Control Synthesis, Characterization, Analysis And Application Of Anisotropic Silver Nanoparticles

Localized surface plasmon resonance (LSPR) is a particular property of the noble metal nanoparticles that has been applied extensively in various fields such as in sensing, and surface enhanced spectroscopy. It is vital to tune effectively LSPR of noble metal nanoparticles for the applications involved LSPR. LSPR is sensitive to the size, shape, surrounding and composition of the nanoparticles and so on. Many attempts have been made to obtain metal nanoparticles of well-controlled size and shape. Nevertheless, the development of new strategies to systematically manipulate the size and shape of nanoparticles is still a great challenge that is critical for optimizing the LSPR properties of nanoparticles for certain applications. The real-time information of the nano reaction can be obtained by monitoring the optical spectra of nanoparticles because of close relation of spectrum and morphologies of nanoparticles. It is significant to develop the spectroscopy analysis of nanoparticles for research involved nanoparticles. In addition, LSPR can lead the bright and fascinating colors, which have been used as decorative pigments for glass and ceramic dyeing. In particular, anisotropic silver nanoparticles provide not only beautiful colors but also an antibacterial characteristic. Based on the spectroscopy characteristic and promising applications of silver nanoparticles, this thesis is outlined as follow:1. Shape control and LSPR tuning of silver nanoparticles.The transformation from silver nanoprism to silver nanodisk was achieved by heat aging. Moreover, the diameter of silver nanodisks can be tuned by controlling the heating time. LSPR of silver nanoparticles can be tuned systematically in the range of wide wavelength by only controlling heating time during the process of shape transformation and size control.Shape conversion and reconstruction of silver nanoprisms were realized by photoinducing method by changing the concentration of citrate in reaction system. Photoinducing resulted in transformation from silver nanoprism to silver nanodisk under a certain concentration of citrate. LSPR of silver nanoparticles were tuned gradually from 740 nm to 440 nm. Subsequently, continuous light induced silver nanodisk to reconstruct into silver nanoprism after the additional citrate was added in the reaction system. The LSPR band can be photomediated again to the long wavelength region within 620-690 nm. In the shape conversion, the coupling effect of the plasmon resonance and the light source speeds up the photothermal reaction.2. Investigation of fast reaction involved nanoparticles based on time-resolved spectroscopy.Time-resolved extinction spectroscopy was developed to study the kinetics of nanoparticle reaction. Hide ions can etch the silver nanoprisms into the silver nanodisks. A series of time-resolved extinction spectra were obtained during the in situ etching process and the LSPR evolution of the silver nanoparticles was analyzed. Spectral analysis indicated that the conversion of nanoprisms started simultaneously with the emergence of nanodisks when the halide ions were added. The etching rate of different halide ions was evaluated through the in-plane dipole resonance peak intensity of silver nanoplates vs. the reaction time. The relationship between the etching rate and the halide ion concentration shows that the halide ion etching reaction can be considered as a pseudo-first-order reaction. The activation energy of the etching reaction is calculated, which indicates that the etching ability of different halide ions is on the order of Cl-