Manganese Dioxide Nanocomposites Research Articles

Gold nanoclusters anchored manganese dioxide nanocomposites with high structural stability for sensitive detection of methyl parathion

A long-standing goal has been to create a high-energy transfer system for food safety detection. Herein, gold nanoclusters-anchored manganese dioxide (AuNCs@MnO2) nanocomposites are designed by using co-template assembly. Bovine serum albumin is utilized as both skeletons of nucleation and stabilizer to guide the synthesis of the AuNCs@MnO2 nanocomposites under physiological conditions without the use of any potent oxidants and the hazardous organic solvent. The AuNCs@MnO2 nanocomposites exhibit good energy transfer efficiency and structural stability even under high salt conditions and a wide range of pH values. A sensitive sensing platform for the detection of methyl paraoxon has been constructed as a result of the excellent performance of AuNCs@MnO2 nanocomposites. Acetylcholinesterase catalyzes the conversion of the substrate to produce thiocholine, which induces the decomposition of MnO2 and the fluorescence recovery of AuNCs. Coupling with the pesticide inhibition effect, the platform can be employed to quantify methyl parathion with a detection limit of 3.1 pg mL−1. The AuNCs@MnO2-based platform displays high stability and anti-interference capability in food and environment samples, endowing practical application in food safety monitoring.

Intelligent manganese dioxide nanocomposites induce tumor immunogenic cell death and remould tumor microenvironment

The solid tumor often has unique structure and microenvironment that quite different with normal tissue. The tumor microenvironment (TME) of solid tumor is often characterized by mild acid, high glutathione (GSH) level, excessive hydrogen peroxide (H2O2) and hypoxia. These characteristics not only accelerate tumor progression, angiogenesis and metastasis, but also lead to drug resistance and treatment failure. To regulate these adverse factors in TME plays vital roles in improving tumor response to various treatments. In this study, a silk fibroin-cRGDfk-Ce6 conjugate-based MnO2 nanocomposite (SRCM) was fabricated, and its modulation potentials of these adverse factors, enhanced immune cell activation and infiltration in TME were systematically studied in vitro and in vivo. After administration in vivo, the synthesized SRCM quickly targeted to acidic TME, reduced to ultra-small nanosheets and Mn2+, triggered the endogenous H2O2 decomposition and oxygen generation, and converted GSH into GSSG. Therefore, to modulate the adverse factors in TME, while Mn2+ simultaneously enhanced the magnetic resonance imaging (MRI) capability. Together with photodynamic therapy (PDT) and photothermal therapy (PTT), the SRCM effectively induced immunogenic cell death (ICD), antigen-presenting cell (APC) activation, and improved immune-competent cell infiltration. The results demonstrated that the SRCM not only alleviated hypoxia in TME, enhanced PDT efficacy, but also efficiently induced the IDC of tumor cells, corrected the adverse physical, chemical and biological factors in TME, thereby effectively reducing the tumor burden in animal model.

Albumin-manganese dioxide nanocomposites: a potent inhibitor and ROS scavenger against Alzheimer's β-amyloid fibrillogenesis and neuroinflammation.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease pathologically caused by amyloid-β protein (Aβ) aggregation, oxidative stress, and neuroinflammation. The pathogenesis of AD is still uncertain and intricate, and helpful therapy has rarely been recorded. So, discovering amyloid modulators is deemed a promising avenue for preventing and treating AD. In this study, human serum albumin (HSA), a protein-based Aβ inhibitor, was utilized as a template to guide the synthesis of HSA-manganese dioxide nanocomposites (HMn NCs) through biomineralization. The in situ formed MnO2 in HSA endows this nano-platform with outstanding reactive oxygen species (ROS) scavenging capability, including superoxide dismutase-mimetic and catalase-mimetic activities, which could scavenge the plethora of superoxide anion radicals and hydrogen peroxide. More importantly, the HMn NCs show enhanced potency in suppressing Aβ fibrillization compared with HSA, which further alleviates Aβ-mediated SH-SY5Y neurotoxicity by scavenging excessive ROS. Moreover, it is demonstrated that HMn NCs reduce Aβ-related inflammation in BV-2 cells by lowering tumor necrosis factor-α and interleukin-6. Furthermore, transgenic C. elegans studies showed that HMn NCs could remove Aβ plaques, reduce ROS in CL2006 worms, and promote the lifespan extension of worms. Thus, HMn NCs provide a promising tactic to facilitate the application of multifunctional nanocomposites in AD treatment.

Thermal and Rheological Characterization of Aqueous Nanofluids Based on Reduced Graphene Oxide (rGO) with Manganese Dioxide Nanocomposites (MnO2).

Nanofluids have become of interest in recent years thanks to their improved thermal properties, which make them especially interesting for microchannel heat sink applications. In this study, we prepared two aqueous nanofluids based on reduced graphene oxide (rGO) decorated with manganese dioxide (MnO) at a concentration of 0.1 wt.%. The difference between the two nanofluids was in the preparation of the reduced graphene oxide decorated with MnO. In the first case, the manganese salt was mixed with ascorbic acid before GO reduction with NaOH, and in the second case, the GO reduction with NaOH occurred under ascorbic acid. Ascorbic acid not only plays the role of a non-toxic and ecofriendly reducing agent but also acts as an important parameter to control the reaction kinetics. The structural, microstructural and spectral characterizations of the MnO/rGO nanocomposite were conducted via X-ray diffractometry (XRD), Raman spectroscopy, FT-IR, TEM, SEM and EDS analyses. Moreover, the synthesized MnO/rGO nanocomposites were utilized as nanofluids and their stability, thermal conductivity and rheological behaviors were studied. The thermal conductivity of the MnO/rGO and MnOAsA/rGO nanofluids was 17% and 14.8% higher than that of water for the average temperature range, respectively, but their viscosity remained statistically equal to that of water. Moreover, both nanofluids presented Newtonian behavior in the analyzed shear rate range. Therefore, both MnO/rGO and MnOAsA/rGO nanofluids are promising alternatives for use in applications with micro- and millichannel heat sinks.

Fabrication of MnO2 Nanocomposite on GO Functionalized with Advanced Electrode Material for Supercapacitors

A new strategy for supercapacitor formation was carried out in the study using electrodes made of graphene oxide (GO) and manganese dioxide (MnO2) nanocomposites. To the present knowledge, only a few investigations have been carried out concerning the synthesis of GO-MnO2-based nanocomposites and their electrochemical properties, with varying mass ratios, as well as the change in electrochemical properties of their components as MnO2 and GO were tested individually for the enhanced stability and performances. A synthetic method was performed successfully to manufacture MnO2/GO nanocomposites. The findings of the present study show that the composites have a lot of potential as an effective conduction property. A composite of graphene oxide supported manganese dioxide nanocomposites fabricated with the simple soft chemical route. As-prepared nanocomposites can be improved in performance by the interactions between GO and MnO2.

Coconut shell derived activated biochar–manganese dioxide nanocomposites for high performance capacitive deionization

In this study, a Faradaic/electric double-layer hybrid capacitor using coconut shell derived activated biochar (AB) and MnO2 nanocomposite was fabricated for capacitive deionization (CDI) applications. Three different co-precipitation methods including indirect, direct, and acid-assisted grafting oxidation methods were explored to produce the AB-MnO2 nanocomposites. The α-MnO2 with an excellent ion intercalation ability was successfully deposited onto the AB, making the AB-MnO2 an excellent electrode material for CDI application in the presence of neutral Na2SO4 electrolytes. Notably, the AB-MnO2 nanocomposites prepared by indirect co-precipitation method (AB-MnO2-indirect) has shown a high specific surface area of 304 m2 g−1 with high mesopore volume ratio, high capacitance retention, good hydrophilicity and suitable pore texture to shorten the diffusion distance of ions. Cyclic voltammetric (CV) and electrochemical impedance spectroscopic (EIS) spectra showed that the AB-MnO2 yields a quasi-rectangular and symmetric CV plot, and specific capacitances of 410–523 F g−1 at 5 mV s−1 were observed. Moreover, the AB-MnO2-indirect exhibits excellent CDI performance at 1.2 V, and the specific electrosorption capacity of 33.9–68.4 mg g−1 was obtained. Results of this study demonstrate that AB-MnO2 nanocomposites are superior electrochemical materials for CDI application, which can serve as alternative materials for designing an innovative electrochemical technology for water purification, desalination, and energy storage.

Removal of cationic and anionic dyes from aqueous phase by Ball clay – Manganese dioxide nanocomposites

We report novel method to synthesis of Ball clay – Manganese dioxide nanocomposite (BC-MNC) as an effective and eco-friendly adsorbent for the removal of malachite green(MG) and acid blue 25 (AB25) from its aqueous solution. The as synthesized BC-MNC was characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), zeta potential analysis, Brunauer−Emmett−Teller (BET) surface area analysis, Barrett-Joyner-Halenda (BJH) pore size and volume analysis. Many factors such as pH, adsorbent dose, temperature, contact time and initial dye concentrations were optimized to control the adsorption process of MG and AB25 onto BC-MNC. The optimum conditions for removal of MG were found to be pH = 8, adsorbent dose =0.8 g, contact time =70 min and similarly for AB25 was found to be pH = 2, adsorbent dose =0.8 g and contact time =80 min. The equilibrium isothermal data was finely fitted with Langmuir isotherm model for MG and Freundlich isotherm model for AB25. The kinetics data of both MG and AB 25 followed the pseudo-second order kinetics. The thermodynamics factors revealing that the adsorption process of MG was spontaneous and endothermic, and the adsorption of AB25 was spontaneous and exothermic in nature. Moreover, maximum adsorption capacity of BC-MNC for the removal of MG and AB25 was found to be 58.47 mg/g and 1250 mg/g respectively. Thus, the prepared composite has efficient, economical and eco-friendly adsorbent (BC-MNC) for the removal of MG and AB25 respectively.

Synergistic and Competitive Adsorption of Methylene Blue and Rhodamine B on Core-shell Magnetic Manganese Dioxide Nanocomposites

Synergistic and Competitive Adsorption of Methylene Blue and Rhodamine B on Core-shell Magnetic Manganese Dioxide Nanocomposites

Employment of ultrasonic irradiation for production of poly(vinyl pyrrolidone)/modified alpha manganese dioxide nanocomposites: Morphology, thermal and optical characterization

This work explains the production, morphology, and features of novel nanocomposite (NC) established on poly(vinyl pyrrolidone) (PVP) as polymer background and modified alpha manganese dioxide (α-MnO2) nanorod (NR) asan efficient filler. At first, one-dimensional α-MnO2 nanorods (NRs) were produced by a hydrothermal technique and then they were amended with stearic acid (SA) by a solvothermal process. In following, the NCs were made by adding different volumes of α-MnO2-SA NR (1, 3 and 5wt%) in the PVP matrix through ultrasonic irradiation as a green, low-cost, fast, and useful technique. Structural and morphological descriptions confirm crystallinity of α-MnO2-SA NRs and showed that NRs have been separately dispersed in PVP matrix with rod-like morphology and diameter of about 40–60nm. The use of modifier and ultrasonic waves is accountable for good homogeneities of NRs. Thermogravimetric analysis revealed that thermal permanency of the obtained NCs has grown with increasing the α-MnO2-SA content. Also, the UV–vis absorption of NCs was enhanced with the incorporation of the modified α-MnO2 NR in PVP matrix. The substantial perfections in NCs properties are associated to compatible intermolecular relations between the surface modifying groups of the α-MnO2-SA and PVP chain.

Hydrothermally synthesized reduced graphene oxide and Sn doped manganese dioxide nanocomposites for supercapacitors and dopamine sensors

α-MnO2 nanowires and its nanocomposites (rGO-MnO2 and Sn@rGO-MnO2) were synthesized by a facile hydrothermal technique. Two important electrochemical applications of nanocomposites, viz, electrodes for supercapacitor and sensors for a biomolecule, dopamine are reported. The prepared nanowires have been characterized by XRD, which reveals smaller crystallite size of rGO- MnO2 composites compared to pristine MnO2 and the trend is supported by BET analysis. The wrapping of MnO2 NWs with rGO sheets increases the surface area, as well as, creates more dislocations at the interfaces. The correlation between physicochemical properties leads to an enhancement in the electrochemical performance of the materials. The as-fabricated Sn@rGO-MnO2 supercapacitor electrode reveals superior performance. The specific capacitance of 139.05, 309.7 and 460.9 F/g at a scanning rate of 20 mV/s, in an aqueous Na2SO4 solution (1 M) is obtained for MnO2, rGO-MnO2, and Sn@rGO-MnO2 respectively. Also, the reported nanocomposites show excellent performance towards detection of dopamine. Among α-MnO2/GCE, rGO-MnO2/GCE and Sn@rGO-MnO2/GCE based sensors for Dopamine detection, rGO-MnO2/GCE sensor exhibits the highest sensitivity of 433.6 μA/mM and broad linear range, whereas Sn@rGO-MnO2 exhibits lower detection limit of 0.13 μM.

Enhanced catalytic performance of magnetic Fe3O4–MnO2 nanocomposites for the decolorization of rhodamine B, reduction of 4-nitroaniline, and sp3 C–H functionalization of 2-methylpyridines to isatins

A novel biosynthesized nanocatalyst, iron oxide-loaded manganese dioxide nanocomposites (Fe3O4–MnO2 NCs), was fabricated with the aid of a Perilla frutescens leaf extract. The MnO2 is composed of numerous nanoflakes radiating from the center, which results to a flowerlike structure. A change in the flowerlike morphology of MnO2 in Fe3O4–MnO2 NCs was observed due to the distribution of Fe3O4 nanoparticles on the surface of MnO2. To check the catalytic performance of the synthesized NCs, they were utilized as a catalyst for the decolorization of rhodamine B (RhB), reduction of 4-nitroaniline (4-NA), and sp3 C–H functionalization of 2-methylpyridines to isatins for the synthesis of azaarene-substituted 3-hydroxy-2-oxindole derivatives. The Fe3O4-loaded MnO2 exhibited enhanced catalytic ability over MnO2. Moreover, the nanocomposites could be recovered by a magnetic separation technique and reused for five consecutive reactions without significant loss of catalytic ability.

Core–shell magnetic manganese dioxide nanocomposites modified with citric acid for enhanced adsorption of basic dyes

Chemically surface modified core–shell magnetic manganese dioxide nanocomposites were prepared by redox reaction of KMnO4 to MnO2 on the surface of hydrophilic carbon coated magnetite (Fe3O4/C) microspheres in alkaline media, coupling with the modification by citric acid (CA). Properties of the synthesized adsorbent were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and vibration sample magnetometer (VSM) analysis and Brunauer–Emmett–Teller (BET) technique. Characterization results showed that prepared material had well-defined core–shell structure composed of inner magnetite core with superparamagnetic property and outer shell of nano-manganese dioxides modified with citric acid. The adsorption kinetics and isotherm were studied to examine the adsorption efficiency of citric acid modified magnetic manganese dioxide (Fe3O4/C/MnO2-CA) nanocomposites towards methylene blue (MB) as basic dye. The kinetic data were found to fit pseudo-second-order model as compared to pseudo-first-order model. Langmuir isotherm model fitted the experimental data better than the Freundlich isotherm model. The adsorption mechanism study suggested that the hydrogen bonding, electrostatic and electron acceptor-donor interactions were responsible for the adsorption of MB on Fe3O4/C/MnO2-CA nanocomposites.

Halloysite nanotubes induced synthesis of carbon/manganese dioxide coaxial tubular nanocomposites as electrode materials for supercapacitors

Halloysite nanotubes@carbon/manganese dioxide nanocomposites (HNTs@C/MnO2) with coaxial tubular structure were prepared by introducing manganese dioxide on the surface of carbon-coated halloysite nanotubes (HNTs@C). The HNTs@C nanocomposites were synthesized by hydrothermal carbonization of glucose on the surface of HNTs and further activated at high temperature to improve the degree of carbonization. The use of halloysite nanotubes can effectively induce the heterogeneous deposition of carbonaceous species on the surface of the halloysite nanotubes, and then uniformly generate MnO2 nanoflakes via the redox reaction between the carbon and potassium permanganate to construct the hybrid coaxial structure. The as-prepared hybrid materials were characterized by transmission electron microscope, Fourier transform infrared spectrum, X-ray diffraction, and thermogravimetric analysis. The specific capacitance of HNTs@C/MnO23 nanocomposites can reach 274 F g−1 at 1.25 mA cm−2 in 1.0 M Na2SO4 electrolyte after correcting the weight percent of electroactive materials. Furthermore, the special coaxial tubular structure and the manganese dioxide nanoflakes facilitated the ion diffusion between the electrode/electrolyte interfaces. The results indicate that the novel coaxial tubular hybrid nanocomposites can be a promising candidate as electrode material for supercapacitors.