Microwave Synthesis of Electrically Conductive Gold Nanowires on DNA Scaffolds

Biological molecules, in particular DNA, have shown great potential to be used as interconnects of nanodevices and computational elements. In this research, we synthesized electrically conductive gold nanowires for the first time exploiting an electroless and microwave heating method for 120−180 s. Our results indicate that DNA serves as a reducing and nonspecific capping agent for the growth of nanowires. The current voltage (I−V) characteristics of the Au nanowires are continuous, exhibiting Ohmic behavior having low contact resistance with the gold electrodes. The nanowires have a diameter of 10−15 nm in solution and of 20−30 nm in immobilized DNA with resistivity comparable to pure metals. The method is highly selective with deposition confined to the DNA itself. The nanowires we fabricated can be used as building blocks for functional nanodevices, sensors, and optoelectronics

η⁶‑Benzene(tricarbonyl)chromium and Cymantrene Assemblies Supported on an Organostannoxane Platform

A series of η⁶-benzene­(tricarbonyl)chromium and cymantrene-containing [cymantrene = cyclopentadienylmanganese­(I) tricarbonyl] assemblies supported on organostannoxane platforms are reported. The reaction of [Cr­(η⁶-C₆H₅CO₂H)(CO)₃] (L1H) with <i>n</i>-Bu₂SnCl₂ in a 1:1 ratio afforded the tetranuclear derivative [{<i>n</i>-Bu₂Sn}₂(μ₃-O)­(μ-OMe)­(L1)]₂ (<b>1</b>) whereas a similar reaction carried out in a 2:1 stoichiometry afforded the mononuclear derivative [<i>n</i>-Bu₂Sn­(L1)₂] (<b>2</b>). The reaction of (<i>t</i>-Bu₂SnO)₃ with L1H in toluene in a 1:3 ratio afforded the hydroxide-bridged dimer, [<i>t</i>-Bu₂Sn­(μ-OH)­(L1)]₂ (<b>3</b>). A 1:2 reaction between [{η⁶-C₆H₄(COOH)₂<b>-</b>1,3}­Cr­(CO)₃] (L2H₂) and Me₃SnCl afforded a two-dimensional coordination polymer [{Me₃Sn}₂(μ₄-L2)]_<i>n</i> (<b>4</b>). A similar reaction between [{η⁶-C₆H₄(COOH)₂<b>-</b>1,4}­Cr­(CO)₃] (L3H₂) and Me₃SnCl in a 1:2 ratio also afforded a two-dimensional coordination polymer [{Me₃Sn}₂(μ₄-L3)]_<i>n</i> (<b>5</b>). The reaction of L3H₂ with Me₃SnCl in the presence of 4,4′-bipyridine afforded a 1D-coordination polymer [(Me₃Sn)₂(μ-L3)­(μ-4,4′-bipy)]_<i>n</i> (<b>6</b>). The reaction of L3H₂ with (Ph₃Sn)₂O (in a 1:1 ratio) gave a dimer [(H₂O)­SnPh₃(μ-L3)­SnPh₃(MeOH)] (<b>7</b>). The 1:1 reaction of [Mn­(η⁵-C₅H₄COOH)(CO)₃] (L4H) with Me₂SnCl₂ yielded the tetranuclear derivative [{Me₂Sn}₂(μ₃-O)­(L4)₂]₂ (<b>8</b>). A similar reaction of [Mn­{η⁵-C₅H₄C­(O)­CH₂CH₂COOH}­(CO)₃] (L5H) with Me₂SnCl₂ in a 1:1 ratio also afforded a tetrameric derivative [{Me₂Sn}₂(μ₃-O)­(μ₂-OMe)­(L5)]₂ (<b>9</b>). All the compounds were characterized by single crystal X-ray diffraction. Complexes <b>4</b> and <b>5</b> are planar organometallic 2D-coordination polymers

DNA-Mediated Fast Synthesis of Shape-Selective ZnO Nanostructures and Their Potential Applications in Catalysis and Dye-Sensitized Solar Cells

Shape-selective ZnO nanoparticles (NPs) with various morphologies have been synthesized within 2 min of microwave heating by the reaction of Zn­(NO₃)₂·2H₂O with NaOH in the presence of DNA. The size and shape of the materials can be tuned by controlling the molar ratio of Zn­(II) salt to DNA and by altering the other reaction parameters. The role of DNA and other reaction parameters for the formation and growth mechanisms of different morphologies has been elaborated. The potentiality of the DNA–ZnO NPs has been tested in the catalysis reaction for the decomposition of toxic KMnO₄, and the effect of different morphologies on the catalysis reaction has been examined. Moreover, the suitability of the materials is also tested for dye-sensitized solar cell (DSSC) applications, and it was observed that all the morphologies of ZnO NPs can be used as a potential anode material in DSSC applications

Microwave Synthesis of SnWO₄ Nanoassemblies on DNA Scaffold: A Novel Material for High Performance Supercapacitor and as Catalyst for Butanol Oxidation

Self-assembled, aggregated SnWO₄ nanoassemblies are formed by the reaction of Sn­(II) salt and Na₂WO₄·2H₂O in the presence of DNA under microwave heating within 6 min. We have emphasized the natural properties of DNA with its ability to scaffold SnWO₄ nanoassemblies and examined the role of starting reagents on the particles’ morphology. The diameter of the individual particles is ultrasmall and varies from ∼1–2.5 nm. The potentiality of the SnWO₄ nanoassemblies has been tested for the first time in two different applications, such as an anode material in electrochemical supercapacitor studies and as a catalyst for the oxidation of butanol to butanoic acid. From the supercapacitor study, it was observed that SnWO₄ nanoassemblies with different sizes showed different specific capacitance (<i>C</i>_s) values and the highest <i>C</i>_s value was observed for SnWO₄ nanoassemblies having small size of the individual particles. The highest <i>C</i>_s value of 242 F g^–1 was observed at a scan rate of 5 mV s^–1 for small size SnWO₄ nanoassemblies. The capacitor shows an excellent long cycle life along with 85% retention of <i>C</i>_s value even after 4000 consecutive times of cycling at a current density of 10 mA cm^–2. From the catalysis studies, it was observed that SnWO₄ nanoassemblies acted as a potential catalyst for the oxidation of butanol to butanoic acid using eco-friendly hydrogen peroxide as an oxidant with 100% product selectivity. Other than in catalysis and supercapacitors, in the future, the material can further be used in sensors, visible light photocatalysis and energy related applications

Synthesis and Application of DNA−CdS Nanowires within a Minute using Microwave Irradiation

A very fast, electroless, microwave method is described to synthesize electrically conductive CdS nanowires on DNA just within 60 s. The electrical characterization indicates that the CdS wires are continuous, have very low contact resistance, and exhibit Ohmic behavior. Highly selective deposition on DNA is obtained by specific complexation between the Cd(II) ion and DNA, followed by decomposition of thioacetamide to S2− to form CdS. The nanowires are found to have a diameter of 140−170 nm and a length of ∼8−12 μm. The one-step process developed here does not perturb the overall conformation of the DNA chain. The nanowires we fabricated can be used as building blocks for functional nanodevices, tiny computers, sensors, and optoelectronics

Size-Selective Synthesis and Catalytic Application of Polyelectrolyte Encapsulated Gold Nanoparticles Using Microwave Irradiation

Size-controlled gold (Au) nanoparticles (NPs) were synthesized for the first time in large quantities in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) under microwave heating for just 60 s in aqueous solutions. Results showed that the Au NPs were small in size, which could be successfully controlled through varying the PVP to Au(III) molar ratio and by using different molecular weight PVP molecules. The particles were stable for more than three months in ambient conditions. The synthesized PVP−Au NPs exhibited excellent catalytic activity for the reduction of aromatic nitro compounds by NaBH4 in water. The Au NPs helped in the electron transfer process between the BH4− and nitro compounds, which were successfully reduced to their amino derivatives. The present method is beneficial for fast synthesis of Au NPs as well as reduction of different aromatic nitro compounds

Size-Controlled Synthesis and Self-Assembly of Silver Nanoparticles within a Minute Using Microwave Irradiation

Size-controlled silver (Ag) nanoparticles (NPs) and nanochains were synthesized for the first time in large quantities. This was done in the presence of alkaline 2,7-dihydroxy naphthalene (2,7-DHN) as a new reducing agent under microwave heating for just 60 s in a nonionic surfactant (TX-100) media. Results showed that the Ag NPs were small in size, which could be successfully controlled through varying the TX-100 to Ag(I) molar ratio. The formation of Ag nanochains was enhanced by low TX-100 concentrations and high pH. The synthesized particles are stable for more than 3 months in ambient conditions. The proposed method could be extended for the synthesis of other metal and semiconductor nanomaterials with defined sizes and shapes. These particles could find valuable applications in catalysis, nanoelectronics, and surface-enhanced Raman spectroscopic (SERS) studies

Shape-Controlled Catalysis by Cetyltrimethylammonium Bromide Terminated Gold Nanospheres, Nanorods, and Nanoprisms

Shape-controlled Au nanospheres, nanorods, and nanoprisms have been utilized for the first time for selective chemical reduction of different aromatic nitro compounds to the corresponding amino derivatives at room temperature. Careful observation reveals that the reaction was fastest with nanospheres and slowest with nanorods, whereas the rate was intermediate with nanoprisms when keeping the numbers of particles approximately the same. Controlled experiments revealed that our reaction followed the nitroso and hydroxylamine pathway. The yield of the product was very high, and the method should be applicable for very fast catalysis reaction of other nitro compounds

Nickelo-Sulfurization of DNA Leads to an Efficient Alkaline Water Oxidation Electrocatalyst with Low Ni Quantity

Nonprecious metals based electrocatalysts are highly anticipated in electrocatalytic water splitting as the increasing energy demand can be handled by large scale H2 production with minimum expenses. Herein, a facile and faster nickelo-sulfurization of DNA in ambient conditions has been developed that resulted in NiS anchored wirelike assemblies of DNA. The effect of DNA concentration on material stability and electrocatalytic activity was studied, and it was found that, with DNA to Ni2+ ratios of 0.048 and 0.072 M, the NiS anchored DNA colloidal solutions were stable. In addition, it was found that NiS(0.048) with a relatively lower DNA concentration showed better oxygen evolution reaction (OER) activity than NiS(0.072). Overpotentials of 352 and 401 mV were required by NiS(0.048) and NiS(0.072) to deliver a current density of 10 mA cm–2 even with an ultralow quantity of NiS­(0.0123 mg cm–2) in both. The same trend was reflected in the Tafel slopes of NiS(0.048) and NiS(0.072) which showed 58.6 and 112.4 mV dec–1 indicating that the optimum ratio for better OER activity is 0.048. In this study, DNA plays a versatile role such as acting as a stabilizer, scaffold, and a microstructural stage for NiS in solution. Moreover, DNA also acts as an efficient binder and as a conductor of both ions and electrons in its OER activity trend. The proposed method can be used for preparing stable colloids of other metal sulfide based nano-electro-catalysts and can directly be employed for water oxidation in alkaline conditions