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A thorough vibrational characterization of CO2 molecules adsorbed at room temperature on alkali metal exchanged M–ZSM-5 zeolites (M=Li+, Na+, K+, and Cs+) has been obtained: All three fundamental modes (ν1, ν2, and ν3) have been measured in the mid-IR, together with combination bands of the ν1 and ν3 modes with modes at 18, 45, and 60 cm−1. The nature of these low-lying modes is discussed, and it is proposed that these are framework vibrations. Ab initio calculations on molecular models mimicking the building blocks of zeolites revealed the systematic presence of such low-lying modes, and far-IR measurements using synchrotron radiation showed a couple of bands at 55–45 cm−1 in the spectrum of the bare samples, which undergo a slight perturbation upon CO2 adsorption. The presence of combination modes between molecular and framework vibrations lends support to the concept already advanced [Bonelli et al., J. Phys. Chem. B 104, 10978 (2000)] that the CO2 molecule has a primary interaction with the cation and a secondary one with an adjacent oxygen anion; the latter not strong enough to lead to a carbonate species. The occurrence of similar combination bands for CO2 molecularly adsorbed on other systems is also discussed.

An inexpensive and compact carbon dioxide sensor based on a porous silicon (PS) film modified with 3‐amino‐1‐propanol has been demonstrated. The modifying reaction as well as the interaction of carbon dioxide with the PS amine‐terminated surface has been investigated using Fourier Transform Infrared Spectroscopy. Optical reflectivity spectra of PS modified layers display shifts in the Fabry–Perot fringes upon adsorption of carbon dioxide. This shift scales with the CO2 concentration.

Recent investigations strongly suggest that Raman spectroscopy (RS) can be used as a clinical tool in cancer diagnosis to improve diagnostic accuracy. In this study, we evaluated the efficiency of Raman imaging microscopy to discriminate between healthy and neoplastic thyroid tissue, by analyzing main variants of Papillary Thyroid Carcinoma (PTC), the most common type of thyroid cancer. We performed Raman imaging of large tissue areas (from 100 × 100 μm2 up to 1 × 1 mm2), collecting 38 maps containing about 9000 Raman spectra. Multivariate statistical methods, including Linear Discriminant Analysis (LDA), were applied to translate Raman spectra differences between healthy and PTC tissues into diagnostically useful information for a reliable tissue classification. Our study is the first demonstration of specific biochemical features of the PTC profile, characterized by significant presence of carotenoids with respect to the healthy tissue. Moreover, this is the first evidence of Raman spectra differentiation between classical and follicular variant of PTC, discriminated by LDA with high efficiency. The combined histological and Raman microscopy analyses allow clear-cut integration of morphological and biochemical observations, with dramatic improvement of efficiency and reliability in the differential diagnosis of neoplastic thyroid nodules, paving the way to integrative findings for tumorigenesis and novel therapeutic strategies.