Detection of mercury ions based on mercury-induced switching of enzyme-like activity of platinum/gold nanoparticles

Abstract

In this study, bimetallic platinum/gold nanoparticles (Pt/Au NPs) were found to exhibit peroxidase-like activity, and the deposition of mercury was found to switch the enzymatic activity to a catalase-like activity. Based on this phenomenon, we developed a new method for detecting mercury ions through their deposition on bimetallic Pt/Au NPs to switch the catalytic activity of Pt/Au NPs. Pt/Au NPs could be easily prepared through reduction of Au(3+) and Pt(4+) by sodium citrate in a one-pot synthesis. The peroxidase catalytic activity of the Pt/Au NPs was controlled by varying the ratios of Pt to Au. The Pt(0.1)/Au NPs (prepared with a [Au(3+)]/[Pt(4+)] molar ratio of 9.0/1.0) showed excellent oxidation catalysis for H(2)O(2)-mediated oxidation of Amplex® Red (AR) to resorufin. The oxidized product of AR, resorufin, fluoresces more strongly (excitation/emission wavelength maxima ca. 570/585 nm) than AR alone. The peroxidase catalytic activity of Pt(0.1)/Au NPs was switched to catalase-like activity in the presence of mercury ions in a 5.0 mM tris(hydroxymethyl)aminomethane (Tris)-borate solution (pH 7.0) through the deposition of Hg on the particle surfaces owing to the strong Hg-Au metallic bond. The catalytic activity of Hg-Pt(0.1)/Au NPs is superior (by at least 5-fold) to that of natural catalase (from bovine liver). Under optimal solution conditions [5.0 mM Tris-borate (pH 7.0), H(2)O(2) (50 mM), and AR (10 μM)] and in the presence of the masking agents polyacrylic acid and tellurium nanowires, the Pt(0.1)/Au NPs allowed the selective detection of inorganic mercury (Hg(2+)) and methylmercury ions (MeHg(+)) at concentrations as low as several nanomolar. This simple, fast, and cost-effective system enabled selective determination of the spiked concentrations of Hg(2+) and MeHg(+) in tap, pond, and stream waters.

Highly sensitive and specific colorimetric detection of cancer cells via dual-aptamer target binding strategy

“…The bimetallic PtAu nanoparticle (PtAu NP ) has been confirmed to present excellent peroxidase property on catalyzing fluorogenic substrate (Tseng et al, 2012). In our investigation, PtAu NP was synthesized according to the reported method and was used to catalyze the colorimetric reaction of TMB in the presence of H 2 O 2 .…”

“…With increasing the ratio of Pt and Au from Pt 0.5 Au NP to Pt 1 Au NP , the peroxidase activity of bimetallic PtAu NP increases correspondingly. With further increasing the ratio of Pt, however, the peroxidase activity of PtAu NP significantly decreases, which is ascribed to the decreasing of active sites on the particle surface (Tseng et al, 2012). So the Pt 1 Au NP was selected as catalyst to the signal generator.…”

“…The PtAu NP was synthesized with citrate reduction according to previously reported method (Tseng et al, 2012). 100 mL aqueous solution of HAuCl 4 (0.9 mM) and H 2 PtCl 6 (0.1 mM) was stirred under heating in a round-bottom flask.…”

Spectrophotometric determination of mercury(II) ions based on their stimulation effect on the peroxidase-like activity of molybdenum disulfide nanosheets

“…Herein, inspired by the stimulation or inhibition effect on the peroxidase-like activity of various nanomaterials by heavy metal ions [24][25][26][27][28][29], we explored a spectrophotometric assay for the determination of Hg(II), based on its stimulating effect on the peroxidase-like activity of MoS 2 -NSs. The MoS 2 -NSs are found to act as a peroxidase mimic, capable of effectively oxidizing the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 .…”

Signal Amplification for Highly Sensitive Immunosensing

“…Metallic alloy nanomaterials with enzyme-like activities have also attracted great attentions due to their better catalytic properties than monometallic counterparts, such as Pt-Au nanoparticles [55], Au-Pd nanostructures [56] and AuPd bimetallic nanoprobe [57]. These metallic alloy nanomaterials with excellent electrocatalytic performance, large surface area and favorable biocompatibility provide ideal nanoprobes for electrochemical immunosensing.…”