Enhancement of the SPR Effect in an Optical Fiber Device Utilizing a Thin Ag Layer and a 3092A Liquid Crystal Mixture

This paper is a continuation of previous work and shows the enhancement of the surface plasmon resonance effect in a tapered optical fiber device. The study investigated liquid crystal cells containing a tapered optical fiber covered with a silver nanolayer, surrounded by a low refractive index liquid crystal in terms of the properties of light propagation in the taper structure. Silver films with a thickness of d = 10 nm were deposited on the tapered waist area. Measurements were performed at room temperature; liquid crystal steering voltage U from 0 to 200 V, with and without any amplitude modulation with a frequency of f = 5 Hz, and the wavelength λ ranged from 550 to 1200 nm. A significant influence of the initial arrangement of liquid crystals molecules on light propagation was observed. Three types of liquid crystal cells—orthogonal, parallel, and twist—were considered. During the measurements, resonant peaks were obtained—the position of which can also be controlled by the type of liquid crystal cells and the steering voltage. Based on the obtained results, the best parameters, such as highest peak’s width reduction, and the highest SNR value were received for twisted cells. In addition, the present work was compared with the previous work and showed the possibility of improving properties of the manufactured probes, and consequently, the surface plasmon resonance effect. In the presented paper, the novelty is mainly focused on the used materials as well as suitable changes in applied technological parameters. In contrast to gold, silver is characterized by different optic and dielectric properties, e.g., refractive index, extension coefficient, and permittivity, which results in changes in the light propagation and the SPR wavelengths.

Synthesis of Ag Loaded ZnO/BiOCl with High Photocatalytic Performance for the Removal of Antibiotic Pollutants

Ag@ZnO/BiOCl composites were successfully prepared by in situ precipitation and hydrothermal synthesis and used for the photocatalytic degradation of tetracycline hydrochloride antibiotics. An enhanced photodegradation efficiency was detected after loading Ag nanoparticles, which is attributed to the surface plasmon resonance effect. The optimized sample containing 4% Ag showed 80.4% degradation efficiency in 80 min, which is 2.1 and 1.9 times higher than those of ZnO and ZnO/BiOCl, respectively. The major degrading species involved in the photocatalytic process were detected to be super oxide anions and holes. Based on the obtained results, a possible charge transfer and degradation mechanism has been proposed. This study shows that Ag@ZnO/BiOCl catalyst has a good potential for photodegradation of organic pollutants in water.