6. In the Cartesian coordinate system $x O y$, the parabola $\Gamma: y^{2}=2 p x(p>0)$ has a focus at $F$. A tangent line to $\Gamma$ is drawn through a point $P$ on $\Gamma$ different from $O$, intersecting the $y$-axis at point $Q$. If $|F P|=2,|F Q|=1$, then the dot product of vectors $\overrightarrow{O P}$ and $\overrightarrow{O Q}$ is $\qquad$ .