Phosphorescent Sensor Based on Iridium Complex/Poly(vinylcarbazole) Orderly Assembled with Layered Double Hydroxide Nanosheets: Two-Dimensional F枚ster Resonance Energy Transfer and Reversible Luminesc

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• 作者：Yumei Qin ; Jun Lu ; Shuangde Li ; Zhen Li ; Shufang Zheng
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：September 4, 2014
• 年：2014
• 卷：118
• 期：35
• 页码：20538-20544
• 全文大小：474K
• ISSN：1932-7455

文摘

The application study of phosphorescence complexes is important for further investigation and exploration of novel optofunctional materials. In this work, neutral poly(vinylcarbazole) (PVK) and tris[2-(4,6-difluorophenyl)pyridinato-C²,N]iridium(III) (Ir(F₂ppy)₃) were assembled with LDH nanosheets to form ordered ultrathin films (UTFs). These inorganic/organic composite UTFs exhibited cyan luminescence from Ir(F₂ppy)₃, peaking at 471 and 491 nm, due to triplet metal-to-ligand charge transfer and ligand-centered states, respectively. Under PVK maximal excitation at 294 nm, the photoluminescence spectra of the UTFs showed emission from Ir(F₂ppy)₃ rather than from PVK, demonstrating PVK transfer of resonance energy to Ir(F₂ppy)₃. Temporal luminescence spectroscopy revealed that the phosphorescence lifetime of Ir(F₂ppy)₃ molecules increased to 885 ns and fluorescence lifetime of PVK fell to 1.39 ns in the UTFs, which was typical character of the FRET process. This FRET process occurred within the interlayers of LDH nanosheets and can be described as a two-dimensional (2D) process with high efficiency (0.892). Moreover, it was found that the presence of volatile organic compound (VOC) vapors can interrupt this 2D process because of the unique hydrophobic character of the organic interlayers within the UTFs. This function was utilized for a phosphorescent sensor that enables reversible two-state photoemission switching (ON for cyan light of Ir(F₂ppy)₃ vs OFF for blue light of PVK). This phosphorescence sensor demonstrated a fast, highly sensitive, and reversible response toward common VOCs, and this 2D FRET with energy transfer involving the D(singlet) 鈫?A(triplet) process was more efficient compared with that of singlet鈥搒inglet processes. That is, to get the same luminescence intensity, these UTFs can be realized by less frequent excitation of PVK or lower concentrations of Ir(F₂ppy)₃ compared with intrinsic excitation of Ir(F₂ppy)₃.