Humidity Range

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Mircea Dincă - One of the best experts on this subject based on the ideXlab platform.

  • precise control of pore hydrophilicity enabled by post synthetic cation exchange in metal organic frameworks
    Chemical Science, 2018
    Co-Authors: Ashley M Wright, Adam J Rieth, Sungwoo Yang, Evelyn N Wang, Mircea Dincă
    Abstract:

    The ability to control the relative Humidity at which water uptake occurs in a given adsorbent is advantageous, making that material applicable to a variety of different applications. Here, we show that cation exchange in a metal–organic framework allows precise control over the Humidity onset of the water uptake step. Controlled incorporation of cobalt in place of zinc produces open metal sites into the cubic triazolate framework MFU-4l, and thereby provides access to materials with uptake steps over a 30% relative Humidity Range. Notably, the MFU-4l framework has an extremely high water adsorption capacity of 1.05 g g−1, amongst the highest known for porous materials. The total water capacity is independent of the cobalt loading, showing that cation exchange is a viable route to increase the hydrophilicity of metal–organic frameworks without sacrificing capacity.

  • postsynthetic tuning of hydrophilicity in pyrazolate mofs to modulate water adsorption properties
    Energy and Environmental Science, 2013
    Co-Authors: Casey R Wade, Tachmajal Corralessanchez, Tarun C Narayan, Mircea Dincă
    Abstract:

    Metal–organic frameworks (MOFs) have attracted interest as adsorbents in water-based adsorption heat pumps owing to their potential for increased water loading capacities and structural and functional tunability versus traditionally used materials such as zeolites and silica. Although pyrazolate-based MOFs exhibit exceptional hydrolytic stability, the water adsorption characteristics of this class of frameworks have remained unexplored in this context. In this report, we describe the modular synthesis of novel dipyrazole ligands containing naphthalenediimide cores functionalized with –H (H2NDI–H), –NHEt (H2NDI–NHEt), or –SEt (H2NDI–SEt) groups. Reaction of these ligands with Zn(NO3)2 afforded an isostructural series of MOFs, Zn(NDI–X), featuring infinite chains of tetrahedral Zn2+ ions bridged by pyrazolate groups and ∼16 A-wide channels with functionalized naphthalenediimide linkers lining the channel surface. The Type V water adsorption isotherms measured for these materials show water uptake in the 40–50% relative Humidity Range, suggesting hydrophobic channel interiors. Postsynthetic oxidation of Zn(NDI–SEt) with dimethyldioxirane was used to generate ethyl sulfoxide and ethyl sulfone groups, thereby rendering the channels more hydrophilic, as evidenced by shifts in water uptake to the 30–40% relative Humidity Range. Such tunability in water adsorption characteristics may find utility in the design of new adsorbents for adsorption-based heat transfer processes. An original MATLAB script, MOF-FIT, which allows for visual modeling of breathing and other structural deformations in MOFs is also presented.

Ying Zhou - One of the best experts on this subject based on the ideXlab platform.

  • Humidity sensing properties of zno colloid crystals coated on quartz crystal microbalance by the self assembly method
    Ceramics International, 2013
    Co-Authors: Juan Xie, Hu Wang, Yuanhua Lin, Ying Zhou
    Abstract:

    Abstract ZnO colloid crystals were coated on quartz crystal microbalance (QCM) by the self-assembly method. Field emission scanning electron microscopy and X-ray diffraction were used to analyze the morphology and crystal structure of ZnO colloid crystals. The sensing behavior was examined by measuring the resonance frequency shifts of QCM. The device exhibits excellent Humidity sensing properties in the whole Humidity Range from 11% to 95%, such as good linearity, fast response time and recovery time, excellent reliability, and long-term stability. We also discussed the adsorption and desorption of water molecules on ZnO colloid crystals at different Humidity conditions.

  • highly sensitive Humidity sensor based on quartz crystal microbalance coated with zno colloid spheres
    Sensors and Actuators B-chemical, 2013
    Co-Authors: Juan Xie, Hu Wang, Yuanhua Lin, Ying Zhou
    Abstract:

    Abstract Different sizes of ZnO colloid spheres were coated on quartz crystal microbalance (QCM) by the self-assembly method. The device exhibits excellent Humidity sensing properties in the whole Humidity Range from 11% to 95%, such as high sensitivity, good linearity, and fast response/recovery time. The results showed that the Humidity sensitivity of these sensors increased with increasing relative Humidity (RH). Furthermore, the Humidity sensitivity enhanced with increasing size of ZnO colloid spheres. We also discussed the adsorption and desorption of water molecules on different sizes of ZnO colloid spheres in different Humidity.

Dongzhi Zhang - One of the best experts on this subject based on the ideXlab platform.

  • fabrication and characterization of an ultrasensitive Humidity sensor based on metal oxide graphene hybrid nanocomposite
    Sensors and Actuators B-chemical, 2016
    Co-Authors: Dongzhi Zhang, Hongyan Chang, Runhua Liu, Qingzhong Xue
    Abstract:

    Abstract This paper demonstrated a flexible Humidity sensor based on tin dioxide/reduced graphene oxide (RGO) nanocomposite film. The Humidity sensor was fabricated on a polyimide substrate with microelectrodes by using a facile one-step hydrothermal route. The hydrothermal synthesized SnO 2 nanoparticles and SnO 2 /RGO hybrid nanostructures were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Humidity sensing properties of the presented SnO 2 /RGO nano-hybrid sensor were investigated by exposing it to a broad Humidity Range of 11–97%RH at room temperature. Compared with traditional Humidity sensors, the SnO 2 modified graphene sensor demonstrated an ultrahigh sensitivity and a rapid response/recovery characteristic over a full Humidity Range measurement, highlighting the unique advantages of hydrothermal synthesis for sensors fabrication. Finally, the possible Humidity sensing mechanism of the proposed sensor was discussed by using complex impedance spectra and bode diagrams. These observed results demonstrate that RGO modified with metal oxide is promising nanomaterials for constructing high performance Humidity sensors in widespread applications.

  • Humidity sensing properties of chemically reduced graphene oxide polymer nanocomposite film sensor based on layer by layer nano self assembly
    Sensors and Actuators B-chemical, 2014
    Co-Authors: Dongzhi Zhang, Jun Tong, Bokai Xia
    Abstract:

    Abstract Chemically reduced graphene oxide (RGO)/poly(diallylimethyammonium chloride) (PDDA) nanocomposite film sensor with high-performance Humidity properties was reported in this paper. The film sensor was fabricated on flexible polyimide substrate with interdigital microelectrodes structure. By the layer-by-layer nano self-assembly approach, graphene oxide and PDDA were exploited to form hierarchical nanostructure, and then was partially reduced via solution-based chemically reduction for obtaining both conductivity and chemically active defect sites. The effect of hydrobromic acid treatment on the conductivity properties of PDDA/GO film was examined, further verifying the advantage of hydrobromic acid reduction. The Humidity sensing properties of the presented nanocomposite film sensor, such as repeatability, hysteresis, stability, response–recovery characteristics, were investigated by exposing to the wide relative Humidity Range of 11–97% at room temperature. As a result, the sensor exhibited not only excellent sensing behavior to Humidity, but also fast response–recovery time and good repeatability, highlighting the unique advantages of layer-by-layer nano self-assembly for film sensors fabrication. As last, the possible Humidity sensing mechanism of the proposed sensor was discussed in detail.

Qida Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Relative Humidity Sensor Based on Tilted Fiber Bragg Grating With Polyvinyl Alcohol Coating
    IEEE Photonics Technology Letters, 2009
    Co-Authors: Yinping Miao, Hao Zhang, Yuan Li, Haibin Zhou, Weihua Zhang, Qida Zhao
    Abstract:

    A relative Humidity (RH) sensor based on tilted fiber Bragg grating (TFBG) is proposed by utilizing polyvinyl alcohol (PVA) as the sensitive cladding film. RH increasing in the PVA coating will result in reduction of refractive index. Due to the TFBG's sensitivity to ambient refractive index, the spectral properties of PVA-coated TFBG are modified under exposure to different ambient Humidity levels ranging from 20% to 98% RH. The transmission power of TFBG has different linear behaviors for two different Humidity Ranges (20%-74% RH and 74%-98% RH), and the sensitivity for each Humidity Range reaches as high as 2.52 and 14.947 dBm/%RH, respectively. Combining the advantages of optical fiber grating and PVA as a smart material, this design involves simple configuration, low cost, compactness, a small degree of hysteresis, stability, and wide dynamic sensing Range as well. Therefore, the sensor could be applied in real-time RH monitoring for normal as well as extremely humid environments.

Weijian Tian - One of the best experts on this subject based on the ideXlab platform.

  • methylcellulose coated Humidity sensor based on michelson interferometer with thin core fiber
    Sensors and Actuators A-physical, 2019
    Co-Authors: Piaopiao Wang, Bowen Wang, Weijian Tian
    Abstract:

    Abstract A Methylcellulose (MC) film-coated Humidity sensor based on Michelson interferometer (MI) is proposed and experimentally demonstrated. It is fabricated by splicing one end of a short segment thin core fiber (TCF) with a single mode fiber (SMF) and melting the other end into a rounded tip which coated with a MC film. The proposed sensor is linearly responsive to relative Humidity (RH) beyond the Humidity Range 55%RH, with maximum sensitivity of 0.224dB/%RH and 0.133nm/RH demodulated by wavelength and intensity, respectively. Moreover, the MC can be used to develop more types of fiber-optic Humidity sensors due to its great potential performance in RH measurement.