The presence of the free ionic groups makes possible to bind metal ions via a simple aqueous ion exchange procedure and a LY2874455 clinical trial posterior chemical

reduction step with a reducing agent, leads to obtain the nanoparticles within the thin film. However, NVP-BGJ398 Su and co-workers have demonstrated the incorporation of AgNPs with the use of strong polyelectrolytes, such as poly(diallyldimethylammonium chloride) (PDDA) and poly(styrene sulfonate) (PSS), without any further adjustment of the pH [42]. Although the film thickness of the polymeric matrix can be perfectly controlled by the number of layers deposited onto the substrate, a better control over particles size and distribution in the films are not easy to achieve with the in situ chemical reduction and as a result, only yellow coloration is observed. Our hypothesis for obtaining the color is due to a greater degree control

over particles (shape and size distribution) in the films with a real need of maintaining the aggregation state. To overcome this situation, we propose a first stage of synthesis of multicolorAgNPs (violet, green and orange) in aqueous polymeric solution (PAA) with a well-defined shape and size. A second stage is based on the incorporation of these AgNPs into a polyelectrolyte multilayer thin film using the layer-by-layer (LbL) assembly. To our knowledge, this is the first time that a study about the color formation based on AgNPs is investigated in films preserving the original color of the solutions. Methods Materials Poly(allylamine Cisplatin hydrochloride) (PAH) (Mw 56,000), Poly(acrylic acid, sodium salt) 35 wt% solution in water (PAA) (Mw 15,000), silver nitrate (>99% titration)

and boranedimethylamine complex (DMAB) were purchased from Sigma-Aldrich and used without any further purification. Synthesis method of the PAA-capped AgNPs Multicolor silver nanoparticles have been prepared by adding freshly variable DMAB concentration (0.033, 0.33 and 3.33 mM) to vigorously stirred solution which contained Sinomenine constant PAA (25 mM) and AgNO3 concentrations (3.33 mM). This yields a molar ratio between the protective and loading agent ([PAA]/[AgNO3] ratio of 7.5:1. The final molar ratios between the reducing and loading agents ([DMAB]/[AgNO3] ratio) were 1:100, 1:10 and 1:1. The reduction of silver cations (Ag+) and all subsequent experiments were performed at room conditions and stored at room temperature. More details of this procedure can be found in the literature [33]. Fabrication of the multilayer film Aqueous solutions of PAH and PAA with a concentration of 25 mM with respect to the repetitive unit were prepared using ultrapure deionized water (18.2 MΩ · cm). The pH was adjusted to 7.5 by the addition of a few drops of NaOH or HCl.