Efficient desalination of water continues to be a problem facing the society. Advances in nanotechnology have led to the development of a variety of nanoporous membranes for water purification. Here we show, by performing molecular dynamics simulations, that a nanopore in a single-layer molybdenum disulfide can effectively reject ions and allow transport of water at a high rate. More than 88% of ions are rejected by membranes having pore areas ranging from 20 to 60 Å2. Water flux is found to be two to five orders of magnitude greater than that of other known nanoporous membranes. Pore chemistry is shown to play a significant role in modulating the water flux. Pores with only molybdenum atoms on their edges lead to higher fluxes, which are ∼70% greater than that of graphene nanopores. These observations are explained by permeation coefficients, energy barriers, water density and velocity distributions in the pores.

Nanopore-based DNA sequencing has led to fast and high-resolution recognition and detection of DNA bases. Solid-state and biological nanopores have low signal-to-noise ratio (SNR) (< 10) and are generally too thick (> 5 nm) to be able to read at single-base resolution. A nanopore in graphene, a 2-D material with sub-nanometer thickness, has a SNR of ∼3 under DNA ionic current. In this report, using atomistic and quantum simulations, we find that a single-layer MoS2 is an extraordinary material (with a SNR > 15) for DNA sequencing by two competing technologies (i.e., nanopore and nanochannel). A MoS2 nanopore shows four distinct ionic current signals for single-nucleobase detection with low noise. In addition, a single-layer MoS2 shows a characteristic change/response in the total density of states for each base. The band gap of MoS2 is significantly changed compared to other nanomaterials (e.g., graphene, h-BN, and silicon nanowire) when bases are placed on top of the pristine MoS2 and armchair MoS2 nanoribbon, thus making MoS2 a promising material for base detection via transverse current tunneling measurement. MoS2 nanopore benefits from a craftable pore architecture (combination of Mo and S atoms at the edge) which can be engineered to obtain the optimum sequencing signals.

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is an order magnitude larger than previously thought, yet near the low end of known solidsolid interfaces. Our study also reveals unexpected insight into non-uniformities of the MoS2 transistors (small bilayer regions), which do not cause significant self-heating, suggesting that such semiconductors are less sensitive to inhomogeneity than expected. These results provide key insights into energy dissipation of 2D semiconductors and pave the way for the future design of energy-efficient 2D electronics. Keywords: Energy dissipation, 2D semiconductors, thermal boundary conductance, Raman thermometry, MoS2 2The performance of nanoelectronics is most often constrained by thermal challenges, 1, 2 memory bottlenecks, 3 and nanoscale contacts. 4 The former have become particular acute, with high integration densities leading to high power density, and numerous interfaces (e.g. between silicon, copper, SiO2) leading to high thermal resistance. New applications and new form-factors call for dense vertical integration into multi-layer "high-rise" processors for high-performance computing, 3 or integration with poor thermal substrates like flexible plastics (of thermal conductivity 5xlower than SiO2 and nearly 500x lower than silicon) for wearable computing. 5 These are the two most likely platforms for incorporating 2D semiconductors into electronics, yet very little is known about fundamental limits or practical implications of energy dissipation in these contexts.At its most basic level, energy dissipation begins in the ultra-thin transistor channel and is immediately limited by the insulating regions and thermal resistance with the interfaces surrounding it. Herbert Kroemer's observation 6 that "the interface is the device" is remarkably aptfor 2D semiconductors such as monolayer MoS2. These have no bulk, and are thus strongly limited by their interfaces. For instance, even some of the best electrical contacts known today add >50% parasitic resistance to MoS2 transistors when these are scaled to sub-100 nm dimensions. Similarly, thermal interfaces may be expected to limit energy dissipation from 2D electronics, and their understanding is essential. Nevertheless, a key challenge is the need to differentiate heating of the sub-nanometer thin 2D material from its environment. Here, Raman spectroscopy holds a unique advantage, 8, 9 as the temperature of even a monolayer semiconductor can be distinguished from the material directly under (or above) it, if the Raman signatures are distinct. 10Figure 1a shows our typical device structure and measurement setup. We utilize high-qual- Minor, randomly distributed non-uniformities in the temperature seen in Figure 2 are within the uncertainty of the measurement and are also visible in the reference map taken at VDS = 0 (on a hot stage), for which the temperature is known to be uniform, as shown in Supporting Information Figure S4. The uniform self-heating of transistors from CVD-grown MoS2 suggests that any change in energy dissipation around the 2L spots or other non-uniformit...

Hydrogen peroxide is a valuable chemical oxidant with a wide range of applications in a variety of industrial processes, especially in water sanitization. Electrochemical synthesis of hydrogen peroxide (H 2 O 2 ) through two-electron oxygen reduction reaction (2e-ORR) or two-electron water oxidation reaction (2e-WOR) has emerged as an appealing process for onsite production of this chemically valuable oxidant. On-site produced H 2 O 2 can be applied for wastewater treatment in remote locations or any applications where H 2 O 2 is needed as an oxidizing agent. This contribution studies the theoretical efforts in understanding the challenges in catalysis for electrochemical synthesis of H 2 O 2 as well as providing design principles for more efficient catalyst materials.