Generating highly reflective and conductive metal layers through a light-assisted synthesis and assembling of silver nanoparticles in a polymer matrix

Mohamed Zaier,Loïc Vidal,Samar Hajjar-Garreau,Lavinia Balan

doi:10.1038/s41598-017-12617-8

Abstract

The development of metalized surfaces exhibiting mirror properties and/or electric conductivity without heavy equipments and with low metal charge is a big challenge in view of many industrial applications. We report herein on the photo-assembling of silver nanoparticles (AgNPs) in a polymer matrix, carried out within minutes from an acrylate monomer and silver nitrate at room temperature, under air and without any solvents. The top surface of the material gets converted into a continuous silver thin film and a depthwise concentration gradient of AgNPs is created in the polymer, which images the absorption profile of the actinic UV light in the reactive formulation. This specific assembling of the silver@polymer coating induces excellent reflective and conductive properties. The conductance was observed to strongly increase with increasing the exposure from 3 to 30 min due to the formation of a more and more compact metal film. This coating strategy works with a variety of substrates (textile, paper, glass, wood, plastic and stainless steel). Moreover, on flexible surfaces such as textile, the flexibility was preserved. The possibility to use this kind of nanomaterial as a printing ink, with a much lower metal concentration (3 to 5 wt.%) than concurrent inks, was also demonstrated.

Highlights

In the past decades, the deposition of metal nanoparticles (MNPs) at the surface of various substrates for applications such as highly reflective coatings or printing techniques has gained wide interest
Recent reports demonstrated that assembling of silver nanoparticles (AgNPs) inks can be prepared using preformed poly(acrylic acid) or poly(vinylpyrrolidinone) while AgNPs obtained by reduction of an Ag+ salt using ethylene glycol at high temperature or monoethanolamine as reducing agents or via a modified Tollens’ process require ammonium hydroxide and formic acid[25,26,27,28,29]
The highly reactive free radicals stemming from homolytic cleavage of the photosensitive precursor are used to reduce silver cations to AgNPs

Summary

Introduction

The deposition of metal nanoparticles (MNPs) at the surface of various substrates for applications such as highly reflective coatings or printing techniques has gained wide interest. The mirror state requires the continuous application of a reductive voltage to avoid the dissolution of the Ag film into the electrolyte Another chemical method developed recently to generate Ag mirrors is the fluoride-induced reduction of Ag+ cations. Our research group developed MNPs and metal-polymer nanocomposites (silver, gold or palladium) using a photo-induced approach Because it allows activation of chemical reactions at ambient temperature, light acts without inducing collateral damages due to heating of the surrounding media. This approach offers the advantage over concurrent thermally activated processes to generate MNPs in situ and in a photosensitive formulation or in a polymer matrix. The perfect control of the spacial distribution of MNPs and their assembling is clearly a challenge for the synthesis of 3-dimensionally (3D) shaped nanomaterials

Methods

Results

Conclusion