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 report on low temperature photoluminescence studies of ZnO nanowires embedded in different polymers. Comparing the spectra of as-grown and embedded ZnO nanowires, we find a decrease of the deep-level emission and an increase of the near band-edge emission after the embedding process. The near band-edge emission of the embedded ZnO nanowires is dominated by a surface exciton band. The observed effects are independent of the selected polymer. The decrease of the deep-level emission scales with the balling abilities of the different polymers. We propose a model to explain the spectral changes.

We report on the photoluminescence properties of ZnO nanowires treated with a mild Ar plasma. The nanowires exhibited stable and strong enhancement of the near-band-edge emission and quenching of the deep level emission. The low temperature PL revealed a strong hydrogen donor-bound-exciton line in the plasma-treated samples indicating unintentional incorporation of hydrogen during the plasma treatment. To confirm the results, hydrogen was implanted into the ZnO nanowires with a low ion energy of 600 eV and different fluences. The observed result can be related to the passivation of deep centers by hydrogen. The absolute photoluminescence intensity measured by an integrating sphere showed stable and strong UV emission from the treated samples even after several weeks.

We investigated the photoluminescence properties of ZnO nanowires coated with Au, Ag, and Pt nanoparticles deposited by dc sputtering. A strong enhancement of the near-band-edge emission was observed in all metal-coated samples but also if the samples were treated with Ar plasma without any nanoparticle deposition. High-resolution photoluminescence spectroscopy revealed hydrogen-donor-bound-exciton emission in all samples indicating unintentional hydrogen incorporation. A shorter decay time of the near-band-edge emission was observed in all cases. The results indicate that unintentional hydrogen incorporation plays a dominant role when metal deposition is performed by sputtering.

This paper discusses the surface effects and nonlinear optical properties of ZnO nanowires. First, the influence of the large surface-to-volume ratio of the nanowires on their photoluminescence properties is shown. The occurrence of a surface-exciton emission line is demonstrated and its properties are studied in time-integrated and time-resolved photoluminescence measurements. It is further demonstrated that this band is sensitive to surface modifications of the nanowires, such as dielectric and metallic coatings. It is shown that hydrogen can passivate deep defects in ZnO nanowires thereby reducing the defect luminescence and strongly enhancing the near-bandedge excitonic luminescence. The photoluminescence properties of chemically synthesized ZnO nanowires are compared to those of nanowires grown by vapor-transport techniques. The non-linear coefficients of chemically synthesized nanowires are analyzed, and first preliminary measurements of the optical gain of a ZnO nanowire waveguide are analyzed.Zincoxide nanowires under optical excitation.