| The increasingly serious heavy metal ion pollution seriously threatens the safety of the regional ecosystem and human health,the developement of the simple and convenient ultra-sensitive portable detection equipment for the real-time and rapid heavy metal ions detection is crucial for the initial screening,treatment and tracing of pollution The electrochemical analysis technology has the advantages of simple operation,low cost,high sensitivity,and can obtain small size of the device with miniaturization and portability while maintaining the sensing ability.With the rapid development of micro-nano processing technology,electronic information technology,nanotechnology and other fields,the development of electrochemical micro-nano sensing chips is being diversity with new vitality and possibility.However,as a new sensor component,it still faces many challenges in its design,preparation and practical application,such as high cost,difficult mass production,complex operation,poor environmental adaptability,low accuracy of complex samples,and short period of validity.To address the existing problems,herein,high-performance electrochemical sensing electrode is constructed based on micro-nano processing technology.The prepared novel electronic nanomaterials serves as the platform for supporting the designed specific electrocatalytic sensing process and signal amplification strategy to effectively improve the sensing ability.The electrode is not only the supporting substrate of the sensing process,but also responsible for the transmission of electrical signals.Therefore,the preparation of large area,low cost,excellent uniformity,conductivity,biocompatibility and stability electrode is crucial.In this desertation,the main contains and innovative results are as follows:(1)A microfluidic electrochemical sensing chip matrix based on cerium dioxide@gold nanocomposites was designed and fabricated for the ultrasensitive detection of lead ions.The patterned gold layer prepared by vaccum depositon technology serves as the electrode matrix of chip,which presented a porous structure providing an excellent micro-environment for the immobilization of lead ion-specific DNAzyme and its complementary probe,as well as excellent electron transfer ability;The cerium dioxide@gold nanocomposite as electrochemical signal tag and enhancer is connected with the probe,and trigger the cascade reaction for amplifying the electrochemical signal with the help of hydrogen peroxide.The introduction of lead ion activates DNAzyme to break the complementary probe,so as to make the signal tag fall off and complete the ion sensing process.With optimized the conditons.a single chip can realize the ultra-sensitive detection of ten ion samples with the low detection limit of 3.1 pM,good stability and specificity.The research provides a new idea for the integration of micro fluidic chip design and nanomaterial catalysis.and an example for in-situ heavy metal ions analysis to solve the traditional problem of low flux.which presents a potential application prospect in the field of multi-matrix analysis.(2)A laser-induced graphene(LIG)-based electrochemical micro-nano sensing chip was constructed for the sensitive detection of zinc and copper ions.The graphene-based electrode material with three-dimensional porous structure was prepared on the surface of flexible polyimide film by laser-induced graphitization technology.The LIG was modified by dipping reduction and electrochemical deposition technology to obtain flexible nanogold modified graphene-based porous electrode with enhanced loading capacity and conductivity.The modification mechanism of LIG was systematically investigated through Raman.XRD,XPS.and other characterization.Compared with the original LIG,the resistance of the modified LIG-based electrode decreased by 3.9 times and the specific surface area increased by 2.5 times.Based on modified LIG,a copper ion self-assembled network signal label and a zinc ion specific DNAzyme sensing mechanism were designed to realize the copper and zinc ion sensing.The constructed sensing chip realized the quantitative detection of copper and zinc ion with the detection limits of 0.32 nM and 0.34 nM,respectively.Further more,the constructed sensing chip has good stability and flexibility.After 150 bends,it can still maintain about 93%and 94%of the signal strength,and it can still retain 80%of the signal after 2 weeks.The results showed that the proposed nanomaterials modified LIG-based electrode is a high-performance sensing electrode,and possesses potential application prospects in the field of flexible or wearable detection.(3)For the first time,a dual-signal electrochemical micro/nano sensing chip with four terminals based on the principle of electric field-driven bi-directional mass transfer was constructed for zinc ion detection.The chip is composed of the screen-printed Ag/AgCl reference electrode for potential calibration,gold nanomaterial-based working electrode for target recognition and laser-induced graphene working electrode for probe acquisition;By applying voltage bias to the graphene-based electrode,an electric field is formed between the parallel electrodes,driving the zinc ion and probe to move in reverse between the two working electrodes,and realizing the in-situ ultra-sensitive ion sensing;By engineering the proportion of functional groups on the surface of graphene to improve the recovery rate of the probe,the performance of the sensor was optimized;In addition,the mass transfer kinetics is discussed The sensitivity of the chip to detect zinc ions is 33.1 pM,which is two orders of magnitude higher than that without electric field.The chip maintains the sensing performance under different deformation,and exhibits excellent selectivity,stability and flexibility in detecting tap water and sweat.The whole sensing process does not require manual operation steps such as cleaning,incubation,transfer,and other human factors to avoid interference.The chip could be integrated with smartphone-based portable system to detect the actual sample.The results provide the new strategy for in-situ environment and biomedical monitoring devices.(4)An electrochemical micro-nano sensing chip was designed and fabricated based on graphene/molybdenum sulfide composite modified by cerium dioxide and gold nanomateials.The surface of graphene and molybdenum disulfide is rich in oxygen-containing groups,which improved the absorption of divalent ions in the sensing electrode.Molybdenum sulfide nano-sheet was broken by laser carving,further exposing a large number of highly active edges.Ce3+/Ce4+ cycle and Au nanomaterials modification inhibit the recombination of electrons and holes,prolonging the life of carriers and enhancing the conductivity;The low energy barrier of target electroplating/stripping kinetics was also confirmed by calculating the activation energy of the composite using Arrhenius formula.Based on the synergistic effect between composite materials,the sensing chip presented the low detection limit of copper and zinc ion(2.8 ppt and 103.6 ppt),respectively,with excellent stability,flexibility,reusability,and anti-interference performance,making it possible to simultaneously monitor multiple toxic metal ions in complex environments. |
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