Templated green synthesis of plasmonic silver nanoparticles in onion epidermal cells suitable for surface-enhanced Raman and hyper-Raman scattering

Abstract

SummaryWe report fast and simple green synthesis of plasmonic silver nanoparticles in the epidermal cells of onions after incubation with AgNO3 solution. The biological environment supports the generation of silver nanostructures in two ways. The plant tissue delivers reducing chemicals for the initial formation of small silver clusters and their following conversion to plasmonic particles. Additionally, the natural morphological structures of the onion layers, in particular the extracellular matrix provides a biological template for the growth of plasmonic nanostructures. This is indicated by red glowing images of extracellular spaces in dark field microscopy of onion layers a few hours after AgNO3 exposure due to the formation of silver nanoparticles. Silver nanostructures generated in the extracellular space of onion layers and within the epidermal cell walls can serve as enhancing plasmonic structures for one- and two-photon-excited spectroscopy such as surface enhanced Raman scattering (SERS) and surface enhanced hyper-Raman scattering (SEHRS). Our studies demonstrate a templated green preparation of enhancing plasmonic nanoparticles and suggest a new route to deliver silver nanoparticles as basic building blocks of plasmonic nanosensors to plants by the uptake of solutions of metal salts.

Present and Future of Surface-Enhanced Raman Scattering

“…The high sensitivity of SEHRS with respect to the interaction and orientation of the molecules at surfaces enables probing a very local surface environment using vibrational information that is inaccessible by SERS. , This technique will help improve our understanding of molecule–nanostructure interactions, including those utilized in SERS probing. Surface-enhanced hyper Raman scattering spectra of dyes and biological molecules under resonant and nonresonant conditions are typically collected using photon flux densities of 10 26 –10 29 photons cm –2 s –1 , respectively, both from pulsed ,,,,,, and tightly focused continuous-wave (cw) lasers . Many SEHRS experiments have been done using silver nanostructures. ,, More recently, gold NRs and their aggregates were also shown to provide optical properties that are specifically suited to support enhancement of SEHRS …”

“…804,812 This technique will help improve our understanding of molecule−nanostructure interactions, including those utilized in SERS probing. Surface-enhanced hyper Raman scattering spectra of dyes and biological molecules under resonant and nonresonant conditions are typically collected using photon flux densities of 10 26 −10 29 photons cm −2 s −1 , respectively, both from pulsed 795,806,808,814,815,817,820 and tightly focused continuouswave (cw) lasers. 821 Many SEHRS experiments have been done using silver nanostructures.…”

Nanostructured Assemblies of Gold and Silver Nanoparticles for Plasmon Enhanced Spectroscopy Using Living Biotemplates

“…Raman spectroscopy is an analytical technique commonly used in biomedical applications. Over the years, a wide variety of molecular targets have been investigated by SERS using active nanoparticles, mainly gold and silver [2,3,11,12,[26][27][28][29][30][31][32][33][34]. The plasmonic origin of the phenomenon is fully understood [19,37], and nowadays the major effort focuses on the fabrication of new substrates for SERS [38].…”

“…Over the last decade, new methods were developed to minimize the use and generation of hazardous substances, particularly for the synthesis of silver nanoparticles using plant extracts or juices [10]. These green routes provided a huge number of reducing and stabilizing agents [11], which opened the possibility to form new hybrid materials that combine the structural specificity of biological systems with the properties of metallic nanoparticles [12]. Several biological structures have been used as effective biotemplates for the synthesis of noble metal nanoparticles, [13,14], usually aiming to obtain nanoparticles with a fine shape control and sharp size distribution.…”

Mechanistic insights into plasmonic photocatalysts in utilizing visible light

“…Numerous researches have proved that Au and Ag NPs can be synthesized from the chemicals extracted from plants and microorganisms such as fungi, algae, bacteria and yeasts [ 156 – 161 ]. Different types of biomolecules available in plants, for example, polysaccharides, phenolics, or flavonoids are capable of producing metal nanoparticles of different sizes and shapes [ 162 ]. This phytosynthesis is more favourable than that which occurs in microorganisms because it is fast and cost effective and can be readily scaled for realistic applications [ 163 ].…”