The pursuit of single-molecule magnets (SMMs) with better performance urges new molecular design that can endow SMMs larger magnetic anisotropy. Here we report that two-coordinate cobalt imido complexes featuring highly covalent Co═N cores exhibit slow relaxation of magnetization under zero direct-current field with a high effective relaxation barrier up to 413 cm, a new record for transition metal based SMMs. Two theoretical models were carried out to investigate the anisotropy of these complexes: single-ion model and Co-N coupling model. The former indicates that the pseudo linear ligand field helps to preserve the first-order orbital momentum, while the latter suggests that the strong ferromagnetic interaction between Co and N makes the [CoN] fragment a pseudo single paramagnetic ion, and that the excellent performance of these cobalt imido SMMs is attributed to the inherent large magnetic anisotropy of the [CoN] core with |M = ± 7/2⟩ ground Kramers doublet.

Electrochemical atomic force microscopy tip-enhanced Raman spectroscopy (EC-AFM-TERS) was used for the first time to spatially resolve local heterogeneity in redox behavior on an electrode surface in situ and at the nanoscale. A structurally well-defined Au(111) nanoplate located on a polycrystalline ITO substrate was studied to examine nanoscale redox contrast across the two electrode materials. By monitoring the TERS intensity of adsorbed Nile Blue (NB) molecules on the electrode surface, TERS maps were acquired with different applied potentials. The EC-TERS maps showed a spatial contrast in TERS intensity between Au and ITO. TERS line scans near the edge of a 20 nm-thick Au nanoplate demonstrated a spatial resolution of 81 nm under an applied potential of −0.1 V vs Ag/AgCl. The intensities from the TERS maps at various applied potentials followed Nernstian behavior, and a formal potential (E 0 ′) map was constructed by fitting the TERS intensity at each pixel to the Nernst equation. Clear nanoscale spatial contrast between the Au and ITO regions was observed in the E 0 ′ map. In addition, statistical analysis of the E 0 ′ map identified a statistically significant 4 mV difference in E 0 ′ on Au vs ITO. Electrochemical heterogeneity was also evident in the E 0 ′ distribution, as a bimodal distribution was observed in E 0 ′ on polycrystalline ITO, but not on gold. A direct comparison between an AFM friction image and the E 0 ′ map resolved the electrochemical behavior of individual ITO grains with a spatial resolution of ∼40 nm. The variation in E 0 ′ was attributed to different local surface charges on the ITO grains. Such site-specific electrochemical information with nanoscale spatial and few mV voltage resolutions is not available using ensemble spectroelectrochemical methods. We expect that in situ redox mapping at the nanoscale using EC-AFM-TERS will have a crucial impact on understanding the role of nanoscale surface features in applications such as electrocatalysis.

A novel method for synthesizing and photopatterning colloidal crystals via light‐responsive DNA is developed. These crystals are composed of 10–30 nm gold nanoparticles interconnected with azobenzene‐modified DNA strands. The photoisomerization of the azobenzene molecules leads to reversible assembly and disassembly of the base‐centered cubic (bcc) and face‐centered cubic (fcc) crystalline nanoparticle lattices. In addition, UV light is used as a trigger to selectively remove nanoparticles on centimeter‐scale thin films of colloidal crystals, allowing them to be photopatterned into preconceived shapes. The design of the azobenzene‐modified linking DNA is critical and involves complementary strands, with azobenzene moieties deliberately staggered between the bases that define the complementary code. This results in a tunable wavelength‐dependent melting temperature (Tm) window (4.5–15 °C) and one suitable for affecting the desired transformations. In addition to the isomeric state of the azobenzene groups, the size of the particles can be used to modulate the Tm window over which these structures are light‐responsive.

Evidence has recently accumulated that an interconnect under intense electric current can fail by a transgranular slit. A rounded void first forms, enlarges, and drifts. When the void becomes sufficiently large, a narrow slit emerges at the expense of the void, running across the linewidth. In this letter we describe a physical mechanism that explains this instability. Both electric current and surface energy drive atoms to diffuse on the void surface, but in the opposite directions. The slit emerges if the electric current prevails. An approximate analysis shows how the slit selects its width and velocity.