title: Linker-induced anomalous emission of organic-molecule conjugated metal-oxide nanoparticles.
abstract: 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 TiO(2) and CeO(2) 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-nanoparticle 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.
authors.affiliation: Department of Physics, University of Central Florida, Orlando, Florida 32816, USA.
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Turkowski
authors.forename: Suresh
authors.initials: S
authors.lastname: Babu
authors.forename: Duy
authors.initials: D
authors.lastname: Le
authors.forename: Amit
authors.initials: A
authors.lastname: Kumar
authors.forename: Manas K
authors.initials: MK
authors.lastname: Haldar
authors.forename: Anil V
authors.initials: AV
authors.lastname: Wagh
authors.forename: Zhongjian
authors.initials: Z
authors.lastname: Hu
authors.forename: Ajay S
authors.initials: AS
authors.lastname: Karakoti
authors.forename: Andre J
authors.initials: AJ
authors.lastname: Gesquiere
authors.forename: Benedict
authors.initials: B
authors.lastname: Law
authors.forename: Sanku
authors.initials: S
authors.lastname: Mallik
authors.forename: Talat S
authors.initials: TS
authors.lastname: Rahman
authors.forename: Michael N
authors.initials: MN
authors.lastname: Leuenberger
authors.forename: Sudipta
authors.initials: S
authors.lastname: Seal
mesh_terms: D003460:Crystallization / Q000379:methods; D049449:Luminescence; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D009930:Organic Chemicals / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D009930:Organic Chemicals; D010087:Oxides