The main challenge for all electrical, mechanical and optical sensors is to detect low molecular weight (less than 400 Da) chemical and biological analytes under extremely dilute conditions. Surface plasmon resonance sensors are the most commonly used optical sensors due to their unique ability for real-time monitoring the molecular binding events. However, their sensitivities are insufficient to detect trace amounts of small molecular weight molecules such as cancer biomarkers, hormones, antibiotics, insecticides, and explosive materials which are respectively important for early-stage disease diagnosis, food quality control, environmental monitoring, and homeland security protection. With the rapid development of nanotechnology in the past few years, nanomaterials-enhanced surface plasmon resonance sensors have been developed and used as effective tools to sense hard-to-detect molecules within the concentration range between pmol and amol. In this review article, we reviewed and discussed the latest trend and challenges in engineering and applications of nanomaterials-enhanced surface plasmon resonance sensors (e.g., metallic nanoparticles, magnetic nanoparticles, carbon-based nanomaterials, latex nanoparticles and liposome nanoparticles) for detecting "hard-to-identify" biological and chemical analytes. Such information will be viable in terms of providing a useful platform for designing future ultrasensitive plasmonic nanosensors.

Graphene-gold metasurface architectures that can provide significant gains in plasmonic detection sensitivity for trace-amount target analytes are reported. Benefiting from extreme phase singularities of reflected light induced by strong plasmon-mediated energy confinements, the metasurface demonstrates a much-improved sensitivity to molecular bindings nearby and achieves an ultralow detection limit of 1 × 10(-18) m for 7.3 kDa 24-mer single-stranded DNA.

The beautiful interplay between light and matter can give rise to many striking physical phenomena, surface plasmon resonance (SPR) being one of them. Plasmonic immunosensors monitor refractive index changes that occur as a result of specific ligand–analyte or antibody–antigen interactions taking place on the sensor surface. The coronavirus disease (COVID‐19) pandemic has jeopardized the entire world and has resulted in economic slowdown of most countries. In this work, a model of a sandwich plasmonic biosensor that utilizes gold nanorods (Au NRs) for the detection of COVID‐19 SARS‐CoV‐2 spike protein is presented. Simulation results for different prismatic configurations for the basic Kretschmann layout are presented. It is found that a BK7 glass prism‐based SPR sensor has an incremental sensitivity of 111.11 deg RIU−1. Additionally, using Comsol Multiphysics the electric field enhancement observed for various aspect ratios and layouts of Au NRs are discussed in depth.

Surface-enhanced Raman scattering (SERS) typically requires hot-spots generated in nano-fabricated plasmonic structures. Here we report a highly versatile approach based on the use of random gold nano-island substrates (AuNIS). Hot spots are produced through the entrapment of colloidal plasmonic nano-crystals at the interface between AuNIS and a microbubble, which is generated from the localized plasmonic absorption of a focused laser beam. The entrapment strength is strongly dependent on the shape of the microbubble, which is in turn affected by the surface wetting characteristics of the AuNIS with respect to the solvent composition. The laser power intensity required to trigger microbubble-induced SERS is as low as 200 μW μm(-2). Experimental results indicate that the SERS limit of detection (LOD) for molecules of 4-MBA (with -SH bonds) is 10(-12) M, R6G or RhB (without -SH bonds) is 10(-7) M. The proposed strategy has potential applications in low-cost lab-on-chip devices for the label-free detection of chemical and biological molecules.

Development of a microfluidic disc-direct reverse-transcription quantitative PCR platform to perform automated multiplex nucleic acid tests for rapid multiplex detection of disease infection.