Mesoporous Silica-gold Films for Straightforward, Highly Reproducible Monitoring of Mercury Traces in Water

Abstract

Trace-level detection of mercury in waters is connected with several complications including complex multistep analysis routines, applying additional, harmful reagents increasing the risk of contamination, and the need for expensive analysis equipment. Here, we present a straightforward reagent-free approach for mercury trace determination using a novel thin film sampling stick for passive sampling based on gold nanoparticles. The nanoparticles supported on a silicon wafer and further covered with a thin layer of mesoporous silica. The mesoporous silica layer is acting as a protection layer preventing gold desorption upon exposure to water. The gold nanoparticles are created by thermal treatment of a homogenous gold layer on silicon wafer prepared by vacuum evaporation. This gold-covered substrate is subsequently covered by a layer of mesoporous silica through dip-coating. Dissolved mercury ions are extracted from a water sample, e.g., river water, by incorporation into the gold matrix in a diffusion-controlled manner. Thus, the amount of mercury accumulated during sampling depends on the mercury concentration of the water sample, the accumulation time, as well as the size of the substrate. Therefore, the experimental conditions can be chosen to fit any given mercury concentration level without loss of sensitivity. Determination of the mercury amount collected on the stick is performed after thermal desorption of mercury in the gas phase using atomic fluorescence spectrometry. Furthermore, the substrates can be re-used several tens of times without any loss of performance, and the batch-to-batch variations are minimal. Therefore, the nanogold-mesoporous silica sampling substrates allow for highly sensitive, simple, and reagent-free determination of mercury trace concentrations in waters, which should also be applicable for on-site analysis. Successful validation of the method was shown by measurement of mercury concentration in the certified reference material ORMS-5, a river water.

Photoactive Titanium Dioxide Films with Embedded Gold Nanoparticles for Quantitative Determination of Mercury Traces in Humic Matter-Containing Freshwaters

“…Therefore, the development of a more sophisticated structure of the active film covered by a protective layer was necessary. The latter has already been shown in a recent work of the authors, where we reported about mesoporous silica–gold films for efficient chemical-free Hg trace analysis [ 34 ]. Parameters found optimum for mercury accumulation in terms of film thickness and mesopore diameter in that study are used as design targets for the current study.…”

“…These containers were filled with either 6 mL or 8 mL of a Hg 2+ -containing aqueous solution, and accumulation was performed at room temperature on an orbital shaker at 230 rpm for 5 min. These parameters were tested in our previous study and found to be optimum [ 34 ]. Hg concentrations ranged from 5 to 25 ng L −1 .…”

Growth and Functionalization of Particle-Based Mesoporous Silica Films and Their Usage in Catalysis

“…Mesoporous silica films are of large interest in applications such as sensing, catalysis, and drug delivery [1,2,3,4,5,6]. Their large surface area, tunable pore characteristics, and versatile surface functionality are attractive features.…”

Special Issue “Synthesis and Applications of Functionalized Gold Nanosystems”

“…Indeed, the contributions that are grouped in this Special Issue provide a good idea of the directions in which the field is moving. The contributions range from the synthesis of special nanosystems [1,2,3] to their utilization for sensing [4,5,6,7] and magnetic resonance imaging [8,9], surface recognition [10], and bioapplications [11].…”

“…Mercury is well known for its neurotoxicity. To tackle the problem of its detection, Leopold, Linden et al [6] present a straightforward reagent-free approach for mercury traces determination using a novel thin film for passive sampling based on gold nanoparticles. Dissolved mercury ions are extracted from a water sample, e.g., river water, by incorporation into the gold matrix in a diffusion-controlled manner.…”