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The nanocomposites (NCs) of cross-linked polyaniline (CPA) with a variety of carbon nanomaterials (CNMs) (CPA/CNMs NCs) was prepared by the chemical oxidative copolymerization of PANI and p-phenylenediamine (PPDA) with triphenylamine (TPA) in the presence of CNMs. The results of XRD, FTIR and Raman indicated that the CPA/CNMs NCs were effectively synthesized with strong interactions among the constituents. The morphology study demonstrated that CNMs were well coated by CPA and produce a well-aligned nanorod core-shell structure with the large surface area which may be more beneficial to electrical conductivity when used as electrode materials. Differential thermal analysis techniques (TGA-DTG) were used to characterize the thermal stability of NCs. The heat of formation of CPA monomer from TPA, PPDA and aniline (ANI) were computed using Density Functional Theory (DFT) calculations. The NCs of G-MWCNTs demonstrate higher affinity to oxidation of Chlorophenols (CPHs) than glassy carbon electrode (GCE), CPA/GCE and the other NCs. Differential pulse voltammetry (DPV) was used for the trace determination of 2,4-dichlorophenol (2,4-DCP). Under the optimum conditions, the peak current of 2,4-DCP was proportional to its concentration in the range of 0.05-0.6 μmol/L. The detection limit was 7.6 nmol/L. The method was successfully applied for the determination of 2,4-DCP in fish farm water with satisfactory recoveries. The suggested method has an advantage to be used for water samples due to its short analytical time, rapid response, high sensitivity, and excellent selectivity with good reproducibility. K E Y W O R D S 2,4-dichlorophenol sensor, crosslinked polyaniline/G-MWCNTS nanocomposite, density functional theory, electrochemical properties, thermal properties 1 | INTRODUCTION Conducting polymer (CPs) based sensors have the advantages of the processability of environmental, simplicity, high electrical conductivity, mechanical flexibility as well as low cost 1-2 P.ANI in many applications has appeared as one of the most promising CPs materials. 3-6 PANI composites have been used in the fabrication of diverse devices, such as thermoelectric and energy storage devices, biofuel cells and batteries. 7-16 However, the electrochemical applications are the most promising application of these composites. Particularly, in many electroanalytical studies, the fabrication of PANI and PANI composite electrochemical sensors has become a common way and offers high selectivity as well as sensitivity to detect target molecules. 17-19 Crosslinking may be a candidate to enhance the PANI electrical and

Nanocomposites (NCs) of crosslinked polyaniline (CPA)-coated oxidized carbon nanomaterials (OXCNMs) were fabricated as a very sensitive and simple electrochemical sensor to be utilized in 2,4-dichlorophenol (2,4-DCPH) detection. CPA/OXCNMs NCs were prepared by chemical copolymerization of polyaniline with triphenylamine and p-phenylenediamine in the presence of OXCNMs. The CPA/GO-OXSWCNTNCs exhibited a higher affinity for the oxidation of chlorophenols compared to the glassy carbon electrode (GCE), CPA/GCE, and other NCs. Cyclic voltammetry was performed to investigate and assess the electrocatalytic oxidation of 2,4-DCPH on the modified GCE. The compound yielded a well-defined voltammetric response in a Britton-Robinson buffer (pH 5) at 0.54 V (vs. silver chloride electrode). Quantitative determination of 2,4-DCPH was performed by differential pulse voltammetry under optimal conditions in the concentration range of 0.05 to 1.2 nmol L-1 , and a linear calibration graph was obtained. The detection limit (S/N = 3) was found to be 4.2 nmol L-1. In addition, the results demonstrated that the CPA/GO-OXSWCNTs/GCE sensor exhibited a strong anti-interference ability, reproducibility, and stability. The prepared CPA/GO-OXSWCNTs/GCE sensor was used to rapidly detect 2,4-DCPH with a high degree of sensitivity in fish farm water with proven levels of satisfactory recoveries.