Annealing high-temperature treatment of CVD-grown graphene

The emergence of pharmaceutical pollutants through wastewater and drug production waste poses a significant threat to aquatic ecosystems, compromising water quality and ecological balance. Detecting these residues with high sensitivity is a top priority as it allows us to comprehensively address environmental risks and effectively protect our ecosystems.In this study, graphene-based electronic sensors are being explored as a promising solution for achieving highly sensitive detection of pharmaceuticals, leveraging graphene’s exceptional electrical properties. Additionally, to mitigate the impact of surface contamination on carbon materials and accurately assess intrinsic properties, we applied a high-temperature treatment to remove impurities from graphene. The chemical and physical structure of graphene was analyzed using Raman and XPS spectroscopy, while the sensor’s performance was evaluated through conductivity measurements. Raman spectroscopy is the method of choice for characterizing graphene due to its versatility, rapidity, and non-destructive nature. It provides information about the vibrational and rotational modes, creating a fingerprint for molecule identification. The study of peaks G, D, and 2D bands allows for determining the number of graphene layers, doping level, and functionalization of graphene. On the other hand, XPS spectroscopy unveils shifts in C-C bond environments and the presence of physisorbed molecules. An important fact is that molecular water, oxygen, and other functional groups are regularly attached to the graphene surface when exposed to ambient conditions, affecting the pristine response of the material. This thesis project studies graphene’s sensing capabilities for Ibuprofen and explores the effectiveness of high- temperature treatments as pre- and post-deposition cleaning methods to enhance graphene surface sensitivity. A series of high-temperature treatments (100°C for 1 hour, 300°C for 1 hour, 600°C for 1 hour) were applied under vac- uum conditions to graphene on SiO2 substrates to eliminate physisorbed molecules. XPS and Raman spectroscopy analysis unveiled the presence of molecular moieties on the graphene surface, as evidenced by measurements of O1s and C1s components, FWHM(G), and the D/G ratio, respectively. Simultaneously, a homemade collinear four-point probe method was fabricated to assess changes in electrical conductivity upon Ibuprofen deposition. After the pharmaceutical deposition, the galvanostatic current-voltage (G-IV) curve slope increased, indicating an increase in resistance and, thus, a decrease in conductivity. This observation underscores the potential utility of graphene in sensing applications.

• Hlavní autor: Sallo Chabla, Nardy Jacqueline (author)
• Médium: bachelorThesis
• Jazyk: eng
• Vydáno: 2024
• Témata: Grafeno; Tratamientos térmicos; Detección de fármacos; Graphene; Thermal treatment; Pharmaceutical detection
• On-line přístup: http://repositorio.yachaytech.edu.ec/handle/123456789/726