SERS and DFT study of 5F‐PB‐22

Abstract

In this work, a joint experimental and theoretical study on the synthetic cannabinoid, 5F-PB-22 (1-(5-fluoropentyl)-8-quinolinyl ester-1H-indole-3-carboxylic acid) is reported. The molecular vibrations of 5F-PB-22 were investigated by Raman and surface-enhanced Raman spectroscopy (SERS) spectroscopies. In parallel, quantum chemical calculations based on density functional theory (DFT) with the hybrid B3LYP exchange-correlation functional coupled with the standard 3-21G basis set were used to determine the geometrical and vibrational characteristics of 5F-PB-22 and to predict the adsorption geometry of the molecule on the silver colloidal surface. The SERS spectrum of 5F-PB-22 was recorded using a 532-nm laser line and a hydroxylamine phosphate reduced silver colloid as the SERS substrate. SERS and Raman spectral bands have been assigned by comparison with the DFT calculated spectrum. A self-aggregation spectrum was obtained, but in order to obtain a spectrum with NaCl as the aggregating agent, a two-step procedure was developed. It was found that 10-mM NaCl can be used as a trigger for aggregation before adding 5F-PB-22followed by the addition of 20-to 100-mM NaCl to complete aggregation. Using this procedure, 5F-PB-22 was easily detected at 2.12 × 10 −8 M. Based on a predicted molecular adsorption geometry from the calculated molecular electrostatic potential and the SERS spectrum, it is proposed that the quinoline moiety of the molecule lies in a preponderant parallel orientation to the silver surface with the plane of the indole ring being perpendicular to the surface.The molecular orientation is affected by the surface coverage by 5F-PB-22 and the presence of Cl − .

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

“…Alkaseem and Baron reported a joint experimental and theoretical study on the synthetic cannabinoid, 5F‐PB‐22 (1‐(5‐fluoropentyl)‐8‐quinolinyl ester‐1H‐indole‐3‐carboxylic acid). They found that 5F‐PB‐22 was easily detected at 2 × 10 −8 M. Based on a predicted molecular adsorption geometry from the calculated electrostatic potential and the SERS spectrum, it is proposed that the quinoline moiety of the molecule lies in a preponderant parallel orientation to the silver surface with the plane of the indole ring being perpendicular to the surface . Atanasov et al carried out a SERS analyses of thiamethoxam assisted by Ag films and nanostructures that were produced by laser techniques.…”

“…They found that 5F-PB-22 was easily detected at 2 × 10 −8 M. Based on a predicted molecular adsorption geometry from the calculated electrostatic potential and the SERS spectrum, it is proposed that the quinoline moiety of the molecule lies in a preponderant parallel orientation to the silver surface with the plane of the indole ring being perpendicular to the surface. [33] Atanasov et al carried out a SERS analyses of thiamethoxam assisted by Ag films and nanostructures that were produced by laser techniques. Their simple fabrication method and demonstrated efficiency has a direct bearing on human health and food quality by assisting in the detection of small amounts or residue of harmful pollutants.…”

SERS and DFT studies of 2‐(trichloroacetyl)pyrrole chemisorbed on the surface of silver and gold coated thin films: In perspective of biosensor applications

“…[11][12][13] In order to get the higher SERS signal enhancement effect, the SERS substrates should have high sensitivity, uniformity, surface purity, good stability, and reproducibility. [14][15][16] Moreover, the SERS signal enhancement of the probe molecules depends on the particle size, particle shape, and interparticle distance of the metal nanoparticles substrates. In general, SERS signal enhancement mainly occurs because of long-range electromagnetic (EM) and short-range charge-transfer (CT) mechanisms.…”

In Silico Infrared Characterization of Synthetic Cannabinoids by Quantum Chemistry and Chemometrics

“…16 Raman and surface-enhanced Raman spectroscopy (SERS) have been reported for the synthetic cannabinoid 5F-PB-22. 17 A DFTsupported in-depth vibrational characterization of JWH-018 in the solid-state and in solution can also be found. 18 Electronic spectra have been calculated for both JWH-250 and JWH-081.…”

“…Both the IR and the normal Raman spectra of AMB-FUBINACA and α-PVP have been calculated . Raman and surface-enhanced Raman spectroscopy (SERS) have been reported for the synthetic cannabinoid 5F-PB-22 . A DFT-supported in-depth vibrational characterization of JWH-018 in the solid-state and in solution can also be found .…”