The modern medical diagnostic methods of our days (e.g. molecular diagnostics, point-of-care diagnostics) open new horizons in the field of personalized medicine, enabling the early diagnosis of diseases, the selection of medication based on personal needs and the continuous monitoring of the healing process. The new possibilities also pose new challenges for the applicable sensors: the detection limit, sensitivity and selectivity should be better than ever before, with the added necessity to perform a high number of parallel measurements.
Nanomaterials and nanostructures are frequently used to enhance the listed important parameters of sensors. There are also sensor types where the nanomaterial is not just an additive to enhance sensor properties, but is an essential part of signal generation. The so called localized surface plasmon resonance (LSPR), which can be excited in nanoparticle, can be utilized as an ultra-sensitive refraction index sensing method (with sensitivities even around 10-6-10-7 RIU), enabling the detection of even molecular scale interactions on the sensor surface. Besides, the strong plasmon field of nanoparticles also enhance the Raman scattering yield of molecules (with enhancement factors even in the 1010-1011 range), which is the basis of the surface enhance Raman-spectroscopy (SERS) analytical method.
The aim of my research is the development of gold nanoparticle based nanocomposites, embedded in PDMS (poly-dimethyl-siloxane) for LSPR and SERS purposes. The immobilization of the nanoparticles on the surface of the PDMS enables their integration into polymer based microfluidic systems, thus providing convenient sample handling. My work covers the fabrication of nanocomposites, the optimization of the technological parameters of the synthesis (in order to maximize their plasmonic sensitivity and Raman enhancement), and also their characterization with optical spectroscopy, Raman-spectroscopy, and atomic force microscopy (AFM). I demonstrated that the sensors/SERS substrates fabricated with this simple and cost-effective technology can be successfully used for the desired purposes.