scholarly journals Near Room Temperature Light-Activated WS2-Decorated rGO as NO2 Gas Sensor

Sensors ◽  
2019 ◽  
Vol 19 (11) ◽  
pp. 2617 ◽  
Author(s):  
Valentina Paolucci ◽  
Seyed Mahmoud Emamjomeh ◽  
Luca Ottaviano ◽  
Carlo Cantalini
Keyword(s):  
Light Conditions ◽  
Humid Air ◽  
Tem Analysis ◽  
No2 Gas Sensor ◽  
Carrier Mechanism ◽  
Sensitivity Tests ◽  
Influence Of Water ◽  
Sonication Technique ◽  
A Charge ◽  
Adsorption Desorption

The NO2 response in the range of 200 ppb to 1 ppm of a chemoresistive WS2-decorated rGO sensor has been investigated at operating temperatures of 25 °C and 50 °C in dry and humid air (40% RH) under dark and Purple Blue (PB) light conditions (λ = 430 nm). Few-layers WS2, exfoliated by ball milling and sonication technique, with average dimensions of 200 nm, have been mixed with rGO flakes (average dimension 700 nm) to yield WS2-decorated rGO, deposited on Si3N4 substrates, provided with platinum (30 μm gap distance) finger-type electrodes. TEM analysis showed the formation of homogeneous and well-dispersed WS2 flakes distributed over a thin, continuous and uniform underlying layer of interconnected rGO flakes. XPS and STEM revealed a partial oxidation of WS2 flakes leading to the formation of 18% amorphous WO3 over the WS2 flakes. PB-light irradiation and mild heating of the sensor at 50 °C substantially enhanced the baseline recovery yielding improved adsorption/desorption rates, with detection limit of 400 ppb NO2 and reproducible gas responses. Cross sensitivity tests with humid air interfering vapor highlighted a negligible influence of water vapor on the NO2 response. A charge carrier mechanism between WS2 and rGO is proposed and discussed to explain the overall NO2 and H2O response of the WS2–rGO hybrids.

scholarly journals Water-Mediated Electronic Structure of Oligopeptides Probed by Their UV Circular Dichroism, Absorption Spectra, and Time-Dependent DFT Calculations

2020 ◽  
Author(s):  
Anshuman Kumar ◽  
Siobhan E. Toal ◽  
David DiGuiseppi ◽  
Reinhard Schweitzer-Stenner ◽  
Bryan Wong
Keyword(s):  
Circular Dichroism ◽  
Absorption Spectra ◽  
Density Functional ◽  
Time Dependent ◽  
Water Model ◽  
Cd Spectra ◽  
Influence Of Water ◽  
Explicit Consideration ◽  
A Charge ◽  
Circular Dichroïsm

<p>We investigate the UV absorption spectra of a series of cationic GxG (where x denotes a guest residue) peptides in aqueous solution and find that the spectra of a subset of peptides with x = A, L, I, K, N, and R (and, to a lesser extent, peptides with x = D and V) vary as a function of temperature. To explore whether or not this observation reflects conformational dependencies, we carry out time-dependent density functional calculations for the polyproline II (pPII) and β-strand conformations of a limited set of tripeptides (x = A, V, I, L, and R) in implicit and explicit water. We find that the calculated CD spectra for pPII can qualitatively account for the experimental spectra irrespective of the water model. The reproduction of the <i>β</i>-strand UV-CD spectra, however, requires the explicit consideration of water. Based on the calculated absorption spectra, we explain the observed temperature dependence of the experimental spectra as being caused by a reduced dispersion (larger spectral density) of the overlapping NV<sub>2</sub> band and the influence of water on electronic transitions in the β-strand conformation. Contrary to conventional wisdom, we find that both the NV<sub>1</sub> and NV<sub>2</sub> band are the envelopes of contributions from multiple transitions that involve more than just the HOMOs and LUMOs of the peptide groups. A natural transition orbital analysis reveals that some of the transitions with significant oscillator strength have a charge-transfer character. The overall manifold of transitions, in conjunction with their strengths and characters, depends on the peptide’s backbone conformation, peptide hydration, and also on the side chain of the guest residue. It is particularly noteworthy that molecular orbitals of water contribute significantly to transitions in <i>β</i>-strand conformations. Our results reveal that peptide groups, side chains, and hydration shells must be considered as an entity for a physically valid characterization of UV absorbance and circular dichroism. </p>

scholarly journals Water-Mediated Electronic Structure of Oligopeptides Probed by Their UV Circular Dichroism, Absorption Spectra, and Time-Dependent DFT Calculations

2020 ◽  
Author(s):  
Anshuman Kumar ◽  
Siobhan E. Toal ◽  
David DiGuiseppi ◽  
Reinhard Schweitzer-Stenner ◽  
Bryan Wong
Keyword(s):  
Circular Dichroism ◽  
Absorption Spectra ◽  
Density Functional ◽  
Time Dependent ◽  
Water Model ◽  
Cd Spectra ◽  
Influence Of Water ◽  
Explicit Consideration ◽  
A Charge ◽  
Circular Dichroïsm

<p>We investigate the UV absorption spectra of a series of cationic GxG (where x denotes a guest residue) peptides in aqueous solution and find that the spectra of a subset of peptides with x = A, L, I, K, N, and R (and, to a lesser extent, peptides with x = D and V) vary as a function of temperature. To explore whether or not this observation reflects conformational dependencies, we carry out time-dependent density functional calculations for the polyproline II (pPII) and β-strand conformations of a limited set of tripeptides (x = A, V, I, L, and R) in implicit and explicit water. We find that the calculated CD spectra for pPII can qualitatively account for the experimental spectra irrespective of the water model. The reproduction of the <i>β</i>-strand UV-CD spectra, however, requires the explicit consideration of water. Based on the calculated absorption spectra, we explain the observed temperature dependence of the experimental spectra as being caused by a reduced dispersion (larger spectral density) of the overlapping NV<sub>2</sub> band and the influence of water on electronic transitions in the β-strand conformation. Contrary to conventional wisdom, we find that both the NV<sub>1</sub> and NV<sub>2</sub> band are the envelopes of contributions from multiple transitions that involve more than just the HOMOs and LUMOs of the peptide groups. A natural transition orbital analysis reveals that some of the transitions with significant oscillator strength have a charge-transfer character. The overall manifold of transitions, in conjunction with their strengths and characters, depends on the peptide’s backbone conformation, peptide hydration, and also on the side chain of the guest residue. It is particularly noteworthy that molecular orbitals of water contribute significantly to transitions in <i>β</i>-strand conformations. Our results reveal that peptide groups, side chains, and hydration shells must be considered as an entity for a physically valid characterization of UV absorbance and circular dichroism. </p>

Ultrasensitive and light-activated NO2 gas sensor based on networked MoS2/ZnO nanohybrid with adsorption/desorption kinetics study

2021 ◽  
Vol 536 ◽  
pp. 147933 ◽  
Author(s):  
Rishi Ranjan Kumar ◽  
Thangapandian Murugesan ◽  
Ajit Dash ◽  
Cheng-Hsuan Hsu ◽  
Shivam Gupta ◽  
...  
Keyword(s):  
Gas Sensor ◽  
Desorption Kinetics ◽  
Kinetics Study ◽  
No2 Gas Sensor ◽  
Adsorption Desorption

Hydrothermal synthesis of Zeolite NaA from Kaolin

2019 ◽  
Vol 12 (05) ◽  
pp. 1950075 ◽  
Author(s):  
Peng Wang ◽  
Qi Sun ◽  
Yujiao Zhang ◽  
Jun Cao ◽  
Xingmao Li
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Synthesis ◽  
Synthesis Method ◽  
Textural Properties ◽  
Treatment Temperature ◽  
Low Grade ◽  
Tem Analysis ◽  
X Ray ◽  
Zeolite Naa ◽  
Adsorption Desorption

Zeolite NaA was successfully synthesized from low-grade kaolin via hydrothermal synthesis method. The properties of the zeolite NaA were characterized by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray fluorescence (XRF), scanning electron microscopy (SEM)-energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and thermogravimetry (TG)-differential thermal analysis (DTA). TEM analysis indicated the formation of body-centered cubic crystal zeolite NaA and the polycrystallinity of the zeolite NaA structure. The textural properties of the zeolite NaA were further studied by N2 adsorption-desorption technique. In addition, the TG-DTA study confirmed that the heat treatment temperature of the zeolite NaA should be controlled below 600∘C.

Preparation and Characterization of MCM-22 Zeolite by Varying-Temperature Hydrothermal Synthesis

2011 ◽  
Vol 197-198 ◽  
pp. 1587-1590
Author(s):  
Yue Cheng ◽  
Xiao Yuan Su ◽  
Mang Lu
Keyword(s):  
Hydrothermal Method ◽  
Amorphous Material ◽  
Sem Analysis ◽  
Bet Surface Area ◽  
N2 Adsorption ◽  
Tem Analysis ◽  
Synthesis Time ◽  
Xrd Pattern ◽  
Adsorption Desorption

MCM-22 zeolite of high crystallinity was synthesized with varying-temperature hydrothermal method. Zeolite was characterized by means of XRD, SEM, TEM and TG-DTA. XRD pattern showed that the sample was MCM-22 zeolite. SEM analysis indicated that the MCM-22 sample is in the form of thin platelet-like crystals, and no amorphous material. TEM analysis exhibited regular shaped aggregate assembled by the independent growth of many small flaky crystals. N2-adsorption/desorption analysis showed that the pore size and BET surface area of MCM-22 were 3.5 nm and 387.8 m2/g, respectively. By means of the varying-temperature hydrothermal method, synthesis time can be effectively reduced, and energy consumption also decreases.

Characterization of Ru on Activated Carbon Catalysts Prepared by Supercritical Carbon Dioxide Impregnation

2011 ◽  
Vol 396-398 ◽  
pp. 734-738
Author(s):  
San Kui Xu ◽  
Li Min Li ◽  
Rui Li ◽  
Nan Nan Guo ◽  
Peng Zhang
Keyword(s):  
Carbon Dioxide ◽  
Catalytic Activity ◽  
Activated Carbon ◽  
Supercritical Carbon Dioxide ◽  
Tem Analysis ◽  
Excellent Activity ◽  
Supercritical Parameters ◽  
Carbon Catalysts ◽  
Adsorption Desorption ◽  
Supercritical Carbon

In this work, a novel method was reported for preparation of Ru/activated carbon (Ru/AC) catalysts. Supercritical carbon dioxide (SC CO2) was employed as medium for the impregnation of ACs with inorganometallic precursor of RuCl3. The Ru/AC catalysts displayed excellent activity for the catalytic hydrogenation of D-glucose. Selected Ru/AC catalysts were characterized by N2adsorption-desorption, TPR and TEM analysis. The results show that the order of effects on catalytic activity are supercritical temperature > supercritical pressure > amount of co-solvent > time of impregnation. The optimal supercritical parameters for preparing Ru/AC catalyst were 313 K, 8 MPa, 4 ml of methanol and 9 h, respectively. The highest reaction rate of hydrogenation reached 86.35 mmol•min-1g-1Ru, upgrading 42.96% compared with the activity of conventional Ru/AC prepared using aqueous impregnation. The SC CO2 impregnation could result in Ru uniformly dispersed on the outer surface and in the pore of AC, leadingSubscript textto higher dispersion of Ru and enhanced interaction between AC and Ru. Furthermore, the enhanced interaction induces improved reduce temperature. Consequently, the catalytic activity of Ru/AC catalysts is improved significantly.

Influence of Water Adsorption/Desorption Processes on the Selectivity of Vapor  HF  Etching

1995 ◽  
Vol 142 (4) ◽  
pp. 1332-1340 ◽  
Author(s):  
H. Watanabe ◽  
H. Kitajima ◽  
I. Honma ◽  
H. Ono ◽  
R. J. Wilhelm ◽  
...  
Keyword(s):  
Water Adsorption ◽  
Influence Of Water ◽  
Adsorption Desorption

scholarly journals Study on the Hemostasis Characteristics of Biomaterial Frustules Obtained from Diatom Navicula australoshetlandica sp.

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3752
Author(s):  
Yanqing Luo ◽  
Shuangfei Li ◽  
Kun Shen ◽  
Yingjie Song ◽  
Jiangtao Zhang ◽  
...  
Keyword(s):  
Diatom Frustule ◽  
Ftir Analysis ◽  
Clotting Time ◽  
N2 Adsorption ◽  
Tem Analysis ◽  
X Ray ◽  
Unicellular Algae ◽  
Bet Analysis ◽  
Aquaculture Wastewater ◽  
Adsorption Desorption

Diatoms, known as photosynthetic unicellular algae, can produce natural biosilica frustules that exhibit great biocompatibility, superhydrophilicity, and superhemophilicity. In our study, the diatom Navicula australoshetlandica sp. was isolated from aquaculture wastewater and pretreated to obtain frustules so as to explore their hemostasis characteristics. A special “porous web” (6–8 nm) substructure in the ordered nanopores (165–350 nm) of boat-shaped diatom frustule was observed in Navicula australoshetlandica sp. using SEM and TEM analysis. Moreover, X-ray, N2 adsorption–desorption isotherms, and BET analysis showed that the diatom frustule is a mesoporous material with a surface area of 401.45 m2 g−1 amorphous silica. FTIR analysis showed that Navicula australoshetlandica sp. frustules possessed abundant OH functional groups. A low hemolysis ratio was observed for 1–5 mg mL−1 diatom frustules that did not exceed 1.55 ± 0.06%, which indicates favorable hemocompatibility. The diatom frustules exhibited the shortest clotting time (134.99 ± 7.00 s) with a hemostasis material/blood (mg/μL) ratio of 1:100, which is 1.83 times (112.32 s) shorter than that of chitosan. The activated partial thromboplastin time (aPTT) of diatom frustule was also 44.53 s shorter than the control. Our results demonstrate the potential of Navicula australoshetlandica sp. diatom frustules to be used as medical hemostasis material.

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