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Biomedical subjects

P Guyot-Sionnest

Publications and source records attributed to P Guyot-Sionnest.

16 recordsLinked to original sources
PubMed2001

Organic-capped ZnO nanocrystals: synthesis and n-type character.

Wurtzite ZnO nanocrystals capped with trioctylphosphine oxide or alkylamines are synthesized and characterized. These ZnO nanocrystals can be made n-type either by electron transfer doping from reducing species in solution or by above band gap photoexcitation with a UV lamp. The n-type nanocrystals exhibit a strong intraband infrared absorption, an extensive bleach of the interband band-edge absorption, and a complete quenching of the photoluminescence.

Journal Article↗
PubMed2001

Electrochromic nanocrystal quantum dots.

Incorporating nanocrystals into future electronic or optoelectronic devices will require a means of controlling charge-injection processes and an understanding of how the injected charges affect the properties of nanocrystals. We show that the optical properties of colloidal semiconductor nanocrystal quantum dots can be tuned by an electrochemical potential. The injection of electrons into the quantum-confined states of the nanocrystal leads to an electrochromic response, including a strong, size-tunable, midinfrared absorption corresponding to an intraband transition, a bleach of the visible interband exciton transitions, and a quench of the narrow band-edge photoluminescence.

Journal Article↗
PubMed2000

n-type colloidal semiconductor nanocrystals.

Colloidal semiconductor nanocrystals combine the physical and chemical properties of molecules with the optoelectronic properties of semiconductors. Their colour is highly controllable, a direct consequence of quantum confinement on the electronic states. Such nanocrystals are a form of 'artificial atoms' (ref. 4) that may find applications in optoelectronic systems such as light-emitting diodes and photovoltaic cells, or as components of future nanoelectronic devices. The ability to control the electron occupation (especially in n-type or p-type nanocrystals) is important for tailoring the electrical and optical properties, and should lead to a wider range of practical devices. But conventional doping by introducing impurity atoms has been unsuccessful so far: impurities tend to be expelled from the small crystalline cores (as observed for magnetic impurities), and thermal ionization of the impurities (which provides free carriers) is hindered by strong confinement. Here we report the fabrication of n-type nanocrystals using an electron transfer approach commonly employed in the field of conducting organic polymers. We find that semiconductor nanocrystals prepared as colloids can be made n-type, with electrons in quantum confined states.

Journal Article↗