MnO NPs Research Articles

A flexible nanostructured paper of MnO NPs@MWCNTs/r-GO multilayer sandwich composite for high-performance lithium-ion batteries

Designing a high capacity and long cycle life MnO-based composite material for lithium ion batteries (LIBs) is still a great challenge because of the intrinsically low electrical conductivity and dramatic volume variations during lithiation/delithiation. In this paper, the MnO nanoparticles (MnO NPs) are recombined with multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (r-GO) to rationally construct a novel MnO NPs@MWCNTs/r-GO multilayer sandwich structure via electrostatic interaction self-assembly and vacuum filtration processes. As a result, the MnO NPs are closely attracted in the conductive MWCNTs network, and the MWCNTs adsorbed on the surface of MnO NPs can be served as a soft and flexible carbon coating layer to self-adapt the huge volume expansion. For another, the r-GO between two MnO NPs@MWCNTs layers is the cause to form a free-standing paper, enhancing the transverse conductivity of the whole electrode simultaneously. These features will contribute to achieve excellent cycling stability and improved rate capability.

Ultrathin supercapacitor electrodes with high volumetric capacitance and stability using direct covalent-bonding between pseudocapacitive nanoparticles and conducting materials

We introduce high-performance ultrathin supercapacitor electrodes obtained through the direct covalent-bonding layer-by-layer (LbL) assembly (or ligand-exchange LbL assembly) of amine-functionalized multiwalled carbon nanotubes (CNTs) and transition metal oxide nanoparticles (TMO NPs). The main characteristic of our approach is that the internal interfacial resistance of the electrodes can be minimized through the direct covalent-bonding adsorption of densely packed, high-quality TMO NPs onto CNTs without the aid of nonactive binders or insulating NP ligands, and the resulting volumetric capacitance and cycling stability of the electrodes can be significantly enhanced. For this study, well-defined oleic acid-stabilized pseudocapacitive metal oxide nanoparticles (i.e., OA–Fe3O4 and OA–MnO NPs) prepared in toluene were densely adsorbed onto the CNT layer due to the high affinity between the surface of the TMO NPs and the NH2 moieties of the CNTs. The (CNT/OA–Fe3O4 NP)20 multilayer electrode exhibited a high volumetric capacitance of 248±15Fcm−3 (128±7Fg−1) at 5mVs−1 despite the intrinsically low specific capacitance of the Fe3O4 NPs. Additionally, these film electrodes exhibited high performance stability, maintaining 99.2% of their initial capacitance after 1000 cycles. Furthermore, upon the insertion of OA–MnO NPs with high crystallinity and a high theoretical pseudocapacitance value within multilayers instead of OA–Fe3O4 NPs, the formed electrodes (i.e., (CNT/OA–MnO NP)20 multilayers) exhibited a higher volumetric capacitance of 305±10Fcm−3 (183±5Fg−1) (at a scan rate of 5mVs−1) than other conventional ultrathin supercapacitor electrodes, including manganese oxide or iron oxide NPs.

In depth analysis of apoptosis induced by silica coated manganese oxide nanoparticles in vitro

Manganese oxide nanoparticles (MnO NPs) have been regarded as a new class of T1-positive contrast agents. The cytotoxicity of silica coated MnO NPs (MnO@SiO2 NPs) was investigated in human cervical carcinoma cells (HeLa) and mouse fibroblast cells (L929). The changes of cell viability, cell morphology, cellular oxidative stress, mitochondrial membrane potential and cell cycle induced by MnO@SiO2 NPs were evaluated. Compared to HeLa cells, L929 cells showed lower cell viability, more strongly response to oxidative stress and higher percentage in the G2/M phase of cell cycle. The appearance of sub-G1 peak, double staining with Annexin V-FITC/PI and the increase of Caspase-3 activity further confirmed apoptosis should be the major form of cell death. Moreover, the apoptotic pathway was clarified as follows. Firstly, reactive oxygen species (ROS) is generated induced by MnO@SiO2 NPs, then p53 is activated followed by an increase in the bax and a decrease in the bcl-2, ultimately leading to G2/M phase arrest, increasing the activity of caspase-3 and inducing apoptosis.

Formation of octapod MnO nanoparticles with enhanced magnetic properties through kinetically-controlled thermal decomposition of polynuclear manganese complexes

Polynuclear manganese complexes are used as precursors for the synthesis of manganese oxide nanoparticles (MnO NPs). Altering the thermal decomposition conditions can shift the nanoparticle product from spherical, thermodynamically-driven NPs to unusual, kinetically-controlled octapod structures. The resulting increased surface area profoundly alters the NP's surface-dependent magnetism and may have applications in nanomedicine.

Tailored biological retention and efficient clearance of pegylated ultra-small MnO nanoparticles as positive MRI contrast agents for molecular imaging.

A majority of MRI procedures requiring intravascular injections of contrast agents are performed with paramagnetic chelates. Such products induce vascular signal enhancement and they are rapidly excreted by the kidneys. Unfortunately, each chelate is made of only one paramagnetic ion, which, taken individually, has a limited impact on the MRI signal. In fact, the detection of molecular events in the nanomolar range using T1-weighted MRI sequences requires the design of ultra-small particles containing hundreds of paramagnetic ions per contrast agent unit. Ultra-small nanoparticles of manganese oxide (MnO, 6-8 nm diameter) have been developed and proposed as an efficient and at least 1000× more sensitive "positive" MRI contrast agent. However no evidence has been found until now that an adequate surface treatment of these particles could maintain their strong blood signal enhancement, while allowing their rapid and efficient excretion by the kidneys or by the hepatobiliairy pathway. Indeed, the sequestration of MnO particles by the reticuloendothelial system followed by strong uptake in the liver and in the spleen could potentially lead to Mn2+-induced toxicity effects. For ultra-small MnO particles to be applied in the clinics, it is necessary to develop coatings that also enable their efficient excretion within hours. This study demonstrates for the first time the possibility to use MnO particles as T1 vascular contrast agents, while enabling the excretion of >70% of all the Mn injected doses after 48 h. For this, small, biocompatible and highly hydrophilic pegylated bis-phosphonate dendrons (PDns) were grafted on MnO particles to confer colloidal stability, relaxometric performance, and fast excretion capacity. The chemical and colloidal stability of MnO@PDn particles were confirmed by XPS, FTIR and DLS. The relaxometric performance of MnO@PDns as "positive" MRI contrast agents was assessed (r1 = 4.4 mM-1 s-1, r2/r1 = 8.6; 1.41 T and 37 °C). Mice were injected with 1.21 μg Mn per kg (22 μmol Mn per kg), and scanned in MRI up to 48 h. The concentration of Mn in key organs was precisely measured by neutron activation analysis and confirmed, with MRI, the possibility to avoid RES nanoparticle sequestration through the use of phosphonate dendrons. Due to the fast kidney and hepatobiliairy clearance of MnO particles conferred by PDns, MnO nanoparticles can now be considered for promising applications in T1-weighted MRI applications requiring less toxic although highly sensitive "positive" molecular contrast agents.

Water-Soluble and Biocompatible MnO@PVP Nanoparticles for MR Imaging <I>In Vitro</I> and <I>In Vivo</I>

The uniform-sized manganese oxide nanoparticles (the oleic-capped MnO NPs) were synthesized by the thermal decomposition of Mn-oleate complex and were transferred into water with the help of cationic surfactant of cetyltrimethyl ammonium bromide (CTAB), then the poly(vinylpyrrolidone) (PVP) membrane was further coated on to them with the aid of anionic dispersant of poly(styrenesulfonate) (PSS) by layer-by-layer electrostatic assembly to render them water soluble and biocompatible. They were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and MTT assay. In vitro cellular uptake test revealed the MnO@PVP NPs were low cytotoxic, biocompatible and could be used as a T,-positive contrast agent for passive targeting magnetic resonance imaging (MRI). Interestingly, signal enhancement in cerebral spinal fluid (CSF) spaces in vivo experiment suggested that the MnO@PVP NPs can pass through the blood brain barrier (BBB). These results show that MnO@PVP NPs are good candidates as MRI contrast agents with the lack of cytotoxicity and have great potential applications in magnetic nano-device and biomagnetic field.

Improvement of solubility and biocompatibility of MnO based nanoparticles in aqueous solutions

ABSTRACTMnO nanoparticles were surface modified using two different multifunctional polymers. By introducing a PEG group, the long term stability, MRI applicability and sterile filtration could be greatly improved. Furthermore, PEGylated MnO NPs were less toxic compared to non-PEGylated NPs. The results suggest that these nanoparticles are suitable for in vivo applications.

Monodisperse Octahedral α-MnS and MnO Nanoparticles by the Decomposition of Manganese Oleate in the Presence of Sulfur

Octahedral monodisperse α-MnS and MnO nanoparticles have been synthesized by decomposing manganese oleate and elemental sulfur in octadecene at high (250−320 °C) temperature. The chemical composition of the obtained NPs depends on the Mn:S ratio in an unexpected way. Pure α-MnS NP samples are obtained when S:Mn ≥ 2:1, whereas pure MnO NPs require S:Mn ≤ 0.6. Variation of several parameters (concentration of sulfur, heating rate and aging temperature and time) resulted in a α-MnS NP size interval of 11−14 (from Mn monooleate) and 18−30 nm (from Mn dioleate). For MnO NPs only, size control is also possible by addition of free oleic acid (14−24 nm). Analysis of TEM tilting experiments and electron diffraction shows that both α-MnS and MnO nanoparticles have octahedral shape and spontaneously form ordered arrays with strong texture in the {111} direction. Measurement of the magnetic properties showed that α-MnS nanoparticles consist of an antiferromagnetic core and a ferromagnetic-like shell that are exchange coupled below the blocking temperature of the shell (23 K for 29 nm α-MnS NP).