Imaging and spectroscopic analysis of single microdroplets containing p-cresol using the near-infrared laser tweezers Raman microprobe system

The near-infrared (NIR) laser tweezers/Raman microprobe system features two charge-coupled device (CCD) cameras with holographic notch filters (HNFs f or the imaging and spectroscopic analysis of molecules in a single microdro plet (MD), One CCD camera and a HNF are used to record an image of the lase r microprobe in a trapped MD. The other CCD camera and two HNFs are used wi th a polychromator to obtain a Raman spectrum of molecules in the MD. A die lectric multilayer coated beam splitter divides the scattered NIR light int o two optical paths for the cameras. The system provides sufficient sensiti vity to obtain a Raman spectrum of p-cresol contained in a single picoliter toluene MD and sufficient spatial resolution to record an image of the las er microprobe in a trapped MD simultaneously. Furthermore, a difference in the solubility for the p-cresol in bulk solvent and in the MD solvent was c learly observed using this system. (C) 1999 Elsevier Science B.V. All right s reserved.