Surface Derivatization of Colloidal Silver Particles Using Interdigitated Bilayers: A Novel Strategy for Electrostatic Immobilization of Colloidal Particles in Thermally Evaporated Fatty Acid/Fatty Amine Films

Abstract

We have recently demonstrated that interdigitated bilayers of fatty acid molecules self-assemble on nanoscale curved surfaces, thereby highlighting an important difference between self-assembly on planar surfaces where such structures have not been reported to form. On a more practical level, this approach leads to a new strategy for derivatization of colloidal particle surfaces without the use of terminally functionalized molecules. In this paper, we use this new strategy to derivatize colloidal silver particle surfaces with carboxylic acid and amine functional groups and, thereafter, to incorporate the colloidal particles in thermally evaporated conjugate fatty lipid films via electrostatically controlled diffusion from the sol. The diffusion of the colloidal particles in the thermally evaporated organic films has been followed using quartz crystal microgravimetry and modeled on the basis of a 1-D diffusion process and the cluster diffusivities determined. It is observed that both the charge on the clusters and the length of the alkyl tail of the molecules in the secondary monolayer (via a hydrophobic interaction contribution) influence the cluster diffusivity in the thermally evaporated films. The cluster-incorporated films have been further characterized using optical absorption spectroscopy and X-ray photoemission spectroscopy.

Multilayer Langmuir–Blodgett assemblies of hydrophobized CdS nanoparticles by organization at the air–water interface

“…We have previously used this strategy of surface derivatization using interdigitated bilayers with success in the surface modi®cation of silver nanoparticles and, thereafter, in the formation of composites with fatty lipid ®lms. 30 After extraction of the lauric acid-capped CdS nanoparticles into the ODA ®lms (step 2, Scheme 1), the nanoparticles can be dispersed in organic solvents by simple agitation of the nanocomposite ®lms in the solvent. Hydrophobization of the CdS nanoparticles is indicated, but the exact mechanism is not immediately evident.…”

Shape and size selective separation of gold nanoclusters by competitive complexation with octadecylamine monolayers at the air–water interface

“…Electrostatic interaction having a important role in biological and chemical processes [16] have only recently been investigated for the growth of multilayer of polyelectrolyte [17,18] and nanoparticle-polyelectrolyte films [19], as well as micron-sized objects [20]. Sastry's group has synthesized thin films of nanocomposites of surface-modified colloidal particles with fatty lipid molecules via selective electrostatic interaction both in Langmuir monolayers [21][22][23][24][25][26][27][28] and by diffusion in thermally evaporated films [29][30][31][32][33]. Here, we demonstrate that in addition to deposition of a reasonably compact, lamellar multilayer gold colloidal particle film, electrostatic binding can be utilized for the separation of particles of different sizes/shapes by the competitive complexation process.…”

“…To the best of our knowledge, the formation of metal cluster films using a separation technique has not been demonstrated until now. The versatility of this method is that the density of clusters in the LB films can be controlled quite easily through variation of the colloidal solution pH, which modulates simultaneously the charge on the functional groups in the film matrix, as well as on the colloidal particle surface [21,22,29,33]. Besides, the size of the nanoclusters plays a critical role in the separation process of colloid solutions.…”

Role of Particle Size in Individual and Competitive Diffusion of Carboxylic Acid Derivatized Colloidal Gold Particles in Thermally Evaporated Fatty Amine Films

“…One of the routes being seriously pursued uses colloid chemistry for synthesis of the nanoparticles followed by organization in thin film form by a variety of methods such as self-assembly of the clusters and organization at the air−water interface by hydrophobic stabilization of capped clusters . In this laboratory, we have developed an approach for the formation of thin films of nanocomposites of surface-modified colloidal particles with fatty lipid molecules via selective electrostatic interaction both in Langmuir monolayers and by diffusion in thermally evaporated films . The versatility of this method is that the density of clusters in the fatty lipid films can be controlled quite easily through variation of the colloidal solution pH, which modulates simultaneously the charge on the functional groups in the film matrix as well as on the colloidal particle surface. , …”