Nanoporous Surface Research Articles

Investigation of nanotopography on SOCE mediated cell migration via live-cell

The exploration of cell response to nanotopography has attracted considerable attentions for years. This article focuses on the influence of nanotopography on the intracellular Ca2+ dynamics, the most ubiquitous but ignored second messenger. The classic titanium nanotubes (NT) were fabricated by anodization to formulate nanoporous surfaces. Firstly, the store operative calcium entry (SOCE) in endoplasmic reticulum (ER) and functional Ca2+ release-activated Ca2+ (CRAC) channels were significantly enhanced on NT surfaces that revealed by live-cell Ca2+ imaging and fluorescence resonance energy transfer (FRET) identification of orai1-stim1 connection. To investigate the potential implication of Ca2+ elevation, the dynamic cell migration trajectory was monitored by a self-made holder, which could not only be suitable for the opaque implant surface but also guarantee the focus fields identical during samples shifting. The cell migration on NT surface was more vigorous and rapid, which was correlated with higher focal adhesion proteins expression, Ca2+-dependent calpain activity and stim1 level. In conclusion, this study has confirmed the novel ER Ca2+ hemostasis pathway on nanosurfaces and its crucial role in cell migration regulation, which may help for more biofavorable implant surface design.Graphical

Effect of dense packed micro-/nano-porous thin film surfaces developed by a combined method of etching, electrochemical deposition and sintering on pool boiling heat transfer performance

Effect of dense packed micro-/nano-porous thin film surfaces developed by a combined method of etching, electrochemical deposition and sintering on pool boiling heat transfer performance

Ligand presentation inside protein crystal nanopores: Tunable interfacial adhesion noncovalently modulates cell attachment

Protein crystals with sufficiently large solvent pores can non-covalently adsorb polymers in the pores. In principle, if these polymers contain cell adhesion ligands, the polymer-laden crystals could present ligands to cells with tunable adhesion strength. Moreover, porous protein crystals can store an internal ligand reservoir, so that the surface can be replenished. In this study, we demonstrate that poly (ethylene glycol) terminated with a cyclic cell adhesion ligand peptide (PEG-RGD) can be loaded into porous protein crystals by diffusion. Through atomic force microscopy (AFM), force-distance correlations of the mechanical interactions between activated AFM tips and protein crystals were precisely measured. The activation of AFM tips allows the tips to interact with PEG-RGD that was pre-loaded in the protein crystal nanopores, mimicking how a cell might attach to and pull on the ligand through integrin receptors. The AFM experiments also simultaneously reveal the detailed morphology of the buffer-immersed nanoporous protein crystal surface. We also show that porous protein crystals (without and with loaded PEG-RGD) serve as suitable substrates for attachment and spreading of adipose-derived stem cells. This strategy can be used to design surfaces that non-covalently present multiple different ligands to cells with tunable adhesive strength for each ligand, and with an internal reservoir to replenish the precisely defined crystalline surface.

The effect of nanopores on the mechanism of martensitic transformation in pure iron during the heating-cooling cycle: A molecular dynamics study

Numerous molecular dynamics (MD) simulations have been performed to investigate the effect of the nanopores on the martensitic transformation (MT) of pure iron (Fe) during the heating-cooling cycle. As per the simulation results, nanopores can obviously affect the difficulty on MT during the cooling process in two ways: On the one hand, the volume ratio of nanopores to simulation box model (Rp/b) can influence the distribution configuration of stacking fault (SF) to change the type of austenite microstructure during the heating process owing to the obstruction of the nanopores on the dislocation slip. The effect of nanopores is not obvious when Rp/b is less than 2.22 %. The main type of austenitic changes from defect-free/simple-SF types to the intersecting-SF type and, finally, to the dislocation-cell type with an increase in Rp/b from 2.22 % to 17.9 %. The dislocations in intersecting-SF type and dislocation-cell type austenitic microstructures can provide the nucleation site of MT, thus increasing the MT temperature. On the other hand, the high surface energy of the nanopores caused by the incomplete atomic lattice can provide the necessary energy for the nucleation of martensite, which then promotes the occurrence of MT during the cooling process. When the nanopores intersect with the dislocation wall in dislocation-cell type austenitic microstructure, martensite nucleates at the nanopores surface and then grows along the dislocation wall. In the previous investigation of selective laser melting martensitic steel, the nanopore in the microstructure was generally believed harmful to the mechanical property of specimen; however, in this study, it has been observed to promote the MT during solution-quenching heat treatment, which improves the mechanical property by improving the content of martensitic phase. This provides a new perspective in determining the significance of nanopores in microstructures.

Study on the slip behavior of CO2-crude oil on nanopore surfaces with different wettability

Unconventional reservoirs are characterized by a significant amount of micro and nanopores, which pose a critical challenge in accurately assessing the microscopic fluid transport behaviors to enhance oil and gas recovery in such reservoirs. CO2 injection is a promising recovery method for unconventional resources, hence the transport mechanism of CO2-crude oil at the nanoscale deserves further exploration. In this work, the flow and transport behaviors of CO2 and multicomponent crude oil in hydrophilic, neutral, and hydrophobic nanopores were investigated by the molecular dynamics simulation (MD) method. The CO2-crude oil shows a negative slip flow on hydrophilic surfaces, while it has a slip flow on neutral and hydrophobic surfaces. By illustrating the distribution structure of each component in the fluid and the solid-liquid interaction energy, the inherent causes of the slip mechanism of different wettability surfaces were revealed. The transport capacity and permeability of CO2-crude oil in the pores with different wettability were investigated. Modifying the Hagen-Poiseuille equation based on slip characteristics can effectively improve the prediction ability of nanopore permeability. This study is helpful to understand the flow and slip behavior of CO2-crude oil in nanopores of unconventional reservoirs, which provides a theoretical basis for accurately predicting the migration of reservoir fluid in nanopores.

Probing nanopore surface chemistry through real-time measurements of nanopore conductance response to pH changes.

We developed a flow cell apparatus and method for streamlined, real-time measurements of nanopore conductance (G) in response to pH changes. By time-resolving the measurements of interfacial kinetics, we were able to probe nanopore surface coating presence and properties more thoroughly than in our previous work. Nanopores have emerged as a prominent tool for single-molecule sensing, characterization, and sequencing of DNA, proteins, and carbohydrates. Nanopore surface chemistry affects analyte passage, signal characteristics, and sensor lifetime through a range of electrostatic, electrokinetic, and chemical phenomena, and optimizing nanopore surface chemistry has become increasingly important. Our work makes nanopore surface chemistry characterizations more accessible as a complement to routine single-pH conductance measurements used to infer nanopore size. We detail the design and operation of the apparatus and discuss the trends in G and capacitance. Characteristic G vs pH curves matching those obtained in previous work could be obtained with the addition of time-resolved interfacial kinetic information. We characterized native and chemically functionalized (carboxylated) silicon nitride (SiNx) nanopores, illustrating how the method can inform of thin film compositions, interfacial kinetics, and nanoscale chemical phenomena.

CO2 electroreduction in aqueous and acetonitrile solutions on porous cathode fabricated by anode dezincification of CuZn

The rates of the CO2 electrochemical reduction were determined on porous cathodes formed by electrochemical dealloying of CuZn under different regimes of selective anodic dezincification of brass. It was established that the formation of a porous surface proceeds in two following stages: 1) the dissolution of Zn from the CuZn mainly along the grain boundaries with the formation of submicron crevices between them, and 2) electrochemical dezincification of brass grains and formation of nanopores. The zinc content in the nanoporous copper surface is less than 1%. It was proved that anodically dezincified brass porous cathodes demonstrate a significantly higher CO2 reduction current on their surface than smooth copper and brass surfaces. For instance, in aqueous solutions, at an electrode potential of –1.5 V, the value of cathode current density on porous Cu cathodes is between 5 to 9 mAcm–2, while it is only 2.5 and 1.5 mAcm–2 on smooth Cu and CuZn cathodes, respectively. A similar trend is observed in an acetonitrile environment, where the current density of the CO2 electroreduction at the electrode potential of –3.0 V is 22 to 27 mAcm–2, 15 mAcm–2, and 18 mAcm–2 on porous cathodes, Cu cathode, and CuZn cathode, respectively. As the pore size decreases from submicron to submicron-nanosized, there is a tendency for an increase in cathodic currents by approximately 80% and 25% in aqueous and in acetonitrile solutions, respectively. Additionally, CO2 recovery on porous cathodes remains stable during long-term electrolysis at an electrode potential below –1.5 V.

Simulation Study of the Effect of Nanoporous Surfaces on the Adhesion Properties of Cross-Linked Polymer Networks.

We have investigated the effect of surface nanopores on the adhesion behavior between cross-linked polymer networks and metal substrates by molecular dynamics simulations. By increasing the cross-linking ratio of the polymer network, the fracture behavior in tensile mode changed from cohesive failure to interfacial failure. In the case of polymers without cross-links, the breaking strengths were almost the same for systems with flat and porous metal substrates. Conversely, in the case of cross-linked polymer networks, the tensile behavior for the porous metal substrates depended on the cross-linking ratio and structure of the polymer chains. For polymer networks consisting of long polymer chains, the force curves in extension mode before the yield points were almost the same for the systems regardless of the surface roughness caused by nanopores. Meanwhile, for highly cross-linked resin networks consisting of short rigid molecules, the yielding strength of the porous metal surfaces showed slightly higher values than that of the flat metal surfaces. The simulation results revealed that the adhesion behavior between cross-linked polymer networks and rough metal surfaces is related not only to the interfacial area but also to the detailed networking topology of the polymers.

Piranha-etched titanium nanostructure reduces biofilm formation in vitro

ObjectivesNano-modified surfaces for dental implants may improve gingival fibroblast adhesion and antibacterial characteristics through cell-surface interactions. The present study investigated how a nanocavity titanium surface impacts the viability and adhesion of human gingival fibroblasts (HGF-1) and compared its response to Porphyromonas gingivalis with those of marketed implant surfaces.Material and methodsCommercial titanium and zirconia disks, namely, sandblasted and acid-etched titanium (SLA), sandblasted and acid-etched zirconia (ZLA), polished titanium (PT) and polished zirconia (ZrP), and nanostructured disks (NTDs) were tested. Polished titanium disks were etched with a 1:1 combination of 98% H2SO4 and 30% H2O2 (piranha etching) for 5 h at room temperature to produce the NTDs. Atomic force microscopy was used to measure the surface topography, roughness, adhesion force, and work of adhesion. MTT assays and immunofluorescence staining were used to examine cell viability and adhesion after incubation of HGF-1 cells on the disk surfaces. After incubation with P. gingivalis, conventional culture, live/dead staining, and SEM were used to determine the antibacterial properties of NTD, SLA, ZLA, PT, and ZrP.ResultsEtching created nanocavities with 10–20-nm edge-to-edge diameters. Chemical etching increased the average surface roughness and decreased the surface adherence, while polishing and flattening of ZrP increased adhesion. However, only the NTDs inhibited biofilm formation and bacterial adherence. The NTDs showed antibacterial effects and P. gingivalis vitality reductions. The HGF-1 cells demonstrated greater viability on the NTDs compared to the controls.ConclusionNanocavities with 10–20-nm edge-to-edge diameters on titanium disks hindered P. gingivalis adhesion and supported the adhesion of gingival fibroblasts when compared to the surfaces of currently marketed titanium or zirconia dental implants.Clinical relevanceThis study prepared an effective antibacterial nanoporous surface, assessed its effects against oral pathogens, and demonstrated that surface characteristics on a nanoscale level influenced oral pathogens and gingival fibroblasts.Clinical trial registration: not applicable

(Invited) harnessing the Barrier Oxide Layer of Nanoporous Anodic Alumina for Iontronic Sensing

The hemispherical barrier oxide layer (BOL) closing the tips of hexagonally distributed arrays of cylindrical nanochannels in nanoporous anodic alumina (NAA) membranes is structurally engineered by anodizing aluminum substrates in three distinct acid electrolytes at their corresponding self-ordering anodizing potentials. These nanochannels display a characteristic ionic current rectification (ICR) signal between high and low ionic conduction states, which is determined by the thickness and chemical composition of the BOL, and the pH of the ionic electrolyte solution. Rectification efficiency of ionic current associated with the flow of ions across the anodic BOL increases with its thickness, under optimal pH conditions. The inner surface of nanopores in NAA membranes was chemically modified with thiol-terminated functional molecules. The resultant NAA-based iontronic system provides a model platform to selectively detect gold metal ions (Au3+) by harnessing dynamic ICR signal shifts as the core sensing principle. The sensitivity of the system is proportional to the thickness of the barrier oxide layer, where NAA membranes produced in phosphoric acid at 195 V with a BOL thickness of 232 ± 6 nm achieve the highest sensitivity and low limit of detection in the sub-picomolar range. This study provides exciting opportunities to engineer NAA structures with tailorable ICR signals for specific applications across iontronic sensing and other nanofluidic disciplines. Figure 1

(Invited) tamm Plasmon Resonance Sensors Based on Nanoporous Anodic Alumina Photonic Crystals

Nanoporous Anodic Alumina (NAA) is a material with growing interest in nanotechnology and for biological and medical applications. It is a cost-effective nanostructured material obtained by the electrochemical etching of aluminum in acidic electrolytes at the adequate conditions of applied voltage or current, temperature and electrolyte composition [1-4]. The precise control over the diameter of the nanopore allows to create periodic variations of nanopore’s diameter in deep and obtain different photonic crystals e.g.., Gradient-index filters, microcavities, Distributed Bragg Reflectors, etc [5-6]. The optical properties of NAA depend on its nanoporous structure and of its functionalized surface. NAA can be used to fabricate hybrid photonic structures by gold coating on nanoporous anodic alumina photonic crystals surface (NAA-PCs) [7]. In this metal-dielectric photonic structure, we can observe effects of an enhancement of the surface plasmon resonance due to absorption of the light at the interface of metallic layer and the NAA photonic crystal.Tamm plasmon resonance (TPR) can be tuned by engineering the properties and characteristics of the metal film and the porous photonic structure, providing new opportunities to achieve unique plasmonic−photonic structures for different applications (optical switching, lasing, light emission, surface-enhanced spectroscopy, and sensing). One interesting application of TPR is the use as a sensing platform taking advantage of its exceptional optical properties to confine/amplify the light-matter interactions [8-9]. The sensing performance of TPR-NAA−PCs is assessed by the infiltration of their structure with analytical solutions, producing a spectral shift in the Tamm plasmonic resonance. In this work, we evaluate the structural geometry and the optical properties of TPR-NAA-PCs and the assessment of TPR-NAA-PCs as a sensing platform.Figure 1a shows the reflectance spectrum for a TPR-NAA–PCs structure. The spectrum shows the photonic bandgap and the absorption narrow-line associated with the resonant recirculation of light within the plasmon-photonic system. Figure 1b shows the sensing performance of TPR-NAA-PCS. Red-shift on the position of the TPR-NAA-PCs is observed due to the refractive index variation when the nanopores are infiltrated of different analytical solutions (water- ethylene glycol)AcknowledgmentsThis work was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN/FEDER) PDI2021- 128342OB-I00, by the Agency for Management of University and Research Grants (AGAUR) ref. 2017- SGR-1527, COST Action 20126 - NETPORE and by the Catalan Institution for Research and Advanced Studies (ICREA) under the ICREA Academia Award.

Characterization of dealloying and associated stress corrosion cracking: The effect of crystallographic orientation

Selective dissolution (dealloying) of more reactive elements from a solid solution alloy can result in the formation of a nanoporous surface layer enriched in the more noble elements. For example, in Alloy 800 (wt.% Fe-32Ni-21Cr), a remnant nanoporous Ni-rich film is formed following the selective dissolution of Fe and Cr in boiling 50 wt.% NaOH caustic solutions (135–140 °C). This surface film has been proposed to act as a precursor to stress corrosion cracking (SCC) by a cleavage mechanism. This study investigates the effect of crystallographic orientation on the characteristics of a dealloyed layer (i.e., thickness and size of ligaments/pores) formed on Alloy 800. Electron backscattered diffraction (EBSD) is used to correlate grain orientation with the geometry and morphology of the dealloyed layer formed in the boiling caustic environment. Results indicate that the dealloyed layer formed on grains with planes close to the {111} family on the sample surface, has a finer geometry (i.e., a thinner layer compared with other grain orientations and consisting of smaller diameter ligaments). Further SCC experiments on Alloy 800 specimens revealed a lower density of cracks initiated from surface planes that were close to {111}, confirming a link between dealloyed layer geometry, texture, and SCC.

Hydrophilicity degradation and steam-induced rewetting during capillary-fed boiling

Capillary-fed evaporation/boiling is a crucial process that occurs within two-phase heat transfer devices. Herein, we delve into the capillary-fed boiling performance of a grooved wick with an upper width of 200 μm and a depth of 150 μm fabricated by ultrafast laser micromachining and observe a substantially 51.8% reduction in critical heat flux (CHF), from 145.0 ± 3.3 W/cm2 to 70.1 ± 2.9 W/cm2, following five boiling cycles. Comprehensive experimental investigations are conducted to gain insights into the underlying mechanisms. Our analyses confirm that the diminished CHF arises from the hydrophilicity degradation of the evaporator, attributed to the surface adsorption of airborne organics after the dry-out. The superhydrophilic evaporator becomes highly hydrophobic with static contact angles (CAs) greater than 140° after five boiling cycles. Liquid wicking in subsequent boiling tests initiates through a steam-induced rewetting process. Moreover, we present compelling evidence that the undesired hydrophilicity degradation is effectively mitigated on nanoporous surfaces. Consequently, a microgroove-nanoparticle composite wick successfully retains its original boiling performance during repeated boiling tests. These findings enhance the understanding of capillary-fed boiling performance and offer promising avenues for the design of high-performance wicks tailored for ultrathin two-phase heat transfer devices.

Electroosmotic flow, ionic current rectification, and selectivity of a conical nanopore modified with a pH-regulated polyelectrolyte layer: Influence of functional groups profile

Nanopores functionalized with polyelectrolyte (PE) brushes on their surface are widely used to improve the performance of solid-state nanopore-based devices. Since the profile of the functional groups, and therefore, fixed charge density, inside PE layer can be influenced by surrounding conditions and the way a nanopore is modified, it is usually nonuniformly distributed. However, a theoretical model taking account of the presence of a PE layer on the nanopore surface assumes that its functional groups are uniformly distributed. In this study we consider a conical nanopore surface modified with a pH-regulated PE layer. Two types of PE layer are considered: the functional groups are clustered near the PE-liquid interface (type 1), and near the nanopore surface (type 2). We theoretically study the influence of pH, types of PE layer, and bulk salt concentration on the ion transport behavior of the nanopore, and the associated mechanisms are discussed. The dependence of the average electroosmotic flow on relevant driving force and resistive force, including shear stress and drag, is analyzed. The influence of the types of PE layer on the I−V, rectification, and selectivity behaviors of the nanopore depends highly on the levels of pH and applied potential. The larger diffusion flux of type2 polyelectrolyte layer is the most important factor affecting current performance. Knowing the rectification behavior of a nanopore is helpful for estimating the solution pH and understanding the profile of the functional groups in PE. A reversal in selectivity is observed when both pH and bulk salt concentration are low, which can be attributed to that the ionic flux is dominated by H+.

Development of highly sensitive relative humidity sensor based on nanoporous PCPDTBT thin film

A novel type of capacitive humidity sensor with surface-type electrode geometry is presented in the present study. The high sensitivity and significantly high bandwidth associated with this planar-type humidity sensor (Al/PCPDTBT/Al) allow the facile and reliable estimation of ambient humidity. The use of a polymer sensing material Poly[2,6-(4,4-bis-(2-ethylhexyl)− 4 H-cyclopenta[2,1-b;3,4-b՛]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) with hierarchical nanoporous surface morphology and large surface/volume ratio ensures the sensor’s stable performance coupled with swift response to ambient humidity changes. Specifically, at a relatively lower frequency bias signal (i.e., 1 kHz), a fairly higher order of humidity sensitivity has been observed, i.e., 415.07 pF/%RH. While, sensitivities at significantly higher AC signal frequencies (i.e., 10 and 100 kHz) have been experimentally determined to be 345.18 pF/%RH and 154.72 pF/%RH, respectively. Likewise, the resistive sensitivity of the humidity sensor has been estimated to be − 3624.88 kΩ/%RH, − 2381.11 kΩ/%RH and − 1338.14 kΩ/%RH, at 1, 10 and 100 kHz test frequencies, respectively. The operating mechanism of the capacitive humidity sensor relies on an increase in the dielectric constant of the PCPDTBT active sensing layer accompanied by the rise in the ambient humidity levels. In addition to enhanced bandwidth and improved capacitive and resistive sensitivity, the mean response & recovery time of the fabricated device have been recorded to be ∼ 4 min, 17 s and ∼8 min, 43 s, respectively.

Potential and motion design of droplets in a wetting-programable nanoporous surface

In this study, we design a wetting-programable method to create a surface channel for droplets. Superhydrophilic channels can be designed and erased reversibly by selectively masking the wetting and prewetting process on superhydrophobic silicone surfaces with microgroove and nanoporous structures fabricated using a micromachining technique. We found that droplets in this flow channel present a complex wetting behavior. The surface that undergoes infiltration by wetting and prewetting transitions from being a superhydrophobic surface to becoming a superhydrophilic surface. To understand the dynamics of droplet exploration, we measured the spreading distance of the droplet’s leading edge and the spontaneous capillary flow (SCF). The final spreading length of the droplet’s leading edge was also recorded. We found that increasing the prewetting volume enhances the final spreading distance of the droplet’s leading edge and the average SCF speed. Prewetting minimizes the apparent contact angle and pinning, promoting superhydrophilicity and increasing the droplet mobility. To further enhance our control over liquid transport, we incorporated vertical vibration as an active approach to regulate the programmed transport of droplets. We observed a substantial extension in the final spreading distance of the droplet’s leading edge. This extension was attributed to the effective overcoming of the pinning phenomena caused by the application of vertical vibration. With the above-mentioned methods, we achieve guided motion and multi-droplet sequence mixing of droplets with the designed channel shapes. Our results suggest how the wetting behavior dynamics of a multi-level structural surface are affected by prewetting liquid and vertical vibration. This provides insight into the wetting mechanism on porous superhydrophobic/superhydrophilic material.

Effect of Silane Monolayers and Nanoporous Silicon Surfaces on the Matrix-Assisted Laser Desorption Ionization Mass Spectrometry Detection of Sepsis Metabolites Biomarkers Mixed in Solution.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF MS) is a promising strategy for clinical diagnosis based on metabolite detection. However, several bottlenecks (such as the lack of reproducibility in analysis, the presence of an important background in low-mass range, and the lack of organic matrix for some molecules) prevent its transfer to clinical cases. These limitations can be addressed by using nanoporous silicon surfaces chemically functionalized with silane monolayers. In the present study, sepsis metabolite biomarkers were used to investigate the effects of silane monolayers and porous silicon substrates on MALDI-ToF MS analysis (signal-to-noise value (S/N), relative standard deviation of the S/N of triplicate samples (STDmean), and intra-substrates uniformity). Also, the impact of the physicochemical properties of metabolites, with different isoelectric points and hydrophobic-hydrophilic balances, was assessed. Four different silane molecules, with various alkyl chain lengths and head-group charges, were self-assembled in monolayers on plane and porous silicon surfaces. Their surface coverage and conformity were investigated by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The seven metabolites detected on the stainless-steel target plate (lysophosphatidylcholine, caffeine, phenylalanine, creatinine, valine, arginine, and glycerophosphocholine) are also detected on the silanized and bare, plane and porous silicon surfaces. Moreover, two metabolites, glycine and alanine, which are not detected on the stainless-steel target plate, are detected on all silanized surfaces, except glycine which is not detected on CH3 short-modified porous silicon and on the bare plane silicon substrate. In addition, whatever the metabolites (except phenylalanine and valine), at least one of the silicon surfaces allows to increase the S/N value in comparison with the stainless-steel target plate. Also, the heterogeneity of matrix crystallization features is linked to the STDmean which is poor on the NH3+ monolayer on plane substrate and better on the NH3+ monolayer on porous substrate, for most of the metabolites. Nevertheless, matrix crystallization features are not sufficient to systematically get high STDmean and uniformity in MALDI-ToF MS analysis. Indeed, the physicochemical properties of metabolites and surfaces, limitations in metabolite extraction from the pores, and improvement in metabolite desorption due to the pores are shown to significantly impact MS analysis. In particular, in the case of the most hydrophobic metabolites studied, the highest S/N values and the best STDmean and uniformity (the lowest values) are reached by using porous substrates, while in the case of the most hydrophilic metabolites studied, plane substrates demonstrated the highest S/N and the lowest STDmean. No clear trend of surface chemistry was evidenced.

Compact tubular carbon-based membrane bioreactors for the anaerobic decolorization of azo dyes

This research investigates a highly efficient compact tubular ceramic-supported carbon-based membrane reactor integrated with anaerobic biodegradation to decolorize the azo dyes. Two carbon-based membranes, produced using Matrimid 5218 polyimide and graphene oxide solutions, are evaluated for the comparative color removal of three structurally different azo dyes, Acid Orange 7 (AO7), Reactive Black 5 (RB5), and Direct Blue 71 (DB71). Based on FESEM microscopic images, the average pore size of the tubular ceramic-supported carbonized membrane (TCSCM) was approximately 25 nm, while for the tubular ceramic-supported graphene oxide membrane (TCSGOM), it was 12 nm. Additionally, TCSCM had a thinner layer at only 1.10 µm, while TCSGOM was slightly thicker at 2.11 µm. These features influenced the permeate flux of the membrane, in which the TCSGOM exhibited lower permeate flux (18.2 L·m−2·h−1) than the TCSCM (45.6 L·m−2·h−1). However, the anaerobic decolorization results indicated that the TCSGOM bioreactor (B-TCSGOM) was more efficient and effective at removing color from all dye solutions than the TCSCM bioreactor (B-TCSCM) over a wide range of feed concentrations. In both reactors, the highest decolorization was achieved at low feed concentration (50 mg·L−1), and removal was 94 % for AO7, 90 % for RB5, and 88 % for DB71 in B-TCSGOM, whereas 88 %, 85 %, and 69 %, respectively, in B-TCSCM. These suggest that the robust conductive nanoporous surface of B-TCSGOM makes it more effective at removing different azo dye solutions from wastewater.

Metal-Organic Framework Sub-Nanochannels Formed inside Solid-State Nanopore with Proton Ultra-High Selectivity.

Metal-Organic frameworks (MOFs) have the advantages of high porosity, angstrom-scale pore size, and unique structure. In this work, a kind of MOFs, UiO-66 and its derivatives (including aminated UiO-66-(NH2 )2 and sulfonated UiO-66-(NH-SAG)2 ), were constructed on the inner surface of solid-state nanopores for ultra-selective proton transport. UiO-66 and UiO-66-(NH2 )2 nanocrystal particles were in-situ grown at the orifice of glass nanopores firstly, which were used to investigate the ionic current responses in LiCl and HCl solutions when the monovalent anions (Cl- ) were unchanged. Compared with UiO-66-modifed nanopores, the aminated MOFs modification (UiO-66-(NH2 )2 ) can improve the proton selectivity obviously. However, when the UiO-66-(NH-SAG)2 nanopore is prepared by further post-modification with sulfo-acetic acid, lithium ions can hardly pass through the channel, and the interaction between protons and sulfonic acid groups can promote the transport of protons, thus achieving ultra-high selectivity to protons. This work provides a new way to achieve sub-nanochannels with high selectivity, which can widely be used in ion separation, sensing and energy conversion.

Rapid detection of SARS-CoV-2 genetic targets using nanoporous waveguide based competitive displacement assay

Rapid detection of unlabeled SARS-CoV-2 genetic target was demonstrated using a competitive displacement hybridization assay made by a nanostructured anodized alumina oxide (AAO) membrane. The assay applied the toehold-mediated strand displacement reaction. The nanoporous surface of the membrane was functionalized with a complementary pair consisting of Cy3-labeled probe and quencher-labeled nucleic acids through a chemical immobilization process. In the presence of the unlabeled SARS-CoV-2 target, the quencher-tagged strand of the immobilized probe-quencher duplex was separated from the Cy3-modifed strand. A stable probe-target duplex formed and regained a strong fluorescence signal, thus enabling real-time and label-free SARS-CoV-2 detection. Assay designs with different numbers of base pair (bp) matches were synthesized to compare their affinities. Because of the large surface of a free-standing nanoporous membrane, two orders enhancement of the fluorescence was observed, where the detection limit of the unlabeled concentration can be improved to 1 nM. The assay was miniaturized by integrating a nanoporous AAO layer onto an optical waveguide device. The detection mechanism and the sensitivity improvement of the AAO-waveguide device were illustrated from the finite difference method (FDM) simulation and the experimental results. Light-analyte interaction was further improved due to the presence of the AAO layer, which created an intermediate refractive index and enhanced the waveguide's evanescent field. Our competitive hybridization sensor is an accurate and label-free testing platform applicable to the deployment of compact and sensitive virus detection strategies.