Raman Detection Of Mercury Ions And Polycyclic Aromatic Hydrocarbons Based On Au Nanoparticles

Surface-enhanced Raman scattering(SERS) Spectroscopy is a vibrational spectroscopic technique, which can detect low concentrations of analyte through the excitation of localized surface plasmons on electromagnetic field magnification. The synthesis of SERS substrate which can enhance SERS signal is important to the application of SERS. Phytic acid(IP6) and its salts are economical and ‘green’ reagents and liable to chelate with metal ions because of its structure containing six phosphates separately on both sides of the cyclohexane. On the other hand,IP6 molecules can form into the micelle themselves and some free phosphates remaining on the outside of the micelle.IP6 micelles act as a stabilizer and controller in the process of synthesis of nanoparticles.The main contents of this article are as follows:Mercury as heavy metal pollutant is quite harmful to human and organism, so many researchers have devoted to developing a simple method for detection of mercury contamination. In chapter 2, the facile synthesis of a nanocomposition, which is constructed with IP6 stabilized gold nanoparticles(Au NPs) modified by crystal violet(CV) as Raman signal molecule and tri-sodium citrate(TC) as reducer, shortly named CV/TC/IP6/Au NPs. A possible mechanism for the Raman probe is the decreasing intensity of SERS band of crystal violet(CV) with Hg2+ addition due to the reduction of Hg2+ by TC to Hg atom whose competition with CV molecules at the IP6/Au NPs surface, resulting in CV molecules detachment from the surface. Through a series of characterization based on UV-Vis spectrophotometer(UV-Vis), transmission electron microscope(TEM), X–Ray photoelectron spectroscopy(XPS) to prove the mechanism. This simple, economic and high sensitivity method can detect mercury ions in water effectively.Benzo(a)pyrene(Ba P) is a kind of polycyclic aromatic hydrocarbons, which is a highly toxic pollutant in ecosystems and produces from burned oil will increase cancer risk. Therefore, it is important to rapid detecting Ba P in the edible oil without tagging. In chapter 3, examining the feasibility for Ba P detection based on three different SERS substrate, which is gold nanoparticles(Au NPs), IP6, stabilized Au NPs dotted magnetic nanocomposites(AMN) and concentrated IP6 stabilized Au NPs(IP6-Au NPs), respectively. IP6 modification for Au NPs certainly increased the hydrophobic capability of such SERS substrate to catch Ba P molecules from bulk oil. Due to the difficult to detect Ba P from the edible oil, it is important to select high sensitivity substrate through investigation. This simple, economic and high sensitivity method can detect Ba P in the edible oil effectively.Polycyclic aromatic hydrocarbons(PAHs) are environmental and food contaminations, which is harmful to human body. There are many kinds of polycyclic aromatic hydrocarbons, containing more than two benzene compounds. In chapter 3, Bap is a kind of PAHs and we have observed that IP6-Au NPs as SERS substrate can detect Ba P effectively and sensitively. Therefore, in chapter 4, we still use IP6-Au NPs as SERS substrate to detect Ba P, pyrene, anthracene and fluoranthene. Because of different PAHs have different corresponding SERS signals, so we can detect different PAHs at the same time.