Chapter 5 Effect of Surface Stabilization of Nanoparticles on Luminescent
5.2 Experiment Section
5.4.2 Optical Properties and Morphology of ZnO/PHEMA Nanocomposites
oluminescence
As shown in Table I, the photoluminescent properties (emission bands and quantum efficiencies) of ZnO nanoparticles in ethanol solution before and after addition of TPM stabilizer are similar, suggesting that the presence of such silica network on the
aggr
r daylight and under UV light. Both PM-modified and unmodified ZnO/PHEMA nanocomposites afford excellent optical
egations. Figure 5-7 shows the PL spectra of the unmodified ZnO nanoparticle solutions and ZnO/PHEMA nanocomposites with an excitation wavelength at 325 nm. The TPM-modified ZnO nanocomposite with average diameter 3.2 nm is found to be remarkably similar to the initial unmodified nanoparticle solution, as shown in Figure 5-7a. In contrast, the emission peak of unmodified ZnO nanocomposite has a red shift. In Figure 7b, the ZnO/PHEMA nanocomposite with average diameter 2.2 nm of TPM-modified ZnO gives a blue emission peak at 466 nm. Although the emission peaks of the 2.2 nm modified and unmodified ZnO nanocomposites all have red shifts, the TPM stabilizer obviously reduces the degree of shift. Since the emission bands of quantum-sized ZnO nanoparticle depend on the particle size [19,21,23], the longer emission wavelength of ZnO/PHEMA nanocomposites without TPM stabilizer may contribute to the larger agglomerates and particle size increases in the course of thermal polymerization.
Due to good miscibility and dispersibility of the ZnO nanoparticle in HEMA monomers solution, stable optical transparent ZnO/PHEMA nanocomposites were readily obtained by common thermal polymerization. Figure 5-8 shows photographs of the ZnO/PHEMA nanocomposites (ca. 1% wt of ZnO nanoparticles) unde
T
transparent (Figure 5-8a). Additionally, utilizing the precise size control and surface modification of ZnO nanoparticles into bulk nanocomposites allows adjusting the emission colors from blue to orange Figure 5-8(b−d). Moreover, the luminescent properties of ZnO/PHEMA nanocomposoites display remarkable stability. For example, the emission peaks and intensities of these highly transparent nanocomposites were found to maintain similar values even after being aged over three months (see Table I).
TEM
Chapter 5 ZnO Nanocomposites: Result and Discussion
TEM was employed to examine the stability and dispersibility of the ZnO nanoparticles ndergoing thermal polymerization at 70
u
unm ified ZnO, (II) 3.2 nm TPM-modified ZnO and (III) 6.1 nm unmodified ZnO. Both unm
.5 Conclusion
h a layer of ilica nanonetwork through a mild sol-gel route using TPM stabilizing agent have been TPM stabilizer was shown to provide the high dispersion stability of ZnO
ermore, the room mperature PL measurements also show that this surface-modified method can preserve the superior luminescence of ZnO nanoparticles in the nanohybrid films as well as in the initial nanoparticles solution. The surface modification method is believed to be an
oC and postheating procedure at 100 oC. As a epresentative example in Figure 5-9a, large aggregate clusters in the unmodified
nO/PHEMA nanocomposites were easily observed. In contrast, the 3.2 nm PM-modified ZnO particles are well dispersed in the entire PHEMA matrix and the articles size almost unchanged (Figure 5-9b). These observations are consistent with the esults of photoluminescence spectra, clearly supporting the idea that the TPM-surfaced odification really supports superior stability and dispersibility of ZnO nanoparticles into he polymer matrix compared to the unmodified ZnO nanoparicles, probably because of the
ovalent attachment between nanoparticles and polymers.
.4.3 Optical Properties of ZnO/PMMA Nanocomposites
To further evaluate influence of TPM on the dispersibility of ZnO nanoparticles in olymeric bulk, poly(methyl methacrylate) (PMMA) were used to replace PHEMA in the reparation of ZnO nanocomposites. Figure 5-10 is the photographs of ZnO/PMMA anocomposites (a) under daylight and (b) under UV lamp with the samples (I)
od
odified ZnO samples I and III revealed the particle precipitation and aggregation from the PMMA matrix, as the emission regions of samples in Figure 5-10b. In contrast, sample (II) shows a relatively transparent and uniform appearance compared to the unmodified samples, indicating that the TPM stabilizer play an important role on the optical quality of bulk nanocomposites.
5
In conclusion, the preparation of surface-modified ZnO nanoparticles wit s
demonstrated. The
nanoparticles in ethanol solution and preserve the size of nanoparticles near constant over the long periods of time. The TPM-modified ZnO nanoparticles have better spatial separation than the unmodified ZnO nanoparticles in the nanohybrid film. Furth
te
nanocomposites for developing novel electro-optical application.
Semi-conducting conjugated polymer can be used for gain medium of optical device, such as PPV ,poly(p-phenylene vinylene) and m-LPPP, (methyl added Ladder-type Poly-Para-Phenylene), is one of the news studies. The semi-conducting polymers have a large potential, because they have larger quantum fluorescence efficiency and cross-section probability of exciting emission. Besides, we can change the wavelength by changing chemical structure. Because of the special characterizes, they are always studied in thesis field. The basic theory of the luminous quantum-dot/polymer composites is the same as Semi-conducting conjugated polymer. The difference is,
1. The semi-conducting conjugated polymer:
Uni-system: The most of methods are using chemical synthesizing to get polymer or copolymer. When application for preparing thin film devices, using good solvent to solve
olymer become polymer solution. And we dry the solvent after coating at substrates.
2. T
ent substrates.
p
he luminous quantum-dot/polymer:
Bi-system: luminous quantum-dot and polymer (inorganic/organic) By changing size of quantum-dot we can regulate luminous wavelength. And we can have the more applications by changing surface functionality of quantum dot.
By pulse laser exciting, the quantum dots can be a role of gain medium and scattering center that can extend photon path and induced the more photons.
In thesis field, the ultimate target is to achieve electro-luminescence device of organic solid laser. For the target, we need larger gain medium and higher current density by increasing intrinsic mobility and reducing threshold in materials. Such as organic solid laser can compete with traditions inorganic semiconductor laser, and there are many advantages at low cost, low temperature process, and have mass production in differ
HEMA, monomer
ure of ZnO/PHEMA nanocomposites.
Figure 5-1 TEM image and size distribution histogram of fresh unmodified ZnO particles.
absor
Figure 5-2 Time dependence of UV/vis tra: (a) umodified ZnO nanoparticles and (b) TPM-modified ZnO nanoparticles in ethanol. Inset are photographs of the ZnO nanoparticle colloids aging at room temperature for 2 months.
ption spec
Chapter 5 ZnO Nanocomposites: Figure Section
Figure 5-3 Particle diameters versus aging time of the ZnO particles in ethanol.
Chapter 5 ZnO Nanocomposites: Figure Section
Figure 5-4 Powder x-ray diffraction spectra of (a) umodified ZnO nanoparticles, (b) TPM-m
pattern of wurtzite ZnO crystal from JCPDS database is shown in bottom for comparison.
odified ZnO nanoparticles prepared with different aging time. The diffraction
Figure 5-5 FTIR spectra of the (a) unmodified ZnO nanoparticles and (b) TPM-modified ZnO nanoparticles.
Table ⅠLuminescence properties of
PL λmax
TPM-modified ZnO Unmodified ZnO ZnO particle
size(nm)a
Ф )
in ethanol solution (nm)
in ZnO/PHEMA
nanocomposites (nm) Фc (%) in ethanol
solution (nm)
in ZnO/PHEMA
nanocomposite (nm) c (%
.2 0.5
3.2 510 508(510)b 6 506 530(530)b 7.8
2.2 453 467(468)b 1 447 515(520)b 10.2
a: NPs diameters calculated from the shoulder of absorption spectra.
b: PL was recorded after three months of storage.
c: Fluorescence quantum yields of ZnO NPs in ethanol solution were obtained with quinine dye as a standard.
ZnO NPs in solution and ZnO/PHEMA nanocomposites.
Figure 5-6 1H NMR spectra of the (a) pure TPM stabilizer, (b) unmodified ZnO nanoparticles and (c) TPM-modified ZnO nanoparticles dispersed in DMSO-d6.
Figure 5-7 Photoluminescence spectra of unmodified ZnO nanoparticles in ethanol solution., and modified and unmodified ZnO/PHEMA nanocomposites
Chapter 5 ZnO Nanocomposites: Figure Section
Fi pa im
gure 5-8 otograp f transparent / MA nanocomposites with various rticles si (a d ylight and (b r an UV lamp. The luminescence
ages of c os fa at y cles with an average diameter of (b) Ph
zes nano
hs o er da ites ) un
omp bric ed b
ZnO )−(d
Zn
PHE nde arti ) u O p
Chapter 5 ZnO Nanocomposites: Figure Section
Figure 5-9 Cross-section TEM images: (a) 6.1 nm unmodified ZnO particles in PHEMA matrix and (b) 3.2 nm TPM-modified ZnO particles in PHEMA matrix.
Figure 5-10 Photographs of ZnO/PMMA nanocomposites (a) under daylight and (b) under an UV lamp with the samples of (I) 3.2 nm unmodified ZnO, (II) 3.2 nm TPM difi d Z O d (III) 6 1 difi d Z O
5.6 Reference
V. L. Colvin, M. C. Schlamp and A. P. Alivisatos, Nature 370 (1994) 354.
A. P. Alivisatos, Science 271 (1996) 933.
M. H. Nayfeh, O. Akcakir, G. Belomonin, N. Barry, J. Therrien and E. Gratton, Appl.
Phys. Lett., 77 (2000) 4086.
[4]
N. Gaponik, D. V. Talapin, A. L. Rogach, A. Eychmuller and H. Weller, Nano. Lett., 2 (2002) 803.
C. Roland, V. Meunier, B. Larade and H. Guo, Phys. Rev. B 66 (2002) 035332.
M. P. Bruchez, M. Moronne, P. Gin, S. Weiss and A. P. Alivisatos, Science 281 (1998) 2013.
M. Brust, M. Walker, D. Bethell, D. J. Schiffrin and R. Whyman, J. Chem. Soc., Chem.
Commun., 1994, 801-802.
C. L. Li and N. Murse, Langmuir, 20 (2004) 1.
K. Hara, T. Horiguchi, T. Kinoshita, K. Sayama, H. Sugihara and H. Arakawa, Sol.
Energy Mater. Sol. Cells, 64 (2000) 115.
S. Bachir, C. Sandouly, J. Kossanyi and J. C. Ronfard−Haret, J. Phys. Chem. Solids., 57 (1996) 1869.
[18] D. J. Goyal, C. Agashe, M. G. Takwale, V. G. Bhide, S. Mahamuni, and S. K. Kulkarni, J. Mater. Res., 8 (1993) 1052.
[19
[20] . 2854.
[21] S. Sakohara, M. Ishida and M. A. Anderson, J. Phys. Chem. B. 102 (1998) 10169.
[22] H. –M, Xiong, X. Zhao, J. –S. Chen, J. Phys. Chem. B. 105 (2001) 10169.
[23] E. M. Wang and P. C. Searson, Appl. Phys. Lett., 74 (1999) 2939.
[24] N. S. Pesika, Z. Hu, K. J. Stebe and P. C. Searson, J. Phys. Chem. B. 106 (2002) 6985.
[25] L. Guo, S. Yang, C. Yang, P. Yu, J. Wang, W. Ge, and G. K. L. Wong, Appl. Phys. Lett., 76 (2000) 2901.
[26] G. Rodriguez-Gattorno, P. Santiago-Jacinto, L. Rendon-Vazquez, J. Nemeth, I. Dekany [14]
[15]
[16]
[17]
] L. Spanhel and M. A. Anderson, J. Am. Chem. Soc., 113 (1991) 2826.
S. Monticone, R. Tufeu and A. V. Kanaev, J. Phys Chem. B. 102 (1998)
and D. Diaz, J. Phys. Chem. B, 107 (2003) 12597.
M. Shim and P. Guyot-Sionnest, J. Am. Chem. Soc., 123 (2001) 11651.
P. D. Cozzoli, M. L. Curri, A. Agostiano, G. Leo and M. Lomascolo, J. Phys. Chem. B.
107 (2003) 4756.
J. Hambrock, S. Rabe, K. Merz, A. Birkner, A. Wohlfart, R. A. Fischer and M. Driess, J.
Mater. Chem., 13 (2003) 1731.
Mikrajuddin, F. Iskandar, K. Okuyamaa and F. G. Shi, J. Appl. Phys., 89 (2001) 6431.
M. Abdullah, I. W. Lenggoro, K. Okuyama and F. G. Shi, J. Phys. Chem. B. 107 (2003) 1957.
P. Hoyer, R. Eichberger and H. Weller, Ber. Bunsen-Ges. Phys. Chem., 97 (1993) 630.
W. R. Dawson and M. W. Windsor, J. Phys. Chem., 72 (1968) 3251.
[35] M. Haase, H. Weller and A. Henglein, J. Phys. Chem., 92 (1988) 482.
[36] U. Koch, A. Fojtik, H. Weller and A. Henglein, Chem. Phys. Lett., 122 (1985) 507.
[37] M. Nandi, J. A. Coklin, L. Salvati and A. Sen, Chem. Mater., 3 (1991) 201.
[38] X. –Y. Shang, Z. –K. Zhu, J. Yin, and X. –D. Ma, Chem. Mater., 14 (2002) 71.
[39] O. Kohlmann, W. E. Steinmetz, X. –A. Mao, W. P. Wuelfing, A. C. Templeton, R. W.
Murray and C. S. Johnson, Jr, J. Phys. Chem. B. 105 (2001) 8801.
[27]
[28]
[29]
[30]
[31]
[32]
E. A. Meulenkamp, J. Phys. Chem. B. 102 (1998) 5566.
[33]
[34]
Conclusion
resents the study on the synthesis and characteristic of low-dimensional ZnO nanostructures, the well-controlled diameter of ZnO nanorods, the growth of well-aligned ZnO nanotip arrays on the different ZnO substrates, and the investigation of effect of surface stabilization of nanoparticles on luminescent characteristics in
A novel two-step procedure for preparing large-scale growth of single crystal ZnO nanorods on nanostructured substrates by soft solution method without metal catalyst is help of ZnO nanostructured substrate which offers a desirable route for large-scale ZnO nanorods growth.
XRD, Raman, SEM, TEM and HRTEM analysis indicate that the diameters of single crystal
Chapter 6
6.1 Conclusions This project p
ZnO/poly(hydroxyethyl methacrylate) nanohybrid film.
proposed. The low-temperature growth can be achieved via the
Chapter 6 Conclusion
temperature PL spectra of the ZnO nanorods exhibit a strong UV emission of 378 nm and a weak green emission of 580 nm. The low-temperature growth process requires no expensive and p so permitting large-scale fabrication with a relatively low ectrical conductivity of the ITO glass substrates also provide a great potential in future optoelectronic nanodevice applications.
free-standing ZnO nanotip arrays grown on
been extended to synthesize well-aligned nanotip arrays on ZnO microrods. X-ray diffraction analysis shows that the ZnO nanotips are hexagonal wurtzite structure, and the
the ZnO nanotip to be a single crystal. Room temperature photoluminescence of the ZnO nanotips has a strong UV emission band at 378 nm. The field emission of ZnO nanotip arrays shows a turn-on field of about 10.8 V/µm at a current density of 0.1 µA/cm-1 and
Lastly, high transparent and stable luminescent ZnO/Poly(hydroxyethyl methacrylate) nanocomposites have been synthesized via a nanoparticle surface modified method.
ilizing agent in the
stabilizer was shown to provide the high dispersion stability of ZnO nanoparticles in ethanol solution and preserve the size of nanoparticles near constant over the long periods of time.
The T O nanoparticles have better spatial separation than that of unmodified
measurements also show that this surface-modified method can preserve the superior recise vacuum equipment,
cost. In addition, the high optical transparency and el
As seen in Chapter 4, highly aligned and
the ZnO films by soft chemical method are proposed. The soft growing method also has
c-axes of nanotips are perfectly along the substrate surface normal. HRTEM demonstrates
emission current density up to about 1 mA/cm2 at a bias field of 19.5 V/µm.
3-(Trimethoxysilyl)propyl methacrylate (TPM) was used as the stab
simple, mild sol-gel route to prepare the TPM-modified ZnO nanoparticles. The TPM
PM-modified Zn
ZnO nanoparticles in the nanohybrid film. Furthermore, the room temperature PL
nanoparticles solution. The surface modification method is believed to be an efficient approach to fine adjust the luminescent color and uniformity of bulk nanocomposites for developing novel electro-optical application.
ublications
82, 705(2003). (*主持人)(SCI) 計畫編號：NSC-91-2216-E-009-013
2. P.J. Chiang and W.T.Whang*, 2003, “The Synthesis and Morphology Characteristics Study of BAO-ODPA Polyimide/TiO2 Nano Hybrid Films”, Polymer Vol. 44,
2249(2003)(*主持人)(SCI)
計畫編號：NSC-91-2216-E-009-013
. P.J. Chiang and W.T. Whang, 2004,“Physical and Mechanical Properties of Polyimide/titania Hybrid Films”, T Vol 447-48, 359(2004).
計畫編號：NSC-91-2216-E-009-4. S.C. Suen and W.T. Whang*, B.W. Wu, and Y.F. Lai, 2004,“Low temperature
fabrication of carbon nanofibers b of polycyclic aromatic hydrocarbon molecule”, Applied Physics Letters, Vol 84(16), 3157(2004). (*主持人)(SCI)
計畫編號：NSC-92-2216-E-009-003
W.T. Whang*, 2004,“Effect of titania content and plasma treatment on the interfacial adhesion mechanism of nano titania-hybridzed polyimide and copper
Growth, Vol 268, 242(2004). (*主持人)(SCI)
7. C.H. Hung and W.T. Whang*, 2005, “Effect of surface stabilization of nanoparticles on
計畫編號：NSC-92-2216-E-009-003
Hsiao, 2005, “Effect of the Polyimide Structure and ZnO Concentration on the P
3
1. C.H. Hung and W.T. Whang*, 2003, “A Novel Low-temperature Growth and
Characterization of Single Crystal ZnO Nanorods”, Materials Chemistry and Physics.
hin Solid Films, 013
y self-assembling
5. P.J. Chiang and
system”, Polymer, Vol 45, 4465(2004).(主持人) 計畫編號：NSC-92-2216-E-009-003
6. C.H. Hung and W.T. Whang*, 2004, “Low Temperature Solution Approach Towards Highly Aligned ZnO Nanotips and Self-Oriented Nanotips-Rod Arrays”, J. Crystal 計畫編號：NSC-92-2216-E-009-003
luminescent characteristics in ZnO/poly(hydroxyethyl methacrylate) nanohybrid films”, J. Mater. Chem., Vol 15(2), 267~274(2005). (*主持人)(SCI)
8. Shou-Chian Hsu, Wha-Tzong Whang*, Chin-Hsien Hung, Pei-Chun Chiang, Yi-Nan Morphology and Characteristics of Polyimide/ZnO Nanohybrid Films”,
Macromolecular Chemistry and Physics, Vol 206(2), 291-298, (2005)(*主持人)(SCI)
Phys., Vol 44(2), 914~919(2005) (*主持人)(SCI)
9. Y.N. Hsiao, W.T. Whang*, S.H. Lin and K.Y. Hsu, 2005, “Effect of ZnMA on Optical and Holographic Characteristics of Doped PQ/PMMA Photopolymer”, Jpn. J. Appl.
計畫編號：NSC-92-2216-E-009-003