An integrated Bi_2O_3(i-Bi_2O_3) nanostructure with a particle size 10 nm inducing agglomerated structure were synthesized by dissolving bismuth nitrate pentahydrate in diethylene glycol at 180 ℃ with post heat treatment.The prepared i-Bi_2O_3 nanostructures were employed for the construction of Au/i-Bi_2O_3 composite system and characterized by X-ray diffraction pattern,UV-visible diffuse reflectance spectroscopy(DRS),and transmission electron microscopy,X-ray photoemission spectroscopy(XPS) and Energy dispersive X-ray spectroscopy(EDS).The i-Bi_2O_3 nanostructure and Au/i-Bi_2O_3 composite system were found to exhibit high photocatalytic activity than commercial Bi_2O_3 in decomposing salicylic acid under visible light irradiation.The high catalytic activity of i-Bi_2O_3 nanostructure was deduced to be caused by charge separation facilitated by electron hopping between the particles within the integrated structure and space-charge separation between i-Bi_2O_3 and Au.The charge separation behavior in i-Bi_2O_3 nanostructure was further bolstered by comparing the measured.OH radical produced in the solution with i-Bi_2O_3 nanostructure,commercial Bi_2O_3 and Au/i-Bi_2O_3 composite which readily react with 1,4-terephthalic acid(TA) inducing 2-hydroxy terephthalic acid(TAOH) that shows unique fluorescence peak at 426 nm.The space-charge separation between i-Bi_2O_3 and An was confirmed by measuring the electron spin resonance(ESR) spectra. An integrated Bi 2 O 3 (i-Bi 2 O 3) nanostructure with a particle size of 10 nm inducing agglomerated structure was synthesized by dissolving bismuth nitrate pentahydrate in diethylene glycol at 180 ℃ with post heat treatment. The prepared i-Bi 2 O 3 nanostructures were used for the construction of Au / i-Bi_2O_3 composite system and characterized by X-ray diffraction pattern, UV-visible diffuse reflectance spectroscopy (DRS), and transmission electron microscopy, X-ray photoemission spectroscopy (XPS) and Energy dispersive X-ray spectroscopy (EDS) -Bi_2O_3 nanostructure and Au / i-Bi_2O_3 composite system were found to exhibit high photocatalytic activity than commercial Bi_2O_3 in decomposing salicylic acid under visible light irradiation. The high catalytic activity of i-Bi_2O_3 nanostructure was deduced to be caused by charge separation facilitated by electron hopping between the particles within the integrated structure and space-charge separation between i-Bi 2 O 3 and Au. charge sepa ration behavior in i-Bi_2O_3 nanostructure was further bolstered by comparing the measured .OH radical produced in the solution with i-Bi_2O_3 nanostructure, commercial Bi_2O_3 and Au / i-Bi_2O_3 composite which readily react with 1,4-terephthalic acid (TA) inducing 2-hydroxy terephthalic acid (TAOH) that shows unique fluorescence peak at 426 nm. The space-charge separation between i-Bi 2 O 3 and An was confirmed by the electron spin resonance (ESR) spectra.