Raman spectroscopy is a non-destructive analysis technology based on the Raman effect. Through Raman spectroscopy, detailed information on the chemical structure, phase and morphology, crystallinity, and molecular interactions of substances can be analyzed.
The so-called Raman effect refers to the phenomenon that the frequency of light waves changes after being scattered. When molecules scatter high-intensity incident light from a laser source, most of the scattered light has the same wavelength (color) as the incident laser. This scattering is called Rayleigh scattering. However, there is still a very small part (about 1/109) of scattered light whose wavelength (color) is different from that of the incident light. The change in its wavelength is determined by the chemical structure of the test sample (the so-called scattering material). This part of the scattered light is called pull Raman scattering.
It is like the chemical fingerprint of the material because the Raman spectra of different substances are different; then, the type of material can be quickly determined by the comparison of completing the work of material analysis. Because of this, in the subsequent development, Raman spectroscopy has continued to achieve technological breakthroughs, and deeper techniques such as surface-enhanced Raman spectroscopy (SERS) and single-molecule surface-enhanced. Raman scattering (SM-SERS) has been born—non-destructive testing technology.
With the development of technology, related problems have also arisen, including the defect that SERS and SM-SERS signals cannot achieve high repeatability, uniformity, and stability in commercial detection. Under the influence of these defects, SERS and SM-SERS have not achieved the expected results in single molecule and measured molecule level detection. However, the detection capability of SM-SERS technology has reached the ultra-sensitive single molecule level.
Just recently, Professor Fang Jixiang’s team from the School of Life Sciences at a Chinese University achieved a breakthrough in related research. Based on early research on surface-enhanced Raman spectroscopy (SERS) and single-molecule surface-enhanced Raman scattering (SM-SERS), they obtained Progress, Confined-Enhanced Raman Spectroscopy (CERS) and a new mechanism to avoid SM-SERS scintillation signals were proposed. Relevant papers have been published in NANO LETTERS.
The paper mentioned that the discovery of SM-SERS rekindled the industry’s interest in Raman spectroscopy in 1997, but its “on and off” timing fluctuations made SM-SERS very disadvantageous in practical applications.
To solve this problem, Professor Fang’s team adopted the method of building an active encapsulation shell in situ on the surface of silver, gold, or even other plasmonic nanomaterials. The active encapsulation shell can confine and anchor the molecules to be measured on the surface of the plasmonic nanoparticles, thereby preventing the adsorption-desorption behavior of the molecules and thereby avoiding the occurrence of scintillation signals. The content of the paper can be found at ACS Publications.
It is worth mentioning that this research result will help Raman spectroscopy to be better used in medical, chemical, and other fields, and it is also expected to provide an important theoretical basis for the future development of Raman spectroscopy.