TOF‐SIMS matrix effects in mixed organic layers in Ar cluster ion depth profiles

Matrix effects are crucial for analyses using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) in terms of quantitative analysis, depth profiling and imaging. It is often difficult to predict how co‐existing materials will influence each other before such analysis. However, matrix effects need to be curtailed in order to assume the appropriate amount of a target material in a sample. First, matrix effects on different types of organic mixed samples, including a sample composed of Irganox 1010 and Irganox 1098 (MMK sample) and another composed of Irganox 1010 and Fmoc‐pentafluoro‐L‐phenylalanine (MMF sample), were observed utilizing ToF‐SIMS and the dependence of the secondary ion polarity of the matrix effects on the same sample was evaluated. Next, the correction method for the ToF‐SIMS matrix effects proposed by Shard et al. was applied to a comparison of the positive secondary ion results to the negative ones. The matrix effects on the positive ion data in both samples were different from those on the negative ion data. The matrix effect correction method worked effectively on both the negative and positive depth profiles. Copyright © 2017 John Wiley & Sons, Ltd.     

Investigating Pb diffusion across buried interfaces in Pb(Zr0.2Ti0.8)O3 thin films via time‐of‐flight secondary ion mass spectrometry depth profiling

The diffusion of Pb through Pb(Zr_0.2Ti_0.8)O₃(PZT)/Pt/Ti/SiO₂/Si thin film heterostructures is studied by using time‐of‐flight secondary ion mass spectrometry depth profiling. The as‐deposited films initially contained 10 mol% Pb excess and were thermally processed at temperatures ranging from 325 to 700°C to promote Pb diffusion. The time‐of‐flight secondary ion mass spectrometry depth profiles show that increasing processing temperature promoted Pb diffusion from the PZT top film into the buried heterostructure layers. After processing at low temperatures (eg, 325°C), Pb⁺ counts were low in the Pt region. After processing at elevated temperatures (eg, 700°C), significant Pb⁺ counts were seen throughout the Pt layer and into the Ti and SiO₂ layers. Intermediate processing temperatures (400, 475, and 500°C) resulted in Pb⁺ profiles consistent with this overall trend. Films processed at 400°C show a sharp peak in PtPb⁺ intensity at the PZT/Pt interface, consistent with prior reports of a Pt₃Pb phase at this interface after processing at similar temperatures.     

XPS depth analysis of metal/polymer multilayer by vacuum electrospray droplet impact

Recently, the vacuum electrospray droplet impact (V‐EDI) was developed as a cluster ion beam source in our laboratory. In this work, V‐EDI was applied to polymers [polyimide (PI) and polycarbonate (PC)] and metal/polymer multilayer samples (Au/PI and Au/PC). We compared the etching performance of V‐EDI with that obtained by the conventional atmospheric‐pressure EDI (A‐EDI). The nonselective etching was observed for organic and also inorganic samples by V‐EDI as by A‐EDI. Etching rates for the metal and polymer analysis by V‐EDI were almost the same as those observed by A‐EDI. The interlayer components were clearly observed by V‐EDI for multilayer samples of Au and synthetic polymers. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantification of AES depth profiling data of polycrystalline Al films with Gaussian and non‐Gaussian surface height distributions

Sputtering‐induced roughness is the main distortional factor on the depth resolution of measured depth profiles, in particular, for sputtering of polycrystalline metals. Frequently, the surface height distribution of the sputtering‐induced roughness exhibits an asymmetrical feature. In such a case, a non‐Gaussian height distribution function (HDF) has to be applied for the quantification of a measured depth profile. By replacing the usually applied Gaussian HDF with that of an asymmetrical triangle in the Mixing‐Roughness‐Information depth model, measured Auger electron spectroscopy depth profiling data of the interface of polycrystalline Al films on Si are perfectly fitted. The asymmetric triangle height distributions obtained from the best fit are a reasonable approximation of the height distributions measured by atomic force microscopy. Copyright © 2013 John Wiley & Sons, Ltd.     

Improvement of transfection efficiency by galactosylated N-3-guanidinopropyl methacrylamide-co-poly (ethylene glycol) methacrylate copolymers

GalactosylatedN-3-guanidinopropylmethacrylamide-co-poly (ethylene glycol) methacrylate copolymers (galactosylated GPMA-co-PEGMA, GGP) were developed in order to promote transfection efficiency in the presence of serum in this report. First of all, the galactosylated PEGMA-co-GPMA copolymers were prepared via aqueous reversible addition – fragmentation chain transfer polymerization (RAFT) of poly (ethylene glycol) methacrylate (PEGMA) with long circulating chain segment and N-3-aminopropyl methacrylamide (APMA) followed by galactosylation and guanidinylation. After that, GGP/plasmid DNA complexes were examined by a dynamic light scattering and gel electrophoresis. It is showed that GGP copolymers have effective condensing ability. The cytotoxicity of GGP was measured by MTT assay. It was found that all the GGP/plasmid DNA complexes had less cytotoxic effects on HepG2 cells than HeLa cells, and the galactose groups reduced the cytotoxicity of complexes with high charge ratios to HepG2 cells. Finally, the transfection efficiency of the galactosylated PEGMA-co-GPMA copolymers was investigated by luciferase expression assay. The results revealed that the copolymers with galactose groups more than 5.83% could induce the asialoglycoprotein (ASGP) receptor mediated transfection, which improved the transfection efficiency in target cells. The GPMA-co-PEGMA copolymers with 54.57% hydrophilic chain segment PEG should prevent the aggregation of protein on the GGP/pDNA complexes, and GGP with 7.94% galactose graft exhibited the highest transfection in the presence of serum.     

侵蚀滑移计算方法的改进

将二维拉格朗日有限元程序LTZ-2D中侵蚀滑移的计算方法进行了改进.将单元侵蚀判断标准由单一的累积塑性应变标准改为累积塑性应变、单元的硬化因子以及单元相对于滑移线的变形角度的综合判断标准.同时,利用本文的改进算法对侵彻问题进行了数值模拟.计算结果显示,采用改进后的侵蚀滑移计算方法不仅很好地显示了侵彻过程中弹靶的接触面,...     

砂土中锚板抗拔性能试验研究

运用自行研制开发的试验装置和数据采集系统,对锚板在砂土中的抗拔性能进行了试验研究。分析了锚板在松砂和密砂两种情况下抗拔力和位移的关系曲线特征,研究了不同埋深率下抗拔力和破坏系数的变化规律,并根据抗拔力与破坏系数随埋深率的变化趋势得到了松砂和密砂状态下的临界埋深率。试验结果表明,密度对砂土中锚板的抗拔性能有非常大的影响,增加砂土的密实度可以大幅度提高锚板的抗拔承载力并显著减小锚板的位移变形。增加锚板的埋置深度同样也可以大幅提高锚板的抗拔承载力,但抗拔承载力的增加幅度受临界埋深率的限制,临界埋深率随密度增加有增大的趋势。该试验结果可为锚板上拔预测模型的建立及设计提供参考依据。     

Isotope abundance ratio measurements using femtosecond laser ablation ionization mass spectrometry

Accurate isotope ratio measurements are of high importance in various scientific fields, ranging from radio isotope geochronology of solids to studies of element isotopes fractionated by living organisms. Instrument limitations, such as unresolved isobaric inferences in the mass spectra, or cosampling of the material of interest together with the matrix material may reduce the quality of isotope measurements. Here, we describe a method for accurate isotope ratio measurements using our laser ablation ionization time‐of‐flight mass spectrometer (LIMS) that is designed for in situ planetary research. The method is based on chemical depth profiling that allows for identifying micrometer scale inclusions embedded in surrounding rocks with different composition inside the bulk of the sample. The data used for precise isotope measurements are improved using a spectrum cleaning procedure that ensures removal of low quality spectra. Furthermore, correlation of isotopes of an element is used to identify and reject the data points that, for example, do not belong to the species of interest. The measurements were conducted using IR femtosecond laser irradiation focused on the sample surface to a spot size of ~12 μm. Material removal was conducted for a predefined number of laser shots, and time‐of‐flight mass spectra were recorded for each of the ablated layers. Measurements were conducted on NIST SRM 986 Ni isotope standard, trevorite mineral, and micrometer‐sized inclusions embedded in aragonite. Our measurements demonstrate that element isotope ratios can be measured with accuracies and precision at the permille level, exemplified by the analysis of B, Mg, and Ni element isotopes. The method applied will be used for in situ investigation of samples on planetary surfaces, for accurate quantification of element fractionation induced by, for example, past or present life or by geochemical processes.     

In‐Depth TEM Investigation on Structural Inhomogeneity within a Primary LixNi0.835Co0.15Al0.015O2 Particle: Origin of Capacity Decay during High‐Rate Discharge

The structural stability of cathode materials during electrochemical reactions, in particular, under high‐rate discharge, is pertinent to the design and development of new electrode materials. This study investigates the structural inhomogeneity that develops within a single LiNi_0.835Co_0.15Al_0.015O₂ (NCA83) particle during a fast discharging process under different cutoff voltages. Some of the NCA83 particles discharged from a high cutoff voltage (4.8 V) developed surface areas in which the layered structure was recovered, although the interiors retained the degraded spinel structure. These micro‐ and nano‐scale structural inversions from high cutoff voltage seem highly correlated with structural evolutions in the initial charged state, and may ultimately degrade the cycling stability. This study advances understanding of the structural inhomogeneity within primary particles during various electrochemical processes and may facilitate the development of new Ni‐rich cathode materials.     

Enzyme‐Triggered Disassembly of Perylene Monoimide‐based Nanoclusters for Activatable and Deep Photodynamic Therapy

Photodynamic therapy (PDT) exhibits great potential for cancer therapy, but still suffers from nonspecific photosensitivity and poor penetration of photosensitizer. Herein, a smart perylene monoimide‐based nanocluster capable of enzyme‐triggered disassembly is reported as an activatable and deeply penetrable photosensitizer. A novel carboxylesterase (CE)‐responsive tetrachloroperylene monoimide (P1) was synthesized and assembled with folate‐decorated albumins into a nanocluster ( FHP ) with a diameter of circa 100 nm. Once P1 is hydrolyzed by the tumor‐specific CE, FHP disassembles into ultrasmall nanoparticles (ca. 10 nm), facilitating the deep tumor penetration of FHP . Furthermore, such enzyme‐triggered disassembly of FHP leads to enhanced fluorescence intensity (ca. 8‐fold) and elevated singlet oxygen generation ability (ca. 4‐fold), enabling in situ near‐infrared fluorescence imaging and promoted PDT. FHP permits remarkable tumor inhibition in vivo with minimal side effects through imaging‐guided, activatable, and deep PDT. This work confirms that this cascaded multifunctional control through enzyme‐triggered molecular disassembly is an effective strategy for precise cancer theranostics.