Narrow Pore Size Distribution Research Articles

STRUCTURAL INVESTIGATION OF HETERO-STRUCTURED CORE-SHELL SILVER-SILICA HYBRID AS A POTENTIAL AGRO-SENSOR MATERIAL

Investigation into the novel synthesis and structural properties of Heterostructured core shell Silver-Silica (AgSiO2) Nanohybrid is reported herein, for possible utilization as humidity sensing material in Agricultural post-harvest humidity monitoring system and greenhouse farming. The Heterostructured nanoparticles (Ag and SiO2) were synthesized via a chemical reduction method. Structural characterizations were done using X-ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM), UV-Visible spectroscopy, Energy Dispersive X-ray (EDX) spectroscopy and N2 adsorption-desorption techniques. The XRD diffractogram of Ag-SiO2 showed distinct peaks at 2? values of 390, 430, 660 and 790 which was corroborated by the SEM and HRTEM results. EDX convincingly confirmed Ag and SiO2 incorporation into the Ag-SiO2 nanocomposite hetero-structure at 16.7 % and 83.3 % respectively. A Surface Plasmon Resonance absorption peak of 421 nm of Ag was revealed by UV-Visible spectroscopic analysis. An effective and relatively narrow pore size distributions of 3 – 8 nm was revealed by N2 adsorption-desorption for the Ag-SiO2 Nanocomposite. Overall, these properties are promising for effective use as humidity sensing material.

Modulation of pore structure in a microporous carbon for enhanced adsorption of perfluorinated electron specialty gases with efficient separation

Physical adsorption-based separation and recovery of perfluorinated electron specialty gases from N2 contribute to reducing the greenhouse effect and increasing economic value in the electronics industry. Commercial activated carbon materials are promising adsorbents for the practical application due to the industrial-scale production, while they usually characterize an unsatisfactory micropore structures, and the rational modulation to meet the requirement of fluorinated gas adsorption is in demand. In this work, a series of KOH-treated commercial activated carbon (ACK) with KOH/carbon mass ratios of 1 ∼ 4 were systematically characterized and evaluated for adsorptive separation of SF6, NF3, and CF4. Characterization results reveal that KOH treatment largely promotes the modulation of pore structure and results in the extremely narrow pore size distribution at 0.5 ∼ 0.9 nm, highest microporosity of 97.6 % in the optimal ACK1, which are ascribed to etching effect of KOH on carbon framework. Static adsorption results indicate that a simultaneous enhancement in gas uptake and separation selectivity is found in ACK1 compared to the parent AC for all the studied fluorinated gases. Importantly, ACK1 performs a high SF6 uptake of 3.10 mmol·g−1 and the record SF6/N2 selectivity of 683.9 (298 K, 100 kPa) among the reported carbon adsorbents, which is comparable to the top-performing MOFs material. The kinetic adsorption and dynamic breakthrough experiments further verify the fast adsorption rate, excellent separation performance of SF6/N2, and recyclability of ACK1 adsorbent. These findings expand the promising application of commercial AC in the adsorption-based separation of perfluorinated electron specialty gases including SF6, NF3, and CF4.

Porous organic polymer interlayers modulated nanofiltration membranes for ultra-permselective Li+ /Mg2+ separation

The ion-ion precise separation is of paramount importance but presents significant technical challenges. Achieving such an accurate separation utilizing nanofiltration (NF) membranes demands ion-selective channels with appropriate pore geometry structure and charge property. In this work, thinner polyamide (PA) NF membranes with narrower pore size distribution than conventional NF membranes were fabricated via the porous organic polymer (POP) interlayer-mediated interfacial polymerization. The dual-rigid-distorted POP interlayers were incorporated in situ onto the substrates through azo-coupling reactions. The POP interlayers exhibited a high-density adsorption capacity of amine monomers and acted as a space manipulator that regulated their diffusion behavior into the oil phase, enabling their reaction with the acyl chloride. The synergistic effects engendered a uniform PA active layer and impeded further growth of the membrane, compared with the typical PA membranes, facilitating the generation of a thin and a narrow pore size distribution PA active layer with a nanostripe surface. The prepared NF membranes showed an outstanding ion-ion separation factor of Li+/Mg2+ (up to 78.56), almost 18 times that of the pristine NF membrane (4.32), along with a two-fold increase in water permeance. Furthermore, the newly developed NF membranes demonstrate long-term stability under operational pressure, thus highlighting the promising potential of these NF membranes for extracting Li+ from salt-lake brines.

Pyrrolidinium-functionalized Cardo (TPM) poly(arylene ether sulfone)s membranes for acid recovery: The effects of Cardo (TPM) microstructures

To explore the intrinsic correlation between the rigidity and distortion degree of polymer backbones and the diffusion dialysis (DD) performance of anion exchange membranes (AEMs), pyrrolidinium-functionalized poly(arylene ether sulfone)s containing different Cardo (TPM) moieties were prepared. The structures, properties and DD performance of above AEMs were systematically evaluated. As the Cardo (TPM) group angle increased, the d-spacing, fractional free volume, and membrane area resistance increased, and the microphase separation structures, hydrophilicity, and acid flux decreased, mainly because larger Cardo (TPM) group angles are unfavourable for the close packing of polymer chains in space. Both the Cardo-type and TPM-type AEMs exhibited universal ultrahigh H+/Fe2+ selectivity (S > 3819), which was mainly attributed to the synergistic influence of their rigid narrow ion transport channels, small pore diameter (0.48–0.62 nm) and narrow pore size distribution (0.24–0.68 Å). Additionally, due to the high-density amide groups of TPM units, which decreased the hydrophobicity of the polymer skeleton and induced the formation of an additional transport pathway for Fe2+ through hydrogen bonding interactions, the TPM-type AEMs showed both lower acid flux and selectivity, suggesting that the structure of hydrophilic auxiliary groups should be carefully designed when improving the DD performance of AEMs.

Interfacial co-assembly strategy towards gradient mesoporous hollow sheet for molecule filtration

Gradient porous structures enable the fast capillary-directed mass transport and enhance the chemical reaction rate with optimal efficiency and minimal energy consumption. Rational design and facile synthesis of functional mesoporous materials with sheet structure and gradient mesopores still face challenges of stacked structures and unadjustable pore sizes. Herein, an interfacial co-assembly strategy for gradient mesoporous hollow silica sheets is reported. The modulated oil-water interface allows the assembly of gradient mesoporous silica layers on the water-removable ammonium sulfate crystals. The obtained mesoporous silica layers possess narrow pore size distributions (~2.2 nm and ~6.6 nm). Owing to the good mono-dispersity, sheet structure and proper pore size, the designed gradient mesoporous hollow silica sheets can serve as flexible building blocks for fabricating nanoscale molecule filtration device. Experiments reveal that the obtained nanofiltration device shows remarkable gradient rejection rates (range from 23.5 to 99.9%) for molecules with different sizes (range from 1.2 to 4.4 nm).

Crystalline Mesoporous F-Doped Tin Dioxide Nanomaterial Successfully Prepared via a One Pot Synthesis at Room Temperature and Ambient Pressure.

We report the successful one pot synthesis of crystalline mesoporous tin dioxide powder doped with fluoride at ambient pressure and temperature. This material possesses a high surface area, narrow pore size distribution, small average crystallite sizes, and good opto-electrical properties. The existence of fluorine increased the opto-electronic activity of tin dioxide by 20 times, and conductivity by 100 times compared with pristine tin dioxide prepared via the same method. The conductivity of SnO2 in air at 25 °C is 5 × 10-5 S/m, whereas that of F-SnO2 is 4.8 × 10-3 S/m. The structures of these materials were characterized with powder X-ray diffraction, N2 sorption analysis, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and UV-visible spectroscopy. Fluorine occupies the framework of tin dioxide by replacing some of the oxygen atoms. The structure, conductance, and optical properties of these materials are discussed in this paper.

Hydro-mechanical modelling of swell behaviour of bentonite buffer

Hydro-mechanical modelling of swell behaviour of bentonite buffer

Synthesis and characterisation of mesoporous MgAl2O4 hollow spheres as a high-value product in a waste recovery strategy

Micrometre-scale hollow sphere-shaped MgAl2O4 powders were synthesised using a spray-drying method, followed by calcination. An aqueous solution of mixed Mg2+ and Al3+ salts, derived from aluminium slag and serpentine tailings, served as a source of magnesium and aluminium. The secondary raw materials were subjected to acid leaching, and the refined leachates were used to prepare a spray-dried MgAl2O4 precursor, which was heat-treated at temperatures ranging from 550 °C to 1100 °C for 1 h. Characterisation of the resulting MgAl2O4 spinel powders was performed using various physicochemical techniques, including thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and physical adsorption using N2 (BET). The prepared MgAl2O4 spinel demonstrated several unique properties, including ultrafine particles with a uniform distribution (1–5 μm) and minimal particle agglomeration, high sintering activity (beginning at 550 °C), high purity, high specific surface area (110 m2 g-1/750 °C), and open porosity with a narrow pore size distribution (3–7 nm). These properties make the prepared MgAl2O4 spinel a highly valuable product for waste recovery strategies. The simplicity, efficiency, and cost-effectiveness of this process also predispose it to large-scale production of functional mixed metal oxides of various compositions for use in industries such as energy storage, sensing, and 3D printing fillers.

Preparation of sulfonic acid functionalized covalent organic framework solid phase microextraction fibers and their application in the analysis of neurotransmitters in the mouse brain

Neurotransmitters (NTs) are essential for intercellular communication and primarily include monoamine, amino acid, and cholinergic NTs. These molecules play important roles in the body's stress response, motor coordination, neuronal communication, and homeostatic functions. Previous studies have shown that abnormal changes in NT levels are associated with various neurological disorders. Therefore, the development of accurate analytical methods for NT detection will enhance the current understanding on complex neuropathophysiology by providing functional knowledge and techniques for early diagnosis, thereby facilitating the development of new therapeutic options for the related diseases. The solid phase microextraction (SPME) technique combines sample preparation, separation, and enrichment in a single step and is minimally invasive, low cost, solvent free, and high throughput. SPME has been successfully applied to the in vivo analysis of target analytes in animal, human, and plant tissues. The coating material plays a significant role in the development of in vivo SPME methods and must meet various analytical requirements, including a suitable geometry for the SPME device, high extraction capacity, excellent selectivity, and wide extraction coverage for the target analytes. Covalent organic frameworks (COFs) are porous crystalline polymers constructed from organic framework units through strong covalent bonds; these materials are characterized with a low density, large specific surface area, permanent porosity, excellent chemical/thermal stability, and easy functionalization.In this study, a sulfonic acid-functionalized COF material (COF-SO3H) with good crystallinity, excellent chemical/thermal stability, strong hydrophobicity, a uniform mesoporous structure, and narrow pore size distribution was prepared using 2,4,6-triformylphloroglucinol and 1,4-diamino-2-nitrobenzene as monomers. Then, the COF-SO3H was coated onto the surface of stainless-steel fibers and used for in vivo enrichment of NTs. The structural properties of COF-SO3H were characterized using various techniques, such as scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), all of which showed that COF-SO3H had a good crystalline structure and uniform mesopore distribution with a specific surface area of 46.17 m2/g. Compared with the SPME fibers of HLB, C18, MCX, amino, and PXC columns, the prepared COF-SO3H fibers showed better extraction efficiency for the target NTs. Next, the factors affecting SPME efficiency were optimized. The optimal desorption solvent was formic acid-methanol-water (0.5∶49.5∶50, v/v/v), and the optimal extraction and desorption times were 15 min. A method for the in vivo analysis of NTs in the brains of mice was established by combining the COF-SO3H fibers with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) under optimal conditions. The NTs were separated on an Acquity UPLC BEH-C18 analytical column (100 mm×2.1 mm, 1.7 μm) with 0.1% formic acid aqueous solution (A) and acetonitrile (B) as the mobile phases. The flow rate was set to 0.2 mL/min, and the gradient elution procedure was as follows: 0-4 min, 5%B-6%B; 4-7 min, 6%B-5%B; 7-11 min, 5%B. Under optimal conditions, the method showed good linearity (r2>0.99). The limits of quantification (S/N≥5) were in the range of 0.003-0.005 μg/mL and 3-5 μg/mL for monoamine and amino acid NTs, respectively, with RSDs of less than 20%. The method showed good precision (0.80%-9.70%) and accuracy (2.08%-17.72%), with absolute matrix effects in the range of 82.22%-117.92%. These values reflect the good purification and enrichment abilities of the proposed fibers for the target analytes. Finally, the established SPME method was combined with UPLC-MS/MS and successfully applied to quantify target NTs in the brains of mice. The proposed strategy provides a practical method for the in vivo detection and quantitative analysis of NTs and expands the applications of functionalized COF materials for the analysis of various targets.

A novel mesoporous carbon nanospheres-based adsorbent material with desirable performances for dyes removal

Nowadays, the reduction of dye contaminants in the aquatic environment has attracted widespread research attention. In this work, a novel mesoporous carbon nanospheres (MCNs)-based material as an adsorbent for dye removal was achieved by the carbonization of a composite of sucrose and aluminum sulfate without involving any hazardous activators. The as-obtained MCNs were analyzed by TG, XRD, FESEM, TEM, Raman, BET and XPS, meanwhile the batch experiments of Congo red (CR), Malachite green (MG) and Methylene blue (MB) on the MCNs were conducted to explore the impact of adsorption conditions on the adsorption process, respectively. Results show that the MCNs exhibit a uniform spherical morphology as well as partially graphitic structure with a large surface area of 449.25 m2/g, a relatively narrow pore size distribution and a high pore volume of 0.57 cm3 g−1. The unique porous structure of the MCNs endows it with high adsorption capabilities for dyes, including CR (1726.60 mg g−1), MG (980.55 mg g−1) and MB (708.82 mg g−1), suggesting its high adsorption capability for both anionic and cationic dyes. Meanwhile, the adsorption process is demonstrated to follow the Langmuir model and pseudo-second-order kinetic model, respectively, and the main adsorption mechanisms may involve pore filling, π-π conjugation, electrostatic attraction and hydrogen bonding. Furthermore, the as-synthesized adsorbent displays good recyclability performance for remaining relatively high sorption performance even after five regeneration cycles.

Design and synthesis of novel mesostructured nanohybrid materials as antimicrobials

New transparent and monolithic silica hybrid gels with high antibacterial and antifungal activities have been synthesized by soft chemistry. The synthesis has been carried out via sol-gel process, by grafting difunctional-1,3,4-thiadiazole components into a silica network, using 2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS) as a silicon source. The obtained xerogels were characterized using 13C and 29Si CP MAS NMR, FTIR spectroscopy and SEM. The results of this study reveal that the 1,3,4-thiadiazole nuclei have been chemically cross-linked to the silica backbone structure leading to hybrid materials. The pore sizes and specific surface areas were evaluated using N2 adsorption/desorption isotherms. The specific surface area found to be ranged from 302 to 365 m2.g−1. Small particle size with a narrow pore size distribution and an average diameter between 2.5 and 3.5 nm characteristic of a mesoporous structure of xerogels was observed. Scanning electron microscopy showed that the xerogels were formed of spherical nanoparticles whose diameter is of around ten nanometers. Gels antimicrobial activity has been evaluated against Gram-negative and Gram-positive bacteria and the fungus Candida albicans. This study demonstrated significant biosafety of the as-synthesized products and cytocompatibility with normal human skin cells was observed, supporting their potential use as promising candidates for therapeutic application.

Ordered Mesoporous Carbons with Well-Dispersed Nickel or Platinum Nanoparticles for Room Temperature Hydrogen Adsorption.

A facile mechanochemical method was used for the synthesis of ordered mesoporous carbons (OMCs) with well-dispersed metal nanoparticles. The one-pot ball milling of tannins with a metal salt in the presence of a block copolymer followed by thermal treatment led to Ni- or Pt-embedded OMCs with high specific surface areas (up to 600 m2·g-1) and large pore volumes (up to ~0.5 cm3·g-1). The as-prepared OMC-based samples exhibited hexagonally ordered cylindrical mesopores with narrow pore size distributions (average pore size ~7 nm), which implies sufficient long-range copolymer-assisted self-assembly of the tannin-derived polymer upon milling even in the presence of a metal salt. The homogenous decoration of carbons with small-sized metal (Ni or Pt) particles was essential to provide H2 storage capacities up to 0.33 wt.% at 25 °C and under 100 bar. The presented synthesis strategy seems to have great potential in the practical uses of functionalized polymers and carbons for applications in adsorption and catalysis.

Amphiphilic Polyampholytes for Fouling-Resistant and Easily Tunable Membranes.

The versatility of membranes is limited by the narrow range of material chemistries on the market, which cannot address many relevant separations. Expanding their use requires new membrane materials that can be tuned to address separations by providing the desired selectivity and robustness. Self-assembly is a versatile and scalable approach to create tunable membranes with a narrow pore size distribution. This study reports the first examples of a new class of membrane materials that derives state-of-the-art permeability, selectivity, and fouling resistance from the self-assembly of random polyampholyte amphiphilic copolymers. These membranes feature a network of ionic nanodomains that serve as nanochannels for water permeation, framed by hydrophobic nanodomains that preserve their structural integrity. This copolymer design approach enables precise selectivity control. For example, sodium sulfate rejections can be tuned from 5% to 93% with no significant change in the pore size or fouling resistance. Membranes developed here have potential applications in wastewater treatment and chemical separations.

Microfluidic bubble‐generator enables digital light processing 3D printing of porous structures

AbstractThree‐dimensional (3D) printing is an emerging technique that has shown promising success in engineering human tissues in recent years. Further development of vat‐photopolymerization printing modalities has significantly enhanced the complexity level for 3D printing of various functional structures and components. Similarly, the development of microfluidic chip systems is an emerging research sector with promising medical applications. This work demonstrates the coupling of a digital light processing (DLP) printing procedure with a microfluidic chip system to produce size‐tunable, 3D‐printable porosities with narrow pore size distributions within a gelatin methacryloyl (GelMA) hydrogel matrix. It is found that the generation of size‐tunable gas bubbles trapped within an aqueous GelMA hydrogel‐precursor can be controlled with high precision. Furthermore, the porosities are printed in two‐dimensional (2D) as well as in 3D using the DLP printer. In addition, the cytocompatibility of the printed porous scaffolds is investigated using fibroblasts, where high cell viabilities as well as cell proliferation, spreading, and migration are confirmed. It is anticipated that the strategy is widely applicable in a range of application areas such as tissue engineering and regenerative medicine, among others.

Facile Synthesis of Polymer-Reinforced Silica Aerogel Microspheres as Robust, Hydrophobic and Recyclable Sorbents for Oil Removal from Water.

With the rapid development of industry and the acceleration of urbanization, oil pollution has caused serious damage to water, and its treatment has always been a research hotspot. Compared with traditional adsorption materials, aerogel has the advantages of light weight, large adsorption capacity and high selective adsorption, features that render it ideal as a high-performance sorbent for water treatment. The objective of this research was to develop novel hydrophobic polymer-reinforced silica aerogel microspheres (RSAMs) with water glass as the precursor, aminopropyltriethoxysilane as the modifier, and styrene as the crosslinker for oil removal from water. The effects of drying method and polymerization time on the structure and oil adsorption capacity were investigated. The drying method influenced the microstructure and pore structure in a noteworthy manner, and it also significantly depended on the polymerization time. More crosslinking time led to more volume shrinkage, thus resulting in a larger apparent density, lower pore volume, narrower pore size distribution and more compact network. Notably, the hydrophobicity increased with the increase in crosslinking time. After polymerization for 24 h, the RSAMs possessed the highest water contact angle of 126°. Owing to their excellent hydrophobicity, the RSAMs via supercritical CO2 drying exhibited significant oil and organic liquid adsorption capabilities ranging from 6.3 to 18.6 g/g, higher than their state-of-the-art counterparts. Moreover, their robust mechanical properties ensured excellent reusability and recyclability, allowing for multiple adsorption-desorption cycles without significant degradation in performance. The novel sorbent preparation method is facile and inspiring, and the resulting RSAMs are exceptional in capacity, efficiency, stability and regenerability.

Vancomycin-loaded porous chitosan-pectin-hydroxyapatite nanocomposite coating on Ti6Al4V towards enhancing prosthesis antiinfection performance

Cathodic electrophoretic deposition (EPD) was used to fabricate novel porous chitosan/pectin/hydroxyapatite (CS/P/HA) nanocomposite coatings on Ti6Al4V substrates. Rietveld refinement results revealed variations in peak intensity, position, and width, reflecting structural changes resulting from the reduction of the applied voltage from 30 to 10 V. The deposits obtained at 10 V after 1 h of presedimentation exhibited a denser microstructure with narrow pore size distribution compared to the others. The wettability and adhesion strength of coated Ti6Al4V improved with increasing HA content. Release of antibiotic from the composite coating confirmed 40% initial burst release, 50% semi-steady release and 10% residual release. A thick and uniform porous apatite layer was formed on Ti6Al4V after 21 days of immersion in simulated body fluid (SBF). Therefore, CS/P/HA coated Ti6Al4V has the potential for practical antiinfection performance.

Comparative Surface Study of Ru/Cu- and Ag/Cu-Doped RHS Catalysts from Waste Biomass for Biofuel Application.

The present study compares the surface, textural, and catalytic properties of porous silica doped with bimetallic metal ions that was made from rice husk (RH) biomass. Due to the use of a surfactant during the synthesis process, porous RH-silica (RHS) was derived. In situ doping of silver/copper and ruthenium/copper has been achieved via the xerogel and hydrogel formation methods. The prepared catalysts have been analyzed by various methods, such as surface area and narrow pore size distribution, to confirm their porosity. Powder X-ray diffraction, Fourier transform infrared, and electron microscopy examination were further performed for physicochemical characterization of the synthesized materials. Transmission electron microscopy images showed that ruthenium and copper ions were incorporated perfectly, forming a hexagonal mesoporous (MCM-41) texture due to hydrogel formation and the method of preparation. Copper oxide nanoparticles with silver incorporation in RHS form cube-shaped particles for CuO formation on the surface of the silica matrix instead due to the method of preparation. In this case, ruthenium/copper-doped porous silica forms hexagon-shaped particles of RuO formation in the mesoporous matrix. Finally, the acetylation of glycerol using acetic acid on as-prepared catalysts has been studied. The catalytic activity increases with an increase in temperature and optimization of the molar ratio of glycerol and acetic acid. Increases in temperature result in higher selectivity toward triacetin formation instead of the conventional formation of monoacetin. Hence, we compared the surface physicochemical properties, catalytic conversion, and selectivity nature of bimetallic metal (Ru/Cu and Ag/Cu) ions incorporated in RHS prepared by different synthetic routes.

One-Pot Mechanochemical Synthesis of Carbons with High Microporosity and Ordered Mesopores for CO2 Uptake at Ambient Conditions.

Mechanochemical synthesis of ordered mesoporous carbons with tunable mesopores and well-developed irregular microporosity is investigated. This synthesis was carried out by the self-assembly of ecofriendly chemicals such as tannin and glyoxal used as carbon precursors, and triblock copolymer as a soft templating agent. The structural properties of the resulting carbons were tailored by using different block copolymers (Pluronic F127, and P123) as soft templates. The various weight ratios of tannin and block copolymer were employed to tune the textural properties of these carbons. The tannin: Pluronic F127 ratios (1:0.75, 1:1, 1:1.1) gave the ordered mesoporous carbons among a wide variety of the samples studied. The ordered mesoporosity was not observed in the case of Pluronic P123 templated mesoporous carbons. The CO2-activated carbon samples obtained for both Pluronic templates showed a high specific surface area (close to 900 m2/g), large pore volume (about 0.6-0.7 cm3g-1), narrow pore size distribution, and high CO2 uptake of about 3.0 mmol g-1 at 1 bar pressure and ambient temperature.

Preparation of Mesoporous γ-Alumina from Red Mud Waste

In this paper, a novel green and cost-effective synthesis method in this field is presented. Mesoporous γ-alumina was obtained by inorganic in situ crystallization, and sodium aluminate as an aluminum origin was abstracted from red mud. The influence mechanism of the reactant ratio of NaHCO3 to NaAlO2, the reaction temperature and the concentration of the template was systematically investigated. As indicated by the results, the obtained mesoporous γ-alumina possesses extensive specific surface areas, narrow pore size distribution, nearly spherical particle morphology and wormlike structure pores. This green and economical synthesis method can be used for the preparation of alternative mesoporous or various porous materials as well.

Copper Immobilized over 2D Hexagonal SBA-15 for Electrochemical and Colorimetric Sulfite Sensing.

Sulfite (SO32-) is considered a highly toxic anion for living organisms. Herein, we report the synthesis of copper immobilized over a 2D hexagonally ordered mesoporous silica material CuMS as an electrochemical and colorimetric dual-technique-based sensing platform for sulfite detection. The immobilization of copper on silica was achieved through the bis[3-(triethoxysilyl)propyl]tetrasulfide (TEPTS) ligand. Morphological and physical properties of the material were confirmed by several characterization techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N2 sorption, and X-ray photoelectron spectroscopy. The CuMS material retained mesoporosity with a narrow pore size distribution (D ≈ 5.4 nm) and a high Brunauer-Emmett-Teller surface area of 682 m2 g-1 after the immobilization of copper. The prepared catalyst shows promising electrocatalytic activity toward sulfite oxidation. A linear variation in the peak current was obtained for SO32- oxidation in the 0.2-15 mM range with a high sensitivity of 62.08 μA cm-2, under optimum experimental conditions. The limit of detection (LOD) was found to be 1.14 nM. CuMS also shows excellent activity toward colorimetric detection of sulfite anions with an LOD of 0.4 nM. The proposed sensor shows high selectivity toward the sulfite anion, even in the presence of common interferents. The detection of sulfite in white wine with excellent recovery demonstrates the practical applicability of this sensor.