Engineering FeOOH/Fe2O3@Carbon Interfaces With Biomass-Derived Carbon Nanodot/Iron Colloids for Efficient Redox-Modulated Dopamine Voltammetric Detection

The Fe2+/Fe3+ redox couple is effective for voltammetric detection of trace dopamine (DA). However, achieving adequate concentrations with high electroactive surface area (ECSA), DA affinity, and fast interfacial charge transfer is challenging. Consequently, most reported Fe-based sensors have a high nanomolar range detection limit (LOD). Herein, we address these limitations by manipulating the phase and morphology of FeOOH/Fe2O3 heterojunctions anchored on sp2-carbon. FeOOH/Fe2O3 is synthesized by variable temperature aging of unique Fe5H9O15/Fe2O3@sp2-carbon colloidal nanoparticles, which form via chelation between biomass-derived carbon nanodots (CNDs) and Fe2+ ions. At 27 °C and 120 °C, Fe5H9O15/Fe2O3@sp2-carbon transforms into β-FeOOH/Fe2O3 nanoparticles and α-FeOOH/Fe2O3 nanosheet, respectively. The β-FeOOH/Fe2O3 interface exhibits higher eg orbital electron occupancy than α-FeOOH/Fe2O3, thereby facilitating oxygen adsorption and the generation of Fe2+/Fe3+ sites near the polarization potential of DA. This facilitates interfacial electron transfer between Fe3+ and DA. Moreover, its nanoparticle morphology enhances ECSA and DA adsorption compared to α-FeOOH/Fe2O3 nanosheets. With a LOD of ~3.11 nM, β-FeOOH/Fe2O3 surpasses the lower threshold in humans (~10 nM) and matches noble-metal sensors. Furthermore, it exhibits selective detection of DA over 10 biochemicals in urine. Therefore, the β-FeOOH/Fe2O3@sp2-C platform holds promise as a low-cost, easy-to-synthesize, and practical voltammetric DA monitor.

Amorphous Aluminosilicate Nanosheets as Universal Precursors for the Synthesis of Diverse Zeolite Nanosheets for Polymer-Cracking Reactions

Zeolites catalyze some reactions in their molecular-sized pores, but large molecules can react only on their external surface. Zeolite-nanosheets (NSs) have been developed as catalysts for large molecules. The previously reported methods to synthesize zeolite-NSs are specialized for each zeolite type. Here we propose a new method to synthesize various zeolite-NSs from the same amorphous aluminosilicate NSs (AAS-NSs) as a universal precursor. We successfully synthesized the unprecedented AAS-NSs in the hydrophilic space of the stable hyperswollen lyotropic lamellar (HL) phase. The four zeolite types could be obtained from the single-species AAS-NSs. These results imply that this method enables us to synthesize almost all types of zeolite-NSs. Moreover, the synthesized CHA-NSs have great potential for various applications because of their thickness and large external surface area.

Design of a Small Organic Template for the Synthesis of Self-Pillared Pentasil Zeolite Nanosheets

Zeolite nanosheets with excellent mass transfer are attractive, but their successful syntheses are normally resulted from a huge number of experiments. Here, we show the design of a small organic template for the synthesis of self-pillared pentasil (SPP) zeolite nanosheets from theoretical calculations in interaction energies between organic templates and pentasil zeolite skeletons. As expected, the SPP zeolite nanosheets with the thickness at 10-20 nm have been synthesized successfully. Characterizations show that the SPP zeolite nanosheets with about 90% MFI and 10% MEL structures have good crystallinity, the house-of-card morphology, large surface area, and fully four-coordinated aluminum species. More importantly, methanol-to-propylene tests show that the SPP zeolite nanosheets exhibit much higher propylene selectivity and longer reaction lifetime than conventional ZSM-5 zeolite. These results offer a good opportunity to develop highly efficient zeolite catalysts in the future.

Investigation of n-Heptane Hydroisomerization over Alkali-acid-treated Hierarchical Pt/ZSM-22 Zeolites

The design of various hierarchical and morphology ZSM-22 zeolite catalysts is attempted through the post-treatment of different concentrations of NaOH and subsequently, deals with HCl solution including fluosilicic acid (H2SiF6)...

A low-cost route to prepare Fe-doped ZSM-22 zeolite with the assistance of a precursor solution

To decrease the synthesis cost and avoid the migration of framework Fe, an Fe-doped ZSM-22 zeolite was prepared with the assistance of a small amount of precursor solution in the absence of an additional organic template.

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

Zeolites are generally defined as three-dimensional (3D) crystalline microporous aluminosilicates in which silicon (Si⁴⁺) and aluminum (Al³⁺) are coordinated tetrahedrally with oxygen to form large negative lattices and consequent Brønsted acidity. Two-dimensional (2D) zeolite nanosheets with single-unit-cell or near single-unit-cell thickness (~2-3 nm) represent an emerging type of zeolite material. The extremely thin slices of crystals in 2D zeolites produce high external surface areas (up to 50% of total surface area compared to ~2% in micron-sized 3D zeolite) and expose most of their active sites on external surfaces, enabling beneficial effects for the adsorption and reaction performance for processing bulky molecules. This review summarizes the structural properties of 2D layered precursors and 2D zeolite derivatives, as well as the acidity properties of 2D zeolite derivative structures, especially in connection to their 3D conventional zeolite analogues' structural and compositional properties. The timeline of the synthesis and recognition of 2D zeolites, as well as the structure and composition properties of each 2D zeolite, are discussed initially. The qualitative and quantitative measurements on the acid site type, strength, and accessibility of 2D zeolites are then presented. Future research and development directions to advance understanding of 2D zeolite materials are also discussed.

Correlated super-resolution fluorescence and electron microscopy reveals the catalytically active nanorods within individual H-ZSM-22 zeolite particles

Correlative fluorescence and electron microscopy finds heterogeneity in the catalytic activity of H-ZSM-22 zeolite, related to the growth mechanism and structural imperfections.

Design and synthesis of Ga-doped ZSM-22 zeolites as highly selective and stable catalysts forn-dodecane isomerization

Ga-Doped ZSM-22 zeolites were synthesized successfullyviaa hydrothermal method and exhibited better catalytic performance inn-dodecane isomerization.