A kinetic fluorometric method for the determination of nucleic acids using a ternary equilibrium system of nucleic acids—iron (III) tetracarboxy phthalocyanine-poly-lysine coupled with the oxidation reaction between hydrogen peroxide and dl-tyrosine

Using the oxidation reaction between hydrogen peroxide and dl-tyrosine as fluorescence indication, the evident tuning effect of nucleic acids on catalytic activity of mimetic enzyme iron (III) tetracarboxy phthalocyanine (FeC₄Pc) in the presence of poly-lysine was observed and studied. The oxidation reaction between hydrogen peroxide and dl-tyrosine with FeC₄Pc as catalyst gave an intensively fluorescent compound, which has an excitation wavelength of 325 nm and an emission wavelength of 418 nm. The fluorescence was quenched by a proper concentration of poly-lysine due to its association with FeC₄Pc and consequently the descent of the catalytic activity of FeC₄Pc, but recovered by addition of nucleic acids. Under optimal conditions, the recovered fluorescence is proportional to the concentration of nucleic acids. Based on the fact, a kinetic fluorescent method was developed for the determination of nucleic acids. The calibration graphs are linear over the range 10-2000 ng/mL both for fish sperm DNA (FS DNA) and calf thymus DNA (CT DNA). The corresponding detection limits are 1.04 ng/mL for FS DNA and 1.18 ng/mL for CT DNA, respectively. Four synthetic and three real nucleic acid samples were determined with satisfactory results.     

β−cyclodextrins-based inclusion complexes of CoFe2O4 magnetic nanoparticles as catalyst for the luminol chemiluminescence system and their applications in hydrogen peroxide detection

β−cyclodextrins (β−CD)-based inclusion complexes of CoFe₂O₄ magnetic nanoparticles (MNPs) were prepared and used as catalysts for chemiluminescence (CL) system using the luminol-hydrogen peroxide CL reaction as a model. The as-prepared inclusion complexes were characterized by XRD (X-ray diffraction), TGA (thermal gravimetric analysis) and FT-IR. The oxidation reaction between luminol and hydrogen peroxide in basic media initiated CL. The effect of β−CD-based inclusion complexes of CoFe₂O₄ magnetic nanoparticles and naked CoFe₂O₄ magnetic nanoparticles on the luminol-hydrogen peroxide CL system was investigated. It was found that inclusion complexes between β−CD and CoFe₂O₄ magnetic nanoparticles could greatly enhance the CL of the luminol-hydrogen peroxide system. Investigation on the kinetic curves and the chemiluminescence spectra of the luminol-hydrogen peroxide system demonstrates that addition of CoFe₂O₄ MNPs or inclusion complexes between β−CD and CoFe₂O₄ MNPs does not produce a new luminophor of the chemiluminescent reaction. The luminophor for the CL system was still the excited-state 3-aminophthalate anions (3-APA*). The enhanced CL signals were thus ascribed to the possible catalysis from CoFe₂O₄ MNPs or inclusion complexes between β−CD and CoFe₂O₄ nanoparticles. The feasibility of employing the proposed system for hydrogen peroxide sensing was also investigated. Experimental results showed that the CL emission intensity was linear with hydrogen peroxide concentration in the range of 1.0 × 10⁻⁷ to 4.0 × 10⁻⁶ mol L⁻¹ with a detection limit of 2.0 × 10⁻⁸ mol L⁻¹ under optimized conditions. The proposed method has been used to determine hydrogen peroxide in water samples successfully.     

Flow-injection determination of hydrogen peroxide based on fluorescence quenching of chromotropic acid catalyzed with Fe(II)

Flow-injection analysis system (FIA system), which was based on Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide, was developed for the determination of hydrogen peroxide. The chromotropic acid has a fluorescence measured at λ_em = 440 nm (emission wavelength) with λ_ex = 235 nm (excitation wavelength), and the fluorescence intensity at λ_em = 440 nm quietly decreased in the presence of hydrogen peroxide and Fe(II), which was caused by Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide. By measuring the difference of fluorescence intensity, hydrogen peroxide (1.0 × 10⁻⁸-1.0 × 10⁻³ mol L⁻¹) could be determined by the proposed FIA system, whose analytical throughput was 40 samples h⁻¹. The relative standard deviation (RSD) was 1.03% (n = 10) for 4.0 × 10⁻⁸ mol L⁻¹ hydrogen peroxide. The proposed FIA technique could be applied to the determination of hydrogen peroxide in rain water samples.     

Immobilization of [Cu(bpy)2]Br2 complex onto a glassy carbon electrode modified with α-SiMo12O40 and single walled carbon nanotubes: Application to nanomolar detection of hydrogen peroxide and bromate

A simple procedure has been used for preparation of modified glassy carbon electrode with carbon nanotubes and copper complex. Copper complex [Cu(bpy)₂]Br₂ was immobilized onto glassy carbon (GC) electrode modified with silicomolybdate, α-SiMo₁₂O₄₀⁴⁻ and single walled carbon nanotubes (SWCNTs)_. Copper complex and silicomolybdate irreversibly and strongly adsorbed onto GC electrode modified with CNTs. Electrostatic interactions between polyoxometalates (POMs) anions and Cu-complex, cations mentioned as an effective method for fabrication of three-dimensional structures. The modified electrode shows three reversible redox couples for polyoxometalate and one redox couple for Cu-complex at wide range of pH values. The electrochemical behavior, stability and electron transfer kinetics of the adsorbed redox couples were investigated using cyclic voltammetry. Due to electrostatic interaction, copper complex immobilized onto GC/CNTs/α-SiMo₁₂O₄₀⁴⁻ electrode shows more stable voltammetric response compared to GC/CNTs/Cu-complex modified electrode. In comparison to GC/CNTs/Cu-complex the GC/CNTs/α-SiMo₁₂O₄₀⁴⁻ modified electrodes shows excellent electrocatalytic activity toward reduction H₂O₂ and BrO₃⁻ at more reduced overpotential. The catalytic rate constants for catalytic reduction hydrogen peroxide and bromate were 4.5(±0.2) × 10³ M⁻¹ s⁻¹ and 3.0(±0.10) × 10³ M⁻¹ s⁻¹, respectively. The hydrodynamic amperommetry technique at 0.08 V was used for detection of nanomolar concentration of hydrogen peroxide and bromate. Detection limit, sensitivity and linear concentration range proposed sensor for bromate and hydrogen peroxide detection were 1.1 nM and 6.7 nA nM⁻¹, 10 nM-20 μM, 1 nM, 5.5 nA nM⁻¹ and 10 nM-18 μM, respectively.     

Determination of marker pteridins and biopterin reduced forms, tetrahydrobiopterin and dihydrobiopterin, in human urine, using a post-column photoinduced fluorescence liquid chromatographic derivatization method

A liquid chromatographic method for the simultaneous analysis of marker pteridins and biopterin reduced forms, in urine samples is proposed. A Zorbax Eclipse XDB-C18 column was used for the chromatographic separation, using a 98/2 (v/v), citrate buffer (pH 5.5)-acetonitrile mobile phase, in isocratic mode. A post-column photoderivatization was carried out with an on-line photoreactor, located between a diode array detector (DAD) and a fast scanning fluorescence detector (FSFD). Neopterin (NEO), biopterin (BIO), pterin (PT) and dihydrobiopterin (BH2) were determined by measuring native fluorescence, using the photoreactor in OFF-mode, and tetrahydrobiopterin (BH4) was determined by measuring of the induced fluorescence of the generated photoproducts, using the photoreactor in ON-mode. In addition, Creatinine (CREA), as a reference of metabolites excrection in urine, was simultaneously determined using the DAD detector. Detection limits were 0.2, 13.0, 0.3, 0.3 and 3.5 ng mL⁻¹, for NEO, BH2, BIO, PT and BH4, respectively, and 0.4 μg mL⁻¹ for CREA. Ratio values for NEO/CREA, PT/CREA, BH4/CREA, BH2/CREA, NEO/BIO and BIO_total/CREA, in urine samples, of healthy children and adults, phenylketonuric children and infected mononucleosis children, are reported. A comparative study, about the mean values obtained for each of the compounds, by the present procedure and by the classical iodine oxidation method (Fukushimás method), has been performed, in urine samples belonging to healthy volunteers. The values obtained were BH4/CREA: 0.41, BH2/CREA: 0.31 and BIO_total/CREA: 0.73, by the proposed method, and BH4/CREA: 0.35, BH2/CREA: 0.20 and BIO_total/CREA: 0.48, by iodine oxidation method.     

Determination of glucose using a coupled-enzymatic reaction with new fluoride selective optical sensing polymeric film coated in microtiter plate wells

The determination of glucose in beverages is demonstrated using newly developed fluoride selective optical sensing polymeric film that contains aluminum (III) octaethylporphyrin (Al[OEP]) ionophore and the chromoionophore ETH7075 cast at the bottom of wells of a 96-well polypropylene microtiter plate. The method uses a dual enzymatic reaction involving glucose oxidase enzyme (GOD) and horseradish peroxidase (HRP), along with an organofluoro-substrate (4-fluorophenol) as the source of fluoride ions. The concentration of fluoride ions after enzymatic reaction is directly proportional to the glucose level in the sample. The method has a detection limit of 0.8 mmol L⁻¹, a linear range of 0.9-40 mmol L⁻¹ and a sensitivity of 0.125 absorbance/decade of glucose concentration. Glucose levels in several beverage samples determined using the proposed method correlate well with a reference spectrophotometric enzyme method based on detection of hydrogen peroxide using bromopyrogallol red dye (BPR). The new method can also be used to determine H₂O₂ concentrations in the 0.1-50 mmol L⁻¹ range using a single enzymatic reaction involving H₂O₂ oxidation of 4-fluorophenol catalyzed by HRP. The methodology could potentially be used to detect a wide range of substrates for which selective oxidase enzymes exist (to generate H₂O₂), with the high throughput of simple microtiter plate detection scheme.     

Simple and fast spectrophotometric determination of H(2)O(2) in photo-Fenton reactions using metavanadate

This work proposes a spectrophotometric method for the determination of hydrogen peroxide during photodegradation reactions. The method is based on the reaction of H₂O₂ with amonium metavanadate in acidic medium, which results in the formation of a red-orange color peroxovanadium cation, with maximum absorbance at 450 nm. The method was optimized using the multivariate analysis providing the minimum concentration of vanadate (6.2 mmol L⁻¹) for the maximum absorbance signal. Under these conditions, the detection limit is 143 μmol L⁻¹. The reaction product showed to be very stable for samples of peroxide concentrations up to 3 mmol L⁻¹ at room temperature during 180 h. For higher concentrations however, samples must be kept refrigerated (4 °C) or diluted. The method showed no interference of Cl⁻ (0.2-1.3 mmol L⁻¹), NO₃⁻ (0.3-1.0 mmol L⁻¹), Fe³⁺ (0.2-1.2 mmol L⁻¹) and 2,4-dichlorophenol (DCP) (0.2-1.0 mmol L⁻¹). When compared to iodometric titration, the vanadate method showed a good agreament. The method was applied for the evaluation of peroxide consumption during photo-Fenton degradation of 2,4-dichlorophenol using blacklight irradiation.     

Composite film of carbon nanotubes and chitosan for preparation of amperometric hydrogen peroxide biosensor

A new amperometric biosensor for hydrogen peroxide was developed based on cross-linking horseradish peroxidase (HRP) by glutaraldehyde with multiwall carbon nanotubes/chitosan (MWNTs/chitosan) composite film coated on a glassy carbon electrode. MWNTs were firstly dissolved in a chitosan solution. Then the morphology of MWNTs/chitosan composite film was characterized by field-emission scanning electron microscopy. The results showed that MWNTs were well soluble in chitosan and robust films could be formed on the surface. HRP was cross-linked by glutaraldehyde with MWNTs/chitosan film to prepare a hydrogen peroxide biosensor. The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for H₂O₂ in the absence of a mediator. The linear range of detection towards H₂O₂ (applied potential: −0.2 V) was from 1.67 × 10⁻⁵ to 7.40 × 10⁻⁴ M with correction coefficient of 0.998. The biosensor had good repeatability and stability for the determination of H₂O₂. There were no interferences from ascorbic acid, glucose, citrate acid and lactic acid.     

A novel nonenzymatic sensor based on LaNi0.6Co0.4O3 modified electrode for hydrogen peroxide and glucose

In this paper, LaNi_0.6Co_0.4O₃ (LNC) nanoparticles were synthesized by the sol–gel method, and the structure and morphology of LNC nanoparticles were characterized by X-ray diffraction spectrum, scanning electron microscopy and transmitting electron microscopy. And then, LNC was used to modify carbon paste electrode (CPE) without any adhesive to fabricate hydrogen peroxide and glucose sensor, and the results demonstrated that LNC exhibited strong electrocatalytical activity by cyclic voltammetry and amperometry. In H₂O₂ determination, linear response was obtained in the concentration range of 10 nM–100 μM with a detection limit of 1.0 nM. In glucose determination, there was the linear region of 0.05–200 μM with a detection limit of 8.0 nM. Compared with other reports, the proposed sensor also displayed high sensitivity toward H₂O₂ (1812.84 μA mM⁻¹ cm⁻²) and glucose (643.0 μA mM⁻¹ cm⁻²). Moreover, this prepared sensor was applied to detect glucose in blood serum and hydrogen peroxide in toothpaste samples with satisfied results, indicating its possibility in practical application.     

Fluorometric method for the determination of hydrogen peroxide and glucose with Fe3O4 as catalyst

In this paper, we utilized the instinct peroxidase-like property of Fe₃O₄ magnetic nanoparticles (MNPs) to establish a new fluorometric method for determination of hydrogen peroxide and glucose. In the presence of Fe₃O₄ MNPs as peroxidase mimetic catalyst, H₂O₂ was decomposed into radical that could quench the fluorescence of CdTe QDs more efficiently and rapidly. Then the oxidization of glucose by glucose oxidase was coupled with the fluorescence quenching of CdTe QDs by H₂O₂ producer with Fe₃O₄ MNPs catalyst, which can be used to detect glucose. Under the optimal reaction conditions, a linear correlation was established between fluorescence intensity ratio I₀/I and concentration of H₂O₂ from 1.8 × 10⁻⁷ to 9 × 10⁻⁴ mol/L with a detection limit of 1.8 × 10⁻⁸ mol/L. And a linear correlation was established between fluorescence intensity ratio I₀/I and concentration of glucose from 1.6 × 10⁻⁶ to 1.6 × 10⁻⁴ mol/L with a detection limit of 1.0 × 10⁻⁶ mol/L. The proposed method was applied to the determination of glucose in human serum samples with satisfactory results.     

An ultrasensitive iron(III)-complex based hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism

In this communication, the first nonelectrocatalysis-type hydrogen peroxide electrochemical sensor is reported. The electroactive iron(III) diethylenetriaminepentaacetic acid (DTPA-Fe^III) complex is immobilized on the cysteamine (cys) modified nanoporous gold (NPG) films by covalent method. The immobilized DTPA-Fe^III complex quickly communicates an electron with the electrode. Upon addition of hydrogen peroxide, however, hydrogen peroxide inhibits the direct electron transfer of the DTPA-Fe^III complex due to the generation of nonelectroactive DTPA-Fe^III–H₂O₂ complex. Based on quenching mechanism, the first hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism is developed. The novel hydrogen peroxide electrochemical sensor has the ultralow detection limit (1.0 × 10^–14 M) and wide linear range (1.0 × 10^–13 to 1.0 × 10^–8 M) with excellent reproducibility and stability.     

A simple colorimetric FIA method for the determination of pyrite oxidation rates

A method for the rapid determination of the oxidation rate of naturally occurring pyrite (FeS₂) samples is presented. The progress of the oxidation reaction was followed by measurement of the concentration of total dissolved iron using flow injection analysis. Iron was determined using UV-vis detection after reaction with the colorimetric reagent 5-sulfosalicylic acid in the presence of ammonia. The calibration function was linear between 5 and 150 mg L⁻¹, and the detection limit was 0.46 mg L⁻¹. The relative standard deviation was typically less than 1% (n = 10) and the measurement frequency was 60/h. The method was used to quantify the oxidation rate of 10 ground and cleaned pyrite samples (53 μm < x < 106 μm) from various international locations that were subjected to accelerate oxidation in acidic hydrogen peroxide. Results of these experiments showed that there was almost an order of magnitude of difference in oxidation rates of the pyrite samples.     

Hydrogen production from water decomposition by redox of Fe2O3 modified with single- or double-metal additives

Iron oxide modified with single- or double-metal additives (Cr, Ni, Zr, Ag, Mo, Mo-Cr, Mo-Ni, Mo-Zr and Mo-Ag), which can store and supply pure hydrogen by reduction of iron oxide with hydrogen and subsequent oxidation of reduced iron oxide with steam (Fe₃O₄ (initial Fe₂O₃)+4H₂↔3Fe+4H₂O), were prepared by impregnation. Effects of various metal additives in the samples on hydrogen production were investigated by the above-repeated redox. All the samples with Mo additive exhibited a better redox performance than those without Mo, and the Mo-Zr additive in iron oxide was the best effective one enhancing hydrogen production from water decomposition. For Fe₂O₃-Mo-Zr, the average H₂ production temperature could be significantly decreased to 276 °C, the average H₂ formation rate could be increased to 360.9-461.1 μmol min⁻¹ Fe-g⁻¹ at operating temperature of 300 °C and the average storage capacity was up to 4.73 wt% in four cycles, an amount close to the IEA target.     

Effects of microstructure of carbon nanofibers for amperometric detection of hydrogen peroxide

Carbon nanofibers (CNFs) with three microstructures, including platelet-carbon nanofibers (PCNFs), fish-bone-carbon nanofibers (FCNFs), and tube-carbon nanofibers (TCNFs), were synthesized, characterized, and evaluated for electrochemical sensing of hydrogen peroxide. The CNFs studied here show microstructures with various stacked morphologies. The sizes and graphite-layer ordering of the CNFs can be well controlled. Glassy carbon (GC) electrodes modified by CNFs were fabricated and compared for amperometric detection of hydrogen peroxide. Sensors based on PCNFs/GC, FCNFs/GC, and TCNFs/GC were used in the amperometric detection of H₂O₂ in solution by applying a potential of +0.65 V versus Ag/AgCl at the working electrode. The highest electrocatalytic performance was observed for PCNFs/GC among the three types of hydrogen peroxide sensors. The amperometric response of PCNFs/GC retained over 90% of the initial current of the first day up to 21 days. The linear range is from 1.80 × 10⁻⁴ to 2.62 × 10⁻³ M with a correlation coefficient larger than 0.999 and with a detection limit of 4.0 μM H₂O₂ (S/N = 3). The relative standard deviation for detecting 1.80 × 10⁻⁴ M H₂O₂ (N = 8) is 2.1% with an average response of 0.64 μA. The significant diversity of electrocatalytic activity of the CNFs toward the oxidation of hydrogen peroxide may result from the difference of morphologies, textural properties, and crystalline structures.     

A sensitive amperometric sensor for hydrazine and hydrogen peroxide based on palladium nanoparticles/onion-like mesoporous carbon vesicle

Onion-like mesoporous carbon vesicle (MCV) with multilayer lamellar structure was synthesized by a simply aqueous emulsion co-assembly approach. Palladium (Pd) nanoparticles were deposited on the MCV matrix (Pd/MCV) by chemical reduction of H₂PdCl₄ with NaBH₄ in aqueous media. Pd(X)/MCV (X wt.% indicates the Pd loading amount) nanocomposites with different Pd loading amount were obtained by adjusting the ratio of precursors. The particular structure of the MCV results in efficient mass transport and the onion-like layers of MCV allows for the obtainment of highly dispersed Pd nanoparticles. The introduction of Pd nanoparticles on the MCV matrix facilitates hydrazine oxidation at more negative potential and delivers higher oxidation current in comparison with MCV. A linear range from 2.0 × 10⁻⁸ to 7.1 × 10⁻⁵ M and a low detection limit of 14.9 nM for hydrazine are obtained at Pd(25)/MCV nanocomposite modified glassy carbon (GC) electrode. A nonenzymatic amperometric sensor for hydrogen peroxide based on the Pd(25)/MCV nanocomposite modified GC electrode is also developed. Compared with MCV modified GC electrode, the Pd(25)/MCV nanocomposite modified GC electrode displays enhanced amperometric responses towards hydrogen peroxide and gives a linear range from 1.0 × 10⁻⁷ to 6.1 × 10⁻³ M. The Pd(25)/MCV nanocomposite modified GC electrode achieves 95% of the steady-current for hydrogen peroxide within 1 s. The combination of the unique properties of Pd nanoparticles and the porous mesostructure of MCV matrix guarantees the improved analytical performance for hydrazine and hydrogen peroxide.     

Direct electrocatalytic oxidation of nitric oxide and reduction of hydrogen peroxide based on α-Fe2O3 nanoparticles-chitosan composite

α-Fe₂O₃ nanoparticles prepared using a simple solution-combusting method have been dispersed in chitosan (CH) solution to fabricate nanocomposite film on glass carbon electrode (GCE). The as-prepared α-Fe₂O₃ nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM). The nanocomposite film exhibits high electrocatalytic oxidation for nitric oxide (NO) and reduction for hydrogen peroxide (H₂O₂). The electrocatalytic oxidation peak is observed at +0.82 V (vs. Ag/AgCl) and controlled by diffusion process. The electrocatalytic reduction peak is observed at −0.45 V (vs. Ag/AgCl) and controlled by diffusion process. This α-Fe₂O₃-CH/GCE nanocomposite bioelectrode has response time of 5 s, linearity as 5.0 × 10⁻⁷ to 15.0 × 10⁻⁶ M of NO with a detection limit of 8.0 × 10⁻⁸ M and a sensitivity of −283.6 μA/mM. This α-Fe₂O₃-CH/GCE nanocomposite bioelectrode was further utilized in detection of H₂O₂ with a detection limit of 4.0 × 10⁻⁷ M, linearity as 1.0 × 10⁻⁶ to 44.0 × 10⁻⁶ M and with a sensitivity of 21.62 μA/mM. The shelf life of this bioelectrode is about 6 weeks under room temperature conditions.     

A novel tris(2,2′-bipyridine)ruthenium(II)/tripropylamine cathodic electrochemiluminescence in acetonitrile for the indirect determination of hydrogen peroxide

A novel tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) cathodic electrochemiluminescence (ECL) was generated at −0.78 V at the Pt electrode in acetonitrile (ACN), which suggested that the cathodic ECL differed from conventional cathodic ECL. It was found that tripropylamine (TPrA) could enhance this cathodic ECL and the linear range (log-log plot) was 0.2 μM-0.2 mM. In addition, hydrogen peroxide (H₂O₂) could inhibit the cathodic ECL and was indirectly detected with the linear range of 27-540 μM. The RSD (n = 12) of the ECL intensity in the presence of 135 μM H₂O₂ was 0.87%. This method was also demonstrated for the fast determination of H₂O₂ in disinfectant sample and satisfactory results were obtained.     

Osmium (VI) catalyzed chemoselective oxidation of allylic and benzylic alcohols

A mild and highly chemoselective approach to oxidation of allylic, electron rich/deficient benzylic, and heterocyclic alcohols employing catalytic quantities of K₂[OsO₂(OH)₄] (3 mol %) and chloramine-T (50 mol %) is described. The protocol offers short reaction times (25 min–2 h), controlled oxidation, and tolerance to a variety of substrates. A systematic mechanistic study based on the LC-ESI-MS/MS reveals the presence of imidotriooxoosmium species which further reacts with alcohol to give the oxidized product.     

A chemiluminescence sensor for the determination of hydrogen peroxide

A chemiluminescence one-shot sensor for hydrogen peroxide is described. It is prepared by immobilization of cobalt chloride and sodium lauryl sulphate in hydroxyethyl cellulose matrix cast on a microscope cover glass. Luminol, sodium phosphate and the sample are mixed before use and applied on the membrane by a micropipette. The calibration graph is linear in the range 20-1600 μg/L, and the detection limit of the method (3σ) is 9 μg/L. A relative standard deviation of 4.5% was obtained for 100 μg/L H₂O₂ (n = 11). The sensor has been applied successfully to the determination of hydrogen peroxide in rainwater.     

可见光辐射下活性炭-铁酸镍杂化催化剂光催化氧化氨氮

铁酸镍（NiFe₂O₄）中的镍原子抑制其光芬顿催化活性. 然而,活性炭（AC）能激活其光芬顿催化活性,结果导致复合催化剂AC-NiFe₂O₄在过氧化氢存在时可见光辐射下也可催化氧化氨氮. 用X射线衍射（XRD）,透射电镜（TEM）,傅里叶变换红外（FTIR）光谱,紫外-可见漫反射光谱（UV-Vis DRS）,比表面积和振动样品磁强计对催化剂进行了表征. 光催化降解氨氮的实验表明,该复合催化剂在10 h内氨氮的降解率可达到91.0%,而同样条件下没有催化剂时氨氮的去除率只有24.0%. 对照实验表明,裸铁酸镍在可见光辐射下,氨氮的降解率只有30.0%. 这表明活性炭加速了氨氮的氧化速率. 动力学研究表明,氨氮的氧化遵循一级反应动力学规律,其表观反应动力学常数为3.538×10^-3 min^-1. 机理研究表明,氨氮的氧化是通过生成HONH₂ 中间体,然后转化为NO₂^- .8次循环实验表明该复合催化剂容易分离、可循环使用、且催化活性十分稳定. 因此,该催化剂具有潜在的应用价值.