Gold-Silver-Gold SERS Nanotag for Oxidation-Resistant Raman Coding
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Solution Overview
Problem
Current gold-silver composite SERS nanotags face issues with silver oxidation during synthesis and limited coding capacity due to the requirement of Raman dyes with sulfhydryl groups for covalent bonding.
Innovation Solution
A high-stability SERS nanotag is developed with a gold core sequentially coated by a silver and gold shell, where the Raman dye is positioned between the shells, and connected through covalent or adsorption, allowing for a wide range of dye options without sulfhydryl groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a silver shell is used to enhance high-frequency electromagnetic field, then the Raman signal intensity is improved, but the silver shell is oxidized during synthesis causing long-term storage impossible
Solution Approach 1:
The patent employs a composite structure consisting of a gold core, silver intermediate layer, and gold outer shell. This composite design allows the silver layer to provide high-frequency electromagnetic field enhancement for strong Raman signals, while the gold outer shell protects the silver from oxidation, enabling long-term storage stability.
Solution Approach 2:
The patent uses a nested core-shell structure where the silver layer is embedded between the gold core and gold outer shell. This nested configuration allows the silver to be protected from direct exposure to the environment while still functioning to enhance the Raman signal, resolving the contradiction between signal intensity and storage stability.
2Strength
If Raman dyes with sulfhydryl groups are used for covalent connection to the nanotag, then the bonding strength is improved, but the coding capacity of the nanotag is limited
Solution Approach 1:
The patent removes the requirement for sulfhydryl groups from the Raman dyes by using a different connection mechanism. The gold outer shell provides a surface that can interact with various types of dyes through multiple bonding modes, extracting the limitation of sulfhydryl group requirement and enabling broader dye selection for enhanced coding capacity.
Solution Approach 2:
The gold outer shell serves multiple functions: it protects the silver layer from oxidation, provides a platform for Raman dye attachment, and enables versatile dye-dye interactions through its surface properties. This multi-functionality allows the system to work with diverse dye molecules regardless of their specific functional groups, thereby increasing coding capacity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The nanotag achieves ultrastrong stability, preventing silver oxidation and dye leakage, enabling ultrahigh coding capacity and desirable monodispersity, with enhanced Raman signal intensity for improved sensitivity in applications like immunoassays.
Implementation Method 1
surface-enhanced Raman scattering (SERS) coding nanotags are broadly applied in sensing, photocatalysis, biological imaging and other fields
Implementation Method 2
adding tetratetrachloroauric acid into ultrapure water, and quickly adding reductant with a mass volume ratio of 1～2％ after boiling
Implementation Method 3
adding ascorbic acid and injecting AgNO3, then centrifuging and resuspending in CTAC
Implementation Method 4
a Raman dye for generating Raman signal is arranged between the silver shell and the gold shell
Data Source
AI summary
A nanotag includes a gold core, the gold core is sequentially coated with a silver shell and a gold shell, and a Raman dye is arranged between the silver shell and the gold shell; further it discloses a making method for a high-stability SERS nanotag that includes the following steps: a. adding tetrachloroauric acid into ultrapure water, after boiling, quickly adding trisodium citrate, continuously boiling for a few minutes, stopping heating, and cooling; b. adding hexadecyl trimethyl ammonium chloride (CTAC) into product obtained in the step a, stirring, and then adding ascorbic acid and AgNO3, and centrifugating and resuspending in the CTAC; c. adding CTAC into product obtained in the step b, stirring, adding a Raman dye, ascorbic acid and sodium hydroxide, injecting a mixture of tetrachloroauric acid and potassium iodide, and centrifuge the mixture and resuspending in the CTAC.