An experimental study of the bonding geometry and electronic coupling of cis-bis(isothiocyanato)bis(2,2(')-bipyridyl-4,4(')-dicarboxylato)-ruthenium(II) (N3) adsorbed on rutile TiO(2)(110) is presented, along with supporting theoretical calculations of the bonding geometry. Samples were prepared in situ using ultrahigh vacuum electrospray deposition. Core-level photoemission spectroscopy was used to characterize the system and to deduce the nature of the molecule-surface bonding. Valence band photoemission and N 1s x-ray absorption spectra were aligned in a common binding energy scale to enable a quantitative analysis of the bandgap region. A consideration of the energetics in relation to optical absorption is used to identify the photoexcitation channel between the highest occupied and lowest unoccupied molecular orbitals in this system, and also to quantify the relative binding energies of core and valence excitons. The core-hole clock implementation of resonant photoemission spectroscopy is used to reveal that electron delocalization from N3 occurs within 16 fs.

Zinc-protoporphyrin, adsorbed on the rutile TiO(2)(110) surface, has been studied using photoemission spectroscopy and near-edge absorption fine structure spectroscopy to deduce the nature of the molecule-surface bonding and the chemical environment of the central metal atom. To overcome the difficulties associated with sublimation of the porphyrin molecules, samples were prepared in situ using ultrahigh vacuum electrospray deposition, a technique which facilitates the deposition of nonvolatile and fragile molecules. Monolayers of Zn protoporphyrin are found to bond to the surface via the oxygen atoms of the deprotonated carboxyl groups. The molecules initially lie largely parallel to the surface, reorienting to an upright geometry as the coverage is increased up to a monolayer. For those molecules directly chemisorbed to the surface, the interaction is sufficiently strong to pull the central metal atom out of the molecule.

This review focuses on the challenges associated with the design and development of injectable hydrogels of synthetic origin based on FDA approved blocks, such as polyethylene glycol (PEG) and poly(ɛ-caprolactone) (PCL). An overview of recent studies on inverse thermosensitive PEG/PCL hydrogels is provided. These systems have been proposed to overcome the limitations of previously introduced degradable thermosensitive hydrogels [e.g., PEG/poly(lactide-co-glycolic acid) hydrogels]. PEG/PCL hydrogels are advantageous due to their higher gel strength, slower degradation rate and availability in powder form. Particularly, triblock PEG/PCL copolymers have been widely investigated, with PCL-PEG-PCL (PCEC) hydrogels showing superior gel strength and slower degradation kinetics than PEG-PCL-PEG (PECE) hydrogels. Compared to triblock PEG/PCL copolymers, concentrated solutions of multiblock PEG/PCL copolymers were stable due to their slower crystallization rate. However, the resulting hydrogel gel strength was low. Inverse thermosensitive triblock PEG/PCL hydrogels have been mainly applied in tissue engineering, to decrease tissue adherence or, in combination with bioactive molecules, to promote tissue regeneration. They have also found application as in situ drug delivery carriers. On the other hand, the wide potentialities of multiblock PEG/PCL hydrogels, associated with the stability of their water-based solutions under storage, their higher degradation time compared to triblock copolymer hydrogels and the possibility to insert bioactive building blocks along the copolymer chains, have not been fully exploited yet. A critical discussion is provided to highlight advantages and limitations of currently developed themosensitive PEG/PCL hydrogels, suggesting future strategies for the realization of PEG/PCL-based copolymers with improved performance in the different application fields.

Electrospray deposition of fullerenes on gold has been successfully observed by in situ room temperature scanning tunneling microscopy and photoemission spectroscopy. Step-edge decoration and hexagonal close-packed islands with a periodicity of 1 nm are observed at low and multilayer coverages respectively, in agreement with thermal evaporation studies. Photoemission spectroscopy shows that fullerenes are being deposited in high purity and are coupling to the gold surface as for thermal evaporation. These results open a new route for the deposition of thermally labile molecules under ultra-high vacuum conditions for a range of high resolution surface science techniques.

Conjugated porphyrin polymers have stimulated great interest due to their potential applications in nonlinear optics, [1] light harvesting [2] and nanoscale charge transport. [3] As with many other organic materials, interfacial properties are likely to play an important role in their applications in molecular electronics.[4] However, it has not so far been possible to study these effects due to the difficulty in preparing suitable monolayers, since the relevant polymers and oligomers cannot be sublimed. A question of particular interest relates to the influence of the flexibility of such a large molecule on the ordering within interfacial regions.We have investigated the adsorption of two oligomers, a porphyrin tetramer (P4, N = 4; see Figure 1 for structural diagrams), a hexamer (P6, N = 6), and a polymer Pn (N = 30-50) on the Au(111) surface using scanning tunneling microscopy (STM). The porphyrin units have long octyloxy side chains to promote solubility in organic solvents. Our experiments are performed at room temperature under ultrahigh vacuum (UHV) conditions (base pressure 5 10 À11 Torr) and we use UHV electrospray deposition (UHV-ESD) to transfer the oligomers and polymers directly from solution onto a surface. In our approach to UHV-ESD, [5] a volatilized mixture of solvent and solute molecules is produced in atmosphere by electrospray. This mixture enters the UHV system through a small aperture and is passed through a series of differentially pumped chambers, to the Au(111) substrate (for further details see Supporting Information). UHV-ESD and related approaches have been used to introduce nanotubes, fullerenes, dye molecules, and polymers into a UHV environment. [6,7] Images acquired after deposition of a sub-monolayer coverage of P6 (Figure 2) show that, despite their large size, the porphyrin oligomers diffuse on the surface and form