共查询到20条相似文献,搜索用时 359 毫秒
1.
Enzyme-mimicking artificial nanomaterials often termed nanozymes have broad applications in many fields, including biosensing, pollutant degradation and cancer diagnosis. Herein, we introduce a plasmonic gold nanoparticle-modified Mn 3O 4 nanozyme (Mn 3O 4-Au). Visible or near infrared light excitation into the plasmonic absorption band of the surface-bound gold nanoparticles enhances the catalytic oxidation of tetramethylbenzidine (TMB). The mechanism of light-enhanced peroxidase activity is proposed based on the Mn 3O 4 conduction band mediated hot electron transfer from photoexcited gold nanoparticles to H 2O 2 which undergoes further oxygen-oxygen bond cleavage to yield hydroxyl radical. The surface decoration of plasmonic gold nanoparticles endows Mn 3O 4-Au to be a light-regulated nanozyme. 相似文献
2.
The strategy of structurally integrating noble metal and metal oxides is expected to offer exceptional opportunities toward emerging functions of all. We report the creation of an efficient hetero-structured nanocatalyst consisting of Mn 3O 4 core, SiO 2 shell impregnated with noble Ag nanoparticles. The triple nanocatalyst Mn 3O 4/Ag/SiO 2 was synthesized by using a facile three-step approach to disperse Ag nanoparticles between the surfaces of functionalized Mn 3O 4 and SiO 2. The physicochemical structural characterization was performed by XRD and FTIR. The surface morphologies were observed by SEM and TEM. The EDX measurements confirmed the composition of the composite. The nanocomposite has been used as a catalyst for the degradation of Direct blue 78 in the presence of sodium borohydride (NaBH 4). It has a drastic catalytic effect as compared to Mn 3O 4/Ag and Mn 3O 4. The rate constant of Direct blue 78 reduction followed the order: Mn 3O 4/Ag/SiO 2 (0.25166 min −1) > Mn 3O 4/Ag (0.07971 min −1) > Mn 3O 4 (0.00947 min −1). The effects of different reaction conditions of the catalytic reaction have been determined. The catalytic activity of the as- synthesized nanocomposite was examined for the binary dyes system by incorporation of an additional dye (Sunset yellow). Its influence on the degradation rate and efficiency of Direct blue 78 was investigated. The nanocatalyst exhibited excellent catalytic activity towards the complete degradation of both the Direct blue 78 and Sunset yellow. The degradation percentage for these dyes reached 99.33 and 94.68%, respectively. The recovery and reusability of the Mn 3O 4/Ag/SiO 2 nanocomposite was studied in the reduction reaction of Direct blue 78. Five consecutive recovery reaction cycles were performed. They revealed high stability and constant efficiency of the catalyst for four cycles. 相似文献
3.
We report on the synthesis of Mn 3O 4 nanoparticles via a two-step hydrothermal route by using Mn(CH 3COO) 2 as the only starting material and TMAOH and NaOH as hydrolysing agents. XRD and FT-IR analyses confirmed the composition and structure of Mn 3O 4. TEM images showed that spheroid Mn 3O 4 nanostructures obtained by this method have average particle size of 6 and 14 nm for NaOH and TMAOH hydrolyzed samples respectively. Particle size analysis indicated a strong aggregation of nanoparticles and exhibited bi-modal distribution with average size of aggregates as ~250 nm and 1.1 μm for both samples. Zeta potential analysis revealed adsorbed TMAOH species on the surface of Mn 3O 4 nanoparticles hydrolyzed using TMAOH. ESR analyses resulted in broader lines and smaller g values than bulk Mn 3O 4 nanoparticles, probably due to the exchange-coupled system with unlike spins such as canted spin at surface of high-surface-disordered nanoparticles. 相似文献
4.
In this work, ultrafine Cu1.5Mn1.5O4 spinel nanoparticles were successfully synthesized by a sol–gel method combined with two complexing agents, which was firstly employed in the reductive transformation from p-nitrophenol into p-aminophenol. The effect of calcination temperature on the crystal phase and microstructure of Cu1.5Mn1.5O4 nanoparticles was investigated in this article. It was found that Cu1.5Mn1.5O4 nanoparticles with pure spinel phase can be obtained at 500 °C with the help of EDTA acid–citric acid complexing agents. Below 500 °C, there exists some Mn2O3 impure phase. SEM characterization indicated that the particle size of the spinel Cu1.5Mn1.5O4 rapidly increases above 600 °C. The catalytic experimental results show that the Cu1.5Mn1.5O4 nanoparticles prepared at 500 °C exhibit the highest catalytic activity which is even superior to some precious metal catalysts. With the calcination temperature increasing, the catalytic activity of Cu1.5Mn1.5O4 spinel nanoparticles gradually degrades which can be ascribed to the particle size growth of Cu1.5Mn1.5O4. It can also be observed that all the oxide samples, namely CuO, Mn2O3 and Cu1.5Mn1.5O4, possess certain catalytic ability for the transformation from p-nitrophenol into p-aminophenol. However, the catalytic activity of Cu1.5Mn1.5O4 spinel nanoparticles is obviously higher than CuO and Mn2O3. Especially, Mn2O3 alone has very poor catalytic activity in the reduction of p-nitrophenol. 相似文献
5.
This work reports the synthesis of various carbon (Vulcan XC-72 R) supported metal oxide nanostructures, such as Mn 2O 3, Co 3O 4 and Mn 2O 3−Co 3O 4 as heterogeneous Fenton-like catalysts for the degradation of organic dye pollutants, namely Rhodamine B (RB) and Congo Red (CR) in wastewater. The activity results showed that the bimetallic Mn 2O 3−Co 3O 4/C catalyst exhibits much higher activity than the monometallic Mn 2O 3/C and Co 3O 4/C catalysts for the degradation of both RB and CR pollutants, due to the synergistic properties induced by the Mn−Co and/or Mn (Co)−support interactions. The degradation efficiency of RB and CR was considerably increased with an increase of reaction temperature from 25 to 45°C. Importantly, the bimetallic Mn 2O 3−Co 3O 4/C catalyst could maintain its catalytic activity up to five successive cycles, revealing its catalytic durability for wastewater purification. The structure–activity correlations demonstrated a probable mechanism for the degradation of organic dye pollutants in wastewater, involving •OH radical as well as Mn 2+/Mn 3+ or Co 2+/Co 3+ redox couple of the Mn 2O 3−Co 3O 4/C catalyst. 相似文献
6.
In this communication, manganese oxide (Mn 3O 4) nanoparticles were prepared by a facile solution method using starch as capping agent. The nanoparticles were characterized by means of X‐ray diffraction (XRD) and AFM. The results showed that the Mn 3O 4 nanoparticles were single phase, spherical, and uniformly dispersive. The average particle size was evaluated to be approximately 35 nm. 相似文献
7.
In this paper, we have developed a simple, facile, and efficient approach to synthesize polyaniline/Mn 3O 4 (PANI/Mn 3O 4) nanocomposites using aniline as a reducer in the presence of KMnO 4 without any additives or templates. The morphology of the composites is characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results demonstrate that the tetrahedral Mn 3O 4 nanoparticles have uniform sizes and are finely dispersed in the PANI matrix. The crystallinity and chemical constituents of the composites are characterized by powder X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR) and UV-vis spectrophotometry. Moreover, cyclic voltammetry (CV) measurements are used to characterize the electrochemical properties of PANI/Mn 3O 4 nanocomposites. The developed materials give a pair of redox peaks and have better operation stability, which indicates that the composites show distinct electrochemical performance. So the PANI/Mn 3O 4 nanocomposites would have potential applications in bioanalysis, biodetection and so on. 相似文献
8.
Mesostructured manganese oxide (Mn 3O 4) is prepared by a soft‐templating method employing sodium dodecyl sulfate (SDS) as a structure‐directing agent. By removing the template from the as‐prepared mesostructured Mn 3O 4 by extraction or calcination, we successfully synthesized highly crystallized mesoporous Mn 3O 4 or Mn 2O 3, respectively, with different crystalline structures. 相似文献
9.
A novel bidentate Schiff base ligand L ( L = N-(4-amino-2-chloro-phenyl)-2-hydroxybenzaldehyde) and the subsequent octahedral manganese(III) Schiff base complex Mn L 3 have been synthesized and characterized by, FT-IR spectroscopy and elemental analyses (CHN). Additionally, Schiff base ligand has been characterized by 1H NMR spectroscopy. Thermogravimetric analysis of the ligand and its metal complexes reveals their thermal stability and decomposition pattern. Thus, the Mn L 3 complex has been investigated as a novel precursor for the facile preparation of Mn 3O 4 nanoparticles via solid-state thermal decomposition under aerobic conditions, at a temperature of ca. 450 °C The resulting Mn 3O 4 nanocrystals were characterized by FT-IR spectroscopy, X-ray powder diffraction (XRPD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The XRPD studies reveal the characteristic diffraction peaks indexed to the Mn 3O 4 hausmanite structure, while the absence of additional peaks tends to clearly indicate the high purity of the sample. In addition, the TEM/SEM investigations displayed the nanoplate shape of the rather monodisperse crystalline Mn 3O 4 nanoparticles, with an average diameter of ca. 10 nm. The statistical distribution of the nanoparticles size has to be provided with an histogram graphic. 相似文献
10.
Carbon‐coated Mn 3O 4 nanowires (Mn 3O 4@C NWs) have been synthesized by the reduction of well‐shaped carbon‐coated bixbyite networks and characterized by TEM, X‐ray diffraction, X‐ray photoelectron spectroscopy, and electrochemical experiments. To assess the properties of 1D carbon‐coated nanowires for their use in supercapacitors, cyclic voltammetry and galvanostatic charging–discharging measurements were performed. Mn 3O 4@C NWs could be charged and discharged faster and had higher capacitance than bare Mn 3O 4 nanostructures and other commercial materials. The capacitance of the Mn 3O 4@C NWs was 92 % retained after 3000 cycles at a charging rate of 5 A g ?1. This improvement can be attributed to the carbon shells, which promote fast Faradaic charging and discharging of the interior Mn 3O 4 core and also act as barriers to protect the inner core. These Mn 3O 4@C NWs could be a promising candidate material for high‐capacity, low‐cost, and environmentally friendly electrodes for supercapacitors. In addition, the magnetic properties of the as‐synthesized samples are also reported to investigate the influence of the carbon coating. 相似文献
11.
Heating hydrous manganese (II) hydroxide gel at 85 °C for 12 hours produces Mn 3O 4 nanoparticles. They were characterized by X-ray powder diffraction (XRD) and infrared spectroscopy (FTIR). The particle size
estimated from the SEM and X-ray peak broadening is approximately 32 nm, showing them to be nanocrystalline. EPR measurements
confirm a typical Mn 2+signal with a highly resolved hyperfine structure.
相似文献
12.
Novel Mn 3O 4-promoted double p?n junction MgAl 2O 4/CeO 2/Mn 3O 4 heterojunction photocatalyst was constructed by one-step synthesis method and two-step synthesis method. The X-ray powder diffraction, Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, optical and photoluminescence demonstrated that the MgAl 2O 4/CeO 2/Mn 3O 4 heterojunction photocatalyst was synthesized by the two-step synthesis method comprehends a high crystallinity, charge carrier migration and separation efficiency, and relatively low optical absorption coefficient. The MgAl 2O 4/CeO 2/Mn 3O 4 heterojunction photocatalysts were efficiently used as simulated sunlight-driven n-n and p-n double junction photocatalyst for the simultaneous degradation of methylene blue (MB) dye. The continuous double p?n junction MgAl 2O 4/CeO 2/Mn 3O 4 heterojunctions strengthened the function of single n-n or p-n junction and guided the charge carrier migration and separation direction; thus, the oxidation and reduction reactions occur at the active site of spatial separation and prevent the recombination of electrons and holes. The results suggest that the continuous double p?n junction MgAl 2O 4/CeO 2/Mn 3O 4 heterojunctions are very promising candidate material for enhancing the photocatalytic activity in the photocatalytic degradation of MB dye. 相似文献
13.
The semiconductor realization is a very significant stage in gas sensor application. Herein, the Mn 3O 4 semiconductor was deposited using chemical spray pyrolysis. The effect of deposition temperature on structural, vibrational optical and electrical Mn 3O 4 thin layers properties were investigated through: X-ray diffraction, Raman spectroscopy, UV-visible spectrophotometer, and two points electrometers respectively. The X-ray diffraction showed the appearance of spinel phase of tetragonal Mn 3O 4 with strong formation direction along (101) plan and without any secondary phase indicating the formation of pure Mn 3O 4. The Raman spectroscopy confirmed the results obtained in XRD and certified the high-quality formation of Mn 3O 4. In addition, the crystallinity improvement (the increase of crystallite size and the decrease of dislocation density) was caused by the increasing of deposition temperature from 350 °C to 450 °C. Optical properties such as transmittance, absorbance and band gap energy were extracted by UV-Visible spectrophotometer. Thus, low transmittance, high absorbance and small band gap energy were observed at the highest substrate temperature (450 °C). The electrical conductivity showed good values between 4.83 and 13.89 mS.cm −1. These properties make Mn 3O 4 an appropriate material to be used as a sensitive layer in gas sensors applications. 相似文献
14.
Enhancement of Fe 3O 4 /Au nanoparticles (Fe 3O 4 /Au NPs ) catalyst was observed in the oxidative degradation of methyl orange by employing H 2O 2 as oxidant. To evaluate the catalytic activity of Fe 3O 4 /Au nanoparticles, different degradation conditions were investigated such as the amounts of catalyst, H 2O 2 concentration and pH value. Based on our data, methyl orange was degraded completely in a short time. The enhanced catalytic activity and increased oxidation rate constant may be ascribed to synergistic catalyst‐activated decomposition of H 2O 2 to •OH radical, which was one of the strong oxidizing species. Besides, Fe 3O 4 /Au nanoparticles have exhibited satisfying recycle performance for potential industrial application. 相似文献
15.
Spinel Li 4Mn 5O 12 nanoparticles are successfully prepared by water-in-oil microemulsion method and characterized by X-ray diffraction and scanning electron microscopy. The Li 4Mn 5O 12 nanoparticles have sphere-like morphology with particle size less than 50 nm. The Li 4Mn 5O 12 and activated carbon (AC) were used as electrodes of Li 4Mn 5O 12/AC supercapacitor, respectively. The electrochemical capacitance performance of the supercapacitor was investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The results showed that the single electrode was able to deliver specific capacitance 252 F g ?1 within potential range 0–1.4 V at a scan rate of 5 mV s ?1 in 1 mol L ?1 Li 2SO 4 solution, and it also showed high coulombic efficiency close to 100%. This material exhibited a good cycling performance. 相似文献
16.
The LaF 3 surface-modified LiCr 0.05Mn 1.95O 4 samples were synthesized by co-precipitation method and characterized by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray detector (EDX). HAADF-STEM and EDX observations showed that LaF 3 deposited on the surface of LiCr 0.05Mn 1.95O 4 particles. When tested as the cathode materials for lithium-ion battery, the LaF 3-modified LiCr 0.05Mn 1.95O 4 exhibited significantly improved cyclic and rate performances at high temperature (55?°C). Electrochemical impedance spectrum analyses demonstrated that the surface of LiCr 0.05Mn 1.95O 4 modified by LaF 3 was much more stable during the electrochemical process and could greatly facilitate the charge–transfer reaction, which may be attributed to the protection of active material by LaF 3 from the HF attack. 相似文献
17.
In this paper, an azo-containing Schiff base complex of manganese [Mn 2+-azo ligand@APTES-SiO 2@Fe 3O 4] immobilized on chemically modified Fe 3O 4 nanoparticles has been used as a magnetically retrievable catalyst for the alcoholysis of different epoxides to their corresponding alkoxy alcohols with methanol, ethanol and n-propanol. The newly magnetic nanoparticles (MNPs) were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and vibrating sample magnetometry (VSM). 相似文献
18.
Single-crystalline Mn 3O 4 nanoframes and hollow octahedra were firstly prepared via a polyethylene glycol template-assisted route under hydrothermal conditions. The synthesized Mn 3O 4 nanoframes showed both square-shaped hollow interiors and the outward solid rims while their relative octahedra displayed hollow cores of about 75 nm. In addition, the formation mechanisms of Mn 3O 4 hollow nanostructures and the key roles of polyethylene glycol templates were discussed. 相似文献
19.
Lithium manganese oxide crystals with composition (Li 0.91Mn 0.09)Mn 2O 4 were synthesized by a flux method. The crystals have a structure closely related to that of the cubic spinel LiMn 2O 4, but 9% of the lithium ions in the tetrahedral 4 a site are substituted by Mn 2+ ions. This substitution lowers the average Mn oxidation state below 3.5+, resulting in a Jahn–Teller distortion of the MnO 6 octahedron. 相似文献
20.
Ca 2Mn 3O 8 and Cd 2Mn 3O 8, which contain Mn 4+ monolayers, have been prepared and characterized. Their magnetic susceptibility and electron paramagnetic resonance (EPR) behavior have been examined in detail. The Mn 4+ moments in both Ca 2Mn 3O 8 and Cd 2Mn 3O 8 order antiferromagnetically near 60 and 10°K, respectively. Although the Néel temperature in Ca 2Mn 3O 8 is in reasonable agreement with molecular-field theory, that in Cd 2Mn 3O 8 is well below its expected value. It is proposed that these results, as well as those in the calcium manganite series CaMnO 3 → Ca 2MnO 4, may reflect the chemical influence of the divalent cation in modifying the MnO covalent mixing. 相似文献
|