2. Experimental procedure
All chemicals were used as purchased without further purification.
2.1. Synthesis of CdTe powder
Nanostructured CdTe powder was synthesized by a solvothermal method similar to the route of Li and coworkers [16] using elemental cadmium and tellurium. Over 3.3 mmol Cd powder (Aldrich 99.5%) and 3.6 mmol Te powder (Acros 99.8%) were pestled in an achate mortar to obtain a fine and homogenous mixture. This powder was placed in a 50 ml Teflon-lined stainless steel autoclave. Subsequently, the autoclave was filled with 30 ml of ethylene diamine (Acros 99%) as solvent, sealed and maintained at 180 °C for three days without further shaking or stirring. After cooling down to room temperature the black precipitate obtained was separated from the solvent by centrifugation at 4000 min−1 for 30 min and washed several times with ethanol and hot distilled water. The product was dried in vacuum at 100 °C for 10 h.
The characterization of the powder was carried out via X-ray diffraction (XRD) using a STOE Stadi-P diffractometer (Cu-Kα1=1.54051 Å). For scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) a ZEISS DSM-982 Gemini was applied. A QUANTACHROME Quadrasorb volumetric adsorption isotherm measurement apparatus was used for the determination of nitrogen physisorption isotherms. The powders were cooled to 77 K in glass sample tubes and exposed to nitrogen gas at a series of precisely controlled pressures. Adsorbed volume as a function of measured partial pressure afforded the nitrogen physisorption isotherm. Specific surface areas were calculated from the isotherms via BET (Brunauer–Emmet–Teller)-equation at relative pressures of p/p0=0.1–0.3