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.

Pradeep Thalappil

Department Of Chemistry

Panikkanvalappil Ravindranathan Sajanlal

Agglomeration

Particle size analysis

Polyaniline

Scanning electron microscopy

FLOWER-LIKE NANOPARTICLES

NEEDLE-LIKE AGGREGATES

POLYANILINE TEMPLATES

Nanostructures

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

Purpose: The purpose of this study was to understand the subsurface thermal behaviour of a tissue phantom embedded with large blood vessels (LBVs) when exposed to near-infrared (NIR) radiation. The effect of the addition of nanoparticles to irradiated tissue on the thermal sink behaviour of LBVs was also studied. Materials and methods: Experiments were performed on a tissue phantom embedded with a simulated blood vessel of 2.2 mm outer diameter (OD)/1.6 mm inner diameter (ID) with a blood flow rate of 10 mL/min. Type I collagen from bovine tendon and agar gel were used as tissue. Two different nanoparticles, gold mesoflowers (AuMS) and graphene nanostructures, were synthesised and characterised. Energy equations incorporating a laser source term based on multiple scattering theories were solved using finite element-based commercial software. Results: The rise in temperature upon NIR irradiation was seen to vary according to the position of the blood vessel and presence of nanoparticles. While the maximum rise in temperature was about 10 °C for bare tissue, it was 19 °C for tissue embedded with gold nanostructures and 38 °C for graphene-embedded tissues. The axial temperature distribution predicted by computational simulation matched the experimental observations. Conclusions: A different subsurface temperature distribution has been obtained for different tissue vascular network models. The position of LBVs must be known in order to achieve optimal tissue necrosis. The simulation described here helps in predicting subsurface temperature distributions within tissues during plasmonic photo-thermal therapy so that the risks of damage and complications associated with in vivo experiments and therapy may be avoided. © 2016 Informa UK Limited, trading as Taylor &amp; Francis Group.

Fulltext

International Journal of Hyperthermia

Subsurface thermal behaviour of tissue mimics embedded with large blood vessels during plasmonic photo-thermal therapy

Photothermal therapy using (Near Infrared) NIR region of EM spectrum is a fast emerging technology for cancer therapy. Different types of nanoparticles may be used for enhancing the treatment. Though the treatment protocols are developed based on experience driven estimated temperature increase in the tissue, it is not really known what spatiotemporal thermal behavior in the tissue is. In this work, this thermal behavior of tissue models is investigated with and without using nanoparticles. An increased temperature inside tissue compared to surface is observed which is counter intuitive from the present state of knowledge. It is shown from fiber level microstructure that this increased temperature leads to enhanced damage at the deeper parts of biomaterials. Nanoparticles can be utilized to control this temperature increase spatially. A multiple scattering based physical model is proposed to explain this counterintuitive temperature rise inside tissue. The results show promising future for better understanding and standardizing the protocols for photothermal therapy. Copyright © 2014 American Scientific Publishers.

Journal of Biomedical Nanotechnology

Anomalous subsurface thermal behavior in tissue mimics upon near infrared irradiation mediated photothermal therapy

The success of laser hyperthermia in the treatment of cancer depends on the extent of heat diffusion to the cancerous tissue. Understanding and optimising hyperthermia treatment requires accurate measurement and control of temperature distribution. This paper reports experimental and theoretical results of surface temperature distribution and thermal lagging effect in tissue-mimics during laser irradiation. Experiments are conducted on bio-tissue mimics embedded with and without gold nanostructures irradiated by a continuous wave diode-pumped solid state laser having wavelength of 1064 nm. The experimental results of surface temperature distribution are compared with the computational prediction, obtained by solving numerically the Pennes bio-heat transfer based on classical Fourier model and on the dual phase lag model. Based on the multiple scattering phenomenon a new model for the laser attenuation in tissues is proposed. It compares well with the experimental data. In addition, the qualitative nature of damage to bio-tissue upon laser irradiation has been examined experimentally using atomic force microscopy to demonstrate the denaturation potential of the surface temperature, when gold nanostructures are used to mitigate temperature rise. © 2013 Elsevier Masson SAS. All rights reserved.

International Journal of Thermal Sciences

Investigation of non-Fourier effects in bio-tissues during laser assisted photothermal therapy

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.

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

An efficient method to introduce magnetic attributes to highly complex Au mesostructures by overlayer growth is demonstrated. The overlayer is nanostructured in all the cases investigated. A possible mechanism for the reduction of ions on the surface of Au mesoflowers and the consequent formation of hybrid mesoflowers is discussed. We studied the magnetic hysteresis behavior of Au/Ni, Au/Co, and Au/Pt/Ni mesoflowers at room temperature. Compared to the bulk metals, a decrease in saturation magnetization was observed in all the three hybrid magnetic mesoflowers, which may be due to the nanoscale structure. Assemblies of various magnetic mesoflowers extending over hundreds of micrometers on indium tin oxide (ITO) substrates have been made by magnetic field-induced self-assembly. Particles are assembled to form elongated chains, oriented parallel to the direction of the applied magnetic field. © 2010 American Chemical Society.

Journal of Physical Chemistry C

Magnetic mesoflowers: Synthesis, assembly, and magnetic properties

Macromolecular Rapid Communications

Macromol. Rapid Commun. 12/2007

Polymer

Electrically conductive hydrogel composites made of polyaniline nanoparticles and poly(N-vinyl-2-pyrrolidone)

Nano Letters

Polyaniline Nanofiber Gas Sensors:  Examination of Response Mechanisms

Synthesis and Optical Properties of “Branched” Gold Nanocrystals

Chemistry of Materials

Highly Oriented Gold Nanoribbons by the Reduction of Aqueous Chloroaurate Ions by Hexadecylaniline Langmuir Monolayers

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

Journal	Langmuir
ISSN	07437463
Open Access	No