1 M phosphate-buffered solution (PBS, pH = 7.0). Neutral PBS was obtained by mixing NaH2PO4 and Na2HPO4 solution (0.1 M). A conventional three-electrode system was used with Ag/AgCl (saturated with KCl) and platinum as the reference electrode and counter electrode, respectively. PtCu NC modified glassy carbon electrode (GCE,

Ф = 3 mm) served as the working electrode. Typically, GCE was carefully polished with 0.05 μm alumina powders. Then, 5 μL of PtCu NC suspension (5 mg/mL) was cast onto the GCE and dried in air. Finally, 3 μL 1% Nafion solution was dipped onto the modified electrode. Results and discussion Characterizations As shown in Figure 1a, no Cu2O (JCPDS 65–3288) residue remains in the final products. Compared to pure Pt (JCPDS 65–2868), all diffraction peaks shift to large angle direction. NVP-LDE225 The diffraction peaks located at around 41.2°, 48.1°, and 70° can be indexed to cubic PtCu alloy (JCPDS 48–1549). The average particle size of PtCu was calculated to be 2.9 nm according to the Scherrer equation: (1) where B is the full width at half maximum (FWHM), λ is the X-ray wavelength (1.5406 Å), and

K is a shape factor (about 0.89). On account of the fact that Proteasome inhibitor the Cu2O/Cu redox pair value is 0.36 V, which is much lower than that of PtCl6 2-/Pt (0.735 V), therefore, Cu2O crystals can be used as the reducing agent and sacrificial template for the synthesis of cubic PtCu NCs. The formation process of PtCu NCs can be explained in the following equations: (2) (3) Figure 1 XRD patterns and SEM, TEM, and HRTEM images. XRD patterns of Cu2O and PtCu NCs (a). SEM image of the Cu2O template (b) and PtCu NCs (c). TEM (d) and HRTEM (e, f) images of the PtCu NCs. The insets of (b) and (c)

are the SEM images of single Cu2O crystal and PtCu NC, respectively. The inset of (d) is the TEM image of a single PtCu NC. The insets of (e) and (f) are the SAED pattern and lattice fringes of PtCu NC, respectively. According to the above equations, the coexistence Non-specific serine/threonine protein kinase of Cu can be attributed to the disproportionation reaction of Cu (I). The reactions can simultaneously produce metallic Cu and Pt in the presence of H+, resulting in the formation of PtCu alloy. Figure 1b,c shows the scanning electron microscope (SEM) images of the prepared Cu2O template and the cubic PtCu NCs, respectively. The cubic Cu2O crystals have an average edge length about 200 nm, and the surface of the Cu2O crystals is smooth, uniform, and regular. However, the surface of PtCu NCs changes into rough and porous, indicating the formation of PtCu aggregates. It is clear that the PtCu NCs maintain the morphology of the Cu2O template and the interiors are hollow. The transmission electron microscope (TEM) image of PtCu NCs (Figure 1d) further provides convincing evidence of the hollow structure. For a further investigation, high-resolution transmission electron microscope (HRTEM) images were taken and displayed in Figure 1e,f.