Electrodes Modification Based on Metal-Free Phthalocyanine: Example of Electrochemical Sensors for the Detection of Acetic Acid

Electroanalytical properties of tetra-tert-butyl phthalocyanine (PcH 2 -tBu) modified electrodes are studied by cyclic voltammetry (CV). The modified electrodes are obtained by CV deposition techniques on gold (Au) and glassy carbon (C) screenprinted electrodes (SPEs) and used for the electrochemical detection of acetic acid (AA). Based on the CV experiments, the electrodeposition mechanism is detailed. The modified PcH 2 -tBu electrodes reveal one oxidation and one reduction peak within the potential window of the working electrodes. In the presence of the analyte (acetic acid), the modified electrodes show sensitivity in the range of 10 mM to 400 mM. For the PcH 2 -tBu modified Au electrode, a limit of detection (LOD) of 5.89 mM (based on the +0.06 V peak) was obtained while for the PcH 2 -tBu modified C electrode a LOD of 17.76 mM (based on the +0.07 V peak) was achieved. A signal decay of 17%, based on 20 experiments, is obtained when gold is used as working electrode. If carbon is used as working electrode a value of 7% is attained. A signal decay is observed after more than 50 cycles of experiments and is more pronounced when higher concentrations of acetic acid are used. A mechanism of sensing is proposed at the end

Consumer responses and willingness-to-pay for hibiscus products: A preliminary study

The rise in diseases like obesity and diabetes is a worldwide challenge. The consumption of functional products such as hibiscus, which has been proven to be high in bioactive compounds and dietary fiber, providing it with anticancer, antiaging, anti-inflammatory and satiety properties, should be promoted. In the U.S., promoting the consumption of hibiscus products can be a good approach to increase fiber consumption and to reduce risk of obesity, diabetes, and hypertension. However, information about knowledge of this functional product among consumers is still sparse and increasing consumption requires designing and marketing desired products made from hibiscus. Therefore in this preliminary study, we assessed consumer response to hibiscus products and investigated whether providing information about potential health benefits could impact consumer willingness-to-pay (WTP) for three types of non-alcoholic hibiscus beverages: ready-made tea, bottled juice, and kombucha. Our web-based survey was distributed through QualtricsXM and a convenience sampling method was chosen. Most participants identified themselves as female, 18–34 years old, with a graduate degree. Most participants (81%) had consumed hibiscus products before and 57% had a weekly food budget lower than $60. Overall, tea and juices were the most liked hibiscus beverages, respectively. Although taste and health benefits were ranked as the main reasons to consume hibiscus beverages, additional information about hibiscus health benefits did not significantly affect WTP for these products. Without additional health benefit information, consumer WTP for non-alcoholic hibiscus beverages ranged from$2.9 to $3.60 for kombucha and$4.08–4.97 for Ready-made-tea. This study provides valuable insights that can support future research on hibiscus products and promote the development of novel hibiscus-based foods and beverages that are appealing to the U.S. market

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Electrochemical Sensors Based on Screen-Printed Electrodes: The Use of Phthalocyanine Derivatives for Application in VFA Detection

Here, we report on the use of electrochemical methods for the detection of volatiles fatty acids (VFAs), namely acetic acid. We used tetra-tert-butyl phthalocyanine (PcH2-tBu) as the sensing material and investigated its electroanalytical properties by means of cyclic voltammetry (CV) and square wave voltammetry (SWV). To realize the electrochemical sensing system, the PcH2-tBu has been dropcast-deposited on carbon (C) orgold (Au)screen-printed electrodes (SPEs) and characterized by cyclic voltammetry and scanning electron microscopy (SEM). The SEM analysis reveals that the PcH2-tBu forms mainly aggregates on the SPEs. The modified electrodes are used for the detection of acetic acid and present a linear current increase when the acetic acid concentration increases. The Cmodified electrode presents a limit of detection (LOD) of 25.77 mM in the range of 100 mM–400 mM, while the Aumodified electrode presents an LOD averaging 40.89 mM in the range of 50 mM–300 mM. When the experiment is realized in a buffered condition, theCmodified electrode presents a lower LOD, which averagesthe 7.76 mM. A pronounced signal decay attributed to an electrode alteration is observed in the case of the gold electrode. This electrode alteration severely affects the coating stability. This alteration is less perceptible in the case of the carbon electrode

Electrodes Modification Based on Metal-Free Phthalocyanine: Example of Electrochemical Sensors for the Detection of Acetic Acid

Electroanalytical properties of tetra-tert-butyl phthalocyanine (PcH2-tBu) modified electrodes are studied by cyclic voltammetry (CV). The modified electrodes are obtained by CV deposition techniques on gold (Au) and glassy carbon (C) screen-printed electrodes (SPEs) and used for the electrochemical detection of acetic acid (AA). Based on the CV experiments, the electrodeposition mechanism is detailed. The modified PcH2-tBu electrodes reveal one oxidation and one reduction peak within the potential window of the working electrodes. In the presence of the analyte (acetic acid), the modified electrodes show sensitivity in the range of 10 mM to 400 mM. For the PcH2-tBu modified Au electrode, a limit of detection (LOD) of 5.89 mM (based on the +0.06 V peak) was obtained while for the PcH2-tBu modified C electrode a LOD of 17.76 mM (based on the +0.07 V peak) was achieved. A signal decay of 17%, based on 20 experiments, is obtained when gold is used as working electrode. If carbon is used as working electrode a value of 7% is attained. A signal decay is observed after more than 50 cycles of experiments and is more pronounced when higher concentrations of acetic acid are used. A mechanism of sensing is proposed at the end

Functionalized CNTs-Based Gas Sensors for BTX-Type Gases: How Functional Peripheral Groups Can Affect the Time Response through Surface Reactivity

Herein we present gas sensor responses of functionalized carbon nanotubes (CNTs) toward benzene and xylene vapors. The functional moieties are phthalocyanine and porphyrin derivatives which possess a central part delimited by the macroring and different peripheral groups (aryl or alkyls) surrounding the macroring. The sensor devices based on QCM (quartz crystal microbalance) and resistive transducers are performed simultaneously to elucidate the sensing mechanism. The sensing performance from the two transducers recorded at room temperature revealed different behavior but complementary to understand the mechanism. Our findings show that if the aromatic VOCs bear methyl groups (xylene), the desorption profile is slow and the response time too long, while in the absence of a methyl group (benzene) the desorption profile is very rapid with a shorter response time. This illustrates that the whole gas response is driven by an interplay between the π–π interaction and the π–alkyl or alkyl–alkyl interactions, i.e., van der Waals (VdW) interactions. The analysis of the adsorption–desorption profile shows that the interaction mechanism is based on a synergy between many interactions that proceed collectively or separately to strengthen or weaken the gas–material interaction. Thus, the presence of alkyl groups on both sides (VOCs and functional moieties) inherently contributes to define the gas material interaction

An innovative gas sensor system designed from a sensitive organic semiconductor downstream a nanocarbonaceous chemical filter for the selective detection of NO2 in an environmental context

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Elaboration of SWNTs-based gas sensors using dispersion techniques: Evaluating the role of the surfactant and its influence on the sensor response

International audienceThis paper describes the preparation of the CNTs-based gas sensors, which are achieved by the utilisation of aqueous dispersions of carbon nanotubes (CNTs) using NaDDBS as a surfactant. The sensors are made of IDEs (Interdigitated electrodes) on which the CNTs dispersion are dropcast deposited. The sensing layers are characterized by Raman and IR spectroscopy as well as SEM analysis and electrical characterization (I-V). Finally, the sensor response and relative resistance change (ΔR/R) versus concentration under low NO2 gas concentrations are reported. The sensor performance is evaluated by focusing on the influence of the surfactant and the annealing process on the final sensor. The effect of the surfactant has been investigated in order to establish the optimal conditions for the realization of the sensors using dispersion route. Although the use of surfactant provides stable dispersions, the annealing treatment of the sensor before sensing experiments need to be correctly tuned for good sensor performance. Indeed, even if the presence of surfactant does not drastically hinder the sensor response, a major problem comes from its residue after decomposition under certain annealing conditions (≥300 °C). In fact the surfactant residue seems to obstruct active sites on the sensor surface and therefore render the sensor unusable. Lower annealing conditions (≤150 °C) seem to be the optimum

Comparison of InP Schottky diodes based on Au or Pd sensing electrodes for NO2 and O3 sensing

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