Using Op-Amp to amplify DC?
Yes, you can amplify a DC voltage. Many signals in applications such as temperature, pressure, weighing, etc., change so slowly that they can be considered DC. The amplifiers that condition these signals will often use op-amps1 to buffer and boost the signal level.

1 "Op-amp" is an abbreviation of "operational amplifier". It is not an initialisation or acronym so we don't write it as OPAMP.