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Enhancement of visible-light photocurrent generation by sol-gel anatase TiO2 films was achieved by binding small polyol molecules to the TiO2 surface. Binding ethylene glycol onto the surface, enhancement factors up to 2.8 were found in visible-light photocurrent generation experiments. Density functional theory calculations identified midgap energy states that emerge as a result of the binding of a range of polyols to the TiO2 surface. The presence and energy of the midgap state is predicted to depend sensitively on the structure of the polyol, correlating well with the photocurrent generation results. Together, these results suggest a new, facile, and cost-effective route to precise surface band gap engineering of TiO2 toward visible-light-induced photocatalysis and energy storage. ispartof: ACS Omega vol:2 issue:10 pages:6309-6313 ispartof: location:United States status: published

A highly reproducible and controllable deposition procedure for gold nanostructures on a titanium dioxide (TiO2) surface using femtosecond laser light has been demonstrated. This is realized by precisely focusing onto the TiO2 surface in the presence of a pure gold ion solution. The deposition is demonstrated both in dot arrays and line structures. Thanks to the multi-photon excitation, we observe that the deposition area of the nanostructures can be confined to a degree far greater than the diffraction limited focal spot. Finally, we demonstrate that catalytic activity with visible light irradiation is enhanced, proving the applicability of our new deposition technique to the catalytic field. ispartof: Nanoscale vol:9 issue:35 pages:13025-13033 ispartof: location:England status: published

Metal nanoparticle photo-deposition on TiO2 enhances the semiconductor catalytic activity. We show for the first time that strong adsorption of simple diol-molecules improves the photo-deposition, by introducing a TiO2 midgap state and blocking active sites. The resulting photo-deposited gold nanoparticles are mono-dispersed and well-distributed over the TiO2 particles. The photo-catalytic activity of the Au/TiO2 systems obtained in ethyleneglycol was significantly enhanced compared to those prepared in conventional solvents, such as water and ethanol.

We reveal nanoscale morphological changes on the surface of a silver nanowire (AgNW) in the conventional surface-enhanced Raman scattering (SERS) measurement condition. The surface morphology changes are due to the surface plasmon-mediated photochemical etching of silver in the presence of certain Raman probes, resulting in a dramatic increase of Raman scattering intensity. This observation indicates that the measured SERS enhancement does not always originate from the as-designed/fabricated structures themselves, but sometimes with contribution from the morphological changes by plasmon-mediated photochemical reactions. Our work provides a guideline for more reliable SERS measurements and demonstrates a novel method for simple and site-specific engineering of SERS substrate and AgNW probes for designing and fabricating new SERS systems, stable and efficient TERS mapping, and single-cell SERS endoscopy.

Owing to their fundamental importance and practical applications, anatase TiO2 crystals with well-defined {001} and {101} facets attracted intensive research interests. In this study, we systematically investigated solvent dependence of the photoreaction of the different coexposed crystal facets during noble metal photodeposition. By examining the deposition position in each solvent, we revealed that solvents play a pivotal role on the facet selectivity. On the basis of density functional theory calculations, the solvent molecules were found to modify both the crystal facet electronic structure and the {001}-{001} heterojunction. These modifications are not only the origin of diverse charge-carrier pathways but are also responsible for carrier accumulation at specific facets that increase their reductive power. These findings are vital for a better understanding of photocatalytic materials and an improved design for the next-generation materials. ispartof: ACS Omega vol:2 issue:7 pages:4032-4038 ispartof: location:United States status: published

ispartof: Advanced Materials Technologies vol:1 issue:2 status: published

In this study, we theoretically investigate the sensing potential of 2D nano- and micro-ribbon grating structuration on the surface of Kretschmann-based surface plasmon resonance (SPR) biosensors when they are employed for detection of biomolecular binding events. Numerical simulations were carried out by employing a model based on the hybridization of two classical methods, the Fourier modal method and the finite element method. Our calculations confirm the importance of light manipulation by means of structuration of the plasmonic thin film surfaces on the nano- and micro-scales. Not only does it highlight the geometric parameters that allow the sensitivity enhancement compared with the response of the conventional SPR biosensor based on a flat surface but also describes the transition from the regime where the propagating surface plasmon mode dominates to the regime where the localized surface plasmon mode dominates. An exhaustive mapping of the biosensing potential of the 2D nano- and micro-structured biosensors surface is presented, varying the structural parameters related to the ribbon grating dimensions, i.e., the widths and thicknesses. The nano- and micro-structuration also leads to the creation of regions on biosensor chips that are characterized by strongly enhanced electromagnetic (EM) fields. New opportunities for further improving the sensitivity are offered if localization of biomolecules can be carried out in these regions of high EM fields. The continuum of nano- and micro-ribbon structured biosensors described in this study should prove a valuable tool for developing sensitive and reliable 2D-structured plasmonic biosensors.