Anionic Surfactant Sodium Dodecyl Sulfate Research Articles

Release mechanism of doxazosin from carrageenan matrix tablets: Effect of ionic strength and addition of sodium dodecyl sulphate

The polyelectrolyte matrix tablets loaded with an oppositely charged drug exhibit complex drug-release mechanisms. In this study, the release mechanism of a cationic drug doxazosin mesylate (DM) from matrix tablets based on an anionic polyelectrolyte λ-carrageenan (λ-CARR) is investigated. The drug release rates from λ-CARR matrices are correlated with binding results based on potentiometric measurements using the DM ion-sensitive membrane electrode and with molecular characteristics of the DM-λ-CARR-complex particles through hydrodynamic size measurements. Experiments are performed in solutions with different ionic strength and with the addition of an anionic surfactant sodium dodecyl sulphate (SDS). It is demonstrated that in addition to swelling and erosion of tablets, the release rates depend strongly on cooperative interactions between DM and λ-CARR. Addition of SDS at concentrations below its critical micelle concentration (CMC) slows down the DM release through hydrophobic binding of SDS to the DM-λ-CARR complex. On the contrary, at concentrations above the CMC SDS pulls DM from the complex by forming mixed micelles with it and thus accelerates the release. Results involving SDS show that the concentration of surfactants that are naturally present in gastrointestinal environment may have a great impact on the drug release process.

Interaction of Sodium Dodecyl Sulfate with Lipid Monolayer Studied by Sum-Frequency Generation Spectroscopy at Air–Water Interface

We employed vibrational sum-frequency generation (VSFG) spectroscopy to obtain molecular-level understanding of interaction of anionic surfactant sodium dodecyl sulfate (SDS), in low bulk concentration at the micromolar level, with lipid monolayer zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at the air–water interface. These results are different from those reported at higher bulk concentration of SDS at millimolar level. At very low concentration neither DPPC nor SDS produces any VSFG signal in the CH stretch region in the water subphase, but with the same concentration DPPC produces typical VSFG spectra at the SDS subphase due to interaction between these two molecules. The interaction leads to polar ordering of DPPC molecules with enhancement of VSFG intensity in the CH vibrational region of the hydrophobic tails. The interaction between the lipid and SDS molecules is influenced by concentrations of both lipid and SDS. Hydrophobic interactions between long alkyl chains of SDS and DPP...

Analysis of basic drugs by liquid chromatography with environmentally friendly mobile phases in pharmaceutical formulations

Basic drugs are positively charged in the usual working pH (2–8) in reversed-phase liquid chromatography. This gives rise to a strong association with the residual ionized silanols in conventional silica-based stationary phases, which is translated in poor peak shape and high consumption of organic solvent to get appropriate retention times. Micellar mobile phases containing surfactants give rise to modified stationary phases, where silanols are masked, improving the peak shape. However, mobile phases containing the anionic surfactant sodium dodecyl sulfate (SDS) require a small amount of organic solvent to conveniently decrease the retention of cationic analytes. An alternative is the use of mixed micellar mobile phases prepared with SDS and the more polar non-ionic surfactant Brij-35, which modulates the retention of basic drugs to practical analysis times, eliminating the need of organic solvent. Two simple chromatographic procedures for the control of the β-adrenoceptor antagonists atenolol, celiprolol, metoprolol, oxprenolol and propranolol in pharmaceutical formulations were developed and compared, using 0.15M SDS/15% 1-propanol and 0.15M SDS/0.05M Brij-35 at pH3 with UV detection. Both methods were validated according to the ICH guideline. Satisfactory recoveries were achieved, with intra- and inter-day relative standard deviations usually below 2% for both micellar modes. Sample preparation was simple and only required solubilization and filtration previously to injection.

Model studies on the interactions of a Cu(II)-quinone complex with surfactant micelles and DNA explore its induction of apoptosis in human MDA-MB-231 breast adenocarcinoma cells

The interactions of copper complex (CuQ2) of 1-amino-4-hydroxy-9,10-anthraquinone (QH) with calf thymus DNA, anionic surfactant sodium dodecyl sulfate (SDS), and cationic surfactant cetyltrimethylammonium bromide (CTAB) were investigated in an aqueous solution at physiological pH (7.4). Affinities of such molecule to DNA and surfactant micelles, a model for a biological membrane, are important in determining its biological action. Using different models, various binding parameters were evaluated in both of molecule–DNA interaction and molecule–surfactant interaction. The study showed that hydrophobic interaction plays a major role in the binding of CuQ2 to surfactant micelles. In addition, the hydrophobic interaction has an important role in the distribution of CuQ2 between micelle-water phases. Gibbs free energy for the binding and distribution of CuQ2 between the bulk aqueous medium and surfactant micelles were calculated. In order to correlate the physicochemical properties deciphered from the aforementioned studies with the biological property of the molecule, CuQ2 was treated with MDA-MB-231 breast adenocarcinoma cells where it was found that the molecule affects the viability of the cancer cells. Fluorescent staining of the treated cells with AO/EB and Hoechst indicated that the CuQ2 induces apoptosis, suggesting its use in the treatment of breast cancer.

Complexation of a Globular Protein, β-Lactoglobulin, with an Anionic Surfactant in Aqueous Solution.

The complexation of a globular protein, β-lactoglobulin (BLG), and an anionic surfactant sodium dodecyl sulfate (SDS) in aqueous media was investigated using capillary zone electrophoresis, electrophoretic, static, and dynamic light scattering, and small-angle X-ray scattering in a considerably high protein concentration range (0.27 mM < CP < 3 mM). On increasing the molar concentration CR of the surfactant, cooperative binding of SDS to BLG starts at CR/CP ≈ 1; the BLG-SDS complex consists mainly of the BLG dimer and approximately 20 SDS molecules, where BLG takes a compact conformation similar to that of the native BLG up to CR/CP ≈ 20. At CR/CP higher than 30, the BLG dimer in the BLG-SDS complex dissociates into a unimer, but the dissociated BLG unimer still takes a compact conformation at least at 30 < CR/CP < 65.

Study of the Removal of Aniline from Wastewater via MEUF Using Mixed Surfactants

In this paper, the anionic surfactant sodium dodecyl sulfate (SDS) and the bio-surfactant rhamnolipid are mixed to achieve micellar-enhanced ultrafiltration, and the associated aniline removal efficiency is investigated. The impacts of five factors, including the mixing ratio of the SDS concentration to the rhamnolipid concentration, the pH, the salinity, the operating pressure, and the aniline concentration in the feed solution, on the aniline rejection and the membrane permeation flux are explored. The aniline rejection mechanism of the rhamnolipid mixture surfactant is analyzed. This study shows that the effect of these factors on the aniline rejection is in the order of pH &gt; mixing ratio &gt; operating pressure &gt; aniline concentration &gt; salinity; the factors that affect the membrane permeation flux are in the order of mixing ratio &gt; operating pressure &gt; salinity &gt; pH &gt; aniline concentration. Under the optimal test conditions (i.e., SDS:rhamnolipid = 8:2, pH = 5, salinity = 250 mmol/L, operating pressure = 3.5 bar, aniline concentration = 1.5 mM), the verification test results showed an aniline rejection of 78.36%.

On the Morphology of the SDS Film on the Surface of Borosilicate Glass.

Surfactant films on solid surfaces have attracted much attention because of their scientific interest and applications, such as surface treatment agent, or for micro- or nano-scale templates for microfluidic devices. In this study, anionic surfactant sodium dodecyl sulfate (SDS) solutions with various charged inorganic salts was spread on a glass substrate and dried to form an SDS thin film. Atomic force microscopy (AFM) was employed to observe the micro-structure of the SDS thin film. The effects of inorganic salts on the morphology of the SDS film were observed and discussed. The results of experiments demonstrated that pure SDS film formed patterns of long, parallel, highly-ordered stripes. The existence of the inorganic salt disturbed the structure of the SDS film due to the interaction between the cationic ion and the anionic head groups of SDS. The divalent ion has greater electrostatic interaction with anionic head groups than that of the monovalent ion, and causes a gross change in the morphology of the SDS film. The height of the SDS bilayer measured was consistent with the theoretical value, and the addition of the large-sized monovalent ion would lead to lowering the height of the adsorbed structures.

Impact of the type of emulsifier on the physicochemical characteristics of the prepared fish oil-loaded microcapsules

Fish oil microcapsules were successfully prepared from fish oil-in-water emulsions using chitosan as shell material and anionic surfactants sodium dodecyl sulphate (SDS), sodium dodecylbenzenesulfonate (SDBS), sodium cholate (cholate), and sodium deoxycholate (DOC) as emulsifiers. The type of emulsifier influenced the physicochemical characteristics of the prepared microcapsules to different extents. The microcapsules formed with DOC showed the least mean effective diameter (MED) of 500 nm. Emulsion formed with DOC exhibited the smallest MED of 100 nm. The emulsions showed negative zeta potential values which became positive after encapsulation with chitosan. The surfactants showed little influence on thermal stability. Microcapsule suspensions showed creaming over storage. Fish oil at higher loading in SDS microcapsules showed higher primary and secondary oxidation. All microcapsules showed sustained release but the values varied depending upon the surfactants. The emulsion and microcapsules formed with DOC showed better morphology and stability despite its lower loading and encapsulation efficiency.

Spectroscopic and conductometric study of interaction of anionic surfactants with [Co(phen)3]F2·2H2O complex

A new complex [Co(phen)3]F2·2H2O has been synthesized and characterized by elemental analysis, FTIR studies, magnetic measurements, electronic absorption measurements and single crystal X-ray diffraction analysis. The crystals are triclinic in the P-1 space group, with a=11.9520(8), b=12.8152(9), c=15.1013(11)Å, α=98.175(2)°, β=91.601(2)°, γ=114.8700(10)°. The crystal structure displays OH⋯F and OH⋯O hydrogen-bond interactions. Solubilization of [Co(phen)3]F2·2H2O by anionic surfactants sodium dodecyl sulphate (SDS) and sodium stearate (SS), in aqueous solutions in the premicellar and micellar concentration ranges has been investigated by using UV–visible spectroscopy and electrical conductivity measurements. The equilibrium model was used to evaluate thermodynamic parameters of complex-surfactant interaction like standard entropy (ΔSm), free energy (ΔGm) and enthalpy (ΔHm) of micelle formation. The disruption of structured water in the near environment of hydrophobic groups of surfactants is responsible for the increase in critical micelle concentration (CMC) with the rise in temperature. The negative value of ∆Gm and ΔHm indicate that solubilization of complex in micelles of both surfactants was spontaneous, in addition to enthalpy and entropy driven. UV–visible spectroscopy uncovers the quantitative measure of interaction of complex with surfactant in terms of partition constant (Kx), binding coefficient (Kb), binding free energy (ΔGb) and free energy of partition (ΔGp). The results obtained suggested that the critical micelle concentration of both surfactants is increased due to the presence of complex in micellar medium. Complex exhibited significant radical scavenging potential against DPPH radical and hemolytic effect against RBCs. Further, the complex exhibited no substantial cytotoxic effect against 3T3 cell line.

Effect of poly (sodium 4-styrenesulfonate) on the ionization constants of acid-base indicator dyes in aqueous solutions

Presently, the acid-base equilibria of indicators fixed in surfactant micelles are described thoroughly. In contrast, analogous studies with polyelectrolytes are few in number. As a result, though the interactions of polyelectrolytes with dyes in aqueous solution have been studied for a long time, the research was mainly added up to metachromasy and solvatochromism. The properties of the polyion coils as media for the acid-base interactions of pH-indicators are less elucidated. The present article is aimed to fill this gap to a certain degree. A set of indicator dyes is examined via the spectrophotometric method in aqueous solutions of poly (sodium 4-styrenesulfonate), NaPSS, with molar weight of ≈70×103g mol−1. First, this colloidal system is characterized by the dynamic light scattering method. Then, we report the apparent ionization constants, Kaapp, of a series of dyes of different structure and charge types, neutral red, methyl yellow, rhodamine B, pseudoisocyanine, quinaldine red, and pinacyanol. The Kaapp values of the indicators are substantially influenced by polyelectrolyte concentration and the ionic strength of solutions. The selection of the appropriate polyelectrolyte : dye concentration ratio allows avoiding the interfering influence of the metachromasy of dyes. The shifts of pKaapp as compared with the values in water, pKaw, are different for the dyes studied, and qualitatively agree with those observed for the same compounds in micellar solutions of an anionic surfactant sodium dodecylsulfate, NaDS. The effects are, however, less expressed than in NaDS micelles. This is in line with (i) less negative zeta-potential of the NaPSS coils as compared with that of the NaDS micelles at the same ionic strength of the bulk phase and (ii) the lack of the hydrocarbon core in the case of the pseudophase of this polyelectrolyte. The study of salt effects, i.e., the dependence of pKaapp vs. the ionic strength allows estimating the degree of binding of Na+ ions, β, by the polyions. In accord with Manning’s theory, this parameter appeared to be constant and is within the range of 0.6≤ β≤0.8, similar to that in NaDS micelles. Additives of tetraalkylammonium salts display marked influence on both size distribution of the polyelectrolyte species and pKaapp values of indicators.

Denaturation of proteins by surfactants studied by the Taylor dispersion analysis.

We showed that the Taylor Dispersion Analysis (TDA) is a fast and easy to use method for the study of denaturation proteins. We applied TDA to study denaturation of β-lactoglobulin, transferrin, and human insulin by anionic surfactant sodium dodecyl sulfate (SDS). A series of measurements at constant protein concentration (for transferrin was 1.9 x 10−5 M, for β- lactoglobulin was 7.6 x 10−5 M, and for insulin was 1.2 x 10−4 M) and varying SDS concentrations were carried out in the phosphate-buffered saline (PBS). The structural changes were analyzed based on the diffusion coefficients of the complexes formed at various surfactant concentrations. The concentration of surfactant was varied in the range from 1.2 x 10−4 M to 8.7 x 10−2 M. We determined the minimum concentration of the surfactant necessary to change the native conformation of the proteins. The minimal concentration of SDS for β-lactoglobulin and transferrin was 4.3 x 10−4 M and for insulin 2.3 x 10−4 M. To evaluate the TDA as a novel method for studying denaturation of proteins we also applied other methods i.e. electronic circular dichroism (ECD) and dynamic light scattering (DLS) to study the same phenomenon. The results obtained using these methods were in agreement with the results from TDA.

Foams Stabilized by In Situ-Modified Nanoparticles and Anionic Surfactants for Enhanced Oil Recovery

Foams have been widely used in oilfields for effective profile control and displacement. However, foams stabilized by surfactants lack long-term stability, especially in an oil reservoir. Here, we have studied the in situ modification of positively charged AlOOH nanoparticles via the adsorption of the anionic surfactant sodium dodecyl sulfate (SDS) and the characterization of foam stabilized by AlOOH nanoparticles in synergy with SDS under different conditions. Changes in the zeta potential and adsorption isotherm of the AlOOH nanoparticles confirmed their modification. The most stable foam was obtained with an SDS/AlOOH concentration ratio of 5:1; further increases of the SDS concentration led to a decrease and subsequent increase in foam stability. The relationships between the zeta potential, three-phase contact angle, nanoparticle aggregate size, and foam stability were comprehensively analyzed, revealing that foam stability was affected by all of these factors. We concluded that nanoparticles with pa...

The effect of surfactants in the silsesquioxane solution for LbL films assembly

The interaction of surfactants and hydrophobic polymers in solution has attracted substantial interest due to the broad application in industry. In this study, the interactions of the nonionic surfactant polyethylene glycol-p-(1,1,3,3 tetramethylbutyl)-phenyl ether (Triton X) and anionic surfactant sodium dodecyl sulfate (SDS) with a cationic polymer 3-chloride-n-propylpyridinium silsesquioxane (SiPy+Cl−) and their effects on the layer-by-layer (LbL) film assembly with nickel tetrasulfonated phthalocyanine (NiTsPc) have been analyzed by surface tension, viscosity, and Brewster angle microscopy. As Triton X and SDS surfactants are inserted in the solution containing the polycation SiPy+Cl−, they are immediately incorporated in the hydrophobic nanodomains present in the silsesquioxane skeleton. The association between polyelectrolytes and oppositely charged surfactants starts at very low surfactant concentrations far below the critical micelle concentration, named critical aggregation concentration (cac), which was determined for both surfactants in the presence of SiPy+Cl− (cac Triton X = 2.4 × 10−6 and SDS = 8.2 × 10−7 mol L−1). The coexistence of mixed and pure micelles containing only Triton X and SDS also occurs in higher surfactant concentrations. The implication of these aggregates adsorption on the surface was analyzed in thin films by using the LbL technique. Multilayered films were obtained in presence of surfactants, (T-SiPy/NiTsPc) n or (S-SiPy/NiTsPc) n to compare with LbL films in absence of surfactant (SiPy/NiTsPc) n , and these films were characterized by UV–Vis, FTIR, and Raman spectroscopies to analyze the molecular interactions and to investigate the presence of specific interactions between the polyelectrolytes. The formation of LbL film in the architectures (T-SiPy/NiTsPc) n or (S-SiPy/NiTsPc) n is more efficient in relation to (SiPy/NiTsPc) n LbL films since the presence of the surfactants causes a greater amount of material to be deposited on each bilayer formed. The results of UV–Vis indicate that the film in the presence of SDS has a higher amount of material added to each bilayer. The electrochemical studies of (S-SiPy/NiTsPc)3 film show that the charge transfer resistance is lower than the one observed for the other architectures. Thus, the characteristic hopping electron effect of LbL film may be responsible for lower capacitance and lower resistance of the films. When the surfactant SDS is present, a higher oxidation peak current of dopamine is seen.

Refolding of SDS-Unfolded Proteins by Nonionic Surfactants

The strong and usually denaturing interaction between anionic surfactants (AS) and proteins/enzymes has both benefits and drawbacks: for example, it is put to good use in electrophoretic mass determinations but limits enzyme efficiency in detergent formulations. Therefore, studies of the interactions between proteins and AS as well as nonionic surfactants (NIS) are of both basic and applied relevance. The AS sodium dodecyl sulfate (SDS) denatures and unfolds globular proteins under most conditions. In contrast, NIS such as octaethylene glycol monododecyl ether (C12E8) and dodecyl maltoside (DDM) protect bovine serum albumin (BSA) from unfolding in SDS. Membrane proteins denatured in SDS can also be refolded by addition of NIS. Here, we investigate whether globular proteins unfolded by SDS can be refolded upon addition of C12E8 and DDM. Four proteins, BSA, α-lactalbumin (αLA), lysozyme, and β-lactoglobulin (βLG), were studied by small-angle x-ray scattering and both near- and far-UV circular dichroism. All proteins and their complexes with SDS were attempted to be refolded by the addition of C12E8, while DDM was additionally added to SDS-denatured αLA and βLG. Except for αLA, the proteins did not interact with NIS alone. For all proteins, the addition of NIS to the protein-SDS samples resulted in extraction of the SDS from the protein-SDS complexes and refolding of βLG, BSA, and lysozyme, while αLA changed to its NIS-bound state instead of the native state. We conclude that NIS competes with globular proteins for association with SDS, making it possible to release and refold SDS-denatured proteins by adding sufficient amounts of NIS, unless the protein also interacts with NIS alone.

Thermodynamic properties of ibuprofen sodium salt in aqueous/urea micellar solutions at 298.15 K

Thermodynamic, surface and micellar properties of anti-inflammatory drug sodium 2-(4-isobutylphenyl) propionate (sodium salt of ibuprofen (NaIBF)) in aqueous/urea solution were studied by surface tension measurements at 298.15 K in the presence of anionic surfactant sodium dodecylsulfate (SDS). Critical micelle concentration (cmc), surface tension at cmc (γcmc), maximum Gibbs surface excess (Γmax), minimum surface area per surfactant molecule at the air/water interface (A min) etc. were determined in pure water as well as in aqueous urea solution. The theories of Clint, Rosen and Rubingh have been applied to describe the interactions between these amphiphiles at the interface and in the micellar solution. Various thermodynamic parameters have been calculated and discussed in detail.

Study on thermally-induced aggregates transformation and its mechanism in cetyltrimethyl ammonium bromide/sodium dodecyl sulfate surfactants mixtures

Thermally-induced formation of wormlike micelles (WLMs) in mixed surfactant solutions is investigated. The mixtures are composed of cationic surfactant cetyltrimethyl ammonium bromide (CTAB) and anionic surfactant sodium dodecyl sulfate (SDS). The rheological characteristics, thermal curves and transmittance spectrum are obtained with Rheometer, differential scanning calorimeter (DSC) and TURBISCAN Lab stability analyzer, respectively. The Arrhenius equation is introduced to calculate the activation energy. Microscopic observation is captured with freeze-fracture transmission electron microscope (FF-TEM) at various temperatures. The results reveal that the zero-shear viscosity of the mixed solutions fluctuates at 20°C −50°C and a specific thermal-thickening phenomenon occurs in the aforementioned temperature range. When the temperature reaches 35°C, the rheological properties of the mixed solution behave distinctly compared with those beyond 35°C. There are two endothermic peaks in the DSC curve and a dramatic change in the transmittance spectrum. The FF-TEM microscopic images show that the bundled anisotropic aggregates convert into WLMs as the temperature increases from 20°C to 40°C. This study reveals that the transformation of aggregates is induced by temperature. Moreover, the WLMs form during the process of temperature elevation as is proved by the rheological behavior, FF-TEM microscopic images and the activation energy (236.5KJmol−1). The current study also suggests a simple approach to obtain the WLMs at accurate temperatures.

Removal of pyridine from its wastewater by using a novel foam fractionation column

Many of pyridine compounds are considered as typical hazardous refractory organics due to their acute toxic properties and teratogenic effects. Therefore, it is great significant to develop a separation technology with the characters of low energy consumption and environmental compatibility to efficiently remove pyridine from its wastewater. In this work, foam fractionation was used to remove pyridine from its wastewater and a novel foam fractionation column was designed for enhancing interfacial adsorption by vertical sieve tray and strengthening foam drainage by floating tongue type tray, in which bubble diameter was monitored for adjusting feeding flow rate and air flow rate in the continuous foam fractionation process. By comparing the foam properties and the adsorption properties of three anionic surfactants (sodium dodecyl sulfate, sodium alcohol ether sulfate and sodium alpha-olefin sulfonate), sodium dodecyl sulfate was chosen as the optimal collector to remove pyridine at pH 4.5. Under the optimal operating conditions, the enrichment ratio and removal percentage of pyridine could reach as high as 34.5 and 90.2%, simultaneously. Above results indicated that foam fractionation was a practicable technology to efficiently remove a hazardous material from its wastewater by designing an effective foam fractionation column.

Voltammetric determination of epinephrine and xanthine based on sodium dodecyl sulphate assisted tungsten trioxide nanoparticles

This work reports the voltammetric determination of epinephrine (EP) and xanthine (XA) using gamma irradiated tungsten trioxide (WO3) nanoparticles. WO3 NPs synthesized by anionic surfactant sodium dodecyl sulphate (SDS) assisted template method was subjected to gamma rays under different doses (0-150 kGy). The experimental results revealed that the 50 kGy irradiation on SDS-WO3 NPs led to significant changes in crystallite size and morphology which enriched its electrocatalytic activity greatly. The electrochemical behaviors of EP and XA at 50 kGy gamma irradiated SDS-WO3 modified glassy carbon electrodes (GCE) were studied by cyclic voltammetry and differential pulse voltammetry. The outcomes confirmed that the proposed electrode demonstrate excellent electrocatalytic activity towardsthe oxidation of EP and XA in phosphate buffer solution (PBS, pH 7.0). The fabricated electrode possess lowest detection limit of 1.8nM and 2.2nM for EP and XA respectively with the very wide dynamic linear range of 9nM to 1mM. Finally, the modified sensor was successfully implemented to detect EP and XA in the human serum samples with excellent selectivity, good stability and reproducibility.

Interaction of surfactants with block-copolymer systems in the presence of Hofmeister anions

The interactions of block copolymers poly (ethylene oxide butylene oxide), E58B7 and E58B11 with anionic surfactant sodium dodecyl sulfate and cationic surfactant cetyltrimethylammonium bromide were studied by using different techniques such as surface tension, conductivity, and dynamic light scattering. The effect of salts in the Hofmeister series on polymer–surfactant systems was also investigated. The interactions were found to be dependent on both surfactant and polymer concentrations. The results were utilized to compute different thermodynamic parameters including enthalpy of micellization (ΔHm), entropy of micellization (ΔSm), free energy of adsorption (ΔGads) and free energy of micellization (ΔGmic). For diblock-copolymer surfactant systems the negative value of (ΔGmic) shows that the process of micelle formation is thermodynamically favorable. The solubilization in surfactant micelles altered the physicochemical properties of the block copolymer. The value of critical aggregation concentration decreases with the addition of Hofmeister anions, and the decrease is more pronounced for sodium fluoride as compared to sodium iodide.

Design and synthesis of a Cu(II)-complex-based carbazole-hemicyanine hybrid for fluorescent sensing of H2S in SDS micellar solution

A novel fluorescent chemosensor HACBA with carbazole-hemicyanine fluorophore as signal reporter and N,N,N'-tri(2-pyridylmethyl)ethylenediamine (TPEA) as binding sites was designed and synthesized. Its assemblies with anionic surfactant sodium dodecyl sulfate (SDS) show improved fluorescence emission stability and enhanced fluorescence intensity. HACBA/SDS system can selectively recognize Cu2+, which led to a dramatic fluorescence quenching. The in situ resultant HACBA-Cu(II)/SDS ensemble functioned as a highly selective and sensitive sensor for H2S with a turn-on fluorescent response. Our results show that the “on-off-on” molecular switch occured through the reversible formation-dissociation reaction between HACBA-Cu(II) complex and HACBA/CuS in the SDS micellar solution, and at least 3 cycles of on-off-on switches were observed.