Chemically and biologically modified nanoparticles are increasingly considered as viable and multifunctional tools to be used in cancer theranostics. Herein, we demonstrate that coordination of alizarin blue black B (ABBB) to the TiO₂nanoparticle surface enhances the resulting nanoparticles by (1) creating distinct fluorescence emission spectra that differentiate smaller TiO₂nanoparticles from larger TiO₂nanoparticle aggregates (both in vitro and intracellular) and (2) enhancing visible light activation of TiO₂nanoparticles above previously described methods to induce in vitro and intracellular damage to DNA and other targets. ABBB–TiO₂nanoparticles are characterized through sedimentation, spectral absorbance, and gel electrophoresis. The possible coordination modes of ABBB to the TiO₂nanoparticle surface are modeled by computational methods. Fluorescence emission spectroscopy studies indicate that ABBB coordination on TiO₂nanoparticles enables discernment between nanoparticles and nanoparticle aggregates both in vitro and intracellular through fluorescence confocal microscopy. Visible light activated ABBB–TiO₂nanoparticles are capable of inflicting increased DNA cleavage through localized production of reactive oxygen species as visualized by plasmid DNA damage detected through gel electrophoresis and atomic force microscopy. Finally, visible light excited ABBB–TiO₂nanoparticles are capable of inflicting damage upon HeLa (cervical cancer) cells by inducing alterations in DNA structure and membrane associated proteins. The multifunctional abilities of these ABBB–TiO₂nanoparticles to visualize and monitor aggregation in real time, as well as inflict visible light triggered damage upon cancer targets will enhance the use of TiO₂nanoparticles in cancer theranostics.