Worm-like mesoporous carbon synthesized from metal–organic coordination polymers for supercapacitors

A green and efficient route has been employed to synthesize a worm-like mesoporous carbon with high specific surface area (2587 m² g^?1) and large pore volume (3.14 cm³ g^?1). Three electrochemical methods have been used to measure its electrochemical performance. Worm-like mesoporous carbon performs the high specific capacitance (344 F g^?1) at constant-current densities of 50 mA g^?1.     

A serial of 2D Co-Zn isomorphous metal–organic frameworks for photodegradation and luminescent detection properties

A series of 2D isomorphous MOFs [M (HBTC)(BMIOPE)·DMF·H₂O]_n (M = Zn ( 1 ), Zn_0.7Co_0.3 ( 2 ), Zn_0.5Co_0.5 ( 3 ), Zn_0.3Co_0.7 ( 4 ), Co ( 5 ), H₃BTC = 1,3,5-benzenetricarboxylic acid, BMIOPE = 4,4′-bis(2-methylimidazol-1-yl)diphenyl ether) were synthesized to investigate the correction between the center metal ions and the photocatalytic behaviors. The photocatalytic results show that with the increase of Co²⁺ content, the photodegradation properties are continuously improved from 1 to 5 , which fully indicate that only changing metal ions could regulate the photodegradation properties. In detail, 1 is an inactive photocatalyst to degrade methylene blue (MB), while 5 exhibits preeminent photocatalytic properties under visible light irradiation. Moreover, 1 shows good selective sensing toward Fe³⁺, Cr³⁺, UO₂²⁺, CrO₄²⁻ and Cr₂O₇²⁻ ions in aqueous solution. To the best of our knowledge, 1 is the first MOF example for the optical detection of Fe³⁺, Cr³⁺, UO₂²⁺, CrO₄²⁻ and Cr₂O₇²⁻ ions in aqueous solution.     

Electrochemical sensor based on super-magnetic metal–organic framework@molecularly imprinted polymer for Sarcosine detection in urine

Accurate determination of Sarcosine (SAR) in urine with high sensitivity and selectivity is important, because it was recently recommended as a prospective biomarker for prostate cancer (PCa) and significant for the early identification of PCa. In this study, an electrochemical sensor based on Fe₃O₄ incorporated metal–organic frameworks (MOFs) @molecularly imprinted polymer (MIP) was constructed for SAR detection. Magnetic Fe₃O₄ nanoparticles embedded zeolitic imidazolate framework-8 (ZIF-8) was used as the support of MIP. MIP provides specific recognition sites for template molecules SAR and MOFs increase the rate of mass transfer and adsorption capacity due to the porous structure. The synthesized super-magnetic Fe₃O₄@ZIF-8@MIP was self-assembled onto an Au electrode in magnetic field and used as the sensing unit of electrochemical sensor. Cyclic voltammetry was used to monitor the electrochemical behavior, and the binding of SAR resulted in a reduction in the measured current. The results revealed a wide linear range from 1 to 100 pM towards trace SAR determination, with extremely low limit of detection down to 0.4 pM. In conclusion, the Fe₃O₄@ZIF-8@MIP based sensor provides a selective, sensitive, and convenient method for SAR diagnosis and other cancer marker detection.     

RNA aptamer-based optical nanostructured sensor for highly sensitive and label-free detection of antigen–antibody reactions

Developments of optical protein sensors with nanostructure based on the noble metals have currently received great attention for their high efficiency and simultaneous analysis of various important biomolecules from proteomics to genetics. In this study, we exploited the absorbance spectra of gold-capped nanoparticles substrate for label-free detections of antigen–antibody reactions using a specific thiolated RNA aptamer. These synthesized RNA aptamers have been optimized to bind to the Fc portion of the human IgG1 subclass, due to their ability to orient antibodies direction on the gold surface. After attaching the anti-fibrinogen antibodies on the surface via these linkers, our thiolated RNA aptamer-based nanostructured sensors were easily applicable to specific detections of fibrinogen with a limit of detection of 0.1 ng/mL. These nanostructured sensor-based models will open a way to display numerous immunosensors as well as to develop other functionally similar sensors which could then be expanded into multi-arrays assay systems.     

Flexible bis(pyridyl-tetrazole) ligand-induced ring-containing metal–organic coordination polymers: synthesis,structures, and properties

Three coordination polymers (CPs), [Co(3-bptzp)(BDC)] (1), [Zn(3-bptzp)(BDC)] (2), and [Cd(3-bptzp)(BDC)] (3) (3-bptzp = 1,4-bis(5-(3-pyridyl)tetrazolyl)propane, H₂BDC = 1,3-benzenedicarboxylic acid), were synthesized under hydrothermal conditions. The CPs were structurally characterized by single-crystal X-ray diffraction, infrared spectroscopy (IR), elemental analyses, and powder X-ray diffraction (PXRD). Complexes 1–3 represent the first examples of CPs based on the flexible bis(pyridyl-tetrazole) 3-bptzp. Structure analyses reveal that 1–3 are 1-D ring-containing polymeric chains. For 2 and 3, adjacent 1-D chains are extended to 2-D supramolecular networks by hydrogen bonding. Dye adsorption properties of 1–3, electrochemical properties of 1, and fluorescent-sensing behaviors of 2 and 3 have also been investigated.     

A series of new hybrid compounds constructed from Dawson-type phosphomolybdates and metal–organic coordination complexes

In this study, a series of compounds based on Dawson-type phosphomolybdates, H₃(C₆NO₂H₆)₂[K(H₂O)₃(C₆NO₂H₅)₃][P₂Mo₁₈O₆₂] ? 5.5H₂O (1), (C₆NO₂H₆)₆[Ln(H₂O)₇(C₆NO₂H₅)₂]₂[P₂Mo₁₈O₆₂]₂·13.5H₂O (Ln = Ce (2), La (3)) have been synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopy methods, TG analysis, and single-crystal X-ray diffraction. Compound 1 consists of [P₂Mo₁₈O₆₂]^6? building units joined by potassium-pyridine-3-carboxylic acid complexes, resulting in a wavelike polyoxometalate (POM) chain, which further interacts with each other via intermolecular interactions to form a 3-D supramolecular channel framework containing guest water molecules. Compounds 2 and 3 possess a 3-D supramolecular framework with 1-D tunnel constructed from [P₂Mo₁₈O₆₂]^6? and mononuclear lanthanide coordination complex fragments. To the best of our knowledge, 1 not only represents the first example of 1-D hybrid assembly based on Dawson-type phosphomolybdate, but also the first hybrid compound constructed from Dawson-type POMs and alkali–metal coordination complex fragments.     

Structure,dynamics, and solvation in a disordered metal–organic coordination polymer: a multiscale study

Metal–organic coordination polymers are a growing class of technologically-important materials in which transition metal ions are connected by multitopic organic chelators to form a 3-D network structure. While the structures of many highly-ordered metal–organic frameworks have been determined, far less structural information is available about the more common disordered materials. Our study combines pair distribution function analysis from total X-ray scattering, ab initio quantum mechanical calculations, and all-atom molecular dynamics to explore the structure and dynamics of a poorly-ordered branched coordination polymer. The polymer structure is highly flexible and dynamic, and is dramatically affected by its solvation state, a finding with far-reaching implications for the incorporation of coordination polymers into nanocomposite materials.     

CuS–MWCNT based electrochemical sensor for sensitive detection of bisphenol A

The rapid and simple detection of bisphenol A is very important for the safety and reproduction of organisms. Here, a sensitive and reliable electrochemical sensor was established for bisphenol A detection based on the high amplification effect of copper sulfide-multi-walled carbon nanotube (CuS–MWCNT) nanocomposites. The flower-like CuS–MWCNT were successfully synthesized by a simple hydrothermal method accompanied by polyvinylpyrrolidone (PVP). Compared with bare glassy carbon electrode (GCE), CuS–MWCNT modified GCE could amplify the electrochemical signals in about ten times, which was attributed to the synergistic effect of CuS and MWCNT. The MWCNT could increase the specific surface area of electrodes and improve the electrode activity. The integration of CuS could further enhance the electrode conductivity as well as accelerate the electron transfer rate. Raman spectra and transmission electron microscope (TEM) were used to characterize the successful fabrication of CuS–MWCNT nanocomposites and its uniform and monodispersed morphology. Under optimizing conditions, the oxidation currents of bisphenol A via the differential pulse voltammetric (DPV) showed a good linear relationship with its concentration in a wide range of 0.5–100 μM, with a detection limit of 50 nM. This electrochemical sensor of bisphenol A provided a convenient and economical platform with high sensitivity and reproducibility, which had great potential in environmental monitoring.     

Hydrothermal syntheses,structures, and properties of four metal–organic coordination polymers assembled from V-shaped tetracarboxylate ligands and N-donor ancillary ligands

A series of four metal–organic frameworks, namely, [Cu(sdpa)_0.5(2,2′-bpy)]·H₂O (1), [Zn₂(sdpa)(2,2′-bpy)₂(H₂O)₂]·3H₂O (2), [Zn₂(sdpa)(4,4′-bpy)]·3H₂O (3), [Cd₂(sdpa)(4,4′-bpy)_1.5(H₂O)₂](4), have been hydro(solvo)thermally synthesized through the reaction of 2,3,2′,3′-sulfonyldiphthalic acid (H₄sdpa) with divalent copper, zinc and cadmium salts in the presence of ancillary nitrogen ligands (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine) and structurally characterized by elemental analysis, IR and X-ray diffraction. Both complex 1 and 2 show metal–organic chain structure, and the adjacent chains are further linked by π?π and C–H?π interactions for 1 and hydrogen bonds and π?π interactions for 2 to form 3D supramolecular structure. In complex 3, two Zn1 and two Zn2 atoms appear alternately and are bridged by sdpa⁴⁻ anion ligands to form an infinite Zn-sdpa chain. Such chains are further linked together through 4,4′-bpy ligands in four orientations to form a robust 3D metal–organic network. In compound 4, a 3D Cd-sdpa metal–organic network is accomplished through sdpa⁴⁻ anion ligands, and further stabilized by 4,4′-bpy in six orientations. Their luminescence and thermal analysis have also been investigated.     

Three-dimensional metal–organic frameworks: Two Ag(I) coordination polymers of TTF derivatives with axially chiral helical motifs

Two novel 3D coordination polymeric networks based on Ag(I) and TTF derivatives, [Ag₄(tces-TTF)₂(CF₃SO₃)₂](CF₃SO₃)₂ (tces = 2,3,6,7-tetra(cyanoethylsulfanyl)) (1) and [Ag₂(bmdt)₂](SbF₆)₂ · acetone (bmdt = 4,5-bis(methylsulfanyl)-1,3-dithiole-2-thione) (2), were synthesized and crystallographically characterized. Both 1 and 2 have axially chiral helical motifs and these helices were assembled in a similar way: spiral up along b axis infinitely. In addition, complex 2 forms a “cds” network with a topology of 6⁵.8. The conductivity of complex 1 was measured at RT with a σ value of 3.47 × 10⁻⁶S cm⁻¹ due to the S?S contacts in the molecules, while 2 is an insulator at RT.     

pH-Controlled assembly of two POM-based inorganic–organic hybrid copper coordination polymers: synthesis,structures and properties

Transition Metal Chemistry - Two POM-based copper coordination polymers constituted by Keggin-type polyoxometalates (POMs), [Cu2 (SiW12O40)2 (Fbtx)3 (H2O)4]n (1) and {[Cu2 (SiW12O40) (Fbtx)2...     

Facile synthesis of an optical sensor for CO32− and HCO3− detection

A novel fluorogenic signalling probe (E)-3-(4-methoxyphenyl)-4-[(4-nitrobenzylidene)amino]-1H-1,2,4-triazole-5(4H)-thione (6) for the carbonate and bicarbonate ions has been developed through microwave assisted Schiff base formation reaction. The anion recognition occurs through hydrogen bonding assessed by ¹H NMR titration experiments. The photophysical results of probe 6 corroborates its applicability as an optical sensing platform for carbonate as well as bicarbonate ions in mixed aqueous organic media depending on pH of reaction solution. The fluorescence emission signal enhancement at 424 nm and considerable shift in the signal position as well as molar absorptivity to the probe absorption bands upon CO₃^2? and HCO₃^? addition suggest the affinity of probe 6 towards these ions in comparison to a variety of competitive ions in aqueous/ethanol (7:3, v/v) at neutral pH and ambient temperature. From the fluorescence titration experiment, the limit of detection was calculated to be 1.91 μM.     

Plasmonics for the study of metal ion–protein interactions

The study of metal–protein interactions is an expanding field of research investigated by bioinorganic chemists as it has wide applications in biological systems. Very recently, it has been reported that it is possible to study metal–protein interactions by immobilizing biomolecules on metal surfaces and applying experimental approaches based on plasmonics which have usually been used to investigate protein–protein interactions. This is possible because the electronic structure of metals generates plasmons whose properties can be exploited to obtain information from biomolecules that interact not only with other molecules but also with ions in solution. One major challenge of such approaches is to immobilize the protein to be studied on a metal surface with preserved native structure. This review reports and discusses all the works that deal with such an expanding new field of application of plasmonics with specific attention to surface plasmon resonance, highlighting the advantages and drawbacks of such approaches in comparison with other experimental techniques traditionally used to study metal–protein interactions.

Multiplex sensor for detection of different metal ions based on on–off of fluorescent gold nanoclusters

In this study, a multiplex fluorescence sensor for successive detection of Fe³⁺, Cu²⁺ and Hg²⁺ ions based on “on–off” of fluorescence of a single type of gold nanoclusters (Au NCs) is described. Any of the Fe³⁺, Cu²⁺ and Hg²⁺ ions can cause quenching fluorescence of Au NCs, which established a sensitive sensor for detection of these ions respectively. With the introduction of ethylene diamine tetraacetic acid (EDTA) to the system of Au NCs and metal ions, a restoration of fluorescence may be found with the exception of Hg²⁺. A highly selective detection of Hg²⁺ ion is, thus, achieved by masking Fe³⁺ and Cu²⁺. On the other hand, the masking of Fe³⁺ and Cu²⁺ leads to the enhancement of fluorescence of Au NCs, which in turn provides an approach for successive determination of Fe³⁺ and Cu²⁺ based on “on–off” of fluorescence of Au NCs. Moreover, this assay was applied to the successful detection of Fe³⁺, Cu²⁺ and Hg²⁺ in fish, a good linear relationship was found between these metal ions and the degree of quenched fluorescent intensity. The dynamic ranges of Hg²⁺, Fe³⁺ and Cu²⁺ were 1.96 × 10⁻¹⁰–1.01 × 10⁻⁹, 1.28 × 10⁻⁷–1.27 × 10⁻⁶ and 1.2 × 10⁻⁷–1.2 × 10⁻⁶ M with high sensitivity (the limit of detection of Fe³⁺ 2.0 × 10⁻⁸ M, Cu²⁺ 1.9 × 10⁻⁸ M and Hg²⁺ 2 × 10⁻¹⁰ M). These results indicate that the assay is suitable for sensitive detection of these metal ions even under the coexistence, which can not only determine all three kinds of metal ions successively but also of detecting any or several kinds of metal ions.     

Recent trends in the liquid chromatography–mass spectrometry analysis of organic contaminants in environmental samples

An overview of liquid chromatography–mass spectrometry methods used for the determination of trace organic contaminants in environmental samples is presented. Among the organic contaminants the focus is given on five groups of emerging contaminants that raised most concern as environmental contaminants and therefore attracted attention of a research community: pharmaceuticals, drugs of abuse, polar pesticides, perfluorinated compounds and nanoparticles. Various aspects of current LC–MS methodology, using tandem and hybrid MS instruments, including sample preparation, are discussed.     

A rational design of the multiwalled carbon nanotube–7,7,8,8-tetracyanoquinodimethan sensor for sensitive detection of acetylcholinesterase inhibitors

A new, simple and effective amperometric acetylcholinesterase biosensor was developed using screen-printed carbon electrodes modified with carbon nanotubes (MWCNTs)–7,7,8,8-tetracyanoquinodimethane (TCNQ). The design of the biosensor was based on the supramolecular arrangement resulted from the interaction of MWCNTs and TCNQ. This arrangement was confirmed by spectroscopic and electrochemical techniques. Two different supramolecular arrangements were proposed based on different MWCNTs:TCNQ ratios. The synergistic effect of MWCNTs and TCNQ was, for the first time, exploited for detection of thiocholine at low potential with high sensitivity. The biosensor developed by immobilization of acetylcholinesterase (AChE) in sol–gel allowed the detection of two reference AChE inhibitors, paraoxon-methyl and chlorpyrifos with detection limits of 30 pM (7 ppt) and 0.4 nM (0.1 ppb), respectively. Efficient enzyme reactivation was obtained by using obidoxime.     

A selective coumarin-based “turn-on” fluorescent sensor for the detection of cysteine and its applications for bioimaging

A coumarin-based compound (1) was designed and synthesized as a new turn-on fluorescent probe for the detection of cysteine. The in vivo imaging of Hi5 cell and Caenorhabditis elegans had further confirmed the cysteine detection by compound 1.     

Polycarboxylate-assisted assembly of cobalt(II) metal–organic coordination polymers from a “V”-shaped tri-pyridyl-bis-amide ligand

The aim of this study was to explore the influence of the position and angles of carboxyl groups of polycarboxylates on constructing coordination polymers. Three Co(II) metal–organic coordination polymers based on a tri-pyridyl-bis-amide ligand, namely [Co(L)(1,2-BDC)(H₂O)₂]·2H₂O (1), [Co(L)(1,4-BDC)(H₂O)₂]·2H₂O (2) and [Co(L)₂(BTEC)_0.5]·H₂O (3) (L = N,N′-bis(pyridine-3-yl)pyridine-2,6-dicarboxamide, 1,2-H₂BDC = 1,2-benzenedicarboxylic acid, 1,4-H₂BDC = 1,4-benzenedicarboxylic acid, H₄BTEC = 1,2,4,5-benzenetetracarboxylic acid), have been obtained by tuning the auxiliary polycarboxylate ligands. Structural analyses reveal that complexes 1–3 display diverse structures. Complex 1 displays a meso-helical chain linked by L ligands, which is further extended into a three-dimensional supramolecular framework through hydrogen-bonding interactions. The 1,2-BDC with a chelating coordination mode only acts as the hydrogen bond acceptor. In complex 2, the 1,4-BDC anions connect adjacent Co(II) atoms to form a linear chain, which is connected by hydrogen-bonding interactions to construct a 3D supramolecular network. Complex 3 exhibits a chain, which is composed of left-/right-handed Co-L helical chains and Co-BTEC linear chain. The 1D chains are ultimately extended into a two-dimensional supramolecular network by hydrogen-bonding interactions. Moreover, the thermal stability and the fluorescent properties of the title complexes and the electrochemical behaviors of a bulk-modified carbon paste electrode with complex 2 have been investigated at room temperature.