Natural halloysite nanotubes (HNTs) were functionalized with a silane coupling agent with the aim of tuning the loading rate and dispersion of precious-metal nanoparticles. The samples were characterized by FTIR spectroscopy, TEM, and XPS. The results indicated that a large number of precious-metal nanoparticles were anchored on the surface of the silanized HNTs, with an average diameter of ∼3 nm. The functionalized HNTs contain a large number of functional groups (−NH2 or −SH groups) that have one lone electron pair and can form a chemical bond complex with nanoparticles. Because of bond formation between the nanoparticles and the functional groups, most of the nanoparticles (NPs) are anchored by the functional groups, resulting in the formation of nanoparticle–functional group complexes. Bond formation between the nanoparticles and the functional groups was demonstrated, and furthermore, atomic-level interfaces for NPs anchored onto functionalized HNTs were depicted. The chemical immobilization of precious-metal nanoparticles onto silanized HNTs could avoid particle aggregation and movement, thus leading to a higher catalytic efficiency.

•Composite PCMs were prepared by impregnating lauric acid into modified sepiolite.•The loadage of lauric acid inside the modified sepiolite could reach up to 60 wt%.•Composite PCMs had latent heat (125.2 J/g) and phase change temperature (42.5 °C).•Form-stable composite PCMs showed promising potential for thermal energy storage.A series of novel composite phase change materials (PCMs) were prepared by impregnating lauric acid (LA) into the chemically modified sepiolite (SEP) via a vacuum impregnation method. Modification strategy was developed to improve the adsorption capacity of SEP, and the effects of thermal and chemical modification on the physical and chemical properties of SEP were investigated. The loading of LA inside the acid treated SEP could reach up to 60 wt%, which was 50% higher than that of pristine SEP. The corresponding latent heats of the composite PCMs exhibited 125.2 J/g at the melting temperatures of 42.5 °C and 113.9 J/g at the freezing temperatures of 41.3 °C, respectively. The increased latent heat could be attributed to the better microstructure of the modified SEP. The thermal conductivity (0.59 W/(m·k)) of the composite PCMs was higher than that of LA. The composite PCMs presented chemical and thermal reliability after 200 thermal cycling tests. The form-stable composite PCMs could be the promising candidate material for thermal energy storage.Download high-res image (101KB)Download full-size image

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.

An enhanced antibacterial activity of Fe2O3 nanoparticles was achieved by controlling the distribution density of Fe2O3 nanoparticles on modified kaolinite nanosheets (Fe2O3–KlnKAc) by adjusting the pH value of the reaction system. A proper distribution density of Fe2O3 nanoparticles generating higher levels of hydroxyl radicals led to a higher antibacterial activity.

Carbon hybridized montmorillonite nanosheets (C/MMT) were successfully prepared by mixing intercalation, hydrothermal carbonization and calcination pyrolysis of montmorillonite and sucrose. The amount adsorbed on C/MMT reaches 0.84 g g−1 at a Congo red concentration of 1.0 g L−1, which could be attributed to their special structures and synergistic sorption.

•Coal-series kaolinite was structurally modified to prepare silica nanosheets (SNSs).•Ag nanoparticles (AgNPs) of about 5 nm were uniformly on Sn2+-activated SNSs.•Ag/Sn2+-SNSs hybridized PEG to produce a novel composite phase change material.•The composite PCM still remained good thermal reliability after 200 cycles.•Hierarchical porous structure of Ag/Sn2+-SNSs benefited the thermal conductivity.This paper reported on the synthesis of silica nanosheets (SNSs) by structurally modifying natural coal-series kaolinite mineral (Kc). Ag nanoparticles (AgNPs) of about 5 nm were uniformly attached on the surface of Sn2+-activated SNSs to form an emerging hierarchical porous nanostructure, which was further hybridized with polyethylene glycol (PEG) to produce PEG@Ag/Sn2+-SNSs. The maximum loading capacity and melting enthalpy of PEG@Ag/Sn2+-SNSs could reach 66.1% and 113.9 J/g, respectively, and its thermal conductivity showed up to 0.84 W/(m K). The results demonstrated that well dispersion of AgNPs and hierarchical porous structure of Ag/Sn2+-SNSs could synergically enhance the thermal conductivity. Intriguingly, the introduction of AgNPs could lead to the obvious decrease of the melting and solidifying period, and simultaneously promoted the heat transfer of the composite phase change material (PCM). Furthermore, the composite PCM could retain good thermal reliability after 200 cycles, indicating its potential application in the thermal energy storage system. Atomic-level mechanism for the enhanced thermal conductivity of the composite PCM was also discussed.Download high-res image (328KB)Download full-size image

Natural halloysite nanotubes (HNTs) were hybridized with metal–organic frameworks (MOFs) to prepare novel composites. MOFs were transformed into carbon by carbonization calcination, and palladium (Pd) nanoparticles were introduced to build an emerging ternary compound system for hydrogen adsorption. The hydrogen adsorption capacities of HNT-MOF composites were 0.23 and 0.24 wt%, while those of carbonized products were 0.24 and 0.27 wt% at 25 °C and 2.65 MPa, respectively. Al-based samples showed higher hydrogen adsorption capacities than Zn-based samples on account of different selectivity between metal and hydrogen and approximate porous characteristics. More pore structures are generated by the carbonization reaction from metal–organic frameworks into carbon; high specific surface area, uniform pore size, and large pore volume benefited the hydrogen adsorption ability of composites. Moreover, it was also possible to promote hydrogen adsorption capacity by incorporating Pd. The hydrogen adsorption capacity of ternary compound, Pd-C-H3-MOFs(Al), reached 0.32 wt% at 25 °C and 2.65 MPa. Dissociation was assumed to take place on the Pd particles, then atomic and molecule hydrogen spilled over to the structure of carboxylated HNTs, MOFs, and the carbon products for enhancing the hydrogen adsorption capacity.

The in situ synthesis of mesoporous nanotubes from natural minerals remains a great challenge. Herein, we report the successful synthesis of mesoporous silica nanotubes (MNTs) with a varying inner-shell thickness and a preserved clay outer shell from natural-halloysite nanotubes (HNTs). After the enlargement of the lumen diameter of the tubular aluminosilicate clay by acid leaching, uniform mesopores were introduced by a modified pseudomorphic transformation approach, while the clay outer shell was well-preserved. Using density functional theory calculations, the atomic structure evolution and the energetics during Al leaching and Si–OH condensation were studied in detail. After the leaching of Al ions from the HNTs, local structural changes from Al(Oh) to Al(V) at a medium leaching level and to Al(Td) at a high leaching level were confirmed. The calculated hydroxylation energy of two kinds of silica components in the acid-leached HNTs (the distorted two-dimensional silica source in the inner shell and the intact aluminosilicate structure in the outer shell) was 0.5 eV lower or 1.0 eV higher than that of bulk silica, which clarifies the different behavior of the silica components in the hydrothermal process. The successful synthesis of reactive MNTs from HNTs introduces a new strategy for the synthesis of mesoporous nanocontainers with a special morphology using natural minerals. In particular, MNT samples with numerous reactive Al(V) species and a specific surface area up to 583 m2/g (increased by a factor of 10) are promising drug-loading nanocontainers and nanoreactors.

•Natural kaolin clay (KC) is chemically modified to form SiO2-AlOOH (SA) nanosheets.•CuO nanoparticles are well dispersed on SA nanosheets to prepare CuO/SA catalyst.•CuO/SA catalyst shows high catalytic activity for CO conversion up to 94.9%.•Surface hydroxyl groups of SA can promote CO oxidation by the chemisorption.Emerging hierarchical porous SiO2-AlOOH (SA) composite nanosheets were synthesized via structural reorganization of natural layer kaolin clay (KC). CuO nanoparticles were further attached on SA by in-situ chemical precipitation method for CO catalytic oxidation. The results demonstrated the relationship between synthesis, structure and performance of the catalytic system. Hydroxyl-group-rich SA composite nanosheets with high specific surface area could ensure the well dispersion of CuO nanoparticles through in-situ loading method without high-temperature calcination, further increasing the Cu active sites and retaining adequate hydroxyl groups. Hierarchical porous structure resulting from self-assembly of nanostructures (varisized sheets and particles) showed excellent physical adsorption performance for reactant gases. DRIFTS and XPS results revealed the possible role of three main surface reactive sites in this CuO/SA catalytic system: the coordinatively unsaturated Cu2+ of Si(Al)OCu bonds adsorbed gaseous CO, the Cu2+ with anionic vacancies on highly-dispersed CuO nanoparticles adsorbed gaseous O2, and the surface hydroxyls could promote CO oxidation by the chemisorption of gaseous CO as a formation of formate species to increase the CO concentration around the Cu active sites. A Langmuir–Hinshelwood mechanism of the hydroxyl-assisted CuO/SA for enhancing CO catalytic oxidation was also proposed.Download high-res image (75KB)Download full-size image

•CeO2-ZnO/HNTs ternary nanocomposite was synthesized through a precipitation method in ethanol system.•The improved antibacterial activity of CeO2-ZnO/HNTs against Escherichia coli with 8% cell viability was achieved.•The enhanced efficacy of the nanocomposite was achieved by HNTs dispersion and CeO2 modification.A novel antibacterial nanocomposite, CeO2-ZnO/HNTs was prepared by a homogeneous co-precipitation method in ethanol solution. ZnO and CeO2 nanoparticles with sizes of approximately 8 and 4 nm, respectively, were dispersively precipitated onto the surface of halloysite nanotubes (HNTs). HNTs served as a template for reducing the agglomeration of ZnO nanoparticles and improving the interface reactions between the nanocomposite and bacteria cells. CeO2 nanoparticles were introduced to suppress the recombination of electron-hole pairs, and narrow the energy gap of ZnO nanoparticles. The synergistic effects of ZnO, CeO2 nanoparticles and HNTs led to the superior antibacterial activity of the CeO2-ZnO/HNTs nanocomposite against gram-negative Escherichia coli.

Well crystallized gamma alumina (γ-Al2O3) with high thermal stability is as an important catalyst support. A series of first row transition metal (TM) doped aluminas with ordered mesoporous structures and homogeneous distribution of TM in the bulk structure has been synthesized by a one-pot method. The structures are studied by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM), while the electronic properties are explored by X-ray photoelectron spectroscopy (XPS), valence band XPS, and UV–vis spectra. To explore the influence of TM dopants on atomistic properties (bond length, charge state, band edge, and redox properties) of γ-Al2O3, the cation distribution of TM dopants is studied in detail by combining experiments and density functional theory (DFT) calculations. The cooperative effect of TM dopants and intrinsic defects in γ-Al2O3 induces a doping mechanism distinct from that in other spinel oxides; the concentration of Al vacancies (VAl) decreases with increasing atomic number of the TM dopant as a result of charge compensation effects. Such variation could be used to tailor the properties and alter the reactivity of γ-Al2O3.

Pristine halloysite nanotubes (HNTs) were pretreated to produce mesoporous silica nanotubes (MSiNTs), which was further impregnated with polyethenimine (PEI) to prepare an emerging nanocomposite MSiNTs/PEI (MP) for CO2 capture. Thermogravimetric analysis (TGA) was employed to analyze the influences of PEI loading amount and adsorption temperature on CO2 adsorption capacity of the nanocomposite. The Brunauer–Emmett–Teller (BET) surface area (SBET) of MSiNTs was six times higher than that of HNTs, and the corresponding pore volume was more than two times higher than that of HNTs. The well dispersion of PEI within the nanotubes of MSiNTs benefits more CO2 gas adsorption, and the adsorption capacity of the nanocomposite could reach 2.75 mmol/g at 85 °C for 2 h. The CO2 adsorption on the nanocomposite was demonstrated to occur via a two-stage process: initially, a sharp linear weight increase at the beginning, and then a relatively slow adsorption step. The adsorption capacity could reach as high as 70% within 2 min. Also, the nanocomposite exhibited good stability on CO2 adsorption/desorption performance, indicating that the as-prepared emerging nanocomposite show an interesting application potential in the field of CO2 capture.

Y2O3 functioned palygorskite (Pal) composite as a novel adsorbent has been successfully synthesized and characterized, which shows stable and rapid decolorization performance for methyl blue (MB). HRTEM images showed that Y2O3 nanoparticles with size about 2–5 nm evenly dispersed on palygorskite, and the increase of the binding energy of Y2O3 (Y3d5/2) confirmed that several bonds such as Y–OH and Y–O–Si were existed in Y2O3/Pal adsorbent. Y2O3 modification greatly increased the number of negatively charged groups as Y2O3/Pal showed lower negative zeta potential than that of Pal. Therefore, the electrostatic interaction between Y2O3/Pal and MB is impossible to be the adsorption mechanism. What's more, it is found that the adsorption isotherm obeys the Langmuir model, with the maximum adsorption capacity greatly enhanced to 1579.06 mg g−1, exhibiting potential applications in wastewater treatment.

Lithium orthosilicate (Li4SiO4)-based sorbents were synthesized using a low cost and naturally available mineral resource (halloysite) as silicon source for high temperature CO2 capture. Halloysite nanotubes (HNTs) were acid-treated by 6 M HCl for 6 h to leach diaspore-like sheet to produce Si source (H6), which showed the best extraction effects. Pure Li4SiO4 (P-LS) and H6-Li4SiO4 (H6-LS) were thermally analyzed under a CO2 flux. X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), nitrogen adsorption, and thermogravimetric (TG) analysis were used to examine the character of the phase, morphology, and CO2 chemisorption properties of the samples. The Li4SiO4 sorbent was synthesized at 800 °C for 4 h (H6-LS800), and the metal impurities especially aluminum were doped into the structure of H6-LS800, resulting in the increased surface area. Thermal analysis indicated the maximum CO2 adsorption capacity of H6-LS800 reached up to 34.45%, with the temperature range from 350 to 720 °C, which had a better CO2 adsorption than P-LS. In addition, H6-LS800 sorbent exhibited excellent adsorption–desorption performance.

•The rod-like nesquehonite has been successfully prepared from natural talc.•Temperature and ammonia dosage affect the crystal phase and size of the product.•Growth process of nesquehonite accords with the solution-liquid–solid mechanism.The feasibility of synthesis of nesquehonite powders from natural talc was evaluated both through theoretical and experimental approaches. The change of the Gibbs free energy was − 318 kJ/mol with its corresponding equilibrium constants (K) of 5.53 × 1055, which indicated that the reaction could proceed spontaneously. Pure phase of nesquehonite was successfully obtained from natural talc at a low temperature and ambient pressure under the action of ammonia. The effects of reaction temperature and ammonia dosage on the precipitation of MgCO3·3H2O have been investigated. XRD and SEM results demonstrated that the reaction temperature had a significant impact on the crystal phase of the products, while the ammonia dosage showed no serious effect on the morphology of the products, but had important influence on the length of the crystals. With the optimization of operating conditions (reacted at 60 °C with 8 mL ammonia), the nesquehonite crystals were prepared and could grow up to a length of about 19.31 μm and a width of 0.96 μm. During the crystallization process, the nesquehonite crystals were transformed from magnesium bicarbonate obtained from magnesium, and have a preferential orientation growth in the (002) direction. The growth process of nesquehonite crystals accorded with the solution-liquid–solid mechanism.Download full-size image

•Fully stabilized ZrO2 can be obtained through doping 8mol% Sm2O3.•No luminescent from Sm3+ is detected on optical spectra of the products.•Oxygen vacancies in the SDZ play as 3 interesting roles.This work reports the synthesis and characterization of samaria doped zirconia (SDZ) nanoparticles by solvothermal method. The samples were characterized by XRD, SEM, UV–vis and PL spectra. Effect of oxygen vacancies on the phase and optical properties were carefully discussed. The as-prepared products showed cubic structured nanoparticles with average size of 1.1 nm. Fully stabilized cubic ZrO2 could be obtained via doping 8mol % of Sm2O3 into its lattice. UV-blue absorption spectra of ZrO2 host showed obscure absorption edge, while those doped by Sm3+ showed distinguished spectra. No luminescence from Sm3+ center could be observed on PL spectra of all of the samples. Nine different Gaussian-Lorentz amplitude bands should be used to fully deconvolve the acquired PL spectra, and all of them were proven to be originated from oxygen vacancies. The oxygen vacancies in SDZ played as the roles of phase stabilizer, quencher of Sm3+ fluorescence, and PL center of UV-blue emission.

The fluorescence and room temperature activity of a palygorskite supported Y2O3:(Eu3+,Au3+) nanocomposite were investigated to design a fluorescence-indicated catalyst. The effects of Au3+ doping on the structure and surface properties of the host material were systematically characterized. The fluorescence intensity of Y2O3:Eu3+ was affected by Au3+ doping, which was related to the crystallinity of Y2O3. Excess Au3+ ions were segregated to the host surface and reduced to metallic Au. The local symmetry of Eu3+ was reduced by Au3+ doping, which benefited the energy transfer between Eu3+ and Au3+. Energy absorbed by Eu3+ was transferred from Au3+ to metallic Au, where electrons were produced. These electrons were absorbed by O2 to change into O2−, which acted as the oxidant for ortho-dichlorobenzene (o-DCB). The variation of fluorescence intensity during the catalytic reaction was observed. The room temperature catalytic activity of the nanocomposite under UV irradiation was revealed. The as-synthesized nanocomposite might have potential applications in environmental fields.

Correction for ‘Au encapsulated into Al-MCM-41 mesoporous material: in situ synthesis and electronic structure’ by Liangjie Fu et al., RSC Adv., 2015, 5, 20414–20423.

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.

Form-stable composite phase change materials (PCMs) for use in wallboards were prepared by absorbing stearic acid (SA) and lauric acid (LA) eutectic mixtures into the pores of expanded perlite (EP) via vacuum impregnation. The microstructure, thermal properties and the thermal reliability of the composite PCMs were characterized by thermogravimetric and differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The results indicate that the maximum SA–LA absorption of the EP was as high as 65 wt% without any melted SA–LA leakage. The latent heat of the composite PCMs was 119.0 J g−1 at its melting temperature of 31.69 °C and 117.4 J g−1 at its freezing temperature of 30.01 °C. A thermal cycling test showed that the composite PCMs have excellent structural stability and thermal reliability after 100 melt–freeze cycles. A gypsum-based building wallboard containing 6 wt% SA–LA/EP had a low density (0.924 g cm−3), high mechanical strength (2.19 MPa), and remarkable heating preservation performance. These properties indicate that the composite PCMs that we used for wallboards can be considered an efficient heating preservation material for practical applications in building energy conservation.

The feasibility of mineral carbonation of a desulfurization residue for sequestering CO2 was evaluated both through theoretical and experimental approaches. The carbonation reaction, including carbonation of Ca(OH)2 and CaSO4, occurred through a kinetically controlled stage with an activation energy of 20.21 kJ mol−1. The concentration of ammonia, CO2 flow rate, liquid to solid ratio and temperature impacted on the carbonation ratio of the desulfurization residue through their direct and definite influence on the rate constant. Concentration of ammonia and liquid to solid ratio were the most important factors influencing the desulfurization residue carbonation in terms of both the carbonation ratio and reaction rate. Under optimized conditions the carbonation ratio could reach approximately 98% when using industry-grade CO2. The crystalline phases of the carbonated desulfurization residue were calcite and vaterite with spherical and granular morphology. CO2/O2/N2 mixed gas was also used as the simulated desulfurization fuel gas in the carbonation reaction and it had a relatively minor effect on the carbonation ratio. However, it slowed the carbonation reaction and produced a carbonation product with a smaller average particle size, which included high purity (≥99%) white calcite. The carbonated desulfurization residue reported herein showed a rapid CO2 sequestration ratio, high CO2 sequestration amount, low cost, and a large potential for in situ CO2 sequestration in the electricity and steel industry.

•Tungsten tailing powders were mechanically and chemically activated.•Mechanical activation made the tailing particles amorphous.•Chemical activation provided the available elements for cement application.•Activated tungsten tailing powders were suitable for qualified Portland cement.Tungsten tailing powders were activated by mechanical and chemical methods for use as cementitious material in mortar. The composition, microstructure and properties of tungsten tailing were characterized with X-ray fluorescence, X-ray diffraction, scanning electron microscopy, Fourier transformation infrared spectroscopy, differential scanning calorimetry and thermogravimetry. The results showed that garnet was the major mineral in the tailing, which possessed excellent chemical and structural stability but poor cementitious property. Mechanical milling and chemical activator were used to activate the tailing. The activation effects and structural evolution of activated tungsten tailing were assessed, and the possible mechanism was discussed. A series of cement mortar samples was prepared to evaluate the cementitious property of the activated tailing. Effects of activation condition and mixture proportion on mechanical strength of cement mortar were investigated. The mechanical and chemical activations could synergistically improve the cementitious property. The properties of cement mixed with 20% of the activated tailing were well comparable with those of 42.5 ordinary Portland cement. The activated tailing as cementitious material could be used to solve the tailings pollution and reduce cost in cement industry.Download full-size image

Hydrothermal synthesis of lithium metasilicate (Li2SiO3) has been systematically studied in aqueous alkaline environments by varying the Li/Si molar ratios of the solid materials and the hydrothermal temperatures. The phase structures and morphologies of the as-synthesized samples were investigated in detail by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and N2 porosimetry. The morphology of Li2SiO3 varied from nanoparticles to nanosheets and nanotubes with the reaction conditions. A Li/Si molar ratio of 2 at 190 °C was ideal for the formation of pure nanosheets with a characteristic width of 100–200 nm and a typical length of 0.2–1.5 μm. Li2SiO3 nanoparticles were formed at lower Li/Si molar ratios, while most of the dispersed nanosheets curled to form nanotubes at higher Li/Si molar ratios. Nanotubes were formed at 210 °C and Li/Si molar ratio of 2, which possessed a typical inner diameter of ~20 nm, an outer diameter of 35 nm and a length ranging from 75 to 275 nm. An alkaline hydrothermal environment was beneficial to the formation of nanosheets and nanotubes. Atomic-level variations of the product structure from nanoparticles to nanosheets and nanotubes were depicted. A mechanism for the formation of different morphologies of Li2SiO3 was clarified.

Natural halloysite nanotubes (HNTs) modified with 3-aminopropyltriethoxysilane were used as an aspirin carrier. The structure, drug loading and release profiles of samples were characterized by X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and UV-spectrophotometry. The Higuchi model Q = kt0.5 was employed to analyze the dissolution data in detail. The results indicated that the modification of HNTs could improve the amount of aspirin from 3.84 to 11.98 wt%. The physical state of aspirin was nanocrystalline and amorphous affected by the confined space of HNTs, which significantly enhanced the dissolution rate created by a burst release within the first hour. The linearity of the Higuchi equation indicated that the aspirin release mechanism for modified HNTs was fitted to Fick's diffusion and the dissolution rate was slower than that of natural HNTs. The as-synthesized N-HNTs could have interesting potential application in drug carrier systems.

•Multi-scale porous CeO2 can be synthesized by EISA method using P123 as the template.•Step-by-step reduction is found through deconvolving the TPR curves.•Calcinations the precursor to at least 600 °C can obtain CeO2 with clean surface.Ceria (CeO2) powder with multi-scale porosity was synthesized by evaporation induced self-assembly (EISA) strategy using tri-block copolymer (P123) as the template. The product was characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), and N2 adsorption–desorption isotherms. Reducing property and repeatability were tested by temperature programmed H2 reduction (TPR). Oxygen storage capacity (OSC) was calculated according to the Gaussian–Lorentz deconvolving to the TPR curves. The results showed that the product possessed multi-scale porosity, sizes of the pores were in the ranges of ∼40 μm, ∼2 μm and <0.3 μm, respectively. Specific surface area of the porous CeO2 was 32.5 m2/g. Mechanism in the reduction of surface, near surface and inner parts of porous CeO2 were discussed. Carbonate groups remained on the surface when CeO2 were calcined below 600 °C. The initial H2-TPR yielded an OSC of 383 mol O2/g, which was attributed to oxygen release from the surface nanocrystals, (near) surface sites as well as the inner parts. While the repeated tests showed an OSC of 418 mol O2/g, which was associated with the diminished reaction before 620 °C and the enhanced reduction around 782 °C. A schematic was proposed for the preparation of CeO2 with multi-scale porosity in the amended EISA strategy, based on the characterization results, and the strategy may provide a candidate to obtain catalyst with excellent properties.Graphical abstract

•Highly ordered mesoporous Ce0.5Zr0.5O2 was prepared in an aqueous solution.•The complex plus de-complex strategy was adapted into preparing mesostructures.•The product show fairly good pilot scale TWC performances.•A tentative mechanism of the strategy was proposed based on the experimental results.Synthesis of ordered mesoporous ceria-zirconia (CeO2–ZrO2, M-CZ) solid solution in water-based conditions have challenged scientists for a long time due to the extremely different chemical properties of cerium and zirconium cations. This study discuss the synthesis of highly ordered mesoporous Ce0.5Zr0.5O2 solid solution in aqueous solution through a new complex and de-complex method using di-cationic Gemini as the template. The method takes advantage of the coordinative capability of citric acid (CA) to allow the coexistence of inorganic resources in mild basic solutions and uses the strong oxidic capability of H2O2 to precipitate Ce and Zr cations homogeneously. Through this strategy, the combination between inorganic–organic groups in aqueous solution was avoided, whereas coordination between inorganic–organic species was realized. Mechanisms show that the formation of peroxycarboxylic groups (–COOOH) from the reaction between metal-CA molecular and hydroxyl radical (OH) was the key process. Meso-scale micelles were formed during hydrothermal treatment, while hexagonally arranged pores with narrow size distribution were obtained in the calcination procedure. The surface area of the calcined product was 228 m2 g−1 with a pore volume of 0.7 cm3 g−1, whereas oxygen storage capacity was 652 μmol g−1. The M-CZ product illustrated fairly good pilot-scale three-way catalytic (TWC) performances thanks to the thin pore walls in the mesostructures. A complete (100%) conversion of CO and NOy at 340 °C was detected in the engine pedestal tests. The complex and de-complex strategy may provide a new route for the preparation of ordered mesoporous composite oxides.

•Spherical CdS nanoparticles were uniformly assembled onto kaolinite rods.•CdS/kaolinite nanocomposites showed better luminescence properties than pure CdS.•Hydrogen bonds could be formed between kaolinite and polyvinylpyrrolidone.•Atomic-level interaction between CdS particles and kaolinite surfaces was depicted.Sphere-like cadmium sulfide (CdS) nanoparticles were uniformly assembled on kaolinite to synthesize CdS/kaolinite nanocomposite via a microwave irradiation process in aqueous solution with the assistance of polyvinylpyrrolidone (PVP). Cadmium ions were incorporated into the surface of kaolinite and hydrophilic PVP, and reacted with an introduced sulfur source under a microwave field to obtain the CdS/kaolinite nanocomposite. Meanwhile, the hydrogen bonds formed between hydroxyl groups of kaolinite and N atom in the pyrrolidone-ring of PVP. Therefore, CdS nanoparticles could be easily assembled on kaolinite rods by using this process, the addition of PVP was beneficial to the well deposition of CdS nanoparticles on kaolinite rods, while the diameter of CdS nanoparticles could be controlled via adjusting the experimental parameters. The as-synthesized CdS/kaolinite nanocomposite showed better luminescence properties than pure CdS nanoparticles, indicating its potential applications in the optoelectronic fields. Atomic-level interfacial interaction between the CdS nanoparticles and the kaolinite surfaces was depicted, and a mechanism for assembling CdS nanoparticles on kaolinite rods was in detail discussed.

The well crystallized mesoporous spinel gamma alumina (γ-Al2O3) has been widely studied as an important catalyst support. However, the tailoring of alumina catalyst is still an unresolved challenge when considered at the atomic level. On the basis of experimental characterization, it is found that the electronic structure of γ-Al2O3 could be continuously tailored by metal doping via one-pot route. Combined with density functional theory (DFT) calculations, the nature of geometric and electronic structure evolution upon Cu doping in γ-Al2O3 is investigated. The structure of γ-Al2O3 and the influence of intrinsic defects are studied at first. Considering the nano effect and the charge compensation effects of these intrinsic defects, the doping mechanism of Cu inside γ-Al2O3 lattice are in detail explored at the atomic level. At low doping level the excess electrons from VO or Ali would over compensate Cu dopants, leading to the formation of Cu+ species. As the doping level increases, the preferred doping sites change from Oh sites to Td sites, while electrons from Ali correlate the Cu species, and an electronic phase transition is observed.

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.

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.

In this work, we report on white light generation by defect chemistry modification in a single-solid SnO2:Eu3+/Al-MCM-41 composite. The samples were carefully characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms, UV-vis diffuse reflectance spectra and luminescence spectra. It is found that the mesoporous material Al-MCM-41 with a large specific surface area (1040 m2 g−1) and narrow pore size distribution (2.7 nm) was successfully prepared via pretreating kaolin through a simple ball milling approach. SnO2:Eu3+ nanocrystals with fine crystalline nature and ultra-small particle sizes were successfully incorporated into the channels of the host matrix Al-MCM-41 through a hydrothermal route. Contrary to the theoretical predictions of the quantum size effects, SnO2:Eu3+/Al-MCM-41 composites showed an abnormal band gap narrowing with particle size reduction, which can be well-defined as a function of surface defects and Eu3+ doping effects. By varying the Sn/Si molar ratios and Eu3+ doping concentration, the highly defective SnO2:Eu3+/Al-MCM-41 composites exhibited tunable defect chemistry mediated broad band emission and typical Eu3+ red emission that could modulate the color of light and improve the color rendering index (CRI). As a result, a maximum external quantum efficiency of 37.2% and white light with the color coordinates of (0.26, 0.22) in the CIE1931 color space were observed for the SnO2:(6.13%)Eu3+/Al-MCM-41 composite with a Sn/Si molar ratio of 0.183 when it was excited by near-ultraviolet light.

•Gemini was successfully used to synthesis mesoporous Ce0.5Zr0.5O2 materials.•A OSC up to 0.58 mol O2/mol Ce was obtained without any structural changes.•Step by step redox circles in the sample were detected.Mesostructured Ce0.5Zr0.5O2 solid solutions (M-CZ) were hydrothermally synthesized using Gemini surfactant as the template. X-ray diffraction (XRD), small-angle X-ray diffraction (SAXRD), N2 adsorption–desorption isotherms and high-resolution transmission electronic microscopy (HRTEM) were adopted to characterize the samples. The product had a surface area of 123.5 m2 g−1 with maximum oxygen storage capacity (OSC) of 0.58 mol O2/mol Ce. Oxygen anions in the M-CZ can be repeatedly released and resumed during the redox recycles. Reduction of Ce4+ to Ce3+ or lower valence and Zr4+ to Zr3+ were fulfilled with an obvious color change during the temperature programmed reduction (TPR) process, while the crystal structure of the product remained unchanged even after severe reduction. The mesostructure of the product can improve the reductive ability of Ce4+ and Zr4+ cations, which was beneficial to the enhancement of OSC.

•Au nanoparticles were assembled on palygorskite to form nanocomposites.•Au nanoparticles existed in the form of Au and Au2O3.•Oxygen vacancy of Au2O3 was beneficial to the enhancement of catalytic property.•Reaction rate of o-DCB showed second order with activation energy of −3.4 kJ/mol.Au nanoparticles were assembled on palygorskite (PAL) to form Au/PAL nanocomposites via a deposition–precipitation method. Samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and gas chromatography (GC). Results indicated that Au nanoparticles, with a particle size of 2–7 nm, were uniformly immobilized on the surface of PAL with the coexistence of Au and Au2O3. Ortho-dichlorobenzene (o-DCB) was first fixed on Au2O3 then completely oxidized to CO2, H2O, HCl by metallic Au. The reaction rate of o-DCB was approximately second order with calculated activation energy of −3.4 kJ/mol, while the reaction order of O2 was zero order under sufficient oxygen. The catalytic activity could reach 99% at a Au/(Au + Au2O3) molar ratio of 0.83, three times of that without PAL support. Mechanism for enhanced catalytic activity under Au–Au2O3 coexistence system was discussed.

Aluminum-containing hexagonally ordered mesoporous silica Al-MCM-41 was synthesized by hydrothermal treatment of leached products produced by pre-grinding and subsequent acid leaching of natural kaolin, without addition of silica or aluminum regents. The resulting Al-MCM-41 had a high surface area of 1041 m2/g, a pore volume of 0.97 mL/g, and an average pore diameter of 3.7 nm with narrow pore size distribution centered at 2.7 nm. During the synthesis process of Al-MCM-41 from natural kaolin, the evolutions of chemical environments for Si and Al atoms should be emphasized. Wide angle X-ray diffraction (WAXRD), high-resolution transmission electron micrographs (HRTEMs), solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR), Fourier transform infrared spectroscopy (FT-IR) were used to trace the variations of chemical structures. Pretreatment of grinding and subsequent acid leaching acted as an important role in the whole synthesis process. NMR spectroscopy showed that Q3 structure (Si(SiO)3(OH)), condensed Q4 framework structure (Si(SiO)4), also the octahedral and tetrahedral Al existed in the leached sample and Al-MCM-41, with higher chemical contents of Q4 structure and the octahedral Al in final product Al-MCM-41 than those in the leached sample. A possible mechanism for the formation of Al-MCM-41 from natural kaolin was suggested.Graphical abstractHighlights► Mesoporous Al-MCM-41 with surface area of 1041 m2/g is synthesized from kaolin. ► Pretreatment for kaolin is essential to the successful production of Al-MCM-41. ► A general mechanism for the formation of Al-MCM-41 from kaolin is proposed.

Silica nanotubes (SiNTs) were synthesized by acid-leaching the natural halloysite nanotubes (HNTs). Transmission electron microscopy (TEM) and scanning electron microscope (SEM) images showed that SiNTs retained the morphology of HNTs. The specific surface area (183.6 m2/g) and pore volume (0.74 cm3/g) of SiNTs were three times higher than those of HNTs, which indicated more active groups on the surface of SiNTs than HNTs. The 29Si nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) were used to trace the variations of chemical structures. NMR spectroscopy demonstrated the disappearance of Q2 structure (Si(OSi)2(OH)2) and Q4 framework structure (Si(SiO)4), and the partial chemical shift of Q3 structure (Si(SiO)3(OH)) from HNTs to SiNTs. Photoluminescence (PL) analysis showed the higher blue PL intensity of SiNTs than that of HNTs, which indicated that the as-synthesized SiNTs could have potential application in the fields of light localization and optical devices.Graphical abstractHighlights► Silica nanotubes (SiNTs) were synthesized from natural halloysite (HNTs). ► SiNTs retained the tubular morphology as the natural halloysite. ► Atomic structure analysis conformed the chemical shift from HNTs to SiNTs.

This paper reported a successful preparation of CaCO3/anhydrite composites of anhydrite coated with nanosized CaCO3 by chemical precipitation route using the Ca(OH)2–H2O–CO2 reaction system. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and BET multiple-point nitrogen adsorption method. The results demonstrated that nanosized CaCO3 of 70 nm in average size was coated on the surface of anhydrite. The whiteness of the CaCO3/anhydrite composites can reach 85.8%, higher than that of the original anhydrite (63.1%). The surface of the CaCO3/anhydrite composites became rough without sharp edges, and its specific surface area was four times of that of the original anhydrite. This approach of surface nanocrystallization modification could ensure anhydrite an efficient application in the paper, rubber and plastic industries. A possible mechanism for coating of CaCO3 nanoparticles on the surface of anhydrite was also suggested.Graphical abstractHighlight► Nanosized CaCO3 is successfully coated on the surface of the anhydrite. ► Coating of nanosized CaCO3 is beneficial to the increase of anhydrite whiteness. ► Possible mechanism for nano coating is suggested.

The fluorescence and room temperature activity of a palygorskite supported Y2O3:(Eu3+,Au3+) nanocomposite were investigated to design a fluorescence-indicated catalyst. The effects of Au3+ doping on the structure and surface properties of the host material were systematically characterized. The fluorescence intensity of Y2O3:Eu3+ was affected by Au3+ doping, which was related to the crystallinity of Y2O3. Excess Au3+ ions were segregated to the host surface and reduced to metallic Au. The local symmetry of Eu3+ was reduced by Au3+ doping, which benefited the energy transfer between Eu3+ and Au3+. Energy absorbed by Eu3+ was transferred from Au3+ to metallic Au, where electrons were produced. These electrons were absorbed by O2 to change into O2−, which acted as the oxidant for ortho-dichlorobenzene (o-DCB). The variation of fluorescence intensity during the catalytic reaction was observed. The room temperature catalytic activity of the nanocomposite under UV irradiation was revealed. The as-synthesized nanocomposite might have potential applications in environmental fields.

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.

An enhanced antibacterial activity of Fe2O3 nanoparticles was achieved by controlling the distribution density of Fe2O3 nanoparticles on modified kaolinite nanosheets (Fe2O3–KlnKAc) by adjusting the pH value of the reaction system. A proper distribution density of Fe2O3 nanoparticles generating higher levels of hydroxyl radicals led to a higher antibacterial activity.

Carbon hybridized montmorillonite nanosheets (C/MMT) were successfully prepared by mixing intercalation, hydrothermal carbonization and calcination pyrolysis of montmorillonite and sucrose. The amount adsorbed on C/MMT reaches 0.84 g g−1 at a Congo red concentration of 1.0 g L−1, which could be attributed to their special structures and synergistic sorption.