functionalized zno microbelt as improved co sensor

Abstract Miniaturized gas sensors are increasingly important to monitor the quality of air in a wide range of human environments. Semiconductor metal oxides have proved to be a useful family of materials, in this direction. Unfortunately, metal oxide sensors need a high temperature to respond to any target gas. In order to work around this limit, we fabricate hybrid sensors consisting in single zinc oxide microbelts decorated with organic molecules. Fluorinated tetraphenylporphyrin (H 2 TTPF) is deposited via supersonic molecular beam and considerably improve the performance of the microsensor. The microdevice is investigated with XRD, SEM and AFM techniques. While the as-is ZnO microbelt shows no response up to 150°C, the H 2 TTPF decorated microsensor shows a clear and quick response even at 75°C

Recent Progress in Ohmic/Schottky-Contacted ZnO Nanowire Sensors

We review the recent progress of zinc oxide (ZnO) nanowire sensors with ohmic-contacted and Schottky-contacted configurations and the enhancement of the performances of Schottky-contacted ZnO NW sensors (SCZNSs) by the piezotronic effect. Comparing with the traditional ohmic-contacted ZnO NW sensors (OCZNSs), the SCZNSs have higher sensitivities and faster responses controlled by the barrier height at the metal-semiconductor (M-S) interface. The piezotronic effect was applied to tune the Schottky barrier height (SBH) with the strain-induced piezoelectric polarization charges at the interface of the M-S contact. The piezotronic effect can thus improve the detection limitation, sensitivity, and response time of the SCZNSs in different applications, such as UV detection, gas and bio/chemical sensing. These piezotronic-enhanced SCZNSs may find potential applications in human-machine interfacing and flexible electronics skin technologies

Piezotronics/piezo-phototronics: Devices and applications

Piezoelectric effect has been widely used in electromechanical sensing, actuation and energy harvesting, which produces polarization charges under mechanical deformation in materials lacking inversion symmetry or with polarization domains. Conventional piezoelectric materials such as PZT and PVDF are electrically insulating and hence not feasible for constructing functional electronics or optoelectronics. The effect of mechanically-induced polarization on electronic and optoelectronic processes of charge carriers in piezoelectric materials has therefore been long overlooked. Semiconductor materials such as ZnO, GaN and CdS with wurtzite or zinc blende structures also possess piezoelectric properties but are not as extensively utilized in piezoelectric sensors and actuators as PZT due to their relatively small piezoelectric coefficients. The coupling of piezoelectric polarization with semiconductor properties in these materials has resulted in both novel fundamental phenomenon and unprecedented device applications, leading to the increasing research interests in the emerging field of piezotronics and piezo-phototronics. The basic of piezotronics and piezo-phototronics lies in the fact that strain-induced polarization charges at interface can effectively modulate the local band structure and hence the charge carrier transport across local junctions/contacts by exerting substantial influence on the concentration/distribution of free carriers and interfacial electronic charged states in the device. Fundamental physics about the piezotronics and piezo-phototronics are systematically illustrated at first in this dissertation. Functional electronic/optoelectronic devices based on piezoelectric semiconductor materials are presented to demonstrate the practical applications of the piezotronic and piezo-phototronic effects, including nanowire/microwire transistors, nanowire logic circuits, bio/chemical sensors and photo detectors. By successfully applying the piezotronic and piezo-phototronic effects in a wide range of electronics/optoelectronics, we have shown the universality of these two effects to be utilized in various practical applications as effective approaches to modify the physical properties of charge carriers in piezoelectric semiconductors.Ph.D

Fundamentals of Ornamental Plants in Removing Benzene in Indoor Air

The concentration of benzene in indoor air has received appreciable attention due to its adverse health effects. Although phytoremediation has been considered as an eco-friendly method to remove benzene, it is unclear how to select plants with a high removal rate. In this study, we evaluated the benzene removal efficiency of four common ornamental plants, Epipremnum aureum, Chlorophytum comosum, Hedera helix and Echinopsis tubiflora, and we also explored the factors impacting benzene removal efficiency. The removal efficiency of all plants in this study averaged at 72 percent. The benzene absorption rates of Epipremnum aureum, Hedera helix and Chlorophytum comosum were 1.10, 0.85 and 0.27 µg·m−3·cm−2, respectively. This is due to the different transpiration rates and chlorophyll concentrations in the plants. The benzene removal efficiency of crassulacean acid metabolism plant (Echinopsis tubiflora) was 23% higher than C3 plant (Epipremnum aureum) under dark conditions. This can be attributed to the fact that the characteristic of Echinopsis tubiflora stomata is different from Epipremnum aureum stomata, which is still open under dark conditions. Therefore, Echinopsis tubiflora can take up more benzene than Epipremnum aureum. For different initial benzene concentrations, the benzene removal efficiency of Echinopsis tubiflora was always great (50–80%), owing to its high rate of transpiration and concentration of chlorophyll. Our findings indicate that transpiration rate and chlorophyll concentration can be used as reference parameters to facilitate ornamental plant screening for indoor air quality improvement

Theoretical Study of Triboelectric-Potential Gated/Driven Metal–Oxide–Semiconductor Field-Effect Transistor

Triboelectric nanogenerator has drawn considerable attentions as a potential candidate for harvesting mechanical energies in our daily life. By utilizing the triboelectric potential generated through the coupling of contact electrification and electrostatic induction, the “tribotronics” has been introduced to tune/control the charge carrier transport behavior of silicon-based metal–oxide–semiconductor field-effect transistor (MOSFET). Here, we perform a theoretical study of the performances of tribotronic MOSFET gated by triboelectric potential in two working modes through finite element analysis. The drain-source current dependence on contact-electrification generated triboelectric charges, gap separation distance, and externally applied bias are investigated. The in-depth physical mechanism of the tribotronic MOSFET operations is thoroughly illustrated by calculating and analyzing the charge transfer process, voltage relationship to gap separation distance, and electric potential distribution. Moreover, a tribotronic MOSFET working concept is proposed, simulated and studied for performing self-powered FET and logic operations. This work provides a deep understanding of working mechanisms and design guidance of tribotronic MOSFET for potential applications in micro/nanoelectromechanical systems (MEMS/NEMS), human-machine interface, flexible electronics, and self-powered active sensors

Changes in the carbon storage of Inner Mongolian grasslands with N addition (A and C) and P addition (B and D).

<p>Total C storage including C storage of ANPP, litter, roots, SOC, SIC (i.e. top 100-soil layer). Data are presented as mean ± 1 SD (n = 6). See Table 1 for N and P addition and abbreviations.</p

Changes in SIC within 0–30 cm and 0–100 cm soil layers with N addition.

<p>Changes in SIC within 0–30 cm and 0–100 cm soil layers with N addition.</p

Soil C sequestration of grasslands in the 0–100 cm soil layer with N addition and P addition.

<p>STC, soil total carbon; SOC, soil organic carbon; SIC, soil inorganic carbon.</p