NOVELTY - An anti-reflective product, comprises a substrate (318); and a homogeneous anti-reflective film (320) adhered to at least one surface of the substrate, where the anti-reflective film comprises nanoparticles (324) having an average diameter smaller than at least some wavelengths of incident light, and where the anti-reflective product has a reflectivity of less than about 4% across a 400-nm to 900-nm spectrum. The anti-reflective film is transparent.    USE - As anti-reflective product (claimed) for chemical deposition, particularly continuous deposition of anti-reflective films; and for producing particular products including, without limitation, anti-reflective coated lenses, scratch-resistant, anti-reflective coated lenses, fuel cell electrode membranes, photovoltaic films, solar cells, flexible solar cells, solar catalytic microreactors, wearable electronics, and biomedical films.    ADVANTAGE - The anti-reflective product has a reflectivity of less than about 4% across a 400-nm to 900-nm spectrum. The anti-reflective product has a percent transmittance greater than about 80% across a 400-nm to 900-nm spectrum. The product has an indentation hardness of at least 400 MPa, and/or elastic modulus of at least 10 GPa. The product can withstand a scratch load force of at least 400 mN without delamination of the anti-reflective film from the substrate. Uniform and highly oriented surface morphologies of films deposited using the product are clearly improved compared to films deposited by a conventional batch process. The process can be used at low temperatures as a post-deposition, high-temperature annealing step is obviated. The product provides a constant flux of reactant solution that allows control over the homogeneous reaction of chemical bath solution before the solution impinges on the substrate. Because a micromixer is used, reagent volumes are decreased compared to conventional processes with resulting decrease in waste material generated. The process also can be used to synthesize nanomaterials in the required volumes at the point of application, reducing human exposure to potentially hazardous materials as well as reducing the need to transport and store such potentially hazardous materials. These advantages allow manufacturing process flexibility and reduce costs relative to known processes. Because high-temperature annealing processes are avoided, candidate substrate materials are increased, and include flexible substrate materials, such as polymeric materials, that cannot be used for known, high-temperature chemical bath deposition processes.    DETAILED DESCRIPTION - An anti-reflective product, comprises a substrate (318); and a homogeneous anti-reflective film (320) adhered to at least one surface of the substrate, where the anti-reflective film comprises nanoparticles (324) having an average diameter smaller than at least some wavelengths of incident light, and where the anti-reflective product has a reflectivity of less than about 4% across a 400-nm to 900-nm spectrum. The anti-reflective film is transparent. The substrate is flat. The at least one surface of the substrate is textured. The substrate is glass or is polycarbonate or is an eyeglass lens. The anti-reflective film is adhered to two surfaces of the eyeglass lens. The anti-reflective film comprises: a continuous first layer comprising a polymer containing metal alkoxides, and/or metalloid alkoxides; and a second layer comprising nanoparticles. The anti-reflective product further comprises a third layer comprising the polymer. INDEPENDENT CLAIMS are included for the following:    (1) an apparatus comprising: a substrate having a first major planar surface and a second major planar surface; an anti-reflective film disposed on the first major planar surface, where the film comprises nanoparticles having an average diameter smaller than at least some wavelengths of incident light; and a microchannel reactor disposed on the second major planar surface, where the microchannel reactor is coated with nanostructured catalysts. The nanoparticles have an average size less than 400 nm. In the apparatus, less than about 0.5% of solar radiation is reflected. The microchannel reactor coated with nanostructured catalysts is configured to perform endothermic reaction. The anti-reflective film on the first major planar surface is capable of absorbing solar radiation and the solar radiation provides energy for the endothermic reaction;    (2) a method for preparing an anti-reflective coating, involving 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 to provide an anti-reflective coating comprising nanoparticles smaller than at least some wavelengths of incident light on the substrate; or providing a substrate; applying a first polymer solution comprising a first polymer and a solvent to the substrate to provide a first polymer layer on a surface of the substrate; at least partially drying the first polymer layer; applying the nanoparticle solution comprising nanoparticles having an average diameter smaller than at least some wavelengths of incident light to the first polymer layer to provide an anti-reflective film comprising at least one nanoparticle layer. The method further involves providing energy to the deposition material to produce reactive species, where the energy is thermal, chemical, microwave, photochemical, electrochemical, plasma, and/or ultrasonic; and    (3) an anti-reflective product prepared by the method.    DESCRIPTION OF DRAWING(S) - The figure shows schematic diagram of system for depositing nanostructured thin films onto a substrate.    Continuous-flow reactor system (300)    Pumps (302, 304)    Heat exchangers (306, 308)    First mixer (310)    Microchannel extractor (314)    Second mixer (316)    Substrate (318)    Anti-reflective film (320)    Nanoparticles (324)