Synthesis and hydrogen production kinetics of temperature-responsive aluminum-poly(N-isopropylacrylamide) core-shell nanoparticles

We report here on the synthesis of air-stable aluminum nanoparticles (Al NPs) capped with a temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAM). These core-chell particles display temperature-dependent hydrogen production kinetics upon hydrolysis. Kinetic studies show that the bimolecular rate constant below the critical solution temperature (CST) is 2.85 x 10(-4) L mol(-1) s(-1) (at 20 degrees C), which is nearly twice that of the rate constant (1.6 x 10(-4) L mol(-1) s(-1)) above the CST (at 40 degrees C). This non-Arrhenius behavior is proposed to originate from collapse of the capping layer above the CST which creates a less permeable capping layer. The core-shell nanoparticles were characterized with powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy with total attenuated reflection (FTIR-ATR), and differential scanning calorimetry coupled with thermogravimetric analysis (DSC/TGA). Transmission electron microscopy (TEM) confirms the Al NPs are core-shell structures and the composite particle size distribution ranges from 22 nm to 40 nm.