Terahertz Time-Domain Spectroscopy of
Glucose and Uric Acid
Prashanth Upadhya, Yao-Chun Shen, Giles Davies & Edmund Linfield
Cavendish Laboratory, Cambridge University
Contents
Introduction
Experiment
Far-infrared absorption
 Glucose and sucrose
 Uric Acid & its derivative
Temperature & structural dependent absorption
Conclusions
Introduction
many intrinsic resonances predicted in the THz regime
 vibrational modes in polynucleotides
…Powell et al
 base twisting and librational modes in DNA structure
… Young et al
low frequency collective vibrational modes
 distinguish between different isomeric configurations in retinal molecules
…Walther et al
 finger print of conformational state – benzoic acid
…Walther et al
Vacuum capable THz-TDS set-up
useful bandwidth of 0.1- 3.0 THz
 spectral resolution of better than 1 cm-1
Sample preparation
pellets (1.2-1.4mm) with matrix for low temperature
measurements (polyethylene:sample::8:1)
 pure sample pellets ( 0.3- 0.7mm) for room temperature
measurement – to observe distinct peaks
Particle size – ESEM measurement
 Submicron particle size – minimise scattering effect on
observed spectra
Far-infrared absorption in Glucose
60
Absorption (a.u.)
50
D-Fructose
L-Glucose
D-Glucose
40
30
20
10
0
0.5
1.0
1.5
Frequency (THz)
2.0
2.5
Far-infrared absorption in Glucose
60
Absorption (a.u.)
50
D-Fructose
L-Glucose
D-Glucose
D-Fructose
40
30
20
L-Glucose
10
0
0.5
1.0
1.5
Frequency (THz)
2.0
2.5
D-Glucose
Dependence on crystallanity
25
Crystalline
Solution
Absorption (a.u.)
20
15
10
5
0
0.5
1.0
1.5
2.0
2.5
Frequency (THz)
 Intermolecular vibrational modes
3.0
Absorption in molecule containing glucose
structure
25
Sucrose
L-Glucose
Absorption (a.u.)
20
15
10
5
0
0.5
1.0
1.5
2.0
Frequency (THz)
2.5
3.0
Absorption in molecule containing glucose
structure
25
Sucrose
L-Glucose
Absorption (a.u.)
20
15
Sucrose
10
5
0
0.5
1.0
1.5
2.0
2.5
3.0
Frequency (THz)
 absorption tend to depend on molecular
environment
L-Glucose
L-Glucose - absorption peaks at low temperature
35
Absorption (a.u.)
30
25
300K
20
204K
15
103K
10
5
0
0.0
4K
0.5
1.0
1.5
2.0
2.5
3.0
Frequency (THz)
 many distinct absorption peaks at low temperature
We observed terahertz absorption as a
result of intermolecular interaction
&
also dependence on structural change in a
molecule
……… in other molecules?
Far-infrared absorption in Uric Acid
20
Uric Acid
Allantoin
Absorption (a.u.)
15
10
5
0
0.5
1.0
1.5
2.0
Frequency (THz)
2.5
3.0
Far-infrared absorption in Uric Acid
20
Uric Acid
Allantoin
Absorption (a.u.)
15
Allantoin
10
5
0
0.5
1.0
1.5
2.0
2.5
3.0
Frequency (THz)
 structural dependence of absorption
Uric Acid
Temperature dependence
Uric Acid
Allantoin
40
25
35
20
25
Absorption (a.u.)
Absorption (a.u.)
30
200K
20
15
100K
10
5
4k
15
10
205K
98K
5
4K
0
-5
0.0
300K
300K
0
0.5
1.0
1.5
2.0
Frequency (THz)
2.5
3.0
0.0
0.5
1.0
1.5
2.0
2.5
Frequency (THz)
 stronger temperature dependence in allantoin
 change in energy surfaces of molecules at low temperature
3.0
Uric Acid - absorption line profile
 change in position and width of peaks with
temperature
Conclusions
Demonstrated use of THz-TDS to study far-infrared
response of some isomeric and derived structures of
glucose and uric acid
Observed absorption due to collective
intermolecular modes
Strong temperature and structural dependence of
absorption
Theoretical model analysis required to understand
the underlying dynamics
Acknowledgements
EPSRC
Royal Society
Toshiba Research Europe
Association of Commonwealth Universities
and thanks to
Dr. M. B. Johnston
Dr. A. Dowd