Acquiring Raman Spectra Under Strong Fluorescence Interference Using Scratched Potassium Bromide Pellets

Raman spectroscopy is a powerful analytical tool; however, it is highly susceptible to fluorescence interference, which can overwhelm the spectroscopic signals under strong fluorescence. Several approaches have been developed to overcome this problem, including photobleaching, changing the laser wavelength, time‐resolved Raman spectroscopy, and surface‐enhanced Raman spectroscopy. However, owing to the hardware and technical limitations of individual Raman laboratories, fluorescence interference remains a widespread challenge. In this study, we developed a novel KBr‐pellet method to suppress strong fluorescence interference and acquire high‐quality Raman spectra. Unlike the conventional method of mixing KBr with a sample, this method involves fabricating unique stripes of the sample material on a scratched KBr pellet to enable the selection of optimal points to acquire clear Raman signals. This technique was successfully applied to several highly fluorescent samples. High‐quality Raman spectra were obtained using only 532‐ or 633‐nm lasers, which would otherwise be nearly impossible without alternative lasers or enhancement substrates. The mechanism of fluorescence quenching may be the effective nanoscale contact between KBr and sample molecules that enables the fluorescence energy to be transferred to the KBr crystals and dispersed as heat. The proposed method can also effectively isolate target materials from complex samples, even for very low sample concentrations. The new KBr‐pellet method enabled Raman spectra to be obtained from practical samples under strong fluorescence interference. This convenient, inexpensive, and powerful method is expected to become a routine approach for fluorescence suppression during daily Raman analysis.