Flexible MA2Z4 (M = Mo, W; A = Si, Ge and Z = N, P, As) monolayers with outstanding mechanical, dynamical, electronic, and piezoelectric properties and anomalous dynamic polarization.

We systematically investigate the mechanical, dynamical, and piezoelectric properties of MA2Z4 monolayers (M = Mo, W; A = Si, Ge and Z = N, P, As) based on first-principles calculations. The structural properties, cohesive energy and formation energy analyses show that all of the considered MA2Z4 monolayers are dynamically stable. Ab initio molecular dynamics simulations further indicate that the MA2Z4 monolayers can sustain stability at high temperatures. The MA2Z4 monolayers exhibit isotropic mechanical properties with the bearable largest strains exceeding 25% and 30% in the armchair and zigzag directions. All MA2Z4 monolayers exhibit semiconducting properties, and the band gaps change in a wide range. The piezoelectric constants e11 and d11 increase from 3.21 × 10-10 to 8.17 × 10-10 C m-1 and 0.73 to 6.05 pm V-1, respectively. We reveal that the piezoelectric coefficients are closely related to the ratio of the polarizabilities of the isolated anions and cations. Infrared spectroscopy indicates that the piezoelectricity is the overlap of the intrinsic dipole moments existing in the inner MZ2 monolayer and outer A2Z2 bilayer. Besides, the Born effective charges quantificationally show the contribution of component atoms to polarization. The anomalous dynamic polarization around M atoms is found, which is generated from the anti-bonding of the last occupied orbital. Our results indicate that the MA2Z4 monolayers have great potential in piezotronics and piezo-phototronics fields.

A study of the Rashba effect in two-dimensional ternary compounds ABC monolayers (A = Sb, Bi; B = Se, Te; C = Br; I).

The structure and electronic and spintronic properties of two-dimensional (2D) ternary compounds ABC (A = Sb, Bi; B = Se, Te; C = Br; I) monolayers are investigated using the first-principles method. The ABC monolayers possess typical Janus structures with a considerable potential gradient normal to the surface, inducing intrinsic Rashba spin splitting (RSS) at the conduction band minimum near the Γ point. Among them, the splitting strength of the BiSeI monolayer is the largest and its Rashba coefficient can reach 1.84 eV Å. The projected energy band of the BiSeI monolayer suggests that the RSS state is mainly rooted in the Bi-pz orbital. The RSS strength can be modulated by applying the in-plane strain. The tensile strain can improve the RSS strength, which is ascribed to the increase of the potential gradient normal to the surface. These results indicate that these 2D ternary compounds have great potential for application in tunable spintronic devices.

Ultrahigh thermoelectric performance of Janus α-STe2 and α-SeTe2 monolayers.

Janus α-STe2 and α-SeTe2 monolayers are investigated systematically using first-principles calculations combined with semiclassical Boltzmann transport theory. Janus α-STe2 and α-SeTe2 monolayers are indirect semiconductors with band gaps of 1.20 and 0.96 eV, respectively. It is found that they possess ultrahigh figure of merit (ZT) values of 3.9 and 4.4, respectively, at 500 K, much higher than that of the pristine α-Te monolayer (2.8). The higher ZT values originating from Janus structures reduce lattice thermal conductivities remarkably compared with the pristine α-Te monolayer. The much higher phonon anharmonicity in Janus monolayers leads to significantly lower lattice thermal conductivity. It is also found that electronic thermal conductivity can play an important role in thermoelectric efficiency of materials with quite low lattice thermal conductivity. This work suggests the potential applications of Janus α-STe2 and α-SeTe2 monolayers as thermoelectric materials and highlights that using a Janus structure is an effective way to enhance thermoelectric performance.

Interface dependence of electrical contact and graphene doping in graphene/XPtY (X, Y = S, Se, and Te) heterostructures.

The electrical contact and graphene (Gr) doping for Gr/XPtY (X, Y = S, Se, and Te) van der Waals (vdW) heterostructures are studied by using first-principles methods. The intrinsic electronic properties of Gr and PtXY are preserved due to the weak vdW interactions. We find that the types of interfacial electrical contact and Gr doping are closely related to the interface chalcogen atoms. The n-type Ohmic contact is formed in the Gr/SPtY (Y = S, Se, and Te) systems. The n-type and p-type Schottky contacts are realized in the Gr/SePtY and Gr/TePtY systems, respectively. The physical mechanism of different contact types can be analyzed based on the charge transfer between the Gr and XPtY layers. For all the heterostructures, the contact type and Schottky barrier height can be effectively modulated by the external electric field and interlayer coupling. The Gr doping type and charge-carrier concentration are also investigated. The p-doping, p-doping, and n-doping are obtained in Gr for the Gr/SPtY, Gr/SePtY, and Gr/TePtY systems, respectively. The highest carrier concentration of the Gr layer can reach 1.69 × 1013 cm-2 for the Gr/TePtTe system. The results indicate that Gr/XPtY heterostructures are potential candidates for improving the performance of high-efficiency nano electronic devices.

Remarkable Rashba spin splitting induced by an asymmetrical internal electric field in polar III-VI chalcogenides.

Herein, the Rashba spin orbit coupling (SOC) of polar group III-VI chalcogenide XABY (A, B = Ga, In; X ≠ Y = S, Se, Te) monolayers is investigated based on density functional theory. The different electronegativities of X and Y atoms lead to an asymmetrical internal electric field in the XABY monolayer; this implies that the internal electric field between A and X is not equal to that between B and Y. Mirror symmetry breaking in the XABY monolayer induces a remarkable Rashba spin splitting (RSS) at the conduction band minimum (CBM). Moreover, it is demonstrated that an external electric field and an in-plane biaxial strain can affect the internal electric field by varying the charge distribution, and this further manipulates the RSS. Under a positive external electric field and tensile strain, the RSS at the CBM exhibits a near-linear increasing behavior, whereas under a negative external electric field and compressive strain, the RSS displays a monotonous decreasing pattern. In addition, we explored the influence of interlayer coupling and substrate on the RSS. The stacking pattern of bilayer structures has a significant impact on the RSS. The investigation of SInGaSe on the Si(111) substrate suggests that the Rashba band is situated inside the large band gap of the substrate. Overall, our investigations suggest that the polar group III-VI chalcogenides are promising candidates for future spintronic applications.

Thermal Stability of Ag13- Clusters Studied by Ab Initio Molecular Dynamics Simulations.

Identification of the geometric structures of silver clusters is of great importance in future nanotechnologies due to their superior properties. Nevertheless, some ground-state structures are still in academic debate, partly because the experiments and theoretical calculations are not performed at the same temperatures. For example, silver clusters usually have compact configurations. However, a combined experimental and theoretical study proposed that the most stable structure of Ag13- had a two-coordinated atom. By using the CALYPSO approach for the global minima search followed by first-principles calculations, we discovered that a more compact trilayer Ag13- cluster was the ground state, in accordance with another three works published recently. In addition, its O2 adsorption structure is also energetically favored. By tracing characteristic bond changes in ab initio molecular dynamics (MD) simulations, we confirmed that, compared with other isomers, this trilayer structure and its O2 adsorption structure also had the highest thermal stability. This work emphasized the thermal stability concept in theoretical calculations, which may be a necessary supplement to explain the experimental observations on cluster science.

Driving interference control by side carbon chains in molecular and two-dimensional nano-constrictions.

The quantum interference effect offers a unique route to control the charge transport through nanoscale constrictions. The carbon atomic chain, which is an sp-hybridized carbon allotrope, has recently stimulated interest to construct ultimate nano-devices. Instead of using the carbon atomic chain as an electron transmitting channel interconnecting nano-components, we explore the possibility of using side carbon chains to change the phase of the transmitting electrons and influence the interference pattern of the nano-device. Interference pattern modulation is a general phenomenon which is demonstrated in a benzene molecular device, a zigzag graphene nanoribbon device and a SiC nanoribbon device. Odd-even oscillation dependence of the conductance on the length of the side carbon chain is found. Two criteria, i.e. large magnitude of the local state in the side carbon chain and proper length of the side carbon chain, must be satisfied simultaneously to achieve effective interference modulation. By carefully choosing the position and length of the side carbon chains, the transmission zero can be moved to the Fermi energy. Moreover, the transmission zero induced by destructive interference at the Fermi energy can be very robust against strain. This work provides a new possibility to construct nano-devices with carbon atomic chains.

A Series of Lanthanide Compounds Constructed from Ln8 Rings Exhibiting Large Magnetocaloric Effect and Interesting Luminescence.

A series of lanthanide compounds, [Ln8(CH2OHCH2OH)8(SO4)12]· m(C2H7N)· nH2O (Ln = Gd (1), Sm (2), Tb (3), La (5), m = 2, n = 2; Ln = Eu (4), m = 0, n = 8), which contain Ln8 rings by sulfate and glycol as the ligand have been synthesized and characterized. Besides, small organic amine and l-tartaric acid act as dual templating roles during the synthetic process. Magnetic investigation of compound 1 reveals the existence of weak antiferromagnetic interactions between GdIII ions and the data of magnetic entropy change (-Δ Sm) is 36.86 J K-1 kg-1 (108.55 mJ cm-3 K-1) for Δ H = 7 T at 2.0 K, which is comparatively large among GdIII based compounds. Additionally, because of the excellent luminescence properties of SmIII, TbIII, and EuIII, compounds 2-4 were investigated.

Heparanase-1-induced shedding of heparan sulfate from syndecan-1 in hepatocarcinoma cell facilitates lymphatic endothelial cell proliferation via VEGF-C/ERK pathway.

Heparanase-1/syndecan-1 axis plays critical roles in tumorigenesis and development. The main mechanism includes heparanase-1 (HPA-1) degrades the heparan sulfate chain of syndecan-1 (SDC-1), and the following shedding of heparan sulfate from tumor cell releases and activates SDC-1 sequestered growth factors. However, the significance of Heparanase-1/syndecan-1 axis and its effects on the microenvironment of lymphatic metastasis in hepatocellular carcinogenesis (HCC) procession have not been reported. Herein, we found that HPA-1 could degrade the heparan sulfate on hepatocarcinoma cell surface. Importantly, HPA-1-induced shedding of heparan sulfate chain from SDC-1 facilitated the release of vascular endothelial growth factor C (VEGF-C) from SDC-1/VEGF-C complex into the medium of hepatocarcinoma cell. Further studies indicated that VEGF-C secretion from hepatocarcinoma cell promoted lymphatic endothelial cell growth through activating extracellular signal-regulated kinase (ERK) signaling. Taken together, this study reveals a novel existence of Heparanase-1/syndecan-1 axis in hepatocarcinoma cell and its roles in the cross-talking with the microenvironment of lymphatic metastasis.

Au cluster adsorption on perfect and defective MoS2 monolayers: structural and electronic properties.

The adsorption of Aun (n = 1-4) clusters on perfect and defective MoS2 monolayers is studied using density functional theory. For the pristine MoS2 monolayer, our results show that the electrons are transferred from the support to the adsorbed Au clusters, thus a p-doping effect is achieved in the pristine MoS2 monolayer by the Au cluster adsorption, which is in good agreement with the experimental findings. The adsorption of Au clusters can introduce mid-gap states, which modify the electronic and magnetic properties of the systems. The adsorbates containing an odd number of Au atoms can introduce a spin magnetic moment of 1 µB into the perfect MoS2 monolayer, while those systems containing an even number of Au atoms are spin-unpolarized. Two categories of defects, i.e., a single S vacancy and Mo antisite defect with one Mo atom replacing one S atom, are considered for the defective monolayer MoS2. Compared with the pristine MoS2 monolayer, the adsorption energies for Au clusters are significantly increased for the MoS2 monolayer with a single S vacancy, and there are more electrons transferred from the MoS2 monolayer with an S vacancy to the Au clusters. The mid-gap states and odd-even oscillation magnetic behavior can also be observed when Au clusters are adsorbed on the MoS2 monolayer with an S vacancy. For those systems of Au clusters on MoS2 monolayers with Mo antisite defects, the adsorption energies as well as the magnitude and the direction of transferred charge are similar to those for the MoS2 monolayer with an S vacancy. The spin-polarizations appear in all systems with Mo antisite defects. Our investigations suggest that the electronic and magnetic properties of MoS2 nanosheets can be effectively modulated by the adsorption of Au clusters.

Enantiomerically pure lanthanide-organic polytungstates exhibiting two-photon absorption properties.

Two enantiomerically pure polytungstates, Na2[(CH3)2NH2]3{Na⊂[Ce(III)(H2O)(CH3CH2OH)(L-tartH3)(H2Si2W19O66)]}·3.5H2O (L-1) and [(CH3)2NH2]7{Na⊂[Ce(III)(H2O)(CH3CH2OH)(D-tartH3)(Si2W19O66)]}·2.5H2O (D-1), were successfully synthesized. Structural analysis indicates that chiral tartrate ligands directly connect with novel lacunary [Si2W19O66](10-) polytungstate units. Strong induced optical activity in the polyoxometalate (POM) units is manifested by circular dichroism spectroscopy. Z-scan analysis revealed that L-1 and D-1 are the first chiral POM-based complexes that exhibit two-photon absorption properties typical of the third-order nonlinear optical response.

A novel dumbbell-like polyoxometalate assembled of copper(II)-disubstituted monovacant keggin polyoxoanions with a tetranuclear copper cluster.

A dimeric Keggin polyoxometalate, [Cu(bpy)(µ2-OH)]4[(H2O)(bpy)2HPW11Cu2O39]2·2CH3CH2OH·10H2O (1), constructed from two dicopper(II)-substituted monovacant Keggin polyoxoanions bridged by a Cu4 cluster, has been hydrothermally synthesized. Magnetic analysis indicates predominantly an antiferromagnetic interaction between copper(II) centers. Compound 1 also shows very high catalytic activity for the esterification of phosphoric acid with equimolar lauryl alcohol to monoalkyl phosphate ester.

GATA6 inhibits the biological function of non-small cell lung cancer by modulating glucose metabolism.

PURPOSE: This study aims to explore the role of GATA6 in lung cancer, with a focus on its impact on metabolic processes. METHODS: We assessed GATA6 expression in lung cancer tissues and its association with patient prognosis. In vitro cell function experiments were conducted to investigate the effects of altered GATA6 levels on lung cancer cell proliferation and migration. Mechanistic insights were gained by examining GATA6's influence on glucose metabolism-related genes, particularly its effect on c-Myc mRNA expression. RESULTS: Our study revealed significant down-regulation of GATA6 in lung cancer tissues, and this down-regulation was strongly correlated with unfavorable patient prognosis. Elevating GATA6 levels effectively inhibited the proliferation and migration of lung cancer cells in our cell function experiments. Mechanistically, we found that GATA6 suppressed the expression of c-Myc mRNA, impacting genes related to glucose metabolism. As a result, glucose uptake and metabolism in lung cancer cells were disrupted, ultimately impeding their malignant behaviors. CONCLUSION: Our study provides crucial insights into the metabolic regulation of GATA6 in lung cancer cells. These findings have the potential to offer a solid theoretical foundation for the development of novel clinical treatments for lung cancer.

Strain-induced orbital polarization and multiple phase transitions in Ba2MnWO6 from first principles.

Electronic structures of double perovskite Ba2MnWO6 with epitaxial strain are explored by using methods based on density functional theory. An in-plane compressive strain is found not only resulting in a semiconductor-metal transition (SMT), but also altering the magnetic structures, from different kinds of antiferromagnetic to ferromagnetic orders. Orbital polarization and different orbital occupancies of Mn d(z(2)) and d(x(2)-y(2)) states, induced by the epitaxial strain, are employed to understand the SMT. The rich magnetic phase transitions are rationalized by a magnetic stabilization mechanism. Our results show that many technological applications may be carried out in the material with the control of epitaxial strain.

Anisotropic thermal expansion of silicon monolayer in biphenylene network.

Materials with a negative thermal expansion property are of great importance in the emerging family of two-dimensional materials. For example, mixing two materials with negative and positive coefficients of thermal expansion avoids volume changing with temperature. In this work, based on first-principles calculations and Grüneisen's theory, we investigated the thermal expansion properties of a silicon monolayer in biphenylene networks. Our results show that the thermal expansion is greatly negative and anisotropic, as the linear thermal expansion coefficient along the a-direction is significantly smaller than the one along the b-direction, even at high temperatures. At 300 K, the thermal expansion coefficients along the two lattice directions are -17.010 × 10-6 K-1 and -2.907 × 10-6 K-1, respectively. By analyzing the Grüneisen parameters and the elastic compliance, we obtained an understanding of the giant negative thermal expansion of the material. Rigid unit modes are also responsible for the negative thermal expansion behavior. Our work provides fundamental insights into the thermal expansion of silicon monolayer in biphenylene networks and should stimulate the further exploration of the possible thermoelectric and thermal management applications of the material.

LncRNA CAI2 contributes to poor prognosis of glioma through the PI3K-AKt signaling pathway.

AIMS: We aim to explore new potential therapeutic targets and markers in human glioma. BACKGROUND: Gliomas are the most common malignant primary tumor in the brain. OBJECTIVE: In the present research, we evaluated the effect of CAI2, a long non-coding RNA, on the biological behaviors of glioma and explored the related molecular mechanism. METHOD: The expression of CAI2 was analyzed using qRT-PCR in 65 cases of glioma patients. The cell proliferation was determined with MTT and colony formation assays, and the PI3K-AKt signaling pathway was analyzed using western blot. RESULT: CAI2 was upregulated in human glioma tissue compared with the matched, adjacent nontumor tissue and was correlated with WHO grade. Survival analyses proved that the overall survival of patients with high CAI2 expression was poor compared to that of patients with low CAI2 expression. High CAI2 expression was an independent prognostic factor in glioma. The absorbance values in the MTT assay after 96 h were .712 ± .031 for the si-control and .465 ± .018 for the si-CAI2-transfected cells, and si-CAI2 inhibited colony formation in U251 cells by approximately 80%. The levels of PI3K, p-AKt, and AKt in si-CAI2-treated cells were decreased. CONCLUSION: CAI2 may promote glioma growth through the PI3K-AKt signaling pathway. This research provided a novel potential diagnostic marker for human glioma.

L- and D-[Ln(HCO2)(SO4)(H2O)](n) (Ln = La, Ce, Pr, Nd, and Eu): chiral enantiomerically 3D architectures constructed by double -[Ln-O](n)- helices.

A total of 10 three-dimensional chiral coordination compounds L- and D-[Ln(HCO(2))(SO(4))(H(2)O)](n) (Ln = La, Ce, Pr, Nd, and Eu) have been synthesized without any chiral auxiliary and characterized by IR, thermogravimetric, and elemental analyses. Their structures were determined by single-crystal X-ray structural analysis, which shows that L-[Ln(HCO(2))(SO(4))(H(2)O)](n) (Ln = La, Ce, Pr, Nd, and Eu) crystallize in space group P4(3) and are laevogyrate and isostructural. The chiral frameworks of L-[Ln(HCO(2))(SO(4))(H(2)O)](n) are constructed from L-helical Ln-O cluster chains, while adjacent L-type helical -[Ln-O](n)- chains are connected through O-Ln-O linkages to form chiral intertwined Ln-O double helices of left-handedness. D-[Ln(HCO(2))(SO(4))(H(2)O)](n) crystallize in space group P4(1), and their chiral frameworks consist of D-helical Ln-O cluster chains. The observed second-harmonic-generation efficiencies of [La(HCO(2))(SO(4))(H(2)O)](n), Ce(HCO(2))(SO(4))(H(2)O)](n), [Pr(HCO(2))(SO(4))(H(2)O)](n), [Nd(HCO(2))(SO(4))(H(2)O)](n), and [Eu(HCO(2))(SO(4))(H(2)O)](n) are 0.7, 0.8, 0.7, 0.5, and 0.7 times that of urea, respectively. It is particularly interesting that [Pr(HCO(2))(SO(4))(H(2)O)](n) shows good two-photon absorption.

Ferroelectric control of band alignments and magnetic properties in the two-dimensional multiferroic VSe2/In2Se3.

Our first-principles evidence shows that the two-dimensional (2D) multiferroic VSe2/In2Se3experiences continuous change of electronic structures, i.e. with the change of the ferroelectric (FE) polarization of In2Se3, the heterostructure can possess type-I, -II, and -III band alignments. When the FE polarization points from In2Se3to VSe2, the heterostructure has a type-III band alignment, and the charge transfer from In2Se3into VSe2induces half-metallicity. With reversal of the FE polarization, the heterostructure enters the type-I band alignment, and the spin-polarized current is turned off. When the In2Se3is depolarized, the heterostructure has a type-II band alignment. In addition, influence of the FE polarization on magnetism and magnetic anisotropy energy of VSe2was also analyzed, through which we reveal the interfacial magnetoelectric coupling effects. Our investigation about VSe2/In2Se3predicts its wide applications in the fields of both 2D spintronics and multiferroics.

Multi-shaped strain soliton networks and moiré-potential-modulated band edge states in twisted bilayer SiC.

Tuning the interlayer twist angle provides a new degree of freedom to exploit the potentially excellent properties of two dimensional layered materials. Here we investigate the structural and electronic properties of twisted bilayer SiC under a series of twist angles using first principle calculations. The interplay of interlayer van der Waals interactions and intralayer strain induces dramatic in-plane and out-of-plane displacements. The expansion or contraction of specific stacking domains can be interpreted as the result of the energy minimization rule. By means of order parameter analysis, the triangular or hexagonal strain soliton networks are found to separate adjacent stacking domains. The unique overlapped zigzag atom lines in strain solitons provide a unique characteristic for experimental imaging. The top valence band and bottom conduction band evolve into flat bands with the smallest band width of 4 meV, indicating a potential Mott-insulator phase. The moiré-potential-modulated localization pattern of states in the flat band, which is dependent sensitively on the structure relaxation, controls the flat band width. The moiré-pattern-induced structural and electronic properties of twisted bilayer SiC are promising for application in nanoscale electronic and optical devices.

Electric control of nearly free electron states and ferromagnetism in the transition-metal dichalcogenides monolayers.

Using the first-principles calculations, we explore the nearly free electron (NFE) states in the transition-metal dichalcogenidesMX2(M= Mo, W;X= S, Se, Te) monolayers. It is found that both the external electric field and electron (not hole) injection can flexibly tune the energy levels of the NFE states, which can shift down to the Fermi level and result in novel transport properties. In addition, we find that the valley polarization can be induced by both electron and hole doping in MoTe2monolayer due to the ferromagnetism induced by the charge injection, which, however, is not observed in other five kinds ofMX2monolayers. We carefully check band structures of all theMX2monolayers, and find that the exchange splitting in the top of the valence band and the bottom of conduction band plays the key role in the ferromagnetism. Our researches enrich the electronic, spintronic, and valleytronic properties ofMX2monolayers.