Comparison of SERS microscope laser illumination modes. Here we present SERS spectra of BPE (10 µm concentration) measured on Au nanopillars substrate at point (black), DL line (red), and WL (blue) illumination modes; zoomed spectra in the range 1750–1950 cm−1 for SNR demonstration. All presented spectra were acquired at equal conditions: 0.2 mW µm−1 of laser intensity, laser wavelength 785 nm, exposure time 0.1 s, 10× magnification microscope objective. SNR was measured as signal divided on RMS noise.
MCR and NNLS decomposed results of hydrate and anhydrous solid-state forms of theophylline. (a) Optical image of TP MH at 25 °C with laser line illumination (white line) from the Raman microscope (b) concentration profile of solid-state forms during isothermal dehydration at 50 °C for 90 minutes starting from TP MH to TP AH form II, via TP MS1 and TP MS2 (c1–4) chemical concentration maps (cut out artefacts from 1.8 mm laser line) of TP MH (c1), TP MS1 (c2), TP MS2 (c3), TP AH form II (c4) in the particle during dehydration where the laser line is illuminated, (d1–4) Raman spectra for TP MH, TP MS1, TP MS2 and TP AH form II respectively, (e1–e4) area plots showing only the dehydration profiles of TP metastable intermediates at four isothermal conditions (45, 50, 60 and 65 °C) where the colour under the area plots matches the TP metastable intermediates as shown in the concentration profiles. The stable forms of TP were taken into consideration for the area plots.