DCE Phase Research Articles

Fully automatic quantification for hand synovitis in rheumatoid arthritis using pixel-classification-based segmentation network in DCE-MRI.

A classification-based segmentation method is proposed to quantify synovium in rheumatoid arthritis (RA) patients using a deep learning (DL) method based on time-intensity curve (TIC) analysis in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). This retrospective study analyzed a hand MR dataset of 28 RA patients (six males, mean age 53.7years). A researcher, under expert guidance, used in-house software to delineate regions of interest (ROIs) for hand muscles, bones, and synovitis, generating a dataset with 27,255 pixels with corresponding TICs (muscle: 11,413, bone: 8502, synovitis: 7340). One experienced musculoskeletal radiologist performed ground truth segmentation of enhanced pannus in the joint bounding box on the 10th DCE phase, or around 5min after contrast injection. Data preprocessing included median filtering for noise reduction, phase-only correlation algorithm for motion correction, and contrast-limited adaptive histogram equalization for improved image contrast and noise suppression. TIC intensity values were normalized using zero-mean normalization. A DL model with dilated causal convolution and SELU activation function was developed for enhanced pannus segmentation, tested using leave-one-out cross-validation. 407 joint bounding boxes were manually segmented, with 129 synovitis masks. On the pixel-based level, the DL model achieved sensitivity of 85%, specificity of 98%, accuracy of 99% and precision of 84% for enhanced pannus segmentation, with a mean Dice score of 0.73. The false-positive rate for predicting cases without synovitis was 0.8%. DL-measured enhanced pannus volume strongly correlated with ground truth at both pixel-based (r = 0.87, p < 0.001) and patient-based levels (r = 0.84, p < 0.001). Bland-Altman analysis showed the mean difference for hand joints at the pixel-based and patient-based levels were -9.46 mm3 and -50.87 mm3, respectively. Our DL-based DCE-MRI TIC shape analysis has the potential for automatic segmentation and quantification of enhanced synovium in the hands of RA patients.

Femtoliter oil droplets act as CO2 micropumps for uninterrupted electrochemiluminescence at the water|oil interface

Interfacial effects are well-known to significantly alter chemical reactivity, especially in confined environments, where the surface to volume ratio increases. Here, we observed an inhomogeneity in the electrogenerated chemiluminescence (ECL) intensity decrease over time in a multiphasic system composed of femtoliter water droplets entrapping femtoliter volumes of the 1,2-dichloroethane (DCE) continuous phase. In usual electrochemiluminescence (ECL) reactions involving an ECL chromophore and oxalate ([C2O4]2−), the build-up of CO2 diminishes the ECL signal with time because of bubble formation. We hypothesised that relative solubilities of chemical species in these environments play a dramatic role in interfacial reactivity. Water droplets, loaded with the ECL luminophore [Ru(bpy)3]2+ and the coreactant [C2O4]2− were allowed to stochastically collide and adsorb at the surface of a glassy carbon macroelectrode. When water droplets coalesce on the surface, they leave behind femtoliter droplets of the DCE phase (inclusions). We report the surprising finding that the addition of multiple interfaces, due to the presence of continuous phase’s femtoliter inclusions, allows sustained ECL over time after successive potential applications at the triple-phase boundary between water droplet|electrode|DCE inclusion. When femtoliter droplets of DCE form on the electrode surface, bright rings of ECL are observed during the simultaneous oxidation of [Ru(bpy)3]2+ and [C2O4]2−. Control experiments and finite element modelling allowed us to propose that these rings arise because CO2 that is generated near the 1,2-dichloroethane droplet partitions in due to relative solubility of CO2 in 1,2-dichloroethane and builds up and/or is expelled at the top of the droplet. The small droplets of the DCE phase act as micropumps, pumping away carbon dioxide from the interface. These results highlight the unexpected point that confined microenvironments and their geometry can tune chemical reactions of industrial importance and fundamental interest.

Separation of an ε-poly-L-lysine derivative by solvent extraction under a controlled interfacial potential difference.

This paper describes the availability of a 1,2-dichloroethane (DCE)-water (W) interfacial system under a controlled interfacial potential difference for the separation of polycationic species. The system was applied to the production of polyethylene glycol-modified ε-poly-L-lysine (PEG-εPL). PEG-εPL is produced by a fermentation process, and the crude product contains a significant amount of non-modified εPL, which is hardly separated by conventional chromatographic techniques. Both εPL species exist in fully protonated forms under certain acidic conditions, and an extractant, dibenzo-18-crown-6 (DB18C6), associates with their ammonium groups to stabilize the polycations in DCE. Despite the polydispersity of the samples, the εPL and crude PEG-εPL give well-defined cyclic voltammetric waves due to the DB18C6-assisted transfer of the polycations at the polarizable DB18C6 (DCE) | (W, pH ~ 3) interface with midpoint potentials useful for a rough prediction of ion partition equilibria. Thus, the partition experiment was performed using the DB18C6, Bu4N[(CF3SO2)2N] (DCE) | crude PEG-εPL, Li[(CF3SO2)2N] (W, pH ~ 3) interfacial system, of which the potential difference was controlled to enable selective extraction of polycationic PEG-εPL by partition of the [(CF3SO2)2N]- ion. The extract could be collected from the DCE phase and was found to consist of highly purified PEG-εPL.

Simultaneous electropolymerization/Au nanoparticle generation at an electrified liquid/liquid micro-interface

Free-standing nanocomposite thin-films for bioimplantation and (electro)catalysis are still an immature field despite the need for new materials. Herein, the micro liquid|liquid interface between water|1,2-dichloroethane (w|DCE) positioned at the tip of a pulled pipette has been exploited to generate a free-standing thin-film incorporating Au NPs electrogenerated in situ by reduction of a gold salt in the aqueous phase and using 2,2′:5′,2″-terthiophene (TT) as monomer/electron donor dissolved in the DCE phase. Low pH of the aqueous phase generated incomplete, poorly formed films, as evidenced by TEM and AFM images of the final film. At high pH the half-wave potential of the electron transfer wave shifted to lower potentials (∼0.35 V versus simple ion transfer of AuCl4–) with repeated cyclic voltammetric cycling indicating improved thermodynamics. Imaging of films produced at pH's >5.5 were robust. These results indicate the need of a Brønsted base to capture protons and facilitate TT+•, radical cation coupling. TEM and AFM imaging are complemented by in situ impedance spectroscopy measurements that show an increase in the capacitive nature of the interface as [TT] and pH increases along with increased cycling of the potential. Curve fitting using equivalent circuit models required the addition of a second capacitator element to mimic the generation of a porous film at the liquid|liquid interface, i.e., a liquid|solid|liquid interface. By reducing the required overpotential, one can prevent overoxidation of the monomer/polymer. AFM measurements of formed thin-films mechanically deposited onto silicon substrates were found to be ∼0.4 μm in thickness with Au NP radius increasing concomitantly with distance away from the w|DCE interface.

Light-induced electron transfer/phase migration of a redox mediator for photocatalytic C-C coupling in a biphasic solution.

Photocatalytic molecular conversions that lead to value-added chemicals are of considerable interest. To achieve highly efficient photocatalytic reactions, it is equally important as it is challenging to construct systems that enable effective charge separation. Here, we demonstrate that the rational construction of a biphasic solution system with a ferrocenium/ferrocene (Fc+/Fc) redox couple enables efficient photocatalysis by spatial charge separation using the liquid-liquid interface. In a single-phase system, exposure of a 1,2-dichloroethane (DCE) solution containing a Ru(II)- or Ir(III)-based photosensitizer, Fc, and benzyl bromide (Bn-Br) to visible-light irradiation failed to generate any product. However, the photolysis in a H2O/DCE biphasic solution, where the compounds are initially distributed in the DCE phase, facilitated the reductive coupling of Bn-Br to dibenzyl (Bn2) using Fc as an electron donor. The key result of this study is that Fc+, generated by photooxidation of Fc in the DCE phase, migrates to the aqueous phase due to the drastic change in its partition coefficient compared to that of Fc. This liquid-liquid phase migration of the mediator is essential for facilitating the reduction of Bn-Br in the DCE phase as it suppresses backward charge recombination. The co-existence of anions can further modify the driving force of phase migration of Fc+ depending on their hydrophilicity; the best photocatalytic activity was obtained with a turnover frequency of 79.5 h-1 and a quantum efficiency of 0.2% for the formation of Bn2 by adding NBu4+Br- to the biphasic solution. This study showcases a potential approach for rectifying electron transfer with suppressed charge recombination to achieve efficient photocatalysis.

Selective electrochemical capture and release of uranyl from aqueous alkali, lanthanide, and actinide mixtures using redox-switchable carboranes.

We report the selective electrochemical biphasic capture of the uranyl cation (UO22+) from mixed-metal alkali (Cs+), lanthanide (Nd3+, Sm3+), and actinide (Th4+, UO22+) aqueous solutions to an organic, 1,2-dichloroethane (DCE), phase using the ortho-substituted nido-carborane anion, [1,2-(Ph2PO)2-1,2-C2B10H10]2− (POCb2−). The reduced POCb2− is generated by electrochemical reduction of the closo-carborane, POCb, prior to mixing with the aqueous mixed-metal solution. Subsequent UO22+ release from the captured product, [UO2(POCb)2]2−, was performed by galvanostatic bulk electrolysis of the DCE phase and back-extraction of UO22+ to a fresh aqueous phase. The selective capture and release of UO22+ was confirmed by combined ICP-OES and NMR spectral analyses of the aqueous and organic phases, respectively, against the newly synthesized nido-carborane complexes, [[CoCp*2][Cs(POCb)]]2, [CoCp*2]3[Nd(POCb)3], [CoCp*2]3[Sm(POCb)3], and [CoCp*2]2[Th(POCb)3].

Fluorination Effect on the Gibbs Transfer Energy for Methylene Group from 1,2-Dichloroethane or 1,1,1,2,3,4,4,5,5,5-​Decafluoropentane to Water.

The ion-transfer reactions of alkyl and perfluoroalkyl carboxylate ions (CH3(CH2)n-2COO- and CF3(CF2)n-2COO-) at 1,2-dichloroethane (DCE) | water (W) and 1,1,1,2,3,4,4,5,5,5-decafluoropentane (DFP) | W interfaces were investigated. These ions gave reversible or quasi-reversible voltammetric waves due to their ion transfer across the interfaces, and the formal potentials and the formal Gibbs transfer energies from a non-aqueous solvent to water, ΔG°'tr,α→W (α = DCE and DFP), were determined. The ΔG°'tr,α→W for CH3(CH2)n-2COO- and CF3(CF2)n-2COO- linearly increased with n, allowing for estimating ΔG°'tr,α→W for methylene groups. The estimated value of ΔG°'tr,DCE→W for the -CH2- group was higher than that of ΔG°'tr,DCE→W for the -CH2- group, whereas the ΔG°'tr,DCE→W for the -CF2- group was lower than that of ΔG°'tr,DCE→W for the -CF2- group, indicating that the -CH2- (or -CF2-) group is more favorably (or unfavorably) solvated in the DCE phase compared to the DFP phase. From the estimated values, the fluorination effect of alkyl chains on partitioning the alkyl group between the biphase media has also been discussed.

Radiomics Analysis Based on Automatic Image Segmentation of DCE-MRI for Predicting Triple-Negative and Nontriple-Negative Breast Cancer.

Purpose To investigate whether quantitative radiomics features extracted from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) could be used to differentiate triple-negative breast cancer (TNBC) and nontriple-negative breast cancer (non-TNBC). Materials and Methods This retrospective study included DCE-MRI images of 81 breast cancer patients (44 TNBC and 37 non-TNBC) from August 2018 to October 2019. The MR scans were achieved at a 1.5 T MR scanner. For each patient, the largest tumor mass was selected to analyze. Three-dimensional (3D) images of the regions of interest (ROIs) were automatically segmented on the third DCE phase by a deep learning segmentation model; then, the ROIs were checked and revised by 2 radiologists. DCE-MRI radiomics features were extracted from the 3D tumor volume. The patients were randomly divided into training (N = 57) and test (N = 24) cohorts. The machine learning classifier was built in the training dataset, and 5-fold cross-validation was performed on the training cohort to train and validate. The data of the test cohort were used to investigate the predictive power of the radiomics model in predicting TNBC and non-TNBC. The performance of the model was evaluated by the area under receiver operating characteristic curve (AUC), accuracy, sensitivity, and specificity. Results The radiomics model based on 15 features got the best performance. The AUC achieved 0.741 for the cross-validation, and 0.867 for the independent testing cohort. Conclusion The radiomics model based on automatic image segmentation of DCE-MRI can be used to distinguish TNBC and non-TNBC.

Electrochemically controlled Au nanoparticle nucleation at a micro liquid/liquid interface using ferrocene as reducing agent

Gold nanoparticles (NPs) have become ubiquitous owing to their stability, plasmonic and catalytic properties, as well as biocompatibility, such that intensive research has been conducted with the aim of controlling the final NP size and morphology. Since the 1990′s, the liquid/liquid interface has been a means of generating Au NPs via dissolution of Au salts in the aqueous phase and hydrophobic capping agents into the organic phase. Herein, by employing the micro interface between two electrolytic solutions (ITIES), specifically water/1,2-dichloroethane (w/DCE), Au NPs were electrolytically generated using ferrocene (Fc) dissolved in the DCE phase as both electron donor and capping agent, while KAuCl4 was dissolved in the aqueous phase. By varying the pH, Au salt:Fc concentration ratio, potential, and time of reaction, the size and morphology, 20–400 nm and spherical or cubic, respectively, can be controlled. Voltammetric analysis was used to investigate interfacial electron transfer from Fc(org) to AuCl4−(aq). However, at open-circuit-potential and during amperometry highly polydisperse nano-sheets, rods, and cubes were also observed. Critically, the micropipette apparatus with integrated syringe could be easily industrialized as a NP dispensing apparatus coupled with parallelization to rapidly modify substrate surfaces with size and morphologically controlled Au NPs.

Self-perturbation of the salt partition at the water/1,2-dichloroethane interface

Open circuit potential (OCP) measurements of the partition of tetrapentylammonium chloride (TPeACl) at the water/1,2-dichloroethane (DCE) interface reveal two remarkable processes. First one is characterized by a substantial drop and further decay of the OCP from its expected equilibrium value. This process has been previously investigated and ascribed to the anomalous extraction of the salt driven by its accumulation in the hydrated salt clusters in the DCE phase. The second process, which has been observed for the first time in the present study, is characterized by the short-term potential spikes overlapping the long-term OCP records. These spikes are assumed to be associated with the collision and fusion of the hydrated salt clusters or their aggregates produced by the former process with the water/DCE interface. Self-perturbation of the steady-state salt partition by a single cluster or aggregate impact offers a new approach to study kinetics and the mechanism of the hydrated salt cluster formation.

Origin of chronoamperometric responses associated with impacts of single electrolyte droplets at a polarized liquid/liquid interface

Chronoamperometric measurements at a constant potential are used to study the single impacts of the water-in-DCE emulsion droplets containing an electrolyte (tetrapropylammonium chloride, TPrACl) at a polarized water(W)/1,2-dichloroethane (DCE) interface. The impacts give rise to the spike-like current transients, which are characterized by the initial current step (time constant less than 2 ms) followed by a slower exponential current decay with a time constant in tens of milliseconds. It is shown that the theoretical treatment of the current spikes can be based on a modification of the bulk electrolysis model including (1) the droplet collision at the W/DCE interface, (2) a partial coalescence (fusion) of the droplet with the impacted interface, (3) a reorganization of the electric double layer leading to the propagation of the interfacial potential difference from the impacted interface to the surface of the droplet, and (4) stripping (bulk electrolysis) of TPrA+ from the droplet to the DCE phase accompanied by the chloride depletion into the bulk water phase. On assuming that the stripping of TPrA+ is the rate-determining step of the impact event, the theoretical relationships for the current transient are derived, which are confirmed by the experimental data. An analysis of the current transients yields the charge corresponding to the ionic content of the droplets, which is used to evaluate the droplet diameter. Droplet size distribution with the droplet diameter of around 8 μm is verified by an analysis of the microscopic images of the W-in-DCE emulsion, and in part also by the dynamic laser scattering measurements. It is shown that the frequency of the droplet collisions with the W/DCE interface (1–10 Hz) is controlled by migration of the negatively charged droplets towards the interface.

Voltammetric Analysis of Redox Reactions and Ion Transfer in Water Microdroplets.

We report a set of voltammetric experiments for studying redox reactions and ion transfer in water microdroplets emulsified in 1,2-dichloroethane (DCE). The electrochemistry of microdroplets (rdrop ∼ 700 nm) loaded with either ferrocyanide ([Fe(CN)6]4-) or ferricyanide ([Fe(CN)6]3-), chosen due to their hydrophilic nature, was tracked using cyclic voltammetry. These heterogeneous reactions necessitated ion transfer at the droplet interface to maintain charge balance in the two liquid phases during oxidation or reduction, which was facilitated by the tetrabutylammonium perchlorate ([TBA][ClO4]) salt in the DCE phase. Experiments were performed with (1) a single macrodroplet (10-7 L) on a macroelectrode (r ∼ 1.5 mm), (2) millions of microdroplets (10-15 L) adsorbed on to a macroelectrode (r ∼ 1.5 mm), and (3) at the single microdroplet level via observing individual microdroplet collisions at an ultramicroelectrode (r ∼ 5 μm). We demonstrate that when millions of microdroplets are adsorbed onto a macroelectrode, there are two surprising observations: (1) the half-wave potential (E1/2) for the [Fe(CN)6]3-/4- redox couple shifts by +100 mV, which is shown to depend on the number of droplets on the electrode surface. (2) The reduction of [Fe(CN)6]3-, which is assisted by the transfer of TBA+ into the water droplet, displays two waves in the voltammogram. This dual-wave behavior can be explained by the formation of TBAxK3-xFe(CN)6, which is soluble in DCE. Additionally, we demonstrate that the adsorption of microdroplets onto an electrode surface offers significant amplification (×103) of the water/oil/electrode three-phase boundary when compared to the adsorption of larger macrodroplets, permitting a rigorous evaluation of heterogeneous chemistry at this distinct interface. In combination, these experiments provide new energetic and mechanistic insights for droplet systems, as well as reactivity differences between microscale and bulk multiphase systems.

Comparison of biparametric MRI to full multiparametric MRI for detection of clinically significant prostate cancer.

Multiparametric magnetic resonance imaging (MP-MRI) and MRI/ultrasound (US) fusion-guided biopsy are becoming more widely used techniques for prostate cancer (PCa) diagnosis and management. However, their widespread adoption and use, where available, are limited by cost and added time. These limitations could be minimized if a biparametric MRI (BP-MRI) focusing on T2-weighted and diffusion-weighted imaging is performed. Herein we report the cancer detection rate of BP-MRI compared with full MP-MRI. Biopsy-naive and prior negative biopsy patients with clinical suspicion for PCa underwent MP-MRI with an imaging protocol incorporating narrow field-of-view T2-weighted, diffusion-weighted, and DCE pelvic MRI. Then patients underwent MRI/US fusion-guided biopsy of target lesions between November 2013 and October 2017. The pathology results were compared to the positivity of the DCE sequence compared to the BP-MRI findings alone. There were 648 targeted lesions biopsied in 344 patients. We defined biparametric screen filter positivity as both T2-weighted and diffusion-weighted imaging positivity for the same lesion. The majority of target lesions (552/648, 85%) were screen filter positive. For those that were screen filter negative, a minority (14/96, 15%) had DCE-positive findings. Of these, 2/3 (67%) cancer-positive cases were seen on T2-weighted imaging. For those 82 that were screen filter negative and DCE negative, the DCE phase would not have added imaging suspicion. Only 3/82 (3.7%) were cancer positive; 2 with low risk, grade group 1 cancer and 1 with intraductal carcinoma, all identified on targeted T2-weighted MRI positivity. BP-MRI for the evaluation of PCa and for guiding MRI/US fusion-targeted biopsy has the advantages of reducing cost, time, and contrast exposure of MP-MRI by eliminating the DCE phase. These benefits are realized without forfeiting valuable diagnostic information, as shown by similar cancer detection rates of BP-MRI and MP-MRI in this study, particularly for clinically significant cases of PCa.

Ion-Transfer Voltammetry at a Water/1,2-Dichloroethane Interface Using Photoionization by Ultraviolet Irradiation: Detection of Cation Radicals of p-Phenylenediamine Derivatives.

We have attempted to detect electrically neutral substances by ion-transfer voltammetry at an interface between two immiscible electrolyte solutions (ITIES), such as an interface between water and 1,2-dichloroethane (a W/DCE interface), by irradiating the interface with ultraviolet light (200 - 300 nm). In the present work, while considering the facts that p-phenylenediamine derivatives are soluble in DCE, but insoluble in water, and that cation radicals of the derivatives are fairly stable in various media, we photoionized the derivatives in a DCE phase by ultraviolet irradiation, and after that carried out ion-transfer voltammetry at a W/DCE interface. As a result, we could successfully observe ion-transfer waves of cation radicals of the derivatives from the W to DCE phase. Namely, the cation radicals are generated in the DCE phase by ultraviolet irradiation, and subsequently distributed into the W phase. In addition to these ion-transfer waves, we also found that facilitated proton-transfer waves by the derivatives were shifted to a more negative potential region after ultraviolet irradiation, because of hydrogen chloride formed from photodecomposition of DCE by ultraviolet irradiation.

Effect of Ultraviolet Irradiation on Proton Transfer Facilitated by 5,10,15,20-Tetraphenyl-21H,23H-porphine and Its Metal Complexes at a Water/1,2-Dichloroethane Interface.

We examined photochemical effects by ultraviolet irradiation on facilitated proton transfer at a water/1,2-dichloroethane (W/DCE) interface by ion-transfer voltammetry using a Xe flash lamp. 5,10,15,20-Tetraphenyl-21H,23H-porphine (H2TPP) or its metal complex, such as cobalt (Co(II)TPP), zinc (Zn(II)TPP), and nickel (Ni(II)TPP) complexes, was added into the DCE phase as an ionophore for the facilitated proton transfer. After we irradiated the W/DCE interface through the W phase, the voltammetric waves for proton transfer facilitated by H2TPP and Co(II)TPP were remarkably enhanced and shifted to the lower potential region, compared to those before irradiation. We confirmed from the pH and argentometric titrations that such enhancements and shifts of the waves were caused by hydrogen chloride (HCl) produced by photodecomposition of DCE. On the other hand, the waves for proton transfer facilitated by Zn(II)TPP and Ni(II)TPP were very small from the beginning, and showed neither enhancement nor any shift upon irradiation.

SECM study of hydrogen photogeneration in a 1,2-dichloroethane | water biphasic system with decamethylruthenocene electron donor regeneration

This paper reports light driven hydrogen evolution reaction (HER) at 1,2-dichloroethane|water (DCE|W) interface using photoexcited decamethylruthenocene (DMRc) as electron donor. DMRc is in situ regenerated by electroreduction of its oxidized form (DMRc+) formed during HER as a by-product. This enables continuous HER using small amount of DMRc. Proton transfer from the acidic aqueous phase to the DCE phase is ensured by negative chemical polarization of the liquid|liquid interface. The reduction of protons in DCE occurs only after excitation of DMRc by light. Voltammetry performed with the organic droplet-modified glassy carbon electrode immersed in the aqueous electrolyte solution of various anions, indicated that oxidation of DMRc is followed by an anion insertion from water into the organic phase. We demonstrate that DMRc can be electrochemically regenerated at the microelectrode positioned close to the interface between two immiscible electrolyte solutions (ITIES) by the scanning electrochemical microscopy. Regeneration of the electron donor allows further development of biphasic system towards continuous hydrogen generation platform.

Silver(I) Extraction with Benzo-18-Crown-6 Ether from Water into 1,2-Dichloroethane: Analyses on Ionic Strength of the Phases and their Equilibrium Potentials

Extraction constants (Kex &amp; Kex±) for the extraction of silver picrate (AgPic) by benzo-18-crown-6 ether (B18C6) into 1,2-dichloroethane (DCE) were determined at 298 K and various ionic strength (I)-values of a water phase with or without excess HNO3. Here the symbols, Kex and Kex±, were defined as [AgLPic]DCE/P and [AgL+]DCE[Pic−]DCE/P with P = [Ag+][L]DCE[Pic−] and L = B18C6, respectively; [ ]DCE refers to the concentration of the corresponding species in the DCE phase at equilibrium. Simultaneously, KD,Pic (= [Pic−]DCE/[Pic−]) and K1,DCE (= Kex/Kex±) values for given I and IDCE values were determined, where the symbol IDCE shows I of the DCE phase. Also, equilibrium potential differences (Δφeq) based on the Pic− transfer at the water/DCE interface were obtained from the analysis of the KD,Pic [= KD,PicS exp{−(F/RT) Δφeq}] values; the symbol KD,PicS shows KD,Pic at Δφeq = 0 V. On the basis of these results, I dependences of logKex and logKex± and IDCE ones of logK1,DCE and logKex± were examined. Extraction experiments of AgClO4 and AgNO3 by B18C6 into DCE were done for comparison. The logKex±-versus-Δφeq plot for the above Ag(I) extraction systems with Pic−, ClO4−, and NO3− gave a good positive correlation.

Temperature effect in the ion transfer kinetics at the micro-interface between two immiscible electrolyte solutions

Electrochemical impedance spectroscopy (EIS) was used to investigate the kinetics of the tetraethylammonium (TEA+) ion transfer across the water/1,2-dichloroethane (DCE) interface supported at the tip of a thick-wall microcapillary at various temperatures. EIS measurements were carried out at the equilibrium Galvani potential difference, which was controlled by the partition of TEA+ present in both the aqueous and DCE phase. The apparent standard rate constant k0 of the TEA+ ion transfer and the diffusion coefficient Dw of TEA+ in the aqueous phase were determined at five temperature values in the range 15–35°C. The values k0=0.47±0.12 at 20°C and k0=0.52±0.17cms−1 at 25°C agree well with those obtained by EIS and noise analysis under the same or similar experimental conditions in our previous studies. Comparable effects of temperature on k0 and Dw, as indicated by nearly equal slopes of the plots of log k0 and log Dw vs. the reciprocal absolute temperature, point to the absence of an energy barrier for the ion to overcome in the interfacial region. On the other hand, the experimental values of k0 are significantly smaller than the upper limit of k0 for the diffusion-type process (ca. 100cms−1). The deceleration of the ion motion in the interfacial region could be ascribed to the slow relaxation of the interface, the favorable deformation of which is likely to control the interfacial ion transfer. The effect of temperature on the capacitance of the electric double layer at the water/DCE interface was found to be negligible, in an agreement with the prediction based on the simple Verwey-Niessen model of the back-to-back space charge (diffuse) layers.

On an Expression of Extraction Constants without the Interfacial Equilibrium-Potential Differences for the Extraction of Univalent and Divalent Metal Picrates by Crown Ethers into 1,2-Dichloroethane and Nitrobenzene

An idea on interfacial equilibrium-potential differences () which are generated for the extraction of univalent metal picrate (MPic) and divalent ones (MPic2) by crown ethers (L) into high-polar diluents was improved. These potentials were clarified with some experimental extraction-data reported before on the M = Ag(I), Ca(II), Sr(II) and Ba(II) extraction with 18-crown-6 ether (18C6) and benzo-18C6 into 1,2-dichloroethane (DCE) and nitrobenzene (NB). Consequently, it was demonstrated that the values from the extraction-experimentally obtained logKD,Pic ones are in agreement with or close to those calculated from charge balance equations in many cases, where the symbol, KD,Pic, denotes an individual distribution constant of Pic﹣ into the DCE or NB phase. Also, it was experimentally shown that extraction constants based on the overall extraction equilibria do not virtually contain the terms in their functional expressions.

Composite PET Membrane with Nanostructured Ag/AgTCNQ Schottky Junctions: Electrochemical Nanofabrication and Charge-Transfer Properties

Large-area nanostructured Ag/Ag-tetracyanoquinodimethane (TCNQ) Schottky junctions are fabricated electrochemically on a mesoporous polyethylene terephthalate (PET) membrane-supported water/1, 2-dichloroethane (DCE) interface. When the interface is polarized, Ag(+) ions transfer across the PET membrane from the aqueous phase and are reduced to form metallic Ag on the PET membrane, which reacts further with tetracyanoquinodimethane (TCNQ) in the DCE phase to form nanostructured Ag/AgTCNQ Schottky junctions. Once the mesoporous membrane is blocked by metallic Ag, a bipolar mechanism is proposed to explain the successive growth of AgTCNQ nanorods and Ag film on each side of the PET membrane. Due to the well-formed nanostructure of Ag/AgTCNQ Schottky junctions, the direct electrochemical behavior is observed, which is essential to explain the physicochemical mechanism of its electric performance. Moreover, the composite PET membrane with nanostructured Ag/AgTCNQ Schottky junctions is tailorable and can be assembled directly into electric devices without any pretreatment.