Extended Data Fig. 3: Interaction of l-Cys with high-index planes.

a, Atomic structure of a chiral nanoparticle at the initial stage. SEM image (i) and TEM images (ii and iii) of a chiral nanoparticle after 20 min of growth. Because the nanoparticle was oriented along the 〈110〉 direction, the projected boundaries in the TEM image consist of chirally distorted edges. The high-resolution TEM image of distorted edges corresponds to the red dotted box in ii. The atoms of the microfacets are marked with coloured circles, and different colours are assigned to the Miller index of each microfacet. Using microfacet nomenclature, the microstructure of (551) can be divided into three units of (111) and two units of \((11\bar{1})\). Inset, corresponding fast Fourier transform (FFT) showing typical patterns along the \([1\bar{1}0]\) zone. b, Temperature-programmed desorption spectra of l-Cys of 432 helicoid I and a low-index cubic nanoparticle, with monitoring of CO₂ (m/q = 44 amu). As the temperature was raised at a rate of 3 K min⁻¹, helium carrier gas flowed over the dried nanoparticle sample. The distinguishable temperature-programmed desorption peak at 635 K for 432 helicoid I indicates a specific interaction of l-Cys with a kink atom on the gold surface. Cys on the cube (100) surface shows no observable peak at high temperatures. c, Cyclic voltammograms for a cube, a high-index stellated octahedron (with differentiated {321} facets) and 432 helicoid I, with l-Cys measured in 0.1 M KOH-ethanol solution at a scan rate of 0.1 V s⁻¹. Negative peaks between about −1.8 V and −1.1 V originate from the reductive desorption of l-Cys by the cleavage of an Au–S bond, Au–SR + e⁻ → Au + RS⁻. Desorption peaks at more negative potentials indicate the higher adsorption energy of l-Cys on high-index gold surfaces.