Ag nanoparticles decorated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/chitosan nanocomposite: synthesis,characterization and application toward electrochemical sensing of hydrogen peroxide

We studied a rapid, sensitive and selective amperometric sensor for determination of hydrogen peroxide by electrodeposited Ag NPs on a modified glassy carbon electrode (GCE). The modified GCE was constructed through a step by step modification of magnetic chitosan functional composite (Fe₃O₄–CH) and high-dispersed silver nanoparticles on the surface. The resulted Ag@Fe₃O₄–CH was characterized by various analytical methods including Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and cyclic voltammetry. The proposed sensor employed Ag@Fe₃O₄–CH/GCE as the working electrode with a linear current response to the hydrogen peroxide concentration in a wide range from 0.01 to 400 µM with a low limit of detection (LOD = 0.0038 µM, S/N = 3). The proposed sensor showed superior reproductivity, sensitivity and selectivity for the detection of hydrogen peroxide in environmental and clinical samples.     

Electrochemical sensor using graphene/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanosheets functionalized with garlic extract for the detection of lead ion

Based on the modulated electronic properties of Fe₃O₄-graphene (Fe₃O₄/GN composite) as well as the outstanding complexation between Pb²⁺ and natural substances garlic extract (GE), a novel electrochemical sensor for the determination of Pb²⁺ in wastewater was prepared by immobilization of Fe₃O₄/GN composite integrated with GE onto the surface of glassy carbon electrode (GCE). Fe₃O₄/GN composite was employed as an electrochemical active probe for enhancing electrical response by facilitating charge transfer while GE was used to improve the selectivity and sensitivity of the proposed sensor to Pb²⁺ assay. The electrochemical sensing performance toward Pb²⁺ was appraised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave voltammetry (SWV). Under the optimized condition, the sensor exhibited two dynamic linear ranges (LDR) including 0.001 to 0.5 nM and 0.5 to 1000 nM with excellent low detection limit (LOD) of 0.0123 pM (S/N =?3) and quantification limit (LOQ) of 0.41 pM (S/N =?10). Meanwhile, it displayed remarkable stability, reproducibility (RSD of 3.61%, n =?3), and selectivity toward the assay for the 100-fold higher concentration of other heavy metal ions. Furthermore, the novel sensor has been successfully employed to detect Pb²⁺ from real water samples with satisfactory results.     

Application of spinel-structured MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles for simultaneous electrochemical determination diclofenac and morphine

The paper describes a sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF). The surface of a MgFe₂O₄/graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor was characterized by cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The electrode showed an efficient synergistic effect in term of oxidation of DCF and MOR, with sharp oxidation peaks occurring at +0.370 and 0.540 V (vs Ag/AgCl) at pH 7.0. The calibration plot for MOR is linear in the 50 nM to 920 μM concentration range, and the detection limit is 10 nM (at a signal-to-noise ratio of 3). The respective data for DCF are 100 nM to 580 μM, with a 60 nM LOD. The sensor was applied to the determination of MOR and DCF in spiked serum and urine samples, with recoveries ranging between 91.4 and 100.7 %.

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Graphical abstract A sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF) is described. The surface of MgFe₂O₄/graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor showed an efficient synergistic effect in terms of oxidation of DCF and MOR. The calibration plot for MOR is linear in the 50 nM to 920 μM concentration range, and the detection limit is 10 nM. The respective data for DCF are 100 nM to 580 μM, with a 60 nM LOD.

     

Synthesis,structural, and electrochemical properties of NaCo(PO<Subscript>3</Subscript>)<Subscript>3</Subscript> cathode for sodium-ion batteries

A new Co-base sodium metaphosphate compound, NaCo(PO₃)₃, has been synthesized here by solid-state method. The crystal structure is refined by the Rietveld method, and the results reveal that NaCo(PO₃)₃ has an orthorhombic structure with the space group of P2 ₁ 2 ₁ 2 ₁ and lattice parameters of a = 14.2453(2) Å, b = 14.2306(1) Å, and c = 14.2603(2) Å. Its typical morphology and chemical composition are confirmed by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The valence states of all elements and the internal/external vibrational modes of NaCoP₃O₉ compound are measured by X-ray photoelectron and vibrational spectrum, where a typical feature of the (PO₃)^? polyanion group is observed. Meanwhile, the electrochemical properties of NaCo(PO₃)₃ cathode for sodium-ion batteries are also elevated and an initial discharge capacity of 33.8 mAh/g can be obtained at 0.05 C within 1.5–4.2 V. After 20 cycles, a discharge capacity of 26.7 mAh/g can be obtained and a well-kept oxidation–reduction plateau is still observed for NaCo(PO₃)₃ cathode, indicating the good reversibility of this metaphosphate electrode.     

Non-isothermal crystallization kinetics of Ti<Subscript>20</Subscript>Zr<Subscript>20</Subscript>Hf<Subscript>20</Subscript>Be<Subscript>20</Subscript>(Cu<Subscript>50</Subscript>Ni<Subscript>50</Subscript>)<Subscript>20</Subscript> high-entropy bulk metallic glass

The crystallization transformation kinetics of Ti₂₀Zr₂₀Hf₂₀Be₂₀(Cu₅₀Ni₅₀)₂₀ high-entropy bulk metallic glass under non-isothermal conditions are investigated using differential scanning calorimetry. The alloy shows two distinct crystallization events. The activation energies of the crystallization events are determined using Kissinger, Ozawa and Augis–Bennett methodologies. Further, we observe that similar values are obtained using the three equations. The activation energy of the initial crystallization event is observed to be slightly small as compared to that of the second event. This implies that the initial crystallization event may have been easier to be occurred. The local activation energy (E(x)) maximizes in the initial stage of crystallization and keeps dropping in subsequent crystallization process. The non-isothermal crystallization kinetics are further analyzed using the modified Johnson–Mehl–Avrami (JMA) equation. Further, the Avrami exponent values are observed to be 1.5 < n(x) < 2.5 for approximately the entire period of the initial crystallization event and for most instances (0.1 < x < 0.6) of the second crystallization event, which implies that the mechanism of crystallization is significantly controlled by diffusion-controlled two- and three-dimensional growth along with a decreasing nucleation rate.     

Synthesis and characterization of a new monophosphate (C<Subscript>6</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b = 7.6942(4), c = 8.1473(5) Å, α = 114.997(3), β = 92.341(3), γ = 113.136(3), V = 329.14(3) ų, Z = 1, and D_x = 1.565 g cm^?3. The crystal structure has been determined and refined to R = 0.030 and R _w(F ²) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H₂PO₄] _n ^n? chains with (C₆H₁₆N₂)²⁺ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, ¹³C and ³¹P MAS NMR spectroscopies and Ab initio calculations.     

Ascorbic acid amperometric sensor using a graphene-wrapped hierarchical TiO<Subscript>2</Subscript> nanocomposite

An ascorbic acid (AA) amperometric sensor was fabricated based on a glassy carbon electrode (GCE) modified with a reduced graphene oxide-wrapped hierarchical TiO₂ (RGO—TiO₂) nanocomposite. The RGO—TiO₂ nanocomposite was synthesized via the facial wet chemical method and characterized by scanning electron microscopy and X-ray diffraction. Cyclic voltammetry and amperometric techniques were employed to investigate its electrocatalytic performance towards the AA oxidation. The combined advantages of RGO and TiO₂ provide the electrode with higher current response and lower oxidation potential compared with those of bare GCE and TiO₂ modified GCE. The proposed electrode can be used for the determination of AA in the wide concentration range from 1 to 1500 µM with the detection limit of 0.5 µM. The proposed electrode was successfully used to determine AA in vitamin C tablets and spiked fruit juice.     

Electro-deposition of gold nanostructures on carbon paste electrode: a platform with signal amplification for voltammetric study and determination of pyridoxine (vitamin B<Subscript>6</Subscript>)

For the first time, the electrochemical synthesis of gold nanostructures was done at the surface of carbon paste electrode. This device was used as a simple and sensitive electrochemical sensor for measurement of pyridoxine (Vitamin B₆, VB₆). The diffusion coefficient (D) and the kinetic parameters such as electron transfer coefficient (α) and catalytic rate constant (k) for VB₆ were also determined using electrochemical approaches. The cyclic voltammetry method showed VB₆ oxidation reaction with irreversible characteristics was diffusion-controlled at low scan rates. Using differential pulse voltammetry (DPV), the peak current was linearly dependent on VB₆ concentration in the ranges of 1.9–110.8 and 110.8–257.0 μM, with detection limit of 74.0 nM, respectively. Results showed there is no interference of other vitamins in oxidation of VB₆. DPV was used to quantify of VB₆ in some real samples by the standard addition method. The modified electrode showed good sensitivity and stability.     

Enhanced and tunable oxygen carrier and amperometric sensor based on a glassy carbon electrode assembly of a hemoglobin-chitosan-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> composite

The authors have prepared organized assemblies of a hemoglobin-chitosan(CS)@Fe₃O₄ composite on glassy carbon electrodes (GCEs) via three strategies with the aim of preparing tunable Hb-coated GCEs with good stability and long-term oxygen storage capability. The formation and morphology of the Hb-CS@Fe₃O₄ composite was characterized by scanning electrochemical microscopy, XRD and UV–vis spectroscopy. It is shown that Hb is fully integrated into the CS@Fe₃O₄ and can be manipulated by a magnetic field whilst maintaining its biological activity. In the absence of oxygen, a surface-controlled electrode process occurs with an interfacial electron transfer rate (k _s) of 2.14 s^?1. The modified GCE also has a favorable oxygen storage lifetime (almost 6 h). One Hb-CS@Fe₃O₄ film on the electrode displays particularly good electrocatalytic reduction activity towards oxygen. The linear range for detection of O₂ is 1.2?×?10^?7?~?2.0?×?10^?4 mol L^?1 with a detection limit of 4.0?×?10^?8 mol L^?1. In our opinion, this method has great potential in terms of enhanced oxygen storage capability of Hb, which can be applied in special situations such as space operations, down hole mining, mountaineering and diving.

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Graphical Abstract Hb-CS@Fe₃O₄ composites were prepared by three strategies, and oxygen carrying capability was studied. The corresponding modified electrode constructed on the basis of the magnetic field environment was superior in terms of stability, sensitivity and O₂ storage time, showing wider linear range and lower detection limit.

     

Synthesis,crystal structure of a new tetranuclear Ni<Stack><Subscript>2</Subscript><Superscript>II</Superscript></Stack>Cu<Stack><Subscript>2</Subscript><Superscript>II</Superscript></Stack> complex containing a macrocyclic ligand

The first inorg/organic hybrid complex incorporating the macrocyclic oxamide, of formula [(NiL)₂Cu₂(μ-NSC)₂(NSC)₂] (1), (NiL, H₂L = 2, 3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien), have been synthesized and structurally characterized. The crystals crystallize in the triclinic system, space group P-1, for (1) a = 8.319(3) Å, b = 10.434(4) Å, c = 14.166(5) Å, a = 107.030(5)°, β  =  91.257(5)°, γ = 107.623(5)°. The complex involved both bridging N, S-ligand, and oxamide ligand, C–H?S interactions and NCS → Ni weak coordination interactions making the complex superamolecular.     

Photoelectrochemical aptasensor for sulfadimethoxine using g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> quantum dots modified with reduced graphene oxide

A novel photoelectrochemical (PEC) aptasensor with graphitic-phase carbon nitride quantum dots (g-C₃N₄; QDs) and reduced graphene oxide (rGO) was fabricated. The g-C₃N₄ QDs possess enhanced emission quantum yield (with an emission peak at 450 nm), improved charge separation ability and effective optical absorption, while rGO has excellent electron transfer capability. Altogether, this results in improved PEC performance. The method is making use of an aptamer against sulfadimethoxine (SDM) that was immobilized on electrode through π stacking interaction. Changes of the photocurrent occur because SDM as a photogenerated hole acceptor can further accelerate the separation of photoexcited carriers. Under optimized conditions and at an applied potential of +0.2 V, the aptasensor has a linear response in the 0.5 nM to 80 nM SDM concentration range, with a 0.1 nM detection limit (at S/N =?3). The method was successfully applied to the analysis of SDM in tap, lake and waste water samples.

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Graphical abstract Graphitic-phase carbon nitride (g-C₃N₄) quantum dots (QDs) and reduced graphene oxide (rGO) were used to modify fluorine-doped SnO₂ (FTO) electrodes for use in a photoelectrochemical (PEC) aptasensor. SDM oxidized by the hole on valance band (VB) of g-C₃N₄ QDs promote the separation of electron in the conductive band (CB), which made the changes of photocurrent signal.

     

Coordination Chemistry of the Magic Inorganic Building Block {Fe<Superscript>II</Superscript>[Mo<Subscript>6</Subscript>P<Subscript>4</Subscript>O<Subscript>31</Subscript>]<Subscript>2</Subscript>}: Hydrothermal Synthesis and Crystal Structure of a New Reduced Ferrous Molybdophosphate

A new reduced ferrous molybdophosphate composite solid of the formula, [(C₁₀H₁₄N₂)H]₄[Fe^II ₁₀Mo^V ₂₄(H₂PO₄)₄(HPO₄)₁₂(PO₄)₄(H₂O)₁₆(OH)₁₆O₄₄]·12H₂O, has been synthesized from a reaction mixture of MoO₃, FeSO₄·7H₂O, C₂H₂O₄·2H₂O, nicotine, H₃PO₄, and H₂O under hydrothermal conditions. The crystal data: monoclinic, space group C2/m, a = 24.4349(124), b = 12.9935(66), c = 14.7281(74) Å, β = 104.87(1) Å, V = 4520(4) Å³, Z = 2, R ₁  = 0.0874, wR ₂  = 0.2179. The structure is built from the building blocks of the formula, {Fe^II[Mo₆P₄O₃₁]₂}, consisting of a network of MO₆ (M = Fe, Mo) octahedral and PO₄ tetrahedral linked through their vertices. The connectivity of the building blocks with two pairs of face-sharing dinuclear Fe(II) clusters of the formula of [Fe^II ₂(H₂O)₄O₅] on which a phosphate group is hanging gives rise to one-dimensional chains with eight-membered apertures. The remarkable hydrogen bonded interactions between the chains form a unique and interesting framework with three-dimensional intersecting tunnels where the protonated nicotine molecules as structuring templates and crystallization water molecules are situated.     

Direct electrochemistry and electrocatalysis of cytochrome <Emphasis Type="Italic">c</Emphasis> based on dandelion-like Bi<Subscript>2</Subscript>S<Subscript>3</Subscript> nanoflowers

The direct electrochemistry and electrocatalysis of cytochrome c (Cyt c) based on dandelion-like bismuth sulfide (d-Bi₂S₃) nanoflowers have been developed. The morphologies and composition of the d-Bi₂S₃ were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Then, the electrochemical behaviors of Cyt c immobilized within the d-Bi₂S₃/chitosan film and its electrocatalytic ability toward hydrogen peroxide (H₂O₂) reduction were investigated by cyclic voltammetry. The electron transfer rate constant was estimated to be 13.1 s^?1, suggesting that a fast direct electron transfer was realized. The prepared Cyt c/d-Bi₂S₃/chitosan nanobiocomposite-modified electrode possessed excellent electrocatalytic ability toward H₂O₂ reduction that showed linearity in the range from 0.5 μM to 1.56 mM with a correlation coefficient of 0.9993. The detection limit was 0.2 μM on signal-to-noise ratio of 3. In addition, the d-Bi₂S₃ nanoflowers may be also applied to direct electron transfer of other redox proteins.     

High-sensitive amperometric hydrazine sensor based on chemically synthesized zinc nitroprusside nanoparticle-supported carbon ceramic electrode

Zinc nitroprusside (ZnNP) nanoparticles were fabricated at the surface of zinc powder-doped carbon ceramic electrode (CCE) by a chemical derivatization process. This modified electrode was characterized by scanning electron microscopy, atomic force microscopy and cyclic voltammetry techniques. The charge transfer rate constant (k _s) and charge transfer coefficient (α) were calculated for the electron exchange reaction of the ZnNP thin film. The ZnNP nanoparticle-modified CCE (ZnNP|CCE) showed good electrocatalytic activity toward hydrazine oxidation. The limit of detection (S/N = 3) and sensitivity were found to be 0.16 µM and 0.21 µA/µM, respectively. The mechanism of hydrazine electrooxidation at the electrode surface was studied. Finally, the ZnNP|CCE was successfully used for the determination of trace amount of hydrazine in different spiked and real samples.     

Fabrication and characterisation of a mixed oxide-covered mesh electrode composed of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> and its capability of generating hydroxyl radicals during the oxygen evolution reaction in electrolyte-free water

A mixed oxide-covered mesh electrode composed of NiCo₂O₄ (MOME-NiCo₂O₄) was prepared on a stainless-steel substrate using thermal decomposition (slow-cooling rate method). Surface, bulk and electrochemical properties of MOME were studied using different techniques, namely scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV) with determination of the electrochemical porosity (?) and morphology factor (φ) parameters, quasi-stationary polarisation curves (PC) and electrochemical impedance spectroscopy (EIS). SEM images revealed a good coverage of the metallic wires by a compact oxide layer (absence of cracks). XRD analysis confirmed the formation of the spinel NiCo₂O₄ with the presence of NiO. The ‘in situ’ surface parameters denoted as ? and φ exhibited values of 0.39 and 0.33, respectively, revealing that the electrochemically active surface area is mainly confined to the ‘outer/external’ surface regions of the oxide layer. The PC was characterised by two Tafel slopes distributed in the low (b ₁ = 46 mV dec^?1) and high (b ₂ = 59 mV dec^?1) overpotential domains. The corresponding apparent exchange current densities were j ₀₍₁₎ = (3.43 ± 0.11) × 10^?6 A cm^?2 and j ₀₍₂₎ = (6.70 ± 0.08) × 10^?6 A cm^?2, respectively. The EIS study accomplished in the low-overpotential domain revealed a Tafel slope (b ₁) of 51 mV dec^?1. According to the spin-trapping reaction using N,N-dimethyl-p-nitrosoaniline (RNO), the MOME-NiCo₂O₄ electrode exhibited good performance for the generation of weakly adsorbed hydroxyl radicals (HO^?) during the OER in electrolyte-free water.     

Graphene oxide wrapped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Au nanostructures as substrates for aptamer-based detection of <Emphasis Type="Italic">Vibrio parahaemolyticus</Emphasis> by surface-enhanced Raman spectroscopy

The authors describe a sensitive surface-enhanced Raman scattering (SERS)-based aptasensor for the detection of the food pathogen Vibrio parahaemolyticus. Nanostructures consisting of Fe₃O₄@Au particles wrapped with graphene oxide (GO) were used both as SERS substrates and separation tools. A first aptamer (apt 1) was immobilized on the Fe₃O₄@Au/GO nanostructures to act as a capture probe via the affinity binding of aptamer and V. parahaemolyticus. A second aptamer (apt-2) was modified with the Raman reporter molecule TAMRA to act as a SERS sensing probes that binds to the target the same way as the Fe₃O₄@Au/GO-apt 1. The sandwich formed between Fe₃O₄@Au/GO-apt 1/V. parahaemolyticus and apt 2-TAMRA can be separated with the aid of a magnet. The concentration of V. parahaemolyticus can be quantified by measurement of the SERS intensity of TAMRA. Under optimal conditions, the signal is linearly related to the V. parahaemolyticus concentration in the range between 1.4 × 10² to 1.4 × 10⁶ cfu·mL^?1, with a detection limit of 14 cfu·mL^?1. Recoveries ranging from 98.5% to 105% are found when analyzing spiked salmon samples. In our perception, the assay described here is a useful tool for quantitation of V. parahaemolyticus in real samples.

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Graphical abstract GO wrapped Fe₃O₄@Au nanostructures were synthesized as the substrate and modified with with a first aptamer (apt 1) to capture V. parahaemolyticus. TAMRA labelled aptamer 2 was then used as signal probe. The V. parahaemolyticus concentrations are closely related to the Raman intensity of TAMRA.

     

Carbon ceramic electrodes modified with mixed oxides SiO<Subscript>2</Subscript>/SnO<Subscript>2</Subscript> for determination of levofloxacin

The preparation of a carbon ceramic electrode modified with SnO₂ (CCE/SnO₂) using tin dibutyl diacetate as precursor was optimized by a 2³ factorial design. The factors analyzed were catalyst (HCl), graphite/organic precursor ratio, and inorganic precursor (dibutyltin diacetate). The statistical treatment of the data showed that only the second-order interaction effect, catalyst × inorganic precursor, was significant at 95% confidence level, for the electrochemical response of the system. The obtained material was characterized by scanning electron microscopy (MEV), X-ray diffraction (XRD), RAMAN spectroscopy, XPS spectra, and voltammetric techniques. From the XPS spectra, it was confirmed the formation of the Si–O–Sn bond by the shift in the binding energy values referred to Sn 3d3/2 due to the interaction of Sn with SiOH species. The incorporation of SnO₂ provided an increment of the electrode response for levofloxacin, with Ipa = 147.0 μA for the ECC and Ipa = 228.8 μA for ECC/SnO₂, indicating that SnO₂ when incorporated into the silica network enhances the electron transfer process. Under the optimized working conditions, the peak current increased linearly with the levofloxacin concentration in the range from 6.21×10^?5 to 6.97×10^?4 mol L^?1 with quantification and detection limits of 3.80×10^?5 mol L^?1 (14.07 mg L^?1) and 1.13×10^?5 mol L^?1 (4.18 mg L^?1), respectively.     

The hemoglobin-modified electrode with chitosan/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposite for the detection of trichloroacetic acid

A hemoglobin (Hb)-modified electrode based on chitosan/Fe₃O₄ nanocomposite coated glassy carbon has been constructed for trichloroacetic acid (TCA) detection. The structure of chitosan/Fe₃O₄ nanocomposite was investigated using energy-dispersive X-ray analysis (EDS) and X-ray diffraction (XRD) patterns. The electron transfer rate constant (k _s) of Hb was estimated for as high as 3.12 s^?1. The immobilized Hb exhibited excellent electro-catalytic activity toward the reduction of TCA. The response current regressed to the concentration of TCA within the range of 5.70 μM to 205 μM with a detection limit of 1.9 μM (S/N = 3).     

Catalytic removal of soot particles over MnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> catalysts prepared by the auto-combustion method

Soot removal for exhaust gas from diesel engine has been addressed due to the more stringent legislation and environmental concerns. MnCo₂O₄ catalysts were systematically prepared using glucose as a fuel via the auto-combustion method and applied for soot removal. The as-prepared samples were characterized by X-ray diffraction (XRD), O₂-temperature-programmed oxidation (TPO) reaction and H₂-temperature-programmed reduction reaction (H₂-TPR). The catalytic activities for soot combustion were evaluated by micro activity test (MAT) with a tight contact mode between soot and catalysts. Compared with catalysts prepared by the solid state method without glucose, auto-combustion method in the presence of glucose can decrease the synthetic temperature, avoiding high temperature treatment and sintering. The catalysts prepared with glucose could catalyze soot oxidation effectively and the derived values of T₁₀, T₅₀, and T₉₀ were 326, 408, and 468 °C in a tight contact mode, respectively, showing a significant drop of T₁₀, T₅₀, and T₉₀ by 156, 177, and 178 °C for non-catalytic reaction.     

Thermal analysis on C<Subscript>6</Subscript>H<Subscript>10</Subscript>Ge<Subscript>2</Subscript>O<Subscript>7</Subscript>-doped MgB<Subscript>2</Subscript>

Additives to MgB₂ can improve the superconducting functional characteristics, such as critical current density (J _c) and irreversibility field (H _irr). Recently, we have shown that repagermanium (C₆H₁₀Ge₂O₇) is an effective additive, enhancing both J _c and H _irr. To look into details of the processes taking place during the reactive sintering, a thermal analysis study (0.167 K s^?1, in Ar) is reported. We used differential scanning calorimetry between 298 and 863 K and simultaneous thermogravimetric—differential thermal analysis between 298 and 1233 K. Samples were mixtures of powders with composition 97 mol% MgB₂ and 3 mol% C₆H₁₀Ge₂O₇. Up to 863 K, repagermanium decomposes by multiple steps and forms amorphous phases. A reaction with MgB₂ is not observed. Above this temperature, partial decomposition of MgB₂ occurs. Crystalline Ge and MgO are detected before formation of Mg₂Ge and MgB₄, when temperature approaches the melting point of Ge (1211 K). Carbon substitution for boron in the crystal lattice of MgB₂ is observed for samples heated above 863 K. The amount of substitutional C does not significantly change with temperature.