The Preparation Of Gold Nanoparticles And The Applications In Detection Of Copper Ions

In recent years, the rapid development of industrialization causes various degreesof pollution of water environment, especially the heavy metal pollution of drinkingwater, which seriously affects the human health. Most of thetraditional analytical methods of Cu²⁺ion need large instruments, such as, atomicabsorption spectrometry （AAS）, inductively coupled plasma-mass spectrometry（ICP-MS）, which are expensive but can not be achieved rapid field test. Thus a newmethod with simple, rapid and high sensitivity, which also detects Cu²⁺ion on-site inaqueous is of great value in research and practical applications. Owing to the uniqueoptical properties, gold nanoparticles have received great attention and have beenwidely employed in fields of analysis and detection. In this paper, based on the goldnanoparticles colorimetric method, we discuss the application of gold nanoparticles indetermination of Cu²⁺ion in aqueous system. The main research are as follows:1. AuNPs were first stabilized by CTAB in NH₃-NH₄Cl （0.6M/0.1M） solutions.Then thiosulfate （S2O32-） ions were introduced and AuNPs were gradually dissolvedby dissolved oxygen. With the further addition of Cu²⁺, Cu（NH₃）4²⁺oxidized AuNPsto produce Au（S2O3）23-and Cu（S2O3）35-, while the later was oxidized to Cu（NH₃）4²⁺again by dissolved oxygen. The dissolving rate of AuNPs was thereby remarkablypromoted and Cu²⁺acted as the catalyst. Subsequent tests confirmed the nanoparticlecolorimetric sensor as a sensitive （LOD=5.0nM or0.32ppb） and selective.2. A new method based on the fact that copper （Ⅱ） tetra-ammine complexcatalytic oxidizing gold nanorods （GNRs） in the S2O32--leaching system has beendeveloped for the determination of Cu²⁺in aqueous solution. The etching procedurewould lead to a dramatic decrease of the GNRs in length but little in diameter, causingthe longitudinal surface plasmon resonance （LSPR） absorption blue shifts andsolution color changed. In this study, the colorimetric and label-free design for Cu²⁺with highly sensitive and selective was reported. The sensor possessed a surprisingsensitivity which allowed the clear visual detection of Cu²⁺ion ranging from3×10^-8to5×10^-7M, with a limit of detection2.7nM. Furthermore, the cost-effective probe wassuccessfully applied to monitor Cu²⁺in shellfish samples, showing the simple and rapid practicality for the detection of Cu²⁺in real samples.3. As a strong oxidant in HBr buffer, Cu²⁺ion can oxidize the gold nanorods,which Br-act as a ligand with gold to reduce the electron potential.With the oxidationetching proceeding, the aspect ratio of GNRs decreased, resulting in the longitudinalsurface plasmon resonance （LSPR） absorption decreased sharply and shifted toshort-wave direction, accompanied by a color change from blue to slight red.We caneasily read out by naked eyes when a containment level of3.1nM in solution.