Sandra Hernandez-Aldave

The effect of a polybenzimidazolium anion exchange polymer on improving sensitivity and selectivity toward the electrochemical detection of Δ⁹-tetrahydrocannabinol (Δ⁹-THC) has been investigated.

Oxygen depolarised cathode technology in support of achieving CO₂ gas diffusion electrodes industrial performance.

We describe a fast and reliable procedure for the efficient extraction of nitrites in cured meat using microwave-assisted heat and report their in situ determination via voltammetry using an anion-exchanger ionene, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), and nitrogen-doped graphite nanoplatelets (NGNPs). Cyclic voltammetry and chronoamperometry were utilized to evaluate the concentration of the redox mediator within the film and apparent diffusion coefficient. To investigate the suitability of the composite material for sensing applications, HMT-PMBI/NGNPs were tested for their detection of nitrite in bacon samples without the need of any pretreatments or dilutions. HMT-PMBI/NGNP coated electrodes showed enhanced sensitivity in the detection of nitrite ions in bacon with a limit of detection (LoD) of 0.64 µM, sensitivity 0.52 µA µM⁻¹ cm⁻², and operating in a linear range between 1–300 μM. The results highlight that the determination of nitrites in cured meat using microwave extraction is in good agreement with standard procedures such as the ISO 2918 and the AOAC International 973.31 methods.

The utilization of carbon dioxide is a major incentive for the growing field of carbon capture. Carbon dioxide could be an abundant building block to generate higher-value chemical products. Herein, we fabricated a porous copper electrode capable of catalyzing the reduction of carbon dioxide into higher-value products, such as ethylene, ethanol and propanol. We investigated the formation of the foams under different conditions, not only analyzing their morphological and crystal structure, but also documenting their performance as a catalyst. In particular, we studied the response of the foams to CO₂ electrolysis, including the effect of urea as a potential additive to enhance CO₂ catalysis. Before electrolysis, the pristine and urea-modified foam copper electrodes consisted of a mixture of cuboctahedra and dendrites. After 35 min of electrolysis, the cuboctahedra and dendrites underwent structural rearrangement affecting catalysis performance. We found that alterations in the morphology, crystallinity and surface composition of the catalyst were conducive to the deactivation of the copper foams.

Electrocatalysis plays a prominent role in the development of carbon dioxide utilisation technologies. Many new and improved CO₂ conversion catalysts have been developed in recent years, progressively achieving better performance. However, within this flourishing field, a disconnect in catalyst performance evaluation has emerged as the Achilles heel of CO₂ electrolysis. Too often, catalysts are assessed in electrochemical settings that are far removed from industrially relevant operational conditions, where CO₂ mass transport limitations should be minimised. To overcome this issue, gas diffusion electrodes and gas-fed electrolysers need to be developed and applied, presenting new challenges and opportunities to the CO₂ electrolysis community. In this review, we introduce the reader to the fundamentals of gas diffusion electrodes and gas-fed electrolysers, highlighting their advantages and disadvantages. We discuss in detail the design of gas diffusion electrodes and their operation within gas-fed electrolysers in both flow-through and flow-by configurations. Then, we correlate the structure and composition of gas diffusion electrodes to the operational performance of electrolysers, indicating options and prospects for improvement. Overall, this study will equip the reader with the fundamental understanding required to enhance and optimise CO₂ catalysis beyond the laboratory scale.

We report for the first time a procedure in which Nafion/Graphite nanoplatelets (GNPs) thin films are fabricated using a modified layer-by-layer (LbL) method. The method consists of dipping a substrate (quartz and/or glassy carbon electrodes) into a composite solution made of Nafion and GNPs dissolved together in ethanol, followed by washing steps in water. This procedure allowed the fabrication of multilayer films of (Nafion/GNPs)_n by means of hydrogen bonding and hydrophobic‒hydrophobic interactions between Nafion, GNPs, and the corresponding solid substrate. The average thickness of each layer evaluated using profilometer corresponds to ca. 50 nm. The as-prepared Nafion/GNPs LbL films were characterized using various spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), FTIR, and optical microscopy. This characterization highlights the presence of oxygen functionalities that support a mechanism of self-assembly via hydrogen bonding interactions, along with hydrophobic interactions between the carbon groups of GNPs and the Teflon-like (carbon‒fluorine backbone) of Nafion. We showed that Nafion/GNPs LbL films can be deposited onto glassy carbon electrodes and utilized for the voltammetric detection of caffeine in beverages. The results showed that Nafion/GNPs LbL films can achieve a limit of detection for caffeine (LoD) of 0.032 μM and linear range between 20‒250 μM using differential pulse voltammetry, whereas, using cyclic voltammetry LoD and linear range were found to be 24 μM and 50‒5000 μM, respectively. Voltammetric detection of caffeine in beverages showed good agreement between the values found experimentally and those reported by the beverage producers. The values found are also in agreement with those obtained using a standard spectrophotometric method. The proposed method is appealing because it allows the fabrication of Nafion/GNPs thin films in a simple fashion using a single-step procedure, rather than using composite solutions with opposite electrostatic charge, and also allows the detection of caffeine in beverages without any pre-treatment or dilution of the real samples. The proposed method is characterized by a fast response time without apparent interference, and the results were competitive with those obtained with other materials reported in the literature.

Ionomers have attracted considerable interest in electroanalysis due to the possibility of fabricating electrode coatings capable of preconcentrating sub-micromolar concentrations of cations or anions of analytical relevance. In this work, we describe the electroanalytical performances of an ionomer (TPQPCl)/graphite nanoplatelets composite material towards the development of an amperometric sensor for detection of ascorbic acid. Graphite nanoplatelets at different concentrations were dispersed in ethanolic solutions containing TPQPCl. The as-prepared TPQPCl/graphite nanoplatelet-coated electrodes were characterised using Fe(CN)₆ ^4−/3− as an anionic redox probe. The results evidence the good preconcentration capability of the positively charged TPQPCl towards the incorporation of negatively charged species. By tuning the ionomer/graphite nanoplatelets ratio, it is possible to detect simultaneously ascorbic acid even in the presence of dopamine as an interference species. The TPQPCl/graphite nanoplatelet-coated electrodes were able to detect ascorbic acid in the linear range of 5–10 000 μM with a limit of detection calculated as 4.8 μM using linear sweep voltammetry. Finally, the TPQPCl/graphite nanoplatelet-coated electrodes were tested towards detection of ascorbic acid in vitamin C tablets and orange juice without any sample pretreatment.

Phosphorene is a new two-dimensional material which is commonly prepared by exfoliation from black phosphorus bulk crystals that historically have been synthesized from white phosphorus under high-pressure conditions. The few layers of phosphorene have a direct band gap in the range of 0.3–2 eV and high mobility at room temperature comparable to epitaxial graphene. These characteristics can be used for the design of high speed digital circuits, radio frequency circuits, flexible and printed systems, and optoelectronic devices. In this work, we synthesized black phosphorus from red phosphorus, which is a safer solid precursor, using sonochemistry. Furthermore, via a variety of microscopy and spectroscopy techniques, we report characterization results of the sonochemically synthesized black phosphorus in addition to the commercial black phosphorus. Finally, we describe the air stability of black phosphors and the crystalline structure of the synthesized material. This is the first result of sonochemical or solution-based synthesis of black phosphorus based on readily available low-cost red phosphorus. This solution-based synthesis of black phosphorus is suitable for printable applications of nanomaterial.