108
Chapter 3
3.1. Introduction
In-situ deposition technique is a versatile technique for the preparation of
nanoparticles of very low size. There were several reports in the literature
Chapter 3
regarding this technique and the successful application of the same [1-5].
Polyethylene oxide (PEO) mediated synthesis of nanomaterials of inorganic
Synthesis and Characterisation of
Calcium Phosphate Nanoparticles
sulphates and phosphates were reported by Radhakrishnan and his coworkers
recently [3-5]. In this technique the calcium salt is dissolved in PEO and
stoichiometric amounts of sulphates or phosphates were added to the mixture. On
digesting the mixture the formation of tiny particles occurs. The particles can be
easily obtained from the reaction mixture because the residual components are either
volatile or easily removable. So white powders of calcium phosphate were obtained by
this in-situ deposition technique. Calcium phosphate nanoparticles are excellent
protein carrying agents and have stable structure over a period of time [6-8].
Abstract
3.2. Nanoparticle characterization by XRD
The in-situ prepared nanoparticles of calcium phosphate were characterized by
various analytical methods such as XRD and TEM. From XRD measurements it
was concluded that the particle size was around 10 nm. The TEM analysis
confirmed that the particles are of size in 10 nm regimes and have narrow size
distribution. Also with increase in concentration of PEO the particle size
decreased.
Nanoparticles of calcium phosphate were characterized by XRD as well as TEM
techniques. Figure 3.1.1(a-f) corresponds to the XRD patterns of nanoparticles
obtained, (a) corresponds to the calcium phosphate without PEO and (b-f) for
calcium phosphate with PEO concentration from 2:1 to 32:1 respectively. In the
figure, there are a number of crystalline forms reported for calcium phosphate
existing in both anhydrous and hydrated states. The calcium phosphate without
any polymer shows 3 types of phases. Most of the peaks in diffraction patters
correspond to β calcium orthophosphate (major phase) while the minor phase
contains calcium orthophosphate primary along with small amount of calcium
metaphosphate hydrate respectively. With increase of PEO concentration, there
occurs a large change in the diffraction patterns compared to curve A. A large
number of peaks are suppressed and peaks at 2θ of 31.90 broaden with increase
of PEO concentrations from 42 to 89%. Only two peaks are clearly seen. The
peak at 31.90 corresponds to all the three states (Ca3(PO4)2, Ca3(H2PO4)2,
Results of this chapter have been communicated for publication in Chemistry of
Ca3(PO3)23H2O) and at 25.10 corresponds to the minor phase Ca3(H2PO4)2. It is
Materials
interesting to note the extent of broadening from 42 to 89%. This shows that the
small size of crystals, which could be associated due to good molecular level
108
Chapter 3
3.1. Introduction
In-situ deposition technique is a versatile technique for the preparation of
nanoparticles of very low size. There were several reports in the literature
Chapter 3
regarding this technique and the successful application of the same [1-5].
Polyethylene oxide (PEO) mediated synthesis of nanomaterials of inorganic
Synthesis and Characterisation of
Calcium Phosphate Nanoparticles
sulphates and phosphates were reported by Radhakrishnan and his coworkers
recently [3-5]. In this technique the calcium salt is dissolved in PEO and
stoichiometric amounts of sulphates or phosphates were added to the mixture. On
digesting the mixture the formation of tiny particles occurs. The particles can be
easily obtained from the reaction mixture because the residual components are either
volatile or easily removable. So white powders of calcium phosphate were obtained by
this in-situ deposition technique. Calcium phosphate nanoparticles are excellent
protein carrying agents and have stable structure over a period of time [6-8].
Abstract
3.2. Nanoparticle characterization by XRD
The in-situ prepared nanoparticles of calcium phosphate were characterized by
various analytical methods such as XRD and TEM. From XRD measurements it
was concluded that the particle size was around 10 nm. The TEM analysis
confirmed that the particles are of size in 10 nm regimes and have narrow size
distribution. Also with increase in concentration of PEO the particle size
decreased.
Nanoparticles of calcium phosphate were characterized by XRD as well as TEM
techniques. Figure 3.1.1(a-f) corresponds to the XRD patterns of nanoparticles
obtained, (a) corresponds to the calcium phosphate without PEO and (b-f) for
calcium phosphate with PEO concentration from 2:1 to 32:1 respectively. In the
figure, there are a number of crystalline forms reported for calcium phosphate
existing in both anhydrous and hydrated states. The calcium phosphate without
any polymer shows 3 types of phases. Most of the peaks in diffraction patters
correspond to β calcium orthophosphate (major phase) while the minor phase
contains calcium orthophosphate primary along with small amount of calcium
metaphosphate hydrate respectively. With increase of PEO concentration, there
occurs a large change in the diffraction patterns compared to curve A. A large
number of peaks are suppressed and peaks at 2θ of 31.90 broaden with increase
of PEO concentrations from 42 to 89%. Only two peaks are clearly seen. The
peak at 31.90 corresponds to all the three states (Ca3(PO4)2, Ca3(H2PO4)2,
Results of this chapter have been communicated for publication in Chemistry of
Ca3(PO3)23H2O) and at 25.10 corresponds to the minor phase Ca3(H2PO4)2. It is
Materials
interesting to note the extent of broadening from 42 to 89%. This shows that the
small size of crystals, which could be associated due to good molecular level
110
Synthesis and Characterisation of Calcium Phosphate Nanoparticles
Chapter 3
109
(PEO: CaCl2)
FWHM (2θ), radians
Particle size (L), nm
Calcium phosphate (a)
0.00174
82.4
Since CaCl2 is first complexed with PEO, only certain crystalline phases of calcium
2:1 (b)
0.0134
10.65
phosphate is allowed to grow as compared to a large number of phases getting
4:1 (c)
0.0156
9.24
8:1 (d)
0.0162
8.96
16:1 (e)
0.0176
8.02
32:1 (f)
0.0181
7.82
mixing. Thus on comparing curve a with curve b to f in figure 3.1, it is obvious that
the effect of polymer plays a prominent role on the structure and growth behaviour
of calcium phosphate crystals (in the curves the y axis indicates the intensity.
developed in normal free precipitation. From the XRD patterns, the crystallite size
was calculated using Scherrer formula.
0
d ( A) = k λ
(3.1)
∆ 2θ cos θ
Table 3.1. XRD values for the calcium phosphate nanoparticles
0
where k, the order of reflection, λ is 1.542 A θ, the diffraction angle and ∆2θ is the
full width at half maximum (FWHM). As the concentration of the PEO increases
the particle size decreases. The corresponding data for the nanoparticles is given
in Table 3.1.
3.3. Nanoparticle characterization by TEM
The TEM images of the particles are shown in figure 3.2 (a-c), which are taken for
2:1, 4:1 and 32: 1 respectively. The particles were made a suspension in alcoholic
medium and the images were taken by putting the particles on a copper grid. The
alcohol evaporated and the particles could be seen clearly in the images. The
particle size distributions for each concentration were calculated using image
Figure 3.1:
(a)
(b)
(c)
(d)
(e)
(f)
XRD patterns for the calcium phosphate nanoparticles (a) Calcium
Phosphate without PEO. The PEO: CaCl2 ratio in (b) 2:1, (c) 4:1, (d)
8:1 (e) 16:1 and (f) 32:1 (in the x axis 2θ and in y axis intensity is
plotted)
analyzer software.
(a)
100 nm
(b) 100 nm
(c)
100 nm
Figure 3.2. TEM image of the calcium phosphate nanoparticles (PEO: CaCl2,
(a) 2:1, (b) 4:1, (c) 32:1)
110
Synthesis and Characterisation of Calcium Phosphate Nanoparticles
Chapter 3
109
(PEO: CaCl2)
FWHM (2θ), radians
Particle size (L), nm
Calcium phosphate (a)
0.00174
82.4
Since CaCl2 is first complexed with PEO, only certain crystalline phases of calcium
2:1 (b)
0.0134
10.65
phosphate is allowed to grow as compared to a large number of phases getting
4:1 (c)
0.0156
9.24
8:1 (d)
0.0162
8.96
16:1 (e)
0.0176
8.02
32:1 (f)
0.0181
7.82
mixing. Thus on comparing curve a with curve b to f in figure 3.1, it is obvious that
the effect of polymer plays a prominent role on the structure and growth behaviour
of calcium phosphate crystals (in the curves the y axis indicates the intensity.
developed in normal free precipitation. From the XRD patterns, the crystallite size
was calculated using Scherrer formula.
0
d ( A) = k λ
(3.1)
∆ 2θ cos θ
Table 3.1. XRD values for the calcium phosphate nanoparticles
0
where k, the order of reflection, λ is 1.542 A θ, the diffraction angle and ∆2θ is the
full width at half maximum (FWHM). As the concentration of the PEO increases
the particle size decreases. The corresponding data for the nanoparticles is given
in Table 3.1.
3.3. Nanoparticle characterization by TEM
The TEM images of the particles are shown in figure 3.2 (a-c), which are taken for
2:1, 4:1 and 32: 1 respectively. The particles were made a suspension in alcoholic
medium and the images were taken by putting the particles on a copper grid. The
alcohol evaporated and the particles could be seen clearly in the images. The
particle size distributions for each concentration were calculated using image
Figure 3.1:
(a)
(b)
(c)
(d)
(e)
(f)
XRD patterns for the calcium phosphate nanoparticles (a) Calcium
Phosphate without PEO. The PEO: CaCl2 ratio in (b) 2:1, (c) 4:1, (d)
8:1 (e) 16:1 and (f) 32:1 (in the x axis 2θ and in y axis intensity is
plotted)
analyzer software.
(a)
100 nm
(b) 100 nm
(c)
100 nm
Figure 3.2. TEM image of the calcium phosphate nanoparticles (PEO: CaCl2,
(a) 2:1, (b) 4:1, (c) 32:1)
112
Synthesis and Characterisation of Calcium Phosphate Nanoparticles
Chapter 3
111
10.4
figure 3.3. Around 400 particles were taken for the analysis. It can be seen
10.2
that majority of the particles have small size around 10 nm. Thus the in-situ
10.0
Particle size (nm)
Particle size distribution curves for the three compositions are given in
deposition technique is very good to obtain narrow distributed nanoparticles.
We can see that for each concentration there are a few particles with large
size.
9.8
9.6
9.4
9.2
9.0
8.8
Particle size distribution
Particle size distribution
45
60
40
35
50
N o .o f p articles
45
40
35
30
25
20
15
10
5
0
N o .o f p articles
N o .o f p a rt ic le s
Particle size distribution
30
25
20
15
10
5
5
10
15
20
25
0
5
Particle size (nm)
(a)
2:1
0
10
15
20
25
4:1
10
15
20
25
30
35
40
30
Figure 3.4. Effect of PEO concentration on particle size of calcium phosphate
20
10
0
5
10
15
Particle size (nm)
Particle size (nm)
(b)
5
Concentration of PEO: CaCl2(g/100ml)
0
0
0
8.6
(c)
32:1
Figure 3.3. Particle size distribution of the calcium phosphate nanoparticles
(PEO: CaCl2, (a) 2:1, (b) 4:1, (c) 32:1)
The particle size reduction against concentration of PEO is shown in figure 3.4.
The particle size reduction is attributed to the increase in the amount of oxygen
atoms available from PEO matrix as we increase the concentration [5]. This
enables the suppression of the formed particles and reduces the size further.
20
The particle size reduction can be mathematically expressed as a general
equation, with respect to the concentration of PEO used, like
y = −0.42 x + 10.732
(3.2)
This linear equation gives a negative slope, which indicates that the
concentration of PEO is directly related to the particle size reduction. The yield
of the calcium phosphate was recorded as 83 and 72% for 4:1 and 16:1 ratios
respectively. Calcium phosphate nanoparticles obtained with the concentration
ratio 4:1 (particle size approximately 10 nm) were exclusively used for further
studies in this thesis.
3.4. Conclusion
Calcium phosphate nanoparticles were synthesized by the polymer induced
crystallization technique. The obtained particles were characterized by XRD and
TEM analysis. From XRD, using Scherrer formula the particle size was calculated
and it was found that the particle size is in the order of 10 nm. TEM images also
supported the above analysis. The particle size distribution was measured and it
was found to be narrow. Further the size of the particles reduced with respect to
increase in concentration of PEO due to the increased availability of the oxygen
atoms in PEO.
112
Synthesis and Characterisation of Calcium Phosphate Nanoparticles
Chapter 3
111
10.4
figure 3.3. Around 400 particles were taken for the analysis. It can be seen
10.2
that majority of the particles have small size around 10 nm. Thus the in-situ
10.0
Particle size (nm)
Particle size distribution curves for the three compositions are given in
deposition technique is very good to obtain narrow distributed nanoparticles.
We can see that for each concentration there are a few particles with large
size.
9.8
9.6
9.4
9.2
9.0
8.8
Particle size distribution
Particle size distribution
45
60
40
35
50
N o .o f p articles
45
40
35
30
25
20
15
10
5
0
N o .o f p articles
N o .o f p a rt ic le s
Particle size distribution
30
25
20
15
10
5
5
10
15
20
25
0
5
Particle size (nm)
(a)
2:1
0
10
15
20
25
4:1
10
15
20
25
30
35
40
30
Figure 3.4. Effect of PEO concentration on particle size of calcium phosphate
20
10
0
5
10
15
Particle size (nm)
Particle size (nm)
(b)
5
Concentration of PEO: CaCl2(g/100ml)
0
0
0
8.6
(c)
32:1
Figure 3.3. Particle size distribution of the calcium phosphate nanoparticles
(PEO: CaCl2, (a) 2:1, (b) 4:1, (c) 32:1)
The particle size reduction against concentration of PEO is shown in figure 3.4.
The particle size reduction is attributed to the increase in the amount of oxygen
atoms available from PEO matrix as we increase the concentration [5]. This
enables the suppression of the formed particles and reduces the size further.
20
The particle size reduction can be mathematically expressed as a general
equation, with respect to the concentration of PEO used, like
y = −0.42 x + 10.732
(3.2)
This linear equation gives a negative slope, which indicates that the
concentration of PEO is directly related to the particle size reduction. The yield
of the calcium phosphate was recorded as 83 and 72% for 4:1 and 16:1 ratios
respectively. Calcium phosphate nanoparticles obtained with the concentration
ratio 4:1 (particle size approximately 10 nm) were exclusively used for further
studies in this thesis.
3.4. Conclusion
Calcium phosphate nanoparticles were synthesized by the polymer induced
crystallization technique. The obtained particles were characterized by XRD and
TEM analysis. From XRD, using Scherrer formula the particle size was calculated
and it was found that the particle size is in the order of 10 nm. TEM images also
supported the above analysis. The particle size distribution was measured and it
was found to be narrow. Further the size of the particles reduced with respect to
increase in concentration of PEO due to the increased availability of the oxygen
atoms in PEO.
Synthesis and Characterisation of Calcium Phosphate Nanoparticles
113
3.5 References
1.
H Schmidt, Appl Organometal Chem 15 (2001) 331
2.
M Figlarz, F Fievet, JP Lagier (1985) US Patent Specification No 4, 539,
041
3.
S Radhakrishnan, J Cryst Growth 141 (1994) 437
4.
C Saujanya, S Radhakrishnan, J Mater Sci 33 (1998) 1063
5.
C Saujanya, S Radhakrishnan, Polymer 42 (2001) 6723
6.
BioSante Pharmaceuticals, Inc. 175 Olde Half Day Road Lincolnshire,
Illinois USA 60069 www.biosantepharma.com
7.
HT Schmidt, BL Gray, PA Wingert, AE Ostafin, Chem Mater 16 (2004)
4942
8.
S Mishra, S Sonawane, A Mukherji, HC Mruthyunjaya, J Appl Polym Sci
100 (2006) 4190
Part I
Polystyrene/calcium phosphate
nanocomposites