Graphene Paste Research Articles

Ultra-low-cost coal-based carbon electrodes with seamless interfacial contact for effective sandwich-structured perovskite solar cells

The high cost of hole transporting materials (HTMs) and noble metallic electrodes limits the applications of perovskite solar cells (PSCs). Carbon materials, including carbon nanotube, graphene, and carbon paste, have been utilized for HTMs and noble-metal-free PSCs. Unlike other carbon materials, coal has extensive sources and lower price. A simple preparation process and an effective sandwich structure for the use of this material in PSCs were obtained by hot-pressing method. After the key parameters were adjusted, the power conversion efficiencies are 10.87% (0.3 cm2) and 8.72% (1 cm2). Therefore, devices with coal-based carbon electrodes have better stability than conventional devices. Our work proposes a promising future for the commercialization of low-cost and highly stable PSCs.

Pattern recognition of melatonin using stochastic sensors

Modified graphene paste stochastic sensors detect melatonin in biological fluids, whole blood, and pharmaceutical products.

Persian waxing of graphite: towards green large-scale production of graphene.

Large quantities of high-quality graphene has been produced through a green and up-scalable method based on the exfoliation and dispersion of graphene in a sugar-based wax, by mimicking the Scotch tape approach to enable the production of graphene paste with unprecedently high concentration of 30% in weight exhibiting ultrahigh stability.

Preparation of pristine graphene paste for screen printing patterns with high conductivity

Graphene conductive pastes are poised to apply in making flexible electronics via a screen-printing way because of its excellent electrical and mechanical properties. In this paper, a new formulation of a pristine graphene-based paste was presented consisting of the conductive filler of graphene, a mixed solvent of terpineol, dipropylene glycol methyl ether, cyclohexanone, and the auxiliaries of ethylcellulose, Span-85 and 1,4-butyrolactone. The paste containing 20 wt% of the graphene was prepared and showed excellent dispersibility and stability. The screen-printed patterns on a polyimide substrate achieved a high conductivity of 9 × 104 S/m and had excellent mechanical flexibility.

Electrochemical Determination of the KRAS Genetic Marker for Colon Cancer with Modified Graphete and Graphene Paste Electrodes

ABSTRACTThe determination of KRAS was performed using electrochemical sensing devices based on graphite and graphene pastes, modified with a phthalocyanine-boron dipyrromethene (BODIPY) and azulenes dyes. The limits of quantification for KRAS were 1.54 × 10−4 µg/mL using the sensor based on the phthalocyanine-BODIPY dye and graphite, 2.64 × 10−7 µg/mL using the sensor based on 2,6-bis((E)-2-(furan-2-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine/TiO2Pt/reduced graphene oxide, and 3.84 × 10−3 µg/mL using the sensor based on 2,6-bis((E)-2-(thiophen-3-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine/TiO2Pt/reduced graphene oxide. Recovery measurements demonstrated the suitable analytical performance of these sensors for the early detection of colon cancer by the analysis of whole blood samples.

Silver Nanoparticle Modified Graphene Paste Electrode for the Electrochemical Detection of Lead, Cadmium and Copper

Silver Nanoparticle Modified Graphene Paste Electrode for the Electrochemical Detection of Lead, Cadmium and Copper

Voltammetric determination of lead and cadmium in vegetables by graphene paste electrode modified with activated carbon from coconut husk

A multilayer graphene paste electrode (MGPE), consisting of graphene flakes and mineral oil, was modified with activated carbon (AC). The AC was produced from coconut husk using zinc chloride as the activating agent. The AC/MGPE was fabricated by substituting an amount of the multilayer graphene (MG) with the AC, and the resulting paste was packed in a Teflon syringe. The electrode was used to simultaneously detect lead (Pb2+) and cadmium (Cd2+) via anodic stripping voltammetry (ASV). The amounts of MG and AC in the electrodes were varied by substituting the amount of the former with the latter (by percent) and the best electrode was found to consist of 5% AC and 95% MG. The optimal parameters, accumulation time, deposition time, and deposition potential were determined. The optimized parameters were used on the said best electrode to determine the calibration curve and limit of detection. The peak current had a linear relation with the concentration of the heavy metals with a correlation value (R2) of 0.9956 and 0.9973 for Cd2+ and Pb2+, respectively. After which the electrode was used to detect heavy metals in vegetable samples, and the results were verified via atomic absorption spectroscopy. The heavy metal concentrations that were detected in most of the samples were above the maximum limit as dictated by the World Health Organization.

Synthesis and characterization of the thermally reduced graphene oxide in argon atmosphere, and its application to construct graphene paste electrode as a naptalam electrochemical sensor

New insight into the preparation of sensitive carbon–based electrochemical electrode is provided by examining the properties of thermally reduced graphene oxide (TRGO). In this paper, TRGO was prepared by thermal reduction of graphene oxide (GO) in argon atmosphere, and characterized by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), and atomic force microscopy (AFM). Results showed that thermal reduction in argon was effective to remove oxygen-containing functional groups in GO, and graphene sheets were obtained. Furthermore, TRGO was used to prepare thermally reduced graphene oxide paste electrode (TRGOPE) which showed excellent conductivity and fast electron transfer kinetics confirmed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrode was applied to determination of the pesticide naptalam (Nap) in square–wave voltammetric (SWV) mode. The corresponding current at approx. +1.0 V increased linearly with the Nap concentration within two linear dynamic ranges (LDR) of 0.1–1.0 μmol L−1 (LDR1) and 1.0–10.0 μmol L−1 (LDR2). The limits of detection (LOD) and quantification (LOQ) for Nap were calculated as 0.015 μmol L−1 and 0.051 μmol L−1, respectively. In comparison to the carbon paste electrode (CPE) the results showed that the TRGOPE possesses advantages in terms of linearity, sensitivity and detectability.

Chiral magnetic-nanobiofluids for rapid electrochemical screening of enantiomers at a magneto nanocomposite graphene-paste electrode

The development of highly sensitive and selective enantiomeric platforms towards the rapid screening of active pharmaceutical ingredients (APIs) is nowadays a crucial challenge in several fields related to pharmacology, biomedicine, biotechnology and (bio)sensors. Herein, it is presented a novel, facile and generic methodology focused on exploiting the synergistically and electrocatalytic properties of chiral magnetic-nanobiofluids (mNBFs) with electrochemical enantiobiosensing at a magneto nanocomposite graphene paste electrode (mNC–GPE). The feasibility of this approach has been validated by chirally recognizing tryptophan (TRP) enantiomers as a proof-of-concept. For this aim, a specific chiral mNBF based on an aqueous dispersion of cobalt ferrite loaded with gold nanoparticles carrying a thiolated β-cyclodextrin (β–CD-SH/Au/CoFe2O4–NPs) has been synthesized and used towards the supramolecular discrimination of TRP enantiomers at an advanced graphene-paste transducer via cyclic voltammetry. This strategy, which is the first demonstration of applicability of chiral mNBFs for electrochemical enantiorecognition, opens up new approaches into enantio(bio)sensing.

Near term commercial applications for graphene, composites and conductive pastes

Near term commercial applications for graphene, composites and conductive pastes

Exploring the electrochemical performance of graphite and graphene paste electrodes composed of varying lateral flake sizes.

We report the fabrication, characterisation (SEM/EDX, TEM, XRD, XPS and Raman spectroscopy) and electrochemical properties of graphite and graphene paste electrodes with varying lateral flake sizes. The fabricated paste electrodes are electrochemically analysed using both outer-sphere and inner-sphere redox probes, namely; hexaammineruthenium(iii) chloride, N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), potassium ferrocyanide(ii) and ammonium ferrous(ii) sulphate. Upon comparison of different graphite paste electrodes, a clear correlation between the lateral flake sizes (La), ranging from 1.5 mm-0.5 μm, and electrochemical activity (heterogeneous electron transfer (HET) kinetics) is evident, where an improvement in the HET is observed at smaller lateral flake sizes. We infer that the beneficial response evident when employing laterally smaller flakes is due to an increased number of edge plane like-sites/defects available upon the electrode surface, facilitating electron transfer. Interestingly, given that the overall lateral flake sizes of the graphenes utilised (10.0-1.3 μm) were significantly smaller than those studied previously, an improvement in HET kinetics was also evident with the reduction of lateral flake size; the extent to which is redox-probe dependent. Improvements are observed up to a distinct point, termed the 'lateral size threshold' (ca. ≤2 μm) where the electrochemical reversible limit is approached. Further support is provided from density functional theory (DFT), exploring the electronic structure (i.e. HOMO-LUMO) as a function of flake size, which demonstrates that the coverage of edge plane like-sites/defects comprising the geometric structure of the relatively small graphene flakes is such that effectively the entire flake has become electrochemically active. In this study, the importance of lateral flake size with respect to electrochemical reactivity at carbon-based electrodes has been demonstrated alongside a structural relationship upon HET performance, a phenomenon that has not previously been described in the literature. Such work is both highly important and informative for the field of electrochemistry and electrode performance, with potential implications in a plethora of areas, ranging from novel renewable energy sources to electroanalytical sensing platforms.

Mechanical Properties of Graphene-Rubber Nanocomposites

This research focused on development of wearable sensor device by using Prevulcanized Natural Rubber (PV) and Epoxidized Natural Rubber (ENR 50) latex incorporated with graphene oxide (GO), graphene paste, graphene powder and reduced graphene oxide (rGO) powder. The compounding formulation and calculation were based on phr (parts per hundred rubber) and all the samples were then tested for mechanical properties using Instron 5565 machine. It was found that the sonication effects on tensile strength may have better quality of tensile strength compared to non-sonicated GO. For PV incorporate GO, the optimum loading was best determined at loading 1.5 phr with or without sonication and similar result was recorded for PV/G. For ENR 50 incorporate graphene paste and rGO powder nanocomposite shows the best optimum was at 3.0 phr with 24 hours’ sonication.

Graphene materials for lead (II) extraction: an equilibrium study

The present paper describes a study on the adsorption of lead (II) ions on graphene materials obtained via exfoliation of a hydrolyzed expanded graphite intercalation compound. An equilibrium studies were performed implementing the empirical Freundlich and Langmuir isotherm models. It was found that all the isotherms are fitted well by those models, indicating the efficiency of the graphene materials as an adsorbent of heavy metals. The applicability of the two isotherms for sorption processes shows that both monolayer adsorption and heterogeneous energetic distribution of active sites on the adsorbent surface may take place. The maximum experimental lead (II) adsorption capacities of the materials under study – few-layered oxidized graphene suspension, multi-layered graphene paste, and few-layered graphene paste – were found to be 850, 230 and 170 mg/g, respectively. Due to the high sorption characteristics and unique physical and chemical properties of these materials, the adsorption technologies developed herein can act as good sustainable options for the future in heavy metal removal from industrial effluents.

A Sensitive Electrochemical DNA Biosensor for Anticancer Drug Topotecan Based on Graphene Carbon Paste Electrode

Linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) at graphene paste electrode (GPE) were applied to study the interaction of the anticancer drug topotecan with ds-DNA. A linear dependence was observed for the topotecan concentration level from 0.7 to 90.0 μM and the limit of detection of the topotecan was achieved 0.37 μM under the optimal conditions. Moreover, the application of analysis was studied for real samples and the outcomes showed the good ability of the proposed DNA biosensor for sensitive, quick, easy, and cost effective measurement of topotecan in specimens of human blood serum and urine samples.

A Label-Free Electrochemical Biosensor Based on Carbon Paste Electrode Modified with Graphene and ds-DNA for the Determination of the Anti-Cancer Drug Tamoxifen

As an oral nonsteroidal antiestrogen drug, tamoxifen (TMX) has been widely utilized for the prevention and treatment of breast cancer. In the current research, using differential-pulse voltammetry (DPV), an electrochemical investigation of the interaction between TMX and salmon-sperm double-stranded DNA (ds-DNA) was conducted with a graphene paste electrode (GPE). To determine TMX, a simple and sensitive biosensor was fabricated through this interaction. A linear dynamic range between 8.0 × 10−7 and 8.5 × 10−5 M was exhibited by DPV for TMX. Finally this modified electrode was used for determination of TMX in TMX tablet, serum and urine samples.

Graphene-Flakes Printed Wideband Elliptical Dipole Antenna for Low-Cost Wireless Communications Applications

This letter presents the design, manufacturing and operational performance of a graphene-flakes based screenprinted wideband elliptical dipole antenna operating from 2 GHz up to 5 GHz for low cost wireless communications applications. To investigate radio frequency (RF) conductivity of the printed graphene, a coplanar waveguide (CPW) test structure was designed, fabricated and tested in the frequency range from 1 GHz to 20 GHz. Antenna and CPW were screen-printed on Kapton substrates using a graphene paste formulated with a graphene to binder ratio of 1:2. A combination of thermal treatment and subsequent compression rolling is utilized to further decrease the sheet resistance for printed graphene structures, ultimately reaching 4 Ohm/sq. at 10 {\mu}m thicknesses. For the graphene-flakes printed antenna an antenna efficiency of 60% is obtained. The measured maximum antenna gain is 2.3 dBi at 4.8 GHz. Thus the graphene-flakes printed antenna adds a total loss of only 3.1 dB to an RF link when compared to the same structure screen-printed for reference with a commercial silver ink. This shows that the electrical performance of screen-printed graphene flakes, which also does not degrade after repeated bending, is suitable for realizing low-cost wearable RF wireless communication devices.

Multimode microsensors based on Ag–TiO2–graphene materials used for the molecular recognition of carcinoembryonic antigen in whole blood samples

Ag–TiO2–graphene pastes modified with inulin, and l-alanine tert-butyl ester nitrate were proposed for the molecular recognition of carcinoembryonic antigen in whole blood samples.

Selective and Sensitive Electro Chemical Determination of D-Cycloserine Using Graphene Paste Sensor and its Application Studies

Graphene have attracted considerable attention in synthesis and electrochemical applications. In the present study, graphene paste electrode (GPE) was used to study electrochemical behavior of D-Cycloserine (DCS) using cyclic (CV), staircase (SCV) and square wave (SWV) voltammetric techniques. The electrochemical sensor showed excellent enhancement and adsorptive ability towards the electrooxidation of DCS. The electro-oxidation mechanism was proposed. Experimental parameters, such as the surface area of electrode, scan rate and pH of solution were optimized. Under the optimized conditions, the oxidation peak current was proportional to DCS concentration in the range between 1.0×10-8 - 1.5×10-7 M for SCV and 1.0×10-8 - 1.1×10-7 M for SWV and the detection limit was 2.80 nM for SCV and 3.70 nM for SWV. The proposed SCV method was observed to be simple, fast and inexpensive and hence, could be readily adopted for quality control in pharmaceutical products.

Amperometric enzyme-free glucose sensor based on the use of a reduced graphene oxide paste electrode modified with electrodeposited cobalt oxide nanoparticles

The authors describe a non-enzymatic amperometric sensor for glucose that was prepared by electrodeposition of cobalt oxide nanoparticles on a graphene paste that is readily obtained by mixing reduced graphene oxide (r-GO) nanosheets and mineral oil in a mortar. An electrode was prepared and characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Cobalt oxide nanoparticles were electrochemically deposited on the electrode, and their morphology was characterized by field emission scanning electron microscopy. Cyclic voltammetric and chronoamperometric studies showed the modified electrode to display electrocatalytic activity toward the direct oxidation of glucose, best at a working potential of 0.45 V (vs. SCE) in 0.1 M NaOH solution. The sensor exhibits a linear response in the 40 to 4000 μM glucose concentration range, has a detection limit as low as 1.4 μM (at an S/N ratio of 3), and a sensitivity of 1.21 μA∙μM−1∙cm−2. The electrode was successfully applied to the determination of glucose in (spiked) human serum where it showed recoveries between 97.2 and 103.4 %.

Conductive Screen Printing Inks by Gelation of Graphene Dispersions

This paper describes the gelation of highly concentrated graphene/polymer dispersions triggered by mild heating. The gel formation is only dependent on the concentration of graphene with 3.25 mg mL−1 as the minimum value for graphene network formation. The graphene gel is then utilized for the preparation of colloidally stable and highly concentrated (52 mg mL−1) graphene pastes that demonstrate excellent performance in screen printing down to lines of 40 μm in width. Printed patterns dried at 100 °C for only 5 min exhibit sheet resistances of 30 Ω −1 at 25 μm thickness, thus, removing the need for long‐time high temperature annealing, doping, or other treatments. Such a low drying temperature, high printing definition, and compatibility with industrially relevant plastic and paper substrates brings high‐volume roll‐to‐roll application in printed flexible electronics within reach.