Silver-doped calcium phosphate nanopowders prepared by electrostatic spraying

Silver-doped calcium phosphate nanopowders were successfully prepared by the cost-effective electrostatic spray-pyrolysis process. The properties of the silver-doped nanopowder annealed at 500°C for 30 min were investigated through X-ray diffraction analysis, field emission scanning electron microscope, and Fourier transform infrared spectroscopy. The silver-doped nanopowders with 70–90 nm particle size showed an antibacterial performance against Escherichia coli.     

火焰原子吸收光谱法测定钙的样品预处理方法的应用进展

对近年来国内火焰原子吸收光谱法测定钙的样品预处理方法的进展进行了评述,内容包括干灰化法、酸消解法、微波消解和其他方法。     

Bioactive calcium phosphate coating formed on micro-arc oxidized magnesium by chemical deposition

In order to improve the bioactivity of the micro-arc oxidized magnesium, a calcium phosphate coating was formed on the surface of micro-arc oxidized magnesium using a chemical method. The microstructures of the substrate and the calcium phosphate coating before and after the simulated body fluids (SBF) incubation were characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy and scanning electron microscopy. The results showed that the calcified coating was composed of calcium deficient hydroxyapatite (HA) and dicalcium phosphate dihydrate (DCPD). After SBF incubation, some new apatite formation on the calcified coating surface from SBF could be found. The corrosion behaviours of the samples in SBF were also investigated by potentiodynamic polarization curves and immersion tests. The results showed that calcium phosphate coating increased the corrosion potential, and decreased the hydrogen gas release.     

VUV-UV excited luminescent properties of LnCa4O(BO3)3:RE (Ln=Y, La, Gd; Re=Eu, Tb, Dy, Ce)

Calcium lanthanide oxyborate doped with rare-earth ions LnCa₄O(BO₃)₃:RE³⁺ (LnCOB:RE, Ln=Y, La, Gd, RE=Eu, Tb, Dy, Ce) was synthesized by the method of solid-state reaction at high temperature. Their fluorescent spectra were measured from vacuum ultraviolet (VUV) to visible region at room temperature. Their excitation spectra all have a broadband center at about 188 nm, which is ascribed to host absorption. Using Dorenbos’ and Jφrgensen's work [P. Dorenbos, J. Lumin. 91 (2000) 91, R. Resfeld, C.K. Jφrgensen, Lasers and Excite States of Rare Earth [M], Springer, Berlin, 1977, p. 45], the position of the lowest 5d levels E(Ln,A) and charge transfer band E_ct were calculated and compared with their excitation spectra.Eu³⁺ and Tb³⁺ ions doped into LnCOB show efficient luminescence under VUV and UV irradiation. In this system, Ce³⁺ ions do not show efficient luminescence and quench the luminescence of Tb³⁺ ions when Tb³⁺ and Ce³⁺ ions are co-doped into LnCOB. GdCOB doped with Dy³⁺ shows yellowish white light under irradiation of 254 nm light for the reason that Gd³⁺ ions transfer the energy from itself to Dy³⁺. Because of the existence of Gd³⁺, the samples of GdCOB:RE³⁺ show higher excitation efficiency than LaCOB:RE³⁺ and YCOB:RE³⁺, around 188 nm, which indicates that the Gd³⁺ ions have an effect on the host absorption and can transfer the excitation energy to the luminescent center such as Tb³⁺, Dy³⁺ and Eu³⁺.     

卫星搭载紫花苜蓿种子的拉曼光谱分析

为了了解卫星搭载对紫花苜蓿种子化学特性的影响,揭示空间诱变机理,文章利用傅里叶变换拉曼光谱法对卫星搭载当代的紫花苜蓿种子进行了研究。结果表明,与地面对照相比,飞行组在358和553 cm-1处的峰强增加,814,1 122,1 531,1 743 cm-1处的峰强降低,通过谱带归属发现,增强的358和553 cm-1分别与DNA和Ca2+有关,降低的4个峰与糖类、脂类有关。这说明经过卫星搭载后,苜蓿种子的DNA和Ca2+的量出现增加趋势,糖类与脂类的量出现降低趋势。其可能原因是(1)种子主动修复诱变产生的DNA损伤时,消耗部分贮存能量所致;(2)空间飞行过程中的超重导致种子细胞内的Ca2+ 浓度升高;(3)飞行因子导致种子提前萌发,DNA大量合成与复制,种子储藏的能量提前降解消耗。这一结果将对苜蓿空间诱变机理研究有重要参考价值。     

Peroxyoxalate-chemiluminescence of Tinopal CBS as a commercially important optical brightener: Mechanistic study and quantification

The peroxyoxalate-chemiluminescence arising from reaction of bis(2,4,6-trichlorophenyl)oxalate with hydrogen peroxide in the presence of a brightener Tinopal CBS (2,2′-((1,1′-biphenyl)-4,4′-diyldi-2.1-ethenediyl)bisbenzene sulfonic acid, disodium salt) has been studied. The relationship between the chemiluminescence intensity and concentrations of bis(2,4,6-trichlorophenyl)oxalate, sodium salicylate (as catalyst), hydrogen peroxide and Tinopal CBS is reported. The chemiluminescence parameters including intensity at maximum chemiluminescence, time at maximum intensity, total light yield, theoretical maximum level of intensity and pseudo-first-order rate constants for the rise and fall of the chemiluminescence burst (k_r and k_f) were evaluated from computer fitting of the resulting intensity-time plots. The activation parameters E_a, ΔH^‡, ΔS^‡ and ΔG^‡ for the rise and fall steps were evaluated from the temperature dependence of k_r and k_f values. The results were discussed in terms of chemically initiated electron transfer between a reactive intermediate and Tinopal CBS as fluorescence activator. A possible mechanism involving dioxetanone derivatives as intermediates is proposed. Since there is a linear relationship between reciprocal of chemiluminescence intensity and reciprocal of fluorescer concentration, an analytical method based on partial least squares (PLS) regression was proposed for quantitative determination of Tinopal CBS. Satisfactory results were obtained with percent relative prediction error (RPE%) of 2.52 and detection limit of 2.7×10⁻⁵ M.     

Inverted Micellar Enhanced Organic Peroxyoxalate Chemiluminescence

The use of neutral surfactant polyoxyethylene (9) dodecyl ether (AEO9) and polyoxyethylene (10) hexylphenol ether (TX-10) as an additive to enhance the chemiluminescence of peroxyoxalate reaction using bis(2-butoxycarbonyl-3,4,6-trichlorophenyl) oxalate (BBTPO) and hydrogen peroxide as the energy source in organic media with 9,10-diphenylanthracene as a fluorophore had been investigated. The oxidation of BBTPO in both AEO9 and TX-10 inverted micelles produced significantly improved intensity and efficiency of the chemiluminescence relative to that in normal organic media. It was found that in AEO9 and TX-10 inverted micellar media the enhancement of chemiluminescence was mainly due to the improvement of the reaction excitation efficiencies, but only slightly contributed by the increase of the fluorescence efficiency.     

The Synthesis and Characterizations of Calcium Phosphate Nanoparticles via β‐Cyclodextrin,Poly(oxyethylene)5 Nonyl Phenol Ether and Cyclohexane Medium

In this work, the calcium phosphate nanoparticles have been produced by new reverse micro emulsion method containing β‐cyclodextrin, poly(oxyethylene)₅ nonyl phenol ether and cyclohexane. Scanning electron microscope, transmission electron microscope, fourier transform infrared spectroscope and X‐ray diffraction were used to characterize the particles. The sizes of the nanoparticles were identified between 70‐80 nm. In conclusion, these results suggested that the developed reverse micro emulsion system based nanoparticles seem to be a promising formulation for calcium phosphate nanoparticles synthesis and it has immense potential in delivery of drugs and vaccines.     

Calcium Ion-Induced Stabilization and Refolding of Agkisacutacin from <Emphasis Type="Italic">Agkistrodon Acutus</Emphasis> Venom Studied by Fluorescent Spectroscopy

Agkisacutacin isolated from the venom of Agkistrodon acutus is a coagulation factor IX / coagulation factor X-binding protein with marked anticoagulant- and platelet-modulating activities. Ca²⁺ ion-induced stabilization and refolding of Agkisacutacin have been studied by following fluorescent measurements. Ca²⁺ ions not only increase the structural stability of agkisacutacin against GdnHCl denaturation, but also induce its refolding. The GdnHCl-induced unfolding of the apo-agkisacutacin and the purified agkisacutacin is a single-step process with no detectable intermediate state. Ca²⁺ ions play an important role in the stabilization of the structure of agkisacutacin. Ca²⁺-stabilized agkisacutacin exhibits higher resistance to GdnHCl denaturation than the apo-agkisacutacin. It is possible to induce refolding of the unfolded apo-agkisacutacin merely by adding 1 mM Ca²⁺ ions without changing the concentration of the denaturant. The kinetic result of Ca²⁺-induced refolding provides evidences for that agkisacutacin consists of at least two refolding phases and the first phase of Ca²⁺-induced refolding should involve the formation of the compact Ca²⁺-binding site regions, and subsequently, the protein undergoes further conformational rearrangements to form the native structure.