Biosynthesis of Metallic Nanoparticles and Their Applications - Intracellular Delivery: Fundamentals and Applications - page 396

3.6 Optical, Bio-Imaging, Bio-Labeling Applications

The metallic nanocrystals are held at the center due to their photo-induced nonlinear
optical properties. In particular, the unique optical properties associated with NPs
and their composite materials include a high- or low-refractive index, high transpar-
ency, novel photoluminescence properties, photonic crystal, and plasmon resonance
(Iskandar 2009 ). In nanoregime (hundreds to thousands of atoms) optical and
electro-optical properties of materials can be tuned by varying the physical size of
the crystal, leading to new phenomena, such as surface plasmon resonance in Au
and AgNPs and the size dependent band gap of semiconductor (Talapin et al. 2009 ).
Scientists are therefore able to tailor the electronic structure and properties without
introducing any changes in the sample chemical composition. Methods for NP
synthesis that allow control of NP characteristics, including size distribution, mor-
phology, crystallinity, purity, and composition are of particular note (Iskandar
2009 ). Several methods for the synthesis of NPs and their composite materials have
been reported previously. However, to be feasible for utilization in industrial scale,
the process needs to be simple, low-cost, and able to operate continuously with a
high production rate. Therefore, utilization of the biosynthesis approach may be
beneficial (Table 5 ).
Non-pathogenic, fast-growing fungus Trichoderma viride (habited in dead
organic materials) was used to biosynthesis small (2-4 nm), highly dispersed
AgNPs (Fayaz et al. 2010b ). Interestingly, photoluminescence measurements

Table 5 Electrochemical and sensing applications
NP Organism used Application Reference

Ag Trichoderma viride Blue orange emission

- photoluminiscence

Fayaz et al. ( 2010b )

Ag Parthenium

hysterophorus

Photoluminescence Sarkar et al. ( 2010 )

Ag Coriandrum sativum

leaf

Reverse sat. absorption, optical
limiting

Sathyavathi et al. ( 2010 )

CdTe Saccharomyces
cerevisiae

CdTe QDs for biolabeling and
biosensing

Bao et al. ( 2010a )

CdTe Escherichia coli CdTe QDs for biolabeling and

biosensing

Bao et al. ( 2010b )

Au-Ag Saccharomyces

cerevisiae

Vanillin sensor Zheng et al. ( 2010a )

Au Eggshell Glucose sensor Zheng et al. ( 2010b )

Se Bacillus subtilis H 2 O 2 sensor Wang et al. ( 2010 )

CdS Schizosaccharomyces
pombe

Construction of ideal diode Kowshik et al. ( 2002 )

Au Escherichi coli Direct electrochemistry of

hemoglobin

Du et al. ( 2007 )

Au Scutellaria barbata Direct electrochemistry of 4-NP Wang et al. ( 2009 )