Near-infrared surface plasmon resonance sensor with a graphene-gold surface architecture for ultra-sensitive...

Binding behaviors of proteins are important for applications in the field of biochemistry. Though a standard assay has a favorable limit of detection (LOD), it is mainly limited to indirect observation via fluorescence labeling. We reported and demonstrated a novel label-free sensing approach based on a near-infrared (NIR) surface plasmon resonance (SPR) sensing chip modified with a graphene-gold surface architecture in this paper. The NIR excitation wavelength can greatly improve the sensitivity of SPR sensing derived from the wavelength modulation-based methodology. Moreover, benefiting from the excellent electro-optical properties of graphene in NIR range, the graphene-gold surface architecture was built to further improve the sensing sensitivity. Experimental results proved the superiority over most of those reported previously in terms of ultra-sensitivity (39,160 nm/RIU) and resolution (5.107 × 10^-7 RIU). We detected human immunoglobulin G (IgG) to confirm the ability to enhanced-sensitive detection with a graphene overlayer. This sensor provides surface-specific detection schemes with a large linear dynamic range of ng/ml (pM) to fg/ml (aM) and a LOD of 7.2 fg/ml (48 aM) using gold nanoparticles (GNPs) as amplification labels. The proposed method provides a simple and effective strategy to improve sensitivity and LOD for biochemical detection in a rapid, ultrasensitive, and nondestructive manner.