Nanoporous Substrates Research Articles

Achieving High Response of Poly (3-Hexylthiophene-2,5-Diyl) Molecules to Gaseous Ammonia Using Anodic Aluminum Oxide Nanoporous Substrate Operated Under 1 V

Achieving High Response of Poly (3-Hexylthiophene-2,5-Diyl) Molecules to Gaseous Ammonia Using Anodic Aluminum Oxide Nanoporous Substrate Operated Under 1 V

Controlled organosilica networks via metal doping for improved dehydration membranes with layered hybrid structures

• bis(triethoxysilyl)ethane (BTESE)-derived sols were doped with metal ions (Al and Zr) • Metal doped BTESE sols were coated on polymer support forming layered-hybrid structure. • Metal doped BTESE layered hybrid membranes improved PV dehydration performance. • Zr-BTESE showed water permeance > 10 -6 mol/(m 2 s Pa) with H 2 O/IPA > 10,000. A layered hybrid membrane consisting of an organosilica top layer on a polymeric nanoporous substrate was successfully fabricated using bis(triethoxysilyl)ethane (BTESE)-derived organosilica sols doped with metal ions (Al and Zr). These membranes were applied to the dehydration of aqueous alcohol solutions including methanol (MeOH), ethanol (EtOH) and isopropanol (IPA). Metal-doped BTESE sols and gels were characterized via dynamic light scattering analysis (DLS), Fourier Transform Infrared spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), the isotherms of N 2 sorption, laser scanning confocal microscopy (LSM), and scanning electron microscopy (SEM). During the dehydration of an IPA solution at 105 °C, the separation factors for Al-BTESE- and Zr-BTESE-derived membranes reached 8,000 and 10,000, respectively, which exceeded the separation factor for undoped BTESE membranes and indicates that doping with metal ions improves the dehydration performance of layered-hybrid membranes. In addition, Zr-BTESE-derived membranes prepared via the rinse method showed water permeance of 1.8 × 10 -6 mol m −2 s −1 Pa −1 , which is sufficiently high and compares favorably to that of polymer substrates. These membranes also showed a separation factor that was higher than 10,000. Correlations among the permeance ratios for H 2 O/MeOH, H 2 O/EtOH, and H 2 O/IPA were successfully predicted using modified gas translation (mGT) and bimodal pore models.

A simple and reliable approach for the fabrication of nanoporous silver patterns for surface-enhanced Raman spectroscopy applications

The fabrication of plasmonic nanostructures with a reliable, low cost and easy approach has become a crucial and urgent challenge in many fields, including surface-enhanced Raman spectroscopy (SERS) based applications. In this frame, nanoporous metal films are quite attractive, due to their intrinsic large surface area and high density of metal nanogaps, acting as hot-spots for Raman signal enhancement. In this paper, we report a detailed study on the fabrication of nanoporous silver-based SERS substrates, obtained by the application of two successive treatments with an Inductively Coupled Plasma (ICP) system, using synthetic air and Ar as feeding gases. The obtained substrates exhibit a quite broad plasmonic response, covering the Vis–NIR range, and an enhancement factor reaching 6.5 times, 10^7, estimated by using 4-mercaptobenzoic acid (4-MBA) as probe molecule at 532 nm. Moreover, the substrates exhibit a quite good spatial reproducibility on a centimeter scale, which assures a good signal stability for analytical measurements. Globally, the developed protocol is easy and cost effective, potentially usable also for mass production thanks to the remarkable inter-batches reproducibility. As such, it holds promise for its use in SERS-based sensing platforms for sensitive detection of targets molecules.

Vertical nanoporous GaN substrates for photonic engineering: Lu2O3:Eu single crystal thin films as an example

To improve the efficiency of light extraction, the vertical-oriented nanoporous (NP) GaN film as scattering medium as well as light-coupling component was prepared by electrochemical (EC) etching followed by annealing process. The Lu2O3:Eu film as fluorescence medium was deposited on the NP-GaN substrate via pulse laser deposition (PLD) method, which has out-of-plane epitaxial relationship of Lu2O3 (222) || GaN (0002). By changing etching and annealing conditions, the average pore diameter, pore density and pore sidewall roughness of NP-GaN are controlled. The experiment shows that the photoluminescence (PL) intensities and quantum efficiencies of epitaxial films are related to the pore density and sidewall roughness of NP-GaN substrates. Due to the scattering effect of nanopores and light-coupling inside Lu2O3:Eu films on the NP-GaN substrates, the PL intensities were enhanced 13–96% compared with that of the films on as-grown GaN substrates, although the crystal quality of the epitaxial film becomes worse with the increase of porosity of the substrates.

Nanoporous nickel thin film anode optimization for low-temperature solid oxide fuel cells

Thin film solid oxide fuel cells (TF–SOFCs) having anode–substrate nanostructure that was optimized for the low-temperature operation were fabricated. Nickel thin film anodes with four different anode thicknesses were deposited on anodic aluminum oxide templates, nanoporous substrates having two different pore sizes, by the sputtering method. Subsequently, a yttria-stabilized zirconia (YSZ) electrolyte and platinum cathode were deposited on them, which completed the entire fuel cell structure. The anode nanostructure of fuel cells in six combinations was analyzed by the cross-sectional view, surface microscopy method, and three-dimensional morphology observation. Those investigations enabled the anode nanostructure to be identified, such as the anode porosity and the roughness of the interface between anodes and electrolytes. Then, the six TF–SOFCs were electrochemically characterized in a 500 °C operating environment. The maximum power densities were obtained through the i–V–P curves, and the highest performance of 294.1 mW/cm2 was measured in the cell having a combination of 200 nm–sized porous aluminum anodic oxide (AAO) and 1200 nm–thick Ni anode. This showed up to 20.1% improvement over the other cells. EIS analysis showed that the optimized ohmic and faradaic resistance originated from each part of the unique TF–SOFC structure.

Template-directed synthesis of zeolitic imidazolate framework-8 derived Zn–Al layered double oxides decorated on the electrochemically anodized nanoporous aluminum substrate for thin film microextraction of chlorophenols followed by determination with high-performance liquid chromatography

In this work, hierarchical ZIF-8 coated anodized aluminum foil was prepared through in situ template-directed method without addition of any zinc salt. The hierarchical sorbent was synthesized by the formation of the final HZIF-8 on the previously created layered double oxide (LDO) template. The LDO template was created by calcining the firstly in situ prepared desired layered double hydroxide (LDH) precursor coated on the electrochemically anodized porous Al foil in an air atmosphere. The microextraction ability of the extracting device was studied through direct immersion thin film microextraction (DI-TFME). The extracted analytes were quantified by high-performance liquid chromatography equipped by UV detector (HPLC-UV). The present strategy was used for the simultaneous extraction and quantification of four selected chlorophenols (CPs) (as model analyte). The variables of the TFME were optimized using response surface methodology (Plackett-Burman and Box-Behnken design). Under the obtained optimum condition, the prepared film presented acceptable extraction properties including low limits of detection (0.03-0.22 µgL−1), good linear ranges (0.2–200 µgL−1, r2 > 0.9918) and satisfactory reproducibility (relative standard deviation, 3.6 < RSD < 5.8% for one film as inter- and intra-day RSD, 4.8 < RSD < 5.3% for film to film). Moreover, the obtained enrichment factors were in the range of 56-76. The kinetics and adsorption isotherm of the selected analytes adsorption to the prepared sorbent were also investigated. The maximum adsorption capacities of the selected analytes on the prepared sorbent were in the range of 26.4-80.1 mg g−1. The adsorption isotherm obeyed the Langmuir and Freundlich models. Moreover, the adsorption of the selected chlorophenols on the prepared film followed the pseudo-second-order kinetic model. Finally, the HZIF-8 film was utilized for the quantification of selected CPs in different types of water and wastewater samples. The results showed satisfactory relative recoveries (93–102%) and acceptable precisions (3.6 < RSD < 9.2%).

Surface Modification of Nanoporous Anodic Alumina during Self-Catalytic Atomic Layer Deposition of Silicon Dioxide from (3-Aminopropyl)Triethoxysilane.

Changes associated to atomic layer deposition (ALD) of SiO2 from 3-aminopropyl triethoxysilane (APTES) and O3, on a nanoporous alumina structure, obtained by two-step electrochemical anodization in oxalic acid electrolyte (Ox sample) are analysed. A reduction of 16% in pore size for the Ox sample, used as support, was determined by SEM analysis after its coverage by a SiO2 layer (Ox+SiO2 sample), independently of APTES or O3 modification (Ox+SiO2/APTES and Ox+SiO2/APTES/O3 samples). Chemical surface modification was determined by X-ray photoelectron spectroscopy (XPS) technique during the different stages of the ALD process, and differences induced at the surface level on the Ox nanoporous alumina substrate seem to affect interfacial effects of both samples when they are in contact with an electrolyte solution according to electrochemical impedance spectroscopy (EIS) measurements, or their refraction index as determined by spectroscopic ellipsometry (SE) technique. However, no substantial differences in properties related to the nanoporous structure of anodic alumina (photoluminescent (PL) character or geometrical parameters) were observed between Ox+SiO2/APTES and Ox+SiO2/APTES/O3 samples.

Nanoscale Venturi-Bernoulli Pumping of Liquids.

We use molecular dynamics simulations to show that the Venturi-Bernoulli effect can pump liquids at the nanoscale. In particular, we found that water flowing in an open reservoir close to a static substrate experiences a friction which converts its kinetic energy into breaking of hydrogen bonds. This water flowing under friction acquires a lower density, which can be used in pumping fluids positioned under a nanoporous substrate.

Interactions of an Imine Polymer with Nanoporous Silica and Carbon in Hybrid Adsorbents for Carbon Capture.

Efficient carbon capture from stationary point sources can be achieved using hybrid adsorbents comprising nanoporous substrates coated with imine polymers. The physical properties of the CO2-adsorbing, nanodispersed polymers are altered by their interactions with the substrate, which in turn may impact their capture capacity. We study silica and carbon nanoporous substrates with different pore morphologies that were impregnated with polymer imine with the goal of characterizing the polymer dispersions in the pores. For silica and carbon samples, the mean densities of confined poly(ethylene imine) (PEI) were measured as functions of polymer loading and temperature using small-angle neutron scattering. Strong densification is found for imine polymers imbibed in mesoporous carbon. PEI in nanoporous silica does not experience this strong densification. At high loadings, plugs form, preferably at the pore throats, and can reduce accessible porosity. CO2 capture measurements show that PEI interactions with the substrate play an important role. PEI in carbon shows the highest capture capacity at low temperatures and the lowest CO2 adsorption at high temperatures, making it well-suited for temperature swing adsorption applications.

Tuning dendritic structure at nanoporous alumina/aluminium interface for uniform electrodeposition of metals for nanocomposite coatings

Highly ordered nanoporous structures developed by anodising aluminium and its alloys have potential applications in various fields, including wear-resistant coatings in tribology. Filling nanopores with different metals and solid lubricants provide a nanocomposite coating which has a higher hardness. A major hurdle in developing the nanocomposite coatings is that a thick non-conducting barrier layer at the interface between the nanoporous alumina and aluminium substrate. Creating a conducting path at the interface between nanoporous alumina and aluminium without weakening the interfacial strength are expected to have significant advantages for developing tribological coatings. In this work, we systematically modified the interface by the voltage reduction process at different rates and created a dendritic structure at the interface. The dendritic structures growth at the interface is monitored by measuring the capacitance using an LCR meter. The capacitance exponentially decreased with increase in voltage reduction rate. The cross-sectional view of scanning electron microscopy images interface shows that the dendritic structure thickness linearly increases with a decrease in voltage reduction rate. After interface modification, the copper into the nanopores using pulse electrodeposition method. The scanning electron microscopy images show that the capacitance of 0.8–1.2 µF and ∼1 V/15 s voltage reduction rate gives nearly uniform filling of nanopores over a large area.

Correction to: Fabrication of gold‑silver bimetal nanoparticles/silicon nanoporous pillar array substrate and surface‑enhanced Raman scattering detection

A correction to this paper has been published: https://doi.org/10.1007/s00339-021-04396-x

Decimeter-Scale Atomically Thin Graphene Membranes for Gas-Liquid Separation.

Graphene holds great potential for fabricating ultrathin selective membranes possessing high permeability without compromising selectivity and has attracted intensive interest in developing high-performance separation membranes for desalination, natural gas purification, hemodialysis, distillation, and other gas-liquid separation. However, the scalable and cost-effective synthesis of nanoporous graphene membranes, especially designing a method to produce an appropriate porous polymer substrate, remains very challenging. Here, we report a facile route to fabricate decimeter-scale (∼15 × 10 cm2) nanoporous atomically thin membranes (NATMs) via the direct casting of the porous polymer substrate onto graphene, which was produced by chemical vapor deposition (CVD). After the vapor-induced phase-inversion process under proper experimental conditions (60 °C and 60% humidity), the flexible nanoporous polymer substrate was formed. The resultant skin-free polymer substrate, which had the proper pore size and a uniform spongelike structure, provided enough mechanical support without reducing the permeance of the NATMs. It was demonstrated that after creating nanopores by the O2 plasma treatment, the NATMs were salt-resistant and simultaneously showed 3-5 times higher gas (CO2) permeance than the state-of-the-art commercial polymeric membranes. Therefore, our work provides guidance for the technological developments of graphene-based membranes and bridges the gap between the laboratory-scale "proof-of-concept" and the practical applications of NATMs in the industry.

Fast Evaporation Enabled Ultrathin Polymer Coatings on Nanoporous Substrates for Highly Permeable Membranes

SummaryThin polymer coatings covering on porous substrates are a common composite structure required in numerous applications, including membrane separation, and there is a strong need to push the coating thicknesses down to the nanometer scale to maximize the performances. However, producing such ultrathin polymer coatings in a facile and efficient way remains a big challenge. Here, uniform ultrathin polymer covering films (UPCFs) are realized by a facile and general approach based on rapid solvent evaporation. By fast evaporating dilute polymer solutions spread on the surface of porous substrates, we obtain ultrathin coatings (down to ∼30 nm) exclusively on the top surface of porous substrates, forming UPCFs with a block copolymer of polystyrene-block-poly(2-vinyl pyridine) at room temperature or a homopolymer of poly(vinyl alcohol) (PVA) at elevated temperatures. Upon selective swelling of the block copolymer and crosslinking of PVA, we obtain highly permeable membranes delivering ∼2–10 times higher permeance in ultrafiltration and pervaporation than state-of-the-art membranes with comparable selectivities. We have invented a very convenient but highly efficient process for the direct preparation of defective-free ultrathin coatings on porous substrates, which is extremely desired in different fields in addition to membrane separation.

Binding enhancements of antibody functionalized natural and synthetic fibers.

Development of low cost biosensing using convenient and environmentally benign materials is important for wide adoption and ultimately improved healthcare and sustainable development. Immobilized antibodies are often incorporated as an essential biorecognition element in point-of-care biosensors but these proteins are costly. We present a strategy of combining convenient and low-cost surface functionalization approaches for increasing the overall binding activity of antibody functionalized natural and synthetic fibers. We demonstrate a simple one-step in situ silica NP growth protocol for increasing the surface area available for functionalization on cotton and polyester fabrics as well as on nanoporous cellulose substrates. Comparing this effect with the widely adopted and low cost plant-based polyphenol coating to enhance antibody immobilization, we find that both approaches can similarly increase overall surface activity, and we illustrate conditions under which the two approaches can produce an additive effect. Furthermore, we introduce co-immobilization of antibodies with a sacrificial “steric helper” protein for further enhancing surface activities. In combination, several hundred percent higher activities compared to physical adsorption can be achieved while maintaining a low amount of antibodies used, thus paving a practical path towards low cost biosensing.

Wetting dynamics of nanoliter water droplets in nanoporous media

HypothesisThe Lucas-Washburn (L-W) equation is the classical theory to describe the dynamics of spontaneous imbibition in single micro-channels and micro-scale porous media. However, for nanoliter droplets imbibition in nanoporous media, the L-W equation may not be suitable, due to the nanoscale liquid-solid interactions, e.g., contact line pinning and capillary condensation. In addition, for an intrinsically hydrophobic nanoporous substrate, spontaneous imbibition of a nanoliter droplet is hypothesized to occur if capillary condensation had occurred internally already. ExperimentsA nanoporous carbon scaffold was synthesized and used as a model nanoporous medium. A recently-developed micro-injection technique was used to generate a series of nanoliter water droplets (2.8–34 nL); the entire wetting dynamics (i.e., apparent contact angle and droplet volume as a function of time) were observed inside an environmental scanning electron microscope. FindingsThe L-W equation does not describe the wetting dynamics of nanoliter water droplets in nanoporous media. A new theoretical model is developed to characterize the corresponding dynamics. It is demonstrated that, even for an intrinsically hydrophobic nanoporous substrate, spontaneous imbibition of a nanoliter droplet can occur if capillary condensation had occurred internally already.

Nano-PAA-CuCl2 Composite as Fenton-Like Reusable Catalyst to Enhanced Degrade Organic Pollutant MB/MO

The treatment of organic dye contaminants in wastewaters has now becoming more imperative. Fenton-like degradation of methylene blue (MB) and methyl orange (MO) in aqueous solution was investigated by using a nanostructure that a layer of CuCl2 nanoflake film grown on the top surface of nanoporus anodic alumina substrate (nano-PAA-CuCl2) as catalyst. The new nano-PAA-CuCl2 composite was fabricated with self-assembly approach, that is, a network porous structure film composed of CuCl2 nanoflake grown on the upper surface of nanoporous anodic alumina substrate, and the physical and chemical properties are characterized systematically with the X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and high-resolution transmission electron microscopy (HRTEM), Energy Dispersive Spectrometer (EDS), X-ray photoelectron spectroscopy (XPS). The experimental results showed that the nano-PAA-CuCl2 catalyst presented excellent properties for the degradation of two typical organic pollutants such as MB and MO, which were almost completely degraded with 8 × 10−4mol/L nano-PAA-CuCl2 catalyst after 46 min and 60 min at reaction conditions of H2O2 18 mM and 23 mM, respectively. The effects of different reaction parameters such as initial pH, H2O2 concentration, catalyst morphology and temperature were attentively studied. And more, the stability and reusability of nano-PAA-CuCl2 were examined. Finally, the mechanism of MB and MO degradation by the nano-PAA-CuCl2/H2O2 system was proposed, based on the experimental data of the BCA and the temperature-programmed reduction (H2-TPR) and theoretical analysis, the reaction kinetics belonged to the pseudo-first-order equation. This new nanoporous composite material and preparation technology, as well as its application in Fenton-like reaction, provide an effective alternative method with practical application significance for wastewater treatment.

Fabrication of gold-silver bimetal nanoparticles/silicon nanoporous pillar array substrate and surface-enhanced Raman scattering detection

A novel gold-silver/silicon nanoporous pillar array substrate was prepared by a droplet-confined deposition technique and a replacement reaction method. Its surface-enhanced Raman scattering behaviors to R6G were studied. The substrate has not only high detection sensitivity, but also good signal uniformity and stability. The SERS detection limit is down to 10–13 M. The enhancement factor is 2.9 × 105 and the maximal relative standard deviation is only 9.2% at 10–7 M R6G. Moreover, it has a well stability with a slight drop in the spectrum intensity after placed for 35 days in air. This work suggested that the novel substrate has a potential application in environmental detection.

Stability improvement for dried droplet pretreatment by suppression of coffee ring effect using electrochemical anodized nanoporous tin dioxide substrate.

A novel nanoporous analytical platform is reported to improve the stability of the dried droplet method (DDM). This nanoporous platform was made of tin dioxide (Np SnO2) substrate by electrochemical anodization from tin (Sn) slide. The DDM is a widely used sample pretreatment in analytical chemistry that involves placing a droplet of solution onto the substrate and drying for analytical testing. However, during the droplet drying process, the solutes would converge at the droplet edge and cause inhomogeneous solutes distribution. This is the coffee ring effect (CRE). The Np SnO2 has irregular nanopores, which allows droplet solutions to penetrate into the substrate rather than spreading out, effectively suppressing CRE. Theoretical models were built to explain the formation of CRE on blank tin (Sn) substrate and suppression of CRE on Np SnO2. Better results were obtained in detecting lithium (Li) using the Np SnO2 by laser-induced breakdown spectroscopy (LIBS). The line scanning results indicated that the Li emission line (670.8nm) intensities on Np SnO2 substrate had lower relative standard deviation (RSD = 3.3%) than those on Sn substrate (RSD = 31.5%), which illustrate suppression of CRE and stability improvement on Np SnO2 substrate. Furthermore, Licalibration curves were built for LIBS with DDM. The curve using Np SnO2 substrate had better linearity (R2 = 0.997), higher precision (RSD = 4.2%), and higher sensitivity (LOD = 0.13mg/L) than that by Sn substrate (R2 = 0.954, RSD = 17%, and LOD = 1.21mg/L). All in all, the anodic Np SnO2 substrate can suppress CRE in DDM and hence improve the stability and precision of subsequent analysis. Graphical abstract.

Growing vertical aligned mesoporous silica thin film on nanoporous substrate for enhanced degradation, drug delivery and bioactivity

Mesoporous silica thin film has been widely used in various fields, particularly the medical implant coating for drug delivery. However, some drawbacks remain with the films produced by traditional method (evaporation-induced self-assembly, EISA), such as the poor permeability caused by their horizontal aligned mesochannels. In this study, the vertical aligned mesoporous silica thin film (VMSTF) is uniformly grown alongside the walls of titania nanotubes array via a biphase stratification growth method, resulting in a hierarchical two-layered nanotubular structure. Due to the exposure of opened mesopores, VMSTF exhibits more appealing performances, including rapid degradation, efficient small-molecular drug (dexamethasone) loading and release, enhanced early adhesion and osteogenic differentiation of MC3T3-E1 cells. This is the first time successfully depositing VMSTF on nanoporous substrate and our findings suggest that the VMSTF may be a promising candidate for bone implant surface coating to obtain bioactive performances.

Immobilization of Photocatalytic ZnO Nanopowders Using Anodized Nanoporous Alumina Substrates

Nanoporous Al₂O₃ substrates with an average pore size of about 150 nm were prepared via anodization of Aluminum plates. Depending on the anodization condition, the surface area of the anodized Al₂O₃ was increased more than six-fold. Solution-combusted ZnO nanopowders were prepared as a function of fuel/oxidant ratios. At a fuel/oxidant ratio of 0.8, ZnO powder showed excellent powder characteristics such as average particle sizes of 30 nm and spherical shape. Electrical properties of SCM ZnO nanopowders with different fuel/oxidant ratios were investigated by Hall measurement. The carrier concentration of SCM ZnO nanopowders at the fuel/oxidant ratio of 0.8, was the highest, three-fold higher than that of any commercial ZnO powders. Using spray coating, these nanopowders were coated onto Al₂O₃ substrates for immobilization. To evaluate the photo-catalytic effect, Ag ions were removed from the wastewater via photocatalysis. The photocatalytic efficiency with the SCM ZnO nanopowders on nanoporous Al₂O₃ substrates was 2.5-fold higher than that with the SCM ZnO nanopowders on normal Al₂O₃ substrates. However, commercial zinc oxide powders did not show any photocatalytic phenomena. The large difference in photocatalytic efficiency was probably attributed to the characteristics of SCM ZnO nanopowder and the large surface area of anodized Al₂O₃.