Low-energy electron irradiation assisted diffusion of gold nanoparticles in polymer matrix

• The results indicate that low energy electrons can effectively be used for the synthesis of nanoparticles of different sizes.
• This study leads to a definite conclusion that gold nanoparticles have been synthesized in surface region of the PVA sheet.
• The size of nanoparticles decreases with increasing electron fluence.
• The depth of diffusion of Au atoms at maximum fluence was found to be ~1.5 μm.

A simple and controllable method to synthesize nanoparticles in the surface region of polymers was used by low energy electron irradiation. Using this method, gold nanoparticles have been synthesized by irradiating gold coated PVA (Polyvinyl Alcohol) sheets. This method was easy in operation and even period of few minutes was sufficient to obtain the nanoparticles. The coatings (~10 μm) made from a mixture of ethanol and HAuCl4 on PVA sheets (~150 μm) by simple drop cast method were irradiated with 30 keV electrons, at room temperature and 10−6 mbar vacuum level. The electron fluence was varied from coating to coating in the range of 0 to 24×1015 e/cm2. The irradiated samples were characterized by the UV–Vis, XRD, SEM and RBS techniques. The plasmon absorption peak at ~539 nm in UV–Vis spectra was an evidence for the initiation of the growth of gold nanoparticles. The X-ray diffraction results and the blue shift in the plasmon absorption peak reveal that the size of nanoparticles could be tailored in the range from 58 to 40 nm by varying the electron fluence. The diffusion of gold in the PVA was confirmed by the Rutherford backscattering spectroscopy and scanning electron microscopy techniques. This method of synthesis of metal nanoparticles by low energy electron beam irradiation has the key importance in the development of new fabrication techniques for nanomaterials.