Forensic Analysis of Color Toners by Raman Spectroscopy

Abstract

Raman spectroscopy has recently become more popular for the chemical analysis of several types of materials of forensic interest. The Raman technique allows the measurement of the inelastic scattering of light due to the vibrational modes of a molecule when irradiated by an intense monochromatic source such as a laser. Forensic laboratories must often work with small samples in order to determine the type of material and its possible manufacturer for investigatory and evidence purposes. This paper describes the analysis of a color photocopied document for the identification of the particular type of toner used in the generation of the document.     

Independent Component Analysis Applied to Raman Spectra for Classification of In Vitro Human Coronary Arteries

Abstract

Optical diagnostic methods, such as near‐infrared Raman spectroscopy allow quantification and evaluation of human affecting diseases, which could be useful in identifying and diagnosing atherosclerosis in coronary arteries. The goal of the present work is to apply Independent Component Analysis (ICA) for data reduction and feature extraction of Raman spectra and to perform the Mahalanobis distance for group classification according to histopathology, obtaining feasible diagnostic information to detect atheromatous plaque. An 830 nm Ti:sapphire laser pumped by an argon laser provides near‐infrared excitation. A spectrograph disperses light scattered from arterial tissues over a liquid‐nitrogen cooled CCD to detect the Raman spectra. A total of 111 spectra from arterial fragments were utilized.     

Label‐free monitoring of inflammatory tissue conditions using a carrageenan‐induced acute inflammation rat model

Although the confirmation of inflammatory changes within tissues at the onset of various diseases is critical for the early detection of disease and selection of appropriate treatment, most therapies are based on complex and time‐consuming diagnostic procedures. Raman spectroscopy has the ability to provide non‐invasive, real‐time, chemical bonding analysis through the inelastic scattering of photons. In this study, we evaluate the feasibility of Raman spectroscopy as a new, easy, fast, and accurate diagnostic method to support diagnostic decisions. The molecular changes in carrageenan‐induced acute inflammation rat tissues were assessed by Raman spectroscopy. Volumes of 0 (control), 100, 150, and 200 µL of 1% carrageenan were administered to rat hind paws to control the degree of inflammation. The prominent peaks at [1,062, 1,131] cm^?1 and [2,847, 2,881] cm^?1 were selected as characteristic measurements corresponding to the C–C stretching vibrational modes and the symmetric and asymmetric C–H (CH₂) stretching vibrational modes, respectively. Principal component analysis of the inflammatory Raman spectra enabled graphical representation of the degree of inflammation through principal component loading profiles of inflammatory tissues on a two‐dimensional plot. Therefore, Raman spectroscopy with multivariate statistical analysis represents a promising method for detecting biomolecular responses based on different types of inflammatory tissues.     

拉曼光谱在气化炉合成气成分分析中的应用

煤气化装置中,采用在线分析系统对气化炉合成气的气体组分进行实时的监测分析。气化炉合成气洗涤塔出口合成气具有高温、高压、高水份、多杂质、易结晶等特点。为解决传统的分析测量方法在实际运行中出现的弊端和问题,该文据此具体工况,进行了研究并重新设计。经过对比分析,提出了采用基于激光技术的气相拉曼光谱仪进行分析测量的优化解决方案。通过实际改造运行结果得出,拉曼光谱分析仪在响应实时性、测量精确性、系统复杂性、维护便利性、操作安全性乃至寿命周期成本等方面都具有其独特的优越性,是一种理想可靠的分析测量方案。     

拉曼光谱应用于硅微悬臂梁的应力特性测试

介绍了一种基于拉曼光谱频移来实现微结构应力测试的方法。利用该方法,实现了标准体硅腐蚀工艺形成的八梁支撑的微悬臂梁中应力分布的测试。测试结果表明EPW体硅腐蚀形成的梁—质量块系统中梁与质量块上存在40～160MPa的张应力,微梁上的残余张应力平均达到100MPa;对微结构上的不同位置,边缘的残余应力普遍要比中心位置的大一些。     

拉曼光谱的广泛应用及分辨率的重要性

从物质结构的基本知识出发，从而说明拉曼光谱直接反映了分子或晶格的振动、转动能级，由此说明拉曼光谱的广泛应用。重点讨论了拉曼光谱仪分辨率的重要意义，由能级间隔的数值，估计了不同研究对象、不同应用领域对光谱分辨率的要求。     

基于拉曼光谱仪的MEMS动态应力测试系统

微机电系统(MEMS)动态应力的瞬态特性决定了传统的应力测试系统无法直接满足它的测试需要。介绍了一种依据高频调制原理设计实现的基于拉曼光谱仪的MEMS动态应力测试系统,该测试系统是一个典型的光—机—电集成的MEMS测试系统。利用此测试系统对硅微谐振器支撑梁根部的单点进行了动态应力测试,测试结果与理论分析相吻合。实验表明,此测试系统具有高精度、非接触式、无损伤等特点,能很好地满足MEMS动态应力测试的需求。     

Noninvasive Quantification of Cutaneous Oedema in Patch Test Reactions by Fiber Optic Near-Infrared Fourier Transform Raman Spectroscopy

The major aim of the present study was to quantitatively differentiate various degrees of positive patch test reactions by estimating relative water content noninvasively using fiber optic near-infrared Fourier transform (NIR-FT) Raman spectroscopy. The specific intent was to examine its technical applicability and reproducibility in reading patch tests at 48 and 72 hr. Instrumental measurements at 63 patch test sites were compared visually in 19 patients with suspected allergic contact dermatitis. Raman spectra were measured in vivo in skin reacting to patches on the back using a fiber optic technique. Negative (–), doubtful (?+) and positive patch test reactions (+; ++/+++) could be separated by means of measured differences in absolute values of the 3250 cm^–1 peak (ratio I₃₂₅₀/I₂₉₄₀): at 48 hr the mean increases were 0.31(–), 0.40(?+); 0.45(+); 0.69(++/+++) and at 72 hr they were 0.31(–); 0.34(?+); 0.42(+); 0.60(++/+++). At 48 hr significant differences (p<0.05) were shown between all reactions, but not between negative and doubtful reactions at 72 hr. These findings indicate that cutaneous oedema in patch test reactions can be noninvasively quantified based on positive patch test reactions by NIR-FT Raman spectroscopy, with continuous data grading of reaction intensity suitable for clinical studies at 48 and 72 hr. We also demonstrated good technical reproducibility of patch test reactions evaluation by NIR-FT Raman spectroscopy at 48 and 72 hr, showing that this method can be used to monitor the dynamics of these reactions and display the results spectroscopically.     

Quantification of anhydrous ethanol and detection of adulterants in commercial Brazilian gasoline by Raman spectroscopy

Raman spectroscopy can be used to evaluate the quality of fuels in a remote, rapid, and nondestructive manner without the need for reagents. In this study, Raman was used to quantify anhydrous ethanol in commercial gasoline and to detect peaks due to compounds commonly used for the adulteration of commercial gasoline. Samples of commercial gasoline were collected from fuel stations in the region of Santos, SP, Brazil. Samples of naphtha from the refinery, pure ethanol, and ethanol diluted in distilled water at concentrations close to the range used in the gasoline were also obtained and characterized. Raman spectra were collected using a dispersive Raman spectrometer (830?nm, 2?cm^?1 resolution in the 400–1800?cm^?1 spectral range). As expected, the spectra of commercial gasoline showed pronounced peaks of naphtha and ethanol. By using the peak intensities of the ethanol diluted in water, the ethanol concentration was found to be in the range of 27%?±?1% in most of the samples; some samples presented ethanol concentrations as high as 28.8%, suggesting adulteration. Some samples presented peaks at 766, 798, and 995?cm^?1 with higher intensities, suggesting the presence of an adulterant with organic characteristics, such as solvents with aromatic rings. Raman spectroscopy has been shown to be effective in determining the adulteration of commercial gasoline, which may contribute to rapid quality control of fuels at the point of sale.     

The use of post‐mortem Raman spectroscopy in explaining friction and wear behaviour of sintered polyimide at high temperature

Due to their thermal stability and high strength, polyimides are an aromatic type of polymer that is used in sliding equipment functioning under high loads and elevated temperature. However, its tribological behaviour under high temperature and atmospheric conditions is not fully understood. It has been reported that a transition from high towards lower friction occurs ‘somewhere’ in the temperature region between 100°C and 200°C; however, a correlation with changes in the polyimide molecular structure remains difficult to illustrate and it is not certain whether or not this transition is correlated to lower wear. In the present work sliding experiments under controlled bulk temperatures between 100°C and 260°C are performed. A transition is observed in both friction and wear at 180°C which is further explained by microscopic analysis of the transfer film on the steel counterface and Raman spectroscopy of the worn polymer surfaces. A close examination of the spectra reveals transitions in relative intensity of certain absorption bands, pointing to different orientation effects of the molecular conformation at the polymer sliding surface at 180°C. Copyright © 2006 John Wiley & Sons, Ltd.     

Study on Raman and SERS spectra of filter paper and silica gel plate

万方数据知识服务平台-中外学术论文、中外标准、中外专利、科技成果、政策法规等科技文献的在线服务平台。     

拉曼特征峰提取在多组分混合溶液检测中的应用

拉曼光谱作为一种快速、无损检测技术受到越来越多的关注,已经广泛应用于食品安全监督、纺织纤维分析、危险品和毒品的检测、考古鉴定等多个领域。本文主要利用不同物质的拉曼光谱所具有的明显特征峰,提出了一种基于拉曼光谱特征峰提取的多组分混合溶液检测方法。该方法可以直接测得混合溶液的激光拉曼光谱,然后经过光谱预处理与特征峰提取、特征峰匹配的方法,能够定性的识别出混合溶液中的主要物质成分。利用甲醇、甲苯、丙酮、乙醇分别进行混合识别,从而验证了算法的有效性。实验结果表明,整个识别过程快速、有效,需要样品量少、无需前处理,测试过程对样品无损,不产生化学污染物,是对混合溶液检测的一种有效方法。     

基于荧光显微拉曼光谱的细菌快速解耦检测方法

在细菌检测环境中往往存在多种活细菌、死菌以及非生物微颗粒,它们形态和大小相近且耦合寄居在一起,这使得普通的菌类检测方法在检测细菌的种类和含量时很难奏效。提出一种细菌快速解耦检测方法,该方法采用荧光微视技术与拉曼光谱分析技术相结合,利用荧光微视技术实现活菌与非生物微颗粒及死菌的解耦检测,并且实现活菌的定位;利用拉曼光谱技术对定位活菌进行数据采集并结合Ward聚类分析法构建各种活菌的解耦检测模型。实验证明所提出解耦方法的对活菌的解耦检测精度达到了94%以上,且检测时间仅为普通显微拉曼光谱法的1/9。适用于烧伤伤口细菌感染检测等要求检测精度高、速度快的场合。     

拉曼光谱在纺织检测中的应用及其发展前景

纺织品检测一直受到社会各界的共同关注,因为其不仅关系到人们生活安全问题,也关系到国际交易的公平问题.拉曼光谱技术虽然发展时间较短,但却非常迅速地在纺织品检测领域占有了重要位置.这种技术存在着特有的快捷、便携、对样品无损、无二次污染和不受溶剂水影响等优点,当然也存在荧光较强、谱库不完善的问题.在纺织行业,拉曼光谱技术可以用于检测纤维组分、偶氮染料和甲醛等物质的快速检测.随着新的技术的不断融合,拉曼光谱在纺织行业的作用也会越来越大.     

Near Infrared Raman Spectroscopy System for Real Time Monitoring of Fast Processes: A Resin Composite Photopolymerization Application

Abstract

This work describes the implementation of a technique for data monitoring using dispersive near‐infrared Raman spectroscopy that presents the advantage of non‐invasively being capable to make real time fast measurements. The degree of conversion of an odontological resin composite (A3, Z100^®, 3 M), photopolymerized by an LED (450 nm, 230 mW), was measured as an application of the technique. The Raman system consisted of a 785 nm Ti:Sapphire laser, a Chromex spectrograph with an entrance slit of 200 µm, and a liquid nitrogen cooled CCD detector. The system allowed acquisition of Raman spectra at times as short as 6 s. The progress of the photopolymerization was followed by obtaining Raman spectra every 6 s during 84 s. The intensity of the 1640 cm^?1 Raman peak, attributed to the aliphatic carbon double bonds, was chosen to calculate the conversion degree of the resin photopolymerization. Results showed that the degree of conversion presented an exponential growth, reaching a maximum of 50% after 60 s. Findings seem to confirm the trustworthiness of the system.     

Near-field Raman imaging of morphological and chemical defects in organic crystals with subdiffraction resolution

In this study we report on the application of an aperture near‐field optical microscope for Raman imaging of organic materials. Spectral analysis and detailed Raman imaging are performed with integration times of 100 ms per point, without the aid of field enhancement effects. The studied samples consist of two high Raman‐efficiency molecular samples: a 7,7′,8,8′‐tetracyanoquinodimethane crystal showing surface defects and a 7,7′,8,8′‐tetracyanoquinodimethane thin film characterized by the presence of submicrometre‐sized organometallic copper–salt complexes. In the first case, the effect of the surface deformation was studied, whereas in the second sample we were able to chemically image the formation of salt complexes. Subdiffraction resolution was achieved in both studies.     

Short‐Term Response of Human Osteoblast‐Like Cells on Titanium Surfaces With Micro‐ and Nano‐Sized Features

Since the way that human bone cells behave on contact with different surfaces topographies seems to be crucial to osseointegration, the aim of the present study is to evaluate the participation of some micro‐ and nanosized features of Ti surfaces in the short‐term response of primary human osteoblast‐like cells (HOC). Surfaces were prepared as ground (G‐Ti), hydrofluoric acid etched (HF‐Ti), and sandblasted/HF‐etched (SLA‐Ti), and analyzed using both three‐dimensional (3D) profilometer and atomic force microscope (AFM). Cell morphology was assessed using scanning electron microscopy (SEM) after 4 and 24 h in culture. Cell viability, adhesion, and spreading were also evaluated 4 and 24 h after seeding over each surface. Data were compared by analysis of variance (ANOVA) complemented by Duncan test. Cell morphology, cell counting, and membrane integrity (Neutral Red, NR) were not affected by surface treatment at any time. However, HF‐Ti presented the smallest surface area and did not increase tetrazolium hydroxide (XTT) reduction from 4 to 24 h. On the other hand, a higher level of spreading was only found on the rougher and isotropic SLA‐Ti at 4 h. In conclusion, although all evaluated Ti surfaces allowed HOC short‐term adhesion, the finer topography introduced by HF as single treatment did not favor HOC mitochondrial activity and spreading. The rougher and more complex SLA surface seems to provide a better substrate for HOC short‐term response. SCANNING 34: 378‐386, 2012. © 2012 Wiley Periodicals, Inc.     

Investigation of microstructured chitosans by coherent anti‐Stokes Raman microscopy

This work describes application of coherent anti‐Stokes Raman scattering (CARS) microscopy technique for analytical characterization of microstructured materials based on chitosan. We demonstrate that nitrogen–hydrogen vibration band in the high wavenumber region of CARS spectrum prevails over response from oxygen–hydrogen vibrations and can be used as a spectral marker of chitosan. The chemically selective imaging is experimentally demonstrated by applying CARS microscopy to discriminate between chitosan and polystyrene microparticles. CARS microscopy was shown to be a valuable tool for characterization of polluted chitosan fibre from utilized engine filter material. A possibility to observe foreign material pieces on the surface of the polluted chitosan fibre is demonstrated and discussed.