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The performance optimization of photoluminescent (PL) materials is a hot topic in the field of applied materials research. There are many different crystal defects in photoluminescent materials, which can have a significant impact on their optical properties. The luminescent properties and chemical stability of materials can be effectively improved by adjusting lattice defects in crystals. We systematically studied the effect of doping ions on the energy transfer upconversion mechanism in different defect crystals by changing the matrix alkali metal ions. Meanwhile, the influence mechanism of crystal defect distribution on luminescence performance is explored by adjusting the ratio of Na–Li. The PL spectra indicate that changing the alkaline ions significantly affects the luminescence performance and efficiency of UCNPs. The change in ion radius leads to substitution or gap changes in the main lattice, which may alter the symmetry and strength of the crystal field around doped RE ions, thereby altering the UCL performance. Additionally, we demonstrated the imaging capabilities of the synthesized upconversion nanoparticles (UCNPs) in cellular environments using fluorescence microscopy. The results revealed that Na0.9Li0.1LuF4–Yb, Er nanoparticles exhibited significantly enhanced fluorescence intensity in cell imaging compared to other compositions. We further investigated the mechanism by which structural defects formed by doping ions in UCNPs with different alkali metals affect energy transfer upconversion (ETU). This work emphasizes the importance of defect regulation in the ETU mechanism to improve the limitations of crystal structure on the luminescence performance and promote the future application of upconversion nanomaterials, which will provide important theoretical references for the exploration of high-performance luminescent materials in the future. [ABSTRACT FROM AUTHOR]

The performance optimization of photoluminescent (PL) materials is a hot topic in the field of applied materials research. There are many different crystal defects in photoluminescent materials, which can have a significant impact on their optical properties. The luminescent properties and chemical stability of materials can be effectively improved by adjusting lattice defects in crystals. We systematically studied the effect of doping ions on the energy transfer upconversion mechanism in different defect crystals by changing the matrix alkali metal ions. Meanwhile, the influence mechanism of crystal defect distribution on luminescence performance is explored by adjusting the ratio of Na–Li. The PL spectra indicate that changing the alkaline ions significantly affects the luminescence performance and efficiency of UCNPs. The change in ion radius leads to substitution or gap changes in the main lattice, which may alter the symmetry and strength of the crystal field around doped RE ions, thereby altering the UCL performance. Additionally, we demonstrated the imaging capabilities of the synthesized upconversion nanoparticles (UCNPs) in cellular environments using fluorescence microscopy. The results revealed that Na0.9Li0.1LuF4–Yb, Er nanoparticles exhibited significantly enhanced fluorescence intensity in cell imaging compared to other compositions. We further investigated the mechanism by which structural defects formed by doping ions in UCNPs with different alkali metals affect energy transfer upconversion (ETU). This work emphasizes the importance of defect regulation in the ETU mechanism to improve the limitations of crystal structure on the luminescence performance and promote the future application of upconversion nanomaterials, which will provide important theoretical references for the exploration of high-performance luminescent materials in the future.

The luminescence and scintillation properties of Ce3+ doped alkali phosphate glasses 56P 2 O 5 :8Gd 2 O 3 :5Al 2 O 3 :1CeBr 3 :30XCl (PGAC:X, X = Li/Na/K/Rb/Cs) were studied for their potential applications in gamma and alpha detection. In the Fourier Transform Infrared Spectroscopy (FTIR), X-ray Luminescence (XRL), Photoluminescence (PL), and transmittance spectra, the red shift was found and explained by the concept of optical basicity. Broad Ce3+ emission and energy transfer from Gd3+ to Ce3+ were observed in XRL and PL measurements. Scintillation performance was studied by irradiating the samples under 137Cs gamma and 241Am alpha sources. The fast, intermediate, and slow decay components under gamma and alpha excitation were found around 30, 200 and 3000 ns, respectively. The decay time increased slightly from PGAC:Li to PGAC:Cs, indicating the less effective transition from Gd3+ to Ce3+. The alpha decay time was longer than the gamma decay time, revealing the Pulse Shape Discrimination (PSD) capability of the glasses for particle identification. The XRL intensity reduced significantly from PGAC:Li to PGAC:Cs samples did not reflect the scintillation tendency. By successfully detecting gamma and alpha scintillation signals, the scintillation performance of all samples was found to be similar. In general, all samples can be used for gamma and alpha detection. Using Rb+ or Cs+ ions is favorable in terms of high density and light yield, while Li+ ions enhance the transmittance and homogeneity. Furthermore, a correlation between P–O–H groups within the glass matrix and scintillation performance was also observed. [ABSTRACT FROM AUTHOR]

The mineral raw Egyptian kaolinite was used as a precursor in the synthesis of two sodalite phases (sodium sodalite (Na.SD) and potassium sodalite (K.SD)) according to the low alkali fusion technique. The synthesized Na.SD phase demonstrates enhanced total basicity (6.3 mmol OH/g), surface area (232.4 m2/g), and ion exchange capacity (126.4 meq/100 g) compared to the K.SD phase (217.6 m2/g (surface area), 96.8 meq/100 g (ion exchange capacity), 5.4 mmol OH/g (total basicity). The catalytic performance of the two sodalite phases validates the higher activity of the sodium phase (Na.SD) than the potassium phase (K.SD). The application of Na.SD resulted in biodiesel yields of 97.3% and 96.4% after 90 min and 60 min, respectively, while the maximum yield using K.SD (95.7%) was detected after 75 min. Robust base-catalyzed reactions using Na.SD and K.SD as catalysts were suggested as part of an operated transesterification mechanism. Moreover, these reactions exhibit pseudo-first order kinetics, and the rate constant values were estimated with consideration of the change in temperature. The estimated activation energies of Na.SD (27.9 kJ.mol−1) and K.SD (28.27 kJ.mol−1) reflected the suitability of these catalysts to be applied effectively under mild conditions. The essential thermodynamic functions, such as Gibb's free energy (65.16 kJ.mol−1 (Na.SD) and 65.26 kJ.mol−1 (K.SD)), enthalpy (25.23 kJ.mol−1 (Na.SD) and 25.55 kJ.mol−1 (K.SD)), and entropy (−197.7 J.K−1.mol−1 (Na.SD) and −197.8 J.K−1.mol−1 (K.SD)), display the endothermic and spontaneous nature of the two transesterification systems. [ABSTRACT FROM AUTHOR]

The effect of alkali ions (Na+ and K+) on the hydrothermal synthesis of olivine lithium metal phosphates in the P excess system was investigated by taking the synthesis of LiMn0.8Fe0.19Mg0.01PO4 as a case study. It is found that the coexisting Na+ can compete with Li+ to partly form NaMnPO4 as an impurity when the Na+/Li+ ratio exceeds the critical value, and this is not the case for the coexisting K+. These behaviors should be related to the difference in the ionic size of the alkali ions which also leads to a very different process of LiMn0.8Fe0.19Mg0.01PO4 formation. The samples derived from the K+‐coexisting reaction system can deliver much higher reversible capacities as compared with the sample derived from the Na+‐coexisting reaction system. This study provides new insights into the chemistry of the hydrothermal synthesis of olivine lithium metal phosphates, with an important implication for controllable synthesis and property manipulation. [ABSTRACT FROM AUTHOR]

Electrochemical doping is a promising method to modify the photoelectrochemical performance of semiconductors. The published works using H ions as compensated cations have shown increased photocurrents, but theories vary about the causes of the improvement of photoelectrochemical performance. In this paper, we present the effects of cation ion and the key factors of enhancement using alkali sulfates ((Li/Na/K) 2 SO 4) as the electrolyte for electrochemical doping. The effective electrode surface area (ECSA) was increased for the WO 3 film after electrochemical doping. The Li-ion, with the smallest radius and thereby the highest potential to insert into the WO 3 cell, results in the Li ion inserted WO 3 with the highest photocurrent in the three electrochemically doped samples. To investigate the possible factors affecting the photoelectrochemical performance, the electrochemically doped samples and a control sample were annealed under inert gas (Ar). The lower photocurrents were observed for the electrochemically doped samples after annealing, confirming that the key factors are the increase of the effective electrode surface area caused by electrochemical doping and ion compensation, rather than the ions themselves and the chemical bonds between alkali ions and W or O. Image 1 • Electrochemical doping was performed for WO 3 particle based film. • Enhanced photoelectrochemical activity was gained after treatment. • The effect of cations for electrochemical doping was studied. • Inserted model (Li) shows better performance than the absorption model (K) or complex model (Na). [ABSTRACT FROM AUTHOR]

Maintaining gradients of solvated protons and alkali metal ions such as Na+ and K+ across membranes is critical for cellular function. Over the last few decades, both the interactions of protons and alkali metal ions with phospholipid membranes have been studied extensively and the reported interactions of these ions with phospholipid headgroups are very similar, yet few studies have investigated the potential interdependence between proton and alkali metal ion binding at the water–lipid interface. In this short review, we discuss the similarities between the proton–membrane and alkali ion–membrane interactions. Such interactions include cation attraction to the phosphate and carbonyl oxygens of the phospholipid headgroups that form strong lipid–ion and lipid–ion–water complexes. We also propose potential mechanisms that may modulate the affinities of these cationic species to the water–phospholipid interfacial oxygen moieties. This review aims to highlight the potential interdependence between protons and alkali metal ions at the membrane surface and encourage a more nuanced understanding of the complex nature of these biologically relevant processes. [ABSTRACT FROM AUTHOR]

Abstract The Tm3+, Yb3+ co-doped CaZrO 3 phosphor samples have been synthesized through solid state reaction method in the absence and presence of alkali metal ions (i.e. Li+, Na+, K+). The X-ray diffraction (XRD) study shows the formation of CaZrO 3 crystal with orthorhombic phase. The Tm3+, Yb3+ co-doped CaZrO 3 phosphor emits intense upconversion emission in blue (474 nm) and NIR (799 nm) regions due to 1G 4 → 3H 6 and 3H 4 → 3H 6 transitions of Tm3+ ions, respectively on excitation with 980 nm radiation. The emission intensity is significantly enhanced in the presence of alkali ions due to charge compensation and asymmetry in the crystal field. The emission intensity in the case of Na+ co-doped phosphor is maximum and at 1 W pump power, it is increased by ∼44 and ∼31 times in blue and NIR regions, respectively as compared to without alkali ions co-doped phosphor. The downshifting emission in blue region has been observed due to oxygen vacancy and Tm3+ ions on excitation with 277 and 360 nm radiations which is enhanced significantly in the presence of alkali ions. Thus, the intense blue emission by this material is suitable for blue and white light emitting phosphors. Graphical abstract Image 1 Highlights • The Tm, Yb: CaZrO 3 phosphor has been synthesized by solid state reaction method. • The crystallinity and particle size is increased in the presence of alkali ions. • The optical band gap decreases in the presence of alkali ions. • The Na+ co-doped phosphor show ∼44 times enhancement in UC blue emission. • The downshifting emission in blue region is observed due to oxygen vacancy. [ABSTRACT FROM AUTHOR]

The local structure of Rb+ in a cation‐exchange resin soaked in superheated water up to 160 °C is studied via X‐ray absorption fine structure (XAFS) analysis. The first hydration shell structure of Rb+ is not changed when Rb+ is transferred from bulk superheated water into the resin soaked therein. Our previous chromatographic study with utilizing superheated water as an eluent indicated that separation selectivity between alkali cations decreases and the relative affinity of small ions toward ion‐exchange resins is enhanced. This strongly suggests that countercations in superheated water undergo different interactions compared to those in ambient conditions. However, XAFS spectral analysis for a Rb+‐form resin show that Rb+ remains hydrated similar to in bulk superheated water. In contrast, XAFS of a minor amount of Rb+ in a Cs+‐form resin suggests that even at ambient temperatures, Rb+ tends to form direct ion pairs with sulfonate cation‐exchange groups. The invasion of sulfonate groups into the first hydration shell of Rb+ becomes more obvious as temperature increases. The hydration structure of Rb+ cannot be maintained when it is surrounded by poorly hydrated Cs+ because of the limited availability of water molecules for forming complete hydration shells around Rb+. The sulfonate groups invade the first coordination shells of Rb+ to compensate for the shortage of water molecules. [ABSTRACT FROM AUTHOR]

The supersulfated cementitious system gains increasing popularity for lowering carbon emissions of the construction industry. However, the alkali-silica reaction (ASR) behavior of this sulfate-rich cement is still unclear. This study first reports the characteristics and suppressing mechanisms of ASR in supersulfated cement (SSC). The results show that nearly no ASR-induced expansion is found in the SSC even if 100% glass aggregates are used, while the expansion ratio of the traditional OPC is twenty times higher than the SSC. In the SSC, the further hydration of unreacted slag during the ASR test refines the pore size and enhances the compressive strength of the matrix. Meanwhile, the consumption of the alkali ions in the pore solution during the formation of N-A-S-H gel reduces the concentration of the alkali ions and the contact possibility with the aggregates. The high bulk electrical resistance of the SSC can mitigate the diffusion of alkali ions from the external solution to the mortar. Moreover, the higher Al/Si ratio of C-A-S-H in the SSC than C–S–H in the OPC system results in a higher adsorption capacity of Na+ due to the more negatively charged surface, reducing the concentration of alkali ions in the pore solution. Furthermore, the high concentration of SO 4 2− in the pore solution of SSC can inhibit the diffusion of OH−. As a result, the low-carbon SSC system would be a promising cementitious material to mitigate the ASR risk. [ABSTRACT FROM AUTHOR]

C3S pastes containing 0%, 5%, 10%, and 15% nano-SiO2 mixed with de-ionized water and alkali solutions were prepared. When C3S was completely hydrated, the pastes were ground into powders with a particle size less than 80 μm. Adsorption and desorption characteristics of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water immersed in alkali solutions and those in C3S-nano SiO2 pastes mixed with alkali solutions, were investigated. Meawhile, the adsorption mechanisms of alkali ions were discussed. Results showed that the contents of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water increased with increasing substitution levels of nano-SiO2 and/or the initial alkali concentrations. In C3S-nano SiO2 pastes mixed with de-ionized water, each paste was characterized by having a fixed alkali-adsorption capacity that was essentially independent of alkali concentration. No obvious difference between the adsorption capacity of a given paste for K+ and Na+ was observed. Adsorption of alkali ions in the pastes is considered to be caused by surface force which is related to the BET specific surface area of the paste, and charge compensation of C-S-H gel, mainly by electrostatic interactions. In C3S-nano SiO2 pastes mixed with alkali solutions, alkali ions may enter the structure of C-S-H gel to replace a part of Ca2+ in the interlayer. This assumption is supported by the structural characterization of C-S-H gel using 29Si MAS NMR. [ABSTRACT FROM AUTHOR]

Highlights • Red emission bands of Eu3+ doped CaZrO 3 phosphors. • Charge compensation and decrease of defects induced by codoped alkali ions. • Enhancements of luminescent properties of CaZrO 3 :Eu3+ by codoped alkali ions. Abstract CaZrO 3 :5%molEu3+ and CaZrO 3 :5%molEu3+/5mol%A+ (A = Li, Na, K) phosphors were synthesized by a solid state reaction. Effects of codoped alkali ions on luminescent properties of CaZrO 3 :5%molEu3+ was investigated. The XRD and FTIR measurements show that the all of synthesized phosphors have the same phase with pure CaZrO 3. The excitation and emission spectra indicate that the codoped alkali ions enhance the Eu3+ emission intensity significantly. Moreover, the decay lifetime is also prolonged by the addition of alkali ions. The enhancements of luminescent properties for CaZrO 3 :5%molEu3+ can be attributed to the charge compensation and decrease of Ca2+ vacancies induced by the addition of alkali ions. [ABSTRACT FROM AUTHOR]

The Tm 3+ , Yb 3+ co-doped gadolinium tungstate phosphor in presence and absence of alkali ions (i.e. Li + , Na + and K + ) has been synthesized through solid state reaction method. The structural characterization confirms the crystalline nature with coexistence of the two monoclinic phases. The phase fraction varies on addition of alkali ions. The Tm 3+ , Yb 3+ co-doped phosphor emits intense blue and near infrared emissions centered at 472 and 793 nm due to 1 G 4 → 3 H 6 and 1 G 4 → 3 H 5 transitions, respectively and a weak red emission at 655 nm due to 1 G 4 → 3 F 4 transition of Tm 3+ on excitation with 976 nm. The emission intensity of near infrared band dominates over the blue and red bands. When the alkali ions are added in the Tm 3+ , Yb 3+ co-doped phosphor, the emission intensity of the bands is enhanced significantly due to modification in the local crystal field. The emission intensity is highest for K + incorporation compared to Li + and Na + due to its occupancy at the interstitial sites. The lifetime measurement reveals an enhancement in the emission intensity. The pump power dependent emission intensity plots confirm the involvement of three photons for blue and two photons for red and NIR emissions. Thus, the Li + , Na + and K + incorporated Tm 3+ , Yb 3+ co-doped gadolinium tungstate phosphor emitting intense blue and NIR radiations may be useful for photonic devices, bio-imaging and solar converters. [ABSTRACT FROM AUTHOR]

The Er 3+ /Yb 3+ co-doped calcium zirconate phosphors have been synthesized through solid state reaction method. The structural characterizations confirm the crystalline nature of the phosphor. The Er 3+ , Yb 3+ co-doped phosphor emits intense green emission centered at 523 and 544 nm due to the 2 H 11/2  →  4 I 15/2 and 4 S 3/2  →  4 I 15/2 transitions, respectively and weak red emission at 662 nm due to 4 F 9/2  →  4 I 15/2 transition of Er 3+ on excitation with 976 nm radiation. The emission intensity of the green band dominates over the red band. When the alkali ions (Li + , Na + , K + ) are added in the Er 3+ /Yb 3+ co-doped phosphor, the emission intensities of bands enhance significantly. The fluorescence intensity ratio correspond to 523 and 544 nm peaks at different temperatures have been obtained which confirm the temperature sensing ability of the samples. In presence of alkali ions, the temperature sensor sensitivity increases and is maximum for K + co-doped phosphor. It is found that the energy gap between 2 H 11/2 and 4 S 3/2 levels increases with crystallinity in order of K + >Na + >Li + > without alkali ion. Thus, the Li + , Na + and K + incorporated Er 3+ , Yb 3+ co-doped calcium zirconate phosphor may be useful for photonic devices and temperature sensor. [ABSTRACT FROM AUTHOR]

Biomembranes assemble and operate at the interface with electrolyte solutions. Interactions between ions in solutions and the lipid affect the membrane structure, dynamics and electrostatic potential. In this article, I review some of the experimental and computational methods that are used to study membrane-ions interactions. Experimental methods that account for membrane-ion interactions directly and indirectly are presented first. Then, studies in which molecular dynamics simulations were used to gain an understanding of membrane-ion interactions are surveyed. Finally, the current view on membrane-ion interactions and their significance is briefly discussed. [ABSTRACT FROM AUTHOR]

In this work, a new long-life alkali ion source is proposed that is based on alkali halide salts doped in nano-γ-alumina (Al2O3). Depending on the polarity, the ion source produces both alkali and halide ions. The source was characterized using different techniques such as scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier transform infrared (FT-IR), and ion mobility spectrometry (IMS). SEM images confirm a strong interaction between the alkali halide (MX) and nano-γ-alumina. The average particle size of the doped nanoparticles was calculated to be 44 nm by TEM. Formation of new phases (KAlCl2O and K3AlF6) was confirmed by XRD and that of Al–O–K group in the synthesized particles by FT-IR. Alkali and halide ion peaks were observed by IMS in the positive and negative modes, respectively. The lifetime of the ion source for different alkali halides was measured to range from 216 to 960 h. The total ion current emitted from the source was about 2 µA, while it was 12 nA at the collector plate of the IMS. Finally, application of the new source in ion mobility spectrometry was demonstrated by observing ion mobility spectra of compounds ionized via cation and anion attachment reaction. [ABSTRACT FROM AUTHOR]

The control of morphology, elemental composition and phase composition of Cu 2 ZnSnS 4 (CZTS) nano-crystals depends on the control of complex formation and surface stabilization of nano-particles in solution-based synthesis in oleylamine. At temperatures ≥280 °C, the control of nano-crystal's morphology and homogenous growth is difficult because of fast poly-nuclear growth occurring at higher temperatures. In the present work the effect of oleylamine complex formation with different alkali ions (Na + , K + and Cs + ) on nano-crystals growth at synthesis temperature of 280 °C was studied. It was found that nano-powders synthesized in the presence of Na + and K + ions showed the formation of crystals of different sizes - small nano-particles (18 nm-30 nm), large aggregated crystals (few nm to 1 μm) and large single crystals (1 μm - 4 μm). The presence of Cs + ions in the nano-powder synthesis in oleylamine-metal precursor-CsOH solution promoted growth of nano-crystals of homogenous size. It is proposed that the formed oleylamine-Cs complexes a) enhance the formation and stabilization of oleylamine–metal (Cu, Zn and Sn) complexes before the injection of sulphur precursor into the oleylamine–metal precursor solution and b) after addition of sulphur stabilize the fast nucleated nano-particles and promote diffusion limited growth. [ABSTRACT FROM AUTHOR]

A novel and sensitive detection system was introduced based on amperometry inside flame for rapid determination of total alkali ions in the human cerebrospinal fluids (CSFs) at nM levels. For this purpose, a triangular (Y-shaped) three-electrode system included two stainless steel rods as well as a brass disk as working, counter and pseudo reference electrodes inside H 2 /air flame. In the fabricated system, mixture of H 2 and air was introduced to the flame through a capillary hole along the working electrode. The analyte was introduced to the flame as electrolyte through the formation of aerosols using a sonicator and N 2 as carrier gas. The inter-electrode distance was set to 2.0 mm. Based on one at a time method, the optimum flow rates of H 2 , air and N 2 were 375, 259 and 2.6 mL min -1 , respectively. Solution of HCl (0.45 M) was also selected as supporting electrolyte. Maximum sensitivity (peak current) was observed at DC potential of −36.0 ± 1.0 V (vs. the pseudo reference electrode). According to the figures of merit under the optimized condition, this system had linear dynamic ranges between 250-12000 ng mL -1 for Li+, 180–11400 ng mL -1 for Na + , 200–12000 ng mL -1 for K + and 110–6400 ng mL -1 for Cs + . Relative standard deviation (RSD) for 8 replicate analyses of Na+ as selected model was ∼7.0%. Based on 90% of maximum response (t90), the response time was estimated to be 3.0 s. No interference was observed, when introducing at least 1000-fold excess of foreign species such as Ag + , Ni 2+ , Mg 2+ , Zn 2+ , Fe 3 +, NH 4 + , acetone, ethanol, CH3COO - , NO3 - , Cl - , oxalate, SO4 -2 , tartrate, and PO4 -3 . However ∼20% positive error was observed during introduction of ∼500-fold excess of some alkaline earth metal cations such as Ba 2+ and Ca 2+ . The validity of this method was evaluated via analyses of different water samples. The reliability and application of this method was finally evaluated via determination of total alkali ions in different CSFs. Good correlation was observed between the total concentrations of alkali ions and Alzheimer’s disease (AD) in various patients. This method was therefore applicable for discrimination and prediction of AD via analyses of alkali species in the CSFs. [ABSTRACT FROM AUTHOR]

Rb + - and Cs + -exchanged Beta zeolites (Rb x Na 1− x β and Cs x Na 1− x β) of varying exchange degrees ( x = 0–1.00) were employed to catalyze the gas-phase dehydration of lactic acid (LA) for sustainable production of acrylic acid (AA) in a flow fixed-bed reactor at 360 °C, using an aqueous solution of LA (10 mol% or 35.7%) as the reaction feed at a weight hourly space velocity by LA of 2.1 h −1 . An appropriate window of the ion exchange degrees for highly selective AA production (≥60 mol%) was determined for either series of the samples, i.e., x = 0.85–0.98 for the Rb x Na 1− x β and x = 0.71–0.90 for the Cs x Na 1− x β samples. The best performing catalysts Rb 0.95 Na 0.05 β, and Cs 0.81–0.90 Na 0.19–0.10 β offered the highest AA selectivity (ca. 70 mol%) and yield (ca. 60–65 mol%) for reaction periods of longer than 10 h. Measurements of the surface acidity and basicity of the catalyst samples by temperature-programmed desorption of NH 3 and CO 2 showed that the highly selective catalysts in such widows should have both weakly acidic and weakly basic surface sites with suitably balanced acidity and basicity. The acid-catalyzed decarbonylation/decarboxylation and base-catalyzed condensation of LA, which lead respectively to formation of acetaldehyde and 2,3-pentanedione, always occurred as the competing reactions over the investigated catalysts. Observations on the catalyst selectivity changes for these competing reactions clearly demonstrate that the suitably balanced acidity and basicity at the catalyst surface is the key to the high selectivity for the desired dehydration reaction. [ABSTRACT FROM AUTHOR]

The radioluminescence (RL) spectra of three types of quartz have been compared to those obtained from wavelength resolved thermally stimulated luminescence (TSL) measurements. A detailed numerical deconvolution into Gaussian components allowed to identify which of the bands are involved in either types of luminescence processes. The blue “A band” at 2.51 eV was confirmed to dominate both RL and TSL spectra in samples exposed to prolonged irradiation. The UV emission of the 110 °C TSL peak was found to be composite. Analogously to what previously reported for RL spectra, an annealing at 500 °C for 10 min induced a strong enhancement of the “C band” at 3.42 eV. This effect was particularly evident in natural and pre-irradiated quartz. A second intense UV component, the “M band” at 3.7 eV, was found to contribute to both TSL and RL spectra of samples annealed at 1000 °C for 10 min. A further broad UV emission seems to be involved only in RL emission but not in the TSL one. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkali ions pre-intercalated enlarges the interlayer distance of Ti 3 C 2 T x MXene. • DFT calculation shows that Na-MXene has the lowest Na+ diffusion energy barrier. • Na-MXene significantly improves sodium storage performance. Two-dimensional (2D) materials, Ti 3 C 2 T x MXene, have great potential for rapidly and stabilized sodium storage because of their excellent electrical conductivity and rich redox active sites. However, affected by the interaction of hydrogen bonds and van der Waals forces, Ti 3 C 2 T x MXene nanosheets are prone to collapse and re-stacking, which is not conducive to the ions diffusion and electrons transport, affects the electrochemical performance. Herein, we prepared 3D wrinkled Ti 3 C 2 T x MXene architectures with alkali ions (Na+, K+, Li+) pre-intercalation by continuous stirring treatment of Ti 3 C 2 T x MXene in aqueous borohydride (NaBH 4 , KBH 4 , LiBH 4) solution for sodium storage. This structure effectively enlarges the interlayer distance of Ti 3 C 2 T x MXene nanosheets and shortens the sodium ion diffusion path. Benefitting from the superiority of the structure, Na+ pre-intercalated Ti 3 C 2 T x MXene has the most excellent sodium storage performance, high reversible capacity of 256 mA h g−1 at 100 mA g−1 after 100 cycles, and amazing long-cycle stability of 168 mA h g−1 at 2000 mA g−1 after 6000 cycles. The density functional theory (DFT) calculation shows that the Ti 3 C 2 T x MXene pre-intercalating with Na+ significantly reduces the diffusion energy barrier, greatly improves the embedding and diffusion kinetics of Na+. This novel three-dimensional wrinkled Ti 3 C 2 T x MXene structure with alkali ions pre-intercalated can better broaden the application prospects of MXene-based materials in energy storage fields. [ABSTRACT FROM AUTHOR]

Three new complexes of 1,3-diethyl-2-thiobarbituric acid (C 8 H 11 N 2 O 2 S, HDETBA) with Li + , Na + , K + alkali ions were synthesized. The complexes have been prepared by neutralization of 1,3-diethyl-2-thiobarbituric acid with the corresponding metal hydroxide in aqueous solution. The colorless crystals have been investigated using X-ray single crystal and powder techniques and characterized by differential scanning calorimetry, thermogravimetry and infrared spectroscopy. The compounds of MDETBA with M = Li and M = Na crystallize in the monoclinic lattice with a = 10.678(1) Å, b = 7.2687(9) Å, c = 13.202(2) Å, β = 108.841(2)°, Z = 4, V = 969.8(2) Å 3 , S.G. P 2 1 / n and a = 10.534(2) Å, b = 7.604(1) Å, c = 14.186(1) Å, β = 108.964(4)°, Z = 4, V = 1074.6(3) Å 3 , S.G. P 2 1 / n , respectively. Сompound KDETBA crystallizes in the orthorhombic lattice with a = 4.2541(6) Å, b = 14.739(2) Å, c = 16.635(3) Å, Z = 4, V = 1043.1(3) Å 3 , S.G. P 2 1 2 1 2 1 . In Li(I) and Na(I) complexes, the DETBA − ion is in cis -configuration and, in the K(I) complex, this ion is in trans -configuration. The reason for the transformation from cis - to trans -configuration has been rationalized. [ABSTRACT FROM AUTHOR]

We report on an abnormal migration phenomenon of alkali ions in calcium silicate glasses, induced by 250 kHz, 800 nm femtosecond laser irradiation. The diameter of the laser-affected zone is not dependent on the glass-transition temperature of glass samples. Elemental analysis by Electro-Probe Microanalyzer demonstrates that K ions migrate to the periphery of the laser-affected zone, while Cs ions show an opposite tendency in the two alkali ions coexisting glass. The possible mechanism on the observed abnormal phenomenon is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Study of alkali ions approaching an electrode surface. • The energetics follow the Hofmeister series. • Li+ and Na+ show signs of structure making. • K+ and Cs+ shows signs of structure breaking. The approach of alkali ions from an aqueous solution towards a gold electrode has been studied by biased molecular dynamics. In accord with the Hofmeister series, Li+ and Na+ show signs of structure making, K+ and Cs+ of structure breaking. For all ions the potential of mean force at first rises, when the ion approaches the surface, passes through a maximum and then drops again to a local minimum. For the structure breaking ions Cs+ and K+ the solvation energies in the minima are the same as in the bulk, for Na+ and Li+ they are a little higher. [ABSTRACT FROM AUTHOR]