Surfactant-free Conditions Research Articles

Synthesis and characterization of Bismuth titanate perovskite materials for hydrogen production

In this work, a simple, low-cost, precursor free and a single step synthetic technique has been used for synthesis of Bismuth titanate (BT) perovskite nanomaterials, under surfactant free conditions. The powdered X-ray diffraction method has been employed for confirmation of crystal structure and surface morphology of synthesized nanoparticles were confirmed by FESEM analysis. The nanoparticles showed the band gap of 3.25 eV, calculated with the help of Tauc plot by diffused reflectance spectroscopy (DRS-UV). The efficiency of nanoparticles to act as photocatalyst was assessed by hydrogen evolution reaction carried out by water splitting, utilizing a photochemical cell reactor having xenon lamp. The reaction was carried out in the presence of triethanolamine (TEOA) and methanol acting as scavengers. It was reported that maximum hydrogen yield 39.24 µmol/g was obtained with methanol.

Biodegradable magnesium fuel-based Janus micromotors with surfactant induced motion direction reversal

The speed and motion directionality of bubble-propelled micromotors is dependent on bubble lifetime, bubble formation frequency and bubble stabilization. Absence and presence of bubble stabilizing agents should significantly influence speed and propulsion pattern of a micromotor, especially for fast-diffusing molecules like hydrogen. This study demonstrates a fully biodegradable Janus structured micromotor, propelled by hydrogen bubbles generated by the chemical reaction between hydrochloric acid and magnesium. Six different concentrations of hydrochloric acid and five different concentrations of the surfactant Triton X-100 were tested, which also cover the critical micelle concentration at a pH corresponding to an empty stomach. The Janus micromotor reverses its propulsion direction depending on the availability and concentration of a surfactant. Upon surfactant-free condition, the Janus micromotor is propelled by bubble cavitation, causing the micromotor to be pulled at high speed for short time intervals into the direction of the imploding bubble and thus backwards. In case of available surfactant above the critical micelle concentration, the Janus micromotor is pushed forward by the generated bubbles, which emerge at high frequency and form a bubble trail. The finding of the propulsion direction reversal effect demonstrates the importance to investigate the motion properties of artificial micromotors in a variety of different environments prior to application, especially with surfactants, since biological media often contain large amounts of surface-active components.

Facet nanoarchitectonics of visible-light driven Ag3PO4 photocatalytic micromotors: Tuning motion for biofilm eradication

The customized design of micro-/nanomotors represents one of the main research topics in the field of micro-/nanomotors; however, the effects of different crystal facets on micromotor movement are often neglected. In this work, self-propelled amorphous, cubic, and tetrahedral Ag3PO4 particles were synthetized using a scalable precipitation method. Their programmable morphologies exhibited different motion properties under fuel-free and surfactant-free conditions and visible light irradiation. Differences in these motion properties were observed according to morphology and correlated with photocatalytic activity. Moreover, Ag3PO4 micromotors are inherently fluorescent, which allows fluorescence-based tracking. Furthermore, bacterial biofilms represent a major concern in modern society since most of them are antibiotic resistant. The as-prepared self-propelled particles exhibited morphologically dependent antibiofilm activities toward gram-positive and gram-negative bacteria. The enhanced diffusion of the particles promoted biofilm removal in comparison with static control experiments, realizing the possibility of a new class of light-driven biofilm-eradicating micromotors that do not require the use of both H2O2 and UV light.

Terbium doped zinc ortho titanate nanocomposite for optical application – A complementary theoretical calculations

Zinc ortho titanate nanomaterial was synthesized hydrothermally under surfactant free conditions. The crystalline nature of the synthesized nano composite has been affirmed by PXRD analysis. FTIR analysis reports the existence of Ti-O and Zn-O metal organic bonds at 495 and 558 cm-1 respectively. UV cut off wavelength was found to be 232 nm which is evident that the narrow transparent window was in the entire visible region. The structural morphology and elemental analyses have been confirmed by SEM and EDX respectively and as well characterized by photoluminescence, scanning electron microscopy and thermal analysis. The SEM image is further analyzed and compared with laser speckle image processing. Thermal analysis evidenced the stability of the nano composite up to 990 °C which suitable to thermal devices. To reinforce the experimental findings, theoretical calculations were carried out using DFT functional B3LYP/cc-pvtz level of basis set through Gaussian 09 program.

Cationic Polymerization of Hexamethylcyclotrisiloxane in Excess Water.

Ring-opening ionic polymerization of cyclosiloxanes in dispersed media has long been discovered, and is nowadays both fundamentally studied and practically used. In this short communication, we show some preliminary results on the cationic ring-opening polymerization of hexamethylcyclotrisiloxane (D3), a crystalline strained cycle, in water. Depending on the catalyst or/and surfactants used, polymers of various molar masses are prepared in a straightforward way. Emphasis is given here on experiments conducted with tris(pentafluorophenyl)borane (BCF), where high-molar polymers were generated at room temperature. In surfactant-free conditions, µm-sized droplets are stabilized by silanol end-groups of thus generated amphiphilic polymers, the latter of which precipitate in the course of reaction through chain extension. Introducing various surfactants in the recipe allows generating smaller emulsions in size with close polymerization ability, but better final colloidal stability, at the expense of low small cycles’ content. A tentative mechanism is finally proposed.

Thermal performance analysis of a low volume fraction Al2O3 and deionized water nanofluid on solar parabolic trough collector

The present work analyzes the performance of unshielded receiver tube integrated solar parabolic trough collector where Al2O3/deionized (DI) water nanofluid of low concentrations was used as heat transfer fluid (HTF) element. Nanofluid is synthesized at various volume fractions starting from 0.2 to 1.0% with surfactant-free condition, by ultrasonic technique. Several researchers investigated the performance of higher nanofluid concentrations (1.0–5.0%) with and without surfactants on parabolic trough solar collector. The outdoor experiments are conducted for two HTF flow rates of 0.010 kg s−1 and 0.015 kg s−1. When the nanofluid is subjected as HTF, the DI water acted as a base fluid. While DI water is allowed to flow through the absorber, it performs both as HTF and heat storage fluid. The synthesized nanofluid at various volume fractions is allowed to flow through the receiver for the purpose of analyzing the thermal performance and compare the results with DI water. The collector efficiency increases with the mass flow rate as well as the concentration of nanofluid. For 0.015 kg s−1, the maximum efficiency was calculated as 59.13% (hourly) and 58.68% (average).

Synthesis and potent antimicrobial activity of CoFe2O4 nanoparticles under visible light

The nanoparticles of Cobalt ferrite are synthesized using polyethylene glycol as a solvent by the solvothermal method in a surfactant-free condition. Nanoparticles that were synthesized were determined by using various techniques such as Diffuse Reflection Spectroscopy (DRS), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive X-ray spectroscopy (EDAX). The Scanning electron microscope confirmed the range of spherical nanoparticles in the size of 20–33 nm.An excellent match was observed between the calculated particles size in the X-ray diffraction and electron microscopes results. Furthermore, their antimicrobial efficacy was determined by MIC, MBC, IC50 and disc diffusion method on Gram-negative (Pseudomonas aeruginosa and Escherichia coli) and Gram-positive (Staphylococcus aureus, Bacillus cereus) bacteria. The results indicated an acceptable bacteriostatic and bactericidal effects of this nanoparticles. Additionally, it was seen that by the increase in the concentration of nanoparticles, their antimicrobial property would increase. Background and objectiveIn recent years, antibacterial materials have found a special place to avoid the overuse of antibiotics. In this study, the antibacterial effects of CoFe2O4 nanoparticles on Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Bacillus cereus, were investigated due to their importance as human pathogens in nosocomial infection. MethodologyIn this study, the antibacterial effects of CoFe2O4 nanoparticles such as MIC, MBC, IC50, and disc diffusion method were examined. FindingsAccording to the results, CoFe2O4 nanoparticles exhibited potent antibacterial activity against the bacteria that were examined, especially Bacillus cereus. The MBC (Minimum Bactericidal Concentration) of CoFe2O4 nanoparticle on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus was between 0.12-0.48 mg/ml and MIC (Minimum Inhibition Concentration) on these bacteria detected between 0.06-0.24 mg/ml. The least IC50 determined for Bacillus cereus with a concentration of 0.061 mg/ml. Pseudomonas aeruginosa and Bacillus cereus identified as the most resistant and sensitive bacteria in the disc diffusion method, respectively.

Zinc titanate nanomaterials—photocatalytic studies and sensitization of hydantoin derivatized porphyrin dye

ZnTiO3 cubic nanomaterials were synthesized hydrothermally under surfactant free conditions, in presence of the inexpensive material urea. Calcination at 6000C yields highly crystalline hexagonal stoichiometric ZnTiO3 phase (as confirmed from powder X-ray diffraction, X-ray photoelectron spectra and Raman studies). This is in contrast to earlier reports, which said that ZnTiO3 can be synthesized at much higher temperature i.e. 9450C. Distinct signatures of Zn-O and Ti-O vibrations were manifested in the IR spectra with concomitant decrease in intensity of -NH and -CO stretching frequencies of urea. Thus urea plays a critical role in formation and stabilization of the ZnTiO3phase. The ZnTiO3 nanomaterials showed much superior photo catalytic efficiency than TiO2 nanomaterials due to enhanced electron–hole separation in the former because electrons can easily get transferred from the conduction band (CB) of Ti to CB of Zn. Surface studies indicate larger pore volume and pore diameter of the ZnTiO3 nanomaterials. The ZnTiO3 nanomaterials also get effectively sensitized by a porphyrin dye (PHy) synthesized with hydantoin anchoring groups. Electron injection rate from PHy to ZnTiO3 is much higher than from PHy to TiO2 implying the prospect of using the titanate nanomaterials as photoanode materials in dye sensitized solar cells (DSCs).

Self-assembled micro-stripe patterning of sessile polymeric nanofluid droplets

When sessile nanofluid droplets evaporate, solid nanoparticles can be organized in a wide variety of patterns on the substrate. The composition of the nanofluid, internal flow type of droplet and the rate of drying affect drop geometry, and the final pattern. Using poly(lactic-co-glycolic acid)-block-poly(ethylene glycol)(PLGA-b-PEG) as the example, we produced micro-stripe patterning from nanoparticles by drying of sessile fluid droplets. We investigated the nanoparticle properties and flow dynamics to clarify their effects on the patterning. Nanoparticles were prepared by hydrodynamic flow focusing using a T-junction microfluidic device with high production efficiency and the ability to generate an extremely narrow size distribution. PLGA-b-PEG was prepared as oil phase in acetonitrile and water/oil flow rate was changed from 1 to 3 at constant oil phase flow rate (50 μL/min). Then, nanofluid was collected on the surface as sessile droplets within acetonitrile/water binary dispersed phase. Depending on size, charge and size-distribution, the nanoparticles deposited on the surface exhibited various patterns. Dynamic Light and X-ray Scattering measurements showed that, approximately 100 nm particles with relatively low PDI (0.04) were produced for the first time in surfactant free conditions in a microfluidic device and they generated self-assembled ordered patterns, which are regulated by the type of internal flow in the sessile nanofluid droplet during sequential evaporation of acetonitrile and water.

Interfacial Activity of Gold Nanoparticles Coated with a Polymeric Patchy Shell and the Role of Spreading Agents.

Gold patchy nanoparticles (PPs) were prepared under surfactant-free conditions by functionalization with a binary ligand mixture of polystyrene and poly(ethylene glycol) (PEG) as hydrophobic and hydrophilic ligands, respectively. The interfacial activity of PPs was compared to that of homogeneous hydrophilic nanoparticles (HPs), fully functionalized with PEG, by means of pendant drop tensiometry at water/air and water/decane interfaces. We compared interfacial activities in three different spreading agents: water, water/chloroform, and pure chloroform. We found that the interfacial activity of PPs was close to zero (∼2 mN/m) when the spreading agent was water and increased to ∼14 mN/m when the spreading agent was water/chloroform. When the nanoparticles were deposited with pure chloroform, the interfacial activity reached up to 60 mN/m by compression. In all cases, PPs exhibited higher interfacial activity than HPs, which were not interfacially active, regardless of the spreading agent. The interfacial activity at the water/decane interface was found to be significantly lower than that at the water/air interface because PPs aggregate in decane. Interfacial dilatational rheology showed that PPs form a stronger elastic shell at the pendant drop interface, compared to HPs. The significantly high interfacial activity obtained with PPs in this study highlights the importance of the polymeric patchy shell and the spreading agent.

Synthesis and Characterization of Superparamagnetic NiBaO2 Nano-Oxide Using Novel Precursor Complex [Ba(H2O)8][Ni(dipic)2

In this paper, for the first time, synthesis of [Ba(H2O)8][Ni(dipic)2] complex and preparation of NiBaO2 nano-oxide are reported through thermal decomposition under surfactant free condition. This novel complex was characterized by Fourier transform infrared spectroscopy (FT-IR), ultra violet–visible spectroscopy, conductivity measurement and elemental analysis. Formation of novel nanoparticles was supported by FT-IR and energy-dispersive X-ray spectroscopy and the orthorhombic structure of nanocrystals was confirmed by powder X-ray diffraction analysis. In addition, size distribution as well as uniform morphology of prepared nano-oxide were recorded by dynamic light scattering analysis and field-emission scanning electron microscopy, respectively. Magnetic features measured by vibrating sample magnetometer, illustrate superparamagnetic behavior of the oxide.

Green synthesis of copper nanoparticles using Ginkgo biloba L. leaf extract and their catalytic activity for the Huisgen [3 + 2] cycloaddition of azides and alkynes at room temperature

During this study, we report the green synthesis of copper nanoparticles (Cu NPs) using Ginkgo biloba L. leaf extract as a reducing and stabilizing agent under surfactant-free conditions. The formation of Cu NPs is monitored by recording the UV–vis absorption spectra. The green synthesized Cu NPs are characterized by TEM, EDS, FT-IR and UV–visible techniques. According to UV–vis results, the synthesized Cu NPs by this method are quite stable even after one month indicating the stability of Cu NPs. In terms of environmental impact and economy, metallic Cu NPs offer several advantages over homogeneous and traditional heterogeneous catalysts. In addition, due to the increased metal surface area, Cu NPs shows very high catalytic activity for the Huisgen [3+2] cycloaddition of azides and alkynes at room temperature. Furthermore, the catalyst can be simply recovered and reused several times with almost no loss in activity.

Self‐emulsion polymerization of baylis–hillman‐derived α‐hydroxymethyl‐substituted acrylates

Amphiphilic alkyl α-hydroxymethyl acrylates can be polymerized via self-emulsion polymerization (i.e., without surfactants) under conventional radical and reversible addition-fragmentation chain transfer polymerization conditions. The α-hydroxymethyl acrylates can be copolymerized at very low percentages (∼5%) with conventional monomers such as butyl acrylate under surfactant free conditions. The hydroxyl group of the α-hydroxymethyl acrylates in the resultant latex could potentially be used for further functionalization or for modulation of surface properties.

Size- and charge-controllable polystyrene spheres for templates in the preparation of porous silica particles with tunable internal hole configurations

Abstract Studies on the synthesis of polystyrene spheres have steadily increased in number. However, information regarding control of the physicochemical properties (i.e., size and charge) of polystyrene and its application as a template for the structure of materials remains limited. The purpose of our study was to synthesize surfactant-free polystyrene spheres with a controllable size (from 80 to 350 nm) and charge (from −50 to +40 mV) using a single-step and facile process, and to demonstrate their applications as templates for facilitating the production of porous particles with a tunable internal hole structure. Different from other polystyrene synthesis methods, the present synthesis procedure was conducted under surfactant-free conditions. To control polystyrene size and charge, several reaction parameters (i.e., temperature, styrene amount, and initiator concentration and type (cationic and anionic)) were investigated. To investigate the effectiveness of our synthesized polystyrene as a structure template, the synthesized polystyrene spheres were mixed with a host material and used in a spray method. As models of a host material, 15-nm silica nanoparticles and tetramethyl orthosilicate were used. These raw materials were selected because information about the exploitation of these materials remains limited. The results of the spray method showed that flexibility in the control of the size and surface charge of the polystyrene template made it possible to assist in the creation of particles with different hole configurations, including porous and hollow particles with control over the hole cavity, the internal structure, and the external shape. In addition, a theoretical explanation and a design for the mechanism of a hole-structured formation were also added, which would be important for the scaling-up prediction and estimation.

Controlled charged amino acids of Ti-binding peptide for surfactant-free selective adsorption

The adsorption mechanism of titanium-binding peptide (TBP) on metal oxide substrates was investigated by evaluating the adsorption behavior of ferritins with various alanine-substituted TBPs. Results revealed that (a) a positively charged amino acid, lysine (K) or arginine (R), in TBP can anchor ferritin to negative zeta-potential substrates, (b) the adsorption force of K is stronger than R, and (c) local electrostatic interactions and flexibility of TBP directly affect adsorption. Based on these findings, selective ferritin adsorption on SiO2 with TiOX patterned surfaces in a surfactant-free condition was demonstrated. Alanine-substituted TBP with one positively charged amino acid (K) and one negatively charged amino acid (D), achieved ferritin-selective adsorption without a surfactant. The importance of controlled electrostatic forces between TBP and a substrate for selective adsorption without a surfactant was clearly demonstrated.

Tandem acoustic emulsion, an effective tool for the electrosynthesis of highly transparent and conductive polymer films

In this paper, we reported a new technique for the preparation of a highly clear and transparent emulsified aqueous solution containing immiscible monomer (3,4-ethylenedioxythiophene, EDOT) droplets with diameters of a few tens of nanometers under surfactant-free conditions using tandem acoustic emulsification. The nanoemulsion prepared by this method was highly stable, even in the absence of surfactants. Furthermore, we demonstrated that the electropolymerization from the clear and transparent emulsified solutions containing EDOT nanodroplets enabled the formation of highly conductive transparent polymer (PEDOT) films. Appropriate sonication time length for each step and stability of the emulsions during the sonication steps were also systematically investigated in the tandem operation.

Direct synthesis of 8-aryl tetrahydroquinolines via pd-catalyzed ortho-arylation of arylureas in water

An efficient protocol for the direct synthesis of 8-arylated tetrahydroquinolines via Pd-catalyzed ortho-arylation of aryl ureas with aryl iodides was developed. The reaction proceeded smoothly in water under ligand-free and surfactant-free conditions, providing the desired products in high yields with remarkable functional group tolerance.

Preparation of a Highly Clear and Transparent Nanoemulsion under Surfactant-Free Conditions Using Tandem Acoustic Emulsification and Its Application to Electropolymerization

not Available.

Preparation and characterization of core‐shell nanoparticles containing poly(chlorotrifluoroethylene‐co‐ethylvinylether) as core

AbstractCore shell latex particles with a glassy core and a low Tg polymeric shell are usually preferred. More so, the glassy core happens to be a fluoropolymer with a shell polymer that helps in processability. We describe here the preparation and characterization of core shell nanoparticles consisting of poly(chlorotrifluoroethylene‐co‐ethylvinylether) as core encapsulated in poly(styrene‐acrylate) copolymer shell using seeded emulsion polymerization method under kinetically controlled monomer starved conditions. Properties of the emulsion using surfactants (fluoro/conventional) and surfactant free conditions were investigated. Average size (100 nm), spherical shape and core–shell morphology of the latex particles was confirmed by dynamic light scattering and transmission electron microscopy. Absence of CF and CCl peaks in X‐ray photoelectron spectroscopy proves that cores are completely covered. Polymerization in the presence of fluorocarbon surfactant was found to give optimum features like narrow size distribution, good shell deposition and no traces of agglomeration. Films of core shell latex particles exhibited improved transparency and enhanced water contact angles thus making them suitable for applications in various fields including coatings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Precision AFM Measurements of Dynamic Interactions between Deformable Drops in Aqueous Surfactant and Surfactant-Free Solutions

The atomic force microscope (AFM) has provided unprecedented opportunities to study velocity-dependent interactions between deformable drops and bubbles under a range of solution conditions. The challenge is to design an experimental system that enables accurate force spectroscopy of the interaction between deformable drops and thus the extraction of accurate quantitative information about the physically important force-separation relation. This step requires very precise control and knowledge of the interfacial properties of the interacting drops, the drive conditions of the force-sensing cantilever, the disposition of the interacting drops on the substrate and on the cantilever, and transducer calibrations of the instrument in order to quantify the effects of approach velocities and interfacial deformation. This article examines and quantifies in detail all experimental conditions that are necessary to facilitate accurate processing of dynamic force spectroscopy data from the AFM using the well-defined system of tetradecane drops in aqueous solutions under surfactant and surfactant-free conditions over a range of force magnitudes that has not been attained before. The ability of drops to deform and increase the effective area of interaction instead of decreasing the distance of closest approach when disjoining pressure exceeds the Laplace pressure means that the DLVO paradigm of colloidal stability as being determined by a balance of kinetic energy against the height of the primary maximum is no longer valid. The range of interfacially active species present in alkane-aqueous systems investigated provides insight into the applicability of the tangentially immobile boundary condition in colloidal interactions.