A graphite-polyurethane composite electrode (GPUE) was modified by electrodeposition of copper nanoparticles (CuNP) followed by electrochemical treatment in NaOH (GPUE-CuNP), in order to prepare an amperometric sensor for the determination of cysteine (Cys). Cyclic votammograms of Cys solutions at GPUE-CuNP allowed the description of a sequence of electrochemical reactions involving Cys oxidation and Cu/Cu+ equilibrium, generating a stable Cys-Cu+ complex. The presence of these nanoparticles was confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) data. Hence, the developed device was then used as a Cys amperometric flow detector in a wall-jet system, after evaluation of flow injection parameters in an undescribed approach. In this system, a limit of detection (LOD) of 4.24 µmol L-1 was obtained with an analytical frequency of 36 determinations h-1. Intra-day and inter-day reproducibility and repeatability of the modified surface was evaluated. Then the GPUE-CuNP performance was investigated in the determination of Cys content in food supplements. Interference tests were carried out with pyridoxine, ascorbic acid, tryptophan and SO4 2- ions. The main interference was attributed to the interaction of some of these substances with copper oxides.

This study aimed to synthesize a composite material composed of bio-based, porous carbon matrix and Cu nanoparticles through a simple, low-cost, and environmentally friendly method. Concentrated Kraft black liquor was used as a carbon precursor, and Cu nanoparticles were homogeneously deposited on the carbon matrix using electrochemical deposition. The textural properties determined using N2 isotherms indicated increased surface area of a carbon matrix with a micro-mesoporous structure. Voltammetric tests demonstrated that the composite exhibited catalytic properties for electrochemical CO2 reduction. Compared to the bio-based, porous carbon sample (C matrix), the bio-based carbon electrode electrochemically decorated with Cu nanoparticles (C–Cu composite) exhibited increased current values of approximately 2.4 times, a potential shift of approximately 90 mV, and an onset potential of −1.02 V, under CO2 saturation.

A novel electrochemical sensor based on a glassy carbon electrode, modified with reduced graphene oxide and copper nanoparticles (GC/rGO-CuNPs), was developed for the determination of glyphosate herbicide (GLY) by differential pulse voltammetry (DPV). The proposed material was synthesised by a chemical method and characterised by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Voltammetric tests showed that the anodic peak at 30 mV, due to the Cu0 to Cu2+ oxidation process, decreased linearly with small additions of GLY; this inhibition was used to quantify the pesticide content in water by DPV. The GC/rGO-CuNPs electrode was evaluated and optimised for the determination of GLY in tap water samples without any pretreatment, achieving a linear response in the range of 0.1 to 1.1 µmol L−1 with a detection limit of 0.19 µmol L−1 (R2 = 0.9996). This study provides a new application for graphene-based sensors and a promising alternative for GLY analysis.

The fabrics with copper or copper oxide deposition are of considerable interest because of exceptional antibacterial properties, which are useable in medical, textiles, and hygiene applications. Unfortunately, the conventional techniques take long pro-cessing time, complex equipment, and combination of several processing steps (nano-particles synthesis and their deposition on fabrics). In this novel study, cathodic cage plasma deposition assisted with copper cathodic cage is used for the synthesis of the copper oxide on polyester and polyamide fabrics. For the enhancement of synthesis efficiency, the effect of cathodic cage lid thickness is also investigated. The samples are assessed by using scanning electron microscopy, elemental dispersive spectros-copy, and X‐ray photoelectron spectroscopy. It is found that using cathodic cage plasma deposition, fabrics can be successfully synthesized by the copper oxide with comparatively small treatment time, cost‐effectively, and environmentally friendly. Interestingly, cathodic cage plasma treatment is already proved to be working effec- tively on industrial scale; thus, it is predicted to be of noteworthy importance for fab- rics processing on large‐scale garments manufacturing and hospitals.

According to the International Diabetes Federation (IDF), in 2021 approximately 537 million adults (20 to 79 years) suffered from diabetes, which corresponds to a total of 10.5 % of the world’s adult population, and its prevalence is predicted to rise dramatically in the following years. Since glucose sensors constitute an effective approach for diabetes management, by providing precise information about glucose levels, the glucose sensor market has experienced enormous growth in the last few years. However, due to the high cost of the commercially available glucose detection solutions and since the rise in the number of diabetic patients has been more pronounced in low and middle-income countries, there is a high demand for low-cost glucose monitoring systems. In order to address the lack of inexpensive glucose sensors issue, this thesis aims to meet the presented necessity in three strands: the development of a glucose sensor based on copper nanoparticles (CuNPs) and Laser-Induced Graphene (LIG), fabricated on paper substrate. Firstly, the LIG technique offers a rapid and simple method for the production of graphitized material, which is an extremely conductive composite and valuable for the sensing field, without the need for expensive and complex fabrication techniques. Moreover, it allows the LIG production on paper, which is a more sustainable, flexible, economic and easily accessible alternative than other commonly used substrates. For the non-enzymatic glucose detection, a cheap copper precursor was selected for the laser-induced CuNPs formation, presenting highly catalytic activity towards the glucose oxidation. Thus, CuNPs and LIG composites were simultaneously synthesized in one fabrication step, allowing for a large-scale sensor production. LIG was fabricated with a sheet resistance value as low as 14.8 Ω sq−1. The sensor showed good glucose sensing performance (267 μA mM−1 cm−2 sensitivity, 11 μM detection limit, and high selectivity and reproducibility) with a linear range within the glucose concentration range detected in sweat (20 μM - 1.79 mM), opening the possibility of integrating this method into a wearable and non-invasive glucose monitoring system.