CO Shift Research Articles

Synthesis and structural characterization of novel di-substituted pyridine-2,6-dicarboxylic acid hydrazide oxo-quinazoline derivative and Cu(II) pincer complex

Crystal and molecular structures of novel pyridine-2,6-dicarboxylic acid (pdc) hydrazide derivative (H2L) dimethanol solvate (H2L = N,N'-bis(2-methyl-4-oxoquinazolin-3(4H)-yl)pyridine-2,6-dicarboxamide) and its copper(II) complex were determined by the single-crystal X-ray diffraction. In the crystal structure, these non-planar molecules form specific cavities that are populated by methanol molecules (held by OH⋯O and NH⋯O hydrogen bonds). Additional stabilization is achieved through a series of offset face-to-face π⋯π interactions between aromatic moieties. The compound is the first structurally described pdc hydrazide derivative containing quinazoline moieties. The reaction of the H2L with copper(II) chloride in methanol resulted in the formation of a new methanol/water solvate containing discrete CuCl2L molecules. Cu(II) ion is coordinated by three nitrogen atoms (two from hydrazide and one from pyridine moieties) in a chelate fashion. Two chloride ions complete distorted square pyramidal coordination geometry. Unlike in H2L molecules, in CuCl2L the hydrazide N-atoms are deprotonated, and coordinated to Cu(II), while quinazoline N-atoms are protonated. In its crystal structure, CuCl2L molecules form dimeric motifs via OH⋯O, NH⋯O, OH⋯Cl hydrogen bond interactions. The adjacent dimers are stacked along the crystallographic b- and c-axis through NH⋯Cl and offset face-to-face π⋯π interactions. The FT-IR spectra analysis indicates a significant shift of CO stretching vibrations of uncoordinated carbonyl groups, that can be attributed to the electron-withdrawing effect of Cu(II) ion. The TG analysis indicates that the weakly bounded solvent molecules evaporate at lower temperatures and that the compound is stable up to 300 °C.

Experimental and numerical analysis of the CO shift process for purified hydrogen production in an integrated gasification fuel cell

The Korean government has recently begun to focus on securing adequate hydrogen production to meet demands for the development and disseminaetion of sustainable technologies. This study describes a Korean national project developed for this hydrogen production purpose. In this study, we investigated the CO shift process for producing purified hydrogen in an integrated gasification fuel cell using experimental and numerical analyses. First, we successively designed and constructed a system with a syngas input of 160 Nm3/h; this system was efficiently operated for 45 h and we thus classified the operation into five spans (Start-Up, Heat-Up, Syngas Feeding, Steady-State, and Shut-Down). For example, in the span of State-State, the syngas load from 160 to 200 Nm3/h under the same H2O feeding conditions. Second, based on a computational flow dynamic model and its verification (comparison with experimental results), we conducted a parameter study on the effects that water injection has on the high-temperature CO shift reactor and showed that cases with a well-designed heat removal system yielded higher CO than other cases. The results of this study can be used as a guideline to develop CO shift processes at commercial grades (i.e., 10,000 Nm3/h syngas) for the production of purified hydrogen.

Recent Progress on Hydrogen-Rich Syngas Production from Coal Gasification

Coal gasification is recognized as the core technology of clean coal utilization that exhibits significant advantages in hydrogen-rich syngas production and CO2 emission reduction. This review briefly discusses the recent research progress on various coal gasification techniques, including conventional coal gasification (fixed bed, fluidized bed, and entrained bed gasification) and relatively new coal gasification (supercritical water gasification, plasma gasification, chemical-looping gasification, and decoupling gasification) in terms of their gasifiers, process parameters (such as coal type, temperature, pressure, gasification agents, catalysts, etc.), advantages, and challenges. The capacity and potential of hydrogen production through different coal gasification technologies are also systematically analyzed. In this regard, the decoupling gasification technology based on pyrolysis, coal char–CO2 gasification, and CO shift reaction shows remarkable features in improving comprehensive utilization of coal, low-energy capture and conversion of CO2, as well as efficient hydrogen production. As the key unit of decoupling gasification, this work also reviews recent research advances (2019–2023) in coal char–CO2 gasification, the influence of different factors such as coal type, gasification agent composition, temperature, pressure, particle size, and catalyst on the char–CO2 gasification performance are studied, and its reaction kinetics are also outlined. This review serves as guidance for further excavating the potential of gasification technology in promoting clean fuel production and mitigating greenhouse gas emissions.

Multifluid computational fluid dynamics simulation for sawdust gasification inside an industrial scale fluidized bed gasifier

Scarcity of fossil fuels, and to fulfill the energy demand of the increasing population, researchers need to shift their attention to the alternative of fossil fuels. It would be impractical and time-consuming to conduct extensive experiments on Fluidized Bed Gasifiers (FBG) of varying fuel types, sizes, geometries and operating conditions. The objective of the current research work is focused on numerical simulation of hydrodynamics behavior and sawdust gasification in an industrial scale FBG using the Eulerian-Eulerian multifluid model. For the accurate prediction of thermal and hydraulic performance (bed voidage, suspension density, pressure drop, heat transfer, and combustion kinetics), one should incorporate the correct parameters in the Computational Fluid Dynamics (CFD) simulation of a fluidized bed gasifier. It includes the multiphase gasification modeling using the Eulerian-Eulerian approach with an user defined heterogeneous reaction kinetics. The adopted CFD methodology is validated with experimental data and extended for the prediction of gasification characteristics of sawdust by incorporating eight heterogeneous (moisture release, volatile cracking, tar cracking, tar oxidation, char combustion, CO₂ gasification, steam gasification, methanation reaction) and five homogeneous oxidation of CO, CH₄, H₂, forward and backward water gas shift (WGS) reactions. In the result section, composition of gasification products is analyzed, along with the hydrodynamics of sawdust and sand phase, heat transfer between the gas, sand and sawdust, reaction rates of different homogeneous and heterogeneous reactions are being analyzed along the height of the domain.

Gasification of a bituminous coal in 15MWth KEDA®circulating fluidized-bed gasifier with high-temperature preheating

The industrial-scale high-temperature preheating air-blown KEDA®circulating fluidized-bed (KEDA®CFB) gasification process has been developed by KEDA(ANHUI) Clean Energy Co., Ltd. to produce industrial fuel gas. This paper presents the design and the first operational results of a 15MWth industrial-scale demonstration KEDA®CFB plant where about 3.6 tons bituminous coal was gasified per hour. The influences of the steam to coal ratio (SC), the equivalence ratio (ER), and the oxygen concentration (OC) on gas composition, gas high heating value (HHV), carbon conversion efficiency (CCE), and cold gas efficiency (CGE) were investigated systematically. It is shown that increasing SC from 0.18 to 0.38 favors the water–gas reaction and CO–shift reaction that causes H2 and CO2 content in the raw gas to rise. As ER increases to 0.27, it is conducive to the partial combustion and Boudouard reactions of char, and the HHV and CGE of gas products are 6.38 MJ/Nm3 and 66.8%, respectively. As OC increased from 21 vol% to 27 vol%, the CCE increased from 71.8% to 79.8% mainly due to the increase of gasification reaction rate and residence time. The operational results in this work can significantly contribute to the design and operation of industrial-scale gasifiers, and the development of numerical models.

Origin of Higher CO Oxidation Activity of Pt/Rutile than That of Pt/Anatase

Herein, we show that the weak interaction of CO with Pt/TiO2 under the CO oxidation condition is the origin of higher CO oxidation activity of Pt/rutile than that of Pt/anatase. The results of CO temperature-programmed desorption (TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) indicate that the onset temperatures of CO desorption on freshly prepared Pt/rutile and Pt/anatase are the same. However, the CO-TPD curves of Pt/rutile after the reaction test show that the desorption temperature of CO shifts to a lower temperature, while that for Pt/anatase does not change. The in situ pulse reaction using DRIFTS reveals that CO on Pt/rutile reacted with oxygen faster than CO on Pt/anatase. IR spectra with peak deconvolution of adsorbed CO on Pt/rutile exhibit that CO adsorbed on the terrace sites of Pt clusters on rutile (2089 cm–1) reacts readily with O2. These results indicate that the higher low-temperature activity of Pt/rutile is related to its weaker interaction with CO compared with Pt/anatase under the reaction conditions. Our findings deepen the fundamental understanding of metal–support interaction and CO oxidation on Pt/TiO2 catalysts.

The Effect of Metallicity on the Nonequilibrium Abundance of Hydrogen-dominated Exoplanet Atmospheres

The atmospheric metallicity greatly influences the composition of exoplanet atmospheres. The effect of metallicity on the thermochemical equilibrium is well studied, though its effect on the disequilibrium abundance is loosely constrained. In this study, we have used the quenching approximation to study the effect of metallicity on the quenched abundance for a range of parameters (temperature: 500–2500 K, pressure: 10−4–103 bar, metallicity: 0.1–1000× solar metallicity). We determine the chemical timescale by finding rate-limiting steps in a reduced chemical network with a network-analysis tool and the thermochemical equilibrium abundance. The equilibrium abundance results are similar to the literature. The CO, H2O, and CO2 abundances increase with metallicity in the parameter range considered. The CH4 abundance increases with metallicity for CO/CH4 < 1 and is unaffected for CO/CH4 > 1. The chemical timescale of CO shows minimal change with metallicity, while the CH4 chemical timescale is inversely proportional to atmospheric metallicity. The quench level of CO shifts into the high-pressure region, and the quench level of CH4 shows complex behavior with metallicity. We benchmarked the quenching approximation with a one-dimensional photochemistry-transport model for two test exoplanets (GJ 1214 b and HD 189733 b) and found it to be in good agreement. We also found that the quenching approximation is a powerful tool to constrain atmospheric parameters. We demonstrated this by constraining the metallicity and transport strength for the test exoplanets HR 8799 b, HD 189733 b, GJ 436 b, and WASP-39 b.

Stratigraphic variations in chromite chemistry through the UG-2 and UG-2E chromitites, bushveld igneous complex: implications for chromitite petrogenesis

ABSTRACT Chromitite petrogenesis in layered intrusions is important because some chromitites host economic Ni-Cu-platinum group element mineralization. Cryptic layering, which could be useful to reconstruct the chromitite origin, has been documented for some chromitites. Here, we document cm-scale stratigraphic profiles of the major and trace element contents in chromite across two chromitite seams from the Bushveld Igneous Complex. One set is from a massive UG-2 seam from the western limb, the other from a chromitite seam in the Turfspruit area of the northern limb, considered stratigraphically equivalent to the UG-2 (henceforth the ‘UG-2 equivalent’ or ‘UG-2E’). Stratigraphic profiles across the massive UG-2 only show a gradual increase in V contents (from bottom to top) and subtle variations in Mg#, Cr#, Mn, Zn, Co, Ti, and Ga contents. In contrast, the UG-2E profiles show significant variations in Mg# but not in Cr#, and distinct shifts in Mn, Zn, Co, Ni, Ti, and Ga contents and Fe3+/∑Fe values. These shifts correlate in part with variations in chromite abundance but also occur in sections as massive as the UG-2 reference. We argue that, in general, the presence of cryptic layering is more consistent with chromitite formation via gravitational settling or in situ crystallization rather than via slurries.

CoP aerogels assisted by selenite etching as high activity electrocatalysts for water splitting

Producing Hydrogen by electrolysis of water is a sustainable renewable energy conversion method. The most important is to design and prepare high performance electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water electrolysis. Herein, aerogels of Se/CoP and Se/Fe–CoP with unique 3D porous structure have been synthesized for HER and OER, respectively, through a simple and controllable strategy of sol-gel, parkerising and doping. The catalysts of Se/CoP AGs and Se/Fe–CoP AGs served as cathode and anode have only overpotentials of 105 mV and 230 mV, and the assembled electrolytic cell by them has a voltage of 1.59 V to reach a current density of 10 mA cm−2. The mechanism of the enhanced electrocatalytic activity can be attributed to their original structure and the electronic regulation: 3D porous aerogel with high specific surface area and well–developed pore structure provides rich exposed active sites and guarantees effective ion diffusion and H2/O2 release during water splitting; the electronic modulation is achieved by selenite etching and Fe heteroatom doping to result the binding energy shift of Co to improve the catalytic performance. This work provides an effective way for the application of aerogel materials in the electrical decomposition of water.

Two-Electron-Induced Reorganization of Cobalt Coordination and Metal-Ligand Cooperative Redox Shifting Co(I) Reactivity toward CO2 Reduction.

Electrochemical reorganization of complex structures is directly related to catalytic reactivity; thus, the geometric changes of catalysts induced by electron transfer should be considered to scrutinize the reaction mechanism. Herein, we studied electron-induced reorganization patterns of six-coordinate Co complexes with neutral N-donor ligands. Upon two-electron transfer into a Co center enclosed within a bulky π-acceptor ligand, the catalytic site exhibited different reorganization patterns depending on the ligand characteristics. While a bipyridyl ligand released Co-bound solvent (CH3CN) to open a reaction site, a phenanthroline ligand caused Co-Narm (side "arm" of NNN-ligand) bond dissociation. The first electron transfer occurred in the Co(II/I) reduction step and the second electron entered the bulky π-acceptor, of which redox steps were assigned from cyclic voltammograms, magnetic moment measurements, and DFT calculations. In comparison, the Co complex of [NNNNCH3-Co(CH3CN)3](PF6)2 ([1-(CH3CN)3](PF6)2) showed a high H2 evolution reactivity (HER), whereas a series of Co complexes with bulky π-acceptors such as [NNNNCH3-Co(L)(CH3CN)](PF6)2 (L = phen ([2-CH3CN](PF6)2), bpy ([3-CH3CN](PF6)2), [NNNNCH3-Co(tpy)](PF6)2 ([4](PF6)2), and [NNNCH2-Co(phen)(CH3CN)](PF6)2 ([5-CH3CN](PF6)2)) suppressed the HER but rather enhanced the CO2 reduction reaction. The metal-ligand cooperative redox steps enabled the shift of Co(I) reactivity toward CO2 reduction. Additionally, the amine pendant attached to the NNNNCH3-ligand could stabilize the CO2 reduction intermediate through the hydrogen-bonding interaction with the Co-CO2H adduct.

Development of biomaterials based on plasticized polylactic acid and tea polyphenols for active-packaging application

Bioactive-packaging films based on polylactic acid (PLA), acetyl tributyl citrate (ATBC), and tea polyphenol (TP) were prepared by melt blending. Results of mechanical-property test revealed that adding ATBC and TP can significantly improve mechanical properties of PLA. The shift of CO to lower wavelengths in FTIR and the morphology of the films in SEM indicated physical or chemical interactions in the PLA/ATBC/TP films. The antioxidant, and antibacterial activities of the PLA/ATBC films increased dramatically (P<0.05) with increased TP amount. The antioxidant activity of the films with 1 % TP was equivalent to that of 300 mg/L l-ascorbic acid, whereas PLA/ATBC/TP films with 0.5 % and 1 % TP concentration were effective in inhibiting Staphylococcus aureus and Escherichia coli within almost 5 h (P<0.05). The PLA films changed from transparent to opaque and from yellow to red after combining with ATBC or TP, respectively. The overall migration of the films in 3 % acetic acid and 10 % ethanol did not exceed the overall migration limit. All these findings indicated potential of the PLA/ATBC/TP films in active-packaging application.

Identifying the realistic catalyst for aqueous phase reforming of methanol over Pt supported by lanthanum nickel perovskite catalyst

In-situ supply of H2 by aqueous phase reforming (APR) of methanol is promising but still challenging due to the unsatisfied activity and stability of catalyst. Herein, we prepared lanthanum nickel perovskite supporting Pt catalysts and evaluated their performance in methanol APR. A transformation from lanthanum nickel perovskite into LaCO3OH happened after APR. The characterizations results reveal that these two perovskite catalysts transformed into LaCO3OH supporting Pt and NiOx structure. We further prepared Pt-NiOx/LaCO3OH catalyst to verify it. Combining with temperature programmed surface reaction, a possible mechanism is proposed. The transformed catalyst possessed more metallic Pt sites and more abundant active OH groups, which are beneficial for methanol decomposition and CO shift, respectively. In addition, although the structure transformation happened for perovskite supporting Pt catalyst, it presented extremely excellent stability with only 7% loss of its highest rate of hydrogen production after 315 h on stream.

Low-emission and energetically efficient co-gasification of coal by incorporating plastic waste: A modeling study

The issues of global plastic waste generation and demand for hydrogen energy can be simultaneously resolved by gasification process. In this regard, feasibility and efficiency of steam and air co-gasification of coal by incorporating five different and prevalent types of plastic waste were investigated in this modeling study. All steam and air coal/plastic waste co-gasification types were multi-objective optimized utilizing a response surface methodology. The best co-gasification types were selected using VIekriterijumsko KOmpromisno Rangiranje (VIKOR) analysis. Overall, the results showed that incorporating plastic waste into coal gasification improved hydrogen concentration in the syngas and increased normalized carbon dioxide production due to the high carbon content of plastic waste and activation of water-gas and CO shift reactions. VIKOR analysis revealed that steam coal/low density polyethylene was the best optimized co-gasification type with hydrogen concentration of 62.8 mol %, normalized carbon dioxide production of 2.60 g/mol, based on the feedstock entering the system, and energy efficiency of 76.6%. Increasing gasifier temperature enhanced hydrogen concentration and decreased normalized carbon dioxide production. The energy efficiency was markedly improved by increasing the moisture content and decreasing the ratio of steam/feedstock. This study confirmed the hypothesis of efficient utilization of plastic waste in coal/plastic waste co-gasification.

Winter Daytime Warming and Shift in Summer Monsoon Increase Plant Cover and Net CO2 Uptake in a Central Tibetan Alpine Steppe Ecosystem

AbstractOver the past decades, human‐induced climate change has led to a widespread wetting and warming of the Tibetan Plateau (TP), affecting both ecosystems and the carbon cycling therein. Whether the previously observed climate changes stimulate carbon uptake via enhanced photosynthesis or carbon loss via enhanced soil respiration remains unclear. Here we present 14 years of observations of carbon fluxes, meteorological variables and remotely sensed plant cover estimations from a central Tibetan alpine steppe ecosystem at Nam Co, the third largest lake on the TP. Using modified Mann‐Kendall trend tests, we found a significant increasing daily net carbon uptake of 0.5 g C m−2 decade−1, which can be explained by a widespread greening at the southern shore of lake Nam Co. The Plateau‐wide changes in temperature and precipitation are locally expressed as an increasing diurnal temperature range during winter, higher water availability during spring, higher cloud cover during early summer and less water availability during late summer. While these changes differ over the course of the year, they tend to stimulate plant growth more than microbial respiration, leading to an increased carbon uptake during all seasons. This study indicates that during the 14 years study period, a higher amplitude in winter temperatures and an earlier summer monsoon promote carbon uptake in a central Tibetan alpine steppe ecosystem.

Structural Origin and Vibrational Fingerprints of the Ultrafast Excited State Proton Transfer of the Pyranine-Acetate Complex in Aqueous Solution.

The excited state proton transfer (ESPT) reaction from the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS or pyranine) to an acetate molecule has been investigated in explicit aqueous solution via excited state ab initio molecular dynamics simulations based on hybrid quantum/molecular mechanics (QM/MM) potentials. In all the trajectories, the direct proton transfer has been observed in the excited state within 1 ps. We find that the initial structural configuration extracted from the ground state distribution strongly affects the ESPT kinetics. Indeed, the relative orientation of the proton donor-acceptor pair and the presence of a water molecule hydrogen bonded to the phenolic acid group of the pyranine are the key factors to facilitate the ESPT. Furthermore, we analyze the vibrational fingerprints of the ESPT reaction, reproducing the blue shift of the acetate CO stretching (COac), from 1666 to 1763 cm-1 testifying the transformation of acetate to acetic acid. Finally, our findings suggest that the acetate CC stretching (CCac) is also sensitive to the progress of the ESPT reaction. The CCac stretching is indeed ruled by the two vibrational modes (928 and 1426 cm-1), that in the excited state are alternately activated when the proton is shared or bound to the donor/acceptor, respectively.

From Intermolecular Interaction Energies and Observable Shifts to Component Contributions and Back Again: A Tale of Variational Energy Decomposition Analysis

Quantum chemistry in the form of density functional theory (DFT) calculations is a powerful numerical experiment for predicting intermolecular interaction energies. However, no chemical insight is gained in this way beyond predictions of observables. Energy decomposition analysis (EDA) can quantitatively bridge this gap by providing values for the chemical drivers of the interactions, such as permanent electrostatics, Pauli repulsion, dispersion, and charge transfer. These energetic contributions are identified by performing DFT calculations with constraints that disable components of the interaction. This review describes the second-generation version of the absolutely localized molecular orbital EDA (ALMO-EDA-II). The effects of different physical contributions on changes in observables such as structure and vibrational frequencies upon complex formation are characterized via the adiabatic EDA. Example applications include red- versus blue-shifting hydrogen bonds; the bonding and frequency shifts of CO, N2, and BF bound to a [Ru(II)(NH3)5]2 + moiety; and the nature of the strongly bound complexes between pyridine and the benzene and naphthalene radical cations. Additionally, the use of ALMO-EDA-II to benchmark and guide the development of advanced force fields for molecular simulation is illustrated with the recent, very promising, MB-UCB potential. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Transition-metal redox evolution and its effect on thermal stability of LiNi Co Mn O2 based on synchrotron soft X-ray absorption spectroscopy

The correlations between electronic structure evolution and thermal stability of layered LiNi x Co y Mn z O 2 cathodes are investigated systematically based on the synchrotron soft X-ray absorption spectroscopy and micro-calorimetry. Based on the synchrotron soft X-ray absorption spectroscopy experiments, the fundamental electronic structures of layered LiNi x Co y Mn z O 2 (NCM) are investigated systematically and the data of transition-metal (TM) L - and O K -edges spectra are collected. Distribution of Ni ions under different oxidation states is evaluated according to linear combination fit. It is found that the ratio of Ni 4+ expands with the increase of Ni since it dominates in charge compensation during charging, and that the existence of Ni 3+ is nearly negligible in delithiated NCM. The valence state of Co also strongly depends on Ni content, the perceptible position shift of Co L 3 -edge absorption peak towards higher energy in Ni-rich material agrees well with the small voltage plateau at around 4.2 V. The stability of Mn is verified as no obvious spectral change with the Mn L -edge is observed. Moreover, as Ni content rises, the O 2 p holes near the Femi level increases with higher oxidation state of Ni, indicating the enhanced hybridization of O 2 p -TM 3 d . Delithiated NCMs with higher Ni content are prior to lose electron existing in highly hybridized Ni 3 d -O 2 p bands upon heating, which accounts for the pronounced O 2 release in phase transitions and the deterioration in thermal stability. These detailed observation of the electronic structure evolution is one of the key ingredients to improving the electrochemical and thermal performance of NCM.

Line parameters of the 4-0 band of carbon monoxide by high sensitivity cavity ring down spectroscopy near 1.2 µm

The room temperature spectrum of the very weak third overtone band of carbon monoxide in natural isotopic abundance is recorded by cavity ring down spectroscopy (CRDS) referenced to a frequency comb, between 8206 and 8465 cm−1. The sensitivity of the recordings (noise equivalent absorption on the order of αmin ∼ 5 × 10−12 cm−1) allowed for measuring lines with intensity as weak as 1 × 10−30 cm/molecule at a recording pressure limited to 10.0 Torr. The use of low pressure values (1.0 and 10.0 Torr) helped to minimize the impact of profile effects on the derived line positions and line intensities. The line profile analysis was performed using the speed dependent Nelkin-Ghatak model for the 10 Torr recordings while the Voigt profile was found sufficient to account for the line shapes recorded at 1.0 Torr.Overall, line parameters of 227 transitions are derived. The observed transitions belong to the 4-0 band of the 12C16O, 13C16O, 12C18O and 12C17O isotopologues present in natural abundance in the sample and to the 5-1 hot band of 12C16O. For a large part of the observations, line positions are reported with accuracy as good as 4 × 10−6 cm−1 (∼120 kHz). The self-induced line shift of the 4-0 band is reported for the first time from the position values at 1 and 10 Torr. Using literature values of the 1-0, 2-0 and 3-0 bands, the vibrational dependence of the self-induced pressure shift in CO is discussed. The experimental values of the 12C16O v = 4 energy levels J < 26 are reproduced with a standard deviation of 2.5 × 10−6 cm−1 (75 kHz). The intensities of the 12C16O lines reported with an accuracy better than 1% show an overall good agreement with literature values in particular with those included in the HITRAN database.

Characterization of oxide-supported Cu by infrared measurements on adsorbed CO

Infrared spectroscopy on CO chemisorbed on Raney Cu and materials with Cu dispersed as nanoparticles on oxide supports was used to evaluate support effects on the Cu surface properties. The C-O frequency (νC-O) is sensitive to the charge on the adsorption site with νC-O being high on Cu+, intermediate on Cu0, and low on Cu−, whereby this method can probe the charging state of the Cu surface. The Raney Cu reference demonstrates the complex analysis of the IR band intensity, which can be susceptible to dipole coupling. This means that the most intense IR bands may be higher frequency bands strengthened by such coupling effects rather than the bands arising from the most abundant sites. The νC-O of the major band attributable to CO adsorbed on the metallic surface follows the order: Cu/SiO2 > Raney Cu > Cu/Al2O3 > Cu/TiO2. Given the charge-frequency relationship these support-dependent frequency shifts are attributed to changes in the charging of the Cu surface caused by support effects. The Cu surface is more electron deficient for Cu/SiO2 and electron enriched for Cu/TiO2. For the Cu/ZnO(/Al2O3) samples, which are important as industrial methanol synthesis catalysts, band assignments are complicated by a low νC-O on Cu+ sites connected to the ZnO matrix. However, Cu/ZnO(/Al2O3) has a spectral feature at 2065-68 cm−1, which is a lower frequency than observed in the Cu single crystal studies in the literature and thus indicative of a negative charging of the Cu surface in such systems. Experiments with co-adsorption of CO and electron-withdrawing formate on Cu/ZnO and Cu/SiO2 show that νC-O in the adsorbed CO shifts upwards with increasing HCOO coverage. This illustrates that the surface charge is donated to the electron-withdrawing formate adsorbate, and as a result co-adsorbed CO experiences a more charge depleted Cu surface that yields higher νC-O. The support-dependent surface charging may thus affect the interaction with adsorbates on the metal surface and thereby impact the catalytic properties of the Cu surface. Dilution of the samples in KBr, which has been used in many studies in the literature, had pronounced effects on the spectra. The presence of KBr leads to an increase in νC-O indicative of an electron depleted surface attributed to transfer of electron-withdrawing bromine species from KBr to the sample.

Selective binding of Ni2+ and Cu2+ metal ions with naphthazarin esters isolated from Arnebia euchroma.

Naphthazarin esters (C1-C4) isolated from the roots of Arnebia euchroma are found as skilled dual chemosensors for Ni2+ and Cu2+ among Pb2+ , Na2+ , K2+ , Hg2+ , Mg2+ , and Ca2+ metal ions. C1-C4 esters exhibited a red shift of 54 nm with Ni2+ and 30 nm with Cu2+ metal ions in absorption. There is a formation of red-shifted bands between 517 and 613 nm in the absorption spectrum of C1-C4 sensors on binding with Ni2+ and Cu2+ ions. The addition of Ni2+ and Cu2+ ions to sensors C1-C4 stimulates a remarkable color change from reddish pink to purple and light blue, respectively. These color changes can be identified with the naked eye. The significant downfield shifts of CO and OH peaks in nuclear magnetic resonance (NMR) spectrum confirm the chelation as binding mechanism. With ultraviolet-visble and NMR studies, it is found that C1-C4 esters possessed notable selectivity and sensitivity toward Ni2+ and Cu2+ over other metal ions.