CO Shift Research Articles

Optical Interference-Free Surface-Enhanced Raman Scattering CO-Nanotags for Logical Multiplex Detection of Vascular Disease-Related Biomarkers.

Matrix metalloproteinases (MMPs), specifically MMP-2, MMP-7, and MMP-9, have been discovered to be linked to many forms of vascular diseases such as stroke, and their detection is crucial to facilitate clinical diagnosis. In this work, we prepared a class of optical interference-free SERS nanotags (CO-nanotags) that can be used for the purpose of multiplex sensing of different MMPs. Multiplex detection with the absence of cross-talk was achieved by using CO-nanotags with individual tunable intrinsic Raman shifts of CO in the 1800-2200 cm-1 region determined by the metal core and ligands of the metal carbonyl complex. Boolean logic was used as well to simultaneously probe for two proteolytic inputs. Such nanotags offer the advantages of convenient detection of target nanotags and high sensitivity as validated in the ischemia rat model.

Determination of pressure in aqueo-carbonic fluid inclusions at high temperatures from measured Raman frequency shifts of CO2

Due to the presence of additional volatiles and/or electrolytes in CO 2 -H 2 O fluids, the total pressure of many natural aqueo-carbonic fluid inclusions at high temperatures as determined using microthermometry is usually made with considerable uncertainty. In this paper, we present the results of our high P - T in situ Raman scattering study of high-density aqueo-carbonic fluids, with and without a small amount of CH 4 and NaCl, whose objective is to derive a new method for pressure determination in aqueo-carbonic fluid inclusions at high temperatures. The measurement of the Fermi dyad bands at temperatures up to 400 °C and pressures up to 1200 MPa is described. The manner in which the frequency shifts and intensity of Raman bands are governed by pressure, temperature, presence of CH 4 in carbonic and NaCl in aqueous fluids is discussed. From the monotonic dependence of the frequency shifts of the lower Fermi dyad band ν − and the Fermi resonant splitting D ( D = ν + − ν − ) with pressure and temperature, the pressure (in MPa) in aqueo-carbonic fluid inclusions at elevated temperatures can be determined directly by using the following two polynomial equations: P ( MPa ) = − 16 + 1 . 232 × T − 53 . 72 × ( Δ ν − ) − 1 . 83 × 10 − 3 × T 2 + 24 . 46 × ( Δ ν − ) 2 − 0 . 292 × T × ( Δ ν − ) , P ( MPa ) = − 26 + 1 . 501 × T + 193 . 24 × ( Δ D ) − 1 . 61 × 10 − 3 × T 2 + 5 . 436 × ( Δ D ) 2 + 0 . 158 × T × ( Δ D ) , where T is in °C, Δ ν − and Δ D represent frequency shifts (in cm −1 ) of the lower band and the resonant splitting relative to the reference values measured at 23 °C and 6 MPa, respectively. Based on the attainable accuracy of the fitted peak positions and the results from fitting of Raman frequency shifts’ dependence with pressure and temperature, the uncertainty in pressure determination is about 50 MPa for pressures determined from ν − and 40 MPa from that determined from D .

The R&D of a Novel Sulfur Tolerant CO Shift Catalyst and Its Application in the Integrated Low Water Gas Ratio Process

The QDB-5 sulfur tolerant CO shift catalyst, with anti-methanation property by supported compositing alkali promoters, has been proved to effectively reduce the outlet methane content in the condition of a low water gas ratio. Thus, a new technology based on a lower water/gas ratio than before has been developed with the new catalyst. The CO conversion at lower temperatures and catalyst stability were confirmed by long term industrial application. The high temperature catalyst performance also showed a better result than the conventional commercial catalyst, with higher CO conversion and well controlled methane outlet. Our research and the industrial application of catalyst have shown the importance of alkali metals as core promoters for such kind of catalysts.

Synthesis of Novel Cobalt-Containing Polysilazane Nanofibers with Fluorescence by Electrospinning.

Emission in the nanostructured materials is important in micro/nanoelectronic devices. We report here a strategy for the processing of micron and submicron fibers from a cobalt-containing hyperbranched polysilazane by electrospinning. The electrospun nanofibers have uniform average diameters of ~600 nm and lengths of ~10 μm. The photophysical properties of polycobaltsilazane (PCSN) are studied using UV-VIS and photoluminescence spectroscopies. PCSN fibers display a series of emission peaks between 490 and 615 nm. The Co(II) doping into polysilazane leads to the emission from 465 to 415 nm. The emission wavelength shift of Co(III)-containing polysilazane is specific under 340 and 470 nm excitation wavelengths, respectively, while it is not observed with metal-free polysilazane. Thermogravimetric analysis-Differentical thermal analysis (TGA-DTA) profiles also show good thermostability of the PCSN fibers at 800 °C under Ar atmosphere. The use of PCSN offers both enhanced ceramic yields against ~5 wt % starting material and the fluorescence intensity of polymeric fibers.

In-situ X-ray absorption study of ceria-supported Pd-Cu nanoparticles for oxygen-enhanced water gas shift

The detailed structures of bimetallic Pd-Cu on various CeO2 and Al2O3 supports were investigated by X-ray absorption technique in-situ in hydrogen and WGS conditions. No indication of the neighboring Pd atoms in both Pd-K edge and Cu-K edge EXAFS fittings showed that Pd is highly dispersed in the lattice of metallic Cu. The Cu-Cu bond distance was markedly shortened by alloying with Pd and correlated to decrease of coordination number, which reflects particle size. A higher coordination number for Pd-Cu than that for Cu-Cu on Al2O3 support suggested that Pd is in the interior of the nanoparticles on Al2O3 while these coordination numbers were close on CeO2 support indicating a uniform distribution of Pd and Cu atoms. The CO shift activity was not simply correlated to the Cu-Cu bond distance or particle size, but the high activity of Pd-Cu/CeO2 was attributed to surface Pd interacting with Cu on CeO2 surface.

Nickel membranes for in-situ hydrogen separation in high-temperature fluidized bed gasification processes

The Heatpipe Reformer provides an allothermal gasification process for the generation of hydrogen-rich synthesis gas. This synthesis gas can be used for generation of hydrogen for applications like fuel cells, engines, storage or the chemical industries. Conventional processes for hydrogen production involve CO Shift reactors to enhance hydrogen yield followed by hydrogen separation using gas scrubbing technology. The Institute of Energy Process Engineering (FAU-EVT) follows the approach to apply hydrogen permeable membranes as separation step directly in the reformer. This also allows higher hydrogen yields due to an additional shift of the gasification reactions to the product side as one product is continuously removed.This paper gives an overview on membranes in high temperature applications. It focuses on the temperature range from 750 to 900 °C required for biomass gasification processes. Existing approaches to high temperature hydrogen separation like palladium composite membranes or ceramic materials show advantages and disadvantages mainly regarding stability and prices. The presented approach applies commercial nickel capillary tubes as membranes. Vacuum increases the partial pressure difference between permeate and retentate. This remedies the need for a sweep gas, which is needed with all membranes that cannot withstand a physical pressure difference.In the experimental section several commercial nickel capillaries were tested for their hydrogen permeability and the results from a parameter study regarding the influence of synthesis gas components like CO, CH4 and H2O on permeation are shown. The nickel membranes were also tested in hydrogen containing H2S, which can be present in synthesis gas in concentrations of up to 1000 ppm.

Stark Effect and Nonlinear Impedance of the Asymmetric Ag-CO-Ag Junction: An Optical Rectenna

We present first-principles analysis of the Stark effect of CO adsorbed on an atomically sharp silver asperity, and current versus potential (I–V) characteristics of the Ag-CO-Ag junction. The analysis supports the suggestion that CO-bridged plasmonic junctions represent rectifying nanoantennas at optical frequencies and that the CO vibrational spectrum serves as a molecular voltmeter [M. Banik et al. ACS Nano 2012, 6, 10343]. The Stark effect is principally controlled by the field-induced charge redistribution between the antibonding 2π*-orbitals of CO and the s-electrons of Ag. The Stark tuning rate of the CO stretch, 1.5 × 10–6 cm–1/V cm–1, is ∼25% larger on atomically sharp asperities than on flat Ag, and remains constant over a large window of applied fields (±0.8 V/A). As such, both sign and strength of local electric field can be quantitatively determined by the vibrational shift of CO. The I–V curve of the Ag-CO-Ag junction is nonlinear, rendering it an effective rectifier with responsivity S = (∂...

The catalytic properties of K modified PtSn/Al2O3 catalyst for acetic acid hydrogenation to ethanol

Acetic acid hydrogenation catalysts based on platinum and tin supported alumina were modified by adding potassium with different loading amounts and various impregnation sequences. The modification of K caused red shift of CO adsorbed peak, decreased Pt 4d5/2 binding energy and enhanced carbonyl group adsorption, which can promote the selectivity to ethanol. The block effect of K on acid sites was able to restrain side reaction. Further co-impregnation of Pt and Sn to K-doped support led to the poor dispersion of Pt active sites bringing about the low catalytic activity. While catalysts prepared by impregnating PtSn into K-doped alumina were not proper for acetic acid hydrogenation, but adding 0.5wt.%K into PtSn catalyst enhanced both selectivity of ethanol from 37% to 64% and conversion of acetic acid from 88% to 93%. Further increasing potassium loading caused little change on catalytic behavior.

Vibrational spectroscopic, structural and quantum chemical studies on N-phenyl-3-pyridinecarboxamide

Stable molecular structure of N-phenyl-3-pyridinecarboxmide (Nicotinanilide) was predicted through conformational analysis and the vibrational spectral analysis was carried out using experimental and theoretical methods. The calculated and experimentally observed vibrational frequencies of the molecule were assigned and compared. The observed red shift in CO stretching vibrations confirms the mesomeric effects of the CO functional group. The n→π* and π→π* electronic transitions of the molecule were predicted from the theoretically simulated ultraviolet–visible spectra and were validated experimentally. Natural bond orbital analysis was performed to investigate the intra-molecular stabilization interactions, which are responsible for the bioactivity and the nonlinear optical property of the molecule. Molecular reactivity and the possible reactive sites of the molecule were investigated based on the frontier molecular orbitals analysis and Fukui functions respectively. The total electron density mapped with the molecular electrostatic potential surface was plotted to confirm the possible reactive sites of the molecule. The title molecule is identified to be a potential candidate for pharmaceutical applications.

Synthesis of ZrO2- Based Catalyst for Coke Oven Gas CO Shift via an Orthogonal Experiment Design

An orthogonal experiment design was adopted for synthesis and optimization of ZrO2-Based catalyst for coke oven gas CO shift. The influence of the operating parameters on catalytic properties was investigated, with a composition being similar to typical industrial heterogeneous catalysts for WGS process. The experimental CO conversion data was analyzed by marginal and variance analysis. The optimal operating parameters for ZrO2-Al2O3 based catalyst were suggested by CO conversion.

Catalyst development for steam reforming of methane and model biogas at low temperature

Low temperature steam reforming (400–550°C) for the production of hydrogen offers significant advantages compared to the conventional process. The milder operating conditions lead to lower operation costs and cost of construction materials. Additionally, no CO shift reactor is required due to favorable temperature for the WGS reaction. In this work, we report the catalytic performance of Ni and Rh catalysts supported on La2O3–ZrO2 and La2O3–CeO2–ZrO2 for their application in a multifuel membrane reformer operating at low temperature. The performance of the catalysts is assessed in different operating conditions in methane steam reforming (GHSV, temperature, H2O/CH4 ratio) as well as in reforming of model biogas. Stability tests were conducted up to 90h on stream (1bar and 7bar) and the tendency toward carbon formation was investigated. All catalysts were active in the reforming reactions at 400–550°C and the catalysts supported on La2O3–CeO2–ZrO2 showed superiority in activity and stability probably due to the presence of ceria in the support which contributes to the reforming rate and the resistance to carbonaceous deposits. Ni(10)CeZrLa exhibited remarkably stable performance with minimum amount of carbon formed after 90h (ca. 0.05wt%). TPO and TPH analysis of the carbonaceous deposits showed that the dominating type of carbon is highly reactive and can be easily removed by oxidation or hydrogenation at 500°C. This fact makes the catalyst even more promising for the proposed low temperature process, since the catalyst can be hydrogenated by using part of the H2 production stream without further heating of the reactor.

13C NMR substituent-induced chemical shifts in 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-ones (thiones)

In the present, study mostly novel ten 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-ones and ten 4-(substituted phenyl)-3-phenyl-1,2,4-oxadiazol-5(4H)-thiones were synthesized. These oxadiazole derivatives were characterized by IR, 1H NMR, 13C NMR and elemental analyses. Their 13C NMR spectra were measured in Deuterochloroform (CDCl3). The correlation analysis for the substituent-induced chemical shift (SCS) with Hammett substituent constants (σ), Brown Okamoto substituent constants (σ+, σ−), inductive substituent constants (σI) and different of resonance substituent constants (σR, σRo) were performed using SSP (single substituent parameter), DSP (dual substituent parameter) and DSP-NLR (dual substituent parameter-non-linear resonance) methods, as well as single and multiple regression analysis. Negative ρ values were found for all correlations (reverse substituent effect). The results of all statistical analyses, 13C NMR chemical shift of CN, CO and CS carbon of oxadiazole rings have shown satisfactory correlation.

Insights into the Anomalous Vibrational Frequency Shifts of CO2 Adsorbed to Metal Sites in Microporous Frameworks

Diffuse reflectance infrared (IR) spectroscopy was used to study the structure and dynamics of H2 and CO2 adsorbed within the isostructural metal–organic frameworks M2L (M = Mg, Mn, Fe, Co, Zn; L = 2,5-dioxidobenzene-1,4-dicarboxylate) referred to as M-MOF-74 and CPO-27-M. Cluster models of the primary adsorption site were excised from periodic models that were optimized using plane-wave density functional theory at the Perdew–Burke–Ernzerhof (PBE) level. Models incorporating an adsorbed H2 or CO2 were optimized using dispersion-corrected density functional theory (DFT), and the anharmonic vibrational frequencies of the adsorbate were calculated using the discrete variable representation method. The calculated vibrational frequency shifts reveal the same trend among the M2L materials as those observed experimentally and provide insight into the origins of these shifts. Our experimental spectra of adsorbed CO2 confirm a unique blue shift of the ν3 mode for molecules adsorbed in Mg2L, while the frameworks assembled from transition metals induce a red shift. By shifting the focus to the CO2 local vibrational modes, a deeper insight into the influence of “back bonding” (metal d-electron density donation into CO2 π* orbitals) is revealed; for Mg2L there is a near-complete cancellation of the opposing local mode contributions to the observed frequency shift. Additional spectral features in the CO2 ν3 region are assigned to (1) the ν3 mode of the 13CO2 isotopologue, (2) a combination mode involving a ν2 excitation, and (3) librational sidebands arising from center-of-mass motion of the adsorbed molecule on the surface. Interestingly, below 100 K we observe the appearance of a new band that is distinct from the primary ν3 band observed at room temperature. This band is attributed to an alternate, localized orientation of CO2 adsorbed to the metal site, which is supported by the DFT model.

Novel sour water gas shift catalyst (SWGS) for lean steam to gas ratio applications

Dry powder coal gasification is emerging as one of the most energy efficient methods for coal conversion. However, the low steam content, high temperature and high content of CO in the raw syngas make it difficult for a conventional sour water gas shift catalyst to be directly used for syngas conditioning. Conventional sour water gas shift takes place at very high steam to carbon monoxide ratio (H2O/CO), often 2 or above, but the H2O/CO ratio from a dry powder coal gasifier is often less than 0.8. To develop a sour water gas shift catalyst suitable for the lean steam raw syngas, we have prepared a series of MgAl2O4 spinel modified alumina supported CoMoOx catalysts by changing the content of K2O in the promoter, and tested them under lean steam to carbon monoxide (H2O/CO) ratio conditions for sour water gas shift process. Our results show that the addition of potassium into the catalyst increases the catalyst water gas shift activity at a lean steam to gas ratio, and that catalyst activity increases with the K2O content increase in 0–10wt.% range; the potassium additive helps to increase the dispersion of MoO3 and improves catalyst strength and surface area. The increase of K2O content leads to higher catalyst activity for the CO shift reaction with little methane yield, reducing the hot spot formation in the catalyst bed. This may be due to the high K2CO3 content in the catalyst enhancing the surface affinity to steam in the syngas, and the basicity of K2CO3 depresses methane formation over the MoS2 active site. The 10.0wt.% of K2O-containing SWGS catalyst showed the highest stability even in the absence of H2S in the feed gas for up to 90min, and little H2S is released from the catalyst (reverse sulfurization) under such conditions. The optimized K2O-containing SWGS catalyst, e.g., QDB-5-10 has been used in an industrial plant for 2years in a coal to methanol plant and showed stable and unique performance under the lean steam conditions, allowing the 1st stage SWGS reactor to be well within control. The potassium carbonate included in the catalyst is stable and little leachate occurred even after 2-years of use time on stream.

Molecular insights accompanying aggregation in amino acid ionic liquids

Molecular interactions between 1-Ethyl-3-methylimidazolium cation ([Emim]) and hydrophobic amino acids anions (AA) viz., glycine [Gly], alanine [Ala], valine [Val], leucine [Leu], and isoleucine [Ile] have been studied employing the M05–2X based Density Functional Theory (DFT). It has been shown that the emergent hierarchy in the binding energy, viz., [Emim]-[Ile]∼[Emim]-[Leu]>[Emim]-[Val]>[Emim]-[Ala]>[Emim]-[Gly]; is attributable both to the number of hydrogen bonds and to the CH---π interactions. Molecular electrostatic potential (MESP) serves as a tool for building of [Emim]x[AA]y (x, y=1, 2) molecular aggregates. Molecular Electron Density (MED) topographic investigations further revealed an interesting correlation between the electron density at the bond critical point of the hydrogen bond from the acidic proton and the ion-pair binding energies. Normal coordinate-analysis brings forth that the [Emim][AA] ion-pair binding accompanied by the frequency up-shift (blue-shift) of the NH stretching relative to the isolated AA anion; with the largest shift of 54cm−1 occurring for [Emim][Leu]. On the other hand, frequency shifts ranging from 49cm−1 in [Leu] to 34cm−1 in [Ile], in the opposite direction have been noticed for the CO stretching mode. The direction of frequency shifts of characteristic CO, NH and CH vibrations are justified using the ‘Quantum Theory of Atoms in Molecules’ approach in conjunction with Natural-Bond-Orbital analysis. Frontier orbital analysis and hardness parameters together validate the trends in the binding strengths of ion-pairs as well as in aggregates underlying amino acid based ILs.

Effect of Pt cocatalyst in Pt/TiO2 studied by in situ FTIR of CO adsorption

In situ transmission infrared spectroscopy was used to study the role of Pt cocatalyst in Pt/TiO2 using CO as a probe molecule. An 11 cm−1 redshift of CO adsorbed on Pt/TiO2 was observed under irradiation in the absence of changes in the CO coverage or sample temperature. In contrast, no CO shift was detected on Pt/Al2O3. This indicates that the redshift of the CO adsorption peak is due to the photogenerated electron transfer from TiO2 to Pt, and this accounts for the increased photocatalytic activity by the loaded Pt cocatalyst.

Models for B12-conjugated radiopharmaceuticals. Cobaloxime binding to new fac-[Re(CO)3(Me2bipyridine)(amidine)]BF4 complexes having an exposed pyridyl nitrogen.

New mononuclear amidine complexes, fac-[Re(CO)3(Me2bipy)(HNC(CH3)(pyppz))]BF4 [(4,4'-Me2bipy (1), 5,5'-Me2bipy (2), and 6,6'-Me2bipy (3)] (bipy = 2,2'-bipyridine), were synthesized by treating the parent fac-[Re(I)(CO)3(Me2bipy)(CH3CN)]BF4 complex with the C2-symmetrical amine 1-(4-pyridyl)piperazine (pyppzH). The axial amidine ligand has an exposed, highly basic pyridyl nitrogen. The reaction of complexes 1-3 with a B12 model, (py)Co(DH)2Cl (DH = monoanion of dimethylglyoxime), in CH2Cl2 yielded the respective dinuclear complexes, namely, fac-[Re(CO)3(Me2bipy)(μ-(HNC(CH3)(pyppz)))Co(DH)2Cl]BF4 [(4,4'-Me2bipy (4), 5,5'-Me2bipy (5), and 6,6'-Me2bipy (6)]. (1)H NMR spectroscopic analysis of all compounds and single-crystal X-ray crystallographic data for 2, 3, 5, and 6 established that the amidine had only the E configuration in both the solid and solution states and that the pyridyl group is bound to Co in 4-6. Comparison of the NMR spectra of 1-3 with spectra of 4-6 reveals an unusually large "wrong-way" upfield shift for the pyridyl H2/6 signal for 4-6. The wrong-way H2/6 shift of (4-Xpy)Co(DH)2Cl (4-Xpy = 4-substituted pyridine) complexes increased with increasing basicity of the 4-Xpy derivative, a finding attributed to the influence of the magnetic anisotropy of the cobalt center on the shifts of the (1)H NMR signals of the pyridyl protons closest to Co. Our method of employing a coordinate bond for conjugating the fac-[Re(I)(CO)3] core to a vitamin B12 model could be extended to natural B12 derivatives. Because B12 compounds are known to accumulate in cancer cells, such an approach is a very attractive method for the development of (99m)Tc and (186/188)Re radiopharmaceuticals for targeted tumor imaging and therapy.

Effects of non-local exchange on core level shifts for gas-phase and adsorbed molecules.

Density functional theory calculations are often used to interpret experimental shifts in core level binding energies. Calculations based on gradient-corrected (GC) exchange-correlation functionals are known to reproduce measured core level shifts (CLS) of isolated molecules and metal surfaces with reasonable accuracy. In the present study, we discuss a series of examples where the shifts calculated within a GC-functional significantly deviate from the experimental values, namely the CLS of C 1s in ethyl trifluoroacetate, Pd 3d in PdO and the O 1s shift for CO adsorbed on PdO(101). The deviations are traced to effects of the electronic self-interaction error with GC-functionals and substantially better agreements between calculated and measured CLS are obtained when a fraction of exact exchange is used in the exchange-correlation functional.

A reduced dimensionality NMR pulse sequence and an efficient protocol for unambiguous assignment in intrinsically disordered proteins.

Resonance assignment in intrinsically disordered proteins poses a great challenge because of poor chemical shift dispersion in most of the nuclei that are commonly monitored. Reduced dimensionality (RD) experiments where more than one nuclei are co-evolved simultaneously along one of the time axes of a multi-dimensional NMR experiment help to resolve this problem partially, and one can conceive of different combinations of nuclei for co-evolution depending upon the magnetization transfer pathways and the desired information content in the spectrum. Here, we present a RD experiment, (4,3)D-hNCOCAnH, which uses a combination of CO and CA chemical shifts along one of the axes of the 3-dimensional spectrum, to improve spectral dispersion on one hand, and provide information on four backbone atoms of every residue-HN, N, CA and CO chemical shifts-from a single experiment, on the other. The experiment provides multiple unidirectional sequential (i → i - 1) amide (1)H correlations along different planes of the spectrum enabling easy assignment of most nuclei along the protein backbone. Occasional ambiguities that may arise due to degeneracy of amide proton chemical shifts are proposed to be resolved using the HNN experiment described previously (Panchal et al. in J Biomol NMR 20:135-147, 2001). Applications of the experiment and the assignment protocol have been demonstrated using intrinsically disordered α-synuclein (140 aa) protein.

Optically Induced Indirect Photonic Transitions in a Slow Light Photonic Crystal Waveguide

We demonstrate indirect photonic transitions in a silicon slow light photonic crystal waveguide. The transitions are driven by an optically generated refractive index front that moves along the waveguide and interacts with a signal pulse copropagating in the structure. We experimentally confirm a theoretical model which indicates that the ratio of the frequency and wave vector shifts associated with the indirect photonic transition is identical to the propagation velocity of the refractive index front. The physical origin of the transitions achieved here is fundamentally different than in previously proposed refractive index modulation concepts with fixed temporal and spatial modulation frequencies; as here, the interaction with the refractive index front results in a Doppler-like signal frequency and wave vector shift. Consequently, the bandwidth over which perfect mode frequency and wave vector matching is achieved is not intrinsically limited by the shape of the photonic bands, and tuning of the indirect photonic transitions is possible without any need for geometrical modifications of the structure. Our device is genuinely nonreciprocal, as it provides different frequency shifts for co- and counterpropagating signal and index fronts.