Absence Of Surfactant Research Articles

Direct photodissociation of toluene molecules to photoluminescent carbon dots under pulsed laser irradiation

Herein, we report a facile method of direct photodissociation of toluene molecules to photoluminescent carbon dots (CDs) under pulsed laser irradiation in the absence of surfactants or catalysts. The as-synthesized CDs with diameters 1.3–4.0 nm present regular emission peaks and the crystallographic structure of these species has been identified as graphite 2H from the analysis of high resolution transmission electron microscope (HRTEM) images, X-ray photoelectron spectroscopy (XPS) and Raman spectrum. In addition, First-Principle calculations were performed to discuss the photon-induced excitation in the photodissociation process. The results demonstrate that electrons can be transited from Highest Occupied Molecular Orbital (HOMO) to Lowest Unoccupied Molecular Orbital (LUMO) in toluene molecule by 248 nm single photon excitation process and the Stark effect plays a crucial role in the photodissociation process. These CDs exhibit excellent stable emission due to the stability of crystal structure, which could be considered for promising luminescent applications.

Core–shell Fructus Broussonetia-like Au@Ag@Pt nanoparticles as highly efficient peroxidase mimetics for supersensitive resonance-enhanced Raman sensing

Synthesis of core–shell Fructus Broussonetia-like Au@Ag@Pt nanoparticles via galvanic replacement and reagent reduction.

Study of two impinging flow microsystems arranged in series. Application to emulsified biofuel production

Development of alternative fuels and improvement of their combustion is a necessity in a general context of scarcity of fossil energy resources and of environmental pollution. In particular, the use of water dispersed in biofuels is known to improve combustion quality of diesel engine and to reduce pollution in gas emissions. This work aims at contributing in the development of a compact continuous emulsifier that could be used to feed energy systems. In order to fulfil requests such as convenient size of water droplets, absence of surfactant and needed flow rates of biofuel, the association of two micro-systems in series is investigated and compared to the use of a single one. The comparison of the emulsions obtained by the different systems is made in terms of mean size and size distribution of the water droplets in the dispersion, and process energy consumption. In the absence of surfactant, depending on applied flow-rates and water fraction, the use of two micro-systems in series allows to reduce the mean size of droplets by a factor 2 to about 3. Flow phenomena which lead to water phase fragmentation are described thanks to high-speed visualization of the flows in the micro-channels.

Ultrafast synthesis of flower-like ordered Pd3Pb nanocrystals with superior electrocatalytic activities towards oxidation of formic acid and ethanol

Ordered intermetallic nanocrystals with high surface area are highly promising as efficient catalysts for fuel cell applications because of their unique electrocatalytic properties. The present work discusses about the controlled synthesis of ordered intermetallic Pd3Pb nanocrystals in different morphologies at relatively low temperature for the first time by polyol and hydrothermal methods both in presence and absence of surfactant. Here for the first time we report surfactant free synthesis of ordered flower-like intermetallic Pd3Pb nanocrystals in 10 s. The structural characteristics of the nanocrystals are confirmed by powder X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The as synthesized ordered Pd3Pb nanocrystals exhibit far superior electrocatalytic activity and durability towards formic acid and ethanol oxidation over commercially available Pd black (Pd/C). The morphological variation of nanocrystals plays a crucial role in the electrocatalytic oxidation of formic acid and ethanol. Among the catalysts, the flower-like Pd3Pb shows enhanced activity and stability in electrocatalytic formic acid and ethanol oxidation. The current density and mass activity of flower-like Pd3Pb catalyst are higher by 2.5 and 2.4 times than that of Pd/C for the formic acid oxidation and 1.5 times each for ethanol oxidation.

Ordered Pd2Ge Intermetallic Nanoparticles as Highly Efficient and Robust Catalyst for Ethanol Oxidation

Pd2Ge nanoparticles were synthesized by superhydride reduction of K2PdCl4 and GeCl4. The syntheses were performed using a solvothermal method in the absence of surfactants, and the size of the nanoparticles was controlled by varying the reaction time. The powder X-ray diffraction (PXRD) and transmission electron microscopy data suggest that Pd2Ge nanoparticles were formed as an ordered intermetallic phase. In the crystal structure, Pd and Ge atoms occupy two different crystallographic positions with a vacancy in one of the Ge sites, which was proved by PXRD and energy-dispersive X-ray analysis. The catalyst is highly efficient for the electrochemical oxidation of ethanol and is stable up to the 250th cycle in alkaline medium. The electrochemical active surface area and current density values obtained, 1.41 cm2 and 4.1 mA cm–2, respectively, are superior to those of the commercial Pd on carbon. The experimentally observed data were interpreted in terms of the combined effect of adsorption energies of CH3CO and OH radical, d-band center model, and work function of the corresponding catalyst surfaces.

Titania-Silica Materials for Enhanced Photocatalysis.

Mesoporous titania-organosilica nanoparticles comprised of anatase nanocrystals crosslinked with organosilica moieties have been prepared by direct co-condensation of a titania precursor, tetrabuthylortotitanate (TBOT), with two organosilica precursors, 1,4-bis(triethoxysilyl) benzene (BTEB) and 1,2-bis(triethoxysilyl) ethane (BTEE), in mild conditions and in the absence of surfactant. These hybrid materials show both high surface areas (200-360 m(2) g(-1) ) and pore volumes (0.3 cm(3) g(-1) ) even after calcination, and excellent photoactivity in the degradation of rhodamine 6G and in the partial oxidation of propene under UV irradiation, especially after the calcination of the samples. During calcination, there is a change in the Ti(IV) coordination and an increase in the content of SiOTi moieties in comparison with the uncalcined materials, which seems to be responsible for the enhanced photocatalytic activity of hybrid titania-silica materials as compared to both uncalcined samples and the control TiO2 .

Facile synthesis, characterization and magnetic property of CuFe12O19 nanostructures via a sol–gel auto-combustion process

Copper hexaferrite (CuFe12O19) nanostructures were prepared by a simple route utilizing maltose-assisted sol–gel process. The morphology, phase structure, composition and purity of nanostructures can be controlled by type of surfactant and also adjusting the Cu:surfactant, Cu:Fe and Cu:reductant ratios. The bean-shape structures are formed in the absence of the surfactant when the molar ratio of Cu:Fe and Cu:reductant are 1:12 and 1:26, respectively. The agglomerated spherical nanoparticles with diameters ranging from 7 to 20nm are obtained in the presence of triplex, when ratio of Cu:reductant is 1:26. In the absence of surfactant and also in the presence of triplex, the samples are found to be CuFe12O19. When polymer is used, there are still the peaks of CuFe12O19 and also some boad peaks in XRD patterns, because of the small size and encapsulation of nanostructures with polymer. Magnetic measurments show superparamagnetic behavior for the all samples. The Ms for the samples obtained in the presence of polymer shows that the coating of magnetic nanostructures does not always increase Ms. FT-IR frequency bands in the range 463–626, 607 and 542cm−1 correspond to the formation of metal oxides in ferrites.

A Convenient Surfactant‐Mediated Hydrothermal Approach to Control Supported Copper Oxide Species for Catalytic Upgrading of Glucose to Lactic Acid

AbstractHerein, we discuss a convenient surfactant‐mediated hydrothermal approach to control supported copper oxide species in a highly reproducible way and investigate their effect on the catalytic upgrading of glucose to lactic acid. Careful characterization using XRD, Raman spectroscopy, and temperature programmed reduction (TPR) studies revealed paramelaconite (Cu4O3) loaded on MgO as the catalytically active species. It was also found that the cuprite (Cu2O) phase can be prepared in the presence of N,N‐dimethyldodecylamine N‐oxide (DDAO) while the tenorite (CuO) phase was obtained in the absence of surfactant. The use of cetyltrimethylammonium bromide (CTAB) selectively gave the Cu4O3 phase as the supported species. The above‐mentioned systematic approach demonstrates that substantial improvement in the catalytic activity (or other properties) can be achieved by careful selection of the synthetic conditions for generation of desired Cu species through a simple and inexpensive preparation route.

Effect of peroxide depolymerization of chitosan on properties of chitosan sulfate particles produced from this substance

Effect of the oxidative destruction of chitosan on the rate at which a dispersed phase is formed in its dilute solutions in the presence of sulfate ions and on the composition, size and ζ-potential of submicrometer chitosan sulfate particles being formed was studied. It was found that the particle size steadily decreases as the molecular mass of chitosan becomes smaller, and the sedimentation stability of aqueous dispersions increases in the absence of surfactants. The \(\nu _{SO_4 } :\nu _{NH_2 }\) molar ratio in chitosan sulfate particles is independent of the molecular mass of chitosan and varies within the range 0.45–0.46. A pH-dependence of the sign of the ζ-potential with isoelectric point at pH 5.0 was found for particles based on destructed chitosan.

CO2 mobility control using CO2 philic surfactant for enhanced oil recovery

CO2 enhanced oil recovery by using newly synthesized CO2 philic surfactant as CO2 mobility control agent is reported. Nonyl phenol ethoxylate sulphonate (NPES) was prepared by the esterification of alcohol with maleic anhydride followed by its sulphonation. Effect of interfacial tension (IFT) between CO2 and brine using NPES was investigated to verify the CO2 philicity of the surfactant. The detailed account of effects of pressure and temperature on IFT between CO2/brine in the presence and absence of surfactant on specified pressure and temperature conditions is studied and discussed. NPES effectively lowered the IFT between CO2/brine (30 mN/m) to less than 5.23 mN/m. Foam quantity was improved by using betaine as foam booster. The static foam endurance properties in the presence and absence of oil were also examined prior to the actual performance test of surfactants using a reservoir core plug sample. It was noted that the foam stability was 900 s in the presence of oil at 90 °C in CO2 environment. The effect of foam by using synthesized NPES on mobility of CO2 is also presented. The CO2 mobility reduction factor was found to be 3.1. It is concluded that NPES has great potential for CO2-EOR applications.

The role of functional monomers on producing nanostructured lattices obtained by surfactant-free emulsion polymerization – A novel approach

Nanostructured lattices were prepared in a single step emulsion polymerization reaction in the absence of surfactants by exploring the so called “pickering” stabilization mechanism. The synthesis protocol and the properties of the obtained particles were evaluated and discussed simultaneously considering processing and formulation aspects with special emphasis to the chemical properties of the functional monomers selected on the present study. Colloidal silica was used to ensure the physical stability required to produce nanoparticles as a result of the emulsion polymerization route. Three different monomers including methyl metacrylate (MMA), styrene (Sty) and vinyl acetate (VAC) were used to structure the particles of interest. Four different functional polymers including acrylic acid (AA), styrene sulfonate (StySO3), hydroxyethyl methacrylate (HEMA) and dymethylamino ethyl methacrylate (DMAEMA) were evaluated.The obtained lattices were comparatively characterized regarding to surface tension, particle size distribution, morphological aspects, viscosity, zeta potential and colloidal stability.The one-step pickering emulsion polymerization proved to be an effective approach to prepare lattices of industrial interest without the use of surfactants. The obtained particles presented average mean diameters ranging from 155 to 345nm with relatively low polydispersity indices (0.39–2.02). The most promising behavior was experimentally verified once selecting the styrene sulfonate (StySO3) as the functional monomer. The hydroxyethyl methacrylate (HEMA) also proved to be an interesting alternative although its limitation related to high surface tension applications. The high resolution images registered with the HRSEM-FEG technique explicit morphological aspects that effectively contribute to elucidate the “pickering” stabilization mechanism and the resultant core–shell structure derived thereof.

Stability of a bi-layer free film: simultaneous or individual rupture events?

We consider the stability of a long free film of liquid composed of two immiscible layers of differing viscosities, where each layer experiences a van der Waals force between its interfaces. We analyse the different ways in which the system can exhibit interfacial instability when the liquid layers are sufficiently thin. For an excess of surfactant on one gas–liquid interface, the coupling between the layers is relatively weak and the instability is manifested as temporally separated rupture events in each layer. Conversely, in the absence of surfactant, the coupling between the layers is much stronger and the instability is manifested as rupture of both layers simultaneously. These features are consistent with recent experimental observations.

The effect of polyoxyethylene (40) stearate surfactant on novel synthesis of mesoporous γ-alumina from Kano kaolin

Mesoporous γ-alumina was synthesized by acid extraction of alumina from Kano kaolin using polyoxyethylene (40) stearate (PS) as a surfactant. The synthesized alumina was characterized using X-ray diffraction (XRD), N2 adsorption–desorption, Fourier transform infra-red spectroscopy (FTIR), field emission scanning electron microscopy attached with energy-dispersive X-ray (FESEM–EDX), and thermogravimetric analysis (TG–DTA). High-purity mesoporous γ-Al2O3 with relatively large surface area and narrow pore size distribution was obtained. For comparison the preparation in the absence of surfactant was also carried out. In this study mesoporous alumina was also obtained even in the absence of the surfactant, however, the addition of PS resulted in modification on physical properties and morphology. The surface area increased from 169.0m2/g to 222.7m2/g, pore size from 4.4nm to 5.6nm and pore volume from 0.32cm3/g to 0.45cm3/g. Crystallite size was also found to increase from 2.68nm to 3.33nm after the addition of the surfactant.

Role of surfactants on metal mediated cerium(IV) oxidation of valeraldehyde at room temperature and pressure

The short chain straight fatty acid, valeric or pentanoic acid is chemically significant for its huge applications in variety of industrial target compounds including plasticizers, lubricants, biodegradable solvents, perfumery and pharmaceuticals. Synthesis of valeric acid has been achieved by the cerium(IV) oxidation of a straight C5 chain valeraldehyde which is a precursor of organic compounds. Ce(IV) is selected as an alternative oxidizing agent in place of higher valent metals. The oxidation kinetics of valeraldehyde has been investigated under pseudo-first-order conditions in acidic medium at 30°C. Several transition metal salts: Cr(III), Mn(II), Cu(II), Ir(III) and Ru(III) have been introduced to observe their effect on reaction rate6. Three different representative non-functional surfactants: Cetyltrimethylammonium bromide (CTAB; cationic), Sodium dodecylsulphate (SDS; anionic) and 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS; zwitterionic) catalyze the reaction significantly. Ir(III) and Ru(III) enhance the oxidation rate in the presence and absence of surfactant. Cr(III), Mn(II) and Cu(II) interestingly inhibit the reaction rate. CMC values of the surfactants have been determined by spectrofluorometry and conductometry. The oxidized product valeric acid has been characterized by NMR and FTIR spectroscopy. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) experiments support the aggregation of surfactants Ru(III) in association with CTAB micellar catalyst that exhibited a dramatic ~330 fold rate enhancement compared to the uncatalyzed reaction path.

Sol–gel synthesis of vanadium doped titania: Effect of the synthetic routes and investigation of their photocatalytic properties in the presence of natural sunlight

The development of visible-light effective TiO2 photocatalysts allows low cost degradation of toxic non-biodegradable organic pollutants. In the present study a series of vanadium doped titania (V-TiO2) photocatalysts with V-to-Ti of 0.03, 0.06 and 0.1 were synthesized by either one-step or two-step modified sol–gel approaches. Titanium oxychloride solution was used as a titania source while vanadium pentaoxide was used as a vanadia source to form V-TiO2 in the absence of surfactants. One-step process was performed through the reaction of the TiO2 source with vanadium source. In two-step route the Ti(OH)4 gel was preformed through gelation of the TiO2 source using ammonium solution and then peptized in the acidic vanadium solution. The physicochemical properties of the samples were examined by XRF, XRD, UV–visible DRS, SEM-EDAX, TEM, DTA-TGA, XPS and nitrogen gas physisorption studies analyses. It was observed that the morphology, crystal structure and photochemical properties of the obtained samples were largely dependent on the calcination temperature, synthetic approach and V-to-Ti ratios. Calcination of the samples yielded large ultrafine and perhaps monodispersed particles with different sizes depending on the synthetic technique. The photocatalytic performance of the samples was tested in the photodegradation of methylene blue in the presence of natural sunlight. The photocatalytic activities of the samples synthesized by two-step route were higher than that of the samples yielded through one-step approach. Thus, the present report suggest systematic, convenient and cost-effective sol–gel techniques to yield V-TiO2 photocatalysts with harnessed photocatalytic performance for decolorization of toxic organic pollutants in the presence of natural solar irradiation.

Dual Cross-Linked Carboxymethyl Sago Pulp-Gelatine Complex Coacervates for Sustained Drug Delivery

In the present work, we report for the first time the complex coacervation of carboxymethyl sago pulp (CMSP) with gelatine for sustained drug delivery. Toluene saturated with glutaraldehyde and aqueous aluminum chloride was employed as cross-linkers. Measurements of zeta potential confirm neutralization of two oppositely charged colloids due to complexation, which was further supported by infrared spectroscopy. The coacervates encapsulated a model drug ibuprofen and formed microcapsules with a loading of 29%–56% w/w and an entrapment efficiency of 85%–93% w/w. Fresh coacervates loaded with drug had an average diameter of 10.8 ± 1.93 µm (n = 3 ± s.d.). The coacervates could encapsulate only the micronized form of ibuprofen in the absence of surfactant. Analysis through an optical microscope evidenced the encapsulation of the drug in wet spherical coacervates. Scanning electron microscopy revealed the non-spherical geometry and surface roughness of dried drug-loaded microcapsules. X-ray diffraction, differential scanning calorimetry and thermal analysis confirmed intact and crystalline ibuprofen in the coacervates. Gas chromatography indicated the absence of residual glutaraldehyde in the microcapsules. Dual cross-linked microcapsules exhibited a slower release than mono-cross-linked microcapsules and could sustain the drug release over the period of 6 h following Fickian diffusion.

The Effect of Surfactants on the Stability of Sodium Hypochlorite Preparations

IntroductionThe purpose of the present study was to assess the effect of the presence of surfactants over time on free available chlorine (FAC), pH, viscosity, and surface tension of sodium hypochlorite (NaOCl) preparations. MethodsThree preparations containing surfactant (Chlor-XTRA 6% [Vista Dental Products, Racine, WI], Hypocelle 4% Forte [Dentalife, Ringwood, Australia], and White King Lemon [Pental, Shepparton, Australia]) and 2 without, Vista 6% (Vista Dental Products) and Hypocelle 4% Forte plain (Dentalife), were tested. The solutions were stored in closed plastic bottles and protected from light at a constant 20°C for 213 days. FAC was measured using iodometric titration, whereas pH, surface tension, and viscosity were measured using a pH meter, pendant drop method, and rheometer, respectively. The influence of the type of solution and the presence of surfactant over time on FAC was compared with the aid of linear regression models. Two-way analysis of variance was used to evaluate the effect of passage of time and the type of solution on surface tension and the effect of the presence or absence of surfactant on the solutions. The Bonferroni test was used for multiple comparisons (post hoc) and to evaluate the effect of the presence of surfactant between solutions from the same manufacturer (α = 0.05). ResultsDegradation of available chlorine was faster in the presence of surfactant when comparing solutions from the same manufacturer [Chlor-XTRA versus Vista (P < .001) and for Hypocelle 4% Forte versus Hypocelle 4% Forte plain (P = .024)]. There was a gradual decline in pH over time, but viscosity remained stable. The surface tension of all products decreased over time (P = .025, F). ConclusionsThe presence of surfactant hastened the degradation of FAC in all affected NaOCl solutions. The observed changes in pH and viscosity were minor, whereas their surface tension showed a significant decrease.

Influence of surfactants on unsaturated water flow and solute transport

AbstractSurfactants can reduce soil water retention by changing the surface tension of water and the contact angle between the liquid and solid phases. As a result, water flow and solute transport in unsaturated soil may be altered in the presence of surfactants. In this study, the effects of a representative nonionic surfactant, Triton X‐100, on coupled water flow and nonreactive solute transport during unsaturated flow conditions were evaluated. Batch reactor experiments were conducted to measure the surfactant sorption characteristics, while unsaturated transport experiments were performed in columns packed with 40–270 mesh Ottawa sand at five initial water contents. Following the introduction of surfactant solution, the rate of water percolation through the sand increased; however, this period of rapid water drainage was followed by decreased water percolation due to the reduction in soil water content and the corresponding decrease in unsaturated hydraulic conductivity behind the surfactant front. The observed changes in water percolation occurred sequentially, and resulted in faster nonreactive solute transport than was observed in the absence of surfactant. A one‐dimensional mathematical model accurately described coupled water flow, surfactant, and solute transport under most experimental conditions. Differences between model predictions and experimental data were observed in the column study performed at the lowest water content (0.115 cm3/cm3), which was attributed to surfactant adsorption at the air‐water interface. These findings demonstrate the potential influence of surfactants additives on unsaturated water flow and solute transport in soils, and demonstrate a methodology to couple these processes in a predictive modeling tool.

Study of surfactant-free lead sulfide nanocrystals-P3HT hybrid polymer solar cells

Surfactant free nanocrystals (NCs) of lead sulfide (PbS) prepared using Continuous Spray Pyrolysis (CoSP) technique had been dispersed in poly (3-hexylthiophene) (P3HT) and used in hybrid polymer solar cells (HSCs) to study the role of surfactant free NCs in these devices. Absence of surfactant on PbS NCs improves the polymer–NCs interface and is responsible for an efficient electronic interaction between the two materials. FTIR results show a shift in the characteristics band for the blends confirming the proper bonding between the polymer and NCs. Hybrid polymer solar cells with configuration ITO/PEDOT:PSS/P3HT:PbS/Al have been fabricated with different PbS loading. With the increase in PbS NC content, the device efficiency increases first and then decreases, the device having 30wt% of PbS NCs shows the best performance with an energy conversion efficiency of 1.6%, an open circuit voltage of 0.42V, a short-circuit current density of 9.90mA/cm2, and a fill factor of 0.40 under Air Mass 1.5G illumination with the irradiation of 100mW/cm2. Structural and morphological investigations show that better performance is achieved with the optimum amount of PbS NCs due to good distribution and interconnection in the polymer layer.

A novel and improved surfactant-modified Prussian Blue electrode for amperometric detection of free chlorine in water

A surfactant-modified Prussian Blue (PB) electrochemical sensor has been developed. Benzethonium was used to assist the electrodeposition of PB onto a glassy carbon electrode (GCE). The surface coverage (ΓFe3+0) was 7.75×10−8molcm−2, five times higher than the value obtained in the absence of surfactant, and the film thickness of ca. 123nm. SEM, EDX, Raman were used to characterize the electrodes while their electrochemical analysis proved a superior performance for the surfactant modified PB film. Cyclic voltammetry and amperometry were used to study the sensor ability to detect chlorine, and the main experimental variables were optimized. Under optimized conditions, the sensor presented a sensitivity of 12μAppm−1cm−2, a linear range from 9ppb to 10ppm and a reproducibility of 4.2%. For the first time, we proved the sensor performance for real applications. Thus, chlorine was determined in tap water and the obtained concentrations validated with a standard colorimetric method. The obtained results showed that our sensor is highly performant and reliable for applications involving determinations of environmental residual chlorine.