Synthesis and Characterization of ZnO

Nanoshells for Hydrogen Detection

Normarieli M. Passalacqua AlvaradoRISE Program

CIM LaboratoryMentor: W. Otaño Ph.D.

CIMCentro de

Investigación en

Materiales

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

Fibers

Some uses are:

Tissue scaffolds, e.g., filtration of proteins

Delivery of drugs to the humans cells

Gas sensors

Energy storage

Catalysis

Zinc Oxide

Semiconductor with large number of applications.

Has good chemical and physical properties.

Low cost

ElectrospinningTechnique

Fig 2. Fiber deposition

http://ppl.ippt.gov.pl/18-few-words-about/17-electrospinning

Sputtering

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

Problem

What we want?

Detect gases such as hydrogen using ZnO.

Hypothesis

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

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.

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

Results and Discussion

Fig 3. Fibers of PEO

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.

Results and Discussion

Zn deposited and then heated to form the ZnOnanoshells structures.

Fig 6. B01 (x10) deposited to 3 mtorr with a thickness of 400 nm.

Fig 7. B02 sample (x15) deposited to 10 mtorrwith a thickness of 400 nm.

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

Cu

rre

nt

(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.

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

Cu

rre

nt

(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.

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

Cu

rre

nt

(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.

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.

Acknowledgements

RISE program

CIM laboratory

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 electrospunPVA/zinc acetate composite fiber as precursor. J. Elselvier, 7:176-178.

Synthesis and Characterization of ZnO

Nanoshells for Hydrogen Detection

Normarieli M. Passalacqua AlvaradoRISE Program

CIM LaboratoryMentor: W. Otaño Ph.D.

CIMCentro de

Investigación en

Materiales