Environmental chemistry and toxicology of mercury , Environmental chemistry and toxicology of mercury , کتابخانه مرکزی دانشگاه علوم پزشکی تهران

Environmental chemistry and toxicology of mercury

New applications of self-assembled monolayers of thiol compounds on gold electrodes are reviewed. They include: (i) exploitation of electrical control of self-assembly of thiol compounds for electrically-addressable immobilization of receptor molecules onto sensor arrays; (ii) a spreader-bar technique for formation of stable nanostructures; and, (iii) use of self-assembled monolayers as selective filters for chemical sensors.

New electroanalytical applications of self-assembled monolayers

A sensor for the in situ detection and measurement of low concentrations of gaseous mercury is presented. The sensor is based upon a dual delay line SAW oscillator with a gold-coated delay path. Gaseous mercury interacts rigorously with the gold film, forming an amalgam. The resulting increase in film mass is manifested as a decrease in oscillation frequency. Measurement of gas concentration is achieved by differentiating the sensor response at room temperature or by operating the sensing element at a temperature where gas-film reaction kinetics result in equilibrium rates of mercury amalgamation and desorption. This equilibrium value of amalgamated mercury is highly dependent upon the gas concentration. Thus, the delay line oscillation frequency is a sensitive measure of gaseous mercury concentration. Responses of this sensor to gaseous mercury concentrations in the ppb range are presented. The sensor response features are analyzed in terms of response shape, response magnitude, response time, and linearity at 25/spl deg/C and 200/spl deg/C.

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A surface acoustic wave mercury vapor sensor

Diffusion behavior of mercury into both gold and silver electrodes of polished and roughened quartz crystal microbalances (QCMs) is presented. Several QCM devices were exposed to mercury vapor for 8 h and allowed to desorb for 5 h under controlled nitrogen atmosphere. The process was repeated for different Hg concentrations of 1.02, 1.87 and 3.65 mg/m3 at an elevated temperature of 40 °C. The chemical composition and surface morphology of each QCM surface was characterized by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS), Secondary Ion Mass Spectroscopy (SIMS), Atomic Force Microscope (AFM) and Field Emission Secondary Electron Microscope (FE-SEM). The Ag electrodes were found to contain up to 16% more adsorbed/amalgamated Hg by mass than the Au samples. It was found that the ratio of amalgamated to adsorbed Hg is less for Au than Ag. SIMS analysis confirmed high Hg diffusion through rough substrates, 40 days after Hg exposure. In situ sticking probability of the tested mercury vapor concentrations to Au and Ag surfaces at 40 °C was found to drop at quicker rates than the reported Hg–Au and Hg–Ag room temperature values. Overall, in the context of Hg vapor phase gas sensing applications, the rougher gold substrate was found to outperform the other samples due to its superior adsorption/desorption properties.

Mercury diffusion in gold and silver thin film electrodes on quartz crystal microbalance sensors

Mercury detection in air using a coated piezoelectric sensor

A quartz resonator with a built‐in microheater used as a piezoelectric sorption sensor for mercury vapors in the air is presented. With the construction presented here a maximum sensitivity of 3×10−6 g/m3 can be reached. The built‐in microheater heats the crystal up to 150 °C and regenerates the sensor without dismounting it from the equipment. The sensor can be used in devices for environmental pollution control and in cases in which precise determination of low mercury vapor concentrations in air is necessary.

D. Y. Yankov

Papers

Piezoelectric sorption sensor for mercury vapors in air using a quartz resonator