Raman spectral vibrational frequencies are used to probe the local chemical environment surrounding molecules in solution and adsorbed to gold nanostars. Herein, the impacts of functional group protonation on monosubstituted benzene derivatives with amine, carboxylic acid, or hydroxide are evaluated. Changes in binding affinity and orientation are apparent by evaluating systematic variations in vibrational frequencies. Notably, the electron donating abilities of these functional groups influence the vibrational frequency of the ring breathing mode, thus leading to improved spectral interpretation. Furthermore, gold nanostars are used to investigate the impact of molecular protonation on the adsorption of benzoic acid/benzoate to gold. The changes in molecular protonation are measured using zeta potential and the surface-sensitive technique, surface-enhanced Raman scattering. These methods reveal that pH variations induce carboxylate protonation and electron redistribution that weaken molecular affinity, thereby causing the molecule to adopt a perpendicular to parallel orientation with respect to the nanostar surface. Functional group identity influences the ring breathing mode frequency as a function of changes in electron donation from the functional group to the ring in solution as well as molecular affinity to and orientation on gold. This exploitation of vibrational frequencies facilitates the elucidation of molecule behavior in complex systems.

1.
J. C.
Lindon
,
G. E.
Tranter
, and
D.
Koppenaal
,
Encyclopedia of Spectroscopy and Spectrometry
(
Academic Press
,
2016
).
2.
Interpreting Infrared, Raman, and Nuclear Magnetic Resonance Spectra
, edited by
R. A.
Nyquist
(
Academic Press
,
San Diego
,
2001
).
3.
S.
Dutta
 et al,
ACS Appl. Mater. Interfaces
5
,
8724
(
2013
).
4.
J.-M.
Delabar
,
J. Raman Spectrosc.
7
,
261
(
1978
).
5.
A. A.
Howard
,
G. S.
Tschumper
, and
N. I.
Hammer
,
J. Phys. Chem. A
114
,
6803
(
2010
).
6.
C.
Outeiral
 et al,
Chem. Sci.
9
,
5517
(
2018
).
7.
D.
Lin-Vien
 et al,
The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules
(
Elsevier
,
1991
).
8.
G.
Demirel
 et al,
J. Mat. Chem. C
6
,
5314
(
2018
).
9.
P.
Cao
,
R.
Gu
, and
Z.
Tian
,
J. Phys. Chem. B
107
,
769
(
2003
).
10.
H. K.
Turley
 et al,
J. Phys. Chem. Lett.
8
,
1819
(
2017
).
11.
M.
Moskovits
,
D. P.
DiLella
, and
K. J.
Maynard
,
Langmuir
4
,
67
(
1988
).
12.
J. R.
Lombardi
,
Faraday Discuss.
205
,
105
(
2017
).
13.
C.
Jing
and
Y.
Fang
,
Chem. Phys.
332
,
27
(
2007
).
14.
G.
Hu
 et al,
J. Phys. Chem. C
111
,
8632
(
2007
).
15.
A. M.
Wright
 et al,
J. Phys. Chem. A
117
,
5435
(
2013
).
16.
D.
Jung
 et al,
Appl. Surf. Sci.
425
,
63
(
2017
).
17.
X.
Wang
 et al,
Anal. Chem.
88
,
915
(
2015
).
18.
L.
Chen
 et al,
Analyst
141
,
4782
(
2016
).
19.
K. W.
Kho
 et al,
ACS Nano
6
,
4892
(
2012
).
20.
J.
Xie
,
J. Y.
Lee
, and
D. I. C.
Wang
,
Chem. Mater.
19
,
2823
(
2007
).
21.
W.
Xi
and
A. J.
Haes
,
J. Am. Chem. Soc.
141
,
4034
(
2019
).
22.
H.
de Puig
 et al,
J. Phys. Chem. C
119
,
17408
(
2015
).
23.
H.
Ohshima
,
J. Colloid Interface Sci.
168
,
269
(
1994
).
24.
G.
Socrates
,
Infrared and Raman Characteristic Group Frequencies: Tables and Charts
(
Wiley
,
2001
).
25.
K. C.
Gross
 et al,
J. Org. Chem.
66
,
6919
(
2001
).
26.
E. V.
Soriano
 et al,
Biochem
47
,
1346
(
2008
).
27.
A.
Kütt
 et al,
J. Org. Chem.
73
,
2607
(
2008
).
28.
I. J.
Hyams
,
R. T.
Bailey
, and
E. R.
Lippincott
,
Spectrochim. Acta, Part A
23
,
273
(
1967
).
29.
W.
Xi
 et al,
J. Phys. Chem. C
122
,
23068
(
2018
).
30.
B.
Giese
and
D.
McNaughton
,
J. Phys. Chem. B
106
,
101
(
2002
).
31.
R. O. C.
Norman
and
R.
Taylor
,
Electrophilic Substitution in Benzenoid Compounds
(
Elsevier
,
1965
), Vol. 3.
32.
G. E.
Maciel
and
J. J.
Natterstad
,
J. Chem. Phys.
42
,
2752
(
1965
).
33.
R.
Stewart
and
K.
Yates
,
J. Am. Chem. Soc.
82
,
4059
(
1960
).
34.
Y.-C.
Liu
 et al,
Thin Solid Films
374
,
85
(
2000
).
35.
D. L.
Pavia
,
G. M.
Lampman
, and
G. S.
Kriz
,
Introduction to Spectroscopy: A Guide for Students of Organic Chemistry
(
Harcourt Brace College Publishers
,
2001
).
36.
J. S.
Kumar
 et al,
Spectrochim. Acta, Part A
152
,
509
(
2016
).
37.
S.-Y.
Tang
and
C. W.
Brown
,
J. Raman Spectrosc.
3
,
387
(
1975
).
38.
D. S.
Warren
and
A. J.
McQuillan
,
J. Phys. Chem. B
112
,
10535
(
2008
).
39.
X.
Gao
,
J. P.
Davies
, and
M. J.
Weaver
,
J. Phys. Chem.
94
,
6858
(
1990
).
40.
K.
Zheng
 et al,
J. Raman Spectrosc.
41
,
632
(
2010
).
41.
J.
Gao
 et al,
Spectrochim. Acta, Part A
104
,
41
(
2013
).
42.
M.
Pagannone
,
B.
Fornari
, and
G.
Mattei
,
Spectrochim. Acta, Part A
43
,
621
(
1987
).
43.
P. M.
Wojciechowski
 et al,
J. Chem. Phys.
118
,
10900
(
2003
).
44.
A.
Blacha-Grzechnik
 et al,
Vib. Spectrosc.
71
,
30
(
2014
).
45.
J. C.
Evans
,
Spectrochim. Acta
16
,
428
(
1960
).
46.
M.
Fleischmann
 et al,
Electrochim. Acta
28
,
1545
(
1983
).
47.
J. C.
Evans
,
Spectrochim. Acta
16
,
1382
(
1960
).
48.
N.
Ornelas-Soto
 et al, in
3rd International Conference on Applications of Optics and Photonics
(
International Society for Optics and Photonics
,
2017
).
49.
K. R.
Karnati
and
Y.
Wang
,
Phys. Chem. Chem. Phys.
20
,
9389
(
2018
).
50.
F.
Chen
et al.,
J. Am. Chem. Soc.
128
,
15874
(
2006
).
51.
F.
Hao
et al.,
Nano Lett.
7
,
729
(
2007
).
52.
F.
Tarazona-Vasquez
and
P. B.
Balbuena
,
J. Phys. Chem. B
108
,
15992
(
2004
).
53.
J.-W.
Park
and
J. S.
Shumaker-Parry
,
J. Am. Chem. Soc.
136
,
1907
(
2014
).
54.
S. M.
Ansar
et al.,
J. Phys. Chem. C
117
,
8793
(
2013
).
55.
G.
Lu
,
T. Z.
Forbes
, and
A. J.
Haes
,
Analytst
141
,
5137
(
2016
).
56.
S.
Burikov
et al.,
Mol. Phys.
108
,
2427
(
2010
).
57.
W.
Xi
,
B. K.
Shrestha
, and
A. J.
Haes
,
Anal. Chem.
90
,
128
(
2018
).
58.
P.
Gao
and
M. J.
Weaver
,
J. Phys. Chem.
89
,
5040
(
1985
).
59.
R.
Di Felice
and
A.
Selloni
,
J. Chem. Phys.
120
,
4906
(
2004
).

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