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Formation of epitaxial heterostructures via post-growth self-assembly is important in the design and preparation of functional hybrid systems combining unique properties of the constituents. This is particularly attractive for the construction of metal halide perovskite heterostructures, since their conventional solution synthesis usually leads to non-uniformity in composition, crystal phase and dimensionality. Herein, we demonstrate that a series of two-dimensional and three-dimensional perovskites of different composition and crystal phase can form epitaxial heterostructures through a ligand-assisted welding process at room temperature. Using the CsPbBr

Objective O-glycosylation is the most common post-translational modification of proteins, which is involved in many pathophysiological processes including inflammation. Acute liver injury is characterized by an excessive, uncontrolled inflammatory response, but the effects of aberrant O-glycosylation on acute liver injury are yet to explore. Here we aimed to investigate the role of defective O-glycosylation in D-galactosamine (GalN)/lipopolysaccharide (LPS)-induced acute liver damage in mice. Material and methods Experimental mice were administrated with an O-glycosylation inhibitor (benzyl-a-GalNac, 5 mg/kg) at 24 h before administration of GalN/LPS. At 12 h after GalN/LPS administration, mice were sacrificed to collect blood and liver samples for further analysis. Results We found that benzyl-a-GalNac treatment-induced abundant expression of Tn antigen, which is an immature O-glycan representing abnormal O-glycosylation. Benzyl-a-GalNac pretreatment exacerbated considerably GalN/LPS-induced liver damage in mice, evidenced by significantly reduced survival rates, more severe histological alterations, and notable elevation of multiple inflammatory cytokines and chemokines. Mechanistically, benzyl-a-GalNac could trigger endoplasmic reticulum (ER) stress in the liver of mice, demonstrated by the elevated expression of glucose-regulated protein 78 (GRP78) and C/EBP-homologous protein (CHOP), both of which are hallmarks for ER stress. Inhibition of ER stress by 4-phenylbutyric acid (4-PBA) markedly abrogated benzyl-a-GalNac-mediated enhanced hepatotoxicity and systemic inflammation in GalN/LPS-treated mice. Conclusions This study demonstrated that inhibition of O-glycosylation caused by benzyl-a-GalNac aggravated GalN/LPS-induced liver damage and systemic inflammation, which may be due to activation of ER stress.

To further improve the quantum efficiency of atomically thin transition metal dichalcogenides (TMDs) is crucial for the realization of high-performance optoelectronic applications. To this regard, a few chemical or physical approaches such as superacid treatment, electrical gating, dielectric screening, and laser irradiation have been developed. In particular, the laser irradiation appears to be a more efficient way with good processability and spatial selectivity. However, the underlying mechanism especially about whether chemisorption or physisorption plays a more important role is still debatable. Here, we unravel the mystery of laser irradiation induced photoluminescence enhancement in monolayer WS2 by precisely controlling irradiation time and environment. It is found that the synergetic effect of physisorption and chemisorption is responsible for the photoluminescence enhancement, where the physisorption dominates with more than 74% contribution. The comprehensive understanding of the adsorption mechanism in laser-irradiated TMDs may trigger the potential applications for patterned light source, effective photosensor and ultrathin optical memory.

Two-dimensional (2D) phenylethyl ammonium (PEA+)-methyl ammonium (MA+) lead iodide ((PEA)2(MA)[Pb2I7]) hybrid perovskite exists as temperature-dependent dimorphs exhibiting an ill-defined phase transition occurring over the 150–200 K range. Raman scattering, photoluminescence, optical absorbance and solid state MAS NMR spectroscopic methods are employed to investigate the structural complexity, disorder and structure/function of this system. The Raman and 1H MAS NMR data indicate that the lower bounds of the phase transition at ∼150 K are characterised by attenuated rotational modes and slower motional dynamics throughout the disordered MA+ organic sublattice, inducing a strengthening of the MA+⋯I hydrogen bonds and a 5 meV increase in the excitonic and photoluminescence energies. It is evident that different recombination mechanisms are dominant for the room temperature and low temperature phases reflecting the importance of MA+ dynamics in the optical properties of the material. Single crystal X-ray studies are unable to position the organic cations within the Pb2I7 framework; however, 1H/13C MAS NMR measurements describe elements of local structural disorder based on conformational isomerism within the PEA+ sublattice. Concomitant I− and Pb2+ migration and [Pb2I7]3− framework defects create stacking disorder, dislocations and dispersed octahedral tilting leading to additional disorder and distributed MA+ and PEA+ cation dynamics.\ud \ud

Two-dimensional materials offer an exciting platform that enables the creation of van der Waals heterostructures with rich functions and intriguing physical properties that stem from different band alignments and diverse interlayer interactions. However, further exploration of two-dimensional van der Waals heterostructures is hindered by the limited coupling strength and lack of efficient methods for tuning the interlayer interactions. Here, by using a two-step chemical vapour deposition method, we realize high-quality 2H-stacked WSe2–MoSe2 heterostructures with strong interlayer coupling, and effective tuning of their interlayer interaction by hydrostatic pressure. We unambiguously establish the strong coupling nature in these WSe2–MoSe2 heterostructures through the existence of exclusive interlayer excitons instead of the typical intralayer excitons. We further demonstrate efficient tuning of the interlayer coupling by using pressure engineering, and observe a clear evolution and transition of interlayer excitons in WSe2–MoSe2 heterostructures with a pressure-induced band changeover, which is further confirmed by first-principles calculations. Our findings provide new opportunities for producing, exploring and tuning van der Waals heterostructures with strong interlayer coupling that can lead towards the realization of future excitonic devices based on tailor-made, atomically thin, two-dimensional stacks. High-quality WSe2–MoSe2 heterostructures support strong coupling between the two layers, which is associated with tight hybridization and effective charge separation. In these structures, the bands of the interlayer excitons can be pressure-engineered.

Ultrathin zeolite membranes are of paramount importance in accelerating gas transport during membrane separation, and lowering down their membrane thicknesses to submicron scale is deemed to be very challenging. Herein, we develop an advanced approach of surface gel conversion for synthesis of submicron-thick pure silica MFI (silicalite-1) zeolite membranes. Viscous gel is prepared by finely adjusting the precursor composition, enabling its reduced wettability. The unfavorable wetting of the support surface can effectively prevent gel penetration into alumina support voids. Aided by the seeds, the surface gel is directly and fully crystallized into an MFI zeolite membrane with minimal water steam. A membrane with a thickness of 500 nm is successfully acquired and it is free of visible cracks. Additionally, the as-synthesized membranes exhibit rapid and selective separation of hexane isomers by virtue of unprecedentedly high n-hexane permeance of 24.5×10−7 mol m−2 s−1 Pa−1 and impressive separation factors of 13.3-22.6 for n-hexane over its isomers. This developed approach is of practical interest for sustainable synthesis of high-quality zeolite membranes.

Potassium ion hybrid capacitors (PIHCs) have drawn considerable attention due to the fact that they can combine the merits of high energy density of potassium ion batteries (KIBs) and high power density of supercapacitors. However, the sluggish kinetics caused by the large radius of K+ largely hinder the practical application of PIHCs. In this work, we report a nitrogen and sulfur co-doped 3D hierarchical porous carbon (N, S-3DHPC-600) as an anode for KIBs, possessing boosted potassium storage performance in terms of high reversible capacity, superior durability and rate capability. This N, S-3DHPC-600 electrode provides a large surface area, highly interconnected micro/mesoporosity, high ratio of pyridinic N/pyrrolic N and enlarged interlayer distance, which could promote the fast intercalation/deintercalation of K+, improve the surface charge capacity and maintain the structural stability of electrode material. As expected, a PIHCs device is constructed by employing this N, S-3DHPC-600 as an anode and AC-800 as a cathode, delivering exceptionally high energy/power densities (130.6 Wh Kg−1/16800W Kg−1), as well as a long cycle life (86.8% capacity retention after 5000cycles).

Flexibly manipulating optical and electrical properties of 2D materials is of great importance to extend their functional applications in the advanced optoelectronic field. Herein, a type II 2D/0D ...

Carrier-exciton interactions in two-dimensional transition metal dichalcogenides (TMDs) is one of the crucial elements for limiting the performance of their optoelectronic devices. Here, we have experimentally studied the carrier-exciton interactions in a monolayer MoS2-based two-terminal device. Such two-terminal device without a gate electrode is generally considered as invalid to modulate the carrier concentration in active materials, while the photoluminescence peak exhibits a red shift and decay with increasing applied voltages. Time-resolved photoluminescence spectroscopy and photoluminescence multipeak fittings verify that such changes of photoluminescence peaks result from enhanced carrier-exciton interactions with increasing electron concentration induce the charged exciton increasing. To characterize the level of the carrier-exciton interactions, a quantitative relationship between the Raman shift of out-of-plane mode and changes in electron concentration has been established using the mass action model. This work provides an appropriate supplement for understanding the carrier-exciton interactions in TMD-based two-terminal optoelectronic devices.

Transition metal disulfides (TMDs) have achieved intensive attention in the field of energy storage materials owing to their natural layered structures. However, most TMDs are in the semiconductor phase with inferior electrical conductivity, which has prevented their widespread applications. The 1T-phase vanadium disulfide, in contrast, exhibits some metal characteristic qualities, which enable it to be a superb intercalation host material for Li-ion batteries. We herein demonstrate high rate capability, and the capacity retention can achieve 84.4% after 1000 cycles. In situ synchrotron X-ray diffraction (XRD) results reveal that the VS2 electrode exhibits a typical solid solution reaction, which is of great help in inhibiting the structural transition. Density functional theory (DFT) calculations further indicate that the monolayer 1T-phase VS2 can withstand the high lithiation rate without structural changes and possesses a lower energy barrier with unrestricted diffusion pathways. This work is quite significant and reliable for the subsequent study on two-dimensional materials.

Metal phosphorus trichalcogenides (MPX3: M = Fe, Co, Ni, Cd, Mn; X = S or Se) represent a family of two-dimensional (2D) layered materials with an exceptional response to high pressure and a remarkable structural flexibility originating from the weak interlayer coupling. Despite their interest for applications, the knowledge about pressure-driven phase transitions of cadmium compounds is still limited. In this paper, we fill this gap and provide an accurate description of the structural evolution of CdPS3 by combining high-pressure experiments and first-principle calculations. We have performed high-throughput screening of the low-energy stacking configurations and found a phase evolution starting with [Formula: see text] space group at 12 GPa using the generalized evolutionary metadynamics method. Then, high-pressure experiments have been used to reveal a structural transition from phase-I ([Formula: see text]) to phase-II ([Formula: see text]) to phase-III ([Formula: see text]), which is marked by the appearance and vanishing of the Raman band at approximately 30–250 cm−1 in good agreement with our theoretical predictions. Our study paves the way to the understanding of pressure-induced phase transitions in weak interlayer coupling 2D CdPS3 materials.

Combining the unique properties of hybrid halide perovskites and in-plane anisotropic potential of two-dimensional materials, corrugated layered perovskites are excellent candidates for novel optoelectronic devices. Here, we report strong in-plane anisotropy in a two-dimensional hybrid halide perovskite with corrugated inorganic sheets. We assigned the angle-dependent Raman spectra to particular orientations of the crystals where the method applied is suitable for fast determination of the in-plane crystallographic axes. We demonstrated strong in-plane anisotropy of the optoelectronic properties: electrical measurements showed that changes of photoconductivity and angle-resolved reflectance spectroscopy exhibited variation of the band structure. Employing first-principles calculations, we confirmed the observed anisotropy of the dielectric response. Photoluminescence spectroscopy revealed an anomalous energy shift of μ20 meV dependent on the relative orientation of the crystals and polarization of the excitation light. Using temperature-dependent analysis of the photoluminescence spectra, we obtained the anisotropic exciton-phonon coupling strength as well as the angle-dependent average phonon energy involved, which contributes to the shift of the photoluminescence peak maximum. This discovery of the in-plane anisotropic behavior in layered 2D perovskites could be expected to spur new functionalities in optical and optoelectronic device applications. Ministry of Education (MOE) The authors gratefully acknowledge the Ministry of Education (MOE) of Singapore for the funding of this research through the following grants, AcRF Tier 1 (Reference No: RG195/17); AcRF Tier 1 (RG165/19); AcRF Tier 3 (MOE2016-T3-1-006 (S)). J.Y. acknowledges the National Natural Science Foundation of China (Grant No. 11704185), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20171021), and the funding for "High-level talents in six industries" of Jiangsu Province (Grant No. XCL-020).

Room-temperature-high-efficiency light-emitting diodes based on metal halide perovskite FAPbI3 are shown to be able to work perfectly at low temperatures. A peak external quantum efficiency (EQE) of 32.8%, corresponding to an internal quantum efficiency of 100%, is achieved at 45 K. Importantly, the devices show almost no degradation after working at a constant current density of 200 mA m-2 for 330 h. The enhanced EQEs at low temperatures result from the increased photoluminescence quantum efficiencies of the perovskite, which is caused by the increased radiative recombination rate. Spectroscopic and calculation results suggest that the phase transitions of the FAPbI3 play an important role for the enhancement of exciton binding energy, which increases the recombination rate.

Monoamine oxidases (MAO-A and MAO-B) are the two flavin adenine dinucleotide (FAD) enzymes that play an important role in neurotransmitter homeostasis and in protection against biogenic amines. The two MAO enzymes are related to various diseases such as neurological disorders, cancer or other systemic diseases. It is crucial to distinguish these two subtypes in order to explore the pathogenesis and pathophysiology of different diseases. In this review, the relationship between MAOs and related diseases is briefly introduced. Additionally, we summarize the recent advances in small molecule fluorescent probes for specific detection of MAO-A and MAO-B.

Carrier-exciton interactions in two-dimensional transition metal dichalcogenides (TMDs) is one of the crucial elements for limiting the performance of their optoelectronic devices. Here, we have experimentally studied the carrier-exciton interactions in a monolayer MoS

Resolving the structure–property relationships of two-dimensional (2D) organic–inorganic hybrid perovskites is essential for the development of photovoltaic and photoelectronic devices. Here, pressure (0–10 GPa) was applied to 2D hybrid perovskite flakes mechanically exfoliated from butylammonium lead halide single crystals, (C4H9NH3)2PbI4, from which we observed a series of changes of the strong excitonic emissions in the photoluminescence spectra. By correlating with in situ high-pressure X-ray diffraction results, we examine successfully the relationship between structural modifications in the inorganic PbI42– layer and their excitonic properties. During the transition between Pbca (1b) phase and Pbca (1a) phase at around 0.1 GPa, the decrease in ⟨Pb–I–Pb⟩ bond angle and increase in Pb–I bond length lead to an abrupt blue shift of the excitonic bandgap. The presence of the P21/a phase above 1.4 GPa increases the ⟨Pb–I–Pb⟩ bond angle and decreases the Pb–I bond length, leading to a deep red shift of the excitonic bandgap. The total band gap narrowing of ∼350 meV to 2.03 eV at 5.3 GPa before amorphization, facilitates (C4H9NH3)2PbI4 as a much better solar absorber. Moreover, phase transitions inevitably modify the carrier lifetime of (C4H9NH3)2PbI4, where an initial 150 ps at ambient phase is prolongated to 190 ps in the Pbca (1a) phase along with enhanced photoluminescence (PL), originating from pressure-induced strong radiative recombination of trapped excitons.The onset of P21/a phase shortens significantly the carrier lifetime to 53 ps along with a weak PL emission due to pressure-induced severe lattice distortion and amorphization. High-pressure study on (C4H9NH3)2PbI4 nm-thin flakes may provide insights into the mechanisms for synthetically designing novel 2D hybrid perovskite based photoelectronic devices and solar cells. Ministry of Education (MOE) Accepted version T.T.Y., J.X.Y., and Z.X.S, gratefully acknowledge the Ministry of Education (MOE) for the following grants: AcRF Tier 1 (Reference No: RG103/16); AcRF Tier 2 (MOE2015-T2-1- 148); AcRF Tier 3 (MOE2011-T3-1-005). J.X.Y. is supported by the National Natural Science Foundation of China (Grant No. 11704185) and the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20171021). T.C.S. receives funding from the Ministry of Education Academic Research Fund Tier 1 Grant RG173/16, Tier 2 Grants MOE2015-T2-2- 015 and MOE2016-T2-1-034, and from the Singapore (NRF) through the Singapore−Berkeley Research Initiative for Sustainable Energy (SinBeRISE) CREATE Program and the Competitive Research Program NRF-CRP14-2014-03. S.H.W. is supported by the National Key Basic Research Program of China (2016YFB0700700) and National Natural Science Foundation of China (51672023, 11634003, U1530401). S.J. and J.F. thank Dr. Zhongwu Wang and Dr. Ruipeng Li for their assistance and acknowledge the support from Custom Electronics Inc. and Binghamton University. CHESS was supported by the NSF award DMR-1332208.

The creation of crystal phase heterostructures of transition metal chalcogenides, e.g., the 1T/2H heterostructures, has led to the formation of metal/semiconductor junctions with low potential barriers. Very differently, post-transition metal chalcogenides are semiconductors regardless of their phases. Herein, we report, based on experimental and simulation results, that alloying between 1T-SnS2 and 1T-WS2 induces a charge redistribution in Sn and W to realize metallic Sn0.5W0.5S2 nanosheets. These nanosheets are epitaxially deposited on surfaces of semiconducting SnS2 nanoplates to form vertical heterostructures. The ohmic-like contact formed at the Sn0.5W0.5S2/SnS2 heterointerface affords rapid transport of charge carriers, and allows for the fabrication of fast photodetectors. Such facile charge transfer, combined with a high surface affinity for acetone molecules, further enables their use as highly selective 100 ppb level acetone sensors. Our work suggests that combining compositional and structural control in solution-phase epitaxy holds promises for solution-processible thin-film optoelectronics and sensors., Controlling the composition and crystal phase of layered heterostructures is important. Here, the authors report the liquid-phase epitaxial growth of Sn0.5W0.5S2 nanosheets with 83% metallic phase on SnS2 nanoplates, which are used as 100 ppb level chemiresistive gas sensors at room temperature.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted intense interests owing to their fascinating physical properties and potential applications. In addition, the properties of few-layer TMD materials can be tuned by their thickness as well as the stacking sequence. For instance, MoS2/WS2/MoSe2/WSe2 undergoes a transition from the indirect-band-gap to direct-band-gap semiconductors with their thickness reduced to monolayer; the weak van der Waals (vdWs) interaction between the layers in TMDs endows various stacking sequences that can be facilely obtained by different methods. Hence, thickness and stacking sequence can be used to modulate the electronic band structures, valley polarization and nonlinear optical properties, providing additional useful and convenient ways to manipulate the materials and fabricate devices with novel functionalities. Here we review recent progress in thickness and stacking engineering for TMD materials in structural, optical and electronic properties. Last, we offer our perspectives and challenges in this research field.

The structural stability of the organometal halide perovskites (CH3NHjPbX3, where X = Br, I, Cl) is highly correlated with the rotation of the methylammounium (MA) cations and the tilting of the PbX 6 octahedra. Hydrogen-bonding is the link between organic molecules and inorganic cages. In this study, the hydrogen-bonding status between the H atoms of the methylammonium (MA) cation and the halide ions is resolved through temperature-dependent experiments combined with theoretical analysis.

One step synthesis of the natural product indirubin by reductive coupling of isatin with KBH4 is described and a possible mechanism for the reaction is proposed. Eleven indirubin derivatives were obtained easily from the corresponding substituted isatin.

Two-dimensional (2D) materials such as graphene have inspired a worldwide upsurge of research interests since 2004 when graphene were firstly obtained by Andre Geim using mechanical exfoliation from highly oriented pyrolytic graphite. In spite of the excellent carrier mobility of graphene, the lack of a band gap impedes its applications in areas like nanoelectronics and solar cell. Although various methods have been developed to realize the band gap opening, the resulting structures are accompanied by adverse side effects, such as dramatically increased effective mass, distorted lattice, and/or damaged layer integrity, resulting in the loss of majority of its superior properties. Parallel to the intensive world-wide effort to engineer the band structure of graphene, scientists start to study other 2D materials beyond graphene. For example, molybdenum oxide and molybdenum sulfide, which possesses the layered structure as graphene, can be viewed as the potential candidates. Inspired by graphene, such 2D materials beyond graphene now have drawn more attention for its electrical and optical properties. PHYSICS and APPLIED PHYSICS

Cu nanowires, as promising candidates in many fields because of their merits, are commonly prepared by the solution phase based synthesis which is a simple and scalable method. However, precise control of the morphology, particularly surface roughness, of Cu nanowires is still challenging; and moreover, detailed formation mechanisms of Cu nanowires, in solution phase based synthesis, are still unclear. We here show the morphology manipulation of Cu nanowires by adjusting the stirring rate and the amounts of ethylenediamine and hydrazine (N2H4), yielding Cu nanowires with either smooth or rough surface. Importantly, according to our experimental results and theoretical investigation, new functions of ethylenediamine and N2H4 are found, and a growth process of Cu nanowires is proposed accordingly. In addition to typically accepted roles of ethylenediamine and N2H4, we find that ethylenediamine can facilitate the growth of Cu nanowires by etching Cu oxides and even Cu on the surface of Cu nanowires. Meanwhile, N2H4 molecules can modulate the growth of Cu nanowires as a capping agent, which can be easily influenced by stirring. Additionally, the as-synthesized Cu nanowires with different morphologies exhibit different optical and catalytic properties. This study provides new fundamental insights into the growth mechanism of Cu nanowires, and thus can facilitate controlled synthesis of Cu nanowires for further applications, including electronics, catalysis, and sensing.

The layer-by-layer assembly of 2D transition metal dichalcogenide monolayer blocks to form a 3D stack, with a precisely chosen sequence/angle, is the newest development for these materials. In this way, one can create "van der Waals heterostructures (HSs)," opening up a new realm of materials engineering and novel devices with designed functionalities. Herein, a detailed systematic review of transition metal dichalcogenide stacking-engineered heterostructures, from controllable fabrication to typical characterization, and stacking-correlated physical behaviors is presented. Furthermore, recent advances in stacking design, such as stacking sequence, twist angles, and moiré superlattice heterojunctions, are also comprehensively summarized. Finally, the remaining challenges and possible strategies for using stacking engineering to tune the properties of 2D materials are also outlined.

Due to the easy intralayer gliding and weak interlayer van der Waals interaction in transition metal dichalcogenides (TMDs), ion (particularly Li+) intercalation has been used to modify and tune their atomic structures to obtain the desired optical, electronic and chemical properties for future optoelectronics and energy storage applications. A good understanding of the transformative structures during intercalation is critical. In this paper, we investigate the structural transformation dynamics of 2H-MoS2 using electrochemical Li+ intercalation for 2H-MoS2. The introduction of Li+ changes the local symmetry of the MoS2 in favor of the dT phase, clearly indicated by the appearance of Raman peaks of the dT phase. Further Li+ insertion causes the samples to become single-layer-like, characterized by the disappearance of the 32 cm−1 Raman peak. We also observe for the first time that the photoluminescence (PL) emission gradually redshifts with decreasing intensity, followed by eventual vanishing of the PL peak in the dT-MoS2 phase. By the nudged elastic band (NEB) calculations, we propose the 2H–1T–dT phase transition mechanism of MoS2 for Li+ intercalated samples. Our claims are supported by high resolution-transmission electron microscopy (HR-TEM). Our study deepens the understanding of the phase transition dynamics upon lithium intercalation, which is of great value to possible optoelectronic devices based on the phase engineering of TMDs. The new Li-stabilized dT-MoS2 phase does not possess inversion symmetry and may present a feasible way to achieve Weyl state tuning in a single material via phase engineering.

Manipulation of valley pseudospins is crucial for future valleytronics. The emerging transition metal dichalcogenides (TMDs) provide new possibilities for exploring the interplay among the quantum degrees of freedom, including real spin, valley pseudospin, and layer pseudospin. For example, spin–valley coupling results in valley-dependent circular dichroism in which electrons with particular spin (up or down) can be selectively excited by chiral optical pumping in monolayer TMDs, whereas in few-layer TMDs, the interlayer hopping further affects the spin–valley coupling. In addition to valley and layer pseudospins, here we propose a new degree of freedom—stacking pseudospin—and demonstrate new phenomena correlated to this new stacking freedom that otherwise require the application of external electrical or magnetic field. We investigated all possible stacking configurations of chemical-vapor-deposition-grown trilayer MoS2 (AAA, ABB, AAB, ABA, and 3R). Although the AAA, ABA, 3R stackings possess a sole peak with lower degree of valley polarization than that in monolayer samples, the AAB (ABB) stackings exhibit two distinct peaks, one similar to that observed in monolayer MoS2 and an additional unpolarized peak at lower energy. Our findings provide a more complete understanding of valley quantum control for future valleytronics.

In spite of the tremendous development in the semiconductor industry, the Moore’s Law is believed to soon reach its limit and traditional microelectronic devices are currently facing challenges such as high energy consumption and the short-channel effect. As an alternative, two-dimensional (2D) layered transition metal dichalcogenide (TMDC) materials show the ability to restrain the carriers in a 1 nm physical limit and demonstrate high carrier mobility, tunable band gap, and excellent manufacture compatibility, which will hopefully give birth to revolutionary changes in nanoelectronics. In this chapter, we review the most recent progress of 2D TMDC in field-effect transistors (FETs). We present the achievements in carrier mobility and electrical contacts. We also point out the emerging directions for further development.

Resolving the structure-property relationships of two-dimensional (2D) organic-inorganic hybrid perovskites is essential for the development of photovoltaic and photoelectronic devices. Here, pressure (0-10 GPa) was applied to 2D hybrid perovskite flakes mechanically exfoliated from butylammonium lead halide single crystals, (C

The performance of sodium ion batteries (SIBs) is mainly determined by the electrochemical activity and kinetic feature of electrode materials. High performance relies largely on the scrupulous design of nano-architectures and smart hybridization of bespoke active materials. It is fundamentally important for establishing a relationship between the structure/chemistry of these materials and their properties. Herein, we developed a novel synergistic Ni3S2-MoS2 core-shell nanofiber superstructure on 3D Ni/graphene foam by a one-step PVP-assisted hydrothermal reaction. Such hierarchical nanofibers can provide the homogeneous atomic heterointerface with porous hierarchical structure, resulting in the maximization of synergistic interaction. This unique structure results in very high specific capacity and rate capability as well as extremely long-term cycle stability. As anode electrode of SIBs, it exhibits a very high reversible specific capacity of 568 mAh g−1 at a current density of 200 mA g−1 with excellent rate capability (283 mAh g−1 at 5 A g−1), and the specific capacity can be well-maintained to 207 mAh g-1 at 5 A g−1 even after 400 cycles. The strategy developed in our study can open a new way to prepare other layered-material-based hybrid superstructure for next-generation energy storage devices. MOE (Min. of Education, S’pore) Accepted version

Pressure can drive deformation of materials' microscopic morphology, phase transitions, accompanied by changes in physical and chemical properties. In this work, we demonstrate that MAPbBr3 Nanoparticles (NPs) split along (210) planes into nanoslices during cubic-orthorhombic phase transformation at ∼2 GPa, and gradually sinter into uniform large single-crystalline nanoplates upon amorphization and recrystallization after the pressurization. Instead of pressure-driven direct assembly in previous metallic/inorganic semiconductor nanoparticles, the pressure-induced splitting in the organic-inorganic hybrid lead perovskites correlates with the structural nature of PbBr6 octahedra tilting and MA cations ordering under compression. Compared to the initial perovskite NPs, the pressure-resulting large nanoplates exhibit a ∼15 times photoluminescence (PL) enhancement and a 50% carrier lifetime shortening. Our results provide new insights into the microscopic growth mechanisms of organic-inorganic hybrid perovskite nanomaterials under high pressure, and demonstrate a new method for engineering their morphology and associated optoelectronic properties.

High pressure (HP) can drive the direct sintering of nanoparticle assemblies for Ag/Au, CdSe/PbS nanocrystals (NCs). Instead of direct sintering for the conventional nanocrystals, this study experimentally observes for the first time high-pressure-induced comminution and recrystallization of organic-inorganic hybrid perovskite nanocrystals into highly luminescent nanoplates with a shorter carrier lifetime. Such novel pressure response is attributed to the unique structural nature of hybrid perovskites under high pressure: during the drastic cubic-orthorhombic structural transformation at ≈2 GPa, (301) the crystal plane fully occupied by organic molecules possesses a higher surface energy, triggering the comminution of nanocrystals into nanoslices along such crystal plane. Beyond bulk perovskites, in which pressure-induced modifications on crystal structures and functional properties will disappear after pressure release, the pressure-formed variants, i.e., large (≈100 nm) and thin (10 nm) perovskite nanoplates, are retained and these exhibit simultaneous photoluminescence emission enhancing (a 15-fold enhancement in the photoluminescence) and carrier lifetime shortening (from ≈18.3 ± 0.8 to ≈7.6 ± 0.5 ns) after releasing of pressure from 11 GPa. This pressure-induced comminution of hybrid perovskite NCs and a subsequent amorphization-recrystallization treatment offer the possibilities of engineering the advanced hybrid perovskites with specific properties.

The structural stability of the organometal halide perovskites (CH 3 NH 3 PbX 3 , where X = Br, I, Cl) is highly correlated with the rotation of the methylammonium (MA) cations and the tilting of the PbX6 octahedra, leading to a series of structural phase transitions upon cooling. However, the hydrogen-bonding status and the relationship with the electronic properties remain unclear and need to be addressed. In this study, the various status of the hydrogen-bonding between the H atoms of the MA cation and the halide ions is resolved by combining ab initio calculations with temperature-dependent Raman scattering and powder X-ray diffraction (XRD) measurements on MAPbBr 3 hybrid perovskites. The consequent dynamical change in the electronic band structures, triggers indirect bandgap to direct bandgap along with ∼60-fold photoluminescence emission enhancement upon cooling.