Proton Displacement Research Articles

Binding of transition metals by soluble and silica-bound branched poly(ethyleneimine): Part I: Competitive binding equilibria

Competitive binding of sulfuric acid and copper, nickel and zinc sulfates by soluble and silica-bound branched poly(ethyleneimine) has been studied at 25 °C. The binding equilibria were measured by batch experiments using potentiometric and spectroscopic methods. The results were correlated with a chelation model based on a one-step proton displacement and complexation reaction. The calculated results have been compared with those obtained by means of the NICA adsorption model. According to proton titration results, the silica-supported BPEI is less basic than the soluble polymer. Anchoring on the silica matrix also decreases the metal binding strength of BPEI, but the affinity relative to acid binding remains practically unchanged. The chelation model was shown to explain satisfactorily the proton displacement data and the dependence of metal binding on concentration and pH. Moreover, the estimated parameter values characterizing the average number of protons displaced by the metal cation are in reasonable agreement with the values determined experimentally. The H/Me ratio was higher for nickel than for copper, and the difference can be explained by the complex structures inferred from the absorption spectra of the soluble and supported BPEI. At the pH range of practical interest, a comparable correlation was obtained with the NICA model. A satisfactory agreement with the experimental data was also found, when the models were used to predict the simultaneous binding of two metals. The results of the supported BPEI showed that copper can be separated at pH 4.5 with good capacity and selectivity in the presence of 100-fold concentration of nickel or zinc. In the presence of high zinc concentration, a marked competition effect wais observed in nickel binding at pH 5.5 and only a moderate selectivity could be obtained.

Binding of Pb(II) in the system humic acid/goethite at acidic pH

The study of Pb(II) binding to the system humic acid/goethite in acidic medium is reported in the present paper. From a macroscopic point of view, we have constructed the experimental sorption isotherms (using atomic absorption spectroscopy) and compared them with the prediction of the additivity rule. It is found that this system presents positive deviations, that is, the amount sorbed is about an order of magnitude higher than predicted. Apart from this, microscopic and structural aspects have also been studied using in situ and ex situ infrared spectroscopy. These results suggest that the presence of Pb(II) increases the amount of humic acid bound to the oxide. It is proposed that proton displacement due to the interaction between humic substances and the oxide, along with the formation of ternary complexes with the Pb(II) cation bridging the oxide and the humic substances (Type A complexes), cause the deviation from additivity.

Fluorescent properties of hydrogen-bonded ellipticine: A special effect of fluoride anion

Fluorescence properties of ellipticine, a plant alkaloid, was studied in the presence of hydrogen-bond acceptors, such as F −, CH 3COO −, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and N-methylimidazole in different solvents. Global analysis of the spectrophotometric titration data proved that ellipticine deprotonation in the ground state occurred only in the case of the interaction with two F − anions in acetonitrile. The fluorescence band of the 1:1 complex of anions showed large Stokes shift implying significant proton displacement upon excitation along the hydrogen-bond. The lack of ellipticine-DBU complex emission was rationalized by quick proton transfer in the excited state. The kinetics and mechanism of the excited ellipticine quenching were also revealed.

Interaction of 2‐Hydroxy‐substituted Nile Red Fluorescent Probe with Organic Nitrogen Compounds

The fluorescent properties of 2-hydroxy Nile red dye (HONR) proved to be highly sensitive to the basicity of hydrogen bond acceptors. Fluorescence quantum yields and fluorescence decay profiles were measured as the function of the concentration of organic nitrogen compounds in solvents of various polarities. The detailed mechanism and the kinetics of the fluorescence quenching were revealed with the combined analysis of the steady-state and time-resolved spectroscopic data. The relative contribution of the competing reaction steps was found to be very sensitive to the basicity of the additive and to solvent polarity. The most profound change appeared in the unimolecular deactivation pathways of the excited hydrogen-bonded HONR, whereas the formation rate of this species varied to a lesser extent. The dissociation into excited HONR and ground-state base was able to compete with the energy dissipation only when 2,4,6-trimethylpyridine was used as hydrogen bond acceptor in toluene. The bimolecular quenching of the excited hydrogen-bonded complex played significant role in apolar solvents. Proton displacement along the hydrogen bond in the excited complex led to excited ion pairs in polar media.

Spectrophotometric Studies of the Reaction of Zinc(II) with Some Azo‐Triazol Compounds and Its Application to the Spectrophotometric Determination of Microamounts of Zinc(II)

A new, simple, and sensitive quantitative spectrophotometric method for the rapid determination of zinc(II) using six azo compounds based on 3‐amino‐1,2,4‐triazole, namely {3‐(2,4‐dihydroxy‐1‐phenylazo)‐1,2,4‐triazole) (I), 3‐(2‐hydroxy‐5‐methyl‐1‐phenylazo)‐1,2,4‐triazole) (II), 3‐(2‐hydroxy‐5‐acetyl‐1‐phenylazo)‐1,2,4‐triazole) (III), 3‐(2‐hydroxy‐5‐ethylcarboxylate‐1‐phenylazo)‐1,2,4‐triazole) (IV), 3‐(2‐hydroxy‐5‐formyl‐1‐phenylazo)‐1,2,4‐triazole) (V), and 3‐(2‐hydroxy‐5‐bromo‐1‐phenylazo)‐1,2,4‐triazole) (VI), has been developed for use in aqueous media containing 40% (v/v) methanol. Linear calibration graphs are obtained up to 2.6, 5.9, 5.2, 5.2, 8.2 and 9.0 µg mL−1 using ligands I, II, III, IV, V, and VI, respectively. Absorption maxima, molar absorptivities, and Sandell's sensitivities of 1:2 (M:L) complexes were found to be 490, 530, 505, 520, 550, and 510 nm, 4.86×104, 2.10×104, 1.26×104, 0.10×104, 0.19×104, and 0.29×104 L mol−1 cm−1, and 0.0014, 0.0031, 0.0052, 0.0662, 0.0348, and 0.0225 µg cm−1 for ligands I, II, III, IV, V, and VI, respectively. Using the masking agents, the color reactions are free from interference by more than 30 ions investigated. The method has been applied to the spectrophotometric determination of trace amounts of zinc in pharmaceutical formulations and human hair samples. A study of some zinc solid complexes showed that chelation takes place through one nitrogen atom of the azo group and proton displacement from the hydroxyl group.

High-energy proton irradiation effects in GaAs devices

In this paper, we compare the energy dependences (53 and 115 MeV) of proton displacement damage coefficients for p/sup +/n GaAs solar cells with previously reported calculations of nonionizing energy loss (NIEL). Deep level transient spectroscopy (DLTS) was used to generate damage coefficients from the introduction rates of defects. New damage coefficients generated from GaAs bulk LEDs light output (1-530 MeV) are also reported. The damage coefficients from these devices for proton energies E>10 MeV vary but are bounded by the total and Coulombic NIEL.

Spectroscopic and electrochemical studies of ruthenium and osmium complexes of salicylideneimine-2-thiophenol Schiff base

The reactions between [M 3(CO) 12], M=Ru and Os, and salicylideneimine-2-thiophenol Schiff base in THF under reflux gave [Ru(CO) 4(satpH)] and [Os(CO) 3(satpH 2)] complexes. Structures of the two complexes were proposed on the basis of spectroscopic studies. Magnetic study of [Ru(CO) 4(satpH)] suggested that a change in oxidation state of the ruthenium atom from zero to +1 was achieved via oxidative addition of the SH group with a proton displacement to give a low-spin d 7 electronic configuration. UV-Vis spectra of the two complexes in different solvents exhibited visible bands due to metal-to-ligand charge transfer. Electrochemical investigation of the free ligand and complexes showed some cathodic and anodic irreversible peaks due to interconversions through electron transfer.

In-flight annealing of displacement damage in GaAs LEDs: a Galileo story

A recent failure of Galileo's magnetic recorder was attributed to LED degradation. Annealing the culprit OP133 proved successful: irreplaceable data, taken during the encounter with Jupiter's previously unvisited moon Amalthea, was recovered. Annealing test data for both proton and electron displacement damage combined with a simple device temperature model explains some details of the failure and the partial recovery of recorder motor function.

Interaction of triplet C60with p-tert-butyl-calixarenes and their complexes with pyridine derivatives

The interaction of triplet excited C60 with p-tert-butyl-calix[n]arenes (BCXn, n = 4, 6 or 8) and with their 2,4,6-trimethylpyridine (TMP) and pyridine complexes has been studied with laser flash photolysis experiments. It has been found that in polar solvents 3C60 is quenched by BCX6 via electron transfer, producing C60−˙ radical anion with a yield of 0.45 ± 0.07 in benzonitrile. In contrast, no reaction occurs in nonpolar media or with BCX4 and BCX8. Upon the addition of TMP, the rate of quenching is enhanced considerably due to the formation of TMP-BCXn complexes. The significant deuterium isotope effect indicates that the electron movement from the calixarene to the triplet excited C60 is coupled to the proton displacement from the calixarene to the base. In the presence of pyridine, which has weaker hydrogen-bonding power, the enrichment of the solvate shell in the proton acceptor molecules may play an important role in promoting triplet C60 quenching.

Total dose and displacement damage effects in a radiation-hardened CMOS APS

A 512/spl times/512 CMOS active pixel sensor (APS) was designed and fabricated in a standard 0.5-/spl mu/m technology. The radiation tolerance of the sensor has been evaluated with Co-60 and proton irradiation with proton energies ranging from 11.7 to 59 MeV. The most pronounced radiation effect is the increase of the dark current. However, the total ionizing dose-induced dark current increase is orders of magnitude smaller than in standard devices. It behaves logarithmically with dose and anneals at room temperature. The dark current increase due to proton displacement damage is explained in terms of the nonionizing energy loss of the protons. The fixed pattern noise does not increase with total ionizing dose. Responsivity changes are observed after Co-60 and proton irradiation, but a definitive cause has not yet been established.

Binding affinity and capacities for ytterbium(3+) and hafinum(4+) by chemical entities of plant tissue fragments.

The binding affinity of ytterbium (Yb3+) and hafinum (Hf4+) to ligands of chemical entities of fragments of bermudagrass tissues and their resistance to exchanging Yb with other ligands and to displacement by protons were investigated. Chemical entities of acid resistant NDF (ARNDF), 0.1 N acid detergent fiber (0.1 N ADF), and permanganate cellulose (CELL) were prepared from fragments of bermudagrass hay (Cynodon dactylon [L.] Pers.) obtained by grinding to pass a 2-mm sieve. 175Ytterbium and Yb, as YbCl3, were initially bound to each preparation by soaking for 12 h in pH 5.5 borate buffer to obtain Yb bound onto ligands having affinity constants for Yb equal to or greater than that for the weakly stable borate ligand, Yb > or = borate. The fraction of Yb > or = borate was measured and fragments then sequentially exposed to acetate, citrate, nitrotriacetate (NTA), and EDTA ions to allow exchange of Yb from Yb > or = borate with ligands having affinity constants for Yb equal to or greater than acetate (Yb > or = acetate), citrate (Yb > or = citrate), NTA (Yb > or = NTA), and EDTA (Yb > or = EDTA) ions. Binding of Yb > or = borate indicated the existence of two species of ligands: strong ligands binding essentially 100% of added Yb at levels of 1 to 1,300 ppm (0.1 N ADF) and at 1 to 7,000 ppm (ARNDF); and weaker ligands binding 4 and 8% of the Yb, respectively, at levels of added Yb greater than 1,300 ppm and 7,000 ppm. Ytterbium > or = acetate of ARNDF, but not 0.1 N ADF, was as resistant to exchange as Yb > or = citrate. Ytterbium > or = borate was exchanged extensively (85% or greater) with soluble ligands having affinity constants > or = NTA. Ytterbium resistance to proton displacement at pH of 1.5 increased with Yb > or = EDTA > Yb > or = NTA > Yb > or = citrate > Yb > or = acetate. Very efficient binding of Yb to CELL suggested that such chemical preparations are not representative of native cellulose. Hafnium (4+) was strongly bound to plant tissues rendering both Hf and Hf-bound DM insoluble at a pH of 1.5 and insoluble in a modified NDF solvent without EDTA. It is concluded that Yb specifically applied as Yb > or = acetate and Hf4+ are indelible markers for estimating sojourn time of undigested plant tissues at the normal pH of the rumen. Because of its resistance to proton displacement, Hf4+ would be an indelible marker for estimating sojourn time in more acidic postgastric segments of the gastrointestinal tract.

Energy dependence of proton damage in optical emitters

The energy dependence of proton displacement damage effects is investigated for light-emitting diodes (LEDs) and laser diodes. Injection-enhanced annealing occurs more rapidly when devices are irradiated with protons below 50 MeV compared with annealing from 200-MeV protons. A different interpretation of damage in amphoterically doped LEDs is used to show that the dependence of damage on energy is relatively flat for energies above 50 MeV, in contrast to older results in the literature that show a continued decrease in damage at higher energies.

Transfer Reactions of Rydberg (Quasi-Rydberg Molecular) Electrons in Condensed Media: V. Large Proton Displacement in the N–H Bond upon Photoionization of Diphenylamine via Highly Excited Triplet State T* in Methanol at 77 K

The mechanism of large proton displacements in polarized R–Hδ+ bonds, which involves the formation of a triplet complex R···H* (H* is the excited hydrogen atom) in the T* state upon the capture of an excited π* electron onto the p, d, and f quasi-Rydberg proton orbitals in Hδ+ (part IV) is further substantiated. It is assumed that the proton displaced upon photoionization of added diphenylamine molecules (Ph2NH) via the complex Ph2N···H* in methanol at 77 K can be fixed by the polarization of the medium in the vicinity of the diphenylaminyl radical (Ph2N···H+sol) formed. When the solution is thawed up to 106 K, the protons returns to Ph2N to afford the radical cation Ph2NH+.

Biosorption of monovalent and divalent ions on baker's yeast

Biosorption of monovalent ions Na + and K +, by deactivated protonated yeast ( Saccharomyces cerevisiae) at controlled pH, was compared with biosorption of divalent ions Ca 2+ and Mg 2+ to help to understand the underlying binding mechanisms. The adsorption for monovalent ions was accompanied by H + release. Divalent ions were sorbed by proton displacement, and also an additional mode not accompanied by release of H +. The sorption uptake of both monovalent and divalent metal ions increased with pH in the range 3–7 peaking at 6.75. Equilibrium sorption isotherms at pH=6.75 showed that the total maximum biosorptive capacity for metal ions decreased in the following order: Ca>Mg>Na⩾K.

Proton displacement damage in light-emitting and laser diodes

The effects of proton displacement damage on light-emitting diodes (LEDs) and laser diodes are discussed, comparing the radiation sensitivity of current technology devices with older devices for which data exist in the literature. Injection-enhanced annealing is discussed, along with the issue of energy dependence of proton displacement damage. New characterization methods are proposed for light-emitting diodes that complement measurement of light output and provide a better indication of nonradiative recombination centers.

Chemfet Based Microsensors Covered with Ion-Partitioning Polymeric Membranes

The development of a new type of microsensors based on chemically sensitive field-effect transistors (CHEMFETs) covered with polymeric bulk ion-partitioning membranes is presented. For the construction of the microsensor, a PVC plasticized membrane containing two ionophores, one selective to protons and the other to the analyte cation of interest, is placed on the gate of a pH sensitive field-effect transistor which acts as the transducer. With the use of thin (5–10 μm) ion-partitioning membranes onto the pH-sensitive ISFET gate, the proton displacement out of the membrane and to the pH sensitive gate is fast and reversible. This displacement generates a signal that is directly related to the analyte concentration found in the test solution. Comparing the performance of CHEMFETs and ISEs selective to the monovalent potassium cation and the divalent calcium ion validates this novel CHEMFET response mechanism.

Dynamic Properties of Proton Transfer in the Anharmonic-Interaction Hydrogen Bond Systems**The project supported by Natural Science Foundation of Shandong Province of China (No. Q99A03) and National Natural ScienceFoundation of China under Grant No. 19974034

We analyze the properties of the excited solitary-wave model in the case of anharmonic-interaction of heavy ionic lattice in hydrogen bond systems. In this case, some new phenomena appear. We find different types of solutions for the proton displacement and influences on the kinks and pulse solitary waves by numerical calculation. For each of them we have presented a direct relation with the effective potential of the system.

Hydrochemical distribution patterns in stream waters, Trøndelag, central Norway

A regional geochemical sampling program of stream waters has been carried out in the Nord-Trøndelag region of central Norway. This area has hitherto been little affected by regional anthropogenic sources of pollution. Hydrochemical trends appear to be dominated by interplay of two main factors: (i) input of sea salts via marine aerosols in precipitation: and (ii) geological sources (mineral weathering). Factor (i) results in a predominance of Na-Cl waters near the coast, and may also be partially responsible (via proton displacement from soil ion-exchange sites by marine cations) for lower pH values in near-coastal waters. Further inland, the importance of marine salts decreases and waters become dominantly Ca-(Na)-HCO 3. Sub-regional anomalies in geochemical maps for, e.g. nitrate and copper may indicate anthropogenic sources for these parameters from agriculture or mining activities.

Use of 1 H NMR to study transport processes in porous biosystems

The operation of bioreactors and the metabolism of microorganisms in biofilms or soil/sediment systems are strongly dictated by the transport processes therein. Nuclear magnetic resonance (NMR) spectroscopy or magnetic resonance imaging (MRI) allow nondestructive and noninvasive quantification and visualisation (in case of MRI) of both static and dynamic water transport phenomena. Flow, mass transfer and transport processes can be measured by mapping the (proton) displacement in a defined time interval directly in a so-called pulsed field gradient (PFG) experiment. Other methods follow the local intensity in time-controlled sequential images of water or labelled molecules, or map the effect of contrast agents. Combining transport measurements with relaxation-time information allows the discrimination of transport processes in different environments or of different fluids, even within a single picture element in an image of the porous biosystem under study. By proper choice of the applied NMR method, a time window ranging from milliseconds to weeks (or longer) can be covered. In this paper, we present an overview of the principles of NMR and MRI techniques to visualise and unravel complex, heterogeneous transport processes in porous biological systems. Applications and limitations will be discussed, based on results obtained in (model) biofilms, bioreactors, microbial mats and sediments.

Use of (1)H NMR to study transport processes in porous biosystems.

The operation of bioreactors and the metabolism of microorganisms in biofilms or soil/sediment systems are strongly dictated by the transport processes therein. Nuclear magnetic resonance (NMR) spectroscopy or magnetic resonance imaging (MRI) allow nondestructive and noninvasive quantification and visualisation (in case of MRI) of both static and dynamic water transport phenomena. Flow, mass transfer and transport processes can be measured by mapping the (proton) displacement in a defined time interval directly in a so-called pulsed field gradient (PFG) experiment. Other methods follow the local intensity in time-controlled sequential images of water or labelled molecules, or map the effect of contrast agents. Combining transport measurements with relaxation-time information allows the discrimination of transport processes in different environments or of different fluids, even within a single picture element in an image of the porous biosystem under study. By proper choice of the applied NMR method, a time window ranging from milliseconds to weeks (or longer) can be covered. In this paper, we present an overview of the principles of NMR and MRI techniques to visualise and unravel complex, heterogeneous transport processes in porous biological systems. Applications and limitations will be discussed, based on results obtained in (model) biofilms, bioreactors, microbial mats and sediments.