Nanoporous Layer Research Articles

Why do metals become superhydrophilic during nanosecond laser processing? Design of superhydrophilic, anisotropic and biphilic surfaces

This research investigates the impact of the surrounding environment on the characteristics of copper, nickel and tin during nanosecond laser processing. By comparing the results of processes conducted in vacuum and air, we conclude that changes in wetting properties cannot be solely attributed to development of surface microstructure. To elucidate this phenomenon, we conducted model experiments using a tin target. Laser processing parameters for the tin target were established, involving deep cavity melting without ablation, resulting in highly evolved material morphology. Under these conditions, laser processing in air did not lead to metal hydrophilization. Therefore, our study demonstrates that the primary cause of changes in material wetting properties during nanosecond laser processing is the re-deposition of ablation products onto the material surface. These products form a nanoporous layer that enhances wicking capabilities and subsequently serves as a sorbent for various impurities, gradually leading to the hydrophobization of most commonly used materials. The proposed mechanism opens the possibility for the development of new methods to create materials with biphilic and anisotropic wetting properties. The key insight lies in the control of the thickness of the nanoporous layer, as it emerges as a pivotal factor dictating wettability properties and wicking capability.

Nanoscale investigations of femtosecond laser induced nanogratings in optical glasses.

Femtosecond (fs) laser irradiation inside transparent materials has drawn considerable interest over the past two decades. More specifically, self-assembled nanogratings, induced by fs laser direct writing (FLDW) inside glass, enable a broad range of potential applications in optics, photonics, or microfluidics. In this work, a comprehensive study of nanogratings formed inside fused silica by FLDW is presented based on high-resolution electron microscopy imaging techniques. These nanoscale investigations reveal that the intrinsic structure of nanogratings is composed of oblate nanopores, shaped into nanoplanes, regularly spaced and oriented perpendicularly to the laser polarization. These nanoporous layers are forced-organized by light, resulting in a pseudo-organized spacing at the sub-wavelength scale, and observed in a wide range of optical glasses. In light of the current state of the art, we discuss the imprinting of nanoporous layers under thermomechanical effects induced by a plasma-mediated nanocavitation process.

Obtaining a nanoporous Layer by the Anodizing Process on AISI 316L Steel to Obtain Better Corrosion Resistance Properties in Metallic Biomaterials Applications

Obtaining a nanoporous Layer by the Anodizing Process on AISI 316L Steel to Obtain Better Corrosion Resistance Properties in Metallic Biomaterials Applications

Obtaining of Antibacterial Nanoporous Layer on Ti7.5Mo Alloy Surface Combining Alkaline Treatment and Silver: In Vitro Studies

In the present study, a combination of alkaline treatment and silver was used to produce an antibacterial nanolayer on the Ti7.5Mo alloy surface. The antibacterial response and osteogenesis were evaluated by assessing the adhesion and proliferation of S. aureus and S. epidermidis, as well as the adhesion, viability, and expression levels of genes involved in osteogenic differentiation in the mouse pre-osteoblast cell line MC3T3-E1. The potential stimulus of extracellular remodeling was evaluated using zymography. Our results showed that there is no difference in cytotoxicity after silver immobilization. Protein activity (MMP9) progressively increased for theTi7.5Mo alloy, both untreated and after alkaline treatment. However, the highest increase in protein activity was observed when the alloy was in direct contact with immobilized silver nanoparticles. The surfaces containing silver showed a better response in terms of colony formation, meaning that less bacterial adhesion was detected. The results showed that the layer formed was effective in reducing bacterial activity without altering cell viability.

Glycerol-tailored asymmetric polyethersulfone membranes with uniform ion transport for stable lithium metal batteries

Advancing the performance and stability of lithium metal batteries is crucial for future energy storage devices. One of the major challenges for practical applications of Li metal batteries is to mitigate the formation of Li dendrites during cycling. In this work, we prepared a series of asymmetrically structured polyethersulfone (PES) membranes, consisting of a nanoporous skin layer and a bulk with macrovoids, by incorporating different amounts of glycerol during membrane preparation. Under optimal conditions, the asymmetric PES membrane made with 1.2 wt% of glycerol (PES-G1.2) possesses a thin skin layer with a uniform nanopore distribution, which is ideal for regulating the ion flux near the Li anode surface, thus suppressing Li dendrite formation. Our results demonstrate that the PES-G1.2 possesses exceptional ionic conductivity of 1.76 mS cm−1, Li+ transference number of 0.52, and high compatibility with Li electrode. Additionally, the Li/PES-G1.2/LiFePO4 cells also present a remarkable rate capability with specific capacity of 150 mAh g−1 at 0.2 C and 81 mAh g−1 at 10 C, respectively, and 90 % of capacity can be retained after 100 charge-discharge cycles under 0.2 C. These findings shed light on the unique properties of asymmetric porous membrane as well as its promising potential for applications in lithium metal batteries.

Formation of a nano-porous structured Cu layer by selective etching of a brass layer and sinter-bonding to achieve direct Cu–Cu bonding

A nano porous structured (NPS) Cu layer was fabricated by a Zn plating-annealing-selective etching process. Furthermore, sinter-bonding was performed by thermocompression after forming the NPS Cu layer instead of the conventional paste sinter-bonding process. The sinter-bonding produced a dense Cu–Cu joint with minimal oxidation by infiltrating the reducing agent into the NPS Cu layer. Sinter-bonding was performed with under a pressure of 5 MPa at 300 °C in air, and excellent bonding strength of 27 MPa was achieved after a bonding time of 1 min. Moreover, the bonding strength increased to 35 MPa by bonding for 1 min while blowing N2. The optimal thickness of the NPS Cu layer for short-duration sinter-bonding was established, and the oxidation of Cu was suppressed by the infiltration of a reducing agent. Consequently, an excellent shear strength was achieved by sinter-bonding using the NPS Cu layer.

Nanostructured Catalyst Layer Allowing Production of Ultralow Loading Electrodes for Polymer Electrolyte Membrane Fuel Cells with Superior Performance.

This study introduces a simple method to produce ultralow loading catalyst-coated membrane electrodes, with an integrated carbon "nanoporous layer", for use in polymer electrolyte membrane fuel cells or other electrochemical devices. This approach allows fabrication of electrodes with loadings down to 5.2 μgPt cm-2 on the anode and cathode (total 10.4 μgPt cm-2, Pt3Zn/C catalyst) in a controlled, uniform, and reproducible manner. These layers achieve high utilization of the catalyst as measured through electrochemical surface area and mass specific activities. Electrodes composed of Pt/C, PtNi/C, Pt3Co/C, and Pt3Zn/C catalysts containing 5.2-7.1 μgPt cm-2 have been fabricated and tested. These electrodes showed an impressive performance of 111 ± 8 A mgPt-1 at 0.65 V on Pt3Co/C with a power density of 31 ± 2 kW gPt,total-1, about double that of the best previous literature electrodes under the same operating conditions. The performance appears apparently mass transport free and dominated by electrokinetics over a very wide potential range, and thus, these are ideal systems to study oxygen electrokinetics within the fuel cell environment. The improved performance is associated with reduced "contact resistance" and more specifically a reduction in the resistance to lateral current flow in the catalyst layer. Analytical expressions for the effect illuminate approaches to improve electrode design for electrochemical devices in which catalyst utilization is key.

Cell volume expansion and local contractility drive collective invasion of the basement membrane in breast cancer.

Breast cancer becomes invasive when carcinoma cells invade through the basement membrane (BM)-a nanoporous layer of matrix that physically separates the primary tumour from the stroma. Single cells can invade through nanoporous three-dimensional matrices due to protease-mediated degradation or force-mediated widening of pores via invadopodial protrusions. However, how multiple cells collectively invade through the physiological BM, as they do during breast cancer progression, remains unclear. Here we developed a three-dimensional in vitro model of collective invasion of the BM during breast cancer. We show that cells utilize both proteases and forces-but not invadopodia-to breach the BM. Forces are generated from a combination of global cell volume expansion, which stretches the BM, and local contractile forces that act in the plane of the BM to breach it, allowing invasion. These results uncover a mechanism by which cells collectively interact to overcome a critical barrier to metastasis.

Formation of TiO2 nanoporous layer on the surface of Ti13Nb13Zr titanium alloy treated by ECAP-Conform and Rotary Swaging

This paper focuses on the formation of nanoporous layer on the surface of the third-generationbiomedical Ti13Nb13Zr titanium alloy widely used in the biomedical field. First of all, the alloy was asubject to equal channel angular pressing (ECAP) + conform treatment (ECAP-Conform) and RotarySwaging forging. Then the anodic oxidation method with 0.5 wt% HF electrolyte was used to preparea uniformly arranged porous layer on the surface of the samples with the different microstructurefrom EACP-Conform. The features of the formed porous layer were investigated. The effects ofoxidation time and oxidation voltage on the porous morphology of the surface porous layer wereinvestigated in detail. The optimal anodic oxidation parameters for the formation of surface porouslayer were established. The hydrophobic properties of the samples were tested and the contact angleswere calculated. Finally, the weightlessness of body fluid corrosion in Hanks´ solution was simulated.

Thermal desorption from zeolite layer for VOC detection

Volatile organic compounds (VOCs) are being considered for a wide range of applications, since they provide information on specific processes (e.g., metabolic processes in humans and plants). To date, environmental VOCs detection can be accomplished with low selectivity using both portable photoionization techniques or using gold standard laboratory techniques (e.g., gas and liquid chromatography, mass spectrometry), getting higher performances and limitations in terms of portability, availability of equipment and of consumption of time. Hereafter, a modified photoionization technique based on a thin zeolite layer for the selective adsorption of VOCs was investigated, exploiting the processes of thermal adsorption and desorption. Zeolite through the inherent nanoporous structure possesses specific electrical characteristics, strongly influenced by the adsorption of the molecules within the framework. Experimental analysis of its electrical and adsorption/desorption properties of propionic and succinic acids was performed. Results demonstrated how the use of a thin nanoporous layer allows to increase the selectivity of commercial photoionization detector during VOC detection, evidencing the potentiality of this technique for the development of low-cost and high-performance sensors in various applications.

Scalable Preparation of Polyimide Sandwiched Separator for Durable High-Rate Lithium-Metal Battery.

The ever-growing demands for efficient energy storage accelerate the development of high-rate lithium-metal battery (LMB) with desirable energy density, power density, and cycling stability. Nevertheless, the practical application of LMB is critically impeded by internal temperature rise and lithium dendrite growth, especially at high charge/discharge rates. It is highly desired but remains challenging to develop high-performance thermotolerant separators that can provide favorable channels to enable fast Li+ transport for high-rate operation and simultaneously homogenize the lithium deposition for dendrite inhibition. Polyimide-based separators with superior thermal properties are promising candidate alternatives to the commercial polyolefin-based separators, but previous strategies of designing either nanoporous or microporous channels in polyimide-based separators often meet a dilemma. Here, a facile and scalable approach is reported to develop a polyimide fiber/aerogel (denoted as PIFA) separator with the microporous polyimide fiber membrane sandwiched between two nanoporous polyimide aerogel layers, which can enable LMBs with remarkable capacity retention of 97.2% after 1500 cycles at 10 C. The experimental and theoretical studies unravel that the sandwiched structure of PIFA can appreciably enhance the electrolyte adsorption and ionic conductivity; while, the aerogel coating can effectively inhibit dendrite growth to realize durable high-rate LMBs.

Surface nanocrystallization of pure iron achieved by anodization-reduction treatment and its effect on lower-temperature nitriding behaviors

In this work, a novel method named anodization-reduction composite treatment was designed to achieve surface nanocrystallization on pure iron materials. Subsequently, this method was employed as pretreatment for gas nitriding of pure iron and its effect was studied systematically. The experimental data illustrated that a 1.3 μm thick Fe2O3 layer with nanoporous structure was successfully fabricated by anodization treatment in solutions containing 0.1 M NH4F and 1 M H2O. After hydrogen reduction at 400 °C, the nanoporous Fe2O3 layer was transformed to pure layer with nanoparticles stacked structure. Additionally, each particle is composed of several pure iron grains with size of 2–10 nm. After lower-temperature gas nitriding at 400 °C, a dense compound layer composed of Fe3N and Fe4N phases with thickness of 3 μm was formed on surface of anodization-reduced sample. The anodization-reduced nitrided sample show the higher hardness, lower friction coefficient and improved wear resistance than those of original nitrided sample. The acceleration of nitriding process may be attributed to the increased adsorption area of nitrogen atoms, rapid diffusion effect in nanocrystalline and more nucleation sites for nitrides. This paper provides a novel surface nanocrystallization method for iron to reduce its nitriding temperature or duration.

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.

Rapid and sensitive point-of-need aflatoxin B1 testing in feedstuffs using a smartphone-powered mobile microfluidic lab-on-fiber device

Rapid, high-frequency, and accurate identification of aflatoxin B1 (AFB1) is crucial for ensuring food safety and reducing population mortality. Herein, we constructed Smartphone powered Mobile mIcrofluidic Lab-on-fiber dEvice (SMILE) comprising a compact optical system, fiber nano-bioprobe-embedded microfluidic-chip system, mini-photodetector, and software application to facilitate the rapid and sensitive point-of-need quantitative testing for AFB1. The elegant optical design of SMILE significantly improves light transmission efficiency, detection sensitivity, and portability by integrating a compacted all-fiber optical structure with a fiber nano-bioprobe-embedded microfluidic chip. Furthermore, the nanopore layer of the fiber nano-bioprobe improves detection sensitivity by increasing the biorecognition molecule number and enhancing the interaction between the evanescent field and dye. Through an indirect competitive immunoassay mechanism, SMILE achieves sensitive quantitative detection of AFB1 with a detection limit of 0.08 µg/L. Herein, SMILE was validated using several feedstuff samples tested with a simple aqueous extraction protocol, demonstrating good correlation with high-performance liquid chromatography for AFB1-contaminated feedstuffs. The immunoassay process is completed within 12 min, boasting high sensitivity, specificity, reusability, and reproducibility. Owing to its sensitivity, portability, flexibility, plug-and-play, and smartphone integration, SMILE is highly scalable for rapid and high-frequency point-of-need testing for AFB1 and other trace contaminants.

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.

Manufacturing an Organic Solar Cell and Comparing with Different Dyes

A solar cell was manufactured from local materials and was dyed using dyes extracted from different organic plants. The solar cell glass slides were coated with a nano-porous layer of Titanium Oxide and infused with two types of acids, Nitric acid and Acetic acid. The organic dyes were extracted from Pomegranate, Hibiscus, Blackberry and Blue Flowers. They were then tested and a comparison was made for the amount of voltage they generate when exposed to sunlight. Hibiscus sabdariffa extract had the best performance parameters; also Different plants give different levels of voltage.

Hierarchical isoporous membrane filters for simultaneous reduction of pressure drop and efficient removal of nanoscale airborne contaminants

Isoporous membranes with well-defined pore architectures offer a unique design approach to achieve a multi-scale porous network. For instance, isoporous membranes with progressively smaller pore sizes can be stacked to create a hierarchical pore network in which each length scale and the gradient of the pore network are deterministic by design. In this paper, we introduce a hierarchically-arranged multilayer isoporous air filter that comprises an ultrathin (thickness <1μm) nanoporous active filtration layer and a microporous support layer. To maximize airflow and thereby reduce pressure drop across the membrane, we engineered a gap between the nanoporous and microporous membranes by designing and fabricating microscale spacer structures akin to feed spacers used in spiral wound reverse osmosis membranes. We demonstrated that such hierarchical isoporous membranes with integrated spacers (HIM-S) can retain high filtration efficiency (>95%) for ultrafine, most penetrating particle size (MPPS) while simultaneously reducing the pressure drop across the membrane (by ∼86%).

Numerical Investigation on Pool Boiling Heat Transfer of Silica and Alumina Nanofluids

Surface modification through pool boiling of nanofluid is an efficient technique in delaying critical heat flux and attaining high heat flux at lower wall superheat temperature. The method of involving phase interaction, bubble evolving and dynamics phenomenon, and distribution of vapor void fraction altogether is the motivation behind current topic. The present work will contribute to the recovery and reuse of the wastewater and incinerator heat, cooling of high heat flux generating micro-electronics chips, and cooling of fast breeder test reactors. In the present study, the nucleate pool boiling of SiO2/water and Al2O3/water nanofluid are studied numerically and the effect of wall superheat temperature and heat flux on active nucleation site density, bubble departure diameter, and bubble waiting time are studied. The effect of various heater surface material and nanofluid concentration on wall superheat temperature and heat transfer coefficient are also investigated. A two-phase Eulerian approach, heat flux wall-partitioning model, and Rensselaer Polytechnic Institute boiling model are considered to simulate the current model. The pool boiling of nanofluids resulted in the formation of nano-porous layer on heater surface because of microlayer evaporation process that enhanced the heat transfer coefficient and reduced the wall superheat temperature.

Spectroelectrochemical Investigation of the Local Alkaline Environment on the Surface-Nanostructured Au for the Conversion of CO2 to CO

The electrocatalytic conversion of carbon dioxide (CO2) into fuels could potentially achieve a sustainable carbon-based economy. The engineering of nanostructured metal electrodes can enhance their activity and selectivity by controlling their local chemical environment; however, direct observation is challenging. In this study, we investigate the molecular-level reaction mechanism of a nanoporous-structured Au electrode for the conversion of CO2 to carbon monoxide (CO) using surface-enhanced infrared absorption spectroscopy (SEIRAS). We designed a well-structured nanoporous Au layer (with a depth distribution of 56.3 nm) on a Si prism using a high-temperature non-aqueous anodization process and characterized the nanoporous Au electrode using atomic force microscopy (AFM) and X-ray absorption spectroscopy (XAS). The in situ SEIRAS results demonstrated that the nanoporous Au electrode has a dominant active site, promoting the linear CO intermediate and suppressing the bridging CO intermediate when compared with the non-structured Au electrode. We also revealed a high local pH at a reaction potential of −0.9 V and the slow diffusion kinetics of local CO32– at an open-circuit potential. These findings provide deeper insights into the electrochemical kinetics and corresponding mechanisms occurring in the electric double layers and highlight the potential for the design of efficient electrocatalysts for CO2 reduction.

Metal-Organic Framework-Decorated Nanochannel Electrode: Integration of Internal Nanoconfined Space and Outer Surface for Small-Molecule Sensing.

Ionic current measurement has been the dominant signaling strategy in nanochannel-based sensors. However, the direct probing of the capture of small molecules is still challenging, and the sensing potential of the outer surface of nanochannels is always ignored. Here, we report the fabrication of an integrated nanochannel electrode (INCE) with nanoporous gold layers modified on two sides of nanochannels, and its application for small-molecule analysis was explored. Metal-organic frameworks (MOFs) were decorated inside and outside of nanochannels, enabling the reduction of pore size to several nanometers, which is among the thickness range of the electric double layer for confined ion diffusion. Combined with excellent adsorption characteristics of MOFs, the developed nanochannel sensor successfully constructed the internal nanoconfined space that could directly capture small molecules and instantly generate a current signal. The contribution of the outer surface and the internal nanoconfined space to diffusion suppression to electrochemical probes was investigated. We found that the constructed nanoelectrochemical cell was sensitive in both the inner channel and the outer surface, signifying a novel sensing mode with integration of the internal nanoconfined space and the outer surface of nanochannels. The MOF/INCE sensor showed excellent performance toward tetracycline (TC) with a detection limit of 0.1 ng·mL-1. Subsequently, sensitive and quantitative detection of TC down to 0.5 μg·kg-1 was achieved in actual chicken samples. This work may open up a new model of nanoelectrochemistry and provide an alternative solution in the field of nanopore analysis for small molecules.