Functionalized Silver Nano-Sensor for Colorimetric Detection of Hg2+ Ions: Facile Synthesis and Docking Studies

Abstract

In the present study, we describe the facile synthesis of silver nanoparticles (AgNPs) and their nanostructures functionalized with 2-aminopyrimidine-4,6-diol (APD-AgNPs) for Hg²⁺ ion detection. The promising colorimetric response of APD-AgNPs to detect Hg²⁺ ions was visible with naked eyes and spectroscopic changes were examined by using a UV-Visible spectrophotometer. The aggregation of APD-AgNPs upon addition of Hg²⁺ ions was due to the chelation effect of the functionalized nanostructures and results in a color change from pale brown to deep yellow color. The probing sensitivity was observed within five minutes with a detection limit of about 0.35 µM/L. The TEM images of APD-AgNPs showed polydispersed morphologies with hexagonal, heptagonal and spherical nanostructures with an average size between 10 to 40 nm. Furthermore, the sensing behavior of APD-AgNPs towards Hg²⁺ ions detection was investigated using docking and interaction studies.

Keywords: Hg2+ detection; TEM analysis; docking studies; silver nanoparticles.

Scheme 1

Synthetic pathway of APD-AgNPs (top) and its Hg²⁺ sensing property (bottom).

Figure 1

X-ray diffraction spectrum of APD-AgNPs-Hg²⁺ complex.

Figure 2

Absorption spectra showing (a) SRP bands of APD-AgNPs and (b) APD-AgNPs-Hg²⁺ complex. Inset image showing colorimetric digital picture of APD-AgNPs and APD-AgNPs-Hg²⁺ complex.

Figure 3

(a) Electronic absorption spectra of APD-AgNPs solutions with various concentrations of Hg²⁺ in the range of 0 to 65 µM L⁻¹ increasing in steps of 5 µM L⁻¹; (b) Linear relationship between the absorbance intensity of APD-AgNPs versus Hg²⁺ ion concentration at 538 nm.

Figure 4

TEM images of (a) APD-AgNPs, (b) APD-AgNPs-Hg²⁺ complex and (c) HRTEM of APD-AgNPs-Hg²⁺ complex with SAED image (inset).

Figure 5

Image showing the interaction of Hg²⁺ with N1, N3, N4 and N9 of APD-AgNPs ring with the bond length of 3.655 Å, 3.858Å, 3.480 Å and 3.257 Å respectively, forming a APD-AgNPs-Hg²⁺ complex.