Transient Response and Ionic Dynamics in Organic Electrochemical Transistors

The rapid development of organic electrochemical transistors(OECTs)has ushered in a new era in organic electronics,distinguishing itself through its application in a variety of domains,from high-speed logic circuits to sensitive biosensors,and neuromorphic devices like artificial synapses and organic electrochemical random-access memories.Despite recent strides in enhancing OECT performance,driven by the demand for superior transient response capabilities,a comprehensive understanding of the complex interplay between charge and ion transport,alongside electron–ion interactions,as well as the optimization strategies,remains elusive.This review aims to bridge this gap by providing a systematic overview on the fundamental working principles of OECT transient responses,emphasizing advancements in device physics and optimization approaches.We review the critical aspect of transient ion dynamics in both volatile and non-volatile applications,as well as the impact of materials,morphology,device structure strategies on optimizing transient responses.This paper not only offers a detailed overview of the current state of the art,but also identifies promising avenues for future research,aiming to drive future performance advancements in diversified applications.

Droplet microfluidic chip for precise monitoring of dynamic solution changes

In this work,an automated microfluidic chip that uses negative pressure to sample and analyze solutions with high temporal resolution was developed.The chip has a T-shaped channel for mixing the sample with a fluorescent indicator,a flow-focusing channel for generating droplets in oil,and a long storage channel for incubating and detecting the droplets.By monitoring the fluorescence intensity of the droplets,the device could detect changes in solution accurately over time.The chip can generate droplets at frequencies of up to 42 Hz with a mixing ratio of 1:1 and a temporal resolution of 3–6 s.It had excellent linearity in detecting fluorescein solution in the concentration range 1–5μM.This droplet microfluidic chip provides several advantages over traditional methods,including high temporal resolution,stable droplet generation,and faster flow rates.This approach could be applied to monitoring calcium ions with a dynamic range from 102 to 107 nM and a detection limit of 10 nM.

Solvation Structure and Dynamics of Mg(TFSI)_(2) Aqueous Electrolyte

Using ab initio molecular dynamics(AIMD)simulations,classical molecular dynamics(CMD)simulations,small-angle X-ray scattering(SAXS),and pulsed-field gradient nuclear magnetic resonance(PFG-NMR),the solvation structure and ion dynamics of magnesium bis(trifluoromethanesulfonyl)imide(Mg(TFSI)_(2))aqueous electrolyte at 1,2,and 3 m concentrations are investigated.From AIMD and CMD simulations,the first solvation shell of an Mg;ion is found to be composed of six water molecules in an octahedral configuration and the solvation shell is rather rigid.The TFSI^(-)ions prefer to stay in the second solvation shell and beyond.Meanwhile,the comparable diffusion coefficients of positive and negative ions in Mg(TFSI)_(2)aqueous electrolytes have been observed,which is mainly due to the formation of the stable[Mg(H_(2)O_(6))_(2)]^(+)complex,and,as a result,the increased effective Mg ion size.Finally,the calculated correlated transference numbers are lower than the uncorrelated ones even at the low concentration of 2 and 3 m,suggesting the enhanced correlations between ions in the multivalent electrolytes.This work provides a molecular-level understanding of how the solvation structure and multivalency of the ion affect the dynamics and transport properties of the multivalent electrolyte,providing insight for rational designs of electrolytes for improved ion transport properties.

Effect of Ion Dynamics on the Evolution of Electron Phase-space Holes

The evolution of two-dimensional（2D） electron phase-space holes（electron holes） has been previously investigated with electrostatic Particle-in-Cell（PIC） simulations,which neglect ion dynamics.The electron holes are found to be unstable to the transverse instability,and their evolution is determined by the combined action between the transverse instability and the stabilization by the background magnetic field.In this paper,the effect of ion dynamics on the evolution of an electron hole is studied.In weakly magnetized plasma(Ωe<ωpe,whereΩe andωpe are electron gyrofrequency and plasma frequency,respectively),the electron hole is still unstable to the transverse instability. However,it evolves a little faster and is destroyed in a shorter time when ion dynamics is considered. In strongly magnetized plasma(Ωe>ωpe),the electron hole is broken due to the lower hybrid waves, and its evolution is much faster.

Structural,Electrical,and Lithium Ion Dynamics of Li2MnO3 from Density Functional Theory

The layered Li2MnO3 is investigated by using the first-principles calculations within the GGA and GGA-t-U scheme, respectively. Within the GGA4-U approach, the calculated intercalation voltage （ranges from 4,5 V to 4.9 V） is found to be in good agreement with experiments. From the analysis of electronic structure, the pure phase Li2MnO3 is insulating, which is indicative of poor electronic-conduction properties. However, further studies of lithium ion diffusion in bulk Li2MnO3 show that unlike the two-dimensional diffusion pathways in rock salt structure layered cathode materials, lithium can diffuse in a three-dimensional pathway in Li2MnO3, with moderate lithium migration energy barrier ranges from 0.57 to 0.63 e V.

Frequency Switches at Transition Temperature in Voltage-Gated Ion Channel Dynamics of Neural Oscillators

Understanding of the mechanisms of neural phase transitions is crucial for clarifying cognitive processes in the brain. We investigate a neural oscillator that undergoes different bifurcation transitions from the big saddle homoclinic orbit type to the saddle node on an invariant circle type, and the saddle node on an invariant circle type to the small saddle homoclinic orbit type. The bifurcation transitions are accompanied by an increase in thermodynamic temperature that affects the voltage-gated ion channel in the neural oscillator. We show that nonlinear and thermodynamical mechanisms are responsible for different switches of the frequency in the neural oscillator. We report a dynamical role of the phase response curve in switches of the frequency, in terms of slopes of frequency-temperature curve at each bifurcation transition. Adopting the transition state theory of voltagegated ion channel dynamics, we confirm that switches of the frequency occur in the first-order phase transition temperature states and exhibit different features of their potential energy derivatives in the ion channel. Each bifurcation transition also creates a discontinuity in the Arrhenius plot used to compute the time constant of the ion channel.

Pricing a Chained Dynamic Fund Protection Under Vasicek Interest Rate Model with Stochastic Barrier

Dynamic fund protection provides a guarantee that the account value of the investor never drops below a barrier over the investment period.In order to reduce the downside risk taken by vendors,Han,et al.(2016)proposed a chained dynamic fund protection(CDFP),whose protection is activated only if the value of basic fund reaches a predefined upper protection line.Motivated by them,we consider a new CDFP plan under a stochastic interest rate environment.The explicit pricing formula for a CDFP is obtained when the protection lines are proportional to a zero-coupon bond.Furthermore,the authors present some numerical results for the value of CDFP at time 0 to show how the model parameters impact the value of CDFP.

Ion dynamics in ultrafast laser ablation of copper target

We investigate the angular distribution and average kinetic energy of ions produced during ultrafast laser ablation （ULA） of a copper target in high vacuum. Laser produced plasma （LPP） is induced by irradiating the target with Ti：Sapphire laser pulses of -50 fs and 800 nm at an angle of incidence of 45°. An ion probe is moved along a circular path around the ablation spot, thereby allowing characterization of the time-of-flight （TOF） of ions at different angles relative to the normal target. The angular distribution of the ion flux is well-described by an adiabatic and isentropic expansion model of a plume produced by solid-target laser ablation （LA）. The angular width of the ion flux becomes narrower with increasing laser fluence. Moreover, the ion average kinetic energy is forward-peaked and shows a stronger dependence on the laser pulse fluence than on the ion flux. Such results can be ascribed to space charge effects that occur during the early stages of LPP formation.

Molecular Dynamics Simulation on Hydrogen Ion Implantation Process in Smart-Cut Technology

The hydrogen ion implantation process in Smart-Cut technology is investigated in the present paper using molecular dynamics（MD） simulations.This work focuses on the effects of the implantation energy,dose of hydrogen ions and implantation temperature on the distribution of hydrogen ions and defect rate induced by ion implantation.Numerical analysis shows that implanted hydrogen ions follow an approximate Gaussian distribution which mainly depends on the implantation energy and is independent of the hydrogen ion dose and implantation temperature.By introducing a new parameter of defect rate,the influence of the processing parameters on defect rate is also quantitatively examined.

Optical properties and dynamic process in metal ions doped on CdSe quantum dots sensitized solar cells

In recent years, the nanostructure for solar cells have attracted considerable attention from scientists as a result of a promising candidate for low cost devices. In this work, quantum dots sensitized solar cells with effective performance based on a co-sensitized Cd S∕Cd Se：Mn2＋（or Cu2＋） nanocrystal, which was made by successive ionic layer absorption and reaction, are discussed. The optical, physical, chemical, and photovoltaic properties of quantum dots sensitized solar cells were sensitized to Mn2＋and Cu2＋dopants. Therefore, the short current（JSC）of the quantum dot sensitized solar cells is boosted dramatically from 12.351 mA∕cm2 for pure Cd Se nanoparticles to 18.990 mA∕cm2 for Mn2＋ions and 19.915 mA∕cm2 for Cu2＋ions. Actually, metal dopant extended the band gap of pure Cd Se nanoparticles, reduced recombination, enhanced the efficiency of devices, and improved the charge transfer and collection. In addition, Mn2＋and Cu2＋dopants rose to the level of the conduction band of pure Cd Se nanoparticles, which leads to the reduction of the charge recombination, enhances the lightharvesting efficiency, and improves the charge diffusion and collection. The results also were confirmed by the obtained experimental data of photoluminescence decay and electrochemical impedance spectroscopy.

Micro-nondestructive detection of the moisture and ion of rice seeds during germination under salt stress

Salt stress is one of the major stress factors limiting rice productivity.Its damaging effects include water deficit due to osmotic stress,and ionic toxicity caused by ionic stress.It is very important to study the salt-tolerance mechanism of rice under salt stress,in order to improve the salt-tolerance capacity of rice and thereby increase the yield.In this experiment,the low field nuclear magnetic resonance(LF NMR)technique and the traditional dry-weight weighing method,the non-invasive micro-test technique(NMT)and the inductively coupled plasma emission spectrometry(ICP-AES)were applied to analyze the distribution of water and the flow of K^(+)and Na^(+)of rice seeds during germination under NaCl stress.The results suggested that for all different NaCl concentrations,as germination hours grew,the amplitude of NMR signals of the bound water that of the free water and the total amplitude all increased gradually.And the higher the NaCl concentration is,the weaker the increase trend is.In addition,the moisture content of the seeds and the total amplitude of NMR signals were positively correlated.The regression equation was y=191.53x+1463.6,the correlation coefficient was R=0.9823,and the determination coefficient was R2=0.9650.By this regression equation,the moisture content of each state of water during seed germination can be calculated.When without NaCl stress,the rice seeds absorbed K^(+)in the germination process.However,when under NaCl stress at different concentrations,K^(+)efflux was detected.The contents of K^(+)and K^(+)/Na^(+)were lower than that under the control condition.The higher NaCl concentration is,the lower the K^(+)and K^(+)/Na^(+)contents are.These results are in consistence with the K^(+)and Na^(+)contents detected by the inductively coupled technique.These empirical data offer a reference for the study of rice-seeds’response mechanism under salt stress during germination and the screening of germplasm resources,and also put forward a new method of biopsy micro-nondestructive test for plants under stress.

Storage dynamics of ions on graphene

Carbon has been widely utilized as electrode in electrochemical energy storage,relying on the interaction between ions and electrode.The performance of a carbon electrode is determined by a variety of factors including the structural features of carbon material and the behavior of ions adsorbed on the carbon surface in the specific environment.As the fundamental unit of graphitic carbons,graphene has been employed as a model to understand the energy storage mechanism of carbon materials through various experimental and computational methods,ex‐situ or in‐situ.In this article,we provide a succinct overview of the state‐of‐the‐art proceedings on the ion storage mechanism on graphene.Topics include the structure engineering of carbons,electric gating effect of ions,ion dynamics on the interface or in the confined space,and specifically lithium‐ion storage/reaction on graphene.Our aim is to facilitate the understanding of electrochemistry on carbon electrodes.

Ion Transport Mechanism in ClC-Type Channel Protein under Complex Electrostatic Potential

In order to illustrate the ion transport mechanism of chloride channel（Cl C） protein,a type of Cl C protein,Cl C-ec1,from Escherichia coli is embedded into an explicit membranewater system by using software VMD. Then a parallel molecular dynamics（MD） simulation is employed to equilibrate the Cl C-ec1 structure for 27.5 ns at temperature 298.15 K. Based on this equilibrated structure,we compute the channel geometric size variation and electrostatic potential distribution along the channel. Meanwhile,Cl^- transport process is simulated using oriented random walk method under variable external potential. The simulation result shows that Cl^- transport velocity depends on the width of the narrowest channel region. Mutation of negative glutamate E148 can produce positive potential,which is beneficial for Cl^- transport,around external Cl^- binding region in the channel. The simulated current-voltage curves about Cl^- transporting in Cl C-ec1 protein agree with Jayaram＇s experimental results.

Bioinspired ionic control for energy and information flow

The control of ion transport by responding to stimulus is a necessary condition for the existence of life.Bioinspired iontronics could enable anomalous ion dynamics in the nano-confined spaces,creating many efficient energy systems and neuromorphic in-sensor computing networks:Unlike tradi-tional electronics based on von Neumann computing architec-ture,the Boolean logic computing based on the iontronics could avoid complex wiring with higher energy efficiency and programmable neuromorphic logic.Here,a systematic summary on the state of art in bioinspired iontronics is pre-sented and the stimulus from chemical potentials,electric fields,light,heat,piezo and magnetic fields on ion dynamics are reviewed.Challenges and perspectives are also addressed in the aspects of iontronic integrated systems.It is believed that comprehensive investigations in bioinspired ionic control will accelerate the development on more efficient energy and information flow for the futuristic human-machine interface.