A Sensitive Colorimetric Detection Method for Aluminium Ion (III) Based on Asymmetrically PEGylated Gold Nanoparticles

An effective , accurate and stable colorimetric detection method for aluminium ion (Al-3(+)) through chelation based on the large-sized gold nanoparticles (AuNPs) asymmetrically modified with polyethylene glycol (PEG) and citrate was developed. Initially, citrate-stabilized AuNPs with different sizes (13 nm, 26 nm , 38 nm) were synthesized to explore the correlation between particle dimensions and detection sensitivity. The detection limit of 38 nm AuNPs was as low as 1 mu mol/L by visual observation which demonstrated that sensitivity couold be improved by increasing the particle size. In the following, citrate-stabilized AuNPs were modified on the glass slide , through which some binding sites on the surface of AuNPs were concealed. The stabilizing agent PEG was introduced onto the exposed surface of AuNPs and characterized by laser dynamic scattering instrument (DLS) , field-Emission scanning electron microscopy (FE-SEM) , transmission electron microscopy (TEM) and energy dispersive spectrum (EDS) . The aggregation behavior was further adjusted in an oriented and controllable manner to form oligomers which could remain stable in aqueous solution for a long time. Such an asymmetrical modification could significantly improve the dynamic detection range (1 mu mol/L - 100 mmol/L) , and a linear correction curve (y = 0. 06485x +0.60851 , R-2 = 0.99) was obtained. Nine common metal ions were also investigated , which exhibited the good selectivity of detection system to Al3+. PEG and citrate modified AuNPs could be applied in the detection of spiked tap water sample.