There's nothing + (subject) + can + (verb)

There's' is a contraction of the words 'there is.' When using the word 'nothing' you are suggesting that something cannot happen or be done.

Here are some examples:

"There's nothing you can harm."
"There's nothing the police can identify."
"There's nothing we can agree on."
"There's nothing we can join."
"There's nothing she can cook."
"There's nothing my dog can learn."

By using the word 'cannot' or 'can't' you change the expression to mean that all is possible.

Here are some examples:

"There is nothing I cannot ask for."
"There's nothing we cannot accomplish."
"There's nothing our dog cannot open."
"There's nothing that truck cannot move."