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

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

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

Microwave-Initiated Facile Formation of Ni₃Se₄ Nanoassemblies for Enhanced and Stable Water Splitting in Neutral and Alkaline Media

Molecular hydrogen (H₂) generation through water splitting with minimum energy loss has become practically possible due to the recent evolution of high-performance electrocatalysts. In this study, we fabricated, evaluated, and presented such a high-performance catalyst which is the Ni₃Se₄ nanoassemblies that can efficiently catalyze water splitting in neutral and alkaline media. A hierarchical nanoassembly of Ni₃Se₄ was fabricated by functionalizing the surface-cleaned Ni foam using NaHSe solution as the Se source with the assistance of microwave irradiation (300 W) for 3 min followed by 5 h of aging at room temperature (RT). The fabricated Ni₃Se₄ nanoassemblies were subjected to catalyze water electrolysis in neutral and alkaline media. For a defined current density of 50 mA cm^–2, the Ni₃Se₄ nanoassemblies required very low overpotentials for the oxygen evolution reaction (OER), viz., 232, 244, and 321 mV at pH 14.5, 14.0, and 13.0 respectively. The associated lower Tafel slope values (33, 30, and 40 mV dec^–1) indicate the faster OER kinetics on Ni₃Se₄ surfaces in alkaline media. Similarly, in the hydrogen evolution reaction (HER), for a defined current density of 50 mA cm^–2, the Ni₃Se₄ nanoassemblies required low overpotentials of 211, 206, and 220 mV at pH 14.5, 14.0, and 13.0 respectively. The Tafel slopes for HER at pH 14.5, 14.0, and 13.0 are 165, 156, and 128 mV dec^–1, respectively. A comparative study on both OER and HER was carried out with the state-of-the-art RuO₂ and Pt under identical experimental conditions, the results of which revealed that our Ni₃Se₄ is a far better high-performance catalyst for water splitting. Besides, the efficiency of Ni₃Se₄ nanoassemblies in catalyzing water splitting in neutral solution was carried out, and the results are better than many previous reports. With these amazing advantages in fabrication method and in catalyzing water splitting at various pH, the Ni₃Se₄ nanoassemblies can be an efficient, cheaper, nonprecious, and high-performance electrode for water electrolysis with low overpotentials

NiTe₂ Nanowire Outperforms Pt/C in High-Rate Hydrogen Evolution at Extreme pH Conditions

Better hydrogen generation with nonprecious electrocatalysts over Pt is highly anticipated in water splitting. Such an outperforming nonprecious electrocatalyst, nickel telluride (NiTe₂), has been fabricated on Ni foam for electrocatalytic hydrogen evolution in extreme pH conditions, viz., 0 and 14. The morphological outcome of the fabricated NiTe₂ was directed by the choice of the Te precursor. Nanoflakes (NFs) were obtained when NaHTe was used, and nanowires (NWs) were obtained when Te metal powder with hydrazine hydrate was used. Both NiTe₂ NWs and NiTe₂ NFs were comparatively screened for hydrogen evolution reaction (HER) in extreme pH conditions, viz., 0 and 14. NiTe₂ NWs delivered current densities of 10, 100, and 500 mA cm^–2 at the overpotentials of 125 ± 10, 195 ± 4, and 275 ± 7 mV in 0.5 M H₂SO₄. Similarly, in 1 M KOH, overpotentials of 113 ± 5, 247 ± 5, and 436 ± 8 mV were required for the same current densities, respectively. On the other hand, NiTe₂ NFs showed relatively poorer HER activity than NiTe₂ NWs, which required overpotentials of 193 ± 7, 289 ± 5, and 494 ± 8 mV in 0.5 M H₂SO₄ for the current densities of 10 and 100 mA cm^–2 and 157 ± 5 and 335 ± 6 mV in 1 M KOH for the current densities of 10 and 100 mA cm^–2, respectively. Notably, NiTe₂ NWs outperformed the state-of-the-art Pt/C 20 wt % loaded Ni foam electrode of comparable mass loading. The Pt/C 20 wt % loaded Ni foam electrode reached 500 mA cm^–2 at 332 ± 5 mV, whereas NiTe₂ NWs drove the same current density with 57 mV less. These encouraging findings emphasize that a NiTe₂ NW could be an alternative to noble and expensive Pt as a nonprecious and high-performance HER electrode for proton-exchange membrane and alkaline water electrolyzers

Core-Oxidized Amorphous Cobalt Phosphide Nanostructures: An Advanced and Highly Efficient Oxygen Evolution Catalyst

We demonstrated a high-yield and easily reproducible synthesis of a highly active oxygen evolution reaction (OER) catalyst, “the core-oxidized amorphous cobalt phosphide nanostructures”. The rational formation of such core-oxidized amorphous cobalt phosphide nanostructures was accomplished by homogenization, drying, and annealing of a cobalt­(II) acetate and sodium hypophosphite mixture taken in the weight ratio of 1:10 in an open atmosphere. Electrocatalytic studies were carried out on the same mixture and in comparison with commercial catalysts, viz., Co₃O₄-Sigma, NiO-Sigma, and RuO₂-Sigma, have shown that our catalyst is superior to all three commercial catalysts in terms of having very low overpotential (287 mV at 10 mA cm^–2), lower Tafel slope (0.070 V dec^–1), good stability upon constant potential electrolysis, and accelerated degradation tests along with a significantly higher mass activity of 300 A g^–1 at an overpotential of 360 mV. The synergism between the amorphous Co_<i>x</i>P_<i>y</i> shell with the Co₃O₄ core is attributed to the observed enhancement in the OER performance of our catalyst. Moreover, detailed literature has revealed that our catalyst is superior to most of the earlier reports

Multi-Ruthenocene Assemblies on an Organostannoxane Platform. Supramolecular Signatures and Conversion to (Ru–Sn)O₂

The reaction of ruthenocene carboxylic acid (RcCOOH) with [<i>n</i>-BuSn­(O)­OH]_<i>n</i>, (Ph₃Sn)₂O, and (PhCH₂)₃SnCl afforded hexameric compounds [RSn­(O)­OOCRc]₆, <i>R</i> = <i>n</i>-Bu (<b>1</b>), Ph (<b>2</b>), and PhCH₂ (<b>3</b>), respectively. These possess a prismane type Sn₆O₆ core which supports a hexa-ruthenocene periphery. Compounds [{<i>n</i>-Bu₂Sn}₂(μ₃-O)­OOCRc₂]₂ (<b>4</b>) and [<i>n</i>-Bu₂Sn­(OOCRc)₂]­(<b>5</b>) were formed in the reaction of RcCOOH with <i>n</i>-Bu₂SnO in 1:1 and 2:1 reactions, respectively. Compound [<i>t</i>-Bu₂Sn­(μ–OH)­OOCRc]₂ (<b>6</b>) is a dimer containing two ruthenocene units, and it was formed in the reaction of RcCOOH with (<i>t</i>-Bu₂SnO)₃ in a 3:1 ratio. Compounds <b>1</b>–<b>6</b> show an extensive supramolecular organization in the solid state as a result of several intermolecular interactions. Compound <b>1</b> could be converted quantitatively to a pure phase of the binary oxide, (RuSn)­O₂ at 400 °C

Reactions of RTeCl₃ (R = 2‑phenylazophenyl) with Diorganophosphinic Acids. Te–C Bond Cleavage and Stabilization of the TeO Motif in an Umbrella-Shaped Te₅O₁₁P₂ Multi-metallacyclic Framework

The reaction of 1,1,2,3,3-pentamethyltrimethylenephosphinic acid <i>cyc</i>P­(O)­OH and (C₆H₁₁)₂P­(O)­OH with monoorganotellurium trichloride RTeCl₃ (R = 2-phenylazophenyl) in benzene at room temperature afforded two pentanuclear complexes, [(RTe)₄(TeO)­(μ-O)₆(<i>cyc</i>PO₂)₂]·THF­(<b>1</b>) [<i>cyc</i>PO₂ = 1,1,2,3,3-pentamethylene phosphinate] and [(RTe)₄(TeO)­(μ-O)₆{(C₆H₁₁)₂PO₂}₂]·2C₆H₆ (<b>2</b>). The reactions leading to the formation of <b>1</b> and <b>2</b> involve a Te–C bond cleavage. <b>1</b> and <b>2</b> are isostructural complexes and contain a Te₄P₂O₆ macrocyclic framework that is part of a Te₅O₁₁P₂ multi-metallacyclic framework. Both of these compounds contain a central inorganic TeO connected to four other tellurium centers through four μ-O bridges

DNA Aided Formation of Aggregated Nb₂O₅ Nanoassemblies as Anode Material for Dye Sensitized Solar Cell (DSSC) and Supercapacitor Applications

Herein, we report the synthesis of niobium pentoxide nanoassemblies in ambient conditions by dissolving niobium pentachloride in aqueous DNA solution and stirring for 30 min with intermittent microwave heating for about 3 min. In the chain-like assemblies thus formed, one may easily alter the specific average diameter of individual particles by varying the concentration ratio of starting precursor solution. The individual size of the Nb₂O₅ particles varied to 7 ± 2 nm ranges, whereas the chain length varied to 1 ± 0.3 μm ranges. The synthesized DNA aided Nb₂O₅ nanoassemblies had been utilized in two different potential energy related applications, such as an anode material in a dye sensitized solar cell (DSSC) and in electrochemical supercapacitor studies. From electrochemical studies on Nb₂O₅ nanoassemblies as an anode for supercapacitor applications, a key finding was that these nanoassemblies exhibited varying specific capacitance (<i>C</i>_S) values for two different morphologies. The small sized chain like nanoassemblies had shown greater specific capacitance than the other one with larger average chain diameter. We had observed <i>C</i>_S values as high as 42.6 F g^–1 at a scan rate of 5 mV s^–1 for Nb₂O₅ nanoassemblies of smaller sizes. Moreover, the cycling study revealed that Nb₂O₅ nanoassemblies possessed a relatively good cycle life with 60% retention of <i>C</i>_S value even after 4000 cycles. The present work will certainly encourage exploring a new opportunity for the synthesis of other metal or mixed metal based oxide materials at low time scales in room temperature using a biomolecular scaffold for further catalysis based applications for various reactions and other energy storage applications such as Li-ion batteries

Pt Nanoparticle Anchored Molecular Self-Assemblies of DNA: An Extremely Stable and Efficient HER Electrocatalyst with Ultralow Pt Content

An efficient electrocatalytic hydrogen evolution reaction (HER) with ultralow loading of Pt has been under intense investigation to make the state-of-the-art Pt economically affordable for water electrolyzers. Here, colloidally synthesized Pt nanoparticles of average size 3.5 ± 0.3 nm were successfully anchored on molecular self-assemblies of DNA. The synthesized Pt@DNA colloidal solution was directly assessed for the electrochemical hydrogen evolution reaction (HER) in 0.5 M H₂SO₄ with a loading of 5 μL of Pt@DNA colloidal solution that corresponds to a Pt equivalent of 15 μg/cm². The excellent adhesion of DNA onto GC and FTO substrate electrodes, the conductivity of DNA, and its stability upon potentiostatic electrolysis and accelerated degradation have made the synthesized, stable Pt@DNA colloidal solution an advanced HER electrocatalyst. The Pt@DNA–GC interface without binder required overpotentials of −0.026 and −0.045 V for current densities of 10 and 20 mA/cm², respectively. The potentiostatic electrolysis and accelerated degradation tests did not affect the electrocatalytic activity, and the observed increase in overpotential was highly negligible. The extreme stability of the Pt@DNA–GC interface was witnessed during an aging study carried out by keeping the working electrode in the electrolyte solution for more than 10 days and acquiring linear sweep voltammograms (LSVs) at intervals of 24 h. Under the same experimental conditions, the commercial Pt/C 10 wt % catalyst with Nafion binder had failed to compete with our colloidal Pt@DNA. These findings certainly indicate the advantageous use of electrocatalyst-loaded DNA molecular self-assemblies for the HER which has never been observed before