Change Of Open Circuit Potential Research Articles

Advanced titanium implants: combating corrosion and infection with cutting-edge coatings

Abstract The presented research investigates the corrosion behavior of commercially pure titanium (cp-Ti) and amorphous calcium phosphate–chitosan (ACP@ChOL) coatings enriched with selenium on titanium in simulated body fluid (SBF). Using potentiodynamic polarization techniques, it was sought to derive essential corrosion parameters – corrosion potential, corrosion current density, breakdown potential, and passivation current. This study pioneers a comparative analysis of the corrosion stability of both samples. SEM/EDS analysis of surfaces pre- and postpotentiodynamic measurements offered insights into morphology and elemental composition. The aim was to elucidate the corrosion mechanism by integrating these techniques. Additionally, spontaneous corrosion behavior over 7 days, monitoring changes in open circuit potential, polarization resistance, and impedance were investigated. Furthermore, the antimicrobial efficacy of ACP@ChOL enriched with Se on titanium was assessed against Escherichia coli, Staphylococcus aureus, and Candida albicans, as well as in vitro release of Se. The presented study extends understanding, offering a unique perspective on the corrosion behavior and antimicrobial attributes of ACP@ChOL coatings enriched with Se on titanium. This composite material exhibits promise for medical applications, presenting an innovative avenue for addressing corrosion concerns and potentially reducing antibiotic reliance.

Decentralized touch-based micronutrition sensor towards personalized nutrition: Parallel detection of sweat ascorbic acid and zinc ions

The zinc (Zn) and ascorbic acid (AA) micronutrient duo has received a considerable attention in individual’s nutrition plans, particularly after the recent pandemic, owing to its distinct beneficial impact on boosting the immune system. Accordingly, there are growing needs for frequent and decentralized measurements of the trace element and micronutrient levels towards well-balanced personalized nutrition. Leveraging natural sweat sampling from the fingertip, we describe here a disposable electrochemical sensor array, consisting of neighboring Zn ion (Zn(II)), and AA electrodes, towards parallel touch-based on-site monitoring of dynamically-changing sweat Zn(II), and AA levels, following the intake of the corresponding nutrition supplements.. A highly permeable poly (vinyl alcohol) (PVA) hydrogel, placed on the dual-electrode sensor array, served for transferring the sweat from the fingertip onto the electrode surface. Zn(II) measurements were performed on a bismuth/Nafion modified screen printed electrode (SPE) with square-wave anodic stripping voltammetry (SWASV), while the AA detection relied on recording of the open circuit potential (OCP) change, on the tetrathiafulvalene-7,7,8,8-tetracyanoquinodimethane (TTF-TCNQ) immobilized SPE. Rapid decentralized measurements of sweat Zn(II) and AA temporal profiles were carried out on the fingertip sweat of healthy subjects after consuming pill supplements in connection to the disposable strip along with hand-held electrochemical analyzer. The utility of the touch-based disposable Zn(II)/AA multisensory platform for parallel measurements of this pair of micronutrients was demonstrated towards personalized nutrition by providing real-time monitoring of the dose-response relationship. Our findings indicate that the new sweat nutrition sensing device holds considerable promise for guiding dietary interventions and enhancing personalized nutrition.

Spatially Resolving Heterogeneous Chemistry on SOFC Electrodes with Operando Optical Methods

Carbon fouling (or coking) is one of the primary degradation mechanisms that leads to performance loss and eventual failure in high temperature, solid oxide electrochemical cells (SOCs). Accumulated carbon blocks electrocatalytic sites at three phase boundaries, impedes transport through porous electrode structures and can react with common electrode materials such as Ni to form carbides that disintegrate in a process described as metal dusting. Operando Raman studies examining carbon remediation through gasification showed surprising results. (J. Phys. Chem. C, 119 (2015) 7637.) When comparing carbon removal from Ni-YSZ cermet anodes at 750˚C by gas phase H2O, O2, and CO2, experiments measuring intensity of the carbon ‘G’ band, Raman studies showed that H2O was most effective, removing all observable carbon in a matter of seconds. Similar amounts of O2 required approximately one minute to remove detectable carbon, and CO2 required even longer and never removed all of the observable carbon. These results were supported by changes in the SOC open circuit potential. These Raman measurements, however, sampled only a single location on the anode. Work described in this presentation shows the anode surface chemistry to be considerably more heterogeneous than might be inferred from the Raman data. A combination of near-IR thermal imaging (NIRTI), Fourier transform IR emission spectroscopy (FTIRES), voltammetry and downstream mass spectrometry (MS) exhaust analysis have begun to spatially resolve processes associated with carbon gasification from coked Ni-cermet anodes at 800˚C, and show that carbon gasification proceeds through a sequence of steps involving both surface and gas phase reactions.

Preparation of pH-sensitive surface based on mixed oxides of titanium and iridium for early detection of inflammation around the implant

The surface of an implant used during operation is a preferred site for the attachment of harmful microorganisms. These subsequently affect the surrounding tissue with their metabolic products, including the tissue's pH. The possibility of sensing the pH around the implant could be a way of detecting the infection in the early stages. Transition metal oxides can be used for these applications. The most common alloys used for the manufacture of implants are titanium alloys which are characterized by a passive TiO2 surface layer that can be modified. In this work, the Ti–6Al–4V alloy whose surface was nanostructured was used. Iridium particles were subsequently deposited on the prepared surface by various methods to increase the sensitivity to pH change. The potentiostatic mode was chosen as the most suitable method of deposition. Energy dispersive analysis and X-ray photoelectron spectroscopy verified the success of iridium particle deposition. The electrochemical response was measured in a physiological saline solution and monitoring the open circuit potential change proved to be the most appropriate sensing method. After subsequent oxidation process, the prepared surface showed a sensitivity of 64 mV/pH at 37 °C.

Electrochemical impedance response of the nanostructured Ti–6Al–4V surface in the presence of S. aureus and E. coli

Implant infections associated with biofilm are a significant problem in current healthcare. Early detection of the development of bacterial infection would allow the deployment of antibiotic treatment to suppress complications. Biofilm detection can be based on the changes in the electrochemical response of a metal oxide sensor. The nanostructured surface of titanium alloys provides a large active/geometric surface area ratio and may respond to the presence of bacteria by changing its behaviour. In this work, the changes in impedance response of nanostructured Ti–6Al–4V alloy surface in the presence of E. coli and S. aureus were studied. The nanostructures were prepared by anodic oxidation in a fluoride ions-containing environment. The change in impedance spectra and open circuit potential of the prepared surfaces was monitored for 48 h. Furthermore, a series of measurements in model systems were carried out to help identify the processes leading to the change in the electrochemical behaviour of the surface. The measurements showed significant changes in the surface impedance response over a wide range of frequencies and for both bacterial strains. Based on the results, the implantable sensor based on the nanotubular titanium oxide seems to be a possible and simple way how to detect bacterial infection.Graphical

Surface area independent response of closed bipolar electrodes

Here, we demonstrated the application of a closed bipolar electrode to measure the change in open circuit potential (OCP) of Prussian blue/white as a function of [Cl−] concentration independently of electrode surface area. In this bipolar scheme, a potentiostat holds a constant voltage across two separate cells linked by a shared electrode that is sensitive to [Cl−] on one end and electrodeposited by Prussian Blue on the other. As [Cl−] is added to the sample compartment, the ion associates with Ag+ to produce Ag/AgCl, altering the junction potential. This change is balanced electrochemically by a shift in the ratio of Prussian blue/ Prussian white. A second potentiostat is used to monitor these changes over the Prussian blue electrode, yielding a for the quantification of chloride. We measured a range of 1.0 mM – 55 mM [Cl−] over various electrode surface areas, demonstrating that the signal response is independent of electrode area. Additionally, the system had the capability to translate signal across a single bipolar electrode while using differently sized electrodes in each compartment, a property that could be beneficial for microarrays or signal amplification.

Identification of Photoacidic Behavior Using AC and Open-Circuit Photoelectrochemical Techniques

Photoacids are molecules whose acidity increases through absorption of light. When the excited-state lifetime of a photoacid is sufficiently long, proton transfer from its thermally equilibrated electronic excited state results in a transient change in pH and/or pOH, which is commonly detected using spectroscopic techniques. Herein we expand this measurement toolkit by introducing alternating AC and open-circuit photoelectrochemical techniques that characterize photoacidic behavior from a model photoacid, the sodium salt of 8-hydroxypyrene-1,3,6-trisulfonate, dissolved in aqueous solutions in a thin-pathlength two-electrode cell. Continuous illumination of protonated photoacids in their electronic ground state results in significant and reproducible changes in low-frequency impedance and open-circuit potential. When these molecules are made to be non-acidic, via deprotonation using more alkaline pH conditions or methoxylation via synthesis, electrochemical data measured in the dark and under illumination are nearly identical. Best fits of AC electrochemical data to a simplified equivalent circuit support that photoelectrochemical responses are likely due to changes in local proton concentration at the electrode∣electrolyte interface, and not changes in proton flux due to mass transfer, as previously suggested. Collectively, our results provide further insight into the utility of these photoelectrochemical techniques to probe photoacidic behavior.

Wear reduction of orthopaedic implants through Cryogenic Thermal Cycling

BackgroundMaterial wear caused by relative micromotion of multi-part orthopaedic implants can impact physiology near the implant site and ultimately lead to revision surgery. Cryogenic Thermal Cycling (CTC) is a process that refines and stabilizes the crystal lattice structure of materials by introducing them to temperature modulation cycles that include extremely low temperatures. This method has been proven to significantly improve the performance and wear life capabilities of mechanical components in an efficient, sterile and non-polluting process. This technical note is aimed to evaluate the impact of CTC on wear resistance at head-neck taper connections used in total hip arthroplasty (THA). MethodsMock up components (heads and trunnions) using the same materials representative of THA implants were manufactured for this study. Components were placed into a custom-designed cooling chamber in which they underwent CTC. Short-term Incremental Cyclic Fretting Corrosion (ICFC) testing was conducted on thermally cycled and control (untreated) components, subjected to a full simulated gait with periodically increasing incremental peak loads (modified BioPuls Dual Station ASTM Hip Simulator). Corrosion-related electrical activity was measured for samples with and without CTC. A long-term wear test was also conducted to evaluate corrosion and fretting under double peak compression loading (no rotation). ResultsFrom the short-term tests, samples that underwent CTC showed a significantly reduced corrosion current at the maximum testing compression load of 3,300 N (p = 0.048). The elevated corrosion onset load seen in the treated components did not reach significance (p = 0.152) and no significant difference in the mean change in open circuit potential (OCP) was observed (p = 0.471). Longer-term wear testing found variable differences in CTC and control components with respect to damaged surface areas. ConclusionCTC was shown to be a viable method to reduce short-term corrosion-related electrical activity in THA head-neck taper connections. While consistent differences were not seen in longer-term measures of corrosion, further study is warranted to evaluate the potential of CTC in the context of reducing wear in modular THA implants.

On-Line Measurement and Characterization of Electrochemical Corrosion of 304L Stainless Steel Pipe Wall in High-Speed Cl-Containing Solution

Fluid-induced metal corrosion failure is one of the main causes of pipe wall damage. In this paper, aimed at the corrosion failure of stainless-steel pipe wall in high-speed flowing liquid, a self-made micro three-electrode electrochemical test system was used to test the electrochemical characteristics of the pipe under different flow rates and different Cl− concentrations. In the experiment, the changes of open circuit potential, polarization curve and impedance spectrum of 304L stainless steel surface were obtained. At the same time, the corrosion rate of the material under different conditions was obtained by fitting. The results show that the corrosion rate varied non-linearly with increasing flow velocities. In addition, with the increase of Cl− concentration, the corrosion rate increased at a slower rate. The material surface under high concentration and high flow rate conditions was subject to physical cutting and electrochemical reactions, showing an activated and easy pitting corrosion state. The results of this study can provide data for failure analysis and life extension of pipelines and equipment in service.

Potentiometric Biosensors Based on Molecular-Imprinted Self-Assembled Monolayer Films for Rapid Detection of Influenza A Virus and SARS-CoV-2 Spike Protein.

Rapid, yet accurate and sensitive testing has been shown to be critical in the control of spreading pandemic diseases such as COVID-19. Current methods which are highly sensitive and can differentiate different strains are slow and cannot be conveniently applied at the point of care. Rapid tests, meanwhile, require a high titer and are not sufficiently sensitive to discriminate between strains. Here, we report a rapid and facile potentiometric detection method based on nanoscale, three-dimensional molecular imprints of analytes on a self-assembled monolayer (SAM), which can deliver analyte-specific detection of both whole virions and isolated proteins in microliter amounts of bodily fluids within minutes. The detection substrate with nanoscale inverse surface patterns of analytes formed by a SAM identifies a target analyte by recognizing its surface nano- and molecular structures, which can be monitored by temporal measurement of the change in substrate open-circuit potential. The sensor unambiguously detected and differentiated H1N1 and H3N2 influenza A virions as well as the spike proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Middle-East respiratory syndrome (MERS) coronavirus in human saliva with limits of detection reaching 200 PFU/mL and 100 pg/mL for the viral particles and spike proteins, respectively. The demonstrated speed and specificity of detection, combined with a low required sample volume, high sensitivity, ease of potentiometric measurement, and simple sample collection and preparation, suggest that the technique can be used as a highly effective point-of-care diagnostic platform for a fast, accurate, and specific detection of various viral pathogens and their variants.

Potentiometric and SERS Detection of Single Nanoparticle Collision Events on a Surface Functionalized Gold Nanoelectrode

Single-entity electrochemistry is of fundamental importance and shows promise for ultrasensitive biosensing applications. Recently, we have demonstrated that various charged nanoparticles can be detected individually based on the non-redox open-circuit potential (OCP) changes induced by their collision events on a floating carbon nanoelectrode (CNE). Unlike the widely used amperometry approach, the potentiometric method provides the label-free detection of individual nanoscale entities without redox mediators in the solution. However, the CNE lacks specificity for molecular recognition during the collision events because of the limited methods of surface functionalization for carbon surfaces. Herein, we used surface-functionalized gold nanoelectrode (GNE) to overcome this limitation of CNE. The GNE modified with Raman reporter molecule also enabled surface-enhanced Raman spectroscopy (SERS) measurements. By using simultaneous time-resolved OCP and SERS measurements, both the OCP and SERS signals induced by the “hit-n-run” type of gold nanoparticle (GNP) collision events can be better understood. Also, by introducing a zwitterionic molecule, we formed near “stealth” surface and demonstrated that the non-specific adsorptions of GNPs to the surface of GNE have been suppressed, allowing continuous detection of hit-n-run events for over 30 min.

Experimental and theoretical studies of acridine orange as corrosion inhibitor for copper protection in acidic media

The corrosion process commonly limits the use of copper in practical applications. The use of corrosion inhibitors is one of the effective methods to reduce the corrosion rate of copper. In this research, the inhibition effect of acridine orange (3,6-bis(dimethylamine)acridine) (AcO) for the protection of copper in 0.5 ​M ​H2SO4 solution was studied. For this aim, the change of open circuit potential with exposure time (Eocp-t), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), anodic and cathodic potentiodynamic polarization measurements (PP) and chronoamperometry (CA) techniques were used. Some quantum chemical parameters (EHOMO, ELUMO and dipole moment) were calculated and discussed. The AcO film formed over the copper surface was examined by SEM, EDX, AFM and contact angle measurements. The electrochemical data showed that AcO is an effective corrosion inhibitor even at low concentrations (ranging between 99.1% and %99.4 ​at concentrations from 0.01 ​mM to 1 ​mM). The corrosion rate of copper decreases in the presence of the inhibitor by reducing both anodic and cathodic rates, which is depended on its concentration. This compound behaves as mixed-type corrosion inhibitors with predominantly cathodic type. Its adsorption on the copper surface obeys Langmuir adsorption isotherm. The value of adsorption equilibrium constant (Kads) and the standard free energy of adsorption were ΔGads 1.298 x 103 ​M−1 and -27.71 ​kJ/mol in the case of 0.5 ​M ​H2SO4 solution containing 1.0 ​mM AcO, which shows the adsorption is high and spontaneous. The adsorbed inhibitor film over the metal increase contact angle of the surface, which suggests the more hydrophobic properties of the surface are increasing coming from the orientation of hydrophobic sites to the electrolyte. The zero charge potential (Epzc) studies showed that the surface charge of the metal is positive in the corrosive media containing the inhibitor. Quantum chemical calculations showed that the binding of inhibitor molecules to the metal surface takes place through N atoms of the inhibitor.

The behavior of carboxylated and hydroxylated polythiophene as bioreceptor layer: Anti‐human IgG and human IgG interaction detection based on organic electrochemical transistors

AbstractThe sensing properties of poly 3‐(3‐carboxypropyl) thiophene‐2,5‐diyl (PT‐COOH) and hydroxylated polythiophene (PT‐OH) as bioreceptor layers were studied and are discussed in this paper. The polymer films cover the channel region of the OECT devices and anti‐human IgG was immobilized on the polymer films. We use threshold voltage (Vth) change as a sensing signal to detect the interaction between anti‐human IgG and human IgG. By adding different concentrations of human IgG, Vth difference can be observed on anti‐human IgG immobilized polymer films, with optimized detection from a blend of the two polymers. Open circuit potential (OCP) measurement was also done on the OECT devices based on the same anti‐human IgG and human IgG interaction pair to help us understand the mechanism behind the antibody functionalization and the interaction between antibody and antigen. Importantly, the observed positive OCP change for the PT‐OH system was self‐consistent with the negative OECT Vth change that was obtained, since the latter is applied to the gate while the former is measured at the channel.

Long-term in vitro corrosion behavior of Zn-3Ag and Zn-3Ag-0.5Mg alloys considered for biodegradable implant applications

In this paper, Zn-3Ag and Zn-3Ag-0.5Mg alloys were studied in terms of applicability as biodegradable implant materials. The performed tensile, compression and bending tests indicate a high strengthening effect induced by the Ag and Mg additions, additionally resulting in grain size refinement. It was shown that sustaining plastic strain during deformation depends on the applied stress causing asymmetric mechanical behavior of the tested Zn-based materials. Electrochemical measurements and immersion tests in Hanks' solution lasting up to 180 days revealed that Ag and Mg contribute to the change of the Zn matrix's open circuit potential and the formation of micro-galvanic cells between the Zn grains and precipitates. The fine-grained microstructure and evenly distributed small precipitates led to uniform corrosion occurring via pit formation on the corroded surface due to intergranular and micro-galvanic corrosion mechanisms. The corrosion rate of the Zn-3Ag-0.5Mg alloy after 180 days was almost twice that of pure Zn and the Zn-3Ag alloy.

Effect of head size and rotation on taper corrosion in a hip simulator.

AimsThis study investigates head-neck taper corrosion with varying head size in a novel hip simulator instrumented to measure corrosion related electrical activity under torsional loads.MethodsIn all, six 28 mm and six 36 mm titanium stem-cobalt chrome head pairs with polyethylene sockets were tested in a novel instrumented hip simulator. Samples were tested using simulated gait data with incremental increasing loads to determine corrosion onset load and electrochemical activity. Half of each head size group were then cycled with simulated gait and the other half with gait compression only. Damage was measured by area and maximum linear wear depth.ResultsOverall, 36 mm heads had lower corrosion onset load (p = 0.009) and change in open circuit potential (OCP) during simulated gait with (p = 0.006) and without joint movement (p = 0.004). Discontinuing gait’s joint movement decreased corrosion currents (p = 0.042); however, wear testing showed no significant effect of joint movement on taper damage. In addition, 36 mm heads had greater corrosion area (p = 0.050), but no significant difference was found for maximum linear wear depth (p = 0.155).ConclusionLarger heads are more susceptible to taper corrosion; however, not due to frictional torque as hypothesized. An alternative hypothesis of taper flexural rigidity differential is proposed. Further studies are necessary to investigate the clinical significance and underlying mechanism of this finding.Cite this article: Bone Jt Open 2021;2(11):1004–1016.

Non-Destructive Degradation Diagnostics of Lithium-Ion Cells Considering Aging-Related Changes in the Shape of the Half-Cell Open Circuit Potential Curve of Silicon-Graphite

Analyzing changes in the quasi-stationary open circuit potential (OCP) curve during aging is a well-established method for the non-destructive diagnosis of degradation occurring in lithium-ion cells during calendar and cycle aging. It allows detecting and quantifying different degradation modes, especially loss of lithium inventory and loss of active material at a specific electrode, without the need of opening up the cells and performing post-mortem analysis. In order to obtain information on the degradation, the quasi-stationary OCP curve measured from an aged cell is reconstructed based on the half-cell OCP curves of the electrode materials. For this purpose, both half-cell OCP curves are linearly scaled and relatively shifted against each other until the difference between cathode and anode OCP fits the measured full-cell OCP. The parameters for the scaling and shifting of the half-cell OCP curves obtained during this optimization procedure are quantitative indicators of the degradation modes that have occurred in the full-cell. Usually, half-cell OCP curves obtained from pristine electrode material are used in this process and the shape of the half-cell OCP curves is assumed invariant during aging.While this assumption is probably justified for graphite and most established cathode materials, there are a number of recent publications describing a change in the shape of the OCP curve of blended silicon-graphite electrodes during cycle aging. This change is probably mainly caused by a decrease in the relative contribution of the silicon to the overall electrode capacity because of its faster degradation in comparison with the graphite. In this study, we investigate the influence of aging-induced changes in the shape of the OCP of silicon-graphite on the applicability of the method for non-destructive degradation analysis described above for cells containing silicon-graphite as anode material. We also present possible extensions of this method to consider changes on the half-cell level.In the scope of this study, we cycle commercial lithium-ion cells containing nickel-rich nickel manganese cobalt oxide (NMC-811) as cathode material and silicon-graphite as anode material until different degradation stages are reached. We then measure the quasi-stationary OCP of the full-cell and subsequently open the cells to extract samples from both electrodes. Afterwards, we measure the quasi-stationary OCP curve of the electrode samples by building coin-cells containing an electrode sample as cathode and lithium metal as anode.We reconstruct the full-cell OCP curves at different degradation stages by linear scaling and shifting of half-cell OCP curves both obtained from pristine electrodes and from the electrodes extracted from aged cells as shown in figure 1. This allows us to analyze whether the accuracy of the full-cell OCP reconstruction can be improved by using half-cell OCP curves of aged electrodes. We also present the changes in the quantitative results concerning the occurrence of different aging modes depending on whether pristine or aged half-cell OCP curves are used to reconstruct the full-cell OCP.In addition to this, we present an extended method for non-destructive degradation diagnostics that contains silicon-specific active material degradation as an additional aging mode. We analyze to which degree this method is capable of determining the loss of silicon-related capacity in the anode from full-cell OCP measurements.These results are relevant for both science and application as lithium-ion cells containing blended silicon-graphite as anode material are increasingly used due to their high specific capacity. Adapting the methods for aging diagnosis to this anode material is necessary to obtain valid results from experiments investigating the degradation of full-cells containing silicon-graphite anodes. Furthermore, expanding the existing models describing the aging-related change in full-cell OCP curves by considering changes in the shape of the half-cell OCP curves is a first step for the development of reliable algorithms for electrode-specific state of health estimation for cells containing silicon-graphite. Such algorithms could then be used on-board as part of the functionality of battery management systems.Figure 1: Reconstruction of the open circuit potential curve of a cycle aged full-cell based on both half-cell open circuit potential curves obtained from pristine and cycle aged electrodes Figure 1

Potentiometric Detection of Single Nanoparticle Collision Events on a Surface Functionalized Gold Nanoelectrode

Electrochemistry single-entity methods are of fundamental importance and show promise for ultrasensitive chemical and biological sensing applications. Recently, we have demonstrated that various nanoparticles can be detected individually based on the open circuit potential (OCP) changes induced by their collision events on a floating carbon nanoelectrode. Unlike the widely used amperometry approach, the potentiometric method provides the label-free detection of individual nanoscale entities without redox mediators in solution. However, the carbon nanoelectrode is chemically inert and limited in surface functionalization. Here, I will present our recent progress of using surface functionalized gold nanoelectrode (GNE) to replace the carbon nanoelectrode for potentiometric single-entity studies. By utilizing the advantage of mixed surface functionalization of GNE with the Raman reporter molecule and polyethylene glycol or zwitterionic molecules, we formed near ‘stealth’ GNE surface and demonstrated that the non-specific adsorptions of nanoparticles to the GNE surface can be minimized, allowing continuous hit-n-run events for over 30 minutes. The surface functionalized GNE also enabled surface enhanced Raman spectroscopy (SERS) measurements. By using simultaneous time-resolved OCP and SERS measurements, both the OCP and SERS signals induced by the hit-n-run type of collision events can be better understood.

Synthesis and properties of core–shell halloysite–polyaniline nanocomposites

We consider physico-chemical specificity (open circuit potential and pH changes) of the chemical oxidative aniline polymerization in the presence of halloysite nanotubes (HNTs) and morphology, structure and properties of the new nanocomposites of HNTs with polyaniline (PANI) doped by p-toluenesulfonic acid. We find that specificity of the PANI properties in such nanocomposites appears obviously due to adsorption on the HNTs surface and specific interactions of all participants of the polymerization process. The study of the open circuit potential and pH changes in the polymerization system and properties of the synthesized HNT/PANI nanocomposites revealed the strong dependence of their morphology, molecular structure, conductivity, thermostability and sensor behavior on the contents of the doped PANI. These findings indicate existence of specific interactions between the PANI component and the HNT surface, which significantly improved properties of the PANI component in the synthesized HNT/PANI nanocomposites as compared with that of the pure PANI. The best thermostability and sensing behavior were found for the synthesized HNT/PANI nanocomposites with the lowest contents of the doped PANI. In particular, the strongest sensor responses to gaseous ammonia are observed in the case of HNT/PANI nanocomposite with lowering the doped PANI content. This work shows for the first time applicability of HNT/PANI nanocomposites for gas sensing.

Detection of Surface Charge Enhancement in Magnetoelectric Nanoparticles Induced by AC Magnetic Field Stimulation using Single Entity Approach

Magneto-electric nanoparticles (MENPs), composed of a piezoelectric shell and a ferromagnetic core, exhibited enhanced cell uptake and controlled drug release due to the enhanced localized electric field (surface charge/potential) and the generation of acoustics, respectively, upon applying alternating current (AC) magnetic (B)-field stimulation. This research, for the first time, implements an electrochemical single-entity approach to probe AC B-field induced strain mediated surface potential enhancement on MENP surface. The surface potential changes at the single-NP level can be probed by the open circuit potential changes of the floating carbon nanoelectrode (CNE) during the MENP-CNE collision events. The results confirmed that the AC B-field (60 Oe) stimulation caused localized surface potential enhancement of MENP. This observation is associated with the presence of a piezoelectric shell, whereas magnetic nanoparticles were found unaffected under identical stimulation.

Long-Term Activity of Thermoplastic Gel Electrolyte in a Photo-Electrochemical Assembly Involving Poly Bithiophene (PBTh) as Photoactive Working Electrode

Evidence for the long period of a sustainable function of a thermoplastic gel electrolyte (TPGE) consists of polyethylene glycol (PEG)/I2/I- in propylene carbonate (PC) was recorded. The studied photoactive assembly consists of PBTH/FTO/TPGE I2/I-/Platinized FTO. The study showed that the assembly regenerates the expected photoelectrochemical (PEC) quantities such as photocurrent, and other dielectric properties with infrequent use through an elapsed period of 18 months. The behavior of PBTh/occluded with CdS was mentored during this period and showed a similar result. PEC studies indicated the presence of p-p type hole accumulations interface, evident from the initial sharp rise in photocurrent. The change of open circuit potential (dVoc) indicates that the shortest electron lifetime is 100 ms. The behavioral outcome of the assemblies within the period of study refracts stability of the electrode and the long life cycle of the electrolyte.