Is being a higher rank lattice a first order property?

We show that there is a sentence $\phi$ in the first order language of groups such that a finitely generated group $\mathrm{\Gamma }$ satisfies $\phi$ if and only if $\mathrm{\Gamma }$ is isomorphic to a group of the form ${\mathrm{P}\mathrm{S}\mathrm{L}}_n(O)$, where $n\ge 3$ and $O$ is a ring of $S$-integers in a number field.