# Functionalized Carbon-Based Electrochemical Sensors for Food and Alcoholic Beverages Safety
## 3 Carbon Nanomaterial-Based Electrochemical Sensors
### CnTs
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Analytes** & **Materials** & **Electrochemical Techniques** & **Linear Range** & **Detection Limit** & **Sample** & **Ref.** \\ \hline Gallic acid & MCPE & CV and DPV & 0.5–15 \(\upmu\)M & 0.3 \(\upmu\)M & Wines & [84] \\ Phenolic antioxidants & MWCNT & DPV & ND & ND & Wines & [85] \\ Phenolic compounds & Fe\({}_{3}\)O\({}_{4}\)/MCPE & CV and DPV and & 0.22–0.26 \(\upmu\)M & 0.08 \(\upmu\)M & Wines & [86] \\ Catechol & AuNP-MWCNT & CSI & 0–1.0 \(\upmu\)M & 3.7 \(\upmu\)M & Wines & [88] \\ Catechin & Pt/MnO\({}_{2}\)/f-MWCNT & SWV & 2–950 \(\upmu\)M & 0.02 \(\upmu\)M & Wines & [89] \\ Glucose & GOX-NFM/MWCNT & CV and CA & 1–3 mM & 20 \(\upmu\)M & Beer & [90] \\ TBHQ & CuO NFs/NH\({}_{2}\)-CNTs & DPV & 0.01–3.9 \(\upmu\)M & 3 nM & Edible oils & [91] \\ Bisphenol A & MWCNTs-BCD/SPCE & CV & 125 nM–2 \(\upmu\)M & 13.76 \(\upmu\)M & Water & [92] \\ Methyl parathion & MWCNT/zirconia & CV & 19.9–176.8 \(\upmu\)M & 9 nM & Ethanolic & [93] \\ Semicarbazide & MIP/SWNTs-COOH/CS & CV and PDV and & 0.04–0.6 \(\mathrm{ng\ mL^{-1}}\) & 0.025 \(\mathrm{ng\ mL^{-1}}\) & Sheep casings & [94] \\ \hline \hline \end{tabular}  
* MCPE: modified carbon paste electrode; CV: cyclic voltammetry; CA: chronomorpometry; DPV: differential pulse voltammetry; SWV: square wave voltammetry; ESI: electrochemical impedance spectroscopy; mM: millimolar; \(\upmu\)M: micromolar; nM: nanomolar; ng: nanogram; MWCNT: multi-walled carbon nanotube; Fe\({}_{3}\)O\({}_{4}\): ferrorforcro oxide; AuNPs: gold nanoparticles; Pt: platinum; MnO\({}_{2}\): manganese dioxide; GOX: glucose oxidase; NFM: nylon nanofibrous membrane; TBHQ: _tert_-butyl hydroquinone; CuO: copper oxide; NFs: nanoflowers; \(\upbeta\)CD: \(\upbeta\)-cyclodextrintrin; SPCE: screen-printed carbon electrode; MIP: molecularly imprinted polymer; SWNTs: single-walled carbon-nanotubes; CS: chitosan.  
\end{table} 
Table 2: Application of electrochemical sensors based on CNT-based materials associated with electrochemical techniques for the detection of different target analytes in foods and beverages. Furthermore, [PERSON] et al. [91] reported a novel CuO \(\mathrm{NF/NH_{2}}\)-CNT composite synthesized using the hydrothermal and ultrasound-assisted method. As shown in Figure 4d, this composite as a working electrode material was used for detecting cytotoxic food preservative _tert_-butyl hydroquinone (TBHQ). In this work, 3D CuO nanoflowers (NFs) with exceptional chemical stability, non-toxicity, and electron correlation effects could improve the reproducibility, testing repeatability, and stability of electrochemical sensors. An excellent recovery efficiency in the range of 95.90-104.87% and a maximum relative standard deviation (RSD) of 2.71% were obtained using Oils analysis. Recently, Bisphenol A (BPA), one of the most extensively used plasticizers, was detected based on the reversibility and irreversibility of electrochemical redox reactions. [PERSON] and co-workers [92]  
Figure 4: CNT-based electrochemical sensors for food and alcoholic beverage safety. **(a)** Schematic diagram of the phenolic compounds’ electrochemical sensor preparation. Reprinted with permission from [86]. Copyright MDPI, 2021. **(b)** SWV experiments for various concentrations of 0, 5, 10, 15, 30, and 60 mM of green tea leaves extract diluted with catechin concentration. Reprinted with permission from [89]. Copyright The Royal Society of Chemistry, 2015. **(c)** Sensing mechanism. OX and RED are the oxidized and reduced mediator forms, respectively. Reprinted with permission from [90]. Copyright Hindawi, 2016. **(d)** Schematic illustration of TBHQ detection. Reprinted with permission from [91]. Copyright Elsevier, 2021. **(e)** CV curves of different electrodes and different scan rates in an aqueous electrolyte. Reprinted with permission from [92]. Copyright Elsevier, 2020. **(f)** The schematic diagram of the fabrication procedure of the sensor. Reprinted with permission from [94].