Identification and classification of organic and inorganic components of particulate matter via Raman spectroscopy and chemometric approaches

In this paper, a novel method for developing a tree‐like classifier which differentiates between organic and inorganic particulate matter by means of Raman spectroscopy is introduced. The algorithm is fully automatic and optimises itself without any human interaction. This method uses a tree‐like structure to classify Raman spectra as a decision tree. On every knot of this tree, the optimal classifier is automatically obtained, tested and trained. The optimal classifier is an artificial neural network, linear discriminant analysis or a support vector machine, where different kernels are possible. The support vector machine is optimised by the simulated annealing method to achieve the best possible classifier. After the training, a hold‐out experiment with two completely independent sets of Raman spectra was tried to show the abilities of this method for real‐world application. Copyright © 2010 John Wiley & Sons, Ltd.     

分光光度法研究可吸入性颗粒物的吸收特性

探讨用紫外可见光分光光度法研究采样在滤膜上的粗颗粒(PM10-2.5)和细颗粒(PM2.5)的光学吸收特性.结果表明:细颗粒质量虽小,但对光的吸收比粗颗粒贡献大,而粗颗粒对某些波长的光吸收特征非常明显.     

吉林省查干湖水体悬浮颗粒物光谱吸收特性研究

用分光光度计法确定查干湖复杂光学特性水体悬浮颗粒物的光谱特性与吸光幅度,在室内可控实验中利用定量滤膜技术对2009年7月15日和10月12日两期水体采集样品处理获得了以藻类色素颗粒和非色素颗粒(无机沉积物,有机碎屑)两种光活性颗粒物质为主要贡献的总悬浮颗粒物吸收光谱,结果显示7月份总悬浮颗粒物光谱吸收谱形在400～42...     

Biomolecular component analysis of cultured cell nucleoli by Raman microspectrometry

Distinct cellular domains, such as structure–function compartments of the cell nucleus and cytoplasmic organelles, are responsible for numerous macromolecular processes essential for cell functions. Spectroscopic analysis of specific cellular domains opens a way for noninvasive characterization of their molecular content and monitoring of their function. Confocal Raman spectroscopy was employed here for characterization of the complex molecular organization of major structure–function compartment of the cell nucleus, the nucleolus. The Raman spectra obtained in the nucleoli were processed by biomolecular component analysis (BCA). BCA was used to determine the contribution of each major type of macromolecules (proteins, DNA, RNA and lipids) to the complex molecular composition of nucleoli. A notable cell‐to‐cell variability in the macromolecular composition of nucleolus was found. At the same time, we observed a correlation between the concentrations of major types of biomolecules in this nuclear compartment. In particular, the averaged concentration of RNA increases along with increase in protein concentration, while an inverse dependence between the concentrations of RNA and DNA was found. Variations in the nucleolar concentrations of lipids were also noticed. Manifestations in spectral variations of proteins for individual nucleoli, shown by BCA, are discussed and interpreted. We also compared utility of BCA and principal component analysis for biomolecular studies and conclude that BCA is a more powerful and informative technique for studies of macromolecular composition and its variations in specific subcellular domains. Copyright © 2012 John Wiley & Sons, Ltd.     

Microbiological identification by surface-enhanced Raman spectroscopy

New methods for pathogens identification are of growing interest in clinical and food sectors. The challenge remains to develop rapid methods that are more simple, reliable, and specific. Surface-enhanced Raman spectroscopy (SERS) appears to be a promising tool to compete with current untargeted identification methods. This article presents the intensive research devoted to the use of SERS for bacterial identification, from the first to the very recent published results. Compared to normal Raman spectroscopy, the introduction of nanoparticles for SERS acquisition introduces a new degree of complexity. Bacterial Raman fingerprints, which are already subject to high spectral variability for a given strain, become then very dependent on numerous experimental parameters. To overcome these limitations, several approaches have been proposed to prepare the sample, from the microbiological culture conditions to the analysis of the spectrum including the coupling of nanoparticles on the bacterial membrane. Main strategies proposed over the last 20 years are examined here and discussed in the perspective of a protocol transfer towards industry.     

Resonant Raman‐based cytochrome C biosensor as a tool for evaluating the oxidative properties of the diesel exhaust particulate matter

Air pollution mostly originating from car exhaust and industrial emissions is seriously endangering human health. The study of toxic effects of particulate matter (PM) is a subject of very active research that covers a broad field from biology to chemistry and technology. The main issue of these works is the understanding of the oxidative properties of PM. In this paper, we present a quantitative analytical method based on the resonance Raman spectroscopy of cytocrome c that can be used to monitor the oxidative reactions that may take place between biological samples and PM. Copyright © 2016 John Wiley & Sons, Ltd.     

Vibrational transitions in Rydberg matter clusters from stimulated Raman and Rabi‐flopping phase delay in the infrared

Recently, rotational spectra of giant Rydberg matter (RM) clusters were studied in the radio frequency range (Mol. Phys. 105 (2007) 933–939), giving high‐precision bond distances in the nanometer range. However, the theoretical and experimental problem of vibrational motion or, rather, coupled electronic‐vibrational motion in the RM clusters is still unsolved; but it is expected that broad phonon bands will exist. Spectroscopic signatures from space make it likely that RM is a common form of matter in the Universe, and phonon bands in this spectroscopic range have not been taken into account so far. Spectroscopic results are now reported on transitions in the range 0.01–20 cm⁻¹, using primarily infrared (IR) lasers to probe the RM in a tunable open cavity with a Fabry–Perot interferometer to aid in the identification of the shifts. Stimulated Raman scattering from electronic transitions and Rabi‐flopping from electronic states in the clusters are observed. The broad stimulated Raman peaks are assigned to one and two consecutive vibrational (electronic‐vibrational) transitions. Theoretical values predicted for vibrations (phonon maxima) and electronic processes are in reasonable agreement with the experimental results. Improved calculations are needed to verify the assignments of the vibrational phonon distributions. Copyright © 2008 John Wiley & Sons, Ltd.     

凝聚态物质中的光声喇曼效应理论

用热弹性理论系统地分析了凝聚态物质的光声喇曼效应,分别导出了连续和脉冲激光泵浦下的光声喇曼信号表达式,并做了数值估算.     

硫酸镁的气溶胶微粒的共焦显微拉曼光谱研究(英文)

应用共焦显微拉曼光谱技术研究了硫酸镁气溶胶微粒。在基片的不同位置得到了不同形态的微粒,并对其相应的结构变化进行了详细探讨     

Raman identification of lonsdaleite in Popigai impactites

Micro‐Raman spectroscopy and X‐ray diffraction method (XRD) were used to characterize impact carbonaceous rocks excavated from the Popigai crater (Siberia). The deconvolution of the first‐order Raman spectra of the rocks containing different amounts of carbon phases (diamond, lonsdaleite and graphite) allowed the identification of lonsdaleite spectrum. The most intensive band at 1292–1303 cm⁻¹ was ascribed to A_1g vibration mode of lonsdaleite, whereas the less intense band at 1219–1244 cm⁻¹ was attributed, in agreement with previously reported ab initio calculations, to E_2g vibration mode. The established correlation between the intensities of Raman and XRD peaks permits a rough estimation of lonsdaleite/diamond phase ratio in the impact rocks using micro‐Raman measurements. The second‐order Raman spectra of lonsdaleite–diamond rocks were recorded. Copyright © 2014 John Wiley & Sons, Ltd.     

Raman identification of H2CO in aqueous solutions

Aqueous formaldehyde solutions of mole fraction from 0.05 to 0.20 were studied by Raman spectroscopy at temperatures up to 180 °C. The previously unreported Raman spectrum of formaldehyde under its non‐hydrated form H₂CO has been identified, in addition to the already known bands from methanediol CH₂(OH)₂ and poly(oxymethylene)glycols HO(CH₂O)_nH formed by hydration and subsequent polymerization of the formaldehyde molecules. The experimental spectrum of formaldehyde in solutions agrees perfectly with the theoretical calculations. Copyright © 2010 John Wiley & Sons, Ltd.     

Cosmogenic beryllium-7 in soil,rainwater and selected plant species to evaluate the vegetal interception of atmospheric fine particulate matter

Beryllium-7 is a radionuclide produced in the upper atmosphere by cosmic-ray spallation with ions of carbon, oxygen and nitrogen. It is one of radionuclides that can be used to trace the fine particulate matter of 2.5-µm diameter (PM_2.5) and smaller. In this work, ⁷Be was determined in leaves of 10 plant species collected from streets, parks and open land and in 5 consecutive rains over Alexandria, Egypt. ⁷Be levels were also measured in soil covered by each type of plant as well as in the nearest uncovered soil to be reference values to determine its intercepted amount and consequently PM_2.5. The lowest interception, 17.7?%, was by Ficus elastica L., while Ficus retusa L. intercepted about 45?%. Radiologically, the annual effective dose due to the usage of Thymelea hirsute plant leaves as a medicine and Nicotiana glauca Graham for smoking were 0.013 and 0.66 µSv, respectively. The observed levels in rainwater indicated that ⁷Be decreased consecutively from 3.1 Bq kg^–1 in the first rain to 0.71 Bq kg^–1 in the last one during the 2016/2017 rain season. The wet deposition of ⁷Be is less than 1?% of its total deposition on the ground.     

Surface optical Raman modes in GaN nanoribbons

Raman scattering studies were performed in GaN nanoribbons grown along [1 0 0]. These samples were prepared inside Na‐4 mica nanochannels by the ion‐exchange technique and subsequent annealing in NH₃ ambient. Detailed morphological and structural studies including the crystalline orientation were performed by analyzing the vibrational properties in these GaN nanoribbons. Pressure in the embedded structure was calculated from the blue shift of the E₂(high) phonon mode of GaN. Possible red shift of optical phonon modes due to the quantum confinement is also discussed. In addition to the optical phonons allowed by symmetry, two additional Raman peaks were also observed at ∼633 and 678 cm⁻¹ for these nanoribbons. Calculations for the wavenumbers of the surface optical (SO) phonon modes in GaN in Na‐4 mica yielded values close to those of the new Raman modes. The SO phonon modes were calculated in the slab (applicable to belt‐like nanoribbon) mode, as the wavenumber and intensity of these modes depend on the size and the shape of the nanostructures. The effect of surface‐modulation‐assisted electron–SO phonon scattering is suggested to be responsible for the pronounced appearance of SO phonon modes. A scaling factor is also estimated for the interacting surface potential influencing the observed SO Raman scattering intensities. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopy for the analysis of coal: a review

The advances in the characterization of amorphous carbons by Raman spectroscopy over the last four decades are of interest to many industries, especially those involving the combustion, gasification and pyrolysis of coal. Many researchers report on the Raman character of the natural organic matter in carbon‐containing compounds, such as coal, and relate the Raman bands to the structural order of the amorphous carbons. The basis of most of these studies evolved around the assignment of the G (graphitic, ∼1580 cm⁻¹) band to crystalline graphite and any other bands, called D bands, (disorder, various from 1100 to 1500 cm⁻¹) to any type of structural disorder in the graphitic structure. Concerning coal analysis, the information gained by Raman investigations has been used to describe char evolution as a function of temperature, the presence of catalysts and different gasification conditions. In addition, researchers looked at maturation, grade, doppleritization and many more aspects of interest. One aspect that has, however, not been addressed by most of the researchers is the natural inorganic matter (NIM) in the carbon‐containing compounds. Micro‐Raman spectroscopy (MRS) has many advantages over other characterization tools, i.e. in situ analysis, nondestructive, no sample preparation, low detection limit, micrometer‐scale characterization, versatility and sensitivity to many amorphous compounds. With the distinct advantages it has over that of other molecular characterization tools, such as powder X‐ray diffraction (PXRD), Fourier‐transform infrared spectrometry (FT‐IR) and scanning electron microscopy with X‐ray detection (SEM/EDS), it is surprising that it has not yet been fully exploited up to this point for the characterization of the NIM in coal and other amorphous carbons. This paper reviews the work published on the Raman characterization of the natural organic matter (NOM) of coals and reports on preliminary results of the NIM character of various South African coals, whereby various inorganic compounds and minerals in the coal have been characterized. Copyright © 2010 John Wiley & Sons, Ltd.     

Detection and identification of explosives by surface enhanced Raman scattering

Surface Enhanced Raman Scattering (SERS) has undergone an important development over the last few years, particularly in the detection and identification of extremely low traces of explosives. The large number of studies and results generated by this increasing research makes a comprehensive overview necessary. This work reviews in detail that research focused on the identification of explosives by SERS, including TNT, DNT, RDX, PETN, TATP, HMTD, perchlorate, etc. either in bulk state, in solution or in vapor phase. In brief, TNT and DNT have been widely studied by SERS due to its aromatic structure and LODs down to 5–10 zg and 10^?17–10^?13 M have been achieved. The other explosives have been quite less researched; therefore, few results are available to be compared and a bit more modest LODs have been reached such as 10^?13 M for RDX, 10^?4 M for TATP, 5 pg for PETN, or 10^?9 M for perchlorate. In addition, the challenges of detecting both explosives vapors and perchlorate anion by SERS are thoroughly discussed.     

麻黄素和左旋咪唑显微拉曼测试分析

在可见光激发下，利用显微拉曼技术得到了黄素和左旋旋咪唑的拉曼谱，并将它们的拉曼谱和甲基安非地明做了对比分析，麻黄素和甲基安非他明同属单取代苯，其分子结构十分相似，由于取代基的成分不同一样，因而拉曼谱中一些峰的相对强度和位置发生了变化。左旋咪唑由于取代基上为咪唑亚塞唑，其拉曼谱中主要谱线位置和强度明显不同于麻醉黄素和甲基安非他明。实验结果表明，利用显微拉曼技术在短时间内，对致幻药物进行准确快速的检测分析，将这一技术应用于运动比赛中，有助于对参赛人员服用违禁药物的检测和分析。     

Origin of salt mixtures and mixed salts in atmospheric particulate matter

The atmospheric particulate matter contains components of natural and anthropogenic origin, some of them are sulphates and nitrates. Considering the usual occurrence of many ions in the atmosphere and the presence of water, the generation of salt mixtures and mixed salts is possible as a consequence of dissolution–precipitation processes within water droplets, e.g., in fog or haze. This contribution presents the Raman spectroscopic study of the sodium–potassium nitrate system, which generates a salt mixture of both compounds. A phase transition of a KNO₃ crystal within a single solution droplet was observed. Additionally, we postulate the atmospheric generation of the mixed salt Na₃(NO₃)(SO₄)·H₂O (darapskite) by dissolution–precipitation processes, because Na⁺, SO₄^2–, and NO₃^– can be usually found in the atmosphere. The polarized Raman spectra of synthetic darapskite are reported. Copyright © 2011 John Wiley & Sons, Ltd.     

水的低频受激拉曼散射

利用532 nm的脉冲激光进行了水的受激拉曼散射研究. 水的低激发光能量下主要表现为受激Stocks和反Stocks 3426 cm^-1谱线; 在能量大于140 mJ时出现低频率313 cm^-1受激Stocks谱线, 同时出现后向3389和3268 cm^-1 的受激Stocks谱线. 实验结果表明, 在较强的激光作用下, 水的结构表现为冰的Ⅷ相.     

分子束外延PbTe单晶薄膜的反常拉曼光谱研究

采用分子束外延(MBE)方法在BaF₂(111)衬底上生长了高质量的PbTe单晶薄膜， 拉曼光谱测量观察到了表面氧化物的振动模、布里渊区中心(q≈0)纵光学(LO)声子振动模以 及声子-等离子激元耦合模振动.随着显微拉曼光谱仪激光光斑聚焦深度的改变，各拉曼散射 峰的峰位、积分强度、半高宽等都表现出不同的变化趋势. 随着激光光斑聚焦位置从样品表 面上方3μm处变化到表面下方3μm处，PbTe外延薄膜的LO声子频率从119cm^-1移 动到124cm^{-1关键词： PbTe外延薄膜 拉曼散射 纵光学声子}