The design of artificial molecular machines often takes inspiration from macroscopic machines. However, the parallels between the two systems are often only superficial, because most molecular machines are governed by quantum processes. Previously, rotary molecular motors powered by light and chemical energy have been developed. In electrically driven motors, tunnelling electrons from the tip of a scanning tunnelling microscope have been used to drive the rotation of a simple rotor in a single direction and to move a four-wheeled molecule across a surface. Here, we show that a stand-alone molecular motor adsorbed on a gold surface can be made to rotate in a clockwise or anticlockwise direction by selective inelastic electron tunnelling through different subunits of the motor. Our motor is composed of a tripodal stator for vertical positioning, a five-arm rotor for controlled rotations, and a ruthenium atomic ball bearing connecting the static and rotational parts. The directional rotation arises from sawtooth-like rotational potentials, which are solely determined by the internal molecular structure and are independent of the surface adsorption site.

An extensive redistribution of spin density in TBrPP-Co molecules adsorbed on a Cu(111) surface is investigated by monitoring Kondo resonances at different locations on single molecules. Remarkably, the width of the Kondo resonance is found to be much larger on the organic ligands than on the central cobalt atom-reflecting enhanced spin-electron interactions on molecular orbitals. This unusual effect is explained by means of first-principles and numerical renormalization-group calculations highlighting the possibility to engineer spin polarization by exploiting interfacial charge transfer.

Narrow graphene nanoribbons (GNRs) constructed by atomically precise bottom-up synthesis from molecular precursors have attracted significant interest as promising materials for nanoelectronics. But there has been little awareness of the potential of GNRs to serve as nanoscale building blocks of novel materials. Here we show that the substitutional doping with nitrogen atoms can trigger the hierarchical self-assembly of GNRs into ordered metamaterials. We use GNRs doped with eight N atoms per unit cell and their undoped analogues, synthesized using both surface-assisted and solution approaches, to study this self-assembly on a support and in an unrestricted three-dimensional (3D) solution environment. On a surface, N-doping mediates the formation of hydrogen-bonded GNR sheets. In solution, sheets of side-by-side coordinated GNRs can in turn assemble via van der Waals and π-stacking interactions into 3D stacks, a process that ultimately produces macroscopic crystalline structures. The optoelectronic properties of these semiconducting GNR crystals are determined entirely by those of the individual nanoscale constituents, which are tunable by varying their width, edge orientation, termination, and so forth. The atomically precise bottom-up synthesis of bulk quantities of basic nanoribbon units and their subsequent self-assembly into crystalline structures suggests that the rapidly developing toolset of organic and polymer chemistry can be harnessed to realize families of novel carbon-based materials with engineered properties.

Electron donor-acceptor molecular charge transfer complexes (CTCs) formed by alpha-sexithiophene (6T) and tetrafluoro-tetracyano-quinodimethane (F4TCNQ) on a Au(111) surface are investigated by scanning tunneling microscopy, spectroscopy, and spectroscopic imaging at 6 K. New hybrid molecular orbitals are formed in the CTCs, and the highest occupied molecular orbital of the CTC is mainly located on the electron accepting F4TCNQ while the lowest unoccupied molecular orbital is predominantly positioned on the electron donating 6T. We observed the conductance switching of F4TCNQ inside CTCs, which may find potential applications in novel molecular device operations.

A range of artificial molecular systems has been created that can exhibit controlled linear and rotational motion. In the further development of such systems, a key step is the addition of communication between molecules in a network. Here, we show that a two-dimensional array of dipolar molecular rotors can undergo simultaneous rotational switching when applying an electric field from the tip of a scanning tunnelling microscope. Several hundred rotors made from porphyrin-based double-decker complexes can be simultaneously rotated when in a hexagonal rotor network on a Cu(111) surface by applying biases above 1 V at 80 K. The phenomenon is observed only in a hexagonal rotor network due to the degeneracy of the ground-state dipole rotational energy barrier of the system. Defects are essential to increase electric torque on the rotor network and to stabilize the switched rotor domains. At low biases and low initial rotator angles, slight reorientations of individual rotors can occur, resulting in the rotator arms pointing in different directions. Analysis reveals that the rotator arm directions are not random, but are coordinated to minimize energy via crosstalk among the rotors through dipolar interactions.

Objectives: In the United States, home health agencies (HHAs) provide essential services for patients recovering from post-acute care and older adults who are aging in place. During the COVID-19 pandemic, HHAs may face additional challenges caring for these vulnerable patients. Our objective was to explore COVID-19 preparedness of US HHAs and compare results by urban/rural location. Design: Cross-sectional study. Setting/Participants: Using a stratified random sample of 978 HHAs, we conducted a 22-item online survey from April 10 to 17, 2020. Methods: Summary statistics were computed; open-ended narrative responses were synthesized using qualitative methods. Results: Similar to national data, most responding HHAs (n ¼ 121, 12% response rate) were for-profit and located in the South. Most HHAs had infectious disease outbreaks included in their emergency preparedness plan (76%), a staff member in charge of outbreak/disaster preparedness (84%), and had provided their staff with COVID-19 education and training (97%). More urban HHAs had cared for confirmed and recovered COVID-19 patients than rural HHAs, but urban HHAs had less capacity to test for COVID-19 than rural HHAs (9% vs 21%). Most (69%) experienced patient census declines and had a current and/or anticipated supply shortage. Rural agencies were affected less than urban agencies. HHAs have already rationed (69%) or implemented extended use (55%) or limited reuse (61%) of personal protective equipment (PPE). Many HHAs reported accessing supplemental PPE from state/local resources, donations, and do-it-yourself efforts; more rural HHAs had accessed these additional resources compared with urban HHAs. Conclusions/Implications: This survey reveals challenges that HHAs are having in responding to the COVID-19 pandemic, particularly among urban agencies. Of greatest concern are the declines in patient census, which drastically affect agency revenue, and the shortages of PPE and disinfectants. Without proper protection, HHA clinicians are at risk of self-exposure and viral transmission to patients and vulnerable family members.

Heterogeneous interfaces exhibit remarkable material properties resulting from their structural motifs, the judicious placement of functional chemical groups, etc. It has been a long-standing challenge to manipulate and design interface structures at the atomic level to achieve new functionalities. Here, we demonstrate that by modifying the length of the backbone in alkanolamines one can control the packing density of organic monolayers adsorbed on rutile TiO2 and the interaction strength between their amine functional group and the substrate. As a result, we observed strikingly different activities in CO2 capture by the amine functional group of different alkanolamines on TiO2(110). Synchrotron photoelectron spectroscopy at near-ambient CO2 pressures showed that adsorbed 2-amino-1-ethanol (monoethanolamine, MEA) is inactive, whereas the amine group in 3-amino-1-propanol (3AP)/TiO2(110) readily reacts with and captures CO2. Our results suggest that the geometry of the interface plays a decisive role in the reactivity of adsorbed functionalized organic molecules, such as solid-supported alkanolamines for CO2 capture.

Oligoethylene-end-capped polylactides were synthesized through the ringopening polymerization of L-lactide with alcohol-terminated oligoethylenes as macroinitiators. The polymerization of L-lactide was carried out in bulk at 130 8C in the presence of stannous octoate and primary alcohols with four different molecular weights: 350, 425, 550, and 700 g/mol. The end-capped copolymers that formed had a number-average molecular weight of approximately 40,000 (weight-average molecular weight/number-average molecular weight ¼ 1.7) according to gel permeation chromatography and were highly crystalline in comparison with the similarly formed homopolymer of L-lactide. The copolymer structure was characterized by Fourier transform infrared, NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and differential scanning calorimetry analysis. This work focused on developing more crystallizable and hydrolytically stable polylactide derivatives that could potentially be used as compatibilizers in polylactide-polyolefin blends or as nucleating agents for poly(L-lactide) or other polyesters. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5257-5266, 2005