Logic Control of Enzyme-Like Gold Nanoparticles for Selective Detection of Lead and Mercury Ions

Abstract

Functional logic gates based on lead ions (Pb(2+)) and mercury ions (Hg(2+)) that induce peroxidase-like activities in gold nanoparticles (Au NPs) in the presence of platinum (Pt(4+)) and bismuth ions (Bi(3+)) are presented. The "AND" logic gate is constructed using Pt(4+)/Pb(2+) as the input and the peroxidase-like activity of the Au NPs as the output; this logic gate is denoted as "Pt(4+)/Pb(2+)(AND)-Au NPPOX". When Pt(4+) and Pb(2+) coexist, strong metallophilic interactions (between Pt and Pb atoms/ions) and aurophilic interactions (between Au and Pb/Pt atoms/ions) result in significant increases in the deposition of Pt and Pb atoms/ions onto the Au NPs, leading to enhanced peroxidase-like activity. The "INHIBIT" logic gate is fabricated by using Bi(3+) and Hg(2+) as the input and the peroxidase-like activity of the Au NPs as the output; this logic gate is denoted as "Bi(3+)/Hg(2+)(INHIBIT)-Au NPPOX". High peroxidase-like activity of Au NPs in the presence of Bi(3+) is a result of the various valence (oxidation) states of Bi(3+) and Au (Au(+)/Au(0)) atoms on the nanoparticle's surface. When Bi(3+) and Hg(2+) coexist, strong Hg-Au amalgamation results in a large decrease in the peroxidase-like activity of the Au NPs. These two probes (Pt(4+)/Pb(2+)(AND)-Au NPPOX and Bi(3+)/Hg(2+)(INHIBIT)-Au NPPOX) allow selective detection of Pb(2+) and Hg(2+) down to nanomolar quantities. The practicality of these two probes has been validated by analysis of Pb(2+) and Hg(2+) in environmental water samples (tap water, river water, and lake water). In addition, an integrated logic circuit based on the color change (formation of reddish resorufin product) and generation of O2 bubbles from these two probes has been constructed, allowing visual detection of Pb(2+) and Hg(2+) in aqueous solution.

A Simple Paper-Based Colorimetric Device for Rapid Mercury(II) Assay

“…Recently, many works have discovered that mercury ions could interact with other metal nanoparticles to form bimetallic NPs4748. In addition, it was also confirmed that the citrate around the surface of metal NPs was essential to promote the process of these combinations.…”

A Highly Sensitive Colorimetric Method for Copper Ions Detection Based on Controlling the Peroxidase-like Activity of Au@Pt Nanocatalysts

“…3 Recently, many metallic nanoparticles with enzyme-like activity, termed as "enzyme mimics", have attracted considerable interest. 17 These enzyme mimics have demonstrated broad application in detecting various targets, such as metal ions, 18,19 anions, [20][21][22] small molecules [23][24][25] and nucleotide acid, 26 etc. Among various metallic nanoparticles, the (gold core)@ (platinum shell) nanoparticle possessed unique catalytic properties and attracted special attention.…”

Honeycomb-like nitrogen-doped porous carbon supporting Pt nanoparticles as enzyme mimic for colorimetric detection of cholesterol

“…Therefore, in recent years, much effort has been devoted to the construction of novel artificial enzymes as highly stable and low-cost alternatives to natural enzymes. A series of inorganic nanomaterials including Au NPs [3], Fe 3 O 4 NPs [4], Co 3 O 4 NPs [5], V 2 O 5 nanowires [6], carbon dots [7], graphene oxide [8], single-walled carbon nanotubes [9] and metallic nanocomposites [10] have been found to present unexpected enzyme-like activities. As the most known one, noble metal platinum (Pt) is chemically inert at bulk scales but can serve as the important catalysts at nanoscales because of their unique size, shape and the increased specific surface area [11].…”