Sustainable Synthesis of Multifunctional Nanomaterials for Sensing and Catalytic Applications

Abstract

Nanotechnology has enable us to develop various novel and advanced materials with
unique optical, catalytic, magnetic, electrical and, structural properties for various
exciting applications. With the progress of nanoscience and technology, emphasis of the
materials are changed from simple nanomaterials to the multi-functional nanomaterials
(MFNMs) because of their improved as well as multiple activities. In general, the
MFNMs are made with the combination of different components in the same structure,
which in turn not only show the additive properties of individual components but also
new properties because of the synergistic effect. Multifunctionality in nanomaterials
can be achieved in two ways, either by changing the morphology (anisotropic, hollow),
or the composition (doped, QDs, heterostructures, core/shell, and yolk/shell). Over the
years, continuously growing research interest on this area is mainly because of unique
advantages in various applications such as catalysis, sensors, environmental remediation,
photovoltaics, energy storage, biomedical, and so on. In recent years, the sustainable
routes of nanomaterials are preferred over the conventional chemical routes, which is
also applicable for the MFNMs.
In view of the importance of MFNMs, the overall aim of this thesis is to develop
novel MFNMs via green synthesis route with improved properties for sensing and
catalytic applications. In this study following materials were developed: the hollow and
doped nanostructures (TiO2, -Fe2O3) synthesized using natural fibers templates. The
metallic (Au, Ag, Pd), alloy (Au-Pd), and metal oxides/hydroxide (-Fe2O3, β-FeOOH)
NPs were synthesized using the renewable resources (green tea extract and glucose)
in aqueous medium. The carbon dots (C-dots) and graphitic carbon were synthesized
from tender coconut water and glucose under hydrothermal condition, respectively. The
Ag NPs were deposited on semiconductor (AgBr, TiO2) and polymer (PVP) materials
by photo-mediated and dissolution approach for the development of plasmonic catalyst,
respectively. The C-dots were used for fluorometric thiamine sensor with ultra-low level
detection (280 nM) and bio-imaging of fungus cells. β-FeOOH nanorods were used for
sulfide ions and thiamine detection with ultra-low level detection limits of 2.19 μM and
44 nM, respectively. The Ag deposited PVP structures showed enhanced SERS activity
for the sensing and detection of very low level (nM) organic molecules. Metal NPs (Au,
Ag, Pd) decorated -Fe2O3 magnetic hollow tubes showed excellent recyclable catalytic
reduction of 4-nitrophenol to 4-aminophenol. Carbon-doped high surface area TiO2
multi-tubes showed visible light induced photo-reduction activity for Cr(VI) reduction
to Cr(III). Graphitic carbon coated Au-Pd alloy showed stable, durable, and enhanced
electro-catalytic activity for ethanol oxidation. The Au/AgBr–Ag and TiO2/Ag core/shell
heterostructures were also showed very good visible-light driven photocatalytic and
photo-electrochemical activity. The present research work addresses a new perspective
for green synthesis of distinct novel MFNMs and provide valuable insight into the role
of the multi-functional properties to stimulate the outstanding sensing and catalytic
applications.