In this brief review, we present some illustrative computational results on the use of atomic clusters to model the solid substrate surfaces, aiming to interpret the phenomena associated with surface-enhanced Raman scattering (SERS) experiments. Using this technique, organic molecules undergo interactions with silver nanoparticles, producing characteristic chemical and spectroscopic enhancements. We exemplify that the small Agn cluster model can reproduce typical chemical enhancements that occur on vibrational modes of the molecules considered, including aromatic compounds, amino acids, pesticides, herbicides etc. Analyses are made for not only the ground state but also for the first excited S1 state, which shows a reverse charge transfer trend. Two different mechanisms are considered to construe the effects induced by the incident light during the SERS phenomena. More importantly, the charge transfer mechanism allows selective and quantitative measurements of the molecule considered in its mixture with several other organic compounds. These results matter for the design of efficient mobile sensors that are expected to potentially detect pollutants and toxic compounds present in the environment and in food and agricultural products rapidly.