Detection of Methylene Blue Organic Dye Using Silver Nanowires as Surface-Enhanced Raman Spectroscopy Substrates
Horace Andrew Husay1*, Laureen Ida Ballesteros2, Jeremias Armonia1, Debinya Buenafe2, Juferd Cayabyab1, Mary Donnabelle Balela3, Ian Jasper Agulo4, Elmer Estacio1, Arnel Salvador1, Armando Somintac1
1National Institute of Physics, University of the Philippines Diliman, Quezon City, Metro Manila, Philippines
2Materials Science and Engineering Program, University of the Philippines Diliman, Quezon City, Metro Manila, Philippines
3Department of Mining, Metallurgical, and Materials Engineering, University of the Philippines Diliman, Quezon City, Metro Manila, Philippines
4Department of Physical Sciences, University of the Philippines Baguio, Baguio City, Benguet, Philippines
* Presenter:Horace Andrew Husay,
The detection of trace amounts of microbial and inorganic contaminants in liquids is one of the challenges in providing safe drinking water for rural communities. Several techniques such as filtration, sedimentation, chemical precipitation, and Raman spectroscopy have been proposed to quantify the presence of these contaminants. Among these methods, surface-enhanced Raman spectroscopy (SERS) has become an important tool in detecting and fingerprinting of water contaminants with minimal preparation. Nanostructures based on copper, gold, and silver have been established as SERS substrates. The challenge in SERS is to provide low-cost substrates in order to make the technique more accessible to basic laboratories. In this work, we investigated the use of silver nanowires (Ag NWs) as SERS substrates for detecting methylene blue (MB) organic dye. The Ag NWs were synthesized by electroless deposition in ethylene glycol with polyvinyl pyrrolidone as a surfactant. Scanning electron microscopy images confirmed that the Ag NWs have diameters of about 80 nm and lengths of at least 20 μm. The MB dyes with varying concentrations were prepared by dissolving MB powders in water. To prepare the dyes for Raman spectroscopy, the Ag NWs were first dropped on a filter paper followed by an additional drop of the dye with varying concentration. Raman spectroscopy was performed by optically exciting the samples with a 785 nm laser and using a series of optics to collect and focus the signal to a spectrometer equipped with a CCD detector. We have shown that the Ag NWs were able to enhance the Raman signatures of MB by at least a factor of 1000. Furthermore, we were also able to detect MB dye concentrations ranging from 10-2 to 10-7 M.

Keywords: silver nanowires, surface-enhanced Raman spectroscopy, nanotechnology, nanostructures, organic dyes