Surface Functionalized Boron Doped Diamond Electrochemical Electrode And Trace Detection Of Environmental Contaminants

Diamond is a wide band gap semiconductor with unique electrical,physical,chemical and mechanical properties.As a kind of material with excellent properties,it has been widely used in practical fields.The combination of diamond with nanomaterials and biomaterials can fully expand the field of practical application of diamond and make it more excellent in some aspects of application,so as to obtain a wider application prospect and practical value.In this paper,the preparation of micro-nano structure on diamond surface by different methods is studied.On the one hand,nanopyramid diamond was prepared by hydrogen plasma treatment and the mechanism of its formation was also studied.The surface area of diamond was increased by micro-nano structure and the surface was hydrophobic by hydrogen plasma treatment.The nanopyramid diamond electrode was used to detect the concentration of nonylphenol?4-NP?.The diamond film uniformly modified by gold nanoparticles was realized by the combination of secondary ion sputtering and high temperature rapid annealing.The biosensor was successfully prepared by modifying aptamers on the basis of diamond film modified by gold nanoparticles.It is very sensitive in the specific detection of polychlorinated biphenyls-77?PCB-77?.The main results are as follows:?1?Diamond surface nanostructures were successfully prepared by different methods.The mechanism of preparing boron-doped diamond?BDD?nanopyramids by hydrogen plasma treatment is that the carbon source evaporated by hydrogen plasma treatment forms nanopyramidal particles on the surface of BDD by secondary nucleation.There are a large number of pits and nanoscale pyramids on the surface of nanopyramid BDD.Hydrogen plasma treatment has many advantages,such as no pretreatment,simple operation,high efficiency and so on.It provides a new way in the field of micro-nano processing of superhard carbon materials.Gold nanoparticles modified BDD were prepared by ion sputter and thermal oxidation.The size and density of gold particles on diamond surface were regulated by adjusting the time of sputtering gold film and thermal oxidation.?2?Nanopyramid diamond electrode obtained by hydrogen plasma treatment of BDD was used for trace detection of 4-NP.The sensor has the advantages of reusable,good stability,strong specificity and low detection limit in the detection of 4-NP.The linear detection range of the sensor is 1.0×10^-71.0×10^-9 M.The detection limit of4-NP?0.26 nM?was three orders of magnitude lower than that of as-grown BDD.This is caused by two factors.On the one hand,there are a large number of pits and nanoscale pyramids on the surface of BDD,which is beneficial to increase the surface area and reaction site.On the other hand,hydrogen termination leads to hydrophobic surface and 4-NP is easier to reach the surface of nanopyramid BDD electrode than molecules of water.Physical adsorption makes it easier for 4-NP molecules to reach the surface of nanopyramid BDD for oxidation and the theoretical calculation is in good agreement with the experimental results.This study will be of great significance for the detection of low concentration and trace substances by diamond sensors in a wide range of industrial fields.?3?Gold nanoparticles about 13 nm with a density of about 2.5×10¹¹/cm² can be uniformly modified on the diamond surface by secondary ion sputter and thermal oxidation.Under the action of Au-S covalent bond,the aptamers can be self-assembled on the gold nanoparticles.The aptamers and mercaptohexyl were further modified to prepare sensors for the detection of PCB-77.The linear detection range of the sensor is 1.0×10^-151.0×10^-11 M.The detection limit of PCB-77 reaches0.32 fM.The trace detection of PCB-77 has been successfully realized.The detection concentration can be adjusted to the range measured by dilution of the solution.The original concentration can be calculated to extend the measurement range from fM to the actual range of concentration.The experimental results show that the aptasensor has good sensitivity,specificity,reproducibility and recyclability.These advantages can be attributed to the synergistic effect of BDD film,gold nanoparticles,aptamers and mercaptohexol:BDD substrate has low background signal;dense gold nanoparticles significantly increase the absorption site of aptamers;the high sensitivity of aptamers with high affinity and specificity to PCB-77;the added mercaptohexol molecule stretching the adaptive ligands to capture more PCB-77 and occupying the empty sites of gold nanoparticles to further reduce the non-specific adsorption.For the above reasons,the sensor has high sensitivity.In this paper,the micro-nano structure and surface functionalization of diamond surface have been realized,and important results have been obtained in the trace detection of environmental pollutants.It is proved that the diamond film has unique advantages such as high stability,anti-poisoning and the specific recognition with biological aptamers.The experimental data were provided for the development of a new diamond based electrochemical sensor.The method of preparing micro-nano structure of diamond surface and surface functionalization could be consulted from the published paper.