Effect of acid/base on the third-order optical nonlinearity of polypyrrole

•The composites of polypyrrole were prepared and characterized.•Different optical nonlinearities were observed for the polypyrrole-based materials.•The possible mechanisms for the different nonlinear properties were presented.

Polypyrrole (PPy) and its acid/base composites (PPy·H2SO4, PPy·HCl and PPy·NH3·H2O) were successfully synthesized and were characterized respectively by using fourier transform infrared, ultraviolet/visible absorption, X-ray diffraction, transmission electron microscopy and Raman spectroscopic techniques. The nonlinear optical properties of PPy and its acid/base composites were investigated using nanosecond Z-scan measurements at 532 nm. At the identical linear transmittance, the saturable absorption of pure PPy was changed to reverse saturable absorption by doping with acid (HCl and H2SO4) and base (NH3·H2O). The possible mechanisms for the different nonlinear properties were also discussed.