Luminescence of dye-doped KAP and KDP nanorods

Abstract

Rods of potassium acid phthalate (KAP) and potassium dihydrogen phosphate (KDP) doped with rhodamine 6G (Rh 6G) were grown using the template approach. Pores of hundreds of nanometers in diameter were obtained in polycarbonate (PC) foils after heavy ions irradiation and subsequent chemical etching. Crystallization from solution was used for filling the pores and the nanostructures were characterized using scanning electron microscopy and photoluminescence spectroscopy studies. SEM images of micro- and nano-rods (300 nm and 2.5 μm diameter) indicate a crystalline growth tendency. When exciting the PC foils containing rods of 100 nm diameter emission bands appear at 581 nm for Rh 6G doped KAP and at 602 nm for Rh 6G doped KDP. A shift of the emission bands towards red was observed when the luminescent properties of the rods with diameters of 100 nm were compared with the luminescent properties of the bulk crystals and of the micrometrical sized rods.

Introduction

Up to now the studies of gain media for solid-state dye lasers have been mainly restricted to polymers or glasses. Recently, dye-doped single crystals such as potassium acid phthalate (KAP) and potassium dihydrogen phosphate (KDP) have been reported to present extremely interesting optical properties (Benedict et al., 2003, Barbon et al., 2004, Enculescu, 2009, Velikhov et al., 2007). One of the most important features of such host materials is their high optical quality. Moreover, in the case of dye-doped crystals some problems related to the fabrication of dye-doped materials for lasing media can be overcome.

Over the past years fabrication of complex architectures at micro and nanometric level has attracted great interest. In terms of ultraminiaturized light sources for example, semiconductor materials such as ZnO nanowires were shown to exhibit lasing effects, the report of Peidong Yang's group (Huang et al., 2001) generating an avalanche of studies in the field. In order to use such nanoobjects for technological applications one important step is finding the appropriate conditions to prepare these nanostructures with high structural and morphological qualities.

The template approach is in particular promising for the controlled fabrication of nanosized objects with given geometrical properties (shape, diameter, length). Using electrochemical deposition this method is successfully applied for semiconducting and metallic nanowires (Enculescu et al., 2007a, Ohgai et al., 2006), whereas crystalline insulating nanorods have been grown by means of solution crystallization Dobrev et al., 1998, Enculescu et al., 2007b, Enculescu, 2008).

This paper presents our most recent study on luminescent properties of rhodamine 6G (Rh 6G) doped potassium hydrogen phthalate and potassium dihygrogen phosphate nanorods grown by crystallization process from solution in track-etched polymer templates.