DNA‐Templated Semiconductor Nanoparticle Chains and Wires

Abstract

Confining the growth of semiconductor materials to the low nanometer regime provides access to size quantization phenomena that may be exploited for a range of applications, such as probing intracellular processes, chemical and biological sensing, and nanometer-scale electronics.[1-4] Whilst control over length scales is well-developed for many types of materials, their form (e.g., dimensionality) and subsequent organization into hierarchical and functional systems remains challenging. One approach that is proving successful in addressing these problems is the use of biopolymers as templates, scaffolds, and interconnects. [5][6][7][8][9][10] DNA has been particularly effective in this regard and has been used to grow and/ or organize both inorganic (e.g., CdS, ZnS) [11][12][13][14][15][16][17] and molecular-based (e.g., polyaniline) semiconductor materials. [18][19][20] Here, we report the use of DNA strands, both surface-immobilized and in solution, to template the growth and organization of the binary semiconductor CdS. Through careful optimization of the reaction conditions and the state of the DNA, we have been able to control the reaction and prepare quantum-confined CdS as either 1D chainlike assemblies of particles or as uniform nanowires. The latter were subsequently integrated into a simple two-terminal electrical device to demonstrate the utility of these materials as possible nanometerscale electronic components.Reactions of cadmium and sulfide ions on surface-bound DNA employed two different surface types: mica, and alkyl monolayers on single-crystal Si(111). The mica surfaces allowed the DNA molecules to be anchored via interactions between the metal ions, the surface oxygen functionalities, and the phosphate groups. The alkyl monolayers on Si(111) provide an inert, flat surface on which DNA may be conveniently aligned by combing. [21,22] On mica substrates k-DNA was spotted onto a freshly cleaved surface and allowed to incubate with Cd(NO 3 ) 2 for 10 min. at room temperature. After rinsing, the surface was treated with a solution of 1 mM Na 2 S. Initially aqueous sulfide solutions were used, but in these cases rapid precipitation occurred and randomly deposited material was observed. Instead, treatment with 1 mM Na 2 S in a 1:1 water/ethanol mixture (v/v) gave the desired selective growth of CdS on the DNA template. Figure 1 shows a typical atomic force microscopy (AFM) image of the surface after reaction.Nanoparticles can be seen adhering on the DNA strands, resulting in a beads-on-a-chain appearance. The particles are also highly monodisperse, with diameters (width data) in the range 11.3-16.7(±1.4) nm (average 14.2 nm ± 10 %). Furthermore, there is a notable registry of the particles along the length of some of the polymer chains. In marked contrast, reactions at DNA that had been aligned through combing onto alkylated Si(111) produced material that was much less regular in appearance. After reaction, the surface was found to contain randomly coiled strands, indicating that the DNA is mobile dur...

Self‐Assembly of DNA‐Templated Polypyrrole Nanowires: Spontaneous Formation of Conductive Nanoropes

“…Nanowires of Au, [3][4][5][6][7][8] Pt [9][10][11][12] and Pd, [13][14][15] binary semiconductors [16][17][18] and conducting polymers [19][20][21] have all been prepared using this method. The advantages of DNA as a template are: (i) it is a chemically robust material which can be obtained in high purity; (ii) single molecules of DNA many micrometres long are available and (iii) DNA composition and structure are well defined.…”

Electrochemical aptasensor based on one-step synthesis of Cu2O@aptamer nanospheres for sensitive thrombin detection

“…In principle, the growth of nanomaterials on DNA as template is suitable for improving the conductivity of the nanomaterial while retaining the advantages of large aspect ratio and chemical stability. DNA-templated synthesis has yielded various nanomaterials including metals [25][26][27], semiconductors [28,29], polymers conductors [30,31], and polymer-metal hybrids [32]. Hassanien et al reported the formation of copper nanowire using the chemical reduction of Cu (II) in the presence of double strands DNA (dsDNA) [33].…”

DNA-templated assemblage of ZnS nanoparticle wires

“…Among the biological molecules, deoxyribonucleic acid (DNA) is a potentially ideal template to dictate the precise positioning of molecules into any deliberately designed structure due to its remarkable molecular recognition properties and structural features. Many kinds of metallic [3][4][5] and semiconductor nanowires have been prepared by DNA template, but till now CdS nanowire is the only realization of semiconductor nanowires synthesized with DNA template [6][7][8].…”