Mesoporous Network Research Articles

Mesoporous Networks of N-Vinylpyrrolidone with (di)Methacrylates as Precursors of Ecological Molecular Imprinted Polymers.

Mesoporous polymer networks were prepared via the cross-linking radical copolymerization of non-toxic hydrophilic N-vinylpyrrolidone (VP) with triethylene glycol dimethacrylate (TEGDM) and poly(ethylene glycol) methyl ester methacrylate (PEGMMA) in bulk, using appropriate soluble and thermodynamically compatible macromolecular additives with a branched structure as porogens. The branched copolymers of various monomer compositions were obtained by radical copolymerization in toluene, controlled by 1-decanethiol, and these materials were characterized by a wide set of physical chemical methods. The specific surface areas and surface morphology of the polymer networks were determined by nitrogen low-temperature adsorption or Rose Bengal (RB) sorption, depending on the copolymer compositions and scanning electron microscopy. The electrochemical properties of RB before and after its encapsulation into a branched VP copolymer were studied on a glassy carbon electrode and the interaction between these substances was observed. Quantum chemical modeling of RB-VP or RB-copolymer complexes has been carried out and sufficiently strong hydrogen bonds were found in these systems. The experimental and modeling data demonstrate the high potency of such mesoporous polymer networks as precursors of molecularly imprinted polymers for the recognition of fluorescent dyes as nanomarkers for biomedical practice.

Polyoxotungstate intercalated self-assembled nanohybrids of Zn-Cr-LDH for room temperature Cl2 sensing

This article reports the preparation of mesoporous layered nanohybrids of zinc chromium layered double hydroxide (Zn-Cr-LDH) and polyoxotungstate (POW) anions via an exfoliation-reassembling process. The hybridization of Zn-Cr-LDH and POW anions leads to forming a layer-by-layer intercalated structure with a randomly interconnected mesoporous nanoplate network composed of ‘restacked POW intercalated Zn-Cr-LDH nanosheets’ (Zn-Cr-WO). The gas-sensing performance of the pristine Zn-Cr-LDH and Zn-Cr-WO was investigated for oxidizing (NO2 and Cl2), and reducing (LPG, H2, H2S, CO and NH3) gases at room temperature. The Zn-Cr-WO nanohybrids displayed the highest selectivity towards Cl2. The Cl2 gas response for the pristine Zn-Cr-LDH is 25.2% which further increased to 66.8% after hybridization with POW anions. The Zn-Cr-WO nanohybrids showed fastest response and recovery times of 5 and 133 s, respectively, at room temperature.

Highly efficient and accelerated photoreduction of nitrobenzene over visible-light-driven PtO@Cr2O3 nanocomposites

PtO nanoparticles (NPs) were anchored mesoporous Cr2O3 networks through a surfactant-modified approach to synthesize PtO@Cr2O3 nanocomposites at varying PtO NPs contents, and the synthesized materials were evaluated by the reduction of nitrobenzene under visible light illumination. TEM images revealed PtO NPs (5 nm) with good distribution on the mesoporous Cr2O3 with a diameter of ∼20–30 nm. The obtained PtO@Cr2O3 nanocomposites exhibited highly Cr2O3 nanocrystallites with rhombohedral Cr2O3 structure and a large surface area of 85–110 m2/g. PtO@Cr2O3 nanocomposites revealed visible light absorption with red-shifted during the introduction of Cr2O3 NPs. The conversion efficiency of nitrobenzene increased up to 38%, 78% and 100% for 0.3, 0.6, 0.9 and 1.2%PtO@Cr2O3 photocatalysts within 60 min of illumination, which elucidating a nitrobenzene reduction effectively to yield aniline, where the conversion of nitrobenzene using bare Cr2O3 NPs was achieved only 6%. The obtained mesoporous 0.9%PtO@Cr2O3 nanocomposites exhibited the best photocatalytic reduction of nitrobenzene to aniline under visible light illumination with reduction rate of 3660.8 mmolL−1min−1 and reduction efficiency of 100% after 30 min. Interestingly, the reaction rate constant (k) and the photoreduction rate values over 0.9%PtO@Cr2O3 photocatalyst was fostered 47 and 22.5 folds larger than the obtained for bare Cr2O3. The significant improvement of mesoporous PtO@Cr2O3 nanocomposites could be attributed to the Cr2O3 modified by PtO sensitization, the mesoporous structure of Cr2O3 NPs and the synergic effects of PtO and Cr2O3. The recycling experiments of nitrobenzene photoreduction after five cycles runs were reduced slightly, which verified these candidates are considered a promising and superior for practical applications.

Concerted effect of boron and porosity on shear thickening behavior of hybrid mesoporous silica dispersions

In the present work, the influence of porosity and boron on shear thickening behavior of hybrid mesoporous silica has been studied. Three different levels of boron modification were performed by varying the molar composition of boric acid viz., 1.5 mmol, 2.5 mmol, and 3.5 mmol in a co-condensation approach. The incorporation of boron in mesoporous silica network was confirmed by various techniques such as Fourier transform infra-red (FTIR), and 11B solid- state nuclear magnetic resonance (NMR) spectroscopy. The morphology and particle size were confirmed by using scanning and transmission electron microscopy. To evaluate the effect of boron and porosity on the shear thickening behavior, dispersions were prepared from mesoporous boron- modified silica (MSiB), control mesoporous silica (MSi), non-porous boron-modified silica (SiB), and control non-porous silica (Si) in polyethylene glycol. The shear thickening behavior was studied using steady shear rheology. The dispersion prepared from different loadings of synthesized MSiB containing 1.5 mmol boron showed more than 16 times increase in viscosity (657.7 Pa.s) compared to that of MSi (39.2 Pa.s) at a fairly low volume fraction (φ = 0.15) of silica. It is expected that the highly ordered mesoporous architecture of hybrid silica has improved the interaction between the particle and the dispersing medium through hydrogen bonding. The porous morphology of the hybrid mesoporous silica as well as the incorporation of boron in the silica network favors the formation of a frictional contact network, and a transition from continuous shear thickening (CST) to discontinuous shear thickening (DST) behavior was observed. Therefore, silica prepared via incorporation of boron as well as porosity can be material of interest in variety of applications, for example, soft body armors, sporting goods, and shear thickening electrolytes for high impact resistant batteries.

Molecular Cage-Mediated Radial Gradient Porous Sponge Nanofiber for Selective Adsorption of a Mustard Gas Simulant.

Poisons and poisonous weapons in armed conflict, especially chemical warfare agents (CWAs), pose serious threats to global security. Porous materials have recently been regarded as promising candidates to defend personnel in a CWA-contaminated environment, but challenges remain for integrating these materials into protective garments without sacrificing the intrinsic flexibility of fibers. Here, we report a rigid-flexible coupling hypercross-linking methodology to create flexible sponge-like nanofibers featuring hierarchical radial gradient porous nanoarchitectures, in which the inner structure is a mesoporous multichambered network, and the outer structure is a dense domain with a microporous network structure. Experimental and computational evidence supports the contention that sponge nanofibers with distinctive pore topology and robust bendability can be designed by manipulating the flexibility of building blocks. The resulting heterogeneous nanofibers exhibit integrated properties of spatially selective superstructures, abundant micropores, interconnected mesopores, a high surface area (579 m2 g-1), remarkable flexibility, and exceptional CWA affinity, which are extraordinarily effective for adsorptive performance (498 mg g-1). The successful synthesis of these materials might inspire the development of chemical protective materials in an efficient, self-standing, and structurally adaptive form.

Elucidating the effects of oxygen- and nitrogen-containing functional groups in graphene nanomaterials for applied electrochemistry by density functional theory

Graphene nanomaterials functionalized with oxygen groups [graphene oxide (GO) and reduced GO (rGO)] are either doped with element nitrogen or nitrogen-containing aromatic moieties followed by the investigation of electrochemical properties that generally show enhanced electroanalytical performance. We studied structural, morphological, and physical–chemical properties using correlative techniques. While we attribute their improved properties promoted simultaneously by topologically interconnected mesoporous network morphology, the presence of heteroatom species, and lattice vibrational structure, the complex interpretation requires the need to supplement the experimental observations with theoretical calculations for further insights. The complex interplay of pore size and redox properties revealing distinctive supercapacitive (ion-adsorption controlled) and pseudocapacitive (diffusion-controlled) energy storage mechanistic contributions arises from the combined effects of oxygen and nitrogen functional groups, most likely located on the basal plane and at the pore edge plane sites. The density functional theory calculations provided band structure and electron transfer from Mulliken and Hirshfeld population analyses helping discern the nature of various functional groups in diverse graphene. Interestingly, while quaternary (N—Q) and pyridinic-N-oxides (N—O) on the basal planes show enhanced capacitance due to positive charge and thus an improved electron transfer at higher current loads identified in nitrogen-doped aerogel (AG/nitrogenated) and GO-derived rGO by chemical and electrochemical properties, the other important functional groups affecting the energy storage are pyridinic (N-6) and pyrrolic (N-5) nitrogen groups on the edge of the rGO nanosheet in association with carboxylic (—COOH) and quinone (C=O) functional groups in nitrogenated functional graphene/graphene aerogel and rGO coated polyaniline, contributing to a pseudocapacitive character.

Electronically Integrated Mesoporous Ag–TiO2 Nanocomposite Thin films for Efficient Solar Hydrogen Production in Direct Sunlight

The synthesis of mesoporous TiO2 by a solution‐based assembly process and Ag/TiO2 nanocomposites is provided. The efficacy of Ag/TiO2 nanocomposite as photocatalyst in thin‐film form is demonstrated for solar hydrogen generation in sunlight. Integration of Ag with TiO2 dramatically enhanced the H2 production: with 1 wt% Ag on TiO2 (TiAg‐1), the H2 yield was observed to be 4.59 mmol h−1 g−1, which is 2.3 (30) times larger than 0.5 wt% Ag on TiO2. TiAg‐1 shows 4.3 times higher activity in film form compared with its powder counterpart. High photocatalytic efficiency is attributed to the surface plasmon resonance effect of Ag, electronic integration of Ag with TiO2, and subsequent valence band broadening, large distribution of Ag nanoparticles and abundant Ag‐TiO2 Schottky junctions, and the later minimizes electron–hole recombination. Interparticle mesoporous network increases necking and the high surface area offers easy accessibility of the reactants to a large number of active sites.

Three-Dimensional-Printed Silica Aerogels for Thermal Insulation by Directly Writing Temperature-Induced Solidifiable Inks.

Silica aerogels are attractive materials for various applications due to their exceptional performances and open porous structure. Especially in thermal management, silica aerogels with low thermal conductivity need to be processed into customized structures and shapes for accurate installation on protected parts, which plays an important role in high-efficiency insulation. However, traditional subtractive manufacturing of silica aerogels with complex geometric architectures and high-precision shapes has remained challenging since the intrinsic ceramic brittleness of silica aerogels. Comparatively, additive manufacturing (3D printing) provides an alternative route to obtain custom-designed silica aerogels. Herein, we demonstrate a thermal-solidifying 3D printing strategy to fabricate silica aerogels with complex architectures via directly writing a temperature-induced solidifiable silica ink in an ambient environment. The solidification of silica inks is facilely realized, coupling with the continuous ammonia catalysis by the thermolysis of urea. Based on our proposed thermal-solidifying 3D printing strategy, printed objects show excellent shape retention and have a capacity to subsequently undergo the processes of in situ hydrophobic modification, solvent replacement, and supercritical drying. 3D-printed silica aerogels with hydrophobic modification show a super-high water contact angle of 157°. Benefiting from the low density (0.25 g·cm-3) and mesoporous silica network, optimized 3D-printed specimens with a high specific surface area of 272 m2·g-1 possess a low thermal conductivity of 32.43 mW·m-1·K-1. These outstanding performances of 3D-printed silica aerogels are comparable to those of traditional aerogels. More importantly, the thermal-solidifying 3D printing strategy brings hope to the custom design and industrial production of silica aerogel insulation materials.

Toward a Scalable Fabrication of Perovskite Solar Cells under Fully Ambient Air Atmosphere: From Spin-Coating to Inkjet-Printing of Perovskite Absorbent Layer

Up until now, the vast majority of perovskite solar cells (PSCs) have relied on the spin-coating of perovskite precursor solution under inert fully controlled conditions, with the performance of solar cells that are developed by alternative techniques and under an ambient atmosphere to lag far behind. This impedes the technology transfer from the laboratory to industrial large-scale production; thus, the investigation of new scalable techniques should be thoroughly considered. The present work constitutes one of the few investigations on the application of inkjet-printing as an advanced alternative technique to the conventional spin-coating technique used for the fabrication of fully ambient air-processed perovskite absorbent layers for carbon-based hole transport layer-free PSCs. A systematic study of the characteristics of the perovskite material and solar cells indicated that the coffee-ring effect combined with poor ink penetration into the mesoporous network of the anode semiconductor were the main reasons for obtaining poor perovskite structure morphology and lower PSC performance by inkjet-printing, which arises from a lower internal quantum efficiency and an increased charge transfer and recombination rate. On the other hand, the crystallinity and optical characteristics of the materials obtained by the compared techniques did not differ considerably, while small differences were observed in the hysteretic behavior and long-term stability of the solar cells.

Effect of the carbon mesoporous structure on the transport properties of confined lithium chloride aqueous solutions

Accurate determination of fluid dynamics in confined carbons with pore size distribution (PSD) ranging from micro to mesopores is a fundamental aspect for many relevant applications, such as lithium battery electrodes, supercapacitors, or fuel cells. Here we present a synthesis route that enables the preparation of carbons with tailored PSD, which are characterized by nitrogen adsorption methods and nuclear magnetic resonance (NMR). The combination of micro and mesopores is determined straightforwardly by the determination of confined water self-diffusion coefficients and longitudinal relaxation times. Employing 2D-NMR experiments pore interconnectivity was characterized, determining exchange rates for water between micropores, mesopores, and bulk solution. Furthermore, their functionality was tested in simple ion release experiments of a solution of LiCl carried out both by conductivity and NMR experiments. We found that the lithium release rate can be set by tailoring the connectivity between micro and mesopores. For samples with mesopores larger than 5 nm and a small content of micropores, ion mobility is mainly restricted by the material's porosity. On the other hand, tortuosity analysis reveals that carbon wall-ion interaction is the main factor of the sluggish diffusion in materials with a large fraction of micropores well connected to the mesopore network.

Electrochemical Lithiation/Delithiation of ZnO in 3D-Structured Electrodes: Elucidating the Mechanism and the Solid Electrolyte Interphase Formation.

Conversion/alloy active materials, such as ZnO, are one of the most promising candidates to replace graphite anodes in lithium-ion batteries. Besides a high specific capacity (qZnO = 987 mAh g-1), ZnO offers a high lithium-ion diffusion and fast reaction kinetics, leading to a high-rate capability, which is required for the intended fast charging of battery electric vehicles. However, lithium-ion storage in ZnO is accompanied by the formation of lithium-rich solid electrolyte interphase (SEI) layers, immense volume expansion, and a large voltage hysteresis. Nonetheless, ZnO is appealing as an anode material for lithium-ion batteries and is investigated intensively. Surprisingly, the conclusions reported on the reaction mechanism are contradictory and the formation and composition of the SEI are addressed in only a few works. In this work, we investigate lithiation, delithiation, and SEI formation with ZnO in ether-based electrolytes for the first time reported in the literature. The combination of operando and ex situ experiments (cyclic voltammetry, X-ray photoelectron spectroscopy, X-ray diffraction, coupled gas chromatography and mass spectrometry, differential electrochemical mass spectrometry, and scanning electron microscopy) clarifies the misunderstanding of the reaction mechanism. We evidence that the conversion and alloy reaction take place simultaneously inside the bulk of the electrode. Furthermore, we show that a two-layered SEI is formed on the surface. The SEI is decomposed reversibly upon cycling. In the end, we address the issue of the volume expansion and associated capacity fading by incorporating ZnO into a mesoporous carbon network. This approach reduces the capacity fading and yields cells with a specific capacity of above 500 mAh g-1 after 150 cycles.

A novel cellulose‐derived carbon aerogel@Na2Ti3O7 composite for efficient photocatalytic degradation of methylene blue

AbstractA scale‐up and sustainable method was developed to fabricate novel photocatalyst cellulose‐derived carbon aerogel@Na2Ti3O7 composite (CAT) by in situ growth of Na2Ti3O7 nanowhisker on the surfaces of fibers. With a three‐dimensional (3D) mesoporous network interconnected structure and a high specific surface area (248.92 m2/g), CAT exhibited excellent photocatalytic activity and methylene blue (MB) removal rate (98.3%). The photocatalytic experimental results showed that the CAT could degrade MB in the aqueous solution within 90 min. Compared with most reported catalysts, CAT exhibited a higher MB removal rate and shorter catalytic time. Therefore, the photocatalyst CAT based on environmentally friendly and low‐cost cellulose displayed great application potential in the degradation of MB.

Investigation on structural, morphological and electrochemical properties of Mn doped WO3 nanoparticles synthesized by co-precipitation method for supercapacitor applications

The work reported here, demonstrates the synthesis of pristine WO3 and Manganese (Mn)-doped through the hydraulic acid-assisted precipitation method. Structural, morphological, compositional, optical and electrochemical properties of the synthesized samples were analysed. The structural analysis through X-ray diffraction studies confirmed the monoclinic phase of WO3 as well as the substitutional incorporation of Mn inWO3 lattice. A bandgap value of 2.9 eV was estimated from Optical analysis using Kubelka-Munk model. The defect centered luminescence as a consequences of Mn doping was analyzed using photoluminescence spectroscopy (PL). FT Raman Spectroscopic data also reconfirmed the monoclinic structure of the sample and incorporation of Mn into the lattice of Mn-doped WO3. The surface morphological study was performed using Field Emission Scanning Electron Microscope (FESEM), which exhibits the development of mesoporous networks. The Conductivity, dielectric and electrochemical studies were performed on these mesoporous structures to inveterate the impact of Mn doping. A dynamic increment in AC conductivity was observed with doping even at room temperature. Most significantly, we prove that Mn doped WO3 for the first time, Nanoparticles are an outstanding candidate for applications for supercapacitors. Pure and Mn doped WO3 electrochemical properties cyclic voltammetry measurements have been used to analyze samples. The results showed the excellent electrochemical efficiency on 1 wt% Mn doped WO3 electrode (1178 F/g specific capacitance at 2 mA/cm2 and charge transfer ability) for supercapacitors.

Hierarchical Co3O4@CoAl hydrotalcite grown on Ni foam for high-performance asymmetric supercapacitors

The pineapple flower-like hierarchical Co3O4@CoAl-layered double hydroxides (Co3O4@ CoAl-LDH) with 3D mesoporous network structure were designed and in-situ synthesized on nickel foam (NF) through a facile two-step hydrothermal route for supercapacitors. The Co3O4@CoAl-LDH displayed a greater specific capacitance of 949.7C g−1 (1899.4 F g−1) at 1.0 A g−1, better rate capability and higher cycle stability comparing with the pristine Co3O4 and CoAl-LDH on NF. At the same time, the as-fabricated Co3O4@CoAl-LDH//activated carbon (Co3O4@CoAl-LDH//AC) device delivered outstanding energy densities of 77.58 and 36.03 Wh kg−1 at a power density of 754.83 and 7813.73 W kg−1, respectively, and excellent rate capability and outstanding long-term cycle stability (84.99% retention of the initial value at 5 A g−1 after 20,000 cycles). The superior electrochemical performances showed that the Co3O4@CoAl-LDH was a promising candidate as electrode materials for high-performance energy storage devices.

Hybrid MXene/reduced graphene oxide aerogel microspheres for hydrogen evolution reaction

Hybrid MXene/reduced graphene oxide aerogel microspheres (MXene/rGOAMs),where MXenes are two-dimensional (2D) transition metal carbides, with abundant macro/meso/micro multi-scale pores and self-supporting structure, are prepared by electrospraying followed by freeze-drying and then thermal annealing. A center-diverging structure with well-aligned microchannels is formed within each microsphere, which can be maintained after thermal reduction. Such highly ordered 3D hybrid mesoporous network has been tested for the hydrogen evolution reaction (HER) because it may prevent the stacking of the 2D layers, thus enhancing the mass transfer. Actually, in the case of Ti3C2Tx/rGOAMs, obtained with an optimized MXene:GO mass ratio and after a thermal treatment at 400 °C, a better HER performance with respect to the bulk Ti3C2Tx aerogel or the MXene/GO composite is observed (η10=-336 mV), suggesting an accelerated mass transfer through different inter-sheets when the 3D mesoporous microsphere networks are created. The Ti3C2Tx/rGOAMs also exhibit enhanced HER activity compared to rGOAMs, suggesting that the MXene plays a key role due to the presence of titanium atoms with a low valence state.Graphical abstract

Tailoring mesoporous silica nanomaterials from molecular simulation: Modelling the interplay of condensation reactions, surfactants and space-fillers during self assembly

We outline a coarse-grained model of silica nanoparticles, hexadecetyltrimethylammonium bromide surfactants and triamethylbenzene spacers for the analysis of mesoporous silica nanomaterials (MSN) formation from molecular simulation. Starting from random configurations, molecular dynamics simulations of annealing an artificial melt allow the unprejudiced investigation of silica-surfactant/spacer self-assembly. In analogy to the experimental syntheses protocol, the second step consists of removing the spacer and surfactant species from the system, followed by condensation reactions between the silica precursors. In our coarse-grained model, this intergrowth of the silica network is described by effective potentials that mimic atomistic simulations based on quantum/classical approaches. On this basis, rapid screening of pore structures as functions of surfactant and spacer concentration is demonstrated. After characterization of the self-organization process, we finally back-map the coarsened models into atomic structures, now enabling the detailed analyses of MSN loading by guest molecules – as illustrated for gemcitabine and ibuprofen, respectively. Guest-host interactions of ibuprofen in concave and convex domains of mesoporous silica networks. • Holistic multi-scale modelling of MSN formation rationalizes the interplay of spacers, surfactants and precursors. • Differently shaped pores are rationalized from the fine details of silica colloid association and ripening reactions. • Back-mapping into atomic detail structures enables the in-depth analyses of incorporating pharmaceutical guest molecules.

Synthesis of self-assembled hierarchical AlPO-34 microspheres by using an ionic liquid and its application in heavy metal removal.

Hierarchical AlPO-34 molecular sieves microspheres were synthesized in a [BMIm]Br ionic liquid without template or complex post-treatment process. The formation mechanism of such framework structures and their morphology were investigated. [BMIm]Br was proven to serve as both solvent and sole provider of the structure directing agent. The organic amine in the compound affects the framework density of the crystals and promotes the formation of a chabazite (CHA) type framework. After ageing for 1 h the AlPO-34 microspheres are formed due to the aggregation properties of the ionic liquid. The hierarchical mirosphere has a relatively high Brunauer–Emmett–Teller surface area and a considerably uniform mesoporous channel network. The hierarchical AlPO-34 microspheres were used as absorbers of heavy metal cations and showed a higher loading capacity and distribution coefficient compared with the AlPO-34-NH.

Charge modulation of CNTs-based conductive network for oxygen reduction reaction and microwave absorption

Carbon nanotube (CNTs) based composite materials are popular in various fields. However, traditional strategies for the electric conductivity modulation of CNTs is complicated and improper in large-scale applications. Herein, a novel CNTs-based hollow microsphere is prepared through facile spray drying and one-step pyrolysis. This unique interpenetration microsphere conductive network is constructed by nitrogen-doped CNTs embedded with Co nanoparticles (Co–N–C), which is compactly entangled by commercial CNTs. By the strong charge polarization and electron redistribution on the surface of Co–N–C, the monohybrids exhibit excellent bifunctional applications. The Co–N–C/CNTsHS shows excellent oxygen reduction reaction (ORR) performance including the high half-wave potential (0.87V), outstanding stability and methanol tolerance. Benefited from the improved dielectric property of Co–N–C, the Co–N–C/CNTsHS exhibits superior microwave absorption (MA) performance, with a maximum reflection loss of −60.2 dB and the bandwidth of 5.1 GHz at a thickness of only 2.5 mm. The enhanced performance can be attributed to three dimension (3D) hollow mesoporous conductive networks, which accelerate electron transfer and modulate charge distribution of Co–N–C. This work puts forward a new idea of charge modulation of CNTs and lays a foundation for the preparation of excellent bifunctional materials.

Bi2O3-sensitized hierarchically mesoporous ZnO nanoparticles for Hg(II) reduction

Herein, an affordable and novel approach to design Bi2O3-sensitized hierarchically mesoporous ZnO nanoparticles (NPs) with a variety of Bi2O3 contents is achieved for Hg(II) reduction upon visible light exposure. TEM images of both ZnO and 3% Bi2O3/ZnO samples exhibit nanoscale spherical-like structures with a regular shape and a particle size of ~30 nm. The incorporation of Bi2O3 on hierarchically mesoporous ZnO networks allows visible light to be harvested in a broad range, and the mesoporous 3% Bi2O3/ZnO heterostructure demonstrates the best photocatalytic efficiency for Hg(II) reduction with a value of ~100% after 60 min. The photoreduction rate over the 3% Bi2O3/ZnO heterostructure is enhanced 10 and 20 times more than that of TiO2-P25 and ZnO NPs. The rate constant of the 3% Bi2O3/ZnO heterostructure is 16.8 and 33.6 fold larger than that of TiO2-P25 and ZnO NPs. The superior Hg(II) photoreduction performance could be ascribed to the synergistic effect, excellent visible-light harvest, large surface area, and pore volume provided by incorporating Bi2O3 and the heterojunction design between p-type Bi2O3 and n-type ZnO. This alignment of the electronic bands provides charge carrier separation, thereby decreasing the recombination rate. Finally, the mechanisms and kinetics for the photocatalytic reduction of Hg(II) are proposed.

Fabrication of target specific solid-state optical sensors using chromoionophoric probe-integrated porous monolithic polymer and silica templates for cobalt ions.

The article demonstrates the design of two solid-state sensors for the capturing of industrially relevant ultra-trace Co(II) ions using porous monolithic silica and polymer templates. The mesoporous silica reveals high surface area and voluminous pore dimensions that ensures homogeneous anchoring of 4-((5-(allylthio)-1,3,4-thiadiazol-2-yl)diazenyl)benzene-1,3-diol, as the chromoionophore. We report a first of its kind solid-state macro-/meso-porous polymer monolithic optical sensor from a monomeric chromoionophore, i.e., 2-(4-butylphenyl)diazenyl)-2-hydroxybenzylidene)hydrazine-1-carbothioamide. The monolithic solid-state sensors are characterized using HR-TEM-SAED, FE-SEM-EDAX, p-XRD, XPS, 29Si/13C CPMAS NMR, FT-IR, TGA, and BET/BJH analysis. The electron microscopic images reveal a highly ordered hexagonal mesoporous network of honeycomb pattern for silica monolith, and a long-range macroporous framework with mesoporous channels for polymer monolith. The sensors offer exclusive ion-selectivity and sensitivity for trace cobalt ions, through a concentration proportionate visual color transition, with a response kinetics of ≤ 5min. The optimization of ion-sensing performance reveals an excellent detection limit of 0.29 and 0.15ppb for Co(II), using silica- and polymer-based monolithic sensors, respectively. The proposed sensors are tested with industrial wastewater and spent Li-ion batteries, which reveals a superior cobalt ion capturing efficiency of ≥ 99.2% (RSD: ≤ 2.07%).