Recycled PETg embedded with graphene, multi-walled carbon nanotubes and carbon black for high-performance conductive additive manufacturing feedstock

The first report of conductive recycled polyethylene terephthalate glycol (rPETg) for additive manufacturing and electrochemical applications is reported herein. Graphene nanoplatelets (GNP), multi-walled carbon nanotubes (MWCNT) and carbon black (CB) were embedded within a recycled feedstock to produce a filament with lower resistance than commercially available conductive polylactic acid (PLA). In addition to electrical conductivity, the rPETg was able to hold >10 wt% more conductive filler without the use of a plasticiser, showed enhanced temperature stability, had a higher modulus, improved chemical resistance, lowered levels of solution ingress, and could be sterilised in ethanol. Using a mix of carbon materials CB/MWCNT/GNP (25/2.5/2.5 wt%) the electrochemical performance of the rPETg filament was significantly enhanced, providing a heterogenous electrochemical rate constant, k0, equating to 0.88 (±0.01) × 10−3 cm s−1 compared to 0.46 (±0.02) × 10−3 cm s−1 for commercial conductive PLA. This work presents a paradigm shift within the use of additive manufacturing and electrochemistry, allowing the production of electrodes with enhanced electrical, chemical and mechanical properties, whilst improving the sustainability of the production through the use of recycled feedstock

New electrochemical approach for the measurement of oxidative DNA damageVoltammetric determination of 8-oxoguanine at screen-printed graphite electrodes

© 2017 Elsevier B.V. Simplification and miniaturisation of analytical methods for the direct detection of DNA damage is a challenging area of research and screen-printed electrodes are a promising alternative approach to analytically/electroanalytically monitor the species involved. In this work we demonstrate that screen-printed graphite macroelectrodes (SPEs) provide useful electrochemical signatures to study the behaviour of 8-oxoguanine (8-oxoGua), which is the most frequent and important marker of oxidative DNA damage and it is widely considered as a biomarker, via differential pulse voltammetry (DPV). Under the optimum experimental conditions, the proposed electrochemical sensing protocol towards 8-oxoGua using SPEs is demonstrated to be possible over the concentration range of 0.1–12 μM. The response of the SPEs is superior over routinely utilised glassy carbon electrodes in terms of sensitivity with a limit of detection (3σ) found to correspond to 0.33 μM. Reproducibility and repeatability of the proposed methodology at low and high concentrations were also demonstrated. Quantification of 8-oxoGua in the presence of other nucleobases and different compounds of interest which are present in biological fluids was successfully accomplished. Furthermore, proof-of-concept demonstrating the potential use of the developed SPE based methodology for the detection of 8-oxoGua in real complex samples as demonstrated in simulated biological samples (human semen)

Synthesis and Characterization of a New Cobalt(II) Complex with 2-(2-Pyridyl)Imino-N-(2-Thiazolin-2-yl)Thiazolidine (PyTT)

The compound aquanitrate-кObis[2-(2-pyridy)-imin-кN-N-(2-thiazin-кN-2-y)thiazidine]cbat() nitrate has been isolated and characterized by single crystal X-ray diffraction, IR spectroscopy, UV-Vis-NIR diffuse reflectance and magnetic susceptibility measurements. The environment around the cobalt atom may be described as a distorted octahedral geometry with the ligand-metal-ligand bite angles varying between 84.07(8)° and 98.66(8)°.The metallic atom is coordinated to two thiazoline nitrogens [av. Co-N =2.067 Å], two imino nitrogens [av. Co-N =2.122 Å], one oxygen atom of the nitrate group monodentate [Co-O(1)= 2.249(2) Å] and the oxygen atom of the water molecule [Co-O(IW)= 2.105(2) Å]. Electronic UV-Vis-NIR spectral data and the calculated magnetic moment are indicative of octahedral Co(ll) complexes. In the same way as other PyTT complexes, the organic moiety preserves the imino-thiazolidine form detected in the structure of PyTT

The Effect of Slicer Infill Pattern on the Electrochemical Performance of Additively Manufactured Electrodes

In this work we report the dramatic effects that changing the infill pattern has on the electrochemical performance of an additively manufactured electrode made from commercial filament. Electrodes were produced using six different slicing patterns and imaged to confirm how the infill pattern altered the working electrode surface. These electrodes were then electrochemically characterised against the near-ideal outer sphere redox probe [Ru(NH3)6]3+, the common inner sphere probe [Fe(CN)6]3−, and then used for the electroanalytical determination of acetaminophen. It was found that changing the infill pattern had a dramatic effect on the electrochemical performance of the electrodes. Over the course of the manuscript, it can be seen that Aligned Rectilinear and Rectilinear infill patterns perform consistently well and offer good reproducibility. On the other hand, Concentric infill pattern had noticeably poor inter-electrode reproducibility and the Hilbert Curve infill was one of the worst performing electrodes in many categories. For future work in this field, we recommend the infill pattern is always reported within the experimental section to allow other researchers to repeat work properly. Additionally, when optimising an electroanalytical sensing platform, we encourage researchers to optimise the infill pattern as it has direct influence on the analytical parameters

Multi-walled carbon nanotubes/carbon black/rPLA for high-performance conductive additive manufacturing filament and the simultaneous detection of acetaminophen and phenylephrine

The combination of multi-walled carbon nanotubes (MWCNT) and carbon black (CB) is presented to produce a high-performance electrically conductive recycled additive manufacturing filament. The filament and subsequent additively manufactured electrodes were characterised by TGA, XPS, Raman, and SEM and showed excellent low-temperature flexibility. The MWCNT/CB filament exhibited an improved electrochemical performance compared to an identical in-house produced bespoke filament using only CB. A heterogeneous electrochemical rate constant, of 1.71 (± 0.19) × 10−3 cm s−1 was obtained, showing an almost six times improvement over the commonly used commercial conductive CB/PLA. The filament was successfully tested for the simultaneous determination of acetaminophen and phenylephrine, producing linear ranges of 5–60 and 5–200 μM, sensitivities of 0.05 μA μM−1 and 0.14 μA μM−1, and limits of detection of 0.04 μM and 0.38 μM, respectively. A print-at-home device is presented where a removable lid comprised of rPLA can be placed onto a drinking vessel and the working, counter, and reference components made from our bespoke MWCNT/CB filament. The print-at-home device was successfully used to determine both compounds within real pharmaceutical products, with recoveries between 87 and 120% over a range of three real samples. This work paves the way for fabricating new highly conductive filaments using a combination of carbon materials with different morphologies and physicochemical properties and their application to produce additively manufactured electrodes with greatly improved electrochemical performance

The Mediatorless Electroanalytical Sensing of Sulfide Utilizing Unmodified Graphitic Electrode Materials

The mediatorless electroanalytical sensing of sulfide is explored at a range of commercially available graphitic based electrodes namely, edge and basal plane pyrolytic graphite (EPPGE and BPPGE, respectively), boron-doped diamond (BDDE), glassy carbon (GCE) and screen-printed electrodes (SPE). The electrochemical performance is evaluated in terms of current density/analytical signal and oxidation potential, where the GCE and SPE are found to possess the optimal electrochemical responses. The electroanalytical performance of the GCE is explored towards the electrochemical sensing of sulfide and it is found that it is hampered by sulfide passivation, thus requiring pretreatment in the form of electrode polishing between each measurement. We demonstrate that SPEs provide a simple analytically comparable alternative, which, due to their scales of economy, create disposable, one-shot sensors that do not require any pretreatment of the electrode surface. To the best of our knowledge, this is the first report using mediatorless SPEs (bare/unmodified) towards the sensing of sulfide. In addition, the electroanalytical efficacy of the SPEs is also explored towards the detection of sulfide within model aqueous solutions and real drinking water samples presenting good apparent recoveries, justifying the plausibility of this graphitic mediatorless screen-printed platform

High yield synthesis of hydroxyapatite (HAP) and Palladium Doped HAP via a wet chemical synthetic route

© 2016 by the authors; licensee MDPI, Basel, Switzerland. A novel procedure for the synthesis of both hydroxyapatite (HAP) and palladium doped HAP via a wet chemical precipitation method is described herein. X-ray Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) and Fourier Transform Infrared (FT-IR) Spectroscopy are utilised to characterise the synthesised material’s morphology, structure and crystallinity. The developed synthetic protocol produces high purity HAP with an average yield of 83.7 (±0.10)% and an average particle size of 58.2 (±0.98) nm, such synthesis has been achieved at room temperature and within a time period of less than 24 h. Additionally, in order to enhance the overall conductivity of the material, a range of Pd (2, 4 and 6 wt %) metal doped HAP has been synthesised, characterised and, for the first time, applied towards the competitive electrocatalytic detection of hydrazine, exhibiting a linear range of 50–400 μM with a limit of detection (3σ) of 30 µM

Dissemination, implementation, and evaluation of an effective school-based intervention to promote physical activity in adolescents: a study protocol

Adolescents around the world do not engage in sufficient physical activity and the Spanish context is no exception. Understanding the educational context as a complex system, school-based multi-level and multi-component interventions seem to be an effective strategy to reverse this trend. Moreover, a co-creational approach seems to facilitate the mobilization of community partnerships and the engagement of stakeholders in the intervention process. This study aims to describe the dissemination, implementation, and evaluation process of an effective school-based intervention program in another setting using the replicating effective programs framework and a co-participatory approach. This study will be conducted in two Spanish secondary schools located in the region of Aragon (experimental vs. control school) in a sample of adolescents in the second grade (13–14 years old). To evaluate the effectiveness, different health behaviors such as physical activity, sleep, sedentary time with screens, nutrition, and psychosocial variables will be quantitatively measured at baseline and after the implementation of the intervention. Qualitative methods will also be used to better understand the implementation process and the co-creation approach, as well as to provide insights into the sustainability of the intervention program. The current study has the potential to provide strong information about the dissemination, implementation, and evaluation process of school-based programs to promote healthy behaviors among adolescents

Mixed Graphite/Carbon Black Recycled PLA Conductive Additive Manufacturing Filament for the Electrochemical Detection of Oxalate

Mixing of graphite and carbon black (CB) alongside recycled poly(lactic acid) and castor oil to create an electrically conductive additive manufacturing filament without the use of solvents is reported herein. The additively manufactured electrodes (AMEs) were electrochemically benchmarked against a commercial conductive filament and a bespoke filament utilizing only CB. The graphite/CB produced a heterogeneous rate constant, k0, of 1.26 (±0.23) × 10-3 cm s-1 and resistance of only 155 ± 15 Ω, compared to 0.30 (±0.03) × 10-3 cm s-1 and 768 ± 96 Ω for the commercial AME. Including graphite within the filament reduced the cost of printing each AME from £0.09, with the CB-only filament, to £0.05. The additive manufacturing filament was successfully used to create an electroanalytical sensing platform for the detection of oxalate within a linear range of 10-500 μM, achieving a sensitivity of 0.0196 μA/μM, LOD of 5.7 μM and LOQ of 18.8 μM was obtained. Additionally, the cell was tested toward the detection of oxalate within a spiked synthetic urine sample, obtaining recoveries of 104%. This work highlights how, using mixed material composites, excellent electrochemical performance can be obtained at a reduced material cost, while also greatly improving the sustainability of the system

Pencil it in: Exploring the Feasibility of Hand-Drawn Pencil Electrochemical Sensors and their Direct Comparison to Screen-Printed Electrodes

We explore the fabrication, physicochemical characterisation (SEM, Raman, EDX and XPS) and electrochemical application of hand-drawn pencil electrodes (PDEs) upon an ultra-flexible polyester substrate; investigating the number of draws (used for their fabrication), the pencil grade utilised (HB to 9B) and the electrochemical properties of an array of batches (i.e, pencil boxes). Electrochemical characterisation of the PDEs, using different batches of HB grade pencils, is undertaken using several inner- and outer-sphere redox probes and is critically compared to screen-printed electrodes (SPEs). Proof-of-concept is demonstrated for the electrochemical sensing of dopamine and acetaminophen using PDEs, which are found to exhibit competitive limits of detection (3σ) upon comparison to SPEs. Nonetheless, it is important to note that a clear lack of reproducibility was demonstrated when utilising these PDEs fabricated using the HB pencils from different batches. We also explore the suitability and feasibility of a pencil-drawn reference electrode compared to screen-printed alternatives, to see if one can draw the entire sensing platform. This article reports a critical assessment of these PDEs against that of its screen-printed competitors, questioning the overall feasibility of PDEs’ implementation as a sensing platfor