Fluorescent superlattices of gold nanoparticles: A new class of functional materials

Abstract

Fluorescent three-dimensional (3-D) superlattices of dansyl glutathione protected gold nanoparticles, with potential applications in molecular detection, have been synthesized at an air/water interface by controlling the pH of the nanoparticle suspension. The number of fl uorophores per nanoparticle was calculated to be ~127. Morphologies of the superlattice crystals were examined using scanning electron microscopy (SEM). Most of the crystals observed were triangular in shape. High-resolution transmission electron microscopy (HRTEM) and small angle X-ray scattering (SAXS) were used to study the packing of nanoparticles in these crystals. Both these studies showed that the nanoparticles were arranged in a face-centered cubic (fcc) pattern with a particle-particle distance (center-center) of ~10.5 nm. Evolution of the crystal morphologies with time was also examined. The fl uorescence properties of these triangles were studied using confocal fl uorescence imaging and confocal Raman mapping, which were in good agreement with the morphologies observed by SEM. The superlattice exhibits near-infrared (NIR) absorption in the range 1100-2500 nm. Easy synthesis of such functional nanoparticle-based solids makes it possible to use them in novel applications. We utilized the fl uorescence of dansyl glutathione gold superlattice crystals for the selective detection of bovine serum albumin (BSA), the major protein constituent of blood plasma, based on the selective binding of the naphthalene ring of the dansyl moiety with site I of BSA.

Multifunctional nanoparticles: Analytical prospects

“…In a recent study, Pradeep et al [98] have developed fluorescent three-dimensional (3D) super lattices of dansylglutathionate/Nacetylglutathionate protected gold nanoparticles, with potential applications in molecular detection. Morphologies of the superlattice crystals were examined using scanning electron microscopy (SEM) and most of the crystals observed were triangular in shape.…”

Fe3O4 octahedral colloidal crystals

“…They are also of major significance for potential technological applications based on their unique collective physicochemical properties [2,3,[8][9][10][11][12][13][14]. The classic strategy to obtain colloidal crystals is similar to solar salt production, namely, slowly evaporating the nanocrystal colloidal solution on a solid substrate [1,3,9,10,[14][15][16].…”

“…The classic strategy to obtain colloidal crystals is similar to solar salt production, namely, slowly evaporating the nanocrystal colloidal solution on a solid substrate [1,3,9,10,[14][15][16]. More recently, other techniques including electrostatic assembly [5], pH-controlled assembly [8,17], polarnonpolar solvent diffusion precipitation [7,13,18,19] and colloidal sphere assembly [20][21][22] have also been developed. However, there still remain three key challenges in this emerging field: (1) improving ease of bottom-up assembly as well as reducing the cost of solvent and time; (2) overcoming the mechanical constraint imposed by matrices and improving the stability of the colloidal crystal products; (3) crafting products with uniform crystal morphologies and a sufficient number of nano-building blocks.…”

Micro- and nanostripes of self-assembled Au nanocrystal superlattices by direct micromolding

“…Many interesting phenomena and processes such as single electron transport [11], metal-insulator transitions [12,13], and magnetic transitions [7,14] have been revisited at the mesoscale using nanocrystal arrays as model systems. Besides two-dimensional (2-D) arrays, linear (1-D) assemblies [15] as well as three-dimensional (3-D) assemblies of nanocrystals (supracrystals) [16,17] have also been fabricated.…”