Fawzi S. Kodeh

Nanostructured copper oxide-cotton fibers: synthesis, characterization, and applications

Copper oxide nanoparticles were prepared and subsequently deposited onto surface of the cotton fibers by ultrasonic irradiation. The structure and morphology of the coated and un-coated cottons were examined by X-ray diffraction and scanning electron microscopy/energy dispersive X-ray analysis. These methods revealed that of CuO nanoparticles are crystalline and corresponds to monoclinic phase, and that these nanoparticles are physically adsorbed onto the cotton fiber surface. They have an average crystallite size of 10 nm; the physical and chemical properties of the treated cotton fibers are markedly different from those of the untreated cotton fibers. The CuO-cotton fiber nanocomposites were tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures and showed a significant antimicrobial activity; whereas its analogous CuS-coated cotton material formed by the reaction CuO-coated cotton fibers with H2S showed no activity.

Behaviour of phenol red pH-sensors in the presence of different surfactants using the sol-gel process

Phenol red was immobilised into a polysiloxane matrix using a sol-gel process to form pH optical sensors. The sol-gel was obtained by hydrolysis of tetraethoxysilane (TEOS) in the presence of phenol red (PR) and the appropriate surfactant. Different surfactants, namely cetyltrimethylammonium bromide (CTAB), dodecyldimetyl amino-oxide (GLA) and Triton X-100 (TX-100), were employed. Interestingly, the use of surfactants significantly improved the mesostructure of the silica and increased the porosity of the system. The two response pH ranges were shifted to pH 0.0–3.0 and pH 10.5–1.5M [OH−] compared with those of the free PR (pH 0.0–3.0 and pH 6.5–9.5). It is found that the pH response and the pKa shift of the phenol red were dependent, not only on the silica matrix but also on the ionic properties of surfactants. In the case of ionic surfactants such as CTAB or GLA, there was further shift to more acidic and more basic pH, whereas in the case of non-ionic surfactants such as TX-100 no significant change of the pH curve was observed.

Sol–gel encapsulation of bromothymol blue pH indicator in presence of Gemini 12-2-12 surfactant

A sol–gel approach was used to encapsulate bromothymol blue (BTB) C27H28Br2O5S pH indicator into mesoporous silica material, in presence of ethanediyl-1,2-bis(dimethyldodecylammonium chloride) (Gemini 12-2-12) surfactant. An ordered mesoporous inorganic matrix including Gemini 12-2-12 and BTB was obtained. It is found that encapsulated BTB/Gemini 12-2-12 exhibit same behavior for pH change as that of the free BTB, which indicate that only physical interaction between BTB molecules and host mesoporous silica network are obtained. The addition of Gemini 12-2-12 surfactant has increased the porosity of the host silica material and increased its sensing capability. The presence of Gemini 12-2-12 surfactant has shifted pKa values of the system to more acidic in comparison with that of free BTB, BTB entrapped silica and BTB/CTAB entrapped silica.

Thin film optical BTB pH sensors using sol–gel method in presence of surfactants

Bromothymol blue (BTB) thin films were prepared by depositing a thin layer of a solution containing tetraorthosilicate and BTB pH indicator in the presence of surfactants, namely cetyltrimethylammonium bromide (C19H42BrN, CTAB) or dodecyldimethylamine oxide (C14H31NO, 69%), C16H35NO (11%), Genaminox LA onto a glass slide substrate. CTAB or GLA surfactants were used to improve the mesostructure of the host material and to increase its porosity. Optical BTB thin films were found to be sensitive against pH and behave as free BTB. This provides evidence for weak interactions between the BTB molecules and the host silica matrix. The effects of the sol mixture on the stability and reproducibility and the colorimetric response to solutions of different pH were examined and pKa values were determined. The BTB thin film sensors showed an advantage over the encapsulated monolithic sensors in which the thin film sensors exhibit a faster response time than the monolithic disks. These pH sensors showed reproducibility and high stability behavior.

Novel pH-responsive swing gate system for adsorption and controlled release of BTB and MG dyes using amine functionalized mesoporous SBA-15 silica

Abstract Adsorption of anionic bromothymol blue (BTB) and cationic malachite green (MG) dyes on mono-, di- and triamine/ammonium functionalized mesoporous SBA-15 silica was investigated. The adsorbents were prepared via a post-synthesis grafting method of SBA-15 material using 3-aminopropyltrimethoxysilane, [1-(2-aminoethyl)-3aminopropyl]trimethoxysilane and 1-[3-(trimethoxysilyl)-propyl]-diethylenetriamine, followed by acidification in HCl solution to convert the attached surface amine groups to positively charged ammonium moieties. The release of BTB and MG species from free amine or ammonium functionalized adsorbents was controlled by adjusting the pH of solution. This system is proposed to be used as delivery modulation design system in which an ionically controlled molecular gate is created by using free amine/ammonium functionalized mesoporous materials with pH-responsive groups at the pore outlets. Results showed that the functionalized amine/ammonium SBA-15 materials act as a swing gate system and allow controlled selective adsorption–release of BTB and MG adsorbents and resulted in clean separation between them.Graphical Abstract

Sol–gel entrapment of bromothymol blue (BTB) indicator in the presence of cationic 16E1Q and 16E1QS surfactants

Sol–gel entrapment method was used to entrap bromothymol blue (BTB) pH indicator into mesoporous silica materials in the presence of cationic surfactants: 2-(hexadecyloxy)-2-oxoethyl-N,N,N-triethyl ammonium iodide (16E1Q) and 2-(hexadecyloxy)-2-oxoethanaminium-p-toluene sulfonate (16E1QS). The use of this new family of surfactants has modified the morphology and porosity of silica host matrix for better sensing capability and for faster response toward pH change. The physical interactions between BTB molecules and host mesoporous silica network were based on the nature of the surfactant. The presence of surfactants has shifted pKa values of more basic in comparison with that of BTB-entrapped silica system.Graphical Abstract

Behavoir of Trapped Bromothymol Blue into Sol-Gel Matrix in Presence of CTAB

Encapsulation of bromothymol blue (BTB) into a polysiloxane network was prepared using sol-gel method without using a catalyst. The co-entrappment of the bromothymol blue (BTB) and surfactant cetyltrimethyl ammonium bromide (CTAB) was used to modify the properties of the sol-gel matrixes which may provide a highly porous materials and made the polysiloxane network an excellent host for sensing molecules. Monolithic disks of trapped BTB were obtained with no leaching. Polarized light microscopy shows that a almost unique particle sizes distributions were formed. The immobilized BTB shows a response for various pH solutions, the feature of absorption spectra of the immobilized BTB was almost the same as that of the solutions.