NOVELTY - Anti-reflective product comprises: a substrate; and an anti-reflective film adhered to at least one surface of the substrate. The anti-reflective film comprises nanoparticles having an average diameter smaller than at least some wavelengths of incident light, and the anti-reflective product has a reflectivity of less than 4% across a 400-900 nm spectrum.    USE - The product is useful to prepare anti-reflective coatings (claimed), which are useful in solar catalytic micro reactor for performing endothermic reactions, to produce anti-reflective coated lenses, fuel cell electrode membranes, photovoltaic films, solar cells, flexible solar cells, solar catalytic micro reactors, wearable electronics, photonic, thermoelectric, biomedical films, or chemical/biological sensor sorbents.    ADVANTAGE - The anti-reflective product improves uniform and highly oriented surface morphologies of films deposited, and provides thin films with high performance, higher crystallinity and less porosity, compared to films deposited by a conventional batch process. The method: is flexible; reduces cost compared to conventional methods; can be performed at low temperatures and thus avoids as a post-deposition, high-temperature annealing steps; provides more reliable and reproducible deposition by reducing deposition of unsuitable layers; decreases the amount of waste materials generated; allows control over the homogeneous reaction of chemical bath solution; and synthesizes nanomaterials in the required volumes at the point of application and thus reduces human exposure to hazardous materials, and reduces the need to transport and storage of the hazardous materials.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) an apparatus, comprising: a substrate having a first major planar surface and a second major planar surface; the anti-reflective film disposed on the first major planar surface; and a microchannel reactor disposed on the second major planar surface, where the microchannel reactor is coated with nano-structured catalysts; and    (2) preparing the anti-reflective coating, comprising: providing a substrate; providing a first reactant solution; providing a second reactant solution; combining the first reactant solution with the second reactant solution to form a deposition material; and applying the deposition material to the substrate.