Rapid fabrication of complex nanostructures using room-temperature ultrasonic nanoimprinting

Despite its advantages of scalable process and cost-effectiveness, nanoimprinting faces challenges with imprinting hard materials (e.g., crystalline metals) at low/room temperatures, and with fabricating complex nanostructures rapidly (e.g., heterojunctions of metal and oxide). Herein, we report a room temperature ultrasonic nanoimprinting technique (named nanojackhammer) to address these challenges. Nanojackhammer capitalizes on the concentration of ultrasonic energy flow at nanoscale to shape bulk materials into nanostructures. Working at room temperature, nanojackhammer allows rapid fabrication of complex multi-compositional nanostructures made of virtually all solid materials regardless of their ductility, hardness, reactivity and melting points. Atomistic simulations reveal a unique alternating dislocation generation and recovery mechanism that significantly reduces the imprinting force under ultrasonic cyclic loading. As a proof-of-concept, a metal-oxide-metal plasmonic nanostructure with built-in nanogap is rapidly fabricated and employed for biosensing. As a fast, scalable, and cost-effective nanotechnology, nanojackhammer will enable various unique applications of complex nanostructures in optoelectronics, biosensing, catalysis and beyond.

Conformational Control of DNA Origami by DNA Oligomers, Intercalators and UV Light

DNA origami has garnered great attention due to its excellent programmability and precision. It offers a powerful means to create complex nanostructures which may not be possible by other methods. The macromolecular structures may be used as static templates for arranging proteins and other molecules. They are also capable of undergoing structural transformation in response to external signals, which may be exploited for sensing and actuation at the nanoscale. Such on-demand reconfigurations are executed mostly by DNA oligomers through base-pairing and/or strand displacement, demonstrating drastic shape changes between two different states, for example, open and close. Recent studies have developed new mechanisms to modulate the origami conformation in a controllable, progressive manner. Here we present several methods for conformational control of DNA origami nanostructures including chemical adducts and UV light as well as widely applied DNA oligomers. The detailed methods should be useful for beginners in the field of DNA nanotechnology.

Towards 3D self-assembled rolled multiwall carbon nanotube structures by spontaneous peel off

Controlling the 3D assembly of individual nanomaterials can be a challenging task. However, it opens up opportunities for the production of increasingly complex nanostructures. Unusual rolled multiwall carbon nanotube structures are synthesized here by simply inducing a change of precursor composition during the growth of multiwall carbon nanotube forests. The multiwall carbon nanotube structures are comprised of nitrogen-doped and undoped sections, and are obtained via a detailed peel off and roll mechanism. These results open new doors for the development of increasingly complex nanostructures.

Hierarchically porous Au nanostructures with interconnected channels for efficient mass transport in electrocatalytic CO2reduction

Electrocatalytic CO2reduction is a promising way to provide renewable energy from gaseous CO2. The development of nanostructures improves energy efficiency and selectivity for value-added chemicals, but complex nanostructures limit the CO2conversion rates due to poor mass transport during vigorous electrolysis. Herein, we propose a three-dimensional (3D) hierarchically porous Au comprising interconnected macroporous channels (200–300 nm) and nanopores (∼10 nm) fabricated via proximity-field nanopatterning. The interconnected macropores and nanopores enable efficient mass transport and large active areas, respectively. The roles of each pore network are investigated using reliable 3D nanostructures possessing controlled pore distribution and size. The hierarchical nanostructured electrodes show a high CO selectivity of 85.8% at a low overpotential of 0.264 V and efficient mass activity that is maximum 3.96 times higher than that of dealloyed nanoporous Au. Hence, the systematic model study shows the proposed hierarchical nanostructures have important value in increasing the efficiency of expensive Au.

Self-supported CdSe nanowire/nanosheet photoanodes on cadmium foil via in situ hydrothermal transformation of CdSe(en)0.5 complex nanostructures

Self-supported Cd(OH)2/CdSe NS photoanodes prepared via in situ hydrothermal transformation approach display 7.6 times higher photocurrent than that of CdSe(en)0.5. The role of Cd(OH)2 during PEC transformation is extensively proposed.