Liangjie Fu

Perovskite LaFeO3/montmorillonite nanocomposites: synthesis, interface characteristics and enhanced photocatalytic activity.

Perovskite LaFeO3/montmorillonite nanocomposites (LaFeO3/MMT) have been successfully prepared via assembling LaFeO3 nanoparticles on the surface of montmorillonite with citric acid assisted sol-gel method. The results indicated that the uniform LaFeO3 nanoparticles were densely deposited onto the surface of montmorillonite, mainly ranging in diameter from 10 nm to 15 nm. The photocatalytic activity of LaFeO3/MMT was evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation, indicating that LaFeO3/MMT exhibited remarkable adsorption efficiency and excellent photocatalytic activity with the overall removal rate of RhB up to 99.34% after visible light irradiation lasting for 90 min. The interface characteristic and possible degradation mechanism were explored. The interface characterization of LaFeO3/MMT suggested that LaFeO3 nanoparticles could be immobilized on the surface of montmorillonite with the Si-O-Fe bonds. The abundant hydroxyl groups of montmorillonite, semiconductor photocatalysis of LaFeO3 and Fenton-like reaction could enhance the photocatalytic degradation through a synergistic effect. Therefore, the LaFeO3/MMT is a very promising photocatalyst in future industrial application to treat effectively wastewater of dyes.

Enhanced performance and interfacial investigation of mineral-based composite phase change materials for thermal energy storage

A novel mineral-based composite phase change materials (PCMs) was prepared via vacuum impregnation method assisted with microwave-acid treatment of the graphite (G) and bentonite (B) mixture. Graphite and microwave-acid treated bentonite mixture (GBm) had more loading capacity and higher crystallinity of stearic acid (SA) in the SA/GBm composite. The SA/GBm composite showed an enhanced thermal storage capacity, latent heats for melting and freezing (84.64 and 84.14 J/g) was higher than those of SA/B sample (48.43 and 47.13 J/g, respectively). Addition of graphite was beneficial to the enhancement in thermal conductivity of the SA/GBm composite, which could reach 0.77 W/m K, 31% higher than SA/B and 196% than pure SA. Furthermore, atomic-level interfaces between SA and support surfaces were depicted, and the mechanism of enhanced thermal storage properties was in detail investigated.

Carbon hybridized halloysite nanotubes for high-performance hydrogen storage capacities

Hybrid nanotubes of carbon and halloysite nanotubes (HNTs) with different carbon:HNTs ratio were hydrothermally synthesized from natural halloysite and sucrose. The samples display uniformly cylindrical hollow tubular structure with different morphologies. These hybrid nanotubes were concluded to be promising medium for physisorption-based hydrogen storage. The hydrogen adsorption capacity of pristine HNTs was 0.35% at 2.65 MPa and 298 K, while that of carbon coated HNTs with the pre-set carbon:HNTs ratio of 3:1 (3C-HNTs) was 0.48% under the same condition. This carbon coated method could offer a new pattern for increasing the hydrogen adsorption capacity. It was also possible to enhance the hydrogen adsorption capacity through the spillover mechanism by incorporating palladium (Pd) in the samples of HNTs (Pd-HNTs) and 3C-HNTs (Pd-3C-HNTs and 3C-Pd-HNTs are the samples with different location of Pd nanoparticles). The hydrogen adsorption capacity of the Pd-HNTs was 0.50% at 2.65 MPa and 298 K, while those of Pd-3C-HNTs and 3C-Pd-HNTs were 0.58% and 0.63%, respectively. In particular, for this spillover mechanism of Pd-carbon-HNTs ternary system, the bidirectional transmission of atomic and molecular hydrogen (3C-Pd-HNTs) was concluded to be more effective than the unidirectional transmission (Pd-3C-HNTs) in this work for the first time.

Hierarchical MoS2 intercalated clay hybrid nanosheets with enhanced catalytic activity

Emerging hierarchical MoS2/pillared-montmorillonite (MoS2/PMMT) hybrid nanosheets were successfully prepared through facile in-situ hydrothermal synthesis of MoS2 within the interlayer of cetyltrimethylammonium bromide PMMT, and their catalytic performance was evaluated by the reduction reaction of 4-nitrophenol (4-NP) using NaBH4 as a reductant. Microstructure and morphology characterization indicated that MoS2/PMMT exhibited hybrid-stacked layered structures with an interlayer spacing of 1.29 nm, and the MoS2 nanosheets were intercalated within the montmorillonite (MMT) layers, with most of the edges exposed to the outside. The catalytic activity and stability of MoS2/PMMT were both enhanced by the MMT. With the MoS2/PMMT as the catalyst, the apparent reaction rate constant of the 4-NP reduction was 0.723 min−1 and was maintained at ~0.679 min−1 after five reaction cycles. The structural evolution of MoS2/PMMT and the possible catalysis mechanism for the reduction reaction of 4-NP were investigated. The as-prepared MoS2/PMMT hybrid nanosheets are promising candidates for catalytic application in the water-treatment and biomedical fields. The strategy developed in this study can provide insights for designing hybrid nanosheets with diverse heterogeneous two-dimensional (2D) nanomaterials.

Controlled Assembly of Sb2S3 Nanoparticles on Silica/Polymer Nanotubes: Insights into the Nature of Hybrid Interfaces

Silica nanotubes can serve as high aspect ratio templates for the deposition of inorganic nanoparticles to form novel hybrids. However, the nature of the interfacial binding is still an unresolved challenge when considered at the atomic level. In this work, novel nanocomposites have been successfully fabricated by the controlled nucleation and assembly of Sb2S3 nanoparticles on the surface of mercaptopropyl-functionalized silica/polymer hybrid nanotubes (HNTs). The Sb2S3 nanoparticles were strongly attached to the HNTs surface by interactions between the pendent thiol groups and inorganic sulfur atoms. Detailed analysis of the geometric and electronic structure using first–principle density functional theory demonstrates charge transfer from the nanoparticles to the underlying HNTs at the Sb2S3/HNTs interfaces. Formation of a packed array of Sb2S3 nanoparticles on the HNTs results in mixing of the electronic states of the components, and is mediated by the mercaptopropyl bridges between Sb2S3 and the outer layer of the HNTs.

Insights into the nature of Cu doping in amorphous mesoporous alumina

Mesoporous alumina can serve as a framework for metal doping to form a novel nanocomposite. However, the nature of metal doping in amorphous mesoporous Al2O3 (aMA) is still obscured at the atomic level. This paper reports the one-pot synthesis of Cu-doped amorphous mesoporous alumina. Density functional theory calculations were carried out to reveal the geometric and electronic structure evolution upon Cu doping. Lattice distortion, metal distribution and charge compensation effects are the key factors responsible for the doping mechanism in aMA. The doped metal atoms prefer the predominant penta-coordinated (V) sites, and coexist with intrinsic defects, forming species with varied structures, influenced by the local structure, doping concentration and chemical environment. The most stable structures are formed under the balance of the above factors. The reduction of Cu+ to a metallic phase is hindered by the surrounding amorphous alumina reservoir. The dispersed Cu2+ species were proved to show higher catalytic activity.

Au encapsulated into Al-MCM-41 mesoporous material: in situ synthesis and electronic structure

Au supporting mesoporous material Al-MCM-41 composites were successfully prepared by encapsulation of the in situ synthesized gold nanoparticles into Al-MCM-41; herein palygorskite clay was used as the Si and Al sources and cetyltrimethylammonium bromide (CTAB) as the template and coupling agent. The obtained Al-MCM-41 possessed a well-defined two-dimensional hexagonal structure with a relative large specific surface area and pore size distribution of 3.9 nm, which was ideal to house very small Au nanoparticles (∼3 nm). Using this in situ encapsulation route, the highly ordered Al-MCM-41 was simultaneously generated with the gold nanoparticles incorporated into the pores and the Au3+ species well dispersed in the frameworks. The electronic structure and optical properties of Au/Al-MCM-41 were investigated in detail. The partial reduction of Au3+ species by incorporation of Al3+ from clay sources was confirmed by XPS results and DFT calculations, and the higher catalytic activities of Au/Al-MCM-41 over Au-MCM-41 were evaluated.

3D ordered macro–mesoporous indium doped Al2O3

Three-dimensional ordered macro–mesoporous (3DOMM) Al2O3 and In doped Al2O3 have been successfully synthesized via a dual-templating approach with a colloidal crystal template and surfactant block copolymers. The samples were characterized using X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible (UV-vis) and photoluminescence (PL) spectroscopy. The results indicate that the indium dopants are dispersed well within the mesoporous framework, and the incorporation of indium could efficiently promote the optical properties of the composite. The as-synthesized 3DOMM structures have a large surface area (>200 m2 g−1), and the luminescence intensity of 3DOMM In doped Al2O3 with an In/Al molar ratio of 7% (3DOMM 7In–MAl) is two times higher than that of 3DOMM Al2O3 (3DOMM MAl). Further theoretical calculations, based on first-principle density functional theory (DFT), demonstrate that In doping facilitates the formation of oxygen vacancies, and the hybridization of oxygen vacancy defect states and In 5s, 5p states induce some hybrid states below the conduction band edge. The blue shift of absorption edges of 3DOMM 7In–MAl compared to pure 3DOMM MAl could be attributed to the electron transfer from oxygen vacancies to In atoms.

Synthesis and magnetic property of SiO2 coated Fe3O4/palygorskite

SiO2 coated Fe3O4/palygorskite magnetic nanocomposites (MNCs) were successfully synthesized via coprecipitation route. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM) and magnetic properties. The results indicated that SiO2 was coated on the surface of Fe3O4/palygorskite through the hydrolysis of tetraethyl orthosilicate (TEOS) and the orientation changing of MNCs could be realized by external magnetic field. The interfaces of the composite were further elucidated at atomic level. We believe that the as-prepared SiO2 coated Fe3O4/palygorskite MNCs could show potential application in the fields of functional nanomaterials.

MECHANOCHEMICAL SYNTHESIS OF NiO NANOPARTICLES: INSIGHT INTO THE NATURE OF PREFERRED GROWTH ORIENTATION

Nickel oxide (NiO) nanoparticles were synthesized by calcination at 400°C to 700°C for 8 h of the precursor obtained via mechanochemical reaction of Ni(NO3)2 ⋅ 6H2O with citric acid as a dispersant. The nanoparticles were characterized by thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The kinetics of different surfaces of the nanocrystals under nonisothermal conditions was investigated. The activation energies for different lattice planes of NiO nanoparticles were determined using the Arrhenius equation, revealing their preferred orientation. The growth of NiO obeyed the general theory that nanoparticles with the largest surface energy tend to form. XRD data reveal that the NiO nanoparticles possess preferred (111) or (200) orientations that reflect their complex activity. The nature of preferred growth orientation was found to be negative diffusion activity among different lattice surfaces, which indicates that oxygen atoms diffuse from low oxygen concentration on the lattice surface to high concentration on the lattice surface.