SURFACE SCIENCE: How to Power a Nanomotor

Formic acid adsorption and decomposition on clean and atomic oxygen pre-covered Cu(100) surfaces

Formic acid adsorption and decomposition on clean Cu(100) and two atomic oxygen pre-covered Cu(100) surfaces have been studied using surface science techniques including scanning tunneling microscopy, low-energy electron diffraction, x-ray photoelectron spectroscopy, and infrared reflection-absorption spectroscopy. The two atomic oxygen pre-covered Cu(100) surfaces include an O-(22 ×2)R45° Cu(100) surface and an oxygen modified Cu(100) surface with a local O-c(2 × 2) structure. The results show that the O-(22 ×2)R45° Cu(100) surface is inert to the formic acid adsorption at 300 K. After exposing to formic acid at 300 K, bidentate formate formed on the clean Cu(100) and local O-c(2 × 2) area of the oxygen modified Cu(100) surface. However, their adsorption geometries are different, being vertical to the surface plane on the former surface and inclined with respect to the surface normal with an ordered structure on the latter surface. The temperature programmed desorption spectra indicate that the formate species adsorbed on the clean Cu(100) surface decomposes into H₂ and CO₂ when the sample temperature is higher than 390 K. Differently, the proton from scission of the C-H bond of formate reacts with the surface oxygen, forming H₂O on the oxygen modified Cu(100) surface. The CO₂ signal starts increasing at about 370 K, which is lower than that on clean Cu(100), indicating that the surface oxygen affiliates formate decomposition. Combining all these results, we conclude that the surface oxygen plays a crucial role in formic acid adsorption and formate decomposition.

Poly(ionic liquid)s Based Brush Type Nanomotor

A brush type nanomotor was fabricated via assembly assistant polymerization of poly(ionic liquid) and surface grafting polymerization. The method for large-scale fabrication of brush nanomotors with soft surfaces is described. These soft locomotive particles are based on core-shell brush nanoparticles assembled from poly(ionic liquid) as core and thermoresponsive PNIPAM as brush shells on which platinum nanoparticle (PtNP) were grown in situ. The particles show non-Brownian motion in H₂O₂ solution.

Construction of Asymmetrical Hexameric Biomimetic Motors with Continuous Single-Directional Motion by Sequential Coordination

The significance of bionanomotors in nanotechnology is analogous to mechanical motors in daily life. Here the principle and approach for designing and constructing biomimetic nanomotors with continuous single-directional motion are reported. This bionanomotor is composed of a dodecameric protein channel, a six-pRNA ring, and an ATPase hexamer. Based on recent elucidations of the one-way revolving mechanisms of the phi29 double-stranded DNA (dsDNA) motor, various RNA and protein elements are designed and tested by single-molecule imaging and biochemical assays, with which the motor with active components has been constructed. The motor motion direction is controlled by three operation elements: (1) Asymmetrical ATPase with ATP-interacting domains for alternative DNA binding/pushing regulated by an arginine finger in a sequential action manner. The arginine finger bridges two adjacent ATPase subunits into a non-covalent dimer, resulting in an asymmetrical hexameric complex containing one dimer and four monomers. (2) The dsDNA translocation channel as a one-way valve. (3) The hexameric pRNA ring geared with left-/right-handed loops. Assessments of these constructs reveal that one inactive subunit of pRNA/ATPase is sufficient to completely block motor function (defined as K = 1), implying that these components work sequentially based on the principle of binomial distribution and Yang Hui's triangle.