The concentration dependent SERS studies of a bioactive 4-chlorobenzylidene derivative: Experimental and DFT investigations

In this work, the vibrational spectroscopy of the compound (E)-4-(tert-butyl)-Nˈ-(4-chlorobenzylidene)benzyhydrazide (TCB), which was studied in conjunction with theoretical calculations, is applied for Surface Enhanced Raman Scattering (SERS) studies. The assignments of the vibrational modes were completed with Density Functional Theory (DFT)/B3LYP/6-311++G*. The information gathered is utilized to determine the chemical and electrical characteristics in addition to wavenumber measurements. The TCB molecule's chemisorbed status on colloidal nanoparticles is confirmed by acquired red shift and decreased intensity behavior in the UV–VIS spectrum analysis. Additionally, the SERS spectra at varied concentrations and the chemisorption of the molecule with metal cluster were recorded and examined. Additionally, a silver cluster-based theoretical SERS model is put forth. The findings presented here will help in the construction of more dependable SERS sensors by thoroughly describing the concentration-dependent profile of analyte orientation

DFT, TD-DFT and SERS analysis of a bioactive benzohydrazide's adsorption in silver hydrosols at various concentrations

SERS was used to analyze the surface adsorption of a benzohydrazide derivative on silver nanoparticles. Density functional theory (DFT) calculations were used to determine the vibrational assignments in the surface-enhanced Raman scattering (SERS) spectra of (E)-4-methyl-Nˈ-[4-(trifluoromethyl)benzylidene]benzohydrazide (TFB) at various concentrations. TFB mostly adsorbs through C=O group and rings with silver. On the silver surface, however, the adsorption takes place through the ring's π-electrons. As concentration of silver hydrosol changes, changes in orientation of TFB occur. TFB is adsorbed with a binding affinity of −131.74 kcal mol−1, suggesting a chemisorption process according to theoretical analysis. The time dependent-DFT analysis gives an adsorption of 310 nm for TFB while with silver complex there is a peak to higher values as a doublet at 520 and 688 nm with lowering of intensity as expected. The changes of thermodynamical parameters during adsorption are all are negative suggesting the adsorption process is spontaneous and exothermic

Concentration dependent SERS study of a bioactive methylsulfonyl derivative

Concentration dependent surface enhanced Raman scattering (SERS) studies of biologically active methylsulfonyl derivative (BMSP) are reported. Out of various concentrations, SERS at 10-3 M gives maximum enhancement. The experimental results are supported by theoretical investigations. BMSP exhibited selective micro molar activity against Staphylococcus aureus. The interaction of charge transfer between Ag and S atoms is confirmed by the enhanced bond length values. Reduction in ionization potential suggests that the BMSP-Ag6 system has stronger electron donating characteristics than BMSP. The electrophilicity index of the adsorbed system containing BMSP and silver cluster represent biological activity and the adsorption process is chemisorption. Presence of CH3 modes in the SERS spectrum suggest that the molecule adopts a tilted orientation, and that para-substituted phenyl ring is more slanted than poly-substituted phenyl ring. Presence of ring stretches, bending modes for all concentrations suggest that the BMSP molecule may tilt, resulting in an interaction with the metal surface and there is an orientation change for the molecule with respect to the metal surface as concentration changes

Experimental and DFT investigations of SERS Profile of a Bioactive Hydroxybenzamide Derivative

Surface enhanced Raman scattering (SERS) experiments were used to evaluate the adsorption and orientation of 5-bromo-N-[4-bromo-3-(trifluoromethyl)phenyl]-2-hydroxybenzamide (BTB) adsorbed on silver colloid and the results were compared to normal Raman spectra of BTB. Density functional theory (DFT) analysis was used to theoretically validate the observed spectra of BTB. BTB and BTB-Ag6 molecular structures were optimized at first. The BTB molecule is adsorbed with the Ag6 with energy of −10.67 eV through atoms, O9, F22 and Br17 atoms. The charge transfer interaction between Ag6 clusters and BTB, which lead to BTB adsorption on Ag6 metal clusters, is confirmed by the Frontier Molecular Orbitals (FMOs) study. The BTB chemisorbed on silver with a tilted orientation, as confirmed by SERS spectral analysis and the accompanying results were theoretically justified

DFT, SERS-concentration and solvent dependent and docking studies of a bioactive benzenesulfonamide derivative

Spectroscopic analysis, DFT studies and surface enhanced Raman scattering (SERS) of antimicrobial bioactive 4-[(5-tert-butyl)2-hydroxybenzylidene]amino-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide (THPB) have been studied on different silver sols. Intensity and hence enhancement variations are observed for Raman and SERS bands. Observed changes in the ring modes may be due to surface π-electron interactions and presence of this indicated that molecule is inclined with respect to the metal surface. Changes in orientation are seen in SERS spectra depending on concentration. The molecular docking results show that binding affinity and interactions with the receptors may be supporting evidence for further studies in design further THPB pharmaceutical applications. Reactivity properties are obtained from DFT analysis

Insights into the Adsorption Nature of a Bioactive Anticancer Derivative of Benzenesulfonate on Silver Colloids at Various Concentrations: Experimental and DFT Investigations

Density functional theory was used in the present study to report and validate the 4-chloro-2-[(3,5-dichlorophenyl)carbamoyl]phenylbenzenesulfonate’s (CPB) IR, Raman and SERS spectra. The molecular systems, CPB and CPB-Ag6 were initially optimized. Frontier molecular orbital study demonstrates that in CPB-Ag6 complex, charge transfer (CT) interaction occurs between Ag and molecule. CT interaction in the examined systems was further verified by the MEP surface. The CPB is chemisorbed on Ag6 with affinity and a tilted orientation through lone pair electrons of atoms, according to Raman and SERS spectral analyses. Additionally, there was good correlation between the theoretical and observed results. The current study thus lays the path for designing robust SERS active substrates that will be useful for creating biosensors related to the CPB molecule

Concentration dependent SERS profile of p-tolyl 2-acetamido-3-(4-fluorophenyl)propanoate (AFP) in silver colloidal nanohydrosols: Experimental and DFT investigations

Based on Density Functional Theory (DFT) calculations and the Surface Enhanced Raman Scattering (SERS) technique, the adsorption properties of p-tolyl 2-acetamido-3-(4-fluorophenyl)propanoate (AFP) on silver surface were examined. The title compound, AFP showed balanced inhibition of acetyl- and butyrylcholinesterase along with mild cytotoxicity of HepG2 cells according to the previous study. After adsorption on silver surface, the structural properties of AFP exhibit a small modification, indicating an interaction between the AFP and Ag6 cluster. Experimental research on AFP and SERS spectra at various concentrations was conducted. Raman frequencies for AFP and AFP adsorbed on silver were computed. FMOs for AFP and AFP adsorbed on the silver surface were conducted. After AFP was adsorbed on the silver, the energy gap was dramatically lowered. The greater bioactivity of AFP is caused by the lowering energy gap, which denotes the electron delocalization. According to SERS spectrum analysis, AFP was adsorbed on silver with a tilted orientation. As a result, the current study has been used as a model system to comprehend how silver nanoprticles (NP) interact with AFP. Silver nanoparticles are successfully used for the treatment of different diseases alone or in association with other active components and the incorporation of AFP with silver nanocolloids will act as a nanodrug delivery system