Multifunctional modified silver nanoparticles as ion and pH sensors in aqueous solution.

Silver nanoparticles capped with mercaptoacetic acid and 2-aminoethanethiol short-chain alkanethiols were prepared by a one-step method in aqueous solution for monitoring pH and a range of heavy metal ions. The mode of transduction is optical, based on the change in aggregation of the nanoparticles in solution. Because of the different ionic interactions between the modified nanoparticles, these nanoparticle sensors can rapidly detect Pb(2+), Cu(2+) and Fe(2+), with detection limits as low as 1 × 10(-5) M, 5 × 10(-7) M and 5 × 10(-5) M respectively, as well as having the ability to detect Cu(2+) ions from Pb(2+) and Fe(2+). Furthermore, the same functionalised nanoparticles are also sensitive to pH; exhibiting a good linear dynamic response between pH 1 and 10.