Graphene/silver nanoparticles‐based surface‐enhanced Raman spectroscopy detection platforms: Application in the study of DNA molecules at low pH

Abstract

The aim of this work is to develop a surface‐enhanced Raman spectroscopy (SERS)‐active platform based on a mixture of graphene/Ag nanocomposite and a silver colloid for biomedical applications and to test it in the case of DNA molecules at low pH. Graphene/silver nanocomposites were synthesized by the reduction process and were characterized by transmission electron microscopy, X‐ray powder diffraction patterns, and thermogravimetric analysis. The following graphene/Ag composites were prepared: (a) “thermally reduced graphene oxide” (TRGO), containing about 2–3% silver nanoparticles (AgNPs); (b) TRGO 1 (graphene with crowded AgNPs 20%); and (c) TRGO 2 (graphene with ordered AgNPs 20%). Different mixtures of these systems with a silver colloid were tested not only by ultraviolet‐visible spectrophotometry but also by SERS in the presence of the test substance crystal violet. Moreover, the time stability of the mixtures of graphene/AgNPs composite (TRGO 1) with the silver colloid was tested for crystal violet. Based on these results, the platform with the best SERS enhancement properties was selected for DNA analyses at low pH values. Chemical stability under acidic conditions has been found for nucleic acid systems, in the presence of graphene/crowded AgNPs 20% and silver colloid. This chemical stability has been discussed considering a hydracid catalyzed electrophilic hydration reaction mechanism characteristic to the trans‐1,3‐butadiene‐type building moieties from graphene.

Rapid, Ultrasensitive, and Quantitative Detection of SARS-CoV-2 Using Antisense Oligonucleotides Directed Electrochemical Biosensor Chip

“…This decrease in I G / I D value can be attributed to the surface-enhanced Raman scattering (SERS) caused by the presence of the AuNPs on gold electrodes. Furthermore, the graphitic wavenumber is also downshifted from 1584 to 1581 cm –1 , which indicates the increased π–π interactions between the oligonucleotide (ssDNA) and graphene. ,, Once the viral sample encounters the sensor, viral RNA hybridizes with the AuNP-capped ssDNA, allowing a more accurate electrochemical measurement. The ssDNA probes have been designed based on a previous report from our research group and are described in the following section.…”

Configurational Effects on Strain and Doping at Graphene-Silver Nanowire Interfaces

“…An intensity enhancement of both peaks are observed at the graphene-covered AgNW region compared to graphene only, suggesting a surface-enhanced Raman scattering (SERS) effect [21]. SERS originates from the resonant response from localised surface plasmons, where the metal nanostructure serves as a hotspot to strengthen the surrounding electric field [22]. The intensity ratio I2D/IG being larger than 1 also confirms the enveloping graphene is monolayer [23].…”

Surface-enhanced Raman spectroscopy for bioanalysis and diagnosis

“…12,15 Several environmental parameters, such as pH or temperature, can affect the surface adsorption of the bioanalytes, and thus can influence also their spectral fingerprint. 16 Importantly, SERS is user-friendly, compared with other highly sensitive techniques (such as mass spectrometry), and is applicable to aqueous solutions without the need for complex sample preparation protocols. Overall, SERS is quickly becoming an analytical technique of choice for successful applications in bioanalysis, disease detection and diagnosis.…”