We all know how spectroscopy and other analytical technologies have played important roles in detecting fraud and in authentication. Paper collages, or photomontages, are part of the art market that is seeing much interest amongst collectors. It is difficult to detect forgeries just through expertise. The use of NIR imaging offers a number of ways to identify forgeries or authenticate the collage non-destructively; from determining the glue used to the revealing of printing on the back of the pieces or paper, which often have been taken from books and magazines.
It is not every issue that one of our articles starts with a quotation in medieval English, and it is appropriate as two of our articles cover the use of spectroscopy in cultural heritage. This is yet another field where the rich information provided by spectroscopy, along with its non-destructive nature (for many techniques), portability and ability to generate chemical images make it the answer to many questions. Kate Nicholson, Andrew Beeby and Richard Gameson are responsible for the medieval English at the start of their article “Shedding light on medieval manuscripts”. They describe the general use of Raman spectroscopy for the analysis of historical artefacts, and, in particular, their work on medieval European manuscripts and 18th century watercolour pigments. They stess the importance of checking the actual laser power density to avoid damage to priceless artefacts.
Terahertz spectroscopy and imaging of Paleolithic cave etchings, 14th century paintings in a church and a mid-20th century Italian painting are all described. This helps demonstrate the versatility of the technique as well as its potential in cultural heritage preservation.
Much of the exterior surface of plants is covered by the cuticle. This plays a vital role in protecting the plant from water loss, attack by pests and pathogens and damage from UV radiation. Infrared spectroscopy is very useful in characterising cuticles, as we learn in “Infrared spectroscopy as a tool to study plant cuticles” by José Heredia-Guerrero, José Benítez, Eva Domínguez, Ilker Bayer, Roberto Cingolani, Athanassia Athanassioua and Antonio Heredia. The authors point out that, whilst still in its early stages, infrared spectroscopy has provided valuable information about the functional groups, chemical structure and arrangement and interactions of plant cuticle components.
Mark Tobin and colleagues describe “Fourier transform infrared spectroscopy and imaging of dragonfly, damselfly and cicada wing membranes”. Insects and plants have evolved highly specialised surfaces such as being highly water repellent or superhydrophobic, which also confers self cleaning properties. This is of interest to materials scientists to help in the development of manufactured materials with similar properties. High spatial resolution FT-IR spectroscopy and imaging provide useful information about the complex chemical patterning that contributes to this functionality.
It is possible to obtain both infrared spectra and thermal analysis data of individual layers in a cross-sectioned multilayer film. Since both techniques are AFM-based, the topographical features can be readily linked to the spectroscopic and thermal data at a much higher spatial resolution than previously achievable.
“Optical spectroscopy in therapy response monitoring: an awakening giant” by Arja Kullaa, Surya Singh, Jopi Mikkonen and Arto Koistinen looks at the important advances made by optical spectroscopy techniques, such as diffuse optical spectroscopic imaging (DOSI), Raman, diffuse reflectance and fluorescence spectroscopy, in changing how cancer is managed in patients. The ability to repeatedly monitor tumour dynamics to see how effective a particular treatment has been has enormous potential for us all.
“Elucidating structural and compositional changes in plant tissues and single cells by Raman spectroscopic imaging” is the topic of the next article by Batirtze Prats Mateu, Barbara Stefke, Marie-Theres Hauser and Notburga Gierlinger. Understanding plant cells is important for the best use of plants in traditional and new applications. Raman spectroscopic imaging represents one of the best ways to unravel the molecular structure in the native environment of plant tissues.
The authors describe “Multisensor hyperspectral imaging as a versatile tool for image-based chemical structure determination”. They describe the features of a software package that allows the combined analysis of hyperspectral data from different imaging techniques. This multisensor approach providing complementary information has many advantages.
Curtis Marcott, Tadashi Awatani, Jiping Ye, David Gerrard, Michael Lo and Kevin Kjoller give us a “Review of nanoscale infrared spectroscopy applications to energy related materials”. Fuel cells, photovoltaics and specialised polymers for fracking are all considered.
This article describes an application of spectral imaging for the differentiation of tumour and normal cells. The authors also introduce the concept of a spectral barcode, which has had success with some tissues and has potential in others.
With continuing food scares around the world, food producers need every tool they can get to prevent contamination of their products at every stage of production. Hyperspectral reflectance imaging in the NIR combined with chemometrics shows much promise for the detection and identification of foreign bodies among food grains.
There are a number of approaches, and by combining FT-IR imaging methodology with microfluidics devices, the opportunity to study live cells by FT-IR imaging in controlled environments is now possible.
“Measuring brain activity using functional near infrared spectroscopy: a short review” by Felix Scholkmann and Martin Wolf looks at the various methods for performing fNIRS and some applications that demonstrate why this non-invasive, safely applicable, portable and cost-effective method is now an integral part of the techniques used in neuroscience.
Whilst fireworks are a great entertainment, they can also be used for illegal activities as well as potentially containing dangerous chemicals. The combination of Raman spectroscopy and SEM-EDS turns out to be a very efficient analytical method. In fact, these complementary techniques may also be used to analyse other kinds of pyrotechnic artefacts, low explosive formulations, high explosives, explosion residues etc.
Nati Salvadó, Salvador Butí and Trinitat Pradell have used a number of techniques to investigate changes in pictorial techniques in Catalan paintings in the 15th century. The combination of different techniques is of particular value. The use of synchtrotron radiation as a light source is also an advantage.
We have previously investigated the topographic and quantitative changes in the distribution of trace metals in spinal cords from ALS and control patients. X-ray fluorescence microscopy was used to investigate their metallic nature and distribution in single nerve cells. A deeper understanding of the neurodegenerative processes in ALS requires focus on the biochemical changes occurring in nervous tissue of such a disorder. For this purpose, we have undertaken an infrared microspectroscopy study. While metals are suggested to play a pivotal role in the pathogenesis of ALS, they typically do not occur in tissues as free ions. This results in the presence of the complex mechanisms of metal ions buffering that protect cells against their toxic effects. Metal homeostasis is regulated by several proteins. Such proteins containing metal cofactor are called metalloproteins.
Imaging of organic and inorganic constituents of tablets represents a considerable challenge and no single spectroscopic approach can provide definitive characterisation of all components and/or satisfy key measurement criteria such as sensitivity, specificity, resolution and speed of analysis. Laser ablation in combination with ICP emission spectrometry represents a powerful new tool for imaging elemental distribution in pharmaceutical tablets.
Peter Wilhelm,a Boril Chernev,a Peter Pölt,a Gerald Kothleitner,a Klaus-Jochen Eichhorn,b Gisela Pompe,b Nikola Johnerc and Alexander Piryc
aResearch Institute for Electron Microscopy, Graz University of Technology; Steyrergasse 17, A-8010 Graz, Austria. E-mail: email@example.com
bInstitute of Polymer Research Dresden; Hohe Straße 6, D-01069 Dresden, Germany
Chemical imaging spectroscopy is an exciting new analytical advance that answers commonly asked questions such as what chemical species are in a sample, how much of each is present, and most importantly, where are they located? Through the fusion of traditional infrared spectroscopy with powerful microscopic and macroscopic imaging capabilities, chemical imaging spectroscopy answers all these questions simultaneously, in a single rapid measurement.