(74d) Palladium Nanopartcle Coated Tobacco Moasic Virus Sensing Layer Based Surface Acoustic Wave Hydrogen Sensors

Bio-nanotechnology is aimed at design and synthesis of novel biological materials. These materials could be used to design optical, biomedical and electronic devices. One such example of nanoscale biological system is a virus. Viruses have been given a lot of attention for assembly of nanoelectronic materials. Tobacco Mosaic Virus (TMV) is a well-known plant virus contagious to tobacco leaves. TMV has a 300 nm long tubular structure with an outer diameter of 18 nm and an axial canal 4 nm in diameter. Strains of this virus have been previously coated with metals, silica or semiconductor materials and formed end-to-end nano-rod assemblies. In this work, a genetically engineered TMV with cysteine residues on the outer surface has been utilized to coat Pd clusters. Pd clusteres were nucleated and deposited on the engineered TMV surface by the chemical reduction of palladium chloride anions. It was found that wild type TMV do not accept Pd coatings. In this work, these Pd cluster-coated engineered TMV particles were studied for hydrogen gas detection with the help of Surface Acoustic Wave (SAW) resonators. The coating of a gas sensing material attenuates the surface wave magnitude, and shifts the resonant frequency of the SAW resonators. Exposure of the desired gas causes the resonant frequency to shift further due to absorption or reaction with the sensing material. This change can be directly calibrated to determine concentration of gas absorbed. The increased surface area of Pd exposed to hydrogen, a result of decorating TMV with Pd nanoparticles (about 2.3 nm), was seen to enhance sensitivity and improve response time. High robustness and stability were observed when compared to conventional hydrogen sensors. Repeatability was also observed when tested for a week using a range of concentration (0-2.5 volume %) of hydrogen. The sensor shows very good response (3-6 seconds) and recovery (3-6 seconds) times with observed shifts of about 250 Hz. Larger frequency shifts may be achieved by increasing the TMV-Pd coating thickness. The frequency of the device was observed to increase upon hydrogen exposure, which is opposite to the expected behavior if hydrogen absorption by Pd (mass-loading) is the mechanism.