A method of preparing large area patterned 2D arrays of uncapped gold (Au) nanoparticles has been developed. The pattern has been formed using self-assembly of uncapped Au nanoparticles. The Au nanoparticles were synthesized via toluene/water two phase systems using a reducing agent and colloidal solution of Au nanoparticles was produced. These nanoparticles have been prepared without using any kind of capping agent. Analysis by TEM showed discrete Au nanoparticles of 4 nm average diameter. AFM analysis also showed similar result. The TEM studies showed that these nanoparticles formed self-assembled coherent patterns with dimensions exceeding 500 nm. Spin coating on silicon substrate by suitably adjusting the speed can self-assemble these nanoparticles to lengths exceeding 1 𝜇m.

We show the evolution of Raman spectra with a number of graphene layers on different substrates, SiO₂/Si and conducting indium tin oxide (ITO) plate. The 𝐺 mode peak position and the intensity ratio of 𝐺 and 2𝐷 bands depend on the preparation of sample for the same number of graphene layers. The 2𝐷 Raman band has characteristic line shapes in single and bilayer graphene, capturing the differences in their electronic structure. The defects have a significant influence on the 𝐺 band peak position for the single layer graphene: the frequency shows a blue shift up to 12 cm^-1 depending on the intensity of the 𝐷 Raman band, which is a marker of the defect density. Most surprisingly, Raman spectra of graphene on the conducting ITO plates show a lowering of the 𝐺 mode frequency by ∼ 6 cm^-1 and the 2𝐷 band frequency by ∼ 20 cm^-1. This red-shift of the 𝐺 and 2𝐷 bands is observed for the first time in single layer graphene.