On the other hand, the peak at m/z = 4568.50 correspond to the simulated pattern of protonation. However, the origin of these hydrides is confirmed through the ESI-MS analysis of a deuterated NC synthesized using NaBD4. The notable m/z shift of approximately +2 unequivocally indicates that the hydrides in the Cu18PTT NC are derived from the reducing agent (Figure ). In addition, the ESI-MS experiment confirms the neutral charge state of Cu18PTT NC, indicating the presence of a single Cu(0) atom within the structure. X-ray excited Cu LMM Auger electron spectroscopy reveals peaks at 915.815 eV and 918.736 eV for the Cu18PTT NC, corresponding to Cu(I) and Cu(0), respectively, as determined from Gaussian-Lorentzian band fitting (Figure ). Notably, the peak at ~918.736 eV, indicative of Cu(0), is absent in the two Cu11 NCs, confirming that Cu(0) is uniquely present in Cu18PTT NC. Furthermore, the X-ray absorption near-edge structure (XANES) spectra at the Cu K-edge of the individual NCs reveal a distinct difference in the pre-edge peak around ~8980 eV between the Cu11 NCs and Cu18PTT NCs. The slight lower intensity in the pre-edge peak of Cu18PTT NC than Cu11 NCs, attributed to the presence of a mixed Cu(0)/Cu(I) oxidation state (Figure ). However, the Cu-K edge Fourier transform-extended X-ray absorption fine structure (FT-EXAFS) data confirms that there is no change in ligand coordination on the Cu. This is evident from the persistent peak observed at ~1.8 Å, which is attributed to Cu-P or Cu-S bonding (Figure ). In addition, theoretical Bader charge analysis confirms that the Cu(0) atom is located at the center of the core (Figure ), bridging two Cu5 geometries, consistent with the previously reported structure of the Cu18SAdm NC. The bulk purity of these NCs is verified by the XPS survey spectra (Figure ).