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Faradays legendary Molecules of Gold have stimulated intense interest (over 165 years) but have only recently begun to yield their secrets to modern methods of chemical analysis. Here(in), we demonstrate how striking charging patterns emerge directly from native electrospray of large, gold-rich molecules that were generated by reduction of various (8) small gold(I)thiolate complexes [-RS-Au(I)-SR-], followed by extensive thermochemical processing to enrich the most robust forms. In each case (R), electrospray ionization of a picomolar solution yields a characteristic series of abundant, highly resolved peaks at related (m/z)-ratios, that can be used to deduce charges {z e+} and hence a distinct molecular mass, {MR}. A plot of {MR} versus thiolate-mass {mL} yields a straight line with slope 60.0 (the ligand count) and an intercept of 28,364-Da, the mass of 144 Au-atoms. i.e., a unique molecular composition {197Au144(SR)60}. This formula agrees with the unique chiral-icosahedral structure-model, c@12@42@60@(30,60), the Pd145(CO)60-structure, that features a massively-compact globular Au114-core (~1.6-nm) and an intrinsically chiral (I) outer shell (~2.0-nm) with 12 distinct ligand types of 5-fold equivalence], denoted by Martin et al. as virus-like on the basis of its resemblance of icosahedral-virus capsids. 

Poly(amino acid)-coated gold nanoparticles hold promise in biomedical applications, particularly because they combine the unique physicochemical properties of the gold core, excellent biocompatibility, and easy functionalization of the poly(amino acid)-capping shell. Here we report a novel method for the preparation of robust hybrid core–shell nanosystems consisting of a Au 144 cluster and a densely grafted polylysine layer. Linear polylysine chains were grown by direct N -carboxyanhydride (NCA) polymerization onto ligands capping the gold nanocluster. The density of the polylysine chains and the thickness of the polymer layer strongly depend on the amount and concentration of the NCA monomer and the initiator. The optical spectra of the so-obtained core–shell nanosystems show a strong surface plasmon resonance (SPR)-like band at 531 nm. In fact, despite maintenance of the gold cluster size and the absence of interparticle aggregation, the polylysine-capped clusters behave as if they have a diameter nearly 4 times larger. To the best of our knowledge, this is the first observation of the growth of a fully developed, very stable SPR-like band for a gold nanocluster of such dimensions. The robust polylysine protective shell makes the nanoparticles very stable under conditions of chemical etching, in the presence of glutathione, and at different pH values, without gold core deshielding or alteration of the SPR-like band. This polymerization method can conceivably be extended to prepare core–shell nanosystems based on other mono- or co-poly(amino acids). 

The authors designed a structurally stable nano‐in‐nano (NANO²) system highly capable of bioimaging via an aggregation‐enhanced NIR excited emission and photoacoustic response achieved based on atomically precise gold nanoclusters protected by linear thiolated ligands [Au₂₅(SC_nH_2n+1)₁₈,n =4–16] encapsulated in discoidal phospholipid bicelles through a one‐pot synthesis. The detailed morphological characterization of NANO²is conducted using cryogenic transmission electron microscopy, small/wide angle X‐ray scattering with the support of molecular dynamics simulations, providing information on the location of Au nanoclusters in NANO². The photoluminescence observed for NANO²is 20–60 times more intense than that of the free Au nanoclusters, with both excitation and emission wavelengths in the near‐infrared range, and the photoacoustic signal is more than tripled. The authors attribute this newly discovered aggregation‐enhanced photoluminescence and photoacoustic signals to the restriction of intramolecular motion of the clusters’ ligands. With the advantages of biocompatibility and high cellular uptake, NANO²is potentially applicable for both in vitro and in vivo imaging, as the authors demonstrate with NIR excited emission from in vitro A549 human lung and the KB human cervical cancer cells.