Hybrid Heterostructures for SPR Biosensor

Surface plasmon resonance (SPR) based biosensors have been enormously studied in the last decade for their better sensitivity. In recent years hybrid heterostructures are getting popularity to implement these SPR biosensors for their superior sensing capability. This chapter demonstrates the details of SPR technology with two recently studied prism-based hybrid heterostructures. These heterostructures are made up of conventional SPR biosensors with two additional layers of recently invented transition metal dichalcogenides, platinum di-selenide (PtSe2), and highly sensitive 2D material, tungsten di-sulfide (WS2). Angular interrogation method is discussed to investigate the sensing capabilities of the sensors which prove the superiority of the Ag-PtSe2-WS2 structure. The sensing capability of this structure has been found at least 1.67 times higher than that of the conventional non-hybrid structures, respectively, with comparable FOM and QF. A comparison table has been provided at the end of this chapter which also shows the impressive performance of the hybrid heterostructures for SPR biosensors. Proper demonstration with a suitable example of this chapter will emphasize the potential use of hybrid heterostructure based SPR biosensors in prospective medical diagnostics and biomedical detection applications

2D Nanomaterial-Based Hybrid Structured (Au-WSe2-PtSe2-BP) Surface Plasmon Resonance (SPR) Sensor With Improved Performance

As a promising optical method used in a variety of applications surface plasmon resonance (SPR) sensors are employed over a wide range of boundaries. This research proposes a highly sensitive SPR based sensor with a novel hybrid structure using transition metal dichalcogenides (e.g. WSe 2 , PtSe 2 ) along with black phosphorene (BP) through comprehensive numerical study. To analyze and evaluate the performances of the proposed sensor, the widely used transfer matrix method (TMM) was used. The performances of the sensor were measured in terms of reflectivity, sensitivity, detection accuracy (DA), and figure of merit (FOM). The sensor structure was optimized by changing different structural parameters of the hybrid architecture to obtain better performances. The results revealed that insertion of PtSe 2 with WSe 2 and BP over a gold layer of the conventional structure improved the performance of the sensor and the maximum sensitivity of the sensor was measured as 200 deg/RIU with a FOM of 17.70 RIU −1 . As well, the light penetration through the optimized sensor is investigated using the finite element method (FEM) based software. With this kind of high sensing capabilities, it may be convinced that the proposed sensor can be applied in different fields of biosensing to detect liquid biological and biochemical samples or analytes

Thin films sensor devices for mycotoxins detection in foods: applications and challenges

Mycotoxins are a group of secondary metabolites produced by different species of filamentous fungi and pose serious threats to food safety due to their serious human and animal health impacts such as carcinogenic, teratogenic and hepatotoxic effects. Conventional methods for the detection of mycotoxins include gas chromatography and high-performance liquid chromatography coupled with mass spectrometry or other detectors (fluorescence or UV detection), thin layer chromatography and enzyme-linked immunosorbent assay. These techniques are generally straightforward and yield reliable results; however, they are time-consuming, require extensive preparation steps, use large-scale instruments, and consume large amounts of hazardous chemical reagents. Rapid detection of mycotoxins is becoming an increasingly important challenge for the food industry in order to effectively enforce regulations and ensure the safety of food and feed. In this sense, several studies have been done with the aim of developing strategies to detect mycotoxins using sensing devices that have high sensitivity and specificity, fast analysis, low cost and portability. The latter include the use of microarray chips, multiplex lateral flow, Surface Plasmon Resonance, Surface Enhanced Raman Scattering and biosensors using nanoparticles. In this perspective, thin film sensors have recently emerged as a good candidate technique to meet such requirements. This review summarizes the application and challenges of thin film sensor devices for detection of mycotoxins in food matrices.This work was funded by Project POCI-01–0145-FEDER-006984 - Associate Laboratory LSRE-LCM, Project UID/BIO/04469/2013 - CEB and strategic project PEst-OE/AGR/UI0690/2014 - CIMO all funded by European Regional Development Fund (ERDF) through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI)—and by national funds through FCT—Fundação para a Ciência e a Tecnologia I.P. Andréia O. Santos also acknowledges the research grant provided by the Associate Laboratory LSRE-LCM under the Projects UID/EQU/50020/2013 and POCI-01-0145-FEDER-006984. Andreia Vaz acknowledges the research grant provided by the Portuguese Foundation for Science and Technology (FCT), reference number SFRH/BD/129775/2017. The APC was kindly waived by MDPI.info:eu-repo/semantics/publishedVersio

Nanoelectromechanical Sensors based on Suspended 2D Materials

The unique properties and atomic thickness of two-dimensional (2D) materials enable smaller and better nanoelectromechanical sensors with novel functionalities. During the last decade, many studies have successfully shown the feasibility of using suspended membranes of 2D materials in pressure sensors, microphones, accelerometers, and mass and gas sensors. In this review, we explain the different sensing concepts and give an overview of the relevant material properties, fabrication routes, and device operation principles. Finally, we discuss sensor readout and integration methods and provide comparisons against the state of the art to show both the challenges and promises of 2D material-based nanoelectromechanical sensing.Comment: Review pape

Two-dimensional material-based nanosensors for detection of low-molecular-weight molecules

Low-molecular-mass small molecules play important roles in biological processes and often serve as disease-related biomarkers for diagnosis. Accurate detection of small molecules remains challenging for conventional sensors due to their limited sensitivities. Two-dimensional (2D) materials, thanks to their atomic level thickness, can be extraordinarily sensitive to external perturbations and therefore well-suited for sensing applications. This dissertation explores the use of 2D materials, including primarily graphene and transition metal dichalcogenides, in the detection of low-molecular-weight and low-charge molecules. This work starts with the study of methods that allow for efficient and clean transfer of graphene grown on Cu using chemical vapor deposition (CVD), which is a critical step for achievement of large-area and high-quality graphene for device fabrication. In addition to the conventional wet-etching transfer method, we have studied on the method of electrochemical delamination, which is more time-efficient and allows for recycling of the Cu foil. Generation of bubbles during the electrochemical reaction is minimized by tuning the experimental parameters, thereby minimizing transfer-induced damages to graphene. We then fabricate the graphene-based field effect transistor (FET) and use the graphene FET as biosensors. First, the sensor is configured as an electrolyte-gated FET. With appropriate biochemical functionalization of the graphene, the FET sensors have been used to detect multiple small-molecule biomarkers including glucose and insulin via their affinity binding with receptors. Then, on a flexible substrate, we demonstrate real-time measurement of tumor necrosis factor alpha, a signal protein that regulates immune cells. We then simplified the sensor structure using a bottom local-gate to replace the external electrode as required in the previous electrolyte gated FET. Using the bottom local-gated FET sensor we have carried out real-time monitoring of the variation of pH in solutions. In addition to the electrical sensors, highly sensitive and multifunctional plasmonic sensors have also been developed by combining the unique optical properties of graphene with engineered metallic metasurfaces. The plasmonic sensors operating in mid-infrared region are configured as either metallic metasurface or hybrid graphene-metallic metasurface. Using a metallic metasurface, we demonstrate simultaneous quantification and fingerprinting of protein molecules. Using a hybrid graphene-metallic metasurface, we demonstrate optical conductivity-based ultrasensitive biosensing. In contrast to refractive-index-based sensors, the sensitivity of the hybrid metasurface sensor is not limited by the molecular masses of analytes. A monolayer of the sub-nanometer chemicals can be readily detected and differentiated on the hybrid metasurface. Reversible detection of glucose is carried out via the affinity binding of glucose with boronic acid immobilized on the graphene of the hybrid metasurface. The lowest detection limit achieved in our work is 36 pg/mL, which is considerably lower than that for the existing optical sensors. Despite the high sensitivity of graphene, the zero band-gap of graphene fundamentally impedes its use in digital electronic devices. In contrast, two-dimensional semiconductors, such as transition metal dichalcogenide (TMDC) with non-zero band gaps, holds great potential for developing practical electronic devices and sensors. Monolayers of TMDC materials are particularly attractive for development of deeply scaled devices, although the contact resistance between metal and the monolayer TMDC has been so large to significantly limit the performance of the devices. We present a high-performance monolayer MoS2 FET with a monolayer graphene as bottom local gate. The graphene gate is found to significantly improve the dielectric strength of the oxide layer compared to the lithographically patterned metal gate. This in turn allows for the use of very thin gate dielectric layer (~5 nm) and application of a strong displacement field to lower the contact resistance. Benefiting from the low contact resistance, the monolayer MoS2 FET offers a high on/off ratio (108) and low subthreshold slope (64 mV/decade). Additionally, thanks to the highly efficient electrostatic coupling through the ultrathin gate dielectric layer, short-channel (50 nm and 14 nm) devices are realized that exhibit excellent switching characteristics. In summary, this dissertation presents significant contributions to 2D material-based electronic and optoelectronic nanosensors, especially for detection of small molecules. Perspectives are made in the end of the thesis, on future studies needed to realize practical applications of these sensors and other 2D material-based products

Laser-Scribed Conductive, Photoactive Transition Metal Oxide on Soft Elastomers for Janus On-Skin Electronics and Soft Actuators

Laser-assisted fabrication of conductive materials on flexible substrates has attracted intense interests because of its simplicity, easy customization, and broad applications. However, it remains challenging to achieve laser scribing of conductive materials on tissue-like soft elastomers, which can serve as the basis to construct bioelectronics and soft actuators. Here, we report laser scribing of metallic conductive, photoactive transition metal oxide (molybdenum dioxide) on soft elastomers, coated with molybdenum chloride precursors, under ambient conditions. Laser-scribed molybdenum dioxide (LSM) exhibits high electrical conductivity, biocompatibility, chemical stability, and compatibility with magnetic resonance imaging. In addition, LSM can be made on various substrates (polyimide, glass, and hair), showing high generality. Furthermore, LSM-based Janus on-skin electronics are developed to record information from human skin, human breath, and environments. Taking advantage of its outstanding photothermal effect, LSM-based soft actuators are developed to build light-driven reconfigurable three-dimensional architectures, reshapable airflow sensors, and smart robotic worms with bioelectronic sensors

Advanced Electrochemical and Opto-Electrochemical Biosensors for Quantitative Analysis of Disease Markers and Viruses

The recent global events of the SARS-CoV-2 pandemic in 2020 have alerted the world to the urgent need to develop fast, sensitive, simple, and inexpensive analytical tools that are capable of carrying out a large number of quantitative analyses, not only in centralized laboratories and core facilities but also on site and for point-of-care applications. In particular, in the case of immunological tests, the required sensitivity and specificity is often lacking when carrying out large-scale screening using decentralized methods, while a centralized laboratory with qualified personnel is required for providing quantitative and reliable responses. The advantages typical of electrochemical and optical biosensors (low cost and easy transduction) can nowadays be complemented in terms of improved sensitivity by combining electrochemistry (EC) with optical techniques such as electrochemiluminescence (ECL), EC/surface-enhanced Raman spectroscopy (SERS), and EC/surface plasmon resonance (SPR). This Special Issue addresses existing knowledge gaps and aids in exploring new approaches, solutions, and applications for opto-electrochemical biosensors in the quantitative detection of disease markers, such as cancer biomarkers proteins and allergens, and pathogenic agents such as viruses. Included are seven peer-reviewed papers that cover a range of subjects and applications related to the strategies developed for early diagnosis

Laser-Scribed Conductive, Photoactive Transition Metal Oxide on Soft Elastomers for Janus On-Skin Electronics and Soft Actuators

Laser-assisted fabrication of conductive materials on flexible substrates has attracted intense interests because of its simplicity, easy customization, and broad applications. However, it remains challenging to achieve laser scribing of conductive materials on tissue-like soft elastomers, which can serve as the basis to construct bioelectronics and soft actuators. Here, we report laser scribing of metallic conductive, photoactive transition metal oxide (molybdenum dioxide) on soft elastomers, coated with molybdenum chloride precursors, under ambient conditions. Laser-scribed molybdenum dioxide (LSM) exhibits high electrical conductivity, biocompatibility, chemical stability, and compatibility with magnetic resonance imaging. In addition, LSM can be made on various substrates (polyimide, glass, and hair), showing high generality. Furthermore, LSM-based Janus on-skin electronics are developed to record information from human skin, human breath, and environments. Taking advantage of its outstanding photothermal effect, LSM-based soft actuators are developed to build light-driven reconfigurable three-dimensional architectures, reshapable airflow sensors, and smart robotic worms with bioelectronic sensors

Opto-Thermal Characterization of Plasmon and Coupled Lattice Resonances in 2-D Metamaterial Arrays

Growing population and climate change inevitably requires longstanding dependency on sustainable sources of energy that are conducive to ecological balance, economies of scale and reduction of waste heat. Plasmonic-photonic systems are at the forefront of offering a promising path towards efficient light harvesting for enhanced optoelectronics, sensing, and chemical separations. Two-dimensional (2-D) metamaterial arrays of plasmonic nanoparticles arranged in polymer lattices developed herein support thermoplasmonic heating at off-resonances (near infrared, NIR) in addition to regular plasmonic resonances (visible), which extends their applicability compared to random dispersions. Especially, thermal responses of 2-D arrays at coupled lattice resonance (CLR) wavelengths were comparable in magnitudes to their counterparts at plasmon wavelengths. Opto-thermal characterization of 2-D arrays was conducted with a white light irradiation in the current work. Finite element analysis involving a three-dimensional (3-D) COMSOL model mimicked the heat transfer and average temperature increases in these systems at plasmon resonances with a ≤ 0.5 % discrepancy at the absorbed, extinguished power of the radiation. All-optical, mesoscopic characterization of 2-D arrays involving trichromatic particle analysis allowed detailed investigation of effects of particle populations and ordering on the optical signals of plasmon and CLR in addition to indicating a critical point of emergence for CLR. Overall, engineering these thermoplasmonic metamaterials for enhanced optothermal dissipation at visible to near-IR radiation supports their rapid implementation into emerging sustainable energy and healthcare systems