Excess Al3 Research Articles

Siderophore coated magnetic iron nanoparticles: Rational designing of water soluble nanobiosensor for visualizing Al3+ in live organism

This article aims to establish the judicious use of iron-binding chemistry of microbial chelators in order to functionalize the surface of iron nanoparticles to develop non-toxic nanobiosensor. Anchoring a simple siderophore 2,3-dihydroxybenzoylglycine (H3L), which bears catechol and carboxyl functionalities in tandem, on to the surface of Fe3O4 nanoparticles has developed a unique nanobiosensor HL-FeNPs which showed highly selective and sensitive detection of Al3+ in 100% water at physiological pH. The biosensor HL-FeNPs, with 20nM limit of detection, behaves reversibly and instantly. In-vivo bio-imaging in live brine shrimp Artemia confirmed that HL-FeNPs could be used as fluorescent biomarker for Al3+ in live whole organisms. Magnetic nature of the nanosensor enabled HL-FeNPs to remove excess Al3+ by using external magnet. To our knowledge, the possibility of microbial chelator in the practical development of Al3+ selective nanobiosensor is unprecedented.

Influencing factors on heterogeneous water oxidation catalysis by di-μ-oxo dimanganese complex on mica as a synthetic model of photosystem II

The influencing factors on heterogeneous water oxidation catalysis (WOC) were investigated in a synthetic photosystem II model developed by adsorbing [(OH2)(terpy)MnIII(μ-O)2MnIV(terpy)(OH2)]3+ (terpy = 2,2′:6′,2″-terpyridine) (1) as an oxygen evolving center onto mica. For chemical WOC using a Ce4+ oxidant, the catalytic activity of 1 on mica increased by a factor of 2.3 or 1.4 by co-adsorption (0.015 mmol g−1) of redox-inactive trications of Al3+ or Ce3+ with 1 (0.15 mmol g−1), respectively, whereas it decreased by co-adsorption (0.25 mmol g−1) of excess Al3+ or Ce3+. The cooperative catalysis by two equivalents of the adsorbed 1 for water oxidation could be facilitated by enrichment of 1 by trications at their low co-adsorption conditions. The decreased catalytic activity at high trications co-adsorption conditions could be explained by impeded penetration of Ce4+ oxidant ions into a mica interlayer. For photochemical WOC containing a [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) photoexcitation center in mica, the drying treatment at 65 °C under the vacuum after 1 adsorption was required in adsorbate preparation, possibly to maintain favorable arrangement of 1 and [Ru(bpy)3]2+ in a mica interlayer. The drying treatment at 65 °C under the vacuum after [Ru(bpy)3]2+ adsorption inactivated the photochemical WOC. The proton-coupled electron transport from interior [Ru(bpy)3]2+ centers to ones near the surface in mica is considered to be suppressed by the drying treatment, which could be responsible for the inactivated photochemical WOC.

Effect of Aluminum Treatment on Proteomes of Radicles of Seeds Derived from Al-Treated Tomato Plants.

Aluminum (Al) toxicity is a major constraint to plant growth and crop yield in acid soils. Tomato cultivars are especially susceptible to excessive Al3+ accumulated in the root zone. In this study, tomato plants were grown in a hydroponic culture system supplemented with 50 µM AlK(SO4)2. Seeds harvested from Al-treated plants contained a significantly higher Al content than those grown in the control hydroponic solution. In this study, these Al-enriched tomato seeds (harvested from Al-treated tomato plants) were germinated in 50 µM AlK(SO4)2 solution in a homopiperazine-1,4-bis(2-ethanesulfonic acid) buffer (pH 4.0), and the control solution which contained the buffer only. Proteomes of radicles were analyzed quantitatively by mass spectrometry employing isobaric tags for relative and absolute quantitation (iTRAQ®). The proteins identified were assigned to molecular functional groups and cellular metabolic pathways using MapMan. Among the proteins whose abundance levels changed significantly were: a number of transcription factors; proteins regulating gene silencing and programmed cell death; proteins in primary and secondary signaling pathways, including phytohormone signaling and proteins for enhancing tolerance to abiotic and biotic stress. Among the metabolic pathways, enzymes in glycolysis and fermentation and sucrolytic pathways were repressed. Secondary metabolic pathways including the mevalonate pathway and lignin biosynthesis were induced. Biological reactions in mitochondria seem to be induced due to an increase in the abundance level of mitochondrial ribosomes and enzymes in the TCA cycle, electron transport chains and ATP synthesis.

Stimulation of Root Growth Induced by Aluminum in <i>Quercus serrata</i> Thunb. Is Related to Activity of Nitrate Reductase and Maintenance of IAA Concentration in Roots

Aluminum (Al) is the most abundant metal in the earth’s crust. Excess Al3+ released by soil acidification in soil solution is thought to be a growth limiting factor to many cultivated plant species, but it has been reported to stimulate plant growth in some crop and tree species in certain concentration of Al3+. Previously, we had reported that Al treatment enhanced root development, uptake from growth media and in vivo nitrate reductase (NR) activity of roots. NR is one of the key enzymes in nitrogen metabolism and acts at the first step of nitrate assimilation in plants. In this study, we investigated the process of Al-induced root development in an early stage, focusing on the change in in vitro NR activity, and indole-3-acetic acid (IAA) and cytokinins concentration in roots of Quercus serrata seedlings, which were treated for 1 h with Al or Ca. In Al-treated roots, NR activity increased and IAA concentration was maintained at the same level as pretreatment, and indole-3-acetyl-L-aspartic acid (IA-Asp), which is a metabolic intermediate of IAA degradation, was not detected in roots. In Ca-treated roots, NR activity increased, but IAA concentration decreased as IA-Asp concentration increased. Thus, the maintenance of IAA concentration in Al-treated roots seems to result from suppression in the process of IAA decomposition. Al treatment increased the length and number of second lateral roots but Ca treatment did not. We concluded that root development induced by Al in the early stage was related to NR activity and maintenance of IAA concentration.

Preparation and properties for aluminum-doped zinc oxide powders with the coprecipitation method

Zinc oxide powders of different Al doping contents (AZO) were prepared with the coprecipitation method from zinc nitrate solution and aluminum nitrate solution in this study. The effects of process parameters such as the Al doping content, calcination temperature and calcination time etc. on electric conductivity were examined quantificationally. The AZO powders had good electric conductivity than that of zinc oxide powders. The resistivity of the AZO powders significantly depended on the Al doping content, calcination temperature and calcination time. The minimum resistivity 179.2 Ω·cm was obtained from the 2 mol% Al doped powders in this work, which were prepared at the calcination temperature 1300°C for 2 h. The AZO powders were also characterized with the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results show that when the Al doping content is less than 2 mol%, the Al3+ enters into the ZnO lattice to form the solid solution, and causes the current carrier increase and the resistivity drop, but the excessive Al3+ doping brings the ZnAl2O4 spinel phase generate, resulting in the resistivity increase.

Aluminum Tolerance of Two Wheat Cultivars (Brevor and Atlas66) in Relation to Their Rhizosphere pH and Organic Acids Exuded from Roots

Phytotoxicity of aluminum (Al) has become a serious problem in inhibiting plant growth on acid soils. Under Al stress, the changes of rhizosphere pH, root elongation, absorption of Al by wheat roots, organic acids exuded from roots, and some main factors related to Al-tolerant mechanisms have been studied using hydroponics, fluorescence spectrophotometry, and high performance liquid chromatography (HPLC). Two wheat cultivars, Brevor and Atlas66, differing in Al tolerance are chosen in the study. Accordingly, the rhizosphere pH has a positive effect on Al tolerance. Atlas66 (Al-tolerant) has higher capability to maintain high rhizosphere pH than Brevor (Al-sensitive) does. High pH can reduce Al3+ activity and toxicity, and increase the efficiency of exuding organic acids from the roots. More inhibition of root elongation has been found in Brevor because of the exposure of roots to Al3+ solution at low pH. Brevor accumulate more Al in roots than Atlas66 even at higher pH. Al-induced exudation of malic and citric acids has been found in Atlas66 roots, while no Al-induced organic acids have been found in Brevor. These results indicate that the Al-induced secretion of organic acids from Atlas66 roots has a positive correlation with Al tolerance. Comprehensive treatment of Al3+ and H+ indicates that wheat is adversely influenced by excess Al3+, rather than low pH.

Electroluminescence in magnesium-doped Al2O3 crystals

Electroluminescence (EL) was investigated in Al2O3:Mg single crystals containing thermally generated [Mg]0 centers when a current in excess of 10 μA was passed through the samples in the temperature interval 323—673 K. The EL is emitted from a narrow region at the negative electrode suggesting an electron-hole recombination process due to the injection of electrons which recombine with holes. EL bands at 3.8, 2.5, 1.8, and 1.5 eV were observed. The bands at 3.8, 1.8, and 1.5 eV are related to photoluminescence (PL) bands previously attributed to F + centers, Cr3+, and Ti3+, respectively. The PL band at 2.5 eV has been tentatively associated with excess Al3+ in the form of interstitials. The dependence of the EL spectra on the electrical current and temperature was also studied.

Investigation on lattice constants of Mg-Al spinels

Mg-Al spinel is the most typical material in the family of chemical compounds with spinel crystalline structure that exhibits many applications [1, 2]. In general, it can be noted as MgO-n·Al2O3. MgAl2O4 spinel is an fcc structure of oxygen ions with a lattice parameter of 0.808 nm. There are eight molecules in its unit cell, in which there are 64 tetrahedral symmetry sites and 32 octahedral ones. In the perfect case, magnesium ions occupy 8 tetrahedral positions and aluminum ions occupy 16 octahedral sites [3]. In many cases, this MgO-n·Al2O3 compound is nonstoichiometric, n is not equal to 1. Form 1 up to 7.3, the excess Al3+ ions occupying tetrahedral sites, substitute for Mg2+ ions [4]. This causes a proportional decrease of lattice parameter with the amount of excess Al3+ due to a smaller diameter of Al3+ than that of Mg2+. In the present paper, we show the result of the unit cell parameters of Mg-Al spinels solid solutions with XRD and provide a formula for calculating the lattice parameter of such Mg-Al spinel compounds, which has a good physical meaning compared with that given by Sigalovsky et al. [5]. In our experiments ultra-fine powders of Mg-Al spinel were prepared with a method of high temperature solid reaction. Reagent grade AlNH4(SO4)2·12H2O and MgSO4·7H2O were mixed based on different n in de-ionized water. These solutions were calcimined at 1080 ◦C for 4–5 h to obtain a single spinel phase powder with being high pure, good disperse and homogeneous. The obtained powders were measured by XRD using Cu-Kα radiation on a D/max rA diffractometer. The XRD patterns of the obtained powder samples are given in Fig. 1. The stoichiometric spinel XRD pattern (a pattern labelled n= 1.0) is the same as the standard powder XRD pattern [6]. For the non-stoichiometric spinel samples, the peaks shift to the direction in higher values of 2θ as n increases. That means the distance of (hkl) plane dhkl became smaller according to the following expression:

Formation and Stability of β‐Quartz Solid‐Solution Phase in the Li‐Si‐Al‐O‐N System

The development of crystalline phases in lithium oxynitride glass‐ceramics was examined, with particular emphasis placed on the effect of the nitrogen source (AlN or Si3N4) on the formation and stability of a β‐quartz solid‐solution (ss) phase. Oxynitride glasses derived from the Li‐Si‐Al‐O‐N system were heat‐treated at temperatures up to 1200°C to yield glass‐ceramics in which β‐quartz(ss) and β‐spodumene(ss) of approximate composition Li2OAl2O34SiO2 formed as major phases and in which X‐phase (Si3Al6O12N2) and silicon oxynitride (Si2N2O) were present as minor phases. The nitrogen‐containing β‐quartz(ss) phase that was prepared with AlN was stable at 1200°C; however, the use of Si3N4 as the nitrogen source was significantly less effective in promoting such thermal stabilization. Lattice parameter measurements revealed that AlN and Si3N4 had different effects on the crystalline structures, and it was proposed that the enhanced thermal stability of the β‐quartz(ss) phase that was prepared with AlN was due to both the replacement of oxygen by nitrogen and the positioning of excess Al3+ ions into interstitial sites within the β‐quartz(ss) crystal lattice.

Effects of Solution Chemistry on the Hydrothermal Synthesis of Kaolinite

AbstractThe hydrothermal synthesis of kaolinite was examined in the Al2O3-SiO2-H2O system to study inhibitory effects of additional ions on the formation of kaolinite. Syntheses were carried out with amorphous starting materials and salt solutions of various concentrations in Teflon pressure vessels at 220°C for 5 days. The reaction products were characterized by XRD, IR, DTA-TG, NMR and TEM. In all of the runs using solutions with cation concentrations less than 0.001 M, no significant effect on the formation of kaolinite was observed. The inhibitory effect of the univalent cations Li+, Na+ or K+ was less than that of divalent cations such as Mg2+ or Ca2+. The addition of trivalent Fe3+ or excess Al3+ ions interfered with the formation of kaolinite significantly. Sulfate and acetate solutions interfered with the formation of kaolinite more than chlorides and nitrates. No crystalline product was obtained using a 1.0 M basic solution of carbonate or hydroxide. The addition of the lithium ion to the system affected the crystallization of kaolinite only slightly. The use of 0.1 M LiCl and LiNO3 solutions for the syntheses improved crystallization of kaolinite along the [001] direction.

Annealing effects and oxide structure in alumina tunnelling barriers

In this work the authors have studied changes in aluminium-oxide-aluminium tunnel barrier parameters that result from annealing at different temperatures with and without an applied potential difference. They identify two processes: irreversible increase in mean barrier height which takes place under all conditions and reversible changes in the internal field produced by applied bias. They explain the observations in terms of a detailed microscopic model involving excess Al3+ in the barrier region and field-induced movement of ions. The model implies that the oxide grows by the classic Cabrera-Mott mechanism with aluminium as the mobile species, and it sheds light on the nature of the oxide and of the interfacial regions in this technologically important system.

ChemInform Abstract: The Structure of Coprecipitated Aluminophosphate Catalyst Supports.

Abstract Porous aluminophosphates, which are useful as catalyst supports for polymerization, isomerization, or other hydrocarbon conversions, can be made by coprecipitation when an acidic solution of A13+ and PO43− ions is neutralized. When the P Al ratio in solution is equal to or greater than one, A1PO4 is obtained often as a crystalline material, leaving the excess phosphate in solution. However, when excess Al3+ is present in solution ( P Al ) then it also precipitates and the resulting support retains a similar P Al ratio to that in solution. In this study the structure of such aluminophosphates has been examined by means of X-ray diffraction and high resolution solid state NMR spectroscopy using both 27Al and 31P nuclei. These materials are not simple coprecipitated mixtures of A12O3 and A1PO4. In fact, no evidence for the presence of either species was detected. Instead they appear to be amorphous structures in which the phosphate is randomly dispersed, and the aluminum exists in one octahedral and several different tetrahedral environments. Results from ethylene polymerization over these catalysts also support this view.