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To explore the effects of microenvironmental adjustments on fluorescence, a pH-sensitive nano-composite system based on fluorescence resonance energy transfer (FRET) was constructed. The model system included a modified triblock copolymer (polyhistidine-b-polyethylene glycol-b-polycaprolac-tone) and gold nanoparticles. A near-infrared dye was used as the donor, and spectrally matched gold nanorods, attached after C-terminus modification with a-lipoic acid, were used as the receptor to realize control of the FRET effect over the fluorescence intensity for two polymer configurational changes (i.e.,“folded” and “stretched” states) in response to pH. After synthesis and characterization, we investigated the self-assembly behavior of the system. Analysis by quartz crystal microbalance revealed the pH sensitivity of the polymer, which exhibited “folding” and “stretching” states with changes in pH,providing a structural basis for the FRET effect. Fluorescence spectrophotometry investigations also revealed the regulatory impact of the assembled system on fluorescence.