REDUCTIVE ELECTROSYNTHESIS OF CUBTC TYPE METAL- ORGANIC FRAMEWORKS AND ITS APPLICATION AS GLUCOSE ELECTROCHEMICAL SENSOR

• Main Author: Unvaresi Misonia Beladona, Siti
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/52142
• Institution: Institut Teknologi Bandung

Metal-Organic Frameworks (MOFs) are porous materials constructed from metal ions and organic ligands as linkers via coordination bonding. Properties of MOFs such as large surface area, high porosity, variable host-guest interactions and feasible in modification, make MOFs as multifunctional materials for various applications, for example as electrochemical sensor. CuBTC type MOFs with H?BTC ligand (1,3,5-benzenetricarboxylic acid) also known as HKUST-1 has widely employed as electrochemical sensor. To increase its sensitivity and selectivity toward analytes, MOFs must be synthesized and directly deposited as thin film on the surface of the electrode. However, synthesis methods of MOFs on the surface of the electrode are still very limited and rarely reported. In this study, the reductive electrosynthesis method was used to deposit thin film of CuBTC type MOFs crystals on the surface of brass metal and glassy carbon (GC) electrodes. The GCE/CuBTC was applied as working electrode for glucose detection. Cu(NO?)?.3H?O salt was used as the source of Cu²? metal ions and H?BTC as organic ligands dissolved in DMF solvent containing NBu?PF? electrolyte. The reductive electrosynthesis on brass metal was conducted at -1.6, -1.9 and -2.2 V for 10, 15 and 20 minutes, while on GC electrode was conducted at -1.0, -1.3 and -1.6 V for 5, 10 and 15 minutes, at room temperature. CuBTC was also synthesized using solvothermal method at a temperature of 80 ? for 20 hours as a comparison. CuBTC resulted from reductive electrosynthesis and solvothermal methods was characterized by PXRD, FTIR and SEM. Cyclic voltammetry measurement was conducted to analyze the performance of CuBTC type MOFs as an electrochemical sensor for glucose detection using working electrode of GCE and GCE/CuBTC at various scan rate of 0.02-0.1 V s?¹, while variation of glucose concentration (50- 600 ?M) was measured using the differential pulse voltammetry method. PXRD and FTIR characterization revealed that the optimum potential and reaction time for CuBTC using reductive electrosynthesis method on brass metal and GC electrode were -1.9 V for 20 minutes and -1.3 V for 15 minutes, respectively. SEM images of CuBTC using reductive electrosynthesis method showed octahedral shape crystals that were in accordance to the solvothermal method, approximately 1.8 and 20 ?m for reductive electrosynthesis and solvothermal methods, respectively. Cyclic voltammetry measurements pointed out that the oxidation and reduction peaks of Cu²?/³? on GCE were observed at 0.2 V and -0.2 V, respectively, but there was no oxidation peak of glucose. Meanwhile, an additional peak at 0.45 V observed on GCE/CuBTC indicated the oxidation reaction of glucose to gluconolactone. Performance of GCE/CuBTC toward glucose using cyclic voltammetry at various scan rate showed a linear relationship between the root of scan rate plot toward the peak oxidation and reduction currents calculated by Randles-Sev?ik equation. This explained that the process was controlled by diffusion to the electrode surface. Differential pulse voltammetry measurements generated a linear concentration range at 50-600 ?M with R² value of 0.9959 and limit of detection of 74.65 ?M on GCE/CuBTC. Based on these results, synthesis of CuBTC type MOFs using reductive electrosynthesis method is more efficient in terms of reaction time and energy than solvothermal method, since CuBTC can be deposited directly on the surface of the GCE and be employed as glucose electrochemical sensor material.