Demonstration of cross reaction in hybrid graphene oxide/tantalum dioxide guided mode resonance sensor for selective volatile organic compound

Abstract This paper experimentally demonstrates a crossed reaction of pure and hybrid graphene oxide (GO)/tantalum dioxide (TaO2) as a volatile organic compound (VOC) absorber in a guided mode resonance (GMR) sensing platform. The proposed GMR platform has a porous TaO2 film as the main guiding layer, allowing for more molecular adsorption and enhanced sensitivity. GO is applied on top as an additional VOC absorber to increase the selectivity. The hybrid sensing mechanism is introduced by varying the concentration of the GO aqueous solution. The experimental results show that the pure TaO2-GMR has a high tendency to adsorb most of the tested VOC molecules, with the resonance wavelength shifting accordingly to the physical properties of the VOCs (molecular weight, vapor pressure, etc). The largest signal appears in the large molecule such as toluene, and its sensitivity is gradually reduced in the hybrid sensors. At the optimum GO concentration of 3 mg/mL, the hybrid GO/TaO2 -GMR is more sensitive to methanol, while the pure GO sensor coated with GO at 5 mg/mL is highly selective to ammonia. The sensing mechanisms are verified using the distribution function theory (DFT) to simulate the molecular absorption, along with the measured functional groups measured on the sensor surface by the Fourier transform infrared spectroscopy (FTIR). The crossed reaction of these sensors is further analyzed by means of machine learning, specifically the principal component analysis (PCA) method and decision tree algorithm. The results show that this sensor is a promising candidate for quantitative and qualitative VOCs detection in sensor array platform

Fabrication and Characterization of Ag–Ta Thin Films by Co-Magnetron Sputtering as Alternative Layer for High Reflection of NIR Radiation

Silver–tantalum (Ag–Ta) thin films were fabricated by magnetron co-sputtering on silicon (Si) wafer (100) and glass slide substrates at room temperature. The Ag–Ta thin films were prepared at various deposition times of 5, 10, 20 and 30 s and the physical, structural and optical properties of the Ag–Ta thin films were investigated. It was determined that the thicknesses of the films were 7, 9, 17 and 33 nm, respectively. The results revealed that an increase in the film thickness leads to a monotonic increase in FCC and BCC phase of Ag and Ta, respectively. The work function and stoichiometric of the Ag–Ta thin films were investigated by ultraviolet and X-ray photoemission spectroscopies (UPS and XPS), respectively. The potential of Ag–Ta thin films to be used as low-emission coating was investigated using a spectrophotometer. A UV–VIS–NIR spectrophotometer was used to measure the spectral reflectance in the wavelength range from 300 to 2000 nm. The results showed that the Ag–Ta thin film deposited for 30 s exhibited higher reflectance in NIR region than those of 5, 10, 20 and 30 s. It demonstrated an average reflectance of about 80% and slightly decreased to 75% after being kept in the air atmosphere for 28 days. It can be likewise proposed as an alternative thin film with high reflectance of NIR radiation single layer to develop industrial low-emission coating for cost-effective, clean, and easy adaptation to a large area coating