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Article ; Online: Excited state dynamics of Zn-salophen complexes.

O'Keeffe, Patrick / Catone, Daniele / Turchini, Stefano / Paladini, Alessandra / Dalla Cort, Antonella / Bodo, Enrico / Piccirillo, Susanna

Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology

2022 Volume 21, Issue 6, Page(s) 923–934

Abstract: Zn-salophen complexes are a promising class of fluorescent chemosensors for nucleotides and nucleic acids. We have investigated, by means of steady state UV-Vis, ultrafast transient absorption, fluorescence emission and time dependent density functional ... ...

Abstract	Zn-salophen complexes are a promising class of fluorescent chemosensors for nucleotides and nucleic acids. We have investigated, by means of steady state UV-Vis, ultrafast transient absorption, fluorescence emission and time dependent density functional theory (TD-DFT) the behavior of the excited states of a salicylidene tetradentate Schiff base (Sal), its Zn(II) coordination compound (Zn-Sal) and the effect of the interaction between Zn-Sal and adenosine diphosphate (ADP). TD-DFT shows that the deactivation of the excited state of Sal occurs through torsional motion, due to its rotatable bonds and twistable angles. Complexation with Zn(II) causes rigidity so that the geometry changes in the excited states with respect to the ground state structure are minimal. By addition of ADP to a freshly prepared Zn-Sal ethanol solution, a longer relaxation constant, in comparison to Zn-Sal, was measured, indicative of the interaction between Zn-Sal and ADP. After a few days, the Zn-Sal-ADP solution displayed the same static and dynamic behavior of a solution containing only the Sal ligand, demonstrating that the coordination of the ADP anion to Zn(II)leads to the demetallation of the Sal ligand. Fluorescence measurements also revealed an enhanced fluorescence at 375 nm following the addition of ADP to the solution, caused by the presence of 2,3-diamino naphthalene that is formed by demetallation and partial decomposition of the Sal ligand. The efficient fluorescence of this species at 375 nm could be selectively detected and used as a probe for the detection of ADP in solution.
MeSH term(s)	Adenosine Diphosphate ; Ligands ; Salicylates/chemistry ; Zinc/chemistry
Chemical Substances	Ligands ; Salicylates ; salophen (118-57-0) ; Adenosine Diphosphate (61D2G4IYVH) ; Zinc (J41CSQ7QDS)
Language	English
Publishing date	2022-01-28
Publishing country	England
Document type	Journal Article
ZDB-ID	2072584-X
ISSN	1474-9092 ; 1474-905X
ISSN (online)	1474-9092
ISSN	1474-905X
DOI	10.1007/s43630-021-00165-0
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: Injecting Electrons into CeO

Spurio, Eleonora / Pelli Cresi, Jacopo Stefano / Ammirati, Giuseppe / Pelatti, Samuele / Paladini, Alessandra / D'Addato, Sergio / Turchini, Stefano / O'Keeffe, Patrick / Catone, Daniele / Luches, Paola

ACS photonics

2023 Volume 10, Issue 5, Page(s) 1566–1574

Abstract: The electron injection efficiency and the steady state absorptance at different photon energies for a composite system made of Au NPs embedded in a cerium oxide matrix are reported. Cerium oxide can be coupled with plasmonic nanoparticles (NPs) to ... ...

Abstract	The electron injection efficiency and the steady state absorptance at different photon energies for a composite system made of Au NPs embedded in a cerium oxide matrix are reported. Cerium oxide can be coupled with plasmonic nanoparticles (NPs) to improve its catalytic properties by visible-light absorption. The present work is a study of the ultrafast dynamics of excited states induced by ultraviolet and visible-light excitation in Au NPs combined with cerium oxide, aimed at understanding the excitation pathways. The data, obtained by femtosecond transient absorption spectroscopy, show that the excitation of localized surface plasmon resonances (LSPRs) in the Au NPs leads to an ultrafast injection of electrons into the empty 4f states of the surrounding cerium oxide. Within the first few picoseconds, the injected electrons couple with the lattice distortion forming a polaronic excited state, with similar properties to that formed after direct band gap excitation of the oxide. At sub-picosecond delay times, we observed relevant differences in the energetics and the time dynamics as compared to the case of band gap excitation of the oxide. Using different pump energies across the LSPR-related absorption band, the efficiency of the electron injection from the NPs into the oxide was found to be rather high, with a maximum above 30%. The injection efficiency has a different trend in energy as compared to the LSPR-related static optical absorptance, showing a significant decrease in low energies. This behavior is explained considering different deexcitation pathways with variable weight across the LSPR band. The results are important for the design of materials with high overall solar catalytic efficiency.
Language	English
Publishing date	2023-05-03
Publishing country	United States
Document type	Journal Article
ISSN	2330-4022
ISSN	2330-4022
DOI	10.1021/acsphotonics.3c00184
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Article ; Online: A Study of Photoinduced Coherent Vibrations in Gold-Nanorod Dispersions.

Toschi, Francesco / Catone, Daniele / Mario, Lorenzo Di / O'Keeffe, Patrick / Paladini, Alessandra / Cresi, Jacopo Stefano Pelli / Turchini, Stefano

Journal of nanoscience and nanotechnology

2020 Volume 20, Issue 7, Page(s) 4557–4562

Abstract: Upon photoexcitation with a femtosecond laser pulse, the plasmonic resonance of a nanorod can couple with coherent vibrational modes generating a regular oscillating pattern in the transient absorbance of the nanostructure. The dynamics of the plasmon ... ...

Abstract	Upon photoexcitation with a femtosecond laser pulse, the plasmonic resonance of a nanorod can couple with coherent vibrational modes generating a regular oscillating pattern in the transient absorbance of the nanostructure. The dynamics of the plasmon resonances of these materials are probed through femtosecond transient absorption spectroscopy in the spectral region between 400 nm and 1600 nm. Whereas in the visible range the spectra are comparable with the findings reported in the literature, the analysis of the transient NIR spectra revealed that their oscillation frequencies vary with wavelength, resulting in a strong distortion of the transient features that can be related to the specific lengths distribution of the nanorods contained in the sample. These findings suggest that in the design of efficient and highly sensitive gold-nanorod based plasmonic sensors a narrow size distribution of nanostructures is required.
Language	English
Publishing date	2020-01-21
Publishing country	United States
Document type	Journal Article
ISSN	1533-4899
ISSN (online)	1533-4899
DOI	10.1166/jnn.2020.17870
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Article: Ultrafast Charge Carrier Dynamics in Vanadium-Modified TiO₂ Thin Films and Its Relation to Their Photoelectrocatalytic Efficiency for Water Splitting

Piccioni, Alberto / Catone, Daniele / Paladini, Alessandra / O’Keeffe, Patrick / Boschi, Alex / Kovtun, Alessandro / Katsikini, Maria / Boscherini, Federico / Pasquini, Luca

Journal of physical chemistry. 2020 Nov. 27, v. 124, no. 49

2020

Abstract: Light absorption and charge transport in oxide semiconductors can be tuned by the introduction, during deposition, of a small quantity of foreign elements, leading to the improvement of the photoelectrocatalytic performance. In this work, both unmodified ...

Abstract	Light absorption and charge transport in oxide semiconductors can be tuned by the introduction, during deposition, of a small quantity of foreign elements, leading to the improvement of the photoelectrocatalytic performance. In this work, both unmodified and vanadium-modified TiO₂ thin films deposited by radio-frequency magnetron sputtering are investigated as photoanodes for photoelectrochemical water splitting. Following a structural characterization by X-ray diffraction, atomic force microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, photoelectrocatalysis is discussed based on ultrafast transient absorbance spectroscopy measurements. In particular, three different pump wavelengths from UV to the visible range are used (300, 390, and 530 nm) in order to cover the relevant photoactive spectral range of modified TiO₂. Incident photon-to-current conversion efficiency spectra show that incorporation of vanadium in TiO₂ extends water splitting in the visible range up to ≈530 nm, a significant improvement compared to unmodified TiO₂ that is active only in the UV range ≲390 nm. However, transient absorbance spectroscopy clearly reveals that vanadium accelerates electron–hole recombination upon UV irradiation, resulting in a lower photon-to-current conversion efficiency in the UV spectral range with respect to unmodified TiO₂. The new photoelectrocatalytic activity in the visible range is attributed to a V-induced introduction of intragap levels at ≈2.2 eV below the bottom of the conduction band. This is confirmed by long-living transient signals due to electrons photoexcited into the conduction band after visible light (530 nm) pulses. The remaining holes migrate to the semiconductor–electrolyte interface where they are captured by long-lived traps and eventually promote water oxidation under visible light.
Keywords	Raman spectroscopy ; X-ray diffraction ; X-ray photoelectron spectroscopy ; absorbance ; absorption ; atomic force microscopy ; oxidation ; photocatalysis ; radio waves ; ultraviolet radiation ; vanadium
Language	English
Dates of publication	2020-1127
Size	p. 26572-26582.
Publishing place	American Chemical Society
Document type	Article
Note	NAL-AP-2-clean
ISSN	1932-7455
DOI	10.1021/acs.jpcc.0c06790
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Measurement of the conformational switching of azobenzenes from the macro- to attomolar scale in self-assembled 2D and 3D nanostructures.

Quintano, Vanesa / Diez-Cabanes, Valentin / Dell'Elce, Simone / Di Mario, Lorenzo / Pelli Cresi, Stefano / Paladini, Alessandra / Beljonne, David / Liscio, Andrea / Palermo, Vincenzo

Physical chemistry chemical physics : PCCP

2021 Volume 23, Issue 20, Page(s) 11698–11708

Abstract: It is important, but challenging, to measure the (photo)induced switching of molecules in different chemical environments, from solution through thin layers to solid bulk crystals. We compare the cis-trans conformational switching of commercial ... ...

Abstract	It is important, but challenging, to measure the (photo)induced switching of molecules in different chemical environments, from solution through thin layers to solid bulk crystals. We compare the cis-trans conformational switching of commercial azobenzene molecules in different liquid and solid environments: polar solutions, liquid polymers, 2D nanostructures and 3D crystals. We achieve this goal by using complementary techniques: optical absorption spectroscopy, femtosecond transient absorption spectroscopy, Kelvin probe force microscopy and reflectance spectroscopy, supported by density functional theory calculations. We could observe the same molecule showing fast switching in a few picoseconds, when studied as an isolated molecule in water, or slow switching in tens of minutes, when assembled in 3D crystals. It is worth noting that we could also observe switching for small ensembles of molecules (a few attomoles), representing an intermediate case between single molecules and bulk structures. This was achieved using Kelvin probe force microscopy to monitor the change of surface potential of nanometric thin 2D islands containing ca. 106 molecules each, self-assembled on a substrate. This approach is not limited to azobenzenes, but can be used to observe molecular switching in isolated ensembles of molecules or other nano-objects and to study synergistic molecular processes at the nanoscale.
Language	English
Publishing date	2021-05-12
Publishing country	England
Document type	Journal Article
ZDB-ID	1476244-4
ISSN	1463-9084 ; 1463-9076
ISSN (online)	1463-9084
ISSN	1463-9076
DOI	10.1039/d1cp00740h
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Article ; Online: Carrier dynamics in silicon nanowires studied via femtosecond transient optical spectroscopy from 1.1 to 3.5 eV.

Tian, Lin / Di Mario, Lorenzo / Sivan, Aswathi K / Catone, Daniele / O'Keeffe, Patrick / Paladini, Alessandra / Turchini, Stefano / Martelli, Faustino

Nanotechnology

2019 Volume 30, Issue 21, Page(s) 214001

Abstract: We present femtosecond transient transmission (or absorbance) measurements in silicon nanowires in the energy range 1.1-3.5 eV, from below the indirect band-gap to above the direct band-gap. Our pump-probe measurements allow us to give a complete picture ...

Abstract	We present femtosecond transient transmission (or absorbance) measurements in silicon nanowires in the energy range 1.1-3.5 eV, from below the indirect band-gap to above the direct band-gap. Our pump-probe measurements allow us to give a complete picture of the carrier dynamics in silicon. In this way we perform an experimental study with a spectral completeness that is lacking in the whole literature on carrier dynamics in silicon. A particular emphasis is given to the dynamics of the transient absorbance at the energies relative to the direct band gap at 3.3 eV. Indeed, the use of pump energies below and above 3.3 eV allowed us to disentangle the dynamics of electrons and holes in their respective bands. The band gap renormalization of the direct band gap is also investigated for different pump energies. A critical discussion is given on the results below 3.3 eV where phonon-assisted processes are required in the optical transitions.
Language	English
Publishing date	2019-02-04
Publishing country	England
Document type	Journal Article
ZDB-ID	1362365-5
ISSN	1361-6528 ; 0957-4484
ISSN (online)	1361-6528
ISSN	0957-4484
DOI	10.1088/1361-6528/ab044a
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Article: Interband Transitions Are More Efficient Than Plasmonic Excitation in the Ultrafast Melting of Electromagnetically Coupled Au Nanoparticles

Magnozzi, Michele / Alabastri, Alessandro / Bisio, Francesco / Canepa, Maurizio / Catone, Daniele / O’Keeffe, Patrick / Paladini, Alessandra / Proietti Zaccaria, Remo / Toschi, Francesco

Journal of physical chemistry. 2019 June 13, v. 123, no. 27

2019

Abstract: We investigated the effects of ultrafast laser excitation of Au nanoparticles (NPs) having strong interparticle electromagnetic coupling by irradiating the NPs either at interband or plasmon-resonance wavelengths (13–100 J/m2 fluence regime). We observed ...

Abstract	We investigated the effects of ultrafast laser excitation of Au nanoparticles (NPs) having strong interparticle electromagnetic coupling by irradiating the NPs either at interband or plasmon-resonance wavelengths (13–100 J/m2 fluence regime). We observed that interband excitation is significantly more efficient than plasmonic excitation in reshaping, coalescing, and ultimately sublimating the NPs, despite the light-absorption cross section of interband excitation being almost half that of plasmonic irradiation. We ascribed this to the different localizations of radiation-induced heat sources in the strongly coupled NPs in the two cases. Interband excitation induces homogeneous heat generation in Au, and so the conventional NP heating pathway is followed, eventually leading to overall melting, coalescence, and ablation of Au. Plasmonic irradiation, on the other hand, promotes strong localization of the heat sources within small energetic hot spots, a fact that we suggest may lead to nonthermal effects that melt and reshape the NPs only on the local scale, leaving the system otherwise relatively unscathed.
Keywords	gold ; heat ; irradiation ; melting ; nanogold ; wavelengths
Language	English
Dates of publication	2019-0613
Size	p. 16943-16950.
Publishing place	American Chemical Society
Document type	Article
ISSN	1932-7455
DOI	10.1021/acs.jpcc.9b03668
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Ultrafast optical spectroscopy of semiconducting and plasmonic nanostructures and their hybrids.

Catone, Daniele / Di Mario, Lorenzo / Martelli, Faustino / O'Keeffe, Patrick / Paladini, Alessandra / Stefano Pelli Cresi, Jacopo / Sivan, Aswathi K / Tian, Lin / Toschi, Francesco / Turchini, Stefano

Nanotechnology

2020 Volume 32, Issue 2, Page(s) 25703

Abstract: The knowledge of the carrier dynamics in nanostructures is of fundamental importance for the development of (opto)electronic devices. This is true for semiconducting nanostructures as well as for plasmonic nanoparticles (NPs). Indeed, improvement of ... ...

Abstract	The knowledge of the carrier dynamics in nanostructures is of fundamental importance for the development of (opto)electronic devices. This is true for semiconducting nanostructures as well as for plasmonic nanoparticles (NPs). Indeed, improvement of photocatalytic efficiencies by combining semiconductor and plasmonic nanostructures is one of the reasons why their ultrafast dynamics are intensively studied. In this work, we will review our activity on ultrafast spectroscopy in nanostructures carried out in the recently established EuroFEL Support Laboratory. We have investigated the dynamical plasmonic responses of metal NPs both in solution and in 2D and 3D arrays on surfaces, with particular attention being paid to the effects of the NP shape and to the conversion of absorbed light into heat on a nano-localized scale. We will summarize the results obtained on the carrier dynamics in nanostructured perovskites with emphasis on the hot-carrier dynamics and in semiconductor nanosystems such as ZnSe and Si nanowires, with particular attention to the band-gap bleaching dynamics. Subsequently, the study of semiconductor-metal NP hybrids, such as CeO
Keywords	covid19
Language	English
Publishing date	2020-08-25
Publishing country	England
Document type	Journal Article
ZDB-ID	1362365-5
ISSN	1361-6528 ; 0957-4484
ISSN (online)	1361-6528
ISSN	0957-4484
DOI	10.1088/1361-6528/abb907
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Article ; Online: Ultrafast Formation of Small Polarons and the Optical Gap in CeO

Pelli Cresi, Jacopo Stefano / Di Mario, Lorenzo / Catone, Daniele / Martelli, Faustino / Paladini, Alessandra / Turchini, Stefano / D'Addato, Sergio / Luches, Paola / O'Keeffe, Patrick

The journal of physical chemistry letters

2020 Volume 11, Issue 14, Page(s) 5686–5691

Abstract: The ultrafast dynamics of excited states in cerium oxide are investigated to access the early moments of polaron formation, which can influence the photocatalytic functionality of the material. UV transient absorbance spectra of photoexcited ... ...

Abstract	The ultrafast dynamics of excited states in cerium oxide are investigated to access the early moments of polaron formation, which can influence the photocatalytic functionality of the material. UV transient absorbance spectra of photoexcited CeO
Language	English
Publishing date	2020-07-02
Publishing country	United States
Document type	Journal Article
ISSN	1948-7185
ISSN (online)	1948-7185
DOI	10.1021/acs.jpclett.0c01590
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Article: The last mile of molecular reaction dynamics virtual experiments: the case of the OH(N = 1-10) + CO(j = 0-3) reaction.

Laganà, Antonio / Garcia, Ernesto / Paladini, Alessandra / Casavecchia, Piergiorgio / Balucani, Nadia

Faraday discussions

2012 Volume 157, Page(s) 415–36; discussion 475–500

Abstract: By exploiting the potentialities of a recently implemented grid empowered molecular simulator based on the combination of collaborative interoperable service oriented computing and the usage of high performance - high throughput technologies, the results ...

Abstract	By exploiting the potentialities of a recently implemented grid empowered molecular simulator based on the combination of collaborative interoperable service oriented computing and the usage of high performance - high throughput technologies, the results of crossed molecular beam experiments have been virtually simulated and compared with the real (measured) laboratory data for the reactive system OH + CO. The direct comparison of theoretically predicted laboratory angular distributions with experimental raw data avoids possible uncertainties associated with the analysis of crossed beam experiments, in which trial centre-of-mass functions are tested until the best-fit of the experimental data is achieved. To make such a comparison as accurate as possible, the rotational distributions of the OH radicals employed in previous crossed beam experiments have been characterized by laser-induced-fluorescence. The capability of performing massive calculations using grid-distributed technologies has allowed the running of quasiclassical trajectory calculations for all the initial rotational states of the OH radicals present in the beam (from the ground rotational state N(OH) = 1 up to N(OH) = 10) on three different potential energy surfaces and the comparison of related outcomes.
Language	English
Publishing date	2012-11-30
Publishing country	England
Document type	Journal Article
ISSN	1359-6640
ISSN	1359-6640
DOI	10.1039/c2fd20046e
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