Fluorescent silica nanoparticles and glass surfaces for the detection and removal of Pd(II) ions

Fluorescent chemosensors based on silica nanoparticles and silicate glass slides were well designed and prepared. The as-prepared fluorescent silica particles and glass slides exhibited highly selective sensing and absorbing abilities to Pd²⁺ ions in aqueous phase. SiO₂ nanoparticles were first synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS), and then –NH₂ groups were introduced to silica by treating with 3-aminopropyltriethoxysilane (APTES). Subsequently, 4-amino-1,8-naphthalic anhydride (ANA) was incorporated with the reaction of –NH₂ groups. Finally, salicylaldehyde (SA) was introduced by the reaction between amino groups in ANA and the –CHO groups in SA. Thus, the fluorescent silica nanoparticles were obtained. This method was expanded to prepare fluorescent silicate glass slides. Upon the addition of Pd²⁺ ions, the fluorescence quenched immediately. These chemosensors were selectively sensitive to Pd²⁺ ions as low as 10 μM. The absorption efficiency of fluorescent nanoparticles and glass slides for Pd²⁺ reached to 38.38 and 27.50 %, respectively. And the chemosensors also could be easily recycled and reused for at least five times. Fluorescent silica nanoparticles with only ANA or SA (not ANA and SA together) also exhibited the sensing ability to Pd²⁺ ions; however, it showed the shortage of Pd²⁺ ions selectivity. It suggested that it is necessary to introduce both ANA and SA for the high sensitivity and selectivity to Pd²⁺ ions.