Second-Harmonic Generation Measurements of Electrostatic Biopolymer-Surfactant Coadsorption at the Water/1,2-Dichloroethane Interface
نویسندگان
چکیده
The electrostatic coadsorption of the synthetic polypeptide poly-L-glutamic acid (pGlu) and the cationic hemicyanine surfactant trans-4-[4-(dibutylamino)styryl]-1-methylpyridinium iodide (D-CH3) is observed at the water/1,2-dichloroethane (DCE) interface with the spectroscopic technique of optical second-harmonic generation (SHG). The adsorption isotherm of D-CH3 to the water/DCE interface is obtained with a combination of resonant surface SHG and interfacial tension measurements. In the presence of polyanionic pGlu in the aqueous phase at a pH of 8.5, the limiting surface coverage of the cationic surfactant is enhanced by a factor of 3.7. In contrast, no such enhancement is observed in the presence of pGlu for the adsorption of the neutral zwitterionic hemicyanine surfactant trans-4-[4-(dibutylamino)styryl]-1-(3-sulfopropyl)pyridinium hydroxide inner salt hydrate (D-(CH2)3-SO3) to the water/DCE interface. Additionally, no enhancement in surfactant adsorption is observed for D-CH3 when the pGlu in the aqueous phase is replaced with a solution of the monomer L-glutamic acid. These observations demonstrate that the coadsorption of pGlu and D-CH3 is a multipoint electrostatic adsorption interaction at the water/DCE interface.
منابع مشابه
Optical Second-harmonic Generation Measurements of Molecular Adsorption and Orientation at the LiquidlLiquid Electrochenical Interface
The surface-sensitive spectroscopic technique of optical second-harmonic generation (SHG) is applied to the in situ study of molecular adsorption at the interface between two immiscible electrolyte solutions (ITIES). The resonant SHG from molecules which exhibit a large non-linear optical response at a specific wavelength can be used to measure the relative surface coverage of surfactants at th...
متن کاملSecond harmonic generation measurements of molecular orientation and coadsorption at the interface between two immiscible electrolyte solutions
Resonant optical second harmonic generation (SHG) is obtained from monolayers of 4-n-octyloxybenzoic acid (OBA) and noctyl-4-hydroxybenzoate (OHB) adsorbed at the water/ 1,2dichloroethane interface. The polarization dependence of the SHG from pure monolayers of OBA and OHB indicates that the molecular axis of the OBA molecules is tilted 6” closer to the surface normal than that of the OHB molec...
متن کاملExamination of the Electrochemical Interface between Two Immiscible Electrolyte Solutions by Second Harmonic Generation
The potential-induced accumulation of electrolyte ions at the water/1,2-dichloroethane (DCE) electrochemical interface has been examined by total internal reflection second harmonic generation (TIR SHG). TIR SHG experiments provide the first direct optical measurements of the accumulation of the base electrolytes, tetraphenylarsonium (Ph4As) and tetraphenylborate (Ph4B), in the interfacial regi...
متن کامل2-Dimensional porphyrin self-assemblies at molecular interfaces.
The heterodimer formed by electrostatic association of zinc(II) meso-tetrakis(N-methylpyridyl)porphyrin (ZnTMPyP) and zinc(II) meso-tetrakis(p-sulfonatophenyl)porphyrin (ZnTPPS) exhibits a strong affinity for the interface between water and 1,2-dichloroethane (DCE). Surface tension measurements using the quasi-elastic light scattering (QELS) technique reveal that the heterodimer adsorption can ...
متن کاملSurface second harmonic generation from coumarin 343 dye-attached TiO2 nanoparticles at liquid–liquid interface
The nonlinear optical properties of coumarin 343 (C343) dye-attached TiO2 nanoparticles in the size range 5–8 nm adsorbed at the interface of water/1,2-dichloroethane have been studied by using the surface second harmonic generation technique. No second harmonic (SH) response was observed from the bare TiO2 nanoparticles adsorbed at the interface, however, a strong SH response was measured from...
متن کامل