Quantifying defects in graphene via Raman spectroscopy at different excitation energies.

We present a Raman study of Ar(+)-bombarded graphene samples with increasing ion doses. This allows us to have a controlled, increasing, amount of defects. We find that the ratio between the D and G peak intensities, for a given defect density, strongly depends on the laser excitation energy. We quantify this effect and present a simple equation for the determination of the point defect density in graphene via Raman spectroscopy for any visible excitation energy. We note that, for all excitations, the D to G intensity ratio reaches a maximum for an interdefect distance ∼3 nm. Thus, a given ratio could correspond to two different defect densities, above or below the maximum. The analysis of the G peak width and its dispersion with excitation energy solves this ambiguity

Role of fluid and melt inclusion studies in geologic research

Although fluid inclusions were apparently known to early naturalists, actual research on fluid and melt inclusions began only in the mid‐1800s and grew very slowly for the next 100 years. R ussian scientists began systematic studies of inclusions in the 1930s, but it was not until about 1960 that publications mentioning or using fluid inclusions began to increase from a few each year to the present annual level of about 700. Early research focused on ore deposits, first on temperatures and salinities of ore fluids and then on their stable isotopic and major element compositions. Later work extended to fluids in sedimentary and metamorphic environments. Publications using or mentioning melt inclusions only began to increase in number in about 1980 and have grown to today's level of about 200 per year. Early work on melt inclusions focused on igneous rocks with an emphasis on immiscibility and volatile elements and then on rare elements. Recent research on both fluid and melt inclusions has taken advantage of single inclusion analytical methods to investigate speciation and partitioning in both natural and experimental magmatic and aqueous systems. Observations on fluid and melt inclusions began in the mid‐1800s, but research publications were rare until about 1960 for fluid inclusions and 1980 for melt inclusions. Currently, about 700 reports mentioning fluid inclusions and another 200 mentioning melt inclusions are published each year. Research has evolved from measurements on individual inclusions to analysis of bulk inclusions to present efforts to analyze individual natural and experimental inclusions and derive geochemical data and models from them.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/100331/1/gfl12055.pd