Spectral Analysis Studies Of Mercury Ion By Using Sulfide Or Gold Nanoparticles

Mercury is one of the most toxic elements on human beings and higher organisms. Soluble mercury can enter the human body from the food chain and accumulate in human body, resulting in great harm to human health. Therefore, mercury ions analysis of environmental samples is one of the most important indicators to assess environmental quality. The development of Hg²⁺ sensor of high selectivity, high sensitivity, low cost and simple operation has become research focus.The unique nature of nano-materials is expected to meet the basic requirements for building a sensor, such as extensive function, high sensitivity, fast response, wide detection range, good selectivity and good stability and so on. In this paper, several forms of nano- material have been prepared by means of simple methods, and successfully applied to the spectral analysis for Hg²⁺. These methods that applied to the determination of mercury ion in environmental samples are simple, rapid, high sensitivity for mercury ions analysis, and do not require a special pre-treatment. The major contents are as follows:(1) Based on DNA as a template, CdS nanoparticles (⁵ nm) has been synthesized in aqueous solution using alternate dialysis and layer-by-layer assembly method, and is applied to spectral analysis of Hg²⁺. The resultant well-dispersed CdS nanoparticles present a strong ?uorescence peak at 339 nm and RLS bands around 394 nm, which is characterized by TEM, UV-vis, ?uorescence and resonance light scattering (RLS) spectra. Interestingly, it was found that the quenching of ?uorescence and the enhancing of RLS intensity are strongly dependent on the concentration of Hg²⁺, which is due to the forming of Hg-S bond. In optimized conditions, the sensor show a good linear relationship over the range of 0.01-100μM, with a remarkable low detection limit as low as 1 nm, and show a good selectivity to mercury ions.(2) Using citrate as a stabilizing agent at room temperature, we synthesize CuS and PbS nanoparticles in aqueous phase via a similar method. And the synthetic conditions under different pH values and the ratio of sodium sulfide and copper sulfate or lead sulfate on concentration have been studied. The intensity change of resonance light scattering (IRLS) of nano-particles as-prepared directly relates to different concentrations of Hg²⁺. We have studied the effects of RLS between CuS or PbS nanoparticles and mercury ions under the conditions of different pH values and the different ratio of sodium sulfide and copper sulfate or lead sulfate on concentration. The results show that in the optimum experimental conditions, the IRLS of CuS and PbS corresponding to c(Hg²⁺) has a good linearity in the range of 0.01-100μM and 0.001-100μM seperately. Thus, the method of determine trace mercury in water is established.(3) SnCl₂ can react with the Hg²⁺ to form metal mercury in acid medium, and metal mercury react with gold nanoparticles once again to form nanocomposites, which has a maximum RLS peak at 395nm. According to these phenomena, the trace mercury in the water was determined by RLS technique. Experiments showed that the change of RLS intensity (IRLS) against the nanocomposites is proportional to the concentration of Hg²⁺ in the range of 0.1-50μmol/L. The correlation coefficient of linear equations is 0.991 with the detection limit of 0.068μmol/L.