Giant Optical Anisotropy in 2D Metal-Organic Chalcogenates.

Optical anisotropy is a fundamental attribute of some crystalline materials and is quantified via birefringence. A birefringent crystal gives rise to not only asymmetrical light propagation but also attenuation along two distinct polarizations, a phenomenon called linear dichroism (LD). Two-dimensional (2D) layered materials with high in-plane and out-of-plane anisotropy have garnered interest in this regard.

Understanding Ion-Beam Damage to Air-Sensitive Lithium Metal With Cryogenic Electron and Ion Microscopy.

It is essential to understand the nanoscale structure and chemistry of energy storage materials due to their profound impact on battery performance. However, it is often challenging to characterize them at high resolution, as they are often fundamentally altered by sample preparation methods. Here, we use the cryogenic lift-out technique in a plasma-focused ion beam (PFIB)/scanning electron microscope (SEM) to prepare air-sensitive lithium metal to understand ion-beam damage during sample preparation.

Scalable Superior Chemical Sensing Performance of Stretchable Ionotronic Skin via a π-Hole Receptor Effect.

Skin-attachable gas sensors provide a next-generation wearable platform for real-time protection of human health by monitoring environmental and physiological chemicals. However, the creation of skin-like wearable gas sensors, possessing high sensitivity, selectivity, stability, and scalability (4S) simultaneously, has been a big challenge. Here, an ionotronic gas-sensing sticker (IGS) is demonstrated, implemented with free-standing polymer electrolyte (ionic thermoplastic polyurethane, i-TPU) as a sensing channel and inkjet-printed stretchable carbon nanotube electrodes, which enables the IGS to exhibit high sensitivity, selectivity, stability (against mechanical stress, humidity, and temperature), and scalable fabrication, simultaneously.

Enhanced Selectivity of MXene Gas Sensors through Metal Ion Intercalation: In Situ X-ray Diffraction Study.

Gas molecules are known to interact with two-dimensional (2D) materials through surface adsorption where the adsorption-induced charge transfer governs the chemiresistive sensing of various gases. Recently, titanium carbide (TiCT ) MXene emerged as a promising sensing channel showing the highest sensitivity among 2D materials and unique gas selectivity. However, unlike conventional 2D materials, MXenes show metallic conductivity and contain interlayer water, implying that gas molecules will likely interact in a more complex way than the typical charge transfer model.

Ten Nanometer Scale WO/CuO Heterojunction Nanochannel for an Ultrasensitive Chemical Sensor.

The fabrication of p-n heterostructures of a metal oxide semiconductor (MOS) showed that a large amount of heterojunction interfaces is one of the key issues in MOS gas sensor research, since it could significantly enhance the sensing performance. Despite considerable progress in this area, fabrication of an ideal p-n heterojunction sensing channel has been challenging because of morphological limitations of synthetic methods in the conventional bottom-up fabrication based on precursor reductions. In this study, a 10 nm scale p-n heterojunction nanochannel was fabricated with ultrasmall grained WO/CuO nanopatterns in a large area (centimeter scale) through unique one-step top-down lithographic approaches.

Edge-Functionalized Graphene Nanoribbon Chemical Sensor: Comparison with Carbon Nanotube and Graphene.

With growing focus on the use of carbon nanomaterials in chemical sensors, one-dimensional graphene nanoribbon (GNR) has become one of the most attractive channel materials, owing to its enhanced conductance fluctuation by quantum confinement effects and dense, abundant edge sites. Due to the narrow width of a basal plane with one-dimensional morphology, chemical modification of edge sites would greatly affect the electrical channel properties of a GNR. Here, we demonstrate for the first time that chemically functionalizing the edge sites with aminopropylsilane (APS) molecules can significantly enhance the sensing performance of the GNR sensor.

An Ultrastable Ionic Chemiresistor Skin with an Intrinsically Stretchable Polymer Electrolyte.

Ultrastable sensing characteristics of the ionic chemiresistor skin (ICS) that is designed by using an intrinsically stretchable thermoplastic polyurethane electrolyte as a volatile organic compound (VOC) sensing channel are described. The hierarchically assembled polymer electrolyte film is observed to be very uniform, transparent, and intrinsically stretchable. Systematic experimental and theoretical studies also reveal that artificial ions are evenly distributed in polyurethane matrix without microscale phase separation, which is essential for implementing high reliability of the ICS devices.

Metallic TiCT MXene Gas Sensors with Ultrahigh Signal-to-Noise Ratio.

Achieving high sensitivity in solid-state gas sensors can allow the precise detection of chemical agents. In particular, detection of volatile organic compounds (VOCs) at the parts per billion (ppb) level is critical for the early diagnosis of diseases. To obtain high sensitivity, two requirements need to be simultaneously satisfied: (i) low electrical noise and (ii) strong signal, which existing sensor materials cannot meet.

Tunable Volatile-Organic-Compound Sensor by Using Au Nanoparticle Incorporation on MoS.

Controlling the charge concentrations of two-dimensional (2D) materials is a critical requirement for realizing versatility and potential application of these materials in high-performance electronics and sensors. In order to exploit the novel chemical-sensing characteristics of 2D materials for sensitive and selective sensors, various functionalization methods are needed to ensure efficient doping of channels based on 2D materials. In the present study, the gas-sensing performance of MoS has been significantly enhanced by controlled Au nanoparticle functionalization.

Superior Chemical Sensing Performance of Black Phosphorus: Comparison with MoS2 and Graphene.

Superior chemical sensing performance of black phosphorus (BP) is demonstrated by comparison with MoS2 and graphene. Dynamic sensing measurements of multichannel detection show that BP displays highly sensitive, selective, and fast-responsive NO2 sensing performance compared to the other representative 2D sensing materials.