Hongxu Guo

Highly Dispersible and Stable Copper Terephthalate Metal–Organic Framework–Graphene Oxide Nanocomposite for an Electrochemical Sensing Application

A highly dispersible and stable nanocomposite of Cu(tpa)-GO (Cu(tpa) = copper terephthalate metal-organic framework, GO = graphene oxide) was prepared through a simple ultrasonication method. The morphology and structure of the obtained composite were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis, Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). On the basis of the characterization results, the binding mechanism of the Cu(tpa) and GO was speculated to be the cooperative interaction of π-π stacking, hydrogen bonding, and Cu-O coordination. The electrochemical sensing property of Cu(tpa)-GO composite was investigated through casting the composite on a glassy carbon electrode (GCE), followed by an electro-reduction treatment to transfer the GO in the composite to the highly conductive reduced form (electrochemically reduced graphene, EGR). The results demonstrated that the electrochemical signals and peak profiles of the two drugs of acetaminophen (ACOP) and dopamine (DA) were significantly improved by the modified material, owing to the synergistic effect from high conductivity of EGR and unique electron mediating action of Cu(tpa). Under the optimum conditions, the oxidation peak currents of ACOP and DA were linearly correlated to their concentrations in the ranges of 1-100 and 1-50 μM, respectively. The detection limits for ACOP and DA were estimated to be as low as 0.36 and 0.21 μM, respectively.

A novel highly selective colorimetric sensor for aluminum (III) ion using Schiff base derivative

A novel colorimetric sensor, 2-hydroxy naphthaldehyde isonicotinoyl hydrazone (HINH), was easily synthesized by the condensation of isoniazid and 2-hydroxy-1-naphthaldehyde. The as-prepared compound showed effective colorimetric single selectivity and high sensitivity for aluminum cation in CH3CN/H2O (1:3) binary solutions. The detection limit is 1.0×10(-8) M Al(3+) based on UV-vis changes.

β-Cyclodextrin functionalized graphene as a highly conductive and multi-site platform for DNA immobilization and ultrasensitive sensing detection

A versatile nanocomposite containing β-cyclodextrin and graphene (CD-GR) was prepared through a simple chemical reduction method. The characterization experiments show that the nanocomposite remains the flake-like morphology of GR, but its solubility and stability in aqueous solution are greatly improved. Then the nanocomposite was modified at glassy carbon electrode (GCE) surface, and was used as a functional matrix for the covalent immobilization of probe DNA using 2,4,6-trichloro-1,3,5-triazine (TCT) as the crosslinker. Due to the synergetic effect of large surface area of GR and rich hydroxyl of CD, the probe density for the developed biosensor was determined to as high as 3.82×10(13) molecules cm(-2). Meanwhile, the biosensor shows high hybridization efficiency and hybridization kinetic. When the biosensor was applied for the impedance-based hybridization test, a wide linear range from 1.0×10(-16) to 1.0×10(-12) M and an ultralow detection limit of 3.4×10(-17) M were achieved. The biosensor also displays excellent stability, selectivity, and reproducibility.

Facile one-pot fabrication of Ag@MOF(Ag) nanocomposites for highly selective detection of 2,4,6-trinitrophenol in aqueous phase

Ag@MOF(Ag) nano-composites were fabricated through one-pot facile reflux reaction from the raw materials of AgNO3 and 2-aminoterephthalic acid, and were then characterized through SEM, TEM, XRD, XPS, and FTIR, which showed a high fluorescence quantum yield (10.6%) and exhibited outstanding selectivity and excellent sensitivity for 2,4,6-trinitrophenol (TNP) over a concentration range of 1-29μM in water. The fluorescence quenching mechanism may be attributed to hydrogen-bonding interactions and resonance energy transfer.

Facile one-step mechanochemical synthesis of [Cu(tu)]Cl·1/2H2O nanobelts for high-performance supercapacitor

A facile one-step mechanochemical process from CuCl2·2H2O and thiourea (tu) to fabricate novel [Cu(tu)]Cl·1/2H2O nanobelts has been observed for the first time, and the nanobelts were used as an electrode material for a supercapacitor. The [Cu(tu)]Cl·1/2H2O nanobelts with staggered arrangement have lengths longer than 10 μm, and exactly straight nanobelts are 300 nm in width, and the extreme ends of nanobelts are around 30–50 nm in width. The specific capacitance of the [Cu(tu)]Cl·1/2H2O nanobelts was up to 1145 F g−1 at scan rate of 5 mV s−1 and 922 F g−1 at current density of 10 A g−1 in a 2 M KOH electrolyte. Simultaneously, the retention was maintained at 72.4% after 500 cycles at 10 A g−1. The corresponding equivalent circuit for the [Cu(tu)]Cl·1/2H2O was also discussed. This study provides a facile, green, and large-scale method to fabricate novel nano-complexes with high supercapacitor activity.

Three coordination polymers built from planar tetranuclear clusters and 5-sulfoisophthalic acid

Three coordination polymers built from planar tetranuclear clusters and H3sip ligands, Pb2Cl(sip)(bipy) (1), Pb2Br(sip)(H2O) (2), and Ni4(sip)2(pyz)2(H2O)8(OH)2·2H2O (3) (H3sip = 5-sulfoisophthalic acid, bipy = 2,2′-bipyridine, and pyz = pyrazine), have been hydrothermally synthesized and characterized by IR, TGA, and single-crystal X-ray diffraction. Compound 1 features a 2-D layer-like structure containing tetranuclear square [Pb4(SO3)2] clusters. Complex 2 has a 3-D open framework architecture constructed from tetranuclear cluster [Pb4Br2(SO3)2] inorganic building blocks. The tetranuclear units, [Ni4(OH)2(COO)4], in 3 are interlinked through carboxylates and µ2-pyz ligands to generate a 2-D layer structure. The connecting modes between tetranuclear clusters and organic ligands in the three compounds are discussed in this article. In the solid state at room temperature, yellow photoluminescence in 1 and 2 are observed.