In-situ Electrochemical Monitoring Method Of Potassium And Calcium Ions In Plant

With the increase in global population and the demand for food,agricultural production has become increasingly important.To meet this demand,agricultural scientists are constantly exploring new technologies and methods to study the growth and development mechanism of crops to improve the yield and quality.Among them,mineral ions play a crucial role in plant growth and development,and their deficiency or excess can significantly impact crop yield.Therefore,it is an important issue in agricultural production to accurately monitor the information of mineral ions in plant systems.However,current methods for sensing mineral ions in plants still face challenges,which mainly rely on in-vitro detection that involves specialized equipment,complicated operation process,and sample pretreatment.Although the fluorescence method allows for in-situ detection,it is still susceptible to the background fluorescence interference in complex biological media.In order to solve the above problems,the objective of this project is to realize the in-situ sensing of mineral nutrient content in plants.The research was carried out in four parts:the construction of sensing method,the optimization of sensing method and testing of sensing performance,the structure optimization and enhancement mechanism of sensing device,and the feasibility evaluation of in-situ sensing in plants.Micro-scale sensing devices were designed and manufactured in this research,achieving ultra-high sensitivity and high selectivity sensing of changes in mineral ions content.On this basis,a flexible ion sensing device based on printing technology was constructed,which verified its feasibility for in-situ sensing of mineral ions in plants.（1）To address the demand for highly selective detection methods for mineral ions sensing in plants,an ion sensing method based on the Nernst response was proposed,which realized high selectivity sensing by constructing all-solid-state ion selective electrodes based on nano-transduction layer.Ion selective thin film technology was employed to ensure high selectivity for the target ions.A typical two-dimensional nanomaterial,tungsten disulfide（WS₂）nanosheet film,derived from transition metal chalcogenides,was employed as the ion-electron transconductance layer,which effectively avoids the influence of water layer on the electrode performance and greatly improves the detection sensitivity by enhancing the ion-electron transfer efficiency in the sensing process.The mechanism underlying the highly selective detection of mineral ions was investigated,confirming the ability to achieve higher detection sensitivity,wider detection range,and better stability.The construction of an all-solid-state ion-selective electrode sensing method based on the WS₂ nano-transduction layer provides an effective method and approach for highly selective sensing of mineral ions.（2）To address the need for high sensitivity of detection methods for mineral ions sensing in plant systems,an ion sensing method based on super-Nernst response was proposed,which realized highly sensitive ion sensing by combining organic electrochemical transistor（OECT）technology with ion-sensitive thin film technology.The OECT devices were firstly prepared and the operation mechanism based on the ion-electron circuit model was explored,which verified the application advantages of this technology in ion sensing.The signal amplification characteristics of the OECT devices were demonstrated to be a key factor in achieving ultra-sensitive detection of ions.Based on this,it was applied to develop ion sensing devices with super-Nernst response combined with ion-selective thin film.The incorporation of a polyelectrolyte layer effectively mitigated the impact of polymers in the ion-selective membrane on device performance.Finally,the sensing performance of the prepared devices was investigated for monovalent（potassium）and divalent（calcium）cations,and the voltage detection model and current detection model were developed respectively,demonstrating superior sensitivity compared to the traditional ion-selective electrodes.The OECT ion sensing method based on the super-Nernst response provides a foundation for the highly sensitive sensing of mineral ions.（3）In view of the problem of low sensitivity and large trauma when traditional detection methods are used for mineral ions sensing in plants,this project proposes the utilization of vertical OECT to construct implantable ion sensing devices.Traditional ion detection devices are prone to irreversible damage to the plant body in practical applications,and it is difficult to ensure the detection accuracy after miniaturization,which makes it difficult to meet the needs of in-situ ion sensing in plants.Considering this,this project aims to design the source and drain electrodes of the OECT as a vertical stacking structure.On the one hand,this structure successfully realizes the conversion of the channel length from the micron to submicron scale,which significantly improves the performance of the OECT devices and ensures the ion detection accuracy.On the other hand,the structure can realize the miniaturization of the detection area,which greatly reduces the damage to plants during implantation detection.The OECT ion sensing method based on the vertical structure provides technical support for the in-situ sensing of mineral ions in plants.（4）Aiming at the problems of the complicated and expensive preparation of OECT sensing devices,a printed ion sensing device based on flexible substrate was developed,and a sensing method for in-situ detection of mineral ions in plants was established.The screen-printing technology was utilized to realize the layer-by-layer printing of OECT ion sensing device based on the vertical structure.This technology was applied to flexible substrate polyimide（PI）films to construct miniaturized and implantable flexible ion sensing devices.On this basis,the sensing area of the device was designed in a needle-like tip shape,which ensures the operability of the device in practical application and reduces the damage to the plant body caused by the implantation.The results show that the device can work normally in the plant environment without interference from other substances in plant fluids.It enables real-time in-situ monitoring of changes in ions content within the plant and causes minimal damage to the plant.The miniaturized and implantable flexible ion sensing device provides an effective method and approach for the in-situ sensing of mineral ions in plants.