Oxidation-state speciation of

The analytical utility of chemically modified microelectrodes for oxidation-state speciation of redox couples by cyclic voltammetry has been explored. [Re(I)(DMPE)3]+/[Re(II)(DMPE)3]2+, where DMPE = 1,2-bis(dimethylphosphino)ethane, was studied at carbon-fiber microelectrodes of approximately 5 microm in radius coated with Nafion-entrapped solgel-derived silica (Nafion-silica) composite. The results are compared with cyclic voltammetry of [Fe(CN)6]3-/[Fe(CN)6]4- at bare carbon-fiber microelectrodes. At both microelectrodes, the cathodic and anodic limiting currents are linearly proportional to the concentrations of the reducible and oxidizable species of a redox couple, respectively. The shape of the cyclic voltammogram and the magnitude of the steady-state limiting current are not affected by the potential at which the scan starts. Speciation of both forms of a redox couple could be achieved voltammetrically at the microelectrodes. However, a considerably slower scan rate was required to achieve steady state at the modified electrode because of the smaller diffusion coefficients of [Re(I)(DMPE)3]+ and [Re(II)(DMPE)3]2+ in the Nafion-silica composite. The detection limit at the modified electrode was considerably lower (5 x 10(-9) M for [Re(I)(DMPE)3]+) than at the bare electrode (6 x 10(-5) M for [Fe(CN)6]3- and [Fe(CN)6]4-) because of the substantial preconcentration of [Re(I)(DMPE)3]+ by the Nafion-silica composite.     

Electroanalytical determination of trace chloride in room-temperature ionic liquids

The electroanalytical quantification of chloride in [C4mim][BF4], [C4mim][NTf2], and [C4mim][PF6] ionic liquids has been explored using linear sweep and square wave voltammetry. Cathodic stripping voltammetry at a silver disk electrode is found to be the most sensitive. The methodology is based on first holding the potential of the electrode at +2.0 V (vs Ag wire), to accumulate silver chloride at the electrode. On applying a cathodic scan, a stripping wave is observed corresponding to the reduction of the silver chloride. This stripping protocol was found to detect ppb levels of chloride in [C4mim][BF4], [C4mim][NTf2], and [C4mim][PF6]. Although other methods for chloride have been reported for [BF4](-)- and [PF6](-)-based ionic liquids, no methods have been reported for [NTf2](-) ionic liquids.     

Structural analysis of ionic organotin(IV) compounds using electrospray tandem mass spectrometry

A novel electrospray ionization (ESI) mass spectrometric approach for the structure elucidation of ionic organotin(IV) compounds or complexes with weakly bonded ligands as for example monodentate carboxylates or sulfonates is proposed using both positive-ion and negative-ion ESI tandem mass spectra. The ionization mechanism of organotin(IV) compounds involves the cleavage of the most labile bond with an ionic character yielding two complementary ions, [Cat]+ and [An]-. Positively charged species containing tin atom, [Cat]+, are analyzed in the positive-ion mode and negatively charged species without the tin atom, [An]-, in the negative-ion mode. Fragmentation patterns of [C24H29N2Sn]+, [C21H22NSn]+, and [C17H30NSn]+ ions are proposed based on the detailed interpretation of MSn spectra, which is simplified by an easy recognition of characteristic tin isotopic clusters in particular fragment ions. Proposed fragmentation mechanisms are supported by comparison with MSn spectra of deuterium-labeled analogues. The applicability of this method is illustrated on two sets of organotin(IV) compounds, including seven [2,6-bis(dimethylaminomethyl)phenyl]diphenyltin(IV) derivatives with small inorganic counteranions X (Br, NO3, SCN, BF4, SeCN, CN, PF6), six organotin(IV) complexes containing two C,N-chelating ligands with azo dyes, and the identification of unknown hydrolysis products.     

Estimation of Concentration and Bonding Environment of Water Dissolved in Common Solvents Using Near Infrared Absorptivity

Integrated near infrared (NIR) absorbance has been used to determine the absorptivity of the υ₂ + υ₃ combination band of the asymmetric stretch (υ2) and the bending vibration (υ3) for water in several organic solvents. Absorptivity measured in this way is essentially constant across the absorption envelope and is found to be 336 L mol⁻¹ cm⁻¹ with a standard deviation of 4 L mol⁻¹ cm⁻¹ as estimated from a least squares fit of a straight line to data from water concentrations between 0.01 mol/L and 0.06 mol/L. Absorptivity measured from the peak maximum of the υ2 + υ3 combination band of water varies with the type of hydrogen bonding of the water molecule because the shape of the NIR absorption envelope changes with the hydrogen bonding.Because the integrated NIR absorptivity of the υ₂ + υ₃ combination band of water is essentially constant across the absorption envelope, the NIR absorption envelope reflects the distribution of hydrogen bonding of the water. The shape and location of the absorption envelope appear to be governed mostly by the number of hydrogen bonds from the water molecules to easily polarized atoms. Water that is a donor in hydrogen bonds to atoms which are not easily polarized (such as the oxygen of a typical carbonyl group) absorbs near 5240 cm⁻¹ to 5260 cm⁻¹. Water that donates one hydrogen bond to an easily polarized atom (such as a water molecule oxygen) absorbs near 5130 cm⁻¹ to 5175 cm⁻¹, and water that donates two hydrogen bonds to easily polarized atoms is estimated to absorb near 5000 cm⁻¹ to 5020 cm⁻¹. Water donating two hydrogen bonds to other water molecules may be said to be in a water-like environment. In no case does a small amount of water absorbed in a host material appear to have a water-like environment.     

ESI-MS/MS for the differentiation of diastereomeric pyrimidine glycols in mononucleosides

Pyrimidine glycols, or 5,6-dihydroxy-5,6-dihydropyrimidines, are primary lesions in DNA induced by reactive oxygen species. In this article, we report the preparation and tandem mass spectrometry (MS/MS) characterization of the two cis diastereomers of the glycol lesions of 2'-deoxyuridine, 5-methyl-2'-deoxycytidine, and thymidine. Our results show that collisional activation of the [M + Na]+ ions of all the three pairs of cis isomers and that of the [M + H]+ ions of the 2'-deoxyuridine glycols and 5-methyl-2'-deoxycytidine glycols give a facile loss of a water molecule. Interestingly, the water loss occurs more readily for the 6S isomer than for the 6R isomer. Likewise, product ion spectra of the [M - H]- ions of the two cis isomers of the 2'-deoxyuridine glycols and thymidine glycols show more facile loss of water for the 6S isomer than for the 6R isomer. MS/MS acquired at different collisional energies gave similar results, which establishes the reproducibility of spectra.     

镁含量对MmNi5-x(CoAlMn)x/Mg复合储氢合金吸氢性能的影响

借助扫描电镜、X- ray及吸氢性能测试装置研究了镁含量对机械合金化制备的 Mm Ni5- x ( Co Al Mn) x/Mg纳米晶复合储氢材料的性能的影响。结果表明 ,随着镁含量的增加 ,合金的活化性能表现出差 -好 -差的变化趋势。当镁含量达到50 wt%时 ,材料无法被活化。镁含量对吸氢量也有影响 ,具体表现为 ,随着镁含量的增加 ,材料的吸氢量增加。     

Atmospheric pressure covalent adduct chemical ionization tandem mass spectrometry for double bond localization in monoene- and diene-containing triacylglycerols

We report a method to elucidate the structure of triacyl-glycerols (TAGs) containing monoene or diene fatty acyl groups by atmospheric pressure covalent adduct chemical ionization (APCACI) tandem mass spectrometry using acetonitrile as an adduct formation reagent. TAGs were synthesized with the structures ABB and BAB, where A is palmitate (C16:0) and B is an isomeric C18 monoene unsaturated at position 9, 11, or 13 or an isomeric diene unsaturated at positions 9 and 11, 10 and 12, or 9 and 12. In addition to the species at m/z 54 observed in previous CI studies of fatty acid methyl esters, we also found that ions at m/z 42, 81, and 95 undergo covalent reaction with TAGs containing double bonds to yield ions at m/z 40, 54, 81, and 95 units greater than that of the parent TAG: [M + 40]+, [M + 54]+, [M + 81]+, and [M + 95]+ ions. When collisionally dissociated, these ions fragment to produce two or three diagnostic ions that locate the double bonds in the TAG. In addition, ions [RCH=C=O + 40]+ and [RCH=C=O + 54]+ formed from collisional dissociation are of strong abundance in MS/MS spectra, and collisional activation of these ions produces two intense confirmatory diagnostic ions in the MS3 spectra. Fragment ions reflecting neutral loss of an sn-1-acyl group from [M + 40]+ and [M + 54]+ are more abundant than those reflecting neutral loss of an sn-2-acyl group, analogous to previous reports for protonated TAGs. The position of each acyl group on the glycerol backbone is thus determined by the relative abundances of these ions. Under the conditions in our instrument, the [M + 40]+ adduct is at the highest signal and also yields all information about the double bond position and TAG stereochemistry. With the exception of geometries about the double bonds, racemic TAG isomers containing two monoenes or dienes and a saturate can be fully characterized by APCACI-MS/MS/MS.     

Effects of mobile-phase additives, solution pH, ionization constant, and analyte concentration on the sensitivities and electrospray ionization mass spectra of nucleoside antiviral agents

The effects of various mobile-phase additives, solution pH, pKa, and analyte concentration on electrospray ionization mass spectra of a series of purine and pyrimidine nucleoside antiviral agents were studied in both positive and negative ion models. The use of 1% acetic acid resulted in good HPLC separation and the greatest sensitivity for [M + H]+ ions. In the negative ion mode, 50 mM ammonium hydroxide gave the greatest sensitivity for [M - H]- ions. The sensitivities as [M + H]+ ions were significantly larger than the sensitivities as [M - H]- ions for purine antiviral agents. Vidarabine monophosphate and pyrimidine antiviral agents, however, showed comparable or greater sensitivities as [M - H]- ions. The sensitivity as [M + H]+ showed no systematic variation with pH; however, the sensitivity as [M - H]- did increase with increasing pH. At constant pH, the ion intensity of the protonated species increased with increasing pKa. At higher analyte concentrations, dimer (M2H+) and trimer (M3H+) ions were observed. [M + Na]+ adducts were the dominant ions with 0.5 mM sodium salts for these compounds. The spectra of the more basic purine antiviral agents showed no [M + NH4]+ adduct ions, but [M + NH4]+ ions were the major peaks in the spectra of the less basic pyrimidine antiviral agents with ammonium salts. The ammonium adduct ion was formed preferentially when the proton affinity of the analyte was close to that of NH3. Abundant [M + OAc]- ions were observed for all of the antiviral agents except vidarabine monophosphate from solutions with added HOAc, NaOAc, and NH4OAc. The utility of mobile phases containing 1% HOAc or 50 mM NH4OH was demonstrated for chromatographic separations.     

Ionic liquids as an attractive alternative solvent for thermal lens measurements

The use of ionic liquids (ILs) as a solvent for thermal lens measurements has been investigated. It was found that ILs provide a better medium for thermal lens measurements than water. Specifically, not only the ILs offer at least 20 times higher sensitivity than water but that the enhancement can be appropriately adjusted by changing either the cation or the anion of the ILs. For example, the sensitivity in [BMIm]+[Tf2N]- is approximately 26 times higher than in water. It can be increased up to 31 times by changing the anion to [PF6]- (i.e., [BMIm]+[PF6]-) or to 35 times by changing the cation to [OMIm]+ (i.e., [OMIm]+[Tf2N]-). In fact, the sensitivity of thermal lens measurements in ILs is comparable to those in volatile organic solvents such as benzene, carbon tetrachloride, and hexane. However, the ILs are more desirable as they have virtually no vapor pressure. Furthermore, additional sensitivity enhancement (up to 42 times higher than that in water) can be achieved by simply adding surfactants into the ILs. Based on the thermal conductivity (k) and dn/dT values, calculated from the measured thermal time constant tc and thermal lens strength theta, it is evident that the observed sensitivity enhancement by the ILs is due to their relatively better thermooptical properties. More specifically, the enhancement is due not to the relatively modest lowering of the thermal conductivity but rather to the substantial increase in their dn/dT values. Because of the relationship between dn/dT and drho/dT, it is expected that ILs can serve as an attractive and superior solvent not only for thermal lens measurements but also for other photothermal and photoacoustic techniques as well. Also equally important is the fact that the thermal lens technique in particular and photothermal techniques, in general, can offer a unique means to determine themooptical and thermal physical properties of the ILs (e.g., thermal conductivity, thermal diffusivity, and phase transition temperatures). This type of data is currently lacking but is of extreme importance for implementing ILs as a solvent in various industrial applications.     

A study on water adsorption onto microcrystalline cellulose by near-infrared spectroscopy with two-dimensional correlation spectroscopy and principal component analysis

Water adsorption onto microcrystalline cellulose (MCC) in the moisture content (M(c)) range of 0.2-13.4 wt % was investigated by near-infrared (NIR) spectroscopy. In order to distinguish heavily overlapping O-H stretching bands in the NIR region due to MCC and water, principal component analysis (PCA) and generalized two-dimensional correlation spectroscopy (2DCOS) were applied to the obtained spectra. The NIR spectra in four adsorption stages separated by PCA were analyzed by 2DCOS. For the low M(c) range of 0.2-3.1 wt %, a decrease in the free or weakly hydrogen-bonded (H-bonded) MCC OH band, increases in the H-bonded MCC OH bands, and increases in the adsorbed water OH bands are observed. These results suggest that the inter- and intrachain H-bonds of MCC are formed by monomeric water molecule adsorption. In the M(c) range of 3.8-7.1 wt %, spectral changes in the NIR spectra reveal that the aggregation of water molecules starts at the surface of MCC. For the high M(c) range of 8.1-13.4 wt %, the NIR results suggest that the formation of bulk water occurs. It is revealed from the present study that approximately 3-7 wt % of adsorbed water is responsible for the stabilization of the H-bond network in MCC at the cellulose-water surface.     

Redox mediation and photomechanical oscillations involving photosensitive cyclometalated Ru(II) complexes, glucose oxidase, and peroxidase

Intact photosensitive cyclometalated RuII derivatives of 2-phenylpyridine or N,N-dimethylbenzylamine cis-[Ru-(C approximately N)(LL)X2]PF6 [C approximately N = o-C6H4-py or o-C6H4CH2NMe2; LL = 1,10-phenanththroline (phen), 2,2'-bipyridine (bpy), or 4,4'-Me2-2,2'-bipyridine (Me2bpy); X = MeCN or pyridine (py)] are efficient mediators of glucose oxidase (GO) from Aspergillus niger and horseradish peroxidase (HRP). Their redox potentials in an aqueous buffer are in the range 0.15-0.35 V versus SCE, and the rate constants for the oxidation GO(red) (where red indicates reduced) by the electrochemically generated RuIII species equal (1.7-2.5) x 10(6) M(-1) s(-1) at pH 7 and 25 degrees C. The redox potentials of all complexes decrease cathodically by 0.4-0.6 V upon irradiation by visible light because of the photoinduced solvolysis of acetonitrile or py ligands. These in situ generated species display an even better mediating performance with HRP, although their behavior toward GO is different. The loading of a ruthenium unit into the protein interior brings about large catalytic currents in a self-assembled system GO-Ru-D-glucose. The estimated rate constant for intramolecular electron transfer from FADH2 of the active site at RuIII, k(intra), equals 4.4 x 10(3) s(-1). This suggests that the distance between the redox partners is around 19 A. The value of 21 A was obtained through the docking analysis of a possible closest-to-FAD localization of a Ru-containing fragment derived from the irradiated complex cis-[Ru(o-C6H4-py)-(phen)(MeCN)2]PF6. The operational stability of the GO-Ru assemblies depends on the nature of complex used, the highest being observed for cis-[Ru(o-C6H4-py)(Me2-bpy)(MeCN)2]PF6 (2). UV-vis studies of interaction of 2 with GO revealed photomechanical oscillations in the system GO-Ru-D-glucose. When irradiated complex 2 is mixed with GO and D-glucose, the absorbance at 510 nm increases because of the enzymatic reduction of RuIII to RuII. The absorbance drops rapidly and then increases as in the first cycle after shaking the reaction solution. Many cycles are possible, and the rate of absorbance increase does not depend on a cycle number. A plausible mechanism of the oscillations is presented.     

Nonmolecular solvents in separation methods: dual nature of room temperature ionic liquids

Room temperature ionic liquids (RTIL) are molten salts starting to be used as nonmolecular solvents in separation methods mainly for their extremely low vapor pressure and thermal stability. RTILs are formed by an anion associated to a cation. This intrinsic structure gives them a dual nature. When used as additives in RPLC mobile phases to enhance basic compound separation, RTILs lose their particular physicochemical properties to become just salts. However, a given RTIL is not equivalent to another one made with the same cation. It is shown that both the anion and the cation contribute to solute retention and peak efficiency extending beyond simple "salting-out" or ion-pairing effects. Nine different alkyl-methyl-imidazolium ionic liquids with different alkyl chain length and chloride or BF(4-) or PF(6-) anions were used as additives (50 mM max. conc.) in the liquid chromatography separation of some cationic basic solutes on a Kromasil C18 column. It is shown with sodium salts and an acetonitrile-water 30/70 v/v mobile phase that anions can adsorb on the stationary phase surface according to their lyotropic character. They can also form ion pairs with the cationic basic solutes. Alkyl-imidazolium cations also adsorb on the C18 bonded stationary phase due to hydrophobic character depending on their alkyl chain length. Anion adsorption dramatically increases the cationic solute retention factors when cation adsorption decreases them. The cation adsorption is mainly responsible for peak shape and efficiency enhancements. RTILs are additives that enhance the basic cationic solute peak shape changing peak position. A wise choice of the appropriate combination of anion lyotropy with imidazolium cation hydrophobicity allows playing with solute selectivity and analysis duration.     

A validated liquid chromatography/tandem mass spectrometry assay for cis-amminedichloro(2-methylpyridine)platinum(II) in human plasma ultrafiltrate

The clinical use of platinum drugs as anticancer agents has encountered problems when relating pharmacokinetic profiles with efficacy and toxicity is attempted. This has been mainly due to the lack of specific and sensitive analytical methodology to examine concentrations of the unbound drug in plasma. The presence of a carbocyclic ring on the new drug, cis-amminedichloro(2-methylpyridine)platinum(II) (ZD0473) suggested that it would be possible to develop the first stable isotope dilution LC/MS assay for a platinum drug in human plasma ultrafiltrate samples. The dichloro form of the drug exists in equilibrium with at least two aquated forms in plasma. The molecular form of the drug, therefore, depends on the length of time that the plasma sample is maintained at room temperature before freezing. Therefore, we have developed a method that quantitatively converts the aquated species back to the dichloro form of the parent drug so that a single molecular species can be analyzed. Selected reaction monitoring was performed on the transition of m/z 393 [M + NH4]+ to m/z 304 [M + NH4 -NH3 - 2 x HCl]- for ZD0473, and m/z 400 [M + NH4]+ to m/z 310 [M + NH4 - NH3 - HCl - 2HCl]+ for [2H7]ZD0473. The standard curves were fitted to a quadratic regression over the range from 10 to 5000 ng/mL in human plasma ultrafiltrate. The lower limit of quantitation for ZD0473 was 10 ng/mL for 100 microL of plasma ultrafiltrate. This simple, rapid, reliable, and sensitive method of quantitation had excellent accuracy and precision. The method provided adequate sensitivity for the analysis of plasma ultrafiltrate samples from a phase II study in which ZD0473 was administered to patients as an intravenous infusion at a dose of 150 mg/m2.     

离子液体中微波辅助合成纳米TiO2／PMMA及其光催化活性

微波加热法制备了[Bmim]BF4、[Bmim]PF6、[Amim]BF4三种离子液体,并分别以该离子液体为反应介质,在微波辐射条件下合成了纳米TiO2／PMMA复合材料,在高压汞灯照射下用甲基橙溶液对其光催化降解活性进行了测试,并用XRD、IR和TG对该复合材料的结构进行了测试和表征,结果表明,分别以这三种离子液体作为反应的介质,采用微波辐射加热能够制备出纳米TiO2／PMMA复合材料。该复合材料不需要经过高温煅烧就表现出较高的光催化活性,离子液体的存在均能够显著提高复合材料的光催化活性,但三种离子液体中又以[Bmim]PF6作介质所制得的复合材料催化活性为高。     

Liquid chromatography/mass spectrometry methods for distinguishing N-oxides from hydroxylated compounds

This study describes the application of liquid chromatography/mass spectrometry (LC/MS) methods for distinguishing between aliphatic and aromatic hydroxylations and between hydroxylations and N-oxidations. Hydroxylations and N-oxidations are common biotransformation reactions of drugs. Electrospray (ESI) and atmospheric pressure chemical ionization (APCI) were used to generate ions from liquid chromatographic effluents. ESI-MS, ESI-MS/MS, APCI-MS, and APCI-MS/MS experiments were performed on several metabolites and derivatives of loratadine (a long-acting and nonsedating tricyclic antihistamine) using an ion trap mass spectrometer (LCQ) and a triple-quadrupole mass spectrometer (TSQ). The observations are as follows: (1) LC/ESI-MS produced predominantly [M + H]+ ions with minor fragmentation. (2) LC/ESI-MS/MS data, however, showed a predominant loss of water from metabolites with aliphatic hydroxylation while the loss of water was not favored when hydroxylation was phenolic. N-Oxides (aromatic and aliphatic) showed only a small amount of water loss in the MS/MS spectra. (3) Under LC/APCI-MS conditions, aliphatic hydroxylation could be readily distinguished from aromatic hydroxylation based on the extent of water loss. In addition, N-oxides produced distinct [M + H - O]+ ions. These [M + H - O]+ ions were not produced in the APCI-MS spectra of hydroxylated metabolites. (4) Similar to the ESI-MS/MS spectra, the APCI-MS/MS spectra from the (M + H)+ ions of N-oxides yielded a small amount of water loss but no [M + H - O]+ ions. These results indicate that LC/APCI-MS can be used to distinguish between hydroxylated metabolites and N-oxides.     

Acetonitrile covalent adduct chemical ionization mass spectrometry for double bond localization in non-methylene-interrupted polyene fatty acid methyl esters

Covalent adduct chemical ionization (CACI) using a product of acetonitrile self-reaction, (1-methyleneimino)-1-ethenylium (MIE; CH2=C=N+=CH2), has been investigated as a method for localizing double bonds in a series of 16 non-methylene-interrupted fatty acid methyl esters (NMI-FAME) of polyenes with three and more double bonds. As with polyunsaturated homoallylic (methylene-interrupted) FAME and conjugated dienes, MIE (m/z 54) reacts across double bonds to yield molecular ions 54 mass units above the parent analyte. [M + 54]+ ions of several 20- and 22-carbon FAME that include one double bond in the C2-C3 position separated by two to five methylene units from a three, four, or five C homoallylic system dissociated according to rules for the homoallylic system, with an additional fragment corresponding to cleavage between the lone double bond and the carboxyl group and defining the position of the lone double bond. Triene FAME with both methylene and ethylene interruption yielded characteristic fragments distinguishable from homoallylic trienes. Fragmentation of fully conjugated trienes in the MS-1 spectra yields ratios of [M + 54]+/[M + 54 - 32]+ (loss of methanol) near unity, which distinguishes them from homoallylic FAME having a ratio of 8 or more; collisionally activated dissociation of [M + 54]+ yields a series of ions, including some rearrangement products, indicative of double bond position. Unlike conjugated dienes, fully conjugated triene diagnostic ion signal ratios did not follow any pattern based on double bond geometry. Partially conjugated trienes behave similarly to monoenes and conjugated dienes, yielding [M + 54]+/[M + 54 - 32]+ of 2-3 and, permitting them to be assigned as partially conjugated FAME using the MS-1 spectrum. They yield unique MS/MS spectra with weaker but assignable fragment ions, along with a diagnostic fragment that locates the lone double bond and permits 6,10,12-octatrienoate to be distinguished from 6,8,12-octatrienoate. The presence of a triple bond did not affect fragment formation in a methylene-interrupted yne-ene but did change fragments in a conjugated yne-ene. These data extend the principle of double bond localization by acetonitrile CACI-MS/MS to double bond structure in complex FAME found in nature.     

Photochemical production of hydrogen from water using microporous porphyrin coordination lattices

In this study, we investigated the photochemical production of hydrogen from water using bio-inspired heterogeneous microporous porphyrin coordination lattices (PCLs), [Ru2(MTCPP)BF4] (M = H2 (PCL-1), Zn (PCL-2); TCPP = Tetrakis(4-carboxyphenyl)porphyrin), under visible (380 nm <) and UV (320 nm <) light irradiations. In the presence of Na2EDTA (as a sacrificial donor) and MV2+ (methyl-vilologen; as a electron relay), PCLs exhibits photocatalytic activity for hydrogen evolution; the maximum amounts of turnover numbers (TONs) of PCL-1 and PCL-2 at 24 h irradiation were 20.8 and 29.9, respectively. In the catalytic reactions, the relation between PCLs and MV2+ was similar to the relation between a [cytochrome c3 hydrogenase] pair and lysine residues in enzymatic reactions. By using the hydrogen production rate and the MV+ (methyl-vilologen radical-cation) concentration, kinetic parameters such as affinities between MV+ and PCLs, maximum reaction rate, and total efficiency of the reaction are introduced using the Michaelis-Menten equation. These parameters indicated that PCLs are good artificial enzyme model catalysts. The stability of the PCLs after the catalytic reactions was confirmed by X-ray photoelectron spectroscopy and Fourier transform-infrared spectra. These results indicated that the frameworks of PCLs are stable for this catalytic reaction.     

Wavelength-modulation laser hygrometer for ultrasensitive detection of water vapor in semiconductor gases

Water vapor is measured by use of a near-infrared diode laser and wavelength-modulation absorption spectroscopy. Humidity levels as low as 5 nmol/mol [1 nmol/mol = 1 ppb (1 ppb equals 1 part in 10(9))] of water vapor in air are measured with a sensitivity of better than 0.2 nmol/mol (3varsigma). The sensitivity, linearity, and stability of the technique are determined in experiments conducted at the National Institute of Standards and Technology, Gaithersburg, Maryland, by use of the low frost-point humidity generator over the range from 5 nmol/mol to 2.5 mumol/mol of water vapor in air. The pressure-broadening coefficients for water broadened by helium [0.0199(6) cm(-1) atm(-1) HWHM] and by hydrogen chloride [0.268(6) cm(-1) atm(-1) HWHM] are reported for the water line at 1392.5 nm.     

Ionic-liquid-induced microfluidic reaction for water-soluble Ce(1 - x)Tb(x)F3 nanocrystal synthesis

Luminescent lanthanide nanocrystals (NCs) are proposed to be a promising new class of fluorescent labeling agents due to their attractive optical and chemical features including low toxicity, wide photoluminescence (PL) emission and high resistance to photobleaching. In this paper, an ionic-liquid-induced synthesis of Ce(1 - x)Tb(x)F(3) nanoparticle was investigated via utilizing a capillary microreactor. Ionic liquid-[bmim]BF(4) acts as both a fluoride source and stabilizing solvent during the reaction, which was shown to be a key factor that governs luminescence intensity of the obtained nanoparticles. The luminescent properties can be greatly improved by optimizing the volume percentage of [bmim]BF(4). Furthermore, the reaction temperature exerts an influence on the properties of the prepared samples. Experimental results show that the colloidal solutions of Tb(3+)-doped CeF(3) NCs exhibit the characteristic emission of Ce(3+) 5d-4f and Tb(3 + 5) D(4)-(7)F(J) (J = 6-3) transitions with (5)D(4)-(7)F(5) green emission at 542 nm as the strongest peak. The as-prepared samples are found dispersible in water with the quantum yield (in aqueous solution) as 12%, which indicates a potential application on biolabels, light-emitting diodes (LEDs) and redox luminescent switches.     

Supramolecular Soft Material Enabled by Metal Coordination and Hydrogen Bonding: Stretchability,Self-Healing,Impact Resistance, 3D Printing,and Motion Monitoring

Metal coordination can significantly improve the macroscopic performance of many materials by enhancing their dynamic features. In this study, two supramolecular interactions, Fe³⁺–carboxylic acid coordination, and structural water-induced hydrogen bonding, into an artificial polymer were introduced. Various attractive features, including flexibility and stretchability, are achieved because of the bulk state and dynamic hydrogen bonds of poly(thioctic acid-water) (poly[ TA - H ]). These unique features are considerably enhanced after the incorporation of Fe³⁺ cations into poly[ TA - H ] because metal coordination increased the mobility of the poly[ TA - H ] chains. Thus, the poly(thioctic acid-water-metal) (poly[ TA - HM ]) copolymer exhibited better flexibility and stretchability. Moreover, notable underwater/low-temperature self-healing capacity is obtained via the synergistic effect of the metal and hydrogen bonding. Most of the impact energy is quickly absorbed by poly[ TA - H ] or poly[ TA - HM ] and effectively and rapidly dissipated via reversible debonding/bonding via the interactions between the metal and hydrogen. Macroscopic plastic deformation or structural failure is not observed during high-speed (50–70 m s⁻¹) impact experiments or high-altitude (90 m) falling tests. Furthermore, poly[ TA - HM ] displayed good thermal molding properties, which enabled its processing via 3D fused deposition modeling printing. Poly[ TA - HM ] also showed considerable effectiveness for monitoring complicated, dynamic, and irregular biological activities owing to its highly pressure-sensitive nature.