Flow-injection analysis of hydrogen peroxide based on carbon nanospheres catalyzed hydrogen carbonate-hydrogen peroxide chemiluminescent reaction

A flow-injection chemiluminescence (CL) system with high sensitivity, selectivity, rapidity, and reproducibility is proposed for the determination of hydrogen peroxide (H(2)O(2)) in water samples. The system is based on the reaction of hydrogen peroxide and hydrogen carbonate solution. Carbon nanospheres (CNSs) prepared from aqueous glucose solution are used to enhance the weak CL. The CL intensity was found to be directly proportional to the concentration of H(2)O(2) present in the sample solutions. The effects upon the CL of several physicochemical parameters, including the concentration of the reagents, the mixing order of the reagents, flow rate, pH, particle size of CNSs and other relevant variables, were studied and optimized. The proposed method exhibited advantages in a larger linear range of 5.0 × 10(-8) to 3.0 × 10(-6) mol L(-1) and a lower limit of detection of 1.0 × 10(-9) mol L(-1) (S/N = 3). This method has been successfully applied to the evaluation of H(2)O(2) in tap water and snow water with recoveries from 80 to 110%. The relative standard deviation (RSD) was less than 8% for intra- and inter-assay precision. Based on the kinetic curve, the CL spectrum, fluorescence spectrum, UV-visible spectrum, and electron spin resonance (ESR) spectrum of NaHCO(3)-H(2)O(2)-CNSs system, a possible CL mechanism was proposed. Superoxide ion radical (˙O(2)(-)) and hydroxide radical (˙OH) were generated during the reaction of NaHCO(3) and H(2)O(2). They were the key intermediates for the production of hole-injected and electron-injected CNSs in the CL process.     

Fluorosurfactant-capped gold nanoparticles-enhanced chemiluminescence from hydrogen peroxide-hydroxide and hydrogen peroxide-bicarbonate in presence of cobalt(II)

Nonionic fluorosurfactant (FSN)-capped gold nanoparticles (GNPs) remain excellently stable at a wider pH range and high ionic strength, which is useful to investigate some CL systems involved in high salt and a strict pH range. In this study, we utilized FSN-capped GNPs of different sizes to distinguish the emitting species from H2O2-Co2+-NaOH and H2O2-Co2+-NaHCO3 systems. When the pH of FSN-capped gold colloidal solution was adjusted to 10.2 by dropwise addition of 0.05 M NaOH, the CL intensity of H2O2-Co2+-NaHCO3 system was enhanced 6-fold or 60-fold respectively in the presence of FSN-capped 14 nm or 69 nm GNPs with comparison to H2O2-Co2+-NaOH. The variation of CL spectra and UV-vis spectra, as well as the quenching effect of reactive oxygen species scavengers were studied in detail to understand the CL enhancement mechanisms of FSN-capped GNPs on the two systems. For H2O2-Co2+-NaOH system, the gold(I) complexes intermediate and singlet oxygen dimol species were proposed as the emitting species. The excited states of the carbon dioxide dimers and singlet oxygen dimol species were considered responsible for the light emission of H2O2-Co2+-NaHCO3 system. To our knowledge, this work is the first time to study the two CL systems simultaneously using nanoparticles.     

Temperature dependent thermodynamic model of the system H(+)-NH₄(+)-Na(+)-SO₄²⁻-NO₃⁻-Cl⁻-H₂O

A thermodynamic model of the system H(+)-NH?(+)-Na(+)-SO?2?-NO??-Cl?-H?O is parametrized and used to represent activity coefficients, equilibrium partial pressures of H?O, HNO?, HCl, H?SO?, and NH?, and saturation with respect to 26 solid phases (NaCl(s), NaCl·2H?O(s), Na?SO?(s), Na?SO?·10H?O(s), NaNO?·Na?SO?·H?O(s), Na?H(SO?)?(s), NaHSO?(s), NaHSO?·H?O(s), NaNH?SO?·2H?O(s), NaNO?(s), NH?Cl(s), NH?NO?(s), (NH?)?SO?(s), (NH?)?H(SO?)?(s), NH?HSO?(s), (NH?)?SO?·2NH?NO?(s), (NH?)?SO?·3NH?NO?(s), H?SO?·H?O(s), H?SO?·2H?O(s), H?SO?·3H?O(s), H?SO?·4H?O(s), H?SO?·6.5H?O(s), HNO?·H?O(s), HNO?·2H?O(s), HNO?·3H?O(s), and HCl·3H?O(s)). The enthalpy of formation of the complex salts NaNH?SO?·2H?O(s) and Na?SO?·NaNO?·H?O(s) is calculated. The model is valid for temperatures < or approximately 263.15 up to 330 K and concentrations from infinite dilution to saturation with respect to the solid phases. For H?SO?-H?O solutions the degree of dissociation of the HSO?? ion is represented near the experimental uncertainty over wide temperature and concentration ranges. The parametrization of the model for the subsystems H(+)-NH?(+)-NO??-SO?2?-H?O and H(+)-NO??-SO?2?-Cl?-H?O relies on previous studies (Clegg, S. L. et al. J. Phys. Chem. A 1998, 102, 2137-2154; Carslaw, K. S. et al. J. Phys. Chem. 1995, 99, 11557-11574), which are only partly adjusted to new data. For these systems the model is applicable to temperatures below 200 K, dependent upon liquid-phase composition, and for the former system also to supersaturated solutions. Values for the model parameters are determined from literature data for the vapor pressure, osmotic coefficient, emf, degree of dissociation of HSO??, and the dissociation constant of NH? as well as measurements of calorimetric properties of aqueous solutions like enthalpy of dilution, enthalpy of solution, enthalpy of mixing, and heat capacity. The high accuracy of the model is demonstrated by comparisons with experimentally determined mean activity coefficients of HCl in HCl-Na?SO?-H?O solutions, solubility measurements for the quaternary systems H(+)-Na(+)-Cl?-SO?2?-H?O, Na(+)-NH?(+)-Cl?-SO?2?-H?O, and Na(+)-NH?(+)-NO??-SO?2?-H?O as well as vapor pressure measurements of HNO?, HCl, H?SO?, and NH?.     

Reactive oxygen species scavenging ability of a new compound derived from weathered coal

The scavenging activity of three fulvic acids (named XWCS-1, XWCS-4, and XWCS-8 according to time taken for ozonolysis) obtained by ozonolysis of humic acid extracted from Xinjiang (China) weathered coal and a fulvic acid (named XWCFA) extracted from the same coal towards reactive oxygen species such as superoxide radical (O(2)(.)(-)) and hydroxyl radical ((.)OH) was investigated with an electron spin resonance (ESR)-spin trapping method using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap. O(2)(.)(-) was generated with a hypoxanthine-xanthine oxidase system. (.)OH was generated by three different methods; (i) FeSO(4)-hydrogen peroxide (H(2)O(2)) system, (ii) Cu(en)(2)-H(2)O(2) system, and (iii) UVB photolysis of H(2)O(2). At physiological pH, XWCS-1 had the greatest O(2)(.)(-) scavenging activity, followed by XWCS-4, XWCS-8 and XWCFA. XWCFA had the greatest ?OH scavenging activity among the four fulvic acids, whereas XWCS-1 and XWCS-4 enhanced the production of (.)OH from a metal-catalyzed hydroxyl radical generating system, suggesting that these molecules act as prooxidants in the presence of metal ion.     

Active oxygen species generated from photoexcited fullerene (C60) as potential medicines: O2-* versus 1O2

To characterize fullerenes (C(60) and C(70)) as photosensitizers in biological systems, the generation of active oxygen species, through energy transfer (singlet oxygen (1)O(2)) and electron transfer (reduced active oxygen radicals such as superoxide anion radical O(2)(-)* and hydroxyl radical *OH), was studied by a combination of methods, including biochemical (DNA-cleavage assay in the presence of various scavengers of active oxygen species), physicochemical (EPR radical trapping and near-infrared spectrometry), and chemical methods (nitro blue tetrazolium (NBT) method). Whereas (1)O(2) was generated effectively by photoexcited C(60) in nonpolar solvents such as benzene and benzonitrile, we found that O(2)(-)* and *OH were produced instead of (1)O(2) in polar solvents such as water, especially in the presence of a physiological concentration of reductants including NADH. The above results, together with those of a DNA cleavage assay in the presence of various scavengers of specific active oxygen species, indicate that the active oxygen species primarily responsible for photoinduced DNA cleavage by C(60) under physiological conditions are reduced species such as O(2)(-)* and *OH.     

Chemiluminescence behavior of sodium hydrogen carbonate in the potassium permanganate-hydrogen peroxide reaction

Chemiluminescence (CL) phenomenon of hydrogen peroxide with potassium permanganate in the presence of sodium hydrogen carbonate was reported. Effects of the surfactant on the CL system were investigated. Nonionic surfactants could effectively increase the CL signal. Radical scavengers and organic reagents such as nitro blue tetrazolium chloride (NBT), cytochrome c, sodium azide, ascorbic acid, thiourea, tert-butanol and dimethyl sulphoxide were used to study the emitting species. CL emission spectrum was recorded and the results showed that the maximal emission wavelengths of NaHCO₃-H₂O₂-KMnO₄ system were 440 and 634 nm. The mechanism was discussed based on electron spin resonance (ESR) spectra, fluorescence spectra and UV-vis absorption spectra. The addition of rhodamine B or uranine into this CL system enhanced the CL signal. It was due to part of the energy transfer from singlet oxygen and excited triplet dimers of two CO₂ molecules to rhodamine B or uranine. The CL could be induced by excited rhodamine B or uranine.     

The synthesis and spectroscopic characterisation of hydrotalcite formed from aluminate solutions

Raman spectroscopy has been used to characterise nine hydrotalcites prepared from aluminate and magnesium solutions (magnesium chloride and seawater). The aluminate hydrotalcites are proposed to have the following formula Mg(6)Al(2)(OH)(16)(CO(3)(2-))·xH(2)O, Mg(6)Al(2)(OH)(16)(CO(3)(2-),SO(4)(2-))·xH(2)O, and Mg(6)Al(2)(OH)(16)(SO(4)(2-))·xH(2)O. The synthesis of these hydrotalcites using seawater results in the intercalation of sulfate anions into the hydrotalcite interlayer. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structures. The spectra have been conveniently subdivided into spectral features based upon the carbonate anion, the hydroxyl units and water units. This investigation has shown the ideal conditions to form hydrotalcite from aluminate solutions is at pH 14 using a magnesium chloride solution at a volumetric ratio of 1:1. Changes in synthesis conditions resulted in the formation of impurity products aragonite, thenardite, and gypsum.     

EPR study of gamma irradiated N-methyl taurine (C3H9NO3S) and sodium hydrogen sulphate monohydrate (NaHSO3·H2O) single crystals

EPR study of gamma irradiated C(3)H(9)NO(3)S and NaHSO(3).H(2)O single crystals have been carried out at room temperature. There is one site for the radicals in C(3)H(9)NO(3)S and two magnetically distinct sites for the radicals in NaHSO(3). The observed lines in the EPR spectra have been attributed to the species of SO(3)(-) and RH radicals for N-methyl taurine, and to the SO(3)(-) and OH radicals for sodium hydrogen sulfate monohydrate single crystals. The principal values of the g for SO(3)(-), the hyperfine values of RH and OH proton splitting have been calculated and discussed.     

Stabilization of the tautomers HP(OH)2 and P(OH)3 of hypophosphorous and phosphorous acids as ligands

Treatment of [CpRu(PPh(3))(2)Cl] 1 with the stoichiometric amount of H(3)PO(2) or H(3)PO(3) in the presence of chloride scavengers (AgCF(3)SO(3) or TlPF(6)) yields compounds of formula [CpRu(PPh(3))(2)(HP(OH)(2))]Y (Y = CF(3)SO(3) 2a or PF(6) 2b) and [CpRu(PPh(3))(2)(P(OH)(3))]Y (Y = CF(3)SO(3) 3aor PF(6) 3b) which contain, respectively, the HP(OH)(2) and P(OH)(3) tautomers of hypophosphorous and phosphorous acids bound to ruthenium through the phosphorus atom. The triflate derivatives 2a and 3a react further with hypophosphorous or phosphorous acids to yield, respectively, the complexes [CpRu(PPh(3))(HP(OH)(2))(2)]CF(3)SO(3) 4 and [CpRu(PPh(3))(P(OH)(3))(2)]CF(3)SO(3) 5 which are formed by substitution of one molecule of the acid for a coordinated triphenylphosphine molecule. The compounds 2 and 3 are quite stable in the solid state and in solutions of common organic solvents, but the hexafluorophosphate derivatives undergo easy transformations in CH(2)Cl(2): the hypophosphorous acid complex 2b yields the compound [CpRu(PPh(3))(2)(HP(OH)(2))]PF(2)O(2) 6, whose difluorophosphate anion originates from hydrolysis of PF(6)(-); the phosphorous acid complex 3b yields the compound [CpRu(PPh(3))(2)(PF(OH)(2))]PF(2)O(2) 7, which is produced by hydrolysis of hexafluorophosphate and substitution of a fluorine for an OH group of the coordinated acid molecule. All the compounds have been characterized by elemental analyses and NMR measurements. The crystal structures of 2a, 3a and 7 have been determined by X-ray diffraction methods.     

The fidelity of spin trapping with DMPO in biological systems

Unlike direct ESR, spin trap methodology depends on the absolute fidelity of the spin trap reaction. Two alternative reactions of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) leading to radical adduct artifacts have been discovered and investigated: inverted spin trapping and the Forrester-Hepburn nucleophilic mechanism. These two alternate pathways to radical adducts are a combination of one-electron oxidation and nucleophilic addition, in either order. In biological systems, serious artifacts have been reported due to the Forrester-Hepburn mechanism, which is initiated by the addition of a nucleophile to DMPO. It has recently been demonstrated that (bi)sulfite (hydrated sulfur dioxide) can react with DMPO via a nonradical, nucleophilic reaction, and it has been further proposed that DMPO/(?)SO(3)(-) formation in biological systems is an artifact and not the result of spin trapping of sulfur trioxide anion radical ((?)SO(3)(-)). The one-electron oxidation of (bi)sulfite catalyzed by horseradish peroxidase (HRP)/hydrogen peroxide (H(2)O(2)) has been reinvestigated by ESR spin trapping with DMPO and oxygen uptake studies to obtain further evidence for the radical reaction mechanism. In the absence of DMPO, the initial rate of (bi)sulfite-dependent oxygen and H(2)O(2) consumption was determined to be half of the initial rate of DMPO/(?)SO(3)(-) radical adduct formation as determined by ESR, demonstrating that, under our experimental conditions, DMPO exclusively forms the radical adduct by trapping the (?)SO(3)(-).     

Dynamics of vibrational overtone excitations of H2SO4, H2SO4-H2O: hydrogen-hopping and photodissociation processes

Photochemical processes of sulfuric acid (H2SO4) and sulfuric acid monohydrate (H2SO4-H2O) following overtone excitation of the OH stretching mode are studied by classical trajectory simulations using the semiempirical PM3 potential suface in "on the fly" calculations. The main results are the following: (1) In the excitation of H2SO4 to the fifth OH-stretch overtone, hopping of the H atom between oxygen atoms is found to take place in 22% of the trajectories, only once during simulations of 400 ps. (2) All the trajectories for H2SO4 show a rapid cis-trans isomerization. (3) The photolysis of H2SO4 into SO3 + H2O takes place in 5% of the trajectories on a time scale of approximately 9 ps. (4) Only low overtone levels of H2SO4-H2O have sufficiently long lifetimes to be spectroscopically relevant. Excitation to these OH stretching overtones is found to result in the dissociation of the cluster. H hopping or dissociation of H2SO4 does not take place.     

Inhibition of superoxide dismutase, Vitamin C and glutathione on chemiluminescence produced by luminol and the mixture of sulfite and bisulfite

In a system which consisted of luminol (3-aminophthalhydrazide), cobalt sulfate (CoSO4), alkaline buffer and the mixture of NaSO3 and sodium bisulfite (NaHSO3) (sulfite and bisulfite=3:1, m/m), a strong chemiluminescence (CL) was observed using a BPCL ultra-weak luminometer. The CL signals resulted from 3-aminophthalate (the product of oxidized luminol), and were affected by the buffer pH, buffer medium and the concentrations of luminol, CoSO4 and the NaSO3-NaHSO3 mixture. The observation that the CL intensities were inhibited by superoxide dismutase (SOD), Vitamin C (Vc) and glutathione (GSH) in a dose-dependent manner suggested that superoxide radical (O2*-) was involved in the CL reaction and responsible for oxidation of luminol.     

Collision induced complex formation following electron capture of SO2-H2O complex interacting with argon atoms

Electron capture dynamics of SO(2)-H(2)O(Ar)(n) complexes (n = 0-2) have been investigated by means of direct ab initio molecular dynamics (MD) method in order to elucidate the effects of solvent argon on the reaction dynamics of SO(2)-H(2)O. The neutral complex of SO(2)-H(2)O has a C(s) symmetry, and the sulfur of SO(2) interacts with the oxygen of H(2)O with an eclipsed form. In the SO(2)-H(2)O(Ar)(n) complexes, the dipole of H(2)O interacts with the argon atoms in the most stable structure. Following the electron capture of the complex SO(2)-H(2)O, the complex anion SO(2)(-)(H(2)O) is dissociated directly into SO(2)(-) + H(2)O. On the other hand, the electron capture of SO(2)(H(2)O)(Ar)(n) argon complex (n = 1-2) leads to the anion-water complex SO(2)(-)(H(2)O) because the collision of H(2)O with the Ar atom causes a rebound of H(2)O from Ar atom to the SO(2)(-) anion. The argon solvent enhanced the SO(2)(-)(H(2)O) complex formation. The reaction mechanism of SO(2)(H(2)O) in the participation of argon atoms was discussed on the basis of the present results.     

Existence of a new reactive intermediate oxygen species in hypoxanthine and xanthine oxidase reaction

We investigated a hypoxanthine (HPX) and xanthine oxidase (XOD) reaction by using a luminol analog 8-amino-5-chloro-7-phenylpyrido[3,4-d]pyridazine-1,4-(2H,3H)dione sodium salt (L-012)-mediated chemiluminescence (CL) response. Addition of a high activity of superoxide dismutase (SOD), a potent O2* scavenger, and of a high concentration of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), a potent spin trapping agent, diminished completely the CL response. Whereas a high concentration of dimethyl sulfoxide (DMSO), as a potent *OH scavenger could not attain to the complete diminishment of the CL response. It has been reported that luminol monoanion reacts with *OH to form luminol radical, and then resultant luminol radical reacts with O2* to elicit CL response. Complete scavenging for *OH is assumed to result in lack of luminol radical, which in turn induces lack of CL response. However, our results did not support the idea. Furthermore, we examined the effect of L-012 on the DMPO-OOH formation in the presence or absence of DMSO in the HPX-XOD system by applying an electron spin resonance (ESR)-spin trapping method. The DMPO-OOH formation was inhibited even in the presence of DMSO, and the rate constant (k2) between L-012 and O2* obtained in the presence of DMSO was 9.77 x 10(2) M(-1) s(-1) and the constant in the absence of DMSO was 2.97 x 10(3) M(-1) s(-1). The data suggests that L-012 is converted to a radical form that reacts with O2* even under the conditions of the absence of *OH. From these, we postulate that the existence of a reactive intermediate oxygen species in the HPX-XOD system.     

Influence of the boron atom on the solvatochromic properties of 4-nitroaniline-functionalized boronate esters

Para-nitroaniline derivatives with peripheral 1,2- and 1,3-diol functionalities [O(2)N-C(6)H(4)-NR(1)-CH(2)CH(OH)CH(2)OH; O(2)N-C(6)H(4)-NR(1)-CH(CH(2)OH)(2); R(1) = -H, -CH(3)] covalently bonded to the amino group are esterified with various para-substituted phenylboronic acids [R(2)-C(6)H(4)-B(OH)(2); R(2) = -OCH(3), -CH(3), -H, -Br, -CHO, -NO(2), -B(OH)(2)], and the solvatochromic properties of these esters are investigated in 33 solvents of different polarity. To interpret the solvent effects, the established linear solvation energy (LSE) multiparameter equations of Kamlet-Taft and the improved Catalán scales are used. Although the boron atom is separated by two or three sp(3)-hybridized carbon atoms from the actual chromophore, solvation effects have a significant positive solvatochromic effect on the nitroaniline unit (R(1) = -CH(3)) as result of the solvent acting as a donor at the boron atom. The influence of the substituent R(2) on the coefficient b of the LSE relationship according to Kamlet-Taft and Catalán, which reflects the quantitative influence of the hydrogen-bonding acceptor or the electron-pair donor capacity of the solvent on the position of the UV-vis absorption maximum, can be determined via a linear Hammett relationship [b = f(σ(p))]. The interpretation of the effects is based on the electronic influence of the solvated boronic acid ester unit on the 4-nitroaniline group, predominantly through inductive interactions.     

Generation of fullerenyl cation (EtO)2P+(OH)CH2-C60+ from RC60-H and from RC60-C60R (R = CH2P(O)(OEt)2)

A novel fullerenyl cation (EtO)2P+(OH)CH2-C60+ was generated by simply dissolving the monofunctionalized hydrofullerene RC60-H or singly bonded dimer RC60-C60R (R = CH2P(O)(OEt)2) in oxidizing acids such as H2SO4 and FSO3H. The cation was also formed in CH2Cl2 by one-electron oxidation with aminium radical cation and was used for further functionalization of C60.     

Oxidation of phenol in aqueous acid: characterization and reactions of radical cations vis-à-vis the phenoxyl radical

Aqueous sulfuric acid containing up to approximately 14 M acid (H0 > or = -7.0) was used as solvent in pulse radiolytic redox studies to characterize cationic transients of phenol (C6H5OH) and map their reactions. The primary radical yields were first measured to correlate the variation in various radical concentrations as a function of increasing acid fraction in the solvent. Compared to their respective values at pH 2, the G(Ox*) increased with almost a linear slope of approximately 0.024 micromol J(-1) for H0(-1) (or pH(-1)) up to H0 -6.0 (Ox* = *OH + SO4*-), whereas G(H*) increased with a slope of approximately 0.033 micromol J(-1) for H0(-1) (or pH(-1)) up to H0 -5.0. In the presence of > 10 M acid (H0 < -5.0), phenol was oxidized to its radical cation, C6H5OH*+, which further reacted with phenol and generated the secondary, dimeric radical cation, (C6H5OH)2*+, following an equilibrium reaction C6H5OH*+ + C6H5OH <==> (C6H5OH)2*+, with K(eq) = 315 +/- 15 M(-1). The two cationic radicals were characterized from their individual UV-vis absorption spectra and acidity. The C6H5OH*+ absorption peaks are centered at 276 and 419 nm, and it was found to be more acidic (pKa = -2.75 +/- 0.05) than (C6H5OH)2*+ (pKa = -1.98 +/- 0.02), having its major peak at 410 nm. On the other hand, in the presence of < 6.5 M acid the C6H5O* reactions followed the radical dimerization route, independent of the parent phenol concentration.     

添加物对1-甲氧基-2-丙醇催化氧化制甲氧基丙酮反应的影响

The system W Ⅵ H 2O 2 has good selectivity for methoxyacetone in oxidation of 1 methoxy 2 propanol. The effects of acid and base additives on selectivity for methoxyacetone were studied. The results showed that the acid additive, i.e. NaHSO 4, was favorable to Na 2WO 4 H 2O 2 system, while the base additive NEt 3 was favorable to other tungsten compounds. A 71 2% of yield of methoxyacetone with 98 9% of selectivity for methoxyacetone was obtained in Na 2WO 4 H 2O 2 NaHSO 4 MeCOMe oxidation system.     

Kinetic analysis of superoxide anion radical-scavenging and hydroxyl radical-scavenging activities of platinum nanoparticles

There are few reports on the physiological effects of metal nanoparticles (nps), especially with respect to their functions as scavengers for superoxide anion radical (O2(.-)) and hydroxyl radical (.OH). We tried to detect the scavenging activity of Pt nps using a hypoxanthine-xanthine oxidase system for O2(.-) and using a Fenton and a UV/H2O2 system for .OH. Electron spin resonance analysis revealed that 2 nm particle size Pt nps have the ability to scavenge O2(.-) and .OH. The calculated rate constant for the O2(.-)-scavenging reaction was 5.03 +/- 0.03 x 10(7) M (-1) s (-1). However, the analysis of the Fenton and UV/H 2O 2 system in the presence of Pt nps suggested that the .OH-scavenging reaction cannot be determined in both systems. Among particle sizes tested from 1 to 5 nm, 1 nm Pt nps showed the highest O2(.-)-scavenging ability. Almost no cytotoxicity was observed even after adherent cells (TIG-1, HeLa, HepG2, WI-38, and MRC-5) were exposed to Pt nps at concentrations as high as 50 mg/L. Pt nps scavenged intrinsically generated reactive oxygen species (ROS) in HeLa cells. Additionally, Pt nps significantly reduced the levels of intracellular O2(.-) generated by UVA irradiation and subsequently protected HeLa cells from ROS damage-induced cell death. These findings suggest that Pt nps may be a new type of antioxidant capable of circumventing the paradoxical effects of conventional antioxidants.     

Temperature-/solvent-dependent low-dimensional compounds based on quinoline-2,3-dicarboxylic acid: Structures and fluorescent properties

A series of 0-D, 1-D, and 2-D metal-organic compounds through reactions of quinoline-2,3-dicarboxylic acid (2,3-H(2)qldc) with transition metal salts MCl(2), namely, M(2,3-Hqldc)(2)(H(2)O)(2) (M = Co(1), Zn(4) and Cd(7)), [M(3-qlc)(2)(H(2)O)(2)](n) (M = Co(2), Zn(5) and Cd(8)), M(2-qldc-3-OCH(3))(2)(CH(3)OH)(2) (M = Co(3) and Zn(6)) and [Cd(2,3-qldc-OCH(3))(μ(2)-Cl)](2n) (9) (where, 3-Hqlc = quinoline-3-carboxylic acid and 2-qldc-3-OCH(3) = 3-(methoxycarbonyl)quinoline-2-carboxylic acid), were synthesized and characterized by elemental analysis, IR, thermogravimetric analysis (TG), and single-crystal X-ray diffraction. When the temperature ranged from room temperature to 70 °C, three isomorphous mononuclear complexes 1, 4 and 7 were obtained in H(2)O/H(2)O + CH(3)OH. As the temperature rose further to above 90 °C, due to the decomposition of 2-position carboxyl group in ligand 2,3-H(2)qldc, the same reactions, respectively, produced three isomorphous 2-D layer-like structures 2, 5 and 8 with 4(4) topology in water. By contrast, when the mixed solvent of H(2)O + CH(3)OH at a 1?:?1 ratio (v/v) was applied, the three above-mentioned reactions respectively gave compounds 3, 6 and 9 with the 3-position esterification of 2,3-H(2)qldc. Compounds 3 and 6 are mononuclear and isomorphous, while complex 9 has a 1-D double-stranded chain-like structure connected by two μ(2)-Cl bridges. Obviously, these results reveal that the reaction temperature and solvent play a critical role in structural direction of these low-dimensional compounds. Meanwhile, the photoluminescent property of the selected compounds is also investigated.