Gemini Surfactant-Induced Cysteine-Capped Copper Nanoclusters Self-Assembly with Enhanced Peroxidase-Like Activity and Colorimetric Glutathione Sensing.

We have prepared a novel assembly with copper nanoclusters (CuNCs) and imidazolium-based gemini surfactants (different chain lengths). These novel mimic enzymes formed through the assembly of nanocluster-gemini surfactants have been utilized in creating colorimetric sensors to detect biomolecules. Yet, understanding the method for detecting glutathione (GSH) and its sensing mechanism using this specific assembly-based colorimetric sensor poses a significant challenge. Because of the role of surface ligands, the complexes of cysteine-capped CuNCs (Cys-CuNCs) and gemini surfactants exhibit strong amphiphilicity, enabling them to self-assemble like a molecular amphiphile. We have investigated the kinetics and catalytic capabilities of this Cys-CuNCs@gemini surfactant assembly through peroxidase-like activity. Additionally, a sensitive and simple-to-use colorimetric sensing approach for glutathione (GSH) is also disclosed here, demonstrating a low limit of detection, by using this peroxidase-like activity of Cys-CuNCs@gemini surfactant assemblies. Thus, the remarkable advantages of the Cys-CuNCs@gemini surfactant nanozyme make it suitable for the precise colorimetric detection of GSH, demonstrating excellent sensitivity and reliable selectivity. Additionally, it performs well in detecting GSH in various soft drinks.

Study of the self-assembly of a gemini surfactant induced by anionic QDs in aqueous solution.

The interaction of anionic quantum dots (QDs) with a gemini surfactant (1,1'-(propane-1,3-diyl-2-ol)bis(3-hexadecyl-1H-imidazol-3-ium)) bromide [C16Im-3OH-ImC16]Br2 in water has been investigated, yielding a unique class of luminescent self-assemblies. Instead of engaging with the QDs directly, the dimeric surfactant self-associates into micelles first. After adding [C16Im-3OH-ImC16]Br2 to aqueous solutions containing QDs, two types of structural formations, supramolecular and vesicles, were confirmed. A variety of intermediary structures, including cylindrical and oligomers of vesicles are found to be present. Field-emission scanning electron microscopy (FESEM) and confocal laser scanning microscopy (CLSM) were used to investigate the luminescent and morphological properties of the self-assembled nanostructures in the first turbid (Ti) and second turbid (Tf) regions. FESEM images show discrete spherical vesicles in the mixture's Ti and Tf regions. The presence of self-assembled QDs in these spherical vesicles makes them naturally luminescent, according to CLSM data. Because the QDs are equally distributed in the micelles, their self-quenching is greatly reduced and their luminescence is effectively sustained. We have also demonstrated the successful encapsulation of dye rhodamine B (RhB) into these self-assembled vesicles using CLSM without any structural disturbance. The discovery of luminescent self-assembled vesicles from a QD-[C16Im-3OH-ImC16]Br2 combination might lead to new potential in controlled release drug delivery and sensing.

Synthesis, aggregation behavior and drug-binding interactions of fatty acid-imidazolium-based surface-active ionic liquids.

The renewable fatty acid-based surface-active ionic liquids (SAILs) containing ethyl-substituted imidazolium head groups were prepared and structurally analyzed by Fourier transform infrared spectroscopy (FTIR), 1HNMR and 13CNMR spectroscopy. The products were named as; 3-ethyl-1-(2-dodecanoyl oxy) ethylimidazolium bromide [C12Eeim]Br, 3-ethyl-1-(2-tetradecanoyl oxy) ethylimidazolium bromide [C14Eeim]Br and 3-ethyl-1-(2-hexadecanoyl oxy) ethylimidazolium bromide [C16Eeim]Br. The critical micelle concentration (cmc) values of the three SAILs have been evaluated using conductivity measurements, probe-less UV-visible spectroscopy and fluorescence spectroscopy. The obtained cmc values were compared with the earlier reported non-functionalized SAILs such as [Cnmim]Br and [Cneim]Br where n = 12, 14, 16. The values were found to be 3-9 times lower mainly due to the presence of ester chain and also ethyl substituted imidazole ring. Thermodynamic parameters were evaluated by conductivity data at three different temperatures. Further, the aggregation behavior of SAILs with anesthetic drug, lidocaine hydrochloride (LC) has been studied using fluorescence. The fluorescence and UV-visible studies showed strong synergistic interactions operating between SAILs and drug molecules involving H bonding and cation-π interactions. The interactions grew stronger with the elongation of SAIL-chain length (12-16C). Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements suggested the formation of vesicles in SAIL-LC mixtures. These studies may thus offer an effective candidate which would serve as vectors for drug molecules in terms of their enhanced solubilization, permeability and target-specific delivery.

Effect of various additives on the performance of a newly developed PVC based potentiometric sensor for anionic surfactants.

A new poly(vinyl chloride) PVC membrane electrode to determine monomer concentrations of dodecylbenzenesulphonate ions (DBS(-)) based on a neutral ion-pair carrier complex of dodecyltrimethylammonium-dodecylbenzenesulphonate (DTA(+)-DBS(-)), is reported here. The electrode exhibits a slope of 51.25 mV per decade for DBS(-) ions. The DBS(-) ion selective electrode (ISE) can determine monomer units down to concentrations as low as 3.32x10(-4) M. The effect of three kinds of additives, i.e. alcohols, glycols and triblock polymers on the performance of the surfactant selective electrode is studied systematically. The effect of foreign anions along with primary ions on the performance of ion-selective electrode is investigated in terms of potentiometric selectivity coefficients, which were determined using the fixed interference method (FIM) at 1.0x10(-2) M concentration of foreign anions. The sensor responds well to the surfactant ions in the presence of additives at lower concentration. The Gibbs free energy of micelle formation (DeltaG(m)) of sodium dodecylbenzenesulphonate (SDBS) in the presence of various additives is calculated and found to vary differently with respect to the increase in the amount of additives. The sensor worked in the acidic pH range with a short response time of 30 s. The lifetime of the sensor is more than three months. The sensor was further used to determine the amount of DBS(-) in local detergents. This method of determining anionic surfactants was found to be quite accurate when compared with classical methods.

Investigations on mixed micelles of binary mixtures of zwitterionic surfactants and triblock polymers: a cyclic voltammetric study.

Cyclic voltammetry has been employed to investigate the mixed micellar behavior of the binary mixtures of different zwitterionic surfactants such as 3-(N,N-dimethylhexadecylammonio)propane sulfonate (HPS), 3-(N,N-dimethyltetradecylammonio)propane sulfonate (TPS) and 3-(N,N-dimethyldodecylammonio)propane sulfonate (DPS) with three triblock polymers (L64, F127 and P65) by using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as an electroactive probe at 25 degrees C. Critical micellar concentration (cmc) has been determined from the plots of variation in peak current (i(p)) versus the total concentration of surfactant/triblock polymer. Diffusion coefficient of the electroactive species has also been reported. The regular solution theory approximation has been used to determine various micellar parameters of ideal systems. The variation in micellar mole fraction (X(1)) of the zwitterionic surfactant supports the formation of mixed micelles, which are rich in triblock polymer component in the surfactant rich region of the mixture and vice versa. The regular solution interaction parameter (beta) suggests the formation of mixed micelles due to the synergistic interactions in case of HPS/TPS/DPS+F127/P65 systems and gets affected by EO/PO ratio of triblock polymers.

Mixed micelle behavior of Pluronic L64 and Triton X-100 with conventional and dimeric cationic surfactants.

The mixed micellar properties of a triblock copolymer, Pluronic L64, (EO)13(PO)30(EO)13, and a nonionic surfactant, Triton X-100, in aqueous solution with conventional alkyl ammonium bromides and their dimeric homologues were investigated with the help of fluorescence and cloud point measurements. The composition of mixed micelles and the interaction parameter, beta, evaluated from the critical micelle concentration (cmc) data for different mixtures using Rubingh's and Motomura's theories are discussed. It has been observed that the mixed micelle formation between monomeric/dimeric alkyl ammonium bromides and L64 was due to synergistic interactions which increase with the increase in hydrophobicity of the cationic component. On the other hand, synergistic mixing was observed in the mixed micelles of Triton X-100 and monomeric cationic surfactants, the magnitude of which decreases slightly with the increase in hydrophobicity of the cationic component. Antagonistic interactions were observed in the case of Triton X-100 and dimeric cationic surfactants.