We report the influence of an Al(2)O(3) shell on the photoluminescence emission of ZnO nanowires. At room temperature, the spectrum of the core-shell nanowires shows a strong reduction of the relative intensity of the green defect emission with respect to the near-band-edge emission. At 5 K an increase of the relative intensity of the surface exciton band with respect to the donor-bound exciton emission is observed. Annealing the core-shell nanowires at 500 °C does not increase the green defect luminescence at 5 K. We propose a model explaining the spectral changes.

The highly hydrated ionic liquid tetrabutylammonium hydroxide (TBAH) is an efficient ionic liquid precursor (ILP) for the fabrication of zinc oxide mesocrystals. Upon reaction of TBAH with zinc acetate, individual nanometer‐sized ZnO building blocks assemble into highly correlated ZnO mesocrystals. The mesocrystals are up to ca. 10 µm in length and the larger crystals have a channel running along the long crystal axis.

We use tapered silica fibers to inject laser light into ZnO nanowires with diameters around 250 nm to study their waveguiding properties. We find that high-order waveguide modes are frequently excited and carry significant intensity at the wire surface. Numerical simulations reproduce the experimental observations and indicate a coupling efficiency between silica and ZnO nanowires of 50%. Experimentally, we find an emission angle from the ZnO nanowires of about 90 degrees , which is in agreement with the simulations.

Room-temperature near-band-edge photoluminescence of ZnO is composed of contributions from free-exciton recombination and its longitudinal-optical phonon replica. By tracking the photoluminescence of ZnO nanowires from 4K up to room temperature, the authors show that the relative contributions of these emission lines show a strong variation for samples grown under different conditions. The varying coupling strengths of the excitons and phonons thus lead to a significant shift of the energy position of the room-temperature photoluminescence. They verify that this is not caused by laser heating or stress/strain but is most probably related to crystalline imperfections in the surface region.

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