Jaroslav Kováč

Surface plasmon resonance (SPR)-based sensors have attracted huge interest due to their ability to provide real-time sensing of a wide range of quantities, while still boasting high sensitivity, low cost, and electromagnetic immunity. Among various types of these sensors, waveguide-based sensors show great promise in terms of integrability into more complex circuits while still maintaining similar sensitivity and versatility as their stand-alone counterparts. This paper presents the results of investigation based on design and simulation of optimal parameters for multimode SPR-based waveguide sensor sensitive to any commonly used liquid analytes. The sensitivity for a wider range of analytes is achieved by utilisation of SiON material platform because refractive index adjustability of SiON offers a way to tailor sensor’s sensitivity to exact applications and analytes. One of the research goals in this work was to show that multi-mode waveguides may be suitable for such sensors with comparable sensitivity and higher transmission rates as single-mode waveguides. To showcase design possibilities, two variations with the same design and material’s refractive index adjustment only were investigated, and their optimal parameters have been found. Sensitivity for all commonly used liquid analytes was validated, with sensitivity rising to 1400 nm/RIU for label-free refractive index sensing, even without the use of any sensitivity-enhancing structures.

Ternary wittichenite Cu3BiS3 nanocrystals were prepared mechanochemically using a planetary ball mill from elemental copper, bismuth and sulfur in a stoichiometric ratio in only 5 min. The orthorhombic wittichenite Cu3BiS3 was nanocrystalline with an approximate crystallite size of 38 nm ± 9 nm, as confirmed by Rietveld refinement. The nanocrystalline character of orthorhombic Cu3BiS3 was also proven by transmission electron microscopy. The measured Raman spectrum confirmed the formation of pure wittichenite Cu3BiS3. The morphology characterization demonstrated the homogeneity of the sample. The value of the specific surface area for pure mechanochemically prepared Cu3BiS3 after 5 min was 2.7 m2g−1. The optical properties were investigated using UV–Vis absorption and micro-photoluminescence spectroscopy. From the absorption UV–Vis spectrum, the value of the bandgap energy was determined to be 1.52 eV, which creates an assumption for the use of wittichenite Cu3BiS3 in photovoltaic applications. The optoelectrical properties of the prepared Cu3BiS3 nanocrystals were verified by current–voltage measurements in the dark and under white light illumination. The photocurrent increased by 26% compared to the current in the dark at a voltage of 1 V. The achieved results confirmed a very fast and efficient way of synthesizing a ternary wittichenite Cu3BiS3, which can be used for applications in solar cells.