When the reducing agent is increased from 0.033 selleck chemical to 6.66 mM DMAB in the

same mixture of AgNO3 and PAA, the maximum absorption band is shifted to shorter wavelengths (region 1). Figure 5 shows the UV–vis absorption bands when the reducing agent DMAB concentration is increased in 25 mM PAA solution (fifth line in Figure 1). As can be seen in Figure 5, an increase of the reducing agent DMAB produces an absorption band shift to shorter wavelengths. An intense absorption band at 410 nm is observed when the highest DMAB proportion (6.66 mM) is added to the mixture and an orange color is obtained, indicating the synthesis of spherical AgNPs (corroborated by TEM). Figure 5 UV–vis absorption spectra of silver solutions at a constant PAA concentration. They are prepared with different DMAB concentrations at a constant PAA concentration of 25 mM (fifth line of the silver multicolor map of Figure 1).

The spectra reveal that the evolution of the absorption bands as a function of the DMAB added to the solution shows just the opposite behavior to the phenomenon observed when PAA was added. The position of the maximum absorption bands shifted to shorter wavelengths when DMAB concentration was increased, and the resulting colors are formed in a different order (from violet to orange) during the synthesis process. According to the results shown in Figure 5, the evolution of both regions demonstrated that an absorption band at long wavelengths (region 2) is obtained in the first steps of color formation (violet or blue) with selleck chemicals llc lower DMAB molar in the solution. However, when the DMAB molar was increased, Tyrosine-protein kinase BLK the maximum absorption band shifted to short wavelengths (region 1) with a corresponding change of color (brown or green). Furthermore, when higher DMAB molar was added to the solution (with orange color only), a new intense absorption band appeared at 410 nm which was indicative of the formation of nanoparticles with spherical shape. These same spectral absorption variations in both regions have been observed with higher PAA

concentrations (100 or 250 mM). Similar to what was made in the preceding section, Figure 6 was also plotted in order to show a clearer picture of the evolution of the optical absorption bands (regions 1 and 2) when the concentration of DMAB was increased. In Figure 6, it is easy to identify the absorbance increase in region 2 from 0.033 to 0.33 mM DMAB. Conversely, from 0.33 to 6.66 mM DMAB, the absorbance in region 2 decreased. The absorbance of region 1 always increases with the DMAB concentration. In view of these results, the influence of the DMAB concentration in the color of the synthesized AgNPs is also clear. Figure 6 Evolution of UV–vis maxima absorption bands of silver sols in regions 1 and 2. Absorption bands in regions 1 and 2 are 400 to 500 nm and 600 to 700 nm, respectively. They are prepared with different DMAB concentrations at a constant molar PAA concentration (25 mM) and a constant molar DMAB concentration.