scholarly journals Water Adsorption Properties of Free and Dehydrated β-Cyclodextrin Studied by near Infrared Spectroscopy and Gravimetry

2016 ◽  
Vol 689 ◽  
pp. 143-147 ◽  
Author(s):  
Alfred A. Christy
Keyword(s):  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Water Adsorption ◽  
Near Infrared ◽  
Adsorption Properties ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Near Infrared Spectra ◽  
Adsorption Of Water

β-cyclodextrin, like other carbohydrates has a tendency to adsorb water molecules and the properties are attributed to the hydroxyl groups in the molecules. β-cyclodextrin, the cyclic oligomer of glucose has a hydrophobic interior and hydrophilic exterior. The cyclic structure favours the formation of hydrogen bonds between the OH groups on the adjacent glucose units and affects the formation of hydrogen bonds with water molecules. The hydoxyl groups engaged in hydrogen bondings can be eliminated at high temperatures and the adsorption properties of the dehydrated β-cyclodextrin will depend on the new functional groups formed. The aim of the report is to discuss the issue of the water adsorption properties of free and dehydrated β-cyclodextrin. Dry β-cyclodextrin and dehydrated β-cyclodextrin at temperatures 250, 300 and 350 °C were allowed to adsorb water from a humidity controlled air environmennt and the evolving near infrared spectra were measured using a near infrared spectrometer equipped with a transflectance accessory. The near infrared spectra in the region 10,000-4000 cm-1 and their second and fourth derivative profiles were used in studying the variation in the adsorption characteristics of dehydrated β-cyclodextrin. The results of the analyses show that the adsorption of water by β-cyclodextrin decreses at 300 °C compared to 200 and 250 °C. Dehydration forms more of the ethereal type-O-bonds in the molecule and explains the decrease in the water molecular adsorption at higher dehydration temperatures.

Comparison of Water Adsorption Properties of Cellulose and Cellulose Nanocrystals Studied by Near-Infrared Spectroscopy and Gravimetry

2017 ◽  
Vol 735 ◽  
pp. 235-239 ◽  
Author(s):  
Thamonwan Angkuratipakorn ◽  
Jirada Singkhonrat ◽  
Alfred A. Christy
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Cellulose Nanocrystals ◽  
Water Adsorption ◽  
Near Infrared ◽  
Adsorption Properties ◽  
Water Molecules ◽  
Oh Groups ◽  
Adsorption Processes ◽  
Adsorption Of Water

The adsorption properties of water molecules on cellulose and cellulose nanocrystals (CNCs), isolated from defatted rice bran (DRB) by 55% sulfuric acid hydrolysis under sonication were investigated. The powdered samples of cellulose and CNCs were analysed by using near infrared spectroscopy (NIR) and gravimetry at 38% and 55% humidities. Small amounts of samples were dried under vacuum at 120°C and the NIR spectra of the dry samples and their spectra during the adsorption water molecules were measured by using an NIR spectrometer equipped with a transflectance accessory and a DTGS detector. The quantitative adsorption of water molecules by the samples was determined by gravimetry. Second and fourth derivative profiles of the NIR spectra were used in understanding the chemistry of adsorption of water molecules and the adsorption processes by the samples. The results show that the adsorption of water molecules by the cellulose samples gives rise to three prominent peaks that can be related to the water molecules engaged in hydrogen bonding with C2, C3 and C6-OH groups on the glucose units of the cellulose polymers. Furthermore, the cellulose nanocrystals adsorb twice as much of water as the cellulose polymer. It is also clear from the results that C2 and C3-OH groups in the glucose units adsorb water molecules at a faster rate than the C6-OH group and responsible for nearly 50% of the water adsorption.

scholarly journals Comparison of adsorption properties of commercial silica and rice husk ash (RHA) silica: A study by NIR spectroscopy

2021 ◽  
Vol 19 (1) ◽  
pp. 426-431
Author(s):  
Alfred A. Chirsty ◽  
Pathmanathan Sivarukshy
Keyword(s):  
Silica Gel ◽  
Rice Husk ◽  
Infrared Spectra ◽  
Near Infrared ◽  
Rice Husk Ash ◽  
Adsorption Properties ◽  
Water Molecules ◽  
Silanol Groups ◽  
Near Infrared Spectra ◽  
Adsorption Of Water

Abstract Adsorption properties of Silica gel (commercial silica), rice husk ash (RHA) silica, and their hydrothermally treated products towards water molecules were studied in this work. RHA silica was prepared by heating rice husk to 650°C for 4 h after pretreatment with hydrochloric acid. Portions of the samples of silica were evacuated at 200℃ and then allowed to adsorb water molecules from the surrounding air at either 42 or 50% humidity. The near infrared spectra of these samples were measured at different time intervals during their adsorption of water molecules. The evolved near infrared spectra were analyzed using second derivative techniques. Adsorption properties of these samples were further studied by gravimetric analysis. Surface functionalities and adsorption evolution of water molecules on silica samples studied showed that the adsorption of water molecules on commercial silica gel sample and RHA silica Samples takes place readily with hydrogen-bonded silanol groups on the surfaces of the samples. This adsorption arising from the OH stretching and bending vibrations of these water molecules gives rise to a band at 5,270 cm−1 in the near infrared region. The adsorbed water molecules then continue at the free silanol groups which is indicated by the absorption around 5,314 cm−1. The results clearly show that the silica made from rice husk adsorb water in the same manner as the commercial silica, but the quantity of water molecules adsorbed is less compared to commercial silica used in this experiment. However, the study clearly shows that the rice husk silica can replace the commercial silica as a substitute for desiccant purposes in industry.

scholarly journals Comparison of Water Adsorption Characteristics of Oligo and Polysaccharides of α-Glucose Studied by Near Infrared Spectroscopy

2014 ◽  
Vol 1035 ◽  
pp. 476-482 ◽  
Author(s):  
Alfred A. Christy
Keyword(s):  
Near Infrared ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Hydrogen Bond Formation ◽  
Oh Groups ◽  
Adsorption Characteristics ◽  
Near Infrared Spectra ◽  
Adsorption Of Water ◽  
Ethereal Oxygen ◽  
Combination Frequencies

The adsorption properties of water molecules on oligo and polysaccharides are attributed to the OH groups of the glucose rings in the molecules. The water molecules are adsorbed onto OH groups by hydrogen bond formation. Near infrared spectroscopic and gravimetric techniques were used in analysing the adsorption characteristics of malto-oligosaccharides and some polysaccharides. Near infrared spectra of the dry oligo and polysaccharides were acquired during the adsorption of water molecules at a relative humidity of 50-55%. The amounts of water adsorbed by the samples were also recorded by an analytical balance. Second derivative techniques were used in decomposing the OH combination frequencies of the adsorbed water molecules in the region 5300-5000 cm -1.The results indicate that the water molecules are adsorbed on to C2 and C3-OH groups at a higher rate compared to the adsorption onto C1-OH groups in the molecules. Adsorption also takes place onto the ethereal oxygen atoms in the glucose rings in malto-oligosaccarides. The gravimetric results show that the adsorption of water molecules increases with the number of glucose units in the malto-oligosaccharides except maltotriose which has the highest adsorption over a period of 75 minutes. Furthermore, the adsorption characteristics of amylose and amylopectin are similar.

Surface Functionality and Water Adsorption Studies of α-Aluminium (III) Oxide Nanoparticles by near Infrared Spectroscopy

2019 ◽  
Vol 803 ◽  
pp. 104-108
Author(s):  
Peraya Hiranmartsuwan ◽  
Natthaya Siangdee ◽  
Alfred A. Christy
Keyword(s):  
Water Adsorption ◽  
Near Infrared ◽  
Free Water ◽  
Oxide Surface ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Second Derivative ◽  
Gravimetric Analysis ◽  
Nanoparticle Surface ◽  
Adsorption Of Water

The adsorption of water on aluminium (III) oxide nanoparticle surface was studied by near infrared (NIR) spectroscopy. The comparison of NIR spectra at 40% and 60% humidity were reported in this work and were analyzed using second derivative techniques. The second derivative spectra were used to understand the chemistry of adsorption of water molecules. Small amounts of samples were dried under vacuum at 230 °C before the analysis. The analysis of the spectra confirms the presence of three different hydroxyl groups on aluminium (III) oxide surface. The spectra acquired during the adsorption of water molecules show the characteristic peaks in the range of 5400-5100 cm-1 corresponding to the combination band of water molecules hydrogen bonded with hydroxyl groups. There is also evidence for the presence of free water in the bulk of aluminium oxide. Furthermore, the mass of water adsorption on Al2O3 nanoparticle surface have been determined by gravimetric analysis. The gravimetric analysis confirms the adsorption of water molecules by aluminium (III) oxide surface.

Analysis of Water Adsorption on Chitosan and Its Blends with Hydroxypropylcellulose

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Maria Mucha ◽  
Kazimierz Wańkowicz ◽  
Jacek Balcerzak
Keyword(s):  
Hydrogen Bonds ◽  
Thermodynamic Parameter ◽  
Solid Surface ◽  
Mass Fraction ◽  
Water Adsorption ◽  
Vapour Phase ◽  
Heat Of Adsorption ◽  
Water Molecules ◽  
Monomolecular Layer ◽  
Adsorption Of Water

AbstractChitosan (CH) and hydroxypropylcellulose (HPC) adsorb water easily by hydrogen bonds formed with hydroxyl and amide groups present in their structures. Heat of adsorption is a thermodynamic parameter which is used to estimate the type of adsorbate molecule bond on a solid surface, among the others. Adsorption of water from vapour phase on chitosan, hydroxypropylcellulose and blends of both biopolymers in the form of films were carried out. Isotherms of water adsorption in the samples were described by the GAB equation. Correlations between mass fraction of chitosan in the sample (wf) and the values of GAB coefficients were obtained. From parameter c in the GAB equation mean heat of adsorption of the first monomolecular layer of water molecules E1, and pure molar heat of adsorption q were determined.

scholarly journals The Nature of Silanol Groups on the Surfaces of Silica, Modified Silica and Some Silica Based Materials

2014 ◽  
Vol 998-999 ◽  
pp. 3-10 ◽  
Author(s):  
Alfred A. Christy
Keyword(s):  
Silica Gel ◽  
Near Infrared ◽  
Water Molecules ◽  
Modified Silica ◽  
Near Infrared Reflectance ◽  
Modified Silica Gel ◽  
Silanol Groups ◽  
Near Infrared Spectra ◽  
Chemically Modified Silica ◽  
Adsorption Of Water

Silica gel, a material that is produced from the condensation polymerisation of silicic acid, contains surface silanol groups formed during the condensation. The silanol groups on the surface are mostly of free and vicinal silanol groups. These silanol groups can be modified in several different ways. Thermal treatment and hydrothermal treatment can be carried out to alter the concentration proportions between free and hydrogen bonded silanol groups on the surface. They can also be chemically treated with suitable chlorosilanes to modify the silanol groups into polar or non polar materials that can be used in separation science.This article explores the chemical nature of silanol groups on the surfaces of different materials. Near infrared reflectance spectroscopy was used as the instrumental technique in this study. The silanol groups classifications were made by analyzing the near infrared spectra obtained during the adsorption of water molecules. Absorption of the combination frequencies of water molecules in the region 5500- 5000 cm-1were used in characterizing the silanol groups on the surfaces. Second derivative technique was employed in the resolution and detailed analysis of these absorptions.The study reveals that the materials contain free, vicinal and gem silanol groups. Silica gel contains free and vicinal silanol groups, thermally treated silica gel contains fewer vicinal silanol groups compared to the base silica gel, and hydrothermally treated silica gel contains higher concentrations of vicinal silanol groups compared to the base silica gel. Furthermore, the chemically modified silica gel contains vicinal or geminal silanol groups depending on the type of functionality introduced.

Near Infrared Spectroscopic Examination of Charred Pine Wood, Bark, Cellulose and Lignin: Implications for the Quantitative Determination of Charcoal in Soils

2007 ◽  
Vol 15 (5) ◽  
pp. 307-315 ◽  
Author(s):  
James B. Reeves ◽  
Gregory W. McCarty ◽  
David W. Rutherford ◽  
Robert L. Wershaw
Keyword(s):  
Carboxylic Acids ◽  
Infrared Spectra ◽  
Near Infrared ◽  
Direct Determination ◽  
Pine Wood ◽  
Oh Groups ◽  
Spectral Changes ◽  
Near Infrared Spectra ◽  
Material Temperature

The objective of this research was to investigate the effect of charring on near infrared spectra of materials likely to be present in forest fires in order to determine the feasibility of determining charred carbon in soils. Four materials (cellulose, lignin, pine bark and pine wood) and char from these materials created by charring for various durations (1 to 168 h) and at various temperatures (200 to 450°C) were studied. Near infrared spectra and measures of acidity (total acids, carboxylic acids, lactones and phenols as determined by titration) were available for 56 different samples (Not all samples charred at all temperatures/durations). Results showed spectral changes that varied with the material, temperature and duration of charring. Examination of spectra and correlation plots indicated that changes in the constituents of the materials in question, such as loss of OH groups in carbohydrates, rather than direct determination of typical products produced by charring, such as carboxylic acids, lactones and phenols, were the basis for the spectral changes. Finally, while the spectral changes resulting from charring appeared to be relatively unique to each material, PLS calibrations for total acids, carboxylic acids, lactones and phenols were successfully created (with R2 of 0.991, 0.943, 0.931 and 0.944, respectively) indicating that there is a sufficient commonality in the changes to develop calibrations without the need for unique calibrations for each specific set of charring conditions (i.e. material, temperature and time of heating).

scholarly journals Discrimination of mineral waters using near infrared spectroscopy and aquaphotomics

2014 ◽  
Vol 68 (2) ◽  
pp. 257-264 ◽  
Author(s):  
Jelena Muncan ◽  
Lidija Matija ◽  
Jovana Simic-Krstic ◽  
Srecko Nijemcevic ◽  
Djuro Koruga
Keyword(s):  
Infrared Spectra ◽  
Near Infrared ◽  
Dynamic Properties ◽  
Mineral Waters ◽  
Molecular Organization ◽  
Human Organism ◽  
Water Molecules ◽  
Near Infrared Spectra ◽  
Healthy Functioning

Despite that water is one of the most studied materials today its dynamic properties are still not well understood. Water state in human organism is of high importance for normal healthy functioning of human body. Different kinds of water are usually classified according to its present solutes, and concentrations of these solutes, but though it is known that water molecules can form clusters around present solutes, classification of waters based on types of water molecular organization and present clusters is not present in current literature. In this study we used multivariate analysis for classification of commercial mineral waters based on their near infrared spectra (NIR). Further, we applied Aquaphotomics, a new approach for interpretation of near infrared spectra of water, which gives insight into organization of water molecules in each of these waters.

scholarly journals Porous Si Partially Filled with Water Molecules—Crystal Structure, Energy Bands and Optical Properties from First Principles

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 396
Author(s):  
Ya. Shchur ◽  
O. Pavlyuk ◽  
A.S. Andrushchak ◽  
S. Vitusevich ◽  
A.V. Kityk
Keyword(s):  
Optical Properties ◽  
Hydrogen Bonds ◽  
First Principles ◽  
Energy Band ◽  
Visible Range ◽  
Band Spectrum ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Porous Si ◽  
Oh Groups

The paper reports the results on first-principles investigation of energy band spectrum and optical properties of bulk and nanoporous silicon. We present the evolution of energy band-gap, refractive indices and extinction coefficients going from the bulk Si of cubic symmetry to porous Si with periodically ordered square-shaped pores of 7.34, 11.26 and 15.40 Å width. We consider two natural processes observed in practice, the hydroxylation of Si pores (introduction of OH groups into pores) and the penetration of water molecules into Si pores, as well as their impact on the electronic spectrum and optical properties of Si superstructures. The penetration of OH groups into the pores of the smallest 7.34 Å width causes a disintegration of hydroxyl groups and forms non-bonded protons which might be a reason for proton conductivity of porous Si. The porosity of silicon increases the extinction coefficient, k, in the visible range of the spectrum. The water structuring in pores of various diameters is analysed in detail. By using the bond valence sum approach we demonstrate that the types and geometry of most of hydrogen bonds created within the pores manifest a structural evolution from distorted hydrogen bonds inherent to small pores (∼7 Å) to typical hydrogen bonds observed by us in larger pores (∼15 Å) which are consistent with those observed in a wide database of inorganic crystals.

Near-infrared spectra of Ba(NO2)2•X2O (X = H,D) at 10 K. A local-mode approach

1997 ◽  
Vol 75 (8) ◽  
pp. 1099-1105 ◽  
Author(s):  
Ian M. Walker ◽  
Paul J. McCarthy
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Near Infrared ◽  
Fermi Resonance ◽  
Strong Hydrogen Bond ◽  
Local Mode ◽  
Morse Oscillator ◽  
Near Infrared Spectra ◽  
Bifurcated Hydrogen Bond

The fundamental and overtone vibrational spectra of Ba(NO2)2•X2O (X=H,D) have been interpreted using the local mode model. The calculated parameters are consistent with the structure, which has one strong hydrogen bond and one weak bifurcated hydrogen bond. Evidence for Fermi resonance between stretch and bend features having similar energies is discussed. Evidence for the breakdown of the simple Morse oscillator model, which was quite successful for [Formula: see text] hydrogen bonds, is also presented. Keywords: overtone, spectra, near-infrared, hydrates, local-mode model.

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