# Recent Developments in Plasmonic Sensors of Phenol and Its Derivatives
###### Abstract  
Many scientists are increasingly interested in on-site detection methods of phenol and its derivatives because these substances have been universally used as a significant raw material in the industrial manufacturing of various chemicals of antimicrobials, anti-inflammatory drugs, antioxidants, and so on. The contamination of phenolic compounds in the natural environment is a toxic response that induces harsh impacts on plants, animals, and human health. This mini-review updates recent developments and trends of novel plasmonic resonance nanomaterials, which are assisted by various optical sensors, including colorimetric, fluorescence, localized surface plasmon resonance (LSPR), and plasmon-enhanced Raman spectroscopy. These advanced and powerful analytical tools exhibit potential application for ultrahigh sensitivity, selectivity, and rapid detection of phenol and its derivatives. In this report, we mainly emphasize the recent progress and novel trends in the optical sensors of phenolic compounds. The applications of Raman technologies based on pure noble metals, hybrid nanomaterials, and metal-organic frameworks (MOFs) are presented, in which the remaining establishments and challenges are discussed and summarized to inspire the future improvement of scientific optical sensors into easy-to-operate effective platforms for the rapid and trace detection of phenol and its derivatives. p 2021 2  
Phenol--also called benzenol, or mono-hydroxybenzene--has been known as the simplest compound of the aromatic alcohol group. Its main structure includes a benzene ring and a hydroxyl group (--OH) binding directly to one C atom of the aromatic ring. Although phenol can be toxic and its solutions with high concentration induce burned skin, it has been widely used as either primal raw materials or significant intermediates for the modern industrial manufacturing of many household products. For example, phenol with a suitable concentration has been used as one of the important ingredients in a mouth rinse thanks to its efficient bactericidal features. In industrial products, phenol has been widely adapted to use as an indispensable material to manufacture synthetic textiles, phenolic resins, plastics, dyes, and aspirin. Besides the benefits, phenols also caused serious chemical accidents through leakage [15], attracting many concerns of environmental scientists and governments owing to its negative risk impact on humans and the environment. For example, some researchers have recently investigated the ecotoxicity of phenol on four marine microalgae [16], the toxicological effects of phenol and cresols on aquatic organisms [17], and deriving hazardous concentrations of phenol in soil ecosystems [18]. Recently, various optical sensor techniques have been developed, such as colorimetric [19; 20], fluorescence [21; 22], LSPR phenomenon [23; 24], and plasmon-enhanced surface enhanced Raman scattering (SERS) [25; 26; 27]. Among these techniques, the SERS method based on plasmonic resonance nanomaterials is promising because of its high specific, selective, and sensitive detection capability. Combining nanostructured materials, as an effective plasmonic resonance phenomenon, with Raman spectroscopy is becoming a potential analytic tool for trace detection of analyte molecules with many advantages such as easy-to-use, low-cost, specific targets, and on-site detection.