congratulation to Our new paper in Journal of Optic
Temperature Dependent Random Laser Performance of Au@Cu and Cu@Au Core-Shell Nanoparticles in a Rhodamine 6G–PNIPAM Smart Polymer Matrix Medium
Mariam Kadhim Jawad, J. M. Jassim, S. F. Haddawi, S. M. Hamidi
Abstract:
This study aimed to investigate the temperature-dependent performance of random lasers using Rhodamine 6G (R6G) dye embedded in a thermoresponsive PNIPAM polymer matrix with Au, Cu, Au@Cu, and Cu@Au nanoparticles serving as scattering centers. At 25 °C, only fluorescence was observed due to the hydrophilic state of PNIPAM, resulting in high optical absorption and insufficient refractive index contrast for lasing. As temperature increased to 30–45 °C, PNIPAM became hydrophobic, enhancing index contrast and reducing absorption, which facilitated random lasing. Among the nanoparticles, Au showed the highest emission intensity (62618 a.u.) and narrowest FWHM (4.6 nm), followed by Cu@Au (59908 a.u., 5.3 nm), attributed to the strong plasmonic response of the Au shell. Conversely, Au@Cu and Cu exhibited weaker outputs due to higher damping and less effective plasmonic resonance. Temperature-dependent spectral analysis showed that Cu had the most pronounced bandwidth narrowing (7.5 nm to 3.4 nm), while Au@Cu demonstrated the highest intensity modulation (30913 a.u. to 65195 a.u.). A temperature-induced blue shift in peak emission was observed, most prominently in PNIPAM alone (6.2 nm), with smaller shifts in nanocomposite systems due to varied thermal coupling. These results highlight the pivotal role of PNIPAM’s thermal transition in controlling random laser behavior, offering new strategies for designing tunable or thermally stable laser systems.
