Cationic Gemini Surfactants Research Articles

Phase behaviour and temperature-responsive properties of a gemini surfactant/Brij-30/water system.

The phase behaviour of a ternary system composed of cationic gemini surfactant 2-hydroxypropyl-1,3-bis(myristyldimethylammonium chloride) (14-3(OH)-14(2Cl)), nonionic surfactant polyoxyethylene laurel ether (C12H25(OCH2CH2)10OH, Brij-30) and H2O was studied and its phase diagram was determined. In several different phase regions identified in the phase diagram, the viscoelastic worm-like micellar solution region was investigated. The focus of the investigation was the increase in the viscosity of the micellar solution with the temperature and the Brij-30 content, as suggested by a partial region of the triangular phase diagram. With an increase in the Brij-30 content or temperature, one-dimensional micellar growth occurred, and a maximum appeared in the zero-shear viscosity, η0, versus Brij-30 content or temperature curves; this was true for mixed solutions containing 14-3(OH)-14(2Cl) and Brij-30 in different mass ratios (WBrij-30/W14-3(OH)-14(2Cl)). After the maximum point, the decrease in viscosity is the result of the micellar shortening in the size with Brij-30 content and of the micellar branching in the network structure with temperature. This rheological analysis was performed to investigate the structural changes in different solutions as well as the effects of various factors on micellar growth. Various techniques were used to study the phase-transition processes occurring in this system, including cryogenic transmission electron microscopy, small-angle X-ray scattering measurements, and differential scanning calorimetry. The transition mechanisms of the aggregates were analysed on the basis of the obtained results.

Effect of Spacer and Alkyl Chain Groups of the Synthesized Cationic Gemini Surfactants on the Surface Modification of Nano Na-Montmorillonite and its Dye Adsorption from Textile Waste Water

Effect of Spacer and Alkyl Chain Groups of the Synthesized Cationic Gemini Surfactants on the Surface Modification of Nano Na-Montmorillonite and its Dye Adsorption from Textile Waste Water

Interaction between Surfactants and SiO2 Nanoparticles in Multiphase Foam and Its Plugging Ability

To improve the stability of foam fluids, SiO2 nanoparticles and trace amount of Gemini cationic surfactant were combined with the main foaming agent, nonionic surfactant, to form a tricomponent multiphase foam. The stability of the multiphase foam was assessed through two parameters of half-life time and dilational modulus. The interaction between surfactants and nanoparticles were studied though surface tension, adsorption amount, and ζ potential measurement. The effects of saline ions and temperature on foam stability were also investigated. The plugging ability of the tricomponent multiphase foam was assessed using a sandpack model. The optimized tricomponent multiphase foam was 10 times more stable than corresponding foam without nanoparticles in terms of half-life time and also resisted to saline and temperature to a certain degree because the adsorption of nanoparticles at the interface improved the mechanic strength of foam film. The tricomponent multiphase foam showed more excellent plugging abili...

An ester-functionalized cationic gemini surfactant mediated structural transitions of porcine serum albumin (PSA) via binding interaction

Keeping in mind the contemporary environmental concern raised over the disposal of surfactants into water bodies, we synthesized biodegradable cationic gemini surfactant ethane-1,2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride (16-E2-16), which bears easily cleavable ester functionalities (betaine type arrangement) in its spacer. This research article encompasses an in vitro analysis of the interaction between the synthesized gemini surfactant and a serum transport protein, porcine serum albumin (PSA) under physiological mimetic conditions. A multi-technique approach was exploited to explore the structural alterations induced in PSA at different concentrations of 16-E2-16. Fluorescence measurements unraveled a substantial interaction between PSA and 16-E2-16 (Kb∼104M−1). Synchronous and three-dimensional fluorescence spectra further validated the binding of 16-E2-16 with PSA. Pyrene emission fluorescence depicted an increased hydrophilicity experienced by the probe molecules on account of their expulsion into the solvent due to a comparatively stronger binding of the gemini surfactant with PSA. The UV–vis studies established the ground state complexation of the gemini with PSA. Interestingly, far-UV CD results demonstrated the stabilization of secondary structure of PSA at concentrations below and above the CMC of 16-E2-16. Near-UV CD spectra revealed negligible changes in the tertiary structure of PSA. Additonally, CV scans depicted electrochemically inactive 16-E2-16−PSA complex formation and thus reinforced the findings of spectroscopic investigations. Overall, it is inferred that 16-E2-16 binds efficiently with PSA affecting both its microenvironment and conformation. Owing to these favorable interactions, 16-E2-16 may find its application as a prospective excipient in drug, skincare and immunoassay reagent formulations, in which serum albumins are frequently used.

Interactions between Formation Rock and Petroleum Fluids during Microemulsion Flooding and Alteration of Heavy Oil Recovery Performance

In situ emulsification/solubilization is an oil recovery technique routinely used to mobilize residual oil after the secondary oil production (waterflooding). The oil is produced after a subsequent reduction of interfacial tension between stranded crude oil and water in the reservoir. Herein, a recovery method is presented for heavy crude oils whose scheme consists of injection of a fully solubilized (or emulsified) oil. Theoretically, the fully solubilized oil, referred hereinafter as microemulsion formulation, reduces the viscous forces that keep residual oil stranded. Different microemulsion formulations were prepared ex situ from two heavy oils (API 11.5 and 16.6), micellar slugs (formulated from cationic Gemini surfactant), and low-saline water (0.1 wt % NaCl). Tertiary heavy oil recovery consisted of displacing residual oil from a waterflooded core by a specific microemulsion formulation followed by low-saline water, which acted as buffer solution. Thirty-one percent of initial oil-in-place (IOIP) was recovered from the waterflooded core by microemulsion followed by an incremental oil recovery of about 20% of IOIP with chase water. The oil recovery efficiency by microemulsion and chase water floodings was lowered to 15 and 28%, respectively, in a strong oil-wet core (i.e., non waterflooded core). Despite the promising results presented herein, the performance of the microemulsion formulations and thus the oil recovery efficiency were found to be strongly dependent on (1) the nature of the core, i.e., its mineralogy, (2) the wetting state of plug, and (3) the chemical composition advancing fluid. The microemulsion formulations prompted a series of chemical reactions which subsequently altered their performance as a displacing agent. Ion tracking analysis of the effluent fractions showed that the pH and concentration in divalent and/or monovalent ions were also altered at each stage of production. When the plug was not waterflooded, the oil was produced along with a deposit of sludge and a high emulsion cut. However, the use of preflush enriched with an alkali (Na2CO3) was found to abate both effects. Furthermore, the spectral analysis of effluent fractions revealed the formation of calcium bridges which are thought to alter the efficiency of microemulsion formulations. Also, a series of chemical schemes are proposed in this investigation to support these results. Lastly, this investigation proposes a simplified electrostatic model that explains further the formation of clusters which were promoted by propagation of displacing fluids.

Bio‐/Environment‐Friendly Cationic Gemini Surfactant as Novel Corrosion Inhibitor for Mild Steel in 1 M HCl Solution

AbstractBio‐/environment‐friendly cationic gemini surfactant, ethane‐1,2‐diyl bis(N,N‐dimethyl‐N‐hexadecylammoniumacetoxy)dichloride, referred to as 16‐E2‐16, was synthesized and characterized. Corrosion inhibition effects of 16‐E2‐16 on mild steel (MS) surface in 1 M HCl solution at 30, 40, 50 and 60 °C were evaluated using gravimetric analysis, potentiodynamic polarisation and electrochemical impedance spectroscopy measurements. The nature of the protective inhibitor film formed on the MS surface was analysed by SEM, EDAX and FT‐IR, while TGA was used to assure the thermal behaviour and stability of the film at high temperature. The formation of [inhibitor‐Fe2+] on the surface of MS was confirmed by UV–visible spectroscopy. The inhibition efficiency of the studied inhibitor increased with increasing concentration and solution temperature. The compound behaved as a mixed type inhibitor and acted by blocking the electrode surface by means of adsorption obeying the Langmuir adsorption isotherm. Surface active properties and corrosion inhibition effects of 16‐E2‐16 in the presence of inorganic (NaI) and organic (NaSal) salts were also investigated and are discussed. Density functional theory calculations have been carried out to correlate the efficiency of the compound with its intrinsic molecular parameters.

Amido‐Amine‐Based Cationic Gemini Surfactants: Thermal and Interfacial Properties and Interactions with Cationic Polyacrylamide

AbstractExperimental studies were conducted to investigate thermal and interfacial properties of two in‐house synthesized amido‐amine‐based cationic gemini surfactants namely: dodecanoic acid [3‐({4‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐butyl}‐dimethyl‐amino)‐propyl]‐amide dibromide (12‐4‐12) and dodecanoic acid [3‐({6‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐hexyl}‐dimethyl‐amino)‐propyl]‐amide dibromide (12‐6‐12). Thermogravimetric analysis showed the excellent thermal stability of surfactants and no structural degradation was observed at temperatures up to 250 °C. The long‐term thermal stability of the surfactants was investigated with the aid of spectroscopic techniques such as nuclear magnetic resonance (NMR (1H and13C) and Fourier transform infrared (FTIR) spectroscopy. Both surfactants were found to be thermally stable, and no changes in structure were observed after aging for 10 days at 90 °C. The interfacial tension of the surfactants was measured at three different temperatures (30, 60, and 80 °C), and the results showed a decrease in interfacial tension with increasing temperature and increasing spacer length of the surfactants. Rheological measurements were used to assess the interactions between the cationic gemini surfactant and cationic polyacrylamide. The addition of cationic surfactant reduced the viscosity and storage modulus of the polymer at low shear rate and frequency due to surfactant–polymer interactions and charge screening. The investigated surfactant–polymer system has great potential in high‐temperature carbonate reservoirs, where conventional anionic surfactants are not recommended due to high adsorption.

Molecular connectivity indices for modeling the critical micelle concentration of cationic (chloride) Gemini surfactants

The molecular connectivity indices were used to derive the simple model relating the critical micelle concentration of cationic (chloride) gemini surfactants to their structure. One index was selected as the best to describe the effect of the structure of investigated compounds on critical micelle concentration consistent with the experimental results. This index encodes the information about molecular size, the branches, and also the information about heteroatoms. The selected model can be helpful in designing novel chloride gemini surfactants.

Self‐assembly properties of ultra‐long‐chain gemini surfactant with high performance in a fracturing fluid application

ABSTRACTA new cationic gemini surfactant (C25‐6‐C25), which had a special structure consisting of ultra‐long hydrophobic chains and amide groups, was synthesized using a main feedstock source obtained from rapeseed for thickening purposes. The 12 mmol L−1 C25‐6‐C25 fluid containing 0.19 mol L−1 potassium chloride (KCl) exhibited highly elastic properties at the angular frequency of 0.04–10 rad s−1. Its viscosity could be maintained at 55 mPa s for 1.5 h under a shear rate of 170 s−1 at 110 °C and it also showed a good proppant‐suspending property. C25‐6‐C25/KCl fluid exhibited high viscoelasticity and good performance, which were attributed to intermolecular forces, hydrogen bonding, and the shielding effect of electrostatic repulsion by KCl. Thus, C25‐6‐C25 is a very promising candidate for fracturing. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44602.

Surface activity, micellization and solubilization of cationic gemini surfactant-conventional surfactants mixed systems

In this paper, we have studied the mixed surfactant systems containing a cationic gemini surfactant N,N′-bis(dimethyldodecyl)-1,2-pentanediammonium dibromide (12-5-12) with several differently charged surfactants (cationic/anionic/non-ionic/zwitterionic) by using surface tension, small angle neutron scattering (SANS) under standard condition. All the surfactants have same dodecyl chain but different in polar head group viz. Sodium dodecyl trioxyethylene sulphate (SDES)(anionic), dodecyl trimethyl ammonium bromide (DTAB) (cationic), 3-[dodecyldimethyl ammonio] propane sulphonate (C12-PS)(zwitterionic), hexaethylene glycol monododecyl ether (C12E6)(non-ionic) and dimethyl dodecyl amine oxide (DMDAO) (cationic-non-ionic). The Clint, Rubingh, Maeda and Rosen approaches were employed to determine various parameters like critical micelles concentration (CMC), surface excess concentration (Гmax), surface pressure at CMC (πCMC), minimum area per molecule (Amin) etc. as well as thermodynamic parameters. Solubilization of some polycyclic aromatic hydrocarbons (PAHs) have done in single as well as in mixed surfactant systems. Order of solubilization capacity of PAHs compounds are different in pure/mixed surfactant micelles. The solubilization efficiency towards naphthalene, anthracene, and pyrene were measured and the molar solubilization ratio (MSR), deviation ratio (R) and micelle-water partition coefficient (km) were evaluated for single and mixed systems.

A Mathematical Approach to a More Accurate Determination of Critical Micelle Concentration and Other Thermodynamic Parameters of 14‐2‐14 Gemini Surfactant in Water–Organic Solvent Mixed Media at Variable Temperatures

AbstractTo explore how the solvent characteristics influence the self‐aggregation of the cationic gemini surfactant dimethylene‐1,2‐bis(tetradecyldimethylammonium bromide) (14‐2‐14) and to obtain various energetic parameters, conductometric experiments were performed on the binary mixtures in the presence of commonly used organic solvents; formamide (FA), acetonitrile (AN) and 2‐methoxyethanol (ME) in aqueous solutions at varying temperatures (298.15–323.15 K) and compositions. The procedure suggested by Carpena et al. has been utilized to analyze conductivity–concentration plots in order to obtain critical micelle concentration (CMC) and degree of counterion dissociation (α) of the micelles. This method provides more accurate results as compared to conventional treatments, and the experimental error for the evaluation of micellar parameters is reduced significantly. The results revealed that, although the process of micellization becomes less favorable with the increase in composition of FA, AN and ME in mixed systems, the increase in CMC at compositions lower than 20% (v/v) of the organic solvents is relatively less, indicating that water character is dominant in the bulk phase. As the enthalpy of micellization became more negative, the corresponding entropy change became less positive and enthalpy–entropy compensation phenomenon has been observed for 14‐2‐14 in all the mixtures within the studied temperature range.

Cationic gemini pyrrolidinium surfactants based sweeping-micellar electrokinetic chromatography for simultaneous detection of nine organic pollutants in environmental water

A series of novel cationic gemini surfactants with pyrrolidinium head groups, 1,1′-(butane-1,s-alkyl) bis (1-alkylpyrrolidinium) (Cn-4-CnPB, n=12, 14, 16), were employed as carriers in sweeping–micellar electrokinetic chromatography (sweeping-MEKC) for simultaneous detection of nine organic water pollutants, including polycyclic aromatic hydrocarbons, sulfonamides and steroids. The sweeping and separation conditions were optimized. Cn-4-CnPB (n=12, 14, 16) were compared with cetyltrimethylammonium bromide (CTAB) in terms of their abilities to preconcentrate and separate the nine analytes. Under the optimized conditions, the sensitivity enhancement factors based on the peak height (SEFsHeight) were ca. 310–580 of C16-4-C16PB, which were higher than those of C14-4-C14PB (120–290) and C12-4-C12PB (110–160). Meanwhile, the SEFsHeight of C16-4-C16PB were higher than those of 30% (v/v) methanol-modified CTAB (140–320). The C16-4-C16PB based sweeping-MEKC, coupled with offline solid phase extraction and UV detection (228nm), was used to analyze spiked environmental water samples. The nine analytes were successfully separated and detected. The limit of detection (S/N=3) was in range of 2.79–3.76ng/mL, and the recovery ranged from 70.8% to 95.5% with the RSDs less than 9.89%. This study confirms that the C16-4-C16PB based sweeping-MEKC has significant advantages over the CTAB based sweeping-MEKC and it is a promising method for sensitive and simultaneous detection of polycyclic aromatic hydrocarbons, sulfonamides and steroids in environmental water samples.

Rapid and efficient enantioseparation of (S)-amlodipine by surface-imprinted core-shell polymer microspheres.

We present a protocol for the preparation of surface-imprinted polymer microspheres by core-shell precipitation polymerization for the enantioseparation of (S)-amlodipine. In this work, submicron mesoporous silica microspheres were prepared with gemini cationic surfactant as soft template. Molecularly imprinted polymers were coated on the silica supports with a low level of crosslinking, and the thickness of the thin-walled imprinted shell was about 45 nm. The material showed fast binding kinetics for (S)-amlodipine (within only 20 min for complete equilibrium), and the saturation adsorption capacity reached 309.2 mg/g, indicating the good accessibility of binding sites and improved mass transfer for target molecule. The imprinted microspheres exhibited an appreciable enantiomeric excess of (S)-amlodipine of 11.3% when used as a glass chromatography column for the enantioseparation of (S)-amlodipine from amlodipine besylate without extra chiral additives. The surface-imprinted materials display potentially amplification for industrial enantioseparation of (S)-amlodipine.

Nonviral gene-delivery by highly fluorinated gemini bispyridinium surfactant-based DNA nanoparticles

Biological and thermodynamic properties of a new homologous series of highly fluorinated bispyridinium cationic gemini surfactants, differing in the length of the spacer bridging the pyridinium polar heads in 1,1′ position, are reported for the first time. Interestingly, gene delivery ability is closely associated with the spacer length due to a structural change of the molecule in solution. This conformation change is allowed when the spacer reaches the right length, and it is suggested by the trends of the apparent and partial molar enthalpies vs molality. To assess the compounds’ biological activity, they were tested with an agarose gel electrophoresis mobility shift assay (EMSA), MTT proliferation assay and Transient Transfection assays on a human rhabdomyosarcoma cell line. Data from atomic force microscopy (AFM) allow for morphological characterization of DNA nanoparticles. Dilution enthalpies, measured at 298K, enabled the determination of apparent and partial molar enthalpies vs molality. All tested compounds (except that with the longest spacer), at different levels, can deliver the plasmid when co-formulated with 1,2-dioleyl-sn-glycero-3-phosphoethanolamine (DOPE). The compound with a spacer formed by eight carbon atoms gives rise to a gene delivery ability that is comparable to that of the commercial reagent. The compound with the longest spacer compacts DNA in loosely condensed structures by forming bows, which are not suitable for transfection. Regarding the compounds’ hydrogenated counterparts, the tight relationship between the solution thermodynamics data and their biological performance is amazing, making “old” methods the foundation to deeply understanding “new” applications.

Synthesis, interface activity and oil flooding experiment with an authentic sandstone microscopic model of cationic gemini surfactant

ABSTRACTIn this work, a series of cationic gemini surfactants with different hydrophobic tails were prepared and characterized by element analysis, IR spectra, and 1H NMR spectra. The influencing factors of physic-chemical properties of these surfactants were carefully studied. The critical micelle concentration (CMC) of all the surfactants ranged from 3.87 × 10−4 mol L−1 to 8.97 × 10−4 mol L−1 and the values (γcmc) also ranged from 28.62 mN m−1 to 34.07 mN m−1 at CMC level by surface tension experiments. The consequences of the oil/water interface tension experiments indicated that all these prepared surfactants could lower oil/water interface tension to ultra-low with the combination of Na2CO3. C12-2-C12, and C14-2-C14 were chosen as the representative to evaluate the displacement efficiency in the oil flooding experiments using authentic sandstone microscopic model. The results showed that these surfactants could effectively improve the displacement efficiency by 10–20%.

Interfacial dynamic properties and dilational rheology of mixed anionic and cationic Gemini surfactant systems at air–water interface

The interfacial dynamic properties and dilational rheology of sulfonate Gemini surfactant (SGS-12), two bisquaternary ammonium dibromides with different carbon chain lengths (BQAS-12, 16), and two mixed anionic and cationic Gemini surfactant solutions (SGS-12/BQAS-12 and SGS-12/BQAS-16) air–water interface were investigated using the drop shape analysis. Results indicate that the adsorption mechanism of surfactants is diffusion-controlled at dilute concentrations, whereas the adsorption process gradually shifts to a mixed kinetic-diffusion control with increasing the surfactant concentration. The surface tension of the mixtures reaches the minimum value when the molar ratios of SGS-12/BQAS-12 and SGS-12/BQAS-16 mixtures are 6:5 and 8:5, respectively. The effects of oscillating frequency and concentration on the dilational properties were also examined. As the dilational frequency increases, the dilational modulus of these surfactants increases gradually, but the phase angle decreases. The dilational elasticity peaks at a certain concentration, which is less than the critical micelle concentration. Moreover, the effects of SGS-12 concentration on the dilational interfacial rheology of the BQAS-12/SGS-12 and BQAS-16/SGS-12 mixtures were studied. The surface activities of these mixtures show positive correlation with the phase angle. Moreover, the surface film mainly exhibits viscosity as the surface tension reaches the minimum.

Complex formation between cationic gemini surfactant and sodium carboxymethylcellulose in the absence and presence of organic salt

Complex formation between cationic gemini surfactant 12-6-12 and anionic polyelectrolyte sodium carboxymethylcellulose (NaCMC) has been investigated in the absence and presence of organic salt sodium benzoate (NaBz) by turbidity, conductivity, isothermal titration microcalorimetry (ITC), ζ potential, light microscopy and SEM measurements. In the absence of salt, the NaCMC/12-6-12 system experiences the aggregate transitions from fibrous structure of the polymer NaCMC to soluble beaded structured NaCMC/12-6-12 aggregates and then to precipitated networklike cross-linked structured NaCMC/12-6-12 aggregates with increasing 12-6-12 concentration. The addition of salt is found to markedly influence the formation of NaCMC/12-6-12 complexes. When the NaBz concnetration is less than or equal to 0.10M, the phase behavior of the NaCMC/12-6-12/NaBz system is similar to that of NaCMC/12-6-12 in the absence of salt, but the lower 12-6-12 concentration is needed for the formation of precipitation. When the NaBz concnetration is greater than or equal to 0.15M, the phase behavior include no NaCMC/12-6-12/NaBz complex formation, soluble long and dense threadlike micelles, coacervate with a structure of the three-dimensional connected network by entanglement of threadlike micelles, and precipitate with a structure of mat by entanglement of threadlike micelles with increasing 12-6-12 concentration. The salt effect on NaCMC/12-6-12 complex formation is mainly explained as the result of the salt on the gemini surfactant 12-6-12. However, the presence of polymer significantly enlarges the limits of coacervation, especially at higher salt concentration.

Influence of Amine-Based Cationic Gemini Surfactants on Catalytic Activity of α-Chymotrypsin

The α-chymotrypsin activity was tested in aqueous media with the presence of novel cationic amine–based gemini surfactant, with different spacer chain lengths and head group size, and also compared with the cationic cetyltrimethylammonium bromide (CTAB) and cetyltriphenylphosphonium bromide (CTPB) surfactants and aqueous buffer only. The p-nitrophenyl acetate (PNPA) hydrolysis rate was monitored in the presence of the surfactant concentration at 30°C. Most of these gemini surfactants gave higher catalytic activity as compared to cationic CTAB and CTPB. The highest superactivity was measured in the presence of gemini 16-12-16, [dodecanediyl-1,12-bis(cetyldimethylammonium bromide)] surfactant at pH 7.5. The catalytic reaction follows the Michaelis–Menten mechanism. The catalytic rate constants, kcat, show the same profile that the catalytic affinity; KM being enhanced with increasing space chain length. The results are favorable for considering that the amine-based gemini surfactant influences more than both the aqueous and cationic micellar media.

Refolding of urea denatured cytochrome c: Role of hydrophobic tail of the cationic gemini surfactants

The refolding of urea denatured horse heart cytochrome c (h-cyt-c) under the influence of ester based cationic gemini surfactants [ethane-1, 2-diyl bis(N, N-dimethyl-N-alkylammoniumacetoxy) dichlorides] 16-E2-16, 14-E2-14 and 12-E2-12 (n-E2-n) was performed by using UV–visible, fluorescence and circular dichroism (CD) spectroscopic techniques. We found that n-E2-n geminis promote the formation of molten globule (MG) like state upon addition into the urea denatured h-cyt-c. The comparative study of refolding of denatured h-cyt-c with n-E2-n, cationic gemini surfactant show stabilization of MG-like state influenced by hydrophobic interactions. The formation of MG-like state from the unfolded protein confirms the presence of some regular structures induced by n-E2-n gemini surfactants. Thermodynamic parameters for refolding of h-cyt-c by n-E2-n were also measured and the m-values of all the refolded states of h-cyt-c by n-E2-n show marked difference. The higher m-values correspond to the larger hydrophobic chain length indicates that refolding ability of the n-E2-n depends on the alkyl chain length. The result is related to the stronger hydrophobic forces due to the presence of two head groups and two hydrophobic hydrocarbon tails. This study showed that these cationic gemini surfactants were efficiently utilized in the protein refolding studies.

Synthesis of Multibranched Gold Nanoechinus Using a Gemini Cationic Surfactant and Its Application for Surface Enhanced Raman Scattering.

High-yield multibranched Au nanoechinus possessing lengthy and dense branched nanorods on the surface were synthesized using a seed-mediated surfactant-directed approach in the presence of gemini cationic surfactant N,N,N'N'-tetramethyl-N,N'-ditetradecylethane-1,2-diaminium bromide (C14C2C14Br2), HAuCl4, AgNO3, and ascorbic acid. C14C2C14Br2 surfactant provides a versatile template in designing the unique morphology of Au nanoechinus with the assistance of AgNO3. UV-vis spectroscopic analysis proves that Au nanoechinus possess a unique intense broad localized surface plasmon resonance (LSPR) peak, which extends from 400 to 1700 nm in the NIR region making a highly potential platform for biomedical applications. Systematic time-dependent TEM, UV-vis-NIR, and XRD analysis were performed to monitor the morphological evolution of multibranched Au nanoechinus. It was found that the surface of branched nanorods of Au NE preferentially grew along (111) crystal planes. Furthermore, as-synthesized Au nanoechinus shows excellent SERS enhancement ability for dopamine inside HeLa cells.