Presentacion oral invitada: Understanding and designing conjugated polymer nanoparticles for practical aplications

PALACIOS, RODRIGO EMILIANO

Sarasota

Conferencia; 29th Inter-American Photochemical Society (I-APS) Winter Conference; 2020

Inter-American Photochemical Society

Conjugated polymers (CPs) are organic semiconductors of great relevance due to their application in organic-electronic devices, such as solar cells, light emitting diodes, and field effect transistors, among others. It is generally accepted that electronic excitations in CPs are localized in relatively short segments (5-12 monomers) called quasi-chromophores that act largely independently, so that a polymer chain can be considered as a multicromophoric system. Thus, the performance of CP-based devices depends to a large extent on elementary photoinduced energy transfer (ET) processes that occur between these quasi-chromophores and dopants or impurities present in the polymer matrix. In particular, the efficiency of ET from CP to dopant is associated with a benchmark parameter named Antenna Effect (AE). Conjugated polymer nanoparticles (CNP) are nanostructured systems that can be manufactured controlling particle size as well as the amount and spatial distribution of dopant dyes. This allows their use as model systems for the study of confined ET processes and also for their use in a series of practical applications that critically depend on AE.In this talk I will describe our work in the development of doped CNP and in the characterization of intraparticle ET processes using conventional spectroscopic techniques, measurements of single particle fluorescence and computational modeling. Through the modeling of experimental measurements, the influence of several parameters on the ET process and on the AE was determined, such as: quantity and location of dopants and traps, exciton diffusion length and particle size. (1) The knowledge obtained allowed the optimization of CNP for applications where efficient photoexcitation of "photoactive" molecules is required. To discuss some applications of these materials I will summarize our work in the development of CNP as efficient photosensitizers of reactive oxygen species (2) and their successful use in photodynamic therapy protocols against brain and colorectal cancer cells (3) and in photodynamic inactivation of antibiotic-resistant bacteria of clinical relevance (4). Finally, I will describe our recent work using CNP as efficient macro-photoinitiators of vinyl polymerization to form biocompatible macro and nano hydrogels in aqueous media in the absence of co-initiators.