Polarised infrared microspectroscopy of edge-oriented graphene oxide papers

We have performed FTIR transmission microspectroscopy on graphene oxide papers oriented with the nominal lattice planes parallel to the infrared optical axis. By polarising the IR light for samples of this geometry, spectral contributions of oriented oxide species are isolated from broad convoluted bands. Analysing the data alongside previous works, including experiments where samples were perturbed by reduction, dehydration and deuteration, we tabulate the most likely assignments for the observed spectral bands

Elucidating the Significance of Copper and Nitrate Speciation in Cu-SSZ-13 for N₂O Formation during NH₃-SCR

Unwanted N2O formation is a problem that has been noted in selective catalytic reduction (SCR) where copper zeolite catalysts are utilized. With its immense global warming potential and long-term stability, elevated atmospheric N2O has already been identified as a future challenge in the war on climate change. This paper explores the phenomenon of N2O formation during NH3-SCR over Cu-SSZ-13 catalysts, which are currently commercialized in automotive emissions control systems, and proposes a link between N2O production and the local copper environment found within the zeolite. To achieve this, a comparison is made between two Cu-SSZ-13 samples with different copper co-ordinations produced via different synthesis methods. A combination of synchrotron X-ray absorption near-edge spectroscopy, UV–vis, Raman, and density functional theory (DFT) is used to characterize the nature of copper species present within each sample. Synchrotron IR microspectroscopy is then used to compare their behavior during SCR under operando conditions and monitor the evolution of nitrate intermediates, which, along with further DFT, informs a mechanistic model for nitrate decomposition pathways. Increased N2O production is seen in the Cu-SSZ-13 sample postulated to contain a linear Cu species, providing an important correlation between the catalytic behavior of Cu-zeolites and the nature of their metal ion loading and speciation

Investigating the history of volatiles in the solar system using synchrotron infrared micro-spectroscopy

keywords: Synchrotron infrared micro-spectroscopy, CM chondrite meteorite, Murchison, Aqueous alteration, Asteroids adsurl: https://ui.adsabs.harvard.edu/abs/2018InPhT..94..244K adsnote: Provided by the SAO/NASA Astrophysics Data Syste

Far-IR/THz spectral characterization of the coherent synchrotron radiation emission at diamond IR beamline B22

Diamond is the new UK 3rd generation light source that opened to users since 2007 and now allocates more than 22 operational beamlines. Beamline B22 is dedicated to Infrared microspectroscopy and started operations in December 2009. By exploiting the Diamond SR source brightness it is optimized for mid-IR (2-25 μm wavelength) absorption spectroscopy, for fingerprint microprobe analysis and imaging mostly in Life Sciences but also Materials Sciences and Cultural Heritage. Vibrational spectroscopy analysis on condensed matter and material sciences can be performed at B22 by means of Fourier transform IR interferometry in a broader range from the visible up to the so-called THz region. Due to the uniquely wide B22 front end design (30 × 50 mrad 2 angle and about 32 mm vacuum vessel internal height), the IR beamline B22 operational range spans across the far-IR/THz region, with effective performances tested up to 2 mm wavelength or, equivalently, well below 0.15 THz (FE cut off ~4 mm wavelength). Especially in low-alpha mode of operation of Diamond, by compressing the e- bunch length to a few millimeters coherent SR emission can be stimulated at comparable wavelengths. In the far-IR, a dramatic intensity increase can be observed at Diamond even at only a few μA of circulating current. A summary of the first performances so far achieved in the Far-IR/THz on the IR beamline B22 is here reported for what concerns the CSR emission at Diamond; this is for the storage ring running in dedicated low-alpha mode both in a stable configuration, as well as in the so-called "bursting" or unstable CSR emission. The former is particularly interesting to reach the longest wavelengths (<20 cm -1) so to address the lower energy vibrational modes in condensed matter, the latter is promising for the wider spectral far-IR/THz coverage allowed (around 100 cm-1), and consequently appealing for extending the spectroscopy capability into a broader range of applications. © 2011 Springer-Verlag

Molecular force transfer mechanisms in graphene oxide paper evaluated using atomic force microscopy and in situ synchrotron micro FT-IR spectroscopy

The mechanical properties of graphene oxide (GO) paper are critically defined both by the mechanical properties of the constituent GO sheets and the interaction between these sheets. Functional carbonyl and carboxyl groups decorating defects, expected to be predominantly sheet edges of the GO, are shown to transfer forces to the in-plane carbon–carbon bonding using a novel technique combining atomic force microscopy (AFM) to mechanically deform discrete volumes of GO materials while synchrotron Fourier-transform infra-red (FTIR) microspectroscopy evaluated molecular level bond deformation mechanisms of the GO. Spectroscopic absorption peaks corresponding to in-plane aromatic C[double bond, length as m-dash]C bonds from GO sheets were observed to shift during tensile tests. Importantly, FTIR provided information on clear absorption peak shifts from C[double bond, length as m-dash]O bonds linking along the GO sheet edges, indicating transfer of forces between both C[double bond, length as m-dash]C and C[double bond, length as m-dash]O bonds during tensile deformation. Grüneisen parameters were used to quantitatively link the macroscopic FTIR peak shifts to molecular level chemical bond strains, with relatively low bond strains prevalent when applying external forces to the GO paper suggesting probing of hydrogen bonding interactions. We propose a mechanistic description of molecular interactions between GO sheets in the paper from these experiments, which is important in future strategies for further modification and improvement of GO-based materials

Broadband dielectric behavior of an MIL-100 metal–organic framework as a function of structural amorphization

The performance of modern electronics is associated with multi-layered interconnects, encouraging the development of low-k dielectrics. Herein, we studied the effects of phase transition from crystalline to amorphous on dielectric, optical, and electrical properties of MIL-100 (Fe) and Basolite F300 metal–organic frameworks obtained using different synthesis techniques in both the radio (4–1.5 MHz) and infrared (IR, 1.2–150 THz) frequency regimes, which are important for the microelectronics, IR optical sensors, and high-frequency telecommunications. The impact of amorphization on the broadband dielectric response was established based on the following: (1) by comparison of the dielectric characteristics of commercially available amorphous Basolite F300 versus mechanochemically synthesized crystalline MIL-100 (Fe) in the MHz region and (2) by tracking the frequency shifts in the vibrational modes of the MIL-100 structure in the far-IR (phonons) and mid-IR regions. We showed that various parameters such as the pelleting pressure, temperature, frequency, density, and degree of amorphization greatly affect the dielectric properties of the framework. We also investigated the influence of temperature (20–100 °C) on the electric and dielectric responses in the MHz region, which are crucial for all electronic devices