Synthesis and Characterization of Vapour Sensors Based on Photonic Crystals: Performance and Mechanical Studies

JOSEFINA MORRONE; JUAN IGNACIO RAMALLO; PAULA C. ANGELOMÉ; M. CECILIA FUERTES

San Sebastián

Workshop; International Workshop on Self-assembly and Hierarchical Materials in Biomedicine: Drug Delivery, Tissue Engineering, Sensing and Safety Issues; 2018

The design and construction of one-dimensional porous photonic crystals (PCs) and Tamm plasmon based sensors is presented in this work. PCs are multi-layered materials with a periodic modulation of the layers refractive index on a scale comparable to the wavelength of visible light, which gives them intense colours due to reflection.1 These materials can be modified with a thin layer of a noble metal, to give rise to a new type of sensors based on the Tamm plasmon resonance2,3. When these devices are built using porous layers, they can be used as sensors for vapour and liquid substances, which condense inside the pores.The PCs were synthesized by alternated deposition of titanium and silicon oxides with controlled porosity. For the Tamm sensor construction, a gold thin film was deposited over the highest refractive index layer (TiO2) of the PCs2. The gold layer was then protected with a very thin porous titania film, to obtain a more robust device. This protective layer does not significantly affect the device?s optical and sensing properties. In this work, the performance of these sensors was evaluated varying their functionality. For each device the variation of the minimum specular reflectivity of the stop band for the Tamm mode in the presence of organic solvents was measured. The sensing capabilities were determined as a function of time for both liquid and vapour phase of the same compound; and the sensitivity differences between devices was compared. In addition, the mechanical properties of the protective layer were studied by nanoindentation4,5(indentation modulus and hardness) and scratch test (critical load and plastic deformation).6 It was determined that the response to scratching of the protected sensors presents a more elastic performance than the uncoated sensor. The effective protection provided by the coatings during handling was verified.