Probing Molecular-Scale Oxidative Generation of Quinone Methides and Their Transformation Using Tip-Enhanced Raman Spectroscopy.

Quinone methides (QMs) are very important intermediates in chemistry. These species are most often generated in situ with metal oxidants and transition metal complexes. Here, tip-enhanced Raman spectroscopy (TERS) has been implemented to investigate the in situ oxidative generation of a QM species from alkylphenols facilitated by a transition metal complex. Using TERS, the metal oxidant-mediated transformation of a phenol species has been observed. The subsequent oxidative addition reaction of QM has also been identified based on distinct vibrational features, which have been assigned based on density functional theory (DFT). This study may establish TERS as a chemical detection tool for various QM-mediated reactions.

Tandem Quantification of Multiple Carbohydrates in Saliva Using Surface-Enhanced Raman Spectroscopy.

The detection of carbohydrates in human body fluids is critical for disease diagnosis and healthy monitoring. Despite recent advances in glucose sensing, multiplex detection of different carbohydrates within a single assay that is capable of efficiently providing richer health information remains challenging. Herein, we report a versatile surface-enhanced Raman spectroscopy-based platform for the quantitative detection of monosaccharides (glucose, fructose, and galactose) in one test using a displace-and-trap mechanism. Moreover, due to the use of multiple optical interference-free (1800-2200 cm-1) signal-independent Raman probes, the detection range of this platform (0.125-7 mg/dL) perfectly covers physiological concentrations, enabling the quantitative detection of glucose and galactose in clinical human saliva samples. This work provides a noninvasive and high-efficiency potential tool for the screening of clinical diabetes and other carbohydrate-related diseases.