Enhanced Sensitivity and Piezochromic Contrast through Single-Direction Extension of Molecular Structure

Two piezochromic materials containing phenanthro[9,10-d]imidazole and tetraphenylethylene (M1 and M2) were developed. A supra-amplification piezochromic effect originating from their various long-to-short axis ratios was discovered in high-pressure experiments. Based on the linear relationship between applied pressure and emission-peak wavelength during pressurizing and depressurizing cycles, quantitative sensitivity for piezochromism could be denoted. M2 displayed higher piezochromic contrast (102 nm) and better sensitivity (11.19 nm GPa(-1)) than M1 (69 nm and 6.12 nm GPa(-1)), which helps to develop a more comprehensive general strategy to evaluate pressure-responsive performance.