Water-Ice Microstructures and Hydration States of Acridinium Iodide Studied by Phosphorescence Spectroscopy.

Ice has been suggested to have played a significant role in the origin of life partly owing to its ability to concentrate organic molecules and promote reaction efficiency. However, the techniques for studying organic molecules in ice are absorption-based, which limits the sensitivity of measurements. Here we introduce an emission-based method to study organic molecules in water ice: the phosphorescence displays high sensitivity depending on the hydration state of an organic salt probe, acridinium iodide (ADI). The designed ADI aqueous system exhibits phosphorescence that can be severely perturbed when the temperature is higher than 110 K at a concentration of the order of 10-5 M, indicating changes in hydration for ADI. Using the ADI phosphorescent probe, it is found that the microstructures of water ice, i.e., crystalline vs. glassy, can be strongly dictated by a trace amount (as low as 10-5 M) of water-soluble organic molecules. Consistent with cryoSEM images and temperature-dependent Raman spectral data, the ADI is dehydrated in more crystalline ice and hydrated in more glassy ice. The current investigation serves as a starting point for using more sensitive spectroscopic techniques for studying water-organics interactions at a much lower concentration and wider temperature range.

Crystal Plane Reconstruction and Thin Protective Coatings Formation for Superior Stable Zn Anodes Cycling 1300 h.

Some new insights into traditional metal pretreatment of anticorrosion for high stable Zn metal anodes are provided. A developed pretreatment methodology is employed to prefer the crystal plane of polycrystalline Zn and create 3.26 µm protective coatings mainly consisting of organic polymers and zinc salts on Zn foils (ROZ@Zn). In this process, Zn metal exhibits a surface-preferred (001) crystal plane proved by electron backscattered diffraction. Preferred (001) crystal planes and ROZ coatings can regulate Zn2+ diffusion, promote flat growth of Zn, and prevent side reactions. As a result, ROZ@Zn symmetrical cells exhibit superior plating/stripping performance over 1300 h. Impressively, it is significantly prolonged over 40 times in comparison to the bare Zn symmetric cell at 5 mA cm-2 . Moreover, Zn//MnO2  button cells have a high capacity retention of 96.3% after 1600 cycles and pouch cells have a high capacity 122 mAh g-1  after 200 cycle at 5 C. This work provides inspiration for high stable aqueous Zn metal batteries using the developed metal pretreatment of anticorrosion, which will be a viable, low-cost, and efficient technology. More interesting, it demonstrates the availability of reconstructing crystal planes by the largely heterogeneous reaction activation of the different crystal planes to H+ .

Fe3O4-Mg(OH)2 nanocomposite as a scavenger for silver nanoparticles: Rational design, facile synthesis, and enhanced performance.

Silver nanoparticles (AgNPs) are considered as emerging contaminants because of their high toxicity and increasing environmental impact. Removal of discharged AgNPs from water is crucial for mitigating the health and environmental risks. However, developing facile, economical, and environment-friendly approaches remains challenging. Herein, an Fe3O4-Mg(OH)2 nanocomposite, as a novel magnetic scavenger for AgNPs, was prepared by loading Fe3O4 nanoparticles on Mg(OH)2 nanoplates in a one-pot synthesis. Batch removal experiments revealed that the maximum removal capacities for the two model AgNPs (citrate- or polyvinylpyrrolidone-coated AgNPs) were 476 and 442 mg/g, respectively, corresponding to partition coefficients 8.03 and 4.89 mg/g/µM. Removal feasibilities over a wide pH range of 5-11 and in real water matrices and scavenger reusability with five cycles were also confirmed. Both Fe3O4 and Mg(OH)2 components contributed to the removal; however, their nanocomposites exhibited an enhanced performance because of the high specific surface area and pore volume. Chemical adsorption and electrostatic attraction between the coatings on the AgNPs and the two components in the nanocomposite was considered to be responsible for the removal. Overall, the facile synthesis, convenient magnetic separation, and high removal performance highlight the great potential of the Fe3O4-Mg(OH)2 nanocomposite for practical applications.

Abiotic Formation of Calcium Oxalate under UV Irradiation and Implications for Biomarker Detection on Mars.

A major objective in the exploration of Mars is to test the hypothesis that the planet has ever hosted life. Biogenic compounds, especially biominerals, are believed to serve as biomarkers in Raman-assisted remote sensing missions. However, the prerequisite for the development of these minerals as biomarkers is the uniqueness of their biogenesis. Herein, tetragonal bipyramidal weddellite, a type of calcium oxalate, is successfully achieved by UV-photolyzing pyruvic acid (PA). The as-prepared products are identified and characterized by micro-Raman spectroscopy and field emission scanning electron microscopy. Persistent mineralization of weddellite is observed with altering key experimental parameters, including pH, Ca2+ and PA concentrations. In particular, the initial concentration of PA can significantly influence the morphology of weddellite crystal. Oxalate acid is commonly of biological origin; thus calcium oxalate is considered to be a biomarker. However, our results reveal that calcium oxalate can be harvested by a UV photolysis pathway. Moreover, prebiotic sources of organics (e.g., PA, glycine, alanine, and aspartic acid) have been proven to be available through abiotic pathways. Therefore, our results may provide a new abiotic pathway of calcium oxalate formation. Considering that calcium oxalate minerals have been taken as biosignatures for the origin and early evolution of life on Earth and astrobiological investigations, its formation and accumulation by the photolysis of abiological organic compounds should be taken into account.

Bandgap adjustment assisted preparation of >18% Cs y FA1-y PbI x Br3-x -based perovskite solar cells using a hybrid spraying process.

The preparation of Cs y FA1-y PbI x Br3-x -based perovskite by ultrasonic spraying has valuable application in the preparation of tandem solar cells on textured substrates due to its excellent stability and the advantages of large-area uniform preparation from the spraying technology. However, the bandgap of perovskite prepared by spraying method is difficult to adjust, and perovskites with a wide bandgap have the issue of phase instability. Here, we improved the crystallinity of the perovskite by simply controlling the post-annealing temperature. The results show that perovskite film prepared by hybrid spray method has the best crystallinity and device performance at a post-annealing temperature of 170 °C. On this basis, the bandgap of perovskite was changed from 1.53 eV to 1.76 eV by controlling the ratio of the organic halogen precursor solution. When the bandgap is 1.57 eV, a perovskite solar cell with an efficiency of 18.31% is obtained.

Removal and recovery of silver nanoparticles by hierarchical mesoporous calcite: Performance, mechanism, and sustainable application.

The widespread use of silver nanoparticles (AgNPs) inevitably leads to the environmental release of AgNPs. The released AgNPs can pose ecological risks because of their specific toxicity. However, they can also be used as secondary sources of silver metal. Herein, hierarchical mesoporous calcite (HMC) was prepared and used to remove and recover AgNPs from an aqueous solution. The batch experiments show that the HMC has high removal percentages for polyvinylpyrrolidone- and poly (vinyl alcohol)-coated AgNPs (PVP- and PVA-AgNPs) over a wide pH range of 6-10. The adsorption isotherms indicate that the maximum removal capacities are 55 and 19 mg g-1 for PVP-AgNPs and PVA-AgNPs, respectively, corresponding to partition coefficients (PCs) of 0.55 and 0.77 mg g-1 µM-1. Furthermore, the removal performance is also not impaired by coexisting anions, such as Cl-, NO3-, SO42-, and CO32-. Their removal mechanisms can be ascribed to the electrostatic attraction and chemical adsorption between the HMC and polymer-coated AgNPs. Calcium ions on the HMC surface serve as active sites for coordination with the oxygen-bearing functional groups of AgNP coatings. Moreover, the AgNPs adsorbed onto HMC show high catalytic activity and good reusability for the reduction of the organic pollutant 4-nitrophenol. This work may pave the way not only to remove metal nanopollutants from waters but also to convert them into functional materials.

Growth of Compact CH3NH3PbI3 Thin Films Governed by the Crystallization in PbI2 Matrix for Efficient Planar Perovskite Solar Cells.

As a convenient preparation technique, a two-step method, which is normally done by spin-coating CH3NH3I onto PbI2 film followed by a thermal annealing, is generally used to prepare solution-processed CH3NH3PbI3 films for planar perovskite solar cells. Here, we prepare the compact CH3NH3PbI3 thin films by the two-step method at a low temperature (<80 °C) and investigate the effects of PbI2 crystallization on the structure-property correlation in the CH3NH3PbI3 films. It is found that the importance of the crystallization in PbI2 matrix lies in governing the transition from the (001) plane of trigonal PbI2 to the (002) plane of tetragonal CH3NH3PbI3 in the rapid reaction process for atoms to coordinate into perovskite during spin-coating, which actually determines the morphology and the type of vacancy defects in resulting perovskite; a better crystallized PbI2 film has a much stronger ability to react with CH3NH3I solution and produces larger CH3NH3PbI3 grains with a higher crystallinity. The CH3NH3PbI3/TiO2 planar solar cell derived from a better crystallized PbI2 film exhibits significantly improved performance and stability as the result of the higher crystallinity inside the perovskite film. Moreover, it is demonstrated that the crystalline PbI2 film matrix subjected to the annealing after a slow heating process prior to contacting CH3NH3I solution is more effective for CH3NH3PbI3 formation than that with a direct annealing history. The results in this paper provide a guide for preparing high-quality CH3NH3PbI3 thin films for efficient perovskite solar cells and CH3NH3PbI3 interfacial films over the layers susceptible to temperature.

One-step synthesis of Ag2O@Mg(OH)2 nanocomposite as an efficient scavenger for iodine and uranium.

Ag2O nanoparticles anchored on the Mg(OH)2 nanoplates (Ag2O@Mg(OH)2) were successfully prepared by a facile one-step method, which combined the Mg(OH)2 formation with Ag2O deposition. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and nitrogen physisorption analysis. It was found that Ag2O nanoparticles anchored on the Mg(OH)2 nanoplates show good dispersion and less aggregation relative to the single Ag2O nanoaggregates. In addition, iodide (I-) removal by the Ag2O@Mg(OH)2 nanocomposite was studied systematically. Batch experiments reveal that the nanocomposite exhibits extremely high I- removal rate (<10min), and I- removal capacity is barely affected by the concurrent anions, such as Cl-, SO42-, CO32- and NO3-. Furthermore, I- and UO22+ could be simultaneously removed by the nanocomposite with high efficiency. Due to the simple synthetic procedure, the excellent removal performances for iodine and uranium, and the easy separation from water, the Ag2O@Mg(OH)2 nanocomposite has real potential for application in radioactive wastewater treatment, especially during episodic environmental crisis.

Preparation of hollow core/shell microspheres of hematite and its adsorption ability for samarium.

Hollow core/shell hematite microspheres with diameter of ca. 1-2 µm have been successfully achieved by calcining the precursor composite microspheres of pyrite and polyvinylpyrrolidone (PVP) in air. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET) gas sorptometry. Temperature- and time-dependent experiments unveil that the precursor pyrite-PVP composite microspheres finally transform into hollow core/shell hematite microspheres in air through a multistep process including the oxidation and sulfation of pyrite, combustion of PVP occluded in the precursor, desulfation, aggregation, and fusion of nanosized hematite as well as mass transportation from the interior to the exterior of the microspheres. The formation of the hollow core/shell microspheres dominantly depends on the calcination temperature under current experimental conditions, and the aggregation of hematite nanocrystals and the core shrinking during the oxidation of pyrite are responsible for the formation of the hollow structures. Moreover, the adsorption ability of the hematite for Sm(III) was also tested. The results exhibit that the hematite microspheres have good adsorption activity for trivalent samarium, and that its adsorption capacity strongly depends on the pH of the solution, and the maximum adsorption capacity for Sm(III) is 14.48 mg/g at neutral pH. As samarium is a typical member of the lanthanide series, our results suggest that the hollow hematite microspheres have potential application in removal of rare earth elements (REEs) entering the water environment.

Two-dimensional silica sieve plates mimicking the diatom valve.

Sieve and take: A biomimetic strategy was designed to fabricate two-dimensional silica sieve plates (SSP) by use of catanionic surfactants as composite template and L-tartrate with hydroxyl and carboxyl groups as regulator. Tartrate was found to combine two capabilities in the formation of SSP structures: the connection of adjacent silica structures through H bonding and the separation of adjacent structures through electrostatic repulsion.

Formation of asymmetrical structured silica controlled by a phase separation process and implication for biosilicification.

Biogenetic silica displays intricate patterns assembling from nano- to microsize level and interesting non-spherical structures differentiating in specific directions. Several model systems have been proposed to explain the formation of biosilica nanostructures. Of them, phase separation based on the physicochemical properties of organic amines was considered to be responsible for the pattern formation of biosilica. In this paper, using tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) as silica precursor, phospholipid (PL) and dodecylamine (DA) were introduced to initiate phase separation of organic components and influence silica precipitation. Morphology, structure and composition of the mineralized products were characterized using a range of techniques including field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), infrared spectra (IR), and nitrogen physisorption. The results demonstrate that the phase separation process of the organic components leads to the formation of asymmetrically non-spherical silica structures, and the aspect ratios of the asymmetrical structures can be well controlled by varying the concentration of PL and DA. On the basis of the time-dependent experiments, a tentative mechanism is also proposed to illustrate the asymmetrical morphogenesis. Therefore, our results imply that in addition to explaining the hierarchical porous nanopatterning of biosilica, the phase separation process may also be responsible for the growth differentiation of siliceous structures in specific directions. Because organic amine (e.g., long-chair polyamines), phospholipids (e.g., silicalemma) and the phase separation process are associated with the biosilicification of diatoms, our results may provide a new insight into the mechanism of biosilicification.

Morphology-controlled synthesis of flowerlike ZnO nano/microstructures and their photocatalytic property.

Flowerlike ZnO nano/microstructures (FZNM) have been synthesized on glass substrates by a simple hydrothermal method. The as-prepared samples are composed of many radially oriented nano/submicron rods, which are single crystalline with a hexagonal structure and grow along the [001] direction. The diameter of ZnO nano/submicron rods ranges from 20 nm to 1 microm. With prolonged reaction time, the number of the nano/submicron rods of each ZnO flowerlike will decrease, while further prolonged reaction time, the amount increase actually. The reaction time is one key factor to control the sizes of the rods and the morphology of flowerlike structures. The possible growth mechanism has been discussed and proposed. A preliminary study on photocatalytic property of as-synthesized flowerlike structure reveals that morphology and size significantly influenced the photocatalytic activity for a solution of methylene blue (MB). Moreover, it is found that the annealed product exhibited higher photocatalytic performance.

Abnormal calcium "sparks" in cardiomyocytes of post-myocardial infarction heart.

In ischemic hypertrophic myocardium, contractile dysfunction can be attributed to the decreased calcium induced calcium release (CICR) in cytoplasm. This study aimed to investigate the electrophysiological properties and the expression of L calcium channel subunits in post-MI myocardium. The ischemic heart remodeling model was established in SD rats. The expressions of calcium channel subunits were determined by realtime RT-PCR. Whole cell patch clamp was used to record the electrophysiological properties of L calcium channel. The results showed that the L calcium channel agonist Bayk 8644 induced the significantly decreased CICR in the rat cardiomyocyte 6 weeks after myocardial infarction (MI). In the post-MI cardiomyocytes, the amplitude of I(CaL) decreased dramatically and the inactivation curve of the current shifted to more negative potential. At mRNA level, the expression of the calcium channel alpha1c, beta2c subunits decreased dramatically in the ventricle of post-MI rats. The expression of alpha2/delta subunit, however, remained constant. It is concluded that the abnormal expression of the L calcium channel subunits in post-MI cardiomyocytes contributes to the ICaL decrease at early stage of the ischemic remodeling in cardiomyocytes, which leads to the decreased CICR in the cell and contractile dysfunction of myocardium.

Abnormal Calcium "Sparks" in Cardiomyocytes of Post-myocardial Infarction Heart / 华中科技大学学报（医学）（英德文版）

In ischemic hypertrophic myocardium, contractile dysfunction can be attributed to the decreased calcium induced calcium release (CICR) in cytoplasm. This study aimed to investigate the electrophysiological properties and the expression of L calcium channel subunits in post-MI myocardium. The ischemic heart remodeling model was established in SD rats. The expressions of calcium channel subunits were determined by realtime RT-PCR. Whole cell patch clamp was used to record the electrophysiological properties of L calcium channel. The results showed that the L calcium channel agonist Bayk 8644 induced the significantly decreased CICR in the rat cardiomyocyte 6weeks after myocardial infarction (MI). In the post-MI cardiomyocytes, the amplitude of ICaL decreased dramatically and the inactivation curve of the current shifted to more negative potential. At mRNA level, the expression of the calcium channel alphalc, beta2c subunits decreased dramatically in the ventricle of post-MI rats. The expression of alpha2/delta subunit, however, remained constant.It is concluded that the abnormal expression of the L calcium channel subunits in post-MI cardiomyocytes contributes to the ICaL decrease at early stage of the ischemic remodeling in cardiomyocytes,which leads to the decreased CICR in the cell and contractile dysfunction of myocardium.