Vegetable oil-based feeds are regarded as an alternative source for the production of fuels and chemicals. Paraffins and olefins can be produced from these feeds through catalytic deoxygenation. The fundamentals of this process are mostly studied by using model compounds such as fatty acids, fatty acid esters, and specific triglycerides because of their structural similarity to vegetable oils. In this Review we discuss the impact of feedstock, reaction conditions, and nature of the catalyst on the reaction pathways of the deoxygenation of vegetable oils and its derivatives. As such, we conclude on the suitability of model compounds for this reaction. It is shown that the type of catalyst has a significant effect on the deoxygenation pathway, that is, group 10 metal catalysts are active in decarbonylation/decarboxylation whereas metal sulfide catalysts are more selective to hydrodeoxygenation. Deoxygenation studies performed under H2 showed similar pathways for fatty acids, fatty acid esters, triglycerides, and vegetable oils, as mostly deoxygenation occurs indirectly via the formation of fatty acids. Deoxygenation in the absence of H2 results in significant differences in reaction pathways and selectivities depending on the feedstock. Additionally, using unsaturated feedstocks under inert gas results in a high selectivity to undesired reactions such as cracking and the formation of heavies. Therefore, addition of H2 is proposed to be essential for the catalytic deoxygenation of vegetable oil feeds.

Disk-shaped semiconductor nanostructures provide enhanced architectures for low-threshold whispering gallery mode (WGM) lasing with the potential for on-chip nanophotonic integration. Unlike cavities that lase via Fabry-Perot modes, WGM structures utilize low-loss, total internal reflection of the optical mode along the circumference of the structure, which effectively reduces the volume of gain material required for lasing. As a result, circularly resonant cavities provide much higher quality (Q) factors than lower reflection linear cavities, which makes nanodisks an ideal platform to investigate lasing nanostructures smaller than the free-space wavelength of light (i.e., subwavelength laser). Here we report the bottom-up synthesis and single-mode lasing properties of individual ZnO disks with diameters from 280 to 900 nm and show finite difference time domain (FDTD) simulations of the whispering gallery mode inside subwavelength diameter disks. These results demonstrate ultraviolet WGM lasing in chemically synthesized, isolated nanostructures with subwavelength diameters.

We propose and realize a substrate-free metal-cavity surface-emitting microlaser with both top and sidewall metal and a bottom distributed Bragg reflector as the cavity structure. The transfer-matrix method is used to design the laser structure based on the round-trip resonance condition inside the cavity. The laser is 2.0 m in diameter and 2.5 m in height, and operates at room temperature with continuous-wave mode. Flip-bonding the device to a silicon substrate with a conductive metal provides efficient heat removal. A high characteristic temperature about 425 K is observed from 10 to 27 °C.

Semiconductor plasmonic Fabry-Perot lasers at submicron and nanometer scales exhibit many characteristics distinct from those of their conventional counterparts at micron scale. The differences originate from their small sizes and the presence of plasma metal in the cavity. To design a laser of this type, these features have to be taken into account properly. In this paper, we provide a comprehensive approach to the design and performance evaluation of the plasmonic Fabry-Perot nanolasers. In particular, we show the proper procedure to obtain the key parameters for lasing action, which are usually neglected in the conventional semiconductor Fabry-Perot lasers but become important for nanolasers.

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