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1.
Artigo em Inglês | MEDLINE | ID: mdl-33557516

RESUMO

Bimetallic organic frameworks (Bi-MOFs) have been recognized as one of the most ideal precursors to construct metal oxide semiconductor (MOS) composites, owing to their high surface area, various chemical structures, and easy removal of the sacrificial MOF scaffolds through calcination. Herein, we synthesized Zn/Ni Bi-MOF for the first time via a facile ion exchange postsynthetic strategy, formed a three-dimensional framework consisting of infinite one-dimensional chains that is unattainable through the direct solvothermal approach, and then transformed the Zn/Ni Bi-MOF into a unique ZnO/NiO heterostructure through calcination. Notably, the obtained sensor based on a ZnO/NiO heterostructure exhibits an ultrahigh response of 280.2 toward 500 ppm n-propanol at 275 °C (17.2-fold enhancement compared with that of ZnO), remarkable selectivity, and a limit of detection of 200 ppb with a notable response (2.51), which outperforms state-of-the-art n-propanol sensors. The enhanced n-propanol sensing properties may be attributed to the synergistic effects of several points including the heterojunction at the interface between the NiO and ZnO nanoparticles, especially a one-dimensional chain MOF template structure as well as the chemical sensitization effect of NiO. This work provides a promising strategy for the development of a novel Bi-MOF-derived MOS heterostructure or homostructure with well-defined morphology and composition that can be applied to the fields of gas sensing, energy storage, and catalysis.

2.
J Am Chem Soc ; 141(43): 17166-17173, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31599579

RESUMO

Magnetism in the two-dimensional limit has become an intriguing topic for exploring new physical phenomena and potential applications. Especially, the two-dimensional magnetism is often associated with novel intrinsic spin fluctuations and versatile electronic structures, which provides vast opportunities in 2D material research. However, it is still challenging to verify candidate materials hosting two-dimensional magnetism, since the prototype systems have to be realized by using mechanical exfoliation or atomic layer deposition. Here, an alternative manipulation of two-dimensional magnetic properties via electrochemical intercalation of organic molecules is reported. Using tetrabutyl ammonium (TBA+), we synthesized a (TBA)Cr2Ge2Te6 hybrid superlattice with metallic behavior, and the Curie temperature is significantly increased from 67 K in pristine Cr2Ge2Te6 to 208 K in (TBA)Cr2Ge2Te6. Moreover, the magnetic easy axis changes from the ⟨001⟩ direction in Cr2Ge2Te6 to the ab-plane in (TBA)Cr2Ge2Te6. Theoretical calculations indicate that the drastic increase of the Curie temperature can be attributed to the change of magnetic coupling from a weak superexchange interaction in pristine Cr2Ge2Te6 to a strong double-exchange interaction in (TBA)Cr2Ge2Te6. These findings are the first demonstration of manipulation of magnetism in magnetic van der Waals materials by means of intercalating organic ions, which can serve as a convenient and efficient approach to explore versatile magnetic and electronic properties in van der Waals crystals.

3.
Chem Commun (Camb) ; 55(83): 12567-12570, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31577281

RESUMO

Amorphous bimetallic coordination polymers have been prepared by a mild room temperature solution phase method and utilized as an OER electrocatalyst. Their excellent performance with an overpotential of 228 mV at 10 mA cm-2 and a Tafel slope of 30.3 mV dec-1 exhibits their great potential in the field of the OER.

4.
Materials (Basel) ; 12(16)2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31430932

RESUMO

In view of the existing problems of stope roadways, which are difficult to maintain under the influence of high ground and mining-induced stresses, the structural characteristics and movement regularities of stopes surrounding rocks were analysed. Through the construction of a three-dimensional mechanical model of the coordination support of a stope, the adaptability index of the support in stope is presented, and its mechanism of operation is expounded. Yielding-resisting sand column (YRSC) sidewall-support technology with satisfactory compressibility and supporting strength was developed. The structure and actual mechanical properties of the YRSC were investigated through laboratory experiments, and the optimum ratio of filling materials was obtained. The good applicability of the load and deformation adaptability index of the three-dimensional coordination support in the stope and YRSC sidewall-support technology were demonstrated in practice at the No. 12306 working face of the Dongda coal mine. It was shown that the designed carrying capacity and compression of the sand columns satisfied the site requirements. The actual stress and deformation of the YRSC exhibited three stages: Slow growth at the initial stage, a large increase in the medium term, and a stable trend at the end. The adaptability index of the three-dimensional coordination support in the stope considers all bearing structure units of the stope as an interconnected whole, and the stability conditions of the stope roadway can be quantitatively described. The supporting effect of the YRSC is remarkable and can be applied to the construction of tunnels, bridge systems and other engineering fields.

5.
Inorg Chem ; 58(15): 9897-9903, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31291102

RESUMO

Two kinds of ternary thorium nitride compounds, ThNF and ThNCl, are synthesized. Via the refinement of X-ray diffraction patterns, the accurate crystal structure of the two compounds is solved. Although ThNF and ThNCl share a similar structure with MNX (M = Ti, Zr, Hf; X = Cl, Br) compounds, the interaction between adjacent ThNF and ThNCl layers is not a van der Waals gap. For ThNF, the strong electronegativity of F ions leads to the bonding of Th to the F both in the nearest neighbor layer and the next nearest neighbor layer, which results in the absence of a van der Waals gap between ThNF layers. However, for ThNCl, the reason for the absence of a van der Waals gap could be attributed to the large Th-Cl bond length due to the partially covalent Th-Cl bond as well as the flat ThN layer. It is the absence of van der Waals gap that results in the failure of intercalating cations into ThNF and ThNCl. Our result reveals the reason for unsuccessful intercalation in ThNF and ThNCl, thereby providing a deeper understanding for the interlayer interaction in ternary layer structures in metal nitride halides.

6.
Langmuir ; 23(11): 6385-90, 2007 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-17451260

RESUMO

A series of liquid-crystalline polysiloxanes synthesized by cholest-5-en-3-ol (3beta)-10-undecenoate and 4'-octanoyloxy-biphenyl-4-yl 4-allyloxy-3-sulfo-benzoate were prepared in a one-step reaction with sulfonic acid group contents ranging between 0 and 2.73 wt %. All the polymers displayed smectic mesophases with a large temperature range for the mesophases. With an increase of sulfonic acid containing mesogens in the polymers, the temperature of the glass transition did not change greatly, while the temperature of the clear point decreased. The hydrogen-bonding mesogen aggregates in the domains disturb the liquid-crystalline molecular mobility and orientation, leading to a decrease in temperature from the mesophase to the isotropic transition. Unlike the polymers containing lower sulfonic acid mesogens, some polymers showed a dendritic texture of the SmB* phase, indicating that the sulfonic mesogens enhanced the rigid moieties of the supermolecular structure of the liquid-crystalline phases. All the polymers displayed sharp and strong peaks at low angles around 2theta approximately 2.6 degrees and broad peaks at wide angles around 2theta approximately 17 degrees in X-ray measurements. The intensity of the strong peak at low angles in the X-ray profiles decreased with an increase of sulfonic acid mesogens in the polymer systems.

7.
Opt Express ; 15(16): 10175-81, 2007 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-19547366

RESUMO

The optical properties of polymer liquid crystal cell exhibiting polymer blue phases (PBPs) have been determined using ultraviolet-visible spectrophotometry, polarizing optical microscopy (POM), differential scanning calorimetry (DSC), X-ray measurements, FTIR imaging and optical rotation technique. PBPs are thermodynamically stabile mesophases, which appear in chiral systems between isotropic and liquid crystal phases. A series of cyclosiloxane-based blue phase polymers were synthesized using a cholesteric LC monomer and a nematic LC monomer, and some of the polymers exhibit PBPs in temperature range over 300 degrees in cooling cycles. The unique property based on their structure and different twists formed and expect to open up new photonic application and enrich polymer blue phase contents and theory.

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