•Synthesis of new conjugated chromophores carrying double proton transfer segments.•Formation of nano organic aggregation particles in THF/H2O mixed solution.•Naked-eye fluorescence color switching of the aggregates under UV irradiation.•Strong potential application in developing multicolor organic aggregates.New conjugated dye C1 (2, 2′-((5-(2-(4-methoxyphenyl)ethenyl)-benzene-1, 3-diyl)-bis-(nitrilomethylylidene))-diphenol) carrying double proton transfer segments and its reference C2 (N, N′-(5-(2-(4-methoxyphenyl)-ethenyl)-benzene-1, 3-diyl)-bis-(1-phenylmethanimine)) were synthesized. The SEM and TEM images showed that cubic-shaped aggregates of C1 were formed with sizes of 300–500 nm in THF/H2O mixed solution at 12 h. The spectral properties of aggregation states of the molecules in different ratios of THF/H2O were further investigated. The fluorescence emission spectra under different aggregation time intervals indicated that C1 exhibited remarkable aggregation induced emission enhancement. The keto emission of C1 showed an increase firstly and then a decrease with increasing aggregation time. Hence, the enhanced fluorescence color switching from bright yellow to pure blue under UV lamp was observed by our naked eyes. In contrast, C2 could not show obvious AIEE properties under identical experimental conditions. This is the first successful attempt to achieve naked-eye fluorescence chromism of new organic chromophores inspired by aggregation and ESIPT together.

For developing high performance supercapacitors (SCs), it is critical to fabricate advanced electrode materials with porous nanostructures and high surface area to facilitate the transport of ions and electrons and impede the volumetric variation during cycling. Herein, we reported the fabrication of free-standing two dimensional (2D) mesoporous ZnCo2O4 thin sheets (CQU-Chen-Zn-Co-O-1) consisting of 3D ultrathin nanoflake array frameworks by facile decomposition of a mixed aqueous solution of zinc ion (Zn2+), cobalt ion (Co2+) and acetic acid (CH3COOH, AA) under hydrothermal condition without any additive agent. The resulting CQU-Chen-Zn-Co-O-1 delivers a high capacitance of 2.72 F cm−2 at 2.02 mA cm−2 and high rate capability of 59.76% from 1.01 to 10.1 mA cm−2 and superior cycling performance of 3.5% loss after 5,000 cycles. Furthermore, an assembled asymmetric supercapacitor (CQU-Chen-Zn-Co-O-1//active carbon (AC)) device exhibits high energy density of 33.98 and 9.78 Wh kg−1 at power density of 8 and 0.8 kW kg−1, respectively, as well as good cycling performance of 6.7% loss after 10,000 cycles. These results show that the ZnCo2O4 thin sheets display great potential in energy storage applications.Download high-res image (172KB)Download full-size image

•Synthesis of amphiphilic phenanthridine dyes in mild conditions.•Preparation of nano aggregates of the dyes in mixed organic solvent/H2O solutions.•Reversible excited state proton transfer occurrence for nano aggregates of the dyes.•Observation of intensified ESPT fluorescence color by naked-eyes.This study presented nano aggregates of new amphiphilic phenanthridine dyes with hydroxy group displaying intensified fluorescence emission of reversible intermolecular excited state proton transfer in mixed organic solvent/H2O solutions.Download high-res image (225KB)Download full-size image

•New conjugated containing strong electron-donating groups were prepared.•Formation of nanoscale aggregation particles in DMF/H2O mixed solution through re-precipitation method.•Observation of naked-eye fluorescence color switching of target dyes under UV-lamp irradiation.•Potential application in developing multicolor AIEE dyes.In this study, a variety of new conjugated containing strong electron-donating groups were prepared for formation of organic nano-scale aggregates. The properties and aggregation modes of these aggregates were investigated on basis of time dependent absorption, fluorescence emission spectra as well as scanning electron microscope images. The results show that nano organic aggregates could be yielded by the linear dyes in mixed DMF/H2O solvent through a simple re-precipitation method, while no aggregates of the branched dyes were produced. X-ray diffraction of single crystal and X-ray diffraction patterns of the powders results demonstrate that the linear dyes tend to show ordered molecular arrangements, while the armed dyes do not exhibit such a tendency. A remarkable fluorescence switching process under 365 nm lamp was observed for the target aggregates. This study successfully provides real examples of organic aggregates in mixed DMF/H2O solvent which have great capacity to show enhanced fluorescence color switching.

In this study, a variety of branched target dyes containing double internal proton transfer segments were synthesized. For comparison, some linear analogs including a single internal proton transfer part were synthesized. The corresponding reference molecules lacking proton transfer segments were also prepared. The properties and aggregation modes of these dye aggregates were investigated on the basis of scanning electron microscopy images, transmission electron microscopy images, dynamic light scattering, X-ray diffraction, UV/visible absorption spectra and fluorescence emission spectra. The results showed that molecular aggregates with the morphologies of nano-scaled rounded or cubic particles of the target branched dyes could be yielded in mixed organic solvent/H2O solution. A remarkable emission enhancement and fluorescence switching process (from bright yellow to luminous pure blue) under 365 nm lamp irradiation was observed for these target branched dye nanoaggregates. However, no aggregates of the reference branched dyes free of hydroxyl groups were formed and no obvious spectral variations were found. In contrast, all the studied linear dyes yielded molecular nanoaggregates in mixed organic solvent/H2O solution, and only intensified single normal blue fluorescence emission was presented. This study provided real examples of some branched organic dye aggregates which were capable of displaying naked-eye enhanced fluorescence color switching under an UV lamp.

A new zeolitic-like microporous coordination polymer (PCP), [Zn2(L)·2H2O]·guest (named NTU-17), with crb (BCT) topology was designed and prepared. Interestingly and unusually, it is the first time that such rod-shaped NTU-17 crystals could be converted to morphology-preserved carbon rods with exclusive micropores and a large surface area by using a facile method of direct thermal transformation. Gas adsorption and selectivity showed that these PCP dependent carbon rods are suitable solid adsorbents for CH4 purification.

As one kind of important p-type semiconductors, Cr2O3 has been widely used for optical and electronic devices due to its high electrical conductivity and special optoelectronic characteristics, as well as high chemical and thermal stability. In this paper, single-crystalline Cr2O3 nanoplates embedded in carbon matrix were successfully synthesized through direct thermal decomposition of a trinuclear cluster complex of [Cr3O(CH3CO2)6(H2O)3]NO3·CH3COOH ([Cr3O]) in Ar atmosphere. The synergetic effect of the plate-like structure and embedding in carbon matrix contributes to the enhanced electrochemical performance of the Cr2O3-C nanoplates. Owing to different crystallinity and composition, the obtained products at 400, 500, 600, and 700 °C with different carbon content of 12.52, 8.26, 5.35 and 3.27% exhibited enhanced battery-type electrode materials in three-electrode system with high specific capacitance (823.11, 781.65, 720.72, and 696.73 F g−1 at 1 A g−1) and remarkable cycling stability (about 0.3, 2.7, 4.5 and 5.6% loss of its initial capacitance after 5000 charge-discharge cycles at a current density of 5 A g−1). Furthermore, an assembled asymmetric device (Cr2O3-C nanoplates (positive electrode)//activated carbon (AC, negative one)) with an extended operating voltage window of 1.8 V achieves a specific capacitance of 58.06 F g−1 at the current density of 1 A g−1 and an energy density of 26.125 W h kg−1 at power density of 0.9 kW kg−1, as well as superior cycling stability with 91.4% capacitance retention after 10,000 cycles. The results indicate that the Cr2O3 nanoplates embedded in carbon matrix show promising potential to construct high-performance energy storage devices.Single-crystalline Cr2O3 nanoplates embedded in carbon matrix with different crystallinity have been synthesized by calcination of a trinuclear complex of [Cr3O(CH3CO2)6(H2O)3]NO3·CH3COOH in Ar atmosphere. The assembled asymmetric device (Cr2O3-C nanoplates//AC) with an extended operating voltage window of 1.8 V can produce the highest energy density of 26.125 W h kg−1 at power density of 0.9 kW kg−1.Download high-res image (107KB)Download full-size image

Olivaceous two-dimensional (2D) multi-layer graphene-like Co3O4 thin sheets (CQU-Chen-Co-O-1) with vertically aligned nanosheets as basic building units were first prepared on a large scale by direct hydrothermal decomposition of a mixed aqueous solution of cobalt(II) nitrate and acetic acid without the assistance of any template or surfactant. The resulting products exhibited excellent pseudocapacitive performance with a high specific capacitance of 1752 and 1862 F g−1 at the current density of 5 mV s−1 and 1 A g−1, respectively, as well as good rate capability (63.64% capacitance surplus) and high cycling performance (99.5% surplus after 2000 cycles).

Amorphous three-dimensional (3D) nanoflake array-assembled porous 2D cobalt–oxalate coordination polymer thin sheets (CQU-Chen-OA-Co-1-1) were first synthesized by using a facile hydrothermal route under electro-magnetic stirring. The resulting material exhibited excellent pseudocapacitive performance with a high specific capacitance of 702.75 F g−1 at 1 A g−1 and remarkable cycling stability.

•Fe3O4 nanosheets were prepared by a surfactantless sonochemical process.•The prepared Fe3O4 nanosheets display single-crystalline structure with a lateral size altering from 50 to 120 nm and a thickness ranging from 10 to 20 nm.•The prepared nanosheets are ferromagnetic property at room temperature.•The prepared Fe3O4 nanosheets would have potential applications in diverse fields.Fe3O4 nanosheets were successfully synthesized via a facile sonochemical route by direct ultrsound treatment of the mixture solution of FeSO4, NaOAc, and NaOH in the air. The results of X-ray diffraction (XRD), infrared spectra (IR), and X-ray photoelectron spectroscopy (XPS) showed that a purity phase of Fe3O4 was obtained after sonochemical reaction. And results from transmission electron microscopy (TEM) indicated that the as-prepared Fe3O4 nanosheets display single-crystalline structure with a lateral size altering from 50 to 120 nm and a thickness ranging from 10 to 20 nm, which was also confirmed by selected area electron diffraction (SAED) and HRTEM (high resolution TEM) analysis. In addition, magnetic measurements showed that the saturated magnetization of the obtained Fe3O4 nanosheets was ferromagnetic property at room temperature. It was found that the sonochemical process played a key role in the formation of Fe3O4 nanosheets and a possible growth mechanism was also discussed.Graphical abstractSingle-crystal Fe3O4 nanosheets were successfully synthesized by a facile surfactantless sonochemical process.

Flower-like NiFe2O4 superstructures consisting of nanosheets have been successfully synthesized by direct thermolysis of a heterometallic oxo-centered trinuclear complex [NiFe2O(CH3COO)6(H2O)3·2H2O] (NiFe-HOTC) at 400 °C for 6 h in a horizontal tube furnace. The composition and structure of the products were investigated by X-ray diffraction (XRD) and infrared spectra (IR). XRD analysis revealed a pure ferrite phase with high crystallinity. Morphological investigation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed NiFe2O4 flowers with average diameter varying from 0.5 to 3 μm consist of nanosheets with average edge length in the range of 60–300 nm and thickness of about 30 nm. Furthermore, energy dispersive X-ray analysis (EDX) demonstrated that the atom ration of Ni, Fe and O is 1:2:4. In addition, magnetic measurements showed that the obtained flower-like NiFe2O4 are ferromagnetic at room temperature.Flower-like NiFe2O4 superstructures consisting of nanosheets were synthesized by direct pyrolysis of a heterometallic oxo-centered trinuclear complex [NiFe2O(CH3COO)6(H2O)3·2H2O].Highlights► Flower-like NiFe2O4 superstructures were synthesized by direct pyrolysis of a heterometallic oxo-centred trinuclear complex [NiFe2O(CH3COO)6(H2O)3·2H2O] at 400 °C for 6 h. ► The synthesized flower-like NiFe2O4 superstructures are consist of nanosheets with average edge length in the range of 60-300 nm and thickness of about 30 nm. ► The synthesized products are ferromagnetic with the saturation magnetization value of 43.25 emu/g and the coercivity value of 122 Oe.

In the present work, core–shell CoFe2O4–carbon composite nanoparticles (CCNPs) were synthesized via the thermolysis of a heterometallic trinuclear complex [CoFe2O(CH3COO)6(H2O)3·2H2O] in a one-end closed horizontal tube furnace. The products were characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD and EDX analyses revealed a pure ferrite phase with high crystallinity and the composition elements of C, Co, Fe and O with the rate of Co, Fe, and O to the CoFe2O4 theoretical value. Raman spectroscopy indicates amorphous carbon in the products. Morphological investigation by SEM and TEM showed the CCNPs have an average particle size of 50 nm coated with carbon on the surface. The reaction temperatures were evaluated and magnetic measurement shows that the formed CCNPs have smaller saturation magnetization than bulk cobalt ferrite at room temperature.Core–shell CoFe2O4–carbon composite nanoparticles were successfully prepared by thermal decomposition of a heterometallic trinuclear complex of [CoFe2O(CH3COO)6(H2O)3·2H2O].

Spongy CuO was successfully synthesized via direct pyrolysis of Cu3(btc)2 (btc = benzene-1,3,5-tricarboxylate) microporous metal-organic framework (MOF) in a horizontal tube furnace in the air, in which the Cu3(btc)2 was used as the Cu source and complexing molecule precursor. The as-prepared products were characterized by a series of techniques including XRD, SEM, EDX, TEM, and SAED. Results from SEM showed that the as-prepared spongy CuO with average diameter altering from 10 to 20 μm consists of nanosheets with average edge length in the range of 80–200 nm and thickness of about 30 nm, which was also confirmed by TEM analysis. The XRD and SAED results showed that a purity phase of CuO was obtained after pyrolysis. It was also found that the reaction temperature played a key role in the formation of spongy CuO microstructures. The spongy material could be found potential application in various fields such as catalysis, absorption, and gas sensing.Graphical AbstractSpongy CuO with nanosheets was synthesized via direct pyrolysis of Cu3(btc)2 (btc = benzene-1,3,5-tricarboxylate) microporous metal-organic framework (MOF).Research Highlights► Spongy CuO was synthesized via direct pyrolysis of Cu3(btc)2 (btc = benzene-1,3,5-tricarboxylate) microporous metal-organic framework (MOF) in the air. ► Spongy CuO with average diameter altering from 10 to 20 μm consists of nanosheets with average edge length in the range of 80–200 nm and thickness of about 30 nm. ► The effect of reaction temperature on the morphology of spongy CuO and formation mechanism were discussed.

A facile route for the production of high quality monodisperse Fe3O4/silica nanocomposite microspheres (NMs) with embedded structures has been successfully established by employing a solution-based route via direct decomposition of tetraethyl ortho-silicate (TEOS) in solution under the presence of freshly synthesized Fe3O4 nanoparticles (NPs). This method is based on a two-step process, involving: (i) synthesis of Fe3O4 NPs by coprecipitaiton of Fe2+ and Fe3+ with NH3·H2O in solution at room temperature; (ii) formation of Fe3O4/silica NMs by direct decomposition of TEOS in the presence of dispersed Fe3O4 NPs of (i) under mechanical stirring at room temperature. The effects of the concentration of TEOS and pH value have been investigated in detail to optimize the synthetic conditions. XRD, XPS, FTIR, EDS, SEM, and TEM were used for the characterization of the synthesized products. It is found that the synthesized Fe3O4/silica NMs with as typical values average diameters of 0.25–4 μm obtained under the optimized conditions were nearly monodisperse, superparamagnetic with a relatively high saturation magnetization value, which implies potentially promising applications in engineering and biomedicine areas. Moreover, a possible formation mechanism of NMs was also proposed. Meanwhile, this general approach could be extended to prepare other metal oxide/silica NMs.

We describe here a one-step solid-state process for the synthesis of metal three-dimensional (3D) superstructures from a metal-organic framework (MOF). Novel symmetrical coralloid Cu 3D superstructures with surface interspersed with clusters of Cu nanoparticles were successfully synthesized by thermolysis of the [Cu3(btc)2] (btc=benzene-1,3,5-tricarboxylato) MOF in a one-end closed horizontal tube furnace (OCTF). The obtained products were characterized by TGA, FT-IR, XRD, EDX, SEM, TEM, HRTEM and SAED. Different reaction conditions were discussed. Furthermore, the synthesized Cu samples were converted into CuO microstructures by in-situ calcination in the air. In addition, the possible formation mechanism was also proposed. This method is a simple and facile route, which builds a direct linkage between metal-carboxylate MOF crystals and metal nano- or microstructures and also opens a new application field of MOFs.Novel symmetrical coralloid Cu 3D superstructures were synthesized by thermolysis of the [Cu3(btc)2] (btc=benzene-1,3,5-tricarboxylato) MOF microcrystals in a one-end closed horizontal tube furnace (OCTF).

A series of uniform spinel ferrite MFe2O4 (M = Ni, Co, Mn, and Zn) nanoparticles (NPs) were successfully synthesized on a large scale by direct hydrothermal decomposition of the trinuclear heterometallic oxo-centered acetate cluster of [MFe2O(CH3CO2)6(H2O)3]nH2O in solution. The crystal structure, composition and size of the synthesized NPs were characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometer (ICP-AES), transmission electron microscope (TEM) and high-resolution (HRTEM). Magnetic investigation revealed that all the synthesized MFe2O4 NPs showed superparamagnetic properties at room temperature. The possible formation mechanism was also proposed.

Amorphous three-dimensional (3D) nanoflake array-assembled porous 2D cobalt–oxalate coordination polymer thin sheets (CQU-Chen-OA-Co-1-1) were first synthesized by using a facile hydrothermal route under electro-magnetic stirring. The resulting material exhibited excellent pseudocapacitive performance with a high specific capacitance of 702.75 F g−1 at 1 A g−1 and remarkable cycling stability.

Olivaceous two-dimensional (2D) multi-layer graphene-like Co3O4 thin sheets (CQU-Chen-Co-O-1) with vertically aligned nanosheets as basic building units were first prepared on a large scale by direct hydrothermal decomposition of a mixed aqueous solution of cobalt(II) nitrate and acetic acid without the assistance of any template or surfactant. The resulting products exhibited excellent pseudocapacitive performance with a high specific capacitance of 1752 and 1862 F g−1 at the current density of 5 mV s−1 and 1 A g−1, respectively, as well as good rate capability (63.64% capacitance surplus) and high cycling performance (99.5% surplus after 2000 cycles).

A new zeolitic-like microporous coordination polymer (PCP), [Zn2(L)·2H2O]·guest (named NTU-17), with crb (BCT) topology was designed and prepared. Interestingly and unusually, it is the first time that such rod-shaped NTU-17 crystals could be converted to morphology-preserved carbon rods with exclusive micropores and a large surface area by using a facile method of direct thermal transformation. Gas adsorption and selectivity showed that these PCP dependent carbon rods are suitable solid adsorbents for CH4 purification.