Enhancing sensing sensitivity for long period grating sensor with colloidal gold nanoparticles

摘要

We propose a simple method to improve the spectral sensitivity and detection limit of long period grating sensor for chemical sensing, in which the grating surface is modified by colloidal gold nanoparticles. The transmission spectra and optical properties of gold nanospheres change with the different refractive index of the environment near the surface of gold nanospheres. The sensor response of gold colloids increases linearly with solvents of increasing refractive index. The results for the measurement of sucrose solutions showed that the slope of wavelength shifts increased from -18 (nm/RIU) to -24 (nm/RIU); while for changes of peak depth, its slope increased from 37 (dB/RIU) to 60 (dB/RIU). The accuracy of concentration measurement for salt water solution was increased from 0.6% to 0.2%, and limit of detection can be improved from 0.04 % to 0.02 %. When the colloidal gold surface was modified with a dimitrophenyl compound (DNP), results showed that the signal increase linearly with increasing concentration of the analyte, and the detection limit of the sensor for anti-DNP is 9.5x10~(-10) M.