Layer dependent thermal transport properties of one- to three-layer magnetic Fe:MoS.

Two-Dimensional transition metal dichalcogenides have been the subject of extensive attention thanks to their unique properties and atomically thin structure. Because of its unprecedented room-temperature magnetic properties, iron-doped MoS (Fe:MoS) is considered the next-generation quantum and magnetic material. It is essential to understand Fe:MoS's thermal behavior since temperature and thermal load/activation are crucial for their magnetic properties and the current nano and quantum devices have been severely limited by thermal management.

Photoswitchable optoelectronic properties of 2D MoSe/diarylethene hybrid structures.

The ability to modulate optical and electrical properties of two-dimensional (2D) semiconductors has sparked considerable interest in transition metal dichalcogenides (TMDs). Herein, we introduce a facile strategy for modulating optoelectronic properties of monolayer MoSe with external light. Photochromic diarylethene (DAE) molecules formed a 2-nm-thick uniform layer on MoSe, switching between its closed- and open-form isomers under UV and visible irradiation, respectively.

Advances in Two-Dimensional Magnetic Semiconductors via Substitutional Doping of Transition Metal Dichalcogenides.

Transition metal dichalcogenides (TMDs) are two-dimensional (2D) materials with remarkable electrical, optical, and chemical properties. One promising strategy to tailor the properties of TMDs is to create alloys through a dopant-induced modification. Dopants can introduce additional states within the bandgap of TMDs, leading to changes in their optical, electronic, and magnetic properties.

An Ultralow Power Mixed Dimensional Heterojunction Transistor Based on the Charge Plasma pn Junction.

Development of a reliable doping method for 2D materials is a key issue to adopt the materials in the future microelectronic circuits and to replace the silicon, keeping the Moore's law toward the sub-10 nm channel length. Especially hole doping is highly required, because most of the transition metal dichalcogenides (TMDC) among the 2D materials are electron-doped by sulfur vacancies in their atomic structures. Here, hole doping of a TMDC, tungsten disulfide (WS ) using the silicon substrate as the dopant medium is demonstrated.

Au-on-Ag nanostructure forSERS monitoring of catalytic reactions.

Dual-functionality Au-on-Ag nanostructures (AOA) were fabricated on a silicon substrate by first immobilizing citrate-reduced Ag nanoparticles (Ag NPs, ∼43 nm in diameter), followed by depositing ∼7 nm Au nanofilms (Au NFs) via thermal evaporation. Au NFs were introduced for their catalytic activity in concave-convex nano-configuration. Ag NPs underneath were used for their significant enhancement factor (EF) in surface-enhanced Raman scattering (SERS)-based measurements of analytes of interest.

Improving the Optical Quality of MoSe and WS Monolayers with Complete -BN Encapsulation by High-Temperature Annealing.

We improved the optical quality and stability of an exfoliated monolayer (ML) MoSe and chemical vapor deposition (CVD)-grown WS MLs by encapsulating and sealing them with both top and bottom few-layer -BN, as tested by subsequent high-temperature annealing up to 873 K and photoluminescence (PL) measurements. These transition-metal dichalcogenide (TMD) MLs remained stable up to this maximum temperature, as seen visually. After the heating/cooling cycle, the integrated photoluminescence (PL) intensity at 300 K in the MoSe ML was ∼4 times larger than that before heating and that from exciton and trion PL in the analogous WS ML sample was ∼14 times and ∼2.

Stabilization of Chemical-Vapor-Deposition-Grown WS Monolayers at Elevated Temperature with Hexagonal Boron Nitride Encapsulation.

Chemical vapor deposition (CVD)-grown flakes of high-quality monolayers of WS can be stabilized at elevated temperatures by encapsulation with several layer hexagonal boron nitride (BN), but to different degrees in the presence of ambient air, flowing N, and flowing forming gas (95% N, 5% H). The best passivation of WS at elevated temperature occurs for -BN-covered samples with flowing N (after heating to 873 K), as judged by optical microscopy and photoluminescence (PL) intensity after a heating/cooling cycle. Stability is worse for uncovered samples, but best with flowing forming gas.

Experimental and Computational Investigation of Layer-Dependent Thermal Conductivities and Interfacial Thermal Conductance of One- to Three-Layer WSe.

Two-dimensional materials such as graphene and transition metal dichalcogenides (TMDCs) have received extensive research interest and investigations in the past decade. In this research, we used a refined opto-thermal Raman technique to explore the thermal transport properties of one popular TMDC material WSe, in the single-layer (1L), bilayer (2L), and trilayer (3L) forms. This measurement technique is direct without additional processing to the material, and the absorption coefficient of WSe is discovered during the measurement process to further increase this technique's precision.

The effects of substitutional Fe-doping on magnetism in MoSand WSmonolayers.

Doping of two-dimensional (2D) semiconductors has been intensively studied toward modulating their electrical, optical, and magnetic properties. While ferromagnetic 2D semiconductors hold promise for future spintronics and valleytronics, the origin of ferromagnetism in 2D materials remains unclear. Here, we show that substitutional Fe-doping of MoSand WSmonolayers induce different magnetic properties.

Computational study of the water-driven graphene wrinkle life-cycle towards applications in flexible electronics.

The ubiquitous presence of wrinkles in two-dimensional materials alters their properties significantly. It is observed that during the growth process of graphene, water molecules, sourced from ambient humidity or transferred method used, can get diffused in between graphene and the substrate. The water diffusion causes/assists wrinkle formation in graphene, which influences its properties.

Enabling room temperature ferromagnetism in monolayer MoS via in situ iron-doping.

Two-dimensional semiconductors, including transition metal dichalcogenides, are of interest in electronics and photonics but remain nonmagnetic in their intrinsic form. Previous efforts to form two-dimensional dilute magnetic semiconductors utilized extrinsic doping techniques or bulk crystal growth, detrimentally affecting uniformity, scalability, or Curie temperature. Here, we demonstrate an in situ substitutional doping of Fe atoms into MoS monolayers in the chemical vapor deposition growth.

Controlled edge dependent stacking of WS-WS Homo- and WS-WSe Hetero-structures: A Computational Study.

Transition Metal Dichalcogenides (TMDs) are one of the most studied two-dimensional materials in the last 5-10 years due to their extremely interesting layer dependent properties. Despite the presence of vast research work on TMDs, the complex relation between the electro-chemical and physical properties make them the subject of further research. Our main objective is to provide a better insight into the electronic structure of TMDs.

Conceptual design considerations for a wireless intraocular pressure sensor system for effective glaucoma management.

As a leading form of preventable visual impairment, it is imperative to assess glaucoma treatment as a function of intraocular pressure (IOP). IOP can spike throughout the day. This necessitates a device that can (1) monitor IOP outside of clinical visits by providing a memory when IOP exceeds a set threshold indicating the possibility for glaucomatous damage to occur; and (2) accurately assess IOP.

A stretchable and bendable all-solid-state pseudocapacitor with dodecylbenzenesulfonate-doped polypyrrole-coated vertically aligned carbon nanotubes partially embedded in PDMS.

We present an all-solid-state flexible and stretchable pseudocapacitor composed of dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS))-coated vertically aligned carbon nanotubes (VACNTs) partially embedded in a polydimethylsiloxane (PDMS) substrate. VACNTs are grown via atmospheric-pressure chemical vapor deposition on a Si/SiO substrate and transferred onto PDMS. Then, the PPy(DBS) film is coated with a surface charge of 300 mC cm on individual carbon nanotubes (CNTs) via electropolymerization.

Influence of Transition Metal Dichalcogenide Surfaces on Cellular Morphology and Adhesion.

This article presents the effect of transition metal dichalcogenide (TMD) surfaces and their geometric arrangements on resulting cellular morphology and adhesion. WS and MoS on SiO and polydimethylsiloxane (PDMS) substrates were utilized as cell culture platforms, and cell-substrate interactions were probed via analysis of cellular morphometric features (i.e.

A carbon nanotube-embedded conjugated polymer mesh with controlled oil absorption and surface regeneration via in situ wettability switch.

This paper presents a mesh-type absorbent made of a carbon nanotube (CNT)-embedded polypyrrole dodecylbenzenesulfonate (PPy(DBS)) surface for controlled absorption and release of oils and regeneration of polymer surfaces toward continuous oil/water separation. The mesh absorbs dichloromethane (DCM) under oxidation in aqueous environment and releases them under reduction via in situ switching of underwater wettability. CNTs were grown out of stainless steel surfaces and embedded into the PPy(DBS) film, which enhanced the switchable wettability as well as the surface regeneration.

Reduction in Step Height Variation and Correcting Contrast Inversion in Dynamic AFM of WS Monolayers.

A model has been developed to account for and prevent the anomalies encountered in topographic images of transition metal dichalcogenide monolayers using dynamic atomic force microscopy (dAFM). The height of WS monolayers measured using dAFM appeared to be increased or decreased, resulting from the interactions between the tip and the surface. The hydrophilic SiO substrate appeared higher than the weakly hydrophilic WS when the tip amplitude was low or at a high set point (high force).

Graphene-vertically aligned carbon nanotube hybrid on PDMS as stretchable electrodes.

Stretchable electrodes are a critical component for flexible electronics such as displays, energy devices, and wearable sensors. Carbon nanotubes (CNTs) and graphene have been considered for flexible electrode applications, due to their mechanical strength, high carrier mobility, and excellent thermal conductivity. Vertically aligned carbon nanotubes (VACNTs) provide the possibility to serve as interconnects to graphene sheets as stretchable electrodes that could maintain high electrical conductivity under large tensile strain.

On-Demand Capture and Release of Organic Droplets Using Surfactant-Doped Polypyrrole Surfaces.

In this paper, we demonstrate the controlled capture and release of dichloromethane (DCM) droplets on dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) surfaces in an aqueous environment. The droplets captured on oxidized PPy(DBS) surfaces were released on-demand via a reduction process at ∼0.9 V, with controlled release time and droplet morphology.

Nanotexturing of Conjugated Polymers via One-Step Maskless Oxygen Plasma Etching for Enhanced Tunable Wettability.

A one-step maskless oxygen plasma etching process is investigated to nanopattern conjugated polymer dodecylbenzenesulfonate doped polypyrrole (PPy(DBS)) and to examine the effects of nanostructures on the inherent tunable wettability of the surface and the droplet mobility. Etching characteristics such as the geometry and dimensions of the nanostructures are systematically examined for the etching power and duration. The mechanism of self-formation of vertically aligned dense-array pillared nanostructures in the one-step maskless oxygen plasma etching process is also investigated.

Graphene-Assisted Antioxidation of Tungsten Disulfide Monolayers: Substrate and Electric-Field Effect.

Transition metal dichalcogenides (TMDs) have emerged as promising materials to complement graphene for advanced optoelectronics. However, irreversible degradation of chemical vapor deposition-grown monolayer TMDs via oxidation under ambient conditions limits applications of TMD-based devices. Here, the growth of oxidation-resistant tungsten disulfide (WS ) monolayers on graphene is demonstrated, and the mechanism of oxidation of WS on SiO , graphene/SiO , and on graphene suspended in air is elucidated.

Effects of Electropolymerization Parameters of PPy(DBS) Surfaces on the Droplet Flattening Behaviors During Redox.

We present a systematic study on the effects of electropolymerization parameters of polypyrrole-dodecylbenzenesulfonate (PPy(DBS)) surfaces on the flattening behaviors of organic droplets during reduction and oxidation (redox). PPy(DBS) surfaces were fabricated under varying electropolymerization conditions, including voltage, surface charge density, and dopant electrolyte (DBS) concentration. The flattening behaviors on different PPy(DBS) surfaces were characterized by analyzing droplet behaviors and energy-dispersive X-ray spectroscopy (EDS) data.

Lateral actuation of an organic droplet on conjugated polymer electrodes via imbalanced interfacial tensions.

This paper presents a new mechanism for the controlled lateral actuation of organic droplets on dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) electrodes at low voltages (∼0.9 V) in an aqueous environment. The droplet actuation is based on the tunable surface wetting properties of the polymer electrodes induced by electrochemical redox reactions.

In Situ Control of Underwater-Pinning of Organic Droplets on a Surfactant-Doped Conjugated Polymer Surface.

Controlling the pinning of organic droplets on solid surfaces is of fundamental and practical interest in the field of material science and engineering, which has numerous applications such as surface cleaning, water treatment, and microfluidics. Here, a rapid in situ control of pinning and actuation of organic droplets is demonstrated on dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) surfaces in an aqueous environment via an electrochemical redox process. A dramatic change of the pinning results from the transport of DBS(-) molecules between the PPy(DBS) surface and the aqueous environment, as well as from a simultaneous alternation of the surface oleophobicity to organic liquids during the redox process.