scholarly journals Gas molecules sandwiched in hydration layers at graphite/water interfaces

2020 ◽  
Vol 22 (24) ◽  
pp. 13629-13636 ◽  
Author(s):  
Hideaki Teshima ◽  
Qin-Yi Li ◽  
Yasuyuki Takata ◽  
Koji Takahashi
Keyword(s):  
Frequency Shift ◽  
High Water ◽  
Water Density ◽  
Adsorbed Gas ◽  
Gas Molecules ◽  
Gas Layer ◽  
Hydration Layers

Frequency shift-distance curves reveal that each adsorbed gas layer is sandwiched between hydration layers with high water density.

Exciton localization in MoSe2monolayers induced by adsorbed gas molecules

2019 ◽  
Vol 114 (17) ◽  
pp. 172106 ◽  
Author(s):  
Tommaso Venanzi ◽  
Himani Arora ◽  
Artur Erbe ◽  
Alexej Pashkin ◽  
Stephan Winnerl ◽  
...  
Keyword(s):  
Exciton Localization ◽  
Adsorbed Gas ◽  
Gas Molecules

Measurement of Solvent Vapor Absorption by Polydimethylsiloxane Using Quartz Crystal Microbalance

2008 ◽  
Author(s):  
W. W. F. Leung ◽  
C. Chao ◽  
C. H. Cheng ◽  
K. F. Lei ◽  
D. Ngan ◽  
...  
Keyword(s):  
Frequency Shift ◽  
Gas Sensor ◽  
Quartz Crystal Microbalance ◽  
Quartz Crystal ◽  
Specific Area ◽  
Small Mass ◽  
Crystal Oscillator ◽  
Solvent Vapor ◽  
Adsorbed Gas ◽  
Micro Electromechanical System

A new micro-electromechanical system (MEMS) gas sensor has been developed using quartz crystal microbalance (QCM) with adsorbent coated in form of nanofibers on the QCM sensor. The nanofibers with fiber diameter typically around 200–300 nm increases the specific surface area to enhance adsorption. The QCM is made to oscillate at its natural resonance frequency. Upon exposure of the gas sensor to a given gas, the adsorbed gas onto the nanofibers adds a small mass which changes the natural frequency of the oscillation. By detecting the frequency shift due to adsorption of a given gas, the presence of the gas is detected, and by measuring the frequency shift, the amount of gas being adsorbed at a given pressure and temperature is quantified via the Sauerbrey equation [1]. A circuit has been developed to read the frequency shift due to the energy dissipation in the QCM coated with Polydimethylsiloxane (PDMS) nanofibers under the environment of several solvent vapors. The developed circuit includes two crystal oscillator circuits, two QCM’s which are respectively 1MHz reference QCM and a coated QCM, RC filter and AND gates. The results of the frequency shift between the reference QCM and the coated QCM were recorded on the oscilloscope so as to investigate the relationships between the frequency shift and the amount of vapor adsorbed for different gases. Ultimately, Volatile Organic Compounds (VOCs) are the target to be monitored and a MEMS based sensor will be developed similar to the present QCM gas sensor discussed herein. This work provides the feasibility study for using nanofiber coating to enhance the adsorbent specific area and a stand-alone QCM sensor for making measurement.

Electron and ion transport in gaseous methanol and water: density and temperature effects

1983 ◽  
Vol 61 (7) ◽  
pp. 1664-1670 ◽  
Author(s):  
Norman Gee ◽  
Gordon R. Freeman
Keyword(s):  
Water Vapor ◽  
Cross Section ◽  
Cross Sections ◽  
Saturated Vapor ◽  
Water Density ◽  
Saturated Water Vapor ◽  
Methanol Vapor ◽  
Flexible Molecules ◽  
Saturated Water ◽  
Gas Molecules

Electron and cation mobilities in methanol and water vapor measured at 293 ≤ T (K) ≤ 617 were used to estimate the corresponding momentum transfer cross sections. The electron cross sections correlate with the square of the dipole moment. Unlike the nonpolar gases, where the average cross section for electrons σavc.c is only 0.01–0.1 times that for cations σavc.+, methanol has σav.c ≈ 0.5σavc.+ and water has σavc.c ≈ σavc.+. The thermal electrons exchange energy with the molecules mainly through molecular rotational modes, as opposed to elastic modes.The onset of electron quasilocalization in the saturated vapor occurs at nql ≈ 5 × 1025 molecules/m3 (nql/nc = 0.010) in methanol and 3 × 1025 (nql/nc ≈ 0.003) in water. These are about 10-fold lower densities than in hydrocarbons, where nql/nc ≈ 0.1. The loffe–Regel limit for quasifree states gives nql ≈ 0.36 × (Tnμc)ql, which holds quite well when the gas molecules are relatively rigid. However, for flexible molecules such as the n-alkanes larger than propane, the loffe–Regal limit predicts too large values for nql.The density normalized mobility of cations nμ+ in saturated methanol vapor is constant at 1.02 × 1021 molecules/m V s up to 67 × 1025 molecules/m3 (25 Amagats). In saturated water vapor nμ+ = 1.87 × 1021 molecules/m V s up to 30 × 1025 molecules/m3 (11 Amagats).

scholarly journals The adsorption of non-polar gases on alkali halide crystals

1939 ◽  
Vol 173 (954) ◽  
pp. 349-367 ◽  
Keyword(s):  
Gas Phase ◽  
Three Dimensional ◽  
Adsorbed Layer ◽  
Partition Functions ◽  
Configurational Energy ◽  
Adsorbed Gas ◽  
The Difference ◽  
Gas Layer ◽  
Alkali Halide Crystals ◽  
Made In

In recent years many important theoretical advances have been made in the application of quantum statistics to adsorption problems. Fowler (1935), adopting the Langmuir picture of a monomolecular adsorbed gas layer, derived from purely statistical considerations the equation p = ( θ /1- θ ) ((2 πm ) 3/2 ( kT ) 5/2 )/ h 3 ( b g ( T )/ v s ( T ) e -x/kT , in which the undetermined constants of Langmuir’s original equation (1918) are given explicitly in terms of the partition functions, b g ( T ) and v s ( T ) belonging to atoms in the gas phase and in the adsorbed layer respectively and x , which is the difference in energy of an atom in the gas phase and in the lowest adsorption level on the surface. In subsequent developments the change in the energy of adsorption as a function of θ (the fraction of the surface covered) has been introduced in the above equation using ( a ) the Bragg and Williams approximations (Fowler 1936 a ) and ( b ) the Bethe method (Peierls 1936) to determine the configurational energy. Further applications and extensions of these methods to special adsorption problems have been carried through by Roberts (1937) and by Wang (1937), and Rushbrooke (1938) has examined the validity of the assumption, which is implicit in all this work, namely, that v s ( T ) is independent of the configuration. In addition, an approach to the solution of the statistical configuration problem when molecules condense in two layers simultaneously has recently been made by Cernuschi (1938) and developed by Dube (1938). In order to evaluate correctly the summations v s ( T ) occurring in equation (1), the Schrödinger equation for an atom moving in the three-dimensional potential field of the substrate should be solved, but this has so far proved prohibitively difficult. In the past it has been customary, and for practical purposes it is possibly generally sufficient, to substitute classical partition functions for these summations.

scholarly journals PENGARUH PENGGUNAAN PATI KULIT NANAS (Ananas comosus (L.) Merr.) SEBAGAI BAHAN PENGIKAT PADA GRANUL CTM

PHARMACON ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 203
Author(s):  
Tekla Kalalo ◽  
Paulina V. Y. Yamlean ◽  
Gayatri Citraningtyas
Keyword(s):  
Moisture Content ◽  
High Water ◽  
Flow Time ◽  
Angle Of Repose ◽  
Ananas Comosus ◽  
High Water Content ◽  
Wet Granulation ◽  
Water Density ◽  
Pineapple Peel ◽  
Binder Solution

ABSTRACTThe biggest component found in pineapple peel are water and starch. One of the excipient that usually used in granule is starch that can used as disintegrant, filler and binder. This study aims to formulate and evaluate granule preparations with Pineapple peel starch binder at concentration of 4%, 6%, 8% and 10%. The Pineapple peel dried with oven and then mashed up with blender and precipitated in water until obtained starch. The Pineapple peel starch made as a binder in four formulations of granule based on different concentrate of Pineapple peel starch, they are F I 4%, F II 6%, F III 8% and F IV 10%. The Granules made by method of wet granulation by adding binder solution of pineapple peel starch to four formulations, and then dried and evaluated. The result evaluation of organoleptic gave the best result in formula III and IV, flow time of each formula has time a flow time that not too far different, 5.04-5.57 seconds, angle of repose in formula I-IV meet the requirements and formed the smallest angle in formula I 28°, real density of each formula about 1.09-1.82 g/ml and meet the requirements because they are bigger than water density, while the moisture content and loss on drying doesn’t meet the requirements because has high water content. The conclusion is Pineapple peel starch can’t be used as a binder in CTM granule. Keywords : Pineapple, Starch, Binder, Granules, Wet Granulation ABSTRAKKomponen terbesar yang terdapat dalam kulit Nanas ialah air dan pati. Salah satu bahan tambahan yang sering digunakan dalam pembuatan granul ialah pati yang dapat berfungsi sebagai bahan penghancur, bahan pengisi dan bahan pengikat. Penelitian ini bertujuan untuk memformulasikan dan mengevaluasi sediaan granul CTM dengan bahan pengikat pati kulit Nanas pada konsentrasi 4%, 6%, 8% dan 10%. Kulit nanas dikeringkan dengan oven kemudian dihaluskan dengan blender dan diendapkan dalam air sampai diperoleh butiran pati. Pati kulit Nanas dibuat sebagai bahan pengikat pada empat formulasi granul berdasarkan konsentrasi pati kulit Nanas yang berbeda yaitu F I 4%, F II 6%, F III 8% dan F IV 10%. Granul dibuat dengan metode granulasi basah yaitu dengan menambahkan larutan pengikat pati kulit Nanas pada empat formulasi, kemudian dikeringkan dan dievaluasi. Hasil evaluasi organoleptis memberikan hasil terbaik pada formula III dan IV, waktu alir dari tiap formula memiliki waktu yang tidak jauh berbeda yaitu 5,04-5,57 detik, sudut diam pada formula I-IV memenuhi persyaratan dan membentuk sudut terkecil pada formula I yaitu 28°, BJ sejati dari tiap formula berkisar dari 1,09-1,82 g/ml sehingga memenuhi persyaratan karena lebih besar dari BJ air, porositas dari formulasi I-IV memenuhi persyaratan yang memiliki range 46%-67,4%, sedangkan pada kandungan lembab dan kadar air tidak memenuhi persyaratan karena memiliki kandungan air yang terlalu tinggi. Kesimpulannya pati kulit Nanas tidak dapat digunakan sebagai bahan pengikat pada granul CTM.Kata Kunci : Nanas, Pati, Bahan Pengikat, Granul, Granulasi Basah

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