Insights into surface chemistry down to nanoscale: an accessible colour hyperspectral imaging approach for scanning electron microscopy

Chemical imaging (CI) is the spatial identification of molecular chemical composition and is critical to characterising the (in-) homogeneity of functional material surfaces. Nanoscale CI on bulk functional material surfaces is a longstanding challenge in materials science and is addressed here. We demonstrate the feasibility of surface sensitive CI in the scanning electron microscope (SEM) using colour enriched secondary electron hyperspectral imaging (CSEHI). CSEHI is a new concept in the SEM, where secondary electron emissions in up to three energy ranges are assigned to RGB (red, green, blue) image colour channels. The energy ranges are applied to a hyperspectral image volume which is collected in as little as 50 s. The energy ranges can be defined manually or automatically. Manual application requires additional information from the user as first explained and demonstrated for a lithium metal anode (LMA) material, followed by manual CSEHI for a range of materials from art history to zoology. We introduce automated CSEHI, eliminating the need for additional user information, by finding energy ranges using a non-negative matrix factorization (NNMF) based method. Automated CSEHI is evaluated threefold: (1) benchmarking to manual CSEHI on LMA; (2) tracking controlled changes to LMA surfaces; (3) comparing automated CSEHI and manual CI results published in the past to reveal nanostructures in peacock feather and spider silk. Based on the evaluation, CSEHI is well placed to differentiate/track several lithium compounds formed through a solution reaction mechanism on a LMA surface (eg. lithium carbonate, lithium hydroxide and lithium nitride). CSEHI was used to provide insights into the surface chemical distribution on the surface of samples from art history (mineral phases) to zoology (di-sulphide bridge localisation) that are hidden from existing surface analysis techniques. Hence, the CSEHI approach has the potential to impact the way materials are analysed for scientific and industrial purposes

Microbial systematics and taxonomy: relevance for a microbial commons

The issues of microbial taxonomy and potential interactions with a microbial commons are discussed, with emphasis on three components: characterization; classification; and nomenclature. The current state of technology and the spectrum of methods that are used for phenotypic and genotypic characterization of prokaryotes, classification at different taxonomic levels and points of prokaryote nomenclature are reviewed. While all taxonomic ranks comprise a cohesive systematic framework for microorganisms, the prokaryotic genus and species provide the "working unit" of taxonomy. Since 2004, the number of validly published genera and species has increased by approximately 50%. Extensive development of technology will continue to enable ever higher resolution characterization and more refined classification of microorganisms. Characterization and classification at the species level may be most relevant for bacterial taxonomy, although reproducible differentiation at the strain level will probably prove to be more relevant for a microbial commons. A dynamic microbial taxonomy, albeit with well-founded and stable guidelines for defining microorganisms, provides an efficient organizational system for dealing with the enormous spectrum of microbial diversity. (C) 2010 Elsevier Masson SAS. All rights reserved.Antimicrobial treatment and prevention of infection