Chiral electromagnetic fields generated by arrays of nanoslits.

Using a modal matching theory, we demonstrate the generation of short-range, chiral electromagnetic fields via the excitation of arrays of staggered nanoslits that are chiral in two dimensions. The electromagnetic near fields, which exhibit a chiral density greater than that of circularly polarized light, can enhance the chiroptical interactions in the vicinity of the nanoslits. We discuss the features of nanostructure symmetry required to obtain the chiral fields and explicitly show how these structures can give rise to detection and characterization of materials with chiral symmetry.

Probing the chemical and electronic properties of the core-shell architecture of transition metal trisulfide nanoribbons.

Ultraviolet and X-ray photoelectron spectroscopies are used to probe the chemical and electronic structure of an amorphous, 2-20 nm-thick shell that encases the crystalline core in core-shell nanoribbons of TaS(3). The shell is chemically heterogeneous, containing elemental sulfur and a with a notable (S(2))(2-) deficiency over the crystalline TaS(3) core. We find nanoribbon stability to be substrate-dependent; whilst the ribbons are stable on the native oxide of a silicon surface, mass transport of sulfur species between the amorphous shell and a gold substrate leads to a significant change in the electronic properties of the nanomaterials. Our observations may have general implications for the incorporation of nanostructured transition metal chalcogenides into electronic devices.

Ultrasensitive detection and characterization of biomolecules using superchiral fields.

The spectroscopic analysis of large biomolecules is important in applications such as biomedical diagnostics and pathogen detection, and spectroscopic techniques can detect such molecules at the nanogram level or lower. However, spectroscopic techniques have not been able to probe the structure of large biomolecules with similar levels of sensitivity. Here, we show that superchiral electromagnetic fields, generated by the optical excitation of plasmonic planar chiral metamaterials, are highly sensitive probes of chiral supramolecular structure. The differences in the effective refractive indices of chiral samples exposed to left- and right-handed superchiral fields are found to be up to 10(6) times greater than those observed in optical polarimetry measurements, thus allowing picogram quantities of adsorbed molecules to be characterized. The largest differences are observed for biomolecules that have chiral planar sheets, such as proteins with high ß-sheet content, which suggests that this approach could form the basis for assaying technologies capable of detecting amyloid diseases and certain types of viruses.

Asymmetric photoelectron transmission through chirally-sculpted, polycrystalline gold.

Strong circular dichroism is observed in core-level photoelectron transmission through a chirally-etched polycrystalline Au surface, consistent with a chiral dependence on the electron's orbital angular momentum.

Sulfur the archetypal catalyst poison? The sulfur-induced promotion of the bonding of unsaturated hydrocarbons on Cu(111).

We have shown using a combination of temperature-programmed desorption and UV photoelectron spectroscopy that the presence of preadsorbed atomic sulfur promotes the bonding of cyclic unsaturated hydrocarbons (benzene and cyclohexene) to Cu(111). This promoting behavior of sulfur can be rationalized in terms of the ability of adsorbed sulfur to influence the balance between charge donation from the adsorbate to metal, and back-donation from the metal to adsorbate. The effects of sulfur on Cu(111) are dramatically different from those observed in previous studies on Pt(111), which found that it caused a downward shift in the desorption temperature of adsorbed benzene, through purely steric effects.