Deciphering the Molecular Mechanism of Substrate-Induced Assembly of Gold Nanocube Arrays toward an Accelerated Electrocatalytic Effect Employing Heterogeneous Diffusion Field Confinement

The complex electrocatalytic performance of gold nanocubes (AuNCs) is the focus of this work. The faceted shapes of AuNCs and the individual assembly processes at the electrode surfaces define the heterogeneous conditions for the purpose of electrocatalytic processes. Topographic and electron imaging demonstrated slightly rounded AuNC (average of 38 nm) assemblies with sizes of ≤1 μm, where the dominating patterns are (111) and (200) crystallographic planes. The AuNCs significantly impact the electrochemical performance of the investigated electrode [indium-tin oxide (ITO), glassy carbon (GC), and bulk gold] systems driven by surface electrons promoting the catalytic effect. Cyclic voltammetry in combination with scanning electrochemical microscopy allowed us to decipher the molecular mechanism of substrate-induced electrostatic assembly of gold nanocube arrays, revealing that the accelerated electrocatalytic effect should be attributed to the confinement of the heterogeneous diffusion fields with tremendous electrochemically active surface area variations. AuNC drop-casting at ITO, GC, and Au led to various mechanisms of heterogeneous charge transfer; only in the case of GC did the decoration significantly increase the electrochemically active surface area (EASA) and ferrocyanide redox kinetics. For ITO and Au substrates, AuNC drop-casting decreases system dimensionality rather than increasing the EASA, where Au-Au self-diffusion was also observed. Interactions of the gold, ITO, and GC surfaces with themselves and with surfactant CTAB and ferrocyanide molecules were investigated using density functional theory.

Catalytic pyrolysis (Ni/Al-MCM-41) of palm (Elaeis guineensis) oil to obtain renewable hydrocarbons

The present work aims to evaluate the potential of Al-MCM-41 and Ni/Al-MCM-41 catalysts for the production of renewable hydrocarbons through the fast pyrolysis of palm oil. Al-MCM-41 mesoporous material was synthesized by the hydrothermal route. The Ni/Al-MCM-41 catalyst was obtained by the wet impregnation method of the Al-MCM-41 material (support) previously synthesized with 2.3% metal in relation to the support mass. The thermal pyrolysis of palm oil yielded many oxygenated compounds with a very high molecular mass. The pyrolysis of the oil under the action of Al-MCM-41 presented greater selectivity when compared to thermal pyrolysis, obtaining 63% of hydrocarbons in the C11-C15 region. The catalytic pyrolysis of the oil with Ni/Al-MCM-41 showed a high deoxygenation rate, obtaining a hydrocarbon percentage equal to 78%, in addition to obtaining a percentage of hydrocarbons equal to 46% in the region of interest, viz., C11-C15, demonstrating the potential of the Ni/Al-MCM-41 catalyst for renewable hydrocarbons production (bio-jet fuel) from palm oil.

Utilization of iron tailings to prepare high-surface area mesoporous silica materials

Iron tailings are fine, stable and complex materials, which are mainly composed of minerals and metal oxides. Residual silicon in iron tailings can be used to prepare mesoporous silica materials applied to energy storage, environmental protection and other fields. This paper reported a novel synthesis strategy from iron tailings to high-surface area hexagonally ordered mesoporous silica materials in an innovative non-hydrothermal system at room temperature. A pretreatment process involving acid leaching and hydrothermal alkaline reaction was vital to the successful utilization of iron tailings. X-ray fluorescence (XRF) data suggested that about 95% of the silicon of iron tailings changed to the silicate as a silicon source. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂-adsorption-desorption isotherms, Fourier transform infrared (FTIR) spectroscopy, Thermogravimetry and differential scanning calorimetry (TG-DSC) and ²⁹Si solid-state nuclear magnetic resonance (NMR) spectroscopy. The SAXRD patterns of mesoporous silica materials exhibited an intense (100) diffraction peak and two weak (110, 200) diffraction peaks, corresponding to characteristic of the ordered mesoporous lattice. TEM images further confirmed the hexagonally ordered porous structure of mesoporous silica materials. The WAXRD patterns and ²⁹Si MAS NMR spectra of the samples indicated that mesoporous silica materials were composed of amorphous SiO₂. The obtained mesoporous silica materials had a high surface area of 1915 m²/g and pore volume of 1.32 cm³/g. Furthermore, the evolution from iron tailings to mesoporous silica materials was elucidated and a proposed synthesis mechanism was discussed. Collectively, these results provided an insight into efficient recycling of iron tailings and the production of advanced functional materials from solid waste.

Pd Nanoparticles and MOFs Synergistically Hybridized Halloysite Nanotubes for Hydrogen Storage

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.

Bifunctional catalyst Pd–Al-MCM-41 for efficient dimerization–hydrogenation of β-pinene in one pot

A new type of bimetallic palladium and aluminum incorporated mobile crystalline materials (Pd–Al-MCM-41) as bifunctional catalysts has been hydrothermally synthesized.

Emerging integrated nanoclay-facilitated drug delivery system for papillary thyroid cancer therapy

Nanoclay can be incorporated into emerging dual functional drug delivery systems (DDSs) to promote efficiency in drug delivery and reduce the toxicity of doxorubicin (DOX) used for thyroid cancer treatment. This paper reports the expansion of the basal spacing of kaolinite nanoclay was expanded from 0.72 nm to 0.85 nm, which could provide sufficiently spacious site for hosting doxorubicin molecules and controlling the diffusion rate. A targeted design for papillary thyroid cancer cells was achieved by introducing KI, which is consumed by the sodium-iodide symporter (NIS). As indicated by MTT assays, confocal laser scanning microscopy and bio-TEM observations, methoxy-intercalated kaolinite (KaolinMeOH) exhibited negligible cytotoxicity against papillary thyroid cancer cells. By contrast, DOX-KaolinMeOH showed dose-dependent therapeutic effects in vitro, and KI@DOX-KaolinMeOH was found to act as a powerful targeted therapeutic drug. Furthermore, active and passive targeting strategies played a role in the accumulation of the drug molecules, as verified by an in vivo bio-distribution analysis.

Amine-Impregnated Mesoporous Silica Nanotube as an Emerging Nanocomposite for CO2 Capture

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.

Pd modified kaolinite nanocomposite as a hydrogenation catalyst

Natural kaolinite nanorod without surface modification served as a mild and outstanding stabilizer for supporting Pd nanoparticles.

Lithium orthosilicate with halloysite as silicon source for high temperature CO2 capture

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.

Size dependence of silver nanoparticles in carboxylic acid functionalized mesoporous silica SBA-15 for catalytic reduction of 4-nitrophenol

Silver nanoparticles with a size around 3 nm are formed within the mesopores of –COOH functionalized mesoporous silica SBA-15, and they are highly active in the catalytic reduction of 4-nitrophenol.

Sepiolite supported stearic acid composites for thermal energy storage

In this paper, novel composite phase change materials (PCMs) were prepared by absorbing stearic acid (SA) into sepiolite (α-sepiolite, β-sepiolite) via a vacuum impregnation method.

Y2O3 functionalized natural palygorskite as an adsorbent for methyl blue removal

The methyl blue adsorption isotherm on Y₂O₃/Palygorskite obeys the Langmuir model, with the maximum adsorption capacity greatly enhanced to 1579.06 mg g⁻¹, exhibiting potential applications in wastewater treatment.