Lithium Ion Intercalation-Induced Metal-Insulator Transition in Inclined-Standing Grown 2D Non-Layered Cr2S3 Nanosheets.

Gate-controlled ionic intercalation in the van der Waals gap of 2D layered materials can induce novel phases and unlock new properties. However, this strategy is often unsuitable for densely packed 2D non-layered materials. The non-layered rhombohedral Cr2S3 is an intrinsic heterodimensional superlattice with alternating layers of 2D CrS2 and 0D Cr1/3. Here an innovative chemical vapor deposition method is reported, utilizing strategically modified metal precursors to initiate entirely new seed layers, yields ultrathin inclined-standing grown 2D Cr2S3 nanosheets with edge instead of face contact with substrate surfaces, enabling rapid all-dry transfer to other substrates while ensuring high crystal quality. The unconventional ordered vacancy channels within the 0D Cr1/3 layers, as revealed by cross-sectional scanning transmission electron microscope, permitting the insertion of Li+ ions. An unprecedented metal-insulator transition, with a resistance modulation of up to six orders of magnitude at 300 K, is observed in Cr2S3-based ionic field-effect transistors. Theoretical calculations corroborate the metallization induced by Li-ion intercalation. This work sheds light on the understanding of growth mechanism, structure-property correlation and highlights the diverse potential applications of 2D non-layered Cr2S3 superlattice.

Heat- and Pressure-driven Room-temperature Polymorphic Transition Accompanied with Switchable SHG Signal in a New Chiral Hexagonal Perovskite.

Endowing room-temperature polymorphs with both long-term stability and easy interconvertibility is a big challenge due to the complexity of intermolecular interactions. Herein, we present a chiral hexagonal perovskite (R-3-hydroxy-1-methylpiperidinium)[CdCl3 ] having two room-temperature crystalline forms featuring obviously distinct second-harmonic-generation (SHG) signals with a high switching contrast of ~18 times. The two room-temperature forms could be long-term stable yet easily interconvertible through an irreversible thermal-induced phase transition and a pressure-driven backward transition, by switching hydrogen bonds via collective reorientation of ordered homochiral cations. Based on the essential role of homochiral organic cations in inducing switchable hydrogen bond linkages, this present instance provides good evidence that relatively irregular organic cations could induce more obvious inorganic chain deformations, thus endowing polymorphs with significantly different SHG signals at room temperature.

Thermoelectric Properties of n-Type Bi4O4SeX2 (X = Cl, Br).

The multiple anion superlattice Bi4O4SeCl2 has been reported to exhibit extremely low thermal conductivity along the stacking c-axis, making it a promising material for thermoelectric applications. In this study, we investigate the thermoelectric properties of Bi4O4SeX2 (X = Cl, Br) polycrystalline ceramics with different electron concentrations by adjusting the stoichiometry. Despite optimizing the electric transport, the thermal conductivity remained ultra-low and approached the Ioffe-Regel limit at high temperatures. Notably, our findings demonstrate that non-stoichiometric tuning is a promising approach for enhancing the thermoelectric performance of Bi4O4SeX2 by refining its electric transport, resulting in a figure of merit of up to 0.16 at 770 K.

An unprecedented hexagonal double perovskite organic-inorganic hybrid ferroelastic material: (piperidinium)2[KBiCl6].

An unprecedented A2MIMIIIX6-type double perovskite adopting a fully hexagonal BaNiO3-type structure, (piperidinium)2[KBiCl6], undergoes a 2/mF1[combining macron] ferroelastic phase transition at 285 K with a spontaneous strain of 0.0615, arising from the order-disorder transition of organic cations together with the synchronous displacement of inorganic chains.

T-square resistivity without Umklapp scattering in dilute metallic Bi2O2Se.

Fermi liquids (FLs) display a quadratic temperature (T) dependent resistivity. This can be caused by electron-electron (e-e) scattering in presence of inter-band or Umklapp scattering. However, dilute metallic SrTiO3 was found to display T2 resistivity in absence of either of the two mechanisms. The presence of soft phonons as possible scattering centers raised the suspicion that T2 resistivity is not due to e-e scattering. Here, we present the case of Bi2O2Se, a layered semiconductor with hard phonons, which becomes a dilute metal with a small single-component Fermi surface upon doping. It displays T2 resistivity well below the degeneracy temperature in absence of Umklapp and inter-band scattering. We observe a universal scaling between the T2 resistivity prefactor (A) and the Fermi energy (EF), an extension of the Kadowaki-Woods plot to dilute metals. Our results imply the absence of a satisfactory understanding of the ubiquity of e-e T2 resistivity in FLs.

Switching hydrogen bonds to readily interconvert two room-temperature long-term stable crystalline polymorphs in chiral molecular perovskites.

It is challenging to endow polymorphs with both long-term stability and easy interconvertibility. We demonstrate an interesting example that two room-temperature polymorphs could be long-term stable yet easily interconvertible, at a pressure of ∼4.8 MPa and a temperature of 120 °C, by switching hydrogen bonds via collective reorientation of organic cations in chiral molecular perovskites.

[Vacuum-assisted biopsy and wire localization for the diagnosis of non-palpable breast lesions].

OBJECTIVE: To compare the effectiveness and accuracy of the use of vacuum-assisted biopsy (VAB) versus wire localization (WL) in the diagnosis of non-palpable breast lesions (NPBL). METHODS: Ninety-seven consecutive women with NPBL were randomized into VAB group and WL group. All specimens were identified by mammography. The patients were requested to score the cosmetic appearance of their breast after operation, and a numerical rating scale was used to measure pain on the first postoperative day. Underestimation rates for atypical ductal hyperplasia (ADH) and ductal carcinoma in situ (DCIS) were recorded if open surgical biopsy revealed DCIS and invasive cancer, respectively. Clear margins were also recorded in the two groups. RESULTS: VAB and WL located all the NPBL successfully. In the VAB group, the specimen volume was smaller than that of the WL group (2.3 cm(3) vs. 18.4 cm(3), P = 0.03). Underestimation rates of ADH and DCIS in the VAB group were 16.7% and 11.1%, respectively. The diagnostic accordance rate of VAB was 97.9%, the false negative rate was 2.1%, and there was no false positive case. The means of the numerical rating pain scale were different in both groups (1.7 for VAB vs. 2.5 for WL, P = 0.02). When cosmetic results were taken into account, 40 VAB patients had excellent outcomes and 8 good outcomes, compared with 25 excellent and 24 good for the WL group. There were better cosmetic outcomes with the VAB procedure (P < 0.05). CONCLUSION: VAB is highly reliable and may avoid diagnostic open surgery in the majority of patients with benign lesions. However, because of the underestimation of histologic diagnosis and tumor margin involvement, VAB can not be used to completely substitute wire localization.