Printed Graphene Electrodes Research Articles

Printed graphene electrodes for textile-embedded triboelectric nanogenerators for biomechanical sensing

Textile triboelectric nano-generators (TENGs) are emerging as a promising solution for wearable self-powered sensing technology. However, achieving textile TENGs with excellent output performance in conformable devices, while using textile compatible techniques, is still a challenge. In this work, a highly efficient flexible triboelectric textile is developed by using printed graphene electrodes with polydimethylsiloxane (PDMS) and the textile itself as the triboelectric pair. To achieve this, a textile planarization technique with a polyurethane adhesive was employed, along with three different deposition methods: graphene droplet films (GDF), graphene immersion films (GIF), and graphene spray films (GSF). The result was a flexible textile electrode that surpassed non-planarized devices in all three printing techniques, with a 4-fold improvement and a power density of 3.08 µW/cm². Moreover, by increasing the TENG contact area through the use of four parallel devices measuring 3 × 3 cm² each, the power output reached an effective power of 60 µW. The flexible TENG presents a stable output performance under strong deformation and its sensitivity to movement was explored as wearable sensor to monitor biomechanical movements. This work provides a versatile method for constructing flexible triboelectric textile fabrics using only industrial compatible printing textile processes, paving the way to the seamless integration of self-powered wearable sensing technology into textiles.

Printed Graphene Electrode for ITO/MoS2/Graphene Photodiode Application

Lightweight and flexible electronics have recently emerged at the forefront of optoelectronic applications. In this regard, graphene electrodes enable opportunities for new photodiode devices. In this paper, we formulated and tested graphene ink using the standard inkjet printing technique. It was shown that the maximum conductivity of ink was achieved for 14 print passes of the graphene layer. Moreover, we deposited Molybdenum Disulfide (MoS2) ink in the same pattern and used it as an active layer. We put MoS2 ink on an Indium-Tin-Oxide (ITO) glass substrate and then deposited graphene ink as a top electrode to fabricate an ITO/MoS2/graphene device. The fabricated device showed good rectification behavior and high ON/OFF switching behavior with a max photocurrent of 15 µA at +2 V. The technique thus paves the way for low-cost, low-temperature processing of electronics and one-step fabrication.

MnO2-decorated highly porous 3D-printed graphene supercapacitors for photosynthetic power systems

3D printed graphene electrodes decorated with nanoporous MnO2 and thylakoid membranes isolated from spinach leaves enable more efficient harvesting and storage of photosynthetic electrons produced from photosynthesis in thylakoid membranes.

Aerosol-jet-printed graphene electrochemical immunosensors for rapid and label-free detection of SARS-CoV-2 in saliva

Rapid, inexpensive, and easy-to-use coronavirus disease 2019 (COVID-19) home tests are key tools in addition to vaccines in the world wide fight to eliminate national and local shutdowns. However, currently available tests for SARS-CoV-2, the virus that causes COVID-19, are too expensive, painful, and irritating, or not sufficiently sensitive for routine, accurate home testing. Herein, we employ custom-formulated graphene inks and aerosol jet printing to create a rapid electrochemical immunosensor for direct detection of SARS-CoV-2 spike receptor-binding domain (RBD) in saliva samples acquired noninvasively. This sensor demonstrated limits of detection that are considerably lower than most commercial SARS-CoV-2 antigen tests (22.91 ± 4.72 pg ml−1 for spike RBD and 110.38 ± 9.00 pg ml−1 for spike S1) as well as fast response time (∼30 min), which was facilitated by the functionalization of printed graphene electrodes in a single-step with SARS-CoV-2 polyclonal antibody through the carbodiimide reaction without the need for nanoparticle functionalization or secondary antibody or metallic nanoparticle labels. This immunosensor presents a wide linear sensing range from 1 to 1000 ng ml−1 and does not react with other coexisting influenza viruses such as H1N1 hemagglutinin. By combining high-yield graphene ink synthesis, automated printing, high antigen selectivity, and rapid testing capability, this work offers a promising alternative to current SARS-CoV-2 antigen tests.

Prussian blue nanoparticles anchored on activated 3D printed sensor for the detection of L-cysteine

The use of 3D printing technology has enabled the development of low-cost and versatile electrochemical sensors. Commercial conductive filaments have been widely used due to their easiness of acquisition ready for application, and the possibility of surface modification. Generally, these filaments are composed of polymers and conductive material. However, it can present different compositions according to the manufacturing, which includes other additives and impurities. Iron has been reported as one of these impurities in conductive filaments based on polylactic acid and graphene. In this case, we have explored the presence of iron species for the electrochemical synthesis of stable nanoparticles of Prussian blue on 3D printed graphene electrodes. Prussian blue was used for the catalyst and electro-oxidation of L-cysteine amino acid, which is a biomarker related to several health problems and neurodegenerative diseases, such as Alzheimer's and Parkinson's. An arrangement of all 3D printed electrodes was used and presented comparable results to a conventional electrodes array. Also, the proposed sensors have shown good sensitivity, selectivity in presence of other amino acids, repeatability, and intra-day reproducibility for L-cysteine detection, compared to other 3D printed sensors obtained at different ages. The detection of L-cysteine was performed in spiked human blood serum samples, demonstrating no significant matrix interference.

Morphology and electrical properties of high-speed flexography-printed graphene.

Printed graphene electrodes have been demonstrated as a versatile platform for electrochemical sensing, with numerous examples of rapid sensor prototyping using laboratory-scale printing techniques such as inkjet and aerosol jet printing. To leverage these materials in a scalable production framework, higher-throughput printing methods are required with complementary advances in ink formulation. Flexography printing couples the attractive benefits of liquid-phase graphene printing with large-scale manufacturing. Here, we investigate graphene flexography for the fabrication of electrodes by analyzing the impacts of ink and process parameters on print quality and electrical properties. Characterization of the printed patterns reveals anisotropic structure due to striations along the print direction, which is related to viscous fingering of the ink. However, high-resolution imaging reveals a dense graphene network even in regions of sparse coverage, contributing to robust electrical properties even for the thinnest films (< 100nm). Moreover, the mechanical and environmental sensitivity of the printed electrodes is characterized, with particular focus on atmospheric response and thermal hysteresis. Overall, this work reveals the conditions under which graphene inks can be employed for high-speed flexographic printing, which will facilitate the development of graphene-based sensors and related devices.

A 3D printed graphene electrode device for enhanced and scalable stem cell culture, osteoinduction and tissue building

Bone related diseases and disorders increasingly impact human health. Electrical stimulation (ES) has been shown to promote osteogenesis and healing of bone defects. Graphene, is an electrically conductive and biocompatible material with good mechanical properties (strength with flexibility), and therefore shows significant promise as a cell-compatible electrode for ES. Graphene-based scaffolds may therefore be used for 3D cell and tissue support, including 3D osteoinduction. We have fabricated 3D graphene electrode structures to provide ES to human adipose stem cells (ADSCs). The assemblies support ADSC growth and differentiation, with ES augmenting proliferation and osteogenesis. Our findings expand our previous work on developing graphene-based cell culture platforms for bone engineering, demonstrating their adaptability and amalgamation for more scalable and high throughput stem cell maintenance, osteoinduction and tissue building. Furthermore, the devices have the potential to be employed for a variety of other cells and tissues for research and therapeutics, including regenerative medicine.

Graphene based electrochemical immunosensor for the ultra-sensitive label free detection of Alzheimer's beta amyloid peptides Aβ(1-42).

An immunosensor capable of high sensitivity detection of beta-amyloid peptides, shown to be a reliable biomarker for Alzheimer's disease, has been developed using screen printed graphene electrodes (SPGEs) modified with ultra-thin layers of polymerised 1,5-diaminonaphthalene (pDAN). Electropolymerization of 1,5-diaminonaphthalene (DAN) was performed to coat the graphene screen printed electrodes in a continuous polymer layer with controlled thickness. The surface characteristics of pristine graphene and polymer modified graphene electrodes were examined using Raman and X-ray photoelectron spectroscopy. The effects of polymer thickness on the electron transfer rates were investigated. An immunosensor for selective detection of beta amyloid peptides Aβ(1–42) was developed via biofunctionalization of the pDAN modified SPGE with the anti-beta amyloid antibody used as the peptide bioreceptor. The immunosensor has been used for specific detection of Aβ(1–42) with a linear range of 1 pg mL−1 to 1000 pg mL−1 and showed 1.4 pg mL−1 and 4.25 pg mL−1 detection and quantification limit, respectively. The biosensor was further validated for the analysis of spiked human plasma. The immunosensor enables rapid, accurate, precise, reproducible and highly sensitive detection of Aβ(1–42) using a low-cost SPGE platform, which opens the possibilities for diagnostic ex vivo applications and research-based real time studies.

Development of a fast and sensitive method for the determination of As(III) at trace levels in urine by differential pulse anodic voltammetry using a simple graphene screen–printed electrode

A simple and fast anodic voltammetric method was employed to determine traces of As(III) in urine samples using commercial screen–printed graphene electrodes without subsequent modification. To obtain a sensitive and selective method for As(III) determination, the effects of various parameters such as pH, supporting electrolyte concentration, accumulation potential (Eacc), accumulation time (tacc), and potential scan conditions were studied. The optimum experimental conditions were chosen to be as follows: pH of 2.8 (0.01 mol L−1 phosphate buffer), scan increment of 4 mV, pulse width of 80 ms, pulse period of 0.5 s, and pulse amplitude of 200 mV. Differential pulse voltammograms were obtained by scanning from −0.80 V to 0.80 V without applying an accumulation step. Under these conditions, one peak was observed at 0.27 V due to As0 oxidation. After optimizing the experimental conditions, the anodic peak current for As was found to be linearly related to its concentration up to ca. 5.0 μg L−1, with detection and quantitation limits (DLs, QLs) of 0.28 µg L−1 and 0.92 µg L−1, respectively. The developed method was validated by the determination of As(III) in spiked tap water from our laboratory, which showed an As(III) concentration of 50.64 ± 0.10 μg L−1 (spiked with 50.0 μg L−1); two urine samples (where As was not detected) spiked with As(III) 0.73 μg L−1 and 0.91 μg L−1 (in the cell) showed an As(III) concentration of 0.70 μg L−1 and 0.91 μg L−1, respectively. The method was successfully applied to the determination of Astotal in 16 urine samples obtained from workers occupationally exposed to inorganic arsenic compounds without previous treatment. The results obtained for Astotal were compared with measurements made by an external analytical laboratory, which used HG–AAS. To determine Astotal, As(V) was reduced in the presence of thiosulfate in an acid medium. The electrode showed good stability and repeatability.

3D Printed Mechanically Robust Graphene/CNT Electrodes for Highly Efficient Overall Water Splitting.

3D printing of graphene electrodes with high mechanical strength has been a growing interest in the development of advanced energy, environment, and electronic systems, yet is extremely challenging. Herein, a 3D printed bioinspired electrode of graphene reinforced with 1D carbon nanotubes (CNTs) (3DP GC) with both high flexural strength and hierarchical porous structure is reported via a 3D printing strategy. Mechanics modeling reveals the critical role of the 1D CNTs in the enhanced flexural strength by increasing the friction and adhesion between the 2D graphene nanosheets. The 3DP GC electrodes hold distinct advantages: i) an intrinsically high flexural strength that enables their large-scale applications; and ii) a hierarchical porous structure that offers large surface area and interconnected channels, endowing fast mass and/or charge and ions transport rate, which is thus beneficial for acting as an ideal catalyst carrier. The 3DP GC electrode integrated with a NiFeP nanosheets array exhibits a voltage of 1.58 V at 30 mA cm-2 as bifunctional electrode for water splitting, which is much better than most of the reported Ni-, Co-, and Fe-based bifunctional electrocatalysts. Importantly, this study paves the way for the practical applications of 3D printed graphene electrodes in many energy conversion/storage, environmental, and electronic systems where high flexural strength is preferred.

Facile synthesis of paper based graphene electrodes for point of care devices: A double stranded DNA (dsDNA) biosensor

The demand for high-quality graphene for electronic applications is increasing due to its high carrier mobility and electrical conductivity. In this connection, printing technology is a reliable method towards the fabrication of conductive, disposable graphene-based electrode for low-cost sensor application. Herein, we aimed to report the synthesis of high-quality graphene nanosheets obtained by electrochemical exfoliation of biomass-derived from corn cob. The conductive ink was prepared from this exfoliated graphene and was utilized for the preparation of paper-based graphene electrode towards double stranded DNA (dsDNA) sensor application. This paper, based graphene electrode opens the possibility of direct electrochemical analysis of analyte without any sample preparation. In this study, two irreversible oxide peaks were obtained from paper-based printed graphene electrode, corresponds to oxidation of guanine (G) and adenine (A) of dsDNA in the linear range of 0.2 pg mL−1 to 5 pg mL−1 with the detection limit of 0.68 pg mL−1 and the sensitivity of 0.00656 mA pg−1 cm−2. Further, a small-scale printable circuit is fabricated using this graphene shows good conductivity of 1.145x103(S/m).

Washable and flexible screen printed graphene electrode on textiles for wearable healthcare monitoring

Electrocardiogram (ECG) is an essential route to monitor and prevent cardiovascular related disease. Conventional silver/silver chloride (Ag/AgCl) electrodes are not able to be used for long-term monitoring due to the drying of gel and skin irritation. Graphene has been investigated as a promising material for wearable health-monitoring electronics. Here, a graphene-coated textile electrode was developed for ECG monitoring. The graphene electrode was prepared by screen printing graphene ink on a pre-modified textile substrate. The electrical resistance of the graphene textile electrode can be controlled by increasing the printing passes. The ECG signals obtained by the graphene textile electrode showed comparable performance to the conventional Ag/AgCl electrode. The graphene textile electrode shows satisfactory washability, high flexibility and good tortuosity. The performance of the ECG signal shows negligible change over nine washing cycles and 2000 bending cycles. Overall, the screen-printed graphene textile electrode in this work presents an inexpensive fabrication platform solution for long-term healthcare monitoring in wearable electronics.

Oxygen Plasma/Bismuth Modified Inkjet Printed Graphene Electrode for the Sensitive Simultaneous Detection of Lead and Cadmium

In this work, a simple procedure for the preparation of an inkjet printed disposable graphene electrode is reported. Commercial graphene ink was printed on a kapton substrate and the resulting electrode was 30 min treated by oxygen plasma, then modified by a bismuth salt. The as prepared electrode was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), laser scanning microscopy (LSM) and scanning electron microscopy (SEM) coupled to energy-dispersive X-ray spectroscopy (EDX). The sensing properties of the characterized electrodes were then investigated using cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS). Afterwards, these electrodes were exploited in a comparative way for the electroanalysis of Cadmium(II) and Lead(II) ions. An increase in the electrode sensitivity due to its modification and to the presence of bismuth was observed. Some preliminary experiments based on stripping square wave voltammetry highlighted the interest of using the proposed disposable inkjet printed electrodes for the electrochemical detection of heavy metals in tap water.

Fabrication of label-free electrochemical food biosensor for the sensitive detection of ovalbumin on nanocomposite-modified graphene electrode

In this work a highly sensitive label-free electrochemical food biosensor for the detection of egg allergen ovalbumin (Ova) was developed using nanocomposite consisting of iron oxide (Fe3O4) and palladium (Pd) nanoparticles with conducting polymer chitosan (CS). Pd nanoparticles were synthesized and seeded onto Fe3O4 nanoparticles, and dispersed in CS to form the nanocomposite. The nanocomposite (Fe3O4-Pd/CS) was drop-casted onto a screen printed graphene electrode (SPGE). Subsequently, 4-ABA was electrografted onto the modified SPGE/Fe3O4-Pd/CS. Carbodiimide chemistry was performed for the covalent conjugation of Ova-antibody (Ova-Ab) onto the electrode surface. The bimetallic nanocomposite portrayed excellent electrocatalytic effect due to the synergistic conductive effect of the Fe3O4-Pd nanomaterials and CS polymers and facilitated the electron movement between electrode surface and redox buffer. Additionally, ABA also enhanced electronic current on the surface of the electrode. Featuring high electron conductivity, the developed food biosensor demonstrated a large linear range to detect the Ova between 0.01 pg/mL – 1 µg/mL with a low limit of detection of 0.01 pg/mL. Furthermore, the proposed food biosensor portrayed very good selectivity with a high potential to detect Ova in real food sample.

Screen printed graphene electrodes on textile for wearable electrocardiogram monitoring

This work demonstrated a dry electrode for electrocardiogram (ECG) monitoring based on graphene-coated cotton fabric by screen printing process. The cotton fabric was fully covered by the graphene flakes, which makes the sheet resistance of cotton fabric reaches as low as 42.2 Ω/sq. The ECG signals obtained from the graphene-coated textile electrode show comparable performance with the Ag/AgCl electrode under both sitting, standing, and rotating conditions. The Pearson correlation coefficient between the conventional commercial electrode and the graphene-coated textile electrode is 99.47%. The graphene-coated textile electrode exhibited an excellent flexibility with an increase resistance of 4.5% after 1000 bending cycles. The graphene-coated textile electrode after bending showed good performance for ECG signal acquisition.

3D Printed Graphene Electrodes Modified with Prussian Blue: Emerging Electrochemical Sensing Platform for Peroxide Detection.

3D printing technologies have been considered an important technology due to the ease manufacturing of objects, freedom of design, waste minimization, and fast prototyping. In chemistry, this technology potentializes the fabrication of conductive electrodes in large scale for sensing applications. Herein, we reported the modification of a 3D printed graphene electrode with Prussian blue. The modified electrode (3DGrE/PB) was characterized by microscopy (SEM and AFM) and spectroscopic techniques, and its electrochemical properties were compared to the traditional electrodes: glassy carbon, gold, and platinum. The 3DGrE/PB was used in the sensing of hydrogen peroxide in real-world samples of milk and mouthwash, and the results obtained according to the technique of batch-injection analysis were satisfactory for the concentration range typically found in such samples. Thus, 3DGrE/PB can be used as a new platform for sensing of molecular targets.

Wearable multifunctional printed graphene sensors

The outstanding properties of graphene have initiated myriads of research and development; yet, its economic impact is hampered by the difficulties encountered in production and practical application. Recently discovered laser-induced graphene is generated by a simple printing process on flexible and lightweight polyimide films. Exploiting the electrical features and mechanical pliability of LIG on polyimide, we developed wearable resistive bending sensors that pave the way for many cost-effective measurement systems. The versatile sensors we describe can be utilized in a wide range of configurations, including measurement of force, deflection, and curvature. The deflection induced by different forces and speeds is effectively sensed through a resistance measurement, exploiting the piezoresistance of the printed graphene electrodes. The LIG sensors possess an outstanding range for strain measurements reaching >10% A double-sided electrode concept was developed by printing the same electrodes on both sides of the film and employing difference measurements. This provided a large bidirectional bending response combined with temperature compensation. Versatility in geometry and a simple fabrication process enable the detection of a wide range of flow speeds, forces, and deflections. The sensor response can be easily tuned by geometrical parameters of the bending sensors and the LIG electrodes. As a wearable device, LIG bending sensors were used for tracking body movements. For underwater operation, PDMS-coated LIG bending sensors were integrated with ultra-low power aquatic tags and utilized in underwater animal speed monitoring applications, and a recording of the surface current velocity on a coral reef in the Red Sea.

(Invited) Emerging Nanomaterial Inks for Additive Manufacturing of Wearable Sensors

The versatility of direct write techniques such as aerosol jet printing (AJP) and ink jet printing (IJP) has recently intersected with two-dimensional (2D) materials research to enable novel wearable sensors. Graphene and 2D transition metal nitrides, carbides and carbonitrides (MXenes) are of particular interest for wearable sensor applications due to their biocompatibility and multifunctional nature. However, these 2D materials must be contacted by biocompatible metals, e.g. platinum, in order to enable functional devices such as wearable and/or implantable electrochemical sensors and neural interfaces.[1 - 3] In this study, we report the printing of 2D materials, graphene, titanium carbide Mxenes (Ti3C2), and platinum nanoparticles via AJP and IJP. Ink characterization was performed with atomic force microscopy, scanning and transmission electron microscopy (SEM and TEM), DLS and Raman spectroscopy. Graphene sheets were obtained via solvent assisted exfoliation and then dispersed in 85:15 cyclohexanone/terpineol to formulate graphene inks at a concentration of 3.5 mg/ml.[4,5] Graphene sheets exhibited an average thickness of 16 nm +/- 15 nm and crystal domains with lateral dimensions ranging from ~50 nm to 200 nm. Platinum ink (20 wt.%) was formulated with the dispersion of platinum nanopowders and 70:30 water/ethylene glycol mix. Dispersed platinum nanoparticles exhibited an average particle size of 7.8 nm +/- 2.3 nm. Finally, an AJP compatible multi-layered MXene ink was obtained by in situ HF etching of the pre-cursor Ti3AlC2 MAX phase.[6] The obtained colloidal suspension containing 2D MXene flakes was sonicated with deionized water for 3 hours at 55 W. The resultant ink had a concentration of 1 mg/mL and an average flake size of 100 nm +/- 10 nm, as confirmed by dynamic light scattering (DLS) measurements. Platinum, graphene and Ti3C2 inks have demonstrated good compatibility with an Optomec Aerosol Jet 200 and a Dimatix 2850 materials inkjet printer, while platinum and graphene have shown additional compatibility with IJP. For good electrical conductivity graphene was sintered at 390 C for one hour and platinum was sintered at 450 C for 130 hours, while MXenes showed good conductivity without sintering. Optical microscopy, SEM, stylus profilometry, and two/four-point resistance measurements were used to examine the quality of the printed MXene and platinum structures. Initial printing with MXenes resulted in feature heights ranging from ~ 620 nm to 4.80 µm, depending on the number of print passes denoted as N. Our most uniform prints were N = 15 and N = 20 having a height of 2.50 µm +/- 0.10 µm and 3.50 µm +/- 0.10 µm, respectively. Electrical resistance varied between R = 568 kΩ and R = 60 kΩ for N = 5 and N = 25 respectively. Platinum exhibited good electrical conductivity as R = 70 Ω for N = 10, having a height of 3 µm and a feature width of ~50 µm. Furthermore, the electrochemical properties of fully inkjet printed graphene electrodes on a flexible polyimide substrate for pH and electrolyte sensing were investigated. Printed electrodes consisted of a printed 1x1 cm graphene square with a total of 17 layers with printed silver contact pads and a SU-8 as a passivation layer. Electrochemical activity of inkjet printed graphene electrodes was demonstrated with both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements in a room temperature 10 mM ferricyanide aqueous solution (1 M KCl supporting electrolyte). Ag/AgCl and platinum electrodes were used as the reference and counter electrode, respectively. Additionally, pH sensing capabilities were investigated by measuring the potentiometric response of polyaniline coated graphene electrodes over three different pH values (4, 7 and 10). The response of printed and flexible graphene electrodes was comparable to that of a conventional glass electrode. In conclusion, AJP compatible Ti3C2 MXene inks along with AJP and IJP compatible platinum and graphene inks have been developed. Printing of these biocompatible materials is intended to support the fabrication of nanomaterial based flexible hybrid electronics such as biosensors for electrochemical sensing of a broad spectrum of biomarkers, and also neural interface systems. Furthermore, our results provide new fundamental insights on role of structure-property-performance correlations in printed graphene electrodes for electrochemical sensing. The combination of our works highlight the significant potential of novel material inks for additively manufactured wearable sensors. [1] Kenry et al., Microsystems Nanoeng., Sep. 2016. [2] Sinha et al., Trends Analyt Chem, 2018. [3] A. Sridhar et al., Mater. Matters, 2009. [4] J. N. Coleman et al., Acc. Chem. Res., 2013. [5] F. Torrisi et al., ACS Nano, 2012. [6] M. Alhabeb et al., Chemistry of Materials, 2017.

Laser-derived graphene: A three-dimensional printed graphene electrode and its emerging applications

Abstract Printing of binder-free graphene electrodes directly on substrates has the potential to enable a large number of applications. Though conventional processing techniques such as ink-jet, screen-printing, and roll coating methods offer reliable and scalable fabrication, device performance has often been limited by re-stacking of the graphene sheets and by presence of passive binders and or additives. Laser-based, direct-write technologies have shown promise as a reliable, maskless, and template-free patterning method. Thus, laser-derived graphene (LDG) electrode is emerging as a promising three-dimensional graphene electrode that can be simultaneously derived from precursor carbons or polymers and patterned upon laser exposure. The LDG can be obtained through irradiation by a variety of laser sources including CO2 infrared laser and femtosecond laser pulses, depending on the nature of the starting carbon precursors. Controlling the microstructure, amount and types of doping, and post-deposition methods enable a variety of applications including energy storage, catalysis, sensing and biomedicine. In this review article, we discuss recent progress in using laser-based fabrication of printed 3D graphene electrodes and its wide spectrum of applications. The review also discusses the material aspects of 3D graphene electrodes and provides an outlook for future potential.

Enhanced performance of 3D printed graphene electrodes after electrochemical pre-treatment: Role of exposed graphene sheets

3D printing has been reported as a remarkable technology for development of electrochemical devices, due to no design constraints, waste minimization and, most importantly, fast prototyping. The use of 3D printed electrodes for electroanalytical applications is still a challenge and demand efforts. In this work, we have developed low-cost and reproducible 3D-printed graphene electrodes for electrocatalytic detection of dopamine. Electrocatalytic features were enhanced after electrochemical pre-treatment. The oxidation and reduction at different potential ranges, in 0.1 mol L−1 phosphate buffer solution (pH = 7.4), are used to modulate the structural and morphological characteristics of the electrodes. Since, the electrochemical properties of the electrodes, including electron transfer kinetic and the electrocatalytic activity, are strongly influenced by electronic properties and the presence of functional groups. Raman spectroscopy, SEM and AFM microscopes and electrochemical techniques were used to characterize the 3D electrodes before and after the electrochemical pre-treatments. Finally, the performances of the 3D-printed graphene electrodes were evaluated towards dopamine sensing. The best performance was achieved by oxidation at + 1.8 V vs. SCE for 900 s and reduction from 0.0 V to -1.8 V vs. SCE at 50 mV s−1. The proposed sensor presented linear response from 2.0 μmol L−1 to 10.0 μmol L−1, with detection limit of 0.24 μmol L−1.