Raman spectroscopy and quantum-mechanical analysis of tautomeric forms in cytosine and 5-methylcytosine on gold surfaces

Nguyen, Dinh Bao; Nguyen, Thanh-Danh; Kim, Sang Soo; Joo, Sang‐Woo

doi:10.1016/j.saa.2016.11.004

Cited by 7 publications

(6 citation statements)

References 28 publications

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“…It is very difficult to separate the contribution of each mechanism by purely experimental means, and consequently, the quantum chemical calculations are necessary. Although there are several papers in the literature − on the SERS of DNA bases adsorbed on different metal nanostructures, especially Ag, Au, and their bimetallic nanostructures, the CT enhancement contribution in the SERS has not been studied for the DNA bases on metal surfaces. It is important to note that the absorption lines that are appropriate for our calculations are those with no other absorption lines near them.…”

Section: Resultsmentioning

confidence: 99%

“…The displacement of the position of LSPR of the metal nanostructure in the UV spectrum due to the interaction between the nanostructure and adsorbate and change in its intensity have been used as a tool for the sensing of DNA bases with nanostructures. The IR and SERS spectra have been employed to obtain information about the adsorption geometry of DNA bases on the surface of nanostructures. − …”

Section: Introductionmentioning

confidence: 99%

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Theoretical Spectroscopic Study on the Au, Ag, Au/Ag, and Ag/Au Nanosurfaces and Their Cytosine/Nanosurface Complexes: UV, IR, and Charge-Transfer SERS Spectra

Farrokhpour

Ghandehari

2019

J. Phys. Chem. C

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The first part of this work is related to the calculation of the absorption spectra of pure Ag and Au nanosurfaces, bimetallic nanosurfaces composed of Ag and Au metals (Au/Ag and Ag/Au), and the nanosurfaces interacted with cytosine (CYT/Au, CYT/Au/Ag, CYT/Ag, and CYT/Ag/Au). Comparison of the absorption spectra and changes in the total and partial density of states of the systems allowed the effect of metallic structures of the sublayer and adsorbate on the intensity and position of the maximum of the spectra to be explored. The absorption lines responsible for the charge transfer from CYT to nanosurfaces due to the electronic excitation for each CYT/nanosurface were determined, and the effect of sublayers on these electronic transitions was studied. In the second part of this work, the effect of the metallic structure of the sublayer on the infrared spectrum of CYT adsorbed on the Au/Ag and Ag/Au nanosurfaces was studied, and the vibrational bands of CYT that were sensitive to the metallic structure of the sublayer were determined. In addition, the frequency-dependent Raman spectra of CYT adsorbed on the selected nanosurfaces were calculated at several wavelengths corresponding to electronic excitation charge transfer from CYT to the nanosurface. The vibrational bands of CYT showing the intensity enhancement due to the charge transfer in the Raman spectrum for each nanosurface were determined. The theoretical spectroscopic results presented in this work are very useful for the interpretation of experimental results, especially when CYT is adsorbed on nanosurfaces such as Ag, Au, and their bimetallic nanosurfaces.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theoretical Spectroscopic Study on the Au, Ag, Au/Ag, and Ag/Au Nanosurfaces and Their Cytosine/Nanosurface Complexes: UV, IR, and Charge-Transfer SERS Spectra

Farrokhpour

Ghandehari

2019

J. Phys. Chem. C

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“…In most cases, the mechanism of the interactions between gold nanoparticles (AuNPs) and active substances remains a mystery, although it could be useful for understanding the release mechanism of the active substance or its activity within cells. The interaction between gold clusters, surfaces, or AuNPs and biomolecules has attracted the attention of scientists for many years: [ 11 ] (Au 8 , Au 20 with alanine, tryptophan), [ 12 ] (gold surface with cytosine, 5-methylcytosine), [ 13 ] (Au 13 with guanine), [ 14 ] (Au n with guanine-cytosine, adenine-uracil, n = 5–10), [ 15 ] (Au 1 with pyridine). The first experimental study that showed a direct interaction of pyridine with the gold surface was published in 1991 [ 16 ].…”

Section: Introductionmentioning

confidence: 99%

“…We have applied the density functional theory (DFT), which is a quantum-mechanical method offering tools for the investigation of interatomic and intermolecular interactions in new molecular systems. The studies employing DFT enabled us to provide reliable three-dimensional (3-D) molecular structures and numerous spectral properties of biologically and pharmacologically active molecules as was shown in the literature [ 11 , 12 , 13 , 14 , 15 , 16 ]. Bearing this in mind, we hope to obtain by means of DFT a reasonable estimation of the molecular structure, binding energy, and vibrational spectra of the Au n –AB conjugates.…”

Section: Introductionmentioning

confidence: 99%

Design and Molecular Modeling of Abiraterone-Functionalized Gold Nanoparticles

et al. 2018

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The aim of our work was the synthesis and physicochemical characterization of a unique conjugate consisting of gold nanoparticles (AuNPs) and a pharmacologically active anticancer substance abiraterone (AB). The direct coupling of AB with gold constitutes an essential feature of the unique AuNPs–AB conjugate that creates a promising platform for applications in nanomedicine. In this work, we present a multidisciplinary, basic study of the obtained AuNPs–AB conjugate. Theoretical modeling based on the density functional theory (DFT) predicted that the Aun clusters would interact with abiraterone preferably at the N-side. A sharp, intense band at 1028 cm−1 was observed in the Raman spectra of the nanoparticles. The shift of this band in comparison to AB itself agrees well with the theoretical model. AB in the nanoparticles was identified by means of electrochemistry and NMR spectroscopy. The sizes of the Au crystallites measured by XRPD were about 9 and 17 nm for the nanoparticles obtained in pH 7.4 and 3.6, respectively. The size of the particles as measured by TEM was 24 and 30 nm for the nanoparticles obtained in pH 7.4 and pH 3.6, respectively. The DLS measurements revealed stable, negatively charged nanoparticles.

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“…In particular, this resonance Raman effect occurs when the wavelength of the Raman excitation falls within the electronic excitation band of the molecule/metal complex. The first contribution, which affects both positions and relative intensities of the SERS bands differently, can be simulated well by DFT (density functional theory) calculations on the basis of the ground state of the model systems as molecules linked to metal adatoms, also recently performed [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. The second contribution could be analyzed instead within a time-dependent DFT approach, by calculating the excitation bands of the ligand/metal complex, which experimentally cannot be observed in the UV–visible absorption spectrum owing to the extremely low concentrations of the complex.…”

Section: Introductionmentioning

confidence: 96%

DFT and TD-DFT Study of the Chemical Effect in the SERS Spectra of Piperidine Adsorbed on Silver Colloidal Nanoparticles

et al. 2022

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The surface-enhanced Raman scattering (SERS) spectra of piperidine adsorbed on silver/chloride colloids were studied by a combined density functional theory (DFT)/time dependent DFT (TD-DFT) approach. The mechanism of chemical enhancement on the Raman signals is due to at least two contributions: the first comes from the changes in the molecular force constants and the dynamic polarizabilities of the normal modes, when the molecule is chemisorbed. DFT calculations satisfactorily reproduce the SERS spectra of piperidine adsorbed on silver, showing that the species formed on the silver particle is a complex formed by a deprotonated piperidine linked to a silver cation. A second contribution to the SERS chemical enhancement is due to a resonance Raman effect occurring when the wavelength of the Raman excitation falls within the electronic excitation band of the molecule/metal complex. Actually, the SERS spectra of piperidine show a significant dependence on the wavelength of the laser excitation, with a marked enhancement in the green-light region. TD-DFT calculations on the most-probable complex explain this behavior, because a strong excitation band of the complex is calculated in the green spectral region. This pinpoints that a resonance between the exciting radiation and the absorption band of this complex is responsible for this enhancement effect.

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Raman spectroscopy and quantum-mechanical analysis of tautomeric forms in cytosine and 5-methylcytosine on gold surfaces

Cited by 7 publications

References 28 publications

Theoretical Spectroscopic Study on the Au, Ag, Au/Ag, and Ag/Au Nanosurfaces and Their Cytosine/Nanosurface Complexes: UV, IR, and Charge-Transfer SERS Spectra

Theoretical Spectroscopic Study on the Au, Ag, Au/Ag, and Ag/Au Nanosurfaces and Their Cytosine/Nanosurface Complexes: UV, IR, and Charge-Transfer SERS Spectra

Design and Molecular Modeling of Abiraterone-Functionalized Gold Nanoparticles

DFT and TD-DFT Study of the Chemical Effect in the SERS Spectra of Piperidine Adsorbed on Silver Colloidal Nanoparticles

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