The bandgap is a fundamental property inherent to semiconductor materials such as silicon (Si) and germanium (Ge), determining their electronic and optical properties. Furthermore, combining Si and Ge allows for the potential to manipulate the optical and electronic properties of mixed materials. Various synthetic methods for Si/Ge nanoparticles (NPs) have been investigated, and there is a need to develop a simpler method for Si/Ge NP synthesis. We present a modified one-pot synthesis method to fabricate [Formula: see text]-butyl Si/Ge NPs using a streamlined, room-temperature process that excludes surfactants. Ge–Ge, Ge–Si, and Si–Si optical phonons were exhibited by [Formula: see text]-butyl-Si/Ge NPs at 285, 400, and 485[Formula: see text]cm[Formula: see text], respectively, in Raman analysis. The Si-to-Ge ratios of the [Formula: see text]-butyl-Si/Ge NPs ranged from 0.40:0.60 to 0.47:0.53 according to high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX) analysis. The PL spectrum ([Formula: see text][Formula: see text]nm) of [Formula: see text]-butyl-Si/Ge NPs closely resembled those of Ge NPs ([Formula: see text][Formula: see text]nm); this result is discussed in relation to those obtained from reported theoretical calculations.