How to store √ and ✓ (tick mark) symbols

I am trying to store √ and ✓ symbols in an nvarchar(50) column.

Here is code sample

vtick.Text = "√";
vvtick.Text = "✓";

INSERT INTO qstnscon (vt,pt) VALUES ('"+vtick.Text+"','"+vvtick.Text+"')";

But instead it stores simple characters (e.g. v). What is causing this problem?