Halloysite nanotubes (HNTs) showed natural nanotubular structures with similar chemical composition to kaolin. This paper reviewed the exciting applications of HNTs due to their abundantly deposit, ...nanoscale lumens, high length-to-diameter ratios, and relatively low surface hydroxyl group density. HNTs have been used as ideal templates for conveniently immobilizing nanoparticles, which could enable the construction of designed nano-architectures that are extremely attractive as supports for heterogeneous catalysts and for use in the fuel cells and related technologies that exploited the inherent ‘smallness’ and hollow characteristics of the nanoparticles. The recent developments in this area by exploring the various techniques with which HNTs could be functionalized with metal nanoparticles, and the diverse applications of the resulting materials overviewed in detail. The corresponding interfacial characteristics of the nanocomposites were emphasized.
Display omitted
•Halloysite nanotubes (HNTs) have notubular structures with low surface group density.•The wide applications of HNTs-metal composites were in detail summarized.•The techniques for functionalizing HNTs with metal nanoparticles were reviewed.•The interfacial characteristics between metal nanoparticles and HNTs were analyzed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Novel antimicrobial nanocomposite incorporating halloysite nanotubes (HNTs) and silver (Ag) into zinc oxide (ZnO) nanoparticles is prepared by integrating HNTs and decorating Ag nanoparticles. ZnO ...nanoparticles (ZnO NPs) and Ag nanoparticles (Ag NPs) with a size of about 100 and 8 nm, respectively, are dispersively anchored onto HNTs. The synergistic effects of ZnO NPs, Ag NPs, and HNTs led to the superior antibacterial activity of the Ag-ZnO/HNTs antibacterial nanocomposites. HNTs facilitated the dispersion and stability of ZnO NPs and brought them in close contact with bacteria, while Ag NPs could promote the separation of photogenerated electron-hole pairs and enhanced the antibacterial activity of ZnO NPs. The close contact with cell membrane enabled the nanoparticles to produce the increased concentration of reactive oxygen species and the metal ions to permeate into the cytoplasm, thus induced quick death of bacteria, indicating that Ag-ZnO/HNTs antibacterial nanocomposite is a promising candidate in the antibacterial fields.
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.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This paper aimed at developing a novel form-stable composite phase change material (PCM) by using stearic acid (SA) to hybridize coal-series kaolinite (Kc) via vacuum impregnation method. The ...obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The thermal properties of the composite were characterized by using differential scanning calorimetry (DSC) and thermal cycling test analysis technique. Natural kaolin (K) was also used as the support to make further investigation on the thermal properties of the kaolinite-based composite PCM. The crystallinity of SA in SA/Kc (90.1%) was higher than that of SA/K (84.9%). The SA/Kc composite showed an enhanced thermal storage capacity compared with the SA/K composite. The latent heats of melting (66.30 J/g) and freezing (65.60 J/g) for SA/Kc were higher than those of SA/K sample (59.25 and 59.01 J/g, respectively). Furthermore, the SA/Kc composite PCM showed an excellent stability after up to 200 thermal cycling. The corresponding mechanism was discussed in detail.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The physicochemical aspects of four soft kaolins were investigated using X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation ...infrared spectroscopy (FTIR), differential scanning calorimetry-thermogravimetry (DSC-TG) specific surface area and surface zeta potential measurements. The correlation between degree of crystal order, thermal stability, morphology and surface characteristics of the kaolinites were examined and discussed. The endothermic peak temperatures, in particular, showed a clear positive correlation with the calculated crystallinity index of the kaolinites. The physicochemical characteristics of a natural kaolinite rod were considered in greater detail. Rod-like kaolinite had lower degree of order and zeta potential (pH<3) than the platy kaolinites but was more ordered than expected for halloysite, and did not show a distinct central void. A schematic morphology for the proposed arrangement of curved kaolinite layers making up the rods is presented.
► Obvious correlation exists between crystallinity and morphology of kaolinites. ► Rod-like kaolinite has lower order degree and zeta potential than flake-like one. ► Kaolinite rods possibly originate from the layers wrapping and tube stacking.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper reported on the synthesis of silica nanosheets (SNSs) by structurally modifying natural coal-series kaolinite mineral (Kc). Ag nanoparticles (AgNPs) of about 5nm 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 113.9J/g, respectively, and its thermal conductivity showed up to 0.84W/(mK). 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.
Display omitted
•Coal-series kaolinite was structurally modified to prepare silica nanosheets (SNSs).•Ag nanoparticles (AgNPs) of about 5nm 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.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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 A1 leaching and Si-OH condensation were studied in detail. After the leaching of A1 ions from the HNTs, local structural changes from Al（Oh） to A1（V） at a medium leaching level and to AI（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 AI（V） species and a specific surface area up to 583 m^2/g （increased by a factor of 10） are promising drugloading nanocontainers and nanoreactors.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Trace ethylene poses a significant challenge during the storage and transportation of agricultural products, causing over-ripening, reducing shelf life, and leading to food waste. Zeolite-supported ...silver adsorbents show promise for efficiently removing trace ethylene. Herein, hierarchical Ag/NZ5(X) adsorbents were prepared via different ammonia modifications, which featured enhanced ethylene adsorption ability. Ag/NZ5(2.5) exhibited the largest capacity and achieved near-complete removal at room temperature with prolonged efficacy. Characterization results indicated that the ammonia modification led to the formation of a hierarchical structure in the zeolite framework, reducing diffusion resistance and increasing the accessibility of the active sites. Additionally, desilication effects increased the defectiveness, generating a stronger metal-support interaction and resulting in a higher metal dispersion rate. These findings provide valuable insights into the development of efficient adsorbents for removing trace ethylene, thereby reducing food waste and extending the shelf life of agricultural products.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Display omitted
► Mesoporous Al-MCM-41 with surface area of 1041m2/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.
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 1041m2/g, a pore volume of 0.97mL/g, and an average pore diameter of 3.7nm with narrow pore size distribution centered at 2.7nm. 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.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
Death from acute hemorrhage is a major problem in military conflicts, traffic accidents, and surgical procedures, et al. Achieving rapid effective hemostasis for pre-hospital care is ...essential to save lives in massive bleeding. An ideal hemostasis material should have those features such as safe, efficient, convenient, economical, which remains challenging and most of them cannot be achieved at the same time. In this work, we report a rapid effective nanoclay-based hemostatic membranes with nanoclay particles incorporate into polyvinylpyrrolidone (PVP) electrospun fibers. The nanoclay electrospun membrane (NEM) with 60 wt% kaolinite (KEM1.5) shows better and faster hemostatic performance in vitro and in vivo with good biocompatibility compared with most other NEMs and clay-based hemostats, benefiting from its enriched hemostatic functional sites, robust fluffy framework, and hydrophilic surface. The robust hemostatic bandages based on nanoclay electrospun membrane is an effective candidate hemostat in practical application.
PDF
