title: Aggregation of Congo red with surfactants and Ag-nanoparticles in an aqueous solution.
abstract: Self aggregation, sorption, and interaction of Congo red, with cetyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS), Ag(+) ions and silver nanoparticles have been determined spectrophotometrically. Congo red self-aggregation was identified from UV-visible spectra due to the shrinkage in an absorption band at 495 nm. The shape of the absorbance spectrum changed entirely with increasing [Congo red] but wavelength maxima remain unchanged. The molar absorptivity was found to be 9804 mol(-1) dm(3) cm(-1) at 495 nm. Absorption spectra of Congo red with Ag(+) ions show an isosbestic point. The complex formation constant and difference in absorption coefficients were found to be 8.5 × 10(4) mol(-1) dm(3) and 11,764 mol(-1) dm(3) cm(-1), respectively. Silver nano-particles could not be used for the catalytic degradation of Congo red because it results in the formation of a strong complex with them. Sodium dodecylsulfate did not show any significant interaction with this dye. Congo red was also used as a probe to determine the critical micellar concentration of CTAB.
authors.affiliation: Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia.
authors.forename: Shaeel Ahmed
authors.initials: SA
authors.lastname: Al-Thabaiti
authors.affiliation: Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia.
authors.forename: Elham Shafik
authors.initials: ES
authors.lastname: Aazam
authors.affiliation: Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia. Electronic address: drkhanchem@yahoo.co.in.
authors.forename: Zaheer
authors.initials: Z
authors.lastname: Khan
authors.affiliation: Nanoscience Research Laboratory, Department of Chemistry, Jamia Millia Islamia (Central University), New Delhi 110025, India.
authors.forename: Ommer
authors.initials: O
authors.lastname: Bashir
keywords: Ag-nanoparticles; CTAB; Congo red; Shrinkage; Solubilization