Silica Layer Research Articles

Water-Soluble Quantum Dots for Inkjet Printing Color Conversion Films with Simultaneous High Efficiency and Stability.

Water-soluble quantum dots (QDs) are necessary to prepare patterned pixels or films for high-resolution displays with less environmental burden but are very limited by the trade-off between photoluminescence and stability of QDs. In this work, we proposed synthesizing water-soluble QDs with simultaneous excellent luminescence properties and high stability by coating the amphiphilic poly(maleic anhydride-alt-1-octadecene)-ethanol amine (PMAO-EA) polymer on the surface of silane-treated QDs. These coated QDs show a photoluminescence quantum yield (PLQY) as high as 94%, and they have good photoluminescence stability against light irradiation and thermal attacks, owing to the suppression of the nonradiative recombination by the polymer layer and the isolation of oxygen and water by the silica layer. The water-soluble QDs, mixed with ethylene glycol, enable inkjet printing of QD color conversion films (QD-CCFs) with an average diameter of 68 μm for each pixel and a high PLQY of 91%. The QD-CCFs are demonstrated to fabricate red-emitting mini-LEDs by combining with blue mini-LED chips, which have an external quantum efficiency as high as 25.86% and a luminance of 2.44 × 107 cd/m2. We believe that the proposed strategy is applicable to other water-soluble QDs and paves an avenue for inkjet printing environmentally friendly QD-CCFs for mini/micro-LED displays.

Unveiling the influence of MTMS:TEOS ratios in silica layer membranes enhanced by cetyltrimethylammonium bromide

Silica-based thin-layer membranes, meticulously coated on alumina tubes, were synthesized from methyltrimethoxysilane (MTMS) and tetraethylorthosilicate (TEOS), which were further modified with cetyltrimethylammonium bromide (CTAB) and subsequently deployed for the brine desalination. Comprehensive characterization of the membrane materials was conducted employing Fourier Transform Infrared (FTIR) spectrophotometry, Gas Sorption Analysis (GSA), Thermogravimetric Analysis combined with Differential Scanning Calorimetry (TGA-DSC), Scanning Electron Microscopy (SEM), and an optical tensiometer. A detailed investigation was executed on the effects of varying MTMS:TEOS mole ratios, 10:90 (STL-1), 25:75 (STL-2), 50:50 (STL-3), 75:25 (STL-4), and 90:10 (STL-5), elucidating their impact on the structural attributes and functionalities of silica. These parameters were subsequently correlated with their respective desalination efficacies. The FTIR analysis underscored an evident association between the escalation in cyclic siloxane and methyl groups vis-à-vis increasing MTMS concentrations. An elevated MTMS content conferred the silica matrix with diminished porosity, augmented thermal resilience, a more refined surface, and pronounced hydrophobicity, albeit at the cost of reduced surface area and pore volume. Remarkably, the STL-5 silica membrane manifested optimum desalination metrics, boasting a salt rejection percentage of 99.99 % and a water flux rate of 5.61 kg m−2 h−1, thereby accentuating the intrinsic trade-off existing between salt rejection and water flux.

TEM and zeta potential titration as suitable techniques for investigating the joining of modified ceramic surfaces

Transmission Electron Microscopy (TEM-EDS) and Zeta potential titration of ceramic surfaces allowed researchers to go inside their adhesion mechanism when joined with an adhesive. The case study concerned the plasma Corona treatment to improve the joint strength between SiC surfaces joined with an epoxy adhesive. The formidable mechanical and chemical properties inherent to silicon carbide pose challenges in applying conventional methods like mechanical machining and wet etching for surface texturing. Exploring alternative strategies, plasma Corona treatment which is an Atmospheric Pressure Plasmas (APPs) process emerges as a potential solution. The mechanism of chemical interaction and mechanical interlocking between plasma-treated surfaces and the epoxy adhesive used for the joining was never explored in detail and proven. The presence of layers with different crystallographic natures and chemical compositions was assessed by TEM-EDS: an amorphous silica layer was produced by the corona activation treatment and it created a mechanical anchoring system when penetrated by the adhesive. The zeta potential titration as a function of pH evidenced that untreated SiC had a surface with amphoteric functional groups, while the Corona treatment induced the formation of surface functional groups (OH) with a strong acidic behavior on SiC. The investigated epoxy adhesive exposed a prevalence of basic amino groups. Zeta potential titration curves highlighted the chemical interaction between the treated SiC surfaces and the epoxy adhesive: the large electrostatic attraction between the OH groups of the treated SiC and the amino groups of the epoxy adhesive had a role in the mechanical strength of the joining. TEM and Zeta potential titration can be proposed as suitable techniques to evaluate the effectiveness of the plasma corona discharge system in modifying the surface of SiC and to solidify its standing in comparison to other established surface modification techniques to improve SiC-based joints.

Exploring non-stoichiometric SiOx thin film for non-volatile memory application

This article explores the electrical performance of capacitive memory and resistive switching (RS) devices based on thin films of a single active layer of Silicon oxide (SiOx). The fabricated device Au/SiOx/p-Si displayed frequency-dependent characteristics ranging from 200 kHz to 1 MHz w.r.t capacitance. The charge trapping nature was also investigated, which revealed a charge storage density (N) of order 1010 cm−2 and a low trapping density of interface (Dit) ∼2.65 × 1011 eV−1 cm−2. Furthermore, the device exhibits bipolar RS behavior while maintaining a stable endurance for 1000 DC sweeping cycles and a good retention period of > 103 s. The major pathway of the conduction mechanism in these devices is attributed to the accumulation of oxygen vacancies near the Au/SiOx interface. The conduction in this device is predominantly governed by trap-mediated space-charge-limited current (SCLC) and ohmic conductions.

Optimized film thicknesses for maximum refractive index sensitivity and figure of merit of a bimetallic film surface plasmon resonance sensor

In this paper, a simple surface plasmon resonance (SPR) optical sensor with a bimetallic gold-silver film is proposed and its parameters are optimized based on reflectance spectra analysis. In comparison with most SPR sensors, which use single gold films, the evanescent field of this bimetallic configuration at the analyte–metal interface enables the sensing with substantially enhanced refractive index (RI) sensitivity and figure of merit (FOM). The proposed structure comprising a BK7 glass substrate, an adhesion layer of chromium, a gold-silver plasmonic layer, and a protective layer of silicon dioxide is employed in the Kretschmann configuration for liquid analyte sensing. In order to achieve the best sensing properties, the gold-silver layer thickness ratio is varied, and a thorough analysis of reflectance spectra is performed based on RI sensitivity and FOM. For this purpose, a liquid analyte of aqueous solutions of NaCl is employed for angles of incidence 63∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ $$\\end{document} and 64∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ $$\\end{document}, respectively. Moreover, based on the analysis, an optimized gold-silver layer thickness ratio is selected, and a sensitivity of 41,592 nm per RI unit (RIU) and FOM of 424 RIU-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document} are reached. The designed bimetallic SPR structure proves to be advantageous compared to single-gold-film structures employed for sensing applications.

Towards a better understanding of the effect of protein conditioning layers on microbial adhesion: a focused investigation of fibronectin and bovine serum albumin layers on SiO2 surfaces.

The interaction of foreign implants with their surrounding environment is significantly influenced by the adsorption of proteins on the biomaterial surfaces, playing a role in microbial adhesion. Therefore, understanding protein adsorption on solid surfaces and its effect on microbial adhesion is essential to assess the associated risk of infection. The aim of this study is to evaluate the effect of conditioning by fibronectin (Fn) or bovine serum albumin (BSA) protein layers of silica (SiO2) surfaces on the adhesion and detachment of two pathogenic microorganisms: Pseudomonas aeruginosa PAO1-Tn7-gfp and Candida albicans CIP 48.72. Experiments are conducted under both static and hydrodynamic conditions using a shear stress flow chamber. Through the use of very low wall shear stresses, the study brings the link between the static and dynamic conditions of microbial adhesion. The results reveal that the microbial adhesion critically depends on: (i) the presence of a protein layer conditioning the SiO2 surface, (ii) the type of protein and (iii) the protein conformation and organization in the conditioning layer. In addition, a very distinct adhesion behaviour of P. aeruginosa is observed towards the two tested proteins, Fn and BSA. This effect is reinforced by the amount of proteins adsorbed on the surface and their organization in the layer. The results are discussed in the light of atomic force microscopy analysis of the organization and conformation of proteins in the layers after adsorption on the SiO2 surface, as well as the specificity in bacterial behaviour when interacting with these protein layers. The study also demonstrates the very distinctive behaviours of the prokaryote P. aeruginosa PAO1-Tn7-gfp compared to the eukaryote C. albicans CIP 48.72. This underscores the importance of considering species-specific interactions between the protein conditioning layer and different pathogenic microorganisms, which appear crucial in designing tailored anti-adhesive surfaces.

Mechanistic insights into the co-recovery of nickel and iron via integrated carbon mineralization of serpentinized peridotite by harnessing organic ligands.

The rising need to produce a decarbonized supply chain of energy critical metals with inherent carbon mineralization motivates advances in accelerating novel chemical pathways in a mechanistically-informed manner. In this study, the mechanisms underlying co-recovery of energy critical metals and carbon mineralization by harnessing organic ligands are uncovered by investigating the influence of chemical and mineral heterogeneity, along with the morphological transformations of minerals during carbon mineralization. Serpentinized peridotite is selected as the feedstock, and disodium EDTA dihydrate (Na2H2EDTA·2H2O) is used as the organic ligand for metal recovery. Nickel extraction efficiency of ∼80% and carbon mineralization efficiency of ∼73% is achieved at a partial pressure of CO2 of 50 bars, reaction temperature of 185 °C, and 10 hours of reaction time in 2 M NaHCO3 and 0.1 M Na2H2EDTA·2H2O. Extensive magnesite formation is evidence of the carbon mineralization of serpentine and olivine. An in-depth investigation of the chemo-morphological evolution of the CO2-fluid-mineral system during carbon mineralization reveals several critical stages. These stages encompass the initial incongruent dissolution of serpentine resulting in a Si-rich amorphous layer acting as a diffusion barrier for Mg2+ ions, subsequent exfoliation of the silica layer to expose unreacted olivine, and the concurrent formation of magnesite. Organic ligands such as Na2H2EDTA·2H2O aid the dissolution and formation of magnesite crystals. The organic ligand exhibits higher stability for Ni-complex ions than the corresponding divalent metal carbonate. The buffered environment also facilitates concurrent mineral dissolution and carbonate formation. These two factors contribute to the efficient co-recovery of nickel with inherent carbon mineralization to produce magnesium carbonate. These studies provide fundamental insights into the mechanisms underlying the co-recovery of energy critical metals with inherent carbon mineralization which unlocks the value of earth abundant silicate resources for the sustainable recovery of energy critical metals and carbon management.

Oxide scale microstructure and failure mechanism of alloy 601 under varying metal dusting conditions

Chemical plants which process highly carbonaceous gases at elevated temperatures are prone to catastrophic corrosion by metal dusting. Typically, commercial alloys with high amounts of protective oxide scale formers (Cr, Al, and Si) are used in these environments. However, scale failure is still frequently observed after an incubation time initiating pits. In this study, the microstructure and subsequent metal dusting-induced failure of the oxide scale on the commercial Ni-based alloy 601 was analyzed. Samples were exposed in different aggressive metal dusting gases and characterized using metallographic cross sections, electron beam microanalysis (EPMA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and transmission electron microscopy (TEM). A thin and protective chromia scale formed in some regions with a continuous silica layer below. Across most of the alloy 601 surfaces, internal oxidation of Al could be linked to metallic particles in the outer scale. Additionally, MnCr2O4 was observed in the outer scale. Together with pores in the chromia, the spinel and metallic particles in the outer scale combined to provide pathways for carbon ingress. After exposure in a gas with a higher driving force for carbon deposition, a higher amount of carbon was incorporated in the growing oxide scale, resulting in earlier scale failure and metal dusting pit initiation.Graphical

How the geometry of patterned surfaces affects the thickness distribution of the oxidized silica layer on polydimethylsiloxane (PDMS) after ultraviolet/ozone treatment.

It is well established that a thin silica-like surface layer is formed when a cross-linked PDMS structure is subjected to ultraviolet/ozone treatment. Due to surface geometry, especially near the corners, this silica-like surface layer has non-uniform thickness, which can impact many mechanical properties, including adhesion and fracture strength. Here we use a simple analytic model based on diffusion of reactive species to predict the thickness of the oxidized surface layer near the corners. We demonstrate that these corner solutions can be patched together to determine the thickness of the oxidized layer in complex geometries.

Magnetite-silica core-shell nanostructures: Application for photodynamic therapy

Magnetite nanoparticles have been synthesized with chemical co-precipitation. The surface of magnetite nanoparticles was coated with an inorganic silica layer by hydrolyzing and condensing tetraethyl orthosilicate. An XRD investigation supports the cubic inverse spinel structure of Fe3O4 nanoparticles. The average crystallite size of the magnetite nanoparticles produced by the peak broadening was 13 nm. The UV-visible spectrum of methylene blue-loaded magnetite-silica nanoparticles shows a strong hump at 657 nm. According to TEM examination, the nanoparticles are polydisperse and almost spherical in form.The average size of the nanoparticles is 14.39 nm plus 1.66 nm, and they have a polydispersity index of 0.12%.The size and shape of the core-shell particles are not uniform, according to a SEM examination. There is no distinguishing morphology in any sample.The magnetic results depicts the superparamagnetic behaviour of nanoparticlesmakes them suitable for photodynamic therapy.

Atomic Layer Deposition for Tailoring Tamm Plasmon-Polariton with Ultra-High Accuracy

In this study, we demonstrate the potential capability to control Tamm plasmon-polaritons (TPP) by applying atomic layer deposition (ALD) as a highly precise technique for plasmonic applications. Applications in plasmonics usually require tens of nanometers or less thick layers; thus, ALD is a very suitable technique with monolayer-by-monolayer growth of angstrom resolution. Spectroscopic ellipsometry and polarized reflection intensity identified the TPP resonances in the photonic band gap (PBG) formed by periodically alternating silicon oxide and tantalum oxide layers. The sub-nanometer control of the Al2O3 layer by ALD allows precise tailoring of TPP resonances within a few nanometers of spectral shift. The employing of the ALD method for the fabrication of thin layers with sub-nanometer thickness accuracy in more complex structures proves to be a versatile platform for practical applications where tunable plasmonic resonances of high quality are required.

Prominently enhanced luminescence from a continuous monolayer of transition metal dichalcogenide on all-dielectric metasurfaces

Abstract 2D materials such as transition metal dichalcogenides (TMDCs) are a new class of atomic-layer materials possessing optical and electric properties that significantly depend on the number of layers. Electronic transitions can be manipulated in artificial resonant electromagnetic (EM) fields using metasurfaces and other designed nanostructures. Here, we demonstrate prominently resonant enhancement in the photoluminescence (PL) of atomic monolayer, WS2, doped with a small quantity of Mo. The excitonic PL showed a strong enhancement effect on a higher-order magnetic resonance of all-dielectric metasurfaces consisting of periodic arrays of Si nanopellets. The PL intensity witnessed a 300-fold enhancement compared to the reference PL intensity on a flat silicon dioxide (SiO2) layer, which suggests a drastic change in the dynamics of photoexcited states. Confocal PL microscopy and the analysis revealed that the single photons were coherently emitted from the TMDC monolayer on the metasurface. Furthermore, examining the PL lifetime in the ps and ns timescales clarified two exponential components at the prominent exciton PL: a short-time component decaying in 22 ps and a long-time component lasting over 10 ns. Therefore, we can infer that the radiative components were significantly activated in the TMDC monolayer on the metasurfaces in comparison to the reference monolayer on a flat SiO2 layer.

Ultrastable Dual-Matrix meditated CsPbBr3 composites with enhanced photoluminescence quantum yield and robust circular polarization luminescence

Metal halide perovskite materials have emerged as a focal point of research in the field of circularly polarized luminescence (CPL). However, striking a delicate balance between several crucial parameters, including large luminescence dissymmetry factors (glum), high photoluminescence quantum yields (PLQY), and long-term stability, has proven to be a challenging endeavor. Here, this study presented a pioneering strategy for crafting robust CPL-active inorganic nanomaterial composites utilizing dual-matrix of chiral nematic mesoporous silica (CNMS) and inorganic passivation Cs4PbBr6 layer. The use of free-standing CNMS hard templates provided a confined growth environment for all-inorganic CsPbBr3 perovskite nanocrystals, enabling the conversion of unpolarized light emission into CPL. Through further advancements in the form of effective passivation with inorganic Cs4PbBr6 layer, superior optical performance and stability were achieved in the system. The figure of merit (FM) value for the resultant CsPbBr3/Cs4PbBr6@CNMS composite film reached −7.8 × 10−2, surpassing the performance of current advanced systems. Moreover, the surface passivation, along with the protection offered by the dual-matrix encapsulation, enhanced the resilience of composite film to harsh environments with robust performance. The successful integration of the CPL materials into a circularly polarized light-emitting diode device confirmed their applicability in CPL displays and luminescence applications. This work establishes a reliable and efficient method for the development of high-performance CPL materials and applications.

Structural Effects on ORR Performances of Carbon-Free Connected Platinum–Cobalt Catalysts with Chemically Ordered Superlattice Structures

Polymer electrolyte fuel cells (PEFCs) have been considered as the promising next-generation energy-conversion technology, owing to their high energy efficiency and clean emissions. However, a sluggish oxygen reduction reaction (ORR) rate and the low durability of conventional catalysts in PEFCs limit the wider commercialization. To address these issues, our group has developed a carbon-free, connected Pt1–Fe1 catalyst with a porous hollow capsule structure. This catalyst comprises the nano-sized network formed by the connection of Pt1–Fe1 nanoparticles and exhibits an enhanced ORR specific activity (9 times higher than a commercial Pt/C) as well as excellent durability against start-stop operations due to the carbon-free structure.[1,2] However, during the load cycle operation, iron is dissolved from the catalyst, leading to the loss of ORR activity and the degradation of polymer electrolytes caused by the Fenton reaction.In this work, carbon-free and iron-free connected Ptx-Co1 catalysts with chemically ordered superlattice structures have been developed for the first time, as shown in Fig. 1(a). In addition, the metal compositions and chemically ordered (superlattice) degrees in the catalysts were controlled to investigate the structural effects on ORR activity and durability of the connected Ptx-Co1 catalysts.Herein, we employed the silica-coating method for the catalyst synthesis, which involves the combination of silica coating and high-temperature annealing. As shown in Fig. 1(b), the surface of the Ptx-Co1 nanoparticles/SiO2 sample was coated with thin silica layers to prevent the detachment of Ptx–Co1 nanoparticles from the SiO2 template as well as the large catalyst agglomeration and coalescence during the annealing process. We controlled the chemically ordered degrees of the connected Pt1–Co1 and Pt3–Co1 catalysts by using different annealing temperatures. The XRD patterns of the catalysts showed the peaks corresponding to L10 type and L12 type chemically ordered structures for the connected Pt1–Co1 and Pt3–Co1 catalysts annealed at 600°C, respectively. These two catalysts possessed ordered degrees (S) of ca. 50–60%. The TEM images of the connected Ptx–Co1 catalysts showed the formation of connected Ptx–Co1 nanonetwork and porous hollow capsule structures.The electrochemical measurements of ORR activity and durability were conducted in a 0.1 M HClO4 electrolyte solution. The connected Pt1–Co1 and Pt3–Co1 catalysts achieved 6- and 10-times higher ORR specific activities than that of Pt/C, respectively. Subsequently, the ORR activity and load cycle durability (0.6 V for 3 s Û 1.0 V for 3 s at 60 °C) of the connected Pt3–Co1 catalyst with different ordered degrees (S = 0%, 28%, and 58%) were evaluated. As the ordered degrees in the connected Pt3–Co1 catalysts were higher, the ORR specific activity was increased. Also, the retention of the specific activity of the ordered catalyst (S = 58%) was higher than that of the disordered catalyst (S = 0%) after 10,000 load cycles. The STEM-EDX line mapping results showed that 83% of the alloyed Co retained in the catalyst with a higher ordered degree even after 10000 load cycles, whereas the disordered and lower ordered catalysts retained lower Co ratios after the test, indicating the suppression effect of an ordered structure on metal dissolution. In addition, the L12 ordered Pt3–Co1 structure remained in the connected catalyst (S = 58%) after load cycle test, confirmed by the TEM diffraction analysis.In summary, we successfully developed the connected Ptx-Co1 catalysts with chemically ordered superlattice structures. In addition, we clarified the structural effects of metal composition and ordered degree in connected Ptx-Co1 catalysts on ORR activity and load cycle durability. These results provide useful guidelines for the design of advanced ORR catalysts towards high-performance PEFCs. Acknowledgement The part of this presentation is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Conformal Electrodeposition of Mesoporous Silica over High Aspect Ratio (AR>100) Nanomesh Electrodes

The high surface area provided by the nanopores of ordered mesoporous silica thin films enables a wide range of electrochemical applications such as sensors, catalysis, energy storage and ion-selective membranes. Further improvements are possible by coating such thin films on large surface area electrodes with high aspect ratios (> 100) to increase the active surface area. Atomic layer deposition (ALD) is often preferred to deposit conformal thin film oxides on high aspect ratio structures. Such vapor-phase depositions are limited by the available surface reactive sites to deposit thin films of thickness ranging from sub-nanometer to few tens of nanometer. However, there is a tradeoff in terms of deposition time/cycles to achieve quality films especially when high aspect ratios (>100) substrates are introduced. Electrochemistry offers an alternative, versatile method to conformally coat layers on 3D electrode surfaces. The electrochemically assisted self-assembly (EASA) of mesoporous silica, utilizes electrochemical reactions to locally increase the pH near the electrode surface, which in turn catalyzes the silica gelation and surfactant self-assembly, thus causing the controlled growth of mesoporous silica thin films [1]. Recently, our group has shown that good quality mesoporous silica films with thickness between 20-2000 nm could be achieved by controlling the hydrodynamic layer in a rotating disc electrode setup [2]. Moreover, EASA of mesoporous silica offers meso-channels that are aligned perpendicular to the underlaying conductive substrate which is optimal for mass-transport.In this follow-up work, we demonstrate a reliable, electrochemically controlled, conformal deposition of mesoporous silica onto large surface area nanomesh electrodes with an aspect ratio close to 100. Nanomesh electrodes developed in our group at imec, is built up of a regularly spaced (50 nm), inter-connected network of vertical and horizontal nanowires of diameter ~40 nm. These electrodes offer an 80x area enhancement (80 cm2 per geometric cm2) while maintaining a porosity close to 75%. We show that, the extent of silica deposition over these nanomesh electrodes can be electrochemically controlled from conformal coatings (~10 nm thick) uniformly coating the whole nanomesh architecture to complete fill and overfill of the nanomesh electrodes (~4 µm thick). Furthermore, excellent mass-transport properties of various silica coated nanomesh electrodes has been demonstrated using a ruthenium hexaammine redox probe. Finally, the area enhancement offered by the silica coated Ni nanomesh is demonstrated using the characteristic accumulation of a positively charged [Ru(NH3)6]3+ probe within the negatively charged silica nanochannels, which shows 55x increase for the amount of charge from the probe stored in the coated nanomesh, compared to a planar silica layer, consistent with the expected surface area enhancement of the 4 µm thick nanomesh electrodes.

Oxysulfide-Based Photocatalyst Sheet Modified with Silica Layer for Z-Scheme Overall Water Splitting at Atmospheric Pressure

Photocatalytic water splitting using particulate photocatalysts is considered as an ideal route to produce economically cheap renewable, and transportable H2 utilizing sunlight [1]. Photocatalyst sheets are directly scalable and have recently gained interest because a benchmark STH conversion efficiency of 1.0% was achieved at near ambient pressure using the one composed of Rh, La-codoped SrTiO3 and Mo-doped BiVO4 (BVO:Mo) as the H2- and O2- evolution photocatalysts (HEP and OEP), respectively. However, such systems absorb only a little portion of the sunlight due to the weak visible light absorption of the doped SrTiO3 [2]. To utilize longer wavelength visible light, our group has recently studied photocatalyst sheets composed of Ga-doped La5Ti2Cu0.9Ag0.1O7S5 (LTCA:Ga) (HEP) and BVO:Mo (OEP) with Au as conducting layer. The combination of LTCA:Ga/Au/BVO:Mo modified with Rh/Cr2O3 and CoO x as reduction and oxidation cocatalysts, respectively, achieved an STH efficiency of 0.4% under reduced pressure, but this was far lower than the oxide-based sheet system and the activity was decreased sharply against background pressure [3]. Considering intense visible light absorption of LTCA (λabs ~ 700 nm) and the associated maximum theoretical energy conversion efficiency for this combination, improvements in the net STH efficiency and activation under atmospheric pressure is highly indispensable.In this study, LTCA photocatalysts with different dopants were applied to the sheet system in combination with hydrothermally synthesized BVO:Mo and the resulting sheets were modified with CoO x /Cr2O3/Rh cocatalysts in an attempt to upgrade the water splitting activity. Moreover, surface modification onto LTCA-based photocatalyst sheets with a thin amorphous TiO2 and SiO2 layer were evaluated at elevated pressure and high temperature.Doped LTCA were synthesized by a conventional solid-state reaction in sealed evacuated quartz tubes similar to previous studies [3]. Precursors were blended inside a glove box. BVO:Mo (Mo 0.1 mol%) was synthesized by a hydrothermal method [4]. Photocatalyst sheet was fabricated by the particle transfer method [3]. SiO2 and TiO2 layers functioning as molecular sieves were deposited onto the cocatalyst-modified sheet from titanium tetraisopropoxide (TTIP) or tetraethyl orthosilicate (TEOS) by photo-decomposition and hydrolysis method, respectively, to prevent backward reactions at elevated pressure [5]. Photocatalytic water splitting reaction was carried out at different temperatures and pressures using a closed gas circulation system.Rh cocatalyst was first adsorbed and photo-deposited onto the doped LTCA/Au/BVO:Mo(h) sheet [3]. Gas evolution rates were significantly enhanced upon deposition of Cr2O3 layer as the oxygen reduction reaction (ORR), a backward reaction, was majorly suppressed promoted by uncovered Rh surface under the measured condition. Photocatalyst sheet composed of doped LTCA/Au/BVO:Mo(h) with optimal dopant amounts and cocatalysts loadings showed the H2 and O2 evolution rates of 110 and 54 µmol/h, respectively, under visible light irradiation and yielded an STH of 0.67% at 4 kPa and temperature 301 K [6]. The water splitting activity was improved by 1.6 times under reduced pressure compared to the previously studied LTCAGa/Au/BVO:Mo. However, this activity was highly sensitive against background pressure as nearly 90% reduced upon increasing pressure from 2 to 90 kPa owing to the predominating ORR occurring on LTCA and exposed Au surface. To suppress this backward reaction, TiO2 layer was coated to suppress ORR but the sheet failed to work at a temperature higher than 318 K due to the condensation of such layer. However, SiO2 layer coated sheet effectively suppressed ORR backward reaction and stably work under hot water and elevated pressure [6]. Consequently, under optimized condition SiO2 deposited sheet achieved an STH of 0.4% at 90 kPa at temperature 333 K.Doped LTCA materials were applied to the photocatalyst sheet systems as HEP along with BVO:Mo and Au layer as OEP and conductive layer, respectively, for Z-scheme pure water splitting under visible light. This combination achieved an STH of 0.67% at reduced pressure. This STH is considered as one of the highest values recorded for OWS systems involving non-oxide photocatalysts. The activity of the photocatalyst sheet was found negatively dependent onto background pressure due to the ORR on LTCA and Au layer. Surface modifications with SiO2 layer activated the sheet under atmospheric pressure. These findings will contribute to the improvement in the STH for other systems under realistic condition where OWS is likely to be conducted at an ambient pressure. References Nandy et al. Chem. Sci. 2021, 12, 9866-9884.Wang et al. Nat. Mater. 2016, 15, 611-615.Chen et al. ACS Catal. 2023, 13, 3285-3294.Li et al. Energy Environ. Sci., 2014, 7, 1369-1376.Pan et al. Angew. Chem. Int. Ed. 2015, 54, 2955-2959.Nandy et al. Joule, 2023, under revision.

Effect of Secondary Oxidants (CO2 and/or H2O) on Oxidation of Fe-20Cr-(Mn, Si)

Ferritic heat resisting alloys are widely used in industry owing to their combination of economy, reasonable strength, and high temperature corrosion resistance. Alloy design centres on forming and maintaining an external, slow growing protective oxide scale by selective oxidation of the desired metal, commonly chromium. Design methods based on diffusion theory succeed when the service environment is oxygen or clean, dry air. However, they can fail badly when secondary oxidants (like CO2 and water vapour) are present, which is commonly the case in energy production etc. This work investigates the effect of CO2 and H2O on corrosion behaviour of Fe-20Cr, in comparison with that in pure O2. The alloying effect of Si and Mn on oxidation behaviour of Fe-20Cr in different gases is also investigated.Model alloys Fe-20Cr, Fe-20Cr-1Si, Fe-20Cr-2Mn (all in wt%) were arc melted and annealed. Sample coupons were cut, ground, mechanically polished to 3mm finish, and further electro-polished to remove subsurface deformation zones. They were then exposed to Ar-2O2, Ar-20H2O-2O2, Ar-20CO2-2O2, Ar-CO2-H2O and Ar-CO2-H2O-O2 (all vol%) gas mixtures, at 650°C for 150h. Corrosion products and cross-sections were examined using optical microscopy, X-ray diffraction, Raman Spectroscopy and scanning electron microscopy equipped with energy dispersive X-ray spectrometry.The alloy behaved protectively in Ar-2O2, forming a very thin Cr2O3 layer on its surface. However, when CO2 or/and H2O was added to oxygen, breakaway oxidation resulted, forming thick multi-layered oxide scales. Detailed analysis revealed that this multi-layered structure contains four layers, where the outer layer was Fe2O3, overlying an Fe3O4 layer and FeCr2O4 spinel innermost layer, and an internal oxidation zone was formed beneath the scale. In the low environment of Ar-20CO2-20H2O, Fe3O4 layer, FeCr2O4 spinel layer and internal oxidation zone formed a three-layered structure. No Fe2O3 was found, which is attributed to the decrease in oxygen partial pressure.Carburisation of Fe-20Cr also resulted from exposure to the three CO2-bearing gases. The deepest and densest internal carburisation zone formed in Ar-20CO2-2O2. In Ar-20CO2-20H2O-2O2 and Ar-20CO2-20H2O, internally precipitated carbides were sparser, but still obvious.Silicon addition dramatically improved the oxidation resistance of Fe-20Cr. Weight gains in all gases were sharply decreased compared with those of Fe-20Cr. As with Fe-20Cr, a very thin Cr2O3 layer on the Si-bearing alloy reacted in Ar-2O2,together with a thin underlying silica layer, indicating that the alloy was fully protected. Unlike Fe-20Cr, the Fe-20Cr-1Si alloy was also protected in Ar-20CO2-2O2. However, when water vapour was present, the alloy started to go into breakaway, forming local Fe-rich oxide nodules. In Ar-20H2O-2O2, some small nodules, consisting of external Fe2O3 and inner spinel were distributed on an otherwise thin, protective chromia scale. In Ar-20H2O-20CO2-2O2 and Ar-20H2O-20CO2, an additional Fe3O4 layer was observed in nodules, between Fe2O3 and inner spinel. Thus, for Fe-20Cr-1Si samples, Fe3O4 can only be observed if 20%CO2 and 20%H2O were both present. Additionally, some small internal oxide particles were observed at breakaway nodule areas in all these three gasses. Internal carbides were found only under the big iron oxides nodules grown in Ar-20CO2-20H2O-2O2.Manganese addition did not much influence the corrosion resistance of Fe-20Cr. In general, oxide morphologies were similar to those of Fe-20Cr. In Ar-2%O2 gas, a thin Mn rich chromium oxide layer was formed over the entire alloy surface, indicating that sample was fully protected. Multi-layered thick oxides developed when CO2 or/and H2O were added. For high gases with the addition of H2O or CO2 (Ar-20H2O-2O2, Ar-20CO2-2O2, and Ar-CO2-H2O-O2), three-layered oxide structures were found to be made up of Fe2O3, Fe3O4, and spinel layers, in sequence from the outer surface to the inner alloy. It is worth noting that the oxide layers were not completely continuous in Ar-20CO2-2O2. About 15% of the cross-section area was protected which indicated that Mn can slightly improve the corrosion resistance in dry CO2 and O2 environments. In lower oxygen partial pressure gas (Ar-CO2-H2O), no Fe2O3 was found, and only Fe3O4 and spinel constituted the oxide scale. The main difference was that the internal oxidation zone became tiny on Fe-20Cr-2Mn samples. Internal carbides were still found under inner oxide in all CO2 bearing gases, most obviously in Ar-20CO2-2O2. However, in all cases the carbide quantities were far less than those in Fe-20Cr, indicating that Mn addition partially inhibited carburisation.After the thermodynamics of the reaction product phase assemblages are considered, this complex pattern of reaction products is discussed in terms of the permeability of different oxides to carbon- and hydrogen-bearing species, along with interactions between secondary oxidants on oxide surfaces and grain boundaries.

Tumor Microenvironment-Specific Driven Nanoagents for Synergistic Mitochondria Damage-Related Immunogenic Cell Death and Alleviated Immunosuppression.

Despite significant breakthroughs in immunotherapy, the limitations of inadequate immune stimulation and stubborn immune resistance continue to present opportunities and challenges. Therefore, a two-pronged approach, encompassing the activation of immunogenic cell death (ICD) and blocking the indoleamine 2,3-dioxygenase (IDO)-mediated pathway, is devised to elicit systemic anti-tumor immunity and alleviate immunosuppression. Herein, a tumor microenvironment (TME)-specific driven nanoagent is composedof a tetrasulfide bond-bridged mesoporous silica layer (MON) coated up-conversion nanoparticles as a nano-carrier, combines Fe2+ , curcumin, and indoximod for operating chemodynamic therapy/chemotherapy/immunotherapy. The consumption of glutathione (GSH) caused by MON degradation, the Fenton reaction of Fe2+ , and curcumin triggering mitochondrial damage collectively exacerbate the oxidative stress, leading to a violent immunoreaction and reversal of the immunosuppressive TME through a combination of IDO-inhibitors. Meanwhile, upconversion luminescence (UCL) imaging serves as a significant guiding tool for drug delivery and the treatment of nanoagents. In vivo and in vitro experiment results demonstrate that the nanosystem not only effectively inhibits the growth of primary tumors but also induces immune priming and memory effects to reject re-challenged tumors. The strategy as a complementary approach displays great potential for future immunotherapy along with other multimodal treatment modes.

Precise arrangement of metal atoms at the interface by a thermal printing strategy.

The kinetics and pathway of most catalyzed reactions depend on the existence of interface, which makes the precise construction of highly active single-atom sites at the reaction interface a desirable goal. Herein, we propose a thermal printing strategy that not only arranges metal atoms at the silica and carbon layer interface but also stabilizes them by strong coordination. Just like the typesetting of Chinese characters on paper, this method relies on the controlled migration of movable nanoparticles between two contact substrates and the simultaneous emission of atoms from the nanoparticle surface at high temperatures. Observed by in situ transmission electron microscopy, a single Fe3O4 nanoparticle migrates from the core of a SiO2 sphere to the surface like a droplet at high temperatures, moves along the interface of SiO2 and the coated carbon layer, and releases metal atoms until it disappears completely. These detached atoms are then in situ trapped by nitrogen and sulfur defects in the carbon layer to generate Fe single-atom sites, exhibiting excellent activity for oxygen reduction reaction. Also, sites' densities can be regulated by controlling the size of Fe3O4 nanoparticle between the two surfaces. More importantly, this strategy is applicable to synthesize Mn, Co, Pt, Pd, Au single-atom sites, which provide a general route to arrange single-atom sites at the interface of different supports for various applications.

Controlling Silicification on DNA Origami with Polynucleotide Brushes.

DNA origami has been used as biotemplates for growing a range of inorganic materials to create novel organic-inorganic hybrid nanomaterials. Recently, the solution-based silicification of DNA has been used to grow thin silica shells on DNA origami. However, the silicification reaction is sensitive to the reaction conditions and often results in uncontrolled DNA origami aggregation, especially when growth of thicker silica layers is desired. Here, we investigated how site-specifically placed polynucleotide brushes influence the silicification of DNA origami. Our experiments showed that long DNA brushes, in the form of single- or double-stranded DNA, significantly suppress the aggregation of DNA origami during the silicification process. Furthermore, we found that double-stranded DNA brushes selectively promote silica growth on DNA origami surfaces. These observations were supported and explained by coarse-grained molecular dynamics simulations. This work provides new insights into our understanding of the silicification process on DNA and provides a powerful toolset for the development of novel DNA-based organic-inorganic nanomaterials.