The SERS (Surface Enhanced Raman Scattering) technique is known to be a powerful method for chemical and biological sensing applications. It is an extemly effective and fast tool to analyze molecules by highly increasing the Raman signal intensity coming from molecules which have been attached to our 4n4SERS substates
01 | SECURE
Robust and easy to use. With their EXTREMELY HIGH DAMAGE THRESHOLD, 4n4SERS substrates won't let you down, even if full power of your Raman laser is applied for best results.
02 | SENSITIVE
Distinct strong LOCALIZED SURFACE PLASMON RESONANCE (LSPR) effect of HighQuant nanoparticles un-locks orders of magnitude improvement of the limit of detection.
03 | REPRODUCIBLE
Reproducibility of the nanoparticles utilized significantly improves the SPOT TO SPOT REPRODUCIBILITY and thus speed, cost and reliability of the characterization.
Figure 1 shows a Transmission Electron Microscopy (TEM) image of the surface of a 4n4SERS substrate. Due to the small size and their Localized Plasmon Surface Resonance (LSPR) eﬀect, noble metal nanoparticles have optical and electromagnetic properties that are significantly different from those of bulk materials. They show an enhanced surface-enhanced Raman scattering (SERS) and chemical stability as a result. These properties make them of value in diagnostics at molecular level by taking advantage of the enhanced optical properties of HighQuant NPs.
Figure 1: Transmission electron microscopy (TEM) images of the surface of a 4n4SERS substrate 
4n4SERS Substrates Optical Properties – Distinct strong Localized Surface Plasmon Resonance (LSPR)
The strong light-matter interaction of the metallic NPs occurs because the conduction electrons on the metal surface undergo a collective oscillation when excited by light at specific wavelengths. This oscillation results in unusually strong scattering and absorption properties. That allows metallic NPs to show effective absorbance (scattering & absorption) cross sections several times larger than their physical cross section.
4n4SERS Substrates Optical Properties – Laser Power Scaling - Damage Threshold
Figure 3: shows the Laser power scaling using 4n4SERS substrates. No sign of damage up to an intensity of > 3 kW/cm² has been observed. Full laser power can be applied supporting lowest limit of detection and full utilization of high-end Raman systems. Even at maximum laser power of 373 mW, neither damage nor a hysteresis in the result was observed. It can be stated that the damage threshold is beyond the maximum power density obtained.
Figure 2: 4n4SERS Type B substrates with 8 active SERS sensitive spots each, optimized for NIR applications (785 & 1064 mn).
Figure 3: Laser power scaling using 4n4SERS substrates. No sign of damage up to an intensity of > 3 kW/cm², allowing for full utilization of high-end Raman systems .
Figure 2: shows 4n4SERS substrates combining ease of use end economy by integrating 8 active SERS sensitive spots onto a single unit, compatible to a standard microscopy slide and optimized for 785 & 1064 nm. Please ask for other wavelengths.
4n SERS Substrates Optical Properties – Reproducibility of Measurements
Figure 4: shows the spot to spot comparison of measurements from 3 different test points from a 4n4SERS substrate, demonstrated close to the limit of detection using a moderate Raman laser power level of 145 mW @ 785 nm. For a confidence level of 1 x σ, the reproducibility is better than +/- 12%. The analyte characterized is melamine in water at a concentration of 0.5 ppm.
Figure 4: Reproducibility tests compare results from the 3 different test points of one 4n SERS substrate 
Limit of Detection for 4n SERS substrates
Supported by the high quality and concentration of HighQuant metallic nanoparticles, 4n4SERS substrates can detect analytes in extremely low levels of concentration. As an example, 100 ppb of melamine can be detected at a power level of 50% from the Ramanlaser in water (Figure 5). Again, the reproducibility of the measurement which was carried out on 3 independent test spots at the limit of detection is remarkable and shows a reproducibility of of better than +/- 13% for a confidence level of 1 x σ.
Figure 5: Reproducibility tests compare results from the 3 different test points of one 4n4SERS substrate at the limit of detection. 
The results were obtained in the project MODERNA under the Programme Beyond Europe, sponsored by the Austrian Federal Government in collaboration with the Austrian Research Promotion Agency FFG under the contract # 874147. Specific measurements were provided by  Federal University of Pernambuco, UFPE, Recife, Brazil, and  RECENDT Research Center for Non Destructive Testing GmbH, Linz, Austria.
4n4SERS substrates offer an excellent platform for obtaining the most from your Raman setup:
SECURE / Robust and easy to use. With their EXTREMELY HIGH DAMAGE THRESHOLD, 4n4SERS substrates won't let you down, even with when full power of your Raman laser is utilized for best results
SENSITIVE Distinct strong LOCALIZED SURFACE PLASMON RESONANCE (LSPR) effect of HighQuant nanoparticles un-locks orders of magnitude improvement of the limit of detection.
REPRODUCIBLE results mean improved efficiency, less time and money spent due to excellent SPOT TO SPOT REPRODUCIBILITY.
Multiple use allows you to utilize 8 individual active SERS sensitive spots integrated on each SERS stipe, compatible to a microscopy slide. 4n4SERS substrates are available in different packages, providing you with 16 ato 96 individual active SERS sensitive spots of 5 mm in diameter.