Nonionic Surfactant Polyoxyethylene Research Articles

Complete biodegradability assessment of polyoxyethylene glycerol ester non-ionic surfactant: Aerobic, anaerobic, combined biodegradation and inhibitory effects

Aerobic and anaerobic biodegradability have become one of the most relevant characteristics for all contaminants. This is especially important in case of surfactants, which are discharged in wastewater treatment plants or directly into the aquatic bodies. The aim of this study is the integral assessment of the biodegradability of the non-ionic surfactant polyoxyethylene glycerol ester PGE-OE17. The aerobic and anaerobic biodegradation of PGE-OE17 was evaluated at different initial surfactant concentrations, and the evolution of the toxicity of the surfactant and its by-products was followed during the aerobic and anaerobic processes using bacteria Vibrio fischeri. PGE-OE17 was not completely biodegradable neither aerobically nor anaerobically, and the increase in the initial surfactant concentration had a negative effect in the biodegradation. Toxicity of the surfactant solutions and degradation by-products had a first increase followed by a gradual decrease during both tests, revealing that toxic substances released can harm the microorganisms and therefore hinder the biodegradation. Additionally, combined aerobic-anaerobic biodegradation tests were performed, consisting in a first aerobic treatment of different duration and initial concentration, followed by a complete anaerobic treatment. Results showed that a balance between aerobic and anaerobic biodegradation duration can maximize the biodegradation rates in comparison with only aerobic or anaerobic tests.

General adsorption isotherm for polyoxyethylene alkyl ethers CnEOm adsorbed at the water/air surface

An empirical adsorption isotherm model is presented based on fundamental thermodynamic equations of adsorption for the homologous series of the nonionic surfactants polyoxyethylene alkyl ethers (CnEOm) at the aqueous solution surface to determine the surface tension and surface pressure isotherms, surface equation of state, and molar characteristics for the adsorbed surfactant molecules. The new model describes the surface properties of CnEOm much better than the original Langmuir adsorption model used as thermodynamic basis. The analysis of the results shows that the increase of the alkyl chain length n (hydrophobic part) leads to an increase in the adsorption activity, while the increase of hydrophilic head group given by the number of EO units m, leads to a better solubility in water, and hence, to a smaller adsorbed amount. The results also show that the ethylene oxide group mainly influences the molar surface area.

Effect of mixed surfactants on foam stabilization: A molecular dynamics simulation

Mixed surfactants have antagonistic or synergistic effects on the air/liquid interface of foams, representing two opposite interactions about destroying or stabilizing foams. In this paper, mixed surfactant systems containing non-ionic surfactant polyoxyethylene alkyl ether (AEO) and anionic surfactant sodium dodecyl sulfate (SDS) were discussed by molecular dynamics simulation to study the mechanism of decreasing stability of SDS foam after AEO was added. The results showed that with the addition of AEO, the interaction between SDS molecules is weakened, and the thickness of hydrated shell around the polar head of SDS decreases. In order to simulate the process of foam drainage and rupture, steered molecular dynamics (SMD) containing two external forces on the foam film was performed. One is about the z-axis vertical external force, representing the stability of SDS hydrated layer at the interface; the other is about the external force in horizontal direction, representing the rupture process of the liquid film. The simulated results showed that the higher the concentration of AEO in the mixed surfactant interface layer, the smaller the external force to destroy the foam film interface. In addition, the free energy change of AEO molecules from the water phase through the SDS layer to the air phase further showed that the addition of AEO can reduce the stability of SDS foam films and play a defoaming role in the studied system. The simulated conclusions were consistent with the experimental results about the decreasing stability of SDS foam after AEO was added.

An empirical model to represent the CMC behavior of aqueous solutions of homologous series of nonionic surfactants, related to its chemical constitution

Critical Micelle Concentration (CMC) is a fundamental property of surfactants in (aqueous) solution. The importance of defining the CMC of an aqueous surfactant solution is related to the different behavior and performance of the given system below and above its CMC, which has impact on the usage of this type of systems for different industrial applications. In this work, an empirical model is presented, based on the fundamental equation for the thermodynamics of micellization of a given homologous series of surfactants with the same chemical nature, to estimate the corresponding CMC. This simple model contains three adjustable parameters and allows predicting the log[CMC] of the nonionic surfactants polyoxyethylene alkyl ethers (CnEm) in aqueous solution. The analysis of the three parameters showed that the hydrophobic characteristics play the major role in micelle formation. The polarity of the molecules is also important, but its effect is less pronounced. The proposed model is compared with other empirical models and its quality to estimate the CMC is superior.

Lubrication performance of MXene/Brij30/H2O composite lamellar liquid crystal system

The lamellar liquid crystal (LLCS) system constructed by surfactant aggregation was demonstrated to exhibit superior tribological properties due to its unique lamellar structure and creep recovery properties. However, the lubrication performance of this kind of liquid crystal system was greatly hindered by its soft nature. Emerging as two-dimensional material, MXene has been promising candidate in tribology on account of its unique layer structure and versatile composition. Taking account of the above fact, herein, nonionic surfactant polyoxyethylene lauryl ether (Brij30), MXene (Ti3C2Tx), and H2O were employed to construct a triple-component composite LLCS system and the related tribological properties were systematically investigated. The results demonstrated that the lubrication performance of the liquid crystal system formed in the presence of Ti3C2Tx was significantly improved compared with that of Brij30/H2O LLCS. The average friction coefficient of the composite LLCS system was in the range of 0.1155–0.1266, and the best lubrication performance was achieved when the Ti3C2Tx content was kept as 6 mg/mL. MXene is also able to achieve good dispersion in liquid crystal systems. The enhanced lubrication performance of the composite LLCS system was mainly due to the synergistic effect of MXene nanosheets and LLCS. In addition, the iron oxides generated by the reaction during the friction process also promote lubrication. It is believed that the current work provides an alternative method for the development of MXene/LLCS-lubricating materials.

Foam flushing with soil vapor extraction for enhanced treatment of diesel contaminated soils in a one-dimensional column

A limitation of soil vapor extraction (SVE) remediation for total petroleum hydrocarbons (TPHs) in the unsaturated zone is the inability to remove the less volatile petroleum mixture compounds in diesel fuel. SVE combined with foam flushing may have the potential to enhance dissolution or mobilization of soil sorbed diesel and allow mobilized diesel to move to the SVE extraction well. A nonionic surfactant polyoxyethylene (20) sorbitan monooleate (TW80) was selected for generating foam, and a procedure to incorporate the oxidant sodium persulfate (SPS) in generating TW80/SPS foam to deliver chemical oxidation, was also studied. Both TW80 and TW80/SPS foams exhibited 96–98% quality under 8–32 mM of TW80 and 10–50 mM of SPS. The addition of SPS in TW80 solution resulted in elevated ionic content and degradation of TW80, which may reduce the foam stability and have minor effects on foam quality. Through analysis of interrelationships among column flushing experimental parameters, it was shown that the foam quality was reduced to 42–47% when foam flushed through a diesel contaminated soil column. Moreover, the results of column flushing tests operated for 12 h indicated that the effectiveness of removal of diesel by different foams followed the order of TW80 foam (53%) > TW80/SPS foam (37%) >N2 gas flow alone (3%). It was shown that foam flushing could be an alternative approach, rather than using N2 gas flow alone (SVE), in enhancing SVE for reducing diesel contamination in the unsaturated zone.

Wetting and Drying of Aqueous Droplets Containing Nonionic Surfactants CnEm.

This paper presents a systematic study of the wetting and drying of aqueous pico-liter droplets containing nonionic surfactants polyoxyethylene alkyl ethers (CnEm; n = 10, 12, 14, m = 6 or 8) in comparison with the anionic surfactant sodium dodecyl sulfate (SDS). The spreading and drying of droplets on hydrophilic substrates were studied by tracking the three-phase contact line (TCL) and by interferometry. CnEm droplets undergo phase separation during drying: a water-rich droplet retracts and leaves behind a thin film that is postulated to be a surfactant mesophase. This thin film either retracts or breaks up into small droplets on a longer time scale. The receding contact angle of the water-rich droplet on the thin film in the late stage of drying of CnEm droplets is independent of hydrophobicity of substrates, supporting the inference that a mesophase is present on the surface. Both CnEm and SDS solutions inhibit spreading on hydrophilic surfaces, which is attributed to Marangoni contraction as a result of a surface tension gradient across the gas-liquid interface. More pronounced suppression of spreading is observed in the case of CnEm solutions, possibly due to the phase transition of surfactant solution in the vicinity of the initial TCL leading to a viscous phase at the TCL that pins the droplet. Tracer particle measurements reveal that mild Marangoni flows exist for droplets with surfactant concentrations well above the critical micelle concentration (CMC). Origins of the surfactant gradients that result in Marangoni flows are discussed.

Enhanced anti-inflammatory potential of degradation resistant curcumin/ferulic acid eutectics embedded in triglyceride-based microemulsions

Negligible solubility of curcumin in water combined with rapid degradation have limited its medical applications. In this contribution, eutectic mixture of curcumin with one of its degradation products (ferulic acid) was encapsulated into long and medium chain triglycerides oils and stabilised by the non-ionic surfactant polyoxyethylene oleyl ether Brij® O10 (C18:1E10) and bile acid derivative (sodium deoxycholate). Thermal and spectroscopic analysis confirmed the presence of curcumin as solid nanocrystals embedded within the microemulsion droplets. UV-spectroscopy and LC-MS studies of formed microemulsions revealed that degradation of curcumin in water was significantly reduced with more than 83% of curcumin remained intact after 24 h 1H NMR results showed that curcumin remained stable upon heating in the range between 297K and 327 K with no signs of degradation to ferulic acid. The results showed solubility enhancement of curcumin with a range of 3–5 mg/mL. NF-κB reporter cell assay revealed low cytotoxicity and three folds stronger anti-inflammatory potential compared to curcumin. Microemulsions remained stable for over 12 months with extended stability of formulations that contained curcumin/ferulic acid in glyceryl tricaprate based microemulsions. Overall these results suggest novel role for particle engineering via using ferulic acid as stability and activity enhancer for curcumin through free radicals scavenging mechanism.

Strong additive and synergistic effects of polyoxyethylene nonionic surfactant-assisted protein MALDI imaging mass spectrometry

Protein MALDI imaging mass spectrometry (MALDI-IMS) holds a great promise to acquire spatial distribution information of proteins on biological tissue, but it suffers from the small number of proteins detected by direct MALDI-IMS detection. Ionic surfactants have been extensively used for protein extraction to improve the number of proteins detected in tissue samples by LC-MS analysis, but seldom by direct MALDI-IMS detection. Nonionic surfactants are milder than ionic surfactants and protein native structures are remained after extraction, which favors the spatial resolution of direct MALDI-IMS. However, nonionic surfactants are less effective than ionic surfactants. In this report, we utilized polyoxyethylene nonionic surfactants (PNS) to pre-incubate the tissue section, followed by the on-tissue trypsin digestion and then direct MALDI detection of in-situ formed peptides. For the first time, we observed that the additive effect of PNS and the synergistic effect of the mixed PNS in improving the number of peptides detected. Specifically, the peptides detected were 73.0–90.7% distinct when the different PNS (Tween 80 or Triton X-100 alone or their mixture) was used. Taking advantage of this additive effect, the 96 proteins including 12 transmembrane proteins were detected, corresponding to a ~10-fold improvement compared to MALDI-IMS without surfactant. When the mixed surfactants were used to replace Tween 80 and Triton X-100 alone, the optimized surfactant concentration decreased 20–100-fold and the number of peptides detected with m/z > 2500 Da was improved 15-fold. The additive and synergistic effects of PNS suggested that the interaction mode between each PNS and proteins is highly variable. Benefiting from the strong additive effect and diversity of PNS, further improvement of the number of proteins detected by MALDI-IMS is clearly feasible.

Fluorescence quenching of chloroquine by Cu2+ in micelles

Abstract Fluorescence quenching, very often, has been employed as a suitable technique for characterization of the immediate environment of a fluorophore. This paper reports the absorption and fluorescence characteristics of an antimalarial drug, chloroquine, in presence of the salt copper chloride (CuCl2) in aqueous and micellar systems. Chloroquine fluorescence was quenched considerably by the copper ion (Cu2+); quenching ability of Cu2+ in micellar solution of the cationic surfactant cetyltrimethylammonium chloride (CTAC) is higher than that in water while for the nonionic surfactant polyoxyethylene (20) cetyl ether (Brij 58) it has much lower quenching efficiency. Downward deviations in Stern-Volmer (SV) plots were observed for all the systems. Possibly, the chloroquine molecules are inserted somewhat deeper inside the micelles of Brij 58 as compared to the CTAC micelles and in Brij 58 micelles the fluorophore might be less exposed to the aqueous phase to become available for the metal ion quenching.

Surfactants at environmentally relevant concentrations interfere the inducible defense of Scenedesmus obliquus and the implications for ecological risk assessment

The ecotoxicology of surfactants is attracting wide attention due to the rapidly expanding global application. As interspecific relationships play one of the central roles in structuring biological communities, it is necessary to take it into risk assessments on surfactants. With this aim, our study investigated the interference of three common surfactants on the inducible defense of a freshwater phytoplankton Scenedesmus obliquus. Nonlethal environmentally relevant concentrations (10 and 100 μg L−1) of several surfactants were set up. Results showed that growth and photosynthetic efficiency of Scenedesmus were inhibited during first 96 h, but recovered in the later stage. Surfactants interfered inducible defense of Scenedesmus against Daphnia grazing, and the interference was related to chemical characteristics of surfactants. The anionic surfactant sodium dodecyl sulfate (SDS) enhanced the colony formation even without grazing cues, whereas fewer defensive colonies were formed under the effects of cationic surfactant benzalkonium bromide (BZK) and nonionic surfactant polyoxyethylene (40) nonylphenol ether (NPE). These findings highlighted the sensitivity of grazer-induced morphological defense of Scenedesmus to surfactants even at nonlethal concentrations, which potentially affects the energy and information flow between trophic levels. This study appeals for more attention to take interspecific relationships into consideration in assessing the potential ecological risk of pollutants.

Modulation of Antimicrobial Peptide Conformation and Aggregation by Terminal Lipidation and Surfactants.

The function and properties of peptide-based materials depend not only on the amino acid sequence but also on the molecular conformations. In this paper, we chose a series of peptides Gm(XXKK)nX-NH2 (m = 0, 3; n = 2, 3; X = I, L, and V) as the model molecules and studied the conformation regulation through N-terminus lipidation and their formulation with surfactants. The structural and morphological transition of peptide self-assemblies have also been investigated via transmission electron microscopy, atomic force microscopy, circular dichroism spectroscopy, and small-angle neutron scattering. With the terminal alkylation, the molecular conformation changed from random coil to β-sheet or α-helix. The antimicrobial activities of alkylated peptide were different. C16-G3(IIKK)3I-NH2 showed antimicrobial activity against Streptococcus mutans, while C16-(IIKK)2I-NH2 and C16-G3(IIKK)2I-NH2 did not kill the bacteria. The surfactant sodium dodecyl sulfonate could rapidly induce the self-assemblies of alkylated peptides (C16-(IIKK)2I-NH2, C16-G3(IIKK)2I-NH2, C16-G3(VVKK)2V-NH2) from nanofibers to micelles, along with the conformation changing from β-sheet to α-helix. The cationic surfactant hexadecyl trimethyl ammonium bromide made the lipopeptide nanofibers thinner, and nonionic surfactant polyoxyethylene (23) lauryl ether (C12EO23) induced the nanofibers much more intensively. Both the activity and the conformation of the α-helical peptide could be modulated by lipidation. Then, the self-assembled morphologies of alkylated peptides could also be further regulated with surfactants through hydrophobic, electrostatic, and hydrogen-bonding interactions. These results provided useful strategies to regulate the molecular conformations in peptide-based material functionalization.

Mixed micelles formed by biological surfactant sodium deoxycholate and nonionic surfactants in aqueous solution

The interaction between biological surfactant sodium deoxycholate (NaDC) and nonionic surfactants polyoxyethylene (n) nonylphenol ether (NPn) for the formation of micelles in aqueous solution were investigated. Surface tension, interfacial dilational viscoelasticity, and transmission electron microscopy (TEM) were characterized to systematically study the interaction between NaDC and NPn in buffer solution. At last, the mechanism of the interaction between NPn and NaDC were analyzed. The surface tension results show that the interaction between NaDC and NPn was displayed synergism action. The composition of the mixed systems has been estimated on account of the regular solution theory, Clint’s equation, Rubingh theory and Rosen theory. The surface dilational rheology provided abundant effective information on the feature of adsorbed layers. From the oscillating barrier measurements, the peak values of the dilational modulus moved to lower concentrations in NaDC/NPn binary system compared to single surfactant. The dilational elasticity of the binary system decreased distinctly on the basis of the rigid structure of NaDC. The interaction of these two substances was proved directly by TEM images, that the boundaries of the aggregates are clearer due to the protection of NPn molecules. The new complex systems have potential application in environmental protection.

Role of surfactants in accelerating or retarding persulfate decomposition

When surfactants are coupled with persulfate-based ISCO (in situ chemical oxidation) to facilitate the remediation of soil-sorbed hydrophobic organic contaminants or non-aqueous phase liquids, surfactant selection is critical in avoiding excessive nonproductive consumption of persulfate and ensuring proper longevity of persulfate. In this study, the kinetics and mechanisms of the decomposition of persulfate in the presence of simple organic compounds containing primary basic building blocks of nonionic and anionic surfactants were first examined to elucidate the impact of individual building blocks to persulfate decomposition. Further kinetic and mechanistic studies were then carried out in the presence of representative surfactants from the four families of surfactants frequently applied in subsurface remediation. The results indicate that alkyl polyoxyethylene nonionic surfactants significantly accelerated initial persulfate decomposition due to radical-chain processes induced by the oxyethylene functional groups, whereas alkylphenol polyoxyethylene nonionic surfactants retarded initial persulfate decomposition by quenching the radical-chain processes by the aromatic rings. On the other hand, alkyl sulfonate anionic surfactants and alkylbenzene sulfonate surfactants retarded initial persulfate decomposition to some extent; Coulomb repulsion of SO4−/S2O82− and surfactant anion/radical, and entry of surfactant radical anion from the pseudo-aqueous phase into the pseudo-micellar phase may contribute to retarding initial persulfate decomposition. Overall, the results offer insightful structure-based guidance in selecting proper surfactants for surfactant-enhanced persulfate-based ISCO.

Uniform two-dimensional crystals of polystyrene nanospheres fabricated by a surfactant-assisted spin-coating method with polyoxyethylene tridecyl ether

Spin-coated self-assemblies of colloidal particles have been developed recently as an attractive close-packed monolayer of the particles for a variety of applications, but they are limited by the small area of their monolayers, especially given their low uniformity and monolayer coverage on large-area substrates. We report several noteworthy characteristics of a close-packed monolayer of polystyrene nanospheres (PS NSs) fabricated using a simple and inexpensive spin-coating method with a PS NS suspension mixed using the nonionic surfactant polyoxyethylene (12) tridecyl ether (PEO-TDE). In our study, we show that the PEO-TDE surfactant offers excellent wettability, surface tension, and a slow solvent evaporation rate of the PS NS suspension, similar to the conventional surfactant Triton X-100. We demonstrate that the relatively high monolayer coverage with reduced defects is produced when introducing the PEO-TDE surfactant. Specifically, monolayer coverage of more than 95% on a Si substrate was achieved, which is much better than that with the typical Triton X-100, and is one of the highest coverage rates realized by a spin-coating method. This excellent uniformity of the PS NS monolayer with high monolayer coverage is mainly attributed to the relatively low viscosity of the PS NS suspension, even at high concentrations of PEO-TDE. Moreover, the PEO-TDE surfactant provides highly uniform monolayers on a large-scale glass substrate even for large-sized PS NSs. We also highlight the fact that the PEO-TDE surfactant has another advantage in that the spin-coating process of the PS NS suspension can be done under common ambient laboratory conditions, unlike those required for the highly toxic Triton X-100. We therefore conclude that PEO-TDE can be a useful surfactant during the fabrication of close-packed monolayers for various applications owing to its simple and straightforward control of PS NSs, its uniform and high surface coverage, and due to the safety of the fabrication process.

DEVELOPMENT OF A POTENTIOMETRIC SENSOR SENSITIVE TO POLYSORBATE 20

Polyoxyethylated sorbitans (polysorbates) are widely used in the chemical, pharmaceutical, and cosmetic industries, but only quantitative determination is used mainly for chromatographic methods. In this paper, the results of the development and testing of a potentiometric sensor sensitive to nonionic surfactant polyoxyethylene sorbitan monolaurate (polysorbate-20) are presented. An anion of the heterogeneous acid of the Keggin structure (12-molybdophosphate heteropolyacid) was used as a counterion to obtain the electrode-active substance for the potentiometric sensor membrane. Polysorbate-20 does not form cations when dissociating in water and cannot directly interact with heteropolyanion; therefore, a cationic complex of polysorbate-20 with barium ions was previously prepared (similar to the interaction of metals with crown ethers). The resulting ion associate meets the basic requirement for the electrode-active substance of plasticized film polyvinyl chloride membranes of potentiometric sensors (poor water solubility and good solubility in organic solvents). Phthalic acid derivatives (dibutyl phthalate and dioctyl phthalate) were used as solvent-plasticizers for a polyvinyl chloride membrane. To determine the optimum conditions for the functioning of a potentiometric sensor sensitive to polysorbate-20, the influence of various factors on the electrode characteristics was studied. Quantitative content of the ionic associate in the polyvinyl chloride membrane, the nature of the membrane solvent-plasticizer, pH of a series of standard polysorbate-20 solutions) on the electrode characteristics of the plasticized membrane of the potentiometric sensor (sensitivity or slope of the electrode function, lower limit of linearity and minimum detectable concentration of polysorbate-20, which can be determined with the help of the developed potentiometric sensor) was studied. The optimal conditions for using the developed potentiometric sensor were found. The developed sensor allows for a short period of time (5–10 min) determining the quantitative content of polysorbate-20 in industrial products at the level 10–5–10‑6 mol/l. The potentiometric sensor sensitive to polysorbate-20 can be used for the development of a potentiometric method for determining the clinical reception of polysorbate-20 in various types of industrial products.

Phenanthrene degradation using Fe(III)-EDDS photoactivation under simulated solar light: A model for soil washing effluent treatment

In this work, for the first time, the nonionic surfactant polyoxyethylene-(20)-sorbitan monooleate (Tween 80, C64H124O26) aided soil washing effluent was treated by enhanced activation of persulfate (PS) using Fe(III)-EDDS (EDDS: ethylenediamine-N, N-disuccinic acid) complexes under simulated solar light irradiation. The performance of this system was followed via the production and reactivity of radical species (SO4-, HO, Cl2-) and degradation of phenanthrene (PHE) used as a model pollutant in soils. Different physico-chemical parameters such as the concentration of reactive species and pH were investigated through the PHE degradation efficiency. The second-order rate constants of the reactions for generated radicals with PHE and Tween 80 in solution were identified through competitive reaction experiments under steady-state conditions and application of nanosecond laser flash photolysis (LFP) as well. A kinetic approach was applied to assess the selectivity and reactivity of photo-generated radicals in aqueous medium in order to explain the observed degradation trends. This work proposes an innovative technology of management of soil washing solutions using Fe(III)-EDDS complexes and solar light for the activation of persulfate.

Interactions of Tween 20, 60 and 80 with dye molecules: Spectroscopic analysis

The behaviour of the pyrene (Py), 8-anilino-1-napthalenesulfonic acid ammonium salt (ANS) and Pyronin Y (PyY) in the Tween series of polyoxyethylene nonionic surfactants contained aqueous solutions was investigated using the fluorescence spectroscopic technique. The object of investigations were the interactions between the given dye and the surfactant in a wide range of surfactant concentrations and the temperature range from 293 to 318K. The obtained spectra were the basis for determination of the critical micelle concentrations (CMC) of the surfactants, thermodynamic analysis of the dye-surfactant binding process and correlation with the micropolarity and microviscosity of the dye environment. The parameters changes with concentration and temperature were also studied from the intermolecular interactions in the solution of a given surfactant.

Biological Oxidase Enzyme Mimetic Cu‐Pt Nanoalloys: A Multifunctional Nanozyme for Colorimetric Detection of Ascorbic Acid and Identification of Mammalian Cells

AbstractNanomaterials serving as artificial enzymes of the new generation (nanozymes), exhibit enhanced catalytic performance, excellent stability, low cost of production, and other associated properties of nanoparticles. This emerging field of nanozymes has broad‐spectrum potential applications in the bridging area nanotechnology and biomedicine. Among metal‐based nanozymes, bimetallic nanoparticles have been found to show enhanced catalytic performance and display ability to catalyze multistep reactions typically not observed in their monometallic counterparts. Herein, we report the synthesis of Cu−Pt based bimetallic nanoalloys coated with a nonionic surfactant polyoxyethylene cholesteryl ether. The characterization data suggest that the developed nanoalloys have an almost uniform distribution of Cu and Pt (1:1) elements; therefore, this novel technique could be used for the large‐scale synthesis of Cu−Pt based nanozymes in a one‐step procedure. Further investigations showed that these bimetallic nanoalloys possess excellent biological oxidase enzyme‐like activity and the catalytic activity could be performed at harsh conditions of pH and temperature. Oxidase activity of Cu−Pt nanoalloys was utilized for the sensitive detection of ascorbic acid in the sub‐micromolar concentration range. Supplementing ATP in the oxidase reaction, the nanozyme showed enhanced catalytic activity, which was used for the detection of human liver cells.

Mixed micellization and surface properties of non-ionic/cationic surfactants

We investigate the surface properties of aqueous binary mixtures of our cationic surfactant O-dodecyl-N,N′-diisopropylisourea hydrochloride (ISO-DIC C12) with commercially available nonionic surfactant polyoxyethylene p-(1,1,3,3-tetramethylbutyl)phenyl ether (TritonX-100) at different temperatures (288 to 303 K). The micellization behavior of the binary systems is studied by determining the surface tension and other important physicochemical parameters, such as the critical micelle concentration (CMC), surface tension at the CMC(γcmc), Krafft Temperature (TK), maximum excess concentration (Γmax), minimum surface area per molecule (Amin), surface pressure at the CMC (Пcmc), and the adsorption efficiency (pC20) at the air/water interface. The study has additionally covered the calculation of thermodynamic parameters of micellization, including the standard Gibbs free energy, the standard enthalpy, the standard entropy, the free energy, and the Gibbs free energy of adsorption at air/water interface. The CMC values of the binary systems determined by experimental data are used to evaluate the micellar composition in the mixed micelle, the interaction parameter β and the activity coefficients f1(ISO-DIC C12) and f2 (polyoxyethylene p-(1,1,3,3-tetramethylbutyl)phenyl ether) using the theoretical treatment proposed by Clint and Rubingh. Our results reveal that the proposed binary systems possess enhanced surface activity compared to those of the individual surfactants.