alexa
Reach Us +441474556909
Electron Work Functionand#8211;An Effective Parameter for <em>In-situ</em> Reflection of Electron Activities in Various Processes | OMICS International
ISSN: 2155-6210
Journal of Biosensors & Bioelectronics

Like us on:

Make the best use of Scientific Research and information from our 700+ peer reviewed, Open Access Journals that operates with the help of 50,000+ Editorial Board Members and esteemed reviewers and 1000+ Scientific associations in Medical, Clinical, Pharmaceutical, Engineering, Technology and Management Fields.
Meet Inspiring Speakers and Experts at our 3000+ Global Conferenceseries Events with over 600+ Conferences, 1200+ Symposiums and 1200+ Workshops on
Medical, Pharma, Engineering, Science, Technology and Business

Electron Work Function–An Effective Parameter for In-situ Reflection of Electron Activities in Various Processes

Dongyang Li*

Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada

*Corresponding Author:
Dongyang Li
Department of Chemical and Materials Engineering
University of Alberta, Edmonton
Alberta T6G 2V4, Canada
Tel: 780-492-6750
E-mail: [email protected]

Received Date: July 13, 2013; Accepted Date: July 14, 2013; Published Date: July 15, 2013

Citation: Li D (2013) Electron Work Function–An Effective Parameter for In-situ Reflection of Electron Activities in Various Processes. J Biosens Bioelectron 4:e123. doi: 10.4172/2155-6210.1000e123

Copyright: © 2013 Li D This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Visit for more related articles at Journal of Biosensors & Bioelectronics

Electron work function (EWF) is the minimum energy required to move electrons at the Fermi level from inside a conducting material to its surface with zero kinetic energy [1,2]. This fundamental parameter largely reflects electron activities and is directly related to chemical, physical, and mechanical properties of materials [2-8]. Recent studies have shown that EWF can be used as a sensitive parameter to characterize many surface properties of biomaterials. As an example [9], the affinity of medical implant materials for bacteria can be characterized by EWF. Figure 1A illustrates the adhesive forces of nanocrystalline stainless steel samples with different gran sizes. As shown, as the grain size decreases, the adhesion decreases due to the fact that the passive film becomes more protective, blocking the interaction between the steel and surrounding media. Such a trend is consistent with the variations in electron work function, as shown in Figure 1B. A higher surface EWF corresponds to a higher degree of reluctance for interacting with the environment. The decrease in the number of bacteria bound to the surfaces with an increase in EWF provides direct evidence.

biosensors-bioelectronics-Adhesive

Figure 1: A: Adhesive force decreases as the size of nano-grains decreases.
B: Corresponding changes in electron work function.
C: Corresponding changes in the number of bacteria on the surfaces. The grain size of Original surface is 10 and S.B. stands for the sand-blasted surface [9].

Another example is the use of EWF in analyzing the photocatalyical activity of TiO2 nanotubes (TNTs). TNTs have been used for different applications such as DNA biosensor [10], detection of bacteria [11] and toxic compounds [12]. TNTs have also been explored for immobilizing proteins and enzymes in biomaterial and biosensor applications [13,14]. Many of the application are related to the photocatalytic activity of TNTs, which is usually evaluated by variations in photocurrent and absorbance under illumination. However, the photocurrent response or absorbance does not provide sufficient information for full understanding of the photocatalytic behaviour of TNAs.

Recent studies have demonstrated that the electron work function is a very sensitive parameter for in-situ analysis of photocatalytic activity of TNTs [15]. Figure 2 illustrates variations in the work function of TiO2 nanotubes with different tube lengths (corresponding to the anodization duration; the larger the anodization duration, the longer the nanotubes). Figures 2A, C, E and G illustrate variations in EWF of the TNAs illuminated successively by lights having wavelengths of 670 nm, 650 nm, 550 nm, 450 nm, 420 nm, 400 nm and 390 nm. As shown, EWF of the TNAs was relatively stable when they were illuminated by lights of 670 nm and 620 nm, indicating that the photonic energies of the lights are not sufficient to excite electrons in the TNAs. While when the wavelength of incident light is in the absorption range of TNAs lower than 550 nm, electrons can be excited accompanied with an apparent decrease in EWF. The observed decrease in EWF with a decrease in the wavelength of incident light is an indication of photoninduced electron-hole separation, which requires photons with their energy above a certain level.

biosensors-bioelectronics-illumination

Figure 2: The effect of illumination with different wavelengths from 390 nm to 670 nm (A, C, E, G) and from 670 nm to 390 nm (B, D, F, H), on changes in EWF of TNAs-2 h, TNAs-12 h, and TNAs-16 h.
Anodization potential=20 V; Annealing temperature=45°C [15].

The TNAs were also illuminated successively by the lights with different wavelengths in a reversed order. Corresponding variations in EWF are illustrated in Figures 2B, D, F and H. As shown, after illuminated by 390 nm-light, TNAs-2 h did not respond much to lights with longer wavelengths, indicating that almost no e- -h+ recombination occurred in the TNAs under illumination with lower photon energies. Or in other words, continuous illumination with lower photon energies could sustain the state of electrons that were initially excited by photons with higher energies, or suppress e- -h+ recombination. However, for TNAs anodized for 4 h, their EWF raised up under illumination in a range of longer wavelengths (550-670 nm) after 390 nm illumination. This suggests that e- -h+ recombination occurred, which could not be suppressed by illumination with the lower photon energies in this wavelength range. The recombined e- -h+ pairs could be re-separated under the illumination with the lower-energy photons, but the electrons could only be excited to relatively lower energy states that correspond to higher EWF. This range of longer wavelengths, which could not suppress e- -h+ recombination, extended to 420-670 nm for TNAs- 12 h and TNAs-16 h. It appears that longer TNAs do not only provide more recombination centers as suggested [16,17], but also have larger driving forces for e- -h+ recombination.

The above observations demonstrate that EWF is related to the photocatalytic process involving electron-hole separation and recombination. The study clearly shows that EWF is an effective parameter reflecting the photocatalytic behavior of TiO2 nanotubes, and helps to get an insight into the semiconductors’ photo-activities with different views that may not be achieved using traditional techniques, such as diffuse reflection spectrum and photo-electrochemical measurement.

In conclusion, EWF has been demonstrated to be a sensitive parameter with great potential for a variety of sensor applications.

References

Select your language of interest to view the total content in your interested language
Post your comment

Share This Article

Relevant Topics

Article Usage

  • Total views: 11933
  • [From(publication date):
    August-2013 - Nov 14, 2018]
  • Breakdown by view type
  • HTML page views : 8162
  • PDF downloads : 3771
 

Post your comment

captcha   Reload  Can't read the image? click here to refresh

Peer Reviewed Journals
 
Make the best use of Scientific Research and information from our 700 + peer reviewed, Open Access Journals
International Conferences 2018-19
 
Meet Inspiring Speakers and Experts at our 3000+ Global Annual Meetings

Contact Us

Agri and Aquaculture Journals

Dr. Krish

[email protected]

+1-702-714-7001Extn: 9040

Biochemistry Journals

Datta A

[email protected]

1-702-714-7001Extn: 9037

Business & Management Journals

Ronald

[email protected]

1-702-714-7001Extn: 9042

Chemistry Journals

Gabriel Shaw

[email protected]

1-702-714-7001Extn: 9040

Clinical Journals

Datta A

[email protected]

1-702-714-7001Extn: 9037

Engineering Journals

James Franklin

[email protected]

1-702-714-7001Extn: 9042

Food & Nutrition Journals

Katie Wilson

[email protected]

1-702-714-7001Extn: 9042

General Science

Andrea Jason

[email protected]

1-702-714-7001Extn: 9043

Genetics & Molecular Biology Journals

Anna Melissa

[email protected]

1-702-714-7001Extn: 9006

Immunology & Microbiology Journals

David Gorantl

[email protected]

1-702-714-7001Extn: 9014

Materials Science Journals

Rachle Green

[email protected]

1-702-714-7001Extn: 9039

Nursing & Health Care Journals

Stephanie Skinner

[email protected]

1-702-714-7001Extn: 9039

Medical Journals

Nimmi Anna

[email protected]

1-702-714-7001Extn: 9038

Neuroscience & Psychology Journals

Nathan T

[email protected]

1-702-714-7001Extn: 9041

Pharmaceutical Sciences Journals

Ann Jose

[email protected]

1-702-714-7001Extn: 9007

Social & Political Science Journals

Steve Harry

[email protected]

1-702-714-7001Extn: 9042

 
© 2008- 2018 OMICS International - Open Access Publisher. Best viewed in Mozilla Firefox | Google Chrome | Above IE 7.0 version