There are still many scientific and engineering challenges that need to be addressed before a true sustainable hydrogen economy can be realized. Three of these challenges include sustainable hydrogen generation without CO2 emissions, effective storage of this hydrogen for specific applications, and expanding the limited existing hydrogen infrastructure. Here we demonstrate (i) the fabrication of hierarchical bulk nanoporous aluminum with the coexistence of macroscopic and mesoscopic ligament/pore structures, with the mesoscopic ligaments in the range of 10–20 nm; (ii) the use of this aluminum to produce hydrogen on-site with a yield of ∼52–90% by hydrolysis with “pure” water, without incorporation of any catalyst or reaction promoter in the aluminum-water system; and (iii) the combustion of this aluminum in air under ambient conditions, which implies that this material could be attractive as a combustion fuel catalyst, e.g., to enhance the ignition and combustion of solid propellants. The inclusion of secondary aluminum or carbon-free primary aluminum in our process will make it possible to produce hydrogen with reduced carbon footprint for on-site and on-board applications using only nanoporous aluminum and water.

Nanostructured Sn as negative electrode material in Mg-ion batteries suffers from very slow magnesiation kinetics when its nanoscale feature sizes are not in the sub-100 nm range. Herein, we use electrochemical experiments in combination finite element modeling (FEM) to demonstrate a cost-effective route to nanostructured Sn for high performance Mg-ion battery anodes. Using FEM we found that antagonistic stresses developed during dealloying of Mg 2 Sn induce pulverization of the dealloyed material and formation of nanostructured Sn with the characteristic feature size in the sub-100 nm range. These results were further confirmed through electrochemical experiments using a Mg halfcell consisting of bulk Mg 2 Sn particles with an average characteristic size larger than 10 μm as the working electrode, cycled versus Mg metal as counter and reference electrodes, and all-phenyl complex (APC) electrolyte. Ex situ electron microscopy and diffraction techniques were used to study the working electrode material in the pristine, demagnesiated, and remagnesiated forms. The results suggest that the starting micrometer-sized Mg 2 Sn particles are converted into nanostructured β-Sn with characteristic sizes ranging from 10 to 50 nm during the first demagnesiation. Electrochemical performance of the in situ formed nanostructured Sn was further investigated during subsequent (de)magnesiation cycles in combination with electrochemical impedance spectroscopy (EIS). EIS studies suggest the formation of passive films on the Mg 2 Sn electrode. A reversible capacity of 300 mAh/g was demonstrated over 150 cycles at the rate of C/5 after application of a combined sequence of regular galvanostatic cycling with an oxidative pulse to control the passive film formation. This work is expected to open new avenues for cost-effective routes to high performance alloytype Mg-ion battery anodes without complex nanosynthesis steps.

Although certain therapeutic agents with immunogenic properties may enhance antitumor immunity, cancer cells can eliminate harmful cytoplasmic entities and escape immunosurveillance by orchestrating autophagy. Here, an ingenious in situ self-assembled nanomicelle dissolving microneedle (DMN) patch was designed for intralesional delivery of immunogenic cell death-inducer (IR780) and autophagy inhibitor (chloroquine, CQ) coencapsulated micelles (C/I-Mil) for efficient antitumor therapy. Upon insertion into skin, the self-assembled C/I-Mil was generated, followed by electrostatic binding of hyaluronic acid, the matrix material of DMNs, accompanied by the dissolution of DMNs. Subsequently, photothermal-mediated size-tunable C/I-Mil could effectively penetrate into deep tumor tissue and be massively internalized via CD44 receptor-mediated endocytosis, precisely ablate tumors with the help of autophagy inhibition, and promote the release of damage-associated molecular patterns. Moreover, CQ could also act as an immune modulator to remodel tumor-associated macrophages toward the M1 phenotype via activating NF-κB. In vivo results showed that the localized photoimmunotherapy in synergy with autophagy inhibition could effectively eliminate primary and distant tumors, followed by a relapse-free survival of more than 40 days via remodeling the tumor immunosuppressive microenvironment. Our work provides a versatile, generalizable framework for employing self-assembled DMN-mediated autophagy inhibition integrated with photoimmunotherapy to sensitize superficial tumors and initiate optimal antitumor immunity.

Dealloyed nanoporous metals made of very-reactive elements have rarely been reported. Instead, reactive materials are used as sacrificial components in dealloying. The high chemical reactivity of nonprecious nanostructured metals makes them suitable for a broad range of applications such as splitting water into H2 gas and metal hydroxide. On the other hand, the same high chemical reactivity hinders the synthesis of nanostructured metals. Here we use a pH-controlled dealloying strategy to fabricate bulk nanoporous Zn with bulk dimensions in the centimeter range via the selective removal of Al from metastable face-centered cubic bulk Zn20Al80 at. % parent alloys. The corresponding bulk nanoporous Zn exhibits a hierarchical ligament/pore architecture characterized by primary ligaments and pores with an average feature size in the submicrometer range. These primary structures are made of ultrafine secondary ligaments and pores with a characteristic feature size in the range of 10–20 nm. Our bulk nanoporous Zn can split water into H2 and Zn­(OH)2 at ambient temperature and pressure and continuously produce H2 at a constant rate of 0.08 mL/min per gram of Zn over 8 h. We anticipate that in this hierarchical bulk architecture, the macropores facilitate the flow of water in the bulk of the material, while the mesopores and ultrafine ligaments provide a high surface area for the reaction of water with Zn. The bulk nanoporous Zn/water system can be used for on-board or on-demand H2 applications, during which H2 is produced when needed, without prior storage of this gas compressed in cylinders as it is currently the case.

The synthesis of nanoporous Mg with minimal surface oxide coverage has been hindered by its high chemical reactivity. Herein, we demonstrate the fabrication of three-dimensional bicontinuous nanoporous Mg with ligament and pore sizes in the range of 20–30 nm using air-free electrolytic dealloying with recovery of the sacrificial material. The starting material consists of a magnesium–lithium parent alloy with lithium as the sacrificial component. During selective electrolytic leaching in an anhydrous lithium-conducting organic electrolyte solvent, the sacrificial lithium is stripped from the magnesium–lithium parent alloy used as the working electrode and plated on a pure lithium foil used as the counter electrode, enabling sacrificial element recovery, making the process eco-friendly. The morphology of the fabricated nanoporous Mg was thoroughly investigated using electron microscopy techniques, inductively coupled plasma (ICP) spectroscopy, X-ray photoelectron spectroscopy (XPS), small-angle X-ray scattering (SAXS), and X-ray diffraction. The synthesized nanoporous Mg is attractive for energy conversion and storage applications. Here, we show that it can produce hydrogen on-demand by hydrolysis with pure water and that it can also be used as a high-capacity lithium-ion battery anode.

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The photogating effect in hybrid structures has manifested itself as a reliable and promising approach for photodetectors with ultrahigh responsivity. A crucial factor of the photogating effect is the built-in potential at the interface, which controls the separation and harvesting of photogenerated carriers. So far, the primary efforts of designing the built-in potential rely on discovering different materials and developing multilayer structures, which may raise problems in the compatibility with the standard semiconductor production line. Here, we report an enhanced photogating effect in a monolayer graphene photodetector based on a structured substrate, where the built-in potential is established by the mechanism of potential fluctuation engineering. We find that the enhancement factor of device responsivity is related to a newly defined parameter, namely, fluctuation period rate (P f). Compared to the device without a nanostructured substrate, the responsivity of the device with an optimized P f is enhanced by 100 times, reaching a responsivity of 240 A/W and a specific detectivity, D*, of 3.4 × 1012 Jones at 1550 nm wavelength and room temperature. Our experimental results are supported by both theoretical analysis and numerical simulation. Since our demonstration of the graphene photodetectors leverages the engineering of structures with monolayer graphene rather than materials with a multilayer complex structure. it should be universal and applicable to other hybrid photodetectors.

Malignant tumor has become an urgent threat to global public healthcare. Because of the heterogeneity of tumor, single therapy presents great limitations while synergistic therapy is arousing much attention, which shows desperate need of intelligent carrier for co-delivery. A core‒shell dual metal–organic frameworks (MOFs) system was delicately designed in this study, which not only possessed the unique properties of both materials, but also provided two individual specific functional zones for co-drug delivery. Photosensitizer indocyanine green (ICG) and chemotherapeutic agent doxorubicin (DOX) were stepwisely encapsulated into the nanopores of MIL-88 core and ZIF-8 shell to construct a synergistic photothermal/photodynamic/chemotherapy nanoplatform. Except for efficient drug delivery, the MIL-88 could be functioned as a nanomotor to convert the excessive hydrogen peroxide at tumor microenvironment into adequate oxygen for photodynamic therapy. The DOX release from MIL-88-ICG@ZIF-8-DOX nanoparticles was triggered at tumor acidic microenvironment and further accelerated by near-infrared (NIR) light irradiation. The in vivo antitumor study showed superior synergistic antitumor effect by concentrating the nanoparticles into dissolving microneedles as compared to intravenous and intratumoral injection of nanoparticles, with a significantly higher inhibition rate. It is anticipated that the multi-model synergistic system based on dual-MOFs was promising for further biomedical application.