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Mitochondria, as vital energy supplying organelles, play important roles in cellular metabolism, which are closely related with mitochondrial pH (∼ 8.0). In this work, a novel multimodal fluorescent probe was employed for ratiometric and colorimetric detection of pH. The probe is designed to work by controlling benzothiazole phenol-hemicyanine system as the interaction site and hemicyanine connected by conjugate bonds as the mitochondrial targeting, which also could make the fluorescence of probe red-shifted. This system results in a perfect ratiometric fluorescent response, whose emission changed from red to blue under pH 2.0-10.0, having a broad linear range (pH = 3.0-10.0). And the marked colour change (light yellow to deep purple via naked eye under pH 2.0-11.0) could be used to construct the test strip colorimetry and smartphone APP detection method, realizing the fast, portable, and accurate detection of pH in vitro and environment. Besides, the probe owns the characteristics of easy loading, high selectivity and staining ability of mitochondria, and low cytotoxicity, thereby allowing imaging of pH values and real-time monitor the subcellular mitochondria pH changes caused by drugs in living cells. It thus could be used to monitor the organ-specific dynamics related to transitions between pathological and physiological states.

As a multifunctional signaling molecule, hydrogen sulfide (H2S) plays an essential role in diverse physiological and pathological processes. The two-photon fluorescence probes detecting H2S selectively in vivo could be useful tools to better study the mechanism of diseases. Then, an efficient two-photon lysosome-specific probe 1 has been developed to detect endogenous H2S in living cells and mice. Probe 1 displays excellent properties with 28-fold fluorescence enhancement, marked color changes in naked-eye and fluorescence, high selectivity and sensitivity, and low detection limit (0.22 μM) to H2S. These remarkable properties of probe 1 enable its practical applications in detecting H2S in environment (wastewater) and food (beer). Moreover, as a two-photon probe under near infrared excitation at 790 nm, probe 1 can monitor the level changes of endogenous H2S of lysosome and tumor in living system with good membrane permeability and high imaging resolution. Specially, the probe detecting H2S distribution in lysosome could provide more evidences to explain the association of target-organelle and H2S.

Cys (Cysteine), Hcy (homocysteine), and GSH (glutathione) are three important kinds of biothiols, playing crucial roles in the variety of pathological and physiological processes. It is greater challenges to simultaneously identify different biothiols due to their similar molecular structures and chemical characteristics. In this work, we employed a multi-emissive fluorescent probe by sulfonyl benzoxadiazole (SBD) with halogen chloride unit as the interaction site based on aromatic substitution-rearrangement strategy to discriminate Cys and Hcy/GSH. The response of probe 1 to Cys would generate FRET and cause a red-shift of fluorescence emission, while Hcy/GSH only lead to different degrees of fluorescence enhancement owing to PET. The probe showed good selectivity, high sensitivity, and low detection limits to three biothiols (Cys: 0.86 μM, Hcy: 0.48 μM and GSH: 0.54 μM). Such capability of the probe could be demonstrated to successfully quantitatively detect the concentrations of Cys/Hcy/GSH in human plasmas. In addition, the probe was also successfully applied for imaging biothiols in lysosomes and real-time monitoring GSH changes in living cells through two-photon fluorescence microscopy.

A novel ratiometric fluorescent chemodosimeter has been developed for reusable detection of Hg

A highly selective ratiometric ESIPT fluorescent probe has been designed for the detection of palladium species of all the typical oxidation states (0, +2, +4). The probe exhibits a ratiometric fluorescence response towards the palladium species in about 20 min at room temperature based on the excited state intramolecular proton transfer (ESIPT) process. Moreover, the probe can discriminate different palladium species (Pd0, Pd2+, Pd4+) under different detection conditions. Furthermore, the probe can be used to quantitatively detect palladium in drinking water with a low detection limit (15.6 nM, 1.66 ppb). Additionally, it could be used as a two-photon palladium probe for bioimaging with low cytotoxicity and autofluorescence.

A novel turn-on fluorescent probe, which coumarin-fused coumarin was used as fluorophore to link with 2, 4- dinitrodiphenyl ether moiety that has high selectivity and sensitivity for H2S and thiols, was designed and synthesized. Our probe YB can sensitively react with H2S and GSH to release free fluorophore with strong fluorescence signals. The probe YB could use as a significant molecular imaging tool to study the endogenous GSH in living cell and a practical detector for H2S in the papermaking wastewater.

A two-photon fluorescent probe for Cu-2- and S2- has been strategically prepared with naphthalimide derivative platform (NPE) covalently grafted onto the surface of magnetic core-shell Fe3O4@SiO2 nanoparticles. The probe (NPE-Fe3O4@SiO2) exhibits selective response to Cu2+ with enhanced fluorescence and efficient separation of Cu2+ with external magnetic field. The consequent product NPE-Fe3O4@SiO2-Cu of NPE-Fe3O4@SiO2 and Cu2+ can work as an excellent sensor for S2- by removing Cu2+ from the complex with fluorescence decreased, recovering the fluorescence of the probe. Therefore, the constituted Off-On-Off type fluorescence monitoring system means the probe is resumable. Moreover, the probe has been used to quantitatively detect Cu2+ and S2- with low detection limits, which are 0.28 mu M and 0.12 mu M, respectively. Furthermore, the probe shows low cytotoxicity and excellent membrane permeability, which has been successfully applied for monitoring Cu2+ and S2- in living cells and imaging Cu2+ in deep-tissue with two-photon excited fluorescence. (C) 2018 Published by Elsevier B.V.

A new and simple fluorescent probe for detection of Cue(2+) has been synthesized and characterized. The probe displays high selectivity and sensitivity for Cu2+ with remarkably weakened fluorescence intensity and red shift. Moreover, this probe has been successfully applied to detect Cu2+ by one- and two-photon excited fluorescence with low detection limits (

Lysosome pH is known to be acidic (4.5–5.5) and has emerged as a critical physiological factor for lysosome activities and functions. Herein, we designed a novel ratiometric lysosome-targeted fluorescence resonance energy transfer (FRET) pH probe, which was fabricated by integrating the coumarin moiety (donor) with the naphthalimide moiety (acceptor). The sensing mechanism was essentially an integration of ICT and FRET processes, leading to the simultaneous intensity enhancement of coumarin and naphthalimide with a pH increase. Furthermore, morpholine was introduced as a lysosome-targeted group. Moreover, the probe could respond to pH in a proportional relationship at very broad range from pH 4.5 to 11.0 and showed remarkable advantages, including rapid response, high sensitivity and selectivity, suitable pKa of 5.62, and good reversibility. Furthermore, the probe was successfully used as a ratiometric TP lysosome-targeted fluorescence probe, not only for imaging of lysosomal pH, but also for visualizing chloroquine-induced changes of intracellular pH in real time in living cells with low cytotoxicity and autofluorescence. These proof-of concept studies demonstrate the practical application of the probe in biological systems.

A novel ratiometric ESIPT fluorescent probe, which is specific for palladium species of all the typical oxidation states (0, +2, and +4), has been designed. Notably, based on the excited state intramolecular proton transfer (ESIPT) process, the probe exhibits a ratiometric fluorescent response to palladium species with a low detection limit (9.0 nM, 0.96 ppb) in about 1.5 min at room temperature. Moreover, it has been successfully used as a two-photon ratiometric fluorescent palladium probe for in vivo and three-dimensional imaging with low cytotoxicity and autofluorescence. Compared with other reported palladium probes, the probe displays a shorter ratiometric response time and lower detection limit in milder test conditions. All of the results indicate that the probe may be favorable for environmental and biological applications.

Developing a facile method to fabricate new heterogeneous Metal-Organic Framework (MOFs) based catalysts with high catalytic activity and stability has drawn significant attention. Herein, we demonstrate a simple in-situ pyrolysis reduction strategy to fabricate a novel three-dimensional (3D) Cu-based catalyst, which displays an outstanding performance for the decomposition of 4-nitrophenol (4-NP). Detailed characterization including SEM, FTIR, XPS, ICP-OES, HRTEM, SAED, XRD and BET confirmed the formation of the Cu/C porous composites (Cu/C-PC). Taking advantage of enormous Cu particles in the composite as well as ultrahigh surface area (196.7 m2/g) of carbon support, Cu/C-PC presents prominent catalytic activity for the hydrogenation reduction 4-NP to 4-aminophenol (4-AP) with apparent rate constant (Kapp) of 0.0267 s−1 (the ratio of Kapp to the catalyst amount is 119 s−1 g−1), which is dramatically higher than that previous reports. On the contrary, after being washed successively (Cu/C-PC-AW) by FeCl3, HCl aqueous solution and deionized water, the Cu/C porous composite materials exhibit fairly weak catalytic activity. The catalytic performance of Cu/C-PC is better than Cu, Cu2O and CuO nanoparticles as well as other catalysts in previous reports. Furthermore, Cu/C-PC shows excellent reusability, indicating its potential applications in treatment of water pollution.

As a multifunctional signaling molecule, hydrogen sulfide (H

A novel turn-on fluorescent probe, which coumarin-fused coumarin was used as fluorophore to link with 2, 4- dinitrodiphenyl ether moiety that has high selectivity and sensitivity for H

Gaseous mixtures of diatomic hydrogen isotopologues and helium are often encountered in the nuclear energy industry and in analytical chemistry. Compositions of stored mixtures can vary due to interactions with storage and handling materials. When tritium is present, it decays to form ions and helium-3, both of which can lead to further compositional variation. Monitoring of composition is typically achieved by mass spectrometry, a method that is bulky and energy-intensive. Mass spectrometers disperse sample material through vacuum pumps, which is especially troublesome if tritium is present. Our ultimate goal is to create a compact, fast, low-power sensor that can determine composition with minimal gas consumption and waste generation, as a complement to mass spectrometry that can be instantiated more widely. We propose calorimetry of metal hydrides as an approach to this, due to the strong isotope effect on gas absorption, and demonstrate the sensitivity of measured heat flow to atomic composition of the gas. Peak shifts are discernible when mole fractions change by at least 1%. A mass flow restriction results in a unique dependence of the measurement on helium concentration. A mathematical model is presented as a first step toward prediction of the peak shapes and positions. The model includes a useful method to compute estimates of phase diagrams for palladium in the presence of arbitrary mixtures of hydrogen isotopologues. We expect that this approach can be used to deduce unknown atomic compositions from measured calorimetric data over a useful range of partial pressures of each component.

Hydrogen isotope gas exchange within palladium powders is examined using a batch-type reactor coupled to a residual gas analyzer (RGA). Exchange rates in both directions (H2 + PdD and D2 + PdH) are measured in the temperature range 178–323 K for the samples with different particle sizes. The results show this batch-type exchange is closely approximated as a first-order kinetic process with a rate directly proportional to the surface area of the powder particles. An exchange rate constant of 1.40 ± 0.24 μmol H2/atm cm2 s is found for H2 + PdD at 298 K, 1.4 times higher than that for D2 + PdH, with an activation energy of 25.0 ± 3.2 kJ/mol H for both exchange directions. A comparison of exchange measurement techniques shows these coefficients, and the fundamental exchange probabilities are in good agreement with those obtained by NMR and flow techniques.

A novel ratiometric fluorescent chemodosimeter has been developed for reusable detection of Hg2+. The chemodosimeter responds to Hg2+ sensitively and selectively with a remarkable fluorescence change from green to blue through hampering the excited state intramolecular proton transfer (ESIPT) process. This recyclable chemodosimeter can remove Hg2+ from water by forming a unique mercury-containing compound, which could be reused in the presence of NaBH4. Moreover, the chemodosimeter exhibits a ratiometric fluorescence response to Hg2+ with a very low detection limit (1.0 ppb), and it can be used to detect Hg2+ in drinking water. Furthermore, the ratiometric chemodosimeter has been successfully used for imaging Hg2+ in living cells and tissues using two-photon fluorescence microscopy due to the remarkable emission change from green to blue. This provides a novel testing method for detecting Hg2+ in living cells and tissues with low cytotoxicity and autofluorescence.

A two-photon fluorescent probe for Cu

A new and simple fluorescent chemodosimeter, 7-ally1-2-methylquinolin-8-ol, has been synthesized for resumable detection of Hg2+. The chemodosimeter displays a highly sensitive and selective response to Hg2+ with remarkably fluorescence intensity enhanced in aqueous solution containing 0.2% organic cosolvent. Moreover, this resumable chemodosimeter can remove Hg2+ from water by forming a mercury containing compound, which could be restored to chemodosimeter 1 by the addition of NaBH4. Furthermore, the chemodosimeter has been successfully applied for Hg2+ detection in drinking water by both one- and two-photon excited fluorescence with low detection limits (

This investigation examines how equilibrium pressures of single isotope metal–hydrogen systems can be used to determine the separation behavior of hydrogen isotopes in a mixed-isotope metal hydroge...

A novel water-soluble colorimetric and fluorescent palladium probe with excellent selectivity and sensitivity has been designed. Notably, based on a palladium triggered terminal allyl ether cleavage reaction, the probe could detect and discriminate Pd(0) and Pd(2+)/Pd(4+) in about 2.5 min at room temperature with a low detection limit (0.29 ppb) and significant colour change (from light yellow to pink). The probe could serve as an excellent "naked-eye" colorimetric probe for selective and quantitative determination of palladium in aqueous solutions. Moreover, it could be used as a two-photon palladium probe for in vitro/vivo and three-dimensional imaging with low cytotoxicity and autofluorescence.

2LiNH2–MgH2 is considered an attractive material for reversible hydrogen storage. In an attempt to improve the hydrogen storage characteristics of the 2LiNH2–MgH2 system, the activation mechanism of the material, as well as the improvement in hydrogen absorption rates through doping were explored. Differential Scanning Calorimetry (DSC) investigations reveal that the initial and irreversible conversion process 2 LiNH 2 + MgH 2 ⇒ 2 LiH + Mg ( NH 2 ) 2 is exothermic, indicating it is energetically favorable for this initial conversion of the starting material. The exothermicity of this first step explains why the original starting material (2LiNH2 + MgH2) is never regenerated during re-hydrogenation of the desorbed product. Adding catalytic amounts (

Hydrogen storage materials with high capacity are highly desirable. Currently none of the existing storage materials can meet the requirement of motor vehicle applications. We report a new hydrogen storage generation system, LiAlH4 + NH3. The two components are stored in separate containers when there is no demand for hydrogen, while the two components mix, hydrogen can be generated, up to 13 wt.% H2 at ambient temperature, on-demand. The H2 formation is exothermic with a high rate, suggesting that this is unlikely to be a reversible hydrogen storage material. More investigation is needed to improve or to maximize the degree of conversion.

Isotherms for H2/D2–Pd0.8Ag0.2 systems have been measured over a low temperature range, 198–323 K. Such low temperature data for this system have not been obtained previously. The absorption kinetics was found to be fast. The isotherms at low temperatures are compared with literature values at or above 313 K, as well as those for H2(D2)–Pd systems. The H/D isotope effect and the separation factors in the plateau range over Pd0.8Ag0.2 are calculated at various temperatures and discussed, based on the isotherms. Enthalpies are extracted from van’t Hoff plots and compared with calorimetric values and the results from the literature for both absorption and desorption processes. A method is given for using isotherm information from single isotope systems to estimate the separation factor for the mixed isotope systems and this is a helpful tool. The challenge of measuring absorption isotherms at low temperatures and low pressures is discussed. Sample pre-treatment, non-soluble impurity accumulation in an absorption process and thermal transpiration effects are examined.

Absorption isotherms at 323 K for the H−D−Pd system were measured by introducing H2 and D2 into Pd in sequence. The method using addition of isotopes to the system in sequence to investigate isotope exchange effects has not been previously reported. The equilibrium absorption pressure in the plateau region of the mixed-isotope system varies with the ratio of H/D in the solid phase. It lies between those of the single-isotope systems of H−Pd and D−Pd. Higher equilibrium pressures are associated with high D/H ratios in the solid phase. A model proposed previously (Luo, W.; Cowgill, D.; Causey, R.; Stewart, K. J. Phys. Chem., B 2008, 112, 8099) for mixed isotope hydride desorption, which correlates the equilibrium plateau pressure of the mixed H−D system with the fractions of D and H in the solid and the equilibrium plateau pressures of the single-isotope systems, is also successfully applied to absorption. When D2 is introduced into the H−Pd system in the plateau region, both the H−D exchange processes in t...

A Sieverts' apparatus coupled with a residual gas analysis is used to measure the concentration variations of hydrogen isotopes in the gas and solid phases during exchange and isothermal decomposition of mixed hydrides. beta-phase palladium hydrides with known ratios of H:D, Pd(H x D 1- x ) y (0x1, y0.6), are prepared by H 2 with PdD y or D 2 with PdH y exchange, and their desorption isotherms are reported here at 323 K. A higher equilibrium pressure in isothermal desorption of mixed hydrides is associated with a higher ratio of D/H in the initial mixed hydrides in beta-phase. The composition of the gas desorbed from a mixed hydride varies; i.e., the ratio of D/H in gas decreases with the sum of (H + D) in Pd. The values of the separation factor alpha during desorption at 323 K and during H-D exchange at 248 K are discussed and compared with those in the literature. Desorption isotherms of mixed isotope hydrides are between those of the single isotope hydrides of H-Pd and D-Pd, however, plateaus slope more than those of pure isotope hydrides. The origin of the plateau sloping in the mixed hydrides can be attributed to the compositional variations during desorption, i.e., the equilibrium pressure is greater when D/H ratio in solid is greater. A simple model is proposed in this study that agrees well with experimental results.

Metal amide containing material is one of the more promising hydrogen storage materials for motor vehicular “on-board” applications. One of the issues related to the application of metal–N–H storage systems is NH 3 -formation that takes place simultaneously with H 2 release. NH 3 in desorbed hydrogen, when feeding a fuel cell, will not only damage the catalyst in the fuel cell, but also accelerate the material degradation. Accurate determination of the amounts of NH 3 in the H 2 is, therefore, very important. A novel method to quantify NH 3 in the desorbed H 2 , the Draeger Tube, is reported to be suitable for this purpose. The results indicate that the concentration of NH 3 in the desorbed H 2 from the (2LiNH 2 + MgH 2 ) system increases with desorption temperatures, from 180 ppm at 180 °C to 720 ppm at 240 °C. The capacity loss after 270 cycles at a temperature of 200 °C is 25%, with 1/3 of the loss due to NH 3 -formation. More research is needed to determine the cause for the remaining capacity loss. This cyclic stability is very encouraging for a material prior to any formulation optimization. A water-saturated air exposure of the desorbed sample at 220 °C for 21 h, after a sequence of air-exposures at lower temperatures, was found to not affect its capacity or kinetics in subsequent desorption runs.

Hydrogen energy may provide the means to an environmentally friendly future. One of the problems related to its application for transportation is “on board” storage. Hydrogen storage in solids has long been recognized as one of the most practical approaches for this. Recently the hydrogen storage system, (Li 3 N + 2H 2 ⇔ LiNH 2 + 2LiH), was introduced by Chen et al. [P. Chen, Z. Xiong, J. Luo, J. Lin, K.L. Tan, Nature 420 (2002) 302–304. [1] ]. This type of material has attracted a great attention of the researchers from the metal hydride research community due to its high reversible storage capacity, up to 11.5 wt%. Currently the Li–Mg–N–H system has been shown to be able to deliver 5.2 wt% reversibly at a H 2 pressure of 30 bar and temperature of 200 °C. The accessibility of the capacity beyond 5.2 wt% is being actively explored. One of the issues related to the application of the metal–N–H storage systems is NH 3 formation that takes place simultaneously with H 2 release. NH 3 formation will not only damage the catalyst in a fuel cell, but also accelerate the cyclic instability of the H-storage material since the metal–N–H system turns into a metal–H system after loosing nitrogen and, therefore, it would not function at the temperature and pressure range designed for the metal–N–H system. The accurate determination of the amounts of NH 3 in the H 2 is, therefore, very important and has not been previously reported. Here a novel method to quantify NH 3 in the desorbed H 2 , the Draeger Tube, is reported as being suitable for this purpose. The results indicate that the concentration of NH 3 in desorbed H 2 increases with the desorption temperature. For the (2LiNH 2 + MgH 2 ) system the NH 3 concentration was found to be 180 ppm at 180 °C and 720 ppm at 240 °C.

The H-storage system, (LiNH 2 + MgH 2 ), has been exposed to water-saturated air and its subsequent rates of H 2 desorption and absorption have been determined. Not only are there no adverse effects of the exposures, but also there is a small positive effect on the rates and final wt% H.

The hydrogen storage in metal–N–H systems is reviewed. Exemplary systems including Li–N–H, Mg–N–H, Li–Mg–N–H and Li–Al–N–H are highlighted. Analyses and discussions are focused on the thermodynamics and kinetics of the respective systems.

Stepwise solid-state reaction between LiNH2 and LiAlH4 at a molar ratio of 2:1 is investigated in this paper. It is observed that approximately four H atoms are evolved from a mixture of LiNH2–LiAlH4 (2:1) after mechanical ball milling. The transformation of tetrahedral [AlH4]– in LiAlH4 to the octahedral [AlH6]3– in Li3AlH6 is observed after ball milling LiAlH4 with LiNH2. Al–N bonding is identified by using solid-state 27Al nuclear magnetic resonance (NMR) measurements. The NMR data, together with the results of X-ray diffraction and Fourier transform IR measurements, indicate that a Li–Al–N–H intermediate with the chemical composition of Li3AlN2H4 forms after ball milling. Heating the post-milled sample to 500 °C results in the liberation of an additional four H atoms and the formation of Li3AlN2. More than 5 wt % hydrogen can be reversibly stored by Li3AlN2. The hydrogenated sample contains LiNH2, LiH, and AlN. The role of AlN in the reversible hydrogen storage over Li–Al–N–H is discussed.

We have developed a new method to measure the composition of gaseous mixtures of any two hydrogen isotopes, as well as an inert gas component. When tritium is one of those hydrogen isotopes, there is usually some helium present, because the tritium decays to form helium at a rate of about 1% every 2 months. The usual way of measuring composition of these mixtures involves mass spectrometry, which involves bulky, energy-intensive, expensive instruments, including vacuum pumps that can quite undesirably disperse tritium. Our approach uses calorimetry of a small quantity of hydrogen-absorbing material to determine gas composition without consuming or dispersing the analytes. Our work was a proof of principle using a rather large and slow benchtop calorimeter. Incorporation of microfabricated calorimeters, such as those that have been developed in Sandia’s MicroChemLab program or that are now commercially available, would allow for faster measurements and a smaller instrument footprint.

Isothermal and non-isothermal kinetic measurements on the chemical reaction between Mg(NH2)(2) and LiH, as well as the thermal decomposition of Mg(NH(2))(2), give apparent activation energies of 88.1 and 130 kJ/mol, respectively, which reveal that the thermal decomposition of Mg(NH2)(2) is unlikely to be an elementary step in the chemical reaction of Mg(NH2)(2) and 2LiH. The H-D exchange between H(delta+) in Mg(NH2)(2) and D(delta-) in LiD gives evidence for the coordinated interaction between amide and hydride. The observed linear and nonlinear kinetic growth in the reaction of Mg(NH2)(2)-2LiH indicates that the reaction rate is controlled by the interface reaction in the early stage of the reaction and by mass transport through the imide layer in the later stage. Both particle size and degree of mixing of the reacting species affect the overall kinetics of the reactions.

Three Li–Mg–N–H samples with LiH/Mg(NH2)2 molar ratio of 1/1, 2/1 and 3/1 were prepared and investigated. Remarkable differences were observed in the temperature dependence of hydrogen desorption, subsequent absorption and P-C isotherms over these three samples. It was revealed that the reduction of LiH content induced the desorption of ammonia. Higher content of LiH pushes the hydrogen desorption to a higher temperature region.

Hydrogen desorption from the mixture of Mg(NH2)2 and 2LiH presents two pressure-dependent segments at a given temperature – ∼2/3 of the hydrogen is released at relatively higher pressures and forms a pressure plateau and the other 1/3 is desorbed at lower pressures. The overall reaction heat measured in a differential scanning calorimeter is 44.1 kJ/mol H 2, while the heat-of-desorption of H2 in the higher pressure plateau is about 38.9 kJ/mol H2, a favorable thermodynamics for PEM Fuel Cell application. However, the relatively higher activation energy (Ea = 102 kJ/mol) sets a kinetic barrier. © 2005 Elsevier B.V. All rights reserved.

The kinetics of the hydrogen sorption of Ti-doped direct-synthesized NaAlH4 has been studied by measuring sorption rates at various temperatures and applied pressures. Formation and decomposition rate equations for NaAlH4 and Na3AlH6 are proposed, and pre-exponential factors and activation energies have been calculated for these reactions. These equations were used to calculate alanate decomposition curves. The results fit the experimental data very well. The predictive capabilities of this empirical approach provide a very useful modeling tool for optimizing the performance of the alanates over a range of hydrogen absorption temperatures and pressures. Under a typical hydrogen-loading condition (constant pressure), the optimum temperature for “fast fill” can be determined.

One of the problems related to the employment of hydrogen-based fuel cells for vehicular transportation is “on board” storage. Hydrogen storage in solids has long been recognized as one of the most practical approaches for this purpose. The capacity of existing storage materials is markedly below that needed for vehicular use. Recently Chen et al. [Nature 420 (21) (2002) 302; J. Phys. Chem. B 107 (2003) 10967] reported a lithium nitride/imide system, with a high capacity, 11.5 wt.%, however, its operating temperature and pressure are not satisfactory for vehicular application. In this research a new storage material has been developed, which is from the partial substitution of lithium by magnesium in the nitride/imide system. The plateau pressure of this new Mg-substituted system is about 30 bar and 200 °C with a H capacity of 4.5 wt.% and possibly higher. This is a very promising H-storage material for “on board” storage for vehicular applications.

A novel method has been developed to monitor the nucleic acids ligation process. Molecular beacon was employed here to convert the ligation information into fluorescence signal quickly and quantitatively. This method provides effective and original approach to researching the dynamic ligation process and the interactions between nucleic acids and ligase. An analytical method for T4 DNA ligase based on this way has been built up with a linear detection range from 2.3¹0−4 U/mL to 0.23 U/raL. It is rapid and sensitive to detect 2.8 ×10−5 U T4 DNA ligase in 10 min.

A general method for ensuring the self-consistent assignment of thermodynamic parameters in simulations of electrochemical— chemical systems is described. An essential part of the method is the identification of thermodynamically superfluous reactions (TSRs) which are defined as reactions in which the value of Km or Em°. is a function of one or more previously specified values of Km or Em° for other reactions. A TSR can be removed from the system without altering the final equilibrium distribution of concentrations. However, a TSR can modify the time-dependent behavior of the system significantly. By identifying a TSR, assignment of an athermodynamic value for its equilibrium constant or formal potential can be precluded. The value of the equilibrium constant Km or formal potential Em° associated with any given TSR can be computed. This approach, which is designed to function in a cyclic voltammetric simulator which can generate and solve the requisite kinetic equations for any user-specified mechanism, is also generally applicable to any chemical or electrochemical simulation.

The V–H (D) systems have been investigated using reaction calorimetry at 298 and 323 K over hydrogen contents from H (D)/V=0→≊1.8. Relative partial molar enthalpies have been determined by absorption of small increments of hydrogen in the single phase regions; for regions where two solid phases coexist, integral or plateau enthalpies are obtained by absorption (desorption) of either large or small amounts of hydrogen. The following calorimetric results were obtained for the two solid phase plateau regions: ‖ΔH‖=40.6 kJ/mol H, 40.8 kJ/mol D for (α + β) and ‖ΔH‖=19.1 kJ/mol H and 23 kJ/mol D for (β’+γ) and (α’+e), respectively. Calorimetric data, relative partial molar enthalpies are also given for the single phase regions. Several phase boundaries are intersected as the hydrogen contents increase in this temperature range and the behavior of the enthalpies at the phase boundaries has been determined and is discussed in relation to the nature of the coexisting phases.

Publisher Summary The high mobility of interstitially dissolved hydrogen atoms allows equilibrium to be established at relatively low temperatures making these metal–hydrogen (M–H) systems unique, in that their phase diagrams can be quite readily determined at low temperatures. This chapter concerns the experimental aspects of phase diagram determination for the M–H systems; however, some theoretical aspects of the M–H systems phase diagrams are needed because otherwise distinctions among various degrees of equilibrium vis-a-vis the resulting phase diagrams is unclear. The chapter introduces various ways to present the M–H phase equilibria, the useful rules relating the phase diagrams to the reaction enthalpy of the M–H systems, and the difference between local equilibrium and complete equilibrium in multicomponent systems. Various techniques for M–H phase diagram determinations in both open and closed systems are also discussed in the chapter.

Hydrogen energy may provide the means to an environmentally friendly future. One of the problems related to its application for transportation is “on-board” storage. Hydrogen storage in solids has long been recognized as one of the most practical approaches for this purpose. The H-capacity in interstitial hydrides of most metals and alloys is limited to below 2.5% by weight and this is unsatisfactory for on-board transportation applications. Magnesium hydride is an exception with hydrogen capacity of ∼ 8.2 wt.%, however, its operating temperature, above 350 ° C, is too high for practical use. Sodium alanate (NaAlH4) absorbs hydrogen up to 5.6 wt.% theoretically; however, its reaction kinetics and partial reversibility do not completely meet the new target for transportation application. Recently Chen et al. [1] reported that ( Li 3 N + 2 H 2 ⇔ LiNH 2 + 2 LiH ) provides a storage material with a possible high capacity, up to 11.5 wt.%, although this material is still too stable to meet the operating pressure/temperature requirement. Here we report a new approach to destabilize lithium imide system by partial substitution of lithium by magnesium in the (LiNH2+LiH⇔Li2NH+H2) system with a minimal capacity loss. This Mg-substituted material can reversibly absorb 5.2 wt.% hydrogen at pressure of 30 bar at 200 ° C. This is a very promising material for on-board hydrogen storage applications. It is interesting to observe that the starting material (2LiNH2+MgH2) converts to ( Mg ( NH 2 ) 2 + 2 LiH ) after a desorption/re-absorption cycle.