Hg Amalgam Research Articles

A colorimetric platform for sensitive sensing of Hg2+ and S2− based on Se-AuNPs with Hg2+-activated peroxidase-like activity

Herein, the selenium (Se) modified gold nanoparticles (Se-AuNPs) was synthesized using cerium doped carbon dots (Ce-CDs) as a reducing agent and template. As desired, Se-AuNPs displays enhanced peroxidase (POD)-like activity in the presence of Hg2+. The mechanism for the enhanced activity was attributed to the increased affinity between Se-AuNPs-Hg2+ and the substrate, in which Se and Au elements have a strong binding capacity to Hg2+, forming Hg–Se bonds and Au–Hg amalgam to generate more ·OH. This POD-like activity of Se-AuNPs-Hg2+ correlates with the colorimetric reaction by the catalytic reaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2. The oxidation of TMB was completely inhibited by the introduction of the reductive S2−. Based on the above findings, a strategy for the colorimetric detection of Hg2+ and S2− by Se-AuNPs was established with linear ranges of 0.33–66 μg/L and 0.625–75 μg/L, and low detection limits of 0.17 μg/L and 0.12 μg/L (3.3 δ/k), respectively. When the colorimetric probes for detection of Hg2+ and S2− was applied in environmental water samples, the recoveries were in the range of 90.3–108.0 %. This method will provide a new idea for the colorimetric detection strategy of Hg2+ due to the strong interaction between Hg and Se.

Use of Metallic Mercury in Artisanal Gold Mining by Amalgamation: A Review of Temporal and Spatial Trends and Environmental Pollution

The introduction of mercury (Hg) into the environment by anthropogenic activities has resulted in negative implications for ecosystem functions and human health. Unlike the legacy of huge environmental pollution left by historic gold rushes in several developed countries, gold-rich nations in the developing world are currently witnessing what could qualify as a “new gold rush”, conducted primarily by small-scale mining operators and characterized by the use of metallic Hg (Hg0) in the amalgamation process to extract gold from crude ores. Once introduced into the environment, Hg0 can undergo biogeochemical transformations to produce Hg species such as methyl-Hg, with well-established adverse impacts on living organisms. This review summarizes published data on both historical and recent trends of the use of Hg0 in artisanal gold mining (AGM) on a global scale and emphasizes the impacts of AGM on the environment. To achieve this, we used citations from research conducted in North and South America, Europe, Asia, Africa, Australia, and New Zealand, obtained from several search engines and databases. Our findings show that, in addition to the well-known environmental and human health adverse effects of gold mining with Hg0, gold extraction by the Hg amalgamation technique is boosting the economy in parts of Africa, South America, and Asia. Unfortunately, this appealing aspect of AGM may not be easily halted, pending the creation of alternative employment. Therefore, there is a clear need for the development of safe and affordable gold extraction and purification technologies. Ultimately, the growth of this specific economic sector should be regulated to help protect both the environment and human health. Information compiled in this review should help to (i) improve the mapping of AGM-impacted soil and aquatic systems on a global scale and (ii) stimulate discussions and research on how to take down current barriers to the development and implementation of safe AGM methods.

Nano-mineral assemblages in mercury- and silver-contaminated soils: records of sequestration, transformation, and release of mercury- and silver-bearing nanoparticles.

Mercury-bearing nano-mineral assemblages (Hg-NMAs) are chemically and mineralogically heterogeneous, micrometer-sized aggregates of nanoparticles (NPs) found in contaminated soils and sediments. Although these NMAs control sequestration and release of Hg that is a global contaminant, our understanding is limited with respect to the conditions of different types of Hg-NMAs, the diversity of its minerals, the size distribution of its NPs and whether mineral replacement and alteration reactions in these NMAs result in the release of Hg-bearing NPs. For this purpose, Hg-NMAs in four sediment samples from the Guanajuato Mining District (GMD) in Mexico, a region that was polluted by Hg and silver (Ag) due to historical mining involving Hg amalgamation, are characterized at the micro- and nanoscale. Microscale examinations with SEM show that the majority of Hg-NMAs occurs in mineral surface coatings (MSC) and fillings in fractures within quartz grains and are enriched in Hg and sulfur (S) relative to Ag, and in S and selenium (Se) relative to chloride (Cl). Examinations at the nanoscale show that Hg-NMAs contain (a) residuals of the patio process such as amalgam phases and elemental Ag; (b) associations of Hg- and Ag-sulfide NPs with pyrite and marcasite; (c) associations of Hg- and Ag-sulfide NPs with goethite and clay minerals along the rims of the MSC. The latter minerals replaced the Fe-Si-rich matrix at high-water rock ratios most likely due to an increase in porosity during flooding of the Pastita River. Consequently, the rims are depleted in Hg-Ag-sulfide NPs relative to the unaltered Fe-Si-rich matrices indicating that changes in the physiochemical conditions of soils and sediments in the GMD can result in the release of Hg-Ag-bearing NPs. In this context, this study discusses whether release and dissolution of Hg-Ag-bearing NPs contribute to the recently observed elevated gaseous elemental Hg concentrations in the soil, interstitial air and ambient air, and to the fate and effects of Hg in local aquatic environments.

Mercury deposition to lake sediments near historic gold mines in northern Canada

Mercury (Hg) contamination in aquatic systems can lead to adverse human and environmental health outcomes. Yellowknife, a city in Canada’s Northwest Territories, is a historic mining community, with two large gold mines (Giant Mine and Con Mine) that used Hg amalgamation methods to extract gold between ∼1938 and 1960. We analyzed dated sediment cores from 20 small lakes to investigate the spatial and temporal Hg deposition patterns within 50 km of Giant Mine. Breakpoint analysis of the within-lake z-score normalized anthropogenic Hg flux indicates two significant time periods of changing emission rates. The first is a significant increase in Hg deposition rate (∼1925) during the time of gold exploration in the region and onset of Hg amalgamation (1938) and the second is a significant decrease in deposition rate that begins around the time of the cessation of Hg amalgamation at Giant Mine (∼1959). Sediment Hg concentrations exceeded the Canadian Council for Ministers of the Environment Interim Sediment Quality Guideline (ISQG) for Hg (0.17 mg/kg dw) in 55% of the lakes (n = 11) during mining (1948–1999). All lakes within 5 km of the Giant Mine roaster stack exceeded CCME ISQG during mining (n = 8), with a 4-fold increase in total Hg concentration observed during mining at these near-field (<5 km from stack) sites. We observed evidence of enriched Hg in near-field, mid-field, and far-field sites. The elevated sedimentary Hg concentrations during mining in near-field sites would have posed a hazard to human and wildlife health during the height of emissions, however the significant decrease in Hg concentrations since the closure of mines in the region demonstrate the potential for recovery in these aquatic ecosystems.

Miniaturized ascorbic acid assay platform based on point discharge atomic emission spectrometry coupling with gold filament enrichment

BackgroundMiniaturized microplasma-based atomic emission spectrometry (AES) has been extensively used for element analysis in recent years due to the advantages of low power consumption, low gas consumption, relatively low manufacturing and running cost, and the potential for real-time and field analysis. However, few applications in bioassay detection have been reported based on microplasma AES systems because of their relatively low sensitivity and the absence of indirect analytical strategies. It is still a challenge to develop a simple, sensitive, and portable microplasma-based AES bioassay approach. ResultsIn this work, a portable analytical system was designed based on point discharge chemical vapor generation atomic emission spectrometry (PD-CVG-AES) coupling with gold filament enrichment. The detection of ascorbic acid (AA) was realized indirectly by means of the highly sensitive analysis of Hg2+. The measurement was based on Ag + can decrease the concentration of Hg2+ by forming Ag–Hg amalgam in the presence of the reductant SnCl2, while AA can pre-reduce Ag + to Ag0, leading to the generation of silver nanoparticles (Ag NPs). The pre-reduce procedure can decrease the generation of Ag–Hg amalgam, resulting in the recovery of Hg2+ signal. The dissociative Hg2+ was further detected by PD-CVG-AES combination of gold filament enrichment, which significantly improved the detection sensitivity for both Hg2+ and AA. Under optimal conditions, the limit of detection (LOD) of AA is as low as 19 nM with a relative standard deviation (RSD, n = 5) of 0.7 %. SignificanceThe developed novel analytical strategy obviously broadens the application of microplasma-based AES, and it is well demonstrated by the determination of AA in several traditional Chinese medicines (TCMs), offering a higher level of sensitivity compared to current AA detection techniques. It has potential for future application in point-of-care testing (POCT) assays.

Tuning Chemical Interface Damping: Competition between Surface Damping Pathways in Amalgamated Gold Nanorods Coated with Mesoporous Silica Shells.

The mechanism of mercury (Hg) amalgamation in gold nanorods coated with a mesoporous silica shell (AuNRs@mSiO2) and the effect of chemical treatments on the localized surface plasmon resonance (LSPR) spectral changes in single amalgamated AuNRs@mSiO2 remains unclear. In this study, we investigated Hg amalgamation and inward Hg diffusion in single AuNRs@mSiO2 without structural deformation via dark-field scattering spectroscopy and X-ray photoelectron spectroscopy. Then, we investigated the chemisorption of thiol molecules on single amalgamated AuNRs@Hg-mSiO2. Unlike previous studies on single AuNRs, the thiolation on single AuNRs@Hg-mSiO2 resulted in a redshift and line width narrowing of the LSPR peak within 1 h. To determine the chemical effect, we investigated the competition between two surface damping pathways: metal interface damping (MID) and chemical interface damping (CID). When we exposed amalgamated AuNRs@Hg-mSiO2 to 1-alkanethiols with three different carbon chain lengths for 1 h, we observed an increase in the line width broadening with longer chain lengths owing to enhanced CID, demonstrating the tunability of CID and LSPR properties upon chemical treatments. We also investigated the competition between the two surface damping pathways as a function of the time-dependent Au-Hg surface properties in AuNRs@Hg-mSiO2. The 24-h Hg treatment resulted in increased line width broadening compared to the 1-h treatment for the same thiols, which was attributed to the predominance of CID. This was in contrast to the predominance of MID under the 1-h treatment, which formed a core-shell structure. Therefore, this study provides new insights into the Hg amalgamation process, the effect of chemical treatments, competition between surface decay pathways, and LSPR control in AuNRs@mSiO2.

Metal ions-regulated chemical vapor generation of Hg2+:mechanism and application in miniaturized point discharge atomic emission spectrometry assay of oxalate in clinical urolithiasis samples

It is well known that the coexisting metal ions could significantly influence the atomic spectroscopy (AS) analysis. In this work, a cation-modulated mercury ions (Hg2+) strategy via chemical vapor generation (CVG) was developed for oxalate assay due to the phenomenon that the Ag + can significantly reduce the Hg2+ signal. The regulation effect was studied in depth via experimental investigations. Since Ag + can be reduced to silver nanoparticles (Ag NPs) by reductant SnCl2, the decrease of the Hg2+ signal is attributed to the formation of a silver-mercury (Ag–Hg) amalgam. Due to the oxalate can react with Ag + to generate Ag2C2O4, which can reduce the generation of Ag–Hg amalgam, a portable and low-power point discharge chemical vapor generation atomic emission spectrometry (PD-CVG-AES) system was constructed to quantify the content of oxalate via monitoring the signal of Hg2+. Under optimal conditions, the limit of detection (LOD) was as low as 40 nM in the range of 0.1–10 μM for oxalate assay, while exhibiting good specificity. This method was applied to quantitative oxalate in 50 clinical urine samples of urinary stones patients. The levels of oxalate detected in clinical samples were consistent with clinical imaging results, which is promising for point-of-care testing in clinical diagnosis.

Improved refractive index sensitivity of localized surface plasmon resonance inflection points in amalgamated gold nanorods with mesoporous silica shell

Mesoporous silica coated gold nanorods (AuNRs@mSiO2) are very promising as multifunctional localized surface plasmon resonance (LSPR) sensors. Here, we described the refractive index (RI) sensitivities of single AuNRs@mSiO2 before and after mercury (Hg) amalgamation without their structural deformation. The amalgamated AuNRs@mSiO2 showed significant improvement in the RI sensitivity than the AuNRs@mSiO2 before the Hg amalgamation with the respect to RI changes of local environments. LSPR scattering inflection points (IFs) were then investigated to determine the LSPR sensing performance of single AuNRs@mSiO2 before and after Hg amalgamation. The RI sensitivity at the LSPR IF in the low-energy side was higher than the wavelength shifts in the conventional LSPR maximum peak. Furthermore, the amalgamated AuNRs@mSiO2 exhibited better RI sensitivity at the LSPR IFs than non-amalgamated AuNRs@mSiO2. Thus, we provide a deeper understanding of how Hg amalgamation affects RI sensitivity in single AuNRs@mSiO2.

Influence of mercury amalgamation on three‐dimensional orientation of single gold nanorods coated with mesoporous silica shell

AbstractHerein, we performed single‐particle studies to reveal three‐dimensional spatial orientational changes in the AuNR cores coated with mesoporous silica shell (AuNRs@mSiO2) following mercury (Hg) amalgamation. Defocused orientation imaging technique was used to determine the tilting angle of single AuNR cores after Au–Hg amalgam formation. Single amalgamated AuNR cores inside the silica shell were randomly tilted between 0° and 20° with respect to the glass slide on which they were deposited; no orientational changes were observed for AuNRs@mSiO2 following Hg amalgamation. This study will help in better understanding the effect of silica shell on the morphological and orientation alterations of single AuNRs@mSiO2 induced by Hg amalgamation.

Widespread elevated concentrations of gaseous elemental mercury in Guanajuato, Mexico, centuries after historical silver refining by mercury amalgamation

Silver (Ag) production in Hispanic America between the 16th and 19th centuries is thought to be one of the largest sources of anthropogenic mercury (Hg) emissions in history. Recent reviews of the chemistry behind the patio process, which used Hg amalgamation to extract Ag from ore, reveal that a large amount of the Hg may not have been immediately released to the atmosphere; instead, it may have been captured in the form of calomel (Hg2Cl2, in which Hg exists as monovalent HgI) and remained in the local environment. Here we show that Hg used in the patio process centuries ago in the Guanajuato Mining District of Mexico continues to elevate present-day concentrations of gaseous elemental mercury (GEM) throughout the region. In the ground-level air, GEM ranged from 8 to 454 ng m−3, exceeding the Northern Hemispheric average (~1.4 ng m−3) by up to two orders of magnitude. Much higher concentrations, up to 44,700 ng m−3, were found in the interstitial air of reprocessed mineral wastes, sediment, and soil. These highly elevated present-day GEM values are due, at least in part, to the disproportionation of legacy calomel, as supported by the presence of HgI in the reprocessed wastes and by the GEM release pattern from calomel disproportionation. Our results imply that the contribution of historical Ag refining to atmospheric Hg emissions must be re-evaluated to account for calomel and its subsequent disproportionation and releases of GEM to the present-day.

Single-particle spectroelectrochemistry: electrochemical tuning of plasmonic properties via mercury amalgamation in mesoporous silica coated gold nanorods without structural deformation.

This paper elucidates the mercury (Hg) amalgamation induced by electrochemical reduction on gold nanorods coated with mesoporous silica shell (AuNRs@mSiO2) using single-particle spectroelectrochemistry. First, the silica shell significantly enhanced the structural stability of AuNR cores after Hg amalgamation with the application of linear sweep voltages (LSVs). Thus, we were able to focus on the spectral changes of AuNRs@mSiO2 induced by the deposition of Hg without the disturbance of structural deformation, which also strongly affects localized surface plasmon resonance (LSPR) properties. Second, following the application of LSVs in the presence of Hg2+, a remarkable blueshift of the LSPR peak was observed, caused by the lowering of the work function due to the Hg adsorption, donating electron density to Au. Furthermore, the LSPR linewidth also dramatically increased after the Hg deposition with LSV. Lastly, the evolution of the Hg amalgamation process was directly observed by monitoring real-time LSPR peaks and LSPR linewidth shifts of a single AuNRs@mSiO2 in the Hg solution according to the application of the electrochemical potential. Moreover, the results showed the possibility of the in situ tuning of the LSPR properties of AuNRs@mSiO2 by Hg deposition via electrochemical potential manipulations without the disturbance of the structural variations of AuNR cores.

Single-particle study: effects of mercury amalgamation on morphological and spectral changes in anisotropic gold nanorods.

This study investigated the amalgamation of gold nanorods (AuNRs) exposed to Hg(II) solution and its effects on structural and spectral changes in single AuNRs using scanning electron microscopy and total internal reflection scattering microscopy. First, Hg adsorption on AuNR surfaces formed AuNRs@Hg core-shell structures. Afterwards, they transformed to AuNRs@AuHg alloy shell structures in air due to the slow inward diffusion of Hg over time. The aspect ratio (AR) of the AuNRs@AuHg formed by the amalgamation was significantly decreased compared to that of bare AuNRs. Furthermore, the Hg coating on AuNRs induced a dramatic blue shift of the localized surface plasmon resonance (LSPR) peak and linewidth broadening, followed by a red shift and linewidth narrowing of the LSPR peak due to inward diffusion of Hg into the AuNR core. Finally, we investigated the effects of oxygen plasma treatment on the structural changes of AuNRs@AuHg and found that their AR was a decreasing function of the plasma treatment time. More notably, a major structural change was observed 5 min after the plasma treatment. Therefore, fundamental information on the relationship among amalgamation process, plasma treatment time, structural change, and LSPR peak and linewidth is provided at the single-particle level.

Highly Electrocatalytic Conversion and Separation of Organometallic Ions to Vapor on an Au-Modified Nickel Foam Cathode: A Classic Application for Mercury Speciation Analysis at the μg/L Level

A simple, accurate, and sustainable electrocatalytic conversion strategy has been used for the speciation analysis of trace mercury. An Au- or Ag-modified nickel foam electrode (Au/NFE or Ag/NFE) prepared by cyclic voltammetry was used first as a cathode for the gaseous conversion of organomercury. The mechanism of improving the electrochemical inertness of methylmercury is considered to be the migration of charge centers and the weakening of C–Hg bonds caused by the formation of Au–Hg amalgam. A large specific surface area, high catalytic activity, and low transport resistance allow an effective conversion of 0.1 μg L–1 level organomercury on the Au/NFE surface. The difference of gaseous conversion behavior under current control also provides a green way for the analysis of mercury speciation. A lower limit of detection (4.9 pg g –1 for Hg2+ and 5.5 pg g –1 for CH3Hg+), stronger anti-interference ability, more than 180 sample analysis capacities, and less than 8% signal fluctuation, importantly, confirmed that the electrocatalytic conversion technology based on the gold/silver-modified NFE is very suitable for the analysis of ultratrace methylmercury in complex matrix samples, such as animal and plant samples.

Source identification of atmospheric particle-bound mercury in the Himalayan foothills through non-isotopic and isotope analyses

This study reports on the sources of atmospheric particle-bound mercury (HgP) in less studied regions of Nepal based on the analysis of stable mercury (Hg) isotopes in aerosol samples from two neighboring areas with high and low anthropogenic emissions (Kathmandu and Dhulikhel, respectively) during 2018. Although the Indian monsoon and westerlies are generally regarded as the primary carriers of pollutants to this region via the heavily industrialized Indo-Gangetic Plain, the concentrations of total suspended particles (TSP) and HgP in Kathmandu were higher than those in Dhulikhel, thus suggesting a substantial contribution from local sources. Both isotopic (δ200Hg and Δ199Hg) and non-isotopic evidence indicated that dust, waste burning, and industrial byproducts (without Hg amalgamation) were the major sources of Hg in Kathmandu during the study period. Mercury may have been transported via air masses from Kathmandu to Dhulikhel, as indicated by the similar organic carbon/elemental carbon ratios and seasonal trends of TSP and HgP in these two locations. Local anthropogenic sources were found to contribute significantly to atmospheric Hg pollution through dust resuspension. Therefore, dust resuspension should be considered when evaluating the long-range transport of air pollutants such as Hg, particularly in anthropogenically stressed areas.

Challenging the traceability of natural gold by combining geochemical methods: French Guiana example

Considering the high economic importance and worldwide distribution of gold, the ability to identify its provenance is critical and challenging to ensuring a responsible supply chain from deposit to consumer, especially within conflict-affected areas. Here we present an innovative approach to trace the provenance of natural gold from French Guiana through a combination of geochemical and statistical methods. This approach is divided in three steps and allows the identification of illicit gold, the certification of the declared gold origin coming from legal operators and, in some cases, the identification of unknown gold. French Guiana was chosen as a demonstration case of our approach because it is a well-known conflict-affected area where illegal mining is widespread. In the first step, we showed that the use of illegal Hg amalgamation can be easily revealed by looking the gold grain morphology with an optical microscope or by detecting the Hg with laser-induced breakdown spectroscopy that allow direct detection on the field. In the second and principal step, we demonstrated that a declared provenance of gold can be certify with a high degree of confidence by measuring the Ag content of a gold grain population and by checking it against a database with the Kolmogorov-Smirnov statistic. In the final step that allows the identification of the origin of unknown gold, we used (i) the content of minor elements (Cu and Hg), (ii) the identification of mineral inclusions and their relative proportions within samples and (iii) the trace element composition of natural gold grains determined by LA-ICP-MS and coupled with a permutational multivariate analysis of variance and a similarity percentage analysis. This method allows the identification of the provenance of 69% of the gold samples; the provenance of other gold populations (31%) cannot be identified because of their geological similarity with other groups. The traceability of natural gold can be guaranteeing with our innovative approach, in particular by certifying declared gold population provenance. Further challenges to be addressed will be the implementation of such approach in others conflict-affected regions to support the global supply chain of gold.

Defective molybdenum disulfide nanosheet for elemental mercury capture in simulated flue gas

Two-dimensional transition-metal dichalcogenides have gained increasing concerns because of their distinct structural features and also display great potential in mercury removal. Herein, a defect-rich MoS2 nanosheet is synthesized by using hydrothermal method and applied for adsorptive capture of elemental mercury (Hg0) in simulated flue gas at low temperature. It exhibits excellent Hg0 removal performance due to its ultra-thin lamellar and defective structures with ample exposed adsorption sites. The Hg0 removal efficiency of the defective MoS2 nanosheet is all above 93% when the reaction temperature is within 25–150 °C. Besides, presence of NO has no influence on Hg0 removal, while SO2 subtly reduces the Hg0 removal efficiency due to competitive adsorption. Mo4+, S2−, and S22− ions take part in the Hg0 removal process, which transfers Hg0 into Mo–Hg amalgam and HgS. The process of Hg0 adsorption on the defective MoS2 nanosheet obeys the pseudo-first-order and pseudo-second-order kinetic model.

Aggregation-free optical and colorimetric detection of Hg(II) with M13 bacteriophage-templated Au nanowires

An optical and colorimetric biosensor comprising gold nanowires (Au NWs) templated with genetically engineered M13 bacteriophages expressing a specific Au binding peptides tyrosine–glutamic acid–glutamic acid–glutamic acid (Y3E) is fabricated by silver nitrate and surfactant-mediated biomineralization process. The diameter of the Y3E–Au NWs is around 10 nm and an oriented growth mechanism is identified for the continuous growth of the NWs by interconnecting M13 bacteriophages. The flexible Au NWs have formed an enriched Hg(II) binding sites on its surface and the surface-coated silver nanophase functions as a receptor for more efficient Hg(II) binding. Amalgamation-based colorimetric and optical Hg(II) biosensing of Au NWs are scrutinized in the presence of wild-type M13 bacteriophage-templated Au NWs and spherical Au nanoparticles. It is demonstrated that in comparison with the spherical Au nanoparticles, Y3E–Au NWs exhibits an aggregation-free optical and colorimetric sensor for Hg(II). Mechanistic investigation for the aggregation-free sensor and the Au–Hg amalgam crystals are carried out using TEM, STEM-EDX and XPS analyses.

Synthesis, Characterization and Reactivity of Nitrosyl Ruthenium Complexes with the Non-stereoidal Anti-inflammatory Diflunisal

The Na2[Ru(NO)Cl3 (df)] (I) and cis-[Ru(NO)(df)(cyclen)]Cl2 (II) complexes (df=diflunisal (5-(2,4-difluorophenyl)-2-hydroxybenzoic acid, cyclen=1, 4, 7, 10-tetraazacyclododecane) have been synthesized and characterized by elemental analysis, electronic (UV-Vis) and vibrational (FTIR) spectroscopic techniques. FTIR data suggests different modes of coordination of the ligand diflunisal in these complexes, i.e., coordinated in the bidentate form in the compound I and in the monodentate form in the compound II, and that df is coordinated to ruthenium by carboxylate group in a monodentate mode for both complexes. The FTIR spectra also display v(NO) at 1880 cm-1 and 1892 cm-1 for I and II, respectively, indicating a nitrosonium (NO+) character. Electronic spectra suggest that df is coordinated to the metal center in both complexes in catecholate form. Detailed electrochemical studies showed that complexes I and II display {RuNO}6/7 process at -420 mV and at -400 mV (vs. Ag/AgCl) respectively, and df ligand is oxidized at 1120 mV and at 770 mV, respectively. Controlled potential electrolysis at -750 mV or chemical reduction with Zn(Hg) amalgam results in NO release from both complexes.

Photocatalytic reduction and scavenging of Hg(II) over templated-dewetted Au on TiO2 nanotubes

Au nanoparticles over TiO2 nanotubes strongly promote photocatalytic reduction/scavenging of Hg(ii) through the formation of Hg2Cl2 nanowires (or Au–Hg amalgams).

Synthesis of Calixarene-Capped Silver Nanoparticles for Colorimetric and Amperometric Detection of Mercury (HgII, Hg0).

Calixarene-functionalized water dispersible silver nanoparticles have been synthesized and characterized on the basis of UV–vis, IR, X-ray diffraction, and high-resolution transmission electron microscopy analysis, and their sensing properties toward metal ions have been investigated. They selectively detect Hg2+ and Hg0 in solution and vapor phases, respectively, with distinct color change. Interference study with mixture of metal ions revealed no interference from any other metal ions used in this study. Their mechanism of detection involved Hg2+-aided displacement of calixarene moiety from the surface of the functionalized nanoparticles, followed by the formation of Ag–Hg amalgam due to interaction of Hg2+ with Ag0 and also the formation of assembly of Ag0 nanoparticles by dipole–dipole interaction of the bare-surfaced nanoparticles. Electrochemical study revealed that with the aid of functionalized nanoparticles, Hg2+ can be detected amperometrically with high sensitivity. The detection limits obtained for Hg2+ by UV–vis study and amperometry are 0.5 nM (0.1 ppb) and 10 nM (2 ppb), respectively. The new material has been used to detect Hg2+ in aqueous real sample and Hg0 in soil sample.