High Specific Area Research Articles

Plant life history strategies vary in subtropical forests with different disturbance histories: an assessment of biodiversity, biomass, and functional traits.

Disturbance alters environmental conditions in forests. Plants growing in forests with different disturbance histories in diverse environments may adopt varying life history strategies, but few studies focus on this effect. This study comprehensively investigated plant biodiversity, biomass, and functional traits in subtropical forests with two different disturbance histories in east China to explore differences in life history strategies. Biodiversity was slightly higher in disturbed compared to conserved forests. Significantly higher biomass was measured in conserved relative to disturbed evergreen broadleaved forests (P < 0.05). In conserved forests, leaf tissue density (LTD) was significantly higher and leaf thickness (LT), leaf dry matter content (LDMC), twig tissue density (TTD), twig dry matter content (TDMC), bark tissue density (BTD) and dry matter content (BDMC), and stem tissue density (STD) and dry matter content (SDMC) were significantly lower than in disturbed forests (P < 0.05). In terms of associated plant biodiversity, biomass, and functional traits, conserved forests adopted a resource acquisition strategy, reducing biodiversity and developing multiple functional traits such as high leaf area and specific leaf area and low LT, LDMC, TTD, TDMC, BTD, BDMC, STD, and SDMC to support a high biomass accumulation rate. Disturbed forests adopted a resource conservation strategy, enhancing biodiversity and developing converse trait combinations to lower the rate of biomass accumulation. A comprehensive investigation of plant biodiversity, biomass, and functional traits and subsequent assessment of plant life history strategies in conserved and disturbed forests will aid investigations of regional biodiversity and carbon reserves, contribute data to the TRY and Chinese plant trait databases, and improve ecological management and restoration efforts in east China.

Tailoring the Structural and Optical Properties of Cerium Oxide Nanoparticles Prepared by an Ecofriendly Green Route Using Plant Extracts.

The present study explores an environmentally friendly green approach to obtain cerium oxide nanoparticles via a biomediated route using Mellisa officinalis and Hypericum perforatum plant extracts as reducing agents. The as-prepared nanoparticles were studied for their structural and morphological characteristics using XRD diffractometry, scanning electron microscopy, Raman, fluorescence and electronic absorption spectra, and X-ray photoelectron spectroscopy (XPS). The XRD pattern has shown the centered fluorite crystal structure of cerium oxide nanoparticles with average crystallite size below 10 nm. These observations were in agreement with the STEM data. The cubic fluorite structure of the cerium oxide nanoparticles was confirmed by the vibrational mode around 462 cm-1 due to the Ce-08 unit. The optical band gap was estimated from UV-Vis reflectance spectra, which was found to decrease from 3.24 eV to 2.98 eV. A higher specific area was determined for the sample using M. officinalis aqueous extract. The EDX data indicated that only cerium and oxygen are present in the green synthesized nanoparticles.

Prediction of mechanical properties of concrete blended with marble stone powder by artificial neural network

The current research work is mainly concentrated on the mechanical properties concrete blended with marble stone power resulted from waste sludge marble processing it has a high specific area. M25 grade concrete mix design was considered for this research work. The mechanical properties of concrete i.e. compressive strength, unit weight, splitting tensile strength, modulus of elasticity and flexural strength were considered for the study. The compressive strength of these mixes was measured on 150mm ×150mm × 150mm cubes and tension test split tensile test 150 mm dia × 300 mm height cylinders. The concrete unit weight was considered for calculating the elastic modulus of concrete. The investigational values were matched with ACI, CEB-FIP, BIS and AASHTO LRFD empirical equation and regression analysis was done. The empirical equation result was compared with regression analysis of Artificial Neural Network, and conclusion was brough down that regression analysis of artificial neural network had better prediction than that of above-mentioned empirical equations. The study concluded that 15% replacement of marble power attained highest strength and optimum replacement, 25% replacement was concluded as economical replacement to attain designed strength.

Testing for priority effects of tree plantings on natural regeneration in restoration sites in the Brazilian Atlantic Forest

AbstractQuestionsOur study aims to understand whether priority effects or environmental filters drive community assembly in 20‐year‐old restoration areas in the Brazilian Atlantic Forest. For this, we investigated the following questions: (i) does the initial composition of planted communities (distinct combination of ecological groups) affect the natural regeneration regarding functional composition (mean trait values), diversity (functional and taxonomic), and vegetation structure? (ii) Which functional traits of the planted community have the potential to promote or constrain natural regeneration?LocationThe study was carried out in the Poço das Antas Biological Reserve, located in Rio de Janeiro state, Brazil, in a stand of 2.16 hectares with an experimental restoration design established in the year 2000 to test tree species performance of different ecological groups.MethodsIn 2020, we sampled trees with a diameter at breast height greater than 2.5 cm in 20 m × 20 m plots with four replicates per treatment and measured leaf, wood, and seed functional traits. Then, we estimated the diversity (functional and taxonomic richness), functional composition, and vegetation structure of natural regeneration, compared them between treatments, and tested which traits of the planted community influenced them.ResultsNatural regeneration exhibited significant differences between treatments, particularly regarding the diversity dimension (functional and taxonomic) and vegetation structure (basal area and abundance). Wood density, leaf phosphorus content, and leaf C:N ratio of the planted species were associated with natural regeneration (functional composition, diversity, and vegetation structure).ConclusionsPriority effects in conservative tree planting communities affect natural regeneration, while functional convergence observed in acquisitive planting communities suggests the role of environmental filtering. Communities with low wood density, low C:N ratio, and high specific leaf area, which characterize an acquisitive resource‐use strategy, exhibited higher functional and taxonomic diversity of natural regeneration, leading to the desired trajectory in ecological restoration.

Improving the composite-structured supercapacitor assembled with Ni–Co-layered double hydroxide and polymer cement electrolyte through structural optimization

The optimized nickel–cobalt double hydroxide electrode by electrodeposition has a high specific area capacitance of 10.53 F cm−2. Capacitors assembled using the optimized electrodes have a specific capacitance of up to 1.442 F cm−2.

P3MOT-decorated metal-porphyrin-based zirconium-MOF for the efficient electrochemical detection of 4-nitrobenzaldehyde.

A novel hybrid composite integrating conductive poly-3-methoxythiophene and PCN-222(Fe) (porphyrin-metal-organic frameworks) was synthesized using an in situ polymerization strategy. Leveraging the large specific area of MOFs and the low electrical resistance of conductive polymers, the modified electrode proved to be a promising candidate for the electrochemical detection of 4-nitrobenzaldehyde. The electrocatalytic response was measured using differential pulse voltammetry techniques and cyclic voltammetry, where the linear concentration range of analyte detection was estimated to be 0-900 μM and the detection limit was 0.233 μM with high selectivity toward the analyte. The sensor demonstrated repeatability and stability, allowing the direct electroanalytical measurement of 4-nitrobenzaldehyde in real samples with reliable recovery. This methodology expands the application of porphyrin MOFs for the electroanalytical sensing of environmental contaminants.

The Effect of Silver Nanoparticles/Titanium Dioxide in Poly(acrylic acid-co-acrylamide)-Modified, Deproteinized, Natural Rubber Composites on Dye Removal.

This work aims to enhance the dye-removal performance of prepared poly(acrylic acid-co-acrylamide)-modified, deproteinized, natural rubber ((PAA-co-PAM)-DPNR) through incorporation with silver nanoparticles/titanium dioxide. The (PAA-co-PAM)-DPNR was prepared by emulsion-graft copolymerization with a grafting efficiency of 10.20 ± 2.33 to 54.26 ± 1.55%. The composites based on (PAA-co-PAM)-DPNR comprising silver nanoparticles and titanium dioxide ((PAA-co-PAM)-DPNR/Ag-TiO2) were then prepared by latex compounding using the fixed concentration of AgNO3 (0.5 phr) and varying concentrations of TiO2 at 1.0, 2.5, and 5.0 phr. The formation of silver nanoparticles was obtained by heat and applied pressure. The composites had a porous morphology as they allowed water to diffuse in their structure, allowing the high specific area to interact with dye molecules. The incorporation of silver nanoparticles/titanium dioxide improved the compressive modulus from 1.015 ± 0.062 to 2.283 ± 0.043 KPa. The (PAA-co-PAM)-DPNR/Ag-TiO2 composite with 5.0 phr of TiO2 had a maximum adsorption capacity of 206.42 mg/g, which increased by 2.02-fold compared to (PAA-co-PAM)-DPNR. The behavior of dye removal was assessed with the pseudo-second-order kinetic model and Langmuir isotherm adsorption model. These composites can maintain their removal efficiency above 90% for up to five cycles. Thus, these composites could have the potential for dye-removal applications.

High ductility cementitious composites incorporating seawater and coral sand (SCS-HDCC) for offshore engineering: Microstructure, mechanical performance and sustainability

In support of sustainable development strategies, engineering construction on remote islands is conductive to promoting the development of marine resources and mitigating increasingly severe resource conflicts. However, marine engineering, facing extreme weather and natural disasters, necessitates concrete with high ductility, durability and crack control capacity. This study evaluates the feasibility of using seawater and coral sand instead of fresh water and river sand to prepare the high ductility cementitious composites (SCS-HDCC). The results indicate that increased coral sand substitution introduces defects and expands the aggregate-matrix interfacial zone due to its rough surface, high specific area, and low strength. Coral sand's internal curing enhances compactness and reduces harmful pores. The dual action of seawater and coral sand, SCS-HDCC matrix is more tenacious, and the damage and blockage during the fiber pull-out process becomes obvious, and the slip hardening coefficient of fiber-matrix interfacial zone increases. SCS-HDCC achieves satisfactory ductility (up to 1.18 %) with initial cracking strength of 4.18 MPa, ultimate tensile strength of 5.66 MPa, and crack width of 71.2 ± 6.74 μm, average crack spacing of 6.02 mm. The SCS-HDCCs prepared in this study offers economic and environmental benefits by reducing economic costs and carbon emissions through transporting raw materials from the continent. The research results have guiding significance for the construction of islands and reefs by SCS-HDCC.

How acid attack and high temperature affect the microstructure of adsorbent geopolymers

Geopolymers (GPs) are versatile materials that have low intrinsic porosity. This characteristic can be used as a motivator for the development of porous GPs, since separation processes require adsorbents with a high specific area. Thus, this work aimed to elucidate how acid attack and calcination affect the microstructure of GPs. For this purpose, a GP was exposed to H2SO4 and 200 °C, being later characterized in terms of morphology, mineralogy, functional groups, and textural properties. Acid etching and calcination proved to be effective strategies for surface area improvement, making the modified GP a strong candidate for use as an adsorbent.

A Sustainable Li-Ion Capacitor Using Sawdust-Derived Activated Carbon Cathode Paired with Prelithiated Al Foil Anode

Activated carbon (AC) has long been recognized as a promising electrode material for energy storage/harvesting devices. The extraordinarily high specific area (e.g., ~2000 m2/g) makes AC almost irreplaceable in some applications, such as electrical double-layer capacitors (EDLCs) and capacitive deionization (CDI). [1] Yet the production of AC is often a concern due to the release of unwanted contaminants, such as waste acids and gaseous CO/CO2, resulting from a series of processes involving heating, burning, and the use of strong acids.In this work, we present an activated carbon cathode that is fabricated following a more sustainable approach, namely by using sawdust waste as the carbon precursor via a physical activation process to modify its surface area and porosity. With the electrochemical performances being characterized by designated cyclic voltammetry (CV), galvanostatic charge-discharge cycling (GCD), and electrochemical impedance spectroscopy (EIS), the activation parameters, such as temperature, activation time and activation gas composition, are expected to be optimized for various application purposes.To quickly demonstrate the technical feasibility, a high-performance Li-ion capacitor (LIC) is assembled using the sawdust-derived AC cathode to pair with a piece of prelithiated Al foil anode (β-LiAl). [2] Such an LIC is considered a hybrid energy storage device that can potentially combine the high energy density of a Li-ion battery with the high power density of a supercapacitor. Despite decent electrochemical performances, the proposed LIC device using a waste-derived cathode and a simple metallic foil anode can indeed help to better realize sustainability. [3] It is believed that such a unique LIC architecture can be a promising alternative to conventional energy storage devices for various applications, such as renewable energy storage, electric vehicles, and portable electronic devices.

3D Imaging of PEMFC Electrode Microstructure by Electron Tomography and 3D FIB/SEM

Scanning and transmission electron microscopies (SEM and TEM) are two imaging techniques widely used in the study of PEMFC electrode microstructure. They have played a significant role in the improvement of electrode components and the understanding of their main degradation mechanisms. However, the currently available description of the electrode microstructure does not allow yet to unambiguously identify the key microstructural factors that limit gas and proton transport within the electrode. These factors are crucial as they control the performance of the PEMFC, especially at high current density, and are therefore the subject of numerous studies, using either fine electrochemical measurements or modeling approaches.The objective of our work is to provide an improved description of the electrode microstructure by giving quantitative information on its porosity at different scales as well as on the ionomer distribution. For this purpose, we develop 3D characterization techniques applied to the PEMFC electrodes such as electron tomography and 3D FIB/SEM.The studied cathode electrode was prepared using TEC10E50E catalyst from Tanaka that is 50 wt % loading of Pt deposited on high-specific area carbon (HSAC), and Nafion D2020. The Pt loading of the electrode is 0.2 mgPtcm-2 and the ionomer/carbon ratio is 0.8.As a first step, electron tomography analyses were performed on the Pt/HSAC powder to determine the distribution of Pt nanoparticles (NPs) which can be located either on the carbon surface (outer NPs) or inside the carbon porosity (inner NPs)[1-3]. Our strategy is to record tilt image series by using two annular detectors: i) a high angle annular detector avoiding Pt NP diffraction contrast for the 3D image reconstruction of Pt NPs (without diffraction artifact) and ii) a lower angle annular detector that enhances carbon contrast for the 3D image reconstruction of the carbon phase. These two segmented images were then combined (Figure 1), allowing the calculation of the NP size histogram but also of the volume and the surface area of the two NP populations (inner and outer NPs).On the second step, the porosity of the electrode was analyzed by 3D FIB/SEM. A volume of around 10 X 10 x 5 μm3 was imaged with a cubic voxel size of 5 × 5 × 5 nm3. The solid phase (carbon, Pt NPs and ionomer) segmentation was based on a composite image created from two electron detectors (secondary and backscattered electrons) and using a machine learning software. Quantitative data such as the total porosity, the pore size distribution or the agglomerate size distribution of the solid phase were extracted from this volume. Figure 2a shows a 2D slice of this segmented volume where the solid phase is in black and the porosity in white.In order to analyze the electrode porosity with a higher spatial resolution, electron tomography experiment was also performed on a 150 nm thick slice of the electrode cut by ultramicrotomy after being embedded in an epoxy resin. The tilt image series were recorded with a pixel size of 0.5 nm and a field of view of 2 x 2 µm2. The 2D slice of the reconstructed volume (Figure 2b) shows that the largest solid agglomerates detected on the 3D FIB/SEM image can be identified as an agglomeration of numerous carbon particles. The challenge now is to quantify the porosity created between these carbon particles and to determine how many Pt NPs are located in these large agglomerates.Finally, the distribution of the ionomer was analyzed within the electrode similarly to [4]. For this analysis, a 150 nm slice of the electrode was cut by cryo-ultramicrotomy without embedding in epoxy resin as described in [5]. TEM images show that the ionomer is not homogeneously distributed on the surface of the entire carbon particles but is often observed in the concave surface created between the carbon particles (Figure 3). These observations suggest a ionomer distribution in agreement with the heterogeneous ionomer coating model proposed by Inoue et al. [6]. We also suggest that a part of the ionomer could be localized in the small pores located inside the large carbon agglomerates described in the previous paragraph. This could explain why the ionomer is so difficult to detect on TEM images. This work has been done in the frame of the FURTHER-FC project. This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under Grant Agreement No 875025. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research. Figure 1

The vertical electrical sounding (VES) of the epikarst: A case study of the covered karst of the Bakony region (Hungary)

The epikarsts of five covered karst areas in the Bakony region are compared. The comparison is based on the specific resistances of the bedrock resistance averages measured by vertical electrical sounding (VES). The average largest specific resistance differences (per area) and the mean values (per profile) were calculated to investigate the characteristics of the epikarst. The mean values of specific resistance were compared using analysis of variance (ANOVA) to determine whether the specific resistances of the areas showed significant differences. The studied karst areas can be categorised as high or low specific resistance areas, and the ANOVA method could be applied to three areas based on the available data. It can be concluded that the mean values of their specific resistances are significantly different. The mean values and standard deviation of the specific resistances of the different areas were analysed. It is described that the karst receives less water in the case of areas with lower specific resistance, while it receives more water in the case of areas with higher specific resistance. Areas with a high specific resistance are less karstified, while areas with a low specific resistance are more karstified. Low specific resistances and small mean values indicate a higher degree of cavity formation in the epikarst, while the decrease in mean values and standard deviation indicates increasing uniformity of the degree of cavity formation in the epikarst. The different degree of cavity formation is explained by the different karstification rates and the exposure of different time of certain areas.

A Facilely Synthesized NiCo2S4 with Two Mutually Reinforcing Active Sites for High-Performance Lithium-Sulfur Batteries.

The shuttle effect and slow conversion kinetics of soluble polysulfides hinder the commercial application of lithium-sulfur batteries (LSBs). In this context, we propose a three-dimensional lamellar-stacked nanostructure of nickel cobalt sulfide (D-NiCo2S4) enriched with lattice defects by manipulating the cations in spinel sulfides. It has an obvious synergistic promotion mechanism for the adsorption and catalysis of lithium sulfides. Specifically, Ni3+ on tetrahedral (Td) sites with strong Ni-S covalency anchors LiPSs, whereas Co3+ on octahedral (Oh) sites promotes a highly efficient catalytic conversion of LiPSs, which is confirmed by experimental results and density functional theory (DFT) calculations. Besides, the crystal defects and distortions in the lamellar region could expose more active sites and enhance the redox reaction kinetics of polysulfides. Hence, Li-S batteries with D-NiCo2S4@S as the cathode show outstanding cycle stability; upon cycling at 1 A/g, the battery achieves a high initial specific capacity of 1001.12 and 655.31 mAh g-1 after 1000 cycles (decay rate as low as 0.05% per cycle), as well as a high initial areal capacity of 3.15 mAh cm-2 under high S loading (4.2 mg cm-2). This work provides a viable scheme for designing efficient bimetal sulfide catalysts and furnishes a rational strategy for constructing LSB cathodes with high specific capacity and high area capacity.

A Facile One-Pot Synthetic Approach Towards CB@PCN-222(Fe) Composites for Simultaneous Electrochemical Detection of Dihydroxybenzene Isomers

A novel porphyrin-metal organic frameworks (MOFs) based hybrid composite was created by combining conductive carbon black (CB) and PCN-222(Fe) (PCN = porous coordination network) via a one-pot strategy. The proposed material unquestionably takes advantage of the high specific area from MOFs and the strong conductivity of CB, which contributes to the contact with analytes and detection sensitivity. A series of analyses showed that the proposed modified electrode could be an alternative candidate for electrochemical detection of dihydroxybenzene isomers. A good linear correlation occurred between the differential pulse voltammetry current and the concentration of hydroquinone (HQ), catechol (CC) and resorcinol (RC) under the optimized conditions. With low detection limits (0.122, 0.094 and 0.243 μM) at the ranges (0.5–280, 0.5–280 and 0.5–320 μM) of these isomers mentioned above, the sensor exhibited good cost-effectiveness, repeatability and stability. Our methodology drives us to directly analyze the dihydroxybenzene isomers in actual samples with dependable recovery, further broadening the electrochemical detection field for environmental pollutants based on porphyrin MOFs.

Inverse priority effects: The order and timing of removal of invasive species influence community reassembly

Abstract An ongoing restoration challenge is to recover native communities after the removal of invasive species. Because priority effects (i.e. the order and timing of species arrival) can strongly determine the trajectory of community assembly, their intentional manipulation is gaining attention to manage invasive plants and achieve restoration goals. Yet, ecologists and conservationists rarely consider how the order and timing of species removal—inverse priority effect—may impact future plant communities. Here, we evaluated the dependence of community reassembly on inverse priority effects by experimentally removing the target invasives Sweetbriar rose (Rosa rubiginosa) and Scotch broom (Cytisus scoparius) in field and mesocosm communities. We manipulated removal order (rose before broom vs. broom before rose) and timing (simultaneously early vs. simultaneously late in the season). We performed a hierarchical modeling of species sommunity to assess differences in community structure in response to order and timing of removal, and to evaluate whether species origin and leaf and seed traits were associated with species responses. We found that the order of removal was as important as timing driving community reassembly. Simultaneous removal favoured nonnatives, more so when performed early. Sequential removals led to contrasting communities. Rose before broom removal also favoured nonnative grasses at expense of native species, whereas the inverse order produced small changes in communities. In general, species with high specific leaf area were boosted, regardless of their seed size. Synthesis and applications. Inverse priority effects are neglected mechanisms that can drive variability in the reassembly of plant communities and can potentially upgrade invasive species management. These historical contingencies suggest the existence of an optimal order of removal that facilitates the recovery of the native community. We found that simultaneous removal promoted secondary invasions to a greater extent than sequential removals. Furthermore, removal order affected post‐removal community structure. In our system, we suggest removing the rose before the broom to hinder nonnatives and pave the way for restoration of native communities. Our results show that manipulation of the order and timing of removal can help to achieve restoration goals.

Loose nanofiltration membranes prepared by rapid co-deposition of HMMP-1 and dopamine for dye/salt highly selective separation

Loose nanofiltration membranes (LNMs) prepared by co-deposition of polyphenols and amine-rich polymers has been considered as an effective method for the efficient treatment of textile wastewater. However, the dye/salt selectivity remains unsatisfactory, due to the low free volume with wide distribution caused by the stacking and tight entanglement of polymeric chain segments. A high dye/salt selective LNM was prepared for the first time by rapid co-deposition of high-valent metal-induced microporous polymer framework (HMMP-1) and dopamine (DA). HMMP-1 with high specific area and suitable pore size can provide additional transfer channels for water/salt, breaking the limitation of free volume generated by polymer stacking and further improving perm-selectivity. In addition, the amine-rich HMMP-1 with a flexible polymer framework can be covalently linked to DA by Michael addition/Schiff base reaction, effectively avoiding the selectivity reduction caused by poor interfacial compatibility. The results showed that the pure water permeance of the optimal membrane (LNM-2) was 57.22 LMH·bar−1, which was 0.65 times higher than that of LNM-1 (without HMMP-1). In addition, LNM-2 exhibited excellent dye/salt selectivity for dye/salt mixtures with different concentrations, reaching >47 (CR/NaCl) and >29 (CR/Na2SO4), respectively, which is more than twice of the conventional membranes reported so far. Moreover, the dye/salt selectivity of LNM-2 still maintained at 28 (CR/Na2SO4) and 55 (CR/NaCl) respectively for 12 h, when salt concentration was 10 g L−1, which fully demonstrated the good stability of LNM-2 and the superiority of HMMP-1 for the design of LNM.

Modification of Pillared Intercalated Montmorillonite Clay as Heterogeneous Pd Catalyst Supports.

Montmorillonite clay was modified by pillaring with AlMn oxides in different Al/Mn ratios and intercalation of two kinds of N-containing polymers (i.e., chitosan (CS) and polyvinyl pyrrolidinone (PVP)) chains. The modified pillared montmorillonite clay (PM) showed a rich two-dimensional layered porous structure with tunable parameters, such as large interlayer spacing, high specific area, and large porous volume. They were then used as supports for Pd nanoparticles. As applied in coupling reactions of aryl halides with terminal alkynes, Pd@CS/AlMn-PM showed better comprehensive catalytic performance than Pd@PVP/AlMn-PM. This was mainly attributed to its higher specific area, stronger chelation to Pd species, and better solvent resistance.

A covalent organic frameworks@gold nanoparticles@graphene nanocomposite based electrochemical sensor for simultaneous determination of trace Cd2+, Pb2+ and Cu2+

It's very exciting to develop an electrochemical sensor for simple, rapid and simultaneous determination of heavy metal ions in Baijiu by applying new nanocomposites. Herein, a novel COFDPTB@gold nanoparticles (AuNPs)@graphene (GR) was obtained via combining COFDPTB synthesized using the Schiff-base condensation between 2, 5-dimethoxyterephthalaldehyde and 1, 3, 5-tris(4-aminophenyl) benzene with AuNPs and GR. Owing to the high porosity and abundant adsorption sites of COFDPTB, the outstanding electrical conductivity of AuNPs and GR, as well as the high specific area and synergy of COFDPTB, AuNPs and GR, the proposed sensor exhibited excellent analysis performance for the detection of Cd2+, Pb2+ and Cu2+. Under optimized conditions, the sensor showed good linearity range of 0.5–18 μM for Cd2+, and both 0.5–6.0 μM for Pb2+ and Cu2+ with the detection limits of 3.025 nM, 5.849 nM and 9.993 nM, respectively. In addition, the recovery measurement suggested the practicality of the prepared sensor.

Sulfone-functionalized metal–organic framework aerogels for selective CO2 capture from natural gas

The accumulation of CO2 in natural gas may reduce the heating value and even pose a risk of corrosion in transport pipelines, making the effective removal of CO2 highly essential. Metal–organic frameworks (MOFs), known for their high specific area and large porosity, show promising application in CO2 capture. However, a major obstacle is their intrinsic fragility and poor physicochemical stability. Herein, we present a sulfone-incorporated in-situ growth and fiber freeze-shaping strategy to develop lightweight, robust, and multiscale porous sulfone-functionalized UiO-67 (UiO-67-SO2) aerogels supported by aramid nanofibers. The resulting UiO-67-SO2 aerogels exhibit remarkable structural features, including a high MOF loading mass (64.39 wt%), low density (5.31 mg/cm3), high specific surface area (769.98 m2g−1), and large porosity (99.24 %). Moreover, owing to the introduction of CO2-philic sulfone groups, the UiO-67-SO2 aerogels exhibit high CO2 adsorption capacity (5.88 mmol/g), a high CO2/CH4 adsorption selectivity (43), and only a 2.77 % decline in their initial CO2 adsorption capacity after 10 cycles. The adsorption energy calculated by density functional theory method further confirms the strong interactions between UiO-67-SO2 aerogels and CO2 molecules. This work presents a promising direction for developing multiscale porous UiO-67-SO2 aerogels for the highly selective removal of CO2 from natural gas.

Low-temperature gas sensor with good long-term stability based on Co3O4/Ti3C2Tx heterojunction

As one of the two-dimensional (2D) nanomaterials, MXene exhibits great potential on gas-sensing owing to its high specific area, rich functional groups and great charge transfer mobility. Herein, electrostatic adsorption and calcination strategies were taken for ZIF-derived Co3O4 and alkalized Ti3C2Tx MXene to fabricate Co3O4/MX7.5 heterojunction. It can be found that Co3O4 nanoparticles (NPs) uniformly grow on the surface of alkalized Ti3C2Tx. Alkalized Ti3C2Tx with lower work function (lower than 3.9 eV) can transfer more electrons towards Co3O4 and promote the redox of Co2+. These increased Co2+ ions can help to adsorb more adsorbed oxygen and produce more oxygen defects, which enhances contact interaction between ethanol molecules and adsorption sites. The formation of heterojunction between Co3O4 and MXene is observed by UV–vis spectra, and this interface effect enhances the ability of gas sensors. Therefore, the sensors based on the obtained Co3O4/MX7.5 heterojunction can operate at a relatively low temperature (140 °C) with a response of 3500 % and a low detection limit of 1 ppm. And it also delivers long-term stability (about 30 days). This work demonstrates practical application for detecting ethanol at a relatively low working temperature and keeping their response in a long term.