Blue-Light-Excitable Yellow Emissive One-Dimensional Hybrid Copper(I) Iodide for White-Light-Emitting Diode and Methanol Sensing Application

Copper(I) halides are promising candidates for advanced optoelectronics, such as white-light-emitting diodes (WLEDs), scintillators, and photodetectors. Designing and synthesizing low-dimensional hybrid copper halides with blue-light excitation remains an enormous challenge. Herein, we have prepared two one-dimensional (1D) hybrid Cu(I)-based metal iodides, namely, (C₆H₇N)CuI and (C₆H₈N)CuI₂ single crystals, by deliberately adjusting the ratio of the reactants 4-methylpyridine (4-MePy) and CuI. (C₆H₇N)CuI crystals are nonluminous, while (C₆H₈N)CuI₂ crystals exhibit an unusual yellow emission with a broad excitation band in the range of 260-500 nm Furthermore, a prototypical WLED is fabricated by combining a commercial 430 nm blue chip and (C₆H₈N)CuI₂ phosphor, which exhibits a correlated color temperature (CCT) of 5645 K and a CIE color coordinate of (0.329, 0.334), thus demonstrating potential application for white lighting. Remarkably, (C₆H₈N)CuI₂ crystals emit red fluorescence upon adsorption of methanol but fail for all other alcohols. Notably, the initial yellow luminescence can be recovered upon volatilization of methanol from the crystals, thus achieving a reversible photoluminescence switching. This work not only presents an important reference of blue-light-excitable hybrid Cu(I)-based metal iodide phosphor for WLEDs but also provides an intriguing fluorescence sensor for the reversible detection of methanol.