Ultrathin ferroic HfO-ZrO superlattice gate stack for advanced transistors.

With the scaling of lateral dimensions in advanced transistors, an increased gate capacitance is desirable both to retain the control of the gate electrode over the channel and to reduce the operating voltage. This led to a fundamental change in the gate stack in 2008, the incorporation of high-dielectric-constant HfO (ref. ), which remains the material of choice to date.

Confinement of Ultrasmall Bimetallic Nanoparticles in Conductive Metal-Organic Frameworks via Site-Specific Nucleation.

Conductive metal-organic frameworks (cMOFs) are emerging materials for various applications due to their high surface area, high porosity, and electrical conductivity. However, it is still challenging to develop cMOFs having high surface reactivity and durability. Here, highly active and stable cMOF are presented via the confinement of bimetallic nanoparticles (BNPs) in the pores of a 2D cMOF, where the confinement is guided by dipolar-interaction-induced site-specific nucleation.

Large-area synthesis of nanoscopic catalyst-decorated conductive MOF film using microfluidic-based solution shearing.

Conductive metal-organic framework (C-MOF) thin-films have a wide variety of potential applications in the field of electronics, sensors, and energy devices. The immobilization of various functional species within the pores of C-MOFs can further improve the performance and extend the potential applications of C-MOFs thin films. However, developing facile and scalable synthesis of high quality ultra-thin C-MOFs while simultaneously immobilizing functional species within the MOF pores remains challenging.

Chemiresistive Hydrogen Sensors: Fundamentals, Recent Advances, and Challenges.

Hydrogen (H) is one of the next-generation energy sources because it is abundant in nature and has a high combustion efficiency that produces environmentally benign products (HO). However, H/air mixtures are explosive at H concentrations above 4%, thus any leakage of H must be rapidly and reliably detected at much lower concentrations to ensure safety. Among the various types of H sensors, chemiresistive sensors are one of the most promising sensing systems due to their simplicity and low cost.

Single-Atom Pt Stabilized on One-Dimensional Nanostructure Support Carbon Nitride/SnO Heterojunction Trapping.

Catalysis with single-atom catalysts (SACs) exhibits outstanding reactivity and selectivity. However, fabrication of supports for the single atoms with structural versatility remains a challenge to be overcome, for further steps toward catalytic activity augmentation. Here, we demonstrate an effective synthetic approach for a Pt SAC stabilized on a controllable one-dimensional (1D) metal oxide nano-heterostructure support, by trapping the single atoms at heterojunctions of a carbon nitride/SnO heterostructure.

Hydrogen Sensors Based on MoS Hollow Architectures Assembled by Pickering Emulsion.

For rapid hydrogen gas (H) sensing, we propose the facile synthesis of the hollow structure of Pt-decorated molybdenum disulfide (h-MoS/Pt) using ultrathin (mono- or few-layer) two-dimensional nanosheets. The controlled amphiphilic nature of MoS surface produces ultrathin MoS NS-covered polystyrene particles one-step Pickering emulsification. The incorporation of Pt nanoparticles (NPs) on the MoS, followed by pyrolysis, generates the highly porous h-MoS/Pt.

The Design and Science of Polyelemental Nanoparticles.

Polyelemental nanoparticles (PE NPs) containing four or more elements in a single NP have intriguing intrinsic properties compared to their single-element counterparts. The fusion of diverse elements induces synergistic effects including new physical and chemical phenomena. However, conventional methods have not offered effective strategies for the uniform creation of PE NPs with high reproducibility.

Pore-Size-Tuned Graphene Oxide Membrane as a Selective Molecular Sieving Layer: Toward Ultraselective Chemiresistors.

Conventional graphene oxide (GO)-based gas membranes, having a narrow pore-size range of less than 0.3 nm, exhibit limited gas molecular permeability because of the kinetic diameters of most volatile organic and sulfur compound (VOCs/VSCs) molecules being larger than 0.3 nm.

Catalytic Metal Nanoparticles Embedded in Conductive Metal-Organic Frameworks for Chemiresistors: Highly Active and Conductive Porous Materials.

Conductive porous materials having a high surface reactivity offer great promise for a broad range of applications. However, a general and scalable synthesis of such materials remains challenging. In this work, the facile synthesis of catalytic metal nanoparticles (NPs) embedded in 2D metal-organic frameworks (MOFs) is reported as highly active and conductive porous materials.

Universal Synthesis of Porous Inorganic Nanosheets via Graphene-Cellulose Templating Route.

Two-dimensional (2D) inorganic nanomaterials have attracted enormous interest in diverse research areas because of their intriguing physicochemical properties. However, reliable method for the synthesis and composition manipulation of polycrystalline inorganic nanosheets (NSs) are still considered grand challenges. Here, we report a robust synthetic route for producing various kinds of inorganic porous NSs with desired multiple components and precise compositional stoichiometry by employing tunicin, i.

High-Resolution, Fast, and Shape-Conformable Hydrogen Sensor Platform: Polymer Nanofiber Yarn Coupled with Nanograined Pd@Pt.

We report a flexible hydrogen sensing platform based on a single-strand yarn consisting of high-density electrospun nanofibers, on which nanograined Pd or Pd@Pt is coated via yarn spinning followed by sputter deposition. In general, Pd undergoes a phase transition to PdH (α-PdH at [H] < 1% and β-PdH at [H] > 2%), in which H atoms act as electron scattering centers, thus increasing the resistance. In our system, the sensors exhibit switchable H sensing behaviors, that is, (i) Δ R/ R > 0 at [H] > 1% by the active electron scattering and (ii) Δ R/ R < 0 at [H] < 1% derived from nanograined Pd effects.

Heterogeneous Metal Oxide-Graphene Thorn-Bush Single Fiber as a Freestanding Chemiresistor.

The development of freestanding fiber-type chemiresistors, having high integration ability with various portable electronics including smart clothing systems, is highly demanding for the next-generation wearable sensing platforms. However, critical challenges stemming from the irreversible chemical sensing kinetics and weak reliability of the freestanding fiber-type chemiresistor hinder their practical use. In this work, for the first time, we report on the potential suitability of the freestanding and ultraporous reduced graphene oxide fiber functionalized with WO nanorods (porous WO NRs-RGO composite fiber) as a sensitive nitrogen dioxide (NO) detector.

Glass-Fabric Reinforced Ag Nanowire/Siloxane Composite Heater Substrate: Sub-10 nm Metal@Metal Oxide Nanosheet for Sensitive Flexible Sensing Platform.

The development of flexible chemiresistors is imperative for real-time monitoring of air quality and/or human physical conditions without space constraints. However, critical challenges such as poor sensing characteristics, vulnerability under toxic chemicals, and weak reliability hinder their practical use. In this work, for the first time, an ultrasensitive flexible sensing platform is reported by assembling Pt loaded thin-layered (≈10 nm) SnO nanosheets (Pt-SnO NSs) based 2D sensing layers on Ag nanowires embedded glass-fabric reinforced vinyl-phenyl siloxane hybrid composite substrate (AgNW-GFRVPH film) as a heater.

Pt-Functionalized PdO Nanowires for Room Temperature Hydrogen Gas Sensors.

In this work, we prepared a well-aligned palladium oxide nanowire (PdO NW) array using the lithographically patterned Pd nanowire electrodeposition (LPNE) method followed by subsequent calcination at 500 °C. Sensitization with platinum (Pt) nanoparticles (NPs), which were functionalized on PdO NWs through a simple reduction process, significantly enhanced the detection capability of the Pt-loaded PdO NWs (Pt-PdO NWs) sensors toward hydrogen gas (H) at room temperature. The well-distributed Pt NPs, which are known chemical sensitizers, activated the dissociation of H and oxygen molecules through the spillover effect with subsequent diffusion of these products to the PdO surface, thereby transforming the entire surface of the PdO NWs into reaction sites for H.

In Situ Coupling of Multidimensional MOFs for Heterogeneous Metal-Oxide Architectures: Toward Sensitive Chemiresistors.

Metal-organic frameworks (MOFs) are used as a new intriguing class of templates, which enable the creation of porous inorganic nanostructures via calcination. In this work, we first introduce in situ coupling of multidimensional MOFs for producing heterogeneous metal-oxide composite with multiple p-n junctions. Controlling relative ratios of two mixed solvents (water and ethanol), in zeolitic imidazolate framework (ZIF) growth, leads to the distinctive morphological evolution such as rod, sheet, and polyhedron particles.

Chitosan-templated Pt nanocatalyst loaded mesoporous SnO nanofibers: a superior chemiresistor toward acetone molecules.

In this work, we introduce a chitosan-Pt complex (CS-Pt) as an effective template for catalytic Pt sensitization and creation of abundant mesopores in SnO2 nanofibers (NFs). The Pt particles encapsulated by the CS exhibit ultrasmall size (∼2.6 nm) and high dispersion characteristics due to repulsion between CS molecules.

An Impedance-Transduced Chemiresistor with a Porous Carbon Channel for Rapid, Nonenzymatic, Glucose Sensing.

A new type of chemiresistor, the impedance-transduced chemiresistor (ITCR), is described for the rapid analysis of glucose. The ITCR exploits porous, high surface area, fluorine-doped carbon nanofibers prepared by electrospinning of fluorinated polymer nanofibers followed by pyrolysis. These nanofibers are functionalized with a boronic acid receptor and stabilized by Nafion to form the ITCR channel for glucose detection.

Feasible Defect Engineering by Employing Metal Organic Framework Templates into One-Dimensional Metal Oxides for Battery Applications.

Facile synthesis of rationally designed nanostructured electrode materials with high reversible capacity is highly critical to meet ever-increasing demands for lithium-ion batteries. In this work, we employed defect engineering by incorporating metal organic framework (MOF) templates into one-dimensional nanostructures by simple electrospinning and subsequent calcination. The introduction of Co-based zeolite imidazole frameworks (ZIF-67) resulted in abundant oxygen vacancies, which induce not only more active sites for Li storage but also enhanced electrical conductivity.

Bimodally Porous WO Microbelts Functionalized with Pt Catalysts for Selective HS Sensors.

Bimodally meso- (2-50 nm) and macroporous (>50 nm) WO microbelts (MBs) functionalized with sub-3 nm Pt catalysts were fabricated via the electrospinning technique followed by subsequent calcination. Importantly, apoferritin (Apo), tea saponin and polystyrene colloid spheres (750 nm) dispersed in an electrospinning solution acted as forming agents for producing meso- and macropores on WO MBs during calcination. Particularly, mesopores provide not only numerous reaction sites for effective chemical reactions, but also facilitate gas diffusion into the interior of the WO MBs, dominated by Knudsen diffusion.

Sub-Parts-per-Million Hydrogen Sulfide Colorimetric Sensor: Lead Acetate Anchored Nanofibers toward Halitosis Diagnosis.

Lead(II) acetate [Pb(Ac)] reacts with hydrogen sulfide to form colored brownish precipitates of lead sulfide. Thus far, in order to detect leakage of HS gas in industrial sectors, Pb(Ac) has been used as an indicator in the form of test papers with a detection limit only as low as 5 ppm. Diagnosis of halitosis by exhaled breath needs sensors able to detect down to 1 ppm of HS gas.

Hierarchical Metal-Organic Framework-Assembled Membrane Filter for Efficient Removal of Particulate Matter.

Here, we propose heterogeneous nucleation-assisted hierarchical growth of metal-organic frameworks (MOFs) for efficient particulate matter (PM) removal. The assembly of two-dimensional (2D) Zn-based zeolite imidazole frameworks (2D-ZIF-L) in deionized water over a period of time produced hierarchical ZIF-L (H-ZIF-L) on hydrophilic substrates. During the assembly, the second nucleation and growth of ZIF-L occurred on the surface of the first ZIF-L, leading to the formation of flowerlike H-ZIF-L on the substrate.

Bioinspired Cocatalysts Decorated WO Nanotube Toward Unparalleled Hydrogen Sulfide Chemiresistor.

Herein, we incorporated dual biotemplates, i.e., cellulose nanocrystals (CNC) and apoferritin, into electrospinning solution to achieve three distinct benefits, i.

Nanoscale PtO Catalysts-Loaded SnO Multichannel Nanofibers toward Highly Sensitive Acetone Sensor.

PtO nanocatalysts-loaded SnO multichannel nanofibers (PtO-SnO MCNFs) were synthesized by single-spinneret electrospinning combined with apoferritin and two immiscible polymers, i.e., poly(vinylpyrrolidone) and polyacrylonitrile.

Metal-Organic Framework-Templated PdO-CoO Nanocubes Functionalized by SWCNTs: Improved NO Reaction Kinetics on Flexible Heating Film.

Detection and control of air quality are major concerns in recent years for environmental monitoring and healthcare. In this work, we developed an integrated sensor architecture comprised of nanostructured composite sensing layers and a flexible heating substrate for portable and real-time detection of nitrogen dioxide (NO). As sensing layers, PdO-infiltrated CoO hollow nanocubes (PdO-CoO HNCs) were prepared by calcination of Pd-embedded Co-based metal-organic framework polyhedron particles.

Hollow Pd-Ag Composite Nanowires for Fast Responding and Transparent Hydrogen Sensors.

Pd based alloy materials with hollow nanostructures are ideal hydrogen (H) sensor building blocks because of their double-H sensing active sites (interior and exterior side of hollow Pd alloy) and fast response. In this work, for the first time, we report a simple fabrication process for preparing hollow Pd-Ag alloy nanowires (Pd@Ag HNWs) by using the electrodeposition of lithographically patterned silver nanowires (NWs), followed by galvanic replacement reaction (GRR) to form palladium. By controlling the GRR time of aligned Ag NWs within an aqueous Pd-containing solution, the compositional transition and morphological evolution from Ag NWs to Pd@Ag HNWs simultaneously occurred, and the relative atomic ratio between Pd and Ag was controlled.