Amorphous carbon (AC) is present in the bulk and on the surface of nanostructured carbon materials (NCMs) and exerts a significant effect on the physical, chemical and mechanical properties of NCMs. Thus, the determination of AC in NCMs is extremely important for controlling the properties of a wide range of materials. In this work, a comparative study of the effect of heat treatment on the structure and content of amorphous carbon in deposited AC film, nanodiamonds, carbon black and multiwalled carbon nanotube samples was carried out by TEM, XPS, XRD and Raman spectroscopy. It has been established that the use of the 7-peak model for fitting the Raman spectra makes it possible not only to isolate the contribution of the modes of amorphous carbon but also to improve the accuracy of fitting the fundamental G and D₂ (D) modes and obtain a satisfactory convergence between XPS and Raman spectroscopy. The use of this model for fitting the Raman spectra of deposited AC film, ND, CB and MWCNT films demonstrated its validity and effectiveness for investigating the amorphous carbon in various carbon systems and its applicability in comparative studies of other NCMs.

The work outlines general ideas on how the frequency and the intensity of proton vibrations of X–H···Y hydrogen bonding are formed as the bond evolves from weak to maximally strong bonding. For this purpose, the Raman spectra of different chemical compounds with moderate, strong, and extremely strong hydrogen bonds were obtained in the temperature region of 5 K–300 K. The dependence of the proton vibrational frequency is schematically presented as a function of the rigidity of O-H···O bonding. The problems of proton dynamics on tautomeric O–H···O bonds are considered. A brief description of the N–H···O and C–H···Y hydrogen bonds is given.

The properties of the intermolecular hydrogen bonds in the monoclinic (Form I) and the orthorhombic (Form II) polymorphs of paracetamol, C₈H₉NO₂, have been studied by single crystal polarized Raman spectroscopy (40 to 3700 cm⁻¹) in a wide temperature range (5 K < T < 300 K) in relation to the dynamics of methyl-groups of the two forms. A detailed analysis of the temperature dependence of the wavenumbers, bandwidths and integral intensities of the spectral bands has revealed an essential difference between the two polymorphs in the strength and ordering of OH⋯O and NH⋯O hydrogen bonds. The compression of intermolecular hydrogen bonds is interrelated with crystal packing and the dynamics of methyl-groups. On structural compression of the orthorhombic polymorph on cooling, a compromise is to be sought between the shortening of OH⋯O and NH⋯O bonds, attractive CH⋯O and repulsive CH⋯H contacts in the crystal structure. As a result of a steric conflict at temperatures below 100 K, N–H⋯O hydrogen bonds become significantly disordered, and an extended intramolecular transition from the conformation “staggered” with respect to the CO bond to the one “staggered” with respect to the NH bond is observed. In most of the studied crystals this transition was only about 60% complete even at 5 K, but in some of the crystals the orientation of all the methyl-groups became staggered with respect to the NH bond at low temperatures. This complete transition was coupled to a sharp shortening of the OH⋯O and NH⋯O hydrogen bonds at <100 K, the appearance of new additional positions of the protons in these H-bonds, and a slight strengthening of the C–H⋯O bonds formed by methyl-groups. The same conformational transition has been observed also in the monoclinic polymorph at T < 80 K. The crystal packing in Form I prevents the O–H⋯O hydrogen bonds from adopting the optimum geometry, and they are significantly disordered at all the temperatures, especially at ≤200 K. The packing of molecules in Form I is also not favourable to form C–H⋯O hydrogen bonds involving methyl-groups. One can conclude from the comparison of diffraction and spectroscopic data that the higher stability of Form I results not from a larger strength of individual OH⋯O and NH⋯O hydrogen bonds, but is a cumulative effect: all the hydrogen bonds together stabilize the structure of the monoclinic polymorph more than that of the orthorhombic polymorph.