Photoinduced charge transfer dynamics in type-II CdSe/CdTe donor−acceptor nanorods were studied in real-time using femtosecond broadband pump−probe spectroscopy. Following photoexcitation of CdTe (λex = 620 nm), spectral bleaching from the state-filling signals of the band-edge optical transitions was measured using a femtosecond white light pulse (λprobe = 350−750 nm). Excitation of the lowest energy CdTe transition shows an ultrafast change in the bleaching signals of both the CdTe and CdSe lowest energy 1S transitions as well as the characteristic carrier transfer band. Our results indicate that interfacial interconduction band electron transfer CdTe to CdSe occurs on the 500 fs time scale in these heteromaterials.

We engineer colloidal quantum dot nanocrystals through the choice of biomolecular ligands responsible for nanoparticle nucleation, growth, stabilization, and passivation. We systematically vary the presence of, and thereby elucidate the role of, phosphate groups and a multiplicity of functionalities on the mononucleotides used as ligands. The results provide the basis for synthesis of nanoparticles using precisely controlled synthetic oligonucleotide sequences.

The use of a biomolecular RNA template for the synthesis of CdS semiconductor nanocrystals is described. Transfer RNA, with a well-defined three-dimensional structure, is used as a scaffold and ligand system in the aqueous synthesis of CdS. We have found that nanocrystal structures can be modulated by the structure of the templating tRNA. When possessing a folded three-dimensional structure, tRNA-templated synthesis yields a single product. If the same tRNA is rendered unstructured through the introduction of destabilizing mutations, a range of products are observed. The results reported indicate that biomolecules can be used to systematically engineer the structures and properties of semiconductor-based materials, and that the synergy between the dimensions of nanostructures and biomolecules provides a means to tune the properties of materials with nanoscale precision.

Mass spectrometry (MS)-based phosphoproteomics remains challenging due to the low abundance of phosphoproteins and substoichiometric phosphorylation. This demands better methods to effectively enrich phosphoproteins/peptides prior to MS analysis. We have previously communicated the first use of mesoporous zirconium oxide (ZrO 2 ) nanomaterials for effective phosphopeptide enrichment. Here we present the full report including the synthesis, characterization, and application of mesoporous titanium dioxide (TiO 2 ), ZrO 2 , and hafnium oxide (HfO 2 ) in phosphopeptide enrichment and MS analysis. Mesoporous ZrO 2 and HfO 2 are demonstrated to be superior to TiO 2 for phosphopeptide enrichment from a complex mixture with high specificity (>99%), which could almost be considered as "a purification", mainly because of the extremely large active surface area of mesoporous nanomaterials. A single enrichment and Fourier transform MS analysis of phosphopeptides digested from a complex mixture containing 7% of α-casein identified 21 out of 22 phosphorylation sites for α-casein. Moreover, the mesoporous ZrO 2 and HfO 2 can be reused after a simple solution regeneration procedure with comparable enrichment performance to that of fresh materials. Mesoporous ZrO 2 and HfO 2 nanomaterials hold great promise for applications in MSbased phosphoproteomics.