In these colors (yellow, orange, or red), the position of their maximum absorption bands in region 1 (400 to 500 nm) and the absence of absorption bands LY294002 concentration in region 2 (600 to 700 nm) indicate the complete synthesis of nanoparticles with spherical shape which is corroborated by TEM (Figure 9, right). Figure 9 UV–vis absorption spectra of silver solutions and TEM micrograph of the reddish sample. UV–vis absorption spectra of silver solutions prepared with different DMAB concentrations at a constant PAA concentration

of 2.5 mM (left), and TEM micrograph of the reddish sample (0.66 mM DMAB) with aggregation of spherical nanoparticles (right). Conclusions In this study, we have successfully synthesized a multicolor silver map as a function of variable PAA and DMAB concentrations with a constant concentration of silver cations using a chemical reduction method. It has been demonstrated that a fine control of both PAA and DMAB concentrations made it possible to obtain a wide range of colors with specific shapes. Initially, only yellow, orange, or red color is obtained with lower PAA concentrations (1.0 or 2.5 mM PAA), whereas violet, blue, green, brown, or orange color is obtained

with higher PAA concentrations (from 5 to 250 mM). Samples have been characterized using TEM and UV–vis spectroscopy in order to verify the shape and evolution of their maximum absorption https://www.selleckchem.com/products/azd4547.html bands in two spectral regions (region 1, 400 to 500 nm; region 2, 600 to 700 nm). Firstly, when PAA concentration varies (from 1 to 250 mM) for a constant DMAB concentration (0.33 mM) and, secondly, when DMAB concentration varies (from 0.033 to 6.66 mM) for a constant PAA concentration (10 or 25 mM), the results indicate that for higher PAA or lower DMAB molar concentrations, TCL an absorption band at longer wavelengths (region 2) appears, which implies violet, blue, or green solutions of AgNPs with hexagonal, triangle, and rod shapes. On the other hand, for lower PAA or higher DMAB concentrations, an intense absorption band at shorter wavelengths

around 410 nm (region 1) appears, which implies orange red solutions of AgNPs of spherical shape. In summary, the fine control of PAA and DMAB concentrations in the AgNPs synthesis makes possible the color selection of the AgNPs solutions, from violet to red, as well as the shape (spherical, rod, triangle, hexagonal, cube), and size (from nanometer to micrometer) of the nanoparticles. To our knowledge, this is the first time that an experimental matrix showing multicolor silver nanoparticle solutions with well-defined shape and size using both protective agent (PAA) and reducing agent (DMAB) has been reported in the bibliography. Acknowledgments The authors express their gratitude to David García-Ros (Universidad de Navarra) for his help with the TEM images. This work was supported in part by the Spanish Ministry of Education and Science CICYT FEDER TEC2010-17805 research grant. References 1.