Abstract
The qualitative analysis of nanodiamonds by FTIR spectrometry as photoacoustic (FTIR-PAS), diffuse-reflectance (DRIFT), and attenuated total reflection (ATR) modalities was evaluated for rapid and nondestructive analysis and comparison of nanodiamonds. The reproducibility and signal-gathering depth of spectra was compared. The assignment of characteristic bands showed that only six groups of bands were present in spectra of all the modalities with appropriate sensitivity: 1760 (C=O stretch, isolated carboxyl groups); 1640-1632 (H-O-H bend, liquid water); 1400-1370 (non-carboxyl C-O-H in-plane bend and CH2 deformation); 1103 (non-carboxyl C-O stretch); 1060 (in-plane C-H bend, non-aromatic hydrocarbons and carbohydrates); 940 cm-1 (out-of-plane carboxyl C-O-H bend). DRIFT provides the maximum number of bands and is capable of measuring hydrogen-bonded bands and CHx groups. ATR provides the good sensitivity for water and C-H/C-C bands in the range 2000-400 cm-1. FTIR-PAS reveals less bands than DRIFT but more intense bands than ATR-FTIR and shows the maximum sensitivity for absorption bands that do not appear in ATR-IR spectra and are expedient for supporting either DRIFT or FTIR-PAS along with depth-profiling. Thus, all three modalities are required for the full characterization of nanodiamonds surface functional groups.