In such case, different optical fiber sensor signals could be multiplexed into a single optical fiber enabling multipoint measurement. Figure 10 UV–vis spectra of the multilayer thin films of 80 bilayers PAH/PAA-AgNPs (violet, green and orange coloration) in comparison with initial colored PAA-AgNPs solutions. Conclusions In this work, highly stable coloredAgNPs were synthesized using a water-based synthesis route using PAA as capping agent. The weak polyelectrolyte nature of the PAA and the excess of Ag + cations respect to the concentration of reducing agent (DMAB) make possible to achieve nanoparticles with

different sizes, shapes and aggregation states. This yields different coloredAgNPs dispersions (violet, green and orange). Such AgNPs have been successfully incorporated into LbL thin films in this website where the adsorption process was carried out that the AgNPs and aggregates (clusters) within the film are maintained, and thus the coloration of the films is also kept.

In order to find more obtain the proper coloration Selleckchem C188-9 of the thin film, a study about the influence of the number of PAH/PAA-AgNPs bilayers added (10, 20, 30, 40 and 80, respectively), the position of the absorption bands (UV–vis spectra) and the pH value of the weak polyelectrolytes solutions have been performed. A pH value of 7.5 or higher value of the PAA-AgNPs solution is the key to preserve the aggregation state of the AgNPs without any further precipitation or loss of coloration. A better definition of the coloration in the films is observed when a higher number of bilayers (thickness) are added during the LbL assembly (mostly in green color) because of Urocanase a better entrapment of both initial clusters and nanometric spherical nanoparticles. This is indicative of a higher number of AgNPs or aggregates of specific shape and size that are

incorporated into the multilayer film. In addition, AFM images reveal a low roughness of the resultant colored films which drastically changes with a thermal treatment due a total evaporation of the polymeric chains (PAH and PAA), making possible to appreciate the number of AgNPs incorporated as a function of bilayers added. To our knowledge, this is the first time that colored PAA-AgNPs of different sizes and shapes are synthesized and incorporated later in LbL assemblies preserving the original color of the solutions. Acknowledgments This work was supported in part by the Spanish Ministry of Economy and Competitiveness CICYT FEDER TEC2010-17805 research grant. The authors express their gratitude to David García-Ros (Universidad de Navarra) for his help with the TEM images. References 1. Abdullayev E, Sakakibara K, Okamoto K, Wei W, Ariga K, Lvov Y: Natural tubule clay template synthesis of silver nanorods for antibacterial composite coating. ACS Appl Mater Interfaces 2011, 3:4040–4046.CrossRef 2.