We present phase-responding Fourier nanotransducers based on plasmonic metamaterials for ultrasensitive control of dynamic characteristics of 2D materials and functional biosensing interfaces. These nanotransducers are designed in such a way that they can confine light in 2D plane contacting with a probed ultrathin sample, gathering information about its properties, and then transmitting the information into discrete optical beams with amplified phase relations. To demonstrate their potential of Fourier transducers in biosensing, we designed Fourier nanotransducers based on periodic gold nanostructures and applied it in a newly developed protocol for the detection of important antibiotic chloramphenicol (CAP). Such biosensing tests showed the lower detection limit at fg mL(-1) level, which several orders of magnitude better than reported in the literature. The implementation of Fourier nanotransducers opens new opportunities for a radical improvement of current state-of-the art plasmonic biosensing technology.

Plasmonic biosensing has emerged as the most sensitive label-free technique to detect various molecular species in solutions and has already proved crucial in drug discovery, food safety and studies of bio-reactions. This technique relies on surface plasmon resonances in ~50 nm metallic films and the possibility to functionalize the surface of the metal in order to achieve selectivity. At the same time, most metals corrode in bio-solutions, which reduces the quality factor and darkness of plasmonic resonances and thus the sensitivity. Furthermore, functionalization itself might have a detrimental effect on the quality of the surface, also reducing sensitivity. Here we demonstrate that the use of graphene and other layered materials for passivation and functionalization broadens the range of metals which can be used for plasmonic biosensing and increases the sensitivity by 3-4 orders of magnitude, as it guarantees stability of a metal in liquid and preserves the plasmonic resonances under biofunctionalization. We use this approach to detect low molecular weight HT-2 toxins (crucial for food safety), achieving phase sensitivity~0.5 fg/mL, three orders of magnitude higher than previously reported. This proves that layered materials provide a new platform for surface plasmon resonance biosensing, paving the way for compact biosensors for point of care testing.

We demonstrate ultrasensitive detection of malaria aptamers performed with the help of graphene protected copper plasmonics. Using better morphology of copper surface as compared to gold, phase sensitive surface plasmon resonance schemes and graphene functionalization protocol for attaching end-tethering of DNA probes we were able to improve the detection level of malaria aptamers by an order of magnitude. This opens a way to associate a dormant bacterial population with chronic inflammatory diseases in blood samples using simple label-free optical detection.

ZnO and Ag-containing ZnO (ZnO/Ag) films with the Ag/Zn molar ratio of 3.3 and 9.1%, respectively were sol-gel coated on biomedical titanium for antibacterial and bioactive surface modification. X-ray diffraction analysis indicates that ZnO peaks increase with the calcination temperature of the samples. Scanning electron microscopy and energy dispersive of X-ray analyses reveal Ag-rich white particles (300~750 nm) on ZnO/Ag samples that were calcined at 400 °C. X-ray photoelectron spectroscopy analysis of ZnO/Ag samples shows that Zn and O exist as ZnO and Ag presents in metallic state. The coating samples exhibit similar UV light-induced hydrophilic conversion behavior. Potentiodynamic polarization test in a Ca-free Hank's balanced solution demonstrates better corrosion resistance of the coating samples compared with the polished sample. In the in vitro bioactivity test using the simulated body fluid, a layer of apatite is gradually deposited on the surface of sample ZnO/9Ag after 12 days of soaking. The MTT assay test shows that ZnO and ZnO/Ag films have weak compatibility with the L929 cells. The antibacterial test against E. Coli by the disk diffusion assay reveals that antibacterial activity of the coating samples increases with silver content of the films.

Surface plasmon resonance (SPR) is an established technique for label-free detection of trace amounts of adsorbents at a metal-dielectric interface [1]. In recent years much effort has been directed at increasing the detection limit of SPR [2]. Previous works [3,4] have in general focused on the use of gold nanoparticles for biosensing. The results of these studies have been promising but are limited in their potential application by the high costs associated with both nanofabrication techniques and gold itself.