Search

A versatile and efficient surface‐enhanced Raman scattering (SERS) substrate based on a hybrid aerogel composed of reduced graphene oxide (rGO) decorated with silver nanoparticles (AgNPs), suitable for highly sensitive label‐free detection of chemical and biological species, is presented. The simple and low‐cost one‐pot hydrothermal synthesis allows obtaining of a 3D nanostructured spongy‐like matrix that shows good spatial distribution of Ag nanoparticles in intimate contact with rGO flakes, characterized by means of several morphological, structural, and compositional techniques. The nanostructured material, tested by SERS analysis with both rhodamine 6G (R6G) and 4‐mercaptobenzoic acid (MBA), shows a satisfying SERS efficiency, quantified in terms of minimum detectable concentration of 10−10 and 10−7m, corresponding to on‐ and off‐resonant excitation, respectively. The versatility of chemical/biochemical functionalization is successfully demonstrated by exploiting different routes, by immobilizing both protoporphyrin IX (PRPIX) and hemin (H) that take advantage of π−π non‐covalent bonding with the graphene layers, as well as thiol‐ended oligonucleotides (DNA probes/aptamers) directly grafted on the AgNPs. Finally, after the successful integration of the hybrid aerogel into a microfluidic chip, the biorecognition of miR222 is obtained demonstrating the reliability of the aerogel substrate as SERS platform for biosensing. [ABSTRACT FROM AUTHOR]

A sharpened control over the parameters affecting the synthesis of plasmonic nanostructures is often crucial for their application in biosensing, which, if based on surface-enhanced Raman spectroscopy (SERS), requires well-defined optical properties of the substrate. In this work, a method for the microfluidic synthesis of Ag nanoparticles (NPs) on porous silicon (pSi) was developed, focusing on achieving a fine control over the morphological characteristics and spatial distribution of the produced nanostructures to be used as SERS substrates. To this end, a pSi membrane was integrated in a microfluidic chamber in which the silver precursor solution was injected, allowing for the real-time monitoring of the reaction by UV–Vis spectroscopy. The synthesis parameters, such as the concentration of the silver precursor, the temperature, and the flow rate, were varied in order to study their effects on the final silver NPs' morphology. Variations in the flow rate affected the size distribution of the NPs, whereas both the temperature and the concentration of the silver precursor strongly influenced the rate of the reaction and the particle size. Consistently with the described trends, SERS tests using 4-MBA as a probe showed how the flow rate variation affected the SERS enhancement uniformity, and how the production of larger NPs, as a result of an increase in temperature or of the concentration of the Ag precursor, led to an increased SERS efficiency. [ABSTRACT FROM AUTHOR]

• In this study, l -cysteine is proposed as reducing/capping agents for the production of Ag nanonets. • Ag nanonets showed different morphologies by varying the synthesis conditions. • Ag nanonets were deposited onto PDMS membranes and their SERS performance tested against 4-MBA as non-resonant probe. • A correlation between morphology and SERS response has been proposed. Highly-branched plasmonic nanostructures are interesting substrates to be exploited in Surface-Enhanced Raman Scattering (SERS) detection, as sources of efficient Raman "hot-spots". In this study, l -cysteine is proposed as reducing/capping agents for the production of Ag nanonets showing different morphologies by varying the synthesis conditions. Substrates are coupled to PDMS membranes and characterized by Raman spectroscopy using 4-MBA to define their SERS performance. Experimental evidences confirm that only the thinnest structures are able to guarantee significant SERS responses. [ABSTRACT FROM AUTHOR]

In this work, metallic silver flower-like and aerogel-like nanostructures deposited onto hydrophobic dielectric substrates (HF-treated Si and PDMS) showed interesting potentialities as solid SERS substrates aimed to high sensitive molecular detection and quantitation. In detail, the nanostructures were incubated in 4-MBA solutions at 10−2 M–10−9 M concentrations. The quantitative analysis confirmed a monotonic increase of the SERS signal intensity as a function of the 4-MBA concentration, following a Langmuir model, thus suggesting a chemisorption phenomenon. The best homogeneity and adhesion strength in liquid media of Ag nanostructures to the solid substrates were reached for the flower-like systems and the aerogel-like ones compared to traditional polyhedral nanostructures (taken as reference substrate), thus making them extremely appealing as a solution for the development of SERS-based sensors. [ABSTRACT FROM AUTHOR]