J. C. Encinas

Conductometric uric acid and urea biosensor prepared from electroconductive polyaniline–poly(n-butyl methacrylate) composites

Abstract Polyaniline–poly( n -butyl methacrylate) (PAn–PBMA) composite films were obtained by casting. The homogeneous films were prepared with poly(vinyl methyl ether) (PVME) and poly(vinyl ethyl ether) (PVEE) as dispersants, and the electric conductivity, mechanical properties and morphology were studied. The PAn integration to the composite is better when PVEE is used as dispersant, but the conductivity is higher when PVME is used. The composites with PVME were tested as chemical sensors for H 2 O 2 and NH 3 , showing good performance. These samples were also tested as biosensor for urea and uric acid using urease and uricase enzymes, respectively. The best results were as chemical sensor for H 2 O 2 , NH 3 , and as biosensors for serum urea determination.

Chemochromic properties of neutral polyaniline throughout cholesterol exposure

This paper presents a novel biosensing platform for cholesterol accomplished by the spin-coating deposition of neutral polyaniline on poly(methyl methacrylate) support and the subsequent covalent immobilization of cholesterol oxidase onto polyaniline surface. The polyaniline film entraps the enzyme and it also acts as an active layer for optical sensing of free cholesterol. The effects of immobilization process of the enzyme over the oxidation state of polyaniline backbone and the optimum pH and temperature conditions for immobilized cholesterol oxidase were studied. The sensibility of the system to cholesterol in concentrations equivalent to those present in human serum evidences its potentiality in an optical method simply based on chemochromic properties of polyaniline.

Selective adsorption of gold and silver in bromine solutions by acetate cellulose composite membranes coated with polyaniline or polypyrrole

This paper presents the selective adsorption of bromine-metallic complexes of Au and Ag on composite membranes, as well as the desorption process and redoping of the conducting polymers. The polyaniline (PANI) and polypyrrole (PPy) membranes exhibited relevant adsorption properties. 72% for gold and 98% for silver with PANI, 50% for gold and 97% for silver with PPy, in bromine complexes. The adsorption capabilities of the composite membranes were attributed to the ion exchange between the dopant and the AuBr4− or AgBr2− complexes. Both materials fitted to a Langmuir isotherm. PANI-based membranes reached 31.4% of gold and 54.4% of silver desorption whereas PPy-based membranes reached 54% of gold and 28.8% of silver. Redoping studies suggested the potential reuse of the PANI-based membranes at least for six cycles of the adsorption/desorption process. The preparation of cellulose acetate membranes modified with poly (acrylic acid) and triphenyl phosphate and coated with the conducting polymers, PANI or PPy was in accordance to our previously reported method. The composite membranes were characterized by FT-IR, scanning electron microscopy, electrical conductivity measurements, I–V, mechanical tests, contact angle measurements, XRD and energy disperse spectroscopy. The novelty of the present work is the combination of electroconductive polymers, for the recovery of metals, and bromide as a leachate, less harmful than the traditionally used leachers.