Unique Mesoporous Structure Research Articles

Hierarchically Self-assembled Super Structural TiO2 Microspheres: Enhanced Excitonic Efficiency as Photocatalyst and Photoanode Material

ABSTRACTComplex three-dimensional (3-D) super structural TiO2 architectures with controlled shape and size were synthesized by a facile hydrothermal synthesis route by using titanium tetrachloride (TiCl4) as the metal precursor and hydrochloric acid (HCl)/ammonium chloride (NH4Cl) as the mineralizer/structure directing agent. Several interesting hierarchical architectures like: (i) nanoparticles assembled spheres (NPAS), (ii) nanowires assembled spheres (NWAS), (iii) nanorods assembled spheres (NRAS), and (iv) nanosheets assembled spheres (NSAS) were achieved by the controlled variation of crystal structure modifier. The synthesized materials were characterised in detail by different analytical techniques and the findings are consistent. To demonstrate the superior performances of the as prepared materials the photocatalytic and photo-voltaic performances were investigated. The results demonstrate that these synthesized materials exhibits enhanced photocatalytic activity (efficiency is ∼ 91%) towards the degradation of RhB and as a photoanode in DSSCs the maximum energy conversion efficiency is ∼5%, attributed primarily to the unique hierarchical mesoporous structure of the TiO2 architectures.

Extreme Light Management in Mesoporous Wood Cellulose Paper for Optoelectronics.

Wood fibers possess natural unique hierarchical and mesoporous structures that enable a variety of new applications beyond their traditional use. We dramatically modulate the propagation of light through random network of wood fibers. A highly transparent and clear paper with transmittance >90% and haze <1.0% applicable for high-definition displays is achieved. By altering the morphology of the same wood fibers that form the paper, highly transparent and hazy paper targeted for other applications such as solar cell and antiglare coating with transmittance >90% and haze >90% is also achieved. A thorough investigation of the relation between the mesoporous structure and the optical properties in transparent paper was conducted, including full-spectrum optical simulations. We demonstrate commercially competitive multitouch touch screen with clear paper as a replacement for plastic substrates, which shows excellent process compatibility and comparable device performance for commercial applications. Transparent cellulose paper with tunable optical properties is an emerging photonic material that will realize a range of much improved flexible electronics, photonics, and optoelectronics.

Electrospun synthesis and electrochemical property of zinc ferrite nanofibers

In this study, zinc ferrite (ZnFe2O4) nanofibers were successfully fabricated by a combination of electrospinning and calcination process. Only peaks of ZnFe2O4 could be observed from X-ray diffractometry patterns, indicating that the formation of pure compound. SEM and TEM images showed the ZnFe2O4 nanofibers possessed good continuous fiber morphology with an average diameter of about 150 nm. Moreover, the lithium storage properties test showed that the ZnFe2O4 nanofibers possessed obviously improved electrochemical properties. It is demonstrated that ZnFe2O4 nanofibers electrode not only deliver a high initial discharge capacity of around 1248 mAh g−1, but also maintained a stable capacity of 625 mAh g−1 after 50 cycles. Meanwhile, the electrodes showed high capacity at higher discharge and charge rate. The excellent lithium storage properties of the ZnFe2O4 nanofibers electrode may be attributed to the high crystallinity, as well as the unique mesoporous and fibrous structures. In addition, the Zn product formed after the conversion reaction of ZnFe2O4 with lithium could further react with lithium to form ZnLix alloy, which could contribute additional capacity.

High-Rate LiTi2(PO4)3@N-C Composite via Bi-nitrogen Sources Doping.

Mesoporous LiTi2(PO4)3@nitrogen-rich doped carbon composites have been synthesized by a novel bi-nitrogen sources doping strategy. Tripolycyanamide (C3H6N6) and urea are proposed for the first time as both nitrogen and carbon sources to achieve a homogeneous nitrogen-doped carbon coating layer via an in situ method. The electrode delivers ultrahigh rate performance and outstanding cycling stability in lithium ion batteries (LIBs). In an organic electrolyte system, the electrode demonstrates high discharge capacities of 120 mAh g(-1) and 87 mAh g(-1) at 20C and 50C, respectively. Moreover, 89.5% of initial discharge capacity is retained after 1000 cycles at 10C. When used as an anode for aqueous LIBs, the electrode also demonstrates superior rate capability with the discharge capacity of 103 mAh g(-1) at 10C, corresponding to 84% of that at 1C. Outstanding cycling stability with capacity retention of 91.2% after 100 cycles at 30 mA g(-1) and 90.4% over 400 cycles at 150 mA g(-1) are also demonstrated. The uniform nitrogen-rich carbon coating and unique mesoporous structure play important roles in effectively suppressing the charge-transfer resistance and facilitating Li ion/electron diffusion, thus leading to the superior electrochemical properties.

Preparation of mesopourous Fe3O4 nanoparticle with template reagent: Tannic acid and the catalytic performance

We report a one-pot hydrothermal method for novel mesoporous Fe3O4 nanoparticles (NPs) preparation based on the reduction of ferric chloride with bifunctional agent: tannic acid (TA). TA acted both as template agent to obtain the mesoporous structure and functional agent to modify Fe3O4 NPs. The facile controlled process resulted in a relatively high surface area (99.5 m2 g−1) and good monodispersity with average diameter ∼200 nm of the synthetic nanoparticles. The high saturation magnetization (54.7 emu g−1) of the nanoparticles made it can be separated quickly from solution media via a magnet. The unique mesoporous structure of the Fe3O4 nanoparticles possessed high active site, and this was proved by studying the catalytic properties through Fenton catalytic degradation with hydrogen peroxide as a model reaction system. As a result, the tannic acid templated mesoporous Fe3O4 NPs (TA–Fe3O4 NPs) showed the very efficient catalytic properties for the degradation of methylene blue (MB) accelerated by the functionalization of TA.

High performance Pd catalysts supported on bimodal mesopore silica for the catalytic oxidation of toluene

A series of bimodal mesoporous silica (BMS-x)-supported Pd catalysts were successfully prepared by a facile sol-gel approach, followed by an impregnation method. The synthesized catalysts were characterized by several analytical techniques and the oxidation of toluene was used to evaluate their catalytic performance. Textural analysis showed that all samples had high surface areas (∼1000 m2/g), large pore volumes (∼1.2 cm3/g) and uniform mesopore size (∼2.6 nm). Defining the level of ammonia solution to within a certain range resulted in the catalysts possessing a typical bimodal mesoporous structure with an intraparticle framework mesopore and an interparticle textural mesopore (18–40 nm). Transmission electron microscopy observations and CO chemisorption results revealed that this unique bimodal mesoporous structure helped to decrease the particle size of Pd nanoparticles and could further enhance their dispersion. Activity tests revealed the Pd/BMS-5–Pd/BMS-20 catalysts with a bimodal mesopore structure possessed superior catalytic performance for the oxidation of toluene compared to Pd/BMS-30 with a unimodal mesopore structure. More importantly, compared with the Pd/MCM-41 and Pd/MCM-48 catalysts, Pd/BMS-15 had improved hydrothermal stability and catalytic performance at a high gas hourly space velocity of 70000 h−1. These results indicate the potential application of the catalysts for the elimination of volatile organic compounds.

Facile synthesis of mesoporous ZnO/Co3O4 microspheres with enhanced gas-sensing for ethanol

Self-assembly mesoporous ZnO/Co3O4 microspheres have been successfully synthesized through a facile solvothermal method without any alkali source combined a post-annealing process. The structure, morphology and surface characteristics of the special microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). It was found that the ZnO/Co3O4 microspheres with diameter of about 0.5–1.5μm were composed of abundant nanoparticles with an average size of 40nm. Gas-sensing properties made clear that the response of mesoporous ZnO/Co3O4 microspheres sensors was as high as 38–43 which was about 5 times higher than pure ZnO gas sensors toward 50ppm ethanol at 275°C. The remarkable improvement in gas-sensing properties of the porous ZnO/Co3O4 microspheres was attributed to their unique mesoporous structure and the extension of the electron depletion layer via the formation of p–n heterojunctions.

Preparation of mesoporous TiO2-B nanowires from titanium glycolate and their application as an anode material for lithium-ion batteries

TiO2-B nanowires with remarkable mesoporous structure via a template-free low-temperature hydrothermal fabrication route have been prepared by employing titanium glycolate (TG) as a precursor. The formation of mesopores in TiO2-B nanowires is caused by the evolvement of vacancies derived from the chains of TG. The product is characterized by X-ray diffraction, Raman spectroscopy, nitrogen adsorption–desorption, and electron microscopy. The lithium-ion storage capacity of mesoporous TiO2-B nanowires is evaluated by galvanostatic measurements. The initial discharge–charge capacities of the material are 310 and 231 mAh g−1 at a current density of 50 mA g−1, respectively. A discharge capacity of 198 mAh g−1 is still retained when charge–discharge at 1.0 A g−1 for 50 cycles, demonstrating the high-rate performance and good cycle ability. The large reversible capacity, high-rate performance, and good cycle ability of the material are attributed to unique mesoporous structure and intrinsic properties of the TiO2-B nanowires. The mesoporous TiO2-B nanowire synthesized from TG is promising for use as an anode material for lithium-ion batteries with high power and energy densities.

Facile synthesis of mesoporous V2O5 nanosheets with superior rate capability and excellent cycling stability for lithium ion batteries

A facile synthesis of mesoporous V2O5 nanosheets has been developed by a simple hydrothermal method and subsequent instantaneous heating and calcination. These V2O5 nanosheets exhibit ultrastable capacity retention at different current density, and also show excellent rate capability, maintaining a reversible capacity of 118 mA h g−1 at 6000 mA g−1 after 1000 cycles. The remarkable performance results from their unique mesoporous nanosheet structure as well as the presence of noticeable amount of tetravalent vanadium ions and the attendant oxygen vacancies in V2O5, which have substantially improved electronic-ionic transport and mitigated the internal mechanical stress induced by the volume variation of the material upon cycling. These results demonstrate the significant potential of mesoporous V2O5 nanosheets for high power and long life batteries. Moreover, the simple and general synthesis method is suitable for the preparation of a variety of electrode material with unique mesoporous nanostructure containing oxygen vacancies for electrochemical batteries and supercapacitors.

An electrochemical exploration of hollow NiCo2O4 submicrospheres and its capacitive performances

Mesoporous NiCo2O4 hollow submicrospheres have been prepared through a facile and scalable soft template method utilizing a reflux route. The as-obtained mesoporous NiCo2O4 hollow submicrosphere electrode exhibits high specific capacitance of 987 F g−1 at 1 A g−1, superior capacity retention rate of 79.4 and 62.8% at 20 and 50 A g−1, and remarkable cycling stability with almost no capacity loss at 5 A g−1 over 5000 cycles. The superior electrochemical performances can be attributed to the unique mesoporous hollow structure with a large specific surface area (189.7 m2 g−1) and superior pore-size distribution (3–5 nm). To further demonstrate its practical application, an asymmetric supercapacitor based on the mesoporous NiCo2O4 hollow submicrospheres as the positive electrode and activated carbon as the negative electrode is fabricated, which manifests high energy density of 27.2 Wh kg−1 at the power density of 102 W kg−1 or high power density of 8.16 kW kg−1 at the energy density of 10.9 Wh kg−1 and exceptional long-term cycling stability with 108.1% of the initial capacity retention at 3 A g−1 over 10000 cycles. These impressive results render this NiCo2O4 hollow submicrospheres promising as one of the most attractive candidates for supercapacitors in practical applications.

Nitrogen/sulfur dual-doped mesoporous carbon with controllable morphology as a catalyst support for the methanol oxidation reaction

Ordered mesoporous carbon (OMC) was synthesized by nano-casting method using novel fluidic precursor – acrylonitrile telomer (ANT). By the penetration of mesoporous silica template with pure ANT, followed by the stabilization, carbonization and removal of the template, we obtained highly ordered mesoporous carbon rods (specific area 408m2g−1). When an acetone solution of ANT (66 and 33wt.%) was used instead of pure ANT, carbon materials with mesopore ranging from 2 to 7nm were obtained (specific area 843 and 1012m2g−1 respectively). Both nitrogen and sulfur atoms were doped into mesoporous carbon with 4 and 0.6at.% using nitrogen containing monomer and sulfur containing chain transfer agent, without involving complicated synthetic technique and poisonous gaseous compounds. This method was proved to be a facile way to synthesize nitrogen and sulfur containing OMC with partially controllable pore distribution and morphology. More importantly, due to unique mesopore structure and heteroatom doping, Pt nano-particles deposited on the OMCs showed electrocatalytic activity as high as 508mAmg−1 Pt in methanol oxidation which is 1.7-fold of activity of Pt deposited on commercial Vulcan carbon black.

Facile complex-coprecipitation synthesis of mesoporous Fe3O4 nanocages and their high lithium storage capacity as anode material for lithium-ion batteries

In this study, high-quality mesoporous Fe3O4 nanocages (MFONs) have been synthesized by a facile complex-coprecipitation method at 100°C with addition of triethanolamine and ethylene glycol. The as-prepared Fe3O4 nanocages possess a mesoporous structure and highly uniform dispersion. When used as an anode material for rechargeable lithium-ion batteries, MFONs anode shows high specific capacities and excellent cycling performance at high and low current rates. At a current density of 200mAg−1, the discharge specific capacities are 876mAhg−1 at the 2nd cycle and 830mAhg−1 at the 100th cycle. Even at the high current density of 1000mAg−1, MFONs anode still retains a stable capacity of 573mAhg−1 after 300 cycles. This superior electrochemical performance is attributed to the unique mesoporous cage-like structure and high specific surface area (133m2g−1) of MFONs, which may offer large electrode/electrolyte contact area for the electron conduction and Li+ storage. Furthermore, the good mechanical flexibility of the mesoporous nanocages can readily buffer the massive volume expansion/shrinkage associated with the reversible electrode reaction. These results indicate that MFONs can be used as a promising high-performance anode material for lithium-ion batteries.

Lactosaminated mesoporous silica nanoparticles for asialoglycoprotein receptor targeted anticancer drug delivery.

BackgroundMesoporous silica nanoparticles (MSNs) have several attractive properties as a drug delivery system, such as ordered porous structure, large surface area, controllable particle size as well as interior and exterior dual-functional surfaces. The purpose of this study was to develop novel lactosaminated mesoporous silica nanoparticles (Lac-MSNs) for asialoglycoprotein receptor (ASGPR) targeted anticancer drug delivery.ResultsLac-MSNs with an average diameter of approximately 100 nm were prepared by conjugation of lactose with 3-aminopropyl triethoxysilane modified MSNs. Characterization of Lac-MSNs indicated a huge Brunauer-Emmett-Teller (BET) surface area (1012 m2/g), highly ordered 2D hexagonal symmetry, an unique mesoporous structure with average pore size of 3.7 nm. The confocal microscopy and flow cytometric analysis illustrated Lac-MSNs were effectively endocytosed by ASGPR-positive hepatoma cell lines, HepG2 and SMMC7721. In contrast, non-selective endocytosis of Lac-MSNs was found in ASGPR-negative NIH 3T3 cells. The cellular uptake study showed the internalization process was energy-consuming and predominated by clathrin-mediated pathway. Model drug docetaxel (DTX) was loaded in the mesopores of Lac-MSNs by wetness impregnation method. In vitro cytotoxicity assay showed that DTX transported by Lac-MSNs effectively inhibited the growth of HepG2 and SMMC7721 cells in a time- and concentration- dependent manner.ConclusionsThese results demonstrated that Lac-MSNs could be a promising inorganic carrier system for targeted intracellular anti-cancer drug delivery.

Mesoporous NiO–CeO2 catalysts for CO oxidation: Nickel content effect and mechanism aspect

Mesoporous NiO–CeO2 catalysts with different nickel contents (meso-NixCe, x=0.05, 0.1, 0.2) were prepared by a KIT-6-templating method and characterized by XRD, N2 physisorption, TEM, Raman, XPS and H2-TPR to understand their catalytic performances in CO oxidation. The introduction of nickel induced an obvious modification of the pore system of ceria, but the pore size and distribution were hardly affected by nickel content. HRTEM, XRD and Raman results clearly depicted free NiO (both clustered and amorphous) and doped nickel species, while XPS suggested the presence of another kind of nickel species (interfacial NiO). Probably owing to the unique mesoporous structures, the interfacial NiO decreased with increasing nickel content, which was coincident with CO oxidation activity. Besides, the comparable apparent activation energy (∼55kJ/mol) for all samples indicated similar reaction pathway was followed. By correlating the catalytic performances with textural and compositional properties, it was found the latter dominated catalytic performance, and interfacial NiO was deduced to be the main active species for CO oxidation. Lastly, a synergetic interaction between atomically neighboring nickel oxide and ceria on the adsorbed reactants was tentatively proposed to understand the reaction mechanism.

Microwave-assisted synthesis of mesoporous Co3O4 nanoflakes for applications in lithium ion batteries and oxygen evolution reactions.

Mesoporous Co3O4 nanoflakes with an interconnected architecture were successfully synthesized using a microwave-assisted hydrothermal and low-temperature conversion method, which exhibited excellent electrochemical performances as anode materials in lithium ion batteries and as catalysts in the oxygen evolution reaction (OER). Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) observations showed the unique interconnected and mesoporous structure. When employed as anode materials for lithium ion batteries, mesoporous Co3O4 nanoflakes delivered a high specific capacity of 883 mAh/g at 0.1C current rate and stable cycling performances even at higher current rates. Post-mortem analysis of ex situ FESEM images revealed that the mesoporous and interconnected structure had been well maintained after long-term cycling. The mesoporous Co3O4 nanoflakes also showed both OER active properties and good catalytic stability. This could be attributed to both the stability of unique mesoporous structure and highly reactive facets.

Nanocrystal-constructed mesoporous CoFe₂O₄ nanowire arrays aligned on flexible carbon fabric as integrated anodes with enhanced lithium storage properties.

A novel and facile two-step strategy is successfully developed for the large-scale fabrication of hierarchical mesoporous CoFe2O4 nanowire arrays (NWAs) on flexible carbon fabric as integrated anodes for highly efficient and reversible lithium storage. The synthesis involves the co-deposition of uniform bimetallic (Co, Fe) carbonate hydroxide hydrate precursor NWAs on carbon fabric and subsequent thermal transformation to spinel CoFe2O4 without damaging the morphology. The as-prepared CoFe2O4 nanowires have unique mesoporous structures, which are constructed by many interconnected nanocrystals with sizes of about 15-20 nm. The typical size of the nanowires is in the range of 70-100 nm in width and up to several micrometers in length. Such a hybrid nanostructure electrode presented here not only simplifies electrode processing, but also promises fast electron transport/collection and ion diffusion, and withstands volume variation upon prolonged charge/discharge cycling. As a result, the binder-free CoFe2O4/carbon fabric composite exhibits a high reversible capacity of 1185.75 mA h g(-1) at a current density of 200 mA g(-1), and a superior rate capability. More importantly, a reversible capacity as high as ∼950 mA h g(-1) can be retained and there is no obvious decay after 150 cycles.

Polydopamine-graphene oxide derived mesoporous carbon nanosheets for enhanced oxygen reduction.

Composite materials combining nitrogen-doped carbon (NC) with active species represent a paramount breakthrough as alternative catalysts to Pt for the oxygen reduction reaction (ORR) due to their competitive activity, low cost and excellent stability. In this paper, a simple strategy is presented to construct graphene oxide-polydopamine (GD) based carbon nanosheets. This approach does not need to modify graphene and use any catalyst for polymerization under ambient conditions, and the obtained carbon nanosheets possess adjustable thicknesses and uniform mesoporous structures without using any template. The thickness of GD hybrids and the carbonization temperature are found to play crucial roles in adjusting the microstructure of the resulting carbon nanosheets and, accordingly their ORR catalytic activity. The optimized carbon nanosheet generated by a GD hybrid of 5 nm thickness after 900 °C carbonization exhibits superior ORR activity with an onset potential of -0.07 V and a kinetic current density of 13.7 mA cm(-2) at -0.6 V. The unique mesoporous structure, high surface areas, abundant defects and favorable nitrogen species are believed to significantly benefit the ORR catalytic process. Furthermore, it also shows remarkable durability and excellent methanol tolerance outperforming those of commercial Pt/C. In view of the physicochemical versatility and structural tunability of polydopamine (PDA) materials, our work would shed new light on the understanding and further development of PDA-based carbon materials for highly efficient electrocatalysts.

Mesoporous silica nanoparticles in target drug delivery system: A review.

Due to lack of specification and solubility of drug molecules, patients have to take high doses of the drug to achieve the desired therapeutic effects for the treatment of diseases. To solve these problems, there are various drug carriers present in the pharmaceuticals, which can used to deliver therapeutic agents to the target site in the body. Mesoporous silica materials become known as a promising candidate that can overcome above problems and produce effects in a controllable and sustainable manner. In particular, mesoporous silica nanoparticles (MSNs) are widely used as a delivery reagent because silica possesses favorable chemical properties, thermal stability, and biocompatibility. The unique mesoporous structure of silica facilitates effective loading of drugs and their subsequent controlled release of the target site. The properties of mesoporous, including pore size, high drug loading, and porosity as well as the surface properties, can be altered depending on additives used to prepare MSNs. Active surface enables functionalization to changed surface properties and link therapeutic molecules. They are used as widely in the field of diagnosis, target drug delivery, bio-sensing, cellular uptake, etc., in the bio-medical field. This review aims to present the state of knowledge of silica containing mesoporous nanoparticles and specific application in various biomedical fields.

POSS-Derived Mesostructured Amphiphilic Polyoxometalate-based Ionic Hybrids as Highly Efficient Epoxidation Catalysts

Novel amphiphilic mesostructured polyoxometalate-based ionic hybrids have been successfully synthesized through designing new POSS-derived mesoporous poly(ionic liquids) (POSS-BMx) to interact with Keggin-type phosphotungstic acid (PW). The obtained ionic hybrids POSS-BMx-PW have good thermal stability, adjustable pore structure and surface wettability. Catalytic tests for H2O2-based epoxidation of cyclooctene, along with comparisons to various counterparts, well demonstrate that POSS-BMx-PW (x = 8, 11) exhibit high activity and selectivity, coupled with convenient recovery and steady reuse. The unique mesoporous structure and the amphiphilic catalyst surface are revealed to be responsible for the catalyst’s excellent performances in epoxidation reaction with H2O2.

Facile synthesis of monodisperse Co3O4 mesoporous microdisks as an anode material for lithium ion batteries

The monodisperse Co3O4 mesoporous microdisks have been successfully prepared through a facile solvothermal synthesis method and subsequent heating treatment. The Co3O4 microdisks are polycrystalline, and have an average diameter of around 2μm with an thickness of 300nm. The specific surface area of Co3O4 mesoporous microdisks is about 108.9m2g−1 with a narrow pore size distribution centered at round 9.68nm. The as-prepared Co3O4 mesoporous microdisks as anode material in lithium ion batteries exhibit a stable specific discharge–charge capacity of 765 and 749mAhg−1 after 30 cycles at a current density of 100mAg−1. The good electrochemical properties could be attributed to the unique mesoporous structure of Co3O4 materials.