Preparation For Noble Metal Nanoparticles With Morphological Characteristics And Applications In Small Biomolecules And Environmental Inorganic Ions Analysis

In this dissertation,flower-like gold nanoparticles(AuNFs) were prepared with a two-step reducing procedure,and the other three kinds of nanoparticles including spherical silver nanoparticles,silver nanoprisms and silver nanoplates were prepared with reported methods.The applications of these nanoparticles in small biomolecules and environmental inorganic ions analysis by using local surface plasmon resonance (LSPR) spectra,scanning electron microscope(SEM) and dark-field light scattering imaging technique.The following is the main points of this dissertation:1.Preparation for AuNFs was achieved with a two-step reducing procedure. Briefly,under alkaline conditions,ascorbic acid was added into solution of hydrogen tetrachloroaurate hydrate,and then excess hydroxylamine hydrochloride was added to reduce the un-reacted hydrogen tetrachloroaurate hydrate.Finally,a highly branched AuNFs was obtained.This rapid and facile method does not require the use of surfactants or polymers as template,and no organic solvent is used in this method. With dopamine,instead of ascorbic acid,the intensity of the LSPR absorption peak of AuNFs colloid appeared a linear blue shift with the increasing concentration of dopamine.Thus,a method of visually detecting dopamine was established.In addition, the interaction of iodine ions with AuNFs was investigated.Experimental results showed that the highly branched AuNFs were fused to sphericity by iodide ions.The LSPR absorption and scattering spectra of AuNFs changed with a color change from blue to red.Dark-field microscope was used to observe the dynamic process of the reaction of AuNFs with iodide ions.This method is useful for the determination of iodide,as well as studying reactions on individual nano-particles.2.Visual detection of chromium ion(Cr³⁺) and cell imaging with silver nanoparticles were studied.It was found that Cr³⁺ can selectively induce the aggregation of citrate-capped silver nanoparticles,resulting in color change,but the other 17 metal ions could not.Linear dependences were found for both LSPR absorbance ratio(A_560nm/A_396nm) and LSPR scattering intensity at 560 nm(I_560nm) of AgNPs on the concentration of Cr³⁺ in the range of 0.5-10.0μmol/l.The change of LSPR of silver nanoparticles enable us visual detecting Cr³⁺ instead of relying on expensive equipments.Mechanism analysis shows that the aggregation is mainly dependent on the chelation of Cr³⁺ ion with citrate capped on silver nanoparticles, forming crosslinking aggregates of silver nanoparticles.This studying for the detection of chromium ions,biological imaging,and research nanoparticles provide a novel approach.3.A method for selective detection of cysteine was established based on the color change of triangular silver nanoprisms.Triangular silver nanoprisms were prepared and applied to make colorimetric detection of cysteine based on our findings that cysteine could lead to the blue shift of the dipole plasmon resonance absorption,but other 19 kinds of natural amino acids could not.SEM pictures show that cysteine can etch the corner of triangular silver nanoprisms.And the shape of silver nanoprisms transformed from triangle to disk.The color changed sequentially from blue through purple,orange and finally to yellow with the increasing of cysteine concentration. Cysteine with a concentration 160 nmol/l can result in a color change that can be discerned with naked eyes.This method not only can be used to detect cysteine,but also can realize the regulation of nano-particle shape.4.We investigated the interactions of silver nanoplates with 21 metal ions and found that mercury ions can cause a significant blue shift of the LSPR absorption spectra of silver nanoplates,while the other metal ions would lead to a slight red shift. We found that low concentrations of mercury ions can etch the edge of silver nanoplates,while high concentrations of mercury ions can make the shape of silver nanoplates transform into a triangle.This is mainly due to the different states of the silver amalgams.This discovery can be used both for visual detecting mercury ions and morphology control of nanoparticles.In summary,several noble metal nanoparticles with morphological characteristics were prepared.And the interactions of these nanoparticles with a number of environmental inorganic ions and small biomolecules were studied.Color changes were observed in all these interactions,so we might establish several visual analytical methods.This study also found some methods to control the shape of nanoparticles. The enhancement of LSPR scattering signal shows the potential application in bioimaging with dark-field light scattering technique.