Tuning structure and luminescence color output of a single upcoversion microcrystal through plasmonic heating effect

Lanthanide doped upconversion (UC) materials have attracted much attention owing to their unique near-infrared to visible upconverted emission characteristics. However, it still remains a challenge for a fine tuning of emission colors in UC materials and especially in microcrystals. In this work, we report a novel method to realize emission color tuning in microrods through the plasmonic heating effect generated by the nano-islands (Au NIs) under 980 nm laser illumination. It is found that Au NIs was a good optical heater system and its temperature can be controlled by changing the excitation power. The structure of single NaYF4 microrod can transform into YOF and Y2O3 by simply altering the local temperature via plasmonic heating effect, which contributes to an excellent crystallinity of YOF and Y2O3 microrods by comparison to conventional heating methods. Importantly, these YOF:Er3+/Yb3+ and Y2O3:Yb3+/Er3+ microrods show much bright and tunable color output from red to yellow and green in contrast to those obtained by conventional heating methods. Furthermore, the local temperature in the plasmonic heater can be obtained by analyzing the integrated intensity ratio of Er3+ emissions from the thermally coupled 2H11/2 and 4S3/2 states, and high local temperature up to 843 K was achieved. Our results provide a new strategy to manipulate the luminescence property of single microcrystal materials and extends the application of surface plasmon to broader fields. •The optical heater was maid composed by Au NIs.•The crystal structure of NaYF4 was transformed into YOF and Y2O3.•The bright tunable colour emission from red to green was obtained by controlling the plasmon thermal effect.•The local temperature in the plasmonic heater was detected in situ via the FIR techniques.