•We synthesized water-soluble striking fluorescent Cu nanoclusters (Cu NCs) by a simple one-pot chemical reduction method.•This proposed synthetic strategy does not need without any auxiliary ...stabilizer, organic agent or strong reducing agents.•The prepared Cu NCs show great stability and biocompatible which is essential for construction assays for biological systems.•The nitrite ions fluorescent sensor was successfully constructed based on the prepared Cu NCs.
The instant and on-site detection of trace aqueous nitrite ions still remains a challenge for environmental monitoring and protection. In this work, we synthesized water-soluble striking fluorescent Cu nanoclusters (Cu NCs) by a green, simple, one-pot and stabilizer-free chemical reduction method. The fluorescence (FL) of the obtained Cu NCs can be selectively and efficiently quenched by the nitrite ions through the oxidation of Cu (0) atoms to Cu (I) in the core of Cu NCs. Under optimal conditions, two excellent linear relationships between the FL quenching degree of the Cu NCs and the concentrations of nitrite ions in the range of 0.0125–125μM and 125–5000μM with a low detection limit of 3.6nM were obtained. More importantly, the portable paper-based sensor has been explored for visual detection of trace nitrite ions in aqueous solution by the appearance of different degrees of blue FL under a UV lamp. The very simple and effective strategy reported here should facilitate the development of portable and reliable FL chemosensors for nitrite ions in pollution control.
An electrochemical sensor was fabricated for arsenite detection using graphene oxide-assisted generation of prussian blue nanoparticles as enhanced redox signal label. The 5′-thiolate-labeled ...(GT)21-ssDNA was first self-assembled on a gold electrode surface via Au-S bond. Graphene oxide can interact with ssDNA through π-π stacking interaction and facilitate the generation of prussian blue nanoparticles on its surface as an electrochemically active indicator. In the absence of arsenite, plenty of graphene oxide/prussian blue nanoparticles can be adsorbed on the electrode surface to produce a stronger redox signal of prussian blue nanoparticles. While in the presence of arsenite, (GT)21-ssDNA can recognize and combine with arsenite via hydrogen bonds to form (GT)21-ssDNA/arsenite complex with a frizzy structure. The conformational change of (GT)21-ssDNA led to less adsorption of graphene oxide/prussian blue nanoparticles on the electrode surface, resulting in a reduced redox response. The arsenite-induced (GT)21-ssDNA structure switching can be used for sensitive detection of arsenite with a linear range from 0.2 to 500 ppb and a detection limit down to 0.058 ppb. Benefiting from (GT)21-ssDNA containing arsenite recognition sequence, the proposed sensor exhibited excellent specificity against other heavy metal ions. The applicability of the electrochemical biosensor for arsenite assay in real water samples demonstrated the great potential of this strategy for trace arsenite detection in environment.
Display omitted Schematic illustration of the sensor fabrication process and the generation of prussian blue nanoparticles on graphene oxide sheets used as electrochemical signal label for As(III) detection.
•Graphene oxide was used as supporting matrix for the in-situ generation of PB NPs.•Adsorption of GO on ssDNA can be regulated by As(III)-induced conformational change of (GT)21-ssDNA.•A sensor for As(III) detection was designed using GO-assisted generation of PB NPs as enhanced signal label.•The sensor showed high sensitivity for As(III) with a detection limit of 0.058 ppb.•The biosensor can be used for selective detection of As(III) in real water samples.
Display omitted
•The SnS2-covalent organic framework van der Waals heterojunction (SnS2COF) was constructed.•With good photoelectric properties, SnS2COF can realize separation and transfer of ...electron-hole.•The electron flow path of heterojunction conforms to Z-scheme by experimental study and theoretical calculation.•SnS2COF can effectively reduce and remove U (VI) from rare earth tailings wastewater under UV/Vis light.
Uranium removal by photocatalytic reduction is one of the most promising methods to reduce radioactive contamination in wastewater. Herein, a Z-scheme van der Waals heterojunction photocatalyst (SnS2COF) was synthesized in situ by combining covalent organic frameworks (COF) with semiconductor (SnS2) for U (VI) reduction in rare earth tailings wastewater. The synthesis method of van der Waals heterojunction is simple and solves the problem of no hanging bond in composite components. In this heterojunction, large areas of van der Waals interaction form high-speed electron transport channels. In addition, it is deduced that SnS2COF fits the Z-scheme heterojunction electron transport mode through the theoretical calculation of the ground state and excited state electron density difference and the related band structure. Under the photoexcitation, the direction of electron flow is reversed, which further promotes the separation of the photogenerated electron (e−)-hole (h+) under the action of the built-in electric field, maintains the high reducibility of the conduction band, and avoids the photocorrosion of SnS2. Compared with inorganic-inorganic heterojunction, SnS2COF has a wider light absorption range, more active sites, and higher e−-h+ separation and transfer efficiency. Therefore, it had a higher U (VI) reduction removal capacity, up to 1123.3 mg g−1, far surpassing the SnS2 and COF counterparts under ultraviolet/visible light. And the U (VI) removal rate reached 98.5 % in rare earth tailings wastewater. The design concept of organic–inorganic heterojunction materials provides an alternative strategy for improving the photocatalytic performance.
We proposed a strategy to synergistically enhance uranium capture capacity through photothermal desalination, and prepared a COF hydrogel (KTG) through a simple process for the first time. KTG with ...ideal broadband light absorption capacity could be used as an outstanding photothermal conversion material. Meanwhile, the built-in elastic honeycomb structure endowed the KTG with good mechanical properties and adequate water transport performance that accelerated the diffusion and mass transfer ability of uranyl. Under a simulated sunlight, the adsorption capacity, selectivity, adsorption rate and cycle capacity of uranium could be significantly improved. Moreover, benefiting from the outstanding photocatalytic performance, KTG exhibited a high anti-fouling activity against marine biological entities, thereby achieving long-term efficient uranium adsorption and solar desalination.
Display omitted
•The first example of COF hydrogel for solar desalination and uranium recovery.•COF hydrogel for synergistically enhance uranium capture through photothermal desalination.•COF hydrogel shows a high evaporation rate and exceptional uranium recovery capacity.•COF hydrogel has high anti-biofouling activity and good reusability.
Capturing of uranium from the natural seawater is considered to be one of the most promising methods to meet the current demand for nuclear energy. Herein, we prepared a reduced graphene oxide-based (rGO-based) covalent organic framework hydrogel (KTG) with three-dimensional porous structure as a platform for enhancing uranium capture capacity through photothermal desalination. Under light irradiation, the KTG produces a local heat that can be used to generate steam while promoting the rapid diffusion of uranium inside the hydrogel 3D network, thereby increasing the adsorption efficiency and capacity of uranium. KTG can achieve exceptional uranium capture capacity (521.6 mg g−1) under one sun irradiation, which is 42.4% higher than that under dark conditions. In addition, excellent photocatalytic activity and mechanical properties make KTG possess high anti-biofouling activity, good reusability, and achieving continuous uranium capture and solar distillation.
Nanozymes are nanomaterials with enzyme-mimetic activity. It is known that DNA can interact with various nanozymes in different ways, enhancing or inhibiting the activity of nanozymes, which can be ...used to develop various biosensors. In this work, we synthesized a photosensitive covalent-organic framework (Tph-BT) as a nanozyme, and its oxidase and peroxidase activities could be reversely regulated by surface modification of single-stranded DNA (ssDNA) for the colorimetric detection of UO
. Tph-BT exhibits excellent oxidase activity and weak peroxidase activity, and it is surprising to find that the UO
-specific DNA aptamer can significantly inhibit the oxidase activity while greatly enhancing the peroxidase activity. The present UO
interacts with the DNA aptamer to form secondary structures and detaches from the surface of Tph-BT, thereby restoring the enzymatic activity of Tph-BT. Based on the reversed regulation effects of the DNA aptamer on the two types of enzymatic activities of Tph-BT, a novel "off-on" and "on-off" sensing platform can be constructed for the colorimetric analysis of UO
. This research demonstrates that ssDNA can effectively regulate the different types of enzymatic activities of single COFs and achieve the sensitive and selective colorimetric analysis of radionuclides by the naked eye.
Display omitted
•We reported a novel colorimetric biosensor for the assay of DNA methyltransferase activity.•Strand displacement amplification was employed for M.SssI activity inhibition assay.•With ...the advantages of SDA, highly sensitive detection of M.SssI activity and inhibition was achieved.
In this paper, we present a colorimetric method for the assay of DNA methyltransferase (MTase) activity based on strand displacement amplification (SDA). In our study, a well-designed hairpin DNA I (HPI) containing the sequence of 5′-CCGG-3′ is specifically recognized by CpG methyltransferase (M.SssI) and HpaII endonuclease. The methylated HPI is able to coexist with all the DNA and enzymes in the solution while the unmethylated HPI can be cleaved into single-stranded DNA (ssDNA) fragments. The amplification can be triggered by the HpaII digestion products hybridization with another hairpin structure DNA II (HPII) to form a duplex, which would be replaced by probe DNA, leading to the aggregation of gold nanoparticles (AuNPs). Simultaneously, ssDNA fragments released from the duplex, and triggered the cycle anew. Varying concentrations of M.SssI in the solution therefore would lead to differences of absorption and color changed from red to pale. A linear response was obtained when the M.SssI concentration ranging from 0.2 to 50UmL−1 with a detection limit of 0.08UmL−1. In addition, the developed assay in this study can also be applied to screen the inhibitors of M.SssI.
A label-free, sensitive and simple method to detect protein kinase based on the selective aggregation of phosphorylated peptide-gold nanoclusters (peptide-AuNCs) triggered by Zr4+ ion coordination is ...developed. The AuNCs were synthesized by peptide without any strong reducing agents, which prevent peptides from being disrupted. Under optimal conditions, a linear relationship between the decreased PL intensity of peptide-AuNCs and the concentration of casein kinase II (CK2) in the range of 0.08–2.0unitmL−1 with a detection limit of 0.027unitmL−1 (3σ) was obtained. The feasibility of this AuNCs-based sensor was further demonstrated by the assessment of kinase inhibition by ellagic acid, 5,6-dichlorobenzimidazole-1-β-d-ribofuranoside, emodin, and quercetin in human serum. As expected, the PL intensity increased with increasing inhibitor efficiency in the presence of inhibitors. The IC50 value (inhibitor concentration producing 50% inhibition) for ellagic acid was estimated to be 0.045μM. With more sophisticated design of the peptide substrate sequences, the detection of other enzymes will be realized. With characteristics of homogeneous, facile, universal, label-free, and applicable for kinase assay, the proposed sensor provides potential application in kinase-related biochemical fundamental research and inhibitor screening.
•We reported a novel fluorescence assay base on peptide-AuNCs for sensitive analysis of protein kinase CK2 activity.•The peptide-AuNCs was synthesized in situ without any coupling and reducing agents.•Sensitive detection of CK2 based on the aggregation quenching mechanism.•Highly sensitive detection of CK2 activity and inhibition was achieved.
Display omitted
•The synthesis of bi-function natural polymers is simple without expensive catalytic agents.•Bi-function natural polymers show superior selectivity and fast adsorption kinetics for ...recovery of gold.•Bi-function natural polymers act as the adsorbents for gold recovery through the synergistic mechanisms of adsorption and reduction.•The PDA-TFN-A exhibits outstanding Au(III) adsorption capacity up to 2771.8 mg/g at pH 2.0.
Designing and synthesizing cost-effective and biodegradable adsorbents for recovering gold from electronic acidic waste have immense sustainable development significance. Herein, three natural macromolecules (polydopamine, chitosan and cellulose) as raw materials were selected to be chemically crosslinked with tetrafluoroterephthalonitrile (TFN) through aromatic nucleophilic reaction, respectively. Then cyano groups of the cross-linked products were converted into amides under alkaline conditions then gained PDA-TFN-A, Chitosan-TFN-A and Cellulose-TFN-A for specifically binding gold. The gold adsorption capacities were 2771.8, 2680.0 and 1992.0 mg g−1 for PDA-TFN-A, Chitosan-TFN-A and Cellulose-TFN-A, respectively. Moreover, various physicochemical and spectroscopic studies provided insight into the binding process, confirming the highly efficient adsorption and in-situ reduction of gold of bifunctional natural polymers based on the interaction of amide functional groups with Au and chloro gold complexes. In addition, the comparative analysis proved the optimum behavior of bi-functional natural polymer PDA-TFN-A with high capacity, selectivity, stability, and fast adsorption kinetics (15 min) for adsorption of gold. This work delineated a promising strategy for the application of eco-friendly natural polymers to solve environmental problems.
Display omitted
•Indium-based MOF is synthesized for the efficient removal of iodine from both the vapor and aqueous.•In-MOF exhibits high hydrostability even in seawater for 30 days.•In-MOF shows ...high selectivity and adsorption capacity for I3-.•In-MOF shows high-efficiency removal for iodine in seawater.
The highly efficient removal of radioactive iodine from nuclear accident-polluted seawater is of great significance for the purpose of environmental protection. Herein, we report an indium-based metal–organic framework, named In-MOF, for highly efficient removing iodine from seawater. In-MOF is constructed by In3+ ions coordinated with tris (4-(1H-imidazol-1-yl) phenyl) amine and exhibits high chemical stability even under seawater for 30 days. Due to the flexible one-dimensional linear structure and high-density charged imidazolium groups, In-MOF possesses a high adsorption capacity (1138 mg/g) for iodine in water. Furthermore, it exhibits high selectivity in the presence of competitive ions, due to forming the unique I-π interactions between iodine and the In-MOF. Notably, these excellent adsorption features endowed In-MOF successfully remove iodine from seawater with a high removal rate of 93.86%. These results are of fundamental importance to understanding iodine uptake and designing materials with high adsorption capacity.
