Property tuning and supramolecular organization of oligo- and polythiophenes for applications in biology and organic electronics

My research activity was focused on the synthesis and characterization of novel thiophene-based oligomers and polymers for the preparation via self-assembly of nanoparticles (0D) and fibers (1D) aimed to application in organic electronics and biophotonics. The first chapter shows an overview of the most recent developments in synthesis and application of oligo- and polythiophenes as organic materials, highlighting the state of the art in synthetic procedures, performances in devices and application in biology as fluorescent probes. The second chapter reports the synthesis of novel classes of selectively sulphur-oxidized oligo- and polythiophenes. Oligomers and polymers containing thiophene-S,S-dioxide and thiophene-S-oxide units in the desired number and position are described. Examples of their application in devices and supramolecular organization inside live cells are given. The third chapter is dedicated to the preparation and characterization of polythiophene based nanoparticles for biophotonics. It is demonstrated that live cells easily uptake poly(3-hexylthiophene) nanoparticles (P3HT-NPs) without toxic effects while preserving their physiological functions. In addition, it is reported that P3HT-NPs can act as “photosensitizers” after internalization in live animals, Hydra vulgaris, modifying their behaviour and genic expression upon white light irradiation. Finally, the preparation of amino-reactive NPs, obtained from a properly functionalized polythiophene, is reported. The ability of the nanoparticles to remain docked on cell membrane and to act as phototransducers under illumination is demonstrated. The fourth chapter reports the synthesis and the supramolecular organization in crystalline, fluorescent and electro-active fibers of oligothiophenes possessing the same core properly functionalized. Further functionalization of the quaterthiophene with different electron withdrawing aromatic terminal units causes the variation of the electronic distribution without altering the growth modalities. In this way a wide tuning of the optical and redox properties of the fibers is obtained. Studies on the effects of the terminal substituents on charge transport properties are currently under way

Semicrystalline Polythiophene-Based Nanoparticles Deposited from Water on Flexible PET/ITO Substrates as a Sustainable Approach toward Long-Lasting Solid-State Electrochromic Devices

info:eu-repo/grantAgreement/EC/H2020/734834/EU FCT/MEC (UIDB/50006/2020). PhD grant SFRH/BD/139171/2018 from FCT/MCTES. We are very grateful to Dr. Carlos Pinheiro and Ynvisible company for discussions and assistance in the assembly of the electrochromic devices.We report the use of films of poly(3-hexylthiophene-2,5-diyl) nanoparticles (P3HT-NPs) prepared with the reprecipitation method employing water as solvent in the absence of surfactants for solid-state electrochromic devices (ECDs) and prove that these displays present enhanced properties when compared to similar ECDs with thin films deposited from chloroform. Films of differently sized nanoparticles (100 to 400 nm) were prepared and spray-coated on flexible PET-ITO substrates and tested for electrochromic properties. ECDs with switching times (t(90)) of 4 s were obtained using P3HT-NPs with a diameter of 100 nm, while those built using P3HT thin film presented longer switching speeds over 13 s for reduction (bleached to colored state). Additionally, the devices were subjected to 1000 cycles using -1.5 V/1.5 V, and the displays using P3HT 100 nm NPs presented higher transmittances (Delta(T) = +/- 20%) when compared with devices with P3HT thin film due to a more efficient oxidation step. Our data show that the availability of colloidal nanoparticles made of conjugated polymers deposited from water is an environmentally sustainable strategy leading to electrochromic devices with improved properties.authorsversionpublishe

Photocatalytic Activity of Polymer Nanoparticles Modulates Intracellular Calcium Dynamics and Reactive Oxygen Species in HEK-293 Cells

Optical modulation of living cells activity by light-absorbing exogenous materials is gaining increasing interest, due to the possibility both to achieve high spatial and temporal resolution with a minimally invasive and reversible technique and to avoid the need of viral transfection with light-sensitive proteins. In this context, conjugated polymers represent ideal candidates for photo-transduction, due to their excellent optoelectronic and biocompatibility properties. In this work, we demonstrate that organic polymer nanoparticles, based on poly(3-hexylthiophene) conjugated polymer, establish a functional interaction with an in vitro cell model (Human Embryonic Kidney cells, HEK-293). They display photocatalytic activity in aqueous environment and, once internalized within the cell cytosol, efficiently generate reactive oxygen species (ROS) upon visible light excitation, without affecting cell viability. Interestingly, light-activated ROS generation deterministically triggers modulation of intracellular calcium ion flux, successfully controlled at the single cell level. In perspective, the capability of polymer NPs to produce ROS and to modulate Ca2+ dynamics by illumination on-demand, at non-toxic levels, may open the path to the study of biological processes with a gene-less approach and unprecedented spatio-temporal resolution, as well as to the development of new biotechnology tools for cell optical modulation

Supramolecular Thiophene-Based Materials: A Few Examples of the Interplay between Synthesis, Optoelectronic Properties and Applications

Abstract Supramolecular nanostructured thiophene based materials with optoelectronic functions are of wide current interest and are playing a crucial role in different fields of nanoscience and nanotechnology. This short review gives a concise report of some particularly interesting examples from our own work concerning thiophene-based supramolecular architectures at multiple length scales, their function and application in devices. We start with some general considerations on the great chemical diversity of thiophene derivatives and their supramolecular architectures. Then we focus on how the supramolecular organization of specific thiophene derivatives may generate nanostructures that enable new functions and applications in devices. For each example, we report the synthesis of the corresponding thiophene derivatives. 1. Introduction 2. Supramolecular Organization may Impart New Functions to the System 3. Supramolecular and Optoelectronic Properties of Oligothiophene-S,S-dioxides 4. Colloidal Nanoparticles formed by Self-Assembly of Thiophene-Based Polymers 5. Conclusions and Outloo

Semiconducting polymers are light nanotransducers in eyeless animals

Current implant technology uses electrical signals at the electrode-neural interface. This rather invasive approach presents important issues in terms of performance, tolerability, and overall safety of the implants. Inducing light sensitivity in living organisms is an alternative method that provides groundbreaking opportunities in neuroscience. Optogenetics is a spectacular demonstration of this, yet is limited by the viral transfection of exogenous genetic material. We propose a nongenetic approach toward light control of biological functions in living animals. We show that nanoparticles based on poly(3-hexylthiophene) can be internalized in eyeless freshwater polyps and are fully biocompatible. Under light, the nanoparticles modify the light response of the animals, at two different levels: (i) they enhance the contraction events of the animal body, and (ii) they change the transcriptional activation of the opsin3-like gene. This suggests the establishment of a seamless and biomimetic interface between the living organism and the polymer nanoparticles that behave as light nanotransducers, coping with or amplifying the function of primitive photoreceptors

Engineered living materials for biomedical application

Resumen del trabajo presentado a la Conference on Advanced Materials and Devices for Nanomed (AMA4MED), celebrada en Valencia (España) del 3 al 4 de mayo de 2022.Peer reviewe

Poly(3-hexylthiophene) nanoparticles for biophotonics: study of the mutual interaction with living cells

We report on the mutual interaction between poly(3-hexylthiophene) nanoparticles (P3HT-NPs) and human embryonic kidney (HEK-293) cells. P3HT-NPs, prepared in sterile conditions and efficiently uptaken within the live cells cytosol, show well-ordered morphology, high colloidal stability and excellent biocompatibility. Electrophysiology and calcium imaging experiments demonstrate that physiological functions of live cells are fully preserved in the presence of P3HT-NPs. From a complementary point of view, the photophysical properties of P3HT-NPs are also mainly maintained within the cellular environment, as proven by in situ time-resolved photoluminescence. Interestingly, we detect slight modifications in emission spectra and dynamics, which we ascribe to the contribution from the P3HT-NPs surface, possibly due to conformational changes as the result of the interaction with intracellular proteins or the formation of NPs aggregates. This work demonstrates that P3HT-NPs are excellent candidates for use as light sensitive actuators, due to their remarkable physical properties, optimal biocompatibility and capability of interaction with living cells

Thermodynamically versus Kinetically Controlled Self-Assembly of a Naphthalenediimide-Thiophene Derivative: From Crystalline, Fluorescent, n-Type Semiconducting 1D Needles to Nanofibers

The control over aggregation pathways is a key requirement for present and future technologies, as it can provide access to a variety of sophisticated structures with unique functional properties. In this work, we demonstrate an unprecedented control over the supramolecular self-assembly of a semiconductive material, based on a naphthalenediimide core functionalized with phenyl-thiophene moieties at the imide termini, by trapping the molecules into different arrangements depending on the crystallization conditions. The control of the solvent evaporation rate enables the growth of highly elaborated hierarchical self-assembled structures: either in an energy-minimum thermodynamic state when the solvent is slowly evaporated forming needle-shaped crystals (polymorph \u3b1) or in a local energy-minimum state when the solvent is rapidly evaporated leading to the formation of nanofibers (polymorph \u3b2). The exceptional persistence of the kinetically trapped \u3b2 form allowed the study and comparison of its characteristics with that of the stable \u3b1 form, revealing the importance of molecular aggregation geometry in functional properties. Intriguingly, we found that compared to the thermodynamically stable \u3b1 phase, characterized by a J-type aggregation, the \u3b2 phase exhibits (i) an unusual strong blue shift of the emission from the charge-transfer state responsible for the solid-state luminescent enhancement, (ii) a higher work function with a "rigid shift" of the electronic levels, as shown by Kelvin probe force microscopy and cyclic voltammetry measurements, and (iii) a superior field-effect transistor mobility in agreement with an H-type aggregation as indicated by X-ray analysis and theoretical calculations