Additive manufacturing or three-dimensional (3D)-printing is an emerging technology that has been applied in the development of novel materials and devices for a wide range of applications, including ...Electrochemistry and Analytical Chemistry areas. This review article focuses on the contributions of 3D-printing technology to the development of electrochemical sensors and complete electrochemical sensing devices. Due to the recent contributions of 3D-printing within this scenario, the aim of this review is to present a guide for new users of 3D-printing technology considering the required features for improved electrochemical sensing using 3D-printed sensors. At the same time, this is a comprehensive review that includes most 3D-printed electrochemical sensors and devices already reported using selective laser melting (SLM) and fused deposition modeling (FDM) 3D-printers. The latter is the most affordable 3D-printing technique and for this reason has been more often applied for the fabrication of electrochemical sensors, also due to commercially-available conductive and non-conductive filaments. Special attention is given to critically discuss the need for the surface treatment of FDM 3D-printed platforms to improve their electrochemical performance. The insertion of biochemical and chemical catalysts on the 3D-printed surfaces are highlighted as well as novel strategies to fabricate filaments containing chemical modifiers within the polymeric matrix. Some examples of complete electrochemical sensing systems obtained by 3D-printing have successfully demonstrated the enormous potential to develop portable devices for on-site applications. The freedom of design enabled by 3D-printing opens many possibilities of forthcoming investigations in the area of analytical electrochemistry.
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•We review the contributions of 3D-printing to fabricate electrochemical sensors.•Different 3D-printing methods are compared highlighting fused deposition modeling (FDM).•Surface treatment and modification with (bio)chemical mediators for improved performance.•Strategies for fabrication of conductive filaments are presented for future applications.•3D-printing of all-in-one electrochemical devices in different designs are assessed.
This current review article focuses on recent contributions to on-site forensic investigations. Portable and potentially portable methods are presented and critically discussed about (bio)chemical ...trace analysis and studies performed outside the controlled laboratory environment to rapidly help in crime scene inquiries or forensic intelligence purposes. A wide range of approaches including electrochemical sensors, microchip electrophoresis, ambient ionization on portable mass spectrometers, handheld Raman and NIR instruments as well as and point-of-need devices, like paper-based platforms, for in-field analysis of latent evidences, controlled substances, drug screening, hazards, and others to assist in law enforcements and solving crime more efficiently are highlighted. The covered examples have successfully demonstrated the huge potential of portable devices for on-site applications. Future investigations should consider analytical validation to compete equality and even replace current gold standard methods.
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•Electrochemical sensors offer good sensitivity for abuse drugs and explosives.•Paper-based devices have revealed desirable performance for point-of-care testing.•NIR and RAMAN instruments have allowed fast screening at the point-of-need.•Portable MS instruments have exhibited good performance for on-site forensic applications.•Electrophoresis chips have provided excellent ability for STR genotyping.
Adequate nutrition before and during pregnancy, as well as postpartum, is among the major contributors to maternal and newborn health. Physiotherapists' knowledge of this area is still scarce, ...although their clinical practice has been linked to newborns' neuropsychomotor development, which, in turn, is influenced by maternal health and nutritional status. Therefore, this study aimed to evaluate the nutritional knowledge of physiotherapists regarding maternal and newborn health. A total of 70 Brazilian physiotherapists (32.2 ± 6.0 years; 72.9% females) were evaluated between November 2019 and February 2020 for their sociodemographic characteristics, professional experience, and nutritional knowledge about maternal and newborn health through a validated questionnaire personally administered by the same trained researcher. Most of the physiotherapists had graduated but had no specialization in maternal and child physiotherapy (96.1% of the females and all the males). The nutritional knowledge about maternal and newborn health was significantly different between the female and male health professionals, as well as between the less and more experienced participants, i.e., female physiotherapists and the more experienced ones had more correct answers on the nutritional questionnaire than the male and less experienced physiotherapists, respectively (
< 0.05). Our results open an interesting window for the future education and training of Brazilian physiotherapists in nutrition.
The fabrication of carbon black/polylactic acid (PLA) electrodes using a 3D printing pen is presented and compared with electrodes obtained by a desktop fused deposition modelling (FDM) 3D printer. ...The 3D pen was used for the fast production of electrodes in two designs using customized 3D printed parts to act as template and guide the reproducible application of the 3D pen: (i) a single working electrode at the bottom of a 3D-printed cylindrical body and (ii) a three-electrode system on a 3D-printed planar substrate. Both devices were electrochemically characterized using the redox probe Fe(CN)63−/4- via cyclic voltammetry, which presented similar performance to an FDM 3D-printed electrode or a commercial screen-printed carbon electrode (SPE) regarding peak-to-peak separation (ΔEp) and current density. The surface treatment of the carbon black/PLA electrodes fabricated by both 3D pen and FDM 3D-printing procedures provided substantial improvement of the electrochemical activity by removing excess of PLA, which was confirmed by scanning electron microscopic images for electrodes fabricated by both procedures. Structural defects were not inserted after the electrochemical treatment as shown by Raman spectra (iD/iG), which indicates that the use of 3D pen can replace desktop 3D printers for electrode fabrication. Inter-electrode precision for the best device fabricated using the 3D pen (three-electrode system) was 4% (n = 5) considering current density and anodic peak potential for the redox probe. This device was applied for the detection of 2,4,6-trinitrotoluene (TNT) via square-wave voltammetry of a single-drop of 100 μL placed upon the thee-electrode system, resulting in three reduction peaks commonly verified for TNT on carbon electrodes. Limit of detection of 1.5 μmol L−1, linear range from 5 to 500 μmol L−1 and RSD lower than 4% for 10 repetitive measurements of 100 μmol L−1 TNT were obtained. The proposed devices can be reused after polishing on sandpaper generating new electrode surfaces, which is an extra advantage over chemically-modified electrochemical sensors applied for TNT detection.
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•3D pen fabricated carbon black/polylactic acid electrodes compared with 3D-printed electrodes.•Morphological analysis shows no difference, except to electrochemical surface treatment.•Highly reproducible planar three-electrode devices were fabricated (RSD = 4%, n = 5).•Similar results to those obtained on 3D-printed or screen-printed electrodes.•Application to TNT detection in a single drop (100 μL placed upon the device).
A general methodology to access valuable 4-(phenylchalcogenyl)tetrazolo1,5-
quinolines was developed by the reaction of 2-azidobenzaldehyde with phenylchalcogenylacetonitriles (sulfur and selenium) ...in the presence of potassium carbonate (20 mol%) as a catalyst. The reactions were conducted using a mixture of dimethylsulfoxide and water (7:3) as solvent at 80 °C for 4 h. This new methodology presents a good functional group tolerance to electron-deficient and electron-rich substituents, affording a total of twelve different 4-(phenylchalcogenyl)tetrazolo1,5-
quinolines selectively in moderate to excellent yields. The structure of the synthesized 4-(phenylselanyl)tetrazolo1,5-
quinoline was confirmed by X-ray analysis.
Three-dimensional printing techniques have been widely used in the fabrication of new materials applied to energy, sensing and electronics due to unique advantages, such as fast prototyping, reduced ...waste generation, and multiple fabrication designs. In this paper, the production of a conductive 3D-printing filament composed of Ni(OH)2 microparticles and graphene within a polylactic acid matrix (Ni-G-PLA) is reported. The nanocomposite was characterized by thermogravimetric, energy-dispersive X-ray spectroscopic, scanning electronic microscopic, Raman spectroscopic and electrochemical techniques. Characteristics such as printability (using fused deposition modelling), electrical conductivity and mechanical stability of the polymer nanocomposite were evaluated before and after 3D printing. The novel 3D-printed disposable electrode was applied for selective detection of glucose (enzyme-less sensor) with a detection limit of 2.4 μmol L−1, free from the interference of ascorbic acid, urea and uric acid, compounds typically found in biological samples. The sensor was assembled in a portable electrochemical system that enables fast (160 injection h−1), precise (RSD < 5%) and selective determination of glucose without the need of enzymes (electrocatalytic properties of the Ni-G-PLA nanocomposite). The obtained results showed that Ni-G-PLA is a promising material for the production of disposable sensors for selective detection of glucose using a simple and low-cost 3D-printer.
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•Production of a conductive 3D-printing filament composed by nickel microparticles and graphene within a PLA matrix.•Fast 3D printing of disposable electrodes for selective detection of glucose (enzyme-less sensor).•Single step fabrication of electrodes modified with nickel nanoparticles.•Direct printing of modified electrodes.
Conductive 3D-printed platforms have been recognized an emerging class of materials with great potential to electrochemistry. However, such 3D-printed electrodes require a surface treatment to remove ...excess of polymer that hinders the electron transfer. We report a fast (2-min) and chemical-free protocol for the surface treatment of 3D-printed conductive electrodes based on reactive cold oxygen plasma. A dramatic improvement of electrochemical activity of 3D-printed carbon black-polylactic acid (CB-PLA) electrodes was verified by the decrease in the peak-to-peak separation of the voltammetric response for the Fe(CN)63-/Fe(CN)64- couple and in the resistance of change transfer. The O2-plasma treatment increased oxide groups and graphitic groups at the CB-PLA surface (verified by XPS) and provided higher rugosity (SEM images) thus higher exposure of conducting carbon sites and increased electroactive area in comparison with CO2-plasma, which explains the improved electrochemical performance using O2-plasma treated electrodes. This protocol is faster and provided improved electrochemical activity compared with electrochemical, chemical, or biological treatments. As proofs-of concept, the benefits of surface plasma treatment of the 3D-printed electrodes were demonstrated towards the electrochemical sensing of dopamine and nitrite, molecules of biological interest, including the analysis of human saliva. Values of sensitivity and detection limit were greatly improved when using O2-plasma treatment for both molecules (up to 100-fold increase in sensitivity for the voltammetric detection of dopamine), suggesting great promises for the development of highly-sensitive electrochemical sensors.
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•Cold plasma treatment of 3D-printed carbon electrodes provides high electron transfer.•Chemical-free and fast (2 min) protocol using reactive oxygen plasma over the electrode.•Decrease in the ∆E of the voltammetric response for the Fe(CN)63-/Fe(CN)64- couple.•Diminution of the resistance of charge transfer after plasma treatment of the surfaces.•Faster and more efficient than electrochemical, chemical, or biological treatments of 3D printed surfaces.
This communication shows the electrochemical synthesis of Prussian blue (PB) films on additive manufactured (3D-printed) electrodes from iron impurities found at the graphene-polylactic acid (G/PLA) ...substrate and its application as a highly selective sensor for H2O2. The 3D-printed G/PLA electrode was immersed in dimethylformamide for 30 min to exposure the iron impurities within the PLA matrix. Next, cyclic voltammograms (200 cycles) in the presence of potassium ferricyanide in 0.1 mol L−1 KCl + 0.01 mol L−1 HCl were performed to grow the PB films. The sensing properties of this novel PB/G/PLA platform were evaluated for the amperometric detection of H2O2 using batch-injection analysis, with a limit of detection of 0.56 μmol L−1 under the application of 0.0 V (vs Ag/AgCl/KClsat.). The applicability of the sensor was demonstrated for the analysis of milk samples (10-fold diluted in the supporting electrolyte), resulting in proper recovery values (94–101%).
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•Novel procedure to produce Prussian blue modified electrode for H2O2 sensing.•Iron impurities in 3D-printed graphene electrodes are accessed after solvent treatment.•Prussian blue is formed at the iron impurities found on the 3D-printed surface.•The protocol involves 200 cyclic voltammograms in ferricyanide and KCl/HCl medium.•Rapid, precise and selctive amperometric detection of H2O2 at 0.0 V vs Ag/AgCl/KClsat.
Midazolam (MID) is a sedative drug which can be added in beverage samples as drug-facilitated-sexual assault (date rape drug). This type of drug has short half-life in biological fluids (not ...detectable) which often prevents the correlation between drug abuse and crime. In this work, we described a simple and low-cost method for fast screening and selective determination of MID in beverage samples (vodka, whiskey and red wine). For the first time, the electrochemical oxidation of MID was used for this purpose. The oxidation mechanism was studied using electrochemical techniques (cyclic and square-wave voltammetry) and computational simulations (density functional theory calculations). Differential-pulse voltammetry, boron-doped diamond electrode (BDDE), and Britton-Robinson (BR) buffer (pH = 2) were selected as electrochemical analysis technique, working electrode and supporting electrolyte, respectively. Different linear response ranges (4–25 μmol L−1 with r = 0.9972; 1–10 μmol L−1 with r = 0.9951; 1–15 μmol L−1 with r = 0.9982) and limits of detection (0.46, 0.43 and 0.33 μmol L−1) were obtained for the analysis of vodka, whisky, and red wine solutions, respectively. The precision and accuracy were satisfactory considering the low relative standard deviation values (RSD < 6.3%, n = 15) and minimal sample matrix effects (recovery values between 87 and 103%).
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•Fast screening and selective determination of midazolam.•The electrochemical oxidation of midazolam has been studied for the first time.•The electrochemical oxidation showed better selectivity than the electrochemical reduction.•The oxidation mechanism was proposed.
•Low-cost electrochemical exfoliation by cyclic voltammetry for GO synthesis.•Background electrolyte, high scan rate and cycle numbers are important for synthesis.•Enhanced performance when compared ...to commercial drop casted ERGO and CRGO.•Reproducible performance and easy surface renewal and storage.
In this study we propose an in situ low-cost electrochemical treatment by cyclic voltammetry (CV) for graphene oxide (GO) synthesis on the surface of graphite/ABS composite electrodes. Higher efficiencies were achieved while CV treatments were carried out in alkaline (KOH) background electrolyte, applying an elevated number of successive cycles (1000) under high scan rate (2000 mV s−1), being the oxidation potential observed at +1.5 V. After treatment, scanning electron microscopy and atomic force microscopy images pointed to an increase on both surface area and roughness; the results for Raman spectroscopy and FT-IR complemented the elucidation, demonstrating structural changes to the electrode after treatment, and confirming the formation of GO. Moreover, a relevant decrease in charge transfer resistance was observed by EIS (Rct, 275 to 50 Ω) and a 5-fold higher heterogeneous electron transfer rate constant (k0, 1.50 × 10−4 cm s−1) were verified after surface electrode treatment, indicating the faster transfer of electrons to redox probes on this surface. Such a surface treatment was thus effective and reproducible (RSD = 5.5%; n = 10) allowing an easy surface renewal just by smooth polishing. Treated electrodes were applied to dopamine (DP) quantification, showing stable amperometric responses, higher peak current intensities (3-fold) and improved detectability of DP when compared to modified electrodes obtained by drop casting (CRGO or ERGO modifications), which indicates that the proposed treatment is simpler and more appropriate. Wide linear range, higher sensitivity and precision were observed in the analytical methods developed for DP via BIA-AMP and SWV.
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