A T-shaped plasmonic array is proposed for application as an effective thermal emitter or biosensor. The reflection and thermal radiation properties of a T-shaped array are investigated theoretically. The angular dependent reflectance spectrum shows a clear resonant dip at 0.36eV for full polar angles. No other significant localized resonant mode is found in the investigated spectral range from 0.12eV to 0.64eV. According to the Kirchhoff s law, the thermal radiation of the proposed structure can lead to a sharp peak at 3.5 νm with low sideband emission. We have also found that the T-shaped structure filled with organic material such as PMMA with different thicknesses (10 nm -50 nm) can lead to significant shift of the resonance wavelength. Thus, the T-shaped structure can also be used as a good sensor for organic materials.