Search

Surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) integrated with mussel-inspired polydopamine (PDA) chemistry was, for the first time, employed for controlled grafting of poly(glycidyl methacrylate) (PGMA) brushes from carbon nanotubes (CNTs). The strategy initially involved deposition of a PDA layer by spontaneous self-polymerization, which is a benign and nonsurface specific way for anchoring 2-bromoisobutyryl bromide to form initiators on the CNTs. Dense and uniform PGMA brushes were then grown via ARGET ATRP using low concentration of Cu catalyst in different solvents. With abundant highly reactive epoxy groups, the PGMA-grafted CNTs could serve as a versatile platform for further modification or functionalization. Ethylenediamine ligands were facilely introduced, imparting the functionalized CNTs with record-high adsorption ability toward uranium ions among CNTs composites. The integrated strategy combining surface-initiated ARGET ATRP technique and PDA chemistry would provide new opportunities for surface engineering of nanomaterials for advanced applications.

The authors have studied the role of different ligands on the surfaces of silver nanoplates for regulating their analytical applications. Citrate-capped silver nanoplates are applied for the detection of chromium ions (Cr3+) based on aggregation of silver nanoplates. Cr3+ can cause aggregation through high affinity between Cr3+ and carboxylate groups of citrates, resulting in a color change from dark yellow to purple and at last colorless. The detection limit is 8.0 nM. This system shows excellent selectivity in the presence of a variety of other metal ions. Further, silver nanoplates coupled with iodide ions are employed for the colorimetric determination of copper ions (Cu2+) based on a new strategy of fusion/oxidation etching nanoplates. When Cu2+ is introduced into this silver nanoplate system, Cu2+ can oxidize I− to iodine (I2), which can further oxidize silver to form silver iodide (AgI). Simultaneously, the solution color changes from dark yellow to colorless. The lower limit detection is 0.27 μM. This assay exhibits excellent selectivity for Cu2+ over other environmental metal ions. It is perceived that this design concept will open up a fresh insight of simple, rapid and reliable detection of other heavy metal ions in drinking water and environmental samples.

A key challenge of photoregulated living radical polymerization is developing efficient and robust photocatalysts. Now carbon dots (CDs) have been exploited for the first time as metal-free photocatalysts for visible-light-regulated reversible addition-fragmentation chain-transfer (RAFT) polymerization. Screening of diverse heteroatom-doped CDs suggested that the P- and S-doped CDs were effective photocatalysts for RAFT polymerization under mild visible light following a photoinduced electron transfer (PET) involved oxidative quenching mechanism. PET-RAFT polymerization of various monomers with temporal control, narrow dispersity (Đ≈1.04), and chain-end fidelity was achieved. Besides, it was demonstrated that the CD-catalyzed PET-RAFT polymerization was effectively performed under natural solar irradiation.

Artificial enzyme mimics based on nanomaterials have attracted sustained attention owing to their multiple advantages compared with natural enzymes. However, there are a few enzyme self-cascade systems for the highly sensitive detection of analytical targets. Herein, we have described a self-cascade catalytic system based on single-component cupric oxide nanoparticles (CuO NPs) for an ultrasensitive fluorescent detection toward glutathione (GSH) and Ag+ ions. The limit of detection is lower for nanomolar (nM) and picomolar (pM) levels for GSH and Ag+, respectively. To the best of our knowledge, for the first time, we find that CuO NPs possess the intrinsic GSH-oxidase and peroxidase-like activity as a dual-functional nanozyme, coupling with terephthalic acid (TA) and GSH to construct a self-cascade fluorescent system. The turn-on fluorescence signal of oxidation hydroxyterephthalate (TAOH) is generated in the presence of GSH. Then, the fluorescence of a reaction mixture is quenched after the addition of A...

Fluorescent polydopamine nanoparticles (FPD) are a kind of promising fluorescent nanoparticles for biosensing and imaging, while the rapid and controllable synthesis of FPD is still challenging. In this paper, we developed a microplasma electrochemistry strategy to regulate the oxidative polymerization process of dopamine, resulting in a controlled formation of FPD. Treating the dopamine solution with microplasma anode could not only generate oxidative species to trigger the nucleation of polydopamine nanoparticles at the plasma-liquid interface, but also provide an acidic environment to inhibit their further growing up during the diffusion process. Thus, uniform FPD with a diameter of 3.1 nm could be prepared within minutes. And, continuous generation of FPD could be achieved without the formation of aggregates when prolonging the reaction time. The obtained FPD had abundant functional groups on the surfaces, showing tunable fluorescent emission properties. These luminescent nanoparticles were demonstrated for highly selective detection of uranium with a detection limit of 2.1 mg/L. The novel microplasma electrochemistry strategy established in this work provided better opportunity for controllable synthesis of FPD, as well as other luminescent nanoparticles, and broadened their application in chemical sensing area.

Oxidant-regulated polymerization of dopamine was exploited, for the first time, for effective surface engineering of the well-defined cylindrical pores of nuclear track-etched membranes (NTEMs) to develop novel catalytic membrane reactor. First, in the presence of a strong oxidant, controlled synthesis of polydopamine (PDA) with tunable particle size was achieved, allowing a homogeneous deposition to the confined pore channels of NTEMs. The PDA interfaces rich in catechol and amine groups provided enhanced hydrophilicity to promote mass transport across the membrane and abundant nucleation sites for formation and stabilization of metallic nanoparticles (NPs). In-situ reductive growth of multiple metallic NPs, including Pd, Ag, and Au, was then achieved inside the cylindrical pores of NTEMs. Using the functionalized membrane as a catalytic reactor, efficient reduction of 4-nitrophenol (4-NP) was demonstrated in a flow-through mode. Moreover, after dissolution removal of the NTEMs, self-sustained one-dimensional (1D) PDA/M (M = Pd, Ag, or Au) hybrid nanotubes (NTs), with determined aspect ratio and a length reaching up to 10 μm, were obtained for catalysis of 4-NP in a batch reaction mode. This study established a facile and versatile method, by rational tuning of the polymerization behavior of dopamine, for effective modification of confined microscale/nanoscale cavities with different surface characteristics. The integration of PDA chemistry with NTEMs would provide more opportunities for development of novel catalytic membrane reactors as well as for the tailored synthesis of functional 1D nanotubes for broadened applications.

A novel colorimetric nanosensor based on stable aggregation of gold nanoparticle (AuNP) triggered by carbon quantum dots (CDs) has been developed for detection of Ag+ ions in the presence of glutathione (GSH). First, the nanosensor is constructed by assembling carbon quantum dots (CDs) “shell” on the surface of gold nanoparticle (AuNP), resulting in the generation of the stable aggregation of CDs/AuNP. The solution color changes from red to blue. In the absence of target, the addition of GSH into the aggregated CDs/AuNP exhibits the dispersion state corresponding to the color change from blue to red, because GSH can prefer to binding with AuNP comparing with CDs. On the contrary, the aggregated CDs/AuNP has been again observed with the color change from red to blue after the target analyte Ag+ ions are added. Therefore, the new sensing strategy based on “aggregation-dispersion-aggregation” or “blue-red-blue” mode can be established for Ag+ detection. This method can selectively detect Ag+ in a linear rang...

We described a rapid and highly sensitive colorimetric method for the detection and quantification of silver ions employing glutathione (GSH)-mediated MnO 2 nanosheets as an artificial oxidase. In this assay,the absorption intensity of the chromogenic reaction system enabled the quantification of silver ions. Under the optimum conditions, the linear response ranged for Ag + was from 10 nM to 800 nM with a correlation coefficient of 0.996. Remarkably, limit of detection in aqueous solutions was 4.23 nM, which was well below United States Environmental Protection Agency (USEPA) permissible limit in drinking water (460 nM). This sensing assay had highly specificity because no significant interference occurred with 10-fold concentration of other metal ions. Moreover, the approach also could be employed to the Ag + detection in real samples. And the recovery of Ag + spiked in tap water ranged from 99.62% to 108.01%. Importantly, the oxidation reaction of TMB to oxTMB by MnO 2 nanosheets completed instantaneously even by naked-eye readout. Therefore, the assay based on GSH-mediated MnO 2 nanosheets is simple, rapid, highly sensitive and selective for the quantification of Ag + in water and practical samples.

Mercury is a common heavy metal element in natural systems and is highly toxic to the human body. Herein, a novel colorimetric detection of Hg2+ ions is proposed based on the aggregation of gold nanoparticles (AuNPs) induced by carbon quantum dots (CDs) with the assistance of glutathione (GSH). In this sensing system, the AuNP/CDs composite forms through Au–N bonds. Simultaneously, the color of the solution turns from wine red to blue. The well-dispersed AuNPs can be restored after the addition of GSH, because GSH competes with CDs to bind onto the surface of AuNPs and protect AuNPs from aggregation. In the presence of Hg2+ ions, GSH can chelate with Hg2+ to form a complex, which subsequently enables CDs to facilitate the aggregation of the AuNPs again. Therefore, according to the red-to-blue color change, a colorimetric sensor is established for the sensitive and selective detection of Hg2+ with a detection limit of 7.5 nM. Moreover, this sensor is successfully used to detect Hg2+ spiked in environmental water. This very simple and cost-effective strategy will promote the development of a colorimetric sensor for the determination of other metal ions in biological and environmental fields.

This study presents a facile hydrothermal approach in a “Tris” buffer solution for fabricating polydopamine (PDA) nanostructures with different morphologies (core–shell, yolk–shell, and hollow spheres), while concurrently tuning their stability, permeability, and reactivity. Structural and morphological transformation of PDA induced by hydrothermal treatments is described in detail. Surface-initiated growth of poly(N-isopropylacrylamide) (PNIPAM), a thermally responsive polymer, was then achieved from the hydrothermally treated PDA by using the activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Interestingly, inward and outward growth of polymer chains from PDA hollow spheres could be manipulated depending on the solvation effect and hydrothermally induced regulation of the pore network in the PDA structure. Hybrid PDA/PNIPAM nanocapsules with tunable morphologies could be obtained. This study provides new insights into PDA’s structural evolution under hydrother...

This study presents a new strategy by integrating surface-initiated atom transfer radical polymerization (SI-ATRP) with bio-inspired polydopamine chemistry to prepare well-defined glass fiber/polymer composites. Firstly, a homogenous PDA layer, which served as a favorable platform facilitating ATRP initiators anchoring, was deposited onto the glass fibers. Controlled growth of poly(glycidyl methacrylate) (PGMA) brushes from the glass fibers were then performed using the initiators for continuous activator regeneration (ICAR) ATRP method. PGMA brushes with defined structure, grafting density (5 wt.% ~ 25 wt.%) and well preservation of chain end-functionality could be obtained by reducing radical initiator ratio and using a high dilution strategy (solvent: monomer=10:1 (V:V)). And, a narrow distribution of molecular weight (PDI≤1.2) could be attained within reduced polymerization time. Laccase, as an enzyme model, was then covalently immobilized to the glass fiber/PGMA composites. The developed bio-composit...

We report on a method for sensitive detection and discrimination of multiple proteins. The peroxidase-like activity of gold nanoparticles (AuNPs) is employed to catalyze the oxidation of 3′,3′,5′,5′-tetramethylbenzidine (TMB) in the presence of H2O2. Depending on the protein, this produces colorations with different absorbance. The catalytic activity of the reaction system is affected because different proteins are absorbed onto the surface of the AuNPs. The absorbance values at 370, 450, and 650 nm are different in the presence of different proteins. The array can discriminate 8 proteins at 50 nM concentration levels with 100% accuracy. It also can discriminate proteins being present in different concentrations and mixtures with different molar ratios of proteins. Human urine spikes with 8 proteins (Concanavalin A), Cytochrome C, Horseradish peroxidase, Human serum albumin, Myoglobin, Pepsin, Trypsin, Papain) can be differentiated by applying hierarchical cluster analysis. The system also can discriminate proteins at different concentrations and the mixtures with different molar ratios in bovine serum. This indicates that the array has a great potential in terms of analyzing biological fluids.

Developing green and efficient technologies for surface modification of magnetic nanoparticles (MNPs) is of crucial importance for their biomedical and environmental applications. This study reports, for the first time, a novel strategy by integrating metal-free photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) with the bioinspired polydopamine (PDA) chemistry for controlled architecture of functional polymer brushes from MNPs. Conformal PDA encapsulation layers were initially generated on the surfaces of MNPs, which served as the protective shells while providing an ideal platform for tethering 2-bromo-2-phenylacetic acid (BPA), a highly efficient initiator. Metal-free PET-ATRP technique was then employed for controlled architecture of poly(glycidyl methacrylate) (PGMA) brushes from the core-shell MNPs by using diverse organic dyes as photoredox catalysts. Impacts of light sources (including UV and visible lights), photoredox catalysts, and polymerization time on the composition and morphology of the PGMA brushes were investigated. Moreover, the versatility of the PGMA-functionalized core-shell MNPs was demonstrated by covalent attachment of ethylenediamine (EDA), a model functional molecule, which afforded the MNPs with improved hydrophilicity, dispersibility, and superior binding ability to uranyl ions. The green methodology by integrating metal-free PET-ATRP with facile PDA chemistry would provide better opportunities for surface modification of MNPs and miscellaneous nanomaterials for biomedical and electronic applications.

Developing facile and robust technologies for effective enrichment of uranium from seawater is of great significance for resource sustainability and environmental safety. By exploiting mussel-inspired polydopamine (PDA) chemistry, diverse types of PDA-functionalized sorbents including magnetic nanoparticle (MNP), ordered mesoporous carbon (OMC), and glass fiber carpet (GFC) were synthesized. The PDA functional layers with abundant catechol and amine/imine groups provided an excellent platform for binding to uranium. Due to the distinctive structure of PDA, the sorbents exhibited multistage kinetics which was simultaneously controlled by chemisorption and intralayer diffusion. Applying the diverse PDA-modified sorbents for enrichment of low concentration (parts per billion) uranium in laboratory-prepared solutions and unpurified seawater was fully evaluated under different scenarios: that is, by batch adsorption for MNP and OMC and by selective filtration for GFC. Moreover, high-resolution X-ray photoelectron spectroscopic and extended X-ray absorption fine structure studies were performed for probing the underlying coordination mechanism between PDA and U(VI). The catechol hydroxyls of PDA were identified as the main bidentate ligands to coordinate U(VI) at the equatorial plane. This study assessed the potential of versatile PDA chemistry for development of efficient uranium sorbents and provided new insights into the interaction mechanism between PDA and uranium.

The development of convenient method for detection and identification of toxic metals ions is of great interest. In this work, we have developed a facile fluorescent sensor array based on luminescence carbon dots for detecting and differentiating a set of metal ions. Three kinds of nitrogen-doped carbon dots were synthesized by hydrothermal treatment of citric acid with three different amino acids ( l -glycine, l -lysine and l -serine). These carbon dots had various surface states and thus exhibited diverse quenching responses to different metal ions. Six metal ions can be well distinguished at various concentrations (100, 50, 20 and 10 μM). The discrimination accuracy of unknown samples was found to be 100% at a concentration as low as 10 μM. In addition, the binary and ternary mixtures of three metal ions (Hg2+, Cu2+, Fe3+) could also be well recognized with this sensor array. This method is simple, label-free, and the sensor arrays could be obtained and expanded easily with large-scale and low-cost. It will broaden the application field of carbon dots sensors and give a new direction of developing sensitive array sensing systems.

The removal and separation of uranium from aqueous solutions are quite important for resource reclamation and environmental protection. Being one of the most effective techniques for metal separation, adsorption of uranium by a variety of adsorbent materials has been a subject of study with high interest in recent years. However, current methods for monitoring the adsorption process require complicated procedures and tedious measurements, which hinders the development of processes for efficient separation of uranium. In this work, we prepared a type of luminescent mesoporous silica-carbon dots composite material that has high efficiency for the adsorption of uranium and allows simultaneous in situ monitoring of the adsorption process. Carbon dots (CDs) were prepared in situ and introduced onto amino-functionalized ordered mesoporous silica (SBA-NH2) by a facile microplasma-assisted method. The prepared CDs/SBA-NH2 nanocomposites preserved the high specific surface area of the mesoporous silica, as well as...

Single nucleotide polymorphisms (SNPs) are the most fundamental internal causes for many genetic diseases. However, the location information on SNPs in a specific DNA sequence is not well acquired through current SNPs detection methods, except for accurate DNA sequencing. Here we report a fluorescence enhancement phenomenon in the process of two silver nanoclusters (AgNCs) approaching closely to form a nanocluster dimer (NCD). The fluorescence intensity is sensitive to the distance between two AgNCs; therefore, the NCD lights into different fluorescence intensities upon binding SNPs targets with mismatched bases at different positions. Interestingly, the fluorescence intensities of the NCD decrease linearly when the position of single mismatched base moves gradually from the middle point to the end of the target DNA. The NCD is a single probe acting as a universal platform to pinpoint various SNP positions. With this single probe, we cannot only identify the existence of SNPs but also pinpoint the location of a specific single mismatched base in the adjacent positions. This strategy is feasible to detect specific gene point mutations in clinical samples.

An extensible multidimensional colorimetric sensor array for the detection of protein is developed based on DNA functionalized gold nanoparticles (DNA-AuNPs) as receptors. In the presence of different proteins, the aggregation behavior of DNA-AuNPs was regulated by the high concentrations of salt and caused different color change; while DNA-AuNPs grew induced by the reduction of HAuCl4 and NH2OH as a reductant on the surface of nanoparticles exhibited different morphologies and color appearance for different proteins. The transducers based on AuNPs modified by specific and nonspecific DNA enables naked-eye discrimination of the target analytes. This extensible sensing platform with only two receptors could simultaneously discriminate ten native proteins and their thermally denatured conformations using hierarchical cluster analysis (HCA) at the concentration of 50nM with 100% accuracy. This opens up the possibility of the sensor array to investigate the different conformational changes of biomacromolecules, and it gives a new direction of developing multidimensional transduction principles based on plasmonic nanoparticle conjugates. Furthermore, the sensing system could discriminate proteins at the concentration of 500nM in the presence of 50% human urine, which indicated this sensor array has great potential ability in analyzing real biological fluids. In addition, the multidimensional colorimetric sensor array is suitable for analysis of target analytes in the resource-restricted regions because of rapid, simple, low cost, and in-field detection with the naked eye.

A fluorescence method for the determination of inorganic pyrophosphatase (PPase) activity has been established based on copper nanoclusters (CuNCs). The polythymine of 40 mer (T40) acts as a template for the reduction reaction from Cu2+ to Cu0 by ascorbic acid (AA). This reaction leads to the formation of fluorescent CuNCs with excitation/emission peaks at 340/640 nm. However, the higher binding affinity between inorganic pyrophosphate (PPi) and Cu2+ hinders the effective formation of CuNCs. This shows low fluorescence intensity. PPase catalyzes the hydrolysis of PPi into Pi during which free Cu2+ ions are produced. This facilitates the formation of fluorescent CuNCs. Thus, the fluorescence intensity was restored. The fluorescence enhancement of the system has a linear relationship with PPase activity in the range 0.3 to 20 mU·mL−1, and the detection limit is0.2 mU·mL−1. The relative intensity (I/I0) at 640 nm for the analytical solution versus system is also employed to screen the inhibitor for PPase with high efficiency.

A fluorometric and colorimetric method are described for the determination of hydrogen peroxide and glucose by integrating copper nanoclusters (CuNCs) into a Fenton-like reaction. The mechanism mainly depends on the fast formation of long-strand DNA-templated CuNCs with strong red fluorescence (with excitation/emission maxima at 340/640 nm) in the absence of H2O2. The DNA can be cleaved into short-oligonucleotide fragments by hydroxy radicals as formed in the Ce(III)-triggered Fenton-like reaction in the presence of H2O2. As a result, short-strand DNA loses the ability as a template for the formation of CuNCs. This leads to a decrease of fluorescence. The colorimetric assay, in turn, is based on the oxidation of colorless Ce(III) ions to the distinctly yellow Ce(IV) ions (with an absorption maximum at 400 nm) by H2O2. Compared with those assays based on the use of enzyme mimics, this method does not require any chromogenic substrates such as ABTS and TMB. Based on the dual-signal readout platform, we successfully achieved the detection of H2O2 and glucose. LODs are as low as 0.266 μM and 2.92 μM. The methods were applied to the sensitive determination of glucose by using glucose oxidase (GOx) which catalyzes the oxidization of glucose to produce H2O2. The practical application was demonstrated by determination of glucose in human serum, with apparent recoveries of 98.4–101.9% and 99.1–105.6%, respectively. The concentration of glucose ranges from 1 to 500 μM and 50 to 600 μM based on the dual-signal readout platform, respectively. This fluorometric and colorimetric dual-mode strategy will pave a new avenue for constructing effective assays for H2O2-related analytes in biochemical and clinical applications.

A selective fluorescent on-off-on probe has have designed for the detection of fluoride (F−) ions based on DNA-templated copper nanocluster (CuNCs) and by using aluminum(III) ions as a bridge. A 40-mer polythymine acts as a template for the reduction of Cu(II) to Cu(0) by ascorbic acid. This result is the formation of red fluorescent CuNCs, with excitation/emission peaks at 340/640 nm. After addition of Al3+ ions, the fluorescence of CuNCs is quenched because the interaction of Al3+ and DNA disturbs the formation of DNA-templated CuNCs. Fluorescence is restored on addition of fluoride to the system. This is due to the desorption of Al3+ from the DNA and the formation of the Al(OH)3F− complex. This system displays a fast fluorometric response to fluoride, with high selectivity over other anions. Fluorescence increases linearly in the 2 to 150 μM F− concentration range, and the detection limit is 1.0 μM. This probe has been successfully used for the detection of F− ions in four brands of toothpaste. The method is rapid, cost-effective, selective, and does not require toxic solvents and reagents.

Although colorimetric methods have been developed for the detection of silver ions (Ag+) based on gold nanoparticles aggregation induced by formation cytosine-Ag+-cytosine complexes or high salt centration with dark field microscopy (DFM). However, this state is usually unstable, resulting in the poor accuracy and repeatability of analytical methods. Herein, we have constructed an assay of Ag+ based on MnO2-coated gold nanoparticle (AuNP@MnO2). MnO2 shell can be reduced into Mn2+ by glutathione (GSH). The maximum absorption peak of AuNP@MnO2 significantly changes from 528 nm to 572 nm. Simultaneously, the color of a single nanoparticle becomes from yellow to green under DFM. However, in the presence of Ag+, the etching process of MnO2 is inhibited because of coordination between GSH toward Ag+. The maximum UV absorption peak of AuNP@MnO2 is basically unchanged. The linear equation for Ag+ detection is obtained in the range from 1.0 pM to 5.0 nM with R2 = 0.983 by using DFM. According to 3σ/k rule (where σ is the standard deviation of five blank samples and k is the slope of regression line), the limit of detection (LOD) is calculated to be 0.39 pM. Furthermore, this approach can be applied to detect Ag+ in real sample, showing the good potential for environmental monitoring and water quality control.

Graphene oxide (GO) membranes with unique nanolayer structure have demonstrated excellent separation capability based on their size‐selective effect, but there are few reports on achieving ion–ion separation, because it is difficult to inhibit the swelling effect of GO nano sheets as well as to precisely control the interlayer spacing d to a specific value between the sizes of different metal ions. Here, selective separation of uranium from acidic radioactive waste containing multication is achieved through a precise dual‐adjustment strategy on d. It is found that GO swelling is greatly restricted in highly acidic solution due to protonation effect. Then the interlayer spacing is further precisely reduced to below the diameter of uranyl ion by increasing the oxidation degree of GO. Sieving uranyl ions from other nuclide ions is successfully realized in pH =3–3 mol L−1 nitric acid solutions., Precisely controlling the interlayer spacing of graphene oxide (GO) membrane in a wide range (11.4–15.5 Å) is realized by using a dual‐adjustment strategy of combining acidity with oxidation degree. Such GO membranes can successfully sieve uranyl ions from other nuclide ions in pH =3–3 mol L−1 HNO3 aqueous, showing their potential application in the treatment of highly acidic radioactive waste.

Photocatalysis-assist transition of uranium from soluble ions to insoluble nanoparticles is benefit for the extraction of uranium but has been rarely realized under air atmosphere. Here we developed a novel graphene aerogel (GA), GA-200, for the photocatalytic removal of uranium from water under visible light and air atmosphere for the first time. By controlling the reduction degree, GA-200 remained numbers of functional groups for anchoring uranium and possessed high photocurrent response and narrow band gap to generate and transfer electrons/holes readily. Under visible light irradiation, neutral (UO2)O2·2H2O nanoparticles were formed and could evacuate from the surface of GA-200 to regenerate the active sites in-situ, resulting in a high removal capacity of 1050 mg/g. The mechanism was further studied. It was found that at the presence of O2 in air, the photochemistry property of uranyl itself played an essential role to generate H2O2 and (UO2)O2·2H2O was formed instead of UO2, which was different from that in oxygen-free atmosphere.

The photoluminescence sensor array has attracted many researchers’ attention because of highly sensitive response to protein analytes. Nevertheless, applying this technology to proteins detection suffers interferences from high short-lived autofluorescence emission and scattering light in real biological sample matrixes. To address this issue, a time-resolved phosphorescent (TRP) sensor array based on Mn-doped ZnS quantum dots (QDs) capped by different ligands was designed. The long lifetime of phosphorescence generated from QDs allows an appropriate time delay to effectively eliminate short-lived fluorescent and scattering light background. Thus, the signal-to-noise ratio of the detection and discrimination capability of the sensing system was improved distinctly for the analysis of proteins. Ten proteins at 500 nM in the buffer containing Rhodamine B (Rh B) were completely distinguished by using steady-state phosphorescent (SSP) measure, which were easily identified at the concentration as low as 10 nM by using TRP mode. The detection limit was 50-fold improved over that by using SSP assay. Most importantly, the identification ability of the same protein at the various concentrations was not sacrificed in the high fluorescent background using this sensing platform. Therefore, proteins spiked in human urine were successfully identified at 500 nM.

In this study, a new kind of short-channel SBA-15 mesoporous silica decorated with polyazamacrocyclic ligands was developed, showing selective binding ability to palladium ions based on host–guest interaction. The established synthesis protocol involved the co-condensation synthesis of an SBA-15 precursor with halogen atoms uniformly incorporated in the mesoporous silica matrix, followed by the anchoring of 1,4,7,10-teraazacyclododecane (Cyclen) ligands via post-grafting. Due to the short straight channels and large pore size facilitating the diffusion of the molecules and ions, the mesoporous silicas were found to possess a high density of the functional Cyclen ligands, as well as high adsorption capacity of Pd(II) in HNO3 solutions. The structure and morphology of the Cyclen functionalized mesoporous silicas were fully characterized. And, the adsorption behavior toward Pd(II) was investigated combined with the theoretical interpretation of the experimental data based on typical kinetic equations, isotherm models and thermodynamic equations. Furthermore, the detailed coordination mechanism between the Cyclen ligands and Pd(II) was examined by high resolution X-ray photoelectron spectroscopy (XPS). A suggested mechanism involving the synergistic effect of four cyclic amines in the Cyclen ligands was proposed to describe the coordination to Pd(II) in HNO3 solutions. Overall, this work provides a facile and effective pathway to build polyazamacrocycle ligand decorated mesoporous silicas with short-channels and large pores, which might be potentially used for molecule recognition and selective enrichment of precious metals.

The salt-induced aggregation, nanoparticle regrowth and self-assembly behaviors of gold nanoparticles (AuNPs) and DNA conjugates could be changed after interaction with different proteins, generating various color changes and a unique fingerprint pattern for each protein. The triple-channel colorimetric signals have been employed for protein discrimination with the naked eye.

This study presents an effective and facile strategy by integrating surface-initiated single electron transfer living radical polymerization (SET-LRP) with mussel-inspired polydopamine (PDA) chemistry for controlled building of a novel class of core–shell magnetic nanoparticles (MNPs) for highly-efficient uranium enrichment. The strategy initially involves the deposition of a PDA encapsulation layer by spontaneous self-polymerization on the Fe3O4 core, which serves as a safety shell and provides an enabling platform for anchoring of 2-bromoisobutyryl bromide (BiBB) to form macro-initiators. Dense polyacrylonitrile (PAN) brushes are grown from the BiBB-attached PDA shell via SET-LRP using Cu(0)/Me6TREN as a catalytic/ligand system, followed by conversion to amidoxime (AO) functionalized polymer brushes. The core–shell Fe3O4@PDA@PAO MNPs exhibit favorable superparamagnetic characteristics and a fast response within 6 s under an applied magnetic field. Due to the strong binding ability of AO ligands, Fe3O4@PDA@PAO shows a remarkable adsorption capacity (qe = 162.5 mg g−1) toward uranyl ions under optimal pH conditions. A study on the adsorption kinetics suggests that the adsorption process might conform to the pseudo-second-order model. We conclude that the Fe3O4@PDA@PAO MNPs have the potential for effective enrichment and magnetic separation of uranium, and the integrative synthetic strategy combining the SET-LRP technique and PDA chemistry would bring extensive opportunities for versatile surface modification of nanomaterials for more demanding applications.

A microplasma electrochemistry (MIPEC) method was developed for the post-functionalization of g-C3N4 at room temperature and atmospheric pressure without harsh condition. The MIPEC method could provide a novel reaction environment with the combination of electrochemistry and plasma chemistry. The photocatalytic performances of treated g-C3N4 for Rhodamine B (RhB) degradation were investigated under different conditions in the aqueous state. g-C3N4 treated by microplasma anode exhibited an improved photocatalytic activity due to the oxidation and protonation effect, while g-C3N4 treated by microplasma cathode presented a decrease of photocatalytic activity due to the reduction effect. Characterizations include XRD, FTIR, PC, EIS under the light, and UV–vis DRS indicated that the as-prepared materials with expected properties were acquired, suggesting that the MIPEC is an effective and controllable method for materials synthesis and modification.

Single nanoporous gold nanowire was introduced as a tunable one-dimensional nano-sensor platform with both SERS and catalytic activity, and it precisely fit the requirement of materials for in situ SERS monitoring of plasmon-assisted catalytic reaction. The nanoporous gold nanowires exhibited much more "hot spots" on their surface and much better SPR effect than the smooth nanowires. We demonstrated that these nanowires could be used as a SERS substrate assuring the sensitivity and reproducibility of Raman signals. Besides, they could be applied as a kind of heterogeneous catalyst for in situ SERS monitoring of the plasmon-assisted catalytic reaction-reduction of p-nitrothiophenol (p-NTP) to p,p-dimercaptoazobenzene (DMAB) at their surface. The SERS and catalytic activity of the nanowires could be respectively optimized by adjusting their dealloying time, similar to the procedure of catalyst screening.

Developing convenient and rapid method for eliminating uranium from massive contaminated water under emergency conditions is highly needed. Herein we developed a novel chemical precipitation strategy based on graphene aerogel capsulated with the degradation products of phytic acid (PAGA). With hydrothermal treatment, graphene oxide was twisted and reduced to generate aerogel, acting as an encapsulator. At the same time, phytic acid (PA) was degraded into various compounds and capsulated into graphene aerogel with a high loading capacity of 85 g/g. After adding PAGA into uranium contaminated water, the degradation products were released out of GA skeleton to combined with uranium and form sediments. The elimination capacity reached up to 3550 mg/g within 40 min and the obtained sediments possessed good stability in the following 72 h. PAGA capsule also presented high removal rate in various water systems, making it a kind of versatile material in the elimination of uranium under emergency conditions.

Molten salt electrolysis is normally conducted with solid anode, such as noble metal or graphite, which has defects such as high cost or emission of carbon oxide. Herein, we report that a microplasma based on atmospheric-pressure glow discharge could act as a kind of gaseous anode for electrolysis in molten salt. When the Ag/Ag+ redox couple was chosen as the research object, the microplasma anode could initiate charge-transfer reactions in the molten salt and Ag could be electrodeposited with current efficiency of above 90%. The microplasma anode has also shown excellent anticorrosive performance in both chloride and carbonate molten salt. Furthermore, the microplasma anode could potentially serve as an excitation source of atomic emission spectrometry (AES), making it possible to determine the concentration of Ag ions in the molten salt in situ and in real-time. With properties such as being carbon-free and having corrosion resistance and extensive utilization for analysis, the microplasma anode has ope...

A selective phosphorescent on-off-on probe with long decay lifetime has been designed for the detection of pyrophosphate ions (PPi). The detection scheme is based on the use of europium(III)-modulated Mn(II)-doped ZnS quantum dots capped with N-acetyl-L-cysteine. Both the aggregation of quantum dots and electron transfer induced by Eu(III) ions cause phosphorescence to be quenched ("off" state). Phosphorescence is, however, restored on addition of PPi to the system ("on" state). The effect is attributed to the removal of Eu(III) from the carboxy groups on the surface of the quantum dots owing to the stronger interaction between PPi and Eu(III). A linear relationship exists between phosphorescence intensity (best measured at excitation/emission wavelengths of 316/594 nm) and PPi concentration in the 400 nM to 6000 nM with a detection limit of 145 nM. An additional attractive feature is provided by the long-lived phosphorescence (1920 μs) of the quantum dots. It can be used to eliminate interference by short-lived fluorescence in biological samples by performing time resolved measurements. The probe was applied to the determination of PPi in spiked in urine samples and gave recoveries in the range from 98 to 105% with RSDs of2.0%. Graphical abstract Schematic of a long-lived phosphorescent on-off-on probe for the sensitive and selective detection of pyrophosphate ions (PPi). It is based on the use of Eu(III)-modulated Mn(II)-doped ZnS quantum dots (QDs). Phosphorescence is quenched of QDs after the addition of Eu

A time-resolved phosphorescence (TRP) is applied to the highly sensitive determination of Fe(II) ions. The method is based on the use of a phosphorescent probe consisting of cysteine-bridged Mn-doped ZnS quantum dots (Mn/ZnS QDs). The presence of cysteine enhances the phosphorescence of the QDs and also increases the efficiency of quenching caused by Fe(II) ions. This results in strongly improved selectivity for Fe(II). The linear response is obtained in the concentration range of 50-1000 nM with a 19 nM detection limit. Phosphorescence is recorded at excitation/emission peaks of 301/602 nm. The interference of short-lived fluorescent and scattering background from the biological fluids is eliminated by using the TRP mode with a delay time of 200 μs. The determination of Fe(II) in human serum samples spiked at a 150 nM level gave a 92.4% recovery when using the TRP mode, but only 52.4% when using steady-state phosphorescence. This demonstrates that this probe along with TRP detection enables highly sensitive and accurate determination of Fe(II) in serum. Graphical abstract Schematic of a novel phosphorescent method for the detection of Fe

The authors describe a colorimetric method for the determination of Hg2+ ions based on the inhibition of the activity of the enzyme urease. The pH value of solution increases when urease hydrolyzes urea, which can be visualized by adding a pH indicator such as Phenol Red (PhR). Mercaptoethanol as a typical thiol is added to the system to improve selectivity because it binds metal ions and then - unlike the Hg2+ mercaptoethanol complex - does not inhibit urease. Hence, the color of the pH indicator PhR turns from yellow to pink as the solution becomes alkaline. The Hg2+ mercaptoethanol complex, in contrast, strongly inhibits urease and the color of the solution remains yellow. The findings were used to design a photometric assay based on the measurement of the ratio of absorptions of PhR at 558 nm and 430 nm. It has a linear response over the 25 to 40 nM Hg2+ concentration range and a 5 nM detection limit. This is well below the guideline values of Hg2+ specified by the US Environmental Protection Agency and the World Health Organization for drinking water (10 nM and 30 nM, respectively). The method was employed to the determination of Hg2+ in water samples spiked with 10 nM levels of Hg2+ where color changes still can be observed visually.

A simple, visible and smartphone readable strategy has been proposed for the sensitive detection and discrimination of multiple proteins. By employing five different concentrations of NaCl salt, AuNP exhibited different aggregation behavior for different proteins because of differential ion strength, leading to diverse color changes. The sensing system could not only discriminate twelve proteins at the concentration of 50 nM in aqueous solution, but it could also discriminate these proteins at 200 nM in the presence of human urine with an accuracy of 100%. More importantly, based on the theory of chromatics, we could directly read out the color value using a smartphone to distinguish twelve proteins, pure Lys and HSA at various concentrations, and the mixture of these two proteins in the presence of human urine with no confusion after a hierarchical clustering analysis (HCA). The inexpensive and convenient colorimetric sensor array using the ubiquitous smartphone for signal readout has great potential for the point-of-care diagnosis without additional devices.

The development of sensitive and cheap sensor arrays for identification of proteins plays an important role in many bioanalytical and clinical investigations. Here, we introduce a multidimensional colorimetric sensor array for the detection of multiple proteins based on acquiring multiple signals along with the reaction time to enhance the discrimination ability. In a single experiment, the unique fingerprint for each protein against the sensor array is generated from a response absorbance signal at three reaction time points (at 10 min, 15 min, and 20 min). Our colorimetric sensing system is able to identify ten proteins not only in aqueous solution at 10 nM but also in human urine at the 50 nM level with an accuracy of 100%. Moreover, the identification of HSA in urine at the nanomolar level within a linear range of 0.05-1.0 μM is achieved. Our sensing array system is sufficiently sensitive for the discrimination of pure HSA, binary mixtures of HSA and Lys at a total concentration of 50 nM in urine. This study indicates that the application of the real-time resolved response signals enables the enhancement of the discrimination ability for protein recognition.

Plasmon-enhanced fluorescence (PEF) generally requires the samples settled on a metal substrate and the effective enhancement distance is less than 100 nm, which limit its application in intracellular sensing. Herein, we report a nano endoscopy with PEF effect for sensing analytes inside the extremely small volume samples. The nano endoscopy was fabricated by assembling single nanoporous gold nanowire (PGNW) on the tip of a tungsten needle. It was accurately manipulated to insert into a micro droplet, and an effective sensing was realized at micrometre scale with submicrometer resolution. By taking lysozyme as a model sensing target, a 23-fold improvement of sensitivity was obtained, comparing with that of smooth gold nanowire (SGNW). These results indicated that the nano endoscopy can realize a high spatial resolution sensing, showing its potential application in intracellular sensing.

We have proposed a doubled nanoplasmonic colorimetric sensor array for protein recognition based on car-bon nanodots (CDs)-induced reversible aggregation of gold nanoparticle (AuNP) with GSH as a regulator. It is found that different kinds of CDs can induce the aggregation of AuNP with different degrees and cause different color change. Adding reduced glutathione (GSH) into the CDs/AuNP system can make the AuNP disperse again accompanying with a second color change. Based on this phenomenon, three kinds of CDs originated from different amino acids and citric acid are used to fabricate a colorimetric sensor array with three sensing elements. Upon addition of target proteins into CDs/AuNP conjugates, the competitive protein-AuNP affinity disrupts the SPR absorption peak of CDs/AuNP, generating cross-reactive three-unit colorimetric signal. Subsequently, GSH is introduced into each unit containing protein samples in situ. The SPR absorption peak of AuNP is substantially affected due to the stronger affinity between AuNP and GSH, producing an-other three-unit response signal. With this strategy, each sensing element can give two output signals to each target protein, which doubles the number of unit from three to six without changing the three-cell configuration, resulting in greatly improved discrimination ability of proteins and identification accuracy of unknown samples. Twelve proteins at 50 nM can be well discriminated by this novel colorimetric sensor array. Moreover, our sensing system is very stable in the high concen-tration of salt, make it suitable for the real sample analysis. This method effectively identifies twelve proteins at 200 nM spiked in human urine.

We developed a unique continuously evolving colorimetric sensor array based on AuNPs decorated by two single-stranded oligonucleotides with different molar ratios for protein discrimination. The number of differential receptors in this sensor array could be easily extended by adjusting the molar ratios of two DNA, resulting in continuously improved discrimination ability. The continuous response data of target samples against our sensing system could be easily obtained and exclude abnormal signals. The sensing system could discriminate twelve proteins at the concentration of 200nM in the presence of 50% human urine with accuracy of 100%, showing feasible potential for diagnostic applications. Remarkably, HSA at various concentrations, the pure Lys and HSA, and the mixture of these two proteins with different molar ratios had been successfully discriminated in LDA plot as well in the presence of human urine sample. This novel strategy will be very promising for the design of cheaper and more reliable sensor arrays for target samples.

Optical cross-reactive sensor arrays have recently been demonstrated as a powerful tool for high-throughput protein analysis. Nevertheless, applying this technology to protein detection is complicated by many external factors, such as the interfering substances, the background noise, and sample environmental changes in the biological matrix. Herein we demonstrate that a ratiometric fluorescence sensor array based on quantum dots can be employed to circumvent these limitations. Several intrinsic dual-emitting Mn-doped quantum dots capped with different organic functional groups were designed as sensing elements. Distinct and reproducible response patterns against the ratiometric sensor array were obtained from ten proteins in a buffer of different pH (pH 5.7, 7.4, and 8.3) and spiked into human urine. Linear discrimination analysis of the response patterns showed successful differentiation of the analytes at concentrations as low as 50 nM with high identification accuracy. Furthermore, this sensor system also enables the detection of these eight proteins (at 500 nM) in human urine without any treatment. The ratiometric fluorescence change from quantum dots for analysis of proteins can eliminate effectively the signal interference from the pH value change and the fluorescent background in human urine. The present study will open a new avenue to improve the discrimination ability of sensor arrays.

We introduce individual nanoporous Au nanowire (AuNW) as a tunable one-dimensional platform for plasmon-enhanced fluorescence, with an enhancement factor of ∼62, which is ∼8-fold higher than that of smooth AuNWs. Besides, nanoporous AuNWs have much lower background emission than smooth AuNWs. These results indicate that nanoporous AuNWs are an excellent optical sensing platform.