Photoelectron spectra of cold aluminum cluster anions Al(n)(-) have been measured in the size range n=13-75 and are compared to the results of density functional theory calculations. Good agreement between the measured spectra and the calculated density of states is obtained for most sizes, which gives strong evidence that the correct structures have been found. In particular the results confirm the occurrence of rather different structural motifs in this size range, from fcc-like stacks over fragments of decahedrons to disordered structures. An analysis of the density of states of representatives of the different structural motifs shows that the electronic structure is strongly influenced by the cluster geometry, and that a clear jelliumlike electron shell structure is present only in some exceptional cases.
Nitrogen dioxide
(NO
2
) is one of the most dangerous
air pollutants that can affect human health even at the ppb (part
per billion) level. Thus, the superior sensing performance of nitrogen
dioxide gas sensors is an imperative for real-time environmental monitoring.
Traditional solid-state sensors based on metal-oxide transistors have
the drawbacks of high power consumption, high operating temperature,
poor selectivity, and difficult integration with other electronics.
In that respect, graphene-based gas sensors have been extensively
studied as potential replacements. However, their advantages of high
sensing efficiency, low power consumption, and simple electronic integration
have been countered by their slow response and poor repeatability.
Here, we report the fabrication of high-performance ultraviolet (UV)-assisted
room temperature NO
2
sensors based on chemical vapor deposition-grown
graphene. UV irradiation improves the response of the sensor sevenfold
with respect to the dark condition attaining 26% change in resistance
at 100 ppm NO
2
concentration with a practical detection
limit below 1 ppm (42.18 ppb). In addition, the recovery time was
shortened fivefold to a few minutes and the excellent repeatability.
This work may provide a promising and practical method to mass produce
room-temperature NO
2
gas sensors for real-time environment
monitoring due to its simple fabrication process, low cost, and practicality.
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