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Large amounts of volatile organic compounds (VOCs) are emitted into the atmosphere from both human and natural sources. A significant portion of VOCs would be oxidized via their reactions with atmospheric oxidants like OH, NO3, ozone, etc. The products of the oxidation reactions are often of low volatility and may condense to form secondary organic aerosols (SOA). To study the effect of VOC oxidation in aerosol formation, we are building an oxidation flow reactor system, which consists of (1) a 22‐l aluminum chamber, (2) an ozone source with an ozone detector, (3) a UV‐C (254 nm) lamp, (4) a photoionization detector to measure the effective VOC concentration, (5) various flow/concentration controlling apparatuses, and (6) a scanning mobility particle sizer to monitor the generated particles. Under the conditions of high UV and ozone levels, the oxidation process can be speeded up by orders of magnitude in this reactor. We hope to use this reactor: (i) to learn the "potential" mass of SOA that can be formed from a given VOC source like a traffic or industry site; (ii) to trace back the SOA source by utilizing the shortened reaction times; (iii) to learn the trends from VOC to SOA. [ABSTRACT FROM AUTHOR]

Extensive effort is dedicated to developing 2D materials as an alternative to Si‐based semiconductor technology. As the size decreases, heat dissipation at various interfaces becomes increasingly important in controlling device performance. On the other hand, the high interfacial thermal resistances can be applied for thermoelectric devices or thermal insulators by achieving ultralow thermal conductivity via nanostructuring. Here, it is found that a) the thermal and electrical conductance of the Au/MoS2 monolayer interface can be tuned by changing the interfacial chemical properties through N‐methyl‐2‐pyrrolidone (NMP) wet cleaning while preserving the MoS2 structure; b) the effectiveness of the NMP cleaning process, which removes surface adsorbates, exhibits a temperature dependence; c) experimental results demonstrate that adequate oxygen adsorbates at the Au/MoS2 interface significantly improve the thermal and electrical conductance, in agreement with the simulation results. The interfacial thermal conductance increases by 339.87% when oxygen adsorbates are partially removed and decreases by 74.37% as a sharp interface exists (oxygen adsorbates are removed) compared to the as‐deposited interfaces. The electrical conductance shows up to 2 order increase after NMP cleaning. This finding can both enhance the heat dissipation in functional devices and provide new options for the interface design of thermal insulating thin films. [ABSTRACT FROM AUTHOR]

Carbon-coated Li4Ti5O12 (LTO) has been prepared using polyimide (PI) as a carbon source via the thermal imidization of polyamic acid (PAA) followed by a carbonization process. In this study, the PI with different structures based on pyromellitic dianhydride (PMDA), 4,4′-oxydianiline (ODA), and p-phenylenediamine (p-PDA) moieties have been synthesized. The effect of the PI structure on the electrochemical performance of the carbon-coated LTO has been investigated. The results indicate that the molecular arrangement of PI can be improved when the rigid p-PDA units are introduced into the PI backbone. The carbons derived from the p-PDA-based PI show a more regular graphite structure with fewer defects and higher conductivity. As a result, the carbon-coated LTO exhibits a better rate performance with a discharge capacity of 137.5 mAh/g at 20 C, which is almost 1.5 times larger than that of bare LTO (94.4 mAh/g). [ABSTRACT FROM AUTHOR]

In this work, a SnO2 bilayers photodiode device is designed, which consists of a thin SnO2 photocurrent generation layer and a SnO2 thick layer on the glass substrate. The SnO2 photocurrent generation layer with high oxygen vacancy concentration is intentionally prepared. With annealing in oxygen ambient, an electrical potential would be built in the surface space charge region in the thin SnO2 photocurrent generation layer, which would drive the photocarriers down to and flow in the photocarrier transportation layer, i.e., the high‐mobility SnO2 thick film on the glass substrate. The designed SnO2 bilayers photodiode device could enhance photocurrent generation and resolution for the SnO2‐based UV‐photodetectors. It is concluded that the width of surface space charge region is the key factor for the enhancement of lifetime of photocarriers and photocurrent generation of the current SnO2 bilayers photodiode. Based on the present experimental results, the width of the surface space charge region is expected to be nearly or less than 3 nm. Moreover, in this work, a theoretical model is developed to calculate the width of the surface space charge region. The calculated width of the surface space charge region (3.26 nm) is close enough to support the present experimental observation. In this work, a SnO2 bilayer photodiode device is designed, which consists of a thin SnO2 photocurrent generation layer and a thick SnO2 layer on the glass substrate. The width of surface space charge region is the key factor for enhancing the lifetime of photocarriers and photocurrent generation of the current SnO2 bilayer photodiode. [ABSTRACT FROM AUTHOR]