LIU Jiang-mei, LIU Wen-han, TENG Yuan-jie etc. Adsorption Behavior of 2-Thiophene Carboxylic Acid on Fe<sub>3</sub>O<sub>4</sub>@Ag Substrate Investigated by Surface-enhanced Raman Scattering[J]. Chinese Journal of Luminescence, 2015,36(12): 1477-1484
LIU Jiang-mei, LIU Wen-han, TENG Yuan-jie etc. Adsorption Behavior of 2-Thiophene Carboxylic Acid on Fe<sub>3</sub>O<sub>4</sub>@Ag Substrate Investigated by Surface-enhanced Raman Scattering[J]. Chinese Journal of Luminescence, 2015,36(12): 1477-1484 DOI: 10.3788/fgxb20153612.1477.
Adsorption Behavior of 2-Thiophene Carboxylic Acid on Fe3O4@Ag Substrate Investigated by Surface-enhanced Raman Scattering
magnetic nanoparticles were firstly synthesized by co-precipitation method
and Fe
3
O
4
@Ag magnetic material which has improved SERS effect was further prepared by reduction of AgNO
3
using sodium citrate. Both density functional theory (DFT) and surface-enhanced Raman scattering (SERS) spectroscopy technique were used to investigate the adsorption behavior and enhancement effect of 2-thiophene carboxylic acid (2-TCA) on the Fe
3
O
4
@Ag surface. The results show that Raman spectra of the theoretical calculation and the determination are basically identical
and the more Ag atoms are introduced in theoretical calculation
the closer the measured value is to the theoretical value. The concentration and pH of the solution have great influence on the Raman enhancement effect
and the solution of 110
-4
molL
-1
at pH=3 can present excellent Raman signal response. The SERS effect increases initially and decreases afterwards with the increasing of concentration
which can be inferred that a lot of 2-TCA molecules are adsorbed and gathered on the Ag surface to form a local "congestion" and interfere the transmission of the excitation light
especially spectroscopic signal scattering. 2-TCA molecule morphology is changed with the increasing of pH
and the adsorption mode is influenced by the molecule morphology. The neutral C
4
H
3
SCOOH is vertically adsorbed on the Ag surface by the formation of SAg coordination bond. However
C
4
H
3
SCOO
-
anion is adsorbed on Ag surface with SAg coordinate bond and OAg covalent bond which is named as "double-bonged" side pattern. Although the adsorption of SAg coordinate bond is weaker than "double-bonged" side pattern
the SERS signal is stronger
because the neutral 2-TCA molecules are more beneficial to the generation of SERS signal comparing with 2-TCA
-
anion. The neutral 2-TCA molecules are gradually transformed into C
4
H
3
SCOO
-
anion with the increasing of pH
which leads to the decreasing of SERS effect gradually after pH
>
3.
关键词
Keywords
references
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