A Nanobionic Light-Emitting Plant.

The engineering of living plants for visible light emission and sustainable illumination is compelling because plants possess independent energy generation and storage mechanisms and autonomous self-repair. Herein, we demonstrate a plant nanobionic approach that enables exceptional luminosity and lifetime utilizing four chemically interacting nanoparticles, including firefly luciferase conjugated silica (SNP-Luc), d-luciferin releasing poly(lactic-co-glycolic acid) (PLGA-LH2), coenzyme A functionalized chitosan (CS-CoA) and semiconductor nanocrystal phosphors for longer wavelength modulation. An in vitro kinetic model incorporating the release rates of the nanoparticles is developed to maximize the chemiluminescent lifetimes to exceed 21.5 h. In watercress (Nasturtium officinale) and other species, the nanoparticles circumvent limitations such as luciferin toxicity above 400 µM and colocalization of enzymatic reactions near high adenosine triphosphate (ATP) production. Pressurized bath infusion of nanoparticles (PBIN) is introduced to deliver a mixture of nanoparticles to the entire living plant, well described using a nanofluidic mathematical model. We rationally design nanoparticle size and charge to control localization within distinct tissues compartments with 10 nm nanoparticles localizing within the leaf mesophyll and stomata guard cells, and those larger than 100 nm segregated in the leaf mesophyll. The results are mature watercress plants that emit greater than 1.44 × 1012 photons/sec or 50% of 1 µW commercial luminescent diodes and modulate "off" and "on" states by chemical addition of dehydroluciferin and coenzyme A, respectively. We show that CdSe nanocrystals can shift the chemiluminescent emission to 760 nm enabling near-infrared (nIR) signaling. These results advance the viability of nanobionic plants as self-powered photonics, direct and indirect light sources.

Response to Comment on "Cryoforged nanotwinned titanium with ultrahigh strength and ductility".

We address the three main points of Guo et al. They claim that we should have used the engineering stress versus engineering strain curves to infer the mechanical properties of our nanotwinned titanium, question our sample design on the basis of a finite-element analysis, and doubt the immobility of some preexisting grain/twin boundaries in our electron backscatter diffraction micrographs. We find their analysis to be groundless and to contain many inconsistencies.

Cryoforged nanotwinned titanium with ultrahigh strength and ductility.

Nanostructured metals are usually strong because the ultrahigh density of internal boundaries restricts the mean free path of dislocations. Usually, they are also more brittle because of their diminished work-hardening ability. Nanotwinned materials, with coherent interfaces of mirror symmetry, can overcome this inherent trade-off. We show a bulk nanostructuring method that produces a multiscale, hierarchical twin architecture in a hexagonal closed-packed, solute-free, and coarse-grained titanium (Ti), with a substantial enhancement of tensile strength and ductility. Pure Ti achieved an ultimate tensile strength of almost 2 gigapascals and a true failure strain close to 100% at 77 kelvin. The multiscale twin structures are thermally stable up to 873 kelvin, which is above the critical temperature for many applications in extreme environments. Our results demonstrate a practical route to achieve attractive mechanical properties in Ti without involving exotic and often expensive alloying elements.

Making ultrastrong steel tough by grain-boundary delamination.

Developing ultrahigh-strength steels that are ductile, fracture resistant, and cost effective would be attractive for a variety of structural applications. We show that improved fracture resistance in a steel with an ultrahigh yield strength of nearly 2 gigapascals can be achieved by activating delamination toughening coupled with transformation-induced plasticity. Delamination toughening associated with intensive but controlled cracking at manganese-enriched prior-austenite grain boundaries normal to the primary fracture surface dramatically improves the overall fracture resistance. As a result, fracture under plane-strain conditions is automatically transformed into a series of fracture processes in "parallel" plane-stress conditions through the thickness. The present "high-strength induced multidelamination" strategy offers a different pathway to develop engineering materials with ultrahigh strength and superior toughness at economical materials cost.