Detection of DNA bases and environmentally relevant biomolecules and monitoring ssDNA hybridization by noble metal nanoparticles decorated graphene nanosheets as ultrasensitive G‐SERS platforms

Abstract

Surface‐enhanced Raman scattering (SERS) and graphene‐mediated surface‐enhanced Raman scattering (G‐SERS) are attractive analytical techniques for the detection of chemical and biological molecules at a single‐molecule level registering their chemical fingerprints. Graphene‐based surface enhancement (or G‐SERS) boosted traditional SERS phenomenon producing signal enhancement from both electromagnetic (EM) and chemical enhancement (CE) mechanisms. Thus, graphene oxide (GO) nanosheets coated with silver (Ag [30 nm]) and gold (Au [40 nm]) nanoparticles smart array platforms, for direct detection and differentiation of DNA bases, namely, adenine (A), cytosine (C), guanine (G), thymine (T), and environmental relevant β‐carotene (β‐C) and malachite green (MG) biomolecules, are developed. The size and interparticle gap were controlled via dispersion and loading on GO surface to achieve optimal enhancement factors. The morphology of these substrates was characterized by scanning electron microscopy and atomic force microscopy. The Raman spectra consisted of discrete bands occurring at (A: 732.8 cm−1; C: 792 cm−1; G: 658 cm−1; T: 796 cm−1; β‐C: 1416 cm−1; MG: 1174 cm−1) that are characteristic of molecular modes of vibration and serve as chemical fingerprint of three‐dimensional structure, intramolecular interaction and steady‐state dynamics, of biomolecule ensemble. The GO‐decorated nanoparticles are capable of sensitive biomolecular detection over a broad concentration range 100 nM to 100 μM with limit of detection (LOD) noted at <1 ppm for A, C, G, T, β‐C, and MG. Moreover, the experimental results illustrated five to six orders of magnitude signal enhancement in the following order: GO/Ag30 > GO/Au40 > Ag30 > Au40 > GO. Moreover, ssDNA probe and complementary target C‐ssDNA were monitored simultaneously during hybridization on the same substrates assigned confidently to base, local chemical structure, and global conformation of resulting dsDNA. The experimental findings suggest a strong GO‐nanoparticle coupling leading to interfacial orbital hybridization (charge transfer) and polarization affected by biomolecule orientation, and it will help in designing ultrasensitive platforms covering range of inorganic nanoparticles and nanostructured surfaces for a wealth of biomedicine and environmental applications.

Applications of surface‐enhanced Raman spectroscopy in environmental detection

“…In discussing SERS nanosubstrates, we have also covered two types which are being used with increasing frequency: graphene‐based and flexible SERS nanosubstrates. Graphene‐based SERS substrates tend to have higher enhancement due to the formation of hot spots in gaps between nanoparticles and graphene structures 43 . Graphene substrates also confer fluorescence quenching abilities and have good biocompatibility, making them optimal for detecting biomolecules in environmental samples.…”

“…Furthermore, a graphene monolayer consists of sp 2 ‐hybridized carbon atoms and is a π‐conjugated system. This allows analyte molecules to adsorb to the surface and interact electronically with the metal and graphene surface, causing Raman enhancement due to the charge‐transfer resonance between the analyte and the metal or graphene surface 43 . One study utilized G‐SERS to detect DNA bases, malachite green (MG) and beta‐carotene 43 .…”

“…This allows analyte molecules to adsorb to the surface and interact electronically with the metal and graphene surface, causing Raman enhancement due to the charge‐transfer resonance between the analyte and the metal or graphene surface 43 . One study utilized G‐SERS to detect DNA bases, malachite green (MG) and beta‐carotene 43 . Through the use of GO nanosheets coated with AgNPs and AuNPs in arrays, small biomolecules were efficiently detected, suggesting that graphene‐based SERS substrates can be used for sensitive and selective detection of particular biological and environmental molecules of interest.…”

Development of core‐satellite‐shell structured MNP@Au@MIL‐100(Fe) substrates for surface‐enhanced Raman spectroscopy and their applications in trace level determination of malachite green in prawn

“…[54,55] In the meantime, the Raman signal of the analyte molecules in the electromagnetic field will be greatly amplified and this enhancement principle is called electromagnetic (EM) enhancement. [56] Generally, the EM enhancement effects of different SERS substrates are closely related to the type, shape, size, and gap between SERS-active nanoparticles. [15,57,58] SERS substrates constructed by spherical AuNPs are widely utilized for SERS detection due to their excellent stability and enhancement effects.…”

Flexible Surface‐Enhanced Raman Scattering Substrates: A Review on Constructions, Applications, and Challenges

“…[ 18,21,88–94 ] Depositing nanostructured noble metal particles on the surface of flexible graphene is the common method to fabricate graphene‐based flexible SERS substrates. [ 21,95–97 ] In addition, in situ reduction of the noble metal ion with a high state is also adopted by researchers in recent years. [ 98,99 ] Further, to increase the contact area between 2D graphene and 3D spatial molecular profiles, the thermally controlled graphene flexible substrate has been fabricated, which with the capability of wrapping on the surface of a 3D biological sample.…”