Nowadays one of the most challenging issues in medical sciences is the early detection of cancer. There are thousands of chemical and biological methods, but more and more popular become using also physical methods, such as quantum effects from novel nanomaterials. One of the widely explore fields, which shows potential applications in medical sciences, is the upconvertion phenomena. The main goal was to obtain gadolinium oxide nanoparticles doped with selected metals to investigate energy transfer between erbium (Er3+) and ytterbium (Yb3+) ions and enhance of the efficiency of upconvertion by doping structures with magnesium ions (Mg2+).
The examined nanoparticles were synthesized by a homogeneous precipitation method for 2 hours at a temperature of 85°C. The crystal structure arrangement was obtained by calcining at a temperature of 990°C for 3 hours. Additionally, nanoparticles were characterized with several methods. The atomic composition of the nanoparticles was analyzed via energy-dispersive X-ray spectroscopy (EDS). The size were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystal structure was characterized by X-ray diffraction (XRD). Optical properties were investigated by using photoluminescence measurements. Finally, nanoparticles were incubated with mouse mammary carcinoma (4T1) cells for 24h to examine their suitability for use in biology as luminescent markers.
As result of research, nanoparticles show luminescence in green emission region - maxima occur at a wavelength of 565 nm ($^4S_{3/2} \Rightarrow ^4I_{15/2}$, $^2H_{11/2} \Rightarrow ^4I_{15/2}$) and in red emission region - maxima occur at a wavelength of 663 nm ($^4F_{9/2} \Rightarrow ^4I_{15/2}$). The optical properties were examined by excitation with a semiconductor laser with a wavelength of 980 nm (continuous wave). An increase in the effectiveness of the upconvertion process was observed - an 8-fold increase in red luminescence efficiency was obtained for nanoparticles doped with 2.5% Mg2+ compared with non-doped nanoparticles (Gd2O3: 1% Er3+, 18% Yb3+). The measurements were carried out at a laser power density of $12 \text{ W} \cdot \text{cm}^{-2}$. The nanoparticles were dissolved in a dimethyl sulfoxide solution. The nanoparticles diameter was 380 nm, 282 nm, and 260 nm (before calcining). The diameters of the obtained nanoparticles - are $302 \pm 37 \text{ nm}$ and 278 + 36 nm (after a calcining) respectively. Obtained upconverting nanostructures show beneficial properties, which make them appropriate material to be used in bioimaging.