Investigating the origin of the raw material of rag paper by Raman spectroscopy

The analysis of a historical document of a registry office from nineteenth century through Raman spectroscopy was performed by comparing with an ensemble of standard samples synthesized from cotton and linen raps. Structural parameters of the fibers of the cellulose, such as crystallinity, chain length, intermolecular interactions and packing, were obtained by the measurement of intensity ratios of some marker features. The results suggested the historical document has a cellulosic support originated from cotton, probably produced without basic pH treatment of the raw material.     

FTIR spectroscopy of biodegraded historical textiles

Fungal attack is a common and severe problem in the storage rooms of museums. Fungi can damage different materials; organic materials are especially sensitive. In this work two different FTIR spectroscopy methods (micro-spectroscopy with diamond anvil cell and ATR) were used to investigate structural changes on biodeteriorated and non-affected textile fibres obtained from different Slovene museums and sacred objects. Several structural changes were observed in spectra of biodeteriorated as well as of non-affected cellulosic fibres, whereas no changes were observed in proteinaceous fibres. In the scope of spectral analysis crystallinity index has also been calculated by comparing two different band ratios. The research showed that the crystallinity index, calculated from the band intensity ratio I₁₃₇₂/I₂₉₀₀ groups fibres into two groups; biodeteriorated fibres predominantly have lower crystallinity index.     

Effect of selected natural dyes in reduction on colour changes of Egyptian linen textiles by fungi

Linen is the most historical Egyptian textile fibre liable to fungal deterioration. Fungal deterioration of dyed linen textiles may appear as undesirable different stains. In order to success in removing of fungal stains from biodeteriorated historical Egyptian dyed linen textiles, it is necessary to understand the nature and causes of these stains, hence their subsequent removal. So this paper aims to investigate the effect of fungi on dyed linen textiles. In this study linen textile samples were experimentally dyed by two different dyes, blue one as an example to vat dye and yellow one as an example to direct dye. This work is done on two of the most important dyes (Turmeric and indigo), which were popular in most of historical periods in Egypt. Dyed linen samples were experimentally biodegraded by thirty different fungal strains isolated previously from historical Egyptian linen samples. The produced change in colours of the biodeteriorated samples was detected visually. Also, the change in reflection spectra and colour differences produced to dyed linen textiles after fungal deterioration, were assessed and evaluated by using spectrophotometer. This study reported that most of tested fungi contribute to discoloration of all tested dyed linen samples. These results indicate that most of stains on historical Egyptian dyed linen textiles, may be fungal stains. The results confirm that undyed linen textiles more liable to fungal biodeterioration than dyed ones. Also the results show that yellow dyed linen textiles are more susceptible to fungal deterioration than blue dyed linen textiles. The obtained results show that Alternaria tenuissima, Chaetomium globosum, Chaetomium sp., Penicillium raistrickii, P. soppi, P. asperum, P. citrinum, Aspergillus carbonarius, A. fischeri, A. nidulans, A. terreus and A. niger, had showed the maximum colour changes of the deteriorated yellow dyed linen samples. The results also show that Alternaria tenuissima, Chaetomium sp., Penicillium asperum, P. citrinum, Aspergillus nidulans and A. spinulosus, had shown the maximum colour changes of the deteriorated blue dyed linen samples.     

Applications of FT Raman Spectroscopy and Micro Spectroscopy Characterizing Cellulose and Cellulosic Biomaterials

FT Raman spectroscopy and micro spectroscopy were used for the investigation of cellulose, cellulose derivatives and cellulosic plant fibres. Lattice structures of cellulose, polymorphic modifications I and II, as well as amorphous structure, were clearly identified by means of FT Raman vibrational spectra. Chemometric models were developed utilizing univariate calibration as well as methods of multivariate data analyses of FT Raman spectral data for the fast prediction of cellulose properties. Cellulose properties like the degree of crystallinity Xc_Raman, the degree of substitution DS_CMC, DS_AC and cellulose reactivity were determined. In situ/ in vivo FT Raman micro spectroscopy was used for the characterization of cellulose structures of flax and hemp fibres. Orientational and stress dependent FT Raman experiments were carried out.     

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

Two new methods based on FT–Raman spectroscopy, one simple, based on band intensity ratio, and the other using a partial least squares (PLS) regression model, are proposed to determine cellulose I crystallinity. In the simple method, crystallinity in cellulose I samples was determined based on univariate regression that was first developed using the Raman band intensity ratio of the 380 and 1,096 cm^?1 bands. For calibration purposes, 80.5% crystalline and 120-min milled (0% crystalline) Whatman CC31 and six cellulose mixtures produced with crystallinities in the range 10.9–64% were used. When intensity ratios were plotted against crystallinities of the calibration set samples, the plot showed a linear correlation (coefficient of determination R ² = 0.992). Average standard error calculated from replicate Raman acquisitions indicated that the cellulose Raman crystallinity model was reliable. Crystallinities of the cellulose mixtures samples were also calculated from X-ray diffractograms using the amorphous contribution subtraction (Segal) method and it was found that the Raman model was better. Additionally, using both Raman and X-ray techniques, sample crystallinities were determined from partially crystalline cellulose samples that were generated by grinding Whatman CC31 in a vibratory mill. The two techniques showed significant differences. In the second approach, successful Raman PLS regression models for crystallinity, covering the 0–80.5% range, were generated from the ten calibration set Raman spectra. Both univariate-Raman and WAXS determined crystallinities were used as references. The calibration models had strong relationships between determined and predicted crystallinity values (R ² = 0.998 and 0.984, for univariate-Raman and WAXS referenced models, respectively). Compared to WAXS, univariate-Raman referenced model was found to be better (root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) values of 6.1 and 7.9% vs. 1.8 and 3.3%, respectively). It was concluded that either of the two Raman methods could be used for cellulose I crystallinity determination in cellulose samples.     

Crystallinity changes in lyocell and viscose-type fibres by caustic treatment

One of the most important treatments performed on cellulosic fibres to improve properties such as dimensional stability, tensile strength and lustre, is mercerisation. The aim of this work was to study the crystallinity, accessibility and unit cell structure changes occurring in three types of regenerated cellulose fibres (lyocell, modal and viscose) that were mercerised with caustic soda solutions of different concentrations. Differences were observed between the behaviour of the viscose type fibres (viscose and modal) and that of the lyocell fibres. For the viscose type fibres, the proportion of crystalline regions increased at low alkali concentrations, while for lyocell fibres a decrease in crystallinity was observed. In all three fibres there was a transformation from cellulose II to amorphous cellulose. While for lyocell the transformation was partial, the modal and in particular the viscose fibres showed a complete transformation, and the swelling agent caused the fibre to dissolve at high caustic concentrations.     

Examination of cellulose textile fibres in historical objects by micro-Raman spectroscopy

The investigation and characterisation of historical objects can be an exacting piece of work because of the small quantity of material that can be investigated and the degradation of the material and its value, which sometimes demands only non-destructive methods. In this study, as one such method, Raman spectroscopy was used to investigate the cellulose fibres of painting canvases and linings. Historical samples of fabrics were taken from different paintings and their linings from different locations in Slovenia. Raman spectra were recorded on the fibres of these historical samples. Additionally, a database of the Raman spectra of modern cellulose fibres was created and compared with the literature data. Differences in the Raman spectra of different cellulose fibres were observed, and on this basis fibres of different types were discriminated. The recorded Raman spectra of historical samples were compared with the database spectra of modern cellulose fibres. Strong luminescence effects because of the changes caused by ageing, degradation products and surface contamination caused difficulties in interpreting the Raman spectra of historical fibres. The luminescence effects were partly overcome by prolonged exposition times and previous "signal quenching" with the laser. The Raman spectra of historical cotton showed no luminescence effects, and only slight differences to the reference spectra of modern cotton fibres appeared, whereas the Raman spectra of historical flax fibres were overwhelmed with luminescence and showed changes in spectra through degradation. The research showed that by using Raman spectroscopy the identification and differentiation of different cellulose fibres and materials that accompany cellulose in the fibres are possible and that degraded and aged material can be differentiated.     

In-situ detection of drugs-of-abuse on clothing using confocal Raman microscopy

This study describes the application of confocal Raman microscopy to the detection and identification of drugs-of-abuse in situ on undyed natural synthetic fibres, and coloured textile specimens. Raman spectra were obtained from drug particles trapped between the fibres of the specimens. Pure samples of cocaine hydrochloride and N-methyl-3,4-methylenedioxy-amphetamine HCl (MDMA-HCl) were used in this study. Raman spectra were collected from drug particles of an average size in the range 5-15 μm. Despite the presence of spectral bands arising from the natural and synthetic polymer and dyed textiles, the drugs could be identified by their characteristic Raman bands. If necessary, interfering bands could be successfully removed by spectral subtraction. Furthermore, Raman spectra were recorded from drug particles trapped between the fibres of highly fluorescent specimens. Interference from the fibres, including background fluorescence, was overcome by careful focusing of the confocal beam and the resulting spectra allow ready differentiation from interference from the fibres substrate bands. Spectra of several drugs-of-abuse on dyed and undyed clothing substrates were readily obtained within 3 min with little or no sample preparation and with no alteration of the evidential material.     

THM PyGC–MS of wood fragment and vegetable fibre forensic samples

Wood fragments and vegetable fibres were investigated using thermally assisted hydrolysis and methylation with pyrolysis gas chromatography–mass spectrometry (THM PyGC–MS). Multiple ion chromatography was used to decrease the interference from cellulosic peaks, and to obtain greater resolution between the lignin peaks. Forty-four wood samples were analysed using THM PyGC–MS. The wood fragments were able to be differentiated into angiosperms (hardwoods) and gymnosperms (softwoods) using principle component analysis (PCA), hierarchical cluster analysis (HCA), and the ratio of syringyl to guaiacyl lignin fragments (S/G ratio). PCA and HCA also differentiated several Monterey pine samples from the rest of the gymnosperms, primarily by the presence of β-pinene, an extractive compound. Other gymnosperm species and the individual angiosperm species were unable to be differentiated. A pilot study investigating the use of THM PyGC–MS for the analysis of vegetable fibres in forensic science found that the fibre types tended to group into two clusters, with one containing cotton, hemp and linen; and the other consisting of hessian, sisal, jute and coir. The seagrass sample was able to be differentiated from both groups. These groups were well separated using PCA, HCA and by the ratio of cinnamyl phenolic derivatives to guaiacyl lignin derivatives (C/G ratio). Some grouping of each fibre type was evident within each cluster, however the separation between the clusters was insufficient to differentiate them using these statistical techniques. THM PyGC–MS of vegetable fibres showed some potential for future use in forensic science.     

The use of polarised Fourier transform Raman spectroscopy in morphological studies of uniaxially oriented PEEK fibres—some preliminary results

The use of Raman spectroscopy to measure crystallinity in uniaxially oriented poly(aryl ether ether ketone) (PEEK) fibres is discussed. It is shown that previously reported measurements based upon the 1608:1597 cm⁻¹ band intensity ratio are affected by molecular orientation, and as such their application to anisotropic samples must be regarded with caution. The use of the crystallinity-sensitive carbonyl bandhead frequency seems to be less sensitive to molecular orientation and so may be applicable to oriented samples—further work is required to calibrate this measurement with oriented samples of known crystallinity. Some preliminary data on the polarisation properties of the 1597 cm⁻¹ ring mode intensity in PEEK fibre bundles is also presented. These data suggest that the band displays perpendicular rather than parallel character with respect to the fibre long axes. Possible reasons for this effect are discussed. The Raman data indicate that molecular orientation is present in both melt-spun and drawn fibres. The spun fibres appear to be amorphous, but drawing induces significant crystallisation.     

Using a fully recyclable dicarboxylic acid for producing dispersible and thermally stable cellulose nanomaterials from different cellulosic sources

We fabricated cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) from different cellulose materials (bleached eucalyptus pulp (BEP), spruce dissolving pulp (SDP) and cotton based qualitative filter paper (QFP) using concentrated oxalic acid hydrolysis and subsequent mechanical fibrillation (for CNFs). The process was green as acid can be easily recovered, and the prepared cellulose nanomaterials were carboxylated and thermally stable. In detail, the CNC yield from the different materials was similar. After hydrolysis, the DP of the cellulose materials decreased substantially, whereas the mechanical fibrillation of the cellulosic solid residues (CSRs) did not dramatically reduce the DP of cellulose. CNCs with different aspect ratios were produced from different starting materials by oxalic acid hydrolysis. The CNCs and CNFs obtained from BEP and QFP possessed more uniform dimensions than those from SDP. On the other hand, CNFs derived from SDP presented the best suspension stability. FTIR analyses verified esterification of cellulose by oxalic acid hydrolysis. The results from both XRD and Raman spectroscopy indicated that whereas XRD crystallinity of CNCs from BEP and QFP did not change significantly, there was some change in Raman crystallinity of these samples. Raman spectra of SDP CNCs indicated that the acid hydrolysis preferably removed cellulose I portion of the samples and therefore the CNCs became cellulose II enriched. TGA revealed that the CNCs obtained from QFP exhibited higher thermal stability compared to those from BEP and SDP, and all the CNCs possessed better thermal stability than that of CNCs from sulfuric acid hydrolysis. The excellent properties of prepared cellulose nanomaterials will be conducive to their application in different fields.     

The discovery of free radicals in ancient silk textiles

Protection of ancient silk textiles from further deterioration is of vital importance to the investigation and preservation of ancient Chinese culture. Ancient silk textiles from several different ages (more than 2000 years ago) and regions were studied by means of Raman and electron paramagnetic resonance (EPR) spectroscopy in an attempt to unveil the deterioration mechanism of silk. The Raman spectra showed two peaks (D and G), which are indicative of carbonization. The EPR spectra of the ancient samples showed a characteristic sharp absorption centered at g∼2.0037 without a hyperfine structure, and have been identified as those of carbon radicals. These free radicals had not been discovered in ancient silk fabrics before, and the discovery may shed light on the deterioration mechanisms of ancient silk textiles.     

Physicochemical properties of chemically and enzymatically modified cellulosic surfaces

Surface characteristics of modified cotton fibers have been studied using electrokinetic analysis (EKA), inverse gas chromatography (IGC) and dynamic contact angle (DCA) determinations. Modifications of cotton surfaces included mercerization, water-proofing, cross-linking, dyeing with a bifunctional reactive dye and cellulase biopolishing. Comparisons are made to linen as an example of a natural cellulosic fiber other than cotton and to rayon as a representative of a regenerated cellulosic fiber. Generally all cellulosic surfaces were bipolar with a slightly higher acidic contribution in the case of the cotton samples. EKA indicated ion dissociation as the predominant mechanism for surface charge in aqueous medium for all cellulosic samples, with the exception of greige cotton and the cotton sample with the hydrophobic finish. Results from EKA and IGC showed good correlation, while DCA yielded unreasonably high basic contributions most likely due to fiber swelling.     

The low temperature Fourier Transform Raman spectrum of polystyrenes

In a previous paper (Jones and Wesley, Spectrochimica Acta 47A (9/10), 1293 (1991)) the Fourier Transform (FT) Raman spectra of various polystyrenes were presented and differences in the spectra in terms of the configuration, conformation and crystallinity of the samples were discussed. In this paper the low temperature FT Raman spectra of polystyrenes are presented. The differences between the spectra as a function of temperature and crystallinity are discussed. It is clear that, although lowering the temperature is advantageous in improving the quality of the spectra, crystallinity is the key to quality in the spectra. Isomeric purity alone seems to be far less advantageous. It is proposed that the band near 1000 cm⁻¹ in this system can be used to estimate the crystallinity. The paper concludes with some comments on the very slow crystallization rate of typical isotactic polystyrene.     

Preparation of three-dimensional cellulose objects previously swollen in a DMAc/LiCl solvent system

Three-dimensionally shaped cellulosic objects were produced via a two-step procedure: swelling of softwood pulp (93 % cellulose; 4.5 % hemicellulose; 54 % crystallinity) in DMAc/LiCl followed by moulding. Swollen cellulose pulp in the form of gel was solidified with two different anti-solvents: distilled water and a combination of 2-propanol and deionized water. The solid cellulose material was further moulded in a custom-built prototype mould. The role of the anti-solvent was to solidify the swollen cellulose fibres and prepare mouldable solid specimens. The anti-solvent was chosen based on the following criteria, viz., recoverability, stable chemical reactivity, availability, cost and previous research in the anti-solvent area. The choice of solidification solvent had a great influence on the structure and mechanical properties of the final cellulose material. Results of different characterisation techniques showed that when the cellulose gel was washed with distilled water, it had a significantly higher number of lithium cations (ICP-MS and Raman), amorphous structure (X-ray) and lower mechanical properties (nanoindentation) compared to samples washed with a combination of 2-propanol and deionized water. An increase in viscosity as previously reported and changes in the NMR and IR spectra of DMAc upon LiCl suggested the formation of an ion-dipol complex, where lithium cations reside adjacent to the oxygen of the carbonyl group of DMAc. The formed macrocation [DMAc_n + Li]⁺ was preserved between cellulose chains in cellulose specimens washed with distilled water and had an essential role in the disruption of initial bonds, thus enhancing mouldability. Electron microscopy (FE-SEM) studies showed that the surface of cellulose after mechanochemical treatment was rough with no presence of fibres.     

Differential thermal and thermogravimetric analyses of bound water content in cellulosic substrates and its significance during cellulose hydrolysis by alkaline active fungal cellulases

Various cellulosic substrates were examined for bound water content by differential thermal analysis (DTA) and thermogravimetry (TG). Samples were heated in the range of 30-100 degrees C at a rate of 3 degrees C/min. DTA vaporization curves for different cellulose samples indicated that the bound water (Wf) was vaporized at higher temperature than free water (Wf) at the surface. Weight loss was observed in two stages, corresponding to Wf and Wb in TG curves. The bound water content was dependent on the degree of crystallinity of cellulose. Among different cellulosic substrates, Walseth cellulose showed the highest bound water content, and it also was found to be the least crystalline. The alkaline-active, alkali-stable cellulase was obtained from the alkalotolerant Fusarium sp. The substrate specificity and viscometric characteristics confirmed the enzyme to be an endoglucanase. The Wb content of Walseth cellulose was lowered during the enzymatic hydrolysis. The possible application of bound water analysis in understanding the hydrolysis of cellulosic substrates of different crystallinity is discussed.     

Characterization of alkali treated flax fibres by means of FT Raman spectroscopy and environmental scanning electron microscopy

Flax fibres grown under well managed conditions were submitted to NaOH chemical treatments, so called Mercerization. The extent of the polymorphic transformation of cellulose I into cellulose II taking place within the crystalline domains of the fibre cellulose was dependent on the alkali concentration. FT Raman spectroscopy turned out to represent an ideal tool for detecting the polymorphic transformation of the cellulosic fine structure of the flax fibres in vivo. In addition to the differences of the FT Raman spectra in the frequency range below 1500 cm(-1), second derivatives of the spectra in the range of the CH stretching vibrations could also be used to distinguish the two polymorphic modifications. The intensity ratio R of the stretching modes v(s)COC and v(as)COC represents a spectral parameter characterising the molecular structure of the flax fibres. As a supplementary tool, Environmental scanning electron microscopy (ESEM) was used to visualize the microstructural fibre properties dependent on the alkali concentrations during the Mercerization.     

On the determination of crystallinity and cellulose content in plant fibres

A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and comprehensive plant fibre analysis for a consistent determination of the cellulose content. Crystallinity determinations were based on X-ray powder diffraction methods using side-loaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements based on the recently published crystal structure of cellulose Iβ followed by integration of the crystalline and amorphous (background) parts were performed. This was shown to be straightforward to use and in many ways advantageous to traditional crystallinity determinations using the Segal or the Ruland–Vonk methods. The determined cellulose crystallinities were 90–100 g/100 g cellulose in plant-based fibres and 60–70 g/100 g cellulose in wood based fibres. These findings are significant in relation to strong fibre composites and bio-ethanol production.     

In-situ detection of single particles of explosive on clothing with confocal Raman microscopy

Confocal Raman microscopy is shown to detect picogram quantities of explosives in-situ on undyed natural and synthetic fibres, and coloured textile specimens leaving potentially evidential materials unaltered. Raman spectra were obtained from pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), and ammonium nitrate particles trapped between the fibres of the specimens. Despite the presence of spectral bands arising from the natural and synthetic polymers and dyed textiles, the explosive substances could be identified by their characteristic Raman bands. Furthermore, Raman spectra were obtained from explosives particles trapped between highly fluorescent clothing fibres. Raman spectra were collected from explosives particles with maximum dimensions in the range 5-10 μm. Spectra of the explosives on dyed and undyed clothing substrates were readily obtained in-situ within 90 s and without sample preparation.     

Synthesis and characterization of zinc oxide nanoparticles

The research is aimed at synthesis and characterization of nanoscaled zinc oxide particles and their application on linen fibrous supports, for thermal properties. To impart thermal activity to the fibrous nanocomposites, nanoparticles as well as fibrous nanocomposites were produced in different hydrothermal conditions of temperature (90 °C). To characterize the nanoparticles composition, their shape, size, and crystallinity, investigations technique, such as Fourier transformed infrared spectroscopy, scanning electron microscopy, and X-ray powder diffractometry were used. Differential scanning calorimetry analysis profiles were also revealed. The thermal treatment of linen fabrics with nanosized ZnO does not modify significantly their thermal stability.