Deposition Of Nanoparticles Research Articles

Perovskite Oxide Catalysts for Enhanced CO2 Reduction: Embroidering Surface Decoration with Ni and Cu Nanoparticles

The imperative reduction of carbon dioxide into valuable fuels stands as a crucial step in the transition towards a more sustainable energy system. Perovskite oxides, with their high compositional and property adjustability, emerge as promising catalysts for this purpose, whether employed independently or as a supporting matrix for other active metals. In this study, an A-site-deficient La0.9FeO3 perovskite underwent surface decoration with Ni, Cu or Ni + Cu via a citric acid-templated wet impregnation method. Following extensive characterization through XRD, N2 physisorption, H2-TPR, SEM-EDX, HAADF STEM-EDX mapping, CO2-TPD and XPS, the prepared powders underwent reduction under diluted H2 to yield metallic nanoparticles (NPs). The prepared catalysts were then evaluated for CO2 reduction in a CO2/H2 = 1/4 mixture. The deposition of Ni or Cu NPs on the perovskite support significantly enhanced the conversion of CO2, achieving a 50% conversion rate at 500 °C, albeit resulting in only CO as the final product. Notably, the catalyst featuring Ni-Cu co-deposition outperformed in the intermediate temperature range, exhibiting high selectivity for CH4 production around 350 °C. For this latter catalyst, a synergistic effect of the metal–support interaction was evidenced by H2-TPR and CO2-TPD experiments as well as a better nanoparticle dispersion. A remarkable stability in a 20 h time-span was also demonstrated for all catalysts, especially the one with Ni-Cu co-deposition.

Versatile MOF-based nanofibrous heterostructures for engineering the CO2 photoreduction activity and selectivity: From CO to C2H5OH

Photocatalytic CO2 reduction is a potential promising strategy for eliminating the global energy crisis and environmental issue. However, the complex reduction pathway leads to multiple possible products with limited efficiency, representing a great barrier for the further development. Herein, we report a Metal-organic framework (MOF) based heterostructure model for the efficient photoreduction of CO2 with full controllable product selectivity between CO and C2H5OH. Novel core-sheath like MOF@TiO2 heterostructures could be efficiently prepared by the layer-by-layer (LBL) growth of HKUST-1 onto Cu-embedded TiO2 nanofibers (NFs), affording covalent heterointerfaces for efficient S-scheme charge separation and promising potential in photocatalytic activity regulation. By improving the CO2 capture and retention via in situ amino-functionalization of HKUST-1, the photocatalytic CO production rate could be greatly promoted from 8.76 ± 0.84 to 43.46 ± 0.86 μmol g−1h−1 accompanied by an enhancement of selectivity from 91.7 % to 98.3 %. Moreover, the product could be efficiently engineered into ethanol with a C2 product selectivity of 94.2 % by introducing Cu nanoparticles (NPs) as the additional CC coupling site. The in situ FT-IR and DFT calculations reveal the mechanistic process and decisive role of amino-functionalization and Cu NPs deposition in photocatalytic activity engineering. This work highlights the key factors and significance of fabricating MOFs based heterostructures with tunable photocatalytic activity for achieving CO2 neutralization.

Functionalization of silver nanoparticles coating cotton fabrics through hydrothermal synthesis for improved antimicrobial properties

Deposition of silver nanoparticles (AgNPs) on the surfaces of cotton fabric (CF) is an approach for producing antimicrobial textile products. CF-AgNPs composites were fabricated ex situ using a simple hydrothermal synthesis of AgNPs, while the fabric was surface modified using a plasma to improve adhesion prior to coating. The morphology and chemical composition of CF-AgNPs nanocomposites were examined using UV–vis spectrophotometry (UV–vis), x-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Study results show uniform deposition of AgNPs on cotton fabrics. The CF-AgNPs composite material exhibits excellent laundering durability and antimicrobial performance against Gram-positive, Staphylococcus aureus and Gram-negative, Escherichia coli pathogens. These findings indicate that the developed fabric can be used in a wide range of biomedical applications, health care and various packaging systems.

Deposition of Pd, Pt, and PdPt Nanoparticles on TiO2 Powder Using Supercritical Fluid Reactive Deposition: Application in the Direct Synthesis of H2O2.

In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium dioxide (TiO2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 K and 15.6 MPa enabled the deposition of uniform mono- and bimetallic nanoparticles smaller than 3 nm on TiO2. Electron-dispersive X-ray spectroscopy demonstrated the formation of alloy-type structures for the bimetallic PdPt nanoparticles. H2O2 is an excellent oxidizing reagent for the production of fine and bulk chemicals. However, until today, the design and preparation of catalysts with high H2O2 selectivity and productivity remain a great challenge. The focus of this study was on answering the questions of (a) whether the catalysts produced are suitable for the direct synthesis of hydrogen peroxide (H2O2) in the liquid phase and (b) how the metal type affects the catalytic properties. It was found that the metal type (Pd or Pt) influenced the catalytic performance strongly; the mean productivity of the mono- and bimetallic catalysts decreased in the following order: Pd > PdPt > Pt. Furthermore, all catalysts prepared by SFRD showed a significantly higher mean productivity compared to the catalyst prepared by incipient wetness impregnation.

Numerical investigation of nanoparticle deposition in a microchannel under the influence of various forces and development of a new correlation

Nanofluid-microchannels have gained prominence in recent years as a means of cooling electronic devices; however, nanoparticle deposition remains a challenge. In this paper, a discrete phase model (DPM) is used to study the effects of various forces on nanoparticle deposition of Al2O3-water nanofluids in a straight microchannel. The results indicate that Brownian motion has a significant impact on nanoparticle deposition. For instance, when Cunningham values vary from 1.2 to 0.2, nanoparticle deposition ratios decrease from 8.69% to 3.41%. When the fluid velocity is <0.6 m/s, the thermophoretic force becomes crucial, whereas Saffman's lift force becomes important when the particle diameter is <10 nm. In addition, gravity and pressure gradient forces can be ignored. Virtual mass and drag forces impact deposition indirectly by changing residence times. Finally, a new correlation has been proposed for calculating particle deposition ratios.

Nanoarchitectonics and electrocatalytic properties of platinum nanoparticles in weak polyelectrolytes‐based multilayer thin films

AbstractIn this study, the electrocatalytic behavior of platinum (Pt) nanoparticles (NPs) in a novel multilayered thin film is investigated for proton exchange membrane fuel cells (PEMFC) applications. The multilayer thin films are assembled by the alternate deposition of branched polyethylenimine (BPEI) and poly(acrylic acid) (PAA) from aqueous solutions through a layer‐by‐layer (LbL) technique. Two extreme assembly pH conditions critically influence the films' physical and morphological characteristics, subsequently affecting their electrochemical behavior. Manipulation of the assembly pH modifies the charge density of the weak polyelectrolytes (BPEI and PAA), leading to variations in physical, structural, and electrochemical properties. The LbL thin films assembled at a pH of 9.5 for BPEI and 4.5 for PAA exhibit significantly greater thickness compared to the same film with all components deposited at pH 4.5. This is attributed to in‐and‐out diffusion of the partially charged polyelectrolytes with coiled polymeric conformation (BPEI at pH 9.5 and PAA at pH 4.5). As‐assembled LbL thin films are used as nanoreactors for the deposition of Pt NPs. The nanoscale control over polymeric conformation and charge density significantly influences electrocatalytic performance. 9.5BPEI/4.5PAA thin films exhibit higher electrocatalytic activity relative to 4.5BPEI/4.5PAA systems. This improved performance in 9.5BPEI/4.5PAA multilayers is ascribed to the fact that more carboxylic acid groups of PAA are coated in an exponentially grown behavior, which provides more active sites available for Pt NPs to be deposited. The multilayer thin films containing uniformly dispersed Pt NPs can be an attractive and advanced hybrid electrode material with great promise for the proton exchange membrane fuel cells.

Functionalization of Carbon Electrode Surface Using Polyaniline and Gold Nanoparticles for Protein Immobilization

This study presents a screen-printed carbon electrode surface functionalization to immobilize proteins. The process involves the deposition of gold nanoparticles on the carbon electrode and subsequent surface modification to immobilize bovine serum albumin–fluorescein isothiocyanate conjugate (BSA-FITC). A combination of conducting polymer and gold nanoparticles was employed to enhance the electrode contact area and current transmission. The electrode surface morphology and properties were evaluated by scanning electron microscopy (SEM) and Raman spectroscopy, showing the porous polyaniline (PANI) film has been formed on the carbon electrode surface with the network of dendritic nanofibers. Gold nanoparticles were evenly distributed on the PANI film to form a nanocomposite material layer on the carbon electrode. The observed size of these gold nanoparticles was significantly smaller than those on the electrode without a PANI film. Additionally, the current transmission of this composite material layer has been verified by cyclic voltammetry (CV). The results show that the amplitude of the redox peak was doubled compared to the bare carbon electrode and gold nanoparticle-only deposited electrode. Moreover, the success of the process was verified by fluorescence and cyclic voltammetry. The fluorescent green color observed under the microscope indicated that BSA-FITC was on the electrode surface. The change of CV signal after each step verified the formation of a new layer on the electrode surface. These results are anticipated to play an important role in developing high-sensitivity immunosensors in the future.

Effect of micro-/nano-porous thin film surfaces prepared by a hybrid method of etching and electrochemical deposition on pool boiling heat transfer performance

Surfaces created using efficient and inexpensive methods are highly demanded in industrial applications of extremely high temperatures. In this study, Composite Nano-particle Coated Over CuO Filmed (CNCCF) surface is prepared through two processes, first through chemical etching to produce a thin film of CuO over bare Cu surface, and secondly deposition of Ni-Al2O3 composite nano-particle over CuO thin filmed copper surface by electrochemical deposition process. The completed CNCCF surface exhibits favorable characteristics for improved boiling heat transmission, such as wettability, roughness, porosity, etc. An experiment on pool boiling is conducted on the CNCCF and bare Cu surface. DI water at atmospheric pressure is used as the boiling fluid. Findings show that the CNCCF surface exhibits enhanced Critical Heat Flux (CHF) and Boiling heat Transfer Coefficient (BHTC) than bare Cu surface. The increased porosity, roughness, and other properties of the CNCCF surface are the cause of this improvement in CHF and BHTC. A high-speed camera is also used to monitor and analyze bubble behavior during boiling on all surfaces, including the Bare Cu. Further evidence for the enhancement of boiling heat transfer on the CNCCF surface comes from the nucleation site density, departure diameter, and frequency characteristics of bubbles.

Ultrafine Ru nanoparticles anchored on N-doped mesoporous hollow carbon spheres as a highly efficient bifunctional catalyst for Li–CO2 batteries

Rechargeable Li–CO2 battery is a facilitative and promising device for the conversion of CO2 to electrochemical energy. However, it remains a challenge to enhance the sluggish decomposition kinetics of lithium carbonate as the discharge product. Herein, the Ru nanoparticles anchored on N-doped mesoporous hollow carbon nanospheres (Ru-AHCNs) are designed as cathode to enhance the electrochemical performance of Li–CO2 battery. The Ru-AHCNs cathode displays a high discharge specific capacity of 11194.4 mA h g−1 at the current density of 100 mA g−1. In addition, the Ru-AHCNs cathode can stably run over 50 cycles and maintain a small overpotential (<1.38 V) with a limited capacity of 1000 mA h g−1 at 100 mA g−1. The excellent stability and catalytic activity of the cathode are ascribed to the following factors: (i) Uniform deposition of Ru nanoparticles in hollow carbon nanospheres can enhance the decomposition of Li2CO3 and provide considerable exposure to active sites. (ii) N-doped mesoporous hollow carbon nanospheres can provide abundant electron transport channels and promote the nucleation of discharge products. These results evidently prove the reversible formation and decomposition of the discharge products, indicating that Ru-AHCNs cathode possesses excellent bifunctional catalytic activity.

When mussel meets lotus leaf and pitcher plant: A combinational biomimetic strategy for Mg-Li corrosion inhibition

Magnesium-lithium alloys hold immense promise as lightweight structural materials due to combination of unique properties. However, their widespread application is hindered by the inherent poor corrosion resistance. This research presents a novel and cost-effective approach to address this obstacle by utilizing metal-phenol networks inspired by mussel as surface modifiers. These networks facilitate the deposition of nanoparticle on magnesium-lithium (Mg-Li) alloys through chemical reactions between phenolic groups and metal ions. The resulting surface is further enhanced by spray-coating a sheet-like biomimetic superhydrophobic surface (SHS) of alkyl-ketone dimer (AKD), subsequently followed by lubricant infusion with dimethylsilicone oil to create a slippery liquid-infused porous surface (SLIPS). Characterization using multiple techniques confirms the chemical composition and morphology of the modified surface, which significantly improves the corrosion resistance of the magnesium-lithium alloy. Importantly, scanning Kelvin probe measurements reveal that SHS and SLIPS enhance the atmospheric corrosion resistance of the material. Further validation in 3.5 wt% NaCl solution demonstrates remarkable effectiveness of SLIPS. During the initial stages of immersion, the impedance magnitude |Z|0.01 Hz for SLIPS reaches a remarkable 3.78 × 107 Ω·cm2, exceeding those of the SHS, TA-LA141, and bare LA141 by 3, 3, and 6 orders of magnitude, respectively. This performance persists even after long-term immersion, with the SLIPS coating still exhibiting an impedance value one order of magnitude higher than the SHS after extended exposure. These results establish the effectiveness of SLIPS as a promising candidate for significantly upgrading the corrosion resistance of Mg-Li alloy, paving the way for their broader utilization in demanding fields.

Celastrol reduces lung inflammation induced by multiwalled carbon nanotubes in mice via NF-κb-signaling pathway

Multiwalled carbon nanotubes (MWCNTs) have numerous applications in the field of carbon nanomaterials. However, the associated toxicity concerns have increased significantly because of their widespread use. The inhalation of MWCNTs can lead to nanoparticle deposition in the lung tissue, causing inflammation and health risks. In this study, celastrol, a natural plant medicine with potent anti-inflammatory properties, effectively reduced the number of inflammatory cells, including white blood cells, neutrophils, and lymphocytes, and levels of inflammatory cytokines, such as IL-1β, IL-6, and TNF-α, in mice lungs exposed to MWCNTs. Moreover, celastrol inhibited the activation of the NF-κB-signaling pathway. This study confirmed these findings by demonstrating comparable reductions in inflammation upon exposure to MWCNTs in mice with the deletion of NF-κB (P50−/−). These results indicate the utility of celastrol as a promising pharmacological agent for preventing MWCNT-induced lung tissue inflammation.

Experimental study of pool boiling performance of Fe3O4 ferromagnetic nanofluid on a copper surface

Nanofluids significantly enhance the critical heat flux of boiling heat transfer. This paper experimentally investigates the pool boiling performance and the influence mechanism of Fe3O4 nanofluids. Compared with deionized water, the 0.001 vol% nanofluid increases a maximum enhancement in critical heat flux by 47.90%. During nanofluid boiling, Fe3O4 nanoparticles are deposited on the surfaces. The nanoparticle deposition surfaces are physically characterized to explain the influence mechanism of Fe3O4 nanoparticles on boiling heat transfer. Nanoparticle deposition modifies the surface micro-morphology, which increases roughness and improves wettability. The changes are essential factors for the enhancement of the critical heat flux. This paper further analyses the boiling results of deionized water on the nanoparticle deposition surfaces. Compared with a polished surface, the critical heat flux and heat transfer coefficient of the nanoparticle deposition surface show maximum increases of 52.39% and 56.19%. Due to the similar enhancement of critical heat flux using the Fe3O4 nanofluid and the nanoparticle deposition surface, it is found that the increased critical heat flux of the nanofluids is attributed to the improvement of surface wettability and roughness by nanoparticle deposition. This study analyzes the mechanism of Fe3O4 nanofluid for enhancing pool boiling heat transfer from the perspective of modifying boiling surface characteristics by nanoparticle deposition, especially in wettability and roughness, which advances the understanding of enhanced boiling heat transfer by nanofluids.

Constructing network structures to enhance stability and target deposition of selenium nanoparticles via amphiphilic sodium alginate and alkyl glycosides

Dietary selenium (Se) supplementation has recently received increasing attention; however, Selenium nanoparticles (SeNPs) exhibit poor stability and tend to aggregate in aqueous solution. Therefore, enhancing the stability of SeNPs and their effective delivery to plants remain challenging. In this study, sodium alginate (SA) and lysozyme (LZ) were reacted via the wet-heat Maillard reaction (MR) to obtain amphiphilic alginate-based polymers (SA-LZ). Alkyl glycosides (APG) were introduced into SA-LZ to enhance the deposition of SeNPs in leaves. Thus, a renewable and degradable polysaccharide-based material (SA-LZ/APG) loaded with Se formed an amphiphilic alginate-based-based shell with a Se core. Notably, the encapsulation of SeNPs into a polysaccharide base (SA-LZ/APG) increased the stabilization of SeNPs and resulted in orange–red, zero-valent, monoclinic and spherical SeNPs with a mean diameter of approximately 43.0 nm. In addition, SA-LZ/APG-SeNPs reduced the interfacial tension of plant leaves and increased the Se content of plants compared to the blank group. In vitro studies have reported that SA-LZ/APG-SeNPs and SA-LZ-SeNPs have significantly better clearance of DDPH and ABTS than that of APG-SeNPs. Thus, we believe that SA-LZ/APG is a promising smart delivery system that can synergistically enhance the stability of SeNPs in aqueous solutions and improve the bioavailability of Se nutrient solutions.

Precise regulation of Mo2N–TiO2 deposited Pt nanoparticles induced synergistic effect for the hydrogenation of cinnamaldehyde

The amalgamation of an appropriate cocatalyst is a proficient technique to expand the efficacy of precious Pt-based catalytic materials. In this study, Mo2N–TiO2 with regularly distributed Mo2N particles were simply prepared for the deposition of precious Pt nanoparticles (NPs). Numerous techniques were implemented to thoroughly explore, how synthesis method influence the bulk structural, interfacial and cata1ytic features of the as-prepared 3 wt%Pt/TiO2 and 3 wt%Pt/Mo2N–TiO2 catalytic materials. The catalytic results obviously show that the 3 wt%Pt/Mo2N–TiO2 catalyst has exceptional hydrogenation performance when compared to 3 wt%Pt/TiO2 catalyst. The 3 wt%Pt/Mo2N–TiO2 catalyst displayed high conversion (72.4 %) of cinnamaldehyde (CAL) with a maximum selectivity (82.1 %) towards CO bond. The excellent hydrogenation performance is attributed to the synergistic interaction taking place between Pt NPs and Mo2N entities of 3 wt%Pt/Mo2N–TiO2. Also, the enhanced standardized dispersal of Pt NPs on the Mo2N–TiO2 surface causes more exposed Pt0 sites on the 3 wt%Pt/Mo2N–TiO2 surface, which is productive for the improved activation and conversion of CO bond of CAL to yield COL. In addition, the 3 wt%Pt/Mo2N–TiO2 catalyst retained its higher catalytic activity for consecutive five successive rounds without substantial loss in either conversion or selectivity.

A comparative pyrolysis study of tetraethoxysilane and tetraethoxymethane: Insight into congener substitution effects on pyrolysis chemistry of siloxane flame synthesis precursors

The pyrolysis of siloxane precursors, such as tetraethoxysilane (TEOS), is commonly employed in the flame synthesis and chemical vapor deposition of silica nanoparticles. In this work, the flow reactor pyrolysis of TEOS is studied using gas chromatography (GC) and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), and the congener substitution effects from the central C atom to the central Si atom are investigated through comparison with its hydrocarbon counterpart tetraethoxymethane (TEOM). Pyrolysis models of TEOS and TEOM are constructed and validated against the measured results. Modeling analysis, including rate of production analysis and sensitivity analysis, provides insights into chemistry in fuel consumption and product formation. In contrast, the observations of silicon-containing products in SVUV-PIMS experiments provide evidence for crucial decomposition pathways of TEOS. It is observed that TEOS exhibits significantly higher stability than TEOM under pyrolysis conditions. The most abundant products in the pyrolysis of TEOS and TEOM are ethylene and ethanol, and TEOS produces more hydrocarbon products than TEOM. The lower pyrolysis reactivity of TEOS is attributed to the slower unimolecular decomposition reaction which dominates the decomposition of TEOS than TEOM. This can be explained by the hindrance of the extremely strong Si-O bond resulting from the significantly different electronegativity between Si and O. The higher initial decomposition temperature of TEOS enhances the contribution of other decomposition channels, such as C-C bond dissociation and H-abstraction reactions, in TEOS consumption. This leads to the abundant formation of hydrocarbon productions such as methane, ethane, and acetaldehyde. As the main pyrolysis product, the ethanol produced by TEOM pyrolysis is four times that of TEOS due to the congener substitution effects. The ethanol formation pathway in TEOS pyrolysis is different from that in TEOM pyrolysis, which is mainly formed via a newly proposed multi-step mechanism, resulting in a lower yield in TEOS pyrolysis.

Bio-inspired deposition of gold nanoparticles onto the surface of kaolin for in vitro management of human ovarian cancer and modulation of the inflammatory response in adenomyosis-induced mice in vivo via the MAPK signaling pathway

A mild and eco-friendly protocol has been developed for the preparation of kaolin-decorated Au nanoparticles mediated by Ephedra root extract as a green reducing and stabilizing agents without any toxic substrates. Structural features of the prepared Au NPs/Kaolin were assessed through FE-SEM, TEM, and XRD techniques. TEM images show the good deposition of Au NPs over the surface of extract-modified kaolin without aggregation. Towards the medicinal application, its antioxidant efficacy was assessed by the DPPH method, and the corresponding IC50 value was obtained as 104 μg/mL. Cytotoxicity of the nanoformulated bio-composite was ascertained through MTT analysis against human ovarian carcinoma cells, i.e., PA-1 and SK-OV-3. The IC50 in those studies was 250 and 119 μg/mL against PA-1and SK-OV-3 cells, respectively. In the in vivo design, tamoxifen was used to induce the experimental adenomyosis model in mice. After treatment, the thymus, spleen, uterine, and body weights of all animals were measured. Then, inflammatory factor expression and myometrial infiltration were determined by qRT-PCR, ELISA, and histology examination in the uterus. Western blotting, qRT-PCR, and immune histochemical (IHC) staining were applied to analyze the MAPK/ERK signaling pathway protein expression. Au NPs/Kaolin bio-nanocomposite ameliorated the adenomyosis symptoms by raising the thymus and spleen index and decreasing the myometrial infiltration. The raised levels of TNF-α, IL-6, and IL-1β in adenomyosis model mice uterus and serum were also reduced after Au NPs/Kaolin bio-nanocomposite treatment. The adenomyosis amelioration of Au NPs/Kaolin bio-nanocomposite was gained by preventing the MAPK/ERK signaling pathway, including decreasing the expressions of protein and mRNA of p-p38/p38, p-JNK/JNK, and p-ERK/ERK.

Optimization of cotton SERS substrates based on different weave structures for surface trace detection

Cotton fabrics have been used to fabricate Surface-enhanced Raman spectroscopy (SERS) substrates due to their excellent properties such as flexibility, hygroscopicity, and large-scale production. The morphology of the SERS substrate has a great influence on the deposition of noble metal nanoparticles and affects the Raman-enhanced signal. Although numerous research reports have been conducted on SERS substrates made from cotton, there has been limited exploration on the impact of the weave structure of cotton fabric on SERS performance. Herein, the cotton SERS substrates were prepared by depositing silver nanoparticles (Ag NPs) on cotton fabrics with different weave structures by a simple vacuum-thermal evaporation method. The influence of substrate morphology on the deposition arrangement of Ag NPs and the enhancement of SERS performance was explored. The analysis findings demonstrate that the cotton SERS substrate displays exceptional Raman signal enhancement performance. Thereinto, the satin SERS substrate exhibited a stronger Raman signal due to its smoother surface favoring the deposition of Ag NPs. The limit of detection for p-aminothiophenol (PATP) was established at a low of 10−8 M, with an RSD value of 9.96%. Moreover, the satin SERS substrate demonstrated an enhancement factor of 5.18 × 105. In addition, it has excellent mechanical flexibility and good hygroscopicity, and thiram on the apple surface can be detected by simple wiping. Cotton SERS substrates show great potential in food safety analysis and monitoring. More importantly, this study provides assistance for the selection of SERS substrates for traditional cotton fabrics, and further promotes the broadening of the application fields of smart cotton fabrics.

Robust, Flexible, and Superhydrophobic Fabrics for High-Efficiency and Ultrawide-Band Microwave Absorption

Microwave absorption (MA) materials are essential for protecting against harmful electromagnetic radiation. In this study, highly efficient and ultrawide-band microwave-absorbing fabrics with superhydrophobic surface features were developed using a facile dip-coating method involving in situ graphene oxide (GO) reduction, deposition of TiO2 nanoparticles, and subsequent coating of a mixture of polydimethylsiloxane (PDMS) and octadecylamine (ODA) on polyester fabrics. Owing to the presence of hierarchically structured surfaces and low-surface-energy materials, the resultant reduced GO (rGO)/TiO2-ODA/PDMS-coated fabrics demonstrate superhydrophobicity with a water contact angle of 159° and sliding angle of 5°. Under the synergistic effects of conduction loss, interface polarization loss, and surface roughness topography, the optimized fabrics show excellent microwave absorbing performances with a minimum reflection loss (RLmin) of −47.4 dB and a maximum effective absorption bandwidth (EABmax) of 7.7 GHz at a small rGO loading of 6.9 wt%. In addition, the rGO/TiO2-ODA/PDMS coating was robust, and the coated fabrics could withstand repeated washing, soiling, long-term ultraviolet irradiation, and chemical attacks without losing their superhydrophobicity and MA properties. Moreover, the coating imparts self-healing properties to the fabrics. This study provides a promising and effective route for the development of robust and flexible materials with microwave-absorbing properties.

X-ray standing wave characterization of the strong metal-support interaction in Co/TiOx model catalysts.

The strong metal-support interaction (SMSI) is a phenomenon observed in supported metal catalyst systems in which reducible metal oxide supports can form overlayers over the surface of active metal nanoparticles (NPs) under a hydrogen (H2) environment at elevated temperatures. SMSI has been shown to affect catalyst performance in many reactions by changing the type and number of active sites on the catalyst surface. Laboratory methods for the analysis of SMSI at the nanoparticle-ensemble level are lacking and mostly based on indirect evidence, such as gas chemisorption. Here, we demonstrate the possibility to detect and characterize SMSIs in Co/TiOx model catalysts using the laboratory X-ray standing wave (XSW) technique for a large ensemble of NPs at the bulk scale. We designed a thermally stable MoNx/SiNx periodic multilayer to retain XSW generation after reduction with H2 gas at 600°C. The model catalyst system was synthesized here by deposition of a thin TiOx layer on top of the periodic multilayer, followed by Co NP deposition via spare ablation. A partial encapsulation of Co NPs by TiOx was identified by analyzing the change in Ti atomic distribution. This novel methodological approach can be extended to observe surface restructuring of model catalysts in situ at high temperature (up to 1000°C) and pressure (≤3 mbar), and can also be relevant for fundamental studies in the thermal stability of membranes, as well as metallurgy.

Modification of nickel wire electrodes with platinum in the presence of copper ions via galvanic replacement reactions

In the galvanic replacement reaction between Ni wire and PtCl42- in an aqueous solution, the deposition of Pt nanoparticles (PtNPs) on Ni wire is generally unfavorable. However, the addition of Cu2+ into an aqueous solution of PtCl42- was found to promote the deposition of PtNPs effectively for the immersion of Ni wire. This promoted deposition of PtNPs on Ni wire could be confirmed by observing the electrocatalytic responses for ethanol oxidation, electrochemical impedance and the surface images. In addition, the EDS analysis showed that the deposited PtNPs did not contain Cu. The formation of PtNPs without containing Cu was also verified by observing the electrocatalytic properties of other alcohols. Although we had previously reported the stepwise modification of Pt on Ag-deposited Ni wire, the Cu2O-modified Ni wire was useless to allow the deposition of PtNPs in a similar stepwise treatment. Hence, the simple preparation using aqueous solutions containing both PtCl42- and Cu2+ can be proposed as a useful approach to modify PtNPs on Ni materials via galvanic replacement reactions.