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B. P. Majee and A. K. Mishra
(SERS) was developed by utilizing interaction between probe molecule and substrate
due to the plasmon resonance or chemical enhancement [4, 5]. The enhanced Raman
signal of pyridine molecule adsorbed on a roughened silver surface was first observed
by Fleishmann and his group in 1974 [5]. SERS has been widely used in the last two
decades for the detection of industrial waste, chemical, food industries and medical
science [6]. Materials, ranging from coinage metals (Au, Ag, Cu) to semiconductors, having high density of hotspots on their rough surface, can be used as active
SERS substrate. In last few years, researchers have investigated different nanomaterials beyond the conventional metals (Au, Ag, Cu) and semiconducting metal oxides
(TiO 2 , ZnO, Cu 2 O etc.). Carbon nanomaterials (Graphene, carbon nanotubes) and
metal dichalcogenides (MoS 2 , MoSe 2 etc.) nanostructures have been identified as
suitable SERS substrates in addition to conventional metals and semiconducting
nanomaterials [1, 7–12]. Among newly studied materials, 2D materials are found
suitable for the SERS applications due to the layer-dependent optical properties,
high surface to volume ration and good stability [9]. Hence, researchers developed
different 2D materials based active SERS substrates with different morphologies
like flower, sheet etc. for the detection of organic pollutants. The chemically inert
surface of 2D materials opposes the deformation and chemical reactions of the probe
molecule with the surface and due to this, the reproducible enhancement is possible
for quantitative analysis. In this chapter, we will discuss the basic principle of SERS,
different ways of calculating enhancement factor, possible mechanism for signal
enhancement and examples of different metals and semiconducting active SERS
substrates for the detection of organic impurities.
2 Brief Discussion on Raman Spectroscopy
The basic principle of Raman spectroscopy is based on the interaction between electromagnetic field (EMF) and materials/molecules, which results in inelastic scattering [13]. The incident EMF i.e. photon interacts with the analyte molecule, and a
dipole moment is induced which is directly proportional to the polarizability of the
molecule. The magnitude of induced dipole moment (μ ind ) depends on the strength
of the incident electric field (E in ) and the polarizability of the molecule (α m ) and it
can be expressed as follows [14]
μ ind = E in (ω inc ).α m
(1)
The efficiency of any scattering process is depending on the scattering crosssection and in case of Raman scattering, the efficiency depends as follows [15]
Efficiency =
dσ r
d
(2)
B. P. Majee and A. K. Mishra
(SERS) was developed by utilizing interaction between probe molecule and substrate
due to the plasmon resonance or chemical enhancement [4, 5]. The enhanced Raman
signal of pyridine molecule adsorbed on a roughened silver surface was first observed
by Fleishmann and his group in 1974 [5]. SERS has been widely used in the last two
decades for the detection of industrial waste, chemical, food industries and medical
science [6]. Materials, ranging from coinage metals (Au, Ag, Cu) to semiconductors, having high density of hotspots on their rough surface, can be used as active
SERS substrate. In last few years, researchers have investigated different nanomaterials beyond the conventional metals (Au, Ag, Cu) and semiconducting metal oxides
(TiO 2 , ZnO, Cu 2 O etc.). Carbon nanomaterials (Graphene, carbon nanotubes) and
metal dichalcogenides (MoS 2 , MoSe 2 etc.) nanostructures have been identified as
suitable SERS substrates in addition to conventional metals and semiconducting
nanomaterials [1, 7–12]. Among newly studied materials, 2D materials are found
suitable for the SERS applications due to the layer-dependent optical properties,
high surface to volume ration and good stability [9]. Hence, researchers developed
different 2D materials based active SERS substrates with different morphologies
like flower, sheet etc. for the detection of organic pollutants. The chemically inert
surface of 2D materials opposes the deformation and chemical reactions of the probe
molecule with the surface and due to this, the reproducible enhancement is possible
for quantitative analysis. In this chapter, we will discuss the basic principle of SERS,
different ways of calculating enhancement factor, possible mechanism for signal
enhancement and examples of different metals and semiconducting active SERS
substrates for the detection of organic impurities.
2 Brief Discussion on Raman Spectroscopy
The basic principle of Raman spectroscopy is based on the interaction between electromagnetic field (EMF) and materials/molecules, which results in inelastic scattering [13]. The incident EMF i.e. photon interacts with the analyte molecule, and a
dipole moment is induced which is directly proportional to the polarizability of the
molecule. The magnitude of induced dipole moment (μ ind ) depends on the strength
of the incident electric field (E in ) and the polarizability of the molecule (α m ) and it
can be expressed as follows [14]
μ ind = E in (ω inc ).α m
(1)
The efficiency of any scattering process is depending on the scattering crosssection and in case of Raman scattering, the efficiency depends as follows [15]
Efficiency =
dσ r
d
(2)