Self-assembly of composite semiconductor nanomaterials: Applications in patterning and photoinduced electron transfer processes
Hoth, Ruth Mistretta
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US and CdSe (CdE) quantum dots were molecularly linked through mercaptoalkanoic acids (MAAs) to anatase TiO 2 nanocrystalline films. TiO 2 films, approximately 4 μm thick, consisted of nanoparticles with diameters approximately 20 nm. Quantum dots were fabricated with diameters as small as 2.5 nm. Particle size increased with variations of reaction time, temperature, and concentration. The position of semiconductor nanoparticles on the TiO 2 surface was controlled by combining the self-assembly process with thiol-ene photopolymerization reactions. CdE surface attachment was turned off within 14 min. Patterning resolution of 40 Aμm was achieved with an ability to tune image color. Nanosecond transient absorption spectroscopy provided evidence for electron injection from US to TiO 2 in CdS-MAA-TiO 2 assemblies. An absorption corresponding to CdS + was observed, indicating a long-lived charge-separated state with τ = 14.7 ± 0.1 μs. Further evidence for electron injection in CdS-MAA-TiO 2 assemblies was the absence of absorption for CdS-MAA-ZrO 2 assemblies.