The liquid-phase exfoliation of tin(II) sulfide to produce SnS nanosheets in N-methyl-2-pyrrolidone is reported. The material is characterized by Raman spectroscopy, atomic force microscopy, lattice-resolution scanning transmission electron microscope imaging, and energy dispersive X-ray spectrum imaging. Quantum chemical calculations on the optoelectronic characteristics of bulk and 10-layer down to monolayer SnS have been performed using a quantum chemical density functional tight-binding approach. The optical properties of the SnS and centrifugally fractionated SnS nanosheet dispersions were compared to that predicted by theory. Through centrifugation, bilayer SnS nanosheets can be produced size-selectively. The scalable solution processing of semiconductor SnS nanosheets is the key to their commercial exploitation and is potentially an important step toward the realization of a future electronics industry based on two-dimensional materials.
The new paradigm of heterostructures based on two-dimensional (2D) atomic crystals has already led to the observation of exciting physical phenomena and creation of novel devices. The possibility of combining layers of different 2D materials in one stack allows unprecedented control over the electronic and optical properties of the resulting material. Still, the current method of mechanical transfer of individual 2D crystals, though allowing exceptional control over the quality of such structures and interfaces, is not scalable. Here we show that such heterostructures can be assembled from chemically exfoliated 2D crystals, allowing for low-cost and scalable methods to be used in device fabrication.
We report the electrochemical detection of the redox active cardiac biomarker myoglobin (Mb) using aptamer-functionalized black phosphorus nanostructured electrodes by measuring direct electron transfer. The as-synthesized few-layer black phosphorus nanosheets have been functionalized with poly-l-lysine (PLL) to facilitate binding with generated anti-Mb DNA aptamers on nanostructured electrodes. This aptasensor platform has a record-low detection limit (∼0.524 pg mL(-1)) and sensitivity (36 μA pg(-1) mL cm(-2)) toward Mb with a dynamic response range from 1 pg mL(-1) to 16 μg mL(-1) for Mb in serum samples. This strategy opens up avenues to bedside technologies for multiplexed diagnosis of cardiovascular diseases in complex human samples.
We
demonstrate a new design of graphene liquid cell consisting
of a thin lithographically patterned hexagonal boron nitride crystal
encapsulated on both sides with graphene windows. The ultrathin window
liquid cells produced have precisely controlled volumes and thicknesses
and are robust to repeated vacuum cycling. This technology enables
exciting new opportunities for liquid cell studies, providing a reliable
platform for high resolution transmission electron microscope imaging
and spectral mapping. The presence of water was confirmed using electron
energy loss spectroscopy (EELS) via the detection of the oxygen K-edge
and measuring the thickness of full and empty cells. We demonstrate
the imaging capabilities of these liquid cells by tracking the dynamic
motion and interactions of small metal nanoparticles with diameters
of 0.5–5 nm. We further present an order of magnitude improvement
in the analytical capabilities compared to previous liquid cell data
with 1 nm spatial resolution elemental mapping achievable for liquid
encapsulated bimetallic nanoparticles using energy dispersive X-ray
spectroscopy (EDXS).
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