Linker-Induced Anomalous Emission of Organic-Molecule Conjugated Metal-Oxide Nanoparticles
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- 作者：Volodymyr Turkowski ; Suresh Babu ; Duy Le ; Amit Kumar ; Manas K. Haldar ; Anil V. Wagh ; Zhongjian Hu ; Ajay S. Karakoti ; Andre J. Gesquiere ; Benedict Law ; Sanku Mallik ; Talat S. Rahman ; Michael N. Leuenberger ; Sudipta Seal
- 刊名：ACS Nano
- 出版年：2012
- 出版时间：June 26, 2012
- 年：2012
- 卷：6
- 期：6
- 页码：4854-4863
- 全文大小：590K
- 年卷期：v.6,no.6(June 26, 2012)
- ISSN：1936-086X
文摘
Semiconductor nanoparticles conjugated with organic- and dye-molecules to yield high efficiency visible photoluminescence (PL) hold great potential for many future technological applications. We show that folic acid (FA)-conjugated to nanosize TiO2 and CeO2 particles demonstrates a dramatic increase of photoemission intensity at wavelengths between 500 and 700 nm when derivatized using aminopropyl trimethoxysilane (APTMS) as spacer-linker molecules between the metal oxide and FA. Using density-functional theory (DFT) and time-dependent DFT calculations we demonstrate that the strong increase of the PL can be explained by electronic transitions between the titania surface oxygen vacancy (OV) states and the low-energy excited states of the FA/APTMS molecule anchored onto the surface oxygen bridge sites in close proximity to the OVs. We suggest this scenario to be a universal feature for a wide class of metal oxide nanoparticles, including nanoceria, possessing a similar band gap (3 eV) and with a large surface-vacancy-related density of electronic states. We demonstrate that the molecule鈥搉anoparticle linker can play a crucial role in tuning the electronic and optical properties of nanosystems by bringing optically active parts of the molecule and of the surface close to each other.