A multi-parametric investigation of the fundamental processes regulating the response of self-assembled nanostructures to multiple stimulations
Abstract
Stimuli responsive materials are finding increasing importance in fields of high social and economic impact that include drug delivery, diagnostics, tissue engineering and ÔsmartÕ optical systems, as well as microelectronics, biosensors, microelectromechanics, coatings and textiles. Although different design approaches have been suggested, in this research project we propose the self-assembly of molecular or nanostructured building blocks as one of the most versatile, straightforward and powerful strategy to achieve stimuli-responsive materials. The response of these architectures, either to environmental or external solicitation, can be, in fact, achieved by exploiting the same inter-components interactions that brings to their assembly. As a consequence self-assembled systems are intrinsically, at least potentially, responsive. Considered the nature of the interactions involved in supramolecular and hetero-supramolecular assembly (hydrogen bond, electrostatic attraction, hydrophobic effect, pi-pi stacking, electronic charge-transfer, etc.), an interesting variety of elemental processes, including protonation/deprotonation, oxidation/reduction and polarity changes, can be easily exploited to trigger system aggregation/disaggregation. Moreover, self-assembled aggregates can be destabilized by temperature fluctuations or upon selective irradiation of light, when suitable components are included in the architectures. Concentration is a very important parameter that affects the stability of self-assembled structures ,which disaggregate upon dilution. Investigating the response of self-organized nanostructures to concentration changes is hence crucial both for fundamental science and application. Response to pH changes is a very simple and effective process that can be exploited to design materials suitable for a wide range of applications, including drug delivery and controlled release. Finally, light is a very versatile, easily controllable and tunable stimulus that allows to activate, specifically and locally, photo-responsive materials. Investigating the response to concentration and pH changes, as well as to light irradiation of self-assembled nano-systems is the fundamental objective of this research project. Recently we demonstrated that perylene bisimide (PBIs) derivatives organize in self-assembled nanostructures that responds to pH and light, as well as to concentration fluctuations. We propose these systems as a very versatile platform suitable to design sophisticated multi-responsive, self-organized nanomaterials. Self-assembly of organic fluorophores in aqueous environment is a well-known, extensively investigated, yet still not completely understood, process. Self-organization typically arises from electronic coupling of the aromatic systems (pi-pi stacking) and if suitably exploited, it yields aggregates with emerging new functionalities, specific of the supramolecular assembly and absent in the individual molecular components. In natural systems, specifically organized chromophoric moieties constitute the active part of light harvesting structures involved in photosynthesis. In the recent years, the application of pi-stacks of dyes is extended toward novel technological areas, including optical recording media, organic photo- and semiconductors, solar cells, and chemical- and bio-sensors. Although the self-assembly of PBIs has been investigated quite in the detail a fundamental study of the effect of external solicitation, in particularly of pH changes and light irradiation, is still missing. This basic study is the main objective of this research project. In particular, considered the dramatic effect of aggregation/disaggregation and morphological reorganization on the fluorescence properties, these processes will be conveniently investigated by fluorescence based techniques.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 12, 2017
- Source ID
- W911NF1610324
Entities
People
- Marco Montalti
Organizations
- Army Contracting Command
- United States Army