A simple and easier chemical method for preparing spongy gold nanocrystals has been developed on the basis of a modified-citrate reduction technique of the corresponding gold salt at 25 degrees C in the absence of template. These... more
A simple and easier chemical method for preparing spongy gold nanocrystals has been developed on the basis of a modified-citrate reduction technique of the corresponding gold salt at 25 degrees C in the absence of template. These nanocrystals possessed autocatalytic behavior and exhibited pronounced catalytic activity in the borohydride reduction of 4-nitrophenol due to their unique spongy morphology.
... Harunar Rashid, Rama Ranjan Bhattacharjee, and Tarun K. Mandal*. Polymer Science Unit and Centre for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India. J. Phys. Chem. ...
Currently, there is a widespread interest in noble metal nanoparticle's (MNPs) synthesis and application as they play important roles in different areas of materials science. Due to their interesting size-and... more
Currently, there is a widespread interest in noble metal nanoparticle's (MNPs) synthesis and application as they play important roles in different areas of materials science. Due to their interesting size-and shape-dependant physicochemical and optoelectronic properties, these MNPs ...
A simple solution-based method to prepare mainly flowerlike zinc oxide (ZnO) nanostructures using the ascorbate ion as a shape-directing/capping agent at relatively low temperature (ca. 30 and 60 degrees C) was described. However, we... more
A simple solution-based method to prepare mainly flowerlike zinc oxide (ZnO) nanostructures using the ascorbate ion as a shape-directing/capping agent at relatively low temperature (ca. 30 and 60 degrees C) was described. However, we observed that different shapes of hierarchical ZnO nanostructures such as flowerlike, spindlelike, and spherical could be obtained with an increase in the synthesis temperature from 60 to 90 degrees C. The effects of other organic capping agents on the shape of hierarchical ZnO nanostructures were also studied. FTIR, FESEM, and XRD characterization were performed on the formed ZnO nanostructures to understand the role of ascorbate in the growth of flowerlike morphology. The nucleation and growth process can regulate by changing the metal precursor and ascorbate ion concentrations. We were able to identify intermediate nanostructures such as spherical/quasi-spherical and spindle that are very much on the pathway of formation of large, flowerlike ZnO nanostructures. Electron microscopy results indicated that these spherical/quasi-spherical ZnO nanoparticles might aggregate through oriented attachment to produce spindlelike and flowerlike nanostructures. On the basis of these results, a possible growth mechanism for the formation of flowerlike ZnO nanostructures was described. The optical properties of these differently shaped ZnO nanostructures were also described. The catalytic activities of the as-synthesized spherical and flowerlike ZnO nanostructures were tested in the Friedel-Crafts acylation reaction of anthracene with benzoyl chloride. The catalysis results indicated that the catalytic activity of flowerlike ZnO nanostructures is slightly higher than the spherical counterpart.
We describe a general one-step facile method for depositing gold nanoparticle (GNP) thin films onto any type of substrates by the in situ reduction of AuCl(3) using a newly designed redox-active ionic liquid (IL), tetrabutylphosphonium... more
We describe a general one-step facile method for depositing gold nanoparticle (GNP) thin films onto any type of substrates by the in situ reduction of AuCl(3) using a newly designed redox-active ionic liquid (IL), tetrabutylphosphonium citrate ([TBP][Ci]). Various substrates such as positively charged glass, negatively charged glass/quartz, neutral hydrophobic glass, polypropylene, polystyrene, plain paper, and cellophane paper are successfully coated with a thin film of GNPs. This IL ([TBP][Ci]) is prepared by the simple neutralization of tetrabutylphosphonium hydroxide with citric acid. We also demonstrate that the [TBP][Ci] ionic liquid can be successfully used to generate GNPs in an aqueous colloidal suspension in situ. The deposited GNP thin films on various surfaces are made up of mostly discrete spherical GNPs that are well distributed throughout the film, as confirmed by field-emission scanning electron microscopy. However, it seems that some GNPs are arranged to form arrays depending on the nature of surface. We also characterize these GNP thin films via UV-vis spectroscopy and X-ray diffractometry. The as-formed GNP thin films show excellent stability toward solvent washing. We demonstrate that the thin film of GNPs on a glass/quartz surface can be successfully used as a refractive index (RI) sensor for different polar and nonpolar organic solvents. The as-formed GNP thin films on different surfaces show excellent catalytic activity in the borohydride reduction of p-nitrophenol.
Abstract The promise of nanotechnology becomes limitless with the possibility of having functionalized molecular agents to illuminate the reservoir and intervene to alter adverse oil recovery conditions. The future reality of the... more
Abstract The promise of nanotechnology becomes limitless with the possibility of having functionalized molecular agents to illuminate the reservoir and intervene to alter adverse oil recovery conditions. The future reality of the reservoir nanoagents concept is herein lab ...
The synthesis of solvent-adoptable monometallic Ni and NiCo alloy nanochains by a one-pot solution phase reduction method in the presence of poly(4-vinylphenol) (PVPh) is demonstrated. The elemental compositions of the as-prepared alloys... more
The synthesis of solvent-adoptable monometallic Ni and NiCo alloy nanochains by a one-pot solution phase reduction method in the presence of poly(4-vinylphenol) (PVPh) is demonstrated. The elemental compositions of the as-prepared alloys are determined by inductively coupled plasma optical emission spectroscopy (ICP-OES) and energy-dispersive X-ray spectroscopy (EDS), which are matching well with the target compositions. The morphology analysis by TEM and FESEM confirms that the nanochains are made up of organized spherical monometallic Ni or bimetallic NiCo alloy nanoparticles (NPs). However, there is no nanochain formation when the alloy is prepared without the polymer PVPh. A possible mechanism for the formation of such NiCo alloy nanochains is discussed. The X-ray diffraction and selected area electron diffraction patterns reveal that the Ni/NiCo alloys are polycrystalline with fcc structure. The obtained Ni or NiCo alloy nanostructures are ferromagnetic with very high coercivity. The polymer Ni/NiCo alloy nanochains are dispersible in both water and organic media that makes them versatile enough to use as catalysts in the reactions carried out in both types of media. The catalytic activities of these Ni/NiCo alloy nanochains are extremely high in the borohydride reduction of p-nitrophenol in water. In organic solvents, these nanochains can act as efficient catalysts, under ligand-free condition, for the C−S cross-coupling reactions of various aryl iodides and aryl thiols for obtaining the corresponding cross-coupled products in good to excellent yield up to 96%. The NiCo nanochain also successfully catalyzes the C−O cross-coupling reaction in organic medium. A possible mechanism for NiCo alloy nanochain-catalyzed cross-coupling reaction is proposed.
ABSTRACT Chiral core-shell nanostructures containing raspberry-like gold cores and well-defined dense organic shells are synthesized by an in situ method using a natural antioxidant catechin as the reducing agent. This method is flexible... more
ABSTRACT Chiral core-shell nanostructures containing raspberry-like gold cores and well-defined dense organic shells are synthesized by an in situ method using a natural antioxidant catechin as the reducing agent. This method is flexible and enables control over the shell thickness by adjusting the molar ratio of catechin to HAuCl4. Transmission electron microscopic analysis shows the formation of core-shell nanostructures with somewhat raspberry-shaped gold cores. The proposed mechanism explains that catechin reduces Au3+ to metallic Au to gold nanostructures and gets oxidized to different oligomeric products that are adsorbed in situ and assembled through H-bonding and form a thick organic shell around the generated gold nanostructures. Each of these oxidized forms of catechin is well-characterized by FTIR, ESI-MS, and MALDI-TOF-MS spectroscopies. This reaction follows a radical pathway as confirmed by electron paramagnetic resonance spectroscopy. Due to the presence of a compact and dense shell, the rate of gold core dissolution sharply decreases compared to that of the dissolution of monolayer protected Au nanoparticles when etched with KCN solution. The optical activity of the core-shell nanostructure is the result of the interaction between chiral shells and gold cores as observed by circular dichroism (CD) spectroscopy. The chiral core-shell Au nanostructures exhibit a CD band at the plasmon resonance frequency ([similar]596 nm). Finally, these chiral core-shell nanostructures are used as an effective catalyst in the borohydride reduction of p-nitrophenol.
ABSTRACT We report a simple method for shape-controlled synthesis of iron oxide spinels such as magnetite (Fe3O4) and maghemite (gamma-Fe2O3) nanostructures using a thermoresponsive polymer poly(vinyl methyl ether) (PVME) by the alkaline... more
ABSTRACT We report a simple method for shape-controlled synthesis of iron oxide spinels such as magnetite (Fe3O4) and maghemite (gamma-Fe2O3) nanostructures using a thermoresponsive polymer poly(vinyl methyl ether) (PVME) by the alkaline hydrolysis of iron salt at low temperature (20 degrees C). Microscopic analysis confirmed the formation of needle- and flower-shaped iron oxide nanostructures depending on reaction conditions. High-resolution transmission electron microscopic analysis of the needle- and flower-shaped nanostructures as well as their corresponding selected area electron diffraction patterns revealed that the formed nanostructures are crystalline in nature. X-ray diffraction study reveals the formation of well-crystalline pure Fe3O4 and gamma-Fe2O3 nanostructures under different reaction conditions. Fourier transform Infra-red spectroscopic analysis confirms the adsorption of PVME on the surface of iron oxide nanostructures. Finally, the magnetic properties of gamma-Fe2O3 and Fe3O4 nanostructures is studied that shows the superparamagnetic behavior of the formed iron oxide nanostructures.
ABSTRACT We report an interesting property of carbon dots: they emit light under charge injection. We synthesized carbon dots in diameter about 20 nm using wet chemistry methods. The photoluminescence quantum efficiency of the carbon dots... more
ABSTRACT We report an interesting property of carbon dots: they emit light under charge injection. We synthesized carbon dots in diameter about 20 nm using wet chemistry methods. The photoluminescence quantum efficiency of the carbon dots dissolved in water was about 11%. We observed strong electrogenerated chemiluminescence (ECL) from the sample. This observation of ECL from carbon dots indicates that they could be a good candidate material for carbon-based electroluminescent devices.
