Structural,magnetic and antibacterial properties of manganese-substituted magnetite ferrofluids

Manganese-substituted magnetite ferrofluids(FFs)Mnx Fe_(1-x)Fe_(2)O_(4)(x=0–0.8)were prepared in this work through a chemical coprecipitation reaction.The controlled growth of FF nanomaterials for antibacterial activities is challenging,and therefore,very few reports are available on the topic.This research focuses on stabilizing aqueous FFs with the tetramethylammonium hydroxide surfactant to achieve high homogeneity.Morphological characterization reveals nanoparticles of 5–11 nm formed by the chemical reaction and nanocrystalline nature,as evident from structural investigations.Mn-substituted magnetic FFs are analyzed for their structural,functional,and antibacterial performance according to the Mn-substituent content.Optical studies show a high blue shift for Mn^(2+)-substituted Mnx Fe_(1-x)Fe_(2)O_(4)with the theoretical correlation of optical band gaps with the Mn content.The superparamagnetic nature of substituted FFs causes zero coercivity and remanence,which consequently influence the particle size,cation distribution,and spin canting.The structural and functional performance of the FFs is correlated with the antibacterial activity,finally demonstrating the highest inhibition zone formation for Mnx Fe_(1-x)Fe_(2)O_(4)FFs.

Comparison of the effect of carbon,halloysite and titania nanotubes on the mechanical and thermal properties of LDPE based nanocomposite films

In this study, titania nanotubes(TNTs) were prepared by hydrothermal method with the aim to compare the properties of these one-dimensional tubular nanostructures' reinforced nanocomposites with the carbon and halloysite nanotubes'(CNTs and HNTs, respectively) reinforced nanocomposites. Low density polyethylene(LDPE) was used as the matrix material. The prepared nanocomposites were characterized and compared by means of their morphological, mechanical and thermal properties. SEM results showed enhanced interfacial interaction and better dispersion of TNTs and HNTs into LDPE with the incorporation of a MAPE compatibilizer,however, these interactions seem to be absent between CNTs and LDPE, and the CNTs remained agglomerated.Contact angle measurements revealed that CNT filled nanocomposites are more hydrophilic than HNT composites, and less than TNT composites. CNTs provided better tensile strength and Young's modulus than HNT and TNT nanocomposites, a 42% increase in tensile strength and Young's modulus is achieved compared to LDPE.Tear strength improvement was noticed in the TNT composites with a value of 35.4 N·mm^(-1), compared to CNT composites with a value of 25.5 N·mm^(-1)·s^(-1). All the prepared nanocomposites are more thermally stable than neat LDPE and the best improvement in thermal stability was observed for CNT reinforced nanocomposites.CNTs depicted the best improvement in tensile and thermal properties and the MAPE compatibilizer effectiveness regarding morphological. mechanical and thermal properties was only observed for TNT and HNT systems.

The Impact of Clay Loading on the Relative Intercalation of Poly(Vinyl Alcohol)-Clay Composites

Polymer clay nanocomposites (PCN) materials are industrially applied because of their unique properties. However many of their physical and chemical properties have not been determined. The formed structures of polymer/clay nanocomposite depend on the nature of interactions between polymer chains and clay platelets. According to the possible modes of interactions between polymer matrix and clay sheets, these nanocomposites can be classified into: intercalated, flocculated and exfoliated nanocomposites. In this work, the morphology of the nanocomposite was studied using X-ray diffraction (XRD) and nanoscaning electron microscopy (NSEM). XRD and NSEM measurements confirmed the intercalation between poly(vinyl alcohol) chains and cloisite®20A sheets. Because of the intercalation between the clay platelets and the PVA chains, as the clay concentration increases as the band intensities in FT-IR spectra increase. On the other hand, the XRD did not provide clear shift of any of the clay peaks for PVA/cloisite® 10A nanocomposites and confirm the non-intercalation between PVA matrix and cloisite®10A platelets. The relative intercalation (RI) of PVA/Cloisite®20A nanocomposites declined with increase in the clay loadings. In contrast, for PVA/Cloisite®10A, RI values slightly increased with increasing the clay loading.

Recent advance in synthesis and application of heteroatom zeolites

Incorporation of heteroatoms into the framewo rk of zeolites has become a significant strategy to improve their performance in catalysis and adsorption,because the obtained heteroatom zeolites exhibit quite different properties from the conventional aluminosilicate zeolites in aspects of surface acidity,pore structures,particle size and so on.In this review,the progress on the heteroatom zeolites including their synthesis and application is highlighted.First,the recent advance on the design and synthesis of different heteroatom zeolites is summarized.Special emphasis is placed on the introduction and comparison of three typical methods,including the direct synthesis,post synthesis and improved direct synthesis,for the traditional heteroatom zeolites(such as TS-1,Sn-MFI,Sn-β) and newly-reported heteroatom zeolites(such as W-MFI,Mo-MFI).According to their intrinsic characteristics,the application of heteroatom zeolites in diverse fields,such as production of fine chemicals,air pollution control and biomass conversion is then discussed.Finally,the challenges and perspective on the future development of heteroatom zeolites in low-cost preparation and practical application are proposed.

Rational construction and triethylamine sensing performance of foam shapedα-MoO_(3)@SnS_(2) nanosheets

Owing to their high surface area,stable structure and easy fabrication,composite nanomaterials with encapsulation structures have attracted considerable research interest as sensing materials to detect volatile organic compounds.Herein,a hydrothermal route is designed to prepare foam shapedα-MoO_(3)@SnS_(2)nanosheets that exhibit excellent sensing performance for triethylamine(TEA).The developed sensor,based onα-MoO_(3)@SnS_(2)nanosheets,displays a high response of 114.9 for 100 ppm TEA at a low working temperature of 175℃with sensitivity higher than many other reported sensors.In addition,the device shows a wide concentration detection range(from 500 ppb to 500 ppm),good stability after exposure to air for 80 days,and excellent selectivity.The superior sensing characteristics of the developed sensor are attributed to the high crystallinity ofα-MoO_(3)/SnS_(2),excessive and accessible active sites provided by the good permeability of porous SnS_(2)shells,and the excellent conductivity of the encapsulation heterojunction structure.Thus,the foam shapedα-MoO_(3)@SnS_(2)nanosheets presented herein have promising practical applications in TEA gas sensing devices.

Stepwise construction of Pt decorated oxygen-deficient mesoporous titania microspheres with core-shell structure and magnetic separability for efficient visible-light photocatalysis

Solid photocatalysts with high specific surface area,superior photoactivity and ease of recycling are highly desired in chemical process,water treatment and so on.In this study,a facile stepwise sol-gel coating approach was utilized to synthesize Pt decorated oxygen-deficient mesoporous titania microspheres with core-shell structure and convenient magnetic separability(denoted as Fe3 O4@-SiO2@Pt/mTiO2-x).These photocatalysts consist of magnetic Fe3 O4 cores,nonporous insulating SiO2 middle layer and mesoporous anatase TiO2-x shell decorated by Pt nanoparticles(~3.5 nm)through wet impregnation and H2 reduction.As a result of high activity of oxygen-deficiency of black TiO2-x by H2 reduction and efficient inhibition of electron-hole recombination by Pt nanoparticles,the rationally designed core-shell Fe3 O4@SiO2@Pt/mTiO2-x photocatalysts exhibit superior photocatalytic performance in rhodamine B(RhB)degradation under visible light irradiation,with more than 98%of RhB degraded within 50 min.These core-shell structured photocatalysts show excellent recyclability under the assistance of magnetic separation with well-retained photocatalytic performance even after running five cycles.This stepwise synthesis method paves the way for the rational design of a high-efficiency recyclable heterogeneous catalyst,including photocatalysts,for various applications.

Recyclable Fenton-like catalyst based on zeolite Y supported ultrafine,highly-dispersed Fe_2O_3 nanoparticles for removal of organics under mild conditions

A versatile wet impregnation method was employed to conveniently and controllably deposit Fe_2O_3 nanoparticles on zeolites including commercial Y, mordenite and ZSM-5 with the similar framework Si/Al ratios and crystal sizes, respectively. The ultrafine Fe_2O_3 nanoparticles in size of 5 nm can be highly dispersed on zeolite Y matrix due to its much better wettability than ZSM-5 and mordenite. By using the obtained Fe_2O_3/zeolite composite as the heterogeneous Fenton-like catalysts, the degradation of phenol as a model reaction was systematically investigated, including the zeolite supports, particle size and dispersion of Fe_2O_3, and reaction conditions of H_2O_2 concentration, temperature, and pH value. The catalyst based on zeolite Y with Fe loading of 9% exhibited the best phenol degradation efficiency (> 90%)in neutral pH within 2 h. Its high catalytic activity in Fenton reaction can be attributed to the bifunctional properties of strong surface BrФnsted acidity and high reactivity of octahedral Fe^(3+) in the highlydispersed ultrafine Fe_2O_3 nanoparticles in size of 5 nm, which were the primary active centers to quickly decompose H_2O_2 into hydroxyl radicals. Since phenol degradation can be performed under mild conditions of ambient temperature (283-323 K) and a wide pH range (4.0-7.0), the catalysts can be easily recovered for recyclable use with stable degradation activity, which own the immense potential in deep treatment of organic pollutants in industrial wastewater.

Hollow TiO2-x porous microspheres composed of wellcrystalline nanocrystals for high-performance lithiumion batteries

Hollow TiO2-x porous microspheres consisted of numerous well-crystalline nanocrystals with superior structural integrity and robust hollow interior were synthesized by a facile sol-gel template-assisted approach and two-step carbonprotected calcination method, together with hydrogenation treatment. They exhibit a uniform diameter of -470 nm with a thin porous wall shell of -50 nm in thickness. The Brunauer-Emmett-Teller （BET） surface area and pore volume are -19 m2/g and 0.07 crnB/g, respectively. These hollow TiOR_x porous microspheres demonstrated excellent lithium storage performance with stable capacity retention for over 300 cycles （a high capacity of 151 mAh/g can be obtained up to 300 cycles at I C, retaining 81.6% of the initial capacity of 185 mAh/g） and enhanced rate capability even up to 10 C （222, 192, 121, and 92.1 mAh/g at current rates of 0.5, 1, 5, and 10 C, respectively）. The intrinsic increased conductivity of the hydrogenated TiO2 microspheres and their robust hollow structure benefidal for lithium ion-electron diffusion and mitigating the structural strain synergistically contribute to the remarkable improvements in their cycling stability and rate performance.

Highly stable hybrid single-micelle:A universal nanocarrier for hydrophobic bioimaging agents

As the first-line technology,micelles play a pivotal role in in vivo delivery of theranostic agents because of their high biocompatibility and universality.However,in complex physiological environments(extreme dilution,pH,and oxidation or reduction,etc.),they generally suffer from structural instability and insufficient protection for encapsulated cargos.It is urgent to reinforce the structural stability of the micelles at the single-micelle level.By using the FDA-approved Pluronic F127 surfactants and indocyanine green(ICG)bioimaging agents as model,herein,we propose the silane-crosslinking assisted strategy to reinforce the structural stability of the single-micelle.Different from the traditional silane hydrolysis under the harsh experimental conditions(acidic,alkaline,and high temperature hydrothermal,etc.),the ICG loaded F127@SiO_(2) hybrid single-micelles(ICG@H-micelles)with controllable sizes(15-35 nm)are synthesized at neutral pH and room temperature,which is crucial for the maintenance of the physicochemical properties of the encapsulated cargos.With the ultra-thin SiO_(2)(<5 nm)at hydrophilic layer of the single-micelle,the structural and fluorescence stability of ICG@H-micelles are much higher than the conventional micelle(ICG@micelles)in the simulated physiological environments of dilution,oxidation or reduction,and low pH.Because of the high structural and fluorescence stability,the ICG@H-micelles also exhibit longer duration time in the tumor and gastrointestinal tract bioimaging.

Enhancement of gemcitabine against pancreatic cancer by loading in mesoporous silica vesicles

Gemcitabine（Gem） is currently the first-line chemotherapeutic drug in management of pancreatic cancer, however the therapeutic efficacy of Gem is limited due to its short half-life and poor cell membrane permeability. Here we designed mesoporous silica vesicles（MSVs） with large pore sizes as a novel drug delivery system. The MSVs were synthesized using cetyltrimethyl ammonium bromide（CTAB） as a structure-directing agent, tetraethoxysilane（TEOS） as silica source in n-hexane/water biliquid system. By virtue of the large pore size and large pore volume of the MSVs, Gem was loaded into the mesoporous of MSVs via ＂nanocasting＂ method. In vitro drug release experiments of gemcitabineloaded MSVs showed an accelerating release of gemcitabine in acidic condition. These fluorescently labeled MSVs could be effectively internalized by both a human（BxPC-3） and a mouse pancreatic cancer cell lines（Pan02）. Additionally, some MSVs could even reach the nuclei of the pancreatic cancer cells. Cell viability assays demonstrated that gemcitabine-loaded MSVs exhibited enhanced anticancer activity in inhibiting the proliferation of Bx PC-3 and Pan02 cells compared with free Gem, while the MSVs alone showed no significant cytotoxicity. Our results indicate that our synthesized MSVs might represent a promising novel drug delivery platform for the treatment of pancreatic cancer.

Facile synthesis of metal-polyphenol-formaldehyde coordination polymer colloidal nanoparticles with sub-50 nm for T_(1)-weighted magnetic resonance imaging

Plant polyphenol-based coordination polymers(CPs) with ultra-small particle size and tailorable compositions are highly desired in biomedical applicatio ns,but their synthesis is still challenging due to the sophisticated coordination assembly process and unavoidable self-oxidation polymerization of polyphenol. He rein,a general ligand covalent-modification mediated coordination assembly strategy is proposed for the synthesis of water-dispersible CPs with tunable metal species(e.g., Gd,Cu,Ni,Zn,Fe)and ultra-small diameter(8.6-37.8 nm) using nontoxic plant polyphenol(e.g..tannic acid,gallic acid) as a polymerizable ligand.Polyphenol molecules react with formaldehyde firstly,which can effectively retard the oxidation induced self-polymerization of polyphenol and lead to the formation of metal ions containing CPs colloidal nanoparticles.These ultrafine nanoparticles with stably chelated metal io ns are highly water dispersible and thus advantageous for bioimaging.As an example,ultra-small Gd contained CPs exhibit higher longitudinal relaxivity(r_(1)=25.5 L mmol^(-1) s^(-1)) value with low r2/r1(1.19) than clinically used Magnevist(Gd-DTPA,r1=3.7 L mmol^(-1) s^(-1)) .Due to the enhanced permeability and retention effect,they can be further used as a positive contrast agent for T1-weighted MR imaging of tumour.