You also made several trials with limes, lemons, with olive oil, a slice of apple or onion, with and without the stone?
Well, after all these tips, I really believed that lemon was the most effective to keep my avocado cut in half so that it does not blacken!
Actually ... It's water!
Yes ... water in a Ziploc bag with a zipper and placed in the fridge! That's all!
The proof? There it is! Watch this short video. They tested all the techniques! See what happens with water after 48 hours! An avocado, not blackened at all!