A Steep-Slope MoS2/Graphene Dirac-Source Field-Effect Transistor with a Large Drive Current.

In the continuous transistor feature size scaling down, the scaling of the supply voltage is stagnant because of the subthreshold swing (SS) limit. A transistor with a new mechanism is needed to break through the thermionic limit of SS and hold the large drive current at the same time. Here, by adopting the recently proposed Dirac-source field-effect transistor (DSFET) technology, we experimentally demonstrate a MoS2/graphene (1.8 nm/0.3 nm) DSFET for the first time, and a steep SS of 37.9 mV/dec at room temperature with nearly free hysteresis is observed. Besides, by bringing in the structure of gate-all-around (GAA), the MoS2/graphene DSFET exhibits a steeper SS of 33.5 mV/dec and a 40% increased normalized drive current up to 52.7 µA·µm/µm (VDS = 1 V) with a current on/off ratio of 108, which shows potential for low-power and high-performance electronics applications.

Programmable Transient Supramolecular Chiral G-quadruplex Hydrogels by a Chemically Fueled Non-equilibrium Self-Assembly Strategy.

The temporal and spatial control of natural systems has aroused great interest for the creation of synthetic mimics. By using boronic ester based dynamic covalent chemistry and coupling it with an internal pH feedback system, we have developed a new chemically fueled reaction network for non-equilibrium supramolecular chiral G-quadruplex hydrogels with programmable lifetimes from minutes, to hours, to days, as well as high transparency and conductivity, excellent injectability, and rapid self-healing properties. The system can be controlled by the kinetically controlled in situ formation and dissociation of dynamic boronic ester bonds between the cis-diol of guanosine (G) and 5-fluorobenzoxaborole (B) in the presence of chemical fuels (KOH and 1,3-propanesultone), thereby leading to a precipitate-solution-gel-precipitate cycle under non-equilibrium conditions. A combined experimental-computational approach showed the underlying mechanism of the non-equilibrium self-assembly involves aggregation and disaggregation of right-handed helical G-quadruplex superstructures. The proposed dynamic boronic ester-based non-equilibrium self-assembly strategy offers a new option to design next-generation adaptive and interactive smart materials.

Supramolecular G4 Eutectogels of Guanosine with Solvent-Induced Chiral Inversion and Excellent Electrochromic Activity.

Supramolecular eutectogels, an emerging class of materials that have just developed very recently, offer a new opportunity for generating functional supramolecular gel materials in biocompatible anhydrous or low-water media. As the first example of supramolecular G4 eutectogels, complexes of natural guanosine and H3 BO3 exhibited excellent gelation capacity in choline chloride/alcohol deep eutectic solvents. The as-prepared supramolecular eutectogels displayed unexpected solvent-induced chiral inversion and significantly high ionic conductivity (up to 7.78 mS cm-1 ), as well as outstanding thixotropic/injectable properties, high thermal stability and excellent electrochromic activity. These features make these versatile supramolecular G4 eutectogels promising candidates for developing next-generation flexible electronics with low environmental impact.

The ARF7 and ARF19 Transcription Factors Positively Regulate PHOSPHATE STARVATION RESPONSE1 in Arabidopsis Roots.

PHOSPHATE STARVATION RESPONSE1 (PHR1) is a key regulatory component of the response to phosphate (Pi) starvation. However, the regulation of PHR1 in this response remains poorly understood. Here, we report that PHR1 is a target of the transcription factors AUXIN RESPONSE FACTOR7 (ARF7) and ARF19 and is positively regulated by auxin signaling in Arabidopsis (Arabidopsis thaliana) roots. PHR1 expression was induced by exogenous auxin and suppressed by auxin transport inhibitors in Arabidopsis roots. In the PHR1 promoter, three auxin-response elements, which are bound directly by ARF7 and ARF19, were shown to be essential for PHR1 expression. The arf7, arf19, and arf7 arf19 mutants showed down-regulated expression of PHR1 and downstream Pi starvation-induced genes in roots; they also exhibited defective Pi uptake in roots and overaccumulation of anthocyanin in shoots. The induction of lateral root formation in response to low Pi and to exogenous auxin was decreased in the phr1 mutant, whereas the expression of LATERAL ORGAN BOUNDARIES-DOMAIN16 (LBD16) and LBD29 was not changed significantly. PHR1 acted independently of LBD16 and LBD29 in the regulation of lateral root formation in response to low Pi. Under low-Pi conditions, lateral root impairment in the arf7 arf19 mutant was partially rescued by constitutive expression of PHR1, demonstrating that reduced PHR1 expression contributed to the arf7 arf19 phenotype. In addition to PHR1, other genes encoding MYB-CC members also were targets of ARF7 and ARF19. Our work thus reveals a mechanism coordinating auxin signaling and the PHR1 regulon in Arabidopsis responses to Pi deficiency.

Palladium-Catalyzed C-N Bond Cleavage of 2 H-Azirines for the Synthesis of Functionalized α-Amido Ketones.

A Pd-catalyzed ring-opening reaction of 2 H-azirines with carboxylic acids was developed. This reaction undergoes nucleophilic addition between 2,3-diaryl-2 H-azirines and carboxylic acids followed by C-N single-bond cleavage and a subsequent thermal rearrangement. This method enables the rapid construction of valuable α-amido ketone derivatives with high atomic efficiency and superb functional group tolerance.

Dual-Functionalized Mixed Keggin- and Lindqvist-Type Cu24-Based POM@MOF for Visible-Light-Driven H2 and O2 Evolution.

The development of logical visible-light-driven heterogeneous photosystems for water splitting is a subject of new research. As the first example of a noble-metal-free photocatalyst for both H2 and O2 production, a high-nuclear {CuI24(µ3-Cl)8(µ4-Cl)6}-based polyoxometalate (POM)@metal-organic framework (MOF) (ZZULI-1) is rationally designed to serve as a robust dual-functionalized photocatalyst. ZZULI-1 exhibits highly efficient photocatalytic H2 evolution (6614 µmol g-1 h-1) and O2 evolution (1032 µmol g-1 calculated for the first 6 min). The {CuI24(µ3-Cl)8(µ4-Cl)6} clusters and mixed POMs not only work as the active units for H2 and O2 production, respectively, but also improve the effective electron transfer between the photosensitizer and ZZULI-1. The highly stable dual-functionalized ZZULI-1 affords new penetrations into the development of cost-effective high-nuclear cluster-based POM@MOFs for efficient solar-to-fuel generation.

Charge-Trap Memory Based on Hybrid 0D Quantum Dot-2D WSe2 Structure.

Recently, layered ultrathin 2D semiconductors, such as MoS2 and WSe2 are widely studied in nonvolatile memories because of their excellent electronic properties. Additionally, discrete 0D metallic nanocrystals and quantum dots (QDs) are considered to be outstanding charge-trap materials. Here, a charge-trap memory device based on a hybrid 0D CdSe QD-2D WSe2 structure is demonstrated. Specifically, ultrathin WSe2 is employed as the channel of the memory, and the QDs serve as the charge-trap layer. This device shows a large memory window exceeding 18 V, a high erase/program current ratio (reaching up to 104 ), four-level data storage ability, stable retention property, and high endurance of more than 400 cycles. Moreover, comparative experiments are carried out to prove that the charges are trapped by the QDs embedded in the Al2 O3 . The combination of 2D semiconductors with 0D QDs opens up a novelty field of charge-trap memory devices.

Stable Layered Semiconductive Cu(I)-Organic Framework for Efficient Visible-Light-Driven Cr(VI) Reduction and H2 Evolution.

Metal-organic frameworks (MOFs) have gained tremendous attention in the fields of environmental restoration and sustainable energy for their potential use as photocatalyst. Herein, a new two-dimensional (2D) Cu(I)-based MOF material showing a narrow forbidden-band of 2.13 eV was successfully constructed using a visible-light-harvesting anthracene-based bipyridine ligand. The as-prepared MOF demonstrates high chemical stability and could be stable in the pH range 2-13, which is favorable for its potential application in photocatalysis. Photocatalytic experiments demonstrate that this Cu(I)-MOF exhibits high reactivity for reduction of Cr(VI) in water, with 95% Cr(VI) converting to Cr(III) in 10 min by using MeOH as scavenger under visible-light illumination. Furthermore, this MOF could behave as a highly active photocatalyst for H2 evolution without additional photosensitizers and cocatalyst. Remarkably, the as-prepared MOF shows enhanced photocatalytic Cr(VI) reduction and H2 evolution performances compared with the pristine light-harvesting ligand under the same conditions. In connection to these, the photocatalytic reaction mechanism has also been probed.

Tunable Robust pacs-MOFs: a Platform for Systematic Enhancement of the C2H2 Uptake and C2H2/C2H4 Separation Performance.

As a modulatable class of porous crystalline materials, metal-organic frameworks (MOFs) have gained intensive research attention in the domain of gas storage and separation. In this study, we report on the synthesis and gas adsorption properties of two robust MOFs with the general formula [Co3(µ3-OH)(cpt)3Co3(µ3-OH)(L)3(H2O)9](NO3)4(guests) n [L = 3-amino-1,2,4-triazole (1) and 3,5-diamino-1,2,4-triazole (2); Hcpt = 4-(4-carboxyphenyl)-1,2,4-triazole], which show the same pacs topology. Both MOFs are isostructural to each other and show MIL-88-type frameworks whose pore spaces are partitioned by different functionlized trinuclear 1,2,4-triazolate-based clusters. The similar framework components with different amounts of functional groups make them an ideal platform to permit a systematic gas sorption/separation study to evaluate the effects of distinctive parameters on the C2H2 uptake and separation performance. Because of the presence of additional amido groups, the MOF 2 equipped with a datz-based cluster (Hdatz = 3,5-diamino-1,2,4-triazole) shows a much improved C2H2 uptake capacity and separation performance over that of the MOF 1 equipped with atz-based clusters (Hatz = 3-amino-1,2,4-triazole), although the surface area of the MOF 1 is almost twice than that of the MOF 2. Moreover, the high density of open metal sites, abundant free amido groups, and charged framework give the MOF 2 an excellent C2H2 separation performance, with ideal adsorbed solution theory selectivity values reaching up to 11.5 and 13 for C2H2/C2H4 (1:99) and C2H2/CO2 (50:50) at 298 K and 1 bar, showing potential for use in natural gas purification.

Eliminating Overerase Behavior by Designing Energy Band in High-Speed Charge-Trap Memory Based on WSe2.

Atomic crystal charge trap memory, as a new concept of nonvolatile memory, possesses an atomic level flatness interface, which makes them promising candidates for replacing conventional FLASH memory in the future. Here, a 2D material WSe2 and a 3D Al2 O3 /HfO2 /Al2 O3 charge-trap stack are combined to form a charge-trap memory device with a separation of control gate and memory stack. In this device, the charges are erased/written by built-in electric field, which significantly enhances the write speed to 1 µs. More importantly, owing to the elaborate design of the energy band structure, the memory only captures electrons with a large electron memory window over 20 V and trap selectivity about 13, both of them are the state-of-the-art values ever reported in FLASH memory based on 2D materials. Therefore, it is demonstrated that high-performance charge trap memory based on WSe2 without the fatal overerase issue in conventional FLASH memory can be realized to practical application.

Tunable SnSe2 /WSe2 Heterostructure Tunneling Field Effect Transistor.

The burgeoning 2D semiconductors can maintain excellent device electrostatics with an ultranarrow channel length and can realize tunneling by electrostatic gating to avoid deprivation of band-edge sharpness resulting from chemical doping, which make them perfect candidates for tunneling field effect transistors. Here this study presents SnSe2 /WSe2 van der Waals heterostructures with SnSe2 as the p-layer and WSe2 as the n-layer. The energy band alignment changes from a staggered gap band offset (type-II) to a broken gap (type-III) when changing the negative back-gate voltage to positive, resulting in the device operating as a rectifier diode (rectification ratio ~104 ) or an n-type tunneling field effect transistor, respectively. A steep average subthreshold swing of 80 mV dec-1 for exceeding two decades of drain current with a minimum of 37 mV dec-1 at room temperature is observed, and an evident trend toward negative differential resistance is also accomplished for the tunneling field effect transistor due to the high gate efficiency of 0.36 for single gate devices. The ION /IOFF ratio of the transfer characteristics is >106 , accompanying a high ON current >10-5 A. This work presents original phenomena of multilayer 2D van der Waals heterostructures which can be applied to low-power consumption devices.

Various and Tunable Transport Properties of WSe2 Transistor Formed by Metal Contacts.

The abundant electronic and optical properties of 2D materials that are just one-atom thick pave the way for many novel electronic applications. One important application is to explore the band-to-band tunneling in the heterojunction built by different 2D materials. Here, a gate-controlled WSe2 transistor is constructed by using different work function metals to form the drain (Pt) and source (Cr) electrodes. The device can be gate-modulated to exhibit three modes of operation, i.e., the tunneling mode with remarkable negative differential resistance, the transition mode with a second electron tunneling phenomenon for backward bias, and finally the conventional diode mode with rectifying characteristics. In contrast to the heterojunctions built by different 2D materials, these devices show significantly enhanced tunneling current by two orders of magnitude, which may largely benefit from the clean interfaces. These results pave the way toward design of novel electronic devices using the modulation of metal work functions.

Metal-Organic Framework Supported on Processable Polymer Matrix by In Situ Copolymerization for Enhanced Iron(III) Detection.

Metal-organic frameworks (MOFs) represent a promising class of porous materials. However, MOFs show poor processability that impedes their full potential in applications. This work develops a composite strategy to skillfully load MOFs on a polymer plate to afford processability for these powder materials. A predesigned mesoporous MOF with active -NH2 groups around the pore walls was prepared and its copolymerization with the -NCO groups of macromonomers (polyurethane acrylate) could be facilely induced by an initiator under mild conditions. Notably, the target MOF-polymer composite is transparent, elastic, and shows enhanced Fe3+ detection compared with that of the individual MOF functional component. This result can be ascribed to the synergistic effect of the composite with newly formed chemical bonds between the MOF particle and polymer matrix.

Quest for the Ncb-type Metal-Organic Framework Platform: A Bifunctional Ligand Approach Meets Net Topology Needs.

A custom-designed bifunctional ligand was used to connect an in situ formed Co3(OH) cluster affording a porous metal-organic framework, which represents the first case of ncb-type networks constructed from a single kind of ditopic ligand. Noticeably, the activated MOF shows high volumetric C2H2 uptake and excellent adsorption selectivity for C2H2/CO2 separation at room temperature with a low sorption heat.

A Mixed-Cluster Approach for Building a Highly Porous Cobalt(II) Isonicotinic Acid Framework: Gas Sorption Properties and Computational Analyses.

A unique channel-type metal-organic framework (MOF) built up from mixed square-planar Co4(µ2-OH)4(µ4-OH) and cuboidal Co4(µ3-OH)4 clusters with an isonicotinic acid ligand has been successfully fabricated that demonstrates the highest specific surface area and high H2 uptake capacities among all of the cobalt(II) isonicotinic acid frameworks reported so far.

Microporous Cobalt(II)-Organic Framework with Open O-Donor Sites for Effective C2H2 Storage and C2H2/CO2 Separation at Room Temperature.

The self-assembly of a bifunctional organic ligand with a formate-bridged rod-shaped secondary building unit leads to a new microporous metal-organic framework (MOF). This MOF shows a moderately high C2H2 storage capacity (145 cm3/g) and an excellent adsorption selectivity for C2H2/CO2 (11) at room temperature. Furthermore, its discriminatory sorption behavior toward C2H2 and CO2 was probed by computational analysis in detail.

Semiconductive Copper(I)-Organic Frameworks for Efficient Light-Driven Hydrogen Generation Without Additional Photosensitizers and Cocatalysts.

As the first example of a photocatalytic system for splitting water without additional cocatalysts and photosensitizers, the comparatively cost-effective Cu2 I2 -based MOF, Cu-I-bpy (bpy=4,4'-bipyridine) exhibited highly efficient photocatalytic hydrogen production (7.09 mmol g-1 h-1 ). Density functional theory (DFT) calculations established the electronic structures of Cu-I-bpy with a narrow band gap of 2.05 eV, indicating its semiconductive behavior, which is consistent with the experimental value of 2.00 eV. The proposed mechanism demonstrates that Cu2 I2 clusters of Cu-I-bpy serve as photoelectron generators to accelerate the copper(I) hydride interaction, providing redox reaction sites for hydrogen evolution. The highly stable cocatalyst-free and self-sensitized Cu-I-bpy provides new insights into the future design of cost-effective d10 -based MOFs for highly efficient and long-term solar fuels production.

Charge Control in Two Isostructural Anionic/Cationic CoII Coordination Frameworks for Enhanced Acetylene Capture.

Two isostructural CoII -based metal-organic frameworks (MOFs) with the opposite framework charges have been constructed, which can be simply controlled by changing the tetrazolyl or triazolyl terminal in two bifunctional ligands. Notably, the cationic MOF 2 can adsorb much more C2 H2 than the anionic MOF 1 with an increase of 88 % for C2 H2 uptake at 298 K in spite of more active nitrogen sites in 1. Theoretical calculations indicate that both nitrate and triazolyl play vital roles in C2 H2 binding and the C2 H2 adsorption isotherm confirms that the enhanced C2 H2 uptake for 2 (225 and 163 cm3 g-1 at 273 and 298 K) is exceptionally high for MOF materials without open metal sites or uncoordinated polar atom groups on the frameworks.

Ligand Symmetry Modulation for Designing Mixed-Ligand Metal-Organic Frameworks: Gas Sorption and Luminescence Sensing Properties.

Herein, we report the synthesis of a new mixed-linker Zn(II)-based metal-organic framework (MOF), {[Zn2(atz)2(bpydb)](DMA)8}n (1) (atz = deprotonated 3-amino-1,2,4-triazole, bpydb = deprotonated 4,4'-(4,4'-bipyridine-2,6-diyl) dibenzoic acid, DMA = N,N-dimethylacetamide), through symmetry modulation of a triazole ligand. The desymmetrized triazole linkers not only bond to the Zn(II) ions to result in a new helical Zn-triazolate chain building unit but also lead to the formation of a highly porous framework (N2 uptake: 617 cm(3)/g; BET surface area: 2393 m(2)/g) with 1D helical channels. The adsorption properties of desolved 1 were investigated by H2, C2H2, CO2, and CH4 sorption experiments, which showed that 1 exhibited high uptake capacity for H2 at 77 K and C2H2 around room temperature. More importantly, the high C2H2 uptake capacity but low binding energy makes this MOF a promising candidate for effective C2H2 capture from C2H2/CO2 and C2H2/CH4 mixed gases with low regenerative energy cost. In addition, 1 shows potential application for the luminescence sensing of small aromatic molecules picric acid (PA) and p-xylene (PX).

Two Isostructural Coordination Polymers Showing Diverse Magnetic Behaviors: Weak Coupling (Ni(II)) and an Ordered Array of Single-Chain Magnets (Co(II)).

Two isomorphic 3-D complexes with the formulas [M3(TPTA) (OH)2(H2O)4]n (M = Ni for 1 and Co for 2; H4TPTA = [1,1':4',1″-terphenyl]-2',3,3″,5'-tetracarboxylic acid) have been synthesized and magnetically characterized. Complexes 1 (Ni(II)) and 2 (Co(II)) have the same 1-D rod-shaped inorganic SBUs but exhibit significantly different magnetic properties. Complex 2(Co(II)) is a 3-D arrangement of a 1-D Co(II) single-chain magnet (SCM), while complex 1(Ni(II)) exhibits weak coupling.