Elektrochemia: wybrane zagadnienia z ćwiczeniami

W ostatnim ćwierćwieczu nastąpił bardzo szybki rozwój elektrochemii. Nowoczesne elektrochemiczne źródła energii, nowe materiały, polimery przewodzące, nanomateriały, sensory i biosensory, rozwój technik pomiarowych, miniaturyzacja sprzętu – to wszystko prowadzi do coraz szerszego zastosowania technologii związanych z elektrochemią we wszelkich dziedzinach życia i nauki. Mamy nadzieję, że książka, którą oddajemy w ręce czytelników, stanie się dla nich przewodnikiem po przedstawionych zagadnieniach współczesnej elektrochemii. Z jednej strony chcemy przybliżyć teoretyczne podstawy wybranych tematów, teorii elektrochemicznych i metod pomiarowych, a z drugiej – pragniemy zaprezentować zbiór instrukcji do ćwiczeń eksperymentalnych wykonywanych w ramach laboratorium z elektrochemii

The role of tannic acid and sodium citrate in the synthesis of silver nanoparticles

We describe herein the significance of a sodium citrate and tannic acid mixture in the synthesis of spherical silver nanoparticles (AgNPs). Monodisperse AgNPs were synthesized via reduction of silver nitrate using a mixture of two chemical agents: sodium citrate and tannic acid. The shape, size and size distribution of silver particles were determined by UV–Vis spectroscopy, dynamic light scattering (DLS) and scanning transmission electron microscopy (STEM). Special attention is given to understanding and experimentally confirming the exact role of the reagents (sodium citrate and tannic acid present in the reaction mixture) in AgNP synthesis. The oxidation and reduction potentials of silver, tannic acid and sodium citrate in their mixtures were determined using cyclic voltammetry. Possible structures of tannic acid and its adducts with citric acid were investigated in aqueous solution by performing computer simulations in conjunction with the semi-empirical PM7 method. The lowest energy structures found from the preliminary conformational search are shown, and the strength of the interaction between the two molecules was calculated. The compounds present on the surface of the AgNPs were identified using FT-IR spectroscopy, and the results are compared with the IR spectrum of tannic acid theoretically calculated using PM6 and PM7 methods. The obtained results clearly indicate that the combined use of sodium citrate and tannic acid produces monodisperse spherical AgNPs, as it allows control of the nucleation, growth and stabilization of the synthesis process.This work was supported by the Polish Ministry of Science and Higher Education within Research Grant No. NN507 350435 and by the National Science Centre Poland Grant No. 2014/13/B/NZ5/01356

Applicability of electrodes modified with composite layers of conducting polymers in electro- and bioelectroanalysis

Obtaining modified electrodes is a response of electrochemistry to continuous development in areas such as technology, electronics, medicine, biology and many others. Modifying layers allow scientists to build electrodes with required properties such as for example: selectivity, stability, precision, durability, range of potentials etc. The aim of the studies was to modify the surface of gold and platinum with the layer of poly(3,4-ethylenedioxythiophene) (PEDOT) and polyaniline (PANI) doped with various organic acids and their salts. Additives such as p–toluenesulfonic acid (PTSA), dodecylbenzene-sulfonic acid (DBSA), poly(4-styrenesulfonic acid) (PSSH) and poly(4-lithium styrenesulfonic acid) (PSSLi) were used. The main application of these electrodes was the determination of ascorbic acid, uric acid and catecholamines (dopamine, epinephrine). Another modification covered the preparation of PEDOT/polyacrylic acid (PAA)/PSSLi layer with available free carboxyl groups and afterwards the immobilization of glucose oxidase via covalent bond through N-(3- dimethylaminopropyl)-N′-ethylcarbodiimide (WSC). The purpose of the research on selected modifications was to find electrodes that could be applied in electroanalysis as sensors to determine chosen biologically active compounds. Low capacity current, wide range of potentials, the ability to work in the broadest pH range, especially physiological pH was required. The third modification gave rise to the honeycomb structure with the increased area of electrode surface and the use of PEDOT/PAA/PSSLi allows us to immobilize enzyme