Development and use of optical sensors in modern analytical chemistry

Abstract

A successful long-term high resolution imaging experiment in marine sediments was performed (17 days within the sample; Paper I). The time correlated calibration procedure was evolved to include parametric sigmoidal and logarithmic functions to provide three of the best performing (optical) pH sensors available up to date (Papers II, III and IV), precision of these sensors were in the 0.0029 – 0.0057 pH units range. New pH sensors have been developed using three different immobilization techniques (Papers II, III and IV). The first experiments using a pH optode to image cellular responses were demonstrated (Paper III). A long (over 3 pH units) linear dynamic range (for an optode) with high performance was shown (Paper IV). Possibly a simple linear normalization method for salinity within the sample matrix was realized (Paper IV). Photoacidity and its change due to immobilization was recognized and utilized as an important feature for optical pH measurements (Paper II). A plasmon enhancement/quenching based fluorescent technique using functionalized gold nanoparticles was developed and implemented on a co-extraction based ammonium sensor (Paper V). This technique demonstrated a limit of detection three orders of magnitude better than previous ammonium sensors (LOD = 1.7 nM vs. ~ 1 µM), and can directly be implemented on more than 25 other cationic species.