In this study, we synthesized silve

In this study, we synthesized silver nanoprisms using a modified wet chemistry method developed by Mirkin et al., without the presence of strong oxidant H2O2 [6]. The procedure includes the preparation of spherical Ag nanoparticles, followed by transformation of the Ag nanospheres into triangular nanoplates in 24 h at room temperature and without light illumination. In a typical experiment, all the apparatus were washed by aqua regia and rinsed with acetone and DI water before use. A volume of 112 mL aqueous solution containing silver nitrate (AgNO3), 8.9 × 10-5 M, trisodium citrate (Na3C6H5O7), 1.6 × 10-3 M, and poly(vinylpyrrolidone) (PVP), 3.75 × 10-5 M were mixed. Then, 1,100 μL of 0.1 M sodium borohydride (NaBH4) was injected into the mixture. The effect of NaBH4 was studied by varying its amounts from 800 to 1,300 μL. Either sodium hydroxide (NaOH) or nitric acid (HNO3) was added to the initial nanoparticles solutions (20 mL) in order to achieve pH control. The images of the synthesized nanoparticles were taken by a transmission electron microscope (JEOL, JEM-1200EX II) and high-resolution transmission electron microscope (JEOL, JEM-2010F) operating at 80 and 200 kV, respectively. All UV–visible absorption spectra of the silver solutions were measured by a spectrophotometer (JASCO V-570) with a light path of 10 mm.

Results and Discussion
Figure 1 shows the transmission electron microscope (TEM) images of silver nanoparticles prepared with different amounts of NaBH4 while all other parameters remained constant. An extremely high mole ratio was used in this experiment, where the ratio of NaBH4 to AgNO3 is above 8. According to Yang et al. [22], the precursor (Ag ions) can be totally consumed when the mole ratio is 5. These prepared spherical Ag nanoparticles would transform into triangular nanoplates within 24 h at room temperature in dark. As the reaction proceeds, the intensity of the peak at 410 nm decreased and a new peak at a longer wavelength appeared in the NIR–Vis–UV absorption spectrum. This red-shift in energy implies the formation of a triangular structure, which is ascribed to the in-plane dipole resonance mode of silver nanoprisms as shown in Figure 2a. The bisector length of the silver nanoprism prepared with 1,100 μL NaBH4 was found to be 113.4 ± 40.8 nm, as shown in Figure 2b for the histogram. In this study, the out-of plane dipole mode did not show in the spectra, suggesting an inhomogeneous mixture of anisotropic nanoparticles in the solution. From TEM images and absorption spectrum, three features were observed. First, as the concentration of reducing agent (NaBH4) increases, the ratio of nanoprism/nanosphere would also increase. Secondly, the size of the formed silver nanoprisms is almost identical regardless the concentration of NaBH4. Finally, the out-off plane quadruple resonance mode is fixed at the same wavelength (331 nm), which implies that the concentration of the reducing agent would not affect the thickness of nanoprism. Consequently, the extreme excess amount of reducing agent is the crucial factor for the transformation.

ผลลัพธ์ (อังกฤษ) 3:

In this study we synthesized, silver nanoprisms using a modified wet chemistry method developed by Mirkin et al, without. The presence of strong oxidant H2O2 [6]. The procedure includes the preparation of spherical, Ag nanoparticles followed. By transformation of the Ag nanospheres into triangular nanoplates in 24 h at room temperature and without light, illumination. In a, typical experimentAll the apparatus were washed by aqua regia and rinsed with acetone and DI water before use. A volume of 112 mL aqueous. Solution containing silver nitrate (AgNO3), 8.9 *, 10-5 M trisodium citrate (Na3C6H5O7), 1.6 *, 10-3 M and poly (vinylpyrrolidone). (PVP), 3.75 × 10-5 M were mixed. Then 1, 100 thermal L, of 0.1 M sodium borohydride (NaBH4) was injected into the mixture.The effect of NaBH4 was studied by varying its amounts from 800, to 1 300 thermal L. Either sodium hydroxide (NaOH) or nitric acid. (HNO3) was added to the initial nanoparticles solutions (20 mL) in order to achieve pH control. The images of the synthesized. Nanoparticles were taken by a transmission electron microscope (JEOL JEM-1200EX II), and high-resolution transmission electron. Microscope, (JEOLJEM-2010F) operating at 80 and, 200 kV respectively. All UV - visible absorption spectra of the silver solutions were measured. By a spectrophotometer (JASCO V-570) with a light path of 10 mm.


Results and Discussion Figure 1 shows the transmission. Electron microscope (TEM) images of silver nanoparticles prepared with different amounts of NaBH4 while all other parameters. Remained constant.An extremely high mole ratio was used in, this experiment where the ratio of NaBH4 to AgNO3 is above 8. According to Yang. Et al. [22], the precursor (Ag ions) can be totally consumed when the mole ratio is 5. These prepared spherical Ag nanoparticles. Would transform into triangular nanoplates within 24 h at room temperature in dark. As the, reaction proceedsThe intensity of the peak at 410 nm decreased and a new peak at a longer wavelength appeared in the NIR - Vis - UV absorption. Spectrum. This red - shift in energy implies the formation of a, triangular structure which is ascribed to the in-plane dipole. Resonance mode of silver nanoprisms as shown in Figure 2A. The bisector length of the silver nanoprism prepared, with 1100 thermal L NaBH4 was found to be 113.4 edge, 40.8 nm as shown in Figure 2B for the histogram. In, this study the out-of plane. Dipole mode did not show in the spectra suggesting an, inhomogeneous mixture of anisotropic nanoparticles in the, solution. From TEM images and, absorption spectrum three features were observed. First as the, concentration of reducing agent (NaBH4). Increases.The ratio of nanoprism / nanosphere would also increase. Secondly the size, of the formed silver nanoprisms is almost identical. Regardless the concentration of NaBH4. Finally the out-off, plane quadruple resonance mode is fixed at the same wavelength. (331 nm), which implies that the concentration of the reducing agent would not affect the thickness of, Consequently nanoprism.The extreme excess amount of reducing agent is the crucial factor for the transformation.