Bioinspired High-Performance Energetic Materials Using Heme-Containing Crystals

Peptide Assembly of Al/CuO Nanothermite for Enhanced Reactivity of Nanoaluminum Particles

Biological self-assembly procedures, which are generally carried out in an aqueous solution, have been found to be the most promising method for directing the fabrication of diverse nanothermites, including Al/CuO nanothermite. However, the aqueous environment in which Al nanoparticles self-assemble has an impact on their stability. We show that using a peptide to self-assemble Al or CuO nanoparticles considerably improves their durability in phosphate buffer aqueous solution, with Al and CuO nanoparticles remaining intact in aqueous solution for over 2 weeks with minimal changes in the structure. When peptide-assembled Al/CuO nanothermite was compared with a physically mixed sample in phosphate buffer for 30 min, the energy release of the former was higher by 26%. Furthermore, the energy release of peptide-assembled Al/CuO nanocomposite in phosphate buffer showed a 6% reduction by Day 7, while that of the peptide-assembled Al/CuO nanocomposite in ultrapure water was reduced by 75%. Taken together, our study provides an easy method for keeping the thermal activity of Al/CuO nanothermite assembled in aqueous solution.

Hydroxyl Radical Generation Through the Fenton-Like Reaction of Hematin- and Catechol-Functionalized Microgels

Hydroxyl radical (^•OH) is a potent reactive oxygen species with the ability to degrade hazardous organic compounds, kill bacteria, and inactivate viruses. However, an off-the-shelf, portable, and easily activated biomaterial for generating ^•OH does not exist. Here, microgels were functionalized with catechol, an adhesive moiety found in mussel adhesive proteins, and hematin (HEM), a hydroxylated Fe³⁺ ion-containing porphyrin derivative. When the microgel was hydrated in an aqueous solution with physiological pH, molecular oxygen in the solution oxidized catechol to generate H₂O₂, which was further converted to ^•OH by HEM. The generated ^•OH was able to degrade organic dyes, including orange II and malachite green. Additionally, the generated ^•OH was antimicrobial against both gram-negative (Escherichia coli) and gram-positive (Staphylococcus epidermidis) bacteria with the initial concentration of 10⁶-10⁷ CFU/mL. These microgels also reduced the infectivity of a non-enveloped porcine parvovirus and an enveloped bovine viral diarrhea virus by 3.5 and 4.5 log reduction values, respectively (99.97-99.997% reduction in infectivity). These microgels were also functionalized with positively charged [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC), which significantly enhanced the antibacterial and antiviral activities through electrostatic interaction between the negatively charged pathogens and the microgel. These microgels can potentially serve as a lightweight and portable source of disinfectant, for an on-demand generation of ^•OH with a wide range of applications.

Laser-Ignited Relay-Domino-Like Reactions in Graphene Oxide/CL-20 Films for High-Temperature Pulse Preparation of Bi-Layered Photothermal Membranes

Light-ignited combustions have been proposed for a variety of industrial and scientific applications. They suffer, however, from ultrahigh light ignition thresholds and poor self-propagating combustion of typical high-energy density materials, e.g., 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane (CL-20). Here, reported is that both light ignition and combustion performance of CL-20 are greatly enhanced by embedding ε-CL-20 particles in a graphene oxide (GO) matrix. The GO matrix yields a drastic temperature rise that is sufficient to trigger the combustion of GO/CL-20 under low laser irradiation (35.6 mJ) with only 6 wt% of GO. The domino-like reduction-combustion of the GO matrix can serve as a relay and deliver the decomposition-combustion of CL-20 to its neighbor sites, forming a relay-domino-like reaction. In particular, a synergistic reaction between GO and CL-20 occurrs, facilitating more energy release of the GO/CL-20 composite. The novel relay-domino-like reaction coupled with the synergistic reaction of CL-20 and GO results in a deflagration of the material, which generates a high-temperature pulse (HTP) that can be guided to produce advanced functional materials. As a proof of concept, a bi-layered photothermal membrane is prepared by HTP treatment in an extremely simple and fast way, which can serve as a model architecture for efficient interfacial water evaporation.

Highly Reactive Metastable Intermixed Composites (MICs): Preparation and Characterization

Highly reactive metastable intermixed composites (MICs) have attracted much attention in the past decades. The MIC family of materials mainly includes traditional metal-based nanothermites, novel core-shell-structured, 3D ordered macroporous-structured, and ternary nanocomposites. By applying special fabrication approaches, highly reactive MICs with uniformly dispersed reactants, "layer-by-layer" or "core-shell" structures, can be prepared. Thus, the combustion performance can be greatly improved, and the ignition characteristics and safety can be precisely controlled by using a certain preparation strategy. Here, the preparation and characterization of the MICs that have been developed during the past few decades are summarized. Traditional preparation methods for MICs generally include physical mixing, high-energy ball milling, sol-gel synthesis, and vapor deposition, while the novel methods include self-assembly, electrophoretic deposition, and electrospinning. Various preparation procedures and the ignition and combustion performance of different MIC reactive systems are compared and discussed. In particular, the advantages of novel structured MICs in terms of safety and combustion efficiency are clarified, based on which suggestions regarding the possible future research directions are proposed.

Tuning the Reactivity of Metastable Intermixed Composite n-Al/PTFE by Polydopamine Interfacial Control

The metastable intermixed composite (MIC) is one of the most popular research topics in the field of energetic materials (EMs). The goal is to invent EMs with tunable reactivity and desired energy content. However, it is very difficult to tune the reactivity of MIC due to its high reactivity and sensitivity caused by enlarged specific surface area and intimate contact between the oxidizers and fuels. Herein, we demonstrated a facile fabrication method that can be used to control the reactivity between the nanoaluminum (n-Al) and poly(tetrafluoroethylene) (PTFE) using an in situ-synthesized polydopamine (PDA) binding layer. It was found that PDA can adhere to both n-Al and PTFE particles, resulting in integrated n-Al@PDA/PTFE MICs. In comparison with traditional n-Al/PTFE MICs, the n-Al@PDA/PTFE showed an increased energy release and reduced sensitivity and more importantly tunable reactivity. By regulating the experimental conditions of coating, the thickness of PDA could be well controlled, which makes the tunable reactivity of n-Al@PDA/PTFE possible. The PDA interfacial layer may increase the preignition reaction (PIR) heat of Al₂O₃/PTFE and therefore the overall reaction heat of n-Al/PTFE. It also reveals that the PDA interfacial layer postponed the PIR, leading to an increase in onset thermal decomposition temperature ( T_o). As T_o increased, a more complete reaction between PTFE and Al nanoparticles could be achieved.

Insensitive ionic bio-energetic materials derived from amino acids

Energetic salts/ionic liquids have received increasing attention as fascinating energetic materials, and the use of renewable compounds is a promising approach to developing energetic materials. Until recently, biomolecules have been used as raw materials to develop neutral energetic compounds, whereas research focused on ionic energetic materials obtained from natural bio-renewable frameworks is scarce. This work systematically investigates ionic bio-energetic materials (IBEMs) derived from sustainable natural amino acids. In addition to combustibility, high density, good thermal stability, and one-step preparation, these IBEMs demonstrated apparent hypotoxicity and insensitivity. Moreover, a theoretical examination was performed to explore their appropriate properties. The intriguing results of this study indicates that IBEMs are potential bio-based energetic materials.

Creation of energetic biothermite inks using ferritin liquid protein

Energetic liquids function mainly as fuels due to low energy densities and slow combustion kinetics. Consequently, these properties can be significantly increased through the addition of metal nanomaterials such as aluminium. Unfortunately, nanoparticle additives are restricted to low mass fractions in liquids because of increased viscosities and severe particle agglomeration. Nanoscale protein ionic liquids represent multifunctional solvent systems that are well suited to overcoming low mass fractions of nanoparticles, producing stable nanoparticle dispersions and simultaneously offering a source of oxidizing agents for combustion of reactive nanomaterials. Here, we use iron oxide-loaded ferritin proteins to create a stable and highly energetic liquid composed of aluminium nanoparticles and ferritin proteins for printing and forming 3D shapes and structures. In total, this bioenergetic liquid exhibits increased energy output and performance, enhanced dispersion and oxidation stability, lower activation temperatures, and greater processability and functionality.