Concerted Photoluminescence of Electrochemically Self-Assembled CuSCN/Stilbazolium Dye Hybrid Thin Films

Abstract

Hybrid thin films of crystalline CuSCN and 4-( N , N -dimethylamino)-4′-( N ′-methyl)stilbazolium (DAS) in three distinctively different nanostructures were obtained by electrochemical self-assembly from a single pot containing all the chemical ingredients. Their optical properties for UV–vis-NIR absorption, photoluminescence (PL), and PL excitation spectra were examined between 77 and 298 K, in comparison with solution and solid powder of DAS tosylate (DAST). Unlike all other dyes we tested before, PL of DAS was not quenched but rather enhanced when hybridized with CuSCN. DAST exhibited a strong exciton–phonon coupling to weaken, broaden, and red shift PL at room temperature, so that it inversely is strongly enhanced, sharpened, and blue-shifted at 77 K. The PL of the same dye in the hybrid thin film, however, shows a slight red shift and only a moderate enhancement at reduced temperatures due to strong exciton stabilization in dielectric environment of CuSCN and concerted PL by energy transfer from CuSCN to DAS luminophore, making it a unique nearly temperature-independent luminescent material.

Optical Properties of CuSCN/Stilbazolium Dye Hybrid Thin Films

“…Using X-ray diffraction, it was found [2,3] that at high concentrations of DAST (approximately 700-800 μmol/dm 3 ) there is a structural phase transition from the rhombohedral -phase to the orthorhombic α-phase of CuSCN in hybrid CuSCN-DAST films. It is likely that significant changes in the optical properties of the investigated sample #4 with a high dye concentration of 1000 μmol/dm 3 are also associated with similar changes in the structure of the hybrid CuSCN-DAST film, and not only with changes in the dye concentration.…”

“…The thickness of the film samples was about 800 nm. The process of production of these samples is described in detail in [2,3].…”

“…In [2,3], the optical and structural properties of hybrid organic-inorganic CuSCN films with stilbazolium dye (4-(N,N-dimethylamino)-4′-(N′-methyl) stilbazolium tosylate (DAST) were studied by optical spectroscopy, photoluminescence, X-ray diffraction and scanning electron microscopy. Using X-ray diffraction, it was found that at high concentrations of DAST dye there is the structural phase transition from the rhombohedral -phase to the orthorhombic α-phase of CuSCN.…”

“…In this case, DAST in the form of a separate phase fills in the gaps between the "teeth of the comb". An analysis of the obtained absorption spectra allowed the authors of [2] to detect a blue shift of the absorption maximum (from 499 nm at DAST = 50 μmol/dm 3 to 487 nm at DAST = 500 mol/dm 3 ). A narrowing of this maximum was also observed with increasing dye concentration.…”

“…Юргелевич 1 , Д.В. Гнатюк 2 , K. Uda 3 , T. Yoshida Проведено еліпсометричну діагностику гібридних органічно-неорганічних плівок тіоціанату міді CuSCN зі стільбазолієвим барвником різної концентрації. Досліджені зразки з концентраціями барвника 4-N,N-диметиламіно-4′-N′-метил-стільбазоліум тозілат, що дорівнювали 0, 25, 250 та 1000 мкмоль/дм 3 , було нанесено на підкладки з оксиду олова, допованого фтором.…”