Anodic Alumina Membranes Research Articles

A gold coating nanoporous anodized alumina oxide membrane as the substrate for rapid surface enhanced Raman spectroscopy detection of conjugated cyanide in fingertip blood

Rapid and sensitive detection of cyanide (free and conjugated) in blood samples is of vital significance for the clinical treatments and forensic verifications of cyanide poisoning. To overcome the disadvantages of conventional in-field detection methods, a facile, rapid and sensitive surface enhanced Raman spectroscopy (SERS) method for the analysis of free and conjugated cyanide using functionalized nanoporous anodic aluminium oxide (AAO) membrane coupled with hand-held Raman spectrometer has been developed in this study. A gold coating nanoporous AAO membrane with a high specific surface area, appropriate surface roughness and super-hydrophobicity has been prepared. The significant SERS signals enhancement benefiting from the high enrichment capacity and strong plasmonic hot-spots effects of the membrane has been achieved for hydrocyanic acid (HCN). Optimal parameters, including substrate modification, dissociation and capture conditions for blood samples have been investigated. The conjugated cyanide in the fingertip blood could be effectively liberated by the addition of H3PO4 and NaBH4, followed by the capture of HCN on the membrane and analyzed based on SERS. The whole detection procedure only needed 2 min, and the limit of detection could reach 10 ng/mL in only ∼ 50 μL fingertip blood. Therefore, this approach is expected to be a powerful point of care testing (POCT) tool for the diagnosis of cyanide poisoning in clinical and forensic applications.

Impact of Nanostructurization of the Pore Walls on the Dynamics of a Series of Phenyl Alcohols Incorporated within Nanoporous Aluminum Oxide Templates

Herein, we studied the impact of surface roughness on the molecular dynamics of a series of phenyl-terminated monohydroxyalcohols under spatial confinement provided by nanoporous anodic aluminum oxide (AAO) membranes of constant (const-AAO) and modulated (modul-AAO) pore diameter using Broadband Dielectric Spectroscopy and Differential Scanning Calorimetry. Interestingly, we observed that both types of AAO membranes affect the behavior of examined associating materials in a different manner. Calorimetric measurements showed that the double glass transition phenomenon, commonly reported for many compounds infiltrated into const-AAO membranes, is not observed in the case of modul-AAO templates, where a single glass transition temperature was detected. Consequently, the dynamics of the dominant process was bulk-like in the whole range of studied temperatures for the samples infiltrated into the latter templates. Moreover, the Debye character of the dominant relaxation process characteristic for bulk samples was lost for the confined samples. Interestingly, the width of the dominant mode was the greatest in the alcohols infiltrated into modulated pores. It was assigned to the higher heterogeneity in the mobility introduced by the nanostructurization of the interface. The presented data emphasize the crucial impact of modulated-induced surface roughness of an applied constrained medium on the dynamics and phase transition of the liquids infiltrated into pores.

Characterization of BiFeO3 nanotube and Y-junction BiFeO3 nanotubes

Multiferroic BiFeO3 (BFO) nanotube arrays (100 nm in diameter and 50 nm in length) were synthesized by the sol-gel method utilizing the anodic aluminum oxide (AAO) membrane technique. The microstructure and chemical components of the BFO nanotubes were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectrometer (XPS). The BFO nanotubes exhibited polycrystalline microstructures. The novel Y-junction BFO nano- tubes were simultaneously fabricated.

Continuous Ion Separations Using Non-Faradaic Capacitive AC Ratcheting

Traditional electrochemical separations processes require Faradaic reactions for sustained currents. We discovered that this limitation can be overcome by oscillating the applied potential across an ion-permeable material that has an asymmetric electric potential profile. We demonstrated this phenomenon for the first time using a flashing ratchet consisting of a nanoporous anodized aluminum oxide membrane infiltrated with salt water and containing metallic contacts on either side. When a symmetric +/-300 mV square-wave potential was applied to the metallic contacts at a frequency of ~100 Hz, an open-circuit potential as large as ~50 mV was observed between Ag/AgCl electrodes immersed in the chloride-containing electrolyte and positioned across the membrane. While this open-circuit potential was determined to be a consequence of net ionic polarization, additional electrochemical data were also consistent with transport of neutral salt across the membrane via a proposed ambipolar transport mechanism. In comparison, application of a DC potential bias resulted in non-Faradaic charging, and a near-zero long-time open-circuit potential. Moreover, high ionic strengths and large pore sizes diminished ratcheting behavior, consistent will more complete screening of surface charges in the nanopores. Collectively, this work represents a new paradigm for direct ion pumping and salt separations that requires no Faradaic reactions or additional transport pathway for ions or electrons.

Research on the gas migration trend and mechanism of the transition flow regime in coal based on MRT-LBM simulation

In order to reveal the process and mechanism of gas flow in a low-permeability coal seam, a new multiple-relaxation-time lattice Boltzmann method (MRT-LBM) model of gas migration in coal micro/nanopores based on Langmuir monolayer adsorption theory, the slip boundary scheme and Bosanquet effective viscosity was established. The software MATLAB was used to carry out the simulation study of uniform pore gas flow based on the MRT-LBM model, and the results were compared and verified with the porous anodic alumina membrane gas flow experimental results. On this basis, the gas flow in coal pores with different micro/nanopore sizes considering adsorption was simulated. The results show that the dimensionless permeability coefficient increases with decreasing pore size under the same pressure, which reflects the subsequent enhancement of the microboundary constraint effect and reveals that the pore system becomes the main controlling factor of coal seam permeability within the coal matrix in the middle and late stages of coal seam gas extraction, while the role of the microboundary constraint effect needs to be considered. The gas adsorption layer weakens the pore gas flow capacity, but for pores with a radius greater than 16 nm, the apparent change in permeability caused by the adsorption layer is less than 5%, and the adsorption effect can be ignored. N2, CH4, and CO2 enter the transition flow regime under different pressure conditions; with gas extraction, the gas pressure decreases, and the difference in the gas flow characteristics of the three gases increases.

Strongly Improving the Sensitivity of Phosphorescence-Based Optical Oxygen Sensors by Exploiting Nano-Porous Substrates.

Sensitivity is one of the crucial factors in determining the quality of a fluorescence/phosphorescence-based gas sensor, and is estimated from the measurement of responses (I0/I, where I0 and I refer to the measured optical intensity of a sensor in absence and presence of analyte molecules) at various concentrations of analytes. In this work, we demonstrate phosphorescence-based optical oxygen sensors fabricated on highly porous anodic aluminum oxide (AAO) membranes showing dramatically high response. These sensors exploit the enormous surface area of the AAO to facilitate the effective interaction between the sensing molecules and the analytes. We spin-coat an AAO membrane (200 nm pore diameter) with a platinum-based oxygen sensing porphyrin dye, platinum(II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP), to fabricate a sensor exhibiting I0/I ~400 at 100% oxygen atmosphere. To address the generality of the AAO membrane, we fabricate a separate sensor with another porphyrin dye, platinum octaethylporphyrin (PtOEP), which exhibits an even higher I0/I of ~500. Both of these sensors offer the highest responses as an optical oxygen sensor hitherto reported. SEM and EDS analysis are performed to realize the effect of the increased surface area of the AAO membrane on the enhanced sensitivity.

High-Performance pH Sensor Electrodes Based on a Hexagonal Pt Nanoparticle Array-Coated Nanoporous Alumina Membrane.

Porous anodic alumina membranes coated with Pt nanoparticles (PAAM/Pt) have been employed as pH sensor electrodes for H+ ion detection. The PAAM was designed using a two-step anodization process. Pt nanoparticles were then sputtered onto the membrane at different deposition times. The membrane’s morphological, chemical, and optical characteristics were carefully assessed following the fabrication stage using a variety of analytical techniques. The potential of the PAAM/Pt sensor electrode was investigated by measuring the potential using a simple potentiometric method. The effects of depositing Pt nanoparticles for 3–7 min on sensor electrode sensitivity were examined. The optimal potentiometric Nernstian response slope for the PAAM/Pt sensor electrode with 5 min Pt sputter coating is 56.31 mV/decade in the pH range of 3.0 to 10 at 293 K. Additionally, the PAAM/Pt sensor electrode’s stability and selectivity in various ions solutions were examined. The sensor electrode had a lifetime of more than six weeks and was kept in a normal air environment.

The fabrication of unwettable superhydrophobic surfaces by reactive wetting of AgCuTi into an AAO template

Multi-level hierarchical surface roughness is the key to natural superhydrophobic materials. In this work, rough surfaces of a novel superhydrophobic material are achieved by the reactive wetting technique. The molten AgCuTi alloy is applied to infiltrate into the porous anodic aluminum oxide (AAO) membrane, and wetting of molten AgCuTi is promoted by the reaction layer formed at the interface between AAO and AgCuTi. The AgCuTi infiltrates the AAO nanopores and forms the first-level surface roughness based on reactive wetting. To release the nanostructures embedded in the AAO pores, hydrothermal etching with NaOH aqueous solution was used to remove AAO. Meanwhile, TiO2 nanostructures are synthesized under hydrothermal conditions, resulting in the second-level surface roughness. After modification, the surface is found to exhibit excellent superhydrophobic properties, including a high water contact angle (WCA) and low roll-off angle (RA). The superhydrophobic surface also shows self-cleaning, mechanical durability and long-term stability. The as-prepared surface exhibits excellent repellence for water solutions with different pH values. This method could be applied to fabricate superhydrophobic surfaces on different kinds of materials, showing broad application prospects.

Functionalised Anodised Aluminium Oxide as a Biocidal Agent.

In this article, we describe the antimicrobial properties of a new composite based on anodic aluminium oxide (AAO) membranes containing propyl-copper-phosphonate units arranged at a predetermined density inside the AAO channels. The samples were prepared with four concentrations of copper ions and tested as antimicrobial drug on four different strains of Escherichia coli (K12, R2, R3 and R4). For comparison, the same strains were tested with three types of antibiotics using the minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests. Moreover, DNA was isolated from the analysed bacteria which was additionally digested with formamidopyrimidine-DNA glycosylase (Fpg) protein from the group of repair glycosases. These enzymes are markers of modified oxidised bases in nucleic acids produced during oxidative stress in cells. Preliminary cellular studies, MIC and MBC tests and digestion with Fpg protein after modification of bacterial DNA suggest that these compounds may have greater potential as antibacterial agents than antibiotics such as ciprofloxacin, bleomycin and cloxacillin. The described composites are highly specific for the analysed model Escherichia coli strains and may be used in the future as new substitutes for commonly used antibiotics in clinical and nosocomial infections in the progressing pandemic era. The results show much stronger antibacterial properties of the functionalised membranes on the action of bacterial membranes in comparison to the antibiotics in the Fpg digestion experiment. This is most likely due to the strong induction of oxidative stress in the cell through the breakdown of the analysed bacterial DNA. We have also observed that the intermolecular distances between the functional units play an important role for the antimicrobial properties of the used material. Hence, we utilised the idea of the 2D solvent to tailor them.

In Situ Imaging of Endogenous Hydrogen Peroxide Efflux from Living Cells via Bipolar Gold Nanoelectrode Array and Electrochemiluminescence Technology.

The integration of a closed bipolar electrode (c-BPE) array and electrochemiluminescence (ECL) detection received a boost in applications in the detection of cell adhesion and disease-related biomarkers. This work proposed a gold nanorod array based c-BPE-ECL system to realize an in situ image of endogenous hydrogen peroxide (H2O2) efflux from living cells and parallel analysis of endogenous H2O2 released from multiple cells by converting electrochemical signals into optical signals. The gold nanorod array with high density was prepared by a repeating chronopotentiometry procedure with anodic aluminum oxide (AAO) membrane as a template. The c-BPE array was fabricated by assembling poly(dimethylsiloxane) (PDMS) chips on both sides of the gold nanorod array. When an appropriate driving potential is applied, H2O2 generated from living cells at the sensing pole was reduced on the gold nanorod, triggering the oxidation of the ECL reagent at the reporting pole, which allowed the detection of H2O2 released from living cells. Under phorbol myristate acetate (PMA) stimulation, H2O2 released from living HeLa, HepG2, MCF-7, and LO2 cells was determined to be 47, 32.4, 25.7, and 6.3 μM, respectively. This indicated that the amount of H2O2 released from PMA-stimulated cancer cells was significantly higher than that from the stimulated normal cells. This work presented a new approach for in situ imaging of H2O2 released from living cells and could also be used to detect other electrochemically active or non-electrochemically active molecules through simple cell surface modification, which may have potential applications in cell apoptosis study and disease diagnosis.

Plasmonic distributed feedback lasing in an anodic aluminum oxide/silver/polymer hybrid membrane.

A hybrid membrane is employed as a high-order plasmonic distributed feedback (DFB) cavity to reduce the lasing threshold of polymer lasers. The hybrid membrane consists of an anodic aluminum oxide (AAO) membrane, a 25 nm thick silver layer and a free-standing polymer membrane. The AAO membrane is fabricated by a low-cost, single chemical etching method. Then, a layer of silver with a thickness of 25 nm is sputtered on the surface of the AAO. Subsequently, a polymer membrane is directly attached to the silver-plated AAO membrane, forming an AAO/silver/polymer hybrid membrane. Under optical pumping conditions, low-threshold, three-order DFB lasing is observed. The proposed laser device exhibited a dual-threshold characteristic because of the evolution from amplified spontaneous emission to DFB lasing. And a significant shift from omnidirectional emission to directional emission lasing can be observed while the pump energy density is beyond the second threshold. Furthermore, the plasmonic enhancement sourced from silver corrugation reveals important improvement effects to the DFB lasing of AAO/silver/polymer hybrid membrane for decreasing threshold, narrowing full width at half maximum (FWHM), and an increasing Q factor. This work may promote the design and production of low-cost and large-area high-order plasmonic DFB polymer lasers.

The Interrelation of Synthesis Conditions and Wettability Properties of the Porous Anodic Alumina Membranes.

The results of studies on the wettability properties and preparation of porous anodic alumina (PAA) membranes with a 3.3 ± 0.2 μm thickness and a variety of pore sizes are presented in this article. The wettability feature results, as well as the fabrication processing characteristics and morphology, are presented. The microstructure effect of these surfaces on wettability properties is analyzed in comparison to outer PAA surfaces. The interfacial contact angle was measured for amorphous PAA membranes as-fabricated and after a modification technique (pore widening), with pore sizes ranging from 20 to 130 nm. Different surface morphologies of such alumina can be obtained by adjusting synthesis conditions, which allows the surface properties to change from hydrophilic (contact angle is approximately 13°) to hydrophobic (contact angle is 100°). This research could propose a new method for designing functional surfaces with tunable wettability. The potential applications of ordinary alumina as multifunctional films are demonstrated.

Encrypted information reading technology at the micro/nano scale based on surface plasma-driven reactions

The plasma exciton induced photocatalytic reaction has considerable potential in terms of controllability and selectivity. In this paper, with the advantage of Raman fingerprinting, the localized photocatalytic reaction driven by surface plasmons is realized by the writing and reading process of encrypted information at the micro/nano scale. A layer of probe molecules (4-nitrobenzenethiol, 4-NBT) was assembled on a gold nanoporous array grown on porous anodic aluminium oxide (AAO) membranes. The focused Raman spot is manipulated in a two-dimensional micro/nano manipulation technique to control the movement of the spot at an excitation wavelength of 633 nm. Probe molecules within the spot trajectory will undergo a photocatalytic reaction to produce p,p'-dimercaptoazobenzene (DMAB) molecules, thereby writing the specific information required. The use of Raman mapping to image the characteristic peaks of formed DMAB under excitation light with a longer wavelength of 785 nm enables the readout of 2D micro/nano cryptograms. Combined with finite-difference time-domain (FDTD) simulations, it was found that the presence of a large number of regularly arranged hot spots on the surface of the array is the key to achieving the efficient photocatalytic reaction. This study enables real-time, lossless recording/reading of encrypted information with the aid of 2D Raman technology. This would be a very interesting research area with broad application in confidential information storage.

Effect of Ni addition on CPP-GMR response in electrodeposited Co-Ni/Cu multilayered nanocylinders with an ultra-large aspect ratio

Effect of Co–Ni alloy composition on the current perpendicular-to-plane giant magnetoresistance (CPP-GMR) response of electrochemically synthesized Co–Ni/Cu multilayered nanocylinders was studied using anodized aluminum oxide membranes (AAOM) with nanochannel diameter D ∼67 nm and length L ∼70 μm. Co–Ni/Cu multilayered nanocylinders, which have an aspect ratio L/D of ∼1,045, were fabricated in the AAOM nanochannel templates by utilizing a pulse-current electrochemical growth process in an electrolytic bath with Co2+, Ni2+ and Cu2+ ions. Co–Ni/Cu alternating structure with Co84Ni16 alloy layer-thickness of 9.6 nm and Cu layer-thickness of 3.8 nm was clearly observed in a nanocylinder with a diameter of 63 nm. The alternating structure was composed from crystalline layers with preferential orientations in hcp-CoNi (002) and fcc-Cu (111). The Co–Ni/Cu multilayered nanocylinders were easily magnetized in the long axis direction because of the extremely large aspect ratio L/D. In Co84Ni16/Cu multilayered nanocylinders, the coercivity and squareness were ∼0.46 kOe and ∼0.5, respectively. The CPP-GMR value was achieved up to 22.5% (at room temperature) in Co84Ni16/Cu multilayered nanocylinders.

A microfluidic-based SERS biosensor with multifunctional nanosurface immobilized nanoparticles for sensitive detection of MicroRNA

Developing sensitive and miniaturized biosensors for the detection of microRNAs (miRNAs) is highly desirable due to their association with early cancer diagnosis and prognosis. Here, a new microfluidic-based biosensor, combined with multifunctional nanosurface and DSN-assisted target recycle amplification strategy, is designed for the detection of miRNA-21. The design of nanosurface includes gold nanoparticles on porous anodic aluminum oxide (AAO) for surface enhanced Raman scattering (SERS) substrate, AuMBA@Ag core-shell nanoparticles for SERS nanotags and single-stranded DNA (ssDNA) in between for miRNA capture and nanotags immobilization. When the target miRNA is present near the nanosurface, it will be captured by ssDNA via hybridization reaction. Then, triggered by the DSN-assisted target recycle process, the freshly formed DNA/miRNA heteroduplexes are cleaved by DSN enzyme into DNA fragments and single-strand miRNA. The SERS nanotags are also dissociated from the nanosurface, leading to decrease of SERS signal. The cleaved target miRNA can be captured and SERS nanotags are released again in the next cycle, resulting in amplification of detection signal. To improve the accuracy of this biosensor, the functionalized AAO membrane is subdivided into two groups - AAO/Au array linked with encoded core-shell SERS nanotags acting as a reactor and primary detector and AAO/Au@Ag array serving as a collector and secondary detector for the dissociative SERS nanotags from the reactor. The decrease of SERS signal in primary detector and increase of signal in secondary detector ensures the accuracy and it is called dual-SERS detection strategy. The detection of miRNA-21 can be achieved with only 30 μL sample and 10 μL enzyme and a wide linear range of 10 fM∼10 nM is obtained. In addition, the microfluidic dual-SERS detection strategy can greatly reduce the possibility of false positive or false negative in single detection mode and it can be applied to the simultaneous detection of multiple miRNAs via integrating different probes.

MOFs-functionalized regenerable SERS sensor based on electrochemistry for pretreatment-free detection of serum alkaline phosphatase activity

Alkaline phosphatase (ALP), widely distributing in the human body, associates with many liver and bone diseases. Herein, we designed a reusable surface-enhanced Raman scattering (SERS) sensor via electrochemical self-assembly of Au nanoparticles (AuNPs) and zinc-based metal organic frameworks (Zn-MOFs) at anodic aluminum oxide (AAO) membrane for detecting ALP activity. The detection is based on the sensitive SERS response of the newly synthesized 2-mercaptoquinone (2-MBQ) modified on AuNPs surface towards ascorbic acid (AA) formed from the dephosphorylation of ascorbic acid 2-phosphate (AA2P) in the presence of ALP. Benefitting from the sieving function of Zn-MOFs and superiority of SERS, the developed sensor exhibited strong anti-interference performance and wide detection range from 1 to 300 U/L with a detection limit of 0.38 U/L, which allowed the direct detection of ALP activity in serum without any pretreatment. Besides, we regenerated the used sensor through the electrochemical oxidation of the reduced probe molecule 2-mercaptohydroquinone (2-MHQ). The regenerated sensor exhibited good maintenance of sensitive response to ALP, in favor of improving the usage efficiency and cutting the test cost. This work provides a promising platform for early diagnosis of ALP-related diseases and paves the way towards developing regenerable and pretreatment-free SERS sensors.

Simulation, analysis, fabrication and characterization of tunable AAO membrane for microfluidic filtration

Microfluidic filtration is an essential process in many biomedical applications. Micro or nanoporous membranes are used for colloidal retention. During the membrane filtration process visualization of various phenomena is challenging. Theoretical models have been proposed to visualize the transport mechanism. In this work, ANSYS Fluent is used for 3D designing of the microfluidic system and Fuzzy simulations are used to study flow rate and velocity, to get the maximum benefit from Anodized Aluminium oxide membrane in practical applications. The proposed method exploits relations between driving force, membrane area, and fluid flow. After optimization of parameters for the filtration, the AAO membrane with desired pore diameter was fabricated using the two-step anodization method. Scanning electron microscope is used for characterization of fabricated AAO membrane. The simulated and theoretical results using computer-based programs are then compared for manipulation of flow rate during the filtration process. Along with the manipulation of flow rate from nanoporous membrane other challenges faced during the filtration process are also highlighted with possible solutions.

An electrochemical membrane-based aptasensor for detection of severe acute respiratory syndrome coronavirus-2 receptor-binding domain

Herein, we report an electrochemical membrane-based aptasensor for the determination of the SARS-CoV-2 receptor-binding domain (SARS-CoV-2-RBD). For this purpose, the nanoporous anodic aluminium oxide membrane (NPAOM) was first fabricated electrochemically. The NPAOM was then functionalized with 3-mercaptopropyl trimethoxysilane (NPAOM-Si-SH). After that, the NPAOM-Si-SH was decorated with gold nanoparticles by using gold ion and sodium borohydride. The NPAOM-Si-S-Aunano was then attached to the surface of the working electrode of a laser-engraved graphene electrode (LEGE). Subsequently, the LEGE/NPAOM-Si-S-Aunano was fixed inside a flow cell that was made by using a three-dimensional (3D) printer, and then thiolated aptamer was transferred into the flow cell using a pump. The electrochemical behavior of the LEGE/NPAOM-Si-S-Aunano-Aptamer was studied using square wave voltammetry (SWV) in the presence of potassium ferrocyanide as a redox probe. The response of the LEGE/NPAOM-Si-S-Aunano-Aptamer to the different concentrations of the SARS-CoV-2-RBD in human saliva sample was investigated in the concentration range of 2.5–40.0 ng/mL. The limit of the detection was found to be 0.8 ng/mL. The LEGE/NPAOM-Si-S-Aunano-Aptamer showed good selectivity to 5.0 ng/mL of SARS-CoV-2-RBD in the presence of five times of the interfering agents like hemagglutinin and neuraminidase as the influenza A virus major surface glycoproteins.

A Micropowered Chemoresistive Sensor Based on a Thin Alumina Nanoporous Membrane and SnxBikMoyOz Nanocomposite.

This work presents and discusses the design of an efficient gas sensor, as well as the technological process of its fabrication. The optimal dimensions of the different sensor elements including their deformation were determined considering the geometric modeling and the calculated moduli of the elasticity and thermal conductivity coefficients. Multicomponent SnxBikMoyOz thin films were prepared by ionic layering on an anodic alumina membrane and were used as gas-sensitive layers in the sensor design. The resistance of the SnxBikMoyOz nanostructured film at temperatures up to 150 °C exceeded 106 Ohm but decreased to 104 Ohm at 550 °C in air. The sensitivity of the SnxBikMoyOz composite to concentrations of 5 and 40 ppm H2 at 250 °C (10 mW) was determined to be 0.22 and 0.40, respectively.

Structural Engineering of the Barrier Oxide Layer of Nanoporous Anodic Alumina for Iontronic Sensing.

The hemispherical barrier oxide layer (BOL) closing the bottom 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. The rectification efficiency of the ionic current associated with the flow of ions across the anodic BOL increases with its thickness, under optimal pH conditions. The inner surface of the 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.