Multicolor Fluorescent Inks Based on Lanthanide Hybrid Organogels for Anticounterfeiting and Logic Circuit Design.

With the rapid development of information technology, the encrypted storage of information is becoming increasingly important for human life. The luminescent materials with a color-changed response under physical or chemical stimuli are crucial for information coding and anticounterfeiting. However, traditional fluorescent materials usually face problems such as a lack of tunable fluorescence, insufficient surface-adaptive adhesion, and strict synthesis conditions, hindering their practical applications. Herein, a series of luminescent lanthanide hybrid organogels (Ln-MOGs) were rapidly synthesized using a simple method at room temperature through the coordination between lanthanide ions and 2,6-pyridinedicarboxylic acid and 5-aminoisophthalic acid. And the multicolor fluorescent inks were also prepared based on the Ln-MOG and hyaluronic acid, with the advantages of being easy to write, color-adjustable, and water-responsive discoloration, which has been applied to paper-based anticounterfeiting technology. Inspired by the responsiveness of the fluorescent inks to water, we designed a logic system that can realize single-input logic operations (NOT and PASS1) and double-input logic operations (NAND, AND, OR, NOR, XOR). The encryption of a binary code can be actualized utilizing different luminescent response modes based on the logic circuit system. By adjusting the energy sensitization and luminescence mechanism of lanthanide ions in the gel structure, the information reading and writing ability of the fluorescent inks were verified, which has great potential in the field of multicolor pattern anticounterfeiting and information encryption.

Highly Flexible K-Intercalated MnO2 /Carbon Membrane for High-Performance Aqueous Zinc-Ion Battery Cathode.

The layered MnO2 is intensively investigated as one of the most promising cathode materials for aqueous zinc-ion batteries (AZIBs), but its commercialization is severely impeded by the challenging issues of the inferior intrinsic electronic conductivity and undesirable structural stability during the charge-discharge cycles. Herein, the lab-prepared flexible carbon membrane with highly electrical conductivity is first used as the matrix to generate ultrathin δ-MnO2 with an enlarged interlayer spacing induced by the K+ -intercalation to potentially alleviate the structural damage caused by H+ /Zn2+ co-intercalation, resulting in a high reversible capacity of 190 mAh g-1 at 3 A g-1 over 1000 cycles. The in situ/ex-situ characterizations and electrochemical analysis confirm that the enlarged interlayer spacing can provide free space for the reversible deintercalation/intercalation of H+ /Zn2+ in the structure of δ-MnO2 , and H+ /Zn2+ co-intercalation mechanism contributes to the enhanced charge storage in the layered K+ -intercalated δ-MnO2 . This work provides a plausible way to construct a flexible carbon membrane-based cathode for high-performance AZIBs.

Nonsteroidal anti-inflammatory drug monitoring in serum: a Tb-MOF-based luminescent mixed matrix membrane detector with high sensitivity and reliability.

The identification of drugs or biomolecules for public health monitoring requires facile analytical technologies with excellent sensitivity, portability and reliability. In the past decades, different sensing materials have inspired the development of various bioanalytical strategies. However, sensing platforms based on powder materials are not suitable for medical diagnosis, which limits further exploration and application of biosensors. Herein, a point-of-care testing (POCT) membrane was designed from an energy competition mechanism and achieved the detection of the nonsteroidal antiphlogistic diclofenac, and exhibited remarkable testing efficacy at the ppb level. The mixed matrix membrane (MMM) sensor consists of electrospun polyacrylonitrile nanofibers and luminescent Tb-MOFs and possess the advantages of high stability, outstanding anti-interference ability, efficient detection (LOD = 98.5 ppb) and easy visual recognition. Furthermore, this MMM sensor exhibits excellent recyclability in serum, which is beneficial for developing a portable and convenient device to distinguish diclofenac in practical sensing applications. Meanwhile, the feasibility and mechanism of this recyclable sensor were verified by theory and experiments, indicating that it is a promising device for diclofenac detection in biological environments to evaluate the toxic effect caused by the accumulation of nonsteroidal drugs.

Surface Reconstruction of Co4N Coupled with CeO2 toward Enhanced Alkaline Oxygen Evolution Reaction.

Constructing the active interface in a heterojunction electrocatalyst is critical for the electron transfer and intermediate adsorption (O*, OH*, and HOO*) in alkaline oxygen evolution reaction (OER) but still remains challenging. Herein, a CeO2/Co4N heterostructure is rationally synthesized through the direct calcination of Ce[Co(CN)6], followed by thermal nitridation. The in situ electrochemically generated CoOOH on the surface of Co4N serves as the active site for the OER, and the coupled CeO2 with oxygen vacancy can optimize the energy barrier of intermediate reactions of the OER, which simultaneously boosts the OER performance. Besides, electrochemical measurement results demonstrate that oxygen vacancies in CeO2 and optimized absorption free energy originating from the electron transfer between CeO2 and CoOOH contribute to enhanced OER kinetics. This work provides new insight into regulating the interface heterostructure to rationally design efficient OER electrocatalysts under alkaline conditions.

A mild reduction of Co-doped MnO2 to create abundant oxygen vacancies and active sites for enhanced oxygen evolution reaction.

Efficient and non-precious-metal-based catalysts (e.g., manganese-based oxides) for the oxygen evolution reaction (OER) remain a substantial challenge. Creation of oxygen vacancies of manganese-based oxides with the aim to enhance their intrinsic activities is rarely reported, and there is a critical requirement for a mild and facile synthesis strategy to create abundant oxygen vacancies on manganese-based oxides. Herein, Co-doped MnO2 nanowires were reduced by NaBH4 solution at room temperature; then, MnCo2O4.5 nanosheets with abundant oxygen vacancies and active sites were formed on the surface of Co-doped MnO2 nanowires. Benefiting from the reduction strategy, the fabricated hierarchical Co-doped-MnO2@MnCo2O4.5 nanowire/nanosheet nanocomposites exhibit higher catalytic activity (an overpotential of 250 mV at a current density of 10 mA cm-2 in 1.0 M KOH solution) than pristine Co-doped MnO2 nanowires. The calculated TOF of Co-doped-MnO2@MnCo2O4.5 is 0.034 s-1 at the overpotential of 300 mV, which is 136-fold higher than that of Co-doped-MnO2. The excellent OER performance was attributed to the synergistic advantages of abundant oxygen vacancies and active sites over the hierarchical nanowire-nanosheet architectures.

Coordination-induced spontaneous resolution of a TPPE-based MOF and its use as a crystalline sponge in guest determination.

In this work, by virtue of a coordination-induced fixation of the propeller-like conformation of the tetraphenylethylene (TPE) backbone, we achieved a spontaneous resolution of conglomerate-forming enantiomers of [Co(TPPE)Cl2]·4DMF (1M and 1P), as unambiguously probed by single-crystal X-ray crystallography. Benefitting from the robust, accessible, and electron-rich 1D channels, the chiral MOF turned out to be a good 'crystalline sponge' to adsorb and determine six liquid guests, of which two (2-butanol and 2-butylamine) are crystallized in an enantiospecific manner.

A novel self-assembled-derived 1D MnO2@Co3O4 composite as a high-performance Li-ion storage anode material.

Manganese dioxide (MnO2) is a high-performance anodic material and applied widely in lithium-ion batteries (LIBs). However, some intrinsic limitations originate from the low ionic conductivity, high polarization, and severe volume expansion of this type of material. In this work, we generated a one-dimensional porous MnO2@Co3O4 composite from a MnOOH@ZIF-67 precursor, which is synthesized via a self-assembly strategy. The one-dimensional porous structure provided more active sites and shorter-ion/electron-diffusion distance, thereby enabling higher Li+ storage capacity and better rate capability than a transition metal oxide alone. The Co3O4 coating buffered the volume change during Li+ insertion/extraction, leading to increased cycling stability of the electrode. When evaluated as the anode of LIBs, MnO2@Co3O4 exhibited a reversible capacity of 647 mA h g-1 at 2000 mA g-1 after 400 cycles. This excellent performance indicated that the MnO2@Co3O4 material could be an attractive potential candidate for Li+ storage.

Electrochemiluminescence immunoassay for the prostate-specific antigen by using a CdS/chitosan/g-C3N4 nanocomposite.

An electrochemiluminescence (ECL) biosensor was fabricated for the evaluation of prostate specific antigen (PSA). The sensor was developed by successively modifying glassy carbon electrode (GCE) electrodes with CdS/Chito/g-C3N4 nanocomposites and DNA1 was labeled at the 5' end with thiol. The aptamer DNA was labeled at the 3' end with a quencher ferrocene (Fc) was ligated to DNA1 by the principle of complementary base pairing. In the absence of PSA, the ECL intensity signal is effectively quenches through the energy transfer and photoexcitation electron transfer between CdS/Chito/g-C3N4 emitter and quencher Fc. After incubation with target PSA, the aptamer DNA interacts with PSA and then moved away from the electrode surface together, which will recover the ECL intensity. Under the optimal conditions, the ECL intensity increases linearly with the logarithm of PSA concentration in the range of 1 pg·mL-1 to 100 ng·mL-1, and the detection limit is 0.14 pg·mL-1 (S/N = 3). The biosensor has been successfully applied to the determination of PSA in serum sample. Graphical abstractSchematic representation of the electrochemiluminescence sensor based on a CdS/chitosan/g-C3N4 nanocomposite, which can be applied to the determination of prostate specific antigen in serum.

A two-dimensional zinc(II)-based metal-organic framework for fluorometric determination of ascorbic acid, chloramphenicol and ceftriaxone.

A two-dimensional zinc(II)-based metal-organic framework [Zn • (BA) • (BBI)] was synthesized from 1,2-benzenediacetic acid and 1,1'-(1,4-butanediyl) bis(imidazole) via a solvothermal reaction. The crystal exhibits good chemical stability in the pH range from 2 to 12, and strong fluorescence with excitation/emission maxima of 270/290 nm. The crystal is shown to by a viable fluorescent probe for the detection of ascorbic acid (AA) and the antibiotics chloramphenicol (CHL) and ceftriaxone (CRO). Fluorescence intensity of crystal dispersion is significantly quenched with increasing concentrations of AA/CHL/CRO. Quenching occurs even in the presence of other substances. The assay is fast (5 s) and has a low detection limit (1.6 ppb for AA, 12 ppb for CHL and 3.9 ppb for CRO). The crystal still has a good quenching effect on AA/CHL/CRO after washing and using for five times. The response of the probe is related to the interplay between the MOF and analytes via energy absorption competition. Graphical abstractSchematic diagram of preparing Zn • (BA) • (BBI) and responding to target analytes. BA: 1,2-phenyldiacetic acid; BBI: 1,1'-(1,4-butanediyl)bis(imidazole); Zn • (BA) • (BBI): Crystal chemical formula.

Synthesis of novel C-doped g-C3N4 nanosheets coupled with CdIn2S4 for enhanced photocatalytic hydrogen evolution.

Photocatalytic hydrogen generation from water splitting has become a favorable route for the utilization of solar energy. An effective strategy, the combination of C-doping with nanocomposite semiconductors, is presented in this work. C-doped g-C3N4 (CCN) was prepared by supramolecular self-assembly and subsequently a number of CdIn2S4/CCN composite photocatalysts were designed and fabricated though in situ decoration of CdIn2S4 crystals on the surface of CCN nanosheets via a hydrothermal method. This unique architecture was able to efficiently promote the transfer and separation of photon-generated charges, enhance light absorption, and significantly increase photocatalytic H2 production. Detailed characterization was performed to analyze the crystal structure, morphology, elementary composition, optical properties and catalytic mechanism. The CdIn2S4/CCN nanocomposites with optimal CdIn2S4 content exhibited a maximum H2 production rate of 2985 µmol h-1 g-1, almost 15 times more than that obtained using pure g-C3N4 (205 µmol h-1 g-1). In addition, the hybrid photocatalysts display good recycling stability under visible-light irradiation. This research may provide promising information for the preparation of more efficient multifunctional hybrid photocatalysts with excellent stability in fine chemical engineering.

A Cd-MOF as a fluorescent probe for highly selective, sensitive and stable detection of antibiotics in water.

Recently, the pollution and damage caused by antibiotics in water have aroused serious concerns. In this situation, it is extremely important to develop a highly effective approach to detect antibiotics in water. In this contribution, we built a Cd-MOF material with stable fluorescence properties, using bbi = 1,4-bis(2-methyl-imidazol-1-yl)butane and H2L = 1,2-phenylenediacetic acid as organic ligands and Cd(NO3)2·4H2O as the metal node. The highly selective response of this MOF probe to ceftriaxone sodium (an antibiotic) can reach up to the ppb level in water, along with a fast response time, acid and alkali resistance, and anti-interference ability.

Electrochemiluminescent biosensor with DNA link for selective detection of human IgG based on steric hindrance.

A highly selective DNA-based electrochemiluminescence (ECL) based biosensor is described for the detection of human IgG. It is exploiting the effect of steric hindrance that affects the strength of the ECL signal in the presence of IgG. Digoxin-linked signaling DNA was specifically bound to IgG, and this causes steric hindrance which limits the ability of DNA to hybridize with capturing DNA attached to a gold electrode. Europium (II) doped CdSe quantum dots were covalently linked to the DNA in order to generate the ECL signal. Using this steric hindrance hybridization method, the ECL signal of the biosensor were proportional to the concentration of IgG with a wide linear range and a 14 pM detection limit. Conceivably, the method can be expanded to the detection of a wide range of proteins for which homologous recognition elements are available.

Bottom-Up Assembly of a Highly Efficient Metal-Organic Framework for Cooperative Catalysis.

In this study, we demonstrate a bottom-up assembly of a monomeric copper complex and a two-dimensional (2-D) heterometallic metal-organic framework (MOF) from a carboxylate-functionalized tridentate Schiff base ligand and metal ions. The obtained 2-D MOF features a unique bimetallic copper center which is different from its monometallic precursor and acts as an efficient heterogeneous catalyst for the Friedel-Crafts reaction and Henry reaction. The MOF catalyst shows a remarkably superior activity compared to its homogeneous counterparts in a wide range of substrates. It is presumably ascribed to the dual activation of the substrates by the active bimetallic copper center confined in the MOF network, which is supported by the significant changes in catalytic activity at low catalyst/substrates ratios when using the 2-D MOF and its precursor as catalysts, respectively. Moreover, the MOF catalyst also shows an excellent stability and recyclability. Our work, therefore, provides a stepwise strategy to design a heterogeneous cooperative catalyst, by taking advantage of the modulated structure of MOF and tunable functionality of the tridentate Schiff base, with high performance in a variety of organic synthesis.

Synthesis of ultrathin WSe2 nanosheets and their high-performance catalysis for conversion of amines to imines.

Tungsten diselenide (WSe2) is the material with the lowest thermal conductivity in the world. Most physical methods are used for the synthesis of tungsten diselenide. Here, a simple colloidal method is reported for the synthesis of WSe2 nanosheets. The composition, valence, size, morphology and properties of the samples were characterized and measured. Results showed that the obtained WSe2 nanosheets with a thickness of 0.7 nm had strong blue fluorescence. Significantly, the synthesized WSe2 nanosheets exhibited excellent catalytic activity for the aerobic coupling of amines to imines, with 100% yield under visible light irradiation and air atmosphere. As a photocatalyst, it exhibited excellent recyclability, and maintained a high yield after 5 cycles. It was found that this reaction could also happen in the presence of natural light by slightly extending the reaction time. Moreover, H2O was used as a solvent in the catalytic process, avoiding expensive and toxic organic solvents. This work provides an efficient, economical and sustainable process for the synthesis of imines and shows the great potential of WSe2 nanosheets as photocatalysts for organic synthesis.

Enhanced photoelectrochemical DNA sensor based on TiO2/Au hybrid structure.

A novel enhanced photoelectrochemical DNA sensor, based on a TiO2/Au hybrid electrode structure, was developed to detect target DNA. The sensor was developed by successively modifying fluorine-tin oxide (FTO) electrodes with TiO2 nanoparticles, gold (Au) nanoparticles, hairpin DNA (DNA1), and CdSe-COOH quantum dots (QDs), which acted as signal amplification factors. In the absence of target DNA, the incubated DNA1 hairpin and the CdSe-COOH QDs were in close contact with the TiO2/Au electrode surface, leading to an enhanced photocurrent intensity due to the sensitization effect. After incubation of the modified electrode with the target DNA, the hairpin DNA changed into a double helix structure, and the CdSe QDs moved away from the TiO2/Au electrode surface, leading to a decreased sensitization effect and photoelectrochemical signal intensity. This novel DNA sensor exhibited stable, sensitive and reproducible detection of DNA from 0.1 µM to 10 fM, with a lower detection limit of 3 fM. It provided good specificity, reproducibility, stability and is a promising strategy for the detection of a variety of other DNA targets, for early clinical diagnosis of various diseases.

A label-free photoelectrochemical biosensor for urokinase-type plasminogen activator detection based on a g-C3N4/CdS nanocomposite.

Herein, we established a novel ultrasensitive photoelectrochemical biosensor for detecting urokinase-type plasminogen activator (u-PA), based on a g-C3N4/CdS nanocomposite. The prepared nanocomposite was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible absorption spectroscopy, and Fourier transform infrared spectroscopy, thus indicating that the nanocomposite was prepared successfully. In the typical process, the prepared nanocomposite was deposited on the surface of a bare FTO electrode. After being air-dried, the g-C3N4/CdS nanocomposite modified electrode was successively incubated with antibody against urokinase-type plasminogen activator and the blocking agent BSA to produce a photoelectrochemical biosensor for u-PA. In the presence of target u-PA antigen, the photocurrent response of the prepared biosensor electrode decreased significantly. The proposed novel photoelectrochemical biosensor exhibited good sensitivity, specificity, and reproducibility for u-PA detection, and a low detection limit of 33 fg mL-1, ranging from 1 µg mL-1-0.1 pg mL-1. The proposed strategy should provide a promising method for detection of other biomarkers.

Highly sensitive electrochemical biosensor for streptavidin detection based on CdSe quantum dots.

An electrochemical biosensor was developed based on a steric hindrance hybridization assay to allow the highly sensitive detection of streptavidin. In the steric hindrance hybridization assay, the signaling strand DNA (sig-DNA) was labeled at the 3' end with CdSe quantum dots (QDs) and at the 5' end with biotin, and capturing strand DNA (the complementary strand of sig-DNA) was labeled at the 5' end with thiol. The steric hindrance effect generated by streptavidin which was bound with the signaling DNA strand. The streptavidin limited the ability of the sig-DNA to hybridize with the cap-DNA, which were linked on the surface of a gold electrode. Therefore, the concentration of streptavidin was detected indirectly based on the concentration of CdSe QDs on the electrode surface. The concentration of CdSe QDs on the electrode surface was detected by differential pulse anodic stripping voltammetry. Under optimal conditions, the streptavidin detection range using the as-prepared biosensor was 1.96pg/mL to 1.96µg/mL and the detection limit was 0.65pg/mL. The experimental results showed that the electrochemical biosensor could detect streptavidin rapidly and accurately.

Colloidal Synthesis and Thermoelectric Properties of CuFeSe2 Nanocrystals.

Copper-based chalcogenides that contain abundant, low-cost and environmentally-friendly elements, are excellent materials for numerous energy conversion applications, such as photocatalysis, photovoltaics, photoelectricity and thermoelectrics (TE). Here, we present a high-yield and upscalable colloidal synthesis route for the production of monodisperse ternary I-III-VI2 chalcogenides nanocrystals (NCs), particularly stannite CuFeSe2, with uniform shape and narrow size distributions by using selenium powder as the anion precursor and CuCl2·2H2O and FeCl3 as the cationic precursors. The composition, the state of valence, size and morphology of the CuFeSe2 materials were examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM), respectively. Furthermore, the TE properties characterization of these dense nanomaterials compacted from monodisperse CuFeSe2 NCs by hot press at 623 K were preliminarily studied after ligand removal by means of hydrazine and hexane solution. The TE performances of the sintered CuFeSe2 pellets were characterized in the temperature range from room temperature to 653 K. Finally, the dimensionless TE figure of merit (ZT) of this Earth-abundant and intrinsic p-type CuFeSe2 NCs is significantly increased to 0.22 at 653 K in this work, which is demonstrated to show a promising TE materialand makes it a possible p-type candidate for medium-temperature TE applications.

Photoelectrochemical immunoassay for human interleukin 6 based on the use of perovskite-type LaFeO3 nanoparticles on fluorine-doped tin oxide glass.

A film of perovskite-type LaFeO3 nanoparticles (NPs) was deposited on fluorine-doped tin oxide (FTO) conducting glass via dipping-lifting and calcination. Scanning electron microscopy shows that the NPs are evenly distributed on the surface of the glass. The modified glass was further coated with antibody against human interleukin 6 (IL-6) to result in a photoelectrochemical immunosensor for IL-6. The well-established photoelectrochemical immunoassay has a linear current response in the range of 0.1 pg·mL-1 to 0.1 µg·mL-1 and a detection limit as low as 33 fg·mL-1. Graphical abstract Schematic of a novel photoelectochemical immunoassay for the measurement of IL-6 based on perovskite-type LaFeO3 nanoparticles. The immunoassay had a higher sensitivity and may also be applied to other bioanalysis and environment monitoring.

Highly Sensitive Electrochemical Dopamine Sensor from Poly(diallyldimethylammonium chloride)-Functionalized Graphene Nanoribbon/Gold Nanoparticle Nanocomposite.

A novel graphene oxide nanoribbon/poly(diallyldimethylammonium chloride)/gold nanoparticle (GONR/PDDA/AuNP) nanocomposite was synthesized successfully and used for the sensitive detection of dopamine. The GONR/PDDA/AuNP nanocomposite was characterized by transmission and scanning electron microscopy. The electrochemical sensor based on GONR/PDDA/AuNP nanocomposite. was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Experimental parameters such as GONR/PDDA concentration, volume ratio of GONR/PDDA to AuNP, scan rates, and pH were studied to investigate their effect on peak currents. Under optimal conditions, the GONR/PDDA/AuNP-based sensor exhibited excellent electrocatalytic activity for the detection of dopamine with a wide linear range from 9.99 x 10(-8) to 8.69 x 10(-4) M and a low detection limit of 3.33 x 10(-8) M. Moreover, the proposed sensor exhibits high sensitivity, good reproducibility, and stability, and could therefore potentially be applied in other bioanalytical systems.