Structural characterization of In2O3 hierarchical microwires synthesized through decomposition thermal treatment of InSe single crystal

In this paper, we report the obtention of In₂O₃ nanostructured microwires by the decomposition thermal treatment of InSe single crystal in two-steps under an oxygen–ammonia flow without the presence of any catalyst. Long In₂O₃ microwires with uniform shape and homogeneous surface were first synthesized through thermal treatment of InSe single crystal at temperature of about 640 °C; then, furnace temperature was increased to 750 °C and, as annealing time proceeded, the obtained microwires served as substrates on which nanorod branches grew. The shape and the structure of the microarchitectures were characterized by means scanning electron microscopy, transmission electron microscopy, selected area diffraction pattern, X-Ray diffraction and Raman spectroscopy. Our results indicated that In₂O₃ primary wires with a clean surface grew in the [100] direction and that the secondary protuberances grew in the [011] direction. A possible growth mechanism of the hierarchical microwires was also proposed.     

Photoalignment and Surface‐Relief‐Grating Formation are Efficiently Combined in Low‐Molecular‐Weight Halogen‐Bonded Complexes

It is demonstrated that halogen bonding can be used to construct low‐molecular‐weight supramolecular complexes with unique light‐responsive properties. In particular, halogen bonding drives the formation of a photoresponsive liquid‐crystalline complex between a non‐mesogenic halogen bond‐donor molecule incorporating an azo group, and a non‐mesogenic alkoxystilbazole moiety, acting as a halogen bond‐acceptor. Upon irradiation with polarized light, the complex exhibits a high degree of photoinduced anisotropy (order parameter of molecular alignment > 0.5). Moreover, efficient photoinduced surface‐relief‐grating (SRG) formation occurs upon irradiation with a light interference pattern, with a surface‐modulation depth 2.4 times the initial film thickness. This is the first report on a halogen‐bonded photoresponsive low‐molecular‐weight complex, which furthermore combines a high degree of photoalignment and extremely efficient SRG formation in a unique way. This study highlights the potential of halogen bonding as a new tool for the rational design of high‐performance photoresponsive suprastructures.     

Microcavity-integrated graphene photodetector

There is an increasing interest in using graphene (1, 2) for optoelectronic applications. (3-19) However, because graphene is an inherently weak optical absorber (only ≈2.3% absorption), novel concepts need to be developed to increase the absorption and take full advantage of its unique optical properties. We demonstrate that by monolithically integrating graphene with a Fabry-Pérot microcavity, the optical absorption is 26-fold enhanced, reaching values >60%. We present a graphene-based microcavity photodetector with responsivity of 21 mA/W. Our approach can be applied to a variety of other graphene devices, such as electro-absorption modulators, variable optical attenuators, or light emitters, and provides a new route to graphene photonics with the potential for applications in communications, security, sensing and spectroscopy.     

Hole Surface Trapping in CdSe Nanocrystals: Dynamics, Rate Fluctuations, and Implications for Blinking

Carrier trapping is one of the main sources of performance degradation in nanocrystal-based devices. Yet the dynamics of this process is still unclear. We present a comprehensive investigation into the efficiency of hole transfer to a variety of trap sites located on the surface of the core or the shell or at the core/shell interface in CdSe nanocrystals with both organic and inorganic passivation, using the atomistic semiempirical pseudopotential approach. We separate the contribution of coupling strength and energetics in different systems and trap configurations, obtaining useful general guidelines for trapping rate engineering. We find that trapping can be extremely efficient in core-only systems, with trapping times orders of magnitude faster than radiative recombination. The presence of an inorganic shell can instead bring the trapping rates well below the typical radiative recombination rates observed in these systems.     

Detection of the early stage of recombinational DNA repair by silicon nanowire transistors

A silicon nanowire-based biosensor has been designed and applied for label-free and ultrasensitive detection of the early stage of recombinational DNA repair by RecA protein. Silicon nanowires transistors were fabricated by atomic force microscopy nanolithography and integrated into a microfluidic environment. The sensor operates by measuring the changes in the resistance of the nanowire as the biomolecular reactions proceed. We show that the nanoelectronic sensor can detect and differentiate several steps in the binding of RecA to a single-stranded DNA filament taking place on the nanowire-aqueous interface. We report relative changes in the resistance of 3.5% which are related to the interaction of 250 RecA·single-stranded DNA complexes. Spectroscopy data confirm the presence of the protein-DNA complexes on the functionalized silicon surfaces.     

Mechanical behaviour modelling of a new anchor system for large diameter GFRP bars

The strong anisotropy of unidirectionally-reinforced FRP composites makes it difficult to design an efficient anchorage for measuring the tensile strength and this difficulty increases together with the cross section area of the specimen. To overcome this difficulty a new anchor system was developed for tension testing of large diameter GFRP bars in a universal testing machine. The anchor body designed and tested consists of two shells, pushed one against the other by the jaws of the testing machine, leaving an inner conical hole. The ends of the bar are provided with resin heads having the shape of the hole inside the anchor body. The present paper details the modelling investigation to verify and improve the shape and hence the performances of this anchor system. The approach adopted consists in a parametric numerical analysis that rests on the experimental data already gathered.