8 research outputs found
The Imaging and Slitless Spectroscopy Instrument for Surveys (ISSIS): expected radiometric performance, operation modes and data handling
ISSIS is the instrument for imaging and slitless spectroscopy on-board WSO-UV. In this article, a detailed comparison between ISSIS expected radiometric performance and other ultraviolet instruments is shown. In addition, we present preliminary information on the performance verification tests and on the foreseen procedures for in-flight operation and data handling
Extraordinary room-temperature photoluminescence in WS2 monolayers
Individual monolayers of metal dichalcogenides are atomically thin
two-dimensional crystals with attractive physical properties different from
their bulk layered counterpart. Here we describe the direct synthesis of WS2
monolayers with triangular morphologies and strong room-temperature
photoluminescence (PL). Bulk WS2 does not present PL due to its indirect band
gap nature. The edges of these monolayers exhibit PL signals with extraordinary
intensity, around 25 times stronger than the platelets center. The structure
and composition of the platelet edges appear to be critical for the PL
enhancement effect. Electron diffraction revealed that platelets present zigzag
edges, while first-principles calculations indicate that sulfur-rich zigzag WS2
edges possess metallic edge states, which might tailor the optical response
reported here. These novel 2D nanoscale light sources could find diverse
applications including the fabrication of flexible/transparent/low-energy
optoelectronic devices
Temperature- and power-dependent phonon properties of suspended continuous WS2 monolayer films
Ultrasensitive gas detection of large-area boron-doped graphene
Heteroatom doping is an efficient way to modify the chemical and electronic properties of graphene. In particular, boron doping is expected to induce a p-type (boron)-conducting behavior to pristine (nondoped) graphene, which could lead to diverse applications. However, the experimental progress on atomic scale visualization and sensing properties of large-area boron-doped graphene (BG) sheets is still very scarce. This work describes the controlled growth of centimeter size, high-crystallinity BG sheets. Scanning tunneling microscopy and spectroscopy are used to visualize the atomic structure and the local density of states around boron dopants. It is confirmed that BG behaves as a p-type conductor and a unique croissant-like feature is frequently observed within the BG lattice, which is caused by the presence of boron-carbon trimers embedded within the hexagonal lattice. More interestingly, it is demonstrated for the first time that BG exhibits unique sensing capabilities when detecting toxic gases, such as NO2 and NH3, being able to detect extremely lowconcentrations (e.g., parts per trillion, parts per billion). This work envisions that other attractive applications could now be explored based on as-synthesized BG