The following article is extracted from Laura Biscaldi's Master'sproject. After three year of engineering curriculum, students are required to perform a six-month individual project in a company or laboratory. During this project, they are expected to use the knowledge and skills they acquired during their studies at Pagora. Laura Biscaldi carried out her final year project in the LGP2 research laboratory (Laboratory of Pulp and Paper Science and Graphic Arts). She especially worked on the behavior of quantum dots (cadmium deprived) in functional inks.
The topic of this paper deals with Quantum dots and their behavior when introduced in printing inks. Quantum dots are nano-sized particles that have optical properties linked to their size, among which photoluminescence. For some years, quantum dots have been the subject of intensive research, because of their very interesting properties, as well as their various applications (such as lightning, healthcare, or photovoltaic energy). Introducing nano-particles in inks enables us to consider applications in the anti-counterfeiting area.
This project was realized in parternship with Damier Boyer, and Rodolphe Valleix, respectively researcher and PhD student at the Clermont-Ferrand Institute of chemistry, who synthesized quantum dots suspension in Isopropanol samples. Their particularity is that they are Cadmium deprived, which is important since cadmium is a heavy metal that can have harmful consequences.
The initial method consists in preparing ink formulation for different printing processes: inkjet, flexography and screen printing. Inkjet is considered in first place since it is the most common process used in research publications dealing with this topic. The first step of the experimental plan was to determine the optimal concentration of Quantum dots in inks as well as the optimal thickness of the ink film for each process in order to obtain the most intense fluorescence. Several substrates were used in order to identify different potential applications: special paper for anti-counterfeiting and polymers for intelligent signing and packaging.
In this article, only the first part of this project will be presented, i.e. the state of the art, which will enable us to understand theoretical aspects of quantum dots, notably how they work.