Colloidal ZnSe quantum dots were successfully synthesized from ZnO in a lauric acid/hexadecylamine mixture. X-ray diffraction patterns indicated that the ZnSe quantum dots possess a wurtzite structure. Transmission electron microscope images of the quantum dots showed that the average diameter are in the range of 25∼60 Å. The size-dependent photoluminescence was controlled from 400 to 440 nm with the quantum yields of 6∼10% at room temperature. After passivation with 1.8 monolayer of ZnS overcoat by a traditional two-step method, the quantum yields of ZnSe/ZnS QDs are increased ∼4.5-fold (quantum yield ∼32%). An in-situ method of overcoating was done by directly injecting TOPS into the flask containing ZnSe, ZnO/lauric acid/ hexadecylamine, and TOPSe. The photoluminescence quantum yields were improved ∼3.8-fold after introduction of 1.6 monolayer ZnSeS overcoat to the ZnSe QDs.

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Two types of electronic nose (EN), different in operational principle, were used to identify the source of spilled oil in an accident. The suspected sources considered were petroleum oil reservoirs and pipelines located near the site of the accident. Gas chromatography/mass spectrometry (GC/ MS), operated in both EI and CI modes, was employed to confirm the identified source. The advantage of multisensors in spatially resolved sensing for direct multicomponent analysis was explored to minimize tedious sample preparation procedures. Subsequent principal component analysis helped in identifying the source. The advantage of fast separation in temporally resolved sensing was explored to rapidly yield compositional information; the resulting graphical representations helped clarify the source. Traditional GC/MS not only confirms the identified spilled oil source, but also provides detailed diagnostic information such as total petroleum hydrocarbons, polycyclic aromatic hydrocarbons and their C1-C4 alkylated homologues, as well as the n-alkanes, which are essential for follow-up remedial and regulatory actions. The main use of the electronic nose was demonstrated to be as a simple and rapid screening method for identifying a spilled oil source.