Bifunctional NH2-MIL-88(Fe) nanooctahedra have been successfully fabricated for highly sensitive and specific recognition as well as efficient removal of arsenate.

Excessive uptake of nitrite has been proven to be detrimental to the ecological system and human health. Hence, there is a rising requirement for constructing effective electrochemical sensors to precisely monitor the level of nitrite. In this work, NiFe-layered double hydroxide nanosheet arrays (NiFe-LDH NSAs) have been successfully fabricated on a carbon cloth (CC) substrate via a facile one-pot hydrothermal route. By integrating the collective merits of macroporous CC and NiFe-LDH NSAs such as superior electrical conductivity, striking synergistic effect between the dual active components, enlarged electrochemically active surface area, unique three-dimensional hierarchical porous network characteristics, and fast charge transport and ion diffusion, the proposed NiFe-LDH NSAs/CC architecture can be served as a self-supporting sensor toward nitrite detection. As a consequence, the resulting NiFe-LDH NSAs/CC electrode demonstrates superior nitrite sensing characteristics, accompanied by broad linear range (5-1000 μM), quick response rate (ca. 3 s), ultralow detection limit (0.02 μM), and high sensitivity (803.6 μA·mM·cm). Meanwhile, the electrochemical sensor possesses timeless stability, good reproducibility, and strong anti-interference feature. Importantly, the resulting sensor can determine nitrite level in tap and lake water with high recoveries, suggesting its feasibility for practical applications. These findings show that the obtained NiFe-LDH NSAs/CC electrode holds great prospect in highly sensitive and specific detection of nitrite.

Eutrophication of water bodies caused by the excessive phosphate discharge has constituted a serious threat on a global scale. It is imperative to exploit new advanced materials featuring abundant binding sites and high affinity to achieve highly efficient and specific capture of phosphate from polluted waters. Herein, water stable Zr-based metal organic frameworks (MOFs, UiO-66) with rational structural design and size modulation have been successfully synthesized based on a simple solvothermal method for effective phosphate remediation. Impressively, the size of the resulting UiO-66 particles can be effectively adjusted by simply altering reaction time and the amount of acetic acid with the purpose of understanding the crucial effect of structural design on the phosphate capture performance. Representatively, UiO-66 particles with small size demonstrates 415 mg/g of phosphate uptake capacity, outperforming most of the previously reported phosphate adsorbents. Meanwhile, the developed absorbents can rapidly reduce highly concentrated phosphate to below the permitted level in drinking water within a few minutes. More significantly, the current absorbents display remarkable phosphate sorption selectivity against the common interfering ions, which can be attributed to strong affinity between Zr-OH groups in UiO-66 and phosphate species. Furthermore, the spent UiO-66 particles can be readily regenerated and reused for multiple sorption-desorption cycles without obvious decrease in removal performance, rendering them promising sustainable materials. Hence, the developed UiO-66 adsorbents hold significant prospects for phosphate sequestration to mitigate the increasingly eutrophic problems.

The rational design of metal-organic frameworks with tailored components and structural features is crucial for achieving the desired functions and expanding the emerging applications. Herein, water-stable bimetallic Fe/Mg metal−organic frameworks (Fe/Mg-MIL-88B) have been successfully fabricated through a facile and effective one-step strategy to access the exceptional arsenic decontamination. Notably, the obtained bimetallic Fe/Mg-MIL-88B architectures are demonstrated to possess a well-defined spindle-like morphology. Interestingly, the Fe/Mg molar ratios within the resultant Fe/Mg-MIL-88B frameworks can be flexibly modulated on demand, leading to the variation of the structural features associated with length/diameter ratio and unit cell parameters along with surface areas. Thanks to the unique structural and compositional merits as well as the synergetic contribution from two active metal centres, the fabricated Fe/Mg-MIL-88B nanospindles exhibit enhanced decontaminant performance toward arsenate in terms of ultrafast sorption kinetics and high sorption capacities, compared to the monometallic Fe-MIL-88B.

Here, we report ZIF-8-reduced graphene oxide (ZIF-8−rGO)-supported bimetallic AuPt nanoparticles (AuPtNPs) as a novel peroxidase mimic for high-sensitivity detection of H 2 O 2 in neutral solution. ZIF-8−graphene oxide (ZIF-8−GO) is first synthesized via a simple wet-chemistry process and subsequently immobilized with AuPtNPs via a reduction method. The resultant AuPt/ZIF-8−rGO shows enhanced peroxidase-like catalytic activity and it is applied for the electrochemical detection of H 2 O 2 in a wide concentration range, from 100 nM to 18 mM, with a very low detection limit of 19 nM (S/N = 3). This good electroanalytical performance of AuPt/ZIF-8−rGO is owing to the ultrasmall size and high dispersion of the AuPtNPs, the strong metal−support interaction between the AuPtNPs and ZIF-8−rGO bisupport, and the sandwich-like structure comprising porous ZIF-8 and loosely packed rGO nanosheets. The AuPt/ZIF-8−rGO is employed for the practical detection of H 2 O 2 in human serum samples with desirable properties. Therefore, the novel AuPt/ ZIF-8−rGO is a promising nanozyme for various biotechnological and environmental applications.

In this work, a simple, general, and sensitive potentiometric platform is presented, which allows potentiometric sensing to be applied to any class of molecule irrespective of the analyte charge. DNA nanostructures are self-assembled on magnetic beads via the incorporation of an aptamer into a hybridization chain reaction. The aptamer− target binding event leads to the disassembly of the DNA nanostructures, which results in a dramatic change in the surface charge of the magnetic beads. Such a surface charge change can be sensitively detected by a polycation-sensitive membrane electrode using protamine as an indicator. With an endocrine disruptor bisphenol A as a model, the proposed potentiometric method shows a wide linear range from 0.1 to 100 nM with a low detection limit of 80 pM (3σ). The proposed sensing strategy will lay a foundation for the development of potentiometric sensors for highly sensitive and selective detection of various targets.

In this paper, a new class of metal-free nanocarbon catalyst-nitrogen (N) and sulfur (S) codoped graphene quantum dot/graphene (NS-GQD/G) hybrid nanosheets-was designed and synthesized for sensitive detection of hydrogen peroxide (HO). NS-GQD/G was prepared through two steps. First, graphene quantum dots (GQDs) were self-assembled on graphene nanoplatelets via hydrothermal treatment to constitute hybrid nanosheets, followed by a thermal annealing procedure using the hybrid nanosheets and thiourea to form the NS-GQD/G hybrid nanosheets. This hybrid material possessed high specific surface area, numerous doping sites and edges, and high electrical conductivity, which leads to ultrahigh performance toward HO electrocatalysis reduction. Under the optimal experimental conditions, the proposed HO sensor displayed an extended linear response in the range from 0.4 μM to 33 mM with a low detection limit of 26 nM (S/N = 3). In addition to desirable selectivity, ideal reproducibility, and long-time stability, this HO sensor exhibited desirable performance in detecting HO in the human serum samples and that released from Raw 264.7 cells. Therefore, the novel NS-GQD/G nanocomposite was a promising metal-free material in the fields of electrochemical sensing and bioanalysis.

A CuS nanoflakes–reduced graphene oxide nanocomposite was synthesized successfully for non-enzymatic glucose sensing.