B18-Core EXAFS
|
A.
Bandyopadhyay
,
S.
Lee
,
D. T.
Adroja
,
M. R.
Lees
,
G. B. G.
Stenning
,
P.
Aich
,
L.
Tortora
,
C.
Meneghini
,
G.
Cibin
,
A.
Berlie
,
R. A.
Saha
,
D.
Takegami
,
A.
Meléndez-Sans
,
G.
Poelchen
,
M.
Yoshimura
,
K. D.
Tsuei
,
Z.
Hu
,
T.-S.
Chan
,
S.
Chattopadhyay
,
G. S.
Thakur
,
K.-Y.
Choi
Diamond Proposal Number(s):
[33369]
Open Access
Abstract: We present an experimental investigation of the magnetic ground state in Ba4NbIr3O12, a fractional valent trimer iridate. X-ray absorption and photoemission spectroscopy show that the Ir valence lies between 3+ and 4+ while Nb is pentavalent. Combined dc/ac magnetization, specific heat, and muon spin rotation/relaxation (µSR) measurements reveal no magnetic phase transition down to 0.05 K. Despite a significant Weiss temperature (ΘW∼−15 to −25 K) indicating antiferromagnetic correlations, a quantum spin-liquid (QSL) phase emerges and persists down to 0.1 K. This state likely arises from geometric frustration in the edge-sharing equilateral triangle Ir network. Our µSR analysis reveals a two-component depolarization, arising from the coexistence of rapidly (90%) and slowly (10%) fluctuating Ir moments. Powder x-ray diffraction and Ir-L3edge x-ray absorption fine structure spectroscopy identify 8–10% Nb/Ir site-exchange, reducing frustration within part of the Ir network, and likely leading to the faster muon spin relaxation, while the structurally ordered Ir ions remain highly geometrically frustrated, giving rise to the rapidly spin-fluctuating QSL ground state. At low temperatures, the magnetic specific heat varies as 𝛾𝑇+𝛼𝑇2, indicating gapless spinon excitations, and possible Dirac QSL features with linear spinon dispersion, respectively.
|
Jul 2024
|
|
B18-Core EXAFS
|
Alberto
Lopez
,
Simone
Amatori
,
Elena
Olivieri
,
Iole
Venditti
,
Giovanna
Iucci
,
Carlo
Meneghini
,
Federica
Bertelà
,
Fabio
Del Bello
,
Wilma
Quaglia
,
Maura
Pellei
,
Carlo
Santini
,
Chiara
Battocchio
Diamond Proposal Number(s):
[25674]
Abstract: In the framework of the design, synthesis and testing of a library of copper complexes and nanostructured assemblies potentially endowed with antitumor and antiviral activity and useful for several applications, from drugs and related delivery systems to the development of biocidal nanomaterials, we present the detailed spectroscopic investigation of the molecular and electronic structure of copper-based coordination compounds and of a new conjugated system obtained by grafting Cu(I) complexes to gold nanorods. More in detail, the electronic and molecular structures of two Cu complexes and one AuNRs/Cu-complex adduct were investigated by X-ray photoelectron spectroscopy (XPS), synchrotron-induced XPS (SR-XPS) and near edge X-ray absorption spectroscopy (NEXAFS) in solid state, and the local structure around copper ion was assessed by X-ray absorption spectroscopy (XAS) both in solid state and water solution for the AuNRs/Cu-complex nanoparticles. The proposed multi-technique approach allowed to properly define the coordination geometry around the copper ion, as well as to ascertain the molecular structures of the coordination compounds, their stability and modifications upon interaction with gold nanoparticles, by comparing solid state and liquid phase data.
|
Mar 2024
|
|
B18-Core EXAFS
|
Fabio
Del Bello
,
Maura
Pellei
,
Luca
Bagnarelli
,
Carlo
Santini
,
Gianfabio
Giorgioni
,
Alessandro
Piergentili
,
Wilma
Quaglia
,
Chiara
Battocchio
,
Giovanna
Iucci
,
Irene
Schiesaro
,
Carlo
Meneghini
,
Iole
Venditti
,
Nitya
Ramanan
,
Michele
De Franco
,
Paolo
Sgarbossa
,
Cristina
Marzano
,
Valentina
Gandin
Diamond Proposal Number(s):
[25674]
Open Access
Abstract: Bis(pyrazol-1-yl)- and bis(3,5-dimethylpyrazol-1-yl)-acetates were conjugated with the 2-hydroxyethylester and 2-aminoethylamide derivatives of the antineoplastic drug lonidamine to prepare Cu(I) and Cu(II) complexes that might act through synergistic mechanisms of action due to the presence of lonidamine and copper in the same chemical entity. Synchrotron radiation-based complementary techniques [X-ray photorlectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS)] were used to characterize the electronic and molecular structures of the complexes and the local structure around the copper ion (XAFS) in selected complexes. All complexes showed significant antitumor activity, proving to be more effective than the reference drug cisplatin in a panel of human tumor cell lines, and were able to overcome oxaliplatin and multidrug resistance. Noticeably, these Cu complexes appeared much more effective than cisplatin against 3D spheroids of pancreatic PSN-1 cancer cells; among these, PPh3-containing Cu(I) complex 15 appeared to be the most promising derivative. Mechanistic studies revealed that 15 induced cancer cell death by means of an apoptosis-alternative cell death.
|
Mar 2022
|
|
I07-Surface & interface diffraction
|
Diamond Proposal Number(s):
[22710]
Open Access
Abstract: The surface region of austenitic stainless steel (SS) is investigated by synchrotron X-ray powder diffraction (XRPD) and X-ray absorption near edge structure (XANES) measurements, because its composition and structure is crucial for the corrosion resistance of SS. Grazing incidence XRPD of a polished AISI 304 bulk steel sample show that the near-surface structure is modified. The concentration of the ferrite phase of Fe, a typical minority phase in AISI 304, increases gradually from 10% to 30% when approaching the surface from 150 nm depth. XANES Fe K-edge investigations of ultra-thin, sputter deposited films also reveal much larger ferrite fractions than expected from the austenitic steel composition of the films. Reasons for the increased ferrite fraction in the surface region of bulk steel and thin films are discussed. However, right at the surface, the trend reverses. Analysis of XANES data for an ultra-thin, 4 nm SS film show that 80% of Fe is oxidized and 20% of metallic Fe is present only in austenite structure, suggesting that ferritic iron is preferentially subject to oxidation. The austenitic Fe is located at more than 2 - 3 nm below the surface where the Ni concentration is > 10%.
|
Feb 2022
|
|
I06-Nanoscience (XPEEM)
|
Diamond Proposal Number(s):
[1658]
Abstract: The physical properties of nanostructured thin films and multilayers depend crucially on their interfaces. The precise knowledge of the interface morphology at the atomic scale is mandatory to reliably understand their macroscopic response. These details become even more critical when dealing with magnetic thin films as the finest structural and/or compositional local changes may affect the magnetic coupling and alter the macroscopic response. Soft X-ray Resonant Magnetic Reflectivity (SXRMR) is a suitable technique in this field, combining specific aspects of x-ray absorption and x-ray scattering processes to simultaneously obtain complementary structural and magnetic information on thin films and multilayers. Here, we present a case study on a MgO/Co/MgO trilayer in which the combined use of SXRMR, x-ray absorption spectroscopy and x-ray magnetic circular dichroism has allowed to reconstruct the elemental and magnetic depth profiles with sub-nanometric resolution and to distinguish fine compositional defects at the Co-on-MgO and MgO-on-Co interfaces.
|
May 2021
|
|
I08-Scanning X-ray Microscopy beamline (SXM)
|
Giovanni
De Giudici
,
Carlo
Meneghini
,
Carla
Buosi
,
Ilaria
Carlomagno
,
Giuliana
Aquilanti
,
Tohru
Araki
,
Diana E.
Bedolla
,
Maria Antonietta
Casu
,
Antonietta
Cherchi
,
Alessandra
Gianoncelli
,
Antonella
Iadecola
,
Andrei C.
Kuncser
,
V. Adrian
Maraloiu
,
Olivier
Mathon
,
Valentina
Rimondi
,
Pierpaolo
Zuddas
,
Daniela
Medas
Diamond Proposal Number(s):
[16496]
Abstract: Biominerals are widespread in Nature and they precipitate to respond to different physiological purposes. A broad knowledge of their chemical and structural properties offers a unique opportunity to improve our capability to reconstruct actual and paleoenvironment. In this work, we show two case studies, bivalves and foraminifera grown in polluted sites that were characterized by applying different and complementary synchrotron radiation-based investigation techniques, mainly focused on the investigation of Zn incorporation in the biomineralized shells. Using scanning transmission X-ray microscopy (STXM) and X-ray micro-fluorescence (µ-XRF), we found the colocalization of elements across the shells, while we obtained information on chemical speciation of Zn by applying X-ray absorption spectroscopy (XAS). Noticeably, instead of metal dispersion in the Ca-carbonate shells, we found traces of several independent phases, in particular for Zn, dispersed generally as microscopic minerals. This work provides fundamental insight into the structural properties, coordinative and chemical environment of some marine biominerals. This new knowledge is fundamental to understand the biogeochemical processes and to develop effective environmental proxies.
|
May 2021
|
|
|
|
Open Access
Abstract: In the present study, the local atomic structure of a Nb3Sn superconductor sample has been probed by X-ray absorption fine structure (XAFS) as a function of hydrostatic pressure (from ambient up to 26 GPa) using a diamond anvil cell set-up. The analysis of the Nb-K edge extended X-ray absorption fine structure (EXAFS) data was carried out combining standard multi shell structural refinement and reverse Monte Carlo method to provide detailed in situ characterization of the pressure-induced evolution of the Nb local structure in Nb3Sn. The results highlight a complex evolution of Nb chains at the local atomic scale, with a peculiar correlated displacement of Nb–Nb and Nb–Nb–Nb configurations. Such a local effect appears related to anomalies evidenced by X-ray diffraction in other superconductors belonging to the same A15 crystallographic structure.
|
Mar 2021
|
|
B16-Test Beamline
B18-Core EXAFS
I08-Scanning X-ray Microscopy beamline (SXM)
|
Debi
Garai
,
Vladyslav
Solokha
,
Axel
Wilson
,
Ilaria
Carlomagno
,
Ajay
Gupta
,
Mukul
Gupta
,
V. R.
Reddy
,
Carlo
Meneghini
,
Francesco
Carla
,
Christian
Morawe
,
Jorg
Zegenhagen
Diamond Proposal Number(s):
[17145]
Open Access
Abstract: This work reports about a novel approach for investigating surface processes during the early stages of galvanic corrosion of stainless steel in situ by employing ultra-thin films and synchrotron X-radiation. Characterized by X-ray techniques and voltammetry, such films, sputter deposited from austenitic steel, were found representing useful replicas of the target material. Typical for stainless steel, the surface consists of a passivation layer of Fe- and Cr-oxides, a couple of nm thick, that is depleted of Ni. Films of ≈ 4 nm thickness were studied in situ in an electrochemical cell under potential control (-0.6 to +0.8 V vs Ag/AgCl) during exposure to 0.1 M KCl. Material transport was recorded with better than 1/10 monolayer sensitivity by X-ray spectroscopy. Leaching of Fe was observed in the cathodic range and the therefor necessary reduction of Fe-oxide appears to be accelerated by atomic hydrogen. Except for minor leaching, reduction of Ni, while expected from Pourbaix diagram, was not observed until at ≈ +0.8 V Cr-oxide was removed from the film. After couple of minutes exposure at +0.8 V, the current in the electrochemical cell revealed a rapid pitting event that was simultaneously monitored by X-ray spectroscopy. Continuous loss of Cr and Ni was observed during the induction time leading to the pitting, suggesting a causal connection with the event. Finally, a spectroscopic image of a pit was recorded ex situ with 50 nm lateral and 1 nm depth resolution by soft X-ray scanning absorption microscopy at the Fe L2,3-edges by using a 80 nm film on a SiN membrane, which is further demonstrating the usefulness of thin films for corrosion studies.
|
Dec 2020
|
|
B16-Test Beamline
B18-Core EXAFS
Optics
|
Open Access
Abstract: An ≈4 nm FeCrNi film, deposited on a Ru/B4C multilayer (ML), is used to study cathodic hydrogen charging in electrolyte. A thin film on a ML allows obtaining precise quantitative information on surface metal composition and oxidation state using the X‐ray standing wave technique combined with near‐edge X‐ray absorption spectroscopy. The metal composition is found being close to the composition of stainless steel (SS) 304, and, as for bulk steel, the outer 2 nm passive layer, consisting of oxidized iron and chromium, is depleted of nickel. Overall, it is found that the film represented a useful replica of the surface of bulk steel. Following exposure to 0.1 m KCl electrolyte at −0.6 V versus Ag/AgCl, 11.3 (±3)% swelling of the film by hydrogen absorption is observed. The estimated absorbed amount is exceeding reported bulk absorption under similar conditions by more than an order of magnitude. Strong hydrogen absorption appears to be enabled by the 2D character of the thin film, i.e., a significantly lower associated strain energy compared with bulk absorption. The strong surface swelling is suggested to be related to the lowering of the pitting corrosion resistance of SS surfaces reported following hydrogen exposure.
|
Apr 2020
|
|
I08-Scanning X-ray Microscopy beamline (SXM)
|
Daniela
Medas
,
Ilaria
Carlomagno
,
Carlo
Meneghini
,
Giuliana
Aquilanti
,
Tohru
Araki
,
Diana
Bedolla
,
Carla
Buosi
,
Maria Antonietta
Casu
,
Alessandra
Gianoncelli
,
Andrei C.
Kuncser
,
V. Adrian
Maraloiu
,
Giovanni
De Giudici
Diamond Proposal Number(s):
[16496]
Abstract: Zinc incorporation into marine bivalve shells belonging to different genera (Donax, Glycymeris, Lentidium, and Chamelea) grown in mine-polluted seabed sediments (Zn up to 1% w/w) was investigated using x-ray diffraction (XRD), chemical analysis, soft x-ray microscopy combined with low-energy x-ray fluorescence (XRF) mapping, x-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). These bivalves grew their shells, producing aragonite as the main biomineral and they were able to incorporate up to 2.0–80 mg/kg of Zn, 5.4–60 mg/kg of Fe and 0.5–4.5 mg/kg of Mn. X-ray absorption near edge structure (XANES) analysis revealed that for all the investigated genera, Zn occurred as independent Zn mineral phases, i.e., it was not incorporated or adsorbed into the aragonitic lattice. Overall, our results indicated that Zn coordination environment depends on the amount of incorporated Zn. Zn phosphate was the most abundant species in Donax and Lentidium genera, whereas, Chamelea shells, characterized by the highest Zn concentrations, showed the prevalence of Zn-cysteine species (up to 56% of total speciation). Other Zn coordination species found in the investigated samples were Zn hydrate carbonate (hydrozincite) and Zn phosphate. On the basis of the coordination environments, it was deduced that bivalves have developed different biogeochemical mechanisms to regulate Zn content and its chemical speciation and that cysteine plays an important role as an active part of detoxification mechanism. This work represents a step forward for understanding bivalve biomineralization and its significance for environmental monitoring and paleoreconstruction.
|
Oct 2018
|
|
