While the general approach of the presented paper is not completely new, the combination of EBL patterning with a specific deposition technique, that is electroless growth, is an original scheme. To cite a few examples, in [35], Gopinath and colleagues demonstrated the use of a combined top down and bottom up fabrication process to obtain multi-scale systems with improved Raman sensing capabilities, where the top-down part of the process is represented by EBL patterning, like in our work. Nevertheless, in the cited paper, the authors utilized electron-beam evaporation for depositing the final nanoparticles. Differently from the described method, electroless growth allows realization of full three-dimensional structures, that is nanospheres, in opposition to disc-like, 2 + 1 dimensional structures, like those that may be obtained using a planar evaporation process.

In [36], Pinna and colleagues obtained nanocomposite thin films formed by mesoporous titania layers loaded with ceria nanoparticles exposing the titania matrix with hard X-rays, where the exposition to hard X-rays triggers the formation of crystalline cerium oxides within the pores inducing the in situ growth of nanoparticles. Differently from this, our method does not require hard-X ray lithography and related instrumentation, including costly synchrotron radiation. Instead, the growth is site selective, and takes place in a solution of silver nitrate and hydrofluoric acid, that are compounds easily found in a chemical lab.

Moreover, in our paper, rather than focusing on specific applications of the technique, we attempt to provide an explanation of the fundamental mechanisms of electroless particle formation at the nanoscale, using a joint experimental, numerical and theoretical approach. Also, none of cited the papers have the resolution and the geometrical/structural control found in our case.Electroless deposition is a technique in which metal ions in solution can be reduced and deposited as metals using appropriate reducing agents, in presence of a catalyst that can accelerate the electroless reaction allowing for the oxidation of the reducing agent. In order to boost the transfer of electrons, both the metal ions and the reducing agent should be adsorbed Drug_discovery onto the catalytic surface. While electroless deposition is a general process, we used here silicon as a plating substrate because it delivers the interesting ability to behave like a catalyst and reducing agent, simultaneously. This means that metal ions can be reduced as atoms on specific patterned sites of a silicon surface without the need of an external reducing agent.