Two-Photon Pumped Lasing from a Two-Dimensional Photonic Bandgap Structure with Polymeric Gain Material
✍ Scribed by C. Bauer; B. Schnabel; E.-B. Kley; U. Scherf; H. Giessen; R.F. Mahrt
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 92 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0935-9648
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✦ Synopsis
In conclusion, we have demonstrated the solvent-induced switchable photoelectrochemical functions of a CdS-nanoparticle/polyacrylamide composite hydrogel. Since other stimuli can induce the shrinking/swelling of polymers, one may envisage other signal-triggered photoelectrochemical systems. Experiments in these directions are under way in our laboratory.
Experimental
Preparation of the CdS-Nanoparticle/Polyacrylamide Composite on Au/ Quartz Crystal: The polyacrylamide film was electropolymerized from an aqueous solution containing ZnCl 2 , (0.2 M), acrylamide, (5 M), and N,N¢-methylenebisacrylamide (0.17 M), by six cyclic potential scans from 0.1 to ±1.5 V vs. SCE. After formation, the hydrogel film on the electrode was immersed in a 0.1 M HCl solution for 10 min, to dissolve precipitated zinc. The resulting polymer on the electrode was then shrunk and swollen several times by immersion in acetone and water, respectively, to wash out any monomer or Zn impurities. Incorporation of the CdS nanoparticles in the polymer film was accomplished by allowing the acetone-shrunken film to swell in the aqueous CdS nanoparticle solution (2 mg mL ±1 ) for 2 min. The resulting film was washed with water and further allowed to shrink by its immersion in acetone. The CdS nanoparticles were further introduced into the polymer film using five ªbreathing inº cycles, as described above.
Assembly of the CdS Nanoparticle Monolayer on Au/Quartz Crystals: The Au/quartz crystals were modified with a cystamine monolayer (0.05 M cystamine in water for 2 h). The resulting functionalized electrode was treated for 2 h with a 2 mL suspension of CdS nanoparticles (2 mg mL ±1 ), which included 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide, EDC, 510 ±3 M in HEPES buffer, 0.05 M, pH 7.5 for 2 h. The resulting electrodes were washed with water.
Microgravimetric Quartz Crystal Microbalance Measurements: Experiments were performed on a QCM analyzer (EG&G model 917) using Au/quartz crystals (AT-cut 9 MHz), the geometrical area of the Au electrodes was 0.20 ± 0.05 cm 2 . The crosslinked polyacrylamide polymer was assembled on the electrode, and the incorporation of the CdS nanoparticles was performed as described above. Prior to each measurement the QCM crystal was dried under a flow of argon, and the crystal frequencies were determined in air.
Photoelectrochemical Measurements: Photoelectrochemical experiments were performed with a home-built photoelectrochemical system that included a 300 W Xe lamp (Oriel, model 6258), a monochromator (Oriel, model 74000), and a chopper (Oriel, model 76994), The electrical output from the cell was sampled by a lock-in amplifier (Stanford Research Model SR 830 DSP). The shutter chopping frequency is controlled by a Stanford Research pulse/delay generator Model DG 535. The photoelectrode consisted of the polyacrylamide/ CdS nanoparticles assembled on the Au/quartz crystal, prepared as described above. A graphite electrode was used as a counter electrode. The photogenerated current was measured between the working and counter electrodes. The aqueous electrolyte solution consisted of 0.02 M triethylamine in 0.1 M phosphate buffer, pH 8.5, and the acetone electrolyte solution was composed of 0.02 M triethylamine and 0.1 M tetrabutylammonium tetrafluoroborate.