Versatility of Reverse Micelles: From Biomimetic Models to Nano (Bio)Sensor Design

This paper presents an overview of the principal structural and dynamics characteristics of reverse micelles (RMs) in order to highlight their structural flexibility and versatility, along with the possibility to modulate their parameters in a controlled manner. The multifunctionality in a large range of different scientific fields is exemplified in two distinct directions: a theoretical model for mimicry of the biological microenvironment and practical application in the field of nanotechnology and nano-based sensors. RMs represent a convenient experimental approach that limits the drawbacks of the conventionally biological studies in vitro, while the particular structure confers them the status of simplified mimics of cells by reproducing a complex supramolecular organization in an artificial system. The biological relevance of RMs is discussed in some particular cases referring to confinement and a crowded environment, as well as the molecular dynamics of water and a cell membrane structure. The use of RMs in a range of applications seems to be more promising due to their structural and compositional flexibility, high efficiency, and selectivity. Advances in nanotechnology are based on developing new methods of nanomaterial synthesis and deposition. This review highlights the advantages of using RMs in the synthesis of nanoparticles with specific properties and in nano (bio)sensor design.

Electrochemical sensor based on rhodium nanoparticles stabilized in zwitterionic surfactant for p-coumaric acid analysis

A new sensor was developed for the analysis of phenolic compounds by coating the surface of a glassy carbon electrode (GCE) with rhodium nanoparticles stabilized in 3-(1-tetradecyl-3-imidazolium) propanesulfonate (ImS3-14), a zwitterionic surfactant. The modifier was found to lower the electron transfer resistance by enhancing the electrical conductivity on the electrode surface. Some phenolic compounds were tested to determine the increase in the electroanalytical response when employing the proposed sensor in comparison to the bare GCE. p-Coumaric acid showed the greatest peak enlargement and, thus, it was selected as the target analyte. Chronocoulometry studies indicated that the increase in the peak is due to the adsorption of the p-coumaric acid on the sensor surface. The optimized analysis conditions were obtained in acetate buffer pH 4.0 employing differential pulse voltammetry, which provided a limit of detection of 472 nmol/L. The recoveries ranged from 98.3% to 104.4%, indicating satisfactory accuracy for the proposed method. The sensor exhibited good repeatability and reproducibility (both intraday and interday) and was applied successfully in the determination of p-coumaric acid in a cellulosic matrix.

Imidazolium-based zwitterionic surfactants: characterization of normal and reverse micelles and stabilization of nanoparticles

This paper presents the physicochemical properties of micellar aggregates formed from a series of zwitterionic surfactants of the type 3-(1-alkyl-3-imidazolio)propane-sulfonate (ImS3-n), with n = 10, 12, 14, and 16. The ImS3-n dipolar ionic surfactants represent a versatile class of dipolar ionic compounds, which form normal and reverse micelles. Furthermore, they are able to stabilize nanoparticles in water and in organic media. Aqueous solubility is too low at room temperature to allow characterization of micellar aggregates but increases with addition of salts, allowing determination of aggregation number and cmc. As expected, these parameters depend on the length of the alkyl chain, and cmc values follow Klevens equation. In the presence of NaClO4, all ImS3-n micelles become anionoid by incorporating ClO4(-) on the micellar interface. A special feature of these surfactants is the ability to form reverse micelles and solubilize copious amounts of saline solutions in chloroform. (1)H NMR and infrared spectroscopic evidence showed that the maximum water to surfactant molar ratio w0 achievable depends on the concentration and type of salt dissolved. Reverse micelles of the ImS3-n surfactants can be used to stabilize metallic nanoparticles, whose size may be tuned by the amount of water dissolved.

Preparation of a graphene-loaded carbon nanofiber composite with enhanced graphitization and conductivity for biosensing applications

G/CNF was prepared for the first time by a facile method and it was successfully applied in laccase based biosensor.