Real-time Registration of Organic Molecules with Low Molecular Weight and Different Functionality: LSPR vs. SPPR

This work is a comparative study of real-time detection of organic molecules with ultimately small weight and different functionality (urea, 60 Da and thiourea, 76 Da) using optoelectronic sensors based on LSPR (localized surface plasmon resonance ) in noble metal nanostructures and SPPR (surface plasmon-polariton resonance) in noble metal thin films. The results of theoretical modeling of LSPR and SPPR response for molecular layers with thickness up to 350 nm reveal strong difference in kinetics of sensor's response. It has been experimentally determined that thiourea detection limit for LSPR technique is about 0.0002 mM/L while for SPPR it is 0.0008 mM/L, and for urea these limits are respectively 10 mM/L and 2.5 mM/L.