Suchergebnisse

In press ; Owing to their great interest for energy storage and sensing applications, multi-layer papers consisting of graphene oxide – carbon nanotube (GO-CNT) hybrid sheets were prepared by in-situ exfoliation of graphite oxide in the presence of oxidized CNTs (oCNTs). For the first time we elucidate the influence of oCNTs on chemisorbed water (CW), i.e. water molecules inherently bound to oxygen functional groups (OFGs) of graphene oxide (GO) and responsible for irreversible structural damage upon thermal reduction processes. We show that oCNTs self-assemble onto GO sheets during the liquid phase processing steps by forming cooperatively strengthened OH···O=C hydrogen bonds between the carboxylic groups of oCNTs and OFGs of GO. At oCNT contents of about 10 to 15 wt. % this leads to the displacement of considerable amounts of CW without altering the original chemical composition of GO. Thermally reduced GO-CNT (rGO-CNT) papers reveal improved sp2 character and an enhancement of the specific capacitance by 75% with respect to thermally reduced GO (rGO), largely due to the effective removal of CW by oxidized CNTs. These findings disclose the relevance of cooperative hydrogen bonding phenomena in graphene oxide paper/film electrodes for the development of improved electrochemical energy storage and sensing devices. ; JDN is thankful for his CSIC PhD grant JAEPre09-01155 covering also his research stay at Rice University. WKM and AMB acknowledge financial support from Spanish MINECO and the European Regional Development Fund through project grants ENE2013-48816-C5-5-R, ENE2016-79282-C5-1-R and the Government of Aragon and the European Social Fund under project DGA-FSE-T66 CNN. RA gratefully acknowledges the support from MINECO through project grants FIS2013-46159- C3-3-P and MAT2016-79776-P. Some of the research has received funding from the European Union FP7 program under Grant Agreement 312483 ESTEEM2 (Integrated Infrastructure Initiative – I3) and from the European Union H2020 program under the grant 696656 Graphene Flagship, and H2020 Marie Skłodowska-Curie grant 642742. ; Peer reviewed

Trabajo presentado al Young Researchers CIS, celebrado online del 6 al 8 de septiembre de 2021. ; Financial support from the Research Projects PID2019-104009RB-I00/AEI/10.13039/501100011033 and the Aragón Government (T43-20R) are gratefully acknowledged. ; Peer reviewed

10 figures, 1 table ; Various types of fluorescent carbon nanoparticles, often called carbon dots (CDs), are synthesized by different polycondensation methods: microwave irradiation, hydrothermal conditions or solution chemistry at ambient temperature with subsequent chemical functionalization. The CDs are deposited on TiO2 films to be probed as electron transport layers in perovskite photovoltaics and the anode for photoelectrochemical water splitting. Nitrogen CDs, which do not contain oxygen, lead to an increase of around 50 mV in the open circuit voltage of perovskite solar cells. All the CD types produce an improved photocurrent in water splitting, particularly CDs that are functionalized with thiol groups and butyl chains. It is demonstrated that the modified electrode is stable under continuous operation. Other electrochemical characteristics of the electrode, such as the voltammogram shape, onset potentials and open circuit potentials, remain nearly unchanged upon the deposition of CDs. Only the incident photon to current conversion efficiency improves clearly, extending the absorption range by around 20 nm towards longer wavelengths. This study provides new data about mechanisms and electrode arrangements for improving the performance of n-type semiconductors in photovoltaic cells and photoelectrochemical hydrogen production. ; This work has been funded by the Spanish MINEICO under the project ENE2016-79282-C5-1-R (AEI/FEDER, UE), the Government of Aragón (Grupo reconocido T03-17R) and associated EU Regional Development Funds (DGA/FEDER, UE). ; Peer reviewed

Talk delivered in 7th International conference on Advanced Hydrogen Energy, ANM conference series 2019, at University of Aveiro, in Aveiro, Portugal, 17-19 July 2019.- 1 Figura ; Carbon dots (CDs) are a class of fluorescent nanoparticles including an extremely rich variety of structures and functional groups. Interestingly, not only the physicochemical properties are affected by the nature of the CD structure, but also their optical behavior. Fluorescence in CDs shows particular characteristics of strong intensity and wavelengths in the visible region. Consequently, an interesting issue arises on how structurally-different CDs modify the electron transport and photoactivity of semiconductor oxides, in particular TiO2. ; This work has been funded by the MINECO and the European Regional Development Fund (ENE 2016-79282-C5-1-R), the Government of Aragón (T03-17R and E14-17R), and the European Commission (H2020-MSCA-ITN-2014-ETN 642742 "Enabling Excellence"). ; Peer reviewed

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.

5 Figuras, 1 Esquema, 1 Tabla .-- Información suplementaria disponible en la página web del editor. ; The preparation of MoS 2 ‐polymer carbon nanodot (MoS 2 ‐PCND) hybrid material was accomplished by employing an easy and fast bottom‐up synthetic approach. Specifically, MoS 2 ‐PCND was realized by the thermal decomposition of ammonium tetrathiomolybdate and the in‐situ complexation of Mo with carboxylic acid units present in the surface of PCNDs. The newly prepared hybrid material was comprehensively characterized by spectroscopic, thermal and electron microscopy imaging means. The electrocatalytic activity of MoS 2 ‐PCND was examined against the hydrogen evolution reaction (HER) and compared with that attributed to the hybrid material prepared by a top‐down approach, namely with MoS 2 ‐PCND(exf‐fun), in which MoS 2 was firstly exfoliated and then covalently functionalized with PCNDs. The MoS 2 ‐PCND hybrid material showed superior electrocatalytic activity against HER with low Tafel slope value and excellent electrocatalytic stability, with an onset potential at ‐0.16 V vs RHE. The superior catalytic performance of MoS 2 ‐PCND was rationalized by considering the catalytic active sites of MoS 2 , the effective charge/energy‐transfer phenomena from PCNDs to MoS 2 and the synergetic effect between MoS 2 and PCNDs within the hybrid material. ; This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642742. Support of this work by the project "Advanced Materials and Devices" (MIS 5002409) which is implemented under the "Action for the Strategic Development on the Research and Technological Sector", which is implemented under the "Reinforcement of the Research and Innovation Infrastructures", funded by the Operational Program "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Ministry of Development and Investments, Greece, and the European Union (European Regional Development Fund) is also acknowledged. A.M.B. and W.K.M. acknowledge Spanish MINEICO (project grant ENE2016-79282-C5-1-R, AEI/FEDER, UE) and the Gobierno de Aragón (Grupo Reconocido DGA T03_17R, FEDER, UE). The SR-EELS studies were conducted at the Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, Universidad de Zaragoza, Spain. The SR-EELS studies were conducted at the Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, Universidad de Zaragoza, Spain. R.A. gratefully acknowledges the support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project grant MAT2016-79776-P (AEI/FEDER, UE) from the Government of Aragon and the European Social Fund under the project "Construyendo Europa desde Aragon" 2014-2020 (grant number E13_17R) and from the European Union H2020 programs "ESTEEM3" (823717) and under the "Graphene Flagship" CORE2 project grant agreement No 785219. ; Peer reviewed

Resumen del trabajo presentado al ChemOnTubes, celebrado en Bruselas (Bélgica) del 3 al 7 de abril de 2016. ; This work has been funded by MINECO and European Regional Development Fund (ENE2013-48816-C5-5-R NANOSOL-MAT), CSIC (project 2015801011 Intramural), Government of Aragón and European Social Fund (DGA-ESF-T66 Grupo Consolidado) and European Commission (H2020-MSCA-ITN-2014-ETN 642742 Enabling Excellence). ; Peer reviewed

Resumen del trabajo presentado a la XXXVII Reunión Bienal de la Real Sociedad Española de Química, celebrada en Donostia-San Sebastián del 26 al 30 de mayo de 2019. ; Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (MAT2016-77290-R), ESF and the Aragón Government (T43-17R) is gratefully acknowledged. ; Peer reviewed

5 Figuras.- 1 Tabla.- Información complementaria disponible en línea en la página web del editor. ; The emission of a bright blue fluorescence is a unique feature common to the vast variety of polymer carbon dots (CDs) prepared from carboxylic acid and amine precursors. However, the difficulty to assign a precise chemical structure to this class of CDs yet hampers the comprehension of their underlying luminescence principle. In this work, we show that highly blue fluorescent model types of CDs can be prepared from citric acid and ethylenediamine through low temperature synthesis routes. Facilitating controlled polycondensation processes, the CDs reveal sizes of 1–1.5 nm formed by a compact network of short polyamide chains of about 10 monomer units. Density functional theory calculations of these model CDs uncover the existence of a spatially separated highest occupied molecular orbital and a lowest unoccupied molecular orbital located at the amide and carboxylic groups, respectively. Photoinduced charge transfer between these groups thus constitutes the origin of the strong blue fluorescence emission. Hydrogen-bond-mediated supramolecular interactions between the polyamide chains enabling a rigid network structure further contribute to the enhancement of the radiative process. Moreover, the photoinduced charge transfer processes in the polyamide network structure easily explain the performance of CDs in applications as revealed in studies on metal ion sensing. These findings thus are of general importance to the further development of polymer CDs with tailored properties as well as for the design of technological applications. ; 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. A.M.B. and W.K.M. further acknowledge Spanish MINEICO (project ENE2016-79282-C5-1-R), the Gobierno de Aragón (Grupo Reconocido DGA T03_17R), and associated EU Regional Development Funds. E.P.U. acknowledges Gobierno de Aragón (Grupo Reconocido DGA E19_17R) and associated EU Regional Development Funds. ; Peer reviewed

The emission of a bright blue fluorescence is a unique feature common to the vast variety of polymer carbon dots (CDs) prepared from carboxylic acid and amine precursors. However, the difficulty to assign a precise chemical structure to this class of CDs yet hampers the comprehension of their underlying luminescence principle. In this work, we show that highly blue fluorescent model types of CDs can be prepared from citric acid and ethylenediamine through low temperature synthesis routes. Facilitating controlled polycondensation processes, the CDs reveal sizes of 1 - 1.5 nm formed by a compact network of short polyamide chains of about ten monomer units. Density functional theory calculations of these model CDs uncover the existence of spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital located at the amide and carboxylic groups, respectively. Photoinduced charge-transfer between these groups thus constitutes the origin of the strong blue fluorescence emission. Hydrogen-bond mediated supramolecular interactions between the polyamide chains enabling a rigid network structure further contribute to the enhancement of the radiative process. Moreover, the photoinduced charge-transfer processes in the polyamide network structure easily explain the performance of CDs in applications as revealed in studies on metal ion sensing. These findings thus are of general importance to the further development of polymer CDs with tailored properties as well as for the design of technological applications. ; 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 further acknowledge Spanish MINEICO (project ENE2016-79282-C5-1-R), the Gobierno de Aragón (Grupo Reconocido DGA T03_17R), and associated EU Regional Development Funds). EPU acknowledges Gobierno de Aragón (Grupo Reconocido DGA E19_17R) and associated EU Regional Development Funds. Technical and human support provided by IZO-SGI, SGIker (UPV/EHU, MICINN, GV/EJ ERDF and ESF) is gratefully acknowledged for assistance and generous allocation of computational resources. ; Peer reviewed

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

Resumen del trabajo presentado al HeteroNanoCarb: "Advances and Applications in Carbon Related Nanomaterials: From pure to doped structures including heteroatom layers", celebrado en Benasque (España) del 7 al 11 de diciembre de 2015. ; This work has been funded by the Spanish Ministry MINECO and the European Regional Development Fund under the project ENE2013-48816-C5-5-R, and the Government of Aragon and the European Social Fund (DGA-ESF-T66 Grupo Consolidado). ; Peer reviewed

We report on the modification of graphene oxide (GO) with poly(vinyl alcohol) (PVA) leading to the mechanical improvement of GO based materials. First, GO was covalently functionalised with PVA by esterification of carboxylic groups on GO with hydroxyl groups of PVA resulting in functionalised f-(PVA)GO. This was carried out for PVA of six different molecular weights. This functionalised graphene oxide could be formed into a paper-like material by vacuum filtration. Papers prepared from f-(PVA)GO showed significant increases in mechanical properties compared to those prepared with GO or with simple mixtures of GO and PVA. The best performance was achieved for PVA functional groups with molecular weights between 50 and 150 kg/mol. Improvements in Young's moduli of 60% and tensile strength of 400% were observed relative to GO-only paper. The improved mechanical properties are attributed to enhanced inter-flake stress transfer due to the covalently bonded PVA. Second, functionalised f-(PVA)GO was used as filler in * Corresponding author. Tel/Fax: +34 976 73-3977 / -3318. E-mail address: wmaser@icb.csic.es (W.K. Maser) 2 PVA-based composites. The application of a pre-selection method allowed the use of only the largest functionalised f-(PVA)GO flakes. This resulted in substantially reinforced PVA-f-(PVA)GO composites. Both modulus and strength increased by 40% relative to the pure polymer for f- (PVA)GO loadings below 0.3 vol.%. ; The authors would like to acknowledge Science Foundation Ireland, (grant number 07/IN.7/I1772), Spanish Ministry of Science and Innovation (MICINN) under project MAT2010-15026, Spanish Research Council CSIC under project 201080E124 and the Government of Aragon (DGA) under Project DGA-T66 CNN. M.C. thanks MICINN for her PhD contract and funding for research stay at TCD under FPI Programme BES-2008-003503. ; Peer reviewed

The robust adhesion of single-walled carbon nanotubes (SWCNTs) to plastic substrates is a key issue toward their use in flexible electronic devices. In this work, semitransparent SWCNT films were prepared by spray-coating on two different plastic substrates, specifically poly(ethylene terephthalate) and poly(vinylidene fluoride). The deposited SWCNT films were treated by dipping in suitable solvents separately, namely, 53% nitric acid (HNO3) and N-methyl pyrrolidone. Direct evidence of SWCNT adhesion to the substrate was obtained by a peel-off test carried out with an adhesive tape. Moreover, these treatments caused enhanced film transparency and electrical conductivity. Electron microscopy images suggested that SWCNTs were embedded in the plastic substrates, forming a thin layer of conductive composite materials. Raman spectroscopy detected a certain level of doping in the SWCNTs after the chemical treatments, which particularly affected metallic nanotubes in the case of the HNO3 treatment. The microscopic adhesion and hardness of the SWCNT films were studied through a nanoscratch test. Overall, the efficiency of selected chemical postdeposition treatments for improving the SWCNT adhesion and the robustness of the resulting SWCNT films are demonstrated on flexible substrates of different chemical compositions. ; This work has been funded by the MINECO and the European Regional Development Fund (ENE 2016-79282-C5-1-R), the Government of Aragón (T03-17R and E14-17R), and the European Commission (H2020-MSCA-ITN-2014-ETN 642742 "Enabling Excellence"). ; Peer reviewed

Hybrid film electrodes were made of nanocrystalline titanium dioxide (TiO2) and various percentages of single‐walled carbon nanotube (SWCNT) fillers up to 5.5 wt%. A complete photoelectrochemical study was performed in both alkaline and acidic conditions by using cyclic voltammetry, potentiostatic photocurrent measurements, and open‐circuit‐potential measurements under UV/Vis irradiation. Dark voltammograms show a transition from a capacitive to a resistive behavior in the TiO2 accumulation region upon increasing SWCNT percentages. In addition, the energy levels of deep electron traps change inside the TiO2 bandgap. The new peak positions correspond to the reduction potentials of SWCNTs, and their associated charge capacities increase with the SWCNT percentage. The modifications observed in dark experiments directly impact on the shape profile of cyclic voltammograms under irradiation. As a consequence, reduction potentials of SWCNTs appear near the cathodic peaks of certain water oxidation intermediates, and may be interacting with them. On the other hand, open‐circuit photopotentials reach maximum values for small SWCNTs percentages around 0.02 wt%. An increase in potentiodynamic and potentiostatic photocurrents is observed for the electrode containing 0.02 wt% SWCNTs, compared to reference TiO2 in acidic conditions. ; The authors thank the Institute for Biocomputation and Physics of Complex Systems (BIFI) for the centrifugation laboratory. This work has been funded by MINECO and European Regional Development Fund (ENE 2016-79282-C5-1-R), Government of Aragon and European Social Fund (DGA-ESF-T66 "Grupo Consolidado") and European Commission (H2020-MSCA-ITN-2014-ETN 642742 "Enabling Excellence"). ; Peer reviewed