A comparative study of the surface-enhanced Raman scattering (SERS) effect of the spherical gold nanoparticles (NPs) and highly uniform and oriented gold nanotriangles (NTs), anchored on indium tin oxide (ITO) coated conducting glass surfaces is reported. Contact and non-contact mode atomic force microscopic (AFM) analyses confirmed that all the triangles observed are equilateral and uniformly stacked. The NTs-coated ITO exhibited intense near-infrared (NIR) absorption and showed an extremely strong SERS activity than the spherical NPs. The NTs showed a very good SERS enhancement factor on the order of 4 × 10 8. The results are interpreted in terms of the increased density of hot spots on the NTs-coated surface. © 2009 American Scientific Publishers.

Pradeep Thalappil

Department Of Chemistry

Panikkanvalappil Ravindranathan Sajanlal

Atomic force

COATED SURFACE

Comparative studies

CONDUCTING GLASS

ELECTRIC-FIELD ASSISTED GROWTH

Gold Nanoparticles

Gold nanotriangles

Hot spot

Indium tin oxide

Near-infrared absorption

NON-CONTACT MODE

SEED-MEDIATED METHOD

SERS

SERS ENHANCEMENT

SURFACE ENHANCED RAMAN

Surface-enhanced Raman scattering

Atomic force microscopy

Electric fields

Gold

Infrared devices

Raman scattering

Surfaces

Fulltext

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

Journal of Nanoscience and Nanotechnology

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 reply to the comments by Diao and coworkers on electric-field-assisted growth of highly uniform and oriented gold nanotriangles on conducting glass substrates, is presented. The authors say that SEM, AFM, and optical images are presented, which suggest that nanotriangles (NTs) are indeed formed. In order to confirm the formation of the NTs, samples were imaged using dynamic force microscopy (DFM), and the results were confirmed for both the parent and the NT surfaces. The non-contact-mode topographic and phase AFM images of NTs that were synthesized under optimized condition showed that most of the NTs observed had an edge length of 400-450 nm. In the UV-vis absorption spectra, the feature at 520nm can be attributed to the transverse plasmon absorption, as is the case for other anisotropic structures. The authors are convinced that the results indicate the electric-field-assisted formation of NTs and were not caused by artifacts of AFM.

Advanced Materials

Reply to "Comments on electric-field-assisted growth of highly uniform and oriented gold nanotriangles on conducting glass substrates"

A novel methodology to fabricate highly aligned array of equilateral gold NTs on ITO substrates was demonstrated. The ITO glass substrate was cleaned with a mild detergent solution, sonicated with deionized water and soaked in 10 % HCl solution for activation. They were then washed with water, dried and annealed at 450°C for 7 h and cooled in a desiccator. The glass slides were dipped in 30 mM APTMS solution in methanol for 1 h. Afterwards, they were washed with methanol and water in sequence and kept at 110°C for 2h. Seed coated substrate and an identical blank ITO glass plate were kept at 5 mm apart such that the conducting surfaces faced each other and were connected to the -ve and +ve terminals of a DC power supply. Contact mode AFM measurements were carried out using a reflux coated nanosensors silicon cantilever. It was observed that at higher potentials, irregular shapes are obtained.

Electric-field-assisted growth of highly uniform and oriented gold nanotriangles on conducting glass substrates

In this paper, we describe a method for the growth of gold nanowires and nanoplates starting from a bilayer array of gold seeds, anchored on electrically conducting indium tin oxide (ITO) substrates. This is based on a seed-mediated growth approach, where the nanoparticles attached on the substrate through molecular linkages are converted to nanowires and nanoplates at certain cetyltrimethylammonium bromide (CTAB) concentration. Our modified approach can be used to make nanowires of several tens of micrometers length at a lower CTAB concentration of 0.1 M. The length of the nanowires can be varied by adjusting the time of the reaction. As the concentration of CTAB was increased to 0.25 M, the nanoparticles got converted to nanoplates. These Au nanoplates are (111) oriented and are aligned parallel to the substrate. © Indian Academy of Sciences.

Journal of Chemical Sciences

Growth of anisotropic gold nanostructures on conducting glass surfaces

The Journal of Physical Chemistry C

Hot Spots in Ag Core−Au Shell Nanoparticles Potent for Surface-Enhanced Raman Scattering Studies of Biomolecules

Proceedings of the National Academy of Sciences

Designing, fabricating, and imaging Raman hot spots

Crystal Growth & Design

Formation of Gold Nanoplates on Indium Tin Oxide Surface: Two-Dimensional Crystal Growth from Gold Nanoseed Particles in the Presence of Poly(vinylpyrrolidone)

Electric field assisted growth of highly surface enhanced Raman active gold nanotriangles

Journal	Journal of Nanoscience and Nanotechnology
ISSN	15334880
Open Access	No