Spider curls will nail the short/inner head of the biceps. The constant tension, especially at the top portion of the movement, can trigger new biceps growth.
Push the dumbbells together while you squeeze and contract the biceps. At the top of the movement, pause for one second before beginning the lowering phase of the rep.
Now extend the set once you fatigue: change the force angle by moving the elbows further back and shortening the range of movement. This will allow you to get a few extra reps.