Category Archives: ChemNanoMat

Mercaptoalkyl Groups Anchored on the Layer Surface of New α‐Zirconium Phosphate Phosphonates for the Stabilization of Gold Nanoparticles

Posted on 9 October 2023 by nMonica Pica, nSimone Lixi, nAnna Donnadio, nMario Casciola, nMorena Nocchettin

Layered zirconium phosphate mercaptoundecylphosphonates were prepared and employed as supports for gold nanoparticles. According to the procedure, different gold species are stabilized by the support: Au ionic species and/or small gold clusters, Au(0) nanoparticles with an average size of 6 nm, or larger Au(0) nanoparticles with an average size of 20 nm.

Abstract

Layered zirconium phosphate mercaptoalkylphosphonates, with general composition Zr(O₃POH)_2-x(O₃P(CH₂)₁₁SH)_x, where x=0.4–1.4, are prepared according to two procedures: direct reaction between a zirconyl salt and a mixture of phosphoric/phosphonic acid in propanol, or topotactic ion exchange reaction of phosphate groups of nanocrystalline α-Zr(O₃POH)₂ with mercaptoundecylphosphonate groups. FT-IR analysis and XPS proves the presence of the mercapto groups and, according to X-Ray diffraction analysis, they result randomly distributed on the layer surface. The solids are used as supports for gold nanoparticles synthesized according to three different methods: reaction of HAuCl₄ with NaBH₄, added after 24 hours (Procedure A), or concomitantly (Procedure B) to the addition of the Au(III) salt to the solid suspension, or by mixing the solid suspension with a colloidal dispersion of gold nanoparticles prepared according to the Turkevich method (Procedure C). The best results were obtained with Procedure B, that provided composites with gold nanoparticles having an average size of (6±2) nm.

Single‐step Production of Photocatalytic Surfaces via Direct Laser Interference Patterning of Titanium

Posted on 9 October 2023 by

To maximize the photocatalytic activity of titanium dioxide, different titanium oxide phases need to be combined with a large surface area. Currently, this is mostly done using multistep processes involving nanoparticle synthesis and a coating process. In this work, highly active surfaces were produced in a single laser processing step and subsequently analyzed.

Abstract

State of the art approaches to produce photocatalytic surfaces generally require multiple processing steps to achieve highly active surfaces. Following recent trends to facilitate the production of active surfaces, this work presents a single-step method to create porous photocatalytic surfaces via direct laser interference patterning (DLIP) of a titanium substrate with pulses in the picosecond range. The resulting surfaces contain a variety of titanium oxides while both their composition and morphology can be controlled through the laser process parameters. This makes it possible to tailor these surfaces for specific applications such as antimicrobial surfaces, implant materials or water treatment. Surface characterization was executed by applying scanning electron microscopy complemented by focused ion beam cross-sectioning and energy dispersive X-ray spectroscopy as well as gracing incidence X-ray diffractometry. The photocatalytic activity achieved by different laser parameters is assessed by methylene blue degradation under UV-A light. As DLIP is already established in industrial applications, this approach could greatly facilitate the use of photocatalytic surfaces for water treatment or medical applications, as it does not require nanoparticle synthesis or additional coating steps.

Towards a Correlation Between Iron/Cobalt Content, Support Pore Size and Metal Particle Size in Supported Catalysts

Posted on 9 October 2023 by

Fe/Co nanoparticles supported on alumina, silica and zeolite 4A were synthesized by co-precipitation at constant pH. Pure Co particles have a larger diameter, but the addition of a small Fe content significantly reduces the diameter. Higher Fe contents do not further decrease the diameter. The pore size of the support seems to influence the particle size.

Abstract

Fe−Co-based catalysts supported on γ-Al₂O₃, Aerosil 200 silica and zeolite 4A were prepared by co-precipitation of the respective nitrates in the presence of ammonium hydroxide. The objective was to demonstrate the influence of Fe/Co mass ratio and support pore size on metal particle size. Catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), N₂ physisorption, Fourier-transformed infrared spectroscopy (FTIR), and scanning (SEM) and transmission (TEM) microscopies. It was demonstrated that the minimal presence of Fe was enough to reduce the average particle diameters by half. Increasing Fe content did not cause proportional decreases in the average particle diameter. The support pore diameter probably played a role in the crystallization step of bimetallic and Fe monometallic catalysts, whose particle diameters were similar to those observed for the pores. This phenomenon was not observed for Co monometallic catalysts.

Chelating Agent‐Assisted‐Bi2WO6 Nanostructured Materials for Electron Transfer‐Driven Ultrafast Catalytic Reduction of Organic and Inorganic Contaminants

Posted on 9 October 2023 by nAshok Barhoi, nAfaq Ahmad Khan, nBhagirath Mahto, nAkash Bisoyi, nSahid Hussainn

Chelating agent (EDTA) assisted Bi₂WO₆ nanomaterials (EDTA-BWO) is synthesized using the hydrothermal method. The EDTA-BWO shows fast catalytic reduction of 4-nitrophenol (4-NP), methyl orange (MO), congo red (CR), and [Fe(CN)₆]³⁻ that proceeds through electron transfer mechanism. The catalyst can be reused up to five times without significant loss of activity.

Abstract

We report a chelating agent-assisted synthesis of Bi₂WO₆ nanomaterials using a facile hydrothermal method. The presence of a chelating agent (EDTA) influences the degree of crystallinity, morphology, and surface area of Bi₂WO₆. Analysis by electron microscopy revealed morphological changes of Bi₂WO₆ from flower-like to multilayered disc-like structures after introducing EDTA. The surface area of pristine Bi₂WO₆ NMs is significantly increased from 31 to 50 m² g⁻¹. We demonstrated the catalytic properties of Bi₂WO₆ and EDTA-Bi₂WO₆ for 4-nitrophenol (4-NP), methyl orange (MO), congo red (CR), and [Fe(CN)₆]³⁻ reductions in the presence of NaBH₄. It was observed that EDTA-Bi₂WO₆ exhibited higher catalytic activity compared to the pristine Bi₂WO₆ NMs. The reduction reactions followed pseudo-first-order kinetics and the rate constant values of EDTA-Bi₂WO₆ for 4-NP, MO, CR, and [Fe(CN)₆]³⁻ reductions were found to be 0.847, 0.584, 0.702, and 0.463 min⁻¹, respectively. The reduction proceeds through electron transfer process over an EDTA-Bi₂WO₆ catalyst in the presence of NaBH₄. Furthermore, EDTA-Bi₂WO₆ also showed ultrafast catalytic performance to dichromate (Cr₂O₇ ²⁻) reduction, compared to pristine Bi₂WO₆. The EDTA-Bi₂WO₆ catalyst could be recycled up to five times without undergoing a significant loss in activity.

Application of Metal/Covalent Organic Frameworks in Separators for Metal‐Ion Batteries

Posted on 9 October 2023 by nXin Song, nXijun Xu, nJun Liun

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted tremendous attention in recent decades. They have emerged as potential materials to modify separators for rechargeable batteries owing to their distinctive merits. This review sought to provide a systematic review of MOF/COF-based separators on their significant properties, fabrication methods, and applications in rechargeable batteries.

Abstract

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are two emerging families of functional materials that have found widespread applications in various fields. With the unique features of large surface area, tunable pore structure, high porosity, and easy surface functionalization, they are considered a kind of promising separators candidates for novel separators in rechargeable batteries. Over the years, many studies on the application of MOF/COF-based separators have been reported with excellent performance. Herein, we highlight the recent progress of MOF/COF separators for advanced batteries. Firstly, the key properties of MOF/COF separators are presented. Then, we summarize the fabrication methods of MOF/COF separators. Afterward, an overview of the applications of MOF/COF based separators in lithium-based batteries, sodium-based batteries, and other secondary batteries. Finally, we present a summary and future outlook of MOF/COF separators, including their potential and current challenges.

Facile Fabrication of Ultrathin Bimetal‐Organic Nanosheets as High‐Performance Anode of Lithium‐Ion Batteries

Posted on 9 October 2023 by

2D CoNi-BDC ultrathin nanosheets (N-CoNi-BDC) were synthesized from a mixed solution of benzenedicarboxylic acid, Ni²⁺, and Co²⁺ through a simple ultrasonic treatment. CoNi-BDC with an irregular bulk morphology (B-CoNi-BDC) was produced when the aforementioned mixed solution was aged without ultrasonic treatment. The N-CoNi-BDC possessed an improved electrochemical performances because of having a more exposed pore structure and higher specific surface area, both of which are important for electrolyte infiltration and ion/electron transport.

Abstract

Two-dimensional metal-organic frameworks (2D MOFs) with more exposed active sites and stable structures are auspicious electrode materials for high-performance lithium-ion batteries (LIBs). In the current work, ultrasonic treatment was used to prepare two-dimensional CoNi-BDC ultrathin nanosheets (N-CoNi-BDC) by coordinating Ni²⁺, Co²⁺, and benzenedicarboxylic acid (BDC). The N-CoNi-BDC was used as the anode of LIBs, demonstrating an exceptional reversible storage capacity of 1358 mAh g⁻¹ after 200 cycles at 0.1 A g⁻¹. In addition, a charging capacity of 757 mAh g⁻¹ was observed at a high current density of 1 A g⁻¹ without observable capacity degradation up to 300 cycles. The superior behavior of N-CoNi-BDC was attributed to its distinct morphology of ultrathin nanosheets with more exposed active sites and stable structures. Ex-situ FTIR and XPS results revealed that the benzene ring, carboxylate, and Ni²⁺ in N-CoNi-BDC were the active parts of lithium-ion storage.

Electrolytic Hydrogen Evolution Study of Porous Tungsten Carbide‐Loaded Pt Derived from ZIFs

Posted on 9 October 2023 by

We used ZIF-8 as a carrier and loaded Pt on its surface to make hydrogen-resolution catalysts. By adjusting the mass ratio of Co@ZIFs and ammonium metatungstate, we obtained catalysts with moderate carbon content and suitable specific surface area, which exhibited very excellent hydrogen evolution reaction activity and good stability.

Abstract

The development of an electrochemical hydrogen evolution catalyst with high activity and low Pt loading and excellent stability is of high significance for the extensive promotion and practical application of hydrogen energy. Hence, we introduced ZIFs and their derivatives with tunable pore size and large specific surface area, which were carbonized at high temperatures and supported with Pt as catalysts for hydrogen evolution reaction. We used ZIF-8 as the seed to obtain the precursor Co@ZIFs, W element was introduced into Co@ZIFs by impregnation method to synthesize WC. A series of Pt/WC catalysts were prepared with WC as support. The best sample Pt/WC-3 in 0.5 M H₂SO₄ with a Pt content of 8.3 wt % has a low overpotential (η₁₀=28 mV), which is much less than the 34 mV of 20% commercial Pt/C and had a Tafel slope of only 18.9 mV dec⁻¹. It is noteworthy that at 8.3% Pt/WC after 40,000 s of continuous operation at 10 mA cm⁻², the overpotential of Pt/WC-3 barely rises by 5%, which indicates its excellent durability.

pH‐Controlled Transition from Disaggregation to Reaggregation of Bis‐indolyl(phenyl)methane−β‐CD Conjugate Appended with Multi‐logic Operations

Posted on 9 October 2023 by

In pure aqueous medium, the transition from disaggregated to reaggregated states of a bis-indole derivative, BIPM, was studied employing β-CD and OH⁻ and the emission modulations were interpreted into the designing of a variety of molecular logic gates, an erase-read-write-read type memory, and a macro-molecular security system.

Abstract

A multifunctional molecular logic system is designed based on the pH-responsive emission properties of bis-indolyl(phenyl)methane (BIPM)−β-CD conjugates in aqueous medium. In our previous studies, BIPM molecules in water were found to form large molecular self-aggregates that disaggregated in presence of β-CD molecules through inclusion complexation. In the present study, transition from the disaggregated to reaggregated form of bis-indolyl(phenyl)methane−β-CD conjugate was followed through alteration of the local pH from 7 to 13.2. The BIPM molecules are expected to reaggregate at high alkaline medium due to the expulsion of probes from the nano-cages of β-CD. The pH dependent emission spectroscopic changes are harvested to design a multi-functional molecular logic system that can mimic the functions of several fundamental logic gates and an ‘erase-read-write-read’ memory unit. A macro-molecular security system with three chemical inputs is also presented that can authenticate all-active-all-possible (3³) three-character passwords with their respective unique fluorescence trajectories. Designing of molecular logic system based on the pH-responsive emission properties of the aggregated and disaggregated forms of an organic probe is rather uncommon and the multifunctional logic, memory and security applications of the present system will carry significant importance in the molecular logic research.

A Portable Nanozyme‐Strip Fabricated by Ru‐ZIF‐8 with Dual Nanozymatic Activity for Detection of Acetylcholine

Posted on 9 October 2023 by nXin Cui, nJiachen Zhang, nYitong Liu, nWen Shao, nYawen Tang, nHanjun Sunn

A Ru-ZIF-8 nanozyme with both esterase like and peroxidase like activities were prepared for acetylcholine (ACh) detection. On the basis of the Ru-ZIF-8 nanozyme, a portable nanozyme strip was developed as a novel biosensor for detecting ACh, which was conducive to promoting the development of multiple enzyme cascade assays.

Abstract

In the present study, the incorporation of Ru into the framework of ZIF-8 resulted in that a Ru-ZIF-8 nanozyme with both esterase-like activity and peroxidase-like activity. Owing to the dual nanozymatic activities of Ru-ZIF-8 nanozyme, the acetylcholine (ACh) detection process utilized only one natural enzyme (choline oxidase), which greatly simplified the detection procedure. In the detection process, nanozyme Ru-ZIF-8 showed esterase-like activity to catalyze the hydrolysis of ACh to choline. Then the generated choline was oxidized by choline oxidase to generate H₂O₂. Finally, Ru-ZIF-8 with peroxidase-like activity was used to catalyze H₂O₂ to oxidize 2,2′-azino-bis (3-ethylbenzothiazo-line-6-sulfonic acid) ammonium salt with a color change. As a result, the linear range for ACh was from 0.01 μM-22 μM with the detection limit (DL) of 5.5 nM. In addition, Ru-ZIF-8 was utilized to fabricate a portable detection test strip. Our work provided a simple, portable, low-cost, highly sensitive and selective assay for the detection of ACh, which paved the way for the development of multi enzyme cascade assays.

Self‐sacrificial Templated Synthesis of Fe/N Co‐doping TiO2 for Enhanced CO2 Photocatalytic Reduction

Posted on 9 October 2023 by

A porous and low bandgap Fe_0.8Ti@C was successfully synthesized by a self-sacrificial template to achieve the self-element and external element doping. Thus, the incorporation between Ti−O−Fe fast channel and oxygen vacancies can efficiently improve the transfer and separation of photogenerated carriers, which can significantly boost its absorption capacity in visible light and enhance its ability to reduce CO₂ into CH₄.

Abstract

As a green photocatalyst, TiO₂ has been widely used in adsorption, desorption and redox reactions, but the wide energy band and moderate visible light absorption have greatly inhibited its applications in photocatalysis. The effective method of enhancing the performance of catalysts is the development of heterojunction and metal-nonmetal co-doping. Herein, Fe−N co-doped TiO₂ heterojunction photocatalysts (Fe_xTi@C) were successfully synthesized by calcining a self-sacrificial template (NH₂−MIL-125(Ti)) injected with Fe³⁺ solution. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption/desorption analysis, and photoelectrochemical tests were used to characterize Fe_xTi@C, showing multiple rutile/anatase TiO₂ heterojunction structure, low bandgap, and significant absorption in visible light. In addition, the Ti−O−Fe tetrahedra and more oxygen vacancies were provided since the doped N is from the pristine MOF and the radii of Fe³⁺ and Ti⁴⁺ are similar, which improved the photocatalytic efficiency of CO₂ reduction to CH₄, especially the Fe_0.8Ti@C reached 7.8-fold and 10.2-fold CH₄ yield increase compared with the original TiMOF template and the undoped Ti@C, respectively. This work presents a simple method for the fabrication of low bandgap semiconductors, and also makes a new attempt at the synergistic effect between the in-situ elements and valence bonds of MOF-derived catalysts.