Other polymers

Abstract

The dual function of polymers as both a reducing and a stabilising agent in the production of colloidal metal nanoparticles (MNPs) offers a simple, low-cost, greener synthesis for MNPs. In this chapter, efforts directed towards the successful production of colloidal MNPs by the exploitation of both ionic and non-ionic polymers will be discussed. Since polymers are weak reducing agents, the reduction potential of the metal salt is critical as well; therefore, most reported examples are regarding gold and silver NPs. Reduction rate, size and particle morphology depend on the molecular weight of the polymer, polymer/metal salt ratio, concentration, pH, temperature and the type of the electron-donating group to metal ions. Ionic polymers, namely polyelectrolytes, are the most successful ones, with good reducing power and enhanced stabilisation of the MNPs through electrosteric effects, and hence will be discussed in detail. Non-ionic polymers are usually considered less effective, and hence examples are scarce. However, such polymers, e.g. poly(N-vinyl pyrrolidone), allow the production of MNPs with different morphologies in kinetically controlled nucleation and growth processes. Possible mechanisms of oxidation/reduction will also be discussed.