Reversibility of disulphide formation and breakage on l-cysteine examined through vibrational modes using in situ Raman spectroscopy.

Abstract: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.

The electronic structure and chemical bonding of three differently prepared samples of graphene oxide paper‐like sheets are studied. Two are created by water filtration of fully oxidized graphene sheets, although one is later intercalated with dodecylamine. The third is created by reducing graphene oxide with hydrazine hydrate. The spectroscopic fingerprints of the aligned epoxide functional groups that unzip the carbon basal plane are found. This unzipping appears to be a result of aging, and the extent to which the basal plane is unzipped can be controlled via the preparation method. In particular, reduction with hydrazine enhances line defect formation, whereas intercalation inhibits the process.The hydroxyl functional group also has a tendency to gather in zones of dense oxidation on the carbon basal plane, a predilection that is not shared by the other prominent functional group species. Finally, the non‐functionalized carbon sites exhibit very similar bonding despite the increase in the sp2/sp3 ratio, confirming that reduction alone is insufficient for producing pristine graphene from graphene oxide. These results are obtained by directly probing the electronic structure of the graphene oxide samples via X‐ray absorption near‐edge structure spectroscopy (XANES) and resonant X‐ray emission spectroscopy (RXES). This work has important significance for the development of graphene oxide as a band gap‐engineered electronic material, as preparation methodology strongly affects not only the initial condition of the sample, but how the electronic structure evolves over time.

Artificial enzyme mimics have gained considerable attention for use in sensing applications due to their high stability and outstanding catalytic activity. We show that cerium oxide nanosheets (NSs) exhibit triple-enzyme mimetic activity. The oxidase-, peroxidase-, and catalase-like activities of the proposed nanoparticles are demonstrated using both colorimetric and electron paramagnetic resonance (EPR) spectroscopy. On the basis of the excellent catalytic activity of cerium oxide NSs toward hydrogen peroxide, an electrochemical approach for the high-throughput detection of H 2 O 2 in living cells was established. This report presents an analytical microfluidic chip integrated with a cerium oxide NS mimic enzyme for the fabrication of a simple, sensitive, and lowcost electrochemical sensor. Three Au microelectrodes were fabricated on a glass substrate using photolithography, and the working electrode was functionalized using cerium oxide NSs. The operation of this biosensor is based on cerium oxide NSs and presents a high sensitivity over a wide detection range, between 100 nM and 20 mM, with a low detection limit of 20 nM and a high sensitivity threshold of 226.4 μA•cm −2 •μM −1 . This microfluidic sensor shows a strong response to H 2 O 2 , suggesting potential applications in monitoring H 2 O 2 directly secreted from living cells. This sensor chip provides a promising platform for applications in the field of diagnostics and sensing.

Sputtered ZnO thin films doped with Nd present efficient down-shifting properties.