NOVELTY - Making hybrid organic-inorganic core-shell nanoparticles, involves: a) providing colloidal organic particles as a template; b) adding at least one inorganic oxide precursor; and c) forming an inorganic shell layer from the precursor on the template to result in core-shell nanoparticles; where the template comprises a synthetic polyampholyte.    USE - For making hybrid organic-inorganic core-shell nanoparticles used as encapsulating agent, as catalyst support, as filler material, or as component in optical coatings; and in coating composition for making an anti-reflective (AR) layer on a substrate (all claimed). Also used for encapsulating a compound such as a pharmaceutical agent; and in drug delivery and biomedical applications. The AR coated substrate is used in applications including window glazing, cover glass for solar modules, including thermal and photo-voltaic solar systems, or cover glass for TV screens and displays; and in articles such as solar panels, like a thermal solar panel or a photo-voltaic module, monitors, and touch-screen displays for e.g. mobile phones, and TV sets.    ADVANTAGE - The method makes hybrid organic-inorganic core-shell nanoparticles with improved control of template particle size and structure, thus has improved performance. With the present method it is possible to make colloidal organic particles or aggregates from a synthetic polyampholyte, where the colloidal particles have an average particle size of 10 to 300 nm. This particle size can be controlled by the co-monomer composition of the polyampholyte, and/or by selecting conditions like temperature, pH, salt concentration, and solvent composition. Selecting and varying conditions to set particle dimensions enables one to make dispersions of colloidal organic particles and subsequently core-shell nanoparticles with different particle size starting from one polyampholyte. The dispersion of core-shell nanoparticles obtained is very stable under different conditions; has increased shelf life or storage time, and it allows altering its concentration and solvent system, making the dispersion suitable for various different application requirements. The AR coated substrate obtained by the method shows good AR properties, in combination with good mechanical performance, like a surface hardness of at least 3H, more preferably at least 4H or 5H, as measured by the pencil hardness test. The AR coated substrate shows a minimum reflection of less than or equal to 2% at a coated side at a certain wavelength. The average reflection over a 425-675 nm wavelength range for a two-sided coated substrate is less than or equal to 3%, preferably less than or equal to 1.5 %.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) core-shell nanoparticles obtained by the method;    (2) coating composition for making an anti-reflective layer on a substrate, comprising the core-shell nanoparticles, at least one solvent and optionally at least one binder; and    (3) process for making an anti-reflective coated transparent substrate involving applying the coating composition to the substrate; and drying and curing the applied coating layer.