Production and printing of graphene oxide foam ink for electrocatalytic applications

We acknowledge support from MINECO, Spain, for MAT2017-87202-P, the Severo Ochoa program (Grant No. SEV-2013-0295) and Graphene Flagship Core Project 2 (Ref: 785219). This work is also funded by the CERCA Programme/Generalitat de Catalunya.A graphene-based ink printed as a foam-like structure with open pores is reported. The production of the ink is easier and faster than using existing methods and the obtained product is stable in water suspension. Electrocatalytic applications of 3D structured electrodes printed onto plastic substrates were explored

Magnetic bead/gold nanoparticle double-labeled primers for electrochemical detection of isothermal amplified Leishmania DNA

A novel methodology for the isothermal amplification of Leishmania DNA using labeled primers combined with the advantages of magnetic purification/preconcentration and the use of gold nanoparticle (AuNP) tags for the sensitive electrochemical detection of such amplified DNA is developed. Primers labeled with AuNPs and magnetic beads (MBs) are used for the first time for the isothermal amplification reaction, being the amplified product ready for the electrochemical detection. The electrocatalytic activity of the AuNP tags toward the hydrogen evolution reaction allows the rapid quantification of the DNA on screen-printed carbon electrodes. Amplified products from the blood of dogs with Leishmania (positive samples) are discriminated from those of healthy dogs (blank samples). Quantitative studies demonstrate that the optimized method allows us to detect less than one parasite per microliter of blood (8 × 10⁻³ parasites in the isothermal amplification reaction). This pioneering approach is much more sensitive than traditional methods based on real-time polymerase chain reaction (PCR), and is also more rapid, cheap, and user-friendly

From nanoparticles to graphene: architecting novel (bio)sensing platforms and devices

La tesis presentada y titulada “De las nanopartículas al grafeno: arquitectando novedosas plataformas y dispositivos para biosensores” presenta el desarrollo de varios biosensores basados en el uso de nanoparticulas y grafeno. Se presentan dos trabajos que han dado lugar a la publicación de dos artículos científicos en la revista SMALL y Biosensors and Bioelectronics. El primer trabajo está enfocado a la detección de DNA de Leishmania usando nanoparticulas de oro como señal electroquímico y partículas magnéticas como método de separación del medio de la muestra a analizar. Además en este trabajo se demuestra el desarrollo de una técnica de amplificación de DNA en la presencia de nanoparticulas, un logro de gran importancia para biosensores ya que se puede extender a varias otras aplicaciones de interés para el diagnóstico. El sensor desarrollado puede ser usado para pruebas rutinarias para la detección rápida de Leishmania de interés para la clínica veterinaria. El segundo trabajo trata sobre la caracterización óptica y electroquímica del grafeno oxidado y su aplicación para la detección de catecol. En este trabajo, el mejoramiento de un electrodo ya existente y ampliamente utilizado es evidente, mejorando tanto a nivel de absorción de enzima utilizada como receptor como en la sensibilidad del dispositivo obtenido. En el tercer trabajo (publicado en la revista ACS Nano), el desarrollo de una nueva metodología de impresión de grafeno oxidado trae importantes avances científicos y tecnológicos en el campo de los dispositivos a base de grafeno. Esta técnica es de bajo coste y fácil de utilizar permitiendo incluso su uso fuera del laboratorio. Este trabajo se ha concluido con la impresión del grafeno oxidado en substratos como plásticos, papel o textiles teniendo una gran importancia en futuras aplicaciones de biosensores portátiles además de los del tipo “wearable” (impresos/integrados en el cuerpo humano o textiles) una tecnología emergente para el campo de los (bio)sensores. Como prueba de concepto, se ha desarrollado un sensor de tipo “pantalla de contacto” / (touch-screen) que permite encender y apagar una pequeña lámpara (LED). Además de estos trabajos experimentales la tesis incluye una revisión bibliográfica sobre el estado del arte de los diferentes materiales de grafeno y su producción, así como de una variedad de aplicaciones que puede tener este material.The thesis presented and entitled "From nanoparticles to graphene: architecting novel (bio)sensing platforms and devices" presents the development of several biosensors based on the use of nanoparticles and graphene. Two works that have led to the publication of two scientific articles in the journal Biosensors and Bioelectronics SMALL and presented. The first work is focused on the detection of Leishmania DNA using gold nanoparticles as an electrochemical signal and magnetic nanoparticles as the separation method through the test sample. Also in this work the development of a DNA amplification technique in the presence of nanoparticles, an achievement of great importance for biosensors as it can be extended to several other applications of interest for the diagnosis demonstrated. The developed sensor can be used for routine for rapid detection of Leishmania of interest for veterinary clinical trials. The second paper deals with the optical and electrochemical characterization of oxidized graphene and its application for the detection of catechol. In this paper, the improvement of an existing and widely used electrode is evident both at improving absorption of enzyme used as receiver and device sensitivity obtained. In the third study (published in the journal ACS Nano), the development of a new methodology printing oxidized graphene brings important advances in science and technology in the field of devices based on graphene. This technique is inexpensive and easy to use even allowing its use outside the laboratory. This work was completed with the printing of oxidized graphene on substrates such as plastics, paper or textiles having a great importance in future applications of portable biosensors addition to the "wearable" (printed / integrated into the human body or textiles) type technology for the emerging field of (bio) sensors. As proof of concept, it has developed a sensor type "touch screen" that allows on and off a small lamp (LED). In addition to these experimental work the thesis includes a literature review on the state of art of different graphene materials and production, as well as a variety of applications that can have this material

Ferrocene-functionalized graphene electrode for biosensing applications

Altres ajuts: Generalitat de Cataluña for SGR support.A novel ferrocene-functionalized reduced graphene oxide (rGO)-based electrode is proposed. It was fabricated by the drop casting of ferrocene-functionalized graphene onto polyester substrate as the working electrode integrated within screen-printed reference and counter electrodes. The ferrocene-functionalized rGO has been fully characterized using FTIR, XPS, contact angle measurements, SEM and TEM microscopy, and cyclic voltammetry. The XPS and EDX analysis showed the presence of Fe element related to the introduced ferrocene groups, which is confirmed by a clear CV signal at ca. 0.25 V vs. Ag/AgCl (0.1 KCl). Mediated redox catalysis of HO and bio-functionalization with glucose oxidase for glucose detection were achieved by the bioelectrode providing a proof for potential biosensing applications

Architecting graphene oxide rolled-up micromotors : a simple paper-based manufacturing technology

A graphene oxide rolled-up tube production process is reported using wax-printed membranes for the fabrication of on-demand engineered micromotors at different levels of oxidation, thickness, and lateral dimensions. The resultant graphene oxide rolled-up tubes can show magnetic and catalytic movement within the addition of magnetic nanoparticles or sputtered platinum in the surface of graphene-oxide-modified wax-printed membranes prior to the scrolling process. As a proof of concept, the as-prepared catalytic graphene oxide rolled-up micromotors are successfully exploited for oil removal from water. This micromotor production technology relies on an easy, operator-friendly, fast, and cost-efficient wax-printed paper-based method and may offer a myriad of hybrid devices and applications

Simple Forster resonance energy transfer evidence for the ultrahigh quantum dot quenching efficiency by graphene oxide compared to other carbon structures

Förster resonance energy transfer (FRET) entails the transfer of energy from a photoexcited energy donor to a close energy acceptor. In this regard, quantum dots (QDs), as donors, are quenched when they are next to an acceptor material. Graphite, carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphene oxide (GO) were explored as energy acceptors of QD FRET donors in the solid phase. In our setup, the higher estimated values of quenching efficiency for each material are as follows: graphite, 66 ± 17%; CNTs, 71 ± 1%; CNFs, 74 ± 07% and GO, 97 ± 1%. Among these materials, GO is the best acceptor of QD FRET donors in the solid phase. Such an ultrahigh quenching efficiency by GO and the proposed simple mechanism may open the way to several interesting applications in the field of biosensing.Peer ReviewedPostprint (published version

Graphene-based biosensors : going simple

The main properties of graphene derivatives facilitating optical and electrical biosensing platforms are discussed, along with how the integration of graphene derivatives, plastic, and paper can lead to innovative devices in order to simplify biosensing technology and manufacture easy-to-use, yet powerful electrical or optical biosensors. Some crucial issues to be overcome in order to bring graphene-based biosensors to the market are also underscored

Ferrocene-functionalized graphene electrode for biosensing applications

A novel ferrocene-functionalized reduced graphene oxide (rGO)-based electrode is proposed. It was fabricated by the drop casting of ferrocene-functionalized graphene onto polyester substrate as the working electrode integrated within screen-printed reference and counter electrodes. The ferrocene-functionalized rGO has been fully characterized using FTIR, XPS, contact angle measurements, SEM and TEM microscopy, and cyclic voltammetry. The XPS and EDX analysis showed the presence of Fe element related to the introduced ferrocene groups, which is confirmed by a clear CV signal at ca. 0.25 V vs. Ag/AgCl (0.1 KCl). Mediated redox catalysis of HO and bio-functionalization with glucose oxidase for glucose detection were achieved by the bioelectrode providing a proof for potential biosensing applications.ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295) and MICINN for the Project MAT2011–25870 and Generalitat de Cataluña for SGR support. The Ministry of Higher Education and Scientific Research of Tunisia (MHESR), the UTM University and the LCAE Laboratory are also acknowledged for research and travel funds granted for AR (LR99ES15).Peer Reviewe

Water activated graphene oxide transfer using wax printed membranes for fast patterning of a touch sensitive device

We demonstrate a graphene oxide printing technology using wax printed membranes for the fast patterning and water activation transfer using pressure based mechanisms. The wax printed membranes have 50 μm resolution, longtime stability and infinite shaping capability. The use of these membranes complemented with the vacuum filtration of graphene oxide provides the control over the thickness. Our demonstration provides a solvent free methodology for printing graphene oxide devices in all shapes and all substrates using the roll-toroll automatized mechanism present in the wax printing machine. Graphene oxide was transferred over a wide variety of substrates as textile or PET in between others. Finally, we developed a touch switch sensing device integrated in a LED electronic circuit.This work was supported by The European Commission Program, FP7-OCEAN, SMS Project (613844). ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295). Nanobiosensors and Bioelectronics Group acknowledges Generalitat de Cataluña for SGR support and the authors would like to acknowledge MICINN for funding this project (grant MAT2014-52485-P; grant MAT2011-25870 for BES-2012-056022).Peer Reviewe