研究目的
To investigate the optical activity of samples prepared under ultra-high vacuum (UHV) conditions using second-harmonic generation circular dichroism (SHG-CD) over a broad spectral range, focusing on the chiroptical properties of R- and S-enantiomer of 1,1'-Bi-2-naphthol (BINOL) films.
研究成果
The SHG-CD setup enables the study of optical activity of UHV-prepared samples with submonolayer sensitivity. The technique provides significant insights into the chiroptical properties of molecular films, with potential applications in the study of asymmetric heterogeneous catalysts.
研究不足
The study is limited by the sensitivity of the SHG-CD technique and the challenges associated with combining UHV sample preparation with laser spectroscopy. The interpretation of results is complicated by the need to disentangle contributions from single molecules and long-range orders.
1：Experimental Design and Method Selection
The study combines a UHV system for sample preparation with a laser spectroscopy setup for linear absorption and nonlinear SHG studies. The setup allows for precise control over sample preparation and contamination minimization.
2：Sample Selection and Data Sources
BINOL films of varying thicknesses were prepared on BK7 substrates under HV conditions, with coverage monitored by a quartz crystal microbalance (QCM).
3：List of Experimental Equipment and Materials
Optical parametric amplifier laser system, photoelastic modulator (PEM), fused silica lenses, Pellin-Broca prisms, monochromator (MC), photomultiplier tube (PMT), and a LabVIEW program for automation.
4：Experimental Procedures and Operational Workflow
Samples were prepared by evaporation of BINOL on glass substrates under HV conditions. SHG-CD experiments were performed at 0 °C to suppress self-ordering effects. Wavelength scans between 225 nm and 340 nm were recorded for films of pure enantiomers and the racemate.
5：Data Analysis Methods
The SH intensity was corrected for the spectrometer function and the anisotropy factor was calculated. The SH spectra were analyzed to determine the optical activity of the samples.
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