IRON DOPED ZIF-8 FOR ENHANCING PERFORMANCE OF ELECTROCHEMICAL SENSOR OF DOPAMINE

• Main Author: Hanifah, Nurul
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/67712
• Institution: Institut Teknologi Bandung

Abnormal levels of dopamine are associated with various neurodegenerative diseases such as Parkinson, schizophrenia, bipolar and Alzheimer. A detection method of dopamine is needed for monitoring and early detection of these diseases. The most accurate and selective dopamine detection methods are High Performance Liquid Chromatography (HPLC), mass spectrometry, and a combination of the two techniques. However, these techniques have some limitation such as complicated, expensive, time consuming, and require professional personnel. In general, electrochemical methods can overcome these shortcomings. Many electrochemical methods have been developed to detect dopamine because dopamine is electroactive material. However, the selectivity of the electrochemical method is affected by the presence of interfering molecules such as uric acid and ascorbic acid due to their similar oxidation potential and present with much higher concentrations than dopamine. Modifying the working electrode with enzymes, antibodies, aptamers, nanomaterials, and molecularly imprinted polymers (MIPs) surface can reduce these limitations. Herein, iron modified Zeolitic Imidazolate Framework 8 (Fe/ZIF8) was synthesized to increase the sensitivity and selectivity of dopamine detection based on electrochemical methods. ZIF-8 which consists of metal zinc (Zn) and organic linker mIM (2-methylimidazole), has excellent properties such as large specific surface area, tunable structure, and high thermal and chemical stability. It was reported that ZIF-8 modified with iron metal (Fe/ZIF-8) showed the best catalytic activity compared to other metal modification. Fe/ZIF-8 have also been widely explored because of its potential as a photocatalyst material, but there has been no research on its application as an electrochemical sensor material. The synthesis of Fe/ZIF-8 was carried out by the simple precipitation method at room temperature. The optimum Fe variation in ZIF-8 is evaluated from the results of Scanning Electron Microscopy – Energy Dispersive X-Ray Spetroscopy (SEM-EDS) and Cyclic Voltammetry (CV) to dopamine. The SEM results show that iron ratio above 5% in ZIF-8 made the size of the material bigger. CV results show that the optimum iron ratio is ZIF-8 with 5% Fe (Fe5/ZIF8). X-Ray Diffraction (XRD) and Brunauer Emmet Teller (BET) was carried out for ZIF8 and Fe5/ZIF8. XRD results showed that the crystallinity of ZIF-8 and Fe5/ZIF8 was very high. The XRD peaks show a SOD-type topology which indicates that iron successfully replacied zinc position in ZIF-8. The resulting Fe5/ZIF-8 was very pure because there is no additional peak from other phases. BET results show that Fe5/ZIF-8 has a larger specific surface area when compared to ZIF-8. The sensor sensitivity and selectivity in detecting dopamine was carried out using the Different Pulse Voltammetry (DPV) and Chronoamperometry (CA). The DPV results showed there are two linear ranges i.e 0.05 ?M – 2 ?M and 2 ?M – 20 ?M. The sensor sensitivities were 199.0 mA/?M and 165.3 mA/?M. The LODs obtained were 0.035 M and 0.6815 M, where the results of the first linear range is still far below the range of dopamine concentrations in urine 0.3 ?M -3.31 ?M. The sensitivity measurement using CA and DPV also showed that the sensor was selective from interfering substances such as uric acid, ascorbic acid, and urea.