Tribological behavior of in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films
Introduction
Since Decher et al. [1], [2], [3] introduced the method for preparing multilayer ultrathin films by the consecutive deposition of oppositely charged polyelectrolytes from dilute aqueous solution by way of intermolecular electrostatic forces onto charged substrates, self-assembled ultrathin multilayer films through this molecular deposition process have been intensively investigated in recent years. The film is termed molecular deposition (MD) film. The popularity of this molecular deposition procedure is due to its simplicity, versatility, and systematical control over the structure and the thickness of the resulting films. Moreover, the materials used in molecular deposition studies can be small organic molecules [4] or inorganic compounds [5], macromolecules [6], biomacromolecules such as proteins [7], DNA [8], or even colloids [9].
The molecular deposition technique is ideally suited to combat the tribological challenges in micro-electro-mechanical systems (MEMS). In our previous study, the tribological behavior of polyelectrolyte molecular deposition films has been studied, and it was found that polyelectrolyte MD films can decrease the adhesive force on a surface [10], and so as to modify the friction surface and reduce the friction force [11]. However, the polyelectrolyte MD film has poor anti-wear behavior [12].
In recent years, nanoparticles composite ultrathin films have attracted a wide spread attention increasingly. Cassagneau et al. [13], [14] synthesized the nanoparticles or nanoplatelets and polymers composite molecular deposition film. Nanoparticles composite ultrathin films are popular in the field of tribology because of their lower friction coefficient and relatively long anti-wear life [15]. We have studied the tribological behaviors of graphite oxide/polyelectrolyte and TiO2/polyelectrolyte composite MD film. It was found that these composite MD films had a much smaller friction force than their substrates and the friction force was dependent on the morphology and/or hardness of the films. Both of them were heated to change the film forming dynamic force from the electrostatic force to covalent bond so as to increase the bonding strength of the films [12], [16]. The commonly used step is that the prepared nanoparticles or nanoplatelets which were processed using surface modification firstly, then the substrates were coated by nanoparticles or nanoplatelets and polymers layer by layer using molecular deposition method. But, it has difficulty to prepare nanoparticles composite MD films using the above-mentioned steps, since it is difficult to control the size of nanoparticles, prevent the reunion of nanoparticles and make the nanoparticles dispersed in the film uniformity. In situ synthesized nanoparticles in ultrathin films may solve the above problems [17]. In this paper, a novel approach toward the fabrication of dispersed Ag nanoparticles is reported. The growth of Ag nanoparticles was achieved in a polyelectrolyte molecular deposition film prepared by the molecular deposition technique. We found that Ag nanoparticles within the MD film possess load-carrying capacity and enhance anti-wear life.
Section snippets
Materials
All materials were used without further purification. Poly(allylamine hydrochloride) with an average molecular weight of 70,000 and poly(acrylic acid) with an average molecular weight of 30,000 were supplied by Aldrich Chemical Co. hereafter referred to as PAH and PAA, having the structural formula:AgNO3 and NaBH4 were supplied by Sinopharm Chemical Reagent Co., Ltd. All the other reagents are analytical reagents. Glass and quartz were used as the substrates. Deionized water (>18 MΩ cm, Millipore
UV–vis spectrum analysis
A UV–vis spectrophotometer was used to evaluate the growth process of multilayer MD films containing in situ Ag nanoparticles. The UV–vis absorption spectra of the (PAH-Ag)/PAA MD films are shown in Fig. 4. It can be seen that the characteristic absorption peaks of Ag nanoparticles appear in the wavelength range from 325 to 550 nm, and the maximum absorption peak occurs at around 420 nm which is the position of the surface-plasmon resonance (SPR) wavelength of Ag nanoparticles [22]. The intensity
Conclusions
In situ Ag nanoparticles/polyelectrolyte composite molecular deposition films have been prepared using the molecular deposition method and the in situ reduction method. Ag nanoparticles were distributed in the films uniformly, and the size of nanoparticles was 15 nm approximately. Tribological characteristics have investigated by the AFM and the micro-tribometer, and the following conclusions can be obtained:
- (1)
The nano-tribological properties with the AFM show that the friction force is lower with
Acknowledgements
This research is sponsored by the National Natural Science Foundation of China (Grant No. 50975288), the National Basic Research Program of China (973, 2007CB607604) and the State Key Laboratory of Tribology Opening Fund at Tsinghua University.
References (25)
- et al.
Thin Solid Films
(1992) - et al.
Thin Solid Films
(1996) - et al.
Material Science and Engineering C
(1999) - et al.
Tribology International
(2005) - et al.
Surface and Coatings Technology
(2000) - et al.
Applied Surface Science
(2008) - et al.
Ultramicroscopy
(2003) Comprehensive Supramolecular Chemistry
(1996)Science
(1997)- et al.
Chemical Communications
(1994)
Journal of the American Chemical Society
Journal of the American Chemical Society
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