Study On Preparation And Electrochemical Sensing Of Hybrid Diamond/Graphite Nanostructured Films

Electrochemical sensors are of great significance in the life and health field,such as ensuring the safety of drinking water and preventing and treating diseases,due to the high sensitivity,low cost,and compatibility with portable technology.The key point to obtain a good electrochemical sensor lies on the development of high-performance electrode material.Hybrid diamond/graphite nanostructured film not only possesses the merits of sp3-bonded diamond and sp2-bonded graphite,such as good mechanical properties,wide potential window,low background current,high electrical conductivity,and superior electrochemical activity,but also has the capability to be microstructurally tailored to achieve typical physical and chemical properties,holding great promises in constructing high-performance electrode in the electrochemical sensing field.In this paper,the study on preparation,microstructure,growth mechanism,electrochemical property,and electrochemical sensing performance is thoroughly carried out based on the hybrid diamond/graphite nanostructured film.The hybrid diamond/graphite(D/G)nanoplatelet film is controllably prepared at high substrate temperature(>1000?)and high methane concentration(?8%)using microwave plasma chemical vapor deposition(MPCVD)system.The D/G nanoplatelet is constituted by the diamond nanoplatelet stem encapsulated in graphite shells.In the nanocrystalline diamond transition layer,the triggering effect along the growth direction caused by the twins and the blocking effect along the line perpendicular to growth direction caused by the surrounding graphite shells are considered to be important for the formation of D/G nanoplatelet.Additionally,the undoped D/G-8%nanoplatelet film electrode,with wide potential window(3.18 V),low background capacitance,and good electrochemical activity,is rationally prepared through manipulating the microstructure.It's proposed that the electrochemical reactions on the thin high-electrochemical-activity graphite shell edges are greatly influenced by the adjacent thick inactive diamond stem,thus,the D/G-8%nanoplatelet film demonstrates the synergistic electrochemical properties of diamond and graphite.The D/G-8%nanoplatelet film shows high signal-to-noise ratio and high sensitivity in the detection of heavy metal ions using anodic stripping voltammetry method.Besides,the individual and simultaneous detections of Zn(II),Cd(II),Pb(II),and Cu(?)verify the superior analytical performance with low limits of detection(<10 ?g·L-1),in well accordance with heavy metal standards for drinking-water.In addition,the hybrid diamond/carbon nanowalls(D/C)film is controllably prepared with an elevated holder using MPCVD system.The D/C film is composed of diamond nanoplatelets and carbon nanowalls(CNWs)constituted by turbostratic graphite phase.The CNWs form initially at the both sides of diamond nanoplatelets,because of the coupling effect coming from the first growth of diamond nanoplatelets as well as the enhanced plasma density on the substrate surface.Additionally,the CuO@D/C electrode composed of hybrid D/C film supporting CuO architecture is rationally designed.The CuO@D/C electrode demonstrates high sensitivity(1650?A·cm-2·mM-1),low detection limit(0.5 ×10-6 M),good long-term stability,and excellent recovery(94.21%?104.18%)in the electrochemical glucose determination,thus holding good potential in the prevention and treatment of diabetes.The outstanding performance of the CuO@D/C electrode can be ascribed to the synergistic effect coming from hybrid D/C film as the effective transducer and CuO nanoparticles as the high-electrocatalytic-activity biorecognition element.Finally,the porous diamond nanostructure is rationally constructed through the in situ hydrogen plasma treatment of hybrid D/C film.In the plasma treatment,the atomic hydrogen is considered to effectively transform sp2-bonded carbon in CNWs to sp3-bonded carbon,which then grows at both sides of the diamond nanoplatelets.The diamond nanoplatelets become thick and interconnected,eventually leading to the formation of the porous diamond nanostructure.This easy and efficient method will benefit the application of the porous diamond nanostructure in electrochemical sensing field.