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Surface plasmons are collective oscillations of free electrons at the interface between metal and dielectric. Surface plasmons can break through the diffraction limit of light, because the electromagnetic field is confined in a very small space near the surface of the nanostructure, which provides a possibility for nanometer-scale light manipulation. By using surface plasmon resonance, the local surface electromagnetic field can be strongly enhanced, which can be used to enhance the molecular fluorescence and Raman signals. In addition, the plasmon relaxation induces thermal electrons which can drive the catalytic reaction of surface molecules to achieve a selective catalytic reaction at normal temperature, which is so-called plasmon mediated chemical reaction (or plasmonic catalysis). As a new type of catalytic system, plasmonic catalysis can mediate chemical reactions that are difficult to occur under various conventional conditions. Due to the complexity and diversity of plasmon catalyzed reactions, it is still a huge challenge to fully characterize the reaction kinetics and understand its reaction mechanism. Characterizing the intermediate and final products in the catalytic reaction accurately and obtaining more detailed information in the reaction process are essential for exploring the theoretical mechanism of plasmon catalysis. In this paper, we review the characterization techniques used in plasmon catalysis in detail in the progress of plasmon catalysis. First, the basic concepts of plasmon catalysis and several common catalytic mechanisms are introduced. Second, the Raman spectroscopy, including the application of surface and tip-enhanced Raman spectroscopy in plasmon catalytic in situ monitoring are reviewed. Then, the other techniques such as gas chromatography, gas chromatography-mass spectrometry, high performance liquid chromatography, scanning transmission electron microscopy, scanning tunneling microscopy, scanning electrochemical microscopy and UV-visible absorption spectroscopy for monitoring plasmon catalyzed reaction are introduced in detail. Finally, the characteristics and advantages of these characterization techniques in the study of kinetic catalytic process and catalytic mechanism of plasmon, and the future development and challenge are mentioned and analyzed.

Due to their future applications in optical communication, nonlocal dark solitons in bulk medium and surface bright solitons have received much attention recently. However, nonlocal surface dark solitons have not been investigated till now. In this paper, 1+1 dimensional nonlocal fundamental and second-order surface dark solitons have been found numerically at the interface between thermal nonlinear medium and linear medium. The relation between the wave shape of nonlocal surface dark soliton and propagation constant and nonlocality degree is investigated. Moreover, the stability of them is analyzed theoretically. The numerical simulation results show that 1+1 dimensional nonlocal fundamental surface dark Solitons are always stable in the domain of their existence, while second-order surface dark solitons are oscillatorily unstable and the width of unstable domain depends more greatly on propagation constant than nonlocality degree of nonlocal nonlinear medium. The figure showing the propagation, with the initial input of noise added, confirms the correctness of stability analysis results.

Due to its future use in communication area, nonlocal spatial optical soliton has been a hot research topic recently. However, because of its special border condition, little research has been done on spatial dark solitons especially on its linear stability. In this paper, a method to analyze linear stability of nonlocal spatial dark soliton is put forward, moreover a numerical simulation and analysis is done on the linear stability of (1+1)-dimensional fundamental and second-order dark soliton in thermal nonlinear medium. Numerical results show that (1+1)-dimensional fundamental nonlocal dark solitons are always stable in their entire existence domain, while second-order dark solitons are oscillatorily unstable and the width of unstable domain depends on propagation constant and nonlocality degree of thermal nonlinear medium. The propagation graphs of initial input with noise addition confirms the correctness of linear stability analysis results.