Non uniform shrinkages of double-walled carbon nanotube as induced by electron beam irradiation

Electron beam-induced nanoinstabilities of pristine double-walled carbon nanotubes (DWCNTs) of two different configurations, one fixed at both ends and another fixed at only one end, were in-situ investigated in transmission electron microscope at room temperature. It was observed that the DWCNT fixed at both ends shrank in its diameter uniformly. Meanwhile, the DWCNT fixed at only one end intriguingly shrank preferentially from its free cap end along its axial direction whereas its diameter shrinkage was offset. A mechanism of "diffusion" along with "evaporation" at room temperature which is driven by the nanocurvature of the DWCNTs, and the athermal activation induced by the electron beam was proposed to elucidate the observed phenomena. The effect of the interlayer interaction of the DWCNTs was also discussed

Oxygen vacancy induced structural variations of exfoliated monolayer MnO2 sheets

We report findings on the structural stability of exfoliated monolayer MnO2 sheets. Our study reveals that monolayer MnO2 sheets display two specific kinds of structural modification under electron irradiation. An atomic reconstruction (2 x 1) and a phase of MnO, induced by ordered oxygen vacancies, were identified by transmission electron microscopy techniques and further characterized by comparison with density-functional theory calculations. These findings are expected to significantly broaden current knowledge of the structural stability of ultrathin layered sheets

Enzyme Biosensors for Point-of-Care Testing

Biosensors are devices that integrate a variety of technologies, containing biology, electronics, chemistry, physics, medicine, informatics, and correlated technology. Biosensors act as transducer with a biorecognition element and transform a biochemical reaction on the transducer surface directly into a measurable signal. The biosensors have the advantages of rapid analysis, low cost, and high precision, which are widely used in many fields, such as medical care, disease diagnosis, food detection, environmental monitoring, and fermentation industry. The enzyme biosensors show excellent application value owing to the development of fixed technology and the characteristics of specific identification, which can be combined with point-of-care testing (POCT) technology. POCT technology is attracting more and more attention as a very effective method of clinic detection. We outline the recent advances of biosensors in this chapter, focusing on the principle and classification of enzyme biosensor, immobilization method of biorecognition layers, and fabrication of amperometric biosensors, as well as the applications of POCT. A summary of glucose biosensor development and integrated setups is included. The latest applications of enzyme biosensors in diagnostic applications focusing on POCT of biomarkers in real samples were described

Inhomogeneous charge transfer within monolayer zinc phthalocyanine absorbed on TiO2(110)

The d-orbital contribution from the transition metal centers of phthalocyanine brings difficulties to understand the role of the organic ligands and their molecular frontier orbitals when it adsorbs on oxide surfaces. Here we use zinc phthalocyanine (ZnPc)TiO (110) as a model system where the zinc d-orbitals are located deep below the organic orbitals leaving room for a detailed study of the interaction between the organic ligand and the substrate. A charge depletion from the highest occupied molecular orbital is observed, and a consequent shift of N1s and C1s to higher binding energy in photoelectron spectroscopy (PES). A detailed comparison of peak shifts in PES and near-edge X-ray absorption fine structure spectroscopy illustrates a slightly uneven charge distribution within the molecular plane and an inhomogeneous charge transfer screening between the center and periphery of the organic ligand: faster in the periphery and slower at the center, which is different from other metal phthalocyanine, e.g., FePcTiO . Our results indicate that the metal center can substantially influence the electronic properties of the organic ligand at the interface by introducing an additional charge transfer channel to the inner molecular part

Surface concentration dependent structures of iodine on Pd(110)

We use photoelectron spectroscopy, low energy electron diffraction, scanning tunneling microscopy, and density functional theory to investigate coverage dependent iodine structures on Pd(110). At 0.5 ML (monolayer), a c(2 × 2) structure is formed with iodine occupying the four-fold hollow site. At increasing coverage, the iodine layer compresses into a quasi-hexagonal structure at 2/3 ML, with iodine occupying both hollow and long bridge positions. There is a substantial difference in electronic structure between these two iodine sites, with a higher electron density on the bridge bonded iodine. In addition, numerous positively charged iodine near vacancies are found along the domain walls. These different electronic structures will have an impact on the chemical properties of these iodine atoms within the layer

A new crystal: Layer-structured rhombohedral In3Se4

A new layer-structured rhombohedral In3Se4 crystal was synthesized by a facile and mild solvothermal method. Detailed structural and chemical characterizations using transmission electron microscopy, coupled with synchrotron X-ray diffraction analysis and Rietveld refinement, indicate that In3Se4 crystallizes in a layered rhombohedral structure with lattice parameters of a = 3.964 ± 0.002 Å and c = 39.59 ± 0.02 Å, a space group of R3m, and with a layer composition of Se-In-Se-In-Se-In-Se. The theoretical modeling and experimental measurements indicate that the In3Se4 is a self-doped n-type semiconductor. This study not only enriches the understanding on crystallography of indium selenide crystals, but also paves a way in the search for new semiconducting compounds. This journal i