Microstructured Waveguides with Polyelectrolyte-Stabilized Gold Nanostars for SERS Sensing of Dissolved Analytes

Abstract

A sensor based on microstructured waveguides (MWGs) with a hollow core inner surface covered with polyelectrolyte-layer-stabilized gold nanostars was developed for the SERS sensing of dissolved analytes. A polyelectrolyte-layer coating over the inner surface of glass cladding served as a spacer, reducing nonlinear optical effects in the glass near plasmonic hotspots of nanoparticles, as a stabilizing agent for thermodynamically unstable gold nanostars and as an optical coating for the fine-tuning of MWG bandgaps. This approach can be used to construct different kinds of SERS sensors for dissolved analytes, providing conservation, the prevention of coagulation, and the drying of a liquid sample for the time required to record the signal.

Microfluidic In Situ Patterning of Silver Nanoparticles for Surface-Enhanced Raman Spectroscopic Sensing of Biomolecules

“…The detection limit of RB in an aqueous solution is as low as 1 pM, which is comparable to existing approaches. 49,50 We also explored the application of the SERS microfluidic system in 51 The second spectral region mainly contains bands that resulted from the deoxyriboselinked phosphodiester network (with a shifting peak at ∼1135 cm −1 ). 52 The last one shows the carbonyl stretching modes at ∼1650 cm −1 and the base residues of adenine (A) at ∼1428 and ∼1350 cm −1 .…”

SERS Platform Based on Hollow-Core Microstructured Optical Fiber: Technology of UV-Mediated Gold Nanoparticle Growth

“…Therefore, UV-mediated chloroauric acid reduction on gold seeds demonstrated its potential in improving SERS signal, and this approach was adopted to HC-MOF, due to the ability of HC-MOF to integrate signal across the entire length with low-volume sensing and to mitigate a problem of sample volume change during measurements [ 12 , 16 , 38 ].…”

“…For MOFs, hollow-core microstructured optical fibers (HC-MOFs) have the advantage of reduced background Raman signal from the fiber material (glass), as the light is confined in the hollow core. The structure of HC-MOFs [ 10 , 15 , 16 , 17 ] is defined by a hollow core surrounded by a microstructured cladding array running along the entire fiber length [ 7 ], which enables transmission phenomena that will be discussed and exploited further. Moreover, the utilization of fibers as Raman sensors can solve the problem of unreliable quantitative measurements in drying drops, where sample concentration and focusing may change rapidly during measurement due to drying [ 16 ].…”

“…The structure of HC-MOFs [ 10 , 15 , 16 , 17 ] is defined by a hollow core surrounded by a microstructured cladding array running along the entire fiber length [ 7 ], which enables transmission phenomena that will be discussed and exploited further. Moreover, the utilization of fibers as Raman sensors can solve the problem of unreliable quantitative measurements in drying drops, where sample concentration and focusing may change rapidly during measurement due to drying [ 16 ]. Meanwhile, HC-MOFs allow the work in a low sample volume [ 12 ], for example, a fiber with a hollow core diameter of 240 µm and length of a few centimeters is filled with just a few microliters for analyte probing.…”

“…Plasmonic nanostructures with the analyte may be in a colloidal solution [ 11 , 14 ] or localized on fiber walls [ 12 , 19 , 20 , 21 , 22 ]. Several material combinations have been used for building SERS substrate on fiber walls, among others, such as graphene oxide with poly(diallyl dimethylammonium chloride) (PDDA) and silver nanoparticles (AgNPs) [ 20 ], (3-mercaptopropyl)trimethoxysilane(MPTMS) and gold nanoparticles (AuNPs) [ 21 ], polycationic poly(allylamine hydrochloride) (PAH), and polyanionic poly(styrene sulfonate) (PSS) multiple layers with AuNPs [ 16 ]. Meanwhile, the amount of plasmonic (gold or silver) nanoparticles loaded in such systems is undetermined.…”