Synthesis and characterization of CdS nanoparticles embedded in a polymethylmethacrylate matrix
Introduction
In the last few years, the production of semiconductor nanoparticles was the focus of much research because of their potential applications in optoelectronics [1], photocatalysis [2], solar energy conversion [3], and water pollutant photodegradation [4]. Devices using the properties of nanoparticles are promising due to the possibility of tailoring a number of optical, electrophysical, and magnetic properties by changing nanoparticle size, which can be controlled during synthesis. Although a wide range of synthetic methods are now available, it seems clear that there is still a major problem associated with the reproducible preparation of materials with good mechanical properties for technological applications. A promising way to prepare these kinds of materials uses the interplay between polymer chemistry and quantum dot synthesis [5].
In contrast to microelectronic circuits, operating via ordered functional elements such as logical gates, polymer nanocomposites use the properties of disordered systems, as the nanoparticles are stochastically dispersed in the system. These properties can be used to manufacture LEDs, photodiodes, solar cells, and sensors and for other technological applications [6].
Two main methods are used to obtain nanoparticles embedded in a matrix [7]: one carries out the nanoparticle synthesis inside the polymeric matrix [8]; the other consists of allowing monomer polymerization after nanoparticle dispersion has occurred [9].
The goal of the present article was to incorporate CdS nanoparticles into a solid matrix where the growth of the particles and their coalescence processes are inhibited. To use the CdS optical properties the matrix must be transparent. CdS nanoparticles, capped with sodium bis(2-ethylhexyl)sulfosuccinate, were embedded in a polymethylmethacrylate (PMMA) matrix by means of a photocuring process, which is photoinduced hardening of a monomeric substrate. PMMA, a vinyl polymer obtained by free radical polymerization of the methylmethacrylate monomer (hereafter MMA), is a thermoplastic transparent material used as a shatterproof replacement for glass. Its refractive index is equal to 1.49, in the range of the typical refractive index of glass (1.3–1.7); whereas its haze (1–3%) is higher than that of glass, which ranges from 0 to 0.17%.
CdS nanoparticles were synthesized in water-in-oil microemulsions, and to stop the growth process an amine was added before extraction. Nanoparticle growth was followed in situ by UV–vis spectroscopy; at the end of the growth process and after the embedding process, the size was confirmed by high-resolution transmission electron microscopy (HRTEM). Before the embedding process, nanoparticle elemental composition was determined using energy-dispersive X-ray (EDX) spectroscopy. Optical properties of the nanoparticles embedded in the polymer matrix were revealed by photoluminescence spectroscopy and compared with those of the nanopowder dispersed in heptane and in MMA.
Section snippets
Materials
Sodium bis(2-ethylhexyl) sulfosuccinate (AOT, Aldrich 98%), cadmium sulfate (Aldrich, 99%), tetrabutylammonium hydrogen sulfide (TBAS, Fluka, 99%), bis(2-ethylhexyl)-amine (BEA, Aldrich, 99%), and n-heptane (Sigma, 99%) were used as received. Water was bidistilled. Methylmethacrylate (99.0%, Aldrich) was purified by using a disposable column, to eliminate the polymerization inhibitor.
Methods
UV–vis absorption spectra were obtained in the range 300–600 nm by using a double-beam Beckman DU-640
CdS nanoparticle synthesis
Among the various methods employed to produce size-controlled nanoparticles, a promising one is based on the use of water-in-oil (w/o) microemulsions. Nanoparticles of many metal sulfides were synthesized in this way by mixing two w/o microemulsions containing the suitable water-soluble metal salt and sodium sulfide, respectively [10], [11]. In this procedure nanoparticles need to be separated from the reaction medium. Bare nanoparticles are thermodynamically unstable with respect to growth and
Conclusions
It has been shown that CdS nanoparticles can be dispersed in MMA monomers and that CdS nanoparticles embedded in a PMMA matrix can be obtained as a transparent yellow solid by a photocuring process, initiated by activating a photoinitiator with 365-nm radiation. Such a material could find interesting optical applications.
The proposed procedure does not damage the CdS optical properties, is fast, and has the advantage of working at room temperature. Before the extraction process, HRTEM
Acknowledgments
The authors are most grateful to Dr. Casinelli (Basel) for preparation of the PMMA ultrathin sections for HRTEM. Financial support from the Consiglio Nazionale delle Ricerche (Progetto Finalizzato Materiali Speciali per tecnologie avanzate II) and from MURST (PRIN-COFIN 2001 “Sintesi di nanoparticelle assistita da microonde”) is gratefully acknowledged.
References (30)
- et al.
J. Phys. Chem.
(1996) - et al.
J. Am. Chem. Soc.
(1979) - et al.
J. Chem. Soc. Faraday Trans. 1
(1984) - et al.
J. Chem. Soc. Faraday Trans. 1
(1989) - et al.
Adv. Mater.
(2000) Adv. Polym. Sci.
(2000)Prog. Polym. Sci.
(2003)- et al.
J. Mater. Sci. Lett.
(2001) - et al.
J. Appl. Phys.
(2003) - et al.
Phys. Status Solidi C
(2003)
Langmuir
Science
J. Chem. Phys.
J. Phys. Chem.
J. Phys. Chem.
Cited by (36)
Enhanced visible light-driven photocatalytic performance of CdSe nanorods
2022, Environmental ResearchCitation Excerpt :Photon absorption with greater or equal to the bandgap of cadmium selenide leads to more photoexcited electrons and reveals the ability of the synthesized CdSe rods towards its application as photoctalyst in the degradation of organic molecules (Liu et al., 2013). Further, it also observed a very small hump around 450 nm in the UV–visible spectrum which is due to first (1s–1s) exciton transition during valence and conduction band (Fendler, 1987) as a consequence of the quantum size effect and threshold wave length of band function of nanoparticle size (Wang and Herron, 1991; Pedone et al., 2005). The intensed absorption of visible light by CdSe nanorod is observed with a bandgap of 2.17 eV which may lead to better photocatalytic performance due to the probably higher charge transfer from bulk to nanoparticle surface.
Investigation of alteration in physical properties of dysprosium orthochromite instigated through cobalt doping
2020, Journal of Alloys and CompoundsHighly efficient upconversion luminescence in hexagonal NaYF<inf>4</inf>:Yb<sup>3+</sup>, Er<sup>3+</sup> nanocrystals synthesized by a novel reverse microemulsion method
2018, Optical MaterialsCitation Excerpt :By varying the concentrations of water and oil phases in the microemulsion system the size, morphology and crystalline phase of nanoparticles can be conveniently tuned. Because of these advantages, reverse microemulsion method is useful to prepare nanoparticles of metals [18,19], metal oxides [20,21], metal sulphides [22] and selenides [23], ceramic [24] and polymers [25]. Only very few reports are available on the synthesis of NaYF4:Yb,Er by reverse microemulsion method [26,27].
Investigation of morphological, structural and electrical properties of CdS/ PMMA nanocomposite film prepared by solution casting method
2017, International Journal of Electrochemical ScienceDispersion and aggregation of quantum dots in polymer-inorganic hybrid films
2013, Thin Solid FilmsCitation Excerpt :Organic–inorganic nanocomposite films containing quantum dots (QDs) have recently attracted considerable attention due to their wide application for organic/polymeric light-emitting diodes [1–6] and solar cells [7–10]. This interest is based on the possibility to combine the strong quantum size confinement effects of QDs [11] and attractive technological properties of polymer hosts [12,13]. Thus, a wide variety of nanocomposites containing different QDs assembled into multilayers have been developed for high-efficient devices [1–3,6,10,12,14].
Cobalt hexacyanoferrate-poly(methyl methacrylate) composite: Synthesis and characterization
2010, Materials Chemistry and Physics