Investigation of PL properties of C-doped SiO2/Si samples after high energy Pb ion irradiation

Amorphous SiO2 thin films with about 400-500 nm in thickness were thermally grown on single crystalline silicon. These SiO2/Si samples were firstly implanted at room temperature (RT) with 100 keV carbon ions to 2.0 x 10(17),5.0 X 10(17) or 1.2 x 10(18) ions/cm(2), then irradiated at RT by 853 MeV Pb ions to 5.0 x 10(11), 1.0 X.10(12) 2.0 x 10(12) or 5.0 x 10(12) ions/cm(2), respectively. The variation of photoluminescence (PL) properties of these samples was analyzed at RT using a fluorescent spectroscopy. The obtained results showed that Pb-ion irradiations led to significant changes of the PL properties of the carbon ion implanted SiO2 films. For examples, 5.0 x 10(12) Pb-ions/cm(2) irradiation produced huge blue and green light-emitters in 2.0 x 10(17) C-ions/cm(2) implanted samples, which resulted in the appearance of two intense PL peaks at about 2.64 and 2.19 eV. For 5.0 x 10(17) carbon-ions/cm(2) implanted samples, 2.0 x 10(12) Pb-ions/cm(2) irradiation could induce the formation of a strong and wide violet band at about 2.90 eV, whereas 5.0 x 10(12) Pb-ionS/cm(2) irradiation could,create double peaks of light emissions at about 2.23 and 2.83 eV. There is no observable PL peak in the 1.2 x 10(18) carbon-ions/cm(2) implanted samples whether it was irradiated with Pb ions or not. All these results implied that special light emitters could be achieved by using proper ion implantation and irradiation conditions, and it will be very useful for the synthesis of new type Of SiO2-based light-emission materials.

Effects of annealing on the photoluminescence of He ion implanted sapphire after 230-MeV Pb ion irradiation

Single crystal sapphire (Al2O3) samples implanted with 110 keV He and irradiated at 320 K by Pb-208(27), ions with energy of 1.1 MeV/u to the fluences ranging from 1 X 10(12) to 5 X 10(14) ion/cm(2) and subsequently annealed at 600, 900 and 1100 K. The obtained PL spectra showed that emission peaks centred at 375, 390, 413, and 450 nm appeared in irradiated samples. The peak of 390 ran became very intense after 600 K annealing. The peak of 390 nm weakened and 510 nm peak started to build up at 900 K annealing, the peak of 390 nm vanished and 510 nm peak increased with the annealing temperature rising to 1100 K. Infrared spectra showed a broadening of the absorption band between 460 cm(-1), and 510 cm(-1) indicating strongly damaged regions being formed in the Al2O3 samples and position shift of the absorption band at 1000-1300 cm(-1) towards higher wavenumber after Pb irradiation.

Pb isotope shifts in the relativistic mean field theory

The ground state properties of the Pb isotopic are studied by using the axially deformed relativistic mean field (RMF) calculation with the parameter set TM1. The pairing correlation is treated by the BCS method and the isospin dependent pairing force is used. The 'blocking' method is used to deal with unpaired nucleons. The theoretical results show that the relativistic mean field theory with non-linear self-interactions of mesons provides a good description of the binding energy and neutron separation energy. The present paper focus on the physical mechanism of the Pb isotope shifts.

Photoluminescence of inert-gas ion implanted sapphire after 230-MeV Pb ion irradiation

In the present work the photoluminescence (PL) character of sapphire implanted with 110-keV He, Ar or Ne ions and subsequently irradiated with 230-MeV Pb was studied. The implantation was performed at 320 and 600 K using fluences from 5.0 x 10(16) to 2.0 x 10(17) ions/cm(2). The Pb ion irradiation was carried out at 320 K. The obtained PL spectra showed peaks at 375, 413 and 450 nm with maximum intensity at an implantation fluence of 5.0 x 10(16) ions/cm(2) and a new peak at 390 nm appeared in the He-implanted and subsequently Pb-irradiated samples. Infrared spectra showed a broadening of the absorption band between 460 and 510 nm indicating strongly damaged regions formed in the Al2O3 samples. A possible PL mechanism is discussed.

Electron emission induced by the interaction of highly charged ions Pb-207(q+) (24 <= q <= 36) with solid surface of Si(110)

The electron emission induced by highly charged ions Pb-207(q+) (24 <= q <= 36) interacting with Si(110) surface is reported. The result shows that the electron emission yield Y has a strong dependence on the projectile charge state q, incidence angle psi and impact energy E. In fitting the experimental data we found a nearly 1/tan psi dependence of Y. Theoretical analysis shows that these processes are closely related to the process of potential electron emission based on the classical over-the-barrier model.

Cd、Pb、Cu、Zn、As复合污染在农田生态系统的迁移动态研究

１９９０—１９９５年中国科学院生态网站联网研究中，在４个生态站对重金属复合污染（Ｃｄ、Ｐｂ、Ｃｕ、Ｚｎ、Ａｓ）进行了田间迁移动态实验研究，表明３年来表土中重金属元素含量缓慢下降，输出量最大支出项目为从表层向下迁移量可比作物地上部分带去量高出几十至数百倍，为污染土壤防治工作中淋洗技术运用指出了应用前景．

Cd~(2+)、Pb~(2+)在根际和非根际土壤中的吸附-解吸行为

采用1次平衡法对Cd2+、Pb2+在小麦根际和非根际土壤中的吸附-解吸行为进行比较研究.结果表明,根际土对Cd2+和Pb2+的吸附能力高于非根际土,2类土壤对Cd2+的吸附等温线与Freundlich方程有较好的拟合性,Pb2+的等温吸附过程可由Langmuir方程与Freundlich方程来描述.双常数方程是描述根际、非根际土Cd2+和Pb2+吸附动力学行为的最优模型,其次为Elovich方程,最差模型是一级动力学方程.Cd2+、Pb2+的解吸存在滞后现象,相比于非根际土,根际土吸附态Cd2+、Pb2+的解吸率更低,Cd2+、Pb2+的解吸量与其初始吸附量之间的关系符合2次幂方程.2类土壤Cd2+、Pb2+的解吸速率随重金属初始浓度的增加而增加,随解吸时间的延长而不断降低.描述根际和非根际土Cd2+、Pb2+的解吸动力学过程的最优模型均为双常数方程,其次为Elovich方程,一级动力学方程拟合效果不佳.

Cd-Pb复合污染条件下3种花卉植物的生长反应及超积累特性研究

采用水培实验方法,研究了3种耐性较强的花卉植物在Cd-Pb复合污染条件下的生长反应及可能的超积累特性.结果表明,花卉植物种不同,其对复合污染的生长反应也不同,它们的耐性大小顺序为蜀葵(AlthaearoseaCav.)>凤仙花(ImpatiensBalsaminaL.)>金盏菊(CalendulaofficinalisL.);Cd对植物生长的影响较大、Pb的影响相对较小.3种花卉植物对重金属的积累量都是根部大于地上部;蜀葵对重金属Cd具有很强的耐性和积累性,在Cd、Pb复合污染条件下极具植物修复的潜力.对于这3种花卉植物,Cd-Pb相互作用效应与多种因素有关,包括重金属之间的浓度组合、植物种和植株部位等,表现得极为复杂,不仅仅是单纯的加和、拮抗或协同作用.

平菇菌丝体对Cd、Pb及其复合污染的生长与富集响应

在PDA平板培养条件下,研究Cd、Pb及其复合污染对平菇菌丝体生长的影响以及平菇菌丝体对生长基质中Cd、Pb的生物富集作用.结果表明,在实验浓度范围内,菌丝生长势、菌落直径和菌丝体干重等均随着重金属浓度的增大而减弱(小)或降低.平菇菌丝体对Cd、Pb均具有生物富集作用,并且随着重金属浓度的增大菌丝体中重金属含量逐渐增大.Cd、Pb复合污染能促进平菇菌丝体对Pb的吸收,而抑制对Cd的吸收.

土壤有效态Pb和Cd与大蒜吸收Pb和Cd的关系

通过对大蒜的重金属添加土培试验,采用DTPA(二乙基胺五乙酸)为有效态铅、镉提取剂,对受试土壤进行浸提检测,分析Pb和Cd在大蒜不同部位的吸收、积累及其与土壤中有效态含量的相关性。根据GB 2762-2005《食品中污染物限量标准》中对食品中Pb、Cd的限量要求,初步确定了本试验条件下,土壤中重金属Pb、Cd有效态的临界值,并以此临界点评价该种土壤中Pb、Cd对大蒜的潜在污染。

细河流域土壤中Hg、Cd、Pb和Zn含量的空间分布特征

利用地统计学方法研究了沈阳市细河流域表层土壤中Hg、Cd、Pb和Zn含量的空间结构及其分布特征。结果表明,土壤中Hg、Cd、Pb和Zn的平均含量均高于其背景值;土壤Cd和Zn含量属中等程度的空间相关,Hg和Pb属于空间弱相关,其空间变异均为随机性因素和结构性因素共同作用的结果,但Cd和Zn含量主要受结构性因素影响,而Hg和Pb主要受随机性因素影响。土壤中Hg、Cd、Pb和Zn空间分布特征表明,4种重金属含量在上游较高,顺流而下含量明显下降;土壤中Hg和Pb含量最大值在四方台地区,Cd和Zn含量最大值分布在甘官和富官一带。细河流域土壤Hg、Cd、Pb和Zn含量空间分异是污水灌溉、固体废弃物堆放、农业生产及交通尾气等因素综合作用的结果。

Stripping voltammetric determination of Pb(II) and Cd(II) based on the multiwalled carbon nanotubes-Nafion-bismuth modified glassy carbon electrodes

In this work, a new method for the simultaneous determination of Pb(II) and Cd(II) on the multiwalled carbon nanotubes (MWNT)-Nafion-bismuth modified glassy carbon electrode (GCE) using square-wave anodic stripping voltammetry has been studied. Scanning electron microscopy was used to investigate the characteristics of the MWNT-Nafion-bismuth modified GCE.

Sensitive determination of Cd and Pb by differential pulse stripping voltammetry with in situ bismuth-modified zeolite doped carbon paste electrodes

Here we investigated the analytical performances of the bismuth-modified zeolite doped carbon paste electrode (BiF-ZDCPE) for trace Cd and Pb analysis. The characteristics of bismuth-modified electrodes were improved greatly via addition of synthetic zeolite into carbon paste. To obtain high reproducibility and sensitivity, optimum experimental conditions for bismuth deposition Were Studied.

Combining chemical reduction with an electrochemical technique for the simultaneous detection of Cr(VI), Pb(II) and Cd(II)

This work herein reports the approach for the simultaneous determination of heavy metal ions including cadmium (Cd(II)), lead (Pb(II)), and chromium (Cr(VI)) using a bismuth film electrode (BFE) by anodic stripping voltammertry (ASV). The BFE used was plated in situ. Due to the reduction of Cr(VI) with H2O2 in the acid medium, on one hand, the Cr(III) was produced and Cr(VI) was indirectly detected by monitoring the content of Cr(III) using square-wave ASV. On the other hand, Pb(II) was also released from the complex between Pb(II) and Cr(VI). Furthermore, the coexistence of the Cd(II) was also simultaneously detected with Pb(II) and Cr(VI) in this system as a result of the formation of an alloy with Bi. The detection limits of this method were 1.39 ppb for Cd(II), 2.47 ppb for Pb(II) and 5.27 ppb for Cr(VI) with a preconcentration time of 120 s under optimal conditions (S/N = 3), respectively. Furthermore, the sensitivity of this method can be improved by controlling the deposition time or by using a cation-exchange polymer (such as Nafion) modified electrode.