CaI2 Research Articles

Optimizing the fatigue‐resistant actuation performance of gel‐based bionic artificial muscles (GBAMs): A comparative study on crosslinking agents

AbstractThe study examined the impact of various calcium salts crosslinking agents on the fatigue‐resistant actuation performance of gel‐based bionic artificial muscles (GBAMs) that exhibited directional bending deflection and generated actuation force when electrically stimulated, thereby converting electrical energy into mechanical energy. Furthermore, a comparative investigation was carried out to examine the mechanical properties, electrochemical characteristics, microstructure, material composition, and actuation lifespan of GBAMs doped with various calcium salts, which were commonly found in biological muscles. Moreover, this research paper offered a comprehensive analysis of the mechanoelectric coupling's contribution towards optimizing the fatigue‐resistant actuation performance of the GBAM. The findings indicated that the GBAM, synthesized through the cross‐linking of calcium iodide doped with a 25% volume fraction of ethanol absolute, exhibited superior mechanical properties, electrochemical characteristics, microstructure, and actuation lifespan when compared to various other calcium salts. Hence, following a comprehensive comparison, it could be deduced that the fatigue‐resistant actuation performance of the GBAM, synthesized using calcium iodide doped with a 25% volume fraction of ethanol absolute as a crosslinking agent, exhibited the highest level of effectiveness when compared to the other four calcium salts.

Scintillator efficiency enhancement potential consequent to the pressure-dependent electronic, optical and elastic properties of CaI2: first-principles calculations

ABSTRACT First-principles calculations are carried out to investigate the effect of pressure (up to 40 GPa) on electronic, optical and elastic properties of the scintillator material calcium iodide, CaI2, by using Perdew–Burke–Ernzerh of generalized gradient approximation (PBE-GGA). The electronic band structure reveals an indirect band gap of 3.89 eV and a direct band gap of 4.35 eV for zero pressure. We have also calculated the pressure dependence of optical properties. The elastic constants and elastic moduli increase nonlinearly with pressure. Decreasing Pugh’s ratio and increasing hardness with pressure indicate a cross-over from ductile to brittle nature at 5 GPa. Analyses of elastic properties show that CaI2 is mechanically stable up to the applied pressure of 40 GPa. The calculated light yield increases linearly with pressure yielding a pressure coefficient of 1327 ph/MeV per GPa due to the decreasing band gap. Light yield increases as much as 62% at 40 GPa.

Efficient Coupling of Complex Fluorooligosaccharides to Phenolic Peptide Mediated by Calcium Iodide

Comprehensive SummaryBesides serving as therapeutic agents and building blocks for glycoprotein synthesis, homogeneous synthetic glycopeptides also benefit understanding function of specific glycoform. However, the selectivity coupling of oligosaccharides to a given peptide remains challenging despite the fact that the synthesis of structure‐defined complex oligosaccharides has been greatly facilitated by chemo‐enzymatic based approaches. Herein, a Ca2+‐promoted glycosylation approach was developed to exclusively modify phenolic peptide using a panel of biologically important glycans.

Actuation performances and microscopic mechanism of a stimuli-responsive artificial muscle based on the chelation of sodium alginate with CaI2·4H2O

With the popularization of energy conservation and environmental protection, a stimuli-responsive artificial muscle (SRAM) prepared by green process of the chelation of sodium alginate (SA) with calcium iodide tetrahydrate (CaI2·4H2O), provides new ideas and prospects for the development and application of smart artificial muscles. In this paper, actuation performances including force density (Fρ , mN/g), working life (τ, s), rise time (τ r, s) and response speed (V F, mN/g·s) of the SRAM with different concentrations of CaI2·4H2O was researched through the test platform of electrically bending force. Furthermore, the microscopic mechanism on mechanical and electrochemical characteristics of the SRAM was analyzed and verified comprehensively by microstructure, energy dispersive spectroscopy, ion channel, infrared spectroscopy and diffraction of x-rays. The experimental results were demonstrated that when the concentration of CaI2·4H2O was within the range of 1.5 g l−1–2.0 g l−1, the SRAM achieved optimal modification, where at 1.5 g l−1 CaI2·4H2O, its specific capacitance and τ were both the maximum values of 93.7 mF g−1 and 1080 s, but internal resistance was the minimum of 3.09 Ω; at 2.0 g l−1 CaI2·4H2O, the Fρ, V F, elastic modulus, yield strength and ion channel of the SRAM reached the largest values of 22.807 mN g−1, 0.1046 mN g−1·s, 20 MPa, 0.18091 MPa and 60.2%, respectively, but τ r obtained the lest of 98 s. Because after being chelated by CaI2·4H2O, the α-L-guluronic blocks in SA molecular chains coagulated with Ca2+ ions, making the synergy between molecular chains of the SRAM stronger, thus forming a three-dimensional ‘egg box’ network structure of polymeric hydrogel.

Efficient Fmoc-Protected Amino Ester Hydrolysis Using Green Calcium(II) Iodide as a Protective Agent.

In order to modify amino acids, the C-terminus carboxylic acid usually needs to be protected, typically as a methyl ester. However, standard cleavage of methyl esters requires either highly basic or acidic conditions, which are not compatible with Fmoc or acid-labile protecting groups. This highlights the need for orthogonal conditions that permit selective deprotection of esters to create SPPS-ready amino acids. Herein, mild orthogonal ester hydrolysis conditions are systematically explored using calcium(II) iodide as a protective agent for the Fmoc protecting group and optimized for a broad scope of amino esters. Our optimized reaction improved on the already known trimethyltin hydroxide, as it produced better yields with greener, inexpensive chemicals and a less extensive energy expenditure.

Synthesis and Structure of a New Bulky Hybrid Scorpionate/Cyclopentadienyl Ligand and its Lithium Complex

AbstractThe reaction of 5‐(1‐adamantyl)‐3‐methyl‐1H‐pyrazole with dibromomethane yields a product mixture of bis(3‐adamantyl‐5‐methylpyrazolyl)methane (H2C(PzAd,Me)2, 2 a), (3‐adamantyl‐5‐methylpyrazolyl)‐(3‐methyl‐5‐adamantylpyrazolyl)methane ((H2C(PzAd,Me)(PzMe,Ad), 2 b) and bis(3‐methyl‐5‐adamantylpyrazolyl)methane (H2C(PzMe,Ad)2, 2 c). Lithiation of sterically congested H2C(PzAd,Me)2 (2 a) and subsequent addition of diphenylfulvene yields lithium 1,1‐bis(3‐adamantyl‐5‐methylpyrazolyl)‐2,2‐diphenyl‐2‐ethyl‐cyclopentadienide, [(thf)Li{Cp−CPh2−CHPzAd,Me}] (3) which is unable to form a thf adduct but can be hydrolyzed to H5C5−CPh2−CHPzAd,Me (4). Adamantyl groups in 5‐position of bis(pyrazolyl)methane, i. e. 2 b and 2 c, prohibit formation of a fulvene adduct. For comparison reasons, [{H5C5−CPh2−CHPzMe2}LiI] (1 b) has been prepared via protolysis of (thf)lithium 1,1‐bis(3,5‐dimethylpyrazolyl)‐2,2‐diphenyl‐2‐ethyl‐cyclopentadienide, [(thf)Li{Cp−CPh2−CHPzMe2}] (1 a), in the presence of calcium iodide.

Stabilization of light emitting Eu2+ centers inside Ca(Sr)I2:Eu particles in glass ceramics. The preliminary concept of synthesis

Glass ceramics in the form of MI2:Eu crystalline particles grown in MO-B2O3 glass (M = Ca, Sr, Ba) through recrystallization from the alloyed melt were fabricated. Eu2+ ions were detected in the CaI2 and SrI2 crystalline particles (not in the BaI2) inside the corresponding glasses. Some amount of Eu2+ centers are expected to originate from the MO-B2O3 glass hosts as well. This was confirmed by correlated electron paramagnetic resonance (EPR), photo- and radioluminescence (PL, RL) measurements. Peculiarities of the Eu2+ distribution and incorporation into the glass ceramics samples as well as charge and energy transfer properties are discussed in detail. Optimal conditions leading to the enhancement of the Eu2+ emission from the CaI2 and SrI2 crystallites inside the glasses were determined.

The Near-infrared Spectrum of the Nuclear Star Cluster: Looking below the Tip of the Iceberg, and Comparisons with Extragalactic Nuclei*

Abstract Long-slit near-infrared (NIR) spectra of the Galactic nuclear star cluster (NSC) are discussed. The spectra sample the major axis of the NSC out to its half-light radius. The absorption spectrum of the central regions of the NSC is averaged over angular scales of tens of arc seconds in order to sample globular cluster-like total luminosities, and the results are compared with model spectra. The equivalent widths of Na i2.21 μm and Ca 2.26 μm outside of the center of the NSC, where light from nuclear bulge stars contributes a large fraction to the total flux, are consistent with solar chemical mixtures. In contrast, the equivalent widths of Na i2.21 μm and Ca i2.26 μm near the center of the NSC are larger than expected from models with solar chemical mixtures, even after light from the brightest evolved stars is removed. The depths of spectroscopic features changing along the major axis of the NSC are consistent with imaging studies that have found evidence of population gradients in the NSC. That Na i2.21 μm and Ca i2.26 μm are deeper than predicted for solar chemical mixtures over a range of evolutionary states is consistent with previous studies that find that the majority of stars near the center of the NSC formed from material that had nonsolar chemical mixtures. The depths of the Na i2.21 μm and Ca i2.26 μm features in the central regions of the NSC are comparable to those in the nuclear spectrum of the early-type Virgo disk galaxy NGC 4491, and are deeper than in the central spectra of NGC 253 and 7793. A spectrum of nebular emission and the youngest stars near the galactic center is also extracted. The equivalent widths of emission features in the extracted NIR spectrum are similar to those in the nuclear spectrum of NGC 253, and it is argued that this agreement is best achieved if the current episode of star formation near the center of the NSC has been in progress for at least a few megayears.

Intermediate-mass Early-type Disk Galaxies in the Virgo Cluster. II. Near-Infrared Spectra and Evidence for Differences in Evolution* † ‡ † ‡

Abstract We discuss near-infrared (NIR) slit spectra of six early-type disk galaxies in the Virgo Cluster that were examined previously at visible/red wavelengths. Despite having similar intrinsic luminosities, colors, and morphologies, the NIR spectrophotometric properties of these galaxies indicate that they are not a homogeneous ensemble differing only in terms of luminosity-weighted age and metallicity. While the depth of the CO(2,0) band is consistent with the centers of these galaxies having solar or slightly sub-solar luminosity-weighted metallicities, galaxy-to-galaxy variations in the depth of the Na i 2.21 μm doublet are found, with Na i2.21 μm lines in three galaxies (NGC 4491, NGC 4584, and NGC 4620) that are deeper than those predicted for a solar chemical mixture and a solar-neighborhood mass function. In contrast, the Ca i2.26 μm triplet shows good galaxy-to-galaxy agreement but tends to be deeper than the model prediction. Considering the depth of the NaD lines, the deep Na i2.21 μm lines are tentatively attributed to a bottom-heavy mass function. This is counter to observed trends between mass function slope and velocity dispersion, and so the possibility of a super-solar [Na/Fe] is also discussed. Two of the three galaxies with deep Na i 2.21 μm (NGC 4584 and NGC 4620) have Sérsic exponents that are consistent with a classical bulge. As for NGC 4491, its central NIR spectrum contains prominent emission lines. The relative strengths of Brγ and H2S(1), the presence of [Fe ii] emission, and the mid-infrared spectral-energy distribution are all consistent with intense recent star formation near the center of that galaxy. The NIR spectrum of NGC 4584 is devoid of line emission in the NIR, suggesting that star formation does not power the emission detected at visible wavelengths from that galaxy. Wavelengths that contain the Ballick–Ramsey C2 band at 1.76 μm are matched by moderately metal-poor E-MILES model spectra with an age of 2 Gyr. The radial age trends in these galaxies are in the opposite sense to those in late-type disk galaxies, and it is concluded that they have evolved in a cluster environment for at least several Gyr.

Исследование влияния температуры на электропроводность спиртовых растворов алкоголятов натрия и калия

Earlier, we studied the electrical conductivity of inorganic salts in a number of alcohols (ethanol, propanol-2, and butanol-1) at room temperature and found that alcoholic solutions of inorganic salts are weak electrolytes. It is known that an increase in the temperature of salt solutions leads to an increase in electrical conductivity due to an increase in the mobility of their ions in the solvent medium. To study the temperature dependence of the electrical conductivity of aqueous solutions of electrolytes, we proposed an approach based on the study of the effect of temperature on the equivalent electrical conductivity of solutions at infinite dilution λ∞. Using this approach, we studied the electrical conductivity of aqueous solutions of a number inorganic salts (nitrates, acetates, and phosphates), carboxylic acids, and amino acids as a function of temperature. It was found that for these solutions the dependence λ∞(Т) is described by the exponential Arrhenius equation λ∞ = Аexp(-E/(RT)). This equation was used to describe the temperature dependence of the ultimate equivalent conductivity for solutions of a number of inorganic salts (calcium and nitrate calcium, cadmium, lithium and potassium iodides, chloride, iodide and ammonium nitrate, silver nitrate and sodium bromide) in ethanol. This article investigated and demonstrated the possibility of describing the experimental data λ∞(Т) for solutions of ethylates, propylates and isopropylates of sodium and potassium in the corresponding alcohols (ethylates in ethanol, propylates in propanol, isopropylates in isopropyl alcohol) using the same equation.

Alkaline Earth Metal Template (Cross-)Coupling Reactions with Hybrid Disila-Crown Ether Analogues.

Alkaline earth metal iodides were used as templates for the synthesis of novel silicon‐based ligands. Siloxane moieties were (cross‐)coupled and ion‐specific, silicon‐rich crown ether analogues were obtained. The reaction of 1,2,7,8‐tetrasila[12]crown‐4 (I) and 1,2‐disila[9]crown‐3 (II) with MgI2 yielded exclusively [Mg(1,2,7,8‐tetrasila[12]crown‐4)I2] (1). The larger Ca2+ ion was then employed for cross‐coupling of I and II and yielded the complex [Ca(1,2,7,8‐tetrasila[15]crown‐5)I2] (2). Cross‐coupling of I and 1,2,4,5‐tetrasila[9]crown‐3 (III) with SrI2 enables the synthesis of the silicon‐dominant 1,2,4,5,10,11‐hexasila[15]crown‐5 ether complex of SrI2 (3). Further, the compounds [Sr(1,2,10,11‐tetrasila[18]crown‐6)I2] (4), [Sr(1,2,13,14‐tetrasila[24]crown‐8)I2] (5), and [Sr(1,2,13,14‐tetrasila‐dibenzo[24]crown‐8)I2] (6) were obtained by coupling I, 1,2‐disila[12]crown‐4 (IV) or 1,2‐disila‐benzo[12]crown‐4 (V), respectively. Using various anions, the (cross‐)coupled ligands were also observed in an X‐ray structure within the mentioned complexes. These template‐assisted (cross‐)couplings of various ligands are the first of their kind and a novel method to obtain macrocycles and/or their metal complexes to be established. Further, the Si−O bond activations presented herein might be of importance for silane or even organic functionalization.

Density Functional Theory Study of Defect Induced Ferromagnetism and Half-Metallicity in CaI2 Based Monolayer for Spintronics Applications

With the rapid advancement of electronics and spintronics industries, the demand for highly efficient materials has been increased for the application of high speed devices and circuits. In the recent past, Ca-based systems have been studied for superconducting properties. Using first-principles density functional theoretical calculations, we have investigated another Ca-based system (CaI2) for its half-metallic properties, which can be promising for ultrafast nonscattering transport. In the domain of spintronics, main group based half-metallic materials have attracted much attention due to their long spin-relaxation time. Here, in this study, we report for the first time ferromagnetism and half-metallicity in calcium iodide (CaI2) based materials with a wide spin-up gap of ∼3.84 eV. Such high spin-up gap in Ca-based half-metallic material is very promising since it can provide nonscattering transport. Among all, Ca0.67δ0.33I2 has a similar pattern to the most well established and thinnest magnet, CrI3 monolayer. Our further investigation predicts that the Ca0.89δ0.11I2 system has a ferromagnetic ground state with Curie temperature of ∼238 K (XY model), which is considerably higher than the reported CrI3 monolayer (45 K). Further to this, such system has a high magnetic anisotropy energy (∼14.11 meV), which indicates that it can prohibit spin fluctuation. Therefore, we report here that alkaline earth metal halide based magnetic materials can be promising for next generation spintronics devices.

High-light-yield calcium iodide (CaI[formula omitted]) scintillator for astroparticle physics

We are developing a high-light-yield calcium iodide (CaI2) scintillator for astroparticle physics experiments. This paper reports our CaI2 scintillator crystal’s scintillation performance. It achieved high light emissions (2.7 times those of NaI(Tl)) at a wavelength that was well within the photomultiplier’s sensitivity region. We also performed a pulse shape discrimination study using alpha and gamma-ray sources, confirming after a brief analysis that CaI2 has excellent pulse shape discrimination potential.

Enhancing efficiency of dye sensitized solar cells based on poly(propylene) carbonate polymer gel electrolytes incorporating double salts

The performance of dye-sensitized solar cells (DSSCs) depends on the ionic conductivity and flexibility of electrolyte. Gel polymer electrolytes (GPEs) consisting poly(propylene) carbonate (PPC) incorporated with double salts (i.e. calcium iodide (CaI2) and tetrabutylammonium iodide (TBAI)) were prepared. X-ray diffraction (XRD) authenticated that the crystallinity of PPC is mitigated after incorporation of different concentrations of CaI2 and TBAI, which is favourable for ion transportation. Fourier-transform infrared spectroscopy (FTIR) unveils the occurrence of complexation between PPC and the double salts. GPE containing 10% of CaI2 and 30% of TBAI exhibits the highest ionic conductivity (1.838 mS cm−1) with the activation energy of 0.156 eV. The fabricated DSSC employing the optimized GPE exhibits the energy conversion efficiency (η) of 5.49%, short circuit current density (Jsc) of 16.6 mA cm−2, open circuit voltage (Voc) of 0.568 V and fill factor (FF) of 54%.

Iodide‐Catalyzed Ring‐Opening Cyclization of Cyclohexane‐1,3‐dione‐2‐spirocyclopropanes

AbstractThe ring‐opening cyclization of 2′,3′‐nonsubstituted and 2′‐electron‐withdrawing group (EWG)‐substituted cyclohexane‐1,3‐dione‐2‐spirocyclopropanes was accomplished using iodide as a catalyst. The nonsubstituted derivatives afforded 3,5,6,7‐tetrahydro‐1‐benzofuran‐4(2H)‐ones in high yields in the presence of trimethylsilyl iodide at room temperature. The EWG‐substituted spirocyclopropanes, in turn, underwent regioselective ring opening followed by cyclization, which gave rise to 2‐substituted tetrahydrobenzofuran‐4‐ones when a combination of tetrabutylammonium iodide catalyst and trifluoromethanesulfonic acid was used, whereas calcium iodide afforded the 3‐substituted derivatives.magnified image

Well-defined styryl and biphenyl calcium complexes from dilithio compounds and calcium iodide: synthesis, structure and reactivity toward nitrous oxide.

Efficient synthesis and structure elucidation of carbon-calcium σ-bonded compounds are of remarkable interest and importance in organometallic chemistry of the heavier s-block metals. In this paper, we report that styryl and biphenyl calcium complexes with well-defined structures can be facilely obtained via metathesis reaction between their corresponding dilithio compound and calcium iodide. Single-crystal X-ray structural analysis of these calcium complexes revealed their unique iodide-bridged or dicalcium-bridged structures. Their reactivity toward nitrous oxide was disclosed.

Calcium-Based Catalytic System for the Synthesis of Bio-Derived Cyclic Carbonates under Mild Conditions

Recently, bio-derived cyclic carbonates have gained significant importance: e.g., as building blocks in non-isocyanate polyurethanes (NIPUs). Herein we report the development of a calcium-based catalyst system for the synthesis of challenging internal and trisubstituted cyclic carbonates from bio-derived epoxides and CO2 under mild reaction conditions. Several crown ethers were tested as ligands in combination with various cocatalysts for the possible activation of CO2. The most active system consists of a dicyclohexyl-functionalized 18-crown-6 ether and triphenylphosphane in addition to calcium iodide. The in situ complexation of Ca2+ by the crown ether was detected by 1H NMR spectroscopy. Interestingly, the addition of triphenylphosphane as a cocatalyst leads to a significant increase in activity, which is similar to or even higher than that of organic superbases such as DBU and TBD. The catalytic system was employed in the conversion of 16 different bio-derived epoxides, including fatty acid esters, oi...

Synthesis and Structural Characterization of Butadienylcalcium‐based Heavy Grignard Reagents and a Ca4[O] Inverse Crown Ether Complex

AbstractThe structure elucidation of heavy Grignard reagents (RAeX, Ae=Ca, Sr, and Ba, X=halides) has been greatly strived after, mainly because of their inaccessibility and remarkable instability. The synthesis of a series of butadienylcalcium compounds is presented, including 1‐calcio‐4‐lithio‐1,3‐butadiene, 1,4‐dicalcio‐1,3‐butadiene, and a Ca4[O] inverse crown ether complex, via the reaction between 1,4‐dilithio‐1,3‐butadienes and calcium iodide in THF. Single‐crystal X‐ray analysis of these unprecedented heavy Grignard reagents revealed unique structural characteristics and bonding modes. Preliminary reaction chemistry was investigated. This study provides a novel class of alkenyl heavy Grignard reagents and a useful synthetic strategy for otherwise unavailable reactive organometallic compounds.

Synthesis and Structural Characterization of Butadienylcalcium-based Heavy Grignard Reagents and a Ca4 [O] Inverse Crown Ether Complex.

The structure elucidation of heavy Grignard reagents (RAeX, Ae=Ca, Sr, and Ba, X=halides) has been greatly strived after, mainly because of their inaccessibility and remarkable instability. The synthesis of a series of butadienylcalcium compounds is presented, including 1-calcio-4-lithio-1,3-butadiene, 1,4-dicalcio-1,3-butadiene, and a Ca4 [O] inverse crown ether complex, via the reaction between 1,4-dilithio-1,3-butadienes and calcium iodide in THF. Single-crystal X-ray analysis of these unprecedented heavy Grignard reagents revealed unique structural characteristics and bonding modes. Preliminary reaction chemistry was investigated. This study provides a novel class of alkenyl heavy Grignard reagents and a useful synthetic strategy for otherwise unavailable reactive organometallic compounds.

Necroptosis Execution is Mediated by Plasma Membrane Nanopores that are Independent of Calcium

Necroptosis is a form of regulated necrosis that results in cell death and content release after plasma membrane permeabilization. However, little is known about the molecular events that mediate the disruption of the plasma membrane. Here, we have quantified the kinetics of calcium and propidium iodide influx during necroptosis using live cell imaging in multiple cell lines used as standard models in necroptosis research. In addition to the commonly used treatment to induce necroptosis via the TNF receptor, we examined other pathophysiologically relevant pathways, such as those involving Toll-like receptors (TLR) 3/4, with relevance during bacterial and viral invasion. We found that early calcium influx upon TNF-induced necroptosis in the presence of a Smac mimetic is mediated by ion channels and is cell-type dependent. Importantly, this early event is mediated by Smac treatment, does not require the activation of the necrosome machinery and is dispensable for necroptosis. Indeed, necroptosis induced by the activation of TLR3/4 pathways does not trigger early calcium influx. Moreover, using osmoprotectants of different sizes, we show that it is membrane pores of less than 4nm in diameter that mediate necroptosis execution in a cell- and treatment-independent manner. Strikingly, extracellular calcium is not required for pore formation. To our best knowledge, this represents the first evidence obtained in living cells regarding the role of membrane pores in necroptosis. Those pores allow the passage of small molecules and ions. Therefore, we settle the debate about ion influx in necroptosis signaling. In fact, our findings reconcile apparent contradictions about the essential role of different ions (i.e calcium or sodium) in necroptosis taking into account that different ions could pass through punched membranes. Collectively, our data demonstrate that early calcium influx does not modulate the size of the later pores formed in the plasma membrane.