Electrolyte-gated Field Effect Transistor Based Biosensors For Application In Food Quality And Safety

The development of fast,sensitive and accurate food quality and safety testing method is an important technical support for the implementation of the national food safety plan,which is of great significance for achieving social sustainable development and safeguarding people's health.Biosensors based on electrolyte-gated field effect transistors have become one of the research hotspots in food quality and safety testing owing to their advantages of easy processing,low cost,good flexibility,good biocompatibility and low operating voltage.In recent years,among electrolyte-gated field effect transistors,organic field effect transistors are represented by organic electrochemical transistors?OECTs?,and the inorganic field effect transistors are represented by a solution-gated graphene transistors?SGGTs?.Both of them have made great progress in the field of biosensors.The applications of organic electrochemical transistors and solution-gated graphene transistors in the field of biosensors have also provided a good solution for the food quality and safety problems.In addition,the development of new functional nanomaterials and the construction of the gate electrode interface with excellent performance are key steps in the development of high performance electrolyte-gated field effect transistors.In this paper,we designed the functional interfaces of carbon nanomaterial composites and metal organic framework nanomaterials and established the detection platform for phenolic compounds and glucose.We used unique mechanism of channel semiconductor oxidation to detect the heavy metal ions and free chlorine.The main findings are as follows:1.Highly sensitive and selective detection of phenolic compounds based on organic electrochemical transistors functionalized with carbon nanomaterialsThe organic electrochemical transistors?OECT?was fabricated with PEDOT:PSS as the organic semiconductor channel,poly?diallyldimethylammonium chloride?and carbon nanomaterials nanocomposites?CNT-PDDA?as the nanomaterial to functionalize gate electrodes.Then we selected gallic acid as the research object to study the detection performance and mechanism of CNT-PDDA modified OECT on phenolic compounds.Carbon nanomaterials can increase the catalytic performance of the gate electrode to phenolic compoud.PDDA can not only improve the dispersion of carbon nanomaterials,but also increase the selectivity to phenolic compounds.Finally,we demonstrated that the optimized OECT sensor could work with a high recovery for rapid and accurate assessment of total phenol content of practical tea samples,which validated the feasibility of rapid detection of phenolic coumpounds and exhibited the application potential of OECTs in the field of rapid food safety detection.2.Highly selective and sensitive detection of copper ion based on organic electrochemical transistor with the PEDOT:PSS oxidation mechanismPEDOT:PSS was used as the organic semiconductor channel to fabricate OECT.Then we selected Cu²⁺as the research object to study the detection mechanism of OECT for heavy metal ions with oxidizing ability.Compared with chemically stable ions like Na⁺,K⁺,Ca²⁺,and Al³⁺,OECT exhibited high sensitivity and high selectivity for Cu²⁺.By studying the presence and absence of gate voltage,we investigated the detection mechanism OECT to Cu²⁺.The detection mechanism of OECT to Cu²⁺was duo to PEDOT:PSS oxidation,which was completely different from these chemically stable ions.Finally,the OECT sensor was applied to quantitative determination of copper ions in tap water,which exhibited the application potential of OECTs in the field of heavy metal ions.3.Highly selective and sensitive detection of free chlorine based on solution-gated graphene transistors with the graphene oxidation mechanismThe solution-gated graphene transistor?SGGT?was fabricated using chemical vapor deposition?CVD?graphene as the channel layer,Au electrode and Ag/AgCl electrode as the gate electrode.Then we selected sodium hypochlorite?NaClO?as the research object to investigate the detection performance and mechanism of OECT for anions with oxidizing ability.Compared with chemically stable anions such as Cl^-,NO₃^-,SO₄^2-,PO₄^3-,and CO₃^2-,SGGT exhibited high sensitivity and high selectivity for ClO^-.By adjusting the voltage of the gold electrode and the silver/silver chloride electrode,the channel current of SGGT increased with the free chlorine concentration in the p-type detection region,while it decreased with the free chlorine concentration in the n-type detection region.We further discussed the detection mechanism of SGGT on free chlorine,and successfully applied SGGT to the detection of free chlorine in tap water and achieved good results,which exhibited the application potential of SGGTs in the field of water pollution.4.Simultaneous detection of glucose and uric acid based on solution-gated graphene transistors functionalized with nanomaterials and enzymeThe solution-gated graphene transistor?SGGT?was fabricated using chemical vapor deposition?CVD?graphene as the channel layer,metal organic framework derived Co₃O₄ hollow nanopolyhedrons as the nanomaterial to functionalize gate.The optimized SGGT showed a high sensitivity to H₂O₂,with a detection limit of 10 nM.We then used glucose as a research object to fabricate a high-performance SGGT enzyme sensor.The SGGT enzyme sensor showed a high sensitivity to glucose,with a detection limit of 100 nM.We further designed two separate Au gate electrodes,modified with GOx-CHIT and BSA-CHIT to achieve the simultaneous detection of glucose and uric acid.Finally we successfully applied SGGT to the detection of glucose and uric acid in real sample and achieved good results,which validated the feasibility of the application of SGGT enzyme sensor in actual samples.