Effect Of Alkali Metal Ions Research Articles

Monovalent ion-graphene oxide interactions are controlled by carboxylic acid groups: Sum frequency generation spectroscopy studies.

Graphene oxide (GO) is a two-dimensional, mechanically strong, and chemically tunable material for separations. Elucidating GO-ion-water interactions at the molecular scale is highly important for predictive understanding of separation systems. However, direct observations of the nanometer region by GO surfaces under operando conditions are not trivial. Therefore, thin films of GO at the air/water interface can be used as model systems. With this approach, we study the effects of alkali metal ions on water organization near graphene oxide films at the air/water interface using vibrational sum frequency generation (SFG) spectroscopy. We also use an arachidic acid Langmuir monolayer as a benchmark for a pure carboxylic acid surface. Theoretical modeling of the concentration-dependent sum frequency signal from graphene oxide and arachidic acid surfaces reveals that the adsorption of monovalent ions is mainly controlled by the carboxylic acid groups on graphene oxide. An in-depth analysis of sum frequency spectra reveals at least three distinct water populations with different hydrogen bonding strengths. The origin of each population can be identified from concentration dependent variations of their SFG signal. Interestingly, an interfacial water structure seemed mostly insensitive to the character of the alkali cation, in contrast to similar studies conducted at the silica/water interface. However, we observed an ion-specific effect with lithium, whose strong hydration prevented direct interactions with the graphene oxide film.

Structural Characterization of the Metalized Radical Cations of Adenosine ([Ade+Li-H]•+ and [Ade+Na-H]•+) by Infrared Multiphoton Dissociation Spectroscopy and Theoretical Studies.

Nucleoside radicals are key intermediates in the process of DNA damage, and alkali metal ions are a common group of ions in living organisms. However, so far, there has been a significant lack of research on the structural effects of alkali metal ions on nucleoside free radicals. In this study, we report a new method for generating metalized nucleoside radical cations in the gas phase. The radical cations [Ade+M-H]•+ (M = Li, Na) are generated by the 280 nm ultraviolet photodissociation (UVPD) of the precursor ions of lithiated and sodiated ions of 2-iodoadenine in a Fourier transform ion cyclotron resonance (FT ICR) cell. Further infrared multiphoton dissociation (IRMPD) spectra of both radical cations were recorded in the region of 2750-3750 cm-1. By combining these results with theoretical calculations, the most stable isomers of both radicals can be identified, which share the common characteristics of triple coordination patterns of the metal ions. For both radical species, the lowest-energy isomers undergo hydrogen transfer. Although the sugar ring in the most stable isomer of [Ade+Li-H]•+ is in a (South, syn) conformation similar to that of [Ado+Na]+, [Ade+Na-H]•+ is distinguished by the unexpected opening of the sugar ring. Their theoretical spectra are in good agreement with experimental spectra. However, due to the flexibility of the structures and the complexity of their potential energy surfaces, the hydrogen transfer pathways still need to be further studied. Considering that the free radicals formed directly after C-I cleavage have some similar spectral characteristics, the existence of these corresponding isomers cannot be ruled out. The findings imply that the structures of nucleoside radicals may be significantly influenced by the attached alkali metal ions. More detailed experiments and theoretical calculations are still crucial.

Location of Carbonate Ions in Metal-Doped Carbonated Hydroxylapatites

The environment model for the description of the location of carbonate ions in apatites predicts that approximately half of the carbonate occupies the apatite channel. This model relies on the influence of entities surrounding the carbonate on its IR spectrum and can be used to determine how various substituents affect the location and structure of that ion. Careful deconvolution (peak-fitting) of the asymmetric carbonate IR region was used to determine the percentage of A-type (channel) ions, A′-type (channel with either a Ca2+ vacancy or substitution of Na+ for Ca2+) ions, and B-type (substitution for phosphate) ions. In our previous applications of this model, we have looked at the effect of alkali metal ions, such as sodium, lithium, and potassium, the ammonium ion, and the rare earth europium ion. In the present work, we explore the incorporation of the first-row transition metal ions and find that they have little effect on the location of the carbonate ion. Like the un-substituted carbonated apatite, these apatites contain about half of the carbonate in the channel, at least in derivatives that contain up to half a mole of the metal ion per mole of apatite. Attempts to incorporate greater amounts of metal ions by aqueous ion-combination reactions generally lead to lower-resolution XRD patterns and IR spectra that produce greater uncertainties in the peak-fitting modeling.

Alkali metal ion-mediated ice nucleation

Understanding the effects of ion specificities on ice nucleation is essential for atmospheric science and biology. Although valence and concentration changes of ions can regulate ice nucleation, it is unclear if alkali metal ions of different species with the same valence can regulate ice nucleation. This study investigated the behavior of ice nucleation on alkali metal ion-modified surfaces with atomic-scale roughness and (sub)nanometer thickness to decouple the effect of alkali metal ions on ice nucleation. The results showed that modulating the type of alkali metal ion could regulate ice nucleation. Additionally, it was found that different hydration shells of alkali metal ions may influence the structure of interfacial water and the thermodynamic phase transition to play a key role in regulating ice nucleation. This study shed light on a long-standing problem of the mechanism of alkali metal ions in ice nucleation and provided a strategy for effectively regulating ice nucleation .

Effects of potassium ions and platinum cocatalysts on the photocatalytic performance of Poly(Heptazine Imides)

In the synthesis of highly crystalline carbon nitride, alkali metal halides are used as high-temperature solvents and structural guiding agents, but the effect of alkali metal ions on the catalytic activity of materials is still unclear. In addition, the shape and size of the cocatalyst also significantly affect the catalytic activity of the material. Therefore, we have carried out the density functional theory calculations to reveal the differences in the structure, electronic, and optical properties, as well as the photocatalytic hydrogen evolution performance of one kind of crystalline carbon nitride called potassium poly(heptazine imide) (K-PHI) and its proton-exchanged counterpart (H-PHI) loaded with different sizes of platinum cocatalysts. The results show that potassium ions have the effect of aggregation electrons in K-PHI, and potassium ions have short-range induced dipole effect on nearby Pt atoms, resulting in slightly better photocatalytic hydrogen evolution activity at these reaction sites. Additionally, Pt cocatalyst with larger load size has better photocatalytic hydrogen evolution activity than small size. This work provides a theoretical basis for the rational design of high-performance metal cocatalysts and exploration of the functionality of alkali metal ions in carbon nitrides.

Effect of alkali metal ions A+ (A = K+, Na+ and Li+) on the photoluminescence properties of Sr3Bi(PO4)3:Sm3+ phosphors prepared by wet chemical synthesis

A series of Sr3Bi(PO4)3:Sm3+ phosphors co-doped with alkali metal A+ (A = K+, Na+ and Li+) ions were synthesized using a wet chemical technique. XRD, morphological, and photoluminescence characteristics were all measured and investigated in detail. The XRD results confirm that Sr3Bi(PO4)3 has a cubic phase and is in the space group I −4 3 d. (220). Under 403 nm excitation, the Sr3Bi(PO4)3:Sm3+ phosphor showed maximum emission at 598 nm. The emission bands were at 562 nm, 598 nm, and 643 nm when stimulated at 403 nm. The optimal Sm3+ ions doping concentration in the Sr3Bi(PO4)3 host matrix is determined to be 0.5 mol %. Furthermore, A+ (A = K+, Na+ and Li+) as the charge compensation co-doped with Sr3Bi(PO4)3:Sm3+ phosphors increases emission intensity, and Sr3Bi(PO4)3:Sm3+, K+ phosphors shows the maximum emission intensity. According to the CIE coordinates of the Sr3Bi(PO4)3:Sm3+, K+ phosphors were (x = 0.617, y = 0.381). The results show that Sr3Bi(PO4)3:Sm3+, K+ phosphors may have been used in w-LEDs.

Highly dispersed Pt clusters within ZSM-5 stabilized by alkali metal ions and Al sites for partial methane oxidation

Zeolite is an ideal material to encapsulate nanoparticles and avoid metal aggregation, but it is challenging to achieve a high degree of metal dispersion inside zeolite. In this work, the Na+ reagent was introduced to synthesize Pt@S-1 and Pt@ZSM-5 to explore the effect of Al sites and alkali metal ions on dispersion of Pt nanoparticles. The properties of four catalysts were characterized by XRD, TEM, CO-TPR, TG and FT-IR, and the effects of alkali metal ions were analyzed combined with POM test results. The introduction of a certain amount of alkali metal ions in Pt@ZSM-5 catalyst consumed part of the hydroxyl group to form stable Pt-Ox(OH)yNa active species, which further improves the stability and dispersity of platinum nanoparticles and promotes the activity of partial oxidation of methane. This stabilization strategy can be extended to other porous materials encapsulating metal nanoparticles.

Boosting high-rate Zn-ion storage capability of α-MnO2 through Tri-ion co-intercalation

Aqueous rechargeable zinc-ion batteries (ARZIBs) have become a research hotspot in recent years because of their high energy density, low cost, rich zinc resources, and high safety. However, defects in the electrochemical performance of cathode materials become a stumbling block for the practical application of ARZIBs. The α-MnO2 cathode material is attracted attention due to its high theoretical capacity and scalable industrial manufacturing, but inherently low electron conduction and poor ion mobility affect transport kinetics, resulting in low capacity and rate capabilities. Here, for the first time, a new α-MnO2 cathode is prepared with co-intercalation of K+, Co2+ and Al3+ through a one-step solution co-precipitation strategy. Taking advantage of the synergistic effect of alkali metal ions and transition metal ions, modified α-MnO2 shows superior high-rate performance (a capacity of 100 mAh g−1 after 800 cycles at 5.0 A g−1) and stable crystal structure. This result is attributed to the enlarged tunnel structure brought about by multi-ion intercalation, which promotes the rapid migration of Zn2+ and improves the transport kinetics. On the basis of the new design of tri-ion co-intercalation, it is hoped that this research will provide theoretical guidance for the preparation of high-capacity Mn-based cathode active materials for ARZIBs.

Effect of alkali metal ions on water structure: insights into the pressure-like effect

Effect of alkali metal ions on water structure: insights into the pressure-like effect

Mechanistic insight into the effects of alkali metal ions on the formation of NOx precursors during the pyrolysis of 2,5-diketopiperazine

The inherent metal ions in food wastes have significant influences on the production of NOx precursors to affect the release of NOx during the incineration process. However, the detailed catalytic mechanism of metal ions remains unclear. Herein, 2,5-diketopiperazine (DKP) was employed as the N-containing model to study the effects of Na+ and K+ on the production of NOx precursors in the pyrolysis process. Based on density functional theory calculations and wave function analyses, all the energy barriers of the initial reactions decrease with the catalysis of Na+, whereas K+ can only promote part of the reactions and with weaker effects than Na+. Because of the varied influence on distinct reactions, Na+/K+ can change the rate-determining steps of the production pathways of NOx precursors. As for the same pathway, Na+ usually results in a relatively lower energy barrier than K+. Elevated temperatures lead to higher rate constants of K+ than Na+ for the favorable production pathways of NOx precursors. With the catalysis of Na+ and K+, the formation of NH3 is always more competitive than HCN and HNCO based on the comparison of overall energy barriers and the rate constants. Particularly, the competitiveness for NH3 production is enhanced by the catalysis of Na+ and K+ according to the increased rate constant advantage over other pathways.

Artificial Water Channels—Progress Innovations and Prospects

Artificial Water Channels—Progress Innovations and Prospects

The effects of alkali metal ions on the physiochemical and catalytic properties of Pd/NiAlOx catalysts for lean methane oxidation

Self-assembled nickel-aluminum mixed oxides (NiAlOx) were prepared by using alkali metal ions as modifiers in a hydrothermal system and employed as the support materials for palladium catalysts. Via tuning the preparation procedure, both the ‘bonded’ and ‘deposited’ alkali metal ions were introduced to the NiAlOx materials for elucidating their effects on the physiochemical and the catalytic properties of Pd/NiAlOx catalysts for lean methane oxidation. Benefiting from the well-dispersed palladium nanoparticles, optimized electronic state of palladium phases, and the favorable structure of host materials, the optimal Pd/NiAl-Na sample exhibited excellent catalytic performance for methane oxidation. Over this sample, complete methane conversion was realized at 401 °C in the presence of 15 vol % water vapor, which was 26 °C lower than that of the Pd/NiAl catalyst (427 °C) at same reaction conditions. Due to the relatively small size of Li+ ions, certain amounts of Li+ incorporated into the NiAlOx lattice and improved the redox properties of NiAl-Li. However, its supported palladium catalysts did not show improved performance in the oxidation of methane. Furthermore, systematic characterizations revealed that the ‘deposited’ alkali metal ions resulted in the agglomeration of palladium nanoparticles and the formation of electron-deficient palladium component, thus exerting negative effect on the activities of palladium phases. It was hoped that this work could provide some fundamental understandings on the roles of alkali metal played in catalytic reaction.

Quantum chemical investigation of the effect of alkali metal ions on the dynamic structure of water in aqueous solutions.

We report quantum chemical molecular dynamics (MD) simulations based on the density-functional tight-binding (DFTB) method to investigate the effect of K+, Na+, and Mg2+ ions in aqueous solutions on the static and dynamic structure of bulk water at room temperature and with various concentrations. The DFTB/MD simulations were validated for the description of ion solvation in aqueous ionic solutions by comparing static pair distribution functions (PDFs) as well as the cation solvation shell between experimental and available ab initio DFT data. The effect of the cations on the water structure, as well as relative differences between K+, Na+, and Mg2+ cations, were analyzed in terms of atomically resolved PDFs as well as time-dependent Van Hove correlation functions (VHFs). The investigation of the VHFs reveals that salt ions generally slow down the dynamic decay of the pair correlations in the water solvation sphere, irrespective of the cation size or charge. The analysis of partial metal–oxygen VHFs indicates that there are long-lived correlations between water and Na+ over long distances, in contrast to K+ and Mg2+.

Effect of Alkali Metal Ions A+ (a = K+, Na+ and Li+) on the Wet Chemical Synthesis and Photoluminescence Properties of Sr3bi(Po4)3:Sm3+ Phosphors

Effect of Alkali Metal Ions A+ (a = K+, Na+ and Li+) on the Wet Chemical Synthesis and Photoluminescence Properties of Sr3bi(Po4)3:Sm3+ Phosphors

Spectroscopic, Thermal, Microbiological, and Antioxidant Study of Alkali Metal 2-Hydroxyphenylacetates.

The structural, spectral, thermal, and biological properties of hydroxyphenylacetic acid and lithium, sodium, potassium, rubidium, and cesium 2-hydroxyphenylacetates were analyzed by means of infrared spectroscopy FT-IR, electronic absorption spectroscopy UV-VIS, nuclear magnetic resonance 1H and 13C NMR, thermogravimetric analysis (TG/DSC), and quantum-chemical calculations at B3LYP/6-311++G** level. Moreover, the antioxidant (ABTS, FRAP, and CUPRAC assays), antibacterial (against E. coli, K. aerogenes, P. fluorescens, and B. subtilis) and antifungal (against C. albicans) properties of studied compounds were measured. The effect of alkali metal ions on the structure, thermal, and biological properties of 2-hydroxyphenylacetates was discussed.

Charge compensation effects of alkali metal ions M+ (Li+, Na+, K+) on luminescence enhancement in red-emitting Ca3Si2O7:Eu3+ phosphors

Red-emitting Ca3Si2O7:Eu3+ and Ca3Si2O7:Eu3+, M+ (M = Li, Na, K) phosphors were prepared via a solid-state reaction. The effects of Eu3+ doping concentration and alkali metal ions M+ co-doping on the structure and luminescence performance of Ca3Si2O7:Eu3+ were investigated. X-ray diffraction patterns demonstrated that the Ca3Si2O7:Eu3+ phase synthesized at 1400 °C was consistent with the standard Ca3Si2O7 structure. Characteristic emission peaks of Ca3Si2O7:Eu3+ phosphors were revealed at 593 nm and 617 nm under excitation at 394 nm, which relate to the 4f electron transitions of Eu3+ ions. After co-doping M+ as a charge compensator, the luminescence intensity of red-emitting Ca3Si2O7:Eu3+, M+ phosphors were significantly improved by 2.62-, 1.80-, and 2.92-fold for Li+, Na+, K+ co-doping, as well as the luminescence lifetime compared with that of Eu3+-doped Ca3Si2O7. Moreover, actual LEDs with excellent chromaticity parameters were manufactured via coating the as-prepared phosphor onto a 395 nm n-UV chip. All results indicate that the Ca3Si2O7:Eu3+, M+ red-emitting phosphor has an excellent potential application as a red component in white light-emitting diodes.

Tuning the surface and optical properties of graphitic carbon nitride by incorporation of alkali metals (Na, K, Cs and Rb): Effect on photocatalytic removal of organic pollutants

Alkali metals have been known for their intercalation properties and can be employed for the separation of stacking in sheet-like materials. In this work, alkali metals (Na, K, Rb and Cs) have been systematically incorporated in varying concentrations in g-C3N4 sheets and their effect on resulting optical, surface and photocatalytic properties have been explored in detail. It was observed that the optical, electronic and surface properties of g-C3N4 were altered upon the incorporation of different alkali metal ions. The band gap and specific surface area of resulting materials were decreased as compared to the pristine g-C3N4. In addition, the alkali metal incorporation in g-C3N4 sheets showed the formation of cyanide groups and nitrogen vacancies in the resulted materials. Further, the photocatalytic activity of g-C3N4 and alkali metal incorporated g-C3N4 was calculated by studying the degradation of acid red 94 dye under visible light irradiation. It was observed that the photocatalytic activity of pristine g-C3N4 sheets was decreased with an increase in the concentration of alkali salt used during the synthesis of alkali metal incorporated g-C3N4. This decrease in the activity could arise due to the decreased surface area, detrimental amount of nitrogen vacancies and high concentration of alkali metal ions incorporated in the structural framework of g-C3N4 sheets. This work provides a unique example of the adverse effect of alkali metal ions on photocatalytic activity of g-C3N4 and paves future directions for the improvement of the performance of g-C3N4 based materials.

Effect of alkali metal ions on the formation mechanism of HCN during pyridine pyrolysis

The catalytic effects of alkali metal ions (Na+ and K+) on NOx precursor formation during coal pyrolysis were investigated using the N-containing compound pyridine as a model compound. Density functional theory calculations at the B3LYP/6-31G (d, p) level of theory were conducted to elucidate the mechanism of pyridine pyrolysis and the pathways for HCN formation. The calculation results indicate that Na+ and K+ have distinct influences on different pyrolysis reactions; these alkali metal ions facilitate the initial hydrogen transfer from C1 to N and C2, whereas they hinder the other hydrogen migration reactions. Both Na+ and K+ significantly reduce the activation energies for C–C bond breakage and triple-bond formation, whereas they increase the activation energies for the isomerization reactions. The different effects essentially result from the distinct charge distributions induced by the two ions. Due to the distinct influences on the different reactions, the rate-determining steps are modulated, affecting the competitiveness of the different possible pathways of HCN formation. The formation of HCN from pyridine is promoted in the presence of Na+ and K+ because all the overall activation energies are decreased for different pathways. The calculation results agree well with previous experimental studies. Thus, the findings offer a new and promising approach to reveal the formation mechanism of NOx and facilitate the control of NOx for coal utilization.

New effect of alkali metal ions on the orientation of cortical microtubule in Spirogyra cell

New effect of alkali metal ions on the orientation of cortical microtubule in Spirogyra cell

Various Effects of Alkali Metal Ions on H2O2 Reduction Reactions at Pt Electrodes

The hydrogen peroxide reduction reaction (HPRR) has attracted much attention because it is involved in the oxygen reduction reaction which is an important cathode reaction in several fuel cell systems. Pt has an excellent electrocatalytic activity toward the HPRR. Thus, the HPRR at Pt electrodes has been widely studied including effects of electrolyte components and additives on it.Katsounaros and Mayrhofer have reported that alkali metal cations such as Li+, Na+, and K+ inhibit the HPRR in basic media [1]. The hydrated alkali metal cations and chemisorbed OH species on Pt, denoted as M+(H2O) x and OHads respectively, non-covalently stabilize each other, leading to the formation of quasi-specifically adsorbed hydrated metal ion clusters that blocks electrochemical reactions. The inhibition becomes stronger as the strength of the non-covalent interaction increases (K+ < Na+ < Li+), and consequently the rest potential decreases in this order, as reproduced in Figure 1a.We have recently found that the HPRR in strongly acidic media is also affected by the alkali metal ions. As shown in Figure 1b, the HPRR is inhibited at U < 0.7 V in the presence of the ions. This indicates that the alkali metal ions inhibit the transport of electroactive species, namely, H+ and H2O2, toward the electrode surface. The HPRR current becomes smaller (in absolute value) in the following order: Li+ < Na+ < K+, that is, the inhibition becomes stronger in the reverse order of the strength of the non-covalent interaction. In this work, to explain this inhibition, we study the HPRR by electrochemical impedance method.Interestingly, the metal ions induce a significance increase in the local pH at the electrode surface (pHs) during the HPRR when the concentration of H2O2 is relatively high, that is, when the HPRR consumes a large amount of H+ [2]. For instance, the pHs becomes strongly basic when 0.01 M H2SO4 + 0.05 M H2O2 + 0.05 M M2SO4 (where M stands for Li, Na, and K) is used as the electrolyte solution. We thus think that the non-covalent interaction can be induced during the HPRR even in the acidic media. Note that the pHs remains acidic in the case of Figure 1b because of the lower concentration of H2O2. In this work, we summarize the above-mentioned effects of the alkali metal ions on the HPRR. REFERENCES [1] I. Katsounaros and K. J. J. Mayrhofer, Chem. Commun., 48, 6660-6662 (2012).[2] Y. Mukouyama, H. Kawasaki, D. Hara, Y. Yamada, S. Nakanishi, J. Electrochem. Soc., 164 (2017) H675. FIGURE CAPTION Figure 1. The current (I) – potential (E) curves for a Pt-plate electrode in basic and acidic solutions measured under potential controlled conditions at a scan rate of 0.01 Vs-1. The basic solutions are 0.05 M alkali hydroxide (denoted as MOH) + 0.01 M H2O2, and the acidic ones are 0.05 M H2SO4 + 0.01 M H2O2 with or without 0.05 M alkali sulfate (denoted as M2SO4). Figure 1