When monochromatic light such as a laser is targeted over a sample, a part of it is transmitted, some is absorbed and some is scattered. Most of the scattered light will have the same wavelength as the incident light.
But a small portion of the scattered light approximately 1 in 107 photons is shifted in wavelength because the molecules have experienced vibrations and rotations during the interaction with the light. The spectrum of this wavelength-shifted light is called the Raman spectrum.
Raman spectra consist of sharp bands that are typical of the specific molecule in the sample. Each line of the spectrum corresponds to a specific vibrational mode of the chemical bonds in the molecule. Since each molecule has its own Raman spectrum, this can be used to characterize the molecular structure and identify chemical compounds.
A small fraction of light is scattered at energies different than that of the incident photons (Raman effect).
The Raman effect is an inelastic process and was first observed in 1928 by Sir.Chandrasekhara Venkata Raman and he was awarded Nobel prize in the year 1930.
Raman spectroscopy is a non-destructive and fast technique. However since only a small fraction of molecules in any sample gives a Raman signal, it is relatively insensitive.
Surface Enhanced Raman Spectroscopy
Surface Enhanced Raman Spectroscopy (SERS) can increase the weak Raman signal by many orders of magnitude, and can extend the range of applications suitable for Raman spectroscopy.
SERS is a surface sensitive technique that results in the enhancement of Raman scattering by molecules adsorbed on to the rough metal surfaces.
The enhancement factor of a molecule that is adsorbed on a rough metal surface can be much more intense in the order of 104 – 1015, than the signal it would emit if deposited on a plain substrate.
This huge enhancement has enabled this technique to be very sensitive that enables detection of even a single molecule.
The mechanism of SERS was first observed in the year 1977 and has ever since generated a huge research interest into Raman spectroscopy being used as a major analytical tool.
It has been demonstrated that the huge enhancement in signal arises mainly due to 2 major mechanisms namely,
Electromagnetic enhancement – proposed by Jeanmarie and Van Duyne in the year 1977, Chemical enhancement – proposed by Albrecht and Creighton in the year 1977.
Highly Sensitive Nanometal Raman Substrates
Highly sensitive Raman substrates from Yashnanotech provide an exclusive solution for trace level molecular analysis using SERS.
These substrates can increase the Raman signal intensity by many orders of magnitude thereby enabling detection of molecules at ultra low concentrations. Such high sensitivity levels reduce your detection limits to less than micromolar concentrations.
Yashnanotech’s highly sensitive Raman substrates provide a cost effective solution for SERS, not compromising on performance.
High enhancement up to 1 million times is achieved due to our unique manufacturing procedures. Substrates are designed such that the nanoparticles have the desired size range and morphology.
These highly sensitive Raman substrates can be used for both dipping as well as spotting techniques. These substrates can be used for both aqueous and organic media.
These SERS substrates are accompanied by an incinerator that facilitates environment friendly disposability of the active area that has been subjected to various chemical and biological analysis. The active area is burnt into ashes inside the incinerator with the nanoproduct converted to the bulk form.
- Colossal enhancement of Raman signal
- Highly Sensitive Nanometal Raman substrates provide an huge enhancement in Raman signal that enables detection of molecules at ultra low concentrations and a very less volume.
- Exceptional cost effectiveness
- These Raman substrates are exceptionally cost effective compared with those available in the international market but the performance is on par with those commercially available.
- Compatible with standard Raman spectrometers
- These Raman substrates can be used directly with the existing Raman spectrometers.
- Easy to handle during investigation
- These Raman substrates are flexible and easy to handle during investigations. Being flexible and easy to use is a key advantage from users point of view.
- Use and throw
- Highly Sensitive Nanometal Raman substrates can be used and thrown away.
- Environment friendly disposability
- An incinerator is provided along with these substrates facilitates environment friendly disposability of the active area. The active area is burnt into ashes inside the incinerator with the nanoproduct converted to the bulk form.
How to use Highly Sensitive Nanometal Raman Substrates
To achieve the maximum advantage of these Highly sensitive Raman substrates, samples should be deposited onto the active surface and analysed with a standard Raman instrument. Different sample deposition techniques such as dipping and spotting can be employed.
Level indicator is the point up to which the substrates can be dipped into samples under investigation. SERS active area is the region where silver nanoparticles are coated in a desired size range and distribution in order to achieve huge enhancement.
Applications of Highly Sensitive Nanometal Raman Substrates
Chemical and biological detection
Pharmaceutical drug development
Typical SEM micrographs of Highly Sensitive Nanometal Raman Substrates
The above images show Ag nanometal specially designed for SERS activity.
The nanometal exhibits the required roughness with non-rounded edges.
Raman spectrum of thiophenol as the analyte molecule recorded on Yashnanotech’s highly sensitive nanometal Raman substrate after dipping in a 1 mM thiophenol solution for 30 mins. The Raman spectrum was recorded on a LabRAM HR apparatus (Horiba, USA) with an excitation wavelength of 632.8 nm from a He-Ne laser and 5mWcm-2.
Substrate performance at ultra low concentrations and volume
Raman spectra of a 0.01 mM concentration of thiophenol by spotting 10 µl
Even at such low concentrations and volume of the analyte, the SERS substrate could detect the molecule under investigation and also give a high Raman intensity.
Substrate performance after dipping into DD water
Two SERS substrates were taken (A and B). While ‘A’ was used as supplied by Yashnanotech, ‘B’ was immersed in 10 ml of distilled water for 30 minutes and dried. This process was repeated consecutively 10 times. Then, ‘B’ was dried and coated with 1mM of thiophenol. Raman spectra recorded around the 1079 cm-1 peak are shown above. The substrate ‘B’ produced similar spectrum as ‘A’, demonstrating that the nanometal was intact.
Raman substrates parameter
Sample spectra of some analytes recorded on
Highly Sensitive Nanometal Raman Substrates
Below examples demonstrate how a strongly SERS active molecule such as thiophenol may be used to promote the Raman activity of molecules which may be moderate in SERS.
A small drop of blood was spotted on a Yashnanotech SERS substrate coated with a monolayer of thiophenol. The spectrum shown is obtained by substracting the thiophenol.
Haemoglobin spectrum obtained by the difference method.
Raman substrates are supplied in units of 5.
For orders please contact
Tel: +91 9820056184