2 research outputs found
Sensitive Cylindrical SERS Substrate Array for Rapid Microanalysis of Nucleobases
In
this work, a cylindrical-substrate array for surface-enhanced
Raman scattering (SERS) measurements was developed to enable analysis
of nucleobases in a few microliters of liquid. To eliminate uncertainties
associated with SERS detection of aqueous samples, a new type of cylindrical
SERS substrate was designed to confine the aqueous sample at the tip
of the SERS probe. Poly(methyl methacrylate) (PMMA) optical fibers
in a series of different diameters were used as the basic substrate.
A solution of poly(vinylidene fluoride)/dimethylformamide (PVDF/DMF)
was used to coat the tip of each fiber to increase the surface roughness
and facilitate adsorption of silver nanoparticles (AgNPs) for enhancing
Raman signals. A chemical reduction method was used to form AgNPs
in and on the PVDF coating layer. The reagents and reaction conditions
were systematically examined with the aim of estimating the optimum
parameters. Unlike the spreading of aqueous sample on most SERS substrates,
particularly flat ones, the new SERS substrates showed enough hydrophobicity
to restrict aqueous sample to the tip area, thus enabling quantitative
analysis. The required volume of sample could be as low as 1 μL
with no need for a drying step in the procedure. By aligning the cylindrical
SERS substrates into a solid holder, an array of cylindrical substrates
was produced for mass analysis of aqueous samples. This new substrate
improves both reproducibility and sensitivity for detection in aqueous
samples. The enhancement factor approaches 7 orders in magnitude with
a relative standard error close to 8%. Using the optimized conditions,
nucleobases of adenine, cytosine, thymine, and uracil could be detected
with limits approaching a few hundreds nanomolar in only a few microliters
of solution
Electrochemical Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy: Correlating Structural Information and Adsorption Processes of Pyridine at the Au(hkl) Single Crystal/Solution Interface
Electrochemical methods are combined
with shell-isolated nanoparticle-enhanced
Raman spectroscopy (EC-SHINERS) for a comprehensive study of pyridine
adsorption on Au(111), Au(100) and Au(110) single crystal electrode
surfaces. The effects of crystallographic orientation, pyridine concentration,
and applied potential are elucidated, and the formation of a second
pyridine adlayer on Au(111) is observed spectroscopically for the
first time. Electrochemical and SHINERS results correlate extremely
well throughout this study, and we demonstrate the potential of EC-SHINERS
for thorough characterization of processes occurring on single crystal
surfaces. Our method is expected to open up many new possibilities
in surface science, electrochemistry and catalysis. Analytical figures
of merit are discussed