Colorimetric Detection of Mercury Species Based on Functionalized Gold Nanoparticles

Abstract

The speciation analysis of heavy metal pollutants is very important because different species induce different toxicological effects. Nanomaterial-assisted optical sensors have achieved rapid developments, displaying wide applications to heavy metal ions but few to metal speciation analysis. In this work, a novel colorimetric nanosensor strategy for mercury speciation was proposed for the first time, based on the analyte-induced aggregation of gold nanoparticles (Au NPs) with the assistance of a thiol-containing ligand of diethyldithiocarbamate (DDTC). Upon the addition of mercury species, because Hg-DDTC was more stable than Cu-DDTC, a placedisplacement between Hg species and Cu 2+ would occur, and thereby the functionalized Au NPs would aggregate, resulting in a color change. Moreover, by virtue of the masking effect of ethylenediaminetetraacetic acid (EDTA), the nanosensor could readily discriminate organic mercury and inorganic mercury (Hg 2+ ), and it is thus anticipated to shed some light on the colorimetric sensing of organic mercury. So, a direct, simple colorimetric assay for selective determination of Hg species was obtained, presenting high detectability, such as up to 10 nM for Hg 2+ and 15 nM for methylmercury. Meanwhile, the strategy offered excellent selectivity toward mercury species against other metal ions. The simple, rapid, and sensitive label-free colorimetric sensor for the determination of Hg species provided an attractive alternative to conventional methods, which usually involve sophisticated instruments, complicated processes, and long periods of time. More importantly, by using mercury as a model, an excellent nanomaterial-based optical sensing platform can be developed for speciation analysis of trace heavy metals, which can lead to nanomaterials stability change through smart functionalization and reasonable interactions.

Gold nanoparticles as efficient sensors in colorimetric detection of toxic metal ions: A review

“…This Hg complex contains two residual thiol groups for Hg and one for organic mercury. As it is known that S groups have a strong affinity for Au, they easily replace the citrate ions on GNP surface leading to binding of Hg-DDTC complex on GNP surface leading to particle aggregation [76].…”

Gold nanoparticles as a localized surface plasmon resonance based chemical sensor for on-site colorimetric detection of arsenic in water samples

“…The reason for color change is possibly due to the inter-particle surface plasmon coupling caused by the aggregation of metal NPs [24]. This color change of NPs depends on the amount of analyte providing a platform for colorimetric based sensors for the detection of various types of substances including metal ions [25][26][27][28][29], iodide [30], proteins [31], sugars [32], bacteria [33], cancer cells [34], antibiotics [35] and DNA [36]. Cao et al demonstrated the analysis of heparin through the measurement of color change from red to blue after the aggregation of AuNPs when heparin is added to the solution [37].…”

Methods and recent advances in speciation analysis of mercury chemical species in environmental samples: a review

“…ICP-MS, [3,41,65] UV, [11,37,80] and DAD [14] are the commonly used detectors in CE. In non-chromatographic techniques, AFS, [40,69,70,82] volatile species generation flame less/flame atomization AFS (VSG-FL/FA-AFS), [81] ET-AAS, [5,17] CV-AAS, [68] ICP-MS, [66] ICP-OES, [82] and UV-vis [83][84][85][86] , MeHg, EtHg, and PhHg is almost comparable to the conventional methods. However, difficulty to discriminate the OrgHg species and its less applicability in complex matrix, the method become invalid at high cations concentration (like sea water samples), and yield false results in the presence of protein molecules (like in urine samples) are the main weaknesses of this technique.…”