Self-Assembly Of Chiral Noble Metal Complex Nanoparticles For Chemo/Biosensing

This dissertation focuses on the self-asembly of chiral noble metal complex nanoparticles for chemo/biosensing applications. The main contents and novelty of the dissertation are summarized as follows:Cysteine is involved in a variety of important cellular functions, including protein synthesis, detoxication, and metabolic processes. Its level in physiological fluids such as plasma and urine has been recognized as an important indicator for a number of clinical disorders. Therefore, it is highly desirable to develop sensitive and selective methods for detecting cysteine in biological fluids. To this end, we have developed a novel circular dichroism (CD) method to probe L-cysteine based on the self-assembly of chiral complex nanoparticles from Ag+ and L-cysteine. The CD method allows probing L-cysteine in biological fluids with high selectivity and sensitivity atμM level without the need for any special synthesis, and any other sample pretreatment procedures except an appropriate dilution.Little attention has been paid to the utilization of chiral nanoparticles as sensors or probes for biological and environmental important targets so far. There may be two reasons for the underdevelopment of chiral nanoparticles as sensors or probes. Firstly, the anisotropy factor of the reported optically active ligand-protected metal clusters or nanoparticles is too small to obtain high sensitivity for detection. Secondly, it is laborious to obtain sufficient chiral nanomaterials for sensing because the subsequent separation procedures such as polyacrylamide gel electrophoresis or silica gel chromatography are usually necessary after synthesis. In this work, we have developed a facile one-step fabrication of chiral Ag-L-cysteine complex nanoparticles with large optical activity within 30 min via self-assembly without the need for any separation and purification for highly sensitive and selective sensing of Hg2+. The induced CD changes of the chiral Ag-L-cysteine complex nanoparticles due to the displacement of Ag+in the chiral nanoparticles by Hg2+ allows high selectivity for Hg2+ over alkali, alkaline earth, and transition heavy metal ions with low detection limit (9 nM). The developed CD assay is practical for detecting trace Hg2+ in aqueous environmental samples without the need for pH adjustment.The interactions between Au(Ⅲ) and L-cysteine complex are investigated by is a kind of chiral nanoparticles well dispersed in water by investigating the interaction of Au(Ⅲ). Chiral Au-D/L-cysteine complex nanoprticles with large optical activity were formed via the self-assembly from Au(Ⅲ) and D/L-cysteine. The process of the self-assembly was monitored by CD, fluorescence spectrometry, UV-vis spectromenrty. The prepared Au-D/L-cysteine complex nanoprticles were characterized by XRD, and TEM. Based on the mechanism of the chiral nonoparticles self-assembly, a method for the determination of enantiomeric excess of cysteine was developed with Au(Ⅲ) as a UV-vis probe. The method does not require the synthesis of chiral probe nor a chiral recognizing detector. This work provides a new strategy for chiral recognition, and an alternative for the determination of enantiomeric excess.