Department of Chemical Sciences, University of Padova, Padova, Italy.
Nat Nanotechnol. 2020 Oct;15(10):868-874. doi: 10.1038/s41565-020-0734-1. Epub 2020 Jul 20.
The development of non-equilibrium synthetic systems provides access to innovative materials with life-like properties. Non-equilibrium systems require a continuous input of energy to retain their functional state, which makes for a fundamental difference to systems that operate at thermodynamic equilibrium. Kinetic asymmetry in the energy consumption pathway is required to drive systems out of equilibrium. This understanding has permitted chemists to design dissipative synthetic molecular machines and high-energy materials. Here we show that kinetic asymmetry also emerges at the macroscopic level by demonstrating that local energy delivery in the form of light to a hydrogel containing gold nanoparticles installs a non-equilibrium steady state. The instalment and maintenance of the macroscopic non-equilibrium state is facilitated by the gel matrix in which motion is governed by diffusion rather than convection. The non-equilibrium state is characterized by a persistent gradient in the surface composition of the nanoparticles embedded in the gel, which affects the fluorescent and catalytic properties of the system. We show that the overall catalytic performance of the system is enhanced under these non-equilibrium conditions. In perspective it will be possible to develop out-of-equilibrium matrices in which functional properties emerge as a result of spatially controlled energy delivery and spatially controlled chemistries.
非平衡合成系统的发展为具有类似生命性质的创新材料提供了途径。非平衡系统需要持续的能量输入来维持其功能状态，这与在热力学平衡下运行的系统有根本的不同。需要在能量消耗途径上存在动力学不对称性来驱动系统远离平衡。这种理解使化学家能够设计耗散合成分子机器和高能材料。在这里，我们通过证明以光的形式向含有金纳米粒子的水凝胶局部提供能量会安装非平衡稳态，在宏观水平上也出现了动力学不对称性。凝胶基质促进了宏观非平衡状态的建立和维持，其中运动由扩散而不是对流控制。非平衡状态的特征是嵌入凝胶中的纳米粒子的表面组成存在持续的梯度，这会影响系统的荧光和催化性质。我们表明，在这些非平衡条件下，系统的整体催化性能得到提高。从长远来看，有可能开发出非平衡基质，其中功能性质是由于空间控制的能量传递和空间控制的化学反应而出现的。
