It has been well documented that ideal SERS conditions occur in the nano sized gaps between metal nanoparticles 1,2 . Aggregation of the nanoparticles is a very simple and effective way to form these gaps3,4. We have investigated the 2 salts most commonly used throughout the literature as aggregating agents. Their absorption spectra were measured over time as the nanoparticles gradually aggregate and fall out of suspension, as well as their effects on SERS spectra. It was found that adding these salts to colloidal silver nanoparticles causes them to form large clusters which provide huge enhancement to the SERS spectra. This is due to the analyte molecules being situated in newly formed “hot spots” between the nanoparticles. This method is shown to be a cheap and simple way to achieve very large SERS enhancement.
Pterins are a group of biological compounds which have potential for use as a possible cancer diagnostic. This
paper considers reproducibility issues using Surface Enhanced Raman Scattering (SERS) for application in pterin
detection.
Raman spectroscopy is a very useful tool for analysing compounds, however its ability to detect low concentrations of a substance are very limited. Surface Enhanced Raman Spectroscopy (SERS) overcomes that issue and is reported to have achieved single molecule detection. Its main shortcoming is the reproducibility of SERS spectra. The variation in signal strength prevents SERS from being usable as a quantitative analytical technique. This variability have been investigated in this work and key factors in improving reproducibility have been considered.
Pterins, such as xanthopterin are studied in this paper. Pterins are a group of biological compounds that are found in
nature in colour pigmentation and in mammal’s metabolic pathways. Moreover, they have been identified in abnormal
concentrations in the urine of people suffering from certain kinds of cancer. The potential for pterin’s use as a cancer
diagnostic points to the importance of SERS detection for pterins.
Optical techniques toward the realization of sensitive and selective biosensing platforms have received considerable attention in recent times. Techniques based on interferometry, surface plasmon resonance, and waveguides have all proved popular, while spectroscopy in particular offers much potential. Raman spectroscopy is an information-rich technique in which the vibrational frequencies reveal much about the structure of a compound, but it is a weak process and offers poor sensitivity. In response to this problem, surface-enhanced Raman scattering (SERS) has received much attention, due to significant increases in sensitivity instigated by bringing the sample into contact with an enhancing substrate. Here we discuss a facile and rapid technique for the detection of pterins using SERS-active colloidal silver suspensions. Pterins are a family of biological compounds that are employed in nature in color pigmentation and as facilitators in metabolic pathways. In this work, small volumes of xanthopterin, isoxanthopterin, and 7,8-dihydrobiopterin have been examined while adsorbed to silver colloids. Limits of detection have been examined for both xanthopterin and isoxanthopterin using a 10-s exposure to a 12 mW 532 nm laser, which, while showing a trade-off between scan time and signal intensity, still provides the opportunity for the investigation of simultaneous detection of both pterins in solution.
Optical techniques towards the realisation of sensitive and selective biosensing platforms have received a
considerable amount of attention in recent times. Techniques based on interferometry, surface plasmon resonance,
field-effect transistors and waveguides have all proved popular, and in particular, spectroscopy offers a large range
of options. Raman spectroscopy has always been viewed as an information rich technique in which the vibrational
frequencies reveal a lot about the structure of a compound. The issue with Raman spectroscopy has traditionally
been that its rather low cross section leads to poor limits-of-detection. In response to this problem, Surface-enhanced
Raman Scattering (SERS), which increases sensitivity by bringing the sample in contact with many types of
enhanceing substrates, has been developed. Here we discuss a facile and rapid technique for the detection of pterins
using colloidal silver suspensions. Pteridine compounds are a family of biochemicals, heterocyclic in structure, and
employed in nature as components of colour pigmentation and also as facilitators for many metabolic pathways,
particularly those relating to the amino acid hydroxylases. In this work, xanthopterin, isoxanthopterin and 7,8-
dihydrobiopterin have been examined whilst absorbed to SERS-active silver colloids. SERS, while far more
sensitive than regular Raman spectroscopy, has its own issues relating to the reproducibility of substrates. In order to
obtain quantitative data for the pteridine compounds mentioned above, exploratory studies of methods for
introducing an internal standard for normalisation of the signals have been carried out.e
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