The Application Of Electrochemical Deposition Technique For Electrochemical Sensor And Latent Fingermark Visualization

Electrochemical deposition is a technique which could generate functionalized thin film or coating of certain substance at either anode or cathode under an applied voltage or current. Due to the advantages of low cost, simple process, easy operation, environment friendly, safety and broad applicability, it has been widely utilized in electroplating, surface modification, anti-corrosion, electrochemical sensors and other fields. Various functional materials such as metal, metal oxide, carbon materials, non-metal oxide and composite materials were deposited onto an electrode by electrochemical deposition technique in order to build an electrochemical sensor with a wide linear range, low detection limit, good stability and selectivity. In addition, electrochemical deposition technique has been further extended to other applications such as forensic investigation in recent years. Latent fingermarks on conductive metallic objects were visualized by spatially selective electrochemical deposition of various materials. Herein, we fabricated electrochemical sensors which were highly efficient in detecting honokiol in the Chinese medicine and biogenic amines in the beverage by electrochemically depositing graphene onto the electrode. Furthermore, we developed a novel method for the visualization of latent fingermarks on conductive metallic objects through electrochemical co-deposition of silver and copper in deep eutectic solvent which is a new kind of ionic liquid. 1) Application of electrochemically deposited graphene modified electrode for electrochemical sensor of honokiolAn electrochemical sensor of honokiol was fabricated by electrochemically reducing and depositing graphene oxide, which could overcome the drawbacks of current graphene modified electrode that is time consuming and unable to prepare homogeneous film with effective modified amounts. The graphene modified electrode with large electrochemical active area was fabricated through the electrochemical reduction and deposition of graphene oxide. The electrochemical sensor based on this modified electrode had a good catalysis effect on honokiol oxidation. After the optimization of four experimental conditions containing the modified amount of graphene, the pH of the electrolyte, accumulation potential and time, the sensor showed a linear range from 5.0×10-9 to 1.0×10-3 M and a detection limit of 1.7 nM. which are better than most sensors of honokiol. Besides, the sensor also has good selectivity, reproducibility and recovery of honokiol in a real sample. 2) An electrochemical sensor of biogenic amines fabricated by electrochemical deposition of grapheneA novel electrochemical sensor of biogenic amines fabricated by electrochemical deposition of graphene. The graphene modified electrode displayed good catalysis and signal amplification in the detection of two biogenic amines containing octopamine and tyramine due to the huge electrochemical active area and faster electron transfer rate of the graphene modified electrode. After optimizing the modified amount of graphene and the pH of the electrolyte, the sensor displayed better performance than most sensors of octopamine and tyramine. The linear detection ranges for octopamine and tyramine were from 5.0 ×10-7 to 4.0×10-5 M and 1.0×10-7 to 2.5×10-5 M. respectively. Moreover, the' detection limits of octopamine and tyramine were 100nM and 30 nM, respectively. Furthermore, the sensor displayed good reproducibility. anti-interference, stability and recovery of octopamine and tyramine in a real sample. 3) The enhancement of latent fingermarks in deep eutectic solvent by co-electrodepositing silver and copper on conductive metallic objectsWe obtained high-resolution enhancement images of latent fingermark (LFMs) on the conductive metallic object in the ionic liquid electrolyte system through electrochemically co-depositing silver and copper films in a deep eutectic solvent for the first time. After the optimization of depositing potential and depositing time, the LFM could be visualized with a high contrast in a short time (1 to 5 minutes). The visualized LFM could provide clear level 2 details information. In addition, the various latent fingermarks including sebaceous LFM, natural LFM, fresh and aged LFM on numerous metallic objects (Mg, Al, Zn, stainless steel, Cu, ITO glass and coins of Renminbi) with different colors, roughness and conductivities were developed by this method. This method is simple, fast, environment friendly, wide objects and depositing substances applicability and high sensitivity, which would be a promising tool for real forensic application.