Applications of graphene-based materials in sensors

This Special Issue compiles a set of innovative developments on the use of graphene-based materials in the fabrication of sensors. In particular, these contributions report original studies on a wide variety of sensors, such as gas sensors for NO2 or NH3 detection, antibody biosensors or mass sensors. All these devices have one point in common: they have been built using graphene-based materials like graphene, graphene oxide, reduced graphene oxide, inkject printing graphene, graphene-based composite sponges, graphene screen-printed electrodes or graphene quantum dots

Sensitivity enhancement of lossy mode resonance-based ethanol sensors by graphene oxide coatings

A layer by layer (LbL) coating made of polyethyleneimine (PEI) and graphene oxide (GO) is deposited onto an optical fiber ethanol sensor based on lossy mode resonances (LMR) in order to improve its response. The new sensor including the PEI/GO coating shows a better linearity and a sensitivity four times higher than the sensor without the coating. To our knowledge, this is the first time that a LbL coating made of PEI and GO is included in an optical fiber sensor based on LMR

Graphene Oxide in Lossy Mode Resonance-Based Optical Fiber Sensors for Ethanol Detection

The influence of graphene oxide (GO) over the features of an optical fiber ethanol sensor based on lossy mode resonances (LMR) has been studied in this work. Four different sensors were built with this aim, each comprising a multimode optical fiber core fragment coated with a SnO2 thin film. Layer by layer (LbL) coatings made of 1, 2 and 4 bilayers of polyethyleneimine (PEI) and graphene oxide were deposited onto three of these devices and their behavior as aqueous ethanol sensors was characterized and compared with the sensor without GO. The sensors with GO showed much better performance with a maximum sensitivity enhancement of 176% with respect to the sensor without GO. To our knowledge, this is the first time that GO has been used to make an optical fiber sensor based on LMR

Lossy Mode Resonance Generation by Graphene Oxide Coatings onto Cladding-Removed Multimode Optical Fiber

In this work, we have studied the suitability of graphene oxide-based thin films to be not only excellent sensitive coatings but also lossy mode resonance (LMR)-generating materials. Thin films of graphene oxide (GO) and polyethylenimine (PEI) fabricated by means of layer-by-layer assembly were selected in this study. Two optical fiber devices with 8 and 20 bilayers of the LMR-generating coating were fabricated and characterized as refractometers. Both devices show no hysteresis and high sensitivity, improving previously reported values. This research opens very promising and exciting possibilities in the field of optical fiber sensors based on LMR, strategically including specific recognition groups to the device surface to exploit this high sensitivity for monitoring a range of target analytes. The carboxylate functional groups at the edges of the GO sheets should provide excellent attachment sites for the required coupling chemistry to realize such devices

High-performance optical fiber humidity sensor based on lossy mode resonance using a nanostructured polyethylenimine and graphene oxide coating

In this study, a rapid optical fiber sensor for humidity with high sensitivity and wide detection range has been constructed, based on lossy mode resonance (LMR). A thin film made of alternating polyethylenimine (PEI) and graphene oxide (GO) layers was selected as sensitive coating. It was deposited on a SnO2-sputtered fiber core in a dip-assisted layer-by-layer assembly. The structure and surface chemistry of the raw materials were investigated by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Key properties such as sensitivity, linearity, hysteresis, stability and response and recovery times were characterized. The sensor exhibited excellent sensitivity, especially at high relative humidity (RH) levels, and short reaction and retrieval periods. This research provides a viable and practical way to fabricate high performance humidity optical fiber sensors with GO-based nanostructured coatings

Optical fiber exhaled breath sensor based on lossy mode resonance using a graphene oxide sensitive coating

Optical fiber sensors (OFS) have attracted increasing attention due to their benefits over traditional sensors, such as small size, biocompatibility, remote sensing ability or safety in flammable environments. Among the different existing configurations of OFS, those based on electromagnetic resonances are very popular as they are reliable, robust and very sensitive. In particular, sensors based on lossy mode resonance (LMR) are very interesting as a wide range of materials, including metal oxides and polymers, can support them and they do not require specific equipment to tune the optical polarization. Graphene-based materials like graphene oxide (GO) or reduced graphene oxide (rGO) have become the most explored materials since Novoselov and Geim achieved its isolation in 2004. Their superior properties, such as high surface area or extreme sensitivity to the external environment, make them ideal candidates for the fabrication of the sensitive coatings required by LMR-based sensors. In this work, the fabrication and characterization of a small and portable exhaled breath LMR-based OFS using GO as sensitive coating is presented. Refractive index changes have been detected showing a fast repetitive behavior with a response time of 150 ms from inhalation to exhalation and a high average sensitivity of 410 nm/RIU

Optical Fibre Sensors Using Graphene-Based Materials: A Review

Graphene and its derivatives have become the most explored materials since Novoselov and Geim (Nobel Prize winners for Physics in 2010) achieved its isolation in 2004. The exceptional properties of graphene have attracted the attention of the scientific community from different research fields, generating high impact not only in scientific journals, but also in general-interest newspapers. Optical fibre sensing is one of the many fields that can benefit from the use of these new materials, combining the amazing morphological, chemical, optical and electrical features of graphene with the advantages that optical fibre offers over other sensing strategies. In this document, a review of the current state of the art for optical fibre sensors based on graphene materials is presented

Route Towards a Label-free Optical Waveguide Sensing Platform Based on Lossy Mode Resonances

According to recent market studies of the North American company Allied Market Research, the field of photonic sensors is an emerging strategic field for the following years and it is expected to garner $18 billion by 2021. The integration of micro and nanofabrication technologies in the field of sensors has allowed the development of new technological concepts such as lab-on-a-chip, which have achieved extraordinary advances in terms of detection and applicability, for example in the field of biosensors. This continuous development has allowed that equipment consisting of many complex devices that occupied a whole room a few years ago, at present it is possible to handle them in the palm of the hand; that formerly long duration processes are carried out in a matter of milliseconds and that a technology previously dedicated solely to military or scientific uses is available to the vast majority of consumers. The adequate combination of micro and nanostructured coatings with optical fiber sensors has permitted us to develop novel sensing technologies, such as the first experimental demonstration of lossy mode resonances (LMRs) for sensing applications, with more than one hundred citations and related publications in high rank journals and top conferences. In fact, fiber optic LMR-based devices have been proven as devices with one of the highest sensitivity for refractometric applications. Refractive index sensitivity is an indirect and simple indicator of how sensitive the device is to chemical and biological species, topic where this proposal is focused. Consequently, the utilization of these devices for chemical and biosensing applications is a clear opportunity that could open novel and interesting research lines and applications as well as simplify current analytical methodologies. As a result, on the basis of our previous experience with LMR based sensors to attain very high sensitivities, the objective of this paper is presenting the route for the development of label-free optical waveguide sensing platform based on LMRs that enable to explore the limits of this technology for bio-chemosensing applications