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Probing the adsorption of 1,10- and ...

Howard University., Chemistry.

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Probing the adsorption of 1,10- and 1,7-phenanthroline-5,6-dione on silver nanosurafce using Raman spectroscopy and density functional theory calculations.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Probing the adsorption of 1,10- and 1,7-phenanthroline-5,6-dione on silver nanosurafce using Raman spectroscopy and density functional theory calculations./
Author:	Onuegbu, Jonathan Ifeanyichukwu.
Description:	122 p.
Notes:	Adviser: Charles M. Hosten.
Contained By:	Dissertation Abstracts International70-03B.
Subject:	Chemistry, Analytical. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3350462
ISBN:	9781109084573

Probing the adsorption of 1,10- and 1,7-phenanthroline-5,6-dione on silver nanosurafce using Raman spectroscopy and density functional theory calculations.
Onuegbu, Jonathan Ifeanyichukwu.

Probing the adsorption of 1,10- and 1,7-phenanthroline-5,6-dione on silver nanosurafce using Raman spectroscopy and density functional theory calculations. - 122 p.

Adviser: Charles M. Hosten.

Thesis (Ph.D.)--Howard University, 2009.

The surface enhanced Raman scattering (SERS) of 1,10-phenanthroline-5,6-dione (phendione) adsorbed on silver nanospheres has been investigated. Normal Raman spectra of synthesized silver phendione complex and uncomplexed ligand were obtained. A comparison of the SERS spectra of phendione on a silver nanosurface, the normal Raman spectra of synthesized silver ion phendione complex, and the normal Raman spectra of solid phendione were performed and the results indicated that there are similarities between surface (adsorbed) species and synthesized complexes. Changes were observed in the frequencies and relative intensities of the uncomplexed ligand frequency bands compared to SERS and Ag+-phendione complex, indicating that the ligand was perturbed upon adsorption on the Ag surface as well as upon coordination to Ag + ion. X-ray crystallography was utilized to characterize the synthesized Ag+ -- phendione complexes. Theoretical calculations (Density Functional Theory (DFT)) in addition to FT-Raman analysis were utilized to assign Raman active bands to the Ag+- phendione complex. Three DFT methods -- B3LYP, BLYP, and P88-BW91 -- were utilized in this study. The assignment of vibrational bands was achieved by comparing the vibrational frequencies of phendione with the frequencies of Ag+-phendione. Evidence was found for Ag-N bond formation with the silver surface, supporting the validity of a chemisorption process. The experimental and calculated data suggest an adsorbate-substrate interaction with perpendicular (with a possible tilt angle) orientation of the molecule with respect to the Ag surface.

ISBN: 9781109084573Subjects--Topical Terms:

586156
Chemistry, Analytical.

Probing the adsorption of 1,10- and 1,7-phenanthroline-5,6-dione on silver nanosurafce using Raman spectroscopy and density functional theory calculations.
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020 $a 9781109084573
035 $a (UMI)AAI3350462
035 $a AAI3350462
040 $a UMI $c UMI
100 1 $a Onuegbu, Jonathan Ifeanyichukwu. $3 1022407
245 1 0 $a Probing the adsorption of 1,10- and 1,7-phenanthroline-5,6-dione on silver nanosurafce using Raman spectroscopy and density functional theory calculations.
300 $a 122 p.
500 $a Adviser: Charles M. Hosten.
500 $a Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1641.
502 $a Thesis (Ph.D.)--Howard University, 2009.
520 $a The surface enhanced Raman scattering (SERS) of 1,10-phenanthroline-5,6-dione (phendione) adsorbed on silver nanospheres has been investigated. Normal Raman spectra of synthesized silver phendione complex and uncomplexed ligand were obtained. A comparison of the SERS spectra of phendione on a silver nanosurface, the normal Raman spectra of synthesized silver ion phendione complex, and the normal Raman spectra of solid phendione were performed and the results indicated that there are similarities between surface (adsorbed) species and synthesized complexes. Changes were observed in the frequencies and relative intensities of the uncomplexed ligand frequency bands compared to SERS and Ag+-phendione complex, indicating that the ligand was perturbed upon adsorption on the Ag surface as well as upon coordination to Ag + ion. X-ray crystallography was utilized to characterize the synthesized Ag+ -- phendione complexes. Theoretical calculations (Density Functional Theory (DFT)) in addition to FT-Raman analysis were utilized to assign Raman active bands to the Ag+- phendione complex. Three DFT methods -- B3LYP, BLYP, and P88-BW91 -- were utilized in this study. The assignment of vibrational bands was achieved by comparing the vibrational frequencies of phendione with the frequencies of Ag+-phendione. Evidence was found for Ag-N bond formation with the silver surface, supporting the validity of a chemisorption process. The experimental and calculated data suggest an adsorbate-substrate interaction with perpendicular (with a possible tilt angle) orientation of the molecule with respect to the Ag surface.
520 $a Intense well resolved spectra of solid 1,7-phendione with high S/N are reported. Assignment of the normal modes was achieved by employing density functional theory calculations using B3LYP, BLYP, and B88-PW91 methods and comparing the frequencies with assigned bands of 1,10-phenanthroline-5,6-dione, an analogue of 1,7-phendione. Results of the DFT calculations were consistent and showed close agreement with the experimental values.
520 $a The Surface Enhanced Raman Scattering (SERS) of 1,7-phenanthroline-5,6-dione (1,7-phendione) adsorbed on a Ag nanosurface is reported. The FT-Raman of solid 1,7-phendione and Ag+ 1,7-phendione complex have been examined. Using Density Functional theory (BLYP and B88-PW91) a complete assignment of the Ag 1,7-phendione in the region of 100 -- 1800 cm-1 is reported. X-ray studies revealed that the Ag metal is bound to the ligand in the ratio of 1:2 (metal : ligand) and that one of the 1,7-phendione ligand hydrolyzed to a gem-diol at one of the quinone carbonyl. Cu 1,7-phendione complex was also synthesized (1:2 metal: ligand ratio). X-ray studies confirmed that the preferred point of interaction between the ligand and the metals (Ag and Cu) ions is the nitrogen atom of the imine moiety at the 7 position and the oxygen atom at the 6 position. DFT calculations on these molecules confirmed that these points of interaction between the ligand and the metal ions produce the lowest energy conformation for the complexes. The presence of an intense band at 1615 cm-1(C=C vibrations), C=N vibrations at1320 cm-1, and the band at 721 cm-1 (band indicative of the adsorption of phenanthroline analogue on metal surface), which were absent in the Raman spectrum of the bulk sample establishes that the 1,7-phendione is not adsorbed flat on the Ag nanosurface.
520 $a SERS active surfaces were prepared by depositing silver films using Tollen's reaction onto barium titanate beads. The SERS activity of the resulting surfaces was probed using two thiols (benzene thiol and 1,2 benzene dithiol) and rhodamine 6-G. The intensity of the SERS signal for the three analytes was investigated as a function of silver deposition time. The results indicate that the SERS intensity increased with increasing thickness of the silver film until a maximum signal intensity was achieved; additional silver deposition resulted in a decrease in the SERS intensity for all of the studied molecules. SEM measurement of the Ag coated barium titanate beads, as a function of silver deposition time, indicate that maximum SERS intensity corresponded with the formation of atomic scale islands of silver nanoparticles. Complete silver coverage of the beads resulted in a decreased SERS signal and the most intense SERS signals were observed at deposition times of 30 minutes for the thiols and 20 minutes for rhodamine 6G.
590 $a School code: 0088.
650 4 $a Chemistry, Analytical. $3 586156
690 $a 0486
710 2 $a Howard University. $b Chemistry. $3 1022406
773 0 $t Dissertation Abstracts International $g 70-03B.
790 $a 0088
790 1 0 $a Bakare, Oladapo $e committee member
790 1 0 $a Butcher, Raymond $e committee member
790 1 0 $a Gultneh, Yilmah $e committee member
790 1 0 $a Hosten, Charles M., $e advisor
790 1 0 $a Prokes, Sharka $e committee member
790 1 0 $a Raghavan, Dharmaraj $e committee member
791 $a Ph.D.
792 $a 2009
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3350462