Este trabajo se centra en la síntesis de nuevos nanohíbridos dador-aceptor (D/A) de politiofeno solubles en medios acuosos y en la elucidación de la interacción electrónica entre las unidades D/A como en el funcionamiento de los nanohíbridos en forma de películas delgadas en aplicaciones optoelectrónicas. Utilizando técnicas de auto-ensamblaje in-situ de politiofeno en presencia de diferentes nanomateriales como son el óxido de grafeno, puntos cuánticos de semiconductores o láminas de dicalcogenuros de metales de transición se ha conseguido la formación de complejos de transferencia de carga, solubles en agua y con superiores propiedades electrónicas de relevancia para el desarrollo de dispositivos optoelectrónicos basados en películas delgadas
1 figure.-- Work presented at the 9th Nanodays Workshop on Advanced Materials, Munich (Germany), Sept. 13-15, 2017 ; Intrinsically conducting polymers form the base for the development of plastic electronic devices and hold great promise in optoelectronic applications such as thin film organic field-effect transitors, OLEDS and solar cells. Control of morphology and aggregation states by nanostructuring is essential for improving the device performance. In the last decade, research has focused on liquid phase assembly processes. These afford conjugated polymers in the form of nanoparticles or nanowires, which are dispersible in aqueous dispersions and allow for the fabrication of thin films with well-defined characteristics from environmentally-friendly solutions. Moreover, the liquid phase self-assembly processes provide unique opportunities for the development of novel composite materials with graphene based materials [1, 2]. Here we present our results of our recent work on the development of novel composite materials based of graphene oxide and poly (3-hexylthiophene) (P3HT) [3]. We show that liquid phase assembly processes in the presence of water-soluble graphene oxide sheets lead to the formation P3HT nanoparticles (P3HTNPs) in intimate contact with surrounding sheets of graphene oxide. During the synthesis, graphene oxide acts as a >good> solvent and induces important changes on the internal aggregation structure and the related interchain coupling. At the same time, the charge-transfer properties as a function of GO concentration are modified. Both effects are intimately coupled and lead to the stabilization of of P3HTNPs-GO donor-acceptor nanostructures offering improved charge transport and charge separation characteristics in thin films. ; Funding by EU (Project H2020-ITN 2014 642742), Spanish MINECO (ENE2013-48816-C5-5-R) and Government of Aragon (DGA-ESF-T66), is gratefully acknowledged.
1 Esquema.- 4 Figuras ; The performance of organic thin film optoelectronic devices strongly relies on the nanoscale aggregate structure of the employed conjugated polymer. Their impact on electronic interface interactions with adjacent layers of graphene, widely reported to improve the device characteristics, yet remains an open issue, which needs to be addressed by an appropriate benchmark system. Here, we prepared discrete ensembles of poly(3-hexylthiophene) nanoparticles and graphene oxide sheets (P3HTNPs–GO) with well defined aggregate structures of either J- or H- type and imaged their photogenerated charge transfer dynamics across their interface by Kelvin probe force microscopy (KPFM). A distinctive inversion of the sign of the surface potential and surface photovoltage (SPV) demonstrates that J-aggregates are decisive for establishing charge transfer interactions with GO. These enable efficient injection of photogenerated holes from P3HTNPs into GO sheets over a range of tens of nanometers, causing a slow SPV relaxation dynamics, and define their operation as efficient hole-transport layer (HTL). Conversely, H-type aggregates do not facilitate specific interactions and entrust GO sheets the role of charge-blocking layers (CBL). The direct effect of P3HT's aggregate structure on GO's functional operation as HTL or CBL thus establishes clear criteria towards the rational design of improved organic optoelectronic devices. ; This work has received funding from the Spanish MINEICO (project grants ENE 2016-79282-C5-1-R and ENE 2016-79282-C5-4-R) and associated EU Regional Development Funds. A.M.B., E.I., and W.K.M. acknowledge funding from European Union's Horizon 2020 research and innovation programme under the Marie Skłodowksa-Curie grant agreement no. 642742. They also acknowledge the Gobierno de Aragón (Grupo Reconocido DGA T03_17R) and associated EU Regional Development Funds. We also acknowledge institutional support from the Unit of Information Resources for Research at the "Consejo Superior de Investigaciones Científicas" (CSIC) for the article-processing charges contribution. ; Peer reviewed
1 Figure.-- Abstract of the work presented at "Current Trends in Electrochemistry", 41st Meeting of the Electrochemisty Group of the Spanish Royal Society of Chemistry, 1st French‐Spanish Atelier/Workshop on Electrochemistry, 6 - 9 July 2021, Paris (France). ; Photoelectrochemical techniques are accurate for the study of intrinsic electronic properties of a great variety of nanostructured semiconductor materials, such as conductive polymers, carbon nanomaterials (GO, CNTs, CDs) or metal oxide nanoparticles. It is also a highly valuable implement to assess charge and/or energy transfer phenomena between the mentioned semiconductors unveiling their role as charge acceptors/donors, blockers/transporters, sensitizers/conditioners, or even as photoelectroactive materials for themselves, thus allowing the tuning of optoelectronic properties of composite materials, for their future application in fields related to energy and environment, such as water splitting, electronics, solar cells or water remediation. This versatility makes photoelectrochemistry a key tool in the field of nanoscience and nanotechnology. ; MINECO and AEI/FEDER/UE (project ENE2016-79282-C5-1-R), European Union (H2020-MSCAITN- 2014-ETN 642742), Gobierno de Aragón (Grupo Reconocido DGA T03_17R, FEDER/UE). ; Peer reviewed
1 figure.-- Talk delivered at the HeteroNanoCarb-2019 Conference, Advances and applications in carbon related nanomaterials: From pure to doped structures including heteroatom layers, 2019, December 09th -- 13th, Centro de Ciencias de Benasque Pedro Pascual in Benasque (Aragon, Spain). ; Photoelectrochemistry is a valuable technique for the study of intrinsic electronic properties of a great variety of nanostructured semiconductor materials, such as conductive polymers or metal oxide nanoparticles. It is also a highly valuable implement to assess charge and/or energy transfer phenomena between the mentioned semiconductors and carbon nanomaterials (GO, CNTs), unveiling their role as charge acceptors/donors, blockers/transporters, sensitizers/conditioners, or even as photoelectroactive materials for themselves, thus allowing the tuning of optoelectronic properties of composite materials, for their future application in fields related to energy and environment, such as water splitting, solar cells or water remediation. This versatility makes photoelectrochemistry a key tool in the field of carbon nanoscience and nanotechnology. ; MINEICO (project ENE2016-79282-C5-1-R, AEI/FEDER, UE), European Union (H2020-MSCA-ITN-2014-ETN 642742 ), Gobierno de Aragón (Grupo Reconocido DGA T03_17R, FEDER, UE).
1 figure.-- Talk delivered at the HeteroNanoCarb-2019 Conference, Advances and applications in carbon related nanomaterials: From pure to doped structures including heteroatom layers, 2019, December 09th -- 13th, Centro de Ciencias de Benasque Pedro Pascual, in Benasque (Aragon, Spain). ; Poly(3-hexylthiophene) (P3HT) is one of the most popular conductive polymers for optoelectronic applications. [1] Their device operation critically depends on the nanocrystalline domain structure, i.e. the aggregate structure acquired by the polymer chains. Most common aggregates' distribution corresponds to H-aggregates, which implies charge transfer across the chains compared to those acquiring a J- aggregate structure with favorable charge transport along the chains. [2] We recently have shown that strong interactions between P3HT and water-dispersible graphene oxide can be obtained upon the formation of P3HT nanoparticles in aqueous dispersions. [3,4] These interactions enable a significant modification of the internal structure of P3HT aggregates towards a structure predominated by J-aggregates. Following this approach, in this work we have synthesized P3HT nanoparticles by the re-precipitation method in the presence of various types of water-soluble carbon nanostructures. Under scrutiny are graphene oxide flakes of different sizes, as well as nanocrystalline cellulose of type I and II. Of all the nanostructures exploited, the rarely investigated nanocyrstalline cellulose of type II, [5] exhibits significantly enhanced synergetic interface interactions with P3HT nanoparticles. This finding not only reveals a great potential towards improved thin film optoelectronic device structures, but even more underlines value of nanocellulose II for the development of green inks of photoactive polymers, ready to be used for printed electronics. ; Funding by EU (Project H2020-ITN 2014 642742), Spanish MINEICO (Project ENE2016-79282-C5-1-R1 (AEI/FEDER, UE), contract BES2017-080020 including FSE, UE, contract IJCI-2016-27789) and Government of Aragon (DGA-T03-17R and FEDER, UE).
Work presented at the NanoteC19 conference, International Conference on Carbon Nanosciene and Nanotechnology, 27th-30th august 2019, Zaragoza (Spain). ; Photoelectrochemistry of nanomaterials is commonly employed in fields related to energy and environmental applications, such as water splitting, solar cells or water remediation. It is a valuable technique for the direct evaluation of the performance for the desired application. In addition, it can be used for the study of intrinsic electronic properties of nanostructured of a great variety of semiconductor materials, such as conductive polymers or metal oxide nanoparticles. It is also a highly valuable implement to assess charge and/or energy transfer phenomena between the mentioned semiconductors and carbon nanomaterials (GO, CNTs), unveiling their role as charge acceptors/donors, blockers/transporters, sensitizers/conditioners, or even as electroactive materials for themselves, thus allowing the tuning of optoelectronic properties of composite materials. This versatility makes photoelectrochemistry a key tool in the field of carbon nanoscience and nanotechnology [1- 4]. ; MINECO (project ENE2016-79282-C5-1-R), European Union (H2020-MSCA-ITN-2014-ETN 642742), Gobierno de Aragón (Grupo Reconocido DGA T03_17R), and associated EU Regional Development Funds.
The self-assembly of novel core-shell nanoensembles consisting of regioregular poly(3-hexylthiophene) nanoparticles (P3HTNPs) of 100 nm as core and semiconducting CdTe quantum dots (CdTeQDs) as shell with a thickness of a few tens of nanometres was accomplished by employing a re-precipitation approach. The structure, morphology and composition of CdTeQDs/P3HTNPs nanoensembles were confirmed by high-resolution scanning transmission microscopy and dynamic light scattering studies. Intimate interface contact between the CdTeQDs shell and the P3HTNPs core leads to the stabilization of the CdTeQDs/P3HTNPs nanoensemble as probed by steady-state absorption spectroscopy. Effective quenching of the characteristic photoluminescence of CdTeQDs at 555 nm, accompanied by simultaneous increase of emission of P3HTNPs at 660 and 720 nm, reveals photoinduced charge-transfer processes. Probing the redox properties of films of CdTeQDs/P3HTNPs further proves the formation of a stabilized core-shell system in the solid-state. Photoelectrochemical assays on CdTeQDs/P3HTNPs films show a reversible on-off photoresponse at a bias voltage of +0.8 V with a three times increased photocurrent compared to CdTeQDs. The improved charge separation is directly related to the unique core-shell configuration, in which the outer CdTeQDs shell forces the P3HTNPs core to effectively act as electron acceptor. The creation of novel donor-acceptor core-shell hybrid materials via self-assembly is transferable to other types of conjugated polymers and semiconducting nanoparticles. This work, therefore, opens new pathways for the design of improved optoelectronic devices. ; This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642742. AMB and WKM gratefully acknowledge financial support from Spanish MINECO under project ENE206-79282-C5-1-R and its associated European Regional Development Fund, as well as the Government of Aragon under project DGA-T66 and associated European Social Fund. RA gratefully acknowledges financial support from Spanish MINECO under project MAT2016 79776-P and its associated European Regional Development Fund, as well as the Government of Aragon under project DGA-E26 and associated European Social Fund. The STEM studies were conducted at the Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon Universidad de Zaragoza, Spain. The authors would like to thank Esteban Urriolabeitía for carrying out the NMR studies. ; Peer reviewed
The game-changing role of graphene oxide (GO) in tuning the excitonic behavior of conjugated polymer nanoparticles is described for the first time. This is demonstrated by using poly(3-hexylthiophene) (P3HT) as a benchmark conjugated polymer and employing an in-situ re-precipitation approach resulting in P3HT nanoparticles (P3HTNPs) with sizes of 50 - 100 nm in intimate contact with GO. During the self-assembly process, GO changes the crystalline packing of P3HT chains in the forming P3HTNPs from H to H/J aggregates exhibiting exciton coupling constants as low as 2 meV, indicating favorable charge separation along the P3HT chains. Concomitantly, π-π interface interactions between the P3HTNPs and GO sheets are established resulting in the creation of P3HTNPs-GO charge-transfer complexes whose energy bandgaps are lowered by up to 0.5 eV. Moreover, their optoelectronic properties, pre-established in the liquid phase, are retained when processed into thin films from the stable aqueous dispersions, thus eliminating the critical dependency on external processing parameters. These results can be transferred to other types of conjugated polymers. Combined with the possibility of employing water based "green" processing technologies, charge-transfer complexes of conjugated polymer nanoparticles and GO open new pathways for the fabrication of improved optoelectronic thin film devices. ; This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 642742. AMB, and WKM acknowledge Spanish MINEICO (project ENE2016-79282-C5-1-R) and the Gobierno de Aragón (Grupo Reconocido DGA T03_17R), and associated EU Regional Development Funds). ; Peer reviewed
