Moleküler Baskılı Floresan Nanoparçacıkların Sentezlenmesi ve Sensör Sistemlerinde Kullanımlarının İncelenmesi

Abstract

In recent years, lanthanide-doped nanoparticles (upconversion nanoparticles - UCNP) have attracted much attention in many different areas because of their superior fluorescence properties, photochemical stability and ability to use in different application areas and they have been preferred over commonly used quantum dot and organic dyes. UCNPs are frequently used in medical imaging, treatment, drug release, forensic sciences, etc. due to their visibility in daylight with naked eyes, strong irradiation properties, non-toxicity, high photo stability, biocompatibility and highly efficient usage. UCNPs of different geometries and sizes can also be used successfully in many sensor applications. In this thesis, ytterbium (Yb) and erbium (Er) doped sodium yttrium fluoride (NaYF4) matrix (β–NaYF4: Yb3+, Er3+) was synthesized as the UCNP structure. The basic red 9 (BR9) molecule, which is an azoic dye, has been selected as a model compound and the UCNP surface was modified with this compound-specific molecularly printed polymer (MIP) and a UCNP-based sensor system has been developed. The synthesis of UCNPs was optimized using different hydrothermal methods, the most suitable synthesis method was determined, and the characterization studies of these nanostructures were carried out. To use the synthesized UCNPs in the sensor system, their surfaces were covered by MIP layer by 3 different methods and the most suitable modification method was determined. In the optimum procedure, UCNP was first modified with tetraethylorthosilicate (TEOS), then with triethoxyvinyl silane (TEVS) to enrich the surface in vinyl groups. In the next step, BR9 imprinted polymeric structure was covered to the surface via reversible addition-fragmentation chain transfer (RAFT) polymerization technique. Morphological properties and chemical structures of the obtained structures were evaluated with various experimental techniques such as fourier transform infrared spectrometer- attenuated total reflectance (ATR-FTIR), scanning electron microscope (SEM), taramalı electron microscope-energy dispersive X-ray analyzer (SEM-EDX), x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD). The binding, recognition and selectivity performances of the molecularly imprinted polymer coated UCNP structures (MIP@UCNP) against the target molecule BR9 were evaluated. It was detected that the obtained MIP@UCNP structures exhibit high binding capacity and reusability and exhibit recognition and selectivity to the azoic target molecule in comparison to other dyes. The limit of detection (LOD) value of the MIP@UCNP was found as 0.7 ppb, which is quite low when compared to the literature. The performance of this sensor system was tested by binding studies with real water samples. It was seen that the method applied in the presence of model BR9 molecule yielded very successful results. The results obtained are promising as they present significant potential for the development of novel sensor platforms specific to different target molecules by carrying out similar experimental techniques.