The production of concentrated dispersions of few-layer graphene by the direct exfoliation of graphite in organosilanes

Daniele Nuvoli
Valeria Alzari
Roberta Sanna
Sergio Scognamillo
Massimo Piccinini
Laura Peponi
Josè Maria Kenny
Alberto Mariani
The production of concentrated dispersions of few-layer graphene by the direct exfoliation of graphite in organosilanes
N A N O E X P R E S SGrapheneOrganosilanesHigh concentrationLiquid exfoliation
We report the formation and characterization of graphene dispersions in two organosilanes, 3-glycidoxypropyl trimethoxysilane (GPTMS) and phenyl triethoxysilane (PhTES) as new reactive solvents. The preparation method was mild and easy and does not produce any chemical modification. The dispersions, which exhibit the Tyndall effect, were characterized by TEM and Raman spectroscopy to confirm the presence of few-layer graphene. Concentrations as high as 0.66 and 8.00 mg/ml were found for PhTES and GPTMS, respectively. The latter is one of the highest values reported for a dispersion of graphene obtained by any method. This finding paves the way for the direct synthesis of polymer nanofiller-containing composites consisting of graphene and reactive silanes to be used in sol-gel synthesis, without any need for solvent removal, thus preventing graphene reaggregation to form graphite flakes.

Background

Graphene, with its unique physical properties [1][2][3][4], is one of the most exciting nanomaterials discovered in the last years. A particularly promising graphene production technique is based on the obtainment of colloidal suspensions from graphite, or its derivatives [5]. In spite of other methods like epitaxial growth [6], chemical vapor deposition [7], and micromechanical exfoliation [8], this approach is both scalable, affording the possibility of high-volume production, and versatile in terms of chemical functionalization, which, on the other hand, is sometimes exploited to favor graphene obtainment and its dispersion. Colloidal graphene suspensions may be advantageous in that they could be used for a wide range of applications including: spray coating, vacuum filtration, or drop casting; moreover, by mixing them with polymers, graphene-based polymer composites can be prepared. In these production methods, the key challenge involves the exfoliation of graphitic materials in a liquid that can disperse graphene sheets in a stable way.

One of the most common methods to obtain graphene by this technique involves the dispersion and exfoliation of graphene oxide [5]. This material consists of graphene sheets which are chemically functionalized with groups such as hydroxy and epoxide, which stabilize them in water. However, this functionalization results in considerable damaging of graphene electronic structure, which becomes a semiconductor. While the epoxide functionalities can be removed by reduction [9], the hydroxy and carboxy cannot be removed [10]. Recently, a significant breakthrough was made when some research groups showed that graphite could be exfoliated by nonchemical solution phase methods with solvents [11][12][13] or surfactants [14,15]. The energy required to exfoliate graphene is balanced by the solvent-graphene interaction for compounds whose surface energy matches that of graphene [11]. By this technique, our research group obtained few-layer graphene sheets by sonication of graphite with N-methyl pyrrolidone [16], isocyanates [17], N-vinyl caprolactam [18], a commercial ionic liquid [19], and an acrylate [20], thus, achieving a graphene concentration as high as 2.21, 3.78, 5.00, 5.33 and 9.45 mg/ml, respectively, which are among the highest reported so far in any liquid.

Analogously in the present work, we used reactive organosilane compounds to obtain stable graphene dispersions. Organosilanes are characterized by the basic structure R n Si(OR) 4 − n , where R is an alkyl, aryl, or organofunctional group, and OR is generally a methoxy or ethoxy group, which can react with the hydroxyl groups and liberate methanol or ethanol. Organo (alkoxy)silanes are used in coating applications for surface treatment, as additives in paints, inks, and adhesives, and as reactive intermediates for silicone resin syntheses and organic resin modifications: The alkoxy group can be exploited for the linkage with inorganic substrates, pigments, fillers and hydroxy functionalized polymers. Organo(alkoxy)silanes are used as precursors for the synthesis of inorganic-organic hybrid materials [21]. In particular, 3-glycidoxypropyl trimethoxysilane (GPTMS) and phenyl triethoxysilane (PhTES) are two of the most commonly used for these purposes. Hydrolysis of the methoxy or ethoxy groups of GPTMS and PhTES gives rise to silanol groups which can condense to form silicate networks [22]. Moreover, GPTMS has an epoxy ring that can be used for organic network formation, for instance, through condensation with diethylenetriamine or ethylenediamine at room temperature; this dual functionality makes GPTMS a strategic component for the preparation of polymer hybrids [23].

In the present work, for the first time PhTES and GPTMS were used for dispersing graphene by direct graphite sonication, without any chemical manipulation. The resulting material was thoroughly characterized by using Raman and UV spectroscopies. Moreover, transmission electron microscopy was used for the statistical analysis concerning the distribution among mono and few-layer graphenes.

Methods

Materials

Phenyl triethoxysilane, 3-glycidoxypropyl trimethoxysilane and graphite flakes (+100 mesh) were purchased from Sigma Aldrich (Sigma-Aldrich Corporation, St. Louis, MO, USA) and used as received without further purification.

Graphene dispersions

Mixtures containing various amounts of graphite flakes and organosilane (5.00 g) were put in a tubular plastic reactor (i.d. 15 mm) and placed in an ultrasonic bath (0.55 KW, water temperature ≈ 25°C) for 24 h. Then, after they were centrifuged for 30 min at 4,000 rpm, the gray to black liquid phase containing graphene was recovered.

Graphene dispersion concentration

In order to determine the graphene concentration, the above dispersion was divided into two fractions with a known volume. The first one was filtered through polyvinylidene fluoride filters (PVDF, pore size of 0.22 μm) in order to directly weigh the amount of dispersed graphene and determine the actual graphene concentration.

Determination of absorption coefficient α

The second aliquot of the above dispersion was analyzed by UV analysis with a Hitachi U-2010 spectrometer (1 cm cuvette, Hitachi Corporation, Tokyo, Japan). The above gravimetric data allowed us to determine the absorption coefficient α: from a known volume of initial dispersion, several dilutions were done and the absorbance at a wavelength of 660 nm was measured [11,17,24]. Absorbance versus concentration plots gave the absorption coefficient α (see Results and discussion) value.

TEM analyses

TEM measurements were performed on a JEOL JEM-2100 TEM instrument (JEOL Ltd., Akishima, Tokyo, Japan), with a LaB6 filament, with an operating voltage of 200 kV.

For the TEM analysis, the solutions were sonicated for 5 min and then cast directly on the 200 mesh cooper grid; eventually, the solvent was evaporated at ambient conditions for 24 h.

Raman spectroscopy

Analyses were performed on graphene flakes obtained after vacuum filtration of dispersions on PVDF filters (pore size 0.22 μm), with a Bruker Senterra Raman microscope (Bruker Corporation, Billerica, MA, USA), using an excitation wavelength of 532 nm at 5 mW. The spectra were acquired by averaging five acquisitions of 5 s with a ×50 objective.

Results and discussion

The feasibility of using organosilanes as effective liquid dispersing media for graphene was investigated. In particular, PhTES and GPTMS were tested with the aim of preparing graphene dispersions that could be directly utilized for further uses without recovering graphene in the solid state, thus avoiding any possible restacking of it to pristine graphite and compromising any previous successful exfoliation process.

As described in 'Methods' section, the procedure used was as simple as possible and envisaged the direct sonication of graphite without any chemical manipulation. A first indication of the nanometric dimensions of the dispersed graphene particles was provided by the occurrence of the Tyndall effect [25]. Both GPTMS ( Figure 1) and PhTES dispersions exhibit graphene light scattering, thus confirming the colloidal nature of these systems.

With the aim of determine the best initial graphite/ liquid medium ratio that allows obtaining the highest graphene concentration, a series of dispersions with   different amounts of graphite was prepared for each of the two organosilanes. In order to find the absorption coefficient α and set-up a reliable method for the determination of graphene concentration in the above media, UV and gravimetric analysis were carried out (see 'Methods' section). Figure 2 shows the Lambert-Beer behavior and the different slopes of the two suspensions, thus indicating that the two media have different dispersibility. Namely, for GPTMS and PhTES, an absorption coefficient of 2,415 and 4,710 ml·mg −1 ·m −1 was respectively found.

The concentrations of graphene in GPTMS and PhTES as functions of the initial graphite concentration are reported in Figures 3 and 4, respectively. As far as the GPTMS dispersion is concerned, a direct proportionality between initial graphite and graphene seems to exist up to 5 wt.% of the initial graphite ( Figure 3). After this value, a decrease of graphene concentration was found. This is probably due to the following observed phenomenon: When high concentrations of graphite are added to the used plastic reactor, it tends to precipitate thus making the subsequent sonication process less effective. It should be highlighted that the maximum concentration of graphene here obtained is one of the highest reported so far by any method [11,21,26,27]. An analogous trend was observed also in the case of PhTES (Figure 4), for which the maximum graphene concentration (0.66 mg/ml) was found when the initial graphite concentration was 2.5 wt.%. Besides, the maximum amount of graphene that can be dispersed in PhTES is much lower than in the case of GPTMS, 0.66 mg/ml instead of 8.0 mg/ml, thus indicating that this latter liquid medium is more effective than PhTES in the dispersing graphene.

TEM was used to investigate the state of the graphene particles dispersed in organosilanes; indeed, this technique is usually employed for the investigation of graphene dispersions [11,12,14,23]. As shown in Figure 5, the images revealed a large quantity of flakes of different types. A larger proportion of flakes were few-layer graphene of various dimensions: in particular, very large flakes (lateral size approximately 1 μm) and smaller flakes with an average lateral size of 100 to 200 nm. It should be underlined that, in all cases, we did not observe graphite aggregates. Despite of what was reported in other applications, a relatively large size distribution is generally not considered a drawback in polymer nanocomposites in which the nanometric dimensions of the filler is the predominant factor influencing the properties of the resulting material [16,18].

A statistical analysis on TEM data was performed in order to verify the exfoliation, thus analyzing carefully the edge of the graphene flakes and measuring the number of layers presented in each flake [12]. At this regards about fifty different images have been observed in order to obtain a significant number of flakes for the statistical analysis. The results are reported in Figure 6.

The flakes present good exfoliation degree with an average number of layers of 2.7 for GPTMS and 2.4 for PhTES; standard deviation was about 0.4 and 0.5, respectively. In both cases, only 14% of the flakes were present more than three layers. Moreover, no more than five layers have been counted in very few flakes thus indicating a narrow dispersion. These results confirm that the exfoliation process was very effective.

Raman spectroscopy is essential for the characterization of graphene. Indeed, it is considered one of the best characterization techniques for discriminating between graphite and graphene [15,[28][29][30]. As shown in Figure 7a, typical Raman signals of graphene recovered from the dispersions of GPTMS and PhTES are very similar, both exhibiting the characteristic graphene peaks. In particular, as far as PhTES is concerned, the G band at 1,577 cm −1 , the 2D band at 2,696 cm −1 , and the disorder-related D peak at approximately 1,346 cm −1 are evident. Similarly, graphene obtained from GPTMS shows the G band at 1,574 cm −1 , the 2D band at 2,701 cm −1 , and the disorder-related D peak at approximately 1,345 cm −1 . The shape and position of the 2D peaks ( Figure 7b) is typical of bilayer graphene (four components with the main peak at approximately 2,701 cm −1 , as confirmed by a deconvolution process [30]). As a comparison, the 2D peak of graphite consists of two components and the main peak is upshifted to 2,713 cm −1 .

The disorder-related D peak is present also in the initial graphite powder, but its intensity is higher for graphene. This finding was already reported in which graphene was produced by sonication of graphite and can be attributed to the new edges produced during the sonication process: Ultrasonic treatment causes the decrease in size of the flakes compared to the original graphite, with a consequent increase of the total edge length [12,24,31]. Comparing the intensity of the peaks and the D/G ratio found in the case of graphene obtained in GPTMS and PhTES, only little differences can be found, thus indicating that the disorder induced by the exfoliation process is very similar. Namely, the D/G ratio is 0.47 for graphene dispersed in GPTMS and 0.65 for that dispersed in PhTES, while the reference value for graphite powder is 0.14.

On the basis of the above concentration results, some considerations about the use of the Hildebrand solubility parameters δ should be done. Indeed, Hernandez et al. [13] stated that these parameters could be the key for envisaging the best graphene solvent media. In particular, they calculated a δ value for graphene equal to ca. 23 MPa 1/2 , this value being the same of N-methyl-2-pyrrolidone [12]. However, GPTMS, the best solvent medium reported here, is characterized by δ = 14.5 MPa 1/2 [32]. This value suggests that graphene solubility parameters should be revised and/or that they are not adequate for any reliable solubility prediction on this respect.

Conclusions

A significant improvement of the methods used so far for graphene obtainment has been carried out. Namely, the two new liquid media in which graphene was found to effectively disperse were investigated. In particular, GPTMS and PhTES were chosen as representatives of the larger family of organosilanes. Both of them are commonly used in sol-gel synthesis; moreover, GPTMS can be also used for the preparation of polymer hybrids. In detail, this compound resulted to be one of the most effective medium found so far for dispersing graphene, allowing for a concentration of this material equal to 8.00 mg/ml. The concentration value found for PhTES is much lower (0.66 mg/ml) but, if especially compared with that of most the reported data [11,22,26,27], it can be considered of interest; for instance, for the preparation of polymer composites, in which an even lower concentration of graphene might result in peculiar final properties of the resulting material [16,18,[33][34][35].

Figure 1
1Tyndall effect exhibited by a graphene dispersion in GPTMS. When the red laser light passes through the dispersion, it is scattered and becomes visible.

Figure 2
2Absorption coefficient α determination. Optical absorbance (660 nm) as a function of graphene concentration in PhTES and GPTMS. A Lambert-Beer behavior is shown, with an absorption coefficient α of 4,710 and 2,415 ml·mg −1 ·m −1 , respectively.

Figure 3
3Graphene concentration in GPTMS as a function of initial graphite concentration. Sonication time = 24 h.

Figure 4
4Graphene concentration in PhTES as a function of initial graphite concentration. Sonication time = 24 h.

Figure 5
5TEM micrographies. Graphene dispersed in GPTMS (a,b) and in PhTES (c,d).

Figure 6
6Statistical analysis. Histograms showing the number of layers per flake measured for graphene obtained by exfoliation of graphite in GPTMS (top) and PhTES (bottom).

Figure 7
7Raman analysis. Spectra of graphene obtained by sonication in PhTES and GPTMS from 5 wt.% of the initial graphite compared with graphite (a). 2D peaks evaluation for this systems (b).
http://www.nanoscalereslett.com/content/7/1/674
AcknowledgmentsThe authors thank GEMPPO at the IEM-CSIC for the use of the TEM.Competing interestsThe authors declare that they have no competing interests.Authors' contributions DN prepared the first dispersions of graphene in organosilanes and also drafted the manuscript. RS and VA performed dispersion analysis. SS developed the dispersion method initially found by DN together with this latter. MP carried out the Raman analysis. LP and JMK performed TEM and statistical analysis. AM coordinated the work. All authors read and approved the final version of the manuscript.
Measurement of the elastic properties and intrinsic strength of monolayer graphene. C Lee, X Wei, J W Kysar, J Hone, Science. 321Lee C, Wei X, Kysar JW, Hone J: Measurement of the elastic properties and intrinsic strength of monolayer graphene. Science 2008, 321:385-388.

Superior thermal conductivity of single-layer graphene. A A Balandin, S Ghosh, W Bao, I Calizo, D Teweldebrhan, F Miao, C N Lau, Nano Lett. 8Balandin AA, Ghosh S, Bao W, Calizo I, Teweldebrhan D, Miao F, Lau CN: Superior thermal conductivity of single-layer graphene. Nano Lett 2008, 8:902-907.

Ultrahigh electron mobility in suspended graphene. K I Bolotin, K J Sikes, Z Jiang, M Klima, G Fudenberg, J Hone, P Kim, H L Stormer, Solid State Commun. 146Bolotin KI, Sikes KJ, Jiang Z, Klima M, Fudenberg G, Hone J, Kim P, Stormer HL: Ultrahigh electron mobility in suspended graphene. Solid State Commun 2008, 146:351-355.

Graphene-based ultracapacitors. M D Stoller, S Park, Y Zhu, J An, R S Ruoff, Nano Lett. 8Stoller MD, Park S, Zhu Y, An J, Ruoff RS: Graphene-based ultracapacitors. Nano Lett 2008, 8:3498-3502.

Chemical methods for the production of graphenes. S Park, R S Ruoff, Nat Nanotechnol. 4Park S, Ruoff RS: Chemical methods for the production of graphenes. Nat Nanotechnol 2009, 4:217-224.

Electronic confinement and coherence in patterned epitaxial graphene. C Berger, Z Song, X Li, X Wu, N Brown, C Naud, D Mayou, T Li, J Hass, A N Marchenkov, E H Conrad, P N First, W A De Heer, Science. 312Berger C, Song Z, Li X, Wu X, Brown N, Naud C, Mayou D, Li T, Hass J, Marchenkov AN, Conrad EH, First PN, de Heer WA: Electronic confinement and coherence in patterned epitaxial graphene. Science 2006, 312:1191-1196.

Carbon monolayer phase. condensation on Ni(111). M Eizenberg, J M Blakely, Surf Sci. 82Eizenberg M, Blakely JM: Carbon monolayer phase. condensation on Ni(111). Surf Sci 1970, 82:228-236.

Electric field effect in atomically thin carbon films. K S Novoselov, A K Geim, S V Morozov, D Jiang, Y Zhang, S V Dubonos, I V Grigorieva, A A Firsov, Science. 306Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, Grigorieva IV, Firsov AA: Electric field effect in atomically thin carbon films. Science 2004, 306:666-669.

Graphene-based composite materials. S Stankovich, D A Dikin, Ghb Dommett, K M Kohlhaas, E J Zimney, E A Stach, R D Piner, S T Nguyen, R S Ruoff, Nature. 442Stankovich S, Dikin DA, Dommett GHB, Kohlhaas KM, Zimney EJ, Stach EA, Piner RD, Nguyen ST, Ruoff RS: Graphene-based composite materials. Nature 2006, 442:282-286.

Liquid exfoliation of defect-free graphene. J N Coleman, 10.1021/ar300009fAcc Chem Res. Coleman JN: Liquid exfoliation of defect-free graphene. Acc Chem Res 2012,: . doi:10.1021/ar300009f.

High-yield production of graphene by liquid-phase exfoliation of graphite. Y Hernandez, V Nicolosi, M Lotya, F M Blighe, Z Y Sun, S De, I T Mcgovern, B Holland, M Byrne, Y K Gun'ko, J K Boland, P Niraj, G Duesberg, S Krishnamurthy, R Goodhue, J Hutchison, V Scardaci, A C Ferrari, J N Coleman, Nat Nanotechnol. 3Hernandez Y, Nicolosi V, Lotya M, Blighe FM, Sun ZY, De S, McGovern IT, Holland B, Byrne M, Gun'Ko YK, Boland JK, Niraj P, Duesberg G, Krishnamurthy S, Goodhue R, Hutchison J, Scardaci V, Ferrari AC, Coleman JN: High-yield production of graphene by liquid-phase exfoliation of graphite. Nat Nanotechnol 2008, 3:563-568.

High-concentration solvent exfoliation of graphene. U Khan, A O'neill, M Lotya, S De, J N Coleman, Small. 6Khan U, O'Neill A, Lotya M, De S, Coleman JN: High-concentration solvent exfoliation of graphene. Small 2010, 6:864-871.

Measurement of multicomponent solubility parameters for graphene facilitates solvent discovery. Y Hernandez, M Lotya, D R Shane, D Bergin, J N Coleman, Langmuir. 26Hernandez Y, Lotya M, Shane DR, Bergin D, Coleman JN: Measurement of multicomponent solubility parameters for graphene facilitates solvent discovery. Langmuir 2010, 26:3208-3213.

Liquid phase production of graphene by exfoliation of graphite in surfactant/water solutions. M Lotya, Y Hernandez, P J King, R J Smith, V Nicolosi, L S Karlsson, Fiona Blighe, F M De, S Wang, Z Mcgovern, I T Duesberg, G S Coleman, J N , J Am Chem Soc. 131Lotya M, Hernandez Y, King PJ, Smith RJ, Nicolosi V, Karlsson LS, Fiona Blighe FM, De S, Wang Z, McGovern IT, Duesberg GS, Coleman JN: Liquid phase production of graphene by exfoliation of graphite in surfactant/water solutions. J Am Chem Soc 2009, 131:3611-3620.

Solution phase production of graphene with controlled thickness via density differentiation. A A Green, M C Hersam, Nano Lett. 9Green AA, Hersam MC: Solution phase production of graphene with controlled thickness via density differentiation. Nano Lett 2009, 9:4031-4036.

Graphene-containing thermoresponsive nanocomposite hydrogels of poly(Nisopropylacrylamide) prepared by frontal polymerization. V Alzari, D Nuvoli, S Scognamillo, M Piccinini, E Gioffredi, G Malucelli, S Marceddu, M Sechi, V Sanna, A Mariani, J Mater Chem. 21Alzari V, Nuvoli D, Scognamillo S, Piccinini M, Gioffredi E, Malucelli G, Marceddu S, Sechi M, Sanna V, Mariani A: Graphene-containing thermoresponsive nanocomposite hydrogels of poly(N- isopropylacrylamide) prepared by frontal polymerization. J Mater Chem 2011, 21:8727-8733.

Synthesis and characterization of graphene-containing thermoresponsive nanocomposite hydrogels of poly(N-vinylcaprolactam) prepared by frontal polymerization. R Sanna, D Sanna, V Alzari, D Nuvoli, S Scognamillo, M Piccinini, M Lazzari, E Gioffredi, G Malucelli, A Mariani, J Polym Sci Part A: Polym Chem. 50Sanna R, Sanna D, Alzari V, Nuvoli D, Scognamillo S, Piccinini M, Lazzari M, Gioffredi E, Malucelli G, Mariani A: Synthesis and characterization of graphene-containing thermoresponsive nanocomposite hydrogels of poly(N-vinylcaprolactam) prepared by frontal polymerization. J Polym Sci Part A: Polym Chem 2012, 50:4110-4118.

Synthesis and characterization of nanocomposites of thermoplastic polyurethane with both graphene and graphene nanoribbon fillers. S Scognamillo, E Gioffredi, M Piccinini, M Lazzari, V Alzari, D Nuvoli, R Sanna, D Piga, G Malucelli, A Mariani, Polymer. 53Scognamillo S, Gioffredi E, Piccinini M, Lazzari M, Alzari V, Nuvoli D, Sanna R, Piga D, Malucelli G, Mariani A: Synthesis and characterization of nanocomposites of thermoplastic polyurethane with both graphene and graphene nanoribbon fillers. Polymer 2012, 53:4019-4024.

High concentration few layer graphene sheets obtained by liquid phase exfoliation of graphite in ionic liquid. D Nuvoli, L Valentini, V Alzari, S Scognamillo, Bittolo Bon, S Piccinini, M Illescas, J Mariani, A , J Mater Chem. 21Nuvoli D, Valentini L, Alzari V, Scognamillo S, Bittolo Bon S, Piccinini M, Illescas J, Mariani A: High concentration few layer graphene sheets obtained by liquid phase exfoliation of graphite in ionic liquid. J Mater Chem 2011, 21:3428-3431.

In situ production of high filler content graphene-based polymer nanocomposites by reactive processing. V Alzari, D Nuvoli, R Sanna, S Scognamillo, M Piccinini, J M Kenny, G Malucelli, A Mariani, J Mater Chem. 21Alzari V, Nuvoli D, Sanna R, Scognamillo S, Piccinini M, Kenny JM, Malucelli G, Mariani A: In situ production of high filler content graphene-based polymer nanocomposites by reactive processing. J Mater Chem 2011, 21:3428-3431.

Hybrid sol-gel-derived polymers: applications of multifunctional materials. G Schottner, Chem Mater. 13Schottner G: Hybrid sol-gel-derived polymers: applications of multifunctional materials. Chem Mater 2001, 13:3422-3435.

Formation of silica/epoxy hybrid network polymers. S R Davis, A R Brough, A Atkinson, J Non-Cryst Solids. 315Davis SR, Brough AR, Atkinson A: Formation of silica/epoxy hybrid network polymers. J Non-Cryst Solids 2003, 315:197-205.

Hybrid organic inorganic epoxy resins prepared by frontal polymerization. S Scognamillo, V Alzari, D Nuvoli, A Mariani, J Polym Sci Part A: Polym Chem. 48Scognamillo S, Alzari V, Nuvoli D, Mariani A: Hybrid organic inorganic epoxy resins prepared by frontal polymerization. J Polym Sci Part A: Polym Chem 2010, 48:4721-4725.

High-concentration, surfactant-stabilized graphene dispersions. M Lotya, P J King, U Khan, S De, J N Coleman, ACS Nano. 4Lotya M, King PJ, Khan U, De S, Coleman JN: High-concentration, surfactant-stabilized graphene dispersions. ACS Nano 2010, 4:3155-3162.

Processable aqueous dispersions of graphene nanosheets. D Li, M B Müller, S Gilje, R B Kaner, G G Wallace, Nat Nanotechnol. 3Li D, Müller MB, Gilje S, Kaner RB, Wallace GG: Processable aqueous dispersions of graphene nanosheets. Nat Nanotechnol 2008, 3:101-105.

Fabrication of high-concentration and stable aqueous suspensions of graphene nanosheets by noncovalent functionalization with lignin and cellulose derivatives. Q Yang, X Pan, F Huang, K Li, J Phys Chem C. 114Yang Q, Pan X, Huang F, Li K: Fabrication of high-concentration and stable aqueous suspensions of graphene nanosheets by noncovalent functionalization with lignin and cellulose derivatives. J Phys Chem C 2010, 114:3811-3816.

Solvent-exfoliated graphene at extremely high concentration. U Khan, H Porwal, A O'neill, K Nawaz, P May, J N Coleman, Langmuir. 27Khan U, Porwal H, O'Neill A, Nawaz K, May P, Coleman JN: Solvent-exfoliated graphene at extremely high concentration. Langmuir 2011, 27:9077-9082.

Raman spectroscopy of graphene and graphite: disorder, electron-phonon coupling, doping and nonadiabatic effects. A C Ferrari, Solid State Commun. 143Ferrari AC: Raman spectroscopy of graphene and graphite: disorder, electron-phonon coupling, doping and nonadiabatic effects. Solid State Commun 2007, 143:47-57.

First-and second-order Raman scattering from finite-size crystals of graphite. R J Nemanich, S Solin, Phys Rev B. 20Nemanich RJ, Solin S: First-and second-order Raman scattering from finite-size crystals of graphite. Phys Rev B 1979, 20:392-401.

Raman spectrum of graphene and graphene layers. A C Ferrari, J C Meyer, V Scardaci, C Casiraghi, M Lazzeri, F S Mauri, F S Piscanec, D Jiang, K S Novoselov, S Roth, A K Geim, Phys Rev Lett. 97Ferrari AC, Meyer JC, Scardaci V, Casiraghi C, Lazzeri M, Mauri FS, Piscanec FS, Jiang D, Novoselov KS, Roth S, Geim AK: Raman spectrum of graphene and graphene layers. Phys Rev Lett 2006, 97:187401-187404.

Raman spectroscopy of graphene edges. C Casiraghi, A Hartschuh, H Qian, S Piscanec, C Georgi, A Fasoli, K S Novoselov, D M Basko, A C Ferrari, Nano Lett. 9Casiraghi C, Hartschuh A, Qian H, Piscanec S, Georgi C, Fasoli A, Novoselov KS, Basko DM, Ferrari AC: Raman spectroscopy of graphene edges. Nano Lett 2009, 9:1433-1441.

Effect of the miscibility between a silane and a sizing agent on silanol condensation. N Suzuki, H Ishida, J Appl Polym Sci. 87Suzuki N, Ishida H: Effect of the miscibility between a silane and a sizing agent on silanol condensation. J Appl Polym Sci 2003, 87:589-598.

Functionalized graphene sheets for polymer nanocomposites. T Ramanathan, A A Abdala, S Stankovich, D A Dikin, M Herrera-Alonso, R D Piner, D H Adamson, H C Schniepp, X Chen, R S Ruoff, S T Nguyen, I A Aksay, R K Prud'homme, L C Brinson, Nat Nanotechnol. 3Ramanathan T, Abdala AA, Stankovich S, Dikin DA, Herrera-Alonso M, Piner RD, Adamson DH, Schniepp HC, Chen X, Ruoff RS, Nguyen ST, Aksay IA, Prud'Homme RK, Brinson LC: Functionalized graphene sheets for polymer nanocomposites. Nat Nanotechnol 2008, 3:327-331.

Enhanced mechanical properties of nanocomposites at low graphene content. M A Rafiee, J Rafiee, Z Wang, H Song, Z Z Yu, N Koratkar, ACS Nano. 3Rafiee MA, Rafiee J, Wang Z, Song H, Yu ZZ, Koratkar N: Enhanced mechanical properties of nanocomposites at low graphene content. ACS Nano 2009, 3:3884-3890.

Functionalized graphene sheet filled silicone foam nanocomposites. R Verdejo, F Barroso-Bujans, M A Rodriguez-Perez, J A De Saja, M A Lopez-Manchado, 10.1186/1556-276X-7-674J Mater Chem. 18Verdejo R, Barroso-Bujans F, Rodriguez-Perez MA, de Saja JA, Lopez-Manchado MA: Functionalized graphene sheet filled silicone foam nanocomposites. J Mater Chem 2008, 18:2221-2226. doi:10.1186/1556-276X-7-674

The production of concentrated dispersions of few-layer graphene by the direct exfoliation of graphite in organosilanes. Nuvoli, Nanoscale Research Letters. Cite this article as. Immediate publication on acceptance 7 Open access: articles freely available online 7 High visibility within the fi eld 7 Retaining the copyright to your article Submit your next manuscript at 7 springeropen.comCite this article as: Nuvoli et al.: The production of concentrated dispersions of few-layer graphene by the direct exfoliation of graphite in organosilanes. Nanoscale Research Letters 2012 7:674. Submit your manuscript to a journal and benefi t from: 7 Convenient online submission 7 Rigorous peer review 7 Immediate publication on acceptance 7 Open access: articles freely available online 7 High visibility within the fi eld 7 Retaining the copyright to your article Submit your next manuscript at 7 springeropen.com


The role of health extension workers in improving utilization of maternal health services in rural areas in Ethiopia: a cross sectional study

Araya Medhanyie
Mark Spigt
Yohannes Kifle
Nikki Schaay
David Sanders
Roman Blanco
Dinant Geertjan
Yemane Berhane
The role of health extension workers in improving utilization of maternal health services in rural areas in Ethiopia: a cross sectional study
R E S E A R C H A R T I C L E Open Access
Background: Community health workers are widely used to provide care for a broad range of health issues. Since 2003 the government of Ethiopia has been deploying specially trained new cadres of community based health workers named health extension workers (HEWs). This initiative has been called the health extension program. Very few studies have investigated the role of these community health workers in improving utilization of maternal health services. Methods: A cross sectional survey of 725 randomly selected women with under-five children from three districts in Northern Ethiopia. We investigated women's utilization of family planning, antenatal care, birth assistance, postnatal care, HIV testing and use of iodized salt and compared our results to findings of a previous national survey from 2005. In addition, we investigated the association between several variables and utilization of maternal health services using logistic regression analysis.Results: HEWs have contributed substantially to the improvement in women's utilization of family planning, antenatal care and HIV testing. However, their contribution to the improvement in health facility delivery, postnatal check up and use of iodized salt seems insignificant. Women who were literate (OR, 1.85), listened to the radio (OR, 1.45), had income generating activities (OR, 1.43) and had been working towards graduation or graduated as model family (OR, 2.13) were more likely to demonstrate good utilization of maternal health services. A model family is by definition a family which has fulfilled all the packages of the HEP.Conclusions:The HEWs seem to have substantial contribution in several aspects of utilization of maternal health services but their insignificant contribution in improving health facility delivery and skilled birth attendance remains an important problem. More effort is needed to improve the effectiveness of HEWs in these regards. For example, strengthening HEWs' support for pregnant women for birth planning and preparedness and referral from HEWs to midwives at health centers should be strengthened. In addition, women's participation in income generating activities, access to radio and education could be targets for future interventions.

Background

In response to inadequate numbers of health personnel, many countries have focused on increasing production and distribution of personnel. This occurred in 1980s particularly in the community health worker cadre although in the 1990s many such programmes faltered [1]. Community health workers (CHWs) are widely used to provide care for a broad range of health issues. However, there is insufficient evidence about the effectiveness of their work in implementing comprehensive primary health care [2]. This lack of knowledge makes it difficult for policy makers to decide how CHWs can best improve the effectiveness of primary health care.

Like in many resource constrained countries, Ethiopia has been training and deploying different categories of volunteer community health workers (VCHWs) in the past decades. These CHWs include trained traditional birth attendants (TTBAs), community based reproductive health agents (CBRHAs) and community health agents (CHAs). However, to accelerate the expansion of primary health care coverage and to ensure equitable access to health services, the government of Ethiopia started deploying specially trained new cadres of community based health workers named Health Extension Workers (HEWs). This initiative has been called the Health Extension Program (HEP). The HEP has been introduced in recognition of the failure of essential services to reach the people at the grassroots level in particular to underserved rural population. It was designed based on the concept and principles of comprehensive primary health care [3][4][5][6].

The health system of Ethiopia is a four level health system, characterized by a primary health care unit (PHCU), and then the district hospital, zonal hospital and specialized hospital. A PHCU has been planned to serve 25,000 people, while a district and a zonal hospital are each expected to serve 250,000 and 1,000,000 people, respectively. Specialized hospitals are planned to serve a catchment area with 5 million people [7].

The lowest level in the Ethiopian health system is a PHCU, comprising one health center and five satellite health posts. Health centers are staffed with a health professional team including midlevel health professionals for instance health officers, nurses, midwives, sanitarians and laboratory technicians. A health center provides comprehensive primary health care which includes promotive, prevention, curative and rehabilitative services. One health center supervises and receives referrals from five satellite health posts. A health post is the operational center for two HEWs. On average, a health post serves a kebele which comprises approximately 1000 households or 5000 people.A kebele is the smallest administrative unit in Ethiopia, but it can include several small villages. By the year 2010, a total of about 34,000 HEWs were trained and deployed throughout the country. In addition about 15,000 health posts were constructed in the country. HEWs are required to spend 75% of their time conducting outreach activities by going from house to house in their respective kebele, while the rest of their time they are supposed to be at the health post. All HEWs have completed high school and received additional training for 1 year at an undergraduate level. The HEWs are also different from the VCHWs in that they are employed in the government health system structure and get monthly salary. They receive more advanced and comprehensive training when compared to VCHWs [3][4][5][6].

With the aim of reducing maternal mortality, HEWs are trained on how to provide care to pregnant mothers through pregnancy, birth and postnatal period. HEWs inform pregnant mothers on safe motherhood when they provide antenatal care (ANC), birth and post natal care (PNC). HEWs also provide family planning services and are trained on how to educate women on the use of iodized salt and HIV testing.

Since the implementation of the HEP, few studies have published findings on the effectiveness of HEWs [8]. These studies have shown their effectiveness in improving utilization of family planning and immunization services. However, none of them investigated the HEWs role in improving utilization of comprehensive maternal health services.

This study focuses on the extent to which these specially trained community health workers have contributed to the improvement of utilization of maternal health services by rural women in Ethiopia. We compare current utilization of maternal health services with the Ethiopian Demographic Health Survey 2005(EDHS 2005) and investigate which variables may be related to good utilization of maternal health services.

Methods

Study design

A cross-sectional survey was undertaken in August-November 2009 to assess utilization to maternal health services by women in rural villages in Ethiopia.

Setting

The study was conducted in Tigray region, Ethiopia. Tigray is one of the nine regions and the northernmost regional state of Ethiopia. The 2007 Ethiopian census showed the population of the region to be 4.3 million of which 80% lived in rural areas and 51% were female [9]. The poor health status of Tigray region is comparable to the rest of the country, showing high infant mortality rate (67/1000), low institutional delivery (8.6%), high HIV prevalence (2.7%), and low family planning utilization (16.5%) [10]. This study was done in three rural districts. The districts studied were Alaje from the Southern Zone, Saesi Tsadamba from the Eastern Zone and Degua Tembien from the South Eastern Zone of Tigray. These districts were selected purposefully in consultation with Tigray regional health bureau. We considered accessibility of the districts to carry out the research in terms of transport. Out of the total 72 kebeles in these districts, 13 of them had health centers. Twelve of them did not have any health facility. The rest 47 rural kebeles were with only health post. From each selected district, three rural kebeles were selected. Rural kebeles with no functional health posts were excluded from the selection. Rural kebeles who have health facilities other than health posts were not also included in the study. All the selected kebeles were with functional health posts and HEWs.

Sample size

We employed the Statcalc sample size calculation for cross-sectional study module of EPI-info version 2002 to determine sample size for our study. A total sample size of 726 households was determined by considering 95% confidence interval, 80% power of study; 1:1 comparison among districts, a contraceptive prevalence rate of 16.2% for Tigray region taken from EDHS 2005, and we assumed that the proportion of contraceptive users would be two times when we did our data collection in 2009.

Study population

Women with under-five children from the nine selected kebeles who were willing and healthy enough to be interviewed were identified to participate in the survey. To select the study participants a sampling frame of households with women who had under-five children was developed from the log book of the HEWs. These log books of HEWs have a list of households in their kebeles. Using systematic random sampling, we selected an average of 80 women with under-five children from each kebele. There was no refusal to participate. When the woman selected for an interview was not available, a neighbouring woman was interviewed. A total of 726 women were interviewed and data from 725 women were included in the analysis; 1 questionnaire was useless because of its incompleteness.

Data collection

We collected data on women's utilization of family planning, antenatal care, delivery care, postnatal care, HIV testing and use of iodized salt. Data on women's utilization of maternal health services by type of health workers were collected. The questionnaire was initially developed in English and then translated to the local language, 'Tigrigna'. The questionnaire was pre-tested among 20 mothers to assure clarity of concepts for respondents.

The data were collected by six data collectors who had completed high school and who had experience in doing questionnaire interviews. Additional training was given for the data collectors to help them understand the nature of the study and the questions. Completed questionnaires were checked for completeness and consistency at the time of interview by supervisors. To ensure rigor in the study, supervisors re-checked the responses for a randomly selected 5% of the questionnaires by going back to the woman's house. Re-checking showed no major problems in data collection.

Outcome variables and definitions

Utilization of maternal health services was collected using the following variables: 1. Family planning: whether the woman has been using contraceptives during the interview period (current utilization) or whether the woman has ever used contraceptives in her lifetime (ever utilization). 2. Antenatal care (ANC): whether the woman attended a health facility for antenatal care (ANC) at least once in her last successful pregnancy. 3. Health facility delivery: whether the woman gave birth at a health facility for her youngest child. 4. Postnatal care (PNC): whether a health professional or community health worker visited the woman at her home within 24 hours of the birth of her youngest child. 5. HIV testing: whether the woman had ever had an HIV test by the time of interview. 6. Use of iodized salt: whether iodized cooking salt (with 15 parts per million based on salt testing kits) was found in the woman's house. This was considered as one of the maternal health services because educating women on utilization of iodized salt and distributing subsidized iodized salt are among the tasks of HEWs.

In addition we measured several other variables such as age, educational status, marital status, religion, year of enrolment into the HEP, household status in relation to working towards graduation or graduated as model family and participation in income generating activities (IGAs). A model family is by definition a family which has fulfilled all the packages of the HEP. Prior to the data collection we checked log books of HEWs on this information. We found the log books had incomplete and inconsistent information on whether a family completed all the packages of the program or not. Hence for this study we took the woman's word whether she said her household had been working towards graduation or graduated as model family or not. IGAs are government or community-initiated activities for local people to earn some money. These IGAs include irrigation schemes, micro-finance credit, safety net, cattle rearing, poultry production and bee keeping.

Data management and analysis

Frequencies of utilization of specific maternal health services were calculated. To estimate changes in the utilization of maternal health services over the years, we compared our findings with findings of the EDHS 2005. The EDHS 2005 was a nationally representative survey of 14,070 women aged 15-49. The data collection of this survey was conducted from April 27-August 30, 2005.

To investigate which factors were associated with good utilization of maternal health service, we used logistic regression. To calculate Adjusted Odds Ratios (AOR) we included all independent variables in one model. The dependent variable was computed by combining the six outcome variables. Using the mean (3.01) as a cutoff point, we categorized utilization of maternal health services into two categories. Women who had utilized 4 and more maternal health services were defined as having good utilization of maternal health services, while those who had utilized less than 4 were considered as having poor utilization of maternal health services. Women's response for questions on religion, marital status and occupation were virtually the same. Therefore, these variables were not used in the analysis.

Ethical considerations

The study was approved by the ethics committee at the College of Health Sciences of Mekelle University, Ethiopia which offered a letter with reference number CHS/236/ A-16/09 dated on 05/March/09. Study participants were informed about the purpose of the study, anticipated benefits, how they were chosen to participate, data collection procedures and their full right to refuse, withdraw from part or all of the study. The participant's name was kept confidential. Verbal informed consent was obtained from each study participant. Verbal consent instead of written consent was chosen as most of the questions in the survey were not sensitive and a great number of rural women in Ethiopia are unable to read and write.

Results

Respondents' characteristics

The mean age of the 725 study participants was 31.4 years ( Table 1) and almost all (99.9%) were orthodox Christians. The mean number of children per woman was 4.15. The majority of participants (86%) participated in at least one income generating activity. Micro-finance credit and the safety net programs were the most reported IGAs.

Utilization of maternal health services

More than half (67%) of the women had ever used contraceptives while 38% of them were current users. ANC visit at health facility was reported by 85% of the women. However less than half (48%) of the women had the World Health Organization (WHO) recommended 4 and more ANC visits. A small number (5%) of the women said that they gave birth at the health facility. A similar percentage (5 %) of the women had PNC check up. More than three quarters (85%) of the women had been tested for HIV. Iodized salt of greater than 15PPM was found in only 13% of the women's households. Using the mean score for utilization of maternal health services as a cutoff point for good and poor utilization of maternal health services, about 37% of the women had good utilization of maternal health services while the rest had poor utilization.

Who offers maternal health services?

The role of the HEWs to improved utilization of maternal health services is greatest in relation to family planning and ANC (Table 2). In regard to advice on family planning; 72% of the mothers reported to have received information on this topic from the HEWs. Forty-four percent of the mothers reported having been visited before delivery by HEWs. However, postnatal care and especially assistance during delivery still seem to be a big problem. The majority of the women (81%) delivered their baby with the help of relatives or friends and only 7% were assisted by the HEWs. Trained traditional birth attendants do better than HEWs in assisting births (20%).

Women's utilization of primary care facilities for maternal health services

Health posts were rarely used by women for delivery services and PNC checkups (Table 3). Only 1% of the study participants gave birth at health posts. A similar percentage of participants had had PNC checkups for their baby at health posts. The utilization of health posts for family planning and ANC by women was relatively higher than for delivery. About 21% of the study participants had obtained contraceptives from the health posts. It seemed that women preferred the health center to the health post for ANC follow up (61% versus 23%).

Comparison of findings of this study on utilization of maternal health services with findings of EDHS 2005

Compared to EDHS 2005 (Table 4), there is an increase in the proportion of women who have utilized family planning, antenatal care, and HIV testing. However, we observed no change in the proportion of women who have used health facility delivery and iodized salt.

Association of respondents' characteristics with utilization of maternal health services

Calculated AOR through logistic regression analysis showed (

Discussion

Since the introduction of HEP in 2003 and deployment of HEWs, there has been an increase in the proportion of women who have utilized family planning, antenatal care, and HIV testing. On the other hand their deployment and work have not showed any improvement in utilization of health facilities for delivery, postnatal check up and use of iodized salt. Primary care facilities; particularly health posts, were almost unutilized by women for maternal health services. Women preferred to visit health centers instead of health posts. Women, who were literate, listened to the radio, participated in income generating activities and had been working towards graduation or graduated as model family were more likely to access and utilize comprehensive maternal health services. Our finding on family planning is in agreement with other studies conducted in Ethiopia [11,12]. These studies showed HEWs have improved access to family  planning. A study conducted in the southern part of Ethiopia found that women who were able to read and write are more likely to access maternal health services, similar to our findings. This study also showed similar to our findings on ANC that the proportion of women who had at least one ANC visit has increased considerably [13]. Nevertheless our study showed the proportion of women who had 4 and more ANC visits as recommended by WHO was still low (48%). Thus concerted effort by HEWs and VCHWs is necessary to educate women about the importance of having four and more ANC visits. Another important achievement observed in our study is the increase in HIV testing. A study on antiretroviral treatment in Ethiopia depicted a similar substantial expansion of access to HIV counselling and testing in Ethiopia [14]. This increase might not be totally attributed to HEWs, because nongovernmental organizations (NGOs) and other stakeholders also play a crucial role in HIV testing and education, through different approaches such as campaigns. HIV programs are highly supported by NGOs and other stakeholders. However, the positive role of HEWs in improving HIV testing and prevention in rural areas is undisputable. In reality, in rural kebeles in Ethiopia, HIV testing and education on HIV prevention is carried out primarily by HEWs. Even HEWs who are not trained for HIV testing organize and coordinate the campaigns for HIV testing. Practically all the health activities including campaigns at rural kebeles in Ethiopia are undertaken and organized by HEWs. The HEWs did not succeed in improving utilization of health facility delivery, PNC check up and use of iodized salt. This calls for urgent interventions into the HEP. Innovative approaches are needed to improve HEWs effectiveness in relation to these services. Similar to our study, another study also showed no progress in skilled birth assistance and postnatal care coverage in Ethiopia since 1998 [12]. Contrary to the findings of a cross sectional study among 60 households in Tigray region which was conducted at the earlier stages of the HEP implementation, our study revealed the proportion of women who were assisted for birth by trained traditional birth attendants (TTBAs) is much higher than those assisted by HEWs [15]. This might be due to the fact that the number of TTBAs in a kebele is higher than the number of HEWs. It might be also TTBAs are tried and tested by women and seen to be experienced in conducting deliveries. Perhaps they could be closer and accessible to village women. On the other hand low competency and confidence of HEWs in assisting births, less favourable working conditions at the health posts, workload and walking long distances at night to assist births at home might also be attributed to this low performance of HEWs in assisting births [16].

Though further research is needed to study the HEWs' performance in birth assistance, we propose several reasons for the present findings of their low participation in this role. First, health facility delivery is demanding in relation to cost, skill and competency. It requires HEWs having the necessary skills and communities having accessible and well-supplied facilities in place. Second, encouraging behavioural change for women to have births at health facility is time consuming work [17][18][19]. Women's preference for having birth at home is a deeply embedded cultural belief. Women may believe that it is appropriate to go to a health facility for birth assistance and check up only if there are visible complications during birth [18]. Other determinants like women's age, education, income, number of children and health seeking behaviour could also influence women's preference on health facility delivery and birth assistance by skilled birth attendant [13]. Thus focused birth preparedness by pregnant women is necessary to encourage every woman to have birth at health facility or assisted by health professionals. It is advisable for HEWs and other community health workers to have effective discussion on birth preparedness with every pregnant woman when they do home based ANC visit. Third, health posts are not well equipped for providing delivery service which is a disincentive for women to use these facilities. Almost all health posts are a single room only, with no waiting room area, water source or electricity. Hence a strong referral system should be established between health posts and health centers (which are better equipped for birth deliveries) until health posts meet the necessary standards for delivery service. Fourth, HEWs' low performance in assisting birth also relates to how HEWs are perceived by the community. The community may regard HEWs as less competent to assist birth. Unpublished reports from Tigray regional health bureau on the HEP indicate that the community perceive HEWs' main task to be health education, sanitation and personal hygiene. Health extension workers were primarily associated with latrine construction. All these reasons and considering HEWs' present workload and the poor conditions of health posts, it may be unrealistic to expect greater involvement in birth assistance by HEWs or that women would choose to give birth at health posts [16][17][18][19][20].

The 1978 Alma Ata Declaration on Primary Health Care [21], and subsequent reviews of primary health care reforms, call for intersectoral collaboration to address socio-economic determinants of community health, in which ensuring universal access to health services is one element [22,23]. In consideration of these other social determinants of women's health, this study looked at whether participating in IGAs had an association with utilization of maternal health services. Logistic regression analysis revealed women who have been participating in three and more income generating activities were 1.72 times more likely to have good utilization of comprehensive maternal health services. The regression analysis also identified women who were literate, listened to the radio, and had been working towards graduation or graduated as model families for HEP were more likely to have good utilization of maternal health services. Hence these potential social factors could be targets for future intervention and support, as a means of increasing health care utilization. Year of enrolment into the HEP was not associated with good utilization of maternal health services. This may be due to the effect of diffusion of the intervention. Households who were enrolled later into the program may have opportunities to learn and share experience on positive health behaviours and information from households that were enrolled earlier.

Strength and limitation of the study

Our study examined utilization of maternal health services among rural women who are difficult to reach. Our study is a cross sectional study and it may be difficult to attribute all the changes in utilization of maternal health services to the deployment of HEWs. Comparing our findings from a local sample with a national survey has its own limitation as the study population of our survey is small in size and from a specific region of the country while the national survey is large in size and representative for the whole country. Nevertheless, similar findings on improvements on utilization of family planning, antenatal care and HIV testing after the introduction of the HEP were observed by other studies conducted in other regions of the country. Thus the conclusions made in our study are most likely hold true not only for our study area but also for other areas in the country irrespective of the difference in socio-demographic characteristics across the country. It is worthy considering the way the outcome index (maternal health service utilization) is constructed, the variables chosen to construct this index and its categorization into good and poor. Had we chosen different variables and categorization to construct this outcome index, the results might have been different. Recall bias might also influence some of the results such as information on whether a household had been working towards graduation or graduated as model family or not and women's involvement in IGA or not, because we took women's word for these variables. Some important determinants of maternal health services utilization, for example distance to health facility, timing and frequency of HEWs visits, and household-decision making practices are not taken into account in our study. We recommend further study on the effect of these factors on utilization of maternal health services by rural women.

Conclusions

This study has shown HEWs have brought essential maternal health care closer to the rural population in Ethiopia. Nevertheless their success is not for all components of maternal health services. HEWs brought improvement in utilization of family planning, ANC and HIV testing but not in assisting births. The perception that HEWs' may be less competent in assisting births, the huge workload they already have, poorly equipped health posts and strong cultural beliefs supporting home births, make it unreasonable at the present time to expect substantial change in where and how women give birth. These challenging factors call for innovative strategies to support the efforts of HEWs in identifying risky mothers, birth preparedness and to improve their referral to health centers where midwives and better facilities for assisting births are available.

Table 1
1Respondents' characteristics, September 2009 (N=725)Characteristics of respondents
Frequency
(no./%)

Number of participants per district

District 1 : Degua Tembien
240(33.1)

District 2: Saesi Tsadamba
244(33.7)

District 3: Alaje
241(33.2)

Age of respondents

24 and less
106(14.6%)

25 and above
619(85.4%)

Educational level

Illiterate (unable to read and write)
576(79.4)

Illiterate (able to read and write)
149(20.6)

Marital status

Yes, currently married
644(88.8%)

Not in a union
81(11.2%)

Do you listen to radio

No
439(60.6)

Yes
286(39.4)

Participation in income generating activities (IGAs)

Poor Participation: in 2 and less IGAs
456(62.9)

Good participation: in 3 and more IGAs
269(37.1)

Year of enrolment in HEP

Do not know
159(21.9)

2004-2006
238(32.8)

2007-2009
328(45.2)

Household status towards graduation as model family

Did not hear about model family
264(36.4)

Have heard but not at all working
towards graduation

278(38.3)

Working towards graduation or
graduated as model family

183(25.2)

Table 5 )
5that women who were able to read and
write (AOR, 1.85; CI 1.22-2.80), listened to a radio
(AOR, 1.45; CI 1.05-2.02), had good participation in
IGAs (AOR, 1.43; CI 1.03-2.00), and had been working
towards graduation or graduated as model family (AOR,

Table 2
2Women's utilization of maternal health services by the type of health workers, September 2009 (N=725) Family planning: In the past 12 months, who among community health workers visited you and talked to you about family planning? *Maternal health services
Frequency (no./%)

Health extension worker
523(72.1)

Community based reproductive health agent
88(12.1)

Community health agent
276(38.1)

Trained and untrained traditional birth attendant
331(45.7)

Not visited
145(20.0)

Antenatal care: Who (community health worker) visited you during
your pregnancy of your youngest child?*

Health extension worker
319(44.0)

Community health agent
98(26.1)

Community reproductive health agent
33(4.6)

Untrained or trained traditional birth attendant
157(41.8)

Was not visited or don´t remember
349(48.1)

Delivery Service: Who assisted you with the delivery of your youngest
child?*

Health professional
31(4.3)

Trained traditional birth attendant
147(20.3)

Untrained traditional birth attendant
29(4.0)

Relative/friend/neighbor
586(80.8)

Health extension worker
49(6.8)

No one
1(0.1)

Post natal care: If a community health worker visited you immediately
after delivery of your youngest child, who was that person?*

Health extension worker
189(26.1)

Community health agent
67(9.2)

Community based reproductive health agent
13(1.8)

Trained and untrained traditional birth attendant
170(23.4)

Was not visited or do not remember
389(53.7)

*Multiple responses were possible.

Table 3
3Post natal care: After your youngest child was born, if a health worker checked your baby, where did that check take place?Women's utilization of primary health care
facilities for maternal health services, September 2009
(N=725)

Maternal health services
Frequency (no./%)

Family planning: Where did you obtain (current method) for the last
time?

Health center
117(16.1%)

Health post
150(20.7)

Others
7(0.8)

Non current users and pregnant mothers
451(62.2)

Antenatal care: Where did you receive antenatal care when you were
pregnant for your youngest child?

Health center
441(60.8)

Health post
163(22.5)

Others
9(1.3)

Did not go to a health facility
112 (15.4)

Delivery service: Where did you give birth for your youngest child?

Home
691(95.3)

Hospital
10 (1.4)

Health center
16(2.2)

Health post
8(1.1)

Your home
6(0.8)

Health post
10(1.4)

Health center
25(3.4)

Hospital
6(0.8)

Didn't had check up
678(93.5)

Table 4
4Comparison of findings of our study with finding of the 2005 EDHS for Tigray region and EthiopiaAccess to maternal health services
National EDHS 2005 (%)
Regional Tigray EDHS 2005 (%)
Our study 2009 (%)

Family planning current users
14.70
16.50
41.80

Antenatal care
27.60
35.30
84.60

Delivery at health facility
5.30
6.10
4.70

Postnatal check up
5.50
8.20
5.30

HIV ever tested
4.00
3.20
85.40

Iodized salt (>15PPM)
19.90
28.00
13.20

Table 5
5Association of respondents' characteristics with utilization of maternal health services, September 2009Characteristics of respondents
Access to maternal health services
Adjusted Odds Ratio

Poor access to MHS Good access to MHS Odds ratio 95% CI-interval

District

Degua Tembien
165(68.8)
75(31.2)
1.00

Saesi Tsadamba
157(64.3)
87(35.7)
1.19
0.81-1.74

Alaje
161(66.8)
80(33.2)
0.87
0.58-1.30

Age of respondent

24 years and less
77(72.6)
29(27.4)
1.00

25 and above
406(65.6)
213(34.4)
1.50
0.92-2.45

Literacy

Illiterate : unable to read and write
397(68.9)
179(31.1)
1.00

Literate : able to read and write
86(57.7)
63(42.3)
1.85*
1.22-2.80

Listening to a radio

No, not at all
312(71.1)
127(28.9)
1.00

Yes
171(59.8)
115(40.2)
1.45*
1.05-2.02

Participation in income generating activities (IGAs)

Poor participation : 2 and less IGAs
324(71.1)
132(28.9)
1.00

Good Participation : 3 and more IGAs
159(59.1)
110(40.9)
1.43*
1.03-2.00

Year of enrolment into HEP

Do not know
117(73.6)
42(26.4)
1.00

2004-2006
156(65.5)
82(34.5)
1.07
0.68-1.70

2007-2009
210(64.0)
118(36.0)
1.37
0.88-2.1

Household status towards being a model family

Did not hear about model family
189(71.6)
75(28.4)
1.00

Have heard about model family but not working towards graduation
202 (72.7)
76(27.3)
0.98
0.66-1.45

Yes, working towards graduation or graduated as model family
92(50.3)
91(49.7)
2.13*
1.40-3.23

*P<0.05.

http://www.biomedcentral.com/1472-6963/12/352
AcknowledgementsThis work was made possible through funding provided by the Teasdale-Corti Global Health Research Partnership Program, a collaborative health research program developed by the four founding partners of the Canadian Global Health Research Initiative -Canadian Institutes of Health Research, International Development Research Centre, Health Canada and Canadian International Development Agencywith input from the Canadian Health Services Research Foundation. We acknowledge the support given by the facilitators of the project, most notably the University of Ottawa and the University of the Western Cape. One of the Authors (AM) is also grateful for the time and stipend he received from "Agencia Española de Cooperación Internacional para el Desarrollo (AECID)", Madrid, Spain to participate in this research. We would like to acknowledge Mr. Awala Equar for his participation in design and data collection. We thank Ron Labonte for reading the final manuscript and providing us constructive feedback. We are grateful for all study participants who take part in this study.Competing interestsThe authors declare that they have no competing interests.Authors' contributions AM and YK contributed to the design, data collection, analysis, and write up. NS, DS and YB contributed to the design, analysis and write up. MS, RB and DGJ contributed to analysis and write up. All authors read and approved the final manuscript.
International Perspective on Primary Health Care Over the Past 30 Years. N Schaay, D Sanders, Health Systems Trust. Barron PRoma-Reardon J. DurbanSchaay N, Sanders D: International Perspective on Primary Health Care Over the Past 30 Years. In Health Systems Trust. Edited by Barron P, Roma-Reardon J. Durban: South African Health Review 2008; 2008. http:// www.hst.org.za/publications/841.

Lay health workers in primary and community health care. S Lewin, J Dick, P Pond, M Zwarenstein, G N Aja, B Van Wyk, X Bosch-Capblanch, M Patrick, 10.1002/14651858.CD004015.pub2doi:10.1002/ 14651858.CD004015.pub2Cochrane Database Syst Rev. 14015Lewin S, Dick J, Pond P, Zwarenstein M, Aja GN, van Wyk B, Bosch- Capblanch X, Patrick M: Lay health workers in primary and community health care. Cochrane Database Syst Rev 2005, (1):CD004015. doi:10.1002/ 14651858.CD004015.pub2.

Federal Ministry of Health of Ethiopia: Health Extension Program in Ethiopia Profile. Ministry of HealthFederal Ministry of Health of Ethiopia: Health Extension Program in Ethiopia Profile. Addis Ababa: Health Extension and Education center. Ministry of Health; 2007.

Federal Ministry of Health of Ethiopia: Essential Health Services Package for Ethiopia. Addis Ababa: Ministry of Health. Federal Ministry of Health of Ethiopia: Essential Health Services Package for Ethiopia. Addis Ababa: Ministry of Health; 2005.

Health Extension Workers improve Tuberculosis case detection and treatment success in southern Ethiopia. A community randomized trial. D G Datiko, B Lindtorn, 10.1371/journal.phone.0005443doi:10.1371/ journal.phone.0005443PLoS One. 455443Datiko DG, Lindtorn B: Health Extension Workers improve Tuberculosis case detection and treatment success in southern Ethiopia. A community randomized trial. PLoS One 2009, 4(5):e5443. doi:10.1371/ journal.phone.0005443.

Federal Ministry of Health of Ethiopia: Health Sector Development Programme III. Addis Ababa: Annual performance report, Ministry of healthFederal Ministry of Health of Ethiopia: Health Sector Development Programme III. Addis Ababa: Annual performance report, Ministry of health; 2010.

Federal Ministry of Health of Ethiopia: Health Sector Development Program III. Addis Ababa: Planning and program department, Ministry of HealthFederal Ministry of Health of Ethiopia: Health Sector Development Program III (2005/6-2009/10). Addis Ababa: Planning and program department, Ministry of Health; 2005.

Responding to the challenge-The Ethiopian Health Extension Programme and back up support for maternal health care. M Koblinsky, F Tain, A Gaym, A Karim, M Carnell, S Tesfaye, Ethiop J Health Dev. Special Issue 1Koblinsky M, Tain F, Gaym A, Karim A, Carnell M, Tesfaye S: Responding to the challenge-The Ethiopian Health Extension Programme and back up support for maternal health care. Ethiop J Health Dev 2010, 24(Special Issue 1):105-109.

Central Statistical Agency of Ethiopia: Ethiopia national census first draft report. Addis Ababa: Centeral Statistics Agency. Central Statistical Agency of Ethiopia: Ethiopia national census first draft report 2007. Addis Ababa: Centeral Statistics Agency; 2008.

Central Statistical Agency and ORC Macro. ] Ethiopia, Macro, Addis Ababa, Ethiopia and Calverton, MarylandCentral Statistical AgencyEthiopia Demographic and Health SurveyCentral Statistical Agency [Ethiopia] and ORC Macro: Ethiopia Demographic and Health Survey 2005. Addis Ababa, Ethiopia and Calverton, Maryland: Central Statistical Agency and ORC Macro; 2006.

Assessment of the training of the first intake of Health Extension Workers. Y Kitaw, Y Ye-Ebiyo, A Said, H Desta, A Teklehaimanot, Ethiop J Health Dev. 213Kitaw Y, Ye-Ebiyo Y, Said A, Desta H, Teklehaimanot A: Assessment of the training of the first intake of Health Extension Workers. Ethiop J Health Dev 2007, 21(3):232-239.

Modeling trends of health and health related indicators in Ethiopia (1995-2008): a time-series study. M W Abraha, T H Nigatu, Health Res Policy Syst. 729Abraha MW, Nigatu TH: Modeling trends of health and health related indicators in Ethiopia (1995-2008): a time-series study. Health Res Policy Syst 2009, 7:29.

Determinants of community based maternal health care service utilization in South Omo pastoral areas of Ethiopia. K Ergano, M Getachew, D Seyum, K Negash, J Med Medical Sci. 20122Ergano K, Getachew M, Seyum D, Negash K: Determinants of community based maternal health care service utilization in South Omo pastoral areas of Ethiopia. J Med Medical Sci 2012, 3(2):112-121.

Van Damme W: Rapid scale-up of antiretroviral treatment in Ethiopia: success and system-wide effects. Y Assefa, D Jerene, S Lulseged, G Ooms, 10.1371/journal.pmed.1000056PLoS Med. 641000056Assefa Y, Jerene D, Lulseged S, Ooms G, Van Damme W: Rapid scale-up of antiretroviral treatment in Ethiopia: success and system-wide effects. PLoS Med 2009, 6(4):e1000056. doi:10.1371/journal.pmed.1000056.

Initial community perspectives on the Health Service Extension Programme in Welkait. H Negusse, E Mc Auliffe, M Maclachlan, Hum Resour Health. 521Negusse H, Mc Auliffe E, MacLachlan M: Initial community perspectives on the Health Service Extension Programme in Welkait, Ethiopia. Hum Resour Health 2007, 5:21.

Study of working conditions of Health Extension Workers in Ethiopia. A Teklehaimanot, Y Kitaw, G /Yohannes, A Girma, S Seyoum, A Desta, H Ye-Ebiyo, Ethiop J Health Dev. 213Teklehaimanot A, Kitaw Y, G/yohannes A, Girma S, Seyoum A, Desta H, Ye-Ebiyo: Study of working conditions of Health Extension Workers in Ethiopia. Ethiop J Health Dev 2007, 21(3):246-259.

Healthcare and cultural practices during pregnancy and childbirth in Korail. T Wahed, 1Dhaka, Bangladesh. Manoshi Research Brief. Dhaka, Bangladesh: ICDDR and BRACWahed T: Healthcare and cultural practices during pregnancy and childbirth in Korail, a slum in Dhaka, Bangladesh. Manoshi Research Brief. Dhaka, Bangladesh: ICDDR and BRAC; 2009:1.

T Wahed, Beyond the inception phase of the birthing centers: acceptance within the community. Manoshi Research Brief. Dhaka, BangladeshWahed T: Beyond the inception phase of the birthing centers: acceptance within the community. Manoshi Research Brief. Dhaka, Bangladesh: ICDDR and BRAC; 2009:2.

Strategies for reducing maternal mortality: getting on with what works. O M Campbell, W J Graham, Lancet. 3689543Campbell OM, Graham WJ: Strategies for reducing maternal mortality: getting on with what works. Lancet 2006, 368(9543):1284-1299.

The effectiveness of policies promoting facility-based deliveries in reducing maternal and infant morbidity and mortality in low and middle-income countries. L Dudley, K Hviding, E Paulsen, 10.1002/14651858.CD007918Cochrane Database Syst Rev. 37918Dudley L, Hviding K, Paulsen E: The effectiveness of policies promoting facility-based deliveries in reducing maternal and infant morbidity and mortality in low and middle-income countries. Cochrane Database Syst Rev 2009, (Issue 3):CD007918. doi:10.1002/14651858.CD007918.

United Nations Children's Fund. Report of the International Conference on Primary Health Care. USSR: Alma Ata1978World Health OrganizationWorld Health Organization, United Nations Children's Fund: Report of the International Conference on Primary Health Care. USSR: Alma Ata; 1978:6-12.

World Health Organization: Report on the review of Primary Health Care in the African region. WHO Regional Office for AfricaBrazzaville, Republic of CongoWorld Health Organization: Report on the review of Primary Health Care in the African region. Brazzaville, Republic of Congo: WHO Regional Office for Africa; 2008.

World Health Organization: The world health report 2008: Primary health care now more than ever. Geneva: World Health Organization. 10.1186/1472-6963-12-352World Health Organization: The world health report 2008: Primary health care now more than ever. Geneva: World Health Organization; 2008. doi:10.1186/1472-6963-12-352

Submit your next manuscript to BioMed Central and take full advantage of: • Convenient online submission • Thorough peer review • No space constraints or color figure charges • Immediate publication on acceptance • Inclusion in PubMed, CAS, Scopus and Google Scholar • Research which is freely available for redistribution. Medhanyie, BMC Health Services Research. 12352The role of health extension workers in improving utilization of maternal health services in rural areas in Ethiopia: a cross sectional study. Submit your manuscript at www.biomedcentral.com/submitCite this article as: Medhanyie et al.: The role of health extension workers in improving utilization of maternal health services in rural areas in Ethiopia: a cross sectional study. BMC Health Services Research 2012 12:352. Submit your next manuscript to BioMed Central and take full advantage of: • Convenient online submission • Thorough peer review • No space constraints or color figure charges • Immediate publication on acceptance • Inclusion in PubMed, CAS, Scopus and Google Scholar • Research which is freely available for redistribution Submit your manuscript at www.biomedcentral.com/submit