Ionic Behavior Research Articles

Roles of strontium and hierarchy structure on the in vitro biological response and drug release mechanism of the strontium-substituted bioactive glass microspheres.

The strontium (Sr) substituted bioactive glasses (BGs) have inimitable advantages for bone generation, but the influences of Sr substitution on bioactivity and biocompatibility are still in debate. A brand novel porous microstructure of Sr-substituted BG microspheres was prepared by an electro-spraying technique combined with phase inversion, in which in vitro biological response (bioactivity, cell viability, alkaline phosphatase (ALP) activity and extracellular matrix (ECM) mineralization) and drug release were clarified in view of physical chemistry and ionic release behavior. The electro sprayed bioactive glass (ESBG) microspheres involved three characteristic pores: <100 nm, 100-1000 nm and >1000 nm. The Sr substitution on molar basis hindered the bioactivity of the samples in some extent but the cell behavior of the MC3T3-E1 cells was not significantly discouraged. The drug release profile was also controlled by amount of Sr substitution. However, the porous structure of the microspheres conferred improvement in bioactivity and provided a distinct three-stage drug release mode. Therefore, the Sr substituted ESBG microspheres may provide an effective way to deliver a steady supply of therapeutic ions and drugs in bone implantation patients.

Regulating the ionic current rectification behavior of branched nanochannels by filling polyelectrolytes

The overlapping of the electric double layer (EDL) in a nanochannel yields many interesting and significant electrokinetic phenomena such as ionic current rectification (ICR), which occurs only at a relatively low bulk salt concentration (∼1 mM) where the EDL thickness is comparable to the nanochannel size. In an attempt to raise this concentration to higher levels and the ICR performance improved appreciably, a branched nanochannel filled with polyelectrolytes (PEs) is proposed in this study. We show that these objectives can be achieved by choosing appropriate PE. For example, if the stem side of an anodic aluminun oxide nanochannel is filled with polystyrene sulfonate (PSS) an ICR ratio up to 850 can be obtained at 1 mM, which was not reported in previous studies. Taking account of the effect of electroosmotic flow, the underlying mechanisms of the ICR phenomena observed are discussed and the influences of the solution pH, the bulk salt concentration, and how the region(s) of a nanochannel is filled with PE examined. We show that the ICR behavior of a branched nanochannel can be modulated satisfactorily by filling highly charged PE and the solution pH.

Impedance spectroscopy study of K+ substituted single crystalline BaTi2O5

K+-ion substituted single crystalline BaTi2O5, Ba1−xKxTi2O5−z (x = 0 to 0.006), was prepared by floating zone method. The effect of K+-ion substitution on the electrical properties of Ba1−xKxTi2O5−z was studied using impedance spectroscopy. Ba1−xKxTi2O5−z showed ferroelectricity and ion/hole mixed conduction in the b-direction. With increasing K+ content from x = 0 to 0.006, the Curie temperature (Tc) decreased from 752 to 722 K, and permittivity decreased from 18,600 to 3970. The ionic conduction behavior (ion blocking at low frequency region) became significant by the K+ substitution showing maximum at x = 0.003. The electrical conductivity of Ba1−xKxTi2O5−z increased with increasing oxygen partial pressure, and was almost 100 times higher than that of BaTi2O5 in the temperature range of 500–650 K. The activation energy of electrical conductivity was 0.8–1.5 eV.

An Interaction of Chloro Substituted Alkoxy Thiourea as Dopant in Carboxymethyl Cellulose (CMC) for Solid Polymer Electrolyte

Alkoxy substituted aryl-thiourea derivatives provide excellent electronic properties due to the present of rigid π-systems within their molecular framework. This study introduces new thiourea derivative with general formula A-ArC(O)NHC(S)NHAr-D which was successfully synthesized with A is noted as aryl group containing chloro (-Cl) substituent ( 1A ), in which acts as electron acceptor, while D represented as –OC n H 2n+1 , the alkoxy chain tail acts as electron donor. Due to its characteristic of D-π-A system, alkoxy thiourea derivatives are applied as dopant in Carboxymethyl Cellulose (CMC) host material in order to form a conductive biopolymer solid polymer electrolyte (SPE) film. The formation of biopolymer-thiourea complex ( 1A-CMC ) has been analyzed through Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) to determine the interaction between CMC and thiourea derivative in the form of film as well as Electrical Impedance Spectroscopy (EIS) for their ionic conductivity behavior. The highest conductivity at ambient temperature (303K) exhibits 1.44 x 10 -7 S cm -1 for CMC-thiourea complexation featuring chloro substitution ( 1A ). Indeed, biopolymer electrolyte materials featuring thiourea derivative as dopant has great potential to be developed as electrical conductor. Due to these findings, these so-called molecular wires candidate has opened wide possibilities to be applied in many micro-electronic devices in the near future.

Investigation of Pr0.2Ce0.8O2-δ@Li2CO3 nanocomposite electrolytes as intermediate temperature ionic conductors: a thermal, structural, and morphological insight

Pr0.2Ce0.8O2-δ@Li2CO3 (PDC-LC) nanocomposite electrolytes were prepared through the co-precipitation of Pr-doped cerium/lithium complex carbonate and its pre-firing and sintering operations. The structural and thermal properties of PDC-LC nanocomposite were investigated by means of X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, and electrochemical impedance spectroscopy. The remarkable presence of oxygen vacancies and the influence of the interfacial interactions between PDC crystallites and amorphous Li2CO3 were deliberately probed by Raman spectroscopy and FEG-SEM, respectively. It was observed that there is a long-range interaction between the PDC crystallites and Li2CO3 phase, which resulted in the tight binding of $$ {\mathrm{CO}}_3^{2-} $$ ions on the facets of PDC nano-crystals and may be well characterized by the shift and broadening of the characteristic Raman spectroscopic peaks of $$ {\mathrm{CO}}_3^{2-} $$ ions in the samples. The X-ray diffraction results confirm the successful incorporation of praseodymium into ceria phase that presented the sole crystalline structure contrarily to the lithium carbonate present as an amorphous phase in the as-prepared samples. The oxygen ionic conductivity behaviors of PDC-LC phase were measured at the intermediate operating temperature range (300–500 °C). However, AC conductivity measurements demonstrated that the conductivities in air atmosphere increased linearly with temperature. The Arrhenius plot of total conductivity showed two different slopes indicating two distinct conduction mechanisms. The interfacial interactions between the PDC and LC phase inside the PDC-LC nanocomposite were responsible for oxygen ionic conductivity.

Temperature-dependent photoconductive properties of Ge-Sb-Te thin films

ABSTRACTThe present paper reports the study of photoconductive properties viz. steady state photoconductivity, dark conductivity , dark activation energy , transient photoconductivity on vacuum evaporated thin films of Ge20Te80-xSbx (x = 0, 2, 4, 6, 10 at. %). At higher concentration of antimony, dark activation energy is found to decrease. A similar trend in the optical band gap is also observed. Optical band gap also decreases with the addition of antimony in the system. This drop in activation energy points towards an increase in the density of defect states in the system. Dark conductivity values are found to increase, and this rise is due to an increase in polarizability of antimony and partial ionic behaviour of the system. Photosensitivity decreases with an increase in the antimony content in the matrix. Photocurrent versus light intensity follows the power law and predominance of bimolecular recombination is found. During transient measurements, the decay rate is found to be non-exponential. A differential lifetime is found to increase with the addition of antimony as a dopant. The study of the decay of photocurrent reveals relaxation processes in the present chalcogenide glassy matrix. This behaviour indicates a slow decay process due to the increase in the density of defect state in the mobility gap. Similar results are also confirmed with an increase in the carrier concentration.

Nanostructured anode materials for low temperature solid oxide fuel cells: Synthesis and electrochemical characterizations

The present assets of fossil fuel-based energy resources are going to be end due to high consumption rate. These resources also are polluting the climate rapidly. With reference to these alarming situations, solid oxide fuel cells have got great attention in the field of energy conversion technologies due to their low emissions, fuel flexibility and higher efficiency characteristics. In the present investigation, two anode materials with compositions Al0.1Mn0.1Zn0.8O (AMZ) and Al0.1Mn0.1Ni0.1Zn0.7O (AMNZ) were prepared via solid state reaction. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were accomplished to investigate the phase and surface morphology study of synthesized materials. The crystallite sizes of the prepared materials have been assessed using Scherer's formula and found to be 52 and 61 nm for AMZ and AMNZ, respectively. The conductivities of AMZ and AMNZ were obtained 4.4 and 5.2 S/cm, respectively at 650 °C. The activation energy was calculated by drawing Arrhenius plots. The prepared materials showed both ionic and electronic conduction behaviour as confirmed by electrochemical impedance measurements. The AMNZ composition has higher value of open circuit voltage (1.01 V) and power density (535 mW/cm2) in hydrogen atmosphere as compared with AMZ at 550 °C, which indicates that Ni contents in anode improvs the properties and can be considered as promising anode material at low temperature for fuel cell applications.

The effect of limonite addition on the performance of Li7La3Zr2O12

Nowadays, Li7La3Zr2O12 (LLZO) based solid electrolytes are attracting much interest because of their enhanced safety in Li-ion batteries. However, their relatively low ionic conductivity compared to liquid electrolytes is the main factor affecting the widespread use. Fe doping of LLZO could raise the ionic conductivity values to one of the highest values measured in the field of garnet type LLZO solid electrolytes. However, high purity and cost Fe2O3 is the unique iron source used in Fe doped LLZO systems. In this study, the potential use of common and cheaper iron source α-FeOOH in the form of limonite ore as a multielement containing alternative Fe source was explored. The concept of the naturally found ore usage as a stabilizing agent in LLZO is first time reported. The results showed that the limonite addition to LLZO increased the ionic behavior and densification by modifying the open and closed porosities. Higher radial shrinkage was observed with increasing limonite content. The increasing sintering time came up with an enhancement on ionic resistance and a drop on grain boundary resistance as well as DC conductivity. The LLZO composition containing 1.250 wt % limonite sintered at 1100 °C for 18 h showed the highest ionic conductivity (0.38 mS/cm) obtained within the study.

Conductivity of ScSZ Ceramics in Vicinity of Polymorphic Phase Transitions

The effect of phase composition on ionic conductivity behavior in scandia-stabilized zirconia ceramics with various scandia concentrations during heating was studied. It was found that the homogeneous single-phase (cubic) ceramics reveals no hysteresis or kinks in Arrhenius plots (log σT versus 1/T) indicating on polymorphic transitions in course of heating within temperature range under study (523 to 823 K). Unlike the homogeneous material, two-phase ceramics demonstrates a conductivity jump in the low temperature range (600-630 K) of Arrhenius plot, which grows with increase in scandia concentration or decrease in grain size and corresponding rise in rhombohedral phase β content at room temperature. It is shown that this effect can be caused by intragrain crystal structure ordering under mechanical stresses arising in rhombohedral phase containing ceramics.

Biologically Coupled Gate Field-Effect Transistors Meet in Vitro Diagnostics

In this paper, recent works on biologically coupled gate field-effect transistor (bio-FET) sensors are introduced and compared to provide a perspective. Most biological phenomena are closely related to behaviors of ions and biomolecules. This is why biosensing devices for detecting ionic and biomolecular charges contribute to the direct analysis of biological phenomena in a label-free and enzyme-free manner. Potentiometric biosensors such as bio-FET sensors, which allow the direct detection of these charges on the basis of the field effect, meet this requirement and have been developed as simple devices for in vitro diagnostics (IVD). A variety of biological ionic behaviors generated by biomolecular recognition events and cellular activities are being targeted for clinical diagnostics as well as the study of neuroscience using the bio-FET sensors. To realize these applications, bioelectrical interfaces should be formed between the electrolyte solution and the gate electrode by modifying artificially synthesized and biomimetic membranes, resulting in the selective detection of targets based on intrinsic molecular charges. Various types of semiconducting materials, not only inorganic semiconductors but also organic semiconductors, can be selected for use in bio-FET sensors, depending on the application field. In addition, a semiconductor integrated circuit device is ideal for the massively parallel detection of multiple samples. Thus, platforms based on bio-FET sensors are suitable for use in simple and miniaturized electrical circuit systems for IVD to enable the prevention and early detection of diseases.

Pressure-Induced Ionic-Electronic Transition in BiVO4**Supported by the National Natural Science Foundation of China under Grant Nos 11774126, 11774174 and 11404133.

Electrical transport properties of bismuth vanadate (BiVO4) are studied under high pressures with electrochemical impedance spectroscopy. A pressure-induced ionic-electronic transition is found in BiVO4. Below 3.0 GPa, BiVO4 has ionic conduction behavior. The ionic resistance decreases under high pressures due to the increasing migration rate of O2− ions. Above 3.0 GPa the channels for ion migration are closed. Transport mechanism changes from the ionic to the electronic behavior. First-principles calculations show that bandgap width narrows under high pressures, causing the continuous decrease of electrical resistance of BiVO4.

Nanocoating inside porous PE separator enables enhanced ionic transport of GPE and stable cycling of Li-metal anode

In this paper, a simple and feasible method for preparing gel polymer electrolyte (GPE) with good ionic transport properties and mechanical stability is proposed. A ZrO2/KH570/PU/P123 layer was formed on the outer and inner pore surfaces of PE separator before in situ polymerization by a simple one-step dipping coating process. This coating layer changes the PE separator surface from hydrophobic to hydrophilic, and therefore facilitates the uniform spreading of the GPE precursor solution on the PE surface to enable the formation of highly uniform GPE. Moreover, it effectively compensates the negative effects of in situ gelatinization on the ionic transport behavior of the final PE-supported GPE. This GPE possesses excellent ion transport properties and mechanical stability, as well as improves the static and dynamic interfacial stability with lithium metal anode. When using metallic lithium and LiCoO2 to assemble cells, this PE-supported GPE affords improved C-rate capability, cycling performance and effective dendrite inhibition.

Synthesis of graphite oxide nanoparticles and conductivity studies of PSF/GO and PSAN/GO polymer nanocomposites

Graphite oxide (GO) nanoparticles were synthesized by modified Hummer method. DLS results suggest that the average size of GO nanoparticles is 140 nm. EDX study confirms the presence of oxygen containing functional groups in GO sheet. Polysulfone (PSF/GO) and Poly (styrene co-acrylonitrile) (PSAN/GO) polymer nanocomposites were prepared by solution casting technique. The ionic and electronic conductivity behaviors of PSF/GO and PSAN/GO polymer nanocomposites were measured. The increased conductivity with increasing GO nanoparticles loading is due to the conductivity chain formation and increased mobility of charge carriers. The effect of crystallinity and free volume on electrical conductivity of PSF/GO and PSAN/GO polymer nanocomposites is explored. PSF/GO and PSAN/GO nanocomposites exhibit high electrical conductivity with low amount of (0.6 wt% and 1.0 wt%) GO loading is due to the formation of GO networks by the strong chemical interaction induced crystallinity of the polymer matrix. This is evident from FTIR and Raman spectroscopy studies.

Ionotronic Neuromorphic Devices for Bionic Neural Network Applications

Transistor- and memristor-based neuromorphic devices have unique non-volatile characteristics. They can overcome the von Neumann bottleneck and can act as building blocks for bionic neural networks. The ionotronic devices, transmitting electronic signals through the migration of ionic species in dielectric and resistive switching electrolyte, have unique ionic relaxation behaviors and biology-comparable relaxation time scales, which impart them great potentials in building bionic neural networks and realizing hardware-based artificial intelligence (AI)/AI chips. In article no. 1800674, Fei Yu and Li Qiang Zhu review recent achievements in ionotronic neuromorphic devices and forecast their potential applications in multifunctional intelligent artificial perception learning systems and AI chips. Fundamental operation mechanisms, basic electrical characteristics and variable conductance functionality of the ionotronic neuromorphic devices are introduced. Various synaptic plasticities and advanced neural functions mimicked on ionotronic devices are summarized.

Ionic Liquid Chelate Extraction Behavior of Trivalent Group 13 Metals into 1-Alkyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imides Using 8-Quinolinol as Chelating Extractant.

Ionic liquid (IL) chelate extraction behavior of trivalent Group 13 metals including aluminum(III), gallium(III) and indium(III) with 8-quinolinol (HQ) was investigated using three 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (CnmimTf2N, n = 2, 4 and 8) ILs. Although the three extraction systems showed similar extraction selectivity among the metals, the extractability order for the metals among the extraction systems was C8mimTf2N > C4mimTf2N > C2mimTf2N, which was the same as the order of hydrophobicity in the IL cation. Only the neutral 1:3 complex species was extracted in use of more-hydrophobic C8mimTf2N, whereas use of less-hydrophobic C4mimTf2N and C2mimTf2N resulted in competitive extraction of neutral 1:3 and cationic 1:2 complexes. For each of the metals, in addition, similar extraction constants were obtained in these three extraction systems.

Brush Swelling and Attachment Strength of Barnacle Adhesion Protein on Zwitterionic Polymer Films as a Function of Macromolecular Structure.

The exceptional hydration of sulfobetaine polymer brushes and their resistance toward nonspecific protein absorption allows for the construction of thin films with excellent antibiofouling properties. In this work, swollen sulfobetaine brushes, prepared by surface-initiated atom transfer radical polymerization of two monomers, differentiated by the nature of the polymerizable group, are studied and compared by a liquid-cell atomic force microscopy technique and spectroscopic ellipsometry. Colloidal AFM-based force spectroscopy is employed to estimate brush grafting density and characterize nanomechanical properties in salt water. When the ionic strength-induced swelling behaviors of the two systems are compared, the differences observed on the antipolyelectrolyte response can be correlated with the stiffness variation on brush compression, likely to be promoted by solvation differences. The higher solvation of amide groups is proposed to be responsible for the lower adhesion force of the barnacle cyprid’s temporary adhesive proteins. The adhesion results provide further insights into the antibiofouling activity against barnacle cyprid settlement attributed to polysulfobetaine brushes.

Microscale Surface Nanostructuration and Catalysis of Metallic Electrodes through Electrochemical Deposition and Dissolution in Ionic Liquids

Incorporation of highly active nanostructures into metallic electrode surface layers is of particular interest for a wide range of potential applications, such as electrochemical sensing and energy storage-conversion systems, because the nanostructures not only can increase the active area accessible to reactant molecules but can also improve electron mobility in the solid ligaments. However, controlling the nano-architecture of electrode surface layers faces great challenges since metals at nanoscale favor low surface areas in order to minimize the surface energy. In the past two decades, several strategies such as template synthesis, surfactant mediated synthesis and dealloying, have been developed to design and fabricate nanostructured electrodes with highly ordered networks and high surface area. We have developed a green-chemistry method based on in-situ electrochemical deposition-dissolution (ECDD) of an active metal on a target metal substrate in ionic liquids to achieve the nanostructuration of metallic electrodes.1-4 As shown in Figure 1A, during electrochemical deposition, a highly reactive metal component such as Zn is introduced via electrodeposition to interact with a less active electrode substrate such as Au to form an alloy phase. During subsequent electrochemical dissolution, the reactive component is selectively removed from the alloy phase leading to the formation of nanostructured surface layers. The nanostructured layers can grow deeper by repeating the process. The most obvious advantage of the ECDD method over other arts is that no net chemicals are consumed and it is a green-chemistry process. This method has been employed to successfully create different nanostructures on single-element metal and alloy electrodes at tens-to-hundreds micrometer scales, which are shown in Figure 1B to E. In this presentation, we will introduce the green-chemistry method based on the electrochemical alloying-dealloying in ionic liquids, the characterization and polarization behavior of resulting surface nanostructures, further catalysis of the nanostructures, and their applications to electrochemical sensing and energy storage conversion.

Mechanical, Electrical, and Ionic Behavior of Lithium‐Ion Battery Electrodes via Discrete Element Method Simulations

Herein, a discrete element method (DEM) approach is proposed to investigate the impact of the calendering process on the electrical and ionic conductivities and on the adhesion strength of Li[Ni1/3 Mn1/3 Co1/3]O2 (NMC)‐based electrodes. For this purpose, key correlations between the microstructure and these electrode‐scale properties are established using the outcomes of the simulations and real experiments. In addition, the evolution of the structure and the development of mechanical stress are also studied numerically during electrochemical cycling, offering a closer insight into the intercalation mechanism. Finally, the impact of the initial noncalendered porosity on the electrode mechanical response is examined, showing that higher initial porosities lead to lower final porosities under same calendering loads. Overall, this work demonstrates the potential of DEM simulations in improving the understanding of the microstructure and mechanics of lithium‐ion electrodes.

First Principles Approach to Study the Structural, Electronic and Transport Properties of Dimer Chitosan with Graphene Electrodes

Chitosan is a candidate biomaterial as an electro-active polymer, since it has its two isomers, referred to as cis (c–CH) and trans (t–CH) chitosan. In this theoretical study, the structural, electronic and transport properties of these two isomers are reported. Calculations based on density functional theory find c–CH and t–CH molecular isomers to be insulating. The device configuration consisting of graphene electrodes and chitosan molecules in the presence of an applied electric field showed a noticeable difference between c–CH and t–CH in I–V curves. From projected density of states and density of states analysis, the calculated forbidden energy gap (Eg) of t–CH is reduced by 0.5 eV; therefore, t–CH shows semiconducting behaviour and works as an ionic electro-active polymer. Charge density curves exhibit the charge distribution and electrostatic interactions of atoms. The aim of this work is to study the ionic electro-active actuator behaviour of chitosan for its various applications such as bioelectronics, biomedical and electrochemical fields.

Synergy of Single-ion Conductive and Thermo-responsive Copolymer Hydrogels Achieving Anti-Arrhenius Ionic Conductivity.

Artificial intelligence sensations have aroused scientific interest from electronic conductors to bio-inspired ionic conductors. The conductivity of electrons decreases with increasing temperature, while the ionic conductivity agrees with an Arrhenius equation or a modified Vogel-Tammann-Fulcher (VTF) equation. Herein, thermo-responsive poly(N-isopropyl amide) (PNIPAm) and single-ion-conducting poly(2-acrylamido-2-methyl-1-propanesulfonic lithium salt) (PAMPSLi) were copolymerized via a facile radical polymerization to demonstrate a very intriguing anti-Arrhenius ionic conductivity behaviour during thermally induced volume-phase transition. These smart hydrogels presented very promising scaffolds for architecting flexible, wearable or advanced functional ionic devices.