The printability of a copolyfluorene-fluorenone (PFFO) photoluminescent nanoparticle aqueous suspension on commercial tracing paper was here investigated. The nanoparticles suspension was obtained by miniemulsification of a suitable preformed photoluminescent organic polymer. The structural, physicochemical, and rheological characteristics of the nanoparticles suspension were first studied before considering its printability by inkjet and flexography techniques. The native properties of the nanoparticles suspension revealed to be more suitable for inkjet printing which was successfully used to print photoluminescent patterns using a very low amount of PFFO. 1. Introduction Since the middle of the last century the interest towards photoluminescent inks increased steadily either in the interior and packaging decorations (e.g., printing paper and cardboard) or mostly in the paper security sector [1, 2]. In the last domain, inks are composed of chromophores which: (i) are not visible under solar light to provide printed images that can not be photocopied, (ii) are readable only under special environments (e.g., ultraviolet light), (iii) can be thermally erasable for rewriting [3]. The luminescence of the majority of these inks originates from pigments [2], metal complexes [3], or specific organic compounds [4]. In the last decade it was demonstrated that a new material class such as organic semiconductors can be used to achieve luminescence [5] offering new opportunities for light-emitting sources [6] and a multitude of other electronic devices. Especially organic conjugated polymers have an excellent processability, since they are soluble in common organic solvents when functionalized with side chains. Thus, conjugated polymer organic solutions were easily processed by spin- or drop-casting, screen-printing [7–9] or inkjet printing [4, 10–13] for the treatment of several kinds of surfaces. To tune luminescent properties, sophisticated control of the polymer luminescence colour, efficiency, and charge-transport properties are required. The emission wavelength depends on the extent of conjugation/delocalization, and can be controlled by the modification of the configuration or conformation of the polymer and by interactions with the local environment. This can be achieved by grafting functional moieties such as electron donor or acceptor groups, which allow the modulation of the electronic structure of the conjugated backbone. Studies, focused on semiconducting polymer chemistry, showed that polymer backbone substitutions or copolymerisation with other
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