cd3p2 is a tetragonal form of cadmium phosphide that was previously synthesized in a tetragonal shell on ZnS core-shell QDs [26]. It has the same room temperature, tetragonal shape as the related CdSe/ZnS QDs and has been reported to exhibit a wide range of optical properties.
Optical Properties: Absorbance and Emission Spectroscopy
The optical properties of the cd3p2 cores and the core-shell NCs were investigated using absorbance (steady state) and time resolved emission spectroscopies. Figure 2a shows the spectra of both the cd3p2 cores and of the cd3p2/Zn3P2 core-shell NCs taken at an excitation wavelength of 430 nm.
Synthesis: In a 50 mL RB flask, 2 mL of purified, stabilized cd3p2 cores are added to the reaction solution and the mixture is heated to 160 degC using a ramp rate of 25 degC/minute (Figure S2). After 3 cycles of evacuation and purging with argon, the reaction is stopped and the flask is opened to a Schlenk line.
CP MAS NMR of cd3p2/Zn3P2: 1H-13C cross polarization MAS NMR is used to examine the coordination sphere of the cd3p2/Zn3P2 NCs. The CP spectrum of the cd3p2/Zn3P2 reveals characteristic peaks at 129.6 and 41.4 ppm which match the a-CH2 resonances of oleylamine, confirming that the amine is stabilizing the cd3p2 NCs.
31P Hahn-echo MAS NMR: The P environment of the cd3p2/Zn3P2 was also examined by 31P Hahn-echo mas NMR. The spectrum of the cd3p2/Zn3P2 shows characteristic peaks at -225 ppm and -6 ppm, which are similar to those seen for oxidized phosphorus and metal phosphides post shelling.