Label-Free and Real-Time Photonic Sensors As Analytical Platforms for Environmental Monitoring of Pollutants and Medical Diagnosis

Nowadays, most diagnostic techniques employ labelled samples with fluorescent markers, making analyses time-consuming and expensive. Recently, the development of highly sensitive and label-free nanoporous-based sensors has shown promising results  for applications in areas such as environmental science, biomedical research and medical diagnostics [1-2]. Among the variety of possible materials, nanoporous anodic alumina (NAA) and nanoporous silicon (NPSi) have demonstrated to be excellent sensing platforms by their outstanding set of properties and cost-effective fabrication processes [3-4]. Optical and photonic properties as reflectance, transmittance, absorbance and photoluminescence can be structurally engineered by modifying the effective medium of these nanoporous materials [5-6]. Furthermore, further chemical functionalization endows these nanoporous platforms with chemical selectivity for detection of specific analytes.

In this scenario, herein, we present some strategies for the production of label-free optical sensors based on NAA and NPSi. These strategies are based on the design and fabrication of specific nanoporous structures with enhanced optical response (e.g. microcavities, Fabry-Pérot structures, filters, etc.) and additional chemical functionalization of the inner surface to make these nanostructures sensitive to specific analytes. Figure 1 shows some scanning electron microscopy (SEM) images of NPSi and NAA structures. Furthermore, we analyze and discuss different detection techniques such as reflectometric interference spectroscopy, photoluminescent spectroscopy and test their performance in the detection of proteins and heavy metal ions. Finally, we discuss about the future and potential applications of these sensing platforms in areas such as environmental monitoring, biotechnology, medical diagnostics, drug screening, food safety and security.

References

[1] Amarie, D., Glazier, J.A., Sensors, 2012, 12, 17262.

[2] Rapp, B.E., Gruhl, F.J., Länge, K., Analytical and Bioanalytical Chemistry, 2010, 398, 2403.

[3] Sailor, M.J., Wu, E.C., Advanced Functional Materials, 2009, 19, 3195.

[4] Md Jani, A.M., Losic, D., Voelcker, N.H., Progress in Materials Science, 2013, 58, 636.

[5] Santos, A., Macias, G., Ferré-Borrull, J., Pallarés, J., Marsal, L.F., ACS Applied Materials & Interfaces, 2012, 4, 3584.

[6] Kumeria, T., Santos, A., Losic, D., ACS Applied Materials & Interfaces, DOI: 10.1021/am403465x.

 

Acknowledgements

This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant No. TEC2012-34397 and AGAUR 2009 SGR 549.