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Silver (Ag) doped and undoped ZnO films were grown on Si (100) substrates by the sol-gel process. Photoluminescence (PL) of two kinds of samples as a function of the excitation intensity has been measured, and PL intensities have been fitted by a power law. It is found that Ag doping increases the intensity of free emission from ZnO and does not change the position and the full width at half-maximum of the free exciton emission. In PL spectra of two kinds of samples under various excitation powers, no visible emission bands related to the deep levels were observed. These results reveal that doped Ag in ZnO films only enhances emission efficiency from free exciton recombination, not giving rise to new emissions.

The well-defined azobenzene-containing homopolymers, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)} (PAHMA), were synthesized via reversible addition fragmentation chain transfer polymerization (RAFT) in anisole solution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and 2,2 0 -azobisisobutyronitrile (AIBN) as the initiator. The first-order kinetic plot of the polymerization and the linear dependence of molecular weights of the homopolymers with the relatively low polydispersity index values (PDIs 1.25) on the monomer conversions were observed. Furthermore, the amphiphilic diblock copolymer, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)}-b-poly{2-(dimethylamino)ethyl methacrylate (DMAEMA)} (PAHMA-b-PDMAEMA), was prepared with the obtained PAHMA as the macro-RAFT agent. The structures and properties of the polymers were characterized by 1 H NMR and GPC, respectively. Interestingly, the amphiphilic diblock copolymers in chloroform (CHCl 3 ) solution (PAHMA 23 -b-PDMAEMA 97 (4 3 10 À5 M, M n(GPC) ¼ 18,400 g/mol, PDI ¼ 1.48) and PAHMA 28 -b-PDMAEMA 117 (6 3 10 À5 M, M n(GPC) ¼ 19,300 g/mol, PDI ¼ 1.51) exhibited the intense fluorescence emission at ambient temperature. Moreover, the fluorescent intensity of PAHMA-b-PDMAEMA in CHCl 3 was sensitive to the ultraviolet irradiation at 365 nm, which increased within the first 10 min and later decreased when irradiation time was prolonged to 30 min or longer. The well distributed, self-assembled micelles composed of azobenzene-containing amphiphilic diblock copolymers, (PAHMA-b-QPDMAEMA)s (QPDMAEMA is quaternized PDMAEMA), in the mixed N,N-dimethyl formamide (DMF)/H 2 O solutions were prepared. Their fluorescent intensities decreased with the increasing amount of water. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: [5652][5653][5654][5655][5656][5657][5658][5659][5660][5661][5662] 2008

A triple-band perfect plasmonic metamaterial absorber based on a metal/insulator/metal (MIM) structure is designed. A new freedom through tuning the thicknesses of each ring structures is introduced to realize a quasi-three-dimensional perfect absorber at three extinction wavelengths by using the finite difference time domain method. The physical machine is explained by the time domain field analyses and the coupled mode theory. The characteristics of the absorber make our proposed strategy applicable for the design of more general multiband and broadband perfect absorbers. In addition, these perfect absorbing metamaterials are found to exhibit excellent performance in refractive index sensing.