Modification of graphene oxide by ATRP: A pH-responsive additive in membrane for separation of salts, dyes and heavy metals

Incorporation of hydrophilic multifunctional compounds in to the polymeric membrane's matrix is one of the useful methods for modification of mixed matrix membranes. Therefore, in this study, preparation and properties of polyethersulfone (PES) mixed matrix membranes with hydrolyzed polymethylmethacrylate (PMMA(hyd)) grafted on graphene oxide (GO-PMMA(hyd)) is investigated as an effective additive to improve permeability and antifouling properties. In this respect, grafting of PMMA(hyd) on the GO surface is done by atom transfer radical polymerization (ATRP) technique and confirm by FTIR, H NMR, EDAX and thermogravimetric analysis (TGA). During membrane formation, the membrane surface porosity improves and the hydrophilic GO-PMMA(hyd) nanoparticles tend to migrate toward the membrane top surfaces which confirms by FE-SEM cross-section images. Moreover, contact angle measurements show that the surface hydrophilicity enhanced after introducing GO-PMMA(hyd). More importantly, prepared nanocomposite membranes show excellent performance in the separation of salts, dyes and heavy metal ions. Furthermore, it can be expected that by creating acid groups on graphene oxide plates, prepared mixed matrix membranes were pH-sensitive, so this claim is examined and proved in membranes

Development of a New Biosensor by Adsorption of Creatinine Deiminase on Monolayers of Micro- and Nanoscale Zeolites

This work is dedicated to the development of creatinine-sensitive biosensor consisting of pH-sensitive field-effect transistor (pH-FET) and creatinine deiminase (CD) immobilized with various types of zeolites, in particular, silicalite, zeolite beta (BEA) and nanobeta, and BEA zeolites, modified with gold nanoparticles and ions. For comparison, the traditional method of CD immobilization in saturated glutaraldehyde (GA) vapor was used. To modify pH-FET with zeolites, a monolayer method of deposition was applied. All basic analytical characteristics of the developed biosensors were compared: linear range of creatinine determination, time of response and regeneration, minimum limit of detection, and response reproducibility within a single biosensor; the calibration curves were plotted. It is shown that the use of zeolites of different types as adsorbents in the development of creatinine-sensitive biosensors resulted in a decrease of time of response and regeneration, an increase in sensitivity of the bioselective element to creatinine, and improvement in reproducibility of preparation of various biosensors, as compared with the method of covalent cross-linking in GA vapor