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The coating of gold nanorods with a silica shell (AuNR@SiO₂) is an effective way to extend their use in a wide variety of biomedical applications including biosensing, drug delivery and photothermal therapy. A silica shell offers numerous advantages as it provides more stability, frees the surface from toxic cetyltrimethylammonium bromide (CTAB), and preserves the rod shape under photothermal conditions. This shell needs to be very thin for applications such as plasmonic biosensing, while a thicker and porous shell is suited for drug encapsulation and further controlled release. We introduce herein a strategy to perform silica coating based on dissociation of tetraethylorthosilicate (TEOS) hydrolysis and condensation reactions. This dissociation is achieved by a pH modulation of the reaction medium, and, depending on selected pH conditions, AuNR@SiO₂ with a thick silica shell having an organized mesoporosity …