Photochemical Characterization of Up-Converting Inorganic Lanthanide Phosphors as Potential Labels

We have characterized commercially available up-converting inorganic lanthanide phosphors for their rare earth composition and photoluminescence properties under infrared laser diode excitation. These up-converting phosphors, in contrast to proprietary materials reported earlier, are readily available to be utilized as particulate reporters in various ligand binding assays after grinding to submicron particle size. The laser power density required at 980 nm to generate anti-Stokes photoluminescence from these particulate reporters is significantly lower than required for two-photon excitation. The narrow photoluminescence emission bands at 520–550 nm and at 650–670 nm are at shorter wavelengths and thus totally discriminated from autofluorescence and scattered excitation light even without temporal resolution. Transparent solution of colloidal bead-milled up-converting phosphor nanoparticles provides intense green emission visible to the human eye under illumination by an infrared laser pointer. In this article, we show that the unique photoluminescence properties of the up-converting phosphors and the inexpensive measurement configuration, which is adequate for their sensitive detection, render the up-conversion an attractive alternative to the ultraviolet-excited time-resolved fluorescence of down-converting lanthanide compounds widely employed in biomedical research and diagnostics.     

Electrospray ionization mass spectrometry and tandem mass spectrometry of clodronate and related bisphosphonate and phosphonate compounds

The bisphosphonate family with a P-C-P structure is a broad class of drugs, widely investigated as potential inhibitors in bone diseases and calcium metabolic disorders. In this study, the mass spectrometric (MS) behavior and fragmentation of clodronate and related bisphosphonate and phosphonate compounds was studied by using negative ion electrospray ionization (ESI) with triple quadrupole and ion trap instruments. The effect of pH on the degree of deprotonation of the polyprotic bisphosphonic and phosphonic acids in negative ion ESI-MS was investigated, and the degree of deprotonation in the ESI mass spectra and the dissociation in the liquid phase were compared. The results provide evidence that the measured ESI mass spectra do not correlate with the chemistry in the liquid phase owing to the decrease in the pH of the solvent droplets during the ion evaporation process and the charge state neutralization in the gas phase. Ion trap MS(n) provided useful information on the fragmentation study of clodronate and related bisphosphonate and phosphonate compounds, in which interesting fragmentation pathways including the direct elimination of carbon monoxide from deprotonated bisphosphonates and formation of a P-P bond were observed. Reactions between the product ions with a -PO(2) group and residual water in the ion trap or in the high-pressure region of the triple quadrupole instrument formed other unexpected fragmentation paths for all the bisphosphonates studied.     

Analysis of reaction by-products in ethylene oligomers by capillary gas chromatography

Summary A gas chromatographic method using temperature-programmed poly-dimethylsiloxane OV-101 and poly(pheny ether) (5 rings) capillary columns was developed to separate and quantify the reaction by-products in ethylene oligomers. It was found that the content of 2-alkyl-1-alkenes, 2-alkenes and n-alkanes in the C₈–C₁₈ -olefin fractions amounts to 29, 10 and 2.6% respectively.     

A comparison of different retention index systems with unsaturated and aromatic hydrocarbons in capillary gas chromatography on PEG 20M

Summary The correction of the reproducibility of retention indices on polar capillary columns with different film thickness, using more polar reference standards instead ofn-alkanes, was investigated. It was found that the replacement ofn-alkanes by 1-alkenes, 3-alkynes and n-alkylbenzenes as standards significantly improves the reproducibility of retention indices and diminishes their temperature increments forn-alkanes,n-alkynes and arenes on PEG 20M columns.     

Cellulose based pH-sensitive hydrogel for highly efficient dye removal in water treatment: kinetic,thermodynamic, theoretical and computational studies

In this paper, a new green pH-sensitive EDTA crosslinked HEC (cellulose-based hydrogel (swelling rate?~?1005%)) adsorbent was successfully elaborated. The synthesis of HEC-EDTA at the high advanced crosslinking degree (up to 92%), was carried out using DAEDT and DMAP as acyl transfer agent, where the lamellar morphology (2D-microstructure) was highly suggested based on the average functionality of the reaction system. The crosslinking degree was confirmed using structural analyzes (FTIR and 13C CP/MAS-NMR) and elemental profile analysis. The new EDTA crosslinked HEC demonstrated a high uptake capacity (~?2000 mg g^?1) to aquatic micropollutants, especially methylene blue as cationic dyes model. The kinetic study showed that the adsorption process was well described by the pseudo-second-order kinetic, while the thermodynamic parameters exhibited a negative effect of temperature indicating a physical adsorption process. In addition, the adsorption capacity was studied varying to the experimental conditions (pH, contact time, concentration, etc.), and the Freundlich model revealed a strong correlation to the experimental data indicating an energetic heterogeneity of the surface active sites. Furthermore, using COMPASS II, the molecular dynamics (MD) simulations were conducted to optimize the chemical system, where the results showed the predominance of non-covalent molecular adsorbent-adsorbate interactions, which governs cluster design and configurations.

     

Adsorption of cationic starch on cellulose studied by QCM-D

The adsorption of cationic starch (CS) from aqueous electrolyte solutions onto model cellulose film has been investigated by the quartz crystal microbalance with dissipation monitoring (QCM-D) and X-ray photoelectron spectroscopy (XPS). The influence of the electrolyte composition and charge density of CS was examined. The adsorption of CS onto cellulose followed the general trends expected for polyelectrolyte adsorption on oppositely charged surfaces, with some exceptions. Thus, as result of the very low surface charge density of the cellulose surface, highly charged CS did not adsorb in a flat conformation even at low ionic strength. The porosity of the film, however, enabled the penetration of coiled CS molecules into the film at high electrolyte concentrations. Differences between the adsorption behavior of CS on cellulose and earlier observations of the adsorption of the same starches on silica could be explained by the different morphologies and acidities of the hydroxyl groups on the two surfaces.     

Projective extensions of semilattices

Sabine Koppelberg has introduced and studied the notion of projective extensions of Boolean algebras. Our aim is to characterize the projective extensions of semilattices. Received December 16, 2004; accepted in final form September 8, 2005.     

Phase separation and crystallinity in proton conducting membranes of styrene grafted and sulfonated poly(vinylidene fluoride)

A series of proton exchange membranes have been prepared by the preirradiation grafting method. Styrene was grafted onto a matrix of poly(vinylidene fluoride) (PVDF) after electron beam irradiation. Part of the samples was crosslinked with divinylbenzene (DVB) or bis(vinylphenyl)ethane (BVPE). Subsequent sulfonation gave membranes grafted with poly(styrene sulfonic acid) and marked PVDF‐g‐PSSA. It was found that the intrinsic crystallinity of the matrix decreased in both the grafting and the sulfonation reaction in all the membranes. The graft penetration and the ion conductivity are influenced strongly by the crosslinker. The ion conductivity is considerably lower in crosslinked membranes than in noncrosslinked ones. Generally, the mechanical strength decreases with crosslinking. The membranes show a regular phase separated structure in which the sulfonated grafts are incorporated in the amorphous parts of the matrix polymer. The phase separated domains are small, of the order of magnitude of 100–250 nm. These were resolved on transmission electron micrographs and on atomic force images but could not be resolved with microprobe Raman spectroscopy. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1741–1753, 1999