Bioinspired Manufacturing: Photoinduced Self-Replication of Metal Nanoparticles in Solution and on Surfaces

Abstract

Self-replication and self-assembly are two processes essential for biological systems. Their ex-vivo reproduction continuously fuels fundamental scientific discoveries and can be essential for sustainable manufacturing. It currently remains unknown whether one can successfully couple these processes for engineered biomimetic systems, especially for robust inorganic components of technological significance. Here we seek to explore into the field of self-replication in search for an inorganic biomimetic system not seen to this date. The first scope of this thesis was to find an inorganic colloidal system with preliminary characteristics of self-replication, using silver nanoparticles as the initial material. As a self-replicating inorganic particle system has never been realized before, there is minimal previous work base off of. As a result, a high-throughput screening method consisting of three steps was developed to comb through a high density of systems in Chapter 3. After over 100 systems, one condition passed the screening steps to be examined more in depth. This screening method will be useful for the discovery of future inorganic self-replicating materials outside of silver. Silver nanoparticles synthesized from a solution of 0.1 mM silver nitrate and 3 mM citrate at a critical pH of 10.3 were found to simultaneously self-replicate and self-assemble in a process driven by light in Chapter 4. Careful selection of illumination, environmental, and media conditions resulted in the growth of the nanoparticles catalyzed by the previously formed ones. Ex-situ characterization methods were used to evaluate the nanoparticle concentration over time, where a sigmoidal curve indicative of autocatalysis and self-replication was confirmed. A series of highly advanced electron microscopy techniques were used to probe in real time the nucleation and self-replication of the silver nanoparticles. It was discovered that the interface of the parent particle created favorable conditions for silver nuclei to form resulting in a chain-like assembly of self-replicated particles. This fundamental understanding of the formation of the nanoparticles was used to develop a computational model describing the kinetics to help support the experimental kinetic trends. The second scope of this thesis was to expand this bioinspired system to various applications in Chapter 5. Realization of coupled self-assembly and self-replication in the vicinity of a substrate resulted in complex neuron-like networks of nanoparticles that allow their utilization for the preparation of conductive coatings for various applications. Furthermore, introducing the self-replicating particles to a highly corrugated surface, i.e. spikey hedgehog particles, the gap between the tips of the spikes can be bridged via radial replication of the silver nanoparticles away from the spike. These suspended nanoparticle bridges on highly corrugated surfaces could have numerous applications in microfluidics, photonic, and sensing. Chirality was another pathway explored as the combination of the plasmonic effect coupled with chirality opens a wide range of applications in sensing, catalysis, and photonics. Illuminating a substrate submerged in a solution of silver precursor and citrate with circularly polarized light created complex chiral silver helicoids on the surface. These helicoids could be tuned on-the-fly to print chiral patterns on any substrate with chiroptical activity extending the entire visible spectrum. The knowledge obtained from this system was applied to the self-replicating system. In the end, it was found that introducing a second metallic salt, copper nitrate, can induce chirality at self-replicating conditions. Overall, this thesis establishes a foothold into inorganic self-replicating materials that have not been experimentally seen before.