Carbon-Based Nanomaterials for Plasmonic Sensors: A Review <s> Introduction <s> This paper reviews recent advances in graphene active plasmonics for terahertz (THz) device applications. Two-dimensional plasmons in graphene exhibit unique optoelectronic properties and mediate extraordinary light–matter interactions. It has been discovered theoretically that when the population of Dirac fermionic carriers in graphene are inverted by optical or electrical pumping, the excitation of graphene plasmons by the THz photons results in propagating surface plasmon polaritons with giant gain in a wide THz range. Furthermore, when graphene is patterned into a micro- or nanoribbon array by grating metallization, the structure acts as an active THz plasmonic amplifier, providing a superradiant plasmonic lasing with a giant gain at the plasmon modes in a wide THz frequency range. These new findings can lead to the creation of new types of plasmonic THz emitters and lasers operating even at room temperature. <s> BIB001 </s> Carbon-Based Nanomaterials for Plasmonic Sensors: A Review <s> Introduction <s> The main challenge for all electrical, mechanical and optical sensors is to detect low molecular weight (less than 400 Da) chemical and biological analytes under extremely dilute conditions. Surface plasmon resonance sensors are the most commonly used optical sensors due to their unique ability for real-time monitoring the molecular binding events. However, their sensitivities are insufficient to detect trace amounts of small molecular weight molecules such as cancer biomarkers, hormones, antibiotics, insecticides, and explosive materials which are respectively important for early-stage disease diagnosis, food quality control, environmental monitoring, and homeland security protection. With the rapid development of nanotechnology in the past few years, nanomaterials-enhanced surface plasmon resonance sensors have been developed and used as effective tools to sense hard-to-detect molecules within the concentration range between pmol and amol. In this review article, we reviewed and discussed the latest trend and challenges in engineering and applications of nanomaterials-enhanced surface plasmon resonance sensors (e.g., metallic nanoparticles, magnetic nanoparticles, carbon-based nanomaterials, latex nanoparticles and liposome nanoparticles) for detecting "hard-to-identify" biological and chemical analytes. Such information will be viable in terms of providing a useful platform for designing future ultrasensitive plasmonic nanosensors. <s> BIB002 </s> Carbon-Based Nanomaterials for Plasmonic Sensors: A Review <s> Introduction <s> Abstract In this study an approach for the fabrication and characterization of a surface plasmon resonance (SPR) based fiber optic sensor for the detection of ethanol in 0–10 mM concentration range has been reported. The sensing probe has been prepared by coating films of silver and silicon over the unclad portion of an optical fiber followed by immobilization of enzyme (ADH) and coenzyme (NAD) entrapped hydrogel layer. The sensor works on spectral interrogation mode of operation. The resonance wavelength has been found to decrease with the increase in ethanol concentration. For the concentration range 0–10 mM, a 30 nm shift in resonance wavelength has been observed. The maximum sensitivity of the sensor has been found to be 21.70 nm/mM near zero concentration of ethanol solution. The calculated values of limit of detection (LOD) and limit of quantification (LOQ) of the sensor are 15.34 μM and 29.63 μM respectively. In addition, the sensor has high selectivity, repeatability and stability. Further, the sensor has various other advantages such as ease of operation, low cost, and fast response. Since the probe has been fabricated on optical fiber, it can work for online monitoring and remote sensing of analyte without any interference of electromagnetic fields. <s> BIB003 </s> Carbon-Based Nanomaterials for Plasmonic Sensors: A Review <s> Introduction <s> Graphene plasmons can couple with vibrations in both extended and local systems, for example, phonons in polar crystals and molecular vibrations in polymers. These interactions are characterized by plasmon-induced transparency features within the plasmon infrared absorption profile. Detection enhancement made possible by graphene-based plasmon-induced transparency has been demonstrated in both polymer and protein films and has shown to offer superior detection capabilities compared to conventional metal dipole plasmonic sensors. Here, we demonstrate the detection of molecular vibrations in minute, residual molecular quantities of solid- and gas-phase molecules down to 50 zeptomol/μm2 using graphene plasmonic sensing platforms. Plasmon-induced transparency enhancement is shown to be sensitive to both the specific molecular coordination of the measured vibrations and to the distribution of modes within the measured vibrational bands. This work could lead to the development of functionalization-free, chemica... <s> BIB004 </s> Carbon-Based Nanomaterials for Plasmonic Sensors: A Review <s> Introduction <s> We theoretically demonstrate a high-sensitivity graphene-plasmon-based refractive index sensor working in the mid-infrared at room temperature. The bulk figure of merit of our sensor reaches values above 10, but the key aspect of our proposed plasmonic sensor is its surface sensitivity, which we examine in detail. We have used realistic values regarding doping level and electron relaxation time, which is the limiting factor for the sensor performance. Our results show quantitatively the high performance of graphene-plasmon-based refractive index sensors working in the mid-infrared. <s> BIB005 </s> Carbon-Based Nanomaterials for Plasmonic Sensors: A Review <s> Introduction <s> Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud forming (cloud condensation nuclei and ice nucleation) capabilities of secondary organic aerosols (SOA). The small size and relatively low mass concentration of SOA in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adopted a new technique for measuring glass forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE) using electrostatic precipitation. Dielectric spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K) that are used to calculate the glass transition temperatures for several cooling rates. IDE-enabled broadband dielectric spectroscopy (BDS) was successfully used to measure the kinetically controlled glass transition temperatures of glycerol and citric acid aerosols with selected cooling rates. The glass transition results agree well with available literature data for these two compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects. <s> BIB006
Sensors find applications in the monitoring of the environment, health, and food quality, in addition to testing and optimization of the best performance of any technique. Various spectroscopic, piezoelectric, optical, electrical, and chemical techniques have been reported in the literature for the fabrication of sensors. For example, a modified broadband dielectric spectroscopic tool, along with interdigitated electrodes, have been reported for the sensing of organic aerosols for environmental applications BIB006 . Similarly, a biological sensor has been reported for the sensing of dopamine (a neurotransmitter) using a photo-electrochemical method utilizing a TiO 2 nanotube array deposited with a CdSe semiconductor [2] . In recent years, a tremendous amount of work has been reported on plasmonic sensors for the measurements of various physical, chemical, and biological parameters. Plasmonic sensors are the most powerful tools to probe and quantify low molecular analytes at low concentration levels due to their label free detection methodology, ease of operation, and high sensitivity. They have detection applications in various areas, ranging from security, environmental monitoring, food safety, pharmaceutics, and biosensing [3] BIB003 BIB004 BIB001 BIB005 . The growing research field of these sensors is now concentrated on the improvement of sensitivity and detection limit, pertaining, especially, to low concentration analytes in biological systems. The use of nanomaterials has brought considerable improvement in the order of sensitivity of plasmonic sensors BIB002 9] . To realize these plasmonic sensors, different types of materials have been used for their fabrication. The choice of material decides the performance of the sensor. In recent years, carbon-based nanomaterials have attracted the attention of the scientific community for the fabrication of plasmonic-based sensors. This is because of their unique where ε m and ε d are the dielectric constants of metal and dielectric and k 0 is the wave vector of light in free space. Figure 1 shows the dispersion plots of surface plasmons and direct light. It may be noted from these plots that the surface plasmons dispersion curve never intersects the dispersion curve of direct light. This implies that no phase matching or momentum matching is possible between these two wave vectors and, therefore, the surface plasmons cannot be excited by direct light. For the excitation of surface plasmons an extra momentum is required. This can be achieved by using some special structures, like prism or grating. Sensors 2019, 19, x FOR PEER REVIEW 2 of 25 chemical, thermal, and optical properties. The present review is focused on carbon-based nanomaterials (CBNs) for their applications in plasmonic sensors.