Fluorescence quenching amplification in silica nanosensors for Au3+. 
In this study silica nanoparticles (SiNPs) were covalently modified by the fluorescence ligand 2-((7-oxo-7H- furo [3, 2-g] chromen-9-yl) oxy)-N-(3-(triethoxysilyl) propyl) acetamide (CTPA) and provided an optical sensor allowing highly sensitive and selective detection for Au(3+).  The probe exhibited a dynamic response range for Au(3+) from 5.0 × 10(-7) to 1.0 × 10(-4) M, with a detection limit of 2.3 × 10(-8) M. Other alkali, earth alkali and transition metal ions, even those that exist in high concentration, had no significant interference with Au(3+) determination.