Owing　to　their　unique,　nanoscale　related　optical　properties,　nanostructures　assembled　from　molecular　photosensitizers　(PSs)　have　interesting　applications　in　phototheranostics.　However,　most　nanostructured　PS　assemblies　are　super-quenched,　thus,　preventing　their　use　in　photodynamic　therapy　(PDT).　Although　some　of　these　materials　undergo　stimuli-responsive　disassembly,　which　leads　to　partial　recovery　of　PDT　activity,　their　therapeutic　potentials　are　unsatisfactory　owing　to　a　limited　ability　to　promote　generation　reactive　oxygen　species　(ROS),　especially　via　type　I　photoreactions　(i.e.,　not　by　1O2　generation).　Herein　we　demonstrate　that　a　new,　nanostructured　phthalocyanine　assembly,　NanoPcA,　has　the　ability　to　promote　highly　efficient　ROS　generation　via　the　type　I　mechanism.　The　results　of　antibacterial　studies　demonstrate　that　NanoPcA　has　potential　PDT　applications.　©　2018　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim