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Dr. Umesh Agarwal
Fiber and Chemical Sciences Research, USDA FS, Forest Products Laboratory,1 Gifford Pinchot Drive Madison, WI, 53726-2398, USA

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Research Keywords & Expertise

0 Raman Spectroscopy
0 plant cell wall
0 Cellulose nanomaterials
0 Understanding roles of lignin and cellulose-crystallinity in the enzyme hydrolysis of wood
0 Wood cell wall nanostructure

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Original research
Published: 13 August 2021 in Cellulose
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In cellulose materials, the cellulose II allomorph is often present either exclusively or in conjunction with cellulose I, the natural cellulose. Moreover, in regenerated and mercerized fibers (e,g., lyocell and viscose), natural cellulose adopts to the crystal structure cellulose II. Therefore, its detection and quantitation are important for a complete assessment of such materials investigations. In the Raman spectra of such materials, a band at 577 cm−1 is typically observed indicating the presence of this allomorph. In the present study, to quantify the content of cellulose II, a calibration method was developed based on the intensity of the 577 cm−1 peak relative to the 1096 cm−1 band of cellulose. For this purpose, in addition to pure cellulose I and cellulose II samples (respectively, Avicel PH-101 and mercerized Avicel PH-101; hence referred to as Avicel I and Avicel II), a set of five samples were produced by mixing them in known quantities of Avicel I and Avicel II. The crystalline cellulose II contents of the samples were calculated based on the X-ray crystallinity of mercerized Avicel I. These seven samples were included in the calibration set and their Raman spectra were obtained. Subsequently, Raman intensity ratios I577/I1096 were calculated by taking ratios of peak intensities at 577 and 1096 cm−1. These ratios were plotted against the % of crystalline cellulose II present in the calibration set samples and the two were found to be linearly correlated (R2 = 0.9944). The set-samples were also analyzed using XRD which were then compared with the Raman method developed here. Compared to XRD, the Raman method was found to be more sensitive at detecting and quantifying cellulose II. Additionally, several cellulose II containing materials were analyzed by the new Raman method.

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner. Detection and quantitation of cellulose II by Raman spectroscopy. Cellulose 2021, 1 -11.

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Carlos Baez, Richard S. Reiner. Detection and quantitation of cellulose II by Raman spectroscopy. Cellulose. 2021; ():1-11.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner. 2021. "Detection and quantitation of cellulose II by Raman spectroscopy." Cellulose , no. : 1-11.

Preprint content
Published: 28 June 2021
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In cellulose materials, the cellulose II polymorph is often present either exclusively or inconjunction with cellulose I, the natural cellulose. Moreover, in regenerated andmercerized fibers (e,g., viscose and lyocell), natural cellulose adopts to the crystalstructure cellulose II Therefore, its detection and quantitation are important for acomplete assessment of such materials investigations. In the Raman spectra of suchmaterials, a band at 577 cm -1 is typically observed indicating the presence of thispolymorph. In the present study, to quantify the content of cellulose II, a calibrationmethod was developed based on the intensity of the 577 cm -1 peak relative to the1096 cm -1 band of cellulose. For this purpose, in addition to pure cellulose I andcellulose II samples (respectively, Avicel PH-101 and mercerized Avicel PH-101; hencereferred to as Avicel I and Avicel II), a set of five samples were produced by mixingthem in known quantities of Avicel I and Avicel II. The crystalline cellulose II contents ofthe samples were calculated based on the X-ray crystallinity of mercerized Avicel I.These seven samples were included in the calibration set and their Raman spectrawere obtained. Subsequently, Raman intensity ratios I 577 /I 1096 were calculatedby taking ratios of peak intensities at 577 and 1096 cm -1 . These ratios were plottedagainst the % of crystalline cellulose II present in the calibration set samples and thetwo were found to be linearly correlated (R 2 = 0.9944). The set-samples were alsoanalyzed using XRD which were then compared with the Raman method developedhere. Compared to XRD, the Raman method was found to be more sensitive atdetecting and quantifying cellulose II. Additionally, several cellulose II containingmaterials were analyzed by the new Raman method.

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner. Detection and quantitation of cellulose II by Raman spectroscopy. 2021, 1 .

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Carlos Baez, Richard S. Reiner. Detection and quantitation of cellulose II by Raman spectroscopy. . 2021; ():1.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner. 2021. "Detection and quantitation of cellulose II by Raman spectroscopy." , no. : 1.

Research article
Published: 26 March 2021 in Biomacromolecules
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Aggregated states of celluloses remain poorly understood, and therefore, the topic requires careful investigation. In this study, Raman, IR, and X-ray diffraction (XRDs) were used to study cotton microcrystalline cellulose (MCC) and MCC that has been ball-milled to various degrees. Raman and IR spectroscopy methods indicated that when these ball-milled samples were wet with water, most underwent conformational changes at the molecular level. Although formation of cellulose II was observed in longer duration ball-milled samples, the changes primarily gave rise to increased contributions in spectral and diffraction regions typically associated with the contributions of crystalline cellulose I. Moreover, when the wet samples were air-dried at 25 °C, the newly formed cellulose I-like structures partly reverted to the previous form present in the initial dry state. These findings explained for the previously reported XRD and NMR observations, where the addition of water resulted in increased crystallinities of cellulose samples. The implications of these findings to cellulose crystallinity measurements and other situations are discussed.

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner. Contributions of Crystalline and Noncrystalline Cellulose Can Occur in the Same Spectral Regions: Evidence Based on Raman and IR and Its Implication for Crystallinity Measurements. Biomacromolecules 2021, 22, 1357 -1373.

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Carlos Baez, Richard S. Reiner. Contributions of Crystalline and Noncrystalline Cellulose Can Occur in the Same Spectral Regions: Evidence Based on Raman and IR and Its Implication for Crystallinity Measurements. Biomacromolecules. 2021; 22 (4):1357-1373.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner. 2021. "Contributions of Crystalline and Noncrystalline Cellulose Can Occur in the Same Spectral Regions: Evidence Based on Raman and IR and Its Implication for Crystallinity Measurements." Biomacromolecules 22, no. 4: 1357-1373.

Original research
Published: 06 January 2021 in Cellulose
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Properties of cellulose nanocrystals (CNCs) depend upon their supramolecular structures, which are important to understand in order to optimize their applications. In this investigation, the structures of CNCs produced upon 48–64% H2SO4 hydrolysis of hydrothermally-treated poplar, bleached kraft pulp, cotton microcrystalline cellulose, bacterial cellulose, tunicin, and cladophora cellulose were comparatively analyzed. TEM provided information on the morphological aspects. Raman, MAS-NMR, and XRD provided information on one aspect of the supramolecular organization, namely, crystallinity (CrI). Other characteristics of supramolecular structure were analyzed by various Raman methods, namely, accessibility to water, exocyclic CH2OH conformation ratio, and chain conformation disorder (CCONDIS)—the last method was developed in the present study. In general, CNCs retained the crystallinity of the starting material irrespective of the measurement method of CrI. Additionally, it was found that crystallite size and supramolecular organization influenced CrI as well. These analyses further indicated that poplar- and pulp-CNCs had significantly higher water accessibility as compared with CNCs from cladophora, bacterial, tunicin, and cotton MCC CNCs, implying higher molecular disorder, which was also reflected in measurements of CH2OH conformation ratio and CCONDIS. The findings indicate that significant differences among the CNCs seem to arise largely from differences between the starting materials. Additionally, considering that CNCs can have very different morphologies and structural properties depending upon how they are produced, the analyses carried out here can characterize such CNCs and estimate their applications.

ACS Style

Umesh P. Agarwal; Richard S. Reiner; Sally A. Ralph; Jeffery Catchmark; Kai Chi; E. Johan Foster; Christopher G. Hunt; Carlos Baez; Rebecca E. Ibach; Kolby C. Hirth. Characterization of the supramolecular structures of cellulose nanocrystals of different origins. Cellulose 2021, 28, 1369 -1385.

AMA Style

Umesh P. Agarwal, Richard S. Reiner, Sally A. Ralph, Jeffery Catchmark, Kai Chi, E. Johan Foster, Christopher G. Hunt, Carlos Baez, Rebecca E. Ibach, Kolby C. Hirth. Characterization of the supramolecular structures of cellulose nanocrystals of different origins. Cellulose. 2021; 28 (3):1369-1385.

Chicago/Turabian Style

Umesh P. Agarwal; Richard S. Reiner; Sally A. Ralph; Jeffery Catchmark; Kai Chi; E. Johan Foster; Christopher G. Hunt; Carlos Baez; Rebecca E. Ibach; Kolby C. Hirth. 2021. "Characterization of the supramolecular structures of cellulose nanocrystals of different origins." Cellulose 28, no. 3: 1369-1385.

Review
Published: 27 April 2019 in Molecules
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This review is a summary of the Raman spectroscopy applications made over the last 10 years in the field of cellulose and lignocellulose materials. This paper functions as a status report on the kinds of information that can be generated by applying Raman spectroscopy. The information in the review is taken from the published papers and author’s own research—most of which is in print. Although, at the molecular level, focus of the investigations has been on cellulose and lignin, hemicelluloses have also received some attention. The progress over the last decade in applying Raman spectroscopy is a direct consequence of the technical advances in the field of Raman spectroscopy, in particular, the application of new Raman techniques (e.g., Raman imaging and coherent anti-Stokes Raman or CARS), novel ways of spectral analysis, and quantum chemical calculations. On the basis of this analysis, it is clear that Raman spectroscopy continues to play an important role in the field of cellulose and lignocellulose research across a wide range of areas and applications, and thereby provides useful information at the molecular level.

ACS Style

Umesh P. Agarwal. Analysis of Cellulose and Lignocellulose Materials by Raman Spectroscopy: A Review of the Current Status. Molecules 2019, 24, 1659 .

AMA Style

Umesh P. Agarwal. Analysis of Cellulose and Lignocellulose Materials by Raman Spectroscopy: A Review of the Current Status. Molecules. 2019; 24 (9):1659.

Chicago/Turabian Style

Umesh P. Agarwal. 2019. "Analysis of Cellulose and Lignocellulose Materials by Raman Spectroscopy: A Review of the Current Status." Molecules 24, no. 9: 1659.

Evaluation study
Published: 25 March 2019 in Journal of Agricultural and Food Chemistry
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Syringyl (S) lignin content and syringyl-to-guaiacyl (S/G) lignin ratio are important characteristics of wood and lignocellulosic biomass. Although numerous methods are available for estimating S lignin units and S/G ratio, in this work, a new method based on Raman spectroscopy that uses the 370 cm-1 Raman band-area intensity (370-area) was developed. The reliability of the Raman approach for determining S content was first tested by the quantitative analysis of three syringyl lignin models by sampling them, separately, in dioxane and in Avicel. Good linear correlations between the 370 cm-1 intensity and model concentrations were obtained. Next, the %S lignin units in various woods were measured by correlating the 370 cm-1 Raman intensity data with values of S units in lignin determined by three regularly used methods – thioacidolysis, DFRC, and 2D-HSQC NMR. The former two methods take into account only the monomers cleaved from β–O–4-linked lignin units whereas the NMR method reports S content on the whole cell wall lignin. When the 370-area intensities and %S values from the regularly used methods were correlated, good linear correlations were obtained (R2 = 0.767, 0.731, and 0.804, respectively, for the three methods). The correlation with the highest R2, i.e., with the 2D NMR method, is being proposed for estimating S units in wood lignins by Raman spectroscopy as, in principle, both represent of the whole cell wall lignin and not just the portion of lignin that gets cleaved to release monomers. The Raman analysis method is quick, uses minimal harmful chemicals, carried out nondestructively, and is insensitive to the wet or dry state of the sample. The only limitations are that a sample of wood contain at least 30% S and not be significantly fluorescent, although the latter can be mitigated in some cases.

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Dharshana Padmakshan; Sarah Liu; Clifton Eldridge Foster. Estimation of Syringyl Units in Wood Lignins by FT-Raman Spectroscopy. Journal of Agricultural and Food Chemistry 2019, 67, 4367 -4374.

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Dharshana Padmakshan, Sarah Liu, Clifton Eldridge Foster. Estimation of Syringyl Units in Wood Lignins by FT-Raman Spectroscopy. Journal of Agricultural and Food Chemistry. 2019; 67 (15):4367-4374.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Dharshana Padmakshan; Sarah Liu; Clifton Eldridge Foster. 2019. "Estimation of Syringyl Units in Wood Lignins by FT-Raman Spectroscopy." Journal of Agricultural and Food Chemistry 67, no. 15: 4367-4374.

Original paper
Published: 18 August 2018 in Cellulose
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A new method is described for producing high-lignin-containing and lignin-free cellulose nanocrystals from poplar wood (HLCNCs and LFCNCs, respectively). This was accomplished by first hydrothermally treating the poplar wood fibers at 170 °C for 45 min in a Parr reactor. For obtaining HLCNCs, the treated fibers were directly hydrolyzed by 64% sulfuric acid whereas for LFCNCs, the fibers were delignified prior to the acid hydrolysis. The CNCs thus produced were characterized using spectroscopy, microscopy, and diffraction techniques and compared with bleached kraft pulp-CNCs. The comparison indicated that while LFCNCs and pulp-CNCs had similar properties, the HLCNCs are expected to be superior for certain applications due to their hydrophobicity that was caused by presence of lignin nanoparticles. Lastly, results of the experiment where treatment temperature was varied during the hydrothermal treatment indicated that crystallinity of the CNCs produced from 200 °C treated poplar was higher compared to 170 °C treated substrate. This implied that CNCs from wood can be produced that have varying degree of crystallinity.

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Christopher Hunt; Carlos Baez; Rebecca Ibach; Kolby C. Hirth. Production of high lignin-containing and lignin-free cellulose nanocrystals from wood. Cellulose 2018, 25, 5791 -5805.

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Richard S. Reiner, Christopher Hunt, Carlos Baez, Rebecca Ibach, Kolby C. Hirth. Production of high lignin-containing and lignin-free cellulose nanocrystals from wood. Cellulose. 2018; 25 (10):5791-5805.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Christopher Hunt; Carlos Baez; Rebecca Ibach; Kolby C. Hirth. 2018. "Production of high lignin-containing and lignin-free cellulose nanocrystals from wood." Cellulose 25, no. 10: 5791-5805.

Journal article
Published: 01 June 2018 in Carbohydrate Polymers
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A new method is proposed for estimation of cellulose crystallinity (CrI) based on 93 cm Raman band in spectra of cellulose I materials. In this method (93-Raman), CrI was determined based on regression that was developed using the ratios of peak-heights of the 93 and 1096 cm Raman bands (I/I). For calibration purposes, a set of eight samples, all derived from cotton microcrystalline cellulose Whatman CC31 were selected. When the peak intensity ratios (I/I) were plotted against the calculated CrIs of the calibration set samples, the plot showed an excellent linear correlation (R = 0.9888). The 93-Raman method was used to estimate crystallinities of a number of cellulose materials including poplar wood samples that were hydrothermally treated at various temperatures. The wood 93-Raman CrI data showed that the method is able to differentiate between organized and crystalline phases of cellulose, a capability lacking in many other CrI estimation methods.

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Carlos Baez. New cellulose crystallinity estimation method that differentiates between organized and crystalline phases. Carbohydrate Polymers 2018, 190, 262 -270.

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Richard S. Reiner, Carlos Baez. New cellulose crystallinity estimation method that differentiates between organized and crystalline phases. Carbohydrate Polymers. 2018; 190 ():262-270.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Carlos Baez. 2018. "New cellulose crystallinity estimation method that differentiates between organized and crystalline phases." Carbohydrate Polymers 190, no. : 262-270.

Journals
Published: 16 April 2018 in Chemical Society Reviews
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Reliable characterization of cellulose nanomaterials is critical for their utilization in various applications.

ACS Style

E. Johan Foster; Robert J. Moon; Umesh P. Agarwal; Michael J. Bortner; Julien Bras; Sandra Camarero-Espinosa; Kathleen J. Chan; Martin J. D. Clift; Emily D. Cranston; Stephen J. Eichhorn; Douglas M. Fox; Wadood Y. Hamad; Laurent Heux; Bruno Jean; Matthew Korey; World Nieh; Kimberly J. Ong; Michael S. Reid; Scott Renneckar; Rose Roberts; Jo Anne Shatkin; John Simonsen; Kelly Stinson-Bagby; Nandula Wanasekara; Jeffrey Youngblood. Current characterization methods for cellulose nanomaterials. Chemical Society Reviews 2018, 47, 2609 -2679.

AMA Style

E. Johan Foster, Robert J. Moon, Umesh P. Agarwal, Michael J. Bortner, Julien Bras, Sandra Camarero-Espinosa, Kathleen J. Chan, Martin J. D. Clift, Emily D. Cranston, Stephen J. Eichhorn, Douglas M. Fox, Wadood Y. Hamad, Laurent Heux, Bruno Jean, Matthew Korey, World Nieh, Kimberly J. Ong, Michael S. Reid, Scott Renneckar, Rose Roberts, Jo Anne Shatkin, John Simonsen, Kelly Stinson-Bagby, Nandula Wanasekara, Jeffrey Youngblood. Current characterization methods for cellulose nanomaterials. Chemical Society Reviews. 2018; 47 (8):2609-2679.

Chicago/Turabian Style

E. Johan Foster; Robert J. Moon; Umesh P. Agarwal; Michael J. Bortner; Julien Bras; Sandra Camarero-Espinosa; Kathleen J. Chan; Martin J. D. Clift; Emily D. Cranston; Stephen J. Eichhorn; Douglas M. Fox; Wadood Y. Hamad; Laurent Heux; Bruno Jean; Matthew Korey; World Nieh; Kimberly J. Ong; Michael S. Reid; Scott Renneckar; Rose Roberts; Jo Anne Shatkin; John Simonsen; Kelly Stinson-Bagby; Nandula Wanasekara; Jeffrey Youngblood. 2018. "Current characterization methods for cellulose nanomaterials." Chemical Society Reviews 47, no. 8: 2609-2679.

Journal article
Published: 01 January 2018 in Polymer
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ACS Style

Liqing Wei; Umesh P. Agarwal; Laurent Matuana; Ronald C. Sabo; Nicole M. Stark. Performance of high lignin content cellulose nanocrystals in poly(lactic acid). Polymer 2018, 135, 305 -313.

AMA Style

Liqing Wei, Umesh P. Agarwal, Laurent Matuana, Ronald C. Sabo, Nicole M. Stark. Performance of high lignin content cellulose nanocrystals in poly(lactic acid). Polymer. 2018; 135 ():305-313.

Chicago/Turabian Style

Liqing Wei; Umesh P. Agarwal; Laurent Matuana; Ronald C. Sabo; Nicole M. Stark. 2018. "Performance of high lignin content cellulose nanocrystals in poly(lactic acid)." Polymer 135, no. : 305-313.

Journal article
Published: 14 October 2017 in Journal of Renewable Materials
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ACS Style

Liqing Wei; Shupin Luo; Armando G. McDonald; Umesh P. Agarwal; Kolby C. Hirth; Laurent M. Matuana; Ronald C. Sabo; Nicole M. Stark. Preparation and Characterization of the Nanocomposites from Chemically Modified Nanocellulose and Poly(lactic acid). Journal of Renewable Materials 2017, 5, 410 -422.

AMA Style

Liqing Wei, Shupin Luo, Armando G. McDonald, Umesh P. Agarwal, Kolby C. Hirth, Laurent M. Matuana, Ronald C. Sabo, Nicole M. Stark. Preparation and Characterization of the Nanocomposites from Chemically Modified Nanocellulose and Poly(lactic acid). Journal of Renewable Materials. 2017; 5 (5):410-422.

Chicago/Turabian Style

Liqing Wei; Shupin Luo; Armando G. McDonald; Umesh P. Agarwal; Kolby C. Hirth; Laurent M. Matuana; Ronald C. Sabo; Nicole M. Stark. 2017. "Preparation and Characterization of the Nanocomposites from Chemically Modified Nanocellulose and Poly(lactic acid)." Journal of Renewable Materials 5, no. 5: 410-422.

Original paper
Published: 18 March 2017 in Cellulose
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Although X-ray diffraction (XRD) has been the most widely used technique to investigate crystallinity index (CrI) and crystallite size (L200) of cellulose materials, there are not many studies that have taken into account the role of sample moisture on these measurements. The present investigation focuses on a variety of celluloses and cellulose containing materials—from loblolly pine wood to tunicin, and evaluated moisture-induced changes in CrI and L200. It was observed that upon introduction of a small amount of water (5%) into P2O5 dried samples, for most samples, both absolute intensity of (200) reflection and its full width at half maximum declined. Moreover, (200) peak position (2θ max) increased when the samples became moist. Although the extent of such changes were material dependent, in general, a greater degree of change was associated with lower sample CrI. For CrI, maximum and minimum increases occurred for oven dried NaOH treated red pine holopulp and tunicin, respectively. For L200, maximum and minimum increases were for wood and tunicin, respectively. Moreover, 2θ max position for (200) reflection increased most for the wood and oven dried NaOH treated red pine holopulp (acid chlorite delignified milled-wood) and least for tunicin. The nonparametric statistical test “sign test” further supported these results. Observations from longer duration drying experiments, post moistening, indicated that the changes to the XRD parameters were reversible to some degree. Based on the findings it is concluded that for most cellulose materials with Segal CrI < 90% the moisture content has a significant bearing on the XRD-estimated CrI and L200 data. Consequently, it is essential that when such materials are compared, their diffractograms should be obtained under similar levels of sample moisture content.

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner; Steve P. Verrill. Effect of sample moisture content on XRD-estimated cellulose crystallinity index and crystallite size. Cellulose 2017, 24, 1971 -1984.

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Carlos Baez, Richard S. Reiner, Steve P. Verrill. Effect of sample moisture content on XRD-estimated cellulose crystallinity index and crystallite size. Cellulose. 2017; 24 (5):1971-1984.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner; Steve P. Verrill. 2017. "Effect of sample moisture content on XRD-estimated cellulose crystallinity index and crystallite size." Cellulose 24, no. 5: 1971-1984.

Book chapter
Published: 01 January 2017 in ACS Symposium Series
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Native celluloses in plant cell walls occur in a variety of highly periodic fibrillar forms that have curvature and varying degrees of twist about their longitudinal axes. Though X-ray measurements reveal diffraction patterns, the celluloses are not crystalline in the traditional sense. The diffraction patterns rather are a consequence of the high degree of spatial periodicity inherent in the fibrils and in their hierarchic organization at different levels in the cell walls. Upon dehydration and exposure to elevated temperatures, the fibrils tend to collapse into linearly parallel structures that are not unlike traditional crystals. However, in alleviating the inherent twist of the fibrils during formation of linear domains, less tightly ordered terminal points are formed at the connection between adjacent linear domains. These domains are less tightly aggregated than the linear domains between which they occur, and are therefore more readily accessible to hydrolytic agents than the tightly aggregated linear domains between which they occur. Hydrolysis at the less tightly aggregated points transforms the tightly aggregated linear domains between them into nanocellulose particles. In consequence nanocelluloses isolated from different native forms, are likely to have structures that are as much a function of the isolation history as they are of the native source. We present data reflecting the effects of different thermal histories on the states of aggregation of cellulose. We also present data that confirm a previously proposed model, which we believe to be representative of nanoscale transformations of higher plant celluloses that occur upon dehydration and exposure to elevated temperatures. We anticipate that they provide a basis for understanding observations made upon preparation of nanocelluloses from higher plant tissues.

ACS Style

Rajai H. Atalla; Rowan S. Atalla; Umesh P. Agarwal. The Nanostructures of Native Celluloses, Their Transformations upon Isolation, and Their Implications for Production of Nanocelluloses. ACS Symposium Series 2017, 1 -18.

AMA Style

Rajai H. Atalla, Rowan S. Atalla, Umesh P. Agarwal. The Nanostructures of Native Celluloses, Their Transformations upon Isolation, and Their Implications for Production of Nanocelluloses. ACS Symposium Series. 2017; ():1-18.

Chicago/Turabian Style

Rajai H. Atalla; Rowan S. Atalla; Umesh P. Agarwal. 2017. "The Nanostructures of Native Celluloses, Their Transformations upon Isolation, and Their Implications for Production of Nanocelluloses." ACS Symposium Series , no. : 1-18.

Book chapter
Published: 01 January 2017 in ACS Symposium Series
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ACS Style

Umesh P. Agarwal; Rajai H. Atalla; Akira Isogai. Preface. ACS Symposium Series 2017, 1 .

AMA Style

Umesh P. Agarwal, Rajai H. Atalla, Akira Isogai. Preface. ACS Symposium Series. 2017; ():1.

Chicago/Turabian Style

Umesh P. Agarwal; Rajai H. Atalla; Akira Isogai. 2017. "Preface." ACS Symposium Series , no. : 1.

Book chapter
Published: 01 January 2017 in ACS Symposium Series
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Cellulose nanomaterials (CNs) are new types of materials derived from celluloses and offer unique challenges and opportunities for Raman spectroscopic investigations. CNs can be classified into the categories of cellulose nanocrystals (CNCs, also known as cellulose whisker) and cellulose nanofibrils (CNFs, also known as nanofibrillated cellulose or NFCs) which when produced exist as aqueous suspensions at very low concentrations. Analysis of these suspensions by Raman spectroscopy is especially rewarding in that the CNs can be analyzed in the native hydrated state without special considerations. Several kinds of information can be derived from the spectra of the nanomaterials such as, estimation of crystallinity (in suspensions and freeze-dried states), measurement of accessibility of the nanomaterials by water, detection and quantitation of cellulose II polymorph in CNs, and effect of drying on the structure of CNs. Moreover, Raman spectra of the nanomaterials contain bands that are associated with chemical functionalities usually present on the surfaces of prepared/modified materials, for example, sulfate esters present on the surfaces of the sulfuric acid produced CNCs. In particular situations, these groups can be quantified by Raman spectroscopy. To accurately estimate crystallinity of CNs, a new method based on ~ 93 cm-1 Raman band is reported. In contrast to the existing crystallinity estimation methods, the 93 cm-1 method has the capability to distinguish between simply “organized” and “organized and crystalline” celluloses. The measurement of the latter fraction is necessary to accurately measure crystallinity. Finally, a few applications of Raman spectroscopy to CN-composites are considered and it is shown that useful information can be obtained from the Raman investigations.

ACS Style

Umesh P. Agarwal. Raman Spectroscopy in the Analysis of Cellulose Nanomaterials. ACS Symposium Series 2017, 75 -90.

AMA Style

Umesh P. Agarwal. Raman Spectroscopy in the Analysis of Cellulose Nanomaterials. ACS Symposium Series. 2017; ():75-90.

Chicago/Turabian Style

Umesh P. Agarwal. 2017. "Raman Spectroscopy in the Analysis of Cellulose Nanomaterials." ACS Symposium Series , no. : 75-90.

Journal article
Published: 24 October 2015 in Cellulose
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The structure of wood cell wall cellulose in its native state remains poorly understood, limiting the progress of research and development in numerous areas, including plant science, biofuels, and nanocellulose based materials. It is generally believed that cellulose in cell wall microfibrils has both crystalline and amorphous regions. However, there is evidence that appears to be contrary to this assumption. Here we show, using 1064-nm FT-Raman spectroscopy, that (1) compared to the crystalline state, cellulose in the never-dried native state is laterally aggregated but in a less-than crystalline state wherein internal chains are water-accessible, (2) hydroxymethyl groups (CH2OH) in cellulose exist not only in the tg conformation but also in the gt rotamer form, and (3) in native-state fibrils, low-frequency Raman bands due to cellulose crystal domains are absent, indicating the lack of crystallinity. Further evidence of the absence of crystallinity of the fibrils was the failure of the normal 64 % H2SO4 hydrolysis procedure to produce nanocellulose crystals from untreated wood. X-ray diffraction data obtained on wood, treated-wood, and wood-cellulose samples were consistent with the new finding and indicated that full-width-at-half-height of the X-ray diffractograms and lateral disorder in samples as measured by Raman were correlated (R2 = 0.95).

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Carlos Baez. Probing crystallinity of never-dried wood cellulose with Raman spectroscopy. Cellulose 2015, 23, 125 -144.

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Richard S. Reiner, Carlos Baez. Probing crystallinity of never-dried wood cellulose with Raman spectroscopy. Cellulose. 2015; 23 (1):125-144.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Carlos Baez. 2015. "Probing crystallinity of never-dried wood cellulose with Raman spectroscopy." Cellulose 23, no. 1: 125-144.

Original research article
Published: 23 September 2014 in Frontiers in Plant Science
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Raman spectroscopy with its various special techniques and methods has been applied to study plant biomass for about 30 years. Such investigations have been performed at both macro- and micro-levels. However, with the availability of the Near-IR (1064 nm) FT-Raman instruments where, in most materials, successful fluorescence suppression can be achieved, the utility of the Raman investigations has increased significantly. Moreover, the development of several new capabilities such as estimation of cellulose-crystallinity, ability to analyze changes in cellulose conformation at the local and molecular level, and examination of water-cellulose interactions have made this technique essential for research in the field of plant science. The FT-Raman method has also been applied to research studies in the arenas of biofuels and nanocelluloses. Moreover, the ability to investigate plant lignins has been further refined with the availability of near-IR Raman. In this paper, a review is provided that is focused on applications of 1064-nm FT Raman to these areas of research. It is hoped that the review will motivate the research community in the plant biomass field to adapt this technique to investigate their specific research needs.

ACS Style

Umesh P. Agarwal. 1064 nm FT-Raman spectroscopy for investigations of plant cell walls and other biomass materials. Frontiers in Plant Science 2014, 5, 490 -490.

AMA Style

Umesh P. Agarwal. 1064 nm FT-Raman spectroscopy for investigations of plant cell walls and other biomass materials. Frontiers in Plant Science. 2014; 5 ():490-490.

Chicago/Turabian Style

Umesh P. Agarwal. 2014. "1064 nm FT-Raman spectroscopy for investigations of plant cell walls and other biomass materials." Frontiers in Plant Science 5, no. : 490-490.

Journal article
Published: 05 September 2014 in Wood Science and Technology
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Influences of fiber orientation and milling on wood cellulose crystallinity were studied using jack pine wood. The fiber orientation effects were measured by sampling rectangular wood blocks in radial, tangential, and cross-sectional orientations. The influence of milling was studied by analyzing the unsieved and sieved milled wood fractions (all WAXS study of the blocks indicated that compared to the pellet, the estimated crystallinities in the radial, tangential, and cross-sectional sampling modes were 5, 2, and 11 % lower, respectively. This suggested that the radial and the tangential faces of the blocks can be used to estimate the crystallinity of wood. With regard to the effect of milling on Raman and Segal-WAXS estimates, the wood crystallinity did not depend upon the particle sizes of the fractionated samples and was similar to that of the original unfractionated ground wood.

ACS Style

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Roderquita K. Moore; Carlos Baez. Impacts of fiber orientation and milling on observed crystallinity in jack pine. Wood Science and Technology 2014, 48, 1213 -1227.

AMA Style

Umesh P. Agarwal, Sally A. Ralph, Richard S. Reiner, Roderquita K. Moore, Carlos Baez. Impacts of fiber orientation and milling on observed crystallinity in jack pine. Wood Science and Technology. 2014; 48 (6):1213-1227.

Chicago/Turabian Style

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Roderquita K. Moore; Carlos Baez. 2014. "Impacts of fiber orientation and milling on observed crystallinity in jack pine." Wood Science and Technology 48, no. 6: 1213-1227.

Research article
Published: 27 December 2012 in Journal of Agricultural and Food Chemistry
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Of the recently developed univariate and multivariate near-IR FT-Raman methods for estimating cellulose crystallinity, the former method was applied to a variety of lignocelluloses: softwoods, hardwoods, wood pulps, and agricultural residues/fibers. The effect of autofluorescence on the crystallinity estimation was minimized by solvent extraction or chemical treatment or both. Additionally, when the roles of lignin and hemicellulose in the Raman crystallinity assessment were investigated, it was found that syringyl lignin containing lignocelluloses generated somewhat higher crystallinity, whereas the presence of hemicellulose reduced the crystallinity. Overall, when autofluorescence was minimized and corrections made for hemicellulose and syringyl lignin contributions, the univariate Raman method performed well and estimated cellulose crystallinity accurately. Moreover, when the Raman and Segal-WAXS methods were compared, we observed that in the absence of significant fluorescence, the Raman method was influenced mostly by hemicellulose and syringyl lignin, whereas the Segal-WAXS was affected by various types of lignin and hemicellulose. It was concluded that the near-IR FT-Raman method with corrections for influences of syringyl lignin and hemicellulose can be used to correctly estimate cellulose crystallinity.

ACS Style

Umesh P. Agarwal; Richard R. Reiner; Sally A. Ralph. Estimation of Cellulose Crystallinity of Lignocelluloses Using Near-IR FT-Raman Spectroscopy and Comparison of the Raman and Segal-WAXS Methods. Journal of Agricultural and Food Chemistry 2012, 61, 103 -113.

AMA Style

Umesh P. Agarwal, Richard R. Reiner, Sally A. Ralph. Estimation of Cellulose Crystallinity of Lignocelluloses Using Near-IR FT-Raman Spectroscopy and Comparison of the Raman and Segal-WAXS Methods. Journal of Agricultural and Food Chemistry. 2012; 61 (1):103-113.

Chicago/Turabian Style

Umesh P. Agarwal; Richard R. Reiner; Sally A. Ralph. 2012. "Estimation of Cellulose Crystallinity of Lignocelluloses Using Near-IR FT-Raman Spectroscopy and Comparison of the Raman and Segal-WAXS Methods." Journal of Agricultural and Food Chemistry 61, no. 1: 103-113.

Journal article
Published: 01 November 2012 in Forest Products Journal
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ACS Style

Sung Phil Mun; Zhiyong Cai; Fumiya Watanabe; Umesh P Agarwal; Jilei Zhang. Thermal Conversion of Pine Wood Char to Carbon Nanomaterials in the Presence of Iron Nanoparticles. Forest Products Journal 2012, 62, 462 -466.

AMA Style

Sung Phil Mun, Zhiyong Cai, Fumiya Watanabe, Umesh P Agarwal, Jilei Zhang. Thermal Conversion of Pine Wood Char to Carbon Nanomaterials in the Presence of Iron Nanoparticles. Forest Products Journal. 2012; 62 (6):462-466.

Chicago/Turabian Style

Sung Phil Mun; Zhiyong Cai; Fumiya Watanabe; Umesh P Agarwal; Jilei Zhang. 2012. "Thermal Conversion of Pine Wood Char to Carbon Nanomaterials in the Presence of Iron Nanoparticles." Forest Products Journal 62, no. 6: 462-466.