They needed the presence of photosensitizer molecules that either generate reactive species (i.e., photodynamic treatment) such as reactive oxygen species (ROS), or absorb light radiation and convert it to heat energy (photothermal therapy). Pure cellulose is devoid of the qualities of the photosensitizer. To absorb light, it is often modified with tiny molecules through covalent and non-covalent interactions. Most of these photosensitizers are substances that are inert against bacteria. However, they work well to inactivate bacteria when employing lowcost light sources like light-emitting diode (LED) lights .