Tungsten disulfide (WS2) nanosheets were obtainable by exfoliation of its bulk crystals using ultra-sonication in a N-methyl-pyrrolidinone (NMP) solution containing 1-vinyl-3-(3-aminopropyl)-imidazolium bromide (VAimBr) ionic liquid (IL). In addition, gold nanoballs (AuNBs) with controllable size and shape were synthesized using 1,3-di (3-bromopropyl)-imidazolium bromide ionic liquid as a functional monomer. AuNBs were self-assembled onto WS2 nanosheet surface to form an AuNB/WS2-IL nano-composite. The AuNB/WS2-IL nanocomposite was drop-coated onto a glassy carbon electrode surface to produce a new interface for immobilization of transthyretin (TTR) through a self-assembled interaction between cysteine residues of TTR and AuNBs. All materials and interfaces were fully characterized. The developed TTR-AuNBs/WS2-IL/GCE electrode was found providing a very high-performance platform for the photoelectrochemical sensing of 2,4,6-tribromophenol (TBP) due to the strong affinity between TBP and TTR. With respect to our results, the photocurrent response of WS2 nanosheets was significantly enhanced after the integration of AuNBs and VAimBr ionic liquid, and the enhancement is greatly beneficial for the photoelectrochemical sensing of TBP. Under optimized experimental conditions, the ratio Ri [R-i = Delta i/i(0)] between the photocurrent variation (Delta i) and the original photocurrent (i(0)) shows good linear relationship (R = 0.997) to the logarithm of TBP concentration (c) in the range from 0.05 nmol L-1 to 500 nmol L-1. The limit of detection is calculated to be 0.023 nmol L-1 (S/N = 3). The photoelectrochemical sensor was employed to determine the spiked TBP in the water samples collected from South-Lake Wuhan China. The excellent recoveries of 95.7% and 98.6% demonstrate that the TTR-AuNBs/WS2-IL/GCE is suitable for practical use to determine trace TBP in real water samples. (C) 2018 Elsevier Ltd. All rights reserved.