SYNTHESIS OF ZINC OXIDE (ZNO) – GRAPHENE NANOCOMPOSITE AND ITS APPLICATION AS CARBON MONOXIDE (CO) GAS SENSOR

• Main Author: Marguna, Satrinia
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/46315
• Institution: Institut Teknologi Bandung

Carbon Monoxide (CO) or referred to as a "silent killer" is a gas that is odorless, colorless, and tasteless. This gas is very poisonous to humans and other air-breathing creatures that need oxygen. The effects of this mild gas poisoning include headaches and nausea at concentrations of less than 100 ppm. Concentrations as low as 667 ppm can cause 50% of the body's hemoglobin to turn into carboxyhemoglobin (HbCO). Carboxyhemoglobin is not effective in delivering oxygen, so some parts of the body do not get enough oxygen. As a result, exposure to this level can be life-threatening. To prevent the danger of CO gas exposure, many gas sensors are developed from various metal oxides. Metal oxides are known to be able to detect oxidizing and reducing gases. In this study, the manufacture of metal oxide-based gas sensors is carried out by depositing a nanocomposite layer of Zinc Oxide (ZnO) - Graphene (Gr) as a sensing layer on the alumina substrate. ZnO-Gr nanocomposite was obtained through the synthesis of Zn (NO3) 2.6H2O precursors and Pure Graphene using the Hydrothermal method at a temperature of 180? C for 12 hours. The sensing layer powder was calcined for 4 hours at 400?C before being deposited. The sensing layer deposition on the alumina substrate was carried out using the doctor blade method at a temperature of 200?C for 2 hours. The ZnO-Gr concentration ratio in this study is 1: 0, 1: 1, 1: 3, 1: 5, and 0: 1. The sensor material characterization carried out in this study was X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and sensor testing of Carbon Monoxide (CO) gas. The results of XRD characterization showed the peak of ZnO and Graphene diffraction crystals in accordance with the ratio of ZnO-Gr concentration performed. SEM test shows that the Hydrothermal method successfully formed ZnO particles with a size of around 500nm. EDS testing shows the elements forming ZnO-Gr. Sensing test with CO gas exposure showed that ratio of ZnO-Gr 1:3, 1:5, 0:1 have capability to work at room and high temperatures (RT & HT). It means that the addition of graphene in dominant can decrease the work temperature and graphene become the active site in RT. The ratio of ZnO-Gr 1:0 (pure ZnO) work at 250?C and 1:1 at 200?C. It shows us that mixing graphene to zinc oxide decreases the temperature work just about 50? C and the zinc oxide still being the active site of the sample. ZnO-Gr 1:0 and 1:1 has the response above 50% which proves that zinc oxide is able to sense CO gas in HT. Sample 1:5 has the highest response (?R) 5.65% of all nanocomposite responses in RT and just needs 160s to response, 65s to recovery in RT of 70ppm CO, in conjunction with 80s to response and 60s to recovery in HT (150?C) of 30ppm CO. There are an increase in responses when the temperature reaches above 200?C in sample ZnO-Gr 1:3 and 1:5. Sample ZnO-Gr 1:3 has the highest response (?R) 7.61% next to sample 1:5 in HT. It means in this temperature level, ZnO sets to be the active site of sample. We can see that ZnO-Gr 1:3 and 1:5 nanocomposites begin to reach pure graphene capability to sense the CO gas in RT and pure zinc oxide capability in HT, where the graphene’s response is 24.53% and coudnt work in HT according to the progressively decrease with increasing temperature.