Various embodiments of the present disclosure pertain to nanocomposites for detecting hydrocarbons in a geological structure. In some embodiments, the nanocomposites include: a core particle; a polymer associated with the core particle; a sulfur-based moiety associated with the polymer; and a releasable probe molecule associated with the core particle, where the releasable probe molecule is releasable from the core particle upon exposure to hydrocarbons. Additional embodiments of the present disclosure pertain to methods of detecting hydrocarbons in a geological structure by utilizing the nanocomposites of the present disclosure.