DNA‐Templated Silver Nanorings

Abstract

Nanostructures of noble metals with well-defined shapes and sizes are increasingly attracting the attention of scientists in the fields of catalysis, electronics, photonics, information storage, optoelectronics, biological labeling, etc. The further development and practical applications of nanostructures are expected to increase rapidly because of their interesting optical, electronic, and magnetic properties. [1] In this context, important knowledge of the direct preparation of metallic nanostructures of controlled size and shape has been developed over the past few years, and various morphologies, such as spherical nanoparticles, [2] nanocubes, [3] nanoprisms, [4] nanoplates, [5] or nanobelts, [5] can now be prepared in a controlled way. However, since these techniques are based on the directed growth of particles in the reaction medium, they can only lead to shapes of a simple topology, such as spheroids, ellipsoids, or polyhedrons. In contrast, nanoparticles with a toroidal shape (nanoring) can not be produced by a direct growth technique. Hence, the only way to produce such a morphology is to use a toroidal template of nanometer-scale dimensions. Elaborate and successful methods to prepare silver or gold rings based on the use of a nanoparticle array or a mesoporous membrane as a primary template, were recently described by Xia and co-workers [6] and Yan and Goedel, [7,8] respectively. However, these techniques provide rings with a minimal size of 0.5 lm that can not be directly dispersed in an aqueous medium. On the other hand, due to the specific interaction between DNA and silver ions, DNA is an ideal template to build silver nanostructures. This principle has been used successfully to produce nanoparticle arrays on a DNA scaffold, [9,10] or DNA-templated silver nanowires. [11,12] However, the ability of DNA chains to form toroidal condensates [13] as a result of the DNA-folding transition (DNA condensation [14] ) has not been hitherto noticed by materials scientists. The ability of DNA to condense into well-defined toroids provides a unique opportunity to use them as templates to create silver toroidal nanostructures (nanorings) of controlled shape and dimensions. In this communication, we describe a one-pot, three-step, simple preparation of well-defined silver nanorings (100 nm in diameter) dispersed in water, based on the use of dilute solutions of DNA condensates as nanostructured templates. DNA is a semiflexible, highly charged polyelectrolyte that assumes an elongated-coil conformation in water due to the electrostatic repulsion between the negatively charged monomers. DNA molecules usually fold into tightly packed toroidal condensates with an outer diameter of typically 70-90 nm [13,14] in the presence of hydrophilic neutral polymers, [15] or upon the addition of a small amount of condensing agent, such as cationic polyamines, [13] multivalent metal cations, [16] and cationic surfactants, [17] to a dilute DNA solution. The role of the condensing agents is to induce an attraction between the DNA m...

Self‐Assembled DNA Hydrogels with Designable Thermal and Enzymatic Responsiveness

“…[ 1 , 2 ] It has been shown that DNA can be precisely designed with specifi c sequences and self-assemble into two-or three-dimensional nanostructures, [3][4][5][6][7][8][9] fabricated to nanomachines or motors, [10][11][12][13] or used as a programmable template to direct the assembly of nanoparticles. [14][15][16][17] Recently, the concept of DNA assembly has been expanded to construct "DNA hydrogels", which are crosslinked networks swollen in an aqueous phase. [18][19][20][21][22][23][24][25][26][27][28][29][30][31] Though hydrogels have great potential in biological and medical applications, [32][33][34][35][36] such as drug and gene delivery, biosensing, and tissue engineering, studying the preparation of DNA hydrogels with designable properties is still in its early stages.…”

Gold nanorings synthesized via a stress-driven collapse and etching mechanism

“…27,28 Here, to the best of our knowledge, we report for the first time a novel and simple strategy for the synthesis of Au nanorings via a one-pot direct solution-based chemical reaction by means of an unusual stress-driven structure collapse and etching mechanism. The as-formed Au nanorings with tailored structures are an exciting new member of the family of Au nanostructures with diverse shapes.…”

Illuminating Dark Plasmons of Silver Nanoantenna Rings to Enhance Exciton–Plasmon Interactions

“…[22,23] Compared to silver nanowires, silver nanorings have less plasmon-propagation loss and higher sensitivity as biosensors in the near-infrared region. [42] Several methods (such as nanostructured template and lithography techniques) have been proposed to prepare silver and gold nanorings; [43][44][45][46][47][48] however, the nanorings prepared thus are polycrystalline. The growth of silver nanorings in the form of a singly twinned crystal is a hard challenge and has not been reported yet.…”