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 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.

scholarly journals Water Structure in Proteins in Solid State Studied by Near Infrared Spectroscopy

2017 ◽  
Vol 735 ◽  
pp. 168-172
Author(s):  
Siraporn Soonthonhut ◽  
Alfred A. Christy
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Water Adsorption ◽  
Near Infrared ◽  
Free Water ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Combination Frequency ◽  
Adsorption Of Water ◽  
Combination Frequencies

Water adsorption in proteins is the crucial process of protein folding and structure stabilizing. Adsorption of water on proteins can be evaluated by near-infrared spectroscopy, a useful technique for observing combination frequency of a water molecule. In this work, albumin, lysozyme, and silk, were used as models for α-helix and β-pleated sheet proteins. Their NIR spectra during water adsorption process were measured by using an NIR spectrometer equipped with a transflectance accessory. Moreover, the quantitative adsorption of water was determined by gravimetric technique. The results indicate that, there are five different NIR absorptions arise from the OH combination frequencies of water adsorbed by albumin in the 5300-5100 cm-1 region. But there are only four absorptions for lysozyme and silk. The OH combination frequencies arising from water molecules in albumin indicate that it acquires free water molecules (5280 cm-1) and adsorbed water molecules through carbonyl-water interactions (5248 and 5160 cm-1) and amino-water interactions (5200 and 5120 cm-1). Interestingly, there is no indication for the presence of free water molecules in lysozyme and silk. Furthermore, the gravimetric results indicate that the rate of water adsorbed follows the order RW.Alb<RW.Lys<RW.Sil and total mass of water adsorbed per gram solid follows the order WAlb<WLys=WSil.

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.

scholarly journals The Nature of Rest Silanol Groups on the Surfaces of Silica Based Solid Phase Extraction Materials

2013 ◽  
Vol 650 ◽  
pp. 66-71 ◽  
Author(s):  
Alfred A. Christy
Keyword(s):  
Infrared Spectroscopy ◽  
Solid Phase Extraction ◽  
Silica Gel ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Solid Phase ◽  
Water Molecules ◽  
Phase Extraction ◽  
Modified Silica Gel ◽  
Silanol Groups

Chemically bonded solid phase materials are very important in separation chemistry. The chemically modified silica gel contains rest silanol groups that can affect the retention properties when they are used for separation of compounds. Some commercially available solid phase extraction (SPE) materials based on silica gel were analysed for rest silanol groups by near infrared spectroscopy. The combination frequency of the water molecules in the 5500- 5000 cm -1 region was used in identifying the nature of water molecules on the surface and the information was used to identify the types of silanol groups on the surface. Second derivative technique was employed in the detailed analysis. Nine different SPE materials including C18, C8, C6H5, NH2, OH, CN, SiOH, SA (SCX) and SB (SAX) were examined by near infrared spectroscopy for rest silanol groups. The results show that the non-polar and polar stationary phases contain vicinal silanol groups and the ion exchange solid phase materials contain free, vicinal and geminal silanol groups.

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.

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