Organization of silver nanowires in a poly(vinyl alcohol) microchanneled hydrogel obtained by cryogenic processes

HERNÁN E. ROMEO; CRISTINA E. HOPPE; IVÁN PARDIÑAS BLANCO; MANUEL A. LOPEZ QUINTELA; ROBERTO J. J. WILLIAMS; YANINA MINABERRY; MATÍAS JOBBÁGY

Estrasburgo, Francia

Congreso; Second International Conference on Multifunctional , Hybrid and Nanomaterials; 2011

Anisotropic noble metal nanoparticles (NPs) are finding applications in diverse fields as photonics, catalysis, sensors, etc.1 Technological interest of these NPs lies in their enhanced fluorescence, non-linear optical properties, near infrared optical resonances and orientation-dependent plasmon excitations.2-3  Design of devices based on NPs requires their dispersion in a solid substrate to obtain free-standing materials, either in the form of bidemensional films or membranes, as well as free standing three-dimensional scaffolds. Certain applications, as in biosensing, also require a proper porosity, in order to assure fast accesibility and direct contact of the analyte with the metal. Biocompatible cryogenic processes, based on freezing of hydrogels and subsequent freeze-drying, have been widely used for scaffold preparation. During the freezing of colloidal aqueous suspensions most solutes are segregated from the ice phase, giving rise to a macroporous structure characterized by “fences” of matter enclosing ice. This method, named ISISA (ice segregation induced self assembly), allows the control of the macroporosity by tuning suitable freezing conditions.4 Combination of unidirectional freeezing with the use of anisotropic NPs and biocompatible hydrogels could produce simultaneous alignment of the nanostructures along the pores following the freezing direction. Hence, application of ISISA to these systems could found interesting applications in sensing,  building novel platafroms for Surface Enhanced Raman Scattering (SERS). In this work silver nanowires dispersed in poly(vinyl alcohol) gels are organized employing the ISISA method. The influence of processing parameters on the morphology and porosity of final materials is analyzed; the influence of texture on the composite´s properties (mechanical, electrical and optical) is also established.