@phdthesis{,
    author = {Lüders, Laura von},
    title = {Development and Characterisation of Noncovalently Functionalised Graphene Field-Effect Transistors and Their Application as Specific Biosensors},
    editor = {},
    booktitle = {},
    series = {},
    journal = {},
    address = {},
    publisher = {},
    edition = {},
    year = {2023},
    isbn = {},
    volume = {},
    number =  {},
    pages = {},
    url = {},
    doi = {},
    keywords = {2D materials, graphene, noncovalent functionalisation, biosensor, drug detection, perylene bisimide, methamphetamine},
    abstract = {This thesis presents a detailed investigation of the development and characterisation of a reliable and specific biosensor based on graphene. The entire procedure involves multiple processing steps, each of which is characterised using various techniques including Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrical measurements. High-quality monolayer graphene is grown via chemical vapour deposition (CVD) and subsequently noncovalently functionalised with one out of two perylene derivatives. Both are found to self-assemble homogeneously on the graphene surface, with layer heights of 1.1 nm to 1.5 nm derived by AFM. The following wet-chemical transfer onto a SiO2/Si substrate finalises the so-called Functional Layer Transfer (FLaT) of graphene. The resulting sample is structured into a graphene field-effect transistor (GFET) array consisting of eleven devices on one chip. Onto the carboxylic groups of the perylene molecules, anti-methamphetamine antibodies (methamphetamine-ABs) are coupled specifically. Indirect measurements using a second antibody conjugated with gold nanoparticles are used to develop and optimise a reliable treatment protocol for the specific functionalisation. The study reveals the stable and homogeneous perylene FLaT graphene surface, with a reliably functionalised methamphetamine-AB monolayer of approximately 5.1 nm. Subsequently, a variety of electrical measurements is conducted and the specificity of the biosensor towards methamphetamine validated. A strong signal dependency with the methamphetamine concentration is found, where the limit of detection is not observed at the lowest concentration of 300 ng/ml. No cross-reactivity towards a placebo molecule of similar size is observed. To investigate the versatility of the protocol, fragment antigen-binding regions (Fab) of the anti-cortisol antibody are immobilised on the perylene functionalised graphene. The homogeneity and coverage of the anti-cortisol Fab fragments can be improved; however, the biosensors do detect cortisol at a concentration of 10 μg/ml. Furthermore, the study examines the stability and lifetime of the methamphetamine-ABs immobilised on the GFETs and reveals that the antibodies remain functional for at least 17 hours in ambient conditions. A comprehensive comparison of the two perylene molecules used indicates a slightly more homogeneous self-assembly of the typically used molecule, but a possibly improved sensing behaviour when using the newly synthesised perylene molecules.},
    note = {},
    
    school = {Universität der Bundeswehr München},
    
}