Polyallylamine-chlorophyllide derivatized gold and silver nanoparticles as optical probes for sensor applications

In this paper we report the polyallylamine-chlorophyllide (PAH-Chl) derivatized spherical gold and silver nanoparticles (AuNp, AgNp). The TEM micrographs showed that zero-valence Au and Ag nanoparticles are stable and well-dispersed in solution. The AuNp (∼25 nm) are bigger than the AgNp (∼20 nm) and the metallic core of AuNp is darker than the less dense AgNp shell. Interestingly, the width of polymer (PAH-Chl) halo surrounding the nanoparticles are significantly different, suggesting a higher deposit of the polymer on AuNp (10 nm) than on AgNp (2 nm).The absorption spectra showed that the Qy band (634 nm) grew steadily with the concentration of Zn(II) and the effect was more pronounced in AuNp/PAH-ChlZn system. The absorbance response at 634 nm, with increasing Zn(II) concentration showed a linear range response up to 400 ppm. The linear regression equation for AuNp/PAH-ChlZn system is expressed as A = 4.0 × 10−2 ppm−1 x + 8.1 × 10−2, R2: 0.9987. The sensitivity for Zn detection is 4.0 × 10−2 ppm−1, four times higher than the PAH-ChlZn complex in solution. The detection limit diminished from 38 ppm to 3.8 ppm of Zn(II) with gold nanoparticles.