Highly activated screen-printed carbon electrodes by electrochemical treatment with hydrogen peroxide

An easy effective method for the activation of commercial screen-printed carbon electrodes (SPCEs) using H2O2 is presented to enhance sensing performances of carbon ink. Electrochemical activation consists of 25 repetitive voltammetric cycles at 10 mV s−1 using 10 mM H2O2 in phosphate buffer (pH 7). This treatment allowed us to reach a sensitivity of 0.24 ± 0.01 μA μM−1 cm−2 for the electroanalysis of H2O2, which is 140-fold higher than that of untreated SPCEs and 6-fold more than screen-printed platinum electrodes (SPPtEs). Electrode surface properties were characterized by SEM, EIS and XPS. The results revealed atomic level changes at the electrode surface, with the introduction of new carbon‑oxygen groups being responsible for improved electro-transfer properties and sensitivity. Our method was compared with other previously described ones. The methodology is promising for the activation of commercial carbon inks-based electrodes for sensor applications.This work was funded by the Spanish Ministry of Economy and Competitiveness (MINECO, http://www.mineco.gob.es/portal/site/mineco/idi), Projects No. BFU2016-75609-P (cofunded with FEDER funds, EU) and CTQ2016-76231-C2-2-R. BGM is a post-doctoral research fellow of the Youth Employment Initiative (JCCM, Spain, cofounded with ESF funds, EU)

Electrochemical performance of activated screen printed carbon electrodes for hydrogen peroxide and phenol derivatives sensing

Screen-printed carbon electrodes (SPCEs) are widely used for the electroanalysis of a plethora of organic and inorganic compounds. These devices offer unique properties to address electroanalytical chemistry challenges and can successfully compete in numerous aspects with conventional carbon-based electrodes. However, heterogeneous kinetics on SPCEs surfaces is comparatively sluggish, which is why the electrochemical activation of inks is sometimes required to improve electron transfer rates and to enhance sensing performance. In this work, SPCEs were subjected to different electrochemical activation methods and the response to H2O2 electroanalysis was used as a testing probe. Changes in topology, surface chemistry and electrochemical behavior to H2O2 oxidation were performed by SEM, XPS, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The combination of electrochemical activation methods using H2SO4 and H2O2 proved particularly effective. A reduction in charge transfer resistance, together with functionalization with some carbon‑oxygen groups on carbon ink surfaces, were likely responsible for such electrochemical improvement. The use of a two-step protocol with 0.5 M H2SO4 and 10 mM H2O2 under potential cycling conditions was the most effective activation procedure investigated herein, and gave rise to 518-fold higher sensitivity than that obtained for the untreated SPCEs upon H2O2 electrooxidation. The electrochemical behavior of acetaminophen, hydroquinone and dopamine is also shown, as a proof of concept upon the optimum activated SPCEs.This work was funded by the Spanish Ministry of Economy and Competitiveness (MINECO, http://www.mineco.gob.es/portal/site/mineco/idi), Projects No. BFU2016-75609-P (AEI/FEDER, UE) and CTQ2016-76231-C2-2-R, and by the Junta de Comunidades de Castilla-La Mancha (Spain), Project No. SBPLY/17/180501/000276/2 (cofunded with FEDER funds, EU). BGM is a post-doctoral research fellow of the Youth Employment Initiative (JCCM, Spain, cofunded with ESF funds, EU)

Glucose Biosensor Based on Disposable Activated Carbon Electrodes Modified with Platinum Nanoparticles Electrodeposited on Poly(Azure A)

Herein, a novel electrochemical glucose biosensor based on glucose oxidase (GOx) immobilized on a surface containing platinum nanoparticles (PtNPs) electrodeposited on poly(Azure A) (PAA) previously electropolymerized on activated screen-printed carbon electrodes (GOx-PtNPs-PAA-aSPCEs) is reported. The resulting electrochemical biosensor was validated towards glucose oxidation in real samples and further electrochemical measurement associated with the generated H2O2. The electrochemical biosensor showed an excellent sensitivity (42.7 μA mM−1 cm−2), limit of detection (7.6 μM), linear range (20 μM–2.3 mM), and good selectivity towards glucose determination. Furthermore, and most importantly, the detection of glucose was performed at a low potential (0.2 V vs. Ag). The high performance of the electrochemical biosensor was explained through surface exploration using field emission SEM, XPS, and impedance measurements. The electrochemical biosensor was successfully applied to glucose quantification in several real samples (commercial juices and a plant cell culture medium), exhibiting a high accuracy when compared with a classical spectrophotometric method. This electrochemical biosensor can be easily prepared and opens up a good alternative in the development of new sensitive glucose sensors.This work was funded by the Spanish Ministry of Economy and Competitiveness (MINECO, http://www.mineco.gob.es/portal/site/mineco/idi), projects Nos. BFU2016-75609-P (AEI/FEDER, UE) and CTQ2016-76231-C2-2-R; the Spanish Ministry of Science, Innovation, and Universities, project No. PID2019-106468RB-I00; and by the Junta de Comunidades de Castilla-La Mancha (Spain), project No. SBPLY/17/180501/000276/2 (cofunded with FEDER funds, EU)

Design and Characterization of Effective Ag, Pt and AgPt Nanoparticles to H2O2 Electrosensing from Scrapped Printed Electrodes

The use of disposable screen-printed electrodes (SPEs) has extraordinarily grown in the last years. In this paper, conductive inks from scrapped SPEs were removed by acid leaching, providing high value feedstocks suitable for the electrochemical deposition of Ag, Pt and Ag core-Pt shell-like bimetallic (AgPt) nanoparticles, onto screen-printed carbon electrodes (ML@SPCEs, M = Ag, Pt or AgPt, L = metal nanoparticles from leaching solutions). ML@SPCEs were characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The results were compared to those obtained when metal nanoparticles were synthesised using standard solutions of metal salts (MS@SPCEs). Both ML@SPCEs and MS@SPCEs exhibited similar cyclic voltammetric patterns referred to the electrochemical stripping of silver or the adsorption/desorption of hydrogen/anions in the case of platinum, proving leaching solutions extremely effective for the electrodeposition of metallic nanoparticles. The use of both ML@SPCEs and MS@SPCEs proved effective in enhancing the sensitivity for the detection of H2O2 in phosphate buffer solutions (pH = 7). The AgPtL@SPCE was used as proof of concept for the validation of an amperometric sensor for the determination of H2O2 within laundry boosters and antiseptic samples. The electrochemical sensor gave good agreement with the results obtained by a spectrophotometric method with H2O2 recoveries between 100.6% and 106.4%.This work was funded by the Spanish Ministry of Economy and Competitiveness (MINECO, http://www.mineco.gob.es/portal/site/mineco/idi), Projects No. BFU2016-75609-P (AEI/FEDER, EU) and CTQ2016-76231-C2-2-R, and by the Junta de Comunidades de Castilla-La Mancha (Spain), Project No. SBPLY/17/180501/000276/2 (cofunded with FEDER funds, EU). B.G–M is a post-doctoral research fellow of the Youth Employment Initiative (JCCM, Spain, cofunded with ESF funds, EU)

The role of recent (1985-2014) patterns of land abandonment and environmental factors in the establishment and growth of secondary forests in the Iberian Peninsula

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985-2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and above-ground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broad-leaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth

The role of recent (1985-2014) patterns of land abandonment and environmental factors in the establishment and growth of secondary forests in the Iberian Peninsula

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985-2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and above-ground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broad-leaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth

Small-scale solar magnetic fields

As we resolve ever smaller structures in the solar atmosphere, it has become clear that magnetism is an important component of those small structures. Small-scale magnetism holds the key to many poorly understood facets of solar magnetism on all scales, such as the existence of a local dynamo, chromospheric heating, and flux emergence, to name a few. Here, we review our knowledge of small-scale photospheric fields, with particular emphasis on quiet-sun field, and discuss the implications of several results obtained recently using new instruments, as well as future prospects in this field of research.Comment: 43 pages, 18 figure

Acceptability and feasibility of a virtual community of practice to primary care professionals regarding patient empowerment: A qualitative pilot study

Background: Virtual communities of practice (vCoPs) facilitate online learning via the exchange of experiences and knowledge between interested participants. Compared to other communities, vCoPs need to overcome technological structures and specific barriers. Our objective was to pilot the acceptability and feasibility of a vCoP aimed at improving the attitudes of primary care professionals to the empowerment of patients with chronic conditions. Methods: We used a qualitative approach based on 2 focus groups: one composed of 6 general practitioners and the other of 6 practice nurses. Discussion guidelines on the topics to be investigated were provided to the moderator. Sessions were audio-recorded and transcribed verbatim. Thematic analysis was performed using the ATLAS-ti software. Results: The available operating systems and browsers and the lack of suitable spaces and time were reported as the main difficulties with the vCoP. The vCoP was perceived to be a flexible learning mode that provided up-to-date resources applicable to routine practice and offered a space for the exchange of experiences and approaches. Conclusions: The results from this pilot study show that the vCoP was considered useful for learning how to empower patients. However, while vCoPs have the potential to facilitate learning and as shown create professional awareness regarding patient empowerment, attention needs to be paid to technological and access issues and the time demands on professionals. We collected relevant inputs to improve the features, content and educational methods to be included in further vCoP implementation. Trial registration: ClinicalTrials.gov, NCT02757781. Registered on 25 April 2016.This study was financed by Instituto de Salud Carlos III and Cofinanced by Fondo Europeo de Desarrollo Regional (FEDER). Ministerio de Economía y Competitividad. Gobierno de España. (PI15/00164, PI15/00586, PI15/00566