We are synthesizing our Ag or AuNPs using different reducing agents available, we would like to know if they influence the role of the colorimetric sensor.
If so, which is the best reducing agent for a colorimetric sensor application using Ag and AuNPs?
[A]The size, shape, porocity and aspect ratio of the Ag/Au NP can change with with the change of reducing agents.
The optical properties of metal nanoparticles are highly influenced by the size, shape, and dielectric environment.
As a colorimetric sensor involves two properties- the absorbance and scattering of light which change with the change of reducing agents.
[B] The suitability of a reducing agent depending upon the characteristic needed for any metal NP. For example:
(i) the best antibacterial activity was observed on using AgNPs prepared from NaBH4 as reducing agent and polyvinyl pyrrolidone (PVP) as stabilizer or protecting agent.
(ii) Given the interest in biomedical applications of Au Np ,now the use of EDTA as a reducing agent is proved to be better than formaldehyde which was previously most commonly used.
My point of discussion is coordination chemistry weather the sensing metal is coordinated to Ag or reducing agent if so if we change the reducing agents do metal sensing will also change?
The changed format of your query is explained in two steps:
[A] Depending upon the nature of reducing agent, the silver/ gold salts get reduced to Ag/Au NP of different sizes either by Chemical Reactions(which may involve complex formation) or Bio chemical Reactions .
For example EDTA reduces the Au(III) salts to Au NP via complex formation while Ag(I) salts[ generally AgNO3 ]when exposed to the fungus Fusarium oxysporum are reduced in solution to Ag NP[5-15 nm) via the formation of an extremely stable silver hydrosol which are stabilized in solution by proteins secreted by the fungus. Here the reduction of the metal ions occurs by an enzymatic process.
[B] It may be noted that the reducing agent has no role to play in the sensor ( after it has produced the NP of the required size/shape). The sensor material results in the formation of a monolayer / multilayer( generally monolayer) of Ag/Au NP adsorbates.
Hello Vinod,
The optical properties of metal nanoparticles are highly influenced by the size, shape,and mixed nature of light and dielectric environment. As a colorimetric sensor involves two properties- the absorbance and scattering of light and illumination is also important here which change with the change of reducing agents.
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