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The influence of surface morphology and the oxidation state on the electrocatalytic activity of nanostructured electrodes is well recognized, yet disentangling their individual roles in specific reactions remains challenging. Here, we investigated the electrooxidation of sulfite ions in an alkaline environment using cyclic voltammetry on copper oxide nanostructured electrodes with different oxidation states and morphologies but with similar active areas. To this aim, we synthesized nanostructured Cu films made of nanoparticles or nanorods on top of glassy carbon electrodes. Our findings showed an enhanced sensitivity and a lower detection threshold when utilizing Cu(I) over Cu(II). Density functional theory-based thermochemical analysis revealed the underlying oxidation mechanism, indicating that while the energy gain associated with the process is comparable for both oxide surfaces, the desorption energy barrier for the resulting sulfate molecules is three times higher on Cu(II). This becomes the limiting step of the reaction kinetics and diminishes the overall electrooxidation efficiency. Our proposed mechanism relies on the tautomerization of hydroxyl groups confined on the surface of Cu-based electrodes. This mechanism might be applicable to electrochemical reactions involving other sulfur compounds that hold technological significance.
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Neurodegenerative diseases (NDDs) are specific brain disorders characterized by the progressive deterioration of different motor activities as well as several cognitive functions. Current conventional therapeutic options for NDDs are limited in addressing underlying causes, delivering drugs to specific neuronal targets, and promoting tissue repair following brain injury. Due to the paucity of plausible theranostic options for NDDs, nanobiotechnology has emerged as a promising field, offering an interdisciplinary approach to create nanomaterials with high diagnostic and therapeutic efficacy for these diseases. Recently, two-dimensional nanomaterials (2D-NMs) have gained significant attention in biomedical and pharmaceutical applications due to their precise drug-loading capabilities, controlled release mechanisms, enhanced stability, improved biodegradability, and reduced cell toxicity. Although various studies have explored the diagnostic and therapeutic potential of different nanomaterials in NDDs, there is a lack of comprehensive review addressing the theranostic applications of 2D-NMs in these neuronal disorders. Therefore, this concise review aims to provide a state-of-the-art understanding of the need for these ultrathin 2D-NMs and their potential applications in biosensing and bioimaging, targeted drug delivery, tissue engineering, and regenerative medicine for NDDs.
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Nanoestruturas , Doenças Neurodegenerativas , Humanos , Doenças Neurodegenerativas/diagnóstico por imagem , Doenças Neurodegenerativas/terapia , Nanoestruturas/uso terapêutico , Sistemas de Liberação de Medicamentos , Engenharia Tecidual , Medicina RegenerativaRESUMO
We present a flow injection system with a multiple pulse amperometric detection (FIA-MPA)-based methodology for the simultaneous analysis of sunset yellow and tartrazine. As transducer, we have developed a novel electrochemical sensor based on the synergistic effect of ReS2 nanosheets and diamond nanoparticles (DNPs). Among several transition dichalcogenides for the sensor development, we have selected ReS2 nanosheets since it yields a better response towards both colourants. Scanning probe microscopy characterization shows that the surface sensor is composed by scattered and stacked ReS2 flakes and large aggregates of DNPs. With this system, the gap between the oxidation potential values of sunset yellow and tartrazine is wide enough to allow the simultaneous determination of both dyes. Under the optimum potential pulse conditions (0.8 and 1.2 V) during 250 ms, a flow rate of 3 mL/min and a volume injection of 250 µL, detection limits of 3.51 × 10-7 M and 2.39 × 10-7 M for sunset yellow and tartrazine, respectively, were obtained. This method exhibits good accuracy and precision with Er minor than 13% and RSD lower than 8% with a sampling frequency of 66 samples per hour. Pineapple jelly samples were analyzed by the standard addition method, obtaining 53.7 mg/kg and 29.0 mg/kg of sunset yellow and tartrazine, respectively. From the analysis of fortified samples, recoveries of 94% and 105% were obtained.
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We present the development of an electrochemical sensor towards melatonin determination based on the synergistic effect between MoS2 nanosheets and cucurbit[8]uril. For the sensor construction cucurbit[8]uril suspensions were prepared in water, and MoS2 nanosheets were obtained by liquid exfoliation in ethanol:water. The sensing platform was topographically characterized by Atomic Force Microscopy. Electrochemical Impedance Spectroscopy experiments allowed us to study the charge transfer process during melatonin oxidation. Moreover, stoichiometry of the resulting complex has also been determined. After the optimization of the sensor construction and the experimental variables involved in the Differential Pulse Voltammetric response of melatonin, detection limit of 3.80 × 10-7 M, relative errors minor than 3.8% and relative standard deviation lower than 4.4% were obtained. The proposed sensor has been successfully applied to melatonin determination in pharmaceutical and biological samples as human urine and serum, with very good recoveries ranging from 90 to 102%.
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Melatonina , Humanos , Molibdênio/química , Limite de Detecção , Técnicas Eletroquímicas/métodosRESUMO
In this work, a novel fluorescence sensor has been designed to solve the actual need of new fast and inexpensive sensing platforms for the analysis of synthetic colorants. It is based on MoS2 quantum dots obtained by a hydrothermal method and incorporated as fluorophore into the matrix of PVC membranes, which are deposited on quartz substrates by spin-coating. It was proven, as in these conditions, MoS2 quantum dots maintain the fluorescent properties that they present in solution. Experiments carried out in solution displayed a maximum emission when they were excited under 310 nm. This initial fluorescence decreases linearly in presence of increasing concentrations of various synthetic colorants namely quinoline yellow, tartrazine, sunset yellow, allura red, ponceau 4R and carmoisine. The two possible mechanisms that can explain this quenching effect, colorants absorbing photons emitted by quantum dots and/or competing with the nanomaterial for photons coming from the excitation source, were evaluated. The most pronounced effect was observed with quinoline yellow, as a result of a mixed mechanism. The optimized methodology developed for the determination of quinoline yellow showed a linear concentration range between 5.4 and 55.0 µg with a limit of detection of 1.6 µg. The sensor was applied to the determination of quinoline yellow in a food colour paste obtaining results in good agreement with those obtained by HPLC-UV-vis measurements.
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In this work, we explore the ability of manganese (II) phosphate (MnP) as a catalytic element for the determination of reactive oxygen species (ROS) in seminal plasma, when MnP is employed as modifier of a glassy carbon electrode. The electrochemical response of the manganese (II) phosphate-modified electrode shows a wave at around +0.65 V due to the oxidation of Mn2+ to MnO2+, which is clearly enhanced after addition of superoxide, the molecule considered as the mother of ROS. Once proved the suitability of manganese (II) phosphate as catalyst, we evaluate the effect of including a 0D (diamond nanoparticles) or a 2D (ReS2) nanomaterial in the sensor design. The system consisting of manganese (II) phosphate and diamond nanoparticles yielded the largest improvement of the response. The morphological characterization of the sensor surface was performed by scanning electron microscopy and atomic force microscopy, while cyclic and differential pulse voltammetry were employed for the electrochemical characterization of the sensor. After optimizing the sensor construction, calibration procedures by chronoamperometry were performed, leading to a linear relation between peak intensity and the superoxide concentration in the range of 1.1 10-4 M - 1.0 10-3 M with a limit of detection of 3.2 10-5 M. Seminal plasma samples were analysed by the standard addition method. Moreover, the analysis of samples fortified with superoxide at the µM level leads to recoveries of 95%.
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Invited for the cover of this issue are two collaborating groups: one at the Universidad Autónoma de Madrid and the other at the Instituto de Ciencia de Materiales de Madrid. The image depicts Cucurbit[8]uril adsorbed on a transition metal dichalcogenide surface letting the cavity open for complex formation with melatonin and allowing efficient electrochemical sensing. Read the full text of the article at 10.1002/chem.202203244.
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Host-guest interactions are of paramount importance in supramolecular chemistry and in a wide range of applications. Particularly well known is the ability of cucurbit[n]urils (CB[n]) to selectively host small molecules. We show that the charge transfer and complexation capabilities of CB[n] are retained on the surface of 2D transition metal dichalcogenides (TMDs), allowing the development of efficient electrochemical sensing platforms. We unveil the mechanisms of host-guest recognition between the MoS2 -CB[8] hybrid interface and melatonin (MLT), an important molecular regulator of vital constants in vertebrates. We find that CB[8] on MoS2 organizes the receptor portals perpendicularly to the surface, facilitating MLT complexation. This advantageous adsorption geometry is specific to TMDs and favours MLT electro-oxidation, as opposed to other 2D platforms like graphene, where one receptor portal is closed. This study rationalises the cooperative interaction in 2D hybrid systems to improve the efficiency and selectivity of electrochemical sensing platforms.
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Background: The World Health Organization has promoted preventive measures for reducing the impact of the pandemic. One of these measures was tests in origin for travelers. Testing strategies for COVID-19 facilitate the overall public health response to the pandemic and contributes to minimize the infection among the population COVID-19. Goal: In this work, we assess the efficiency of diagnostic testing of incoming travelers in the Canary Islands, Spain, during a period of 4 months, with a focus on the economic impact for the regional government. We study the cost-benefit of this measure as well as the potential influence on the number of positive cases in the population. Methods: We processed the real data in the Canary Islands of pre-flight PCR and antigen tests that were required to the residents when traveling back to the Canaries from anywhere in Spain in a period of 4 months, from 14 December, 2020 to 4 April, 2021. As a result, we calculated the economic impact of doing those tests and compare them with the estimated costs of passengers under the hypothesis of entering the islands without testing. The cost-benefit was obtained for different scenarios, where the incoming passengers generated hospitalization and intensive care unit (ICU) costs directly and via transmissions. Results: The incoming testing funded by the government, if applied during the bad evolution of the pandemic with 1.2 ratio of transmission, clearly saved money to the public health system. In addition to the economic impact of this measure, we estimated the potential influence on the number of positive cases in the population according to different scenarios of the propagation of the pandemic. At the beginning of February 2021, the savings were about 130.551,47, with a 95% confidence interval (CI) of 24.677,94-236.425,00. By the end of April 2021, the savings were above 2,000,000 (2.284.788,50 on average and 95% CI of 2.092.914,84-2.476.662,16) and the savings increased as the pandemic evolved. At the end of the period, the savings were twice the expenses. Conclusions: Testing in origin has proved to be a good measure that helped to mitigate COVID-19 spread among regions. Our results confirm that the free PCR or rapid antigen tests produce relevant savings to the public budget. We studied 61.990 reported data during 2020 and 2021 from the travelers from national flights, against 346.449 of total incoming travelers to the Canary Islands in this period. The measure pursued by the Government of the Canary Islands of providing free tests for residents showed a clear benefit for both, limiting the propagation of COVID-19 and reducing the costs of the hospitalizations and ICU admissions. It should be noted that the free testing measure in this period was before starting the vaccination campaigns. As measure of public health in the airports, testing helped to control and make the mobility of travelers secure.
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COVID-19 , COVID-19/diagnóstico , COVID-19/epidemiologia , Análise Custo-Benefício , Humanos , Pandemias/prevenção & controle , Espanha/epidemiologia , ViagemRESUMO
We have designed and prepared an electrochemical biosensor for lactate determination. Through a diazotation process, the enzyme lactate oxidase (LOx) is anchored onto chevron-like graphene nanoribbons (GNR), previously synthesized by a solution-based chemical route, and used as modifiers of glassy carbon electrodes. In a first step, we have performed the grafting of a 4-carboxyphenyl film, by electrochemical reduction of the corresponding 4-carboxyphenyl diazonium salt, on the GNR-modified electrode surface. In this way, the carboxylic groups are exposed to the solution, enabling the covalent immobilization of the enzyme through the formation of an amide bond between these carboxylic groups and the amine groups of the enzyme. The biosensor design was optimized through the morphological and electrochemical characterization of each construction step by atomic force microscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy.The cyclic voltammetric response of the biosensor in a solution of hydroxymethylferrocene in presence of l-lactate evidenced a clear electrocatalytic effect powered by the specific design of the biosensing platform with LOx covalently attached to the GNR layer. From the calibration procedures employed for l-lactate determination, a linear concentration range of 3.4 · 10-5- 2.8 · 10-4 M and a detection limit of 11 µM were obtained, with relative errors and relative standard deviations less than 6.0% and 8.4%, respectively. The applicability of the biosensor was tested by determining lactate in apple juices, leading to results that are in good agreement with those obtained with a well-established enzymatic spectrophotometric assay kit.
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Técnicas Biossensoriais , Grafite , Nanotubos de Carbono , Técnicas Biossensoriais/métodos , Técnicas Eletroquímicas/métodos , Eletrodos , Enzimas Imobilizadas/química , Grafite/química , Ácido Láctico , Oxigenases de Função Mista , Nanotubos de Carbono/químicaRESUMO
Background: Solar ultraviolet radiation (UVR) is one of the main risk factors for non-melanoma skin cancer. In Spain, 11% of the population are outdoor workers. Farmers are among the outdoor workers with the highest levels of chronic sun exposure. Objectives: To study the prevalence of skin cancer in farmers and evaluate their photoprotection habits. Materials & Methods: We performed an observational cross-sectional prospective study of farmers who completed a validated questionnaire on UVR exposure and protective behaviour and underwent a skin examination and skin colorimetry overseen by a dermatologist. Results: The study population consisted of 215 farm workers (84.4% male; mean age: 65.8 ± 14 years; mean years working: 45 ± 18). Actinic keratosis (AK) was detected in 41.4%, basal cell carcinoma (BCC) in 9.8%, and squamous cell carcinoma (SCC) in 1.4%. The most frequent photoprotection measure was the shade (69.3%). Photoaging type was significantly associated with the presence of AK and BCC, and Olson Grade II and III AK lesions correlated with SCC. The number of nevi on the lower extremities was the only predictor of the appearance of BCC. Conclusion: Photoprotection measures were not regularly used by most farm workers and the prevalence of skin cancer lesions was high. The findings underscore the need to improve photoprotection habits and early detection of skin cancer in this population.
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Carcinoma Basocelular , Carcinoma de Células Escamosas , Ceratose Actínica , Neoplasias Cutâneas , Humanos , Masculino , Pessoa de Meia-Idade , Idoso , Feminino , Fazendeiros , Espanha , Estudos Transversais , Prevalência , Estudos Prospectivos , Raios UltravioletaRESUMO
We develop an electrochemical sensor by using 2D-transition metal dichalcogenides (TMD), specifically MoS2, and nanoparticles stabilized with cucurbit[8]uril (CB[8]) incorporated together with them. Two different nanoparticles are assayed: diamond nanoparticles (DNPs) and gold nanoparticles (AuNp). 0D materials, together with TMD, provide increased conductivity and active surface while the macrocycle CB[8] affords selectivity towards the guest methyl viologen (MV2+), also named paraquat. Glassy Carbon (GC) electrodes are modified by drop-casting of suspensions of MoS2, followed by either a CB[8]-DNPs hybrid dispersion or a CB[8]-AuNp suspension. Atomic force microscopy is employed for the morphological characterization of the electrochemical sensor surface while cyclic voltammetry and electrochemical impedance spectroscopy techniques allow the electrochemical characterization of the sensor. The well-stablished signals of CB[8]-encapsulated MV2+ arise in voltammetric measurements when the macrocycle modifies the 0D-materials. Once the sensor construction and differential pulse voltammetry parameters have been optimized for quantification purposes, calibration procedures are performed with the platform GC/MoS2/CB[8]-DNPs. This sensing platform shows linear relations between peak intensity and the MV2+ concentration in the linear concentration range of (0.73-8.0) · 10-6 M with a limit of detection of 2.2 · 10-7 M. Analyses of river water samples fortified with MV2+ at the µM level shows recoveries of 100% with RSD values of 6.4% (n = 3).
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Dissulfetos , Nanopartículas Metálicas , Hidrocarbonetos Aromáticos com Pontes , Ouro , Imidazóis , ParaquatRESUMO
This work presents an on-line fluorescence method for the allura red (AR) determination. The method is based on the fluorescence quenching of dots of MoS2 because of their interaction with the non-fluorescence dye. MoS2-dots were synthetized and characterized by spectroscopic techniques and High Resolution Transmission Electronic Microscopy (HR-TEM). The simultaneous injection of the nanomaterial and the dye in a flow injection analysis system allows the determination of allura red at 1.7 × 10-6 M concentration level with a very good accuracy and precision (Er minor than 10% and RSD lower than 8%) and a sampling frequency of 180 samples per hour. Moreover, the interaction fluorophore-quencher results a dynamic inhibition mechanism. The proposed methodology was applied to the AR analysis in soft beverages and powders for gelatine preparation. Colourant concentrations of 63 ± 2 mg/L (n = 3) and 0.30 ± 0.01 mg/g (n = 3) were found, respectively. These results were validated by high performance liquid chromatography technique.
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Compostos Azo/análise , Dissulfetos/química , Aditivos Alimentares/análise , Molibdênio/química , Pontos Quânticos/química , Espectrometria de Fluorescência/métodos , Bebidas/análise , Corantes Fluorescentes/químicaRESUMO
We employ chevron-like graphene nanoribbons (GNRs) synthesized by a solution-based chemical route to develop a novel electrochemical sensor for determination of the neurotransmitter epinephrine (EPI). The sensor surface, a glassy carbon electrode modified with GNRs, is characterized by atomic force microscopy, scanning electron microscopy and Raman spectroscopy, which show that the electrode surface modification comprises of bi-dimensional multilayer-stacked GNRs that retain their molecular structure. The charge transfer process occurring at the electrode interface is evaluated by electrochemical impedance spectroscopy. The sensor is applied to the determination of EPI, employing as an analytical signal the reduction peak corresponding to the epinephrinechrome-leucoepinephrinechrome transition (E = - 0.25 V) instead of the oxidation peak usually employed in the literature (E = + 0.6 V) in order to minimize interferences. The results obtained demonstrate that chevron-like nanoribbons synthesized by solution methods exhibit reliable electrocatalytic activity for EPI determination. Using differential pulse voltammetry, we obtain a linear concentration range from 6.4 × 10-6 to 1.0 × 10-4 M and a detection limit of 2.1 × 10-6 M. The applicability of the sensor was evaluated by determining EPI in pharmaceutical samples with satisfactory results.
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Técnicas Eletroquímicas/métodos , Epinefrina/análise , Grafite/química , Nanotubos de Carbono/química , Análise Espectral/métodosRESUMO
We have developed electrochemical sensors for the determination of H2O2 in a complex matrix such as human semen as a method to evaluate oxidative stress related to male infertility. Our sensors are based on the modification of conventional electrode surfaces with nanoparticles. We used diamond nanoparticles (DNp) either on glassy carbon or gold surfaces (GC/DNp and Au/DNp sensors, respectively), and copper nanoparticles electrochemically generated directly on glassy carbon surfaces (GC/CuNp). The morphology of the modified electrode surfaces was characterized by Atomic Force Microscopy (AFM), and the H2O2 determination performance evaluated by chronoamperometric measurements at different applied potentials. The best results are obtained for GC/DNp at +1.0 V, Au/DNp at -0.6 V and GC/CuNp at +0.2 V with detection limits (LD) of 1.1 µM, 2.4 µM and 2.6 µM, respectively. The analysis of H2O2 in doped synthetic semen using the GC/CuNp sensor shows the best recoveries, reaching a mean value of 103%. The GC/CuNp sensor was successfully applied to H2O2 analysis in real human semen. In this case, a H2O2 concentration of 1.42 ± 0.05 mM is found and recoveries of 102% on average are obtained.
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Técnicas Eletroquímicas/instrumentação , Peróxido de Hidrogênio/análise , Nanopartículas/química , Estresse Oxidativo , Sêmen/química , Humanos , Masculino , Microscopia de Força AtômicaRESUMO
Many molecules quench their fluorescence upon adsorption on surfaces. Herein we show that the interaction of thiabendazole, a widespread used fungicide of the benzimidazole family, with nanosheets of transition metal dichalcogenides, particularly of WS2, leads to a significant increase, more than a factor of 5, of the fluorescence yield. This surprising effect is rationalized by DFT calculations and found to be related to the inhibition of the intramolecular rotation between the benzimidazole and thiazole groups due to a bonding rigidization upon interaction with the MoS2 surface. This non-covalent adsorption leads to a redistribution of the molecular LUMO that blocks the non-radiative energy dissipation channel. This unusual behaviour does not operate either for other molecules of the same benzimidazole family or for other 2D materials (graphene or graphene oxide). Moreover, we found that a linear dependence of the emission with the concentration of thiabendazole in solution, which combined with the specificity of the process, allows the development of a highly sensitive and selective method towards thiabendazole determination that can be applied to real river water samples. An excellent detection limit of 2.7 nM, comparable to the best performing reported methods, is obtained with very good accuracy (Er ≤ 6.1%) and reproducibility (RSD ≤ 4.1%) in the concentration range assayed.
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An electrochemical sensor for the carcinogen 4,4'-oxydianiline (Oxy) is described. The method is based on the ability of MoS2 nanosheets to preconcentrate Oxy. A glassy carbon electrode (GCE) was covered, by drop-casting, with MoS2 nanosheets that were obtained by exfoliation. X-Ray photoemission spectroscopy indicates that Oxy accumulates on the MoS2 nanosheets through an electropolymerization process similar to that reported for aniline. Both electrochemical impedance spectroscopy and atomic force microscopy were used to characterize the electrode surface at the different stages of device fabrication. Employing the current measured at +0.27 V vs. Ag/AgCl after Oxy adsorption, the modified GCE enables the voltammetric detection of Oxy at 80 nM levels with relative errors and relative standard deviations of <8.3 and <5.6%, respectively, at all the concentrations studied. The method was applied to the selective determination of Oxy in spiked river water samples. Very good selectivity and recoveries of around 95% in average are found. Graphical abstractSchematic representation of 4,4-oxydianiline electrochemical polymerization and preconcentration onto molybdenum disulfide nanosheets for the diamine determination in river waters.
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Carcinógenos/análise , Dissulfetos/química , Molibdênio/química , Nanoestruturas/química , Éteres Fenílicos/análise , Adsorção , Carbono/química , Carcinógenos/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Limite de Detecção , Éteres Fenílicos/química , Rios/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/químicaRESUMO
The authors describe an electrochemical sensor based on the use of diamond nanoparticles (DNPs) and molybdenum disulfide (MoS2) platelets. The sensor was applied to the voltammetric determination of the anticonvulsant valproic acid which was previously derivatized with ferrocene. The MoS2 platelets were obtained by an exfoliation method, and the DNPs were directly dispersed in water and subsequently deposited on a glassy carbon electrode (GCE). The sensor response was optimized in terms of the solvent employed for dispersing the MoS2 nanomaterial and the method for modifying the GCE. Sensors consisting of a first layer of MoS2 dispersed in ethanol/water and a second layer of DNPs give better response. The single steps of sensor construction were characterized by atomic force microscopy and electrochemical impedance spectroscopy. The differential pulse voltammetric response of the GCE (measured at +0.18 V vs. Ag/AgCl) was compared to that of sensors incorporating only one of the nanomateriales (DNPs or MoS2). The formation of a hybrid MoS2-DNP structure clearly improves performance. The GCE containing both nanomaterials exhibits high sensitivity (740 µA â mM-1 â cm-2), a 0.27 µM detection limit, and an 8% reproducibility (RSD). The sensor retained 99% of its initial response after 45 days of storage. Graphical abstract Electrochemical sensor by co-immobilization of MoS2 and diamond nanoparticles (DNP). The formation of a hybrid MoS2-DNP structure enhances the performance of the sensor towards valproic acid derivatized with a ferrocene group, when compared with sensors incorporating only DNP or MoS2.
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Anticonvulsivantes/análise , Diamante/química , Dissulfetos/química , Eletroquímica/instrumentação , Limite de Detecção , Molibdênio/química , Nanopartículas/química , Ácido Valproico/análise , Carbono/química , Eletrodos , Compostos Ferrosos/química , Metalocenos/química , Reprodutibilidade dos Testes , Propriedades de SuperfícieRESUMO
A competitive assay between the antiviral Amantadine and the dye Thionine for the Cucurbit[8]uril cavity was carried out in a flow injection analysis system for the indirect fluorescence detection of Amantadine. Both, Cucurbit[7]uril and Cucurbit[8]uril Thionine complexes were evaluated for the competitive assay. The use of a 12-port injection valve allows the on-line reaction in the flow system. Once optimized all the experimental variables, the methodology developed allows the detection of Amantadine at the 0.16µM level with excellent accuracy (Er ≤ 8.2%) and reproducibility (RSD ≤ 6.3%) for all the concentration range assayed. This one-step turn-on fluorescence methodology allows reaching sampling frequencies of 68 samples per hour. The selectivity of the method was evaluated against different antiviral drugs. Moreover, the performance of the methodology proposed was tested by the Amantadine determination in human serum and pharmaceutical formulations samples. The results demonstrated that the method can be applied to Amantadine determination in real samples of different nature with excellent recoveries, ranging from 83% to 98% depending on the matrix assayed.
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Amantadina/sangue , Antivirais/sangue , Corantes/química , Compostos Macrocíclicos/química , Fenotiazinas/química , Espectrometria de Fluorescência/métodos , Ligação Competitiva , Humanos , Limite de Detecção , Reprodutibilidade dos TestesRESUMO
This study reports a cross-cultural comparison of the vocal pitch patterns of 15 Mexican Spanish-speaking and 15 Belgian Flemish-speaking dyads, recorded during 5min of free-play in a laboratory setting. Both cultures have a tradition of dyadic face-to-face interaction but differ in language origins (i.e., Romanic versus Germanic). In total, 374 Mexican and 558 Flemish vocal exchanges were identified, analyzed and compared for their incidence of tonal synchrony (harmonic/pentatonic series), non-tonal synchrony (with/without imitations) and pitch and/or interval imitations. The main findings revealed that dyads in both cultures rely on tonal synchrony using similar pitch ratios and timing patterns. However, there were significant differences in the infants' vocal pitch imitation behavior. Additional video-analyzes on the contingency patterns involved in pitch imitation showed a cross-cultural difference in the maternal selective reinforcement of pitch imitation. The results are interpreted with regard to linguistic, developmental and cultural aspects and the 'musilanguage' model.