The band gap energies of micro/meso-porous zinc (hydr)oxide and its composites with 2 wt. % and 5 wt. % graphite oxides are reported using three optical characterization techniques. The obtained energy gaps (from 2.84 eV to 2.95 eV) of the composites are smaller than that for zinc oxide (∼3.2 eV) and zinc (hydr)oxide (∼3.06 eV). The band gap narrowing of the composite materials is due to the presence of defects, larger particle size, and weaker confinement. The bonds between zinc (hydr)oxide lattice and the carbon of graphene phase also contribute to this phenomenon. The structural properties of these materials are presented using Transmission Electron Microscopy, Scanning Tunneling Electron Microscopy, X-Ray analysis, and Two-Photon Fluorescence imaging Microscopy.

Time-resolved photoluminescence is used to determine carrier recombination through radiative and nonradiative processes in zinc hydroxide Zn(OH)(2) and its porous composites with graphite oxide (GO). The decay times, measured by a streak camera, are found to be larger for zinc hydroxide (~1215±156 ps) than its composites (~976±81 ps for ZnGO-2 and 742±59 ps for ZnGO-5), but no significant changes in rise times (from 4.0 to 5.0 ps) are recorded. The dominant mechanism for the radiative process is attributed to free carrier recombination, while microporous networks present in these materials are found to be pathways for the nonradiative recombination process via multiphonon emission.

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