New Parameter for Benchmarking Plasmonic Gas Sensors Demonstrated with Densely Packed Au Nanoparticle Layers

Localized surface plasmon resonance (LSPR) gas sensitivity is introduced as a new parameter to evaluate the performance of plasmonic gas sensors. A model is proposed to consider the plasmonic sensors' surface sensitivity and plasmon decay length and correlate the LSPR response, measured upon gas exchange, with an equivalent refractive index change consistent with adsorbed gas layers. To demonstrate the applicability of this new parameter, ellipsoidal gold nanoparticles (NPs) arranged in densely packed hexagonal lattices were fabricated. The main advantages of these sensors are the small and tunable interparticle gaps (18-29 nm) between nanoparticles (diameters: 72-88 nm), with their robust and scalable fabrication technology that allows the well-ordered arrangement to be maintained on a large (cm2 range) area. The LSPR response of the sensors was tested using an LSPR sensing system by switching the gas atmosphere between inorganic gases, namely He/Ar and Ar/CO2, at constant pressure and room temperature. It was shown that this newly proposed parameter can be generally used for benchmarking plasmonic gas sensors and is independent of the type and pressure of the tested gases for a sensor structure. Furthermore, it resolves the apparent disagreement when comparing the response of plasmonic sensors tested in liquids and gases.

Enhanced Absorption Performance of Dye-Sensitized Solar Cell with Composite Materials and Bilayer Structure of Nanorods and Nanospheres

The concept of localized surface plasmon resonance has been applied to increase the absorption efficiency of dye-sensitive solar cells (DSSCs) by using various photoanode structures. A three-dimensional model for a photoanode of the DSSC based on composite materials was developed using COMSOL Multiphysics. Spherical-, rod- and triangular-shaped aluminum nanoparticles were employed in the core of SiO2 to examine the influence of morphology on the performance of DSSCs in the 350–750 nm wavelength range. The UV-Vis absorption results indicated that aluminum nanoparticles with spherical, rod and triangle morphologies had 39.5%, 36.1% and 34.6% greater absorption capability than aluminum-free nanoparticles. In addition, we investigated the effect of plasmonic absorption in DSSCs for photoanodes made of TiO2, SiO2 and bilayer TiO2/SiO2 with and without covering aluminum nanoparticles. The TiO2 and SiO2 nanoparticles had fixed diameters of 90 nm each. The UV-Vis absorption and Tauc curves indicated that the TiO2/SiO2 bilayer structure (with and without aluminum nanoparticles) had greater absorption and lower bandgap energies than individual TiO2 and SiO2 nanoparticles. Furthermore, bilayer photoanode nanostructures were investigated based on nanospheres and nanorods for core–shell Al@SiO2 nanoparticles. The results indicated that a photoanode with nanorod/nanosphere structure had a 12% better absorption capability than a nanosphere/nanorod configuration. This improvement in absorption is attributed to the high surface area, which boosts dye loading capacity and long-term light capture, resulting in greater interaction between the dye and the photon. Our study develops core–shell nanoparticles with optimized shape and materials for bilayer photoanode structures in photovoltaic technology.

Chitosan-TiO2 microparticles LBL immobilized nanofibrous mats via electrospraying for antibacterial applications

The antibacterial materials with biodegradable and biocompatible nature have unveiled novel prospects to combat the bacterial infection, which has always been a troubling and challenging issue in the biomedical field. In this study, chitosan (CS) and Titanium dioxide (TiO₂) microparticles were well immobilized on polylactic acid (PLA) mats by electrospinning-electrospraying hybrid technique. The surface morphology, chemical composition and characteristic group of the mats were characterized. The results indicated that CS/TiO₂ microparticles were successfully immobilized on the surface of PLA mats. In addition, the antibacterial activity and cytotoxicity of the composite mats were investigated to confirm that the layer-by-layer immobilization of CS/TiO₂ microparticles via electrospraying could enhance the antibacterial effect and biocompatibility of the mats. At the same time, the PLA-(CS/TiO₂-1.5%)_1.5 mats exhibited the best performance in antibacterial effect (up to about 95%) and cell viability (nearly 92% and 95% at 3 d and 5 d). The composite mats have great potential as an effective antibacterial material for the biomedical applications.