This chapter reviews new publications on pure nuclear quadrupole resonance (NQR) spectroscopy of inorganic and organometallic compounds, up to the end of 2012.
This report reviews work on vibrational spectroscopy of N-donor ligand metal complexes from 2008-2013. The particular focus is on the examination of excited states using resonance Raman spectroscopy, transient resonance Raman spectroscopy and time-resolved infrared spectroscopy. The report describes some of the basic concepts around each technique and then highlights work from the review period that exemplifies the utility of each method. In addition tables are included that summarise the work using these methods over the review period.
In this chapter we review the applications of Raman spectroscopy and scanning electron microscopy for analysis of the road transport pollution. Raman spectroscopy has been applied on roadside soils and plants and on buildings facades in order to detect traffic emitted compounds. The emission of particles by diesel engines is another important field of study regarding to the air pollution in urban areas. In this sense, apart from Raman spectroscopy, the use of scanning electron microscopy coupled to Energy Dispersive X-ray Spectroscopy (SEM-EDS) plays an important role. In the literature appear several works which focus on the analysis of road dust; particles emitted by brake and tire wear are characterised by SEM images together with X-ray absorption spectra (EDS).
This chapter reviews new publications on pure nuclear quadrupole resonance (NQR) spectroscopy of inorganic and organometallic compounds, up to the end of 2012.
The measurement of the chemical and physical properties of nanostructured materials, including e.g. silicate, carbon nanotubes and fullerenes, is time-consuming, requires expensive instrumental equipment and a lot of user experience. Infrared spectroscopy, especially near-infrared spectroscopy (NIR), coupled with multivariate data analysis (MVA) can be used as a non-destructive, fast, reliable and robust technique for the characterization and classification of nanostructured materials. In this contribution the most relevant milestones reached so far in NIR spectroscopic characterization of nanostructured materials are reviewed, summarized and discussed.
SEM-EDS and micro-Raman spectroscopy have been combined for material characterization in several recent studies. Switching from one to the other is frequently considered as a problem that cannot be solved using specific solutions. Although both techniques have followed a parallel but very different evolution since their introduction in the early 1930s, the concept of Raman-in-SEM first began in the 1980s and the first commercial systems were marketed in the early 2000s. The two main systems and techniques that have been developed and marketed by three manufacturers are presented and described in this chapter. An evaluation of their advantages and limitations is proposed. A metrological study is then proposed for one of these systems, based on the ‘on-axis’ technique using a curved mirror placed under the SEM pole piece. This study allows a discussion of the performance and limitations of Raman spectroscopy when performed in a SEM. A comprehensive review of published work is provided, although papers are rare in the open literature. The technique is essentially used for controls, expert assessments and high technology applications. Advanced techniques that allow the use of Raman-in-SEM spectroscopy are discussed in detail using application examples taken from different fields in geosciences, materials chemistry or from expert assessments. The conclusions of this study show that Raman-in-SEM spectroscopy is to date the first step in the combination of two well-known and mature techniques enabling the synergy between them to be maximised. Raman-in-SEM spectroscopy is relatively easy to set up and effectively complements the capabilities and efficiency of analytical SEM for material characterization. What are the most likely development perspectives that may be considered for this analytical coupling? Today, commercial systems are limited to only point-level micro-Raman analysis at the micrometre scale. In the near future, developments in both hardware and software will probably allow analysts to acquire Raman maps, or to employ multi-technique analyses based on a combination of data from SEM, EDS Raman, etc. New hardware developments may enhance the spatial resolution of both SEM and Raman spectroscopy.
Substantial development in the nanoscience and nanotechnology has been evinced in the last few years due to the availability of sophisticated physical methods to characterize nanomaterials. Among the various physical techniques, X-ray related characterizations are superior for the understanding of the crystal structure, size, shape, composition and electronic structure of inorganic nanomaterials. These techniques include X-ray diffraction, small angle X-ray scattering, X-ray reflectivity, pair distribution function analysis, X-ray photoelectron spectroscopy, energy dispersive X-ray analysis and others. Characterization of the nanomaterials includes not only the determination of size and shape but also the atomic and electronic structures as well as other important properties. In this article we describe some of the important X-ray related methods employed for characterization of nanostructures. In order to provide a feeling for the use of these methods, a few case studies are given.
Films and coatings have become widely used in structures and components to protect the underlying material from mechanical degradation, corrosion, oxidation and high temperatures or improve surface properties. Residual stress generated in these multi-layer systems is one of the main causes of coating delamination and eventual failure. Systematic measurement and monitoring of the residual stresses are a vital basis for integrity evaluation and remaining life prediction. Raman spectroscopy has been recognised as one of the most important approaches to measure the stress in films and coatings. This review considers the measurement of stresses in films and coatings using Raman spectroscopy. It addresses the following questions: what is Raman spectroscopy, why is stress important for films and coatings, how is strain/stress derived from Raman spectra and what confidence do we have in this technique and the limitations. To elucidate specific issues related to the application of the Raman technique for stress measurement, despite the wide range of coatings available, important films and coating are chosen as representative examples.
In this chapter the recent achievements in the use of isotopically labelled molecules for characterization of surfaces by FTIR and other vibrational spectroscopy techniques is reviewed. A brief theoretical background is provided where special attention is paid on the deviations of the experimental results from the theory. Then the application of D-, C-13-, N-15- and O-18-labelling is consecutively considered. For deuterium we first discuss the properties of surface OD groups and then the use of deuterated molecular probes (D-2, CHD2OH, C2D5OH, C6D12). When describing C-13-labelled compounds the application of (CO)-C-13 and (CO)-C-13-O-18 is compared and then other labelled compounds ((CO2)-C-13, (DCN)-C-13, (CH3OH)-C-13, etc.) are considered. In the next section N-15(2), NO isotopologues, ((NH2)-N-15)(2)CO and aminoacids are discussed. For O-18-labelling we first consider the use of surfaces enriched to O-18, then different O-2 adsorption and finally, H-2 O-18 and (CO)-O-18. In all cases the application of isotopic labelling for clarifying the mechanisms of catalytic reactions is also considered.
The past ten years have seen a significantly increasing number of published crystal structures for molecular transition metal complexes at variable pressure, providing quantitative information on structural variations. Spectroscopic measurements at variable pressure have been reported over the past 60 years for a variety of complexes, but luminescence measurements were mostly limited to intense signals until early in this century. The combination of variable-pressure structure variations with spectroscopic trends can lead to detailed new insight on a variety of aspects of electronic structure. This approach holds promise for the in-depth study of many categories of functional materials.
Magnetic resonance imaging (MRI) is a very powerful instrument used extensively in modern medical diagnostics because of its ability to look inside a body in a non-invasive and non-destructive way. Furthermore, MRI is more than just a single tool for extracting structural information. It is more of a sophisticated and versatile toolkit able to provide all sorts of useful information about the internal properties of an object under study and various processes within it, including heat and mass transport, composition and chemical transformations, in a spatially resolved mode. While a living body is different from a catalyst body or a reactor, the in situ and Operando studies in catalysis can clearly benefit from the use of this non-destructive toolkit as a powerful complement to other available spectroscopic tools. This tutorial review gives an introduction to the field and describes the examples of the applications of MRI to the studies of the preparation, deactivation and regeneration of solid catalysts and to the spectroscopy, thermometry and imaging studies of heterogeneous catalysts and model catalytic reactors performed during actual catalytic processes.
Raman sensors are more and more used for various applications. In particular they were recently used for in situ and real time monitoring of inorganic substances in aqueous solution in the sea, in tanks or in vicinity of industrial sites. Among several advantages they provide the identification of many species with a fairly good component resolution and the accurate determination of their concentration. Raman probes are based upon different data treatment of the Raman spectra. Two main methods are emphasized here. In the first method suitable for diluted salts with polyatomic anions, the Raman spectrum exhibits a large and well resolved peak used as the direct signature of a peculiar anion to be detected. Salts with monoatomic anions are studied via their indirect influence on the large OH stretching band of the water. The advantages and limitations of each method are discussed and illustrated with some examples derived from our own experience. The process giving the quantification in the analysis of the species is described, with a particular attention devoted to the data treatment within the calibration procedure. Analysis with lineshape treatment and chemometric methods are both reported and discussed. A comparison with different approaches reported in the literature is provided. Finally, the main devices used for in situ monitoring are briefly described.
Electrochemiluminesence (ECL), also called electrogenerated chemiluminescence, is optical emission that arises from the high-energy electron-transfer reaction between electrogenerated species. ECL is an approach of converting electrical energy into radiative energy. Different from photoluminescence, ECL does not require the use of external light sources and therefore problems derived by light scattering can be avoided.
Optical properties of quantum dots have created a lot of interest within the community due to their size tunable, fundamentally unique properties arising from the quantum confinement effect that are unforeseen in bulk. In this review we have highlighted some of the recent advances in the field including the synthetic challenges and advances to control not only the size but also their shape, internal structure and their coupling with the neighbouring nanocrystals leading to exciting new optical properties. We have further explored the various optical techniques that have been used to understand the electronic structure of not only ensemble and temporally averaged nanostructures but also with temporal resolution as well as single particle microscopy and hence understand the unique size dependent properties. We then explore a few of the unique properties or specialized class of nanocrystals using a combination of various optical properties. The different classes of nanocrystals discussed in this review include materials such as transition metal doped nanocrystals as well as infrared emitting materials. The fundamentally unique processes such as blinking, that is observed in almost all single molecule nanocrystals, or ultrafast processes occurring in these nanocrystals that determine the properties of these materials have also been discussed. The review concludes with a brief discussion on the current and potential applications and a brief outlook for the future of this field.
The phenomenon of surface-enhanced infrared absorption (SEIRA) spectroscopy involves the intensity enhancement of vibrational bands of adsorbates that usually bond through contain carboxylic acid or thiol groups onto thin nanoparticulate metallic films that have been deposited on an appropriate substrate. SEIRA spectra obey the surface selection rule in the same way as reflection-absorption spectra of thin films on smooth metal substrates. When the metal nanoparticles become in close contact, i.e., start to exceed the percolation limit, the bands in the adsorbate spectra start to assume a dispersive shape. Unlike surface-enhanced Raman scattering, which is usually only observed with silver, gold and, albeit less frequently, copper, SEIRA is observed with most metals, including platinum and even zinc. The mechanism of SEIRA is still being discussed but the enhancement and shape of the bands is best modeled by the Bruggeman representation of effective medium theory with plasmonic mechanism playing a relatively minor role. At the end of this report, three applications of SEIRA, namely spectroelectrochemical measurements, the fabrication of sensors, and biochemical applications, are discussed.
The photochemical and photophysical behaviour of metal complexes remains a primary reason for the continuing and increasing interest in their study by both established and more recently developed spectroscopic techniques. The diversity of spectroscopic properties arises in large part from population of the wide range of electronic states accessible to mono- and multi-nuclear metal-centred species, including biomimetic model systems, as well as metalloproteins. Detailed investigation of the vibrational and vibronic energy states under both static and time-resolved conditions is especially important in the development of a more complete understanding of the structure and dynamics of these systems. In many cases these studies focus on their role in biological function and potential application in catalytic and photocatalytic contexts. This report selects a number of recent examples of the use of Raman and resonance Raman methods to probe a variety of metal-centred systems ranging from biomimetic oxidation catalysts to spin-crossover complexes. In addition, the application of techniques developed more recently such as femtosecond stimulated Raman scattering, femtosecond coherence spectroscopy and time-resolved X-ray absorption spectroscopy will be discussed.
Electrochemiluminesence (ECL), also called electrogenerated chemiluminescence, is optical emission that arises from the high-energy electron-transfer reaction between electrogenerated species. ECL is an approach of converting electrical energy into radiative energy. Different from photoluminescence, ECL does not require the use of external light sources and therefore problems derived by light scattering can be avoided. © The Royal Society of Chemistry 2013.
Graphene edges are of particular interest since their orientation determines the electronic properties. Here we present a detailed Raman investigation of graphene flakes with edges oriented at different crystallographic directions. We also develop a real space theory for Raman scattering to analyze the general case of disordered edges. The position, width, and intensity of G and D peaks are studied as a function of the incident light polarization. The D-band is strongest for polarization parallel to the edge and minimum for perpendicular. Raman mapping shows that the D peak is localized in proximity of the edge. For ideal edges, the D peak is zero for zigzag orientation and large for armchair, allowing in principle the use of Raman spectroscopy as a sensitive tool for edge orientation. However, for real samples, the D to G ratio does not always show a significant dependence on edge orientation. Thus, even though edges can appear macroscopically smooth and oriented at well-defined angles, they are not necessarily microscopically ordered.
