Spectroscopic analysis methods provide a great deal of information about material properties, but require complex optics and costly equipment to do so. Recent research at UNAM (National Nanotechnology Research Center) suggests that mobile phone cameras may have what it takes to lower the costs.
The research in question, conducted by Dr. Aykutlu Dâna and published in ACS Photonics, details the acquisition of Raman signals (spectral signatures produced in response to laser excitation, the distributions of which are unique to specific chemical bonds) using the image sensor of a conventional smartphone, and the comparison of this information to that obtained by standard detection equipment. While the camera was no match for the sensors specialized for the job, it was nonetheless able to detect the Raman signals associated with silicon and ethanol, suggesting that it had the sensitivity necessary to perform Raman spectroscopy. And indeed, when the phone was outfitted with the
tools necessary for more detailed spectral analysis (i.e., a collimator and a transmission grating), the composite device was able to successfully resolve the chemical signatures associated with those materials.
The possibility of utilizing smartphones for the appraisal of material properties has attracted international attention, and Dr. Dâna’s work was highlighted in the prestigious physics journal Nature Photonics.
When the spectra were amplified using a signal-enhancing plasmonic substrate, the mobile phone camera proved even more capable, detecting the transitory signals (or “blink events”) that occur when a molecule briefly associates with the signal-enhancing regions of the plasmonic surface. These events allow the extraction of chemical information from single molecules, and have drawn much attention as a means to investigate the changes associated with the movement of an individual molecule. In tandem with the above-mentioned spectrometer setup, the phone camera was also found to be capable of performing this type of analysis, at a frequency of 30 frames per second, in real time.
“This work shows the potential of nanophotonic engineering and plasmonics as a route to high-performance, low-cost sensing solutions,” comments Dr. Dâna. He also notes that he and his team are now working on novel plasmonic surfaces that may in the near future allow array sensing of biomolecules with a mobile phone. Such an approach could enable point-of-care self-monitoring of a patient’s diagnostic parameters, reducing overall health-related costs and assisting in early diagnosis.
Dr. Dâna’s research not only serves as a testament to the progress of contemporary mobile devices, but may also facilitate the development of low-cost handheld equipment for the advanced chemical analysis of a diverse array of materials.
By Alper Özkan (MSN/PhDIII)