This invention provides a fast, cost-effective, and reusable method for fabricating Surface Enhanced Raman Scattering (SERS) substrates using laser-written gratings on single-crystalline gold (Au) films. The resulting SERS substrates demonstrate high sensitivity for detecting trace analytes, including urea and 1,10-phenanthroline, at concentrations as low as 0.01 PPM. Unlike conventional SERS substrates that are often optimized for a specific wavelength and are single-use, this method delivers broadband, reusable substrates with enhanced signal quality and extended storage life. The technique supports scalable fabrication and robust characterization using optical diffraction, without needing chemical reagents.
Figure (1) SERS spectra of urea coated on a grating written on single and poly-crystalline gold films. Measurements were taken (top) near a grating line and (bottom) on an unwritten Au film. Inset shows the SERS spectrum of a diluted sample of milk containing ~30 mg dl-1 urea drop-casted on a single-crystalline grating substrate.
Conventional SERS substrates are often costly, single-use, and optimized only for specific wavelengths. Their fabrication techniques4such as metal island films, electron-beam lithography, and chemical etching4are complex and not easily scalable. There is a strong need for a simpler, reusable, and broadband-compatible SERS substrate that can be fabricated with high resolution, lower cost, and better longevity for real-world sensing applications.
- Reusable SERS Substrates: Substrates can be cleaned and reused multiple times without loss of sensitivity, unlike conventional single-use types.
- Broadband Raman Activity: Works efficiently across a wide range of excitation wavelengths, not limited to a specific laser frequency.
- High Sensitivity Detection: Capable of detecting analytes like urea and phenanthroline at trace concentrations as low as 0.01 PPM.
- Extended Shelf Life: Retains performance for over 18 months, allowing long-term storage and repeated use.
- Simple and Scalable Fabrication: Uses femtosecond laser writing on gold films without requiring chemical etching or surface modification.
The prototype consists of single-crystalline Au (111) films deposited on mica substrates, laser-engraved using a 200 fs yttrium-doped fiber laser at 1030 nm with pulse energies of 0.3–0.6 μJ. Gratings of ~2–3 μm line width are written with a spacing of 8 μm over a 4×4 mm² area. The substrates are characterized using SEM, optical microscopy, and large- area laser diffraction. SERS testing with diluted urea and 1,10-phenanthroline shows Raman signal detection down to 0.01 PPM. Substrates were reused after cleaning and retained their sensing capability without degradation over 18 months.
The technology has been successfully developed and validated in a laboratory setting using direct laser writing on single-crystalline gold films to fabricate reusable, broadband SERS substrates. The substrates have demonstrated high sensitivity in detecting trace levels (as low as 0.01 ppm) of chemical adulterants like urea and 1,10-phenanthroline in milk and water, respectively. Comparative studies show superior surface quality and performance in single-crystalline Au (111) films over poly-crystalline alternatives. The fabrication process is simple, fast, and scalable, and the substrates maintain functionality over extended storage periods. The system is currently operable in controlled lab environments and can be optimized for in-field use through miniaturization into portable, handheld detection units, indicating readiness for pilot-scale deployment.
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This innovation can significantly improve public health monitoring by enabling easy and ultra-sensitive detection of harmful adulterants in consumables like milk and water. Its affordability, reusability, and extended shelf life make it highly suitable for widespread deployment in rural and urban settings alike. It can also benefit environmental testing and biomedical diagnostics by offering a reliable, reagent-free, and portable detection platform, especially in low-resource environments.
- Food Safety and Adulteration Detection: Enables trace detection of adulterants like urea in milk and phenanthroline in water.
- Environmental Monitoring: Suitable for sensing contaminants and trace chemicals in water and soil.
- Biomedical Diagnostics: Detects biologically relevant molecules like urea with high specificity.
- Materials Science and Optoelectronics: Useful in developing plasmonic waveguides, Fresnel lenses, and other nanophotonic devices.
Geography of IP
Type of IP
201721004467
507424