Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields.

Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications

Atomically precise pieces of matter of nanometer dimensions composed of noble metals are new categories of materials with many unusual properties. Over 100 molecules of this kind with formulas such as Au25(SR)18, Au38(SR)24, and Au102(SR)44 as well as Ag25(SR)18, Ag29(S2R)12, and Ag44(SR)30 (often with a few counterions to compensate charges) are known now. They can be made reproducibly with robust synthetic protocols, resulting in colored solutions, yielding powders or diffractable crystals. They are distinctly different from nanoparticles in their spectroscopic properties such as optical absorption and emission, showing well-defined features, just like molecules. They show isotopically resolved molecular ion peaks in mass spectra and provide diverse information when examined through multiple instrumental methods. Most important of these properties is luminescence, often in the visible–near-infrared window, useful in biological applications. Luminescence in the visible region, especially by clusters prot...

Atomically Precise Clusters of Noble Metals: Emerging Link between Atoms and Nanoparticles

Although conventional chemotherapy has been successful to some extent, the main drawbacks of chemotherapy are its poor bioavailability, high-dose requirements, adverse side effects, low therapeutic indices, development of multiple drug resistance, and non-specific targeting. The main aim in the development of drug delivery vehicles is to successfully address these delivery-related problems and carry drugs to the desired sites of therapeutic action while reducing adverse side effects. In this review, we will discuss the different types of materials used as delivery vehicles for chemotherapeutic agents and their structural characteristics that improve the therapeutic efficacy of their drugs and will describe recent scientific advances in the area of chemotherapy, emphasizing challenges in cancer treatments.

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Controlled drug delivery vehicles for cancer treatment and their performance.

Organic Chemistry By Dr. I. L. Finar. Vol. 2: Stereochemistry and the Chemistry of Natural Products. Pp. xi + 733. (London and New York: Longmans, Green and Co., Ltd., 1956.) 40s. net.

Advanced Organic Chemistry

Visible light-responsive photocatalytic technology holds great potential in water treatment to enhance purification efficiency, as well as to augment water supply through the safe usage of unconventional water sources. This review summarizes the recent progress in the design and fabrication of visible light-responsive photocatalysts via various synthetic strategies, including the modification of traditional photocatalysts by doping, dye sensitization, or by forming a heterostructure, coupled with π-conjugated architecture, as well as the great efforts made within the exploration of novel visible light-responsive photocatalysts. Background information on the fundamentals of heterogeneous photocatalysis, the pathways of visible light-responsive photocatalysis, and the unique features of visible light-responsive photocatalysts are presented. The photocatalytic properties of the resulting visible light-responsive photocatalysts are also covered in relation to the water treatment, i.e., regarding the photocatalytic degradation of organic compounds and inorganic pollutants, as well as photocatalytic disinfection. Finally, this review concludes with a summary and perspectives on the current challenges faced and new directions in this emerging area of research.

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Recent developments in heterogeneous photocatalytic water treatment using visible light-responsive photocatalysts: a review

An enhancement in the photocatalytic degradation of low-density polyethylene (LDPE) under solar radiation was accomplished by incorporating titania nanoparticles (TiO2) of size 15 nm in the polythene matrix. The LDPE–TiO2 nanocomposite film was prepared through a simple solution casting technique with 0.1 wt% TiO2 nanoparticles. The photocatalytic degradation of the LDPE–TiO2 nanocomposite was investigated using FE-SEM, FT-IR, XPS, XRD, TGA and photoinduced weight loss analysis. To ensure the wide applicability of the method in environmental remediation, the photocatalytic degradation was carried out under solar radiation. We observed that, when exposed to solar radiation, the composite films showed a significant weight loss of 68% within a period of 200 h, which is a remarkable improvement compared to the previous reports. FT-IR and XPS analysis confirmed the presence of carbonyl groups with a carbonyl index of 19, which led to the degradation of LDPE. FE-SEM analysis revealed the mechanism of degradation of the LDPE matrix on the surface of TiO2 through the formation of pores at the interface. Thus we put forward the development of eco-friendly photodegradable plastic as a solution for the growing concerns of plastic pollution.

Enhancement in the photocatalytic degradation of low density polyethylene–TiO2 nanocomposite films under solar irradiation

Copper(I) n-alkane thiolate systems have been characterized using powder X-ray diffraction, IR spectroscopy, X-ray photoelectron spectroscopy and thermal analyses. The diffraction pattern is composed of a series of peaks, which are indexed to (0k0) reflections of a layered structure. The tilt angle, θ, of the alkyl chains is estimated to be 13°, distinctly different from the silver thiolates, where the chains are near normal to the silver plane. The layers interpenetrate to a small (or negligible) extent. The alkyl chain assembly is different from that of crystalline alkanes. An increase in the alkyl chain order with increase in chain length is evident in the infrared spectra. The chains are essentially all-trans, but gauche conformations are seen near the sulfur end. Upon cooling, an orientational transition occurs resulting in the freezing of the local symmetry around the methyl group. The materials show high thermal stability and desorption is seen only above 500 K. High temperature phase transitions of the materials have been studied by variable temperature powder XRD, variable temperature IR and differential scanning calorimetry. Two distinct transitions; one from an original gauche–trans
(g–t) to a gauche
(g) phase and another subsequent one, to a columnar mesophase, have been identified. The transitions are not fully reversible, conformational changes are observed upon heating and cooling. Thiolates appear to be model systems for the investigation of molecular self-assembly on copper surfaces.

http://www.dstuns.iitm.ac.in/listpdf/95.pdf

An investigation of the structure and properties of layered copper thiolates

Carbon nanostructures as immobilization platform for DNA: A review on current progress in electrochemical DNA sensors.

Self-assembled monolayers (SAMs) have been the preferred material systems to investigate specific properties in several disciplines for nearly 15 years. Advances in various techniques and their application to the study of SAMs have dramatically improved our understanding of these systems. Adaptation of this molecular architecture into three dimensions in the form of monolayer-protected clusters enabled the use of bulk techniques for the study of monolayers. Here we review recent developments in the structural properties and temperature-induced phase transitions of both these SAM structures. While alkanethiols on Au (111) and Ag (111) are taken as archetypal systems to discuss the properties of SAMs on two-dimensional surfaces, their assemblies on Au and Ag cluster surfaces are taken as examples for SAMs on three-dimensional surfaces. A comparison of these two SAMs is provided.

http://www.dstuns.iitm.ac.in/listpdf/108.pdf

Current understanding of the structure, phase transitions and dynamics of self-assembled monolayers on two- and three-dimensional surfaces

http://www.dstuns.iitm.ac.in/listpdf/67.pdf

Neelakandapillai Sandhyarani

Papers

Enhancement in the photocatalytic degradation of low density polyethylene–TiO2 nanocomposite films under solar irradiation

An investigation of the structure and properties of layered copper thiolates

Carbon nanostructures as immobilization platform for DNA: A review on current progress in electrochemical DNA sensors.

Current understanding of the structure, phase transitions and dynamics of self-assembled monolayers on two- and three-dimensional surfaces

A Combined Surface-Enhanced Raman–X-Ray Photoelectron Spectroscopic Study of 2-mercaptobenzothiazole Monolayers on Polycrystalline Au and Ag Films