Hollow conjugated polyelectrolyte (HCPE) microcapsules contain at least one conjugated polyelectrolyte and at least one other polyelectrolyte of complementary charge and the microcapsule has a hollow core. The conjugated polyelectrolyte is a polymer with a multiplicity of charged repeating units where a portion of the charged repeating units form a pi-conjugated sequence. The complementary polyelectrolyte is a polymer with a complementary charged repeating unit to the charged repeating units of the conjugated polyelectrolyte. The HCPE microcapsules can be formed by successively coating a sacrificial core with alternating layers of complementary polyelectrolytes, at least one of which is a conjugated polyelectrolyte. The sacrificial core can be removed to form the hollow center of a HCPE microcapsule. The HCPE microcapsules can be contacted with a medium containing microbes where the HCPE microcapsules associate with the microbes and efficiently kill the microbes when irradiated with light or other electromagnetic radiation.