Methods of preparing monodispersed polydopamine nano- or microspheres are provided. The methods comprise providing a solvent system comprising water and at least one alcohol having the formula R—OH, wherein R is selected from the group consisting of optionally substituted C1-C6 alkyl, optionally substituted C2-C6 alkenyl, optionally substituted C2-C6 alkynyl, optionally substituted C3-C6 cycloalkyl, optionally substituted C3-C6 cycloalkenyl, and optionally substituted C6-C7 aryl; adding dopamine to said solvent system to form a reaction mixture; and agitating said reaction mixture for a time period of 1 to 10 days to form said monodispersed polydopamine nano- or microspheres. Methods of preparing carbon and hollow metal or metal oxide nano- or microspheres using the polydopamine nano- or microspheres are also provided.