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https://www.readbyqxmd.com/read/29677501/the-near-infrared-spectra-of-the-alkali-carbonates
#1
Laurence Hopkinson, Ken J Rutt, Petra Kristova
This study presents the first account of the near-infrared (NIR) spectra of the alkali carbonates: [Cs2 CO3 ] [Rb2 CO3 ] [K2 CO3 ] [Na2 CO3 ] and [Li2 CO3 ]. Seven NIR bands (labelled [A] to [G] inclusive) within the [4000-6000cm-1 ] (2.5-1.66μm) region of interest are common to the five spectra examined, of which six bands [A-C] and [E-G] proved amenable to quantitative study. The first three occur in the range 4067-4493cm-1 (2.458-2.226μm) and are assigned to a [CO3 2- ] 3v3 overtone, Bands [E] and [F] are centred at ca 4902cm-1 (2...
April 11, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/29677497/order-disorder-phase-transition-in-the-peroxidovanadium-complex-nh-4-vo-o-2-2-nh-3
#2
Peter Schwendt, Róbert Gyepes, Jana Chrappová, Ivan Němec, Přemysl Vaněk
Complex NH4 [VO(O2 )2 (NH3 )] (1) undergoes an order-disorder phase transition at Tc ~258K. This transition is accompanied by change in the space group of the orthorhombic lattice and also by significant structural rearrangements of the constituent molecules, which are pertinent mostly to their NH4 + ions and their ammonia ligands. The low-temperature solid state IR and Raman spectra of 1 were corroborated by solid-state computations that employed Gaussian functions as the basis set. Results of these computations yielded excellent agreement with experimental data...
April 10, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/29677467/vibrational-and-nonadiabatic-coherence-in-2d-electronic-spectroscopy-the-jahn-teller-effect-and-energy-transfer
#3
David M Jonas
Femtosecond two-dimensional (2D) Fourier transform spectroscopy generates and probes several types of coherence that characterize the couplings between vibrational and electronic motions. These couplings have been studied in molecules with Jahn-Teller conical intersections, pseudo-Jahn-Teller funnels, dimers, molecular aggregates, photosynthetic light harvesting complexes, and photosynthetic reaction centers. All have closely related Hamiltonians and at least two types of vibrations, including one that is decoupled from the electronic dynamics and one that is nonadiabatically coupled...
April 20, 2018: Annual Review of Physical Chemistry
https://www.readbyqxmd.com/read/29677466/measuring-electric-fields-in-biological-matter-using-the-vibrational-stark-effect-of-nitrile-probes
#4
Joshua D Slocum, Lauren J Webb
Measurement of the electrostatic interactions that give rise to biological functions has been a longstanding challenge in biophysics. Advances in spectroscopic techniques over the past two decades have allowed for the direct measurement of electric fields in a wide variety of biological molecules and systems via the vibrational Stark effect (VSE). The frequency of the nitrile stretching oscillation has received much attention as an electric field reporter because of its sensitivity to electric fields and its occurrence in a relatively transparent region of the infrared spectrum...
April 20, 2018: Annual Review of Physical Chemistry
https://www.readbyqxmd.com/read/29677402/ultrafast-adiabatic-photodehydration-of-o-hydroxymethylphenol-and-formation-of-quinone-methide
#5
Nikola Basaric, Djani Skalamera, Ivana Antol, Kata Mlinaric Majerski, Hrvoj Vancik, David Lee Phillips, Jiani Ma
Photochemical reactivity of 2-hydroxymethylphenol (1) has been investigated experimentally by photochemistry at cryogenic conditions and the detection of reactive intermediates by IR, and the nanosecond and femtosecond transient absorption spectroscopic methods in solutions at room temperature. In addition, theoretical studies were performed to facilitate the interpretation of the experimental results and also to simulate the reaction pathway for a better understanding of the reaction mechanism. The main finding of this work is that photodehydration of 1 takes place in an ultrafast adiabatic photochemical reaction without any obvious intermediate, delivering quinone methide (QM) in the excited state...
April 20, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29676847/synthesis-of-a-molecularly-imprinted-polymer-on-msio-2-fe-3-o-4-for-the-selective-adsorption-of-atrazine
#6
Xin Li, Xiaoguo Ma, Renfeng Huang, Xiaowen Xie, Lihui Guo, Menyuan Zhang
Atrazine contamination of water is of considerable concern because of the potential hazard to human health. In this study, a magnetic molecularly imprinted polymer for atrazine was prepared by the surface imprinting technique using Fe3 O4 as the core, mesoporous silica as the carrier, atrazine as the template and itaconic acid as the functional monomer. The magnetic molecularly imprinted polymer was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and vibration sample magnetometry...
April 20, 2018: Journal of Separation Science
https://www.readbyqxmd.com/read/29676661/atomistic-mechanisms-of-the-double-proton-transfer-in-the-h-bonded-nucleobase-pairs-qm-qtaim-computational-lessons
#7
Ol'ha O Brovarets', Dmytro M Hovorun
In this Review we have summarized and generalized the results of the investigation of the microstructural mechanisms of the tautomerisation by the counter movement of the protons along the neighboring intermolecular H-bonds in 22 biologically important pairs of nucleotide bases in the framework of the original method, which allows to trace the evolution of the physico-chemical parameters, that characterize these processes along the intrinsic reaction coordinate (IRC). It was demonstrated the performance of the introduction of the conception of the key points (KPs) (from nine to five, depending on the symmetry and nature of system), which exhaustively characterize the flow of the tautomerisation processes...
April 20, 2018: Journal of Biomolecular Structure & Dynamics
https://www.readbyqxmd.com/read/29676564/parasites-under-the-spotlight-applications-of-vibrational-spectroscopy-to-malaria-research
#8
David Perez-Guaita, Katarzyna M Marzec, Andrew Hudson, Corey Evans, Tatyana Chernenko, Christian Matthäus, Milos Miljkovic, Max Diem, Philip Heraud, Jack S Richards, Dean Andrew, David A Anderson, Christian Doerig, Jose Garcia-Bustos, Don McNaughton, Bayden R Wood
New technologies to diagnose malaria at high sensitivity and specificity are urgently needed in the developing world where the disease continues to pose a huge burden on society. Infrared and Raman spectroscopy-based diagnostic methods have a number of advantages compared with other diagnostic tests currently on the market. These include high sensitivity and specificity for detecting low levels of parasitemia along with ease of use and portability. Here, we review the application of vibrational spectroscopic techniques for monitoring and detecting malaria infection...
April 20, 2018: Chemical Reviews
https://www.readbyqxmd.com/read/29676516/the-pea-leafminer-liriomyza-huidobrensis-diptera-agromyzidae-uses-the-vibrational-duets-for-efficient-sexual-communication
#9
Jin Ge, Jia-Ning Wei, Ding-Jie Zhang, Chun Hu, De-Zhi Zheng, Le Kang
The pea leafminer (Liriomyza huidobrensis) is a notorious pest of vegetables and ornamental plants worldwide. Despite a large number of studies on its biology and ecology, the courtship behavior and sexual communication of this species remain unclear. Here, we studied the vibrational communication in the sexual interaction of the pea leafminer. On host plant leaves, females and males behaviorally displayed the bobbing-quivering alternation, which finally led to copulation. Moreover, records of laser vibrometry revealed three-signal duets underlying the behavioral alternation...
April 20, 2018: Insect Science
https://www.readbyqxmd.com/read/29676424/anharmonicity-in-a-double-hydrogen-transfer-reaction-studied-in-a-single-porphycene-molecule-on-a-cu-110-surface
#10
S Liu, D Baugh, K Motobayashi, X Zhao, S V Levchenko, S Gawinkowski, J Waluk, L Grill, M Persson, T Kumagai
Anharmonicity plays a crucial role in hydrogen transfer reactions in hydrogen-bonding systems, which leads to a peculiar spectral line shape of the hydrogen stretching mode as well as highly complex intra/intermolecular vibrational energy relaxation. Single-molecule study with a well-defined model is necessary to elucidate a fundamental mechanism. Recent low-temperature scanning tunnelling microscopy (STM) experiments revealed that the cis ↔ cis tautomerization in a single porphycene molecule on Cu(110) at 5 K can be induced by vibrational excitation via an inelastic electron tunnelling process and the N-H(D) stretching mode couples with the tautomerization coordinate [Kumagai et al...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29676420/rationalisation-of-the-optical-signatures-of-nor-dihydroxanthene-hemicyanine-fused-near-infrared-fluorophores-by-first-principle-tools
#11
Cloé Azarias, Miguel Ponce-Vargas, Isabelle Navizet, Paul Fleurat-Lessard, Anthony Romieu, Boris Le Guennic, Jean-Alexandre Richard, Denis Jacquemin
Using a computational approach combining the Time-Dependent Density Functional Theory (TD-DFT) and the second-order Coupled Cluster (CC2) approaches, we investigate the spectral properties of a large panel of nor-dihydroxanthene (DHX)-hemicyanine fused dyes. First we compare the theoretical and experimental 0-0 energies for a set of 14 known synthetic compounds and show that a remarkable agreement between theory and experiment is obtained when a suitable environmental model is selected. In addition, we obtain vibrationally-resolved spectra for several compounds and theory also accurately reproduces the experimental band shapes...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29676413/theoretical-insight-into-the-vibrational-spectra-of-metal-water-interfaces-from-density-functional-theory-based-molecular-dynamics
#12
Jiabo Le, Qiyuan Fan, Laura Perez-Martinez, Angel Cuesta, Jun Cheng
Understanding the structures of electrochemical interfaces at the atomic level is key to developing efficient electrochemical cells for energy storage and conversion. Spectroscopic techniques have been widely used to investigate the structures and vibrational properties of the interfaces. The interpretation of these spectra is however not straightforward. In this work, density functional theory based molecular dynamics simulations were performed to study the vibrational properties of the Pt(111)- and Au(111)-water interfaces...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29675539/lab-on-a-tip-atomic-force-microscopy-photothermal-infrared-spectroscopy-of-atmospherically-relevant-organic-inorganic-aerosol-particles-in-the-nanometer-to-micrometer-size-range
#13
Victor W Or, Armando D Estillore, Alexei V Tivanski, Vicki H Grassian
New developments in nanoscale analytical techniques have paved the way for detailed spectroscopic and microscopic measurements of substrate-deposited aerosol particles on a single particle basis. Atomic force microscopy based photothermal infrared (AFM-PTIR) spectroscopy is a technique that combines the nanometer spatial resolution of AFM with the chemical analysis capabilities of vibrational IR spectroscopy. Herein we demonstrate the capability of AFM-PTIR to investigate single and multi-component systems comprised of inorganic salts and organic compounds relevant to the atmosphere...
April 20, 2018: Analyst
https://www.readbyqxmd.com/read/29675314/first-principles-calculations-of-raman-vibrational-modes-in-the-fingerprint-region-for-connective-tissue
#14
E T Sato, H Martinho
Vibrational spectroscopy has been widely employed to unravel the physical-chemical properties of biological systems. Due to its high sensitivity to monitoring real time " in situ " changes, Raman spectroscopy has been successfully employed, e.g., in biomedicine, metabolomics, and biomedical engineering. The interpretation of Raman spectra in these cases is based on the isolated macromolecules constituent vibrational assignment. Due to this, probing the anharmonic or the mutual interactions among specific moieties/side chains is a challenge...
April 1, 2018: Biomedical Optics Express
https://www.readbyqxmd.com/read/29675208/ultrastable-cationic-three-dimensional-lead-bromide-frameworks-that-intrinsically-emit-broadband-white-light
#15
Chengdong Peng, Zewen Zhuang, Huimin Yang, Guiyang Zhang, Honghan Fei
Herein, we report the unusual broadband white-light emission as an intrinsic property from two cationic lead bromide frameworks. This is the first time that the metal halide materials adopting a purely inorganic positively-charged three-dimensional (3D) topology have been synthesized, thus affording highly distorted PbII centers. The single-component white-light emitters achieve an external quantum efficiency of up to 5.6% and a correlated color temperature of 5727 K, producing typical white-light close to that of fluorescent light sources...
February 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675201/tagging-effects-on-the-mid-infrared-spectrum-of-microsolvated-protonated-methane
#16
Alexander Esser, Harald Forbert, Dominik Marx
Although bare protonated methane is by now essentially understood at the level of intramolecular large-amplitude motion, scrambling dynamics and broadband vibrational spectra, the microsolvated species still offer plenty of challenges. One aspect is the effect of the attached solvent molecules on the infrared absorption spectra of microsolvated CH5 + complexes compared to the bare parent molecule. In this study we analyze, based on ab initio molecular dynamics simulations, protonated methane molecules that have been microsolvated with up to three hydrogen molecules, i...
February 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675192/isotropic-ordering-of-ions-in-ionic-liquids-on-the-sub-nanometer-scale
#17
Hailong Chen, Xin Chen, Jingwen Deng, Junrong Zheng
This article investigates structures of ionic liquids. Using a high-powered multiple-mode two dimensional infrared spectroscopic technique, we measure the anisotropy of interionic vibrational coupling in ionic liquids. Such anisotropy reports the relative orientation between cations and anions. Surprisingly, opposite to the well-propagated idea of ion pairing, a random orientation between the nearest non-spherically symmetric cation and anion is observed in ionic liquids. On the one hand, numerous previous experiments and theoretical calculations have shown that ionic liquids are highly ordered at the mesoscale, forming a bicontinuous nanostructure of ionic domains and hydrophobic domains...
February 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675170/femtosecond-stimulated-raman-evidence-for-charge-transfer-character-in-pentacene-singlet-fission
#18
Stephanie M Hart, W Ruchira Silva, Renee R Frontiera
Singlet fission is a spin-allowed process in which an excited singlet state evolves into two triplet states. We use femtosecond stimulated Raman spectroscopy, an ultrafast vibrational technique, to follow the molecular structural evolution during singlet fission in order to determine the mechanism of this process. In crystalline pentacene, we observe the formation of an intermediate characterized by pairs of excited state peaks that are red- and blue-shifted relative to the ground state features. We hypothesize that these features arise from the formation of cationic and anionic species due to partial transfer of electron density from one pentacene molecule to a neighboring molecule...
February 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675157/the-mechanism-of-a-green-fluorescent-protein-proton-shuttle-unveiled-in-the-time-resolved-frequency-domain-by-excited-state-ab-initio-dynamics
#19
Greta Donati, Alessio Petrone, Pasquale Caruso, Nadia Rega
We simulated an excited state proton transfer in green fluorescent protein by excited state ab initio dynamics, and examined the reaction mechanism in both the time and the frequency domain through a multi resolution wavelet analysis. This original approach allowed us, for the first time, to directly compare the trends of photoactivated vibrations to femtosecond stimulated Raman spectroscopy results, and to give an unequivocal interpretation of the role played by low frequency modes in promoting the reaction...
February 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/29674807/experimental-investigation-of-fan-folded-piezoelectric-energy-harvesters-for-powering-pacemakers
#20
M H Ansari, M Amin Karami
This paper studies the fabrication and testing of a magnet free piezoelectric energy harvester (EH) for powering biomedical devices and sensors inside the body. The design for the EH is a fan-folded structure consisting of bimorph piezoelectric beams folding on top of each other. An actual size experimental prototype is fabricated to verify the developed analytical models. The model is verified by matching the analytical results of the tip acceleration frequency response functions (FRF) and voltage FRF with the experimental results...
June 2017: Smart Materials & Structures
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