Monomer or aggregate? Solution chemistry applications to today's problems

Solution chemistry and reliable equilibria analysis can non-negligibly contribute to recent challenges, even using relatively simple experiments and approaches. Studies aimed to analyse if a molecule is present in the form of a monomer or undergoes auto-aggregation processes, depending on different surroundings conditions, can deserve interest and find practical applications. For instance, analysis of the micelle formation process of amphiphilic block copolymers, dependent on external parameters such as temperature or pH, deserves high interest in connection to the applications in diverse areas as for instance enhanced oil recovery. We will present some aspects of the analysis of small molecules aggregation that we are dealing with in our group. Thioflavin-T (4-(3,6-dimethyl-1,3-benzothiazol-3-ium-2-yl)-N,N-dimethylaniline, TFT) is a fluorescent emicyanine dye (Figure 1) which acts as a molecular rotor. The interest on TFT molecule stays on its peculiar photophysical properties, which can find application in biochemistry and medicine. TFT has been used as common marker in biomedical research over the last 50 years but, more recently, TFT has become a major tool to recognise amyloid fibrils, both in vivo and in vitro. The ability to selectively bind to the fibrils, in particular at the level of -sheet and at hydrophobic amino acid residues, is also correlated to the tendency to auto-aggregate. Therefore, we have analysed, by a thermodynamic and kinetic approach, the mechanistic details of TFT auto-aggregation process and TFT binding to natural DNA. Carbon nanotubes (CNTs) are well known allotropes of carbon that are nowadays widely studied as their unique (thermal, electrical) properties can find application in materials science and frontier technologies. However, both single walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs) being hydrophobic, these tend to agglomerate, deeply limiting their performances. It is therefore important to stabilise the CNTs dispersions either by chemical modification of their surface or by interaction with species that are bound to the surface by van der Waals forces ( stacking interactions). In the frame of the study of the optical, metal ion binding, and dispersing properties of different types of perylene dye derivatives, we have analysed if the Pery-MeI dye could efficiently disperse MWNT solutions.