Organic luminescent materials with multicolour tunable emissions have attracted considerable attention, due to their promising applications in the field of chemo-sensing, flat-panel displays, low-cost and energy-saving sources for next generation liquid-crystal and solid-state lighting.1 A common approach to attain multicolour luminescence is to generate three primary RGB (Red, Green, Blue) colours with controllable and tunable relative intensities covering the whole visible range.1 Recently, we have demonstrated that the emission color of oligofluorene-based nanoparticle was tuned to white and orange-red through fluorescence resonance energy transfer (FRET) by an encapsulated acceptor dye (RB dichromophoric nanoparticle system).2 Herein, we report that a fluorene-based linear π-conjugated oligomer functionalized with amino groups (OF) was synthesized and characterized. By using a reprecipitation method, self-assembled OF nanoparticles (OFNs) with good dispersion and colloidal stability were prepared in aqueous medium. The intense blue emitting OFN was utilized as a donor scaffold for FRET. The efficient energy transfer from OFN to the encapsulated red emitting neutral dye (interior particle FRET) as well as to the green emitting anionic dye adsorbed on the surface of OFN (exterior particle FRET) resulted in the creation of RGB trichromophoric nanoparticle system. Eventually, full color tuning fluorescence including white was successfully achieved in aqueous medium by modulating the FRET efficiency. The white light emitting RGB trichromophoric nanoparticle suspension can be utilized for the detection of Bovine serum albumin in phosphate buffer solution (pH 7.2) associated with visually sensitive responses and low detection limit. References: 1) M. C. Gather, A. Kohnen and K. Meerholz, Adv. Mater., 23, 233 (2011). 2) C. Vijayakumar, K. Sugiyasu, M. Takeuchi, Chem. Sci., 2, 291 (2011).