Simplification of Ink Dating for Forensic Analysis by Thermal Microdesorption Gas Chromatography–Mass Spectrometry

A simplified procedure for obtaining measurements useful for ink dating is presented for forensic analysis. A thermal microdesorption device was employed with gas chromatography–mass spectrometry (GC-MS). The release of phenoxyethanol from the ink entries on paper was studied at several temperatures during a single analysis. A separate thermal desorption unit was not required. Two methods measuring the amount of phenoxyethanol liberated at four temperatures and two temperatures were proposed. The effect of heating of ink samples to 70?°C for 30?minutes applied to fresh and old samples was studied. An illustration how to distinguish between fresh and old samples by the analysis of the same ink entry after the time period of two months is provided.     

Does power ultrasound affect Nafion® dispersions?

The effect of low frequency power ultrasound on Nafion® ionomer used for fabricating proton exchange membrane fuel cell (PEMFC) and water electrolyzer (PEMWE) catalyst inks was investigated. In this study, a series of Nafion® dispersions having three concentrations (10, 5, and 2.5% w/v) were studied under various irradiation durations (t_us), at fixed ultrasonic frequency (f = 42 kHz) and ultrasonic power (P > 2 W), under either controlled or unregulated bulk solution temperature conditions using a laboratory ultrasonic cleaning bath. Viscosity (η), thermal degradation, and glass transition temperature (T_g) for all Nafion® dispersion samples was measured and compared to untreated Nafion® samples. In our conditions, it was found that power ultrasound lowered the viscosity of all tested Nafion® dispersion samples; whilst thermogravimetric and differential scanning calorimetry analyses showed that for all ultrasonically irradiated samples, a negligible overall polymer degradation and no obvious change in T_g was observed under controlled and unregulated bulk temperature conditions. It was found that it is possible that acoustic cavitation causes depolymerisation followed by a polymerisation initiation step during ultrasonication. By comparing the ultrasonically treated and high-shear mixed samples, it was also observed that acoustic and hydrodynamic cavitation played an important role in the reduction of dispersion viscosity.     

Use of copper ink for fabricating conductive electrodes and RFID antenna tags by screen printing

We have synthesized nano-sized copper hydroxide powder and copper (II) neodecanoate complex that can be decomposed to form copper metal films. Copper conductive ink was then prepared by mixing the powder and complex with a binder in terpineol. The lowest resistivity of 12.5 μΩ cm and 5B level of adhesion strength were obtained with 5% addition of epoxy resin as a binder. The copper ink was then applied to fabricate a loop-type RFID antenna tag and the performance of the antenna was compared with that of conventional copper-etched and silver-paste antenna. The fabricated RFID antenna showed comparable performance to the conventional RFID antenna.     

圆珠笔油墨字迹色痕的高效液相色谱分析方法

采用正交实验设计法从多种流动相体系中优选出了圆珠笔油墨字迹色痕的高效液相色谱分析条件。在此条件下分析了105种市售的不同生产厂家和牌号蓝色圆珠笔油墨的字迹色痕,并依据有色成分的差异将这些同色油墨分成了6大类,考察了纸张的影响因素及在该条件下分析结果的重现性和精密度,为进一步分析鉴定圆珠笔字迹色痕的形成时间提供了有利条件。     

Micro-spectrochemical analysis of document paper and gel inks by laser ablation inductively coupled plasma mass spectrometry and laser induced breakdown spectroscopy

Current methods used in document examinations are not suitable to associate or discriminate between sources of paper and gel inks with a high degree of certainty. Nearly non-destructive, laser-based methods using laser induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were used to improve the forensic comparisons of gel inks, ballpoint inks and document papers based on similarities in elemental composition. Some of the advantages of these laser-based methods include minimum sample consumption/destruction, high sensitivity, high selectivity and excellent discrimination between samples from different origins. Figures of merit are reported including limits of detection, precision, homogeneity at a micro-scale and linear dynamic range. The variation of the elemental composition in paper was studied within a single sheet, between pages from the same ream, between papers produced by the same plant at different time intervals and between seventeen paper sources produced by ten different plants. The results show that elemental analysis of paper by LIBS and LA-ICP-MS provides excellent discrimination (> 98%) between different sources. Batches manufactured at weekly and monthly intervals in the same mill were also differentiated. The ink of more than 200 black pens was analyzed to determine the variation of the chemical composition of the ink within a single pen, between pens from the same package and between brands of gel inks and ballpoint inks. Homogeneity studies show smaller variation of elemental compositions within a single source than between different sources (i.e. brands and types). It was possible to discriminate between pen markings from different brands and between pen markings from the same brand but different model. Discrimination of ~ 96–99% was achieved for sets that otherwise would remain inseparable by conventional methods. The results show that elemental analysis, using either LA-ICP-MS or LIBS, provides an effective, practical and robust technique for the discrimination of document paper and gel inks with minimum mass removal (9–15 μg) and minimum damage to the document's substrate.     

油墨组分比例预测模型与方法

因光学特性(吸收系数与散射吸收)与组分比例不呈严格的线性关系,基于K-M理论的配色模型无法保证比例预测精度,针对上述问题,建立了油墨组分比例预测模型与方法。首先利用与组分比例具有强线性相关性的特征波长处的光谱反射率倒数值替换K-M配色理论中的吸收系数与散射系数,引入非线性项,构建油墨混合呈色模型;然后在此基础上建立油墨组分比例预测模型。以两组二元基色油墨混合样本为例,对提出的油墨组分比例预测模型及方法进行验证。实验结果表明,文中方法可预测获得与真实结果较为接近的组分比例,两组实验样本的预测平均偏差分别为1.57%和3.6%,可为目标样油墨组分比例预测提供一种新的方法。     

The unraveling of a polymer chain in a strong extensional flow

By assuming that in a strong extensional flow a polymer molecule in dilute solution is quickly driven into a folded or kinked state in which drag and entropic elastic forces dominate over the Brownian force, we derive kink dynamics equations that describe the unraveling of the molecule in the extensional flow. Solving these equations numerically, we find that although the ends of the chain move, on average, affinely in the flow field until the chain is unfolded to about 1/3 of its fully extended length, large viscous stresses are produced because the solvent must flow around nonextending strands of polymer that lie between neighboring kinks. These predictions are compared with available experimental data and with other theoretical models.     

Stainless steel cloth modified by carbon nanoparticles of Chinese ink as scalable and high-performance anode in microbial fuel cell

Microbial fuel cells(MFCs) have various potential applications.However,anode is a main bottleneck that limits electricity production performance of MFCs.Herein,we developed a novel anode based on a stainless steel cloth(SC) modified with carbon nanoparticles of Chinese ink(Cl) using polypyrrole(PPy)as a building block(PPy/Cl/SC).After modification,PPy/Cl/SC showed a 30% shorten in start-up time(36.4 ± 3.3 h vs.52.3± 1.8 h),33% increase in the maximum current(12.4 ± 1.4 mA vs.9.3± 0.95 mA),and2.3 times higher in the maximum power density of MFC(61.9 mW/m~2 vs.27.3 mW/m~2),compared to Ppy/SC.Experimental results revealed that carbon nanoparticles were able to cover SC uniformly,owing to excellent dispersibility of carbon nanoparticles in Cl.The attachment of carbon nanoparticles formed a fluffy layer on SC increased the electrochemically-active surface area by 1.9 times to 44.5 cm2.This enhanced electron transfer between the electrode and bacteria.Further,embedding carbon nanoparticles into the PPy layer significantly improved biocompatibility as well as changed functional group contents,which were bene ficial to bacteria adhesion on electrodes.Taking adva ntage of high mechanical strength and good conductivity,a large-size PPy/Cl/SC was successfully prepared(50×60 cm~2)demonstrating a promising potential in practical applications.This simple fabrication strategy offers a new idea of developing low cost and scalable electrode materials for high-performance energy harvesting in MFCs.     

NaYF4∶Yb3+/Eu3+上转换发光微纳粒子在防伪识别中的应用研究

稀土掺杂上转换发光微纳粒子在防伪识别方面有着巨大的应用前景。首先采用水热合成法制备了NaYF₄∶Yb3+/Eu3+微纳粒子,通过X射线衍射(XRD)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)对NaYF₄∶Yb3+/Eu3+微纳粒子的尺寸、形貌和结晶度等方面进行了研究,同时使用980 nm的泵浦源对NaYF₄∶Yb3+/Eu3+微纳粒子的发光性能进行了分析;其次将NaYF₄∶Yb3+/Eu3+微纳粒子与酒精按一定比例混合制成丝网印刷剂,结合网络定制的丝网模版在纸上印制了不同字样的防伪图案,风干后将字样暴露在980 nm的激光辐照下,并使用相机对其进行成像研究;最后将印制的字样分成两部分,一部分保存在室内25 ℃恒温环境下,另外一部分保存在冬季一月份室外自然环境下,保存地点均为西安市,一周后对不同环境下的字样再次使用完全相同的实验仪器进行成像测试。实验及测试结果显示,NaYF₄∶Yb3+/Eu3+微纳粒子与NaYF₄标准卡的衍射峰完全一致,没有其他杂质产生;实验合成的微纳粒子外形均为六方体,且平均长度和横截宽度分别为209和175 nm,微纳晶体表面光滑、无缺陷、未弯曲、结晶度较高、分散性较好,电子衍射环与NaYF₄∶Yb3+/Eu3+微纳粒子的312,300和302晶面相对应;NaYF₄∶Yb3+/Eu3+微纳粒子受掺杂离子的影响,在不同的能级跃迁下分别产生蓝、绿、黄、红四种可见光,通过对NaYF₄∶Yb3+/Eu3+微纳粒子荧光光谱分析,Eu3+非对称性比率约为1,表明磁偶极子跃迁与电偶极子跃迁相当;NaYF₄∶Yb3+/Eu3+微纳粒子制成的丝网印刷剂在不同环境下成像结果良好均清晰可见、容易辨识,但受存放环境影响,室内成像结果与最初的成像结果相比变化不大,室外所有成像字符受到自然环境下水汽的影响,亮度均略有下降,但仍能识别。成像结果表明,所制备的NaYF₄∶Yb3+/Eu3+微纳粒子在防伪识别方面具有稳定性、可靠性等特点,但仍受到影响程度可控的自然环境因素影响。综合来看,其在防伪识别方面有着很大的应用前景。     

The discovery and commercialization of group transfer polymerization

Group transfer polymerization (GTP) is a fundamentally new method for polymerization of acrylic monomers, discovered at DuPont over 20 years ago. It allows one to make block and other specialized polymer chain architecture at above ambient temperature. The method uses silyl ketene acetals as initiators and requires a nucleophilic catalyst. DuPont uses the process to make dispersing agents for pigmented inks and automobile finishes. The development of GTP from its discovery to introduction of commercial products is presented. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2855–2860, 2000