Avance 300 spectrometer

Powder X-ray diffraction (PXRD) data were obtained using a Panalytical X’pert diffractometer with a CuKα radiation (λ = 1.54155 Å). Fourier-transform infrared spectroscopy (FTIR) measurements were carried out on solid products using a Thermo Nicolet 5700 spectrometer, employing KBr tablets at a mass ratio of 1:100 (sample:KBr) with a resolution of 4 cm⁻¹ and accumulation of 64 scans. The solid-state ²⁷Al, ³¹P and ²⁹Si NMR spectra were acquired using a Bruker AVANCE 300 spectrometer operating at 7.05 Tesla, equipped with a 4 mm zirconia multinuclear solids probe and magic angle spinning at 12 kHz. Thermagravimetric analysis (TGA) curves and differential thermal analysis (DTA), used to calculate the water content in the LDH precursors, were obtained with a TG-DTA SETSYS Evolution analyzer from SETARAM, using 150 μL alumina crucibles and a heating rate of 5 °C min⁻¹ under air flow of 50 mL min⁻¹.
The scanning electron microscopic (SEM) images were obtained using a Cambridge Scan 360 SEM operating at 1 kV and a Zeiss supra 55 FEG-VP operating at 3 keV. The samples were mounted on conductive carbon adhesive tabs for imaging.

The following instruments were used: melting points (uncorrected), Gallenkamp; IR spectra, Perkin-Elmer Spectrum One FT-IR spectrophotometer with ATR sampling unit; nuclear magnetic resonance spectra, BRUKER Avance 300 spectrometer; chemical shifts are given in parts per million (δ) downfield from tetramethylsilane as internal standard; mass spectra, Varian MAT 311A (EI) or UPLC/Orbitrap MS system (ESI); microanalyses, Perkin-Elmer 2400 CHN elemental analyzer. All tested compounds were >95% pure by elemental analysis.

¹H NMR spectra were obtained by using a Bruker Avance 300 spectrometer (300 MHz). Mass (MS) spectra were performed on a JEOL JMS-600W/JMS-700GC, and elemental analyses (EA) were performed on a Flash EA 1112 (Thermo Fisher Scientific) instrument. Absorption and emission spectra were recorded on a Shimadzu UV-1650PC spectrophotometer and a Varian Cary Eclipse fluorescence spectrophotometer, respectively. Fluorescence lifetimes were measured by the time-correlated single-photon counting (TCSPC) technique, in which a FluoTime 200 instrument (Picoquant) including a 377 -nm pulsed diode laser (fwhm ~70 ps) as an excitation light was used. The decay profiles of fluorescence were investigated by exponential fitting models through FluoFit Pro software. Absolute PL quantum yields were measured by employing a 3.2-in. integrating sphere in a Photon Technology International QM-40 spectrometer, and relative PL quantum yields were obtained using Fluorescein as a reference. The photographs of fluorescence images under illumination at 365 nm were acquired by a Canon (PowerShot G6) camera. A UV lamp (365 nm, 1.2 mW cm⁻²) and a xenon lamp (300 W) equipped with a monochromator (Newport) or a color filter (> 420 nm of Newport) were used as a UV-light source and a visible-light source, respectively. Energy-Filtering Transmission Electron Microscope (EF-TEM) was performed with LIBRA 120 (Carl Zeiss).

Commercially available reagents were used as received without additional purification. Melting points were determined with an SM-LUX-POL Leitz hot-stage microscope (Leitz GMBH, Midland, ON, USA) and are uncorrected. IR spectra were recorded on a 380FT-IR spectrophotometer (Nicolet- Thermo Electron Scientific Instruments LLC, Madison, WI, USA). NMR spectra were recorded with tetramethylsilane as an internal standard using an AVANCE 300 spectrometer (Bruker BioSpin, Wissembourg, France). Splitting patterns have been designated as follows: s = singlet; d = doublet; t = triplet; m = multiplet. Analytical TLC were carried out on 0.25 precoated silica gel plates (POLYGRAM SIL G/UV254) and visualization of compounds after UV light irradiation. Silica gel 60 (70–230 mesh) was used for column chromatography. High resolution mass spectra (electrospray in positive mode, ESI+ or MALDI-TOF MS) were recorded on a Q-TOF Ultima apparatus (Bruker Daltonics, Bremen, Germany). Elemental analyses were found within ±0.4% of the theoretical values.

¹H NMR analysis of purified acemannan was carried out according to the method proposed by Bozzi et al. [32 (link)] with slight modifications reported by Minjares-Fuentes et al. [30 (link)] using a Bruker Avance 300 spectrometer (Billerica, MA, USA) equipped with a 5 mm broadband multinuclear z-gradient (BBO) probehead.
Nicotinamide was used to calculate the area under the curve of the corresponding signal of acetyl groups in order to determinate the relative degree of acetylation (DA) of the acemannan polymer. The relative DA of processed samples in relation to the reference sample was calculated using the following Equation (1):
$$\mathit{Relative} \mathit{degree} \mathit{of} \mathit{acetylation} =\left(\frac{A_{processed}}{A_{reference}}\right)\times 100$$
where A_processed and A_reference are the area under the curve of the signals of acetyl groups corresponding to the processed and reference Aloe vera samples, respectively.

All reagents were purchased from commercial sources and used without treatment, unless otherwise indicated. The products were purified by recrystallization. ¹H and ¹³C NMR spectra were recorded on a Bruker AVANCE-300 spectrometer at 25 °C using TMS as an internal standard and deuterated DMSO (DMSO-d₆) as the solvent. Petroleum ether (PE) used was the fraction boiling in the range 30–60 °C. Elemental analyses were obtained on a Vario EL analyzer.