How can I make sure after a tag is scanned once the URL is no longer availalible?

You can't set an automatic command on an NFC Tag, so there's no way to tell the actual NFC Chip to serve a One-Time URL. So there are 3 broad ways you can achieve this:

Ixkio: Tag Authentication Software
With Ixkio you can manage your NFC Tags remotely, changing the URL and establishing rules within the interface. We offer rules based on the number of tag scans, so you could set up a rule for the first scan and another for all subsequent scans.

Server-Side Commands
Each NFC Chip contains a Unique ID, if they're going to a website you own, you could configure your website to make sure that once someone has come from a specific tag they aren't allowed to visit the same page again. This requires a lot more work but gives you more control over what the cut-off is for changing the URL. e.g. only change the URL once the person has signed-up or verified their email. If you have some development experience this whole process can be greatly simplified using Ixkio to manage the NFC communication to your website.

Custom NFC App
Finally, you could develop your own NFC App to read the tags and then change the data on them. If you required anyone who scanned the tag to download your app first, you could then use the app to the wipe the tag after you collected the data.
Seritag - 28 Nov 2024