LSPR refers to localized surface plasmon resolution. When incident light hits metal nanoparticals, free elelctrons inside the nanoparticals resonate with the electromagnetic field of light. An enhanced electromagnetic field around the nanoparticle (usually less than 10 nm) is formed. Chemical reaction, dielectric constant and the conformational change of biomolecules can affect the resolution frequence of nanoparticals which open a fantastic pathway for conducting bioannalysis. Our gruop has combined i-motif DNA (an pH sensitive DNA) with the LSPR properties of AuNPs and observed spectrum shift of the combined complex (Analytical Chemistry, 2013, 85 (2): 1053¨C1057; Figure 1). Now we can observe the spectrum of sigle nanoparticle under dark field mode of a lab-build nanoparticle scattering spectrum observing system(Chem. Comm. 2014, 50, 5480-5483;Figure 2).
Figure 1. AuNP-i-motif complex and its spectrual response upon pH variation
Figure 2. Biocatalysis recation on single nanoparticles
ATR-SEIRAS refers to attenuated total reflection mode of surface enhanced infared absorption spectrum. Molecules adsorbed on rough surfaces like Au-island-film exhabites enhanced IR absorption. ATR mode of SEIRAS allows a thin layer of molecules on the interface be detected, which greatly reduced the affact of water in IR measurements. Bioreactions which usually occours in aqueous system then can be detected in situ based on this technique. The source of such enhancement is unclear though many people tried to explain it using the theory of surface enhanced Raman sperctrum. Our lab first apply such technique in bioananalysis (Chemical Communications 2012, 48(25): 3052 - 3054; Figure 3) and is now exploring the link between LSPR and SEIRAS through fabricating different nanostructures and testing their IR enhancement factors.
Figure 3. Detecting DNA using ATR-SEIRAS
Figure 3. Detecting of protein using ATR-SEIRAS