Strong green upconversion emission in Zr O2: Yb3+ - Ho3+ nanocrystals

Abstract

The polymerization of styrene in three-component dodecyltrimethylammonium bromide (DTAB) microemulsions is reported. The structure of the unpolymerized microemulsions, determined by conductimetry and quasielastic light scattering (QLS), is consistent with styrene-swollen micelles in equilibrium with regular micelles, both dispersed in an aqueous phase. Polymerization of these transparent microemulsions, monitored by QLS and dilatometry, produced stable, bluish monodisperse microlatices with particle radii ranging from 20 to 30 nm, depending on styrene content. Polymerization initiation appears to occur in the styrene-swollen micelles, and the polymer particles grow by recruiting monomer and surfactant from uninitiated droplets and small micelles. " 1990 American Chemical Society.",,,,,,,,,"http://hdl.handle.net/20.500.12104/44828","http://www.scopus.com/inward/record.url?eid=2-s2.0-0002181259&partnerID=40&md5=4130b49002072b586b0bbdb2c430f033

http://dx.doi.org/10.1021/la00096a002",,,,,,"6",,"Langmuir",,"1040

1044",,"6",,"Scopus

WOS

ChemAbsS",,,,,,,,,,,,"Styrene polymerization in three-component cationic microemulsions",,"Article" "46553","123456789/35008",,"De La Rosa, E., Centro de Investigaciones en Optica, A. P. 1-948, León, Gto. 37150, Mexico; Salas, P., Instituto Mexicano del Petruleo, L. Cárdenas 152, D.F. 07730, Mexico; Desirena, H., Centro de Investigaciones en Optica, A. P. 1-948, León, Gto. 37150, Mexico; Angeles, C., Instituto Mexicano del Petruleo, L. Cárdenas 152, D.F. 07730, Mexico; Rodríguez, R.A., CU Los Lagos, U. de G. at Lagos, Jal. 47460, Mexico",,"De La Rosa, E.

Salas, P.

Desirena, H.

Angeles, C.

Rodriguez, R.A.",,"2005",,"Structural and upconversion emission properties of Zr O2: Yb3+ - Ho3+ nanocrystals were analyzed as function of Yb3+ concentration. Structural characterization shows a crystallite size up to 80 nm and tetragonal and cubic phase as the main crystalline structures. Strong green (540 nm) and weak red (670 nm) and near infrared (760 nm) emission bands were observed with 968 nm excitation. The upconversion is based on two photons absorption either by the energy transfers from Yb3+ ion or by the excited state absorption. The energy transfer efficiency was calculated to be 50% for 2 mol % of Yb3+ diminishing to less than 20% for higher concentration. The Yb3+ concentration also affects the decay time of the green emission of Ho3+ ion diminishing from 140 ?s for 2 mol % of Yb to 76 ?s for higher concentration. " 2005 American Institute of Physics.