Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
American Journal of Microbiological Research
Biomedical Science and Engineering

We are pleased to announce that submissions are now being accepted for peer review for all the journals across all our subject areas in SciEP.

Please submit your manuscript via our online submission system:
http://www.sciepub.com/author/signin

To unsubscribe from our mailing list, please click on the following link: unsubscribe

I am looking forward to hearing from you.

Kind regards,

David Rain
Email:join@sciepub.com
Science and Education Publishing (http://www.sciepub.com)

Effect of Poly Ethylene Glycol on Moisture Sensing of Copper Ferrite Nanocomposite

Richa Srivastava

Department of Physics, University of Lucknow, Lucknow, India

Abstract: Present paper reports, synthesis of CuFe₂O₄ nanocomposite via chemical precipitation route and effect of poly ethylene glycol on their humidity sensing properties. The variations of resistance with and without PEG at different value of %RH of the sensing elements were investigated. The maximum average value of sensitivity was found 13.7 MΩ/%RH respectively over the entire range of relative humidity. Results are found to be reproducible after three months with ±5 % hysteresis. Sensing material synthesized through PEG has been characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD pattern revealed cubic crystal system. The average crystallite size of material was found to be 85.7 nm. SEM images show porous nature of sensing material with a number of active sites throughout the surface. The average size of pores of material was found to be 2µm.

Keywords: humidity, sensors, sensitivity, morphology, composite materials

Received May 15, 2014; Revised January 20, 2015; Accepted February 08, 2015

Citation: Richa Srivastava, Effect of Poly Ethylene Glycol on Moisture Sensing of Copper Ferrite Nanocomposite. American Journal of Sensor Technology, 3 (1). 1-4. January 2015. doi:10.12691/ajst-3-1-1

1. Introduction

In recent years on account of the attractive scientific and industrial applications of Ferrite nanoparticles, novel methods for their synthesis and new approaches for their characterizations have been reported [1,2,3]. It has been reported that different techniques of preparation lead to different phases and different degrees of size control [4,5,6,7]. Humidity affects mankind directly or indirectly. The irreversible effect due to humidity eventually causes permanent damage to the exposed surfaces. Therefore, there is an urgent need to measure and control precisely the humidity in various environments [8]. Ferrites show very good surface reactivity and they have temperature dependent surface morphology [9]. They also show remarkable catalytic properties in oxidation reactions due to the high oxygen ion mobility at the film surface and thus are highly interesting for the development of sensors [6]. Copper ferrite material exposes porous nature and various constructive applications in different fields [10,11].

2. Synthesis of Material

The stoichiometric amount of [CuCl₂.2H₂O] and Fe( NO₃)₃ were separately dissolved in isopropyl alcohol and solution ammonium hydroxide (NaOH) was added drop by drop to obtain material in hydroxide form. Vigorous stirring was done 20-24 h to ensure complete and intimate reaction between various components.

The stoichiometric amount of [CuCl₂.2H₂O] and Fe( NO₃)₃ were separately dissolved in isopropyl alcohol and solution ammonium hydroxide (NaOH) was added drop by drop to obtain material in hydroxide form. Vigorous stirring was done 20-24 h to ensure complete and intimate reaction between various components. We have prepared two samples i.e. without (S₁) and with PEG (S₂). For synthesis of material S₂, poly ethylene Glycol (PEG) was added as capping reagent.

Later the materials were dried for 8-10 h at 100°C in an oven and calcined at 400°C for 2 h, resulting in complete crystallization into powder. The powders of synthesized materials S1 and S₂ were compacted in to pellets of about 3 mm thickness and 9 mm diameter, at a pressure of 618 MPa using hydraulic press (KBR Press, Germany).

Figure 1(a). SEM image of pellet surface of material S₂ at nano scale

Figure 1(b). SEM image of pellet surface of material S₂ at micro scale

3. Characterizations of Material

a. Scanning Electron Microscopy (SEM)

Scanning electron micrograph as shown in Figure 1(a) and 1 (b) reveal that surfaces of the pellet prepared from sample S₂ is macro porous and macro porous and the clustering of the particles occurs over the different crystallites of materials which enables larger surface area for the adsorption of water molecules.

Therefore the pellet can absorb more atmospheric oxygen due to more exposed surface area of the pellet to react yielding high sensitivity towards moisture. The average size of pores was calculated by using Scanning Electron Micrographs. The average size of pores of nanocomposite CuFe₂O₄ was found to be 2µm.

b. X-Ray Diffraction

The crystal structure and phase of the powdered material S₂ was analyzed using X-ray Diffractometer (X-Pert, PRO PANalytical XRD system, Nether land) with Cu Kα radiations as source having wavelength 1.5418 Å. XRD pattern of the synthesized powder shown in Figure 2 reveals that copper ferrite is cubic crystal structure. It illustrate that the sensing material consists of CuFe₂O₄ along with peaks CuO, Fe₂O3. The high intensity peak, centered at 2θ = 35.57º is assigned to cubic crystal system having ‘d’ spacing 2.523 Ǻ and FWHM 0.1171.

Figure 2. XRD pattern of synthesized powder S₂

The average crystallite size (D) of the sensing material can be calculated by the Debye-Scherrer’s formula, which is given by

where K= 0.94 is Scherrer’s coefficient, which depends on the shape of the crystallite and the type of defects present, λ is the wavelength of X-ray radiation, β is the full width at half maximum (FWHM) of the diffraction peak and θ is the angle of diffraction. The average crystallite size of copper ferrite calculated from Debye Scherer’s formula was found to be 85.7 nm.

Experimental set up as shown in Fig. 3 was used for this investigation. A saturated solution of potassium hydroxide was used as a dehumidifier and a saturated solution of potassium sulphate was used as humidifier. The humidifier/dehumidifier was kept in a dish over a stand. Variations in %RH were measured with the help of hygrometer (Huger, Germany) and variations in resistance were measured Kithely Electrometer (Model: 6514). The temperature of the chamber remained the same throughout the observations. The chamber was then dehumidified up to 10%RH.

Figure 3. Experimental-set-up

The prepared pellet of sensing material was put within a conductivity-measuring holder having Cu electrode-pellet-Cu electrode arrangement. The Cu electrode was square-shaped of a side length 1.2 cm having a gap 0.4 cm between them. It was observed that as %RH inside the chamber increases from 10-90%RH, resistance of the sensing material decreases over the entire range of RH. Sensitivity of humidity sensor has been defined as the change in resistance (ΔR) of the sensing element per unit change in %RH [12].

4. Result and Discussions

Sensitivity of sensing pellet was calculated. Figure 4 clearly reflects that as sensing material prepared sample (S₁) without and with PEG (S₂) show that as RH increases, resistance decreases sharply up to 50%RH and shows highest sensitivity in this range followed by a less rapid decrease up to 90%RH as relative humidity increases.

The average sensitivity for samples S₁ and S₂ were found to be 8.11 MΩ/%RH and 13.7 MΩ/%RH over the entire range of relative humidity. From the Figure 5 and Figure 6, it was observed that the sensing pellet prepared from samples S2 (with PEG) shows less hysteresis between the curves for increasing and decreasing relative humidity over the entire range with resistance. The average values of hysteresis were obtained as ±7% and ±2 % from the original curves for samples S₁ and S₂ respectively. The effect of aging after three months from the fabrication of pellet from material S2 was shown in Figure 7. The results were found to be reproducible with ±5% hysteresis.

Figure 4. Variations of resistance for sensing element prepared from S₁ and S₂ with relative humidity

Figure 5. Hysteresis curve for pellet prepared from sample S₁

Figure 6. Hysteresis curve for pellet prepared from sample S₂

5. Humidity Sensing Mechanism

The composite material is porous in nature and has surface oxygen atoms which essentially arise due to the sample preparation technique. When the material adsorbs the humidity, its resistance decreases due to the increase of charge carriers, protons, in the ferrite and water system [12]. The adsorption of water on the surface of the material leads to the dissociation of hydrogen ions. These hydrogen ions bonded with the surface lattice oxygen atom, forms the hydroxyl groups [13] as shown in the equation:

where Oo corresponds to oxygen at lattice sites. The hydroxyl groups thus produced are bonded with the lattice of the atoms and liberate the free electrons [14]. This electron is responsible for electrical conduction.

Figure 7. Reproducibility curve for sensing pellet fabricated from material S₂

6. Conclusion

Nanocomposite CuFe₂O₄ prepared at room temperature gave good humidity sensing properties for water vapors. The maximum average sensitivity 13.7 MΩ/%RH was achieved for sample synthesized through with poly ethylene glycol over the entire range of relative humidity. The poly ethylene glycol achieves a great role for preventing the grain grow and provide the bulky surface area for adsorption of water vapor through the materials which exhibit maximum sensitivity at room temperature. The results are found to be reproducible with less hysteresis. Thus humidity sensor made of CuFe₂O₄ nanocomposite based on electrical resistance is cost effective, easy to fabricate and user friendly and can be used for both indoor and outdoor applications for entire range of the %RH.

Acknowledgement

Dr. Richa Srivastava is highly grateful to University Grants commission Delhi for ‘Post Doctoral fellowship for Women’. No. F.15-79/11(SA-II).

References

[1]   | A. Venkataraman, V.A. Hiremath, S. K. Date, S. D. Kulkarni, A new combustion route to γ-Fe₂O₃ synthesis, Bull. Mater. Sci., 24, 617, 2001.
[2]   | R. Wang, Y. Chen, Y. Fu, H. Zhang, C. Kisielowski, Bicrystalline Hematite Nanowires, J. Phys. Chem. B, 109, 12245, 2005.
[3]   | B. R. V. Narasimhan, S. Prabhakar, P. Manohar, F. D. Gnanam, Synthesis of gamma ferric oxide by direct thermal decomposition of ferrous carbonate, Mater. Lett., 52, 295,2002.
[4]   | P. P. Sarangi, B. Nail, N. N. Ghosh, Synthesis of single-phase α-Fe₂O₃ nanopowders by using a novel low temperature chemical synthesis route, J. Am. Ceram. Soc., 91, 4145, 2008.
[5]   | N. K. Chaudhari, J. S. Yu, Size control synthesis of uniform β-FeOOH to high coercive field porous magnetic α-Fe₂O₃ nanorods, J. Phys. Chem. C, 112, 19957, 2008.
[6]   | O. Latunde, Synthesis of nanostructured iron oxide thin films for photo catalytic hydrogen production, Nnin Reu Res. Accom., 44, 2008.
[7]   | X. Gou, G. Wang, J. Park, H. Liu, J. Yang, Monodisperse hematite porous nanospheres: synthesis, characterization, and applications for gas sensors, Nanotech., 19, 125606, 2008.
[8]   | R. Srivastava and B.C. Yadav, Nanaostructured ZnO, ZnO-TiO₂ and ZnO-Nb₂O₅ as solid state humidity sensor, Advanced Material Letters, 3, 197, 2012.
[9]   | R. Srivastava and B.C. Yadav, Ferrite materials: Introduction, Synthesis techniques and applications as Sensors, International Journal of Green Nanotechnology: Physics and Chemistry, 4, 141, 2012.
[10]   | M. Desai, S. Prasad, N. Venkataramani, I. Samajdar,A.K. Nigam, R. Krishnan, Annealing induced structural change in sputter deposited copper ferrite thin films and its impact on magnetic properties, Journal of Applied Physics, 92220, 2002.
[11]   | P. Kulkarni, M. Desai, N. Venkataramani, S. Prasad, R. Krishnan, Low power RF sputter depositionof oriented copper ferrite films, Journal of Magnetism and Magnetic Materials, 272, e793, 2004.
[12]   | K. Arshaka, K. Twomey, D. Egan, A ceramic Thick Film humidity sensor based on MnZnFerrite, Sensors, 2, 50, 2002.
[13]   | X. Q. Liu, S. W. Tao, Y. S. Shen, Preparation and characterization of nanocrystalline α-Fe₂O₃ by sol-gel process, Sens. Actuators B, 40, 161, 1997.
[14]   | K. Suri, S. Annapoorni, A.K. Sarkar, R.P. Tandon, Gas and humidity sensors based on ironoxide-polypyrrole nanocomposites, Sens. Actuators B, 81, 277, 2002.