Mesoporous amorphous MnO<Subscript>2</Subscript> as electrode material for supercapacitor

A kind of novel mesoporous, electrochemical active material, amorphous MnO₂ has been synthesized by an improved reduction reaction and using supramolecular as template. The synthesized sample was characterized physically by thermogravimetric analysis, X-ray diffraction, transmission electron microscope (TEM), and Brunauer–Emmett–Teller (BET) surface area measurement, respectively. Electrochemical characterization was performed using cyclic voltammetry and chronopotentiometry in 2 mol/l KOH aqueous solution electrolyte. The results of BET and TEM analysis indicated that supramolecular template plays an important role in the process of big specific surface area mesoporous material forming. After sintering at 200 °C, the sample still remained an amorphous structure, and its specific capacitance reached 298.7 F/g and presented a very stable capacitance after 500 cycles. In addition, the electrochemical process, such as ion transfer and electrical condition, was also investigated with electrochemical impedance spectroscopy.     

Synthesis of a fluorescein–porphyrin hybrid and its supramolecular self-assembly with amino-porphyrinatocopper(II) by hydrogen bonding

A fluorescein–porphyrin hybrid (Fl-PTPP) has been synthesized and characterized by UV/Vis, IR, ¹H NMR, ES-MS and elemental analysis. The supramolecular self-assembly of Fl-PTPP with the copper(II) complex of 5-(p-amino-phenyl)-10,15,20-triphenylporphyrin, (CuAPTPP), by hydoxyl-amino type hydrogen bonding was studied using vapor pressure osmometry (VPO) measurements, ES-MS, UV/Vis, ¹H NMR and fluorescence spectroscopic titration. The data indicate formation of a (Fl-PTPP)–CuAPTPP supramolecular complex. Fluorescence strengthening character was observed in a spectroscopic titration experiment for the Fl-PTPP/CuAPTPP system. The association constant of the supramolecular complex was calculated from the fluorescence titration data, and found to be less than that of a carboxyl–carboxyl type hydrogen-bonding system.     

Supramolecular complex formation of β-cyclodextrin polymer with substituted salicylic acid or 3-hydroxy-2-naphthoic acid and their electrorheological behaviors

According to the chemical design, electrorheological properties of supramolecular complex from β-cyclodextrin polymer (β -CDP) were discussed. Six supramolecular complexes of β-cyclodextrin polymer with substituted salicylic acid and 3-hydroxy-2-naphthoic acid were synthesized by the solid-phase self-assembly method, and their component and structure were characterized by NMR, FT-IR, UV-vis and the fluorescence analysis. Then the electrorheological properties of their suspensions in silicone oil were investigated under DC electric fields. It was found that the yield stresses of these supramolecular complex ER fluids were 7.3–9.8 kPa at 4 kV/mm in DC electric field, which were enhanced by 34%–72% compared with that of pure β-CDP. Among them, that of β-CDP/3-hydroxy-2-naphthoic acid ER fluid was the highest. It was also found that the ER effect of supramolecular complexes can be controlled by changing different guests. When the substituted group is at phenyl ring, ER behavior can be slightly adjusted by the different substituted groups, their number as well as their position at phenyl ring. This can be proved by the measurement of dielectric properties.     

Role of ionene in composition of porous structure of template-synthesized silicas

Effect of the presence of I-4 Me-Ph ionene in the supramolecular template (cetyltrimethylammonium bromide) on formation of porous structure of silicas has been studied. As-synthesized nanocomposites were characterized by using thermal analysis. Nitrogen adsorption–desorption measurements, X-ray diffraction and scanning electronic microscopy were applied to determine adsorption-structural characteristics and morphology of particles of the mesoporous templated silicas prepared in basic media.     

Biosynthesis and electrochemical characteristics of LiFePO4/C by microwave processing

The yeast cells are adopted as a template and cementation agent to prepare LiFePO₄/C with high surface area by co-precipitation and microwave processing. The electrochemical properties of the resultant products are investigated. The synthesized LiFePO₄/C is characterized by means of X-ray diffraction, transmission electron microscopy (TEM), Brunauer–Emmett–Teller method, and battery test instrument. The LiFePO₄/C particles with average size of 35-100 nm coated by porous carbon are observed by TEM. The LiFePO₄/C, with the specific surface area of 98.3 m²/g, exhibits initial discharge specific capacity of 147 mAh/g and good cycle ability. The yeast cells as a template are used to synthesize the precursor LiFePO₄/cells compounds. In microwave heating process, the use of yeast cells as reducing matter and cementation agent results in the enhancement of the electrochemical properties.     

Polyaniline composites: improving the electrochemical properties by template synthesis

We have been exploring the idea of using the heterogeneous porosity of inorganic (sol-gel silica) and organic (poly(vinylidene fluoride)) films as a template for the preparation of polyaniline composites. The large size pore distribution (~2.5–800 nm) in both template matrices results in a part of the polyaniline growing more ordered than in films synthesized without spatial restriction. Small-angle X-ray scattering and scanning electron microscopy experiments were done to determine the extreme values of the pore diameters. Using other experimental techniques, including cyclic voltammetry, UV-Vis-NIR spectroscopy, electrochemical impedance and chronopotentiometry, we concluded that the electrochemical properties of polyaniline, such as oxidation and reduction charges, diffusion coefficient and charge-discharge capacity, are improved in these composites. Electronic Publication     

Pulsed Current Electrochemical Synthesis of Nickel Nanoclusters and Application as Catalyst for Hydrogen and Oxygen Revolution

The main objective of this research is to prepare nickel nanoparticles with more porous structure by the pulsed current electrochemical method. A nickel optimized nanopowder was synthesized by using nickel chloride (0.005 M) as precursor, silver nitrate as a nucleation agent (at 0.5% mole of nickel salt in the starting solution), polyvinyl pyrrolidone (PVP) as structure director (with PVP/Ni = 1.7 g/g), ammonia (2 M), and hydrazine as reduction agent (with Hydrazine/Ni = 16 g/g) by pulsed current of 58 mA cm⁻² with a frequency of 12 Hz. The morphology and particle size of each synthesized sample was studied by scanning electron microscopy (SEM). The obtained results showed that temperature has no considerable effect on the morphology and particle size of nickel nanopowder. The nickel nanopowder synthesized in optimum conditions has excellent uniform and a more porous structure including nanoclusters with a particle size of approximately 10–20 nm. The obtained results indicate that the pulsed current electrochemical method can be used as a confident and controllable method for the preparation of nickel nanoparticles. Optimized nickel nanoclusters were used as catalyst for hydrogen and oxygen revolutions. Cyclic Voltammetry results showed that the synthesized nanoclusters can facilitate hydrogen reduction and increase hydrogen and oxygen revolution rates.     

Application of linear-sweep voltammetry to the determination of nucleic acids using crystal violet as an electrochemical probe

A new linear-sweep voltammetric assay of nucleic acids (NAs) based on their interaction with crystal violet (CV) is proposed. In a pH 3.5 Britton—Robinson (B-R) buffer solution, CV had an irreversible voltammetric reductive peak at −0.77 V and the peak current greatly decreased by the addition of NAs. Under the experimental conditions, the decrease in the peak current was used for the NAs assay 0.5–18.0 μg/mL of fish sperm DNA, 0.6–15.0 μg/mL of calf thymus DNA, and 0.8–12.0 μg/mL of yeast RNA. The detection limits (3σ) were 0.32, 0.47, and 0.61 μg/mL for fsDNA, ctDNA, and yRNA, respectively. The binding reaction can be completed after mixing DNA with CV within 10 min and the electrochemical response is stable for 2 h. There are seldom interferences in this method and three synthetic samples were analyzed with satisfactory results. The stoichiometry of the supramolecular complex with the binding number 3 and the binding constant 2.78 × 10¹⁴ is calculated using electrochemical data. The text was submitted by the authors in English.     

LiFePO<Subscript>4</Subscript>/CA cathode nanocomposite with 3D conductive network structure for Li-ion battery

A novel LiFePO₄/Carbon aerogel (LFP/CA) nanocomposite with 3D conductive network structure was synthesized by using carbon aerogels as both template and conductive framework, and subsequently wet impregnating LiFePO₄ precursor inside. The LFP/CA nanocomposite was characterized by X-ray diffraction (XRD), TG, SEM, TEM, nitrogen sorption, electrochemical impedance spectra and charge/discharge test. It was found that the LFP/CA featured a 3D conductive network structure with LiFePO₄ nanoparticles ca. 10–30 nm coated on the inside wall of the pore of CA. The LFP/CA electrodes delivered discharge capacity for LiFePO₄ of 157.4, 147.2, 139.7, 116.3 and 91.8 mA h g⁻¹ at 1 °C, 5 °C, 10 °C, 20 °C and 40 °C, respectively. In addition, the LFP/CA electrode exhibited good cycling performance, which lost less than 1% of discharge capacity over 100 cycles at a rate of 10 °C. The good high rate performances of LiFePO₄ were attributed to the unique 3D conductive network structure of the nanocomposite.     

Electrochromism and electrochemical magnetism in Ni–Fe Prussian blue

We studied the electrochemical and magnetic properties of NiFe Prussian blue. The NiFe Prussian blue was synthesized on Ni electrodes in the form of thin films by an electrochemical technique. Measurements of its magnetic properties show that NiFe Prussian blue with the Fe^{III-low spin (LS)}–CN–Ni^II structure exhibits ferromagnetic properties, with T _c (critical temperature)=25 K. On the other hand, the reduced form, which has the Fe^II-LS–CN–Ni^II structure, is paramagnetic. This means that the magnetic properties can be controlled between ferromagnetic and paramagnetic by an electrochemical method. Furthermore, it is well known that NiFe Prussian blue exhibits electrochromic properties. Hence, this compound is a multifunctional, molecule-based compound in which optical and magnetic properties can be controlled by an electrochemical redox reaction. Contribution to the special issue on “Magnetic field effects in Electrochemistry.”     

Photoinduced electron transfer between adamantanamine-(OCH2CH2)n-phenothiazine and mono-6-p-nitrobenzoyl-β-cyclodextrin

A series of adamantanamine-(OCH₂CH₂)_n-phenothiazine (n = 0, 1, 2, 3) electron donors was synthesized. Photoinduced electron transfer was observed in the supramolecular complex of the phenothiazine derivatives with p-nitrobenzoyl-β-cyclodextrin (NBCD) through binding of the adamantyl group by the NBCD cavity, which is stabilized clearly via hydrophobic interactions in aqueous solution. Detailed Stern–Volmer constants were measured and they were partitioned into dynamic Stern–Volmer quenching constants and static binding constants. The results revealed an efficient electron transfer process inside the supramolecular systems compared to that controlled by diffusion. This observation also indicates that the chain length will influence the electron transfer efficiency of a supramolecular donor–acceptor system.     

Synthesis of Iron Nanoclusters by Pulsed Current Method

The main objective of this research is to prepare iron nanoclusters with more porous structure by the pulsed current electrochemical method. In this method, there are some effective parameters including; pulse amplitude (current amount), pulse frequency, iron salt concentration, sulfuric acid concentration and synthesis temperature, which were optimized by the “one at a time method”. An iron optimized nanopowder was synthesized by using iron sulfate (0.005 M) as precursor and silver nitrate as a nucleation agent (at 0.5% mole of iron sulfate in the starting solution) by pulsed current of 20 mA cm⁻² with a frequency of 14 Hz. The relative gravimetrical density was used as an optimizing parameter for iron nanoparticles synthesis. The morphology and particle size of each synthesized sample was studied by SEM, TEM and XRD. The iron nanopowder synthesized in the optimum conditions has excellent uniform and a more porous structure including nanoclusters with a particle size of approximately 20–40 nm. The obtained results indicate that the pulsed current electrochemical method can be used as a confident and controllable method for the preparation of iron nanoparticles. XRD, EDX and ICP-AES results showed that the iron nanoclusters can be synthesized with high purity by the proposed method.     

A chitosan-templated monolithic siliceous mesoporous-macroporous material

 We synthesised a porous siliceous material via hydrothermal hydrolysis of sodium silicate, using chitosan as a template. As far as we know, this is the first synthesis of siliceous porous material using chitosan as a template in a hydrothermal way. A fibrous material was obtained, whose macroscopic fibres were formed by a spongelike siliceous network with pores having a radius of 0.57 μm. The siliceous walls of the pores were, in turn, of the form of a microporous–mesoporous material; the pore radius distribution was polymodal with maxima at 0.84, 1.0, 1.2 and 1.5 nm and a broad band between 3 and 10 nm. This structure may be due to the aggregation of the hydrated chitosan helices in bundles of parallel fibres with different size and the gelation of the system. The aggregation process might be induced by the addition of silicate. Received: 12 January 2000/Accepted: 7 March 2000     

Synthesis of silica adsorbent and its selective separation for flavone

One kind of built-in silica adsorbent, which has high adsorption selectivity to rutin, was synthesized using molecular imprinting technology by the following steps: synthesis of precursor from the reaction between water soluble rutin (as template molecule) and the functional monomer chloropropyltriethoxysilane, co-hydrolysis of the precursor and tetraethoxysilane (TEOS), sol-gel aging process, and removal of template molecules. The results of adsorption experiment show that this adsorbent has a high adsorption capacity for rutin, and good adsorption selectivity towards rutin even under the interference of a flavone with a similar structure. TEM photos suggest that nanocaves corresponding to rutin were formed inside the adsorbent while FTIR spectra indicate that new bond was generated during the recognition process. __________ Translated from Journal of Tianjin University, 2007, 40(4): 411–415 [译自: 天津大学学报]     

Molecularly imprinted polymer solid-phase extraction coupled to square wave voltammetry at carbon fibre microelectrodes for the determination of fenbendazole in beef liver

A molecularly imprinted polymer was developed and used for solid-phase extraction (MISPE) of the antihelmintic fenbendazole in beef liver samples. Detection of the analyte was accomplished using square wave voltammetry (SWV) at a cylindrical carbon fibre microelectrode (CFME). A mixture of MeOH/HAc (9:1) was employed both as eluent in the MISPE system and as working medium for electrochemical detection of fenbendazole. The limit of detection was 1.9 × 10⁻⁷ mol L⁻¹ (57 μg L⁻¹), which was appropriate for the determination of fenbendazole at the maximum residue level permitted by the European Commission (500 μg kg⁻¹ in liver). Given that the SW voltammetric analysis could not be directly performed in the sample extract as a consequence of interference from some sample components, a sample clean-up with a MIP for selectively retaining fenbendazole was performed. The MIP was synthesized using a 1:8:22 template/methacrylic acid/ethylene glycol dimethacrylate ratio. A Britton–Robinson Buffer of pH 9.0 was selected for retaining fenbendazole in the MIP cartridges, and an eluent volume of 5.0 mL at a flow rate of 2.0 mL min⁻¹ was chosen in the elution step. Cross-reactivity with the MIP was observed for other benzimidazoles. The synthesized MIP exhibited a good selectivity for benzimidazoles with respect to other veterinary drugs. The applicability of the MISPE-SWV method was tested with beef liver samples, spiked with fenbendazole at 5,000 and 500 μg kg⁻¹. Results obtained for ten different liver samples yielded mean recoveries of (95 ± 12)% and (96 ± 11)% for the upper and lower concentration level, respectively.     

Oxidative polymerization of hydroquinone using deoxycholic acid supramolecular template

Polyhydroquinone (PHQ) is a redox-active polymer with quinone/hydroquinone redox active units in the main chain and may have potential applications as a mediator in biosensors and biofuel cells. By the oxidative polymerization of hydroquinone (HQ), PHQ can be easily synthesized, but the reaction lacks control over the structure of the product. Deoxycholic acid (DCA) was introduced as a supramolecular template to control the reaction. The reaction rate is 14 times of that in deionized water and twice of that in buffer. The DCA template increases not only the reaction rate, but also the molecular weight of the polymer obtained. The template effect of DCA was attributed to the supramolecular assemblies of DCA formed in the solution. Cyclic voltammetry study indicated the resulting PHQ was redox-active. While the supramolecular assemblies of DCA provided a template for the oxidative polymerization of HQ, the protons released as a by-product of the oxidative polymerization of HQ in turn enhanced the self-assembly of DCA. As a result, DCA microfibers form and separate out of the solution.     

Thermogravimetry applied to characterization of SBA-15 nanostructured material

Nanoporous silica with narrow pore size distribution has attracted increasing attention as a novel material for separations and reactions involving large molecules. SBA-15 has been synthesized in an acidic medium using a triblock copolymer as template. In this work, the SBA-15 was synthesized by the hydrothermal treatment at 373 K for 48 h, of a gel with the following overall molar composition: 1.0TEOS:0.017P123:5.7HCl:193H₂O, where TEOS is tetraethyl orthosilicate and P123 is poly(ethylene oxide, propylene oxide and 1,4-dioxane). The obtained material was characterized by thermogravimetry, X-ray diffraction, infrared spectroscopy and BET surface area. A kinetic study using the model free model was accomplished in the stage of decomposition of the template (P123). The obtained value of the apparent activation energy was ca. 131 kJ mol^–1.     

Atom transfer radical polymerized PMMA/magnetite nanocomposites and their magnetorheology

We synthesized core/shell-typed magnetic nanoparticle composites using poly(methyl methacrylate) (PMMA) as a shell and magnetite nanoparticle (MN) as a core, in which the PMMA shell was prepared via atomic transfer radical polymerization (ATRP) method. Chemical structure and morphology of the synthesized MN–PMMA nanocomposite were investigated using FT-IR and TEM, respectively. Magnetorheological (MR) fluid was prepared by dispersing synthesized MN–PMMA in non-magnetic medium. Both shear stress and shear viscosity of the MR fluids as a function of shear rate were measured using a rotational rheometer with a magnetic field generator, exhibiting that a yield stress increased with an external magnetic field strength.     

Supramolecular recognition of estrogens via molecularly imprinted polymers

The isolation and preconcentration of estrogens from new types of biological samples (acellular and protein-free simulated body fluid) by molecularly imprinted solid-phase extraction has been described. In this technique, supramolecular receptors, namely molecularly imprinted polymers (MIPs) are used as a sorbent material. The recognition sites of MIPs were prepared by non-covalent multiple interactions and formed with the target 17β-estradiol as a template molecule. High-performance liquid chromatography with spectroscopic UV, selective, and a sensitive electrochemical CoulArray detector was used for the determination of 17β-estradiol, estrone, and estriol in simulated body fluid which mimicked human plasma.     

The gas–liquid tunable self-assembly properties of rod–coil diblock copolymer: donor–acceptor alternating structure served as rod segment

The rod–coil diblock copolymers in which the donor–acceptor alternating structures served as the rod segment were synthesized. The supramolecular self-assembly property of the copolymers was investigated in the methanol atmosphere. By changing the assembly condition, well-defined vesicles and porous films were produced, respectively. Pores with different size dispersions were obtained by tuning the methanol atmosphere. Moreover, porous films were also decorated on diverse substrates with nonplanar structures. The investigation on self-assembly properties of this rod–coil copolymer is the complementarity to the self-assembly of rod–coil copolymers. This is a very useful self-assembly method that can be used to prepare the self-assembly nanostructures with donor–acceptor alternating copolymers.