Ferrocenyl Surfactant Research Articles

Stimuli‐Responsive Nanoplatforms: ZIF‐8‐Decorated Ferrocenyl Surfactant‐Based Vesicles for Synergistic Therapeutic Applications

AbstractOne of the most important issues in the design and preparation of drug delivery systems in the recent years is versatility which includes providing synergistic therapeutic effects and sustainability. This study uses a redox‐active ferrocenyl surfactant (FcN+(CH2CH3)3(CH2)10CH3, Fc(C11) where Fc is ferrocene) and pH responsive Zeolitic Imidazolate Framework‐8 (ZIF‐8) structures to form multifunctional assemblies (Fc(C11)‐AOT/Rhb@ZIF‐8/PDA) that can be used in several application including the drug delivery. The vesicles prepared using AOT‐FC(C11) constitute the core of the structure. Since the location of the ferrocene group in the molecule structure, which is next to head group, the surface of the vesicles is decorated with the ferrocene group which can act as a Fenton reaction catalyst. The polydopamine (PDA) covered ZIF‐8 are used to decorate the surface of the vesicles, creating a truly remarkable structure. The porous structure of ZIF‐8 as well as the core of the vesicles can accommodate drug molecules. With the added NIR‐responsive character upon PDA coating, this assembled structure can be used for phototermal therapy applications. The properties of this designed multifunctional and multi‐responsive system are studied at different pH and under NIR‐laser irradiation and show that it has potential to display a triple chemodynamic/ photothermal/ chemotherapeutic effect.

Fe-CP-based Catalytic Oxidation and Dissipative Self-Assembly of a Ferrocenyl Surfactant Applied in DNA Capture and Release

Fe-CP-based Catalytic Oxidation and Dissipative Self-Assembly of a Ferrocenyl Surfactant Applied in DNA Capture and Release

Investigation on pH and redox-trigged emulsions stabilized by ferrocenyl surfactants in combination with Al2O3 nanoparticles and their application for enhanced oil recovery

Pickering emulsions are regarded as promising chemical flooding agents to control profile in enhanced oil recovery (EOR). Stimuli responsive Pickering emulsions are introduced to simplify the process of subsequent demulsification. In the present work, we construct pH and redox-triggered emulsions stabilized by oxidized 1,1′-ferrocenedicarboxylic acid-(N,N-dimethyldodecylamine)2 (FDA-(DMDA)2-Ox) and Al2O3 nanoparticles. Stable emulsions with low water separation rate (18.5 %) after 12-day storage can be obtained by combining a low concentration of FDA-(DMDA)2-Ox (< 0.07 wt%) and Al2O3 nanoparticles. The emulsions can undergo the conversion of emulsion type (from oil-in-dispersion emulsions to oil-in-water Pickering emulsions) triggered by pH (surface charge switchability of Al2O3 nanoparticles) and emulsification/demulsification switchable behaviors triggered by redox reaction (redox response of FDA-(DMDA)2-Ox). The switch mechanism is revealed via the measurements of optical micrographs, zeta potential, cyclic voltammetry curves, and interfacial tension. Micromodel tests display that both oil-in-dispersion emulsions and oil-in-water Pickering emulsions can improve the displacement efficiency and enhance the sweep efficiency respectively to greatly enhance oil recovery. The pH and redox responsive flooding fluid display promising adaptability to complicated reservoir conditions and convenient implement for subsequent demulsification, transportation and refining

Investigation on novel redox-responsive ferrocenyl surfactants with reversible interfacial behavior and their recycling application for enhanced oil recovery

Stimuli responsive surfactants with reversible properties may effectively solve the problems of traditional surfactants (the switching of interfacial activity and the demulsification difficulty of emulsions) in enhanced oil recovery (EOR). In the present study, we fabricate brand-new redox-responsive double-tailed ferrocenyl surfactants 1,1′-ferrocenedicarboxylic acid-(N,N-dimethyldodecylamine)2 (FDA-(DMDA)2) via the dynamic supramolecular assembly. The reversible redox-responsive interfacial behaviors of ferrocenyl surfactants are estimated by measuring the interfacial tension reduction capacity, emulsifying performance, and wettability reversal ability. Compared with oxidized single-tailed ferrocenyl surfactant (FA-DMDA-Ox), oxidized double-tailed ferrocenyl surfactant (FDA-(DMDA)2-Ox) displays higher interfacial activity, which can be accurately switched by redox trigger. Cyclic micromodel flooding tests show that the FDA-(DMDA)2-Ox can in-situ emulsify the kerosene in pore media, and the addition of Na2SO3 to the produced fluid can achieve the recycle of the surfactants. Oil displacement tests demonstrate that the developed double-tailed ferrocenyl surfactants possess the potential in EOR and recycling.

DNA-involved thermotropic liquid crystals from catanionic vesicles

Thermotropic liquid crystals (TLCs) have created unpredictable applications ranging from sensor to electronic devices. DNA can interact with positively charged cationic and anionic (catanionic) vesicles by electrostatic interaction to form DNA-based TLCs. In the present work, the polarizing optical microscopy (POM) images clearly demonstrate the formation of DNA-involved liquid crystals, we explore the general role of DNA-involved TLC formation and the regulating factors of properties of DNA-based TLCs. We verify the effect of the chain lengths of surfactants and DNA on the formation and properties of TLCs. We found that DNA-involved TLCs constructed by the different surfactants with same chain length present the excellent properties. The position of functional group of ferrocenyl surfactants greatly affects the formation of TLCs. The bulky group closing to the headgroup of surfactant and the strong electrostatic interaction between positively charged catanionic vesicles and DNA affect the formation of TLCs. Furthermore, we found that the shorter DNA strand length, the more consistent fit better with the vesicles to enhance the thermal stability of DNA-based TLCs. The influence factors of the formation of DNA-based TLCs were explored and the importance of interactions to the architecture of DNA-based TLCs also was underscored. Our results may direct the design and synthesis of functional DNA-based TLCs and lay the foundation of applications in the field of electrochemistry and flexible electronic devices.

Amphiphilic conjugates of ferrocene with amino acids and peptides: Design, synthesis, and studies on their aggregation behavior.

A new class of ferrocenyl surfactants based on covalent linkage between amino acids or peptides and ferrocene was designed. Accordingly, five ferrocenyl amphiphiles, FcS1-5, were synthesized, and their aggregation behaviors in aqueous solutions were studied. Compared to the other surfactants containing ferrocenyl units, FcS have a relatively smaller size and low molecular weight and are easy to synthesize. The influences of the number of carboxylic acid head groups and the number of Fc group in the hydrophobic tail, on the stability and aggregation behavior of these amphiphiles in aqueous medium, were explored to deduce the structure property relationships. A combination of fluorescence and dynamic light scattering techniques was used to elucidate the behavior of these molecules. A good agreement between the results obtained using different techniques was observed.

The fabrication of supramolecular assembly with quadruple switchable fluorescence by ionic self-assembly strategy

The supramolecular assembly with quadruple fluorescence switching behavior was fabricated by the complexation of cationic ferrocenyl surfactant, 16-alkyl (ferrocenyl-methyl) ammonium bromide (Fc16AB) and anionic dye molecule, Orange G (OG) via ionic self-assembly (ISA) strategy. The obtained micromaterials exhibited different morphologies (including rod-like fiber, spindle micelle and fiber bundle) and significant switchable fluorescence behavior triggered by the addition of Ce(SO4)2 and the formation of β-CD inclusion, which corresponded to “off” and “on” state of fluorescence behavior respectively. The mechanisms of fluorescence quenching and aggregation-induced emission enhancement caused by each modulation were discussed in detail. The assembly with quadruple switchable fluorescence will be meaningful in the application of multifunctional photoelectric devices.

The construction and modulation of photoelectric functional hierarchical materials based on ionic self-assembly

The photoelectric functional hierarchical materials have been successfully prepared by the simple ionic self-assembly (ISA) strategy from the cationic ferrocenyl surfactant, 16-alkyl (ferrocenyl-methyl)ammonium bromide (Fc16AB) and the anionic alizarin red (AR). The obtained complexes exhibited multiple stimuli-responsive switching behaviour triggered by β-cyclodextrin (β-CD) inclusion, redox species, and pH. The switching mechanism corresponding to each stimulus was studied in detail. Moreover, the fluorescent intensity of binary complexes could be modulated by the concentration of Fc16AB and redox of ferrocene part. The fluorescence switching mechanism upon redox stimulus was studied in detail. Both the complexes fabrication and transition mechanisms were found to be controlled by the inclusion equilibrium and the cooperative binding of noncovalent interactions, including the electrostatic interactions, π-π stacking, and amphiphilic hydrophobic association. This work provides a deep understanding of electro-photo molecular switching device.

Redox-controlled reversible micelles transition and lyotropic liquid-crystalline behavior of novel polymerizable ferrocenyl surfactants

A novel photopolymerizable surfactant with ferrocenyl group, (11-ferrocenylundecyl) (ethyl methacrylate) dimethylammonium bromide (I+), was synthesized through the reaction of 11-bromoundecyl ferrocene and N,N-(dimethylamino) ethyl methacrylate. Based on the results of voltammetric cycle, the small potential difference ΔE was 72 mV, which indicates that the I+ has good redox reversibility. The critical micellar concentration (CMC) values were about 0.5 and 22.7 mM for I+ in the reduction (CMCred) and oxidation state (CMCox) and it could aggregate and disaggregate by using redox reaction and photopolymerization when its concentrations was between their CMCred and CMCox values. The lyotropic liquid-crystalline properties of I+ in water were investigated by X-ray diffraction (XRD) and plarized optical microscope (POM). The results indicate when the concentration of the I+ solution over 40 wt %, an ordered lamellar liquid crystal structure was formed. With increasing concentration, the nanoscopic long-range order improved. Moreover, the lyotropic liquid-crystalline properties of I+ could also be controlled by using redox reaction and photopolymerization. In a word, the novel polymerizable ferrocenyl surfactants are good environmental responsive materials and can potentially act as the drug carrier and the scavenger for removing dissolved organic impurities in water.

Study of new ferrocene-based thioureas as potential nonionic surfactants

Three new thiourea based ferrocenyl surfactants i.e. 1-(decanoyl)-3-(4-ferrocenylphenyl) thiourea (DP), 1-(decanoyl)-3-(4-ferrocenyl-2-methylbenzyl) thiourea (DMth), 1-(decanoyl)-3-(3-ferrocenylphenyl) thiourea (DM) have been successfully synthesized and well characterized by various analytical techniques, such as FT-IR, 1H and 13C NMR, AAS and elemental analysis. Furthermore, the single crystal XRD analysis was done for DP. To evaluate their amphiphilic nature, their CMC was determined through UV–visible spectroscopy that varies between 0.05 mM and 0.5 mM. The DP compound possesses lower CMC, whereas DM has considerably higher CMC value. Cyclic voltammetric technique was used to determine their redox behavior around CMC as well as their redox potentials, which follow the same trend as that of CMC. The DFT calculated energies of HOMO and LUMO orbitals correlate well with the experimentally determined redox potentials.

Alternating Current Cloud Point Extraction on a Microfluidic Chip: the Use of Ferrocenyl Surfactants.

Alternating current cloud point extraction (ACPE) is a preconcentration technique that can be employed in the analysis of membrane proteins on a microfluidic chip. However, the selectivity of ACPE relies on the hydrophobicity of the analytes. In this study, 11-ferrocenyltrimethylundecylammonium bromide (FTMA) was utilized to introduce electrostatic interaction as part of the ACPE technique. The use of ACPE with oxidized FTMA resulted in efficient concentration of fluorescently labeled anionic membrane proteins. We expect the approach outlined in this report to be useful in the preconcentration technique of microchip electrophoresis.

Voltage-responsive reversible self-assembly and controlled drug release of ferrocene-containing polymeric superamphiphiles.

A new type of voltage-responsive comb-like superamphiphilic block polymer PEG113-b-PAA30/FTMA was prepared by the electrostatic interactions of an ionic ferrocenyl surfactant (FTMA) and an oppositely charged double-hydrophilic block polyelectrolyte poly-(ethylene glycol)-b-poly(acrylic acid) (PEG113-b-PAA30) in aqueous solution. An in situ electrochemical redox system was designed to research its electrochemical activity in aqueous solution. The polymeric superamphiphile PEG113-b-PAA30/FTMA could reversibly aggregate to form spherical micelles of 20-30 nm diameter in aqueous solution, and also disaggregate into irregular fragments by an electrochemical redox reaction when its concentration is in the range of the critical aggregation concentration (cacred) of the reduction state to its cacox of the oxidation state. Interestingly, above cacox, the superamphiphile can aggregate into spherical micelles of 20-30 nm diameter, which can be transformed into larger spherical micelles of 40-120 nm diameter after electrochemical oxidation, and reversibly recover initial sizes after electrochemical reduction. Moreover, this reversible self-assembly process can be electrochemically controlled just by changing its electrochemical redox extent without adding any other chemical reagent. Further, rhodamine 6G (R6G)-loaded polymeric superamphiphile aggregates have been successfully used for the voltage-controlled release of loaded molecules based on their voltage-responsive self-assembly, and the release rate of R6G could be mediated by changing electrochemical redox potentials and the concentrations of polymeric superamphiphiles. Our observations witness a new strategy to construct a voltage-responsive reversible self-assembly system.

Control of Dual Stimuli-Responsive Vesicle Formation in Aqueous Solutions of Single-Tailed Ferrocenyl Surfactant by Varying pH and Redox Conditions

This paper reports a method to control the formation and disruption of vesicles from a novel single-tailed surfactant (11-ferrocenylundecylammonium bromide, 11-FAB), which contains two stimuli-responsive groups corresponding to pH variation and redox reaction conditions, by external stimuli. Although 11-FAB is a single-tailed surfactant, pure 11-FAB spontaneously forms vesicles in water. Microscopic observations of 2.5 mM aqueous solutions of pure 11-FAB (pH = 5.2) show that a number of 11-FAB vesicles are giant, with diameters of 10-30 μm. The disruption of vesicles is observed in aqueous 11-FAB solutions under basic conditions. The vesicles are then reformed under acidic conditions. Reduced 11-FAB also forms large vesicles in electrolyte solutions. These vesicles are disrupted by electrochemical oxidation and reformed by subsequent chemical reduction. This reversible disruption and reformation of vesicles is attributed to the drastic change in the molecular structure of 11-FAB. To our knowledge, this is the first report of control over the formation and disruption of vesicles using two stimuli responses.

Mesomorphous Structure and Electrochemical Behavior of Polyelectrolyte-Ferrocenyl Surfactant Complexes

Redox-active polyelectrolyte-surfactant complexes (PSC) were prepared via the ionic self-assembly of sodium polyacrylate (PAAS) and ferrocenyl surfactant, n-alkyl (ferrocenylmethyl)ammonium bromide (Fcn, n = 8, 12, 16, where n is the carbon number of the alkyl chain), in solution. The obtained PAAS-Fcn complex exhibited crystalline and lamellar mesomorphous structure. Moreover, the ferrocenyl moieties formed H-aggregation in the solid complex as known from the blue shift in the ultraviolet-visible spectrum. Cyclic voltammogram (CV) measurements indicated that the reversibility of the electrode process became worse when the surfactant tail length increases because of the more ordered packing in the complex film formed by longer surfactant tails. The present results demonstrate that the electrochemical activity of the redox-active polyacrylate-ferrocenyl surfactant complex can be easily tuned by changing the surfactant tail length. Our work provides a simple and facile approach to the preparation of redox-active polymers with ordered mesomorphous structure by the ionic self-assembly.

Novel redox-active ionic thermotropic liquid crystalline complexes of polyelectrolyte and ferrocenyl surfactants

Abstract Redox-active polyelectrolyte–surfactant complexes (PSC) were prepared via the ionic self-assembly of sodium poly(styrenesulfonate) (PSS) and ferrocenyl surfactant, (11-ferrocenylundecyl)trimethylammonium bromide (FTMA) in aqueous solution. The PSS–FTMA complex exhibited an ordered interdigitated monolayer mesomorphous structure with the long period of d = 3.13 nm, and was in the ionic thermotropic liquid crystal SmA state at room temperature. Interestingly, in the solid complex, the ferrocenyl moieties formed H-aggregation showing an increase in the π–π* energy transfer of cyclopentadienes in the ferrocene moieties as known from the blue-shift in the UV spectrum. The complexes showed higher thermal stability compared with their components due to the ionic interaction. The PSS–FTMA film had a good redox reversibility, which promised to be used in electrochemical sensors.

Reversibly enhanced aqueous solubilization of volatile organic compounds using a redox-reversible surfactant

Surfactant-enhanced remediation (SER) is an effective method for the removal of volatile organic compounds (VOCs) from contaminated soils and groundwater. To reuse the surfactant the VOCs must be separated from the surfactant solutions. The water solubility of VOCs can be enhanced using reversible surfactants with a redox-acive group, (ferrocenylmethyl)dodecyldimethylammonium bromide (Fcl2) and (ferrocenylmethyl)tetradecanedimethylammonium bromide (Fcl4), above and below their critical micelle concentrations (CMC) under reducing (I +) and oxidative (I 2+) conditions. The CMC values of Fcl2 and Fcl4 in I + are 0.94 and 0.56 mmol/L and the solubilization of toluene by Fcl2 and Fcl4 in I + for toluene is higher than the solubilization achieved with sodium dodecyl sulfate, cetyltrimethylammonium bromide and Trition X-114. The solubilization capacity of the ferrocenyl surfactants for each tested VOCs ranked as follows: ethylbenzene > toluene > benzene. The solubilities of VOCs by reversible surfactant in I + were 30% higher than those in I 2+ at comparable surfactant concentrations. The effects of Fcl4 concentrations on VOCs removal efficiency were as follows: benzene > toluene > ethylbenzene. However, an improved removal efficiency was achieved at low ferrocenyl surfactant concentrations. Furthermore, the reversible surfactant could be recycled through chemical approaches to remove organic pollutants, which could significantly reduce the operating costs of SER technology.

Ferrocene‐Based Cationic Surfactants: Surface and Antimicrobial Properties

AbstractA novel series of ferrocenyl surfactants was synthesized by the reaction of ferrocene disulfonic acid with different primary and tertiary fatty amines to produce the corresponding ammonium salts Fc[SO3−+NH3(CH2)nCH3]2, where n = 9, 11, or 15 and Fc[SO3− +NH(CH3)2(CH2)nCH3]2, where n = 7 or 11, respectively, and where Fc = ferrocene. Chemical structures were confirmed by microelemental analysis, FTIR, and 1H NMR spectroscopy. The critical micelle concentration of each prepared surfactant was determined using equilibrium surface tension. Furthermore, air/water interface parameters including effectiveness (πCMC), efficiency (Pc20), maximum surface excess (Гmax), and minimum surface area (Amin) were determined at 30, 40, and 50 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) for both micellization and adsorption processes were recorded. The new synthesized surfactants were screened as antimicrobial agents against different bacterial and fungal organisms.

Ionic Self-Assembled Redox-Active Polyelectrolyte−Ferrocenyl Surfactant Complexes: Mesomorphous Structure and Electrochemical Behavior

Redox-active polyelectrolyte−surfactant complexes (PSC) were prepared via the ionic self-assembly of sodium poly(styrenesulfonate) (PSS) and ferrocenyl surfactant, n-alkyl (ferrocenylmethyl)ammonium bromide (Fcn, n = 8, 12, 16, where n is the carbon number of the alkyl chain), in solution. The PSS−Fcn complex exhibited an ordered lamellar mesomorphous structure with the long period of d = 2.49, 2.94, and 3.74 nm for PSS−Fc8, PSS−Fc12, and PSS−Fc16, respectively. With increasing the length of surfactant alkyl chain, the stacking order was improved. Interestingly, in the solid complex, the ferrocenyl moieties formed H-aggregation showing an increase in the π−π* energy transfer of cyclopentadienes in the ferrocene moieties as known from the blue shift in the UV spectrum. These complexes showed higher thermal stability compared with their components due to the ionic interaction. Cyclic voltammogram (CV) measurements indicated that the electrode process of these redox-active complex films was diffusion-control...

Role of Desorption Kinetics in Determining Marangoni Flows Generated by Using Electrochemical Methods and Redox-Active Surfactants

We report quantitative measurements of Marangoni flows generated at the surfaces of aqueous solutions by using water-soluble redox-active surfactants in combination with electrochemical methods. These measurements are interpreted within the framework of a simple model that is based on lubrication theory and the proposition that the kinetics of the desorption of redox-active surfactants from the surfaces of aqueous solutions plays a central role in determining the strength of the Marangoni flow. The model predicts that the leading edge velocity of the Marangoni flow will decay exponentially with time and that the rate constant for the decay of the velocity can yield an estimate of the surfactant desorption rate constant. Good agreement between theory and experiments was found. By interpreting experimental measurements of electrochemically generated Marangoni flows within the framework of the model, we conclude that the desorption rate constant of the redox-active surfactant Fc(CH(2))(11)-N(+)(CH(3))(3)Br(-), where Fc is ferrocene, is 0.07 s(-)(1). We also conclude that the ionic strength of the aqueous solution has little effect on the desorption rate constant of the ferrocenyl surfactant.

Use of Ferrocenyl Surfactants of Varying Chain Lengths To Study Electron Transfer Reactions in Native Montmorillonite Clay

A series of ferrocenyl surfactants was tested as model compounds to study electron transfer reactions involving structural Fe(III) in clay minerals. The surfactants contain trimethylammonium headgroups, ferrocene tail groups, and intervening hydrocarbon chain lengths of one, six, or 11 carbons. Two factors considered to be decisive for electron transfer were addressed: (1) physical access of the surfactant ferrocene to the reactive sites through hexagonal holes in the clay lattice by X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) and (2) thermodynamic favorability of the overall oxidation/reduction reaction based on experimentally determined oxidation/reduction potentials. In suspensions of clay with the longer chain surfactants, (ferrocenylhexyl)trimethylammonim (FHTMA+) and (ferrocenylundecyl)trimethylammonium (FUTMA+), where electron transfer may be expected to be favored by both factors, physical accessibility, and thermodynamic favorability, ferroecene oxidation was observed by diffuse reflectance infrared spectroscopy (DRIFT), ultraviolet-visible spectroscopy (UV-vis), and visual color changes. In contrast, the shorter chain length surfactant, (ferrocenylmethyl)trimethylammonium (FMTMA+), did not participate in electron transfer with the clay, as substantiated by UV-vis and no visible color changes. Rigid conformation and/or higher oxidation/reduction potential than clay Fe can accountforthe lack of reaction. The utility and limitations of using these surfactants as model compounds is discussed.