1. Synthesis and
Characterization of ZnO
Nanoshells for Hydrogen
Detection
Normarieli M. Passalacqua Alvarado
RISE Program
CIM Laboratory
Mentor: W. Otaño Ph.D.
CIMCentrode
Investigaciónen
Materiales

2. Introduction
Nano materials:
Scale of 10-9 m
Large surface area
Fig 1: Carbon nanotubes
http://www.taringa.net/comunidades/nanotecnologia/5086975/Nanotecnologia-bienvenida-info.html

3. Fibers
Some uses are:
Tissue scaffolds, e.g., filtration of proteins
Delivery of drugs to the humans cells
Gas sensors
Energy storage
Catalysis

4. Zinc Oxide
Semiconductor with large number of applications.
Has good chemical and physical properties.
Low cost

5. Electrospinning
Technique
Fig 2. Fiber deposition
http://ppl.ippt.gov.pl/18-few-words-about/17-electrospinning

6. Sputtering
http://www.angstromsciences.com/magnetron-sputtering-deposition

7. Problem
What we want?
Detect gases such as hydrogen using ZnO.

8. Hypothesis
A ZnO nanometric structure with large surface area
can be used as a sensitive hydrogen gas sensor.

9. Objectives
Create poly (ethylene oxide) micro-to-nano fibers by
electrospinning technique.
Deposit Zn and ZnO by Sputtering on top of fibers.
Create nanoshells by heat treatment.
Use the Energy Dispersive Spectroscopy (EDS) to
characterize composition.
Use the Scanning Electron Microscope (SEM) to study the
nanoshells morphology.
Test the samples as hydrogen gas sensors.

10. Methodology
1) Forming
PEO fibers
D.S. 20cm
V. 20 kV
R: 5ml/h
2) Zn and
ZnO (direct)
deposition
D.P. 3 cm
P.D. 3 y 10
mTorr
3) Heating
of samples
T. 450°C
t= 120 sec
4) Sample
analysis
SEM
6) Electrical
measurements

11. Results and Discussion
Fig 3. Fibers of PEO

12. Results and Discussion
ZnO deposited directly onto the fibers and then
heated to form the nanoshells structures.
Fig 4. A01 (X15) sample deposited to
3 mTorr with a thickness of 50 nm .
Fig 5. A02 (X22) sample deposited to
10 mTorr with a thickness of 50 nm.

13. Results and Discussion
Zn deposited and then heated to form the ZnO
nanoshells structures.
Fig 6. B01 (x10) deposited to 3 mtorr with
a thickness of 400 nm.
Fig 7. B02 sample (x15) deposited to 10 mtorr
with a thickness of 400 nm.

14. Electrical
Measurements
3.30E-05
3.35E-05
3.40E-05
3.45E-05
3.50E-05
3.55E-05
3.60E-05
3.65E-05
3.70E-05
3.75E-05
15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0
Current(A)
Time (min)
Current vs time for ZnO sample :
Sputtering of ZnO
H2 Off
H2 On
Graph 1. Current change in ZnO samples when exposed to hydrogen.

15. Electrical
Measurements
2.68E-03
2.88E-03
3.08E-03
3.28E-03
3.48E-03
3.68E-03
3.88E-03
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00
Current(A)
Time (min)
Current vs time for ZnO sample :
Sputtering of Zn
H2 Off
H2 On
Graph 2. Current change in ZnO samples when exposed to hydrogen.

16. Electrical
Measurements
2.88E-05
2.98E-05
3.08E-05
3.18E-05
3.28E-05
3.38E-05
3.48E-05
3.58E-05
3.68E-05
3.78E-05
2.88E-03
2.98E-03
3.08E-03
3.18E-03
3.28E-03
3.38E-03
3.48E-03
3.58E-03
3.68E-03
3.78E-03
0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00
Current(A)
Time (min)
Current vs time for ZnO sample :
Sputtering of Zn and ZnO
H2 Off
Graph 3. Contrast between the current change in the samples with sputtered
ZnO and those sputtred with Zn.

17. Conclusion
The fibers and the nanoshells structures were
created successfully.
Results show a greater sensitivity percent in those
samples of ZnO nanoshells that were sputtered with
Zn and oxidized in the heat treatment.
However, data indicted lower sensitivity percent for
ZnO nanoshells that were sputtered with Zn and 50%
oxygen in the reactive gas.

18. Acknowledgements
RISE program
CIM laboratory

19. References
Sui, X.; Shao, C.; Lin, Y. 2007. Photoluminescence of polyethylene
oxide-ZnO composite electrospun fibers. J. Elesevier.
48:1459-1463.
Park, J.; Moon, J.; Lee, S.; Lim, S.; Zyung, T. 2009. Fabrication
and characterization of ZnO nanofibers by electrospinning.
J. Elsevier, 9:S210-S212.
Yamazoe, N. 2005. Toward innovations of gas sensor
technology. J. Elsevier. 108:2-14.
Yang, X.; Shao, C.; Guan, H.; Li, X.; Gong, J. 2004. Preparation and
characterization of ZnO nanofibers by using electrospun
PVA/zinc acetate composite fiber as precursor. J. Elselvier,
7:176-178.

20. Synthesis and
Characterization of ZnO
Nanoshells for Hydrogen
Detection
Normarieli M. Passalacqua Alvarado
RISE Program
CIM Laboratory
Mentor: W. Otaño Ph.D.
CIMCentrode
Investigaciónen
Materiales