Amount Of Cetyltrimethylammonium Bromide Research Articles

Ultrasound‐assisted modification of Al2O3@TiO2‐Ce core‐shell structure adsorbent for simultaneous desulfurization and denitrification

AbstractBACKGROUNDIn order to improve the desulfurization and denitrification performance of Al2O3@TiO2‐Ce adsorbent, ultrasound‐assisted surface modification using different pore‐forming agents (CTAB (Cetyl Trimethyl Ammonium Bromide), NH4NO3, and Urea) was introduced into the preparation process of Al2O3@TiO2‐Ce core‐shell structure adsorbent.RESULTSAmong the adsorbent modified by various pore‐forming agent, CTAB modified Al2O3@TiO2‐Ce adsorbent showed the best denitrification efficiency, and the ultrasound‐assisted modification of CTAB had a positive effect on the removal efficiency of SO2 and NOx. The adsorption performance increased with the increase of addition amount of CTAB in the range of 5% to 10% but decreased with the increase of CTAB addition amount in the range of 10% to 20%. Petal‐like wrinkles appeared on the surface of CTAB modified adsorbent, and the distribution of the pores on the surface was dispersed uniformly by ultrasound.CONCLUSIONThe petal‐like wrinkle could effectively increase the specific surface area and pore volume of the adsorbent, and pore size distribution was more evenly, which was considered to be the key to improve the adsorption performance. The SO2 and NOx adsorption followed the pseudo‐first order rate expression, and the adsorption process was limited by both external diffusion and intraparticle diffusion. This work provides an experimental and theoretical basis for the surface modification of simultaneous desulfurization and denitrification adsorbents. © 2020 Society of Chemical Industry

Dual Template, Three-Dimensional Hierarchical Porous Scaffolds Based on Graphene Oxide for Bone Tissue Engineering

Objectives Scaffolds for bone tissue engineering (BTE) are three-dimensional (3D) porous matrices that provide the necessary sites for cell adhesion and proliferation, where the architecture plays an important role. Ideally, BTE scaffolds should have an interconnected network of both large and small pores to facilitate the infiltration of cells and the diffusion of growth factors and nutrients1. Scaffolds for BTE should also enhance osteogenic differentiation to improve bone regeneration. Graphene oxide (GO) can promote osteogenic differentiation of mesenchymal stem cells (MSCs) because it can provide biophysical cues and adsorb biological factors2. However, due to the lack of fabrication strategies, it remains a challenge to develop GO and GO composite scaffolds with a hierarchical architecture for BTE. In this study, we aim to develop a dual-templating method to control the assembly of GO sheets, in order to design and achieve this architecture. Experimental Methods We modified the amphiphilicity of GO by adding different amounts of cetyltrimethylammonium bromide (CTAB), hydroxyapatite (HA), polyacrylic acid (PAA) and elastin from bovine neck ligament. Then we developed GO-CTAB, GO-CTAB-HA, GO-CTAB-PAA and GO-elastin stabilized oil in water emulsions. Afterwards, we froze the emulsions at different temperatures (-190 oC and -20 oC), and upon freeze-drying we produced free-standing scaffolds. We reduced GO-CTAB scaffolds in different conditions to obtain rGO scaffolds. We studied the formation of emulsions and the structural and chemical properties of scaffolds through optical microscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared, and compressive strength tests. We seeded mouse bone marrow MSCs on 2D GO substrates and 3D GO-based scaffolds. Then, we compared the cell proliferation after 10 days of incubation. We also analyzed the cells on GO-based scaffolds after 7 days of incubation using SEM and confocal microscopy, in order to study cell morphology, attachment and infiltration in the scaffolds. Results and Discussion The scaffolds based on GO, GO-HA, GO-GO-PAA, GO-elastin and rGO have interconnected primary pores of 150-300 µm in diameter (Figure 1 a-j), which matches the size of the hexane droplet templates. Freezing at -190 oC results in smaller secondary pores around 10 µm in diameter (Figure 1 a-e) while freezing at -20 oC results in larger secondary pores with diameters around 30-50 µm (Figure 1 f-j). This result shows that the secondary pore formation is controlled by ice nucleation and growth in the aqueous phase of the emulsions at different temperatures. Scaffolds based on GO-HA, GO-PAA and especially GO-elastin show an improved modulus of compression compared to GO-based scaffolds (Figure 1 k). The cell culture using MSCs reveals cell proliferation up to 10 days on 2D GO substrates and 3D GO-based scaffolds (Figure 1 l). Compared to 2D substrates, the large and interconnected pores in 3D scaffolds contribute to the higher cell proliferation result. The cells are well spread on the scaffolds with an elongated shape and filamentous extensions at day 7 (Figure 1m). They infiltrate all the way to the center of GO-based scaffolds through primary pores (Figure 1 m, n). These results indicate that primary pores can facilitate the cell infiltration. Conclusions The rapid development and broad application of graphene-based porous materials requires efficient and facile fabrication methods. We developed a novel strategy to control the assembly of GO sheets using emulsions and ice templates to fabricate GO-based scaffolds with an interconnected and hierarchical porous structure. The ability to fabricate rGO and GO composite scaffolds with similar architectures demonstrates the versatility of this strategy. The GO-based scaffolds show biocompatibility and allow cell infiltration. We expect that this strategy can lead to improvements in the fabrication of GO-type scaffolds for BTE.

One-step in situ preparation of flexible CuS/TiO2/polyvinylidene fluoride fibers with controlled surface morphology for visible light-driven photocatalysis

In this study, flexible CuS/TiO2/polyvinylidene fluoride (PVDF) fibers with controlled surface morphologies were successfully prepared in situ via one-step hydrothermal growth. The morphology was controlled based on the amounts of the Cu source and functional surfactant cetyltrimethylammonium bromide (CTAB) used in the preparation process. When the amount of CTAB was kept constant, the Cu source significantly affected the amount of CuS nanoflowers loaded on the TiO2/PVDF fibers as well as the morphology of the CuS. When the amount of Cu source was kept constant, the addition of CTAB had a key effect on the morphology of the CuS. By decreasing the amount of CTAB, the morphology of the CuS loaded on the TiO2/PVDF fibers gradually changed from dense nanoflowers into small flake particles. Under irradiation with visible light, experiments based on the photodegradation of levofloxacin hydrochloride (LFXH) showed that Cu1C0.01 (CuS/TiO2/PVDF fibers prepared with 1 mmol Cu(NO3)2·3H2O and 0.01 mmol CTAB) obtained the highest degradation efficiency. Due to the morphology of Cu1C0.01 comprising small flake particles, CuS could fully contact with the internal TiO2 and pollutants, thereby allowing photogenerated carriers to fully participate in the photodegradation reaction. Further analysis demonstrated that photogenerated holes (h+) played a key role in the photodegradation of LFXH.

Determination of Vancomycin Hydrochloride in Pharmaceutical Forms and Urine Samples Using Modified Magnetic Iron Oxide Nanoparticles

Magnetic solid-phase extraction is an efficient and low-cost spectrophotometric method that can be utilized for extraction and determination of pharmaceutical compounds. Vancomycin is an antibiotic used in the treatment of life-threatening infections caused by Gram-positive bacteria. This study utilized magnetic solid-phase extraction for the determination of vancomycin hydrochloride (VAN) in different matrices. The separation and determination performed on magnetic iron oxide nanoparticles (IONPs) was modified using cetyltrimethylammonium bromide (CTAB). An azo dye product results from the coupling of VAN with the diazotized 4-aminoacetophenone in alkaline medium. This product was extracted and measured spectrophotometrically at λmax of 456 nm. Factors affecting the efficiency of removing the dye, such as pH of the solution, volume of reagent, CTAB amount, adsorbent amount, extraction time and desorption conditions, were studied. Under optimal extraction conditions, the linearity concentrations range was 0.1–6 µg/mL. The limit of detection and the limit of quantification was calculated to be 0.075 and 0.25 µg/mL, respectively. The method was applied successfully for the fast analysis of VAN in its dosage forms using the CTAB-coated IONPs, and the extraction process could be completed within 10 min.

Surfactant-mediated prepared VO2 (M) nanoparticles for efficient solar steam generation

Herein, for the first time, we demonstrated the potential practicability of VO2 (M) as a low cost and stable photoabsorber coated on a piece of poplar wood (W/S8-M) in solar steam generation of Caspian Sea water. The evaporation rate of 3.63 kg m−2 h−1 and the solar steam generation efficiency of 75.60% for W/S8-M were obtained under 3 sun (3 kW m−2) irradiation within 40 min. The concentration of sodium ions in the seawater decreased from 3138.19 to 6.61 mg L−1 for W/S8-M which is far below the drinking water standards. The pH and electrical conductivity of seawater was decreased after desalination by W/S8-M to a large extent. A surfactant-mediated method using different amounts of cetyltrimethylammonium bromide (CTAB) was used to prepare VO2 (M). It was revealed that the sample prepared by addition of 0.08 g CTAB using hydrothermal method has the smallest particle size of 230 nm, the largest specific surface area of 14.542 m2 g-1, the greatest mean pore size of 43.53 nm, narrow thermal hysteresis width of 4.12 °C, and the lowest semiconductor–metal phase transition temperature of 65.23 °C. For the first time, the ATR-FTIR spectroscopy was used to monitor the SMT of VO2 (M) at different temperatures. We found that the samples have the same unique ATR-FTIR spectra below Tc with the characteristic band at 835 and a shoulder at 1020 cm−1 while at T > Tc, the fairly linear curves without any meaningful band are appeared.

A solution synthesis of Na3V2(PO4)3 cathode for sodium storage by using CTAB additive

Na3V2(PO4)3 (NVP) powders were prepared by solution synthesis method using cetyltrimethylammonium bromide (CTAB) as additive. The structural, microstructure and electrochemical performances of NVP powders were characterized as a function of CTAB amounts. The porous carbon-coated particles were formed by burning of CTAB during calcination at 850 °C. The thickness of carbon layer, specific surface area and contribution of sp2 carbon type domains increased by the increase of CTAB contents. The Na3V2(PO4)3 powders prepared by 0.8 mmol CTAB exhibited a high specific capacity (112.2 mAhg−1, 1C) and a high capability rate performance (88.7 mAhg−1, 10C), due to their higher electronic conductivity and sodium diffusion coefficient.

Fabrication Of TiO₂ Nanoflowers Powder with Various Concentration Of CTAB

Nanostructures titanium dioxide (TiO₂) such as nanoflowers and nanorods have contribute in many application. Among TiO₂ nanostructures, TiO₂ nanoflowers gives high surface area that contribute in good binding properties and reducing internal stress and increasing strength of the ceramics.This paper presents fabrication of TiO₂ nanoflowers powder to overcome the cracking problem in ceramic industry. In this study, fabricated rutile- phased TiO₂ nanoflower powder has been successfully synthesized by using hydrothermal method and the surface morphology, structural properties, and the composition of TiO₂ nanoflower powder also identified. The fabricated TiO₂ are characterized using Field Emission Scanning Electron Microscopy (FESEM) to observe the surface morphology of TiO₂, X-ray Dispersion (XRD) was used to determine the crystallite phase and EDX for element composition in fabricated TiO₂ powder. The synthesized TiO₂ powder was obtained from the reaction between deionized water (DI), hydrochloric acid (HCl), Titanium Butoxide (TBOT) and Cetyltrimethylammonium Bromide (CTAB). The hydrothermal temperature is 150 C̊with fixed hydrothermal time of 10 hours. The parameters varied is the mass of surfactant used, CTAB. The hydrothermal method is proven suitable to fabricate semiconductor materials due to its advantages that parameters are easily modified and can be performed under closed system with low operational temperature. Increased amount of CTAB used make the gap between the nanorod become closer and stronger. The diffraction peaks of all sample hardly changed, but the intensity for each sample was enhanced as the mass of CTAB used increased. The structure also become well crystallined in rutile phase structure.

Facile synthesis of mesoporous Cr2O3 microspheres by spray pyrolysis and their photocatalytic activity: Effects of surfactant and pyrolysis temperature

Mesoporous Cr2O3 microspheres with improved pore structure were prepared by spray pyrolysis method. A precursor solution was nebulized into fine droplets containing chromium salt and cetyltrimethylammonium bromide (CTAB), which were then pyrolyzed to Cr2O3/Cx microspheres inside a tubular furnace, followed by post-heat treatment to eliminate the carbonaceous material. The produced Cr2O3 particles had a diameter of 0.5-1 um and their textural properties could be tuned by adjusting CTAB amount and pyrolysis temperature. The synthesized Cr2O3 microspheres had the highest surface area and pore volume of 52 m2g-1 and 0.3 cm3 g-1, respectively, which surpass those of Cr2O3 prepared using a conventional method such as thermal decomposition, hydrothermal reduction or wet chemical synthesis. The photocatalytic degradation of methyl orange dye (MO) was tested on the prepared Cr2O3 particles. It was determined that the spray pyrolysis-derived Cr2O3 exhibited greater photocatalytic activity than that of commercial TiO2 and Cr2O3 particles prepared by the thermal decomposition of chromium salt.

Preparation and photocatalytic activity of visible light-responsive zinc oxide/activated carbon fiber composites

Herein, in order to improve the photocatalytic performance of zinc oxide (ZnO), a visible light-responsive ZnO/activated carbon fiber (ACF) composite photocatalyst was prepared by immersion-hydrothermal method. The structural, micromorphology, formation procedure, optical properties and photocatalytic activity were researched in detail. The surfactant cetyltrimethylammonium bromide (CTAB) was introduced into the synthesis system. ZnO/ACF composites exhibited excellent photocatalytic activity under simulated visible light irradiation. Especially, when the amount of CTAB was 2.0 mM, the ZnO/ACF composite had the best adsorption performance and photocatalytic activity for the MO solution. The adsorption rate and degradation efficiency of the sample reached 95.6% and 99.4% after 5 h, respectively. We have proposed a possible photocatalytic machanism according to the trapping experiment. Moreover, ZnO/ACF still displayed excellent stability after 5 times repeated use.

Seed-Assisted Synthesis and Catalytic Performance of Nano-sized ZSM-5 Aggregates in a One-Step Crystallization Process

Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide (CTAB) through a facile one-step crystallization process. Commercial ZSM-5 zeolites with a SiO2/Al2O3 ratio comparable to that of ZSM-5 products were treated with alkali and used as the seed particles. The influences of crystallization conditions were investigated, and the possible synthesis mechanism was proposed. ZSM-5 zeolites with different amounts of CTAB added were characterized using many techniques and evaluated in toluene alkylation with methanol. The results showed that a trace amount of CTAB significantly promoted the crystallization of ZSM-5 zeolite, with the morphology changing from hexagonal-shape crystals to uniform spherical aggregates. CTAB may act as the structure-directing agent and assemble the primary crystallites to generate hierarchical ZSM-5 aggregates. The ZSM-5 zeolite with the smallest primary particles of 50–80 nm exhibited large specific surface area, abundant mesopores, and the greatest microporosity. The hierarchical nano-sized ZSM-5 aggregate showed higher toluene conversion and a longer lifetime without compromising the selectivity to xylene and p-xylene in toluene alkylation with methanol.

CTAB-Assisted Synthesis of C@Na3V2(PO4)2F3 With Optimized Morphology for Application as Cathode Material for Na-Ion Batteries

C@Na3V2(PO4)2F3 samples were obtained by using Cetyl Trimethyl Ammonium Bromide (CTAB) as a surfactant. The optimization of the added amount allowed controlling the eventual nanometric morphology of the particles. The morphological and structural properties of these samples were discussed in the light of solid-state techniques as X-ray diffraction, Raman and XPS spectroscopies, and electron microscopy. Galvanostatic test in sodium half-cells revealed that the nanometric spherical and porous particles provided by the addition of intermediate amounts of CTAB showed excellent cycling stability and superior high rate capability reflected in the minimization of the cell polarization and the determination of a high apparent diffusion coefficient.

Mesoporous magnetic nanocomposites: a promising adsorbent for the removal of dyes from aqueous solutions

Water pollution by synthetic organic dyes is mainly regarded as environmental and ecological issues worldwide and requires feasible solutions in face of the short-term risk to human health and stability of eco-systems. Therefore, in this paper, the magnetic mesoporous composites (MMC) were synthesized by surfactant template sol–gel method, using cetyl-trimethylammonium bromide (CTAB) as mesoporous structure generator and investigated for anionic and cationic dyes removal from aqueous solutions. The magnetic iron oxide nanoparticles were obtained by reverse co-precipitation, followed by mesoporous silica coating through modified sol–gel method. The obtained materials were characterized by FT-IR spectroscopy, X-ray diffraction, transmission electron microscopy, Mossbauer spectroscopy, nitrogen adsorption, small-angle X-ray scattering and magnetization measurements. The influence of CTAB amount on the morpho-textural and structural properties of nanocomposites was studied. XRD and Mossbauer spectroscopy showed that the obtained nanocomposites were composed of pure maghemite nanoparticles, and TEM images revealed particles size around 10 nm, embedded in silica matrix. The combination of magnetic properties and high surface area values, up to 695 m2/g, made suitable the obtained nanocomposites to be used as adsorbents. The dye removal efficiency was higher than 90% after the first adsorption and remained above 65% after four adsorption–desorption cycles, indicating that the as-prepared magnetic mesoporous nanocomposites can be considered excellent adsorbent materials for the removal of both anionic and cationic dyes from wastewaters, and the recycling performance revealed the stability of MMC.

One-pot preparation of AgBr/α-Ag2WO4 composite with superior photocatalytic activity under visible-light irradiation

Recently, semiconductor photocatalysts have received much attention in the field of eliminating organic pollutants in waste-water without causing any new accompanied secondary pollution. Herein, we have reported a new visible-light-driven photocatalyst of AgBr/α-Ag2WO4 composites with high efficiency of pollution elimination. A series of composites were prepared with addition of various amounts of cetyltrimethylammonium bromide (CTAB, from 0.1–2.0 m moL) to the Ag2WO4 precipate-containing solution via a facile one-pot hydrothermal route. The as-prepared composites were characterized by various techniques like powder XRD, UV–vis DRS, SEM, element mapping, HR-TEM, XPS and PL analyses. Photo-catalytic behaviors of these AgBr/α-Ag2WO4 composites were examined through the removal of Rhodamine B (RhB) under visible-light radiation. It is confirmed that the AgBr/α-Ag2WO4 composites show the higher photocatalytic ability than pure AgBr and α-Ag2WO4 samples. Particularly, the AgBr/α-Ag2WO4 composite obtained with the addition of 1.0 m moL of CTAB possesses 100% degradation of RhB in 60 min and an outstanding photostability. The enhanced photocatalytic activity of the AgBr/α-Ag2WO4 composite is mainly attributed to the creation of heterojunction on the interface between AgBr and α-Ag2WO4, which can efficiently facilitate the rapid charge separation and recombination reduction of the photo-created electron-holes pairs. A photo-degradation mechanism of AgBr/α-Ag2WO4 composite is also discussed based on the band position and radical trapping tests. As a result, the as-prepared AgBr/α-Ag2WO4 composite is proved to be a promising candidate of photocatalyst for the treatment of wastewater.

Soft Cationic Nanoparticles for Drug Delivery: Production and Cytotoxicity of Solid Lipid Nanoparticles (SLNs)

The surface properties of nanoparticles have decisive influence on their interaction with biological barriers (i.e., living cells), being the concentration and type of surfactant factors to have into account. As a result of different molecular structure, charge, and degree of lipophilicity, different surfactants may interact differently with the cell membrane exhibiting different degrees of cytotoxicity. In this work, the cytotoxicity of two cationic solid lipid nanoparticles (SLNs), differing in the cationic lipids used as surfactants CTAB (cetyltrimethylammonium bromide) or DDAB (dimethyldioctadecylammonium bromide), referred as CTAB-SLNs and DDAB-SLNs, respectively, was assessed against five different human cell lines (Caco-2, HepG2, MCF-7, SV-80, and Y-79). Results showed that the cationic lipids used in SLN production highly influenced the cytotoxic profile of the particles, with CTAB-SLNs being highly cytotoxic even at low concentrations (IC50 < 10 µg/mL, expressed as CTAB amount). DDAB-SLNs produced much lower cytotoxicity, even at longer exposure time (IC50 from 284.06 ± 17.01 µg/mL (SV-80) to 869.88 ± 62.45 µg/mL (MCF-7), at 48 h). To the best of our knowledge, this is the first report that compares the cytotoxic profile of CTAB-SLNs and DDAB-SLNs based on the concentration and time of exposure, using different cell lines. In conclusion, the choice of the right surfactant for biological applications influences the biocompatibility of the nanoparticles. Regardless the type of drug delivery system, not only the cytotoxicity of the drug-loaded nanoparticles should be assessed, but also the blank (non-loaded) nanoparticles as their surface properties play a decisive role both in vitro and in vivo.

Dynamic Equilibrium in the Cetyltrimethylammonium Bromide-Au Nanoparticle Bilayer, and the Consequent Impact on the Formation of the Nanoparticle Protein Corona.

Nanoparticles in ionic solutions are usually surrounded by stabilizing molecules that avoid aggregation and determine their surface properties, which strongly influence their behavior. The present work aims to shed light on the static vs dynamic nature of the cetyltrimethylammonium bromide (CTAB) bilayer on gold nanoparticles and to understand its effects on nanoparticle evolution in biological systems. A systematic study of the CTAB bilayer of Au nanorods and nanospheres was carried out, exploring the role of excess free surfactant in solution on the surface properties of nanoparticles and their colloidal stability. The results indicated the presence of a CTAB bilayer in which the external layer was in rapid dynamic equilibrium with the free surfactant in solution. The internal surfactant layer of the gold nanospheres was also found to be in dynamic equilibrium. Conversely, the gold nanorods had a permanent internal layer. Consequently, the CTAB-nanoparticle dispersions always contained free CTAB in excess to maintain the colloidal stability of the NPs. In contrast, decreasing the free CTAB concentration resulted in nanoparticle aggregation. The impact of the dynamic equilibrium on the exposure of particles to biological fluids and on the formation of the nanoparticle protein corona was studied, revealing the different fates of the nanoparticles, which depended on the amount of free CTAB in solution.

Synthesis of hierarchical ZSM-5 aggregates by an alkali-treated seeds method with cetyltrimethylammonium bromide for the methanol to gasoline reaction

A series of hierarchical ZSM-5 aggregates with a relatively low SiO2/Al2O3 ratio (~ 50) were successfully synthesized using alkali-treated commercial ZSM-5 as seeds and cetyltrimethylammonium bromide (CTAB) as mesogenous template. The effect of the amounts of CTAB on the physicochemical and catalytic properties of the synthesized catalysts was characterized by XRD, FE-SEM, FE-TEM, N2 physical adsorption, ICP-OES, NH3-TPD, Py-IR and TGA. Moreover, the possible formation mechanism of the hierarchical ZSM-5 aggregates was studied. The results indicated that the mesoporosity of the hierarchical ZSM-5 aggregates was greatly enhanced with the addition of CTAB. The primary crystal size of the ZSM-5 aggregates significantly decreased owing to the protective effect of CTAB, which inhibits the further crystal growth. The hierarchical ZSM-5 aggregates prepared with addition of a suitable amount of CTAB showed large specific surface areas and large external surface areas, abundant intercrystalline mesopores and appropriate concentration of acid sites, which resulted in excellent catalytic performance in the methanol to gasoline reaction. The stability of the catalyst was remarkably improved and the gasoline yield was given a rise of 10% compared with the catalyst prepared in the absence of CTAB.

Microwave hydrothermal synthesis, annealing and luminescence properties of BaWO4:3%Eu3+ microcrystals

The uniform BaWO4 microcrystals with scheelite-type tetragonal structure were fabricated via a microwave hydrothermal method. The morphologies and sizes of the products can be tuned by adjusting synthetic conditions including pH value, the amount of cetyltrimethylammonium bromide (CTAB) and the reaction time. The increasing amount of CTAB surfactant (from 0 to 0.05 mmol) causes the morphological transformation from flower-like to octahedron-like. Particularly, in the time-dependent experiments, the nanoparticles prefer to adsorb or nucleate on (111) crystal planes in the growth process, while the (101) planes become narrow or even partly disappear. Doping of Eu3+ (3 mol%) has no effect on the morphology and the phase structure. The emission spectrum (λex = 394 nm) of the BaWO4:3%Eu3+ exhibits the maximum peak at 613 nm, corresponding to 5D0 → 7F2 transition of Eu3+. Moreover, uniform and well-defined octahedron-like crystals have better fluorescence properties than irregular flower-like crystals. Annealing treatment, aiming at removing the residual surfactant on the surface, can effectively improve the crystallization and reduce the defects in the crystals. BaWO4:3%Eu3+ microcrystals with octahedron-like annealed at 850 °C for 2 h has the strongest luminescence properties, which can be considered as a red phosphor for white light-emitting diodes (WLEDs).

Disperse ultrafine amorphous SiO2 nanoparticles synthesized via precipitation and calcination

Disperse ultrafine spherical amorphous SiO2 nanoparticles with high purity are essential for producing SiO2 nanoglass which may show a good toughness. Herein, synthesis of disperse ultrafine spherical amorphous SiO2 nanoparticles with high purity via precipitation and calcination is reported. In the preparation, Na2SiO3·9H2O was used as silicon source, and NH4Cl as a buffer for a catalytic self-condensation of hydroxyl groups during hydrolysis of Na2SiO3 in the alcohol/water solvent system and a slowly hydrolyzed precipitator as well. The main factors affecting the size, dispersity, and shape of amorphous SiO2 nanoparticles including the amount of cetyltrimethyl ammonium bromide (CTAB), different surfactants (sodium dodecyl benzene sulfonate, CTAB, and polyethylene glycol), ethanol/water solvent volume ratio, and different solvent systems were investigated. Well-dispersed spherical amorphous SiO2 nanoparticles with an average particle size of 4.0 nm and a size range of 2―12 nm were synthesized using 0.15 g/L CTAB and 1:1 volume ratio of methanol/water and by calcination. The specific surface area of the SiO2 nanoparticles with an average particle size of 4.0 nm is 584 m2/g. The SiO2 nanoparticles have a purity of 99.4% (mass percent). The disperse ultrafine spherical amorphous SiO2 nanoparticles have a high purity, the finest particle size, and the largest specific surface area achieved so far.

Surfactant-assisted hydrothermal synthesis of nitrogen doped Mo2C@C composites as highly efficient electrocatalysts for hydrogen evolution reaction

We describe a facile surfactant-assisted hydrothermal route to synthesize nitrogen doped Mo2C@C composites in the presence of cetyltrimethylammonium bromide (CTAB) as carbon source and structure guiding agent. The resulting Mo2C@C composites consist of Mo2C nanocrystals with sheet-like morphology and well-dispersed nitrogen element doping. Controllable experiments indicate that the additive amount of CTAB can efficiently tune porous structure and electrochemical activity of the as-prepared Mo2C@C materials. This unique nitrogen doped Mo2C@C composite provides several advantages for electrocatalytic applications: (1) nitrogen doped carbons can prevent the aggregation of Mo2C nanocrystals and render it high conductivity; (2) the homogeneous dispersion of Mo2C nanocrystals provides abundant active sites; (3) 2D morphology, the hierarchical porosity, and high surface areas allow large exposed field of active sites and facilitate mass transfer. As a result, the nitrogen doped Mo2C@C composites deliver superior HER electrocatalytic activities with a low overpotential of only 100 mV and also a low Tafel slope of 53 mV/dec in alkaline condition. Such CTAB-assisted strategy may open up an opportunity towards synthesis of low cost and high performance Mo-based electrocatalysts for various applications, such as water splitting.

CTAB-assisted synthesis of dissilient hollow spherical MoS2 for efficient hydrogen evolution

Dissilient hollow spherical MoS2 was prepared by one-step hydrothermal method using cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The structure and morphology of the prepared materials were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The addition of CTAB plays an important role in controlling the morphology of MoS2. As the amount of CTAB was increased, the morphology of MoS2 changed from flake to hollow sphere and finally broked up. Compared with MoS2 without CTAB and closed hollow spherical MoS2, the dissilient hollow spherical MoS2 showed better electrochemical performance in the hydrogen evolution reaction (HER) and good stability after 1000 cycles. We attribute this improvement to large specific surface area and many catalytic active sites of the dissilient hollow spheres. In general, the optimized catalyst exhibited an onset overpotential of 159 mV, a low Tafel slope of 65 mV dec−1, and relatively good stability.