All the liquid spray commercial preparations I've tried were a joke. I could almost swear I once saw an ant walk through an application I put down, turn around and flip me the bird. The only commercial product I've ever read RVers having success with is a product called Terro
. Although, I've never used it to confirm their claims.
What I found to be effective was boric acid- obtainable from any pharmacy. I dust it, or mix it with water and sugar until it's the consistency of pancake syrup. Then, using a small brush (I use one of the DW's old make-up brushes), I apply it to the areas where I see ants. Carpenter ants especially love the syrup.
Boric acid doesn't work immediately like you see in the Raid commercial where the bugs holler "RAID!", then explode or fall over dead. However, you should expect to observe noticeable results within a few days. It may take multiple applications to completely eradicate the nest.
Boric Acid acts upon the ant's digestive system and they literally starve to death. It's hard to see with small ants, but with large ants like carpenter ants, you can see that when under its effect will not look as robust and their movement will appear erratic.
From what I've read on the web, boric acid is about as toxic as table salt and sometimes used in a 5% water solution as an eye wash. However, to be safe, I wouldn't apply it to any areas that could be accessible by pets and children.