Inorganic Template Research Articles

Hollow phosphorylcholine polymer vesicles prepared by a coaxial electrospray technique

Hollow vesicles composed of a phosphorylcholine polymer were prepared using a coaxial electrospray technique and an inorganic microstructured template. An aqueous solution containing calcium chloride and chitosan, and 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer ethanol solution were electrosprayed from coaxial double needles into a phosphate solution to obtain microparticles composed of calcium phosphate (CaP) and chitosan covered with MPC polymer, followed by the removal of CaP/chitosan template to produce novel hollow vesicles composed of MPC polymer. The resulting hollow vesicles had 300–400 μm in diameter. Investigation using fluorescently labeled MPC polymer revealed that the vesicle membrane was composed of MPC polymer. Model substances with relatively high molecular weights (dextran and polymeric microspheres) were readily encapsulated in the hollow vesicles. Microscopic observations of the mobility of encapsulated microspheres inside a hollow vesicle indicated the fluidity of its aqueous interior. Finally, we succeeded in the encapsulation and cultivation of living yeast cells within the vesicles, which demonstrates that this technique can encapsulate a physiologically active substance in the hollow vesicles and maintain its activity.

GoldHelix: Gold Nanoparticles Forming 3D Helical Superstructures with Controlled Morphology and Strong Chiroptical Property.

Plasmonic nanoparticles, particularly gold nanoparticles (GNPs) hold a great potential as structural and functional building blocks for three-dimensional (3D) nanoarchitectures with specific optical applications. However, a rational control of their assembly into nanoscale superstructures with defined positioning and overall arrangement still remains challenging. Herein, we propose a solution to this challenge by using as building blocks: (1) nanometric silica helices with tunable handedness and sizes as a matrix and (2) GNPs with diameter varying from 4 to 10 nm to prepare a collection of helical GNPs superstructures (called Goldhelices hereafter). These nanomaterials exhibit well-defined arrangement of GNPs following the helicity of the silica template. Strong chiroptical activity is evidenced by circular dichroism (CD) spectroscopy at the wavelength of the surface plasmon resonance (SPR) of the GNPs with a anisotropy factor (g-factor) of the order of 1 × 10-4, i.e., 10-fold larger than what is typically reported in the literature. Such CD signals were simulated using a coupled dipole method which fit very well the experimental data. The measured signals are 1-2 orders of magnitude lower than the simulated signals, which is explained by the disordered GNPs grafting, the polydispersity of the GNPs, and the dimension of the nanohelices. These Goldhelices based on inorganic templates are much more robust than previously reported organic-based chiroptical nanostructures, making them good candidates for complex hierarchical organization, providing a promising approach for light management and benefits in applications such as circular polarizers, chiral metamaterials, or chiral sensing in the visible range.

HNTs‐templated preparation of carbon nanorods by nanocasting method

Carbon nanorods (CNRs) have been attracting increasing interest because of their potential applications in high-performance nanoscale materials and electronic devices. Among the many preparation methods, the nanocasting method via inorganic template materials exhibited a controllable and facile feature. This work was to present a novel preparation of CNRs through the nanocasting method using halloysite nanotubes (HNTs) as the template and polyvinyl alcohol (PVA) as the nanocasting carbon source. For the sake of PVA nanocasted in the hollow structure of HNTs, we adopted the repeated soakage method. The forming process and structure of CNRs were revealed by XRD, FT-IR, SEM, TEM, SAED XPS, Raman and Brunner-Emmet-Teller (BET) characterisation techniques. The results showed that the as-obtained CNRs with the rod-like structure had a high specific surface area of ca. 284 m 2 /g and exhibited typical mesoporous features.

Ion cum molecularly dual imprinted polymer for simultaneous removal of cadmium and salicylic acid.

Ion cum molecularly dual imprinted polymer (DMIP) was synthesized for the simultaneous removal of salicylic acid (SA) and cadmium (Cd) by suspension polymerization method using chitosan (CTS) as functional polymer, epichlorohydrin as cross-linker, and 4-hydroxy benzoic acid (4HBA) as well as Cd as organic and inorganic templates, respectively. Use of the dummy template 4HBA during the synthesis of DMIP had the advantage of creating imprinted cavities in DMIP, which depicted good uptake for SA. Scanning electron microscopy and Fourier transform infrared spectroscopy indicated successful preparation of DMIP. Particle size analysis confirmed polydispersity, and thermal and swelling studies indicated the mechanical stability in DMIP. The rebinding capacities of the DMIP for Cd and SA were found to be 38.46 and 23.81mgg-1 , respectively, under the optimize condition of the time, dose, and concentration. Adsorption isotherm results fitted into Langmuir adsorption isotherm model with the R2 values of 0.994 and 0.995 for Cd and SA, respectively. The presence of intramolecular hydrogen bonding in SA, stability of the template-monomer complexes (CTS-SA and CTS-4HBA), and the involvement of the hydroxyl groups on DMIP for the uptake of SA has been supported by molecular modeling studies using Gaussian 03 software. The electron doublet of the amino groups of DMIP was involved for the uptake of Cd. Lower binding efficiency of DMIP for SA as compared to Cd may be due to the partial participation of hydroxyl group in cross-linking with epichlorohydrin during the synthesis of DMIP.

Hypercrosslinked polyHIPEs as precursors to designable, hierarchically porous carbon foams

Hierarchically porous carbon foams were produced by carbonization of hypercrosslinked polymerized high internal phase water-in-styrene/divinylbenzene emulsions (HIPEs). The hypercrosslinking of these poly(ST-co-DVB)HIPEs was achieved using a dimethoxymethane external crosslinker to ‘knit’ together aromatic groups within the polymers using Friedel-Crafts alkylation. By varying the amount of divinylbenzene (DVB) in the HIPE templates and subsequent polymers, the BET surface area and micropore volume of the hypercrosslinked analogues can be varied systematically, allowing for the production of carbon foams, or ‘carboHIPEs’, with varied surface areas, micropore volumes and pore-size distributions. The carboHIPEs retain the emulsion-templated macropores of the original polyHIPE, display excellent electrical conductivities and have surface areas of up to 417 m2/g, all the while eliminating the need for inorganic templates. The use of emulsion templates allows for pourable, mouldable precursors to designable carbonaceous materials.

FAU-type zeolite nanosheets from additives-free system

The existing concept for preparation of faujasite (FAU) type zeolite nanosheet assemblies is based on use of organic or extra inorganic morphology-directing templates or agents. Herein, a repetitive branching of hierarchically arranged nanolayers of FAU zeolite without employment of any morphology modifiers is demonstrated. This type of crystal growth is achieved only by kinetic control of carefully chosen conditions that border the co-crystallization of FAU- and EMT-type of zeolites. Furthermore, we provide evidence that the branching originates from recrystallization of zeolite nanoparticles followed by formation of submicron faceted crystals that further serve as nutrient for nanosheet structures. These findings open up a simple route to intergrowth of two-dimensional nanostructures of zeolites and may contribute to their scaled up production.

Synthesis and characterization of germanosilicate molecular sieves: GeO2/SiO2 ratio, H2O/TO2 ratio and temperature.

Many synthesis parameters can influence zeolite crystallization, which include the molar ratio of reagents, water content, temperature, the selection of extraframework cations (organic or inorganic template) and so on. In this paper, two new materials, BUCT-1 with cuboid morphology and BUCT-2 with plate-like morphology were obtained based on the synthesis conditions of ITQ-17 by adjusting the GeO2/SiO2 ratio, H2O/TO2 ratio and temperature. The influence of the three factors on crystal size, crystallinity and phase selection and transformation was carefully discussed. Therein, phase selection and transformation is determined by their synergistic effects; while the influence on crystal size and crystallinity is different for different materials, which is caused by the differences in their structure, or in other words, the building unit, and chemical composition. In addition, the structure of BUCT-2 has already been solved as the stacking of sti layers, and it was identified as pure germanate molecular sieves. Meanwhile, through the characterization of XRD, ICP-AES, IR and STA, some topological information on BUCT-1, such as unit cell parameters, pore size and connectivity, was predicted and the work to present its final structure is still going on.

Roughening up polymer microspheres and their diffusion in a liquid.

A simple, versatile approach for the roughening of polymer microparticles surfaces via a deformation technique in the presence of an inorganic matrix is presented here. The process consists of straightforward steps: (1) preparation of a bicomposite colloidal sol, that is polymer particles and inorganic particles, dispersed in a liquid, (2) drying of the mixture onto a suitable hard substrate, (3) heating the dried film above the glass transition temperature of the polymer, and (4) re-dispersion and chemical etching of the inorganic medium. The primary driver is capillary imbibition of the polymer melt into the inorganic colloidal template. In addition, 2D particle tracking experiments of dispersed rough particles in water were performed to probe the diffusional behaviour of the roughened objects in comparison with their smooth precursors. We show that, despite large scale roughness (up to 10% asperity size with respect to particle diameter), Stokes law is obeyed and the particle motion can be modelled simply with the Stokes-Einstein-Sutherland relation.

Achiral polyamine-induced chiral zinc gallophosphates with fused double helix-like strands exhibiting blue to green photoluminescence.

This study found non-chiral polyamines to be effective in inducing chiral frameworks. Four zinc gallophosphates with a chiral UCSB-7 topology were generated from the use of four different linear-chain polyamines as templates. In the structure, helical inorganic strands and templates appeared to fuse into a double helix-like arrangement. Notably, they are the first chiral frameworks to display optical analogues and intriguing photoluminescence properties.

Nanoscale silicon substrate patterns from self-assembly of cylinder forming poly(styrene)-block-poly(dimethylsiloxane) block copolymer on silane functionalized surfaces

Poly(styrene)-block-poly(dimethylsiloxane) (PS-b-PDMS) is an excellent block copolymer (BCP) system for self-assembly and inorganic template fabrication because of its high Flory–Huggins parameter (χ ∼ 0.26) at room temperature in comparison to other BCPs, and high selective etch contrast between PS and PDMS block for nanopatterning. In this work, self-assembly in PS-b-PDMS BCP is achieved by combining hydroxyl-terminated poly(dimethylsiloxane) (PDMS-OH) brush surfaces with solvent vapor annealing. As an alternative to standard brush chemistry, we report a simple method based on the use of surfaces functionalized with silane-based self-assembled monolayers (SAMs). A solution-based approach to SAM formation was adopted in this investigation. The influence of the SAM-modified surfaces upon BCP films was compared with polymer brush-based surfaces. The cylinder forming PS-b-PDMS BCP and PDMS-OH polymer brush were synthesized by sequential living anionic polymerization. It was observed that silane SAMs provided the appropriate surface chemistry which, when combined with solvent annealing, led to microphase segregation in the BCP. It was also demonstrated that orientation of the PDMS cylinders may be controlled by judicious choice of the appropriate silane. The PDMS patterns were successfully used as an on-chip etch mask to transfer the BCP pattern to underlying silicon substrate with sub-25 nm silicon nanoscale features. This alternative SAM/BCP approach to nanopattern formation shows promising results, pertinent in the field of nanotechnology, and with much potential for application, such as in the fabrication of nanoimprint lithography stamps, nanofluidic devices or in narrow and multilevel interconnected lines.

Nitrogen modified templated carbons for energy application: Effect of templates and nitrogen precursors

Nitrogen modified templated carbons were prepared by carbonization at 923 K with dwelling time of 3 h. The effects of nitrogen precursors and templates on the surface area, pore structure and nitrogen loading of modified carbons were studied. Acetonitrile and aniline were used as nitrogen precursors, while zeolite and silica gel as inorganic templates. The surface areas of nitrogen modified carbons were reduced as compared to that of unmodified carbons. The effect is more significant for aniline precursor and zeolite template. Irrespective of nitrogen precursors, zeolite and silica gel templates resulted in mainly microporous and mesoporous carbons respectively. The nitrogen modified templated carbons were tested for hydrogen uptake. The hydrogen uptake of silica gel templated carbons increased on incorporation of nitrogen in spite of decrease in surface area. The high uptake of silica gel templated modified carbon can be attributed to higher activation of hydrogen by nitrogen centers present in the carbon network. However, drop in hydrogen uptake for zeolite templated modified carbons may be attributed to significant decrease in surface area. The hydrogen desorption kinetics was observed to depend on porous structure. Presence of micropores offered higher diffusion resistance, making desorption of hydrogen slower.

Facile fabrication of hierarchical ZnO nanowire aggregates using rose-like peroxide precursor as the inorganic template

The complex rose-like inorganic templates assembled by the ZnO/ZnO2 hybrid nanosheets have been constructed with hydrogen peroxide as an additive to control the structure of a precursor. The surface morphologies of the inorganic templates can be controlled by varying the reaction time and the amount of hydrogen peroxide. The process of the precursor growth takes a dissolution-growth route under hydrothermal conditions. The chemical composition of the precursor is determined by X-ray diffraction (XRD) and Raman analyses, indicating the existence of peroxide in the precursor. Combined with transmission electron microscopy (TEM) data, the ZnO/ZnO2 hybrid precursor is proposed to act as an inorganic template for the growth of secondary crystal structures. The dandelion-like ZnO crystal is fabricated by using rose-like peroxide precursor as the inorganic template. The structural evolution of hierarchical ZnO crystal is studied by monitoring the influence of the reaction time.

Serrated, flexible and ultrathin polyaniline nanoribbons: An efficient counter electrode for the dye-sensitized solar cell

Development of cost-effective counter electrodes (CEs) and enhancement of power conversion efficiency are two persistent objectives for dye-sensitized solar cells (DSSCs). We report a novel method for synthesizing the state of art polyaniline nanoribbons (PANI NRs) CE with serrated, flexible and ultrathin nanostructure by in situ polymerization of aniline on an inorganic template, followed by acid etching. Herein, electrospun vanadium pentoxide (V2O5) nanofibers are chosen as templates to deposit PANI by a chemical bath polymerization method, which are served as the oxidants as well. Owing to its abundant active sites and the good contact performance, the PANI NRs CE shows high catalytic activity and the DSSC based on the PANI-c NRs CE shows a photoelectric conversion efficiency of 7.23% under full sunlight illumination (100 mW cm−2, AM 1.5 G), which is 97.44% that of the Pt-based DSSC (7.42%). Therefore, the high performance of PANI NRs can be considered as a cost-effective CE for the DSSC.

Impact of Interfacial Roughness on the Sorption Properties of Nanocast Polymers

Nanocasting is an emerging method to prepare organic polymers with regular, nanometer pores using inorganic templates. This report assesses the impact of imperfect template replication on the sorption properties of such polymer castings. Existing X-ray diffraction data show that substantial diffuse scattering exists in the small-angle region even though TEM images show near perfect lattices of uniform pores. To assess the origin of the diffuse scattering, the morphology of the phenol–formaldehyde foams (PFF) was investigated by small-angle X-ray scattering (SAXS). The observed diffuse scattering is attributed to interfacial roughness due to fractal structures. Such roughness has a profound impact on the sorption properties. Conventional pore-filling models, for example, overestimate protein sorption capacity. A mathematical framework is presented to calculate sorption properties based on observed morphological parameters. The formalism uses the surface fractal dimension determined by SAXS in conjunction with nitrogen adsorption isotherms to predict lysozyme sorption. The results are consistent with measured lysozyme loading.

Spectral behaviour of TMPyP/layered silicate hybrid nanomaterials in aqueous dispersions of reduced-charge montmorillonites

Spectral properties of tetracationic organic dye, meso-tetrakis(N-methylpyridinium-4-yl) porphyrin adsorbed on layered silicate templates of various layer charge were investigated. A series of reduced charge Nanocor montmorillonites was used as host matrices. The study primarily focuses on the influence of the layer charge on the emission characteristics and photoactivity of prepared materials. Usually, adsorption of dyes such as porphyrins leads to significant changes in their spectral characteristics with the main goal being the preservation of their photoactivity. The spectral changes can be explained in terms of e.g. structural changes (flattening, protonation), as well as molecular aggregation. Hence, the aim of this study is to clarify the way to influence the spectral properties and the subsequent photoactivity of incorporated molecules via a strategy of appropriate combination of a photoactive component with specific inorganic templates.

Hard-template preparation of Au/CeO2 mesostructured catalysts and their activity for the selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

Ordered mesoporous CeO2 has been prepared via a hard-template method using SBA-15 as a structure-directing agent. Leaching with NaOH and thermal treatment at 500 °C enabled the removal of the inorganic template, thus resulting in the formation of long-range ordered CeO2. Nevertheless, small amounts of silica were present in the final oxides. The resulting CeO2 samples were used as supports for Au nanoparticles and the prepared catalysts were tested in the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). Fine tuning of the silica template removal process was necessary to prepare active materials, by maximizing the close contact between the metal and the support, and thus confirming the important role of ceria defects in 5-hydroxymethylfurfural oxidation to 2,5-furandicarboxylic acid.

Amorphous-crystalline TiO2/carbon nanofibers composite electrode by one-step electrospinning for symmetric supercapacitor

In this study, the effects of titanium oxycompound templates on carbon nanofibers electrodes for supercapacitors application were investigated. Meanwhile, hybrid titanium that contains organic and inorganic titanium templates acted as another modification method. The organic and inorganic titanium oxycompounds referred to titanium (IV) oxy-acetylacetonate and titanium dioxide nanopowder, respectively. The morphology structure, and electrochemical properties of the three composite electrodes (TiO2@CNFs, OCTi@CNFs, HybTi@CNFs) were studied. Hierarchical pore structure with specific surface area of 697m2g−1 was achieved in HybTi@CNFs, in which TiO2 revealed amorphous, tetragonal rutile and anatase structure. The electron charge transfer resistance and specific capacitance of HybTi@CNFs were calculated to be 0.34Ω and 280.3Fg−1 (at current density of 1Ag−1), respectively. After 4000 cycles with galvanostatic charge/discharge, HybTi@CNFs can maintain 97.5% of its initial capacitance under 8Ag−1 in a symmetric two-electrode system (6M KOH). These results indicate that OCTi@CNFs is superior to TiO2@CNFs, and HybTi@CNFs has combined the advantages of OCTi@CNFs and TiO2@CNFs, suggesting HybTi@CNFs is an excellent electrode material for supercapacitors.

Nanoporous TiO₂/SnO₂/Poly(3,4-ethylene-dioxythiophene): Polystyrenesulfonate Composites as Efficient Counter Electrode for Dye-Sensitized Solar Cells.

PSS) was developed as an alternative counter electrode for dye-sensitized solar cell (DSSC) through low-temperature process. The TiO₂/SnO₂ template was first fabricated by coating a homogeneous TiO₂ nanoparticles blended paste containing a SnCl₄ aqueous solution on the conductive substrate, followed by annealing at 150 °C. The counter electrode was then completed by spin-coating the PSS aqueous solution into the template and drying at 80 °C. The obtained TiO₂/SnO₂/ PSS (TSP) composite film exhibits more excellent catalytic activity for the tri-iodide reduction than the pristine PSS film, resulting in the significant improvements in the fill factor and efficiency of the cells. The values of the fill factor and efficiency respectively increase from 0.564 and 4.79% to 0.699 and 6.54%. Noted that the photovoltaic performances of the TSP based DSSC is very similar to those of the Pt based one. The fill factor and efficiency of the later are 0.696 and 6.48%, respectively. The outstanding properties of the TSP composite film used as the counter electrode can be ascribed to its prominent synergistic effects. In the TSP composite film, the conducting TiO₂ is applied as the main skeleton material with the in-situ formed SnO₂ as a binder to construct a nanoporous structure for the PSS coating and also to provide numerous high-speed conductive paths for the electron transportation from the substrate to the PSS coating, and the PSS adhered on the TiO₂/SnO₂ skeleton mainly acts as the catalyst to enlarge its surface area allowing for more active sites for the tri-iodide reduction.

Porous Resin Catalyst with Strong Acidity for Hydration Reaction of Butane and Its Catalytic Performance

With nano-alumina modified by the fat acid as an inorganic template for making pores, a new kind of porous resin particle with the large surface was synthesized by emulsion polymerization. Moreover, the sulfonated polystyrene resin was fluorinated to increase its acid strength up to Ho 8.6 and the acid amount of 4.1mmol/g. The ratio of butane to water was increased by packing the catalytic resin with the fixed beds of four stages. Under reaction temperature of 168-174°C, butane to water ratio of 2 mol/mol and WHSV1.0 h-1, hydration reaction conversion was over 15 wt%, with the butyl alcohol selectivity of 99 wt% and a good thermal stability.

Thioether-terminated nickel(ii) coordination clusters with {Ni6} horseshoe- and {Ni8} rollercoaster-shaped cores

We report two polynuclear nickel(ii) compounds whose supramolecular structures are controlled by small inorganic templating anions and π-conjugated Schiff-base ligands (L·SMe3− and HL·SMe2−) with peripheral, structurally exposed methylthioether groups.