abstract
Stable, cost-effective, brightly luminescent, and metal-free organosilica nanoparticles (NPs) were prepared using the Stober method without any thermal treatment above 318 K. The white-light photoluminescence results from a convolution of the emission originated in the NH2 groups of the organosilane and oxygen defects in the silica network. The time-resolved emission spectra are red-shifted, relative to those acquired in the steady-state regime, pointing out that the NPs emission is governed by donor-acceptor (D-A) recombination mechanisms. Moreover, the increase of the corresponding lifetime values with the monitored wavelength further supports that the emission is governed by a recombination mechanism typical of a D-A pair attributed to an exceptionally broad inhomogeneous distribution of the emitting centers peculiar to silica-based NPs. These NPs exhibit the highest emission quantum yield value (0.15 +/- 0.02) reported so far for organosilica biolabels without activator metals. Moreover, the emission spectra and the quantum yield values are quite stable over time showing no significant aging effects after exposure to the ambient environment for more than 1 year, stressing the potential of these NPs as metal-free biolabels.
keywords
ORGANIC-INORGANIC HYBRIDS; BIOLOGICAL APPLICATIONS; ACTIVATOR IONS; LIGHT EMISSION; QUANTUM YIELDS; SPHERES; MONODISPERSE; PHOTOLUMINESCENCE; NANOCRYSTALS; PHOSPHORS
subject category
Chemistry; Materials Science
authors
Brites, CDS; Freitas, VT; Ferreira, RAS; Millan, A; Palacio, F; Carlos, LD
our authors
Carlos Brites
Associate Professor
Luís Carlos
Full professor
Maria Rute de Amorim e Sá Ferreira André
Full professor
Vânia Patrícia Castro Teixeira Freitas
Research FellowshipProjects
acknowledgements
The authors are grateful to Fundacao para a Ciencia e a Tecnologia (FCT, Portugal), COMPETE and FEDER programs (Pest-C/CTM/LA0011/2011, PTDC/CTM/101324/2008), and Integrated Spanish-Portuguese Action PT2009-0131 for financial support. The work in Zaragoza has been supported by the grants MAT2007-61621, MAT2011-25991, and CONSOLIDER CSD2007-00010 from the Ministry of Economy and Competitivity. C.D.S.B. (SFRH/BD/38472/2007) thanks FCT for a grant. We acknowledge P. P. Lima (University of Aveiro) for help with the photoluminescence measurements.