What Is Raman Scattering?

Raman scattering, also called Raman scattering, was discovered by Indian physicist Raman in 1928 and refers to the phenomenon that the frequency of light waves changes after being scattered. In 1930, the Nobel Prize in Physics was awarded to Sir Chandrasekhara Venkata Raman (1888-1970), who was then working at the University of Kolkata, India, in recognition of his research on the scattering of light and the discovery of a law named after him.

1930

In the summer of 1921, sailing

Raman was born on November 7, 1888 in Trichinopolis, southern India. His father was a university professor of mathematics and physics, and he gave him scientific enlightenment education since childhood, and cultivated his love for music and musical instruments. He was gifted, graduated at the age of 16, and won the gold medal in physics in the first place. 19 years old and won with honors

Electrochemical in situ Raman spectroscopy is a method that uses the scattering phenomenon of material molecules to significantly change the frequency of incident light. Monochromatic incident light (including circularly polarized light and linearly polarized light) is used to excite the electrode modulated by the electrode potential. On the surface, the relationship between the scattered Raman spectrum signal (changes in frequency, intensity, and polarization performance) and electrode potential or current intensity is measured. The Raman spectrum of general substance molecules is very weak. In order to obtain an enhanced signal, the electrode surface can be roughened to obtain a Surface Enhanced Raman Scattering (SERS) spectrum with an intensity of 104-107 times higher. When molecules with resonance Raman effect are adsorbed on the surface of the roughened electrode, a surface-enhanced resonance Raman scattering (SERRS) spectrum is obtained, and the intensity can be increased by 102-103.

The measurement device of electrochemical in situ Raman spectroscopy mainly includes two parts: a Raman spectrometer and an in situ electrochemical Raman cell. The Raman spectrometer consists of a laser source, a collection system, a spectroscopic system, and a detection system.The light source generally uses a laser with high energy concentration and high power density.The collection system consists of a lens group. In addition to Rayleigh scattering and stray light, the spectroscopic detection system uses a photomultiplier tube detector, a semiconductor array detector, or a multi-channel charge coupling device. The in situ electrochemical Raman cell generally has a working electrode, an auxiliary electrode and a reference electrode, and a ventilation device. To prevent corrosive solutions and gases from attacking the instrument, the Raman cell must be equipped with a sealed system of optical windows. When the experimental conditions allow, in order to avoid the interference of the solution signal as much as possible, a thin layer solution (the distance between the electrode and the window is 0.1 to 1 mm) should be used. This is very important for the micro Raman system, and the optical window or the solution layer is too thick It will cause the optical path of the microscope system to change, which will reduce the collection efficiency of surface Raman signals. The most common method for electrode surface roughening is the electrochemical oxidation-reduction cycle (ORC) method, which can generally be performed in situ or ex situ ORC.

The research progress of electrochemical in situ Raman spectroscopy is mainly as follows: First, the test system has been broadened to transition metal and semiconductor electrodes through surface enhancement treatment. Although electrochemical in situ Raman spectroscopy is a more sensitive method for on-site detection, only silver, copper, and gold electrodes can give strong SERS in the visible light region. Many scholars have tried to achieve surface-enhanced Raman scattering on transition metal electrodes and semiconductor electrodes with important application backgrounds. The second is to analyze the structure, orientation of the species adsorbed on the electrode surface and the relationship between the SERS spectrum of the object and the electrochemical parameters, and to describe the electrochemical adsorption phenomenon at the molecular level. Third, by changing the frequency of the modulation potential, a "time-resolved spectrum" can be obtained that changes at two potentials to analyze the relationship between the SERS peak of the system and the potential, and solve the problem that the SERS active site on the electrode surface changes with the potential. Bring problems. ^[3]