Microfluidic setup for on-line SERS monitoring using laser induced nanoparticle spots as SERS active substrate

Abstract

A microfluidic setup which enables on-line monitoring of residues of malachite green (MG) using surface-enhanced Raman scattering (SERS) is reported. The SERS active substrate was prepared via laser induced synthesis of silver or gold nanoparticles spot on the bottom of a 200 μm inner dimension glass capillary, by focusing the laser beam during a continuous flow of a mixture of silver nitrate or gold chloride and sodium citrate. The described microfluidic setup enables within a few minutes the monitoring of several processes: the synthesis of the SERS active spot, MG adsorption to the metal surface, detection of the analyte when saturation of the SERS signal is reached, and finally, the desorption of MG from the spot. Moreover, after MG complete desorption, the regeneration of the SERS active spot was achieved. The detection of MG was possible down to 10−7 M concentration with a good reproducibility when using silver or gold spots as SERS substrate.

Study of the Fabrication of Gold Nanoparticle–Graphene-Arrayed Micro/Nanocavities as SERS Substrates Compared to Two Different Angles of Triangular Pyramid Tips

“…Furthermore, MG and the carbaryl molecules were detected by using other methods, respectively. − Li et al used seed-mediated growth and iterative reduction to synthesize Au nanoparticle-coated Fe 3 O 4 magnetic composite nanospheres. MG residues with a detection limit of 10 –7 mol/L were detected using the nanospheres via the SERS technique .…”

“…Buja et al fabricated the Ag or Au nanoparticle spots via focusing a laser beam during the continuous flow. The 10 –7 mol/L MG solution was detected via the SERS active Ag and Au nanoparticle spots . In addition, Bahram et al developed the cloud-point extraction procedure using a pH hydrogel, achieving a detection limit of 4.1 × 10 –9 mol/L for MG in water samples.…”

“…The 10 −7 mol/L MG solution was detected via the SERS active Ag and Au nanoparticle spots. 55 In addition, Bahram et al developed the cloud-point extraction procedure using a pH hydrogel, achieving a detection limit of 4.1 × 10 −9 mol/L for MG in water samples. The extraction process was affected by the HCl and hydrogel concentrations, the salting-out effect, and the extraction time.…”

Detection of Microorganisms in Low-Temperature Water Environments by in situ Generation of Biogenic Nanoparticles

“…The protocol of the DBNG method permits the use of microliter volumes of examined samples and salt solutions. Devices for the production of nanoparticles by chemical methods based on microfluidic labon-a-chip (LOC) technologies have already been demonstrated (Wu et al, 2012;McLeod et al, 2013;Gomez et al, 2014;Buja et al, 2017). So, similar chips for detecting biogenic nanoparticles formed by microorganisms in aqueous samples can be developed (Skladnev et al, 2017b).…”

Raman Spectroscopic Detection in Continuous Microflow Using a Chip-Integrated Silver Electrode as an Electrically Regenerable Surface-Enhanced Raman Spectroscopy Substrate

“…Therefore, several target regeneration methods have been developed to enable multiple measurements with a single SERS substrate. Approaches to remove adsorbed analyte molecules from the target SERS active surface include treatment with chemical solutions such as acids, bases, or organic solvents, − irradiation with light, − or combinations of both including photocatalytic degradation . However, most of the methods mentioned above are rather time-consuming and laborious, and none of them would allow a quasi-instantaneous and reagent-free regeneration of an embedded SERS target.…”