Perpendicular Nanochannels Research Articles

Carbon Nitride Nanosheets as an Adhesive Layer for Stable Growth of Vertically-Ordered Mesoporous Silica Film on a Glassy Carbon Electrode and Their Application for CA15-3 Immunosensor.

Vertically ordered mesoporous silica films (VMSF) are a class of porous materials composed of ultrasmall pores and ultrathin perpendicular nanochannels, which are attractive in the areas of electroanalytical sensors and molecular separation. However, VMSF easily falls off from the carbonaceous electrodes and thereby impacts their broad applications. Herein, carbon nitride nanosheets (CNNS) were served as an adhesive layer for stable growth of VMSF on the glassy carbon electrode (GCE). CNNS bearing plentiful oxygen-containing groups can covalently bind with silanol groups of VMSF, effectively promoting the stability of VMSF on the GCE surface. Benefiting from numerous open nanopores of VMSF, modification of VMSF's external surface with carbohydrate antigen 15-3 (CA15-3)-specific antibody allows the target-controlled transport of electrochemical probes through the internal silica nanochannels, yielding sensitive quantitative detection of CA15-3 with a broad detection range of 1 mU/mL to 1000 U/mL and a low limit of detection of 0.47 mU/mL. Furthermore, the proposed VMSF/CNNS/GCE immunosensor is capable of highly selective and accurate determination of CA15-3 in spiked serum samples, which offers a simple and effective electrochemical strategy for detection of various practical biomarkers in complicated biological specimens.

Space-confined manganese oxides nanosheets for efficient catalytic decomposition of ozone

Ground-level ozone has long posed a substantial menace to human well-being and the ecological milieu. The widely reported manganese-based catalysts for ozone decomposition still facing the persisting issues encompass inefficiency and instability. To surmount these challenges, we developed a mesoporous silica thin films with perpendicular nanochannels (SBA(⊥)) confined Mn3O4 catalyst (Mn3O4@SBA(⊥)). Under a weight hourly space velocity (WHSV) of 500,000 mL g−1 h−1, the Mn3O4@SBA(⊥) catalyst exhibited 100% ozone decomposition efficiency in 5 h and stability across a wide humidity range, which exceed the performance of bulk Mn3O4 and Mn3O4 confine in commonly reported SBA-15. Rapidly decompose 20 ppm O3 to a safety level below 100 μg m−3 in the presence of dust in smog chamber (60 × 60 × 60 cm) was also realized. This prominent catalytic performance can be attributed to the unique confined structure engenders the highly exposed active sites, facilitate the reactant-active sites contact and impeded the water accumulation on the active sites. This work offers new insights into the design of confined structure catalysts for air purification.

Mesoporous silica thin films incorporated chitosan mixed matrix nanofiltration membranes for textile wastewater treatment

AbstractThe demand of nanofiltration (NF) membranes for practical and cost‐effective environmental treatment is exploding. Mixed matrix membranes (MMMs) have attracted tremendous interest on account of combining the benefits of polymer and inorganic fillers. In this study, mesoporous silica thin films with perpendicular nanochannels (SBA‐15(⊥)) incorporated in chitosan (CS) were fabricated for dye wastewater purification. Functional groups, such as amino or epoxy groups were introduced into SBA‐15(⊥) (SBA‐15(⊥)‐NH2, SBA‐15(⊥)‐Epo) for forming covalent bonds with chitosan matrix to improve their compatibility. The excellent performance in dye/salt fractionation in aqueous solution was demonstrated by SBA‐15(⊥)‐Epo/CS MMMs, which realized a cut off of 585 g/mol, 99.9% rejection of Congo red, while maintaining 85% permeation of NaCl. In addition, the separation mechanism of the resulting membrane was explored. The efficient NF performance of SBA‐15(⊥)‐Epo/CS membrane was attributed to its better compatibility between SBA‐15(⊥)‐Epo and chitosan matrix by virtue of the formation of covalent bonds thus to ensure the high dye rejection, and the vertically oriented nanochannels arrangement facilitated the molecule transportation. This work will inspire feasible synthesis of a new generation of MMMs membranes for dye wastewater purification.

Diatom-inspired self-assembly for silica thin sheets of perpendicular nanochannels

HypothesisMultistage silicate self-organization into light-weight, high-strength, hierarchically patterned diatom frustules carries hints for innovative silica-based nanomaterials. With sodium silicate in a biomimetic sol-gel system templated by a tri-surfactant system of hexadecyltrimethylammonium bromide, sodium dodecylsulfate, and poly(oxyethylene-b-oxypropylene-b-oxyethylene) (P123), mesoporous silica nanochannel plates with perpendicular channel orientation are synthesized. The formation process, analogous to that of diatom frustules, is postulated to be directed by an oriented self-assembly of the block copolymer micelles shelled with charged catanionic surfactants upon silication. ExperimentsThe postulated formation process for the oriented silica nanochannel plates was investigated using time-resolved small-angle X-ray and neutron scattering (SAXS/SANS) and freeze fracture replication transmission electron microscopy (FFR-TEM). FindingsWith fine-tuned molar ratios of the anionic, cationic, and nonionic surfactants, the catanionic combination and the nonionic copolymer form charged, prolate ternary micelles in aqueous solutions, which further develop into prototype monolayered micellar plates. The prolate shape and maximized surfactant adsorption of the complex micelles, revealed from combined SAXS/SANS analysis, are of critical importance in the subsequent micellar self-assembly upon silicate deposition. Time-resolved SAXS and FFR-TEM indicate that the silicate complex micelles coalesce laterally into the prototype micellar nanoplates, which further fuse with one another into large sheets of monolayered silicate micelles of in-plane lamellar packing. Upon silica polymerization, the in-plane lamellar packing of the micelles further transforms to 2D hexagonal packing of vertically oriented silicate channels. The unveiled structural features and their evolution not only elucidate the previously unresolved self-assembly process of through-thickness silica nanochannels but also open a new line of research mimicking free-standing frustules of diatoms.

Highly Ordered Nanochannels in a Nanosheet-Directed Thin Zeolite Nanofilm for Precise and Fast CO2 Separation.

Precise molecular and ion separations depend largely on the size and uniformity of the nanochannels in a defect-free microporous nanofilm. Ordered and perpendicular nanochannels with uniform pore size are assembled into a continuous and defect-free film by a "gel nuclei-less" route. The ultrathin (<50 nm) zeolite nanosheets seeding layer induces the formation of defect-free zeolite nanofilms (500-800 nm) with preferential [100] orientation well-aligned to the transport pathway. The large-area and thin silicoaluminophosphate-34 (SAPO-34) nanofilm consisting of uniform and straight nanochannels shows a milestone CO2 permeance of ≈1.0 × 10-5 mol (m2 s Pa)-1 and high CO2 /CH4 and CO2 /N2 selectivities of 135 and 41 in equimolar binary mixtures at room temperature and 0.2 MPa feed pressure, respectively. These results suggest that highly oriented and thin SAPO-34 nanofilms prepared from nanosheets might have great potential for CO2 capture from natural gas, biogas, and flue gas.

Photonic crystal films with high reflectance based on mesoporous silica in the extreme ultraviolet range

In the present work, mesoporous silica films with hexagonally packed perpendicular nanochannels treated as a 2D photonic crystal in extreme ultraviolet (EUV) range are explored by combining theories and experiments. The simulation results show that this film structure exhibits high reflectivities in a wide band range from 5 nm to 11 nm and at broad incidences angle range. The better reflective properties can be ascribed to its excellent photonic crystal structure corresponding to short spectral region. Experimentally, highly ordered mesoporous silica films with vertical mesochannels were fabricated by electrochemically assisted self-assembly method. Moreover, the reflectances of the fabricated film at 5–11 nm region were also tested using synchrotron radiation, which can reach up to 80.4% at 2°from grazing incidence direction. Meanwhile, a relative high reflectance can be maintained at 5–11 nm at incidence angles of 2–7°. This research results offer a new strategy to developing a promising extreme ultraviolet optical film with high reflectance and broad band range.

Advanced Nanoporous Separators for Stable Lithium Metal Electrodeposition at Ultra-High Current Densities in Liquid Electrolyte

Lithium (Li) metal is considered as the ultimate anode material for the development of next-generation batteries.1 However, Li metal electrode forms dendritic structure after cycling which causes an internal short circuit.2, 3 In this work, we grew mesoporous silica thin film (MSTF) with perpendicular nanochannels and ultra-small pore diameter (~5 nm diameter) onto the anodic aluminum oxide (AAO) membrane as the MSTF⊥AAO separator. The nanoporous MSTF⊥AAO separator with novel inorganic structures shows stable Li deposition for more than 1600 h of operation in Li-Li cells under a very high current density and capacity of 10 mA cm–2 and 5 mAh cm–2. The separator gives improved rate capability in Li-NMC batteries. The excellent performance of the MSTF⊥AAO nanoporous separator is due to good wetting of electrolytes, straight nanopores, uniform deposition of Li and blocking the finest dendrite. Our designed separators provide a groundbreaking model to regulate Li plating/stripping behavior. References Cheng, X.-B.; Zhang, R.; Zhao, C.-Z.; Zhang, Q., Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review. Chem. Rev. 2017, 117 (15), 10403-10473.Xu, W.; Wang, J.; Ding, F.; Chen, X.; Nasybulin, E.; Zhang, Y.; Zhang, J.-G., Lithium metal anodes for rechargeable batteries. Energy Environ. Sci. 2014, 7 (2), 513-537.Zhang, S. S., A review on the separators of liquid electrolyte Li-ion batteries. Power Sources 2007, 164 (1), 351-364.

Ordered Mesoporous Zeolite Thin Films with Perpendicular Reticular Nanochannels of Wafer Size Area

Highly ordered mesoporous zeolite thin films (MZTFs) are grown at rigid substrates via molecular interaction from ternary structure-directing agents (SDAs) in a Stober-like condition. The ultrathin films (10–20 nm) were deposited layer-by-layer via self-assembly of β-zeolite seeds and SDAs at 40–50 °C, resulting reticular cellular pores and perpendicular nanochannels with average pore sizes (6.7 ± 1.1 nm). The walls of the nanochannels consist of zeolitic structures in microcrystallines. Compared to cylindrical mesochannels of amorphous silica thin films, the MZTFs with reticular mesochannels demonstrate 5R/6R stretching modes (550–650 cm–1) and significantly enhanced hydrothermal stability. The MZTFs were characterized in top-view and cross-sectional electron microscopies (SEM/HRSEM/HRTEM) as well as X-ray scattering techniques (GIXRD/GISAXS), which confirm a body-centered tetragonal (Im3m) unit cell with unique Moire patterns. Upon calcination, the film thickness is reduced to 10.6 nm with a structure ...

Clickable Bifunctional and Vertically Aligned Mesoporous Silica Films

Getting oriented mesoporous thin films with functionalized pores accessible from the substrate surface remains one key challenge in materials science, and jumping the step forward to multifunctional layers with perpendicular nanochannels has still to be achieved. Here, a general method is introduced combining the electrochemically assisted deposition of ordered and oriented azide‐ and thiol‐functionalized mesoporous silica with a selective sequential azide‐alkyne and thiol‐ene “click chemistry” approach to prepare nanostructured and vertically aligned hybrid films bearing tunable amounts of organo‐functional groups. High‐resolution electron microscopy is used to evidence the high level of mesostructural order and pore orientation, while the effectiveness of the functionalization processes is proven from spectroscopic and electrochemical measurements. Voltammetric data also demonstrate that both the accessibility through the films and the properties of the incorporated functions are maintained upon derivatization. Feasibility of this simple and generic strategy is illustrated here for two couples of model derivatives (ethynylcobaltocenium/vinylferrocene and propargyl alcohol/allyl cyanide) but such stepwise postfunctionalization can be extensively used for the incorporation of a variety of organic functions in mesoporous silica films.

Ultrathin Silica Membranes with Highly Ordered and Perpendicular Nanochannels for Precise and Fast Molecular Separation.

Membranes with the ability of molecular/ionic separation offer potential in many processes ranging from molecular purification/sensing, to nanofluidics and to mimicking biological membranes. In this work, we report the preparation of a perforative free-standing ultrathin silica membrane consisting of straight and parallel nanochannels with a uniform size (∼2.3 nm) for precise and fast molecular separation. Due to its small and uniform channel size, the membrane exhibits a precise selectivity toward molecules based on size and charge, which can be tuned by ionic strength, pH or surface modification. Furthermore, the ultrasmall thickness (10-120 nm), vertically aligned channels, and high porosity (4.0 × 10(12) pores cm(-2)) give rise to a significantly high molecular transport rate. In addition, the membrane also displays excellent stability and can be consecutively reused for a month after washing or calcination. More importantly, the membrane fabrication is convenient, inexpensive, and does not rely on sophisticated facilities or conditions, providing potential applications in both separation science and micro/nanofluidic chip technologies.

MCM-41 mesoporous silica sheet with ordered perpendicular nanochannels for protein delivery and the assembly of Ag nanoparticles in catalytic applications

In this study, well-ordered microscale MCM-41 mesoporous silica sheets of ca. 80 nm thicknesses were first prepared by using water and petroleum ether as cosolvents in the presence of CTAB as template and TEOS as silica precursor. The as-synthesized materials showed excellent bovine serum albumin proteins loading capacity (598 mg protein per gram silica materials), controllable sustained protein release profile, and effective catalytic reduction performance of 4-nitrophenol after high payload of Ag nanoparticles.

A general method for growing large area mesoporous silica thin films on flat substrates with perpendicular nanochannels.

Here we introduce a new synthetic approach to grow mesoporous silica thin films with vertical mesochannels on centimeter-sized substrates via an oil-induced co-assembly process. Adding an oil, i.e., decane, into a CTAB-EtOH-TEOS ammonia solution leads to thin-film formation of mesoporous silica of controlled thickness between 20 and 100 nm with vertical mesochannels on various surfaces. The vertical mesoporous channels were evidenced by grazing incidence small-angle X-ray scattering (GISAXS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) characterizations. Decane played two roles: (a) as a pore expansion agent (up to 5.7 ± 0.5 nm) and (b) inducing vertically oriented hexagonal mesophases of micelle-silica composite. The production of periodic and vertical nanochannels is very robust, over many different substrate surfaces (from silicon to polystyrene), various silica precursors (TEOS, fumed silica, or zeolite seed), and many oils (decane, petroleum ether, or ethyl acetate). This wide robustness in the formation of vertical nanophases is attributed to a unique mechanism of confined synthesis of surfactant-silicate between two identical thin layers of oils on a substrate.

Two-dimensional crystals of mesoporous silica SBA-15 nanosheets with perpendicular and open channels

A preparation of mesoporous silica SBA-15 thin sheets with perpendicular nanochannels (SBA(⊥)) and open ends is reported here. At a synthesis condition of pH = 2 where the silica condensation is extremely slow, micron-sized single-crystal-like hexagonally faceted nanosheets (SBA(⊥)-pH2) with aspect ratio of 10–50 were formed. The nanosheets can attach to each other in sideway to extend the thin sheet. At pH = 5, multi-domain SBA(⊥)-pH5 nanosheets are formed, and stacking attachment of sheets is preferred. Vivid Moiré patterns are observed in large areas of stacked silica sheets, indicating excellent structure order.

Integrated Hollow Mesoporous Silica Nanoparticles for Target Drug/siRNA Co‐Delivery

A hollow mesoporous silica nanoparticle (HMSNP) based drug/siRNA co-delivery system was designed and fabricated, aiming at overcoming multidrug resistance (MDR) in cancer cells for targeted cancer therapy. The as-prepared HMSNPs have perpendicular nanochannels connecting to the internal hollow cores, thereby facilitating drug loading and release. The extra volume of the hollow core enhances the drug loading capacity by two folds as compared with conventional mesoporous silica nanoparticles (MSNPs). Folic acid conjugated polyethyleneimine (PEI-FA) was coated on the HMSNP surfaces under neutral conditions through electrostatic interactions between the partially charged amino groups of PEI-FA and the phosphate groups on the HMSNP surfaces, blocking the mesopores and preventing the loaded drugs from leakage. Folic acid acts as the targeting ligand that enables the co-delivery system to selectively bind with and enter into the target cancer cells. PEI-FA-coated HMSNPs show enhanced siRNA binding capability on account of electrostatic interactions between the amino groups of PEI-FA and siRNA, as compared with that of MSNPs. The electrostatic interactions provide the feasibility of pH-controlled release. In vitro pH-responsive drug/siRNA co-delivery experiments were conducted on HeLa cell lines with high folic acid receptor expression and MCF-7 cell lines with low folic acid receptor expression for comparison, showing effective target delivery to the HeLa cells through folic acid receptor meditated cellular endocytosis. The pH-responsive intracellular drug/siRNA release greatly minimizes the prerelease and possible side effects of the delivery system. By simultaneously delivering both doxorubicin (Dox) and siRNA against the Bcl-2 protein into the HeLa cells, the expression of the anti-apoptotic protein Bcl-2 was successfully suppressed, leading to an enhanced therapeutic efficacy. Thus, the present multifunctional nanoparticles show promising potentials for controlled and targeted drug and gene co-delivery in cancer treatment.

Mesoporous silica SBA-15 sheet with perpendicular nanochannels

Free-standing thin sheet form of mesoporous silica materials with perpendicular orientation is a much desired materials for its possible applications in catalysis, mask, and separation. A three component amphiphile system of sodium dodecyl sulfate/hexadecyltrimethylammonium bromide/pluronic-123(C16TMAB/SDS/P123) was employed to template the condensation of sodium silicates for the formation of SBA(⊥), a thin sheet of SBA-15 with perpendicular nanochannels. SBA(⊥) can be synthesized at SDS/C16TMAB=1.5 and T⩾40°C and shows pH-dependent morphology. It has uniform pore size ∼9nm, homogeneous sheet thickness in the range of 60–300nm and dimension of several microns. We studied in details the structure and morphology of the SBA(⊥) with variation of three experimental parameters: the SDS/C16TMAB ratio, the temperature, and the pH condition in the synthetic gel. It is proposed that the mixed surfactants of SDS and C16TMAB form catanionic vesicle in which the P123 and silicates are condensed. The balanced interaction of P123/silicate with the narrow confinement under surfactant bi-layers of C16TMAB/SDS promoted the formation of perpendicular nanochannels. Low temperature and pH conditions favor stronger segregation of the PPO and PEO–oligosilicate segments in the SBA(⊥) structure which gives the basis of thickness control of the sheet. The control of structure and morphology are discussed with modern theory of microphase separation in block copolymers under confinement.

Mesoporous Silica Platelets with Perpendicular Nanochannels via a Ternary Surfactant System

Mesoporous silica platelets with perpendicular nanochannels (see Figure) have been conveniently prepared by using a ternary cetyltrimethylammonium bromide–sodium dodecylsulfate–Pluronic123 surfactant system as a template and sodium silicate as the silica source. The diameter of the fabricated nanochannels is about 7.0 nm, and the length distribution ranges from 30 to 100 nm.