Nanoporous Features Research Articles

A 3D coupled model of organic matter and inorganic matrix for calculating the permeability of shale

Microstructure-based quantitative computation of the shale permeability is challenging due to the presence of organic matter with nanoporous features. In this study, a new three-dimensional (3D) coupled model is proposed to investigate the micro-scale permeability of organic-rich-shale matrix. The coupled model consists of two subdomains, organic matter and inorganic matrix. They are described by the pore network model (PNM) and continuum model to capture the non-Darcy and Darcy flow, respectively, and the gas flow in the two subdomains are coupled by finite element mortars (Mortar). The convergence error, grid discretization and parallel scheme are also investigated to get the optimal computing parameters for this model. Then, the effects of the total organic content (TOC), kerogen distribution and pore-size distribution on the apparent permeability (AP) of shale matrix are studied using the coupled model with computer-generated PNMs. And on the basis of FIB-SEM images, a Longmaxi shale sample from the Sichuan Basin, China is introduced to build a real shale model. Results show that AP is more sensitive to TOC and pore-size distribution than kerogen distribution. Additionally, in order to analyze the necessity of 3D model, a comparison of 3D and two-dimensional (2D) model is made and the error of 2D model is pointed out. The 3D couple model affords a foundation for further upscaling of shale permeability to REV scale and reservoir scale.

Improved bioactivity of selective laser melting titanium: Surface modification with micro-/nano-textured hierarchical topography and bone regeneration performance evaluation

Selective laser melting (SLM) titanium requires surface modification to improve its bioactivity. The microrough surface of it can be utilized as the micro primary substrate to create a micro-/nano-textured topography for improved bone regeneration. In this study, the microrough SLM titanium substrate was optimized by sandblasting, and nano-porous features of orderly arranged nanotubes and disorderly arranged nanonet were produced by anodization (SAN) and alkali-heat treatment (SAH), respectively. The results were compared with the control group of an untreated surface (native-SLM) and a microtopography only surface treated by acid etching (SLA). The effects of the different topographies on cell functions and bone formation performance were evaluated in vitro and in vivo. It was found that micro-/nano-textured topographies of SAN and SAH showed enhanced cell behaviour relative to the microtopography of SLA with significantly higher proliferation on the 1st, 3rd, 5th and 7th day (P<0.05) and higher total protein contents on the 14th day (P<0.05). In vivo, SAN and SAH formed more successively regenerated bone, which resulted in higher bone-implant contact (BIC%) and bone-bonding force than native-SLM and SLA. In addition, the three-dimensional nanonet of SAH was expected to be more similar to native extracellular matrix (ECM) and thus led to better bone formation. The alkaline phosphatase activity of SAH was significantly higher than the other three groups at an earlier stage of the 7th day (P<0.05) and the BIC% was nearly double that of native-SLM and SLA in the 8th week. In conclusion, the addition of nano-porous features on the microrough SLM titanium surface is effective in improving the bioactivity and bone regeneration performance, in which the ECM-like nanonet with a disorderly arranged biomimetic feature is suggested to be more efficient than nanotubes.

Binder-free activated graphene compact films for all-solid-state micro-supercapacitors with high areal and volumetric capacitances

Micro-supercapacitors (MSCs) hold great promise as highly competitive miniaturized power sources satisfying the increased demand in microelectronics; however, simultaneously achieving high areal and volumetric capacitances is still a great challenge. Here we demonstrated the designed construction of binder-free, electrically conductive, nanoporous activated graphene (AG) compact films for high-performance MSCs. The binder-free AG films are fabricated by alternating deposition of electrochemically exfoliated graphene (EG) and nanoporous AG with a high specific surface area of 2920m2/g, and then dry transferring onto the target substrates with a high-pressure mechanical densification process. Remarkably, the resulting compressed AG films showed uniform morphology in lateral dimensions, high conductivity (60S/cm), nanoporous feature (<10nm), and high packing density (0.8g/cm3). The all-solid-state MSCs (AG-MSCs) based on these AG films simultaneously delivered an unprecedented areal capacitance of 89.5mF/cm2 and volumetric capacitance of 147F/cm3 for MSCs at 10mV/s. Moreover, the fabricated AG-MSCs could be operated at a large scan rate of 10,000mV/s, and showed outstanding cycling stability (capacitance retention of >99.6% after 10,000 cycles). Our results suggested that AG-MSCs are competitive for prospective applications of miniaturized energy storage devices.

Analysis of Gas Molecule Mean Free Path and Gaseous Thermal Conductivity in Confined Nanoporous Structures

This study comprehensively analyzes the mean free path of gas molecules and gaseous thermal conductivity in confined nanoporous structures through a wide range of temperatures and pressures. A simplified unit cell cubic array structure of nanospheres is used to correlate microstructure features with specific surface area and density of nanoporous materials. Zeng’s model is used to describe the mean free path of the gas molecules and the gaseous thermal conductivity in confined nanoporous structures, and experimental gaseous thermal conductivity data from the literature is used to validate the model. The results show that a material’s nanoporous structure features are directly related to specific surface area and density. The mean free path of gas molecules in a confined nanoporous structure decreases with increasing specific surface area and density. Thus, nanoporous materials with a relatively high specific surface area and a higher density are more favorable for confining gaseous thermal conductivity in nanopores. This work shows that \(p=10^{4}\hbox { Pa}\) and \(10^{6}\hbox { Pa}\) are two characteristic pressures at ambient temperatures for the investigated silica aerogel materials. When \(p 10^{6}\hbox { Pa}\), the limiting effect of the nanoporous structure on the movement of gas molecules can be ignored, and so the mean free path of gas molecules in the nanoporous material approaches the mean free path of gas molecules in free space, while the gaseous thermal conductivity approaches the gaseous thermal conductivity in free space. As temperature increases, there exists a maximum value for gaseous thermal conductivity in confined nanoporous materials, but this maximum increases as pressure increases. The maximum gaseous thermal conductivity for the material is also determined in the paper.

Influence of the nanostructure of F-doped TiO2 films on osteoblast growth and function.

The aim of this study was to evaluate the proliferation and mineralization ability of mouse osteoblastic MC3T3-E1 cells on F-containing TiO2 films with different morphology and nanostructure that previously confirmed antibacterial properties. F-containing TiO2 films were fabricated by anodizing Ti-6Al-4V alloy ELI -grade 23. By using a mixture of H2SO4/HF acid at 20 V for 5 and 60 min, a TiO2 film grows with nanoporous (NP) and nanotubular (NT) features, characterized with a pore diameter of 20 and 100 nm, respectively. Fluoride-TiO2 barrier films (FBL) were produced in 1M NH4H2PO4/0.15M NH4F solution at constant voltage controlled at 20 V for 120 min. The amount of F incorporated in the nanostructured oxide films was 6 at % and of 4 at %, for the NP and NT, respectively, while for the FBL film was 12 at %. MC3T3-E1 cells exhibited different behavior when seeded and grown onto these surfaces. Thus, F-doped TiO2 films with NP structures increased proliferation as well as osteogenic gene expression and the mineralization capacity of these osteoblastic cells. These results confirm that anodizing process is suitable to fabricate multifunctional surfaces on Ti-6Al-4V alloy with improved not only antibacterial but also osteogenic properties useful for bone fixation of prosthetic devices

Enhanced MC3T3-E1 preosteoblast response and bone formation on the addition of nano-needle and nano-porous features to microtopographical titanium surfaces

Micro/nanotopographical modifications on titanium surfaces constitute a new process to increase osteoblast response to enhance bone formation. In this study, we utilized alkali heat treatment at high (SB-AH1) and low temperatures (SB-AH2) to nano-modify sandblasted titanium with microtopographical surfaces. Then, we evaluated the surface properties, biocompatibility and osteogenic capability of SB-AH1 and SB-AH2 in vitro and in vivo, and compared these with conventional sandblast-acid etching (SLA) and Ti control surfaces. SB-AH1 and SB-AH2 surfaces exhibited micro/nanotopographical modifications of nano-needle structures and nano-porous network layers, respectively, compared with the sole microtopographical surface of macro and micro pits on the SLA surface and the relatively smooth surface on the Ti control. SB-AH1 and SB-AH2 showed different roughness and elemental components, but similar wettability. MC3T3-E1 preosteoblasts anchored closely on the nanostructures of SB-AH1 and SB-AH2 surfaces, and these two surfaces more significantly enhanced cell proliferation and alkaline phosphatase (ALP) activity than others, while the SB-AH2 surface exhibited better cell proliferation and higher ALP activity than SB-AH1. All four groups of titanium domes with self-tapping screws were implanted in rabbit calvarial bone models, and these indicated that SB-AH1 and SB-AH2 surfaces achieved better peri-implant bone formation and implant stability, while the SB-AH2 surface achieved the best percentage of bone-implant contact (BIC%). Our study demonstrated that the micro/nanotopographical surface generated by sandblasting and alkali heat treatment significantly enhanced preosteoblast proliferation, ALP activity and bone formation in vitro and in vivo, and nano-porous network topography may further induce better preosteoblast proliferation, ALP activity and BIC%.

Nanoporous TiO2 aerogel blocking layer with enhanced efficiency for dye-sensitized solar cells

TiO2 aerogel film possessing nanoporous feature was used as the blocking layer between fluorine-doped tin oxide (FTO) substrate and mesoporous TiO2 layer in dye-sensitized solar cell (DSSC). TiO2 aerogel film was deposited on FTO glass via sol–gel and ambient drying processes and sintered at 500 °C, which exhibited the crystallite size of 5–25 nm, the pore size of 3–10 nm, and the thickness of ∼320 nm. Brunauer–Emmett–Teller (BET) analysis confirmed its nanoporous feature and average pore size of 3.8 nm after annealing at 500 °C. In addition, TiO2 aerogel film showed good interfacial adhesion with FTO and mesoporous TiO2 layer, high transmittance over 70% in the visible-near infrared band, and large band gap of 3.67 eV. The DSSC device based on this aerogel blocking layer showed obviously enhanced photocurrent density (Jsc) and open-circuit voltage (Voc) compared with the cell without blocking layer. The highest conversion efficiency of 6.0% was achieved for P25 TiO2 mesoporous photoanode based on the aerogel blocking layer, improved by 36% than the control cell. The much decreased recombination frequency (aerogel cell: 11.9 Hz; control cell: 31.5 Hz) observed in Nyquist plots, together with the much prolonged electron lifetime (aerogel cell: ∼1 s; control cell: 0.02–0.1 s at 0.2–0.55 V) obtained from open-circuit voltage decay curves, indicated that the increased electron life and retarded recombination at FTO/electrolyte interface were primarily responsible for the efficiency improvement in the aerogel blocking layer based DSSC.

Effect of anodization on corrosion behaviour and biocompatibility of Cp-titanium in simulated body fluid

The objective of this investigation is to study the effectiveness of anodized surface of commercial purity titanium (Cp-Ti) on its corrosion behaviour in simulated body fluid (SBF) and proliferation of osteoblast cells on it, to assess its potentiality as a process of surface modification in enhancing corrosion resistance and osseointegration of dental implants. Highly ordered nano-porous oxide layer, with nano-sized pores, is developed on the surface of Cp-Ti through electrochemical anodization in the electrolyte of aqueous solution of 0·5% HF at 15 V for 30 min at 24 °C. The nano-porous feature of the anodized surface is characterized by field-emission scanning electron microscope (FESEM). Pores of some anodized samples are sealed by exposing the anodized surface in boiling water. Corrosion behaviour of the anodized specimen is studied in Ringer’s solution at 30 ± 2 °C, using electrochemical impedance and cyclic polarization technique. Biocompatibility of the anodized surface is accessed using MG63 osteoblast cells. Both corrosion as well as pitting resistance of Cp-Ti in simulated body fluid are found to be highest in the anodized and sealed condition and followed in decreasing order by those of anodized and unanodized ones. Significantly higher MG63 osteoblast cell proliferations are found on the anodized surface than that on the unanodized one. Anodized Cp-Ti develops nano-size surface pores, like that of natural bone. It enhances corrosion and pitting resistance and also the process of osteoblast cell proliferation on Cp-Ti.

Formation of Nanoporous Features, Flat Surfaces, or Crystallographically Oriented Etched Profiles by the Si Chemical Dry Etching Using the Reaction of F2 + NO → F + FNO at an Elevated Temperature

Chemical dry etching of Si was performed using the reaction of F2 + NO → F + FNO at an elevated temperature. The etched profile, surface morphology, and surface chemical bonding structures, measured by a scanning electron microscope, X-ray photoelectron spectroscopy (XPS), and a Fourier transform infrared spectrometer (FT-IR), were significantly changed when the substrate was heated at 27 and 300 °C. Differences in total energies of Si before and after the chemical reaction with gas molecules in the etching apparatus were theoretically calculated by the density functional theory (DFT) using CAM-B3LYP/6-311G+(d,p) in Gaussian 09. The possible change in chemical bonding structures during and after the Si etching was considered by correlating the measured XPS and FT-IR spectra and the DFT calculation results. When the Si sample was heated at 27∼60 °C, the nanoporous features were observed since molecules present in the gas phase remained in the condensed layer near the Si surface and they reacted with the Si surface at different rates. The chemisorbed F2, F, and FNO promoted Si etching by cleaving different bonds to form dangling bonds, whereas NO and OH, produced from the reaction between H2O and F, inhibited the etching by encapsulating dangling bonds. The etch rate was significantly reduced, and the evolution of the flat surface was observed at 60∼230 °C due to the reduction of chemisorbed F2, F, and FNO on the Si surface. When the Si sample was heated at above 230 °C, the etch rate increased with the temperature due to the amplification of the reaction rate constants of F2, F, and FNO with the Si surface. Unique orientation-dependent etching was observed at these temperatures due to the termination of dangling bonds by F without cleaving the Si–Si lattice bonds. The contribution of NO and OH at above 230 °C was ignored since they desorbed from the Si surface.

From the ZnO Hollow Cage Clusters to ZnO Nanoporous Phases: A First-Principles Bottom-Up Prediction

A family of ZnkOk (k = 12, 16) cluster-assembled solid phases with novel structures and properties has been characterized utilizing a bottom-up approach with density functional calculations. Geometries, stabilities, equation of states, phase transitions, and electronic properties of these ZnO polymorphs have been systematically investigated. First-principles molecular dynamics (FPMD) study of the two selected building blocks, Zn12O12 and Zn16O16, with hollow cage structure and large HOMO–LUMO gap shows that both of them are thermodynamically stable enough to survive up to at least 500 K. Via the coalescence of building blocks, we find that the Zn12O12 cages are able to form eight stable phases by four types of Zn12O12–Zn12O12 interactions, and the Zn16O16 cages can bind into three phases by the Zn16O16–Zn16O16 links of H′, C′, and S′. Among these phases, six ones are reported for the first time. This has greatly extended the family of ZnO nanoporous phases. Notably, some of these phases are even more stable than the synthesized metastable rocksalt ZnO polymorph. The hollow cage structure of the corresponding building block ZnkOk is well preserved in all of them, which leads to their low-density nanoporous and high flexibility features. In addition the electronic integrity (wide-energy gap) of the individual ZnkOk is also retained. Our calculation reveals that they are all semiconductor with a large direct or indirect band gap. The insights obtained in this work are likely to be general in II–VI semiconductor compounds and will be helpful for extending the range of properties and applications of ZnO materials.

Highly Selective Chemical Sensing in a Luminescent Nanoporous Magnet

On the road to chemical sensors: A novel 2D oxamato-based manganese(II)-copper(II) mixed-metal–organic framework (M'MOF) exhibiting non-linear fluorescence and long-range magnetic ordering is reported. This new luminescent nanoporous magnet features highly selective solvent- and gas sorption-induced optical switching behavior, opening the door to potential application for sensing of small molecules. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

First Principles Study of Surface Properties for Silicon Carbide-Derived Structures

Using first-principles ultra-soft pseudo-potential approach of the plane wave based on the density functional theory (DFT), we investigated the surface properties for silicon carbide-derived structure (i.e. SiCDS). The calculated results show that, movement of C and Si atoms caused by Si removal results in surface structural changing, and a nanoporous surface feature can be observed on the SiCDS surfaces when more Si atoms are removed. The mulliken population analysis indicates that the Si removal leads to the stronger chemical bonds between C–Si and the formation of new stronger chemical bands between C–C. From the density of states, as the Si removal proportion increases, C2p becomes gradually dominant in the SiCDS surface state electrons. Moreover, the Si removal leads to evidently different band gaps, indicating that the conductivity for SiCDS surface structures can be adjusted through the Si removal.

Gold nanoparticle-assembled capsules and their application as hydrogen peroxide biosensor based on hemoglobin

Gold nanoparticle-assembled capsules (GNACs) with controllable size and tunable morphology were fabricated through a simple two-step mixing procedure. Cationic polyelectrolyte was first induced to self-assemble into spherical aggregates in the presence of multivalent anions. Then, the aggregates served as an effective template for the self-assembly of gold nanoparticles to form size-controllable capsules. By adjusting the quantity of gold nanoparticles, capsules with various morphologies could be obtained. Because of their unique nanoporous features, the capsules with intact shells were further used to load hemoglobin (Hb) for the fabrication of a novel H 2O 2 biosensor. The results of UV–vis spectroscopy and cyclic voltammetry indicated that the capsules provided a suitable matrix for the immobilization of Hb. Additionally, the resulting biosensor showed a high affinity and good catalytic activity to H 2O 2. With the advantages of the large surface area, good conductivity and biocompatibility, the GNACs can offer a promising platform for the development of biosensors. Moreover, on the basis of the capsule structure, this material may also be expected to apply in some fields such as drug delivery, medical diagnostics and bio-encapsulation.

Morphology Control of Anodic TiO2 Nanomaterials via Cold Work Pretreatment of Ti Foils

Self-organized TiO2 nanostructures fabricated using the convenient method of anodizing Ti foils have attracted much attention for various applications. Properties and performance of the anodic TiO2 nanostructures have proven largely dependent on their morphology. Here we report that the simple cold work pretreatment of Ti foils has a strong impact on the morphology of the subsequently generated anodic TiO2 nanostructures. By increasing the amount of cold work applied to the Ti foil, the morphology of the subsequently generated anodic TiO2 can be converted from self-organized nanotube arrays to an exotic type of nanoporous structures. This exotic type of nanoporous structures features throughout the entire film thickness interwoven tiny tubes whose opening is approximately 30 nm wide. Formation mechanism of the exotic nanoporous structures is proposed. The exotic TiO2 nanoporous materials enabled by the cold-work pretreatment of Ti substrates show higher photocatalytic efficiency than their nanotube counterparts.

Facile chemical rearrangement for photopatterning of POSS derivatives

We report a useful acid-catalyzed crosslinking reaction which enables the direct photopatterning of POSS derivatives to form robust nanoporous matrices. Octakis(dimethylacetoxyethyl siloxy) POSS and octakis(dimethylacetoxypropyl siloxy) POSS were synthesized from commercially available octahydrido-POSS. Both the acetoxyethyl- and acetoxypropyl functionalities were observed to undergo thermal rearrangement at temperatures above 300 °C to form Si–O–Si bonds, thus forming a crosslinked POSS network. Interestingly, the same functionalities were also acid sensitive, and the chemical rearrangement occurred at much lower temperatures. Thus, patterned nanoporous features were lithographically generated when a photoacid generator (PAG) was used as a photosensitive agent to initiate the crosslinking of the POSS derivatives. The dielectric properties were evaluated for the crosslinked POSS films, which had a dielectric constant ∼2.3 and an elastic modulus of ∼2.0 GPa. These materials hold great promise for developing a photopatternable low-k material which eliminates the need for sacrificial layers when patterning low-k dielectric films.

First principles study of surface properties for silicon carbide-derived carbon

The surface properties for silicon carbide-derived carbon (i.e. Si-CDC) are investigated by employing the density functional theory (DFT) plane-wave pseudopotential method. The calculated results show that, the carbon atoms on the Si-CDC first layer, except for the ones linking to sub-layer Si atoms, fall into the second atomic layer, exhibiting a nanoporous surface feature. The Si removal leads to stronger covalent bonding among the C–Si and C–C atoms, implying more stable C atoms on the Si-CDC surface. Different from the case for the SiC, the second atomic layer has the most important contribution on the Si-CDC electrons of surface state. Moreover, the narrower band gap for the Si-CDC surface indicates a superior conductivity.

Recent Developments on Citric Acid Derived Biodegradable Elastomers

Biodegradable elastomers have recently found widespread application in many areas of biomedical engineering such as tissue engineering, drug delivery, and bioimaging. In particular, the recent developments in research have led to the creation of citric acid based polymers with enhanced mechanical properties, novel design strategies for crosslinking, nanoporous features, and unique photoluminescent capabilities. The present review will cover the recent patents involving citric acid derived biodegradable biomaterials within the field of biomedical engineering including poly (diol citrates) and their composites, crosslinked urethane-doped polyesters (CUPEs), poly (alkylene maleate citrates) (PAMCs), poly (xylitol-co-citrates) (PXC), and aliphatic biodegradable photoluminescent polymers (BPLPs). The synthesis, development, and applications of these novel polymers will be discussed along with the current trends and future developments in the biomaterials field.

Biomimetic Improvement of Electrochromic Properties of Indium Nitride

Indium nitride films with microvillus-like nanostructure were fabricated using reactive ion plating with glancing-angle deposition technique. Electrochromic properties of the biomimetic indium nitride films were significantly improved due to expansion of surface area and the nanoporous feature of the microvillus shape. Amplitude of color change agreed with the theoretical value estimated for a simplified structure model with an assumption that all terminating atoms on the nanostructured indium nitride surface behave as active sites for the electrochromic reaction.

Effects of a surfactant-templated nanoporous TiO2 interlayer on dye-sensitized solar cells

A 320 nm thick surfactant-templated nanoporous (STN) TiO2 layer prepared from block copolymer P123 [poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20] was used as an interlayer between a 21 μm thick mesoporous TiO2 layer and a transparent conducting oxide. The thin STN TiO2 interlayer had well-dispersed nanoporous features, which made it possible to adsorb dye molecules in the interlayer. In addition, it provided an enhanced electron lifetime, resulting in a reduced recombination rate and an increased diffusion length. The dye-sensitized solar cell with the thin STN interlayer resulted in a significantly increased overall energy conversion efficiency from 7.11% to 9.22% with an improvement of all parameters (short-circuit current, open circuit voltage, and fill factor).

Ultrathin Films and Hollow Shells with Pillared Architectures Fabricated via Layer-by-Layer Self-Assembly of Titania Nanosheets and Aluminum Keggin Ions

Inorganic multilayer films and hollow shells with pillared architectures have been fabricated layer-by-layer on spherical poly(methyl methacrylate) (PMMA) templates as well as flat substrates through the electrostatic self-assembly technique. Positively charged polyoxocations of aluminum Keggin ions were employed both as inorganic binder and as pillaring agent in electrostatic self-assembly with exfoliated unilamellar crystallites of Ti0.91O2, yielding new types of ultrathin films and core−shell composites. Ultraviolet−visible absorption spectra revealed progressive enhancement of absorbance with increasing deposition cycles, indicating the regular growth of multilayer assemblies of titania nanosheets and aluminum polyoxocations. Evolution of a Bragg peak with a periodicity of ca. 1.5 nm and its enhancement also supported the formation of nanostructured multilayer films and shells, accommodating aluminum polyoxocations in the nanosheet gallery. Depth X-ray photoelectron spectra confirmed their inorganic nature. Calcination at 400 °C produced ultrathin films and hollow shells with alumina pillars between the titania sheets. N2 adsorption results revealed a high specific surface area of 260 m2 g-1 and nanoporous feature for the pillared hollow spheres.