| Abstract [eng] |
The aim of this Master thesis was to fabricate gold nanoparticle modified indium tin oxide (ITO) electrode and evaluate its applicability in electrochemical sensing. Gold nanoparticles were generated by nanosecond laser pulse irradiation of thin, 3–30 nm thick, gold films. Firstly, it was found that diameters and the number of generated nanoparticles per unit area (area density) strongly depends on the thickness of the gold film when it is less than 10 nm. Measured average nanoparticle diameters were ~50 nm for nanoparticles generated in 3 nm thick gold film, and ~90 nm for nanoparticles generated in 5 nm thick gold film. Furthermore, experiments have shown that size, its distribution and area density of generated nanoparticles does not depend on the laser pulse energy and pulse number. Also, it was demonstrated that generated gold nanoparticles exhibit surface plasmon resonance at excitation wavelength of 540 nm and 570 nm for ~50 nm and ~90 nm average diameter nanoparticles, respectively. Finally, two ITO electrodes were modified by different size gold nanoparticles and were characterized by studying the electrochemical activity of the ascorbic acid by cyclic voltammetry method. The study results has shown that ~90 nm average diameter gold nanoparticles significantly enhance the oxidation of the ascorbic acid, which implies higher and faster current response than using electrode modified with ~220 nm average diameter nanoparticles. It is explained by higher surface-to-volume ratio of smaller nanoparticles, which results in higher interface area between the electrode and the analyte, therefore the usage factor of the analyte is higher when electrode is modified with smaller nanoparticles. Moreover, the analysis of the oxidation current peak revealed a linear dependence on the amount of the ascorbic acid. The measured detection sensitivity values were ~2,4 μA/μM and ~0,6 μA/μM for the electrodes modified with ~90 nm and ~220 nm average diameter gold nanoparticles, respectively. In conclusion, the results of this work show that ITO electrode modification with gold nanoparticles, which were generated by nanosecond laser irradiation of thin gold films, can improve the electrochemical sensing performance, and thus it is expected that this approach will generate new opportunities for the development of highly sensitive electrochemical sensors. |
