Cationic or anionic sites? Selectivity optimization of ion-selective electrodes based on charged ionophores

The influence of ionic sites on the selectivities of ionophore-based ion-selective electrodes (ISEs) is described on the basis of a phase boundary potential model. The discussion presented here is significantly more general than previous ones. It is formulated for primary and interfering ions of any charges and it is valid for ISEs based on electrically charged or neutral ionophores. Furthermore, it also applies to membranes that contain more than one type of complex of the primary or interfering ion. It has been believed thus far that only ionic sites of the same charge sign as the primary ion improve the selectivities of ISEs based on charged ionophores. However, it is shown here that the charge sign of the ionic sites that give the highest potentiometric selectivities depends on the charge number of the primary and interfering ions and on the stoichiometry of their complexes with the ionophore. The validity of our model was confirmed experimentally with three ISEs based on different charged ionophores. ISEs based on lasalocid or 1-(N,N-dicyclohexylcarbamoyl)-2- (N,N-dioctadecylcarbamoyl)ethylphosphonic acid monomethyl ester (ETH 5639) as the ionophore responded selectively to Sr2+ or Mg2+, respectively, and discriminated well against other alkaline earth cations when their membranes contained anionic sites. These two electrodes are the first examples of ISEs based on charged ionophores for which maximum selectivities are obtained with membranes containing ionic sites with a charge sign opposite to that of the primary ion. On the other hand, the experimental F- selectivities of membranes based on oxo(5,10,15,20-tetraphenylporphyrinato)molybdenum-(V) improved gradually when the concentration of anionic sites was increased from 0 to 75 mol%. The selectivity-modifying influence of ionic sites for these three types of ISEs can be explained by considering the different stabilities of the 1:2 ion-ionophore complexes of the primary and of the interfering ions.     

The translocation of fullerenic nanoparticles into lysosome via the pathway of clathrin-mediated endocytosis

Manufactured fullerene nanoparticles easily enter into cells and hence have been rapidly developed for biomedical uses. However, it is generally unknown which route the nanoparticles undergo when crossing cell membranes and where they localize to the intracellular compartments. Herein we have used both microscopic imaging and biological techniques to explore the processes of [C(60)(C(COOH)(2))(2)](n) nanoparticles across cellular membranes and their intracellular translocation in 3T3 L1 and RH-35 living cells. The fullerene nanoparticles are quickly internalized by the cells and then routed to the cytoplasm with punctate localization. Upon entering the cell, they are synchronized to lysosome-like vesicles. The [C(60)(C(COOH)(2))(2)](n) nanoparticles entering cells are mainly via endocytosis with time-, temperature-?and energy-dependent manners. The cellular uptake of [C(60)(C(COOH)(2))(2)](n) nanoparticles was found to be clathrin-mediated but not caveolae-mediated endocytosis. The endocytosis mechanism and the subcellular target location provide key information for the better understanding and predicting of the biomedical function of fullerene nanoparticles inside?cells.     

Molecular Baskets in Supercritical CO(2)

Calixarenes are synthetic macrocyclic compounds, described as "molecular baskets" as they possess high ionophoric selectivity and form inclusion complexes with many important ionic guests. In our initial work, hexameric and tetrameric tert-butylcalixarenes, unfunctionalized at the lower rim, are shown to be separable on a diol column using supercritical fluid chromatography with methanol/chloroform-modified CO(2) as mobile phase. The variation in capacity factors for these calixarenes was studied as a function of modifier composition. However, the solubility of these molecular baskets in unmodified supercritical CO(2) is enhanced by fluorination at the upper rim. For example, when p-allylcalix[4]arene is derivatized by a thiol-ene addition reaction with heptadecafluorodecanethiol, CF(3)(CF(2))(7)(CH(2))(2)SH, a solubility of >0.12 mol L(-)(1) in supercritical CO(2) is measured for the p-heptadecafluorodecylthio-n-propylcalix[4]arene at 60 °C and 200 atm. However, subsequent lower rim functionalization to form the tetrahydroxamate derivative, while reducing the solubility, allows supercritical fluid extraction of Fe(III) by the fluorinated calix[4]arene ligands to be studied as a function of temperature and pressure and monitored using UV/visible and atomic absorption spectrometry. In particular, the visible absorption spectra obtained for the extracted Fe(III)-calix[4]arene tetrahydroxamate complex, collected in dimethyl sulfoxide, are indicative of octahedral Fe(III) complexation in a manner similar to that displayed by water-soluble siderophores. Studies on the efficiency and selectivity of Fe(III) extraction are also reported.     

Discrimination between Butylammonium Isomers by Calix[5]arene-Based ISEs

Penta-O-alkylated p-tert-butylcalix[5]arenes 1-5 (R = benzyl, isohexyl, isopropoxyethyl, isopropoxycarbonylmethyl, and tert-butoxycarbonylmethyl, respectively) in a fixed C(5)(v) cone conformation have been studied as ionophores in liquid membrane ion-selective electrodes (ISEs) for n-butylammonium against the other branched butylammonium isomers, alkali metals, and ammonium ions, in terms of detection limits, sensitivity, and selectivity. The highest levels of potentiometric selectivity and detection limits up to 3 × 10(-)(6) M are observed with ISEs based on ionophore 2, where selectivity follows the order n-BuNH(3)(+) ? i-BuNH(3)(+) > s-BuNH(3)(+) > t-BuNH(3)(+). The lower potentiometric selectivity displayed by ISEs based on ionophores 3-5 is ascribed to their affinity for the Na(+) ion of the lipophilic salt present in the membrane, as evidenced by appropriate (1)H NMR competition experiments with Na(+) and n-BuNH(3)(+) ions. Further investigation on the selectivity mechanism of ionophore 2 by means of frequency response analysis shows that the interaction of the linear butylammonium ion with membranes containing 2 involves a lower resistance process than that occurring with the other branched isomers, thus suggesting the presence of a favorable kinetic-controlled mechanism.     

Thermolysis of some transition metal nitrate complexes with 1,4-diamino butane ligand

Four complexes are prepared and characterized having molecular formula [Zn(dab)(2)](NO(3))(2), [Cu(dab)(2)](NO(3))(2).H(2)O, [Ni(dab)(2)](NO(3))(2).2H(2)O and [Mn(dab)(2)](NO(3))(2), where dab: 1,4-diaminobutane. Thermolyses of these complexes were investigated by simultaneous thermogravimetry (TG), derivatives thermogravimetry (DTG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The kinetics of the thermolysis at early stages is investigated using isothermal TG by applying model-fitting and isoconversional method. Thermolytic process is slow in inert (N(2)) and is fast in air atmosphere due to oxidative nature. To investigate the response of these complexes under the condition of rapid heating, ignition delay (D(i)) has been measured. Thermal stability of the complexes was found to increase in the order Mn < Cu < Ni < Zn.     

Kinetics of thermolysis of some transition metal nitrate complexes with 1,6-diaminohexane ligand

Metal nitrate complexes of general formula [M(dah)(2)](NO(3))(2) (where M=Zn, Cu and Ni; dah=1,6-diaminohexane) have been prepared and characterized by elemental analysis, infrared spectroscopy (IR) and gravimetric method. The thermal decomposition has been studied using thermogravimetry (TG). Simultaneous thermogravimetry-differential thermogravimetry-differential thermal analysis (TG-DTG-DTA) and differential scanning calorimetry (DSC) were done in N(2) atmosphere. Isothermal TG of initial decomposition of all these complexes, have been carried out to evaluate the kinetics of early thermolysis. Both, model fitting and isoconversional method have been used for the evaluation of the kinetics of thermal decomposition. Model fitting method have given the single value of activation energy (E) whereas, isoconversional method yields a series of E-value, which vary with extent of conversion. Ignition of the complexes was measured to see the response towards rapid heating with varying amounts. The thermal stability of the complexes was found to be in the order as [Zn(dah)(2)](NO(3))(2)>[Cu(dah)(2)](NO(3))(2) approximately [Ni(dah)(2)](NO(3))(2).     

Protein-repellent silicon nitride surfaces: UV-induced formation of oligoethylene oxide monolayers

The grafting of polymers and oligomers of ethylene oxide onto surfaces is widely used to prevent nonspecific adsorption of biological material on sensors and membrane surfaces. In this report, we show for the first time the robust covalent attachment of short oligoethylene oxide-terminated alkenes (CH(3)O(CH(2)CH(2)O)(3)(CH(2))(11)-(CH═CH(2)) [EO(3)] and CH(3)O(CH(2)CH(2)O)(6)(CH(2))(11)-(CH═CH(2)) [EO(6)]) from the reaction of alkenes onto silicon-rich silicon nitride surfaces at room temperature using UV light. Reflectometry is used to monitor in situ the nonspecific adsorption of bovine serum albumin (BSA) and fibrinogen (FIB) onto oligoethylene oxide coated silicon-rich silicon nitride surfaces (EO(n)-Si(x)N(4), x > 3) in comparison with plasma-oxidized silicon-rich silicon nitride surfaces (SiO(y)-Si(x)N(4)) and hexadecane-coated Si(x)N(4) surfaces (C(16)-Si(x)N(4)). A significant reduction in protein adsorption on EO(n)-Si(x)N(4) surfaces was achieved, adsorption onto EO(3)-Si(x)N(4) and EO(6)-Si(x)N(4) were 0.22 mg m(-2) and 0.08 mg m(-2), respectively. The performance of the obtained EO(3) and EO(6) layers is comparable to those of similar, highly protein-repellent monolayers formed on gold and silver surfaces. EO(6)-Si(x)N(4) surfaces prevented significantly the adsorption of BSA (0.08 mg m(-2)). Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity and static water contact angle measurements were employed to characterize the modified surfaces. In addition, the stability of EO(6)-Si(x)N(4) surfaces in phosphate-buffered saline solution (PBS) and alkaline condition (pH 10) was studied. Prolonged exposure of the surfaces to PBS solution for 1 week or alkaline condition for 2 h resulted in only minor degradation of the ethylene oxide moieties and no oxidation of the Si(x)N(4) substrates was observed. Highly stable antifouling coatings on Si(x)N(4) surfaces significantly broaden the application potential of silicon nitride-coated microdevices, and in particular of microfabricated filtration membranes.     

Large-amplitude Fourier transformed high-harmonic alternating current cyclic voltammetry: kinetic discrimination of interfering Faradaic processes at glassy carbon and at boron-doped diamond electrodes

Significant advantages of Fourier transformed large-amplitude ac higher (second to eighth) harmonics relative to responses obtained with conventional small-amplitude ac or dc cyclic voltammetric methods have been demonstrated with respect to (i) the suppression of capacitive background currents, (ii) the separation of the reversible reduction of [Ru(NH(3))(6)](3+) from the overlapping irreversible oxygen reduction process under conditions where aerobic oxygen remains present in the electrochemical cell, and (iii) the kinetic resolution of the reversible [Ru(NH(3))(6)](3+/2+) process in mixtures of [Fe(CN)(6)](3-) and [Ru(NH(3))(6)](3+) at appropriately treated boron-doped diamond electrodes, even when highly unfavorable [Fe(CN)(6)](3-) to [Ru(NH(3))(6)](3+) concentration ratios are employed. Theoretical support for the basis of kinetic discrimination in large-amplitude higher harmonic ac cyclic voltammetry is provided.     

Ionizable (Thia)calix[4]crowns as highly selective 226Ra2+ ionophores

The 226Ra2+ selectivity of the ionizable (thia)calix[4]crowns 1-4 was determined in the presence of a large excess of the most common alkali and alkaline earth cations. Selective 226Ra2+ (2.9 x 10(-)(8) M) extraction occurs even at extremely high M(n+)/226Ra2+ ratios of 3.5 x 10(7) [M(n+) = Na+, K+, Rb+, Cs+, Mg2+, Ca2+, and Sr2+ (1M)] and an ionophore concentration of 10(-4) M. The selectivity coefficients log(K(Ra)(ex)/K(M)(ex)) are approximately 3.5 for Mg2+, Ca2+, and Sr2+. In the presence of Ba2+, which has very similar chemical properties, only the thiacalix[4]crown-6 derivative 4 showed a selectivity for 226Ra2+. In addition to the remarkable 226Ra2+ selectivities, the effective pH range (pH 8-13) of the thiacalix[4]crown dicarboxylic acids (3 and 4) allows for full regeneration of the ionophores at lower pH values (pH <6).     

Influence of lipophilic inert electrolytes on the selectivity of polymer membrane electrodes

Lipophilic inert electrolytes, i.e., salts without ion-exchange properties, may influence the selectivity of ionophore-based liquid membrane electrodes by affecting the activity coefficients in the organic phase. It is expected by a theoretical model that the addition of a lipophilic salt renders the ion-selective electrode more selective for divalent over monovalent ions. These predictions are confirmed with Ca(2+)-responsive membranes containing the ionophores ETH 2120, ETH 1001, and ETH 129. The effect is especially pronounced with nonpolar membrane phases containing a low concentration of charged species, where up to 2 orders of magnitude selectivity improvement is observed.     

Highly Cooperative Tetrametallic Ruthenium-mu-Oxo-mu-Hydroxo Catalyst for the Alcohol Oxidation Reaction

The tetrametallic ruthenium-oxo-hydroxo-hydride complex {[(PCy(3))(CO)RuH](4)(mu(4)-O)(mu(3)-OH)(mu(2)-OH)} (1) was synthesized in two steps from the monomeric complex (PCy(3))(CO)RuHCl (2). The tetrameric complex 1 was found to be a highly effective catalyst for the transfer dehydrogenation of alcohols. Complex 1 showed a different catalytic activity pattern towards primary and secondary benzyl alcohols, as indicated by the Hammett correlation for the oxidation reaction of p-X-C(6)H(4)CH(2)OH (rho = -0.45) and p-X-C(6)H(4)CH(OH)CH(3) (rho = +0.22) (X = OMe, CH(3), H, Cl, CF(3)). Both a sigmoidal curve from the plot of initial rate vs [PhCH(OH)CH(3)] (K(0.5) = 0.34 M; Hill coefficient, n = 4.2+/-0.1) and the phosphine inhibition kinetics revealed the highly cooperative nature of the complex for the oxidation of secondary alcohols.     

Spatial and spectral imaging of single micrometer-sized solvent cast fluorescent plasticized poly(vinyl chloride) sensing particles

Microscale plasticized PVC particles doped with hydrophobic ionophores are prepared by solvent evaporation of aqueous suspensions of sensing cocktails (poly(vinyl chloride), plasticizer, active sensing components, and tetrahydrofuran) and tested as particulate microoptical sensors. The particles contain either only the chromoionophore ETH 2458 as active reagent or the potassium ionophore BME-44, chromoionophore ETH 5294, and lipophilic anionic sites NaTFPB. The former system functions according to an anion-hydrogen ion coextraction mechanism and shows a Hofmeister anion selectivity pattern, while the latter sensor containing additional ionophores represents the more complex, truly selective optical sensors based on ion-exchange equilibria. Single microspheres are simultaneously characterized spatially and spectrally by fluorescence microscopy, coupled to a spectrometer equipped with a CCD detector. The results indicate that these microspheres respond in complete analogy to traditional thin-film-based optodes previously reported in the literature. The introduction of small, spherical ionophore-based sensing particles that operate on the basis of bulk extraction principles holds the promise of significantly expanding the available chemical palette of microsphere-based analytical assays.     

Ion-selective electrodes based on a pyridyl-containing triazolophane: altering halide selectivity by combining dipole-promoted cooperativity with hydrogen bonding

Triazolophanes are ionophores, with preorganized cyclic cavities that have tunable selectivities for halides. The interaction with halides is based on hydrogen bonding between the eight CH hydrogen atoms of the cavity and the halide anion. The rigidity of the cavity in tetraphenylene triazolophane along with the hydrogen bonding favors planar 1:1 complexation of "snugly" encapsulated chloride and bromide. Manipulating the triazolophane's structure by introducing two pyridyl moieties into the cavity alters the receptor's binding mode. This change adds a dipole-promoted driving force that combines with hydrogen bonding to favor the formation of 2:1 sandwich complexes around halides. The potentiometric response of electrodes based on this new ionophore was evaluated for optimal halide selectivity. The new triazolophane-based electrode showed an anti-Hofmeister selectivity toward iodide with a submicromolar detection limit. The stoichiometry of complexation and the stability constants with different halides were evaluated using a segmented sandwich membranes method. The pyridyl-triazolophane demonstrated a response consistent with a 2:1 sandwich-type complex with iodide, in polyvinyl chloride (PVC) membranes.     

Selectivity behavior and multianalyte detection capability of voltammetric ionophore-based plasticized polymeric membrane sensors

The current response features ofvoltammetric ion-selective polymeric membranes doped with neutral ionophores in view of practical sensor development are elucidated. The membranes are designed to extract ions only under applied external potentials and interrogated by normal-pulse voltammetry and pulsed amperometry. They contain two polarizable interfaces to avoid loss of lipophilic ions at the sample side and to maximize the available potential window. A simple theoretical model is developed that describes the observed current at the end of an uptake pulse to the applied membrane potential, which is the sum of both boundary potentials (at the sample and inner electrolyte side) and the membrane internal iR drop. The results describe how the selectivity of the resulting sensor must be dependent on the applied potential. Evidently, the role of the applied potential is akin to incorporating lipophilic cationic and anionic sites with potentiometric ionophore-based membranes, which are well known to considerably affect membrane selectivity and to define the charge type of the assessed ions. This has important implications for sensor design, as the applied cell potential can be used to tune sensor selectivity. Theory also explains the role of the inner electrolyte on sensor behavior. A maximum measuring range is expected with ions in the inner electrolyte that are difficult to extract into the membrane. This corresponds to Kihara's experimental results and contrasts to common ion-selective electrode practice, where a salt of the analyte ion is normally present in the inner electrolyte. Separate and mixed solution experiments with membranes containing the sodium-selective ionophore tert-butyl calix[4]arene tetramethyl ester and the lithium ionophore ETH 1810 agree very well with theoretical expectations. Multianalyte detection capability with a single sensing membrane is demonstrated in a selectivity-modifying pulsed amperometric detection mode, where each applied voltage yields a different practical selectivity of the sensor. The sensor is altered from being sodium to potassium selective as the magnitude of the applied potential is repetitively varied within the pulse sequence. The sensors show high long-term stability under continuous measuring conditions over 15 h.     

Anticancer Activity of Self-Assembled Molecular Rectangles via Arene-Ruthenium Acceptors and a New Unsymmetrical Amide Ligand

Two new and large molecular rectangles 4 and 5 were synthesized from two different arene-ruthenium [Ru(2)(μ-η(4)-C(2)O(4))(MeOH)(2)(η(6)-p-Pr(i)C(6)H(4)Me)(2)][O(3)SCF(3)](2) (2), and [Ru(2) (p-cymene)(2) (donq) (OH(2))(2)] [O(3)SCF(3)](2) (donq = 5,8-dioxydo-1,4-naphthaquinonato) (3) acceptors and a new unsymmetrical N-(4-(pyridin-4-ylethynyl)phenyl) isonicotinamide (1) donor ligand. X-ray crystallography of 4 confirmed a molecular rectangle. The (1)H NMR spectra of both rectangles 4 and 5 showed a mixture of two structural, head-to-tail (HTL) and head-to-head (HTH) type, isomers in a 1:1 ratio. The cytotoxicities of both rectangles have been established against Colo320 (colorectal cancer), A549 (lung cancer), MCF-7(breast cancer) and H1299 (lung cancer) human cancer cell lines. The cytotoxicity of rectangle 5 was found to be considerably stronger against all cancer cell lines than that of the reference drug cisplatin.     

Growth and characterization of V-shaped IrO(2) nanowedges via metal-organic vapor deposition

We report in detail the synthesis and characterization of V-shaped IrO(2) nanowedges (NWs) with an angle of 110° between the two arms. The NWs were grown on top of rutile (R) phase TiO(2) nanorods (NRs) sitting on a sapphire (SA)(100) substrate via metal-organic chemical vapor deposition (MOCVD) by using (C(6)H(7))(C(8)H(12))Ir and titanium-tetraisopropoxide (TTIP, Ti[OCH(CH(3))(2)](4)) as the source reagents. The surface morphology, structural, and spectroscopic properties of the as-deposited nanocrystals (NCs) were characterized by field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), micro-Raman spectroscopy, transmission electron microscopy (TEM), and selected-area electron diffractometry (SAED). The FESEM images and XRD patterns indicated growth of V-shaped IrO(2)(101) NWs on top of R-TiO(2) NRs. The Raman spectrum showed the nanosize induced redshift and peak broadening of the IrO(2) and rutile phase of TiO(2) signatures with respect to that of the bulk counterparts. TEM and SAED characterizations of IrO(2) NCs showed that the nanowedges were crystalline IrO(2) with a twin plane of (101) and twin direction of [Formula: see text] at the V-junction. The probable mechanisms for the formation of well-aligned IrO(2) NWs are discussed.     

Dicationic ion-pairing agents for the mass spectrometric determination of perchlorate

Perchlorate and other hydrophobic ions can be measured with high sensitivity and selectivity by forming a positively charged ion pair with a dicationic agent. A commercially available reagent, 1,6-bis(trimethylammonium)hexane dibromide (Br(N(CH3)3)(CH2)6(N(CH3)3)Br) allows for the determination of perchlorate by electrospray ionization mass spectrometry as the [(N(CH3)3)(CH2)6(N(CH3)3)ClO4]+ ion. Limits of detection (LODs) are better than those previously observed with custom-synthesized dicationic agents. An LOD of 20 ng/L is readily attainable with a single-quadrupole mass spectrometer.     

Ion-Pair Extraction of Metalloporphyrins into Acetonitrile for Determination of Copper(II)

Equilibrium study of ion-pair extraction of a cationic water-soluble porphyrin [5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin, H(2)tmpyp(4+)] and its metalloporphyrins (MP) into the acetonitrile layer, separated by addition of sodium chloride (4.00 mol dm(-)(3)) to a 1:1 (v/v) acetonitrile-water mixed solvent, was carried out to develop a new and useful method for the determination of a subnanogram amount of copper(II). M denotes Zn(2+), Cu(2+), Co(3+), Fe(3+), and Mn(3+), and P(2)(-) is porphyrinate ion. The extraction and dissociation constants of the ion-pair complexes, defined by K(ex) = [MP(ClO(4))(4)](org)[MP(4+)](aq)(-)(1)[ClO(4)(-)](aq)(-)(4), K(dis,1) = [MP(ClO(4))(3)(+)](org)[ClO(4)(-)](org)[MP(ClO(4))(4)](org)(-)(1), and K(dis,2) = [MP(ClO(4))(2)(2+)](org)[ClO(4)(-)](org)[MP(ClO(4))(3)(+)](org)(-)(1), were determined by taking into account the partition constant of sodium perchlorate (K(D) = 1.82 ± 0.01). The equilibrium constants were found to be K(ex)K(dis,1) = (7.2 ± 1.3) × 10(4), (6.4 ± 0.9) × 10(4), (1.35 ± 0.13) × 10(5), (4.8 ± 0.6) × 10(3), (1.23 ± 0.05) × 10(4), and (1.42 ± 0.07) × 10(3) at 25 °C for the free base porphyrin (H(2)tmpyp(4+)) and the metalloporphyrins of zinc(II), copper(II), cobalt(III), iron(III), and manganese(III), respectively. The K(dis,2) values were (2.9 ± 1.4) × 10(-)(2), (3.1 ± 1.1) × 10(-)(2), (8.0 ± 4.9) × 10(-)(3), and (5.1 ± 2.2) × 10(-)(2) for the free base porphyrins and the metalloporphyrins of zinc(II), copper(II), and cobalt(III), respectively. The results were developed for determination of a trace amount of copper(II) (3 × 10(-)(8)-4 × 10(-)(6) mol dm(-)(3)) in natural water samples using H(2)tmpyp(4+) with a molar absorptivity of 3.1 × 10(5) mol(-)(1) dm(3) cm(-)(1) at a precision of 1.3% (RSD). The determination of copper(II) was not interfered by the presence of 10(-)(4) mol dm(-)(3) of Mn(2+), Co(2+), Ni(2+), Hg(2+), Cd(2+), Ag(+), Cr(3+), V(5+), Al(3+), Mg(2+), Ca(2+), Br(-), I(-), SCN(-), and S(2)O(3)(2)(-) and 10(-)(5) mol dm(-)(3) of Fe(3+), Zn(2+), and Pd(2+).     

O(2)-responsive chemical sensors based on hybrid xerogels that contain fluorinated precursors

We report the development and analytical figures of merit associated with several new O(2)-responsive sensor materials. These new sensing materials are formed by sequestering the luminophore tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ([Ru(dpp)(3)](2+)) within hybrid xerogels that are composed of two of the following methoxysilanes: tetramethoxysilane, n-propyl-trimethoxysilane, 3,3,3-trifluoropropyl-trimethoxysilane, phenethyl-trimethoxysilane, and pentafluorophenylpropyl-trimethoxysilane. Steady-state and time-resolved luminescence measurements are used to investigate these hybrid xerogel-based sensor materials and elucidate the underlying reasons for the observed performance. The results show that many of the [Ru(dpp)(3)](2+)-doped composites form visually uniform, crack-free xerogel films that can be used to construct O(2) sensors that have linear calibration curves and excellent long-term stability. To the best of our knowledge, the [Ru(dpp)(3)](2+)-doped fluorinated hybrid xerogels also exhibit the highest O(2) sensitivity of any reported [Ru(dpp)(3)](2+)-based sensor platform.     

Stable tris(2,2'-bipyridine)ruthenium(III) for chemiluminescence detection

Two exceedingly stable [Ru(bipy)(3)](3+) reagents were prepared by dissolving either [Ru(bipy)(3)](ClO(4))(2) in acetonitrile (containing 0.05 M HClO(4)) or [Ru(bipy)(3)]Cl(2)·6H(2)O in 95:5 glacial acetic acid-acetic anhydride (containing 0.05 M H(2)SO(4)) followed by oxidation with PbO(2). These conveniently prepared solutions provide highly reproducible chemiluminescence detection over long periods of analysis, avoiding the need for recalibration or preparation of fresh reagent solutions and without the complications associated with online chemical or electrochemical oxidations. The reagent prepared in acetonitrile produced much greater signal intensities with a range of analytes and was deemed most suitable for high-performance liquid chromatography (HPLC) with postcolumn chemiluminescence detection.