Introduction of polar azulenes and further functionalization significantly enhance the NLO properties of carbon based materials.

We report the in situ microscopy observation of an unnatural phase of Ni, a highly strained hexagonal close-packed ͑hcp͒ form which we believe is stabilized by heteroepitaxial growth on the ͑001͒ face of MgO. We find that the nanosized hcp nickel islands transform into the normal face-centered cubic structure when the size of the islands exceeds a critical value ͑about 2.5 nm thick with a lateral size of ϳ5 nm͒. The structural transition proceeds via a martensitic change in the stacking sequence of the close-packed planes. The formation of hcp Ni nanostructures with an unusually large crystallographic c / a ratio ͑ϳ6% larger than ideal hcp͒ is very interesting for spintronic and recording applications where large uniaxial anisotropies are desirable.

Development of highly active and robust earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) is of great significance for the broad utilization of alkaline electrolyzers.

Inducing new nonlinear optical (NLO) properties while keeping the thermal stability of carbon-based nanomaterials paves a new path for the application of carbon nanomaterials in optoelectronics. In the present work, azulene units are introduced to spiral carbon nanoribbons to enhance the polarity of the charge distribution in spiral carbon nanoribbons, significantly enhancing the first hyperpolarizabilities of those nanoribbons and making the nanoribbons potential nonlinear optical materials. For example, the static first hyperpolarizability of azulene-defected spiral graphene nanoribbon with eight units (ADSGN8) is 2499.0 × 10–30 esu, whereas that of azulene spiral graphene nanoribbon (SGN8) is only 12.0 × 10–30 esu. The two-dimensional second-order NLO spectra predicted by the sum-over-states model reveal the strong second-order NLO responses of the nanomaterials under external fields, particularly within the visible region of approximately 600.0 nm. The origin of the first hyperpolarizability of azulene-defected spiral carbon nanoribbons is scrutinized and further improvement on the NLO responses of those systems is proposed.

Organic single-crystalline semiconductors with long-range periodic order have attracted much attention for potential applications in electronic and optoelectronic devices due to their high carrier mobility, highly thermal stability, and low impurity content. Molecular doping has been proposed as a valuable strategy for improving the performance of organic semiconductors and semiconductor-based devices. However, a fundamental understanding of the inherent doping mechanism is still a key challenge impeding its practical application. In this study, solid evidence for the "perfect" substitutional doping mechanism of the stacking mode between the guest and host molecules in organic single-crystalline semiconductors using polarized photoluminescence spectrum measurements and first-principles calculations is provided. The molecular host-guest doping is further exploited for efficient color-tunable and even white organic single-crystal-based light-emitting devices by controlling the doping concentration. The clarification of the molecular doping mechanism in organic single-crystalline semiconductor host-guest system paves the way for their practical application in high-performance electronic and optoelectronic devices.