The citrate-mediated shape evolution of transforming photomorphic silver nanoparticles (original) (raw)

Abstract

The photoconversion of photomorphic silver nanoparticles from discs to prisms via citrate mediated growth on the twin plane faces of the nanoparticles is demonstrated. This systematic shape evolution from discs to hexagons and then prisms of increasing aspect ratios is a result of the growth process being confined to specific faces of the growing nanoparticles.

Figures (3)

Shape control of the particles was achieved by irradiating an initial solution of photomorphic AgNPs that were dominated by disc-shapes (dark-transformed)'> at two minute intervals for a total of 16 minutes in a Rayonet photochemical reaction chamber using sixteen 575 nm bulbs (Figure la-d). Figure 1.Transmission electron Images of particles from a solution that was light excited for 0, 2, 8 and 16 minute (a, b, c and d). The scale bar is equal to 100 nm. e) The size-independent shape exclusive directed growth of photomorphic AgNPs from discs to truncated prisms.

Shape control of the particles was achieved by irradiating an initial solution of photomorphic AgNPs that were dominated by disc-shapes (dark-transformed)'> at two minute intervals for a total of 16 minutes in a Rayonet photochemical reaction chamber using sixteen 575 nm bulbs (Figure la-d). Figure 1.Transmission electron Images of particles from a solution that was light excited for 0, 2, 8 and 16 minute (a, b, c and d). The scale bar is equal to 100 nm. e) The size-independent shape exclusive directed growth of photomorphic AgNPs from discs to truncated prisms.

Figure 2. A) Representative UV-vis absorption spectra of a single solution of photomorphic AgNPs evolving from discs to prisms. The spectra were obtained in series at 2 minute intervals from dark exposed at t= 0 through 8 intervals to 16 minutes of photo-transformation. B) A plot of the average particle height versus UV-vis absorbance maxima. The schematics depict the measured average diameter and height of the various particles. Photodevelopment was monitored at each time interval using UV-vis spectroscopy (Figure 2a), and, after sixteen minutes of excitation, the photomorphic particles had a A imax red-shift from 546 to 592 nm. The irradiation process of the AgNPs begins a rapid shape change attributed to the initially high concentration of Ag* present in solution'®; the rate of change decreases versus time. The maxima is due to the in-plane dipole plasmon of anisotropic plate structures.'> According to discrete dipole approximation (DDA),'® the growth of tip-corners to these disc and polygon shaped particles results in a red-shift in absorption.” ray

Figure 2. A) Representative UV-vis absorption spectra of a single solution of photomorphic AgNPs evolving from discs to prisms. The spectra were obtained in series at 2 minute intervals from dark exposed at t= 0 through 8 intervals to 16 minutes of photo-transformation. B) A plot of the average particle height versus UV-vis absorbance maxima. The schematics depict the measured average diameter and height of the various particles. Photodevelopment was monitored at each time interval using UV-vis spectroscopy (Figure 2a), and, after sixteen minutes of excitation, the photomorphic particles had a A imax red-shift from 546 to 592 nm. The irradiation process of the AgNPs begins a rapid shape change attributed to the initially high concentration of Ag* present in solution'®; the rate of change decreases versus time. The maxima is due to the in-plane dipole plasmon of anisotropic plate structures.'> According to discrete dipole approximation (DDA),'® the growth of tip-corners to these disc and polygon shaped particles results in a red-shift in absorption.” ray

Controlled growth of photomorphic silver nanoparticles, with many possible shapes from discs to prism-plates, can be achieved by using light excitation. The light driven shape transformation of these particles follows a distinct pathway. The original suspension of prepared nanoparticles is dominated by discs with rounded edges and tips. With initial light excitation, the discs start to transform to hexagon-shaped nanoparticles. Then, with further light excitation, they convert to hexagon shapes with higher aspect ratios. Finally, the silver nanoparticles transform to truncated prism shapes. In addition, this shape transformation process is size-independent, as even the smallest of the particles were observed to be transformed to prisms. The major importance of this finding is that this remarkable shape transformation process has the ability to accurately and controllably produce nanoparticles of specified shapes in a single reaction vessel with the simple flick of a light switch.

Controlled growth of photomorphic silver nanoparticles, with many possible shapes from discs to prism-plates, can be achieved by using light excitation. The light driven shape transformation of these particles follows a distinct pathway. The original suspension of prepared nanoparticles is dominated by discs with rounded edges and tips. With initial light excitation, the discs start to transform to hexagon-shaped nanoparticles. Then, with further light excitation, they convert to hexagon shapes with higher aspect ratios. Finally, the silver nanoparticles transform to truncated prism shapes. In addition, this shape transformation process is size-independent, as even the smallest of the particles were observed to be transformed to prisms. The major importance of this finding is that this remarkable shape transformation process has the ability to accurately and controllably produce nanoparticles of specified shapes in a single reaction vessel with the simple flick of a light switch.

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