Au(III) or Pd(l1) from chloride solutions have been studied for the different polymers prepared and by varying the composition of the metal solution with mixed aqueous-dioxane media. The results obtained include the polymer capacity and the rate of metal adsorption. Capacity for Pd(II) has been observed much higher than for Au(III) in all cases. The capacity as well as the adsorption rate are enhanced by the incorporation of the spacer in the polymer and also by the presence of dioxane in the metal solution. On the other hand, the adsorption process has shown to be selective for AU(111) or Pd(II) in presence of the base metals Pb(II), Ni(II) and Cu(II).

Phthalocyanines bound to insoluble polystyrene. Synthesis and properties as energy-transfer photosensitizers

Abstract Metallotetracarboxyphthalocyanines (MTCPc, M = Cu, Al) were bound to the amino groups of Amberlite IRA-93 by amide bonding. The insoluble materials obtained were characterized by IR absorption, visible absorption and diffuse reflectance, and ICP atomic emission spectroscopy, and tested for energy transfer under irradiation in the phthalocyanine Q-band. Samples containing A1TCPc are strongly fluorescent both in the solid state and in DMF suspension. Fluorescence quantum yields decrease sharply in toluene suspension. In the solid state, fluorescence may be quantitatively quenched by energy-transfer to an adsorbed dye. Singlet molecular oxygen (1O2) quantum yields were obtained in suspension by monitoring the photooxidation of diphenylisobenzofuran. Values are drastically reduced in DMF suspension and even more in toluene suspension relative to homogeneous solution. This fact is attributed to dye aggregation (M = Cu) and excited-state self-quenching (M = Al). Results can be rationalized by assuming that MTCPc incorporation occurs mainly at the polymer surface and that dye-to-dye interaction in suspension depends strongly on the environment.

Highly efficient and diastereoselective approaches to (+)- and (−)-grandisol

Abstract Two new routes to (+)-grandisol and three new routes to (−)-grandisol are described All of them are highly efficient and diastereoselective The common starting material is an easily available homochiral butenolide

Photochemistry of single wall carbon nanotubes embedded in a mesoporous silica matrix

By embedding single wall carbon nanotubes in a mesoporous silica matrix (SWNT@SiO2) the photochemical properties have been measured upon laser excitation at 266 nm; the SWNT@SiO2 exhibits long-lived emission (lambda em = 400 nm, tau = 0.95 microsecond), transient absorption (lambda max = 390 nm, tau = 11 microseconds) and is able to generate singlet oxygen in D2O.

C60 Fullerene-based materials as singlet oxygen O2(1Δg) photosensitizers: a time-resolved near-IR luminescence and optoacoustic study

The triplet properties of a series of fullerene dihydroderivatives of the o-quinodimethane type and of three representative inclusion complexes with γ-cyclodextrin and calix[8]arenes have been studied. It is found that chemical modification results in a decrease of the singlet oxygen quantum yield relative to C60, with an average ΦΔ = 0.76. On the other hand, encapsulation in either γ-cyclodextrin or calix[8]arene produces greatly varying results depending on host and solvent. Thus, in D2O the γ-cyclodextrin complex of C60 sensitizes O2(1Δg) with ΦΔ = 0.77, while the calixarene complex is totally ineffective, probably due to the occurrence of a fast charge transfer-mediated deactivation process. In CCl4 the calixarene complex acts very much like C60, i.e., ΦΔ = 0.84.

Encapsulation and release mechanisms in coordination polymer nanoparticles.

The interplay of guest encapsulation and release mechanisms in nanoscale metal-organic vehicles and its effect on the drug-delivery kinetics of these materials were investigated through a new multidisciplinary approach. Two rationally-designed molecular guests were synthesized, which consist of a red-fluorescent benzophenoxazine dye covalently tethered to a coordinating catechol group and a protected, non-coordinating catechol moiety. This allowed loading of the guests into compositionally and structurally equivalent coordination polymer particles through distinct encapsulation mechanisms: coordination and mechanical entrapment. The two types of particles delivered their fluorescent cargo with remarkably different kinetic profiles, which could be satisfactorily modeled considering degradation- and diffusion-controlled release processes. This demonstrates that careful selection of the method of guest incorporation into coordination polymer nanoparticles allows selective tuning of the rate of drug delivery from these materials and, therefore, of the time window of action of the encapsulated therapeutic agents.