Addition Of Alkaline Earth Metals Research Articles

Efficient delivery of anticancer 5-fluorouracil drug by alkaline earth metal functionalized porphyrin-like porous fullerenes: A DFT study

Finding and developing effective targeted drug delivery systems has emerged as an attractive approach for treating a wide range of diseases. In the present study, the potential of alkaline earth metal functionalized porphyrin-like porous C24N24 fullerenes for delivering 5-fluorouracil (5FU) anticancer drug is assessed using density functional theory calculations. The goal is to evaluate how the addition of alkaline earth metals to C24N24 enhances the adsorption capabilities of this system towards 5FU drug. The adsorption energies and charge transfers are determined in order to evaluate the strength of the interaction between the 5FU and fullerene surfaces. According to the results, adding alkaline earth metals increases the drug's adsorption energy on the C24N24 fullerene. In all cases, the drug molecule interacts with the metal atom through its CO group. Furthermore, the adsorption strength of the 5FU increases with metal atom size (Ca > Mg > Be), which is connected to the polarizability of these atoms. The adsorption energies of 5FU are shown to be highly sensitive on solvent effects and the acidity of the environment. The adsorption strength of 5FU decreases within the solvent (water), allowing it to be released more easily. The moderate adsorption energies and short desorption times of 5FU imply that it is reversibly adsorbed on the functionalized fullerenes.

Effects of Alkaline Earth Metal Additives on Methylammonium‐Free Lead Halide Perovskite Thin Films and Solar Cells

Organic–inorganic lead halide perovskite solar cells are regarded as one of the most promising technologies for the next generation of photovoltaics due to their high power conversion efficiency (PCE) and simple solution manufacturing. Among the different compositions, the formamidinium lead iodide (FAPbI3) photoactive phase has a bandgap of 1.4 eV, which enables the corresponding higher PCEs according to the Shockley–Queisser limit. However, the photoactive crystal phase of FAPbI3 is not stable at room temperature. The most high‐performing compositions to date have reduced this problem by incorporating the methylammonium (MA) cation into the FAPbI3 composition, although MA has poor stability at high temperatures and in humid environments, which can limit the lifetime of FAxMA1−xPbI3 films. CsxFA1−xPbI3 perovskites are also explored, but despite better stability they still lag in performance. Herein, the additive engineering of MA‐free organic−inorganic lead halide perovskites using divalent cations Sr2+ and Ca2+to enhance the performances of CsxFA1−xPbI3 perovskite compositions is explored. It is revealed that the addition of up to 0.5% of Sr2+ and Ca2+ leads to improvements in morphology and reduction in microstrain. The structural improvements observed correlate with improved solar cell performances at low additive concentrations.

A review on recent advances in dry reforming of methane over Ni- and Co-based nanocatalysts

The recent environmental-related issues such as climate change and global warming have sparked scientists' interest in finding a way to reduce the emission of greenhouse gases through dry reforming of CH4. As a result of this reaction, not only H2 is produced, but also CO2 and CH4 are reduced. Catalysts are needed due to the enhancement of the kinetics of the reaction. Non-noble metals like Ni, Co, etc., have shown promising activity, they are readily available, and have low cost; consequently, they have been widely employed for the reaction. In this paper, the recent advances in the development of the Ni- and Co-based nanocatalysts for DRM reaction, including the use of different supports and promoters, the addition of alkaline earth metals, and new structures like mesoporous silica and dendritic fibrous nano silica as supports were reviewed.

Effect of 6 Wt.% Particle (B4C + SiC) Reinforcement on Mechanical Properties of AA6061 Aluminum Hybrid MMC

Aluminum based hybrid metal matrix composite with more than two particle reinforcement is very much popular for heavy duty application, and the proportion of these particle reinforcement can be controlled to achieve desired mechanical properties (strength and wear resistance). AA 6061 alloys popularly used in aircraft and automobile applications, tends to have inferior tribological property and therefore particle reinforcements are being made to strengthen the matrix. The prime objective of this investigation is to study the effect of varying wt.% of proportionate individual reinforcement (SiC and B4C) on the mechanical properties of a particular composition (6 wt.%) of AA 6061 hybrid composite. The present investigation is done to evaluate the dependance of hard particle reinforcements on the strength and elongation behaviour of hybrid composite. Hardness measurement and uniaxial loading techniques were used to characterize the mechanical properties of the as-cast hybrid composites, whereas OM, XRD and SEM analysis was done to study the distribution of reinforcement within the base (AA 6061) metal matrix phase. The improvement in mechanical properties, such as Vickers hardness, UTS, yield strength and elongation were presented and explained using various hypothesis proposed by previous studies. The role of clustering theory and effect of binary eutectic Mg2Si phase found to be key the enhanced mechanical properties of the hybrid composites. Addition of Alkaline Earth Metal (Mg) during the synthesis process have led to an increase in the elongation of hybrid composite with the increase in wt.% of reinforcement which is analogous to the effect of alkali metals (‘Na’ and ‘Li’) addition that helps in refining the Mg2Si Eutectic phase.

Development of an Online LC‐MS/MS Method for the Investigation of Enzyme Kinetics Using Trypsinization of Apomyoglobin Protein as a Model System

The optimization of enzymatic protein cleavage by trypsin is often performed “in the dark” wherein researchers perform the reaction under different conditions on a laboratory bench for a single or a small selection of time points. Upon quenching of the trypsinization reaction with a strong acid, the resulting protein reaction mixture is injected onto a liquid chromatography column for profiling of the peptide mixture. The arbitrary selection of enzyme reaction time presents a major limitation to this experimental approach. Herein, we present a “real time” optimization of the enzymatic reaction enabled by performing the reaction within a vial in an autosampler with regular sampling of the mixture. Using this method, we are able to simultaneously monitor degradation of the intact protein target and the release of its tryptic peptides. Peptides with missed cleavage sites may appear and then disappear with time as fully tryptic peptides dominate the endpoint of the reaction. The method can be multiplexed in that we can sample many parallel mixtures in series. This allows us to directly compare such variables as pH, solvent, ionic strength, protein to enzyme ratio, enzyme concentration and metal salts on digestion efficiency while always including a positive control for reference. Our liquid chromatograph-tandem mass spectrometry analysis platform uses a Dionex Ultimate 3000 interfaced with a hybrid quadrupole-Orbitrap (Q-Exactive) mass spectrometer capable of mass resolution of 140,000 and a mass accuracy better than 10 ppm. We are able to monitor the efficiency and kinetics of tryptic digestion of apomyoglobin with high resolution in the time dimension. At room temperature, the enzymatic reaction can take in excess of 12 hours to reach completion compared with about 3 hours at 38oC. A low percentage of ethanol (~ 0.1%) added to the reaction mixture was shown to double the yield of most peptides while the addition of alkaline earth metals also had beneficial effects, in particular 10 mM barium chloride. Other metals were shown to either inhibit the degradation of apomyoglobin (zinc) or to prevent the detection of the resulting peptides (lead). Overall, the effects of adding barium in the presence of 0.1% ethanol improved peptide yield as much as 11-fold for the LFTGHPETLEK peptide of apomyoglobin while showing no effect on the tryptic release of the YLEFISDAIIHVLHSK peptide. This method offers a promising strategy for the optimization of targeted protein quantitation as well as a means to study the kinetics and characterize the specificity of other proteolytic enzymes.

Improved photocatalytic performance of nanostructured SnO2 via addition of alkaline earth metals (Ba2+, Ca2+ and Mg2+) under visible light irradiation

Pure and alkaline earth metal (Ba2+, Ca2+ and Mg2+)-doped tin oxide nanoparticles were synthesized by simple co-precipitation, and their structural, optical, functional, morphological and compositional properties were analyzed in detail using powder X-ray diffraction, UV–visible spectroscopy, photoluminescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and energy-dispersive analysis of X-ray (EDAX). XRD revealed the formation of rutile tetragonal structure, and the crystallite size has decreased from 28 to 24 nm by the addition of alkaline metal dopants. FTIR spectra confirmed the presence of fundamental vibration modes of SnO2. The optical band gap energy was decreased to 3.05, 3.19 and 2.98 eV by introducing Ba2+, Ca2+ and Mg2+ ions, respectively. Photoluminescence spectra showed defect-related emission peaks, and their intensities were found to increase in doped SnO2 samples. EDAX spectra confirmed the presence of Sn, O, Ba, Ca and Mg elements. The photocatalytic activity of pure and alkaline metal-doped SnO2 catalyst has been investigated under visible light irradiation by using methylene blue dye. The results showed that the Mg-doped SnO2 catalyst has a higher photodegradation efficiency (~ 95.7%) compared with other investigated samples.

Catalytic reactions of coke with dioxygen and steam over alkaline-earth-metal-doped cerium-zirconium mixed oxides

A series of cerium-zirconium mixed oxides doped with alkaline earth metals was prepared by calcining a mixture of Ce0.8Zr0.2O2 and the nitrate salt of alkaline earth metals at 1173K. The results from X-ray diffraction, Raman spectroscopy and analytical electron microscopy indicated the alkaline earth compounds were dispersed on the surface of Ce0.8Zr0.2O2. The doped mixed oxides were evaluated in the catalytic reaction of solid coke under tight contact conditions with 10 vol.% O2 in He at 693K and with 100vol.% H2O at 993K using thermogravimetric analysis. For coke oxidation with O2, the weight loss was first order in coke, and the measured first order rate constant was proportional to the total surface area of catalyst at low catalyst loadings. For coke gasification with H2O, the weight loss was nearly zero order in coke, and the measured areal reaction rate was independent of the total surface area of catalyst at low catalyst loadings. The addition of alkaline earth metals inhibited coke oxidation with dioxygen but promoted coke gasification with steam.

Fischer–Tropsch synthesis on cobalt catalysts with alkaline earth metal additives

The promotion supported cobalt catalysts for the synthesis of hydrocarbons from CO and H2 with the alkaline earth metals Mg, Ca, and Ba was studied. The introduction of a promoter leads to an increase in selectivity for target higher hydrocarbons, a decrease in methane formation, and an increase in the olefin content of the products. The magnitude of these effects correlates with the electron-donor properties of a promoter, and it increases in the order Mg < Ca < Ba. At the same time, the index of hydrocarbon chain growth of the synthesized alkanes decreases in this case.

Selective aromatization of biomass derived diisobutylene to p-xylene over supported non-noble metal catalysts

To obtain the valuable p-xylene from biomass with a high selectivity, several transition non-noble metals as main components of catalysts for aromatization of diisobutylene were explored. A volcano curve with the top marked by Cr(3d54s1) could be found between the activity and the atomic outer-shell electrons number of transition metals. The further addition of alkaline earth metal showed that the modification of surface properties by Mg doping could improve the catalytic performance. With Cr–Mg–Al–O as catalysts, the enhanced selectivity and single pass yield for the p-xylene formation could be obtained. Meanwhile, the side reaction of cracking could be suppressed, which might be attributed to the increment of the weak/strong acid ratio by Mg addition. Moreover, the catalysts kept a stable catalytic performance in the regeneration and reuse cycles.

Hydrogen production by steam reforming of ethanol over Ni–X/Al2O3–ZrO2 (X = Mg, Ca, Sr, and Ba) xerogel catalysts: Effect of alkaline earth metal addition

A series of alkaline earth metal-promoted nickel catalysts supported on Al2O3–ZrO2 (Ni–X/AZ, X=Mg, Ca, Sr, and Ba) were prepared by an epoxide-driven sol-gel method and a subsequent co-impregnation method. For comparison and reference, promoter-free Ni/Al2O3–ZrO2 catalyst (Ni/AZ) was also prepared by an epoxide-driven sol-gel method and a subsequent impregnation method. The effect of alkaline earth metal addition on the physicochemical properties and catalytic activities of Ni–X/Al2O3–ZrO2 catalysts in the steam reforming of ethanol was investigated. The catalysts were characterized by nitrogen adsorption-desorption, ICP-AES, XRD, TPR, TEM, H2-TPD, NH3-TPD, and EtOH-TPD analyses. It was revealed that addition of alkaline earth metal promoters reduced acidity of the catalysts and positively influenced catalytic activity in the steam reforming of ethanol. Hydrogen yield increased with the introduction of promoter, which was attributed to enhanced nickel dispersion. Nickel surface area and ethanol adsorption capacity of the catalysts were well correlated with hydrogen yield. Hydrogen yield increased with increasing nickel surface area and with increasing ethanol adsorption capacity of the catalysts. Among the catalysts tested, Ni–Sr/AZ catalyst showed the most promising result. It was concluded that addition of alkaline earth metal promoters increased nickel surface area by acting as a spacer, leading to higher ethanol adsorption capacity and hydrogen yield.

Thermodynamic effects of alkaline earth metals on homogenous mercury oxidation during calcium carbonate (CaCO3) and coal combustion

ABSTRACTIn this study, the relationship between mercury (Hg) oxidation and alkaline earth metals, particularly the transformation of alkaline earth metals in a flue gas atmosphere, was investigated. The thermodynamic stability of the alkaline earth metals during the process of coal combustion and corresponding interactions among the alkaline earth metals and S-species and Cl-species were calculated and analyzed using chemical thermodynamics software HSC Chemistry. Data demonstrated that the main Ca products in the high (1600 K) and low (800 K) temperature states were calcium sulfate (CaSO4) and calcium chloride (CaCl2), respectively. As HCl consumption continued (800–400 K) as a result of addition of calcium carbonate (CaCO3), oxidation of Hg was suppressed. Based on previous studies, an Hg/C/H/N/O/S/Cl/Ca chemical and phase equilibrium model was designed using the chemical kinetics simulation software CHEMKIN Pro in order to further elucidate the influence of CaCO3 on oxidation of Hg during the coal combustion process. Data indicated that, as CaCO3 levels increased, equilibrium temperature fell, further supporting the thermodynamic calculation results. Thus, findings suggested that oxidation of Hg in post-combustion gases might be blocked by addition of alkaline earth metals.

Effect of polymers and alkaline earth metals on the catalytic performance of Ni–B amorphous alloy in benzophenone hydrogenation

Abstract Soluble polymers are found to be effective in inhibiting the agglomeration of the active Ni particles in Ni–B amorphous alloy catalysts and then increase the catalysts activity in benzophenone hydrogenation. However, the acidic nature of polyethylene glycol 1000 will cause the dehydration of benzhydrol and decrease its yield. Here, we found that the addition of alkaline earth metals can tune the acid–base properties of the catalysts and overcome this shortcoming. Ba and polyethylene glycol 1000 doped Ni–B was found to exhibit excellent activity and selectivity to benzhydrol due to its larger surface areas, more surface active Ni species, and better acidic properties.

Additive effects of alkaline-earth metals and nickel on the performance of Co/γ-Al 2O 3 in methane catalytic partial oxidation

Abstract Nano-sized γ-alumina (γ-Al 2O 3) was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline-earth metal promoters or nickel (Ni) with different contents were loaded on the γ-Al 2O 3 support. The catalysts were characterized by N 2 adsorption-desorption, X-ray diffraction (XRD) and thermogravimetry analysis (TGA). The activity and selectivity of the catalysts in catalytic partial oxidation (CPO) of methane have been compared with Co/γ-Al 2O 3, and it is found that the catalytic activity, selectivity, and stability are enhanced by the addition of alkaline-earth metals and nickel. The optimal loadings of strontium (Sr) and Ni were 6 and 4 wt%, respectively. This finding will be helpful in designing the trimetallic Co-Ni-Sr/γ-Al 2O 3 catalysts with high performance in CPO of methane.

Influence of Alkaline Earth Metals on Cobalt-Cerium Composite Oxide Catalysts for N&lt;sub&gt;2&lt;/sub&gt;O Decomposition

Catalysts of cobalt-cerium composite oxide doped with series of alkaline earth metals were prepared using the citrate method. Results of catalytic activity tests showed that the addition of alkaline earth metals enhanced the efficiency of N2O decomposition according to the following order: Mg <Ca <Sr,Ba. Characterization of these catalysts was done using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurement, X-ray photoelectron spectroscopy (XPS), oxygen temperature-programmed desorption (O-2-TPD) and hydrogen temperature-programmed reduction (H2-TPR). Results indicated that the addition of alkaline earth metals did not change the crystal structures and specific surface areas of catalysts, but did enhance the electron donation ability of the active site (Co2+). The surface reaction of N2O with Co2+ involved electron donation from Co2+ to the anti-bonding orbital of N2O that resulted in the release of N-2. The desorption of residual oxygen leads to the regeneration of the active site (Co2+) through the donation of electrons back to Co2+. We conclude that the addition of alkaline earth metals promotes surface reactions of N2O with Co2+ by facilitating electron donation from the active site. This process is the rate-determining step for pure cobalt-cerium composite oxide catalysts and the catalytic activity for the decomposition of N2O is thus improved.

Hydrogen Production from Steam Reforming of Hydrocarbons over Alkaline-Earth Metal-Modified Fe- or Ni-Based Catalysts

The steam reforming of isooctane and methylcyclohexane (MCH) was investigated over Fe- and Ni-based catalysts. FeMg/Al2O3 catalyst, effective for CH4 decomposition in the presence of O2/CO2, was active for steam reforming of isooctane, being a little easier to cause C−C bond cleavage than MCH, but the rate of hydrogen production was insufficient, although the rate was only slightly improved by Rh modification, due to raised formation of CH4 and C2. FeMg/Al2O3 catalyst was also less active for the steam reforming of MCH than Ni systems. Modification of FeMg/Al2O3 catalyst with rhodium resulted in the increased formation of aromatic byproducts. The rate of H2 production with Ni/ZrO2 catalyst was found to be 7 times higher than that with FeMg/Al2O3. Furthermore, the stability of the Ni/ZrO2 catalyst was found to be improved by the addition of alkaline-earth metals into the catalyst (M/Ni = 1:2 wt ratio). In particular, the addition of Sr was the most effective and the activity of NiSr/ZrO2 catalyst for the reaction at 973 K remained stable after 100 hours, although below 10% decrease in the rate of H2 formation was observed. On the contrary, above 50% decrease in the rate was observed over Ni/ZrO2 catalyst, after 100 hours. This Sr effect, possibly, could be associated with the formation of mixed oxides consisting of Sr and Zr (or Ni). The NiSr/ZrO2 catalyst was also effective for the steam reforming of model gasoline, which contained organic mixtures with different reforming reactivities such as naphthenes, aromatics, and n- and iso-paraffins.

Tin-Containing Catalysts, Modified with Alkaline Earth Metals in the Oxidative Dimerization of Methane

The effect of addition alkaline earth metals on the physico-chemical properties of M-Sn-O/α-Al2O3 and M-Pb-Sn-O/α-Al2O3 catalysts is studied. The formation of metal metastannates in the M-Sn-O/α-Al2O3 system facilitated the growth of selectivity of the catalysts. Addition of alkaline earth metals into the Pb-Sn-O/α-Al2O3 composition resulted in stabilization of lead in the 4-valent state with formation of metal ortho-plumbates and a decrease in the selectivity for C2 hydrocarbons. The linkage between the basicity of the surface and the catalytic properties of the samples was established.

Crown-containing spironaphthoxazines and spiropyrans. 3. Synthesis and investigation of the merocyanine form of crown-containing spirobenzothiazolinonaphthoxazine

A method for the synthesis of the spirobenzothiazolinonaphthoxazine, stable in the merocyanine form and containing a crown-ether fragment was developed. The complexing properties of the prepared merocyanine compound and the spectroscopic and photochromic characteristics of its complexes with alkaline earth metal cations were studied by NMR and UV spectroscopy. The results were analyzed using quantum-chemical calculations. The addition of alkaline earth metal perchlorates to a solution of a crown ether-containing merocyanine dye in MeCN results in the coordination of metal cations to two binding centers, namely, the crown-ether fragment and the merocyanine oxygen atom. This gives rise to two types of complexes, which differ substantially in their structurally. The complexation induces changes in the UV spectra and influences on the photochromic behavior of the prepared compound.

Factors affecting the dissolution and reduction of oxygen in molten carbonate electrolytes. Part II: Effect of SrCO 3, BaCO 3 and SnO 2 additives

The effect of minority SrCO 3, BaCO 3, and SnO 2 additions to various alkali carbonate electrolytes has been investigated for both oxygen reduction kinetics and also oxide ion activity. Although alkaline earth metal additives were found to assimilate into the melt with relative ease, metal oxides of higher valency were found to be fairly insoluble. In general, addition of earth metal carbonates to the electrolyte provides a means of increasing the effective oxygen solubility. The nature of the improvement appears to vary with the additive used, the amount added, and the original electrolyte composition. In all cases there was a significant increase in background current. In view of surface energy considerations, this is most probably due to increased carbon dioxide diffusion and meniscus effects. In addition to the increase in oxygen dissolution, there appears to be a concurrent increase in the oxide ion activity.

Selective reduction of nitrogen monoxide by propene over cerium-doped zeolites

Our recent study on the catalytic reduction of NO x by propene in the presence of excess oxygen (but in the absence of water vapor) over rare earth-doped zeolites was reviewed and compared with the results for other related catalysts. Of the rare earth-doped zeolites Ce-ZSM-5 was the most active. The high activity of Ce-ZSM-5 was attributed to its high selectivity (high efficiency of the utilization of propene for the reduction of NO and moderate oxidation activity). The addition of alkaline earth metals to Ce-ZSM-5 enhanced the activity considerably and brought about a good performance even at a very high space velocity. The overall reaction was divided into three steps. NO is oxidized to NO 2 in the first step where Ce accelerates the reaction. Then, in the next step NO 2 rapidly reacts with propene to form organic nitro-compounds. In the last step, these intermediates decompose to N 2 in the presence of NO x or O 2, where Ce also functions.

ChemInform Abstract: Catalytic Reduction of Nitrogen Monoxide by Propene in the Presence of Oxygen Over Cerium Ion‐Exchanged Zeolites. Part 1. General Characteristics of the Reaction and Effects of Alkaline Earth Metal Addition.

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