Chemical exfoliation efficacy of semiconducting WS2 and its use in an additively manufactured heterostructure graphene–WS2–graphene photodiode

In the present work, various chemical exfoliation routes for semiconducting two-dimensional (2D) layered material WS₂ are explored, which include magnetic stirring (MS), shear mixing (SM), and horn-tip (HT) sonication. Current–voltage measurements, Raman spectroscopy, and photoluminescence (PL) spectroscopy were used to characterize the drop-casted WS₂ nanosheets produced by these three techniques and our analysis revealed that HT sonication produced the most optimal dispersions. Heterostructure photodetector devices were then fabricated using inkjet printing of the HT sonicated dispersions of WS₂ and graphene. The photodetector device performance was measured using a stream of ON/OFF light pulses generated using a red laser with wavelength λ ∼ 660 nm, and an arbitrary waveform generator. From this analysis, the photoresponsivity and detectivity of the graphene–WS₂–graphene heterostructure devices were calculated to be ∼0.86 A W⁻¹ and ∼10¹³ Jones, respectively. Capacitance–voltage (C–V) and C–frequency (f) measurements were also conducted, where the V was swept from –6 V to +6 V, while the change in C was measured from f ∼ 20 kHz up to 3 MHz to gain insights into the nature of the graphene–WS₂ interface. From the C–V measurements, the C plateaued at ∼324.3 pF from ∼−4 V to +4 V for the lowest f of 20 kHz and it reduced to ∼200 pF from −6 V to ∼−4 V, and similarly from ∼4 V to 6 V, C was ∼190 pF. The decrease in C for V > +4 V and V < −4 V was attributed to the reduction of the interfacial barrier at the electrodes which is suggestive of a Schottky-based photodiode at the graphene–WS₂ interface. A sharp decrease in C from ∼315.75 pF at 25.76 kHz to ∼23.79 pF at 480 kHz (at 0 V bias) from the C–f measurements suggests a strong effect of interface trap density on C built-up at the graphene–WS₂ interface and the ensuing Schottky barrier height. Our work confirms the excellent potential of solution-cast, trilayer graphene–WS₂–graphene heterostructures as a promising photodetector platform using additively manufactured inkjet printing.

Among magnetic stirring (MS), shear mixing (SM), and horn-tip (HT) sonication for the chemical exfoliation of semiconducting WS₂, HT sonication resulted in stable dispersions which were used to demonstrate ink-jet printed graphene–WS₂–graphene photodiodes.     

Effect of remote myofascial release on hamstring flexibility in asymptomatic individuals – A randomized clinical trial

Background

The existence of continuity between fascia and muscles that may be anatomically distant from each other is emphasized in the tensegrity principle. Despite evidence from in vitro studies, there is a dearth of literature concerning the in vivo behavior of these connections.

Differentiation of intracranial Rosai‐Dorfman histiocytosis from meningioma using MR perfusion

Intracranial Rosai‐Dorfman disease may be indistinguishable from meningioma. This distinction is essential, as they are treated very differently. We present two cases where perfusion imaging helped make this distinction, allowing one to be treated successfully without craniotomy. Perfusion imaging may be a powerful adjunct in cases where RDD mimics meningioma.