International Gold Nanoparticles Synthesis
Introduction
Gold nanoparticles have gained significant attention due to their unique optical, electronic, and catalytic properties. Their applications span various fields, including biomedicine, electronics, and optoelectronics. The synthesis of gold nanoparticles has been extensively studied worldwide, leading to the development of numerous methods.
Physical Methods
Physical methods for gold nanoparticle synthesis involve the reduction of gold ions using a reducing agent. Commonly used methods include:
* Laser ablation: A high-intensity laser is focused on a gold target in a liquid, generating gold nanoparticles through rapid evaporation and condensation.
* Electron beam lithography: A focused electron beam is used to create patterns of gold nanoparticles on substrates.
* Sputtering: A gold target is bombarded with ions or atoms, ejecting gold atoms that form nanoparticles upon condensation.
Chemical Methods
Chemical methods involve the reduction of gold ions in solution using various reducing agents. The most common methods include:
* Turkevich method: Gold ions are reduced by sodium citrate in the presence of a protective agent, such as citrate ions.
* Frens method: Gold ions are reduced by sodium borohydride in the presence of a protective agent, such as cetyltrimethylammonium bromide (CTAB).
* Brust-Schiffrin method: Gold ions are reduced by tetraoctylammonium bromide (TOAB) in the presence of a stabilizing ligand, such as dodecanethiol.
Biological Methods
Biological methods utilize enzymes or microorganisms to synthesize gold nanoparticles. These methods include:
* Bacterial synthesis: Bacteria such as Lactobacillus acidophilus produce enzymes that reduce gold ions to form nanoparticles.
* Plant-mediated synthesis: Plants contain compounds that act as reducing agents and stabilizing agents for gold nanoparticles.
* Fungal synthesis: Fungi produce enzymes and other metabolites that aid in the synthesis of gold nanoparticles.
Characterization Techniques
After synthesis, gold nanoparticles are characterized using various techniques to determine their size, shape, and other properties. Common techniques include:
* Transmission electron microscopy (TEM): Provides high-resolution images of nanoparticles, revealing their size and shape.
* Atomic force microscopy (AFM): Measures the topography and surface properties of nanoparticles.
* Ultraviolet-visible spectroscopy (UV-Vis): Detects the characteristic surface plasmon resonance (SPR) band of gold nanoparticles.
* X-ray diffraction (XRD): Determines the crystalline structure and crystal orientation of nanoparticles.
Conclusion
The synthesis of gold nanoparticles has gained international attention, leading to the development of numerous methods. Physical, chemical, and biological approaches have been extensively studied to produce nanoparticles with tailored properties. By utilizing appropriate characterization techniques, researchers can optimize synthesis conditions to obtain gold nanoparticles with specific sizes, shapes, and functionalities for various applications.
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