Síntesis y caracterización de óxido de grafeno reducido funcionalizado con nanopartículas metálicas. Aplicación en el desarrollo de sensores amperométricos basados en materiales nanoestructurados

Abstract

The development of new (bio)sensors is a field in full development within the needs of Analytical Chemistry and society in general. The use of sensors is highly extended in people’s daily life. Different types of glucometers are available on the market, which can report the concentration of glucose in the patient’s blood in real time. Also, one can see today’s need to develop new diagnostic tests for diseases, such as that caused by the SARS-COVID-19 virus. Graphene has become a material of great interest among the scientific community, due to the unique electrical, thermal and mechanical properties that this material possesses with respect to other carbonaceous and 2D materials. Due to its exceptional characteristics and properties, the use of graphene as an alternative conductor material in the development of electrochemical transducers has become widespread and one of the main resources. Nanocomposites are a very interesting alternative in the development of amperometric sensors. Due, especially, to the capacity of integrating several materials with different characteristics in order to obtain a new material with very different physical, mechanical and electrical properties from the original materials that constitute it. The use of nanocomposites has a series of advantages over pure conductors. These advantages are, for example, versatility, durability, ease of surface regeneration and its ability to integrate other modifiers, qualities that provide added value to the developed devices. The electrochemical properties of nanocomposites are highly influenced by the nature of the conductive particles that form it as well as their amount and spatial distribution in the matrix of the nanocomposite. One of the most relevant characteristics of these materials is the similarity in their electrochemical behavior with respect to a microelectrode array. The presence of conductive particles, separated by non-conductive or insulating areas on the electrode surface, mimics the more or less ordered distribution of microelectrodes separated by an electrical insulator, forming the equivalent of a microelectrode array. The electro-analytical response of a microelectrode array depends mainly on the dimensions and separation between the conductive particles. For this reason, it is necessary to optimize the quantity of conductive material and its distribution to obtain the best analytical efficiency. In this context, the first stage of this Thesis is the synthesis of reduced graphene oxide (rGO) by Hummers’ method. This method allows obtaining rGO, from commercial graphite as a starting material, for the manufacture of nanocomposite electrodes based on rGO and an epoxy resin (EpoTek H77). Subsequently, a set of instrumental techniques have been implemented, which, applied in a strategic and systematic way, have allowed the characterization and optimization of the composition of the conductive material as well as the improvement of the electrochemical properties of the nanocomposite electrodes developed with different synthesized conductive materials. Once the properties of the electrochemical transducers were optimized, it was time to improve the analytical properties of these electrochemical sensors through the incorporation of different metallic nanoparticles (NPs) with the aim of introducing an electrocatalytic effect into the analytical device. This way a synthetic methodology was developed, allowing the incorporation ad hoc of different metal NPs (e.g. Au, Ag, Pd) on the rGO’s surface in a simple way and by means of green chemistry. Finally, a (bio)sensor has been developed using the enzyme glucose oxidase (GOD), based on a 2Au/3Pd-NP@rGO nanocomposite. Studying the catalytic effect that bimetallic Au and Pd NPs have upon H2O2. Finally, the effect of ascorbic acid’s presence in electroanalytical measurements (an interferent present in many biological samples) was studied.

Date of Award	27 Jan 2021
Original language	Spanish
Supervisor	Francisco Cespedes Mulero (Tutor)