TiO2 nanoparticles are well known for their photocatalytic activities that can be used for air purification and antibiotic purposes. These nanoparticles need to be well-crystalized, rather than amorphous and preferably in the crystal phase Anatase to produce the best photocatalytic efficiency. Oftentimes, these TiO2 particles are applied in a thin layer to a substrate but, without causing damage to substrate, they lack adequate adhesion. Conventional approaches to applying this coating involve using a TiO2 mixture followed by high temperature sintering. This method does not work very well if the substrate is a plastic or metal. In other approaches like sol-gel, CVD, or PVD the TiO2 tends to be amorphous or mix-phased, being both anatase and rutile phased, unless a high temperature is used. In this work, we will introduce a new, low-temperature coating method where an anodized metal substrate and a plastic air filter, which is pretreated with atomic layer deposition (ALD), are coated with an anatase-phased TiO2 and silica sol-gel mixture. This is then followed by a low-temperature curing and another ALD process. Investigated in this work are the photocatalytic air purification and antibiotic efficacy at various conditions where the TiO2 nanoparticles in the coating are still highly crystalline and photocatalytic.