Mercuric ions induced aggregation of gold nanoparticles as investigated by localized surface plasmon resonance light scattering and dynamic light scattering techniques

With the development of nanosciences, both localized surface plasmon resonance light scattering （LSPR-LS） and dynamic light scattering （DLS） techniques have been widely used for quantitative purposes with high sensitivity. In this contribution, we make a comparison of the two light scattering techniques by employing gold nanoparticles （AuNPs） aggregation induced by mercuric ions. It was found that citrate-stabilized AuNPs got aggregated in aqueous medium in the presence of mercuric ions through a chelation process, resulting in greatly enhanced LSPR-LS signals and increased hydrodynamic diameter. The enhanced LSPR-LS intensity （A/） is proportional to the concentration of mercuric ions in the range of 0.4-2.5 laM following the linear regression equation of A/= -84.7＋516.4c, with the correlation coefficient of 0.983 （n = 6） and the limit of determi- nation （3o-） about 0.10 gM. On the other hand, the increased hydrodynamic diameter can be identified by the DLS signals only with a concentration of Hg2＋ in the range of 1.0-2.5 gM, and a linear relationship between the average hydrodynamic diame- ters of the resulted aggregates and the concentration of Hg2＋ can be expressed as d = -6.16 ＋ 45.9c with the correlation coeffi- cient of 0.994. In such case, LSPR-LS signals were further applied to the selective determination of mercuric ions in lake water samples with high sensitivity and simple operation.

Synthesis of newly cationic surfactant based on dimethylaminopropyl amine and their silver nanoparticles:Characterization;surface activity and biological activity

The chemical structure of newly synthesized cationic surfactants based on Schiff base was confirmed using Fourier transform infrared spectroscopy,proton nuclear magnetic resonance spectroscopy,and mass spectroscopy.The synthesized surfactants were used in the synthesis of silver nanoparticles by a simple one-step method.The silver nanoparticle（AgNPs） formation was confirmed using transmission electron microscopy（TEM）,electron diffraction（SAED）,dynamic light scattering（DLS）,and energy dispersive X-ray spectroscopy（EDX）.The structure of the surfactant played an important role in the synthesis process.Increasing the hydrophobic chain length,the stability,and the amount of surfactant increased the quantity of AgNPs formed.The surface activity of the synthesized cationic surfactants was determined using surface tension measurements at three different temperatures.The synthesized surfactants showed a high tendency toward adsorption and micellization.Increasing the hydrophobic chain length of the synthesized surfactant increased its adsorption.Screening the synthesized cationic surfactants and their nano-form against bacteria and fungi showed that they are highly effective.The silver nanoparticles enhanced the biological activity of the synthesized cationic surfactants.