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Novel water‐soluble methylated chitins (MCHs) were synthesized homogeneously in aqueous alkaline solution. The relatively mild reaction conditions resulted in the MCH with high degree of acetylation (DA >0.76). The chemical structure of the obtained MCHs was analyzed and the degree of methylation substitution (DS) and DA were determined by proton NMR in both D2O and 20% DCl/D2O. The MCH aqueous solutions (DS = 0.46 ~ 0.71) showed a reversible thermosensitive sol–gel–sol transition upon heating and cooling. The gel transition temperature of these MCHs (in the range of 15–85 °C) increased with increasing DS and decreasing polymer concentration. Thermal runaway has been an important safety issue impeding the development of high‐energy‐density zinc‐ion batteries. A smart thermosensitive reversible electrolyte was prepared based on this MCH for the aqueous zinc‐ion battery to prevent thermal runaway. When the temperature of zinc‐ion battery rises or even gets out of control, the thermosensitive electrolyte can quickly gel and inhibit the migration of zinc ions, resulting in increase of the internal resistance and realizing intelligent and efficient thermal self‐protection. Thus the novel thermosensitive methylated chitin shows promise for safe aqueous zinc‐ion batteries. [ABSTRACT FROM AUTHOR]

A series of vanadium phosphate oxide (VPO) catalysts supported on silica (VPO/SiO2) with various mole ratios of V/P (nV:nP=1:0.8-1:3) were prepared through impregnation method. The catalytic activity was evaluated by ammoxidation reactions of several kinds of chloro-substituted toluenes (CT) in a fixed-bed reactor. The catalyst presented the best performance when nV:nP is 1:1.6. The prepared catalysts were characterized by N2 adsorption, hydrogen temperature programmed reduction (TPR) and ammonia temperature programmed desorption (TPD) and etc. The results reveal that P can decrease the bonding energy of V=O and increase the mobility of lattice oxygen which was beneficial for the improvement of the catalysts, while too much P can greatly decrease the average oxidation number of V which leads to deactivation of the catalysts. The surface acidity of the VPO/SiO2 catalysts is affected by nV:nP and the catalyst had the highest surface acidity when nV:nP is 1:1.6. The selectivity of catalysts is proportional to the surface acidity when nV:nP is lower than 1:3.0. [ABSTRACT FROM AUTHOR]

Abstract: Organic carbon coated vanadium dioxide (VO2(B)@C) core–shell structured nanobelts were successfully synthesized using V2O5 and glucose solution as the starting materials by a facile one-step hydrothermal route. The as-obtained core–shell materials were characterized by scanning electron microscope, transmission electron microscopy, X-ray powder diffraction, energy-dispersive X-ray spectrometer, elemental analysis, Fourier transform infrared spectroscopy and Raman measurements. Some parameters, such as, the concentration of glucose and the reaction time, were briefly discussed to disclose the formation process of VO2(B)@C core–shell structured nanobelts. Glucose played a dual role in the hydrothermal process, namely as a reductant to reduce V2O5 to VO2(B), and as a carbon precursor for the organic carbon shell. The proper quantity of glucose (i.g.: 0.27g) was beneficial for the fabrication of VO2(B)@C. Furthermore, the possible formation mechanism of VO2(B)@C core–shell structured nanobelts was proposed. [Copyright &y& Elsevier]

Highlights: [•] Doped VO2(M) was synthesized by a facile one-step hydrothermal route. [•] Doped VO2(M) has belt-like morphology with rectangular cross sections. [•] Some parameters were briefly discussed to the synthesis of W-doped VO2(M). [•] The Tc of doped VO2(M) can be simply tuned by changing the doping concentration. [•] The doped VO2(M) has thermochromic characters and optical switching properties. [Copyright &y& Elsevier]

Abstract: Monoclinic vanadium dioxide VO2(M) shows a fully reversible first-order metal-to-insulator transition (MIT) with the phase transition temperature (T c ) at about 68°C. The large-scale and low-cost synthesis of VO2(M) are a challenge for materials scientists. In this paper, the influence of different additives on the synthesis of VO2 polymorphs by a hydrothermal route was studied. F, Ti, Cr, Fe, Mo, Sn, Sb and W atoms can promote the formation of VO2(M), while Mg, Al, Co and Ni atoms are favorable for the synthesis of VO2(B), whereas, Na, Ca, Mn and Zn atoms have no influence on the formation of VO2(A). It was found that the T c of doped VO2(M) is very sensitive to the doped atoms. Some parameters, such as the temperature, reaction time, initial V2O5/oxalic acid molar ratio, tungstic acid concentration, were briefly discussed to give a systematic overview on the synthesis of W-doped VO2(M). In all cases, the morphologies of the doped VO2(M) show micro- and nano-rods structures. The T c of W-doped VO2(M) can be simply tuned by changing the doping concentration of W atom within appropriate limits. The variable-temperature infrared spectra show that the doped VO2(M) has outstanding thermochromic characters and optical switching properties. Furthermore, the enlarged-scale experiments for the synthesis of doped VO2(M) suggest that the same results can be acquired, which makes this route very suitable for practical application. [Copyright &y& Elsevier]

Abstract: Belt-like X-doped VO2(M) (X=W, Mo, Sn or Fe) with rectangular cross sections were successfully synthesized by a facile one-pot hydrothermal approach. The as-obtained samples were characterized by XRD, XPS, SEM, DSC and variable-temperature IR. The results showed that the additives W, Mo, Sn and Fe could promote the formation of VO2(M) under hydrothermal conditions. The additives had little influence on the morphology of doped VO2(M), but they were the key factor for the synthesis of VO2(M). The W and Mo atoms could effectively reduce the T c of VO2(M), while Sn and Fe atoms had little influence on T c. Furthermore, it was found that the as-obtained doped VO2(M) possessed prominent thermochromic properties and optical switching characters. [Copyright &y& Elsevier]

Abstract: VO2(M) nanobelts encapsulated into carbon core–shell structured composite (VO2(M)@C) was successfully synthesized by the thermal treatment with the precursor V3O7·H2O@C composite under the inert atmosphere. The as-obtained sample was characterized by XRD, EDS, EA, FT-IR, Raman, SEM and TEM measurements. The core exhibited monoclinic phase VO2(M) and the carbon coated on the surface of VO2(M) was amorphous. The average thickness of carbon was about 18.5 nm. The possible formation mechanism of VO2(M)@C was proposed as that the reaction underwent the solid state reaction by the interface reaction between V3O7 core and carbon shell. Furthermore, VO2(M) and VO2(M)@C composite were explored as the cathode materials to apply in lithium-ion batteries, indicating that the VO2(M)@C composite electrode exhibited the better electrochemical properties than that of pure VO2(M), achieving the aim of improving the electrochemical properties of VO2(M). [Copyright &y& Elsevier]

Abstract: Belt-like V2O3 encapsulated into carbon tubes (V2O3/C) core–shell structured composite and vanadium carbide (VC) nanobelts have been successfully synthesized by the thermal treatment with VO2/C core–shell structured composite through adjusting the heating temperature for the first time. The amorphous carbon on the surface of VO2 plays a dual role in this thermal process, namely as the reductant to reduce VO2 to V2O3 or VC, and as the carbon precursor for the V2O3/C carbon shell and VC. The as-obtained samples were respectively characterized by X-ray powder diffraction, energy-dispersive X-ray spectrometer, Raman spectrum, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller. V2O3/C was successfully synthesized at 700–900°C for 2h, and VC nanobelts were successfully prepared at 1000°C for 2h. The as-obtained V2O3/C composite and VC nanobelts contain C–H groups, which will facilitate the linkage of catalytic species or polymers to the surface in their potential applications. V2O3/C composite has higher specific surface area than that of VC due to the amorphous carbon coated on the surface of V2O3. Furthermore, the thermal stability of VC in air was investigated by Thermo-Gravimetric/Differential Thermal Analyzer, revealing that it had good thermal stability and oxidation resistance below 335°C in air. [Copyright &y& Elsevier]

Abstract: Belt-like VO2(A) with a rectangular cross section (VA-RCS) was successfully synthesized using V2O5, H2C2O4·2H2O and H2O as the starting materials by a facile hydrothermal approach. Some synthetic parameters, such as, the reaction time, reaction temperature and concentration of H2C2O4·2H2O, were systematically investigated to control the fabrication of belt-like VA-RCS. The formation mechanism of belt-like VA-RCS was proposed. Subsequently, belt-like VO2(M) with a rectangular cross section (VM-RCS) was prepared by the irreversible transformation of VA-RCS at 700°C for 2h under the inert atmosphere. The phase transition temperature (T c) of VA-RCS and VM-RCS was evaluated by DSC test. The optical switching properties of VA-RCS and VM-RCS were studied by the variable-temperature infrared spectra, and it was found that the as-obtained VA-RCS and VM-RCS could be used as the optical switching materials. Furthermore, the oxidation resistance properties of VA-RCS and VM-RCS were investigated by TGA, indicating that they have good thermal stability and oxidation resistance below 400°C in air. [Copyright &y& Elsevier]

Abstract: VO2(B) nanobelts encapsulated into carbon core–shell structured composite (VO2(B)@C) was successfully synthesized using VO2(B) nanobelts as the cores and glucose as the shells via an environmental hydrothermal method. The “adsorption carbonization growth” (ACG) mechanism was proposed to explain the formation of VO2(B)@C. The influence of synthetic parameters, such as, the reaction temperature, concentration of glucose and reaction time, was systematically investigated to control the fabrication of VO2(B)@C. Subsequently, belt-like V2O3@C core–shell structured composite was prepared by the heating treatment of VO2(B)@C. Furthermore, the electrochemical properties of this novel belt-like V2O3@C core–shell structured composite was studied, indicating that it exhibits an initial discharge capacity of as high as 162mAh/g and the discharge capacity is still 104, 89, 67mAh/g after 30, 50, and 89 cycles, which is much higher than pure V2O3. The phase transition properties of V2O3 powder and V2O3@C composite were investigated by DSC, which revealed that V2O3@C has the same phase transition properties of V2O3. The as-obtained V2O3@C composite has potential applications to the cathode and functional positive temperature coefficient (PTC) materials. [Copyright &y& Elsevier]

Abstract: Sphere- and pod-like α-Fe2O3 particles have been selectively synthesized using NH3·H2O and NaOH solution to adjust the pH value of the designed synthetic system, respectively. The sphere-like α-Fe2O3 particles with diameter about 25nm on average were encapsulated into carbon shells to fabricate a novel core–shell composite (α-Fe2O3@C) through the coating experiments. The catalytic performance of the products on the thermal decomposition of ammonium perchlorate (AP) was investigated by thermal gravimetric analyzer (TG) and differential thermal analysis (DTA). The thermal decomposition temperatures of AP in the presence of pod-like α-Fe2O3, sphere-like α-Fe2O3 and α-Fe2O3@C are reduced by 72, 81 and 109°C, respectively, which show that α-Fe2O3@C core–shell composites have higher catalytic activity than that of α-Fe2O3. [Copyright &y& Elsevier]