Preparation And Modification Of Gold Nano Rodsand Application Inthe Detection Of Enviro Nmental Pollutants

Because of its unique localized surface plasmon resonance(LSPR)effect,metal nanoparticles have been widely used in the fields of detecting and sensing.The LSPR effect of metallic nanoparticles is highly dependent on its size,shape,and the dielectric constant of surrounding medium.As a result,by designing the interaction and chemical reaction between target analytes and nanoparticles,the detection of target analytes could be achieved with high sensitivity and selectivity.Based on the LSPR effect of metallic nanoparticle,two sensing methods for the detection of sulfide anion in aqueous solution and formaldehyde in aqueous solution were developed.An improved synthesis of gold nanorods was studied with 5-bromosalicylic acid as additives,which may significantly reduce the concentration of hexadecyltrimethylammonium bromide(CTAB)surfactant.Such synthesis parameters as the amount of 5-bromosalicylic acid,silver nitrate and seed particles,and the pH value of growth solution were studied.It was found that longitudinal surface plasmon resonance of gold nanorods shifts to longer wavelength by increasing the amount of 5-bromosalicylic acid and silver nitrate,as well as by decreasing the amount of seed particles and pH value of growth solution.The longitudinal surface plasmon resonance wavelength of as-synthesized gold nanorods has a spectra tunability ranging from 572 nm to 820 nm.On the basis of preparation of gold nanorods,Au-Hg nanorods were synthesized based on the affinity between gold and mercury.A rapid and sensitive detection method for sulfide anion(S2-)in aqueous was developed based on LSPR and surface properties of Au-Hg nanorods.The sensing mechanism is based on the quick formation of HgS in the presence of sulfide anions which can change the dielectric properties of Au-Hg nanorods.As a result,the longitudinal surface plasmon resonance peak undergoes a red shift(??).Under optimal condition,?? upon the addition of S2-was found to be proportion to the concentration of S2-in the range of 1×10-5mol/L-1×10-4mol/L.Parameters of detection including temperature,pH value,reaction time and selectivity were studied,which indicated that this method is highly sensitive,stable,and rapid.A rapid and sensitive detection method for formaldehyde detection was developed based on LSPR of gold nanorods,which can eliminate the interference of carmosine.In alkaline enviro nment,formaldehyde may act as a mild reducing agent to reduce Hg2+ to Hg0.As a result,amalgamation between AuNRs and Hg0 takes place,which decreases the aspect ratio.As a result,blue shift of longitudinal surface plasmon resonance wavelength of gold Nanorods will happen.After being coated with polystyrene sulfonate sodium(PSS),the surface charge of gold nanorods is altered from positive to negative.As a result,PSS-coated gold nanorods are stable in presence of carmosine to provide the possibility for formaldehyde detection under interference of carmosine.Upon optimal condition,a linear relationship was fitted between ?? and the concentration of formaldehyde,ranging from 0.1 mg/L-1 mg/L,with correlation coefficient of R2=0.99.This method has potential application in detection of formaldehyde in dyed leather,fabric and artificial wood-based board.