Doping and alloying in atomically precise gold nanoparticles

The recent success in the synthesis and total structure determination of atomically precise gold nanoparticles has provided exciting opportunities for fundamental studies as well as the development of new applications. These unique nanoparticles are of molecular purity and possess well defined formulas （i.e., specific numbers of metal atoms and ligands）, resembling organic compounds. Crystallization of such molecularly pure nanoparticles into macroscopic single crystals allows for the determination of total structures of nanoparticles （i.e., the arrangement of metal core atoms and surface ligands） by X-ray crystallography. In this perspective article, we summarize recent efforts in doping and alloying gold nanoparticles with other metals, including Pd, Pt, Ag and Cu. With atomically precise gold nanoparticles, a specific number of foreign atoms （e.g., Pd, Pt） can be incorporated into the gold core, whereas a range of Ag and Cu substitutions is observed but, interestingly, the total number of metal atoms in the homogold nanoparticle is preserved. The heteroatom substitution of gold nanoparticles allows one to probe the optical, structural, and electronic properties truly at the single-atom level, and thus provides a wealth of information for understanding the intriguing properties of this new class of nanomaterials.

Optically controlled magnetic-field etching on the nano-scale

Electric and magnetic fields play an important role in both chemical and physical reactions.However,since the coupling efficiency between magnetic fields and electrons is low in comparison with that between electric fields and electrons in the visible wavelength region,the magnetic field is negligible in photo-induced reactions.Here,we performed photo-etching of ZrO_(2) nano-stripe structures,and identified an etching-property polarisation dependence.Specifically,the etching rate and etched profiles depend on the structure width.To evaluate this polarisation-dependent etching,we performed numerical calculations using a finite-difference time-domain method.Remarkably,the numerical results revealed that the polarisation-dependent etching properties were determined by the magnetic field distributions,rather than the electric field distributions.As nano-scale structures induce a localised magnetic field,the discovery of this etching dependence on the magnetic field is expected to introduce a new perspective on advanced nano-scale structure fabrication.