Near‐infrared light‐emitting technology is ideal for noncontact diagnostic medical imaging and high‐speed data communications. High‐quality ReSe2 nanosheets of anisotropic single‐crystal structure with a bandgap of 1.26 eV (≈984 nm) are synthesized with an atmospheric pressure chemical vapor deposition (APCVD) method. The as‐synthesized ReSe2 nanosheets‐fabricated light‐emitting transistors (LETs) exhibit nearly symmetric ambipolar characteristics in electrical transport. Judicious selection of asymmetric platinum (Pt)/chromium (Cr) electrodes, with their work functions matching respectively the conduction‐ and valence‐band edges of ambipolar ReSe2, generates a low turn‐on voltage ReSe2‐LET with the balanced number density and field‐effect mobility of bipolar carriers (i.e., electrons and holes). Room‐temperature near‐infrared electroluminescence (NIR EL) from the frequency‐modulated ReSe2‐LET has been observed unprecedentedly with the assistance of a lock‐in detection system. The NIR EL intensity is tested by varying the bias voltage applied to the ReSe2‐LET devices with different channel lengths. The wavelength of the NIR EL from ReSe2‐LET is differentiated with optical bandpass filters. Room‐temperature angle‐dependent two lobe‐shaped EL pattern manifests the inherent anisotropic in‐plane excitonic polarization of the ReSe2 crystal. The highly stable NIR EL from ReSe2‐LETs provides prospective 2D material‐based ultrathin scalable data communication electronics for future development.
Thermodynamic integration (TI) molecular dynamics (MD) simulations for the binding of a pair of a reference ("ref") ligand and an analogous ("analog") ligand to either tagged (with six extra residues at the N-terminus) or untagged p38 kinase proteins were carried out in order to probe how the binding affinity is influenced by the presence or absence of the peptide tag in p38 kinase. This possible effect of protein length on the binding affinity of a ligand-which is seldom addressed in the literature-is important because, even when two labs claim to have performed experiments with the same protein, they may actually have studied variants of the same protein with different lengths because they applied different protein expression conditions/procedures. Thus, if we wanted to compare ligand binding affinities measured in the two labs, it would be necessary to account for any variation in ligand binding affinity with protein length. The pair of ligand-p38 kinase complexes examined in this work (pdb codes: 3d7z and 3lhj, respectively) were ideal for investigating this effect. The experimentally determined binding energy for the ref ligand with the untagged p38 kinase was -10.9 kcal mol(-1), while that for the analog ligand with the tagged p38 kinase was -11.9 kcal mol(-1). The present TI-MD simulation of the mutation of the ref ligand into the analog ligand while the ligand is bound to the untagged p38 kinase predicted that the binding affinity of the analog ligand is 2.0 kcal mol(-1) greater than that of the ref ligand. A similar simulation also indicated that the same was true for ligand binding to the tagged protein, but in this case the binding affinity for the analog ligand is 2.5 kcal mol(-1) larger than that for the ref ligand. These results therefore suggest that the presence of the peptide tag on p38 kinase increased the difference in the binding energies of the ligands by a small amount of 0.5 kcal mol(-1). This result supports the assumption that the presence of a peptide tag has only a minor effect on ΔG values. The error bars in the computed ΔG values were then estimated via confidence interval analysis and a time autocorrelation function for the quantity dV/dλ. The estimated correlation time was ~0.5 ps and the error bar in the ΔG values estimated using nanosecond-scale simulations was ±0.3 kcal mol(-1) at a confidence level of 95%. These predicted results can be verified in future experiments and should prove useful in subsequent similar studies. Graphical Abstract Thermodynamic cycles for binding of two analogous ligands with untagged and tagged p38 kinases and associated Gibbs free energy.
Novel anti‐ambipolar transistors (AATs) are gate tunable rectifiers with a marked potential for multi‐valued logic circuits. In this work, the optoelectronic applications of AATs in cryogenic conditions are studied, of which the AAT devices consist of vertically stacked p‐SnS and n‐ MoSe2 nanoflakes to form a type‐II staggered band alignment. An electrostatically tunable p‐SnS/n‐MoSe2 cryo‐phototransistor is presented with unique anti‐ambipolar characteristics and cryogenic‐enhanced optoelectronic performance. The cryo‐phototransistor exhibits a sharp and highly symmetric anti‐ambipolar transfer curve at 77 K with the peak‐to‐valley ratio of 103 operating under a low bias voltage of 1 V. The high cooling‐enhanced charge mobilities in the cryo‐phototransistor grant this AAT device remarkable photodetection capabilities. At 77 K, the p‐SnS/n‐MoSe2 cryo‐phototransistor, holding a broad photoresponse in the spectral range of 250−900 nm, demonstrates its high responsivity of 2 × 104 A W−1 and detectivity of 7.5 × 1013 Jones with the excitation at 532 nm. The high‐performance p‐SnS/n‐MoSe2 low‐dimensional phototransistor with low operating voltages at 77−150 K is eligible for optoelectronic applications in cryogenic environments. Furthermore, the cryo‐characteristics of this heterostructure can be further extended to design the mul‐tivalued logic circuits operated in cryogenic conditions.
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