Twenty extra-framework S- and C-bearing species including anions (SO42–, SO32–, S2–, S52–, HS–, CO32–, C2O42– and HCO4–), radical anions (S2•–, S3•–, cis- and trans-S4•– and SO4•–) and neutral molecules (CO2, COS, H2S, cis- and trans-S4 and S6) have been identified in natural tectosilicates (members of the sodalite, cancrinite and scapolite groups) using a novel multimethodic approach based on several spectroscopic methods, single-crystal and powder X-ray diffraction, and electron microprobe and wet chemical analyses. Various polysulfide groups were detected in lazurite, haüyne, vladimirivanovite, sapozhnikovite, slyudyankaite, kyanoxalite, balliranoite, marinellite, tounkite, bystrite, sulfhydrylbystrite and meionite. Experimental data on mutual conversions of S-bearing species and structure modulations of these minerals under different temperatures, reducing and oxidizing environment as well as radiation-induced conversions provide a key for their use as markers of the crystallization or transformation conditions in Nature and during synthesis and modification.

Infrared (IR) nanoscopy represents a collection of imaging and spectroscopy techniques capable of resolving IR absorption on the nanometer scale. Chemical specificity is leveraged from vibrational spectroscopy, while light–matter interactions are detected by observing perturbations in the optical near field with an atomic force microscopy probe. Therefore, imaging is wavelength independent and has a spatial resolution on the nanometer scale, well beyond the classical diffraction limit. In this perspective, we outline the recent biological applications of scattering type scanning near-field optical microscopy and nanoscale Fourier-transform IR spectroscopy. These techniques are uniquely suited to resolving subcellular ultrastructure from a variety of cell types, as well as studying biological processes such as metabolic activity on the single-cell level. Furthermore, this review describes recent technical advances in IR nanoscopy, and emerging machine learning supported approaches to sampling, signal enhancement, and data processing. This emphasizes that label-free IR nanoscopy holds significant potential for ongoing and future biological applications.

The natural hydroniumjarosite sample from Cerros Pintados (Chile) was investigated by electron microprobe, single-crystal X-ray diffraction and vibrational spectroscopy (Infrared and Raman). The chemical composition of studied specimens (wt.%, mean of seven analyses) obtained from electron microprobe (in wt.%): Na2O 1.30, K2O 0.23, CaO 0.04, Fe2O3 50.49, Al2O3 0.37, SiO2 0.33, SO3 33.88, H2O (calculated on the basis of Σ(OH–+H3O+) deduced from the charge balance) 13.32, total 99.98, corresponds to the empirical formula (H3O)0.77 +(Na0.20K0.02)∑0.22(Fe2.95Al0.03)∑2.98 (OH)6.12[(SO4)1.97(SiO4)0.03]∑2.00 (calculated on the basis of S + Si = 2 a.p.f.u. (atoms per formula unit)). The studied hydroniumjarosite is trigonal, with space group R m, with a = 7.3408(2), c = 17.0451(6) Å and V = 795.46(4) Å3. The refined structure architecture is consistent with known jarosite-series minerals, including synthetic hydroniumjarosite. However, in the current study the presence of H3O+ is well documented in difference Fourier maps, where characteristic positive difference Fourier maxima, with apparent trigonal symmetry, were localized in the vicinity of the O4 atom in the channel-voids of the structure. The structure of natural hydroniumjarosite, including the H atoms, was refined to R 1 = 0.0166 for 2113 unique observed reflections, with I obs >3σ(I). The present structure model, which includes the position of the H atom within the hydronium ion, is discussed with regard to the vibration spectroscopy results and earlier published density-functional theory (DFT) calculations for the alunite-like structure containing H3O+.

Micro-inclusions (1 –10 μm) in 55 diamonds of cubic habit from the Udachnaya kimberlite pipe have been studied using vibrational spectroscopy. This has revealed a multiphase assemblage in cuboid diamonds from the Udachnaya kimberlite pipe. This assemblage includes carbonates, olivine, apatite, graphite, water and silicate glasses. The micro-inclusions preserve the high internal pressure and give confidence that the original materials were trapped during growth of the host diamond. The internal pressures, extrapolated to mantle temperatures, lie within the stability field of diamond and the relatively low temperatures are typical for the formation of cuboid diamonds. In contrast to previously reported data for African diamonds, the micro-inclusions in the cuboids from Udachnaya are extremely carbonatitic in composition (H2O/(H2O+CO2) ≈5 –20%) with the observed assemblage of microinclusions similar to some types of carbonatites. The low water and silica content testify that the material in the micro-inclusions of the Udachnaya diamonds was near-solidus carbonatitic melt. Vibrational spectroscopy has provided the evidence of carbonatitic melts in cuboid diamonds.

Water-related features were studied using infrared absorption spectroscopy in fibrous diamonds with micro-inclusions. Both OH-stretching and HOH-bending vibrations were observed. The lack of correlation between the intensities of HOH and OH bands in different samples and the complexity of the OH-stretching band indicate that a large fraction of water is present as hydroxyl groups in minerals.

Heating and cooling experiments were performed to elucidate the properties of fluids in micro-inclusions in diamonds. The results of experiments at various temperatures support the presence of several water-related components in individual diamonds. These spectroscopic investigations of fibrous diamonds revealed two or more interrelated water-related components preserved in micro-inclusions. The existence of several water phases or water solutions with different salinity and solutes within one diamond crystal is possible.