# Recent Developments in Plasmonic Sensors of Phenol and Its Derivatives
###### Abstract
Specific studies on the development of several novel nanomaterials have been reported to assist effective Raman platforms including nanogold film-based Raman detection of rhodamine 6G and \(p\)-nitropol [28], Raman detection of multiple analytes based on Ag nanoparticle-modified SiO\({}_{2}\) nanofibrous [29], Ag nanostructure-assisted Raman sensing for monofluoroaetic acid [30], Ag nanoparticle-introduced Raman detection of carbofuran [31], on-site Raman detection of 1,2,3-benzotriazole on colloidal lignin particles [32], Ag-capped silicon nanopillar-based Raman detection of ochratoxin A [33], nano-shell composite array-based Raman sensor for antioxidant [34], and bimetallic plasmonic nanoparticle-assisted Raman detection of hazardous contamination [35]. Moreover, a series of scientific reports on several special metal-organic framework (MOF) structures has been investigated, leading to successful fabrication of novel Raman substrates applied in trace detection of phenol red [36], phenol-soluble modulin [37], and engine oil [38]. Phenolic compounds--such as catechol, \(p\)-nitrophenyl, 2,4-dichlorophenol, 2,6-dichlorophenol (2,6-DCP), cresol, 4-tert-butylphenol, 4-tert-octylphenol, alpha-naphth, dopamine, and so on--have been listed as hazardous substances by the United States Environmental Protection Agency owing to their toxicity [39]. Besides their significant potential application in industrial manufacturing, these compounds still faced some issues including environmental pollution and harmful effects on human health, in their included chemical products such as antioxidants, antimicrobials, and anti-inflammatory reagents that have been widely used in the daily activities of people [40; 41]. In addition, 2,6-DCP--one of the most significant chlorophenol compounds--has been widely applied in industrial manufacturing for several chemicals, medical compounds, and other products, despite being potentially carcinogenic [42]. Recently, organic compounds with high toxicity such as \(p\)-nitropol have been found to cause increasingly serious pollution in environmental water [28]. As bisphenol substances have been considered as having a serious impact on the environment and human health risks, the early monitoring of these compounds is not only significant, but also still has many challenges. Recently, there have been a large number of scientific reviews promising not only therapeutic applications of phenolic acids [43; 44], but also phenolic compound's effects on the environment and human health risk [25; 45]. Furthermore, several authors have investigated varieties of analytical technologies using trace detection of phenolic sub stances such as electrochemical [39; 46; 47; 48; 49], liquid chromatography with diode array and mass spectrometry [50], high performance liquid chromatography [51; 52], conductometric biosensor [53], photoelectrochemical reduction [54], voltammetric detection [55; 56], biosensor electrode [57], and nanomaterial-based sensing [58]. However, these methodologies often require additional procedures for separation of analytes in sample preparation, leading to time-consuming and toxic organic solvents, as well as adverse effects on the environment. Detection of phenols still needs more consideration, focusing on the novel detection methods such as plasmonic resonance-based optical sensors. Plasmonic resonance phenomenon-based Raman sensing has emerged as a scientific tool for detecting analytes using molecular vibrations on nanomaterial surfaces [59]. Raman technology has related to LSPR in terms of introducing nanogap-enhanced plasmonic behaviors on noble metal surfaces [60]. Raman scattering as a supplementary application in which LSPR plays a significant role, has been introduced to pollutant monitoring [61]. Although there have been several reports on surface plasmon-based Raman sensors for detecting phenolic substances [59; 60; 61], there is no literature review, despite their universal application.