Nanoparticle Based Sensors for the Detection of Mercury

Lead Research Organisation: University of Oxford
Department Name: Oxford Chemistry


Many natural gas reservoirs worldwide are contaminated with traces of naturally occurring mercury. Mercury is often present in its elemental form, although it can also be found as mercury sulphide (cinnabar), organo-mercury compounds or ionic halides (S.M WILHELM & n. Bloom 'Mercury in petroleum', Fuel processing technology 63 (2000) 1-27). The safety regulation of mercury wastes disposal imposed by the governments became increasingly strict after the Minamata disease, it was first recognised in Japan in 1956, where more than 2,200 victims were diagnosed as having Minamata disease from the lack of mercury treatment in wastewater before dumping it into the local river. In the US, hydrocarbon combustion was identified as the major anthropogenic sources of mercury emissions to the atmosphere. Mercury is corrosive to metals used commonly in heat exchangers, gas pipelines and storage tanks, and as environmentally hazardous element, it must be removed during petroleum production line before it enters the consumers market. It is important to quantify the mercury concentration since this determines how it is removed. The concentration of mercury within a gas stream is often determined by gas sampling and subsequent laboratory analysis such as purification and pre-concentration procedures. Since mercury often adsorbs on most surfaces once its cools down, the gas sampling method often leads to a significant error. Moreover, it requires professionally trained staff and a long analytical time. This project collaborates with Schlumberger and aims to develop a new mercury sensor. The Compton group has significant experience in the characterisation and electrochemistry of nanoparticles in general. The electrochemical approach of this project will utilise silver nanoparticles (AgNPs) and build on proof-of-concept experiments recently conducted within the group which show that Hg(0) and Hg(II) both react with the nanoparticle either in the case of Hg(0) via amalgam formation or for Hg(II) via galvanic reaction (Analytical Chemistry 2017 89 (13), 7166-7173). The size and capping agents of the AgNPs will be optimised and it is envisaged that by using a range of particle sizes a wider range of concentrations of Hg can be measured. The project firmly embraces two of the research areas identified within the EPSRC vision and strategy, in particular Analytical Science where the 'development of novel techniques... to analyse... chemical systems...' is sought explicitly and Sensors and Instrumentation with impact on the EPSRC research of Physical Sciences, Engineering, Healthcare and Energy. This project falls within the EPSRC Physical sciences research area.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509711/1 01/10/2016 30/09/2021
1950024 Studentship EP/N509711/1 01/10/2017 31/10/2020 Minjun Yang
Description The funding through this award has directly resulted in three already published research articles - one of which appears in Chemical Science with the award holder (MY) as the first author - and at least two more are expected before the close of the project.
Liquid mercury and compounds of mercury in other oxidation states are typically highly toxic and can be found either in nature or in anthropogenic emissions. The works revolves around electrochemical detection of mercury via experimental with numerical simulation to provide physicochemical insights in the bottom up development of electrochemical sensors for the sensitive and selective detection of Hg in different forms. In particular:
• This award led to the development of a novel electrochemical method for the detection of mercury sulphide, a water insoluble mercury mineral commonly found in nature. The insoluble nature of this mineral hinders the electrochemical detection with commonly used techniques; this was overcome by the use of a novel 'carbon composite electrode'. The latter binds the mercury sulphide sample to form a composite which provides electrical conductivity and mechanical rigidity facilitating the redox chemistry over a wide potential window. Moreover, this methodology has the ability to generically facilitate electrochemical sensing of other insoluble materials. This opened up research possibilities including a collaborative project on superconductor ßFe1+xSe which led to a publication, with MY as co-author, in the prestigious journal Angewandte Chemie International Edition.
• The funding directly led to the discovery and electrochemical detection of molecular mercury (II) hydroxide, Hg(OH)2, which was formed in the aqueous phase by virtue of insonation of liquid mercury in water. This new discovery is significant as no spectroscopic techniques report the detection of molecular mercury (II) hydroxide in aqueous solution so opening up a new field research in developing electrochemical sensors for molecular mercury compounds. Furthermore, insonation of the biphasic mixture led to the formation of Hg@HgO core-shell nanoparticles stable for days and characterised by X-ray diffraction for the first time. The current focus is to investigate the application of the newly discovered Hg@HgO core-shell nanoparticles and to develop the electrochemical sensing capability for a finite concentration of molecular mercury (II) hydroxide in the environment including the use of silver nanoparticles as outlined in the project abstract (unpublished work).
• Beyond the experimental projects, simulations are essential to provide new physical insights to the fundamental electrochemical processes including surface adsorption; the latter interactions have profound effects on voltammetry involving liquid mercury. The effects of surface adsorption coupled with mass transport were simulated with mathematical models built using C++; the resulting voltammograms are drastically different for aqueous or for surface redox couple involving adsorption. The latter is affected by non-ideal surface interactions with possibilities of phase transitions seen on the voltammetric timescale. The simulation results are completely general with the aim of impacting a wider scientific community and to provide theoretical grounds for experimentalists without knowledge of simulation. This led to one simulation article published and under construction.
Exploitation Route The research and outcomes achieved under this award have been demonstrated by the three articles accepted for publication. One of which is published in Chemical Science (open access) and highlighted by Chemistry World Magazine (link above); the latter allows knowledge transfer of the work to a non-academic community and increase the awareness of environmental mercury pollution which may exist as molecular mercury (II) hydroxide.
Sectors Chemicals,Environment