MODIFICATION OF TRANSITION METAL CATIONS TO POLYMER-STABILIZED PLATINUM COLLOIDAL CLUSTERS IN ENANTIOSELECTIVE HYDROGENATION OF METHYL PYRUVATE

Modification of transition metal cations to polymer-stabilized Pt colloidal clusters modified with cinchonidine was studied in enantioselective hydrogenation of methyl pyruvate.Compared to the enantiomeric excess(e.e.)value(71.4%) obtained without the presence of metal cations,obvious e.e.enhancement(up to 82.5%)was resulted from the addition of Zn^(2+) but with a certain decrease in activity.The reaction parameters in the presence of Zn^(2+) were also studied.It was found that the Pt colloidal catalysts in the presence of metal cations performed very differently from that in the absence of metal cations.

ADSORPTION MECHANISM OF SOME BIVALENT HEAVY METAL CATIONS IN SOLUTIONS USING MONTMORILLONITE

The frontier orbital energies of montmorillonite molecule and[Me(H_(2)O)_(6)]^(2+)(Me=Cu^(2+),Zn^(2+),Co^(2+)and Ni^(2+))were calculated by INDO method.Results showed that the chemical interaction between montmorillonite molecule and[Cu(H_(2)O)_(6)]^(2+)or[Zn(H_(2)O)_(6)]^(2+)was possible.The experimental results of powder X-ray diffraction and isothermal adsorption supported the above-mentioned calculation results.

Theoretical Studies on the Interaction between Metal Cations and Cytosine, Guanine

The interaction of tetra- and hexa-coordinated compounds of cytosine(C) and guanine(G) with metal cations Ca(2+), Mg(2+), Mn(2+), Ni(2+), Cu(2+), and Zn(2+) have been calculated by using the B3LYP/6-31G method at the 6-31G(d, p) basis set, while the remaining coordination bonds are saturated by water molecules ((H(2)O)(4)). All geometries were optimized without symmetry restrictions. Comparing the interaction energies we obtained the orders of selectivity of C and G for the above metal ions as follows: (a)Cu(2+)>(a)Ni(2+)>(a)Mg(2+)>(a)Mg(2+)>(b)Cu(2+)>(a)Mn(2+)>(b)Zn(2+)> Ni(2+) and (a)Cu(2+)>(a)Ni(2+> a)Zn(2+)>(a)Mg(2+)>(b)Cu(2+)>(a)Mn(2+)>(b)Zn(2+)>(b)Ni(2+) respectively ((a,b) represent tetra- and hexa-coordinated, respectively), which are in good agreement with the experimental facts. Interaction energies of complexes provide a comparatively reliable quantification of the selectivity of dimethyl phosphate anion for the studied metal ions. In addition, the influence of coordination number and coordination structure on the interaction energy and the variation of ionic energy were discussed sufficiently. After analyzing the interaction energies of two kinds of complexes, the 'mutual selectivity'as well as the nature of the interaction between metal ions and ligands was revealed.

Insight into the Effect of Metal Cations in the Electrolyte on Performance for Electrocatalytic CO_(2)Reduction Reaction

This highlight indicates that the local electrostatic interactions between metal cations and key intermediates facilitate the electrocatalytic CO_(2) reduction reaction.Electrocatalytic CO_(2) reduction reaction(CO_(2)RR)has been considered as a promising strategy to achieve a carbon-neutral cycle and produce valuable fuels and feedstocks.

Effects of metal cations on sorption-desorption of p-nitrophenol onto wheat ash

The mutual effects of metal cations （Cu2＋, Pb2＋, Zn2＋, and Cd2＋） and p-nitrophenol （NP） on their adsorption desorption behavior onto wheat ash were studied. Results suggested that Cu2＋, Pb2＋, and Zn2＋ diminished the adsorption and increased the desorption of NP remarkably, while Cd2＋ had no such effect. In contrast, NP diminished the adsorption of Cu2＋, Pb2＋, and Zn2＋ onto ash, however, this suppression effect depended on the initial concentrations of metal cations. NP had no effect on Cd〉 adsorption on ash. Fourier transform infrared （FT-IR） and X-ray absorption spectroscopic （XAS） studies suggested the following mechanisms responsible for the metal suppression effect on NP adsorption： （1） large hydrated Cu2＋, Pb2＋, and Zn〉 shells occupied the surface of ash and prevent nonspecific adsorption of NP onto ash surface; （2） Cu2＋, Pb2＋, and Zn2＋ may block the micropores of ash, resulting in decreased adsorption of NP; （3） cornplexation of Cu2＋, Pb2＋, and Zn2＋ was likely via carboxyl, hydroxylic and phenolic groups of wheat ash and these same groups may also react with NP during adsorption. As a ＂soft acid＂, Cd2＋ is less efficient in the complexation of oxygencontaining acid groups than Cu2＋, Pb2＋, and Zn2＋. Thus, Cd2＋ had no effect on the adsorption of NP on wheat ash.

Study of the Complexation Behavior of Calixarene with Transition Metal Cations by UV-vis and Fluorescent Spectra

A new fluorescent compound based on calixarene skeleton was synthesized. Its complexation ability with transition metal ions, such as Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ and Ag +, was investigated by UV vis and fluorescent spectra.

Effect of Metal Cations on Corrosion Behavior and Surface Structure of Carbon Steel in Chloride Ion Atmosphere

In order to better understand why the corrosion behavior of carbon steel exposed in Nansha atmospheric environment is very serious, the effect of sodium, potassium and magnesium chlorides deposited on carbon steel surface has been studied under atmosphere conditions by wet/dry accelerated test. The difference of corrosion behavior and surface structure in Na+, K+, and Mg2+ containing atmosphere has been investigated by thickness loss, scanning electron microscope, X-ray diffraction and electrochemical techniques. The results indicate that the thickness loss of carbon steel exposed in different metal cations containing atmospheric environment increases in the order of Na+, K+, Mg2+. The hard metal cation can promote the dissolution of the steel to a certain extent. In Mg2+ containing atmosphere, the relative content of β-FeOOH is rather higher and the protective ability index α */γ * decreases in the order of Na+, K+, Mg2+. The corrosion current density of both bare carbon steel and the rusted carbon steel increases in the order of Na+, K+, Mg2+. The polarization resistance and the charge transfer resistance decreases in the order of Na+, K+, Mg2+.

Influence of Metal Cations and Cholesterol on Lipid-amphotericin Membrane

Amphotericin B（AmB） has been widely used in antifungal therapy. AraB molecules combine with cholesterol to form pores that can be toxic to human cells, thus greatly limiting its clinical application. The interaction between Arab and the cell membrane may be influenced by potassimn, sodium and calcium ions. Lq this study, the bilayer in large unilamellar lipid-drug liposomes with or without cholesterol was employed as a model membrane. N-（7-Nitrobenz-2-oxa-1,3-diazol-4-yl）-1,2-dipalmitoyl-sn-glycero-3-phosphoetheanolamine（N-BD-PE） and 1-palmi-toyl-2-[6（7-nitrobenz-2-oxa-1,3-diazol-4-yl）aminodoclecanoyl]-sn-glysero-3-phosphocholine（6-NBD-PC） are two kinds of fluorescent lipid probes, and the NBD group is attached to the polar lipid headgroup in the former, but to the sn-2 fatty acyl chain in the latter. The effect of these metal cations on the lipid-drug membrane was monitored by red edge excitation shift（REES）, fluorescence polarization, and the fluorescence lifetime of lipid probes in hydrophilic and hydrophobic areas of the membrane. These ions have different effects on the lipid-AraB membrane. Cholesterol can strengthen the packing ability of the membrane, which is influenced differently by potassium, sodium and calcium ions. Moreover, the influence of these ions on the membrane may be relative to the method of ion transportation through the membrane. This study is significant to understand the reduction of AraB＇s cellular toxicity.

Third-Order Nonlinear Optical Responses of Bis(15-crown-5)-stilbenes Binding to One-or Two-Alkali Metal Cation(Li^(+),Na^(+)and K^(+))

Bis(15-crown-5)-stilbenes containing crown ether parts have been widely used in a variety of chemical applications,such as cation detectors,because of their ability to selectively bind to alkali metal cations,Bis(15-crown-5)-stilbenes and its derivatives with complexation of one-or two-alkali metal cation(Li^(+),Na^(+)and K^(+))have been theoretically investigat-ed by quantum chemistry methods.The coordination of alkali cations results in partial shrinkage of crown ethers,which directly affected natural distribution analysis charges and molecular orbital energy levels.The number of alkali metal ions has significant effects on absorption spectra and mean second hyperpolarizability.When one alkali metal ion was added to the anticonformer of bis(15-crown-5)-stilbene,the absorption spectra were obvious-ly redshifted and the mean second hyperpolarizability values were slightly increased;while two alkali metal ions were added to bis(15-crown-5)-stilbene,the absorption spectra were ob-viously blue shifted and the mean second hyperpolarizability values decreased.On the other hand,as the radius of the alkali ions increased,the mean second hyperpolarizability values of the compounds increased gradually.It is indicated that the mean second hyperpolarizability value is sensitive to the number and radius of the alkali metal cations,thus the third order nonlinear optical response can be used as a signal to detect the number and type of alkali met-al ions.

Effect of co-doped metal caions on the properties of Y_2O_3:Eu^(3+) phosphors synthesized by gel-combustion method

Y2O3：Eu3＋ phosphors co-doped with different metal cations （Li＋, Na＋, K＋, Mg2＋, Ca2＋） are prepared by the gel- combustion method with Y2O3：Eu3＋, and R（NO3）x （R = Li, Na, K, Mg, Ca） serving as raw materials and glycine as fuel, calcined at 1000 ℃ for 2 h. The synthesized Y203 ：Eu3＋ phosphors doped with different metal cations and doping ratios are characterized by x-ray diffractometry （XRD）, fluorescence and phosphorescent spectrophotometer. The co-doping metal cations are advantageous to the development of Y203：Eu3＋ lattice. All the samples can emit red light peaked at 611 nm under 254-nm excited. The luminescence intensities of co-doping samples are increased because the cations increase the electron transition probability of Eu3＋ from 5D0 level to 7F level. The fluorescence lifetime of Eu3＋ （SD0 --＋7F2） is increased by doping metal cations.

Alkali metal cation doping of metal-organic framework for enhancing carbon dioxide adsorption capacity

Metal-organic frameworks （MOFs） have attracted much attention as adsorbents for the separation of CO2 from flue gas or natural gas. Here, a typical metal-organic framework HKUST-I（also named Cu-BTC or MOF-199） was chemically reduced by doping it with alkali metals （Li, Na and K） and they were further used to investigate their CO2 adsorption capacities. The structural information, surface chemistry and thermal behavior of the prepared adsorbent samples were characterized by X-ray powder diffraction （XRD）, thermo-gravimetric analysis （TGA） and nitrogen adsorption-desorption isotherm analysis. The results showed that the CO2 storage capacity of HKUST-1 doped with moderate quantities of Li＋, Na＋ and K＋, individually, was greater than that of unmodified HKUST-1. The highest CO2 adsorption uptake of 8.64 mmol/g was obtained with 1K-HKUST-1, and it was ca. 11% increase in adsorption capacity at 298 K and 18 bar as compared with HKUST- 1. Moreover, adsorption tests showed that HKUST-1 and 1K-HKUST-1 displayed much higher adsorption capacities of CO2 than those of N2. Finally, the adsorption/desorption cycle experiment revealed that the adsorption performance of 1K-HKUST-1 was fairly stable, without obvious deterioration in the adsorption capacity of CO2 after 10 cycles.

New Approach to Synthesis of Silica with Chemically Bound Guanidine Hydrochloride for Preconcentration of Metal Ions

Guanidine hydrochloride was chemically bonded to surface of modified silica by means of condensation with grafted amino groups. Ion-exchanging and complexing properties of the obtained adsorbent have been studied with respect to cations of Zn(II), Cu(II), Pb(II), Cd(II), Co(II) and metal-containing oxoanions of W(VI), Mo(VI), Cr(VI), V(V). Optimum conditions for quantitative extraction of the studied ions were determined. The structure and composition of Co(II) and Cu(II) complexes on the surface of the synthesized adsorbent have been investigated. The possibility of quantitative determination of cobalt(II) and copper(II) trace amounts after their preconcentration by the synthesized adsorbent was demonstrated.

Releasing characteristics of phosphorus and other substances during thermal treatment of excess sludge

The releasing characteristics of phosphorus, nitrogen compounds, organics, and some metal cations during thermal treatment of excess sludge were investigated. It was found that during heating not only phosphorus, but also nitrogen compounds, organics, and some metal cations could be released in abundance. The maximum orthophosphate （ortho-P） release of about 90 mg/L in concentration was observed at 50℃ in 1 h. Except for volatile fatty acids （VFAs）, comparatively little total nitrogen （TN）, total organic carbon （TOC）, and metal cations were released at the same time. Such results might favor further process of phosphorus recovery. VFAs were considerably released only at 50℃. Acetic, butyric, and propionic acid were the most abundant components in turn and their releasing profiles exhibited good linear relationship with time （R2 = 0.9977, 0.9624, and 0.8908, respectively）. The concentrations of Mg^2＋ and K^＋ increased with time and temperature during thermal treatment, but Ca^2＋ decreased. The release of Mg^2＋ and K^＋ agreed well with TP release （R^2 = 0.9892 and 0.9476, respectively）. Temperature in the experimental range had very little impact on the linear relationships, especially of Mg^2＋. Moreover, the parameter of mixed liquor suspended solids （MLSS） was found to be an important factor for thermal sludge treatment as the released ortho-P and total phosphorus （TP） at 50℃ increased more than one-fold when MLSS was increased from 4000 to 8000 mg/L.

Theoretical Study on the Dehydrogenation Reaction of H_2S by VS^+ (~3Σ^-)

The dehydrogenation reaction of H2S by the ^3Σ^- ground state of VS^＋： VS^＋ ＋ H2S → VS2^＋ ＋ H2 has been studied by using Density Functional Theory （DPT） at the B3LYP/DZVP level. It is found that the reaction proceeds along two possible pathways （A and B） yielding two isomer dehydrogenation products VS2^＋-1 （^3B2） and VS2^＋-2 （^3A1）, respectively. For both pathways, the reaction has a two-step-reaction mechanism that involves the migration of two hydrogen atoms from S2 to V^＋, respectively. The migration of the second hydrogen via TS3 and that of the first via TS4 are the rate-determining steps for pathways A and B, respectively. The activation energy is 17.4 kcal/mol for pathway A and 22.8 kcal/mol for pathway B relative to the reactants. The calculated reaction heat of 9.9 kcal/mol indicates the endothermicity of pathway A and that of -11.9 kcal/mol suggests the exothermicity of pathway B.

Nanoscale resistive switching devices for memory and computing applications

With the slowing down of the Moore’s law and fundamental limitations due to the von-Neumann bottleneck,continued improvements in computing hardware performance become increasingly more challenging.Resistive switching(RS)devices are being extensively studied as promising candidates for next generation memory and computing applications due to their fast switching speed,excellent endurance and retention,and scaling and three-dimensional(3D)stacking capability.In particular,RS devices offer the potential to natively emulate the functions and structures of synapses and neurons,allowing them to efficiently implement neural networks(NNs)and other in-memory computing systems for data intensive applications such as machine learning tasks.In this review,we will examine the mechanisms of RS effects and discuss recent progresses in the application of RS devices for memory,deep learning accelerator,and more faithful brain-inspired computing tasks.Challenges and possible solutions at the device,algorithm,and system levels will also be discussed.

Studies on basicity of alkali metal catron exchanged β and X zeolites by pyrrole-IR spectroscopy

The strength of basic sites has been measured by pyrrole-IR on alkali metal cation exchanged β and X zeolites, as well as NaOH loaded Naβ. The influence of cation type and the structure of zeolites on their basicity has been studied. The acidic and basic properties of the samples were investigated by NH3-TPD and isopropanol reaction. It was shown that the strength of basic sites on samples could be characterized by the shift of vNH band in the pyrrole-IR spectra. The framework oxygen charges were calculated from the Sanderson electronegativity. The changes in basic properties with various alkali metal cation are consistent with the changes of local oxygen charges of the zeolite framework.

Electrifying the future:the advances and opportunities of electrocatalytic carbon dioxide reduction in acid

Transforming carbon dioxide(CO_(2))into products using renewable electricity is a crucial and captivating quest for a green and circular economy.Compared with commonly used alkali electrolytes,acidic media for electrocatalytic CO_(2) reduction(CO_(2)RR)boasts several advantages,such as high carbon utilization efficiency,high overall energy utilization rate,and low carbonate formation,making it a compelling choice for industrial applications.However,the acidic CO_(2)RR also struggles with formidable hurdles,encompassing the fierce competition with the hydrogen evolution reaction,the low CO_(2) solubility and availability,and the suboptimal performance of catalysts.This review provides a comprehensive overview of the CO_(2)RR in acidic media.By elucidating the underlying regulatory mechanism,we gain valuable insights into the fundamental principles governing the acidic CO_(2)RR.Furthermore,we examine cutting-edge strategies aimed at optimizing its performance and the roles of reactor engineering,especially membrane electrode assembly reactors,in facilitating scalable and carbon efficient conversion.Moreover,we present a forward-looking perspective,highlighting the promising prospects of acidic CO_(2)RR research in ushering us towards a carbon-neutral society.

Highly compact and uniform CH3NH3Sn0.5Pb0.5I3 films for efficient panchromatic planar perovskite solar cells

An efficient panchromatic planar perovskite solar cell is developed based on highly uniform,lead-reduced CH3NH3Sn0.5Pb0.5I3 perovskite films with full film-coverage on the substrates.We demonstrate here that full-coverage of the CH3NH3Sn0.5Pb0.5I3 films can be developed by a facile chlorobenzene-assisted spin-coating method.A power conversion efficiency of 7 % is achieved using low-temperature processes,which is among the best-reported performance for panchromatic planar perovskite solar cells with a light-absorption over 1,000 nm.

Synthesis of Mesoporous Lanthanum Phosphate and Its Use as a Novel Sorbent

Mesoporous lanthanum phosphate was synthesized by supramolecular self-assembly of cetyltrimethylammonium bromide and lanthanum nitrate following digestion in phosphoric acid. TGA-DTA, XRD and SEM were employed to study the uncalcined and calcined materials. Sorption behavior of Cr（Ⅲ）, Mn（Ⅱ）, Fe（Ⅲ）, Co（Ⅱ）, Ni（Ⅱ）, Cu（Ⅱ）, Zn（Ⅱ）, Cd（Ⅱ）, Ba（Ⅱ）, Hg（Ⅱ） and Pb（Ⅱ） cations was studied on such materials in water, 3 mol·L^-1 ammonia, 0.01 mol·L^-1 potassium ferrocyanide and 0.01 mol·L^-1 potassium ferricyanide solutions.

Influence of K＋, Na＋ or Ca2＋ Ions on the Interaction Between AmB and Saturated Phospholipids by Langmuir Technique

Interaction between amphotericin B（AmB） and cell membrane is influenced by different metal cations. In the presence of K＋, Na＋ or Ca2＋ ions, the surface pressure-area isotherms and the elastic modulus of an amphotericindipalmitoylphosphatidylcholine（AmB-DPPC） mixed monolayer were discussed. And the excess free energy and entropies of mixing were calculated according to the surface pressure-area isotherms. The phase transition of the mixed monolayer needed a higher concentration of AmB in the sequence Na ＋〉pure buffer〉K＋〉Ca2＋. When the molar fraction of AmB（XAmB） was 0.5, the molecular interaction changed from attraction to repulsion and the mixed monolayer turned to ordered state from disorder state under the induction of K＋ or Ca2＋ ions at all surface pressure in our experiment. At high surface pressure, the disorder of monolayer enhanced in the presence of Na＋ ions at XAmB〉0.1. At different molar ratios of AraB, the influences of these metal cations were discrepant. These cations may influence Arab molecules to form pores on the monolayer. It is helpful to understand the reduction of AmB＇s toxicity as theoretical reference.