In this study we introduce in situ Raman spectroscopy as an effective tool to distinguish between reversible and irreversible thiol modifications in L-cysteine, the most critical host for sulphydryls in proteins and enzymes. We place special emphasis on the conditions under which the formation and breakage of disulphide bonds is reversible and produces free thiol groups. Thiol groups from L-cysteine are highly reactive and are frequently converted into disulphide bonds via reaction with mercaptans, including S-methyl methanethiosulfonate (MMTS). It was previously claimed that disulphide groups can be reversibly introduced in and eliminated from L-cysteine in order to restore a free thiol group, using a reductant such as tris(2-carboxyethyl)phosphine (TCEP). Raman spectroscopy is found to effectively monitor the formation and subsequent breaking of disulphide bonds, and demonstrates that although TCEP is effective in breaking disulphide bonds, an excess of TCEP is required to reversibly form free thiol groups from L-cysteine. These results will be critical for cysteine–metal bonding investigations. Our Raman mode assignment in MMTS and TCEP also provides a benchmark for future studies using these compounds.

In this article, we present an overview of aperture and apertureless type scanning near-field optical microscopy (SNOM) techniques that have been developed, with a focus on three-dimensional (3D) SNOM methods. 3D SNOM has been undertaken to image the local distribution (within ~100 nm of the surface) of the electromagnetic radiation scattered by random and deterministic arrays of metal nanostructures or photonic crystal waveguides. Individual metal nanoparticles and metal nanoparticle arrays exhibit unique effects under light illumination, including plasmon resonance and waveguiding properties, which can be directly investigated using 3D-SNOM. In the second part of this article, we will review a few applications in which 3D-SNOM has proven to be useful for designing and understanding specific nano-optoelectronic structures. Examples include the analysis of the nano-optical response phonetic crystal waveguides, aperture antennae and metal nanoparticle arrays, as well as the design of plasmonic solar cells incorporating random arrays of copper nanoparticles as an optical absorption enhancement layer, and the use of 3D-SNOM to probe multiple components of the electric and magnetic near-fields without requiring specially designed probe tips. A common denominator of these examples is the added value provided by 3D-SNOM in predicting the properties-performance relationship of nanostructured systems.

A new generation of membranes for water purification based on weakly oxidized and nanoporous few-layer graphene is here introduced. These membranes dramatically decrease the high energy requirements of water purification by reverse osmosis. They combine the advantages of porous and non-oxidized single-layer graphene, offering energy-efficient water filtration at relatively low differential pressures, and highly oxidized graphene oxide, exhibiting high performance in terms of impurity adsorption. In the reported fabrication process, leaks between juxtaposed few-layer graphene flakes are sealed by thermally annealed colloidal silica, in a treatment that precedes the opening of (sub)nanometre-size pores in graphene. This process, explored for the first time in this work, results in nanoporous graphene flakes that are water-tight at the edges without occluding the (sub)nanopores. With this method, removal of impurities from water occurs through a combination of size-based pore rejection and pore-edge adsorption. Thinness of graphene flakes allows these membranes to achieve water purification from metal ions in concentrations of few parts-per-million at differential pressures as low as 30 kPa, outperforming existing graphene or graphene oxide purification systems with comparable flow rates.

Graphene–polymer composites show great promise as thermal interface materials. We here offer a deeper understanding of their thermal properties using contactless photothermal deflection techniques.