Distance-determined sensitivity in attenuated total reflection-surface enhanced infrared absorption spectroscopy: aptamer-antigen compared to antibody-antigen.

Distance-dependent signal intensity in immunoassay by attenuated total reflection-surface enhanced infrared absorption spectroscopy is demonstrated by controlling the distance of target proteins away from the enhancement substrate. Based on this optical near-field effect, sensitive detection of protein molecules with a detection limit of 0.6 nM and investigation of the kinetics and thermodynamics of protein-aptamer/antibody interactions can be achieved.

Flat-plateau supercontinuum generation in liquid absorptive medium by femtosecond filamentation.

We have studied filamentation and supercontinuum generation by focusing the intense femtosecond laser pulses into an absorptive medium (CuSO(4) aqueous solution). A broad spectrum from 350 to 950 nm with a flat plateau spanning approximately from 450 to 700 nm with a flatness of 9% is obtained without any additional filters. The results indicate that the absorptive medium not only suppresses the strong surplus femtosecond laser signal but also flattens the supercontinuum spectrum efficiently.