This study reports the critical importance of the particle state in TiO2 immobilized photocatalysis. To address this, TiO2 coatings are prepared using two methods: an Air Assisted Spray with an Automatized Spinning Coating (TiO2-AAS-ASC) and a Spread Coating (TiO2-SCM). The state of the TiO2 particles is investigated using SEM and local gravimetry. It is proven that the TiO2-AAS-ASC displays homogeneity, limited particle agglomeration, close to optimum thickness and stability under flow. Furthermore, the prepared coatings are evaluated in terms of photoactivity using acetone in air mineralization in the 24-49 mu moI/L initial concentration range. This allows Quantum Efficiency evaluations based on absorbed photons and hydroxyl radical consumed. It is proven that the TiO2-AAS-ASC exhibits a close to expected optimum photoactivity and QYs in the 0.4-0.5 range. Furthermore, when the TiO2-AAS-ASC is assessed in terms of QY per unit weight of photocatalyst (QY/W), it shows a value 3 times higher than the TiO2-SCM. This high photon utilization is close to the best possible level expected for an optimized TiO2 coating. (C) 2016 Elsevier B.V. All rights reserved.