Synthesis and Properties of Novel Silver-Containing DNA Molecules

Ag+-Mediated Folding of Long Polyguanine Strands to Double and Quadruple Helixes

Metal-mediated base pairing of DNA has been a topic of extensive research spanning over more than four decades. Precise positioning of a single metal ion by predetermining the DNA sequence, as well as improved conductivity offered by the ions, make these structures interesting candidates in the context of using DNA in nanotechnology. Here, we report the formation and characterization of conjugates of long (kilo bases) homoguanine DNA strands with silver ions. We demonstrate using atomic force microscopy (AFM) and scanning tunneling microscope (STM) that binding of silver ions leads to folding of homoguanine DNA strands in a "hairpin" fashion to yield double-helical, left-handed molecules composed of G-G base pairs each stabilized by a silver ion. Further folding of the DNA-silver conjugate yields linear molecules in which the two halves of the double helix are twisted one against the other in a right-handed fashion. Quantum mechanical calculations on smaller molecular models support the helical twist directions obtained by the high resolution STM analysis. These long guanine-based nanostructures bearing a chain of silver ions have not been synthesized and studied before and are likely to possess conductive properties that will make them attractive candidates for nanoelectronics.

Biomass RNA for the Controlled Synthesis of Degradable Networks by Radical Polymerization

Nucleic acids extracted from biomass have emerged as sustainable and environmentally friendly building blocks for the fabrication of multifunctional materials. Until recently, the fabrication of biomass nucleic acid-based structures has been facilitated through simple crosslinking of biomass nucleic acids, which limits the possibility of material properties engineering. This study presents an approach to convert biomass RNA into an acrylic crosslinker through acyl imidazole chemistry. The number of acrylic moieties on RNA was engineered by varying the acylation conditions. The resulting RNA crosslinker can undergo radical copolymerization with various acrylic monomers, thereby offering a versatile route for creating materials with tunable properties (e.g., stiffness and hydrophobic characteristics). Further, reversible-deactivation radical polymerization methods, such as atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT), were also explored as additional approaches to engineer the hydrogel properties. The study also demonstrated the metallization of the biomass RNA-based material, thereby offering potential applications in enhancing electrical conductivity. Overall, this research expands the opportunities in biomass-based biomaterial fabrication, which allows tailored properties for diverse applications.

DNA-Guided Metallization of Nanomaterials and Their Biomedical Applications

Precise control of the structure of metallic nanomaterials is critical for the advancement of nanobiotechnology. As DNA (deoxyribonucleic acid) can readily modify various moieties, such as sulfhydryl, carboxyl, and amino groups, using DNA as a directing ligand to modulate the morphology of nanomaterials is a promising strategy. In this review, we focus on the use of DNA as a template to control the morphology of metallic nanoparticles and their biomedical applications, discuss the use of DNA for the metallization of gold and silver, explore the factors that influence the process, and outline its biomedical applications. This review aims to provide valuable insights into the DNA-guided growth of nanomaterials. The challenges and future directions are also discussed.

Programmed Assembly of DNA Templates by Silver Nanowires

DNA origami templates are known to exhibit many advantages to integrate functional components at desirable locations for nanoelectronic applications. In order to immobilize conducting or semiconducting species in a bottom-up approach, the programmed assembly of DNA templates is of utmost necessity. This report demonstrates the silver nanowires enabled bridging of two linear DNA origami (DO) nanostructures by utilizing the host-guest interaction of biotin-STV and sequence-specific silver metallization of poly(dG-dC) DNA nanowires (in 10 % yield) using (dA)₁₀ coated AgNPs (15 nm). The enzymatic synthesis of 750 bp, 1500 bp and 3000 bp bis-biotinylated poly(dG-dC), facile synthesis of 1 : 1 biotin-STV and silver-nanowire bridged DNA templates were characterized by gel electrophoresis, atomic force microscope imaging techniques. The strategy utilized here provides a method that can precisely connect heterogeneous templates towards bottom-up fabrication of practical nanoelectronics.

DNA Nanotechnology-Enabled Fabrication of Metal Nanomorphology

In recent decades, DNA nanotechnology has grown into a highly innovative and widely established field. DNA nanostructures have extraordinary structural programmability and can accurately organize nanoscale materials, especially in guiding the synthesis of metal nanomaterials, which have unique advantages in controlling the growth morphology of metal nanomaterials. This review started with the evolution in DNA nanotechnology and the types of DNA nanostructures. Next, a DNA-based nanofabrication technology, DNA metallization, was introduced. In this section, we systematically summarized the DNA-oriented synthesis of metal nanostructures with different morphologies and structures. Furthermore, the applications of metal nanostructures constructed from DNA templates in various fields including electronics, catalysis, sensing, and bioimaging were figured out. Finally, the development prospects and challenges of metal nanostructures formed under the morphology control by DNA nanotechnology were discussed.

Electronic Level Structure of Novel Guanine Octuplex DNA Single Molecules

Throughout the past few decades, guanine quadruplex DNA structures have attracted much interest both from a fundamental material science perspective and from a technologically oriented perspective. Novel guanine octuplex DNA, formed from coiled quadruplex DNA, was recently discovered as a stable and rigid DNA-based nanostructure. A detailed electronic structure study of this new nanomaterial, performed by scanning tunneling spectroscopy on a subsingle-molecule level at cryogenic temperature, is presented herein. The electronic levels and lower energy gap of guanine octuplex DNA compared to quadruplex DNA dictate higher transverse conductivity through guanine octads than through guanine tetrads.

Programmable and Site-Specific Patterning on DNA Origami Templates with Heterogeneous Condensation of Silver and Silica

DNA origami has been widely used as a modular platform for condensation of functional molecules to assemble optical, electronic, and biological components. However, the heterogeneous condensation with greater diversities in chemical composition templated with DNA origami is still challenging. Herein, a programmable deposition method is developed to precisely condense silver-silica nanohybrids on DNA origami templates. First, the site-specific metallization of Ag is achieved by thiol group-initiated silver reduction at the designed areas of DNA origami. Next, cysteamine is used to selectively modify the condensed Ag surface with positively charged amino groups for creating an electronically different environment for site-specific placement of silica by a modified Stöber method. Using these strategies, customized patterning of both silver and silica on tubular and rectangular DNA origami nanostructures is successfully achieved with nanoscale spatial resolution. These findings will greatly facilitate the development of DNA nanotechnology-based bottom-up nanofabrication.

Influence of Silver Nanoparticles on the Biological Indicators of Haplic Chernozem

In recent years, silver nanoparticles (AgNPs) are increasingly used in various industries due to their antibacterial properties, which lead to an increase in pollution of the environment and soil ecosystems. However, the ecological effects of soil pollution by AgNPs were poorly studied than that with AgNPs of other metal-based NPs. The aim of this study is to assess the influence of AgNPs on the biological properties of Haplic Chernozem. Silver was introduced into the soil in the form of AgNPs with a concentration of 0.5; 1; 5; 10; 50, and 100 mg/kg in laboratory conditions. The influence of AgNPs on the biological properties of Haplic Chernozem was assessed 30 days after contamination. The degree of reduction in biological properties depends on the AgNPs concentration in the soil. This study showed that the sensitivity to contamination by AgNPs in the total number of bacteria and enzymatic activity was more than that in the abundance of bacteria of the genus Azotobacter. The integrated index of biological state (IIBS) of Haplic Chernozem was decreased by contamination with AgNPs. Silver nanoparticles in the concentration of 10 mg/kg caused a decrease in the indicator by 13% relative to the control. It also decreased IIBS by doses of 50 and 100 mg/kg by 22 and 27% relative to the control. All used biological indicators could be used for biomonitoring, biodiagnosis, bioindication, and regulation of ecological condition of soil contamination by AgNPs.

Formation of Novel Octuplex DNA Molecules from Guanine Quadruplexes

Guanine quadruplex (G4)-DNA structures have sparked the interest of many scientists due to their important biological roles and their potential use in molecular nanoelectronics and nanotechnology. The high guanine content in G4-DNA endows it with mechanical stability, robustness, and improved charge transport properties-attractive attributes for a molecular nanowire. The self-driven formation of a novel G4-DNA-based nanostructure, coined guanine octuplex (G8)-DNA, is reported herein. Atomic force microscopy and scanning tunneling microscopy characterization of this molecule reveal its organized coiled-coil structure, which is found to be stable under different temperatures and surrounding conditions. G8-DNA exhibits enhanced stiffness, mechanical and thermodynamic stability when compared to its parent G4-DNA. These, along with its high guanine content, make G8-DNA a compelling new molecule, and a highly prospective candidate for molecular nanoelectronics.

Hybrid gold/DNA nanowire circuit with sub-10 nm nanostructure arrays

We report on a simple and efficient method for the selective positioning of Au/DNA hybrid nanocircuits using a sequential combination of electron-beam lithography (EBL), plasma ashing, and a molecular patterning process. The nanostructures produced by the EBL and ashing process could be uniformly formed over a 12.6 in² substrate with sub-10 nm patterning with good pattern fidelity. In addition, DNA molecules were immobilized on the selectively nanopatterned regions by alternating surface coating procedures of 3-(aminopropyl)triethoxysilane (APS) and diamond like carbon (DLC), followed by deposition of DNA molecules into a well-defined single DNA nanowire. These single DNA nanowires were used not only for fabricating Au/DNA hybrid nanowires by the conjugation of Au nanoparticles with DNA, but also for the formation of Au/DNA hybrid nanocircuits. These nanocircuits prepared from Au/DNA hybrid nanowires demonstrate conductivities of up to 4.3 × 10⁵ S/m in stable electrical performance. This selective and precise positioning method capable of controlling the size of nanostructures may find application in making sub-10 nm DNA wires and metal/DNA hybrid nanocircuits.

Moving Electrons Purposefully through Single Molecules and Nanostructures: A Tribute to the Science of Professor Nongjian Tao (1963-2020)

Electrochemistry intersected nanoscience 25 years ago when it became possible to control the flow of electrons through single molecules and nanostructures. Many surprises and a wealth of understanding were generated by these experiments. Professor Nongjian Tao was among the pioneering scientists who created the methods and technologies for advancing this new frontier. Achieving a deeper understanding of charge transport in molecules and low-dimensional materials was the first priority of his experiments, but he also succeeded in discovering applications in chemical sensing and biosensing for these novel nanoscopic systems. In parallel with this work, the investigation of a range of phenomena using novel optical microscopic methods was a passion of his and his students. This article is a review and an appreciation of some of his many contributions with a view to the future.

Detection of quiescent fungi in harvested fruit using CMOS biosensor: A proof of concept study

Postharvest fruit decay is caused by fungal pathogens and leads to major losses. In this study, specific mRNA sequences that are upregulated in the fungus Colletotrichum gloeosporioides during its quiescent stage in fruits, were identified using a CMOS sensor. The identification process was based on sandwich approach, where strands complementary to the C. gloeosporioides mRNA sequences (quiescent stage-specific) were immobilized on the CMOS surface, and exposed to the target complementary reporter strands. In the presence of a target sequence, the reporter strand (linked to the enzyme horseradish peroxidase (HRP)) was left in the system and a measurable light signal was produced. The complementary strands specifically anneal to the mRNA in the sample. The sensitivity of the technology was assessed by mRNA sequences isolated from C. gloeosporioides, and identified as 10 nM RNA. The effect of the pathogenicity state on the sensor performance was also evaluated. The CMOS sensor could detect quiescent fungi, which are barely detectable by other means. The unique capability of the proposed system to detect and recognize the fungus during both pathogenic and quiescent stages, will allow the development of new sensors that can monitor the amount of undetectable quiescent fungi in harvested fruit, enabling improved food management.

Electronic Level Structure of Silver-Intercalated Cytosine Nanowires

Metal-mediated base-paired DNA has long been investigated for basic scientific pursuit and for nanoelectronics purposes. Particularly attractive in these domains is the Ag⁺-intercalated polycytosine DNA duplex. Extensive studies of this molecule have led to our current understanding of its self-assembly properties, high thermodynamic and structural stability, and high longitudinal conductivity. However, a high-resolution morphological characterization of long Ag⁺-intercalated polycytosine DNA has hitherto not been carried out. Furthermore, the electronic level structure of this molecule has not been studied before. Here we present a scanning tunneling microscopy and spectroscopy study of this intriguing nanowire. Its temperature-independent morphological and electronic properties suggest substantial stability, while its emergent electronic levels and energy gap provide the basis for its high conductivity.

Robust DNA-Bridged Memristor for Textile Chips

Electronic textiles may revolutionize many fields, such as communication, health care and artificial intelligence. To date, unfortunately, computing with them is not yet possible. Memristors are compatible with the interwoven structure and manufacturing process in textiles because of its two-terminal crossbar configuration. However, it remains a challenge to realize textile memristors owing to the difficulties in designing advanced memristive materials and achieving high-quality active layers on fiber electrodes. Herein we report a robust textile memristor based on an electrophoretic-deposited active layer of deoxyribonucleic acid (DNA) on fiber electrodes. The unique architecture and orientation of DNA molecules with the incorporation of Ag nanoparticles offer the best-in-class performances, e.g., both ultra-low operation voltage of 0.3 V and power consumption of 100 pW and high switching speed of 20 ns. Fundamental logic calculations such as implication and NAND are demonstrated as functions of textile chips, and it has been thus integrated with power-supplying and light emitting modules to demonstrate an all-fabric information processing system.

Temperature Dependence of the STM Morphology and Electronic Level Structure of Silver-Containing DNA

Understanding the effect of external conditions, temperature in particular, on novel nanomaterials is of great significance. The powerful ability of scanning tunneling microscopy (STM) to characterize topography and electronic levels on a single molecule scale is utilized herein to characterize individual silver-containing poly(dG)-poly(dC) DNA molecules, at different temperatures. These measurements indicate that the molecule is a truly hybrid metal-organic nanomaterial with electronic states originating from both the DNA and the embedded silver. The temperature dependence of this density of states (DOS) leads to the temperature dependent STM apparent height of the molecule-a phenomenon that has not been observed before for other complex nanostructures.

DNA Integration with Silver and Gold Nanoparticles: Enhancement of DNA Optical Anisotropy

DNA integration with silver and gold nanoparticles was carried out by the chemical reduction of silver and gold ions after the formation of their complexes with high molecular DNA in solution. It is shown that, for a good association of DNA with nanoparticles, the ions of silver and gold should be linked with DNA bases rather strongly. The proposed model of gold interaction with DNA is the coordination of gold to N7 guanine in a major groove followed by the transformation of the GC pair to Hoogsteen's type pairing, in which the gold atom is located between the bases and is bonded simultaneously to N7 guanine and N3 cytosine. For gold and silver nanoparticles associated with DNA, the peak of plasmon resonance shifts relative to that of free nanoparticles in solution. AFM (atomic force microscopy) images of both free and associated with DNA nanoparticles were obtained. Binding of high molecular DNA to gold and silver nanoparticles leads to a decrease in the size of its molecular coil in solution, but the bending rigidity of DNA helix (persistent length) does not change. The almost 3-fold increase in the optical anisotropy of DNA was observed when DNA was associated with gold nanoparticles. This result was obtained with the flow birefringence method using a light source with a wavelength of 550 nm, which is close to the peak of the plasmon resonance of gold nanoparticles. For DNA associated with silver nanoparticles, a similar result was obtained when using a light source with a wavelength of about 410 nm.

Scanning Tunneling Microscopy and Spectroscopy of Novel Silver-Containing DNA Molecules

The quest for a suitable molecule to pave the way to molecular nanoelectronics has been met with obstacles for over a decade. Candidate molecules such as carbon nanotubes lack the appealing trait of self-assembly, while DNA seems to lack the desirable feature of conductivity. Silver-containing poly(dG)-poly(dC) DNA (E-DNA) molecules have recently been reported as promising candidates for molecular electronics, owing to the selectivity of their metallization, their thin and uniform structure, their resistance to deformation, and their maximum possible high conductivity. Ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) of E-DNA presents an elaborate high-resolution morphology characterization of these unique molecules, along with a detailed depiction of their electronic level structure. The energy levels found for E-DNA indicate a novel truly hybrid metal-molecule structure, potentially more conductive than other DNA-based alternatives.

Construction and characterization of metal ion-containing DNA nanowires for synthetic biology and nanotechnology

DNA is an attractive candidate for integration into nanoelectronics as a biological nanowire due to its linear geometry, definable base sequence, easy, inexpensive and non-toxic replication and self-assembling properties. Recently we discovered that by intercalating Ag+ in polycytosine-mismatch oligonucleotides, the resulting C-Ag+-C duplexes are able to conduct charge efficiently. To map the functionality and biostability of this system, we built and characterized internally-functionalized DNA nanowires through non-canonical, Ag+-mediated base pairing in duplexes containing cytosine-cytosine mismatches. We assessed the thermal and chemical stability of ion-coordinated duplexes in aqueous solutions and conclude that the C-Ag+-C bond forms DNA duplexes with replicable geometry, predictable thermodynamics, and tunable length. We demonstrated continuous ion chain formation in oligonucleotides of 11-50 nucleotides (nt), and enzyme ligation of mixed strands up to six times that length. This construction is feasible without detectable silver nanocluster contaminants. Functional gene parts for the synthesis of DNA- and RNA-based, C-Ag+-C duplexes in a cell-free system have been constructed in an Escherichia coli expression plasmid and added to the open-source BioBrick Registry, paving the way to realizing the promise of inexpensive industrial production. With appropriate design constraints, this conductive variant of DNA demonstrates promise for use in synthetic biological constructs as a dynamic nucleic acid component and contributes molecular electronic functionality to DNA that is not already found in nature. We propose a viable route to fabricating stable DNA nanowires in cell-free and synthetic biological systems for the production of self-assembling nanoelectronic architectures.

Fabrication of Metal Nanostructures on DNA Templates

Metal nanoarchitectures fabrication based on DNA assembly has attracted a good deal of attention. DNA nanotechnology enables precise organization of nanoscale objects with extraordinary structural programmability. The spatial addressability of DNA nanostructures and sequence-dependent recognition allow functional elements to be precisely positioned; thus, novel functional materials that are difficult to produce using conventional methods could be fabricated. This review focuses on the recent development of the fabrication strategies toward manipulating the shape and morphology of metal nanoparticles and nanoassemblies based on the rational design of DNA structures. DNA-mediated metallization, including DNA-templated conductive nanowire fabrication and sequence-selective metal deposition, etc., is briefly introduced. The modifications of metal nanoparticles (NPs) with DNA and subsequent construction of heterogeneous metal nanoarchitectures are highlighted. Importantly, DNA-assembled dynamic metal nanostructures that are responsive to different stimuli are also discussed as they allow the design of smart and dynamic materials. Meanwhile, the prospects and challenges of these shape-and morphology-controlled strategies are summarized.

Addressing the properties of "Metallo-DNA" with a Ag(i)-mediated supramolecular duplex

The silver-nucleoside complex [Ag(i)-(N3-cytidine)₂]⁺, 1, self-assembles to form a supramolecular metal-mediated base-pair array highly analogous to those seen in metallo-DNA.

The silver-nucleoside complex [Ag(i)-(N3-cytidine)₂], 1, self-assembles to form a supramolecular metal-mediated base-pair array highly analogous to those seen in metallo-DNA. A combination of complementary hydrogen-bonding, hydrophobic and argentophilic interactions drive the formation of a double-helix with a continuous silver core. Electrical measurements on 1 show that despite having Ag···Ag distances within <5% of the metallic radii, the material is electrically insulating. This is due to the electronic structure which features a filled valence band, an empty conduction band dominated by the ligand, and a band gap of 2.5 eV. Hence, as-prepared, such Ag(i)-DNA systems should not be considered molecular nanowires but, at best, proto-wires. The structural features seen in 1 are essentially retained in the corresponding organogel which exhibits thixotropic self-healing that can be attributed to the reversible nature of the intermolecular interactions. Photo-reduced samples of the gel exhibit luminescence confirming that these poly-cytidine sequences appropriately pre-configure silver ions for the formation of quantum-confined metal clusters in line with contemporary views on DNA-templated clusters. Microscopy data reveals the resulting metal cluster/particles are approximately spherical and crystalline with lattice spacing (111) similar to bulk Ag.

Multifunctional behavior of molecules comprising stacked cytosine-AgI-cytosine base pairs; towards conducting and photoluminescence silver-DNA nanowires

DNA molecules containing a 1D silver array may be applied for nanotechnology applications, but first their conducting and photoluminescence behavior must be enhanced. Here we have synthesized and characterized three new helical compounds based on stacked silver-mediated cytosine base pairs [Ag(mC)2]X (mC = N1-methylcytosine; X = NO3 (1), BF4 (2) and ClO4 (3)), that contain uninterrupted polymeric AgI chains that run through the center of the helixes, comparable to related silver-DNA structures. The exposure of nanostructures of [Ag(mC)2]BF4 (2) to cold hydrogen plasma stimulates the reduction of the prearranged AgI polymeric chains to metallic silver along the material. This solvent-free reduction strategy leads to the compound [AgI(mC)2]X@Ag0 (2H) that contains uniformly well-distributed silver metallic nanostructures that are responsible for the new conducting and photoluminescence properties of the material. The presence of silver nanostructures alongside compound 2H has been evaluated by means of X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, and X-ray powder diffraction (XRPD). The conducting and photoactive properties of 2H were studied by electrostatic force microscopy (EFM) and conducting-AFM (c-AFM), and photoluminescence microscopy (PL), respectively. The results demonstrate that the presence of well-organized metallic silver nanoentities on the material is responsible for the novel conductivity and photoactive properties of the material. This methodology can be employed for the generation of multifunctional silver-DNA related materials with tailored properties.

Parallel Guanine Duplex and Cytosine Duplex DNA with Uninterrupted Spines of AgI-Mediated Base Pairs

Hydrogen bonding between nucleobases produces diverse DNA structural motifs, including canonical duplexes, guanine (G) quadruplexes, and cytosine (C) i-motifs. Incorporating metal-mediated base pairs into nucleic acid structures can introduce new functionalities and enhanced stabilities. Here we demonstrate, using mass spectrometry (MS), ion mobility spectrometry (IMS), and fluorescence resonance energy transfer (FRET), that parallel-stranded structures consisting of up to 20 G-Ag^I-G contiguous base pairs are formed when natural DNA sequences are mixed with silver cations in aqueous solution. FRET indicates that duplexes formed by poly(cytosine) strands with 20 contiguous C-Ag^I-C base pairs are also parallel. Silver-mediated G-duplexes form preferentially over G-quadruplexes, and the ability of Ag⁺ to convert G-quadruplexes into silver-paired duplexes may provide a new route to manipulating these biologically relevant structures. IMS indicates that G-duplexes are linear and more rigid than B-DNA. DFT calculations were used to propose structures compatible with the IMS experiments. Such inexpensive, defect-free, and soluble DNA-based nanowires open new directions in the design of novel metal-mediated DNA nanotechnology.

Advances in Synthesis and Measurement of Charge Transport in DNA-Based Derivatives

Charge transport through molecular structures is interesting both scientifically and technologically. To date, DNA is the only type of polymer that transports significant currents over distances of more than a few nanometers in individual molecules. For molecular electronics, DNA derivatives are by far more promising than native DNA due to their improved charge-transport properties. Here, the synthesis of several unique DNA derivatives along with electrical characterization and theoretical models is surveyed. The derivatives include double stranded poly(G)-poly(C) DNA molecules, four stranded G4-DNA, metal-DNA hybrid molecular wires, and other DNA molecules that are modified either at the bases or at the backbone. The electrical characteristics of these nanostructures, studied experimentally by electrostatic force microscopy, conductive atomic force microscopy, and scanning tunneling microscopy and spectroscopy, are reviewed.

High Electrical Conductivity of Single Metal-Organic Chains

Molecular wires are essential components for future nanoscale electronics. However, the preparation of individual long conductive molecules is still a challenge. MMX metal-organic polymers are quasi-1D sequences of single halide atoms (X) bridging subunits with two metal ions (MM) connected by organic ligands. They are excellent electrical conductors as bulk macroscopic crystals and as nanoribbons. However, according to theoretical calculations, the electrical conductance found in the experiments should be even higher. Here, a novel and simple drop-casting procedure to isolate bundles of few to single MMX chains is demonstrated. Furthermore, an exponential dependence of the electrical resistance of one or two MMX chains as a function of their length that does not agree with predictions based on their theoretical band structure is reported. This dependence is attributed to strong Anderson localization originated by structural defects. Theoretical modeling confirms that the current is limited by structural defects, mainly vacancies of iodine atoms, through which the current is constrained to flow. Nevertheless, measurable electrical transport along distances beyond 250 nm surpasses that of all other molecular wires reported so far. This work places in perspective the role of defects in 1D wires and their importance for molecular electronics.

Au/Ag-containing DNA-based nanowires

Direct conductivity measurements of thin uniform gold-coated DNA nanowires are presented. Gold-coated DNA conductive wires deposited on a mica surface are visualized by SEM and conductivity of the wires are measured using nanomanipulators built inside the microscope. The measurements show that the conductivity is limited by defects, and the thicker the coating the higher the conductivity of the wires. These gold-coated DNA nanowires are promising candidates for molecular electronics. DNA-base nanomaterial to be used in new DNA-based molecular electronics.

Silver nanocrystal-decorated polyoxometalate single-walled nanotubes as nanoreactors for desulfurization catalysis at room temperature

Ultrathin nanocrystals generally provide a remarkable catalytic performance due to their high specific surface area and exposure of certain active sites. However, deactivation caused by growth and gathering limits the catalytic application of ultrathin nanocrystals. Here we report Ag nanocrystal-decorated polyoxometalate (Ag-POM) single-walled nanotubes assembled via a concise, surfactant-free soaking method as a new kind of well-defined core-sheath nanoreactor. The diameter of Ag nanocrystals inside polyoxometalate nanotubes can be controlled via simply adjusting the reactant concentration. Ag-POM provided outstanding oxidative desulfurization (ODS) catalytic performance for aromatic sulfocompounds at room temperature. It was suggested that Ag nanocrystals decorated on the inner surface played a key role in adjusting the electronic distribution and enhancing the catalytic activity. The as-prepared Ag-POM nanotubes are promising candidate catalysts with enhanced performance for practical catalytic applications in the gasoline desulfurization industry.

DNA Binding Peptide Directed Synthesis of Continuous DNA Nanowires for Analysis of Large DNA Molecules by Scanning Electron Microscope

Synthesis of smooth and continuous DNA nanowires, preserving the original structure of native DNA, and allowing its analysis by scanning electron microscope (SEM), is demonstrated. Gold nanoparticles densely assembled on the DNA backbone via thiol-tagged DNA binding peptides work as seeds for metallization of DNA. This method allows whole analysis of DNA molecules with entangled 3D features.