<br/>In kraft lignins understanding of structure property relationships is important to make them more useful. Although Raman spectroscopy has been successfully used in the investigations of native and milled-wood lignins, its application to study kraft lignins continues to be challenging. This is primary due to that fact that kraft lignins are intensely colored and therefore, highly fluorescent even at Raman laser excitation wavelength of 1064 nm (near-IR). In the spectra, the fluorescence overwhelms the weak Raman signals and only a few bands with high scattering intensity can be observed. Nevertheless, special techniques in Raman spectroscopy like UV resonance Raman have been applied to study kraft lignins and a limited number of lignin bands have been observed. With the focus on using 1064 nm Raman, our motivation is to detect many more Raman bands than has been the case till now. A number of approaches have been attempted which consisted of sample derivatization, sample bleaching, sampling in deuterated water, and use of silver nano- and micro-particles. Obtained Raman data will be presented and discussed.

On the difficulty of applying 1064-nm Raman spectroscopy to investigate structures of kraft lignins

251st National Meeting (2016)

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