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Transition metal oxides exhibit a rich collection of electronic properties and have many practical applications in areas such as catalysis and ultra-high-density magnetic data storage. Therefore the development of switchable molecular transition metal oxides has potential for the engineering of single-molecule devices and nanoscale electronics. At present, the electronic properties of transition metal oxides can only be tailored through the irreversible introduction of dopant ions, modifying the electronic structure by either injecting electrons or core holes. Here we show that a molybdenum(VI) oxide 'polyoxometalate' molecular nanocluster containing two embedded redox agents is activated by a metallic surface and can reversibly interconvert between two electronic states. Upon thermal activation two electrons are ejected from the active sulphite anions and delocalized over the metal oxide cluster cage, switching it from a fully oxidized state to a two-electron reduced state along with the concomitant formation of an S-S bonding interaction between the two sulphur centres inside the cluster shell.

Scanning tunneling microscopy (STM) is known to provide the highest spatial resolution in real space imaging of materials, and its applications are most common among conductive and semiconductive systems. The high tunneling barrier of insulators diminishes the tunneling probability and thus compromises STM's resolution. This work introduces a simple method to approach this problem, by using STM for high-resolution imaging of insulating materials such as the fourth and fifth generations of poly(amidoamine) hydroxyl-terminated dendrimers. The tunneling barrier is lowered by precoordination with Cu(II) or Pt(II) ions, enabling intramolecular hyperfine features be resolved with 0.2 nm resolution. The spatial distribution, size, and overall number of hyperfine features are consistent with the location of dendrimer termini. The immobilization process deforms dendrimers from the spherical geometry in solution phase to asymmetrical domes in ambient. The ultrahigh vacuum (UHV) environment leads to a higher degree of deformation with reduction of volume. The high-resolution images enable the determination of fundamental parameters of individual dendrimers, including axis, height, asymmetry, and volume. From STM spectroscopy and prior knowledge of dendritic systems, the STM imaging mechanism under UHV is consistent with metal(0) nanoparticles encapsulated by dendrimers, while ambient imaging is most likely via metal-ion-facilitated charge transport. The results from this investigation bring us one step closer toward structural characterization at atomistic level and should enable direct comparison of dendrimer structures with simulations, and deepen our understanding of charge transport in dendrimer systems.

The sociology of nursing, despite decisive interventions by recent commentators, continues to take as its main focus the subordination of nursing to biomedicine. This view reflects analytic stability, as well as institutional inertia. Far less attention has been paid by sociologists to the ways in which nursing is constructing its difference from medicine, and the exercise of the professional imagination that this involves. This paper suggests a strategy by which this might be remedied, which would focus on professional narratives.

A model integrating 3 theoretical perspectives regarding how stereotypes influence person perception was tested. The theories included evaluative extremity theories, assumed characteristics theory, and expectancy violation theory. Predictions were assessed by manipulating the ethnicity, personal appearance, and speech style of target job applicants. These applicants were rated by 109 judges. Results showed that: (a) Judges evaluated job applicants far more on the basis of their personal appearance and speech style than on the basis of their ethnicity; (b) the range of evaluations of African American applicants was larger than the range of evaluations of White applicants; and (c) overall, judges evaluated the African American applicants more favorably than the White applicants. Results strongly supported the model integrating the 3 theories. We discuss the applicability of the model to other research and naturalistic situations.

Enantioselectivity in a chemical reaction arises when a system is placed under a chiral influence. One of the first "chiral influences" to be used to induce asymmetry in a chemical reaction was circularly polarized light (CPL). An enantiomer of a chiral molecule will preferentially absorb one helicity of circularly polarized light (CPL). In pioneering work in the 1930s, Kuhn used this phenomenon to generate an enantiomeric excess (ee) from an initially racemic mixture by enantioselective photodecomposition. 1 Unfortunately the circular dichroism (CD) in the absorption cross-section is very small, with asymmetry factors (g) , 10 -3 , consequently enantioselective photodecomposition is very inefficient, with ee of typically <3% being generated after 99.9% photodecomposition. 2 Although extremely inefficient, nonthermal enantioselective chemistry still interests researchers because of the suggestion that CPL is a chiral influence, which could have contributed to the evolution of chemical asymmetry in nature. 3 Low energy electrons (<5 eV) are far more prevalent in the natural environment than CPL, since they can be generated by solar or cosmic radiation through ionization, and as a consequence are significantly more likely to initiate reactions. Indeed low energy electrons are believed to be responsible for inducing much of the chemistry in the interstellar medium. However, it has until now been believed that since unpolarised electrons are not intrinsically chiral, they could not initiate asymmetric chemistry.We report highly efficient nonthermal enantioselective surface chemistry initiated by unpolarized (nonchiral) low energy secondary electrons, produced by an incident low energy electron beam. A chiral adsorption environment provides the chiral influence required for enantioselectivity. Most significantly the enantioselective chemistry we describe has an asymmetry factor of ≈0.40, which is a least 3 orders of magnitude more efficient than enantioselective photodecomposition by CPL. Consequently, we have been able to enantiomerically enrich an initially racemic mixture (50:50 mixture) through electron induced kinetic resolution.Specifically we show that the electron initiated reactions of R/S-methyl lactate (HOCH(CH 3 )CO 2 CH 3 ) (ML) adsorbed at chiral sites on an intrinsically chiral Cu(643) R surface are significantly more efficient for the R enantiomer. The electron induced depletion of the chiral adsorption state has been monitored with temperature programmed desorption (TPD). Consequently, we have by electron irradiation, been able to enantiomerically enrich with the S enantiomer, an initially racemic mixture of ML adsorbed at chiral sites. An ee of 20% is created after the depletion of only 30% of the initial population of ML molecules. We attribute the highly efficient enantiodependent chemistry to the relative lifetimes of the transient R-and S-ML negative ions, formed by low energy electron attachment, which are intermediates in the electron stimulated chemistry.We have performed experiments in an ult...

Dendrimers have shown great potential in drug delivery because of their enhancement of drug solubility in aqueous media, leading to an increase in in vivo circulation and efficacy to targets. The structure of drug-dendrimer complexes however, is not well-known owing to the difficulties associated with visualizing individual drug molecules attached to dendrimers. Scanning tunneling microscopy (STM) enables visualization of dendrimer intramolecular structures using our approach of metal ion tagging. This work extends the approach to reveal the hierarchical structure of indomethacin-loaded poly(amidoamine) hydroxyl-terminated dendrimers. STM imaging provides structural information such as their height, lateral dimensions, and volume. High-resolution STM images enable the identification and count of individual indomethacin molecules bound to the anterior of dendrimers. Removal of drug molecules by the STM tip allows the calculation of individual drug-dendrimer binding energy, which is consistent with 1-3 hydrogen bonds. These investigations provide new insight into the hierarchical structure and nature of indomethacin-dendrimer interactions and deepen our understanding of the stability and pharmacokinetic behavior of dendrimer-based drug delivery vehicles.

Dendrimers and telodendrimer micelles represent two new classes of vehicles for drug delivery that have attracted much attention recently. Their structural characterization at the molecular and submolecular level remains a challenge due to the difficulties in reaching high resolution when imaging small particles in their native media. This investigation offers a new approach towards this challenge, using scanning tunneling microscopy (STM) and atomic force microscopy (AFM). By using new sample preparation protocols, this work demonstrates that (a) intramolecular features such as drug molecules and dendrimer termini can be resolved; and (b) telodendrimer micelles can be immobilized on the surface without compromising structural integrity, and as such, high resolution AFM imaging may be performed to attain 3D information. This high-resolution structural information should enhance our knowledge of the nanocarrier structure and nanocarrier-drug interaction and, therefore, facilitate design and optimization of the efficiency in drug delivery.