Development of a highly sensitive sensor chip using optical diagnostic based on functionalized plasmonically active AuNPs

Measuring solution concentration plays an important role in chemical, biochemical, clinical diagnosis, environmental monitoring, and biological analyses. In this work, we develop a transmission-mode localized surface plasmon resonance (LSPR) sensor chip system and convenient method which is highly efficient, highly sensitive for detection sensing using multimode fiber. The plasmonically active sensor's surface AuNPs with high-density NPs were decorated onto 1 cm sensing length of various clad-free fiber in the form of homogeneous monolayer utilizing a self-assembly process for immobilization of the target molecule. The carboxyl bond is formed through a functional reaction on the sensor head. Using the significance in the refractive index difference and numerical aperture, which is caused by a variation in the concentration of measuring bovine serum albumin (BSA) protein which can be accurately measured by the output signal. The refractive index variation of the medium analyte layer can be converted to signal output power change at the He-Ne wavelength of 632.8 nm. The sensor detection limit was estimated to be 0.075 ng/mL for BSA protein which shows high sensitivity compare to other types of label-free optical biosensors. This also leads to a possibility of finding the improvement in the sensitivity label-free biosensors. The conventional method should allow multimode fiber biosensors to become a possible replacement for conventional biosensing techniques based on fluorescence.