MnO NPs Research Articles

Ocimum basilicum L. leaves extract-mediated green synthesis of MnO NPs: Phytochemical profile, characterization, catalytic and thrombolytic activities

ObjectiveThe goal of the present work was the identification and quantification of the phenolic profile of sweet basil using LC-ESI-MS and to evaluation the ability of this plant to synthesise manganese nanoparticles MnONPs and evaluation of their catalytic and thrombolytic activities. Material and methodsStandard procedures were used to extract bioactive molecules and test qualitative phytochemical substances. Phenolic compounds were identified and quantified using LC-ESI-MS. Furthermore, visual observation, UV–Vis and FT-IR spectroscopy, scanning and transmission electron microscopes (SEM and TEM), and XRD technique were used to verify the green synthesis of ObE-MnO NPs. Dye degradation of ObE-MnO NPs was studied using photocatalytic and sonocatalytic activities. Moreover, in vitro thrombolytic activity was evaluated by clot lysis. ResultsResults of phytochemical essays showed that the aqueous extract of Ocimum basilicum L. is very rich in different chemical compounds that reduce and stabilize NPs. The results of the characterization of MnONPs show that the formation of these particles was proven by UV–Vis spectrum with the absorption peak at 405 nm, and also by FTIR spectrum at 470-522 cm−1. The study also confirmed that the MnONPs were spherical in shape with an average size of 6.52 ± 0.88 nm using TEM and SEM analysis, and that their size was 13.4 nm, tetragonal, and crystalline by XRD data. Results of catalytique activity show at a time of 240 min, an efficacy level of 70.18% and 58.90% for the photocatalytic and sonocatalytic activities. Ocimum basilicum L. extract and ObE-MnO NPs demonstrated a significant higher percentage of clot lysis by 93.33% and 94.73% respectively. ConclusionIn conclusion, the synthesized NPs made with basil extract were satisfactorily characterized utilizing a range of analytical techniques. ObE-MnO NPs also exhibit efficient catalytic and thrombolytic activities, qualifying their high degree of safety for usage in the environmental, pharmacological and medicinal domains.

Tetragonal crystalline MnO nanoparticles alleviate Pb stress in wheat by modulating antioxidant enzymes in leaves.

Agriculture ecosystems are seriously threatened by lead (Pb) contamination, which impacts plant growth and productivity. In this study, green synthesized manganese oxide nanoparticles (MnO NPs) using citrus peel were used for priming of wheat seeds. For the synthesis of MnO nanoparticles, peel extract of Citrus paradisi and 1mM solution of manganese acetate were stirred and calcinated at 500°C. Successful synthesis of MnO NPs was determined using advanced techniques. In Fourier-transform infrared spectroscopy (FTIR), the presence of amines, alkanes, aldehydes, and alcohol molecules, on the surface of MnO NPs, confirmed their stability. X-ray diffraction analysis described their average size (22nm), while scanning electron microscopy showed tetragonal crystalline shape and nano-flowers structure of MnO NPs. Sharp peaks of energy dispersive x-ray analysis described the presence of oxygen (28.81%) and manganese (71.19%) on MnO NPs. Priming of wheat seeds with synthesized MnO NPs significantly improved the growth attributes of wheat seedlings including the size of leaf, root length, size of shoots, chlorophyll and carotenoid contents, relative water content, decreased relative electrolyte leakage, high proline accumulation and decreased concentration of malondialdehyde. Application of MnO NPs also helped plants to accumulate antioxidant enzymes in their leaves. These results proved that the priming of MnO NPs can greatly reduce lead-induced stress in wheat seedlings and these NPs can alsobe used for the priming of other crops.

Photocatalytic degradation of methylene blue dye using Ba-doped MnO nanoparticles

MnO and Ba-doped MnO NPs were prepared through the chemical reduction method and these NPs were used for the photodegradation of Methylene blue dye (MB) dye in an aqueous medium. The morphological study shows that the MnO NPs have granular shapes while Ba-doped MnO NPs have irregular spherical shapes. XRD results presented that the diameter of MnO and Ba-doped MnO NPs was 30 and 36 nm, respectively. FTIR spectra show peaks in the range of 750–1385 cm−1, which present the metal oxide NPs. The photocatalytic degradation study demonstrated that the MnO and Ba-doped MnO NPs degraded about 73 and 86% dye within 250 min, respectively. The effect of various parameters like pH, initial dye concentration, and catalyst dosage on the photodegradation of dye was also studied. The recovered MnO and Ba-doped MnO NPs also significantly degraded the Methylene Blue dye in aqueous media.

Development and characterization of a non-enzymatic electrochemical biosensor for rapid determination of sorbent-based extracted trazodone and doxepin in complicated samples

BackgroundGiven the importance of achieving optimal therapeutical concentration in patients treated with antidepressants, this study investigates a novel technique for the simultaneous determination of trazodone (TRZ) and doxepin (DOX) in human plasma and serum samples for the first time. ResultsTo achieve simultaneous determination of two antidepressants, TRZ and DOX, a novel detection system was designed: a non-enzymatic voltammetric biosensor based on boron-reduced graphene oxide/manganese oxide nanoparticles (GCE/B-rGO/MnO NPs). The detection was accomplished after pre-concentration and extraction trace amounts of the analytes using the thin film-solid phase microextraction (TF-SPME) technique, which employed polyvinyl alcohol/polyvinyl acetate/copper oxide nanoparticles (PVA/PVAc/CuO NPs) electrospun nanofibers.The successful preparation of composite nanofibers and modified electrodes was confirmed using the evaluation of field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). Also, the composite nanofibers were characterized with attenuated total reflectance-Fourier transform-infrared (ATR-FT-IR) and X-ray diffraction (XRD). In the solution of TRZ and DOX, under optimum experimental conditions, the linear dynamic ranges (LDRs) were 0.1–20.0 μmol L−1 and 0.5–27.0 μmol L−1, respectively. Also, the limit of detection (LOD) values of TRZ and DOX were 0.032 and 0.150 μmol L−1. SignificancePVAc acts as a cross-linking agent for PVA, and their mixture is effective for sample preparation and pre-concentration of analytes in complex matrices. Also, adding CuO NPs to this polymeric mixture enhanced the adsorption efficiency.Taking advantage of the high surface area of MnO NPs and the high electrical conductivity of B-rGO, and considering the superiority of their simultaneous utilization, the constructed electrochemical biosensor is both cost-effective and rapid. It demonstrates excellent stability, repeatability, and sensitivity for the simultaneous determination of TRZ and DOX under optimal conditions.This biosensor, the first of its kind, is specifically designed for the simultaneous determination of TRZ and DOX in human plasma and serum samples, representing a significant advancement in biosensing technology.

Cytotoxic Effect of Biosynthesized Manganese Oxide Nanoparticles on Human Skin Squamous Carcinoma Cell Line (HSSCC) in vitro

The current study intended to biosynthesis of manganese oxide nanoparticles (MnO -NPs) depending on prodigiosin pigment as stabilizing and reducing agent. which produced from environmental isolate of Serratia marcescens . The study of the biosynthesis of MnO NPs was characterized by different techniques, such as ( UV-VIS, XRD, AFM, FE-SEM and FTIR). The results refer, the wavelength of biosynthesis of MnO NPs by using UV-VIS was (284 nm), the average volume was (45) nm). and image FE-SEM shows that the MnO- NPs mainly consists of nanosheets assembled in flower-like shape with different diameters. The cytotoxic effects of (MnO -NPs) on Human Skin Squamous Carcinoma Cell Line (HSSCC) was significant (p≤0.05) comparative with control viability 100%. Maximum effective concentration were 4000 μg/ml for 72hr exposure time which gave the highest inhibition rate 95% comparative with viability control 100%, but the minimum concentration was 3.9 μg/ml which induced proliferation of (HSSCC)cells. So when the exposure time and the concentration was increased, the inhibition rate was increased. Keywords:Serratia marcescens, Human skin squamous carcinoma cell line, cytotoxic effect, prodigiosin, MnO –NP.

2D carbon-supported MnO@C nanoparticles for high capacity and long life lithium-ion battery anode enabled by a relatively green and facile method

MnO is regarded as a promising alternative anode for lithium-ion batteries (LIBs) due to its large specific capacity. Nonetheless, low intrinsical conductivity and large volumetric change of the MnO anode cause fast capacity fading during cycle, and hence its practical use in LIBs is hindered. In spite of many effective solutions for above problems, most of them involve requirement of harmful chemicals or special equipments, are not conducive to development of MnO anode. Herein, a relatively green and facile method is demonstrated to prepare a two dimensional (2D) MnO/C composite (MnO NPs@C Ps), consisting of carbon-coated MnO nanoparticles anchored on 2D carbon plates. The results confirm outstanding electrochemical performances of the MnO NPs@C Ps anode in terms of high capacities and ultra-long lifespan, with 1046.8 mA h g−1 after 500 cycles at 200 mA g−1 as well as 463 mA h g−1 after even 1500 cycles at 1000 mA g−1. The combination of the materials and electrochemical characterizations demonstrates that the rational synergistic effects of nano-sized MnO particles and 2D carbon support contribute to thus outstanding electrochemical performances of the MnO NPs@C Ps anode. It is believed that this work may provide a meaningful insight into development of other advanced metal oxides/carbon composite anodes.

Controllable synthesis of MnO nanoparticles supported on porous carbon as a highly active oxidase mimic for dopamine detection

Mn(II) ion has emerged as a cofactor in heme-copper oxidase to confer O2 reduction to H2O, which shares the similar mechanism with oxidase mimicking reaction, so it is fascinating and interesting to explore the oxidase mimetic activity of Mn(II) compound. Here, MnO nanoparticles supported on porous carbon (MnO NPs/PC) was controllably prepared via in-situ conversion of MnO2 nanobelts supported on porous carbon (MnO2 NBs/PC). The oxidase mimetic activity of MnO NPs/PC was investigated using 3,3′,5,5′-tetramethyl-benzidine (TMB) as chromogenic substrate. MnO NPs/PC shows excellent oxidase mimetic activity with a low kinetic parameter Km of 0.0214 mM and a high Vmax of 7.21 × 10−7 M/s. Due to the inhibition effect on TMB color reaction, dopamine (DA) can be detected using MnO NPs/PC-TMB chromogenic system, even in human serum samples. This work not only provides a controllable synthetic method for small-sized MnO NPs, but also throws the light on MnO oxidase mimetic activity for the first time.

Biosynthesized manganese oxide nanoparticles maintain firmness of tomato fruit by modulating soluble solids and reducing sugars under biotic stress

Nanoparticles have been reported to mitigate biotic and abiotic stresses in different fruits and vegetables. In this study, tomato fruit with black rot symptoms were collected and diagnosed. To control this disease, manganese oxide nanoparticles (MnO NPs) were synthesized in bacterial broth-culture. Based on microscopic, morphological, and genetic analyses, the pathogen causing black rot disease was identified as Aspergillus niger. MnO NPs were successfully synthesized in broth-culture of Bacillus subtilis, following the process of calcination and characterized. Fourier transform infrared (FTIR) spectrum revealed the existence of stabilizing and reducing agents (carboxylic acid, alkenes, and alkyl halides) on the surface of MnO NPs. X-Ray diffraction (XRD) analysis revealed the size (39 nm) and crystal-like nature of synthesized MnO NPs. Energy-dispersive X-ray spectroscopy (EDX) described the mass percentage of manganese (26.4%) and oxygen (23.3%). Scanning electron microscopy (SEM) displayed nearly spherical shape of MnO NPs and confirmed their nano-size. These MnO NPs exhibited significant mycelial growth inhibition of A. niger and notable control of tomato black rot disease of tomato. Though, all concentrations exhibited considerable effects, medium concentration of MnO NPs (2.5 mg/mL) performed best in both in vitro and in vivo analyses. At this concentration, tomato fruit maintained higher percentage of soluble solids, total sugars, reducing sugars and fruit firmness. These results proved very effective application of bacteria supplemented MnO NPs for the control of black rot disease of tomato. To our knowledge, this is the first study of tomato black rot, caused by A. niger in Pakistan.

Sonochemical Synthesized Manganese Oxide Nanoparticles as Fluorescent Sensor for Selenium (IV) Quantification. Application to Food and Drink Samples.

Manganese oxide nanoparticles (MnO Nps), sonochemical synthesized and characterized in our laboratory, are proposed as fluorescent sensor for selenium (Se) determination. The new methodology has been developed based on the enhancing effect of the Se(IV) on fluorescent emission of MnO Nps. Experimental variables that influence on fluorimetric sensitivity were optimized. The calibration graph using zeroth order regression was linear from 0.189ng L-1 to 8.00 × 103µg L-1, with correlation coefficient better than 0.99. Under the optimal conditions, the limits of detection and quantification were of 0.062ng L-1 and 0.189ng L-1, respectively. The trueness of the methodology was assessed through standard addition method obtaining recovery near to 100%. This method showed good tolerance to foreign ions, particularly to Se(VI), and was applied to determination of Se(IV) trace in food and drink samples with satisfactory results. With the intention of preserving the environment from harmful effects, a degradation study of the used nanomaterials has been included for their subsequent disposal.

Novel biosynthesis of MnO NPs using Mycoendophyte: industrial bioprocessing strategies and scaling-up production with its evaluation as anti-phytopathogenic agents

This report provides the first description of the myco-synthesis of rod-shaped MnO NPs with an average crystallite size of ~ 35 nm, employing extracellular bioactive metabolites of endophytic Trichodermavirens strain EG92 as capping/reducing agents and MnCl2·4H2O as a parent component. The wheat bran medium was chosen to grow endophytic strain EG92, which produced a variety of bioactive metabolites in extracellular fraction, which increases the yield of MnO NPs to 9.53 g/l. The whole medium and fungal growth conditions that influenced biomass generation were optimized as successive statistical optimization approaches (Plackett–Burman and Box–Behnken designs). The production improvements were achieved at pH 5.5, WBE (35%), and inoculum size (10%), which increased Xmax to twelve-folds (89.63 g/l); thereby, Pmax increased to eight-folds (82.93 g/l). After 162 h, Xmax (145.63 g/l) and Pmax (99.52 g/l) on the side of µmax and YX/S were determined as 0.084 and 7.65, respectively. ViaTaguchi experimental design, fungus-fabricated MnO NPs reaction was improved by adding 0.25 M of MnCl2·4H2O to 100% of fungal extract (reducing/capping agents) and adjusting the reaction pH adjusted to ~ 5. This reaction was incubated at 60 °C for 5 h before adding 20% fungal extract (stabilizing agent). Also, Pmax was raised 40-fold (395.36 g/l) over the BC. Our myco-synthesized MnO NPs exhibit faster and more precise antagonistic actions against phytopathogenic bacteria than fungi; they could be employed as an alternative and promised nano-bio-pesticide to manage a variety of different types of disease-pathogens in the future.

Hybrids of manganese oxide and lipid liquid crystalline nanoparticles (LLCNPs@MnO) as potential magnetic resonance imaging (MRI) contrast agents.

Due to the health risks associated with the use of Gd-chelates and the promising effects of using nanoparticles as T1 contrast agents (CAs) for MRI, Mn-based nanoparticles are considered a highly competitive alternative. The use of hybrid constructs with paramagnetic functionality of Mn-based nanoparticles is an effective approach, in particular, the use of biocompatible lipid liquid crystalline nanoparticles (LLCNPs) as a carrier of MnO nanoparticles. LLCNPs possess a unique internal structure ensuring a payload of different polarity MnO nanoparticles. In view of MRI application, the surface properties including the polarity of MnO are crucial factors determining their relaxation rate and thus the MRI efficiency. Two novel hybrid constructs consisting of LLCNPs loaded with hydrophobic MnO-oleate and hydrophilic MnO-DMSA NPs were prepared. These nanosystems were studied in terms of their physico-chemical properties, positive T1 contrast enhancement properties (in vitro and in vivo) and biological safety. LLCNPs@MnO-oleate and LLCNPs@MnO-DMSA hybrids exhibited a heterogeneous phase composition, however with differences in the inner periodic arrangement and structural parameters, as well as in the preferable localization of MnO NPs within the LLCNPs. Also, these hybrids differed in terms of particle size-related parameters and colloidal stability, which was found to be strongly dependent on the addition of differently functionalized MnO NPs. Embedding both types of MnO NPs into LLCNPs resulted in high relaxivity parameters, in comparison to bare MnO-DMSA NPs and also commercially developed CAs (e.g. Dotarem and Teslascan). Further biosafety studies revealed that cell internalization pathways were dependent on the prepared hybrid type, while viability, effects on the mitochondria membrane potential and cytoskeletal networks were rather related to the susceptibility of the particular cell line. The high relaxation rates achieved with the developed hybrid LLCNPs@MnO enable them to be possibly used as novel and biologically safe MRI T1-enhancing CAs in in vivo imaging.

Detailed Analysis of Crystal Structure and Optical Properties of Green Synthesized Nanoparticles: Application for Photocatalyst Degradation of Methylene Blue

We report the green chemistry reduction approach method for the synthesis of Manganese Oxide nanoparticles (MnO NPs), Copper Oxide nanoparticles (CuO NPs) and Manganese-doped Copper Oxide nanoparticles (Mn-doped CuO Nps). Aqueous extract from the seeds was used as reducing and capping agents. The detailed crystal structure analysis was investigated; crystallite size, crystallinity, morphological index, x-ray density, bulk density, specific surface area, porosity, Lorentz factor, Lorentz polarization factor and other parameters were calculated. Simple EDX mapping reveals the presence of Mn, Cu, O and C. FTIR analysis was used to determine the bond length of a nanocomposite. In the visible area, nanoparticles have higher optical absorption, with bandgaps varying from 1.79 (MnO), 2.18 eV (CuO) and 1.72 eV (Mn-doped CuO). After 90 min, the photodegradation rate of Mn-doped CuO nanocatalysts was 93.73 % while using a smaller amount of catalyst (0.1 g) at pH 7. The pseudo-first-order MB photocatalytic decomposition kinetic model has a high correlation coefficient value (R2 > 0.95). It was found that Mn-doped CuO NPs have higher photocatalytic efficiency and can be used as potential photocatalysts for industrial dye degradation. HIGHLIGHTS Green synthesis of Mn, Cu, and Mn-doped Cu nanoparticles by Bambusa seeds extract Characterized via XRD (crystal structure), UV-Vis Diffuse Reflectance spectra (UV-DRS), FT-IR (bond length), and FESEM-EDS analysis Photocatalytic degradation of organic methylene blue dye using Mn-doped CuO nanoparticles GRAPHICAL ABSTRACT

Biosynthesis and antibacterial activity of manganese oxide nanoparticles prepared by green tea extract

Amongst chemical and physical techniques, the biosynthesis method of metal nanoparticles has received the interest of many researchers owing to its environmental safety, simplicity and inexpensiveness. Manganese oxide nanoparticles (MnO NPs) were successfully synthesised using green tea extract as the reducing agent and characterised by UV–Vis spectroscopy, X-ray diffractometry and Fourier transform infrared spectroscopy. The shape and size of the MnO NPs were obtained by scanning electron microscopy. The size of the MnO NPs was 20–30 nm. The MnO NPs exhibited strong antibacterial activity against pathogenic bacteria, namely, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa, with inhibition zones of 12, 14 and 18 mm, respectively. Moreover, the minimum inhibitory concentration (MIC) of the MnO NPs was 12.5 U/mL as determined by resazurin microtitre assay. The activities of some antibiotics remarkably increased when combined with MnO NPs (at MIC).

Structural and optical properties of MgNb2O6 NPs: Its potential application in photocatalytic and pharmaceutical industries as sensor

Present research accounts for the production of columbite type MgNb2O6 nanoparticles (MNO NPs) by solution combustion method, its application in photocatalytic degradation and electrochemical sensor studies. The resultant nanoparticles were well characterized by Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and UV–Visible (UV–Vis) spectral studies. PXRD patterns showed that nanoparticles have orthorhombic phase with average crystallite size of ∼29 nm.The energy band gap of the sample was found to be 4.4 eV by Diffused reflectance spectroscopy (DRS) analysis. The MNO photocatalyst matrix influences excellent photocatalytic decolourization of Acid Red-88 (AR-88) and Fast orange red (FOR) dyes under UV light irradiation. The experiment show 86 % and 74 % dye decolourization respectively after 120 min irradiation. The holes (h+) are mainly responsible for excellent photocatalytic activities as confirmed by scavenger test. Electrochemical analysis was carried out to find the reversibility of the electrode reaction of electrode using 0.1 M KCl by Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS) analysis. Thus, the prepared sample plays an excellent role in photocatalysis, electrochemical activity and chemical sensing applications.

Bifunctional Pyrrolidin-2-one Terminated Manganese Oxide Nanoparticles for Combined Magnetic Resonance and Fluorescence Imaging.

Multimodal probes are an asset for simplified, improved medical imaging. In particular, fluorescence and magnetic resonance imaging (MRI) are sought-after combined capabilities. Here, we show that pyrrolidin-2-one-capped manganese oxide nanoparticles (MnOpyrr NPs) combine MRI with fluorescence microscopy to function as efficient bifunctional bio-nanoprobes. We employ a one-pot synthesis for ca. 10 nm MnO NPs, wherein manganese(II) 2,4-pentadionate is thermally decomposed using pyrrolidin-2-one as a solvent and capping ligand. The MnOpyrr NPs are soluble in water without any further postsynthetic modifications. The r1 relaxivity and r2 /r1 ratio indicate that these NPs are potential T1 MRI contrast agents at clinical (3 T) and ultrahigh (9.4 T) magnetic fields. Serendipitously, the as-prepared NPs are photoluminescent. The unexpected luminescence is ascribed to the modification of the pyrrolidin-2-one during the thermal treatment. MnOpyrr NPs are successfully used to enable fluorescence microscopy of HeLa cells, demonstrating bifunctional imaging capabilities. A low cytotoxic response in two distinct cell types (HeLa, HepG2) supports the suitability of MnOpyrr NPs for biological imaging applications.

Dye-Anchored MnO Nanoparticles Targeting Tumor and Inducing Enhanced Phototherapy Effect via Mitochondria-Mediated Pathway.

Phototherapy is a promising treatment method for cancer therapy. However, the various factors have greatly restricted phototherapy development, including the poor accumulation of photosensitizer in tumor, hypoxia in solid tumor tissue and systemic phototoxicity. Herein, a mitochondrial-targeted multifunctional dye-anchored manganese oxide nanoparticle (IR808@MnO NP) is developed for enhancing phototherapy of cancer. In this nanoplatform, IR808 as a small molecule dye acts as a tumor targeting ligand to make IR808@MnO NPs with capacity to actively target tumor cells and relocate finally in the mitochondria. Meanwhile, continuous production of oxygen (O2 ) and regulation of pH induced by the high reactivity and specificity of MnO NPs toward mitochondrial endogenous hydrogen peroxide (H2 O2 ) could effectively modulate tumor hypoxia and lessen the tumor subacid environment. Large amounts of reactive oxide species (ROS) are generated during the reaction process between H2 O2 and MnO NPs. Furthermore, under laser irradiation, IR808 in IR808@MnO NPs turns O2 into a highly toxic singlet oxygen (1 O2 ) and generates hyperthermia. The results indicate that IR808@MnO NPs have the high efficiency of specific targeting of tumors, relieving tumor subacid environment, improving the tumor hypoxia environment, and generating large amounts of ROS to kill tumor cells. It is expected to have a wide application in treating cancer.

Efficient Water Splitting Cascade Photoanodes with Ligand-Engineered MnO Cocatalysts.

The band edge positions of semiconductors determine functionality in solar water splitting. While ligand exchange is known to enable modification of the band structure, its crucial role in water splitting efficiency is not yet fully understood. Here, ligand‐engineered manganese oxide cocatalyst nanoparticles (MnO NPs) on bismuth vanadate (BiVO4) anodes are first demonstrated, and a remarkably enhanced photocurrent density of 6.25 mA cm−2 is achieved. It is close to 85% of the theoretical photocurrent density (≈7.5 mA cm−2) of BiVO4. Improved photoactivity is closely related to the substantial shifts in band edge energies that originate from both the induced dipole at the ligand/MnO interface and the intrinsic dipole of the ligand. Combined spectroscopic analysis and electrochemical study reveal the clear relationship between the surface modification and the band edge positions for water oxidation. The proposed concept has considerable potential to explore new, efficient solar water splitting systems.

Ligand Engineered MnO Catalytic Nanoparticles As an Efficient Charge Transfer Mediator for Photoelectrochemical Water Oxidation

Photoelectrochemical (PEC) water splitting is regarded as one of the most promising approaches for the generation of hydrogen as a renewable and carbon-free fuel. Bismuth vanadate (BiVO4) has been recognized a highly promising photoanode material for solar water splitting. However the PEC performance of BiVO4 remains significantly poorer than the theoretical value due to the severe recombination of photogenerated charge carrier near the solid/electrolyte interface. A novel strategy is therefore essential for the progress of highly efficient PEC water splitting. The band edge positions of semiconductors determine their functionality in photoelectrochemical water splitting. While surface modification on the catalytic surface is known to enable to facilitate modification of the band structure, its crucial role in water splitting efficiency has not yet been fully understood. Here, we firstly demonstrate the ligand engineering effect of manganese oxide Co-catalyst nanoparticles (MnO NPs) on bismuth vanadate (BiVO4)-based cascade anodes, and achieve a remarkably enhanced photocurrent density of 6.25 mA/cm2 at the 1.23 V versus reversible hydrogen electrode. It is the highest value among the previously reported BiVO4-based anodes. We verified that improved photoactivity is closely related to the substantial shifts in band edge energies that originate from both the induced dipole at the ligand/MnO interface and intrinsic dipole of the ligand. In particular, combined spectroscopic analysis and electrochemical study revealed the clear relationship between the surface structure driven by the ligand treatment and the band edge positions of MnO NPs for photoelectrochemical water oxidation. Our systematic study provides general strategy for enabling new active semiconductor photocatalyst and is applicable to solar water splitting system.

Electrospun carbon nanofibers decorated with MnO nanoparticles as a sulfur-absorbent for lithium-sulfur batteries

Shuttle effect of the dissolved polysulfide is a main disadvantage for Li-S batteries, which has been explored by several polar materials to absorb lithium polysulfide with physical and chemical effect. Herein, for the first time, a composite of carbon nanofibers decorated with MnO nanoparticles (CNF-MnO) has been prepared by the facile electrospinning method followed by thermal treatment. SEM and TEM characterization delivered that the MnO NPs on CNF did not change the morphology but decrease the electronic conductivity of CNF-MnO composite. The CNF-MnO composite exhibited excellent electrochemical cyclic stability because of its strong chemical absorption for polysulfide. Interestingly, CNF-MnO composite served as both cathode as well interlayer for Li-S batteries. The CNF-MnO-S as cathode material showed an initial discharge capacity of 683.2 mAh g-1 at 1.0 C and remained 592.0 mAh g-1 even after 250 cycles with the capacity decay of 0.053% per cycle. As well, CNF-MnO as interlayer delivered superior cycling stability even at high current density of 3.0 C, where the capacity still maintained 542.2 mAh g-1 over 200 cycles.

One-pot preparation of hydrophilic manganese oxide nanoparticles as T1 nano-contrast agent for molecular magnetic resonance imaging of renal carcinoma in vitro and in vivo

Magnetic resonance imaging (MRI) contrast agents have become a necessary part for clinical practice to improve the sensitivity for the diagnosis of small lesions and injuries. Among them, manganese oxide nanoparticle (MnO NPs)-based MRI contrast agent attracts more and more attention because of their better performance in the detection of brain disease and positive enhancement in T1-weighted image. However, the relatively low r1 relaxivity and complex synthetic route hampered their wider applications. In this work, we proposed a one-pot approach to prepare hydrophilic MnO NPs via a polyol-like method with poly (ethylene glycol) (PEG) as both a solvent and surfactant. The obtained PEG-MnO NPs displayed a high T1 relaxivity and a low r2/r1 ratio (12.942s−1 mM−1 and 4.66) at 3.0T, which was three times that of the clinical used contrast agent, Magnevist (Gd-DTPA). Additionally, when exposed to the simulated body fluid (SBF), acidic environment or glutathione, PEG-MnO NPs kept stable, favoring their further biological applications. Then, to explore their use for the molecular magnetic resonance imaging of 786-0 renal carcinoma, amino group modified AS1411 aptamer as the targeting molecule was introduced to conjugate with PEG-MnO NPs via covalent coupling reaction. The fabricated nanoprobe, AS1411-PEG-MnO, could clearly visualize 786-0 renal carcinoma cells with MRI in vitro. Furthermore, compared with PEG-MnO NPs, AS1411-PEG-MnO nanoprobe presented a prolonged retention in 786-0 renal carcinoma tumor in vivo. The intravenously injected nanoprobes were eventually excreted from the body through the renal clearance route. These results indicated the potential promising of PEG-MnO NPs as an alternative contrast agent in MRI scanning.