Recently, Prof. Yang’s group from IIM imported UC materials into SERS technique, which realized the sensitive detection under longer wavelengths and low-energy excitation. The corresponding results have been accepted by Journal of Materials Chemistry A (2015, DOI: 10.1039/C5TA03143E) and Analyst (2015, DOI: 10.1039/C5AN00441A).
SERS technique has become one of the most widely used spectroscopic tools for identification and detection of chemical and biological species and molecular imaging and monitoring. The excitation lasers used in most SERS studies are the UV/visible lights because LSPR frequencies of Ag and Au nanostructures locate in the UV/visible range. However, the laser power of UV/visible light may damage the target molecules for the long illumination time. Therefore, it is still an attractive challenge to develop the nanostructures that can not only well match the near-infrared excitation, but generate the high SERS enhancement under relatively lower levels of laser power as well.
Aiming at this problem, researchers synthesized an upconversion microcrystal (NaYF4:Yb,Er) decorated with Ag NPs (NaYF4:Yb,Er@Ag). The UC emission materials can convert infrared radiation into visible light. NaYF4:Yb,Er@Ag showed good Raman enhancement and plasmon photocatalysis behaviors under NIR excitation with a relatively low laser power. Through a series of reasonable experiments, the role of UC materials in this composite substrate was unraveled. The researchers also synthesized another composite substrate NaYF4:Yb,Tm@TiO2@Ag, which can implement photocatalytic degradation of the dyes molecular under non-Ultraviolet excitation. By virtue of monochrome laser lines, SERS analysis provides the direct evidence to prove the capability of UC-initiated non-UV photocatalysis and the improvement of the utilization of non-UV lights on TiO2. The results revealed that this new photocatalytic platform can efficiently utilize different bands of the solar spectrum and it also find new applications in SERS fields.
This work was supported by National Basic Research Program of China, National Instrumentation Program of China and National Natural Science Foundation of China.
Illustration of the relevant processes of energy transfer in UC@Ag particles and the local electric field enhanced by the LSPR of Ag NPs.
Article links：1. http://pubs.rsc.org/en/content/articlelanding/2015/ta/c5ta03143e