22
T. B. Asafa et al.
spectrophotometer, and it measures and compares the initial light intensity before
interaction with a sample (I 0 ) and after passing through it (I). The ratio of
I
I 0
is known
as the transmittance (usually expressed as a percentage, %T ). The absorbance (A) is
expressed as function of transmittance as shown in Eq. 1:
A = − log
%T
100
(1)
The spectroscopic technique operates on the principle of the Beer–Lambert law
given as:
A = log 10
I 0
I
= ε · c · L
(2)
where ‘A’ is the measured absorbance, I 0 is the initial light intensity before interaction
with a sample at a given wavelength, I is the transmitted intensity, L is the path
length through the sample, c is the concentration of the absorbing samples, and
ε is a constant referred to as the “molar absorptivity” or “extinction coefficient.”
The electron in an atom excites and moves from lower energy to higher energy
state when light of sufficient energy falls on the material. The energy state of an
electron can be categorized into the lowest unoccupied molecular orbit (LUMO) and
the highest unoccupied molecular orbit (HOMO). The recognition of the evolution
of bonds being formed is connected with the specific behavior of material sample
which is under investigation. Various bonds formation during electronic transition
for materials is depicted in Fig. 1. The approximate wavelength ranges for electronic
transitions, in addition to their possible list of bonds, functional groups, or molecules
responsible for these transitions are given in Table 1. The strongest bond is sigma
(σ ) while the weakest bond is pi (π ), and all rely on the nature of bond formed in
the material.
UV-vis spectroscopy analysis provides ample information for scientists and practitioners, which includes: identification of chromophore functional group, determination of unknown compound, purity of the material, and determination of energy
band gap. Chromophores are materials with chemical bonds and functional groups
Fig. 1 Electronic transition involving different molecular orbits
T. B. Asafa et al.
spectrophotometer, and it measures and compares the initial light intensity before
interaction with a sample (I 0 ) and after passing through it (I). The ratio of
I
I 0
is known
as the transmittance (usually expressed as a percentage, %T ). The absorbance (A) is
expressed as function of transmittance as shown in Eq. 1:
A = − log
%T
100
(1)
The spectroscopic technique operates on the principle of the Beer–Lambert law
given as:
A = log 10
I 0
I
= ε · c · L
(2)
where ‘A’ is the measured absorbance, I 0 is the initial light intensity before interaction
with a sample at a given wavelength, I is the transmitted intensity, L is the path
length through the sample, c is the concentration of the absorbing samples, and
ε is a constant referred to as the “molar absorptivity” or “extinction coefficient.”
The electron in an atom excites and moves from lower energy to higher energy
state when light of sufficient energy falls on the material. The energy state of an
electron can be categorized into the lowest unoccupied molecular orbit (LUMO) and
the highest unoccupied molecular orbit (HOMO). The recognition of the evolution
of bonds being formed is connected with the specific behavior of material sample
which is under investigation. Various bonds formation during electronic transition
for materials is depicted in Fig. 1. The approximate wavelength ranges for electronic
transitions, in addition to their possible list of bonds, functional groups, or molecules
responsible for these transitions are given in Table 1. The strongest bond is sigma
(σ ) while the weakest bond is pi (π ), and all rely on the nature of bond formed in
the material.
UV-vis spectroscopy analysis provides ample information for scientists and practitioners, which includes: identification of chromophore functional group, determination of unknown compound, purity of the material, and determination of energy
band gap. Chromophores are materials with chemical bonds and functional groups
Fig. 1 Electronic transition involving different molecular orbits