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• A Nano-cavity based multispectral plasmonic refractive index sensor was investigated. • Considering the sensitivity and proximity to the telecommunication window, the structure is designed. • Higher bulk and surface sensitivity for detection of biological analytes • A higher bulk sensitivity of 958.3 nm/RIU for the mode III. • Electric field enhancement and Surface charge distribution was evaluated. In this paper, a Nano-cavity based multispectral plasmonic refractive index sensor for prostate-specific antigen (PSA) detection was investigated. The proposed structure includes two cavities in the form of a T and E shape inside a metal layer. The validity of the findings was verified through the use of the 3D finite difference time domain (FDTD) method. The identification of biomolecules is difficult for conventional biosensors in which there is a very limited amount of analyte, other metrics should be used. In most cases, there is enough analyte to completely cover the sensing surface. Here, in addition to bulk sensitivity, the surface sensitivity was analyzed. The proposed structure has three resonance modes. According to our findings, the designed structure has a bulk sensitivity of 958.3 nm/RIU for the third mode (mode III), 550 nm/RIU for the second mode (mod II), and 637.1 for the first mode (mode I). Having three resonance modes makes this structure a suitable option for use in multispectral applications. The surface sensitivity of 429.4, 457.6, and 465.5 nm/RIU was obtained for surface layer thicknesses of 3.5 nm, 5 nm, and 6.5 nm, respectively. Our results show the proposed structure has good potential in different biological applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stable SPR substrates were fabricated with standard evaporation techniques. [•] Au substrates and SiO2-covered Au substrates were compared. [•] Minimal experimental bulk sensitivity change with additional layers was observed. [•] Experimental results were confirmed by theoretical simulations. [•] Similar bio-assay results for both substrate types. [ABSTRACT FROM AUTHOR]

Abstract: A modified waveguide model for predicting the sensitivity of surface-relief guided mode resonance (GMR) biosensors is presented. The proposed model is a convenient and fast calculation method compared to the current optical simulation tools such as the rigorous couple wave analysis (RCWA). A systematic and theoretical discussion of the GMR geometric structure and sensitivity of the modified model for biosensing is also presented. For a given GMR material, the theoretical maximum sensitivity can be achieved by choosing the proper geometric structure from the model simulations. A comparison of the GMR biosensor sensitivity respectively calculated by the model and the RCWA method shows good agreement. Finally, a suspending GMR structure with a 4.5-fold increase in sensitivity compared to the traditional surface-relief GMR is proposed. [Copyright &y& Elsevier]

Abstract: Bulk sensitivity is inevitable for photoelectron spectroscopy (PES) when one studies bulk electronic structures of strongly correlated electron systems, which are often much different from surface electronic structures. Combination of soft and hard X-ray PES (SXPES and HAXPES) is a promising approach for this purpose by quantitatively evaluating the contribution of the surface in the observed angle integrated PES spectra. Even in the angle resolved PES studies (ARPES), the bulk sensitivity of the SX-ARPES is required to get the real bulk band dispersions and Fermi surface topology, which may be noticeably modified in the surface region as seen in several materials studied in this paper. Although hard X-ray ARPES is feasible, deep attention is required for the discussion of the possible recoil effects for the valence band. Besides, extremely low energy PES (ELEPES) by use of microwave excited Xe, Kr and Ar lamps will be as useful as those by synchrotron radiation and laser to realize a very high resolution of better than 5meV with bulk sensitivity under certain conditions. [Copyright &y& Elsevier]