A strategy for the preparation of bimetallic mesoflowers (MFs) has been demonstrated by a simple overgrowth reaction. We make hybrid MFs containing Au core and shells of different metals, such as Ag and Pt, by tuning the experimental conditions so as to study region-specific overgrowth. This selective growth is attributed to the specific binding affinity of cetyltrimethylammonium bromide (CTAB) at different crystal planes of Au MF surfaces. We also studied the region-specific, composition dependent surface-enhanced Raman scattering (SERS) activity of single bimetallic MFs to understand, their chemical environment. Substrate effects on the SERS activity at single particle level were evaluated by a comparative study of the Raman images of Au, Au/Ag, and Au/Pt MFs. Region-specific SERS activity exhibited by single Au/Ag MF provides an insight into the SERS activity of bimetallic MFs over their monometallic analogues. © 2010 American Chemical Society.

Pradeep Thalappil

Department Of Chemistry

Panikkanvalappil Ravindranathan Sajanlal

Cetyltrimethylammonium bromide

Chemical environment

Comparative studies

CRYSTAL PLANES

Experimental conditions

RAMAN IMAGES

Selective growth

Single particle

Specific binding

Substrate effects

Surface-enhanced Raman scattering

AMMONIUM COMPOUNDS

Binding energy

Bromine compounds

Platinum

Raman scattering

Silver

Substrates

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Langmuir

How low can you go? The visual detection of 2,4,6-trinitrotoluene and Hg2+ at the sub-zeptomole level is demonstrated. This was achieved using a hybrid material that allowed for the development of a single-particle, single-molecule detection technique, which may be the ultimate in ultra-trace sensitivity with selectivity. Copyright © 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Angewandte Chemie - International Edition

Selective visual detection of TNT at the sub-zeptomole level

We present the synthesis of highly anisotropic nickel nanowires (NWs) and large area, free-standing carpets extending over cm 2 area by simple solution phase chemistry. The materials can be post-synthetically manipulated to produce hybrid tubes, wires, and carpets by galvanic exchange reactions with Au 3+, Ag +, Pt 2+, and Pd 2+. All of these structures, especially the hybrid carpets and tubes, have been prepared in bulk and are surface enhanced Raman scattering (SERS) active substrates. Molecules of relevance such as dipicolinic acid (constituting 5-15% of the dry weight of bacterial spores of Bacillus anthracis), dinitrotoluene, hexahydro-1,3,5-triazine (RDX), and trinitrotoluene at nanomolar concentrations have been detected. An enhancement factor of ∼10 10 was observed for the Ni-Au nanocarpet. The reusability of the Ni-Au nanocarpet for SERS applications was tested 5 times without affecting the sensitivity. The reusability and sensitivity over large area have been demonstrated by Raman microscopy. Our method provides an easy and cost effective way to produce recyclable, large area, SERS active substrates with high sensitivity and reproducibility which can overcome the limitation of one-time use of traditional SERS substrates. © 2012 The Royal Society of Chemistry.

Nanoscale

Functional hybrid nickel nanostructures as recyclable SERS substrates: Detection of explosives and biowarfare agents

A simple and versatile method for the synthesis of a wide range of polyaniline (PANI)-based ID and 2D gold nanostructures of uniform size distribution with high colloidal stability is demonstrated. All the nanostructures were synthesized from oligoaniline-coated gold nanoparticle precursors. The nanostructures include nanowires of various sizes, nanoplates, and flower-like nanoparticles. These nanowires showed a pH-dependent shape transformation. Needle-like aggregates of Au/PANI were formed as the pH of the nanowire solution changed to 2.5. At higher pH (10.2), nanowires converted into spherical nanoparticles. Core-shell particles of Au/PANI composites have been achieved by the reversal of the pH of the nanowire from 10.2 to 2.9. The morphology of the nanostructures was studied by TEM and SEM. FTIR, UV-vis, XRD, and LDI MS were utilized for the characterization of the chemical composition of the nanostructures. A mechanism for the nanowire growth is proposed. © 2008 American Chemical Society.

Wires, plates, flowers, needles, and core-shells: Diverse nanostructures of gold using polyaniline templates

Angewandte Chemie International Edition

Plasmon-Driven Synthesis of Triangular Core–Shell Nanoprisms from Gold Seeds

Chemical Society Reviews

Synthesis, properties and perspectives of hybrid nanocrystal structures

Synthesis of Aqueous Au Core−Ag Shell Nanoparticles Using Tyrosine as a pH-Dependent Reducing Agent and Assembling Phase-Transferred Silver Nanoparticles at the Air−Water Interface

Bimetallic mesoflowers: Region-specific overgrowth and substrate dependent surface-enhanced raman scattering at single particle level

Journal	Langmuir
ISSN	07437463
Open Access	No