Thin Silica Layer Research Articles

The First Silver-Based Plasmonic Nanomaterial for Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy with Magnetic Properties.

Nanostructures made of magnetic cores (from Fe3O4) with attached silver plasmonic nanostructures were covered with a very thin layer of silica. The (Fe3O4@Ag)@SiO2 magnetic–plasmonic nanomaterial can be manipulated using a magnetic field. For example, one can easily form homogeneous layers from this nanomaterial using a very simple procedure: deposition of a layer of a sol of such a nanostructure and evaporation of the solvent after placing the sample in a strong magnetic field. Due to the rapid magnetic immobilization of the magnetic–plasmonic nanomaterial on the investigated surface, no coffee-ring effect occurs during the evaporation of the solvent. In this contribution, we report the first example of a magnetic, silver-based plasmonic nanomaterial for shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Nanoresonators based on silver plasmonic nanostructures locally enhance the intensity of the exciting electromagnetic radiation in a significantly broader frequency range than the previously used magnetic SHINERS nanoresonators with gold plasmonic nanostructures. Example applications where the resulting nanomaterial was used for the SHINERS investigation of a monolayer of mercaptobenzoic acid chemisorbed on platinum, and for a standard SERS determination of dopamine, are also presented.

Magnetic iron oxide cores with attached gold nanostructures coated with a layer of silica: An easily, homogeneously deposited new nanomaterial for surface-enhanced Raman scattering measurements

Nanostructures made of magnetic cores (Fe3O4) with many smaller plasmonic (Au) nanostructures attached were covered with a very thin layer of silica. The first example of the application of this type of material for surface-enhanced Raman scattering (SERS) measurements is presented. (Fe3O4@Au)@SiO2 nanoparticles turned out to be very efficient substrates for SERS measurements. Moreover, due to the nanomaterial’s strong magnetic properties, it can be easily manipulated using a magnetic field, and it is therefore possible to form homogeneous layers (with no significant ‘coffee-ring’ effect) of (Fe3O4@Au)@SiO2 nanoparticles using a very simple procedure: depositing a drop of a sol of such nanoparticles and evaporating the solvent after placing the sample in a strong magnetic field. Synthesised (Fe3O4@Au)@SiO2 nanostructures have been used for the SERS detection of penicillin G in milk. Good quality SERS spectra of penicillin G were obtained even at a concentration of penicillin G in milk of 1 nmol/l – this means that the SERS detection of penicillin G in milk is possible at a concentration lower than the maximum residue limit of penicillin G in milk established by the European Commission..

Interfacial Assembly of Anisotropic Core-Shell and Hollow Microgels.

Microgels, cross-linked polymers with submicrometer size, are ideal soft model systems. While spherical microgels have been studied extensively, anisotropic microgels have hardly been investigated. In this study, we compare the interfacial deformation and assembly of anisotropic core-shell and hollow microgels. The core-shell microgel consists of an elliptical core of hematite covered with a thin silica layer and a thin shell made of poly(N-isopropylacrylamide). The hollow microgels were obtained after a two-step etching procedure of the inorganic core. The behavior of these microgels at the oil-water interface was investigated in a Langmuir-Blodgett trough combined with ex situ atomic force microscopy. First, the influence of the architecture of anisotropic microgels on their spreading at the interface was investigated experimentally and by dissipative particle dynamic simulations. Hereby, the importance of the local shell thickness on the lateral and longitudinal interfacial deformation was highlighted as well as the differences between the core-shell and hollow architectures. The shape of the compression isotherms as well as the dimensions, ordering, and orientation of the microgels at the different compressions were analyzed. Due to their anisotropic shape and stiffness, both anisotropic microgels were found to exhibit significant capillary interactions with a preferential side-to-side assembly leading to stable microgel clusters at low interfacial coverage. Such capillary interactions were found to decrease in the case of the more deformable hollow anisotropic microgels. Consequently, anisotropic hollow microgels were found to distribute more evenly at high surface pressure compared to stiffer core-shell microgels. Our findings emphasize the complex interplay between the colloid design, anisotropy, and softness on the interfacial assembly and the opportunities it therefore offers to create more complex ordered interfaces.

Optically Left-Handed Nanopearl Beads with Inductance-Capacitance Circuits at Visible-Near-Infrared Frequencies Based on Scalable Methods.

Optically left-handed materials refract the propagating light in the opposite direction. Most research has focused on the design of various structures, including split-ring resonators, either on planes or in particle cluster forms to resonate with specific light frequencies. However, for particle-based materials, the circuital structures for optical left-handedness have not been fully understood and the effect of interior structure on the optical handedness have not been investigated. Additionally, scalable methods to deploy the unique characteristics of the materials have not been reported so far and are still urgent. Here, optically left-handed nanopearl beads are synthesized in up to 1.25 L solutions. Nanopearl beads contain assembled Au nanocolloids, a dielectric sphere, and a thin silica layer that fixes the assembled structures to sustainably yield unique inductance-capacitance circuits at specific visible-near-infrared frequencies. The frequencies are tunable by modulating the interior structures. Investigation of the circuit structures and Poynting vectors generated within the nanopearl beads suggest the likelihood of their left-handedness. Moreover, the effects of interior structures on the optical handedness of the nanopearl beads are extensively investigated. The results could help commercialize optically left-handed materials and pioneer fields that have not been realized so far.

Efficient beam manipulation with Huygens-geometric metasurface supporting pure magnetic resonances

In this work, we propose the concept of Huygens-geometric metasurface by stimulating two magnetic dipoles with designated phases. A theoretical model is developed to reveal its physical mechanism, and the required conditions for zero-backward scattering are derived. We verify the model with an anisotropic all-dielectric meta-atom, which is composed of a thin silica layer sandwiched by two silicon nanofins. The meta-atom with a maximum conversion efficiency of 98.8% and robust against the variation of the structural parameters can be applied in high-efficiency transmitted beam manipulation, such as beam deflection and focusing. Our work paves the way for the development of high-performance functional meta-devices.

Analysis of the charging kinetics in silver nanoparticles-silica nanocomposite dielectrics at different temperatures

Dielectric nanocomposite materials are now involved in a large panel of electrical engineering applications ranging from micro-/nano-electronics to power devices. The performances of all these systems are critically dependent on the evolution of the electrical properties of the dielectric parts, especially under temperature increase. In this study we investigate the impact of a single plane of silver nanoparticles (AgNPs), embedded near the surface of a thin silica (SiO2) layer, on the electric field distribution, the charge injection and the charge dynamic processes for different AgNPs-based nanocomposites and various temperatures in the range 25°C–110°C. The electrical charges are injected locally by using an Atomic Force Microscopy (AFM) tip and the related surface potential profile is probed by Kelvin Probe Force Microscopy (KPFM). To get deeper in the understanding of the physical phenomena, the electric field distribution in the AgNPs-based nanocomposites is computed by using a Finite Element Modeling (FEM). The results show a strong electrostatic coupling between the AFM tip and the AgNPs, as well as between the AgNPs when the AgNPs-plane is embedded in the vicinity of the SiO2-layer surface. At low temperature (25°C) the presence of an AgNPs-plane close to the surface, i.e., at a distance of 7 nm, limits the amount of injected charges. Besides, the AgNPs retain the injected charges and prevent from charge lateral spreading after injection. When the temperature is relatively high (110°C) the amount of injected charges is increased in the nanocomposites compared to low temperatures. Moreover, the speed of lateral charge spreading is increased for the AgNPs-based nanocomposites. All these findings imply that the lateral charge transport in the nanocomposite structures is favored by the closely situated AgNPs because of the strong electrostatic coupling between them, additionally activated by the temperature increase.

Long-term stable, high accuracy, and visual detection platform for In-field analysis of nitrite in food based on colorimetric test paper and deep convolutional neural networks

Nitrite is one of the most common carcinogens in daily food. Its simple, rapid, inexpensive, and in-field measurement is important for food safety, based on the requirements of the standard from Codex Alimentarius Commission and China. Using polyacrylonitrile (PAN) and thin layer silica gel (SG), p-aminophenylcyclic acid (SA) and naphthalene ethylenediamine hydrochloride (NEH), as carriers and chromogenic agents, respectively, PAN-NSS as nitrite color sensor is proposed. After fixing and protecting of SA and NEH with layer-upon-layer PAN, the validity period of the test paper can be prolonged from 7 days to more than 30 days. The reproducibility of PAN-NSS preparation is ensured by electrospinning. Combined with PAN-NSS, deep convolutional neural network (DCNN) and APP as a visual monitoring platform, which has the functions of rapid sampling, data processing and transmission, intuitive feedback, etc., and provides a fully integrated detection system for field detection.

Photopolymerized Thin Coating of Polypyrrole/Graphene Nanofiber/Iron Oxide onto Nonpolar Plastic for Flexible Electromagnetic Radiation Shielding, Strain Sensing, and Non‐Contact Heating Applications

AbstractThe current work presents the fabrication of micrometer‐thick single‐side‐coated surface‐engineered polypropylene (PP) film for versatile flexible electronics applications. Herein, the authors report, for the first time, photopolymerized thin coating of graphene nanofibers (GNFs) and iron oxide nanoparticles (IONPs) onto non‐polar plastic via surface chemistry. The fabrication is achieved by adopting three consecutive steps; initially corona treated PP films are treated with silane for thin layer silica coating. Then, the silylated PP films are brushed up by pyrrole/GNFs/IONPs mixture, followed by UV exposure. The coated films show surface conductivity in the range of ≈20 S cm−1 at room temperature. Moreover, ≈15 microns of the coated film is tested against electromagnetic waves in the X‐band region (8.2–12.4 GHz) and its shielding behavior (≈24 dB) is confirmed. To demonstrate its wide range of versatility, the coated films are tested against angular strain and oscillatory magnetic fields. The results confirm angle dependent strain sensitivity and induction heating obeying Néel relaxation. To the best of the authors’ knowledge, this is the first synergistic coating archived for mitigating radiation pollution, strain sensing, and non‐contact heating.

Metal‐Organic Frameworks Derived Titanium Oxides via Soft Interface Adaptive Transformation

AbstractHigh‐temperature treatment of metal‐organic frameworks (MOFs) is a promising route to prepare a variety of functional materials with diverse applications. However, it is challenging to prepare highly crystalline metal oxides such as TiO2 with controllable structures and morphologies via direct calcination of MOFs. Here, we report a soft interface adaptive transformation strategy for the synthesis of MOFs derived TiO2 nanoparticles with elaborate structures. The soft interface is constructed by coating a thin silica layer on the external surface of Ti‐MOFs with an octahedral morphology. This soft interface can partially adapt to the significant shrinkage and counteract the contraction force during the MOFs‐to‐TiO2 conversion. As a result, TiO2 hollow octahedrons are formed with a concave morphology, high specific surface area, abundant oxygen vacancy sites, and consequently enhanced photocatalytic activity, which cannot be obtained by direct calcination or coating a thick/rigid silica layer. The opposite impact of the interface on MOFs derived metal oxides and carbon materials is further elucidated. This contribution provides new understandings in the synthesis of MOFs derived functional materials.

Well-Defined Hexagonal Platy Particles of Brucite, Brucite/Silica Core Shell, and Hollow Silica Particle

Abstract Well-defined Mg(OH)2 (brucite) hexagonal platy particles with the lateral size of 80 nm were prepared by precipitation from an aqueous solution of magnesium chloride using a flow reactor with controlled pressure injection. The brucite particles were coated with a thin silica layer by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) catalyzed by ammonium hydroxide to obtain Mg(OH)2@SiO2 core-shell nanoparticle. The heat treatment of the Mg(OH)2@SiO2 in air at 500 °C resulted in the transformation of brucite to periclase MgO. The Mg(OH)2 and MgO cores were removed from Mg(OH)2@SiO2 and MgO@SiO2 core-shell particles by etching with hydrochloric acid to obtain hollow silica particles with a lateral size range of 6 to 12 nm. Meanwhile, heat treatment of the Mg(OH)2@SiO2 at 1000 °C resulted in the transformation of brucite to periclase and forsterite.

Hydrophobic Silica Thin Film derived from Dimethyldimethoxysilane-Tetraethylorthosilicate for Desalination

Silica thin film preparation was carried out from dimethyldimethoxysilane (DMDMS) and tetraethylorthosilicate (TEOS) precursors using the sol-gel method, and the effect of pH on the character of the resulting silica membrane was also studied. The solution pH was varied into 2.21; 3.92; 4.98; 6.44; and 7.21. The resulting xerogel was analyzed using Fourier-transform infrared spectroscopy, Thermogravimetric Analysis, and Gas Sorption Analysis. While the silica thin layer was measured for its hydrophobic character and surface morphology using Scanning Electron Microscope. The presence of DMDMS-TEOS silica thin film had a considerable influence on the hydrophobic nature of the ceramic plate surface. The membrane prepared under neutral conditions produced desirable properties, such as higher thermal stability, greater pore volume, thermal stability, and higher hydrophobicity. For the desalination process, the obtained silica membrane showed excellent separation performance (>99%), especially at low salt concentrations. When the pH increased, the water flux also increased. The thin films worked well for desalination through a pervaporation mechanism.

Super Magnetic Niosomal Nanocarrier as a New Approach for Treatment of Breast Cancer: A Case Study on SK-BR-3 and MDA-MB-231 Cell Lines.

In the present study, a magnetic niosomal nanocarrier for co-delivery of curcumin and letrozole into breast cancer cells has been designed. The magnetic NiCoFe2O4 core was coated by a thin layer of silica, followed by a niosomal structure, allowing us to load letrozole and curcumin into the silica layer and niosomal layer, respectively, and investigate their synergic effects on breast cancer cells. Furthermore, the nanocarriers demonstrated a pH-dependent release due to the niosomal structure at their outer layer, which is a promising behavior for cancer treatment. Additionally, cellular assays revealed that the nanocarriers had low cellular uptake in the case of non-tumorigenic cells (i.e., MCF-10A) and related high viability but high cellular uptake in cancer cell lines (i.e., MDA-MB-231 and SK-BR-3) and related low viability, which is evidenced in their high cytotoxicity against different breast cancer cell lines. The cytotoxicity of the letrozole/curcumin co-loaded nanocarrier is higher than that of the aqueous solutions of both drugs, indicating their enhanced cellular uptake in their encapsulated states. In particular, NiCoFe2O4@L-Silica-L@C-Niosome showed the highest cytotoxicity effects on MDA-MB-231 and SK-BR-3 breast cancer cells. The observed cytotoxicity was due to regulation of the expression levels of the studied genes in breast cancer cells, where downregulation was observed for the Bcl-2, MMP 2, MMP 9, cyclin D, and cyclin E genes while upregulation of the expression of the Bax, caspase-3, and caspase-9 genes was observed. The flow cytometry results also revealed that NiCoFe2O4@L-Silica-L@C-Niosome enhanced the apoptosis rate in both MDA-MB-231 and SK-BR-3 cells compared to the control samples. The findings of our research show the potential of designing magnetic niosomal formulations for simultaneous targeted delivery of both hydrophobic and hydrophilic drugs into cancer cells in order to enhance their synergic chemotherapeutic effects. These results could open new avenues into the future of nanomedicine and the development of theranostic agents.

A Magnetic Nanocomposite Modifier for Improved Ultrasensitive Detection of Hexavalent Chromium in Water Samples

In this work, different electrodes were employed for the determination of Cr(VI) by the cathodic square-wave voltammetry (SWV) technique and the square-wave adsorptive stripping voltammetry (SWAdSV) technique in combination with diethylenetriaminepentaacetic acid. Using SWV, a comparison of the analytical performance of the bare glassy carbon electrode (GCE), ex situ electrodes (antimony-film—SbFE, copper-film—CuFE, and bismuth-film—BiFE), and the GCE modified with a new magnetic nanocomposite (MNC) material was performed. First, the MNC material was synthesized, i.e., MNPs@SiO2@Lys, where MNPs stands for magnetic maghemite nanoparticles, coated with a thin amorphous silica (SiO2) layer, which was additionally functionalized with derived lysine (Lys). The crystal structure of the prepared MNCs was confirmed by X-ray powder diffraction (XRD), while the morphology and nano-size of the MNCs were investigated by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), where TEM was additionally used to observe the MNP core and silica layer thickness. The presence of functional groups of the MNCs was investigated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and surface analysis was performed by X-ray photoelectron spectroscopy (XPS). The hydrophilicity of the modified electrodes was also tested by static contact angle measurements. Then, MNPs@SiO2@Lys was applied onto the electrodes and used with the SWV and SWAdSV techniques. All electrodes tested with the SWV technique were effective for Cr(VI) trace determination. On the other hand, the SWAdSV technique was required for ultra-trace determination of Cr(VI). Using the SWAdSV technique, it was shown that a combination of ex situ BiFE with the deposited MNPs@SiO2@Lys resulted in excellent analytical performance (LOQ = 0.1 µg/L, a linear concentration range of 0.2–2.0 µg/L, significantly higher sensitivity compared to the SWV technique, an RSD representing reproducibility of 9.0%, and an average recovery of 98.5%). The applicability of the latter system was also demonstrated for the analysis of a real sample.

Synthesis of iridium-based nanocomposite with catalase activity for cancer phototherapy

The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) has attracted attention due to its enhanced tumor therapy effect. This study proposes a novel nanoenzyme-based theranostic nanoplatform, IrO2@MSN@PDA-BSA(Ce6), for the combined PTT and PDT of tumors. IrO2 was prepared by a simple hydrolysis method and coated with a thin layer of mesoporous silica (MSN) to facilitate the physical adsorption of Chlorin e6 (Ce6). The PDA coating and IrO2 NPs of the nanoplatform demonstrated an improved photothermal conversion efficiency of 29.8% under NIR irradiation. Further, the Ce6 loading imparts materials with the ability to produce reactive oxygen species (ROS) under 660 nm NIR laser irradiation. It was also proved that the IrO2 NPs could catalyze the hydrogen peroxide (H2O2) in the tumor microenvironment (TME) to generate endogenous oxygen (O2), thereby enhancing the efficiency of PDT. The in vitro and in vivo experiments indicated that the nanocomposite was highly biocompatible and could produce a satisfactory tumor therapeutic effect. Thus, the findings of the present study demonstrate the viability of using theranostic nanoenzymes for translational medicine.

Analysis of growth, yield and control of Cophes notaticeps and Polyphagotarsonemus latus in Jatropha curcas plants under different doses of silicon

The present study aims to evaluate the effects of Si on growth, yield and resistance of Jatropha curcas plants to Cophes notaticeps and Polyphagotarsonemus latus. The study was carried out in two consecutive years with J. curcas plants with 3 years old in 3x2 m spacing. The assays were set up with randomized complete block design with five concentrations (0, 10, 20, 40 and 80 mM L-1) and five replications. It was set up another experiment in a greenhouse following completely randomized factorial design 5x2 with five silicon concentrations (0, 10, 20, 40 and 80 mM L-1) and two water supply: daily irrigation with water volumes according to 50% and 100% of evapotranspiration, six replications and one plant per plot. The present study allows clarifying that J. curcas plants are non-accumulating plants, for accumulating less than 1% of silicon in the leaves. The low accumulation of silicon in the leaves did not significantly inferred in growth of J. curcas, however, the reduction of specific leaf area possibly occurred by the formation of a thin silica layer and reduced the yield by the decrease sunlight absorption. The silicon did not mitigated the damages by Cophes notaticeps and Polyphagotarsonemus latus by the low ability of the plant to accumulate silicon, however, is possible to affirm that the injuries severity by Cophes notaticeps is proportional to stem diameter.

Solid-Phase Fluorimetric Determination of Tetracyclines in Medicinal Preparations on Cellulose Paper and in Thin-Layer Silica Gel Using a Smartphone

Solid-Phase Fluorimetric Determination of Tetracyclines in Medicinal Preparations on Cellulose Paper and in Thin-Layer Silica Gel Using a Smartphone

Growth pattern of the siliceous skeletons of living Spumellaria (Radiolaria) from the Kuroshio Current, offshore southwestern Shikoku Island, Japan

Experimental culture studies of living radiolarians experience many difficulties because radiolarians are too sensitive to be maintained alive in artificial conditions. We here developed an improved experimental protocol in order to detect newly-formed parts of the polycystine radiolarian skeletons after they were labeled with fluorescent markers. Living samples were collected from surface seawater of the Kuroshio Current offshore from Kashiwajima Island, Kochi Prefecture on the island of Shikoku, Japan. The taxonomic composition of the Kashiwajima radiolarian samples varied markedly across the seasons and sampling sites. Spumellaria were usually abundant in samples collected near Kashiwajima, and had high diversity in shell morphology. Here, we performed experimental studies on living spumellarian radiolarians to clarify their siliceous skeletogenesis. Our culture-based research on spumellarians provided the following results.(A) The pattern of silica deposition on the skeleton of Spongaster tetras tetras varies depending on the growth stage. Three ontogenetic stages were identified: (1) young, (2) progressively-growing and (3) fully-grown. Furthermore, novel varied types of skeletal growth modes were determined as follows: (i) rapid growth on the outermost shell with enlargement of shell size and (ii) internal deposition on skeletal components without change in shell size. From measurements of the growth rate of cultured radiolarians, it is assumed that S. tetras tetras cell has at least a month-long life cycle.(B) Spherical spumellarians have their own shell-forming strategy that permits additional silicogenesis while maintaining the taxonomically-specific shape of their shell; the meshwork of their shell surface consists of polygonal-shaped pore-frames formed by heterogeneous patterns of added silica.Our direct observation with fluorescence markers detected a skeletogenesis process of Haliommilla capillacea possessing a fragile spherical shell. We thus confirm the bridge-growth hypothesis for morphogenesis of the polygonal frame as proposed in previous studies. Spongosphaera streptacantha, having extremely long spines, exhibited a special growth pattern of spine elongation in a centrifugal direction, without a change in width. This was achieved by a particular temporal pattern of silicification characterized by an alternating pattern of patchy addition of new silica on the entire part of each blade from the base to the tip. Moreover, a thin layer of new silica was added by a flowing deposition along the edge of the spine. Based on these culture-based studies using living radiolarians, we conclude that Spumellaria control and maintain a particular shell shape by regulating where silicification takes place on the skeleton, particularly depending on the growth stage.

Suppressing the Photocatalytic Activity of Titania by Precisely Controlled Silica Coating.

A homogeneous thin silica layer with the thickness of a few nanometers was successfully deposited on an anatase particle by the hydrolysis and condensation of tetraethyl orthosilicate. The heat treatment of the titania/silica hybrid at 1000 °C led to the densification of the silica layer on the anatase particles. The anatase particle after the silica coating did not transform to rutile, and no change in the crystallite size was seen by the heat treatment at 1000 °C. The coating and subsequent heating were repeated to vary the thickness of the silica layer to obtain each coating with similar thickness by each coating procedure (ca. 3 and 2 nm, before and after the heat treatment). The samples were evaluated for the photocatalytic decomposition of methylene blue by the UV irradiation to find that the decomposition became slower after the coating and subsequent heat treatment, and the repeated procedures led to further suppression of the photocatalytic decomposition of methylene blue. The quite small decomposition rate constant (0.01 h-1) was successfully achieved by the coating and subsequent heating for three times (the thickness of the dense silica layer was ca. 7 nm).

Hydrophilic Antireflection and Antidust Silica Coatings.

We report on the optical and morphological properties of silica thin layers deposited by reactive RF magnetron sputtering of a SiO2 target under different oxygen to total flow ratios [r(O2) = O2/Ar, ranging from 0 to 25%]. The refractive index (n), extinction coefficient, total transmission, and total reflectance were systematically investigated, while field-emission scanning electron microscopy, atomic force microscopy, and three-dimensional (3D) average roughness data construction measurements were carried out to probe the surface morphology. Contact angle measurements were performed to assess the hydrophilicity of our coatings as a function of the oxygen content. We performed a thorough numerical analysis using 1D-solar cell capacitance simulator (SCAPS-1D) based on the measured experimental optical properties to simulate the photovoltaic (PV) device performance, where a clear improvement in the photoconversion efficiency from 25 to 26.5% was clearly observed with respect to r(O2). Finally, a computational analysis using OptiLayer confirmed a minimum total reflectance of less than 0.4% by coupling a silica layer with n = 1.415 with another high-refractive-index (i.e., >2) oxide layer. These promising results pave the way for optimization of silica thin films as efficient antireflection and self-cleaning coatings to display better PV performance in a variety of locations including a desert environment.

Ultrafast Synthesis of Silica-Based Molecular Sieve Membranes in Dielectric Barrier Discharge at Low Temperature and Atmospheric Pressure.

Microporous silica membranes have shown promise as potential candidates for energy-efficient chemical separation. Herein, we report the ultrafast synthesis of silica membranes, on the order of minutes, in atmospheric-pressure, low-temperature plasma. Direct deposition in the discharge region of atmospheric-pressure plasma enables the immediate formation of a thin silica layer on a porous substrate. The plasma-deposited layer had a thickness of ∼13 nm and was confined to the immediate surface of the substrate. With an increase in deposition temperature, we observed an increase in the inorganic nature of the plasma-deposited layer and simultaneous improvement in the membrane performance. Consequently, the resulting membranes exhibited outstanding permeance for small-sized gas molecules, such as H2 (>10-6 mol m-2 s-1 Pa-1), with a high H2/SF6 permeance ratio of ∼6300, providing a nonthermal alternative for the fabrication of silica-based membranes.