## 3 Results and Discussion  
The successful synthesis of PPy-CdSe composite nanorods was verified by electron microscopy (Figure 2). As previous studies have shown, this method can synthesize well-defined polypyrrole nanorods where the diameters of the nanorods closely match the expected pore diameters of the AAOmembrane, as observed by scanning electron microscopy (SEM, Figure 2a). However, it was difficult to observe the embedded CdSe quantum dots with SEM because it mostly provides topographic surface analysis, and the size of quantum dots are similar or smaller than the resolution limit of SEM. Transmission electron microscopy (TEM) would be an acceptable substitute, but the nanorods are too thick to allow transmission of electrons in order to form an image. To characterize the hybrid nanorods with TEM, thinner nanorods were synthesized using a homemade AAO membrane with pore diameters of \(25\pm 5\) nm and a thickness of \(30\) um. The synthesis of composite nanorods can be carried out via the same process with the homemade templates, and this results in thinner nanorods. TEM then enabled the observation of CdSe quantum dots embedded in polypyrrole nanorods (Figure 2b). Each component (PPy, Cd, and Se elements) was also confirmed by an energy-dispersive X-ray spectroscopic spectrum (Figure 2a, inset). Polypyrrole photoluminescence normally does not occur at wavelengths longer than 500 nm, and this is in agreement with our experimental result where no detectable signal was observed in the control polypyrrole nanorods with fluorescence microscopy (Figure 3a,b). Figure 2: Electron micrographs of the CdSe-embedded PPy nanorods synthesized with different AAO template pore sizes, (**a**) 300 nm (SEM) and (**b**) 25 \(\pm\) 5 nm (TEM). The inset in (a) is the EDS spectrum of CdSe-embedded PPy nanorod that shows the C, Cd, and Se elements. Interestingly, the CdSe-embedded polypyrrole nanorods showed photoluminescence signals along the nanowires (Figure 3c,d), which differed from the fluorescence of CdSe quantum dots (Figure 4b). The CdSe quantum dots showed a single photoluminescence peak at 594.5 nm, whereas the photoluminescence peak of the CdSe-embedded polypyrrole nanorods was much broader and could be deconvoluted into three different Gaussian curves (R\({}^{2}\) = 0.996); the wavelengths of the three peaks were 552.1, 591.1, and 662.7 nm (Figure 3e). To test any effect from the electrolyte during the synthesis, CdSe quantum dots were dispersed into the plating solution (w/o pyrrole monomer, 0.1 M) containing tetrahydrofuran and toluene before a dropcast film was prepared for spectroscopy, but no meaningful  
Figure 3: (**a**) An optical micrograph and (**b**) a fluorescence micrograph of the control sample, PPy nanorods without CdSe nanoparticles. No observable photoluminescence was detected for the control sample. (**c**,**d**) Respective data for CdSe-embedded PPy nanorods where emissions from the hybrid nanorods were captured. (**e**) A photoluminescence spectrum from the CdSe-embedded PPy nanorods (black), deconvoluted peak fittings (red, green, and blue dotted lines), and the cumulative peak fitting (magenta). change in photoluminescence was detected (Figure 4c). In contrast, when the CdSe quantum dots were mixed with the plating solution containing pyrrole monomer (the pyrrole molecules are presumably adsorbed onto the quantum dot surfaces), we observed a blue-shift of the single photoluminescence peak to 567 nm (Figure 4d). These data indicate that the photoluminescence of CdSe has been affected by the hybridization with polypyrrole through the interface formation. There are several possible explanations for the observed change in photoluminescence. The changes in energy band structure of the quantum dots by interfacing with polypyrrole can induce chemical and/or physical modification of the surface states [20]. The energy transfers between the quantum dots and polypyrrole can also result in such a change [36].