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There is a growing interest in the design and development organic and inorganic nanomaterials for spectroscopic signal enhancements. In this context three systems will be discussed: (i) single particle spectroscopic investigations and surface enhanced Raman scattering (SERS) of plasmonic nanoassemblies, (ii) chiral luminescence from self-assembled organic nanomaterials and (iii) chiral plasmonic assemblies for the detection of neurodegenerative diseases. Chiral organic nanomaterials synthesized through the self-assembly of molecules have been widely studied using Circular Dichroism (CD). A relatively new technique that is employed in the investigations of chiral luminescent systems is the Circularly Polarized Luminescence (CPL).1 CPL at the respective emission wavelength originates from the chiral centers that exist in a dissymmetric environment in the excited state. The enhancement of luminescence dissymmetry during the self-assembly of molecules is investigated in the solid and solution states. The anisotropy in luminescence is modulated through the controlled self-assembly of perylene bisimide bichromophoric systems. The organic nanomaterials function as an efficient source of chiral light.
Among various inorganic nanomaterials studied, noble metal nanoparticles have been widely used in surface-enhanced Raman scattering (SERS), wherein enhanced Raman signals are observed for molecules placed on the surfaces of nanoparticles.2 The major challenge is to create hotspots; the regions on the nanoparticle surface that exhibits huge electric field enhancements. Isolated Au nanorods, nanorod dimers and quartets were fabricated and used as substrates in SERS for the detection of trace amounts of analyte molecules. Single particle investigations of the nanoassemblies helped in direct structure-property correlation. Chirality can be induced in metal nanoparticles by interacting with chiral biomolecules or templates.3 Combination of plasmonic nanomaterials with protein amyloid fibrils led to the formation of hybrid nanostructures that were used for the detection of various neurodegenerative disorders such as Parkinson’s and prion diseases.
1. J. Kumar, T. Nakashima, T. Kawai, J. Phys. Chem. Lett. 2015, 6, 3445 (Perspective Article).
2. R. Thomas, J. Kumar, J. George, M. Shanthil, G. N. Naidu, R. S. Swathi, K. G. Thomas J. Phys. Chem. Lett. 2018 Accepted (Perspective Article)
3. J. Kumar, K. G. Thomas, L. M. Liz-Marzan, Chem. Commun. 2016, 12555 (Feature Article). |