opamp without negative supply
Standard opamps can't work with input voltages close to the power supply, neither V+ or V-. Same for the output: they don't go all the way to V+ or V-. What you need is a rail-to-rail I/O opamp. (There are also opamps which are only input or output rail-to-rail!).
Also, most opamps want a dual supply, often minimum +5V/-5V. Since you're using it as a single supply opamp, your V+ - V- difference may be too low for normal operation.
Look for a single supply opamp. They often work at low power supply voltages only, and most of them will be rail-to-rail I/O.

note: actually, any dual supply opamp can be used as a single supply; since voltage is relative the opamp doesn't know whether V- is a negative voltage or ground. By single supply opamp I mean specifically an opamp which is low voltage, like I mentioned above.