Surfactant-assisted Method Research Articles

Synthesis of CoO/Co(OH)2 Nanosheets Depending on Reaction Temperatures

Transition metal oxides formed by a single or heterogeneous combination of transition metal ions and oxygen ions have various types of crystal structures, which can be classified as layered structures and non-layered structures. With non-layered structures, it is difficult to realize a two-dimensional structure using conventional synthesis methods. In this study, we report the synthesis of cobalt oxide into wafer-scale nanosheets using a surfactant-assisted method. A monolayer of ionized surfactant at the water-air interface acts as a flexible template for direct cobalt oxide crystallization below. The nanosheets synthesized on the water surface can be easily transferred to an arbitrary substrate. In addition, the synthesizing morphological and crystal structures of the nanosheets were analyzed according to the reaction temperatures. The electrochemical properties of the synthesized nanosheets were also measured at each temperature. The nanosheets synthesized at 70 °C exhibited higher catalytic properties for the oxygen evolution reaction than those synthesized at other temperatures. This work suggests the possibility of changing material performance by adjusting synthesis temperature when synthesizing 2D nanomaterials using a wide range of functional oxides, resulting in improved physical properties.

CO Methanation Over SAPO-34 Supported Ni Catalysts

This study investigated carbon monoxide methanation with 15 %NiO doped SAPO-34 zeolite-supported catalysts. The SAPO-34 support was produced by hydrothermal synthesis, and nickel oxide was added to the support by impregnation and surfactant-assisted impregnation method, dissolved in different solvents (water, ethanol, acetone, and 1-propanol). Various characterization techniques, N2 physisorption, XRD, SEM, TEM, and FTIR, were used to determine the physical properties of catalysts. XRD analysis showed that synthesizing the catalysts with surfactant reduced the crystallite size. The average crystal sizes of the catalysts synthesized using the impregnation and surfactant-assisted impregnation methods are between 11.3-7.1 nm and 8.9-7.1 nm, respectively. The N2 physisorption analysis showed that the catalysts with the surfactant assisted impregnation method had higher surface areas among the catalysts produced by the two different preparation methods. It was observed that the surface area of the catalyst increased as the boiling point of the solvent increased. Scanning electron microscopy (SEM) analysis exhibited that the particle size of the catalysts with 1-propanol prepared by impregnation and surfactant-assisted impregnation methods are 118 nm and 86 nm, respectively. According to the results, surfactants cause to produce smaller particles. The CO methanation studies showed that the highest CO conversion values were reached with Ni/SAPO-34 catalyst using 1- propanol prepared by impregnation and other method, which gave 19.2% and 21.1% CO conversion to methane at 375C, respectively. The low methane formation rates showed that most of the CO component was adsorbed on the surface, and some were converted to methane.

The construction of MnOx with rich oxygen vacancy for robust low-temperature denitration

In the present study, manganese oxide (MnOx) with attractive feature of rich oxygen vacancy was constructed by a surfactant-assisted method and explored for NH3-SCR. The obtained MnOx-OV showed distinct performance, with full conversion of NO achieved at the low temperature window of 100–200 °C under a high space velocity of 120,000 mL·g−1·h-1. Besides, good water tolerance was exhibited, as evidenced by the minor drop (13%) of NO conversion under typical low temperature of 125 °C with 10% H2O. Through comprehensive characterization, it was found that the MnOx-OV with rich oxygen vacancy could promote oxygen diffusion and thus induce enhanced oxidative dehydrogenation capacity to NH3, which played a crucial role in facilitating the reaction between NOx and NH3. Regarding the reaction mechanism, Langmuir-Hinshelwood (L-H) pathway was proposed based on the results from in situ DRIFTS and reaction order measurement. The result of present study is expected to provide useful guidance for designing well performed catalysts for low-temperature NH3-SCR.

Non-ionic surfactant-assisted controlled release of oxyresveratrol on dendritic fibrous silica for topical applications

We present a simple and eco-friendly method for controlled drug release using a surfactant-assisted method. Oxyresveratrol (ORES) was co-loaded with a non-ionic surfactant onto KCC-1, a dendritic fibrous silica, using an ethanol evaporation technique. The carriers were characterized using FE-SEM, TEM, XRD, N2 adsorption–desorption, FTIR, and Raman spectroscopy, and the loading and encapsulation efficiencies were assessed using TGA and DSC techniques. Contact angle and zeta potential were used to determine the surfactant arrangement and the particle charges. To investigate the effects of different surfactants (Tween 20, Tween 40, Tween 80, Tween 85, and Span 80) on ORES release, we conducted experiments under different pH and temperature conditions. Results showed that the types of surfactants, drug loading content, pH, and temperature significantly affected the drug release profile. The percentage of drug loading efficiency of the carriers was in the range of 80 %–100 %, and the release of ORES was in the order of M/KCC-1 > M/K/S80 > M/K/T40 > M/K/T20 > MK/T80 > M/K/T85 at 24 h. Furthermore, the carriers provided excellent protection for ORES against UVA and maintained its antioxidant activity. KCC-1 and Span 80 enhanced the cytotoxicity to HaCaT cells, while Tween 80 suppressed the cytotoxicity.

Dual Charge Transfer Generated from Stable Mixed-Valence Radical Crystals for Boosting Solar-to-Thermal Conversion.

Realizing dual charge transfer (CT) based on stable organic radicals in one system is a long-sought goal, however, remains challenging. In this work, a stable mixed-valence radical crystal is designed via a surfactant-assisted method, namely TTF-(TTF+• )2 -RC (where TTF = tetrathiafulvalene), containing dual CT interactions. The solubilization of surfactants enables successful co-crystallization of mixed-valence TTF molecules with different polarity in aqueous solutions. Short intermolecular distances between adjacent TTF moieties within TTF-(TTF+• )2 -RC facilitate both inter-valence CT (IVCT) between neutral TTF and TTF+• , and inter-radical CT (IRCT) between two TTF+• in radical π-dimer, which are confirmed by single-crystal X-ray diffraction, solid-state absorption, electron spin resonance measurements, and DFT calculations. Moreover, TTF-(TTF+• )2 -RC reveals an open-shell singlet diradical ground state with the antiferromagnetic coupling of 2J = -657 cm-1 and an unprecedented temperature-dependent magnetic property, manifesting the main monoradical characters of IVCT at 113-203 K while the spin-spin interactions in radical dimers of IRCT are predominant at 263-353 K. Notably, dual CT characters endow TTF-(TTF+• )2 -RC with strong light absorption over the full solar spectrum and outstanding stability. As a result, TTF-(TTF+• )2 -RC exhibits significantly enhanced photothermal property, an increase of 46.6°C within 180 s upon one-sun illumination.

Unique Tubular BiOBr/g-C3 N4 Heterojunction with Efficient Separation of Charge Carriers for Photocatalytic Nitrogen Fixation.

The industrial ammonia synthesis process consumes a lot of energy and causes serious environmental pollution. As a sustainable approach for ammonia synthesis, photocatalytic nitrogen reduction employing water as the reducing agent has a lot of potential. A simple surfactant-assisted solvothermal method is used to synthesize g-C3 N4 nanotubes with flower-like spherical BiOBr grown inside and outside (BiOBr/g-C3 N4 , BC). The hollow tubular structure realizes the full use of visible light by the multi-scattering effect of light. Large surface areas and more active sites for N2 adsorption and activation are present in the distinctive spatially dispersed hierarchical structures. Particularly, the quick separation and transfer of electrons and holes are facilitated by the sandwich tubular heterojunctions and tight contact interface of BiOBr and g-C3 N4 . The maximal NH3 generation rate of the BiOBr/g-C3 N4 composite catalysts can reach 255.04 μmol⋅ g-1 ⋅ h-1 , and it is 13.9 and 5.8 times that of pure BiOBr and g-C3 N4 . This work provides a novel method for designing and constructing unique heterojunctions for efficient photocatalytic nitrogen fixation.

Exclusive Co-N4 Sites Confined in Two-dimensional Metal-Organic Layers Enabling Highly Selective CO2 Electroreduction at Industrial-level Current.

Due to the rich chemistry of both metal sites and ligands, metal-organic frameworks (MOFs) possess abundant structures and tunable functionalities, which bring new opportunities for the design and fabrication of high-performance materials for catalysis and electrochemical processes. Herein, we first conduct density-functional theory (DFT) calculations and predict that Co-based porphyrin porous organic layers (Co-PPOLs) exhibit good activity for CO2-to-CO conversion because of the low *CO adsorption energy at the Co-N4 sites, which shall facilitate the *CO desorption and gaseous CO formation. Then, we rationally design and prepare novel two-dimensional (2D) Co-PPOLs through a facile surfactant-assisted bottom-up method, which have exclusive Co-N4 sites. The 2D ultrathin feature of Co-PPOLs ensures the exposure of catalytic centers. Together with the large specific surface area, high electrical conductivity and CO2 adsorption capability, the Co-PPOLs achieve outstanding activity and selectivity for electrochemical CO2 reduction to CO with FECO = 94.2% at a moderate cathodic potential (-0.9 V vs. RHE), accompanied with high chemical stability. In addition, Co-PPOLs can reach a high current above 200 mA in a membrane electrode assembly (MEA) reactor, and maintain a high FECO > 90% over 20 h, enabling industrial-level current and near-unity CO selectivity in CO2 electrolysis.

Designing freestanding electrodes with Fe2O3-based conversion type anode material for sodium-ion batteries

Fe2O3-based nanomaterials are promising conversion type anodes due to their high theoretical capacity (∼1000 mAhg−1). However, the issues related to poor electronic conductivity and severe volume change during electrochemical sodiation/desodiation impose serious challenges for practical implementations. Herein, we have proposed a carbon fiber-based freestanding electrode architecture, which can effectively reduce the pulverization and conductivity issue by embedding Fe2O3 nanoparticles on the carbon fiber network. Fe2O3 nanomaterial is synthesized by the surfactant-assisted precipitation method. The conventional Fe2O3 electrode exhibits poor cycling stability, even though it delivered 653 mAh g−1 capacity during 1st discharge cycle. In comparison, the freestanding electrode exhibits an enhanced initial capacity of 1154 mAh g−1 with 70 % capacity retention and 28 times faster Na-ion diffusivity at the 100th cycle. The carbon fiber network provides the conductive backbone facilitating ionic and electronic transport. Furthermore, the repeated sodiation/desodiation process in this electrode indicates good electrochemical stability. This work enlightens the electrode structuring approach, in which 3D carbon fiber-based mat can be used to fabricate binder-less, metal current collector-free, freestanding electrodes for improving electrochemical performance in Na-ion cells.

One-step hydrothermal synthesis of Bi2WxMo1-xO6 solid solution with adjustable energy band coupling with g-C3N4: 2D/2D Z-scheme heterojunction for enhanced photocatalytic HCHO degradation under indoor conditions

In this work, 2D/2D Bi2WxMo1-xO6/g-C3N4 was synthesized via surfactant-assisted one-step hydrothermal method for the degradation of formaldehyde in simulated room environment. We utilized CTAC as surfactant to control the morphologies of Bi2WxMo1-xO6 coupling with g-C3N4 nanosheets. In the hydrothermal method, Mo replaced W to form solid solution which could reduce energy band gap of Bi2WO6. In contrast to Bi2W0.6Mo0.4O6 (43.1%) and g-C3N4 (23.2%), Bi2W0.6Mo0.4O6/g-C3N4 exhibited superior activity (92.4%) of photocatalytic degradation for formaldehyde at the initial concentration of 1 ppm under the relative humidity (RH) of 20%. Meanwhile, we simulated diverse typical indoor conditions to evaluate the applicability of catalysts. More importantly, Bi2W0.6Mo0.4O6/g-C3N4 performed satisfactory stability with 5.5% decrease in degradation efficiency after five cycles. The mechanism of enhanced HCHO conversion was ascribed to the formation of 2D/2D Z-scheme heterojunction between Bi2W0.6Mo0.4O6 and g-C3N4 which increased the accessible interface and promoted the separation of photo-generated carriers for oxidation of formaldehyde.

Study of the anisotropic Sm2Fe17N3 powders with high performance

The strip casting technique was first used in this work to prepare the Sm2Fe17 parent alloys. Next, the Sm2Fe17N3 powders were synthesized using a gas–solid reaction of Sm2Fe17 powders with N2. Then, the anisotropic Sm2Fe17N3 powders with high performance were prepared by a surfactant-assisted grinding method in gasoline solvent. It was found that the coercivity (iHc) of ground powders increases with decreasing the average particle size (Dm), while the saturation magnetization (Ms) decreases. The maximum value of iHc of 17.5 kOe was obtained at the Dm = 1.3 µm. The ground powders with Dm of 3.1 µm show a remanence ratio (Mr/Ms) over 95% and a maximum energy product [(BH)max] of 35 MGOe. The Sm2Fe17N3 powder exhibited a very high iHc of 36.1 kOe at 10 K. Above 300 K, Sm2Fe17N3 powders mixed with epoxy resin showed a low remanence temperature coefficient of α(RT-100°C) = −0.077% °C−1.

Facile Fabrication of Monodisperse Micron-Sized Dual Janus Silica Particles with Asymmetric Morphology and Chemical Environment.

Janus particles are a kind of materials with asymmetric morphology or surface chemical environment. But so far, the preparation of particles with dual asymmetry is still a challenging problem. Hence the cation surfactant hexadecyl trimethyl ammonium bromide and co-surfactant octadecylamine are applied to improve the Pickering emulsion stability, and the micron-sized silica particles are arranged in a single layer at the toluene-water interface through electrostatic interaction. Furthermore, organosilane reagents are added in the preparation process, resulting in the construction of asymmetric hydrophilic or hydrophobic mesoporous precisely onto the micron-sized silica particles surface. The cation surfactant-assisted Pickering emulsion method is simple, effective, and convenience, which can be applied in the synthesis of various dual Janus silica particles for specific applications.

Low-temperature CO oxidation on CuO-CeO2-ZrO2 catalysts prepared by a facile surfactant-assisted grinding method

A series of CuO-CexZr1-xOy mixed oxides with different Ce contents were prepared via a facile surfactant-assisted grinding method, and their catalytic activity for CO oxidation under dry or moist atmosphere were investigated. The results indicate that the catalyst with a Ce content (x) of 0.7 in CexZr1-xOy (CuCe0.7Zr0.3) exhibited the best activity under both dry and moist atmospheres, with the temperatures corresponding to CO conversion of 90 % (T90) at a space velocity of 18000 mL/(gcat·h) being 90 and 120 °C, respectively. Combing with the physicochemical properties of the catalysts obtained by multiple characterization techniques such as ICP-OES, XRD, Raman, N2 sorption, XPS, in situ DRIFTs, H2-TPR, O2-TPD and CO-TPD, the high activity of the CuCe0.7Zr0.3 catalyst can be mainly attributed to the existence of large amounts of highly dispersed CuOx species and oxygen defect sites.

Surfactant-assisted impregnation of SBA-15 with highly dispersed copper species for CO oxidation

Copper containing SBA-15 materials has been prepared through a facile surfactant-assisted impregnation method. The surfactant contained in as-synthesized SBA-15 plays an important role to facilitate the distribution of copper species into the channels. The obtained materials have been fully characterized by several different techniques and the results show that the surfactant-assisted impregnation method is superior to the conventional impregnation method for obtaining Cu-SBA-15 with highly dispersed copper species which are mainly exist as isolated copper species and small clusters. The products exhibit superior CO oxidation activity and stability compared with that of Cu-SBA-15 prepared through the conventional wet impregnation method owning to the more finely dispersed Cu species and active sites.

Copper selenide sensitized low-cost porous coordination polymers towards efficient capture trace gaseous elemental mercury

Mercury, as a highly toxic atmospheric pollutant, poses serious hazards to global health and ecosystems. Developing low-cost sorbents with simultaneous fast capture rate and large uptake capacity to reduce elemental mercury (Hg0) emissions from industrial flue gas remains a formidable challenge. Herein, a rationally designed surfactant-assisted method was developed to construct copper selenide (CuSe) sensitized porous coordination polymers (CAU-10-H) as an efficient Hg remediator. The CuSe/CAU-10-H (0.8NC-CAU) exhibits superior near-100 % gaseous Hg0 removal efficiency over a wide temperature range (30–120 °C), implying its adaptability under different implementations. The equilibrium Hg0 adsorption capacity and initial Hg0 uptake rate of 0.8NC-CAU are 748.09 mg·g−1 and 63.21 μg·g−1·min−1, respectively, surpassing that of conventional sorbents and comparable to the benchmark materials. Furthermore, 0.8NC-CAU can adapt to harsh conditions with different flue gas impurities containing SO2, NO, and H2O to maintain high selectivity and stability, which is advantageous for real-world applications. Density functional theory (DFT) reveals that unsaturated selenium ligands as electron acceptors are critical affinity sites for facilitating Hg0 capture, resulting in stable HgSe species. More importantly, the facile preparation, prominent uptake capacity, and rapid capture rate of the 0.8NC-CAU material make it cost-effective. This work proposes a potential trap for Hg0 capture from industrial flue gas and facilitates the development of hybrid-functionalized materials for environmental remediation.

Iron-doped Co3O4 catalysts prepared by a surfactant-assisted method as effective catalysts for malic acid oxidative decarboxylation

Iron-doped Co3O4 oxides prepared by a surfactant-assisted method exhibited good catalytic activity in malic acid conversion, and the oxygen defects associated with the presence of Co2+ played a key role in catalyst activation for pyruvic acid production.

Mechanical milling processed highly luminescent Cs-Pb-Br perovskite emitters.

We report well-dispersed highly emitting perovskite emitters synthesized via the surfactant-assisted ball-milling method. Both the emitting peaks and the colour purity of the synthesized perovskite emitters can be effectively tuned through additive functionalization and precursor engineering.

Effect of surfactant-assisted hierarchical growth of cupric oxide-hydroxyapatite nanocomposite on the dielectric and electrical transport behavior

The current biomedical appliances require nano biomaterials with promising dielectric and transport properties. For this purpose, expensive, complicated instrumentations or time-consuming synthesis procedures, reducing acceptability of the developed materials, must be excluded. Therefore, for an effective solution to these challenges, proper scaling of electrical properties of nontoxic bioceramics is necessary by choosing eco-friendly surfactant-assisted synthesis methods. The present paper reports Polyvinylpyrrolidone-assisted hydrothermal synthesis of cupric oxide-hydroxyapatite nanocomposite (CuO-HAp-PVP) with crystallite size 25 nm. As observed by electron microscopy, the uniaxial growth of the CuO-HAp-PVP nanostructures elucidate novel flower-like aggregation. The nano-metric attachments of CuO phases are observed on the mesoporous surface (specific area of ∼17.7 m2/g obtained from Brunauer–Emmett–Teller study). The polymeric surfactant-mediated amorphous phases generate internal heterojunctions influencing the polarization process. The dielectric behavior [permittivity ∼6 × 103] and ionic conductivity of the nanocomposite are hence improved. Trap state-dependent bulk carrier conduction is observed by the nonlinear current-voltage characteristics.

TiO2-C nanocomposite synthesized via facile surfactant-assisted method as a part of less energy-consuming LED-based photocatalytic system for environmental applications

A novel facile method was used to incorporate carbon into the titania structure. An alternative synthesis method of carbon-doped TiO2 has been proposed by using a widely used and cheap surfactant. During the process, cetyltrimethylammonium bromide plays a dual role, as a morphology modifier and as a carbon source. The presented approach allows obtained TiO2-C nanostructures to be anatase nanocrystals with carbon being deposited either on the surface or between the TiO2 nanoparticles. The innovative nature of the research subject is related to the design of cheap LED solutions and facile synthesis of TiO2-C for use in novel energy-saving photocatalytic systems. Photocatalytic studies showed promising activity in the oxidation of 4-chlorophenol. Furthermore, it was indicated that LED-based photocatalytic systems allow a significant reduction in energy consumption compared to conventional photocatalytic sets. In addition, the high thermal efficiency of LED systems was confirmed with a thermal imaging camera. Hence, the presented novel LED photocatalytic systems can be an important part of a broad strategy for the protection of the environment.

Colorimetric Assay for Acetylcholinesterase Activity and Inhibitor Screening Based on Metal-Organic Framework Nanosheets.

Alzheimer's disease (AD) is a common chronic neurodegenerative disease that manifests as cognitive impairment and behavioral deficits and severely threatens the health of the elderly. Acetylcholinesterase (AChE) plays a vital role in biological signaling and is an essential target for the early diagnosis and treatment of AD. Herein, 2D Zn-TCPP(Fe) nanosheets (NSs) employing Zn2+ and Fe-bound tetrakis(4-carboxyphenyl)porphyrin ligands were prepared through a surfactant-assisted synthetic method. The ultrathin two-dimensional (2D) metal-organic framework structures exhibited high peroxidase-like activity, which allowed the catalysis of the H2O2-initiated oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB (ox-TMB). Such catalytic performance inspired us to develop a convenient, rapid, and sensitive acetylcholinesterase activity assay, during which AChE can catalyze the substrate acetylthiocholine (ATCh) to produce thiocholine (TCh), and TCh could especially enable the degradation of 2D Zn-TCPP(Fe) NSs accompanied by the reduction of ox-TMB production. Our proposed sensing system exhibited favorable selectivity and sensitivity (LOD of 0.029 mU/mL) and has excellent potential to evaluate AChE activity in human serum samples and to screen AChE inhibitors. This colorimetric assay could provide an alternative pathway for early diagnosis and drug screening of AD, facilitating the development of AD therapy.

Stress-Induced Grain Refinement in Hard Magnetic Mn52Al45.7C2.3 Fabricated Using the Ball-Milling Method.

Mn52Al45.7C2.3 flakes with different sizes were prepared with two distinct surfactant-assisted ball-milling methods using cylindrical and barrel containers. Different microstructure and magnetic properties were measured based on the sequence of the container shape and different ball-milling times (2, 5, and 10 h). Morphology investigations showed that for powders milled in a barrel container, the amount of τ-phase was more compared to the samples milled in a cylindrical container. Moreover, in the powders milled with barrel containers, considerably higher magnetic properties were obtained in terms of saturation magnetization (Ms) and remanent magnetization (Mr) compared to those powders milled with cylindrical containers. Magnetic properties were found to be a function of the ball-milling time. High remanent magnetization and saturation magnetization have been found for powders milled in barrel containers, whereas only mediocre remanent magnetization and saturation magnetization have been measured in the case of milling in cylindrical containers. The highest Ms = 52.49 emu g-1 and Mr = 24.10 emu g-1 were obtained for the powders milled in barrel containers for 2 h. The higher magnetic properties taken from the milling in barrel containers is due to the higher shear stress and more uniform strain distribution induced by the barrel configuration, resulting in the stable τ-phase at a reasonably low-strain microstructure.