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International Journal of Photoenergy
Volume 2012 (2012), Article ID 494636, 5 pages
http://dx.doi.org/10.1155/2012/494636
Research Article

Thin Films Prepared from Nanometer Size TiO2 Absorbs Millimeter Waves

1Department of Electrical and Electronics Engineering, Yeditepe University, Istanbul 34755, Turkey
2Department of Genetics and Bioengineering, Yeditepe University, Istanbul 34755, Turkey

Received 27 July 2012; Accepted 10 October 2012

Academic Editor: Ipek Karaaslan

Copyright © 2012 Mehmet Ali Yesil et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Absorption of average 10 nm size TiO2 nanoparticles deposited on glass surfaces as a thin film using convective assembly technique and drop-casting is studied in the millimeter wave range from 26 GHz to 40 GHz. The millimeter wave responses of the fabricated samples were obtained using a vector network analyzer. Reflection properties of the prepared samples were also measured. Absorption and reflection of TiO2 nanoparticles were more pronounced between 35 GHz and 40 GHz compared to glass-only sample.

1. Introduction

Titanium dioxides find broad range of applications from pigment to cosmetic industry, electronic to pharmaceutical industry [110]. The reason behind their wide applicability is their unique properties such as blocking UV light and photocatalytic activity [11]. Additional exceptional properties such as cleaving proteins at amino acid proline site and behaving as a semiconductor of nanosized TiO2 were also reported [12, 13].

As the nanotechnology progresses, new properties of TiO2, especially in their nanoscale form, are explored. For example, the millimeter wave rotational spectrum of TiO2 at ground state was obtained in [14] for astronomical searches. Microwave absorbing effects and characterization of TiO2 were also studied in [15, 16]. The absorption characteristics of TiO2 nanoparticles have been mostly overlooked and this study aims to fill this gap for numerous engineering applications.

There are a number of methods such as spin coating, dip coating, and drop-casting to prepare relatively uniform thin films from nanomaterials. In this study, we used two different approaches to prepare TiO2 thin films, drop-casting and “convective assembly”. While former approach generates thin film thickness in millimeter range, the latter generates in the micrometer range. The “convective assembly” is an approach to assemble 2D and 3D nano- and micrometer size structures using nano- and micrometer size particles on surfaces in a more controlled manner. The assembly of a number of particles on surfaces was achieved using the approach [17, 18]. The self-assembly of colloidal particles in thin evaporating films is the basis of the technique [19, 20]. It was also used to assemble bacteria-silver nanoparticle and protein-silver nanoparticle structures on glass surfaces [21, 22].

2. Material and Methods

10 nm TiO2 nanoparticles were used to prepare thier thin films on glass surfaces. Figure 1(a) shows the TEM images of TiO2. As seen on the image, the average size of TiO2 nanoparticles is 10 nm. An 8.6 mg of TiO2 was suspended in distilled water. A “convective assembly” was used to deposit TiO2 as a thin film on a glass surface. The details of the experimental setup could be found elsewhere [17]. Briefly, an 80 μL of TiO2 suspension was placed at the cross section of two glass slides, which are soaked in Piranha solution for at least 3 hours to clean the glass surface, one is placed on a moving stage and the other is placed on top of the one placed on the moving stage with an angle of 23°. In order to generate thicker films on the glass surface, 4–6 mL of suspension of TiO2 was placed on the glass cleaned glass slide and the suspension was distributed on the glass surface with the help of another slide. Figure 1(b) shows the images of thin films prepared with two different approaches on the glass surface. The thickness of thin film prepared with convective assembly estimated as 10 μm and the film prepared with drop-casting was estimated as 1 mm.

fig1
Figure 1: (a) TEM image of TiO2 nanoparticles, (b) thin films prepared on glass surfaces using convective assembly and drop-casting.

Figure 2 shows the UV/Vis spectrum of the suspension of TiO2 nanoparticles in water.

494636.fig.002
Figure 2: UV/Vis spectrum of fabricated nanoparticles in water.

Millimeter wave measurement setup is shown in Figure 3. Rohde and Schwarz ZVA40 Network Analyzer was calibrated from 20 to 40 GHz with intermediate frequency at 1 kHz, and the number of calibration points was set to10,000 with source power level at +5 dBm. Network Analyzer as a two-port device can simultaneously measure input reflection and transmission to the other port in terms of Scattering (S) parameters. In this configuration S21 represents signal received at port 2 when input signal is applied to port 1, with 50 Ohm port impedances. S21 is used as the main data for comparison of detection. Wideband conical antennas made by Elmika were used for transmission and reception. Although the antennas were rated from 26.5 to 40 GHz, their port match and gain were found satisfactory starting from 23 GHz. Nevertheless, measurements were carried out relative to glass-only sample, and basis of comparison was made with reference to that sample. Samples were held using Rohacell air-dielectric foams.

fig3
Figure 3: Measurement setup, (a) description, (b) picture of the setup.

3. Results and Discussion

Measurement setup was first used for free space and thin-glass samples to create a reference. Transmission measurement of S21 is recorded for both configurations. Since the samples are in the far field of the receiving and transmitting antennas and reflection from the samples is quite close to each other, one can infer absorption of samples directly from transmission measurements. Comparisons of transmission measurements for free space and glass-only sample are shown in Figure 4. The measurement result is also expressed in dB scale with conversion.

494636.fig.004
Figure 4: Transmission measurements of free-space and glass-only sample.

Next, same measurement setup was used to measure absorption characteristics on TiO2 thin films deposited on glass surface using drop-casting technique. The samples prepared using convective assembly were very thin to produce strong absorption. Therefore, samples prepared through drop-casting were used in the measurements. Results are shown in Figure 5. It is observed that there is a degradation TiO2 deposited glass sample compared to glass-only sample. Especially between 35 GHz to 40 GHz, absorption of TiO2 sample is at least 2.5 to 3 dB higher than that of glass-only sample. The reflection measurements of both samples are also shown in Figure 6. The reflection measurements also show a clear departure from glass-only sample from 35 GHz to 40 GHz.

494636.fig.005
Figure 5: Transmission measurements of TiO2 deposited glass and glass-only samples.
494636.fig.006
Figure 6: Reflection measurements of TiO2 deposited glass and glass-only samples.

The relative percent change in received signal with respect to glass-only sample is shown in Figure 7. TiO2 sample has in excess of 15% relative percent change from 35 to 40 GHz.

494636.fig.007
Figure 7: Relative percent change of TiO2 sample with reference to glass-only sample.

Even though the measurements were carried out at atmospheric pressures and at room temperature, there is a clear difference between glass-only and TiO2 thin film deposited glass samples. The attenuation of TiO2 sample is consistently higher than that of glass-only sample.

References

  1. M. Ramovatar, R. Madhu, P. Ruchita, et al., “Nano-TiO2-induced apoptosis by oxidative stress-mediated DNA damage and activation of p53 in human embryonic kidney cells,” Applied Biochemistry and Biotechnology, vol. 167, no. 4, pp. 791–808, 2012.
  2. M. Valeria and C. Ilaria, “Toxic effects of engineered nanoparticles in the marine environment: model organisms and molecular approaches,” Marine Environmental Research, vol. 76, pp. 32–40, 2012.
  3. M. S. Kim, D. M. Chun, J. O. Choi et al., “Room temperature deposition of TiO2 using nano particle deposition system (NPDS): application to dye-sensitized solar cell (DSSC),” International Journal of Precision Engineering and Manufacturing, vol. 12, no. 4, pp. 749–752, 2011. View at Publisher · View at Google Scholar · View at Scopus
  4. B. J. Shaw and R. D. Handy, “Physiological effects of nanoparticles on fish: a comparison of nanometals versus metal ions,” Environment International, vol. 37, no. 6, pp. 1083–1097, 2011. View at Publisher · View at Google Scholar · View at Scopus
  5. C. Som, P. Wick, H. Krug, and B. Nowack, “Environmental and health effects of nanomaterials in nanotextiles and façade coatings,” Environment International, vol. 37, no. 6, pp. 1131–1142, 2011. View at Publisher · View at Google Scholar · View at Scopus
  6. K. M. Tyner, A. M. Wokovich, D. E. Godar, W. H. Doub, and N. Sadrieh, “The state of nano-sized titanium dioxide (TiO2) may affect sunscreen performance,” International Journal of Cosmetic Science, vol. 33, no. 3, pp. 234–244, 2011. View at Publisher · View at Google Scholar · View at Scopus
  7. F. A. Babakhani, A. R. Mehrabadi, P. N. L. Lens, and M. Sadatian, “Prevention of biofilm formation in water and wastewater installations by application of TiO2 nano particles coating,” Desalination and Water Treatment, vol. 28, no. 1–3, pp. 83–87, 2011. View at Publisher · View at Google Scholar · View at Scopus
  8. C. Cherchi, T. Chernenko, M. Diem, and A. Z. Gu, “Impact of nano titanium dioxide exposure on cellular structure of anabaena variabilis and evidence of internalization,” Environmental Toxicology and Chemistry, vol. 30, no. 4, pp. 861–869, 2011. View at Publisher · View at Google Scholar · View at Scopus
  9. C. C. Lin and W. J. Lin, “Sun protection factor analysis of sunscreens containing titanium dioxide nanoparticles,” Journal of Food and Drug Analysis, vol. 19, no. 1, pp. 1–8, 2011. View at Scopus
  10. M. Hassan Marwa, N. Mohammad Louay, B. Cooper Samuel III, et al., “Evaluation of nano-titanium dioxide additive on asphalt binder aging properties,” Transportation Research Record, vol. 2207, pp. 11–15, 2011.
  11. M. E. Kurtoglu, T. Longenbach, and Y. Gogotsi, “Preventing sodium poisoning of photocatalytic TiO2 films on glass by metal doping,” International Journal of Applied Glass Science, vol. 2, no. 2, pp. 108–116, 2011.
  12. B. J. Jones, M. J. Vergne, D. M. Bunk, L. E. Locascio, and M. A. Hayes, “Cleavage of peptides and proteins using light-generated radicals from titanium dioxide,” Analytical Chemistry, vol. 79, no. 4, pp. 1327–1332, 2007. View at Publisher · View at Google Scholar · View at Scopus
  13. R. Paschotta, “Bragg mirrors,” in Encyclopedia of Laser Physics and Technology, 2009.
  14. P. Kania, M. Hermanns, S. Brünken, H. S. P. Müller, and T. F. Giesen, “Millimeter-wave spectroscopy of titanium dioxide, TiO2,” Journal of Molecular Spectroscopy, vol. 268, no. 1-2, pp. 173–176, 2011. View at Publisher · View at Google Scholar · View at Scopus
  15. S. Horikoshi, A. Matsubara, S. Takayama et al., “Characterization of microwave effects on metal-oxide materials: zinc oxide and titanium dioxide,” Applied Catalysis B, vol. 99, no. 3-4, pp. 490–495, 2010. View at Publisher · View at Google Scholar · View at Scopus
  16. L. B. Zhang, G. Chen, J. H. Peng, J. Chen, S. H. Guo, and X. H. Duan, “Microwave absorbing properties of high titanium slag,” Journal of Central South University of Technology, vol. 16, no. 4, pp. 588–593, 2009. View at Publisher · View at Google Scholar · View at Scopus
  17. M. Culha, M. Muge Yazıcı, M. Kahraman, F. Sahin, and S. Kocagoz, “Surface-enhanced raman scattering of bacteria in microwells constructed from silver nanoparticles,” Journal of Nanotechnology, vol. 2012, Article ID 297560, 7 pages, 2012. View at Publisher · View at Google Scholar
  18. C. E. Ashley, D. R. Dunphy, Z. Jiang et al., “Convective assembly of 2D lattices of virus-like particles visualized by in-situ grazing-incidence small-angle X-ray scattering,” Small, vol. 7, no. 8, pp. 1043–1050, 2011. View at Publisher · View at Google Scholar · View at Scopus
  19. N. D. Denkov, O. D. Velev, P. A. Kralchevsky, I. B. Ivanov, H. Yoshimura, and K. Nagayama, “Mechanism of formation of two-dimensional crystals from latex particles on substrates,” Langmuir, vol. 8, no. 12, pp. 3183–3190, 1992. View at Scopus
  20. N. D. Denkov, O. D. Velev, P. A. Kralchevsky, I. B. Ivanov, H. Yoshimura, and K. Nagayama, “Two-dimensional crystallization,” Nature, vol. 361, no. 6407, p. 26, 1993. View at Scopus
  21. M. Kahraman, M. M. Yazici, F. Şahin, and M. Çulha, “Convective assembly of bacteria for surface-enhanced Raman scattering,” Langmuir, vol. 24, no. 3, pp. 894–901, 2008. View at Publisher · View at Google Scholar · View at Scopus
  22. S. Keskin, M. Kahraman, and M. Çulha, “Differential separation of protein mixtures using convective assembly and label-free detection with surface enhanced Raman scattering,” Chemical Communications, vol. 47, no. 12, pp. 3424–3426, 2011. View at Publisher · View at Google Scholar · View at Scopus