Person: Bañares Morcillo, Luis
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First Name
Luis
Last Name
Bañares Morcillo
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Física
Area
Química Física
Identifiers
33 results
Search Results
Now showing 1 - 10 of 33
Item Contribution of resonance energy transfer to the luminescence quenching of upconversion nanoparticles with graphene oxide(Journal of Colloid and Interface Science, 2020) Méndez González, Diego; Gómez Calderón, Óscar; Melle Hernández, Sonia; González Izquierdo, Jesús; Bañares Morcillo, Luis; López Díaz, David; Velazquez Salicio, M. Mercedes; López Cabarcos, Enrique; Rubio Retama, Benito Jorge; Laurenti, MarcoUpconversion nanoparticles (UCNP) are increasingly used due to their advantages over conventional fluorophores, and their use as resonance energy transfer (RET) donors has permitted their application as biosensors when they are combined with appropriate RET acceptors such as graphene oxide (GO). However, there is a lack of knowledge about the design and influence that GO composition produces over the quenching of these nanoparticles that in turn will define their performance as sensors. In this work, we have analysed the total quenching efficiency, as well as the actual values corresponding to the RET process between UCNPs and GO sheets with three different chemical compositions. Our findings indicate that excitation and emission absorption by GO sheets are the major contributor to the observed luminescence quenching in these systems. This challenges the general assumption that UCNPs luminescence deactivation by GO is caused by RET. Furthermore, RET efficiency has been theoretically calculated by means of a semiclassical model considering the different nonradiative energy transfer rates from each Er3+ ion to the GO thin film. These theoretical results highlight the relevance of the relative positions of the Er3+ ions inside the UCNP with respect to the GO sheet in order to explain the RET-induced efficiency measurements.Item Intracellular pH-Induced Tip-to-Tip Assembly of Gold Nanorods for Enhanced Plasmonic Photothermal Therapy(ACS Omega, 2016) Ahijado Guzmán, Rubén; Bañares Morcillo, Luis; Guerrero Martínez, Andrés; López Montero, Iván; Tardajos Rodríguez, Gloria María; González Rubio, Guillermo; Izquierdo, Jesús G.; Calzado Martín, Alicia; Calleja, MontserratThe search for efficient plasmonic photothermal therapies using nonharmful pulse laser irradiation at the near-infrared (NIR) is fundamental for biomedical cancer research. Therefore, the development of novel assembled plasmonic gold nanostructures with the aim of reducing the applied laser power density to a minimum through hot-spot-mediated cell photothermolysis is an ongoing challenge. We demonstrate that gold nanorods (Au NRs) functionalized at their tips with a pH-sensitive ligand assemble into oligomers within cell lysosomes through hydrogen-bonding attractive interactions. The unique intracellular features of the plasmonic oligomers allow us to significantly reduce the femtosecond laser power density and Au NR dose while still achieving excellent cell killing rates. The formation of gold tip-to-tip oligomers with longitudinal localized surface plasmon resonance bands at the NIR, obtained from low-aspect-ratio Au NRs close in resonance with 800 nm Ti:sapphire 90 fs laser pulses, was found to be the key parameter for realizing the enhanced plasmonic photothermal therapy.Item Threshold Photoelectron Spectroscopy of the CH2I, CHI, and CI Radicals(The Journal of Physical Chemistry A, 2021) Chicharro, David V.; Hrodmarsson, Helgi Rafn; Bouallagui, Aymen; Zanchet, Alexandre; Loison, Jean-Christophe; García, Gustavo A.; García Vela, Alberto; Bañares Morcillo, Luis; Marggi Poullaín, SoniaVUV photoionization of the CHnI radicals (with n = 0, 1, and 2) is investigated by means of synchrotron radiation coupled with a double imaging photoion-photoelectron coincidence spectrometer. Photoionization efficiencies and threshold photoelectron spectra (TPES) for photon energies ranging between 9.2 and 12.0 eV are reported. An adiabatic ionization energy (AIE) of 8.334 ± 0.005 eV is obtained for CH2I, which is in good agreement with previous results [8.333 ± 0.015 eV, Sztáray et al. J. Chem. Phys. 2017, 147, 013944], while for CI an AIE of 8.374 ± 0.005 eV is measured for the first time and a value of ∼8.8 eV is estimated for CHI. Ab initio calculations have been carried out for the ground state of the CH2I radical and for the ground state and excited states of the radical cation CH2I + , including potential energy curves along the C−I coordinate. Franck−Condon factors are calculated for transitions from the CH2I(X̃ 2 B1) ground state of the neutral radical to the ground state and excited states of the radical cation. The TPES measured for the CH2I radical shows several structures that correspond to the photoionization into excited states of the radical cation and are fully assigned on the basis of the calculations. The TPES obtained for the CHI is characterized by a broad structure peaking at 9.335 eV, which could be due to the photoionization from both the singlet and the triplet states and into one or more electronic states of the cation. A vibrational progression is clearly observed in the TPES for the CI radical and a frequency for the C−I stretching mode of 760 ± 60 cm−1 characterizing the CI+ electronic ground state has been extracted.Item Femtosecond predissociation dynamics of ethyl iodide in the B-band(Physical Chemistry Chemical Physics, 2019) Murillo Sánchez, Marta Luisa; Marggi Poullaín, Sonia; Loriot, Vincent; Corrales, Maria Eugenia; Bañares Morcillo, LuisFemtosecond velocity map imaging to disentangle the electronic predissociation of ethyl iodide in the B-band.Item Control of ultrafast molecular photodissociation by laser-field-induced potentials(Nature Chemistry, 2014) Corrales, María Eugenia; González-Vázquez, Jesús; Balerdi, Garikoitz; Sola Reija, Ignacio; Nalda, Rebeca de; Bañares Morcillo, LuisItem Imaging the photodissociation dynamics of internally excited ethyl radicals from high Rydberg states(Physical Chemistry Chemical Physics, 2023) Rubio Lago, Luis; Chicharro, David V.; Marggi Poullaín, Sonia; Zanchet, Alexandre; Koumarianou, Greta; Glodic, Pavle; Samartzis, Peter C.; García Vela, Alberto; Bañares Morcillo, LuisThe site-specific hydrogen-atom elimination mechanism previously reported for photoexcited ethyl radicals (CH3CH2) [D. V. Chicharro et al., Chem. Sci., 2019, 10, 6494] is interrogated in the photodissociation of the ethyl isotopologues CD3CD2, CH3CD2 and CD3CH2 through the velocity map imaging (VMI) detection of the produced hydrogen- and deuterium-atoms. The radicals, generated in situ from photolysis of a precursor using the same laser pulse employed in their excitation to Rydberg states, decompose along the Ca-H/D and Cb-H/D reaction coordinates through coexisting statistical and site-specific mechanisms. The experiments are carried out at two excitation wavelengths, 201 and 193 nm. The comparison between both sets of results provides accurate information regarding the primary role in the site-specific mechanism of the radical internal reservoir. Importantly, at 193 nm excitation, higher energy dissociation channels (not observed at 201 nm) producing low-recoil H/Datoms become accessible. High-level ab initio calculations of potential energy curves and the corresponding non-adiabatic interactions allow us to rationalize the experimental results in terms of competitive non-adiabatic decomposition paths. Finally, the adiabatic behavior of the conical intersections in the face of several vibrational modes – the so-called vibrational promoting modes – is discussed.Item Stark control of multiphoton ionization through Freeman resonances in alkyl iodides(The Journal of Chemical Physics, 2023) Casasús, Ignacio ; Corrales, María ; Murillo Sánchez, Marta Luisa; Marggi Poullaín, Sonia; Oliveira, Nelson de; Limão-Vieira, Paulo; Bañares Morcillo, LuisMultiphoton ionization (MPI) of alkyl iodides (RI, R = CnH2n+1, n = 1–4) has been investigated with femtosecond laser pulses centered at 800 and 400 nm along with photoelectron imaging detection. In addition, the ultraviolet (UV)–vacuum ultraviolet (VUV) absorption spectra of gas-phase RIs have been measured in the photon energy range of 5–11 eV using the VUV Fourier transform spectrometer at the VUV DESIRS beamline of the synchrotron SOLEIL facility. The use of high-laser-field strengths in matter–radiation interaction generates highly non-linear phenomena, such as the Stark shift effect, which distorts the potential energy surfaces of molecules by varying both the energy of electronic and rovibrational states and their ionization energies. The Stark shift can then generate resonances between intermediate states and an integer number of laser photons of a given wavelength, which are commonly known as Freeman resonances. Here, we study how the molecular structure of linear and branched alkyl iodides affects the UV–VUV absorption spectrum, the MPI process, and the generation of Freeman resonances. The obtained results reveal a dominant resonance in the experiments at 800 nm, which counter-intuitively appears at the same photoelectron kinetic energy in the whole alkyl iodide series. The ionization pathways of this resonance strongly involve the 6p( 2 E3/2) Rydberg state with different degrees of vibrational excitation, revealing an energy compensation effect as the R-chain complexity increasesItem A velocity map imaging study of the photodissociation of the à state of ammonia(Physical Chemistry Chemical Physics, 2014) Rodríguez, Javier ; González, Marta ; Rubio-Lago, Luis; Bañares Morcillo, LuisItem Imaging the radical channel in acetaldehyde photodissociation: Competing mechanisms at energies close to the triplet exit barrier(2010) Amaral, Gabriel; Arregui, Andrés; Rubio-Lago, Luis; Rodríguez, Javier; Bañares Morcillo, LuisThe photodissociation of acetaldehyde in the radical channel has been studied at wavelengths between 315 and 325 nm using the velocity-map imaging technique. Upon one-photon absorption at 315 nm, the molecule is excited to the first singlet excited state S1, which, in turn, undergoes intersystem crossing to the first excited triplet state T1. On the triplet surface, the molecule dissociates into CH3 and HCO radicals with large kinetic energy release (KER), in accordance with the well characterized exit barrier on T1. However, at longer wavelengths (>320 nm), which correspond to excitation energies just below the triplet barrier, a sudden change in KER is observed. At these photolysis wavelengths, there is not enough energy to surpass the exit barrier on the triplet state, which leaves the possibility of unimolecular dissociation on S0 after internal conversion from S1. We have characterized the fragments’ KER at these wavelengths, as well as determined the energy partitioning for the radical fragments. A new accurate estimate of the barrier height on T1 is presented.Item Imaging the stereodynamics of methyl iodide photodissociation in the second absorption band: fragment polarization and the interplay between direct and predissociation(2014) González, Marta ; Rodríguez, Javier ; Rubio-Lago, Luis; Bañares Morcillo, LuisStereodynamics imaging disentangles the interplay between direct and predissociation in the onset of the second absorption band of methyl iodide.