Surfactant-assisted Method Research Articles

Photomechanically Induced Magnetic Field Response by Controlling Molecular Orientation in 9-Methylanthracene Microcrystals.

A surfactant-assisted seeded-growth method is used to form single-crystal platelets composed of 9-methylanthracene with two different internal molecular orientations. The more stable form exhibits a photoinduced twisting, as observed previously for 9-methylanthracene microribbons grown by the floating drop method. However, the newly discovered elongated hexagonal platelets undergo a photoinduced rolling-up and unrolling. The ability of the rolled-up cylindrical shape to trap superparamagnetic nanoparticles enables it to be carried along in a magnetic field gradient. The new photoinduced shape change, made possible by a novel surfactant-assisted crystal growth method, opens up the possibility of using light to modulate the crystal translational motion.

Characterization of structural and optical properties of the mesoporous Ce-MCM-41 hybrid materials

Ce-modified mesostructured MCM-41-type hybrid materials with different Si/Ce molar ratios (Si/Ce = 10, 30 and 50) were synthesized by the surfactant-assisted hydrothermal method and their structural and optical properties were characterized by small angle X-ray scattering (SAXS), field emission scanning electron microscopy (FE-SEM) equipped with embedded EDS system, ultraviolet and visible diffuse reflectance (UV–vis DR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Ce-MCM-41 samples show highly ordered 2D porous hexagonal mesostructures and oval and spherical morphologies with particle size between 300 and 600 nm, depending on the incorporated Ce amount. Incorporation of Ce4+ into ordered mesoporous silica generates oxygen defects in ceria-silica composites with the formation of Ce3+ species as confirmed by the XPS analyses. Cerium incorporation modified their structural regularity and resulted in an effective red shifting of the band gap (2.82 eV at 2.64 eV) due to the creation of intermediate energy states. Both asymmetry and broadening of Raman active F2g mode confirmed the presence of the structural defects. These ordered mesoporous Ce-MCM-41 hybrid materials are potentially attractive for their use as novel photocatalysts in the degradation of organic pollutants present in wastewater employing UV and visible light.

High surface graphene nanoflakes as sensitive sensing platform for simultaneous electrochemical detection of metronidazole and chloramphenicol

We demonstrate a mediator-free electrochemical sensitive sensing for detection of metronidazole (MNZ) and chloramphenicol (CAP) in real samples. A few-layered defect-free graphene nanoflakes (GNFs) were synthesized by surfactant-assisted exfoliation method, which was characterized by several methods like XRD, Raman spectroscopy, FE-SEM and TEM images. Cyclic voltammetry and electrochemical impedance spectroscopy were studied to understand the electron transfer behavior of GNFs modified glassy carbon electrode (GCE). Electrochemical behavior of MNZ and CAP was investigated at GNFs/GCE in PBS and observed peak potentials at −0.32 V and − 0.51 V vs. Ag/AgCl. A wider reduction potential window of MNZ and CAP were observed by differential pulse voltammetry which was found to be 280 mV at GNFs/GCE. Amperometry method was employed for detection of the unknown concentration of analytes under hydrodynamic condition. A linear calibration plot was obtained by plotting the concentrations of MNZ and CAP in ranging from 0.5 to 5.5 nM with R2 of 0.9983 and 0.9980, respectively. The detection limit of MNZ and CAP were found to be 0.15 nM and 0.38 nM, this system have shown good stability, excellent reproducibility and free interference from GNFs/GCE. The present method was successfully applied for the determination of MNZ and CAP in drugs and urine samples.

The Role of Neodymium in the Optimization of a Ni/CeO2 and Ni/CeZrO2 Methane Dry Reforming Catalyst

The development of a sustainable economy based on the use of renewable resources and the reduction of greenhouse gases emissions is an important mandate in modern societies to minimize the global warming. The CO2-reforming of methane through a conversion of CO2 and CH4 to syngas is a suitable process for this purpose and there is growing interest in the development of new catalysts for this process’ application at an industrial scale. This study is the first to investigate methane dry reforming activity of nickel supported on CeO2 and CeO2–ZrO2 solid solutions doped with neodymium. The supports were synthesized using a surfactant-assisted co-precipitation method and characterized through several analytical techniques to understand the role of synthesis parameters in the distribution of the dopant as well as in the properties of the supports. Co-doping with Zr and Nd resulted in an enhancement of dry reforming activity of ceria due to a higher dispersion of Ni and changes in the strength of basic sites. It was also shown that the addition of Nd helped to mitigate coking issues by increasing the mobility of surface oxygen in ceria and ceria–zirconia oxides and, accordingly, the rate of oxidation of carbonaceous deposits.

Multifunctional nanoporous magnetic zinc silicate-ZnFe2O4 core-shell composite for bone tissue engineering applications

Multifunctional materials have recently gained substantial attraction in bone tissue engineering because of their capabilities to solve essential problems after implantation including inflammation and osteomyelitis and also bone cancerous tissues through hyperthermia treatment. The aim of this study was to design and develop a new multifunctional composite containing a magnetic zinc ferrite as a core, and nanoporous zinc silicate as a shell via a two-step synthesis strategy to meet all above targets simultaneously. ZnFe2O4 particles are synthesized via solvothermal method and then coated through surfactant-assisted sol-gel method to obtain zinc silicate-ZnFe2O4 composite using cetyltrimethylammoniumbromide (CTAB) as a surfactant. The XRD results show that the composite has a glass-ceramic structure. The FESEM micrographs indicate the increase in the size of ZnFe2O4 particles because of zinc silicate formation around them. The vibrating sample magnetometer (VSM) results reveal that the formation of zinc silicate over ZnFe2O4 particles caused the magnetization saturation (Ms) to be reduced from 43 to 30 emu g−1. The antibacterial activity of the composite is evaluated against S. aureus and E. coli bacteria. Heat generation capability of the composite is assessed in vitro and results show that the composite reached the saturation temperature of 45 °C up to 510 s with 200 Oe magnetic field and constant 200 kHz frequency. Potential application of the composite as a controlled release system is assessed in vitro up to 240 h. The cell compatibility of the composite with different concentrations is assessed using osteoblast-like cells (MG63) up to 48 h.

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain.

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 °C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications.In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 °C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications. In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Surfactant-Assisted Synthesis of Tetragonal Porphyrin Microparticles

ABSTRACTIn an effort to utilize their unique photoactive properties, porphyrin monomers were assembled into tetragonal microparticles by a surfactant-assisted neutralization method through the cooperative interactions between the porphyrin building blocks including π-π stacking, J-aggregation and metal-ligand coordination. Electron microscopy characterization in combination with x-ray diffraction confirmed the three-dimensional ordered tetragonal microstructures with stable crystalline frameworks and well defined external surface morphology. Optical absorption and fluorescence spectroscopy revealed enhanced absorbance properties as compared with the raw porphyrin material, favourable for chromophore excitation and energy transport. With active and responsive optical properties, these new porphyrin microparticles look to serve as promising components for a wide range of applications including sensing, diagnostics, solar cells, and optoelectronic devices.

Unary- or binary-plasmonic nanoparticle-assemblies formed within hollow silica particles with a surfactant-assisted method

In this study, a surfactant-assisted method was employed to successfully prepare plasmonic nanoparticle assemblies encapsulated in hollow silica particles. In this method, silica was precipitated in the presence of plasmonic nanoparticles with single nanometer sizes and an anionic surfactant, sodium oleate (NaOA). The absorption peak of the composite particles was red-shifted compared with that for the well-dispersed suspension of the plasmonic nanoparticles. The extent of red-shift was easily tuned by changing the concentration of nanoparticles incorporated in the hollow silica particles. A binary-nanoparticle assembly, comprising gold and silver nanoparticles, was also prepared. Hence, this method can be extended to the design of novel multifunctional particles based on different nanoparticle assemblies.

Employing surfactant-assisted hydrothermal synthesis to control CuGaO2 nanoparticle formation and improved carrier selectivity of perovskite solar cells

Delafossites like CuGaO2 have appeared as promising p-type semiconductor materials for opto-electronic applications mainly due to their high optical transparency and electrical conductivity. However, existing synthetic efforts usually result in particles with large diameter limiting their performance relevant to functional electronic applications. In this article, we report a novel surfactant-assisted hydrothermal synthesis method, which allows the development of ultrafine (∼5 nm) monodispersed p-type CuGaO2 nanoparticles (NPs). We show that DMSO can be used as a ligand and dispersing solvent for stabilizing the CuGaO2 NPs. The resulting dispersion is used for the fabrication of dense, compact functional CuGaO2 electronic layer with properties relevant to advanced optoelectronic applications. As a proof of concept, the surfactant-assisted hydrothermal synthesized CuGaO2 is incorporated as a hole transporting layer (HTL) in the inverted p-i-n perovskite solar cell device architecture providing improved hole carrier selectivity and power conversion efficiency compared to conventional PEDOT:PSS HTL based perovskite solar cells.

An anionic surfactant-assisted equilibrium adsorption method to prepare highly dispersed Fe-promoted Ni/Al2O3 catalysts for highly selective mercaptan removal

This article proposes a novel sodium dodecylbenzenesulfonate (SDBS)-assisted equilibrium adsorption method for preparing highly dispersed Ni/Al2O3 and Fe-promoted NiFe/Al2O3 thioetherification catalysts. The proposed strategy anchors nickel cations onto the electronegative surface of an Al2O3 support modified by negatively charged DBS− bilayers. As a result, this method achieves highly dispersed Ni nanoparticles without strengthening the metal-support interaction, promoting the reducibility and sulfurization of the supported Ni species. The as-prepared Ni-based catalysts have a smaller size, a higher dispersion of metal nanoparticles, and a greater amount of active metal sulfides than their counterparts prepared by the conventional impregnation method, endowing them with excellent catalytic performance for the highly selective removal of mercaptans. This method provides a new opportunity to prepare highly dispersed metal nanoparticles without a strong metal-support interaction.

High specific surface area supports for highly active Rh catalysts: Syngas production from methane at high space velocity

A series of high specific surface area mesoporous supports (CeO2, CeO2-Al2O3, and Al2O3) were synthesized by the surfactant-assisted precipitation method using cetyltrimethylammonium bromide (CTAB) as template. Highly dispersed Rh-based catalysts were prepared by the wetness impregnation technique. The physico-chemical properties of the as-prepared supports and catalysts were investigated by N2-physisorption, CO-chemisorption, XRD, and H2-TPR measurements. Catalytic performance was evaluated towards the methane steam reforming (MSR) reaction up to 300 h of time-on-stream varying temperature (700–800 °C), steam-to-carbon (S/C = 2–3), and space velocity (88–200 SL·gcat−1·h−1); turnover frequencies were calculated at each reaction condition. All catalysts exhibited high activity strictly connected with high specific surface area (105–325 m2 g−1) and metal dispersion (34.3–84.0%). Significant enhanced stability was observed for Al2O3-containing catalysts towards the MSR reaction at high space velocity.

Enhanced generation of hydroxyl radicals on well-crystallized molybdenum trioxide/nano-graphite anode with sesame cake-like structure for degradation of bio-refractory antibiotic

Anodic electro-catalysis oxidation is a highly effective way to solve the pollution problem of antibiotics in wastewater and receiving water bodies. In this study, for the first time, molybdenum trioxide/Nano-graphite (MoO3/Nano-G) composites are synthesized as anodic catalysts by a surfactant-assisted solvothermal method followed by low-temperature calcination. The effects of the proportion of MoO3 to Nano-G (10, 30 and 50%) on the properties of composites are investigated through structural characterizations and electrochemical measurements. Results indicate that MoO3(30)/Nano-G electrode displays the electro-catalysis degradation efficiency of 99.9% towards ceftazidime, which is much higher than those of Nano-G (46.7%) and dimensionally stable anode (69.2%). The degradation mechanism for ceftazidime is studied by investigating the yields and kinds of active species. Results show that all of the OH, O2− and H2O2 are responsible for the electro-catalytic degradation process, and the produced OH radicals are the major active species for ceftazidime degradation. The synergistic effects between MoO3 and Nano-G greatly contribute to the activation of H2O molecules to produce OH, meanwhile the special sesame cake-like structure facilitates to the exposure of contaminants to OH on active sites to enhance the degradation efficiency. These results suggest that MoO3/Nano-G electrodes can be considered as the promising catalysts for treating bio-refractory organic wastewater.

Influence of PEG Stoichiometry on Structure-Tuned Formation of Self-Assembled Submicron Nickel Particles.

Self-assembled submicron nickel particles were successfully synthesized via the one-step surfactant-assisted solvothermal method. The impact of surfactant and reducing agent stoichiometry is investigated in this manuscript. Different morphologies and structures of Ni particles, including flower-like nanoflakes, hydrangea-like structures, chain structures, sphere-like structures, and hollow structures were prepared through different processing conditions with two parameters such as temperature and time. Based on scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and vibrating sample magnetometry (VSM), the submicron nickel particles show good saturation magnetization and excellent thermal stabilities with a possible growth mechanism for the variety of the structure-tuned formation. Importantly, the microwave absorption properties of the submicron nickel particles were studied. The lowest reflection loss of Ni-P9/T200/H15 with a thin layer thickness of 1.7 mm can reach −42.6 dB at 17.3 GHz.

Cobalt phthalocyanine tagged graphene nanoflakes for enhanced electrocatalytic detection of N-acetylcysteine by amperometry method

We have employed surfactant-assisted exfoliation method to prepare defect-free few-layer graphene flakes on a large scale. Various instrumental techniques like FT-IR, Raman, XRD, and FE-SEM were used to characterize the GNF. It can be used as a substrate to immobilize CoPc-treated GNF-based CPE that exhibits an enhanced electrocatalytic oxidation of NAC in 0.1 M PBS (pH 7.0). An enhanced oxidative peak current response was noted at + 0.33 V vs. Ag/AgCl for CoPc@GNF/CPE whereas the poor oxidation behavior was observed in the case of CoPc@rGO/CPE and CoPc/CPE. Electrochemical oxidation of NAC is a diffusion-controlled irreversible process which involves 2H+/2e− redox reaction. DPV and amperometry were employed for the determination of NAC and its linear ranges from 0.03–0.96 and 0.02–0.38 μM with a detection limit of 11 and 6.5 nM, respectively for CoPc@GNF/CPE. The present system can be exploited for quantitative detection of NAC in drug formulations and urine samples.

Structural, photocatalytic, biological and catalytic properties of SnO2/TiO2 nanoparticles

TiO2 and SnO2/TiO2 nanoparticles with different SnO2 contents (0–20wt%) were synthesized via surfactant-assisted sol-gel method using a cationic surfactant (cetyltrimethylammonium bromide, CTAB). The effects of SnO2 content on the structural, optical, and catalytic activity of TiO2 have been studied by X-ray diffraction (XRD), Transmission electron microscope (TEM), Scanning electron microscope (SEM), Fourier transformer infrared (FTIR) and UV–vis diffuse reflection spectroscopy (DRS). The total surface acidity of the prepared samples was measured by nonaqueous titration of n-butylamine in acetonitrile and the types of Brönsted and Lewis acid sites were distinguish using FTIR spectra of chemisorbed pyridine. XRD patterns analysis indicates that the crystallite size reduced remarkably and the transformation of anatase-to-rutile phase accelerated greatly with increasing the SnO2 content. TEM images exhibit a spherical shape with an average particle size varying in the range 10–24nm and high-resolution TEM images (HRTEM) show lattice fringes with interplanar spacing 0.35nm and 0.32nm which corresponding to anatase and rutile phases, respectively. SEM images show the amount of SnO2 on the TiO2 surface increases with increasing the SnO2 content and the particles of SnO2 were aggregated on TiO2 surface with increasing SnO2 content to 20% wt. The catalytic activity was tested by various applications: Photodegradation of Methylene Blue (MB) and Rhodamine B (RhB) under UV–vis irradiations and synthesis of xanthene (14-phenyl-14H-dibenzo [a,j] xanthene). Antibacterial and antioxidant activities were also studied. The antibacterial property test was carried out via agar disc diffusion method, and the results indicated that the prepared catalysts showed moderate antibacterial activity.

Surfactant-assisted shape separation from silver nanoparticles prepared by a seed-mediated method

So far from the suggestion of a seed-mediated method, there has been considerable development in the controllable synthesis of anisotropic nanoparticles. However, the formed nanoparticles often exhibit considerable polydispersity in their size or shape. In this work, we improved the surfactant-assisted shape separation method that were different from gold nanorods reported previously to purify silver nanotriangles and investigated the important parameters systematically. The results showed that relative amount of CTAB to AgNPs (which was determined by the concentration and volume of CTAB) and the temperature of CTAB were the critical roles in the separation of silver nanotriangles. Silver nanospheres, small nanotriangles and big nanotriangles were separated successfully from their associated nanoparticles by the surfactant-assisted shape separation in twice. The separated nanoparticles have higher regularity and more uniform size, which is important to enlarge the application scope of silver nanomaterials. This improved method allows us to purify silver or other metal nanoparticles prepared by a facile seed-mediated method in high efficiency and yield.

CO2 reforming of CH4 over Ni/SBA-15 prepared by surfactant-assisted impregnation method: Comparative study of surfactant types

This research focused on the influence of surfactant types of surfactant-assisted impregnation method on the properties and catalytic activity of Ni/SBA-15 towards CO2 reforming of CH4 (CRM). Three types of surfactant were used which were nonionic surfactant (poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol), P123), cationic surfactant (cethyltrimethylammonium bromide, CTAB) and anionic surfactant (sodium dodecyl sulfate, SDS) to synthesize Ni/SBA-15(P123), Ni/SBA-15(CTAB) and Ni/SBA-15(SDS), respectively. The synthesized catalysts were characterized using X-ray Diffractometer (XRD), Brunauer-Emmett-Teller (BET) and Fourier-Transform Infrared (FTIR) to study the physical and chemical properties of synthesized catalysts. The CRM was carried out in a stainless steel fixed bed reactor at 800°C and CO2/CH4 ratio = 1/1. The obtained results indicated that the types of surfactant greatly influence the properties and catalytic activity of Ni/SBA-15. The activity of catalysts followed the order of SBA-15 < Ni/SBA-15(SDS) < Ni/SBA-15(CTAB) < Ni/SBA-15 < Ni/SBA-15(P123) with the conversion of CH4 and CO2 over Ni/SBA-15(P123) were about 92% and 82%, respectively and H2/CO ratio of 1.22. The superior catalytic performance of Ni/SBA-15(P123) might be related with the well dispersion of Ni particles which enhanced the stabilization of the active metal sites on SBA-15 and ameliorated the properties of catalyst towards an excellent catalytic performance. This study provides a new perspective on the preparation of Ni/SBA-15, particularly in the influence of surfactant types of surfactant-assisted impregnation method towards an excellent CRM.

Synthesis of fluorapatite nanopowders by a surfactant-assisted microwave method under isothermal conditions

Fluorapatite nanopowders with different amounts of fluoride ions were prepared using the surfactant-assisted microwave method under isothermal conditions. Microwave irradiation was applied for the rapid formation of crystals. A micellar solution of polyoxyethylene (23) lauryl ether was used as a regulator of nucleation and crystal growth. Characterization studies from X-ray diffraction, field-emission scaning electron microscopy and Fourier-transform infrared spectra showed that crystals have an apatite structure and particles of all samples are nano size, with an average length of 50 nm and about 15-25 nm in diameter. Antimicrobial studies have demonstrated that synthesized fluorapatite nanopowders exhibit activity against tested pathogens: Escherichia coli, Staphylococcus aureus and Candida albicans. Activity increased with the amount of fluoride ions. The synthesized fluorapatite nanomaterials are promising as materials in environmental protection and medicine for orthopedics and dental restorations.

Low-temperature solution-phase route to sub-10 nm titanium oxide nanocrystals having super-enhanced photoreactivity

High-purity anatase nanocrystals were prepared by using a low-temperature surfactant-assisted solution-phase method.