Based on our experimental observations, the mechanism involved in Au NP-mediated etching of silica can be discussed with the aid of several reported mechanisms/hypotheses for the chemical etching of bare silica. Here, the mechanism mainly comprises the adsorption of fluoride species on the surface and its removal from the surface leaving pit-like structures on the surface. In Au-NP mediated etching, the circular and elongated pit structures are reported as the main etched profiles on silica. This is because the NPs protect their respective deposited region on the silica surface from fluoride penetration. Thus, only the surrounding regions are available for etching, and the contact between Au NPs and silica surface act as the initiating points for the generation of smaller pits at the initial stages. These initiating points may be larger in number in NP-mediated etching compared to that in bare silica etching, where the initiation of etching is expected to be random. With time, these pits grow larger and deeper and form elongated pits and their arrays respectively.