氧化共沉淀法制备纳米级掺锑α—Fe2O3气敏陶瓷粉料

氧化共沉淀法制备纳米级掺锑α┐Ｆｅ２Ｏ３气敏陶瓷粉料王忠春＊＊刘尔生陈耐生＊黄金陵（福州大学化学系福州３５０００２）关键词α－Ｆｅ２Ｏ３陶瓷，锑掺杂气敏材料，纳米材料１９９６－１０－０５收稿，１９９７－０４－２２修回福建省科委资助项目＊＊现在上海硅酸...     

On-Line Separation and Preconcentration of Trace Metals in Biological Samples Using a Microcolumn Loaded with PAN-Modified Nanometer-Sized Titanium Dioxide,and Their Determination by ICP-AES

A flow injection analysis system incorporating a microcolumn of nanometer-sized TiO₂ loaded with 1-(2-pyridylazo)-2-naphthol (PAN) has been used for the development of an on-line multi-element method for simultaneous separation and preconcentration and subsequent determination of Cu²⁺, Co²⁺, Cr³⁺, Y³⁺, Yb³⁺ and Bi³⁺ by ICP-AES. Effects of pH, sample flow rate and volume, elution conditions, adsorption capacity and interfering ions on analyte recovery were examined. The adsorption capacity of nanometer-sized TiO₂ loaded with PAN was 4.73, 18.57, 3.81, 6.14, 4.52 and 20.35mgg^–1 for Cu²⁺, Cr³⁺, Y³⁺, Yb³⁺, Co²⁺ and Bi³⁺, respectively. The method has been applied to the analysis of trace elements in standard reference biological samples, and the results are in good agreement with the certified values.     

半导体纳米材料非线性光学性质的研究进展

半导体纳米材料由于具有重要的理论研究意义和潜在的巨大应用前景而成为当今理论和材料研究的特点，该文综述了半导体纳米材料非线性光学性质的研究进展。     

纳米MgTi2O5的制备

纳米ＭｇＴｉ_２Ｏ_５的制备彭子飞，冯贵武，汪国忠，田兴友，张伟，张立德（中国科学院固体物理研究所合肥２３００３１，安徽大学化学系合肥）关键词ＭｇＴｉ_２Ｏ_５，纳米材料，制备，共沉淀钛酸镁是高频低介电常数的电容陶瓷材料，以往合成ＭｇＴｉ２Ｏ５的方法都采...     

Electrostatic field and charge distribution in small charged dielectric droplets

The charge distribution in small dielectric droplets is calculated on the basis of continuum medium approximation. There are considered charged liquid spherical droplets of methanol in the range of nanometer sizes. The problem is solved by the following way. We find the free energy of some ion in dielectric droplet, which is a function of distribution of other ions in the droplet. The probability of location of the ion in some element of volume in the droplet is a function of its free energy in this element of volume. The same approach can be applied to other ions in the droplet. The obtained charge distribution differs considerably from the surface distribution. The curve of the charge distribution in the droplet as a function of radius has maximum near the surface. Relative concentration of charges in the vicinity of the center of the droplet does not equal to zero, and it is the higher, the less is the total charge of the droplet. According to the estimates the model is applicable if the droplet radius is larger than 10 nm.     

EMR study of magnetic inhomogeneities in crystalline bulk and nanometer-sized La0.7Ca0.3MnO3

Electron magnetic resonance (EMR) was studied on crystalline bulk and nanometer-sized samples of the same La_0.7Ca_0.3MnO₃ manganite compound aiming to compare their magnetic homogeneities. The results obtained show that single-crystalline bulk sample is less homogeneous than the nanocrystalline one. Except for higher homogeneity, the nanometer-sized sample also demonstrates a weaker magnetic anisotropy. As a result, well-pronounced coexistence of different magnetic phases (coexistence of ferromagnetic and paramagnetic resonance signals) is observed in the bulk sample, while it is absent in the nanocrystalline one. It is suggested that such strong difference is directly connected to the difference in structural state of the samples.     

Speciation of selenomethionine and selenocystine using online micro-column containing Cu(II) loaded nanometer-sized Al2O3 coupled with ICP-MS detection

A flow injection online speciation procedure by using micro-column packed with Cu(II) loaded nanometer-sized Al₂O₃ coupled to inductively coupled plasma mass spectrometry (ICP-MS) for the separation and determination of selenomethionine (SeMet) and selenocystine (SeCys₂) has been developed. The main factors affecting the separation and preconcentration of SeMet and SeCys₂ including pH value, sample flow rate, eluent concentration, eluent volume and flow rate, and interfering ions have been investigated. It was found that SeCys₂ could be selectively retained by micro-column packed with Cu(II) loaded nanometer-sized Al₂O₃ at pH 4.0, and the retained SeCys₂ could be eluted by 1.0 mol L⁻¹ HNO₃, while SeMet was not retained and passed through the micro-column directly at this pH. Both SeMet and SeCys₂ could be quantitatively adsorbed by the micro-column at pH 9.0, and the retained SeMet and SeCys₂ could be easily eluted with 1.0 mol L⁻¹ HNO₃. The content of SeMet was obtained by subtracting the SeCys₂ from the total content of seleno amino acids. With the enrichment factor of 7.8 and 7.7, the limits of detection (LODs) for SeMet and SeCys₂ were found to be 24 pg Se mL⁻¹ and 21 pg Se mL⁻¹, respectively. The relative standard deviations (RSDs) for SeCys₂ and SeMet with seven replicate determinations of 1.0 ng mL⁻¹ SeMet and SeCys₂, were 2.1% and 1.6%, respectively, the sampling frequency of 8 h⁻¹ was obtained. The proposed method was applied to the speciation of SeMet and SeCys₂ in selenized yeast, human urine and serum with satisfactory results.     

自催化还原制备微米和纳米级空心镍球的研究

提出了一种新型的制备超细空心金属镍粉的方法.通过FESEM,TEM和XRD衍射对该制备方法进行了研究,并考察了有关工艺参数对产物粒径和粒度分布的影响.研究认为,通过在胶核表面发生自催化还原反应,形成金属镍壳,同时胶核发生自分解,最后可得到空心金属镍球.控制反应物浓度和NaOH的配比可得到粒径均匀的镍球;通过调整这两个参数可得到粒度在微米或纳米尺度的空心镍球.     

热分解法制备纳米氧化钕

采用热分解法以2-硝基苯甲酸和硝酸钕为原料制备了纳米氧化钕微粉,利用正交设计对合成条件进行了优化,得出了最佳的合成条件,即原料2-硝基苯甲酸与硝酸钕物质的量比2.5∶1,溶液pH值5.5,反应时间3h、干燥时间8 h,在此条件下制得了平均粒径为15 nm的氧化钕微粉,并利用XRD和TEM对制得的纳米微粉进行了结构表征.     

Simultaneous on-line preconcentration and determination of trace metals in environmental samples using a modified nanometer-sized alumina packed micro-column by flow injection combined with ICP-OES

A novel organic reagent 3-(8-quinolinylazo)-4-hydroxybenzoic acid (QAHBA) was synthesized for chemically modified nanometer-sized alumina, and it was characterized with infrared spectrum and ¹H NMR spectra. By using modified nanometer-sized alumina as micro-column packing material, a new method of flow injection (FI) on-line preconcentration coupled to ICP-OES was developed for simultaneous determination of trace metals (Ag, Pd, Au, Ga, In and Nb) in geological and environmental samples. The effects of pH, sample flow rate, sample volume, elution and interfering ions on the recovery of the analytes have been investigated. Under the optimized operating conditions, the adsorption capacity of the modified nanometer-sized alumina for Ag, Pd, Au, Ga, In and Nb were found to be 5.1, 7.6, 17.7, 15.6, 8.1 and 12.3 mg g⁻¹, respectively. With 4 min preconcentration time and 24 s elution time, the enrichment factor was 10 and the sample frequency was 10 h⁻¹. The detection limits of this method for Ag, Pd, Au, Ga, In and Nb were 0.12, 0.44, 0.27, 0.19, 0.54 and 0.18 μg l⁻¹, respectively, while the R.S.D.s were 1.6, 2.3, 4.5, 1.6, 1.9 and 1.7% (n = 7, c = 50 ng ml⁻¹), respectively. The proposed method has been applied to the determination of these trace metals in geological-certified reference materials and natural water samples with satisfactory results.