Baiyi Zu

Nanostructure-based optoelectronic sensing of vapor phase explosives – a promising but challenging method

Optoelectronic sensing of gas phase hazardous chemicals is a newly explored field, which shows great advantages towards low concentration sensing when compared to normal gas sensing in the dark. Here, based on the recent progress on nanostructured vapor phase explosive gas sensors operated in dark conditions, the attractiveness of developing optoelectronic sensors for vapor phase explosive detection was highlighted. Furthermore, we try to propose some new insights to enhance optoelectronic sensing of vapor phase explosives. We suggest employing photocatalysis principles to enhance the sensitivity and employing a molecular imprinting technique (MIT) to enhance the selectivity.

Transition‐Metal‐Doped p‐Type ZnO Nanoparticle‐Based Sensory Array for Instant Discrimination of Explosive Vapors

The development of portable, real-time, and cheap platforms to monitor ultratrace levels of explosives is of great urgence and importance due to the threat of terrorism attacks and the need for homeland security. However, most of the previous chemiresistor sensors for explosive detection are suffering from limited responses and long response time. Here, a transition-metal-doping method is presented to remarkably promote the quantity of the surface defect states and to significantly reduce the charge transfer distance by creating a local charge reservoir layer. Thus, the sensor response is greatly enhanced and the response time is remarkably shortened. The resulting sensory array can not only detect military explosives, such as, TNT, DNT, PNT, PA, and RDX with high response, but also can fully distinguish some of the improvised explosive vapors, such as AN and urea, due to the huge response reaching to 100%. Furthermore, this sensory array can discriminate ppb-level TNT and ppt-level RDX from structurally similar and high-concentration interfering aromatic gases in less than 12 s. Through comparison with the previously reported chemiresistor or Schottky sensors for explosive detection, the present transition-metal-doping method resulting ZnO sensor stands out and undoubtedly challenges the best.

Surface Superoxide Complex Defects-Boosted Ultrasensitive ppb-Level NO2 Gas Sensors

Sn(4+) -O2 (-•) centers are intentionally created in SnO2 nanoflowers by a thermodynamically instable synthetic process. The resulting SnO2 nanoflower-based sensor is confirmed to be the most sensitive ppb-level chemiresistor NO2 sensor to date. The Sn(4+) -O2 (-•) centers with strong gas-adsorbing and high eletron-donating capability towards NO2 molecules decisively determine the sensor sensitivity.

Simple metal/SiO2/Si planar photodetector utilizing leakage current flows through a SiO2 layer

Silicon wafers covered with a thermally grown high-quality SiO2 layer were often used as the substrate to house different nanostructures to fabricate photodetection devices. No reports have ever challenged directly fabricating photodetectors utilizing leakage current through non-high-quality SiO2 films and the intrinsic light absorption properties of Si. Herein, we show that metal/SiO2/Si planar photodetectors could be easily fabricated by simply depositing two metal electrodes (such as, Au, Ag and Al) on top of SiO2/Si wafer in which the SiO2 layer is of non-high quality. The responsivity, stability, photoresponse characteristics and light intensity sensitivity are systematically evaluated. Our results clearly show that the present conveniently and cost-effectively fabricated metal/SiO2/Si planar photodetectors are of great advantage as compared to many of the nanostructure-based photodetectors constructed on SiO2/Si substrate.

A F-ion assisted preparation route to improve the photodegradation performance of a TiO2@rGO system-how to efficiently utilize the photogenerated electrons in the target organic pollutants

A comparison of the work function of reduced graphene oxide (rGO) and the conduction band position of TiO2 reveals that the density of TiO2 particles grown on rGO could affect the photodegradation efficiency of a TiO2@rGO heterojunction. Herein, with the introduction of F-ions into the preparation route, F-doped shaped TiO2 nanocrystals are densely and uniformly decorated on rGO sheets via the ice bath hydrolyzation method. Thus, more dye molecules are adsorbed on the surface of TiO2 and the photogenerated electrons in the excited dye molecules could be efficiently utilized to improve the overall photodegradation efficiency. The as-prepared F-doped TiO2@rGO heterojunction showed extremely high photocatalytic efficiency under UV-vis light irradiation compared with that of the commercial P25 and the mixture of F-TiO2 and rGO. It is proved that the ice bath hydrolyzation preparation route is crucial to improve the photodegradation efficiency of the final product since the pure TiO2@rGO heterojunction is also much more efficient than the mixture of F-TiO2 and rGO. The present work provides new insights into efficiently utilizing the photogenerated electrons in the target organic pollutants.